Modelling of wastewater treatment plant operation under

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Modelling of wastewater treatment plant operation under variable conditions

Modelowanie pracy oczyszczalni ścieków w zmiennych warunkach

BEATAKOŃCZAK,PIOTRZAWADZKI,MICHAŁPIECZONKA

ModellingofthewastewatertreatmentplantinŻory,PolandwascarriedoutusingtheBioWin2.1simulationprogrambasedontherealdataregardingacquiredin2016-2017.Itwasmadethestaticanddynamiccalibrationofthedevelopedmodelofthetreatmentplant.Thecalibrationandverificationprocedurewasperformed.InordertodeterminetheoptimalworkingconditionsfortheWWTPŻory,aseriesofsimulationtestswerecarriedout(44simulationsoftheWWTPŻorymodelwork).Thesimulationswerecarriedoutfor:variablewastewatertemperature,uniformandunevendistributionofwastewatertoindividualbiologicalsequences,atvariablesludgeageandrateoftheinternalrecirculation,andvariableoxygenconcentrationinthenitrificationanddenitrificationtanks.Itwasalsoinvestigatedtheinfluenceoftheexternalcarbonsourcedosing,andthemanagementmethodofwastewatersrecycledfromdewateringsystem,ontheeffectivenessofnitrogenremovalinsimulationconditions.ThesimulationstudiesresultedindeterminationoftheoptimalparametersfortheWWTPŻorywork,consideringthevariableinflowparameters,inordertointensifyremovalofthenitrogencompoundsbybiologicalmeans,andtoachievethetargetconcentrationofthetotalnitrogenattheoutlet,i.e.10mgN/L.Key words: modelling; activated sludge model; BioWin; computational simulation; wastewater treatment plant

ModelowanieoczyszczalniściekówwŻorachprowadzonozwykorzystaniemprogramusymulacyjnegoBioWin2.1woparciuodanerzeczywistepozyskanewlatach2016-2017.Dokonanokalibracjistatycznejidynamicznejopra-cowanegomodeluoczyszczalni.Przeprowadzonoprocedurękalibracyjnąiweryfikacyjną.Wceluokreśleniaopty-malnychwarunkówpracydlaOSŻorywykonanoszeregbadańsymulacyjnych(44symulacjepracymodelowejOSŻory).Symulacjeprowadzonodla:zmiennejtemperaturyścieków,równomiernegoinierównomiernegorozdziałuściekówdoposzczególnychciągówbiologicznych,przyzmiennymwiekuosaduczynnego,stopniurecyrkulacjiwewnętrznejistężeniutlenuwkomorzetlenowejidenitryfikacji.Zbadanotakżewpływdozowaniazewnętrznegoźródławęglaisposobugospodarowaniawodaminadosadowyminaefektywnośćusuwaniaazotuwwarunkachsymulacyjnych.EfektemprzeprowadzonychbadańsymulacyjnychbyłowyznaczenieoptymalnychparametrówpracyOSŻoryzuwzględnieniemzmiennychparametrówdopływu,wceluintensyfikacjiusuwaniazwiązkówazotunadrodzebiologicznejiosiągnięciudocelowegostężeniaazotuogólnegonaodpływie,tj.rzędu10mgN/L.Słowa kluczowe: modelowanie, model osadu czynnego, BioWin, symulacja komputerowa, oczyszczalnia ścieków

Introduction

Biological treatment of wastewater onthebasisofactivesludgeisamethodcom-monly used in the treatment of municipalwastewater. Exploitation of a municipalwastewater treatment plant (WWTP) isacomplicatedtaskduetotheneedtocon-trol several technological processes at thesametime,insuchawayastoachievethereduction of pollutants, required by law.Therearedifferenttypesofprocessesbasedontheactivesludgemethod,includingsequ-

entialbiologicalreactors(SBR–Sequencing Batch Reactor),membranebioreactors(MBR–Membrane Bioreactor) and conventionalactivesludge.Eachoftheseprocessesusesadifferentconfigurationoftheactivesludgeandtheformofsolid/liquidseparation.

The complexity of wastewater treat-mentprocesseshasincreasedsignificantlyover the last decade due to the need toremovecarbon,nitrogenandphosphoruscompounds simultaneously. Currently,modelling and computer simulations areusedtodesignawastewatertreatmentsys-

temanditscontrol,aswellastopredictthesystembehaviour.Mathematicalmodellingis an integral part of the design of thewastewater treatmentsystem.Thecompli-catednatureofthissystemimpliestheneedtosupport thedesignandoperationwiththeuseofcomputerprograms.Theappli-cationofmathematicalmodelsallows foranalysis, which in a short time and ata low financial outlay enables to obtainmany technological solutions, togetherwiththesimulationofeventsinthecondi-tionstypicalfortherealsystem[1-3].

