• Biological phosphorus removal;
  • Activated sludge;
  • Anoxic phosphate uptake;
  • Polyphosphate-accumulating bacteria;
  • Acinetobacter

Abstract Activated sludge samples from pilot plants using different processes for enhanced biological phosphorus removal were investigated for the occurrence of polyphosphate-accumulating bacteria. All samples showed a direct correlation between the relative number of phosphate-accumulating bacteria and phosphate uptake. Various species of bacteria with polyphosphate granules were found in sludge flocs, but in every case Acinetobacter-like cells formed part or the main part of the polyphosphate-accumulating bacterial population. The spectrum of the bacteria with stored polyphosphates varied, depending on the sewage composition on the one hand and on the processes used for phosphorus removal on the other hand.