Electrochemical treatment of olive mill waste powered by photovoltaic solar energy

Abstract

The proposed photovoltaic electrochemical (PV-EC) process combines autonomous and environmentally friendly photovoltaic solar energy with the capability of the combined electrocoagulation/electrooxidation process to effectively remediate toxic olive mill wastewaters and simultaneously produce electrolytic hydrogen. The photovoltaic array can be connected directly to an electrochemical reactor without batteries increasing, in this way, system sustainability and eliminating the environmental threat of poor battery disposal management. The PV-EC system is proved versatile according to the instantaneous solar irradiation by adjusting the wastewater flow rate to the current intensity supplied by the photovoltaic array. Operating parameters affecting the efficiency of the proposed process, such as wastewater flow rate, conductivity, current density, electroprocessing time and solar irradiance were studied and optimal conditions were investigated. The experimental results showed that the initial COD of 21000 mg/dm3 and turbidity of 162 NTU of the olive mill waste sample, were effectively reduced to 122 mg/dm3 and 0 NTU, respectively, after treating the wastewater by both, batch wise and continuously operated electrocoagulation and electrooxidation or combination of the two processes. The proposed process is a safe method for effective treatment of toxic and recalcitrant wastes, such as oily olive mill wastewaters, especially for applications in remote and isolated locations with lack of electric grid.