Long-term fouling evolution of polyvinyl chloride ultrafiltration membranes in a hybrid short-length sedimentation/ ultrafiltration process for drinking water production

Abstract

Despite the rapid increase of ultrafiltration (UF) membranes in water treatment, the UF performance in large-scale drinking water treatment plants (DWTPs) in long-term operation has not been well understood. This study was carried out to investigate the fouling evolution of two types of polyvinyl chloride (PVC) hollow fiber UF membranes in a hybrid coagulation/short-length sedimentation/UF process. Water quality analysis showed that safe drinking water could be produced in the life time (i.e., 5 years) of the UF membranes. The fractions with large molecular weight (e.g., biopolymers), microbial by-product and aromatic protein II in raw water were easily removed, and the formation potentials of most disinfection by-products except trihalomethanes were found to decrease in the DWTP. Constant filtration fluxes were maintained for both types of UF membranes, while PVC composite membranes exhibited higher anti-fouling properties than PVC alloy membranes. The key fouling factors varied with operation time, and the top three factors were hydraulically cleaning efficiency, temperature and chemical oxygen demand using statistical analyses. Finally, the evolution model of membrane fouling in the first 5-year with potential fouling factors was established using artificial neural network, and membrane fouling of another year was predicted after UF membranes were replaced with new ones.