Olive mill wastewater is a by-product generated by the olive oil industry. In Greece, the majority of olive oil extraction industries use three-phase centrifugation systems (decanters) which produce,as by-product, a stream of Olive Mill Wastewater (OMW). OMW is characterized by its high organic load containing large amounts of proteins, lipids, polysaccharides, a high C/N ratio and phytotoxic components, such as phenolic compounds, that may inhibit microbial degradation