Electrochemical treatment of real wastewater with low or high conductivity

Abstract

In the last years, many efforts have been devoted to the development of electrochemical processes for the effective treatment of wastewater contaminated by organic pollutants resistant to conventional biological processes and/or toxic for microorganisms [1–5]. It was shown that some electrochemical approaches, including the direct anodic oxidation at suitable anodes such as boron-doped diamond (BDD) and/or electro-Fenton (EF) at suitable operating conditions and cells [1–6] can allow to treat effectively a very large number of organic pollutants. However, most of the investigations were performed using synthetic wastewater. Hence, it is now mandatory to study the problems connected to the passage from synthetic wastewater to the real ones. The treatment of a real wastewater characterized by low or high conductivity was here performed in various kinds of cells. The electrolyses carried out in conventional cells without supporting electrolyte were characterized by very high TOC removals but excessively high energetic consumptions and operating costs. The addition of sodium sulphate, as supporting electrolyte, allowed to strongly reduce the cell potentials and consequently the energetic consumptions and the operating costs. The best results in terms of both TOC removal, energetic consumptions and operating costs were obtained using a cell with a very low inter-electrode distance with no addition of a supporting electrolyte. In the case of wastewater with high conductivity, the utilization of a reverse electrodialysis process was attempted in order to reduce the energetic consumptions.