Chloramination Of Water Research Articles

Effect of silver in severely nitrified chloraminated bulk waters

Chloramine has been widely used in many water utilities as a secondary disinfectant because of increased concern over disinfection by-products (DBPs) formation. However, its popularity has been affected due to microbial acceleration, which is traditionally believed to be by nitrifying organisms or their products such as nitrite and pH value which change substantially under nitrifying conditions. With the traditional belief in mind, the conventional approach to solve ‘chloramine decay’ was aimed at killing or flushing out nitrifiers. We have recently shown that either soluble microbial products (SMPs) released by microbes or changes in natural organic matter (NOM) characteristics under nitrified conditions could be responsible for the acceleration. With this new insight, a new control strategy was attempted by dosing silver at a concentration of 0.1 mg-Ag/L to the nitrified bulk waters obtained in a laboratory scale system. Accelerated chemical and microbial chloramine losses were significantly reduced after the addition of silver. These results are very promising for future applications.

Reactivity of chlorine dioxide with amino acids, peptides, and proteins

Amino acids, proteins, and peptides are found ubiquitously in waters. They can form harmful byproducts during water treatment by reaction with disinfectants. Chlorination and chloramination of water containing natural organic matter is known to result in the production of toxic substances, often referred to as disinfection byproducts. The main advantage of using chlorine dioxide (ClO2) over other known chlorine-containing disinfectants is the minimization of the formation of harmful trihalomethanes. Because ClO2 is a promising alternative to other chlorine-containing disinfectants, the chemistry of ClO2 interactions with amino acids, proteins, and peptides should be understood to ensure the safety of potable water supplies. Here, we present an overview of the aqueous chemistry of ClO2 and its reactivity with amino acids, peptides, and proteins. The kinetics and products of the reactions are reviewed. Only a few amino acids have been reported to be reactive with ClO2, and they have been found to follow second-order kinetics for the overall reaction. The rate constants vary from 10−2 to 107 M−1 s−1 and follow an order of reactivity: cysteine > tyrosine > tryptophan > histidine > proline. For reactions of histidine, tryptophan, and tyrosine with ClO2, products vary depending largely on the molar ratios of ClO2 with the specific amino acid. Products of ClO2 oxidation differ with the presence or absence of oxygen in the reaction mixture. Excess molar amounts of ClO2 relative to amino acids are associated with the production of low molecular weight compounds. The oxidation of the biochemically important compounds bovine serum albumin and glucose-6-phosphate dehydrogenase by ClO2 suggests a denaturing of proteins by ClO2 by an attack on tryptophan and tyrosine residues and relates to the inactivation of microbes by ClO2.

The impact of bromide/iodide concentration and ratio on iodinated trihalomethane formation and speciation

The objective of this study was to evaluate the formation and speciation of iodinated trihalomethanes (I-THMs) from preformed chloramination of waters containing bromide (Br −) and iodide (I −) at a Br −/I − weight ratio of 10:1. The factors investigated were pH, iodide to dissolved organic carbon (I −/DOC) ratio, and NOM characteristics, specifically SUVA 254. A Br −/I − ratio of 1:2 was also evaluated to determine the importance of Br − and I − concentrations and ratio on I-THM formation and speciation. Regulated triholamethanes (THMs) were measured alongside I-THMs for a more complete understanding of trihalomethane formation. The results showed that, in general, both I-THM and THM formation increased with decreased pH. Greater formation at lower pH was likely attributed to monochloramine decomposition and the formation of additional oxidants and substituting agents, most notably chlorine. For pH ≥ 7.5, I-THM yield increased with increasing I −/DOC ratio and decreasing specific ultraviolet absorbance (SUVA 254) of the water. The Br −/I −, Br −/DOC and I −/DOC ratios were important factors for I-THM and THM speciation. At pH 6, dichloroiodomethane (CHCl 2I) and bromochloroiodomethane (CHBrClI) were the dominant species at the common bromide and iodide levels. For pH ≥ 7.5 and for elevated bromide and iodide levels, iodoform (CHI 3) was always the dominant specie regardless of the Br −/I − ratio. The results demonstrated that it is important to examine I-THM formation and speciation at typical Br −/I − ratios (∼10) of natural waters, which have often been overlooked in previous investigations, in order to obtain practical and relevant results.

