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Ill Chemical Quality of Water in the Distribution System Even if one could eliminate the causes of contamination associated with pipe breakages, cross-connections, back-siphonages, and other factors in- herent in water distribution systems, there would still be changes in the physical, chemical, and biological properties of the water as the result of either chemical or biological activity. Chemical activity producing changes in water quality within the distribution system is associated with corrosion, leaching, deposition, and reactions involving water treatment chemicals and their residuals. Each of these topics is discussed separately in this section. The materials comprising pipes, pumps, storage reservoirs, and other system components can corrode through contact with water or may leach constituents in water over time. Solubility and kinetic factors will deter- mine whether these constituents will deposit (precipitate) onto pipe walls or whether the materials used in the conveyance system will partially dissolve or corrode into the water. 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. 18

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Chemical Quality of Water in the Distribution System 19 CHEMICAL WATER QUALITY INDEXES A number of water quality indexes have been used to predict whether water will corrode materials used in distribution systems or home plumb- ing units. In most cases, these indexes are used as a criteria for water treatment control, but they can also be used as guide to the selection of materials. Their principal advantage is simplicity, but they are not always perfect predictors. Long-term tests of materials are more costly to con- duct, but provide more direct evidence of water quality and its potential to corrode given materials. The oldest and most widely used index is the Langelier Index, which is based on the solubility of calcium carbonate and the potential of the water to deposit a scale that would protect the pipe. This index has been applied to both metal and asbestos-cement pipe. A simplified version of the Langelier Index, called the Aggressiveness index, was developed especi- ally for asbestos-cement pipe to predict whether the water will either deposit a protective scale or seek calcium carbonate saturation by dissolv- ing the pipe's cement. A third index, the Saturation Index, is based on solubility characteristics of a number of compounds, not just calcium car- bonate. Its potential application for asbestos-cement pipe is discussed below. Langelier Index The Langelier Index was developed in 1936 in order to investigate sys- tematically the chemical relationships involved in the corrosion of iron or galvanized pipe (Langelier, 1936~. It is sometimes referred to as the cal- cium carbonate saturation index or simply as the Saturation Index. (To avoid later confusion with the term Saturation Index, which is used for a number of constituents in addition to calcium carbonate, the term Lange- lier Index is used herein). The Langelier Index (LI) can be defined as follows: LI = pH = pHs, where (1) PHS = saturation pH, the pH at which water of the measured calcium and alkalinity concentration is in equilibrium with solid calcium carbonate and pH = actual or measured pH of the water.

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20 DRINKING WATER AND HEALTH In its simplest form, which is applicable between pH 7.0 and pH 9.5, the equation for calculating pHs is as follows: pHs = (pK2' -pKst) + pCa2+ + pAlk, where (2) pK2' = negative logarithm of second dissociation constant for car- bonic acid (H2CO3), , _ [H+] [CO32 2 [HCO3 - ~ pKs, = negative logarithm of the solubility product of calcium car- bonate (CaC03), Ks' = [Ca2+~[CO32- i, pCa2+ = negative logarithm of the molar concentration of calcium, and pAlk = negative logarithm of the equivalents of alkalinity (titrable base), assuming that [Ark] = tHCO3- i. The terms K2' and Ks' are dependent upon temperature and ionic strength, which is a measure of ionic composition of the water. Correc- tions for temperature and ionic strength are made for each calculation. The utility of the Langelier Index is that it predicts whether calcium carbonate will precipitate, dissolve, or be in equilibrium with solid calcium carbonate. If it precipitates, calcium carbonate can form a pro- tective scale on pipes including asbestos-cement (A/C) or metal pipe. 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 car- bonate and will tend to precipitate and form a scale. When LI = 0, water is at equilibrium. When LI ~ 0, water is undersaturated with respect to solid calcium car- bonate and protective calcium carbonate scales on the pipe may dissolve. Aggressiveness Index The A/C pipe industry developed the concept of an Aggressiveness Index for use as a guide in determining whether A/C pipe would be appropriate

