Effects of High Voltage Electrical Discharge Plasma on Olive Mill Wastewater Treatment

High voltage electrical discharge plasma technology (HVED) is considered as a promising technology for wastewater remediation due to its fast removal rate and environmental compatibility. Olive mill wastewater (OMWW) treatment presents crucial environmental issues because of its high organic load and intense toxicity and phytotoxicity. The effect of cold plasma at frequencies of 60 Hz and 120 Hz, with injected gas (air, oxygen and nitrogen) and with and without the addition of FeCl 3 x6H 2 O, during 30 min, on degradation and removal of organic compounds, as well as polyphenols from OMWW, were investigated. The efficiency of cold plasma was monitored by pH, temperature, electroconductivity, redox potential, oxygen saturation and reduction of chemical oxygen demand (COD) and polyphenols. The best removal efficiency of 50.98% of organic compounds was achieved at 120 Hz with nitrogen and the addition of FeCl 3 x6H 2 O, and a 60.32% reduction of polyphenols at a frequency of 60 Hz with the air and FeCl 3 x6H 2 O added was obtained. Also, the plasma treatment resulted in a decrease in coloring intensity, with the most significant color change at 120 Hz with the addition of FeCl 3 x6H 2 O with nitrogen and air.