Chloramination of nitrogenous contaminants (pharmaceuticals and pesticides): NDMA and halogenated DBPs formation

Disinfection with chloramines is often used to reduce the production of regulated disinfection by-products (DBPs) such as trihalomethanes (THMs) and haloacetic acids (HAAs). However, chloramination can lead to the formation of N-nitrosamines, including N-nitrosodimethylamine (NDMA), a probable human carcinogen. Previous research used dimethylamine (DMA) as a model precursor of NDMA, but certain widely used tertiary dimethylamines (e.g. the pharmaceutical ranitidine) show much higher conversion rates to NDMA than DMA. This study investigates the NDMA formation potential of several tertiary amines including pharmaceuticals and herbicides. The reactivity of these molecules with monochloramine (NH 2Cl) is studied through the formation of NDMA, and other halogenated DBPs such as haloacetonitriles (HANs) and AOX (Adsorbable Organic Halides). Several compounds investigated formed NDMA in greater amounts than DMA, revealing the importance of structural characteristics of tertiary amines for NDMA formation. Among these compounds, the pharmaceutical ranitidine showed the highest molar conversion to NDMA. The pH and dissolved oxygen content of the solution were found to play a major role for the formation of NDMA from ranitidine. NDMA was formed in higher amounts at pH around pH 8 and a lower concentration of dissolved oxygen dramatically decreased NDMA yields. These findings seem to indicate that dichloramine (NHCl 2) is not the major oxidant involved in the formation of NDMA from ranitidine, results in contradiction with the reaction mechanisms proposed in the literature. Dissolved oxygen was also found to influence the formation of other oxygen-containing DBPs (i.e. trichloronitromethane and haloketones). The results of this study identify several anthropogenic precursors of NDMA, indicating that chloramination of waters impacted by these tertiary amines could lead to the formation of significant amounts of NDMA and other non-regulated DBPs of potential health concern (e.g. dichloroacetonitrile or trichloronitromethane). This could be of particular importance for the chloramination of wastewater effluents, especially during water reuse processes.

Decomposition of Free Chlorine with Tertiary Ammonium

The reaction of free chlorine with tertiary ammonium or amine compounds in aqueous solution was studied by the amperometry at a rotating Pt-disk electrode. The amperometric method can be applied to follow the concentration of free chlorine (c(Cl)) even in the presence of chloramine species. By addition of mono- and dibutylammonium to the solution containing free chlorine, the step-like decrease in c(Cl) was observed, indicating the rapid formation of the stable chloramine species. By addition of tributylammonium, the c(Cl) was decreased exponentially to nearly zero even if the free chlorine was present initially in excess. The c(Cl)-t curves can be explained by tributylammonium-species-catalyzed decomposition of free chlorine to chloride ion. The catalytic decomposition was observed also with the tertiary-ammonium-based anion-exchange resins. Furthermore, the anion-exchange resins exhibited the decomposition of not only free chlorine but also chloramines in water.

Formation of N-Nitrosodiphenylamine and Two New N-Containing Disinfection Byproducts from Chloramination of Water Containing Diphenylamine

