Pilot Study of a Low-Pressure Membrane System Treating Surface Water of the Qiantang River

To meet increasingly stringent drinking water regulations and to accommodate worsening water quality due to pollution, a large water company in southeast China evaluated hollow fiber membrane technology to upgrade one of its water treatment plants. Pilot studies using a Pall microfiltration (MF) unit were performed to provide information for the process design of the plant. Low-pressure membranes (microfiltration and ultrafiltration) were determined to be cost-effective and reliable technology to integrate into the existing treatment plant. The results of the pilot studies indicate that pretreatment had a strong impact on membrane performance. Three different pretreatment trains were tested. The treatment train consisting of coagulation – sedimentation – GAC filter proved to be the most effective based on the rate of increase in trans-membrane pressure (TMP). Water quality monitoring at the various points of the treatment train indicated excellent removal of fecal coliforms and oxidized (iron and manganese) by MF, and NH3 reduction via nitrification in GAC filters. These data demonstrated that low-pressure microfiltration membrane can be effectively integrated with traditional treatment processes to provide high quality water regardless of raw water quality.