Hydroxytyrosol recovery from olive mill wastewater: process optimization and development of a pilot plant

The olive oil industry is a sector of high relevance in the economy of the European Union; indeed, three quarters of the world production is concentrated in the South Europe. Unfortunately, the commonly used milling techniques generate huge amounts of highly polluting olive mill wastewater (OMWW) as a side-product. If released in the environment, not treated OMWW have a detrimental impact on land and water because of the large amount of phytotoxic phenolic compounds contained. At the same time, due to their powerful antiradical properties, polyphenols represent the center of a very valuable market niche, where they find application in cosmetic and nutraceutic fields. Consequently, the mandatory (for evident environmental reasons) depollution of OMWW associated with an efficient and selective recovery of the phenolic fraction could be economically very advantageous. In the present study, a new methodology employing activated charcoal as the adsorbent phase was developed in order to depollute OMWW and simultaneously recover a fraction enriched in hydroxytyrosol, the most abundant and valuable phenolic compound present in this matrix. Moreover, to evaluate the technical and economic feasibility of the process at a pre-industrial level, this strategy was submitted to a scale-up process and a pilot plant prototype was developed.