Enhanced nitrate removal efficiency in wetland microcosms using an episediment layer for denitrification

Area of Science:

• Environmental Science
• Microbiology
• Ecological Engineering

Background:

• Microbial denitrification is crucial for nitrogen removal in treatment wetlands.
• The macroporous structure of the denitrification zone can influence nitrate removal efficiency.

Purpose of the Study:

• To investigate how variations in the macroporous structure of the denitrification zone affect nitrate removal.
• To compare nitrate removal in a sediment-only treatment versus a treatment with an episediment layer.

Main Methods:

• Utilized flow-through wetland microcosms with distinct denitrification zone structures.
• Compared a sediment-only treatment with a treatment featuring a distinct episediment layer of loosely aggregated litter.
• Analyzed vertical nitrate profiles using diffusive and turbulent mixing models.

Main Results:

• The episediment treatment showed a 33% greater average denitrification rate compared to the sediment-only treatment (p < 0.0001).
• Denitrification reaction kinetics were close to first order in both treatments (k(epi) = 0.21 d(-1), k(sed) = 0.12 d(-1)).
• Approximately 40% of nitrate removal in the episediment treatment occurred within the episediment layer itself.

Conclusions:

• Enhancing the episediment layer in treatment wetlands can significantly increase denitrification rates.
• The macroporous structure, specifically the presence of an episediment layer, plays a vital role in nitrate removal efficiency.
• Findings support optimizing episediment design for improved nitrogen management in treatment wetlands.