The olive oil extraction, performed by the 3-phases process, results on a large amount
of an effluent, usually known as Olive Mill Wastewater (OMW). It is mainly produced in
the Mediterranean area, with the exception of Spain that is one of the major producers
but mostly use the 2-phases process. OMW represents a major environmental problem
due to its high organic content, being characterized by a strong acidic smell and an
intensive brown to dark color due to the presence of biodegradable, recalcitrant and
biostatic compounds. OMW phytotoxicity can be attributed to the phenolic compounds
(Lanciotti et al, 2005).
Owing to their instability, OMW phenols tend to polymerise during storage into
condensed high-molecular-weight polymers that are difficult to degrade (Crognale et al,
2006). Thus, uncontrolled OMW disposal can create severe risks to water and soil
quality. OMW is currently concentrated by evaporation in open pools, but this method is
not satisfactory because a black foul-smelling sludge, difficult to remove, is produced.
Instead of disposal solutions an approach of using this waste as a resource to be
valorized is of greater interest. In fact, OMW contains sugars, lipids, mineral elements
and phenolic compounds (10 % of the organic matter) that could be either directly
recovered by chemical extraction and subsequent purification, or utilized as a basis for
fermentative processes
