Water Disinfection and Natural Organic Matter - ACS Publications

Chapter 1

Water Disinfection and Natural Organic Matter: History and Overview 1

2

Roger A. Minear and Gary L. Amy 1

Institute for Environmental Studies, Department of Civil Engineering, University of Illinois, 1101 West Peabody Drive, Urbana, IL 61801-4723 Department of Civil, Environmental, and Architectural Engineering, University of Colorado, Boulder,CO80309

Downloaded by 188.255.134.164 on August 24, 2015 | http://pubs.acs.org Publication Date: November 19, 1996 | doi: 10.1021/bk-1996-0649.ch001

2

Historical Developments With the introduction of chlorine in drinking waters in the early part of this century (Sawyer et al, 1994), a new era was started regarding public health protection and the evolution of trust in safe drinking waters. This did not preclude the need for maintenance of control for individual toxic chemicals and specific aesthetic features of the product water. This latter element was an integral component to public health considerations in that safe waters must also be palatable in order to prevent consumers from seeking alternative sources of more aesthetically pleasing water which might in fact not be biologically and chemically safe. Much of the early control and setting of standards related to a few select chemical and biological safety parameters plus a series of what were essentially aesthetic indices. Natural organic matter (NOM) was one of these indices, indirectly, as it was reflected in the removal of color from product waters. Although iron could also impart a yellow color to waters, typically the undesirable color causing substances originated from naturally occurring humic substances. Much research among the engineers and water chemists of the 1950s to 1970s was directed at characterization and removal of these substance from drinking waters. Prominent and representative of these efforts was the work of A. P. Black and his students at the University of Florida (For example, Black and Christman, 1963a,b; Black and Willems, 1961). In the late 1950s to the early to mid 1960s, the fundamental nature of aquatic humic substances was the subject of debate among researchers (Christman, 1968; Shapiro, 1957,1958). At the end of that decade, it was generally accepted that natural water color was principally the result of humic substances and that these humic substances were complex polyfunctional organic molecules of varying molecular weight, ranging up to relatively large macromolecules, and this characterization continued into the 1970s (Christman

0097-6156/96/0649-0001$15.00/0 © 1996 American Chemical Society

In Water Disinfection and Natural Organic Matter; Minear, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1996.

2

WATER DISINFECTION AND NATURAL ORGANIC MATTER


and Ghassemi, 1966, Gjessing, 1965, 1970, 1976). Continued characterization relied upon newly evolving instrumental techniques. The book by Thurman (1985) and extensive work by the U.S. Geological Survey on Suwannee River humic substances (USGS 1989) have collected much of the current understanding based on the research efforts to that time. Among the common practices for removing this undesirable color for domestic drinking waters was bleaching out the color by use of the strong oxidizing power of free chlorine (HOC1 and OCf ); however, the common disinfection practice of the time was to ensure that a residual of free chlorine was achieved in the disinfection process so this frequently led to oxidation of nitrogen and organic species in the process. It wasn't until the early 1970s when the work of the Dutch water chemist, Johannes Rook (1974) demonstrated that the chlorination of Amsterdam drinking water produced chloroform and other trihalomethane species in the finished waters. US studies completed in the mid to late 1970s (Westrick, 1990) also confirmed the Dutch findings and touched off a flurry of Trihalomethane (THM) related research in the Drinking Water field around the world. At this time, a scientist at Oak Ridge National Laboratory was completing a Ph.D. in which radio-labeled chlorine was used to study products produced upon chlorination of domestic waste waters and model compounds. Associated with his continuing interest in this research area and the evolving concerns relative to human health implications, Robert Jolley, along with assistance from the US EPA and other colleagues, initiated in 1975, what was to become a series of 6 "Chlorination Conferences" (Jolley et al. 1978, 1980, 1983a, 1983b, 1985, 1990). These conferences became a forum for presentation of the active research related in one way or another to water disinfection. As the implications of the presence of THMs in drinking waters were pondered by the regulatory agencies in the United States and other countries, the linkage between the science and evolving regulations became in integral part of the "Chlorination Conferences." Phil Singer has portrayed this interrelation ship in a series of excellent review publications (Singer, 1992, 1993, 1994). Regulatory evolution focused initially on THM control and means of reducing the quantities produced. Three targets existed: the organic precursor (NOM), the disinfectant type and dose, and the removal of THM compounds themselves. The branching web of research directions spawned by these foci included engineering processes, biological studies relating microbial disinfection, human health implications and the basic chemistry associated with all these activities. The original focus on THMs has evolved in several areas: * expanded interest in disinfection by-products (DBPs) associated with other (alternative) disinfectants,


