Nitrogen removal performance and functional genes distribution patterns in solid-phase denitrification sub-surface...

Area of Science:

• Environmental Engineering
• Microbiology
• Water Treatment

Background:

• Constructed wetlands are effective for wastewater treatment.
• Optimizing substrate materials and aeration can enhance nitrogen removal efficiency.
• Understanding microbial community dynamics is crucial for process improvement.

Purpose of the Study:

• To evaluate the nitrogen removal performance of an up-flow vertical flow constructed wetland (AC-VFCW) with ceramsite and poly(3-hydroxybutyrate-hydroxyvalerate) (PHBV).
• To investigate the simultaneous nitrification and denitrification process and the distribution of key nitrogen transformation genes.
• To elucidate the functional division of microbial communities along the substrate depth.

Main Methods:

• An AC-VFCW was constructed using ceramsite and 5% PHBV as substrate with micro-aeration.
• Nitrogen removal efficiencies (NH4+-N, TN) were measured.
• Quantitative PCR was used to quantify the abundance of nitrification (AmoA) and denitrification (NirS, nosZ) genes at different substrate depths.

Main Results:

• The AC-VFCW achieved high removal efficiencies: 90.4% for NH4+-N and 92.1% for TN.
• Simultaneous nitrification and denitrification were observed.
• Nitrification genes (AmoA) were enriched in the lower substrate layers (-10 and -50 cm).
• Denitrification genes (NirS) dominated the bottom layer, while nosZ genes were abundant in the middle and top layers, indicating a functional stratification.

Conclusions:

• The AC-VFCW with PHBV and micro-aeration is highly effective for nitrogen removal.
• The substrate PHBV promotes the enrichment of nitrification and denitrification microbial communities.
• A distinct functional zonation of nitrogen transformation genes along the flow direction was established, optimizing the simultaneous nitrification and denitrification process.