IDENTIFICATION OF TIO2 UV DISINFECTION BY-PRODUCTS IN DRINKING-WATER/

Due to concern over the presence of trihalomethanes (THMs) and other c hlorinated byproducts in chlorinated drinking water, alternative disin fection methods are being explored. One of the alternative treatment m ethods currently being evaluated for potential use with small systems (less than 3300 people) is titanium dioxide (TiO2) photocatalysis. Usi ng a combination of unconventional GC/MS and GC/FT-IR techniques, we i dentified organic disinfection byproducts (DBPs) formed by photocataly tic treatment of water with TiO2 and ultraviolet (UV) light. The ident ifications also reflect the effects of ultrafiltration prior to treatm ent with TiO2/UV as well as secondary chlorination. Only a single orga nic DBP (tentatively identified as 3-methyl-2,4-hexanedione) was obser ved in ultrafiltered raw water treated with TiO2/UV alone. When chlori ne 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 sol e disinfectant. However, one byproduct, tentatively identified as dihy dro-4,5-dichloro-2(3H)furanone, was formed only by a combination of Ti O2/UV and chlorine disinfection. Although many chlorinated DBPs were p roduced when chlorine was used as a secondary disinfectant, the number and concentration of these chlorinated DBPs were lower than when chlo rine was used as the sole disinfectant.