Concentrations Of Disinfection By-products Research Articles

Chlorination and chloramination of tetracycline antibiotics: Disinfection by-products formation and influential factors

Formation of disinfection by-products (DBPs) from chlorination and chloramination of tetracycline antibiotics (TCs) was comprehensively investigated. It was demonstrated that a connection existed between the transformation of TCs and the formation of chloroform (CHCl3), carbon tetrachloride (CCl4), dichloroacetonitrile (DCAN) and dichloroacetone (DCAce). Factors evaluated included chlorine (Cl2) and chloramine(NH2Cl) dosage, reaction time, solution pH and disinfection modes. Increased Cl2/NH2Cl dosage and reaction time improved the formation of CHCl3 and DCAce. Formation of DCAN followed an increasing and then decreasing pattern with increasing Cl2 dosage and prolonged reaction time. pH affected DBPs formation differently, with CHCl3 and DCAN decreasing in chlorination, and having maximum concentrations at pH 7 in chloramination. The total concentrations of DBPs obeyed the following order: chlorination>chloramination>pre-chlorination (0.5h)>pre-chlorination (1h)>pre-chlorination (2h).

Bioanalytical and chemical evaluation of disinfection by-products in swimming pool water

Pool water disinfection is vital to prevent microbial pathogens. However, potentially hazardous disinfection by-products (DBP) are formed from the reaction between disinfectants and organic/inorganic precursors. The aim of this study was to evaluate the presence of DBPs in various swimming pool types in Brisbane, Australia, including outdoor, indoor and baby pools, and the dynamics after a complete water renewal. Chemical analysis of 36 regulated and commonly found DBPs and total adsorbable organic halogens as well as in vitro bioassays targeting cytotoxicity, oxidative stress and genotoxicity were used to evaluate swimming pool water quality. Dichloroacetic acid and trichloroacetic acid dominated in the pool water samples with higher levels (up to 2600 μg/L) than the health guideline values set by the Australian Drinking Water Guidelines (100 μg/L). Chlorinated DBPs occurred at higher concentrations compared to tap water, while brominated DBPs decreased gradually with increasing pool water age. Biological effects were expressed as chloroacetic acid equivalent concentrations and compared to predicted effects from chemical analysis and biological characterisation of haloacetic acids. The quantified haloacetic acids explained 35–118% of the absorbable organic halogens but less than 4% of the observed non-specific toxicity (cytotoxicity), and less than 1% of the observed oxidative stress response and genotoxicity. While the DBP concentrations in Australian pools found in this study are not likely to cause any adverse health effect, they are higher than in other countries and could be reduced by better hygiene of pool users, such as thorough showering prior to entering the pool and avoiding urination during swimming.

Water treatment implications after the High Park Wildfire, Colorado

This study evaluated effects of the 2012 High Park Wildfire in the Cache la Poudre River Watershed in Colorado on source water quality and water treatment. The formation of disinfection by‐products (DBPs) was evaluated by treating water samples with chlorine following uniform formation conditions. The efficacy of alum coagulation for reducing dissolved organic carbon (DOC) and DBP concentrations was also evaluated. Postwildfire thunderstorms and spring snowmelt increased DOC and DBP concentrations relative to base‐flow conditions. Alum coagulation effectively reduced DOC concentrations (by 30–60% at a dose of 50 mg/L) and DBP formation (i.e., total trihalomethanes reduced by 60–80% at a dose of 50 mg/L). The Fort Collins water treatment facility responded to the High Park Wildfire by increasing environmental monitoring, using multiple water supplies, and constructing a presedimentation basin to effectively deliver high‐quality drinking water to its customers in the year following the fire.

Comparison of anion exchange resins and aluminum-based coagulants for natural organic matter (NOM) removal and disinfection by-product (DBP) formation

Anion exchange resins (AERs) were compared with aluminum-based coagulants for reducing disinfection by-product (DBP) precursor concentrations from a source water collected in northeast Ohio, USA. Three AERs (IRA-910, IRA-958, and MIEX) were evaluated to determine which resin would remove the most natural organic matter (NOM) and moieties responsible for DBP formation. All the AERs were found to be highly proficient at NOM removal specifically the moieties that absorb UV254 (i.e., chromophores) over 75 min of contact time; however, MIEX removed NOM at a faster rate than IRA-910 and IRA-958 resins. Enhanced coagulation was effective at removing approximately 35% of the NOM and 40–60% of the chromophores and fluorophores (i.e., excitation–emission matrix pairs A and C). DBP formation was determined as a function of pH for the different NOM removal processes. MIEX treatment resulted in significant reduction in DBP concentrations when compared to chlorinating the raw source water. MIEX generally out-performed enhanced coagulation for reducing DBP formation. However, alum was found to remove more NOM and resulted in less DBPs compared to aluminum chlorohydrate. This could impact water utilities trying to balance the health effects due to DBP exposure verses chemical/sludge management costs.

