Comparison of Biofiltration Media in Treating Industrial Stormwater Runoff

Abstract

Biofiltration systems have become one of the most commonly used best management practices in dealing with stormwater runoff. Stormwater runoff is inherently variable, with the contaminants present depending greatly on the land use of the catchment basin. This study characterized the stormwater collected from an industrial site in northeastern Minnesota. It was determined the pollutants of concern for this site are dissolved heavy metals (Aluminum, Copper, Iron) and bacteria. Different media exhibit different strengths and weaknesses in the removal of pollutants in these biofiltration systems. As a result, there is not a universal combination of media that can adequately treat all stormwater. 18 bio-based media were tested in batch experiments to determine if they possessed any capacity for heavy metal removal. Eight media (APTsorb, bioAPT, biochar, marble, sand, vermiculite, and zeolite) that showed good removal were studied further in downward flowing column experiments. These column experiments determined that all materials demonstrated some capacity for dissolved metal removal with the exception of sand. However, marble performed the best by a significant margin, removing over 10 mg/cm3 of iron, 4 mg/cm3 of aluminum, and 2 mg/cm3 of copper. The four materials that were determined to have the largest removal capacity for heavy metals (APTsorb, compost, marble, zeolite) were tested in an additional column experiment in which the synthetic stormwater was inoculated with E. coli. Marble again performed the best removing 100% of E. coli throughout the duration of a 56-hour continuous flow column experiment. This characterization process provides valuable information on the effectivity and longevity of a variety of media in the design of future biofiltration systems.