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Wildfires are complex phenomena that have served a vital role in ecosystem function for millennia. However, thermal alterations to dissolved organic matter's (DOM) solubility and chemical features can change disinfection byproduct (DBP) formation dynamics. Physicochemical changes to DOM are influenced by several factors, the most prominent being heating temperature. In this study, mineral soil samples were collected from fire‐prone areas, artificially heated in a muffle furnace to simulate wildfire heating, and leached. As heating temperature increased, chloroform and dichloroacetic acid yields decreased and increased, respectively. Of particular interest was the stimulation of dichloroacetonitrile, a highly toxic and unregulated DBP, at moderate heating temperatures. To demonstrate further insight into the chemical attributes of wildfire‐impacted DOM, optical properties were used as proxy measurements. This work provides water utilities with information on how wildfires can alter DBP formation potential, and a means to investigate correlations between intrinsic optical measurements and DBP yields. [ABSTRACT FROM AUTHOR]

The photochemical properties of dissolved organic matter (DOM) have been of interest to scientists and engineers since the 1970s. Upon light absorption, chromophoric DOM (CDOM) can sensitize the formation of different short-lived reactive intermediates (RIs), including hydroxyl radical (OH), singlet oxygen (1O2) and superoxide radical anion (O2·[sup -]). In addition, a fraction of the excited singlet states in CDOM decays into excited triplet states (3CDOM*), which are also important photochemical transients in environmental systems. These RIs have a significant impact on different processes in sunlit waters, including degradation of organic contaminants and the inactivation of pathogens. Due to their transient nature and low steady-state concentrations, the use of common analytical techniques for the direct measurement of these species is impractical. Therefore, specific probe compounds (PCs) are used. PCs include furfuryl alcohol for 1O2, and terephthalic acid for •OH. In this publication, we present a critical review of the use of PCs for the assessment of the formation of photochemically generated RIs. We first introduce the concept of a PC, including the kinetic treatment and necessary assumptions needed to conduct a specific measurement. Afterward, we present short overviews of the most studied RIs and review relevant issues regarding the use of specific PCs for their measurement. We finalize by offering recommendations regarding the use of PCs in environmental photochemistry. [ABSTRACT FROM AUTHOR]

The temperature dependence of the photochemical production of the hydroxyl radical (•OH) from dissolved organic matter (DOM) was investigated by measuring the apparent temperature dependence of the quantum yield (Φa) for this process. Temperature dependent Φa values were analyzed using the Arrhenius equation. Apparent activation energies obtained for DOM isolates purchased from the International Humic Substances Society ranged from 16 to 34 kJ mol–1. Addition of 40 units mL–1 catalase, used to hinder the hydrogen peroxide (H2O2)-dependent pathway to •OH, did not impact the observed activation energy. However, an increase in activation energy was observed in lower molecular weight DOM obtained by size fractionation. We also measured the temperature dependence of p-benzoquionone photolysis as a model compound for DOM and observed no temperature dependence (slope p = 0.41) for the formation of phenol from oxidation of benzene (the •OH probe used), but a value of about 10 kJ mol–1 for p-benzoquinone loss, which is consistent with formation of a quinone-water exciplex. These data provide insight into DOM photochemistry as well as provide parameters useful for modeling steady state •OH concentrations in natural systems. [ABSTRACT FROM AUTHOR]

Abstract: In 2010, an estimated 1.87 million gallons (7079 cubic meters) of chemical dispersants were applied to open ocean waters in the Gulf of Mexico as part of the response to the Deepwater Horizon blowout. This unprecedented volume of dispersant application highlighted the importance of dispersant chemical formulations, raising questions of dispersant fate and transport in the open ocean and spurring research into formulation improvements. The research presented here elucidates the contribution of photolytic processes to the degradation of two solvent constituents of these dispersant mixtures: propylene glycol (PG) and 2-butoxyethanol (2-BE). A series of photodegradation experiments were conducted to determine the contribution of direct photolysis and indirect photolysis via hydroxyl radical (HO ) to compound degradation. Experiments were performed using both deep UV light sources (low pressure (LP) and medium pressure (MP) mercury vapor ultraviolet (UV) lamps) and a solar simulator. Sample matrices included ultrapure water, nitrate amended water, hydrogen peroxide (H2O2) spiked water, Gulf of Mexico seawater, and a surface water from Boulder, CO. Experiments included determination of the molar absorption coefficients (ε) and the HO reaction rate constants (k HO ) of the individual compounds. Data illustrated that significant direct photolysis of either PG or 2-BE from sunlight is unlikely. The kHO for PG and 2-BE were determined to be 6.15 × 108 M−1 s−1 and 1.15 × 109 M−1 s−1, respectively. Solar simulation and UV experiments indicate that in natural systems, neither PG nor 2-BE is expected to undergo significant, rapid degradation due to direct or indirect photolysis. PG and 2-BE are effectively degraded through indirect photolysis in the presence of high HO concentrations, suggesting UV/H2O2 is a feasible possibility for the treatment of waters containing PG and 2-BE. [Copyright &y& Elsevier]

The excitation of dissolved organic matter (DOM) from sunlight produces a range of reactive intermediates, including triplet-excited state dissolved organic matter (3DOM*), hydroxyl radical (HO•), and singlet oxygen (1O2). These intermediates are important for the inactivation of pathogens and for the degradation of trace organic contaminants (OC) within natural and engineered systems. However, halides found in the background matrix can alter the photoproduction rates by promoting or quenching the formation of these intermediates. Apparent quantum yields (Φa) for 1O2, HO• , and steady state 3DOM* concentrations photoproduced from DOM isolates were determined with varying concentrations of chloride and bromide. Fluorescence quantum yields were measured as well to probe the photophysics of the system. The maximum fluorescence quantum yield (ΦF) decreased with the addition of halides, representing a quenching of the excited singlet state of DOM. In contrast, the steady state concentrations for 3DOM* were enhanced, suggesting intersystem crossing from the singlet state to the triplet state was increased by the presence of halides. The Φ for 1O2 was increased with the addition of halides, which was expected following the (DOM* results because the mechanism for 1O2 production occurs through the inactivation of 3DOM* by dissolved oxygen. Although HO' production would be expected to follow 1O2, the opposite trend was seen, which suggests the formation of HO• does not occur through the same precursor. Understanding the impact of specific quenchers on DOM could be a key to understanding the true formation potential for reactive intermediates and is especially important in estuaries and wastewater impacted aquatic systems. [ABSTRACT FROM AUTHOR]

Singlet oxygen (¹O2) plays an important role in the inactivation of pathogens and the degradation of organic contaminants. The present study looks at the surface steady-state concentration of ¹O2 and quantum yields (ΦSO) for organic matter present in or derived from wastewater (WWOM), including those that are partially treated and after undergoing oxidation. The surface steady state concentrations of ¹O2 ranged from 1.23 to 1.43 × 10-13 M for bulk wastewaters under simulated sunlight. The ΦSO values for these samples varied from 2.8% to 4.7% which was higher than the values observed for the natural organic matter isolates evaluated (1.6-2.1%). Size fractionation of WWOM resulted in ΦSO increases, with a value of up to 8.6% for one of the <1 kDa fractions. Furthermore, oxidation of WWOM by hypochlorous acid (HOCl) and molecular ozone also resulted in an increase in ΦSO, with the highest measured value being 9.3%. This research further explores the correlations between the photosensitizing properties of WWOM and optical characteristics (e.g., absorbance, E2:E3 ratio). Making use of easily measurable absorbance values, a model for the prediction of ¹O2 steady-state concentrations is proposed. [ABSTRACT FROM AUTHOR]

