Self-adaptation of tolerant microalgae-bacterial consortia in landfill leachate: Simultaneous achievement of efficient nitrogen removal and value-added utilization

• NH 4 + -N in LL decreased from 689.3 mg L −1 to 0.6 mg L −1 by a self-adapted consortium. • The consortium self-adapts to harsh conditions, enhancing stress recovery via EPS, enzymes , and photosynthesis . • Converting recovered pollutants into biofuels provides energy for extreme condition adaptation. Effectively and inexpensively removing nitrogen from raw landfill leachate is challenging due to high nitrogen levels that hinder common microorganisms and microalgae survival. In this study, a novel self-adapted microalgae-bacterial consortium with high tolerance to landfill leachate was developed. The results indicate that the microalgae-bacterial consortium achieves 96.3 % removal of the inhibitory factor free ammonia and a total nitrogen removal rate of 106.0 mg N/L d −1 , while also facilitating carbon sequestration. Stoichiometric balance analysis and metagenomic metabolic reconstruction revealed that the primary nitrogen removal pathways in the microalgae-bacterial consortium are assimilation (41.9 %) and nitrification–denitrification (21.4 %). Notably, extracellular polymeric substances (EPS) resistant to environmental pressure adsorbed 12.8 % nitrogen pollutants while increasing EPS secretion by 38.0 %, which is conducive to the harvest of consortium. Furthermore, the self-adaptive mechanisms of the microalgae-bacterial consortium were revealed for tolerating landfill leachate. The microalgae-bacterial consortium self-adapted to landfill leachate stress by enhancing electron flux and antioxidant enzyme activity, restoring photosystem II function and mitigating oxidative damage. Additionally, the conversion of recovered nitrogen pollutants into starch and triacylglycerols by the consortium provides a material energy foundation for self-adapting to extreme conditions. This study may offer a promising alternative for the environmentally resource treatment of complex wastewater. However, issues including long-term stability and scalability need further investigation.