Effect of feeding length and dissolved oxygen on biochemical storage under anoxic conditions

Poly-β-hydroxyalkanoates (PHA), as one of internal polymers stored in microorganisms, plays an important role in the enhanced biological phosphorus removal process. Six identical anoxic-aerobic sequencing batch reactors (SBRs) were used to investigate the effect of feeding length and dissolved oxygen (DO) concentrations on biochemical storage of activated sludge. The results indicated that the feeding length had insignificant influence on biochemical storage under anoxic conditions. The storage levels of PHA were decreased slightly with gradual increasing of feeding length from 10min to 60 min, 90 min and 120 min. The maximum difference was 0.21 mmolC/L and the f was fluctuated between 0.84 and 0.90. Keeping DO to be low concentration in aerobic stage was more favorable for increasing the storage of PHA, compared to high DO concentration. The PHA storage amounts were 3.1 mmolC/L and 5.0 mmolC/L under high DO (2.0 mg/L) and low DO (0.5 mg/L) in two reactors with feed length of 90 min, respectively. The biomass acclimated to long feeding length could store more substrate when feeding length changing from long time into short time. Moreover, the PHA production amount was higher under high DO concentration than that under low DO concentration