Nitrogen removal performance in planted and unplanted horizontal subsurface flow constructed wetlands treating...

Area of Science:

• Environmental Science
• Water Treatment Engineering
• Ecology

Background:

• Constructed wetlands are engineered systems mimicking natural wetlands for wastewater treatment.
• Nitrogen removal in constructed wetlands is influenced by various factors including carbon-to-nitrogen ratio and vegetation.

Purpose of the Study:

• To investigate the impact of vegetation on nitrogen dynamics in horizontal subsurface flow constructed wetlands (HSSFCWs).
• To evaluate the effect of different influent Chemical Oxygen Demand (COD) to Nitrogen (N) ratios on nitrogen removal efficiency.

Main Methods:

• Microcosm HSSFCWs were operated with varying COD/N ratios (1:1, 4:1, 8:1).
• Comparison of nitrogen species (NH4, NO3, TIN) removal in planted (Canna indica L.) and unplanted systems.
• Analysis of nitrogen removal at different depths within the wetland.

Main Results:

• Increased COD/N ratios enhanced NO3 and Total Inorganic Nitrogen (TIN) removal in both planted and unplanted wetlands.
• Planted HSSFCWs showed significantly improved NH4 reduction, particularly at higher COD/N ratios (up to 26% increase at 8:1).
• NH4 removal was greater in planted wetlands at deeper sections (20-40 cm), while NO3 removal increased with depth uniformly.

Conclusions:

• Vegetation in HSSFCWs can enhance nitrogen removal, specifically ammonia, when an adequate carbon source is present.
• The effectiveness of vegetation in nitrogen removal is dependent on the influent COD/N ratio.
• While vegetation offers benefits, sufficient carbon availability is crucial for optimal nitrogen load reduction in HSSFCWs.