The formation of total organic halogen (TOX), carbonaceous disinfection byproducts (DBPs) (trihalomethanes (THMs) and haloacetic acids (HAAs)), and nitrogenous DBPs (trichloronitromethane (TCNM) or chloropicrin, haloacetonitriles (HANs), and nitrosamines) was examined during the chlorination or chloramination of intracellular organic matter (IOM) extracted from Microcystis aeruginosa, Oscillatoria sp. (OSC), and Lyngbya sp. (LYN). The percentage of unknown TOX (22-38%) during chlorination indicated that the majority of DBPs were identified among THMs, HAAs, TCNM, and HANs. Bromide was readily incorporated into DBPs with speciation shifting slightly from dihalogenated species to trihalogenated species. During formation potential testing with chloramines, nitrosamine yields from IOM were measured for N-nitrosodimethylamine (NDMA, 10-52 ng/mgC), N-nitrosopyrrolidine (NPYR, 14 ng/mgC), N-nitrosopiperidine (NPIP, 3.7-5.5 ng/mgC), and N-nitrosomethylethylamine (NMEA, 2.1-2.6 ng/mgC). When IOM was added to a natural water matrix, the nitrosamine yields were not realized likely due to competition from natural organic matter. Ozonation increased NDMA and NMEA formation and reduced NPYR and NPIP formation during subsequent chloramination. In addition, ozone oxidation of IOM formed detectable concentrations of aldehydes, which may contribute to DBP formation. Finally, bioluminescence-based test results showed that >99% of the IOM extracted from OSC and LYN was biodegradable. Therefore, a biological treatment process could minimize this source of DBP precursor material during drinking water treatment. [ABSTRACT FROM AUTHOR]

Abstract: Advanced oxidation treatment using low pressure UV light coupled with hydrogen peroxide (UV/H2O2) was evaluated for the oxidation of six pharmaceuticals in three wastewater effluents. The removal of these six pharmaceuticals (meprobamate, carbamazepine, dilantin, atenolol, primidone and trimethoprim) varied between no observed removal and >90%. The role of the water quality (i.e., alkalinity, nitrite, and specifically effluent organic matter (EfOM)) on hydroxyl radical (ure was evaluated and used to explain the differences in pharmaceutical removal between the three wastewaters. Results indicated that the efficacy of UV/H2O2 treatment for the removal of pharmaceuticals from wastewater was a function of not only the concentration of EfOM but also its inherent reactivity towards emoval of pharmaceuticals also correlated with reductions in ultraviolet absorbance at 254nm (UV254), which offers utilities a surrogate to assess pharmaceutical removal efficiency during UV/H2O2 treatment. [Copyright &y& Elsevier]

The reduction of ultraviolet (UV) absorbance at 254 nm (UV254) and true color were identified as appropriate surrogates to assess the oxidation of six pharmaceuticals (i.e., carbamazepine, meprobamate,dilantin, primidone, atenolol, and iopromide) during ozonation of wastewater. Three tertiary-treated wastewaters were evaluated during oxidation with ozone (O3) and O3 coupled with hydrogen peroxide (O3/H2O2). The correlation between pharmaceutical oxidation and removal of UV254 was dependent upon the reactivity of each specific compound toward ozone, as measured by the second-order rate constant (k"O3). Oxidation of compounds with k"O3 > 10³ M-1 s-1 correlated well (R² > 0.73) with UV254 reduction between 0-50%. Oxidation of compounds with apparent k"O3, < 10 M-1 s-1 resulted primarily from hydroxyl radicals and correlated well (R² > 0.80) with the UV254 reduction of 15-65%. The removal of true color also correlated well (R² > 0.85) with the oxidation of pharmaceuticals during the ozonation of two wastewaters. These correlations demonstrate that UV254 reduction and true color removal may be used as surrogates to evaluate pharmaceutical oxidation in the presence or absence of dissolved ozone residual during advanced wastewater treatment with O3 or O3/H2O2. The use of online UV254 measurements would allow wastewater utilities to optimize the ozone dose required to meet their specific treatment objectives. [ABSTRACT FROM AUTHOR]

The changes in polarity of natural organic matter (NOM) across a pilot-scale conventional water treatment plant with pre-ozonation and biofiltration were analyzed using the polarity rapid assessment method (PRAM). PRAM is a novel method developed for the characterization of the polarity of NOM in environmental samples. Characterization was accomplished by monitoring UV absorbance (UVA) at 254 nm. Under ambient conditions, the NOM was characterized as highly anionic (.50%), with limited hydrophobic (10-25%) and hydrophilic (0-10%) domains. Results showed temporal variations in the polarity of NOM entering the pilot plant. These differences were ascribed to changes in water blend and variability in NOM characteristics. Changes in NOM chemistry were also observed as the organics passed through the treatment process. Ozonation decreased the hydrophobicity and increased the polarity of NOM, confirming results from previous research utilizing resin fractionation methods. Coagulation, flocculation and biofiltration resulted in the decrease of the hydrophobic and hydrophilic character of the chromophoric NOM. However, these polarity changes varied during the pilot plant run, suggesting a more precise evaluation of NOM through unit operations is warranted. [ABSTRACT FROM AUTHOR]

Three tertiary-treated wastewater effluents were evaluated to determine the impact of wastewater quality (i.e. effluent organic matter (EfOM), nitrite, and alkalinity) on ozone (O3) decomposition and subsequent removal of 31 organic contaminants including endocrine disrupting compounds, pharmaceuticals, and personal care products. The O3 dose was normalized based upon total organic carbon (TOC) and nitrite to allow comparison between the different wastewaters with respect to O3 decomposition. EfOM with higher molecular weight components underwent greater transformation, which corresponded to increased O3 decomposition when compared on a TOC basis. Hydroxyl radical ( OH) exposure, measured by parachlorobenzoic acid (pCBA), showed that limited OH was available for contaminant destruction during the initial stage of O3 decomposition (t <30s) due to the effect of the scavenging by the water quality. Advanced oxidation using O3 and hydrogen peroxide did not increase the net production of OH compared to O3 under the conditions studied. EfOM reactivity impacted the removal of trace contaminants when evaluated based on the O3:TOC ratio. Trace contaminants with second order reaction rate constants with O3 ()>105 M−1 s−1 and OH (k OH)>109 M−1 s−1, including carbamazepine, diclofenac, naproxen, sulfamethoxazole, and triclosan, were >95% removed independent of water quality when the O3 exposure () was measurable (0–0.8mgmin/L). O3 exposure would be a conservative surrogate to assess the removal of trace contaminants that are fast-reacting with O3. Removal of contaminants with and k OH >109 M−1 s−1, including atrazine, iopromide, diazepam, and ibuprofen, varied when O3 exposure could not be measured, and appeared to be dependent upon the compound specific k OH. Atrazine, diazepam, ibuprofen and iopromide provided excellent linear correlation with pCBA (R 2 >0.86) making them good indicators of OH availability. [Copyright &y& Elsevier]

Abstract: Fulvic acid standards from Suwannee River, Pony Lake, Elliot Soil, Waskish Peat, and Nordic Reservoir were characterized by liquid chromatography coupled to quadrupole time-of-flight mass spectrometry (LC-QTOF-MS) operating in negative electrospray ionization mode. The method employed a commercially available stationary phase that resulted in a distinctive chromatographic peak for each of the fulvic acid samples that differed in width and retention time at peak maximum. The QTOF-MS, operating in TOF mode, revealed that the unique chromatographic peak shapes were the result of the relative fraction of hydrogen and oxygen contained in various fulvic acid components. Those species that contained larger amount of hydrogen displayed a larger mass defect and were retained longer on the LC column, indicating reduced polarity. This is supported by a reduction in the degree of fragmentation related to polar functional groups as the mass defect and retention time increased. Lastly, the analysis of even and odd mass (at m/z 1 greater) ion intensity ratios revealed a correlation to the percent nitrogen of the various standards. [Copyright &y& Elsevier]

Abstract: A method has been developed for the quantification of the formation of formaldehyde during the advanced oxidation treatment (AOT) of wastewater destined for reuse. This method uses solid-phase microextraction (SPME) with on-fiber derivatization followed by gas chromatography–mass spectrometry (GC–MS) analysis. Based on calculated method detection limits (MDL) and ambient background levels, the method reporting (MRL) limit for formaldehyde was set at 10μg/L. Precision for formaldehyde using this technique resulted in 23% relative standard deviation (RSD), while the internal standard, acetone-d6, was only 6%. This method was used to evaluate the formation of formaldehyde in bench scale UV–AOT experiments using natural organic matter (NOM) fortified reagent water and tertiary treated wastewater effluent. Results suggest that the formation of formaldehyde increases in both the reagent water and wastewater matrices with increasing UV exposure and hydrogen peroxide concentrations, with overall higher concentrations of formaldehyde in the wastewater samples. No appreciable amount of formaldehyde formation was observed when UV was applied in the absence of hydrogen peroxide in both matrices tested. [Copyright &y& Elsevier]

