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III. The Chemistry of Disinfectants in Water: Reactions and Products
Pages 139-250

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From page 139...
... Although there is now a rapidly growing body of scientific literature on chlorine by-products in drinking waters, comparable information for other disinfectants is very scarce. The subcommittee believed that reviewing chlorine by-products in detail, while saying little about other disinfectants, could suggest (probably erroneously)
From page 140...
... , chlorine dioxide, and, finally, ozone. PRECURSOR COMPOUNDS AND THE HALOFORM REACTION Since 1975, many investigators have assumed that the ubiquitous appearance of chlorofo~ (CHCl3)
From page 141...
... The rate-limiting step in the haloform reaction is the ionization that produces carbanions, and, apparently, simple ketones are not representative of those which react quickly to produce chloroform under conditions in water treatment plants. Studies with model compounds, which are discussed in the section pertaining to chlorine chemistry, have shown
From page 142...
... The fraction that is soluble in acid is commonly labelled "fulvic acid," and that material precipitated by acid but soluble in ethyl alcohol is "hymatomelanic acid." Soils vary widely in their relative compositions of these acids, but aquatic organic material behaves operationally as fulvic acid (Black and Christman, 1963) , which typically contains more oxygen and less nitrogen than the humic acid fraction in both soil and aquatic organic matter.
From page 143...
... Significant changes occur in the humification process as reflected by comparative functional group data for lignin and soil humic acid (Table III- 1~. This process, which is oxidative in nature, may strongly affect the characteristics of aquatic humic matenal.
From page 144...
... It is not possible to model natural aquatic humic material with a desirable degree of chemical accuracy, and it certainly is not possible to state that THM's, which appear in chlorinated water containing humic substances, are derived by the classic haloform reaction. The ultimate concern for public health protection is, of course, the fact that THM's are formed during the chlorination of drinking water sources.
From page 145...
... A later study, the EPA National Organic Monitoring Survey (NOMS) , included analyses of samples that had been taken from the water supplies of 113 cities (Brass et al., 1977)
From page 146...
... 146 to CSs _ .5 3 .0 ~ _ :r .O ~ Cd ~C .g ~ ^~ D := V, ~ ·O := o J!
From page 147...
... 147 at V\~.4 E9 -all= at i ' j 5 a 3 ~, ~ ~ R ~ sac a ~ ° a ~ - ~ ~ ~ os e ~— ~ ~ R ~ Is ~ ~ ~ ~
From page 148...
... ion (C1+) , has been proposed as an important reactant in aqueous solutions of organic compounds (Carlson and Caple, 1978)
From page 149...
... The tea "haloform reaction" is often mentioned as the mechanism by which THM's are produced when natural waters are chlorinated. This has not been validated definitively in actual water treatment systems.
From page 150...
... The presence of THM's in laboratory-chlorinated waters that had been taken from a lake in a "peaty region" helped confirm Rook's hypothesis. Later laboratory studies involving the chlorination of aqueous solutions of humic substances (e.g., Babcock and Singer, 1977; Hoehn et al., 1978; Stevens et al., 1976)
From page 151...
... reported results of an extensive 2-yr THM monitoring program at a water treatment plant and at the distribution system of a northern Virginia water supply that was supplied by a reservoir. Mean finished-water THM concentrations varied seasonally and were from 1 to 2 orders of magnitude greater than those found in the source water.
From page 152...
... 152 DRINKING WATER AND HEALTH 300 100 ~ 50 z o IS a: at at O at I, ~ 1.0 o J 10 5 0.5 E ll l'111 o.
From page 153...
... One water treatment plant is on the Delaware River; the other is on the
From page 154...
... is present in the river water. The haloform reaction for acetone is extremely slow (Bell and Lidwell, 1940; Morris and Baum, 1978~.
From page 155...
... Therefore, conclusions that are derived from these laboratory studies should be extended with caution to systems that contain the more complex and diverse forms of phenols that exist in nature. REACTION PRODUCTS FROM CHLORINATED SURFACE WATERS AND SEWAGE EFFLUENTS Because of the difficulties of interpreting in-plant studies involving analyses of influent and effluent grab samples, most of the investigations discussed below are limited to those involving analyses of pairs of influent water or sewage samples that differed only in that one of each pair was chlorinated in the laboratory.
From page 156...
... They observed that aromatic compounds (unspecified) were found in finished water but not in the raw water samples.
From page 157...
... (1976) identified extractable volatile organics in limeclarified, tertiary-treated sewage from the Blue Plains pilot plant near Washington, D.C.
