EnvironmentalHealthPerspectives Vol. 69, pp. 31-44, 1986



# Occurrence of 

# By-Products of 

# Strong 

# Oxidants Reacting with 

# Drinking 

# Water 

# Contaminants-Scope of the 

# Problem

by 

# Rip 

# G. Rice* and Maria 

# Gomez-Taylort

This paperdescribes results ofadetailed literature review ofthe organic and inorganic by-products that have been identified as being formed in aqueous solution with four of the strong oxidizing/disinfecting agents commonly employed in drinking water treatment. These agents are: chlorine, chlorine dioxide, chloramine, and ozone. Significant findings include the production of similar nonchlorinated organic oxidation products from chlorine, chlorine dioxide, and ozone. In addition, all three chlorinous oxidants/disinfectants canproduce chlorinated by-products under certain conditions. The presence of chloronitrile compounds in drinking waters is indicated to arise from reactions of chlorine or chloramine to amine/amide functions in amino acids or proteinaceous materials, followed by dehydrohalogenation. These nitriles could hydrolyze to produce the corresponding chloroacetic acids. It is concluded that to minimize the presence of oxidation by-products in drinking waters, the concentrations ofoxidizable organic/inorganic impurities shouldbe loweredbefore any oxidizing agent is added.



## Introduction

This paperis concernedwiththeby-products ofchemical oxidizing agents that are used in the treatment of 

### drinkingwater 

### (chlorine, chlorine 

### dioxide, ozone, chloramine), sometimes for

### disinfection, sometimes forchemical oxidation, and sometimes for both purposes. Most ofthe chemicals currentlyused as disinfectants also are powerful 

### oxidizingagents, and manytimes, watertreatment processes use these chemical 

### oxidizingagentsduring pretreatment, rather than 

### during the terminal disinfectant step. For example, potassium permanganate and ozone are used for iron and manganese or taste and odor removal. It is thus important for health effects 

### professionals to 

### recognize that the so-called disinfection 

### by-products will be present 

### following oxidative pretreatment, even though disinfection may not yet have been practiced 

### during the water treatment process. As a 

### result, the water treatment 

### specialist must understand the chemistries involved in the 

### following topics: the 

### by-products ofthe chemical 

### oxidizing agents as they are reduced while 

### doing their oxidation/disinfectionworkduringwatertreatment; reactions ofchemical 

### oxidizing agents with organic materials present at the point of addition of 

### oxidant/disinfectant, i.e., by-prod-

*Rice International Consulting Enterprises, 1331 Patuxent Drive, Ashton, MD 20861. tU.S. Environmental ProtectionAgency, 401 M Street SW, Washington, DC 20460. ucts of 

### organic materials; and reactions of 

### chemical ox

### idizing agents with 

### inorganic materials present at 

### the point of addition of 

### oxidant/disinfectant, i.e., by-products of 

### inorganic materials. 

## Objectives

This 

### paper summarizes the most 

### significant findings of a detailed 

### survey of the 

### literature, funded by the U.S. Environmental Protection 

### Agency (EPA), Office of

### DrinkingWater. The 

### objectives ofthis

### programwere to 

### survey and 

### analyze the 

### published literature 

### dealing with known oxidation 

### chemistries of products 

### formed whenvarious 

### oxidizingagents areused

### during

### drinking water treatment processes. 

### Eight 

### specific oxidizing agentswere 

### studied; first

### prioritywas

### givento

### chlorine, chlorine 

### dioxide, ozone, and 

### chloramine; second

### priority

was 

### given to potassium 

### permanganate, hydrogen per

### oxide, bromine, and iodine. The

### major findings ofthis 

### study

### arepresented inthis


### paper for the four

### first-priority compounds. Eachofthe 

### first-priority oxidants 

### will be discussed in 

### terms of the 

### by-products ofthe oxidants themselves 

### (e.g., thosematerials which form from the oxidant as it is 

### reduced),

as well as 

### by-products isolated as a 

### consequence of oxidation ofthe soluble substrates. In the case of

### halogen 

### oxidants, we will also discuss some of the 

### halogenated materials obtained 

### during treatment of soluble substrates.RICE AND GOMEZ-TAYLOR

Table 1. Relative oxidation power ofvarious oxidizing species.

Oxidation potential, Relative oxidation Species at 25°C, Va powerb Hydroxyl free radical 2.80 2.05 Ozone 2.07 1.52 Hydrogen peroxide 1.77 1.30 Permanganate ion 1.49 1.10 Hypochlorous acid 1.49 1.10 Chlorine 1.36 1.00 Hypobromous acid 1.33 0.98 Chlorine dioxide 1.275 0.94 Monochloramine 1.16 0.85 Hypoiodous acid 0.99 0.73

aRelative to the hydrogen electrode. 

### bBased on chlorine as reference ( = 1.00).


## Chemistry of Oxidants/Disinfectants

Oxidation is defined as a loss of electrons; reduction

as a gain of electrons. 

### During oxidation/reduction reactions, as one component (the soluble substrate

= SS) is chemically oxidized, the oxidizing agent is chemically reduced. Halogen-containing oxidants/disinfectants provide an additional complication, however, in that these materials also can 

### undergo halogenation reactions. It should be recognized, however, that the 

### halogen compounds commonlyused indrinkingwater treatment 

### (particularlychlorine) giverise tobothhalogenationand oxidation/reduction reactions and that these reactions usually occur 

### simultaneously. Furthermore, it has been estimated that in the case of chlorine added to aqueous solutions 

### containing soluble 

### organic substrates 

### capable of 

### being 

### oxidized/chlorinated, only 10% of the chlorine added results in the production of chlorinated compounds 

### (1,2). Thus 90% of the chlorine added reacts solely as an oxidizing agent, producing nonchlorinated 

### organic oxidation 

### products.



### Oxidation Potentials

Some measure of the ability of the various oxidants
to oxidize soluble substrates can be gathered from consideration of their relative oxidation potentials, shown inTable 1 forthe oxidants included inthisproject. However, it should be appreciated that each chemical oxidationreaction

### proceeds at a

### specific reactionrate, governed by kinetics, and affected by a variety of 

### factors, such as concentrations of 

### substrate/oxidant, temperature, 

### pH, the presence of other materials capable of reacting with the 

### oxidant, and the production of oxidation by-products, many of which also can react with the oxidant. It must also be realized that even 

### though some oxi

### dizing agents with high oxidation potentials also are excellent disinfecting agents (ozone, chlorine, 

### hypochlorous acid, chlorine 

### dioxide), other strong oxidants are
poordisinfectants (permanganate, hydrogenperoxide).



### Oxidant 

### Characteristics
Table 2 compares the 

### pertinent attributes of each of the 

### eight oxidants/disinfectants considered inthis 

### study Table 2. Comparison of relative effectiveness of oxidants/ disinfectants.

Disinfecting Oxidizing Halogenation Oxidant efficiency efficiency capability
Chlorine High High Low CGO2 (pure) High High Low C102 (made High High Variable, from NaClO2 depending on

+ excess amount of free chlorine) chlorine C1NH2 Low Low Low Ozone High High Zero (except when bromide is present) KMnO4 Low High Zero H202 Low Moderate Zero Bromine High Low High Iodine High Very low Low

