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Treatment of organic contaminants using the electro-Fenton (EF) process is efficient but generates toxic by-products. The aim of the present study was to assess the residual toxicity associated to the treatment of real mine effluents using EF and to perform a preliminary techno-economic analysis to compare the costs of different techniques. Two mine effluents from northern Quebec with different concentrations of thiosalts (ME low and ME high ) were tested for acute toxicity to Daphnia magna, before and after EF treatment. The higher toxicity of untreated ME low compared to ME high , despite its lower thiosalts content (58 vs 199 mg/L), suggests the presence of an unidentified toxic species, which was removed during EF treatment, or that higher thiosalts concentrations mitigate the toxicity of other toxicants. EF treatment of ME high , initially non-acutely toxic (50% mortality), resulted in the elimination of D. magna mortality. A preliminary techno-economic analysis conducted for northern Quebec vs the rest of Canada and the USA showed that energy consumption was the main contributor (52-95%) to the total operating costs. Electricity-related costs nearly doubled (55%) for northern Quebec relative to the rest of Canada. These findings provide new insights for the potential application of the EF for the treatment of thiosalts in mine water, for operations in central jurisdictions and in remote northern areas., Competing Interests: Declaration of competing interest The authors declare that there is no conflict of interest., (Copyright © 2022 Elsevier B.V. All rights reserved.)

Abstract: French River water (Nova Scotia, Canada) was separated into six different natural organic matter (NOM) fractions, including hydrophobic acids, bases and neutrals and hydrophilic acids, bases and neutrals. The raw water, as well as each of the NOM fractions were analysed for disinfection by-product (DBP) formation potential before and after advanced oxidation with UV/TiO2 to determine the efficacy of this treatment for the removal of DBP precursors. The UV/TiO2 treatment was carried out with a nanostructured thin film (NSTF), coated with TiO2 which is compared with the use of a TiO2 suspension. For the raw river water, removals of total trihalomethane formation potential (TTHMFP) and total haloacetic acid formation potential (THAA9FP) were found to be approximately 20% and 90%, respectively, with 50 mJ/cm2 UV exposure and 1mg/L TiO2. For the fractionated samples, approximately 75% of both trihalomethane (THM) and haloacetic acid (HAA) precursors were found to be associated with the hydrophobic acid fraction. For this individual fraction the same UV/TiO2 treatments exhibited approximately 20–25% removal of both TTHMFP and THAA9FP, suggesting that the fractionation process may have affected the treatability of HAA precursors or may have altered the results of the oxidation processes. [Copyright &y& Elsevier]