Grantee Research Project Results
2000 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: Clemson University
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, 2000 through March 1, 2001
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 (DBP) formation and treatability is critical for providing safe water and for meeting current drinking water regulations (e.g., the D/DBP rule). Of primary importance is understanding dissolved organic matter (DOM) 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 and 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 natural organic matter (NOM) molecule and among different DOM molecules. Similarly, reactivity of bulk water represents the combined reactivity of many different molecules and molecular moities. 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:
Two high-SUVA (Myrtle Beach and Charleston) and two low-SUVA surface waters (Troy and Rennselaer) were fractionated using three physicochemical separation processes (i.e., activated carbon, XAD-8 adsorption and coagulation). For each water, approximately 50 to 60 fractions were obtained, each having different SUVA values. The fractions were chlorinated according to the uniform formation condition protocol. The formation of THM, HAA9, HANs, chloropicrin, chloral hydrate, and cyanogen chloride was quantified. The relation between the formation and speciation of DBPs and the SUVA of each fraction was examined. Different batches were collected from the two surface waters at different dates to evaluate the impact of temporal and transient (i.e., storm event) changes in source water quality on DOM fractionation and the DBP formation and speciation. Experimental procedures are presented in detail elsewhere (Kitis, et al., 2000; Kitis, et al., 2001).
The results showed that each separation process fractionated NOM by preferentially removing high-SUVA components from waters. For each natural water, a single and strong correlation was observed between the SUVA values of DOM fractions and their THM and HAA9 formations, independent of the separation processes used to obtain the fractions. Therefore, the correlation obtained for each water appears to represent its natural DBP reactivity profile. However, SUVA is not a universal predictor of DOM reactivity, because a unique DBP reactivity profile was obtained for each water tested. 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. DBP speciation also correlated well with SUVA of DOM fractions in a single water. High-SUVA DOM fractions produced more THMs, whereas low-SUVA fractions were more reactive in forming HAA9. Low-SUVA DOM fractions were found to be more reactive toward bromine, shifting speciation toward brominated DBPs. However, with decreasing SUVA, THMs exhibited a larger shift towards brominated DBP species than did HAA9. Formation of trichloroacetic acid was dominant over dichloroacetic acid for high-SUVA fractions, whereas the opposite was observed for low-SUVA fractions.
The reactivity profile concept (i.e., understanding how reactivity is correlated to SUVA) may allow water utilities to optimize the degree of treatment required to comply with D/DBP regulations. The reactive components that require removal, and the degree of treatment necessary to accomplish this removal, may be directly obtained from the relationship between SUVA removal and the degree of treatment (e.g., alum dose).
Because all the preliminary experimental evidence suggests strongly that there is a unique DBP reactivity profile for each natural water as a function of its SUVA distribution, this finding currently is being further tested for two surface waters with significantly different DOM characteristics (i.e., Myrtle Beach and Tomhannock). Myrtle Beach primarily is composed of DOM hydrophobic in character, whereas Tomhannock water has more hydrophilic DOM components. In these experiments, in addition to the three physicochemical separation processes employed previously, two new techniques for DOM fractionation are being used. One technique involves isolation of DOM using reverse osmosis (RO) and followed by ultrafiltration to subsequently fractionate DOM into different size components. The second approach is to fractionate DOM after RO isolation into hydrophobic and hydrophilic components by using an XAD-8 column separation at low pH.
A major difference between ultrafiltration and the three techniques described previously is that DOM fractionation mechanism is completely different?ultrafiltration fractionates DOM based on size. A major difference between the XAD-8 column separation and XAD-8 batch adsorption experiments described previously is that nearly all DOM components are recovered (because of expected high DOC mass balance <90%), while in the batch adsorption technique, only the reactivity of DOM components remaining in solution was measured.
For DOM isolation, a field scale RO system was built and tested for its effectiveness. In addition, the impact of RO isolation on the subsequent reactivity between DOM and chlorine was examined (Kitis, et al., 2001b). DOM mass balances (quantified as dissolved organic carbon) ranged from 96.1 to 102.1 percent for the three waters tested, and DOM mass recoveries of 93.9 to 98.2 percent indicated successful isolation, minimal fractionation, and negligible loss of organic matter. RO isolates were diluted using distilled and deionized water in the laboratory to reconstitute the source waters. Both source water (collected at the time of isolation) and reconstituted source water samples were chlorinated. Formation of several DBPs (e.g., THMs, HAA9, HANs, and HKs) were measured. For all waters tested, DBP formation of source and corresponding reconstituted source water agreed within 95 percent confidence intervals. Therefore, RO isolation had no impact on the DOM reactivity of the three low-hardness surface waters tested in this study. In addition, the degree of bromine substitution, as expressed by the bromine incorporation factor, was calculated. Comparison of bromine incorporation factors for source and reconstituted source waters further indicated that, as with the total DBP formations, bromine speciation and the relative occurrence of individual species in THMs and HAA9 did not change as a result of the isolation. Overall, in terms of DBP formation, RO isolation appears to maintain the integrity and reactivity of DOM.
Future Activities:
Future work will evaluate the impact of operational conditions on the effectiveness of DOM isolation by RO and whether there is any impact of commonly used XAD isolation process on the DBP reactivity of isolates obtained from natural waters. The observed DBP reactivity profile concept will be further tested for waters having a range of hydrophobicity, measured by the relative proportion of hydrophobic and hydrophilic DOM components. Using physicochemical fractionation, DOM components with different SUVA values will be obtained. The impact of bromine incorporation by these fractions will be examined. Additional physicochemical characterization of the fractions will be attempted to provide insight to the differences in the bromine incorporation by different DOM components. The formation and speciation kinetics of brominated DBPs will be investigated as a function of SUVA, water chemistry, and reaction conditions.Journal Articles on this Report : 1 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) |
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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.