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Chemical Quality of Water in the Distribution System 21 in a given situation. The original purpose of the index was to ensure the structural integrity of the pipe. More recently, it has been used to predict whether water quality degradation would occur from pipe dissolution. The Aggressiveness Index is a simplified form of the Langelier Index and has some shortcomings, which are noted below. The Aggressiveness index (AI) is defined as follows: AI = pH + log (AH), 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. At a selected temperature (14C) and ionic strength (0.01) and by converting to alkalinity and calcium concen- trations in mg/liter, it can be shown that: AI = LI + 12.0 (Schock and Buelow, 1980~. (4) Application of the Aggressiveness Index to determine when A/C pipe should be used has been incorporated into standards published by the American Society for Testing and Materials (1976) and the American Water Works Association (1975b, 1980~. The need for water quality guidelines is also acknowledged by the A/C Pipe Producers Association (198()~. The most recent standards apply the Aggressiveness and Langelier Indexes to relate water quality and the use of A/C pipe (Table III-1~. These standards recommend that nonaggressive water (AI -12.0) be used with Type I (nonautoclaved) or Type II (autoclaved) A/C pipe. Type II pipe is recommended for moderately aggressive water (AI between 10 and 12~. For highly aggressive water, "the serviceability of pipe for such applica- tions should be established by the purchaser in conjunction with the manufacturer" (American Water Works Association, 1980~. Recognizing the relationship between water quality and the use of A/C pipe, the U.S. En- vironmental Protection Agency ( 1 979a) recently proposed that the Ag- gressiveness Index should be -12 for water transported through A/C pipe in order to prevent adverse effects. Data published by Millette et al. (1979) provide a perspective on the typical quality of water in the United States as it pertains to the use of A/C pipe. Through a sampling of representative utilities throughout the

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22 DRINKING WATER AND HEALTH TABLE III-1 The Relationship of Water Quality.(Expressed as Aggressiveness and Langelier Indexes) to Asbestos-Cement (A/C) 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. Furthermore, 16.5% of the water supplies could be classified as very aggressive. They concluded that these data suggest that as many as 68.5% of the U.S. water systems carry water that is potentially capable of corroding A/C Type I pipe and that water supplies with very aggressive waters ~ ~ 10) may be significantly corrosive to any type of pipe, including cast iron, galvanized, and other types of pipes. When using the Aggressiveness Index, one could assume that the me- chanism for A/C pipe deterioration by aggressive waters is related to release of calcium from the cement portion of the pipe. If the water is in fact attacking the pipe, the cement could be dissolving into the water. This would leave the asbestos fibers unprotected or not encapsulated within the cement matrix. This would leave the fibers free to be released into the water. These fibers could be released individually or in bundles. Hallenbeck et al. (1978) theorized that once fibers are released into the water, they can be further broken down so that counts of asbestos fiber from the breakdown products are even higher. Thus, if A/C pipe is used, there is a potential for consumers to be exposed to significant concentra- tions of asbestos in some drinking water supplies. The use of the Aggressiveness Index represents an advance over the original preconception that A/C pipe is not subject to the effects of water quality. As recently as a decade ago, Bean (1970) stated that A/C pipe does not require lining, even with soft water, which could be classified as aggressive water. Since that time, both manufacturers and pipe producers have acknowledged that it is not judicious to use A/C pipe with aggressive water. Thus, the Aggressiveness index has been a means for alerting sup- pliers and users that A/C pipe cannot be used under all situations and

