Eawag - Swiss Federal Institute of Aquatic Science and Technology

Prof. Dr. Urs Von Gunten Tel. +41 58 765 5270 Inviare e-mail

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Prof. Dr. Urs Von Gunten Tel. +41 58 765 5270 Inviare e-mail

Die Forschung der letzten Jahre umfasste Oxidations- und Desinfektionsprozesse, und photochemische Transformationen.

Kinetische Untersuchungen, Entwicklung von Konzepten zur Charakterisierung von Oxidations- und Desinfektionsprozessen, Charakterisierung von Matrixkomponenten, Übertragung von molekularen Erkenntnissen auf Grossanlagen:

Verständnis über die Auswirkung von Br•/BrO• auf die Bildung von Bromat
Ermittlung der Reaktionskinetik von Br•/BrO• mit funktionellen Gruppen in DOM
Bildung von bromhaltigen Oxidationsnebenprodukten

Charakterisierung von gelösten organischem Material (DOM) relevant für die Aktivität mit Oxidationsmitteln wie Ozon
Ermittlung der relevanten funktionellen Gruppen in DOM, verantwortlich für die Bildung von Oxidationsnebenprodukten und reaktiven Sauerstoffspezies
Ermittlung unbekannter Oxidationsnebenprodukte

Ozonation is one of the treatments used in wastewater treatment plants (WWTPs) to remove MPs, reducing their discharge to the aquatic environment...

SWO3T: Bioanalytical Strategies for Evaluating Wastewater Ozonation Treatment

Characterization of wastewater treatment with suspect und non-target screening for the evaluation of ozonation and activated carbon treatment

SCREEN-O3TP

Bildung und Schicksal von Transformationsprodukten bei der Wasserbehandlung mit Ozon und biologischer Nachbehandlung

TRANSFO3RM

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Ozonation is increasingly applied in water and wastewater treatment for the abatement of micropollutants (MPs). However, the transformation products formed during ozonation (OTPs) and their fate in biological or sorptive post-treatments is largely unknown. In this project, a high-throughput approach, combining laboratory ozonation experiments and detection by liquid chromatography high-resolution mass spectrometry (LC-HR-MS/MS), was developed and applied to identify OTPs formed during ozonation of wastewater effluent for a large number of relevant MPs (total 87). For the laboratory ozonation experiments, a simplified experimental solution, consisting of surrogate organic matter (methanol and acetate), was created, which produced ozonation conditions similar to realistic conditions in terms of ozone and hydroxyl radical exposures. The 87 selected parent MPs were divided into 19 mixtures, which enabled the identification of OTPs with an optimized number of experiments. The following two approaches were considered to identify OTPs. (1) A screening of LC-HR-MS signal formation in these experiments was performed and revealed a list of 1749 potential OTP candidate signals associated to 70 parent MPs. This list can be used in future suspect screening studies. (2) A screening was performed for signals that were formed in both batch experiments and in samples of wastewater treatment plants (WWTPs). This second approach was ultimately more time-efficient and was applied to four different WWTPs with ozonation (specific ozone doses in the range 0.23-0.55 gO₃/gDOC), leading to the identification of 84 relevant OTPs of 40 parent MPs in wastewater effluent. Chemical structures could be proposed for 83 OTPs through the interpretation of MS/MS spectra and expert knowledge in ozone chemistry. Forty-eight OTPs (58%) have not been reported previously. The fate of the verified OTPs was studied in different post-treatment steps. During sand filtration, 87-89% of the OTPs were stable. In granular activated carbon (GAC) filters, OTPs were abated with decreasing efficiency with increasing run times of the filters. For example, in a GAC filter with 16,000 bed volumes, 53% of the OTPs were abated, while in a GAC filter with 35,000 bed volumes, 40% of the OTPs were abated. The highest abatement (87% of OTPs) was observed when 13 mg/L powdered activated carbon (PAC) was dosed onto a sand filter.

Gulde, R.; Rutsch, M.; Clerc, B.; Schollée, J. E.; von Gunten, U.; McArdell, C. S. (2021) Formation of transformation products during ozonation of secondary wastewater effluent and their fate in post-treatment: from laboratory- to full-scale, Water Research, 200, 117200 (16 pp.), doi:10.1016/j.watres.2021.117200, Institutional Repository

Wünsch, R.; Mayer, C.; Plattner, J.; Eugster, F.; Wülser, R.; Gebhardt, J.; Hübner, U.; Canonica, S.; Wintgens, T.; von Gunten, U. (2021) Micropollutants as internal probe compounds to assess UV fluence and hydroxyl radical exposure in UV/H₂O₂ treatment, Water Research, 195, 116940 (13 pp.), doi:10.1016/j.watres.2021.116940, Institutional Repository

Pre-oxidation is often used before disinfection with chlorine to decrease the reactivity of the water matrix and mitigate the formation of regulated disinfection byproducts (DBPs). This study provides insights on the impact of oxidative pre-treatment with chlorine dioxide (ClO₂), ozone (O₃), ferrate (Fe(VI)) and permanganate (Mn(VII)) on Suwannee River Natural Organic Matter (SRNOM) properties characterized by the UV absorbance at 254 nm (UV₂₅₄) and the electron donating capacity (EDC). Changes in NOM reactivity and abatement of DBP precursors are also assessed. The impact of pre-oxidants (based on molar concentration) on UV₂₅₄ abatement ranked in the order O₃ > Mn(VII) > Fe(VI)/ClO₂, while the efficiency of pre-oxidation on EDC abatement followed the order Mn(VII) > ClO₂ > Fe(VI) > O₃ and two phases were observed. At low specific ClO₂, Fe(VI) and Mn(VII) doses corresponding to < 50% EDC abatement, a limited relative abatement of UV₂₅₄ compared to the EDC was observed (~ 8% EDC abatement per 1% UV₂₅₄ abatement). This suggests the oxidation of phenolic-type moieties to quinone-type moieties which absorb UV₂₅₄ and don't contribute to EDC. At higher oxidant doses (> 50% EDC abatement), a similar abatement of EDC and UV₂₅₄ (~ 0.9-1.2% EDC abatement per 1% UV₂₅₄ abatement) suggested aromatic ring cleavage. In comparison to the other oxidants, O₃ abated the relative UV₂₅₄ more effectively, due to a more efficient cleavage of aromatic rings. For a pre-oxidation with Mn(VII), ClO₂ and Fe(VI), similar correlations between the EDC abatement and the chlorine demand or the adsorbable organic halide (AOX) formation were obtained. In contrast, O₃ pre-treatment led to a lower chlorine demand and AOX formation for equivalent EDC abatement. For all oxidants_, trihalomethane formation was poorly correlated with both EDC and UV_254. The EDC abatement was found to be a pre-oxidant-independent surrogate for haloacetonitrile formation. These results emphasize the benefits of combining EDC and UV₂₅₄ measurement to understand and monitor oxidant-induced changes of NOM and assessing DBP formation.

Rougé, V.; von Gunten, U.; Allard, S. (2020) Efficiency of pre-oxidation of natural organic matter for the mitigation of disinfection byproducts: electron donating capacity and UV absorbance as surrogate parameters, Water Research, 187, 116418 (10 pp.), doi:10.1016/j.watres.2020.116418, Institutional Repository

Hypochlorous acid (HOCl) is typically assumed to be the primary reactive species in free available chlorine (FAC) solutions. Lately, it has been shown that less abundant chlorine species such as chlorine monoxide (Cl₂O) and chlorine (Cl₂) can also influence the kinetics of the abatement of certain organic compounds during chlorination. In this study, the chlorination as well as bromination kinetics and mechanisms of 12 olefins (including 3 aliphatic and 9 aromatic olefins) with different structures were explored. HOCl shows a low reactivity towards the selected olefins with species-specific second-order rate constants <1.0 M⁻¹s⁻¹, about 4-6 orders of magnitude lower than those of Cl₂O and Cl₂. HOCl is the dominant chlorine species during chlorination of olefins under typical drinking water conditions, while Cl₂O and Cl₂ are likely to play important roles at high FAC concentration near circum-neutral pH (for Cl₂O) or at high Cl⁻ concentration under acidic conditions (for Cl₂). Bromination of the 12 olefins suggests that HOBr and Br₂O are the major reactive species at pH 7.5 with species-specific second-order rate constants of Br₂O nearly 3-4 orders of magnitude higher than of HOBr (ranging from <0.01 to >10³ M⁻¹s⁻¹). The reactivities of chlorine and bromine species towards olefins follow the order of HOCl < HOBr < Br₂O < Cl₂O ≈ Cl₂. Generally, electron-donating groups (e.g., CH₂OH- and CH₃-) enhances the reactivities of olefins towards chlorine and bromine species by a factor of 3-10², while electron-withdrawing groups (e.g., Cl-, Br-, NO₂-, COOH-, CHO-, -COOR, and CN-) reduce the reactivities by a factor of 3-10⁴. A reasonable linear free energy relationship (LFER) between the species-specific second-order rate constants of Br₂O or Cl₂O reactions with aromatic olefins and their Hammett σ⁺ was established with a more negative ρ value for Br₂O than for Cl₂O, indicating that Br₂O is more sensitive to substitution effects. Chlorinated products including HOCl-adducts and decarboxylated Cl-adduct were identified during chlorination of cinnamic acid by high-performance liquid chromatography/high resolution mass spectrometry (HPLC/HRMS).

