Experimental Studies On Chemical Pre-Oxidation For Ammonia Nitrogen, Manganese And Organic Compound Pollution Of Raw Water

Jiaxing District has very severe water pollution problem, the surface water is mainly composed of water in category V and below. The permanganate index, ammonia nitrogen, iron and manganese exceed the maximum contaminant limit. So it is a kind of water with high concentration of organics, ammonia nitrogen, iron and manganese. The conven-tional water treatment processes fail to guarantee the safety of drinking water. Currently, the study of pre-treatment techniques mainly focuses on micro-polluted water source which is unable to meet the requirement of drinking water safety in Jiaxing District. As a result, it is urgent to develop a pre-oxidation technique to deal with heavily polluted wa-ter source.This paper mainly discussed the ability of three different pre-oxidants: ozone, po-tassium permanganate and chlorine to control various pollutants in the raw water and their influences on the treated water. The content of this paper is summarized below:Study the ability of these three pre-oxidants to remove organics, ammonia nitrogen and manganese in water, the optimum dosage, the ideal contact time and the effect of pH on contaminant removal. This study suggested that: the optimum dosage for potassium permanganate is 0.6mg/L, the ideal contact time is 15 min; the optimum dosage ozone is 1.5mg/L, the ideal contact time is 5 min; the optimum dosage for pre-chlorination is 2mg/L, the ideal contact time is 20 min. These three oxidants have different removal ef-ficiencies on CODMn, better removal rate for UV254 and Mn is achieved while only few ammonia nitrogen were removed after pre-oxidation.Compare the ability of the oxidants to against the impact of the pollutants by changing the concentration of the pollutants. The study indicated that all the oxidants have strong ability against the impact of the organic pollutants but the ability against the impact of manganese varies among oxidants.These pre-oxidants were compared comprehensively in three aspects: oxidation ef-ficiency, safety performance, technology economy .The study showed that by comparing those mentioned above, potassium permanganate is able to remove disinfection by-product precursors and to ensure the biological stabilization in water. If the ozone pre-oxidation is utilized, it is recommended that it go with the biological pre-oxidation. And pre-chlorination leads to the disinfection by-product increased.