in 

### terms of

### their relative ability to 

### disinfect, to oxidize, and to halogenate.


## By-Products of 

## Strong Oxidants/ Disinfectants

Pertinent 

### literature reports for each of the four pri
### mary 

### oxidants/disinfectants (chlorine, chlorine dioxide, 

### chloramine, and

### ozone) willbe summarizedwith

### respect totheirreactionswithspecifictypesof

### organicmaterials that are or canbe expected to be encountered indrink

### ingwater

### supplies: by-products ofthe

### disinfectantitself, reactions with inorganic substrates, 

### reactions with or

### ganic 

### aliphatic substrates, reactions with amino 

### acids, reactions with organic aromatic 

### substrates, reactions with 

### heterocyclic substrates, and reactions with humic and fulvic substrates. However, onlythemajor

### findings of the literature 

### study are 

### discussed, 

### particularly as they relate to drinking water treatment.


## Specific By-Products of 

### Oxidants/ 

### Disinfectants
Chlorine. As is widely understood by water treatment 

### specialists, chlorine gas reacts withwaterat apH value just below 7 toproduce hypochlorous acid 

### (HOCI) and chloride ion 

### (C-):

C12 + H20

-- HOCl + ClAs the 

### pH is 

### raised, hypochlorous acid dissociates to 

### hypochlorite ion 

### (OCI) -. 

### However, thisisan

### equilibrium reaction which is controlled entirely 

### by pH:

HOCI + H20 = (OCl)- + H3O

When these 

### species (HOCI, OCI-) oxidize 

### substrates, the chlorine moieties are 

### chemicallyreduced to chloride ion:

HOCl [or (OCl)-] + SS SSOXid + Clwhere 

### SS denotes soluble substrate and 

### SSOxd denotes oxidized soluble substrate. 32STRONG OXIDANT BY-PRODUCTS INDRINKING WATER



### Chloride ion cannot 

### be reoxidized 

### by free 

### chlorine, and, therefore, once 

### formed, it remains as apermanent 

### by-product. 

### Chlorine Dioxide. 

### Unlike chlorine, pure chlorine dioxide 

### (CG02) does not react at 

### significant rates with water or ammonia at neutral pH ranges. However, because 

### chlorine dioxide usually is generated in 

### drinking water treatment plants by reaction of chlorine with chlorite ion, solutions of

### C102maycontain some amount offree chlorine. Thus the use ofchlorine dioxide 

### might be 

### expected to 

### produce some of the same chlorination products as does chlorine, but at much lower concen

### trations, depending upon how much free 

### chlorine is present after synthesis 

### of 

### C102. Photolysis experiments byZika etal. (3) showed that 

### C102 

### decomposes to chlorite 

### ion, C102

. 

### However, chlorite ionalsohas a short lifetime in full sunlight 

### (less than 10 

### min), 

### decomposing to 

### Cl02 and 

### hypochlorite anion 

### (OCI-). Therefore, under 

### sunlight conditions,

even pure chlorine 

### dioxide, synthesized to contain no free chlorine, canphotolyze toproducehypochlorite ion. At acid

### pH, this reactionwill 

### produce HOCI, which can 

### undergo chlorination reactions. 

### Zika et al. 

### (3) also showed that the 

### major stable end products of 

### photolysis 

### of C102 in aqueous 

### solution are 

### Cl-, chlorate ion 

### (ClO37), and oxygen. The first two 

### speciesare

### producedthroughhydrolysisofchlorousacid 

### anhydride 

### (CI203) and thedimeric formofchlorinemonoxide 

### (C1202), with 

### C10- and 

### Cl

. Free radicals also are involved in the reaction sequences. When chlorine dioxide 

### undergoes reaction as a chemical oxidant, it is reduced to chlorite ion. Ifother strong 

### oxidizing agents are present in solution (ozone and/or 

### freeresidual chlorine, forexample) chlorite canbereoxidized back to 

### C102. However, ozone will continue to oxidize chlorite (or 

### C102) to chlorate ion 

### (C103 ). Thus when both ozone and 

### chlorite/CI02 are present 

### initially in 

### aqueous solution, Fiessinger et al. 

### (4) consider 

### C102 to 

### be merely an 

### intermediate reactionproduct between chlorite and chlorate ions.
In 

### conducting studies at 

### operating French water treatment

### plants, Fiessingeretal. 

### (4) showedthat

### granularactivated

### carbon 

### (GAC) decomposes chloriteionbut not chlorate ion. 

### Thus, when both 

### Cl02 and ozone are used in 

### drinking water treatment 

### processes, these researchers recommend either that ozone should be used anditsresidualallowedto

### decaybeforeaddition

### of

### C102,

orthat

### C102 treatment should

### befollowedby

### GACtreatment 

### (to decompose chlorite ion) before 

### ozonation. Monochloramine. Monochloramine can be 

### generated 

### by 

### adding chlorine to a solution 

### containing am

### monia, byadding ammonia to a solution containing free residual 

### chlorine, or

### bypremixingpure solutions ofam

### monia and 

### chlorine, then 

### adding the 

### preformed chloramine 

### solution to the water to be treated. 

### Addition of ammonia to a 

### chlorine solution has the 

### disadvantage offirst

### developingafree

### chlorineresidual, which 

### will produce many chlorinated and/or oxidation 

### products initially. Addition of chlorine to an ammonia Table 3. Major by-products ofprimary oxidants/disinfectants.

Oxidant/disinfectant Major by-products Chlorine HOCI, (OCl)-, C1- Chlorine dioxide (C102)

, (Cl03)O

, C1-, + chlorine

(ifprepared using excess chlorine) Monochloramine Excess chlorine or ammonia, depending

on method ofpreparation; hydrolysis to HOCI/(OCI)- Ozone Oxygen, (OH)-

solution minimizes 

### development of free residual chlorine, except at the 

### specific point ofaddition of chlorine. The third overcomes 

### the disadvantages ofthe first two 

### methods. 

### On the other 

### hand, monochloramine 

### hydrolyzes slowly in aqueous 

### solution, producing hypochlorite (at alkaline pH) or hypochlorous acid (at acid pH). This hydrolysis occurs 

### faster at lower pH levels (5). Thus the 

### opportunity for 

### chlorination reactions occurring through hypochlorous 

### acid/hypochlorite always is 

### present, even with 

### preformed monochloramine solutions. Ozone. 

### Ozone (03) reacts by two different mechanisms in aqueous solution. At low pH (below 6), ozone reactsdirectlyas the 

### ozonemolecule. AthighpH (above 8), ozone dissociates into

### hydroxyl freeradicals 

### [(OH)'], which are the 

### oxidizing species. Between 

### pH 6 and 8,

ozone reacts byeitherorbothpathways, with

### hydroxyl free radicals 

### predominating as the pH approaches 8. 

### Combining ozone with ultraviolet radiation or with 

### hydrogen peroxide 

### accelerates the 

### production of 

### hydroxyl free radicals from ozone. Hydroxyl free radicals also are generated from hydrogen peroxide (H202), which is 

### produced 

### duringmany ozone oxidations of or

### ganic materials, or which can be added 

### during or 

### prior to ozonation. The presence of free radical scavengers, particularly bicarbonate 

### ion, decreases the 

### accelerating effects of hydroxyl freeradicals onoxidationreactions. The

### major 

### by-product of the reduction of ozone is oxygen. 

### Summary. Table 3 shows the 

### major 

### by-products formed 

### during the reduction of the four 

### primary oxidants/disinfectants.



### Reactions of 

### Oxidants with Inorganic 

### Substrates

Chlorine. 

### Bromide ion, nitrite 

### ion, ammonia, sul

### fide, iron(II), and 

### manganese(II) are components fre

### quently encountered in 

### drinking water 

### supplies. Each of these materials is reactive with free chlorine 

### (hypochlorous acid). The divalent metallic ions and sulfide ion are oxidized to their 

### higher valence states. Nitrite ion

### formsnitrate 

### ion, andbromide ionis 

### oxidizedto free bromine. In turn, free bromine 

### hydrolyzes to 

### produce hypobromous acid and 

### hypobromite ion. Ammonia reacts with free chlorine to 

### produce mono

### chloramine, dichloramine, and 

### nitrogen trichloride, de

### pending on the stoichiometries of the reactants as well 33RICE AND GOMEZ-TAYLOR

as on the 

### solution pH. Under proper 

### conditions, monochloramine 

### may be the only product formed. If sufficient excess chlorine is present, all 

### ammonia-nitrogen

canbe 

### converted to elemental nitrogen (the 

### breakpoint chlorination process). 

### ChlorineDioxide. 

### Unlike 

### chlorine, there isnomore than slight 

### reaction of pure chlorine dioxide with ammonia or 

### water. Additionally, the reaction of bromide ion with 

### chlorine dioxide is 

### thermodynamically unfa

### vorable, and does not occur 

### (6). 

### Aqueous solutions 

### containing 1.5 x 

### 10- M C102 and exposed to 

### sunlight produced chloride and chlorate 

### ions

asthemajor

### ionicproducts. However, whenthe solution also contained 1 x 

### 10-4 M bromide 

### ion, bromate ion 

### (BrO3 ), was 

### observed as an additional product. 

### Although the 

### Cl02 was 

### photolyzed during the first few minutes, the concentration of BrO3 

### increased only gradually on 

### continued exposure to sunlight. The Br- concentration first decreased to 50% ofthat 

### added initially, and then increased as the reaction 

### proceeded. This 

### finding was 

### interpreted as 

### showing an initially rapid 

### oxidation of Br- to OBr-, which then reacted 

### photochemically to 

### produce BrO3 and Br-. Monochloramine. Bromide ion reacts 

### slowly with monochloramine 

### (NH2CI), producing 

### bromochloramine 

### (NHBrCl), not hypobromite ion (6). Hypobromite ion reacts

### rapidly

### withNH2CI, probablyproducing

### NHBrCl (7). Nitrite ion

### catalyzes 

### thereactionbetweenchloramine and

### bromide ion, but is not itselfoxidized

### by

### NH2C1 (8). Ozone. As a 

### general rule of 

### thumb, any oxidizable 

### inorganic material will 

### be oxidized when treated with

ozone. Bromide ion is oxidized with ozone 

### rapidly to 

### produce 

### hypobromous 

### acid/hypobromite[HOBr/(OBr)]. Hypobromite ion 

### decomposes back to bromide ion. Therefore, bromide ion can act as a catalyst in the destruction of ozone. Excess ozone oxidizes 

