Grantee Research Project Results

2000 Progress Report: Formation and Stability of Ozonation By-Products in Drinking Water

EPA Grant Number: R826833
Title: 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, 1999 through October 31, 2000
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 are often 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 then 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 which influence their relative concentrations. Their kinetics of formation and stability need to be characterized and in order 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:

In the second year of this project, we have made headway in the development of new analytical methods for determining three distinct groups of proposed ozonation by-products that hitherto have not been identified in ozonated waters. These include organic peroxides, epoxides, and multi-functional carbonyl containing organic by-products. In the absence of many commercial standards for these compounds, our efforts have focused on evolving strategies for maximizing isolation from the aquatic matrix and enhancing detection for low molecular weight representative compounds from each of these classes. The peroxides are separated on a C-18 column by high performance liquid chromatography (HPLC) and then a post-column reaction converts the individual species into hydroxyl radicals which then react with para-hydroxyphenylacetic acid at pH 11 to produce a fluorescent dimer whose detector response is directly proportional to the concentration of organic peroxide in the original sample. Current detection limits are in the range 10-30 µg/L but these can probably be lowered by an order of magnitude using a preconcentration approach. Epoxides are extracted from water after derivatization with difluoroaniline but the kinetics of the latter reaction are slow and are impacting a realistic minimum quantitation limit. Carbonyl-containing compounds that have not been amenable to derivatization with PFBHA are successfully isolated from water using 2,4-dinitrophenylhydrazine which produces fingerprint diode-array spectra following resolution of individual components by HPLC. On-line preconcentration permits detection at the 10 nanomolar level and the technique is compatible with electrospray mass spectrometric detection which will be used to identify new such by-products.

Future Activities:

Each of the subgroups of potential ozone by-products for which methods are currently being developed, will be evolved into practical techniques that permit quantitation down to the low nanomolar level. This will involve the use of preconcentration techniques. Concurrent with this effort is the on-going use of laboratory-scale ozonation of coagulated surface waters to provide a matrix upon which these methods can be applied. The final stage of this research will involve an application of these methods to a limited occurrence study in ozonated waters generated from a cross-section of natural waters across the country that vary in chemical character that might impact the quantity and types of by-products formed. This survey also will obtain occurrence data for the groups of byproducts identified in the first year of this study.

Journal Articles:

No journal articles submitted with this report: View all 18 publications for this project

Supplemental Keywords:

disinfection, water, disinfection by-products, 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 effects

Relevant Websites:

http://www.unc.edu/~weinberg/hswrsrchFrame.html#Formation Exit
http://www.unc.edu/~weinberg/Discussion-Forum/WelcomePage.html Exit

Progress and Final Reports:

Original Abstract

1999 Progress Report

Final Report