Research On Mathematical Models Of Aerobic Granules Based On Population Balance Equation

With self-flocculating of microbial cells, aerobic granular sludge is microbialaggregates formed by biofilm enwrapping action. The advantages of aerobicgranular sludge, i.e., high density, structural stability, better settleability and higherbiological retention rate, make it able to treat waste water containing organicsubstance and toxic substance with high concentration. However, optimal operatingcondition of the formation and stability of aerobic granular sludge are still unableto be determined. Therefore, based on population balance equations, the model ofaerobic granular sludge was developed to model the process of aerobic granulation.The model is useful to control the process of aerobic granulation, and providesguidance for the stable operation of aerobic granulation reactor.Based on the investigation of latest research results of aerobic granular sludgeand population balance equations, the model containing breakage, growth and sinkprocess was developed, and solved using Matlab software. During building thebreakage model, breakage function and selection rate constant were determined.The breakage model was verified by the breakage experiment, and satisfactoryconsistence was obtained. Based on the observed yield, etc, the growth ratefunction which was basically in accord with the actual granulation was built.Referring to the pre-existing mathematical model of activated sludge,sedimentation model was built. Settling rate was calculated by Takacs formula.1-Dflux model and population balance equation were combined to simulate the numberdistribution of aerobic granular sludge during granule settling.Finally, population balance equations containing breakage, growth andSettling process was tested by the existing experiment research of aerobic granularsludge. Satisfactory consistence was obtained. During the test, population balanceequation containing different processes is applied to simulate aeration, settling,discharging, and feeding period. This also provides guidance for the mathematicalmodel of aerobic granular sludge based on population balance equations.