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Home , Safe Drinking Water Act, Water

Ozone and the Safe Act

Rip G. Rice, Ph.D. and Paul K. Overbeck

Presented at 24th Annual WQA Convention

Ft. Lauderdale, FL March 20, 1998

Courtesy of:

Mazzei Injector Corporation | 500 Rooster Dr. | Bakersfield, CA 93307 USA | Phone: 661-363-6500

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1 and the Safe Act

Abstract

Since the initial passage of the Safe Drinking Water Act in 1973, the use of ozone to treat drinking water in the has been encouraged increasingly by EPA’s evolving drinking water regulations. The evolution of these regulations is traced and their impact on the uses of ozone in potable in the United States. is discussed Some statistics are included, in particular a listing of over 250 U.S. municipal drinking water utilities currently using ozone. A listing of 140 “small” water using ozone – defined by the EPA as serving less than 10,000 persons (producing less than 1 mgd) also is included. A surprising number of additional installations (> 400) are in single family homes and small .

Introduction

With the identification of halogenated organic compounds formed in drinking water as a result of chlorination (Rook, 1974; Bellar et al., 1974), the U.S. Congress quickly enacted the Safe Drinking Water Act in 1973. This original SDWA charged the U.S. EPA to develop and promulgate a number of regulatory initiatives. Subsequent SDWA amendments (1986 and 1996) have added additional regulatory mandates to the EPA, many of which encourage the use of ozone. Those regulatory developments which encourage the use of ozone will be discussed in this . The Safe Drinking Water Act of 1973

One of the major regulations which resulted from the original 1973 SDWA, from the standpoint of ozone, is the so-called “THM Regulation”, promulgated in 1979. This regulation requires large utilities (those serving > 10,000 persons) to meet a maximum contaminant limit (MCL) of 0.010 mg/L (= 100 µg/L) of the total of the four (chloroform, chlorodibromomethane, bromodichloromethane, and bromoform).

Prior to promulgation of the THM Regulation in 1979, the U.S. EPA had surveyed waters produced at 80 U.S. water utilities, sampling their finished waters and analyzing for the four THMs. The only two U.S. ozone plants operating with ozone at that time (Whiting, IN and Strasburg, PA) were included in this National Organics Reconnaissance Survey (the NORS). Significantly, the levels of THMs found at the two ozone plants were the lowest of the other 78 plants. These results, as might be expected, caught EPA’s regulatory attention.

As a result, EPA sponsored two projects which involved surveying selected European and Canadian drinking water treatment plants using ozone and also those using dioxide. In the first survey, a U.S. team of experts, operating under an EPA grant to a municipally-oriented not-for-profit organization, was assembled consisting of an ozone technologist (the senior author), a consulting engineer, a public professional, and several water treatment experts. With the cooperation of the International Ozone Association, contacts were established with

2 European water research institutes and water utilities. During May, 1977, this survey team spent 30 days visiting water plants using ozone (and some using as ) in France, Germany, Belgium, and Switzerland, two water research institutions, and attended five days of technical conferences on ozone which were held in and Berlin. In the Fall of 1977, the survey team visited about a dozen Canadian water treatment plants, all in the Province of Québec, using ozone and chlorine dioxide, and then several U.S. plants using chlorine dioxide.

It was during this initial EPA-sponsored European survey project that the survey team observed the process of combination of ozonation followed by sand filtration then filtration through granular activated carbon (GAC). Both the Germans and the French had discovered and pilot tested this process about the same time, and several full-scale European plant were operating the process in the mid-1970s. In essence, during ozonation, some of the biorefractory organics are converted to more biodegradable materials by chemical oxidation. Polar groupings are added to some of the dissolved organics, and some of the larger dissolved organic are cleaved into smaller oxygenated fragments by the oxidative action of ozone. At the same time, dissolved oxygen levels in the water are increased as a side-benefit of the ozonation process.

Regardless of the specific mechanisms involved, when these now much more readily biodegradable organic molecules pass through the GAC columns, they encounter natural , which develop in virgin GAC after only a few weeks of operation and which thrive in the GAC macropores in the absence of a residual (chlorine, chlorine dioxide, or chloramine). These aerobic microorganisms are capable of rapidly mineralizing the biodegradable organics, converting them to and water in a few minutes of empty bed contact time (5-10 min EBCT).

This particular combination of ozonation followed by GAC filtration was termed Biological Activated Carbon (BAC), and was of such interest to EPA regulators that the survey team was sent back to Europe the following year (1978) specifically to study this process combination in more detail. By such water treatment combinations of ozone/biofiltration, Europeans were found to be lowering the levels of THM precursors prior to terminal chlorination or addition of chlorine dioxide. A key to success of the BAC and other ozone/biofiltration processes (involving sand or sand/anthracite rather than GAC medium) was the elimination of chlorination prior to ozonation and biofiltration. This avoids the formation of halogenated organics in the early treatment stages which are neither readily biodegradable nor readily oxidized, even by ozone.

Compliance with the THM rule was required by 1981, and during the between 1981 and 1986, the Congress was busy developing the first amendments to the 1973 SDWA. In the interim, the U.S. drinking had available two reports written by the survey team (Miller et al., 1978; Rice et al., 1982), the first describing European and Canadian experiences with ozone and chlorine dioxide, and the second describing the BAC process as practiced in Europe. Additionally, the survey published a paper pointing out the many applications of ozone in drinking water treatment (Rice et al., 1981).

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The Safe Drinking Act Amendments of 1986

Whereas the 1973 SDWA had attracted the attention of the U.S. water treatment industry to ozone and chlorine dioxide, it was the SDWA Amendments of 1986 that caused the U.S. water industry to focus on these two oxidants/. In implementing the Congressional mandates of the 1986 Amendments, EPA notified the water industry that it would be regulating three new microorganisms present in waters, Giardia lamblia cysts, enteric viruses, and bacteria. In addition, the Standard Plate Count group underwent a name change to Heterotrophic Plate Count (HPC).

