Using a combination of spectral identification techniquesgas chromatography coupled with low- and high-resolution electron-impact mass spectrometry (GC/EI-MS), low- and high-resolution chemical ionization mass spectrometry (GC/CI-MS), and infrared spectroscopy (GC/IR)we identified many drinking water disinfection byproducts (DBPs) formed by ozone and combinations of ozone with chlorine and chloramine. Many of these DBPs have not been previously reported. In addition to conventional XAD resin extraction, both pentafluorobenzylhydroxylamine (PFBHA) and methylation derivatizations were used to aid in identifying some of the more polar DBPs. Many of the byproducts identified were not present in spectral library databases. The vast majority of the ozone DBPs identified contained oxygen in their structures, with no halogenated DBPs observed except when chlorine or chloramine was applied as a secondary disinfectant. In comparing byproducts formed by secondary treatment of chlorine or chloramine, chloramine appeared to form the same types of halogenated DBPs as chlorine, but they were generally fewer in number and lower in concentration. Most of the halogenated DBPs that were formed by ozone−chlorine and ozone−chloramine treatments were also observed in samples treated with chlorine or chloramine only. A few DBPs, however, were formed at higher levels in the ozone−chlorine and ozone−chloramine samples, indicating that the combination of ozone and chlorine or chloramine is important in their formation. These DBPs included dichloroacetaldehyde and 1,1-dichloropropanone.

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Using a combination of mass spectrometry and infrared spectroscopy, disinfection byproducts were identified in ozonated drinking water containing elevated bromide levels and in ozonated water treated with secondary chlorine or chloramine. Only one brominated byproductdibromoacetonitrilewas found in the water treated with only ozone. This compound was found only in one of the three treatment rounds and was also present in the untreated, raw water but at levels 20 times lower than in the ozonated water. Many more byproducts were identified when secondary chlorine or chloramine was applied after ozonation. A number of these byproducts have not been reported previously. When comparing low-bromide water to water with elevated bromide, a tremendous shift in speciation was observed for samples treated with secondary chlorine or chloramine. Without high bromide levels, chlorinated species dominate (e.g., chloroform, trichloroacetaldehyde, tetrachloropropanone, dichloroacetonitrile, trichloronitromethane); with elevated bromide levels (1 mg/L), these shift to brominated species (e.g., bromoform, tribromoacetaldehyde, tetrabromopropanone, dibromoacetonitrile, tribromonitromethane). An entire family of bromo- and mixed chlorobromopropanones was identified that was not present in library databases and has not been reported previously. They were observed mainly in the ozone−chloramine samples but were also present in ozone−chlorine-treated water. These brominated byproducts were also observed in water treated with only chloramine or chlorine.

Because the performance of powdered activated carbon (PAC) for uses other than taste and odor control is poorly documented, the purpose of this article is to critically review uses that have been reported and to analyze means of employing PAC more efficiently. The extent of adsorption of synthetic organic chemicals on PAC is strongly dependent on the type of compound being removed. The reported removals of trihalomethanes and trihalomethane precursors by PAC range from poor to very good. In selecting the point of addition of PAC, consideration must be given to the degree of mixing, the contact time between the PAC and the water, the PAC residence time, and the minimization of interference of adsorption by treatment chemicals. One of the main advantages of PAC is its low capital cost.

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.