• Author / Uploaded
• RaineSanchezLabioso

• Categories
• Tratamiento de aguas residuales
• Ingeniería Ambiental
• Ciencias fisicas
• Ciencia
• Química

Citation preview

Wastewater Engineering Treatment and Resource Recovery

Fifth Edition Metcalf & Eddy I AECOM Revised

by

George Tchobanoglous

Contributing Authors:

Professor Emeritus of Civil and Environmental Engineering Unive rsity of California at Davis

Mohammad Abu-Orf North America Biosolids Practice Leader. AECOM

H. David Stensel

Gregory Bowden Wastewater Technical Leader, AECOM

Professor of Civil and Environmental Engineering University of Washington. Scattle

Ryujiro Tsuchihashi Wastewater Technical Leader, AECOM

Franklin Burton Consulting Engineer LosAllo);, CA

William Prrang Wastewater Treatment Technology Leader. AECOM

WASTEWATER ENGIN EE RIN G: TREATM ENT AND RESO URCE RECOVERY. FIFfIl EDITION Pub lished by McGraw- Hili Education, 2 Penn Piau, New York. NY 10121. Copyright © 20 14 by McGmw-H ili Educat ion. All rights rescrved. Printed in the United States of America. Previous editions Q 2003. 1991. a nd I !J79. No pari of this publicut io n may be reproduced or distribu ted in any form or by any means, or stored in a dambasc or retrieval sy~tem, withoot the prior written conse nt of McGraw -Hili Education. includin g. but not limited to. in any network or other e lectronic storage or tmnsmission. or broadcast for distance learn ing. Some ancillaries. including e lectronic and prinl components. may not be avai lable 10 c ustomers olllsicte the United Slates. This book is printed on acid-free paper_ I 234567890 QVSfQVS I 09876543 ISBN 978-0-07- 3401 18-8 MI-II D 0--07-340118-8 Senior Vice President. Prod uc l~ & Markel~: Kurl L Simnd Vice President, Ge neral Manager: Marry u11!ge Vice President. Co ntent Production & Tec hnology Services: Kimberly Meriwelher Dt,viJ G lobal Brand Manager: R"ghothmrum Sriniva.fall Execut ive Br,lfld Manager: /Jill Stenqui,ok "Water Reuse: Issues, Technologies and Applications," a companion textbook to this lexllxlok. He is a tec hnical pmctice coordinator for AECOM's watt;:r reuse leadership team. Ryuji roTsuchihashi is a membt:r of tllt: Water Environment Federation. American Society of Civil Engineer. and International Water Association, and has been an e mployee of AECOM for 10 years. during which he has worked on various projccts in the Unitoo State. Australia. Jordan. and Canada.

Franklin Burton served as vice pre.('1',,,"1'1' 12

H'

39

C(llIIlllell'-Mi,I' HC(1CWfS 111 St'rit'S wilh Ref/c/ioll

10

f'fI'/('(!,mbleml' wilit MBR SYSltllU 738

Processes for Biological Nitrogen RernO\'al 795 Process De'l't'iopmelll 796 Ol'en'jell' ofTYI1i!J' of /Jiulugiwl Nilmg(ll-R"movlI! Pmel'Ss!.'.\' 797 Generol Prm:ess DaiKll COlisidt'mliulls 802 Prealloxic iJenilrijicU/ioll PrtJCessl's 804 Postalloxic DellitrijiclIIiOir Processes 831 U'II' 1)0 (lnd Cyclic Ni/rijiC;lIlimvDellilrifiClIliOI! Processes 833 A/lemlllj" e Process Conjigllrwiolls for /Ji%giml Njlr"gel1 Remo)"(l/ 8]8 l)ellitrijicari(JIl with £rtema' Carborl Adflit/OJr 848

Key IVIISIIIII'tller COII.I'lilltelll,~ for PrrxfH

8-3

754

Seque"ejng BOlch Reactor Process Desigll 77] S/(lged Ac/i'"(I/ed-Sludge Procl'SS Design 782 IIllerIUU;I'C PIYJeesses for BOD Rcmoml IIlId NilrijiCa/iOIl 786

Suspended Growth Biological Treahnent Processes

8-1

Gellem' Pmcess Duign Considem/iOlrs Complele ·Mix Ac/im/er/·Slmige Prm.'cSJ Dcsigil 754

xiii

8-10

Analysis of Liquid-Solids SeparJtion for Activmcd-S ludge Processes with Clarincrs 889 Solids Sf'{)(lmtioll by Secondary C/llrifiers 889 Assessmg Sludge Thickening Clraraclerislics 891 elnrijil'r /}esI811 Based Oil Solids F/IU Analy.I'i,\'

1:\9]

Clarijier Oesigll BlUed 0/1 Slate Poilll AllalJ.fis 900

8-11 752

Design Considerations fOf Secondary Clarifiers 906 Types of Sedimelltation Tllllk 906 Side,wl/u De,nlr 910

Contents

xiv

Flow Dislribuliol/ 910 Tmlk 1,,11'1 Design 910 Wcir P/(/CCmCIll and Loa(ling

Desigll of Plly,fial1 Facililie.f

912 912

SC/lJII Remom/ lind MmwXc/1/cllf

8-12

Solids Separation for Membrane Biorellctors Design Parameter 9 13 Membrane Properties 914 Membrane Design llntl OfH!mling C//(/rt/clerislifs 917 Membral/e Usage 917 Membrane rouling Isslle,f 917 Prohlems and Discussion TOI)ics

9

9-.

9-2

9-5 91 3

919

941

Inu"Oduc!ion to Attuch(,.,(! Growth Processes 943 'f'ype$ of Alluched Gm ....111 Proces.fc.f 943 Mlll'S Trwl,qer Limi/fl/iolls ill AI/trdled Growth f>nx'esses 947 Non~lIb lnerged

Attached Growth

l>roce~s

9-3

Sequential Combi ned Tricklin g Filter 1I1ld Suspended Solids Proce...ses 987 l' fQCess JJel'f~lopment 987 I'mass ApplimlitHlS 9117 Trictling Filler/SlJlids Contact Proce.u 988 Trkklillg Fillerllktil'flled Sff/{Ige Pmce~'s 990 Series TricHing- Filltr !Ielivored-Slrf(ige Pmee.f.f 997 Intcgr.ltoo FiJ\(,.-d· Film Activated Sludge Process 997 Proce.~s Dndopmelfl 998 Prrn:css !If/plicaliOlIS I{XX) IF!IS Proce.fS !Il/wIII/ages and Disadl'lllltages 1002

1027

9-7

Attached Growth Dcnit rillcalion Proce~se.~ 1034 I'rocess Development 1034 Descriplion and Alw1ir;alion of Af/ache(/ Grow,h Denilrificalion Pnx'esse.f 1035 I'rocess DHigll Analysis nf l'o,flOl/(}xic Allached Grow/h Dellilrificalilill 1037 Operational C()lIJitil'f(lIillns for P(}J'/(Illuxic AllaC'hed Growlh Denirrijkmion 1041

9-8

Emerging Biofilm Processes 1045 Membmne Biofilm Rellclors 1045 Biofi/m Airlifl ReaCI()r,~ 1046

947

Gtmerol Pmce~'s l)e,~ai,,,ilJll 947 Trickling Fillmass AnalYJ'iJI'" BOD RelllO l'tll 972 l'mee.I's Allllly,I'i~Ior Ni/rificllTiOIl 978

1008

MOiling Bed Biofilm Rc:\ctor (M BB R) 10 15 IJlIl'/(gm/llul 101 5 MIlHR ProcessApplicalion.f 1016 MllIlR Process Adl'(I11/oges and /}islIdwmtages 1016 Desigl! ()fPhysical H,eilities 1019 MlJIlR ProceJ.f DesiSn AI/(I/ysis 1020 BOD Relll(Jl'al {lml Ni/rific(lfion Design 1021 Submerged Aerobic Attached Growth Processes 1026 Process Dn'e/opmelll 1026 Process IIpplicaliO/I.1 1027 Process Admllfagf's (Illd Di.mdvallfages DesiSl1 of Ph pica I fileililin 1029 HAF I'rocess De.1igll Alollysis 1031 FIJ/JR Process De,l'ix" Alullysis 1034

AHached Growth and Combined Biological Treatment Processes

1003

WAS ProcesJ' DeSig11 Analysis 1005 BO/} am/ Nilrification Design Approach

Aembic Gm/rules Reactor

1046

I'roblems a nd Discussion Topics

10

1046

Anaerobic Suspended and AHached Growth Biological Treatment Processes

1059

'0-'

ll lC! Rationale for Anaerobic Treatment At/vall/uges of Antlembic Trelllmeni l'mL'f:il.¥l!.! 106 1 DiJ',u/~lIlIltIgES IIf AlIlIembic Trealmftnt Processes 1062 SlImmltry Asseument 1063

1001

'0-2

Development of Anuerobic Tc(;h nologies 1063 Hiswrical Deve/0l'lIIeI!IS in LiqllefactiOIl 1063 Trellllllelll "fWl/sleM'lIter Sludges 1065 Tre(llmelll 'if High Strength Wl/SIeS 1066 FIII/Jre De\'f'-Iopmen/s 1067

xv

Conten"

'0-3

Ava ilable Anaerobic Technologies T)Pt'!i of Anaerobic Tt'ciuwlogies

1067 1067

AplHicalioll of AIIlJt'robic Technofogie.r

,0-4

1071

Fundamenta l Consideratio ns in the Application o f

Anaerobic Treatment Processes

1075

Ch(lrtieteriSlic.f of/III! WilSlell'at",r

1075

Pretreatment of WllSlewater 1080 Expected Gas "roducliol1 1083 EIIerg)' Production Pole/Ilia/ lOSS Sulfide Production 1088 Amillonia fflXicily

' 0-5

1 1-6

1090

Design Considerations for Implementation

of Anaerobic Treatment Processes 1090 Tremmelr! Efficiency Needed 109 1 General Process Design Paramill ers 109 1 Process Imp/ememotion Issues 1093 , ()-6

Process Design EJlamples Anaerobic CO/1/(J(." Process

Use ofSimufotiOfl Models

1095

1107

Codigeslion of Organic Wastes with Municipal Sludge 1108

1109

Separation Processes for Removal of Residua l Constituents

! [ 17

11-1

Need for Addi lional Wastcwu ter Treatment

11-2

Overview of Techllologies Used for Removal of Res idu al Puni culme and Dissolved ConStituents J 120

1120

Sepclratlon Processes Based all Mass

Unit Processes for the Removal of Residual Particulate and Dissolved Const i tuent~ 1123 Typien/ Pmces:r Flow Diagm/tls 1 124 Process Pcrfomlllnce £Xpec/(lliQn.~ 1125

Introduct ion to Depth Filtration 1129 Desai/,tio/l oflhe Fiflrolion Pmuss 1129 Filler Hydmulics 1134 M{KJeling the Fil/mlioll Process 1142

11-5

Depth "'1Itl1l.lion: Selection and Design Considerm ions

1144

Membrane Fillration Proces!;Cs

[175

1181

11-8

Electrodialysis 1217 [hscription of lire E/ecrrotiiolysis Process 1217 Electmdia/ys6' RINer.fai 1218 Power Co/Urlllrptioil 1220 O~nrting Comiderotio,u 1222 Electrodialysis Vel)"us Reverse Osmosis 1223

11-9

Adsorption 1224 Applicatiolls for Adsorption 1224 TYIH!.I' of Adsorbellf.f 1224 FUlldalllcl/tals of Adsorpfioll l'roceSM!S 1227 DeI'eiorHllelll of Adsorpfion ISOlhl'nns 1227 AdsorptiOlr of Mixwres 1232 Adsorplion Ctr/Krdry 1232 SIIIIII/ Scale COIIIIIIII TestJ 1240 Analysis 0/ Powdered AClimted Corbot/ Contactor 1243

Trall.geT 1120 Tram./ornra/jOl! Ba,5ed all Chemical and lJialogical Processes 1122 ApplicOliol1 of Unil Proceues!or Relllm'u{ of fie.5idua/ COIlSliruents 11 23

11-3

Surface Filtration 1171 Ami/able Filmuiol! Tee/urologies 1172 DacriptiOir of the Surface Fillration PrrJI.:e,I'.' Per/omrmrce of S"rface Fi/It!rII 1178 Desigll Considerations llSO Pi/at P/mr/ SlurJiel' llSO

Membrane Process Temrintllogy 1181 Membrane Process Classification 1182 Melllhrlllll! Conlrlillmelll Veuels 118S Operalional Modes for Pres.fllr;zed Conjigumtir}llS 1189 PmCt!S.f AnalYfi.f for MF "'U/ Uf' Memhranes 1190 Operating Slroll'git:.ffor MF and UF Membranes 1192 Prm:e.u Allalysis for Reverse Osmosis 1193 Memhrane Fouling 1198 CO/rlml of Membrane Fouling 1201 Apl,Uralion and Performance 0/ Memb((lIJes 1204 FnnC encountered in natu ral waters and wastewate r in whic h one Iiler of snrn ple weighs llpproxi mately one kilogmm, the unit~ of mglL or g/mJ are inte rc h:lngeable wi th ppm. The terms IJarts IJer bi/lio/l (ppb) and pll rt.~ per trillion (ppt) are used interc hangea bly with J,tglL and nglL, respec ti vely. Dissolvc 100 0.002-50

Trorwniuion electron (TEM)

D

Sconning electron (SEM)

0.2-> 100

lmoge analysis Particle COI.Jnter~

0.2-> 100

Coociuctivi ty difference

0.005-> 100

Equivolent light scaitel"ing

0. 2- > 100

light blockage Separation ond analysis

Ceotrifugotian

0.08-> 100

Field flow froctioootion

0.09- > I 00

Gel

~ Ilfotion

< 0.0001-> 100

chromatography

0.05-> 100

Sedimentotion

M.embrone filtration (see Chop. 11) oAdapted from levine et 01. (1985).

O.OC()]- I

---

2-3

Figure 2- 7 Size ron90s of organic constituents in woslewaler and size $eporolion and m!!'Osuremenl te; of water, /II

+ 55.6 ... 55 .6

and n..... (55.6)5.11 X 10

6

" . .... 2.84 X I0 ~ mole D:!L

4.

Determ ine the saturation concen trat ion of oxygen.

C "'"

(

2.84 X 1O-~ mole O!)( 32 g )( 10 L

,

mole O ~

1

mg)

Ig

(I g/ 1()3 ms)

"" 9.09 mg/L

Solution-Method 2 Using Eq. 12-49)

I. The density of air at 20 0 e from Appendix B is 1204 kglm ~ . 2. The percent of oxygen in air frOIl1 Appendix B is about 23. 18 percent oxygen by weight. 3. Dctcmline the satomtion concentration of oxygen. a. From Table 2- 7, at 20oe, the unitlcss form of Henry's constant is

H" "" 30.75 b. Using Eq (2-49), the value of C, is

C.

C =, H.

C ~ ~('::..2"04::.::.kg/ = ",,,,),,, ( '"GoO'gIk,=g,,)(~O;:: .2,3= 18) ,30.15 :::: 9.08 g/m' :::: 9.08 mg/L

Comment

The computed values (9.09 and 9.08 Illg/L) are essentially the Same as the value given in Appendix E (9.09 mgIL). It should be noleJ that the values for the Henry's law constant given in Table 2-7 will vary depending on Ihe source lind the method used to derive them. Also. the rekllionship at di fferent tempcHllures is !I01 li near.

Oxygen (01 ). Dissolved oxygen (DO) is requ ired for lite respiration uf aerobic microorgan isms as well as nil other aerobic life fonus. However. 0 1 is only slightly sol uble in waler. The aClUal quanlity of O 2 (and other gases too) Ihat Cilll be presem in a solulion is governed by (1) the solubility of the gas, (2) Ihe partial ]l re~sure of the gas in the atmos phere. (3) Ihe tempcrnturc. and (4) Ihe concentration of the impurities in the water

2-4 Inorganic Norroelolic Constituents

103

(e.g., sulinity, suspended solid~). The interrel;ltionship of these variahles is delineated in Chap. 6 and is illustrated in Appendix E, where the effect of temperature :md salinity on DO concentration is presented. Because the rate of biochemical reactions that usc Ol increases with increasing temperature. dissolved oxyge n levels tend to be more c ritical in the summer months. The problem is compounded in summer months becau (often a panel of subjects) arc exposed to odors that havc been dilutcd with cxlor-free air, and the number of dilutions required to reduce an odor to its minimum

Detectability.

Table 2-9

Factors that must be considered for the complete characterization of an odor

Factor

Desuiption

Choroeter

Relates to the mental a!oSOCiations mode by the subject in :lensing the odor. Determination con be quite subjective. Typical odo.. descriplors are listod in the last column of Table 2-8. The number of dilutions required to reduce on odor to its minimum detectable threshold odor concentrotion (MDTOCj. The rotative ploosantness or unpleasantness of the odor !IeOsed by the

Detedobility 10100

Ive>hokil Hedonics 11one)

subject. Intensity

The preceived re lative slrength of the odor above the detection thre!ohold. Usually measured by the bumol oIfoctomctc,- or oolC\J1ated from the OfT (dilutiOfl$ 10 thrmhold ratiol when the relationPlip is esloblidled.

Persistence

The rote at which the odor intensify chonges with concentration. Pe~isleoce con be repre:lented as a dose response function.

106

dopier 2 Wosrewotef Cooroderistics

Gas sample lor odor 8roi1!ysis

Figure 2-17 dossificolion 01 melhods used 10

deled odors.

I

I Analytical tesUng

Sorlsory tosting

I Odor cha racte r (doscripto~)

Odor threshold (detection)

Hedonic tone (arlnoyarlce)

""'"

irltensity (strength)

I

GC ana lysis

GerMS ana lysis

Mon itoring individ ual

""""'","

GC • gas chromlltoorllphy MS • mass spectrometry

detectable threshold odor w ncenlratio n (MDTOC) a re noted . The detectable odor concentration, reported as the dil utio ns to the MOTOC, commonly called lfi/utions-to,hreshold (Off) is given by the followi ng ex.pression: DfT =

Vol ume of odor free air

-:-;:7==:=;=="Volu me of odorous air

12-52)

Thus, if four volumes of odor free ai r must be added to o ne volume of odorous air to red uce the odorant to its MOTOC, the odor concentration wou ld be reponed as 4 Drr. It shou ld be noted that a nu mber of other measures are used to define the i n te n ~i t y of an odor including the Ef)~ value which represents the number of times an odorous "ir sample must be di luted before the average pe rson (50 percentile) can barely detect an odor in the diluted sample. To date, dctectubility is the o nl y factor thai has been used in thc developmen t of stmutory regulations for nuisance odors. The upplica tion of Drr values to assess odor im pacts is considered in Sec. 16-3 in C hap. 16. The threshold ooor of a water or wustcwater sample is determ ined by d il uti ng the sample with odor-free water. Dependi ng o n the natu re of the odorous constituents, the diluted sample can be heated to enhance the releuse of di luted odorous constituellls. T he "threshold ooor number" (TON) corresponds to the greatest dilution of the sample wi th odur frcc wilier :II which un odor is j ust perceptible. T he recom mended sample s ize is 200 mL. The numerical value of the TON is detemli ncd as follows:

TO N ::

A

+

B

A

12-53)

where TON :: threshold odor number A :: mL of sample I) :: mL of odor free water The ooor emanati ng from the liquid sample is de termined as discussed above wi th huma n subjects (often a panel of subj ects). Deta ils for this procedure may be found in Standard Methods (2012). I'crsistcncc, Persiste nce corres po nds to thc rale at which u perceived odor intensi ty decreases as the odor is dil uted. Typicall y odor intensity is dcfi ned as

I :: ke

!2-54}

2-d Inorganic Noometol1ic ConsHtuenls

107

where I = odor intensity, ppm,. n-butanol C = cOllcentr.ltion of odor. number of di lutions t, n = coefficients for each specific odor or combinatio n of odors Three odor inte n ~ity measuremcnL" at differen t di lutio ns are used to establish the dose response. When Eq. (2-54) is linearized and plotted. the slope of the line of best fit corresponds to II. Thus. as the slope of Ihe line decrea~s. the odor is more persistent. The application of Eq. (2-54) is illustrated in Example 2-8.

Sensory Measurement of Odors. It has been shown tha t. under carefully controlled conditions, the sensory (organo leptic) measurement of odors by the human olfactory system can provide meaningful and reliable information. Therefore. the sensory method is oftcn used to measure the odors emanating from wastewater-treatment facilit ies. The a va ilcn developed to measure odors at their source without usi ng sampling containers. A field olfactometer is a hand-held device in w hich odorous air ca n be passed sequentially thl"Oug h a series of grad uated orifices and mixed (diluted) with air that has been purified by passing through aCli va ted carbon. The orifices lIre ty pically sized to pl"Ovide o rr values of2, 4,7,15,30, and so on. The dilulion r'Jtios arc dete rmined by the ratio of the size of Ihe odorous to purified ai r inlets. T'Wo common ly used fi eld olfaClometers, the Scento lllcte .... (Barnebey-Chcney, 1987) and the Nasa.l Range .... (SI. Croix Sensory. 2006).

Table 2-10

Types of errors in the sensory detection of odors

Type of error

Description

AOOplotion and odoptolion

CI"O$S

When exposed OJ(llinually to 0 bockground concenlrotion of on odor, the wbjed is unoble 10 detect the presence of thot odor otlow concentrations. When removod from the bac::kground odor concentroHan, the subject's olfoctory system will recover quickly. Ultimately, be unable to detect lhe presence of on odor 10 which his syslem hos adopted. o subject with on odopteo' olfoctory $)'stem will

Sample modificotion

aoth the concentrotion ond composition of odorous 9CI~s ond vopon can be modified in ~e collection conloinen. ond in odor detection devices. To minimi:te problems os5OCioted with $(Imple modification, the period of odor conloinlflCflt should be minimi:ted Of eliminoted, ond minimum conlocl ~d be ollowod with ony reoctive surfaces.

Subjoctivity

When the slibjed has knowledge of the presence of on odor, random error con be introduced in sensory measurements. Often, knowledge of the odor moy be inferred from other sensory sigools wch os $OlIOCI, ~ghl, Of lauch.

SynOl'"9ism

When more Ihon one odoront is present in 0 somple, il has been observed thol it is fXIssible for a wbje

119fl

5.0

Silver

119fl

2.3

linc"

""/l

Dieldrin'

119fl

0,0019

0.00014

Lindone

""/l ""/l ""/l

0.16

0.063

0.01

0.005

Tribvtyllin PAHs.....

11 15

58

0.049

° limits apply 10 the overoge ooncenlrotion ~ 011 samples coI!eded during the overoging period Idoifr-24-h period; monthly-,alendor month),

may be mel os c d-d ovemge. If oompliance j~ 10 be determined bo~ on a 4·d average, then concentrations af lour 24·h composile samples must be reported as well as the average of lour. • Comf)lionce will be based an the practical quontifi,otjon level (POL), 0.07 iPiJfL. d PAHs • polynucll!Or aromatic hydroc;crbons. oComplionc:e will be bmed on the prodicol qvonlifkoti

+ (/Cr10'i- + (8d +

C)H +-JoIlCO,•

+

a +8(/-3c

2

1-1 .,0

+

~·N H •;

+

2dCr J ..

12-65)

c wheret/ = - + - - - - 3 6 3 2 211

(I

b

Although it would be expected that the V'dlue of ttl(" ultimate carbonaceOliS BOD would be as high as the COD, thi~ i~ seldom the casco SO!Tlf of the reasons for the observed dill"ercnccs arc (IS follows: (I) many organic substances which arc diffic ul t to oxidize biOlogically, such as lignin. can be oxidized chemically, (2) inorplIlie s ubstances that ure oxidized by the dichronUlte increase the apparent org:mic content ::If the sample, (3) certain organic substances may be toxic to the microorganisms used in the BOD test, and (4) high COD \'alue.~ may occur because of the presence of inorganic suhstances with which the dichromate can reac t. From nn opcmlional standpoint, one of the m li n advantages of the COD tcst is that it can be completed in about 2.5 h, compared to 5 or more d for the BOD test. To reduce the time further, H mpid COD le~t that takes only about 15 min has been developed. As new methods of biologicallreatment hi!ve l)Cen developed, especia ll y with respec t to biologicul nutrient removal. it has become more important to fraction"te the COD. The principal fmctions are particulate lind soluble COD. In biOlogical treatment studies, the particulate and soluble fruc tions arc fmetionated further to assess wastewater treatability (see discussion in Chap. 8, See. 8-2), Frnctions that have been used include (a) readily biodegradllble soluble COD. (b) slowly biodegrada ) Ie colloidal and particulate (enmeshed) COD. (c) nonbiodcgradablc soluble COD. and (d) Ilonbiodegmdab le colloidal and particulate COD. The readily biodegradable soluble COD is often fmctionatcd further into complex COD that can fcrmcnt to volatile fatty acids (VFAs) and short chain VFAs (see Fig. 8-4 in Chap. 8). Unfortunately, as noted previously. there is lillie standardization on the definition o f sol uble versus particulate COD. Where filt rmion is the technique used to fractionate the sample, the rc:lutive di stribution betwcen soluble and particu lute COD will vary greatly depending on the pore sizc of thc filh:r. An al ternative method used to de termine the soluble COD involves precipitation o f th e suspended solids and u portion of the colloidal material. The COD of the clarified liquid corresponds to the soluble COD.

Total ond Dissolved Organic Ca,'b on (TOC and DTOC) The TOC test. done instrumentally, is used to determine the total organic carbon in an aqueous sample. The test methods for TOe utiliLl heat and oxygen, ultraviolet mdiation, chemical oxidants. or some combination of these mcthods to convert organic carbon to carbon dioxide which is measured with an infrared HNO, + H,o HNO! + In0 1 -+ HNO j

NH) + 20 2 -+ HNOJ Determine the ThOD.

+ H10

ThOD = (312 + 4/2) mole Olimole glycine = 7/2 mole 0 2/molc glycine X 32 g/inolc O 2 = 112 g Ol /mole glycine

Interrelationships between 800, COO, and TOC Typical values for the ratio of BOD/COD for untrcmcd municipal wastewater are in the range from 0.3 10 0.8 (see Tablc 2- 15). Lf the BOD/COD ratio for untrcnted wastewater is 0.5 or greater. thc waste is considered to be easily tn!lItablc by biological means. If the ratio is below about 0.3. either the waste may have .wmc toxic components or acclimated micro~ organisms may be required in its stabilization. T1C corresponding BOOfrQC ratio for untrc:Ilt..'d wastewater varie." from 1.2 to 2.0. In using these ratios it is imponant to remember

Table 2-15

Comparison of ratios of various parameters used to characterize wastewater

Type of walt.water

Untreated

BOD/COD

0.3-0.8

BOD!TOC

1.2-2.0

After primary senling

0.4-0.6

0.8-1.2

Finol effluent

0.1-0.3"

0.2-o.Sh

"CBOD/COO. bCBOD/TOC.

126

dKJpter 2 wostewoter Charocteris~cs

thutthey wi ll change signilicantly with the degree of Trcatment the was te has undergone, as reported in Table 2-1 5. The theoretical basis for these ratios is explored in Example 2- 11.

EXAMPLE 2-11

Solurion

Oetenninarion of BOD/COD, BOD/TOC, and TOC/COD ratios

Detclmine the theoretical BODICOD. BODrrOC. and Toc/BOD ratios for the compound C~H .,N 02' Assun1l:: the value of lhe BOD first-order reaction rale constant is 0.23/d (base e) (0. IOld base 10). I.

Determine the COD of the compound using Eq. (2-57). C I H ,NO ~

+

50 1 ~5CO l

mw C sH.,N02

::

+ NH J + 2H 10

113. mw 50 2

::

160

COD = 160/113 :: 1.42 mg Ojmg CsH.,N02

2.

Determine the BOD of the compound. BOD UBOD :: (I

~ l' ~.t ~)

= (I

~ e~o.2J)(S) =

I

~

0.32 = 0.68

1300 :: 0.68 X 1.42 mg O!mg CsH)NOl :: 0.97 mg BOD/mg CSH.,NO l

3.

Determine the TOe of the compound. TOC = (5

4.

x 12)/ 11 3 = 0.53 mg TOCJmg Cj H, NO z

Determine BOD/CO D. BODrroc. and TOCIBOD ratios. BOD :: 0.68 X 1.42 :: 0.68 COD 1.42 BOD 0.68 x 1.42 --= = 1.82 TOC 0.53

TOC

0.53

COD = 1.42 = 0.37

Respirometric Characterization of Aggregate Organic Constituents, Determination of the BOD value and the corresponding rate constant k j can be accompl ished more effective ly Ilsing a respirometer a... compared to usi ng the bottle technique as described above (Young and Baumann, 1976a. I 976b; Young, et al. . 2003). Respirometers are devices (hal are used to measure the rate of respira tion of living microorganisms in aerobic, (moxie, and anaerobic environments.

Description. Modem headspace-gas respirometers work by maintaining a constant oxygen pressure over a sample containing microorganisms Ihat are in the process of metabolizing an organic substra te by replacing the oxygen as it is consumed by the microorgani sms. Oxygen replacement is accompli shed by means of an electrolysis cell. a bubble-type now cell, or by transducer-controlled pneumatic injection. An example of a

2-6 Aggregate Organic Constiluenls

~

_____ __

~ ~ ~ ~

127

__ !hQQ.CI!.Cpg

C,,,"'" S&ero formation. Molds or Wtrue fungi " produce microscopic unlh (hyphae), which coIloctiveIy form a filomeolous mo!.S coiled the mycelium. Yeosb are fungi that cannot fo.m a mycelium and are therefore unicellukw-. Fungi hove the ability to grow under low-moisture, low nitrogen conditions and oon ioIeroto on environment with a relotivety low pH. Tho ability of the fungi to survive under low pH end nitrofJen-limiting conditions, coupled with their ability to degrodo cellulose, makes them very important in the compo5ling of sludge. Protozoa oro motile, microscopic eukoryoles that are usually single cells. The majority of protozoa oro aerobic heterotrophs, some are oerololeront anaerobes ond a lew are anaerobic. Prolozoo oro generally on order of magnitvde larger thcm baclctio ond often consume bacteria as on energy source. In effect, the protozoa oct as polishers of the effIucnb from biologitol woste Irootment processes by consuming bacteria and particulolo of90nk moitcf".

Helminths

Rotifers

Helminth is a gooernlterm used to describe worms collectively. Clouifiecl as invertebrates, helminths ore u~lty elongated, fIot, or round. The three stoge~ of helminth development oro oggs, larvol, odull. WoMwide, worms u-e one of the principal CCJU$Ofive agenb of humon disease. Rotifen. are aerobic hetorotrophic animal eukoryotes. The name is derived from

the fact that they hove two sels of rotating cilia an their hood whicn are used for motility and capturing food. Rotifen. are very effective in consuming di~ and Rocculoted Ixx:teria and 5m01l particles of organic molter. Their presence in an effiuent indicotes a highly efficient aerobic biologital purification pro:::css.

Algae

Algae ore unil;ellular or multicellular, outolrophk, photosynthetic eukoryoies or prokoryotos. They ore of importonce in biologicaltreotmenl processes. In wastewater treolmant logooni, the ability of algae h;o produce oxygen by photo~ynthesis is vitol to the ecology 01the water environment. Tho blue-green algae cyonobocterio is a prokaryotic organism.

Vi ruses

Viruses ore composed of 0 nucleic ocid core (either DNA or RNAI surrounded by on outer sholl of prolcin coiled a capsid. Viruses are infectious ogeob thaI only multiply within a host cell, where they redired the cell's biochemical system to reproduce themselves. Viru:;es con olw exist in on extracollular slolo in which the virus particle (known as a virani is meiobolicalty inert. Boderiaphoges oro viruses that infec::1bacteria as the host; they hove not been implicated in humon infections.

2-9 Biologicol Constituents

Table 2-22

Typical data on the

Mic

shope, size, and resistant forms of classes of microorganisms and

Baderio

nism

Shape !idify and the di~ incubated. Alter incubation, colonie$ formed on the ogar ore counted. Results are reported as colony forming units per milliliter (cfu/ml). In the spread plate me!hod, diluted KImple is spread on a surface culture dish containing a suitable culture medium.

Boderial counts

Sample is passed through 0 membrane Filter and the filter placed right side lip in contact with on agar Of oIher ~id media. After incubation, colonies formed on the surfoco of the filter oro counted.

