Understanding microbial shift of Enhanced Biological Phosphorus Removal process (EBPR) under different Dissolved Oxygen (DO) concentrations and Hydraulic Retention Time (HRTs)

Enhanced biological phosphorus removal effectiveness is specifically conditional to systems ecology and microbial community structure. Understanding process operation aids in comprehension of microbial communities and their underlying mechanisms to improve the Enhanced biological phosphorus removal process control and troubleshooting. The performance of biological phosphorus removal (BPR) in sequential batch reactors under various aeration strategies was investigated for different dissolved oxygen (DO) concentrations and hydraulic retention times (HRT). The results showed that DO as an operational factor, highly influences P-removal performance and phosphorus accumulating organism's (PAO) dominance where high P-removal is achieved at lower DO levels. The results in this study showed, 0.8 mg/L DO concentration could achieve successful BPR with higher than 90 % removal, due to a shift in bacterial population towards PAOs. The considerable higher P-release and uptake performance have also been observed, due to a substantial decrease in glycogen accumulating organisms (GAO) abundance at low DO levels. Thus, controlled aeration at low DO concentrations, provided a selective advantage for PAOs over GAOs in microbial competition, by minimizing the putative GAOs abundance. Further investigation on high aerobic retention time, showed a decline in PAOs population and increase in GAO's activity. In addition, combination of high HRT and high DO level indicated limited P-removal and further process failure with low anaerobic P-release. Therefore, controlling DO at low levels and aerobic HRT at optimal duration promotes BPR accompanied with lower operational, controlling the system in reduction of undesirable (GAO) microbial community proliferation.