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Chemical Quality of Water in the Distribution System 23 that it is not resistant to corrosion in all cases. It is also simpler to calculate than the Langelier Index. Since the Aggressiveness Index (as well as the Langelier Index) is based on calcium carbonate saturation, it should yield a fairly accurate predic- tion of "nonaggressiveness" provided by a protective calcium carbonate coating if water is oversaturated (Schock and Buelow, 1980~. However, if the water is undersaturated with calcium carbonate, there is no reason to expect the Aggressiveness Index to predict with accuracy the dissolution of A/C pipe since calcium carbonate is only a minor constituent of the ce- ment and calcium silicate is the predominant pipe component. F;urther- more, the Aggressiveness Index does not account for temperature and ionic strength as does the Langelier Index. Finally, the Aggressiveness In- dex fails to account for protective chemical reactions in drinking water. The Aggressiveness Index has been used for several years by pipe manufacturers and the water supply industry. Therefore, the majority of the data on water quality and A/C pipe deterioration contains informa- tion oil the Aggressiveness Index, calcium, and alkalinity of the water. In the absence of a better predictor of pipe performance. this index has been used extensively and is still a simple first approximation for predict . . ~ ring pipe performance. Saturation Index The Saturation Index has been proposed by Schock and Buelow (1980) for use in predicting performance of A/C pipe under given water quality con- ditions. In this approach, both the solubility of pipe components and the possible protective coating of constituents in the water are considered. The cement matrix of A/C pipe is a complicated combination of more than 100 compounds and phases. Since electrochemical corrosion is not an issue, the corrosion of A/C pipe is governed by solubility considera- tions. Possible dissolution reactions in A/C pipe include: Ca(OH)2 (s) - Ca+2 + 20H-, Ca3SiO5(s) + 5H2O - 3Ca+2 + H4SiO4O+ 60H-, Ca2SiO4(s) + 4H2O - 2Ca+2 + H4SiO4O+ 40H-, Ca3Al2O6(s) + 6H2O - 3Ca+2 + 2Al +3 + 120H -, (5) (6) (7) (8) where s indicates the solid phase. The first constituent, Ca(OH)2, is lime, and the others are tricalcium silicate, dicalcium silicate, and tricalcium aluminate. Solubility constants for pure solids in Reactions 5, 6, and 7 are 10-5 20, 10-8 6, and 10- ~6. For

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24 DRINKING WATER AND HEALTH Reaction 8, it is not known. The actual solubility constants in pipe are dif- ficult to estimate, since solids in pipe are highly substituted. Schock and Buelow (1980) concluded that these materials are soluble under typical water quality conditions, but that they dissolve slowly. 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. These phenomena have been observed in several studies that are described below. Schock and Buelow (1980) have also used chemical equilibrium calcula- tions to estimate whether calcium carbonate film would form to protect pipe. Protection by metal precipitation has also been modeled for iron, zinc, manganese, and silica since they could form dense solids. Models were estimated using the aqueous chemical equilibrium com- puter program called REDEQL.EPAK (Schock and Buelow, 19801. The thermodynamic state of saturation was quantified by the Saturation Index (SI), defined as the logarithm of the ratio of the ion activity product (IAP) to the solubility product constant (Kso). For example, for hydroxyapatite, the equilibrium reaction is: Cas(PO4~0H`s' = 5Ca2+ + 3PO4 3- + OH (9) Assuming activity coefficients equal to unity, the Saturation Index (SI) would be: [Ca2+~5[PO4 3- ]3~0H SI = log K so (10) If the solid and solution are in equilibrium, IAP = KSo and SI = 0. If the solution is supersaturated, the SI is ~ 0, and undersaturation occurs if SI <0. The results of SI calculations are shown in Figure III-1. Initial water quality is 1.0 mg/liter calcium, 24 mg/liter total carbonate, 0.24 mg/liter magnesium, 0.5 mg/liter zinc, 0 mg/liter iron, 0 mg/liter phosphate, 20 mg/liter sodium, and 11-33 mg/liter chlorine. Based on this model, zinc hydroxycarbonate [Zns(CO3~2(OH)6] would precipitate if the pH was higher than 8. None of the other species would precipitate. Schock and Buelow (1980) suggested that zinc hydroxycarbonate, once precipitated, could be converted by reactions with silicates in the A/C pipe to a zinc silicate coating, which is hard and should provide good protection. This approach to predicting pipe performance by modeling equilibrium characteristics of a number of protective solids in addition to calcium car- bonate appears to contribute to the understanding of A/C pipe. Schock

