Olive mill wastewaters (OMW) constitute an important environmental problem due, among other things, to their high phenolic content. The phytotoxicity of polyphenols makes them resistant to biological treatment. A three-step process comprising adsorption-concentration, catalytic hydrogenation and regeneration on a fixed bed of adsorbent-catalyst was investigated to remove such compounds. Tyrosol (2-(4-hydroxyphenyl)-ethanol) was taken as representative of the polyphenols present in OMW. The catalytic hydrogenation of tyrosol by 30 g kg(-1) ruthenium/activated carbon catalyst was carried out in order to establish the reaction mechanism and kinetics necessary for the design of a pilot-scale reactor. Total conversion of tyrosol into non-aromatic compounds was achieved under mild conditions of temperature and pressure. The overall rate of tyrosol removal at 4 MPa and 353 K was 11.26 g h(-l) g(catalyst)(-1). (C) 2003 Society of Chemical Industry.