A biological removal of phosphorus and nitrogen by endogenous denitrification process was investigated using a pilot-scale plant. Denitrification rate decrease exponentially as the aeration period preceeding denitrification zone increased. The influent phosphorus concentration, BOD-SS loading, and magnesium and potasium concentration affected the removal of phosphorus.
A laboratory work on the bacterium, Acinetobacter calcoaceticus, which has been considered to be responsible for the biological phosphorus removal, was carried out to clarify the effect of temperature on the growth and its biochemical properties. These results suggested that some micro-organisms other than A. calcoaceticus might be also contributed to the phosphorus removal.