Chlorine monochloramine

Since the initial observation on the occitrrence and formation of THMs, additional research has shown that all chemical disinfectants (chlorine, monochloramines, ozone, and chlorine dioxide) can form various types of disinfection byproducts (DBFs). 

Rodriguez E, Sordo A, Metcalf JS, Acero JL (2007) Kinetics of the oxidation of cylindros-pennopsin and anatoxin-a with chlorine, monochloramine and permanganate. Water Res 41 2048-2056. doi 10.1016/j.watres.2007.01.033... 

Chloramine, like chlorine, is an oxidizing biocide used for disinfection. Three species collectively make up chloramines, also known as combined chlorine monochloramine, NH Cl dichloramine, NHCl and nitrogen trichloride (trichloramine), NCI3. Of these, monochloramine has the highest standard reduction potential furthermore, it is less prone to impart chlorinous taste and odor to water like other forms of chloramine. As a result, monochloramine is preferred for disinfection applications. 

A number of perhalides aie known, and one of the most stable is ammonium tetiachloioiodide [19702 3-3] NH IQ. Ammonia reacts with chlorine in dilute solution to give chloramines, a reaction important in water purification (see Cm,ORAMINES AND BROMAMINEs). Depending upon the pH of the water, either monochloramine [10599-90-3] NH2CI, or dichloramine [3400-09-7] NHCI2, is formed. In the dilutions encountered in waterworks practice, monochloramine is neady always found, except in the case of very acidic water (see Bleaching AGENTS Water). 

SuperchlorinationShock Treatment. Superchlorination or shock treatment of pool water is necessary since accumulation of organic matter, nitrogen compounds, and algae consumes free available chlorine and impedes disinfection. Reaction of chlorine with constituents of urine or perspiration (primarily NH" 4, amino acids, creatinine, uric acid, etc) produces chloramines (N—Cl compounds) which are poor disinfectants because they do not hydrolyze significantly to HOCl (19). For example, monochloramine (NH2CI) is only 1/280 as effective as HOCl against E. coli (20). 

In reahty the chemistry of breakpoint chlorination is much more complex and has been modeled by computer (21). Conversion of NH/ to monochloramine is rapid and causes an essentially linear increase in CAC with chlorine dosage. Further addition of chlorine results in formation of unstable dichloramine which decomposes to N2 thereby causing a reduction in CAC (22). At breakpoint, the process is essentially complete, and further addition of chlorine causes an equivalent linear increase in free available chlorine. Small concentrations of combined chlorine remaining beyond breakpoint are due primarily to organic chloramines. Breakpoint occurs slightly above the theoretical C1 N ratio (1.75 vs 1.5) because of competitive oxidation of NH/ to nitrate ion. Organic matter consumes chlorine and its oxidation also increases the breakpoint chlorine demand. Cyanuric acid does not interfere with breakpoint chlorination (23). 

The total concentration or amount of chlorine-based oxidants is often expressed as available chorine or less frequendy as active chlorine. Available chlorine is the equivalent concentration or amount of Cl needed to make the oxidant according to equations 1—4. Active chlorine is the equivalent concentration or amount of Cl atoms that can accept two electrons. This is a convention, not a description of the reaction mechanism of the oxidant. Because Cl only accepts two electrons as does HOCl and monochloramines, it only has one active Cl atom according to the definition. Thus the active chlorine is always one-half of the available chlorine. The available chlorine is usually measured by iodomettic titration (7,8). The weight of available chlorine can also be calculated by equation 5. 

Some nitrate is also formed, thus the HOCl/NH stoichiometry is greater than theoretical, ie, - 1.7. This reaction, commonly called breakpoint chlorination, involves intermediate formation of unstable dichloramine and has been modeled kinetically (28). Hypobromous acid also oxidizes ammonia via the breakpoint reaction (29). The reaction is virtually quantitative in the presence of excess HOBr. In the case of chlorine, Htde or no decomposition of NH occurs until essentially complete conversion to monochloramine. In contrast, oxidation of NH commences immediately with HOBr because equihbrium concentrations of NH2Br and NHBr2 are formed initially. As a result, the typical hump in the breakpoint curve is much lower than in the case of chlorine. 

