Factors influencing disinfection by-products formation in drinking water of six cities in China

Based on the measured chemical and physical data in drinking water from six cities in China, the factors including total organic carbon (TOC), ultraviolet absorbance at 254 nm (UV254), pH, applied chlorine dosage, temperature, concentrations of bromide ion and several chemical elements which possibly affect the formation of trihalomethane (THM) and haloacetic acid (HAA) have been studied. The results showed that: in all factors, TOC and UV254 have definite correlations with total THM, but have nonsignificant relationships with total HAA. In the studied pH range of 6.5-8.5 for drinking water, the total THM concentration increased with the increasing of pH value, but the total HAA concentration slightly decreased. A low but significant relationship (r = 0.26, p < 0.01) occurred between total THM and applied chlorine dosage. Similar relationship (r = 0.21, p < 0.01) was found between total HAA and applied chlorine dosage. When the water temperature was low, the variation of THMs and HAAs was little, but in warmer water, the concentration of THMs and HAAs varied quickly. The extent of bromine incorporation into the DBPs increases with increasing bromide ion concentration. Based on the effect of chemical elements for the DBPs remove effect, the polyferric chloride could be a preferred flocculant agent in waterworks.