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Chemical Quality of Water in the Distribution System 25 6 4 X 2 LO By o of o 2 _ _ G V) -6 -8 ZnS(CO3)2 (OH )6 ZnCO3 - CaCO3 (calcite) Zn(OH )2 ............ Cal OH )2 10 1 1 1/1 1 1 1.. ~; 1 O- 5 6 7 8 9 10 . ' . - pH FIGURE III-1 Saturation Index diagram for model system. and Buelow (1980) have demonstrated the applicability of the Saturation Index to several model systems. Although it is more difficult to use than the LangeJier Index, it is expected to produce more accurate predictions. CORROSION Uhlig (1971) defined corrosion as "the destructive attack of a metal by chemical or electrochemical reaction with its environment." He also noted that the term "rusting" applies to the corrosion of iron or iron-base alloys to form corrosion products consisting mostly of hydrous ferric oxides. Therefore, other metals can corrode, but not rust. 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 poten- tially hazardous chemicals. For example, protective coatings on pipes could leach such hazardous constituents into the water, or chemicals added to the water to inhibit corrosion could be toxic. Before discussing all of these concerns, it is necessary to consider some of the mechanisms of cor- rosion, its inhibition, and measurement.

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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. The reduction of metallic cor- rosion resulting from economic incentives is likely to benefit human health; however, corrosion-inhibiting additives or coatings selected without full awareness of their possibly toxic nature may be counter- productive. The Corrosion Process Corrosion is most often considered to be an electrochemical process. That is, electrons move through the corroding metal, and separate (but not necessarily distant) locations at the metal-water interface act as anodes and cathodes for the oxidation and reduction half cell reactions that oc- cur. For example, as described by Larson (1971), the corrosion of an iron surface in contact with water can involve the following reactions: Anode: Fe - Fe++ + 2e-, Cathode: 2e- + 2H2O - H2 + 20H-. This cathodic reaction will generally occur slowly, but a faster alternative one will occur in the presence of oxygen: Cathode: 2e- + H2O + ~/2 O2 - 20H-. For both cathodic reactions, two hydroxide ions will be produced and an alkaline condition will result near the cathode. However, the ferrous ion can be further oxidized by oxygen and precipitate ferric hydroxide: 2Fe++ + SH2O + I/2 O2 - 2Fe(OH)3 + 4H+. This clearly generates acid. In neutral or near-neutral water, dissolved oxygen is necessary for ap- preciable corrosion of iron (Uhlig, 19711. The initial high rate of corrosion will diminish over a period of days as the rust film is formed and acts as a barrier to oxygen diffusion. The steady-state corrosion rate will be higher as the relative motion of the water increases with respect to the iron sur- face. Increased temperatures can also increase iron corrosion when it is controlled by diffusion of oxygen to the metal surface.

