Isolation and characterization of a microorganism involved in sulfide-oxidizing autotrophic denitrification in a vertical fixed-bed reactor

This study evaluates the microbial community involved in autotrophic denitrification by sulfide oxidation, applied in the post-treatment of anaerobic effluent. The enrichment of the bacterial community and autotrophic denitrifying community was performed with biomass samples collected from a vertical fixed bed reactor operated under the following condition: autotrophic nitrate reduction with excess sulfide. The nitrate reduction condition with N/S ratio of 0.8 showed the highest concentration of autotrophic denitrifying microorganisms. The isolated bacterium was identified as Pseudomonas stutzeri - like organism. The maximum specific growth rate of the population (μmax) was 0.037 h−1, with doubling time of 18.7 h. The cell yield (Y) was 0.15 gSSV gN−1 and denitrification rate was of approximately 0.24 gN gSSV h−1. The data obtained point to the feasibility of applying the isolated species in the autotrophic denitrification process using sulfide as electron donor.