Reactions of ferrate(VI) during water treatment generate perferryl(V) or ferryl(IV) as primary intermediates. To better understand the fate of perferryl(V) or ferryl(IV) during ferrate(VI) ...oxidation, this study investigates the kinetics, products, and mechanisms for the reaction of ferrate(VI) with 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) (ABTS) and self-decay of ferrate(VI) in phosphate-buffered solutions. The oxidation of ABTS by ferrate(VI) via a one-electron transfer process produces ABTS•+ and perferryl(V) (k = 1.2 × 106 M–1 s–1 at pH 7). The perferryl(V) mainly self-decays into H2O2 and Fe(III) in acidic solution while with increasing pH the reaction of perferryl(V) with H2O2 can compete with the perferryl(V) self-decay and produces Fe(III) and O2 as final products. The ferrate(VI) self-decay generates ferryl(IV) and H2O2 via a two-electron transfer with the initial step being rate-limiting (k = 26 M–1 s–1 at pH 7). Ferryl(IV) reacts with H2O2 generating Fe(II) and O2 and Fe(II) is oxidized by ferrate(VI) producing Fe(III) and perferryl(V) (k = ∼107 M–1 s–1). Due to these facile transformations of reactive ferrate(VI), perferryl(V), and ferryl(IV) to the much less reactive Fe(III), H2O2, or O2, the observed oxidation capacity of ferrate(VI) is typically much lower than expected from theoretical considerations (i.e., three or four electron equivalents per ferrate(VI)). This should be considered for optimizing water treatment processes using ferrate(VI).
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IJS, KILJ, NUK, PNG, UL, UM
Various oxidants such as chlorine, chlorine dioxide, ferrateVI, ozone, and hydroxyl radicals can be applied for eliminating organic micropollutant by oxidative transformation during water treatment ...in systems such as drinking water, wastewater, and water reuse. Over the last decades, many second-order rate constants (k) have been determined for the reaction of these oxidants with model compounds and micropollutants. Good correlations (quantitative structure–activity relationships or QSARs) are often found between the k-values for an oxidation reaction of closely related compounds (i.e. having a common organic functional group) and substituent descriptor variables such as Hammett or Taft sigma constants. In this study, we developed QSARs for the oxidation of organic and some inorganic compounds and organic micropollutants transformation during oxidative water treatment. A number of 18 QSARs were developed based on overall 412 k-values for the reaction of chlorine, chlorine dioxide, ferrate, and ozone with organic compounds containing electron-rich moieties such as phenols, anilines, olefins, and amines. On average, 303 out of 412 (74%) k-values were predicted by these QSARs within a factor of 1/3–3 compared to the measured values. For HO reactions, some principles and estimation methods of k-values (e.g. the Group Contribution Method) are discussed. The developed QSARs and the Group Contribution Method could be used to predict the k-values for various emerging organic micropollutants. As a demonstration, 39 out of 45 (87%) predicted k-values were found within a factor 1/3–3 compared to the measured values for the selected emerging micropollutants. Finally, it is discussed how the uncertainty in the predicted k-values using the QSARs affects the accuracy of prediction for micropollutant elimination during oxidative water treatment.
