Study On Membrane Fouling Control For A Submerged Membrane Bio-reactor

Submerged membrane bio-reactor is a latest wastewater treatment process and membrane fouling control is the key to its spread. In the paper, the membrane fouling process and fouling control methods for a submerged membrane bio-reactor were studied. At first, the mechanism of membrane fouling was analyzed. Then, pertinent membrane fouling control countermeasures to facilitate long-term operation were investigated. The experiments showed that the cake layer resistance was dominant among the total trans-membrane resistance and was the main source of membrane fouling. Microorganism contamination could not be neglected in long-term operation. Therefore, membrane-fouling control should focus on effectively control the accumulation of cake layer and microbes. In order to optimizing the hydraulic condition in the reactor, constant aeration and intermittent pumping was conducted and optimal aeration quantity, pumping period and pause period were identified which could slow down cake layer accumulation and flux decline. Hydraulic rinse through constant aeration could hold the convection transfer from the sludge mixture to membrane surface and boost up the counter-diffusion and transfer along the membrane surface so that flux could be recovered to a certain degree. By comparing MBR combined with conventional activated sludge system and bio-film system, the latter showed its advantage in reducing the COD concentration difference between the outside and inside of the membrane, resisting the accumulation of dominant contaminants and relaxing the trend of flux decline. As to different membrane module styles, the flat module was more tolerant to membrane fouling than bunch module since the former was easy to have its hollow fibers and mixture among them vibrant with the disturbance of aeration. To control the microbe contamination, chemical cleaning using sodium hypochlorous had satisfactory result for eliminating organic and bacteria contamination.