### hypobromite ion to bromate 

### ion, the reaction

### proceeding faster with 

### increasingpH. In the presence of

### ammonia, bromide is oxidized

### byozone to

### hypobromite which, in

### turn, reacts with ammonia to 

### produce bromamine. Nitrite ion reacts almost 

### instantaneouslywith ozone, 

### forming nitrate ion. 

### Ozone reacts 

### slowlywith

### hypochlorite ion, 

### producing 77% chloride ion and 23% chlorate ion. The rate of re

### action decreases with 

### decreasing pH (as the more stable-to-ozonation

### HOCI is formed from

### hypochlorite 

### ion). Therefore, 

### applying ozone to 

### drinkingwater 

### containing free 

### hypochlorite ion 

### destroys both, 

### decreasing the ef

### ficiency ofboth reagents 

### (9). Because ofthe 

### low

### yield ofchlorate ion

### produced dur

### ingozone oxidationof

### hypochlorite ion, significant quantities are not 

### expected to form in

### drinking water treatment

### plants. To ensure 

### thetotal absence ofchlorate 

### ion, however, 

### ozonation should be conducted in the absence 

### of free 

### residual chlorine. Ozone reactswith

### chloramine, producingchloride and nitrate ions. The reaction is 

### independent of 

### pH and is about 20% as fast as the reaction of ozone with

### hypochTable 4. Inorganic oxidation/halogenation products obtained from the four primary oxidant/disinfectants.

Inorganic Oxidation/halogenation constituent product Oxidant Ammonia Chloramines Chlorine Nitrite ion Nitrate ion Chlorine, ozone Bromide ion Hypobromite ion CI02,a ozone, Cl2

Hypobromite + bromate C102,a ozone BrNHCl ClNH2 Hypochlorite ion Chlorate ion (23%) + Ozone

chloride ion (77%) ClNH2 Chloride + nitrate ions Ozone Fe 2; Mn 2 Fe 3; Mn 4 C12, C102, ozone Mn+4 MnO4- (permanganate) Ozone

a In intense 

### sunlight.

lorite ion. Chlorate 

### ion is not produced in this 

### reaction 

### (9). Ozoneoxidizesbromaminetonitrateandbromideions 

### (9). Ozone does not oxidize chloride ion to 

### chlorine, 

### hypochlorite, or 

### chlorate at any meaningful rate 

### under 

### drinkingwatertreatment

### plantozonationconditions 

### (9). Ozone oxidizes chlorite ionto chlorine dioxide; inturn chlorine dioxide is 

### oxidized by ozone to chlorate ion. Therefore, drinking water ozonation should be conducted in the absence of these two chlorine species 

### (chlorite ion and 

### chlorine dioxide) (9). Ferrous iron is 

### oxidized rapidly to ferric ions, 

### which hydrolyze, 

### producing the insoluble ferric 

### hydroxide. Manganous ion is 

### oxidized quickly to manganic 

### ion, which 

### hydrolyzes and precipitates as manganese dioxide. 

### Continuedozonationresolubilizesmanganese inthe form ofpermanganate ion. 

### Cyanide ion is 

### rapidly oxidized to cyanate 

### by ozone, which 

### slowly hydrolyzes to nitrogen and 

### CO2. Ozone oxidizes sulfide ion to free 

### sulfur, then to sulfite 

### ion, and 

### ultimately to sulfate ion. 

### Summary. Chlorine canreactwithammoniatoproduce

### monochloramine, dichloramine, and

### nitrogentrichloride. Bromide ion is oxidized to hypobromite. Nitrite ion is oxidized to 

### nitrate, and ferrous 

### and manganous ions are oxidzed to the ferric 

### and manganic forms, re

### spectively. Chlorine dioxide does not react with water or am

### monia, but does oxidizebromide ionto

### hypobromiteand 

### bromate, but 

### only in intense 

### sunlight and with 

### high concentrations 

### of 

### C102. Chloramine reacts with bromide ion to 

### produce BrNHCI, not hypobromite. Nitrite ion is not oxidized
to nitrate 

### by monochloramine. Ozone oxidizes 

### nearly
anyoxidizable 

### constituent, except 

### ammonia at 

### drinking water

### pHranges. Bromide ionis oxidizedto

### hypobromite, thentobromate ion. 

### Hypochlorite ionis oxidized to chloride ion (77%) and 23% chlorate ion. 

### Chloramine is oxidized to chloride and nitrate ions. Table 4 summarizes the 

### inorganic oxidation/halogenation 

### products that have been obtained from the four oxidants/disinfectants.STRONG OXIDANT BY-PRODUCTS INDRINKING WATER



### Reactions of Oxidants/Disinfectants with 

### Organic Aliphatic Substances
Chlorine. 

### Acyl compounds and 

### 1,3-diketones (and 1,3-dihydroxyaromatic materials) readily undergo the haloform reaction during aqueous chlorination, producing trihalomethanes (THMs) and nonchlorinated acids (10). However, THMs alsoareproducedfromotherpre
### cursors (humic and fulvic acids, for 

### example) and 

### by reactionmechanisms, notyetclearlydefined, otherthan the haloform reaction. Aldehydic groups in unsaturated compounds can be 

### oxidized to 

### acid groups 

### during aqueous 

### chlorination, without incorporating chlorine into the molecule (11- 13). Insimulatingthemigrationofvinyl chloridemonomer 

### (VCM) from 

### PVC 

### pipes into 

### water, Ando and 

### Sayato (14) showedthat 

### injectionof10mg/L quantities ofVCM intodeionizedwater, 

### followedbyvarious concentrations 

### ofsodium

### hypochlorite, convertedthe

### vinylchlorideinto 

### chloroacetaldehyde and chloroacetic acid:

H2C
= CHC1 + HOCI -1 C1CH2CHO + C1CH2COOH



### Itmaybe significant that additional chlorinationdidnot appear to 

### take place. During aqueous 

### chlorination, other unsaturated ali

### phatic compounds appear to add the elements of 

### HOCI (HO and 

### Cl) across the double bond to form 

### chlorohydrins (15,16):

R-C=C-R' + HOC1-*R-C-C-R' J HO C1

These 

### compounds then can react further 

### (15) (1) byde

### hydrochlorination, i.e., a

### chlorohydrincanformanepoxide, which itself may further react with water to produce a 

### glycol):

R C- R' 

### R-RHC1 R C 

### _C R' +HOH

HO Cl 0 R -C- C -R'

HO OH (2) 

### byammoniation; i.e., as in

### thepresence 

### ofammonia,

a 

### chlorohydrin can 

### form aminoalcohols and/or 

### glycols:

R C,-C-R' + NH3

R -C-C-R'and/or R C- R'

HO NH2 HO bH

Carlson and 

### Caple (16) studied the aqueous chlorination of the 

### mono-unsaturated oleic acid over a wide
range of 

### pH values 

### (1.8 to 

### 11.2) and chlorine concentrations 

### (0.51 to 10.2 

### mg/L) and in 

### the presence 

### of ammonia. 

### They identified a number of the 

### expected products of addition across the 

### double 

### bond, along with a 

### low

### yield of the 

### 9,10-epoxystearic acid: CH3(CH2)7CH

- CH(CH2)7COOH



### Aliphatic amines reactwithaqueous chlorinetoproduce N-chloroorganic 

### compounds (N-chloroamines). Under virtually all 

### conditions of temperature and pH encountered in 

### drinking 

### water treatment plants, 99% of the free available 

### chlorine was found to react 

### within 0.5 second with a variety of 

### commonlypresent amines and amino acids to formN-chloroamines andN-chloroamino acids (17). 

### N-Chloroorganic compounds are even less bactericidal than monochloramine. Thus the 

### presence oforganonitrogen compounds reduces the effectiveness of chlorine as a 

### disinfectant. Chlorine Dioxide. C102 generally produces more oxidation and less chlorinationoforganicmaterials than does HOCI. Saturated aliphatic hydrocarbons are neitheroxidizednor

