Simultaneous removal of phosphorus, zinc, and lead from oligotrophic ecosystem by iron-driven denitrification:...

Based on the current situation of complex pollution caused in surface water by oligotrophic condition and heavy metal release from river and lake bottom sediments. This study aimed to achieve the simultaneous removal of nitrate, phosphorus, Zn²⁺ and Pb²⁺ through microbial approach. At nitrate concentration of 4.82 mg L^-1, carbon to nitrogen ratio of 1.5, pH of 6.0, and Fe²⁺ concentration of 5.0 mg L^-1, the nitrate removal efficiency of Zoogloea sp. FY-6 reached 95.17%. The addition of pollutants under these conditions resulted in 88.76% removal of total phosphorus at 18 h, and 85.46 and 78.59% removal of Zn²⁺ and Pb²⁺ respectively, and there was competition for adsorption between Zn²⁺ and Pb²⁺. Extracellular polymers and fluorescence excitation-emission substrates confirmed that Fe²⁺ reduced heavy metal toxicity through promoting bacterial production of secretions and promotes denitrification as a carbon source. Meanwhile, contaminant removal curves and Fourier transform infrared spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy demonstrated the synchronous removal of Zn²⁺ and Pb²⁺ mainly through biological action and the formation of nanoscale iron oxides. Biological-iron precipitation also provided adsorption sites for phosphorus. This research provides the theoretical foundation for applying microorganisms to restore oligotrophic source water (rivers and lakes) containing complex pollutants.