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Three emerging contaminants (amitriptyline hydrochloride (AH), methyl salicylate (MS) and 2-phenoxyethanol (PE)) frequently found in wastewaters were selected to be individually degraded in ultra-pure water by the advanced oxidation process (AOP) constituted by the combination of UV radiation and chlorine. The influence of pH, initial chlorine concentration and nature of the contaminants was firstly explored. The trend for the reactivity of the selected compounds was deduced: AH > MS > PE. A later kinetic study was carried out focused on the evaluation of the first-order rate constants and the determination of the partial contribution to the global reaction of the direct photochemical pathway and the radical pathway. In a second stage, the simultaneous oxidation of mixtures of the selected contaminants in several types of water was also performed by the same combination UV/Cl2. The efficiency of this combined system UV/Cl2was compared to other oxidants such as the UV/and UV/H2O2AOPs, and the influence of the operating variables was discussed. Results confirmed that the UV/Cl2system provides higher elimination efficiencies among the AOPs tested. The presence of dissolved organic matter and bicarbonate ions in the water matrix caused a decrease in the treatment efficiency. [ABSTRACT FROM AUTHOR]

The removal of three emerging contaminants (ECs) (amitriptyline hydrochloride (AH), methyl salicylate (MS) and 2-phenoxyethanol (PE)) dissolved in several water matrices by means of their adsorption onto powdered activated carbon (PAC) and granular activated carbon (GAC) has been investigated. When dissolved in ultrapure water, adsorption of the ECs followed the trend of AH > MS > PE, with a positive effect of the adsorbent dose. According to the analysis of the adsorption isotherms and adsorption kinetics, PAC showed strongly higher adsorption efficiency in both capacity and velocity of the adsorption, in agreement with its higher mesoporosity. Equilibrium isotherm data were fitted by Langmuir and Freundlich models. Pseudo-second order kinetics modeled very successfully the adsorption process. Finally, the effect of the presence of dissolved organic matter (DOM) in the water matrices (ultrapure water, surface water and two effluents from wastewater treatment plants) on the adsorption of the selected ECs onto PAC was established, as well as its performance on the removal of water quality parameters. Results show a negative effect of the DOM content on the adsorption efficiency. Over 50% of organic matter was removed with high PAC doses, revealing that adsorption onto PAC is an effective technology to remove both micro-pollutants and DOM from water matrices. [ABSTRACT FROM PUBLISHER]

The removal of 11 selected emerging contaminants (ECs, acetaminophen, metoprolol, caffeine, antipyrine, sulfamethoxazole, flumequine, ketorolac, atrazine, isoproturon, 2-hydroxybiphenyl and diclofenac) by micellar-enhanced ultrafiltration (MEUF) has been investigated. Anionic sodium dodecylsulfate (SDS), non-ionic surfactants Triton X-100 (TX-100) and Tween 20 (TW-20), and cationic surfactants cetylpyridinium chloride (CPC) and cetyl trimethyl ammonium bromide (CTAB) were used. The retention coefficients of the selected compounds were determined in order to evaluate the separation efficiency of ECs from surfactant micelles. It was found that cationic surfactants were more appropriated for the removal of negatively charged and hydrophobic ECs. However, the presence of surfactant decreased the permeate flux due to the concentration polarization and membrane fouling. Among surfactants, the best results in terms of lower membrane fouling and higher retention of ECs were obtained with CPC. In addition, the effects of the MWCO of UF membranes and the water matrix on ECs and CPC removal and on membrane fouling were also evaluated. The increase of the feed CPC concentration improved the removal of ECs, although the permeate flux decreased. The removal of ECs and CPC was not affected by trans-membrane pressure. According to these results, solubilisation of ECs in the micelles and retention of the micelles by the membrane govern the overall retention process. [ABSTRACT FROM AUTHOR]

One important disadvantage of using ultrafiltration (UF) and nanofiltration (NF) for reclamation of secondary effluents from municipal wastewater treatment plants (WWTPs) is the necessity to dispose of the UF and NF retentates. Different advanced treatments including coagulation (iron and alum), oxidation (chlorine, permanganate and ozone) and powdered activated carbon (PAC) adsorption were compared for their efficiencies in removing 11 selected micropollutants and effluent organic matter (EfOM) from UF and NF retentates generated in the filtration of secondary effluents. Ozone exhibited better micropollutants and UV 254 removal efficiencies than chlorine and permanganate. Similar abatement of organics was observed when the same specific oxidant dose was applied to UF and NF retentates. Coagulation preferentially removed high molecular weight compounds, being ineffective for the elimination of most micropollutants. In general terms, iron coagulation was more efficient than alum, since iron achieved higher DOC and UV 254 removal at lower molar doses. In addition, PAC was an effective method for removing micropollutants, especially hydrophobic and aromatic compounds. The hybrid coagulation/ozonation process improved micropollutants and EfOM (DOC and UV 254 ) removal. A specific ozone dose of 1 mg O 3 mg DOC −1 was able to almost completely remove selected micropollutants from the UF retentate. The final effluent, which is likely more biodegradable and less toxic, could be recirculated to biological treatment processes in the WWTP, avoiding the continuous discharge of non-biodegradable micropollutants through the WWTP effluents. [ABSTRACT FROM AUTHOR]

