The relatively high fluidization velocities and low Sbof the sulfur flakesmeant they were far from ideal for this purpose. With an expansion velocity in the same range as sand, the sulfur grains remainan option, but their use will require a taller biofilter to achievea reasonable HRT. The sulfur powder showed promise due to itsvery high Sb, very low fluidization velocities, and reasonable surface area-based cost efficiency.