Excess nitrogen in water bodies can trigger eutrophication, posing a threat to the ecosystem. The treatment of nitrogenous wastewater and removal of nitrogen compounds from water bodies is essential to improve and maintain water quality. To address this issue, the immobilized heterotrophic nitrifying-aerobic denitrifying bacterium Alcaligenes faecalis ( A. faecalis ) was combined with ecological floating island (EFI) to improve nitrogen removal performance, and the optimal operating conditions were determined. EFI supplemented with immobilized ...