UV Disinfection Byproducts in Drinking Water

Environ. Sci. Technol. 1996, 30, 3327-3334

Identification of TiO2/UV Disinfection Byproducts in Drinking Water SUSAN D. RICHARDSON,* ALFRED D. THRUSTON, JR., AND TIMOTHY W. COLLETTE Ecosystems Research Division, National Exposure Research Laboratory, U.S. Environmental Protection Agency, Athens, Georgia 30605

KATHLEEN S. PATTERSON, BENJAMIN W. LYKINS, JR., AND JOHN C. IRELAND Water Supply and Water Resources Division, National Risk Management Research Laboratory, U.S. Environmental Protection Agency, Cincinnati, Ohio 45268

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.

* Corresponding author telephone: (706)355-8304; fax: (706)3558302; e-mail address: [email protected].

S0013-936X(96)00142-3 This article not subject to U.S. Copyright. Published 1996 by the American Chemical Society.

Introduction Due to concern over the presence of trihalomethanes (THMs) and other chlorinated byproducts in chlorinated drinking water (1), 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 in combination with ultrafiltration. Small water treatment systems currently serve approximately 25 million people in the United States (2), and it is these small systems that most frequently exceed drinking water standards set by the U.S. Environmental Protection Agency (EPA). Consequently, if additional regulations are implemented (as expected) (3), these small systems may find it even more difficult to meet the regulatory requirements. Package plants, which are water treatment units that arrive at a site virtually ready to use, are currently being evaluated as feasible treatment options for small systems. TiO2 photocatalysis and ultrafiltration technologies may be adaptable for use in package plants. TiO2 photocatalysis has been reported to kill microorganisms (4, 5) and is not expected to produce THMs when used to treat drinking water. TiO2 photocatalysis is believed to act by the following mechanism. When TiO2 is illuminated at wavelengths of light less than 388 nm, an electron is excited from the valence band to the conduction band, leaving an electronic vacancy called a hole (hvb+) in the valence band. This hole then reacts with OH- ions in water and H2O molecules to produce hydroxyl radicals (•OH), one of the most powerful oxidizing agents known (6, 7). This photocatalytic oxidation process has been shown to successfully degrade a wide variety of organic contaminants, including trichloroethylene, THMs, pesticides, polychlorinated biphenyls (PCBs), and polyaromatic hydrocarbons (PAHs), into nontoxic compounds (8-15) such as simple mineral acids, carbon dioxide, and water. As a result, if TiO2 photocatalysis is used to treat drinking water, it has the potential to degrade raw water contaminants as well as DBPs as they are being formed. In addition, sunlight (which starts at a wavelength of 300 nm) can be used as the light source (4, 8, 16), which could allow this method to be a potentially inexpensive technique for degrading organic contaminants and disinfecting drinking water. Several good review articles are available (17-19). Although the photocatalytic destruction of organic contaminants is fairly well understood, nothing is known about the formation of DBPs from TiO2/UV treatment of drinking water. Thus, the objective of this effort was to identify any potentially harmful byproducts. A drawback to using TiO2 photocatalysis as a disinfectant for drinking water is the lack of a residual disinfectant to maintain disinfection throughout a municipal distribution system. Because the hydroxyl radicals formed by TiO2 photocatalysis are highly reactive and are short-lived in water, a small drinking water treatment plant will probably need to use a secondary disinfectant, such as chlorine (in addition to TiO2/UV treatment), to maintain a residual disinfectant in the distribution system. Because of this, we investigated the effect of secondary chlorination on the formation of DBPs in this system. We also investigated the effect of ultrafiltration (prior to treatment with TiO2/UV),

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FIGURE 1. TiO2 photoreactor showing flow configuration.

