Biochar Selection for Escherichia coli Removal in Stormwater Biofilters

Abstract

Biochar’s capacity to remove pathogens from stormwater can vary by orders of magnitude, which makes it challenging for stormwater managers to select specific biochar from suppliers. In this study, the removal of Escherichia coli (E. coli) in model biofilters packed with sand and biochar from four suppliers was tested and correlation equations were developed that link short-term and long-term bacterial removal capacities of biochar with its commonly reported properties: surface area, carbon content, ash content, and volatile organic carbon content. The E. coli removal capacity of biochar was positively correlated with its surface area and carbon content and negatively correlated with ash content and volatile organic matter. Despite the presence of nutrients in stormwater, E. coli in pore water in biofilter did not grow between infiltration events, indicating biochar may continue to remove pathogens after rainfall. Overall, the results could help the selection of biochar from suppliers for the treatment of stormwater and inform the suppliers to tailor biochar production conditions to enrich specific biochar properties.