The optimization of chlorine dose in water treatment process in order to reduce the formation of disinfection by-products

The main threat to human health is associated with organic compounds, which are found in the natural water ecosystem. The law relating to drinking water quality protects consumers’ health. Thus, the need to remove disinfection by-products (DBP) precursors requires the application of high-efficient water treatment processes. Usually, chlorine is used to disinfection, and then, haloforms are generated. Well-calibrated model, estimating the concentration of DBP in treated water, can be a useful tool for predicting the quantity of trihalomethanes in water in the distribution network. Such a model makes it also possible to identify the critical control points in the monitoring process. This paper presents the statistical analysis of chloroform formation in treated water, based on laboratory tests. The chloroform concentration is expressed as a function of factors, which determine kinetics of the chemical reaction of organic compounds with chlorine. Two new variables—the ratio of total organic carbon and chloroform and the ratio of chlorine consumption and chlorine dose, both obtained after 1 h of the reaction—were taken into account. From the function predicting the chloroform concentration, one can determine the optimal dose of chlorine in the disinfection of water in dynamic operational conditions.

Ballast water treatment using UV/TiO2 advanced oxidation processes: An approach to invasive species prevention

Spread of marine invasive species (MIS) via ships’ ballast water causes global biotic homogenization and extinctions. In this study, a UV/TiO2 ballast water treatment system (BWTS) was designed to reduce transport of MIS. UV dose profiles simulated by computational fluid dynamics indicated that, depending on the flow rate and UV light intensity, the average applied UV dose was 260mJ/cm2. Combined UV/TiO2 treatment produced excess hydroxyl radicals that were confirmed by high performance liquid chromatography using a trapping agent. We then compared the effectiveness of UV/TiO2 BWTS against UV-alone BWTS at two different UV doses (i.e., 100% and 75%). We found that, even though UV alone reduced the abundance of all tested organisms, UV/TiO2 significantly reduced the abundance of all groups and led to a greater reduction than UV alone. Each trial should include the storage of treated ballast water for at least 120h according to Guideline G8 of the International Maritime Organization. Comparison tests after 120h of storage period showed that the plankton densities of treated water for UV/TiO2 treatment in the ⩾50μm group further deceased from 4 to 2 individuals (ind.)/m3, whereas those for UV-alone treatment increased from 6 to 57ind./m3, revealing that UV/TiO2 treatment had the potential to inhibit plankton regrowth, but UV alone did not. Although the efficacy of both strategies increased after 120h of storage period, the densities of microbes in discharge samples from the UV/TiO2 treatment were significantly lower than those in samples from UV-alone treatment. Moreover, the advantages of UV/TiO2 at low UV dose (i.e., 75%) were much greater and the concentrations of disinfection by-products (e.g., trihalomethanes, haloacetic acids) were observed in levels of 0.01–1μg/L.

Disinfection by-product occurrence in selected European waters

In this paper we report the findings of a European survey of regulated and emerging disinfection by-products (DBPs) in drinking waters in selected regions that were part of epidemiology studies. The levels of DBPs found reflected the diverse regions from which the samples were collected, the different treatment/disinfection processes and the different source waters. In addition to a wide range of concentrations of DBPs (e.g. median trihalomethanes (THMs) of 8–85 μg L –1 ), bromine incorporation was quite diverse (e.g. some waters were highly dominated by bromine-containing DBPs, whereas others only had chlorine-containing species). Bromine incorporation was highest in the haloacetonitriles (HANs) and was lowest in the trihalogenated haloacetic acids (THAAs). In addition, the ratios of THMs to HAAs, THMs to HANs, and THAAs to dihalogenated HAAs varied. Exposure assessment based on THMs alone was not sufficient for indicating the presence of emerging DBPs of health concern. Occurrence studies must include a more diverse group of analytes to better understand exposure to DBPs of health concern.