since ultrafiltration has been shown to remove DBP precursor material and microorganisms (20-22). Rather than attempting to identify only targeted byproducts, our objective was to identify every compound that was detected in the sample extracts. Samples also were analyzed separately for THMs and haloacetic acids. Five of the six haloacetic acids targeted in our analyses (chloro-, bromo-, dichloro-, trichloro-, and dibromoacetic acid) are being proposed for future regulation (3). Samples studied represented the following treatment variations: (1) raw water, (2) raw water + chlorine, (3) ultrafiltered raw water, (4) ultrafiltered raw water + chlorine, (5) ultrafiltered raw water + TiO2/UV, and (6) ultrafiltered raw water + TiO2/ UV + chlorine. Gas chromatography/mass spectrometry (GC/MS) is the common analysis tool for identifying compounds in environmental samples. Typically, identifications are made using low-resolution electron-impact (EI) mass spectrometry. This type of analysis is sufficient for regulated compounds that have been well characterized and whose spectra are in a library database. However, unknown pollutants, such as newly identified DBPs, are often impossible to identify from GC/EI-MS alone, as many of these compounds are not present in any library database. As a result, we use a combination of several mass spectrometry techniques as well as infrared spectroscopy to identify these unknown byproducts. Spectral techniques employed include GC combined with high- and lowresolution electron-impact mass spectrometry (GC/EI-MS), low-resolution chemical ionization mass spectrometry (GC/ CI-MS), and Fourier transform infrared spectroscopy (GC/ FT-IR). Although much effort was made to identify byproducts, it is likely that extremely polar compounds (as well as thermally labile and higher molecular weight compounds) escaped detection. For those compounds that were targeted for identification (THMs and haloacetic acids), quantitative analyses were performed; semiquantitative analyses were performed for the remaining untargeted compounds because standards were not available for many of them.

Experimental Section TiO2/UV Treatment and Sample Preparation. Mill Creek raw water (Cincinnati, OH) was treated using ultrafiltration (10 000 molecular weight cutoff) and then recirculated through a TiO2/UV photoreactor. In addition to removing DBP precursor material and microorganisms, ultrafiltration

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FIGURE 2. TiO2/UV treatment process. (Numbers identify six sampling points).

was used to remove turbity in the incoming raw water, to allow good penetration of the UV light through the water, and also to minimize deposition of particulate matter onto the TiO2 surface. The reactor consisted of a series of stainless steel tubes, each lined with a TiO2-coated fiberglass mesh with a UV lamp at the center (5). Figure 1 shows a schematic of the TiO2/UV photoreactor. Ultrafiltered raw water was recirculated through this unit for approximately 24 h. A portion of this treated water was subsequently chlorinated. Chlorine residuals ranged from 2 to 3 mg/L. The treatment process and sampling points are shown schematically in Figure 2. The treatment variations included the following: (1) raw water, (2) raw water + chlorine, (3) ultrafiltered raw water, (4) ultrafiltered raw water + chlorine, (5) ultrafiltered raw water + TiO2/UV, and (6) ultrafiltered raw water + TiO2/UV + chlorine. Aliquots of treated water were removed for separate analysis of the haloacetic acids (chloro-, bromo-, dichloro-, trichloro-, bromochloro-, and dibromoacetic acid) (23) and THMs (23). The haloacetic method involves the acidification of the treated water sample (to pH 0.5), followed by extraction with methyl tert-butyl ether, derivatization with diazomethane, and analysis by GC with electron capture detection (ECD). The THM method involves extraction of the treated water sample with methyl tert-butyl ether and analysis by GC-ECD. The remaining water was then concentrated by adsorption on Amberlite XAD resins. Preparation of the resins