N-nitrosodiphenylamine (NDPhA) is a disinfection byproduct (DBP) in drinking water. However, it is not known what governs the formation of NDPhA and which precursor(s) in the raw water is responsible for its formation. We report here diphenylamine (DPhA) as a key precursor of NDPhA, and we describe the effect of water pH and chloramination conditions on the formation of NDPhA. To identify precursors of NDPhA, raw water samples were collected from the same drinking water system in which NDPhA was previously detected. Analysis of the raw water samples showed the presence of 1.3 ng/L of DPhA and no detectable NDPhA. Seven hours after the treatment of the raw water with chloramines, the concentration of DPhA decreased to 0.4 ng/L with corresponding formation of NDPhA (0.4 ng/L). Controlled experiments involving chloramination of DPhA in water showed that chloramines were essential to the formation of NDPhA, and that increasing the pH from 4 to 10 resulted in 64-fold enhancement in NDPhA formation. Removal of DPhA and formation of NDPhA was found by mass imbalance, which led to the identification of two new DBPs, phenazine (MW 180 Da) and a chlorinated phenazine derivative (MW 216 Da), using liquid chromatography tandem mass spectrometry and gas chromatography mass spectrometry. Both new DBPs were detected only in the treated water and not in the raw water. Phenazine and N-chlorophenazine have never been reported as DBPs and neither their occurrence in drinking water nor their health effects are known.

Evaluation of chromogenic technologies for use in Australian potable water

To compare the use of MI agar, Membrane Lactose Glucoronide Agar (MLGA), CM1046 agar and Colilert-18 (Defined Substrate Technology, IDEXX Laboratories Pty. Ltd., Sydney) on Australian potable water. Both potable (n = 369) and nonpotable waters (n = 35) were analysed by membrane filtration using chromogenic agars as well as Colilert-18 over a period of 12 months. Recoveries of stressed organisms on these chromogenic media were also investigated. Agar-based chromogenic technologies compared favourably to Colilert-18 for chlorinated waters, but there are possible limitations when using these agars for chloraminated waters. Additionally, the breakthrough of problematic organisms, especially oxidase positive organisms, may lead to misrepresentation or over-estimation of E. coli and total coliforms, particularly on MLGA and CM1046. The recovery of stressed organisms was favoured in the Colilert-18 system when compared to chromogenic agars. MI agar performed better than the other chromogenic agars with respect to recovery and colour identification and discrimination of organisms, and compared favourably with Colilert-18. The use of chromogenic agars in chloraminated waters should be done cautiously. This study provides comparison data for laboratories looking to adopt chromogenic technologies, and is especially important for Australian laboratories wanting to uptake the use of MI agar (as used in USEPA method 1604) for routine use and for gaining accreditation. Additionally, to the best of our knowledge, this is the first reported evaluation of these agars in chloraminated waters and is especially timely as the use of this disinfection agent is increasing.

Effects of quenching methods on HAA determination in chloraminated waters

This study examined the effects of using ammonium chloride (NH4Cl), a chlorine quenching agent recommended by US Environmental Protection Agency method 552.3, on haloacetic acid (HAA) determination under different chloramination scenarios simulated in laboratory experiments. During the early reaction times for the surface water tested in this study (dissolved organic carbon of 3 mg/L), results showed that HAA concentration was overestimated up to 9 μg/L because of the use of NH4Cl. In all chloramination scenarios, positive errors decreased with increasing reaction time. Among the various quenching agents or methods tested, sodium arsenite (NaAsO2) and stoichiometric amounts of sodium sulfite (Na2SO3) were found to be appropriate for HAA determination in chloraminated samples. However, they have some limitations for use in practical applications. Immediate extraction of samples without using any quenching agent resulted in positive errors in HAA determination because of the low pH conditions (pH < 1) coupled with high temperature after the addition of sulfuric acid during HAA extraction. Adjusting sample pH to high values and using ascorbic acid for quenching chloramine were found to be unsuitable for HAA samples.

Critical evaluation of the NSF 61 Section 9 test water for Lead

The authors evaluated the NSF 61 Section 9 protocol from the perspective of test water chemistry and lead‐leaching propensity. Overall, the test water proved representative of a typical water supply. However, some chloraminated waters with lower pH and lower alkalinity can be more aggressive than the Section 9 water, especially after months of exposure. As a result, products that are certified under NSF Section 9 might still cause compliance problems with US Environmental Protection Agency regulations for lead. Moreover, similar problems may be expected to affect approximately 16% of the US population served by private water supplies and cistern‐type systems, which also are considered aggressive to lead leaching. To account for these concerns, the authors recommend that the Section 9 pass/fail criterion be tightened and that product information be made available that details possible limitations of the products relative to lead leaching in certain corrosive water supplies.

