Drinking Water and Health, Volume 4 (1982) / Chapter Skim
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III Chemical Quality of Water in the Distribution System
III Chemical Quality of Water in the Distribution System
Pages 18-107
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From page 18... ...
Chlorine and other treatment chemicals added at the water treatment plant or in the distribution system itself can continue to react with organic compounds in the water. Thus, the chemical content of water at the consumer's tap may be different from that of water leaving the treatment plant or other source as a result of its contact with materials in the distribution system and the time available for reactions to progress.
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From page 19... ...
A simplified version of the Langelier Index, called the Aggressiveness index, was developed especially for asbestos-cement pipe to predict whether the water will either deposit a protective scale or seek calcium carbonate saturation by dissolving the pipe's cement. A third index, the Saturation Index, is based on solubility characteristics of a number of compounds, not just calcium carbonate.
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From page 20... ...
If calcium carbonate dissolves in water of a given quality, calcium carbonate scale, previously deposited at the water-pipe interface, will be removed, thus exposing the pipe surface to the corrosive effects of the water. The Langelier Index is interpreted as follows: When LI > 0, water is supersaturated with respect to solid calcium carbonate and will tend to precipitate and form a scale.
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From page 21... ...
, where AI = Aggressiveness Index, A = total alkalinity, mg/liter as calcium carbonate, and H = calcium hardness, mg/liter as calcium carbonate. The Aggressiveness Index does not incorporate the corrections for temperature and ionic strength.
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From page 22... ...
Pipea Aggressiveness to Aggressiveness Langelier A/C Pipe Index Index Highly aggressive water < 10.0 < - 2.0 Moderately aggressive water 10.0 to 11.9 - 2.0 to-0.1 Nonaggressive water -12.0 -O a From American Water Works Association, 1980. United States, they determined that 52(~o of the water supplies had water that was at least moderately aggressive (Aggressiveness Index between 10 and 121.
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From page 23... ...
Since the Aggressiveness Index (as well as the Langelier Index) is based on calcium carbonate saturation, it should yield a fairly accurate prediction of "nonaggressiveness" provided by a protective calcium carbonate coating if water is oversaturated (Schock and Buelow, 1980~.
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From page 24... ...
Pipe dissolution by Reactions 5 through 8 would increase pH, calcium, and alkalinity of water in contact with the pipe. The Langelier Index or Aggressiveness Index would also increase.
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From page 25... ...
A principal concern about corrosion in water distribution systems is the possibility that its products will have an adverse impact on the health of consumers exposed to them. Moreover, materials introduced into this system to mitigate corrosion might themselves provide a source of potentially hazardous chemicals.
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From page 26... ...
26 DRINKING WATER AND HEALTH Although the economic impact of corrosion in water distribution systems is not of direct concern in this report, it is of some importance because it provides an incentive for reducing corrosion. Ultimately, this may have either a positive or negative effect on the generation of corrosion products to which the consumer is exposed.
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From page 27... ...
Two principal types of electrochemical corrosion cells are of concern in water distribution systems (Larson, 1971; Uhlig, 19711. The first results from a galvanic cell, which is due to the contact of two different metals.
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From page 28... ...
One example of erosion corrosion occurs near joints and elbows of copper pipes when water flows at high velocities. It is apparent from the above discussion that the corrosion process is highly complex and is influenced by a large number of factors, including the nature of the corrodible materials, the physicochemical quality of the water, and the physical structure and hydrodynamics of the distribution system.
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From page 29... ...
Olsen and Sybalski (1949) suggested that the "iron bacteria" initiated tubercle formation on pipe walls and that this process was the critical factor for the corrosion of iron pipes.
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From page 30... ...
A water with a positive Langelier Index is oversaturated with calcium carbonate, which would tend to form a protective coating on the pipe, thereby reducing corrosion. A water with a negative Langelier Index would be undersaturated with calcium carbonate.
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From page 31... ...