included consecutive washes with 0.1 N NaOH, distilled water, and methanol. After being washed, the resins were purified by consecutive 24-h Soxhlet extractions with methanol, ethyl acetate, and methanol. Resins were stored in methanol at room temperature. Prior to use, the methanol was replaced with distilled water. After each column was packed with resin, they were rinsed with 0.1 N HCl, followed by a rinse with 0.1 N NaOH. This step was then repeated. A third acid rinse was followed by a distilled water rinse. The water samples (100 L) were acidified to pH 2 by in-line addition of HCl prior to passage through columns containing a combination of XAD-8 resin (130 mL) over XAD-2 resin (130 mL). Each column was eluted with approximately 800 mL of ethyl acetate. Residual water was removed from the ethyl acetate eluents by using separatory funnels to drain off the water layers, followed by the addition of sodium sulfate. Half of each sample eluent was reserved for mutagenicity testing. The mutagenicity work will be reported in a separate publication. The remaining eluents (each equivalent to approximately 50 L of treated water) were shipped to the National Exposure Research Laboratory in Athens, GA. At the laboratory, the samples were concentrated to 1.0 mL by rotary evaporation. Sample extracts were analyzed by GC/MS and GC/FT-IR after concentration and were stored under refrigeration when not in use. In addition to the raw water control and the ultrafiltered raw water control, three other blanks were analyzed: (1) distilled water was recirculated through the TiO2/UV unit and concentrated in the same manner as the treated samples, (2) ethyl acetate was passed through the XAD resins and concentrated, and (3) distilled water was treated with chlorine and concentrated. The latter blank was done to determine whether there were any artifacts due to the reaction of residual chlorine with the ethyl acetate or with resin impurities. TOC and TOX Determinations. Total organic carbon (TOC) concentrations were determined using the persulfate-ultraviolet oxidation method, and the adsorptionpyrolysis-titrimetric method was used for total organic halide (TOX) analyses (24). GC/MS Analysis. High-resolution GC/EI-MS analyses were performed on a VG 70-SEQ high-resolution hybrid mass spectrometer, equipped with a Hewlett Packard Model 5890A gas chromatograph. The mass spectrometer was operated at an accelerating voltage of 8 kV and at a resolution of 10 000. Low-resolution GC/MS analyses were performed at a resolution of 1000 on either a Finnigan 4500 mass spectrometer or a VG 70-SEQ mass spectrometer. Positive chemical ionization experiments were accomplished by using methane or 2% ammonia in methane gases. Injections of 2 µL of the extract were introduced via a split/ splitless injector onto a J&W Scientific DB-5 chromatographic column (30 m, 0.25 mm i.d., 0.25 µm film thickness). The GC temperature program consisted of an initial temperature of 35 °C, which was held for 4 min, followed by an increase at a rate of 9 °C/min to 290 °C, which was held for 30 min. Transfer lines were held at 280 °C, and the injection port was controlled at 250 °C. Semiquantitative concentrations of DBPs were determined by using an internal standard, 2,2′-difluorobiphenyl, and by using an external standard containing the EPA’s “priority pollutants” (25). Concentrations reported for DBPs identified in the resin extracts are approximate as standards for many of the DBPs identified are not available.

GC/FT-IR Analysis. GC/FT-IR analyses were performed on a Hewlett Packard Model 5890 Series II GC interfaced to a Hewlett Packard Model 5965B infrared detector (IRD). Spectra were generated at 8 cm-1 resolution with a useful range of 4000-700 cm-1. Injections of 2 µL of the extracts were introduced onto a Restek Rtx-5 column (30 m, 0.32 mm i.d., 0.5 µm film thickness) with a heated on-column injector (280 °C). The GC temperature program consisted of an initial temperature of 35 °C, which was held for 4 min, followed by an increase at a rate of 9 °C/min to 280 °C, which was held for 30 min. Transfer lines were held at 280 °C, and the light pipe was controlled at 280 °C.