Comparison of colorimetric and membrane introduction mass spectrometry techniques for chloramine analysis

Three methods for the determination of chloramines in water were compared using pH-buffered nanopure water and natural organic matter (NOM) solutions. We investigated whether the N,N-diethyl-p-phenylenediamine (DPD) colorimetric method and/or an adapted indophenol method (Hach MonochlorF) are suitable for determining the concentration of monochloramine in drinking water. Membrane introduction mass spectrometry (MIMS) was used as a reference analysis method to determine the different chloramine species in water. All methods measured monochloramine accurately in Nanopure water, but the DPD colorimetric method measured higher residuals (inorganic and organic chloramines) than MonochlorF or MIMS when in the presence of NOM due to organic chloramines. The indophenol method (MonochlorF) accurately detected only monochloramine and not other chloramine forms. Overall, the monochloramine concentration measured by MonochlorF was comparable with the MIMS results. A combined chlorine residual approach by the DPD colorimetric method does not differentiate between monochloramine and organic chloramines. Therefore, DPD colorimetric methods can overestimate disinfection efficacy in chloraminated water systems because of interference from organic chloramines that have no or poor bactericidal ability. Compared with the DPD colorimetric method, MonochlorF is a better choice for chloraminated water systems.

Triclosan Reactivity in Chloraminated Waters

Triclosan, widely employed as an antimicrobial additive in many household personal care products, has recently been detected in wastewater treatment plant effluents and in source waters used for drinking water supplies. Chloramines used either as alternative disinfectants in drinking water treatment or formed during chlorination of nonnitrified wastewater effluents have the potential to react with triclosan. This study examined triclosan reactivity in chloraminated waters over the pH range of 6.5-10.5. Experimental and modeling results show that monochloramine directly reacts with the phenolate form of triclosan; however, the reaction is relatively slow as evinced by the second-order rate constant k(ArO)-NH2Cl = 0.025 M(-1) s(-1). Kinetic modeling indicates that for pH values less than 9.5, reactions between triclosan and two monochloramine autodecomposition intermediates, hypochlorous acid (k(ArO)-HOC = 5.4 x 10(3) M(-1) s(-1)) and dichloramine (k(ArO)-NHCl2 = 60 M(-1) s(-1)), are responsible for a significant percentage of the observed triclosan decay. The products of these reactions include three chlorinated triclosan byproducts as well as 2,4-dichlorophenol and 2,4,6-trichlorophenol. Low levels of chloroform were detected after 1 week at pH values of 6.5 and 7.5. The slow reactivity of triclosan in the presence of chloramines explains the recalcitrance of this species in nonnitrified wastewater effluents.

Numerical simulation of chloramines formation in turbulent flow using a multi-fluid micromixing model

A study has been performed to investigate the use of Computational Fluid Dynamics (CFD) for the analysis of ammonia injection methods to produce chloramines in water containing residual free chlorine. In this study, the Reynolds-averaged Navier–Stokes Equation and turbulence model were combined with chloramines kinetic models to predict downstream spatial distribution of residual free chlorine. As part of this study, a CFD model with the RNG k – ɛ turbulence model was combined with a multi-fluid microscale model (MFM) to investigate the impact of micromixing on the free chlorine residual. All model predictions were compared with experimental measurements of the free chlorine residual at different upstream and downstream locations from the ammonia injection point. Three types of ammonia diffusers were simulated and tested in the presented work. The results showed that the incorporation of the MFM approach can enhance the numerical prediction of the free chlorine spatial distribution. In addition, the modeling results confirmed the experimental observation that multi-nozzle diffusers displayed better mixing performance than the cone-shape diffuser with a single nozzle in a pilot-scale reactor.

