Maria José Farré

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. The water treatment train consisted of coagulation, sand filtration, chlorination, addition of lime and fluoride, storage, and chloramination. Nonspecific toxicity peaked midway through the treatment train after the chlorination and storage steps. The dissolved organic matter concentration decreased after the coagulation step and then essentially remained constant during the treatment train. Concentrations of AOXs increased upon initial chlorination and continued to increase through the plant, probably due to increased chlorine contact time. Most of the quantified DBPs followed a trend similar to that of AOXs, with maximum concentrations observed in the final treated water after chloramination. The mostly chlorinated and brominated DBPs formed during treatment also caused reactive toxicity to increase after chlorination. Both genotoxicity with and without metabolic activation and the induction of the oxidative stress response pathway showed the same pattern as the nonspecific toxicity, with a maximum activity midway through the treatment train. Although measured effects cannot be directly translated to adverse health outcomes, this study demonstrates the applicability of bioanalytical tools to investigate DBP formation in a drinking water treatment plant, despite bioassays and sample preparation not yet being optimized for volatile DBPs. As such, the bioassays are useful as monitoring tools as they provide sensitive responses even at low DBP levels.

Factors affecting the formation of disinfection by-products during chlorination and chloramination of secondary effluent for the production of high quality recycled water

During the production of high quality recycled water by reverse osmosis membrane filtration secondary effluent must be disinfected to limit biofouling on the membrane surface. Advanced Water Treatment Plants in South East Queensland, Australia use disinfectant contact times ranging from 30 min up to 24 h. Disinfectants such as chlorine and chloramines react with effluent organic matter to generate disinfection by-products (DBPs) which could be potentially hazardous to human health if the water is destined for supplementing public water supplies. In this context, secondary effluents are of concern because of their high total organic carbon content which can act as DBP precursors. Also, effluent organic matter may form different DBPs to those formed from natural organic matter during conventional drinking water treatment, either in quantity, identity or simply in the abundance of different DBPs relative to each other. It cannot be assumed per se with certainty that DBP formation will be affected in the same way by operational changes as in drinking water production. Response surface modelling has been employed in this study at the bench scale to investigate the effect of reaction time (0-24 h), pH (5.5-8.5), temperature (23-35 °C), disinfection strategy (chlorine vs chloramines used prior to membrane treatment) and the interaction between these different parameters on DBP formation during disinfection of secondary effluent. The concentration of halogenated DBPs formed during the first 24 h of reaction with the different disinfectants followed the order chlorination >> in line-formed monochloramine > pre-formed monochloramine. Contact time with chlorine was the major influencing factor on DBP formation during chlorination, except for the bromine-containing trihalomethanes and dibromoacetonitrile for which pH was more significant. Chlorination at high pH led to an increased formation of chloral hydrate, trichloronitromethane, dibromoacetonitrile and the four trihalomethanes while the opposite effect was observed for the other targeted DBPs. Temperature was identified as the least influencing parameter compared to pH and reaction time for all DBPs in all the disinfection strategies, except for the formation of chloral hydrate where pH and temperature had a similar significance and bromoform that was similarly affected by temperature and reaction time. Chloramines employed at pH 8.5 reduced the concentration of all studied DBPs compared to pH 5.5. Furthermore, reaction time was the most significant factor for trichloronitromethane, chloroform, trichloroacetonitrile, dichloroacetonitrile and bromochloroacetonitrile formation while pH was the most influencing factor affecting the formation of the remaining DBPs.

Fate of N-nitrosodimethylamine, trihalomethane and haloacetic acid precursors in tertiary treatment including biofiltration

The presence of disinfection by-products (DBPs) such as trihalomethanes (THMs), haloacetic acids (HAAs) and N-nitrosamines in water is of great concern due to their adverse effects on human health. In this work, the removal of N-nitrosodimethylamine (NDMA), total THM and five HAA precursors from secondary effluent by biological activated carbon (BAC) is investigated at full and pilot scale. In the pilot plant two filter media, sand and granular activated carbon, are tested. In addition, we evaluate the influence of ozonation prior to BAC filtration on its performance. Among the bulk of NDMA precursors, the fate of four pharmaceuticals containing a dimethylamino moiety in the chemical structure are individually investigated. Both NDMA formation potential and each of the studied pharmaceuticals are dramatically reduced by the BAC even in the absence of main ozonation prior to the filtration. The low removal of NDMA precursors at the sand filtration in comparison to the removal of NDMA precursors at the BAC suggests that adsorption may play an important role on the removal of NDMA precursors by BAC. Contrary, the precursors for THM and HAA formation are reduced in both sand filtration and BAC indicating that the precursors for the formation of these DBPs are to some extent biodegradable.

