Investigation of selective filtration characteristics of filter media for pavement runoff treatment

Abstract

Abstract Filter media with porous structures have been employed in some filtration systems to improve the filtration efficiencies of pavement runoff pollution. However, there is no solid support to select the appropriate type due to the lack of understanding of the selective filtration characteristics of different filter media. In this study, five filter media with different porous structure were selected, and the corresponding filtration characteristics were investigated by self-developed filtration test equipment. The effects of type, layer thickness, and grain size of the filter media on the filtration efficiencies of pavement runoff were evaluated. Then, according to the dominant pollutants in the pavement runoff, an optimum configuration of the filter media was proposed by Fuzzy Comprehensive Evaluation Method. Besides, the particle size distributions of the influent and effluent runoff, the microstructures, and element mapping of the filter media before and after filtration tests were characterized by Laser particle analyzer, scanning electron microscope (SEM), and X-ray energy dispersive spectrometer (EDS), respectively. The results show that filter media provide significant selective filtration characteristics for treating different runoff pollutants, which are also grain-size related, especially for Zeolite. Compared with a single type of filter medium, the combination groups show significantly better filtration efficiencies. Specifically, Vesuvianite and Slag show superior capability to remove pollutants due to their special porosity microstructures which result in remarkable adsorption effects on runoff particles.