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Water Environ Res. 2002 Sep-Oct;74(5):428-36.

Microbiology of enhanced biological phosphorus removal in aerated-anoxic Orbal processes.

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  • 1Department of Civil and Environmental Engineering, Unviersity of Wisconsin-Madison, 53706, USA.


The traditional process for enhanced biological phosphorus removal (EBPR) in wastewater treatment involves an anaerobic zone followed by an aerobic zone. Although there is no strict anaerobic zone in aerated-anoxic Orbal processes, phosphorus removal in excess of that required for cell growth does occur. The microbial ecology of polyphosphate-accumulating organisms (PAO) in two full-scale Orbal wastewater treatment plants was investigated using flow cytometry to physically separate PAO from non-PAO and fluorescent in situ hybridization (FISH) to identify organisms. Although Candidatus Accumulibacter phosphatis, an uncultured organism associated with EBPR in acetate-fed laboratory-scale reactors, was detected, it did not seem to be the dominant PAO in these processes. Comparative FISH analyses of the activated sludge and the PAO-rich subpopulation did not reveal the presence of a dominant group of PAO in these full-scale plants. Rather, the analysis suggested that the operational characteristics of aerated-anoxic processes might select for a diverse PAO community that is significantly different from that observed in acetate-fed laboratory reactors or in traditional EBPR configurations.

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