Study On Emergency Treatment Process For Sudden Organic Pollution Of Souce Water In Zhenjiang

In recent years, China's sudden source water pollution incidents especially organic pollution incidents frequently happened, posing a serious threat to security of urban water supply. China's current emergency treatment of water in the security area is still very weak. Once the incidents happened, water supply was stopped. For water treatment workers, how to deal with the pollutants quickly and effectively and establish a perfect contingency plan for sudden water pollution incident is an issue.Based on the specific circumstances of the source water, three categories with a total of seven kinds of the compounds which are representative, high risk of sudden pollution and enormous harm, much lasting impact (herbicide category: atrazine, ametryn, molinate; organic chemical category: nitrobenzene, bisphenol A, diethyl phthalate; oil category: diesel)were scientifically and systematically selected as the object of study on contingency plan for source water organic pollution.Considering the aspect of practicality and economy, contingency plan should increase the necessary emergency facilities on the basis of existing waterworks facilities in the water plant. By simulating waterworks in the day-to-day production, the pilot test model was used to conduct a feasibility study of emergency measures as strengthened conventional treatment, activated carbon adsorption, chemical oxidation, and so on.Pilot tests show that conventional process of removing oil pollution has achieved good results. When oil pollution was less than 10 mg/L, coagulant dosage of 10 mg/L is enough to get the water accord with the standard. Atrazine, ametryn, molinate, bisphenol A, nitrobenzene, diethyl phthalate, and other small molecular organic pollution can not be effectively removed by strengthened conventional treatment.Powdered activated carbon and granular activated carbon have good results for removing high concentration of organic pollutants in water, such as pesticides, petroleum and organic chemicals studied in this paper. Adsorption kinetics study shows that the fast adsorption of organic by powder activated carbon was at the first 30 min, then activated carbon can complete about 70% of the adsorption capacity, The pseudo second-order adsorption kinetics can be better fitting atrazine, ametryn, molinate, bisphenol A and diethyl phthalate adsorption process. Adsorption isotherms research shows that Freundlich adsorption isotherm model is better fitting atrazine, ametryn and molinate adsorption equilibrium than the Langmuir adsorption isotherm model. Adsorption isotherm model formula can be used to calculate the theoretical dosage of powdered activated carbon needed by target substance. The dynamic adsorption of cabon-sand column indicates that factors influencing adsorption-filter effect include filtering layer structure, the initial concentration of pollutants and filtration rate.When powdered activated carbon adsorption is applied by water plant, the activated carbon should be added in the water intake of waterworks, so the adsorption time can be extended and its adsorption capacity can be full used. As activated carbon dosage is increased, the removal efficiencies of pollutants slow down in growth. The best dosage of powdered activated carbon depends on the nature and the initial concentration of the pollutants, and whether deep treatment follows or not. Existence of granular activated carbon layer made the demand of PAC dosage decrease significantly. Adding powdered activated carbon affects the effluent turbidity after coagulation and precipitation, especially when activated carbon dosage is higher than 20 mg/L, so enhanced coagulation should be taken. High concentration of powdered activated carbon can remove some extent of the low pollutants concentration without the impact of its initial concentration.Among the organics studied in this paper, bisphenol A can be removed by potassium permanganate pre-oxidation; Ametryn, molinate and Bisphenol A can be removed by pre-chlorination. The products and their toxicity of potassium permanganate oxidation or chlorination need to be studied further. Potassium permanganate and chlorine could affect activated carbon adsorption of the organic compounds. Powdered activated carbon combined with potassium permanganate has no synergy in removal of the compounds that can not be oxidized by potassium permanganate.