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Chemical Quality of Water in the Distribution System 27 Because the rates of electrochemical processes are related to the elec- trochemical potential at the metal-solution interface, processes affecting potential can hasten or reduce the rate of corrosion. This applies par- ticularly to "cathodic protection," which is an important approach to cor- rosion control. This process involves the external application of electric current, modifying the electrochemical potential at the metal-solution in- terface, thereby arresting the tendency for metal ions to enter solution. In some portions of the water systems, such as water tanks, a more easily cor- roded metal such as magnesium or zinc can be used as a sacrificial anode, and cathodic protection is achieved without the use of an impressed source of current. 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. The rate of the resultant corrosion is increased by greater differences in electrochemical potential between the two metals, as well as by increased mineralization of the water. For such a cell, the anodic metal corrodes, and the cathodic metal is, in effect, protected. Thus, when zinc-coated (galvanized) steel corrodes, the zinc will generally do so at the expense of the iron. Galvanic corrosion can be a problem when, for example, copper is in contact with iron, which will tend to corrode by galvanic action. The other and often more important corrosion cell is the concentration cell. This cell involves a single metal, but different portions of the metal are exposed to different aqueous environments. Such a cell could be generated by one region of an iron surface exposed to oxygen and another one nearly protected from oxygen by rust or other surface coatings. Similarly, differences in pH, metal, or anion concentrations could generate such a concentration cell. As noted above for the corroding iron system, the anodic and cathodic reactions generate different corrosion products, which can enhance the ability of the concentration cell to cause corrosion. Corrosion can also be classified with respect to the resulting outward appearance or altered physical properties of the piping (Uhlig, 19711. Uniform corrosion takes place at a generally equal rate over the surface. Pitting refers to a localized attack resulting, in some cases, in marked depressions. In water containing dissolved oxygen, oxide corrosion prod- ucts can deposit at the pitting site and form tubercles. Dezincification is a corrosive reaction on zinc alloys (e.g., brass, which contains copper) in which the zinc corrodes preferentially and leaves behind a porous residue of copper and corrosion products. Soft waters high in carbon dioxide con- tent may be particularly aggressive to brass. Erosion corrosion can result when the protective (often oxide) film is removed, such as by abrasion oc

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28 DRINKING WATER AND HEALTH curring in fast-moving waters. Normally, many metals in contact with water will form such a protective oxide coating. 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. Biologically Mediated Corrosion The role of microorganisms in the corrosion of metal pipe in the water distribution system has been recognized for some time (Hadley, 19481. Microorganisms may influence corrosion by affecting the rate of cathodic or anodic activity, producing corrosive end products and metabolites, creating electrolytic concentration cells on the metal surface, and disrup- ting or breaking down the protective film (natural or otherwise) at the metal surface. The microorganisms may be heterotrophic or autotrophic and may grow under aerobic or anaerobic conditions. The pipe surface, joints, valves, and gates provide a wide variety of niches for the growth of many different microorganisms that can alter the chemical and physical habitat and produce conditions very different from those observed in the water passing through the pipe. Although water in the distribution network is generally well aerated, containing several milligrams of oxygen per liter, microenvironments without oxygen may oc- cur in the pipe. Concentrations of organic matter promote the growth of aerobic microorganisms that deplete the oxygen and create anaerobic con- ditions. Tuberculation, sediments, and pipe joints can yield protected en- vironments in which neither dissolved oxygen nor disinfectant residuals can penetrate. Under anaerobic conditions, low oxidation-reduction potentials occur, and, in the presence of sulfate, sulfate-reducing bacteria may proliferate. Desulfovibrio desulfuricans can grow autotrophically under the above conditions, reduce the sulfate to sulfite, and oxidize the hydrogen. Uhlig (1971) suggested that an iron surface aids the process by which sulfate- reducing bacteria function. These anaerobic bacteria generally possess hydrogenate enzymes that act on hydrogen and require ferrous iron (Booth and Tiller, 1960~. Since the possible corrosion products of iron pipe are ferrous iron and hydrogen, the sulfate reducers may provide a mechanism for the continual removal of corrosion products, thereby in- fluencing the equilibrium of the corrosion reaction (Lee and O'Connor,

