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

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 ll 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 ll 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- mine decomposition rates, compared capable of identifying targeted micro- anes [HNMs], chloramines producing decay rates in actual distribution sys- organisms using the 16S rRNA gene, N-nitrosodimethylamine [NDMA], and tems with rates in model systems, and the subunit A of the ammonia mono- in certain circumstances iodinated characterized chloramine decomposi- oxygenase (amoA) gene for ammonia- DBPs [I-DBPs]). tion products. The research team found oxidizing bacteria (AOB), and the amoA It is important to remember that the that the rate of monochloramine decay gene for ammonia-oxidizing archaea formation of DBPs is water matrix- increased as pH and ammonia con- (AOA). This project successfully specific. One must always consider the centrations decreased. Valentine and demonstrated the ability of microarray risk trade-offs associated with various his team also produced two models technology to detect the presence or treatment scenarios. Utilities must use

4 OF 8 © 2019 THE WATER RESEARCH FOUNDATION. ALL RIGHTS RESERVED. LAST UPDATED: May 2019 a battery of tests to select the most levels. Polyamine-derived precursors Ozonation/chlorination signifi- appropriate treatment while success- were also destroyed by various pre- cantly enhanced HNM formation as fully minimizing unintended conse- oxidants. In pre-oxidation testing of compared to chlorine alone, while quences and protecting public health. water with a very high dose (6.0 mg/L as chloramination (using preformed the active ingredient) of polyDADMAC, monochloramine), alone or after ozo- N-Nitrosamines NDMA formation potential (FP) nation, produced the fewest HNMs. N-NITROSAMINES ARE A LARGE increased. However, in waters with low Similar to drinking water treatment, group of chemicals suspected to be polyDADMAC doses (<– 0.8 mg/L as the HNM formation was greatly reduced by carcinogenic. The most frequently active ingredient), as used at full-scale applying preformed monochloramine detected N-nitrosamine in drinking plants, NDMA formation did not appear rather than chlorine (Cl2), especially water is N-nitrosodimethylamine to be exacerbated, as was observed in after pre-ozonation. (NDMA). NDMA is classified as a prob- the bench-scale testing of the very high In addition to the disinfectant type, able human carcinogen, based on polyDADMAC dose. factors affecting the formation and animal studies. Although both chlori- Powdered activated carbon (PAC) speciation of DBPs in drinking water nation and chloramination have been and granular activated carbon include DOC nature and characteristics, implicated in reaction mechanisms (GAC) removed watershed-derived pH, bromide (Br-) concentration, and that result in NDMA formation, it is a precursors. Low doses of PAC other water quality parameters. In this DBP preferentially formed by chlora- (e.g., ~5–10 mg/L) were often effec- study, HNM formation was at apprecia- mines. Sources of NDMA precursors tive. GAC was able to remove NDMA FP ble levels for certain conditions under include treated wastewater and certain better than that of the bulk TOC. PAC uniform formation conditions (UFC) polymers used in drinking water treat- removed, in limited tests, polyamine- (e.g., up to 25 μg/L for Br-/DOC ratio of ment (e.g., polyDADMAC, polyamine). derived precursors, but did not remove 100 and pH=8). The results indicated In the last several years, WRF has polyDADMAC-derived precursors. GAC that the major precursors of THMs funded several projects that investi- did not appear to be effective at remov- and HNMs were different in nature and gate NDMA occurrence, formation, ing polyDADMAC-derived precursors. reactivity, as the treated water exhibited and control strategies to prevent NDMA Thus, polymer management and the significantly lower THM formation than formation while minimizing unintended use of alternative polymers must also raw water, while HNM concentrations consequences. One of the most recent be considered. formed in the raw and treated waters studies dealing with control of NDMA were comparable at ambient conditions. was Controlling the Formation of Halonitromethanes However, some similarities were noted Nitrosamines During Water Treatment THE IMPACT OF OXIDATION/disin- regarding the formation of these two (4370), which developed improved fection, operating conditions, and classes of DBPs. For both THMs and strategies for minimizing nitrosamine water quality parameters on the HNMs, formation increased with pH formation during drinking water treat- formation of halonitromethanes (6 to 8), and treated waters had higher ment and provided treatment guidance (HNMs) in drinking water and waste- amounts of brominated THM and HNM for utilities. water effluents was investigated in species as compared to the raw waters The research showed that pre- Formation of Halonitromethanes and due to the removal of DOC, but not Br-, oxidation effectively destroyed Iodo-Trihalomethanes in Drinking during conventional treatment. watershed-derived precursors in the Water (4063). following order: ozone > chlorine > The results of the study showed Iodinated DBPs (I-DBPs) MPUV > LPUV > permanganate. Ozone that among the five disinfection sce- I-DBPS SUCH AS IODINATED THMS was often effective at low exposure/ narios tested, the order of HNM for- (I-THMs) and iodoacids are formed when contact time (CT). At higher exposure mation in molar concentrations and iodine-containing water is disinfected (e.g., longer free chlorine contact yields on a dissolved organic carbon with chlorine or chloramine. Research times), chlorine was more effective (DOC) and dissolved organic nitro- shows that the formation of I-DBPs is than at low exposure. Chlorine was gen (DON) basis was in the order of favored during chloramination, espe- more effective in the pH range of ozonation-chlorination >> chlorina- cially when chlorine or ozone is used as 8 to 9 and in warmer water. Ozone and tion >– ozonation-chloramination >> a pre-oxidant in the treatment process. MPUV were more effective at higher pH chloramination. When water contains multiple iodinated