DBP Formation in Hot and Cold Water Across a Simulated Distribution System: Effect of Incubation Time, Heating Time, pH, Chlorine Dose, and Incubation Temperature

This paper demonstrates that disinfection byproducts (DBP) concentration profiles in heated water were quite different from the DBP concentrations in the cold tap water. Chloroform concentrations in the heated water remained constant or even decreased slightly with increasing distribution system water age. The amount of dichloroacetic acid (DCAA) was much higher in the heated water than in the cold water; however, the maximum levels in heated water with different distribution system water ages did not differ substantially. The levels of trichloroacetic acid (TCAA) in the heated water were similar to the TCAA levels in the tap water, and a slight reduction was observed after the tap water was heated for 24 h. Regardless of water age, significant reductions of nonregulated DBPs were observed after the tap water was heated for 24 h. For tap water with lower water ages, there were significant increases in dichloroacetonitrile (DCAN), chloropicrin (CP), and 1,1-dichloropropane (1,1-DCP) after a short period of heating. Heating of the tap water with low pH led to a more significant increase of chloroform and a more significant short-term increase of DCAN. High pH accelerated the loss of the nonregulated DBPs in the heated water. The results indicated that as the chlorine doses increased, levels of chloroform and DCAA in the heated water increased significantly. However, for TCAA, the thermally induced increase in concentration was only notable for the chlorinated water with very high chlorine dose. Finally, heating may lead to higher DBP concentrations in chlorinated water with lower distribution system temperatures.

Minimizing raw water NOM concentration through optimized source water selection

Natural organic matter (NOM) is present in all raw water supplies and is the major precursor to chlorinated disinfection by‐products (DBPs). Reducing the amount of NOM entering treatment plants and better understanding the character of NOM in raw water supplies are essential for optimizing treatment and meeting more‐stringent regulations. A study of the unfiltered New York City (NYC) water supply system evaluated the extent to which alternative raw water selection strategies could reduce finished water DBP concentrations. A two‐year monitoring program was conducted to establish spatial and temporal patterns of DBP precursors in NYC's upstate reservoirs. System operations modeling was driven with a statistically generated, long‐term time series of dissolved organic carbon concentrations for each reservoir as a proof‐of‐concept evaluation of alternative operating rules to minimize precursor transport to terminal reservoirs. Results found that DBP precursors varied widely among reservoirs and over time but that modified reservoir operations could substantially reduce finished water DBP concentrations.

Relating water quality monitoring to disinfection by-product formation in four pilot treatment streams

With increasing focus on the health implications from disinfection by-products (DBP) in drinking waters, appropriate monitoring parameters are required that can give rapid information on the potential of a treated water to form DBPs. Given that the most effective strategy for the reduction of concentrations of DBPs is the removal of their precursor, natural organic matter, parameters that relate to organic concentration and character are the most likely candidates. A project utilising four different treatment procedures applied to common source water was evaluated for DBP formation over three characteristic water quality periods and the link to key monitored parameters evaluated. Results showed that DBP formation was independent of the source water quality or treatment technology applied but was correlated to treated water dissolved organic carbon, and more strongly to the UV absorbance at 254 nm.

Discharges of produced waters from oil and gas extraction via wastewater treatment plants are sources of disinfection by-products to receiving streams

Fluids co-produced with oil and gas production (produced waters) are often brines that contain elevated concentrations of bromide. Bromide is an important precursor of several toxic disinfection by-products (DBPs) and the treatment of produced water may lead to more brominated DBPs. To determine if wastewater treatment plants that accept produced waters discharge greater amounts of brominated DBPs, water samples were collected in Pennsylvania from four sites along a large river including an upstream site, a site below a publicly owned wastewater treatment plant (POTW) outfall (does not accept produced water), a site below an oil and gas commercial wastewater treatment plant (CWT) outfall, and downstream of the POTW and CWT. Of 29 DBPs analyzed, the site at the POTW outfall had the highest number detected (six) ranging in concentration from 0.01 to 0.09μgL−1 with a similar mixture of DBPs that have been detected at POTW outfalls elsewhere in the United States. The DBP profile at the CWT outfall was much different, although only two DBPs, dibromochloronitromethane (DBCNM) and chloroform, were detected, DBCNM was found at relatively high concentrations (up to 8.5μgL−1). The water at the CWT outfall also had a mixture of inorganic and organic precursors including elevated concentrations of bromide (75mgL−1) and other organic DBP precursors (phenol at 15μgL−1). To corroborate these DBP results, samples were collected in Pennsylvania from additional POTW and CWT outfalls that accept produced waters. The additional CWT also had high concentrations of DBCNM (3.1μgL−1) while the POTWs that accept produced waters had elevated numbers (up to 15) and concentrations of DBPs, especially brominated and iodinated THMs (up to 12μgL−1 total THM concentration). Therefore, produced water brines that have been disinfected are potential sources of DBPs along with DBP precursors to streams wherever these wastewaters are discharged.

