Drinking Water And Disinfection Byproduct

Drinking Water and Disinfection Byproducts (DBPs)

ENS 790 Fall ’98 - Spring ’99 Drinking Water and Disinfection Byproducts (DBPs)

ENS 790 Fall ’98 - Spring ‘99

ABSTRACT

Throughout recorded history humankind has found it necessary or desirable to process drinking water. The Egyptians filtered water through pottery. Modern day water processing is designed to improve the appearance and smell of drinking water, remove suspended particles and kill bacteria and parasites. In addition, our modern lifestyle has introduced other threats to drinking water supplies – chemical pollution.

The following paper presents an overview of disinfection byproducts (DBPs). DBPs result from the application of chlorine and ozone during the disinfection stage of water processing. While chlorine and ozone do not appear to cause cancer in laboratory animals they react with or catalyze reactions that produce carcinogens.

Background information is provided on drinking water treatment and EPA regulatory efforts. Table of Contents

Background 1

Disinfection Byproducts 2

Regulation of Water Quality by the US Environmental Protection Agency 5

Bibliography 11

Background

Humans consume water drawn from a variety of sources – underground springs and wells, surface water from lakes and streams and cisterns replenished by rainwater. In the United States an average of 15-20 gallons per person is used daily for bathing, another 15-25 gallons is used for excreta disposal and one- half gallon is used for drinking and cooking. Yet, for all the effort and expense expended to provide potable water we continue to use the same water for our lawns, fire fighting, street cleaning and car washing. (Moeller)

Depending on the sources from which the water is drawn, consumption exposes the individual to one or more of the following: bacteria, viruses, parasites and naturally occurring toxic minerals such as aluminum, chromium and arsenic. In addition, minerals such as calcium, magnesium and iron, while not toxic, can add unattractive color or odor to the water or contribute to “hard water”.

In some instances, radioactive gas and minerals are found in water. Radon is found in all water but particularly water that has passed through granite or shale. Radon evaporates quickly from water and consequently may be a problem with underground water but less so with surface water. (Ingram)

While surface waters are more easily contaminated by microorganisms and toxic organic chemicals, ground water supplies are increasingly being contaminated by nitrates, volatile organic chemicals and other industrial chemical products.

Organic contaminants are universally found and are natural products such as humic and fulvic acids, terpenes, tannins, amino acids and peptides. (Suffet and Malaiyandi)

Ground water serves as a source of drinking water for approximately 50% of the United States. In 1992 more than 10% of community water wells and more than 5% of rural domestic wells were contaminated with one or more substances – primarily agricultural pesticides. More than 1% of the wells were contaminated in excess of health limits. Waterborne diseases account for 80% of all illnesses in the developing world. (Moeller) A 1992 survey reported by the EPA found that “… at least a trace of one” Volatile Organic Chemical in 28% of the water systems serving more than 10,000 people and 17% of those systems serving fewer than 10,000 people. (USEPA OGWDW 1998b.)

Community drinking water is usually processed through one or more stages – disinfection, filtration, chemical pretreatment and sedimentation. Disinfection, while not designed to sterilize the water, is intended to kill or disable pathogens. Filtration removes solids and many microbes such as Giardia and Cryptosporidium whose hard shells protect them from chlorine and UV treatments. (Ingram) Chemical pretreatment (flocculation) with chemicals such as alum forms floc – clumps of impurities – which settle out of the water and are easily filtered. Sedimentation in holding ponds allows heavy particles to settle from the water. (USEPA 1989.)

Under EPA regulations, residual disinfection is required to be carried in the finished water to the points of distribution so as to kill or disable microbes in the distribution system. Herein lies the paradox. As mentioned, chemicals are employed during the flocculation and disinfection phases or water processing and may contribute to unwanted residuals or produce compounds that were not present in the raw water.

