PHOSPHATE-UPTAKE UNDER ANOXIC CONDITIONS AND FIXED-FILM NITRIFICATIONIN NUTRIENT REMOVAL ACTIVATED-SLUDGE SYSTEM

Simultaneous enhanced biological phosphate uptake and biological denit rification under anoxic conditions were investigated in a modified lab -scale nutrient removal activated sludge system. The aim of the experi ments was to find whether poly-P bacteria are capable of taking up pho sphate under anoxic conditions by utilising nitrate as an electron acc eptor. The phosphate uptake in anoxic conditions was compared to that in aerobic environment in batch tests. The results of the long-term op eration of continuous-flow lab-scale system as well as the results of batch tests showed that the anoxic phosphate uptake with simultaneous denitrification after preceding anaerobic substrate uptake could signi ficantly reduce the extent of competition for organic substrate betwee n poly-P bacteria and denitrifiers. A side-stream nitrification in fix ed-film reactor enabled to reduce the losses of organic carbon by aero bic oxidation and to stabilise the slow-growing population of nitrifer s in the system. Copyright (C) 1996 Elsevier Science Ltd