Research And Application Of Membrane Technology For Drinking Water Production In Insular Villages And Towns

Security and guarantee of drinking water are basic conditions of the development of marine economy and the improvement of living standard of insular residents. Available natural water resource is limited on islands, and desalination of brackish water and seawater are important means for solving the problem of lacking of fresh water resource on islands. According to the special insular natural geographical conditions and operating requirements, it is of great significance to develop high-performance, economical and practical membrane technology and devices for drinking water treatment in insular villages and towns.On the basis of systematic investigation and concrete analysis of the water resources and water quality in insular villages and towns in Zhoushan city, and according to the three typical kinds of salt water on islands(raw water whose salt content changes seasonally, brackish water and seawater), three salt water treatment devices by membrane technology and demonstration bases are established respectively. Main researches are as follows.(1) Aiming at the great variety of commercial membranes, four kinds of nanofiltration and reverse osmosis membranes are researched under different operational conditions. Finally, after comparison and theoretical analysis of nanofiltration and reverse osmosis membranes through water quality, water yield, energy consumption and operational cost, ultra low pressure reverse osmosis membrane is used as the best technology for brackish water desalination, and that is confirmed by demonstration devices. And high pressure-tolerance reverse osmosis membrane is used for seawater desalination.(2) In order to reduce the investment cost and improve the inlet water quality of reverse osmosis membrane, raw water-pumping device is developed according to the geographical conditions in insular pools and reserviors. Meanwhile, improved PLC technology is used which controls the device to wash the reverse osmosis membrane by production water of RO instead of raw water before stopping operation every time. Experiments indicate that these two methods effectively prevent membrane fouling, extend the cleaning period and operational life span of RO membrane and reduce the running cost. Moreover, homemade energy recovery device is used in the equipment of seawater desalination, which increases the import substitution rate of the equipment.(3) There are four key factors that affect the application and popularization of drinking water treatment devices in insular villages and towns:quality of the production water, cost of investment, cost of operation and operational guidance. Finally, after development, manufacture, experiment and partial improvement of the divices, three pieces of salt water treatment equipment are established:(1)one for desalination of brackish water in Liuheng island(4m3·h-1);(2)one combining UF and RO for desalination of salt water and purification of fresh water in Huni island(5m3·h-1);(3)one for seawater desalination in Taimen town(1m3·h-1). These three pieces of equipment are operated automatically, run stably, and the production water all reaches the national standards for drinking water quality(GB5749-2006). Moreover, power consumption and cost of every ton production water all reach the technical and economical requirements of the project.