### chlorinatedbyC102. Aliphaticalcohols

can be oxidized with 

### C102 to 

### allphatic acids,which gen

### erally are stable to further oxidation by 

### C102. Unsaturated 

### aliphatic acids (e.g., oleic acid) produce

a variety of 

### compounds during treatment with 

### C102. These 

### compounds include ketones alpha to the point of unsaturation; chloroketones at the originally unsaturated carbon atoms; chlorohydrins; dichloro addition products; and the 

### epoxide. This last type of compound probablyis formedbyaddition of

### HOC1 across the double 

### bond, forming the chlorohydrin, which then dehydrochlorinates to form the 

### epoxide. 

### Formation of this 

### epoxide from oleic acid treated with C102 has been observed 

### by two teams of investigators (18,19).

CH3 -(CH2)7 -CH = CH

- (CH2)7 -COOH + C102

-CH -CH

-

### HCL> -CH CHPrimary aliphatic 

### amines are essentially unreactive with 

### C102. Secondary aliphatic amines react very 

### slowly. Tertiary aliphatic amines react rapidly to produce

### aldehydes and

### secondary

### allphaticamines, without 

### formingN-oxides. However, amines which cannot give
up an 

### a-hydrogen atom 

### during oxidation 

### (such as in 

### quinuclidine) do 

### produce N-oxides during treatment with 

### C102. Chloramine. Aldehydes and ketones 

### produce amides or chloroimines when treated with monochloramine (20,21). 

### Chloroimines derived fromaldehydes can produce nitriles, 

### probably by undergoing dehydrohal

### ogenation (21).

R

- CHO + NH2Cl°CI R -CH= N -C HC1 aldehyde chloroimine R-C N
nitrile



### Some olefins react with

### NH2Cl by adding the

- Cl and 35RICE AND GOMEZ-TAYLOR

-NH2

### moieties across the

### doublebond, producingchlo

### roamines (22).

H H

R-CH=CH-R' + NH2C1- R-I

- -R'

