Experimental Study On Enhanced Coagulation To Mopanshan Reservoir Water

Mopanshan reservoir is the main source of drinking water for Harbin; however, the quality of this water has been deteriorated in recent years, resulting in the trend of eutrophication and increase of organic contaminants. With respect to the treatment of drinking water, Enhanced Coagulation (EC) can achieve good effect on organic contaminants removal, including disinfection by-product formation potentials which mainly consist of humic substances. As an ultimate safeguard of human health, the process of EC greatly improves the quality of drinking water. Begun with the analysis of quality characteristics of Mopanshan reservoir water, researches on four types of coagulant, the dosage of optimum coagulant, temperature, pH value and coagulant aid through the series of jar tests were comprehensively studied, as well as optimal coagulant synthesis and influence on coagulation effects exerted by basicity of it in the dissertation.The results were indicated that Poly Aluminum Chloride(PAC) were strongly adaptable to low temperature and low turbidity water of Mopanshan reservoir. The satisfied hydraulic conditions were mixing rate of 250r/min,mixing time of 100s, first flocculating velocity of 80r/min, first flocculating time of 11min second flocculating velocity of 25r/min, second flocculating time of 7min and sedimentation time of 30min. And the coagulation effect of PAC got better along with the increase of water temperature. However, coagulation effect of PAC was influenced slightly when pH value of raw water floctuate conventionally. The results of the research on coagulant aid were as follows. Polyacrylamide(PAM) could improve the density of alum particle which could play a positive role in enhancing coagulation effect on turbidity removal itself as long as being dried, ground and dissolved. Alum particle was also proved to be effective on decrease the dose of PAC, which was a result with economic value. The improvement of organic compounds removal was indicated that chitosan (CTS) could enhance the coagulation effect productively; The further research on CTS was indicated that HC1 solution can be considered as a better solvent of CTS because of the inhibition on the contribution of organic matter on treated water. And the CTS which had a high viscosity showed a better activity on improving coagulation effect by PAC. At the same time, according to the current experimental data, the correlation between CODMn and UV254 was relatively high for Mopanshan reservoir water.Based on the research of industrial synthesis of PAC and optimization of technics condition, an array PAC with different basicities was synthesized through different mass ratios between calcium aluminate powder and industrial synthetic hydrochloric acid. The results of experiment showed that optimal turbidity and organic compounds removal rate was achieved at basicity 85%-90% of PAC, which, to a certain extent, has positive impact on pH value of treated water as well.In this project, the removal of organic contaminants in raw water was significantly improved. Meanwhile, the turbidity value was reduced and the economic cost of actual operation was lowered on the basis of maintaining the existing processing in Harbin Mopanshan Water Treatment Plant.