Zinc-glassy phosphates have also been used to control corrosion in water distribution systems, presumably by forming a protective film at the pipe surfaces (Schweitzer, 1970~. Although most of the corrosion inhibitors that may be added to public water supplies are relatively innocuous inorganic chemicals that are unlikely to cause adverse human health effects at the concentrations used, there should be a continuing evaluation of any possible effects, especially taking into account the results of animal and other toxicity tests.
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From page 32... ...
The latter is probably of the greatest concern because of its known toxicity and the results of numerous studies indicating that it can be corroded readily and accumulate in concentrations higher than generally accepted healthrelated maximum contaminant levels, e.g., 0.05 mg/liter, which was specified in the Interim Primary Drinking Water Regulations (U.S. Environmental Protection Agency, 1979a, 1980~.
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From page 33... ...
Lane and Neff (1969) pointed out that blending to a final hardness of 60 to 90 mg/liter (calcium carbonate hardness)
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From page 34... ...
The corrosion problem they encountered arose in a public water supply system in New Jersey after a hard well-water supply (260 mg/liter calcium carbonate hardness) used for many years was replaced by a much softer surface water source (68 mg/liter hardness)
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From page 35... ...
In the first volume of Drinking Water and Health (National Academy of Sciences, 1977) , it was reported that the high concentrations of several heavy metals in household tap water samples from Dallas, Texas, could be attributed to corrosion at various points in the distribution system.
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From page 36... ...
and lead concentrations were clearly higher in the running water samples than in the raw water. Dangel concluded that most of the increases in metal concentration occulted in the service lines and plumbing inside the buildings.
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From page 37... ...
of the EPA Interim Primary or Secondary Dr~nking Water Regulations (U.S. Environmental Protection Agency, 1979a,b, 1980)
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From page 39... ...
in Various Water Samples Servicing Several Residences in Bennington, Vermont Interior Plumbing Service Line Street Main 0.17 0.11 0.16 0.12 0.17 0.15 0.15 0.19 0.33 0.17 0.44 0.10 0.18 0.14 0.54 0.45 0.13 0.86 0.60 0.46 0.10 0.0s 0.11 0.06 0.07 0.20 0.45 0.16 0.59 0.15 a From McFa'Ten et al., 1977.
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From page 40... ...
. CEPA Interim Primary Drinking Water Regulations (U.S.
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From page 41... ...
The authors concluded that additional water treatment, such as raising the pH to 8.5, was needed to prevent corrosion of lead in these systems. In 1976 and 1977, an attempt was made to reduce this lead corrosion in the Boston area.
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From page 42... ...
The potential release of asbestos fibers from A/C pipe in the water distribution system is but one potential source of asbestos contamination in potable water supplies. Other sources include natural erosion of asbestos-containing minerals and dumping of asbestos-containing materials from industrial projects, such as those contributing asbestos fibers to the drinking water of Duluth, Minnesota, and other nearby communities using Lake Superior water supplies (Cook et al., 1974~.
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From page 43... ...
At the time of the publication of the first volume of Drinking Water and Health (National Academy of Sciences, 1977) , the concern about the release of fibers from A/C pipe was noted, and the relationship between soft water and dissolution of the calcium carbonate in the pipe was mentioned.
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From page 44... ...
USE OF ASBESTOS-CEMENT PIPE Originally introduced in Italy during the early 1900's, A/C pipe is now widely used in potable water distribution systems throughout the world. The formulation of A/C pipe from Portland cement and asbestos fibers was originally developed in an effort to provide a corrosion-resistant material of sufficient strength to be used for transmission of water.
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From page 45... ...
Typically, the asbestos fibers comprise less than 20C7o of the A/C pipe (A-C Pipe Producers Association, 1980; American Water Works Association, 1978a,b)
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From page 46... ...
The pipe shall be formed under pressure and cured. The finished pipe shall be free from organic materials (American Water Works Association, 1980)
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From page 47... ...