Absolute second-order rate constants for the reaction between the hydroxyl radical (OH) and eight water samples containing non-isolated effluent organic matter (EfOM) collected at different wastewater and reclamation sites were measured by electron pulse radiolysis. The measured rate constants ranged from 0.27 to 1.21 x 109 M-1C s-1, with an average value of 0.86 (±0.35) x 109 M-1C s-1. These absolute values were 3-5 times faster than previously reported values using natural organic matter and wastewater isolates. The obtained rate constants were correlated (R¹ > 0.99) to bulk EfOM properties through an empirical equation that included terms relating to the polarity, apparent molecular weight and fluorescence index of the effluent organic matter. The obtained data were used to model steady state 0H concentrations during UV advanced oxidation. The steady-state OH concentration was lower than that obtained using previously reported values for the reaction with dissolved organic matter, indicating that accurate measurement of reaction rate constants at specific sites would greatly improve the design and prediction of the removal of organic contaminants. These results will improve the ability of researchers to accurately model scavenging capacities during the advanced oxidation process treatment of wastewaters. [ABSTRACT FROM AUTHOR]

The characterization of dissolved organic matter (DOM) in drinking water sources is important as this material contributes to the formation of disinfection by-products (DBPs) and affects how water treatment unit operations are optimized. Drinking water utilities often draw water from sources impacted by multiple tributaries, with possible shifts in DOM concentrations and reactivity over time, depending on specific environmental conditions. In this study, results are presented on the characterization of DOM under varying ambient conditions from the four main tributaries of Lake Mead, a large reservoir in the southwest United States. The tributaries include the Las Vegas Wash (LVW), Muddy River (MR), Virgin River (VR) and the upper Colorado River (UCR). One additional sample was collected at the outflow of the reservoir (lower Colorado River (LCR)). The DOM was characterized by both bulk parameters (specific ultraviolet absorbance (SUVA)) and specific physicochemical properties, i.e. size, polarity and fluorescence. The analyses were performed emphasizing limited changes in its natural configuration by eliminating analytical preparation steps, excluding sample filtration (0.45μm filter). Results indicate that each tributary had a different molecular weight distribution, as well as fluorescence properties, which helped in the identification of the relative source of DOM (allochthonous versus autochthonous). The largest apparent molecular weight distribution was observed for DOM samples collected at the MR site, which is fed mostly by groundwater seepage. The smallest apparent molecular weight was observed for DOM collected at the LCR site, suggesting that retention in the reservoir resulted in a decrease in molecular weight as a probable result of photo oxidation and microbial processes. Fluorescence analysis aided the differentiation of DOM by clearly identifying waters that were affected by microbial activity (LVW, UCR, and LCR), either by wastewater influence or by autochthonous processes, versus limited microbial influence (MR and VR). Polarity analysis revealed clear differences in the hydrophobic/hydrophilic nature between waters, including temporal differences within individual waters at a particular site. The DOM from the LVW and VR sites had higher hydrophobic character, as measured by retention onto non-polar sorbents. Additionally, the DOM collected at the LCR had the least hydrophobic character. This type of analysis would be beneficial to utilities who want to better understand and manage their source waters, especially in the evaluation of temporal variation within a watershed. [Copyright &y& Elsevier]

Abstract: para-Chlorobenzoic acid (p-CBA) is typically used as a probe compound to indirectly quantify hydroxyl radicals formed during advanced oxidation processes used in drinking water and wastewater treatment. A method has been developed for the sensitive analysis of p-CBA in water using liquid chromatography–tandem mass spectrometry (LC–MS/MS). A reporting limit in water of 100ng/L was determined for the method, which is 40-fold lower than the 4.0μg/L reporting limit of the widely used liquid chromatography with UV detection (LC-UV) method. The method was found to be robust in difficult matrices such as wastewater and highly selective, unlike LC-UV which relies on non-specific detection at 234nm. The detection of p-CBA below 1μg/L during bench-scale ozonation of wastewater after hydrogen peroxide addition was demonstrated. Duplicate samples were analyzed by LC–MS/MS and LC-UV and results were found to be comparable at concentrations quantifiable by both methods. [Copyright &y& Elsevier]

The polarity rapid assessment method (PRAM) characterizes the polarity of aqueous natural organic matter (NOM) by quantifying the amount of material adsorbed onto different solid-phase extraction (SPE) sorbents. The analysis is performed under ambient conditions resulting in the elimination of pretreatment steps that may alter the chemical characteristics of the NOM, allowing an accurate representation of its polarity as it exists in the environment. Additionally, analysis only requires 200 mL of sample and can be performed in 2 h. In this paper, the underlying theory of the method is presented, followed by its optimization, with emphasis on the development of conditions for the analysis of NOM in natural waters. A series of organic probe compounds showed that the most important physicochemical property describing the interaction between the NOM and the SPE sorbents was the hydrophobic surface area, allowing for the estimation of the hydrophobic character under ambient conditions. Evaluation of the effects of chemical concentration, pH, and ionic strength show that (1) concentration did not have an effect on PRAM characterization as long as the pH and ionic strength remained constant; (2) changes in pH and ionic strength resulted in considerable changes in PRAM characterization, as a result of the changes in configuration of the NOM; and (3) PRAM characterization of NOM can be completed in the concentration range of <10 mg C/L, although this range could be expanded by evaluating the effect of concentration on a site-specific basis. Results indicate that measurement of both ultraviolet absorption and dissolved organic carbon show complementary results as they measure different aspects of NOM. [ABSTRACT FROM AUTHOR]

Disinfection byproduct (DBP) formation in tertiary wastewater was examined after ozonation (O3) and advanced oxidation with O3 and hydrogen peroxide (O3/H2O2). O3 and O3/H2O2 were applied at multiple dosages to investigate DBP formation during coliform disinfection and trace contaminant oxidation. Results showed O3 provided superior disinfection of fecal and total coliforms compared to O3/H2O2. Color, UV absorbance, and SUVA were reduced by O3 and O3/H2O2, offering wastewater utilities a few potential surrogates to monitor disinfection or trace contaminant oxidation. At equivalent O3 dosages, O3/H2O2 produced greater concentrations of assimilable organic carbon (5–52%), aldehydes (31–47%), and carboxylic acids (12–43%) compared to O3 alone, indicating that organic DBP formation is largely dependent upon hydroxyl radical exposure. Bromate formation occurred when O3 dosages exceeded the O3 demand of the wastewater. Bench-scale tests with free chlorine showed O3 is capable of reducing total organic halide (TOX) formation potential by at least 20%. In summary, O3 provided superior disinfection compared to O3/H2O2 while minimizing DBP concentrations. These are important considerations for water reuse, aquifer storage and recovery, and advanced wastewater treatment applications. [Copyright &y& Elsevier]

Background Products containing humic acids (HA) and fulvic acids (FA) have significant commercial potential; however, unknown to the consumer, some products may be mislabeled or contain adulterants. The prevalence of mislabeling and adulterants is found primarily in FA products. Using UV-Vis spectroscopy to differentiate between real and fake FA products is practical and desirable. Objective The objective of this study was to expand the dataset generated using a UV-Vis-based method proposed by Mayhew et al. 2023. Methods In total, 30 test samples were used to generate 90 test portions (three replicates per test sample) for analysis using the UV-Vis methodology outlined in Mayhew et al. 2023, which in this study is referred to as the UVAC (UV absorbance confirmation) method. Results None of the 13 FA test samples investigated were determined as humified using the UVAC method. The FA samples studied consisted of two IHSS standards, five commercial FA products (CFAP), and six full FA fractions (SFA), which were isolated from six known solid humic material sources (SHMS). There was a leonardite, a humalite, and four peat sources used as the SHMS. Analysis of the neutralized extract of the SHMS found only 3/6 SHMS were determined as humified. Six HA (SHA) test samples were also generated by isolating the HA from the SHMS, and only 3/6 SHA were determined as humified. Conclusions Given the high prevalence of false determinations, more work is needed to improve the method so that it can be used by industry or regulators. Highlights The proposed method failed to determine IHSS FA standards as humified. Although the method is practical, it needs improvement and further study before it can be used for reliable differentiation of real from fake FA. [ABSTRACT FROM AUTHOR]