Results and Discussion Figure 3 shows the GC/MS chromatograms obtained for (a) raw water, (b) ultrafiltered raw water, (c) ultrafiltered raw water treated with TiO2/UV, and (d) ultrafiltered raw water treated with TiO2/UV + chlorine. Immediately evident is the reduction in background in the GC/MS chromatograms when TiO2/UV treatment is used. This background was likely due to high molecular weight, nonchromatographable organic compounds, such as humic substances. Because TiO2/UV treatment is known to degrade organic compounds and DBP precursors (26), the reduction in background was not surprising. It is likely that TiO2/UV treatment not only eliminated precursor material (natural organic matter) but also degraded byproducts that were initially formed by the reaction of hydroxyl radicals (•OH) with natural organic matter (NOM). Ultrafiltration also reduced the amount of NOM, as was evident in a lowered TOC (by 25%) and a lower background in the GC/MS chromatograms. The initial TOC of the raw water was 5.9 mg/L. Ultrafiltration lowered it to 4.4 mg/L, and TiO2/UV treatment lowered it further to 2.6 mg/L, for a total reduction in TOC of 57% (as compared to the raw water). The ability of TiO2/UV treatment to degrade chlorinated organic compounds was evident in the destruction of chlorinated compounds that were present in the raw water sample. Dichlorobenzene, pentachlorophenol, and two isomers of trichlorobenzene present in the raw water were missing from the water treated with TiO2/UV. In addition, the TOX of the raw water was reduced by 52% when the water was treated with ultrafiltration and TiO2/UV. However, two herbicidessatrazine and metolachlorsthat were present in the raw water were not completely degraded in the TiO2/UV-treated samples. This was surprising as Pelizzetti et al. have shown that atrazine can be significantly degraded by TiO2/UV treatment (15). However, in that study, aqueous suspensions of TiO2 powder were used, and the conditions were optimized for pollutant degradation. For our work, TiO2-coated mesh was used, and the conditions were chosen primarily for drinking water treatment, not for pollutant degradation. Therefore, it was not a goal to completely mineralize organic pollutants; as a result, a significant amount of TOC (43%) remained after treatment with ultrafiltration and TiO2/UV. In another study that utilized TiO2-coated mesh, Kiserow and Pugh demonstrated that the extent of atrazine degradation depends on the number of layers of TiO2-coated mesh used (27). It is likely that further optimization of our system could improve the degradation of organic pollutants. The labeled peaks in chromatograms c and d of Figure 3 represent the disinfection byproducts identified. Compounds that were found in the blanks are labeled with


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FIGURE 3. GC/MS chromatograms for (a) raw water, (b) ultrafiltered raw water, (c) ultrafiltered raw water + TiO2/UV, (d) ultrafiltered raw water + TiO2/UV + Cl2.

asterisks. Peaks that are not labeled are indicative of compounds already present in the raw water that were not

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DBPs. Table 1 lists the identifications made for byproducts extracted with resins and the different spectral techniques

TABLE 1

Disinfection Byproducts Identified in Resin Extracts compound identified

EI-MS library match

HREI-MS

LRCI-MS

IR

X

X

X

X X X

X X X X X

X X X

X X

X X X X X X

X X X X X X X X X

X X X

X X X

X X X

X X

EPA regulated

TiO2/UV Disinfection Byproducts 1. 3-methyl-2,4-hexanedionea TiO2/UV + Cl2 Disinfection Byproducts X X X

1. bromodichloromethane 2. trichloroacetaldehyde (chloral hydrate) 3. dichloroacetonitrile 4. 1-chloroethanol acetate 5. 1,2-dichloro-2-methyl butanea 6. bromodichloroacetonitrile 7. dibromochloromethane 8. bromodichloroacetaldehydea 9. bromochloroacetonitrile 10. 1,1,1-trichloro-2-propanone 11. 2,3-dichloro-3-bromopropane nitrilea 12. 3,4-dichlorobutane nitrile 13. chlorodibromoacetaldehydea 14. bromochloromethyl acetatea 15. trans-2,3,4-trichloro-2-butene nitrilea 16. dihydro-4,5-dichloro-2(3H)furanonea 17. benzaldehyde 18. cis-2,3,4-trichloro-2-butene nitrilea 19. 3-methyl-2,4-hexanedionea 20. 1,1,5,5-tetrachloropentanea 21. benzeneacetaldehyde 22. chloromethyltoluenea,b 23. 1-chloro-3,3,3-trichloro-1-propen-1-aminea 24. hexachloroethane 25. 1,3,3-trimethyl-1-7-oxabicyclo[4.1.0]heptane-2,5-dione 26. benzeneacetonitrile 27. 2,6,6-trimethyl-2-cyclohexene-1,4-dione 28. chloromethylbenzaldehydea,b 29. methylpyrrolidinoyl chloridea,b 30. dimethyl ethyl phenola,b 31. dichloromethylbenzaldehydea,b 32. R-(chloromethyl)benzenemethanol 33. 1,2,3,4,5,5-hexachloro-1,3-cyclopentadiene 34. dibromoxylenola,b 35. dibromoxylenola,b a

