Speciation Of Disinfection By-products Research Articles

Biodegradability of DBP precursors after drinking water ozonation

Ozonation is known to generate biodegradable organic matter, which is typically reduced by biological filtration to avoid bacterial regrowth in distribution systems. Post-chlorination generates halogenated disinfection byproducts (DBPs) but little is known about the biodegradability of their precursors. This study determined the effect of ozonation and biofiltration conditions, specifically ozone exposure and empty bed contact time (EBCT), on the control of DBP formation potentials in drinking water. Ozone exposure was varied through addition of H2O2 during ozonation at 1 mgO3/mgDOC followed by biological filtration using either activated carbon (BAC) or anthracite. Ozonation led to a 10% decrease in dissolved organic carbon (DOC), without further improvement from H2O2 addition. Raising H2O2 concentrations from 0 to 2 mmol/mmolO3 resulted in increased DBP formation potentials during post-chlorination of the ozonated water (target Cl2 residual after 24 h = 1–2 mg/L) as follows: 4 trihalomethanes (THM4, 37%), 8 haloacetic acids (HAA8, 44%), chloral hydrate (CH, 107%), 2 haloketones (HK2, 97%), 4 haloacetonitriles (HAN4, 33%), trichloroacetamide (TCAM, 43%), and adsorbable organic halogen (AOX, 27%), but a decrease in the concentrations of 2 trihalonitromethanes (THNM2, 43%). Coupling ozonation with biofiltration prior to chlorination effectively lowered the formation potentials of all DBPs including CH, HK2, and THNM2, all of which increased after ozonation. The dynamics of DBP formation potentials during BAC filtration at different EBCTs followed first-order reaction kinetics. Minimum steady-state concentrations were attained at an EBCT of about 10–20 min, depending on the DBP species. The rate of reduction in DBP formation potentials varied among individual species before reaching their minimum concentrations. CH, HK2, and THNM2 had the highest rate constants of between 0.5 and 0.6 min−1 followed by HAN4 (0.4 min−1), THM4 (0.3 min−1), HAA8 (0.2 min−1), and AOX (0.1 min−1). At an EBCT of 15 min, the reduction in formation potential for most DBPs was less than 50% but was higher than 70% for CH, HK2, and THNM2. The formation of bromine-containing DBPs increased with increasing EBCT, most likely due to an increase in Br−/DOC ratio. Overall, this study demonstrated that the combination of ozonation and biofiltration is an effective approach to mitigate DBP formation during drinking water treatment.

Application of Classification Trees for Predicting Disinfection By-Product Formation Targets from Source Water Characteristics

Abstract Formation and speciation of disinfection by-products (DBPs) depend on source water constituents. Many studies have sought to model the formation of DBPs using both source water and in-plant operational data, and although sometimes highly predictive of DBP formation, these models are limited in their applicability. To create regional models that could apply to multiple plants within a watershed, classification trees were used to predict finished water DBP parameters from source water constituents collected at multiple locations in a watershed. Data were from a field study conducted in the Monongahela River in southwestern PA from May, 2010 to September, 2012, incorporating six different sites. Classification trees were used to predict violation of, or compliance with, four threshold values that have regulatory and operational significance, namely, the total trihalomethanes (TTHMs) maximum contaminant level (MCL) (regulatory standard of 80 μg/L), 80% of the TTHMs MCL (64 μg/L), a bromine incorporat...

