Two biofilm reactors, using pumice stone and Poraver as biofilm supports, were run, based on the optimization of sulphide production using a factorial design. The maximum H2S concentrations reached were 10 and 15 mm, respectively, both being appropriate for metal precipitation in effluents. The set-up of the pumice stone biofilm reactor is suitable for application in the mining area in the Bolivian Andean region, where this material is widely available. The use of specific primers for sulphate-reducing bacteria groups permits the identification of the sulphide-producing bacteria present in biofilms.