Biofilters are one of the most popular stormwater treatment systems due to their low size requirement and high potential to remove a wide range of pollutants. However, traditional biofilter media such as compost and sand have limited capacity to remove pollutants, particularly in high flow conditions. To increase the adsorption capacity of traditional biofilter media such as compost and sand, they are mixed with waste-derived amendments such as scrap iron, drinking water treatment residues, woodchips, and biochar. This presentation describes the results of a series of laboratory studies that demonstrate the benefits and risk of waste-derived amendments. The benefits of waste-derived amendments include cost, availability of material, increase in infiltration, water holding capacity and contaminant removal, whereas risks include leaching of residual contaminants from wastes and shifts in biofilter microbiome that could diminish its overall ecosystem function. The presentation shares the results of laboratory column experiments that were designed to test the performance of these amendments. While the addition of biochar increase removal of a wide range of contaminants and shift microbiome of the biofilter, metal oxide-based amendments increase removal of anionic contaminants and fecal indicator bacteria. Although mixing compost with iron filings decreased contaminant removal capacity of iron filing, it provided a long-term benefit: iron filings lowered the decomposition rate of compost and increased its performance lifetime. Overall, the results show that there are many opportunities to utilize waste-derived amendments in stormwater biofilters, but the unintended consequences of each amendment should be considered.

Waste-derived amendments in stormwater biofilters: Do the benefits outweigh the risks?

2019 Fall National Meeting

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