Enhanced biological phosphorus removal in a semi full-scale SBBR

A 17 m(3) Sequencing Batch Biofilm Reactor (SBBR) was operated for enhanced biological phosphorus removal and nitrification for a period of 384 days. Enhanced biological phosphorus removal (EBPR) activity was instantly induce d after start-up of EBPR operation mode and low phosphate effluent values w ere reached from the first batch onward. Process stability with regard to n itrification and EBPR were very good although high nitrate loads from backw ashing disturbed the P removal performance. Due to anoxic conditions in the beginning of the cycle. readily degradable COD was depleted by dentrificat ion. Consequently, particulate matter was the main carbon source for phosph orus accumulating organisms. Anaerobic hydrolysis or fermentation was found to be the rate limiting process in the SBBR cycle. Simultaneous dentrifica tion occurred in the first 30 minutes of aeration and - to a lesser extent - during the remaining aeration time, enhancing nitrogen removal and indire ctly also phosphorus removal.