This paper discusses the identification of organic disinfection byproducts (DBFs) at a pilot plant in Evansville, IN, which uses chlorine dioxide as a primary disinfectant. Unconventional multispectral identification techniques (gas chromatography combined with high-and lowresolution electron-impact mass spectrometry, low-resolution chemical ionization mass spectrometry, and Fourier transform infrared spectroscopy) were used to identify more than 40 DBFs in finished water at a chlorine dioxide pilot plant in Evansville, IN. Treatment variations included the use of liquid versus gaseous chlorine dioxide and the use of residual chlorine. Among the more unusual compounds identified were a series of maleic anhydrides, which are believed to have been formed from maleic acids during the extraction and concentration process, and halopropanones.

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 (TiO 2 ) 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 TiO 2 and ultraviolet (UV) light. The identifications also reflect the effects of ultrafiltration prior to treatment with TiO 2 /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 TiO 2 / UV alone. When chlorine was used as a secondary disinfectant (following treatment with TiO 2 /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 TiO 2 /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.

Drinking water samples were prepared in a pilot-scale treatment plant by chlorination (Cl2), chloramination (NH2Cl), ozonation (O3), or O3 followed by Cl2 or NH2Cl; and the nonvolatile acidic organics of the raw and treated waters were extracted by XAD/ethyl acetate and evaluated for mutagenicity in Salmonella (-S9). The extracts were 2-8 times more mutagenic in TA100 than in TA98, and the mutagenic potencies of the water extracts ranked similarly in both strains: Cl2 > O3 + Cl2 > NH2Cl > O3 + NH2Cl > O3 > raw. 3-Chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), which was estimated to account for approximately 20% of the mutagenic activity of the extracts, was shown to be the most potent compound tested thus far in a prophage-induction assay in Escherichia coli and a forward-mutation assay in Salmonella TM677. The mutations in approximately 2,000 revertants of TA98 and TA100 induced by MX and the water extracts were analyzed by colony probe hybridization and polymerase chain reaction/DNA sequence analysis. The water extracts and MX produced similar mutation spectra, which consisted in TA100 of predominantly of GC-->TA transversions in the second position of the CCC (or GGG) target of the hisG46 allele. This spectrum resembles that produced by large aromatic compounds and is distinct from that produced by alkylating agents and the semivolatile drinking water mutagen dichloroacetic acid. In TA98, MX and those water extracts resulting from the introduction of the chlorine atom produced 50-70% hotspot 2-base deletions and 30-50% complex frameshifts (frameshifts with an adjacent base substitution--mostly GC-->TA transversions as found in TA100). No other compound or mixture is known to induce such high frequencies of complex frameshifts. These results suggest that MX and "MX-like" compounds (possibly halogenated aromatics, such as halogenated polycyclic aromatic hydrocarbons) account for much of the mutagenic activity and specificity of the nonvolatile organics in drinking water and that these halogenated organics are especially capable of promoting misincorporation by the DNA replication complex. This study provides further evidence that the mutation spectrum of a complex mixture reflects the dominance of one or a few classes of chemical mutagens within the mixture.

No abstract

No abstract