Five different materials including DEC, PAC, bentonite clay, activated clay and Macrosorb were examined for their color and COD removal efficiencies on the activated sludge system. DEC is a specific organic flocculent which is stable in water, it reacts with dyes, forming an insoluble complex easily settling together with the activated sludge. Therefore, DEC can be directly added into the biological reactor. PAC used in this study, was made of coconut husks, and has been commercially named as P 325-MMC 3. The particle size of the PAC was previously determined using ASTM D 2862 method by the seller. Maximum 90% of PAC has passed through 200 No. screen (75 μ) and maximum 80% has passed through 325 No. screen (45 μ). Bentonite clay was in powdered form (61.4% SiO2). Activated clay was a modification of powdered activated bentonite processed with H2SO4. Macrosorb is a registered trademark, and is the trade name for a range of particulate adsorbents that can be classified as “synthetic inorganic clays”.