In this paper a pre-design study is presented of an industrial bio-reactor projected for implementation in a wastewater treatment plant (Jerez de la Frontera, Spain) for recovery of ferric sulfate used for the removal of H2S in a biogas stream. The recovery process includes oxidation of ferrous sulfate formed in the process of absorption of H2S by iron-oxidizing bacteria such that the ferric solution can be re-used in the absorption process. The bacteria used were selected from Acidithiobacillus ferrooxidans cultures, immobilized on polyurethane supports. Collection of preliminary data was done using a 450 mL bench scale bioreactor of and a 500 L pilot plant. Based on the data obtained for oxidation rates a bioreactor volume of 6, 6 m3 and 223.000 support particles was estimated necessary for the treatment of a maximum gas flow of 300 Nm3/h, with an H2S load of 7000 mg/Nm3.