drinż.BeataKończak–CentralMiningInstitute,DepartmentofWaterProtection,PlacGwarków1,40-166Katowice,phone+482592628,correspondingauthor’se-mail:[email protected],https://orcid.org/0000-0003-4398-7653mgrinż.PiotrZawadzki–CentralMiningInstitute,DepartmentofWaterProtection,PlacGwarków1,40-166Katowice,phone+48322592801,correspondingauthor’se-mail:[email protected],https://orcid.org/0000-0003-1020-5926mgrinż.MichałPieczonka–ŻoryWaterSupplyandSewageCompany,Wodociągowa10,44-240Żory,correspondingauthor’se-mail:[email protected]

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Themost frequentlyusedmathematicalmodelsforthedesignofbiologicalwastewa-ter treatment are the ASM active sludgemodels,suchasASM1,ASM2,ASM2dandASM3.Themodelshavebeenproposedbythe International Water Association (IWA).The models with the active sludge or theASM-basedmodelsarebuiltintomostofthecurrently used simulation programs, i.e.ASIM, BioWin, GPS-X, WEST, DESASS.When designing a model of a treatmentplant, its calibration is important, i.e.ada-ptationtothesetofinformationonthewaste-waterqualityparametersat individual sta-ges of treatment, in a full-scale treatmentplant[4].Sofar,severalcalibrationmethodshavebeendeveloped[5-8],thankstowhichitispossibletomimictheworkingconditionsofthetreatmentplantintheexistingstate.

Thesimulationprogramsareincreasin-gly usedasa support tool in the fieldofdesign,commissioningoroperationoftheWWTP,andinparticularforoptimizationofitsoperationconditions[9-14].

Objective of the work

Theobjectiveof theworkwastosup-port the decision making process in thefieldofoptimizingtheoperationofwaste-water treatment plant in Żory (WWTPŻory), by applying modelling of variousscenariosofthemechanicalandbiologicalwastewater treatment plant in Żory, atvariableoperationparametersoftreatmentprocesses. The modelling of the WWTPwas carried out using the BioWin 2.1simulationprogrambasedontherealdatacollectedintheyears2016-2017.

General characteristics of the object

The Wastewater Treatment Plant inŻoryislocatedintheSilesianvoivodeship.TheWWTPŻoryoperatesonthebaseonthe classic 3-stage BARDENPHO system,referredtoastheA2/Osystem.Accordingto the assumptions of the process, thewastewater along with the active sludgeflowssequentiallythroughthechamberor

a separated anaerobic, anoxic and oxy-gen zone [15]. The designed equivalentnumberofinhabitantsis69791.Theave-ragedailyflow(ADF)ofrawwastewatertothe treatment plant is 8128.0 m3/d. Thequalityofthetreatedwastewaterdoesnotexceed the assumed design parameters.Periodically,however,itwasnotedslightlyexceeded concentrationof the total nitro-genattheoutflow,causedbylowtempera-tureofwastewaterorirregularityofinflow.Thesimulationstudyaimedatdevelopingvariousscenarios for theoperationof thetreatment plant in conditions of variableinflowparameters,inordertooptimizeitsoperationandadaptittotheseconditions.

Modelling of the wastewater treatment plant operation

Modellingof the treatmentplantope-ration was carried out using the BioWin2.1simulationprogram,distributedbytheCanadian company Envirosim AssociatesLtd. The developed model of the WWTPŻorytreatmentplanttookintoaccountthewastewaterandsewagesludgelineaswellasthetechnologicallineofthewastewaterfromdewateringofdigestedsludge(Figu-re 1) and was configured based on theactualtechnicalandtechnologicaldataofdevicesandfacilitiesoftheWWTPŻory.

Themodel includes the loadofpollu-tants, recycled with the wastewater from

dewateringprocesstakingfromthemecha-nical thickeners and filter presses to thebeginning of the technological system,internalrecirculation(IR)ofnitrates to thepre-denitrification zones, excess sludgerecirculation to the biological chambers,dosingofPAXasaprecipitationagentforexcess phosphates, daily unevenness ofwastewaterflowingintotheindividuallinesof the WWTP Żory, and changes in theairinglevelofthetransitionchamber.

Forconfigurationofthemodeltheactu-aldatawereused,regardingflow,BOD5,totalsuspendedsolids(TSS),alkalinity(pH),total nitrogen (TN) and total phosphorus(TP),obtainedfromthemeasurementcam-paigns carried out in the period of24.08.2016–30.08.2016, 02.11.2016–08.11.2016, 22.03.2017–28.03.2017(Table1).

For calibrationandverificationof themodel therewereusedresultsconcerningqualityof the treatedwastewaterdischar-ged from the system in the period of25.08.2016-31.08.2016, 03.11.2016-09.11.2016 and of 23.03.2017-29.03.2017, concerning the key indica-tors, i.e.: COD, BOD5, TN, N-NH4 andN-NO3, general suspension (Table 1). Inorder to calibrate the model, the asses-smentofcomplianceoftheresultsobtainedduring simulation testswith the real datawas made for the following indicators:COD,BOD,TN,N-NH4.

