Emergent Treatment For Pesticide Endocrine Disrupting Chemicals In Source Water By Powdered Activated Carbon

In recent years, as agricultural development there are more and more dependence on pesticides. As a result, many kinds of pesticide Endocrine Disrupting Chemicals (EDCs) have been detected in source water for drinking water supply. These pesticides have stable chemical properties, with longer half-life period and hardly biodegradation. Especially in case of incidents of pesticides EDCs contamination, they may threat to human health due to the fact that it is not effective for conventional water treatment processes to remove them.In this paper, the adsorption technology using powdered activated carbon (PAC) was applied as an emergency treatment to remove pesticide EDCs from source water. Adsorption performances of PAC on four common pesticides (2,4-D,furadan,atrazine,carbaryl) were studied by small-scale tests. The results showed that adsorption equilibrium of the PAC could be reached 60 min later, and about 90 % of removal efficiency could be achieved in deionized water.The study on adsorption kinetics of four pollutants showed that Lagergren second-order adsorption rate equation was much better than Lagergren second-order adsorption rate equation. The main process of adsorption of PAC was at the adsorption reaction stage. The results also showed that Freundlich isothermal adsorption had the best regression level, and the theory dosing rate of PAC could be calculated by using the above isothermal adsorption. In addition, the effects of PAC dosing rate, initial concentrations of contaminants and water quality on adsorption performance were investigated. By increasing the dosage of PAC, extending adsorption time, and reducing the amount of the background organisms, treatment efficiency could be improved even when source water polluted by high concentrations of EDCs.A pilot study on the removal of 2,4-D and furadan by PAC was carried out in moving emergency treatment guidance water plant using Luan River. Removal efficiencies of the pollutants by using conventional process and PAC+conventional process were compared in this pilot study. The results indicated that the conventional process did't have obvious effect on pollutants removal. Moreover, the PAC should be added before coagulation process, polyaluminum chloride should be selected as coagulant. The optimum dosages of PAC were also determined in the conditions of different initial concentrations of 2,4-D and furadan. The single process of potassium permanganate (KMnO₄) and the combination process of PAC and KMnO₄ to remove 2,4-D/furadan were studied ,which showed that single process of KMnO₄ had no obvious effects on removal efficiencies, and the combination process of PAC and KMnO₄ had worse removal efficiency than single use of PAC. Therefore, it is not suggested to add KMnO₄ with PAC to remove 2,4-D and furadan.