Study On Combined Technics Of Multistage Bio-contact Oxidation And Membrane Separation

Membrane fouling is the bottleneck which limits its development in the research and practice of conventional membrane bioreactor (MBR). MBR couldn't run normally, life of membrane was shortened and the cost for MBR was increased because of membrane fouling. Sludge deposits on parts of membrane surface, bacterial secretion in it plays an important role in zoogloea cohered, and it sticks to membrane or enters membrane channel, then causes membrane fouling. In the study, activated sludge was replaced by multistage biological contacting oxidation, the combined process of multistage bio-contact oxidation and membrane separation was formed, and equipment of the combined process was made, the main purpose is decreasing membrane fouling.The effect of operating vacuum and aeration quantity in the part of membrane separation to membrane flux was studied, and then the best operation condition was determined, under the temperature of 18-22℃, corresponding membrane flux is suitable when the operating vacuum is 0.014-0.02MPa and the aeration quantity is 0.2m3/h-0.3m3/h. So 0.02MPa operating vacuum and 0.3m3/h aeration quantity were chosen in the study. The membrane flux is 40 L/(h·m2) at the moment.Treatment effect of combined process on domestic sewage was studied, results show that: the combined process has good effect on domestic sewage of lower or higher concentration, volumetric loadings of CODCr and NH3-N are respectively 4.4 kg/(m3·d) and 0.13 kg/(m3·d), and running is stable. Effluent quality can reach national discharge standard I when influent CODCr concentration is lower than 1200mg/L and influent NH3-N concentration is lower than 50mg/L.Treatment effect of combined process on soybean wastewater was studied, effluent quality is better than water quality standards of intermediate water of DaLian.Membrane flux during experiment was monitored, ultrafiltration membrane was cleaned for the first time when the experiment went along 135days, after cleaning, the membrane flux renewal reaches 95%, and it has not obvious change in after experiment. Compared with conventional MBR, the combined process of multistage bio-contact oxidation and ultrafiltration membrane achieves the goal of reducing membrane fouling indeed, thus the operation cost is decreased.