The data do not supply sufficient information to calculate either the Langelier Index or the Aggressiveness Index. Fiber analyses were performed using particle and fiber counts from magnified electron microscope photographs combined with a radioactive tracer technique.
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From page 48... ...
48 a, no .= A; I: .
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From page 49... ...
This observation is based on the fact that water with a high Aggressiveness Index, but not saturated with calcium carbonate, has attacked A/C pipe. · Control of calcium carbonate saturation may, under certain situations, prevent deterioration of A/C pipe.
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From page 50... ...
, as was its alkalinity (approximately 4 mg of calcium carbonate per liter) and calcium content (2 mg/liter)
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From page 51... ...
Based on alkalinity increases in the distribution system, the authors concluded that the water system was losing approximately 455 metric tons of transmission and distribution piping annually as calcium carbonate. No comment was made about the potential introduction of asbestos fibers from the A/C pipe.
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From page 53... ...
population to asbestos in drinking water. Some of the highest concentrations of asbestos fibers were attributed to A/C pipe (Table III-11~.
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From page 54... ...
54 CD = C: hi: o a> ." a: a' a' Ct o ._ Ct C)
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From page 55... ...
have summarized a number of EPAsponsored studies pertaining to deterioration of A/C pipe under varying water quality conditions. In an update on the Connecticut study, they indicated that source waters in 45 Connecticut A/C pipe systems were thought to be very aggressive because the Aggressiveness Indexes were less than 10.
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From page 57... ...
In the systems with an Aggressiveness Index exceeding 11.56, there were either no asbestos fibers or their occurrence was very inconsistent, regardless of the combinations of pH, alkalinity, and calcium hardness. Unfortunately, water quality data from field studies were insufficient to calculate Saturation Indexes.
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From page 58... ...
(1980) agreed that calcium carbonate saturation can be used to prevent attack on A/C pipe.
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From page 59... ...
This may be applicable in situations where the water itself is not attacking the pipe, but where occasional high asbestos fiber concentrations have been attributed to residues remaining from improper maintenance procedures. Some tapping devices on the market today force debris from cutting operations to be flushed from the pipe, preventing contamination of drinking water with those fibers.
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From page 60... ...
Another approach to preventing the occurrence of asbestos fibers in drinking water supplies has been to restrict the use of A/C pipe by legal means. Some cities have either banned the future use of A/C pipe or are in the process of considering such bans.
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From page 61... ...
The Aggressiveness Index, a simplified version of the Langelier Index, has been used extensively in the water supply field. Since both the Langelier Index and the Aggressiveness Index are based on calcium carbonate solubility.
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From page 62... ...
The use of plastics in distribution systems and home services within the United States has been summarized by compiling the results of a questionnaire distributed by the American Water Works Association (1979~. Based on responses received from 514 water suppliers, the approximate percentages of all types of plastic pipe used for distribution system mains were as follows: 80% PVC, 13~o PE, To polybutylene (PB)
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From page 63... ...
In some cases, there is a small residual of unpolymerized monomer in the finished pipe. Some monomers, such as unpolymerized vinyl chloride in PVC pipe, have toxic.properties and are a potential source of concern if they leach out into potable water.
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From page 64... ...
The concentrations were lower at high pH's, but even at pH 9.0 they exceeded the U.S. Public Health Service drinking water standard of 0.05 mg/liter.
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From page 65... ...
Sections of PVC and nonplastic water pipes were thoroughly rinsed with tap water for several hours, then filled with drinking water and stored for 24 hours. Volatile organics were analyzed with closed loop stripping and gas chromatography/mass spectrometry.
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From page 66... ...
. Several volatile halogenated organic compounds were detected at levels higher than those found in the raw water, suggesting that they had leached from the PVC pipe.
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From page 67... ...
Pipes ranged in diameter from 15 to 100 mm and in age from 2 months to 5.5 years. In Italy, water from 32 u PVC distribution pipes containing lead in the pipe varying from 0.031~o to 1.619%, had less than 0.07 mg/liter lead in 31 water samples.