Li, J.; Jiang, J.; Manasfi, T.; von Gunten, U. (2020) Chlorination and bromination of olefins: kinetic and mechanistic aspects, Water Research, 187, 116424 (12 pp.), doi:10.1016/j.watres.2020.116424, Institutional Repository

Walpen, N.; Houska, J.; Salhi, E.; Sander, M.; von Gunten, U. (2020) Quantification of the electron donating capacity and UV absorbance of dissolved organic matter during ozonation of secondary wastewater effluent by an assay and an automated analyzer, Water Research, 185, 116235 (12 pp.), doi:10.1016/j.watres.2020.116235, Institutional Repository

Remucal, C. K.; Salhi, E.; Walpen, N.; von Gunten, U. (2020) Molecular-level transformation of dissolved organic matter during oxidation by ozone and hydroxyl radical, Environmental Science and Technology, 54(16), 10351-10360, doi:10.1021/acs.est.0c03052, Institutional Repository

Lim, S.; McArdell, C. S.; von Gunten, U. (2019) Reactions of aliphatic amines with ozone: kinetics and mechanisms, Water Research, 157, 514-528, doi:10.1016/j.watres.2019.03.089, Institutional Repository

The abatement of organic micropollutants during oxidation processes has become an emerging issue for various urban water systems such as drinking water, wastewater, and water reuse. Reaction kinetics and mechanisms play an important role in terms of efficiency of these processes and the formation of transformation products, which are controlled by functional groups in the micropollutants and the applied oxidants. So far, the kinetic and mechanistic information on the underlying reactions was obtained by experimental studies; additionally, predictive quantitative structure–activity relationships (QSARs) were applied to determine reaction kinetics for the oxidation of emerging compounds. Since this experimental approach is very laborious and there are tens of thousands potential contaminants, alternative strategies need to be developed to predict the fate of micropollutants during oxidative water treatment. Due to significant developments in quantum chemical (QC) computations in recent years and increased computational capacity, QC-based methods have become an alternative or a supplement to the current experimental approach.
This Account provides a critical assessment of the current state-of-the-art of QC-based methods for the assessment of oxidation of micropollutants. Starting from a given input structure, QC computations need to locate energetic minima on the potential energy surface (PES). Then, useful thermodynamic and kinetic information can be estimated by different approaches: Experimentally determined reaction mechanisms can be validated by identification of transition structures on the PES, which can be obtained for addition reactions, heavy atom transfer (Cl⁺, Br⁺, O·) and H atom transfer (simultaneous proton and electron transfer) reactions. However, transition structures in the PES cannot be obtained for e^–-transfer reactions.
Second-order rate constants k for the reactions of micropollutants with chemical oxidants can be obtained by ab initio calculations or by QSARs with various QC descriptors. It has been demonstrated that second-order rate constants from ab initio calculations are within factors 3–750 of the measured values, whereas QSAR-based methods can achieve factors 2–4 compared to the experimental data. The orbital eigenvalue of the highest occupied molecular orbital (E_HOMO) is the most commonly used descriptor for QSAR-based computations of k-values.
In combination with results from experimental studies, QC computations can also be applied to investigate reaction mechanisms for verification/understanding of oxidative mechanisms, calculation of branching ratios or regioselectivity, evaluation of the experimental product distribution and assessment of substitution effects. Furthermore, other important physical-chemical constants such as unknown equilibria for species, which are not measurable due to low concentrations, or pK_a values of reactive transient species can be estimated. With further development of QC-based methods, it will become possible to implement kinetic and mechanistic information from such computations in in silico models to predict oxidative transformation of micropollutants. Such predictions can then be complemented by tailored experimental studies to confirm/falsify the computations.

Tentscher, P. R.; Lee, M.; von Gunten, U. (2019) Micropollutant oxidation studied by quantum chemical computations: methodology and applications to thermodynamics, kinetics, and reaction mechanisms, Accounts of Chemical Research, 52(3), 605-614, doi:10.1021/acs.accounts.8b00610, Institutional Repository

In response to water scarcity and an increased recognition of the risks associated with the presence of chemical contaminants, environmental engineers have developed advanced water treatment systems that are capable of converting municipal wastewater effluent into drinking water. This practice, which is referred to as potable water reuse, typically relies upon reverse osmosis (RO) treatment followed by exposure to ultraviolet (UV) light and addition of hydrogen peroxide (H₂O₂). These two treatment processes individually are capable of controlling many of the chemical and microbial contaminants in wastewater; however, a few chemicals may still be present after treatment at concentrations that affect water quality.
Low-molecular weight (<200 Da), uncharged compounds represent the greatest challenge for RO treatment. For potable water reuse systems, compounds of greatest concern include oxidation products formed during treatment (e.g., N-nitrosodimethylamine, halogenated disinfection byproducts) and compounds present in wastewater effluent (e.g., odorous compounds, organic solvents). Although the concentrations of most of these compounds decrease to levels where they no longer compromise water quality after they encounter the second treatment barrier (i.e., UV/H₂O₂), low-molecular weight compounds that are resistant to direct photolysis and exhibit low reactivity with hydroxyl radical (·OH) may persist. While attempts to identify the compounds that pass through both barriers have accounted for approximately half of the dissolved organic carbon remaining after treatment, it is unlikely that a significant fraction of the remaining unknowns will ever be identified with current analytical techniques. Nonetheless, the toxicity-weighted concentration of certain known compounds (e.g., disinfection byproducts) is typically lower in RO-UV/H₂O₂ treated water than conventional drinking water.
To avoid the expense associated with managing the concentrate produced by RO, environmental engineers have begun to employ alternative treatment barriers. The use of alternatives such as nanofiltration, ozonation followed by biological filtration, or activated carbon filtration avoids the problems associated with the production and disposal of RO concentrate, but they may allow a larger number of chemical contaminants to pass through the treatment process. In addition to the transformation products and solvents that pose risks in the RO-UV/H₂O₂ system, these alternative barriers are challenged by larger, polar compounds that are not amenable to oxidation, such as perfluoroalkyl acids and phosphate-containing flame retardants.
To fully protect consumers who rely upon potable water reuse systems, new policies are needed to prevent chemicals that are difficult to remove during advanced treatment from entering the sewer system. By using knowledge about the composition of municipal wastewater and the mechanisms through which contaminants are removed during treatment, it should be possible to safely reuse municipal wastewater effluent as a drinking water source.

Marron, E. L.; Mitch, W. A.; Gunten, U. von; Sedlak, D. L. (2019) A tale of two treatments: the multiple barrier approach to removing chemical contaminants during potable water reuse, Accounts of Chemical Research, 52(3), 615-622, doi:10.1021/acs.accounts.8b00612, Institutional Repository

Krasner, S. W.; Lee, C. F. T.; Mitch, W. A.; von Gunten, U. (2018) Impact of combined chlorination and chloramination conditions on N-Nitrosodimethylamine formation, Journal AWWA, 110(12), 11-24, doi:10.1002/awwa.1128, Institutional Repository

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 (UV₂₅₄ or UV₂₈₀) 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.

Önnby, L.; Salhi, E.; McKay, G.; Rosario-Ortiz, F. L.; von Gunten, U. (2018) Ozone and chlorine reactions with dissolved organic matter - Assessment of oxidant-reactive moieties by optical measurements and the electron donating capacities, Water Research, 144, 64-75, doi:10.1016/j.watres.2018.06.059, Institutional Repository

Önnby, L.; Walpen, N.; Salhi, E.; Sander, M.; von Gunten, U. (2018) Two analytical approaches quantifying the electron donating capacities of dissolved organic matter to monitor its oxidation during chlorination and ozonation, Water Research, 144, 677-689, doi:10.1016/j.watres.2018.06.060, Institutional Repository

Rougé, V.; Allard, S.; Croué, J.-P.; von Gunten, U. (2018) In situ formation of free chlorine during ClO₂ treatment: implications on the formation of disinfection byproducts, Environmental Science and Technology, 52(22), 13421-13429, doi:10.1021/acs.est.8b04415, Institutional Repository

Liu, Z.-Q.; Shah, A. D.; Salhi, E.; Bolotin, J.; von Gunten, U. (2018) Formation of brominated trihalomethanes during chlorination or ozonation of natural organic matter extracts and model compounds in saline water, Water Research, 143, 492-502, doi:10.1016/j.watres.2018.06.042, Institutional Repository

Ozonation and subsequent post-treatments are increasingly implemented in wastewater treatment plants (WWTPs) for enhanced micropollutant abatement. While this technology is effective, micropollutant oxidation leads to the formation of ozonation transformation products (OTPs). Target and suspect screening provide information about known parent compounds and known OTPs, but for a more comprehensive picture, non-target screening is needed. Here, sampling was conducted at a full-scale WWTP to investigate OTP formation at four ozone doses (2, 3, 4, and 5 mg/L, ranging from 0.3 to 1.0 gO₃/gDOC) and subsequent changes during five post-treatment steps (i.e., sand filter, fixed bed bioreactor, moving bed bioreactor, and two granular activated carbon (GAC) filters, relatively fresh and pre-loaded). Samples were measured with online solid-phase extraction coupled to liquid chromatography high-resolution tandem mass spectrometry (LC-HRMS/MS) using electrospray ionization (ESI) in positive and negative mode. Existing non-target screening workflows were adapted to (1) examine the formation of potential OTPs at four ozone doses and (2) compare the removal of OTPs among five post-treatments. In (1), data processing included principal component analysis (PCA) and chemical knowledge on 31 possible oxidation reactions to prioritize non-target features likely to be OTPs. Between 394 and 1328 unique potential OTPs were detected in positive ESI for the four ozone doses tested; between 12 and 324 unique potential OTPs were detected in negative ESI. At a specific ozone dose of 0.5 gO₃/gDOC, 27 parent compounds were identified and were related to 69 non-target features selected as potential OTPs. Two OTPs were confirmed with reference standards (venlafaxine N-oxide and chlorothiazide); 34 other potential OTPs were in agreement with literature data and/or reaction mechanisms. In (2), hierarchical cluster analysis (HCA) was applied on profiles detected in positive ESI mode across the WWTP and revealed 11 relevant trends. OTP removal was compared among the five post-treatments and 54–83% of the non-target features that appeared after ozonation were removed, with the two GAC filters performing the best. Overall, these data analysis strategies for non-target screening provide a useful tool to understand the behavior of unknown features during ozonation and post-treatment and to prioritize certain non-targets for further identification.

