Degradation of olive mill wastewater by different methods and antioxidant activity of olive mill wastewater extraction

Abstract

Olive wastewater (OMW) is an important environmental problem due to the high phenol level and contains organic substances such as sugars, organic acids, polyalcohols, pectins, colloids, tannins, and lipids. Removing OMW is difficult because of the high concentrations of chemical oxygen demand (COD), biochemical oxygen demand, and phenolic compounds. In this study, we concentrated on the degradation of OMW to solve this problem. The degradation of OMW at high pressure and temperature (with H2O2 and without H2O2), at room temperature and atmospheric pressure with H2O2, at room temperature and atmospheric pressure with O3, and with ultrasound-assisted ozonation, was investigated by means of COD, phenolic compounds, and sulfur analyses. The results showed that the method of high pressure and temperature with H2O2 was the most successful. H2O2 at high pressure (O2) and temperature removed 89.2% of COD, 91.5% of phenolic compounds, and color of OMW. With this result, we showed that the use of O2 atmosphere instead of N2 is important for degradation and also especially for color removing. In addition, the antioxidant property of OMW was also examined. Fourier-transform infrared spectroscopy of the extracts revealed vibration bands corresponding to acid, alcohol, and ketone groups. The results showed that high pressure and temperature treatment is very effective for removing phenolic compounds from olive oil wastewater. In addition, 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging potential of OMW in the Cukurova area of Turkey was studied and the IC50 value of OMW was determined to be 118 µg/mL.