EPA-453/R-94-080AAIREMISSIONSMODELSFORWASTEANDWASTEWATERU.S.EPAContractNo.68DlOll8November1994preparedfortheU.S.EnvironmentalProtectionAgencyOfficeofAirQualityPlanningandStandardsResearchTriangleParkNorthCarolina277115.0SURFACEIMPOUNDMENTSANDOPENTANKSThissectiondiscussestheapproachusedtoestimateairemissionsfromsurfaceimpoundmentsandopentoptanks.Theemissionmodelsaredescribed,modelfacilitiesaredefined,andexamplecalculationsarepresented.5.1NARRATIVEDESCRIPTIONOFEMISSIONSANDMODELUNITSEmissionsfromsurfaceimpoundmentsandopentanksoriginatefromtheuncoveredliquidsurfacethatisexposedtotheair.Themodelusedtoestimateemissionsfromtheliquidsurfaceisbasedonanoverallmasstransfercoefficientthatincorporatestworesistancestomasstransferinseries--theliquid-phaseresistanceandthegas-phaseresistance.Numerouscorrelationsareavailabletoestimatetheindividualmasstransfercoefficients(orresistances),andtheydependuponthecompound’spropertiesandthesystem’sparameters.Therecommendedcorrelationsandtheirapplicabilityaredescribedinsubsequentsections.Theemissionestimatingprocedurealsoincorporatesaflowmodelthatdescribesthemethodofoperation.Forflowthroughsystems,theimpoundment’sortank’scontentsmaybecompletelymixed,plugflow,orsomewhereinbetweenwithvaryingdegreesofbackmixingoraxialdispersion.Biologicallyactiveimpoundmentsandaerationtankscanbedesignedforeithercompletelymixedorplugflow,andbothtypesofflowmodelsarediscussedforthesetypesofsystems.Fordisposalimpoundments,thecontentsareassumedtobewellmixed,andthebulkconcentrationisexpressedasafunctionoftime.Anexpressionforbiodegradationisincorporatedforthoseunitsspecifically5-1designedforbiodegradation,suchastreatmentimpoundmentsorwastewatertreatmenttanks.Fortheseunits,therelativeratesofairemissionsandbiodegradationaredeterminedtoassessthepredictedextentofeachmechanism.Thegeneralapproachthatisusedtoestimateemissionscomparestherelativeratesofairemissions,biodegradation,andremovalwiththeeffluent.Severaldifferenttypesofmodelunitsarepresentedandincludemasstransfertotheairfromquiescent,mechanicallyaerated,diffused-air,andoil-filmliquidsurfaces.Theothermajordifferenceamongthetypesofmodelunitsisthetypeofflowmodelthatisused.Forflow-throughsystems,thedegreeofmixingcanrangefromcompletemixingtoplugflow(nomixing),andbothcasesarepresented.Fordisposalunitswithnoflowout,emissionsareafunctionoftime,andaverageemissionsareestimatedforsomespecifiedtimesincedisposal.Themajordifferenceintheemissionequationsistheliquid-phaseconcentrationthatisusedforthedrivingforceformasstransfertotheair.Thesimplestcaseisrepresentedbywell-mixedsystemsinwhichthedrivingforceisrepresentedbyCL,theliquid-phaseconcentrationinthebulkliquid,whichisalsoequaltotheeffluentconcentration.Relativeremovalratescanbecomparedforthiswell-mixedcasefromasimplematerialbalance.Forplugflow,integrationisrequiredbecausethedrivingforceformasstransferchangesastheliquidflowsthroughthesystem.Thisconcentrationisafunctionoflocationortime(whichareequivalentinplugflow)andisexpressedasC(denotingadependenceontime).TheeffluentfromaplugflowsystemisdenotedasCe•Fordisposalimpoundments,thedrivingforceconcentrationchangeswithtimeandisalsodenotedasCt;however,thereisnoeffluentfromadisposalimpoundment.Theintegrationrequiredforplugflowisfromt=0,whenthematerialfirstenterstheunit,tot=residencetime,whenthematerialleavestheunit.Fordisposalunits,theintegrationisfromt=0,whenthematerialisfirstplacedintheunit,to5-2t=timesincedisposal,whichmustbespecifiedtoestimateaverageemissions.Theintegratedformsoftheseemissionequationsareverysimilar.Thewell-mixedflowmodelisrecommendedandisthemodelusedinthecomputerprogramaccompanyingthisreport.Thisflowmodelismoregenerallyapplicablethanplugflow,thecalculationsaremorestraightforward,andthetwotypesgivesimilarresults.Theonlyexceptionisaflowthroughimpoundmentwithanoilfilmsurface,whichusestheplugflowmodelbecausetheoilfilminhibitsmixing.Bothmodelsyieldanestimateofairemissions,biodegradation,andthequantityleavingwiththeeffluent.Itisimportanttorecognizethatthequantityleavingwiththeeffluentmayalsoeventuallycontributetoairemissions,especiallyfortreatmentunitsinseriesorfordischargestostreamsorpubliclyownedtreatmentworks.Equationsarepresentedforestimatingthevariousremovalrates,andexamplecalculationsfordifferenttypesofimpoundmentsarealsoprovided.Examplecalculationsarenotpresentedseparatelyforopentanksbecausetheprocedureisanalogoustothatusedforimpoundments.Ingeneral,opentankswillhavedifferentinputparametersthatwillaccountfordifferencesinemissionratescomparedtoimpoundments.Forexample,theliquidsurfaceareaforopentankswillbeless,andthefetch-to-depth(F/ID)ratiowillbemuchlowerfortanks.Iftheopentankhasawindbarriertoreducethewindvelocity,thereducedwindvelocitycanbeusedinthemasstransfercorrelations.Inaddition,themodelingapproachaccountsfortheshorterretentiontimesintanks(ontheorderofhours)comparedtoimpoundments(ontheorderofdays).Foropentanks,themasstransfercorrelationofSpringerisrecommendedforwindspeedslessthan3.25rn/s.andthecorrelationofMacKayandYeunisrecommendedforwindspeedsgreaterthan3.25rn/s.Botharediscussedinthefollowingsection.5-3

