Phosphorus metabolism and population dynamics in a biological phosphate-removal system with simultaneous anaerobic phosphate stripping.

In this study, the metabolism of phosphorus and changes in population dynamics were investigated via simultaneous chemical stripping in sidestream in an acetate-fed sequencing batch reactor. The synthesized intracellular polyphosphate (poly-P) by polyphosphate-accumulating organisms (PAOs) gradually decreased when the biomass was subjected to 83 d of P stripping. Initially, the P removal efficiency of the system improved from 94.3% to 96.9%. Thereafter, a relatively high level of P in effluent was observed, during which time the stoichiometric ratios of Prelease/HAcuptake decreased, Glycogendegraded/HAcuptake and poly-β-hydroxyvalerate/PHA increased. The results revealed that a metabolic shift from polyphosphate-accumulating metabolism to glycogen-accumulating metabolism. Correspondingly, PAOs declined to less than 1% of the population, glycogen-accumulating organisms proliferated to almost 20% instead. The results of PCR–DGGE also indicated that the microbial community structure considerably changed in response to the gradually decreasing poly-P content. These findings imply that intracellular poly-P level is important for the stable of P removal system. Furthermore, it suggests that it is not a stable and effective way for P recycling from anaerobic stage of the biological P removal system in sidestream.