Cl NH2



### Oleic acid

### plus chlorine inthe

### presence ofammonia

### produces 

### the same two 

### 9,10-chlorohydrins isolated from chlorine 

### alone; however, the 

### 9,10-glycol and the 9,10- 

### epoxystearic acid also are 

### obtained (16).

CH3 -(CH2)7 -CH = CH

- (CH2)7 -COOH + HOCI +

NH3 ---CH -CH- + -CH H +

OH O1 OHi I

-CH -CH- +

- CH- HOH H O

Chlorine transfer from the 

### monochloramine-nitrogen
atom to the 

### nitrogen atom of 

### amines, amino 

### acids, and 

### peptides, occurs readilyin

### aqueous solutionoverthe

### pH range 2-10. This 

### transfer occurs 

### both 

### indirectlyby

### hydrolysis of 

### NH2Cl to 

### produce 

### HOCl, as well as 

### by a directreaction

### of

### NH2Cl. Reaction

### products are

### organic N-chloro 

### derivatives, or 

### organochloroamines (17). 

### Ozone. Ozone oxidations of 

### aliphatic compounds proceed through 

### organic ozonides, 

### peroxides, diperoxides, 

### triperoxides, hydroalkyl 

### peroxides, and peroxyacids. These 

### types of

### intermediates are 

### readily isolated in 

### nonaqueous solvents. In 

### aqueous solvents, however, these 

### intermediates are 

### unstable, decomposing 

### rapidly
to form 

### simpler products 

### (aldehydes, ketones, carbox

### ylic acids, and 

### H202). Although ozone is 

### capable of 

### oxidizing many 

### organic 

### compounds 

### completely to 

### CO2 and water, this conversion 

### normally requires large doses of ozone 

### (> 3 moles 

### O3/mole of 

### organic 

### compound) and 

### long reaction times 

### (sometimes hours). 

### Under 

### drinking water treatment 

### plant ozonation 

### conditions (1 to 5 

### mg/L 

### applied ozone 

### dosage; 5 to 20 minutes contact 

### time), 

### organic com

### pounds more 

### often are 

### only

### partially oxidized. The oxidized

### organicmaterials

### usuallyaremore

### polar, oflower molecular

### weight, more 

### biodegradable, andmore read

### ily removed from 

### solution by 

### chemical treatment and 

### filtration. Oxalic acid 

### (HOOC-COOH) is 

### commonly found as a "final" oxidation

### productofmany

### aliphatic 

### (andaromatic and

### heterocyclic) 

### organic materials, because ofits very slowrate ofoxidationwith ozone. Acetic acid is another "final" oxidation 

### product which also is resistant to further 

### oxidation with ozone. Formic acid 

### and 

### formaldehyde also are 

### formed in the later stages of 

### oxidation of many 

### organic materials. 

### However, these two 

### organic 

### compounds are 

### rapidlyoxidized to 

### CO2 and water upon continued ozonation. 

### Ozone oxidation rates of intermediate 

### organic oxidation 

### products usually are slower 

### than the oxidation rates of the original 

### compounds. In general, 

### ozonation of 

### aliphatic unsaturated com

### pounds results in 

### cleavage of the 

### double bond(s), pro

### ducing

### aldehydes, ketones, and/or

### carboxylicacids. Formation of the latter 

### compounds results in a 

### decrease in 

### pH values. Ozonation of oleic acid has 

### produced 

### small quantities of the same 

### epoxide isloated during chlori

### nation of 

### oleic acid 

### (16). 

### Hydrocarbons also have 

### been isolated during ozone oxidation of

### unsaturated aliphatic compounds, although in minor 

### amounts. The 

### longer length of the carbon chains in

### thesehydrocarbonproducts suggests cleavage of the double bond, followed by 

### formation of a hydrocarbon free 

### radical, then 

### coupling of two 

### hydrocarbon free radicals. 

### Chlorinated aliphatic compounds are oxidized by

ozonemore 

### slowlythanare the 

### correspondingnonchlorinated materials. Ozonation or 

### UV/ozonation ruptures 

### carbon-chlorine bonds, forming chloride ion and the

same 

### aldehydes, ketones, and/or carboxylic acids produced 

### by ozonation of their nonchlorinated 

### analogues. The 

### following aliphatic compounds have 

### been shown to be unreactive to ozone, under drinking water treatment plant conditions: oxalic acid, 

### acetic acid, 

### glycerol,

urea, saturated

### aliphaticandalicyclic

### hydrocarbons, pe

### largonic acid, hexanoic acid, octanoic acid, and the ex

### plosive RDX 

### (cyclonite). Discussion. 

### HOCl adds across the double bond of oleic acid to produce the 

### corresponding chlorohydrins and small amounts of the 

### epoxy derivative. 

### Chlorine dioxide

### produces the same 

### chlorohydrins, the

### vic-dichloro 

### derivative, and the 

### epoxide. Chloramine forms the 

### chlorhydrins, the 

### vic-glycol, and small amounts of the 

### epoxide. Ozone produces small amounts ofthe 

### epoxide. 

### Chlorine, ozone, and

### C102producehigher

### yields ofcom

### pounds inwhich the 

### original oleic double bondwas ruptured. Chlorine dioxide with 

### aliphatic compounds 

### generally produces more 

### oxidation products than 

### chlorination products, particularlyifithasbeen

### generatedtobe free of residual chlorine. Amine and amido functions react rapidly with free chlorine 

### (99% in about 0.5 

### sec), forming N-chloro derivatives, which are even less 

### bactericidal than monochloramine. More 

### importantly, when free ammonia and

an 

### organic amine or amide are 

### present, added chlorine
reacts 

### preferentially with the 

### organic nitrogen before it reacts with the ammonia to form chloramines. 

### Chlorine dioxide does not reactwith

### primaryamines,
reacts very slowly with secondary amines, and with 

### tertiary amines 

### ClO2 produces secondary 

### aliphatic amines, without 

### formingN-oxides. 

### With

### aldehydes and 

### ketones, monochloramine

### produces chloroimines, which 

### (from aldehydes) decompose to

### produce

### nitriles. NH2Cl adds across olefinic double bonds to 

### produce chloroamines. 

### The chlorine atom in monochloramine transfers 

### rapidly to the 

### nitrogen function inamines, 

### amino acids, and 

### peptides, producing N-chloro derivatives. These 36STRONG OXIDANT BY-PRODUCTS INDRINKING WATER

react 

### further to 

### produce nitriles (see next section 

### for 

### details). Ozone generally is not reactive with saturated ali

### phatic 

### hydrocarbons. However, other types of

### aliphatic 

### compounds, particularly olefins, are 

### readily oxidized 

### through 

### ozonides, peroxides, and 

### hydroperoxide intermediates to form 

### aldehydes, ketones, and acids. A

### byproduct 

### ofall 

### organic oxidations with ozone is 

### hydrogen peroxide. In the 

### presence of

### more ozone, however, 

### the H202 is 

### decomposed into 

### hydroxyl free 

### radicals, which

are more 

### powerful 

### oxidizingagents thanthe ozonemolecule.



### Reactions of 

### Oxidants/Disinfectants with Amino Acids

Amino 

### acids are liberated 

### bymicroorganisms in natural media and are found in raw water 

### supplies in concentrations of 5 to 

### 2,000 

### ,ug/L, either in the free state

or combined as 

### peptides, nucleic 

### acids, purines, pyrim

### idines, and 

### proteins (23). Flocculation/decantation does not 

### necessarily remove amino 

### acids duringwater treat

### ment, and they can 

### be present at the 

### final disinfection stage. 

### These nontoxic materials can be 

### changed struc

### turally upon treatment with 

### oxidizing (disinfection) agents. 

### Chlorine. Amino acids react with 

### aqueous chlorine to formN-mono- or

### N,N-dichlorinated derivatives, de

### pending on whether chlorine is added in excess. 

### Subsequent 

### decomposition of these 

### compounds is affected 

### by the nature of the 

### original amine 

### group. If it was a 

### primary amine, the 

### decomposition 

### products are alde

### hydes, ketones, carbonic 

### acid, chloride 

### ion, and ammonia. If it was a 

### secondary amino 

### group, the same 

### products are 

### formed, except that the 

### corresponding amine 

### replaces the ammonia 

### (24). 

### Trehy and Bieber 

### (25) identified 

### dichloroacetonitrile

as a 

### product of chlorination of 

### tyrosine in water:

p-HOC6H4

- CH2CH(NH2)COOH + HOCI -1 C12CH

- CN

tyrosine dichloroacetonitrile
Sakuri and Sawamura (26) found that

### monochloroglycine, formed in the first stage of the reaction ofglycine with 

### hypochlorite, was further chlorinated to give di

### chloroglycine by the action of excess hypochlorite. The formed 

### dichloroglycine underwent 

### decarboxylation and 

### dehydrochlorination to form 

### HCN, which then was chlorinated by chlorine or 

### by excess 

### hypochlorite to form cyanogen 

### chloride, C1CN. One mole of

### glycine required three moles ofhypochlorite for the formation of the equivalent CICN.

H2NCH2COOH HOCY Cl NHCH2COOH -C C12NCH2COOH glycine chloroglycine dichloroglycine

HCN C C1CN

cyanogen chloride 

### Qualls and

### Johnson (27) showed that the rate 

### ofchlo

### rination of ammonia was 

### considerably slower 

### than the rate of 

### chlorination of glycylglycine. This peptide out

### competed ammonia for the available 

### HOCI until an excess of 

### HOCI was added 

### beyond that required to 

### form 

### N-chloroglycylglycine. Le

### Cloirec et

### al. (28) isolated

### the

### followingcompounds from the chlorination of alanine 

### [CH3CH 

### (NH2)COOH] using chlorine/amino acid 

### ratios (x) between 0.5 

### and 6: 

### NH2Cl (chloramine), NHCl2 + NCl3 

### (dichloramine + 

### nitrogentrichloride), CH3CHO (acetaldehyde), CH3CN (acetonitrile), CH3CH = NH 

### (acetimine), and 

### CH3COOH (traces) (acetic acid). Alanine was 

### totally destroyedwhenxwas 

### equal to or

### greater than 2. Dich

### loramine and

### nitrogentrichloride appearedatx = 1 and 

### increasedwhen

### xwas 

### above 2.5. Both

### acetaldehyde and acetonitrile were 

### present in 

### solution, the concentration 

### of acetaldehyde peaking at almost 

### the original alanine concentration when x approached 

### 1.5. The 

### concentration of 

### acetonitrile increased rapidly 

### as the concentration of 

### acetaldehyde decreased, peaked when x = 

### 4, and then decreased only 

### slowly afterward. 

### These observations indicated that 

### acetaldehyde may be an intermediate in the 

### formation of acetonitrile. To 

### verifythis 

### hypothesis, a 

### solutionwas 

### prepared containing 

### acetaldehyde and 

### the 

### chloramines formed 

### by the action of 

### NaOCl on 

### NH4' under the same conditions. 

### Acetonitrile formed at 

### essentiallythe 

### same rate 

### as during the 

### chlorination of 

### alanine and at the expense of 

### acetaldehyde. Chlorine Dioxide. 

### Allphatic amino acids oxidize 

### slowly in the presence of 

### C102 free of

### residual chlorine and form nonchlorinated 

### oxidation products. Glycine produced formaldehyde and 

### CO2. Phenylalanine produced small 

### quantities of 

### benzylic 

### acid, benzoic 

### acid, mandelic acid, and traces of

### phenylacetaldehyde. 

### Sulfur-containing amino acids 

### (cystine and methio

### nine) oxidize at the S-atoms to produce bisulfoxide and sulfonic acid 

### derivatives. Monochloramine. Inthe

### presence of

### amines, amino 

### acids, and/or

### peptides, chloramine is even less effective

as a 

### disinfectant, because of its 

### tendency to form N

### organochloramines by chlorine 

### transfer, with concomitant destruction of NH2Cl. For 

### example, with small amounts of

### glycine (0.1-0.25 mg/L) present in ammoniatedwater, the 

### addition ofchlorine 

### formsN-chloroglycine 

### preferentially to 

### forming NH2C1 (29). 

### N,N-Dichloro-a-amino acids 

### decompose 

### rapidly, forming

### uitriles, CO2, and chloride 

### ion. This reaction is at least one order of 

### magnitude faster than the corre

### spondingdecomposition ofN-monochloro-a-amino acids (30). This is a second 

### pathway to the 

### production of nitriles in chlorinated waters. 

### Peptides formN-chloro 

### derivatives with monochlor

### amine 

### only at the terminal

-

### NH2 groups. Amide nitrogen atoms in the 

### body of the 

### peptide chains are unreactive to 

### NH2Cl (30). Ozone. The amino acid 

### alanine is 

### decomposed read

### ilyby ozonation 

### liberatingall ofthe 

### organic nitrogen as both ammoniumandnitrate ions 

### (31). No 

### acetonitrile is 37RICE AND GOMEZ-TAYLOR



### formed by ozonation of alanine (28). Phenylalanine is less readily decomposed by ozone, and 30% to 75% of the 

### organic nitrogen remains 

### combined in the 

### organic oxidation products (31). Small amounts 

### (but larger than trace 

### quantities) of polymeric materials (molecular weight 500 to 70,000)

are 

### produced during ozonation of 

### phenylalanine, indicating that it is possible to synthesize 

### polymeric materials 

### by ozonation of this 

### type of difunctional mono

### meric compound (28). 

### Discussion. Whenaminoacidsor proteinaceousma

### terials (peptides) are treated with chlorine, N-mono

### chloro and/or 

### N,N-dichloro derivatives are 

### produced rapidly. Even when ammonia is present, these N-chloroamino derivatives are produced selectively over the formation ofmonochloramine. Upon furtherreaction of these chlorinated 

### compounds, nitriles, hydrogen cyanide, and 

### cyanogen chloride have been identified, par

### ticularlywhen the molar ratio ofchlorine to amino acid (alanine) is as high as 4. The decomposition rate of N,N-dichloro-a-amino acids is 

### at least one order of

### magnitude faster than that of the corresponding N-monochloro-a-amino acid. It has been proven that acetaldehyde produces ace