### C) FtFt HiM D U1U1 

### Q H 

### 11 CD CD HCD 

### CD M CD CD 0 CD 

## 0 l- FtCl) MM 

### 11 Fthh I 

### 1 CD

CD Ft H-HiCj) 

### CD f-C F—a 

### CD H FtH-r-l,F- ntIj- 

### FCH-CD 

## 0 10

CD 0 CD H-C) 

### CDP) -O l- CD

0 H-M Cl) CD CD rt(D C’JH 

### 0 CD CD Cl) 

## H-CD CD

i C) 

## 0 0 Md H-Cl)

II Il II II CD C) Ft 

## 0 h 

### II II II Ii ‘t5 H- H- II Cl) 

### C)

‘10 CD CD CD CDd FtC) Ft H-Cl) 

### L’J

CD CD—.HiCi2 1 Cl) ‘1 HHiH,H-CD 1CD CD 

## CD 0 ‘- 

### Ht-hQ H-Cl) H HCD Cl) CD ‘1 H 

## 0 H- 

### C) Ft HQ C) HO 

## CD H-Cl) 

### CD CD Ft< CO 

## CD H- < 

### ‘IC) H-H-CD 

## O H-< H- 

## .0 C) C) H-CD Cl) 

### .0 CD CD H- CD 1 II 

### 1 HCD CD 

## HO FCCI)C)H- I 

### 1 Cl) CD 

### iC) CD (-.JC) 

### 11 H-H-CD 0 

### Cl)CDCDH d H- CD H- Ft CD Cl) CD H-CD CD 

## 0C) Cl) Ft 

### C) CD H- D H Cl) t— 5 Cl) 

## Z 0H H-H-CD HI) 

## c-tJ CD H Ft Cl) Fl- 

### HH- 

## C) Cl) H Ft Cl) LxJ



### ‘‘IM Cl) 

## d CD---O Ft 

### -1 Cl) Cl) t0 H-CD CD LXICI) 

### CDPJH- CD 

## S CD 

## 5 Cl) 11 FtQ 

### i 0 

## CD CD IH C) CD CD CD ct’I CD H- i—ti5 HCDH-5 

## S Cl) Cl) CDQ CD H-Hz H-HiCl) 0 CD CD CD CD Cl) CD H 

## 0 CD CD Cl) II

— 

### tn 

## 0 CD Cl) C) Cl) Cl) 

## 0 CD t-3 OC) Cl) H-• Ft Hi 

### C) Cl) CD Cl)• H-5 H-X 

## 0 0 Cl) 

## 5 Ft H Cl) 

## S CD Ft Cl) Cl) 

### H-C FtH- CD ‘1

— 5 CD ‘1 

## 0 ‘1 Hi Fl-Ft Cl) I1j 

### iCl) Ft Cl) 

## CD CD HCD Cl) Ft HiCD 

## CDI 011 0 Cl) Cl)

Ft 

### ‘1 Cl) + <

—‘ 

### C) 

## ‘1 0 CD 0 CD H

## 0 C)QCD CD Cl) 

### d CD ‘1 H-C C) CD Cl) 

## S Ft IICfl 0

OCDi Ft H, 

### ‘1 Cl) CD 0 

### CD Hi 

### tn FtCD 

### tnFt Cl) ‘1 

### CD CD Ft

- 

### Ft Hi

- 

### CD Ft CD HiCD CD Cl) 

### C) Hi 

### CD ‘1 Q Cl) Cl) 

### OHi Cl) ‘1 CDQ

CDd0 CD Cl) 

## 0 CD CD H CD CDI H-CD Hi

1 Cl) C) 

### H CD H Cl) 

### C) H- 

### MC) H- CD Cl) 011

f-tU Hi 

## C CD 0’I CDQ CD H- Ft• OH MOO 1 11W’d C) CD CD .0 CD CD CD CD H- Hi FtCJ) 

## 5

CDCDPJ 0 ‘1 Hi 

### CD Cl) Cl) CD CD HiQ H- Cl)

Ft 5 -11 CD Hi Cl) 

### H-C) OFt Hi Cl) 

### CD CD Cl) HH- 

### C) Ft Hi 

### C) H- Cl) 

### 0 d Ft 

### H- H- Cl) 

### 0 5 00H Hi 

### C C) Ft

- C) 

## p 

## 5

H- CD H- 

### CD Cl) 

### CD Ft H- H- 

### C Cl) 

### C C

Cl)C)H- 

### C) Hi 

### CD Ft 

### Cl) D— 

## CD Cl) H Ft Cl) Ft 

### (DO H- 1-h 

### C) CD CD CD CD CD FtH

### Cl) H- Ft 

### CD H- Ft 

### Ft’1 Ft5 C Q

‘IFt 

### C)

- 

### Cl) Ft 

## 5 HCl)

- 

### Hi H-tn C) 

## 5 (DM0 Ft 

### H- CD H- CD CD H 

### C Cl) CD 

### (1)0

- 

### CD 

## S (1) H-Cl)Q CD 

## S C) CD 

## 5

H-FtCD

—. 

