Chlorination of drinking water from natural sources results in the formation of several organic compounds as disinfection by products. The most widely studied among them is a group of compounds collectively called trihalomethanes (THMs), some of which are reported to be toxic for human consumption. Consequently water supply authorities in some countries are forced to resort to costly corrective measures in order to reduce their levels below the maximum concentration limits (MCL) set by the environmental protection and health authorities. It is well established by now that the formation of such
compounds is due to reactions between chlorine and some precursor organics originally present in raw water.
In the City of Nablus which located in the northern West Bank- Palestinian Territory, a water system network serves about 177,000 people in Nablus and its surrounding localities, consist of, four wells, five springs, nine operating storage tanks,13 pump stations, distribution network consists of about 279 km of water pipes of different diameter, material and ages, The treatment process used for disinfecting drinking water is chlorination, by using sodium hypochlorite, the Unaccounted for Water (UFW) is over 30% and the supply is intermittent due to water shortages, so contaminants can intrude into the pipe network and the rooftop storage tanks and react with chlorine to form disinfection by – products (DBPs), which may cause cancer and some other diseases.