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h i g h l i g h t sORP measurement can be used for nitrate supply control. Biogas desulphurization was achieved without a reduction in methane concentration. A high EC CRIT of 120 g S m À3 h À1 can be achieved using polypropylene Pall rings.a r t i c l e i n f o b s t r a c tHydrogen sulphide (H 2 S) is one of the most problematic contaminants in biogas. In this study, a biotrickling filter with a working volume of 2.4 L and packed with polypropylene Pall rings was tested for its ability to remove H 2 S from biogas under anoxic conditions. The influence of the H 2 S inlet concentration, nitrate feeding regime (manual and controlled) and liquid flow rate on the elimination capacity of the biotrickling filter was studied. The results indicate that 99% of the H 2 S was removed for H 2 S inlet loads lower than 120 g S m À3 h À1 when using controlled nitrate feeding by ORP.

a b s t r a c tThe present work aims to use a two-stage biotrickling filters for simultaneous treatment of hydrogen sulphide (H 2 S), methyl mercaptan (MM), dimethyl sulphide (DMS) and dimethyl disulphide (DMDS). The first biofilter was inoculated with Acidithiobacillus thiooxidans (BAT) and the second one with Thiobacillus thioparus (BTT). For separate feeds of reduced sulphur compounds (RSC), the elimination capacity (EC) order was DMDS > DMS > MM. The EC values were 9.8 g MM-S /m 3 /h (BTT; 78% removal efficiency (RE); empty bed residence time (EBRT) 58 s), 36 g DMDS-S /m 3 /h (BTT; 94.4% RE; EBRT 76 s) and 57.5 g H2S-S /m 3 /h (BAT; 92% RE; EBRT 59 s). For the simultaneous removal of RSC in BTT, an increase in the H 2 S 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). In the two-stage biofiltration, the RE did not decrease on increasing the H 2 S concentration from 75 to 432 ppmv.