Bacterial counts

Multiple-tube fermentation

Sample is diluted serioly and added to fermentotion tubes ond incubated. Pmilive hAles (cloudy) are counted. Based on the principle 01 dilution to extinction, a~ illustrated on Fig. 2-33, !foe most prohoble number per 100 mL (MPN/IOO ml) is computed using the Poisson distribution for eICtreme values.

Bocteriol counts

Enzyme wb5trate coliform lest

Enqme Ixned me!hcxb u~ 10 simufto~ delerminc IokII coIil'oon Ixdcrio cwxI E. coli. Boderiol e....zyrTlBs present in I0I01 coliform group hydrolyze on added subs/rale resulting in a color chonge (yellawl. E. coli decrve 0 Auorogeoic wb$trcole. resoling in the release of

Totol coliform bacterio ond E. coli

Pour and $f'rood plote method

Membrane

'i'ter technique

Hele,ahophic pIoie coont (HPC)

1Ioorogon, -"Kh """'~ ondo- """""'" I"". Pour plate, spread plate, or membrane filter method, os de5Cribed oboYe, can be used 10 determine HPC. CoIonie$ al bocteria, derived from pain, chains, duslers, ar single cells, ore measured. The results ore reported os colony forming unib per milliliter (CFU/ml).

Bocteriol counts

146

Chaplcr 2

I Table 2-23

Wastewotor Choroderistics

(Continued)

Descriptio"

Ty pical applicatio"

A single 100 mt 50mple is tested for- the P·A of coliform organ' isms using (] seledive media, The P·A Ie$t is used for hig11y treated somples such as efRuent from a ""'(Iter treatment pIont.

Presence of bocIerio

Agar overlay method

Sample is mixed with ogar and E. coli. Solution poured onto solid agar plale and incubated. If califphoge are present, the bacterial cells will lyse resulting in the presence of clear !pOh. cleo.- :IpOO, ca lled ploq~, ore reported as plaque forming uni\!. (e.g., pfu/ l00 ml).

Coliphage countsb

TIs~ue

Virus assays are performed in the labomtory by inoculating !.ample con:enlrule onlo monoIayen of OJltured cells (hence the name timte culture). Buffalo Green ,o\-\onkey Kidney {GBNlKI is most common cell line for- enleroviru$e$. Virus ~oy the infect· ed cells. The destroyed cells appear as a hole or plaque in the eel monoIc,-er. Eoch pIoque (plaque forming ~t or PRJ) is the resu~ of the presence of a ~ngle or a dump of viru5e5.

Virus counts

Respiration gases

M.oosurement of the rote of gas conSl.Hl1ption or production, i.e., oxygen COI"lwmplion, carOOn dia.>r.ide evolution, and methane evoIutioo.

Microbial odivily ond substrate conver~on

Microelectrodes

uha'~ne probes are inserted into a microbial sample followed by continuous measurement of various eell activi ties, including oxygen uptake and nilrote reduction.

Microbial octivily

lobeled constituents

Introduction of a rodiolobeled constilue!lts into a microbial sample, including (a) labeled substrate foI~ by measurement of labeled carbon within the cell, liquid, and evolved as carbon dioxide and Ib) labeled thymidine followed by the measurement of the rote of incorporation inlo DNA.

Microbial octivily and wlY.;lrale conveniorl

cell products

Methods include meawrement of (0) proteins expressed uoder variable conditions, (b) enzyme odivily through the production of Auorescent products generated by the hydroly'i' of Ruorescein diacetole, Ie) dehydrogenase octivily through the reductiorl of tctrazolium KIlt" and {d] metabolically active biomo" through the odonylote energy charge, or rotio of AlP 10 10101 odenylotes.

Microbial activily

Fluorescent immunolobeling

An antibody is togged with a Auorescent dye. Once togged, on ontibody becomes attoched to on antigen associated with o microorganism; the sample can then be exomined u~ng Auoresceoce microscopy. Fluor05Cein isothiocyonote (FrTe) is the most ccrnmonly used Auorescent dye.

Spotial distribution of antigen, detectioo of bacteria, virus, protazoa, helminths

Enzyme·linked immuno!oOrbent assay (ELISA)

An enzyme'antibody probe is added 10 0 sample containing on anrigcn. After ottochment, the sub~trate for ~le eozyme is added 10 the sample, resulting in a color change.

Quonti~calion

Test Culture methods (conti"ued) Presence·absence (p·AI te~

culture (09Or overlay method)

Physiological methods

Immunological methods

af biomass in biofilms, vorious ossays

(continued)

2-9 Biological Constiluoots

1 Table 2-23

147

(Continued)

Test

Description

Typical application

Cloning

The procen of cloning COI'I$;st$ of the inoortion of on isolated frogment of DNA of interest into a hosl cell, typically E. coli. The host cell, or clone, then generales iclenllcol replicates of the DNA frogment. The DNA frogmen~ are typically analyzed by seqvencing.

Replication 01 genetic material

Nucleic acid probes

A nvcleic acid probe is a molewle hoving a strong interaction with a known complementary genomic sequence unique ta the ta rgeted organism(s) and possessing a moons for detection. Typical methods include (a) Auores· cent in-situ hybridization (FISH), (bl detection of DNA or RNA on gels following electrophoresis, and Ic) screening geno expression using on array of gono probes known as microorrays.

Identification 01 specific microorgoni$llls, including spoIial distribution in Roo and biafilms

Pdymerose chain reaction (PCR)

AmpIi~cotion of the DNA of the genome of the microorgon-

Amplification of genetic mokltiol

Nucleic-acid methods

i~s

being tested by using complementary DNA fragmelll-$ known as primers 10 bind 10 target DNA of virus The primer triggers a reoction ~ich results in the prodvction 01 many millions 01 cop~ of the microorganism DNA. Examples include reverse transcription PeR IRT·PCRI, nested PCR, multiplex PCR, integrated cell cultvre PCR (lCC-PCR), and real-lime quantitative PCR IqPCR). Sequoncing

The coding of genelic mole rial can be delermined throlJgh the process of seqlJencing, which usually tokes place al commerciallaborolories. The DNA seqveflCe con then be compored 10 oolobofoOS 10 determine the relatioruhip of the genetic material to other orgoni$llls !hot have hod their DNA sequenced. The 16S rRNA region of the sequence hos been found 10 be the mas! useful for determining the identity of isolated microorganisms.

Restriction frogment lenglh polymorphism (RFLP)

A method !hat

U!oeS

enzymes to cut purified DNA

or

PCR

proclum into small fragments at specific sogments of the

Identification of i!dated microorgani!>lTls

Microbial community fingerprint

genome. The frogments are then analyzed by gel or capillary electrophore~i~ to obtoin a microbial community fingerpri nt.

Gel gradient electrophoresi~

A method that subjects PCR fragments to on increasing concentration of denoturcnt (DGGE) Q( temperclure (TGGE) 10 a llow for visuolizotion 01 diversity in the genetic material resulting from differential melting Q( denaturing of the PCR frogments.

Microbial community diversity

Metogenomic$

The analysis of the collective genetic materiol recovered

Microbial commonity divefsity ond meloboli~

from an environment $Omple.

"Adopted from Ingraham and Ingraham 119951, Madigan et 01. (20091, Maier er al. (2009I,and Stonier et a!. 119861. b A bacteriophage is a virus thot infects and replicates within bacteria. A calipllage is a type of bacteriophage that infects E. coli.

148

Chapter 2

Wa~tewoter Choroderistics

Figure 2-29 Schemo~c 01 plate cullure method~ u:!ed lor the enumeration

of bocterio : (oj pour plate on d (b) 5preod plote.

Add iquid

Place sample 01 bacterial dilLJIioo In emply petri dish

nutrient agar

Mix bacIoriai semple and agar by swi1ing

Bacleriet ooIonies

grow in and 00 solklifled (Irowth

",

medium

,

Bacterial

-

dilution

-

Place sample of

...,...

~ •• : .

o·

Bacterial colonies

glOW on sur1&elths and slJC(:ilk enzyme substfules that serve as the sole carbon source are added 10 various Wi.Lstewater samples. When melabolized by total col iform and £ coli. the specific enzyme subSlr;lIes produce a ycllow color and or fl uoresce. After incubation. samples cootainillg colifonll org.. ni sm.~ tum yellow, and sample..'> containing E. mli will fluoresce when exposed to long.wave UV illuminmion [see Fig. 2-33(a)1. The enzymatic test can be used in twu differem modes: presence/absence and quantification. [n the pre...enceJabsence mode the chcmicu[ ingredients are added to 100 tilL bottles containing the sample to be :maIYI..ed. The quantification mode can be carried out using Ihe multiple-tube method 01" speciali7.ed appamlus ~uch as the Colilen -[&/Quanti-Tmy method [see Fig. 2-33(b)]. The re.'>ull,> are reponed as present or absent in a [00 mL sample and as MP N/ IOOmL in Ihe quantification test. Heterotrophic Plate Count. The heterotrophic plate count (lIPC) is a procedure for estimating the number of live heterotrophic bacteria in wastewater samples. The 1'11'(: method

8o~ l es

_

Waler

~m"

Walar sample adOOd 10 100 mL samplel reagant boIlle

,oj

\

........

ind icates IOtal coliform absent

"""" '0

100 mL botti

7

100.0

1.0

2.25

Sp.O~

YClrieg Ferrous bi c"rbona!e (Sol uble)

Fe(OH )l

+

16-131

CO,

~rrou s

Cmoon

hytlrmide (Very sllgh!ly soluble)

(Soluble)

d io~ ide

If sullicient al ka li nity is nOI available. lime is often added in exces.~ in conj unc tion with ferrous sulfate. The reaction of ferrous sulfnte with li me i ~ as fo llows 2 x 56 115 CaO

178

Fe(HCO)2

+

2Ca(OH)1

Fe1Tous

Calciu m

bicmbonme

hydro~ idc

(soluble)

(Slightl y soluble)

2 x tOO

89.9

+='

Fe(OH)l Ferrou... hydmlitle {Very ~l igh!ly soluble)

+

2CaCOJ

2 x 18

+

2H2O

(6-14)

Calcium cn bOllale (Some .... h.at :>oluble )

The fe rro us hyd roxide can be oxidi"..cd to fe rric hyd roxide, the final fo rm desired, by oxygen dissolved in the Wltste wate r. The reaction is 89.9

Fc(O H)l Ferrous hydwlide (Very slightly soluble)

In x IS

l f4 X 32

+

1140 l

+ W I-IP

Oxygen (Solub l~ )

+='

,"'-, Fe{O H)l Ferric

16-151

hydrtu.iride (Soluble)

+

6CO z

16-16}

Carbon dioxide (Soluble)

Ferric Chloride and Lime.

[f lime is added to supplement the na tural a lkal inity of the wastewater, the followi ng reaction can be assumed to occur:

2 x 162.2 2 FeCIJ Ferric chlQride (Soluble)

) x 56 (as c aO) 3Ca(OH)1 ;:!

+

C~lcium

hydroxide 99 percent of the o rglmic constitue nts (as mcas ured by a TOC mass balance) are mineral ized (Stefan and Bolton. 1998; Steran et al.. 2(00) .

6- 9 PHOTOLYSIS Pho to l),sis is a process by which const ituents are broken down by ex posure imd absorption of photons from a light SOUTce. As wit h AOPs. the primary usc of photolysis is for the removal of Irace organic compounds in wa ter reuse applicmions. In natural systems, sunlight is the ligh t source for pho tol ysis reactions. however, in engineered systems, ultraviolet (U V) lamps are used to produce the photonic energy. The photons that are absorbed c ause the electrons in the outer orbital of some compounds to become unstable and split o r become reactive. The e ffect iveness of the photo lysis process depends, in part, on the characteristics of the reclaimed wa ter. structure of the compounds, design of the photolysis reactor. and dose and wavelength of the applied light. TIU! photo lysis rate can be estimated from the mte Ht which thc compound absorbs ligh t and the photonic e fficiency of the reaction (q uantum yield).

Applications for Photolysis Pho tol ysis mny be used for the removal of various compounds, such as NDMA (see Chap. 1) and other tr.lce o rganic conslituents. It s hould be noted Ihnt man y compounds are not removed using photolysis alone, and that the addition of hydrogen peroxide can

S:Z:Z

Cheple( A.) = ba~e 10 e xtinction coellicient or molar absorptivity of light absorbing solute at wavelength A. Umole·cm A = wavelength, nm C "" concentration of light absorbing solute. molclL or = length or light path. cm k( A) "" absorptivity (base 10), Ife m The exti nction coeffi cient is a fu nction of wavelength because as tnc wavelength decreases more energetic photons are absorbed and the abso rptivity of a light absorbing compound inc reases. Val ues o r the extinction coefficie nts for several compounds at various wa\'clengths are given in Table 6-18. The usc o r Eq. (6- 6 1) is presented in Example 6-7.

Table 6-18

Selected quanfum yields and extinction coefficients for compounds commonly found in water.

Com

unci

Primary qumm.m yield in aqueous phase, mole/e instein

Extinction coefficient at

253.7 nm, _ _ _...;;; L1.;,; mole.c:m 3.8

NO, HCXI !ot 330 nml

0 .23

OCJ

0.23

HOCI

15 190 53.4

OCI

0.52

155

0,

0 .5

3300

0.44

J08

CI0

2

Sodium chlorite

0.72

TCE

0 .54

9

PC,

0.29

205

NOMA

0.3

Water ~ .tomptOO

1974 0.OCOOO61

from Crillenden et 01. [20 12).

524

Chapter 6 Chemical Unit Prooosses

526

Chapter 6 Ch&micol Unil

Pr{A) = quan tum yield of the constituc nt at wavelength A, mole/einstcin e '(A) = the extinc tion coefficie nt of the constituent (ba.'>C e), Umole ·cm C; = the concentratio n of the constituent, molelL k' (A) = measured absorptivity of the watcr matrix at wavelength (base e) A, lIem k = pseudo-first orde r rate coeffic icnt, l Is After o bta ining the nlle law, r""J' an appropriAte reacto r model may be used for determination of the ex pected performance.

Electrical Efficiency. The electrical energy req uire ment for photolytic reac tions is sig nifican t due to the process ine fficie ncies. Consequently. il is important to compare process e ffic iency on the b.as is of e lectrical usage per amount o f compound d estruction. One such meas ure is the e lectrical e fficiency per log orde r (EfJO) of compound destructio n (Bolton an d ClIter, 1994). The definition of EEiO is the electric al e nergy (i n kWh ) required to reduce the concentrution o f a constitue nt by one order of mag nitude for 3785 L (1000 U.S. gallo ns) of water. p,

EE/ O =

---'~(;-;c~.)'(fOr batc h systems)

(-671

Vlog -

C,

EE/ O

=-

(c.)

p

.

(for contmuous flow systems)

Qlog

(-681

C f

where EFJO "" e lectrical efficiency per log order reduction . kWh/m] p :0 lamp power out p ut, k W t = irradiation ti me. h V = reactor volume . m l C1 = initilll concentl"atiotl, mglL C, = fina l concentrJ.l ion. mglL Q = water flowm te. mJIh For a fl ow th rough system, the power input can be d ivided by the EIYO to obtain an estimate of the flow ratc that can be treated in a given reac tion a nd achieve o ne order o f magnitude reduc tion in cuncentnttion. Conseque ntl y. EEIO is a conven ient measure because it can be used to esti mate the ene rgy that is required (0 redu ce the contaminant concentmtio n by one o rder o f magn itude. Because o f the variabi lity in wa"tewater c haracteristics. the fe 8.5

Heavy sca le wi ll form Scale will fo rm No difficu lties Water is aggressive Water is very aggressive

6 - 10 ; as the reactor substrate coneentmt ion increases for a givcn biomass concentration.

,,.

~

kXS K, + S

---

(7-121

S90

Chopler 7 Funoon16'l1ols of BioIogiCllI TrllCllment

where ' •• "" su bstrate utilization rate per uni t of reactor volume, g!mJ'd k "" maxim um specific substrate utiliZdary

System boundary

I')

V

Sludge 0". Xli' S

(0)

Figure 7-12 Schematic diog ram of activated sludge process with model nomenclalure: 10) with wosting from the Iludge return line and (b) with wasting from the aeration tonic

598

Chapter 7

Fundamentals of Biological Treatment

operating and design parameter for activated sludge processes (Lawrence and McCany, 1970). The SRT is t.he average time the activated sludge solids are in the system. Assuming that the solids inventory in the clarifier shown on Fig. 7- 12(a) is negligible compared to that in the aeration tank. the SRT is detenn ined by dividing the mass of solids in the aeration tank by the solids removed daily via the effiuent and by wasting for process control. For many activated sludge processes, where good flocculation occurs and the clarifier is designed properly, the effluent VSS is typically less than 15 glmJ • Where the effluent VSS is low, excess solids must be removed from the system by wasting. Wasting is accomplished most commonly hy remov ing biomass (sludge) from the clarifier underflow recycle line a,> shown on Fig. 7- 12(a). Alternatively, wa'>ting can be accomplished from the aeration tank as shown on Fig. 7- 12(b). The average SRT for the process flow diagram shown on Fig. 7-12(a) is given as SRT =

vx

17-311

(Q

where SRT = solids retention time, d V = reactor volume (i.e., aem/ion tank), m3 Q = influcnt Ilowrate, mJ/d X = concentration of biomass in the aeration tank, g VSS/m 3 Q.. = waste sludge Ilowmte, mJ/d X, = concentration of biomass in the eflluent, g VSS/mJ XII = concentration of biomass in the return ac tivated sludge line from the clarificr, g VSS/m3 Based on Eq. (7-3 1), the SRT can be controlled by the wasting rate. Increasing the value for Q.. in Eq. (7-31) resulL'\ in a lower SRT. Sim ilarly, it can be shown that by wasting from the aeration Lank. the SRT can be controlled by wasting a given percentage of the aeration tank volume each day. The inverse of the SRT is the sol ids wasted per day divided by the solids present.

(Q - Q.)X, SRT

+ Q.x,

VX

17- 32)

At steady state operation, where the influent tlowrate and substrate concentration is constant, the reactor biomass concentration is constant, and the net biomass growth mte per day is equal 10 the sol ids wasting nile, [Ihe numerator in Eq. (7- 32)]. If the product of r" the net biomass growth rate per unit volume (glm3 ·d) [see Eq (7- 21)] and the volume, V, is substituted for the numerator in Eq. (7-32), it can be shown thulthc invcrse of the SRT is the net specific biomass growth ratc. _ , _ _ Vrx _ f!( _ SRT - VX - X - 14.ct

17-33)

Thus, based on Eq. (7- 33), controlling the SRT by sl udge wasting afTects the net specific biomass growth rate, and the reactor s ubstrate concentration. For a CMAS system the reactor etllucnt dissolved substrate concentration is equal to the reactor concentration.

Biomass Moss Balance A mass balance for the mass of microorganisms in the complete-mix reactor shown on Fig. 7-12(a) can be written as follows:

7--6 Modeling

Su~pended

Growth Treatment

Processe~

599

J. General word statement: Ratc of accu mulation of microorganism withinlhe systcm

rale of flow of microorganism into the systcm

TalC of flow of microorganism out of the systcm

boundary

boundary

boundary

+

net growth of microorganism within the

(7-34)

boundary

2. Simplified word statement:

Accumulntion = intlow - outflow

+ net growth

[7-35[

+ "V

[7- 36)

3. Symbolic represcntation;

an electron acceptor in addition to nitrate in the anoxic zone for oxidation of imracellular PHA. However, nitrite concentrations greater than 2.0 glml are inhibitory to phosphate uptake under both anoxic and aerobic conditions. with a greater effect unde r aerobic conditions. At 6.0 Wm3, aerobic uptake of phosphate by PAOs is severely limiled (Sailo et al.. 20(4).

7- 14 ANAEROBIC FERMENTATION AND OXIDATION Anaerobic fermentation and oxidation processes are uscd primarily for the treatment of waste sludge (see Fig. 7-26) and high-strength organic wastcs. In warm climutcs, anaerobic fermentation has been used as a pretreatment step for conventional biological treatment. Applications for dilute waste slream~ have also been demo nstr.ttcd. A major

Figure 7-26 Views of onOefobic digeslers: (0) An~ora, Tur~ey, ond (b) Ti gord, OR.

656

Chap/ef- 7 Fundomentol, of Biobgicol Treolmenl

advantage of anaerobic fe rme ntalion and oxidation processes are lower b i oma~s yields and e nergy production in the form of methane from the biological convcrsion of organ ic substrates. Altho ugh most fermentation processes are operated in thc mcsophilic te mperature mnge (30 10 35 ~C), there is increased interest in thermophilic fe rme ntat ion alollc or before mesophi lic fermcntation for municipal sludge processing. The latte r is te rmed temperature phased anaerobic digestion (TPAD) and is typically designed with a sludge SRT of 3 to 7 d in the first thermophilic phase at 50 10 6O"C and 7 to 15 d in the fi nal mesophilic phase ( Han and Dague, 1997). Thermophilic anaerobic digestion Jlrocesses, considered in Chap. 13, arc used to accomplish high pathogen kill 10 produce Cluss A biosolids(defined in ChHp. 14) that can be used in the Uni ted Sllltes for unrestric ted reuse appl ications. Anaerobic treatment for high-strength industrial wastewaters h a.~ been s how n to provide a very cost-effective altcrnati\'e to acrobic processes with savings in enel-gy. nutrient addition, and reactor volumc. Because the emuent quality is not as good all that obtained wi th aerobic treatme nt, anaerobic treatment is com monly used as a pretreat me nt step prior to discharge to a municipal collcctio n system or is followed by an ae robic process. Suspended and nttac hed growth a naerobic tre:llmeOl process designs for liq uid streams are presented in Chap. 10, .md unaerobic digester designs for sludge treatment arc presented in Chap. 13.

Process Description Three basic steps are involved in the overall anaerobic oxidation of a waSle: ( I) hydrolysis. (2) acidogencsis (also known as fermentation or anaerobic oxidation), and (3) methanogenesi s. The three sleps a re illustrated schematically on Fig. 7- 27, which shows the fate of solids through hydrolysis, vola tile fatty acids (VFAs) and hydrogen production to methane. An intermediate step, termed acetogcnesis, occurs for some of the VFAs produced from acidogenesis. The stani ng point on the schematic for a pan icular applicat io n depends on the na tu re of the wasle to be processed. Sometimes the procell~ ;s intentionally stopped midway such as when primary solids are fennented ;n gravity thickeners, and the supernatant, which is ric h in VFAs, is used for EBPR.

Figure 7- 27

ICompoaite wasle IM.teMi I

I

biodegradable COD in onoerabic processing o f w051c soIid~. (Aoopled from jerr;1 and McCorty, 1963, 1981, and Boistone eI 01., 2006.1 FOle of

" Acetic acid (72%)

" M&In-(IOO"1'o)

'"

F.mnenlation (AcIOOgenesis)

7-14 Anaerobic Fermentation and Oxidation

657

Hydrolysis. The first basic step, in which particu late malerial is converted to soluble compounds that can then be hydrolyzed further to simple monomers that are used by bacteria that perform fermentation, is termed hydrolysis. For some high strength soluble industrial wastewaters, fermentation may be the first step in the anaerobic process. Hydrolysis is carried out with extracellular enzymes produced by a variety of facultative and obligate anaerobes (Confer and Logan, 1998; Song et aI., 2005). Lipids are broken down to long chain fatty acids (LCFAs) by lipases produced by bacteria that include ButyriJlibrio sp., Clostridium sp., and AnaeroJlibrio IipolYlica. Peptide and amino acid are due to bacteria exhibiting extracellular protease activity including C/ostridiwlI proICO/Ylicum, £u/XicICriulI1 sp., and Peplococcus {//werohicus (Mcinerney, 1988). Acidogenesis. The second basic step, which is done by bacteria, is at·idogellesis (al so termed fermentation) and results in the production of VFAs, CO 2, and hydrogen as shown on Fig. 7- 27. In the ferme ntation process. substrates serve as both the electron donors and acceptors. The principal fermentation products from the sugars and amino acids are (lcetate, propionate, butyrate, CO2 , and hydrogen. Fermentation of the LCFAs results in the production of acetate, CO 2 , and hydrogen. A larger fraction of the LCFA COD is converted 10 hydrogen than that for the sugars and amino acids.

Ac:etogenesis.

Acetogene,~i~ refers to further fermentation by bacteria to convert intermediate products of acidogenesis (propionate and butyrate) to also produce acetate, CO 2, and hydrogen. Thus, the final products of fermentation are acetate, hydrogen , and CO•. which are the precursors of methane formation. The free energy change associ:lted with the conversion of propionate and bUlyrate to acetate and hydrogen requires thaI hydrogen be at low concentrations in the system (Hz < 10-· atm), or the reaction will no! proceed (McCarty and Smith, 1986). Most of the hydrogen produced comes from the oxidation of LCFAs and intermediate VFAs to acetic acid and is referred to as anaerobic oxidation.

Methanogenesis. The third basil: step. melfulIlugcllcsis, is (;arrieu out by a group of Archaea organisms known wlb:tively as methanogens. Two groups of mt:lhallogenic organisms are involved in methane production. One group, It'Tmed (lcelic/aslic metlulIIogens, split acetate into methane and carbon dioxide. The second group, termed hydrogenutilizing methanogens or hydrogellolrophic merhanogl1lls, use hydrogen as the electron donor and COl as the electron acceptor to produce methane. Bacteria within anaerobic processes, termed acefOgel1s, are also able to use CO 2 to oxidiLC hydrogen and form acetic acid. However. the acetic acid will be wnverted to methane, so the impact of this reaction is minor. As shown on Fig. 7-27, about 72 percent of the methane produced in anaerobic digestion is from acelate format ion. The composition of the gils produced from a stable fermentat ion and methanogenesis operation typically contllins about 65 percent methane and 35 percent CO 2. A higher lipid fraction in the waste resu lts in a higher methane fraction in thc digester gas (Li et aL 2002).

Microbiology The group of nonrnethanogcnic microorganisms responsible for hydrolysis and fermenta tion consists of a divcrsc group of facultative and obligate anaerobic bacteria. Organisms isolated from anacrobic digesters include Clostridium spp., Peplococcus mwerobus, Bifidobaclerium spp., DeSlllplwvibrio spp., CorynebacteriulII spp., Ulclob(lcillus, Actinomyces, Staphylococcus, and £scherit'hiu coli. Other physiological groups presenl include those producing proteolytic, lipolytic, ureolytic, or cellulytic enzymes.

658

Chapter 7

Fundomenlob 01 BiolO9ie r:ltions to determine acceptable transient londi ng rates that can be used without causing an unstable d igester cond it ion as shown in [he follow ing example. Dctail s on the BMP test procedure can be found in Conklin e\ al. (2008). An application o f the ACN concept to evaluate an acce ptable tran· sient loadi ng in an anae rob ic reac tor is illustraled in Example 7-1 1.

662

Chopter 7 f..,ndamentols of Riologicol TrooImcnt

EXAMPLE 7-11

Estimating tne Acceptable Transient Load for Codigestion Given the following anaerobic sludge digestion operming information and results from a OMP test for a high strength food waste to be added 10 the digester for codigestiol1, determine what volume of food waste cau be added as a tmnsient Icxtd without causing digeste r instability. Parameter

Unil

Value

Digester averoge feed rote

ml/d

1000

d

Dige51er SRT

g/m l

85,OC:O

Dige51et' average CH. production role

mJ/d

16,OC:O

RMP overage ocetote V.... 01 $landord condition$

g/m

2. I.

800,000

3

%

Codigest biodegrodability fraction I.

0.5

mlCHJml·d

CodiQe$t COD concentration

Solution

20

Dige!Jer average feed COO

90

Portion of methane produced from acetate utilization for anaerobic digester and codigest waste = 70 percent Gas production at ~ t anda rd conditions = 0.35 m 1 CHJkg COD Determine the digester ACN. D ige.~ter average acetate COD utilizatio n rate, VpI"

a.

VpI' = kg acetate COD use(VmJ,d

Acetate COD used per day = 0.70( 16J)(Xlm J fdC H.)( b.

Di ge~ t er

273 )[ 0 3C I 0 273+ 3 5 ( .3501 Hi kgC D)

1= 2S,363 kgCODfd

volume = Q(7),7 = SRT = 20 d

Volume = (1000 ml /d)(20 d) "" 20,000 ml

Vpi'

""

(28,363 kg COD/d)/(20,OOO 01 3 ) = 1041 kg at:ctate CO D/m~· d

c. BMP tcst digestt:r sludge acetate uti lization rate, V..... ' g COD/LA

V"",, = (

0.65m' CH,) [ m1 ' d

1 (0.35m'CHi kgCOD)

1=

1.86 kg acetate COD/m 3 ·d

d. ACN = V.....IVpI:: 1.86/1.41 :: 1.32

Thus. the digeste r Illclh:mogen s hn\'e capacity for 32% more acetate. 2.

Dctemline the codigest volume that t:a n be added. a. Additional acetate COD loading :: 0.32(28.363 kg CODfd) = 11 ,954 kg acetate COD/d

b. Acetate COD available in codigest feed = (800.000 g COD/mlXO.90 g degradJg CODXO.70 g acetate COD/g COD) = 504,000 g acetate CO D/mJ

7-15

Biological Removd of Toxic rocess:' Re.'- 1. WPCf: 63.3. 208---219. Stephens, H. L.. and H. D. Stcnscl (1998) "Effect o fOpcnll;n g Conditions on Biological Phosphorus RCl11ovul:' Witlf'" Em',nm, He.I·. J.. 68, 3. 362-369. Strand. S. E .. G. N. Harem. und I!. D_ Sccnsel (1999) "Activatcu Sluuge Yield Reuuction Using Che mi cu l Uncouplers." nhter &,,·i('{)ll. Res.. 71 .4. 454-458. Str:tub. A. J . A. S . Q. Con!.:lin. J. F. Ferguson. and H. D. Stcnsel (2006) "Usc ofthcADMI to Investig~tc the Efrect~ of Acetoch~tic Methanogeni c PopulCS:' Mierobiol., 150. 11.3741- 3748. Yang. Q., X. Lill. C. Pengo S. Wan g, H. Sun. and Y. Pe ng (2009) "N 20 Production d urin g Nitroge1l Removal via Nitrite from Domestic Wa.~tcw"ter Ma in Source.~ flod Coo trol Method ," Em·ircm. Sci. Techul)f .. 43.24.9400-9406. M

696

Chapter 7 Fundomenlol, 01 Biological Treotment

Yu. R.. M. J. Kampschrcllr. M. C. M. van Loosdrccht. and K. Chandr.m (2010) "Moch:mis ms and Specific Directionality of AlU otrophi c Nitrous O;o;.ide and Nitric O;o;.ide Gcnenuion du ri ng Transient Ano;o;.ia:· Environ. Sd. Techno/., 44. 4. 1313-1 3 19. Zan. D.. and E. Bock ( 1998) " Hi gh Kale of Aerobic Nitri ficat ioo and Denitrification by NilfYI.WlT/(J l1US eli/fOp/ill Grown in a Fcrmemor with Complete Biomass Rctclltiun in the Presence of Gaseous N02 or NO." Mdl. Mkrubiol .. 1(i9, 4. 282- 286. Zhang T.. L. Yeo A. H. Y. Tong. M. F. Shao. and S. Lok (2011 ) "Ammonia-Oxidizing Arch aea and Ammonia-Oxidizing Bacte ria in Six Full-Scale Wastewater Treaunent Bioreactors:' App1M icrobiol, 8iolech""l. 9 1. 4 , 1215--1225. Zhang. T., Y. Lill. aud H. H. P. Fling (2005) "Efrect of pH Chan ge on the Performaoce and M icrobial Co mmunity of Enhanced Biological Phosphate Remuval Process." Bi(){e dmol. 8ioellg .. 92. 2.173- 182, Zinder. S. B .. and M. Koch ( 1984) "Non-Acttic1astic Mcthanogenesis from Acelnte: Acetate Oxidation by a Thermophilic Syntropic Coculture," Archiwll Microbio.. 138,3.263-272.