Schollée, J. E.; Bourgin, M.; von Gunten, U.; McArdell, C. S.; Hollender, J. (2018) Non-target screening to trace ozonation transformation products in a wastewater treatment train including different post-treatments, Water Research, 142, 267-278, doi:10.1016/j.watres.2018.05.045, Institutional Repository

Knies, J.; Brookes, S.; Schubert, C. J. (2007) Re-assessing the nitrogen signal in continental margin sediments: new insights from the high northern latitudes, Earth and Planetary Sciences Letters, 253(3-4), 471-484, doi:10.1016/j.epsl.2006.11.008, Institutional Repository

N-nitrosamines are a group of potent human carcinogens that can be formed during oxidative treatment of drinking water and wastewater. Many tertiary and quaternary amines present in consumer products (e.g., pharmaceuticals, personal care and household products) are known to be N-nitrosodimethylamine (NDMA) precursors during chloramination, but the formation of other N-nitrosamines has been rarely studied. This study investigates the specific and total N-nitrosamine (TONO) formation potential (FP) of various precursors from nitrogen-containing micropollutants (chlorhexidine, metformin, benzalkonium chloride and cetyltrimethylammonium chloride) and tertiary and quaternary model amines (trimethyl amine, N,N-dimethylbutyl amine, N,N-dimethylbenzyl amine and tetramethyl ammonium). All the studied nitrogenous micropollutants displayed quantifiable TONO FP, with molar yields in the range 0.04–11.92%. However, the observed TONO pools constituted mostly of uncharacterized species, not included in US-EPA 8270 N-nitrosamines standard mix. Only the quaternary ammonium compound benzalkonium chloride showed quantifiable NDMA FP (0.56% molar yield), however, explaining only a minor fraction of the observed TONO FP. The studied model amines showed molar NDMA yields from 0.10% (trimethyl amine) to 5.05% (N,N-dimethylbenzyl amine), very similar to the molar TONO yields. The comparison of the FPs of micropollutants and model compounds showed that the presence of electron donating functional groups (such as a benzyl group) in tertiary and quaternary amine precursors leads to a higher formation of NDMA and uncharacterized N-nitrosamines, respectively. LC-qTOF screening of a list of proposed N-nitrosamine structures has enabled to identify a novel N-nitrosamine (N-nitroso-N-methyldodecylamine) from the chloramination of benzalkonium chloride. This finding supports the hypothesis that different functional groups in quaternary amines can act as leaving groups during chloramination and form differing N-nitrosamine structures at significant yield. Molar TONO yields determined for micropollutants were finally validated under experimental conditions closer to real water matrices, confirming their representativeness also for lower concentration ranges.

Piazzoli, A.; Breider, F.; Gachet Aquillon, C.; Antonelli, M.; von Gunten, U. (2018) Specific and total N-nitrosamines formation potentials of nitrogenous micropollutants during chloramination, Water Research, 135, 311-321, doi:10.1016/j.watres.2018.02.019, Institutional Repository

von Gunten, U. (2018) Oxidation processes in water treatment: are we on track?, Environmental Science and Technology, 52(9), 5062-5075, doi:10.1021/acs.est.8b00586, Institutional Repository

Tentscher, P. R.; Bourgin, M.; von Gunten, U. (2018) Ozonation of Para-substituted phenolic compounds yields p‑benzoquinones, other cyclic α,β-unsaturated ketones, and substituted catechols, Environmental Science and Technology, 52(8), 4763-4773, doi:10.1021/acs.est.8b00011, Institutional Repository

To protect the ecosystem and drinking water resources in Switzerland and in the countries of the downstream catchments, a new Swiss water protection act entered into force in 2016 aiming to reduce the discharge of micropollutants from wastewater treatment plants (WWTPs). As a consequence, selected WWTPs must be upgraded by an advanced treatment for micropollutant abatement with suitable and economic options such as (powdered) activated carbon treatment or ozonation. WWTP Neugut (105′000 people equivalent) was the first WWTP in Switzerland to implement a long-term full-scale ozonation. Differing specific ozone doses in the range of 0.35–0.97 g O₃/g DOC were applied to determine the adequate ozone dose to fulfill the requirements of the Swiss water protection act. Based on this assessment, a specific ozone dose of 0.55 g O₃/g DOC is recommended at this plant to ensure an average abatement of the twelve selected indicator substances by ≥80% over the whole treatment. A monitoring of 550 substances confirmed that this dose was very efficient to abate a broad range of micropollutants by >79% on average. After ozonation, an additional biological post-treatment is required to eliminate possible negative ecotoxicological effects generated during ozonation caused by biodegradable ozonation transformation products (OTPs) and oxidation by-products (OBPs). Three biological treatments (sand filtration, moving bed, fixed bed) and granular activated carbon (GAC, fresh and pre-loaded) filtration were evaluated as post-treatments after ozonation. In parallel, a fresh GAC filter directly connected to the effluent of the secondary clarifier was assessed. Among the three purely biological post-treatments, the sand filtration performed best in terms of removal of dissolved organic carbon (DOC), assimilable organic carbon (AOC) and total suspended solids (TSS). The fresh activated carbon filtration ensured a significant additional micropollutants abatement after ozonation due to sorption. The relative abatement of the indicator substances ranged between 20 and 89% after 27′000 bed volumes (BV) and was still substantial at 50′000 BV. In an identical GAC filter running in parallel and being fed with the effluent of the secondary clarifier, the elimination was less efficient. Seven primary OTPs (chlorothiazide and six N-oxides) formed during ozonation could be quantified thanks to available reference standards. Their concentration decreased with increasing specific ozone doses with the concomitant formation of other OTPs. The seven OTPs were found to be stable compounds and were not abated in the biological post-treatments. They were sorbed in the fresh GAC filter, but less efficiently than the corresponding parent compounds. Two OBPs, bromate (BrO₃⁻) and N-nitrosodimethylamine (NDMA), were formed during ozonation but did not exceeded 5 μg/L for bromate and 30 ng/L for NDMA at the recommended specific ozone dose of 0.55 g O₃/g DOC. NDMA was well abated in all post-treatments (minimum 41% during fixed bed filtration, maximum 83% during fresh GAC filtration), while bromate was very stable as expected.

Bourgin, M.; Beck, B.; Boehler, M.; Borowska, E.; Fleiner, J.; Salhi, E.; Teichler, R.; von Gunten, U.; Siegrist, H.; McArdell, C. S. (2018) Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: abatement of micropollutants, formation of transformation products and oxidation by-products, Water Research, 129, 486-498, doi:10.1016/j.watres.2017.10.036, Institutional Repository

Krasner, S. W.; Westerhoff, P.; Mitch, W. A.; Hanigan, D.; McCurry, D. L.; von Gunten, U. (2018) Behavior of NDMA precursors at 21 full-scale water treatment facilities, Environmental Science: Water Research and Technology, 4(12), 1966-1978, doi:10.1039/C8EW00442K, Institutional Repository

Breider, F.; Salihu, I.; von Gunten, U. (2018) Formation of N-nitrosamines by micelle-catalysed nitrosation of aliphatic secondary amines, Environmental Science: Processes and Impacts, 20(10), 1479-1487, doi:10.1039/C8EM00335A, Institutional Repository

Spahr, S.; von Gunten, U.; Hofstetter, T. B. (2017) Carbon, hydrogen, and nitrogen isotope fractionation trends in N-nitrosodimethylamine reflect the formation pathway during chloramination of tertiary amines, Environmental Science and Technology, 51(22), 13170-13179, doi:10.1021/acs.est.7b03919, Institutional Repository

In this study, nitrate formation from ammonium and/or dissolved organic nitrogen (DON) was investigated as a novel surrogate parameter to evaluate the abatement of micropollutants during ozonation of synthetic waters containing natural organic matter (NOM) isolates, a natural water and secondary wastewater effluents. Nitrate formation during ozonation was compared to the changes in UV absorbance at 254 nm (UVA₂₅₄) including the effect of pH. For low specific ozone doses UVA₂₅₄ was abated more efficiently than nitrate was formed. This is due to a relatively slow rate-limiting step for nitrate formation from the reaction between ozone and a proposed nitrogen-containing intermediate. This reaction cannot compete with the fast reactions between ozone and UV-absorbing moieties (e.g., activated aromatic compounds). To further test the kinetics of nitrate formation, two possible intermediates formed during ozonation of DON were tested. At pH 7, nitrate was formed during ozonation of acetone oxime and methyl nitroacetate with second-order rate constants of 256.7 ± 4.7 M^-1s^-1 and 149.5 ± 5.8 M^-1s^-1, respectively. The abatement of the selected micropollutants (i.e., 17α-ethinylestradiol (EE2), carbamazepine (CBZ), bezafibrate (BZF), ibuprofen (IBU), and p-chlorobenzoic acid (pCBA)) was investigated for specific ozone doses ≤1.53 mgO₃/mgDOC and its efficiency depended strongly on the reactivity of the selected compounds with ozone. The relative abatement of micropollutants (i.e., EE2 and CBZ) with high ozone reactivity showed linear relationships with nitrate formation. The abatement of micropollutants with intermediate-low ozone reactivity (BZF, IBU, and pCBA) followed one- and two-phase behaviors relative to nitrate formation during ozonation of water samples containing high and low concentrations of nitrate-forming DON, respectively. During ozonation of a wastewater sample, the N-nitrosodimethylamine formation potential (NDMA-FP) during chloramination decreased with increasing specific ozone doses. A good correlation was obtained between NDMA-FP abatement and nitrate formation. Therefore, nitrate formation after pre-ozonation may be a useful parameter to estimate the reduction of the NDMA-FP during post-chloramination. Overall, the results of this study suggest that nitrate formation (possibly in combination with UVA₂₅₄ abatement) during ozonation of DON-containing waters may be a good surrogate for assessing the abatement of micropollutants and the NDMA-FP.

