Study On Combination Processes Of Watertreatment Based On Flotation-sedimentation Tank Treating Reservoir Water Derived From Yellow River

This subject was supported by "the Research and Demonstration of Flotation Technology as the Core of the Integration"(2008ZXO7422-003), part of the research of "Major Science and Technology Program for Water Pollution Control and Treatment". Flotation-sedimentation treatment process for reservoir water derived from Yellow River was carried on in this paper. The study mostly aimed at the removal characteristics by the combination processes of potassium permanganate pre-oxidation, sand/GAC-sand filter with flotation-sedimentation tank.The contents of this paper included four aspects:the optimum operating parameters study of flotation-sedimentation process; comparative study of the flotation unit and sedimentation unit; combination process of sand/GAC-sand filter and flotation-sedimentation; combination process of potassium permanganate pre-oxidation and flotation-sedimentation.The optimum operating parameters study of flotation-sedimentation process. Considering the pollutant removal efficiency and power consumption, it was recommended the optimal dosage of PAFC as a coagulant was3mg (Al3+)/L and the best reflux ratio was10%when running the flotation unit, the optimal dosage of PAFC was5mg(Al3+)/L and sludge discharge cycle was2d when running the sedimentation unit.Comparative study of the flotation unit and sedimentation unit. The sedimentation unit water was better than the flotation unit for the removal when the turbidity was2.55NTU-3.80NTU, CODMn value was2.56mg/L-2.97mg/L, average TOC was higher than3.323mg/L of raw water. Overall the flotation unit was better than the sedimentation unit for the removal of UV254. According to removal effects of turbidity, organics and energy consumption, from July to September, it was better to run sedimentation unit for treating reservoir water from Yellow River.Combination process of flotation-sedimentation tank and sand/GAC-sand filter. Sedimentation unit had good removal efficiency for the conventional indicators. Sand filter was no significant removal of CODmn、UV254and TOC for sedimentation unit but had good intercept effect of particulate matter. Odor level analysis gradually decreased with process flow of the flotation-sedimentation tank and sand filter. GSM of flotation-sedimentation tank effluent was under detection limit. Sedimentation unit on THMFP removal was mainly to the CHCI3and CHCl2Br removal. Flotation-sedimentation tank was better removal of THMFP than combination process. THMFP, GSM and MIB contents of combination process effluent were under prescribed limits of the 《Standards for Drinking Water Quality》(GB5749-2006). The average removal of chlorophyll a, blue-green algae and particulate matter by combination process were76.95%,86.31%and99.22%and the removal effect was stable. The flotation unit optimal dosage of PAFC was3mg(Al3+)/L, lower than5mg(Al3+)/L of sedimentation unit in combination process of flotation-sedimentation tank and GAC-sand filter. Flotation unit and GAC-sand filter had good removal efficiency for the conventional indicators. GAC-sand filter had good removal effect of CODMn, UV254and TOC for flotation unit effluent. Flotation-sedimentation tank had obvious removal effect of CHCl2Br, CHClBr2and CHBr3. Totally, combination process of flotation unit and GAC-sand filter was better in conventional indicators, THMFP, chlorophyll a, blue-green algae and particle matter removal than combination process of sedimentation unit and sand filter. Flotation-sedimentation tank and GAC-sand/sand filter combination processes could effectively decrease three halogenated methane formation potential (THMFP), which made water quality better and more security.Combination process of potassium permanganate (KMnO4) pre-oxidation and flotation-sedimentation+sand/GAC-sand filter. The KMnO4had the effect of coagulation-supporting to remove turbidity, odor and UV254when it was used with coagulant. The optimal dosage of KMnO4was0.3mg/L. Combination process of KMnO4pre-oxidation, flotation-sedimentation tank and sand filter were more than90%of the removal of turbidity, algae and particulate matters. Odor level analysis gradually decreased with process flow. Influent and effluent GSM contents of each unit were under the detection limit. KMnO4pre-oxidation increased CHCl3removal of flotation-sedimentation tank and sand filter, had little effect on THMFP removal of flotation-sedimentation tank and slightly increased THMFP removal of sand filter. After pre-oxidation of0.3mg/L KMnO4, CODMn, UV254and turbidity removal rates of flotation-sedimentation tank and GAC-sand filter combination process were increased by20.52%,20.17%and13.88%. Odor level analysis gradually decreased with process flow, from raw water level4to effluent level1.6. Influent and effluent GSM contents of each unit were under the detection limit. KMnO4pre-oxidation increased CHCl3and CHBr3removal of flotation-sedimentation tank, had little effect on THMFP removal of flotation-sedimentation tank and increased THMFP removal of sand filter to a certain degree. THMFP and GSM contents of combination process effluent were under prescribed limits of the 《Standards for Drinking Water Quality》(GB5749-2006). Average removal rates of chlorophyll a, blue-green algae and particle matter were66.64%,95.44%and99.34%, which removal effect was stable. Potassium Combination process of KMnO4pre-oxidation, flotation-sedimentation tank and GAC-sand filter could effectively decrease THMFP, which made water quality better and more security.