PHOSPHATE UPTAKE KINETICS IN RELATION TO PHB UNDER AEROBIC CONDITIONS

Abstract

A characteristic of the biological phosphorus removal process is the interaction between different intracellular components. Therefore, an understanding of the effects of the intracellular components on biological phosphorus removal is essential for the practical application of the process. In this study, the stoichiometry of poly-hydroxybutyrate (PHB) to P-uptake and the kinetics of uptake of ortho-phosphate in relation to PHB were investigated under aerobic and substrate limiting conditions in batch experiments with activated sludge from a biological phosphorus removal process. The stoichiometry of PHB to P-uptake was investigated by determination of the degradation rate of PHB under aerobic conditions in the presence and absence of ortho-phosphate in the bulk liquid. The degradation of PHB as a function of time was described by a first-order equation. The presence of ortho-phosphate increased the rate of PHB degradation significantly, confirming that the uptake of ortho-phosphate directly required PHB. The fraction of PHB used for uptake of ortho-phosphate from the bulk liquid was estimated to be 30%. Furthermore, batch experiments confirmed that the uptake rate of ortho-phosphate under aerobic conditions was highly dependent on the concentration of PHB in the biomass. The observed uptake rate of ortho-phosphate as a function of the PHB concentration was mathematically described by a Monod equation. The maximum uptake rate of the sludge was estimated to be 14 (mg-P/g-VSS)/h. The obtained results add to the understanding of the mechanisms of the biological phosphorus removal process under the stress conditions with limiting substrate supplies present in the full-scale wastewater treatment process. Furthermore, the results indicate that control strategies to stabilise the process should focus on a maintenance and optimal utilisation of PHB. © 1998 Elsevier Science Ltd. All rights reserved