Fungal-bacterial-algal systems for simultaneous removal of nitrates and heavy metals: metabolic and mechanistic studies

Deteriorating environmental quality, significantly driven by the release of untreated industrial effluent, jeopardizes water ecosystems and threatens human health. Conventional treatment methods often struggle to efficiently remove such complex effluents. This paper proposed a novel fungal-bacterial-algal (FBA) symbiotic system capable of simultaneously and efficiently removing nitrate (NO₃^--N), Zn²⁺, and Cu²⁺ from industrial wastewater. By optimizing the carbon-to-nitrogen ratio, pH, and hydraulic retention time, the system demonstrated outstanding removal performance even under heavy metal stress conditions. Product metabolism analysis indicates synergistic enhancement of microbial activity within the fungal-algal symbiosis. Precipitation characterisation demonstrated that FBA achieves heavy metal immobilization and removal through biomineralization and adsorption mechanisms. Microbial community and gene prediction analyses revealed interspecies functional synergistic mechanisms. This study provides an efficient and sustainable solution for treating complexly polluted industrial wastewater.