Experimental Study On Combined Process Of High-efficient Hydraulic Coagulation-clarification And Mechanical Sludge Thickening

With economic development, the increase of population and water shortages in many areas, drinking water is polluted in some cities, the health of residents is threatened. The release of "drinking water health standards" (GB5749-85) can not meet the needs of people's health in 1985. Therefore, the Ministry of Health and the National Standardization Management Committee has revised a new mandatory national "drinking water health standards" (GB5749-2006). The drinking water targets in new standards have increased from 35 to 106, 71 more than the one. Indicators of drinking water turbidity from 5NTU in 1976 to 3NTU in 1985, then to 1NTU in 2001, so the turbidity of water quality standards in China is very important.Water treatment plants produce large amounts of drinking water, at the same time, it also had a lot of sludge water, the waste water is mainly from the sedimentation tank, clarifier and filter backwash water. The total amount of sludge water is generally about 4% to 7% of treatment plant water in the water purification plant.and the the number is increassing. At present, sludge in most of the water purification plant in our country is not treated essentially but is pured out directly into water bodies, resulting certain environmental and social problems. State Environmental Protection Administration has demanded that, the sludge water of new or constructing large water purification plant must be addressed, then pured out after treated since 2000.For these reasons, the paper design the equipment based on existing information and relevant scientific literature for the design basis, flocculation dynamics and sedimentation management. On the basis of a guidance, clarification and sludge concentration test equipment is innovatively designed. Through the study and research of the test equipment, starting with analysis of coagulation mechanism, according to raw water characteristics, studying the conventional coagulant and flocculant aluminum polyacrylamide on the treatment effect of low temperature and low turbidity. The paper also studied how to improve the hydraulic loading and the return of the sludge on the impact of coagulation; at last, studying that the sludge thickening performance and scraper speed influence the concentration of the sludge properties and that the polymer flocculant PAM influence the sludge thickening performance.Data analysis shows that under the conditions of low temperature and low turbidity, the turbidity of high-efficient hydraulic coagulation-clarification and mechanical sludge thickening testing equipment can still be controlled under 3NTU; when the up flow rate of sedimentation increased to 6mm/s, the dosage of flocculant PAC is in the 25 ~ 35mg/L, while adding flocculant polyacrylamide 0.06 ~ 0.07mg/L, turbidity can be still controlled under 3NTU; open the return of sludge, the return location ahead, craper slow stirring, when the dosage amount of polyacrylamide is 0.16mg/L, the optimum stirring speed is 2r/min. and after 6h concentrated, sludge rate of containing solid is 4% or more.