Effect of COD /N and COD /P ratios on the PHA transformation and dynamics of microbial community structure in a denitrifying phosphorus removal process

Background A lab‐scale anaerobic‐anoxic/nitrification (A 2 N) two‐sludge sequencing batch reactor (SBR) system was operated to assess the relationship among intracellular polymer conversions, bacterial population dynamics and nutrient removal performance in response to the varying influent COD/N/P . Results Complete nutrient removal was achieved in the A 2 N‐SBR in Run 3 where the COD/P and COD/N were 20.6 and 6.9, respectively. This coincides well with the highest P release/HAc uptake ratio occurring in Run 3, confirming high abundance of denitrifying phosphorus accumulating organisms (DPAOs) in the biomass. Under the stress of N or P limitation, more poly‐β‐hydroxyalkanoates (PHA) was synthesized, with the increasing proportion of poly‐hydroxyvalerate (PHV) in PHA. The population biodiversity decreased with increasing carbon loading when P loads were maintained at constant levels, and recovered to the initial level after P loading decreased . Conclusions Increasing COD/P promoted anaerobically synthesized PHA amount and favored P removal. Also, PHB seems to be the crucial internal carbon source relating to P release and uptake, whereas high nitrogen and P removal efficiencies always relate to a high proportion of PHV in PHA. Increasing carbon loading led to a decreased biodiversity of the community structure but favored higher PAO enrichments, if only P loading is not limited.© 2012 Society of Chemical Industry