Isolation of a Novel Heterotrophic Nitrification–Aerobic Denitrification Bacterium Serratia marcescens CL1502 from Deep-Sea Sediment

A novel bacterium capable of simultaneous heterotrophic nitrification and aerobic denitrification was isolated from deep-sea sediment of the North Atlantic and identified as Serratia marcescens CL1502. The aim of this study was to study the ability, influence factors, and application in application to tannery wastewater nitrogen removal by S. marcescens CL1502. Results showed that S. marcescens CL1502 had good ability to remove NH₄⁺-N, NO₃^‑-N, and NO₂^‑-N. High average NH₄⁺-N, NO₃^‑-N, and NO₂^‑-N removal rates of 4.57 mg/(L·h), 4.60 mg/(L·h), and 4.42 mg/(L·h) were observed. The optimum carbon source for heterotrophic NH₄⁺-N removal by S. marcescens CL1502 was glucose. Higher C/N ratios were favorable to heterotrophic NH₄⁺-N removal. S. marcescens CL1502 had a good tolerance to salinity (1–5%) and Cr(III). In addition, application of strain CL1502 in actual tannery industry wastewater resulted in chemical oxygen demand (COD), NH₄⁺-N, and TN removal efficiencies of 63.1%, 76.7%, and 72.9%. This is the first report of S. marcescens carrying out the process of simultaneous nitrification and denitrification. These results demonstrate the potential of the bacterium for use in tannery wastewater treatment for the efficient removal of ammonia.