Polysulfide Concentration and Chain Length in the Biological Desulfurization Process: Effect of Biomass Concentration and the Sulfide Loading Rate

Abstract

Removal of hydrogen sulfide (H 2 S) can be achieved using the sustainable biological desulfurization process, where H 2 S is converted to elemental sulfur using sulfide-oxidizing bacteria (SOB). A dual-bioreactor process was recently developed where an anaerobic (sulfidic) bioreactor was used between the absorber column and micro-oxic bioreactor. In the absorber column and sulfidic bioreactor, polysulfides (S x 2– ) are formed due to the chemical equilibrium between H 2 S and sulfur (S 8 ). S x 2– is thought to be the intermediate for SOB to produce sulfur via H 2 S oxidation. In this study, we quantify S x 2– , determine their chain-length distribution under high H 2 S loading rates, and elucidate the relationship between biomass and the observed biological removal of sulfides under anaerobic conditions. A linear relationship was observed between S x 2– concentration and H 2 S loading rates at a constant biomass concentration. Increasing biomass concentrations resulted in a lower measured S x 2– concentration at similar H 2 S loading rates in the sulfidic bioreactor. S x 2– of chain length 6 (S 6 2– ) showed a substantial decrease at higher biomass concentrations. Identifying S x 2– concentrations and their chain lengths as a function of biomass concentration and the sulfide loading rate is key in understanding and controlling sulfide uptake by the SOB. This knowledge will contribute to a better understanding of how to reach and maintain a high selectivity for S 8 formation in the dual-reactor biological desulfurization process.