The ozonation of 1 H -benzotriazole (BZ) and 3-methylindole (ML), two emerging contaminants that are frequently present in aquatic environments, was investigated. The experiments were performed with the contaminants (1 μM) dissolved in ultrapure water. The kinetic study led to the determination of the apparent rate constants for the ozonation reactions. In the case of 1 H -benzotriazole, these rate constants varied from 20.1 ± 0.4 M −1 s −1 at pH = 3 to 2143 ± 23 M −1 s −1 at pH = 10. Due to its acidic nature (p K a = 8.2), the degree of dissociation of this pollutant was determined at every pH of work, and the specific rate constants of the un-dissociated and dissociated species were evaluated, being the values of these rate constants 20.1 ± 2.0 and 2.0 ± 0.3 × 10 3 M −1 s −1 , respectively. On the contrary, 3-methylindole does not present acidic nature, and therefore, it can be proposed an average value for its rate constant of 4.90 ± 0.7 × 10 5 M −1 s −1 in the whole pH range 3–10. Further experiments were performed to identify the main degradation byproducts (10 mg L −1 of contaminants, 0.023 g h −1 of ozone). Up to 8 intermediates formed in the ozonation of 3-methylindole were identified by LC–TOFMS, while 6 intermediates were identified in the ozonation of 1 H -benzotriazole. By considering these intermediate compounds, the reaction mechanisms were proposed and discussed. Finally, evaluated rate constants allowed to predict and modeling the oxidation of these micropollutants in general aquatic systems. [ABSTRACT FROM AUTHOR]

The effectiveness of single oxidants and several AOPs was studied for the degradation of five selected emerging contaminants: Benzotriazole, N,N-diethyl-m-toluamide or DEET, Chlorophene, 3-Methylindole and Nortriptyline HCl. First-order rate constants and half-life times for the degradation of each compound in ultra-pure water were deduced and compared. The AOPs were later applied to the degradation of these ECs present in three real waters: public reservoir water, and two secondary effluents from municipal wastewater plants. The effect of the variables on the ECs elimination was established. Finally, a cost estimation based on the operating costs was established for the degradation of 3-Methylindole by the single oxidants and AOPs tested. [ABSTRACT FROM AUTHOR]

Abstract: Second-order rate reaction constants of micropollutants with chlorine are essential for evaluating their removal efficiencies from water during chlorine disinfection. In this study, the reactions of five selected emerging contaminants with unavailable kinetic data (Benzotriazole, N,N-diethyl-m-toluamide or DEET, Chlorophene, 3-Methylindole, and Nortriptyline HCl) with chlorine and bromine have been investigated, and their apparent second-order rate constants have been determined as a function of the pH. For the chlorination process, the intrinsic rate constants for the elementary reactions of the ionized and neutral species were also evaluated. The sequence of reaction rates was Methylindole>Chlorophene>Nortriptyline HCl>Benzotriazole>DEET. The bromination of the selected emerging contaminants in ultra-pure water provided exactly the same sequence of reaction rates as in the chlorination process, although higher values of rate constants. The efficiency of the chlorination process for the degradation of these ECs when present in several aqueous systems (surface water from a public reservoir, and two effluents from municipal wastewater treatment plants) was investigated. During wastewater or drinking water treatment, chlorine is a good option for the degradation of Methylindole, and in a lower extent for Chlorophene and Nortriptyline. However, it is not a suitable oxidant for the abatement of Benzotriazole and DEET. Finally, chlorination in the presence of bromide revealed that low bromide concentrations enhanced slightly the degradation of the selected compounds during chlorine oxidation. [Copyright &y& Elsevier]

Abstract: The photolysis of five frequent emerging contaminants (Benzotriazole, Chlorophene, N,N-diethyl-m-toluamide or DEET, Methylindole, and Nortriptyline HCl) was investigated in ultrapure water under monochromatic ultraviolet radiation at 254 nm and by a combination of UV and hydrogen peroxide. The results revealed that the photolysis rates followed first-order kinetics, with rate constant values depending on the nature of the specific compound, the pH, and the presence or absence of the scavenger tert-butanol. Quantum yields were also determined and values in the range of 53.8 × 10−3 − 9.4 × 10−3 mol E−1 for Benzotriazole, 525 × 10−3 − 469 × 10−3 mol E−1 for Chlorophene, 2.8 × 10−3 − 0.9 × 10−3 mol E−1 for DEET, 108 × 10−3 − 165 × 10−3 mol E−1 for Methylindole, and 13.8 × 10−3 − 15.0 × 10−3 mol E−1 for Nortriptyline were obtained. The study also found that the UV/H2O2 process enhanced the oxidation rate in comparison to direct photolysis. High-performance liquid chromatography coupled to electrospray ionization quadrupole time-of-flight mass spectrometry (HPLC-ESI-QTOF-MS) technique was applied to the concentrations evaluation and further identification of the parent compounds and their by-products, which allowed the proposal of the degradation pathways for each compound. Finally, in order to assess the aquatic toxicity in the photodegradation of these compounds, the Vibrio fischeri acute toxicity test was used, and the results indicated an initial increase of this parameter in all cases, followed by a decrease in the specific case of Benzotriazole, DEET, Methylindole, and Chlorophene. [Copyright &y& Elsevier]