### tonitrile in thepresence ofthe intermediate chlorinated amino acids. 

### This leads to 

### speculation that other alde

### hydes may also be nitrile precursors in the presence of chlorinated amino acids. More studies are 

### required to confirm this 

### hypothesis. It thus would 

### appear that to minimize the formation of 

### nitriles, 

### HCN, and cyanogen 

### compounds, the formation of

### N,N-dichloroamino acids should be 

### avoided,

or at least minimized. This can be 

### accomplished either 

### by removing the amino acids 

### before chlorine is 

### added,

or

### byavoidingtheadditionof

### largequantities ofchlorine 

### (i.e., breakpoint chlorination). 

### Since amino acids are 

### ubiquitous in raw water 

### supplies, treatment conditions should 

### be 

### developed for their 

### removal, or at least for rupturing the 

### carbon-nitrogen bond to eliminate the 

### organic amine functional

### group, 

### before additionofchlorine. Neither 

### chlorine dioxide nor ozone

### producesN-chlorinated derivatives ofamino acids. In 

### fact, both oxidants 

### decompose many amino acids and 

### peptides, 

### although 

### C102 appears to be unreactive with many amino acids. With

### alanine, for

### example, 

### C102is

### unreactive, but ozone converts 

### all the 

### organic nitrogen to 

### ammonium and nitrate ions. This would suggest that

### preozonation ofraw water 

### supplies could be used to 

### destroy amino 

### acids, prior to chlorination or chloramination. However, 

### phenylalanine is not as 

### easily oxidized,

evenwithozone; some 30 to 75% ofthe 

### organicnitrogen remains bound in the 

### organic oxidation 

### products. As 

### before, more studies should be conducted to confirm these 

### potentials.



### Reactions of 

### Oxidants/Disinfectants with 

## Organic Aromatic and 

## Cyclic Compounds

The three strong oxidants 

### (chlorine, chlorine 

### dioxide, ozone) act 

### similarly as chemical 

### oxidizing agents with respect to phenols, aromatic amines and amino acids, and

### pesticides. That

### is, aromaticrings arehydroxylated in a first step, then quinones are produced as initial 

### reaction 

### intermediates. With higher dosages and/or longer reaction 

### times, ring rupture generally occurs, leadingto the formationofaliphaticmono- anddi-acids. Chlorine also produces chlorinated 

### aromatic materials, which lead to chlorinated aliphatic compounds 

### upon ring rupture. Yields of ring-chlorinated products

are 

### higher at lowmolar ratios ofchlorine to phenol. At higher ratios, ring-ruptured products predominate. Pure chlorinedioxidebehavesmore like chlorine than

ozone with respect to phenol, in that similar products

are obtained as with 

### the use of HOCI. This statement applies, however, only if

### the concentration ofphenol is in 

### stoichiometric excess over that of the 

### C102. When chlorine dioxide is present in excess, p-benzoquinone and aromatic 

### carboxylic acids areproduced (32). On the other

### hand, aromatic amino 

### acids undergo oxidationre

### actions, rather than 

### chlorination, with pure 

### C102. Chlorine produces small yields of nonchlorinated 

### epoxy derivatives from 

### abietic acid and cholesterol. 

### Ozone also 

### produces the same epoxy 

### compounds from cholesterol and abietic acid (15,16), and from acenaphthylene as well (33). 

### Ozone (34) and chlorine dioxide (35) have been shown to oxidize the pesticides Parathion and Malathion ini

### tially to the more toxic intermediates, paraoxon and malaoxon, respectively. Continued ozonation has been shown to 

### destroy these 

### intermediates, producing 

### simpler decomposition products. Hoffmann and Eichels

### dorfer (36) showed that ozonation of 

### heptachlor produced a 

### quantitative yield of

### heptachlor epoxide, which itself is 

### stable to further decomposition by ozone. A number ofpesticides are resistant to chemical oxidation, even by ozone. If these pesticides are present in water supplies, procedures other than chemical oxidation must be used for their removal. 

### Ozonation of

### phenol can 

### produce 

### resorcinol, which is

a know THM precursor. The initial rate of oxidation of 

### phenolicmaterialswithozone isveryfast, 

### reflectingthe

ease of oxidation of these materials. During continued 

### ozonation, however, their rates of oxidation slow con

### siderably, reflectingthe slower oxidizabilityoftheiroxidation products. 

### Ozonation of chlorinated aromatic 

### compounds ruptures the carbon-chlorine bonds, producing chloride ions and ring-ruptured, aliphatic products. Aniline produces the same oxidation 

### products as 

### phenol during ozonation, plus nitrate ions and ammonia (37,38). Some oxidative 

### coupling of 

### phenolic materials has beenobservedas aresultof

### ozonation, producinghigher molecular 

### weight materials 

### (39). This behavior 

### might partially explain the 

### ability of ozone to microflocculate 

### soluble 

### impurities in water 

### supplies. The ratio of the concentration of 

### 5-day 

### biochemical
oxygen demand to total 

### organic carbon concentration 

### (BOD5/TOC) increases upon ozonation and increases faster after 

### ring rupture has occurred (37). This shows that some 

### biorefractory compounds canbe

### partially ox38STRONG OXIDANT BY-PRODUCTS INDRINKING WATER

idized during ozonation to produce organic materials which are more easily 

### biodegradable. Polycycic aromatic compounds and some pesticides (40) have been shown to be readily adsorbed by humic 

### materials 

### and soil particles, which provide a shielding effect toward ozonation. Monochloramine in the 

### presence of excess ammonia 

### reacts with some aromatic hydrocarbons 

### (benzene, toluene, o-, m-, andp-xylene, andnaphthalene) toproduce


### cyanogen chloride (41,42). With phenol, 

### p-aminophenol is produced initially, and chlorophenols are identified after the solution has stood for several days (43-45). Aromatic acids, which are 

### normally THM precursors, do not 

### produce THMs with 

### chloramine, but rather form the 

### corresponding chlorophenolic aromatic acids (46).



### Reactions of 

### Oxidants/Disinfectants with Heterocyclic Compounds

Amino 

### acids, nucleic acid bases, purines, and pyrimidines have been identified in surface 

### water supplies, 

### particularlywhen

### algae levels inthe rawwater 

### supplies

are high 

### (23). Purines and 

### pyrimidines also are components of nucleic acids in bacteria and are known to produce mutagens upon chlorination. These materials


### may be 

### precursors for nitriles and 

### chloroform (47). 

### Chlorine. 5-Chlorouracil and 

### 5-chlorocytosine were identified in the acid 

### hydrolysates of the nucleic acids 

### separated from bacteria after 

### parts-per-million (ppm) chlorine disinfection of water 

### supplies (48). Patton et al. 

### (49) and Gould et al. 

### (50,51) confirmed that 

### cytosine and uracil react with 

### HOCI in aqueous solution to produce the 5-chloro derivatives. 

### 5-Chlorouracil has been shown to be 

### mutagenic. FranssenandvanderPlas (52) isolated 5-monochloroand 

### 5,5-dichlorobarbituric acids fromthe chlorinationof barbituric acid and its derivatives. 

### Chlorine Dioxide. 

### Nitrogen 

### heterocycles generally produce oxidation 

### products rather than chlorination 

### products upon treatment with 

### C102. Chloramine. Lin and Carlson 

### (53) studied the reaction of a number of 

### environmentally significant het

### erocycles with aqueous 

### chlorine, chlorine dioxide and chloramine. 

### Chloramine 

### generallywas 

### quite unreactive with these 

### heterocycles, except at low 

### pH, where 

### hy

### drolysis to forma 

### significant amount of

### HOCI 

### occurred, yielding increased amounts of chlorinated products. In 

### general, chloramine 

### required much 

### longer reaction times to 

### produce > 95% reaction than did 

### hypochlorite

or 

### C102 at 

### pH 7.0. 

### Summary. Chlorination of uracil and 

### cytosine produces the 

### mutagenic 5-chloro derivatives. Chlorine dioxide 

### generally produces oxidation 

### products rather than chlorinated derivatives. 

### Chloramine reacts 

### very 

### slowly, if at 

### all, with 

### heterocyclic 

### materials, except at lowpH ranges (-3), where 

### hydrolysis to 

### HOCl occurs, 

### allowingchlorination tooccur. Ozone

### produces a

### variety of

### nonchlorinated 

### heterocyclic oxidation 

### products. 

### Reactions of 

### Oxidants/Disinfectants with 

### Humic and Other Natural 

### Materials

Chlorine. Fromthe 

### aqueous chlorinationofvarious aquatic humic materials, 

### Stevens et al. (54) identified 98 specific organic compounds, including 47 discrete compounds 

### containing chlorine and 51 discrete compounds that didnot contain

### chlorine. De Leer et al. (55) 

### identified over 

### 100 different 

### reactionproducts 

### fromthe chlorination of soil humic acid material. Christman et al. (56) showed that the products of exhaustive chlorination ofaquatic humic

### materials generally fall into three broad 

### structural categories: nonchlorinated substituted

### aromatics, chlorinated straightchain 

### acids, and nonchlorinated 

### straight-chain aliphatic acids. From the 

### aqueous chlorination of humic materials, nonvolatile 

### halogen-containing materials account for about 43% of the total organic halogen found. 

### Chloroform 

### represents about 95% of the volatile 

### organics formed. The nonvolatile 

### halogenated fraction is produced in higher yield under acidic conditions compared to that produced under alkaline conditions. 

