A trickle bed reactor was used to improve ferrous sulphate oxidation rate with Thiobacillus ferrooxidans immobilised in BSPs (Biomass Support Particles). A maximum iron(II) oxidation rate of 4.4 gL−1h−1 was observed at a dilution rate D = 0.9 h−1. The ability of the reactor to operate under non-aseptic conditions due to the chemoautotrophy and acidophilia of the bacterium makes industrial application promising.