### C) Cl) Cl) H 

### 5 —CD Ft 

## 5 C) Ft H-Hi 

## 5 Ft Cl) Ft H-Ft H- Cl)- 

### C) O 0 Cl)

OHi



### - 5 

### FtFt0H- 0

- 

### 0 CD

FtH- Cl) 

### H-’1 I 

## 5 FtCD C) -. 

## S (DCDd CD H-

— 

### Cl) CD CDH-H- —S 

### Ft Cl) 

## ctCD CD 

## S CD CD Cl) Cl) Hi Cl) 

### CD CD

—• 

### H-tn Cl) H 

### Cl) i CD 

## C HiCl) 

### 0 FtH-Ft 

## CDHFt ‘1 1 CD CD C) CD CD 5H-- H-5 1 Hi CD CD Ft

CD 51 Cl) FtCD



### Ui Cl) 

## C CD 0 CD Ui Ft 

## < 0

H- I 

### Hi Cl) 

## S

- 

### (1 M Cl) H Cl)



## CD CD

### Ct CtCD CD

H- H- 

## 5

CD P) Pi

Hh



### H

O

H- 

## <

- CI) P)

th



### Pi P) H

CD H

Ct CD P)

CDC)

- 

### CD 

## ‘iOd

(12 Ct

dCi2



### ii Ct—

P2

Ct CDH- —2

OH

H- C) 

## S

CJ2

H- Ct



### CD

hi, 

### Ci) 

### H

H

### CD H



### C)

) 

### CDCl)

H

Cti xi



### CD

CD Ct çt


### C)

H,CD :J



### CD

Ct H

### C) H- 

### Ci)



### CD

C)CD

H- Ct H



## < H- HH- 

### 0 i

CD 

# cio

hh)

(12 

# w ii 0 

## ctd

H-CD hi,H- 

### 0 h 

## 5 Cl) 

### 0 H

HH (ni CD ) 

### p2 

### Ctd H Ii 

### Ct CD 9) CD Ct i HH- CD 0 CD CD H



### O

H- 

### 9)



## - 

## b H CD



### :i Cl) CD H- 

### 0

Ci) 

### 9) 9) 

## ctctb 9) H

J< H-HCD

QCD

H- Cl) H I 

### H

### CD C) d H- 

### ‘d 9) Ci)

Cl) 

### 0 Ii C) ‘d Ct



### I H- Ct 

### 9) 

## d HH- H- 

### H- Ci) H

i CD 0 CD HHCD i C) 9)9) )i 59-I 

## 5

Ct 

### COOP) 

## bP2

H- CD 

## d H 

### Cl) 

### H Ci)



### H-OCt Ct Ci) CD Cl) 

## ct

- 

### D) 9)- Ct Ct

H HCD Ii Ii



## - 9) 9)

H- (.)tJC)



### 0(i) Ci)

CD C) hi, hl

CD 0 (n CD CD

H 0 Ct h

H- H, I 

### H

H-CtC) C)
9) 0 0 

## -Sd CD CD Ii

CD 9) CD CD H

ctH, 

### CD

H hi,

- 

### H- H

Ct CD CtO Ci) C) 92

9) 

### H- çt



### IJ1CD 5CD H 

### (1) CD H- 

## 0

H CD H,Ct



# o

- 

### H, Cl) H, CD 9)

M Ct Ci) 

### ct 9) (f)H, H

## d CD Ct<— 

### 9)

C) I 

### C) H- CC 

# o H Ct CD ç-t



### i 0) 

## < 9) 92

Ci) 

### Cl)

Ct CD 9) H- CD
9) HCD

Ct CD CD 

### CD Cl) h 

### 9) i H H, CD Ci) Ct H

### CD H-CD CD

Ct Cth



### C) 

## < CD h Ixj



### CD 0

C) 9)

CD
(i)Ci)

Ct 

## ctpi

O

--

ID



### Ii

II

Ct



## o CD 

## S

CD

Ii

92

Ii



### CD



## 0 H,

01

0 

### C)

Ct



### CD

CD

Ii



### CD

Cl)

Cl)

H



## 0

H,



## 0

CD ct5 Ci) HCt



## COO



## S CD CD



## CD CD CD
Ci) H Ct 

## 5 H

Ct 

### Ci) H- 

## 0 CJ2



### H- 

## 5

5 k< 

## CD CD H- 

## < 9) H- Ci) H 

## < CD

Ct CD Ci) 

### H-t

### CD HQ 

## CD, H- 9) H

Ct H, 

### 9)

(n H1CD H5



### CD H-CD 9)



## S Ii bf—Ct

H- H- CD 9) H

### 0)Q CD
P9)CtCD 

## 5

H-

Ct çt



### H- Ii 

## 0 I 

### H



### 1CD CD C) (1)0 9)9)

9) i I 

### H

H H CD HCt Ct H, 

## 5 S Ci) H- H, 

## 0

9)- C) CD 9)

Ci) 9) I 

### U) CD

CI) H CD I 

### H



## H 

## dw

CtC)ct

Ii 

## CD 0 9) J 

### 9) (120)9)

du2< 

### CD<

Ci) Ii H-Cl) CD 

### H,0 Ct5



## CD C) CD CDP) 

## b

CD iS Cl) CD

Pi Ci) Ci) 

### CD C) ct



### 0 h H- CC



### CD CD 0 C) Ii

H,(j) 

### 09) CD H,

H-

- 

### Ci) Ci) 

### CD C) (1) Ct hi, H



### H-CO H-COO

CD 

## 1Ctfrd 9) CD

Ct 

### H- CD C) 

### Q



## Ct CD Ct

Ii 

### rtO Cl) H,O

CD JH,

— 

### H,

H H- 

### H- CD



## < Cl) CC 9-IC) Ci)

i H- Ct

Ci) CD 

## Q CD 

## H

CD Cl) 

## 5

CD CtP)

Ct Cl) Ct

H-

• 

### CD

0 CD H



## d Ci) CD

Cl) 92 H 

### COD) Ct

CD Cl)



### H- Ct 9)

OCi)

(I)



### CtHO

H- 

## C)

CD H 

### 9)

CI) H- Ct 

### 9) CD



## SI

CDd

9) H

C1)Ct

H- CD

Ct

Ci) 

### C)

O

O H, C) H

### CD

9) Ctj 

### Cl)

Cl) 92



### Ct 

## p 

## < H- Ct 

## O 0 H

H 0

CD P).

