Heterotrophic nitrification and related functional gene expression characteristics of Alcaligenes faecalis SDU20 with the potential use in swine wastewater treatment

A new heterotrophic nitrifying bacterium was isolated from the compost of swine manure and rice husk and identified as Alcaligenes faecalis SDU20. Strain SDU20 had heterotrophic nitrification potential and could remove 99.7% of the initial NH4+-N. Nitrogen balance analysis revealed that 15.9 and 12.3% of the NH4+-N were converted into biological nitrogen and nitrate nitrogen, respectively. The remaining 71.44% could be converted into N-2 or N2O. Single-factor experiments showed that the optimal conditions for ammonium removal were the carbon source of sodium succinate, C/N ratio 10, initial pH 8.0, and temperature 30 degrees C. Nitrification genes were determined to be upregulated when sodium succinate was used as the carbon source analyzed by quantitative real-time polymerase chain reaction (qRT-PCR). Strain SDU20 could tolerate 4% salinity and show resistance to some heavy metal ions. Strain SDU20 removed 72.6% high concentrated NH4+-N of 2000 mg/L within 216 h. In a batch experiment, the highest NH4+-N removal efficiency of 98.7% and COD removal efficiency of 93.7% were obtained in the treatment of unsterilized swine wastewater. Strain SDU20 is promising in high-ammonium wastewater treatment.