Biodegradation of Polyphenolic Compounds from Olive Mill Wastewaters (OMW) During Two-Stage Anaerobic Co-digestion of Agro-industrial Mixtures

Abstract

Due to OMW toxicity, low pH values, polyphenols, oils and fats content, and high organic load their uncontrolled disposal to the sea, rivers and soil causes problems to both environment and public health. Olive mill wastewater (OMW) is a phenolic-rich industrial effluent that can be advantageously valorized by the anaerobic digestion to the methane and agricultural fertilizer productions. The aim of this study was to determine the influence of anaerobic co-digestion of OMW in mixture with cheese whey (CW) and liquid cow manure (LCM) on phenolic fraction derived from OMW. Total phenol content of the two-stage anaerobically co-digested agro-industrial mixtures was significantly decreased (up to 50% degradation for both mixtures in a ratio of 55% OMW:40% CW:5% LCM, v/v/v and 80% OMW:20% CW). Main phenolic compounds namely Gallic acid, hydroxytyrosol, tyrosol, p-coumaric acid and oleuropein were identified in OMW samples. All five individual phenols in all OMW mixtures were degraded to a large extent (80% degradation for the mixture in a ratio of 55 OMW:40 CW:5% LCM and 80 OMW:20% CW and 100% degradation for 20 OMW:80% LCM.