1 These newly formed compounds are disinfection byproducts or DBPs and some of them are hazardous to humans and animals.

Disinfection Byproducts

For reasons of economy and in an effort to reduce DBPs as the EPA Maximum Contaminant Levels are reduced, a variety of disinfection techniques have been tried or are in use including: chlorination, ozonation, chloramination, titanium dioxide, chlorine dioxide (Richardson, et. al.), UV radiation, ultrasound and electromagnetic fields. (Environmental Science & Technology 31(3):120A-121A)

Chlorination in one form or another (chlorine, chlorine plus ammonia (chloramination), chlorine dioxide) for disinfection purposes to fight, for example, typhus and cholera dates back to the early 1900s in the United States. It was used as a coagulant aid in 1914. (The American Water Works Association 1971) (Betts 1998a.) Chlorine dioxide is used in about 300 plants in the United States and several thousand in Europe and chlorine or chloramines are used by most drinking water utilities in the United States. (Betts 1998b.)

Water chlorination is of two types, free residual and combined residual chlorination. In free residual chlorination the chlorine is applied to the water to produce a free residual that is carried throughout the distribution system. In combined residual the chlorine is applied so as to produce, with natural or added ammonia, a combined chlorine residual. The combined residual does not have the oxidation capacity of free chlorine and requires about twenty-five times as much to produce the same bacterial killing capacity as free chlorine. (The American Water Works Association)

Chloroform (CHCl3) was first reported in drinking water in the 1970s. (Xie and Reckhow) It is one of a family of compounds called Trihalomethanes (THMs) which are frequently found in finished water. The EPA uses Total Trihalomethanes (TTHMs) as a measure of disinfection byproducts and as a surrogate for the presence of a host of other byproducts such as halogenated phenols and aldehydes. (Suffet and Malaiyandi) (These are products that are produced by the chlorination process. Other contaminants such as copper and lead can be added in the distribution system but such contaminants are beyond the scope of this paper.)

THMs are formed during the disinfection process as chlorine combines with organic material in the raw water e.g. humic acids, amino acids, terpenes and tannins. Instant tea mixed with cold water has been shown to develop similar byproducts. (Wu et. al.)

The formation process is not well understood because humic substances are not well defined and the pH and temperature of the water being treated affects the outcome. There were surprisingly few stoichiometric equations in the articles and books reviewed for this paper. In fact it has been stated “There are limitations to all the known methods of disinfection, and all chemical disinfectants produce byproducts.” (Betts 1998 a.)

In 1979 the EPA set a limit of 0.10 mg/L of Total THMs (TTHMs) measured on a running annual average. A number of considerations at that time led the EPA to regulate THMs. Among the

2 considerations were: the potential human health effects, THMs are the most ubiquitous synthetic organic chemical in United States drinking water and are at the highest concentration of any organic chemical in drinking water; THMs are inadvertently introduced during water preparation; monitoring is feasible and the presence of THMs frequently signals the presence of other halogenated and oxidized byproducts of the chlorination process. (Suffet and Malaiyandi)

An interesting study was completed in 1994 at an Evansville, IN Pilot Plant that used ClO2 as a primary disinfectant. As a disinfectant, ClO2 is equal to or superior to Cl2. Chlorine dioxide is more soluble in water, is effective over a wide pH range, is effective in controlling taste and odor, is effective in removing iron and manganese and chlorine dioxide does not react with amines to form chloramines.

While the EPA regulations focus on measuring chlorine, chloramines, chlorine dioxide, TTHMs, chlorite, bromate and total organic carbon the objective of the Evansville study was to identify every byproduct in finished water, not just the targeted DBPs.

Various treatments were used including, for example, gas and liquid ClO2 along with Cl2 as a residual disinfection and sand filtration.

The study found that halogenated byproducts were produced only when chlorine residual was added after ClO2 treatment and not when ClO2 was used alone. The study also concluded that THMs were not produced when ClO2 was reacted with humic acid.

