[Influence of wastewater initial pH on enhanced biological phosphorus removal in sequencing batch reactor (SBR)]

Two laboratory-scale sequencing batch reactors (SBRs) were operated continuously to investigate the influence of wastewater initial pH on enhanced biological phosphorus removal (SBR1: pH = 6.8; SBR2: pH = 7.6). Results show that SBR2 exhibits greater anaerobic phosphorus release than SBR1. During aerobic stage, SBR2 degrades less polyhydroxyalkanoates (PHA) than SBR1, and the ratio of glycogen synthesis to PHA degradation in SBR2 is much less than that of SBR1, but SBR2 takes up more phosphorus. Further studies show that due to less glycogen synthesis in SBR2 than in SBR1, lower PHA degradation in SBR2 doesn't result in lower phosphorus uptake. The higher phosphorus uptake and PHA utilization efficiency in SBR2 is probably caused by its more phosphorus accumulating organisms (PAO). At the end of aerobic phase, SBR2 has significantly higher phosphorus removal efficiency than SBR1 (93.67% against 65.06%). Thus, the efficiency of enhanced biological phosphorus removal can be significantly improved by controlling the initial pH of wastewater. This method is much more convenient than controlling the entire process pH of wastewater biological treatment.