effects of anaerobic reaction time and sludge age on the biological phosphorus removal in sbr

in this research, a plot consisting of two sequencing batch reactors (sbr) both reactors were anaerobic stageand its aeration time was had the primary anaerobic stage witling change inthe'touilr:eaction time (9.5 hours).the average concentration of influent phosphorus and rector were 7.5 and 800 miligram per litre respectively. in two months periods the average effeciencies of phosphorus removal for the blank reactor and the second reactor with anaerobic reaction times, of 2,3, and 4.5 hours were 16%, 26%, 64%, and 99% respectively. in the reactor with anaerobic of 4.5 hours, increasing the sludge age from 5 days to 10 days resulted in decreasing of phosphorus removal efficiency from 99% to 87%. . in general, the result of this investigation show that the increases of anaerobic reaction time can increase the efficiency of phosphorus 'removal, because of the prevalence of phosphorus removing . microrganisms over other species. also the accurate control of additional sludge volume (sludge age) has an appropriate effect on the removal efficiency.