Strategies for the removal of halides from drinking water sources, and their applicability in disinfection by-product minimisation: A critical review

The presence of bromide (Br(-)) and iodide (I(-)) in source waters leads to the formation of brominated and iodinated disinfection by-products (DBPs), which are often more toxic than their chlorinated analogues. The increasing scarcity of water resources in Australia is leading to use of impaired and alternative water supplies with high bromide and iodide levels, which may result in the production of more brominated and iodinated DBPs. This review aims to provide a summary of research into bromide and iodide removal from drinking water sources. Bromide and iodide removal techniques have been broadly classified into three categories, namely; membrane, electrochemical and adsorptive techniques. Reverse osmosis, nanofiltration and electrodialysis membrane techniques are reviewed. The electrochemical techniques discussed are electrolysis, capacitive deionization and membrane capacitive deionization. Studies on bromide and iodide removal using adsorptive techniques including; layered double hydroxides, impregnated activated carbons, carbon aerogels, ion exchange resins, aluminium coagulation and soils are also assessed. Halide removal techniques have been compared, and areas for future research have been identified.

Understanding the operational parameters affecting NDMA formation at Advanced Water Treatment Plants

N-nitrosodimethylamine (NDMA) can be formed when secondary effluents are disinfected by chloramines. By means of bench scale experiments this paper investigates operational parameters than can help Advanced Water Treatment Plants (AWTPs) to reduce the formation of NDMA during the production of high quality recycled water. The formation of NDMA was monitored during a contact time of 24h using dimethylamine as NDMA model precursor and secondary effluent from wastewater treatment plants. The three chloramine disinfection strategies tested were pre-formed and in-line formed monochloramine, and pre-formed dichloramine. Although the latter is not employed on purpose in full-scale applications, it has been suggested as the main contributing chemical generating NDMA during chloramination. After 24h, the NDMA formation decreased in both matrices tested in the order: pre-formed dichloramine>in-line formed monochloramine≫pre-formed monochloramine. The most important parameter to consider for the inhibition of NDMA formation was the length of contact time between disinfectant and wastewater. Formation of NDMA was initially inhibited for up to 6h with concentrations consistently <10 ng/L during these early stages of disinfection, regardless of the disinfection strategy. The reduction of the contact time was implemented in Bundamba AWTP (Queensland, Australia), where NDMA concentrations were reduced by a factor of 20 by optimizing the disinfection strategy.

Bioanalytical and chemical assessment of the disinfection by-product formation potential: Role of organic matter

Disinfection by-products (DBP) formed from natural organic matter and disinfectants like chlorine and chloramine may cause adverse health effects. Here, we evaluate how the quantity and quality of natural organic matter and other precursors influence the formation of DBPs during chlorination and chloramination using a comprehensive approach including chemical analysis of regulated and emerging DBPs, total organic halogen quantification, organic matter characterisation and bioanalytical tools. In vitro bioassays allow us to assess the hazard potential of DBPs early in the chain of cellular events, when the DBPs react with their molecular target(s) and activate stress response and defence mechanisms. Given the reactive properties of known DBPs, a suite of bioassays targeting reactive modes of toxic action including genotoxicity and sensitive early warning endpoints such as protein damage and oxidative stress were evaluated in addition to cytotoxicity. Coagulated surface water was collected from three different drinking water treatment plants, along with reverse osmosis permeate from a desalination plant, and DBP formation potential was assessed after chlorination and chloramination. While effects were low or below the limit of detection before disinfection, the observed effects and DBP levels increased after disinfection and were generally higher after chlorination than after chloramination, indicating that chlorination forms higher concentrations of DBPs or more potent DBPs in the studied waters. Bacterial cytotoxicity, assessed using the bioluminescence inhibition assay, and induction of the oxidative stress response were the most sensitive endpoints, followed by genotoxicity. Source waters with higher dissolved organic carbon levels induced increased DBP formation and caused greater effects in the endpoints related to DNA damage repair, glutathione conjugation/protein damage and the Nrf2 oxidative stress response pathway after disinfection. Fractionation studies indicated that all molecular weight fractions of organic carbon contributed to the DBP formation potential, with the humic rich fractions forming the greatest amount of DBPs, while the low molecular weight fractions formed more brominated DBPs due to the high bromide to organic carbon ratio. The presence of higher bromide concentrations also led to a higher fraction of brominated DBPs as well as proportionally higher effects. This study demonstrates how a suite of analytical and bioanalytical tools can be used to effectively characterise the precursors and formation potential of DBPs.

