Using a combination of spectral identification techniquesgas 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.
When chemical or microbial contaminants are assessed for potential effect or possible regulation in ambient and drinking waters, a critical first step is determining if the contaminants occur and if they are at concentrations that may cause human or ecological health concerns. To this end, source and treated drinking water samples from 29 drinking water treatment plants (DWTPs) were analyzed as part of a two-phase study to determine whether chemical and microbial constituents, many of which are considered contaminants of emerging concern, were detectable in the waters. Of the 84 chemicals monitored in the 9 Phase I DWTPs, 27 were detected at least once in the source water, and 21 were detected at least once in treated drinking water. In Phase II, which was a broader and more comprehensive assessment, 247 chemical and microbial analytes were measured in 25 DWTPs, with 148 detected at least once in the source water, and 121 detected at least once in the treated drinking water. The frequency of detection was often related to the analyte's contaminant class, as pharmaceuticals and anthropogenic waste indicators tended to be infrequently detected and more easily removed during treatment, while per and polyfluoroalkyl substances and inorganic constituents were both more frequently detected and, overall, more resistant to treatment. The data collected as part of this project will be used to help inform evaluation of unregulated contaminants in surface water, groundwater, and drinking water.
In vitro bioassays are sensitive, effect-based tools used to quantitatively screen for chemicals with nuclear receptor activity in environmental samples. We measured in vitro estrogen (ER), androgen (AR), and glucocorticoid receptor (GR) activity, along with a broad suite of chemical analytes, in streamwater from 35 well-characterized sites (3 reference and 32 impacted) across 24 states and Puerto Rico. ER agonism was the most frequently detected with nearly all sites (34/35) displaying activity (range, 0.054-116 ng E2Eq L). There was a strong linear relationship (r = 0.917) between in vitro ER activity and concentrations of steroidal estrogens after correcting for the in vitro potency of each compound. AR agonism was detected in 5/35 samples (range, 1.6-4.8 ng DHTEq L) but concentrations of androgenic compounds were largely unable to account for the in vitro activity. Similarly, GR agonism was detected in 9/35 samples (range, 6.0-43 ng DexEq L); however, none of the recognized GR-active compounds on the target-chemical analyte list were detected. The utility of in vitro assays in water quality monitoring was evident from both the quantitative agreement between ER activity and estrogen concentrations, as well as the detection of AR and GR activity for which there were limited or no corresponding target-chemical detections to explain the bioactivity. Incorporation of in vitro bioassays as complements to chemical analyses in standard water quality monitoring efforts would allow for more complete assessment of the chemical mixtures present in many surface waters.
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 byproductdibromoacetonitrilewas 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.
This article describes the disinfection by-product (DBP) characterization portion of a series of experiments designed for comprehensive chemical and toxicological evaluation of two drinking-water concentrates containing highly complex mixtures of DBPs. This project, called the Four Lab Study, involved the participation of scientists from four laboratories and centers of the U.S. Environmental Protection Agency (EPA) Office of Research and Development, along with collaborators from the water industry and academia, and addressed toxicologic effects of complex DBP mixtures, with an emphasis on reproductive and developmental effects that are associated with DBP exposures in epidemiologic studies. Complex mixtures of DBPs from two different disinfection schemes (chlorination and ozonation/postchlorination) were concentrated successfully, while maintaining a water matrix suitable for animal studies. An array of chlorinated/brominated/iodinated DBPs was created. The DBPs were relatively stable over the course of the animal experiments, and a significant portion of the halogenated DBPs formed in the drinking water was accounted for through a comprehensive qualitative and quantitative identification approach. DBPs quantified included priority DBPs that are not regulated but have been predicted to produce adverse health effects, as well as those currently regulated in the United States and those targeted during implementation of the Information Collection Rule. New by-products were also reported for the first time. These included previously undetected and unreported bromo- and chloroacids, iodinated compounds, bromo- and iodophenols, and bromoalkyltins.
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