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► We develop 18 QSARs for reaction of water treatment oxidants with organic compounds. ► Tested oxidants for QSARs include chlorine, chlorine dioxide, ferrate and ozone. ► The developed QSARs predict accurately the k-values for organic micropollutants. ► Predicted k-values are useful to assess the transformation efficiency of micropollutants.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
Chemical oxidation processes have been widely applied to water treatment and may serve as a tool to minimize the release of micropollutants (e.g. pharmaceuticals and endocrine disruptors) from ...municipal wastewater effluents into the aquatic environment. The potential of several oxidants for the transformation of selected micropollutants such as atenolol, carbamazepine, 17α-ethinylestradiol (EE2), ibuprofen, and sulfamethoxazole was assessed and compared. The oxidants include chlorine, chlorine dioxide, ferrate
VI, and ozone as selective oxidants versus hydroxyl radicals as non-selective oxidant. Second-order rate constants (
k) for the reaction of each oxidant show that the selective oxidants react only with some electron-rich organic moieties (ERMs), such as phenols, anilines, olefins, and deprotonated-amines. In contrast, hydroxyl radicals show a nearly diffusion-controlled reactivity with almost all organic moieties (
k
≥
10
9
M
−1 s
−1). Due to a competition for oxidants between a target micropollutant and wastewater matrix (i.e. effluent organic matter, EfOM), a higher reaction rate with a target micropollutant does not necessarily translate into more efficient transformation. For example, transformation efficiencies of EE2, a phenolic micropollutant, in a selected wastewater effluent at pH 8 varied only within a factor of 7 among the selective oxidants, even though the corresponding
k for the reaction of each selective oxidant with EE2 varied over four orders of magnitude. In addition, for the selective oxidants, the competition disappears rapidly after the ERMs present in EfOM are consumed. In contrast, for hydroxyl radicals, the competition remains practically the same during the entire oxidation. Therefore, for a given oxidant dose, the selective oxidants were more efficient than hydroxyl radicals for transforming ERMs-containing micropollutants, while hydroxyl radicals are capable of transforming micropollutants even without ERMs. Besides EfOM, ammonia, nitrite, and bromide were found to affect the micropollutant transformation efficiency during chlorine or ozone treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
To isolate bacteria responsible for the biodegradation of naphthalene, BTEX (benzene, toluene, ethylbenzene, and o-, m-, and p-xylene), and aliphatic hydrocarbons in petroleum-contaminated soil, ...three enrichment cultures were established using soil extract as the medium supplemented with naphthalene, BTEX, or n-hexadecane. Community analyses showed that Paraburkholderia species were predominant in naphthalene and BTEX, but relatively minor in n-hexadecane. Paraburkholderia aromaticivorans BN5 was able to degrade naphthalene and all BTEX compounds, but not n-hexadecane. The genome of strain BN5 harbors genes encoding 29 monooxygenases including two alkane 1-monooxygenases and 54 dioxygenases, indicating that strain BN5 has versatile metabolic capabilities, for diverse organic compounds: the ability of strain BN5 to degrade short chain aliphatic hydrocarbons was verified experimentally. The biodegradation pathways of naphthalene and BTEX compounds were bioinformatically predicted and verified experimentally through the analysis of their metabolic intermediates. Some genomic features including the encoding of the biodegradation genes on a plasmid and the low sequence homologies of biodegradation-related genes suggest that biodegradation potentials of strain BN5 may have been acquired via horizontal gene transfers and/or gene duplication, resulting in enhanced ecological fitness by enabling strain BN5 to degrade all compounds including naphthalene, BTEX, and short aliphatic hydrocarbons in contaminated soil.
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IZUM, KILJ, NUK, PILJ, PNG, SAZU, UL, UM, UPUK
Ozonation of municipal wastewater effluent has been considered in recent years as an enhanced wastewater treatment technology to abate trace organic contaminants (micropollutants). The efficiency of ...ozonation for micropollutant abatement depends on (1) the reactivity of ozone and OH radical (&z.rad;OH) with the target micropollutant, (2) the dosage of ozone and the stability of ozone and &z.rad;OH in a given water matrix, (3) the removal of undesirable effects (
e.g.
, biological activities) of a micropollutant after structural transformation, and (4) the biodegradability of transformation products in biological post-treatment. In this article, recent advances in predicting organic micropollutant abatement during ozonation of municipal wastewater effluents are reviewed with a focus on (i) principle-based approaches for describing and modeling the reaction kinetics of ozone and &z.rad;OH, (ii) transformation products and pathways, (iii) changes of biological activities, and (iv) biodegradation of transformation products in biological post-treatment. Using the chemical kinetics based on ozone and &z.rad;OH rate constants (
i.e.
, compound-specific information) and exposures (
i.e.
, water matrix-specific information), a generalized prediction of the abatement efficiency of various micropollutants in varying water quality appears to be possible. QSAR-type correlations based on Hammett coefficients or quantum chemical energy calculations or (semi)empirical models have been developed for predicting the ozone and &z.rad;OH rate constants and exposures, respectively. Models based on the ozone and &z.rad;OH reaction rules can be used to predict the transformation products of micropollutants by ozone and &z.rad;OH. Reaction rule-based models in combination with the chemical kinetics information will enable the prediction of transformation product evolution during ozonation. The biological activities of transformation products have been assessed by an effect-driven approach using
in vitro
bioassays. Biological activities with specific modes of action (
e.g.
