Spatial conversion characteristics of sulfur and nitrogen via desulfurization denitrification under rapidly changing hydraulic conditions

The sulfur-nitrogen-contained wastewater treatment system needs fast start-up, efficient collaboration, and stability, to break through the application bottleneck of biological desulfurization-denitrification. An integrated sleeve bioreactor was adopted to analyze the coupling performances of sulfate-reduction and sulfide-based denitrification process. The spatial-temporal distribution of functional bacteria and genes was studied under rapidly changing hydraulic conditions. The transformation law of carbon-sulfur-nitrogen was clarified. The removal efficiencies of sulfate, total organic carbon, and nitrite reached 90 %, 98 %, and 99 %, respectively. Thermovirga, Desulfomicrobium and Desulfobulbus were the main functional bacteria in the external sleeve, while Sulfurovum and sulfurimonas were in the internal sleeve. The dominant functional genes sat, sqr, norBC, and nosZ had relative abundances of 1.02 ‰, 3.09 ‰, 0.63 ‰ and 0.51 ‰, respectively. The sleeve alleviated the toxic effects of sulfide and nitrite. It realized the spatial separation and enrichment of different dominant bacteria, improving the load shock resistance of bioreactor. The rapidly changing hydraulic retention time promoted the spatial transference of sulfate-reducing bacteria and brought the appearance of sulfide-based denitrification bacteria in external sleeve. It enhanced the stability of microbial community structure. This optimized microbial community structure provided a rich diversity of functional genes to ensure a collaborating degradation of sulfur and nitrogen. The main transformation pathways included the assimilated sulfate reduction, sulfur partial oxidation and denitrification. Rapidly decreasing hydraulic retention time facilitated the accumulation of elemental sulfur. The unique structure and operation exhibited strong resistance to loads and hydraulic shocks. This work provides a reference value for efficiently removing multiple pollutants in sulfur-nitrogen-polluted wastewater.