From page 158...
... These compounds are unusual constituents of chlorinated waters. The pentachloroethane is not an ordinary commercial material and, therefore, would probably not have an industrial origin.
From page 159...
... demonstrated a marked increase in concentrations of chlorinated organic compounds at a water treatment plant when Rhine River water was chlorinated to breakpoint. Activated carbon treatment reduced these concentrations, the removal ranging from 28% to 69% of the influent TOC1 concentrations.
From page 160...
... that were high in comparison to dosages used in water treatment plants at pH 7.5 and 11.0 at 10°C. He obtained yields of chloroform ranging from 50% to 100% of the theoretical yields (0.5-1.0 mol of chloroform per mole of precursor)
From page 161...
... (1978b) have reacted several phenolic humic model compounds with hypochlorous acid in dilute aqueous solution.
From page 163...
... are not highly reactive with hydrochlorous acid at nearneutral pH's that are encountered in water treatment. Biphenyl reactions with chlorine under conditions that are normally found at water treatment plants were not significant.
From page 164...
... Their data suggested that the high THM concentrations that were observed during the summer months may have been related, at least in part, to the chlorophyll-a concentrations in the reservoir water near the raw water intakes of treatment plants. Thompson (1978)
From page 165...
... Keith- et al. concluded that although chloral is an industrial product, its appearance in the CCE from these two water supplies is strong evidence that the compound was produced in some manner by chlorination.
From page 166...
... Objectives of this water treatment are to provide disinfecting residual that is more persistent than free chlorine in distribution systems and to reduce the unpleasant tastes and odors that are associated with the formation of chlorophenolic compounds (Symons et al., 1977~. Thus, this process utilizes the formation of monochloramine (NH2C1)
From page 167...
... , postammoniation is the most often used em monia~hlorine water treatment process. The Inventory of Municipal Water Supplies (U.S.
From page 168...
... reported that aqueous dichloramine solutions are more stable than previously thought and, thus, may be more significant in the water treatment process. Nitrogen bichloride is a bright yellow liquid with a strong irritating odor and lach~matory fumes.
From page 169...
... The rate of its formation, shown in Reaction 4, is extremely rapid at the concentrations and conditions of water treatment. At the pH range of most water supplies, the reaction is usually 90% complete in approximately 1 min.
From page 170...
... Thus, nitrogen bichloride is the only chloramine at pH values less than 3. At chlorine-to-ammonia molar ratios greater than 2, nitrogen bichloride occurs in diminishing proportions up to pH values of 7.5.
From page 171...
... , NH2C1 ~ OH- ~ NH2OH + C1 at pH 8 has a reaction half-time of 350 yr. Therefore, not occur in water treatment.
From page 172...
... , 10 of the 80 water supplies sampled had been disinfected with chloramines. The concentration of THM's in the finished water of these utilities
From page 173...
... Because reactions in organic solvents have limited value in predicting by-products of the chloramine water treatment process7 they were not included in Table III-5. Reactions of chloramides, such as chloramine-T (p-CH3C6H4SO2NCl-Na+)
From page 174...
... 174 ·g o V, · — V Cal .~ ·3 o .= o m 4, CJ it: O ·3 ._ O O ._ CJ Cal ~0 o Cal Cal D U
From page 175...
... 175 to ~ G)
From page 176...
... 176 ~ _ ~ Q~ o ~ s :E s To ~ of _ e: of ~ Cal C Cot Cal ~ at Cal _ U
From page 181...
... 181 Cal eo _ .
From page 182...
... The reaction summaries in Table III-6 include several substrates, e.g., carbohydrates that might be present in water supplies. They indicate that reaction by-products such as aldonic acids could occur in the chloramine water treatment process.
From page 183...
... Also in contrast to both bromine and chlorine, the diatomic form of iodine (I2) is fairly stable in aqueous solutions and can be the predominant species in neutral-to-acidic solutions.
From page 184...
... Bromine and iodine By-Products Found in Drinking Water or Selected Nonpotable Waters EXPERIENCE WITH DRINKING WATER SUPPLIES Since neither bromine nor iodine are used to disinfect major public water supplies, it is only possible to establish the tendency of these disinfec
From page 185...
... This indicated that the THM formation kinetics favored bromine selectively. Rook's observations have been confirmed in many water treatment systems throughout the world.
From page 186...
... They treated Ohio River waters with hypochlorous acid (HOC1) , hypochlorous acid plus iodide, monochloramine (NH2C1)
From page 187...