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Chemical Quality of Water in the Distribution System 97 a small part of the total nitrogen is present as free ammonia. Reactions with organic nitrogen compounds involve both cleavage of compounds such as protein and heterocyclic nitrogen-containing compounds and the formation of N-chloro organic species (Morris, 1967), which may be analytically mistaken as free chloramines. There are insufficient data to permit further characterization of these reactions or their effects on water quality in distribution systems. It is clear from even the earliest data on hypochlorite ion and aquatic humic reactions that the ultimate concentra- tion of total trihalomethanes (TTHM) is a function of reaction time, temperature, and pH, given an initial total aqueous carbon value and the presence of chlorine as hypochlorite ion. The analytical methodology for TTHM recognizes these variables and distinguishes between trihalo- methane values measured at any point in time (instantaneous THM) and those values for samples held in bottles for longer periods (5-7 days) (THM formation potential) (Stevens and Symons, 1976~. Recent studies (Brett and Calverly, 1979; DeMarco, personal communication, 1980) have verified that THM values actually increase with residence time in distribu- tion systems as long as both chlorine and organic precursors are available. It cannot be ascertained whether this phenomenon is due to simple homogeneous reaction kinetics of the hectic materials and hypochlorite ion or to more complex heterogeneous reactions controlled by the physical size and shape of the humic macromolecules. It is also possible that com- plex homogeneous reactions occur with rate-controlling steps involving the production of chloroform from several sites in the humic macro- molecules, the reactivities of which are dependent on partial oxidation by hypochlorite ion. 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. In these cases, supported by data on real systems, samples at the consumer tap (3 days system residence) may be approximately twice the THM values leav- ing the plant (Brett and Calverley, 1979~. Reaction of hypochlorite ion with extraneous organic material in a distribution system is probable, although the dominant reaction products may not be THM's. Organic nitrogen compounds have already been men- tioned and additional humic input from soil contact should not be disregarded. Humic/hypochlorite ion reactions form a variety of other chlorinated and unchlorinated reaction products in laboratory experiments (Table III-22. Since the rates of these processes have not been investigated, it is

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98 DRINKING WATER AND HEALTH TABLE III-22 Nonvolatile Reaction Products of Humic Materials and Hypochlorite Ion" h Ch lorinated Nonch lorinated 2-Chloropropanoic acid Dichloroacetic acid Trichloroacetic acid I -Chloroprop-2-ene 1,3-dicarboxylic acid 2,3-Dichlorosuccinic acid Dichloron~aleic acid Dichlorofumaric acid Benzoic acid Hydroxytol uene Trihydroxybenzene Hydroxybenzoic acid Benzene dicarboxylic acid Benzene tricarboxvlic acid Benzene tetracarboxylic acid Benzene pentacarboxylic acid UFron~ Christian et c`/1980. h Analytical procedure involved n~ethylation ~ ith diazn~ethane. Therefore. all acids Here identified as their methyl esters. not possible to state whether their concentrations might be expected to in- crease in distribution systems. Indeed, investigators have not even searched for them in real water distribution systems. As discussed above, the ubiquity of PAM's in water distribution systems is well known (Blumer, 1976~. They may enter drinking water via at- mospheric deposition in open reservoirs or through leaching from lining materials in distribution systems. The presence of hypochlorite ion in distribution systems may affect the qualitative distribution of the PAM's in drinking water. Alben (1980b) reported that abundant oxygenated and halogenated PAM's were found in chlorinated coal tar leachate samples, whereas parent PAM's, alkyl- and nitrogen-substituted PAM's, were predominant in unchlorinated samples. At chlorination levels of 50 mg/liter, the dominant PAH in leachate samples was fluorene, whereas phenanthrene dominated unchlorinated samples. Carlson et al. (1975, 1978) have shown that exposure of PAM's to aqueous chlorine reduces their concentration and produces material more lipophilic than the parent hydrocarbon (Table III-23. The relevance of the reactions and reaction products listed in Table III-23 to real distribu- tion systems has not been established. The effect of increased lipophilicity on bioaccumulation factors is unknown as is the nature of the effect of chlorine substitution on car- cinogenicity of the compounds. However, it is known that the car- cinogenicity of chemical compounds is enhanced by the halogen content. The growth of algae in the reservoirs of distribution systems may result in the release of significant quantities of metabolic products into the