THE TREATMENT RULE (the SWTR)

Beginning in early 1987, EPA published an Advanced Notice of Proposed Rulemaking for a Surface Water Treatment Rule (SWTR), by which systems treating surface waters and serving greater than 10,000 persons would be required to show that they were able to attain primary disinfection of these new microorganisms (primary meaning in the treatment plant). At the same time, the term secondary disinfection was introduced which applies to treated waters in distribution systems.

It is not practical for a water treatment system to monitor Giardia cysts, enteric viruses, or any microorganism, for that , in real time on-line -- only after the fact. Recognizing this, the EPA developed the “CT” concept, which is the arithmetic product of the concentration (C, in mg/L) of a disinfectant multiplied by the time (T, in minutes) that the disinfectant is in contact with the water. As long as the product of C x T equals or exceeds a specific number set by the agency for the Giardia cysts, the inactivation of a certain percentage of these microorganisms which might be present in the waters being disinfected would be ensured.

Each microorganism specified in the SWTR (U.S. EPA, 1989) and its Guidance Manual (U.S. EPA, 1990) has a specific set of CT values, which also are a function of pH (particularly for chlorine), and temperature. The lower the required CT value, the more effective is the specific disinfectant, meaning that a specific level of microorganism inactivation can be guaranteed with lower concentrations and/or shorter contact times for the more effective disinfectants. EPA also presented the disinfecting efficiency of any disinfectant in terms of logarithms of microorganism inactivation, or log-inactivations.

If a water containing a viable microorganism concentration of 10,000/mL is treated with a disinfectant such that the number of viable microorganisms is reduced to 1,000/mL (90% inactivation), then 1-log inactivation has been attained. If the level is reduced to 100/mL (99% inactivation), two-logs of inactivation have been attained; if reduced to 10/mL (99.9% inactivation), 3-logs, etc. In publications leading to the SWTR itself, EPA presented a series of CT tables for the four disinfectants in use: chlorine, chlorine dioxide, ozone and chloramine. Table I shows the CT values to attain 99.9% (3-logs) inactivation of Giardia cysts for the four disinfectants mentioned above. Note that the values for ozone are significantly lower than for any of the other disinfectants.

4 With respect to viruses, EPA advised that if sufficient primary disinfectant is added to ensure 3- logs of Giardia cyst inactivation, credit would be allowed for at least 4-logs of simultaneous enteric virus inactivation.

Taken by itself, the fact that ozone has the lowest CT values for inactivating Giardia cysts (and therefore enteric viruses), is considerable encouragement for ozone as a result of promulgation (in 1991) of the SWTR. However, even more encouragement to consider ozone came from EPA during the development of the SWTR. The agency warned those utilities who might seek to attain the higher CT values required for i9nactivating Giardia cysts and viruses by simply adding additional chlorine and/or additional chlorine contact time. A Disinfectants/Disinfection By- Products (D/DBP) rule was being developed, and halogenated organics would be the primary target of this future regulation. Consequently, even though the primary disinfection requirements of the SWTR certainly can be met by increased use of chlorine, most utilities choosing this approach probably would not be able to meet the requirements of the D/DBP rule.

TABLE I. CT VALUES FOR DISINFECTANTS TO INACTIVATE 99.9% (3-logs) OF GIARDIA LAMBLIA CYSTS Disinfectant pH < 1°C 5°C 10°C 15°C 20°C 25°C

6 165 116 87 58 44 29 Free Chlorine at 2 mg/Lb 7 236 165 124 93 62 41 8 346 243 182 122 91 61 9 500 353 265 177 132 88 Ozone 6-9 2.9 1.9 1.43 0.95 0.72 0.48 Chlorine 6-9 63 26 23 19 15 11 Dioxide Chloramine, 6-9 3,800 2,200 1,850 1,500 1,100 750 (preformed)c a These CT values for free chlorine, chlorine dioxide, and ozone will guarantee greater than 99.99% inactivation of enteric viruses.

b CT values will vary depending on concentration of free chlorine. Values indicated are for 2.0 mg/L of free chlorine. CT values for different free chlorine concentrations are specified in tables in the Guidance Manual (U.S. EPA, 1990).

c To obtain 99.99 percent inactivation of enteric viruses with preformed chloramines requires CT values > 5,000 at temperatures of 1, 5, 10, and 15(C.

5 THE BROMATE ION ISSUE

In the mid-1980s, the future of ozone in drinking water treatment seemed rosy and bright. However, Japanese researchers had just reported that bromate ion apparently is capable of causing carcinomas in rats (Kurokawa et al., 1986). What has bromate ion to do with ozone? Plenty, if bromide ion is present in waters being ozonated. Bromate ion is formed by the oxidation of bromide ion, which is present in the majority of raw waters throughout the world. Think back to the four trihalomethanes. Three of them contain at least one bromine . Why do brominated THMs form when water is treated with chlorine? Because chlorine is readily capable of oxidizing bromide ion to hypobromous /hypobromite ion (free bromine):

Br- + HOCl ----> HOBr + Cl-

As soon as HOBr is formed, it equilibrates (in water) with hypobromite ion, just as (HOCl) equilibrates with hypochlorite ion.

- + HOBr + H2O <====> OBr + H + H2O

Hypobromous acid is a good brominating agent and, once formed, is capable of brominating organic materials which are THM precursors to produce the brominated THM species (and other brominated organics) readily detectable by current analytical procedures.

Ozone also oxidizes bromide ion readily to the HOBr/hypobromite ion couple – except that ozone, being a much stronger oxidant than any of the chlorine species present in aqueous , has the additional capability to oxidize hypobromite ion (not HOBr) further to produce bromate ion (Haag and Hoigné, 1984; 1984;). Chlorine apparently is not a sufficiently powerful oxidant to oxidize hypobromite ion to bromate ion, except under some unusual circumstances not usually present in normal potable plants.

