Grantee Research Project Results
Final Report: Brominated DBP Formation and Speciation Based on the Specific UV Absorbance Distribution of Natural Waters
EPA Grant Number: R828045Title: Brominated DBP Formation and Speciation Based on the Specific UV Absorbance Distribution of Natural Waters
Investigators: Kilduff, James E. , Karanfil, Tanju
Institution: Rensselaer Polytechnic Institute , Clemson University
EPA Project Officer: Hahn, Intaek
Project Period: March 1, 2000 through March 1, 2003
Project Amount: $391,473
RFA: Drinking Water (1999) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
The objective of this research project was to understand the characteristics of natural waters that influence disinfection byproduct (DBP) formation and treatability, which is critical for providing safe water and for meeting current drinking water regulations. DBPs are comprised of several organic and inorganic compounds that are formed by reactions between chemical oxidants, naturally occurring dissolved organic matter (DOM), and bromide. Trihalomethanes (THMs) and haloacetic acids (HAAs) are the two major classes of DBPs commonly found in waters disinfected with chlorine. Other DBPs of interest include haloacetonitriles (HANs) and haloketones (HNs). The presence of DBPs in drinking water is undesirable because they are potentially toxic, carcinogenic, and mutagenic to humans. To comply with current and forthcoming regulations, drinking water utilities must continue to develop strategies to minimize DBP formation.
Research conducted since the first discovery of THMs in drinking water has identified dissolved organic carbon (DOC), chlorine (disinfectant), and bromide concentrations as the primary factors controlling DBP formation and speciation (e.g., Singer, 1994). The DOC in natural waters results from DOM, a heterogeneous mixture of complex organic materials including humic substances, hydrophilic acids, proteins, lipids, amino acids, and hydrocarbons. Because different DOM components exhibit different reactivity with disinfectants, knowledge of DOM structure and how it relates to reactivity is central to understanding how to control DBPs. The primary goal of this research was to relate DOM composition with the formation and speciation of THMs and HAAs with a focus on bromine incorporation.
While sophisticated fractionation and characterization of organic matter in natural waters yields important information, one bulk water parameter, the specific ultraviolet absorbance (SUVA) (i.e., SUVA=UV/DOC), has proven to be a useful and robust predictor of both reactivity with oxidants and treatability. SUVA determination (usually SUVA254) of a water sample yields a single aggregate value that represents the response of a distribution of chromophores within a single DOM molecule and among different DOM molecules. Similarly, reactivity of bulk water represents the combined reactivity of many different molecules and molecular moities. As an approach to relate DOM composition with the formation and speciation of THMs and HAAs, our objective was to examine how SUVA, and more importantly, how the distribution of SUVA in a source water, influences DBP production. Once the most reactive components and their characteristics are identified, such information will be useful for optimizing treatment goals, tailoring precursor removal technologies, and devising disinfection strategies to comply with the U.S. Environmental Protection Agency Disinfectants/DBP rule.
Summary/Accomplishments (Outputs/Outcomes):
The results of this research project demonstrate that reverse osmosis (RO) isolation is an effective and rapid technique for isolating large quantities of DOM from natural waters. Rejection of organic carbon was greater than 99 percent, and fouling was minimized and DOM mass recovery was high during low-pressure operation (<700 kPa or 100 psi) using a module-based recovery of about 15 percent or less. The RO isolation process did not change the physicochemical properties of source water DOM characterized by SUVA254, and by the subsequent DBP formation and speciation quantified as THM, HAA9, HAN, and HK. In addition, RO isolate and 0.45-µm filtered source exhibited similar behavior in terms of: (1) flux decline during nanofiltration; (2) adsorption by XAD-8 resin, as expressed in terms of the trend in the HPL/HPO ratio as a function of the column distribution coefficient, k'; (3) uptake by granular activated carbon; (4) their ability to reduce uptake of TCE by DOM-preloaded granular activated carbon; and (5) size distribution measured by size exclusion chromatography. These results provide strong evidence that RO isolation preserved the integrity of DOM for the three low-hardness surface waters tested in this study in terms of DBP reactivity and other DOM properties, such as size, polarity, charge density, and isoelectric point.
The results of this research further demonstrate that: (1) DOM isolation and/or fractionation procedures using XAD-8 adsorption and ultrafiltration (UF) do not alter either the SUVA or the reactivity of DOM (in terms of DBP formation and speciation) as compared to the source water, at least for the techniques described in this study; and (2) although XAD-8 adsorption and UF fractionate DOM with significantly different mechanisms for each water tested, strong and unique correlations were observed between SUVA and THM and HAA9 yields, independent of the fractionation process employed. Because there was no consistent trend between the molecular weight and DBP formation for the UF fractions of the two waters tested in this study, aromaticity of DOM components is more important than the size for predicting DBP formation. These results support the finding that SUVA is a distributed parameter that varies among DOM components, reflects the degree of DOM heterogeneity, and represents an important property of natural waters that can be used to predict DBP formation.
