Which are the polyphosphate accumulating organisms in full-scale activated sludge enhanced biological phosphate...

To see if the compositions of the microbial communities in full scale enhanced biological phosphorus removal activated sludge systems were the same as those from laboratory scale sequencing batch reactors fed a synthetic sewage.

Biomass samples taken from nine full scale enhanced biological phosphate removal (EBPR) activated sludge plants in the eastern states of Australia were analysed for their populations of polyphosphate (polyP)-accumulating organisms (PAO) using semi-quantitative fluorescence in situ hybridization (FISH) in combination with DAPI (4'-6-diamidino-2-phenylindole) staining for polyP.

Very few betaproteobacterial Rhodocyclus related organisms could be detected by FISH in most of the plants examined, and even where present, not all these cells even within a single cluster, stained positively for polyP with DAPI. In some plants in samples from aerobic reactors the Actinobacteria dominated populations containing polyP.

The PAO populations in full-scale EBPR systems often differ to those seen in laboratory scale reactors fed artificial sewage, and Rhodocyclus related organisms, dominating these latter communities may not be as important in full-scale systems. Instead Actinobacteria may be the major PAO.

These findings illustrate how little is still known about the microbial ecology of EBPR processes and that more emphasis should now be placed on analysis of full-scale plants if microbiological methods are to be applied to monitoring their performances.