Temporal variations of disinfection byproduct precursors in wildfire detritus

The Rim Fire ignited on August 17, 2013 and became the third largest wildfire in California history. The fire consumed 104,131 ha of forested watersheds that were the drinking water source for 2.6 million residents in the San Francisco Bay area. To understand temporal variations in dissolved organic matter (DOM) after the wildfire and its potential impacts on disinfection byproduct (DBP) formation in source water supply, we collected the 0–5 cm ash/soil layer with surface deposits of white ash (high burn severity) and black ash (moderate burn severity) within the Rim Fire perimeter in Oct 2013 (pre-rainfall) for five sequential extractions, and in Dec 2013 (∼87 mm cumulative precipitation) and Aug 2014 (∼617 mm cumulative precipitation) for a single water extraction. Water-extractable DOM was characterized by absorption and fluorescence spectroscopy and DBP formation tests. Both increasing cumulative precipitation in the field or number of extractions in the lab resulted in a significant decrease in specific conductivity, dissolved organic carbon, and DBP formation potential, but an increase in DOM aromaticity (reflected by specific UV absorbance). However, the lab sequential leaching failed to capture the increase of the NOx−-N/NH4+-N ratio and the decrease in pH and dissolved organic carbon/nitrogen ratio of ash/soil extracts from Oct 2013 to Aug 2014. Increasing cumulative precipitation, inferring an increase in leaching after fire, led to an increase in DOM reactivity to form trihalomethanes, haloacetic acids, and chloral hydrate, but not for haloketones, haloacetonitrile, or N-nitrosodimethylamine, which were more related to the original burn severity. This study highlights that fire-affected DBP precursors for different DBP species have distinct temporal variation possibly due to their various sensitivity to biogeochemical alterations.

Formation of halogenated disinfection by-products in cobalt-catalyzed peroxymonosulfate oxidation processes in the presence of halides

Sulfate radicals (SO4−) generated by activation of peroxymonosulfate (PMS) and persulfate (PS) are highly oxidative and applied to degrade various organic pollutants. This research was designed to investigate formation of halogenated by-products in Co2+ activated PMS process in the presence of halides and natural organic matter (NOM). It was revealed that no halogenated by-products were detected in the presence of Cl− while 189 μg/L bromoform and 100.7 μg/L dibromoacetic acid (DBAA) were found after 120 h when 2 mg/L NOM, 0.1 mM Br−, 1.0 mM PMS, and 5 μL Co2+ were present initially. These products are known as disinfection by-products (DBPs) since they are formed in water disinfection processes. Formation of DBPs was even more significant in the absence of Co2+. The data indicate that both PMS and SO4− can transform Br− to reactive bromine species which react with NOM to form halogenated by-products. Less DBP formation in Co2+-PMS systems was due to the further destruction of DBPs by SO4−. More DBPs species including chlorinated ones were detected in the presence of both Cl− and Br−. However, more brominated species produced than chlorinate ones generally. The total DBP yield decreased with the increase of Cl− content when total halides kept constant. This is one of the few studies that demonstrate the formation of halogenated DBPs in Co2+/PMS reaction systems, which should be taken into consideration in the application of SO4− based oxidation technologies.

Comparative study on DBPs formation profiles of intermediate organics from hydroxyl radicals oxidation of microbial cells

This study assessed the characteristics of disinfection byproducts (DBPs) formation from intermediate organics during UV/H2O2 treatment of activated sludge and algae cells under various reaction conditions. The DBPs including trihalomethanes (THMs), haloacetic acids (HAAs), haloketones (HKs) and haloacetonitriles (HANs) in UV/H2O2-treated and chlorinated water were measured. The results showed that both dissolved organic carbon (DOC) and dissolved organic nitrogen (DON) increased during the initial stage of UV/H2O2 treatment due to the lysis of sludge and algae cells, which enhanced the formation of both C- and N-DBPs; however, both DOC and DON decreased after longer reaction times. During the UV/H2O2 treatments, THMs formation potential (THMFP) peaked earlier than did HAAs formation potential (HAAFP). This shows that the dissolved organics released from lysis of microbial cells in the early stages of oxidation favor the production of THMs over HAAs; however, HAAs precursors increased with the oxidation time. Chlorination with bromide increased the formation of THMs and HAAs but less HKs and HANs were produced. Comparisons of normalized DBP formation potential (DBPFP) of samples collected during UV/H2O2 treatments of four different types of organic matter showed that the highest DBPFP occurred in filtered treated wastewater effluent, followed by samples of activated sludge, filtered eutrophicated pond water, and samples of algae cells. With increasing oxidation time, the dominant DBP species shifted from THMs to HAAs in the samples of activated sludge and algae cells. The DBPFP tests also showed that more HAAs were formed in biologically treated wastewater effluent, while the eutrophicated source water produced more THMs.

