Study On Disinfection By-product Levels In Centralized Water Supply From A Southern Rural Area

Drinking water disinfection technique has played an irreplaceable role in ensuring the water biological safety and protecting the prevalence of waterborne infectious diseases. The species and levels of disinfection by-products are varied in drinking water disinfection process by the different disinfectants’ application and disinfection patterns; and have a close relationship with the natural organic matter in raw water and the organic compound content of the halogen as well. The disinfection by-products on adverse health impact and control techniques have been increasingly concerned because of the formation of disinfection by-products in the course of drinking water disinfection, although it brings a maximum benefit for human life.ObjectivesThe levels of disinfection by-products and possible influencing factors in the centralized water supply from a southern rural area are explored, and the tests for boiled water sample and boiled water sample which is placed into the next day are carried out prospectively to understand the increase and decline of the water disinfection by-products levels.MethodsThe15rural centralized water supply waterworks in study site are selected and raw water、filtered water、finished water samples are collected to determine the varieties of DBPs and their formation of relevant indicators. The water analysis methods in lab are in according with "Standard examination methods for drinking water"(GB/T5750-2006). The level of disinfection by-products and possible related influencing factors are evaluated. The8waterworks are selected to collect the finished water to boil, and the boiled water which is placed into a thermos bottle from8to12hours, and then the DBPs test is carried out to explore the change of DBPs levels through boiling and stored.Results1. There are2finished water samples which do not conform to "sanitary standard for drinking water"(GB5749-2006), and the contents, for chlorate and Triholomethanes(THMs) are1.59mg/L,1.133respectively.2. The chlorinated disinfection by-products are mainly triholomethanes (trichloromethane) and haloacetic acids (dichloroacetic acid and trichloroacetic acid). There are same DBPs species as in process of hloramine disinfection, but the contents are lower. The DBPs are mainly chlorate and chlorite in process of chlorine dioxide disinfection and THMs and HAAs are not detected.3. Volatile THMs in DBPs have been significantly reduced after boiled. The boiling can remove partial volatile DBPs, and however it is not effective to remove nonvolatile DBPs. The boiled water which is placed into8to12hours has been significantly increased the dichloroacetic acid contents.ConclusionsThe DBPs contents are not compliance with the "sanitary standard for drinking water"(GB5749-2006) in finished water from some suerveyed rural centralized waterworks. The chlorinated disinfection by-products are mainly triholomethanes and haloacetic acids. Volatile DBPs’THMs reduced significantly after boiled, and however it is not effective to remove nonvolatile DBPs. The boiled water which is placed into8to12hours has significantly increased dichloroacetic acid contents.