Identification of TiO2/UV Disinfection Byproducts in Drinking Water

Due to concern over the presence of trihalomethanes (THMs) and other chlorinated byproducts in chlorinated drinking water, alternative disinfection methods are being explored. One of the alternative treatment methods currently being evaluated for potential use with small systems (less than 3300 people) is titanium dioxide (TiO2) photocatalysis. Using a combination of unconventional GC/MS and GC/FT-IR techniques, we identified organic disinfection byproducts (DBPs) formed by photocatalytic treatment of water with TiO2 and ultraviolet (UV) light. The identifications also reflect the effects of ultrafiltration prior to treatment with TiO2/UV as well as secondary chlorination. Only a single organic DBP (tentatively identified as 3-methyl-2,4-hexanedione) was observed in ultrafiltered raw water treated with TiO2/UV alone. When chlorine was used as a secondary disinfectant (following treatment with TiO2/UV), several chlorinated and brominated DBPs were formed, among them some halomethanes and several halonitriles. Most of these halogenated DBPs were the same as those observed when chlorine was used as the sole disinfectant. However, one byproduct, tentatively identified as dihydro-4,5-dichloro-2(3H)furanone, was formed only by a combination of TiO2/UV and chlorine disinfection. Although many chlorinated DBPs were produced when chlorine was used as a secondary disinfectant, the number and concentration of these chlorinated DBPs were lower than when chlorine was used as the sole disinfectant.