Suspended Growth Biological Treatment Processes 8-\

INTRODUCnON TO THE ACTIVATED SLUDGE PROCESS

7()()

His/orical Development of Activated Sludge Process 701 Basic Process Description 701 Evolution of the Conventional Activated Sludge Process Nutrient Removal Processes 706 8-2

WASTEWATER CHARACTERIZAnON 707 Key Wastewater Constituents for Process Design

702

707

Measuremen t Methods for Wastewater Characterization 712

Recycle Flows ond Loadings 7' 6 8-3

FUNDAMENTALS OF PROCESS SELECTION, DESIGN, AND CONTROL

Overall Considerations in Treatment Process Implementalion Important Factors in Process Selection and Design 717

7 17

7 17

Process Control 726 Operational Problems in Activated Sludge Systems with Secondary Clarifiers Operational Problems with MBR Systems 738 8-4

SELECTOR TYPES AND DESIGN CONSIDERATION

732

738

Selector Types and Design Considerations 739

Poor Settling Even With Use of Selector 741 8-5

ACTIVATED SLUDGE PROCESS DESIGN CONSIDERATIONS

742

Steody-State Design Approach 7 4 2 Use of Simulation Model 744 Model Matrix Format, Components, and Reactions 747 Other Simulation Model Applications 751 8~

PROCESSES FOR BOD REMOVAL AND NITRIFICAnON

Overview of BOD Removal and Nitrification Pro.:esses

752 752

General Process Design Considerations 754 Complefe-Mix Activated Sludge Process Design 754 Sequencing Balch Reactor Process Design 771

Staged Activated Sludge Process Design 782 Alternative Processes for BOD Removal and Nitrification 786 8-7

PROCESSES FOR BiOlOGICAL NITROGEN REMOVAL 795

Process Development 796 Overview of Types of Biological Nifrogen-Removol Processes

General Process Design Considerations

797

802

Preanoxic Denitrification Processes 804 Postanoxic Denitrification Processes 831 low DO and Cyclic Nitrification/Denitrification Processes 833 Allernotive Process Configurations for Biological Nitrogen Removal

838 697

698

Choplef 8 Su~ Growtl. BioIogkol Treatment Processes

Denitrification with External Carbon Addition Process Control and Performance 860

848

8-8

PROCESSES FOR ENHANCED BIOLOGICAL PHOSPHORUS REMOVAL 861 Process Development 861 Overview of Enhanced Biological Phosphorus Removal Processes 862 General Process Design Considerations 864 Operationa! Factors That Affect Enhanced Biological Phosphorus Removal 878 Enhanced Biological Phosphorus Removal Process Design 880 Provision for Chemical Addition 883 Process Control and Performance Optimization 884

8-9

AERATION TANK DESIGN FOR AG IVATED SLUDGE PROCESSES 885 Aeration System 885 Acra/ion Tonks and Appurtenances 886

8-10

ANALYSIS OF lIOUID-SOLIDS SEPARATION FOR AGIVATED SLUDGE PROCESSES WITH CLARIFI ERS 8B9 Solids Separation by Secondary Clorifiers 889 Assessing Sludge Thickening Characteristics 891 Clarifier Design Based on Solids Flux Analysis 893 Clarifier Design Based on State Point Analysis 900

8-11

DESIGN CONSIDERATIONS FOR SECONDARY CLARIFIERS 906 Types of Sedimen tation Tonk 906 Sidewaler Depth 9 I 0 Flow Distribution 9 J 0 Tank Inlet Design 9 I 0 Weir Placement and Loading 912 Scum Removal and Management 9' 2

8-12

SOUDS SEPARATION FOR MEMBRANE BIOREAGORS 913 Design Parameter 9 ' 3 Membrane Properties 9' 4 Membrane Design and Operating Characteristics 917 Membrane Uwge 9' 7 Membrane Fouling Issues 9' 7 PROBLEMS AND DISCUSSION

TO~CS

919

REFERENCES 934

WORKING TERMINOLOGY Term

Definition

Activated sludge process

Biological treatment process thai involves the convorsion of organic ma tter ond/or other constit· uents in the wastewater to gases end cell tissue by a large mess of aerobic microorganisms mointoined in suspension by mixing and aera tion, The microorganisms form flocculent particles that are separated from the process effluen t in a sedimentation tonk Iclorifier) and are returned subsequently to the oerotion process Of wosted.

Chapter 8

Su>pended Growth BioIogkal Treotment Proc&SSes

699

Term

Definition

Aerobic !oxic) processes

Biological treatment processes thol occur in the prl!!>ence alfree dissolved oxygen; oxygen is consumoo by aerobic microorganisms in oxida~on/ledlJCtion reactions to produce energy for cell growth and cell maintenance.

Al'"lClerobic processes

8iologicaltreolment processes that occur in the absence

Ano~ic proces~

Biological treatmen t process that occurs in the absence of free dissolved oxygen where ni trate and nitrite ore used a s the main electron acceptors in b iological oxidation/reduction reactions; denitrilicalian is on e~ample of on anoxic process .

Biomou

The tatol mass of solids in a reactor consisting mainly of organic:: matter and microorganisms.

Biological nutrient removal IBNR)

The term applied to the removal of nitrogen and p~phorus in biologicol treorment processes.

Denitrification

The biological process by which nitrote or nitrite producls.

En hanced biological pho~. phorus removal !EBPR)

Removal of phosphorus by extraordinary storage in bacteria selected in anaerobic/aerobic process configuration and subsequen t solids sepora tKHI.

Hindered !>ettling

Settling which occurs when the oclivated sludge floes interfere with each other as they settle .

Facultative proces.ses

BioJogicaltreotment processes in which the organi5ms can function in the presence Of absence of molecular oxygen.

Ferrnefltotiofl

The conversion of organic motter to volotile latty acids in the absence of oxygen, nitrote, and nitrite.

Membra ne biQrlXlctor (MBR)

A process that combines a suspended growth proce!>5 wi th a membrone !>eparofi oo system within the process oeration tonk; membrone separation is accomplished by either microfiltrotion or ultra fi ltration

Membrane Aux

The rate of Row across a membrane per unit of surface areo, l/m1 ·h.

Mixed liquor suspended solids (MlSS)

The biomass contained in a treatment reoclor used to bring about treOlment of the organic material in wastewater.

Nitrificotiofl

The two-step biological process by which ni troge n Imostly in the form of ammonia) is converted to nitrite and then 10 nitrote.

NocardioForm foam

A thick layer 01 brown. biological/com caused by a filomenlou5 bacteria thotlorms on the top of oeration tanks and secondary clo rifie.-s.

Nonbiodegradable volatile suspended solids (nbVSS)

The$9 are suspended solids contained in inRuent wostewoler to activated sludge processes that are organic but not biodeg radable. They impact sludge production.

Phosphorus accumulating organisms (PAOs)

HeterotrophiC bocteria selected in EBPR processes tha t have the a bility for high introcellulor phosphorus storage.

Reodily biodegradable

Dissolved biodegradable Ofganic substrates which are removed by bac teria mlJCh foste!" thon colloidal or porlic::ulote degradoble COD. The rbeOD impacts spotia l oxygen domond, EBPR remova l efficiency, and denitrification rotes

COD (rbeOD) Sequencing batch reactor

ISSRI

IS

01 oxygen.

reduced ta ni trogen and other go5l!Ous end

An S8R is a bak:h fill a nd draw activated sludge treatment process. It involves a treotment sequence of fill, react, settling. supernatant d ecanti ng, ond idle. Activated sludge aeration ond liquid solids sepa ra tion occurs in the some tonk.

Simulation models

Mathemoticol models, based on 0 set of equations. used to assess the effects of kinetics and changes in the wastewoter choracte!"izes on process periormaoce.

Simultaneous nitrification and denitrification {SNdN)

Nitrogen removal occurs in !.Ome activated sludge Roc Of in a biolilm due to nitrification in aerobic outer loyer and denitrification in interior due to the lock of dissolved oxygen and presence of nitrate or nitrite.

700

Chapter 8 Suspended ~owth Biologicol holment ProceM.es

Term

Definition

Sludge production

The omount of solids pwduced during lhe biological procusing of wastewater including inRuent nonbiodegradable ~I ids ond the biomass resulting from the conversion of organic.

Sludge yield

The amount of $OIids produced relative to the amount of BOO or coo removed during the biological proce~in9 of wastewater.

Solids Aux analysis

A method used to determine the oreo required for hindered $(IlIling based solids Imoss) flux.

Solids retention time (SRT]

The ovoroge period 01 time in which solids remain in a suspended growth procBu(also coiled sludge oge) .

00

on analysis of the

Slogoo process

Processes which occur with more thon one independent reoc:lof or comportment in series.

Surface overRow role

The hydraulic flawrate applied relative to the clarifier surface oreo (m J /m 2 ·d).

Suspended growth processes

Biological Trea tment processes in which microorganisms responsible for the conversion of organic matter or other constituents in the wastewater to gases and cell tissue are maintained in suspension within the liquid.

Volumetric Ofganic loading role

The amount 01 BOD or COO applied 10 the aeration Ionk volume per day le.g., kg BOD or COD/mJ,d).

The theory of biological wnstewater trent ment is presen ted and discussed in detail in Chap. 7. Biological treaTment proccsscf';. as nOled in Chap. 7. may be dil~~ ifi ed as aerobic and anaerobic suspended g rowth, allached growth. and various combinations thereof. The focus of this chapter is on suspended growt h trea tment processes as exemplified by the activated sludge proce..~s for BOD and nitrificati on and for nitrogen nnd phosphorus removal. Attache(1 growth and cOfnbincd processes are di scus..o.ed in C hap_ 9. and sus pended a nd attac hed growt h anaerobic processes are considered in Chap. 10. Incl uded in th is chapter are (I) introduction to the nctiv:lIcd sludge process. (2) wastewater characleri zmion, (3) fund:l mentals of process !>election, desig n. and control. (4) selector types and design considerations, (5) usc of simulation models fo r activated sl udge process design cons iderations, (6) proces..~~ for BOD rc mov31 and ni tri fication, (7) processes for biologica l ni trogen removal. (8) processes for enhanced biological phosphorus removal. (9) aeration lank design for activatcd sludge proce."se.". (10) analysis of liquid scramtion for acti vated sludge proce...scs with clari fi ers, (I I) design considerations for secondarily Clarifierll, and (12) solids . 18,000 mglL) exist under operation at normal design flux values, the membranes can become what is termed "sludged up" and special cleaning methods may be needed to regain the expected operating flux. Certain wastewater substances must be prevented from entering the treatment facility or MBR system to maintain proper membrane operation. Cooking oils and grease can collect on membrane surfaces and lead to excessive foul ing that can only be removed by special membf'dne cleaning methods.

8-4 SELECTOR TYPES AND DESIGN CONSIDERATION A selector is a small tank (30 to 60 min contact time) or a series of tanks located before the process aeration tank in which the incoming wastewater is mixed with return sludge under aerobic, anoxic, or anaerobic conditions. The purpose of including a selector as part of the activated sludge process is 10 create a cond ition that favors the growth of floc-forming bacteria and suppress the growth of fi lamentous bacteria that cause sludge bulking as described in the previous sectiun. The use of selector designs in activated sludge is, as noted previously, more common because of the many other advantages, such as nitrogen and phosphorus removal, in addition to improved sludge settling. By improving sludge settling, the activated sludge treatment capacity may be increased, as higher MLSS concentrations are usually possible. The hydraul ic capacity of the secondary clarifiers is also increased. The cause of sludge bulking and the types and desig n cons iderations for the selectors used fo r the control of filamentous bacteria are described in this section.

8- A Selector Type> or.::! Design Ccmiderction

739

Selector Types and Design Considerations The concept of a selector involves the llse of a specific bioreactor design that favors the growth of floc-forming bacteria instead of filamentous bacteria to provide an activated sl udge with better sett ling and thickeni ng properties. Various types of anaerobic, aerobic and anoxic selectors are shown on Figs. 8-15(a), 8- 15(b), and 8- 15(c), respectively. Mlxa!"

m,. luent

Ai,

-'" t::> .J..

Second",), clarifier

+

Elliu

;------

I,

------- ---- ----

Anaerobic sciec10r

Ae,ation tank Return activated sludge Sludge

I')

,m_,

Prima,),

'"

",

"

~

Seconda')' da ~ie

, ,

+

Aerated high F/M selecto,

"

~

--------- ---- --

'f-= 'f-= 'f-=

r-t.

;-- "' Ellioo

Aeration tank

Return activated sludge Sludge

(b) Mixers Primary elll\JBl1!

Ai,

'" r:- '" p '" p L-

L-

I-

L-

-

-+ -------- ------ -

clarifiar

l

Elllu

'"'

Aeration tank

Anoxic selector Return activated slu (0)

""""","

r

,

Sludge

(d)

Figure 8-15 Typical selector configurations: la) anaerobic/aerobic, (b) high F1M, (el anoxic selector, (d) view 01 plug.now 'eodo' (token Irom en d 01 aeration tonk) with anoxic selectors. The pipe in t\,e bollom righl is used 10 relurn mixed liquor suspended solid! 10 anoxic selector! o. shown in (e) above and (e) axial· flow pump 01 end 01 aeration Ihon used 10 used to pump t\,e return mixed liquor 10 the anoxic selector •.

740

Chopler 8

Suspended

Growtn 8iological Treatment f'roce~l

O.' ,---~-~--~--,

Figure 8-16 IIiU$/rolion 01 kinetic base !declOr model with higher specific growth rote lor filomentous bacteri o 01 low sub$trote conce ntrotionl.

Nonlilamentous tomlS'O-_-1

1:

0.3

] o

0.2

f

il

Filamenlo us forms

0.1

'"

20

""

The selector reactor precedcs the activated sludge ae ration ta nk and may be de~igned as separaTe reactio n stage for a complete-mi x reactor or as individual compartments in a plug-flow system. Sequencing batch reac tors may also be operated 10 e mploy the selector concept. The goa l in the selector is to have most of the inllucnt rbeOD consumed by the floc -forming bacteria, instead of the fil a mento us bacteria. Se lector designs, as described below. are based o n eit her kine tic or metabolic mechanis ms (Albertson, 1987; Jenkins et al .. 2(04; and Wanner, 1994). The ldnetics-based selecto r designs are called high FIM ,fefec/ors. and the metabolic-based selectors are either anoxic or anaerobic processes.

11

Kinetics-Based Selector.

Se lector designs based on a biokinetic model provide for reactor substrate concentr:ations that result in fa ster substrate uptake by the floc-forming bacteria. While fi l amentou~ bacteria arc more eflicient for substrate ulill7..1110n at low subst rate concenlT25"C), the initial stages of a multi-staged nitrificlltion system. and low dissolved oxygen concentration. Matrix Model Format. A long li st of complex equations would be needed to desaibc the various rcuctions in an activated sludge process involving numerous components such as org:m ic substrntes (soluble and particulate), inorganic substrates (ammonia. nitrate. and

746

Chapler 8 Suspended Growth Biological Treatment ProcesMlS

I

Table 8-11

Key process components in ASM2d and types of reactions affecting their reactor concentration Reactions or input Model component

Dissolvad O~

""'00

Symbol

"" S,

Acetate

5.

Ammonia

s....

Production or input

Depletion

• • • •

• Consumption by ~, Xo\\Il' x.....o

InAuent wastewoter Aeration

Biod.grodotion by Fermentation by ~

InAventwwr • Fermentation of 51

• • • •

• InAuent wastewoter

•

Oxida~on

InAvenl wastewater Hydrolysis of Xs

• •

Hydrolysis of organic N • Hydrolysis of cell decoy products

Nilrote

s,."

Phosphorus

s.c.

• O...iOOtion of s..... by X""" • InAuent wostewolef" • Hydrolysis of orgonia

Alkalinity

5~

• •

InAvenl wostewolef" During biological reduction

x..

Uptake by x....o BiodcgrocioTion by ~

by autotrophic bacteria

(X,t,IJT)

•

Synthesis uptake by

•

Synthesis

x.., X,t,IJT, ~

• Synthesis upklke by x... x...n, ~ • Ano...ic and oerobic uptoke by x....o • During Sr.u. oxidation by x..n

ofs,." Biodegradable particulate

X,

COO Slowly biodegradable COD

X,

Ordil'lOry heterOlroplu

x..

Phosphorus occumubting heteralrophs

x..,

Stored PHA

• • • •

InAuenl wostewoter Cell decay InAvenl wostewoter Cell decay

• Hydrolysis by x..

• Growth from Sf, S" • Grow1h from using x.....

• Cell decay • Cell decoy

x..

• Production in olloerobic :tone by x.., from 5.

• Biodegroclotion by x.....o in aerobic

Stored polyphosphote

J(,

•

During oxidation of X".,.,

• Release in onaerobic conditions by

Ammonia oxidi:ting bacteria

X~

•

Growth during

St.t. oxidation

and ooollic :tones

x..,

• Cell decoy

phosphorus), dissolved oxygen, and various heterotrophic and autotrophic bacteria. Instead of presenting the model in terms of nume rous equations. a more general matrix model approach has been :Idopted. Process reactions and the stoichiometric factors that link the components to the various reactions nre presented in a matrix model formnt. Thc advantage of the matrill format i~ that a relati vely si mple. concise format can be used to describe the proeess . The purpose of this section is to provide a basic introduction to the matrix model approach showing the components, reactions. and stoichiometric coefficients for the acti vated sludge process model and how the mutrix formut can be uscd to describe the process. In addition, the approach can also be used to illustrate how the matrix

S-S Activoted $lodge Process ~ign Considerations

747

model can be intcrprdedto describe a complete sct of equations for a given process component. For example, the Activated Sludge Modd No.2 (ASM2d) ( Uenzc et al.. 1995) is used to describe basic feature~ of a comprehensive activated sludge model.

Model Matrix Format, Components, and Reactions A convenient matrix format is used to describe the model without having to present the largc number of equations involved. The ASM2d model includes 19 components and accounts for 2 1 process reac tions. Somc of the component and reaction terms nrc desc ribed here to illustrate the basic model formal.

Process Reactions and Stoichiometric Coefficients. Fourteen key com]JOnents related to the biological processes are described in Table 8- 11. An example of some of the process reactions and the corresponding stoichiometric rate cocfficient..~ are given in Tables 8-12 and &-13, respectively. The stoichio metric coefficients are used to relate

Table 8-12

I Example of process rate equations selected from ASM2d iProc:e55

i'

Proce55 rate equations, rl

Hydrolysis Proce sses Aerobic Hydrolysis

2

Anoxic Hydrolysi~

He terotrophic Organisms,

x..

:SJ(K, ;'Zx};."lx"

4

Aerobic Growt!, on SF

"~Ko,:- ~)(K' : ,J (s. : 5,) IGrowth~xx,,)

S

Aerobic Growth on SA

6

Anoxic Growth on S,

"~Ko, :- ~)(K. ': s.)(S. ': sJ (Growth...XX~ f1H(T)NO>{K~ K : ~)(~,~~)(Kf; SJ(SA ; S}GrowthtCr floc particles, us ua lly the result of ha ving biological selectors in the activated sludge desig n, result in bener settl ing and Ihickening and a more effi cie nt cI:lrifier performance. ~urface overflow rate (SOR), defined as follows, is related 10 the time needed to allow parlicle separation from the eflluent liquid flow.

Surface Overflow Rate. The SOR = Q

(8-80)

A

where SOR = surface overflow rate , mJJm~ 'd Q = influenl tlowrate. Ill J/d A = clarifier surface area. m 2 Overflow nlles are based on wastewater flowmtcs instead o f on the mixed-liquor flowrates to the clarifier, which includes the inllUCll t and re(;yde sludge t1owrates, because the overt1ow mte is equivalent to an upward flow velocity. The return sludge flow is drawn off the bottom of the led. The sludge is discharged to a collection trough that runs the length of the tan\;;.

Other Types for Clarifi ers. Othe r types of settl ing tanks that are used include stacked clarifiers. and tube and plate seHlers (see Chap. 5). Stac ked clari fi ers (see Fig. 5-45 in Chap. 5) arc used in installations where limited land area is availabl e for clarifiers. Stacked clarifiers arc used at the Deer Island Wastew ater Trea tment Plant in Boston, MA, for seconda ry sedimentation a nd were selected because of limited land area. Clarifi

cation Tank Impro vemen ts. nle eClicien cy of conventional or shallow clarifier s may be improved by the installat ion of tubes or parallel plates to establis h laminar flow (sec Fig. 5-25 in Chap. 5). Constructed of bundles of tubes or plntes set at sclected angles (usually 6(0) from the horizontal. tube and plate seltlers have a ve ry short settling distance and circulnt ion is da mpened because of the s mall size of the tubes. Solids that collect in the wbes or on the platcs lend to slide o ut due to gravitat io nal forces. The major dr.lw back in wastewater treatme nt is a tendenc y of the lU bes and plates to clog because of the accumulation of biol ogical growth. grease. and small objects that pass through coarse screens. Anot her drawba ck that ca n occur is if the c haracte ris tics of the MLSS c hange, the fixed angle of the plates or lUbes may no longer be optimal.

8- 11

Figure 8-51

Flow ports

IbI troveling

~

-

eo.l$iderolion~

for Secondory Clarifiers

"

0

""'-

0

n

"'. ~

,.,.

0 I

11

,. ~~ ...,. g

Travel

-

O~ U

"

~ ,",=

:b

E1evlltioo

Traveling

-

Sludgo

travel

Wateriovej

SkimmlllQ

Skimming position

,

~!.

",'

EMluent

weir

l1Effluenl

=~ r,;~.=-=ooO="'="':::::PO=';=""'=========::y'r I

//'

i ~ Scr(lw

:::::Y (0)

Collecting

PI(JII/s by Microscopic Invl'.fligation. IWA Publishing. London. Ekumll, C. A .. P. L Dold. and G.v.R. Marais ( 1986) "Prucclhlres for Determining 111nuent COD Fnlctions and the Maximum Specific Growth Rmc of J Ictcrotrophs in Activated Sludge Systems:' Willer Sci. Tee/wol.. H~ . 6. 91 - 114. Eknmn. G. A.. I. P. Srebritz. and G.v. R. Marais (1983) "Considcrlllions in the Process Design of Nutrien t Removal Activated Sludge Processes ." Wate. Sci. 'fechnol. 15.3-4. 2R3-318. fi lius. J.. O. Katchis, K. Ramalingml1. LA. Carrio. and K. Gopalakrishan (2000) "Determination of Nitrifier Growth Rates in New Yuri;. City Water Pollution Control Plants," f'roceedillgs of/hI' IVEF 7]01 ACE. Anaheim. CA. Fi llos. J" K. RlIm alingam. R. Jezek, A, Deur. and K. Bcckmann (2007) "Specific Dcnitrificntion Rates with Alternate External Sources Of Organic Cmbon." ProL'eedings ()Jllu~ 10111 International CfJllfert'lIce OIl Envirolll/l('llta/ ScienCf' (wei Teel"1O/0K)'. Kos Island. Greece. Gall D. L.. H. L. Gough. R.H. Bucht:r. J.E Fergusun. and H. D. Stensel (2008) "Anaerobic Co..Digcs tion of Municipal Sludge and Biodiesel Fuel Production By- Products." Proceedings oJtht IV£F 81-" ACE. October. 22. 2008. Chicago.1L. Giraldo. E.. P. Jjemba. Y. Liu. and S. Muthukristman (201Ia) "Presence and Significnnceof Anammox species lind Ammonia OxidiZing Arch:ten. AOA. in Full Scale Membmne l3iorcac(Ors for Total Nitrogen Removnl." PrrJ(;eeding.\· ()fl/!/! IWA (!lui WE'" NII/riml ReL'uvery Ulill Mwwgemem Ccm/erellfC. Miami. FL. Giraldo, E... P. Jjemba. Y. Liu. and S. Muthukrishnan (201 Ib) "Ammonia Oxidi ting Archaea. AOA. Population and Kinctic Changes in II Full Si.'alc Si multan.c:ous Ni trogen and Phosphorous Removal MBR:' Proceedings oflVEF 84'" ACE. Los Angeles. CA. Grady. C. P. L., Jr.. G. T. Daigger, :md H.C. Lim ( 1999) Biological Wa.\lI'watl'r Treamuml. 2d cd .. Marcel Dekker. Inc .. New York. Grady, C. P. L. Jr., W. Gujer, G.v. R. Marois. nnd T. Matsuo (1986) "A Model for Single·Sludge Wnstewllter Treatment Systems," Watu Sci. Teclmul.. 18. 6, 47-f, 1. Gu. A'z. llnd A. Onnis.Hayden (2010) I'rolocol to EI'a/iulle A/1I'f/1mil'l' Exlc"W/ CUI'bon SOIIIl:es for De,ti/I'ijicmiOll a/ FIIII·St'tlle WaSl/!waleT Trelllmc/1/ Plan/s. NUTRI R06b. Water Environment Research Foundation. Alexandria. VA. Guerrero. J.. C. Taya. A. Guisasola. and l .A. Baeza (2{J 12) "Glycerol as a Sole Carbon Source for Enhanced Biological Phosphorus Removal," n~ler Res" 46. 9. 2983-2991. Gujer. W.. M . Henlt:. T. MillO. lind M.C.M. van Loo,trecht (1999) "Activated Sludge :'v1odeJ No.3." Wall!r Sci. Tt'chuol.. 3!( 1. 183- 193. Gulglielmi. G.. D. Chi.mlni. S.J . Judd. and G. Andreollola (2007) "Flux Criticality lind SUSlllin:lbility in ~ Hollow Fiber Submerged Membrane Bioreactor for Municipal Wastewater Treatment." J. M I'/Ilhr. Sci .. 289. 1-2.241 -248. Gilnder. B.• and K. Krauth ( 19(9). " Replacement of Secondary Clarification by Membrane Sepamtion-Result.s with Tubular. Plate nnll Hollow Fiber Modules." n~ler Sci. Ttchnol .. 40 . 4- 5.31 1-3 18. Heidmun. J. A.. F. D. Bishop. und J.B. Stamberg (1975) "Carbon. Nitrogen. and Phosphorus Removal in Staged Nitrificatioll·Dcnitrificlltion Activ;lted Sludge Treatment." AIChE Symp()jillm Scrie~. 145. 71-lI:t Henze. M.. C. P. L. Gmdy.lr.. W. Gujer. G. \'. R. Marai.~ . ;llId T. Matsuo (1987) "A General Model for Sillgle Sludge Wastewater Treatment Systems." lVatu Res. ( G .B.). 21. 5. 505-515. Hcnze, M. (1991 ) "Capabilitie~ of Biological Nitrogen Removal Processes from Wastewater." w.-,ter Sci. T/'Cfmnf.. 23.4-6. 669-679. Henze. M .. W. GujeT. T Mino. T. M:lIsuo. M. C. Wen tzel. ;lnd G.v.R. MarJis (1995) Ac/il'Qled Sllidge Model No.2 .. IAWQ Scientific and Technical Report No. 3. IAWQ. London.

R~

931

Henze, M., W. Gl.ljer, T. Mino, and M. C. M. v:m Loosdrecht (2{)()()) Acril"(lfed Sludge Modell' ASM I , ASM2, ASM2d, (I/ul ASMJ. IAWQ Scientific and Technkal Repon . IAWQ. 1WA Publishing. London. I [cnzc. M., M. C. M. van Loosdrecht, G. A. Ebma. and D. Brdjanovic (2008) Bi%gic,,' Wf,slclI"alcr TrcatmCIII: Pr,"lIdple. Mmlclillg. and Desigll, IWA Publishing, London. Hong, S. N .. Y. D. Peng, and R. D. Holbrook (1997) "Enhancing Deni triti e:u ion in the Secondary Anoxic Zone by RAS Addit io n: A Full Scale Evaluation," Proceeilings oflhe WEF 70" ACE, 4[ [-417. 1cnkins. D .. M. G. Ri charos, and G. T. Daigger (2004) MalUlllil)1l Iht CmlJts ami COII/roi of Acth'(l/c(1 Sludge nu/killg, Foaming. and Olhe,. So/ids SepllnlliOIl Problems. 3rd ed.. Lewis Publishers, Ann Arbor, M[. Johannessen, E.. R. W. Samswg. and H. D. Sten(/!'Iling and f)e.~igll. Editt.-d by M. Henle, M. C. M . l..oosdrechl. G. A. Ekam3, and D. BrdjarKwic. IWA Publi ~hing. London. Kang, S. J.. (1987) Handbook, Relro/illing ponvsfor P/wsphorus Hemoml ill the Che:mpeClke B~y DraillQKt &15,"11. EPA 62.5/6-87-017. U.S. Enyironmental Protection Agency, Cincinnati, OH. Ke, 0 .. and L. Jun~in (2(X)9) .. Effcct of Sludge Retention Ti me on Sludge Characteristics and Membnurc Fouling of Mcmbw ne Biorcaetor," J. E,win",. Sci .. 21 , 10. 1329 - 1335. Keinath, T. M. (1985) "Opemtional D}'namic~ and Control of Secondury Clarifiers," J. WPC"'~ 57, 7,770-776. Keinath. T. M., M. D. Ryckman, C. H. Dana, and D. A. Hofe r(1 977) "Activated Sludge-Unilied System Design ;lIId Oper"'Jtion:' J. E1Ivinm. ElIg. - ASC£, 103 . .5.829-849. Koch. F. A .. alld W. K. Oldham (1985) "Oxidation-Reduction Pote ntiu! - A Too l for Monitoring, Control and Optimi7"lIion of Biological Nutrient Remov:lI Systems." Warer Sci. n ,,·hlloi.. 17, 11/12,259- 281. Koros, W. J .. Y. H. Ma. and T. Shimidzu (1996) "Terminology for Membrnnes and Membrnnc Processes." J. Membr. Sci .. 120.2.149-1.59. Krampe. J.. and K. Krauth (2003). "Oxygen Tmnsfer into Aetiy~ted Sl udge with High MLSS Cun!;cntnttions," W,ut"rSd. Tedmol.. 47, 11,297- 303. Kruit , J.. J. Il ulshcek, and A. Visscr (2002) "Sulking Sl udge Solved"?!". Wnl Proc,mos

Figure 9-7 Typicol lriclding fiher underdroi n~: (0) lChemolic of uOOerdroin for rock tricking filter, (b) view of concroto beom underd m in ~y$lem For rock filter, (e) view of vilriFied cloy block unde of vclocity heads D = packing depth, III L = liquid loading !'ed Growth Processes

981

_ (BOD)-O."

R" - 0.82 TK N = 0.82 (6.4)

0.41

= 0.36 glm 2 ·d

5.

Dctcrmine the hyd raulic loading ratc. volume Fi lter area = - d h ept

6400 mJ

=

6.lm

= [049 m2

Hydraulic loading ratc, q Q (8000 ml/d)(IOl LI[ m )(dl!440 min)(minJ60s) ' q "" - = = 009Um 2 ·s A 1049m" .

6.

To meet the minimum hydraulic loading rate given previously as 0.5 Um 2 ·s, recirculation wi ll be required. Estimate the effluent NH4-N concentration using Eq. (9-23). NH 4-N o = 20.81(BOD L)lfi3(NH.-NJu2(Iv) 0.J6(T) - OI2

(8000 ml/d)( 160 g/m') BODL =

576,000

,

= 2.22 g/m-·d

rn 2

NH.j-NL = (0.32 g/m 2 ·d)/0.9 = 0.36 glm2 'd (from step 3) Iv =

(8000 m 1Id)( I ()3 Lli mJ )

NH ~- N,

6000

57,

m

1

,

=

13.9 Lhw·d

= 20.81(2.22) 1·°l(O.36)1 .52(13.9)-o·J6(20) - O.ll =

1.2 mg/ L

.. . (100)[(25 - 1.2) mg/LJ PercelllllltnficatlOn = = 95 .2% (25 mg/L)

Comments

The computed value for the volume required based on the BOD volumeuic loading rate is higher than that predicted by the volumetric oxidation mte (Daigger et al. (1994). For the wastewater BODIN ratio. the specific nitrification rate is close to that predicted based on the BODtrKN mtio using Eq. (9- 22) and the percent nitrification is close to that predicted by Eq. (9-23).