- - - O3 + OBr ----> [O2 + BrOO ] ----> 2 O2 + Br (77%)

- 2 - 2 O3 + OBr ----> 2 O + BrO3 (23%)

Notice that only 23% of the hypobromite ion when oxidized with ozone goes directly to the bromate ion. The balance (77%) is reduced to bromide ion. One might expect that if other ozone-demanding constituents are present in waters being ozonated (such as , , nitrite ion, ion, many organics, etc.) that very little ozone would be available to oxidize hypobromite ion further to bromate ion. This expectation is further justified on the basis of ozonation rates of the usual water contaminants such as those just mentioned being an order of magnitude faster than the rate of ozone oxidation of hypobromite ion to produce bromate ion. However, since some 77% of the hypobromite ion returns to bromide ion, then the reformed bromide ion can re-oxidize to hypobromite ion upon continued ozonation, which can again become a source for the formation of more bromate ion.

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Since bromate ion had been shown by the Japanese to be an animal , it then must become a suspected carcinogen as well. Consequently, the finding of animal carcinogenicity of bromate ion, which (apparently) can only be formed upon ozonation of waters containing bromide ion, resulted in a major slowdown in the regulatory rush to ozone. EPA added bromate ion to its list of disinfection by-products proposed for regulation – at an MCL of 10 µg/L (see later discussion).

Because the accepted mechanisms of ozone formation of bromate ion all involve oxidation of the hypobromite ion, then any chemical trick that can be applied to the candidate water to minimize the concentration of hypobromite ion can be expected to minimize or even prevent the formation of bromate ion. In fact, three such chemical tricks have been developed. Detailed explanations of these approaches are too complex for this presentation. However they are summarized below. Readers are referred to cited just below for the details.

1. Conduct ozonation at pH 6.5 or below. At this pH, oxidized bromine species are present entirely as HOBr, and no hypobromite ion can be present (Haag and Hoigné, 1982; 1984).

2. Add small amounts of to the water prior to ozonation. When ozone is added, bromide ion is oxidized to HOBr which immediately reacts with ammonia to produce monobromamine, NH2Br. Although this brominated ammonia derivative slowly oxidizes during ozonation (to produce bromide and ions), the reaction is slow enough that if the ozonation is completed within five minutes, there will be insufficient hypobromite ion formed to result in significant bromate ion production (von Gunten and Hoigné, 1992).

3. Conduct the ozonation allowing only minimal levels of dissolved ozone in the water. In this manner of treatment, the reactions of ozone-demanding materials other than bromide ion (and subsequently, hypobromite ion) will outcompete the bromine species for ozone, because its relative concentration will be low.

One additional point – since ozone readily oxidizes bromide ion to produce free bromine (as does chlorine), which is a good brominating agent, brominated organics can be expected to be identified as analytical techniques are developed to look for these types of organic materials. Bromoform, CHBr3, already has been identified in some ozonated waters, although it is logical to expect that brominated organic , aldehydes, ketones, and mixed functional compounds will be identified in the future.

It should be clear to the astute reader that the bromate ion situation erases one of the older marketing clichés of ozone vendors. The statements that “over-ozonation can do no harm” or “ozone does not produce halogenated organics” no longer hold when sufficient bromide ion is in the waters to be ozonized.

7 Author’s Caution: Dealers and distributors of ozonation equipment – know the bromide ion concentrations in waters which are candidates for ozonation. If bromide levels are high and the waters are otherwise low in ozone-demanding impurities – either one of the chemical tricks may be appropriate. For those marking small water treatment systems, an anion exchange pretreatment step to remove bromide ion would seem to be effective in minimizing the chances for bromate ion to form during ozonation.

Consequently, by the early 1990s, the drinking water industry found itself with a dilemma with respect to ozone: although it is clearly the most effective chemical oxidant and primary disinfectant available, it is also capable of producing unacceptable levels of bromate ion, a suspected human carcinogen based on animal studies, if the water to be ozonized contains “high” levels of bromide ion. How high is high? That depends on the ozonation conditions and what else is in the water to be ozonized.

CRYPTOSPORIDIUM PARVUM AND

While water treatment professionals were chewing on this dilemma, a new microorganism cyst entered the drinking water scene, parvum. This cyst is reminiscent of a walnut, having a very hard outer shell, but stuffed full of viable (e.g., infective) sporozoites (worm-like even smaller species) which ultimately leave the mother cyst to make their own way in – incidentally causing cryptosporidiosis if ingested, an intestinal disease which makes healthy people mighty sick, and can kill people who are immunocompromised, as happened in Milwaukee, Wisconsin during its now infamous outbreak in the early 1990s.

Cryptosporidium parvum represents another dichotomy for the water industry and drinking water regulators. This cyst organism is difficult to remove by filtration because of its small size (~5- µm). What makes it even more problematic is that the oocysts can elongate when pressured and narrow to just over 1-µm. It is also so resistant to chemical disinfectants that chlorine has essentially no effect on it. It is possible that upon very long term storage (days) in chlorinated water, perhaps 0.5-log of inactivation of Cryptosporidium may be credited, but that point has yet to be confirmed. EPA and microbiologists are debating this possibility at present. Chloramine also has no effect. And although a synergistic benefit of chlorination followed by chloramine has been reported in laboratory studies using pure water samples (Finch et al., 1994), this effect has yet to be proven in the field in real-world waters. Only chlorine dioxide and ozone have been proven to be effective for the chemical inactivation of C. parvum, and, as might be anticipated from the CT values for inactivating Giardia lamblia (Table I) ozone is an order of magnitude more effective than is chlorine dioxide.

The dichotomy for regulators is that although ozone is effective in the inactivation of C. parvum, about 3-6 times as much ozone is required for this cyst as required to inactivate Giardia lamblia cysts. Although this is fine if one is selling ozonation equipment, there is the problem of the formation of bromate ion. The more ozone that must be added over a longer contact period, the more bromate ion formation that can be expected, assuming the presence of bromide ion in the original water to be treated.

8 As an aside, a team of microbiologists at the University of Alberta (Edmonton, Alberta, Canada) and elsewhere under the direction of Prof. Finch currently is assembling available data on ozone inactivation of C. parvum. The initial objective of this work is to develop kinetic models for C. parvum inactivation with ozone, and then to produce a Cryptosporidium-Ozone CT Inactivation Table. These results are expected to be available in early 1999, and will specify ozonation conditions and parameters under which specific amounts of C. parvum inactivation can be ensured.