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Chemical Quality of Water in the Distribution System 99 water. The excretion of a wide variety of relatively complex organic struc- tures is apparently common to almost all species of algae and is not con- fined to stressed cells (Barnesq 19781. Excretion of glycolate by Chlorella and Chla'~'ydon~o~zas is well documented, and green algae tend to reduce glycolate excretion in favor of higher molecular weight compounds as the cultures age. Many other types of compounds have been identified in cultures of various species (Table III-241. Decomposition of algal biomass is another source of reactive organic material. Approximately one-half of the biomass may be converted to soluble, short-chain fatty acids in the presence of oxygen and bacteria. The remainder may be converted to refractory humic-like substances. The reactivity of these materials with hypochlorite ion or with chloramines is virtually unexplored. SUMMARY AND CONCLUSIONS Although one can describe possible reactions between various organic substrates and different oxidants in distribution systems, hard scientific data on real distribution systems are extremely limited. Data suggest that THM concentrations continue to increase in the distribution system as long as both organic precursors and chlorine are present. 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-methyl- naphthalene 2-Chlorofluorene U From Carlson er al.. 1978.

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100 DRINKING WATER AND HEALTH TABLE III-24 Some Extracellular Products of Algae`' Compound Type Examples Acid salts Malate, glycerate, lactate, citrate, oxalate, mesotartrate Ketoacids a-Ketoglutaric, cx-ketosuccinic, pyruvic, hydroxypyruvic, cx-ketobutyric, a-ketovaleric N-Compounds Proteins, peptides, nucleic acids, free amino acids Carbohydrates Arabinose, glucose, mannitol, glycerol, com plex polysaccharides Lipids C lo fatty acids (from Ochro''`~`c~s dr ''7ic`~) Enzymes and Acid and alkaline phosphomonoesterase phosphorus (several species), high-molecular-weight compounds organophosphorus compounds Vitamins Ascorbate, pantothenate, nicotinate, thiamine, biotin Volatiles Formaldehyde, acetaldehyde, methyl ethyl ketone, furfuraldehyde, acetone, valeralde hyde, heptanal, geosmin Miscellaneous 2,9-Dicetyl-9-azobicyclot4.2.1.1non-2,3-ene compounds (very fast death factor; from A',ahae'' flosaquae) a From Barnes. ~ 97~3. pipe linings or excretion products from algae in open reservoirs. Unfor- tunately, no existing experimental evidence would permit testing of these assumptions. REFERENCES A-C Pipe Producers Association. 1980. A/C Pipe and Drinking Water. A-C Pipe Producers Association, Arlington, Va. 20 pp. Ackerman, J. 1980. Bellotti weighs suit over water pipe hazard. The Boston Globe, June 16, 1980,pp.17, 24. Alben, K. 1980a. Coal tar coatings of storage tanks. A source of contamination of the potable water supply. Environ. Sci. Technol. 14:468-470. Alben, K. 1980b. Gas chromatographic mass spectrometric analysis of chlorination effects on commercial coal tar lechate. Anal. Chem. 52:1825-1828 American National Standard Institute. 1980. American National Standard for Cement- Mortar Lining for Ductile-Iron and Gray-lron Pipe and Fittings for Water. Standard A21.4-80. American National Standard institute, New York. American Petroleum institute. 1971. Introduction. Pp. 1-2 in Petroleum Asphalt and Health. Medical Research Report No. EA 7103. American Petroleum institute, Washington, D.C.