Fig. 1. The WWTP Żory model taking into account the biological part of the wastewater treatment plant devel-oped in the BioWin simulator. Own study. PST – preliminary settling tank, DFC – dephosphatation chamber, DNC – denitrification chamber, TC – transitional chamber, NC – nitrification chamber, SST – secondary settling tank, DP – dewatering press, CFC – closed fermentation chamber

Table. 1. The average weekly values of basic indicators of quality of the wastewater, inflowing and outflowing, from the period of 24.08.2016 – 29.03.2017, for configuration and simulation of the BioWin mod

DateFlow COD TN TP N-NO3 pH TSS N-NH4 N-NO2 TOC BOD5 Temp.

m3/d mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L mg/L °C

INFLOWINGWASTEWATER

24.08.2016–30.08.2016 7812 666 90,5 13,32 0,91 6,9 422 75,5 0,241 355 275 21

02.11.2016–08.11.2016 8789 728 96,23 12,46 0,98 7,1 539 76,7 0,264 345 331 14

22.03.2017–28.03.2017 10613 633 89,71 7,51 1,02 7,1 645 69,1 0,239 332 293 15

TREATEDWASTEWATER

25.08.2016–31.08.2016 7298 40,9 13,46 1,40 10,93 7,4 12 0,024 0,051 19 5 17

03.11.2016–09.11.2016 8473 34,9 18,50 0,77 13,53 7,5 8 1,69 0,312 55 6 13

23.03.2017–29.03.2017 10030 54,8 21,3 0,88 6,23 7,5 23 9,69 0,997 21 7 13


W Calibration of the model

Aspartofthesimulation,astaticanddynamiccalibrationofthemodelwerecar-riedout.Thestaticcalibrationconsistedofselection of the stoichiometric and kineticconstants.Apartofthestoichiometricandkinetic constants values were adopted atthelevelproposedintheBioWinGeneralModel.Theproportionsbetweentheorga-nic compound fractions expressed asCOD,i.e.themolecularfractionandnon-degradablefraction,andtheeasilydecom-posed fraction,havebeenexperimentallydetermined.Thecalibrationprocedurewasperformedbasedontheresultsoftherese-arch from the measurement campaign,carried out in the period of 25-30.08.2016(Table1,untilthemodelobtainscon-formity,intermsofthemainindicatorssho-wing the efficiency of the treatment, i.e.TSS, COD, TN, N-NO3, N-NH4 and TP,withrealvalues.Verificationofthemodelwasmadeforthedatafromthemeasure-ment campaign carriedout in theperiod03.11.2016–09.11.2016(Table1).Theobtainedvalueswereinlinewiththeave-ragevaluesofpollutant concentrations inthe treated wastewater measured in thisperiod.Atthisstage,thestaticcalibrationof themodelhasbeencompleted.Subse-quently,themodelwascalibrateddynami-cally,selectingthevalueofswitchingfunc-tions forautotrophicbacteriaandhetero-trophic bacteria by changing the maxi-mumgrowth rateofautotrophsuA (from0.5to0.9)andtheoxygenconcentrationlimit for the denitrification process (from0.0 mg/L to 0.3-0.5 mg/L), in order toachieveveryhighconvergenceoftherealresults with the values obtained from themodel.

Simulation tests

Aseriesofsimulationtests(44simula-tionsoftheWWTPŻorymodelwork)wereperformed,thetaskofwhichwastodeter-minefurtherdirectionsofactivitiestoopti-mize the operation of the WWTP Żorysewage treatment plant and to increaseefficiencyofthenitrogenremoval,soastoachievethetotalnitrogenconcentrationattheoutletintherangeof10mg/L(targetvalue)and15mg/L(limitvalue).

Results and their discussion

Model 0 – Simulation of the WWTP Żory work in different seasons (summertime, wintertime)

Thesimulationtestswerecarriedoutatvariable temperature of incomingwaste-

water, i.e. 22°C (summertime) and 8°C(wintertime).TheresultsoftheanalysesaresummarizedinFigure2.

The effective denitrification occurswhentheorganiccompoundsintheamo-

unt of 7 times higher than the load ofnitrogencompoundsaresuppliedintothebiological system. It has been observedthatinthewintertimethereisasignificantshortage of organic compounds flowinginto the WWTP, and the COD/TN ratiovalue amounts to 4–6. Stable conditionsforthedenitrificationprocessareobtainedwhen the COD/TN ratio value is higherthan 5.88 (in the summertime) and 6.13(in the wintertime) [16]. In the case ofwastewater flowing into the WWTP Żorytheirquality in the summertimemeets theaboverequirementsbecausetheCOD/TNratio value exceeds 7. However, in thewintertime it is advisable to dispense anexternal source of organic carbon. Foreffectivedenitrification,itisalsoimportantwhat part of organic contaminants makethereadilybiodegradableorganiccompo-unds (expressed by the BOD5 indicator).Theanalysisshowedthatinthesummerti-me, in themorningandin theafternoon,theamountofreadilybiodegradableorga-nic compounds is insufficient, what maycontributetotheinhibitionofthedenitrifi-cationprocess.However,intheeveningtheBOD5/TN ratio exceeds the value 2.5,andevenisabove4.5,thereforetheeffec-

tivedenitrificationispossible.However,inthewintertimethereisashortageofeasilydecomposable organic compounds, whatmayresultininhibitionofthedenitrificationprocess(BOD5/TN<2.5)(Figure2).