However, returning to the original purpose of the study, 68 compounds were identified in the finished water. 22 of the compounds were in the raw water, 12 of the compounds are EPA regulated but only 2 (carbon tetrachloride and 1,4-dichlorobenzyne) are regulated under the Safe Drinking Water Act and amendments. Many of the substances are mutagenic or carcinogenic and are regulated by EPA under the Comprehensive Environmental Response, Compensation and Liability Act (CERCLA), the Resource Conservation and Recovery Act (RCRA) and the Clean Water Act (CWA) but are not regulated in drinking water. Some of the 68 compounds were not found on any list. (Richardson et. al. 1994.)

Because of the presence of DBPs, alternative disinfection methods are being explored. One method that has been investigated for small water systems (serving less than 3,300 people) is the use of titanium dioxide (TiO2) and UV light. The photocatalysis of titanium dioxide is expected to kill microorganisms and not produce THMs. When titanium dioxide is illuminated at wavelengths less than 388 nm it reacts - with OH and H2O to produce hydroxyl radicals (OH). The process degrades THMs, pesticides and a number of other substances into non-toxic compounds. Sunlight starts at 300 nm so the process, if perfected, could rely on natural sunlight. (Richardson et. al. 1996.)

The difficulty with the titanium dioxide treatment is that a substantial amount of total organic carbon remained after filtration and the process leaves no residual disinfectant. Consequently, chlorine will probably be needed as a secondary (residual) disinfectant to remain in the water system and contribute to the formation of the DBPs that are found when chlorine is used alone.

An advantage of considering titanium dioxide is that it is one of the top 50 chemicals in the United States and doesn’t require a power source to be activated. (Chang)

3 Ozonation was first used in France in 1906 as a primary disinfectant and as an oxidant to control flora, odor and color. It was also used to reduce manganese and iron. It has also been used to enhance flocculation. The disadvantage of ozone is that it is unstable. It decomposes to O2 at a rate proportional to pH and in drinking water with a pH of 8.0 its half life is less than one hour leaving no disinfection capacity for the distribution system. Because of it is unstable it must be generated where it is used. Another disadvantage of ozone is that it reacts with natural organic substances and contributes to biological growth thus requiring the use of other disinfectants or filtration. (Glaze) It continues to be used in Europe and to a limited extent in Canada and the United States.

Ozone can aid the biodegradability of organic matter and can also contribute to bacterial regrowth. It has also been shown to decrease granulated activated carbon’s ability to remove halogenated organics.(Ribas et. al.) . Ozone does not eliminate the production of DBPs. When bromide containing waters are ozonated, bromate may be formed. Bromate is classified as potentially carcinogenic by the International Agency for the Research on Cancer.

A Maximum Contamination Level (MCL) of 10g/L has been established in the United States and Europe. (Van Guten and Oliveras) The possible mechanism has been explained as follows: - - Br + O3  OBr + O2

- - OBr + O3  BrO2 + O2 - - BrO2 + O3  BrO3 + O2

Other byproducts can also be formed during the ozonation process. When drinking water is contaminated with olefines (tetrachloroethene, trichloroethene, vinal chloride) the products formed upon degredation by ozone were unknown. In one experiment 16 byproducts resulted when 8 olefines were subjected to ozone. (Dowideit and Von Sonntag.)

Chloramination (chlorine plus ammonia) is used to avoid or limit the tastes and odors that sometimes develop from the use of chlorine. However chloramination too has the ability to produce DBPs as shown by the following equations:

2 NH3 + 2 Cl2  N2 + 6 HCl

4 NH2Cl + 3 Cl2 + H2O  N2 + N2O + 10 HCl

2 NHCl2 + H2O  N2O + 4 HCl

HOCl + NHCl2 + H2O  2 NO2 + 5 HCl

What actually happens in a given situation depends on the pH. (The American Water Works Association)