While the presence of iron is generally not seen as favorable for UV-based treatment systems due to lamp fouling and decreased UV transmittance, we show that low levels of iron can lead to improvements in the abatement of chemicals in the UV-hydrogen peroxide advanced oxidation process. The oxidation potential of an iron-assisted UV/H 2 O 2 (UV 254 + H 2 O 2 + iron) process was evaluated at neutral pH using iron levels below USEPA secondary drinking water standards (<0.3 mg/L). Para -chlorobenzoic acid (pCBA) was used as a hydroxyl radical (HO ) probe to quantify HO steady state concentrations. Compounds degraded by different mechanisms including, carbamazepine (CBZ, HO oxidation) and N -nitrosodimethylamine (NDMA, direct photolysis), were used to investigate the effect of iron on compound degradation for UV/H 2 O 2 systems. The effects of iron species (Fe 2+ and Fe 3+ ), iron concentration (0–0.3 mg/L), H 2 O 2 concentration (0–10 mg/L) and background water matrix (low-carbon tap (LCT) and well water) on HO production and compound removal were examined. Iron-assisted UV/H 2 O 2 efficiency was most influenced by the target chemical and the water matrix. Added iron to UV/H 2 O 2 was shown to increase the steady-state HO concentration by approximately 25% in all well water scenarios. While CBZ removal was unchanged by iron addition, 0.3 mg/L iron improved NDMA removal rates in both LCT and well water matrices by 15.1% and 4.6% respectively. Furthermore, the combination of UV/Fe without H 2 O 2 was also shown to enhance NDMA removal when compared to UV photolysis alone indicating the presence of degradation pathways other than HO oxidation. [ABSTRACT FROM AUTHOR]

A correction to the article "Nitrosamine Formation During Chloramination" in a 2013 issue is presented.

Sunlight irradiation is known to contribute to microbial inactivation in natural treatment systems (NTS) and surface waters via both direct and indirect processes. This study investigated the influence of various types of organic matter (OM) on endogenous and exogenous photoinactivation of Enterococcus faecalis. Solar simulator exposure experiments were conducted in surface waters and wastewater and in the presence of natural OM isolates and a singlet oxygen (1O2) sensitizer, methylene blue. Presence of both natural and anthropogenic OM resulted in increases in inactivation rates of 17-67% compared to sensitizer-free experiments. This suggests that, while direct and endogenous photoinactivation is hindered with increasing depth due to light screening by OM, its role as a photosensitizer in the formation of reactive intermediates (predominantly involving 1O2) is greater than its negative impact due to light screening at levels typically found in NTS. Specifically, increases in light absorbance (particularly at shorter wavelengths) are estimated to reduce direct and endogenous processes by up to 41% under our experimental conditions; however, presence of external photosensitizers enhances exogenous inactivation processes to a greater degree. A novel approach is presented to help estimate endogenous and exogenous inactivation rates of E. faecalis as a function of depth in the presence of OM based on common optical measurements. Implications of this knowledge in informing design parameters (e.g., depth and retention time) of NTS are discussed, thus contributing to both fundamental understanding of photoinactivation processes in surface waters and improvement of treatment unit design. [ABSTRACT FROM AUTHOR]

The photochemical degradation of five pharmaceuticals was examined in two secondary wastewater effluents. The compounds, which included atenolol, carbamazepine, meprobamate, phenytoin and primidone, were evaluated for both direct and sensitized photolysis. In the two wastewaters, direct photolysis did not lead to significant compound degradation; however, sensitized photolysis was an important removal pathway for the five pharmaceuticals. Upon solar irradiation, hydroxyl radical (HO ) was quantified using the hydroxylation of benzene and singlet oxygen ( 1 O 2 ) formation was monitored following the degradation of furfuryl alcohol. Degradation via sensitized photolysis was observed following five-day exposures for atenolol (69–91%), carbamazepine (67–98%), meprobamate (16–52%), phenytoin (44–85%), and primidone (34–88%). Varying removal is likely a result of the differences in reactivity with transient oxidants. Averaged steady state HO concentrations ranged from 1.2 to 4.0 × 10 −16 M, whereas the concentrations of 1 O 2 were 6.0–7.6 × 10 −14 M. Partial removal due to presence of HO indicates it was not the major sink for most compounds examined. Other transient oxidants, such as 1 O 2 and triplet state effluent organic matter, are likely to play important roles in fates of these compounds. [ABSTRACT FROM AUTHOR]

Intracellular organic matter (IOM) from cyanobacteria may be released into natural waters following cell death in aquatic ecosystems and during oxidation processes in drinking water treatment plants. Fluorescence spectroscopy was evaluated to identify the presence of IOM from three cyanobacteria species during simulated release into natural water and following oxidation processes (i.e. ozone, free chlorine, chloramine, chlorine dioxide). Peak picking and the fluorescence index (FI) were explored to determine which IOM components (e.g., pigments) provide unique and persistent fluorescence signatures with minimal interferences from the background dissolved organic matter (DOM) found in Colorado River water (CRW). When IOM was added to ultrapure water, the fluorescence signature of the three cyanobacteria species showed similarities to each other. Each IOM exhibited a strong protein-like fluorescence and fluorescence at Ex 370 nm and Em 460 nm (FDOM), where commercial fluorescence sensors monitor. All species also had strong phycobiliprotein fluorescence (i.e. phycocyanin or phycoerythrin) in the higher excitation range (500–650 nm). All three IOM isolates had FI values greater than 2. When IOM was added to CRW, phycobiliprotein fluorescence was quenched through interactions between IOM and CRW-DOM. Mixing IOM and CRW demonstrated that protein-like and FDOM intensity responses were not a simple superposition of the starting material intensities, indicating that interactions between IOM and CRW-DOM fluorescing moieties were important. Fluorescence intensity in all regions decreased with exposure to ozone, free chlorine, and chlorine dioxide, but the FI still indicated compositional differences compared to CRW-DOM. The phycobiliproteins in IOM are not promising as a surrogate for IOM release, because their fluorescence intensity is quenched by interactions with DOM and decreased during oxidation processes. Increases in both FDOM intensity and FI are viable qualitative indicators of IOM release in natural waters and following oxidation and may provide a more robust real-time indication of the presence of IOM than conventional dissolved organic carbon or UV absorbance measurements. [ABSTRACT FROM AUTHOR]

Photochemical properties of dissolved organic matter (DOM) are of interest due to their effects on natural and engineered systems, including the fate and transport of organic contaminants and pathogen inactivation. DOM absorbs energy and produces different reactive intermediates (RI), including the hydroxyl radical (HO·), singlet oxygen (1O2), and excited triplet states (3DOM*). Recently, a new set of DOM samples, including natural organic matter (NOM), the hydrophobic organic acid fraction (HPOA), and the transphilic acid fraction (TPIA) from the Suwannee River, were collected. Apparent quantum yields for the formation of HO·, 1O2, and 3DOM* were measured for DOM samples using a solar simulator. Values were 2.09-4.20×10−4 for triplet states, 2.74-6.54×10−2 for singlet oxygen, and 0.95-1.65×10−5 for hydroxyl radical for the different samples. In addition, fluorescence quantum yields were measured with obtained values between 0.79-1.3×10−2. In some cases, values obtained were different from older DOM samples, indicating potential changes in properties of DOM in the Suwannee River over time. [ABSTRACT FROM AUTHOR]

The photochemical formation of hydroxyl radical (HO•) from effluent organic matter (EfOM) depends upon the chemical properties of this heterogeneous mixture. In this study, two EfOM samples collected from wastewater treatment plants (WWTP A and B) were fractionated by both hydrophobicity (bulk and non-humic) and apparent molecular weight (AMW). The apparent quantum yield for HO• formation (ΦHO•) and the maximum fluorescence quantum yield (ΦF) were subsequently measured for each subfraction. The formation rates of HO• (considering only the hydrogen-peroxide-independent pathways) for the bulk waters were 4.8 × 10–10 and 9.6 × 10–11 M s–1 for WWTP A and B, respectively. For the AMW fractions, the values of ΦHO• increased as the AMW of the material decreased. For the WWTP A sample, the ΦHO• increased from 2.54 × 10–4 (bulk water) to 6.29 × 10–4 for the <1 kDa fraction, and for the WWTP B sample, the value of ΦHO• increased from 6.50 × 10–5 for bulk water to 3.45 × 10–4 for the <1 kDa fraction. In the case of fluorescence, the values of ΦF ranged from 2.37 × 10–4 (bulk water) to 3.48 × 10–4 (<1 kDa fraction) for WWTP A and 3.19 × 10–4 (bulk water) to 5.75 × 10–4 (<1 kDa fraction) for WWTP B. There was a linear correlation between ΦHO• and ΦF, suggesting that different photophysical processes occur in the chemical components of the fractions. Understanding the formation of HO• from EfOM is essential for understanding wastewater-impacted aquatic systems because these results influence the photochemical degradation and mineralization of trace organic contaminants. [ABSTRACT FROM AUTHOR]

