Kinetics of anaerobic orthophosphate release and substrate uptake in enhanced biological phosphorus removal from synthetic wastewater

This paper presents some new results about the kinetics of orthophosphate release and substrate uptake occurring under anaerobic conditions in a lab-scale activated sludge plant consisting of an anaerobic first and an aerobic second step A/O-process. The synthetic wastewater contained acetate, peptone and yeast extract. The mixed culture was enriched from activated sludge samples from a large-scale plant with enhanced biological phosphorus removal. Anaerobic batch experiments were carried out with this enriched mixed culture using acetate as the only source for carbon and energy. In the first experiments, high acetate concentration was only partly consumed by the bacterial culture, resulting in a nearly total emptying of the poly-P-store (poly-P-limitation). In the next experiments, only a relatively low acetate concentration was added, resulting in a total acetate uptake and in partial emptying of the poly-P-store (acetate-limitation). This experimental strategy was successful in studying the complex kinetics of the anaerobic process in enhanced phosphorus removal. Most of the calculated kinetic coefficients depend on temperature; a dependence on pH cannot be postulated with certainty. A comparison with known results shows conformity but also differences.