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The Role and Behavior of Chloramines in Drinking Water

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The Role and Behavior of Chloramines in Drinking Water The Role and Behavior of Chloramines in Drinking Water May 2019 Djanette Khiari, The Water Research Foundation LAST UPDATED: MAY 2019 CHLORAMINATION HAS BEEN USED funded more than 70 research projects they play in water quality improvements in drinking water treatment since the on the optimization of chloramination for drinking water utilities. Using doc- early 1900s, but its use has been low while considering chloramine-related umented information from 68 utilities compared to that of chlorine. In recent issues, such as key factors to consider that use chloramines, the report identi- years, many utilities implemented chlo- when making the switch to chlora- fies critical parameters for controlling ramine, primarily to comply with the mines, prevention and mitigation of chloramination and spells out a chlora- U.S. Environmental Protection Agency’s nitrification events, minimization of mination optimization strategy. (EPA) Stage 1 and Stage 2 Disinfectants disinfection by-products, and lead and A Guide for the Implementation and and Disinfection Byproducts Rules copper release related to chloramine Use of Chloramines (2847) summa- (D/DBPR). Chloramines are less reac- use. What follows is a summary of rizes the current state of knowledge tive than chlorine and produce lower the relevant chloramine- related WRF regarding chloramine use and synthe- concentrations of trihalomethanes reports. For an overview of chlora- sizes the information into step-by- step (THMs) and haloacetic acids (HAAs). mine use in water treatment and a procedures for using chloramines in a In drinking water treatment, chlora- discussion of the concerns associ- water system. mines are primarily used as a secondary ated with chloramine use, refer to the Finally, Long- Term Effects of disinfectant to provide a residual in the archived WRF webcast, “Talking About Disinfection Changes on Water Quality distribution system. The three forms of Chloramines: A Discussion of the (2940) documents the long- term effects inorganic chloramines are mono-, di-, Concerns and Questions Regarding of disinfectant changes on distribution and tri-chloramine. Chloramines are Water Treatment.” This webcast is system conditions, including changes a class of disinfectants formed by the available for on- demand viewing on in microbial community, chemical reaction of chlorine and ammonia. The the WRF website. composition, and aesthetic character- ratio at which chlorine and ammonia istics. The report contains issue papers are fed determines the species of chlo- Switching to Chloramines on microbial quality, chemical quality ramine produced. Monochloramine is ALTHOUGH THE ECONOMIC ANALYSIS (DBPs, corrosion, metal release, and the preferred species, as it is more for the Stage 2 D/DBP Rule produced particle characteristics), and aesthetic effective and less likely to cause taste- by the EPA estimated that more than quality impacts associated with disin- and-odor problems. 50% of surface water systems would fectant changes. In addition to minimizing the for- use chloramines as a secondary dis- mation potential of THMs and HAAs, infectant, the switch to chloramina- Nitrification chloramines are more stable than tion has been somewhat slower than TWO-THIRDS OF THE MEDIUM AND chlorine and therefore last longer in expected. The 2004 AWWA secondary large systems in the United States using the distribution system. Chloramine disinfection practices survey found chloramination experience nitrification stability is advantageous in distri- that 29% of community water systems episodes to some degree. Nitrification bution systems with long detention currently use chloramines for second- can significantly alter water quality times. Chloramination can be a com- ary disinfection and that another 3% and can result in violations of coliform, plex process and improper operations are converting to chloramine use loss of disinfectant residual, as well as can sometimes result in unintended (Seidel et al. 2005). overall increased microbial growth in consequences including nitrification, Switching to chloramines is certainly the affected areas. Therefore, utili- formation of non-regulated DBPs, and not easy and requires extensive plan- ties using chloramines are concerned deleterious effects on some elasto- ning and a thorough understanding of about nitrification events that occur meric materials used in the distribution source water characteristics and sys- when chloramines decay in the dis- system. Since chloramine use has been tem operations. Utilities considering tribution system. The use of chlora- increasing, water professionals need such a switch need to consider issues mines can cause biological instability to understand the various aspects of ranging from public perception to com- and promote the growth of nitrifying chloramination with the goal to better patibility of chloramines with the dis- bacteria. When chloramines decom- manage and operate their systems and tribution system. Optimizing Chloramine pose, ammonia is released and can be minimize unintended consequences. Treatment: Second Edition (2760), an oxidized to nitrite and nitrate. This pro- Since the mid-1980s, The Water update to an earlier report, is a manual cess, known as nitrification, is believed Research Foundation (WRF) has on the use of chloramines and the role to be facilitated by ammonia-oxidizing © 2019 THE WATER RESEARCH FOUNDATION. ALL RIGHTS RESERVED. 