Abstract: Depending on drinking water treatment conditions, oxidation processes may result in the degradation of cyanobacteria cells causing the release of toxic metabolites (microcystin), odorous metabolites (MIB, geosmin), or disinfection byproduct precursors. In this study, a digital flow cytometer (FlowCAM®) in combination with chlorophyll-a analysis was used to evaluate the ability of ozone, chlorine, chlorine dioxide, and chloramine to damage or lyse cyanobacteria cells added to Colorado River water. Microcystis aeruginosa (MA), Oscillatoria sp. (OSC) and Lyngbya sp. (LYN) were selected for the study due to their occurrence in surface water supplies, metabolite production, and morphology. Results showed that cell damage was observed without complete lysis or fragmentation of the cell membrane under many of the conditions tested. During ozone and chlorine experiments, the unicellular MA was more susceptible to oxidation than the filamentous OSC and LYN. Rate constants were developed based on the loss of chlorophyll-a and oxidant exposure, which showed the oxidants degraded MA, OSC, and LYN according to the order of ozone > chlorine ∼ chlorine dioxide > chloramine. Digital and binary images taken by the digital flow cytometer provided qualitative insight regarding cell damage. When applying this information, drinking water utilities can better understand the risk of cell damage or lysis during oxidation processes. [Copyright &y& Elsevier]

The application of advanced oxidation processes (AOPs) for the treatment of wastewater is hindered by scavenging of the hydroxyl radical (HO•) by effluent organic matter (EfOM). This scavenging is directly proportional to the second-order reaction rate constant between EfOM and HO• (kEfOM-HO•). To understand the kinetics of this reaction as a function of the subcomponents of EfOM, four wastewater samples were fractionated by ultrafiltration into distinct apparent molecular weight (AMW) fractions (<1, <3, <5, and <10 kDa), and their kEfOM-HO• values were quantified. In general, the values for kEfOM-HO• decreased as the AMW increased. The values of kEfOM-HO• for the bulk waters varied between 6.32 and 14.1 × 108 MC-1s-1 (units of per molar carbon concentration per second). In the case of the <1 kDa fraction, the values of kEfOM-HO• varied from 14.3 to 35.0 × 108 MC-1s-1, or approximately 2.31(±0.24) times that of the corresponding bulk waters. For the <3 kDa, <5 kDa, and <10 kDa fractions, the kEfOM-HO• values were 1.83(±0.25), 1.32(±0.23), and 1.26(±0.35) times that of the bulk waters, respectively. Based on the obtained results, the variability and general magnitude of the kEfOM-HO• values were attributed to the production and reactivity of soluble microbial products (SMP), a major component of EfOM. Two samples collected at a wastewater treatment facility with different treatment variables had different kEfOM-HO• values, indicating that wastewater treatment processes will impact overall HO• scavenging by EfOM and should be considered during the implementation of AOPs. [ABSTRACT FROM AUTHOR]

A screening technique has been developed that allows the rapid, real-time detection and identification of major transformation products of organic contaminants during aqueous oxidation experiments. In this technique, a target contaminant is dissolved in buffered water and chlorinated by the addition of sodium hypochlorite to give a free chlorine residual of 3 mg/L. Solution from the reaction vessel is combined with methanol and pumped directly into the electrospray ionization source of a quadrupole time-of-flight mass spectrometer (QTOF MS). The real- time decay of the target contaminant and the formation! decay of transformation products are then monitored using the QTOF MS. Subsequently, accurate mass measurements with internal mass calibration (<5 ppm mass error) and product ion scans are employed to identify these transformation products. Unlike other techniques, it requires no liquid chromatography, derivatization, or quenching of residual chlorine, all of which can interfere with transformation product analysis. To validate the technique, aqueous chlorination experiments were performed on triclosan, a previously studied environmental contaminant. Earlier research showing that triclosan underwent chlorine addition to form mono- and dichlorinated transformation products was successfully reproduced, demonstrating the feasibility of the technique. In addition, the technique revealed the formation of a stable oxygen radical-containing transformation product resulting from the oxidation of either mono- or dichlorinated triclosan. This triclosan transformation product was determined to have an empirical formula of C12H4O3Cl4 with 3.9 ppm mass error. Furthermore, atorvastatin, a commonly prescribed medication and enviromnental contaminant, was subjected to aqueous chlorination and studied with the technique. Atorvastatin underwent hydroxylation to form two transformation products with the empirical formulas C33H34FN2O6 (1.8 ppm mass error) and C26H29O5NF (2.9 ppm mass error). [ABSTRACT FROM AUTHOR]

• Indirect photolysis is the primary photodegradation pathway for most cyanotoxins. • Direct photolysis is relevant for most, but not all, cyanotoxins mentioned. • There are large knowledge gaps in the photochemistry of cyanotoxins. Cyanotoxin-producing harmful algal blooms (HABs) are a global occurrence and pose ecotoxicological threats to humans and animals alike. The presence of cyanotoxins can seriously harm or kill nearby wildlife and restrict a body of water's use as a drinking water supply and recreational site, making it imperative to fully understand their fate and transport in natural waters. Photodegradation contributes to the overall degradation of cyanotoxins in environmental systems, especially for those present in the photic zone of surface waters. This makes photochemical transformation mechanisms important factors to account for when assessing the persistence of cyanotoxins in environmental systems. This paper reviews current knowledge on the photodegradation rates and pathways of cyanotoxins that can occur over the course of HABs. Sensitized, or indirect, photolysis contributes to the degradation of all cyanotoxins addressed in this paper (anatoxins, cylindrospermopsins, domoic acids, microcystins, and nodularins), with hydroxyl radicals (•OH), excited triplet states formed from the absorption of light by dissolved organic matter (3DOM*), and photosynthetic pigment sensitized pathways being of primary interest. Direct photolysis pathways play a less significant role, but are still relevant for most of the cyanotoxins discussed in this paper. Image, graphical abstract [ABSTRACT FROM AUTHOR]

Atmospheric iron solubility varies depending on whether the particles are collected in rural or urban areas, with urban areas showing increased iron solubility. In this study, we investigate if the iron species present in different environments affects its ultimate solubility. Field data are presented from the Platte River Air Pollution and Photochemistry Experiment (PRAPPE), aimed at understanding the interactions between organic carbon and trace elements in atmospheric particulate matter (PM). 24‐hr PM2.5 samples were collected during the summer and winter (2016–2017), at three different sites on the Eastern Colorado plains: an urban, agricultural, and a mixed site. Downtown Denver had an average total and water‐soluble iron air concentration of 181.2 and 7.7 ng m−3, respectively. Platteville, the mixed site, had an average of total iron of 76.1 ng m−3, with average water‐soluble iron concentration of 9.1 ng m−3. Jackson State Park (rural/agricultural) had the lowest total iron average of 31.5 ng m−3 and the lowest water‐soluble iron average, 1.3 ng m−3. The iron oxidation state and chemical speciation of 97 samples across all sites and seasons was probed by X‐ray absorption near edge structure (XANES) spectroscopy. The most common iron phases observed were almandine (Fe₃Al₂Si₃O₁₂) (Denver 21%, Platteville 16%, Jackson 24%), magnetite (Fe3O4) (Denver 9%, Platteville 4%, Jackson 5%) and Fe (III)dextran (Denver 5%, Platteville 13%, Jackson 5%), a surrogate for Fe‐organic complexes. Additionally, native iron [Fe(0)] was found in significant amounts at all sites. No correlation was observed between iron solubility and iron oxidation state or chemical speciation. Key Points: Large prevalence of the Si‐Fe complexes suggests a large contribution from natural, crustal sourcesNo observed seasonal change in iron oxidation stateNo observed relationship between iron oxidation state and water‐soluble iron [ABSTRACT FROM AUTHOR]