Reductive electrochemical remediation of emerging and regulated disinfection byproducts

Long-term exposure to low concentrations of disinfection byproducts (DBPs) in drinking water has been associated with increased human-health risks of bladder cancer and adverse reproductive outcomes. In this study, we investigated electrochemical reduction utilizing a resin-impregnated graphite cathode for the degradation of 17 DBPs (i.e. halomethanes, haloacetonitriles, halopropanones, chloral hydrate and trichloronitromethane) at low μg L(-1) concentration levels. The reduction experiments were potentiostatically controlled at cathode potentials -700, -800 and -900 mV vs Standard Hydrogen Electrode (SHE) during 24 h. At the lowest potential applied (i.e. -900 mV vs SHE), the disappearance of DBPs from the solution after 24 h of reduction was >70%, except for chloroform (32%), 1,1-dichloropropanone (48%), and chloral hydrate (31%). Due to the participation of several removal mechanisms (e.g. electrochemical reduction, adsorption, volatilization and/or hydrolysis) it was not possible to distinguish the removal efficiencies of electrochemical reduction of individual compounds. Adsorption of the more hydrophilic DBPs (i.e. haloacetonitriles, chloral hydrate, and 1,1-dichloropropanone) onto the electrode seems to be affected by the cathode polarization, as the removals observed in the open circuit experiments were significantly higher than the ones obtained in electrochemical reduction under the same conditions. The overall efficiency of reduction was estimated based on the analyses of the released Cl(-), Br(-) and I(-) ions. Nearly complete C-I bond cleavage was achieved at all three potentials applied, and from the theoretically predicted release of I(-) ions, calculated based on the removed DBPs, 86 ± 9 to 92 ± 1% was measured in the catholyte solution at -700 to -900 mV vs SHE. Debromination efficiencies obtained were 74 ± 3, 79 ± 6 and 68 ± 4% at -700, -800 and -900 mV vs SHE, while for C-Cl bond cleavage the obtained values were 69 ± 1, 72 ± 1 and 76 ± 4%, respectively. Nevertheless, dechlorination efficiencies are to be considered as approximate, since an increase in Cl(-) concentration was observed in the open circuit experiments due to the hydrolysis of some of the chlorine-containing DBPs. Although the Coulombic efficiencies for DPBs dehalogenation were only 1.9 ± 0.3 (-900 mV vs SHE) -4.1 ± 0.2% (-700 mV vs SHE), relatively low energy consumption of the process was observed, estimated at 72 ± 2 Wh m(-3) at -900 mV vs SHE for the concentration range of DBPs in this study (i.e. 65.3-129.7 μg L(-1)). The study demonstrated that reductive electrochemical treatment has the potential to be a modern remediation technology for the removal of low concentrations of halogenated DBPs in water.

