Experimental Research On Municipal Sewage Treatment By Membrane Bioreator

Membrane Bioreactor (MBR) is a novel wastewater treatment technology. With the prevention of membrane, the reactor can keep very high sludge concentration to reduce the sludge loading rate and enhance the treatment efficiency. Researches on MBR technology develop very fast all over the world, which mainly focus on, the removal of organic waste, nitrogen and phosphorous and other influential factors for the municipal wastewater treatment and reuse, the optimization of operation parameter, membrane fouling mechanisms and membrane fouling control measures.However, some limiting factors still exist for the wide spread of MBR in municipal wastewater treatment and reuse. With the more and more stringent of wastewater treatment criteria, the removal of TN and TP in MBR has become a very important parameter in real projects. The membrane bioreactor can provide advantages for the growth of nitrification bacteria, however, the long sludge retention time (SRT) in the membrane bioreactor is in contrary with the short SRT needed for phosphorous removal, so it's difficult to realize satisfied phosphorous removal efficiency in the traditional MBR, and researches on simultaneous nitrogen removal and phosphorous removal in MBR are still needed. Membrane fouling is also an influential factor for the application of MBR technology and the increase of project cost. So the researches on membrane fouling mechanism, nitrogen and phosphorous removal efficiency are key points for application of MBR technology.The purpose of this paper is, basing on traditional MBR and SBR, to construct Two-stage membrane bioreactor (TSMBR) to treat municipal wastewater and realize simultaneous nitrogen and phosphorous removal. Nitrogen removal and phosphorous can be removed in different chambers. After operation for a short period, the removal of COD, Ammonium-Nitrogen, total nitrogen (TN), and total phosphorous (TP) efficiencies were 94%,93%,90%,90%, and the system represented good wastewater treatment ability. Intermediate aeration was used during the operation, and trans-membrane pressure (TMP) was kept and 0.15bar~0.18bar. The membrane fouling didn't increase with the reduction of aeration and the wastewater treatment effects were acceptable. Membrane fouling was also studied through the analysis of sludge concentration (MLSS), extra-cellular polymeric substance (EPS), TMP, sludge settling ability (SVI), sludge loading and etc. Reasons for membrane fouling and membrane fouling control measures were also discussed.During the last period of operation, the release of sludge was stopped in the system. With the increase of sludge concentration, the TMP increased and severe membrane fouling occurred. After analysis of the variation of sludge concentration, the critical sludge concentration of this system should be around 7000~8000mg/L. Physical and chemical clean were performed for the fouled membrane and the TMP recovered 97.3%.