REGULATORY NEGOTIATION OF EVOLVING DRINKING WATER REGULATIONS

By the early 1990s, EPA had proposed a D/DBP rule, in two stages, for public comment. Utilities would be required to meet the requirements of Stage 1 shortly after promulgation. Stage 2 requirements were proposed, but the industry was advised that these more stringent requirements would not take effect until at least five years from the date of promulgation of Stage 1 requirements, and also not before a further review of available data on the issues could be made. Specifics of this rule and its proposed requirements will be discussed later in this paper (See SDWA Amendments of 1986).

Comments received on this proposal reflected the many unique complexities of this proposed rule. The many issues involved [e.g., how to ensure microbial disinfection while minimizing disinfection by-products (DBPs), what to do about Cryptosporidium parvum, how to isolate C. parvum, how to determine the viability of C. parvum, what to do about regulating DBPs in small systems, how to in the D/DBP rule, etc.] were so intertwined and intricate that rather than continue developing this rule in the usual manner, EPA devised a new approach. This involved inviting the many stakeholders in the regulatory process to participate in a regulatory negotiation (a so-called “Reg-Neg” process) with the agency.

This historic approach to developing new drinking water regulations began in 1992, and after several months of negotiation, the stakeholders recommended (and the EPA concurred) the following actions in 1993:

1. The D/DBP rule cannot be developed and promulgated separately from a revised microbial rule (termed at that time the Enhanced Surface Water Treatment Rule -- the ESWTR – which would address, among other items, control of C. parvum). EPA cannot take the chance of promulgating a D/DBP rule which might cause some utilities to compromise on disinfection in order to ensure meeting new by-product MCLs.

2. Insufficient information was available about C. parvum (its enumeration, measurement of its viability, methods of removal and inactivation) so that an ESWTR could not be developed quickly – along a parallel time-line as the D/DBP rule.

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3. Insufficient information was available about the effectiveness of current and “advanced” water treatment processes for the removal of precursors of halogenated byproducts of most regulatory interest (THMs, haloacetic acids, haloacetonitriles, haloaldehydes, etc.) to justify setting more stringent MCLs. Forcing the water industry to install advanced technologies (e.g., ozone, GAC, membranes, etc.) which were not yet considered to have sufficient design, engineering, operation and (above all) cost information, could be a costly mistake on the part of the agency.

4. A D/DBP Rule should be promulgated in two stages, as proposed by EPA, with a second Reg-Neg review of additional information prior to setting Stage 2 MCLs.

5. EPA should promulgate an Information Collection Rule (ICR) which would require at least the larger U.S. water utilities to perform certain analyses of plant raw waters, as well as treatment process effectiveness in coping with influent microorganisms and in controlling DBPs proposed for regulation in Stages 1 and 2 of the D/DBP rule. Based on data obtained from the ICR, the Reg-Neg advisory committee then could make better judgements and recommendations concerning regulatory approaches for both an ESWTR and Stage 1 of the D/DBP rule.

6. Following completion of the ICR and simultaneous promulgation of the ESWTR and Stage 1 of the D/DBP rule, a “Reg-Neg-2" process would be scheduled for about 1999.

Armed with this advice and consensus of the Reg-Neg stakeholders committee, EPA proposed three rules – the ICR in early 1994 and the D/DBP and Enhanced Surface Water Treatment Rules in July of 1994. All three of these rules held considerable encouragement for the use of ozone.

The Information Collection Rule

Originally proposed in early 1994, an 18-month program was envisioned to begin in late 1994 by which surface water treatment systems serving more than 100,000 persons and ground water systems serving more than 50,000 persons would report information monthly for 18 consecutive months on raw parameters (microbial, , bromide ion, etc.), the effectiveness of existing treatment processes to cope with these parameters, and specified water quality parameters (microbial and DBP – see later discussion of the D/DBP rule) of the finished waters. With this information in-hand by 1996, it was expected that Stage 1 of the D/DBP rule and an Interim ESWTR (IESWTR) rule could go forward during the time period 1997-1999.

Unfortunately, the inability to provide an analytical method whereby C. parvum oocysts could be enumerated and viability determined routinely held up promulgation of the ICR until 1996 (U.S. EPA, 1996), by which time the Safe Drinking Water Act Amendments of 1996 had been passed by the U.S. Congress (see next major section -- but discussion will continue at this point so as not to fragment the current ICR situation).

10 Even now, many specialists in the microbiological field are not in agreement that the method included in the ICR as promulgated will provide satisfactory data on C. parvum occurrence and viability. EPA’s position is that it will provide comparative data upon which to an IESWTR.

The data-gathering and reporting phase of the ICR began in July 1997, and is scheduled for completion by December 31, 1998. Some 503 large U.S. drinking water utilities are reporting information monthly to the EPA currently. In addition, an ICR Data Analysis team of experts in various aspects of data handling and water treatment are developing the procedures by which the data submitted to the EPA under the ICR will be analyzed and published beginning in 1999.

By the time the data collection phase of the ICR was initiated (July 1997), there were more than 200 U.S. water treatment plants in operation using ozone; several more will be starting up new ozonation facilities between July 1997 and December 1998. About two dozen of these ozone- using water plants are covered by the ICR and are reporting data. It will be of great encouragement for the use of ozone when the information being supplied by the ICR ozone plants is assembled and made public. Some early information of ozone water plants (ICR size and below) was developed by the International Ozone Association and presented to EPA during 1997 (see discussion of the M/DBP Expedited Rule Advisory Committee in a later section). Ozone plant performance information will show how efficiently ozone, in many cases followed by a biofiltration step, is providing primary disinfection and lowering the levels of DBPs to levels which meet the D/DBP rule requirements.

In addition to the above-mentioned water quality and process performance information, the ICR has an additional requirement for the reporting plants, and those treating surface water in particular. When the D/DBP rule was proposed in 1994, best available technology (BAT) for meeting Stage 1 requirements was defined as “enhanced coagulation” followed by chlorination (not chloramination). This is a logical regulatory approach. Since most of the DBPs (caused by chlorination) are organic, it is logical that if a treatment plant can enhance the removal of organics (analyzed as total organic carbon, TOC) prior to the addition of chlorine, it stands to reason that the concentrations of halogenated organic by-products will be lowered, while maintaining the use of chlorination to attain primary disinfection.

