Experimental Research On Micro-polluted Surface Water Treatment By MBR Process

With the conflict of serious water pollution and stringent sanitary standard for drinking water quality, it is necessary to develop new technology for micro-polluted water treatment. Under such circumstances, membrane bioreactor (MBR) and MBR-PAC (PAC, powdered activated carbon) processes were tested for its feasibility to apply to practical projects for drinking water production. Series of lab-scale experiments were conducted with the focus on the treated water quality and membrane fouling conditions.Continuous lab-scale test proved that using MBR for micro-polluted lake water treatment could achieve treated water with good quality. Dosing PAC into MBR helped to improve the treated water quality and relieve membrane fouling. When the raw water quality belonged to the third or forth class in the Standard for Surface Water Environmental Quality, turbidity, CODMn and ammonia nitrogen of the treated water from MBR-PAC process could meet the Sanitary Standard for Drinking Water Quality (issued by the Ministry of Health in 2001) and the Water Quality Standards for Urban Water supply (issued by the Ministry of Construction in 2005). At the same time, PAC addition helped to slow the reduction of membrane flux. It reduce the total membrane resistance of MBR from 2.47×1012m-1 to 1.92×1012m-1, and accordingly relieve the membrane fouling effectively.In these experiments, the removal of organic pollutants by MBR was emphatically discussed. It is found that the dominance complementary effect between MBR and PAC exist in organic pollutants removal. Averaged 66.8% of CODMn, 66.9% of UV254 and 97.5% of UV410 could be removed in MBR-PAC process. Through establishing the mass balance equation of organic substrate in MBR, the mathematic expression of organic pollutants removal efficiency could be achieved. Based on the expression, contribution of biodegradation and membrane rejection on organic pollutants removal could be discussed quantificationally. It helped to further evaluate the mechanisms of organic pollutants removal and their specific contributions in MBR.With MBR kept running, the accumulation of inert organic compounds in the bioreactor was found, and index Am, which is named organics accumulative factor in the mixed liquor, was defined to express this phenomena. Comparing the characteristics of the mixed liquor of MBR with or without PAC addition, it is confirmed that both the mixed liquor accumulation and its characteristics have influence on the treated water quality and membrane fouling rate. Dosing PAC in MBR decreased the organic pollutants accumulation in the mixed liquor with the...