Alternative application of preformed monochloramine as a drinking water disinfectant for redosing in long drinking water distribution system servicing remote locations.

Chloramine is the disinfectant of choice for long drinking water distribution systems since it is more stable than chlorine, therefore providing a longer lasting disinfectant residual and producing less disinfection byproducts. However, to deliver safe drinking water in remote areas, redosing stations are used where (mostly) chlorine is added to the water to re-establish a disinfectant residual. In this study, the use of a highly concentrated preformed monochloramine solution instead of chlorine for redosing in tanks or reservoirs along extensive distribution systems was investigated.

Halogenated semivolatile acetonitriles as chloramination disinfection by-products in water treatment: a new formation pathway from activated aromatic compounds.

The use of monochloramine as an alternative disinfectant to chlorine in drinking water treatment can lead to increased formation of emerging nitrogenous halogenated disinfection by-products (DBPs), even when the formation of regulated halogenated DBPs has decreased. In this study, we investigated formation of the semivolatile haloacetonitriles (HANs) from model nitrogen-containing compounds (6 amines, 1 amide, 6 amino acids, and 2 nitrogen-containing aromatic chemicals) and natural organic matter (NOM) reference materials after chloramination. In agreement with previous studies, most amino acids formed dichloroacetonitrile (DCAN).

Halogen-specific total organic halogen analysis: Assessment by recovery of total bromine.

Determination of halogen-specific total organic halogen (TOX) is vital for studies of disinfection of waters containing bromide, since total organic bromine (TOBr) is likely to be more problematic than total organic chlorine. Here, we present further halogen-specific TOX method optimisation and validation, focusing on measurement of TOBr. The optimised halogen-specific TOX method was validated based on the recovery of model compounds covering different classes of disinfection by-products (haloacetic acids, haloacetonitriles, halophenols and halogenated benzenes) and the recovery of total bromine (mass balance of TOBr and bromide concentrations) during disinfection of waters containing dissolved organic matter and bromide.

Organic chloramines in chlorine-based disinfected water systems: A critical review.

This paper is a critical review of current knowledge of organic chloramines in water systems, including their formation, stability, toxicity, analytical methods for detection, and their impact on drinking water treatment and quality. The term organic chloramines may refer to any halogenated organic compounds measured as part of combined chlorine (the difference between the measured free and total chlorine concentrations), and may include N-chloramines, N-chloramino acids, N-chloraldimines and N-chloramides. Organic chloramines can form when dissolved organic nitrogen or dissolved organic carbon react with either free chlorine or inorganic chloramines.

Formation and control of nitrogenous DBPs from Western Australian source waters: Investigating the impacts of high nitrogen and bromide concentrations.

We studied the formation of four nitrogenous DBPs (N-DBPs) classes (haloacetonitriles, halonitromethanes, haloacetamides, and N-nitrosamines), as well as trihalomethanes and total organic halogen (TOX), after chlorination or chloramination of source waters. We also evaluated the relative and additive toxicity of N-DBPs and water treatment options for minimisation of N-DBPs. The formation of halonitromethanes, haloacetamides, and N-nitrosamines was higher after chloramination and positively correlated with dissolved organic nitrogen or total nitrogen.

Formation and reactivity of inorganic and organic chloramines and bromamines during oxidative water treatment.

The formation and further reactions of halamines during oxidative water treatment can be relevant for water quality. In this study, we investigated the formation and reactivity of several inorganic and organic halamines (monochloramine, N-chloromethylamine, N-chlorodimethylamine, monobromamine, dibromamine, N-bromomethylamine, N,N-dibromomethylamine, and N-bromodimethylamine) by kinetic experiments, transformation product analysis, and quantum chemical computations. Kinetic model simulations were conducted to evaluate the relevance of halamines for various water treatment scenarios.

Analysis of halogen-specific TOX revisited: Method improvement and application.

A method was optimised and evaluated for the analysis of total organic halogen (TOX) in drinking water samples. It involved adsorption of organic halogen onto activated carbon, followed by combustion of the activated carbon and adsorbed material, absorption of the resulting hydrogen halide gases in an absorbing solution, and analysis of halide ions in the solution using an on-line ion chromatograph. Careful optimisation and validation of the method resulted in significant improvements compared to previously reported methods.

Analysis of free amino acids in natural waters by liquid chromatography-tandem mass spectrometry.

This paper reports a new analytical method for the analysis of 18 amino acids in natural waters using solid-phase extraction (SPE) followed by liquid chromatography-electrospray tandem mass spectrometry (LC-MS/MS) operated in multiple reaction monitoring mode. Two different preconcentration methods, solid-phase extraction and concentration under reduced pressure, were tested in development of this method. Although concentration under reduced pressure provided better recoveries and method limits of detection for amino acids in ultrapure water, SPE was a more suitable extraction method for real samples due to the lower matrix effects for this method.