Model 1 – Simulations of the influence of change in the wastewater distribution

Duetounevenoperationofthebiologi-calchambersoftheWWTPŻory,resultingmainlyfromthelackofzoningbysepara-tionofthewastewaterintothethreetech-nologicallines(L1,L2,L3),thesimulationswere carried out at the change of thewastewaterdistributionmethod.Inthefirstperiod of the study, the simulations werecarriedoutattheevenwastewaterdistribu-tiontothebiologicalsequences(i.e.33%⋅ADFwasflowingintoeachofthetechnolo-gical lines). In the second period of thesimulation study, the wastewater distribu-tionwasuneven,i.e.toL1=50%⋅ADF,toL2=30%⋅ADF,andtoL3=20%⋅ADF.

The results of modelling showed thattheunevendistributionofwastewaterinflu-ences variation of the active sludge age(SolidRetentionTime,SRT),whichperiodi-callyincreasedupto21daysandrapidlydroppedtothevalueof9days(Figure3).

Fluctuations in thesludgeageatune-venwastewaterinflowleadtobreakdownof the nitrification process and cause anincrease inamountofnitrogen (totalandammonium)intheoutflow(Figure4).The

Fig. 2. Change in ratio BOD5/TN in the wastewater incoming to the WWTP Żory in the summertime and wintertime

Fig. 3. The influence of a meth-od of the wastewater distribution to the tech-nological lines on the stability of the active sludge age in the biolog-ical reactors

Fig. 4. The influence of a method of the wastewater distri-bution to the technologi-cal lines on concentration of the nitrogen com-pounds in the outflow


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amountofammoniumnitrogenintheout-flowequalledevento43.0mg/L.

Model 2 – Simulations of the influence of change in the temperature and the sludge age

Simulation studies were carried out,whichaimwastoselecttheoptimalageofsludgeforagivenseason.Theresultsobta-inedintheBioWinmodelhaveshownthatin the existing wastewater treatment sys-tem,theextensionof thesludgeageover18 days in the summertime results in anincreaseinconcentrationoftheammoniumnitrogen and nitrates in the outflow fromthereactor.Keepingthesludgeageatthelevelof20dayscausesthattheamountoftotal nitrogen in the outflow exceeds thelimit value of 15 mgN/L. The excessivesludge age prolongation decreases thedenitrification efficiency. The reduction inthe denitrification efficiency is caused bythe long sludgeholding in the secondarysettlingtank,whichresultsintheprocessofsecondary denitrification. Then, higherconcentrationsofbasicindicatorsofimpu-ritiesintheoutflowareobserved.Theopti-mal sludge age for this season is 10-15days(Figure5).

Thestudiescarriedoutwiththehelpofthe BioWin program have shown that inthe transitional seasons, i.e. in the springandautumn,theminimumageofsedimentis10days,andtherecommendedageupto 20 days. Extending the sludge ageabove10days results indoublingof thenitrate intake rateand improvesdenitrifi-cationefficiency(Figure6).

Inthewintertime,whenthetemperatureofwastewaterdropsto8°C,theefficiencyofremoving nitrogen compounds decreases(Figure7).Analysisofthemodellingresults

showed that when the sludge age dropsbelow10days,thenitrificationanddenitri-fication process completely breaks down.Extendingofthesludgeageincreaseseffi-ciency of the nitrogen removal from thewastewater. The simulation studies haveshownthattheextensionofthesludgeagein the wintertime affects efficiency of thenitrogenremoval,howeverconcentrationof

thetotalnitrogenattheoutflowisabove10mg/L.Inordertoachievehigherefficiencyof thewastewatertreatmentit isnecessarytotakefurtheroptimizationmeasures.

Model 3 – Simulation of the influence of change of internal recirculation coefficient

Simulationtestswerecarriedoutchan-gingtherateoftheinternalrecirculationinthe rangeof150–550% ⋅ADF. Increasingrateoftheinternalrecirculationfrom300%to400% ⋅ADFcausesgrowingof theeffi-ciency of denitrification, which results in

lowering thenitrateconcentrationandthusthetotalnitrogenintheoutflow.Theefficien-cyofnitrogenremovalincreasesbyapprox.4.3% (Figure 8). Increasing degree of therecirculationabove400%resultsinadecre-aseintheefficiencyofdenitrification,whichismostprobablyrelatedtotherecirculationofexcessiveamountsof theoxygen to thiszone,togetherwithnitrates.Asaresult,theconcentrationofnitratesinthetreatedwaste-waterincreasesbyapprox.12%.