Song, Y.; Breider, F.; Ma, J.; von Gunten, U. (2017) Nitrate formation during ozonation as a surrogate parameter for abatement of micropollutants and the N-nitrosodimethylamine (NDMA) formation potential, Water Research, 122, 246-257, doi:10.1016/j.watres.2017.05.074, Institutional Repository

The efficiency of ozone-based processes under various conditions was studied for the treatment of a surface water (Lake Zürich water, Switzerland) spiked with 19 micropollutants (pharmaceuticals, pesticides, industrial chemical, X-ray contrast medium, sweetener) each at 1 μg L⁻¹. Two pilot-scale ozonation reactors (4–5 m³ h⁻¹), a 4-chamber reactor and a tubular reactor were investigated by either conventional ozonation and/or the advanced oxidation process (AOP) O₃/H₂O₂. The effects of selected operational parameters, such as ozone dose (0.5–3 mg L⁻¹) and H₂O₂ dose (O₃:H₂O₂ = 1:3–3:1 (mass ratio)), and selected water quality parameters, such as pH (6.5–8.5) and initial bromide concentration (15–200 μg L⁻¹), on micropollutant abatement and bromate formation were investigated. Under the studied conditions, compounds with high second-order rate constant k_O3>10⁴ M⁻¹ s⁻¹ for their reaction with ozone were well abated (>90%) even for the lowest ozone dose of 0.5 mg/L. Conversely, the abatement efficiency of sucralose, which only reacts with hydroxyl radicals (·OH), varied between 19 and 90%. Generally, the abatement efficiency increased with higher ozone doses and higher pH and lower bromide concentrations. H₂O₂ addition accelerated the ozone conversion to radical ·OH, which enables a faster abatement of ozone-resistant micropollutants. Interestingly, the abatement of micropollutants decreased with higher bromide concentrations during conventional ozonation due to competitive ozone-consuming reactions, except for lamotrigine, due to the suspected reaction of HOBr/OBr⁻ with the primary amine moieties. In addition to the abatement of micropollutants, the evolution of the two main transformation products (TPs) of hydrochlorothiazide (HCTZ) and tramadol (TRA), chlorothiazide (CTZ) and tramadol N-oxide (TRA-NOX) respectively, was assessed by chemical analysis and kinetic modelling. Both selected TPs were quickly formed initially to reach a maximum concentration followed by a decrease of their concentrations for longer contact times. For the studied conditions, the TP's concentrations at the outlet of the reactors ranged from 0 to 61% of the initial parent compound concentration, CTZ being a more persistent TP than TRA-NOX. Finally, it was demonstrated in both reactors that the formation of bromate (BrO₃−), a potentially carcinogenic oxidation by-product, could be controlled by H₂O₂ addition with a general improvement on micropollutant abatement. Post-treatment by granular activated carbon (GAC) filtration enabled the reduction of micropollutants and TPs concentrations but no changes in bromate were observed. The combined algae assays showed that water quality was significantly improved after oxidation and GAC post-treatment, driven by the abatement of the spiked pesticides (diuron and atrazine).

Bourgin, M.; Borowska, E.; Helbing, J.; Hollender, J.; Kaiser, H.-P.; Kienle, C.; McArdell, C. S.; Simon, E.; von Gunten, U. (2017) Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O₃/H₂O₂: kinetics of micropollutant abatement, transformation product and bromate formation in a surface water, Water Research, 122, 234-245, doi:10.1016/j.watres.2017.05.018, Institutional Repository

Zhao, X.; Ma, J.; von Gunten, U. (2017) Reactions of hypoiodous acid with model compounds and the formation of iodoform in absence/presence of permanganate, Water Research, 119, 126-135, doi:10.1016/j.watres.2017.04.033, Institutional Repository

Soltermann, F.; Abegglen, C.; Tschui, M.; Stahel, S.; von Gunten, U. (2017) Options and limitations for bromate control during ozonation of wastewater, Water Research, 116, 76-85, doi:10.1016/j.watres.2017.02.026, Institutional Repository

Merle, T.; Pronk, W.; von Gunten, U. (2017) MEMBRO₃X, a novel combination of a membrane contactor with advanced oxidation (O₃/H₂O₂) for simultaneous micropollutant abatement and bromate minimization, Environmental Science and Technology Letters, 4(5), 180-185, doi:10.1021/acs.estlett.7b00061, Institutional Repository

The formation and further reactions of halamines during oxidative water treatment can be relevant for water quality. In this study, we investigated the formation and reactivity of several inorganic and organic halamines (monochloramine, N-chloromethylamine, N-chlorodimethylamine, monobromamine, dibromamine, N-bromomethylamine, N,N-dibromomethylamine, and N-bromodimethylamine) by kinetic experiments, transformation product analysis, and quantum chemical computations. Kinetic model simulations were conducted to evaluate the relevance of halamines for various water treatment scenarios. Halamines were quickly formed from the reaction of chlorine and bromine with ammonia or organic amines. Species-specific second-order rate constants for the reaction of chlorine and bromine with ammonia, methyl- and dimethylamine were in the order of 10⁶-10⁸ M⁻¹s⁻¹. The formed halamines were found to be reactive towards phenolic compounds, forming halogenated phenols via electrophilic aromatic substitution (phenol and resorcinol) or quinones via electron transfer (catechol and hydroquinone). At near neutral pH, apparent second-order rate constants for these reactions were in the order of 10⁻⁴-10⁻¹ M⁻¹s⁻¹ for chloramines and 10¹-10² M⁻¹s⁻¹ for bromamines. Quantum chemical computations were used to determine previously unknown aqueous pK_a values, gas phase bond dissociation energies (BDE) and partial atomic charges of the halamines, allowing a better understanding of their reactivities. Kinetic model simulations, based on the results of this study, showed that during chlorination inorganic and organic chloramines are the main halamines formed. However, their further reactions with organic matter are outcompeted kinetically by chlorine. During ozonation, mainly inorganic bromamines are formed, since ozone quickly oxidizes organic amines. The further reactions of bromamine are typically outcompeted by ozone and thus generally of minor importance. The use of peracetic acid for saline ballast water treatment can result in the formation of substantial amounts of bromamines, which can react with dissolved organic matter and contribute to the formation of brominated products.

Heeb, M. B.; Kristiana, I.; Trogolo, D.; Arey, J. S.; von Gunten, U. (2017) Formation and reactivity of inorganic and organic chloramines and bromamines during oxidative water treatment, Water Research, 110, 91-101, doi:10.1016/j.watres.2016.11.065, Institutional Repository

Breider, F.; von Gunten, U. (2017) Quantification of total N-nitrosamine concentrations in aqueous samples via UV-photolysis and chemiluminescence detection of nitric oxide, Analytical Chemistry, 89(3), 1574-1582, doi:10.1021/acs.analchem.6b03595, Institutional Repository

Ozonation of secondary wastewater effluents can reduce the discharge of micropollutants by transforming their chemical structures. Therefore, a better understanding of the formation of transformation products during ozonation is important. In this study, a computer-based prediction platform for the kinetics and mechanisms of the reactions of ozone with organic compounds was developed to enable in silico predictions of transformation products. With the developed prediction platform, reaction kinetics expressed as second-order rate constants for the reactions of ozone with selected organic compounds (k_O₃, M⁻¹ s⁻¹) can be predicted based on an adapted k_O₃ prediction model from a previous study (Lee et al., Environ. Sci. Technol., 2015, 49 , 9925–9935) (average model error of about a factor of 6 for 14 compound classes with 284 model compounds). Ozone reaction mechanisms reported in the literature have been reviewed and, using chemoinformatics tools, encoded into about 340 individual reaction rules that can be generally applied to predict the transformation products of micropollutants. Predictions for k_O₃ and/or transformation products were overall consistent with the experimental data for three micropollutants used as validation compounds (e.g., carbamazepine, tramadol, and triclosan). However, limitations of the current k_O₃ prediction platform were also identified: ambiguous assignment of the n-th highest occupied molecular orbital energy (E_HOMO−n) to the reactive sites, potential errors associated with the use of a gas-phase geometry, and a poor k_O₃ prediction for certain compounds (cetirizine). Therefore, the current prediction tool should not be considered as a substitute for experimental studies and experimental data are still required in the future to obtain a more robust prediction model. Nonetheless, the developed prediction platform, made available as a stand-alone graphical user interface (GUI) application, will provide useful information about aqueous ozone chemistry to various groups of end-users such as environmental chemists, engineers, or toxicologists.

