EFFECT OF CONTINUOUS ADDITION OF AN ORGANIC SUBSTRATE TO THE ANOXIC PHASE ON BIOLOGICAL PHOSPHORUS REMOVAL

The continuous introduction of a biological phosphorus removal (BPR) p romoting organic substrate to the denitrifying reactor of a BPR proces s is examined through a series of batch experiments using acetate as m odel organic substrate. Several observations are made regarding the in fluence of substrate availability on PHA storage/utilization and phosp hate uptake/release. Under anoxic conditions PHB is utilized and phosp hate is taken up, indicating that at least a fraction of the PAO can d enitrify. The rates of anoxic P-uptake, PHB utilization and denitrific ation are found to increase with increasing initial PHB level. At low acetate addition rates the P-uptake and PHB utilization rates are redu ced compared to when no acetate is available. At higher acetate additi on rates a net P-release occurs and PHB is accumulated. For certain in termediate acetate addition rates the PHB level can increase while a n et P-release occurs. Whether the introduction of BPR promoting organic substrates to the denitrifying reactor is detrimental to overall P-re moval appears to be dependent on the interaction between aerobic P-upt ake, which is a function of PHB level, and the aerobic residence time. (C) 1998 Published by Elsevier Science Ltd. All rights reserved.