Synergy between autotrophic denitrification and Anammox driven by FeS in a fluidized bed bioreactor for advanced nitrogen removal

On the basis of the metabolic synergy between autotrophic denitrification (AuDen) and anaerobic ammonium oxidation (Anammox), the feasibility of a novel ferrous sulfide (FeS)-driven AuDen and Anammox coupled system (FS-DADAS) was investigated. The nitrogen removal performance of FS-DADAS was investigated in a labscale fluidized bed bioreactor fed with synthetic wastewater containing NH4+-N and NO3--N. The results of long-term operation (120 days) demonstrated the promising performance of the system with 100% NO3--N removal and NH4+-N concentrations lower than 8.11 mg L-1 in the effluent at a nitrogen loading rate of 0.20 g-N.(L.d)(-1). Sufficient NOi-N was provided by the AuDen for Anammox where a high removal rate of total nitrogen (TN) was achieved. The contribution of Anammox to TN removal was at >80%. The reactor could maintain a stable pH with less SO42- production owing to the fact that Fe(II) and S acted as electron donors. FeS gradually transformed into a sheet-like secondary mineral, FeOOH. AuDen (Thiobacillus) and Anammox bacteria (Candidatus Kuenenia) were successfully retained in the bioreactor, with relative abundance values of 18.82%-23.64% and 3.52%-8.67%, respectively. FS-DADAS is a promising technology for the complete removal of TN from wastewaters with low C/N ratios at low energy consumption.

Automated summary

The novel ferrous sulfide (FeS)-driven autotrophic denitrification (AuDen) and anaerobic ammonium oxidation (Anammox) coupled system (FS-DADAS) shows promising nitrogen removal performance, achieving over 80% total nitrogen (TN) removal in laboratory testing. The system demonstrated stable denitrification effects over long-term operation, with 100% NO3--N removal and NH4+-N concentrations lower than 8.11 mg L-1 in the effluent.