High-rate denitrifying sulfide removal process in expanded granular sludge bed reactor.

An expanded granular sludge bed (EGSB) reactor was adopted to incubate bio-granules that could simultaneously convert 4.8 kg-Sm(-3) d(-1) of sulfide in 97% efficiency; 2.6 kg-Nm(-3) d(-1) of nitrate in 92% efficiency; and 2.7 kg-Cm(-3) d(-1) acetate in 95% efficiency. Mass balance calculation of sulfur, nitrogen, and carbon over the EGSB reactor confirmed the performance results. This noted reactor performance is much higher than those reported in literature. Stoichiometric relation suggests that the nitrate was reduced to nitrite via autotrophic denitrification pathway, then the formed nitrite was converted via heterotrophic denitrification pathway to N(2).