- 

### U,

Ii



### CD

1.092

Ii 

### H- CD

CD 

## Ct

CD



## 9)

‘-j: 

### Ct 9 )



## Ct

H

### 00

Ct



### CD PdC)

‘10

CD $CD

‘1 00)0)

CD HCI) 

### Ct

H i- H

## S II CtCD

WCD



### CDII

II II H-Ct

-



### H

P) OH

CD CtH,92

Ct 

### 9)j 

## 5

CD CD CD OH

## 5 H- CD 1. Q Ci) 

### C)

‘1 

## Q 1. dCt0

CD CD k< 

### H-CD

II

- 

### II HCD 

### 1(0 9) Cl) Cl) H-il CD CC

CC 9) 

## OCD Ci) 9)

H H —il Ci) Ct



### ‘1 

### 9) dH--- Ct



### CD (.0 H

S 

### 9)

CI) 

### C) 1.<



### 0 C) C) OH-H-u

### O Ci) 

### i Ct<



### I Ct (1)02 H (12 

### 9) Ct



### CC 92(1) H-ct 

### 9) Ct

5 

### CtHL

Ct 

## C

S 

### 9) H-bCt U)



### CC 

### Ci) H

## 5 HCD

• CD H

### Ci) CCC) 

## S

H 

### Ct< 00

H

P)CC

H 

## 5 Ct



## o 0 CD CC C1



### H

(.fl 

### CC CD CD

bCD 9)

CC



## S

• H- 

# 5 j<Ct

0) pi 

### CD

5-.-.-



### (.0 OH,



## S

. 

### .0

O II
H

• Ct



## - I

- U) 

### CD 01bythedepthoftheimpoundment.Ethyletherwasusedasthevolatilecomponentinthedesorptionexperiments,inwhichthewindvelocityandF/Dratiowerevaried.Springer’sresultsshowninTable5-1yieldthreedifferentcorrelationsforkLthatdependuponthecombinationofwindspeedandF/IDratioofinterest.Springer’smodelimpliesthatkLisconstantforwindspeedsof0to3.25m/s.AlthoughSpringerexaminedonlythemasstransferofethylether,hisresultsareextrapolatedtoothercompoundsbytheratioofthecompound’sandether’sdiffusivitiesinwatertothe2/3power.ThewindspeedinSpringer’scorrelationisdefinedasthewindspeed10mabovetheliquidsurface.Forpracticalapplicationofhiscorrelation,typicallyreportedvaluesofwindspeedareused.Springer’smodeldoesnotincludethecaseinwhichtheF/IDratioislessthan14andthewindspeedisgreaterthan3.25m/s.Forthisspecificcase,kLwasestimatedfromMacKayandYeun’scorrelationshowninTable5l7,8MacKayandYeun9didnotaddresstheeffectofdepth;however,theircorrelationisbasedondatafrom11organiccompoundsinawellmixedsystem,thecompoundsrepresentabroadrangeofHenry’slawconstants,andtheirgeneralcorrelationisapplicableforthecasedescribedabovethatisnotcoveredbySpringer’scorrelation.Thegas-phasecoefficient(kG)wasestimatedfromthecorrelationofMacKayandMatasuguasshowninTable5l.10Thiscorrelationwasdevelopedfromexperimentsontheevaporationofisopropylbenzene,gasoline,andwaterintoair.Theseresearchersverifiedthatpreviouswork,whichassumedthatthewindvelocityprofilefollowsapowerlaw,couldbeusedtoquantifytherateofevaporationfromasmoothliquidsurface.TheresultwasacorrelationthatexpressedkGasafunctionofwindspeedandthefetchoreffectivediameteroftheliquidsurface.TheindividualmasstransfercoefficientsestimatedfromthecorrelationsinTable5-1areusedinEquation(5-2)toestimate5-6TABLE5-1.EQUATIONSFORCALCULATINGINDIVIDUALMASSTRANSFERCOEFFICIENTSFORVOLATILIZATIONOFORGANICSOLUTESFROMQUIESCENTSURFACEIMPOUNDMENTSLiquidphaseSpringeretal.4(forallcasesexceptF/D3.25m/s)D2/3kL=2.78xDW(0<U10<3.25ether(AllF/Dratios)D2/3kL=[2.605x(F/D)+1.277xl0]Dether(U10>3.25)(m/s)(14<F/D<51.2)-72D2/3(U10>3.25)(m/s)kL=2.611x10U10Dth(F/D>51.2)where,U10=windspeedat10mabovetheliquidsurface,m/s;=diffusivityofconstituentinwater,cm2/s;D=diffusivityofetherinwater,cm2/s;andetherF/ID=fetch-to-depthratio(fetchisthelineardistanceacrosstheimpoundment)GasphaseMacKayandMatasugu(inHwang5):4.82xU°78Sc067d0(m/s)where,Uwindspeed,m/s;GScGSchmidtnumberongassideDGa=viscosityofair,g/cm•s;(continued)5-7