Abstract Oxidation processes are impacted by the type, concentration and reactivity of the dissolved organic matter (DOM). In this study, the reactions between various types of DOM (Suwannee River fulvic acid (SRFA), Nordic Reservoir NOM (NNOM) and Pony Lake fulvic acid (PLFA)) and two oxidants (ozone and chlorine) were studied in the pH range 2–9 by using a combination of optical measurements and electron donating capacities. The relationships between residual electron donating capacity (EDC) and residual absorbance showed a strong pH dependence for the ozone-DOM reactions with phenolic functional groups being the main reacting moieties. Relative EDC and absorbance abatements (UV 254 or UV 280) were similar at pH 2. At pH 7 or 9, the relative abatement of EDC was more pronounced than for absorbance, which could be explained by the formation of UV-absorbing products such as benzoquinone from the transformation of phenolic moieties. An increase in fluorescence abatement with increasing pH was also observed during ozonation. The increase in fluorescence quantum yields could not be attributed to formation of benzoquinone, but related to a faster abatement of phenolic moieties relative to fluorophores with low ozone reactivity. The overall •OH yields as a result of DOM-induced ozone consumption increased significantly with increasing pH, which could be related to the higher reactivity of phenolic moieties at higher pH. The •OH yields for SRFA and PLFA were proportional to the phenolic contents, whereas for NNOM, the •OH yield was about 30% higher. During chlorination of DOM at pH 7 an efficient relative EDC abatement was observed whereas the relative absorbance abatement was much less pronounced. This is due to the formation of chlorophenolic moieties, which exert a significant absorbance, and partly lose their electron donating capacity. Pre-ozonation of SRFA leads to a decrease of chloroform and haloacetic acid formation, however, only after a threshold of > ∼50% abatement of the EDC and under conditions which are not precursor limited. The decrease in chloroform and haloacetic acid formation after the threshold EDC abatement was proportional to the relative residual EDC. Graphical abstract Image 1 Highlights • Ozone (O 3)- and chlorine-DOM reactions were assessed in the pH range 2–9. • For O 3 , the relationship between EDC and absorbance is pH dependent. • For O 3 , benzoquinone formation explained low absorbance/high EDC loss at pH > 7. • For chlorine, UV-absorbing chlorophenols were formed while EDC decreased. • CHCl 3 formation during chlorination of DOM decreased for > ∼50% EDC abatement. [ABSTRACT FROM AUTHOR]

• Dissolved organic matter (DOM) lability can be estimated using FT-ICR MS data. • The molecular lability boundary (MLB) approach is updated using new data. • The fraction of MLB L DOM decreases during heterotrophic and thermal degradation. • The fraction of MLB L OM increases during photo-processing of oils. • MLB L laboratory experimental results extend understanding of DOM from field samples. Patterns in Fourier transform ion cyclotron resonance mass spectrometry (FT-ICR MS) data provide perspective on how organic matter (OM) character is shaped by natural processes. Here, we reevaluate and update the molecular lability boundary (MLB) approach to assess OM lability using a synthesis of FT-ICR MS data. Now included are MLB L (biolability) indices (i.e., the OM proportion of hydrogen-to-carbon ratios ≥ 1.5) of freshwaters, plant litter and biochar leachates, soils, and oils across the US, trends in OM and dissolved OM (DOM) lability from laboratory experiments examining isolated microbial, photochemical, and thermal degradation, and biogeochemical interpretations of biolability patterns across ecosystems influenced by human activity (e.g., fertilizer addition and agricultural management). Photo-processing increased the hydrogen saturation of OM, describing products of higher biolability (>MLB L values). DOM MLB L values decreased during microbial and thermal degradation processes. Laboratory experiments with isolated treatments showed larger changes in MLB L than exhibited by field samples from systems managed by humans. We interpret changes in N- and/or S-containing DOM above the MLB as the production or use of heterogeneously biolabile material. We interpret heterogeneously labile DOM composition to indicate autochthonous production, biomass growth, nutrient accumulation, or biological degradation in stream and soil samples. The most recent data in our synthesis suggest that the MLB approach should be reframed to provide lability indices for biotic, thermal, and photochemical processes. A broader perspective on lability provides a useful tool to decompose large, complex, and process-driven DOM data into more simple and informative indicators of trends in ecosystem form and function. [ABSTRACT FROM AUTHOR]

The optical properties of dissolved organic matter influence chemical and biological processes in all aquatic ecosystems. Dissolved organic matter optical properties have been attributed to a charge-transfer model in which donoracceptor complexes play a primary role. This model was evaluated by measuring the absorbance and fluorescence response of organic matter isolates to changes in solvent temperature, viscosity, and polarity, which affect the position and intensity of spectra for known donor -- acceptor complexes of organic molecules. Absorbance and fluorescence spectral shape were largely unaffected by these changes, indicating that the distribution of absorbing and emitting species was unchanged. Overall, these results call into question the wide applicability of the charge-transfer model for explaining organic matter optical properties and suggest that future research should explore other models for dissolved organic matter photophysics. [ABSTRACT FROM AUTHOR]

The antioxidant capacity and formation of photochemically produced reactive intermediates (RI) was studied for water samples collected from the Florida Everglades with different spatial (marsh versus estuarine) and temporal (wet versus dry season) characteristics. Measured RI included triplet excited states of dissolved organic matter (³DOM*), singlet oxygen (¹O2), and the hydroxyl radical (oOH). Single and multiple linear regression modeling were performed using a broad range of extrinsic (to predict RI formation rates, RRI) and intrinsic (to predict RI quantum yields, FRI) parameters. Multiple linear regression models consistently led to better predictions of RRI and FRI for our data set but poor prediction of FRI for a previously published data set,1 probably because the predictors are intercorrelated (Pearson's r > 0.5). Single linear regression models were built with data compiled from previously published studies (n ≈ 120) in which E2:E3, S, and FRI values were measured, which revealed a high degree of similarity between RI-optical property relationships across DOM samples of diverse sources. This study reveals that oOH formation is, in general, decoupled from ³DOM* and ¹O2 formation, providing supporting evidence that ³DOM* is not a oOH precursor. Finally, FRI for ¹O2 and ³DOM* correlated negatively with antioxidant activity (a surrogate for electron donating capacity) for the collected samples, which is consistent with intramolecular oxidation of DOM moieties by ³DOM*. [ABSTRACT FROM AUTHOR]

Wildfires can greatly alter the vegetation, soils, and hydrologic processes of watersheds serving as drinking water supplies, which may negatively influence source water quality and treatment. To address wildfire impacts on treatment, a drinking water intake below a burned watershed and an upstream, unburned reference site were monitored following the High Park wildfire (2012) in the Cache la Poudre watershed of northern Colorado, USA. Turbidity, nutrients, dissolved organic matter (DOM) character, coagulation treatability, and disinfection byproduct formation were evaluated and compared to pre-fire data. Post-fire paired spatial differences between the treatment plant intake and reference site for turbidity, nitrogen, and phosphorus increased by an order of magnitude compared to pre-fire differences. Fluorescence index (FI) values were significantly higher at the intake compared to the reference site (Δ = 0.04), and higher than pre-fire years, suggesting the wildfire altered the DOM character of the river. Total trihalomethane (TTHM) and haloacetonitrile (HAN4) formation at the intake were 10.1 μg L −1 and 0.91 μg L −1 higher than the reference site. Post-fire water was amenable to conventional treatment at a 10 mg L −1 higher average alum dose than reference samples. The intake was also monitored following rainstorms. Post-rainstorm samples showed the maximum observed FI values (1.52), HAN4 (3.4 μg mg C −1 ) and chloropicrin formation yields (3.6 μg mg C −1 ), whereas TTHM and haloacetic acid yields were not elevated. Several post-rainstorm samples presented treatment challenges, and even at high alum doses (65 mg L −1 ), showed minimal dissolved organic carbon removal (<10%). The degraded water quality of the post-rainstorm samples is likely attributed to the combined effects of runoff from precipitation and greater erosion following wildfire. Wildfire impacts cannot be separated from rainfall effects due to the lack of post-rainstorm samples from the reference site. Results suggest for this study region, wildfire may have consequences for influent water quality, coagulant dosing, and DBP speciation. [ABSTRACT FROM AUTHOR]

