Grantee Research Project Results
1999 Progress Report: Analysis of Organic Byproducts from the use of Ozone/Chlorine and Ozone/Chloramines in Drinking Water Treatment
EPA Grant Number: R825364Title: Analysis of Organic Byproducts from the use of Ozone/Chlorine and Ozone/Chloramines in Drinking Water Treatment
Investigators: Reckhow, David A.
Institution: University of Massachusetts - Amherst
EPA Project Officer: Packard, Benjamin H
Project Period: January 1, 1997 through June 30, 1999
Project Period Covered by this Report: January 1, 1998 through June 30, 1999
Project Amount: $355,795
RFA: Drinking Water (1996) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
The purpose of this project is to test, develop, and refine new and emerging analytical methods for nonvolatile organic disinfection byproducts (DBPs), and to identify new ozonation and mixed ozonation/chloramination byproducts. Special emphasis is placed on new aqueous-phase derivatization agents.
Progress Summary:
In early phases of this work, model carboxylic acidsC known to be ozonation byproductsCwere derivatized using hexylchloroformate, and detected by gas chromatography (GC)-ion trap-mass spectrometry (MS). Even though the procedure was simple, it worked only for mono-, di-, hydroxy- and chlorinated monoacids; it did not work for alpha-ketoacids, which are very common in ozonated waters. In addition, this method did not produce the expected sensitivities or low limits of detection. Therefore, derivatization with ethylchloroformate was explored, making possible the detection of most alpha-ketoacids, but with very low sensitivity and less satisfactory limits of detection than in the previous method. The derivatization yield of ketoacids with ethylchloroformate was found to be highly dependent on the composition of the reaction medium.
Another analytical methodology that was studied involves the determination of carboxylic acids with an high-performance liquid chromatography (HPLC)-MS system. The use of HPLC technique allows the determination of highly polar/hydrophilic compounds that cannot be determined using GC systems, and its combination with mass spectrometry is expected to help in the identification of unknown products of chlorine and chloramination reactions. In our project, determination of carboxylic acids is being done by derivatization with 2-nitrophenylhydrazine (2-NPH). Under the proper conditions, 2-NPH only reacts with acids, avoiding interferences from ketones or aldehydes, compounds that usually are present in real samples. Additionally, the derivative forms a very stable negative ion, allowing its detection by negative ion electrospray mass spectrometry. This helps to reduce background noise from non-reacted reagents or byproducts of the reaction. These selective characteristics of the method should allow the detection of acids (halogenated and non-halogenated) in very low concentrations and with high accuracy.
The derivatization procedure has proven to be simple and fast. Up to the end of this reporting period, a total of 32 acids, including ketoacids, had been qualitatively determined by HPLC-MS after derivatization. Research continues with the goal of optimizing instrumental conditions and reaction conditions, to improve limits of detection. Under actual conditions, up to 100 ppb of propionic acid, a low-molecular weight model byproduct, has been detected using the MS-MS capability of the HPLC-MS system. This has been done without any sample concentration. Limits of detection are expected to improve when alternative reaction and instrument conditions are explored.
Along with the analytical work, several model ozonation byproducts have been chlorinated and chloraminated, and their chlorine demand and total organic halide (TOX) content have been determined. From the set of compounds studied, it was found that, in general, more unknown TOX is formed when chloramine is used as a disinfectant than when chlorine is used. Nevertheless, most of the compounds give rise to higher levels of halogenated acids (mostly as dichloroacetic acid) during chlorination than during chloramination. The comparison of TOX and chlorine demand provides important information on the reaction pathways and relative importance of oxidized products to halogenated ones.
After reaction with chlorine or chloramine, TOX, haloacetic acid (HAA), and pentane extractable compounds (trihalomethanes [THMs], acetonitriles, and chloroacetone) are being measured. From this analysis, it has become clear that some compounds produce large amounts of "unknown TOX," whereas others give rise to compounds that can be almost fully characterized by analysis of the conventional chlorination byproducts. These results are very valuable to our analytical efforts, because they give important clues about the reaction path during chlorination and chloramination. Some byproduct profiles allow one to postulate a priori the structure of major "unknown" halogenated byproducts. We are pursuing the analysis of these proposed compounds, adapting our methods to their predicted structural features. We then will try to identify and quantify them.
Future Activities:
Work will continue in the development of methods of derivatization in aqueous phase using both GC-MS and HPLC-MS. Special interest will be placed on improving method sensitivity and limits of detection, as well as sample isolation and concentration techniques. The study of model compound reactions will be used as a base for future work, optimizing any analytical methodologies to determine reaction products of those compounds.
Water treatment plant sampling will be re-initiated once one of the new methods is deemed ready for field testing. At this point, samples will be analyzed for known byproducts (e.g., aldehydes and ketoacids) using existing methodology, as well as the newer or experimental methodologies developed during this research.
Journal Articles:
No journal articles submitted with this report: View all 8 publications for this projectSupplemental Keywords:
ozone, water, drinking water, chemicals, toxics, oxidants, organics, disinfection, disinfection byproducts, DBPs, oxidation, environmental chemistry, engineering, monitoring, analytical, surveys, measurement methods, northeast, Atlantic coast, Massachusetts, MA, Maine, ME, EPA Region 1., RFA, Scientific Discipline, Geographic Area, Water, Environmental Chemistry, Chemistry, State, Analytical Chemistry, Drinking Water, EPA Region, monitoring, alternative disinfection methods, public water systems, organic byproducts, exposure and effects, chemical byproducts, disinfection byproducts (DPBs), exposure, community water system, Massachusetts (MA), treatment, chlorine-based disinfection, microbial risk management, chloramines, DBP risk management, drinking water contaminants, water treatment, Region 1, drinking water systemRelevant Websites:
http://www.ecs.umass.edu/cee/reckhow/
Progress and Final Reports:
Original AbstractThe perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.