The Experimental Study Of The A/OMBR Treatment On Municipal Sewage

With a large number of municipal sewage discharged in recent years, municipalsewage treatment has become an important direction of sewage treatment in China.Membrane bioreactor (MBR) combined with activated sludge process and membraneseparation technology, not only has a better effect on treating municipal sewage, butalso has the advantages of small occupation area, high resistance to shock loading andeasy operation. But the MBR process for nitrogen and phosphorus removal efficiencyis not good, it has been difficult to achieve nitrogen, phosphorus discharge standardsstipulated by municipal sewage discharge standard in our country. Therefore, makesthe improvement to the MBR process has become a research focus in the field ofwastewater treatment in recent years, and the A/OMBR process is an attempt toimprove MBR process.The A/OMBR process is an improved technology for MBR process and A/Oprocess, this paper mainly studied the effect on removal of organic pollutants ofmunicipal sewage, and the effect on removal of nitrogen and phosphorus.In this experiment, the influent COD concentration was355.72mg/L~510.23mg/L, NH4+-N concentration was17.89mg/L~33.52mg/L, TN concentrationwas35.26mg/L~51.06mg/L and TP concentration was3.63mg/L~4.71mg/L. Withthe reactor A dissolved oxygen concentration is0~0.5mg/L, the reactor O dissolvedoxygen concentration is2.5mg/L~3.0mg/L and20~25℃, this experiment operate for120days continuous and no sludge discharge during the operation system. Throughthe analysis of a large number of experimental data, it shows that the average removalrates on COD, NH4+-N,TN were92.01%,94.81%,86.67%, the average effluent CODconcentration was37.07mg/L, the concentration of NH4+-N was1.34mg/L, theconcentration of TN was6.41mg/L. They all reached municipal sewage dischargestandard(GB18918-2002), it shows that the process has a good removal on organicpollutants and ammonia nitrogen of municipal sewage, and the nitrogen removalefficiency is higher. But the average removal rate of TP is only48.32%, the averageeffluent TP concentration was2.24mg/L, much higher than the discharged limit values of TP which base on municipal sewage discharge standard, it indicate that theprocess of phosphorus removal efficiency is poor, we need to study to enhancephosphorus removal process.The fouling and cleaning on membrane were study in this paper, it found that theintermittent suction and drainage aeration effect can reduce the extent of membranepollution. And the cleaning of chemicals can remove adsorbed on the membranepollution thoroughly, it can return on about90%of the efficiency of the membrane.But the membrane after cleaning is easy to be polluted again.The experiment was also observed the activated sludge by the microscopic, itfound that the dominant species populations of microorganisms is from thefree-swimming ciliates to the attached ciliates and the metazoan, and the filamentousfrom scratch until proliferate become the dominant species in the activated sludge. Inthis process, the protozoa and the metazoa and other micro animal to control totalsludge system through predation on organic compounds and bacteria, make the MLSSin a relatively stable state. But along with the mass proliferateion of the filamentous,it create the micro animal to prey on the efficiency to reduce and the survivalenvironment worsen, it cause the micro animal quantity rapid reduction, therebyreducing the MLSS rose rapidly.