Lee, M.; Blum, L. C.; Schmid, E.; Fenner, K.; von Gunten, U. (2017) A computer-based prediction platform for the reaction of ozone with organic compounds in aqueous solution: kinetics and mechanisms, Environmental Science: Processes and Impacts, 19(3), 465-476, doi:10.1039/C6EM00584E, Institutional Repository

de Vera, G. A.; Gernjak, W.; Weinberg, H.; Farré, M. J.; Keller, J.; von Gunten, U. (2017) Kinetics and mechanisms of nitrate and ammonium formation during ozonation of dissolved organic nitrogen, Water Research, 108, 451-461, doi:10.1016/j.watres.2016.10.021, Institutional Repository

Spahr, S.; Cirpka, O. A.; von Gunten, U.; Hofstetter, T. B. (2017) Formation of N-Nitrosodimethylamine during chloramination of secondary and tertiary amines: role of molecular oxygen and radical intermediates, Environmental Science and Technology, 51(1), 280-290, doi:10.1021/acs.est.6b04780, Institutional Repository

Soltermann, F.; Abegglen, C.; Götz, C.; von Gunten, U. (2016) Bromide sources and loads in Swiss surface waters and their relevance for bromate formation during wastewater ozonation, Environmental Science and Technology, 50(18), 9825-9834, doi:10.1021/acs.est.6b01142, Institutional Repository

Quantenausbeuten, Kinetik und Mechanismen photochemischer Reaktionen, die zum Abbau von Mikroverunreinigungen führen.

Photosensibilisierter Abbau von Phenol- und Anilin-Derivaten, Arzneimitteln und Pestiziden: die komplexe Rolle des gelösten organischen Materials bei der Begünstigung und Hemmung von Oxidationsreaktionen
Photochemisch-induzierte Bildung und Kinetik von oxidierenden Radikalen (Sulfat-Radikal, Carbonat-Radikal): Anwendung auf den Abbau von Mikroverunreinigungen in technischen aquatischen Systemen

Photochemischer Abbau von organischen Schadstoffen
Photochemisch induzierte Bildung von Oxidantien aus chromophorischem organischem Material
Methoden: Photochemische Bestrahlungsexperimente, HPLC Analyse, Blitzlichtphotolyse

Extbase Variable Dump

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Extbase Variable Dump

array(9 items)
   0 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=21889, pid=124)
      originalId => protected21889 (integer)
      authors => protected'Remke,&nbsp;S.&nbsp;C.; von Gunten,&nbsp;U.; Canonica,&nbsp;S.' (62 chars)
      title => protected'Enhanced transformation of aquatic organic compounds by long-lived photooxid
         ants (LLPO) produced from dissolved organic matter' (126 chars)
      journal => protected'Water Research' (14 chars)
      year => protected2021 (integer)
      volume => protected190 (integer)
      issue => protected'' (0 chars)
      startpage => protected'116707 (10 pp.)' (15 chars)
      otherpage => protected'' (0 chars)
      categories => protected'DOM; aquatic photochemistry; transformation kinetics; photosensitizer; pheno
         xyl radicals; organic contaminants' (110 chars)
      description => protected'Dissolved organic matter (DOM) plays a crucial role in the photochemical tra
         nsformation of organic contaminants in natural aquatic systems. The present 
         study focuses on the characterization of a specific effect previously observ
         ed for electron-rich phenols, consisting in an acceleration of the DOM-photo
         sensitized transformation of target compounds at low concentrations (&lt; 1 
         µM). This effect was hypothesized to be caused by DOM-derived "long-lived" 
         photooxidants (LLPO). Pseudo-first-order rate constants for the transformati
         on of several phenols, anilines, sulfonamide antibiotics and phenylureas pho
         tosensitized by Suwannee River fulvic acid were determined under steady−st
         ate irradiation using the UVA and visible wavelengths from a medium-pressure
          mercury lamp. A significant enhancement (by a factor of 2.4 − 16) of th
         e first-order transformation rate constant of various electron-rich target c
         ompounds was observed for an initial concentration of 0.1 <em>μ</em>M compa
         red to 5 <em>μ</em>M . This effect points to a relevant reactivity of these
          compounds with LLPO. For phenols and anilines the enhancement effect occurr
         ed only above certain standard one-electron oxidation potentials. From these
          data series the standard one-electron reduction potential of LLPO was estim
         ated to be in the range of 1.0 − 1.3 V versus the standard hydrogen elec
         trode. LLPO are proposed to mainly consist of phenoxyl radicals formed by ph
         otooxidation of electron-poor phenolic moieties of the DOM. The plausibility
          of this hypothesis was successfully tested by studying the photosensitized 
         transformation kinetics of 3,4-dimethoxyphenol in aqueous solutions containi
         ng a model photosensitizer (2-acetonaphthone) and a model electron-poor phen
         ol (4-cyanophenol) as DOM surrogates.' (1785 chars)
      serialnumber => protected'0043-1354' (9 chars)
      doi => protected'10.1016/j.watres.2020.116707' (28 chars)
      uid => protected21889 (integer)
      _localizedUid => protected21889 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected21889 (integer)modified
      pid => protected124 (integer)
   1 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=19329, pid=124)
      originalId => protected19329 (integer)
      authors => protected'Canonica,&nbsp;S.; Schönenberger,&nbsp;U.' (42 chars)
      title => protected'Inhibitory effect of dissolved organic matter on the transformation of selec
         ted anilines and sulfonamide antibiotics induced by the sulfate radical' (147 chars)
      journal => protected'Environmental Science and Technology' (36 chars)
      year => protected2019 (integer)
      volume => protected53 (integer)
      issue => protected'20' (2 chars)
      startpage => protected'11783' (5 chars)
      otherpage => protected'11791' (5 chars)
      categories => protected'' (0 chars)
      description => protected'Dissolved organic matter (DOM) has been shown to inhibit the oxidation of ar
         omatic amines initiated by excited triplet states, an effect that was attrib
         uted to the reduction of oxidation intermediates back to their parent compou
         nds. The present study focuses on the quantification of an analogous inhibit
         ory effect of DOM on aqueous oxidations induced by the sulfate radical (SO<s
         ub>4</sub><sup>·</sup><sup>–</sup>). Second-order rate constants for the 
         SO<sub>4</sub><sup>·</sup><sup>–</sup>-induced transformation of selected
          anilines and sulfonamide antibiotics were determined by competition kinetic
         s in the presence and absence of DOM from three different isolates at pH 8. 
         In the presence of 1 mg<sub>C</sub> L<sup>–1</sup> of DOM, a significant
          reduction in the rate constant was observed for most of the compounds compa
         red to DOM-free solutions, but for two electron-rich anilines, increases in 
         the rate constant were measured. For 4-cyanoaniline and sulfamethoxazole, th
         e DOM concentration dependence of the rate constant consisted of a sharp dec
         rease up to ∼1.0 mg<sub>C</sub> L<sup>–1</sup> of DOM followed by a re
         gion of slight changes or even increases for higher DOM concentrations (up t
         o 5 mg<sub>C</sub> L<sup>–1</sup>). This behavior was attributed to the o
         ccurrence of the aforementioned inhibitory effect and a counteracting accele
         rated transformation of the contaminants due to reactions with secondary rad
         ical oxidants resulting from DOM oxidation by SO<sub>4</sub><sup>·</sup><su
         p>–</sup>. Both effects of inhibition and secondary oxidants should be con
         sidered when assessing the abatement of aromatic amines in SO<sub>4</sub><su
         p>·</sup><sup>–</sup>-based advanced oxidation processes.' (1732 chars)
      serialnumber => protected'0013-936X' (9 chars)
      doi => protected'10.1021/acs.est.9b04105' (23 chars)
      uid => protected19329 (integer)
      _localizedUid => protected19329 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected19329 (integer)modified
      pid => protected124 (integer)
   2 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=18425, pid=124)
      originalId => protected18425 (integer)
      authors => protected'Leresche,&nbsp;F.; Ludvíková,&nbsp;L.; Heger,&nbsp;D.; Klán,&nbsp;P.; von
          Gunten,&nbsp;U.; Canonica,&nbsp;S.' (111 chars)
      title => protected'Laser flash photolysis study of the photoinduced oxidation of 4-(dimethylami
         no)benzonitrile (DMABN)' (99 chars)
      journal => protected'Photochemical and Photobiological Sciences' (42 chars)
      year => protected2019 (integer)
      volume => protected18 (integer)
      issue => protected'2' (1 chars)
      startpage => protected'534' (3 chars)
      otherpage => protected'545' (3 chars)
      categories => protected'' (0 chars)
      description => protected'Aromatic amines are aquatic contaminants for which phototransformation in su
         rface waters can be induced by excited triplet states of dissolved organic m
         atter (<sup>3</sup>DOM*). The first reaction step is assumed to consist of a
          one-electron oxidation process of the amine to produce its radical cation. 
         In this paper, we present laser flash photolysis investigations aimed at cha
         racterizing the photoinduced, aqueous phase one-electron oxidation of 4-(dim
         ethylamino)benzonitrile (DMABN) as a representative of this contaminant clas
         s. The production of the radical cation of DMABN (DMABN<sup>•+</sup>) afte
         r direct photoexcitation of DMABN at 266 nm was confirmed in accord with pre
         vious experimental results. Moreover, DMABN<sup>•+</sup> was shown to be p
         roduced from the reactions of several excited triplet photosensitizers (carb
         onyl compounds) with DMABN. Second-order rate constants for the quenching of
          the excited triplet states by DMABN were determined to fall in the range of
          3 × 10<sup>7</sup>–5 × 10<sup>9</sup> M<sup>−1</sup> s<sup>−1</sup>
         , and their variation was interpreted in terms of electron transfer theory u
         sing a Rehm–Weller relationship. The decay kinetics of DMABN<sup>•+</sup
         > in the presence of oxygen was dominated by a second-order component attrib
         
