Sulfidogenic activity related to microbial diversity in a biological system employed for sulfate-rich wastewater treatment

Industrial activity disrupts the natural sulfur cycle by the generation of sulfate-rich wastewater. Nonetheless, these effluents can be treated in anaerobic reactors. This study seeks to relate sulfidogenic activity with microbial diversity during the start-up of an anaerobic sulfate-reducing reactor. An anaerobic sludge was characterized employing 16s rRNA assays. The sludge was adapted to sulfate-reducing activity in an up-flow fixed bed reactor with 2 and 1.5 COD/SO^{2 −} ratios. Simultaneous organic matter removal 4 and sulfate conversion to sulfide were analyzed. Finally, a kinetic study was conducted to determine sulfate conversion and sulfide production reaction rates. A first-order model was applied to determine the reaction rates for sulfate and sulfide. Microorganisms employed for bioremediation techniques, like Pseudomonas azotoformans, Desulfovibrio, and Methanolinea sp., were identified in the anaerobic sludge. The decrease in COD/SO^{2 −}ratio did not negatively impact the overall efficiencies in the reactor in terms of COD and sulfate removal and sulfide production, reaching values of 76.54%, 81.53%, and 268.84 mgS^{2 −}/L, respectively. Sulfidogenic activity was higher under higher sulfate concentrations (%H2S-COD = 55.2 for a 1.5 COD/SO² ₄ ⁻ratio). The results indicate a gradual increase in sulfidogenic activity; therefore, sulfate-reducing conditions were attained in the system.