Impact of pre-ozonation on disinfection by-product formation and speciation from chlor(am)ination of algal organic matter of Microcystis aeruginosa

The increasing use of algal-impacted source waters is increasing concerns over exposure to disinfection byproducts (DBPs) in drinking water disinfection, due to the higher concentrations of DBP precursors in these waters. The impact of pre-ozonation on the formation and speciation of DBPs during subsequent chlorination and chloramination of algal organic matter (AOM), including extracellular organic matter (EOM) and intracellular organic matter (IOM), was investigated. During subsequent chlorination, ozonation pretreatment reduced the formation of haloacetonitriles from EOM, but increased the yields of trihalomethanes, dihaloacetic acid and trichloronitromethane from both EOM and IOM. While in chloramination, pre-ozonation remarkably enhanced the yields of several carbonaceous DBPs from IOM, and significantly minimized the nitrogenous DBP precursors. Also, the yield of 1,1-dichloro-2-propanone from IOM was decreased by 24.0% after pre-ozonation during chloramination. Both increases and decreases in the bromine substitution factors (BSF) of AOM were observed with ozone pretreatment at the low bromide level (50μg/L). However, pre-ozonation played little impact on the bromide substitution in DBPs at the high bromide level (500μg/L). This information was used to guide the design and practical operation of pre-ozonation in drinking water treatment plants using algae-rich waters.

Variations of disinfection by-product levels in small drinking water utilities according to climate change scenarios: a first assessment

In Québec, Canada, shifts in climate patterns (i.e., rainfall increase) could have consequences on source water quality due to the intensification of surface/groundwater runoff contamination events, leading to a decline in drinking water treatment efficiency and ultimately disinfection by-products (DBPs) formation following treatment. To assess the impacts of climate change (CC) scenarios on DBP formation, a suite of models linking climate to DBPs was used. This study applies three emissions scenarios (B1, A1B and A2) for three 30-year horizons (2020, 2050 and 2080) in order to produce inputs to test several DBP models (total trihalomethanes (TTHMs), haloacetic acids and haloacetonitriles). An annual increase is estimated for all DBPs for each CC scenario and horizon. The highest seasonal increases were estimated for winter for all DBP groups or species. In the worst-case scenario (A2-2080), TTHMs could be affected more particularly during winter (+34.0%), followed by spring (+16.1%) and fall (+4.4%), whereas summer concentrations would remain stable (−0.3 to +0.4%). Potentially, small water utilities applying only a disinfection step could be more affected by rising TTHMs concentrations associated with CC than those having implemented a complete water treatment process (coagulation–flocculation, filtration and disinfection) with +13.6% and +8.2% increases respectively (A2-2080).

Characterization, DBPs formation, and mutagenicity of soluble microbial products (SMPs) in wastewater under simulated stressful conditions

Soluble microbial products (SMPs) are an important group of components in activated sludge-treated wastewater effluents. Chlorination is the most widely used method for disinfecting wastewater effluents. During chlorination of wastewater effluents, SMPs may act as precursors to form disinfection by-products (DBPs), which may pose adverse impacts on the organisms in the receiving water body. In this study, SMPs were prepared by simulating activated sludge under different stressful conditions, including high ammonia content (HA), high salinity (HS), high levels of heavy metals (HM) and high temperature (HT), as well as a normal state (NS). The molecular weight (MW) distribution of SMPs was characterized using gel permeation chromatography (GPC). Chlorination of SMPs was conducted with sodium hypochlorite. Several species of DBPs were detected using gas chromatography–mass spectrometry (GC–MS). The mutagenicity of SMPs solutions and SMPs solutions treated with chlorination was also evaluated using the umu test. Compared with NS, stressful conditions were induced to produce more low MW components of SMPs. Stressful conditions, had no significant effect on the species of DBPs, but played a crucial role in the levels of DBPs produced in SMPs solutions during chlorination. Among the stressful conditions tested, HT and HS resulted in higher levels of both carbon-containing DBPs (C-DBPs) and nitrogen-containing DBPs (N-DBPs). Levels of C-DBPs and N-DBPs were lower under HM condition. HA stimulated the production of N-DBPs, but had no impact on the levels of C-DBPs. The mutagenicity of SMPs solutions was higher under the stressful conditions than that under NS condition in both before and after chlorination. For each SMPs solution, the mutagenicity of SMPs increased after the chlorination, except for SMPs solution under HM and NS conditions.