We studied the formation of photochemically produced reactive intermediates (RI) from dissolved organic matter (DOM). Specifically, we focused on the effects of variable molecular weight and chemical reduction on the optical properties of DOM (absorbance and fluorescence) and the formation of singlet oxygen (¹O2), DOM triplet excited states (³DOM*), and the hydroxyl radical (?OH). The data are largely evaluated in terms of a charge-transfer (CT) model, but deficiencies in the model to explain the data are pointed out when evident. A total of two sets of samples were studied that were subjected to different treatments; the first set included secondary-treated wastewaters and a wastewater-impacted stream, and the second was a DOM isolate. Treatments included size fractionation and chemical reduction using sodium borohydride. Taken as a whole, the results demonstrate that decreasing molecular weight and borohydride reduction work in opposition regarding quantum efficiencies for ¹O2 and ³DOM* production but in concert for fluorescence and ?OH production. The optical and photochemical data provide evidence for a limited role of CT interactions occurring in lower-molecular-weight DOM molecules. In addition, the data suggest that the observed optical and photochemical properties of DOM are a result of multiple populations of chromophores and that their relative contribution is changed by molecular-weight fractionation and borohydride reduction. [ABSTRACT FROM AUTHOR]

Hardness and DOC removal in a single ion exchange unit operation allows for less infrastructure, is advantageous for process operation and depending on the water source, could enhance anion exchange resin removal of dissolved organic carbon (DOC). Simultaneous application of cationic (Plus) and anionic (MIEX) ion exchange resin in a single contact vessel was tested at pilot and bench scales, under multiple regeneration cycles. Hardness removal correlated with theoretical predictions; where measured hardness was between 88 and 98% of the predicted value. Comparing bench scale DOC removal of solely treating water with MIEX compared to Plus and MIEX treated water showed an enhanced DOC removal, where removal was increased from 0.5 to 1.25 mg/L for the simultaneous resin application compared to solely applying MIEX resin. A full scale MIEX treatment plant (14.5 MGD) reduced raw water DOC from 13.7 mg/L to 4.90 mg/L in the treated effluent at a bed volume (BV) treatment rate of 800, where a parallel operation of a simultaneous MIEX and Plus resin pilot (10 gpm) measured effluent DOC concentrations of no greater than 3.4 mg/L, even at bed volumes of treatment 37.5% greater than the full scale plant. MIEX effluent compared to simultaneous Plus and MIEX effluent resulted in differences in fluorescence intensity that correlated to decreases in DOC concentration. The simultaneous treatment of Plus and MIEX resin produced water with predominantly microbial character, indicating the enhanced DOC removal was principally due to increased removal of terrestrially derived organic matter. The addition of Plus resin to a process train with MIEX resin allows for one treatment process to remove both DOC and hardness, where a single brine waste stream can be sent to sewer at a full-scale plant, completely removing lime chemical addition and sludge waste disposal for precipitative softening processes. [ABSTRACT FROM AUTHOR]

Amicarbazone (AMZ) is an extensively used, broad-spectrum triazolinone herbicide. The literature is scarce regarding experimental data on AMZ photodegradation, whose fate in natural waters has not yet been investigated in detail. By combining laboratory experiments using isolated natural organic matter, literature data, and mathematical simulations, we investigated the sunlight-driven direct and indirect degradation of AMZ. We show that the reaction with hydroxyl radicals () is the main pathway leading to AMZ degradation, with measured second-order reaction rate constant ( kAMZ, OH) equal to 2.05×1010 L/mol·s. Simulations suggest that amicarbazone degradation is favored in shallow water bodies containing low dissolved organic carbon (DOC) and bicarbonate/carbonate concentrations, with herbicide half-life varying from about less than 1 day to more than 2 months. These values of t1/2 are upper limits since the reaction with 3CDOM* was not considered. Finally, the cross-effects of water depth/[DOC] are slightly influenced by nitrate/nitrite and bicarbonate/carbonate concentrations, depending on the pH range. [ABSTRACT FROM AUTHOR]

This study demonstrates that the ideal adsorbed solution theory-equivalent background compound (IAST-EBC) as a stand-alone model can simulate and predict the powdered activated carbon (PAC) adsorption of organic micropollutants found in drinking water sources in the presence of background dissolved organic matter (DOM) under nonequilibrium conditions. The IAST-EBC represents the DOM competitive effect as an equivalent background compound (EBC). When adsorbing 2-methylisoborneol (MIB) with PAC, the EBC initial concentration was a similar percentage, on average 0.51%, of the dissolved organic carbon in eight non wastewater impacted surface waters. Using this average percentage in the IAST-EBC model yielded good predictions for MIB removal in two non wastewater impacted waters. The percentage of competitive DOM was significantly greater in wastewater impacted surface waters, and varied markedly in DOM size fractions. Fluorescence parameters exhibited a strong correlation with the percentage of competitive DOM in these waters. Utilizing such correlations in the IAST-EBC successfully modeled MIB and sulfamethoxazole adsorption by three different PACs in the presence of DOM that varied in competitive effect. The influence of simultaneous coagulant addition on PAC adsorption of micropollutants was also investigated. Coagulation caused the DOM competitive effect to increase and decrease with MIB and sulfamethoxazole, respectively. [ABSTRACT FROM AUTHOR]

Due to the large quantities of dispersants used during the Deepwater Horizon spill in 2010, there were immediate concerns with regards to the fate and transport of the mixture in ocean waters. Direct and sensitized photolysis experiments were carried out for two compounds chosen as surrogates for the Corexit mixture (9500 and 9527) that were applied to surface waters during the oil spill in the Gulf of Mexico. The results showed that direct photolysis did not contribute significantly to the overall degradation (max ~30%), therefore the focus shifted to sensitized photolysis, specifically the degradation stemming from the reaction rate with hydroxyl radical (HOradical dot). The direct photochemical degradation rates for two of the compounds, dioctyl sulfosuccinate (DOSS) and dipropylene glycol butyl ether (DGBE) were measured as 4.29 × 10-6 s-1 and 5.95 × 10-6 s-1, respectively; whereas the overall degradation rate in ocean water was 1.56 × 10-5 s-1 and 2.23 × 10-5 s-1. The formation rates and apparent quantum yields for HOradical dot formation were determined for six ocean water samples. The values ranged from 1.81 × 10-5 near shore to 0.061 × 10-5 for the open ocean. These degradation rates suggest the possibility for photolysis to play a role in the overall fate of Corexit. [ABSTRACT FROM AUTHOR]

Abstract: The release of intracellular microcystin-LR (MC-LR), 2-methylisoborneol (MIB), and geosmin was investigated after the oxidation of three cyanobacteria (Microcystis aeruginosa (MA), Oscillatoria sp. (OSC), and Lyngbya sp. (LYN)). During the oxidation of 200,000 cells/mL of MA, release of intracellular MC-LR exceeded the World Health Organization (WHO) guideline of 1 μg/L during the lowest oxidant exposures (CT) tested: ozone (0 mg-min/L, below the ozone demand), chlorine (<40 mg-min/L), chlorine dioxide (<560 mg-min/L), and chloramine (<640 mg-min/L). As the CT increased, ozone, chlorine, and chlorine dioxide were able to oxidize the released MC-LR. During the oxidation of OSC (2800 cells/mL) and LYN (1600 cells/mL), release of intracellular MIB and geosmin exceeded reported threshold odor values after exposure to chlorine, chlorine dioxide, and chloramine, which have low reactivity with these taste and odor compounds. Ozone oxidation of OSC yielded an increase in MIB concentration at lower exposures (≤2.9 mg-min/L), likely due to insufficient oxidation by hydroxyl radicals. The release of intracellular organic matter (IOM) was also measured to determine the potential of bulk measurements to act as a surrogate for cyanotoxins and metabolite release. In all cases, the dissolved organic carbon (DOC) release was less than 0.25 mgC/L, which lacked the sensitivity to indicate the release of MC-LR, MIB, or geosmin. The fluorescence index proved to be a more sensitive indicator of intracellular organic matter release than DOC for MA. These results illustrate that toxic or odorous compounds may be released from cyanobacteria cells during oxidation processes with minimal changes in the DOC concentration. [Copyright &y& Elsevier]