Certainly, water treatment plants would be free to use other techniques for attaining the primary disinfection requirements of the SWTR while lowering the production of DBPs in their plants. But EPA would require as a minimum “enhanced coagulation”.

What is enhanced coagulation? This can mean different things to different utilities. As a general rule, it means modifying the coagulation process to ensure that removal of TOC is maximized. This can mean lowering the pH of coagulation with alum (to 6-6.5), or to switch to a more effective coagulant, or simply to add more coagulant – hopefully at an optimum pH for that coagulant.

11 But the ICR went further. If a utility required to report data under the ICR finds that it cannot meet the Stage 1 requirements of the D/DBP rule (to be discussed under that topic in the appropriate section below) by application of enhanced coagulation followed by chlorination, then that utility must test, on pilot-plant scale, the application of granular activated carbon adsorption or the use of membranes to reduce levels of DBP precursors in their waters. Both of these technologies usually are more expensive to install and operate than is ozonation plus biofiltration.

Unhappily for those interested in ozone, those who drew up the ICR requirements made a regrettable oversight with respect to ozone. It was not appreciated that there were 150 or more U.S. water plants in operation at the time using ozone for the combined purposes of providing disinfection and lowering of concentrations of halogenated DBPs. Consequently, utilities which could not meet the requirements of Stage 1 of the DBP rule were not given the option of testing ozone (or ozone/biofiltration). They had no choice but to pilot test GAC or membranes.

The Safe Drinking Water Act Amendments of 1996

In these latest amendments, the Congress has charged the EPA to implement numerous regulatory actions. Those affecting and encouraging the use of ozone include promulgating Stage 1 of the D/DBP and IESWTR rules by November 1998, promulgation of a Ground Water Disinfection Rule (the GWDR), and listing technologies whereby small drinking water systems can meet the requirements of EPA’s existing and future drinking water regulations. The status of each of these regulatory activities will be discussed below.

THE M/DBP EXPEDITED RULE ADVISORY COMMITTEE

In March 1997 in response to the 1996 SDWA Amendments and to speed the promulgation of the D/DBP and IESWTR rules by November 1998, the EPA created a Microbial/Disinfection By-Products Expedited Rule Advisory Committee, also known as “the FACA Committee” since it was created under the Federal Advisory Committee Act. The usual stakeholders in the regulations were invited to participate, but additionally, in recognition of the growing number of drinking water plants installing ozone, the International Ozone Association also was invited to be a stakeholder in this and future EPA regulatory deliberations on drinking water regulations.

A primary objective of the M/DBP Advisory Committee was to obtain rapid agreement on regulatory approaches for the first two rules (Stage 1 D/DBP and IESWTR), so that EPA could adhere to the November 1998 Congressionally mandated deadline for promulgation. Such agreement was obtained, and a Memorandum of Agreement by the stakeholders and the EPA was signed on July 15, 1997, whereupon the M/DBP Expedited Rule Advisory Committee was terminated.

12 During the life of this committee, however, the IOA was asked to develop and submit to the committee’s Technology Work Group a number of informational items pertinent to the deliberations of the stakeholders. This information is listed in the appendix to this paper, and is available from the IOA’s Pan American Group office (see Appendix for details).

THE D/DBP RULE

As discussed earlier, this rule is to be promulgated in two stages. In both stages, MCLs are to be set for the four trihalomethanes (THMs), for six haloacetic acids (HAAs -- bromo-, chloro-, and mixed bromochloro-), for bromate ion, and for chlorite ion (a by-product of chlorine dioxide use). In addition, maximum residual levels (MRLs) for chlorine, chlorine dioxide and chloramine will be established. There will be no MRL for ozone, because it will not be present in finished drinking water as it the plant, due do its short half-life. Vendors of small ozone systems should realize that this conclusions is not necessarily true for units installed in individual homes.

MCLs to be attained for all surface water treatment system for the by-products listed in the D/DBP rule are as follows:

Stage 1 Stage 2

Total THMs (TTHMs) 80 µg/L 40 µg/L Total of 6 haloacetic acids (THAAs) 60 µg/L 30 µg/L Bromate Ion 10µg/L to be determined

As pointed out earlier, the Stage 2 MCLs are to be renegotiated during a Reg-Neg 2 process. Currently, the Reg Neg 2 process is scheduled to begin organizationally in December 1998, and to become intensive during early 1999. Notice that haloacetic acids are added to the THMs as the regulated disinfection by-products for the first time. Notice also that the Stage 2 MCLs for TTHMs and THAAs are 50% of those for Stage 1. Even though the actual numbers may change during Reg Neg 2, depending on what health effects data are available by that time, the trend is indicatively clear to lower MCLs. It is also possible that several additional mixed bromochloro- HAAs may be added to the list to be regulated under Stage 2, as analytical procedures for them are developed.

The 10 µg/L MCL for bromate ion was determined by the Reg Neg 1 stakeholders to be the lowest value which could be monitored analytically in the field at present. It is anticipated that by the time of Reg Neg 2, analytical procedures for bromate ion will have evolved to allow a lower value to be set. That presumed value for bromate ion, based on the usual risk assessments is anticipated to be 5 µg/L.

13 In a late 1997 publication (U.S. EPA, 1997), the EPA advised that it has recently completed a chronic study in make rats and male mice for bromate ion. The agency is evaluating this data and plans to provide an opportunity for public comment for the regulatory provisions for bromate ion prior to promulgating the final D/DBP rule in November, 1998.

At this point, one can step back and consider the impacts of just the D/DBP rule on the acceptance of ozone technology. If a drinking water treatment plant currently using conventional treatment and chlorination as the primary disinfectant is in compliance with the THM rule (100 µg/L) and finds that its THAA levels are below 60 µg/L, it does not have to make any changes to be in compliance with the requirements of Stage 1. However, if that plant is not meeting Stage 1 requirements now, it should first test enhanced coagulation before considering movement to an advanced technology (e.g., ozonation). Consequently, the Stage 1 requirements, taken by themselves, do not represent any major encouragement for the water industry to adopt ozone.

