A simple and rapid method to clarificate and recover hydroxytyrosol from olive mill wastewaters

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 Europe. The extraction of olive oil generates huge quantities of wastes that may have a great impact on land and water environments because of their high phytotoxicity. Olive mill wastewater (OMW) represents the main by-product. Approximately 30 million m3of OMW are produced annually just in the Mediterranean area, and a direct reuse of this wastewater in agriculture is strongly limited by the phytotoxicity and antimicrobial effects due in particular to its contents in phenolic compounds, and low pH (4 - 5). However polyphenols are characterized by an important antioxidant activity; therefore, once extracted from OMW, they might find valorization in the cosmetic and pharmaceutical industries, in food technologies, and conversely the physico-chemical parameters of the resulting clarified waters could be much more compatible for a reuse in agriculture. One of the most abundant and important polyphenols contained in OMW is hydroxytyrosol (3,4-dihydroxyphenylethanol) characterized by a very interesting and documented antioxidant activity. In the present study, activated charcoal was applied as adsorbent to clarificate OMW and simultaneously to recover an hydroxytyrosol enriched fraction; optimization and recycle of the adsorbent material was studied too. Moreover to evaluate the feasibility and the economic value at industrial level, the procedure was submitted to a scale-up process and an automatized pilot prototype was developed.