Olive mill effluent (OME) wastewater embodies a challenge for environmental scientists and engineers. It is characterized by high values of COD, BOD, and phenolic content. A series of treatment steps composed of settling, centrifugation, and filtration was consecutively used to condition OME wastewater. The filtrate was then subjected to a post-treatment process, namely adsorption on activated clay. The dynamic response of phenols concentration, pH, and COD. using different concentrations of activated clay, showed a peak at which maximum adsorption capacity was achieved. The maximum adsorption capacity for the tested concentrations of activated clay was reached in less than 4 h. It is thought that adsorption of phenols and organics is reversible and mainly due to hydrophobic interactions. The maximum removal of phenols was about 81%, while it reached about 71% for organic matter.