High-rate biological conversion of sulfide and nitrate in synthetic wastewater to, respectively, elemental sulfur (S-0) and nitrogen-containing gas (such as N-2) was achieved in an expanded granular sludge bed (EGSB) reactor. A novel strategy was adopted to first cultivate mature granules using anaerobic sludge as seed sludge in sulfate-laden medium. The cultivated granules were then incubated in sulfide-laden medium to acclimate autotrophic denitrifiers. The incubated granules converted sulfide, nitrate, and acetate simultaneously in the same EGSB reactor to S-0, N-containing gases and CO2 at loading rates of 3.0 kg S m(-3) d(-1), 1.45 kg N m(-3) d(-1), and 2.77 kg Ac m(-1) d(-1), respectively, and was not inhibited by sulfide concentrations up to 800 mg l(-1). Effects of the C/N ratio on granule performance were identified. The granules cultivated in the sulfide-laden medium have Pseudomonas spp. and Azoarcus sp. presenting the heterotrophs and autotrophs that co-work in the high-rate EGSB-SDD (simultaneous desulfurization and denitrification) reactor.