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Chemical Quality of Water in the Distribution System 103 Distribution System. EPA-670/2-75-036. U.S. Environmental Protection Agency, Cincin- nati, Ohio. 22 pp. Dart. F.J.. and P.D. Foley. 1970. Preventing iron deposition pith sodium silicate. J. Am. Water Works Assoc. 62:663-668 Dart. F.J.. and P.D. Foley. 1972. Silicate as Fe, Mn deposition preventative in distribution systems. J. Am. Water Works Assoc. 64:244-249. Davis. J.B. 1967. Petroleum Microbiolog!. Else~ier Publishing Company, Neu York. Dressman. R.C.. and E.F. McFarren. 1978. Determination of ~invl chloride migration from polyvinyl chloride pipe into cater. J. Am. Water Works Assoc. 70:29-30. Eklund. G.. B. Josefsson, and C. Roos. 1978. The leaching of volatile organic compounds from different types of cater pipes. Vatten 34:207-208. Parish, C.A. 1969. Plastic pipe and cater quality. J. Am. Water Works Assoc. 61:480-482. Goldfarb, A.S., J. Konz, and P. Walker. 1979. Interior Coatings in Potable Water Tanks and Pipelines. Coal Tar Based Materials and Their Alternatives. MTR 7803. Prepared for EPA Criteria and Standards Division, Office of Drinking Water, EPA Contract 570~9-79-001. Mitre Corp., McLean. Va. 140 pp. Gordon. G., R.G. Kieffer, and D.H. Rosenblatt. 1972. The chemistry of chlorine dioxide. Pp. 201-286 in S.J. Lippard, ed. Progress in Inorganic Chemistry. Vol. 15. Wiley- lnterscience, Ned York. Hadley, R.F. 1948. Corrosion by micro-organisms in aqueous and soil environments. Pp. 466-481 in H.H. Uhlig, ed. The Corrosion Handbook. Sponsored by the Electrochemical Society, Inc., Neu York. John Wiley A: Sons, Inc., Neu York. Hallenbeck, W.H., E.H. Chen, C.S. Hesse, K. Patel-Mandlik, and A. R. Wolff. 1978. Is chrysotile asbestos released from asbestos-cement pipe into drinking Hater? J. Am. Water Works Assoc. 70:97-102. Haring, B.J.A. 1978. Human exposure to metals released from Hater distribution systems. ~ ith particular reference to u ater consumption patterns: Trib. CEBEDEAU No. 419:349-355. Henry, C. R. 1950. Preventioin of the settlement of iron. J. Am. Water Works Assoc. 42:887-896. Hoyt, B.P., G.J. Kirmeyer, and J.E. Courchene. 1979. Evaluating home plumbing corrosion problems. J. Am. Water Works Assoc. 71:720-725. Hudson, H.E.. Jr.. and F.W. Gilcreas 1976. Health and economic aspects of Hater hardness and corrosiveness. J. Am. Water Works Assoc. 68:201-204. Iverson, W.P. 1974. Microbial Corrosion of Iron in Microbial Iron Metabolism. Academic Press, Inc., San Francisco, Calif James M. Montgomer . Consulting Engineers, Inc. 1980. Solvent Leaching From Potable Water Plastic Pipes. Final Report. Prepared for the Hazard Alert System. California Department of Health Se~vices/Dcpartment of Industrial Relations. James M. Mont- gome~, Consulting Engineers, Inc., Pasadena, Calif. 67 pp. Karalekas, P.C., Jr., G.F. Craun, A.F. Hammonds, C.R. Ryan, and D. J. Worth. 1976. Lead and other trace metals in drinking cater in the Boston Metropolitan area. J. N. Engl. Water Works Assoc. 90:150-172. Karalekas, P.C., Jr., C.R. Ryan, C.D. Larson, and F.B. Taylor. 1978. Alternative methods for controlling the corrosion of lead pipe. J. N. Engl. Water Works Assoc. 92:159-178. Kay, G.H. 1974. Asbestos in drinking Hater. J. Am. Water Works Assoc. 66:513-514. Kennedy Engineers. 1978. Internal Corrosion Study. Prepared for City of Seattle Water Department, Seattle, Wash. Kimm, V.J. 1978. Memorandum on Coal Tar Pitch Coating, Pascagoula, Miss., to Gary Hutchinson, Water Supply Representative, Region IV, Atlanta, Ga.

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