MINIMAL AEROBIC SLUDGE RETENTION TIME IN BIOLOGICAL PHOSPHORUS REMOVAL SYSTEMS

The methodology for determination of the minimally required aerobic sl udge retention time (SRT(min)aer) in biological phosphorus removal (BP R) systems is presented in this article. Contrary to normal biological conversions, the BPR process is not limited by a SRTmin resulting fro m the maximum growth rate of the organisms. This is because the aerobi c SRT should be long enough to oxidize the amount of poly-hydroxy-alka noates (PHA) stored in the anaerobic phase. This means that the SRTmin aer will primarily depend on the PHA conversion kinetics and the maxim al achievable PHA content in the cell (storage capacity). The model fo r the prediction of the minimally required aerobic SRT as a function o f kinetic and process parameters was developed and compared with exper imental data used to evaluate several operational aspects of BPR in a sequencing batch reactor (SBR) system. The model was proved as capable of describing them satisfactorily. (C) 1998 John Wiley & Sons, Inc.