Five emerging contaminants (1-H-Benzotriazole, N,N-diethyl-m-toluamide or DEET, Chlorophene, 3-Methylindole, and Nortriptyline HCl), frequently found in surface waters and wastewaters, were selected to be photooxidized in several water matrices. Previous degradation experiments of these compounds individually dissolved in ultra pure water were performed by using UV radiation at 254 nm and the Fenton's reagent. These oxidation systems allowed the determination of the quantum yields and the rate constants for the radical reaction between each compound and hydroxyl radicals. Later, the simultaneous photodegradation of mixtures of the selected ECs in several types of water (ultrapure water, reservoir water, and two effluents from WWTPs) was carried out and a kinetic study was conducted. A model is proposed for the ECs elimination, and the theoretically calculated concentrations with this model agreed well with the experimental results obtained, which confirmed that it constitutes an excellent tool to predict the elimination of these compounds in waters. [ABSTRACT FROM AUTHOR]

Chemical degradation of the pharmaceuticals and personalcare products(PPCPs) amitriptyline hydrochloride, methyl salicylate, and 2-phenoxyethanolby means of several advanced oxidation processes, including 254 nmUV radiation and Fenton’s reagent, has been studied in differentwater matrixes, such as ultrapure (UP) and surface waters and twosecondary effluents from wastewater treatment plants. The influenceof the operating variables on the elimination of these compounds inUP water was established, and kinetic parameters for their degradation,such as quantum yields along a pH range of 3–11 and second-orderrate constants for their oxidation by hydroxyl radicals, were determined.Specifically, for the reactions of oxidation of the three PPCPs withhydroxyl radicals, the use of a competition kinetic model in Fenton’sreagent experiments allowed evaluation of their rate constants, whosevalues were (10.3 ± 0.3) × 109M–1·s–1for amitriptyline hydrochloride, (7.1± 0.1) × 109M–1·s–1for methyl salicylate, and (4.3 ± 0.1) ×109M–1·s–1for2-phenoxyethanol. Furthermore, the simultaneous oxidation of theseselected PPCPs in three different water systems (surface water froma reservoir and two secondary effluents) was studied, and the influenceof the operating conditions on the removal efficiency was established.Finally, a kinetic model was proposed for the prediction of the eliminationof these compounds by UV radiation and a UV/H2O2system in these water matrixes, with theoretical results that agreedwell with the experimental ones. [ABSTRACT FROM AUTHOR]

Abstract: The removal of eleven emerging contaminants (acetaminophen, metoprolol, caffeine, antipyrine, sulfamethoxazole, flumequine, ketorolac, atrazine, isoproturon, 2-hydroxybiphenyl and diclofenac) present in a WWTP effluent by applying several combined treatments has been investigated. These combinations were constituted by PAC adsorption and/or coagulation pre-treatments followed by UF, as well as by an UF treatment followed by GAC adsorption post-treatment. PAC pre-treatment decreased membrane fouling, with the advantage that PAC was separated from the final effluent in the UF step. Low PAC dose in the range 10–50mgL−1 in the adsorption pre-treatment was enough in order to remove most of the emerging contaminants and to partially improve water quality parameters. However, if the goal is to reach a high improvement of water quality parameters in the pre-treatment step, a PAC dose above 500mgL−1 was required. Although coagulation pre-treatment did not increase appreciably the permeate flux in the UF step, the final quality of the permeate was improved, especially when the combination Fe(III)/UF was applied. Finally, a significant positive effect of the GAC post-treatment after the UF treatment was appreciated, which led to an increase in the removal of the water quality parameters and a significant elimination of emerging contaminants. [Copyright &y& Elsevier]

The elimination of 11 selected emerging contaminants (acetaminophen, metoprolol, caffeine, antipyrine, sulfamethoxazole, flumequine, ketorolac, atrazine, isoproturon, 2-hydroxybiphenyl and diclofenac) has been investigated by means of ultrafiltration membranes in a cross-flow equipment that operated in continuous regime. Two different aqueous systems were used for dissolving the selected pollutants: ultrapure water and a secondary effluent generated in a municipal wastewater treatment plant. The influence of the MWCO of the membranes, and the nature of the water matrix on the permeate flux was established, and the rejection coefficients of the selected compounds were determined. Additionally, in the UF of the secondary effluent, rejection coefficients of several quality parameters (turbidity, chemical oxygen demand, total nitrogen and phosphorus, and absorbance at 254 nm) were also evaluated. In order to enhance the efficiency of the single UF process, three different combined processes were also tested: two pre-treatments consisting in coagulation (by using aluminum sulfate) and adsorption (by using powdered active carbon) stages followed by the UP stage; and adsorption post-treatment (by using granular active carbon) that was conducted to the permeate of the UP stage. The improvements in the elimination of the selected compounds and the quality pollutant parameters were established and discussed. [ABSTRACT FROM AUTHOR]