Sustainable Bio-Ammonia Recovery from Livestock Wastewater via Biochar-Immobilized Microbial Ammonification

Livestock wastewater is an important source of nitrogen pollution, but it also represents a potential feedstock for nitrogen recovery. In this study, longan wood-derived biochar was used as an immobilization carrier in a bio-ammonification system developed with aerobic and facultative ammonifying bacteria isolated from swine wastewater. The system was designed to enhance microbial retention and promote the conversion of organic nitrogen into ammonium concentration (NH4+-N) under oxygenated conditions. Among the tested strains, Lysinibacillus sp. (strain 4-1) showed the highest ammonification activity, reaching an NH4+-N concentration of 340 mg/L in NB medium within 5 days. In sterilized swine wastewater, the biochar-immobilized strain 4-1 achieved 47.17% organic nitrogen removal. The results suggest that coupling microbial ammonification with biochar immobilization may provide a low-carbon approach for nitrogen recovery from livestock wastewater and facilitate decentralized bio-ammonia production.