Mitigation of N

Area of Science:

• Environmental Engineering
• Microbiology
• Waste Management

Background:

• Landfill leachate poses environmental risks due to nitrogenous compounds and potential N2O emissions.
• Enhanced denitrification requires an external carbon source (C-source) for efficient nitrate removal.
• Anaerobically fermented sewage sludge can serve as a sustainable C-source.

Purpose of the Study:

• To investigate the efficacy of anaerobically fermented sewage sludge as an external C-source for mitigating N2O emissions from landfill leachate.
• To optimize conditions for anaerobic sludge fermentation to maximize VFA production.
• To evaluate the impact of this C-source on denitrification rates and N2O reduction.

Main Methods:

• Sewage sludge underwent thermophilic anaerobic fermentation with increasing organic loading rates (OLR).
• Optimal fermentation conditions were identified based on hydrolysis efficiency, sCOD, and VFA concentrations.
• Sludge-fermentate (SF) was used as the C-source in denitrification tests with landfill leachate (LL), measuring nitrate removal and N2O emissions.

Main Results:

• Optimal fermentation occurred at an OLR of 40.48 g COD/L·d, yielding high hydrolysis efficiency and VFA concentrations.
• SF addition significantly increased the specific nitrate removal rate (KNR) by 5.42 times compared to raw LL.
• SF addition reduced N2O gas emissions by 1.72 times and demonstrated a specific N2O reduction rate (KN2O) of 6.70 mg N/g VSS hr.

Conclusions:

• Anaerobically fermented sewage sludge is an effective external C-source for enhancing denitrification and mitigating N2O emissions from landfill leachate.
• The study demonstrates a viable strategy for simultaneous nitrate and N2O reduction in biological landfill leachate treatment.
• Utilizing fermented organic waste provides a sustainable approach to managing N2O emissions in wastewater treatment plants.