The chemistry of NH2CI involves chlorination, amination, addition, condensation, redox, acid—base, and decomposition reactions. Monochloramine... 

Hypochlorous acid reacts very rapidly and quantitatively with a slight excess of free ammonia forming monochloramine, NH2CI, which reacts at a slower rate with additional HOCl forming dichloramine, NHCI2. Trichloramine is formed when three moles of HOCl are added per mole of ammonia between pH 3—4 (100). Hypochlorous acid in the form of chlorine or hypochlorite is used in water treatments to oxidize ammonia by the process of break-point chlorination, which is based on formation of unstable dichloramine. The instabiHty of NHCI2 is caused by presence of HOCl and NCl (101,102). The reaction is most rapid at a pH of about 7.5 (103). Other nitrogen compounds such as urea, creatinine, and amino acids are also oxidized by hypochlorous acid, but at slower rates. Unstable iV-chloro compounds are intermediates in deammination of amino acids (104,105). 

Interaction of EMT with chlorine and monochloramine has been studied. Electronic spectra of EMT and of its product of oxidation by chlorine and monochloramines have been obtained. X = 470 nm for EMT, 400 nm and... 

The effect of pH alone on chlorine efficiency is shown in Figure 3. Chlorine exists predominantly as HOCl at low PH levels. Between pH of 6.0 and 8.5, a dramatic change from undissociated to completely dissociated hypochlorous acid occurs. Above pH 7.5, hypochlorite ions prevail while above 9.5, chlorine exists almost entirely as OCl. Increased pH also diminishes the disinfecting efficiency of monochloramine. 

Cromeans, T. L., Kahler, A. M., and Hill, V. R. (2010). Inactivation of adenoviruses, enteroviruses, and murine norovirus in water by free chlorine and monochloramine. Appl. Environ. Microbiol. 76,1028-1033. 

The second stage is the formation of dichloramines the monochloramines react further with chlorine. Dichloramine irritates the eyes and nose. 

Ammonia (NH3) and hypochlorite ion (OC1-) combine to produce three different chloramine species—that is, compounds that are derivatives of ammonia in which one or more of the hydrogen atoms has been replaced by a chlorine atom. In order of increasing degree of chlorine substitution, these chloramines are named monochloramine (NH2CI), dichloramine (NHCh), and nitrogen trichloride (NCI3) ... 

Chamberlain E, Adams C (2006) Oxidation of sulfonamides, macrolides, and carbadox with free chlorine and monochloramine. Water Res 40 2517-2526... 

Chlorination and chloramination of a widely used antibacterial additive, triclo-san, which is used in many household personal care products, results in the formation of chloroform, 5,6-dichloro-2-(2,4-dichlorophenoxy)phenol, 4,5-dichloro-2-(2,4-dichlorophenoxy)phenol, 4,5,6-trichloro-2-(2,4-dichlorophenoxy)phenol, 2, 4-dichlorophenol, and 2,4,6-trichlorophenol [119]. The reaction of triclosan with monochloramine is slow, however, compared to chlorine [120]. The chlorophenox-yphenols are formed via bimolecular electrophilic substitution of triclosan. 

Na C, Olson TM (2004) Stability of cyanogen chloride in the presence of free chlorine and monochloramine. Environ Sci Technol 38(22) 6037-6043... 

Reacts with chlorine forming chloramines monochloramine, dichloramine and nitrogen trichloride ... 

Chlorine forms carbonyl chloride, COCl with carbon monoxide suhuryl chloride SO2CI with sulfur dioxide and chloramines (monochloramine, NH2CI, and dichloramine, NHCI2) with ammonia. Chloramines are often found at trace concentrations in sewage wastewater following chlorine treatment. 

