Biochar-Mediated Transport of Escherichia coli in Aggregated Porous Media and a Soil-Lettuce Pot System

Abstract Owing to its detectability, Escherichia coli (E. coli) is a common indicator for studying bacterial transport, and understanding its migration in porous media is critical for risk assessment and mitigation. This study investigates how biochar influences the transport behavior of E. coli in heterogeneous porous media, including quartz sand, gravel, and iron oxide-coated gravel. Column experiments were conducted with PSBC at 0, 2 wt %, and 10 wt % in the tested porous media, whereas AWBC was evaluated only at 2 wt % in gravel and iron oxide-coated gravel. Breakthrough curves, mass balance, and transport parameters were analyzed using a two-region mobile-immobile model. The results showed that PSBC concentration affected E. coli transport in a medium-dependent manner. At 2 wt %, PSBC and AWBC exhibited different effects in gravel and iron oxide-coated gravel. Notably, the effect of iron oxide-coated gravel on biochar-mediated E. coli transport was biochar-dependent: it altered the transport response of PSBC, but not AWBC, in the same way. Overall, biochar altered E. coli retention behavior by modifying surface charge and pore structure, highlighting its potential for mitigating microbial contamination in groundwater and soil systems.