Coupled solar photo-Fenton and biological treatment for the degradation of diuron and linuron herbicides at pilot scale

A coupled solar photo-Fenton (chemical) and biological treatment has been used to remove biorecalcitrant diuron (42 mg l(-1)) and linuron (75 mg l(-1)) herbicides from water at pilot plant scale. The chemical process has been carried out in a 82 l solar pilot plant made up by four compound parabolic collector units, and it was followed by a biological treatment performed in a 40 l sequencing batch reactor. Two Fe(II) doses (2 and 5 mg l(-1)) and sequential additions of H2O2 (20 mg l(-1)) have been used to chemically degrade the initially polluted effluent. Next, biodegradability at different oxidation states has been assessed by means of BOD/COD ratio. A reagent dose of Fe=5 mg l(-1) and H2O2=100 mg l(-1) has been required to obtain a biodegradable effluent after 100 min of irradiation time. Finally, the organic content of the photo-treated solution has been completely assimilated by a biomass consortium in the sequencing batch reactor using a total suspended solids concentration of 0.2 g l(-1) and a hydraulic retention time of 24h. Comparison between the data obtained at pilot plant scale (specially the one corresponding to the chemical step) and previously published data from a similar system performing at laboratory scale, has been carried out.

Second interlaboratory exercise on non-steroidal anti-inflammatory drug analysis in environmental aqueous samples.

Several interlaboratory exercises were organised within the framework of European FP6 project NORMAN. Among others, non-steroidal anti-inflammatory drugs were investigated in different aqueous samples in two sequential ring studies. The aim of both studies was to evaluate the state-of-art in Europe and to determine possible sources of variation, while also attempting to diminish them. In the present paper we discuss the results of the 2nd Interlaboratory study, while the results of 1st round were presented before. The main scope of the 1st exercise organised within NORMAN project was to assess the laboratory proficiency regardless of the analytical method applied, to evaluate the stability of the target compounds during sample storage, and to define possible sources of variation during sample shipment, storage and analysis. In the 2nd round we primarily aimed to diminish these sources of variation by applying two predetermined analytical protocols based on liquid chromatography-mass spectrometry or gas chromatography-mass spectrometry. The two analytical protocols were compared in terms of their ability to determine individual analytes in matrices of different complexity, i.e. tap water, river water and wastewater. Furthermore, the 2nd exercise addressed also the filtration and compared the influence of different filter material categories on the analysis of non-steroidal anti-inflammatory drugs. Results presented herein evaluate laboratory performance using z-score, bias, proximity and Youden plots. Overall, the laboratory performances were found to be satisfactory for determining NSAIDs in aqueous samples. The two analytical protocols, LC-MS and GC-MS, are assessed according to their sensitivity and measurement uncertainty, where the GC-MS proved superior for the analysis of Ibuprofen, Ketoprofen and Naproxen in matrices with higher complexity. Finally, neither the filtration itself, nor the filter materials were shown to significantly affect the determination of NSAIDs.

Towards reducing DBP formation potential of drinking water by favouring direct ozone over hydroxyl radical reactions during ozonation

When ozonation is employed in advanced water treatment plants to produce drinking water, dissolved organic matter reacts with ozone (O3) and/or hydroxyl radicals (OH) affecting disinfection byproduct (DBP) formation with subsequently used chlorine-based disinfectants. This study presents the effects of varying exposures of O3 and •OH on DBP concentrations and their associated toxicity generated after subsequent chlorination. DBP formation potential tests and in vitro bioassays were conducted after batch ozonation experiments of coagulated surface water with and without addition of tertiary butanol (t-BuOH, 10 mM) and hydrogen peroxide (H2O2, 1 mg/mg O3), and at different pH (6-8) and transferred ozone doses (0-1 mg/mg TOC). Although ozonation led to a 24-37% decrease in formation of total trihalomethanes, haloacetic acids, haloacetonitriles, and trihaloacetamides, an increase in formation of total trihalonitromethanes, chloral hydrate, and haloketones was observed. This effect however was less pronounced for samples ozonated at conditions favoring molecular ozone (e.g., pH 6 and in the presence of t-BuOH) over •OH reactions (e.g., pH 8 and in the presence of H2O2). Compared to ozonation only, addition of H2O2 consistently enhanced formation of all DBP groups (20-61%) except trihalonitromethanes. This proves that •OH-transformed organic matter is more susceptible to halogen incorporation. Analogously, adsorbable organic halogen (AOX) concentrations increased under conditions that favor •OH reactions. The ratio of unknown to known AOX, however, was greater at conditions that promote direct O3 reactions. Although significant correlation was found between AOX and genotoxicity with the p53 bioassay, toxicity tests using 4 in vitro bioassays showed relatively low absolute differences between various ozonation conditions.