Abstract: Advanced oxidation processes (AOPs) are an effective treatment technology for the removal of a variety of organic pollutants in both water and wastewater treatment. However, many background constituents in water are highly reactive towards hydroxyl radicals (HO ) and decrease the efficiency of the process towards contaminant oxidation. Up to 95% of the HO scavenging can come from dissolved organic matter (OM). In this study, 28 wastewater effluent samples were analyzed to find correlations between the reactivity of HO with wastewater-derived OM (known as effluent organic matter, EfOM), water quality parameters, treatment train characteristics, and fluorescence-derived data. Rate constants for the reaction between HO and EfOM (k EfOM-HO) were measured using a bench scale UV-based AOP system with methylene blue as an HO probe and confirmed using an electron pulse radiolysis method for a subset of the samples. The EfOM was characterized using a series of physicochemical parameters, including polarity, average molecular size and fluorescence. The kinetic data were analyzed with principal component analysis and Akaike Information Criterion. Four predictors were identified as dominant: chemical oxygen demand, retention onto NH2 extraction medium, fluorescence index, and total organic carbon. These four variables accounted for approximately 62% of the variability in the value of k EfOM-HO The average k EfOM-HO value for EfOM in this study was 2.5 × 108 MC −1 s−1, which is about 31% lower than the 3.6 × 108 MC −1 s−1 value determined for natural organic matter isolates and commonly used in AOP modeling. [Copyright &y& Elsevier]

Abstract: The use of fluorescence spectroscopy for the analysis and characterization of dissolved organic matter (DOM) has gained widespread interest over the past decade, in part because of its ease of use and ability to provide bulk DOM chemical characteristics. However, the lack of standard approaches for analysis and data evaluation has complicated its use. This study utilized comparative statistics to systematically evaluate commonly used fluorescence metrics for DOM characterization to provide insight into the implications for data analysis and interpretation such as peak picking methods, carbon-normalized metrics and the fluorescence index (FI). The uncertainty associated with peak picking methods was evaluated, including the reporting of peak intensity and peak position. The linear relationship between fluorescence intensity and dissolved organic carbon (DOC) concentration was found to deviate from linearity at environmentally relevant concentrations and simultaneously across all peak regions. Comparative analysis suggests that the loss of linearity is composition specific and likely due to non-ideal intermolecular interactions of the DOM rather than the inner filter effects. For some DOM sources, Peak A deviated from linearity at optical densities a factor of 2 higher than that of Peak C. For carbon-normalized fluorescence intensities, the error associated with DOC measurements significantly decreases the ability to distinguish compositional differences. An in-depth analysis of FI determined that the metric is mostly driven by peak emission wavelength and less by emission spectra slope. This study also demonstrates that fluorescence intensity follows property balance principles, but the fluorescence index does not. [Copyright &y& Elsevier]

Abstract: Enhanced coagulation (EC) using ferric chloride was evaluated as a pretreatment process to improve the efficiency of ozone (O3) for the oxidation of trace organic contaminants in wastewater. At the applied dosages (10–30 mg/L as Fe), EC pretreatment removed between 10 and 47% of the dissolved organic carbon (DOC) from the three wastewaters studied. Size exclusion chromatography (SEC) showed that EC preferentially removed higher apparent molecular weight (AMW) compounds. Subsequent O3 testing was performed using an O3:DOC ratio of 1. Results showed that O3 exposures were similar even though the required doses were reduced by 10–47% by the EC pretreatment process. Hydroxyl radical (HOe, measured by parachlorobenzoic acid (pCBA), showed 10% reduction when using a FeCl3 dose of 30 mg/L, likely due to the lower O3 dose and decreased production of HOhe initial phase of O3 decomposition (t < 30 s). The oxidation of 13 trace organic contaminants (including atenolol, carbamazepine, DEET, diclofenac, dilantin, gemfibrozil, ibuprofen, meprobamate, naproxen, primidone, sulfamethoxazole, triclosan, and trimethoprim) was evaluated after EC and O3 treatment. EC was ineffective at removing any of the contaminants, while O3 oxidation reduced the concentration of compounds according to their reaction rate constants with O3 and HOple-para> [Copyright &y& Elsevier]

The temperature-dependent bimolecular rate constants for the reaction of the hydroxyl radical (HO•) with organic matter (OM) (kOM-HO•) have been measured for three natural organic matter (NOM) isolates and three bulk effluent organic matter (EfOM) samples using electron pulse radiolysis and thiocyanate competition kinetics. The range of values for the room temperature kOM-HO• was 1.21-9.37 × 108 MC-1s-1, with NOM isolates generally reacting slower than EfOM samples. The NOM isolates had an average apparent activation energy of 19.8 kJ mol-1, while the EfOM samples had an average value slightly lower (14.3 kJ mol-1), although one NOM isolate (Elliot Soil Humic Acid, 29.9 kJ mol-1) was a factor of 2 times greater than other samples studied. These apparent activation energies are the first determined for OM and HO•, and the Arrhenius plots obtained for NOM isolates (lowest R² > 0.993) suggest that no significant structural changes are occurring over the temperature range 8-41 °C. In contrast, the greater scatter (lowest R² > 0.903) observed for the EfOM samples suggests that some structural changes may be occurring. These results provide a deeper fundamental understanding of the reaction between OM and HO• and will be useful in quantifying HO• reactions in natural and engineered systems. [ABSTRACT FROM AUTHOR]

• The review discusses some issues regarding haloacetate photo(cata)lysis studies. • Various UV technologies exhibit different photo(cata)lytic kinetics, products, and pathways. • Haloacetate susceptibility often increases with molecular weight of substituted halogens. • OH is not the only driver in degrading haloacetates among various UV technologies. • Some knowledge gaps exist in technology comparison criteria and radicals sources. Haloacetic acids (HAAs) are a group of pollutants ubiquitous in natural environment and anthropogenic systems, and therefore in need of control. Photolysis and photocatalysis techniques via ultraviolet (UV)-based technologies have held promise for decades in degrading organic molecules in water, but their capacities in removing HAAs remain to be explored. To better understand the trends in the existing literature and to identify the knowledge gaps that may merit further exploration, this review compares the HAAs photodegradation kinetics, influencing factors, reaction products, pathways, and mechanisms for a variety of UV technologies. The selected UV processes are classified into three types: UV-only photolysis, photooxidation, and photoreduction. Overall, although trends vary significantly depending upon many factors, the photo-susceptibility of HAAs always increases with rising molecular weight of substituted halogen atom(s), with those chlorinated HAAs being the most refractory species. Notably, while many processes proved hydroxyl radical (OH) as the forcing driver, the patterns of kinetics among HAAs were not consistent among processes, suggesting that OH was not the only driver. Compared to earlier studies focusing on specific technologies to treat numerous contaminants through a material perspective, this review commits to understanding the commonalities and differences among multiple UV-based technologies in treating only one group of compound mainly via a chemistry viewpoint. [ABSTRACT FROM AUTHOR]

For decades, photolysis and photocatalysis have been touted as promising environment-benign and robust technologies to degrade refractory pollutants from water. However, extensive, large-scale engineering applications remain limited now. To facilitate the technology transfer process, earlier reviews have advocated to developing more cost-effective and innocuous materials, maximizing efficiency of photon usage, and optimizing photoreactor systems, mostly from material and reactor improvement perspectives. However, there are also some fundamental yet critical chemistry issues in photo(cata)lysis processes demanding more in-depth understanding and more careful consideration. Hence, this review summarizes some of these challenges. Of them, the first and paramount issue is the interference of coexisting compounds, including dissolved organic matter, anions, cations, and spiked additives. Secondly, considerable concerns are pointed to the formation of undesirable reaction by-products, such as halogenated, nitrogenous, and sulfur-containing compounds, which might increase instead of reduce toxicity of water if inadequate fluence and catalyst/additive are supplied due to time and cost constraints. Lastly, a critical issue lies in the uncertainty of current approaches used for identifying and quantifying radicals, especially when multiple radicals coexist together under changing and interconvertible conditions. The review hence highlights the needs to better understand these fundamental chemistry issues and meanwhile calls for more delicate design of experiments in future studies to overcome these barriers. • Some chemistry challenges limiting photo(cata)lysis applications are reviewed. • Coexisting compounds may cause unsatisfying performance of photo(cata)lysis. • Formation of undesirable compounds is a barrier for UV technology application. • Current determination methods for radicals require more in-depth understandings. • Quantifying H 2 O 2 reliably in water might provide useful insights to UV processes. [ABSTRACT FROM AUTHOR]