The Experimental And Modelling To Simultaneous Storage And Growth Of Activated Sludge With Acetate

Recycling valuable resources inwaste water is an important field in wastewatertreatment.Based on monitoring oxygen uptake rate (OUR), proton consumption rate(HPR), polyhydroxyalkanoates (PHA) and chemical oxygen demand (COD) profiles,this study investigated the characteristics of COD storage and consumption by addingdifferent concentrations of acetate and changing the feeding pattern into a sequencingbatch reactor.In addition， the model of SSAG-SMP was developed tosimulatesimultaneous storage and growth processes and analyze the change rules foreach processof activated sludge systems with acetate.(1) The similar profiles of OUR, HPR, PHA and COD were obtained with differentconcentration of acetate dosing in the reactor: OUR, HPR increased instantaneously andreached a peak for a period of time. PHA increased and COD decreased constantly atthe same time.After the consumption of COD, PHA, OUR and HPR began todeclineand gradually stabilized.(2)Storage and growth occur simultaneously during the feast phase, the growthoccurs on the internal storage products during the famine phase, when PHA drops to thelowest level, the activated sludge goes into the endogenous respiration phase.The resultsshowed that COD decreased to the lowest level and PHAreached at the maximumconcentrationcorrespond to the time of OUR and HPR began falling rapidly. Definingthe feast phase from the time adding substratesto reactor toOUR and HPR began fallingrapidly.The corresponding point is the symbol of the end of the feast phase.(3) The feeding pattern has an important effect on storage and consumption ofsubstrates. The similar feast-famine curves of OUR were obtained under thesubstrateaddition time of15min,30min and60min.However, the feast-famine curves of OURwere not obtained under the substrate addition time of120min and300min.With theincreasing of substrate addition time, average and maximum levels of OUR decreasedapparently, meanwhile, the yield of PHA became lower, and even the consumption ofPHA occurred. In addition, OUR and HPR increased slowly under feast phase whichillustrated that the formation of storage products, aerobic growth on substrate andaerobic growth on storage occurredsimultaneously.（4）The model of SSAG-SMP was developed based on the theory of thesimultaneous storage and growth, which combined with formation and degradation kinetics of SMP(UAP and BAP) and demonstrated the physical-chemical interaction ofCO2.Theresults ofusing the model to simulate OUR, COD and HPR coincided with theexperimental data, which proved that the model can simulate activated sludge storageand process accurately.（5） The simulation results of OUR and HPR presented eachprocess’scontribution;During the feast period, OUR and HPR of substrate storage wasalmost two times as fast as that of substrate consumption for direct growth. Inaddition,the formation of storage products, aerobic growth on substrate and aerobicgrowth on storage can occurindependently through deleting the switching function ofKS/KS+SS.The simulation results of COD presented different soluble microbial productcomponent’s contribution to the dynamic change of COD.During the whole reactioncycle,production rate of BAPremained constant. However,UAP increased under feastphase, and decreased under famine phase.（6）TheparameterskPHA,OUR、kPHA,HPRin storage on substrate and YHSTOin growthon storage were calculated bydirectcalculation andlinear regression based on the linearrelationship between OUR、HPR and PHA.The calculation results of two methods wereconsistent, which illustrated that estimation using OUR and HPR is feasible for PHAsynthesis and consumption.