BACKGROUND: Hydrogen sulphide (H 2S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS) are the main odorous compounds found in waste gases from wastewater treatment plants. It is known that two-stage biofiltration can be used for improving the removal efficiency of mixture compounds in gas effluent. So the performance of two biotrickling filters, the first one with Acidithiobacillus thiooxidans (BTA), and the second one with Thiobacillus thioparus (BTT) was researched. RESULTS: For a separately reduced sulphur compounds (RSC) feeding the EC order was: DMDS>DMS>MM. The values of EC were 9.8 g MM-S m -3h -1 (BTT; 78% RE; EBRT 58 s), 36 g DMDS-S m -3h -1 (BTT; 94.4% RE, EBRT 76 s) and 57.5 g H2S-S m -3h -1 (BTA; 92% RE, EBRT 59 s). For simultaneous removal in BTT, the increase of H 2S concentration from 23 to 293 ppmv (EBRT of 59 s) inhibited the RE of DMS (97-84% RE), DMDS (86-76% RE) and MM (83-67% RE). For two-stage biofiltration the RE not decresed for an increased of H 2S concentration from 75 to 432 ppmv. CONCLUSIONS: The RSC removal can be carried out efficiently by two-stage biotrickling filters in series, the first one inoculated with A. thiooxidans and the second one with T. thioparus. The polyurethane foam as carrier for A. thiooxidans immobilization showed very good scale-up possibilities.