Tentative identification.

b

X

X X X X

X X X

X X

X X X

X X

X

X X

X X X X X X X X X

X X

X X X X X X X

X

Exact isomer not known.

TABLE 2

THMs and Haloacetic Acids Identified for TiO2/UV + Cl2 Treatment concn (ppb) THMS 1. chloroform 2. bromodichloromethane 3. dibromochloromethane haloacetic acids 1. dichloroacetic acid 2. trichloroacetic acid 3. bromochloroacetic acid 4. dibromoacetic acid

56.6 14.1 3.4 32.8 33.2 5.5 0.7

applied to identify each compound. Table 2 lists the THMs and haloacetic acids identified in the TiO2/UV + chlorine sample, using standard methods (23). Overall, many DBPs were identified, several of which have not been reported previously. Many of the compounds were not present in any spectral library (NIST or Wiley), and many of the ones that were in the libraries did not give conclusive library matches. Also, several compounds provided little information in their mass spectra, with an absence of molecular ions in many cases. As a result, we used CI-MS frequently to generate molecular ions. Highresolution EI-MS was an indispensable tool for determining

structures, as it provided the necessary empirical formula information for the molecular ion and fragments. It helped to limit the number of possible structures for each unknown DBP. GC/FT-IR was very useful for the choice of a functional group. When two or more compounds co-eluted and their spectra could not be separated using background subtraction, GC/MS analyses were repeated using a column with a different stationary phase (e.g., a DB-1 column). When available, standards were purchased to confirm difficult identifications and to determine a particular isomer precisely when spectra were not conclusive. In this way, GC retention times and spectra of the standards were matched with those of the unknowns. It should be noted that, although we attempted to identify every DBP detected in the samples, several DBPs were present at such low concentrations that there was not sufficient spectral information to enable their identification. Only a single DBP was evident for TiO2/UV treatment alone (Figure 3c). Although it is well known that TiO2/UV photocatalysis degrades organic compounds in water, it was surprising to find only one DBP produced by TiO2/UV treatment. This compound was tentatively identified as 3-methyl-2,4-hexanedione, and its concentration was approximately 50 ppt (ng/L). This DBP was also present in the TiO2/UV + chlorine samples. It is possible that some highly polar compounds as well as thermally labile com-


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FIGURE 4. EI mass spectrum of the TiO2/UV byproduct tentatively identified as 3-methyl-2,4-hexanedione.

