Modified basalt fiber filled in constructed wetland-microbial fuel cell: Comparison of performance and microbial...

Basalt fiber (BF) with modification of iron (Fe-MBF) and calcium (Ca-MBF) were filled into constructed wetland-microbial fuel cell (CW-MFC) for innovative comparison of improved performance under perfluorooctanoic acid (PFOA) exposure. More enhancement on nitrogen and phosphorus removal was observed by Fe-MBF than Ca-MBF, with significant increase of ammonium (NH₄⁺-N) removal by 3.36-5.66 % (p < 0.05) compared to control, even under PFOA stress. Markedly higher removal efficiency of PFOA by 4.76-8.75 % (p < 0.05) resulted from Fe-MBF, compared to Ca-MBF and control BF groups. Besides, superior electrochemical performance was found in Fe-MBF group, with maximum power density 28.65 % higher than control. Fe-MBF caused higher abundance of dominant microbes on electrodes ranged from phylum to family. Meanwhile, ammonia oxidizing bacteria like Nitrosomonas was more abundant in Fe-MBF group, which was positively correlated to NH₄⁺-N and total nitrogen removal. Some other functional genera involved in denitrification and phosphorus-accumulation were enriched by Fe-MBF on electrodes and MBF carrier, including Dechloromonas, Candidatus_Competibacter, and Pseudomonas. Additionally, there were more biomarkers in Fe-MBF group, like Pseudarcobacter and Acidovorax, conducive to nitrogen and iron cycling. Most functional genes of nitrogen, carbon, and sulfur metabolisms were up-regulated with Fe-MBF filling, causing improvement on nitrogen removal.