Artificial microbial consortia engineering: Intensify nitrogen removal from mature landfill leachate by simultaneous nitrification and denitrification

The biological treatment system for the mature landfill leachate typically requires high sludge concentration to maintain nitrogen removal performance under high NH4+-N concentrations. Fluctuation in the native microbial community is frequently observed by environmental factor influences and thereby causes the bioprocessing efficiency to be unstable. In this study, temporal and spatial dynamics in the microbial community structure during the mature landfill leachate biochemical processing were analyzed, and the results showed that Thauera was always the dominant bacterium in the whole process. Subsequently, a co-culture of simultaneous nitrification and denitrification (Co-CSND) consortia was constructed based on a bottom-up construction strategy, including Bacillus haynesii, Bacillus subtilis and Sphingobacterium sp. as the dominant nitrogen removal strains, demonstrating excellent simultaneous nitrification and denitrification capability under high NH4+-N concentration (500 mg & sdot;L-1). After 48 h of co-culture, the removal ratios of NH4+-N and NO3--N reached 98.93 % and 84.55 %, respectively. Large-scale fermentation, immobilization and compounding of the developed Co-CSND consortia were performed and applied to the biological nitrogen removal processing with a daily capacity of 4700 tons of landfill leachate. After 181 days of daily dosing (0.03 %), the treatment capacity of NH4+-N, NO3--N and COD in the whole system was significantly improved (p < 0.01). The proportion of the Co-CSND consortia was increased combined with the functional strains of nitrogen removal capability. The abundance of nitrogen catabolism and critical pathway-related genes in the entire system were effectively enriched. This study provides a new strategy for reinforcement in treating mature landfill leachate by artificial microbial consortia engineering.