Four models of a fixed-bed hydrogen sulfide (H2S) biofilter with immobilized Thiobacillus thioparus DW44 were studied and tested: pseudo-homogeneous model, shell balanced model, deep biofilm model and dispersion model. Modification of the reaction rate kinetics from 0th or 1st order kinetics to purely Monod kinetics were done. For the first time, the pseudo-homogeneous and dispersion models were applied to biological systems; these models were commonly used to model chemical reaction systems only. The deep biofilm model could he suitable for biofilters but the validity of its use should be investigated further by establishing the effective biofilm surface area. The test results showed that the model was solvable when effective biofilm surface area was between 4 and 7 %. This area was assumed to be 5% of the actual surface area of the packings. Of the four models tested, the pseudo-homogeneous model was found to be the best model for the system based on the analysis of residuals and PRESS (Predicted Sum of Squared) values.