Submerged Membrane Bioreactor For Municipal Wastewater Treatment

The submerged membrane bioreactor is a new wastewater treatment technology . It has the characteristics of lower energy consumption , small space requirement , simple treatment process , easier operation and more convenient maintenance . Applying the submerged membrane bioreactor on the treatment of municipal sewage can improve effluent quality to meet more and more strict integrated wastewater discharge standard.The test researched the treatment performance of municipal sewage with the submerged membrane bioreactor .The results indicated that the removal rates of BOD5 were about 90%, the effluent levels of BOD5 were under 8mg/l; the removal rates of COD were between 50%~60%, the effluent levels of COD were about 50mg/l .The treatment of nitrogen and phosphorus of sewage has become the hot of sewage treatment at present. Membrane bioreactor has unique advantages in the treatment of nitrogen. Based on the theories of biological removal nitrogen, the contemporary nitrification/denitrification process and the shortcut nitrification/denitrification process were forced to occur in the submerged membrane bioreactor through controlling levels of dissolved oxygen . Good nitrogen removal was obtained. When the levels of dissolved oxygen in the submerged membrane bioreactor were between 0.9~7.0mg/l , the levels of dissolved oxygen in the submerged membrane bioreactor had little effect on removal rates of nitrogen in the form of ammonium . Removal rates of nitrogen in the form of ammonium exceeded 95% all the time and its effluent levels were between 0.23-1.72mg/l . But the levels of dissolved oxygen in the submerged membrane bioreactor had great effect on the removal rates of total nitrogen. The more higher the levels of dissolved oxygen in the submerged membrane bioreactor were, the lower the removalrates of total nitrogen were. When the levels of dissolved oxygen in the submerged membrane bioreactor were between 1~1.5mg/l , removal rates of total nitrogen exceeded 80%; While the levels of dissolved oxygen in the submerged membrane bioreactor were between 5.8~7.0mg/l , removal rates of total nitrogen decreased to 43.12%~62.85% or so. The pH values in the submerged membrane bioreactor varied between 6.96-8.56.Due to less sludge discharge and longer cell detention time, the biological removal phosphorus efficiency of the submerged membrane bioreactor was not well. The effluent levels of phosphorus were between 1.28mg/l~3.53mg/l.The mechanism of membrane fouling was discussed. The experiment result showed that intermittent pump drainage and aeration could reduce the concentration polarization and the fouling of membrane module.