3 OF 8 THE ROLE AND BEHAVIOR OF CHLORAMINES IN DRINKING Water bacteria (AOB), which use the ammo- of chloramine loss in drinking water. absence of a wide variety of microor- nia as an energy source. These bacteria The more sophisticated model eluci- ganisms in a timely and robust manner. are commonly found in drinking water dates the reactions monochloramine If microarray technology can be cost- systems, and nitrification occurs when undergoes as it decays. The simplified effectively implemented by drinking conditions allow their numbers to rise. model can be used to determine the water utilities, this technology can help Although AOB seem to be implicated theoretical stability of monochloramine utilities overcome several operational in most nitrification events, new infor- in a given finished water supply. concerns. Of particular interest for this mation from WRF and others indicates In the report, Ammonia from study was nitrification in chloraminated that other bacteria may also play a crit- Chloramine Decay: Effects on distribution systems. ical role. Other factors that could play Distribution System Nitrification (553), a role in nitrification include: Greg Harrington of the University of Disinfection Byproducts l Water quality factors Wisconsin and his colleagues studied CHLORINE- BASED DISINFECTANTS pH the influence of ammonia release on like chlorine and chloramine can react Temperature the growth of AOB and evaluated treat- with organic matter of natural and Chloramine residual ment methods to reduce the frequency anthropogenic origin to form regulated Ammonia concentration of nitrification in distribution systems. and non- regulated DBPs, albeit with Chlorine- to- ammonia ratio Harrington and his team also produced different species and concentrations. Concentrations of organic a model that simulates the water qual- Chloramine is a weaker oxidant than compounds ity effects associated with chloramine chlorine and it generally forms less l Distribution system factors decay and nitrification. halogenated byproducts than chlorine. Detention time The focus of the WRF project, In general, the total organic halogen Reservoir design and Characterizing the Microbial Community (TOX) and regulated DBPs (THMs and operation Responsible for Nitrification (4165), was HAAs) concentrations formed during Sediment to validate a high- throughput microar- chloramination are lower that the TOX/ Tuberculation in piping ray and evaluate the microbial com- regulated DBPs produced during chlo- Biofilm munities present in pilot-scale and rination (Khiari et al. 1996). Absence of sunlight full- scale water treatment systems To minimize the formation of these Understanding chloramine decay that are capable of contributing to regulated DBPs and comply with exist- and nitrification events is clearly a nitrification events. A comprehensive ing regulations, water utilities have critical issue in the effective use of this analysis consisting of 112 drinking increasingly been switching to alterna- disinfectant, and WRF has conducted water samples including source water, tive disinfectants, such as chloramine, considerable research on this topic and filter effluent, and chloraminated dis- or installing more advanced and costly will continue this work in the future. tribution systems at both pilot- and treatment processes, such as ozone In a WRF study of chloramine decom- full- scale was conducted to evaluate or granular activated carbon (GAC) to position, Chloramine Decomposition in the presence of different microor- remove precursors. However, while Distribution System and Model Waters ganisms associated with nitrification. reducing the formation of halogenated (937), researcher Richard Valentine For this purpose, a high-throughput DBPs, alternative oxidants have been of the University of Iowa and his col- microarray was designed, validated, shown to favor the formation of other leagues described the influence of and used to analyze different drinking DBPs (e.g., ozone- producing bromate water quality parameters on chlora- water samples. The microarray was and forming more halonitrometh-
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