On the other hand, if a plant must enlarge its treatment capacity, or if the utility must construct a new water treatment plant, its wisest approach is to design that plant or plant expansion to meet the stage 2 requirements. By the time a new or expanded plant is constructed and is on-line, Stage 1 regulations will be in force, and stage 2 requirements will be promulgated within a few years. Thus, the Stage 2 requirements, even though the actual MCL numerical values are not certain, represent major encouragement toward the adoption of ozone treatment.

At the same time that a utility is considering the use of ozone, the bromate ion MCL must be reckoned with. Consequently, testing of waters to be ozonated is not only advised, but prudent, since the formation of excessive bromate ion during ozonation may remove ozone from further consideration at that plant.

Some of the information collected by the International Ozone Association for the M/DBP Expedited Rule Advisory Committee during the first half of 1997 (Rice and Dimitriou, 1997) included a mini-survey of how well existing ozone drinking water plants in the USA were doing with respect to meeting the requirements of the proposed D/DBP rule. Some 30 U.S. water plants using ozone responded to an IOA questionnaire with the following information (see Appendix for details):

1. All of the responding plants that follow ozonation with biofiltration then chlorination (about 45%) meet the Stage 1 requirements of the D/DBP rule today.

2. All of the responding plants that follow ozonation with biofiltration then chloramination (about 45%) meet the Stage 2 requirements of the D/DBP rule today (but with the uncertainty of a Stage 2 bromate ion MCL).

3. At least 19 U.S. water treatment plants (of all sizes) using ozone either do not filter or apply ozone after filtration. When following ozonation with chlorination, Stage 1 requirements are met, and when following ozonation with chloramination, stage 2 requirements are being met.

14 The IESWTR

In the July 1997 Memorandum of Agreement, the stakeholders agreed to tighten current standards as an initial step to better control Cryptosporidium oocysts by filtration. In addition, the stakeholders agreed to EPA’s proposal of allowing 2-logs removal credit for C. parvum by properly operating filters which meet the lowered turbidity standards. Consequently, EPA will require 2-logs removal of C. parvum oocysts in the IESWTR to be promulgated in November 1998.

This regulatory approach to controlling C. parvum oocysts (by filtration alone) is not encouraging for ozone, because there is no regulatory requirement for inactivation of C. parvum oocysts. On the other hand, in the Memorandum of Agreement, EPA agreed to include inactivation of Cryptosporidium oocysts as part of the Reg Neg 2 discussions of the Long Term ESWTR (the LTESWTR), which is to be promulgated simultaneously with the Stage 2 D/DBP rule in 20021. EPA’s explanation for not including inactivation of Cryptosporidium oocysts in the IESWTR has several considerations:

1. Only one disinfectant (ozone) is known to inactivate C. parvum, but at higher dosages than required for the inactivation of Giardia cysts, according to available data.

2. Insufficient information is available at this time on the specifics of inactivation of C. parvum oocysts with ozone to recommend how much ozone will provide how much inactivation.

3. Including an inactivation requirement in the IESWTR would effectively mandate ozone in U.S. drinking water treatment, a costly decision for borderline water plants (with respect to all other aspects of the by-products and microbial regulations), and which have never experienced a Cryptosporidium outbreak.

This EPA regulatory position leaves surface water plants complying with the requirements of the IESWTR in somewhat the same position as the of Milwaukee was in before their now well- known Cryptosporidium outbreak – relying on filtration as a single barrier, rather than upon filtration and chemical inactivation, a multiple-barrier approach to C. parvum. At the time of Milwaukee’s outbreak, the city’s water treatment plants were meeting all applicable drinking water regulations.

1 The LTESWTR has been further divided into the LT1ESWTR and the LT2ESWTR to allow the agency to require compliance with the first by larger systems, then compliance by smaller systems to the second at a later date. Both are intended to have the same requirements.

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THE DISINFECTION RULE

As currently scheduled, EPA is to propose the GWDR early in 1999. This regulation will apply to all public water systems treating that are not under the direct influence of surface waters (there are regulated under the Surface Water Treatment Rule). Since protected groundwaters not influenced by surface waters are not expected to contain cyst (such as Giardia and Cryptosporidium), EPA will be requiring disinfection to protect against enteric viruses and coliform bacteria. Many groundwaters are of such high quality and purity as to need only disinfection as opposed to chemical treatment plus disinfection. For such high quality groundwaters, ozone is applicable, of course, but so also is radiation, at lower cost in many instances.

On the other hand, many groundwaters also contain significant quantities of iron, manganese, nitrite ion and sulfide, and these contaminants are best treated by means of a strong oxidizing agent. With these types of groundwater contamination, ozone is a candidate to provide both oxidation of the contaminants and disinfection. Consequently, promulgation of the GWDR is expected to provide additional encouragement for the use of ozone.

Many groundwaters also are contaminated with chlorinated , such as (TCE), perchloroethylene (PCE), and other chemically-related organic materials. Some of these compounds are even difficult to oxidize by means of ozone alone. Fortunately, ozone can be converted to the more powerful oxidizing agent, the hydroxyl free radical (HO(), which in spite of its microseconds half-life, is capable of destroying these refractory halogenated organics. Conversion of ozone to the hydroxyl free radical occurs whenever UV-radiation or are present with ozone. In some cases, both UV-radiation and hydrogen peroxide are effective for conducting these so-called “advanced oxidations”.

Therefore, for groundwaters contaminated with either easily oxidized impurities or with difficult-to-oxidize organic impurities, ozone and/or ozone advanced oxidation are technologies able to cope with these types of contaminants as well as to meet disinfection requirements to be mandated by the GWDR when it is finally promulgated (expected in 2001).

