Stormwater Treatment using In-ground Permeable Reactive Filter Systems: Batch Test Evaluation of Media

Urban stormwater runoff has been identified as a major source of beach water pollution due to washing off contaminants from road surfaces, lawns, parks and parking lots. Heavy metals, nutrients, PAHs, and disease-causing microorganisms are typical types of contaminants found in urban stormwater runoff. Mitigation of stormwater runoff impact is essential for both public health and the environment. There have been several best management practices developed to mitigate runoff impacts, but many of these are based on volume control such as detention to separate suspended solids. However, in urban setting and in the close proximity of beaches, it is difficult to provide adequate area to meet the detention storage requirements. Therefore, the use of in-ground permeable reactive filter (PRF) system can be a proactive intervening approach for removal of a wide range of contaminants from urban stormwater runoff. Base on the comprehensive literature review and preliminary testing, four different filter media (calcite, zeolite, sand, and iron filings) have been selected. Chemical and physical characteristics of the filter media were determined. Both batch equilibrium and batch kinetic experiments with heavy metals, PAHs, and nutrients solutions were conducted to quantify each filter media adsorption capacity and removal rate for different kinds of contaminants. Practical application of the acquired experimental data in designing of the filter system was also investigated. The results demonstrated that the extent of adsorption and removal depend on the type and concentration of contaminant as well as induced pH changes caused by the filter media. For some contaminants and media combinations, adsorption reached maximum adsorption capacity; however, for some other cases filter media had much higher adsorptive capacity. Each media was effective in removal and adsorption of some particular contaminants; therefore, combination of different filter media is needed to effectively remove all of the contaminants present in typical stormwater run-off. Overall, this study demonstrated that each filter material is effective in removal of selected contaminants from urban stromwater and a combination of theses filter materials will be needed to effectively treat the multiple contaminants in the urban stormwater runoff.