1.

MINEAR & AMY

History and Overview

3

* effectiveness of disinfection with alternative disinfectants, * relative risk factors of products and or processes and use of advances in fields like molecular biology, * continuing interest in the role of NOM and how its characteristics can be related to DBP formation and control,


* analytical chemistry advances and the development of better analysis procedures, and * fundamental understanding of the chemistry involved in disinfection and DBP formation processes.

Overview of DBP and NOM Issues To expand on these themes, it is important to realize that while free chlorine came under much earlier scrutiny (Rook, 1974; Bellar, 1974) in the formation of disinfection by-products (DBPs), alternative chemical disinfectants such as ozone (0 ), chlorine dioxide (C10 ), and chloramines (e.g., NH C1, monochloroamine) each has since been shown to have its own host of DBPs. Trihalomethanes (THMs) and halogenated acetic acids (HAAs) represent the most important groups of chlorination by-products, formed in the presence of natural organic matter (NOM), serving as the organic precursor, and bromide ion (Br~), playing the role of the inorganic precursor. While measurement of Br is straightforward, NOM measurement is achieved through surrogates (Edzwald, 1985): the amount of NOM is quantified through total (TOC) or dissolved (DOC) organic carbon, while NOM character can be deduced by UV absorbance at 254 nm and by specific UV absorbance (SUVA, UVA /DOC), an index of the humic/aromatic character of the ΝΟΜ. 3

2

2

254

Both NOM properties (e.g., molecular weight) and the relative amount of Br affect the magnitude and species distribution of THMs and HAAs. In addition to chlorine dose, THM and HAA formation is also influenced by pH and temperature. Chlorinated drinking water has also been shown to contain haloacetonitriles (HANs), haloketones, and miscellaneous chloro-organic compounds such as chloral hydrate, chloropicrin, cyanogen chloride, and 2,4,6 trichlorophenol (Singer, 1994; Oliver, 1983; Uden, 1983). In the presence of bromide, brominated THMs, brominated HAAs, brominated HANs, cyanogen bromide, and bromopicrin can be formed. Specific compounds constitute only about half of the overall pool of chlorinated organic material (Singer, 1994), as measured by total organic halide (TOX). THMs are the dominant class of chlorination DBPs, followed by the HAAs; reasonable source-specific correlations have been established between THMs and HAAs (Singer and Chang,


4


1989). In a nation-wide survey, the median concentrations of THMs and HAAs were found to be 36 and 17 ug/L, respectively (Krasner, 1989); the proposed DBP regulations will limit THMs and HAAs to 80 and 60 ug/L, respectively. While the health effects of these individual compounds vary (Bull, 1991), MX [3-chloro-4-(dichloromethyl)-5hydroxy-2(5H)-furanone] has been shown to significantly contribute to the mutagenicity of chlorinated drinking water. In the presence of NOM, ozonation produces several groups of organic by-products, including aldehydes, ketoacids, and carboxylic acids (Xie, 1992; Weinberg, 1993), most of which are relatively biodegradable. In the presence of Br", bromate (Br0 ~) is formed during ozonation (Haag and Hoigne, 1983) with influential factors being NOM, ozone dose, Br", pH, and temperature (von Gunten, 1992). Bromate can form through either a molecular ozone or a hydroxyl radical pathway, with the latter predominant in the presence of NOM (Siddiqui, 1995). Proposed regulations will limit Br0 " to 10 ug/L. In the presence of both NOM and Br", organo-bromine (TOBr) compounds such as bromoform, bromoacetic acids, and bromoacetonitriles can form.


