Application of life cycle assessment to Fenton processes in wastewater treatment – A review

This work reviewed the application of life cycle assessment (LCA) to the treatment of wastewaters by Fenton processes. The goal was to identify the major environmental hotspots of the different Fenton processes – conventional homogeneous, intensified homogeneous, and heterogeneous – and assess how LCA can contribute to help industries select the most suitable wastewater treatment process. Overall, energy and chemicals were identified as the major contributors to most environmental impact categories. Indeed, energy was the main environmental hotspot pointed out in 77 % of works reviewed dealing with conventional homogeneous Fenton processes, and in 42 % of works dealing with hybrid and heterogeneous Fenton processes. The environmental burden of energy was attributed mainly to the reliance on fossil sources, and to the low efficiency of voltage transformation operations. Regarding chemicals, hydrogen peroxide was identified as the main contributor, followed by chemicals used for pH adjustment. Chemicals were pointed out as the major environmental hotspot in 23 % of works dealing with conventional homogeneous Fenton processes, and 58 % of works dealing with hybrid and heterogeneous Fenton processes. This work also identified some gaps in current knowledge and indicated directions for future research, including the need for investment in cleaner energy-based processes and the development of highly efficient heterogeneous catalysts. It is equally important to study reaction products arising from Fenton processes, which may present higher toxicity than the original pollutants, and to focus on real wastewater, of highly complex matrices, rather than synthetic solutions of target compounds.