Similar relationships were observedwhen the system worked at the optimumsludgeageforasetpointwastewatertem-perature.Shorteningthesludgeageoftheactive sludge caused an increase in effi-ciencyofremovingofthenitrogencompo-undsbyabout27%.Thisvaluewascalcu-latedonthebaseofthedifferencebetwe-enconcentrationofthetotalnitrogenattheoutletinthesystemofSRT=20dandthesystemofSRT=12dforIR=300%.Incre-asingrateoftheinternalwastewaterrecir-culationfrom300%⋅ADFto400%⋅ADFcausedtheincreaseinefficiencyofremo-vingofthetotalnitrogenbyabout1.25%.Ontheotherhand,increasingrateoftheinternal recirculation above 450% ⋅ ADFcausedtheincreaseinoutflowofthenitro-geninnitratesbyabout2%(Figure9).

Model 4 – Simulation of wastewater treatment process with variable capacity of denitrification zone

Thesimulationstudieswerecarriedoutwithavariablerationbetweenthedenitrifi-cationzonevolumeandtotalreactorvolu-me(VD/VR),intherangeof0.25-0.5bychanging of oxygen concentration in thetransitional chamber, in the range of 0-1mg/L.Theresultsofthesimulationshowedthatconductingthetreatmentprocesswiththe reduced volume of the anoxic zone

Fig. 5. Influence of the active sludge age on concentra-tion of the nitrogen com-pounds in the treated wastewater in the sum-mertime

Fig. 7. Influence of the active sludge age on concentra-tion of the nitrogen com-pounds in the treated wastewater in the winter-time

Fig. 8. Influence of the internal recirculation rate on con-centration of the nitrogen compounds in the treated wastewater – parameters of the system: SRT = 20 d, temperature of waste-water = 22°C

Fig. 6. Influence of the active sludge age on concentra-tion of the nitrogen com-pounds in the wastewa-ter treated during the transitional period


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(VD/VR<0.5)resultsinacompletebreak-downoftheprocessofremovingthenitro-gencompounds from thewastewater.Theamountoftotalnitrogenattheoutletinthiscasewasapprox.50mg/L(Figure10).

The results of simulation tests showedthatdenitrificationispossibleonlywhentheVD/VRratiois50%(concentrationofoxy-gen in the transition chamber – 0 mg/L)(Figure10).Theresultsobtainedaspartofthe computer simulationalso showed thatreducingvolumeoftheanoxiczoneaffectstheprocessofreductionofnitratestogase-ousnitrogen.ItwasfoundthatinasystemwhereVD/VRratiois0.5oxygenintakeisusedprimarilyforprocessesrelatedtothemetabolism of nitrifying and denitrifyingbacteria.Lessoxygenistakenupbymicro-

organismsforcarbonoxidationprocesses.AchangeintheVD/VRratioto0.25hasresulted in lessoxygenbeingusedby thedenitrifyingbacteria.However,theoxygenuptake ratio (OUR) for carbon oxidationhas increased, especially between19pmand4am(Figure11and12).

IntheWWTPŻorytreatmentplantitisusedthewastewatertreatmentprocesswith

pre-denitrification. This solution allows theuseoforganiccompoundscontainedinthewastewater asa sourceof carbon for therespiration processes for the denitrifyingmicroorganisms.Theefficiencyofpre-deni-trification is limited. The literature sourcesreportthatthemaximumefficiencyofremo-

valofthenitratesinthedenitrificationzonein systems with pre-denitrification is up to80%[16].These limitationsresult fromthediscussedabovemaximumrateofrecircula-tionofthenitratesfromtheoxygenzonetotheanoxiczone,thevolumeofthiszone,thequalityandquantityoftheorganiccompo-unds in the wastewater flowing into thiszone.Inordertosupportthedenitrificationprocessesinthesesystems,it ispossibletomaintainsuchoxygenconcentrationin theoxygen chambers that the simultaneousdenitrificationinthiszonewasensured.Theresultsofsimulationtestsforintroducingthesimultaneous denitrification process in theaerobiczonebyloweringtheconcentrationofoxygeninthiszonefrom2mg/Lto0.6mg/Larepresentedbelow.

Model 5 – Simulations of change of the oxygen concentration in the aerobic zone

The simulation studies have shownthatloweringtheoxygenconcentrationintheoxygenchambersfrom2mgO2/Ltoapprox.0.8mgO2/Ldecreasesthecon-centrationoftotalnitrogenintheoutflowbyapprox.2%(Figure13).Thisiscaused

bythedecreaseinconcentrationofnitra-tesinthetreatedwastewater.However,itshouldbenotedthatwiththedecreaseofoxygen concentration in the nitrificationchamber,theconcentrationofammoniumnitrogenintheoutflowincreases,becau-se the livingconditions fornitrifyingmi-croorganismsaredeteriorating,theopti-mumofwhichisattheoxygenconcentra-tionofapprox.2mg/L.Theintroductionofsuchachangeinthesystemcouldse-riouslydisrupttheoperationofthetreat-mentplantduringaperiodoflowtempe-

