Electro-Fenton treatment of contaminated mine water to decrease thiosalts toxicity to Daphnia magna

Area of Science:

• Environmental Science
• Water Treatment Technologies
• Ecotoxicology

Background:

• The electro-Fenton (EF) process is an effective method for treating organic contaminants in industrial wastewater.
• However, concerns remain regarding the generation of toxic by-products and the residual toxicity of treated effluents.
• Mine effluents, particularly those containing thiosalts, pose significant environmental challenges.

Purpose of the Study:

• To evaluate the residual toxicity of real mine effluents after electro-Fenton treatment.
• To conduct a preliminary techno-economic analysis comparing EF treatment costs with other methods.
• To assess the viability of EF for treating thiosalts in mine water, especially in remote locations.

Main Methods:

• Acute toxicity tests using Daphnia magna were performed on mine effluents before and after EF treatment.
• Two types of mine effluents (MElow and MEhigh) with varying thiosalt concentrations were analyzed.
• A preliminary techno-economic analysis focused on energy consumption and operational costs in different geographical regions.

Main Results:

• EF treatment eliminated acute toxicity in MEhigh effluent, which initially showed no mortality to D. magna.
• The higher toxicity of MElow, despite lower thiosalt levels, suggests the presence of other unidentified toxic species removed by EF.
• Energy consumption constituted the largest portion (52-95%) of operating costs, with electricity costs significantly higher in northern Quebec.

Conclusions:

• Electro-Fenton treatment is a viable method for reducing toxicity in mine effluents containing thiosalts.
• The techno-economic analysis highlights energy consumption as a key cost driver, particularly in remote areas.
• EF offers a promising solution for mine water treatment, adaptable to various operational contexts.