Ozone and Small Water Systems

The SDWA Amendments of 1996 required EPA to publish by August 1997 a list of technologies for small water systems (those serving fewer than 10,000 persons) that are capable of meeting the requirements of the Surface Water Treatment Rule. Such a listing was published as directed and is entitled, Small System Compliance Technology List for the Surface Water Treatment Rule. The Amendments also require EPA to identify technologies that are affordable and that can be used to achieve compliance with future EPA drinking water regulations. This second listing is to be published by August 1998. EPA has identified three size ranges of small water systems – those serving 10,000 to 3,301 persons, those serving 3,300 to 501 persons, and those serving fewer than 500 persons.

16 In EPA’s August 1997 listing, ozone appears as a compliance technology capable of meeting the SWTR requirements for all three size categories of small water systems. Such a listing is definite encouragement for the use of ozone by small water systems. The question of affordability of ozone systems, however, is one which still is mystifying to many regulators and water treatment professionals. How can such a complex and -intensive technology as ozone, with the necessity of feed preparation, gas/ contacting, off-gas destruction, instrumentation and automation possibly be miniaturized so as to be affordable by small water systems?

At the time of assembly of the August 1997 Compliance Technology Listing, the IOA was able to show that of the 200+ U.S. water treatment plants using ozone, 90 produce less than 1 mgd of water, and that 40 of those 90 plants serve fewer than 500 people. More recently obtained information now shows that the number of ozone systems serving individual homes, small establishments, and very small communities (< 500 persons) now is at least 400 (see Figure 2 at end of paper). Since so many small systems currently are using ozonation systems, the technology, ipso facto, must be affordable, since none of these ozone installations was forced by regulation.

The remaining question by regulators is, why? What is there about small ozone systems that makes them affordable? Of course, once that question is answered, the next logical question will be, “How well do small ozone systems perform compared to alternative treatment systems, in terms of meeting drinking water regulations vis-à-vis microorganisms (Giardia, Cryptosporidium) and disinfection by-products? It is up to the suppliers of small ozonation systems to be able to answer these questions so that EPA regulators can include ozone without reticence, and even with encouragement as opposed to simply allowing it to be listed, but with little or no supporting backup information.

The Water Quality Association has an established Ozone Task Force, headed by the junior author of this paper. Members of the Ozone Task Force have been instrumental in developing the updated list of small ozone installations and some of the information requested by the U.S. EPA so as to better evaluate ozone for small water system use and regulation. Additionally, the International Ozone Association has established an Ozone Small Systems Committee, also currently chaired by the junior author. Many of the members of WQA’s Ozone Task Force also are members of IOA’s Ozone Small Systems Committee. These groups continue to press forward in the assembly of information pertinent to EPA regulatory initiatives so that ozone will never again be overlooked by EPA drinking water regulators, as it was in the ICR.

Operating U.S. Drinking Plants Using Ozone

According to the most recent count by the senior author, there are more than 250 municipal drinking water treatment plants in the United States that were using ozone at the end of 1997. This list is available as an accompanying handout for this presentation. A second listing of smaller (non-municipal) potable water systems employing ozone totals more than 400. Many of these systems are in individual homes (363), in small business establishments or in clusters of homes, treating mostly well water, although a few have indicated surface water as the raw water source.

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Figure 1 traces the growth in numbers of U.S. municipal water treatment plants using ozone since 1980, at which time only 5 were known to be in existence. Figure 2 breaks down these plants by output volume (mgd).

Growth of U.S. Drinking Water Plants Using Ozone + 363 Residential; March 11, 1998 -- R.G. 300 Ri 250

200

150 100

50

0 '80 '81 '82 '83 '84 '85 '86 '87 '88 '89 '90 '91 '92 '93 '94 '95 '96 '97

Figure 1. Growth of ozone in U.S. municipal drinking water treatment plants.

Figure 2. U.S. water plants using ozone by water output.

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Summary and Conclusions

1. Prior to passage of the Safe Drinking Water Act of 1973, only two municipal drinking water plants in the USA were using ozone -- Whiting, Indiana (since 1940) and Strasburg, Pennsylvania (since 1973). Promulgation of the THM Rule in 1979, coupled with two EPA-sponsored survey reports describing European uses of ozone for potable water treatment stimulated initial U.S. interest in ozone to lower the concentrations of THM precursors.

2. Passage of the Safe Drinking Water Act Amendments of 1986 introduced new microorganisms to the U.S. water industry (Giardia cysts, enteric viruses and Legionella bacteria) for which regulation by EPA became a requirement. Ozone was accepted as the most efficient disinfectant for primary disinfection purposes to meet the requirements of the Surface Water Treatment Rule, promulgated in 1991, and the number of U.S. water treatment plants installing ozone began growing at a faster rate.

3. Discussion of the Disinfectants/Disinfection By-Products Rule in the late 1980s and its formal proposal in 1994 further stimulated U.S. interest in ozone as a means to assist in lowering levels of halogenated organic by-products caused by chlorination. Although only a small number of U.S. water plants are expected to select ozonation to meet the Stage 1 requirements of the D/DBP rule (to be promulgated in November 1998), a significantly higher percentage of plants is expected to install ozone to meet the expected Stage 2 requirements (to be negotiated during 1999 and anticipated to be promulgated in 2002).

4. With recent documented outbreaks of cryptosporidiosis caused by Cryptosporidium parvum oocysts has come the realization that ozone is the only known chemical disinfectant capable of inactivating this microorganism without forming additional halogenated organic by-products of regulatory concern. Many U.S. water plants which already have ozone on-line are adding additional ozone capacity to provide an insurance policy against these infective oocysts.

5. Ozone has been listed as a compliance technology for small water systems (serving fewer than 10,000 persons) by which such systems of all size ranges can expect to meet the primary disinfection requirements of the Surface Water Treatment Rule. A listing of affordable technologies by which small water systems can meet current and future EPA drinking water regulations is to be published by EPA in August 1998, and also is expected to include ozone.

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6. Organic by-products of ozonation are low molecular weight aldehydes, ketones, carboxylic acids, ketoacids, aldehyde-acids, etc., all of which are readily biodegradable. Consequently, if ozonation is followed by a properly designed and operated biofiltration step, these organic ozonation by-products can be mineralized (converted biochemically into carbon dioxide and water) in short periods of time (on GAC with as little as 5-minute empty bed contact time, for example).