... Ten mg/liter of iodine produced 5 to 10 times less total THM than 10 mg/liter of hypochlorous acid. Treatment with monochloramine or monochloramine plus iodide produced even smaller amounts.
From page 188...
... , and various brominated aromatic compounds. Since the seawater was not dechlorinated prior to its passage through the resin, it is not clear which compounds were formed in the seawater and which were formed in the resin by reaction with bromine in the seawater.
From page 189...
... Discussion and Conclusions The unsatisfactory state of knowledge concerning potentially hazardous substances that might be generated in drinking water through disinfection with bromine or iodine results from the absence of data from operational water treatment systems. However, the evidence suggests that the behavior of these halogens will be qualitatively similar to chlorine.
From page 190...
... Two principal methods are used for the preparation of aqueous solutions of chlorine dioxide for water treatment (Gall, 1978; Masschelein, 1967, 1969~. The first, which is used in the United States almost exclusively, is the reaction of sodium chlorite (NaCl02)
From page 191...
... Failure to observe such precautions casts doubts on a number of reported findings of chlorinated products from the reaction of aqueous chlorine dioxide with organic matter. For industrial use, especially in the pulp and paper industry, where much greater amounts are used than in water treatment, chlorine dioxide is prepared by reduction of sodium chlorate (NaCl03)
From page 192...
... Nonetheless, adaptation of some of these processes to conditions of water treatment is being attempted (Gall, 1978) , and practical methods may develop if demand for chlorine dioxide disinfection increases sufficiently.
From page 193...
... al., 1972~. Presumably, the chlorine dioxide will not persist in open basins or reservoirs, although it can remain for days in clean distribution systems.
From page 194...
... Unfortunately, most of the studies were conducted in acidic solutions in which concentrations of chlorine dioxide and organic substrate were much greater than those encountered during water treatment. Consequently, the extent to which the findings are applicable to the pH values and concentrations of organic compounds that are found in drinking water sources is not clear.
From page 195...
... However, no THM's have been detected as reaction products of chlorine dioxide with organic materials, although investigators have looked for them carefully (Miller et al., 1978; Vilagenes et al., 1977~. One complication is encountered when considering the reactions of chlorine dioxide with organic materials: the normal reaction product of chlorine dioxide, chlorite, may also be a reactive agent in some circumstances.
From page 196...
... Also, at the Water Supply Research Laboratory of the Environmental Protection Agency in Cincinnati, chlorophenols were observed as reaction products at a chlorine dioxide to phenol molar ratio of 0.8, but not at 3:1 or 14:1 (Miller et al., 19781. Interestingly, hydroquinone [C6H4-1,4-(OH)
From page 197...
... Consequently, their findings are not clearly relevant to water treatment with chlorine dioxide. Studies with other materials have been sparse and have been confined mostly to acid conditions, pH 1 to 4, and to the concentrations between 1O-3 and 10-i M, which are characteristic of pulp and paper bleaching.
From page 198...
... (1978) reported that several C2 to Cs aliphatic aldehydes were products of the treatment of Ohio River water with chlorine dioxide.
From page 199...
... Discussion Much remains to be learned about the nature of the organic products that are formed in water supplies during oxidative treatment with chlorine dioxide. Clearly, chlorine dioxide, like other aqueous chemical oxidants, is selective in its attack on organic materials, so that only a small fraction, if any, is oxidized completely to carbon dioxide and water.
From page 200...
... , few definitive mechanistic studies have been conducted to confirm this view. Thus, a discussion of the chemistry of ozone by-products that are formed during water treatment is severely limited by a lack of specifically designed studies and by the poor definition of the organic materials involved.
From page 201...
... In practice, ozone doses of a few milligrams per liter are most commonly used in water treatment applications. Ozone gas is generated at the site of application because concentrated mixtures of the substance are subject to detonation.
From page 202...
... However, few studies have been conducted over the full range of conditions that are likely to prevail in a typical water treatment plant. The strong influence of pH and interfering substances such as ammonia (NH3)
From page 203...
... apparently increased. Removal of organics at the water treatment plant in Rouen-laChapelle, France, has been discussed by Rice et al.
From page 204...
... A recent monograph by Rice and Cotruvo (1978) contains papers from a 1976 conference on the products arising from organic materials treated with ozone or chlorine dioxide (C102~.
From page 205...
... Organic amines have yielded both nitrate and nitrite (Rogozhkin et al., 1970~. Again, the dose of ozone could determine the relative yield of the oxidized forms in many cases.
From page 206...
... 206 c, A ~ ~ e lo ·!
From page 209...
