[Performance of a combined bio-chemical sulfidogenic system and microbial characteristics in the presence of H2].

To study and evaluate the performance of the continuously-operated autohydrogenotrophic sulfate reduction technique enhanced with electrochemical method and to improve the sulfate removal efficiency, a combined bio-electrical sulfidogenic system was developed with a three-dimensional bio-cathode. Sulfate reduction rate was elevated markedly owing to H2 mass transfer enhancement, biomass augmentation and electrical field stimulation. Indeed, when a current of 0.50 mA was applied to the system, the average sulfate removal load was 1.94 g/(L x d) during the stable running status and the maximum removal load was 2.23 g/(L x d). Furthermore, the combined bio-electrical system was comparatively more stable in terms of response to the variation of influx load under the same hydraulic conditions. Results of SEM showed that besides the bacteria attached on the surface of the hollow fiber, large amount of biomass was aggregated on the surface and the inner gridding space of the graphite felt. PCR-DGGE analysis indicated that the diversity of the microbial community structure was slightly reduced resulting in an optimized one. The dominant genera were Desulfovibrio and Desulfomicrobium. Enhanced H2 mass transfer, biomass augmentation, optimized microbial community structure and electrical stimulation were the key important factors for the high sulfate reduction efficiency of the system.