3

3

The major by-products associated with chlorine dioxide (Gordon, 1990) include chlorate (C10 ") and chlorite (C10 "); the U.S. EPA has recommended that the combined residuals of C10 , C10 ", and C10 " be less than 1 mg/L. Chloramination significantly reduces but does not eliminate THM formation (Jensen, 1985); cyanogen chloride and TOX represent the major DBP issues with respect to chloramines. 3

2

2

2

3

Since DBPs are formed by all of the above chemical disinfectants, the adoption of alternative disinfectants for DBP control often means only a tradeoff between one group of DBPs versus another. The most effective DBP control strategy is organic precursor removal through enhanced coagulation, biofiltration, granular (or biological) activated carbon (GAC or BAC), or membranes. There has been little success in Br" removal. Other DBP control options include water quality modifications; for example, acid or ammonia addition for bromate minimization. NOM removal is strongly influenced by NOM properties embodying the size, structure, and functionality of this heterogeneous mixture. NOM consists of a mixture of humic substances (humic and fulvic acids) and non-humic (hydrophilic) material. It is the humic substances that are more reactive with chlorine (Reckhow, 1990; Christman, 1983; Collins, 1985) and ozone, both in terms of oxidant/disinfectant demand and DBP formation. Processes such as coagulation, adsorption, and membranes are separation processes which remove NOM intact, while ozonation transforms part of the NOM into biodegradable organic matter (BOM), potentially removable by biofiltration/BAC. Coagulation preferentially removes humic/higher molecular weight NOM; the selectivity of


1.

MINEAR & AMY


5

membranes for NOM removal is largely dictated by the molecular weight cutoff of the (nanofiltration or ultrafiltration) membrane; the use of GAC requires significant empty bed contact times; biofiltration can only remove the rapidly degradable fraction of the BOM. Other than removal at the treatment plant, source (watershed) control represents another control option; for example, the control of algal-derived NOM in water supply reservoirs (Hoehn, 1980).


Purpose of the Symposium and Its Organization Even though the official "Chlorination Conferences" did not continue beyond 1989, research has continued as the issues have become increasingly complex and important. Traditional forums for research presentation continue to be used and this book evolves from one of these, a thematic symposium at a national American Chemical Society meeting. This particular symposium was organized around the theme of DPBs and natural organic matter (NOM), either as a direct precursor or an influential factor in the overall solution chemistry involving DBP formation. The chapters that follow are grouped to reflect general areas of research in the following fashion: Regulatory analysis sets the stage for the driving force behind much of the current research even though the researchers would prefer to argue to the contrary. To this end, it was appropriate to include a focus on the regulatory environment. While pure science is the currency of the researcher, practicality and application play a role in much of the environmental field especially since research costs money. Krasner et al. have provided this linkage. From this point on, the book organization follows the original symposium organization which was in the thematic groupings, Chlorination/Chloramination Products and Reactions; NOM Relationships and Characterization; and Ozone and Other Processes. The ordering is not arbitrary. Chlorine based disinfection is still the dominant process used in the United States whether it be free chlorination or intentional formation of chloramines. Variations in processes and specific configurations with the resultant impact on both DBP formation and disinfection efficiency continue to be the subject of active research. How the characteristics of NOM relate to the overall processes makes research into NOM properties and reactions with both disinfection chemicals and NOM removal processes an area of continuing importance to the water treatment industry. However, improved knowledge in this area reaches beyond only drinking water treatment and it was not the intent to restrict presentations to direct linkage with water treatment.


