Abstract:

Chlorine disinfection is the most common disinfection method in the water supply system in China.Those disinfection byproducts (DBPs) from the method which include carcinogenic,mutagenic and teratogenic effects,have received extensive attention in recent years,among which trihalomethanes (THMs) and haloacetic acids (HAAs) are the most typical and concerned halogenated organic DBPs. Due to the difference in DBPs formation by different organic matters in the raw water through their physical,chemical and biological behaviors in the treating process,the relationship between species distribution characteristic of organic matters in the raw water and DBPs formation is vital for effective reduction of DBP precursors,reasonable water supply process control and final guarantee of drinking water security.Researches on THMs and HAAs precursors have been comprehensively implemented,however,many of them was based on simulated substances (such as resorcinol),or limited in a single precursor (i.e.THMs or HAAs precursor),and thus there was not enough information about the relationship mentioned above.In addition,compared with the total five controlled HAAs by US EPA,only two kinds of HAAs are under control in China,which make the risks of HAAs in DBPs underestimate in some researches.Therefore,in order to get a more comprehensive understanding on the relationship between species distribution characteristic of organic matters in the raw water and DBPs formation,a typical rivertype water source in the Yangtze River Delta was selected and investigated during different hydrological periods.Results showed that organic pollution was most serious in the wet period,then in the level period,the last in the dry period,with humification of the water decreasing in the same order.Distribution of dissolved organic matter (DOM) components in total organic carbon (DOC) of the raw water after resin adsorption process were:hydrophobic acid (HPOA,38%)>hydrophilic fraction (HPI,26%)>transphilic acid (TPIA,16%)>hydrophobic neutral (HPON,12%)>transphilic neutral (TPIN,8%),HPOA(32%)>HPON(22%)>TPIA(20%)>HPI(18%)>TPIN(8%),HPOA(28%)>TPIA(24%)>HPON(20%)>HPI(19%)>TPIN(9%),in the wet period, level period and dry period,respectively.Specific UV absorbance values (SUVA) of DOM components were lower than those in the raw water except HPI.The highest value was in the component HPOA,which was 177 times of that in the raw water.Contributions of hydrophobic organic matters (including hydrophobic acid and hydrophobic neutral) to the formation of THMs and HAAs,were more than 60% and 65% among that of the overall DBPs attributed by all organic matters during the three hydrological periods,indicating hydrophobic organic matters was the major DBP precursors and should be prominently removed in the water supply process.Relationships between organic matters characteristics of the raw water with DBPs formation potential (DBPFP) made few differences during the three hydrological periods,with a high degree of linear correlation of specific THMs formation potential (STHMFP) and SUVA,and a lower degree of linear correlation of specific HAAs formation potential (SHAAFP) and SUVA,indicating that SUVA value could be utilized as an indirect indicator of STHMP and help to facilitate rapid monitoring of changing trends of DBP precursors in the actual production