Fe-C wrapped in polyurethane sponge cubes tied in anoxic zones to enrich multiple denitrifying bacteria enhancing wastewater nitrogen removal

To enhance nitrogen removal in wastewater treatment , a novel method of wrapping waste iron shavings (Fe-C) in polyurethane sponge cubes tied in anoxic zones of a continuous reactor was proposed. Three types of denitrifying bacteria were enriched simultaneously in biofilms and activated sludge , including iron autotrophic denitrifying bacteria (7.83–8.71 %), heterotrophic denitrifying bacteria (10.60–11.95 %), and heterotrophic nitrification-aerobic denitrifying bacteria (23.47–40.06 %). Iron autotrophic denitrifying bacteria ( Dechloromonas and Sphaerotilus ) can remove NO 3 − -N using Fe 2+ as electron donor produced by micro-electrolysis of iron shavings without organic carbon demand, and heterotrophic nitrification-aerobic denitrifying bacteria ( Ferribacterium and Zoogloea ) can simultaneously accomplish nitrification and denitrification under aerobic conditions . The enrichment of these two functional bacteria strengthened the nitrogen removal performance compared to conventional heterotrophic denitrifying process, which could achieve efficient and stable total nitrogen removal (87.4 %) even with low organic carbon. In addition, the synergy of biological and chemical processes through Fe-C micro-electrolysis also enhanced total phosphorus removal (86.0 %).