- 7. Bromate ion, BrO3 , remains the sole deterrent to even more rapid acceptance of ozone as a water treatment technology (other than its additional cost over conventional technologies). This inorganic ozone by-product is formed by ozonation of waters which contain bromide ion. The EPA has established a stage 1 MCL of 10 µg/L for bromate ion, which most municipal water treatment plants can meet by adjustment of ozonation conditions. Consequently, each installation contemplating the use of ozone should check the bromide ion concentration of its raw water and then test the application of ozone to attain its water treatment objective(s) with consideration for the amount of bromate ion which may form under varying experimental conditions. Raw waters containing high levels of bromide might be pretreated effectively by anion exchange.

8. Without any question, the drinking water regulations which have been evolving in the United States have encouraged the application of ozone to remove numerous impurities, to provide primary disinfection, to ensure the inactivation of Cryptosporidium oocysts, and to produce aesthetically acceptable treated water. However, attention should be paid to pretreatment and post(ozone)-treatment to ensure the high quality of product waters so produced in the most cost-effective manner.

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References

BELLAR, T.A.; LICHTENBERG, J.J.; KRONER, R.C., 1974, “The Occurrence of Organohalides in Chlorinated Drinking Water”, J. Am. Water Works Assoc. 66(12):703-706. FINCH, G.R.; BLACK, E.K.; GYÜRÉK, L., 1994, “Ozone and chlorine Inactivation of Cryptosporidium”, in Proc. Water Quality Technology Conf., Nov. 6-10, San Francisco, CA (Denver, CO: Am. Water Works Assoc.), pp. 1303-1318. HAAG, W.R.; HOIGNÉ, J., 1982, “Ozonation of Bromide-Containing Waters: Kinetics of Formation of Hypobromous Acid and Bromate”, Environ. Sci. & Technol. 17:261-267. HAAG, W.R.; HOIGNÉ, J., 1984, “Kinetics and Products of the Reactions of Ozone with Various Forms of Chlorine and Bromine in Water”, Ozone: Science & Engineering 6(2):103- 114. KUROKAWA, Y.; AOKI, S.; MATSUSHIMA, Y.; TAKAMURA, N.; IMAZAWA, T.; HAYASHI, Y., 1986, “Dose-Response Studies on the Carcinogenicity of Bromate in F344 Rats After Long-Term ”, J. Natl. Cancer Inst. 77:977-982. MILLER, G.W., RICE, R.G.; ROBSON, C.M.; SCULLIN, R.L.; KÜHN, W.; WOLF, H., 1978, “An Assessment of Ozone and Chlorine Dioxide Technologies for Treatment of Municipal Water Supplies”, U.S. EPA Report No. 600/2-78-147. RICE, R.G.; ROBSON, C.M.; MILLER, G.W.; HILL, A.G., 1981, “Uses of Ozone in Drinking Water Treatment”, J. Am. Water Works Assoc., 73(1):44-57 (1981). RICE, R.G.; ROBSON, C.M.; MILLER, G.W., CLARK, J.C.; KÜHN, W., 1982, “Biological Processes in the Treatment of Municipal Water Supplies”, U.S. EPA Report No. 600/S2-82-020. RICE, R.G.; DIMITRIOU, M.A., 1997, “Ozone Matures in U.S. Drinking Water Treatment: Impacts of the 1996 Safe Drinking Water Act Amendments”, in Proc. 1997 IOA PAG Annual Conference, Lake Tahoe, NV, Aug. 17-20 (Stamford, CT: Intl. Ozone Assoc., Pan American Group), pp. 1-20. ROOK, J.J., 1974, “Formation of Haloforms During Chlorination of Natural Water”, Water Treatment and Examination 23(Part 2):234-243. U.S. EPA, 1989, "Drinking Water; National Primary Drinking Water Regulations; Filtration, Disinfection; Turbidity, Giardia Lamblia, Viruses, Legionella, and Heterotrophic Bacteria; Final Rule", 54(124):27485-27541. U.S. EPA, 1990, "Guidance Manual for Compliance with Filtration and Disinfection Require- ments for Public Water Systems Using Surface Water Sources" (Denver, CO: Am. Water Works Assoc.), Oct. 1990 Edition, Catalog No. 20271. U.S. EPA, 1996, “National Primary Drinking Water Regulations: Monitoring Requirements for Public Drinking Water Supplies; Final Rule”, Federal Register 61(94):24353-24388. U.S. EPA, 1997, “National Primary Drinking Water Regulations: Disinfectants and Disinfection Byproducts; Notice of Data Availability; Proposed Rule”, Federal Register 62(212):59387- 59557; nb. p. 59397, top of col. 1. VON GUNTEN, U.;. HOIGNÉ, J., 1992, "Factors Controlling the Formation of Bromate During Ozonation of Bromide-Containing Waters", J. Res. & Tech. -- 41(5):299.

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Appendix

Information Developed by the IOA for the M/DBP Advisory Committee in 1997

The following material was compiled in response to questions asked by the M/DBP Expedited Rule Advisory Committee. It is available as “The Reg-Neg Package” for $50 from

Ms. Margit Istok, Executive Director International Ozone Association, Pan American Group 31 Strawberry Hill Avenue Stamford, CT 06902 Tel: 203-348-3542; Fax: 203-967-4845 e-mail: [email protected]

1. Three lists of U.S. water plants known to be (a) in operation (b) under construction and (c) in design as of mid-1997. 2. IOA mini-survey data from 30 U.S. water plants using ozone. 3. Ozone cost data from IOA mini-survey. 4. Issue Paper: Should Biologically Active Filtration (BAF) Be Mandated Whenever Ozone Is Used? (IOA’s position is NO, and supporting information for this position is given). 5. List of U.S. water plants using ozone/BAF and meeting Stage 1 and Stage 2 requirements of the proposed D/DBP rule. 6. Recently published articles on (a) ozone/BAF, (b) DBPs in Canadian drinking water, (c) Bromate levels in European drinking water treatment plants using ozone. 7. Disinfection of Cryptosporidium – Overheads of a May 1997 presentation to the EPA M/DBP Technology Work Group by Prof. C.N. Haas, Drexel University.

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