Tertiary Nitrification. A number of facilities exist where trickling filters with plastic packing are used for nitrification after secondary treatment. Advantages for tertiary nitrification include (I) low energy consumption, (2) simplicity of opcmtion, and (3) stable performance. For tertiary nittification applications, very little BOD is applied to the trickling filter and a thin biofilm develops on the packing that consists of a high proportion of nitrifying bacteria. Elllucnt NH4-N conccntmtions will vary with summer and winter operation and can range from < [.0 rnglL at warm temperatures and from < I to 4 mgfL at cold temperatures. Hydr'Julic loading mtes may mnge from 0.40 to 1.0 Um 2·s and recycle is commonly used to maintain packing sUlface weuing. Some tertiary nittiticalion systems have been consU1Icted without downstream liquid-solids separation because of the [ow net biomass yield by the nittifying Ilacteria. This depends on site specific wastewater chamctetistics and treated ettluent goals.

982

Chapter 9

Attoched Growth and Combined Biological Treatment Processes

Design and Operation, In the design and operation of tertiary nitrifyi ng trickling filters it is important to consider (I) the media type and surface area density, (2) mechanical ventilation, (3) hydraulic loading rdtes and recycle, (4) minimizing slug ammonia loads, and (5) control of predatory micro fauna. It is genemlly well accepted that in the upper ponion of the trickling fi lter the nitril'ication rate is limited by oxygen availability and diffusion inlo the biofilm. To mitigate the oxygen limitation, forced draft air is generall y used to a~sure max.imum oxygen availability. Higher hydraulic ...tes including recirculation that provide better wetting efficiency and agitation of the biofillll ~u rface generally produce better petformance. Distributor speed control to provide a dosing rate in the range 25 to 75 nun/pass and flushing intensity 2:300 mm/pa~s is rtxommended (WEF, 20 11). Because plugging is less of an issue, a medium density packing material is preferred (i.e., specific surface area of 138 m1/m1) to provide more area as a fU llction or the pen;ent of the reactor volume. Equalization of high ammonia concentralion flows from solids processing is reco mmended to minimize sl ug loads and diurnal load fl uctuations to obtai n a low and consistent effluent ammonia concentration. Snail growth [see Figs. 9- IO(a) and (b)] in nitrifying trickling filters has occurred and can result in a serious loss of the nitrifying bacteria population and treatment efficiency. Predation control methocls are discussed after the process design methodology. Nitrification Rate. The rate of nitrification in a trickling fil ter varies with packing media depth and is related 10 bulk liquid oxygen and ammo nia-N concentrations and hydraul ic appl ication mte. In the upper portion of a nilrification tower, the amlllonia-N concenlration may be high enough ~o that the nitrification rale is oxygen limited, and thus zero order with respect to the ammonia-N concentnltion. Further down in the packi ng. as the ammonia-N concentmtion decreases. lhe nilfificalion rdle is limited by the ammonia-N concentration and th u~ decreai>es. The decline in nitrification rate is funher affected by less growth of nitrifying bacteria due to the low amoutll of ammonia-N available. The use of nitrification trickling filters in series with operational modifications has been shown to compensate for this limitation (Boller and Gujer. 1986). The order of operation of the towers is reversed every few days so that a higher nitrifying bacteria JXlPulation can be developed and be available where the ammonia-N concentration is low. Anderson et al. (1994) showed a 20 percent improvement in nitrification efficiency with this method. The nilTification removal efficiency has been related to the packing surface area and correlated with the nitrogen removal rate per unit of surface area (g N/m 2 'd) (Okey and Albertson, 1989; Parker el aI., 1990; WEF, 2011). Boller and Gujer (1986) developed an empirical equation that relates the ammonia-N removal flux from the bulk liquid as a function of the bulk liquid ammonia-N concentration. The ammonia-N removal flux is equal to the nitrification rate per unit area in the biofilm.

iNCl.) = i N·mo.. (K : N

N)

(9- 24)

where iJ,.1.) = N~-N removal flu x, glml'd iN,,,,,,, = maximum ammoni a-N removal flux at temperature T, glm2 'd N = bulk liquid ammonia-N concentration, g/m3 KN = half-velocity ammonia-N coefficient, glm 3 The value of lNmv. has been detennined by observations on zero-order nitrification rates tertiary trickling liller operations where the ammonia-N concentration is significantly greater than KN • As noted above. approximate zero-order nitrification rates may occur in the upper portion of the trickling !iller tower until the ammonia-N concentration decreaCuling. Much of Ihe informat ion presented on the l FAS process with suspended media in Sec. 9-4 is appli· cable 10 the MBBR process. including the chamctcristicsof the biofilm carrier mooia. mooia rete ntion, aer... tion and mixing. and substrate nux into the biofilm. The topics 16°C, respectively (Stensel et al., 1988). Thus, the volumet ric BOD Io.'lding selected should be at the lower mllge of tht:: values shown in Table 9- 18 for wastewater with a higher soluble BOD frm:t ion . BAF processes have Occll operated at low BOD loadings to achieve BOD removal and nitrification. As was discussed in Sec. ~ and 9-5 for trickling fi lters and MBBR pro-cesses, nitrification in a SAF process does not occur until most of the soluble BOD is first re moved so that sulface area is available for nitrifying bacteria. TIle net effect on the process design is that a much lower ovemll volumetric BOD loading is used for combined BOD removal and nitrification SAF processes as shown in Table 9- 17. The DO concentration for nitrification applications should be at least 3 to 4 mg/L to obtain reasonable nitrificlltion I1I tes as the process is often DO limited. Maintaining elevated DO conccntration is difficult

Table 9-17

Process volumetric loadings for biological aerated

Process application

Loading unib

Range

Removal efficiency, %

BOO removol

3.5-5.5

~85

1.8-2.5

~ 85

filters

Tertiary nitrificotion

kg BOD/m1·d kg BOO/mJ·d kg NH~·N/ml ·d

1.0-1.5

~90

Ci

BOD removol one! nilri~aJtion

o Mendozo oAd Stephen..on (1999), WEF 11998), Tchobooogioui et 01. (2003), WEF (2011).

9-6 Submef"ged Aerobic Attached Growth Processes

Table 9-18

Oxygen transfer efficiencies expressed in percent/m of

depth observed for biologicol oerated filters

1033

Test system

O2 transfer

depth, m

efficiency, %/m

DF, sunken

1.6

3.4-S.S

Fu!!-sca!e

Stensel et al. (1988)

DF, sunken

2.0

S.0--8.S

Full-sca)e

WER (2011)

UF, sunken

3.6

1.6-S.8

Lab-scale

Stenstrom et 01. (2008) laurence et 01. (2003)

8AF Design

Test system

Reference

UF, sunken

4.0

5.0

Full-sco)e

UF, floating

3.6

3.6-8.0

lob·scole

Stenstrom et 01. (2008)

UF, floating

3.0

6.7

FuU·scale

laurence et 01. (2003)

in combined BOD removal and nitrification processes due to thc high volumetric oxygen demand for BOD rcmo\'al. An alternative 10 a combined BOD removal lind nitrifil:ulion process is to use two BAF units in series with the first uni t designed at a BOD loading 10 meel a secondary emuenl BOD concentration of less than 15 mgIL and the second stage unit designed for nitrification. With two unit", design and opemting conditions for nitrification are more optimal, with cach unit operating at different DO concentrations, hydraulic application rates, and backwash frequency. Based on nitrification studies, 85 to 90 percent nitrogcn oxidation was found at loadings of 1.5 to 1.8 kg N/mJ·d for tertiary nitrification applications (Payraudeau et aI., 2000). A range of ammonia-N loadings used for tertiary nitrification is shown in Table 9- 17. The volumetric nitrification mte was found to increllse by about 3 percent for each degree centigrade temperature increase from 10°C for all type.og.as

Degas oMm . .

.,f=~:::~

tnftuen~

-;

Soids sep!lrallon

Retum 8Meroble

WaSle

$llIdgo!

iSluctge

Ig) Anaerobic ~Iter IANF)

'"""

Effluent

Media

Recyde

(h) Anoerobic hyb.-id process IANHYB) Entuent

1069

Mod. \

Biogas

Recycle

small size (0. 10 10 0.30 mm) i!'lerl partides of ~ne sand, boKllt, pumice, or plastic. The partides are kepi i!'l r.uspension and mixed by a high upward velocity. The higher velocities leeds to what is called a Auidized bed with 25 10 300 percent bed expansion and the expanded Ruidized bed refers to operation at lower velocity with 15 to 25 percent bed expansion. The$(! reodor, are applicable for soluble wastes or easily degrodod smoll fXlrticulales, such as .....ney. Upflow voIocities may be in the range 01 10 to 20 mlh and COD ioodil'l95 of 20 to 40 ksJmlod hove been 1.1-=1.

A completely mixed reocIor system employing r.uspended anaerobic biomass, a mixing/Rocculolor degassing chamber, liquid-solids separation, and solids recycle so that the SRT is longer than the hydraulic retention time. Designed for a COO loading of in the range of 2 to 5 kg!mJ-d.

An anaerobic fillef (ANF) s~tem is on unmixed reodor s)'$lem employing fixed film anaerobic biomass attoched to supporting media, so tho! a large anaerobic biomass and long SRT con be maintained 10 allow treatment at hydraulic retMtioo times in the range of 1 to 3 d and designed for a COD loading af 510 20 kg/m J·d. It is available in upHow (ANFUI a!'ld down~ ow (ANFD) configuralio!'ls,

A combination of sland-alone anaerobic te.::hnologie$ employing a combination of on upflow anaerobic sludge blanket reactor and anaerobic filler to provide a high biomass concentration and high volumetric orgonic removal rote$ in the lower por. tion and further removal of volatile fotty acids and capture of suspended solids in the upper anaerobic filter portion.

. _ Sludge

-'---l:''=''=''='J """

tn!l~~"c'

Anaerobic ~",

Ii) Anoefobic membraoe process IANMBR)

A mixed reoclol" s~1em employing suspeoded/Roccvlaling onoerobic biomass and a synthetic membrane solids-liquid separation with solids recycle 10 provide a Ions SRI with the short hydraulic retention time. Designed for a COO looding 01 5 Ia 15 kg/mJ·d.

Inftuent MGmbrane

separation urN! Anaerobi(: bioreactor

Retutn soiids

(concentrate)

tcontinued)

Chapter 10 Anoerobic Suspended ond AItoched Growth 8io1ogical Treotrnent Processes

1070

Process

Desc:ription

Ii) Anoerobic baffled reoctor (ABR)

Baffles ora used to direct the Row of wastewater in on upflow mode through a series of upRow onoerobic sludge blonket reactors. The sludge in the reoctor rises and foils with gas production and flaw, but moves through the reactor a t a slow rate. Reactor volatile solids cor"ICenlro~ons vary from 2 to 10 percent. Systems hove been operated with T volues in the range of 6 to 24 hand SRTs in exCe!>S of 30 d. Designed for a COD Iooding of 5 to 10 kg/m1·d. The main limitotions with the ABR process On;! that many Welies hove been limited do laborolo of mechanicol mixing in stage and on opero~ng opprooch 10 moinloin the sludge in the system without resorting to pocking Of" settlers for additional solids coplvre. When 0 signi~cont quantity of solids accvmulotes in the last stage, the inRuent feed point is changed to the effluent sioo, wf1ich helps ta maintain a more uniform sludge blanket. Organic b:Jding roles from 1.0 to 3.0 kg COD/m 3·d with hydraulic retention times ranging from 4 to 12 h arc possible.

A mixed suspooded growth onoerobic process with reaction and soIids·liquid seporation in the loOme VMSeI, much like !hat for aerobic sequencing botch reactors (SMs) I!.OO Chop. 8). The operotion of SBRs CQfl$isi) of four ~: (I ) feed, 121 rcoct, (3) settle, and (4) decont/efllucnt withdrowol. Tho $CHIing velocity of the sludge during the !oeIIIe period before decan~ng the effluent is c;ri~ool. Settling times used ore about 30 min. After sufficient operating ~me, a dense granuloted sludge develops that improves the liquid·soIids separation. At "T volues from 6 to 24 h, the SRT moy range from 50 to 200 d, respectivef)'. At 25°C, 92 to 98 per· cent COD removal wa, achieved a t volumetric Ofgonic loadings of 1.2 to 2.4 kg COD/mJ·d. AI 5°C, COD removal ranged from 85 to 75 percent for COD load· ings from 0.910 2.4 kg/m 3·d, respectively. A completely mixed reocIor $)'$Iem !rooting semi· solids wastes with suspended a1OeI"Obic biomass. The reodor detention time equals the SRT, wnich trIO)' range from 15 to 30 d, with rewired COD kxxling~ typically \e$$ than 4 kg/m 3 ·d.

Effluent

Inftuent

Anaerobic

reactor

In) Plug !low anaerobic system IANPF)

~erD[¥L

InMuent

Anaerobic oeactor

Geoerolly on unmixed reclongular reodor s)'$lem treating semi·soIids waste with high (10 10 18 percent) Iolal solid, concentration. In ~ co~s the rectongulor reactor i~ slightly inclined. Recycle of effluent solids may be done to seed the inRu· enl feed . The feed retention time equols Ihe SRI, wnich may range from 20 to 30 d with COD loadings gcoerolly less than 4 kg/m J-d.

Effluent

Adopted from Nicole/Ie eI 01. (20001, ToItke (2012), Touseef et 01. (2013).

10-3 Avoilable Anaerobic Technologies

1071

strength wastew:ltcrs (Kato et aL, 1999). Sim ilarly, the internal recycle (Ie) reaClOr [see Table I0-3(d) I is essentially two UASB reactors in series with internal recycle and it has also been successful for the treatment of low and vcry high strength wastewaters. The principal advantages in the devclopment of EGSB and IC processes has been to increa~e the volumetric organ ic loading and trealment efficiency. Other anaerobic processes have becn developcd to treat wastes wilh specific characteristic (e.g., colloidal and particulate wastes) .

Combined Processes. Process additions to the uptlow gmnular sludge blanket have been made to improve treatment performance to approach or meet secondary treatment levels. 1l1ese include hybrid anaerobic processes and a combined anaerobic-aerobic process. Hybrid processes typically involve two stages of anaerobic treatment, such lic methanogenesis, which are very

common. However. under certain conditions, such Ul> highly luaded anaerobic reactors, M elliallo.wrcillll may dominate. It has been shown thai the rtlilximum growth rale of MelhallO.WI7:illll is about 2.5 times that for Merlwllomefu at 35°C and its half-velocity coefficient for acetate utilization is about 3.5 limes greater (Conklin et aI., 2(06). The information given in Table 10-1 3 can also be used to approximate the amount of biomass and exce. .dO kg TSS/ml)

reactors as a function

of sludge density and organic loading rate a

M.edium Roccuktnt

~Iudge,

(20 to.40 kg TSS/m

J

)

Gronulor 5lvdge

Area per

feed inlet, m 1

< 1.0 1-2 > 2 < 1-2

0.5-1

> 2 1-2

2-5 0.5-1.0

2- 4

0.5-2.0

>4

> 2.0

1-2 2- 3 1-2

QAdopted from lBIIingo and HulUdf Pol t19911.

or (2) the organic loading mte (OLR). Limiting values for these pammeters are affected by temperature and the type of wastewater being trea ted.

Upflow Velocity. The uptlow velocity, based on the influt: nt flowrJtc. is a critical design parameter. Design upflow velocities recommended for UASB reactors are shown in Table 10-1 7. Upflow velocities wou ld be much higher in EGSB and Ie reactors, which are more likely applied for higher strength ind ustrial wastewaters. When Ihe UAS B reactor is applied for domestic wastewater treatment or for wastcwllter with higher innuent solids concentrations. a lower velocity is needed to better retai n the solids to provide sufficient time for solids capture and reduction by hydrolysis. TIle maximum allowable upflow velocity determines the cross-sectional area of the l"e for UASB systems may mngc from 5 to 15 kg COOl m3 'd and from 10 to 40 kg COOl mj'd for EGSB systems. An example of the effect of temperature on organic loading rate is shown on Fig. 10-10. r"Of a highly soluble wastewater the organic looding rate is reduced by a factor of 5.0 for operdtion at 15 versus 30Q C and by a factor of 4.3 for a wastewater with 30--40% particu lnte COD. TIle reactor process volume is related to the organic loading rate as follow s:

~ Q(5.)

" OLM

OLR

110-20)

where VOIJI = reactor process volume controlled by the organic lomling rate, ml. The process t1esign for a UASB treatment process is illustrated in Example 10-3.

EXAMPLE 10-3

UASB Treatment Process Design Detennine the fol lowing for a UASA treatment process used to treat a sugar beet wastewater, with the characteristic given below, to achieve 90 percent COD removal: a. RCilctor process volume b. Process hydmulic retention time c. Reactor dimensions U. Reactor SRT e. Daily sludge production rate in kg VSS/d f. Excess sludge waste volume in ml/d g. Methane ga:. production rale in ml/d h. Total gas production rate in mJ/d i. Energy available from methane production in kJ/d j. Alkalinity requ irements

1100

Chopler 10 Anaerobic Suspended ond Attoched Growth 8i%gicol Treatment

Procene~

Wastewater chamcteristics:

II,m

Volue

Flowrole

Unit m3/d

( 00

9/ml

12,000

3

91m

600

sfm'

500

os COCO,

500

TSS nbVSS

g/m 3

Alkolinity

'(

Tem~oh.Jre

500

25

Use the design pilrJmeters given below and typical values from Table 10-13: I. From Table 10-[4 YH = 0.08 g VSS/g COD b H = 0.03 g VSS/g VSS·d. 2. Jd = 0.10 g VSS cel l debrislg VSS biomass decuy 3. Methane production at OCC = 0.35 L C HJg COD 4 . Energy content of methane at ooe = 38,846 kJ /m l 5. Percent methane in gas phase = 65 % 6. Height of reaclOr process volume = H III 4. Height of clear zone above the sludge blanket = 0.50 m 8. Height of gas-solids separator = 2.5 rn 9. Reactor length:width ratio = 2.0 ]0. Maximum reaclOr upnow velocity = 1.0 mIh II. Average solids concentration in process vol ume = 30 kg VSS/m 3 Based on dala fro m the treatment of sugar beet wastewater in otber UASB facilities, 90 perce nt COD removal at 2ye, can be achieved with a design organic loading mte of 8.0 kg COD/m 3·d. The wastewater is mainly soluble containing carbohydrate compounds, and a granular sludge is expected. Assume an emuent VSS concentrat ion of 120 glml.

Solution

I.

Determine the reactor process volume. a, Detemline the reaclOr \'olume bused on the muxi mum upflow velocity Eq. (10-18) and Eq. ( 10-19) (500 mJ/d) = 20.8 m1 A= Q = v (1.0 m/h}(24 hJd ) V~

= A(H) = 20.8 m 2(8 m) = 166. 7 m 3

b. Determine the reactor volu me based on the organic loading ratc. From Eq. ( 10-20)

Q SG (500 m'/d)( 12 kg COD/Ill' ) = - - = = 750 m ) ou: OLR (8.0 kg COD/ml'd)

v. 2.

The orgunic loading rate controls the reactor volume design. Determine the process hydmulic retention time. V

Q= 3.

750 m' (500 ml/d) = 1.5 d

Determine the reactor dimensions. a. Reactor urea = (L)( I-V) = 2W(\-V) = 2 W2

De~i9n hample~

10-0 Proceu

I

1101

V 750 m) Area = - = - - = 93.75 m1

H

8m

2).Vl = 93.75 m 2, W = 6.85 m, L = 13.7 m b. TOla1 reaclor height

HT = processing hgt + dear zone hgt + separator hgl Hr 4.

= 8 In + 0.5 m + 2.5 m = 11

m

Reactor dimensions = 13.7 In X 6.85 Determine the reactor SRT. a. From Eq. (7~56). XCV) = p$ S RT b. From Eq. (8-20).

P = Q(YU)(Sd S) ~ I + bu(SRD c.

Sub~titllti n g

X

In

X II

In

+ fi'u( Q)(YH)(S" - S)(SRT) + I + biSRT)

(nbVSS)Q

Eq. (8- 20) into Eq . (7-56),

+ f.tbu(S RT)] + (n bYSS)Q(SRT) + bll(SRT)

(V) = Q(YHXS" - S)(SRT)[J

vss

I

5.. - S == O.90Sn = 0.90( J2,CXXl g COD/1ll3)

s" - S =

10,800 g CO D/m J

(30,000 g VSS/m')(750 m 3) = (500 m 3/d)(O,08 g VSS/g COD)( I 0,800 g CO D/m 3)(SRT)[ I I

+ 0.10(0.03 g/g ,d)(SRT) J

+ (0.03 g/g-d)(S RT)

+ 500 g VSSfm' (500 ml/d)SRT Solving: S RT = 50.2 d

5.

Detennine the daily sludge production mle from Eq. (7- 56). pX. VS5 --

X VS5 (V) - SRT -

(30,000 g VSS/ml)(750 ml)(1 kgll99% of degradable VSS is trans formed 5. MLVSS = 6000 g/ml 6. Settling rute = 24 mId 7. Gas composition = 65% CH 4 and 35% CO~ 8. Use kinetic coefficients and methane production assumption s from Table 10-13. 9. Biomass nutrient content = 12% Nand 2 ,4% P

Solution

I.

Determine design SRT at 25"C. At 90 pert'cnt COD removal the effluent COD is: = (1.0 - 0.90) (60(() mgIL)

= 600 glm'

The assumed effluent VSS concentration equals 150 glml.

10-6 Proces.s ~i9n Examples

Effluent COD from VSS = ( 150 gfm 3 L) 1.8 g CO D/g VSS = 270

g1mJ

Allowable effluent soluble COD = (60) - 270) gllll'

= 330 glrn] Solving for SRT in Eq. (7-46) and substitu ting

K,II +

S~

p..~=Yllk;

bll(SRT)l

S RT(I-lm.... - h ll ) - I SRT = [/J-nw;(S) -

K, + S

b]u ,

Use kinetic cocffi ciems from Table 10--13, I-tm..

=-

0.20 g/g'd

K, = 120 glm]

bll = 0.03 glg-d S RT = [

(0.20 glg'd)(330 g COD/Ill J ) ( 120

+ 330)g COD ml

- (0.03 glg·d)

]- '

= 8.6 d

With a safety of 3.0

Minimal design SRT = 3.0 (8.6) "'" 25.7 d Use SRT = 30 d to complete degradable VSS transformation 2.

Determine sludge production rate. Calcul,lIe nondegmdcd VSS concentration Nonsoluble COD = (6000 - 4000) glm3 = 2000 glm'

Nonsoluble COD as VSS = (2000 g/mJCOD) / (1.8 g CO DIg VSS) =

1110 glml VSS

Degradable frac tion of VSS = 0.8 (given) Nondegraded VSS = 0.20 ( 1110) = 222 g VSS/mJ Use Eq. (8- 20) to determine solids production: p = Q(r;I)(S~ S) x.vss I + b!/SRT)

+ J.,.bll(Q)( YII)(S. - S)(S RT) + I + bu(SRT)

(nbVSS)Q

So - S = COD degraded = Infl uen t COD

- nondegraded VSS COD - e ffluent soluble COD

= 6000 g COD/mJ - 222 g VSSfm1 - 330 g COD/m] = 5270 g COD/Ill) Use fo llowing coefficients from Table 10-14 and assume/J = 0. 15 Yu = 0.08 g VSS/g COD

hI! = 0.03 glg 'd

1105

1106

Chapter 10 Anaerobic Su~nded and Atloched GrOWTh Biological Treatment ProcEl$~

P

. = Q( YIl)(S" - s)11

I

l .VSS

px.vss =

p x.vss 3.

+

+ idbll(SRT)f + (nbVSS)Q

~(S RT)

(500 m' /d)(O.08 g VSS/g COD)(5270 g COD/m')[ 1 + 0. 15(0.03 g1g·d)(30.0 d)l 11 + (0.G3 glg "d)(30.0 d)j

+ (222 g VSS/m' )(SOO m' /d) = 125,925 g VSS/d + 111,000 g VSS/d =

236,925 g VSS/d

Determine reactor volume and 7. n. Dete rmine the volume using Eq (7- 56),

V=

(Px.vdS RT

ML VSS

=

(236,925 g VSS/d)(30 d)

6000 glm)

b. Determine the hydraul ic dClel11 ion lime,

= 1184.6m 3

7,

V 1184.6m' 7= -= =2.4d Q

4.

(500 mJ/d)

Detcmline the methane and total gas production rate and energy production rates. a. Dctcmline the methane gas production mle. From Table 10-13.0.35 Ill' CHikg CODal O°C CO D re moval = methane COD

+ biomass COD

biomass COD "" (1.42 g COD/g VSS)(PK.~ PX •Mo = first tcrm in Pl •VSS calcu lation = 125,925 g VSS/J

Methane COD = COD removed - biomass COD CH 4 COD/d = 500

m3/d (5270 g COD/m) - 1.42 g COD/g VSS (125.925 g VSS/d)

= 2.456,186 g C H. COD/d At standard conditions, methane production rate = (2.456,186 g CH. COD/d)(O,35 L CHJg COD)( 1 m1/ 10J L)

= 859,7 m] C Hjd at DOC Methane production rate at 25"C = (273.15 (859.7 m' CHJ d)

2 3

+ 25)"C

7 .15

'C

= 938.3 m' CH4 /d

b. Determine the total gas production rate.

Gas composition = 65% methane (g iven) (938.3 m} CHid) Total gas production ratc at 25"C "" 0 'C 1 = 1443.6 ml gasJd ( .65 III Him gas) (Note gas rate "" 1443.61500 = 2.9 limes liquid fimvTatc.)

1()-6 Procen ee,ign &le,

C.

1107

Determi ne the energy production rate. From Table 10- 13, e nergy co ntent of methane"" 38,846 kJ/ml at O°c. Energy production rate = (859.7 m l CHJdX38.846 kJ/ml ) = 33.4 X let kJ/d

5.

Determine nutrient requirements. Biomass production rute = 125.925 gVSS/d Given: biomass N = 12% and P = 2.4% ofYSS Nrequired = (125,925)(0.12) = 15.111 gld P req uired = ( 125.925)(0.0 24) = 3022 gld

Influent nutrients: N = (10 glmJ)(500

Jll lId) =

5000 gld

P = (20 glm3)(500 m'/d) = 10,000 gld

There is sufficient phosphorus in the influent, but nitrogen must be added. N addition = ( 15, 111 - 5(00) g N/d

= 10.111 gN/d = 10. 1 kgN/d

6.

Detern1ine alkalin ity requ irement. From Table 1{}-7 at pH = 7.0. T ;..: 25°C. percent CO 2 = 35, alkalinity a~ CaCO,

= 2678 glml

Influent alkalinity = 500 glm) as CaCO, Alkalinity needed = (2678 - 5()() glml as CaCO.1

= 2178 glml as CaCOl (2178 g as caco/ IllJ )] As NaHCOl = [ CO (84 mg NaHCO]/meq) = 3659 g Nat'ICO,/m l J) (50 mglmeq Cn NaHCO/ d = (3659 g1ml)(500 ml/d)(1 kg/IO] g) '" 1830 kg/d 7.

Detem1ine clarifier diameter. (Assume Area =

dega~ifi er

used before clarifier)

(Q, ml/d) (seul ing rale, mId)

=

(500 m' /d) (24 mId)

, = 2083nr .

Diameter = 5.2 m Comments

A considerable amount of energy (i.e .. kJ) is generated by the pnx\ucrion of methanc (CH4 )· The methane could be used to heat the anue robic proc~:.. which wou ld provide more rapid degradation and. Ihus. reduce the anaerobic bioreactor size.

Use of Simulation Models The relatively straightforwm"ll de~ign procedures desc ribed above C'1n be used to obtain a re asonable estimate of rcaclOr volume requirements. e llluent soluble bCOD conecnlration, and gas production. However. as discussed in Sec. 8- 5, in Chap. 8. for aerobic activated

11 0 8

Chopte'Ctor temperature = 35 C Q

2. Hcnt c)(changer recovery efficiency for raising liquid tempernture = 80 percent 3. COD removal efficiency

=

95 pc:rcent

4. COl of gas pha.e = 35 percent and pH = 7.0

1110

Chapler 10 Anoerobk Su~ or>d At!oche.:l

Growth Ri%gical Treotment Proce~~

5. Vallie of melhane=$51 IO'>U 6. Alkalinity is provided as Na HCO J at SO.90lkg Aerohic Ma.lor aerohic treatment oper:uing cOSt items are ene rgy for aeratio n and sludge processing and di sposaL The following assumptions apply:

I. COD removal efficiency = 99 percent 2. gO:/S COD removal = 1.2

3. Actual aeration efficiency - 1.2 kgO/kWh

4. El ectricity costs = $O.08/kWh 5. Net sludge production = 0.3 g TSSfg COD removcd

6. Sludge processing/disposal OO5t ., $0. lOIkg dry SQlids

10-3

A wastewater has a daily al'crage flowrntc of 1000, 2000. or 3000 mJfd (va lue to be selected by instructor) and 4000 mg/L o f an organ ic subst(lIlce with the following approximate composition: C,J{"O""N, S. For anaerob ic treatment at 95 percent degradation determ ine (a) the alkalinity production in mgfL as CaCO); and (b) the approximll\C mole fraction ofCO~. eH •• and H ~ in the gas phase.

1G-4

An industrial waStewater has an average flow rate of 2000 mNd. nn intlucnt COD concentration of 4000.6000. or 8000 mgfL (valuc to be !;elected by instructor). and influent sulfate

concentration of 500 mgfL. T he percent of COD degraded in nn anaerobic treatment process at 3S'C is 9S percent and 98 percent of the sulfate i ~ reduced . Determ ine (a) the amount of mcthune produced in mJ/d: (b) the 1l1110llnt of methane produced in m.l/d. if the sulfate reduction is not accolJnted for; and (c) the amoun t of HIS in the gas phase at a reactor p H value of7.0.

10-5

A suspended growth anaerobic reactor is operated at an S RT of 30 d at a te tnpcrature of 30· C. On a given day. tht: methane gas production rate (mJfd) decreases by 30 percent. List at least fOllr possiblo.: causes thai shuuld be invcst igmcd and briefly explain the mechanism behind eac h one,

10-6

A tOO percen t soluble industrial wastewater is to be treated by an anaerobic cu ntact process cOllsisting of a mixed covered reactor. a degasilier. and gravity sclliing. TIle emuent TSS concentration fr01l1 the clarifier is 120 mgfL. For the following wastewate r characteristics and design as!)u mptions, determine and compare the fo llowing de:; ign p-

-

$eporolion Proc---

Flow controller

~

"-

II "- . /

Sand support

I')

for Rell1(JllOl of I/:e$iduol Constituents

IT ;

--; /

Valve (closed)

~

Motor

r' ...•....•. _...• _... L __._.._.._._. __._.___

Section 1·1

Filtered

water

I

I

~'r~

1 ;;., 0-- sa~so~

Backwash ",at9r valv9

(closed)

/T

Water/air Va lve

Flow control

1_)

valve (opoo, variable)

(b)

01

e~panded

~""OOO

rAIr vatve (open)

~rOl 0

T·· J I

Fi lter underdrain

floor

I

H8i ~t

J.

[J-Io.

I

to-

Flow control

valve (closoo)

Backwash water

1_)

Figure 11-3 GenE!fcl features and operation 01 a conventionol ropid gronuJar medium depth filtor: 10) Row during lilrra fion cycle, ond Ib) flow during backwash cycle.IFrom Tchobanoglous and Sch roeder, 1985.)

is collected in the underdrain system which is also used to reverse the now 10 backwash the fi lter. Filtered water typically is disi nfected before being discharged to the environment. If the filtered water is 10 be reused, it can be disdmrged 10 a storage reservoir or to the rcclaimed wction ptOCe ... ~ 1_90

·f·· --

.. .:.- ....

_______ Primary w,tluent Secondary"IU""n! _-:-: - + - F"iIteI EIIIuoerli . -I( Pmduct .._ -0

X

,- -- .:.-

i-- ---

: --- ':t,

-' )C -_.-

,;.-"",~'x ; - -

--,_ ...

- -- --;--~ --

.. -- ~

.+--.~ , __ 0 . . ; UNnIog_a1"""","-

..•

.. ,-

-~-

:

--

' - 1- ----- . --

Percent at VahJ06 oquat to 0 ' tOM than iodocaled vatue

deplh fillers shown in 'n.ble II - II will vary from 4 to 15 rereenl. By compari son, Ihe backwas h percentages for surface tilters, discussed in the fo llowing section, will typically vary from I to 4 percent. When adding effl uent fi ltration to an existing plant, the impact of the return bize af filter piping and pipe gallery.

