This article evaluates the use of low-basicity aluminium oxychlorides as a coagulant for the treatment of wastewater from petroleum refineries. Aluminium oxychlorides are obtained as wastes in the production of ethylbenzene and isopropylbenzene after Friedel-Crafts-Gustavson processes, where anhydrous A1C1/sub 3/ is used as the catalyst, and also other organic and inorganic chlorine-containing products. It is determined that increases in the concentration of the test coagulants give uniform increases in the efficiency of water treatment. The optimal concentration of aluminium oxychloride for the treatment of wastewater was found to be 40-60 mg/liter.