Combining anoxic denitrifying ability with aerobic–anoxic phosphorus-removal examinations to screen denitrifying phosphorus-removing bacteria

Anaerobic–aerobic (or anaerobic–anoxic) enhanced biological phosphorus- removal (EBPR) processes were generally considered for P removal. However, some isolated polyphosphate-accumulating organisms (PAOs) or denitrifying P-removal bacteria (DPB) may have varied P-removal characteristics under different conditions. This study investigated proper screening procedures for isolating DPB from piggery sludge, enriched sludge, and winery sludge. We combined anoxic denitrifying ability with aerobic–anoxic P-removal examinations to screen the DPBs as compared with conventional anaerobic–aerobic and anaerobic–anoxic P-removal examinations. It was concluded that denitrification ability detection was recommended as the first step of screening. Subsequently, denitrifiers were cultured under an aerobic–anoxic single-stage process using oxygen and nitrate simultaneously as e− acceptors to examine P-removal abilities. We chose single-stage aerobic–anoxic P-uptake denitrifiers (Types I and II) according to the purpose of P removal, whereas well-grown denitrifiers without obvious P removal might be induced by considerable PHB formation. Moreover, under anaerobic–anoxic P-removal examinations, most of the isolated DPBs had no obvious anaerobic P release, but did have significant anoxic P uptake. Pure isolated DPB cultures behaved like enriched sludge, which showed no anaerobic P release but achieved respective N- and P-removal efficiencies of 96% and 86%.