Coculture of the Heterotrophic Nitrification–Aerobic Denitrification Strains Acinetobacter sp. A12 and Paracoccus sp. T8 Enables Effective Biological Nitrogen Removal from Landfill Leachate

Due to their significantly improved metabolic capacity brought by interspecies synergy, microbial consortia can remove nitrogen more rapidly than single strains. In the present study, a coculture system consisting of newly characterized heterotrophic nitrification–aerobic denitrification (HN–AD) strains Acinetobacter sp. A12 and Paracoccus sp. T8 was established and applied for nitrogen removal from a landfill leachate. The coculture system efficiently removed ammonium, nitrate, and nitrite at a low C/N ratio of 5. Moreover, the activity of enzymes related to nitrogen removal (AMO, HAO, and NAP) was significantly increased in the coculture system, in conjunction with higher microbial activity and accumulation of extracellular polymeric substances. After 18 h of treatment with the coculture, 97.10% of ammonia (450 mg/L), 90.66% of total nitrogen (750 mg/L), and 88.34% of total organic carbon (800 mg/L) were removed from the landfill leachate. The functional strains accounted for 84% of the biodiversity, resulting in a significant enrichment of nitrogen metabolism. Our study provides an efficient coculture system for nitrogen removal from landfill leachates.