precursors, complete oxidation is as compared to preformed monochlo- At a pH near 11.0 and free ammonia prevented, which creates a favorable ramine under some circumstances. of 0.5 to 0.7 mg/L as N, hydrazine con-

environment for the formation of these For prechlorination, the Cl2/DOC ratio centrations were as high as 100 ng/L. - I-DBPs. One I-DBP, tentatively identi- and/or the Cl2/I ratio were critical to fied as iodobutanol, has been found in control both the extent of THM and Lead and Copper Release finished waters from treatment plants I-THM formation as well as the ratio RECENT LITERATURE INDICATES located on coasts that can be impacted of THM to I-THM in a water sample. that when some water systems switch

by saltwater intrusion, which is iodide- However, the critical Cl2/DOC ratio to to chloramines, there is a concurring and bromide-rich (Weinberg et al. 2002). control both the concentrations of THM increase of lead in drinking water, per- and I-THM appears to be water specific. haps because chloramines can cause Iodinated THMS Iodine incorporation (hI) dominated lead to leach from pipes, fixtures, and IN ADDITION TO THE formation of over bromine incorporation (hBr) for solder. To investigate this phenomenon,

HNMs, Formation of Halonitromethanes preformed NH2Cl, while the reverse WRF has funded several projects. Effect and Iodo-Trihalomethanes in Drinking trend was observed for prechlorination of Changing Disinfectants on Distribution Water (4063) investigated the formation followed by ammonia addition. System Lead and Copper Release (3107) of iodinated THMs (I-THMs). The project examines the effect of changing dis- investigated the importance of pH, the Hydrazine infectants (from free chlorine to chlo- effect of contact time and dose of pre- HYDRAZINE IS A POTENT carcinogen ramines and vice versa) on metals’ chlorination, and the role of chloram- and is classified by the EPA as a probable leaching rates and leaching levels from ination strategy (chlorine added before human carcinogen with a 10-6 risk level of lead, brass, and copper distribution ammonia vs. preformed monochlora- 10 ng/L in drinking water. While it is well- system components. The first phase of

mine (NH2Cl) and the role of natural known that hydrazine is manufactured by the project is a literature review, while organic matter (NOM) characteristics. the reaction between monochloramine the second phase includes the results of When preformed chloramine is and ammonia, the following two projects laboratory, pipe loop, and field studies. used, I-THM formation and specia- were the first to investigate its formation The study showed that for new tion depended on a combination of in drinking water. (unpassivated) lead-bearing materials Br-/I- ratio and concentrations, natural Formation of Hydrazine as a Chloramine (lead and bronze), lead concentrations organic matter (NOM) characteristics, By-Product (2997) investigated the for- were affected primarily by background and I-/DOC ratios. Generally, I-THM formation of hydrazine during chloram- water quality conditions. In contract, for mation decreased as pH increased for ination. The study showed hydrazine new copper-bearing materials, copper a Br/I-mass ratio of approximately 10. formation was below detection when free concentrations were affected by the However, when the concentrations of ammonia concentration was less than presence of disinfectant (free chlorine Br- and I- were elevated, there was sig- 0.2 mg/L. The research team developed or chloramines), but the observed nificant I-THM formation at higher pH a computer simulation model to evaluate effects were transient. The research due to iodoform formation. The forma- the impact of water quality parameters showed the presence of phosphate tion of iodoform was rarely observed at on hydrazine formation. Results from the inhibitor reduced lead leaching by lower and more typical Br- and I- levels. model agreed with laboratory results. exerting a stabilizing influence on lead I-THM yields did not depend on the The model predicted that at pH < 9.5 and and copper solubility during chloramine - NH2Cl /I ratio, as increasing NH2Cl free ammonia less than 0.5 mg/L, hydra- conversion. For lead plumbing materi- concentrations from the UFC dose of zine formation would be of no significant als that are passivated and likely to have approximately 2.4 mg/L to 5.0 mg/L concern in chloraminated water. developed scales that are rich in lead