# I

CD



## Z hi CD

CU 

## Cl 

# -o

- 

### H * 

### C) 

## Cl Li C)

ii ii CD CU 

## Q

CU II IL LI IL II L—... L..— II II IL II



## Cl

o o CD 

## Cl Cl H- 

## Cl H- H- 1 H, 

### H- CD hi, 

## CD Cl) C) H- 

## >< >< Cl CU hi, H, hi, C) 

## Cl C) i- CD M Cl) 

## Cn 0 Cl) CC H H 

## < CD C) H- 

### Cl) H Cl) H- d H 0 0 

### CD CU çt 

### Cl) c1 H- CC H- 

## Cl CD 0 I 

### H- H- k< 

## < k< CC 

### CD a) 

## 0 < H- 

## Cl H, CD H- 

## 0 CC 

### Q 

## Z

+ + C1 I-i, 

### CU CD H- Cl k< 

### k< M

Cf H H W H- 

### CU 

# o 0 0 H 

### hi, ) 

### CD H C) 1-i H, l- 

### Cf 

### CU 0 H- H 

### CD

- 

### C) Cl) Cf Cf 

### xj Cf C) 

# o h CD °



## >< Cl CD 0 (Q

— l- 

### H 

## Li S ‘-1 Cl) 0 H 

### CD Cl) C) 

### W Cf 

## p H

I 0 W 

### 0 Ct 

## 5 Ii H H-

‘ 

### Cf H, H 

## w Lxi 

## u-i Cl 

### C)

— 

### < Cl) 1’s)

— CC 

## 5 C) CD

- 

## u-i H- 

### CD W5 H- 

## S CD

-. 

### • 

## Cl Cf 

### II 

### j * 

## S s) H 

### çt

. —_ 

# o I)) Cl) CD 0 

### j Cl) Ci) 

### H- H C)

— 

### H- C) 

### i 

## Cl Cl H 0 

### )t:- 

## Cl CD H- H I 

## 5

I-C) 1:-I 

### CD Cf

CU 

### II I



### H- H- 

### Cf H-H 

## u-i Cf 

### CD 

## Co

- 

## hI CD Cl) - 

## u] II 

## Cl

—S * 

### C)



## v Ik M 

## S hi, H * 

## o —5---



### M A Cl) C) + 

## w QS. 

### Cl) CD

• 0

— 

## u-i

—-5 

## 5 a)

5—S 

### -.

____5 

## w Cl) Cl) 

## CU

S H 

## Cl

0 Cl)

0



### U-itheoverallmasstransfercoefficient.Theequilibriumconstantforaconstituentdissolvedinwaterat25°CisestimatedfromEquation(5-4).However,anestimateoftheconcentrationintheliquidphase(CL)isneededinEquation(5-1)toestimateemissions.TheconcentrationCLinEquation(5-1)isthedrivingforceformasstransfer.Foranimpoundmentthatisinstantlyfilledwithwaste,thedrivingforce(CL)istheinitialconcentrationinthewaste.However,thisconcentrationwilldecreasewithtimeastheconstituentislosttotheair,whichsuggeststhatemissionsmayalsodecreasewithtime(assumingconstantKandA).Forflowthroughsystems,theconcentrationmaybecyclicaliftheloadingoftheprocessiscyclical.Continuousflowthroughsystemsmayattainsomeequilibriumconcentration.Theflowmodelassumedforquiescentimpoundmentsandtankswithnobiodegradationisthatthecontentsofthesystemarewellmixedandthatthebulkconcentration(drivingforce)inthesystemisequaltotheeffluentconcentration,CL.Amaterialbalancearoundthissystemyields:orQCKACL+QCLCL=QC./(KA+Q)(5-6)where,Q=volumetricflowrate,m3/s;initialconcentrationinthewaste,g/m3;CequilibriumorblkconcentrationintheLimpoundment,g/moverallmasstransfercoefficient,m/s;andliquidsurfacearea,m2.Thewell-mixedassumptionismadeforthesakeofsimplicityandassumesthatbulkconvectionandwind-inducededdiescombinetomixthebasincontents.Axialdispersionintheflow5-9directionisalsopossible,andsomesystemsmaybedesignedspecificallyforplugflow(e.g.,somebiologicaltreatmenttanks).Anassumptionofplugflowinsteadofwell-mixedflowwouldyieldslightlyhigherestimatesofemissions;however,thedifferenceissmall.CalculationspresentedbyThibodeauxforanaeratedbasinthatwaswell-mixedorhadplugflowshowedthattheplug-flowassumptionyieldedestimatesthatwerehigherby11percentforacetaldehyde,5percentforacetone,and0percent11forphenol.Theapproachdescribedtoestimateemissionsfromquiescentimpoundmentswithnobiodegradationincludesthefollowingsteps:1.EstimatetheindividualmasstransfercoefficientsfromTable5-1.2.EstimatetheequilibriumconstantfromEquation(5-3)3.EstimatetheoverallmasstransfercoefficientfromEquation(5-2)4.Estimatetheliquid-phaseconcentrationfromEquation(5-6)5.EstimateemissionsfromEquation(5-1)Themajorassumptionsassociatedwiththisprocedureare:•Thetwo-resistancemodelandthecorrelationsfortheindividualmasstransfercoefficientsareapplicabletothesystemofinterest.•Theimpoundment’scontentsarewellmixed.•Thereisnosignificantremovalbybiodegradation,seepage,adsorption,orotherformsofdegradation.•Thewastematerialofinterestisaqueouswastewithnoseparateorganicphase.•TheestimateofHenry’slawconstant(equilibriumpartitioningbetweenthevaporandliquid)isreasonablyaccurate.Therecommendedprocedureforquiescentimpoundmentsistoassumethattheliquidiswellmixed.Thisassumptionisusedin5-10thecomputermodelaccompanyingthisreportandisillustratedintheexamplecalculations.However,impoundmentsandtankswithquiescentsurfacescanalsobedesignedforplugflowwiththeuseofbafflesorotherdesigntechniquestoreducetheextentofbackmixing.Inaplug-flowsystem,therateofairemissionsatanypointinthesystemchangesasthematerialflowsthroughthesystem.Thereisnouniformliquidconcentrationwithintheplug-flowunitastherewasinthewell-mixedsystem,andthelowestconcentrationoccursintheeffluent(i.e.,thereisnobackmixingoftheeffluentwiththeinfluent).FOrplugflow,therateofdisappearanceofacompoundbyairemissionsisgivenby:ô(CV)-____=KAC(5-7)ótwhere,=concentrationaftertheplughastraveledtseconds;t=time,S;3V=volume,mandwiththeothersymbolsaspreviouslydefined.RearrangingEquation(5-7)yields:o(c)KA___=-———ôt(5-8)CtVIntegratingEquation(5-8)fromC1att=0toC=CLatt=v/Q(oneresidencetime)gives:(.S)=EXF(i)3whereCL=effluentconcentration,g/m,andwiththeothersymbolsaspreviouslydefined.5-11Theresidencetime,iinseconds,equalsv/QandV=AD(areatimesdepth);consequently,A/Q=l/D.SubstitutingintoEquation(5-9)yieldsanequivalentexpression:CLKt—=1--—I(5-10)CiD)TheratioCL/Cirepresentsthefractionremovedwiththeeffluent;therefore,1-CL/Clrepresentsthefractionthatisemittedairfromtheplug-flowsystem:fair=

