Treatment of parking lot runoff by a tree box filter

Nonpoint source pollutants were usually transported by stormwater runoff, especially in highly urbanized areas. For this reason, studies on stormwater management have been one of the major focuses of the Ministry of Environment of Korea at present. Application of tree box filter, an example of stormwater best management practice, is highly considered in Korea due to its minimal space requirements, applicability in landscaping and good pollutant-removal efficiency. This study investigated the efficiency of a tree box filter in reducing both the pollutant and volume of stormwater runoff generated from a parking lot. This study also identified the relationship between pollutant and volume reduction and the effects of varying amount of rainfall to the overall volume reduction efficiency of the system. The study proved the capability of the tree box filter in improving stormwater runoff quality that was more efficient in total suspended solids (TSS) and soluble heavy metals discharging only 9 and 30% of the inflow load, respectively. In addition, high pollutant reduction of the system was associated with volume reduction of the system especially for TSS in which 20% volume reduction corresponds to at least 80% TSS reduction. The system also exhibited good volume reduction capability, especially for rainfall less than 10 mm. The tree box filter has proved to be an option for a cost-effective stormwater management, since it only requires a minimal space (surface area less than 5% of catchment area) and is applicable at small landscape areas in any urban land uses.