This article is devoted to the results obtained during the physicochemical treatment of colored industrial tannery discharges of the city of Moahammedia by coagulation flocculation. The volume of settled sludge is measured and the supernatant is recovered for the determination of the color of the treated water. The latter is measured on samples previously filtered through fiber membranes. The effectiveness of color removal was investigated by measuring the absorbance at 436, 525 and 620 nm. The aim of this work is to minimize the time, the cost and the means used to carry out the tests. The method of screening experimental designs was applied.