Study of drinking water treatment by ultrafiltration of surface water and its application to China

In China, many water supplies depend on conventional water treatment. Due to unfit soil and water conservation in some regions of China, conventional water treatment has showed some defects for the poor quality of water resource. In addition, advances in membrane technology and increasing requirements on water quality have stimulated ultrafiltration (UF) for water treatment. In this research, UF test apparatus was set up to produce drinking water from raw water of the Binxian Reservoir (China). The performance of UF membranes was investigated. There was a linear relationship between membrane resistance and accumulated permeate water. Using coagulation before UF increased permeate flux and retarded membrane flux decline. Surprisingly, membrane permeate flux in a coagulation/UF process was higher than that in coagulation-sand filtration-UF process with raw water of medium turbidity. UF treatment provided effective turbidity removal. Iron, manganese and aluminum were removed completely. The UF membrane also perfectly removed all coliform bacteria. The reduction of total organic carbon was satisfactory. The treated water quality complied with China's drinking water guidelines. The Ames test showed that the mutagenic activities of membrane permeate water was negative.

UF of surface water with PAN membranes was proven very useful for drinking water production. Fig. 7. Genotoxic activities expressed as induction factors (TA98). Fig. 8. Genotoxic activities expressed as induction factors (TA100). The reduction in turbidity of the UF membrane was very efficient throughout the investigation with permeate turbidity of 0.1 NTU. Iron, manganese and alum were removed completely, except in the coagulation–UF process using PACl as the coagulant. The UF membrane also perfectly removed all coliform bacteria. The reduction of TOC was satisfactory. With the exception of one weak positive effect of raw water samples, the Ames test showed that the mutagenic activities in membrane permeate water were negative. In China, for surface water of high turbidity and fairly variable quality, a coagulation step prior to UF should be considered. The addition of coagulant not only increases the permeate flux but also retards the permeability decline. A new phenomenon was observed in our experiment: membrane flux in the coagulation–UF process was higher than that in the coagulation–sand filtration–UF process with raw water of high turbidity.