Seasonal variations in the pollutant removal performance of an urban stormwater infiltration trench

The primary repercussions of seasonal changes must be addressed in the design, performance, and regulation of stormwater treatment facilities (Emerson & Traver, 2008). Pollutant concentrations in urban stormwater runoff altered by the seasonal variations can affect the pollutant removal efficiency of urban stormwater treatment facilities. In this regard, this study mainly focused on the evaluation of the pollutant removal performance of an urban stormwater infiltration trench (IT) as influenced by seasonal variations. 34 rainfall events from May 2009 to September 2016 were monitored to assess the performance of the facility. Statistical analyses revealed that the lowest mean pollutant removal efficiency of the IT for turbidity (64%), total suspended solids (66%), and chemical oxygen demand (68.5%) was recorded during summer season. From 2009-2016, the daily precipitation experienced during summer months, ranging from 0.1mm to 157.5mm, led to a 4% to 40% decline in the facility’s pollutant removal efficiency. Increased runoff volume disrupts the settling of particles and reduces the hydraulic retention time of the facility (Sharma et al., 2016). Moreover, the biochemical oxygen demand and total nitrogen removal efficiency of the system was lowest on winter season with corresponding values of 39% and 51%, respectively. The average temperature during winter ranged from -3℃ to 0.7℃, thereby causing the soil media layers to freeze and degrade the performance of the facility. Fundamentally, this research can serve as a reference in evaluating best management practices (BMPs) of similar characteristics, especially in terms of hydrologic and governing treatment mechanisms.