A cyanobacterial strain, Spirulina platensis besides two strains of green algae, Dunaliella saline and Chlorella vulgaris and the fungus Pleurotus columbinus were propagated on 10 % concentration of olive mill wastewater at a steady state. For Pleurotus columbinus , it was also propagated on the previous concentration at an agitated state. The most efficient strain for decreasing chemical oxygen demand and phenolic compounds was Pleurotus columbinus propagated at 150 rpm in shaker which diminishes them by laccase enzyme. The second efficient strain in decreasing, chemical oxygen demand and phenolic compounds was Chlorella vulgaris followed by Spirulina platensis while Dunaliella saline which was the least efficient one. Pleurotus columbinus was propagated either in a steady state or an agitated at 150 rpm in shaker donate high amount release of total carbohydrates . The main observation is the small value of growth which may be due to absence of nutrients in the medium. The use of such effective strains will help in minimizing the hazard impact of olive mill wastewater. Accordingly, the waste water produced should be primary treated before being dumped in water bodies.