Spatial Variation of Disinfection By-Product Concentrations: Implications for Minimizing Exposure Misclassification

Spatial Variation of Disinfection By-Product Concentrations: Implications for Minimizing Exposure Misclassification

Pilot study on the removal of TOC, THMs, and HAAs in drinking water using ozone/UV–BAC

The contaminated water is a main source of many waterborne diseases such as cholera, typhoid, etc. causing many serious public health crises, especially in developing countries with the low hygiene condition. In Vietnam, previous studies have reported that industrial and domestic waste cause adverted pollution on Saigon River that supplies water for 30% of 10 million residents in Ho Chi Minh City. Annual monitoring water quality data during 2006–2011 showed that concentration of ammonia and organic matter has been significantly increased and over the allowable limit (COD ##xgt; 10 mg/L). In order to reduce these pollutants in the finished water and for disinfection, a large dose of chlorine (about 3–6 mg/L) needs adding in the treatment process at Tan Hiep water treatment plant. A negative effect of using too much chlorine is the formation of disinfection by-products (DBPs) such as trihalo-methanes (THMs) and haloacetic acids (HAAs). The concentration of THMs in finished water of Tan Hiep plant ranged from 50 to 200 μg/L. In this study, a pilot-scale plant using Ozone/UV process combined with biological activated carbon filter (BAC) was studied on eliminating the organic matters and the DBPs formation in drinking water. With the feed water taken after sedimentation, the combination of Ozone/UV–BAC proved to be very effective in TOC, DOC, UV254, and SUVA removals with percentage reduction of 19.1, 17.6, 30.7, and 16.4%, respectively. The removal efficiency of the combined process was always higher than the sum of treatment efficiency of each process (Ozone/UV or BAC) alone. It was confirmed that the pretreatment of Ozone/UV could help to increase the organic removal of BAC filter. According to the organic reduction, the concentration of DBPs in water has decreased considerably with 70.6% (THMs) and 67.7% (HAAs) removal. DBPs formation potential decreased 39.3% (THMFP) and 46.1% (HAAFP).

Spatial variation of disinfection by-product concentrations: Exposure assessment implications

The use of public water system (PWS) average trihalomethane (THM) and haloacetic acid (HAA) concentrations as surrogates of “personal” exposures in epidemiological studies of disinfection by-products (DBPs) may result in exposure misclassification bias from various sources of measurement error including intra-system variation of DBPs. Using 2000–2004 data from 107 PWSs in Massachusetts, we assessed two approaches for characterizing DBP spatial variability by identifying PWSs with low spatial variability (LSV) and examining differences in LSV across DBP groups and by type of source water and primary disinfectant. We also used spatial differences to examine the association between THM concentrations and indices of social disadvantage; however, we found no correlations or statistically significant differences based on the available data. We observed similar patterns for the percentage of quarterly sampling dates with LSV across different types of source water for all DBPs but not across disinfectants. We found there was little overlap between sites classified as having LSV across different DBP groups. In the main analysis, we found moderate correlations between both approaches (φTHM4 = 0.55; φBrTHM = 0.64; φHAA5 = 0.67); although Method 1 (based on concentration differences between samples) may be better suited for identifying PWSs for inclusion in epidemiological studies because it is more easily adapted to study-specific exposure gradients than Method 2 (based on categorical exposure percentiles). These data reinforce the need to consider different exposure assessment approaches when examining the spatial variation of multiple DBP surrogates as they can represent different DBP mixtures.