Formation and speciation of disinfection byproducts during chlor(am)ination of aquarium seawater

The chemistry associated with the disinfection of aquarium seawater is more complicated than that of freshwater, therefore limited information is available on the formation and speciation of disinfection byproducts (DBPs) in marine aquaria. In this study, the effects of organic precursors, bromide (Br−) and pre-ozonation on the formation and speciation of several typical classes of DBPs, including trihalomethanes (THM4), haloacetic acids (HAAs), iodinated trihalomethanes (I-THMs), and haloacetamides (HAcAms), were investigated during the chlorination/chloramination of aquarium seawater. Results indicate that with an increase in dissolved organic carbon concentration from 4.5 to 9.4mg/L, the concentrations of THM4 and HAAs increased by 3.2–7.8 times under chlorination and by 1.1–2.3 times under chloramination. An increase in Br− concentration from 3 to 68mg/L generally enhanced the formation of THM4, I-THMs and HAcAms and increased the bromine substitution factors of all studied DBPs as well, whereas it impacted insignificantly on the yield of HAAs. Pre-ozonation with 1mg/L O3 dose substantially reduced the formation of all studied DBPs in the subsequent chlorination and I-THMs in the subsequent chloramination. Because chloramination produces much lower amounts of DBPs than chlorination, it tends to be more suitable for disinfection of aquarium seawater.

UV and UV/H2O2 treatment of diazinon and its influence on disinfection byproduct formation following chlorination

Incomplete oxidation of organic micropollutants may result in diverse intermittent oxidation byproducts, significantly affecting disinfection byproducts (DBPs) formation of the original solutions following chlorination. This study investigated DBPs formation from diazinon in solution due to the formation of intermittent oxidation byproducts by UV and UV/H2O2 pre-oxidation. Monochloroacetic acid (MCAA), dichloroacetic acid (DCAA), trichloroacetic acid (TCAA), chloroform (TCM), dichloroacetonitrile (DCAN) and 1,1,1-trichloroacetone (1,1,1-TCP) were detected for chlorinated diazinon solutions that have been treated by UV and UV/H2O2 oxidation. The DBPs formation was found increased significantly in the treated diazinon solutions with UV dose. Solution pH and H2O2 dose also exhibited distinct influences on the DBPs formation depending on the individual DBP species. Speciation and molecular structures of the oxidation byproducts were analyzed via MS and MS/MS spectra. Four main UV oxidation byproducts, (2-isopropyl-6-methyl-4-pyrimidinol (IMP), O-analog diazinon (diazoxon), diethyl thiophosphate (DETP) and diethyl phosphate (DEP)), were also examined individually to identify their relative contributions to DBPs formation. The increase in total DBPs formation of the treated diazinon solutions was found to be attributable mainly to its oxidation product IMP and its secondary oxidation products, while the other two fragments DETP and DEP had little effect. Moreover, its oxidation fragment diazoxon intensified the formation of MCAA, DCAA and TCAA under UV/H2O2 pre-oxidation condition.

Effects of ozonation on disinfection byproduct formation and speciation during subsequent chlorination

Ozone has been widely used for drinking water treatment recently. This study was conducted to investigate the effect of dosing ozone on the formation potentials and speciation of disinfection by-products (DBPs, brominated DBPs in particular) during subsequent chlorination. Trihalomethanes (THMs), trihaloacetic acids (THAAs), dihaloacetic acids (DHAAs), dihaloacetonitriles (DHANs), chloral hydrate (CH)and trichloronitromethane (TCNM) were included. The results showed that the yields of THMs, THAAs and DHAAs reached the maxima at 1.83, 0.65 and 0.56μM, respectively, corresponding to an ozone dose approximately at 2mgL−1. The formation potentials of CH and TCNM increased, while that of DHAN decreased, with the increase of ozone dose up to 6mgL−1. The bromide incorporation factor values of THMs, THAAs, DHAAs and DHANs increased from 0.62, 0.37, 0.45 and 0.39 at O3=0mgL−1 to 0.89, 0.65, 0.62 and 0.89 at O3=6mgL−1, respectively. It indicated that the use of ozone as a primary disinfectant may cause a shift to more brominated DBPs during subsequent chlorination, and the shift may be more evident with increased ozone dose. The total percentage of brominated DBPs (as bromide) reached the maximum value of 55% at 2mgL−1 ozone dose.