10. Filter appurtenances

Filler appurienonces indvde: (I) the under-drain system u~ 10 $lIf>pCIf1 the filtering rraIeriols, collect the filtered efAvent, and distribule the backwash wotef" and a ir {where used); (2) the woshwotcr trough!> used to remove the ~t backwash waler from the filter; and 13) the surfo:e woshing systoms used 10 help remove attochod Il"KlIorial from the liher medium.

Filter Bed Configuration and Filter Medium. Important considerations in individually designed depth filters are the selection of the type of fil ter bed and the corresponding media characteristics. Selection of Filter Red Conliguration. The principal types of non-proprietary filter bed conligur:l tiQns now uscd For w:Istewater filtration may be classified according to the number ofliltering media that are used as mono-medium. dual-media. or multi -media beds (sec Fig. 11-6). In cOllventional down now filters. the distribution of gmin sizes for each medium aft er backwashing is from small to large. Typical design d:lla for mono-medium , and dual- :lnd multi-media filters are presented in Tables 11-15 and 11 - 16. respectively.

11-5 Depth Filtration: Selection and Design Considerations

Table 11-15

Typical design data for depth filters with mono-mediumo

1163

Value Characteristic

Unit

Range

Depth

mm

300-500

Effective size

mm

0.8-1.5

1.3 :s 1.5

Shallow bed

Typical

(stra~fiecH

Anthracite

unifless

1.3-1.8

mJ /m 2 ·min

0.08-0.24

Depth

mm

300-360

Effective size

mm

Uniformity coefficient Filtration rate

400

Sand

Uniformity coefficient Filtration rate

unifless

0.45-0.65 1.2-1.6

ml /m 2 ·min

0.08-0.24

mm mm

6()(}-900

330 0.45 :s 1.5

Conventionol (stratified) Anthracite

Depth Effective size Uniformity coefficient Filtration rate

750

0.8- 2.0

1.3 s 1.5

unifless

1.3-1.8

m3/m 2 ·min

0.08--0.40

mm mm

500-750

Sood Depth

uniriess

0.4-0.8 1.2-1.6

ml /m 1 ·min

0.08-0.24

mm mm

900-2100 2-4

Uniformity coefficient

unitless

1.3- 1.8

Filtration rate

3

Effective size Uniformity coefficient Filtration rate Deep-bed (unstra~fied)

600

0.65 :s 1.5

Anthracite

Depth Effective size

2

m /m 'min

0.08---0.40

mm mm

900-1800 2- 3

1500 2.7 :s 1.5

Sood Depth Effective size Uniformity coefficient Filtration rate

unifless

1.2-1.6

ml /m 1 ·min

0.08---0.40

1200 2.5 s 1.5

Fuzzy filter

Depth Effective size Uniformity coefficient Filtration rate

600-1080

BOO

25-30 1.1-1.2

2B

uni~ess

ml /m 2 ·min

0.60-1.60

mm mm

a Adopted in part from Tchabonog b,os 11988) and Tchabonoglous el 01. (2003). Note: ml /m 2·min X 24.5424 '" gol/ft2·min.

1.1

1164

Chapter 11

Separation Processes for Removol of Res idual Constituents

Table 11-16

Typical design data for dual- and multimedia depth filters'

Value b Characteristi,

Unit

Range

Typical

D.p.

mm

360-900

Effective size

mm

0.8-2.0

720 1.5

unitless

1.3-1.6

:s 1.5

D.p.

mm

180-360

Effective size

mm

0.4-0.8

Dual-media Anthracite (p == 1.60)

Uniformity coefficient Sand (p

= 2.65)

Uniformity coefficient

360 0.65

unirtess

1.2-1.6

m3/m 2 ·min

0.08-0.40

o.p.

mm

240--600

Effective size

mm

1.3-2.0

480 1.6

Llnidess

1.3- 1.6

:s 1.5

Depth

mm

120-480

Effective size

mm

1.0-1.6

1.I

unidess

1.5-1.8

1.5

D.p.

mm

240-600

Effective size

mm

1.0-2.0

480 1.4

Llnirtess

1.4- 1.8

s l.5

Depth

mm

240--480

Effective size

mm

0.4-0.8

0.5

Llnirless

1.3- 1.8

s 1.5

mm

50-150

100

mm

0.2-0.6

Fi l!ration rate

~ 1.5

0.20

Multi-media Anthracite (top layer of quod-media filter, p = 1.60)

Uniformity coefficient Anthracite (socond layer of qvod-media filter, p - 1.60)

Uniformity coefficient

140

Anthracite (top layer of Iri-media filter, p = 1.60)

Uniformity coefficient Sand (p - 2.65)

Uniformity coeffi cient

300

Garnet (p .. 4.2)

Depth Effective size Uniformity coefficient Fil tration rote

uni~ess

1.5-1.8

mJ/m'-min

0.08-0.40

0.35 sl.5 0.20

• Maple:e d istribution range s for sand and anthrac ite used in dual medium depth fj lter~. Note that for sand the 10 percen t si:>:e by weigh t corresponds approximately to the 50 percent si..:e by co unt.

,

,, ,, ,• 9 9

""'

d'Q = 0.45 - 0.65

mm

UC s 1.5

0 0

I

-

t -

" 1----j---j4-H " 120 1---+--++) tt~j

+

o

1/

Anthrac~e

: f--+-+! ~J ~ __C:T~C:C~i':C! -r'T'"m"-mrt , I----l- "I

t ll 'I++---+-i-++++++

o, "-_~"-LLLUOLc--L-L-LLLUl 1.0 10

Selection of Fitte r Medium. Once the type ofti lter to be used has been se lected , the next step is to speci fy the characteristics of the filter medium, or med ia, if more than one is used. Typically, this process involves the selection of the grain size as specitied by the effective size, d lO, uniformity coefficient, Uc. the 90 percent size, the specific gravity, solubility, hard ness, and depth of the various materials used in the filter bed. Typical particle size dist ri bution ranges for sand and anthracite tilteri ng material are shown on Fig. 11 -17. The 90 perccnt siLe lh:signated, iI'IIl> as rcad from a grai n size analysis is used com monly to detcrmine the req uired backwa~h rale for depth filters. The physical properties of filter materials used in depth li lters arc summarized in Table 11 - 17. To avoid extensive 1I1Icrmixing of the individual medi ums in mul ti-media filter beds, the settling nlte of the filter media comprising the dual- and mul ti-media filters must have essentially the same settling velocity, Some intermixing is unavoidable, and the degree of interm ixing in the dllal- a nd multi-media beds depends on the density and size differences of the varioll~ mcdi,!. The following relationship Call be used to establish the appropriate sizes (Kawamura, 2000).

dt

=

(P2-

dl

PI

P~.)O.t061

111-281

P.·

where di' (/,2 = effective size of tilte r medium PI' Pl = density of filter medium p .. = density of water

The application of Eq. (11 - 28) is illustrated in Example 11-4.

Table 11-17

Typical properties of filter materials used in depth filtration'

Filter material Anthrocile

Sued

Gamet

Ilmenite Fuzzy filler medium

Specific gravity

Porosity, ((

1.4-1.75

0.56--0.60

2.55-2.65 3.8- 4.3

0.40-0.46 0.42--0.55

4 .5

0.40-0.5

• Adopted in porI from Cloo$by and Logsdon (19991.

0.87--0.89

Sphericity 0.75-0.85

0.75-0.85

1166

Cf.qJu 11 Seporotion ProcesSE!$ lor Remuvol of l1:esidool Comfitueni'5

EXAMPLE 11-4

Determination of Filter Medium Sizes A dual media filter bed comprised of :;;and and ant hraci te is to be used for the filtration of settled secondary efflu e nt. If the effective size of the sand in the dual medium filler is to be 0.55 mm, dete mlinc the effective size of the anthracite to avoid significant intcnnix ing.

Solution

I.

2.

Summarize the properties of thc fi lter media a. For sand i. Effect ive sizc = 0.55 mm Ii. Specific gravity = 2.65 (see Table 11 -17) b. For anthracite i. Effective size = to be dctermined, mm ii. Specific gravity = 1.7 (sec Table 11 - 17) Compute the effective sizc of the a nthracite using Eq. (11-28)

d = d (P2 I

1

PI _

Pw)O.6l>? Pw

)'.M'

'.65 - 1

d, = 0.55 mm ( 1.7

I

d l = 0.97 mm

Comment

Another a pproac h that call be used to a~ses.." whether intc rmix ing will occur is to compare the nuidized bulk dens i l i e~ of the two adjaccnt layers (e . g . , upper 450 mill sand and lower 100 mm of ant hraci te).

Filter Flowrate Control. The principal methods now used to control the rate of flow through down now gravity filters may be classified as ( I) constant-r..lte filtratio n with fixed head, (2) constant M e fi ltratio n with variable head. a nd (3) variable-declining-rate filtra tion. A variety of other control methods are also in use (Cleasby and Logsdon. 1999; Kawu mur.l, 2OI1le of tI1e filter material rooy be lost duri ng bockwoshing and through the unoordrain system (where the grovel support has been upset and the underdrain system ho~ been inwlled improperly). The loss of the filter material coo be minimized through the Propel" plocemenl of wa~ter troughs and unden:Jrain system. Special barnes have also proved effective.

Loss of filter medium or media !operationall

Depending on the characteristics of the biological Rac, grains of the filter material can become attached to it, forming aggregates light enough to be Rooted away duri ng the bockwashing operation1. The problem can be minimized by the addi tion of an au}(iliary air and/Of" water !.Couring system.

GrOYel mounding

Grovel mounding occurs when the various layers of the wpport grovel ore disnJpled by the application of =cessive rates of Row during the bockwa$hing operation. A grovel wpport with on odditional 60 to 75 mm (2 10 3 in.) layer of high density moteriol, such or gornet, can be used to overcome this problem.

05

ilmenite

- Turbidity breakthrough does not occur with fillers thot operate continuously.

removal of suspended solids and algae from stabilization pond effiuents. and (3) as a prel"realmem operation before microliltralion or UV disinfection. Surface fi ltration is gaining in IXlpularil y because of the high qU:llity effiuent produced. sm:lller foolprillt, low backwash rales, and red uced mainten:ltlcc requirements. lnfOnllation on surface liltration tcchnologies, their performance, and design considerations is presented and discussed in this section.

Available Filtration Technologies The principal types of surface fil tration devices arc identified and described in Table 11 -21. With the exception of the incl ined surface and cart ridge fillers. all of the at her surface fil ters have been used for the fi ltra tion of seconda ry cmuent. Some of the svrface filters have also been used for lhe lilt ratio n of algae for lagoon eflluents. The inclined surface

11--6 s...rIoce Filtration

1173

Table 11-21

Description of some surface filters used in efAuent filtration applications Description

Type

(0) Cloth Madia Filter (CMFI

Effluent

=f A

tnltuent

Sectiocriodical1y by a vacuum header. Ovcr time. particles will ncculTlulate in t.he cloth medium thai can not be removed by a lypical backwash. Thi s accumulation of particles leads 10 increased helldloss across the filter. an increase in the backw:.sh suction pre1>sure. and shoner run lilnes between backwashes. When Ihe backwash ... uc tion pr~surc or operati ng time reaches predetermined selpoi nts. a high pre.ssure spray wa:.h is initiated automatically. The high pressure spray wash flu shcs the particles tlmt have become ludged inside the clolh tilter mcdia in 1 rev of the disk. 11lc tillle inh:rval betwL-en high pressure spray washes is a function of the feed water quality.

11-6 Surfoc:e Filtrotion

Irw;:roaood lhicknoS$ of ralll of p9,licie solids oI filtllr

0.

Filltr fol lowing Unear removal dlle to redOCW due to remova l accumulalioo aulOfiliration loss of water

uq~ Point on lill"" tnters wat&r

i'i

Pont on fil1",r exits wate
.:Implc to be selccted by instructor) using the following experimental dma:

Time, min

0 0.5 1.0 1.5 2.0 2.5 3.0

volume filtered, l Waler s.omple I 2

1.50 2.50

1.50 2.50

3.45 4.36 5.22 6.03

3.48

'''' 5.37 6.28

Volume ~llered, l Time, min

3.5 ' .0 ' .5 5.0 55 60 6.5

Wotef samele I 2 7.17 6.78 7.48 8.03 8.87 8.08 9.67 8.57 10.34 10.97 11.47

11-21 Dclenni ne the COSt (based on the currenl price of electricity) to treat a fiowratc of 2500 ml/d

wilh a TDS cooccntmtion of ] 300 glml aod a cation and anion concentration of O. I3 g-eqlL using an eloctrodialysis unit, Assume the following typical val ues of operation for the electrodia lysis uni t. Product !lowrate = 90% of the fl'Cd water fluwrnte Efficiency of salt removal = 50% The current elliciency ;; 90% [{ eS, sl~nce = 5.0 ohms Number of cell pairs in the st3ck = 350.400. -1-50 (to be l>elocled by in""llctor) AssulIle an energy cost of SO. I 3/kWh and 24 hid opemtion. 11-22 Review and cile three cu rrent articles (within the last five years) dealing the disposal of

nallofihmlion. reverse osmosis, or electrodialysis brine. Whilttypes of pmccss combinations are being proposed'! Whllt lin.:: thc critical i~sues thut ~I;tnd Ollt in y("Our mind'/

1284

Chapter II

Separation Proce~~1 lor Removol

01 Re\iduol Comliluenn

11 - 23 A Wll~tew;ner is to be tn:att:d with HctiV'~led carbon 10 n:move residual COD. The follov.'ing dmn were obtained from a laboratory 'ldsorplioll ~tudy in which I g of activated carbon was added to n beaker cOIllaining t L of was tewater at se lected COD values. Using these data. determi ne Ihe more su itab le iWlhcrm (Langm uir or Fruendl ich) to describe Ihe data ('\ample 10 be sck'(;led by ins tructor"). Eguilibrium COD,

mall

Wastewater som~e number

Iniliol COO,

2

mg/l

140 250

5 12 17

300

340 370 400

30 50 70

23

29 36 50

450

3 0.4 0.9 2 4 6

10

90

110 150

4 5 18 28 36

42 50 63

10

35

11-24 USlIlg the fo ll ow ing isotherm test data, detenlliJlC the Iype of model that best d escribes Ihe dala and Ihe corres pondin g mod e l p~lnllnclers. As~ume thai a I L sa mple volume was used ror each or the isotheml ex perimclIl s. E~ilibrium conamlrotion of

adsorbate in ~ution, C.. ~a/L

Te!J Jlumber

Mo$$ of GAe, rna 0

2 26

158.2

10.2

26.4

15.89 13.02

3

4

0 .001

5.8 3.9

om

0.97

4.33

6.8

01 0.5

0.12

2.76

1.33

6.15

0.022

0.75

0.5

2.1

25.3

11 - 25 Using [he resu lL~ fmm Proble m 11 -23. delerm ine the amount of oc li vated carbon Ihul would be required to lfelt! a nowrate of 41:100 mJ/d 10 a final COD conccntnlt ion of 2 mgtL if the COl) concenlmtion afl er secondary treatment is equ al 10 30 mgtL. 11-26

Dt:~ign

a fi xed-bed activated carbOn p rocess using the follow ing dma. DelemlillC the num -

ber o f conlactors. mode of opef""Jtion. carbon requirements. Ignore the effects of biological activity within the column.

~t od

correspooding bed life.

Com~nd

Mothyloo. Paromeler

Unit

Flowrate

m3/d

C. C. GAC den$ily EBCT

ogIl ogIl gil

11-27 Referring

[0

Chlorobm 4000 500 50 450 10

min

the data presented ill Table

1 1 ~23.

Hepkx:hlor

4500 50 10

450 10

chloride

5000 2000 10 450 10

NDMA 6000

200 10 450 10

prepare a list of the top 5 most and least

readily adsorbable substances. 11-28 Usin g the res ults fmm PrOO.

11 ~ 1 3,

dclennille the amount ofaclivmed carbollthat would be

required to lreat II t10wrillc of 5000 m'/d to a linal COD concentrat ion of 20 mgtL if Ihe COD concen tration after secondary to:atmerll is equ;11 to 120 mg/L.

Probloms and Discussion Topics

1285

11-29 Using the Following carbon :ldwrptlon dala (sample number to be selected by instructor)

delermine the Frellndlich capacity factor (mg for Use in Potable Water." in M. J. McGuire and I. 1·1. Suffet (cds.) Tr('(lfIllelll lu n l1ler by C mllll/flr A c/i l"/lleJ Carboll. American Che mical Society. Wash ington. DC. S(lkuji. R. H. (2006) "What' s New for Membranes in the Regub tory Arcna:' presen ted nt Microli ll ro tio n IV. Nmi ona l Water Re scarch I n~litute, AIl;lhcim/Onll1gc Cou nt y. Omnge.CA. Schippers. J . C .. und Verdollw. J (1980) "11te Modified Fouling Inlk:x. a Method for Determining the Fouling Characteristics of Wmcr:' DI!.wlimlliulI. 32. 137- 148.

.290

Chapter 11

Separctioo Processes lor Rell'lOYOl ol Residual Comtituents

Shaw, D. J. ( 1966) IlIlmdu(;lioll to CQI/uid am! Surface Chemislry. Butterworth, London, England. Sherwood. T. K.. and E A. Hollaway (194() "Pcrfommoce of Pac ked Towers- Liquid Pi lm Data for

Several P... ckings.~ Trans. Am. Inst. Cht'm. Engr'S.. 36, 39-70. Sl3lcr, M. J. ( 1991) Princi,J/es of lun Exchange Techllnfngy. Butterworth Heinemann, New Yorl::. Slechta, A. , anti G. L Culp ( 1%1) "Water Reclamation Studies :11 the SOllt h u lkc Tahoe Public

Utility District." J. WPCF. 39, 5, 787-814. SrKM:yink. V. L.. and R. S. Summers (1999) "Adsorptioll Of Organic COIl1POunds,~ Chap. 13. in R. D. Lettcrm:m (ed.) , Waler Quality AJld Trealmcnl: II Hantl/XXJk ojComlllunity »~l(er SUl'piie.l. 5th ed .. American Waler Works Association, McGraw-HilI. New York. Sontheimer. H., J . C. Crittenden, and R. S. Summers ( 1988) Activated Carboll For Waler bralmenl, 2nd ed., in English, DVGW-Forschungsstelle, Engler-Buntc-lnstilUt, Universitat Karlsru he, Gcnnany. Stephe nson, T.. S. J udd. B. Jefferso n. and K. Brindle (20Cl0) Mcmbmnc Biorcacwrs for WiI.l"lelmler Trelllmenl. lWA Publ ish ing, London. Stover. R. L. (2lX17) "Seawater Reverse Osmosis wi th Isobaric Energy Recovery Devices." Desalinatioll 203 168-1 75. Tuylor. J. S., and M. Wiesner (1999) "Membmnes." C hap. I I, in R. D. Lel1e nnan. ed., Waler Quality And T,.ealmclII: A H,mdbook o/Com",unily Wilter Supplie."i, 5th ed .. American Water Wor"ksAssociation, McGrdw-l lill, New York . Tay lor, J. S., an d E. P. Jacobs ( 1996) "Reverse Osmosi~ a nd Nan ofi hfat io n," Chap. 9. in J. Mallev ia ll e, P. E. Odendaal, and M R. Wiesne r (cds.) Wmer Trelllmel/l Memlmmc Proc,..U,..f. Ame rican Wa ter WOfk~ Assoc iation. published by Mc(jraw-Ilill, New York. T ehobanoglous. G., and R. El iassen ( 1970) "Filtrat io n orTn:atcd Sewage Emucnt;' Journal Snn. Bllg. D il'., ASCB, 96, SA2, 243-265. Tchobn noglous, G., nnd E. D. Sehroeder (1985) ",,/ler Quality: Ch'lfacteri.ffi(.·s, Modeling, Modijiclllil}n. Add ison-Wes ley Publishing Company, Read ing, MA. Tchubaooglous. O. ( 1988) "Filt rat ion of ScclHldary Emucnt for Reuse Applications.'" Presented at the 61st Annual Conference of the WPCF, DaJl us, TX. Tehobanoglous, G., E L. Burton. and II. I). Stcnsd (2003) Wc,..-lell'lIter £nsincering: 1"rcOilll(:,1I (md Reuse. 4 th cd., MdJrnw-HiII, New York.. Tchobllooglous, G., 1-1. Levetcnz, M. H . Ne llor, and J. Crook (2011 ) IJirect I'owhle Rflm~: A Palh Fonvarrl. Wate Rcu sc Research and WateReusc Ca lifornia, Washing ton, DC. Tm ~scl l , R. R., and M. Chang (1999) "Review of Flow Through Porous Media as Applied to Head Loss in Water ,""ilters. J. Environ. Eng., ASCE, 125, 11,998- 1006. USBR (2003) DesollinK Hall(lbook/or Planners. 3"' ed., Desalination Researeh and Developmcnt Progrd lll Rel)Ort Nu. 72, United SillIes Depur\me nt of t.he Int erior, Bu reau uf Reehul1ll1 ion. Voutehkov, N. (201 3) [)emlil/olion Engin,.erillg Plnnnillg alld Design, McGraw- Hili Book. Comp;my. New York.. Wadell, H. ( 1935). "Volume, Shape and Roundncss of Quartz Pm1icles J. Geol., 43, 3. 250-280. WeUcrH u. G. D. (20 13) Personal Com muni ea tiun. C DM Smi th. Los Ange les, CA. Wil f. M. ( 1998) '" Reverse Osmosis Mcmor;Hles for Wa.~!ewatcr RcclanlluilHl," In T. Asano (cd.) Wc/stelH/ter R,.cfmnaliOIl and Reuse. Chap. 7, pp. 263-344, Water Qua li ty Man3gemc nt Li brary. vol. 10. CRC Press, Boca Rmon. FL. Wong, J. (2003) "A Survey of Advanced Mem brane Tech nulugi es and Their Applications in Water Reuse Projects_" Proceedings oflht: 76th AlIllual Techtl icul Exhibilion &. Conference. Water Environme /l! Fedemlion. Alexandria. VA. H

•

Disinfection Processes 12-1

INTRODUCTION TO DISINFECTANTS USED IN WASTEWATER

Characteristics for an Ideal Disinfectant

Disinfection Agents and Methods 1294 Mechanisms Used to Explain Action of Disinfectants Comparison of Disinfectants ' 297 12-2

1294

1294

1296

DISINFECTION PROCESS CONSIDERATIONS 1297 Physical Facilities Used for Disinfection '297 Factors AHecfing Performance 1300 Development of the CT Concept for Predicting Disinfection Performance

1306

Application of the CT Concept to Wastewater Disinfection '307 Performance Comporison of Disinfection Technologies , 308 12-3

DISINFECTION WITH CHLORINE 1312

Characteristics of Chlorine Compounds Chemistry of Chlorine Compounds

13 12 '314

Breakpoint Reaction with Chlorine

13 , 6

EHectiveness of Free and Combined Chlorine as Disinfectants

1320

Measurement and Reporting of Disinfection Process Performance

'322

Fadors that Affect Disinfection of Wastewater with Chlorine Compounds lv10deling the Chlorine Disinfection Process 1328 Required Chorine Dosages for Disinfection 1329 Formation and Control of Disinfection Byproducts (DBPs) 1333 Environmenfollmpocts of Disinfection with Chlorine 1336 12-4

DISINFECTION WITH CHLORINE DIOXIDE

12-5

DECHLORINATION

1337 Characteristics of Chlorine Dioxide 1337 Chlorine Dioxide Chemistry 1337 Effectiveness of Cn/orine Dioxide as a Disinfectant 1338 Modeling the Chlorine Dioxide Disinfection Process 1338 Required Chlorine Dioxide Dosages for Disinfection 1338 Byproduct Formation and Control 1338 Environmenfal/mpacts 1339

Dechlorination Dechlorination Dechlorination Dechlorination Dechlorination 12-6

1323

1339 of Treated Wastewater with Sulfur Dioxide 1339 of Treated Wastewater with Sodium Based Compounds with Hydrogen Peroxide 1342 with Activated Carbon 1342 of Chlorine Dioxide with Sulfur Dioxide ' 342

DESIGN OF CHLORINATION AND DECHLORINATION FACILITIES

Sizing Chlorination Facilitie s

134 ,

1343

' 343

Dijinfection Process Flow Diagrams Dosage Control '347

1344 12'>1

1292

Chepler 12 DisinlediOIl Processe$

Injection and Initial Mixing 1349 Chlorine Contact Basin Design 1349 Assessing the Hydraulic Performance of Existing Chlorine Contact Basins Ouffet Control and Chlorine Residual Measurement '365 Chlorine Storage Facilities 1365 Chemical Containment Facilities 1366 Dechlorination Facilities '366 12-7

DISINFEGKlN WITH OZONE

1367 Ozone Properties 1367 Ozone Chemistry '368 EHecliveness of Ozone as a Disinfectant '369 Modeling the Ozone Disinfection Process 1369 Required Ozone Dosages for Disinfection '372 Estimation of the CT Value '372 Byproduct Forma/ion and Control 1374 Environmental Impacts of Using Ozone 1374 Other Benefits of Using Ozone 1375 Ozone Disinfection Systems Components 1375

1 2-8

OTHER CHEMICAL DISINFEGION METHODS

Peracetic Acid 1379 Use of Peroxone as a Disinfectant 1380 Sequential Chlorination '38' Combined Chemical Disinfection Processes 1 2-9

1378

'38 ,

ULTRAViOlET IUV) RADIATKlN DISINFECTlON Source of UV Radiation J 383

Types of UV Lamps '384 UV Disinfection System Configurations

1382

J387

Quortz Sleeve Cleaning Systems 1390 Mechanism of Inactivation by UV Irradiation 1391 Germicidal Effectiveness of UV Irradiation 1393 Estimating UV Dose 1399 Ultraviolet Disinfection Guidelines 1404 Relationship of UV Guidelines 10 UV System Design 1405 ¥alidation of UV Reactor or System Performance J4 05 Factors AHecting UV System Design '413 Selection and Sizing of a UV Disinfection System 1420 Use of Spot-Check Bioassay to Validate UV System Performance Troubleshooting UV Disinfection Systems J426 Environmenlallmpacts of UV Radiation Disinfection J428 12-10

DISINFECTON BY PASTEURIZATION

1428 Descriplion of the Pasteurization Process J428 Thermal Disinfection Kinetics '429 Germicidal Effectiveness of Pasteurization 1433 Regulatory Requirements 1433 Application of Pasteurization for Disinfection J433 PROBLEMS AND DISCUSSION TOPICS REFERENCES

1442

1434

'422

1359

Chapter 12 Di~infection Processes

1293

WORKING TERMINOLOGY Term

Definition

Absorbance

A measure 01 the amount 01 light 01 0 specilied wavelengrh tha t is absorbed by a solution and the constituents in the solu tion.

Sreakpoint chlorination

A process whereby enough chlorine is odded to react with all oxidizable substances in water such !hat jf additioflol chlorine is added it will remain as free chlorine (5ee below, HOCI + OCI ).

Chlorine residual, totol

The co ncentrotiOfl 01free or combifled chlorifle in water, measured after a specified time period followiflg oddition. Combifled chlorifle rC$idual is measured most commoflly amperometricolly.

Combined chlorine

Chlorioe combined wi!h other compounds [e.g., rnooochioramine (NH:>CII, dichloromifle (NHCI1), and nilTogen lTichlaride lNC IJL amoflg others].

Combined chlorine residual

Chlorine residual comprised of combined chlorifle compounds [e.g ., monochloromine (NH 2 CI), dichloramine [NHCI11, ofld nitrogen trichloride lNCl l ) and others].

cr

The prod uct of disinfectoflt residual, C, clwly

• Adopted in part from Tchobanoglo..,s eI a!. (2003) cmd Crittenden el 01. (2012). ~ See Tobie 12-1 lor 0 description of the charocteris~cs 01 on ideol disinfectant. • Free chlorine (HOd and cx:1- ). dna .. nol applicoble. • Depends on whether chlorine gas or sodium hypchlorile is used 10 combine with nilmgenovs compoondl. f Must be generotecl 05 used. • THMs = trihalomethanes and HAAs = holoocetic odck

Increasing

,W,

12-2 Di~infection Process Considero~ool

Chlonne /)( ctJlome ~p.,,""

c_

.

o, chlorir.e

compolJOds

,,

Dechlorinabon

w!~~~: ... r== l_".\-__ ~I,----1 WWTP t

r--e \

FOfOOmain serves as tubular plvg-Ilow react/)(

Submerged bailles

{.,

\0 improve hydraufic efficoency

(0)

OfI-~s

Off-gas

to thermal destruct unl1

to Ihermal Wlltof be trea

"""

TUn!

00$1

\

1

"j

Ozone Venturi injea/)(

". .,," rIO

~,

" ~

o

,~

(,'

~

J

J\

""

...

""~,

flow control

"'

UV vertical lamp (I)

module WIth sl..t)l)Or1 radt

tnftuent

Return 10

Preheat

hB~ting

react/)(

loop

leactor UV

I~

oriel1ted to !low

~nclicular

HOO100 water

~,

("

/)( steam

Figure 12-1 Types of reodQu used to oe-50

60-75

80-100

UV mdiatioo'

Protozoa (Cryptospor-idium)f Chlorine (/ree)

mg·minIL

2000-2600

4000-5000

Chloramine

mg'min/l

4000-5000

8COO-l0,ooo

Chlorine diollide

mg·mi n/l

120-150

Ozone

mg·min/l

UV radiation

mJ/cm'

4- 4.5 2_5-3

235- 260

350-400

8- 8 .5

12- 13

6- 7

12- 13

Protozoa (Giardia lamblia cysts)V Chlorine (free)

mg·min/l

20-30

45-55

70-80

Chloramine

mg·min/L

400-450

800-900

1100-1300

Chlorine diollide

mg·min/l

5-5.5

9- 11

15-16

Ozooe

mg·min/l

0.25-0.3

0.45--0.5

0.75-0.8

2-2.5

5.5-6.6

11-13

UV radiotion

mJ/cm '

'Adopted in part from AWWA (19911, Boumann and ludwig (1962), Crittenden et 01. (2012), Holf (1986), Code of Federal Regulations - Title 40 (40 CFR 141.2), Muguin et 01. (20091. Montgomery (1985), Robertset 01. (19801. Sung (1974), U.S. EPA (199%). b Reported CT values are highfy temperature and pH sensitive. Disinfection rates will increme by 0 foetor of 2 to 3 for each 10' C increose in temperoture. ' The range of CT volves for 4-log removal i. for the linear portion of the dose-response curve bee Fig. 12-6). Depending on the particle size distribution resulting from the filtration of s.econdory eFHuent, mud> higher a values may be needed ta ochieve a 4-log removal 'The reported CT valuas are for total coliform. Significontly lowe-r a values have been reported for fecal coliform and E coli. ' With the exception of odenovirus which requires 0 much higher UV do.e (o ~ high m 160-200 mJ/cm1 for cting reactions, such us the formation of chloramines (free chlorine and ammoni a), and DBPs can occur. The predominant react ion depends on the applicable ki netic rates for the various reactions. The format ion and control of DI3 Ps is discussed later in this section.

