Water chemicals codex
CI3C
The National Academy of Sciences has recommended specifications for the purity of chemicals used to treat drinking water; the first compilation covers direct additives
Robert Rehwoldt National Research Council Washington, D.C. 20418 The availability and production of potable water are matters of great national and worldwide concern. In the U.S. alone, an estimated 1-2 billion gal of drinking water must be provided each day. To comply with health and other applicable standards for treating that amount of potable water, suppliers used more than 1.2 million tons of chemicals in 1981, according to an American Water Works Association (AWWA) report (Table 1). Large segments of the U.S. population come in contact with chemical additives used for water disinfection, coagulation, softening, corrosion control, fluoridation, and other water treatment functions. Thus, in 1979, a memorandum of understanding was signed by the Food and Drug Administration and the Environmental Protection Agency, by which responsibility for monitoring and controlling these additives, whether direct or indirect, was vested in the EPA. Not long thereafter, in response to a request from EPA, the National Research Council, an arm of the National Academy of Sciences, undertook to recommend minimum acceptable purity specifications for such substances. Accordingly, the Committee on Water Treatment Chemicals was formed and entrusted with the task of developing such specifications, first for direct additives, and later, as feasible, for indirect additives. After two years of deliberations, the committee produced a Water Treatment Chemicals Codex. The codex is meant to supplement existing compendia on water treatment chemicals and is confined to information on purity as it is related to health. It does not address product 616A
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performance, packaging, storage, or handling. Analytical procedures were selected from compendia on methodology and protocol, adopted from manufacturers, or derived from methods set forth in the scientific literature. Data on toxiTABLE 1
Chemicals used for water treatment in 1981 (tons) Coagulation and flocculation Alum Ferric chloride
152 801 15 583
Ferric sulfate
6 196
Polyelectrolytes
4 280
Sodium aluminate
2 650
Ferrous sulfate
1 912
Sodium silicate
1 752
Diatomaceous earth
700
Clay (bentonite)
104
Disinfection and oxidation Hypochlorite
440 222
Chlorine
104 477
Sodium chlorite
6 369
Ammonia gas/liquid
2 497
Potassium permanganate Ammonium salts
793 452
Precipitation and softening Calcium oxide
86 313
Sodium hydroxide
49 093 18 604
Carbon dioxide Soda ash Miscellaneous reagents Fluoride compounds Activated carbon 3
a
349 312
Hydrated lime
15 805 37 327 9 287
Phosphates
8 891
Sodium chloride
6 369
Copper sulfate
1 051
Other chemicals
1 521
Adsorbent Source: AWWA, "1981 Water Utility Operating Data," Denver, Colo., June 1981
cologic aspects were obtained from the scientific literature, from chemical manufacturers, and from the Code of Federal Regulations. Purity requirements The committee recognizes that the assignment of purity requirements depends upon the toxicity of the contaminant and the use patterns of the additive. Although the interpretation of toxicological data concerning these contaminants is at times controversial and depends upon an evolving science, the toxicological data base for water treatment chemical impurities is improving steadily. To arrive at its recommended contaminant limits, the committee met with EPA with the aim of compiling a list of priority chemicals (Table 2). This list was then categorized according to use pattern, that is, those chemicals used in coagulation and flocculation; softening, precipitation and pH control; disinfection and oxidation; and miscellaneous treatment applications. In drafting the monographs in each category, a subgroup of the committee reviewed current data on known impurities in the chemicals, grades of manufactured products, use patterns, and other variables. The committee also developed a list of impurities to be considered. Initially, the list was identical to that of the regulated inorganic impurities specified by the National Interim Drinking Water Regulations developed in response to the Safe Drinking Water Act of 1974. This list was subsequently modified to include those substances for which there is evidence of occurrence as contaminants in water treatment chemicals. The toxicology subgroup of the committee supplied toxicological data on these substances, including information on possible genotoxic or epigenetic (nongenetic cellular damage) effects.
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© 1982 American Chemical Society
NH3FeSO4CaONa Recommended maximum impurities In general, the committee felt that it would be appropriate to utilize the maximum contaminant level ( M C L ) for calculating the allowable contam inant level contributed by an impurity in a water treatment chemical, unless there was no current M C L for that impurity, or where there was new in formation concerning either the tox icity of the contaminant or the current status of the M C L .