### Seegeretal. 

### (57) showedthatat lowchlorine

### dosages, which are more typical of those conditions found in 

### drinking water treatment 

### plants and their distribution systems, a large number of ring-chlorinated 

### aromatic acids is obtained, inaddition to the 

### numerous nonchlorinated aromatic and aliphatic 

### compounds identified by earlier 

### investigators. Chlorinated fulvic acid 

### samples contain about 60%

more 

### organic-bound chlorine than do 

### chlorinated humic acid 

### samples, even when the humic chlorination is conducted over twice the reaction time (58). The 

### principal chlorinated 

### products formed during
aqueous chlorination of fulvic acids at pH 7 are: trichloroacetic acid, 69%; dichloroacetic acid, 9.5%; chloroform, 19%; 

### and 

### dichlorosuccinic acid, 4.5%. These compounds 

### represent 53% of the total organic halogen 

### content, andabout 14% ofthe 

### startingorganicmaterials 

### (about 4% of the original TOC). Note that the amount of trichloroacetic acid is more than 

### triple that of chloroform (59). 

### Cyano-substituted compounds (nitriles) 

### recentlyhave been identified as 

### products of aqueous chlorination of humic/fulvic materials (54,55,60). These 

### compounds include: 

### chloroacetonitrile, dichloroacetonitrile, 

### trichloroacetonitrile, 

### dichloropropanenitrile, dichloropropenenitrile, 

### trichloropropenenitrile, 

### 3-cyanobutanoic acid, and 

### 4-cyanobutanoic acid. It is 

### possible that 

### these com

### pounds arise fromreactions ofchlorinewithaminoacids

or 

### proteinaceous materials to form

### N,N-dichloroamino acids, followed 

### by dehydrohalogenation to the nitriles. Chlorinated 

### aliphatic aldehydes also have been identified. These compounds might be precursors of the ni

### triles, as well as of chlorinated 

### acids, which are 

### logical hydrolysis/oxidation products ofthe above 

### nitriles. For 

### example, di- and trichloroacetaldehydes, and mono-, 

### di-, and trichloroacetic acids 

### (60) could be formed 

### by hydrolysis of the corresponding nitriles. 

### Chloropicrin 

### (Cl3CNO2) has been identified 

### recently 39RICE AND GOMEZ-TAYLOR



### (61), alongwithother

### volatile organic chemicals, 

### during chlorination studies with humic and fulvic 

### materials. Precursors include 

### aminoacids andnitrite ion. 

### Ammonia must be absent. 

### Chloropicrin was formed more 

### rapidly at pH 10 than at pH 7, 

### and the presence of 

### nitrite ion 

### is essential. Duguet et al. (62) and 

### Mallevialle et al. (63), 

### isolated 

### chloropicrin from

### drinkingwater supplies that

### hadbeen 

### prechlorinated. They 

### also showed that the 

### addition of reducing agents to chlorinated drinking water 

### supplies with the objective of 

### destroying excess free 

### residual chlorine, also converts 

### any chloropicrin present to chlo

### roform:

C13- C

- NO2 + reducing agent -> CHC13

In 

### light ofthis fact, it is 

### not surprising that 

### chloropicrin has escaped more 

### general detection and 

### reporting in 

### drinkingwater

### supplies. Ifmore thanthe stoichiometric amount of sulfite or thiosulfate 

### required to 

### quench free 

### residual chlorine is 

### added, 

### chloropicrin will be de

### stroyed. Equally 

### significant, however, the amount of chloroform found will be 

### higher than that 

### actuallyproduced as a result of chlorination. 

### Chloropicrin also has been identified as a 

### product of 

### chlorination of

### resorcinol. Filtration 

### through GAC was found to 

### destroy 

### chloropicrin (62,63). These authors 

### suggest that the 

### simplest way to control 

### chloropicrin formation inwater

### supplies is

### byabandoning

### breakpoint prechlorination. 

### Chlorine Dioxide. 

### Chlorine dioxide does not produce trihalomethanes with humic 

### materials, except when 

### free chlorine is

### present. From

### pure chlorine diox

### ide, the followingfourgeneral classes ofoxidationproducts were 

### obtained at 

### pH 3 

### and 7.8 

### (64): 

### benzenepolycarboxylic acids, aliphatic dibasic acids 

### (greater 

### yields from 

### Cl02 than from 

### Cl2 or 

### KMnO4), carboxyphenyl

### glyoxylic acids, and 

### aliphatic monobasic acids. 

### Com

### pounds identified in these studies were similar to those identifiedduringexperiments

### using

### chlorine, ozone, and 

### potassium permanganate as the oxidants. 

### Several derivatives of furan and dioxane also were 

### identified, as well as several chlorinated 

### compounds. Far fewer chlorinated 

### products are 

### formed by reaction with 

### Cl02 than with 

### Cl2. An average of 30% of the 

### original TOC was removed 

### by treatment with 

### C102. Monochloramine. 

### Chloramination ofhumic and ful

### vic materials 

### produced no identifiable chlorination or 

### oxidation 

### products in 

### diethyl ether extracts, 

### although the fulvic materials tested exerted a demand for 0.13 mole 

### NH2Cl mole ofcarbon 

### after 24 hr at

### pH 9, and the color of

### the fulvic material had been bleached. This behavior 

### might be 

### explained 

### by selective addition reactions 

### of 

### NH2Cl across olefinic sites in the fulvic mole

### cules, thus 

### destroying some or 

### all of the 

### chromophoric moieties 

### (57). Ozone. Ozonation of natural humic and fulvic acids released the 

### pesticides Lindane and 

### DDT, along with 

### iron 

### and manganese cations. 

### With small 

### quantities of

ozone 

### simulating dosages used in

### drinking water treatment 

### plants (0.1 to 2

### mg/L), humic acids 

### depolymerized and, in the 

### majority of 

### experiments, turbidities in

### creased, and 

### BOD5 increased (65). Ozonation of humic and fulvic 

### materials cleaves the polymeric 

### chains (> 1000) and forms lower 

### molecular weight 

### fragments (< 1000) and 

### aliphatic acids and ketones, 

### phenols, and phthalic acids 

### (66,67). Higher 

### molecular weight polymeric humic materials (> 300,000) 

### are decomposed 

### during ozonation into shorter 

### fragments (< 5,000). In 

### addition, the 

### ozonized solutions now containhigher 

### concentrations ofphenolic constituents than are present before 

### ozonation. These phenolic 

### compounds might be 

### liberated by decomposi

### tion of iron 

### and manganese complexes (68). More recent studies have shown 

### that aromatic acids

are virtually 

### eliminated after one 

### hour of ozonation, which conditions provide muchhigher 

### dosages of

### ozone thannormally

### encounteredduring

### drinkingwater ozonation. Insome

### cases, tetrachloro-, and

### pentachloro-, and 

### hexachlorobenzenes have been 

### isolated from solutions ofhumic materials ozonized for 1 hr. 

### These chlorinated compounds 

### probably were present as soil humic contaminants and were released as the humic material de

### composed 

### during ozonation 

### (69). Oxidationoffulvicacids caused

### depolymerization, and several 

### fractions of lower molecular 

### weight materials

were isolated. Ozonation produced 

### more lowmolecular 

### weight 

### compounds from fulvic acids 

### than did KMnO4 oxidation. 

### Ozone/UV produced fewer low molecular 

### weight compounds than ozonation 

### alone, probably causedbymore complete oxidationof

### the carbonto 

### CO2 (70). GAC 

### adsorption rates of 

### ozonized humic acids decrease to a minimum at a 

### range of consumed ozone of 0.13-0.3 

### mg 

### 03/mg organic C, then 

### increase with increased ozone 

### dosage. At 1.08 mg 

### 03/mg C, the bio

### degradability ofthe ozonized solutions 

### quadrupled (71). Because ozonation increases 

### biodegradability of humic and fulvic 

### materials, removal of dissolved organic carbon can be 

### improved further 

### by 

### following ozone oxidation with a 

### biological treatment before chlorination 

### (72). Four major classes of compounds 

### have been isolated fromozonized 

### solutions ofhumicand

### fulvicacids (57,72): 

### benzenecarboxylic acids, 

### aliphatic dibasic acids 

### (C4 to 

### C1o), aliphaticmonobasic acids 

### (C2 and

### higher), and car

### boxyphenylglyoxylic acids. The 

### nonchlorinated, aro

### matic, and 

### aliphatic compounds identified are identical

or

### verysimilartothoseobtainedwhen

### treatingthe same humicorfulvicmaterialswithchlorine, 

### chlorinedioxide,

or 

### potassium permanganate. Discussion. From the complete chlorination of humic and fulvic acids, more than 100 discrete com

