Study On Domestic Wastewater Treatment Using Compound Precoating Dynamic Membrane Bio-reactor

The Membrane bioreactor (MBR) is a new wastewater technology which combined membrane separation with biological treatment technology. There are lots of advantages on MBR, such as high effluent quality, less energy consumption, smaller footprint and less sludge production and so on. However, the high initial membrane cost and membrane fouling reduced dramatically the widespread use of MBR.In this paper, the domestic wastewater was cleaned by compound precoating dynamic membrane bio-reactor(CPDMBR), which was made up of suspended carrier biofilm and precoating dynamic membrane. The filter cloth was used as the filtration module, which was coated by powdered activated carbon(PAC), and then puting fillers into reactor to improve the efficiency of wastewater treatment. Firstly, the suitable concentration of the PAC dynamic membrane have been investigated in this experiment, secondly, the removal efficiency of pollutants in different operational condition and styles. Last but not the least, the reasons of membrane fouling, and the change of membrane flux, and the membrane cleaning method were also discussed.(1) Based on the selection of filter material, the polyester staple fibre was considered as the better choice. The suitable precoating concentration was 0.70 g·L-1.(2) For CPDMBR with pump suction operation, the optimum operating condition was:HRT 9 h, DO3.3～3.8 mg·L-1. During the stable operation, the CPDMBR has a high removal efficiency of pollutants, the average removal rate of COD, TN, TP and turbidity reached 92.59%,73.51%,81.06%,100.00%, respectively.(3) For CPDMBR with gravity outflow, the critical pressure was about 25～30 cm water head drop, which means 2.45～2.94 kPa on the condition that MLSS was 4.9～5.6 mg.L-1 and the aeration intensity was 500 L.h-1. The removal of COD and TN could amount to 93.75% and 67.74%.(4) In the pump suction operation, membrane fouling could be divided into two stages. The resistance arising from cake formation was 78.9% of total resistance, and the resistance due to pore blocking account for17.0%. (5) The running period was 30 days for HDMBR with gravity outflow. The condition of the 600 L·h-1 of aeration intensity and the 4600～5200 mg·L"1 of MLSS slowed effectively the membrane fouling. The cake layer still was the main reason of membrane fouling, which amounted to 90.4% of the total resistance. The membrane recovery coefficient reached to 96% after hydraulic cleaning, and the flux could be recovered to nearly 100% just by brushing.