4 Most of the literature addresses the byproducts found in the finished water, little is mentioned about the routes of human exposure – ingestion, dermal and inhalation. One study analyzed exposure to trichloeoethylene in bathroom shower air. The results indicated that inhalation exposure is a function of water temperature, drop path and the concentration of trichloeoethylene in the water and showed that inhalation exposure was 6 times greater than ingestion exposure based on intake of 2 L/day. Other studies have produced factors of 1.1 to 2.0. Note that shower air is only one route of inhalation. Baths, toilets, dishwashers, washing machines and cooking can increase exposure to DBPs. (McKone)

The EPA, as expressed in its December 1998 regulations, is considering some of the assumptions used when promulgating regulations because recent data indicates that, depending on an individual’s activity pattern, the inhalation and dermal exposure may potentially contribute a significant portion of an individual’s exposure to chloroform. (Federal Register)

Regulation of Water Quality by the US Environmental Protection Agency

The EPA regulates water quality under the Safe Drinking Water Act of 1974 as amended (SDWA). The EPA has established two categories of drinking water standards. Primary standards are enforceable standards that limit the amount of contaminants that can effect public health. Secondary standards are standards recommended by the EPA. Secondary standards are not enforceable by the EPA but states may elect to adopt and enforce standards that are at least as strict as the EPA standard. Secondary standards are concerned with contaminants that produce cosmetic or aesthetic effects.

In December 1998 the EPA issued final regulations promulgating Maximum Contaminant Level Goals (MCLG) and Maximum Contaminant Levels (MCL) for disinfection byproducts. (Federal Register)

An MCLG is a non-enforceable health goal that the USEPA Administrator sets for each contaminant that “may have any adverse effect on the health of persons and which is known or anticipated to occur in public water systems.” Under the Safe Drinking Water Act, the MCLGs are to be set at a level at which “no known or anticipated adverse effect on the health of persons occur and which allows an adequate margin of safety.” (Federal Register) The adverse effect level is expressed in terms of the no observed adverse effect level (NOAEL) which is the highest level of a stressor (any physical, chemical or biological entity that can induce an adverse response) evaluated in a test that does not cause statistically significant differences from the controls. (USEPA 1996.)

The SDWA requires the EPA to publish a National Primary Drinking Water Regulation (NPDWR) whenever it issues a MCLG. The NPDWR specifies either an MCL or a treatment technique that may be used in lieu of establishing an MCL. An MCL is “the maximum permissible level of a contaminant in water which is delivered to the free flowing outlet of the ultimate user of a public water system, except in the case of turbidity where the maximum permissible level is measured at the point of entry to the distribution system. Contaminants added to the water under circumstances controlled by the user are excluded from this definition, except those contaminants resulting from the corrosion of piping and plumbing caused by water quality.” (USEPA OGWDW.)

The EPA set an interim MCL for TTHM of 0.10 mg/L, as an annual average, in November 1979. The annual average is determined from an average of quarterly averages of all samples and applies to total

5 THMs (chloroform, bromodichloromethane (BDCM), bromoform and dibromochloromethane (DBCM)). Toxicological studies conducted since 1974 have shown the first three to be carcinogenic in laboratory animals.

As previously mentioned, TTHMs were used as a surrogate for other contaminants because they frequently signal the presence of other halogenated and oxidized byproducts. Furthermore, the TTHM standard only applied to community water systems that used surface or ground water and served at least 10,000 people and added disinfectant during the water processing treatment. More than 200 million people are served by public water systems that use disinfectant.

When issuing the 1998 regulations, the EPA could not conclude there is a causal link between exposure to DBPs and cancer or reproductive or developmental effects. Some studies have suggested that there is an association between chlorinated surface water and bladder cancer, rectal cancer and colon cancer. A recent study suggests a link between early term miscarriages and drinking water with elevated THMs. (Betts 1998b.) However the EPA has authority to set MCLGs and NPDWRs and will err on the side of public health protection rather than wait until the risks are proven. The EPA also recognizes that there are health benefits to be derived from the disinfection process.

