THE RELATIONSHIP OF BIOMASS TO PHOSPHATE-UPTAKE BY ACINETOBACTER-JUNII IN ACTIVATED-SLUDGE MIXED LIQUOR

The involvement of Acinetobacter in biological excess phosphate remova l from the activated sludge process is widely accepted, though its rol e is not yet clearly defined. To better understand why activated sludg e systems remove phosphate, different cell concentrations of Acinetoba cter junii (10(4), 10(5), 10(6), 10(7), 10(8) cells . ml(-1) initial b iomass) were used as inoculum in a mixed liquor medium containing sodi um acetate. The phosphate uptake capacity was dependent on the biomass concentration. Low initial biomass concentrations triggered the relea se of phosphate once transferred into the mixed liquor. Release of pho sphate increased during active growth and uptake occurred when cells r eached the stationary growth phase. High initial biomass concentration of Acinetobacter junii (10(8) cells . ml(-1)) resulted in uptake of p hosphate during the entire duration of the experiment leading eventual ly to complete phosphate removal.