         
         up>•+</sup> leading to photodegradation of DMABN was estimated not to exce
         ed ≈5 × 10<sup>3</sup> s<sup>−1</sup>.' (1563 chars)
      serialnumber => protected'1474-905X' (9 chars)
      doi => protected'10.1039/C8PP00519B' (18 chars)
      uid => protected18425 (integer)
      _localizedUid => protected18425 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected18425 (integer)modified
      pid => protected124 (integer)
   3 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=15613, pid=124)
      originalId => protected15613 (integer)
      authors => protected'Vione,&nbsp;D.; Fabbri,&nbsp;D.; Minella,&nbsp;M.; Canonica,&nbsp;S.' (68 chars)
      title => protected'Effects of the antioxidant moieties of dissolved organic matter on triplet-s
         ensitized phototransformation processes: implications for the photochemical 
         modeling of sulfadiazine' (176 chars)
      journal => protected'Water Research' (14 chars)
      year => protected2018 (integer)
      volume => protected128 (integer)
      issue => protected'' (0 chars)
      startpage => protected'38' (2 chars)
      otherpage => protected'48' (2 chars)
      categories => protected'antioxidants; sulfadiazine; electron donating capacity; dissolved organic ma
         tter; environmental photochemistry' (110 chars)
      description => protected'Previous studies have shown that the photodegradation of some pollutants, in
         duced by the excited triplet states of chromophoric dissolved organic matter
          (<sup>3</sup>CDOM<sup>*</sup>), can be inhibited by back-reduction processe
         s carried out by phenolic antioxidants occurring in dissolved organic matter
          (DOM). Here, for the first time to our knowledge, we included such an inhib
         ition effect into a photochemical model and applied the model predictions to
          sulfadiazine (SDZ), a sulfonamide antibiotic that occurs in surface waters 
         in two forms, neutral HSDZ and anionic SDZ<sup>−</sup> (pK<sub>a</sub> = 6
         .5). The input parameters of the photochemical model were obtained by means 
         of dedicated experiments, which showed that the inhibition effect was more m
         arked for SDZ− than for HSDZ. Compared to the behavior of 2,4,6-trimethylp
         henol, which does not undergo antioxidant inhibition when irradiated in natu
         ral water samples, the back-reduction effect on the degradation of SDZ was p
         roportional to the electron-donating capacity of the DOM. According to the m
         odel results, direct photolysis and ·OH reaction would account for the majo
         rity of both HSDZ and SDZ<sup>−</sup> photodegradation in waters having lo
         w dissolved organic carbon (DOC < 1 mgC L<sup>−/1</sup>). With higher DOC 
         values (>3–4 mgC L<sup>−1</sup>) and despite the back-reduction processe
         s, the <sup>3</sup>CDOM<sup>*</sup> reactions are expected to account for th
         e majority of HSDZ phototransformation. In the case of SDZ<sup>−</sup> at 
         high DOC, most of the photodegradation would be accounted for by direct phot
         olysis. The relative importance of the triplet-sensitized phototransformatio
         n of both SDZ<sup>−</sup> and (most importantly) HSDZ is expected to incre
         ase with increasing DOC, even in the presence of back reduction. An increase
          in water pH, favoring the occurrence of SDZ<sup>−</sup> with respect to H
         SDZ, would enhance direct photolysis at the expense of triplet sensitization
         . SDZ should be fairly p...' (2140 chars)
      serialnumber => protected'0043-1354' (9 chars)
      doi => protected'10.1016/j.watres.2017.10.020' (28 chars)
      uid => protected15613 (integer)
      _localizedUid => protected15613 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected15613 (integer)modified
      pid => protected124 (integer)
   4 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=14086, pid=124)
      originalId => protected14086 (integer)
      authors => protected'Lee,&nbsp;M.; Merle,&nbsp;T.; Rentsch,&nbsp;D.; Canonica,&nbsp;S.; von Gunte
         n,&nbsp;U.' (86 chars)
      title => protected'Abatement of polychoro-1,3-butadienes in aqueous solution by ozone, UV photo
         lysis, and advanced oxidation processes (O<SUB>3</SUB>/H<SUB>2</SUB>O<SUB>2<
         /SUB> and UV/H<SUB>2</SUB>O<SUB>2</SUB>)' (192 chars)
      journal => protected'Environmental Science and Technology' (36 chars)
      year => protected2017 (integer)
      volume => protected51 (integer)
      issue => protected'1' (1 chars)
      startpage => protected'497' (3 chars)
      otherpage => protected'505' (3 chars)
      categories => protected'' (0 chars)
      description => protected'The abatement of 9 polychloro-1,3-butadienes (CBDs) in aqueous solution by o
         zone, UV–C(254 nm) photolysis, and the corresponding advanced oxidation pr
         ocesses (AOPs) (i.e., O<SUB>3</SUB>/H<SUB>2</SUB>O<SUB>2</SUB> and UV/H<SUB>
         2</SUB>O<SUB>2</SUB>) was investigated. The following parameters were determ
         ined for 9 CBDs: second-order rate constants for the reactions of CBDs with 
         ozone (<I>k</I><SUB>O<SUB>3</SUB></SUB>) (<0.1–7.9 × 10<SUP>3</SUP> M<SUP
         >–1</SUP> s<SUP>–1</SUP>) or with hydroxyl radicals (<I>k</I><B>·</B><S
         UB>OH</SUB>) (0.9 × 10<SUP>9</SUP> – 6.5 × 10<SUP>9</SUP> M<SUP>–1</SU
         P> s<SUP>–1</SUP>), photon fluence-based rate constants (<I>k</I>′) (210
         –2730 m<SUP>2</SUP> einstein<SUP>–1</SUP>), and quantum yields (Φ) (0.0
         3–0.95 mol einstein<SUP>–1</SUP>). During ozonation of CBDs in a natural
          groundwater, appreciable abatements (>50% at specific ozone doses of 0.5 gO
         <SUB>3</SUB>/gDOC to ∼100% at ≥1.0 gO<SUB>3</SUB>/gDOC) were achieved fo
         r tetra-CBDs followed by (<I>Z</I>)-1,1,2,3,4-penta-CBD and hexa-CBD. This i
         s consistent with the magnitude of the determined <I>k</I><SUB>O<SUB>3</SUB>
         </SUB> and <I>k</I><B>·</B><SUB>OH</SUB>. The formation of bromate, a poten
         tially carcinogenic ozonation byproduct, could be significantly reduced by a
         ddition of H<SUB>2</SUB>O<SUB>2</SUB>. For a typical UV disinfection dose (4
         00 J/m<SUP>2</SUP>), various extents of phototransformations (10–90%) coul
         d be achieved. However, the efficient formation of photoisomers from CBDs wi
         th <I>E/Z</I> configuration must be taken into account because of their pote
         ntial residual toxicity. Under UV–C(254 nm) photolysis conditions, no sign
         ificant effect of H<SUB>2</SUB>O<SUB>2</SUB> addition on CBDs abatement was 
         observed due to an efficient direct phototransformation of CBDs.' (1812 chars)
      serialnumber => protected'0013-936X' (9 chars)
      doi => protected'10.1021/acs.est.6b04506' (23 chars)
      uid => protected14086 (integer)
      _localizedUid => protected14086 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected14086 (integer)modified
      pid => protected124 (integer)
   5 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=14074, pid=124)
      originalId => protected14074 (integer)
      authors => protected'Rosario-Ortiz,&nbsp;F.&nbsp;L.; Canonica,&nbsp;S.' (49 chars)
      title => protected'Probe compounds to assess the photochemical activity of dissolved organic ma
         tter' (80 chars)
      journal => protected'Environmental Science and Technology' (36 chars)
      year => protected2016 (integer)
      volume => protected50 (integer)
      issue => protected'23' (2 chars)
      startpage => protected'12532' (5 chars)
      otherpage => protected'12547' (5 chars)
      categories => protected'' (0 chars)
      description => protected'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-live
         d reactive intermediates (RIs), including hydroxyl radical (<SUP><B>·</B></
         SUP>OH), singlet oxygen (<SUP>1</SUP>O<SUB>2</SUB>) and superoxide radical a
         nion (O<SUB>2</SUB><SUP><B>·</B>–</SUP>). In addition, a fraction of the 
         excited singlet states in CDOM decays into excited triplet states (<SUP>3</S
         UP>CDOM*), which are also important photochemical transients in environmenta
         l systems. These RIs have a significant impact on different processes in sun
         lit waters, including degradation of organic contaminants and the inactivati
         on of pathogens. Due to their transient nature and low steady-state concentr
         ations, the use of common analytical techniques for the direct measurement o
         f these species is impractical. Therefore, specific probe compounds (PCs) ar
         e used. PCs include furfuryl alcohol for <SUP>1</SUP>O<SUB>2</SUB>, and tere
         phthalic acid for <SUP><B>·</B></SUP>OH. In this publication, we present a 
         critical review of the use of PCs for the assessment of the formation of pho
         tochemically generated RIs. We first introduce the concept of a PC, includin
         g the kinetic treatment and necessary assumptions needed to conduct a specif
         ic measurement. Afterward, we present short overviews of the most studied RI
         s and review relevant issues regarding the use of specific PCs for their mea
         surement. We finalize by offering recommendations regarding the use of PCs i
         n environmental photochemistry.' (1627 chars)
      serialnumber => protected'0013-936X' (9 chars)
      doi => protected'10.1021/acs.est.6b02776' (23 chars)
      uid => protected14074 (integer)
      _localizedUid => protected14074 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected14074 (integer)modified
      pid => protected124 (integer)
   6 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=14047, pid=124)
      originalId => protected14047 (integer)
      authors => protected'Yuan,&nbsp;C.; Chakraborty,&nbsp;M.; Canonica,&nbsp;S.; Weavers,&nbsp;L.&nbs
         p;K.; Hadad,&nbsp;C.&nbsp;M.; Chin,&nbsp;Y.-P.' (122 chars)
      title => protected'Isoproturon reappearance after photosensitized degradation in the presence o
         f triplet ketones or fulvic acids' (109 chars)
      journal => protected'Environmental Science and Technology' (36 chars)
      year => protected2016 (integer)
      volume => protected50 (integer)
      issue => protected'22' (2 chars)
      startpage => protected'12250' (5 chars)
      otherpage => protected'12257' (5 chars)
      categories => protected'' (0 chars)
      description => protected'Isoproturon (IPU) is a phenylurea herbicide used to control broad-leaf grass
         es on grain fields. Photosensitized transformation induced by excited triple
         t states of dissolved organic matter (<SUP>3</SUP>DOM*) has been identified 
         as an important degradation pathway for IPU in sunlit waters, but the reappe
         arance of IPU in the absence of light is observed after the initial photolys
         is. In this study, we elucidate the kinetics of this photodegradation and da
         rk-reappearance cycling of IPU in the presence of DOM proxies (aromatic keto
         nes and reference fulvic acids). Using mass spectrometry and nuclear magneti
         c resonance spectroscopic techniques, a semi-stable intermediate (IPU<SUB>in
         t</SUB>) was found to be responsible for IPU reversion and was identified as
          a hydroperoxyl derivative of IPU. IPU<SUB>int</SUB> is photogenerated from 
         incorporation of diatomic oxygen to IPU and is subjected to thermolysis whos
         e rate depends on temperature, pH, the presence of DOM, and inorganic ions. 
         These results are important to understand the overall aquatic fate of IPU an
         d structurally similar compounds under diurnal conditions.' (1122 chars)
      serialnumber => protected'0013-936X' (9 chars)
      doi => protected'10.1021/acs.est.6b03655' (23 chars)
      uid => protected14047 (integer)
      _localizedUid => protected14047 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected14047 (integer)modified
      pid => protected124 (integer)
   7 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=14122, pid=124)
      originalId => protected14122 (integer)
      authors => protected'McNeill,&nbsp;K.; Canonica,&nbsp;S.' (35 chars)
      title => protected'Triplet state dissolved organic matter in aquatic photochemistry: reaction m
         echanisms, substrate scope, and photophysical properties' (132 chars)
      journal => protected'Environmental Science: Processes and Impacts' (44 chars)
      year => protected2016 (integer)
      volume => protected18 (integer)
      issue => protected'11' (2 chars)
      startpage => protected'1381' (4 chars)
      otherpage => protected'1399' (4 chars)
      categories => protected'' (0 chars)
      description => protected'Excited triplet states of chromophoric dissolved organic matter (<SUP>3</SUP
         >CDOM*) play a major role among the reactive intermediates produced upon abs
         orption of sunlight by surface waters. After more than two decades of resear
         ch on the aquatic photochemistry of <SUP>3</SUP>CDOM*, the need for improvin
         g the knowledge about the photophysical and photochemical properties of thes
         e elusive reactive species remains considerable. This critical review examin
         es the efforts to date to characterize <SUP>3</SUP>CDOM*. Information on <SU
         P>3</SUP>CDOM* relies mainly on the use of probe compounds because of the di
         fficulties associated with directly observing <SUP>3</SUP>CDOM* using transi
         ent spectroscopic methods. Singlet molecular oxygen (<SUP>1</SUP>O<SUB>2</SU
         B>), which is a product of the reaction between <SUP>3</SUP>CDOM* and dissol
         ved oxygen, is probably the simplest indicator that can be used to estimate 
         steady-state concentrations of <SUP>3</SUP>CDOM*. There are two major modes 
         of reaction of <SUP>3</SUP>CDOM* with substrates, namely triplet energy tran
         sfer or oxidation (<I>via</I> electron transfer, proton-coupled electron tra
         nsfer or related mechanisms). Organic molecules, including several environme
         ntal contaminants, that are susceptible to degradation by these two differen
         t reaction modes are reviewed. It is proposed that through the use of approp
         riate sets of probe compounds and model photosensitizers an improved estimat
         ion of the distribution of triplet energies and one-electron reduction poten
         tials of <SUP>3</SUP>CDOM* can be achieved.' (1563 chars)
      serialnumber => protected'2050-7887' (9 chars)
      doi => protected'10.1039/c6em00408c' (18 chars)
      uid => protected14122 (integer)
      _localizedUid => protected14122 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected14122 (integer)modified
      pid => protected124 (integer)
   8 => Snowflake\Publications\Domain\Model\Publicationprototypepersistent entity (uid=14034, pid=124)
      originalId => protected14034 (integer)
      authors => protected'Leresche,&nbsp;F.; Von Gunten,&nbsp;U.; Canonica,&nbsp;S.' (57 chars)
      title => protected'Probing the photosensitizing and inhibitory effects of dissolved organic mat
         ter by using <I>N,N</I>-dimethyl-4-cyanoaniline (DMABN)' (131 chars)
      journal => protected'Environmental Science and Technology' (36 chars)
      year => protected2016 (integer)
      volume => protected50 (integer)
      issue => protected'20' (2 chars)
      startpage => protected'10997' (5 chars)
      otherpage => protected'11007' (5 chars)
      categories => protected'' (0 chars)
      description => protected'Dissolved organic matter (DOM) can act as a photosensitizer and an inhibitor
          in the phototransformation of several nitrogen-containing organic contamina
         nts in surface waters. The present study was performed to select a probe mol
         ecule that is suitable to measure these antagonistic properties of DOM. Out 
         of nine studied nitrogen-containing aromatic compounds, 4-cyanoaniline, <I>N
         , N</I>-dimethyl-4-cyanoaniline (DMABN), sotalol (a β-blocker) and sulfadia
         zine (a sulfonamide antibiotic) exhibited a marked photosensitized transform
         ation that could be substantially inhibited by addition of phenol as a model
          antioxidant. The photosensitized transformation of DMABN, the selected prob
         e compound, was characterized in detail under UV-A and visible irradiation (
         λ > 320 nm) to avoid direct phototransformation. Low reactivity of DMABN wi
         th singlet oxygen was found (second-order rate constant <2 × 10<SUP>7</SUP>
          M<SUP>–1</SUP> s<SUP>–1</SUP>). Typically at least 85% of the reactivit
         y of DMABN could be inhibited by DOM or the model antioxidant phenol. The ph
         otosensitized transformation of DMABN mainly proceeded (>72%) through demeth
         ylation yielding <I>N</I>-methyl-4-cyanoaniline and formaldehyde as primary 
         products. In solutions of standard DOM extracts and their mixtures the photo
         transformation rate constant of DMABN was shown to vary nonlinearly with the
          DOM concentration. Model equations describing the dependence of such rate c
         onstants on DOM and model antioxidant concentrations were successfully used 
         to fit experimental data.' (1545 chars)
      serialnumber => protected'0013-936X' (9 chars)
      doi => protected'10.1021/acs.est.6b02868' (23 chars)
      uid => protected14034 (integer)
      _localizedUid => protected14034 (integer)modified
      _languageUid => protectedNULL
      _versionedUid => protected14034 (integer)modified
      pid => protected124 (integer)

