BIOLOGICAL PHOSPHORUS RELEASE AND UPTAKE UNDER ALTERNATING ANAEROBIC AND ANOXIC CONDITIONS IN A FIXED-FILM REACTOR

Biological phosphorus removal was investigated in a fixed-film reactor with alternating anaerobic and anoxic conditions. The tests showed th at biological phosphorus removal can be obtained in a fixed-film react or with nitrate as oxidising agent. In the anaerobic period, 0.52 mg o f PO4-P was released per mg of acetate taken up on an average. In the anoxic period, 2.0 mg of PO4-P was taken up per mg of NO3-N reduced on an average. The relationship between potassium released and phosphate released in the anaerobic phase was determined to be 0.37 mg K/mg P, while the relationship between potassium taken up and phosphate taken up in the anoxic phase was determined to be 0.36 mg K/mg P. The phosph orus concentration in the sludge was determined at 8-10% of dry solids .