Fig. 9. Influence of the internal recircu-lation rate on efficiency of the nitrogen removal – parameters of the system: SRT = 12 d, tem-perature of wastewater = 22°C

Fig. 10. Influence of con-centration of oxy-gen in the transitive chamber on con-tent of the individu-al nitrogen forms in the wastewater after treatment

Fig. 11. The value of the oxygen uptake rate for oxidation of the organic compounds and nitrogen contained in wastewater at the ratio VD/VR = 0.5

Fig. 12. The value of the oxygen uptake rate for oxida-tion of the organic com-pounds and nitrogen con-tained in waste-water at the ratio VD/VR = 0.25

Fig. 13. Influence of oxygen con-centration in the oxygen chamber on the concen-tration of nitrogen com-pounds in the treated wastewater (SRT = 12 d, T = 22°C)


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ratures, when the efficiency of nitrifica-tiondecreases.

Model 6 – Simulation of dosing of the external source of organic carbon

The studies simulating dosing of theexternalcarbonsource(ECS)tothereactorchambers were carried out so that theCOD/TNratiowas8,andtheratioBOD5/TNwas5.ComparedtotheresultsintakeninthesummertimeandpresentedinFigure12,itcanbeseenthattheefficiencyoftotalnitrogenremovalincreasedafterdosinganexternalcarbonsource.Theconcentrationoftotalnitrogeninthetreatedwastewaterwasobservednothigher than12mg/L(Figure14).However, in the simulationswhereno

externalcarbonsourcewasdosed,thetotalnitrogencontentattheoutflowwasabout14mg/L in the summertime (Figure 12). Inaddition, the results of simulations carriedoutisintransitionalperiod(T=15°C)showedthat the nitrogen removal efficiency afterdosinganexternalcarbonsourceisstillhighandbelow14mg/L(Figure15).

In the wintertime, despite dosing ofECS, the total nitrogen content in treatedwastewater varied between 15.0 mgN/Land18.5mgN/L,whichresults fromtheinhibition of nitrifying bacteria activity atthese temperatures and the increase inconcentrationoftheammoniumnitrogenattheoutflow(Figure16).

Model 7 – Simulation of change in the management of wastewater recycled from dewatering system

Thewastewaterfromdewateringsystemreturnedtothewastewatertreatmentsystemcontainahardlydecomposable fractionof

thewastewater,whichadverselyaffects thefunctioningofthewholetreatmentplant.

Thesimulationstudieshaveshownthatthewastewatertreatmentplantworksmoreefficientlyatwithouttheinflowofthedewa-teringsewage,and theaveragecontentof

thetotalnitrogenattheoutletdidnotexceedthelimitvalue(cav.TN=14.8mg/L,cav.N-NO3=10.6mg/L,cav.N-NH4=1.06mg/L)(Figu-re17).

Inthesamesystem(withoutreturningwastewaterfromthedewateringsewege)

the external carbon source dosing wassimulated. Simulation tests showed thatthecontentoftotalnitrogen,evenduringthe periods of inflow of the increasedpollutant load, did not exceed thepermissiblevalue,i.e.15mgTN/Lattheoutflow from the treatment plant (Figure18).

SUMMARY

Asa result of the simulation tests, theoptimal parameters of the WWTP Żoryworkweredeterminedinthesummertime,transitional periods and the wintertime.Optimizationofoperationofthetreatmentplantservestoimprovethewastewatertre-atment, especially in scope of removingnitrogencompoundssothattheconcentra-tionoftotalnitrogenattheoutletdoesnotexceed 15 mgN/L, and even maintainedbelow 12.0 mg/L. Table 2 summarizesresults of simulation for 7 treatment plantmodels. Based on the obtained results, itwas found that the highest efficiency ofremoving nitrogen compounds from thewastewater(concentrationoftotalnitrogenattheoutletbelow12.0mg/L)canbeobta-ined thanks to the dosingof the externalsourceofcarbonandpropermanagementof the supernatant water. Dosing of theexternalsourceoftheorganiccarbon(ECS)atthetemperatureof22°Cand15°C,andSRT=12d,15dand18d,allowstoobtainconcentration of TN at the outlet in the

Fig. 14. The concentration of nitrogen compounds in the treated wastewater in the summer-time (SRT = 12 d, T = 22 °C) after dosing of external car-bon source

Fig. 16. Influence of dosing of ECS on the concentration of nitrogen compounds in the treated wastewater in the wintertime (SRT = 20 d, T = 8 °C)

Fig. 17. Simulation tests of the WWTP Żory opera-tion with a limited inflow of leachates to the biological zone (SRT = 20 d, T = 22°C)

Fig. 18.Simulation tests of the WWTP Żory operation with a limited inflow of leachate to the biological zone and at dosing of ECS (SRT = 20 d, T = 22°C)

Fig. 15. The concentration of nitrogen compounds in the treated waste-water in the transi-tive period (SRT = 15 d, 18 d, T = 15 °C) after dosing of external carbon source


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rangefrom9.8mg/Lto13.5mg/L.Limita-tionofinflowofthesupernatantwaterwithsimultaneous dosing of the ECSallows toobtainconcentrationofTNattheoutletintherangefrom10.5mg/Lto13.0mg/L.Lack of the ECS dosing to the biologicchambers results in higher concentrationsoftotalnitrogenattheoutlet,withthetotalnitrogen concentration not exceeding thelimitvalue15.0mg/L.Theimprovementofefficiencyof thewastewatertreatmentcanalsobeachievedbycontrollingtherateofoxygenofthewastewaterinthenitrificationanddenitrificationchamber,aswellasbytheuniformeddistributionofthewastewa-ter to the individual process sequences.Concentration of the total nitrogen in thewastewateraftertreatment,inthesecases,isbelow15,0mg/L.