Chemical Characteristics of Wastewater. It has often becn observed that, for treatment plants of similar design wi th exactl y the SlLme effiuent char.lcteristics measured in temlS of BOD, COD, and nitrogen, the effectiveness of the chlo rin ut ion process \laries significltntl y from plunt to plant. To in\lestig:lte the rea...ons for this observed phenomenon and to assess the effect s of the compounds prese nt in the chlorination process, Sung ( 1974) studied the c haracteris tics of the compounds in untre:lted a nd treated wastewater. Among the mo re important conclusions derived from Sung's study arc the follow ing: I. In the prese nce of interfering organic compounds. the total c hlorine resid ual cannot

be used as a reliable measure for assessing the bactericidal efficiency of chlo rine. 2. The degree of interference of the compounds studied depe nded on their fu nctional groups and thei r chem ical structure. 3. Smuratcd compounds and carbohydrates exert little or no ch lorine demand and do not appe3r to interfere with the c hlorin3tion process. 4. Organic compounds with unsaturated bonds may exert:m immediate c hlorine dcmand, de~nding on thei r func tional groups. In some cases, the resulting compounds may ti tra te as chlorine residual and yet may pos...ess little or no disinfection potential. S. Compounds with polycycl ic ri ngs containing hydroxyl groups and compounds containing su lfur groups react read ily with chlorine to form compounds which have litt le or no bactericidal potenti31, but which s till titmtc as chlori ne residual. 6. To achieve low bacterial counts in the prese nce of interfering o rga nic compounds. additional c hlorine and longer contact times are required. From the results of Sung's work, it is easy to see why the cfficiency of c hlori nation at plan ts with the same general effiuent c harac teristics can be q uite different. Clearl y, it is not the value of the BOD or COD that is significant , but the nature of the orga nic compounds that m3kc up the measured values. Thus, the nature of the treatmcn t process lIscd in an y plan t 31so has an effect on the c hlo rin3tion process. The impact of wastewater ch.ulIcteris· tics on chlo rine disi nfectio n is presented in Tablc 12-13. The presc nce of oxidi7..able compounds suc h as hu mics and iron causes thc inac tivatio n curvc to have a lag o r shoulder affect as shown o n Fig. 12-6. In effect, the added c hlorine is being utili7..ed in the oxidiza· tion of these substances a nd is nOi available for the inactivation of microorga nisms. Because more wastewater treatment plants arc now removing nit rogen, operalional problems with chlorine di.~infcc t ion are now reported more freq ue ntl y. In treatment plams

12-3 Disinfection with Chlorine

1325

Tobie 12-13

IImpact of wastewater constituents on the use of chlorine for wastewater disinfection Constitue nt

Effe. especially where shallow basins are used. has furth er compl icated dosngc control

1348

Chapter 12 Disinfection Procos)es

Table 12-18

Control method

Description

Methods used to

Monual control

Monuol control, ....neo-e the operollx chonges the feed rote 10 suit conditions, ;s the simplest method for controlling the chlorine dose. The required dosage is usualfy determined by measuring the free and/ or the combined chlorine residual at the end of the dllorine conlacl basin and adjusti ng the

control the chlorine dosage for disinfection.;!

chlorine do~ to oblain a the desired residI)Q1. This method worh best where combined chlorine is used for disinfection, and the lIow.-ato doe not vary too rapidly, but con a lso be used where free chlorine residual is vsod. MonI)Q1contral with online efRuent residI)Q1 chlorine monitoring

An online chlorine analyzer is used 10 monitor the chlorine residI)Q1 in the effluent from the chlorine contact basin. The chlorine dose is adjusted monI)Q11y based on the pIont flow· rote and the residual chlorino concentrations. This method works kt where combined chlorine is used for disinfection, and the Rowrate does notllOry too rapidly.

Flow pacing

Tho thlorine Rowrote is paced proportionol to the wastewoter Rowrote os measured by a primory meier such as a magnetic meter, Parshall Rume, or flow lube. This method works best where combined chlorine is used for disinfection.

Flow pacing with online effluent residual chlorine monitoring

The thlorine dosoge is controlled by automatic measurement of the chlorine residual and the wastcwoter Rewrote. An automatic analyzer with signollransmitter and rocorder is required.

Row pacing with online efRuent residuol chlorine monitoring arK! automatic

The control signals obtained from the wostewater Rowmeter and the resiclvol monitor are fed to a programmable logic controller (PlC) to provide more precise conlrol of thlorine dosage arK! ~idlKll . This method works best where combined chlorine is used for disinfection.

="d Flow pacing with online re~duol

dllorine monitoring after initial demand and automatic control

Flow poc;ing with online free and combined residual chlorine monitoring and outomatic conlrol

In thi$ method, the chlorine rll$idool i~ measured 0 short distonce downslream from ~ point of chlorine addition. The readings from tne wa s~aler Rowmeler and tne resiclvol chlorine monitor are led to a PlC to provide more precise control of chlorine dosage one! residual. This meIhod works best where combined chlorine is used for disinfection. This apprC>OCh is used lor the disinfection of nitrified effluents with free chlorine where a variable fElsidual ammonia must be removed to reoc:h !he breakpoint. The free arK! combined chlorine residual concentrotions along with the readings from the wostewater flowmeter are fed to a PlC 10 provide more precise control of chlorine dosage. This opprooch is complex as !he PlC mus/ be programmed 10 recognize tho difference between free arK! combined chlorine re$lduols and be able 10 interpret the doto with respect to the chemistry of the breakpoint reodion. Dola from on online ammonia anolyzer, now ovoiloble lor field use, con a lso be integrated with the otner doto fed to the Ple 10 optimize tne disinfection proce» with free chlOfine.

oAdapIed in port from Kobylinski et 01. (2006).

12-6 Design of Chlorination or>d Dechlorination Focilitie,

1349

because of the increase in chlorine demand needed to disinfec t microorganisms embedded in floc particles. With manual control it is difficult, if not impossible, to mair1t3in a constant cr, system monitoring and control is resource intensive, manual system is resource intensivc; and chemical usage is higher due to residual variability. With automated systems, the abil it)' to maintain the online analyzers is of critical importance if the bene fit ~ of au tomation are to be realized (Hurst, 20 12). Where free chorine is to be used as the disinfectant, dosage control is more difficult, espcci:dJy if the concentration of residual ammoni a in the emuent to be disinfected is somewhat variable. As noted in Table 12- 18, both free and combined chlorine residual monitors can be used in conjunction with readings from the influent wallt

for continuoos

c...... con/ad lank

Continuoo s Injection of tracer using positive dispIIlcement pump

Conduct of Tracer Tests. In trucer studies. 11 tracer (i.e .. a dye. most commonly) is introduced into the infiuc n\ e nd of the rcaCIQ" or basin (0 be studied (sec Fig, 12- 25). The time of its arr ival at the emuenl end is determined by collecting a series of grab Signed UV dose, mJ/cm 2

vol~

UV dose, mJ/cm 2

Predicted, 75% a UV dose, mJ/cm 1

Predicted, 75% PI W dose, mJ/ crn?

PrediOed

75% tronsm inonce l.30

2.237

2.280

2.248

2.227

1.60

2.101

2.077

2.056

2.029

1.78

1.951

1.959

1.936

1.910

1.90

1.902

1.875

1.847

1.824

1.30

2.100

2.060

2.028

2006

1.60

1.850

1.857

1.835

1.809

1.78

1.720

1.739

1.715

1.690

1.90

1.640

1.654

1.627

1.604

55% trorlsmittanoo

2.

Correcllhe lower 75 percent PI val ues for lamp a ging and foul ing. a. To account for lamp aging and foulin g a correction factor of 0.72 will be ap plied. Note: the desigt, e ngineer must decide if add itio nal fac tors of safety may be req uired, depending on local conditions. The UV dose based on lam p aging and fouling is g iven in the followi ng table in which the log- l ran~formed values have been transforme d bac k to arithmetic form.

12-9 UltroviQlet (UV) Radiation Di.infocrioo

Flawrate, Llmin·lamp

Assigned UVdo::.e, mJ/cm1

1419

Predicted uvdo::.e, mJ/cm 2

Predicted LN do::.e at 75% PI, mJ/cm 2

Correction factor for lamp oging and fooling

Design UVdo::.e, mJ/cm 2

75% transmittance

20

172.6

190.5

168.5

0.72

121.4

'0 60

126.2

119.5

107.0

0.72

77.0

89.3

91.0

81.3

0.72

58.5

80

79.8

74.9

66.6

0.72

48.0

20

125.9

114.7

101.5

0]2

73.1

'0 60

70.8

72.0

64.4

0.72

46.4

52.5

54.8

49.0

0]2

35.3

45.1

40.1

0.72

28 .9

55% transmittance

43.7

80

b. T he linear regression equation, the 75 pcrpOI

< 1()6

8.91 X 10l

9.55 >< 1()6

9 .95 x 103

1.13 X 1(}7

4.79 X 10"'

1.03 X 1()"

5.95 X 10-

1.08 X HY

8.35 X 10'

1.19 X 10"

1.00 X lOS

8.95 X 1()6

6.61 X 10"'

l.l1 x lQ7

7.68 x 1(}'

1.00 X

2 3 1 2 3

Wastewater 2, ~ho~/mL

7

1.29 >< 10

1.12 X 10'

Us ing the given data. for water 1 or 2 (wa1 er 10 be selected by instructor), develop design equations based on (I ) Ihc regressi on analys is. (2 ) Ihe 75 percent predi ction interval . alld

Problems ond OiK\luion Topi;clti ng. resulr~

Flowrote.

Botlo~t

logiO MS2 Ixx:teriophoge

Vmin

output, %

itlQ(;tivotion

180 180 180 400 400 400

100 80

560 560 560

100 80

732 732 732

100 80

7.7559 6.7445 5.4219 6.3555 5.383 5.383 5.5775 4.7606 3.5547 5.0718

50

100 80 50

50

4.2549

50

3.2046

12-24 Using Ihe data frorll Problem 12-23, develop the design Curve hused on thc regression anlllysis taking into account flowrate :md ballast selli ngs. PIO! the o rigina l data, the regression curve, and the 75 percent I)rediction in terval.

12-25 Review the current li terature and prep.1fC an :useSSlllenl of the usc of low-press ure lowintensity vel"$us low-pressure high-intensity UV disinfection systems for the di sil1fa.:tion of filtered seco ndary emuenl. A minimum of 3 articles antVor reports dat ing b:Jck to 2005 should bt;: cited in you r assessment.

12-26 Using tile 0 and Z values given in Table 12-36, determine whether the eDPH p.'$te uri7..l1tion requirements of S2°e for 10

~

is s uffici e nt to achieve a 4-log reduction in MS2 coliphuge.

12-21 TIle following data were o btained from a pilot-plant pasteurization lest. Using these data determine the D and Z \"alucs. If the temperature wen: increased to 68~e, how long would ittOlke to achieve u 4-10£ reduction?

Ob--J log nodud;on at indicated time

Temp .. ·C

3,

60

0.25 0.55

65 70

1.80

7, 0.4 1.32 4.35

10, 0.5 1.8 6.00

1442

Chapter 12 Disinfection Processes

REFERENCES BaUma1ln . E. R .. and D. D. Ltl(lwi g (J 962) "Free Avai lable C hl orine Res iduals for Small Nonpubl1c Wmer Supplies:' J. AIVWA, 54. I I. 1379- 1388. Bellar. T. A .. anl.l J. J. Li chtenberg. (1974) "Determin ing Volati le O rg.1nics al Microgram-per- Litre l.cve ls by GllS Ch rom~llogmph y," J. AIVWA, 66, 12, 739-744, Bi ll Smirakos, B" K. Birche r, and A, Salvc son (20 13) " Dcvelopn1 c nt , Chal le nges a nd Validation of ;1 Hig h- Efficie ncy UV Sysle lll for Water Re use and Low Em uent Quality Wastewater:' WEAO 201 3 Techtl1cal Conference, Toronto. O mario, Canada, Black & Veatc h Corpomti o n (2010) Whirl' '.I HfI/!(f/)()()k of Chlnrina/iOll lind AllcrtUlIh'(! f)isilifu·/tIIl/,V, 5th. eli" Joon Wiley & Sons, Inc .. Hobo ken. New Jersey. Blackmer. F.. K. A. Reynolds. C. P. Gerba. and I. L. Pepper (2000) "Usc of Integrat ed Cell Cult urePCR 10 Eva luate the Effecti veness of Poli ovj ru 8 IlmClivati on by Chlo rine." Appl. £lIl'i/OlI. Minvbh!/. , 66. 5, 2267-2208. Blatc hley. E. R. et ;11. ( 1995) "UV Pi k)! Testing: Intensity Distribu tions and Hydrodynamics:' J. E'lI"imll. Eng. ASCI:.: 121, 3. 258- 262, Blul11e, T., I. M"ninez. a nd U. Neis (2002) " Wa~tewater Disinfect ion Us ing Ultrasound an d UV Ligh t:' in U. Ne is (cd.) Uilmwlllu/ in EIII'irol1mt'll/(// Engineering JI. ISS N 0724-0783, IS BN 3-930400-47-2. Blullle, T .. nn d U. Ne is (2004 ) "Combined Acou s tic ~ I -C he micill Method for the Disi nfect ion or Wastewater." C/len/ica/ Il i-ller (Inti Wusle"'Mer Tre(llmell/, 101. VIII. 127- 135. Proceedi ngs of the 11 th Gothenbu rg Symposi um. Orl ando, R... BUllerfl cld. C. T .. E. Walli e, S. Megreg ian. and C. W. C hlllllbers (1943) " lnt1ue nce of pH and Temperature on the SUI'v ival of Coli fo nns and EnteriC pathoge ns When Ex posed to Free C hlorine," U,S. P"blic lIeallil Suvict Rt'llUr/, 58. S I. 1837-1 866. Ca re ll i, C" and C. Lubell0 (2003) "Wastewate r Dis infec tion with PAA and UV Combi ned Treatme nt: a PilO( Phmt Study," Wmer Re" ',, 37, 10.2365- 237 1. C he n. 0 .. X. Dong. a nd R. Gchr (2005) "A llem ati \"e Disi nfectio n Mec hanisms for Wastewa1ers Us ing Co mbined PAAlUV Processes:' in Procel'llirlgs of WEF. IWA ami A rizona m Uer l'olluriull CUll fwl A.I'.wL'ialillll C(}nferellce. Oisinjerlillll 200S, Mesu. AZ. Chick. H, ( 1908) " Invcst igm io n of the Laws of Disinfection." J. Hygiene, Brit ish, 8. 92- 158. Collins, H. F. ( 1970 ) ·'Effe-- 109. Mofidi. A. A .. E. A. Meyer. 1'. M. Wallis. C. I. B. P. Meye r. S. Rarnalingam. and B. M. Colfey (2002) '"Effect o f Ultr-Jviolet Light on Gianl ia lamb lia and Giardia muris Cysl~ as Determined by Anim;tl Infectivity.'" J. Water He.f. . 36. 2098- 2 108. Morrill. A. B. (1932) "Sedimentat ion Blts in Research and Design:' J. AWWA, 24, 9. 1442- 1458. Morri~. l . C . (1966) lbcAcid Ionization Constant of HOC I from 5"C to 35°C:' J. PhY$. Chtm. 70 , 12. 3798-3806. Morris. J. C. (1 975) "Aspec ts o f the Quan titati ve Assessment o f Germicidal Effi ciency," Chap. I. in 1. D. 1oonSOll (ed. ), DisinjecliOll: Waler and WlIslewalu, Ann Arbor Scie nce Publishers. Inc .. Ann Arbor, MI. NRC (1980) " The Di si nf~l ion of Drin ki ng Water" in Drmking Water and Heallh, Vol. 2. Safe Drinking Water Commillee. Bmlni on Toxicology and Environmental Il cal th Ha7ards, Asse mbly of Life Sciences, Natiollll i Research Council. The Nntionlll Academi e.~ Press. Washington. DC. NWR I (1993) UV DisinfcCli(HI Cuidelitre.vjor Wastewater Rec/amlltion ill 31Calijomia (lml UV /)i.~j"fecli(j/I Re.\'lwrch Need.f Itfe/llijicmion. Nmional Wat er Research Institute. Prcp~red for the California Depanmem of Heal th Services. Sacramento. CA. NWRJ :md AWWARF (2000) Ultraviolet Disinjecljoll Guidelil/e:J'/or D,.inki,lg »~ner lIlItl W1I.Yiell'ater Reclamatioll, NWRI -00-03, Nati o nal Water Research Institute and American Water Work s Associati on Research Fournlation, Fountain Va lley. CA. NWR I (2003) Ullnwiolel DisillfectilHl Guidelines/or Drinking Miler and Miler Reuse, 2nd cd., Nutional Water Research Inst itute. Fou ntain Valley, CA. NWR I (20 12) UllfCll'io/el m ." injecli"'l Guideline.l· for I)r;lrk;ng Wmer atlll WllIer Reu.,'e, 3rd cd., Updaled Edi tion, N:ltiona l Water Research Institute, Fount ain Valley, CA. O' Brien. W.l .. G. L. HUnle r. J. 1. Rosson. R. A. Hulsey. and K. E. Cams ( 1996) " Ultravio let SYSIe m Design: P'J st. Present, and Future, Proceedings Disinfecting Wastewater for Disdlilrge & Reuse." IWller Euvi rmrment Federation, Ale~aooria, VA. Ogum a. K.. H. Katuyama, H. Mitani. S. Morita. T. Himta, and S. Ohg3 ki (2001 ) "Detenn ination of l'yrimidine Dime rs in E.fchericilifl Coli and Cryplo.ffH/ridium Pan-um During Ultraviolet Light Inactivation. Photoreactivation and Dark Repair.- Appl. Em·;ml/. Mkmbi"l.. 67 , 4630--4637. Og uma. K.. H. Katllyamll. and S. Ohgaki (2002) " Pho toreactivation of £'f('herichiu coli after Lowor Medi um-Prc.'lSure UV Disi nfection Delem lincd by an Endonuclease Sensitive Site Assay." A,'pl. Em'imn. Microbiol.. 68, 12. 6029--6035. Ogu lll u, K .. H. Kmuyarna. and S. Ohgaki. (2004) "Pholorcactivatu1I1 or Legifme//(I Pneumophilia a fter Inact ivation by I-'lw_ or Medium-Pressure Ultraviolet Lamp." Water Res., 38. I I. 2757- 2763. Ona d e Velasquez, M. 1'.. I. YatlCz- NoguCl. N. M. Rojas-Valencia and c.1. Lugona- Li mon (2005) "OWtlC in the Disinfection of Mun icipal Wa~ tewi\ler Compared with I'crace tic Acill, Hyd rogen Pcro)(idc. and Copper after Ad vanced Primary Treatment,~ Pre.-.emoo at the 17th Intemat iooal Ozone Association World Congress & Exhibition. Strasbourg. France. Parker. J. A.. :md 1. L D3rby ( 1995) "Panicle-Associated Colifo rm in Seconda ry Emuents: Shielding From Ult raviolet Light Di sinf~tion ." Warer Em·jmn. Res.. 67, 7. 1065- 1075. PIlug. l. J.. R. G. Ho lcomb. and. M. M. Gomez.. (2001 ) " Princ iples o f the l1lCnnal Destruction of Microorgan is ms." in 5.5. Block (cd.) Disin!eclio/I. SleriliWliOlI, {md l)resen'uliOlI, Lippillcott Williams & Wilkins, Pbiladelphia, PA. Plummer, J. D .• and S. C. Long (2005) "Enhanceme nl o f Ch lorine Imrclivatiotl with Che mi cal !'ree Sonica tion," Presented lIt the Waler Quality Tech nology COflference. Quebec Ci ty. Canada. QU:I IIs. R. G .• M. P. !-l ynn. andJ . D. Johnson (1983) ''1lle Role ofS uspe ndcd Particles in Ultraviolet Disinfect ion." J. WPCF. 55. 10. 1280- 1285.

o.ou.

1446

Chopter 12 Di~infeclion Proce~ses

QU:llls, R. G .. and J . D. Joh nson (1985) "Modeling and Efficiency of Ult raviolet Disinfection Systems:' Water Ref.. 19.8. 1039-1046. Ra kness, K. L. (2005) Owne in Drillkhtg Waler Trealn!l'HI: Process Desigll. Operalioll mId Oplimimlioll. American Wate r WorKs Association. Denver. CO. Rennede ... J .. B. Marinas, J. Owens, and E. Rice (1999) " Inacttvation of Cryplosporid ium Parvum Oocy~tS with Ozone," Wilier Re~ .. JJ, II, 248 1-2488. Ri cc. R. G. (1996) 0

0.5-1.0

7C>-90

7-9 4-9

2.0-4.0

5{)

H

93-98

2.5-5.0

5{)

5-9

0.8-2.0

7C>-80

90-98 90-98

Type of feed

Untrootod $Iudge

Primary + WAS Anoerobicolly digested bioso!id$ Aerobically digested biosolids BW1:F (20100). bwAS _ waste octM:Ited

$ludge.

H

93-99

13-7 ln1roduction 10 Sludge Slobilizolion

1497

13- 7 INTRODUCTION TO SLUDGE STABILIZATION Sludge is stabilized to ( I) reduce pathogens, (2) elimimlle of1ensive odors, :l1ld (3) inhibit, reduce, or eliminate the polential for putrefaction. 111c success in achievmg these objectives is related to the effect s of the stabilization operation or proces.~ on the volat ile or organ ic fraction of the sludge. Survival of pathogens, release of odors, and ptllrefoct ion occur when mi croorganisms are allowed to tlourish in the organic fraction of the sludge. The means to eliminate the~e nuisance conditions is mainly related to the biological reduction of the volat ile content and the addition of chemicals to the sludge or biosolids to render them unsuitable for the survi val of microorganisms. Stabilization is not prJctieed 3t all wastewater treatment planl~, but it is used by an overwhelming majority of pl:mts ranging in size from small to very large. In addition to the he:thh and aesthetic reasons cited above. stabili zation can result for volume reduction, production of us,1ble gas (methane), and improved sludge dewaterability. The principal methods used for stabilization of sludge are (I) alkaline stabilization, usually with lime: (2) anaerobic digestion: (3) aerobic digestion: and (4) com~ ti ng. These processe..'i are generally defined in Table 13- 23. Each of the processes, with the exception of

Table 13-23

I Description of sludge stabilization processes Proc:e55

Description

Comments

Alkoline oobilization

Addition of on alkaline material, usually lime, to maintain 0 hign pH level to effect the de5hvdion of pothogenic orgonisms.

An odvontoge

Anaerobic digestion

The biological conversion of organic motter by fennentotion in a heated reactor to produce mclhono gd, and di scharged through contined cubes. Two major ty~s of confined systems are the gas lifter lind the gas pis!On Isee Figs. l3-2J(c) and (d)l. The gas li fter system consists of submerged gas pipes or lances inserted into an eductor tube or gas lifter. Compressed gas is released from the Illnces or pipes, and the gas bubbles risco creating an ai r-lift effect. In the gas piston system, glls bubbles are released intermittently at the bottom of a cylindrical tube or piston. The bubbles rise and act like a pislOn, pushing the sludge to the surface. These sy.~l em s are suitable for fi xed, float ing, or gas holder covers. Mechanica l stirring systems commonly use low-speed turbines or mixers lsee Figs. 13-23(e) and (OJ. In both systems, thc rotating impcller(s) displaces the sludge. mi xing

13-9 Anoerobic Digestioo

151 5

Table 13-32

ISummary of advantages and disadvantages of various anaerobic digester mixing systems Type of mixer

Advantages

Disadvantages

All ~y~lems

• Increased rate of bioKllids

• Corrosioo and tear of ferrous metal piping and supports • Equipment wear by grit

rJobi1i:totion

•

Equipment plugging and operalioool interference by rags

• • • •

COfrosion of gas piping and equipment

G :u injeclion. Unconfined: Cover-mounted ~~~

BotIom-mounied diffusers

• lower mointeoonce and less hindrance to deeming than bottommounted diffuWln. Effective agoinst scum buildup

Better movement of bottom deposits thon ((MIr-mounted lances

• • • •

•

High rnoinleoance for compreswr Potential gos-seal problem Compreswr problems if foom geb inside. KIIids deposition Plttgging of gas lances Entire tonk contents are not mixed COfTOSion

01 gas piping ood equipment

High maintenance for compressor Potential gcn-seol problem

• Foaming. Incomplete mixing • Scum formation

•

Diffuser plugging

• Bottom deposits con oller mixing pallerns • Requires digeSler dewatering for maintenance Coofined: Gas lifters

• Belter mixing 000 gos prodvction 000 better movement of bottom deposits than cover mounted lances. lower power requirements than cover movntod lonces

• •

Corrosion of gas piping 000 equipment High maintenonce for compressor

• Potential gos'!.eQ1 problem

• • • • •

Corrosion 01 gas lifter Lifter interferes with digester cleaning Scum buildup Does not provide good lop mixing Requires dige.ter dewatering for maintenance if bottom ~oted

Gas pistons

• Good mixing efficiency • Less wsceptible to plugging due 10 rags

Of

fibrous material

• Provides surfoce ogilolion for monogemenl of scum layer

• Con con1Sue and natural gas neet "ehicles are already in opcmtion. Use of CNG can also be a ~ ubstantial cost savings in areas where gasoline prices are highe r. Several teChnologies are availuble for gus purificmion. The common technologies for gas purilicalion are water adsorption. chemical udsorplion. preSSlUC swing adsorption ( PSA), and c ryogcnie ~eparation.

Digester Heating The heat requirements of digesters consist of thc amount needed ( I) to mise the incoming sludge to digestio n tank te mperatures. (2) to compcns.'lte for the heat losses through w:..lls. 1100r. and roof of the dige~tcr. and (3) to make up the losses that might occur in the piping between the ~ource of heat and the tank. The sludge in digestion tanks is heuted by pumping the sludge through external heat exchangers and buck to the tank.

Analysis of Heat Requirements.

In comp uti ng the e nergy required to heat the incoming sludge to the temperature of the digcs tcr. it is assumed that the specific heat of most sludges is essentially the same as that of watcr. The assumption that the specific heats of sludge and water arc essentially the same has proved to be acccptable for engineering computations. The heal loss through the digestcr sides. top. and bottom is computed using the followin g expression: q "" UA 6 T

113-17)

where q = heat loss, Jls ( Btulh) U = ovcmll cocflicicnt of heal transfer. ll m~ ' s ' oC (Btulft!·h·oF) A = cross·scctional area Ihrough which the heat loss is occurring, m! (ftl ) 6. T = temperature drop across the surface in question. °C (OF ) In computing the hcatlosses from a digester usi ng Eq. (13- 17). it is common practice to considcr the characterist ics of the various heat tr:msfer s urfaces separately and to

develop Intnsfer coefficients for each one. The applicntion of Eq. (13- 17) in the computation of digcster heating requiremcnts is illustrated in Example 13-7.

Heat· Transfer Coefficients. Typical O\'cmll heaHransfcr coefficients are reponed in Table 13-35. As shown, scparate entric.~ are included for the walls, bottom, and top of thl! digester. Digestion tank walls may be surrounded by eanh embankments that serve as

Chapter 13 Processing and Troolmant of Sludges

1526

Table 13-3S

I Typical values for the overall coeHicients of heat transfer for computing digester heat losseso U.S. customary, Btu/ft2·"F·h

51 units, W/m 2 .,,(

300 mm (12 in.} thick, oot insulated

0.83-0.90

4.7- 5. 1

300 mm (12 in.) thick wilh air space plus brkk facing

0.32..{).42

1.8-2. 4

300 mm (12 in.) thick well with inSt/lotion

0.11-0.14

0 .6-0.8

Surrounded by dry earth

0.10-0.12

0 .57--0.68

Surrounded by moist earth

0.19-0.25

1.1-1.4

300 mm (12 in.) thick in contad with moist eorth

0.5

2.85

300 mm (12 in.) thide. in oootoci with

0.3

17

hem Plain coocrele walls labove ground)

Plain collCreie walls (below groond)

Plain concreto noo~

dry earth

Floating coven With 35 mm (1.5 in.) wood With 25 mm

II

deck, built-up roofing, and 00 insulation

in.) insulating board instoned under roofing

0.32-0.35

1.8-2.0

0.16-0.18

0.9-1.0

0.70-0.88

4.0-5.0

0.21 -0. 28

1.2-1.6

0.53-0.63

3.0-3.6

0.70-0.95

4.0-5.4

Fixed concreto covers 100 mm (4 in.) thick

and covered with builh.op roofing , not inwloted

100 mm (4 in.) thick and covered, but insulated with 25 mm (J in.) insulating board 225 mm

19 in.) thick, not insuloted

Fixed steel caven 6 mm (0.25 in.) thick aAciapled in pert from U.S. EPA (1979).

insulation, or they may be of compound construction consisting of approx imately 300 mm ( 12 in.) of concrete, insulalion, or an insulati ng ai r space, plus brick facing or corrugated Ollumin um facing over rigid insulat ion. The heat transfer from plain concrcte walls below ground level and from floors depends on whether they aS a fXlrous ~Iter belt to promote gravity water droirl(]ge.

Hoot drying

The application of heal to evoporalo wolor and radvce the moisture content in biO$Olids below that achievable by conventionol dewatering methods.

Humus

Sludge removed from Iridding ~her$. The reduction of the volume of 0 solid by the thermal destruction of organic mailer. A method of composting, mainly proprietary, thot ocaS a high-temperature gas 10 fluidize solid porticles !usoolly sand and waste sludge and biosolids) to produce and sustain combustion.

contoir'lel".

bosed on the low of conservation of moss.

Moss balonce

A method lor analyzing physical systems

Multiple-hearth incinerator

An incinerator consisting af numerous hearths thol is used for tne thermal destnJdion of orgonic sludge or biosolids.

R..d bod

A treatment s~tem in which biosolids are used to grow reeds, which in tum utilize the woter,

nitrogen, and other

nutrien~ 10

stabilize and dewoler !he biosolids.

The Row properties of a liquid (generolly biosolids and sludge) that include elasticity, viKOSity, and pIo$ticity. Roory drum thickener

A rooting cylindricol screen used 10 thicken liquid streams 01 sludge and biosolids.

Rotary press

A sludge or biosolids dewatering device in which the material to be dewolered flows tnrough a channel that is bound between two rototing screens; filtrate posses through the screens and the dewatered material conti nues through the channel.

Sidestream

A portion 01 the wastewater Row that hos boon diverted from the main treatment process Row for speciolized treatmen t lsee Chap. 15).

Sludge drying beds

Devices used for the dewatering and drying of sludge and bio:solids in wl,ich a !>ami·soIid solution is ~eod over a porous (e.g., sand) Of" impervious medium ~d allowed $Cporote ond oir dry or decant. A term often used os 0 replocementfor sludges thai have not been stobiliUld by ph~icol, chemical Of" biological treatment. The term solids is no! used as a substitute for sludge in this chapter. The mass 01 dry material in sludge is referred to as the solids content.

Thickener

A lank, vessel, or device where residuals or a slurry are concentroted by removing a portion of the woter.

Windrow composting

A method 01 composting where sludge or biosolids are mixed with 0 bulking agont and arronged in windrows (1009 piles) tho! are tumad over periodically and remixed mechanically.

1564

5 Mgolld)

•

WaJ,woter required periodically throughout operating cycle

•

Cannot oblef've dewatering zona 10 optimize/adjust performarn:e

•

low noise < 68 dBA

•

Endo~ design with ~ and O8ro5Ols

hinged access dool'$ «lOtcins

U~ drive motor ranges from 0.37 to 3.7 kw (0.5 to 5 hpj depending on size of \Jnit

• low energy

• Overcming polymer doe. not dog screeo and hinder dewolefing

•

low wearing force reducE!$ odors in dewotered coke

stockpile Electrodl!'WOtering

• •

Mel:;honia are simple and eosy 10 maintoin

• Botch operation • Moderote 10 high copilol costs • Not portiC\llorly suited fa.- larger plant

•

Odor improvement and pathogen kill on the sludge and biosolids

• umiled final dryness achievable

Automatic operation

• Good res\Jlts for difficult sludge t common type of centrifuge design (WEF. 2012). In the cocurrent deSign. the solid phase tr,IVels the full length of the bowl as does the liquid phase. Cocurrent centrifuge designs ure seldom used because of maintenance problems (WEF. 2012). Process Varinbles. Process variables il ffe(; ti ng centri fuge performance, as measured by the sludge cake solids CS of BFPs, conditioned sludge or biosolids arc first introduced on a gravity dminage sect ion where it is allowed to thic kc n. In this section, a majority of thc free water is removed by gr.lVity. f"'O llowing gravity drainage, pressure is appl icd in a low-pressure section, where the sludge is squee7.eS variable... that can be adjusted to optimize performance or min imizeopemtional costs include feed pump speed and now, polymerconcenLration, polymer feed pump speed and flow, polymer mixing intensity, screw rol:Jtional speed, cake discharge outlet pressure, and washwater nushing frequency and dumtion. TIle typical performance of for a screw press system varies from faci lity to facili ty and is impacted by the type of feed, the procc.o;s variables listed above, and the physical condition of the equ ipment and controls. Typical operating performance data for a screw pres... system are presented in Table 14-7. Table 14-7

ITypical dewatering performance of screw presso Process parameter Polymer use Type of feed

Cake saiki.,

Solids

Ib/ton dry TS

g/kg dry TS

8- 20

4- 10

30-40

10-20 17- 22

5-10

25-35

90+

8.5-11

15-22

88-95

10-17.5

22-28

90+

% TS copture, % ' - - -";;':;;;';;';:';;"

Unlreoted sludge Primory Primary plus WAS

WAS

90+

Anaerobically digesled biosolids Primary

2Q-35

Primary plus WAS

2Q-35

10-17.5

17- 25

90+

WAS

17-35

8.5-17.5

15-25

88-95

17- 25

8.5-17.5

15-20

88-95

Aerobically digested WAS

• Bosed on

feedbac~

from

Krew press vendors.

