SIMULTANEOUS NITROGEN AND PHOSPHORUS REMOVAL FROM MUNICIPAL WASTEWATER BY AN ANAEROBIC/AEROBIC/ANOXIC PROCESS IN SEQUENCING BATCH REACTOR

An anaerobic/aerobic/anoxic process(AOA)in sequencing batch reactor(SBR)fed with synthetic municipal wastewater was proposed to investigate the effects of changing feed COD/N/P on the performance of simultaneous COD,nitrogen and phosphorus removal.The AOA-SBR process was stably operated over more than three months.When the ratio of COD:N:P was 800:24:11,the average COD,nitrogen and phosphorus removal efficiencies were 100%,84% and 93%,respectively.It was demonstrated that the increment of carbon substrate had an adverse effect on phosphate-accumulating organisms(PAOs)competing carbon substrate with glycogen-accumulating organisms(GAOs),which inhibited aerobic phosphate uptake.The ratio of anaerobic acetate uptake by PAO to that by GAO is 1:9.Moreover,the ratio of anoxic phosphate uptake to aerobic phosphated uptake,which indicates the fraction of DNPAOs in total PAOs,was experimentally evaluated.The results indicated that the anoxic/aerobic phosphate uptake of AOA-SBR process was much larger than that of A2O and AO processes,the AOA-SBR process allows DNPAOs to take effective part in simultaneous nitrogen and phosphorus removal when a suitable amount of carbon substrate was supplied.