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From page 69... ...
Another approach is to require conformance to standards. Both the American Water Works Association (1975a, 1978b)
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From page 70... ...
However, these proposed regulations excluded certain uses such as water pipes. Based on the evidence collected to date, a combination of materials testing and standards specification has been the typical approach to control.
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From page 71... ...
Sometimes the terms "linings" and "coatings" are used interchangeably, but "linings" in its strict definition will be used herein for the sake of accuracy and to avoid confusion. Frequently, steel or ductile iron pipes are lined with cement mortar, asphalt, coal tar, or compounds containing coal tar, vinyls, or epoxies.
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From page 72... ...
Examples include the polynuclear aromatic hydrocarbons (PAH's) found in coal tar compounds.
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From page 73... ...
They have also been used to line steel water-storage tanks. Coal tar linings are made by combining coal tar pitch with other material to provide the desired properties.
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From page 74... ...
According to the Ductile Iron Pipe Research Association, all U.S. manufacturers of cast- and ductile-iron pipe use an asphalt sealing material derived from the distillaton of petroleum products; this material does not contain any coal tar pitch (Stroud, 1980~.
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From page 75... ...
PAH contamination of raw waters has also been found. There are no drinking water regulations for PAM's or other materials released from linings of distribution systems in the United States.
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From page 76... ...
76 DRINKING WATER AND HEALTH TABLE IIl-15 Polynuclear Aromatic Hydrocarbons Found in Water Structure Name Abbreviation = Anthracene An Benzo(a) anthracene B(a)
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From page 77... ...
Chemical Quality of Water in the Distribution System 77 TABLE III-15 Continued Structure Name Abbreviation Ben%o(~ghi) perylene B(ghi)
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From page 78... ...
personal communication, 1980) coated steel panels with coal tar pitch and immersed them in water.
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From page 79... ...
This test suggests that lower concentrations of PAM's are leached from asphalt coatings than from coal tar coatings, presumably because the asphalt initially contains loner concentrations of these PAH's. Eklund et al.
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From page 82... ...
Information from the analyses of the six PAM's included in the drinking water standards of the World Health Organization (1971) is summarized in Table III-18.
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From page 83... ...
( 1979) analzyed concentrated samples of water from three medium-sized water supplies using the Ames Salmonella test for mutagenicity.
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From page 86... ...
86 As Cal o Ct C)
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From page 87... ...
In Pascagoula (McClanahan' 1978) , two water storage tanks were cleaned and lined with coal tar pitch.
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From page 88... ...
The samples collected at the top and the bottom of the tank were affected differently by flow rate and solar heating. The EPA Region IV used the results of these analyses to estimate the concentration of phenanthrene/anthracene in water that had been exposed to a storage tank lined with coal tar pitch for approximately 1.5 days, an average exposure time under regular operating conditions.
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From page 89... ...
Chemical Quality of Water in the Distribution System 89 TABLE III-19 Constituents Leached from Bayou Cassotte Tank' Pascagoula, Mississippi~ Concentration, ~g/liter 9/6/77 1/1 6/78 2/2 1/80 Bottom Top of Bottom Botton, Top of Constituent of Tank Tank of Tank of Tank Tank Poly,',~clec~r Aro'77c~t' H! ,drocarho'~s Naphthalene 5.4 Methylnaphthalene 0.75 (two isomers)
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From page 90... ...
In April 1980, the EPA recommended that installation of vinyl-lined A/C water pipe be suspended in New England because concentrations of tetrachloroethylene as high as 66S ~g/liter were found in drinking water carried by the pipe. Tetrachloroethylene has been used to apply the lining to the A/C pipe.
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From page 91... ...
Sumn2an' arid Co'~clusio,2s In the United States and abroad, a number of lining materials are used in drinking water distribution systems to protect pipes and tanks. The most common of these materials are coal tar, petroleum asphalt, vinyl, epoxy, or some combination thereof.
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From page 92... ...
