Characterization of Achromobacter denitrificans QHR-5 for heterotrophic nitrification-aerobic denitrification with iron oxidation function isolated from BSIS：Nitrogen removal performance and enhanced SND capability of BSIS

Strain QHR-5, a heterotrophic nitrification-aerobic denitrification bacterium (HNADB) with iron oxidation function, was isolated from biological sponge iron system (BSIS) and identified as Achromobacter denitrificans. The carbon source suitable for growth and nitrogen removal by the strain from the denitrification medium 1(DM1) was investigated. Maximum growth and total inorganic nitrogen (TIN) removal were observed when Seignette salt was the carbon source. Single-factor experiments showed that the highest NO3--N removal performance was achieved when C/N ratio was 17, the shaking speed was 120 rpm, the temperature was 30 ℃, and the pH was 7.0. The heterotrophic nitrification and aerobic denitrification activity with different nitrogen sources (NH4+-N, NO3--N, and NO2--N) showed removal efficiencies of 90.84%, 98.37%, and 60.37%, respectively. With NH4+-N, NO3--N or NH4+-N, NO2--N as mixed nitrogen sources, Strain QHR-5 still showed good denitrification activity. Runs R1 (BSIS) and R2 (BSIS + Strain QHR-5) showed that with higher concentration NO3--N (981.12 mg/L), the TN removal efficiency of R2 increased by 18.32%. Higher TN removal efficiency could be attributed to the aerobic denitrification capability of Strain QHR-5 and the accelerated dissolution of Fe2+ in BSIS due to the iron oxidation function of Strain QHR-5.