Abundance of Candidatus ‘Accumulibacter phosphatis’ in Enhanced Biological Phosphorus Removal Activated Sludge Acclimatized with Different Carbon Sources

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In the present study, the abundance of Candidatus ‘Accumulibacter phosphatis’ and the accumulation of polyphosphate were investigated in five enhanced biological phosphorus removal (EBPR) activated sludge reactors operated with different carbon sources. Fluorescence in situ hybridization (FISH) in combination with 4',6-diamidino-2-phenylindole (DAPI) staining for polyphosphate granules confirmed the accumulation of polyphosphate by Candidatus ‘Accumulibacter phosphatis’ in all the reactors. The abundance of Candidatus ‘Accumulibacter phosphatis’ was determined from the FISH images. When EBPR activity was high and phosphorus content made up around 9% or more of mixed liquor volatile suspended solids (MLVSS), Candidatus ‘Accumulibacter phosphatis’ accounted for over 20% of the eubacteria in the reactors acclimatized with acetate, aspartate, or glucose. Whereas this value was as low as around 10% in the reactors acclimatized mainly with yeast extract, peptone, or glutamate. In these reactors, bacteria affiliated with Actinobacteria were found to accumulate polyphosphate and to contribute to phosphorus removal. Candidatus ‘Accumulibacter phosphatis’ takes part in the removal of phosphorus by using various carbon sources, but its abundance varies according to the type of carbon source.