(1-=1-EXP

(-(5-11)Theaverageemissionrateiscalculatedfrom:EfairQC1(5-12)where,Eemissions,g/s;f=fractionemittedfromEquation(5-11);airQflowrate,m3/s;andC.influentconcentration,g/m3.5.2.2ModelPlantParametersforQuiescentImpoundmentsAmodelfacilitywasdevelopedforquiescentimpoundmentstoillustratetheemissionestimatingprocedure.A1981surveycompiledbyWestat12showedthatthemediansurfaceareaforstorageimpoundmentswasapproximately1,500m2andthatthemediandepthwas1.8m.Detentiontimesrangedfrom1to550days,withoverhalfofthevaluesat46daysorless.Forthisexample,adetentiontimeof20dayswaschosen.Theareaanddepthyieldatotalvolumeof2,700m3,andthedetentiontimeof20daysyieldsaflowrateof1.6L/s(0.0016m3/s)Meteorologicalconditionsarealsoneededasinputparametersfortheemissionmodels.Forthisemissionestimate,5-12

### H



## w Ii

CD

Ft

xj

— 

### CD H



# : 0

II Ii II II

M ID LD

• H-

• U1ID



## w

H H CD

00 

### CD

I I1



### ID ID

II

C) M•

MW —J



### —CD W

CD

Ft N



### CD

CD 3

l- 

### CD

CD

Ft

CD

0

0-,



### Cl) 

## w U, 

### ‘d H- 

### P. 

## c-c

• J 

### i Ft :I)

• Ft



### CD Ft ipj



### Ft 

### CD

Lxi 

### CD l- 

## cQ CD

Cl)

•cl H• 

### HCD



### HO

CD l-



## >< H

flFt

H HH 

### CD 0 

### H

CD

l— CI) 

### Cl) CD

Pi r1 C) HFt HH- 

## $ MH CD



### O I)

—. 

### Ft 

## c-tCj)< l

### CD—’ k<

hi, • 

### H-

- 

### 00 Cl)

l- hi,

I—’ 

### 1) CD p H

0 H- l—

l- CI) 

### CD 

### -C)

(Ii Cl)



### H- U,

•



### CD 0 0 C1)

MID c-1

H 

### Ci) CD



### H

H- C) Ft



### 0 H- Cl) Z

< 

## c-

CD CI) U, 

### Cl)

CD H-

— 

### CD

Ft

Cl) C/) HCD



### C)d

Ft

H- Ft H

hi-i



# N COO

- 

### OH

H3 0

Cl) Cl) 

### WFt$

H- H- H-



### O Ft

—.



### Cl) CD

M,C1



### CD

0 l) l

### FtCD

Cl)

CD C) CD

0 C)



### PCD

CDUi

H Ft 

### CD

‘- 

### i

H) 

### N I) FtCD


### C) H

## H- 0 CD

H- 

# (—to 1J

k<hi,W



### H 

### C)

0



### 0

l-QCl)

CD

—. 

### CD



## d w

II



### O—W 

## d H



### CD DPi



### IUi Ftd

H

## d CD

W-P)

H



### 00 Ftd

I hi, 

### 0 H

W 

### CD

OCD

CD Cl)

Ft



### N H



### CD

CD Ft



### CD CD

II

CD hrJ

— 

### H



## d

II Cl)

M CD

CD



## w

—1

Cl)



### H

0



### Iv

U,



### Cl) 

### M

0

0

U,



### H

0



### 1rj

+

M

—)



### —2

H

0

--2



### H

0

M 

### P1 

### C) Cl)



### 0 CD

C)

Ft Ft

) 

### H

1 xj 

### Lxi 

### CJ)C) H-O

— hi-i 

## dPi

Hi l-- 

### H

### CD H-C) U,



### II C) C_Q



### Ft 

### H M

Lxi H- CDPJ H hi, 

## <1 frFt 0 M

CD 

### -CD

CD Cl) C-Q 

### Ft 

### C) H 

### -O

Ft H- HH- P1 OQ WCD

(ili Cl)



### CD CD CDH- 

### OFt

Ft H M,H

CD I



### Hh 

## —)d b P1

P1 W 

### CD Ft

II CDPI 3 CD

CD (DCI) N



### Ft

— 

### CD CD CD

CD HI



### CD H

CD b-Pi C/)

P1 HCl) Cl)

CD CDCl) H

—o 

# o

Ft U,Ft

U, Ih CI)