Remke, S. C.; von Gunten, U.; Canonica, S. (2021) Enhanced transformation of aquatic organic compounds by long-lived photooxidants (LLPO) produced from dissolved organic matter, Water Research, 190, 116707 (10 pp.), doi:10.1016/j.watres.2020.116707, Institutional Repository

Canonica, S.; Schönenberger, U. (2019) Inhibitory effect of dissolved organic matter on the transformation of selected anilines and sulfonamide antibiotics induced by the sulfate radical, Environmental Science and Technology, 53(20), 11783-11791, doi:10.1021/acs.est.9b04105, Institutional Repository

Leresche, F.; Ludvíková, L.; Heger, D.; Klán, P.; von Gunten, U.; Canonica, S. (2019) Laser flash photolysis study of the photoinduced oxidation of 4-(dimethylamino)benzonitrile (DMABN), Photochemical and Photobiological Sciences, 18(2), 534-545, doi:10.1039/C8PP00519B, Institutional Repository

Previous studies have shown that the photodegradation of some pollutants, induced by the excited triplet states of chromophoric dissolved organic matter (³CDOM^*), can be inhibited by back-reduction processes carried out by phenolic antioxidants occurring in dissolved organic matter (DOM). Here, for the first time to our knowledge, we included such an inhibition effect into a photochemical model and applied the model predictions to sulfadiazine (SDZ), a sulfonamide antibiotic that occurs in surface waters in two forms, neutral HSDZ and anionic SDZ⁻ (pK_a = 6.5). The input parameters of the photochemical model were obtained by means of dedicated experiments, which showed that the inhibition effect was more marked for SDZ− than for HSDZ. Compared to the behavior of 2,4,6-trimethylphenol, which does not undergo antioxidant inhibition when irradiated in natural water samples, the back-reduction effect on the degradation of SDZ was proportional to the electron-donating capacity of the DOM. According to the model results, direct photolysis and ·OH reaction would account for the majority of both HSDZ and SDZ⁻ photodegradation in waters having low dissolved organic carbon (DOC < 1 mgC L^−/1). With higher DOC values (>3–4 mgC L⁻¹) and despite the back-reduction processes, the ³CDOM^* reactions are expected to account for the majority of HSDZ phototransformation. In the case of SDZ⁻ at high DOC, most of the photodegradation would be accounted for by direct photolysis. The relative importance of the triplet-sensitized phototransformation of both SDZ⁻ and (most importantly) HSDZ is expected to increase with increasing DOC, even in the presence of back reduction. An increase in water pH, favoring the occurrence of SDZ⁻ with respect to HSDZ, would enhance direct photolysis at the expense of triplet sensitization. SDZ should be fairly photolabile under summertime sunlight, with predicted half-lives ranging from a few days to a couple of months depending on water conditions.

