Removal of organic matter and nitrogen in municipal wastewater by a new submerged membrane bioreactor

Abstract： This study examined the performance of a new submerged membrane bioreactor for the municipal wastewater, removal characteristics of different molecular weight organic matter, and the effect of operating parameters on removal of organic compounds and nitrogen. Under the continuous inflow and intermittent aerobic conditions, the new submerged membrane bioreactor could remove efficiently the organic matter, nitrogen and heavy metal in the municipal wastewater. Average removal rates of .DOC, CODcr, NH4-N, and T-N reached 75%, 90%, 95%, and 80% respectively. The removal of small molecular weight substance (MW<4,000 daltons) was low. The mediium molecular weight substance (MW=4,000～30,000 daltons) removal rate was more than 90%. The high molecular weight (MW>30,000 daltons) substance was accumulated in the bioreactor, but was removed by submerged micro-filtration membrane at the end. Hydraulic retention time, aeration time, and non-aeration time had considerable influence on removal of organic matter and nitrogen. The most beneficial HRT was 4 hours considering both technology and economy. The best aeration time and non-aeration time were 90min and 30min respectively under the condition of a total cycling time of 120 min.