Stability of an ultrafiltration system for drinking water treatment, using chlorine for fouling control

An ultrafiltration (UF) system for the purification of raw water from the Yangtze River was used as an advanced treatment, following a conventional purification process. We investigated the performance of membrane fouling control, using chlorine for the pre-oxidation of the raw water. The former process was implemented via direct continuous dosing of chlorine prior to coagulation, during which the supernatant was used as an influent into a UF system. Investigations into this option indicated that the optimal dose of chlorine is 1.5 mg/L. These conclusions were reinforced by results from an investigation into molecular weight distribution and hydrophilic and hydrophobic fractions in the water treated with and without chlorine in the UF system. Scanning electron microscopy indicated that loose fragments were formed on the filtration cake during the chlorine/UF process, which was easy to remove by hydraulic washing. The analysis of tensile strength shows that the tensile ability of material is weakened during the chlorine pretreatment of the raw water in the UF system. Meanwhile, the contact angle and the field emission scanning electron microscopy experiment also indicated that the membrane material could be affected by the chlorine, which oxidizes the raw water in the UF system.