Microbiological Studies on Enhanced Removal of Phosphates from Sewage
This report was produced for the Urban Water Research Association of Australia, a now discontinued research program.
Report no. UWRAA 36
Strains of Acinetobacter were isolated from pilot- and laboratory-scale systems which were removing phosphate biologically from sewage. Several isolates accumulated phosphate as polyphosphate to levels of 15-20% of the dry weight of the cells. Selected Acinetobacter isolates were studies to determine how changes ingrowth conditions affected their ability to accumulate polyphosphate. Mutant strains which could not accumulate polyphosphate were obtained from some of the good polyphosphate-accumulating A cinetobacter isolates. From studies on these mutant strains and their parent strains a model has been proposed to explain how polyphosphate is accumulated by Acinetobacter.
The properties of the strains isolated has brought into question the accepted hypothesis that release of phosphate from polyphosphate in the anaerobic zone of plants is essential for removal of phosphate biologically.
The synthesis of poly-ß-hydroxybutyrate, which has been regarded as an essential prerequisite for phosphate removal, has also been studied in several Acinetobacter isolates. Not all isolates which synthesize polyphosphate can form poly-ß-hydroxybutyrate. This again raises some questions on the previous accepted hypotheses.
The information obtained from this study should prove to be applicable to improved operation and design of enhanced phosphate removal treatment systems.