PHENOL DEGRADATION USING MOVING BED BIOFILM REACTORS Bita Ayati*, Hossein Ganjidoust**, Maryam Mir Fattah*** *Associate Prof., ** Full Prof., *** M.Sc. Student Tarbiat Modares Univ., Civil Eng. Dept., Env. Eng. Div., Tehran, Iran Abstract: Phenol may enter the environment from oil refinery discharges, coal conversion plants, municipal waste treatment plant discharges, or spills. It released as a vapor from natural or human made sources contaminated by or containing phenol. It is also found naturally in animal wastes and decomposing organic material. It is used as a general disinfectant, as a reagent in chemical analysis and for the manufacture of artificial resins, medical and industrial organic compounds and dyes. It is also used in the manufacture of fertilizers, explosives, paints and paint removers, drugs, textiles and coke. It is produced in large volume, mostly as an intermediate in the production of other chemicals. MBBR is performed in biofilm system with relatively large carriers. Contrary to most biofilm reactors, MBBR utilizes the whole tank volume for biomass growth. It also has a very low head-loss. It does not need any sludge recycle as compared to activated sludge reactor. This is achieved by having the biomass grow on carriers that move freely in the water volume of the reactor. A cylindrical MBBR was used in this study. The reactor had an internal diameter of 10 cm and effective depth of wastewater in the reactor was about 60 cm. Reactor was filled with polyethylene floating biofilm carriers which is similar to corrugated cylinder. Reactor was working in upflow stream conditions. The circulation of the biofilm carriers inside the reactor was caused by aeration. In this paper, treatment of phenolic wastewater using MBBR is presented. However researches show that phenol acts as an inhibitor in biological systems, but MBBR has had suitable removal. In this study COD from 500 to 3000 mg/L were investigated. COD of 700 mg/L had the best efficiency of about 60 percent during 24 hours; however it had acceptable COD removal till COD of 2500 mg/L.