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In this paper, reaction kinetics, degradation mechanisms and associated toxicity have been assessed in detail concerning the abatement of neonicotinoid insecticide clothianidin (CLO) by ozone-based oxidation in water. The second-order rate constants for the reaction of CLO with molecular ozone (O3) and hydroxyl radical ([rad]OH) were determined by the direct and competition kinetics (with UV/H2O2 system as the radical source) methods, respectively, and estimated to be 103 M−1 s−1 and 3.7·109 M−1 s−1. This suggested a (potential) higher contribution of the indirect mechanism rather than the direct degradative pathway in the CLO ozonation process. Additionally, CLO oxidation was studied through an O3 and O3/H2O2 system for three complex real water matrices with distinct characteristics. DOC content was found to be the main parameter responsible for making difficult the achievement of high CLO degradations, whereas carbonate alkalinity did not exert a great impact on the process efficiency. Results indicated that typical ozone doses (up to 1 mg O3/mg DOC) were not enough for the complete removal of this micropollutant, ranging only from 50 to 80%. The study concerning the transformation products (TPs), performed by means of high-resolution mass spectrometry, allowed to suggest potential degradation routes based on the five major CLO-TPs identified. It was inferred that [rad]OH was involved in the formation of all TPs, whereas O3 was only involved in the formation of two of them. A preliminary toxicity assessment concerning CLO and its TPs during ozonation was conducted at three different trophic levels via the ECOSAR software. Results showed that none of the compounds was classified as very toxic for aquatic organisms, and all TPs exhibited minor toxicity than the parent compound. Changes in molecular structure, such as chlorothiazole ring breakdown, could be the main reason for this considerable decrease in toxicity. Overall, the present study demonstrates that ozonation can be considered a suitable technology alternative for CLO (and associated toxicity) abatement from aqueous matrices., This work was financially supported by MCIN/AEI/10.13039/501100011033, with the project PID2020-112674RB-I00, as well as by the Agency for Management of University and Research Grants of the Government of Catalonia (project 2017SGR131).

In this work, the effect of solar light as a “reducing agent” in Fe(VI)/PMS process for disinfection and decontamination of water was investigated. Single, double and triple-factor disinfection processes were systematically studied against Escherichia coli and validated on sulfamethoxazole. The experiments performed with PMS or Fe(VI) in dark conditions only achieved 1-log reduction in 2 h, while no significant enhancement was found in the Fe(VI)/PMS system. The introduction of solar light in either PMS or Fe(VI) process enhanced the E. coli inactivation, and complete inactivation (6-log) was reached at 90 min. However, the best improvement was achieved with the triple-factor disinfection process (Fe(VI)/PMS/solar light) which presented 6-log reduction at only 40 min. In the case of sulfamethoxazole, more than 70% removal was achieved under the Fe(VI)/PMS/solar light system, while only about 20% was observed with single and double-factor processes. Our study revealed the light spectrum distribution effects and the iron speciation implications. A main role for HO. and the participation of SO4.- was found, without overlooking the direct effects of solar light and PMS itself, as well as the possible involvement of other transient species. Overall, the efficacy of the Fe(VI)/PMS/solar light process against a series of microorganisms combined with the effectiveness at near-neutral pH, suggest its suitability for further assessment in disinfection and/or decontamination of water., Stefanos Giannakis would like to acknowledge the Spanish Ministry of Science, Innovation and Universities (MICIU) for the Ramón y Cajal Fellowship (RYC2018-024033-I) and the ‘NAVIA’ Project (PID2019-110441RB-C32). Núria López is grateful to the Spanish Ministry of Science and Innovation (aids for mobility for short-term research stays of FPU predoctoral staff, grant N° FPU-16/02101) which provided the economic support required to carry out the research stay at UPM.

Background: This work studied the use of the organic fertilizers DTPA-Fe and EDDS-Fe as iron chelates for solar driven photo-Fenton process at natural pH. This process was proposed to investigate its performance on removing a mixture of agrochemicals (propiconazole, imidacloprid and diuron) from pineapple processing wastewater to obtain a suitable effluent to be reused in the agricultural sector. Methods: Experiments were carried out in a solar simulator with a stirred cylindric photoreactor, with a volume of 150 mL and controlled temperature (20°C). The first set of experiments was carried out with ultrapure water to determine optimal iron and H2O2 concentrations. The second was performed with simulated wastewater of pineapple processing. Results: The optimized operational conditions for both iron complexes were 10 mg L-1 of Fe (III) and 25 mg L-1 of H2O2, since more than 80% of micropollutants (MP) (at an initial concentration of 1 mg L-1 of each compound) were removed in only 20 min with both DTPA-Fe and EDDS-Fe. The effect of organic matter and inorganic salts on radicals scavenging and chelates stability was also investigated in the experiments performed with synthetic pineapple processing wastewater. The results disclosed differences depending on the iron complex. Nitrites were the principal component influencing the tests carried out with EDDS-Fe. While carbonates at low concentration only significantly affected the experiments performed with DTPA-Fe, they were the major influence on the MPs removal efficiency decrease. In contrast, the presence of Ca2+ and Mg2+ only influence on this last one. Finally, the results of phytotoxicity disclosed the suitability of treated effluent to be reused in the agricultural sector. Conclusions: This work demonstrated that solar powered photo-Fenton catalysed by iron fertilizer EDDS is a suitable technology for depolluting water streams coming from pineapple processing plants at circumneutral pH, and its subsequent reuse for crop irrigation.

Diclofenac (DCF) is a highly consumed non-steroidal anti-inflammatory drug that is excreted partially metabolized and is poorly removed during wastewater treatment. Previous findings demonstrated that DCF in wastewater treatment plants (WWTP) is partially removed to nitro/nitroso compounds. The reactive nitrogen species, that are microbially produced during nitrification in the activated sludge of WWTP, were suspected to be involved in the transformation of DCF. Therefore, here, we investigated the molecular features governing such biotransformation and the role played by nitrifying bacteria by biodegradation experiments at lab scale in enriched nitrifying sludge bioreactors spiked with DCF and other structurally related non-steroidal anti-inflammatory drugs (NSAIDs). We provided evidence of the incorporation of NO/NO2 groups into DCF originated from ammonia by isotopically labelled biodegradation experiments. Nitroso and nitro-derivatives were tentatively identified for all NSAIDs studied and biotransformation mechanisms were proposed. Our findings from biodegradation experiments performed under different incubation conditions suggested that biotransformation of DCF and its related NSAIDs might not only be microbially mediated by ammonia oxidizing bacteria, but other nitrifiers co-occurring in the activated sludge as ammonia oxidizing archaea and nitrite oxidizing bacteria. Follow-up studies should be conducted to disentangle such complex behaviour in order to improve removal of these contaminants in WWTPs., This study has been financially supported by the EU through the PRIMA project (INWAT 201980E121). This work was supported by the Spanish Ministry of Science and Innovation (Project CEX2018-000794-S). Thermofisher are also acknowledged for their technical support with the Orbitrap software.

Injecting ozone by means of a venturi device causes an increase in the mass transfer coefficient with respect to gas dissolution through a microdiffuser. Moreover, it was observed that significant turbidity levels are not formed (1 NTU) when using a microdiffuser, probably due to the relatively high stirring which avoids formation of intermolecular hydrogen bonds. On the contrary, employing a venturi injector led to the production of high turbidity levels in water (up to 20 NTU). This indicates that formation of supramolecular structures causing this turbidity requires the presence of certain facilitating species which are formed through ozone decomposition mechanisms. The maximum ozone transfer takes place when operating at pH