| Abstract | Urban canals are significant yet underrepresented sources of methane (CH₄), a potent greenhouse gas with a global warming potential 34 times greater than carbon dioxide over a 100-year horizon. These stagnant, shallow, and nutrient-rich water bodies create favorable conditions for anaerobic methanogenesis, but their mitigation potential through artificial aeration remains poorly understood. This study evaluated the effectiveness of venturi pump-induced aeration in reducing methane emissions from a stagnant urban canal at the Asian Institute of Technology (AIT) campus, Pathum Thani, Thailand, with a focus on spatial and temporal methane dynamics. Two experiments were conducted. First, a spatial experiment deployed floating chambers at distances of 1 to 5 meters from a continuously operating venturi pump over three weeks to assess methane flux gradients along the oxygen gradient. Second, a controlled temporal experiment using static chambers with manually introduced methane compared consumption rates between the aerated treatment canal and a non aerated control canal over 96 hours. Water quality parameters including NH₄⁺, NO₂⁻, NO₃⁻, and total organic carbon (TOC) were monitored, and dissolved oxygen was measured across spatial grids before and after aeration. In the spatial experiment, a directional decrease in methane flux was observed from 1 m (204.12 mg/m²/day) to 3 m (137.01 mg/m²/day) in the treatment canal, though the effect was not statistically significant (ANOVA, p > 0.05), likely due to spatially heterogeneous ebullition. Dissolved oxygen in the treatment canal reached 5.62–5.92 mg/L following aeration, representing a biologically meaningful increase from baseline levels. In the temporal experiment, the treatment canal exhibited a steeper rate of methane flux decline (−4,396.6 mg/m²/day²) compared to the control canal (−3,222.8 mg/m²/day²), indicating approximately 36% greater methane consumption potential under aeration. Spearman correlation analysis revealed a statistically significant negative relationship between methane flux and the change in NH₄⁺ (ρ = −0.52, p = 0.009), indicating competition between methanotrophic and nitrifying bacteria for the limited dissolved oxygen supplied by the pump.The findings demonstrate that venturi aeration activates the natural biological methane filter already present in urban canal systems, though a single small-scale unit provides insufficient oxygen to fully suppress emissions dominated by ebullition or to simultaneously optimize both methane oxidation and nitrogen cycling. This study contributes evidence for low-energy venturi aeration as a scalable, low-cost greenhouse gas mitigation strategy for stagnant urban waterways in tropical cities. |
