Olive mill wastes exacerbate environmental problems in Mediterranean countries. These wastes are highly phytotoxic due to polyphenolic compounds, lipids and organic acids, they also contain high percentages of organic matter. For that importance the present study was designed in an attempt to study the effect of different chemical treatments (as pretreatments), aiming to minimize the level of organic load of Olive Mill Waste Water (OMW). The results of different tested parameters [color, pH, Total Dissolved Solids (T.D.S.) ,Chemical Oxygen Demand (C.O.D.) , Biological Oxygen Demand (B.O.D.), Total Polyphenols & Trace elements of Cadmium (Cd⁺²), Copper (Cu⁺²), Zinc (Zn⁺²) and Manganese (Mn⁺²) which were recorded before and after each treatment & discussed.