### pounds have been identified. About half of these are 

### nonchlorinated, and both classes 

### consist of substituted aromatic 

### compounds and 

### straight-chain 

### aliphatic
mono-, 

### di-, and

### polycarboxylicacids. Abouthalfthetotal 

### halogen-containing material is 

### nonvolatile, and chloroform 

### comprises about 95% of the volatile 

### organics produced. Chlorinated

### productsobtainedin

### highest

### yieldinclude trichloroacetic acid 

### (69%), chloroform 

### (19%), dichlo40STRONG OXIDANTBY-PRODUCTS INDRINKING WATER

roacetic 

### acid (9.5%), and 

### dichlorosuccinic acid (4.5%). 

### When 

### chlorination conditions that are 

### closer to those used in 

### drinking water treatment 

### plants (maximum 20 mg/L 

### chlorine doses) are 

### used, more 

### ring-chlorinated aromatic 

### compounds can be isolated. 

### Manynitriles have been isolated from 

### chlorination of humic/fulvic materials, along with 

### chlorinated alde

### hydes and chlorinated 

### acids. As 

### discussed in the preceding 

### section 

### dealing with amino acids, aldehydes in the

### presence of

### ammoniaand chlorine canbeprecursors ofnitriles. 

### Furthermore, hydrolysis of chlorinated ace

### tonitriles 

### (which have 

### been identified from the chlori

### nationofhumic

### materials) wouldbe

### expectedtoproduce the corresponding 

### chloroacetic acids. 

### Chlorination of 

### a-terpineol produces a 

### variety of chlorinated derivatives, 

### plus a 

### nonchlorinated epoxide. At 

### pH 10, the yield of

### epoxide is 39%, 

### which decreases to 1-3% 

### yield at pH 3. 

### Oxidation ofhumic and fulvic materials with 

### chlorine dioxide, ozone, 

### and alkaline 

### permanganate forms nonchlorinated oxidation 

### products, which are similar to 

### those 

### produced during chlorination. The 

### major classes obtained from ozonation are 

### benzenecarboxylic acids, 

### C4-C10 

### aliphatic dibasic 

### acids, C2 and 

### higher 

### aliphatic monobasic 

### acids, and 

### carboxyphenylglyoxylic acids. 

### Ozone oxidation of 

### humic/fulvic materials 

### generally lowers the 

### molecular weights, and sometimes 

### liberates entrapped or 

### complexed 

### pesticides (Lindane and DDT) and 

### heavy metals (iron 

### and manganese). At the same 

### time, turbidities and 

### BOD5 increases. In some cases, the 

### BOD5 

### quadruples. Adsorbability ofthe ozonized or

### ganics can

### decrease at 

### low levels ofozonation (0.13-0.3 mg ozone consumed/mg 

### organic carbon), but then increases 

### with 

### increasing ozone 

### dosage. Monochloramine 

### produces no 

### products as yet identi

### fied, although humics 

### and fulvics exert 

### strong 

### oxidant demands. 

### Higher 

### nonpurgeable total 

### organic halogen concentrations were 

### found (9%-40% 

### higher) withchloramine treatment of

### fulvic materials thanwith chlorine. These

### materials hadhighermolecularweights andwere less 

### polar than the same 

### materials 

### produced by chlorination.



## Conclusions

At our current state 

### of

### knowledge with

### regard to the 

### chemistries of 

### specific organic materials known to be 

### contained in raw water 

### supplies with respect to the oxidants/disinfectants 

### currently available and used in
water treatment, no current water treatment process appears to be 

### able to 

### guarantee the total absence of 

### oxidation 

### products. Reactions 

### of free 

### chlorine and 

### monochloramine with 

### organonitrogen moieties in amino 

### acids, amines, and 

### peptides can 

### produce nitriles 

### by formation of

### N,N-dichloro 

### derivatives, followed by decomposition. Alde

### hydesin

### thepresence 

### of

### ammoniaandchlorine alsohave 

### been shown to

### produce nitriles 

### through the same

### mechanism. Inthe

### presence 

### ofnitrite

### ion, aminoacidsandchlorine produce 

### chloropicrin 

### (nitrotrichloromethane). Addition ofstrongreducingagents converts thismaterial tochlo

### roform. Thus it is 

### possible thatmany

### earlyanalyses for trihalomethanes have not found 

### chloropicrinbecause of the 

### prompt addition of thiosulfate to destroy free residual 

### chlorine. Ifthis has occurred, 

### these analyses for the amount of chloroformproduced 

### during 

### chlorination
mayhavebeen

### overstatedbythe 

### amount of

### chloropicrin converted to 

### chloroform. Since the 

### concentration of amino acids and 

### peptides is highest in raw

### drinkingwater, the preceding 

### conclusions lead to 

### consideration of the 

### recommendation that 

### breakpoint chlorination of raw waters should 

### be abandoned in favor of other procedures that 

### will remove these 

### nitrogen-containing materials 

### before chlorine is added. Tominimize the 

### formation of

### chlorinated organicmaterials, as much organic material as 

### possible should be removed before chlorine is added to 

### the water. Chlorine dioxide 

### generally 

### produces fewer chlorination 

### products than does free chlorine. Amines, 

### amino 

### acids, and

### peptidenitrogengroups donot formN-chloro 

### derivatives with 

### C102. Preoxidation ofwater supplies with ozone or 

### chlorine dioxide 

### before chlorination produces aldehydes, ketones, and acids. 

### Unless the aldehydes are removed 

### (by flocculation, adsorption, or further 

### oxidation) before treatment with ammonia and 

### chlorine, 

### nitriles couldbe 

### produced. Epoxide compounds have been 

### identified in 

### laboratory studies of 

### aqueous solutions of 

### oleic acid, abietic 

### acid, 

### cholesterol, a-terpineol, and acenaphthylene. The

same nonchlorinated 

### epoxy derivative 

### of

### oleic acid was 

### produced by treatment with chlorine, ozone, 

### chlorine 

### dioxide, and chloramine. 

### Abietic acid and cholesterol 

### formed the same 

### epoxy derivatives from chlorine and fromozone 

### (no

### experimentswere conducted

### with

### C102). Chlorination of 

### a-terpineol 

### produced a 

### nonchlorinated
epoxy 

### compound in addition to 

### chlorinated products. Ozonation of

### acenaphthylene produced the 

### corresponding epoxy derivative, in addition to 

### the more 

### nornal oxidation 

### products. 

### Ozonation of 

### heptachlor 

### quantita

### tively produces heptachlor epoxide which is stable to further ozonation. 

### Chlorine dioxide in strong 

### sunlight, and 

### aqueous chlorine 

### (HOCl) oxidizebromide ionto

### hypobromite ion. 

### Ozone alsowill oxidize bromide ion to

### hypobromite ion, and 

### additionally

### will oxidize 

### bromide/hypobromite ions
to bromate ion. 

### Thus, waters 

### containing bromide ion 

### will have the 

### potential for 

### producing not 

### only bromi

### nated trihalomethanes, but other 

### brominated organic materials. Ozone reacts with 

### hypochlorite ions, 

### producing chlo

### ride and 

### chlorate ions; with chlorine 

### dioxide to

### produce chlorate

### ion; with

### chlorite ionto

### produce

### C102andchlorate 

### ion; and with 

### monochloramine to 

### produce 

### chloride and nitrate ions. 

### Therefore, ozonationprocesses should be conducted in the absence of these 

### inorganic materials. 

### Any residual 

### ozone should be destroyed before 4142 RICE AND GOMEZ-TAYLOR

any of these 

### halogenated materials are added for dis

### infection.

This literature study was supported by the United States Environmental Protection Agency (EPA), Office of DrinkingWater, Criteria and Standards Division under Order Number 4W-2943 NTSX, issued to Rip G. Rice, Incorporated. It has been subject to theAgency's review, and has been approved for publication as an EPA document. The senior author is particularly grateful to his coauthor for her able and patient guidance ofthis project, and forher cooperation in the writing of this manuscript. Bothauthors thankDr. JosephA. Cotruvo, Directorofthe Criteria and Standards Division, for suggesting and supporting this study.

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