pounds escaped detection. The mass spectrum of the TiO2/ UV byproduct is shown in Figure 4. Empirical formula assignments shown on the mass spectrum were obtained from high-resolution EI-MS. Because the molecular ion was not obvious, we used methane CI-MS to determine that the molecular weight was 128. From the highresolution data, the complete molecular formula of C7H12O2 was evident as well as losses of an ethyl group (m/z 128 f 99) and CO (m/z 99 f 71). These losses indicate the presence of an ethyl group and a ketone. Although a library match could not be found for this compound, fragment ions and losses were similar to other ketones in the mass spectral library. FT-IR confirmed the presence of a ketone group with a CdO absorbance at 1731 cm-1. At this point, one of the oxygens in the structure could be accounted for; the identity of the other functional group (to account for the second oxygen) was not known. The absence of a C-O stretching peak in the 1100-1200-cm-1 region ruled out the possibility of an ester oxygen, and an ether oxygen was not likely from the mass spectral information. The remaining possibilities included another ketone group (CdO) or an alcohol (OH) group. An alcohol group was ruled out based on the absence of an OH peak in the IR spectrum. Although only a single CdO stretching peak was evident in the IR spectrum, it is likely that this peak represents two ketone groups that are essentially equivalent. From all of the spectral information, this compound was tentatively identified as 3-methyl-2,4-hexanedione. Treatment with secondary chlorine produced many chlorinated and brominated DBPs, including some THMs, haloacetic acids, haloacetaldehydes, and halonitriles. The concentrations of THMs ranged from 3 to 57 ppb (µg/L). Bromoform was the only THM not detected. Four of the six haloacetic acids targeted for analysis were detected: dichloroacetic acid, trichloroacetic acid, bromochloroacetic acid, and dibromoacetic acid. Their concentrations ranged from 0.7 to 33 ppb. Chloroacetic acid and bromoacetic acid were not detected.

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Semiquantitative concentrations of the semivolatile DBPs (Table 1) ranged from approximately 1 to 200 ppt (ng/L). The haloacetaldehydes and halonitriles are included in this set of DBPs. Although most of the halonitriles identified had relatively simple structures, only one of them (dichloroacetonitrile) was in any spectral library. The structures of the halonitriles identified are shown below. Cl

Cl Cl

C

Cl

N

C

C

Cl C

Br

N

C

Br

H

Cl

H

H

C

C

Cl Cl H C

H

Cl

Cl

C

C

C

H

N

H

N

H

Br Cl

Cl

C

C

N

Cl

C

C

C

H

H

H

H

Cl

C

C

H

C

C

C

N

N

Cl

Haloacetonitriles have been reported in previous chlorination studies (28). Most of the halogenated DBPs were traditional chlorination byproducts and were observed in the chlorinated control sample (raw water + chlorine). However, one of the more interesting compounds, tentatively identified as dihydro-4,5-dichloro-2(3H)furanone, was formed only by the combination of TiO2/UV treatment and secondary chlorination. This byproduct, like the one formed by TiO2/ UV treatment alone, required much spectral information to solve its structure. Figure 5 shows the EI mass spectrum for this compound. As before, empirical formula assignments shown on the mass spectrum were obtained from high-resolution EI-MS. First, there was no spectral match for this compound, nor was there any mass spectrum similar to that of this compound. It was immediately apparent from the 2-chlorine isotopic patterns shown in the mass

FIGURE 5. EI mass spectrum of the (TiO2/UV + Cl2) byproduct tentatively identified as dihydro-4,5-dichloro-2(3H)furanone.

spectrum (m/z 96/98/100 and m/z 126/128/130) however that the compound contained at least two chlorines. Because the molecular ion was not clearly evident, methane CI-MS was used to determine the molecular weight of 154. From the high-resolution data, the complete molecular formula of C4H4O2Cl2 was obtained. Although the loss of CO (m/z 154 f 126) suggested the presence of a carbonyl group in the structure, and the loss of C2H2O2 (m/z 154 f 96) suggested the possibility of a cyclic ester, infrared spectroscopy was necessary to substantiate this assignment. Unfortunately, this byproduct co-eluted on the GC/FT-IR system with benzaldehyde. Several attempts were made to improve the chromatographic separation of these two components, including replacing the Rtx-5 column with a DB-WAX column. None of these attempts were completely successful. Therefore, in order to obtain a usable spectrum of this byproduct, the spectrum of benzaldehyde was digitally subtracted from the experimental spectrum. The success of the subtraction was limited, however, because benzaldehyde was present at a significantly higher quantity than this byproduct. Nonetheless, a CdO stretching peak attributable to this byproduct was well separated (spectroscopically) from any absorption of benzaldehyde and was clearly observed at 1802 cm-1. This frequency is quite high and is characteristic of carboxylic acids, dihydrofuranones, and acid chlorides. We could immediately rule out a carboxylic acid because no OH stretching peak was observed in the experimental spectrum. From mass spectral information, the acid chloride functionality could be ruled out. COCl+ ions and ions resulting from the loss of COCl, which are typical for acid chlorides, were not present in the mass spectrum. Furthermore, the subtracted infrared spectrum suggests a C-O stretching peak at 1152 cm-1, which would confirm the presence of the ester linkage, suggesting the dihydrofuranone structure. Unfortunately, it is not possible to unequivocally assign this peak to the byproduct because benzaldehyde exhibits a strong, broad, and complex absorption peak from 1145 to 1225 cm-1,

