Study On Emergency Treatment Technology For Sudden Pollution Of Urban Water Supply

In recent years, china's sudden water pollution incidents frequently happened, a serious threat to urban water supply. At present water treatment plant had no ability to cope with the sudden water pollution accidents. Once the incidents happened, how to ensure municipal safety water supply was a pressing problem.In view of the sudden water pollution incidents, the polluants which are representative and difficult to treat with conventional treatment process were selected as the object of study on emergency treatment technology for sudden pollution of urban water supply. And take the pesticide of chlorothalonil, benzene hexachloride, dichlorvos, chlorpyrifos, atrazine, chemical products of nitrobenzene, m-nitrochlorobenzene, Di-(2-ethylhexyl)phthalate, anionic detergent, alage and taste and odor substance as the object of the study. Adding chemicals was selected as emergency treatment technology considering the characteristics of the emergency facilities on the basis of existing water treatment plant. Activated carbon adsorption and chemical oxidation which were selected as the emergency treatment process of the study were researched.It showns that powdered activated carbon have a good effect on removal of pesticide and chemical products researched in this paper. Adsorption kinetics study shows that the fast adsorption of polluants by powdered activated carbon was at the first 30min, then reached adsorption equilibrium at 120 min. The pseudo second-order adsorption kinetics can be better fitting pesticide and chemical products adsorption process. Adsorption isotherms research shows that Freundlich adsorption isotherms model is fitting pesticide and chemical products adsorption equilibrium. Freundlich adsorption isotherms model can be used to calculate the theoretical dosage of powdered activated carbon facing the sudden water pollution incidents. The factors influencing adsorption-powdered activated carbon effect include the type of powdered activated carbon, adsorbate and water quality conditions.Atrazine, Di-(2-ethylhexyl)phthalate and anionic detergent were selected as the research object of pilot-scale study. The results indicated that the removal rates of atrazine, Di-(2-ethylhexyl)phthalate and anionic detergent by conventional process was 4.34%,6.85% and25.02%, respectively. Using Freundlich adsorption isotherms model to calculate the theoretical dosage of powdered activated carbon, the dosage was 20 mg/L,15 mg/L and 40 mg/L, respectively, slightly higher than theoretical dosage.Chlorine dioxide can efficiency remove Microcystic aeruginosa, Chlorella and Fragilaria capucina. Chlorine dioxide is better removing Microcystic aeruginosa and Chlorella than Fragilaria capucina. The removal efficiency of chlorophyll-a was in positive correlation to chlorine dioxide dosage and the reaction time, and higher in acid environment than in alkaline condition. Pilot-scale study indicated that chlorine dioxide pre-oxidation enhanced the effect of conventional process dealing with source water of high algae. The optimal dosing quantity of chlorine dioxide was 0.3mg/L, at which, the removal rate of degree of turbidity, CODMn and UV254 raised 2.8%,14.78% and 19.81% respectively. The removal efficiency of chlorophyll-a reached to 43.43% after chlorine dioxide pre-oxidation, relieving impact of high algae water to conventional process.As for taste and odor released by algae, the results showed that potassium permanganate, composite potassium permanganate and chlorine dioxide pre-oxidation could enhance the effect of coagulation sedimentation treating GSM and 2-MIB. But when the dosing quantity of chlorine dioxide was over lmg/L, the taste and odor in algae cell released. Powdered activated carbon had good adsorption effect to the taste and odor, adsorbing GSM superior to 2-MIB. The fast adsorption of taste and odor was at the first 30min, then reached adsorption equilibrium at 60 min. The adsorption equilibrium of taste and odor was accord with Freundlich adsorption isotherms model.