Microbial nitrogen removal pathways in integrated vertical-flow constructed wetland systems.

Area of Science:

• Environmental Microbiology
• Wastewater Treatment Engineering
• Wetland Science

Background:

• Constructed wetlands are crucial for wastewater treatment.
• Understanding microbial nitrogen (N) removal pathways is vital for optimizing treatment efficiency.

Purpose of the Study:

• To investigate microbial N removal pathways in planted and unplanted integrated vertical-flow constructed wetlands (IVCWs).
• To compare the abundance and activity of N-transforming bacteria between planted and unplanted systems.
• To identify the dominant N removal mechanisms within IVCWs.

Main Methods:

• Utilized molecular biological techniques and isotope pairing experiments.
• Quantified nitrifying, anammox, and denitrifying bacteria distribution and abundance.
• Measured potential nitrification, anammox, and denitrification rates.
• Correlated microbial abundance with functional rates to confirm SNAD processes.

Main Results:

• N-transforming bacteria were significantly more abundant in planted IVCWs than unplanted ones.
• Potential nitrification, anammox, and denitrification rates were highest in the down-flow column of planted IVCWs.
• Simultaneous nitrification, anammox, and denitrification (SNAD) processes were confirmed.
• The anammox process was identified as the major N removal pathway, accounting for 55.6-60.0% of removal.

Conclusions:

• Planted IVCWs significantly enhance microbial N removal compared to unplanted systems.
• SNAD processes, particularly anammox, are critical for N removal in IVCWs.
• This study deepens the understanding of microbial N removal mechanisms in constructed wetlands.