### HP) M

“Cl) h

II Hi 

### 0



### CD

— h



### —1 H



### C) 3

II U, 

### 0



### 0 CD P1



### M 0 hi,

— Hi



### • 0 H- CD

W 

### C) 0

U, 

### H

CD CI) 

# I

Cl)



### CD C/) CD



### CD

C) HFt Cl)

H- Cl)



### 0 H-

3 HU, 

### Cl) C/)



### M hi, C/)



### • h CD

HO C)

Ft

P1 H

l- 

### CI) 

## 0

(DFt



### 0

CI) 

### P1 h



### CDQ CD

CD Cl)



### CD

HH- Ft

Ftd Cl)

Ft

QCl)



### CDFt



### CD CD

OFti

CD• ‘-<

H I



### Cl)



### i-c-t

CD

H- CD 

## 1 •d

Ft



### CD CD

1



### P1 Ftd

HH



### CD 0 CD

Ft



### CD Cl) 

### C)

II P1

Cl) H



### CD C)

Cl)



### H- C) H 

### <lp)

CD H- Ft

LY’ HCD 

### 0

H

## Q

H- hi,



### 0

II 1



### Cl)

Ft

P1

p1

Ft



### CD

CD

P1

Ft



### CD

0

hi,

M
U,

0 

### C)

1

1



### H



### Ci)

CD

CD

0

hi,

-J



### Cl)

### LJ

CD H- HH 

### Cj) hi, H 

### D) C) hi, H

H

## 0 i



# w C12 Cl)

k< H- H- H



### Ct < < 

## 0 k< H- Hhi, Cr Ct



## 0 k< k< 

### D Hi



### H- HH

h J



### H

C’- çt



### CD CD

h I

### CD 

## b ç1 CD

CD N

l- 

### CD

CD 

## d X H 

### C) 

## E

‘- 

### H- 

## CD i 0 H- CD

Hi Hi

Hi lH Cl)



### ‘-< Ct Cl) CD Cl)

- 

### CD H- ‘Cj h



### H- Cl) (t 

### CD P)

- 

### Ct CD Ct

H- H CD ci

rt 

### P) C) i

‘-< 

### 0 Cl- CD

H- 

### C) C)

0 CD

cii 

### Cl) Cr

H- Cr i-



### ‘- 

### ci) cii

çt



### ClH



### 0



## CD

N



### CD



## CD

H H CD D 

### 0 Ui



### J CD U] CD 0 Ui

H CD



## >< CD 

## ><

H H H C) H

O H 0 0 0

0 I I

W I C)] CD

—. 

### W

Cl) l


### IC) 

### C) C) Cl



### C)

—.- 

### t’) ‘) 

### C) 

## S

Cr1 Cl)

Cl) IC)



## S 0

H 

### H tO 0 tO tO H H

0 

### CD Ui

• 

### 0

- • 

### — 0 —J CD Ui 

### IC) N —1 0 

### 0 

## C)

— 

### CD C) H ci) 0 

## 5 o 

## S S Ui 

## <

W 

### CD

—. 

### CD Cl) 

## 5 5

Cl) W tO



### H

## 5

w

CI)

cii

Ct



### CD I-ij j 

## <

H CD 

### 0 CD I

## 0 Ct H 

### d CD



## CD ci Ct cu 

## S

Cl- 

### CD

H- 

## 0

Cl-



### H 

## S

CD

U] I

## Lxi

(i



# N

H

### Q.

CD

IC C’-

H-fl Cl)

H- C) M 

### CD CD 

## 0 CD C)F— C) 3 l- Ii 

### ?C) II II CD CD —c

- 

### II II CD 0 

### Ui H Cl) 

## < h- Ui

IJ 

## 0 H- HiLl) M bc-f 

### Cl) 

## CC) H- CD p)r-t 

### M



### CD II Ii CD C) H- 

### CD

Hi 

## 0 Cr ><0 H 

# o H 

### II II (.C H- CD Ui 0



### P d ZP H 

### (OH- 

### CD

— 

### CDCr CD H P)CD 0 

### >< LC)

CD Hi 

### H CD 0 Cr I 

### Pi < b Hi 

### CD H- I pi o— DJ U] 

### H CD b 

### d CD C 

### W CD 0


### HH >< C) N CD C) I U]

o çt 

### >< CD C 1QCD O 

### W

‘H 

### HH 3 CD CD 

### II 0 CD CD

uJ 

### WO < 

### H- CD H- H

C H CD I 

### CD 0 CD Cr Cr H H 

# —s L’s) 

### + C) 

### Cl) W 

### ‘H H- ‘-< ‘-< CD 

### CDPJ Ui I

w

—

--- 

### W 

### (DCD H

Cl-CD H-

- ‘— 

### Cl) COD) W 

### ii

,—. 

### ) (U (Ii (I) 

### CD CD 

### C)

- 

### M

(I) —H H- H- 

### H

## 0 0’ F-c-t H

-

- 

### CD C) 0 h 

### (U 0 (Ul- + H

CD Cr

— 

### — — Cl) CD

- 

### H Hi H CD WI H 

### Ui

w 

### - + CD

—

- S— 

### Ii II CD 

### H CD 

### CD

- 

### 0 

### H- Hi H 0

I—

- 

### II

— 

### 0 H H 

### (U Cr ‘JlCD

- 0 

### C) H 0 

### C)

• 

### HI 

### H

CD H H 

### 0 CD

- 

### 0 t’J CD 

### l-’

I 

### C) 

### I CD W 0 CD

CO Hi

—

- 

### CD CD CD 

### >< H0

-. 

