Grantee Research Project Results
1999 Progress Report: Formation and Stability of Ozonation By-Products in Drinking Water
EPA Grant Number: R826833Title: Formation and Stability of Ozonation By-Products in Drinking Water
Investigators: Weinberg, Howard S.
Institution: University of North Carolina at Chapel Hill
EPA Project Officer: Hahn, Intaek
Project Period: November 1, 1998 through October 31, 2001
Project Period Covered by this Report: November 1, 1998 through October 31, 1999
Project Amount: $441,261
RFA: Drinking Water (1998) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
It is generally perceived that disinfection by-products (DBPs) produced by ozonation represent less of a health hazard than those produced by the chlorine-containing disinfectants, at least by the use of short-term bioassays. It also has been noted that the types of oxidation by-products produced by ozonation of natural waters are in many cases the same as compounds produced by natural oxidation processes in streams, lakes, and reservoirs. The implication is that naturally occurring compounds will be safer than "unnatural" compounds such as trihalomethanes (THMs) and haloacetic acids (HAAs) produced by chlorination. However, there are fallacies associated with each of these arguments. Short-term bioassays are not at a stage of development to use in relative risk assessments. Also, the preconcentration methods used to obtain extracts for bioassays may not efficiently trap polar by-products from ozonation of natural waters. Finally, natural waters themselves often are mutagenic, so the argument that ozone produces "natural" organics is not encouraging.
With less than 50 percent of the assimilable organic carbon generated by ozonation remaining unidentified, this project will investigate new methodologies for targeting these, as yet, unidentified by-products. These, together with refined existing techniques, will be employed to study the impact of water quality parameters on the formation and stability of these compounds in distributed drinking waters. The objectives are, therefore, to investigate the relative occurrence of these by-products in treated drinking waters, and to determine water quality, treatment, and distribution system conditions that influence their relative concentrations. Their kinetics of formation and stability need to be characterized and to understand the underlying causes of the relative differences in by-product formation in different waters, a controlled study needs to be conducted in which the various contributory factors are investigated.
Progress Summary:
The first year of this project has focused on evaluating methodologies for accurately targeting carbonyl-containing compounds tentatively identified in a variety of literature results combining field, pilot, and laboratory-scale ozonations. The species targeted in this initial approach include the following compounds: C1-C12 monosaturated aldehydes, glyoxal, methyl glyoxal, dimethyl glyoxal, trans-2-hexenal, formic acid, acetic acid, and oxalic acid, and the three mixed functional pyruvic acid, glyoxylic acid, and keto-malonic acid. It has been determined that previous attempts to quantify these by-products in aquatic matrices involving derivatization techniques may have suffered from inadequate recoveries. This conclusion was derived by synthesizing the relevant oximes and esters and comparing derivatization efficiency in the aquatic medium alongside the pure derivatized standard. Purification of the derivatized standards involves utilizing a step-wise thin layer chromatography with the isolated product assayed by proton NMR. Extraction techniques thus far have continued to demonstrate liquid-liquid extraction as an accomplished means of isolation at the low mg/L level. The project also has begun some initial study of electrospray mass spectrometry of the underivatized species eluted from a preconcentration column with the goal of removing derivatization from the sample preparation procedure.
Future Activities:
The pool of identifiable by-products resulting from the combined use of ozone and postdisinfectant will be expanded by targeting compounds observed in the literature from laboratory studies on synthetic solutions containing natural organic matter (NOM) in a variety of treatment scenarios. This research will utilize a combination of in situ derivatization techniques in combination with solid-phase extraction (particularly microextraction) to target a broad range of polar by-products produced by ozonation that might be subsequently chlorinated by postdisinfectant. Positive identification will be achieved by a combination of complimentary spectroscopic tools. Once the target by-products are established, studies of their formation and stability will be conducted both on a bench-scale and in the field, at actual full-scale treatment plants and their respective distribution systems. The study will have three components: (1) development of analytical methods for new ozonation by-products; (2) bench-scale, controlled, laboratory ozone/chlorination and ozone/chloramination study using waters with differing NOM characteristics from different regions of the United States and ozonated/ disinfected under a variety of solution conditions; and (3) a full-scale plant study to assess the distribution and speciation of by-products in a variety of different waters from geographically diverse regions, with differing water quality, treatment, and distribution system characteristics.
Journal Articles:
No journal articles submitted with this report: View all 18 publications for this projectSupplemental Keywords:
disinfection, exposure, organics, analytical methods, ozonation., RFA, Scientific Discipline, Water, Chemistry, Environmental Chemistry, Analytical Chemistry, Drinking Water, chlorine-based disinfection, community water system, ozonation, treatment, water quality, water quality parameters, chloramines, drinking water system, drinking water contaminants, water treatment, exposure, formation, stability, disinfection byproducts (DPBs), public water systems, alternative disinfection methods, exposure and effectsRelevant Websites:
http://www.unc.edu/~weinberg/hswrsrchFrame.html#Formation 
http://www.unc.edu/~weinberg/Discussion-Forum/WelcomePage.html
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.