Application On Ultra-Low Turbidity Water By Enhanced Micro-Filtration

With the development of social economy, the quality of the source of drinking water in our country is suffering varying degrees of pollution and getting worse day by day. At the same time, drinking water quality index improves continually. In the new 《drinking water sanitary standard)), the total organic matter is commanded, CODMn is not exceeding3mg/L, and turbidity is blow1NTU. In the modern waterworks of Zhejiang Province, turbidity of effluent is commanded to blow0.1NTU.Aim at the ultra-low turbidity of filter inflow (0.5NTU), a study is made of the pilot scale tests and the production tests by enhanced micro-filtration. Homogeneous quartz sand is used as filter material. A pilot-scale research on the influence of inflow turbidity, filtering velocity, coagulant dosing quantity and backwash to the filter was carried out. And a study on short-term flocculation was made. Application on filter by low backwash intensity is studied in the production tests. Optimization study of coagulant dosing quantity is made based on the change of inflow turbidity.Results of the pilot scale tests show that the length of cycle of filter operation is based on the inflow turbidity, filtering velocity and coagulant dosing quantity. High coagulant dosing quantity reduces the cycle of filter operation. For the inflow turbidity in0.21-0.26NTU, the turbidity of filter effluent can reduced blow0.1NTU by using low backwash intensity alone, but it costs long time. By using the filter control technology of low water backwash intensity and short-term flocculation, it can quickly make the turbidity of filter effluent below0.1NTU and greatly extend the cycle of filter operation. Using appropriate backwash intensity and short dosing coagulant aid to keep filter media mature state is a key factor of low turbidity water filtration.Results of the production tests show that the filter effluent is respectively below0.1NTU in lOmins after backwash by using enhanced micro-filtration cooperrated with low backwash intensity treating ultra-low turbidity inflow. The turbidity is blow0.05NTU while the virus particle is blow30/mL after stable run. The cycle of filter operation can be48h. Under the premise of basic consistent of effluent quality, it can save28.6%water and38.9%power consumption by using low backwash intensity than original backwash intensity. Through the optimization of coagulant dosing, the filter effluent water quality is up to standard and extend the filter filtrationcycle at the same time when the inflow quality changes.Therefore, enhanced micro-filtration cooperrated with low backwash intensity treating ultra-low turbidity inflow, the turbidity and virus particle of effluent can reach the standard, and the operating cost of the waterworks can be reduced greatly.