6


As was pointed out in the overview section above, many other disinfection processes are being examined as either replacements for or adjuncts to chlorination processes as means of reducing DBP formation in drinking waters. While ozone is prominent in this effort, it is not exclusive. The collected papers in this third section are a forum for the active research into these alternatives and the potential problems that may be associated with their application.


REFERENCES Black, A.P. and Christman, R.F., "Characteristics of Colored Surface Waters", Journal AWWA, 55:753, (1963a). Black, A.P. and Christman, R.F., "Chemical Characteristics of Fulvic Acids", Journal AWWA, 55:897, (1963b). Black, A.P. and Willems, D.G., "Electrophoretic Studies of Coagulation for the Removal of Organic Color", Journal AWWA, 53:589, (1961). Bellar, T., et al., The Occurrence of Organohalides in Chlorinated Drinking Water", Journal AWWA, 66:703 (1974). Bull, R., and Kopfler, F., "Health Effects of Disinfectants and Disinfection By-Products", AWWA Research Foundation (1991). Christman, R.F., "Chemical Structures of Color Producing Organic Substances in Water" In Symposium on Organic Matter in Natural Waters, D.W. Hood, ed. University of Alaska, pp181-198, (1968). Christman, R.F., "Identity and Yields of Major Halogenated Products of Aquatic Fulvic Acid Chlorination", Environ. Sci. & Technol., 17:10:625 (1983). Christman, R.F. and Ghassemi, M . , "Chemical Nature of Organic Color in Water", Journal AWWA, 58:723, (1966). Collins, M . , et al., "Molecular Weight Distribution, Carboxylic Acidity, and Humic Substances Content of Aquatic Organic Matter: Implications for Removal During Water Treatment", Environ. Sci. & Technol., 20:10:1028 (1986). Edzwald, J., "Surrogate Parameters for Monitoring Organic Matter and Trihalomethane Precursors in Water Treatment", Journal AWWA, 77:4:122 (1985).


1.

MINEAR & AMY


Gjessing, E.T., "Use of 'Sephadex' Gel for the Estimation of Molecular Weight of Humic Substances in Natural Water" Nature, 208: 1091, (1965). Gjessing, E.T., "Ultrafiltration of Aquatic Humus", Environ. Sci. & Technol., 4:437, (1970). Gjessing, E.T., Physical and Chemical Characteristics of Aquatic Humus, Ann Arbor Science, (1976).


Gordon, G., et al., "Minimizing Chlorite Ion and Chlorate Ion in Water Treated with Chlorine Dioxide", Journal AWWA, 82:4:160 (1990). Haag, W., and Hoigné, J., "Ozonation of Bromide-Containing Waters: Kinetics of Formation of Hypobromous Acid and Bromate", Environ. Sci. & Technol., 17:5:261 (1983). Hoehn, R., et al., "Algae as Sources of Trihalomethane Precursors", Journal AWWA, 72:6:344 (1980). Krasner, S., et al., "The Occurrence of Disinfection By-Products in U.S. Drinking Water", Journal AWWA, 81:8:41 (1989). Jensen, J., et al., "Effect of Monochloramine on Isolated Fulvic Acid" Org. Geochem., 8:1:71 (1985). Jolley, R.L., "Water Chlorination: Chemistry. Environmental Impact and Health Effects", Volume 1, Ann Arbor Science Publishers INC. (1978). Jolley, R.L., Gorchev, H . , and Hamilton, D.H., "Water Chlorination: Chemistry, Environmental Impact and Health Effects", Volume 2, Ann Arbor Science Publishers INC. (1978). Jolley, R.L., Brungs, W.A., Cumming, R.B., and Jacobs, V.A., "Water Chlorination: Chemistry, Environmental Impact and Health Effects", Volume 3, Ann Arbor Science Publishers INC. (1980). Jolley, R.L., Brungs, W.A., Cotruvo, J.A., Cumming, R.B., Mattice, J.S., and Jacobs, V.A., "Water Chlorination: Chemistry, Environmental Impact and Health Effects - Chemistry and Water Treatment", Volume 4 (1), Ann Arbor Science Publishers INC. (1983a).


