Enhancing biogas production efficiency through physical, chemical, thermal, and hybrid pre-treatment of olive mill wastewater

Abstract

In this study, various pre-treatment methods were applied to enhance the biogas production efficiency of olive mill wastewater (OMW) collected from the decanter outlet of an olive oil mill operating with a three-phase system. The effects of ultrasonic (US), chemical (HNO₃), microwave (MW), and their combinations on the anaerobic digestion of OMW were evaluated. While HNO₃ pre-treatment alone and in combination with other methods improved biogas production efficiency, MW pre-treatment alone significantly reduced biogas yield. The highest volumetric cumulative biogas production of 231.5 mL (1.78 mL Biogas/gVSd) was achieved in the hybrid HN20 + US10 pre-treated sample, where HNO₃ was applied at 20 % of the total solids in raw OMW, followed by US pre-treatment for 10 min. The total phenol and chemical oxygen demand (COD) removal percentages for the HN20 + US10 pre-treated sample were determined as 25.9 % and 77.2 %, respectively.