Performance of hollow fiber ultrafiltration membrane in a full-scale drinking water treatment plant in China: A systematic evaluation during 7-year operation

Ultrafiltration (UF) was implemented as a process upgrade in a full-scale drinking water treatment plant (DWTP) with a scale of 100,000 m(3).d(-1), and the performance was systematically investigated over seven years of operation. The results showed that the UF system exhibited excellent rejection of particles and improved the removals of organics by 9.0-14.7%. The annual average UF flux decreased from 28.37 to 16.51 L.m(-2).h(-1), and it was necessary to employ various cleaning approaches at an increasing frequency for maintaining stable operation. Compared to the initial scenario, the total cost per m(3) of water for the UF system after 7-year operation increased by 55%. The cost of membrane replacement, energy, waste water and chemicals played a decisive role on operating cost in the lifecycle of the UF system. The content of cations (i.e., Mg, Al, Si, Ca, Mn and Fe), biological metabolites and organic substances in the cake layer increased significantly during long-term UF filtration, which not only aggravated membrane fouling but also affected the organic composition of the drinking water. The excellent integrity of the UF membrane during the 7-year operation was sufficient to prevent breakthrough of the organic substances from metabolic activity of microorganisms and to ensure biological safety of the permeate.