An M C L was thus converted to a Recommended Maximum Impurity Content ( R M I C ) for the additive by the following equation:
RMIC MCL Maximum dosage X safety factor _ MCL (mg/L) Χ 106 mg/kg MD (mg/L) X SF where maximum dosage (MD) for the water treatment chemical was based =
Codex format The basic form of the codex is a series of individual monographs, each dealing with a specific compound. Each monograph contains the following information: • chemical name and alternative acceptable names • Chemical Abstract Service number • chemical formula and formula weight • physical properties • function • use range • purity requirements • bulk sampling procedures • analytical procedures a) Sample preparation—special procedures are noted where appropri ate. In cases where the chemical added is not soluble in water, the ana lytical procedures apply to a leachate of that material as obtained under the conditions described. b) Sample analysis—techniques are given either as citations of existing recognized procedures or as procedures developed specifically for the monograph. TABLE 2
Water treatment chemicals included in the codex Aluminum sulfate
Carbon dioxide
Sodium chlorite
Ammonia
Chlorine
Sodium fluoride
Ammonium hydroxide
Ferric chloride
Sodium hydroxide
Ammonium sulfate
Ferric sulfate
Sodium hypochlorite
Calcium hydroxide
Ferrous sulfate
Sodium metabisulfite
Calcium hypochlorite
Fluosilicic acid
Sodium silicofluoride
Calcium oxide
Potassium permanganate
Carbon, activated. granular and powder
Sodium aluminate Sodium carbonate
Sodium polyphosphate, glassy Sulfur dioxide
on maximum patterns known by the committee to be representative of water treatment practice. The safety factor (SF) used in the calculation of the RMIC was 10, re flecting the view of the committee that no more than 10% of a given MCL value should be contributed by a given impurity in a water treatment chemi cal. Some may argue for a higher safety factor, but 10% was deemed reasonable by the committee in view of other uncertainties and approxima tions relating to the fate of impurities introduced during treatment. A sample calculation of an RMIC is performed as follows. Contaminant mercury (Hg): MCL = 0.002 mg/L Water treatment additive: Maximum dosage (MD) = 500 mg/L Safety factor = 0.1 RMIC _ 0.002 mg Hg/L Χ 106 mg/kg 500mgadditive/LX0.1 RMIC = 0.4 mg Hg/kg additive The codex contains RMIC values for impurities of concern at selected additive dose levels, which are reported to one significant figure. RMIC values defining the purity of each water treatment chemical are also contained in individual monographs and may be used as guidelines for the water works industry. At present, the codex con tains 26 monographs; an additional 15 are expected to be completed by the end of this year. The user should note that if actual dosages applied exceed those upon which the monograph is based, appropriate RMIC values should be extrapolated from the table. In addition, although no documented cases were found, if a contaminant is suspected of creating additional health Environ. Sci. Technol., Vol. 16, No. 11, 1982
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concerns because of radioactivity, R M I C values must be calculated in accordance with radiation limits set forth in the Code of Federal Regulations. The R M I C levels are based upon information available to the committee. It is impossible to recommend maximum content levels for unusual or unexpected impurities, the presence of which would depend upon the method of manufacture and the quality of raw materials used. If unusual raw materials or unusual methods of manufacture go into the preparation of a treatment chemical, the user should require appropriate certification of purity from the vendor or manufacturer, to prove that the chemical is suitable for application to the making of potable water. Analytical methods Preferred sampling, sample preparation, and analytical methods for the determination of impurities are cited. Methods that are cited or appear in the codex should be considered as the preferred analytical procedures; alternative methods may be used if they can be shown to be equivalent. It is recognized that a contaminant
in a water treatment chemical may require special sample preparation or analysis methods, because of the nature of the chemical matrix. For such chemicals, the recommended special procedures are included in the codex. Some areas of concern Although for the most part, the committee relied on published MCLs for recommending impurity limits, there were some areas of concern. For example, the R M I C values for lead are based upon an M C L of 0.05 mg L _ l . There is considerable evidence that lead is more widespread than has been previously thought and that lead poisoning is still a serious problem in the U.S. Therefore, even though the committee finally accepted the current M C L as a basis for calculating an R M I C for lead, supporting material submitted to EPA contained a recommendation that the agency critically evaluate the existing lead standard. Another troublesome case is that of carbon tetrachloride, which is a common contaminant in the manufacture of chlorine. The committee felt that if it made no recommendation for maximum content, it would be shirking its
Committee members: William H. Glaze (chairman) University of Texas, Dallas Richardson, Tex. Charles A. Buescher St. Louis County Water Company St. Louis, Mo.
Robert S. Bryant Stauffer Chemical Company Westport, Conn. Arnold E. Greenberg California Department of Health Services Berkeley, Calif.
John H. Mahon Calgon Corporation Pittsburgh, Pa.
J. Carrell Morris Harvard University Cambridge, Mass.
Nina I. McClelland National Sanitation Foundation Ann Arbor, Mich.
Ronald C. Shank University of California Irvine, Calif.
Gerald E. Stobby, 1980-81 Dow Chemical Company Midland, Mich.
R. Rhodes Trussell James M. Montgomery Consulting Engineers Pasadena, Calif.
duty. However, any attempt to define health risks quantitatively in terms of exposure to a carcinogen—which carbon tetrachloride is suspected of being—is extremely complex; in many cases, appropriate data do not exist. EPA has published a notice of proposed rulemaking for volatile organics; and until that process is completed, the committee has recommended an R M I C for carbon tetrachloride in chlorine of 100 mg k g - 1 . The genotoxic or epigenetic potential of water treatment chemical impurities, which can present yet another problem, was evaluated on a caseby-case basis. Appropriate data bases were investigated, and published risk assessments or other exposure models were considered. Review and revision It is expected that the codex will be reviewed continuously and that annual supplements will be issued. The supplements may contain lists of additional chemicals and revisions of the mongraphs contained in the present codex, as well as revisions of analytical procedures. Distribution of the codex is planned for the end of this year. Information about ordering it can be obtained from the National Academy of Sciences, Washington, D.C. 20418. It is hoped that the Water Treatment Chemicals Codex will be used in conjunction with other existing voluntary standards, such as those developed by the American Water Works Association. It is recommended that more extensive data bases on the purity of drinking water additives be developed and that this information be used continuously to revise and update the codex.
In carrying out its task, the committee was greatly aided by contributions from the toxicologists and persons experienced in analytical procedures:
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Frank J. Baumann California Department of Health Services Los Angeles, Calif.
Joseph Connors Editor, Standard Methods for the Examination of Water and Wastewater Oakland, Calif.
Robert K. Hinderer The B.F. Goodrich Company Cleveland, Ohio
Richard Larson University of Illinois Urbana, III.
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Robert Rehwoldt is currently a senior staff officer of the national Research Council, National Academy of Sciences, in Washington, D.C. Prior to assuming his position at NRC he taught and conducted research on the toxicity of metal ions to aquatic communities. He has published a number of papers in that field and has acted as a consultant in environmental problems. He received his B.S. from Queens College in New York and a Ph.D. in analytical chemistry from Lehigh University.