Vione, D.; Fabbri, D.; Minella, M.; Canonica, S. (2018) Effects of the antioxidant moieties of dissolved organic matter on triplet-sensitized phototransformation processes: implications for the photochemical modeling of sulfadiazine, Water Research, 128, 38-48, doi:10.1016/j.watres.2017.10.020, Institutional Repository

Lee, M.; Merle, T.; Rentsch, D.; Canonica, S.; von Gunten, U. (2017) Abatement of polychoro-1,3-butadienes in aqueous solution by ozone, UV photolysis, and advanced oxidation processes (O₃/H₂O₂ and UV/H₂O₂), Environmental Science and Technology, 51(1), 497-505, doi:10.1021/acs.est.6b04506, Institutional Repository

Rosario-Ortiz, F. L.; Canonica, S. (2016) Probe compounds to assess the photochemical activity of dissolved organic matter, Environmental Science and Technology, 50(23), 12532-12547, doi:10.1021/acs.est.6b02776, Institutional Repository

Yuan, C.; Chakraborty, M.; Canonica, S.; Weavers, L. K.; Hadad, C. M.; Chin, Y.-P. (2016) Isoproturon reappearance after photosensitized degradation in the presence of triplet ketones or fulvic acids, Environmental Science and Technology, 50(22), 12250-12257, doi:10.1021/acs.est.6b03655, Institutional Repository

McNeill, K.; Canonica, S. (2016) Triplet state dissolved organic matter in aquatic photochemistry: reaction mechanisms, substrate scope, and photophysical properties, Environmental Science: Processes and Impacts, 18(11), 1381-1399, doi:10.1039/c6em00408c, Institutional Repository

Leresche, F.; Von Gunten, U.; Canonica, S. (2016) Probing the photosensitizing and inhibitory effects of dissolved organic matter by using N,N-dimethyl-4-cyanoaniline (DMABN), Environmental Science and Technology, 50(20), 10997-11007, doi:10.1021/acs.est.6b02868, Institutional Repository

Abteilung Wasserressourcen und Trinkwasser

Trinkwasserchemie

Willkommen in der Gruppe "Trinkwasserchemie"

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Links

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Forschungsaktivitäten

Forschungsaktivitäten: Oxidations- und Desinfektionsprozesse

Verständnis von reaktiven Bromspezies während der Ozonierung

Verständnis über die Bildung von Oxidationsnebenprodukten und reaktiven Sauerstoffspezies aus organischem Material

Projektkollaborationen

SWO3T: Bioanalytical Strategies for Evaluating Wastewater Ozonation Treatment

SCREEN-O3TP

TRANSFO3RM

Aktuelle Publikationen

Forschungsaktivitäten: Photochemische Transformationprozesse

Photochemische Transformationsprozesse im Zusammenhang mit Schadstoffen und Radikalspezies

Charakterisierung von organischen Radikalspezies produziert aus der Photobestrahlung von Organischem Material ("OROPHOT")

Aktuelle Publikationen

Abteilung Wasserressourcen und Trinkwasser

Trinkwasserchemie

Willkommen in der Gruppe "Trinkwasserchemie"

Kontakt

Links

Neuigkeiten

Mitarbeitende

Forschungsaktivitäten

Forschungsaktivitäten: Oxidations- und Desinfektionsprozesse

Verständnis von reaktiven Bromspezies während der Ozonierung

Verständnis über die Bildung von Oxidationsnebenprodukten und reaktiven Sauerstoffspezies aus organischem Material

Projektkollaborationen

SWO3T: Bioanalytical Strategies for Evaluating Wastewater Ozonation Treatment

SCREEN-O3TP

TRANSFO3RM

Aktuelle Publikationen

Formation of transformation products during ozonation of secondary wastewater effluent and their fate in post-treatment: from laboratory- to full-scale

Micropollutants as internal probe compounds to assess UV fluence and hydroxyl radical exposure in UV/H2O2 treatment

Efficiency of pre-oxidation of natural organic matter for the mitigation of disinfection byproducts: electron donating capacity and UV absorbance as surrogate parameters

Chlorination and bromination of olefins: kinetic and mechanistic aspects

Quantification of the electron donating capacity and UV absorbance of dissolved organic matter during ozonation of secondary wastewater effluent by an assay and an automated analyzer

Molecular-level transformation of dissolved organic matter during oxidation by ozone and hydroxyl radical

Reactions of aliphatic amines with ozone: kinetics and mechanisms

Micropollutant oxidation studied by quantum chemical computations: methodology and applications to thermodynamics, kinetics, and reaction mechanisms

A tale of two treatments: the multiple barrier approach to removing chemical contaminants during potable water reuse

Impact of combined chlorination and chloramination conditions on N-Nitrosodimethylamine formation

Ozone and chlorine reactions with dissolved organic matter - Assessment of oxidant-reactive moieties by optical measurements and the electron donating capacities

Two analytical approaches quantifying the electron donating capacities of dissolved organic matter to monitor its oxidation during chlorination and ozonation

In situ formation of free chlorine during ClO2 treatment: implications on the formation of disinfection byproducts

Formation of brominated trihalomethanes during chlorination or ozonation of natural organic matter extracts and model compounds in saline water

Non-target screening to trace ozonation transformation products in a wastewater treatment train including different post-treatments

Re-assessing the nitrogen signal in continental margin sediments: new insights from the high northern latitudes

Specific and total N-nitrosamines formation potentials of nitrogenous micropollutants during chloramination

Oxidation processes in water treatment: are we on track?

Ozonation of Para-substituted phenolic compounds yields p‑benzoquinones, other cyclic α,β-unsaturated ketones, and substituted catechols

Evaluation of a full-scale wastewater treatment plant upgraded with ozonation and biological post-treatments: abatement of micropollutants, formation of transformation products and oxidation by-products

Behavior of NDMA precursors at 21 full-scale water treatment facilities

Formation of N-nitrosamines by micelle-catalysed nitrosation of aliphatic secondary amines

Carbon, hydrogen, and nitrogen isotope fractionation trends in N-nitrosodimethylamine reflect the formation pathway during chloramination of tertiary amines

Nitrate formation during ozonation as a surrogate parameter for abatement of micropollutants and the N-nitrosodimethylamine (NDMA) formation potential

Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O3/H2O2: kinetics of micropollutant abatement, transformation product and bromate formation in a surface water

Reactions of hypoiodous acid with model compounds and the formation of iodoform in absence/presence of permanganate

Options and limitations for bromate control during ozonation of wastewater

MEMBRO3X, a novel combination of a membrane contactor with advanced oxidation (O3/H2O2) for simultaneous micropollutant abatement and bromate minimization

Formation and reactivity of inorganic and organic chloramines and bromamines during oxidative water treatment

Quantification of total N-nitrosamine concentrations in aqueous samples via UV-photolysis and chemiluminescence detection of nitric oxide

A computer-based prediction platform for the reaction of ozone with organic compounds in aqueous solution: kinetics and mechanisms

Kinetics and mechanisms of nitrate and ammonium formation during ozonation of dissolved organic nitrogen

Formation of N-Nitrosodimethylamine during chloramination of secondary and tertiary amines: role of molecular oxygen and radical intermediates

Bromide sources and loads in Swiss surface waters and their relevance for bromate formation during wastewater ozonation

Forschungsaktivitäten: Photochemische Transformationprozesse

Photochemische Transformationsprozesse im Zusammenhang mit Schadstoffen und Radikalspezies

Charakterisierung von organischen Radikalspezies produziert aus der Photobestrahlung von Organischem Material ("OROPHOT")

Aktuelle Publikationen

Enhanced transformation of aquatic organic compounds by long-lived photooxidants (LLPO) produced from dissolved organic matter

Inhibitory effect of dissolved organic matter on the transformation of selected anilines and sulfonamide antibiotics induced by the sulfate radical

Laser flash photolysis study of the photoinduced oxidation of 4-(dimethylamino)benzonitrile (DMABN)

Effects of the antioxidant moieties of dissolved organic matter on triplet-sensitized phototransformation processes: implications for the photochemical modeling of sulfadiazine

Abatement of polychoro-1,3-butadienes in aqueous solution by ozone, UV photolysis, and advanced oxidation processes (O3/H2O2 and UV/H2O2)

Probe compounds to assess the photochemical activity of dissolved organic matter

Isoproturon reappearance after photosensitized degradation in the presence of triplet ketones or fulvic acids

Triplet state dissolved organic matter in aquatic photochemistry: reaction mechanisms, substrate scope, and photophysical properties

Probing the photosensitizing and inhibitory effects of dissolved organic matter by using N,N-dimethyl-4-cyanoaniline (DMABN)

Micropollutants as internal probe compounds to assess UV fluence and hydroxyl radical exposure in UV/H₂O₂ treatment

In situ formation of free chlorine during ClO₂ treatment: implications on the formation of disinfection byproducts

Effect of operational and water quality parameters on conventional ozonation and the advanced oxidation process O₃/H₂O₂: kinetics of micropollutant abatement, transformation product and bromate formation in a surface water

MEMBRO₃X, a novel combination of a membrane contactor with advanced oxidation (O₃/H₂O₂) for simultaneous micropollutant abatement and bromate minimization

Abatement of polychoro-1,3-butadienes in aqueous solution by ozone, UV photolysis, and advanced oxidation processes (O₃/H₂O₂ and UV/H₂O₂)