Enhanced formation of disinfection byproducts in shale gas wastewater-impacted drinking water supplies.

The disposal and leaks of hydraulic fracturing wastewater (HFW) to the environment pose human health risks. Since HFW is typically characterized by elevated salinity, concerns have been raised whether the high bromide and iodide in HFW may promote the formation of disinfection byproducts (DBPs) and alter their speciation to more toxic brominated and iodinated analogues. This study evaluated the minimum volume percentage of two Marcellus Shale and one Fayetteville Shale HFWs diluted by fresh water collected from the Ohio and Allegheny Rivers that would generate and/or alter the formation and speciation of DBPs following chlorination, chloramination, and ozonation treatments of the blended solutions. During chlorination, dilutions as low as 0.01% HFW altered the speciation toward formation of brominated and iodinated trihalomethanes (THMs) and brominated haloacetonitriles (HANs), and dilutions as low as 0.03% increased the overall formation of both compound classes. The increase in bromide concentration associated with 0.01-0.03% contribution of Marcellus HFW (a range of 70-200 μg/L for HFW with bromide = 600 mg/L) mimics the increased bromide levels observed in western Pennsylvanian surface waters following the Marcellus Shale gas production boom. Chloramination reduced HAN and regulated THM formation; however, iodinated trihalomethane formation was observed at lower pH. For municipal wastewater-impacted river water, the presence of 0.1% HFW increased the formation of N-nitrosodimethylamine (NDMA) during chloramination, particularly for the high iodide (54 ppm) Fayetteville Shale HFW. Finally, ozonation of 0.01-0.03% HFW-impacted river water resulted in significant increases in bromate formation. The results suggest that total elimination of HFW discharge and/or installation of halide-specific removal techniques in centralized brine treatment facilities may be a better strategy to mitigate impacts on downstream drinking water treatment plants than altering disinfection strategies. The potential formation of multiple DBPs in drinking water utilities in areas of shale gas development requires comprehensive monitoring plans beyond the common regulated DBPs.

Removal of disinfection by-products from contaminated water using a synthetic goethite catalyst via catalytic ozonation and a biofiltration system.

The effects of synthetic goethite (α-FeOOH) used as the catalyst in catalytic ozonation for the degradation of disinfection by-product (DBP) precursors are investigated. A biofiltration column applied following the catalytic ozonation process is used to evaluate the efficiency of removing DBP precursors via biotreatment. Ozone can rapidly react with aromatic compounds and oxidize organic compounds, resulting in a decrease in the fluorescence intensity of dissolved organic matter (DOM). In addition, catalytic ozonation can break down large organic molecules, which causes a blue shift in the emission-excitation matrix spectra. Water treated with catalytic ozonation is composed of low-molecular structures, including soluble microbial products (SMPs) and other aromatic proteins (APs). The DOM in SMPs and APs is removed by subsequent biofiltration. Catalytic ozonation has a higher removal efficiency for dissolved organic carbon and higher ultraviolet absorbance at 254 nm compared to those of ozonation without a catalyst. The use of catalytic ozonation and subsequent biofiltration leads to a lower DBP formation potential during chlorination compared to that obtained using ozonation and catalytic ozonation alone. Regarding DBP species during chlorination, the bromine incorporation factor (BIF) of trihalomethanes and haloacetic acids increases with increasing catalyst dosage in catalytic ozonation. Moreover, the highest BIF is obtained for catalytic ozonation and subsequent biofiltration.

