Grantee Research Project Results
2001 Progress 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
Current Institution: Rensselaer Polytechnic Institute , Clemson University
EPA Project Officer: Hahn, Intaek
Project Period: March 1, 2000 through March 1, 2003
Project Period Covered by this Report: March 1, 2001 through March 1, 2002
Project Amount: $391,473
RFA: Drinking Water (1999) RFA Text | Recipients Lists
Research Category: Drinking Water , Water
Objective:
Understanding the characteristics of natural waters that influence disinfection by-product formation and treatability is critical for providing safe water and meeting current drinking water regulations (e.g., the disinfectants/disinfection by-products (D/DBP) rule). Of primary importance is understanding dissolved natural organic matter (DNOM) reactivity. While sophisticated fractionation and characterization of organic mater in natural waters yields important information, one bulk water parameter, the specific ultraviolet absorbance (SUVA), has proven to be a useful, robust predictor of both reactivity with oxidants and treatability. SUVA determination of a water sample yields a single aggregate value that represents the response of a distribution of chromophores within a single NOM molecule and among different dissolved organic matter (DOM) molecules. Similarly, reactivity of bulk water represents the combined reactivity of many different molecules and molecular moieties. The objective of this research is to examine how specific UV absorbance, and more importantly, how the distribution of SUVA in a source water, influences the formation and speciation of brominated DBPs. Such information will be useful for optimizing treatment goals, understanding the effects of treatment processes, and devising strategies to comply with the D/DBP rule.Progress Summary:
In Year 2, our research focused in two different areas:
(1) Evaluation of Experimental Methodologies Used in NOM Isolation and Fractionation for DBP Reactivity Studies
As reported in the first annual report, the impact of reverse osmosis (RO) isolation on the subsequent reactivity between DOM and chlorine was examined (Kitis, et al., 2001b). Overall, it was concluded that in terms of DBP formation, RO isolation appears to maintain the integrity and reactivity of DOM. In the second year of the project, the impact of two additional techniques commonly used in DOM isolation and fractionation (i.e., ultrafiltration (UF) and XAD-8 fractionation) on the DBP reactivity of DOM was investigated using two surface waters (Myrtle Beach (SC) and Tomhannock (NY)). These source waters, each having significantly different SUVA254 molecular weight (MW), distribution, and polarity, were fractionated using XAD-8 resin adsorption and UF, with good DOM mass balance closures (based on dissolved organic carbon). It was found that such fractionation preserved both the SUVA and the reactivity of the source waters, as demonstrated by statistically similar DBP formation and speciation from chlorinated source water and source waters reconstituted from XAD-8 or UF fractions. In addition, there was no evidence of synergistic effects among DOM components when reacting with chlorine.
Consistent trends between DBP yields and MW were not found. Hydrophobic fractions of DOM (isolated by XAD-8) were the most reactive DOM components; however, hydrophilic components also showed appreciable DBP yields, contributing up to 50 percent of total DBP formation. It may be difficult to reduce total DBP formation for waters with large amounts of hydrophilic fractions because they are difficult to remove using conventional water treatment processes.
However, strong, unique correlations were observed between the SUVA of individual fractions, trihalomethane (THM), and haloacetic acid (HAA9) yields, confirming that the aromaticity of DOM components is more directly related to reactivity than other physicochemical properties. The finding of a single correlation independent of the fractionation process employed is notable because XAD-8 adsorption and UF fractionate DOM by significantly different mechanisms. These results provided further support for our finding in the previous project period, 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 used to predict DBP formation.
Secondary conclusions from this investigation include: (1) the column distribution coefficient (k') is an important parameter in designing fractionation experiments and must be considered when comparing results between different studies, and (2) bromine appears to be more effectively incorporated into low UV-absorbing (i.e., low SUVA), low MW, and hydrophilic DOM fractions. The details of the findings from this phase of the study were reported elsewhere (Kitis, 2001; Kitis, et al., 2002a).
