Evaluation of Various Filter Media in Removing Human Pathogens from Stormwater
Discharge and infiltration of contaminated stormwater runoff is one of the leading cause of microbial contamination of surface water bodies and subsurface aquifer. The performance of conventional biofilters, consisting a mixture of sand and compost as filter media, has been reported to be inadequate and inconsistence. Although biochar, a pyrolyzed biomass, have recently demonstrated excellent performance in removing FIBs from stormwater, their efficacy in removing pathogens from stormwater is unknown. This study investigates the removal of pathogens (i.e., Salmonella spp., Staphylococcus spp.) in biochar-amended biofilters and delineates associated removal mechanisms. Laboratory scale column experiments were performed using sand- and biochar-amended sand biofilters to compare their pathogen removal efficiencies with the fecal indicator bacteria and virus (i.e., E. coli and MS2) removal efficiencies. Theoretical prediction of microbial removal in the biofilters were also performed using available theoretical models describing microbial transport in porous media. Experimental results suggest that biochar-amended biofilters performs better than sand biofilters in removing microbial contaminants from stormwater. Moreover, biochar-amended biofilters are more efficient in removing pathogenic bacteria than indicator bacteria or viruses. Our results also suggest that electrostatic interaction plays minor role in bacteria removal in biochar-amended biofilters: hydrophobic interaction is the likely removal mechanism. Findings of this study inform the design of geomedia-amended biofilters which may help reducing microbial contamination in water bodies and promote beneficial use of stormwater runoff in urban settings.
Dr. Nabiul Afrooz is a scientist at SCCWRP who specializes in development, evaluation, and implementation of stormwater control measures. Nabiul has extensive research experience in physicochemical and biological treatment processes in mitigating water pollution resulting from particulate, chemical, and microbial contaminants. He is specifically interested in assessing the effectiveness of existing stormwater BMPs and designing green infrastructures with enhanced performance.