High concentrations of iron and manganese affecting water quality in distribution systems are found not only in groundwaters but also in surface water supplies from deep lakes and eutrophic lakes and in surface waters exposed to mine drainage or acid industrial wastes (O'Connor, 1971~. Calcium carbonate deposition and its effect on water quality have been discussed earlier in this chapter in the sections on chemical water quality indexes and corrosion.
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From page 93... ...
In Nebraska, a survey of 29 water treatment plants practicing iron and manganese removal indicated only 60~o were effective based on their ability to meet EPA secondary criteria of 0.3 mg/liter for iron and 0.05 mg/liter for manganese (Anderson et al., 1973~. Even when the concentrations of iron and manganese in the raw water were quite low in one plant, the deposits accumulated and were flushed in the distribution system following fluctuations in the water's flow pattern.
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From page 94... ...
manganese in a well water when chlorination and elevated pH resulted in the desired oxidation of the manganese. Although a variety of inorganic phosphorus compounds can be used in water treatment, Aulenbach (1971)
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From page 95... ...
Whether this can cause a substantial increase in the exposures of humans to these metals is not known. Reactions Involving Water Treatment Chemicals in the Distribution System Reactions initiated in a water treatment plant may not achieve chemical equilibrium at the treatment site.
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From page 96... ...
The reactions of chlorine with organic carbon in the treatment plant (Rook, 1974; Thomason et al., 1978) and with model organic compounds (Larson and Rockwell, 1979; Norwood et al., 1980; Rook, 1974)
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From page 97... ...
It is attractive to assume that the THM increase is not due solely to additional reaction of hypochlorite ion with extraneous organic precursors in distribution systems, since good correlations have been observed for municipal systems (Brett and Calverley, 1979) between treatment plant effluent samples aged in the laboratory and samples withdrawn from the distribution system after equivalent periods.
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From page 98... ...
As discussed above, the ubiquity of PAM's in water distribution systems is well known (Blumer, 1976~. They may enter drinking water via atmospheric deposition in open reservoirs or through leaching from lining materials in distribution systems.
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From page 99... ...
It is probable that the nonvolatile reaction products of humic material and chlorine also increase in distribution systems, although there are no data for real systems. It is attractive to assume that chlorine will react with trace amounts of other organic substrates in various distribution systems, e.g., PAM's from TABLE III-23 Chlorination Products of Selected Polynuclear Aromatic Hydrocarbons Chlorine PAH, PAH mg/liter ng/liter Product Anthracene 2.0 552 Anthraquinone Phenanthrene 19.3 820 9-Chlorophenanthrene Fluoranthene 17.7 824 2-Hydroxy-3-chloro fluoranthene 1-Methylphenanthrene 21 994 1-Methyl-9-chloro 1-Methylnaphthalene 24 Fluorene 531 24 1,166 phenanthrene 1 -Chloro-4-methylnaphthalene 2-Chlorofluorene U From Carlson er al..
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From page 100... ...
1980. A/C Pipe and Drinking Water.
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From page 101... ...
Water Treatment Plant Design for the Practicing Engineer. Ann Arbor Science Publishers, inc., Ann Arbor, Mich.
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From page 102... ...
1977. Health effects associated with manganese in drinking water.
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From page 103... ...
MTR 7803. Prepared for EPA Criteria and Standards Division, Office of Drinking Water, EPA Contract 570~9-79-001.
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From page 104... ...
Memorandum on Coal Tar Pitch Coating, Pascagoula, Miss., to J.A. Cotruvo, Director, Criteria and Standards Division, Office of Drinking Water, U.S.
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From page 105... ...
Study of the Water Distribution System as a Potential Source of Mutagens/Carcinogens in Drinking Waters. EPA Grant No.
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From page 106... ...
1979d. Statements of Basis and Purpose for Proposed Amendments to the National Interim Primary Drinking Water Regulations and Proposed Special Monitoring Requirements.
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From page 107... ...
1971. International Standards for Drinking Water.
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