Electrochemical treatment of reverse osmosis concentrate on boron-doped electrodes in undivided and divided cell configurations.

An undivided electrolytic cell may offer lower electrochlorination through reduction of chlorine/hypochlorite at the cathode. This study investigated the performance of electrooxidation of reverse osmosis concentrate using boron-doped diamond electrodes in membrane-divided and undivided cells. In both cell configurations, similar extents of chemical oxygen demand and dissolved organic carbon removal were obtained.

To add or not to add: the use of quenching agents for the analysis of disinfection by-products in water samples.

The formation of disinfection by-products (DBPs) is a public health concern due to their potential adverse health effects. Robust and sensitive methods for the analysis of DBPs, as well as appropriate sample handling procedures, are essential to obtain accurate, precise and reliable data on DBP occurrence and formation. In particular, the use of an appropriate quenching agent is critical to prevent further formation of DBPs during the holding time between sample collection and analysis.

Formation of N-nitrosamines from chlorination and chloramination of molecular weight fractions of natural organic matter.

N-Nitrosamines are a class of disinfection by-products (DBPs) that have been reported to be more toxic than the most commonly detected and regulated DBPs. Only a few studies investigating the formation of N-nitrosamines from disinfection of natural waters have been reported, and little is known about the role of natural organic matter (NOM) and the effects of its nature and reactivity on the formation of N-nitrosamines. This study investigated the influence of the molecular weight (MW) characteristics of NOM on the formation of eight species of N-nitrosamines from chlorination and chloramination, and is the first to report on the formation of eight N-nitrosamines from chlorination and chloramination of MW fractions of NOM.

Electrochemical oxidation of reverse osmosis concentrate on boron-doped diamond anodes at circumneutral and acidic pH.

Electrochemical processes have been widely investigated for degrading organic contaminants present in wastewater. This study evaluated the performance of electrochemical oxidation using boron-doped diamond (BDD) electrodes by forming OH() for the treatment of reverse osmosis concentrate (ROC) from secondary-treated wastewater effluents. Since oxidation by OH() and active chlorine species (HClO/ClO(-)) is influenced by pH, the electrochemical oxidation of ROC was evaluated at controlled pH 6-7 and at pH 1-2 (no pH adjustment).

Bioanalytical assessment of the formation of disinfection byproducts in a drinking water treatment plant.

Disinfection of drinking water is the most successful measure to reduce water-borne diseases and protect health. However, disinfection byproducts (DBPs) formed from the reaction of disinfectants such as chlorine and monochloramine with organic matter may cause bladder cancer and other adverse health effects. In this study the formation of DBPs through a full-scale water treatment plant serving a metropolitan area in Australia was assessed using in vitro bioanalytical tools, as well as through quantification of halogen-specific adsorbable organic halogens (AOXs), characterization of organic matter, and analytical quantification of selected regulated and emerging DBPs.

Analysis of halonitriles in drinking water using solid-phase microextraction and gas chromatography-mass spectrometry.

Halonitriles are a class of nitrogen-containing disinfection by-products (DBPs) that have been reported to be more toxic and carcinogenic than the regulated DBPs. While haloacetonitriles (HANs) are often measured in drinking waters, there is little information on the formation, characteristics, and occurrence of other, higher molecular weight halonitriles. Halopropionitriles and halobutyronitriles have been predicted to be highly toxic and carcinogenic, and may have sufficient potency and selectivity to account for epidemiological associations of chlorinated and chloraminated water with adverse health effects.

Powdered activated carbon coupled with enhanced coagulation for natural organic matter removal and disinfection by-product control: application in a Western Australian water treatment plant.

The removal of organic precursors of disinfection by-products (DBPs), i.e. natural organic matter (NOM), prior to disinfection and distribution is considered as the most effective approach to minimise the formation of DBPs.

Analysis of polysulfides in drinking water distribution systems using headspace solid-phase microextraction and gas chromatography-mass spectrometry.

Sulfide and polysulfides are strong nucleophiles and reducing agents that participate in many environmentally significant processes such as the formation of sulfide minerals and volatile organic sulfur compounds. Their presence in drinking water distribution systems are of particular concern and need to be assessed, since these species consume disinfectants and dissolved oxygen, react with metal ions to produce insoluble metal sulfides, and cause taste and odour problems. The analysis of sulfide and polysulfides in drinking water distribution systems is challenging due to their low concentrations, thermal instability and their susceptibility to undergo oxidation and disproportionation reactions.

The formation of halogen-specific TOX from chlorination and chloramination of natural organic matter isolates.

The formation of disinfection by-products (DBPs) is a public health concern. An important way to evaluate the presence of DBPs is in terms of the total organic halogen (TOX), which can be further specified into total organic chlorine (TOCl), bromine (TOBr), and iodine (TOI). The formation and distribution of halogen-specific TOX during chlorination and chloramination of natural organic matter (NOM) isolates in the presence of bromide and iodide ions were studied.