Unconventional Biological Phosphorus Removal — The Impact of Low DO Levels on Performance, Activity and Population Diversity of EBPR at Full-Scale WRRFs

Enhanced biological phosphorus removal (EBPR) treatment plants are designed with aeration zones operated at high DO levels (i.e. 2 mg/L) following unaerated zones. Low DO operation has been considered unfavorable for biological aerobic uptake of phosphorus by PAOs and is avoided in biological P removal plants. However, there are instances where low DO operation (DO=1 mg/L or less) has been proven successful for EBPR operation. The low DO environment has led to phosphate uptake rates under anoxic/low DO conditions similar to aerobic conditions. Multiple studies examined phylogenetic abundance variations and found that in low DO environment GAO clade are detectable, but with low relative abundance and Accumilibacter as the dominant PAO species. This approach can lead to substantial energy-savings while maintaining good bio-P performance.