7

8


Jolley, R.L., Brungs, W.A., Cotruvo, J.Α., Cumming, R.B., Mattice, J.S., and Jacobs, V.A., "Water Chlorination: Chemistry, Environmental Impact and Health Effects - Environment, Health, and Risk", Volume 4 (2), Ann Arbor Science Publishers INC. (1983b).


Jolley, R.L., Bull, R.J., Davis, W.P., Katz, S., Roberts, M.H., and Jacobs, V.A., "Water Chlorination: Chemistry, Environmental Impact and Health Effects", Volume 5, Lewis Publishers (1985). Jolley, R.L., Condie, L.W., Johnson, J.D., Katz, S., Minear, R.A., Mattice, J.S., and Jacobs, V.A., "Water Chlorination: Chemistry, Environmental Impact and Health Effects", Volume 6, Lewis Publishers (1990). Oliver, B., "Dihaloacetonitriles in Drinking Water: Algae and Fulvic Acid as Precursors", Environ. Sci. & Technol., 17:2:80 (1983). Reckhow, D., et al., "Chlorination of Humic Materials: By-Product Formation and Chemical Interpretations", Environ. Sci. & Technol., 24:11:1655 (1990). Rook, J., "Formation of Haloforms during Chlorination of Natural Waters", Water Treat. Exam. 23:234 (1974). Shapiro, J., "Chemical and Biological Studies on the Yellow Acids of Lake Water" Limnol Oceanog., 2:161, (1957). Shapiro, J., "Yellow Acid-Cation Complexes in Lake Water" Science 127:702, (1958). Siddiqui, M . et al., "Bromate Ion Formation: A Critical Review", Journal AWWA, 89:10:58 (1995), Singer, P.C., "Formation and Characterization of Disinfection By-Products", Paper from the First International Conference on the Safety of Water Disinfection: Balancing Chemical and Microbial Risks, International Life Sciences Institute, Washington, DC, (1992). Singer, P.C., "Trihalomethanes and Other By-Products Formed by Chlorination of Drinking Water" in Keeping Pace with Science and Engineering, National Academy Press, pp 141-164, (1993). Singer, P.C., "Control of Disinfection By-Products in Drinking Water", ASCE Journal of Environmental Engineering, 120:4:727 (1994).


1.

MINEAR & AMY


Singer, P.C., and Chang, D., "Correlations Between Trihalomethanes and Total Organic Halides Formed During Drinking Water Treatment", Journal AWWA, 81:8:61 (1989). Thurman, E . M . , Organic Geochemistry of Natural Waters, Nijhoff/Junk, (1985). Uden, P. and Miller, J., "Chlorinated Acids and Chloral in Drinking Water", Journal AWWA, 75:10:525 (1983).


U.S.G.S., Humic Substances in the Suwannee River, Georgia: Interactions, Properties, and Proposed Structures, Open - File report 87-557, (1989). von Gunten, U . , and Hoigne, J., "Factors Affecting the Formation of Bromate During the Ozonation of Bromide-Containing Waters", Aqua, 41:5:299 (1992). Weinburg, H . , et al., "Formation and Removal of Aldehydes in Plants that Use Ozone", Journal AWWA, 85:5:72 (1993). Westrick, J.J., "National Surveys of Volatile Organic Compounds in Ground and Surface Waters", in Significance and Treatment of Volatile Organic Compounds, Christman, et al, eds. Lewis Publishers, 1990. Xie, Y., and Reckhow, D., "A New Class of Ozonation By-Products: the Ketoacids", Proceedings, AWWA Conference (1992).


9

Water Disinfection and Natural Organic Matter - ACS Publications

Recommend Documents