Effects of pH on enhanced biological phosphorus removal metabolisms

Laboratory-scale sequencing batch reactors exhibiting enhanced biological phosphorus removal were analyzed for pH effects on anaerobic phosphorus (P) release, glycogen degradation, and acetate uptake. Samples with non-soluble P/total suspended solids values of either 0.13-0.14 mg/mg (HP) or 0.065-0.075 mg/mg (LP) were analyzed in anaerobic batch tests with excess acetate addition at pH values ranging from 5.2 to 9.5. A polyphosphate-accumulating metabolism (PAM) had a competitive advantage over a glycogen-accumulating metabolism (GAM) at pH > 7.0. Maximum acetate uptake rates by the HP and LP samples occurred at pH values 8.0 and 6.9, respectively. Anaerobic P release/acetate uptake increased with increasing pH at rates similar to previously reported values. Glycogen degradation/acetate uptake decreased with increasing pH above pH 7, which disagreed with previous reports that glycogen degradation/acetate increased or was unaffected by increasing pH. The results suggested that the acetate uptake mechanisms of GAM and PAM may be different.