Theoptimalconditionsfortheprocessofwastewatertreatmentweredetermined:1) Uniformedwastewaterdistribution(33%

xADFforeachtechnologicalsequence),2) Temperatureofthewastewaterandthe

sludgeage,T=22°CandSRT=8–18d,respectively

3) RateoftheinternalrecirculationforT=22°C and SRT = 12 d equal to IR =225–550%,

4) Concentration of oxygen dissolved inthe transitive chamber cO2=0mg/LforT=15°CandSRT=20d,

5) Concentration of oxygen dissolved inthe oxygen chamber cO2 = 0.6–2.0mg/LforT=22°CandSRT=12d,

6) Dosingoftheexternalsourceoforga-niccarbontothewastewateroftempe-ratureT=22°CandSRT=12–20d.

R E F E R E N C E S

[1] Henze,M.,Grady,C.P.L.,Marais,G.,&Matsuo,T.ActivatedSludgeModelNo1inIAWPRC Sci-entific and Technical Reports No 1 (IAWPRC,1987)

[2] Kowalewski, Z., & Preisner, M. Overview ofwastewatertreatmentplantsmodellingsoftware.Preprint at http://home.agh.edu.pl/~kowalew/wp-content/uploads/artyku.pdf(2017).

[3] Zdebik,D.,Korczak,K.,&Głodniok,M.Mode-lingofbiogeneremovalintheprocessofbiologi-cal wastewater treatment in the sequential-flowtechnology. Prace Naukowe GIG. Górnictwo i Środowisko. Główny Instytut Górnictwa, 2,97–112(2010).

[4] Petersen, B., Gernaey, K., Henze, M., & Van-rolleghem, P.A. Calibration of activated sludge

models:acriticalreviewofexperimentaldesignsinBiotechnology for the Environment: Wastewa-ter Treatment and Modelling. Waste Gas Han-dling(Eds.Agathos,S.N.&Reineke,W.)1–80(KluwerAcademicPublishers,2003).

[5] Melcer, H., Dold, P.L, Jones, R.M., Bye, C.M.,Takacs,I.,Stensel,H.D.,Wilson,A.W.,Sun,P.,&Bury,S.Methods for wastewater characterization in activated sludge modeling(WaterEnvironmentResearchFoundation,2003)

[6] Vanrolleghem,P.A., Insel,G., Petersen,B., Sin,G., De Pauw, D., Nopens, I., Weijers, S., &Gernaey,K.Acomprehensivemodelcalibrationprocedure for activated sludge models in Pro-ceedings of WEFTEC 2003, 76th Annual Techni-cal Exhibition and Conference (Water Environ-mentFederation,2003).

[7] Langergraber,G.,Rieger,L.,Winkler,S.,Alex,J.,Wiese,J.,Owerdieck,C.,Ahnert,M.,Simon,J.,&Maurer,M.Aguidelineforsimulationstudiesof wastewater treatment plants. Water Science and Technology. https://doi.org/10.2166/wst.2004.0436(2004).

[8] Liwarska-Bizukojc,&E.,Biernacki,R.Identifica-tionofthemostsensitiveparametersintheacti-vatedsludgemodelimplementedinBioWinsoft-ware. Bioresource Technology. https://doi.org/10.1016/j.biortech.2010.04.065(2010)

[9] Gernaey, K.V., van Loosdrecht, M.C.M.,Henze,M.,Lind,M.,&Jorgensen,S.B.Activatedsludgewastewatertreatmentplantmodellingandsimulation.Stateoftheart.Environmental Model-ling & Software. https://doi.org/10.1016/j.envsoft.2003.03.005(2004).