What would lead you to believe that monochloramine and dichloramine are not regarded as very toxic, at least in an unconcentrated form How are these compounds used How are they related to combined available chlorine ... 

Another kind of reaction, commonly called ammonolysis, occurs when one or more of the hydrogen atoms in the ammonia molecule is replaced by some other atom or radical. For example, chlorine gas (Cl2) reacts directly with ammonia to form monochloramine (NH2C1) and hydrogen chloride (HC1)219. 

The three chemicals most commonly used as primary disinfectants are chlorine, chlorine dioxide and ozone. Monochloramine, usually referred to as chloramine, is used as a residual disinfectant for distribution. 

Monochloramine, used as a residual disinfectant for distribution, is usually formed from the reaction of chlorine with ammonia. Careful control of monochloramine formation in water treatment is important to avoid the formation of di- and trichloramines, because these can cause unacceptable tastes and odours. The formation of nitrite as a consequence of microbial activity in biofilms in the distribution system is a possibility when monochloramine is used as a residual disinfectant, particularly if ammonia levels are not sufficiently controlled. 

Rennecker JL, Driedger AM, Rubin SA, Marinas BJ (2000) Synergy in Sequential Inactivation of Cryptosporidium Parvum with Ozone/Free Chlorine and Ozone/ Monochloramine, Wat. Res. 34, No. 17 4121 130. 

Monochloramine has a higher taste and odor threshold than chlorine. 

First, it is to be noted that the reaction is expressed in terms of HOCl. By the eqnivalence of reactions, however, the above reactions can be manipulated if the equivalent amount of the other two species is desired to be known. In monochloramines and dichloramines, therefore, the chlorine is combined in ammonia they are called combined chlorines. As will be shown in subsequent discussions, the concentration of trichloramine is practically zero during disinfection thus, it is not included in the definition of combined chlorine. 

Now, let us discuss the final fate of trichloramine during disinfection. In accordance with the chloramine reactions [Reactions (17.34) to (17.36)], by the time three moles of HOCl have been added, a mole of trichloramine would have been formed. This, however, is not the case. As mentioned, while the monochloramine decomposes in a stepwise fashion to convert into the dichloramine, its destruction into the nitrogen gas intervenes. Thus, the eventual formation of the dichloramine would be less in fact, much, much less, since, as we have found, formation of the gas is favored over the formation of the dichloramine. In addition, monochloramine and dichloramine, themselves, react with each other along with HOCl to form another gas N2O [NH2CI -1-NHCI2 + HOCl N2O -I- 4H" -I- 4CL]. Also, there may be more other side reactions that could occur before the eventual formation of the dichloramine from monochloramine. Overall, as soon as the step for the conversion of the dichloramine to the trichloramine is reached, the concentration of dichloramine is already very low and the amount of trichloramine produced is also very low. Thus, if, indeed, trichloramine has a disinfecting power, this disinfectant property is useless, since the concentration is already very low in the first place. This is the reason why combined chlorine is only composed of the monochloramine and the dichloramine. Also, it follows... 

In waters and wastewaters, organic amines and their decomposition products such as ammonia may be present, hi addition, ammonia may be purposely added for chloramine formation to produce chlorine residuals in distribution systems. Also, other organic snbstances snch as organic amides may be present as well. Thus, from point A to B, chloro-organic compounds and organic chloramines are formed. Ammonia will be converted to monochloramine at this range of chlorine dosage. 

Beyond point B, the chloro-organic compounds and organic chloramines break down. Also, at this range of chlorine dosage, the monochloramine starts to convert to the dichloramine, but, at the same time, it also decomposes into the nitrogen gas and, possibly, other gases as well. These decomposition reactions were addressed previonsly. 

Note If superchlorination is to be practiced to ensure complete disinfection and it is also desired to have long-lasting chlorine residuals, then ammonia should be added after superchlorination to bring back the chlorine dosage to the point of maximum monochloramine formation. 

Combined chlorine—Chloramines composed of monochloramines and dichloramines. 

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