Zhang Evan G R Davies James Bolton Yang Liu Q. Monochloramine loss mechanisms in tap water. Water Environ Res. 2017 Mar 1. doi: 10.2175/106143017X14902968254421.
Chloramination has been widely applied for drinking water disinfection, with monochloramine (NH₂Cl) the dominant chloramine species. However, under neutral pH, NH₂Cl can autodecompose and react with chemical components in drinking water, thus decreasing disinfection efficiency. In tap water, the NH₂Cl loss rate can be influenced by temperature, pH, Cl/N molar ratio, the initial NH₂Cl concentration and the natural organic matter (NOM) concentration. A good prediction of NH2Cl loss can assist in the operation of drinking water treatment plants. In this research, a kinetic rate constant (k_docr=(3.57 ± 0.54)×〖10〗^6 〖 M〗^(-1) h^(-1)) and a reactive site fraction (S = 0.43 ± 0.06) for the reaction between free chlorine released from NH₂Cl autodecoposition and tap water NOM were derived from a kinetic model to predict the NH₂Cl loss under various conditions. A temperature-dependent model was also developed. The model predictions match well with the experimental results, which demonstrates the validity of the model and provides a convenient and accurate method for NH₂Cl loss calculations.
How ZT, Linge KL, Busetti F, Joll CA. Organic chloramines in drinking water: An assessment of formation, stability, reactivity and risk. Water Research 2016 Feb 11;93:65-73. doi: 10.1016/j.watres.2016.02.006.
Although organic chloramines are known to form during the disinfection of drinking water with chlorine, little information is currently available on their occurrence or toxicity. In a recent in vitro study, some organic chloramines (e.g. N-chloroglycine) were found to be cytotoxic and genotoxic even at micromolar concentrations. In this paper, the formation and stability of 21 different organic chloramines, from chlorination of simple amines and amino acids, were studied, and the competition between 20 amino acids during chlorination was also investigated. For comparison, chlorination of two amides was also conducted. The formation and degradation of selected organic chloramines were measured using either direct UV spectroscopic or colorimetric detection. Although cysteine, methionine and tryptophan were the most reactive amino acids towards chlorination, they did not form organic chloramines at the chlorine to precursor molar ratios that were tested. Only 6 out of the 21 organic chloramines formed had a half-life of more than 3 h, although this group included all organic chloramines formed from amines. A health risk assessment relating stability and reactivity data from this study to toxicity and precursor abundance data from the literature indicated that only N-chloroglycine is likely to be of concern due to its stability, toxicity and abundance in water. However, given the stability of organic chloramines formed from amines, more information about the toxicity and precursor abundance for these chloramines is desirable.
A condominium association served by Moulton Niguel Water District has sued the District over copper pipe leaks that owners believe are caused by corrosive water and that have led to hundreds of thousands of dollars in repairs. Water is supplied to the district by the Metropolitan Water District of Southern California which has been using chloramines since 1984.
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Not everyone believes that using chloramines is so bad. Click here for the news article….
“Those boards include Charlottesville City Council, the Albemarle County Board of Supervisors, The Rivanna Water and Sewer Authority, and the Albemarle County Service Authority. The boards voted to take the use of chloramines off the table and to instead commission a $9,500 study to look at the use of a granular activated carbon filtration system.”
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Tulsa’s water treatment plant will start adding chloramine to disinfect the water supply in addition to chlorine. The city changed to meet higher standards for disinfection byproducts in drinking water. Click here for news article….
Over 10 years ago, environmental group representatives agreed and supported the negotiated Stage II disinfection byproducts rule, which included chloramines…….and now, activist groups and “slip and fall” attorneys are using chloramines to alarm customers and file lawsuits…..see a disconnect here?
Agree to a rule, and then attack when a water system acts to comply with the rule……click here for more…..