A microbial consortium attached onto a polyethylene support was used to evaluate the simultaneous oxidation of sulfide and phenol by denitrification. The phenol, sulfide and nitrate loading rates applied to an inverse fluidized bed reactor were up to 168 mg phenol-C/(l d), 37 mg S(2-) /(l d) and 168 mg NO(3)(-)-N/(l d), respectively. Under steady state operation the consumption efficiencies of phenol, sulfide and nitrate were 100%. The N(2) yield (g N(2)/g NO(3)(-)-N) was 0.89. The phenol was mineralized resulting in a yield of 0.82 g bicarbonate-C/g phenol-C and sulfide was completely oxidized to sulfate with a yield of 0.99 g SO(4)(2-)-S/g S(2-). 16S rRNA gene-based microbial community analysis of the denitrifying biofilm showed the presence of Thauera aromatica, Thiobacillus denitrificans, Thiobacillus sajanensis and Thiobacillus sp. This is the first work reporting the simultaneous oxidation of sulfide and phenol in a denitrifying biofilm reactor. (C) 2008 Elsevier Ltd. All rights reserved.