### C

- Hi 

### H H CD 

### H-Cl)

• 

### CD H

H-

- 

### C) H CHiC) 

### H H, 0

- 

### C) H C) 0 H 

### CHiC H H, I



### HH I 

### 0 CD HH H



### CD

— M

-. W I 

### CDH- 

### C)

I

- 

### CD H-Cr H- M

Cr 0 CD CD

- 

### H

- 

### C)

—. 

### Cr0

— 

### Cr CD]LD

U] H 

### II C) k<Hi

- - 

### W 

### H Ui 

### lCD



### H

• 

### 0Q CD

Hi

- 

### CD -j,p

—

### IW H CD

- 

### 0

- 

### H H-

-_ 

### HIH

H H 

# olo

H-

- 

### III

I 

### Cl) H

0 CD

H 

### (U 0



### H CD

H

## CD

CD

Hi 

## Li C) 

## 0 1’i UI 

## 0 C) 

# cu

H- 

# rt CD H- Ct

H- H- II

- 

### H- 

# S CD II 

# 5

II 1 

### II II

- 

### C)

— 

## P1 

# I H 

### ft CD H- 0 CD 

### C) Cf 

### H CD W— 

# 5 Hct 0 C) CD II H- II II II II CD 

## 0

I 

### CD 

### UI 

# S ii CD

Hi 

# 5 ) 

### UI H 

## >< H Hi CD Cf 

# 5 -1 CD P1 H- H-

- 0 

### H 

### H- H- M M 

## I

H- UI 

## (Q >< 0 Ui H 0 110 + UI 

# I

UI 0 0 

### UI IH

H- 

## < H UI 0 ‘0 

## ><

—. 

### L”J 

# +IC) 0 H- 

# I

II 

## Q I- 0 0’. 

# 5

- — 

## ft IH- C) 

## 0 H 

# HI

I 

### II 

## 5 0 H W P1

- 

### H- 

# CI 0 3 0 0 fa 

### H (1) 

### 0 ‘) 

# So o

—. 

### it 

## 05 UI I I

• • 

### —H I 

### CD 0 CD

— 

### 0 0’, 

### Ix) II II II I Hi 

# 5 C) UI Ui 

# a Hi Hi 

## 0 ‘—.0

• 

# —o 3 II 511

- 

## 0 5 +

>< CD ‘1 UI

- 

# 5 Ui 

### 0

- —. 

### H 

# 5

‘—. 

### ,I 

# 5 cu H 0 

### Ix) 

## d P1

- —

— 

# w ci) lIx) 1 

## 01



# o H t’J Ui’-. 

# o 

# s

• 

# I

I 

# 5

— 

## ‘d

• 

### OUI 

# I— 1 

# MI Ui 0 I 

### H 0 0- 

## 010 ft CD MI

II H P1

— 0 

## CD H Ui 

# I H 

# 5 0 H çt 

# 5 H 

## I H 

## H I

‘— I 

### H- Ix) 0 

# 5 HI

— 

### UI

. 

### O 

## d Hi

—— 

## 0

‘— 

## 1W P1 

# 5

• —I

— 

# 5 F—’ H

### H W 

## 5 0 Ui +

—. __



# I

Ui 

# 5

Ui 

## .b 

## CD 

# I

>< UI 

## 1’i

— I

— 

### Ui 

## P1 Ui 

## .Q UI H Ix) 0- 

## I H 

### F-’----

. 

### 0IH P1 UI 

# HI

0 

### () 

## P1 UI Ui 

# 01

ft ft 0 0 

### C) UI Ii 

### H CD H- CD 0 

### H CD ft 

# WI

0 

### UId 

## 0 5 Ui 

### UIJ Cl)

UI’ •• 

## 0 5

Hi Ix)

5—

— 

### Ui 

# 5

H I 

# w

0 

### H 

## II

H 

## UI

0 

## P1

H
0 

## H Ui H-



### H 0 II M H Ui

0 

# 5

Ui

-5---- 

### Ui



### UI

5- 

## UI Ui H

• -5-_S S.

5— 0



### Ui

UiE=f.QC(Equation5-12)airof.=0.98;air3Q=0.00156m/s;andC0=10g/mE(0.98)(0.00156m3/s)(10g/m3)E0.015g/s=0.47Mg/yr.5.3BIODEGPADATIONThissectionidentifiessomeofthemajordesignfeaturesofbiologicaltreatmentprocesses,suchasactivatedsludgeunitsandimpoundmentsdesignedforbiodegradation.Mathematicalmodelsforbiodegradationarealsopresentedandincorporatedintopredictivefatemodels.5.3.1DescriptionofBiologicalActiveSystemsTheactivatedsludgeprocessisanaerobicbiologicaltreatmentinwhichthepollutantsaredegradedbymicroorganismssuspendeduniformlyinthereactiontank.Oxygenisintroducedbymechanicalmeans,andthemicroorganismsaremaintainedbyrecyclingtheactivatedsludgethatisformed.Inmostunits,thesludgeisremovedbysettlinginaseparateunit,aportionofthesludgeisrecycled,andasmallportioniswasted(removedfromthesystem)onacontinuousbasis.Oxidationorstabilizationimpoundmentsandaeratedimpoundmentsareusedtotreatentireplantwastesaswellastopolishtheeffluentfromothertreatmentprocesses.Solidsusuallysettleoutintheimpoundmentorareremovedinaseparatevessel.Generally,thesolidsarenotrecycled;however,ifthesolidsarereturned,theprocessisthesameasamodifiedactivatedsludgeprocess.13TypicaldesignparametersforanactivatedsludgeprocessaregiveninTable5-3.Twoofthemostcommonlyusedparametersarethefood-to-microorganism(F/M)ratioandresidencetime.TheF/MratiodescribestheorganicloadingonthebiologicalsystemandiscalculatedastheweightofBOD5(biochemical5-17