Possible Biological Mechanism of Phosphorus Removal

Abstract

This paper describes an investigation which was conducted to determine the location and nature of accumulated phosphorus in several enhanced phosphorus-removing activated sludges. Phosphorus accumulations were located by electron microscopy combined with the energy dispersive analysis of X-rays. In all the sludges phosphorus accumulations were located in a specific morphological cell-type, which was also the predominant organism in the sludges. These cells typically occurred in large cell-clusters and were identified as Acinetobacter spp. Quantitative analyses indicated that the intracellular polyphosphate granules contained in excess of 25 % (m/m) phosphorus and a Ca:P ratio between 0,15-0,36. These cells released o-P during anaerobiosis. Factors leading to accumulation were examined and it was found that accumulation was possible under continuous aerobic culture and was enhanced by unidentified fermentation products of raw sewage; these products also induced the accumulation of intracel1ular carbon reserves by the cells. It was concluded that enhanced biological phosphorus removal by activated sludge is dependent on the enrichment of certain Acinetobacter spp in the system.