, receptor-binding activities) were found to be quite efficiently removed, upon slight structural modifications by ozone or &z.rad;OH. The formation of new biological activities has also been observed, which warrants identification of the responsible toxicophore(s) and quantitative exposure-based risk assessment. Finally, there is only limited experimental information on the biodegradability of transformation products; however, biodegradability probability models can be used to make first estimates. In future research, the discussed principle-based approaches can be more actively applied to determine and predict not only the abatement levels of the parent micropollutants but also the formation of transformation products and the consequent changes of biological activities and biodegradability, which determines the overall treatment efficiency.
Ozonation of municipal wastewater effluent has been considered in recent years as an enhanced wastewater treatment technology to abate trace organic contaminants (micropollutants).
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IJS, KILJ, NUK, UL, UM, UPUK
A three‐coordinate low‐spin cobalt(I) complex generated using a pincer ligand is presented. Since an empty dx2-y2
orbital is sterically exposed at the site trans to the N donor of an acridane moiety, ...the cobalt(I) center accepts the coordination of various donors such as H2 and PhSiH3 revealing σ‐complex formation. At this low‐spin cobalt(I) site, homolysis of H–H and Si−H bonds preferentially occurs via bimolecular hydrogen atom transfer instead of two‐electron oxidative addition. When the resulting CoII–H species was exposed to N2, H2 evolution readily occurs at ambient conditions. These results suggest single‐electron processes are favored at the structurally rigidified cobalt center.
Fits to a T: A three‐coordinate low‐spin cobalt(I) complex with an acridane‐based pincer ligand was synthesized. It reacts with H2 and PhSiH3 by σ‐complexation at the cobalt center, which has an empty dx2-y2
orbital. In this example, the homolysis of a σ‐bond by bimolecular hydrogen atom transfer (HAT) occurs rather than oxidative addition.
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BFBNIB, FZAB, GIS, IJS, KILJ, NLZOH, NUK, OILJ, SAZU, SBCE, SBMB, UL, UM, UPUK
This work investigated degradation (measured by qPCR) and biological deactivation (measured by culture-based natural transformation) of extra- and intracellular antibiotic resistance genes (eARGs and ...iARGs) by free available chlorine (FAC), NH2Cl, O3, ClO2, and UV light (254 nm), and of eARGs by •OH, using a chromosomal ARG (blt) of multidrug-resistant Bacillus subtilis 1A189. Rate constants for degradation of four 266–1017 bp amplicons adjacent to or encompassing the acfA mutation enabling blt overexpression increased in proportion to #AT+GC bps/amplicon, or in proportion to #5′-GG-3′ or 5′-TT-3′ doublets/amplicon, with respective values ranging from 0.59 to 2.3 (×1011 M–1 s–1) for •OH, 1.8–6.9 (×104 M–1 s–1) for O3, 3.9–9.2 (×103 M–1 s–1) for FAC, 0.35–1.2(×101 M–1 s–1) for ClO2, and 2.0–8.8 (×10–2 cm2/mJ) for UV at pH 7, and from 1.7–4.4 M–1 s–1 for NH2Cl at pH 8. For FAC, NH2Cl, O3, ClO2, and UV, ARG deactivation paralleled degradation of amplicons approximating a ∼800–1000 bp acfA-flanking sequence required for natural transformation in B. subtilis, whereas deactivation outpaced degradation for •OH. At practical disinfectant exposures, eARGs and iARGs were ≥90% degraded/deactivated by FAC, O3, and UV, but recalcitrant to NH2Cl and ClO2. iARG degradation/deactivation always lagged cell inactivation. These findings provide a quantitative framework for evaluating ARG fate during disinfection/oxidation, and support using qPCR as a proxy for tracking ARG deactivation under carefully selected circumstances.