[10] Ferrer,J.,Seco,A.,Serralta,J.,Ribes,J.,Manga,

Table. 2. Summary of results of simulations carried out using the models 1–8

Modelname VariabletechnologicalparameterConcentrationoftotalnitrogenintheoutflow

TN≤15mg/L TN<12mg/L

Model1–Simulationoftheinfluenceofchangeinthe

wastewaterdistribution

W1:RegulardistributionofwastewaterL1:33%xADFL2:33%xADFL3:33%xADF

YES NO

W2:IrregulardistributionofwastewaterL1:50%xADFL2:30%xADFL3:20%xADF

NO NO

Model2–Simulationoftheinfluenceofchangeinthetemperatureandthesludge

age

W1:T=22°CSRT=8d,12d,15d,18d,20d

YESForSRT=8–18d NO

W2:T=15°CSRT=8d,12d,15d,18d,20d NO NO

W3:T=8°CSRT=8d,12d,15d,18d,20d NO NO

Model3–Simulationoftheinfluenceofchangeofinternal

recirculationcoefficient

W1:T=22°C,SRT=20dIR=150%,200%,300%,350%,400%,500% NO NO

W2:T=22°C,SRT=12dIR=150%,200%,300%,450%,550%

YESForIRZ=225–550% NO

Model4–Simulationofthewastewatertreatmentprocesswithvariablecapacityofdeni-

trificationzone

W1:SRT=20d,T=15°CVD/VR=0,5 YES NO

W2:SRT=20d,T=15°CVD/VR<0,5 NO NO

W3:SRT=20d,T=15°CVD/VR=0,25 NO NO

Model5–Simulationofchangeoftheoxygenconcen-

trationintheaerobiczone

W1:T=22°C,SRT=12dcO2(AC)=0,6mg/L,0,8mg/L,1mg/L,1,8mg/L,2,0

mg/L

YESForcO2(KN)=0,6–2,0mg/L NO

Model6–Simulationofdos-ingoftheexternalsourceof

organiccarbon

W1:T=22°C,SRT=12d YESYES

ConcentrationofTNintheoutflowintherangeof9,8–12,0mg/L

W2:T=15°C,SRT=15d,18d YES YES/NOConcentrationofTNintheoutflowintherangeof

10,5–13,5mg/L

W3:T=8°C,SRT=20d NO NO

Model7–Simulationofchangeinthemanagementof

wastewaterrecycledfromdewateringsystem

W1:T=22°C,SRT=20dNorecycleofsupernatantstothebiologicalchambers

YES/NOConcentrationofTNintheoutflowintherangeof11,0–17,0mg/L

NO

W2:T=22°C,SRT=20dNorecycleofsupernatantstothebiologicalchambers+

dosingofECSYES

YES/NOConcentrationofTNintheoutflowintherangeof

10,5–13,0mg/L


Wod

ocią

gi i

kana

lizac

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J.,Asensi,E.,Morenilla,J.J.,&Llavador,F.DES-SAS: a software tool for designing, simulatingand optimising WWTPs. Environmental Model-ling & Software. https://doi.org/10.1016/j.envsoft.2007.04.005(2008).

[11] Mulas M. Modelling and control of activated sludge processes,PhDthesis,Italy,Caligari(2006)

[12] Nuhoglu,A., Keskinler, B.,&Yildiz, E.Mathe-matical modelling of the activated sludge pro-cess-the Erzincan case. Process Biochemistry.h t t p s : / / d o i . o r g / 1 0 . 1 0 1 6 / j . p r o c -bio.2004.09.011(2005).

[13] Nogaj, T., Randall, A., Jimenez, J., Takacs, I.,Bott, Ch., Miller, M., Murthy, S., & Wett, B.(2015).Modelingoforganicsubstrate transfor-mationinthehigh-rateactivatedsludgeprocess.Water Science and Technology. https://doi.org/10.2166/wst.2015.051(2015).

[14] Ujjaini,S.,Dwaipayan,D.,Trina,B.,Sandip,P., & Tamaghna, Ch. Dynamic simulation ofactivated sludge based wastewater treatmentprocesses: Case studies with Titagarh SewageTreatmentPlant,India.Desalination.https://doi.org/10.1016/j.desal.2009.10.014(201

[15] Heidrich, Z., & Witkowski, A. Urządzenia do oczyszczania ścieków – projektowanie, przykła-dy obliczeń(WydawnictwoSeidel-PrzeweckiSp.zo.o.,2005)

[16] Krzanowski,S.,&WałęgaA.Wpływwłaściwo-ści fizykochemicznych ścieków z przemysłucukierniczegonaaktywnośćczynnegoiefektyw-ność usuwania związków azotu. Infrastruktura i ekologia terenów wiejskich, 1, 163–178(2007).

Terminy okresowych kontroli stanu technicznego obiektów budowlanych - komunikat MR z dn. 18.03.2020 r.

W związku z pojawiającymi się wątpliwościami dotyczącymi ter-minów przeprowadzania kontroli stanu technicznego obiektów budowlanych MR przypomina, że nie musi być ona przeprowadza-na w chwili obecnej. Właściciele lub zarządcy obiektów mają cały rok kalendarzowy na to, aby zapewnić jej realizację.Zgodnie z art. 62 ust. 1 pkt 1 ustawy – Prawo budowlane, obiek-

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dliwe wpływy atmosferyczne i niszczące działania czynników występujących podczas użytkowania obiektu;

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wych, spalinowych i wentylacyjnych).Obiekty budowlane powinny zostać poddane kontroli co najmniej

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Szanowni Państwo,pragniemy poinformować, iż z uwagi na sytuację związaną z roz-

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