Applicated Rearch Of Membrane Technology To The Reuse Of Circulating Discharge Water

Water is an essential substance for the survival of human beings as well as also for the development of society. It is a sort of finite precious resource, which is not substitutable. China is lack of water resources and water is polluted severely, especially in the north of China. With pollution and shortage of water resources being serious day by day, water resources have already become the constraining factor of the power industry. With the strategy of sustainable development and people's consciousness of environmental protection, controlling and decreasing emission of waste water become one of emphases of prevention and control of pollution. In a power plant per-day, more than 70% of water feed to cycling water system. In this system, evaporating wastage is about 70%, discharging wastage is more than 20%. Thus reusing the discharging water is efficaciously to save water. Ultrafiltration and reverse osmosis were used for the treatment of circulating discharge water so as to use it for the make-up water of the boiler.Taking a power plant as an example, the author first analyzes the discharging water quality, then tests in the spot. The permeate water of ultrafiltration and reverse osmosis are used as the supply of boiler feed water treating system. The feasibility and the optimum operating conditions of ultrafiltration followed by reverse osmosis are tested through a series of trials. In the practical application the system operation parameter was determined and operating expenses and problems are described.The experimental result of UF showed that the mode (production: 45 minutes; backwash: 50 seconds) could maintain the membrane performance of rejection and permeability. The product COD_Mn was between 0.48mg/L and 1.42 mg/L, the turbidity was between 0.046NTU and 0.1NTU, SDI≤1.2,residual chlorine < 0.04mg/L. The outlet water quality could meet the requirement of the RO inlet water. The experimental result of RO showed that RO desalination rate was over 98.5%. The electric conductivity of the water from RO was between 11.4—13.1μs/cm , which helped to reduce the load of the following ionic exchange system greatly.On the basis of the above experiments, a project was designed, and an economic analysis was carried out on the plant. This technology created a new way for the utilization of circulating cooling discharge water, which saved water resource and decreased the environmental pollution.