Enhancing low-temperature nitrification biofilter with Acinetobacter harbinensis HITLi7^T for efficient ammonia...

Low temperature has always been a significant limitation for the biological removal of ammonia nitrogen (NH₃-N) from water. Acinetobacter harbinensis HITLi7^T (HITLi7^T) was used to enhance the low-temperature nitrification biofilter (LTNB) with a treatment capacity of 20,000 m³/d. At 2 °C, with an empty bed contact time of 3 h, the LTNB achieved NH₃-N removal levels of 1.2 ∼ 1.5 mg/L. The nitrifying bacteria (Nitrosomonas, Nitrosospira, Nitrospira and Candidatus_Nitrotoga) were significantly enriched. PICRUSt2 and FAPROTAX revealed the nitrification pathway of NH₃-N conversion to hydroxylamine, then to nitrite, and finally to nitrate. The high co-occurrence of HITLi7^T with the nitrifying bacteria suggested that HITLi7^T might also promote the enrichment of nitrifying bacteria. Life cycle assessment showed that LTNB was an economical and environmentally friendly method for NH₃-N removal. These results indicated that HITLi7^T enhanced the nitrification performance of biofilters, improved the cold tolerance of nitrifying bacteria, and had potential for practical applications.