Fractionation of DOM solutions by various physicochemical processes demonstrated how the distribution of SUVA in a source water influences DBP production and identified reactive components. Consistent with the reports in the literature, granular activated carbon and XAD-8 adsorption and alum coagulation preferentially removed high SUVA components from water and UV-absorbing moieties were the major reactive sites responsible for DBP formation. For a single water sample, a single correlation was observed between the SUVA values of DOM fractions and their THMs and HAA9 formations, independent of the separation process used to obtain the fractions. Therefore, the correlation obtained for each water appears to represent its natural DBP reactivity profile. A unique reactivity profile as a function of SUVA was obtained for each water tested; therefore, site-specific reactivity profiles should be developed for each water source. The distribution of SUVA within a source water and its relationship to reactivity were found to be more informative than the source water aggregate SUVA value. Therefore, understanding how reactivity is correlated to SUVA may allow utilities to optimize the degree of treatment required to comply with the D/DBP regulations. In addition, SUVA has promise as a parameter for on-line monitoring and control of DBP formation in practical applications. Periodic development of reactivity profiles will allow utilities to assess and monitor the heterogeneity and reactivity of DOM in source water with time. Whereas SUVA appears to be an accurate predictor of reactivity with chlorine in terms of DBP yield, it was found, however, that low SUVA components of NOM are more efficient at incorporating bromine. The results provided insight to the formation and speciation of HAAs from different DOM components. Formation of trichloroacetic acid (TCAA) was dominant over dichloroacetic acid (DCAA) for high-SUVA fractions, but the formations of TCAA and DCAA were comparable for low-SUVA fractions.
Anion exchange effectively removes DOM from solution and reduces DBP formation during chlorination. It employs a different separation mechanism from other physicochemical techniques that rely on hydrophobic interactions, such as carbon adsorption, hydrophobic resin adsorption, and coagulation. For the Tomhannock Reservoir, Troy, NY water, however, changes in SUVA254 and the correlation between SUVA254 and DBP reactivity were consistent with other physicochemical processes. Still, the specificity of surface interactions that are characteristic of ion exchange processes result in some significant differences compared to these other processes. First, the correlation between SUVA254 and DBP reactivity may depend on resin type, presumably as a result of specific interactions with surface functional groups and/or resin structure. Second, as observed in the Myrtle Beach, SC water, the correlation between SUVA254 and DBP reactivity may be quite different compared to other physicochemical processes. This probably results from the heterogeneous structure of DOM and/or competition among species in solution.
Reference:
Singer PC. Control of disinfection by-products in drinking water. ASCE Journal of Environmental Engineers 1994;120(4):727-744.
Journal Articles on this Report : 7 Displayed | Download in RIS Format
| Other project views: | All 18 publications | 8 publications in selected types | All 8 journal articles |
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Baxley JS, Hepplewhite C, Karanfil T. The efficiency of the ILUV oxidation method for organic nitrogen analysis. Water Science and Technology: Water Supply 2004;4(4):25-32. |
R828045 (Final) |
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Dastgheib SA, Karanfil T, Cheng W. Tailoring activated carbons for enhanced removal of natural organic matter from natural waters. Carbon 2004;42(3):547-557. |
R828045 (Final) R828157 (Final) |
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Kilduff JE, Mattaraj S, Wigton A, Kitis M, Karanfil T. Effects of reverse osmosis isolation on reactivity of naturally occurring dissolved organic matter in physicochemical processes. Water Research 2004;38(4):1026-1036. |
R828045 (Final) R828157 (Final) |
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Kitis M, Karanfil T, Kilduff JE, Wigton A. The reactivity of natural organic matter to disinfection by-products formation and its relation to specific ultraviolet absorbance. Water Science & Technology 2001;43(2):9-16. |
R828045 (Final) |
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Kitis M, Karanfil T, Wigton A, Kilduff JE. Probing reactivity of dissolved organic matter for disinfection by-product formation using XAD-8 resin adsorption and ultrafiltration fractionation. Water Research 2002;36(15):3834-3848. |
R828045 (2001) R828045 (Final) |
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Kitis M, Karanfil T, Kilduff JE. The reactivity of dissolved organic matter for disinfection by-product formation. Turkish Journal of Engineering and Environmental Sciences 2004;28(3):167-180. |
R828045 (Final) |
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Tan Y, Kilduff JE, Kitis M, Karanfil T. Dissolved organic matter removal and disinfection byproduct formation control using ion exchange. Desalination 2005;176(1-3):189-200. |
R828045 (Final) |
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Supplemental Keywords:
drinking water, chemicals, organics, disinfection, environmental chemistry, engineering, analytical chemistry,, RFA, Scientific Discipline, Water, Environmental Chemistry, Environmental Monitoring, Drinking Water, coagulation, public water systems, Safe Drinking Water, natural waters, monitoring, disinfection byproducts (DPBs), drinking water regulations, community water system, natural organic matter, carbon adsorption, chromophores, speciation, treatment, water quality, dietary ingestion exposures, drinking water contaminants, drinking water treatment, ultrafiltration, UV absorbance, drinking water systemProgress 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.