PhosphorusRemoval
Enhancedcoagula.ondrivesplantefficiencyandperformance
THECHALLENGE
A770,000GPDmunicipalwastewatertreatmentplantdischargingtoastreamleadingtoLakeEriewas
havingdifficultymee.ngitstotalaluminum(1.1mg/L)andtotalphosphorus(1.0mg/L)permits. AHer
monthsofdosing60ppmvofeitherferricchlorideorPACpriortothesecondaryclarifier,theplantwas
unabletomeetitspermitlimits. AMemptstomeetthepermitbyincreasingthedosagerateofeither
coagulant were unsuccessful. When higher doses of ferric chloride were aMempted, buried chemical
feedlinescorroded,leadingtoexpensiverepairs.HigherdosesofPACcausedaluminumconcentra.ons
inthefinaleffluenttoexceedtheplant’saluminumpermit.Sincetheplantwasrunningoutofop.ons,
plantmanagementdecidedtoconductafull-scaletrialwithRE100.
TRIALOVERVIEWANDRESULTS
TheplantprocessisshowninFigure1.RE100wasdosedintoboththeprimaryandsecondaryclarifiers
beginningOctober2014.Figure2showstotesofproductawai.nguseinthetrial.Priortothetrial,the
clarifiersdidapoorjobofseMlingsolids.Toimprovesolidsremovalintheprimaryclarifier,16ppmvof
RE100wasadded.Inthesecondaryclarifier,100ppmvofRE100wasaddedtoimproveseMlingandto
bring the phosphorus and aluminum quickly into compliance. Figure 3 shows how the secondary
clarifier’sappearanceimprovedaHer48hoursofRE100dosing.
Figure1.Plantlay-out
Rev022616
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Figure2.RE100totesawai8nguseinthetrialona-25°Fday
Figure3:Secondaryclarifierbefore(leE)andaEer(right)introduc8onofRE100
AsshowninFigures4(a)and4(b)below,RE100successfullyreducedphosphoruswithinthefirstmonth
tomeetpermitlimits.AHeronlyfourdaysofRE100dosing,thephosphorusdroppedfrom1.5ppmTP
tobelow0.5ppmTP.PACaddi.oncausedthealuminumintheeffluenttorisedrama.callyoverthatof
theinfluent(leHhalfofFigure4(a)).AHeronemonthoftrialusage,theplantdecidedtoswitchoverto
RE 100. The plant is now using RE 100 exclusively to meet their TP and Al discharge permits. AHer
severalmonthsofusage,plantmanagementwasabletoop.mizetheprocessandreducethetotalRE
100doseinbothclarifiersto70ppmv.Plantpersonnelarecon.nuingtoop.mizeandhavereducedthe
dosagetoevenlowerlevels.
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Figure4(a).TotalPhosphorusbeforeandaEerSorbX
Figure4(b).TotalAluminumbeforeandaEerSorbX
ADDITIONALBENEFITSOBSERVED
Itwasclearthatmorebiosolidswereremovedastheclarifiers’performanceimproved. Thisposi.vely
impactedsludgevolumesandsludgebeltfilterpress/dewateringopera.ons.Sludgewas.ng,filterpress
cakesolids,andpolymerpumpspeedareshowninTableI.WithRE100,theplantwasted27%lesstotal
sludgebyvolume,filterpresscakesolidsincreasedby34%,andthepolymerpumpspeedwasreduced
by 9%. As waste sludge density increases, less water is sent to the digester and the belt filter press,
whichleadstolesspolymerneededfordewateringaswellasadryerbeltfilterpresscake. Electricity
usageisalsoexpectedtodecline: becausetheclarifiersludgeblanketsaredenser,thesludgewas.ng
pumpsnowrunlessfrequentlythanbefore.
TableI.Solidshandlingresults
Parameter
FerricChloride/PAC
RE100
%Change
Primarysludgewasted,gal/MG
3,070
2,500
-19%
Secondarysludgewasted,gal/MG
2,450
1,540
-37%
Totalsludgewasted,gal/MG
5,510
4,040
-27%
Filterpresscakesolids,%solids
15.7%
21.1%
34%
Polymerpumpspeed
167
152
-9%
BeMercoagula.onledtoimprovementsinotherplantprocessparameters,asshowninTableII.WithRE
100, BOD, ammonia and fecal coliform removals were higher, and sludge landfill costs on a $ per dry
solidsbasiswere25%lower.Theplantalsono.cedthattherota.ngbatchcontactor(RBC)blowersare
ac.vated less frequently, which results in lower electricity usage. Lower BOD, in par.cular, may
contributetolessgrowthontheRBCs,reducingtheairflowneededtosloughoffexcessbiomass.
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TableII.Otherbenefitsobserved
Parameter
FerricChloride/PAC
RE100
InletBOD,mg/L
135.3
112.8
OutletBOD,mg/L
11.4
4.9
BODReduc8on,%
91.6%
95.6%
InletAmmonia,mg/L
13.2
14.3
OutletAmmonia,mg/L
1.4
1.0
%AmmoniaReduc8on
89.4%
93.0%
Fecalcoliform,cfu
19.7
6.3
DisposalCost,$/wettonsludge
$102.90
$102.90
DisposalCost,$/drytonsolids
$655
$488
CONCLUSION:
RE 100 drama.cally improved solids seMling in the plant’s clarifiers, which posi.vely impacted plant
efficiencyandperformance.SinceOctober2014,thisplanthasbeenintotalcompliancewithitsNPDES
dischargepermits.Thehighersolidscontentinthebeltfilterpresscakeandreducedpolymerusagehas
allowedtheplanttoloweritsper-unitcostsofdrysolidsdisposal. Theplantiscon.nuingtoop.mize
theprocessandquan.fyreducedelectricityusagetodetermineaddi.onalcostsavings.
ForREInquiries,pleasecontact:
NeoChemicals&Oxides
PlazaTowerOne,6400S.FiddlersGreenCircle,Suite1610
GreenwoodVillage,CO80111
P:303.843.8040F:303.843.8082
[email protected]
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