Other water quality related regulations were issued in the December 1998 regulations that are beyond the scope of this paper including, for example, a Surface Water Treatment rule, an Information Collection Rule, a Total Coliform Rule, Monitoring Requirements, Laboratory Certification and Analytical Methods.

The 1998 regulations set the following MCLGs and MCLs:

MCLG(mg/L) MCL(mg/L) TTHM N/A 0.080 Chloroform 0 -- Bromodichloromethane 0 -- Dibromochloromethane 0.06 -- Bromoform 0 --

The following provides an overview of procedures, analysis and considerations in setting these limits.

In assessing the health effects of various chemicals and setting contaminant limits the EPA solicits input from outside experts and “stakeholders” such as water supply utilities, state and local health agencies, consumer and environmental groups. Throughout the preamble to the 1998 regulations there is frequent comment about the reliance on the assumption of low dose linearity. This issue arises because much of the scientific information on toxicity and health effects is drawn from high dosage animal studies and extrapolated to the human population. Scientific debate continues but the EPA has taken the position that, at least with respect to chloroform, a non-linear model is appropriate for extrapolating low dose cancer risk. (USEPA 1998c.)

6 The development of the MCLGs starts with the determination of a Reference Dose (RfD) which was formerly termed the Acceptable Daily Intake or ADI. (USEPA.1994b.) The RfD is an estimate of a daily exposure that is likely not to present an appreciable risk during a lifetime. (At times the Lowest Observed Adverse Effect Level (LOAEL) is used. The LOAEL is the lowest dose in an experiment which produced an observable adverse effect. (USEPA OGWDW.)

The RfD is then calculated as follows:

RfD = NOAEL (or LOAEL) / (Uncertainty Factor(s) X Modifying Factor)

The NOAEL and LOAEL are expressed as mg/kg/day. Since the Uncertainty Factor and the Modifying Factor are dimensionless the RfD too is expressed in mg/kg/day.

The selection of the Uncertainty Factor is a matter of professional judgment. The EPA has modified the proposed National Academy of Sciences guidelines so that they will be applied in a consistent manner for EPA purposes. The following four paragraphs are excerpted from Chapter VIII US Environmental Protection Agency National Center for Environmental Assessment. 1994b. Drinking Water Criteria Document for Chloramines. (Final Draft ECAO-CIN-D002 March, 1994) Emphases added.

 Use a 10-fold factor when extrapolating from valid experimental results from studies using prolonged exposure to average healthy humans. This factor is intended to account for the variation in sensitivity among the members of the human population.

 Use an additional 10-fold factor when extrapolating from valid results of long-term studies on experimental animals when results of studies of human exposure are not available or are inadequate. This factor is intended to account for the uncertainty in extrapolating animal data to the case of humans.

 Use an additional 10-fold factor when extrapolating from less than chronic results on experimental animals when there is no useful long-term human data. This factor is intended to account for the uncertainty in extrapolating from less than chronic NOAELs to chronic NOAELs.

 Use an additional 10-fold factor when deriving an RfD from a LOAEL instead of a NOAEL. This factor is intended to account for the uncertainty in extrapolating from LOAELs to NOAELs.

The lowest uncertainty factor used is 10 and allows for inter- and intra- species differences and the use of less than lifetime studies. Professional judgment is required because the Uncertainty Factors do not make provision for the beneficial effects of the disinfectants which gave rise to the DBPs.

The Modifying Factor is greater than zero and less than or equal to 10. The default value is 1 but is to be selected based on the completeness of the data base and the scientific uncertainties of the studies.