QUALITY ASSURANCE FOR DIALYSIS‐QUALITY WATER AND DIALYSIS FLUID: Guidelines for the control of chlorine and chloramine in water for haemodialysis using activated carbon filtration

QUALITY ASSURANCE FOR DIALYSIS‐QUALITY WATER AND DIALYSIS FLUID: Guidelines for the control of chlorine and chloramine in water for haemodialysis using activated carbon filtration

A N-Nitrosodimethylamine (NDMA) precursor analysis for chlorination of water and wastewater

N-nitrosodimethylamine (NDMA) is a potent carcinogen formed during chloramination of water and wastewater treatment plant effluents. A procedure is described for quantifying the concentration of the organic precursors of NDMA that could be formed during chlorination of wastewaters and natural waters. The method involves applying a high dose of monochloramine to a pH-buffered sample followed by a 10-day contact period, during which the monochloramine decays at a rate unrelated to the composition of the sample. Analyses of samples of municipal wastewater effluents and surface waters indicate that the method provides a robust and reproducible measurement of NDMA precursors over a wide range of conditions. A sensitive GC/CI/MS/MS analytical procedure for dimethylamine also is described and used to demonstrate that NDMA formation during chlorination of wastewater and natural waters cannot be explained by dimethylamine concentrations alone.

Effects of isocyanuric acid on the monochlorodimedone chlorinating rates with free chlorine and ammonia chloramine in water

Changes in monochlorodimedone (MCD) chlorinating rates with free chlorine (mixture of HOCl and OCl −) and ammonia monochloramine (NH 2Cl) in water at pH 7 by the addition of isocyanuric acid (H 3Cy) were determined at room temperature. Decreases in MCD absorbance at 290 nm in equimolar (0.04 mM) reactions of MCD and free available chlorine solutions containing H 3Cy (0.01–1.60 mM) were recorded in a stopped-flow spectrophotometer. The rates indicate second-order reactions. Since the rate with free chlorine was high (>7.6×10 6 M −1 s −1), the amounts of free chlorine in the solutions could be distinguished from that of chlorinated cyanurates. The chlorinating rates with chlorinated cyanurates decreased with an increase in H 3Cy concentrations. Plotting the rates against the molar ratio of chlorine to H 3Cy showed a linear correlation and the rates with chlorinated cyanurates (H 2ClCy) was estimated at 0.5×10 5 M −1 s −1. In contrast, the rates with the NH 2Cl solution containing H 3Cy increased with an increase in H 3Cy concentrations, increasing from 1.2×10 to 2.7×10 M −1 s −1 by the addition of 1.55 mM H 3Cy. The DPD color development rates (OD 512/t 1/2/M) with free available chlorine (0.015 mM) declined from 1.3×10 5 to 0.9×10 5 M −1 by the addition of 0.61 mM H 3Cy.

NDMA Formation in Water and Wastewater

N‐nitrosodimethylamine (NDMA) is a carcinogen known to be present in various foods and industrial products. The US Environmental Protection Agency has established a 10–6 cancer risk level for NDMA of 0.7 ng/L. NDMA has been found in the effluents of various water and wastewater plants, but its formation mechanism is not yet understood. This study evaluated NDMA formation during various water and wastewater treatment processes including chlorination and chloramination, ozonation, and ion exchange. On the basis of the limited results obtained in this study, NDMA appears to be a by‐product of the chloramination of water and wastewater, with the level of NDMA formed directly related to the chloramine dose. In the waters tested, NDMA did not form on contact with free chlorine or ozone. Contact of one water with typical levels of amine‐based polymer did not form any measurable NDMA levels (<2 ng/L). Batch testing was conducted with four strong‐base anion exchange resins contacted with untreated groundwater and with buffered deionized water. Results showed that some resins might leach or form NDMA and the level of NDMA produced is a function of the chemical functional group on the surface of the resin.

