Vegetation waters (VW) from olive mill represent one of the greatest environmental problem in the Mediterranean area due to the high COD values and the presence of phyto-toxic and antibacterial polyphenolic components. VW are generally disposed, according to the national laws, by spreading in the agricultural fields with consequences in the field fertility and increasing problems and costs for the stocking and transport. A novel treatment approach based on tangential flow membrane filtrations for the selective separation and total recovery of hydroxytyrosol, water and organic substances is patented by ENEA and Verdiana Company with international publication number WO2005123603. In particular the present experimental study investigates microfiltration (MF) and ultrafiltration (UF) of VW without preliminary centrifugation step, operating with pilot plants with fixed process parameters. Productivity, fouling and cleaning of membranes with different cut-off (statistical pore size distribution), material and configuration are compared. MF/UF permeates are concentrated in reverse osmosis (RO). All the separated effluents are analytically characterized with the principle aim of verify selectivity, purification and yield of polyphenols and in particular hydroxytyrosol. Results show MF as the critical section of the process due to severe fouling and difficulties in the cleaning procedure. UF experiments with ceramic 1 Kd and polymeric 6 Kd present no differences on the selectivity of hydroxytyrosol. RO concentrates all the components with rejection values ranging between 96% and 99%. MF and UF permeates or RO concentrate can be used as functional integrators or in pharmacologic compositions. RO permeate can be used as base for the beverage industry. MF and UF concentrates can be used as fertilizers or in the production of biogas. (c) 2006 Elsevier B.V. All rights reserved.