Enhanced sulfide-driven autotrophic denitrification/ammonium oxidation process via metabolic cooperation of anaerobic bacterial consortia in a packed-bed bioreactor

In this study, a laboratory-scale packed-bed bioreactor (PBBR) was developed to integrate sulfide-driven autotrophic denitrification with anaerobic ammonium oxidation. The system was operated for 322 days under anaerobic conditions and evaluated across three phases: sulfide-driven denitrification, ammonium removal, and the combined enhanced Sulfide-Driven Autotrophic Denitrification/Ammonium Oxidation (SADAO(process. Despite short hydraulic retention times (HRTs), the reactor consistently achieved high nitrogen removal. At an HRT of 3 h, nitrate and ammonium removal approached 97% and 92%, respectively, and even at 1 h HRT, overall nitrogen removal remained above 82%, with a volumetric rate of as high as 55.3 g-N/m³·h. Sulfide was fully consumed, producing elemental sulfur and sulfate as end products. Microbial analysis revealed a stable community dominated by Thiobacillus spp., Georgfuchsia toluolica , and anammox-related Planctomycetes, which enabled the efficient coupling of sulfur oxidation, autotrophic denitrification, and anammox without nitrite accumulation. These interactions supported high-rate, low-HRT nitrogen removal, demonstrating a compact and sustainable strategy for treating nitrate- and ammonium-rich wastewaters.