Laboratory Investigation on Pollutant Removal Effect of Purification Materials for Porous Asphalt Pavement

Abstract

Purification materials have been widely applied as filter media in best management measures including wetlands, bioretention systems, and so forth, whereas their application in permeable pavement is limited and needs further research. This paper aims to explore the feasible applications of water purification materials in permeable pavement materials and structures. Based on laboratory rainfall test and static adsorption test, the possible application of three types of water purification materials, including diatomite, quartz sand, and straw biochar, in porous asphalt pavement and their pollutant removal effect were investigated. The results show that the filter layers can effectively increase the total suspended solids removal rate to 60%–80%. And when the purification materials are applied as alternative fillers in porous asphalt mixture (PA), they can enhance the removal effect of dissolved pollutants, especially heavy metals, by their special chemical properties and the positive influence on microscopic pore structures of PA. The adsorption effect of PA on pollutants is closely related to the environment temperature. The PA adsorption of nutrients and Cu increases with the increase of temperature, but the adsorption effect of Cr is better at lower temperatures. The pseudo-first-order model and the pseudo-second-order model can properly describe the adsorption process of heavy metals Cu and Cr by PA, respectively. The purification schemes that present purification effects under different runoff pollution characteristics are recommended as well.