Monitoring of some disinfection by-products in drinking water treatment plants of El-Beheira Governorate, Egypt

Two water treatment plants (Edfina and Kom-Hamada) in El-Beheira Governorate were selected to monitor disinfection by-products (DBPs) concentrations. A 12-month monitoring program from October 2011 to September 2012 was established for measuring some DBPs and some water quality parameters such as temperature, pH, turbidity, total organic carbon (TOC), ammonia and bromide. The concentrations of DBPs were determined by gas chromatography with ECD (GC-ECD). Trihalomethanes (THMs) and chloral hydrate (CH) were commonly seen in all samples collected from Plant 1 (Edfina) and Plant 2 (Kom-Hamada). THMs mean concentrations ranged from 34.5 to 64.6 μg/L and from 28.2 to 52.8 μg/L for Plant 1 and Plant 2. CH mean concentrations ranged from 3.3 to 6.76 μg/L and from 2.8 to 3.9 μg/L for Plant 1 and Plant 2, respectively. Dichloroacetonitrile (DCAN) mean concentrations ranged from 1.1 to 2.0 μg/L and from 1.2 to 2.1 μg/L for Plant 1 and Plant 2, respectively. Chloropicrin (CP) was detected in Plant 1 only with mean concentration ranging from 0.91 to 1.1 μg/L. Trichloroacetonitrile (TCAN) and dibromoacetonitrile (DBAN) were below the limit of quantification (LOQ) in all samples. Higher concentrations of THMs were measured in summer and spring as compared to winter. DBPs concentrations were higher in Plant 1 than in Plant 2. The DBPs levels in all samples collected from Edfina and Kom-Hamada were generally below the guideline values set by the Egyptian Health Minister in 2007.

Disinfection by-products and ecotoxicity of ballast water after oxidative treatment – Results and experiences from seven years of full-scale testing of ballast water management systems

Since 2005, five different ballast water management systems (BWMSs) based on chlorination treatment have been tested by Norwegian Institute for Water Research (NIVA) according to guidelines from the International Maritime Organization (IMO). 25% and >50% of all the tested discharge samples exhibited acute and chronic toxic effects on algae, respectively. In most cases this toxicity was plausibly caused by a high free residual oxidant (FRO) level (>0.08mgCl/l). Of the 22 disinfection by-products (DBPs) that were identified in treated water at discharge, four compounds were at times found at concentrations that may pose a risk to the local aquatic environment. However, there seemed to be no clear indication that the measured DBP concentrations contributed to the observed algal toxicity. The addition of methylcellulose instead of lignin in the test water to comply with IMO requirements seemed to limit the formation of DBP.

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.

Temporal variability of disinfection by-products concentration in urban public water system

The occurrence of trihalomethanes (THMs) was studied in the drinking water samples from urban water supply network of Karachi city that served more than 18 million people. Drinking water samples were collected from 58 locations in summer (May-August) and winter (November-February) seasons. The major constituent of THMs detected was chloroform in winter (92.34%) and summer (93.07%), while the other THMs determined at lower concentrations. Summer and winter concentrations of total THMs at places exceed the levels regulated by UEPA (80 μg l-1) and WHO (100 μg l-1). GIS linked temporal variability in two seasons showed significantly higher median concentration (2.5%-23.06%) of THMs compared to winter.

Formation of DBPs in the drinking eater of Athens, Greece: a Ten-Year study

The formation of Disinfection By-Products (DBPs) in drinking water results from the reaction of chlorine or other disinfectants added to the water with naturally occurring organic materials, and has raised concerns during the last decades because these compounds are harmful for human health. During the present work, the formation of different categories of DBPs was investigated in four water treatment plants (WTP) using chlorine as disinfectant, and in selected points of the distribution network of Athens, Greece, which is supplied from these four WTP, during a period of ten years. The concentrations of DBPs were generally low and the annual mean concentrations always well below the regulatory limit of the European Union (EU) for the total trihalomethanes (TTHMs). The haloacetic acids (HAAs) have not been regulated in the EU, but during this investigation they often occurred in significant levels, sometimes exceeding the levels of TTHMs, which highlights the importance of their monitoring in drinking water. Apart from THMs and HAAs, several other DBPs species were detected at much lower concentrations in the chlorinated waters: chloral hydrate, haloketones and, in a limited number of cases, haloacetonitriles.

Effects of Chlorine on Disinfection by-Products (DBPs) Formation in Synthetic Drinking Water

This study focused on the effect of chlorine on disinfection by-product (DBPs) formation. The concentration of DBPs and total residual chlorine were measured at the same time in synthetic drinking water. Chlorine demand and DBPs increased with chlorine dose and contact time. The descending DBPs formation potential rank was: TCM > DCAA > TCAA > TCNM > BDCM. Furthermore, a linear relation between the concentrations of DBPs (HAAs, THMs or TNMs) and chlorine demand was discovered, and the coefficients did not correlate with chlorine dose. Emerging N-DBPs such as HANs did not follow those disciplines because of their special structures. These results have instructive meanings to the further control of DBPs.