Electrochemical treatment of highly concentrated wastewater: A review of experimental and modeling approaches from lab- to full-scale

Abstract

This review proposes an insight into the prospects of electrochemistry for the treatment of highly concentrated effluents in three sections. The first section focuses on the challenges inherent to such kind of wastewater, divided into five categories: industrial wastewater (e.g., pharmaceutical, electronics, chemical, food-processing), hypersaline effluents (e.g., RO concentrates), solutions contaminated with a mixture of organic and inorganic contaminants (e.g., leachate, mining), highly viscous solution (or non-Newtonian liquid) (e.g., sludge) and solutions of high COD load but with low pollutant content (e.g., from soil washing). The second section of this review then focuses on the treatment strategies to ensure that the electrochemical treatment is adapted to these very specific waste streams, including the influence of operating conditions, electrode materials and processes (with special emphasis on anodic oxidation, electro-Fenton and electrocoagulation). The final part focuses on the perspectives of electrochemical treatment of challenging wastewater, by giving the engineering parameters to ensure successful upscaling of electrochemical processes in terms of modeling mass transport, charge transfer and hydrodynamics, reactor designs and energy requirements. The review concludes on process combinations, where electrochemistry could complement traditional methods of treatment, in order to improve the overall efficiency of the integrated system.

Cost comparison of advanced oxidation processes for wastewater treatment using accumulated oxygen-equivalent criteria

“…Of course, some differences could be expected with real matrices, such as the presence of turbidity that can affect UV-based processes (as mentioned earlier), while unwanted by-products (e.g., BrO3with O3 or ClO3with electrochemical treatments) could also be formed depending upon the ions present in the matrix (Br -, Cl -, etc.) (Bergmann et al, 2014;Garcia-Rodriguez et al, 2020;Lee et al, 2016;Mousset et al, 2018b;Mousset et al, 2020). The need to develop criteria for suitable comparison between AOPs is important for evaluating the best available technologies as defined by the European Commission (Rizzo et al, 2020).…”

“…AOPs include pure chemical technologies, i.e., Fenton (Fe 2+ /H2O2), as well as ozone-based technologies (O3 at alkaline pH, peroxonation (O3/H2O2)) and photochemical processes such as photo-Fenton (UV/Fe 2+ /H2O2) and H2O2 photolysis (UV/H2O2) (Stefan, 2017). In addition to conventional AOPs, electrochemical AOPs (EAOPs) 4 continuously generate • OH in situ through different modes of action depending upon the electrode materials (Garcia-Rodriguez et al, 2020;Moreira et al, 2017). For example, in anodic oxidation, heterogeneous • OH radicals are generated at the surface of a high O2 evolution overvoltage anode (Martínez-Huitle et al, 2015).…”

A Review on Electrochemical Degradation and Biopolymer Adsorption Treatments for Toxic Compounds in Pharmaceutical Effluents

“…The increase in EAOPs has gained attention as a promising branch of AOPs because of the prevention of pollution problems. However, there are only few studies dealing with real effluents from pharmaceutical industries or synthetic samples, mostly focussing on the removal of PPCs, dyes, phenolic compounds, but very little information on VOCs [12, 24, 86]. The investigation of the application of anodic oxidation (AO) process to the treatment of real pharmaceutical industry effluent using BDD anode has not also been widely investigated [12].…”

Nanostructured electrodes for electrocatalytic advanced oxidation processes: From materials preparation to mechanisms understanding and wastewater treatment applications

“…In parallel, for more than 20 years, electrochemical applications for environmental protection especially in wastewater gained a considerable interest [5,6]. Those based on the generation of very strong oxidizing agents such as hydroxyl radical (  OH) (E 0 (  OH/H2O) = 2.80 V / SHE), namely electrochemical advanced oxidation processes (EAOPs), have shown impressive efficiency [7][8][9][10][11][12][13]. They have the ability to generate continuously and in situ the reactive agents in order to remove partially or completely -according to the treatment strategy [14] -a wide variety of organic pollutants, especially the most biorecalcitrant ones present either at high concentration (chemical oxygen demand (COD) = 1 -100 g-O2 L -1 ) or very low concentrations (i.e.…”