Research On Emergency Treatment Process Of Unexpected Chlorpyrifos Pollution In Source Water

Along with economic development and social progress, the type and quantity of pesticides was increasing. Because of excessive use of pesticides, pesticides leaks caused by transport accidents and other potential hazards, the risk of sudden pollution in the source water in a city was increasing. Chlorpyrifos was a widely used organophoshorus pesticide alternative to high poisoning pesticides like methamidophos and parathion. Either this kind of pesticides which had high efficiency and low toxicity had a long-term effects on the human body or not, especially on children, was gaining widespread attention home and abroad. Chlorpyrifos had become one of the important risk pollutants which could cause sudden water pollution in urban source water.At present, the common measures to deal with emergent organic pollution in source water was mainly coagulation, activated carbon adsorption and chemical pre-oxidation. But studies on emergent chlorpyrifos pollution in source water were few. Based on the establishment of method of determining chlorpyrifos in water by liquid micro-extraction associated with gas chromatography, this paper tested chlorpyrifos removal from the enhanced coagulation, activated carbon adsorption and chemical pre-oxidation. Results showed that for the method of determining chlorpyrifos in water by liquid micro-extraction associated with gas chromatography, the lower detection limit was 8μg/L, while the standard deviation was 2.68~9.24μg/L and the relative standard deviation was less than 6.5%, and recovery with standard addition was 82.51%~106.67%. Enhanced coagulation process could effectively remove chlorpyrifos in source water. When we choose ferric chloride, aluminum suifate and PAC as coagulant, the initial concentration of chlorpyrifos was 195.96μg/L, coagulant dosage was 15mg/L~40mg/L, the maximum removal rate of chlorpyrifos were more than 30%, of which PAC was the best. The removal rate of chlorpyrifos was 50.51% under the conditions of the PAC best dosage 30mg/L. When the initial concentration of chlorpyrifos was high, the concentration of chlorpyrifos after coagulation was still higher than the drinking water health standards(GB5749-2006) which required the concentration of chlorpyrifos lower than 30μg/L in drinking water. So we needed additional measures such as activated carbon treatment. PAC adsorption associated with coagulation had a good effect on the removal of chlorpyrifos. The effect was the best when PAC dosage 30min before coagulation. When the initial concentration of chlorpyrifos excessed 5 times, 10 times, 20times, 30times, 40times, in order to meet the limits required to chlorpyrifos in the drinking water health standards(GB5749-2006), PAC should be used in conjunction with coagulation. When coagulant PAC dasage was 30mg/L, PAC optimal dasage was 10mg/L, 20 mg/L, 30 mg/L, 40 mg/L, 40 mg/L. Potassium permanganate pre-oxidation and hydrogen peroxide pre-oxidation had no signficant effect on the removal of chlorpyrifos. But they both had a certain role in coagulation aid and hydrogen peroxide was better than potassium permanganate. There were no synergistic effect on the removal of chlorpyrifos when they were used associating with powdered actived carbon.