Ecologycal characterization of polyphosphate accumulating organisms in enhanced biological phosphorus removal Processes and its application

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Following five investigations were conducted to clarify the ecophisiology of polyphosphate accumulating organisms (PAOs). (1) Population structure of PAOs in full scale wastewater treatment plants (UTPs), (2) screening for novel groups of PAOs, (3) development of MAR-FISH method for the quantitative evaluation of anaerobic carbon uptake by PAOs and glycogen accumlating organisms (GAOs), (4) the effect of pH on the anaerobic carbon uptake by PAOs and GAOs, and (5) microbial interactions within activated sludge.In (1), DAPI staining for polyphosphate granules was applied to the specimens analyzed with FISH. It was found that Accumulibacter phosphatis and Actino1011 positive Actinobacteria accounted for almost or more than half of total PAOs. In (2), we developed an oligonucleotide probe that detect novel PAOs in Actinobacteria. Also, we confirmed the existence of PAOs in Gammaproteobacteria. From (3) and (4), it was found that pH is not a key factor that affect anaerobic carbon uptake performances of PAOs and GAOs. Yet, our result is contradictory to the outcomes reported by other research groups. In (5), we showed that unknown factors in activated sludge or its supernatant affect the performances of PAOs. Further, we isolated bacteriophages that are lytic to Microlunatus phosphovorus, one of the few isolated PAOs.In conclusion, we confirmed the existence of different PAOs. And the present study reveiled basic ecophysiology of PAOs. Yet, in order to achieve better and more stable performance of enhanced biological phosphorus removal, it is needed to more closely understand the relationships between different microoganisms.