Development of dymanic model for growth of nitrifiers and phosphorus removing bacteria in sequencing batch reators

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The purpose of this study is to develop a non-steady state model which can express nutrient removal in sequencing batch reactors. The model was initially developed based on the IAWQ Activated Sludge Model No.2 (ASM2). A long-term experimental work was also carried out with a sequencing batch reactor (SBR) under anaerobic and aerobic condition. The reactor with an effective volume of 100 L was operated for three months. The cycle time of 6 hours was divided into four phases, which were the first mixing phase (2.0hrs) with feed of synthetic wastewater at a constant rate, the aeration and mixing phase (3.0hrs), the settling phase (0.5hrs) and discharge phase (0.5hrs). In the experiment, SRT and the DO level of aeration phase was controlled at around 20 days and 2.5mg/l, respectively. Experimental data at steady state and transient phase were utilized for the model calibration. Several kinetic parameter values were calibrated to explain the effluent quality at the steady state. The calibration works revealed that effluent P were very sensitive to kinetic parameters related to hydrolysis and fermentation processes and storage processes of PHA and poly-P by phosphorus accumulation organisms (PAO). Then a long-term simulation was conducted with the calibrated model to investigate phosphorus behavior during the start-up period. The model explained the nitrification/denitrifcation and biological P-removal processes satisfactorily. A better prediction was attaind when the denitrification ability by PAO was introduced, which was not considered in the ASM2. The quinon profile analysis was also conducted for activated sludge during a start-up period. Good correlationship between several quinon species and phosphrus removal activity. However it was difficult to identify the specific species for phosphorus removal activity.