Pilot-scale Research on Advanced Treatment of Surface Water from Beijing-Hangzhou Grand Canal with Seasonably Variable Temperature Based on Hollow Fiber Nanofiltration

As the first pilot-scale study based on hollow fiber nanofiltration (HFNF) technology using natural surface water as feed streams in China, the research aims at exploring and developing low-expense and high-efficiency operating technologies for HFNF systems which are expected to be applicable for the advanced treatment of micro-polluted surface water with seasonably variable temperature. During the 240-day pilot testing, the operating conditions of a certain stage could be considered as the optimal ones with average influent pressure of approximately 4.05 bar and membrane flux ranging between 23 LMH and 25 LMH, whose recovery rate was maintained between 80% and 90% and operating expense was approximately 0.5279 RMB per ton of permeate. With the quality of permeates meeting both national standards and local standards of Jiangsu province for high-quality drinking water, the removal rates of suspended particulates and microorganisms of HFNF system were basically equal to those of SWNF system, while the removal rate of organic contaminants was moderately lower and the salt rejection rate declined by approximately 50% compared with those of SWNF system, indicating that the HFNF technology is more adaptable for non-brackish surface water which is limitedly polluted with inorganic salts or minerals. Currently, a universal platform of HFNF membranes is designed for the full-scale demonstration based on the operating parameters and technical solutions obtained from the research involving the prediction model of concentrate reflux ratio, selection methodology of hydraulic cleaning modes, restoration strategy of salt rejection rate, etc.