A pilot was designed for studying the methods of biological purification (aerobic and anaerobic) wastewater from petrochemical industries which are polluted with ammonia derivatives. Then water could be reused after purification in a production cycle. The pilot design was based on five stages: two aerobic, two anaerobic and sedimentation. When the pilot was installed the connections for loading and circulation were made. After installation of the pilot the recycling operation of sediment sludge from the bottom of the settler to the aerobic vessel was started. Since this sludge contains active microorganisms, it could enhance the efficiency of purification process in comparison with those without active sludge. Sampling from the vessels was done every two days, and tests were made for measurement of total alkalinity, ammonia, ammonium ion, suspended solids, COD, nitrogen dioxide and acidity, in which after 30 days from the first circulation, the samples were found to be without ammonia or its derivatives. (C) 2010 Elsevier B.V. All rights reserved.