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Sulfide-driven denitrification process for low C/N ratio wastewater treatment
Chao Wang1, Cong Yu1, Sen Qiao1
1Key Laboratory of Industrial Ecology and Environmental Engineering (Ministry of Education, China), School of Environmental Science and Technology, Dalian University of Technology, Dalian, 116024, China.
Journal of Environmental Management
|August 2, 2025
Summary
This study introduces a novel method using sulfide to boost nitrogen removal in wastewater treatment, achieving 100% total nitrogen removal and recovering nitrous oxide and elemental sulfur. This approach reduces reliance on organic carbon for efficient wastewater management.
Area of Science:
- Environmental Science
- Environmental Engineering
- Microbiology
Background:
- Low carbon-to-nitrogen (C/N) ratio wastewater presents challenges for conventional biological nitrogen removal (BNR).
- Organic carbon is typically required as an electron donor for denitrification, limiting treatment efficiency in low-carbon environments.
- Nitrous oxide (N2O) accumulation during BNR is a significant issue due to its potent greenhouse gas potential.
Purpose of the Study:
- To develop a novel strategy for enhanced nitrogen removal in low C/N ratio wastewater.
- To investigate the use of sulfide (Na2S) as an external electron donor and enzyme inhibitor.
- To enable the recovery of nitrous oxide (N2O) and elemental sulfur (S0) as valuable resources.
Main Methods:
- Systematic investigation of varying Na2S concentrations and C/N ratios.
- Analysis of nitrogen removal efficiency and microbial community structure.
- Transcriptomic analysis to elucidate the molecular mechanisms of Na2S action on microbial pathways.
Main Results:
- Achieved 100% total nitrogen (TN) removal with simultaneous accumulation of N2O (60.5% yield) and S0 (69.1% yield).
- Na2S addition suppressed nitrous oxide reductase (N2OR) activity and downregulated the nosZ gene cluster, redirecting electron flux.
- Microbial community shifted from heterotrophic to autotrophic bacteria with increasing Na2S concentration and decreasing C/N ratio.
Conclusions:
- Sulfide addition is an effective strategy for enhancing nitrogen removal and enabling N2O/S0 recovery in low C/N wastewater.
- This approach reduces the dependency on organic carbon, offering a sustainable wastewater treatment framework.
- The findings provide valuable insights for optimizing sulfur-mediated BNR processes and promoting economy-driven wastewater management.
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