(as Cl2) did not have an appreciable A follow-up study, Quantifying oxide, changes in disinfectant—that effect on I-THM yields. Hydrazine in Chloraminated Water is, conversion to chloramines or some Prechlorination (HOCl contact time) (4141), confirmed that the formation of other low oxidation-reduction potential prior to ammonia addition did not hydrazine in natural water matrices is (ORP) conditions—are likely to cause a always result in lower ITHM concen- highly dependent on pH and ammonia notable increase of lead leaching. trations as compared to preformed concentration. At a pH of 9.9 and free The Role of Free Chlorine, monochloramine. Prechlorination ammonia < 0.2 mg/L as N, hydrazine Chloramines, and Natural Organic Matter sometimes increased I-THM formation concentrations were below 10 ng/L. in the Release of Lead into Drinking Water

(3172) investigated whether natural and PVC. In general, elastomers have utilities switched to chloramines? organic matter (NOM), free chlorine, performed well in the water distribution Journal AWWA, 97(10): 87–97. and chloramines can act synergisti- system; however, with the switch from WEINBERG, S. H., S. W. Krasner, and S. cally to either inhibit or accelerate the chlorine to chloramines, an increase D. Richardson. 2002. The Occurrence release of lead into drinking water. The of elastomer failures has been noted. of Disinfection By-Products (DBPs) study showed that lead oxide is relatively Reported problems associated with of Health Concern in Drinking Water: unstable in water. It is reduced to Pb(II) elastomer failure include increased Results of a Nationwide DBP Occurrence by water, but only very slowly at near leaks and line losses, increased main- Study. Athens, Ga.: U.S. Environmental neutral pH values. It is also reduced by tenance and repair, budget planning dif- Protection Agency, National Exposure NOM quite readily. The reductive capac- ficulties, and customer dissatisfaction. Research Laboratory, Office of ity of the NOM, however, is reduced if it The goal of Performance of Elastomeric Research and Development. is pre-oxidized by free chlorine, consis- Components in Contact with Potable tent with a destruction of reductive NOM Water (2932), was to identify the factors WRF Research Cited in This Article functionalities. However, if free chlorine that contribute to elastomer degrada- ll Optimizing Chloramine Treatment: were present with NOM, no apparent tion and provide a quantitative method Second Edition (2760) reduction of lead oxide occurs, pre- for predicting the performance and life ll A Guide for the Implementation and sumably because it would oxidize any expectancy of in-service elastomer Use of Chloramines (2847) released Pb(II) back to lead oxide. components. Upon completion of the ll Performance of Elastomeric Monochloramine, generally consid- research study, life-cycle degradation Components in Contact with Potable ered an oxidant, was found to reduce curves were developed for generic Water (2932) lead oxide. The amount of Pb(II) formed formulations of serval elastomers. For ll Long-Term Effects of Disinfection was linearly related to the amount of each material, a unique degradation Changes on Water Quality (2940) monochloramine that decomposed via curve was identified for surface hard- ll Chloramine Decomposition in auto-oxidation. This suggests that the ness, elongation, and swell (weight and Distribution System and Model reaction mechanism involved a reac- volume change). These degradation Waters (937) tion of intermediates produced from curves will help utilities specify appro- ll Ammonia from Chloramine Decay: the auto-decomposition of monochlo- priate materials with critical failure Effects on Distribution System ramine, acting as potent reductants modes. In addition, the degradation Nitrification (553) of lead oxide. Because NOM was also curves will help utilities assess the ll Effect of Changing Disinfectants on slowly oxidized by monochloramine, the long-term performance of elastomeric Distribution System Lead and Copper effect of mixtures of monochloramine materials already within their system. Release (3107) and NOM led to more complex behavior ll The Role of Free Chlorine, as each component did not act syner- References Chloramines, and Natural Organic gistically or independently. Studies also EPA (U.S. Environmental Protection Matter in the Release of Lead into showed that lead oxide could oxidize Agency). 2003. Economic Analysis for Drinking Water (3172) iodide and lead to the formation of iodo- the Proposed Stage 2 D/DBPR. EPA ll Formation of Hydrazine as a form in the presence of NOM, a DBP for- 815-D- 03- 001. Washington, DC: EPA Chloramine By-Product (2997) mation mechanism that does not involve Office of Water. ll Formation of Halonitromethanes and a disinfectant. KHIARI, D., S. W. Krasner, C. J. Hwang, R. Iodo-Trihalomethanes in Drinking Chinn, and S. E. Barrett. 1996. Effects Water (4063) Elastomeric Material Degradation of chlorination and chloramination ll Quantifying Hydrazine in ELASTOMERIC MATERIALS HAVE been on the molecular weight distribution Chloraminated Water (4141) widely used for components in drinking of natural organic matter and the ll Characterizing the Microbial water distribution systems. Their use production of high-molecular- weight Community Responsible for has ranged from rubber gaskets to disinfection by-products. In Proc. of Nitrification (4165) valves, hydrants, and fittings, and they Water Quality Technology Conference, ll Controlling the Formation of have proven to be equally adaptable to a AWWA, Boston, Mass. Nitrosamines During Water wide variety of piping materials, includ- SEIDEL, C. J., M. J. McGuire, R. S. Treatment (4370) ing cast iron, ductile iron, steel, copper, Summers, and S. Via. 2005. Have