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Role of Biochar Surface Properties on the Removal of Waterborne Pathogenic Escherichia coli from Stormwater

Waled Suliman
Washington State University
Abstract: 

The designing of biochars with surfaces that have an effect against leaching of bacteria from biochar-based biofilters is a promising approach for removing waterborne pathogens from storm-water. Consensus regarding the contribution of biochar surface properties (i.e. charge, roughness, and surface area) to pathogen deposition/removal is currently not definitive. The present study investigates the efficacy of biochar surface properties on the removal of Escherichia coli in biochar-augmented sand biofilters. We quantified the retention and transport of E. coli pathogenic O157:H7 and non-pathogenic K12 strains in water-saturated Quincy sand columns amended with 20 wt.% pine wood or pine bark biochar produced at 350oC and 600oC.  In this study, we utilized both heat treatment and post-pyrolysis oxidation procedures to modify the surface physicochemical characteristics of biochars used. Our results showed that (1) Oxidized biochar enhanced the transport of E. coli O157:H7 cells due to more repulsive forces and higher negative charge densities; (2) E. coli O157:H7 displayed higher retention then E. coli K12 in biochar-sand columns 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 35%; (4) pine bark biochar produced at 600oC increased the  transport  of E. coli O157:H7 whereas pine wood biochar produced at the same pyrolysis temperature reduced the transport of the same bacterium. These results provide insight into pathogen removal mechanisms in biochar-based biofilters and the importance of biochar production and post-production conditions.

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