Anammox biofilter with denitrification sludge as seed in treating low nitrogen strength wastewater

Deficient seed sludge, low substrate concentrations are recognized as the major barriers for the application of anaerobic ammonia oxidation (Anammox) to treat mainstream wastewater. In this work, anammox biofilter (A-BF) was started up by inoculating denitrification sludge at low nitrogen strength at 25 °C. The total nitrogen removal efficiency (TNRE) and nitrogen removal rate (NRR) reached 74.8 ± 3.4% and 0.81 kg-N m⁻³ d⁻¹ under nitrogen loading rate (NLR) of 1.20 kg-N m⁻³ d⁻¹ with 7.00 mg-NH₄⁺-N L⁻¹ and 10.00 mg-NO₂^--N L⁻¹ as influent. 1.00–2.00 mg-DO L⁻¹ negatively impacted effluent, but the total nitrogen of effluent (TN_eff) was 10.65 ± 2.76 mg L⁻¹, in limit of the standard of Class 1A for municipal WWTP discharge (GB18918-2002). The abundance of Planctomycetes increased from 0.6% to 1.4–2.6%, in which, Candidatus_Brocadia was the dominant genera. The results establish the application feasibility of A-BFs as advanced nitrogen removal technique in treating mainstream wastewater.