The efficiency of alternative pretreatment methods for an olive mill effluent (OME) in producing a final effluent conforming to Turkish Water Pollution Standards for discharge into the public sewage was studied. For this purpose, various treatment alternatives such as acid cracking, chemical coagulation, adsorption and Advanced Oxidation Processes (AOPs) were studied. A significant amount of Chemical Oxygen Demand (COD), total phenol and oil and grease removal were obtained by acid cracking followed by chemical coagulation either using alum or iron chloride salts. Among the alternative chemicals, both Al2SO4 and FeCl3 resulted in the same COD and total phenol removal efficiency in this study (94-95% COD removal and 90-91% total phenol removals). Both H2O2/UV and O-3/UV combinations studied in this paper were found to give practically same COD and total phenol removal efficiencies (over a 99% removal for both COD and total phenol). (c) 2004 Elsevier Ltd. All rights reserved.