Low-dosage nitrate pollutants can contribute to eutrophication in surface water bodies, such as lakes and reservoirs. This study employed assembled denitrifying bacterial-fungal communities as bio-denitrifiers, in combination with zero-valent iron (ZVI), to treat micro-polluted water. Immobilized bacterial-fungal mixed communities (IBFMC) reactors demonstrated their ability to reduce nitrate and organic carbon by over 43.2 % and 53.7 %, respectively. Compared to IBFMC reactors, IBFMC combined with ZVI (IBFMC@ZVI) reactors exhibited enhanced removal efficiencies for nitrate and organic carbon, reaching the highest of 31.55 % and 17.66 %, respectively. The presence of ZVI in the IBFMC@ZVI reactors stimulated various aspects of microbial activity, including the metabolic processes, electron transfer system activities, abundance of functional genes and enzymes, and diversity and richness of microbial communities. The contents of adenosine triphosphate and electron transfer system activities enhanced more than 5.6 and 1.43 folds in the IBFMC@ZVI reactors compared with IBFMC reactors. Furthermore, significant improvement of crucial genes and enzyme denitrification chains was observed in the IBFMC@ZVI reactors. Iron played a central role in enhancing microbial diversity and activity, and promoting the supply, and transfer of inorganic electron donors. This study presents an innovative approach for applying denitrifying bacterial-fungal communities combined with iron enhancing efficient denitrification in micro-polluted water.

Aquatic EcoHealth Group Key Laboratory of Urban Environment and Health Institute of Urban Environment Chinese Academy of Sciences Xiamen China; Fujian Key Laboratory of Watershed Ecology Institute of Urban Environment Chinese Academy of Sciences Xiamen China

Collaborative Innovation Center of Water Pollution Control and Water Quality Security Assurance of Shaanxi Province Xi'an University of Architecture and Technology Xi'an 710055 China; Shaanxi Provincial Field Scientific Observation and Research Station of Water Quality in Qinling Mountains Xi'an University of Architecture and Technology Xi'an 710055 China; School of Environmental and Municipal Engineering Xi'an University of Architecture and Technology Xi'an 710055 China

College of Resources and Environment University of Chinese Academy of Sciences Beijing China; CAS Key Laboratory of Environmental Biotechnology Research Center for Eco Environmental Sciences Chinese Academy of Sciences Beijing China University of Chinese Academy of Sciences Beijing China

Department of Applied Ecology Faculty of Environmental Sciences Czech University of Life Sciences Prague Kamýcká 129 Suchdol Praha 16500 Czech Republic

Department of Biological Sciences Xi'an Jiaotong Liverpool University Suzhou 215123 China

Department of Civil and Environmental Engineering the Pennsylvania State University USA

Papanin Institute for Biology of Inland Waters of Russian Academy of Sciences 109 Borok Nekouz Yaroslavl 152742 Russia

References provided by Crossref.org