Effect of seawater intrusion on formation of bromine-containing trihalomethanes and haloacetic acids during chlorination

This study quantified the formation and speciation of halogenated organic disinfection byproducts (DBPs) during chlorination as a function of seawater intrusion by spiking fresh groundwater with 0.1% to 2% seawater by volume. The four chlorine- and bromine-containing trihalomethanes (THM4) and the nine chlorine- and bromine-containing haloacetic acids (HAA9) were the DBPs investigated. The bromide concentration increased from 38μgL−1 in fresh groundwater to 974μgL−1 in 2% seawater, and upon chlorination the concentration of THM4 increased from 43 to 206μgL−1 and the concentration of HAA9 increased from 39 to 75μgL−1. At 0.4% seawater and higher the THM4 concentration exceeded the U.S. EPA maximum contaminant level of 80μgL−1. Although the mass concentration of HAA9 increased by nearly a factor of 2 over the seawater range of 0% to 2%, the mass concentration of the five regulated HAAs (i.e., HAA5) remained approximately constant. This is because HAA5 excludes four bromine-containing species. The increase in mass concentrations of THM4 and HAA9 with increasing seawater intrusion was the result of an increased molar formation of DBP species and a shift from chlorinated species to brominated species.

Spatial and Seasonal Variations of Disinfection Byproducts (DBPs) in Drinking Water Distribution Systems of Istanbul City, Turkey

This study presents the seasonal and spatial variations of trihalomethanes (THMs) and haloacetic acids (HAAs) in 30 sampling points within three water distribution systems of Istanbul City, Turkey. The effects of surface water quality, seasonal variation, and species differences were examined. The occurrence of chlorinated THMs and HAAs levels was considerably lower in the system in which raw water is subjected to pre-ozonation versus pre-chlorination. Seasonal analysis of the data indicated that the median concentration of four THMs (THM4) was higher than nine HAAs (HAA9) concentrations in all three distribution systems sampling points. For all distribution systems monitored, the highest median THM4 and HAA9 concentrations were observed in the spring and summer season, while the lowest concentrations of these disinfection byproduct (DBP) compounds were obtained in the fall and winter period. Due to the higher level of bromide in supplying waters of these two systems, moderate levels of brominated DBP species have been observed in the Kagithane and Buyukcekmece distribution systems districts. In fact, Spearman partial correlations (Spearman rank correlation coefficients [rs]) tend to be higher among analogues in terms of number and types of substituent, especially TCAA with TCM (rs 0.91), and DBAA with DBCM (rs 0.90). In contrast, the hydraulic (residence time and flow rate) and chemical mechanisms (hydrolysis, volatilization, and adsorption) affect the fate and transport of DBPs in distribution systems. Seasonal and spatial variations of DBPs presented in this study have important implications on regulatory issues and from an epidemiological point of view.

Influencing factors of disinfection byproducts formation during chloramination of Cyclops metabolite solutions

Effects of reaction time, chlorine dosage, pH and temperature on the formation of disinfection byproducts (DBPs), were investigated during the chloramination of Cyclops metabolite solutions. The results showed that some species of DBPs like trichloromethane (TCM), dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA) could accumulate to their respective stable values with a progressive elevation in reaction time and monochloramine concentration. And 1,1,1–2-trichloropropanone (1,1,1-TCP) content decreased correspondingly with a continuous increase of reaction time. The amounts of chloral hydrate (CH), chloropicrin (TCNM), 1,1,1-TCP and DCAA firstly increased and then decreased with increasing monochloramine doses. Higher temperature resulted in a decrease of CH, dichloroacetonitrile (DCAN), 1,1-dichloropropanone (1,1-DCP), 1,1,1-TCP, DCAA and TCAA concentration. pH affected the formation of the different DBPs distinctly. TCM accumulateded with the increase of pH under 9, and DCAA, TCAA, CH and 1,1-DCP decreased continuously with increasing pH from 5 to 10, and other DBPs had the maximum concentrations at pH 6–7.