' 4-2 Dewatering

1583

Filter Presses In a filler press, dewmering is achieved by forcing the waler from the s ludge or biosolids under high pressure. Adv:1ntage.,\ and disadvantages of fi lter presses are included in Table 14--2. When requiring cake solids contents greater than 35 percent on :1 routine basis, use of tilter pre.'\s is oftcn dictated a." other mechanical dewatering devices cannot achieve this high solids content consistentl y. Various types of filter presses have Ix!en used 10 dewatcr sludges or biosolids. The two types used mo~t commonly arc the fixed-volume and variable-volume rect:ssed-plate filte r presse.Cd 011 both sides, thai are supponed face to face in a vcnical position on a frdme with a fixed imd movable hcad (sec Fig. 14-9(a)l. A filter cloth is hung or tilted over each plate. The plates are held together with sufficient force to scal the m to withstand the pressure applied during the filtration process. Hydraulic rams or powered screws are used to hold the pl-90

Flotation thickeners:

5

With chamicals

H

Without chemicals

3-5

ro-95

95 90

Centrifuge thickeners: With chamital,

4-8

Without chemicals

3-.

,

15-30

22

85-98

95

2C>-50

3.

90-98

95

10-35

25

85-98

95

Belt-filre.- pren: With chemica!' Filter pre!>S: With chemicals Cenhifuge dewoief"ing: With chemicals

Table 14-21

Typical BOD and 10101 suspended-sal ids (iSS) concentrations in the recycle Rows from various sludge processesc

BOD, mg/L

Suspended Solids, mg/L

Range

Typi(ol

Range

Typical

100-400

250

80-300

200

,udge

6C>-'00

300

100-350

250

Flotation thickening wbnatent

5C>-1200

250

100-2500

300

Centrifuge thickening centrale

170-3000

1000

5OC>-3000

1000

Aerobic digestion wpernolonl

100-1700

500

100-10,000

3400

5OC>-5000

1000

1000-11 ,500

'500

100-2000

1000

200-20,()(X)

5000

5C>-500

300

101}-2000

1000

Operation Gravity thickening wpemotont: Primary sludge only PrilOOl)'

+ woste activoted

Anaerobic di~tion [two-

stage, high rotol supernatenl Centrifuge dewatering centrale Belt-filter pre$s ~Itrale Recessed·plate· ~11ef"

press

5C>-250

5C>-1000

Sludge lagoon supernatant

10I}-200

5-200

Sludge drying bed underdroinage

2C>-500

2C>-500

filtrale

[continued)

14-7 Solids Mass Balances

I Tobie 14-21 (Conlinued1

BOD, mg/ L Operotion

Range

lncinerolor KI1Ibber woler Depth filter wo1hwater Microscreen womwaier

Carbon od~ womwoler

Suspended Solids, mg/ L

Typical

Compo!Jing Ieochote

1625

Range

TypicClI

2000

500

2(}-6()

600-8000

50-500

100-1000

100-500

240-1000

50-400

100-1000

-Adopted. in port, from U.S. EPA (1987c) ond WEF (2010).

and chamctcristics of recycled flows and loads are not ..ccounted for properly, the facili ties that reccivc them may be underdesigncd significantl y. The major imp..cts of return flows find measures lhat can mitigate these impacts arc summarized in Table 14-22. ImpacT of re turned flow s on the ol'cmll treatmcnt process is discussed in detail ill Chap. 15.

Tobie 14-22

Major impacts and potential mitigation measures for return flows from sludge and bioso!idsprocessing facilitieso Source of return flow ~

.....

thickening

Process ImpClct

impClcte d

MitigCltion measure

Effluent degradation

Sedimentation

Add Rocculent oid oheod of :.edimenlotion tonk Separately thicken primary em biological rJudges Optimi~e grovity th,ckener dilution woter

Floating sludge

Sedimentation

Minimize gravity thickener delefltion time Remove sludge continuously 000 uniformly

Odor release and septicity

Recycle point

RecIvce gravity thickener detention time

by colloidal 55

Returtl Rows ahead of aeroted grit chamber Provide odor containment, ventilation. and treatment (scrubber or bio~ltar)

Biological

Rehlm odorou~ Rows to aerotion tank Remove sludge continuously and uniformly Provide $epOrotc relurtl Row h"oohnent (with other recycle streams)

Solids buildup

Sedimootahoo Biological

~

.....

dewotering

Increase dewatering unit operation lime Remove ~Iudgc continuously and uniformly Include recycle looch in moss IxIlonce onalysis

Effluent degrodotion by colloidal $u~nded solids

Sedimentation

Optimize dewatering units solids capture by improved rJudge conditioning Add "occulent aid ahead of wdimcnlotion tank Rehlm centrote/lihfote ta thickener

Provide separate retum flow treatment (with other recycle Solids buildup

Sedimentation

~lreom5)

Increase dewatering unit operation time (con/inueo')

1626

Cl>ople 12% 105

cm/sb

Soil permeability

>I x

Soil depth

< 0.6

Distance to surface water

< 90 m 1300 ft) 10 any pond or lake u~ for recreational or livestock purposes, Of any surface water lxx!y alRcially classified under state law

Depth to groundwater

m (2 ftJ

-45

(>-30

8-60

0.05--8

Screw preu-filtrate + prenate (o lkalirle orld heat stabilizatiarl for Class AI"

0.3-0.5

400-500

600-1300

120-250

10-20

(>-5

6-14

< I

Aerobic dige!.lion supernatant (mesophilic; cootirlUOUS arld intermittent aeration)

0.1--0.5

100-10,000

100-1700

100-1200

20-400

(>-400

200-350'"

200"

Anaerobic digestion supernatant (two-stage. high-role)

0.1-0.5

1000-11,500

50-5000

8.50-1800

800--1300

0

110-47()1>.
·
< ta;.;;

Se1t1ed ,." particle $ back to the erystal lizOf

~

=6

:;':.::'.". :

~elO

dewatenng end storage

CrystalijZIIf

(e) Peort- proceH

Internal

""""

Sido· Slfllil rn

Dryer

f--j-'Silter

,_ Drain

lank

Blower

(f) Phosnixft process N,,," Mg(OHl:!

rr!lt+f'l'E~'~.~'~'"

,_

Side· stream

Blower

screen

'"'I

Struvila

where mechanical agitation ond oir Ofe provided to strip CO 2 from the sidetroom. Mixer speed and oir Row are adjusted to control the

pH 10 limit the formation of ~ne cry5tols in the stripping ronk. In the crystallizef, mechanical stirring provides mixing and creoles the

hydrodynamic environment conducive ta pelletized ~truvito formation . Stirrer speed and tho product wilhdrowol roto are adjusted to pro' vide the desired pellet size of the harvested product. Magnesium chloride is used as the mogn~ium 50Urce and NoOH is added to control the pH in the range of 8.1 to 8.3 . A cry..tallizer HRT of 0.5 to 1 h is typical. Smollef" crystals ore settled in the sedimentation zone where !hey are rerurned to the crystallizer. Processing the exhaust air through on odor control system may be required.

The Peart- process was developed at the University of British Columbia for the cryltrallization af magnesium ammonium phcnphale and wos introduced at full-scalo by Ostoro Nutrients Recovery Technologies Inc. (USA). The Pear/'" reodar is a Auidized bed crystollizer with a M.'9mentoo cooslructioo where the segment or zone diameter increases from the boItom of the reodof 10 the lop 10 reduce t.e upRow liquid velocity incrementolly and reloin slruvite crystals of various sizes with in eoch zone. A liquid/solids separotian section is Ioc:ated at the top of the reodal". EffIuonl is recirculated to the bottom of the reoctror 10 moinloin the upRaw velocity profile within !he desired range. The HRT based on sideslream Row, is typically less than 1 h. As struvite pellet diameter inaemes, the pellets gradually sink from one zOlle to the nex!. The final product is removed from the bottom zone, seporolad from the liquid by ~eening, dried, and bagged. The efnvent recirculation role and strvvito retootion time are adjusted to Control tho pellet sizo in tho ~nol product. The mognesium 50Urce is typically mogne~um chloride. Sodium hydroxide is used 10 maintain the pH within the desired range. Tho Phosnillll crystallizer, developed by Unitika ltd (Japan), consists of a cylindrical reaction zone with a cooical bottom r.edioo and a larger diameter 1OIids-liquid·gos 5epCIration sectioo 01 the lop. The crystallizer ;s aerated to provide milling and \1:1 increase the pH by stripping CO 2 from the liquid. If required, tho ollhaust air is treated with on odor coolToi system. Tho HRT in the reocfion zone is less than 1 h. Magnosium hydrOll ide is typirolly used as the magnesium source and sodium hydrOXide is added to coolrol pH within the desired range. Lorger struvite pellets that se"le into the cookol section of the reodor

are pumped intermitten~y 10 a roIory drum screen. liquid

oncI associated smoller slruvite particles thot pass through the screens are sent to the mainstream plont ar returned \1:1 tho cryslollizer 10 allow the fino particlos to serve as seed material for s/ruvite pellet growth.

Return 10

CJ)'Slallizef

(continued)

Chapter 15 PIont Recyerg et aI., 2006). While this tech nology has not been applied widely in Nonh America, several procc~~s have Ix.-en in operation in Europe si nce the latc 1980s for the recovery of ammonia from municipal digester sidestrcams. manure digestion sideslreams, landlillicachate, and industrial wastewaters.

15-5

Physiochemical Processe5

lor Ammonia

Recovery ond Destruction

1687

A Ithough su lfuric acid i.~ the least expensive and most common Iy llsed, other types of acids can also be used: Phosphoric acid-produces mono-ammonium phosphme (MAP) or ; bacteria grow in the SBR is in a dense granulated form. the waste sludge is pumped through hydrocyclones to separate tne onammoll granules from the remaining Aoc""loted solids and rerum them to the recdor. ConieCJuently, the solids retention time (SRT) of the anommox boctetia approoches 40 to.50 d and the SRT 01 the remaining solids [ammonia oxidizing bodefia lAOS). heterotroplu, inert solids] is maintained around 10 d, which provides further selective pressure against NOB growth and more stable performance over a range of loading conditions (Welt et 01., 2010).

~

(continued)

lil

•" ~ w

""u ~ c 0 U

'i, c

i

~

t

:;;

• "R 0

-'"• ••

1712

." 0

l

m c

~

0m

"

~

~

..,z

.,

!~

-'m .> ~

-"-

I.~~ l,-. ':;>2..-.'l-

-.

n !1 . ()'j~

It , c

J!

~

•

1•

~ •

••

'"

S

• 0

- 0

~~

•Z g

•~

" ~~ ~~

., "

oo,

:Ql!'

~

&

x

,, •z ~

'~~

~

•~

a

~- : /'~.a:;;:, l-

• Il

0

'?

:!

~

~~ o.

-.

~

!& ~~ ~.:~l£!: 1-

~

'"£

.~

"• ~

•

~

~
:J + O.IIHCO)

---jo

O.44N? + 0.11NO J + 1.11C01 + 2.56H}0

Denitritotion lexternol rbCOO): COO + a NO, + b CO, -+ a HCOl

- 18.6 Ml/kg-N

+ 0.5b Nl + C eifi.,NC1 + d HP Denitritotion [primcrylsocondary sludges): eODvss + e N02 + f CO 2..... a HeOl + O.sf N2 + 9 NH.HCOJ + h H10

: 1- 17.0 + 125.5 x YH'IJ MJ/ kg-suming a sidestrcam alkal inity of 3150 mgIL as CICO). estim:lte the sod.. a~h (N ..1CO,J dosing mte requircd for complete nitrification of the sidestream arnmoniunt-N in a separate reac tor perfol'llling on ly nitrification, Describe how the wda ash dosi ng rc,!uin; ment wuuld change if the sidcstrca m treatment process is modified from nilrificatiOll-ucnilrificat ion to nilrilalion-dClli tri lalion.

REFERENCES w., C, E. Schultz, J. W. Mulder. M. C. M. van Loosdrccht. W. R. L , van def Star. M. Strous, and T. Tokutomi (2001) "The Advance o f AnannllOx,"" w,"/fa 2 I. 36,2.36-37, Abn1:l. W. R .. W. DriesSC/1, R, Ha:lrhuis, :md M. C. M. vml Loosdrecht (2010) "Upgrad ing of Sewage Trees used for the trea tment of odorous gases prc.'iCnt in the vapor phase are (I) biofilters and (2) biotrickling filters (Eweis et al.. 19(8). 'Ille use of microbial growths for the treatment of odors was the s ubject of an early patent by Pomeroy (1957), one of the important early rescarchers in the area of odor ma nagement in wastewater collection and treatment facili ties. Iliofiltcrs. Biofiltcrs arc pac ked-Ix:d filters. In open biolilters (see Fig. 16---1O(u)J. the gases to be treated move upward through the filter bed. In closed biofilters Isee Fi g. 16---1 O(b) I, the gases to be treated are either blown o r drawn through the packing material. As the odorous gascs move through the packing in the biofiher. two processes occur simultaneo usly: sorption (i.e., absorption/adsorption) and bioconversion. Odorous guscs ure absorbed into the moist surface biofilm layer a nd the surfaces of the biofilter packing material. Microorganisms. pri ncipllily bacteria. actinomyeetes, and fungi. lmachcd to the packing material. oxidize the absorbed/adsorbed gases and renew the treatme nt capacity of the packing material. Moi stu re content and temperature are importilnt env ironme ntal condi tions that must be maintllined 10 optimize microorganism activity (Williams and Miller, 1992a. 1992b; Yang and Allen. 1994; Eweis et al.. 1998). Although compost biofilters are used commonly. o nc d rawback is the large surface area (footpri nt) req uired for these uni ts.

Figure 16-10 Typical

poded bed

Trootod",ir

PiIcking material

bioliller~.

(0) open l-J type and (h) enclosed reoctOf type. treated

(.J

Pertoratoo pipe

Gravel layer

,---~

Treated air

(i'1>'!?~T - Wat(l' sprinkle,

to moisten packtng

"; .•,. ;.

Packing material

matClrial

....

~~t: --{l--e>---t--=-~-=--=-~--~-:r

""",,,.,, Steam (b)

inioctClr

Dmln

175 8

Chopler 16

Air Eminio.... from Wostewolef TreoImenl Focir.ti81o ond Their Control

Trnated ait"

coIect"", system Rota~ng

or fixed wastewater dist~butlon

system

Water to moiston packing materlat

To """"""

Plastic packing Pe~0 now. For this method of odor control to be sustainable.t he waste gas must typic.llly contilin 50 percent of the fuel value of the g:ls stream to be combusted. Ca tlll)'t ic oxidatiull. A nameless o,\ idiltioll that occurs in the range fro m 3 10 to 425 ~ C (600 to 800~ F) in the presence ur a catalyst is dc/ined as catalytic oxidation [see Fig. 16- 12(b)[, Common ca\lll y~ts include platinum. palh.ldium, and mbid ium. The decrease in temper:ll ure as compared to complete lhermal oxidation I'ed uces Ihe e nergy req ui rements significantly. Howe\'cr, because the cmaly:-.ts Cim bet'Ome fouled. the gas to be

Addilional

_ dilulioo air. if required

Calalyto:::

Combuslion ~1Jr

inciooralor

_ ,---"0;:'1'''-,

S""

I--+'W+-=

Sl.Wlemeolary

",,'

""'r+-LlI---'

e~cnaroger

(Oplional)

Prvheater Ca!aly!;;1 bed

Prehea1ed VOCs

(bl

'"

! ~me"lary Addilionat

d~ution

,...

sr.

~ reQUlntd

........... , C«_

1,

/'

To

"'"

Preheated VOCs 'oj

,OJ

Figure 16-1 2 Schematic diagrams of thermal procenes for treotment 01 \lOCs: (0) thermal o~idotion, Ib) ~otolytico l oxid izer, Ic) recvperot ive thermal oxid i ~er. and (d) regenera ting the rma l o~idizer.

1760

C~1ef 16

Air Emissions from WosleNoler Treolment Focil,ties ond Their Conrrol

oxidized must not contai n particulate material orCOllstitucnts that wil l resu lt in a residue. Additional infonnation on the physical facilities used for thermal processing of VOCs may be found in Sec. 16-4. RccUI)Crutive and Regenerative Thermal Oxidation. This process involves preheating the odorous gases before pa~si ng them inlO the combustion chamber so that complete oxidation can be ach ieveO. Coml>ustion occurs aI temperatures in lhe range from 425 to 760°C (800 10 I400°F). Reculx:["ative and regenerative thermal oxidation processes are used to reduce fuel (;QlIsumption by prehe 30s)

Detennine if the volume of the biofiher determined in Step 5 is adequatc to treat

the H1S.

16-4 Control of voIotil", Orgonig)

= 0.0427 tonne CHh

N20 emission = (Fuel oil usc, ml/y)(cncrgy contcnt, GJ/ml)(crnission factor, kg-N 2 0/OJ) = (390 m' /y) (38.47 G1/rn 3)(0.569 kg N 2 0/GJ)(l tonncll()h g) = (8536.9 g NP/y)(1 tonnc/ l()l'g) = 0.00854 tonne NzO/y

Total cmissions = (COl emission) GWPcn,

+ =

(CJ-I 4 e mission) GW POI•

+ (NP t:mission) GWPNp 1050.7 X 1.0 + O.()427 X 2 1 + 0.00854

X 31 0

= 1054.2 tonne CO 2 ely

c. Emissions from digester ga~ used. Note CO 2 emission from digester gas combustion is considered "biogenic:- Biogenic emissions arc often not required to be reponed as pan of the GHG em ission but to be reported separately. CO 2 emission = (Digester

ga~

use, ml/y)(cne rgy conte nt. Gllm 3)(emission factor)

= (755,00) mlfy)(O.U224 GJ/m J)(49,353 kg-CO/GJ)( I tonneiHl' g) = (834,657,936 g/y)( 1 ton nc/l 0" g)

= 834.7tonne/y (biogenic) CH 4 e mission = (Digester gas use, mJ/y)(e nergy content, GJ/ml)(emission fac tor) = (755,00) rn J /y)(0.0224 GJ/ mJ)(3.033 kg CH/GJ)(l tOIlIle/I{J> g) = (5 1.294 gCHiYXI tonneJ lO"g) = 0.0513 tonne-C H~/y

N10 e mission = (Digester gas use, mJ/y)(energy content, GJ/ml)(emission fac tor) = (755.000 ml /y)(O.0224 GJ/m J)(0.597 kg N z O/GJ )( 1 tonnelllY' g) = ( 10.096 g N10 /y )(ltonneJI O"g) = O.OlOllonne N 20 /y

16-6

Total emissions

~

Emi5sion of Greenhouse

Ga5eS

1789

(C04 emission) GWPCIl ,

+ (NzO emission) GWPNP = 0.05[3 X 21

+ 0.0[01 X 310

= 4.21 tonnc CO 2 ely

Biogenic emissions = (C0 2 emission) GWPco, = 834.7 =

x

1.0

834.7 tonne COl ely

d. Emissions from digester gas flared. In the LOG Protocol. digester gas flaring is assumed to leave I percent of the methane gas within the digester gas due to incomplete combustion. and no nitrous oxide emission is assumed from the digester gas flaring. The approach taken by the LOG protocol is followed in this example. Similarly to combusted digester gas, CO2 emission is considered "biogenic:' CO 2 emission ::: (Digester gas flared, ml/y)(energy content, GJ/m')(emission factor)

= (290,500 m-1/y)(O.0224 GJ/m 3)(49,353 kg CO/GJ)(I tonnell()6 g) = (834,657,936 g/y)( 1 tonnell ()6 g) = 321.15 tonne/y (biogenic) CH.j c:mission = (Digester ga~ flared, m1/y)(mcthane content) X (incomplete combustion)(mass of methane, g/m3) =

(290,500 m3/y)(O.60)(O.OI)(656 g!m.l)(ltonndl{}6 g)

= (1,143.408 g CH)y)( I tonnell 0" g)

= 1.143 tonne CH,Jy Total emissions = (CH 4 emission)GWP cll , = 1.I43 X 21 = 24.0 tonne CO 2 ely

Biogenic emissions = (COl emission) GWPco, = 321.15 X 1.0 = 321.2 tonne CO 2 ely

e. Emissions from digester gas vented. Of the digester gas vented to the atmosphere. 60 percent is methane, to be reported as Scopc I emission. Carbon dioxide (35 percent) is not counted in the G HG inventory. CH 4 emission = (Digester gas vented, m3/y)(methane content) (mass of methane, glml)

= (2400 m 3/y)(0.60)(656 glm 3)(1

tonnc/lO~

= (944,640 g-CHJy)( 1 tonnc!l 0" g) = 0.945 tonne-CH,Jy

g)

1790

Chapter 16 Air Emissions

from

Wa stewater Treatment Fociliries and Their Control

Total emissions = (CH4 emission) GWPCJI , = 0.945 X 21 = 19. 8 tonne COl ely

f. Determine process N2 0 emissio ns from WWTPwith nitrification/denitrification. In the LGO Protocol , process N20 emission from WWTP wi th ni trification! denitrification i~ estimated using an e mission factor of 7 g-NlO/person/y. Using the given data, the emission is estimated as Process

Np em ission =

[(P"""I X FinOgOme mole/kg

bio~id$

60.3

90.4

120.5

N,

mole/kg

bio~id$

46.6

69.8

93.0

0,

moIelkg biosolids

0

6.2

12.5

CO,

mole/kg bioKJIid s

11.4

11.5

11 .5

HP

mole/kg biowid$

45.1

45.5

45.9

Air added Flue 90S composition

Heal content of odded air at 20·C

MJ/kg

bia~lids

0.524

0.786

1.05

Heal content 01 biosolids at 20"(

MJ/kg biosolids

0.066

0.066

0 ,066

FltIC 90S heo t content at 850' (

MJ/kg biosolids

4.057

5.119

6.180

Ash hoot content at 850"(

MJ/kg biosolids

0.079

0.079

0.079

Energy releosed Imm combustion

MJ/kg biosolids

5.446

5.446

5.446

Hoot loss by evaporation 01 water

MJ/kg biosolids

1.783

1.783

1.783

Syslem heat loss

MJ/kg

bio~lids

0.021

0.023

0.024

Net energy balance

0.095

- 0.7

-1.5

• Un its are per kg biO$Olids on a W1II bo" o. No"': Because value. were colculoted on" Sopfeod.heelond rounded , some volue, may noI match e~octIy with manuol calculations.

4.

Comment

Determine the water conte nt that will allow self-sustained combustion. From Step 3, the heat generated by combustion of chemical co n te n t~ in the biosolids is barely sufficient to maintain the heat balance. The refore in this example, 30 percent solids, 70 percent water content was the limit to s ustain combustion. At water conte nt of 7 1 percent, thc heat b.alance is - 0. 12 MJlkg biosolids. It is important to note that al. stoichiomeuic air flow, the heat content in the flue gas is approximately 4.1 MJlkg biosolid and operational conditions such as excess lIir requ irement a nd operating te mperature. In biosol ids incineration facilities, inlet air is oftcn preheated wi th Oue gll~ to save the use of supple mental fu el. In a lypical incineration faci lity, a solid content of 26 to 28 percent is considered the thres hold needed to sustain combustion without supplemental fuel. but no s ignificant excess e nergy will be ayailable for other purposes. During the pla nt stan up, supplemental fuel must be used to raise the tcm penatu re of the reactor.

17-6

RecovefY ond Urilizotion of Chemicol Energy

1833

Energy Recovery from Syngos There are two approaches to utilize e nergy from syngas. One is to clean the syngas and use it for conventional boilers and engine gencralOrs, oncn referred to as two-stage gasification. The other approach is to use the syngas directly in the thermal oxidation chamber, referred to as close-coupled gasification.

Two Stage Gasification.

In two stage gasification systems, asdepicled on Fig. 17-11 (a), the syngas produced from gasifying the dried biosolids is cleaned and the cleaned syngas can be u. exhaust heat of engine genemtors that has gone through a series of heat exchangers, could be utili7.ed 10 operate heal absorption chillers or other tcchnologies to pro\'idc cooling and refrigeration (see Fig. 17- 16). [n t1bsorption chillers, lithium bromide is used

17-7

Recovery and lhiliwtion of Thermol Energy

'843

Retrigarant vapor

~L

~" ~

COOting water_

'I I - I _

-

~ Liqoo

-

'

,

. ~\

Eva~

"""""'' \:' Diuted

absorbent

""'

absorbent ._,

~Absorber

,

---

Heal SO

y" gellCrnted. Another factor which can affect the selection of an appropriate type of CHP is the size of the faci liry and the goals for energy recovery. Smal l to medium size facilities, with a goal of producing electricity may uSC a technology such as the ORC with - 10-20 percent electrical efficiency to recover energy from excess flue ga.,> generated. Larger facilities with similar goals may select high pressure steam turbines with approximately 15~38 percent electrical efficiency. Economic and operational issues must be evaluated to determine if an add-on CHP system is practical and what the appropriate size and type of syste m should be. Hent Recovery from Wastewater. The le mperuture of wastewate r is typically higher than that of potable water, and the variation in wastewater temperature is smaller than that of ambient temperature (see Fi g. 17-17) th ro ughout a year. The heat from wastewater is a reliable source of thermal energy for benefici:ll uses d uring the colder season, and it can be used as a heat sink during the wanne r season. Depending on the size of the treatment facili ty. the rmal energy can be used to supplement heating requirements within the wastewater treatment facility, or integrated into a district heating/cooling syste m. Because the available heat in wastewater is low, a heat pump is used to extract heat from was tewater ( Pallio. 1977). Depending on the availabi lity of hem, heating of a specific building within a wastewater treatme nt facility may be cons idered, o r it may be integrated into the centralized healing system for the entire trea tme nt plant. The esti mation of heat to be recovered from wastewater is illustrated in Example 17- 7. Heat recovery from raw wastewater in the collection syste m o r at the beginni ng of the treatment faci lity can also be considered. When heat is recovered from raw wastewater, the impac t of lowercd wastewate r te mperatu re on the treatment pelformance must be evaluated (Wanner et al., 2005). In North America, healing or cooli ng capacity of air conditioning equipmenl is often measu red in terms of the tons of refrigeration. One Ion of refri geratio n is approxi mately 12,000 Btulh or 3.5 17 kW. Similurly, the power requireme nt for the heat cxtraction is often expressed in brake horse power (bhp) per ton of refrigeration. One horse power (hp) is approximately 0.745 kW. Thus. if a powe r requ ireme nt for!l hent pump is ratcd as 1.0 bhpl ton. then 0.745 kW is required \0 provide 3.5 17 kW of heat extraction.

Figure 17-17

350,--- - -- - - - - - - - - - - - - ,

Seasanal voriatiOf1 01 ambient temperoture ond WOlfflwoter temperature in north eastern Un ited $totl».

300 25.0

200 15.0

/_,Averaga dA~ high Air Wastewater effluent

\

r-------

10.0

\, AWlra9" lkIy low air

0.0

17-7

EXAMPLE 17-8

Solution

Recovery and Urilization of Thermol Energy

1845

Heat Pump for EHluent Heat Recovery

A water to water heat pump is to be used to provide heating in a building at a wastewater treatment plant. The heat source is treated effluent. The lowest effluent temperature is 12°C, and temperatu re drop of the efflucnt in the shell and tubc heat exchanger is assumed to be 4°C. A 40 percent propylene glycol mixture is used as an intermediate heat transfer medium to extract heat from the cffluent, and the heat pump will have an 8°C entering temperature and a 5°C leaving nuid temperature. The peak heating requirement for the building was estimated to be 360 kW. A heat pump supplier was contacted and a heat pump was selected requiring 0.222 kW electrical input per kW heat output to extract 300 kW from the effluent. I. Calculate the COP for the heat pump, and the heat output and the electrical power input in kW of the heat pump. For simplicity, assume compressor efficiency = I 2. Three circulation pumps, 14, II, and 15kW, are used to transfer effluent to the heat exchanger and to pump the glycol on each side of the heat pump system. Calculate the overall sysl~m COP including pumping pow~r. 3. Given the energy to be e,...lracted from wastewater and assumed tempemlure drop, determine the wastewater nowrate that needs to be transferred to the heat pump system.

I.

Calculate the COP for the heat pump using Eq. (17-24). Power input = 0.222 kW per I kW of output 1.0 COP = - - = 4.5 0.222 Using Eq. (7-25) and ignoring the heat loss from the transfer of the hCinl

rating point

•

Wasted energy

Required energy Flowrate

{O,

{" System curve

shifted by throttling

Operatir>g poinl

Flowrate

Delivery flowrate lower due 10 recirculaling

-----/"-cl- Operating point

Flowrate

{ and technologies rely o n the collection and anal ysis of data that enable the owner to analyze a range of performance me tries to support strategic decision making. Practice of Asset Management. To date, tlte most widespread development a nd imple mentation of AM has been in Australia, New Zealand. and the UK where the performance of all aspects of the water and was tewater industries are more closely regulated. From the experience gai ned in these countries, it is clear that although if takes a number of years to see true fina ncial returns, there are very real benefi L'> by adopti ng more advll nced AM tcc hniques. While reguliltOl)' requi rements in the United States do not require the implementation of AM , many llgcncies including WEF. AWWA. and the Association of Mctropol itan Water Agencies (AMWA) have taken a lead role in promoting AM. The U.S. EPA conti nues to blend education of the principles a nd tools, wilh a formal need for implementation as a compone nt of compliance regulatio ns for individual agencies and owners.

Asset Management Methodologies. There are many AM techniques a nd tcchnologies and it is beyond the scope of this text to discuss each of the m adeq uately. Numerous publications are available to provide guidllnee but the fu ndamental core is in understanding the required performllnce from an asset li nd being lIble to operate lind mai ntain the asset cost-effectively. In general, AM techniq ues inelude (I ) developing an asset inventory. (2) assessment of the condition of asset, (3) determini ng the level of service to be provided, (4) identifying the critical asset to sustain the perform:lncc. (5) dete rmining the cost for Ihe e ntire life cycle of the ll~set . and (6) detc rmining the best lo ng-term strategy. Agencies that have a mature understanding of AM wi ll likely have a belle r understanding of the condition and remllining life of thcir infrastructu re and of the best maintenance methodologies. This level of knowledge can prove to be benefi cial as age ncies, with such an approach. are considered to be well man:lged businesses. Information o n AM is also needed to justify funding either to customers, fi nll ncial institutions. or within their own organization.

Ramifications of Asset Management. While much of the current focus of AM is related to existing infmstruc ture, it is clear that the lifecyc1e of every asset is significantly influenced by the decisions that are made at the concept and design stages. The designer has the opportun ity to determine the o pti mum performance of the asset whi le considering c riteria relevant to operations and mainte nance. TIle correct combi nation of these interrelated fac tors will e na ble the end user to derive the most benefit wit h asset,> that provide the an tici pated levels of service wi th red uced operations. maintenance, fllld energy costs. While the principles of AM are cons idered by many to be the most effective way to manage infrastructure, there are many organizations in the United States that are still in the early stages of developing su itnble approaches. 01);anizations that have adopted more ad vanced AM methodologies arc however seeing benefits both in terms of performance

18-1 Future Chollenges 000 Opportunities

1869

levels and financial management It is clear, therefore, that u more defined implementation of AM should be considered for all aspccts of infrastmctuTC management from the development and justification of need. to the ultimate disposal.