which limits the success of the subtraction. However, this information and the lack of any IR evidence of non-ester functionalities, coupled with the molecular formula and other mass spectral information mentioned earlier, makes a dichlorinated, dihydrofuranone most likely. Because the MS ion at m/z 96 (C2H2Cl2) indicated that the two chlorine atoms were on adjacent carbons, there were two structural possibilities at this point: a dihydrofuranone structure with the two chlorines (on adjacent carbon atoms) adjacent to the carbonyl group or adjacent to the oxygen (in the ring). If a chlorine atom were adjacent to the carbonyl group, we believe that the CdO stretching peak would have been shifted to a frequency significantly higher than 1802 cm-1, based on analysis of related library spectra. Therefore, we believe the correct choice of chlorine position is adjacent to the oxygen. Thus, from all of the spectral information, we tentatively identified this compound as dihydro-4,5-dichloro-2(3H)furanone. Because the structure of this compound suggests that it may not be stable in water (would undergo hydrolysis), it is likely that this DBP was initially present (in the treated water) in a different form. For example, it is possible that the original DBP was a straight-chain chlorinated hydroxy acid that underwent an intramolecular esterification (in the GC or during sample workup) to cyclize and form the chlorinated furanone. In a previous study, we observed a similar type of DBP conversion during a sample workup (29). In that case, the original DBP was a diacid that cyclized to form an anhydride. Although heat from the GC injection port could have caused this conversion, the conversion actually happened during extraction with ethyl acetatesprior to injection of the sample onto the GC. It should be noted that although many chlorinated DBPs were produced when chlorine was used as a secondary disinfectant (following treatment with TiO2/UV), the number and concentration of these chlorinated DBPs were lower than when chlorine was used as the sole disinfectant. This was evidenced in the GC/MS chromatograms as well as in


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a lower TOX. Ultrafiltered raw water treated with TiO2/UV and chlorine exhibited a TOX that was 56% lower than raw water treated with chlorine.

Acknowledgments The authors wish to acknowledge Robert Miller, John Glass, Sr., David Cmehil, and Brad Smith for their contributions to this research; George Yager for assistance with GC/FTIR analyses; and Tashia Sullins for her help in preparing this manuscript. Mention of trade names or commercial products does not constitute endorsement or recommendation for use by the U. S. Environmental Protection Agency.

