Abstract

This study was conducted to quantify emissions of greenhouse gases (GHGs), methane (CH₄) and Nitrous Oxide (N₂O), from free water surface constructed wetlands used for domestic wastewater treatment. All constructed wetlands were monoculture and each plot was planted with Phragmites sp., Cyperus sp., or Canna sp. The average CH₄ and N₂O emissions were in the range of 5.9-11.2 and 0.9-1.8 g/m²/h, respectively. Seasonal fluctuations of CH₄ and N₂O emissions were observed. The highest fluxes of both GHGs occurred during hot rainy season (July-October) followed by summer and the lowest found in cool season. The mean of CH₄ and N₂O emissions from different plants species were significantly different (p<0.05). Average CH₄ emissions from constructed wetlands planted with Phragmites sp., Cyperus sp. and Canna sp. were 11.2, 6.0 and 5.9 mg/m²/h, respectively, while mean N₂O emissions were 0.9, 1.0 and 1.8 mg/m²/h, respectively. Calculated of Global Warming Potential (GWP) found that GWP of CH₄ and N₂O flux from constructed wetlands planted with Cyperus sp., was the highest (669 mg CO₂ equivalent/m²/h), followed by Phragmite sp., (524 mg CO₂ equivalent/m²/h) and Canna sp., (434 mg CO₂ equivalent/m²/h), respectively. These results suggested that municipal wastewater treatment by constructed wetlands planted with Canna sp. and Phragmite sp., had potential of lower GHGs emissions into the atmosphere and Phragmite sp., provided the highest removal rate of Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD).

Keywords:

Constructed wetlands, methane, nitrous oxide, plant species, wastewater treatment,

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