Degradation of aromatic compounds using moving bed biofilm reactors
The removal of toxic phenolic compounds from industrial wastewater is an important issue to be addressed. Phenolic compounds such as phenol, hydroquinone and pyrogallol are used in different industries which end into their wastewaters. They are considered as priority pollutants because of their high toxicity at low concentrations. Phenol is an important raw material in petrochemical, pharmaceutical, plastic, pesticide production industries. Hydroquinone and its derivations is another phenolic compound used in photographic applications, rubber industry, monomer inhibitors, dyes and pigments, antioxidants agricultural chemicals, and other diverse and special applications. The largest demand for hydroquinone is as a photographic developer, principally for black and white film, lithography, photochemical machining, microfilm, and X-ray film (Elves eli at., 1989a). Pyrogallol is also the other phenolic compound that used in photography, lithography and hair dyes production. It is also used as an antioxidant and stabilizer. The use of pyrogallol in the field of cosmetics and medicines is currently declining because of pronounced toxicity (Elves eli at., 1989b). The presence of these pollutants in water and soil has become significant problems. Effective methods for the removal or treatment of them need to be pursued. Many efforts have been made for the biological treatments of wastewater rich in phenolic compounds. Common commercial wastewater treatment methods utilize the combination of physico-chemical and biological treatment. Both chemical and biological processes were used for many years to treat phenolic wastewater.