Study On Generation And Control Technology Of HANs By Conventional Water Treatment Process

At present, our country mainly adopts the chlorine disinfection, accounted for about99%, chlorination has good disinfection effect, low cost, easy to use and easy to management. Disinfection by-products(DBPs) are formed by chloric disinfectant reacting with natural organic matters, More than700kinds of chlorinated disinfection by-products that do harm to human body in drinking water have been found. DBPs have been of great concern since they are carcinogenic and mutagenic, these substances can also cause the liver and the nerve poisoning, metabolic disturbance. In order to ensure the security of drinking water, the research about disinfection by-products has become a focus to research workers.The experiments analyzing the production and removal of HANs and their precursors in each process unit of a water purification plant in Changchun City, by sampling and testing the raw water, sedimentation tank effluent, filter effluent and disinfected effluent of the plant. The results showed that the total content of the precursors of HANs in raw water was44.04μg/L, and the content of DCAN was27.03μg/L, which was the highest and accounted for about61.38percent of the precursors of HANs, BCAN and TCAN respectively accounting for18.98%and14.03%, and the content of DBAN was the least, account for only5.63%. The removal rate to the precursors of HANs of coagulation sedimentation process unit was39%, which was the highest of all processes; followed by26%of the filtration process; after the chlorination, the precursors of HANs were removed some, but the effect was not obvious, and the removal rate was only14%. Due to the oxidation of chlorine, more HANs were produced after disinfection, compared to the filter effluent increased4.91μg/L, of approximately51%.Oxidation experiments, using KMnO4as oxidant, KMnO4dosing quantity is1.5mg/L, PAC dosing quantity is30.0mg/L, the content of HANFP was the least. KMnO4oxidation of organic matter, reduce HANs generation, but the dosage should be controlled within a certain range, too much effect but not good. Disinfection test, chlorine dosing quantity is proportional to the HANs generation. ensure the sterilization effect and Reduce the chlorine dioxide dosing quantity. HANs generation related to the reaction time, the longer the reaction time, generate the more HANs, HANs production decreased significantly after8h.Three simulation process, process three use KMnO4oxidation, chlorine dioxide disinfection, HANs that had been generated was10.20μg/L, which was the least,34%lower than process one. Process two compared to process one HANs decreased by24%. According to the HANs generation, process three was the least, process one was the highest.