The automobile industryâ€™s wastewater not only contains high levels of suspended and total solids such as oil, grease, dyestuff, chromium, phosphate in washing products, and coloring, at various stages of chassis manufacturing but also, a significant amount of dissolved organics,resulting in high BOD or COD loads. Suspended solids can be removed from the wastewater by chemical precipitation. However, the dissolved BOD/COD compound can only be removed by biological or chemical oxidation. Effluent wastewater from the chemical sedimentation stage and the sanitary wastewaters (ratio 1:1 of sanitary to industrial feed rate) at the Bahman automobile factory was characterized and subjected to a biological treatment in a laboratory scale activated sludge unit. Experiments were conducted at different hydraulic and solid retention times. The best results were obtained with o h=20 h of hydraulic and c=20 days of solids retention time (sludge age) resulting in an effluent COD concentration of 60 mg/Lit from an industrial feed and sanitary wastewaters of 920 mg/Lit COD content. The suspended solid content of the activated sludge effluent was approximately 57 mg/Lit. Also according to the results of experiments, kinetics constants k, ks, kd, and y, obtained (0.75, 110, 0.28 and 1.1) respectively and subsequently design equa-tions were developed.