A Laboratory Study on the Filtration and Clogging of the Sand-Bottom Ash Mixture for Stormwater Infiltration Filter Media

The performance of stormwater infiltration systems depends significantly on the infiltration/filtration characteristics of filter media. Sand media have been frequently used due to their abundance and acceptable pollutant removal efficiency. Bottom ash media, which was known to have a high sorption capacity, are being considered as alternative and/or complement filter media to enhance the overall treatment efficiency. To verify the applicability of bottom ash as filter media, a series of 1-D column infiltration tests were conducted in this study. The filtration and clogging characteristics of the sand-bottom ash mixtures at different mixing ratios were investigated with limitedly focusing on the Total Suspended Solids (TSS) present in stormwater runoff. As a result, the presence of bottom ash was identified to improve the TSS removal efficiency in spite of having a significant increase in clogging potential. All media configurations were observed to experience the premature clogging and the clogging state for varying and constant head flow conditions, respectively. The noticeable amount of crushed bottom ash particles brought by seepage force could be accountable for the rapid occurrence of clogging phenomena. Overall, a homogeneous sand filter is preferred as long as the lifespan of filter system is the primary concern.