Design for Energy and Resource Recovery The chemical and heat energy content of wastewater has been delineated and discussed

previously in Chaps. 2. 14. and 17. As noted in the eartier discussions. wastewater treatment plants could potentially become net exporters of energy. and especially so if extemal sources of energy contained in food wa~te and fal~, oils, and grease are illCl uded. The challenge in the fu ture is how to extract the energy in wastewater most effectively. For example. food waste could be ground up in kitchen food waste grinders and transported to the wastewater treatment fac it i ti e~ in the collection system. or it could be interccpled al various upstre.. m locations and extracted from the wastewater using a micro- or clothscrecn such as desc ribed in Sec. 5-9 in Chap. 5. The solids removed from the wastewater cou ld bc placed directl y itllln anaerobic digester. Ahefn(l(ively, conventional aerobic trelllment processes could be replaced with ambient-temperature low hydraulic retention time anaerobic treatment processes (McCarty, 2011). Heat recovered from wastewater could be used for dryi ng screenings as well as in other ap plications. especiall y in the processing of biosolids. The key concept here is to think Hbou1 how the charactcristics of wastewatcr could be altered to enhance the recove ry or energy fmm waslewater. In the future. the recovery of resources from wastewater will occur simultaneously with the recovery of energy. To date, the removal of I, itrogen and phosphorus ha.~ received the grcatest attention as nitrogen and phosphorus discharge standards have become more stringent. The option of recovering. rather than simply removing, these con ~tjtuen l~ has bccnme economi cally feasible. especially from return tlows. Biologic;11 phosphorus removnl was considered in Sec. 8-8 in Chnp. 8. The recovery of nitrogen and phosphorus in the fom, of struvite is considered in Soc. 6-5 in Chap. 6 and Soc. 15-4 in Cha p. 15. The recovery of nitrogen as ammonium sulfate is considered in Sec. 15-5 in Chap. 15. The recovery of resoun;es from fly ash following combustion is considered in Sec. 14-4 in Chap. 14. The recovery of nutrients including nitrogen, phosphorus. and pola,,~ium from urine (sec Table 3-15 in Chap. 3) is another resource recovery opponun ity that has received considerable attention, especially in Europe and Australia. What role urine separation will play in the United States remains to be seen. Clearly, finding the optimum cost and energy-effcctive approach for the recovery of resources. coupled with Ihe recovery of energy and potable water fro m wastewater will be a major challenge in the future.

Design of Wastewater Treatment Plants for Potable Reuse As a result of popUl ation growth . urbll1lization. and clim:l1e change. public water su pp li c~ are becoming stressed, and the chances of tapping new water supplies for metropolitan areas are gelling more difficult. if not impos;sible. As; a consequence. existing and new wHtcr supplies must go further. One way 10 achieve thi .~ objective is by increased w

•-·

"

u 0 0

•

0

'5

;:: N

'" ~

0

• •

•

"

~

~

]

,

~

"

N

>=.

1

2

~

,ro •

• • ~I' • • ,.

•

!

~ ~

!

N

•

,"

.2

2

o~

~¢

t · g.

,• -

~

~

~1l

~

-

~O

>

~'

• 0t

N

~ .~ -~

!1 ~u

"0.:0 0>-

": .!!

~.li

.2

0

0 0 0 u :.:::: -.:; u •

."

;; ~ •~

~

0

~

0

~

0

a

;0

i6Z1t'}/Qn) 1

"

"" 0

0

- /'JOPJl UO!PU:f

~ 0~ §0

-

.::: E

,
en, A. A. 651,652 JJanson. E. C. 53!, 548. 1223 HanlOn. B .. ])\ 1,1312 Uao. X .. 559, 588. 687 ~I ar:l, A .. 672. 687 Uart=m. G. N .. 665 ~Iamell. W. L 1601 Harp. D. L. 1323 Harrcmi'Jcs. P.. 951. IU3!! Harris, R, E. 622 H arri~. S. 1.., 1031 Harrison. J. R., 950. 9~5. 973 Harshtwgcr. J. c.. 672. 687 Hanfelder. J .. 131 l. 1322 llartmao, P.. 651. 685 llarwood. J .. 53 I. S49 'la»l,iulOlo. S" 672. 687 Halch.L.P.. 1 134. 11 35. 1136. 1140 Huoch. P.. 1278 I laug. R. T.. 623. 687. 1601 Hawkes. H. A .. 94-9. 950. 95l! Hawttoome. C I I., 861 lia)den. P. L. 471. 472. 547 Ha)ocs. W. M .. 1724 Ha~cn. A.. 1134. 1135 He. L.. 1076 I lc.I'.J .. IO'XI He. S, M .. 571. 651 Head. I. M .• 620. 622. 685.1034 Hedman.G" 1005 H~R'ma. M .. 1029 ~kidlllao, J. A .• 796. 798 Heidrich. E. S .• 1803. 1863 Hcijll.:n. J. J .. 618. 628. 650. 652, 685. 686. 6M7.740. 1(l·-I6. 1070. 1709 Heincm,tn. T. A. 978, 979.981 Hci:;e. S, M .. 1029 HClsel. C. 1539 lieU. M .. 645. 17J6 Ilellio&a. c.. 618, 687.1709 Hclhlrom. D. G .. 1008. 1019 IlcUstro,". F. 1008. 1019 He lmer.C. ]7]0. 1712. 1735 Ilenry,C .. 1640 Hcn~.e. M .. 587. 591. 5~. 627. 6li6, 687, 707. 745.747. 751. 754. 755. !!O3. 832. 849. 878. 1092, 1096 IIcppcll. N. 1.. 1428 Hering. J. G .. 469, 472 Hennann. N.. 503. 547 HcnnaOO\l>icz. S. W., 9]). 918 Herm:lns.J.H.M .. 1114 Hcnllclink. C. 642 Hernandel-RaquCf. G .. 612, 685 Hewitt. G. I'., 1840. 1863 I~iasa. M .• 705 HlaH,C.W.. 14JI Ilid,ey. R.. 946. 1026, 1014 Higbie. R.. 406. 411. 453 IHggil1:>.1. J.. 949. 950 Ilill. M, J.. 133. 178 1M. R. A.. 1477 Himab. G .. 1482

1957

Hinojosa. J" 637. 686. 850 I'li nton. S. 612. 6117. %11. 970 Hippen. A .. ]7]0. 1712. 1735 Bira.D .. 1722 H tnU~. T .. 1392 1']oadley.A. EA.. 1568 Ho.are. D. S .. 634

w..

Hobbs. P.• 1734 Hobma. S. W.. 1065. 1067

Hofer. D. A.. 900 Iloff. J. C .. 1307. 1309 Hokanson. D. R.. 1255. 1257, 12!W J-Iulbrook. R. D.. 803.1029 HOlcomb. R.G .. 14lO Holcomb, S. P., 1596 Hollaw"y. EA .• 1256 Holllilcr. C.• 665. 687 lIolm. N. C, 624. 626 Hohllllll.l. p" 1839. 1840. 1863 Hollan· Hartwig. L. 646, 687 Hom. L. W.. 1328 Hong. S. N .• 803.1029 Hong,Z.. ]7]~.1720 Hooijmam. C M .. 652, 685 Hoo"er. 5. R.. llO. 178. 564. 576, 586. 687 Hom. H .. 800 Horn. L. J .. 1022 Horne. G,. 638. 806 Hou ~. Y.. 364. 454 llooweling. D .. 588. 877, 884 I~ow. S Y.. 684 Howartl. D .. 453, lOOt HOIO-e. E. W.. 1288 Howe. K. J.• 136. ])7. 139. 178.412. 453. 501. 5 12.514. 518. 520. 521, 523. 526, 547. 1122. 1127.1298.1309.1362,1391,1952 Jh ieil.C" 1771, 1794 1111.5 .. 517,547 liu. 83. 179 111J1xr. M. M .. 503. 547 .l u~r.P.. 1710 Hudson, A .. 1429, 1432 1~ ...d:lOrl. H. F_. 47), 547 Ilugenttol1z. P.. 571. 651. 685 t ' uglles. W. W.. '64. 179

z..

Huitrie.S-J.. I309. 1336.1381.1382 Hull. T" 737. 741. 1005 Hulsbcck.J.. 74 1 Hulsey. R, A .• 1386 Hvlshoff 1'01. L. W" 1083, 10911. 1099 Hultman, B.• 1038 HUJ1ler, O. L . 1348. 1386 Husband, L 1003. 1041 Husson. fl .. 886 Hutson. 5,S" 188. 260

ICLE I-Local Governmellt for 5uslIIinabilily. 1784. 1791. 1794

lEA HiocllCf!!Y. 1783. 1794 Jguchi, T .. 672. 687 lilla. M .. 1841.1863 ll~. J.. 705. 915. 917 Imboden. D. M.• 454. 663. 667. 1771. 1795

1958

Nom. ''''''''

Imhoff. K .. 1064. 1065. 1066 Ingerle. K.. 1736 [ngr"ham.CA .• 141.145-147.179 Ing:rnham, J. L , 141. 145_ 147. 179. ISO Innerebner. G .. 641. 687 Insam. H .. 64I. 687 lranpour. R.• 885

l.$3ac$. S .. 878 IUVA.1405 h'anQva. N., 571, 651

Iza, S, M., 1080

Jocangelo, J. G.. 1200 J ~ubs,

E. P., [202

Jacobs, T., 968, 979, 983 Jaeger, J. c.. 4 18, 452 Jahng. D., 1083 Jain, R. C.. !O3. 179 Julali. Y.. 1336 J nne~. M . L .. 1380 l unovy. l .. lr.. 143, 155.1S6, 179 hnRn, J. L C . 647. 686

l an·is. S.. 968 huregi , P., 410. 453 Jeavons, J .. 1705 Jcfferwn. ll .. 1206 J cgan~ lhan , J .. \083. 1109 l enkins, D .. 469. 472. 495. 534, 616, 655, 712, 733,736,737,740.741, 892, 913. 918. 946. %8,990 Joong, J., 95, 178 l eriJ. J. S.• 946, 687. 1026. 1034 JetteR, M. S. M., 619, 634 , 640, 641, 642. 643. 644,645.647,687.688.1710. 1714. 1735 Jeung. M . K .. 453,1004 l ewell. W. J., 1065 l e/.ck, R.. gsO l iang, T.. 628 Jinw:ne'.• 1. A .• 624, 626 lin. S.. 139) Jjemba, P.. 6 19. 631. 686, 800

loo,G.D.• 1592 Joffc.l., 1328 Jnrre, I ., 1328 Johannessen. E.. 883 John, E. 5 .. ISS) Johnson, A .. 1(»5, 1067 John son. B .• 878 Johnson, C. 1., 156. 179 Johroon. G. R.. 803 Johnson, I. D.. 1396. 1446 lohnson. S. H., 955 Johnson. T. L. 999.1001.1002.1003,1004.1005 JootS, B. E , 532. 549 Jones, G. M.. 1477 Jones, R. M.. 626. 6 27. 628, 6R6, 687. 711,754 Jones, S. B., 1820. 1864

Jonsson.

K., 1038

JOfdc:n. R. M .• 473 1()ITI3, T., 1046

10S5, A.. 503, 547 lubany. I., 628, 686 Judd.S. L 705.9I7,9IR,I206

ludkin)C, J. F.. Jr., 469, 472. 505, 547 J"n~in .

L. , 918 JI,lI'C LSChko. S .. 620

Kaelin, D.. 6T1. 628. 687 Kalhom. T. E . 672. 674. 686 Kalyothnyi, S. V.. 1093, 1 lOS Knmigochi. l.. 657. 688 Kamillochi. K.. 10M Kampschreur. M. I .. 627. 628, 647. 688 Knndl cr. O .. 140. 181 Kang. I . W.. 51 3. 517. 547 Knn, . S. I ., 890 Kaonga. 8 .. 1096 Kaporil. K.. 737 Karim!. A. A.. 515. 548 Karn., S .• 1302 J'.. M. 1'.. 9112, 983 Lykins, B. W., Jr., 1232, 1233

Ma. Y.II .• 917 Maas. A .. 1005 Maas. S" 643, 687 Mad,J .• 521,549

MacMullin, R. 8., 1932, 1939 Ma~"O, R. S .. 1520 MacRlIC. I. C., 639 Mader. C.. 1033 MaoJigall, M. T.. 141. 143. 144. 145-147. 151. 152, 153. 156, 179. 563. 564. 565. 566, 573. ti'i~ Magar. V. S.. 664. 66.5. 6S4 Magba.nua. B. S., 686, 686 Maguin. S. R.. 1309, I3IU. 1382 Mah'if. 13.. 515.548 Mahmood. T.. 70S Mahmoull. A .. 156lI Mahmudov. R., 1565 Mahony. T.. 1096 Maier, R. M .. 95,144, 145- 147. 151, 154. 156. 157. 179 Maill:od~f\lvu, K. Y., 1089 Majetl. N.. 1002 Majone, M .. 741 Makhoul , N .. 161. 179 Makinia. J .. 95. 179.712,848 Malina. J. r., 1097. 1103 Malley, J. 1'" 1382 Malpei. E. 1081 Malseh.A .. I041 Mamais. 0 .. 6~5. 712 Manser. R.. 627. 628. 629. 685. 687 MJr.l. O. 0 .. 1~2. 1~3, 178 Marais. G. v. R.. 627. 650.687. 707. 712, 745. 747.751.754.755. &IX>. 873. 936 Marchesi. V.. 1115 Marinas, II .. 1328. 1446 Marsh:llI. M. M .. 1392 Martin II. G.. 651 Martin, G. I\., 57 1. 651 Martin, N .. 1392. 1393 Maninez. I.. 1382 Maninko.J. M. , 141.14), 144.145-147. 151, 152. 153. 1S6. 179,563.564.565.566.573.658 Martins, A. M .. 740 Masschclc:in. W. J., 342, 453 Masterson. T., 1005 Malschi:. N., 796 M:>lSYm~u, M. R~ 410. 453, 1858, 1864 Matsuo, T .. 627.651, 687. 705. 707, 745. 747, 751.754.755.806. 1082 !l.l:l11cr-Mullu.C..1768.ITII.17Y4 M"Hhieu.l'.. 914 Maupin, M. A, 1118, 260 MJure!, M., 63 1 "burelle. M. T.. 6 31 Maus, L .. 1289 Mavini(-. D. S .• 631. 860. 1~50 M;uwcll, M.• 999. 1001. 1004. 1005

Mazz,---'Cu, 1.. 737 McAdllJl ~, W. H., 1527 Mcardell, C. S .. 503, 547 McCabe. W. L., 1252 McCany, P. L... 6I!. 93. 123. 179,469. 4n. ~8. 580-581,582.583,586. 587. 598, 609, 6 12, 613.614,623, 631, 6~7. 663. 66~, 687. 61:\8, 712, !$61. 1064. 1065. 1067. 1090. 1507. 1802.1859.1864.1869.1900 McCauley, R. E. ~31, 548

1960

Nome Index

McConnell. H.• 987 McGarvey, F.. 1271 M~Ghee, T. J .• 435, 453

McGralh. M .• 796 Mcguric, M. J.• 12SS Mcl-/nrdy, A.C . 57 1,651 Mci nerney. M. J., 6.57 Mc Kendry, P.• 1827. 1864 Mc Ken~ie. D~ 156. 191 Mc Kinney. R. E. . 703 Mc Mahon. K. 0 .• 571. 651

Mc Muny. J .• 468. 469, 472. ~8 McQuarrit. J. P.. 1002. 10m, 1004. 1019. 1020 McW~iner. J. R.. 788 MC3ney, B. J .. 947.1027 Meckes. M.. 1550 Meemhac rl. B. 0 .• 640, 641. 643, 17 10. 1735

Megregian, S .. 1320, 1322 Melcer. H., 626, 627. 664, 007. 669, 71 1. 737,

741. 754,1005,1027, 1030.1032. 1033. 1034 Melharl. G. F.. 1037 Membrana, 1686

Mendez. R.o 643. 687 Mendon-Espinosa. L., 1030. 1032 Mcngelkoch. M., 878

Merktn$, J. C 968 Me lbinger. R., 1520, 1531 Merlo, R. P.. 737. 141. 913, 918. 1005

Merri ll. D. T.. 532. 548 Messick. C .• 1036. 1031 Melcalf & Eddy. Inc .. 202, 261. 435. 453. 474. 701.148],1498,1504, 1546 Mtlcalf, L., 474, ~4g, 556, 1065 l>I elropolilDn Waler Reclamalion Dislricl of Grealer Chicago ( M WRIXiC). 622 M~r, B. P.. 1391, 1397 Meyer, E. A., 1391 , 1397 M iclea. A. I.. 644 M iddlebrooks, E. S., 700 M~lcz.arek. A. T .• 6' I. 652 M ilbury. W. E, 861 Miller, F.C.1757. 176), 1795 Miller. S. W.. 1090 M illetle. J. R.• ~31, 548 Mills. K. M.. 472. 473. 547 Mino, T" 587, 591. 592, 627, 65 I, 686. 687. 701.745.747.751,754.755.832 Mis hnl. P. N .. 1027 MiIDni . H .• 1392 M iyahara • .\.1., 647, 688 Miyahonl, S., 1045 Moce-Uivina. L.. 1434 Moon. G.. 661.1530 Moorman W. H. 1101 .• 1694 Mofidi, A. A .. 1386, 1391, 1392, 1393, 1397 Moigno,A. E, 1064 Mokhayeri. Y.. 637. 686 Molena, R., 634 Moodus, H .• 877 Monlau, E, 1081 Monorl , J.• 590. 617 Monteilll, H. D .. 669 Monlelone. B .• 1392 Moore. E. W.. 122. 179

MOf1I.les. L. A.. 868 Morel. F. M. M.• 469. 472. 548 Morgan, J, J .. 468. 469, 472. 549 Morgan. P. W.. 1065, ]066 Morgenroth. E. . 950. IQI!'i. 1041. J046 MarL T.. 639 Morilll. S.. 1392 Morrill.A, B.. 393,453. 1361. 1932. 1934. 1939 Morris, J. C, 1302. 13 15.1322 MUlyl, M .• 859 M ous~1I. M. S.. 627. 628 Mueller. O. L.. 129. 181 MueJler. II. E. 1083 Mueller. J. G.. 737 MujumduI".A. S .. 1588 Mulbargtr. M . C, 1476, 1479 Mulder, A., 6 18, 640. 641, 1046 Mukkr. J. W., 6 18. 645. 687. 1709. 1715. 1735 Mulder. R., 1046. 1~6 Mullen, M. D.. 674 Muller. A • S49. 879 Muller. CD .. 1108. 1109 Mu n akal~. N .. 1309. 1381.1382 MunieSI. M .. 14 3 M uno~. C .. 6211. 685 Munz.C .. 1768. 1771. 1794 Murn ~urui. C., 8103 M'I1l:a ud, H .. 946.1026 Murphy, K. L . 627, 621! 639. (j4U, 6115 MUmlY. D.. 1311. 13 12 Murthy. S. N .. 97, 178,482.549. 624.626. 627.628.637.645,647.686.687.850.853, 879.950, 1038, 104 1. 1090.1534.1536. 1736.1145.1794. 1859. 1863 MUSlafa. ,1.1 .. 1034 Muthuknshnan. 5 .. 619. 631. 686. 800 MUY-lcr, G" 634. 641, 644,64 5,687,688 MWKDGC, ue Metrorol il,," Waler Reclamalion Districl o f G rcaler Chicago

NACWA . UI! Nal ional Associalion of Clean Waler Agencies Nagase. M .. 1082 Nailo. S . 364. 454 Nakamu ...... ,1.1 .. 672, 687 Nakhla, G., 1083, 1109 Narayanan. 1:1.. 878 NIlSI". S. M.. 1036. 1037 National A~sociallOn of Clean Waler Agencies (NACWA), 1878. ]900 Nalional Renewable Energy LaborJlory (NREL). IjJ9 Nalional Resear.h Coo ncil (NRC), 968, 972. 1307,1869.1900 NUlionul Willer KC!i-ear.h In,lilute (NWK I),

]402. 1404. 1406 Nawa. Y.• 1694 Naydo. W.. 1512. 1520 Neave, S, L. 1065 Ncclhling. J. 8..97. 178. 651. 61\6. 875, 1038 NelS. U.. 1382 KElWrcC, ~a New England Inlerslale Waler Pollut;on Conlrol Commission

Nellor. M. H.. 1157, 1867. 1869. 1872. ISn.l900 Nelson. D .. 1080. 1083. 1108. 1109 Nelson. K .• 156. 179 NcI-5OI\, L. 1>1 .. 639 NercnlJoi',rg, R .. 1045 Neupanc. D., 1038, 1041 New England lnlerstate Water POllUl ion Conlrol Commission (NEIWrcC). 9. 56 New Yor1c SIDle Energy Resear.h and Develnpme m AlIIhnrilY (NY SERDA). 1850. 1864 Newbry. B. W.. 989 Newman, J.. 1027 Newlon,O .. ]477 Ng. W. L (>52 Ni. a. S.• 623. 686 r-;ichola~, D. J . D.647 Nichols. A .. 637, 686. 850 Nicolas. J. C. 672 Nicole lla. 1046. 1070 Nielsen. J. L. 617. 622. 65 I. 652. 685. 688 Nielsen. P. H.. 617 . 622 . 651. 652. 685. 688 Nicminen. S•• 1680 Nieuwenhuijnn. A. F.. 104 1 Nij~kens. P.. 918 Niku. 5., 287. 303 Nmassl, M. V.. 10J6. ]037 Nivillc, K .. 628 NOgIICr1I , D. R.. 622.1015 Nopens, 1.,628 Nordd:ahl. B.. 1686 NordSlrom, D. K.. 532. 547 Norri s. D. P.. 946. 987, 988 NOrlon . L. E.. 969 NOlarllicola. ,1.1 .. 1380 No-·ak. J. T" 879. 1090, 1501. 1565, 1745. 1794 Nowak , 0 .. 627 NRC. see National Rcsear.h Ca.~10r. So, 1335 Pas1Or~lIi. G .• 1002 PaId. G. B .. 1090 Patd. M .. 526. 549, 1208

Pau:n--Id 'i e. V. M.. 653 Paller.;on. R. G.. 103. 179 Panon, J. P.. 669. 688 Patureau. D.. 6J4 Paol. E.. 631 Pavl()1,t:,thi~.

S. G.. IU76, I (It)3. 11011

Paymcul. P.. 1380

"'dyne. W. J .. 6 33 Payr:tudc:au. M .. 1033 Paxmnn.J" 1710. 1735 Pearce.P.,%8. 97'J,IU31 Peck.C. I54 1 Peders.en.J.A" 156, 179 Pedruzi. L., 1002 Pei. R.. 1005 Peladan. J. G .. 1036 . 1037 Pen g, C.. 647 Peng , C. Y.. 1089 Peng. Y.. 628. 647. 800 Pennmgton, R., 1003 PeoI. C .. 1534. 1536 Pepper. I. L.. 63. 64. 95. 144. 145-147, 151, 154.156. )57.17':1. 1326 I"«,..-..J.. 1029. 1036 Perie. M. 1038, IMI Permm, D. 1,... 1240 Pcrl)'. J .. 1178. 1180 Perry. R .. 1839. 1863 Perry. R. 1-1 .. 1724 i'etersen. R" 878 Peter""", S .. 1268 Perino. G .. 1657 PC1!ll1pcl. T .. 645 Pevec, T., 1553 pre'fI'~'J'.

P.. 4611

PIlut. I. J.. 1430 Phel~. C .• 1178, 1180 Phel~. E. B.. 11':1 Phil atlclphi~ Mixer Cntalog, 335. 337. 338. 342 Phillip. W. A .. 1208 Phi llips. H. M .. 999,1001.1003.1004. 100S Picioreanu. C, 628. M4. 645. 647. 688, 101~, 11I5.1735 Pic ~ering. R. L, 622. f\!\5 Pie~enw. P.. 1683. 1684. 1694. 1735 Pillon. A .. 672 P,nnenta-Valc. H.. 1434 Pinkston. K. E.. 503, 548 Pi reI, E. L . 46. 55 l'irn ic. M " 139 Pill. P" 453. 712.1~ Pla7.3. E.. 1038. 1720. 1735 Plummer, J. D .. 1382 l'oduska. R. A. 624 Pohlllnd, F. G .. 10')7, 1103 Polprru;ert C .. 619,631. 1946.1952

1961

Pomeroy. R, D .. 1757. 1794 PQmnM:reni ng· R~r, A .. 620. 621. 688 Ptmimepuy. M .• 1380 Pupe. IL 137. 741.1005 !'orgcs. N .. 130. 178.564.576.586.687 !'ortmann. R. W.. 645 Pooo. I .. 1034 PQrh. M" 634, 647 Potts. L.. 1532 I'ountl, S.. 1534. 1536 Pows. N.. 515. 548

i'r:lkasam, T, R.. 630. 684 Pr:nnanik. A .. 10)8 Pr:m, A. M., 982. 983 Pruu, R. W , 1064 Pnltte. R. D .• 335. 453 Pribil. W.. 1391 Puct.ia.C.,161,179 Puckorius. P.. 531. 548 Pucch ,CoScau. P.• 1108 Row.lJl. A. K., 620. 1034 Rozzi .A., 1002 Rubin. 1\. J., 471, 472. 547 Rubino. V.• 859 Ruchrwcin. D. N.. 1520 Rumm , E. 0 .. 868 Rupen, C. S.. 1392 Rushton, J. I~ .. 454 Ru ~seJi. L. L.. 89. 179 RUSlen, 0 " 1008, 1019, 1022. 1026 1001 , 1004, 1005 Rull, K., Ryan. G .• 1433 Ryan. M. J. . 217. 261

m.

Ryckman, M. D.• 9(X) Ryrfors, 1'.. 1686. 1695. 1735 R),"lllcr, 1. W" 531, 532, 548

Sadic k. T.. 796 Sau. P. 8., 612 Sagbcrg. J>., 1686, 1695. 1735 Sakaji. R. H., 1209. 14()4 Sakakunl. Y.. 1&41.1863 Saki. K .• 1084 $a]amoy, A. A.. 571,6:1 1 Salecker, M .• 1984 Salem. S., 627. 62i1, l701l Salveson. A .. 515. 548. 1404. 1426. 1432, 1433 S:.lveni, R.• 1022 Saman ie~o. F. 1., 281, 303 Sambu~ ili , C.. 108 1 Sam slng. It W.. 8H3 Sa~dc"', R. W., II. 669, 686 Sallders, W. T. M . 1082. 1093. I lOS Saud i,\C. J., 15 12, 1520 Saul.:s, R. L.. 532. 548,1471 SarT'd~in ·S ullh·an, 0 .. 1586 Sas.lki. H .. 657, 688. 1084 Sauayatewa. c., 647. 726 SaundeB. A. M .. 65 1, 652,686 Saunier, R. M., 1311 S~wcy, R.. 402 454 Sawyer, C. N., 68, 9 3, 123. 179, 469.472, 548. 5M0-5SI, IS02. 11164 SCENII IR, sa: ScientifIC Com miUee uo Emerging and Newly Identified Health Risks Schaf"., P. L.. ]531, ]532, ]533. 1539 Sdulk, J .• 641,643. 644.687, 688 Shaucr. I'.• 1041. 1685. 1735 Scoollen.A.A.J. C .. 618.681,1709 ScOOrer. P.• 1079 Scoorrcnberg. S. M .. I041 Schildorfer, H .. 157, 119 5chillk, B.. 587 Schiptler'll, J. c.. 1202 Scllie ife r. K. H.• 570. 621,622.685 Schli~, M ., 969 Schmid, M .• 1710.1735 Sch ,n id. M. C .. 620. 634, 640. 641 . 643. 644, 687, 688 .'khmidl. I., 634. 640. 64 1. 642, 643. 647. 6&4.

'"

SchmIdt. J. E.. 1096

SchllCitier. Y., 647.17 15. 1735 Schnoor, J. L. . 36. 55. 1942, 1952 Schulze. R. J., 53J. 549 Schonberger. L. B.. 156, 178 Schouten. S., 644. 688 Schromm. A.• 622. 1002. 1045 Schroeder, E. D.. 287, 303, 422. 454, 494, 495, 558,960,970. 11 30. 1746. 1757. 1758, 1762. 1763. 1764. 1794, 1795 Schroepfer.G. J .. 119. 179, 1065. J067 Schuler. A. J. , 1005 SchUIt7~ C. E., 1715 SchuI7. ign panllne le," (T). 792- 793 hig h_r-.n e p""",sses. 786-7 88 kinetics. 754-755 low -r-" 'c procc.~.c •• 7l!6. 789-7'D1 proces$C:S.798.

839-'44 enh:ux:ed biological phosphorus removal (EUPR ). 863. 865-870 plu g-now reactor. 702 sequencing mnch re:lCtor (S BR ). 702 su"pended growth tre,tUnen t. 560. 597 trickling filters, 557 hiOOcrcd (wne) sett ling. 360-364 kin-e1ic coeffICients for substrate llilizatioo

(T).593 membrane: biorcactor (MIlR) systems: d~sign par:lmetcrs. 91 3-914 design and opemtin g c hamctcristics

9"

(n .

membnne propert ies, 914-917 membr:lne usage. 917 n1en.brane fouling. 9 17- 919 proce;s con fig ur:lIion. 704-706 microbial growth measurement. 589 mi xed-l iquor fermentation. 877 nitrogen remova l. 795-861 udvml1ages uml limitutiulls uf(n. 846-848 anaerobic digestion TC(:~ le streams

for. 845 B:utknpho proce$~, 845 eyc1ic nitrification/deni tri fication process. 800-802. 83~ denitrification with utem~1 carbon added. 848-860 descriptions of (T). 839- 844 large reaclOr VOl ll1lIC pmce.~s.!I45 low dissol\'ed oxygen (DO) p!'OCCS5. 799-800.833- 835 modified Ludzak-8ungu( MLE) process. 838 postanoxic denitri fication for. 798.

83 1-833 preanoxic dc nitrifH;8tion for, 7'IUUlIliCa1e column \eSIS, 1240-1243 high-p~sure minicolumn (HPMC) ledmiquc. 1240 rnpid smal l sca le col ullln test (RSScr). 1240-1241 type~ ufa!.eS . 792 .wgcd activated sl udge proce.%. 754. 782-786 removal rates from hi gh-rate clarifi~ation (1), 402 temperature effects on. 11 9 (rickling filter dosing as function of load ing (T),959 tric ~ling fIlter removal of: emucnt recircu lation, 969 forced draft "eralion and . 952- 95 3 "mural draft aeration and. 951 ni trificalion and, 953, 978-981 pla,tic packing equ~ti ons for. 972- 978 process alla lysis for, 972- 978 pr":,1 and nitrifIcation nsing (T). 790 Biulogical aL-nIlt:d liller (BAA. 942 adva'1(ages and di>O sol ids production . 601-603 solids rctellIlon lime (S R11, 597-598 substrrue mass b:ilal'lCe. 600 Sl1.\pended metals, 114 Suspended solids: Su also Total suspended solids de pth Iiltration removal of. 1 14 2-1 14 3 im ]lOrlance of (11. 6 3 phospborus content in. 884 rtdOClion offor recycle flow lr'Catmc:nt. 1673-1674 sidcstreams from sludge thickening. 1673 sidcstream. from bio.'lol id s dewatering, 1673- 1674 remvva! of colloiAD) digestion. 1532- 1533 Thickener. 1563 TIlickening processes. 1486- 14% ~clivated sludge liquid-solids ~alion. 1191-893 biosolids land applicalion. 164S--1649 cenlrifugal.1493-14901 co-!'Culing.1487-1488 notalion.1491 -1 4 93 I:mvity.141\&-1491 gmvity belt. 149'--1.1,)6 hydruulic loading rnlCS for gr~vity belts (T). 1495 oo.:cum:nceofmctbodsCf).1487 perform3llCe raoges for rotaty drum thickened wlid (T), 1770 vt)lalili7J1tion. 1768 Vollllilesolids(VS). 73. 76 air ac:robicdipion. 1544-1545 an""rubic digl$tion of, 1500- 15 12 destruction estim ll1ion (11. 1509--1 S 12 high -rate com plete-mix mesophili~ estimation (T), ISIO hydraulic detention times (n, IS 10 loading f:octon 15 10 ~I udg" conccntl'llt ion e ff(."C1S (f). 1510 Van Kletk equation . 15 1 I Volatile suspended wl ids (VSS), 575 acliYe biomass and. 594-595 bi(lIll.lergy in. 129 chlorine disinfection: chemical ch.arnctcriSlics o f wastewatCl". 1324-1325 contact time, 1326-1328

impact of P'lnicles in

t~alal

wastewater, 1325- 1326 impact of wastewatcrconst;tuent~ fI),

,m

initial m ixi ng, 1323-1324 microorganism c haracteristics, 1326 00111:(.:1;1)11 systems for, \1- 10 colloidal particles in, 461-462

color of, 85 definition of, 3 discharge permits hm its for sele