... is reported to be more toxic than its precursor. Nonetheless, the most important byproducts from many organic substrates may have been overlooked because of shortcomings of the analytical method that was used.
From page 211...
... 211 :E :~ ~ o o .O em o ~= o s ~ 8 o o ~ o ~ ~ .O o ,, S ee S o X ~ o Cal 1 _ ~ or .
From page 212...
... 212 ·~: oo ~ _ ~ _ U
From page 213...
... To c rid 'A ch ~D c :e u, - o is c)
From page 214...
... 214 · — C' o V Cal ._ Ct o o o V Cal .i o o cq Cal o o .
From page 219...
... 219 ca o a~ ~ _ =: ~et C~ 3 ~ o ~ :'' N D ·— I I ~ I _ C~ <> X 8 8 g g xo o ~ D ~ I I I "D O r' ce N N N ~ _ — ~ I ~ I ~a I ~a I ~ ^ ~ ~ ~ ~ {.)
From page 221...
... 221 so C ,= al ~ ' ~ m ~ _ ~ ; = ~ cc ~ m ~ ~ ~0 O ~ . I ~ O X of— O ~ I A: (~ _ ~ D mN , into Oo _ dO~ 8::c,~ = I o 1 ins _O I I < )
From page 227...
... Although it has been recognized since 1974 that chlorine produces potentially harmful by-products, such as the ubiquitous chloroform, little attention has been given to the other prospective disinfectants and oxidants such as ozone, chlorine dioxide, chloramines, and the other halogens, bromine and iodine. Quite apart from the question of the efficacy of these substances as alternative disinfectants, there remains the question, "Will the substitution of a disinfectant for chlorine in water treatment merely produce a different set of by-products whose effects on human health may be as significant, or more so, than those by-products known to be produced from chlorine?
From page 229...
... 229 ok C> lo' \Z~ is.
From page 230...
... · From bromine and iodine: THM's and other bromine and iodine analogs of chlorinated species; bromophenols, bromoindoles, and bromoanisoles; plus the halogens themselves, which may remain in drinking water as residual. · From chlorine dioxide: chlorinated aromatic compounds; chlorate (C1O3-)
From page 231...
... REFERENCES Precursor Compounds and the Haloform Reaction Bell, R.P., and O.M. Lidwell.
From page 232...
... 1978. Precursors and mechanisms of haloform formation in the chlorination of water supplies.
From page 233...
... 1976. The occurrence of volatile organics in five drinking water supplies using gas chromatography/m~ss spectrometry.
From page 234...
... 1978. An assessment of ozone and chlorine dioxide technologies for treatment of municipal water supplies, Part
From page 235...
... 1975. Formation of Halogenated Organics by Chlorination of Water Supplies (A Review)
From page 236...
... in two drinking waters: a known precursor in the haloform reaction. Environ.
From page 237...
... 1978. Chlorination and the formation of N
From page 238...
... 1978. Trihalomethane formation from iodine and chlorine disinfection of Ohio River water.
From page 239...
... 1977. Ozone, Chlorine Dioxide, and Chloramines as Alternatives to Chlorine for Disinfection of Drinking Water: State of the Art.
From page 240...
... Water Quality and Treatment. A Handbook of Public Water Supplies, 3rd ed.
From page 241...
... 1932. The photodecomposition of chlorine dioxide solutions.
From page 242...
... 1958. Generation and use of chlorine dioxide in water treatment.
From page 243...
... Ozone/Chlorine Dioxide Oxidation Products of Organic Materials. Proceedings of a Conference held in Cincinnati, Ohio, November 17-19, 1976.
From page 244...
... 1972. Chlorine dioxide in drin~ng water treatment.
From page 245...
... Ozone/Chlorine Dioxide Oxidation Products of Organic Materials. Proceedings of a Conference held in Cincinnati, Ohio, November 17-19, 1976.
From page 246...
... Ozone/Chlorine Dioxide Oxidation Products of Organic Materials. Proceedings of a Conference held in Cincinnati, Ohio, November 17-19, 1976.
From page 247...
... Ozone/Chlorine Dioxide Oxidation Products of Organic Materials. Proceedings of a Conference held in Cincinnati, Ohio, November 17-19, 1976.
From page 248...
... Ozone/Chlorine Dioxide Oxidation Products of Organic Materials. Proceedings of a Conference held in Cincinnati, Ohio, November 17-19, 1976.
From page 249...
... 1977. Ozone, Chlorine Dioxide and Chloramine as Alternatives to Chlorine for Disinfection of Water: State of the Art.


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