A pilot-scale study on iron-driven autotrophic denitrification enhanced by CF-Fe-CS cathode for low C/N wastewater treatment

LÜ Tonghui; AN Facai; SUN Dezhi

doi:10.13205/j.hjgc.202604008

Volume 44 Issue 4

Apr. 2026

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Article Navigation > ENVIRONMENTAL ENGINEERING > 2026 > 44(4): 67-78

LÜ Tonghui, AN Facai, SUN Dezhi. A pilot-scale study on iron-driven autotrophic denitrification enhanced by CF-Fe-CS cathode for low C/N wastewater treatment[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(4): 67-78. doi: 10.13205/j.hjgc.202604008

Citation:

LÜ Tonghui, AN Facai, SUN Dezhi. A pilot-scale study on iron-driven autotrophic denitrification enhanced by CF-Fe-CS cathode for low C/N wastewater treatment[J]. ENVIRONMENTAL ENGINEERING , 2026, 44(4): 67-78. doi: 10.13205/j.hjgc.202604008

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A pilot-scale study on iron-driven autotrophic denitrification enhanced by CF-Fe-CS cathode for low C/N wastewater treatment

doi: 10.13205/j.hjgc.202604008

Beijing Key Laboratory for Source Control Technology of Water Pollution, College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China

Received Date: 2026-03-15
Available Online: 2026-06-06
Publish Date: 2026-04-01

Abstract

Abstract

The effluent from municipal wastewater treatment plants （WWTPs） is characterized by a low carbon-to-nitrogen （C/N） ratio in China. Achieving deep nitrogen removal using traditional heterotrophic denitrification processes requires substantial external carbon source addition， leading to high operational costs and potential secondary pollution. Nitrate-dependent ferrous oxidation （NDFO） presents a promising alternative denitrification technology. However， it faces bottlenecks such as unsustainable iron sources and surface passivation. In this study， a pilot-scale electrochemical-biological coupled system （CF-Fe-CS/NAFO） was constructed， featuring a built-in composite cathode （5% apparent filling rate of carbon felt-iron-chitosan， CF-Fe-CS）， an effective volume of 200 L， and a treatment capacity of 100 L/d. A constant potential of -1.0 V （vs. Ag/AgCl） was applied to the cathode to achieve the in-situ electrochemical reduction of Fe（Ⅲ）. In the test reactor， during stable operation from day 16 to 60 with a hydraulic retention time （HRT） of 48 h and synthetic wastewater containing 15 mg/L NO₃^--N， the effluent NO₃^--N concentration remained consistently below 6.5 mg/L， with a total nitrogen （TN） removal efficiency of 50% to 60%. In contrast， the control reactor （without an applied potential） showed an effluent NO₃^--N concentration above 12 mg/L and a TN removal efficiency below 20%. During continuous operation from day 61 to 74 using real secondary sedimentation tank effluent from a WWTP （influent NO₃^--N： 15.29 mg/L）， the system reduced the effluent NO₃^--N to 6.06 mg/L， maintaining a TN removal efficiency above 50%. From day 74 to 98， as the HRT was sequentially reduced from 48 h to 24 h， 12 h， 6 h， and 3 h， the corresponding effluent NO₃^--N concentrations increased to 9.5 mg/L， 11.9 mg/L， 13.6 mg/L， and 14.6 mg/L， with TN removal efficiencies of 32.6%， 19.9%， 10.9%， and 5.8%， respectively. These results demonstrate that the CF-Fe-CS/NAFO electrochemical system can achieve long-term， stable， and advanced nitrogen removal from WWTP secondary effluent without the need for an external organic carbon source.
- advanced nitrogen removal from WWTPs,
- iron-driven autotrophic denitrification,
- carbon felt-iron-chitosan cathode,
- pilot-scale experiment

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References(43)

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