Study On Characteristics Of Formation And Control Technology Of Disinfection By-Products In Urban Water Supply System

Disinfection by-products that were produced in drinking water disinfection process are a class of compounds which are harmful to human health. Therefore, people take more and more serious attention on the chemical safety problems of drinking water, and at present, there were tested765kinds of chlorinated disinfection by-products that do harm to human body in drinking water had been found, of which there are20kinds of carcinogenic substances,23kinds of suspected carcinogenic substances,18kinds of promote cancer substances, and56kinds of substances which may cause mutation. These substances can cause the liver and the nerve poisoning, metabolic disturbance, premature and so on, except the cancer. Nowadays, disinfection liquid chlorine is widely method which was used in the water purification process disinfection method in our country, in order to ensure the security of drinking water, the research about disinfection by-products has become a focus to research workers.By consulting a large amount of pertinent literature at home and abroad, the paper comprehensively discusses the current research situation and the development of the disinfection by-products in drinking water. According to micro-polluted source water, the raw water of a reservoir of Changchun City is treated as the research object, and its organic composition and characteristics are discussed. The results show that the hydrophobic organic matter accounts for55%of the total soluble organic in raw water and the hydrophilic organic matter accounts for45%. Through studying the formation potential of disinfection by-products formation potential of all the organic matter in raw water, they were found that both haloacetic acids formation potential and trihalomethans formation potential of the hydrophobic organic matter is higher than that of the hydrophilic organic matter, thus, it is known that haloacetic acids formation potential and trihalomethans formation potential mainly comes from the hydrophobic organic matter, and the hydrophobic organic acid is the main precursor of haloacetic acids formation potential and trihalomethans formation potential.The paper studies the control characteristics of the traditional water purification process on disinfection by-products, discusses the removal effect of each treatment unit on disinfection by-products and disinfection by-products precursors.Through the use of potassium permanganate pre-oxidation, dosing a certain amount of coagulant to enhance the coagulation process, changing the disinfection way to optimize the disinfection process, the paper investigates the control effects of these optimization processes on haloacetic acids and trihalomethanes.The results show that in conventional treatment process, the removal efficiency of coagulation and sedimentation on haloacetic acids precursors and trihalomethanes precursors are50.5%and29.0%, respectively; the removal efficiency of filtration on haloacetic acids precursors and trihalomethanes precursors are36.2%and10.2%; the removal efficiency of disinfection on haloacetic acids precursors and trihalomethanes precursors are8.2%and11.1%.Optimized water treatment process uses potassium permanganate as pre-oxidant and uses PAC as coagulant. According to the measure of the amount of organic indicators and the formation of disinfection by-products, the paper determines that the dosages of potassium permanganate and PAC are1.5mg/L and30mg/L by orthogonal experiments.Among the subsequent disinfection process, the formation of haloacetic acids and trihalomethanes increase as the chloramines dosage rise, and they have a certain degree of correlation, and R2are0.9975and0.986, respectively. When the dosage of chloramine is5mg/L, the formation of haloacetic acids is stabilized basicly after chloramine has been disinfeced for20h and the formation of Trihalomethanes is stabilized after24h. In the disinfection process, the dosing sequence of chlorine and ammonia is studied, and the results indicate that when the ratio of chlorine and ammonia is4:1, the formation of trihalomethanes by means of first chlorine, then ammonia is reduced by1.09μg/L compared to the means of first ammonia, then chlorine.Through the comparison tests between three optimization processes and the traditional process, the results show that compared to the traditional process, the formation haloacetic acids and trihalomethanes in effluent of the process C are reduced by72.8%and56.9%.