7 The RfD is then used to develop a Drinking Water Equivalent Level (DWEL) which is the lifetime exposure at which adverse, noncarcinogenic health effects are not anticipated. (The calculation procedure can be used for mediums other than water.) Assuming an average human body weight of 70 kg ( 154 lbs) and daily consumption of 2 L of water the DWEL is determined as follows:

DWEL = (RfD) X (Body Weight in kg) / (Drinking Water Volume in L/day)

The result is expressed as mg / L. Note that in this formulation it is assumed that 100% of the exposure is from drinking water i.e. there is no adjustment for the possibility that the person may be exposed from other sources so that the appropriate drinking water exposure might properly be adjusted to only 80%, for example, of the DWEL developed above.

Here is an example of the application of the formulas. In the March 31, 1998 Notice of Data Availability (USEPA. 1994c.) EPA asked for comment on setting the MCLG for chloroform at 0.3 mg/L. The limit was developed from an RfD of .01mg/kg/d based on a chronic oral study in dogs. The RfD was based on a LOAEL for hepatotoxicity and an uncertainty factor of 1000. 100 was to allow for inter- and intra- species differences and 10 was used because the calculation was based on the LOAEL. (See the fourth bullet above.) (For EPA purposes, acute exposure is a single exposure to a toxic substance which results in severe biological harm or death. Acute exposures are usually characterized as lasting no longer than a day. Chronic is defined as occurring over a long period of time, either continuously or intermittently and is used to describe ongoing exposures and effects that develop only after a long exposure. Chronic exposure is long-term, low-level exposure to a toxic chemical. (US Environmental Protection Agency OGWDW Office Of Water Drinking Water Glossary.))

Thus the formula becomes:

MCLG = ((0.01 mg/kg/d X 70 kg) / (2L/day)) X .8 = 0.3 mg/L (rounded)

The factor of .8 is to allow for the fact that there are other sources of exposure to chloroform. However, as mentioned previously, the EPA in the preamble to the final rule issued in December 1998 (USEPA. 1998a.) expressed concern about the .8 factor which is referred to as a relative source contribution (RSC) factor. The EPA is in the process of developing a policy to account for sources of inhalation and dermal exposures e.g. humidifiers, swimming, hot-tubs and outdoor misters. The EPA is considering an RSC of . 2 in lieu of the .8 because historically .2 has been used for drinking water contaminants other than disinfection DBPs when there is uncertainty in the exposure data. Substituting .2 for .8 in the above formula produces an MCLG of 0.07 mg/L.

The final MCLG for chloroform was set at zero because the EPA was directed under the SDWA to issues a standard by November 1998 and because there are outstanding scientific questions. For reasons of prudent risk management the MCLG was set at the presumptive default level of zero. (USEPA. 1998a.)

Having reviewed the derivation of the MCLG for chloroform, two questions arise. What is the difference between a Maximum Contaminant Limit Goal and a Maximum Contaminant Limit (MCL); why is the MCLG set at zero for three of the THMs and at .06 mg/L for Dibromochloromethane.

8 EPA defines maximum contaminant level (MCL) as the maximum permissible level of a contaminant in water which is delivered to the free flowing outlet of the ultimate user of a public water system, except in the case of turbidity where the maximum permissible level is measured at the point of entry to the distribution system. The maximum contaminant level goal (MCLG) is the maximum level of a contaminant in drinking water at which no known or anticipated adverse effect on the health of persons would occur, and which allows an adequate margin of safety. Maximum contaminant level goals are non- enforceable health goals .

As to the 0.06 mg/L limit for Dibromochloromethane (DBCM), the EPA categorizes DBCM as a possible human carcinogen while Bromodichloromethane (BDCM) and Bromoform are considered as probable. (Chloroform was previously discussed.)

The EPA categorizes carcinogenic potential based on overall weight-of-evidence, according to the following: (USEPA 1994b)

 Group A: Human Carcinogen. Evidence exists from epidemiology studies to support a causal association between exposure and human cancer.

 Group B: Probable Human Carcinogen. Evidence of carcinogenicity in animals with limited (Group B1) or inadequate (Group B2) evidence in humans.

