Purification of micro-polluted reservoir water from the Yellow River by membrane bioreactors combined with pretreatments

To investigate the efficiency of treating micro-polluted reservoir water from the Yellow River using PAC-MBR, four processes combined with coagulation (ployaluminium chloride and ferric chloride), coagulation-sedimentation and coagulation-air flotation were discussed, from the view of pollutants removal and membrane fouling, comparison with conventional treatment process/+UF were also made.The results showed that all these processes guaranteed the turbidity and particle counts of effluent at 0.02 NTU and lower than 50 mL^-1, with the removal efficiency above 98% and 95%, respectively. The average effluent UV₂₅₄ ranged between 0.043 and 0.045 cm^-1, and the removal rate were (18.28±9.35)%, (16.76±6.14)%, (3.23±1.26)% and (6.38±2.26)%, respectively. The average effluent COD_Mn ranged from 1.85 to 1.94 mg/L, with removal efficiency of (4.22±7.49)%, (33.20±6.99)%, (22.20±8.91)% and (41.72±14.25)%, respectively. As for particulate and organic matter, the removal efficiencies of hybrid processes were superior to conventional treatment process and almost equal to UF membrane combined processes in Nanjiao Water Treatment Plant. The NH₃-N removal was above 95%, and the accumulation of NO₂^--N was not found. Considering the effect of eliminating membrane fouling, coagulation-sedimentation and coagulation-air flotation effect were the best, followed by ferric chloride, but that of polyaluminium chloride was the worst.