THE EFFECTS OF OZONATION AND ACTIVATED CARBON ADSORPTION ON TRIHALOMETHANE SPECIATION

Two surface water sources in the southwestern United States were studied in bench-scale experiments examining two trihalomethane (THM) precursor removal processes, activated carbon adsorption and ozone oxidation. Both source waters contained bromide (Br-) leading to brominated THMs upon chlorination. Activated carbon removed THM precursors, as measured by dissolved organic carbon (DOC), while having little effect on bromide. The net result was an increase in the ratio of Br-/DOC and an increase in the relative abundance of brominated THMs. Ozone oxidized higher molecular weight precursor molecules into lower molecular weight by-products which were less reactive with chlorine. Moreover, ozonation appeared to transform Br- to hypobromous acid (an in situ oxidant), leading to an increase in the percentage of brominated THMs.