 Group C: Possible Human Carcinogen. Limited evidence of carcinogenicity in animals in the absence of human data.

 Group D: Not Classified as to Human Carcinogenicity. Inadequate human and animal evidence of carcinogenicity or for which no data are available.

 Group E: Evidence of Noncarcinogenicity for Humans. No evidence of carcinogenicity in at least two adequate animal tests in different species or in both adequate epidemiologic and animal studies.

Based on this scale it would seem that “probable” is a more serious category than “possible” and would lead one to expect that MCLGs would have been established for (BDCM) and Bromoform as well. Based on available evidence, the EPA has categorized these chemicals but because the EPA is unable to determine the mode of carcinogenic action they used the linear extrapolation to estimate lifetime cancer risk whereas for DBCM, based on observed liver toxicity and cancer and non-cancer data the limit was proposed as 0.06 mg/L in 1994 and in the absence of new information the limit was unchanged in the 1998 regulations.

Conclusion

Contamination in water supplies is an important and complex issue. When this paper was undertaken the expectation was that the problem would be well defined from the chemical contaminant standpoint with tables of disinfectant and byproducts listed according to water temperature, pH, the amount of organic matter in raw water etc. However, as noted, the structure of organic matter is not well defined and in fact

9 hundreds of byproducts have been found in drinking water and only a small number have been studied by EPA. (Betts 1998a.) As water sources are diminished and further polluted, disinfection, water preparation and contamination control will be critical to the health of the population.

Bibliography

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Chang, W. 1994. Bacterial activity of TiO2 photocatalyst in aqueous media: toward a solar-assisted water disinfection system. Environmental Science & Technology 28(3):934-938.

10 Dowideit, P. and C. Von Sonntag. 1998. Reaction of ozone with ethene and its methyl-and chlorine- substituted derivations in aqueous solution. Environmental Science & Technology 32(8):1112-1119.

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USEPA. 1996. Proposed Guidelines for Ecological Risk Assessment. EPA/630/R-95/002B.

USEPA. 1998a. Microbial and Disinfection Byproduct Rules. EPA-815-F-98-010.

11 USEPA OGWDW Office Of Water. Drinking Water Glossary. http://www.epa.gov/OGWDW/Pubs/gloss2.html

Van Gunten, U. and Y. Oliveras. 1998. Advanced oxidation of bromide-containing waters: bromate formation mechanics. Environmental Science & Technology 32(1):63-70.

Wu, Wells W., P.A. Chadik, W.M. Davis, D.H. Powell and J.J. Deffino. 1998. Disinfection byproduct formation from the preparation of instant tea. Journal of Agricultural and Food Chemistry 46(8):3272- 3279.

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Additional Readings

Kang, L-S and J.L. Cleasbry. 1995. Temperature effects on flocculation kinetics using Fe(III) coagulant. Journal of Environmental Engineering 121(12):893-901.

Lind, C. 1994. Coagulation control and optimization (Part 1). Public Works 125(11):56-57.

Lind, C. 1994. Raw water preparation. Public Works 125(5):C10-C18.

Lind, C. and K. Ruehl. 1998. A practical summary of water treatment practices (Part 1). Public Works 129(7):52:54.

Sfiligoj, E. 1994. The THM equation (and other bugs). Beverage World 113(Dec):56-57.

USEPA. 1994a. Analytical Methods for Regulated Drinking Water Contaminants; Final Rule. EPA-811- Z-94-006.

USEPA OGWDW. 1998b. Drinking water standards for regulated contaminants. http://www.epa.gov/OGWDW/source/therule.html

USEPA. 1998c. National Drinking Water regulations: Disinfectants and Disinfection Byproducts Notice of Data Availability; Proposed Rule. EPA-815-Z-98-005.

US General Accounting office. 1990. Drinking water Compliance Problems Undermine EPA Program as New Challenges Emerge GAO/RCED-90-127. General Accounting Office, Washington, DC. 72pp.