The aim of this work was to produce a high concentration ferric sulphate solution from coal pyrite tailings that could be used as coagulant for water and wastewater treatment. At laboratory scale it was performed the oxidation of pyrite in an aqueous medium in a packed bed leaching column in an oxidizing environment with the presence of acidophilic bacteria (Acidithiobacillus ferrooxidans) as well as nutrients for bacterial growth. It was indicated that an aqueous solution rich in ferric sulphate can be produced which was found suitable for application in water treatment plants. (C) 2011 Elsevier Ltd. All rights reserved.