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IJS, KILJ, NUK, PNG, UL, UM
The wide use of antibiotics in aquaculture for prophylactic and therapeutic purposes can potentially lead to the prevalence of antibiotic resistance genes (ARGs). This study reports for the first ...time the profile of ARGs from effluents of coastal aquaculture located in South Jeolla province and Jeju Island, South Korea. Using quantitative PCR (qPCR), twenty-two ARGs encoding tetracycline resistance (tetA, tetB, tetD, tetE, tetG, tetH, tetM, tetQ, tetX, tetZ, tetBP), sulfonamide resistance (sul1, sul2), quinolone resistance (qnrD, qnrS, aac(6′)-Ib-cr), β-lactams resistance (blaTEM, blaCTX, blaSHV), macrolide resistance (ermC), florfenicol resistance (floR) and multidrug resistance (oqxA) and a class 1 integrons-integrase gene (intI1) were quantified. In addition, Illumina Miseq sequencing was applied to investigate microbial community differences across fish farm effluents. Results from qPCR showed that the total number of detected ARGs ranged from 4.24 × 10−3 to 1.46 × 10−2 copies/16S rRNA gene. Among them, tetB and tetD were predominant, accounting for 74.8%–98.0% of the total ARGs. Furthermore, intI1 gene showed positive correlation with tetB, tetD, tetE, tetH, tetX, tetZ tetQ and sul1. Microbial community analysis revealed potential host bacteria for ARGs and intI1. Two genera, Vibrio and Marinomonas belonging to Gammaproteobacteria, showed significant correlation with tetB and tetD, the most dominant ARGs in all samples. Also, operational taxonomic units (OTUs)-based network analysis revealed that ten OTUs, classified into the phyla Proteobacteria, Cyanobacteria/Chloroplast, Bacteroidetes, Verrucomicrobia and an unclassified phylum, were potential hosts of tetracycline resistance genes (i.e., tetA, tetG, tetH, tetM, tetQ and tetZ). Further systematic monitoring of ARGs is warranted for risk assessment and management of antibacterial resistance from fish farm effluents.
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•We found prevalence of various ARGs from effluent of coastal aquaculture.•Among the targeted ARGs, both tetB and tetD were predominant.•intI1 had positive correlation with tetracycline and sulfonamide resistance genes.•Network analysis revealed potential host bacteria for ARGs and intI1.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK, ZRSKP
•UV254 inactivation data of 102 viruses were collected from the literature.•An improved prediction model was applied to estimate UV254 photolysis kinetics.•About 70% of kpred, genome fell in the ...range of 1/2 to 2 times of kexp, infectivity.•The predicted UV254 inactivation rate constant for SARS-CoV-2 was 3.168 cm2 mJ−1.•The model can serve for prescreening on emerging and unculturable viruses.
UV254 irradiation disinfection is a commonly used method to inactivate pathogenic viruses in water and wastewater treatment. Model prediction method can serve as a pre-screening tool to quickly estimate the effectiveness of UV254 irradiation on emerging or unculturable viruses. In this study, an improved prediction model was applied to estimate UV254 photolysis kinetics of viral genomes (kpred, genome) based on the genome sequences and their photoreactivity and to correlate with the experimental virus infectivity loss kinetics (kexp, infectivity). The UV254 inactivation data of 102 viruses (including 2 dsRNA, 65 ssRNA, 33 dsDNA and 2 ssDNA viruses) were collected from the published experimental data with kexp, infectivity ranging from 0.016 to 3.49 cm2 mJ−1. The model had fairly good performance in predicting the virus susceptibility to UV254 irradiation except dsRNA viruses (Pearson’s correlation coefficient = 0.64) and 70% of kpred, genome fell in the range of 1/2 to 2 times of kexp, infectivity. The positive deviation of the model often occurred for photoresistant viruses with low kexp, infectivity less than 0.20 cm2 mJ−1 (e.g., Adenovirus, Papovaviridae and Retroviridae). We also applied this model to predict the UV254 inactivation rate of SARS-CoV-2 (kpred, genome = 3.168 cm2 mJ−1) and a UV dose of 3 mJ cm−2 seemed to be able to achieve a 2-log removal by conservative calculation using 1/2kpred, genome value. This prediction method can be used as a prescreening tool to assess the effectiveness of UV254 irradiation for emerging/unculturable viruses in water or wastewater treatment.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NLZOH, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UILJ, UL, UM, UPCLJ, UPUK, ZAGLJ, ZRSKP
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