Transport of Pathogenic and Non-Pathogenic E. coli in Biochar-Amended Soil.

A detailed understanding of the transport of Escherichia coli O157:H7 within the soil-groundwater system is critical to the protection of public health. Although incorporation of biochar, a carbon-rich porous material, into soils has a potential for reducing the leaching of manure-borne pathogens, knowledge concerning the impact of biochar surface functionality on the retention and transport of E. coli O157:H7 is still largely missing. The main objective of this research was to evaluate whether the addition of un-oxidized and oxidized biochar to a sandy soil affected the transport of E. coli strains through water-saturated soil columns. We hypothesized that the transport of E. coli through bio-char-amended soils will depend on biochar surface chemistry. To test our hypothesis, we quantified the transport of E. coli O157:H7 and E. coli K12 in water-saturated column experiments for Quency sand amended with 20% pine wood or pine bark biochars produced at 350 and 600°C using lab scale spoon pyrolysis reactor. Our results showed that (1) Oxidized biochar could enhance the transport of E. coli O157:H7 cells due to surface charge effects; (2) E. coli O157:H7 displayed higher retention then E. coli K12 in biochar-amended soil under experimental pH conditions tested; (3) increased biochar application rates (from 0 to 20%) led to a reduction in the transport of both bacterial strains from 95 to 40%; (4) increased transport was observed for the pine bark biochar produced at 600 ^oC whereas reduced transport was observed for the pine wood biochar produced at the same pyrolysis temperature. Our results suggest that un-oxidized pine wood biochar produced at 350^oC was effective in reducing transport of E. coli strains in the Quincy sand.