Literature Cited (1) National Cancer Institute Report on Carcinogenesis Bioassay of Chloroform; Carcinogenesis Program, Division of Cancer Cause and Prevention: Bethesda, MD, Mar 1976. (2) Water Industry Database: Utility Profiles; American Water Works Association: Denver, CO, 1992. (3) Fed. Regist. 1994, 59 (145), 38668. (4) Wei, C.; Lin, W.-Y.; Zainal, Z.; Williams, N. E.; Zhu, K.; Kruzic, A. P.; Smith, R. L.; Rajeshwar, K. Environ. Sci. Technol. 1994, 28, 934. (5) Ireland, J. C.; Klostermann, P.; Rice, E. W.; Clark, R. M. Appl. Environ. Microbiol. 1993, 59, 1668. (6) Suri, R. P. S.; Liu, J.; Hand, D. W.; Crittenden, J. C.; Perram, D. L.; Mullins, M. E. Water Environ. Res. 1993, 65 (5), 665. (7) Kenneke, J. F.; Ferry, J. L.; Glaze, W. H. The Origin of Chlorinated By-Products from the TiO2-Mediated Photodegradation of Chloroalkenes in Water. In Proceedings of the 208th ACS National Meeting; American Chemical Society: Washington, DC, 1994. (8) Zhang, Y.; Crittenden, J. C.; Hand, D. W.; Perram, D. L. Environ. Sci. Technol. 1994, 28, 435. (9) Matthews, R. W. J. Catal. 1988, 111, 264. (10) Ollis, D. E. Environ. Sci. Technol. 1985, 19 (6), 480. (11) Hsiao, C.-Y.; Lee, C.-L.; Ollis, D. F. J. Catal. 1983, 82, 418. (12) Ollis, D. F.; Hsaio, C.-Y.; Budiman, L.; Lee, C.-L. J. Catal. 1984, 88, 89. (13) Pruden, A. L.; Ollis, D. F. J. Catal. 1983, 82, 404.

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(14) Matthews, R. W. J. Phys. Chem. 1987, 91, 3328. (15) Pelizzetti, E.; Maurino, V.; Minero, C.; Carlin, V.; Pramauro, E.; Zerbinati, O.; Tosato, M. L. Environ. Sci. Technol. 1990, 24, 1559. (16) Pacheco, J. E.; Mehos, M. S.; Turchi, C. S.; Link, H. Proceedings of the First International Conference on TiO2 Photocatalytic Purification and Treatment of Water and Air, London, Canada, Nov 8-13, 1992; Ollis, D., Al-Ekabi, H., Eds.; Elsevier: Amsterdam, 1993; p 547. (17) Fox, M. A.; Dulay, M. T. Chem. Rev. 1993, 93, 341. (18) Legrini, O.; Oliveros, E.; Braun, A. M. Chem. Rev. 1993, 93, 671. (19) Ollis, D. F.; Pelizzetti, E.; Serpone, N. Environ. Sci. Technol. 1991, 25, 1523. (20) Alborzfar, M.; Gron, C.; Jonsson, G. Environ. Int. 1994, 20 (3), 411. (21) Anselme, C.; Mandra, V.; Baudin, I.; Jacangelo, J. G.; Mallevialle, J. Water Supply 1993, 11 (3), 249. (22) Baudin, I.; Anselme, C.; Chevalier, M. R. Aqua (London) 1993, 42 (5), 295. (23) Methods for the Determination of Organic Compounds in Drinking Water, Supplement 1; U.S. Environmental Protection Agency: Cincinnati, OH, July 1990; EPA/600/4-90, 020. (24) Standard Methods for the Examination of Water and Wastewater, 17th ed.; American Public Health Association: Washington, DC, 1989. (25) Keith, L. H.; Telliard, W. A. Environ. Sci. Technol. 1979, 13, 416. (26) Hand, D. W.; Parram, D. L.; Crittenden, J. C. J. Am. Water Works Assoc. 1995, 87 (6), 84. (27) Kiserow, D. J.; Pugh, K. C. Photocatalytic Degradation of Atrazine using TiO2-Impregnated Mesh. In Proceedings of the 206th ACS National Meeting; American Chemical Society: Washington, DC, 1993. (28) Coleman, W. E.; Munch, J. W.; Kaylor, W. H.; Streicher, R. P.; Ringhand, H. P.; Meier, J. R. Environ. Sci. Technol. 1984, 18, 674. (29) Richardson, S. D.; Thruston, A. D., Jr.; Collette, T. W.; Patterson, K. S.; Lykins, B. W., Jr.; Majetich, G.; Zhang, Y. Environ. Sci. Technol. 1994, 28, 592.

Received for review February 14, 1996. Accepted June 11, 1996.X ES960142M X

Abstract published in Advance ACS Abstracts, September 1, 1996.

UV Disinfection Byproducts in Drinking Water

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