(2) Testing the DBP Reactivity Profile Concept
During the first year of the project, four surface waters were fractionated using three physicochemical separation processes (i.e., activated carbon, XAD-8 adsorption, and coagulation) and approximately 50 to 60 fractions, each having different SUVA values were obtained for each water. After chlorination, the DBP reactivity of DOM fractions (i.e., THM and HAA9 yields) closely correlated with SUVA of the fractions independent of the separation process used to fractionate the DOM solution. Since strong correlations and unique patterns were observed for each natural water tested, it was hypothesized that the SUVA distribution of a natural water represents an important characteristic of DOM components controlling the DBP formation. Each source water has an intrinsic "DBP reactivity profile" that is a function of its SUVA distribution, and that can be obtained by using physicochemical bulk water fractionation processes. If this hypothesis is valid, then a single reactivity profile as a function of SUVA should be obtained independent of how the DOM fractions are obtained from a water sample.
In the second year of the project, the hypothesis postulated above was tested by conducting new fractionation experiments using new water samples (Myrtle Beach, SC, and Tomhannock, NY) using five physicochemical separation processes (activated carbon, XAD-8 batch adsorption, alum coagulation, ultrafiltration (UF), and XAD-8 column fractionation). Activated carbon, XAD-8 batch adsorption, and alum coagulation processes fractionated DOM by preferentially removing high-SUVA components from solution. The XAD-8 column method fractionated DOM into hydrophobic and hydrophilic components, while UF separated DOM into different size fractions. Over 40 DOM fractions, characterized using SUVA, were obtained for each water. THM and HAA9 formation after chlorination was quantified for all fractions. For each natural water tested, a strong 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 appears to represent the 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. Periodic development of reactivity profiles will allow utilities to assess and monitor the heterogeneity and reactivity of DOM in a source water with time. The results also provided insight to the formation and speciation of HAAs from different DOM components. Formation of TCAA was dominant over DCAA for high-SUVA fractions, whereas the formations of TCAA and DCAA were comparable for low-SUVA fractions. The details of the findings from this phase of the study were reported elsewhere (Kitis, 2001; Kitis, et al., 2002b).
Future Activities:
Future work will evaluate the formation and speciation of DBPs in the presence of chlorine and chloramines. The role of selected factors (pH, chloramine composition (e.g., Cl/N ratio), bromide concentration, characteristics of NOM) on the formation of DBPs during chlorination and chloramination processes will be systematically investigated. Recently, a report by the American Water Works Association disinfection systems committee indicated that the number of utilities employing chloramines increased from 20 to 30 percent between 1998 and 1999. Despite some of its disadvantages (e.g., poorer disinfection efficiency, nitrification problems in distribution systems), more and more utility is considering chloramines for disinfection with approaching the Stage II of the D/DBP Rule. Therefore, findings from these experiments are expected to provide important information to drinking water industry.DOM also will be isolated from selected surface waters with different SUVA values using reverse osmosis. DOM will be subsequently fractionated into different components using resin adsorption chromatography. DBP formation of each fraction in the presence of chlorine and chloramines will be investigated. The impact of bromine incorporation by these fractions also will be systematically studied. Physicochemical characterization of the fractions will be attempted to provide insight to the differences in the bromine incorporation by different DOM components. The formation kinetics of brominated DBPs will be investigated as a function of SUVA, water chemistry, and reaction conditions.
Journal Articles on this Report : 2 Displayed | Download in RIS Format
Other project views: | All 18 publications | 8 publications in selected types | All 8 journal articles |
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Type | Citation | ||
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Kitis M, Kilduff JE, Karanfil T. Isolation of dissolved organic matter (DOM) from surface waters using reverse osmosis and its impact on the reactivity of DOM to formation and speciation of disinfection by-products. Water Research 2001;35(9):2225-2234. |
R828045 (2000) R828045 (2001) |
Exit Exit |
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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) |
Exit Exit |
Supplemental Keywords:
drinking water, chemicals, organics, disinfection, environmental chemistry, engineering, analytical., 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.