Committee Report: Gasket materials

Elastomers' use‐specific sensitivity to chloramine makes it difficult to develop test methods, pass‐fail criteria, and a standard appropriate for all rubber components.Rubber components are used extensively in water distribution systems, and their long‐term performance is of concern to water utility engineers. Thus, AWWA member utilities asked the AWWA Research Foundation (AWWARF) to investigate how chlorine and chloramine affect these components. In 1992, AWWARF commissioned a study to evaluate the effects of chlorinated and chloraminated water on two types of elastomers: generic specimens of known formulations and sheet stock of unknown formulations. This report responds to the AWWARF research, which concluded that chloraminated waters are more detrimental to most elastomers than waters with equivalent concentrations of chlorine. It also enumerates proposed actions, including developing pass‐fail criteria, related to these findings and explains why it is not currently feasible to develop an AWWA standard for all gaskets used in chloraminated waters.

Effect of Bromide Ion on Haloacetic Acid Speciation Resulting from Chlorination and Chloramination of Aquatic Humic Substances

The objective of this study was to investigate the effect of bromide ion on the distribution of haloacetic acid (HAA) species resulting from the chlorination and chloramination of waters containing aquatic humic substances. Aquatic humic substances were extracted from a surface water and a groundwater and were chlorinated and chloraminated under standard conditions at pH 8 and pH 6 in the presence of bromide concentrations ranging from 0 to 25 μM (0−2 mg/L). The treated waters were analyzed for all nine of the HAA species containing bromine and chlorine. Standards for bromodichloroacetic acid and dibromochloroacetic acid were not commercially available but were synthesized for use in this study. Bromochloro-, bromodichloro-, and dibromochloroacetic acid were readily formed and constituted at least 10% of the total HAA concentration in waters containing as little as 1.2 μM (0.1 mg/L) bromide. The mixed bromochloro HAA species were major components of the total HAA concentration at bromide concentrations found in raw drinking waters. Distribution of the HAA species among the mono-, di-, and trihalogenated forms appeared to be independent of bromide concentration.

Formation of AMES mutagenicity and of the strong bacterial mutagen 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone and other halogenated compounds during disinfection of humic water

Humic water was treated with different disinfectants and examined for mutagenicity, 3-chloro-4-(dichloromethyl)-5-hydroxy-2(5H)-furanone (MX), E-2-chloro-3-(dichloromethyl)-4-oxobutenoic acid (E-MX), adsorbable halogenated organics (AOX), and chloroform. The highest mutagenic activity and the highest concentrations of MX and E-MX were noted for water disinfected with chlorine. An increased proportion of chlorine dioxide in the combined chlorine/chlorine dioxide treatment resulted in a decrease in the mutagenic activity and in the concentrations of MX, E-MX, AOX and chloroform. Ozone treatment prior to chlorination gave a slight decrease in mutagenicity and in the concentrations of MX and E-MX. Although the amount of AOX in monochloramine treated water was comparable to that in chlorinated water chloramination produced considerably lower mutagenicity and lower concentrations of MX and E-MX. MX was responsible for 20 – 50% and E-MX for a few percent of the mutagenic activity generated by the disinfectants.

Determination of Nitrogen Trichloride in Water

This study compares diethylpara‐ phenylene diamine (DPD) results for chlorine and chloramines in water with total chlorine figures obtained iodometrically. A discrepancy arises whenever NCl3 is present, because only half of this compound is recovered. This half appears in the dichloramine fraction. The remaining half of the NCl3, however, can be made to react in the free chlorine fraction by adding a small amount of potassium iodide. In this way the total NCl3 content may be obtained and the dichloramine reading corrected for the NCl3 that appears with it. These conclusions apply only to the low concentrations of NCl3 that may be formed in the chlorination of waters or obtained by diluting freshly prepared stock solutions. Solutions of NCl3 that have been allowed to stand before dilution give inconsistent results.