BIOLOGICAL ANOXIC PHOSPHORUS REMOVAL - THE DEPHANOX PROCESS

Simultaneous enhanced biological phosphate uptake and biological denit rification under anoxic conditions were investigated in a modified lab -scale nutrient removal activated sludge system (DEPHANOX). The aim of the experiments was to find whether it can be technologically covenie nt to use the capability of poly-P bacteria of taking up phosphate und er anoxic condition by utilizing nitrate as electron acceptor. An expe rimental comparison of removal efficiencies with a more conventional t reatment flow scheme (JHB), using low influent TKN/COD ratio, was also carried out. Phosphate uptake in anoxic condition was compared to tha t in oxic environment in batch tests. PHB anoxic and oxic degradation was evaluated by respirometric tests. Results of the long-term operati on of continuous-flow lab-scale system as well as results of batch tes ts showed that the anoxic phosphate uptake with simultaneous denitrifi cation after a previous anaerobic substrate uptake could significantly reduce the extent of competition for organic substrate between poly-P bacteria and denitrifiers. A side-stream nitrification in fixed-film reactor reduced the losses of organic carbon by oxidation and stabiliz ed the slow-growing population of nitrifiers in the system. Copyright (C) 1996 IAWQ.