Photovoltaic electrocoagulation treatment of olive mill wastewater using an external-loop airlift reactor

Over the years, olive mill wastewater (OMW), which is generated from olive oil production has attracted considerable attention as one of the most polluted wastewaters due to its high concentrations of toxic compounds. It is a truism nowadays to guide research towards a novel and efficient technologies in order to treat this hazardous waste. In this paper, detoxification of OMW in an external loop airlift reactor (ALR) by electmcoagulation (EC) powered by photovoltaic solar system as a renewable and sustainable energy source was investigated. The effects of the operating parameters, such as electrolysis time, initial pH, current density (CD), and the axial position of the electrode were studied in continuous flow with two aluminum electrodes. A rate of abatement of about 79.24% for COD, 94.82% for polyphenols and 97.87% for dark color was observed within 40 min of treatment at 32.14 mA/cm(2) current density, a position of the electrodes at 35 cm from the bottom of the riser compartment, and initial pH of 5.6. Furthermore, under these optimal conditions, the power supplied by photovoltaic cells led to amount of electrode dissolved (ELC) and specific energy consumption (SEC) of around 0.1118 kg/m(3) and 9.86 kWh/m(3), respectively. It has been proven that the EC treatment of OMW in ALR coupled with renewable energy source offers a low operation cost (0.2 USD/m(3)) compared to other treatment processes.