Characterization of soluble microbial products as precursors of disinfection byproducts in drinking water supply

Water pollution by wastewater discharge can cause the problem of disinfection byproducts (DBPs) in drinking water supply. In this study, DBP formation characteristics of soluble microbial products (SMPs) as the main products of wastewater organic biodegradation were investigated. The results show that SMPs can act as DBP precursors in simulated wastewater biodegradation process. Under the experimental conditions, stabilized SMPs had DBPFP (DBP formation potential) yield of around 5.6μmolmmol−1-DOC (dissolved organic carbon) and DBP speciation profile different from that of the conventional precursor, natural organic matter (NOM). SMPs contained polysaccharides, proteins, and humic-like substances, and the latter two groups can act as reactive DBP precursors. SMP fraction with molecular weight of <1kDa accounted for 85% of the organic carbon and 65% of the DBP formation. As small SMP molecules are more difficult to remove by conventional water treatment processes, more efforts are needed to control wastewater-derived DBP problem in water resource management.

Examination of disinfection by-product (DBP) formation in source waters: A study using log-transformed differential spectra

Formation of disinfection by-products (DBPs) in ten drinking source waters located in the United States was examined in this study. DBP generation was interpreted in the context of halogenation-induced changes of log-transformed absorbance spectra of dissolved organic matter (DOM) present in the waters. This approach allows probing the behavior of relatively minor structures that can be highly sensitive towards any process of interest, notably DOM halogenation. This concept was applied to examine effects of chlorination time on the kinetics of chlorine consumption and release of several DBP groups such as total trihalomethanes (THM4, including CHCl3, CHCl2Br, CHClBr2 and CHBr3), haloacetic acids (HAA9, including MCAA, MBAA, DCAA, TCAA, BCAA, DBAA, BDCAA, DBCAA and TBAA), haloacetonitriles (THAN4, including TCAN, DCAN, BCAN and DBAN), haloketones (HK2, including DCP and TCP), chloral hydrate (CH) and chloropicrin (CPN). Two alternative parameters, namely the differential logarithm of DOM absorbance at 350 nm (DLnA350) and change of the spectral slope in the range of wavelengths 325–375 nm (DSlope325-375) were introduced to quantify individual DBP species formed and Cl2 consumption. DLnA350 and DSlope325-375, especially DLnA350 were determined to be more reliable than differential absorbance at 272 nm that was utilized in prior applications of differential spectroscopy to characterize DBP formation. Strong linear relationships between DLnA350 values and concentrations of major groups of and individual DBP species (e.g. THM4, HAA9, HAN4 and CPN were found to exist (mostly, R2 > 0.95) and the intercept of these correlations with the y-axis was near zero for the examined water sources. Correlations between DLnA350 values and concentrations of CH and HK2 were also strong but they were nonlinear. The slope of the correlations between the concentrations of major groups of DBP species vs -DLnA350 were also well correlated with SUVA254 and LnA350 for all the examined source waters. It indicates that log-transformations of the absorbance spectra of surface water and parameters based on such transformations (e.g., DLnA350 and DSlope325-375) have a potential to provide an alternative reliable approach to monitor the halogenation of DOM and attendant formation of individual DBP species.

Occurrence and speciation of disinfection by-products in water and air of indoor swimming pools in the province of Quebec (Canada)

Swimming pools’ workers are exposed to potentially high levels of water and air disinfection by-products (DBP) which actual health impacts (e.g., irritation, carcinogenicity, genotoxicity) are stil...

Variation of Disinfection By-Products Formation Potential Species at Several Stages of Drinking Water Treatment Plants

The variation of disinfection by-products (DBPs) at several stages of drinking water treatment plants was investigated in two drinking water plants. The results clearly indicate that the low molecular weight total organic carbon (TOC) which has been identified as primary precursor for chlorinated DBPs was difficult to remove by coagulation. Plant A which used conventional coagulation/sedimentation could not decrease the species of trihalomethanes (THMs) and haloacetic acids (HAAs) formation potential. Biological activated carbon (BAC) was applied in Plant B which removed the maximum amount of TOC, while more kinds of microbial products were produced in BAC unit which could be the potential precursors of DBPs. Therefore, the species of DBPs formation potential still increased in the treatment processes of Plant B. Because different components of organic precursors produced different DBPs species, the processes of Plant B could decrease TOC efficiently but the species of THMs and HAAs formation potential.