Iron oxide amended biosand filters for virus removal

Laboratory studies were performed to determine if the addition of iron oxides throughout biosand filter (BSF) media would increase virus removal due to adsorption. The proposed mechanism is electrostatic adsorption of negatively charged virion particles to positively charged iron oxides formed during the corrosion of zerovalent iron. Initial tests conducted using continuous flow, small-scale glass columns showed high MS2 bacteriophage removal in an iron-amended sand column (5log10) compared to a sand-only column (0.5log10) over 20 pore volumes. Additionally, two experiments with a column containing iron particles revealed 4log10 and 5log10 removal of rotavirus in the presence of 20 mg/L total organic carbon. Full-scale BSFs with iron particles removed >4log10 MS2 for the duration of the experiment (287 days), while BSF with steel wool removed >4log10 MS2 for the first 160 days. Plug flow for the BSF was shown to depend on uniformity between the iron oxide material and sand media grains. The results suggest that the duration of effective virus removal by iron-amended biosand filtration depends on source water conditions and the quantity and composition of iron material added. Overall, this study provides evidence that iron-amended BSFs may advance the field of point-of-use technologies and bring relief to millions of people suffering from waterborne diseases.

► We determined the efficacy of virus removal in conventional and iron-amended biosand filters.
► We demonstrated that iron material integrated uniformly throughout the sand media effectively removed more than 4log10 of MS2 viruses over 280 days.
► We determined that after 200 days in operation, the conventional biosand filter underwent significant ripening and was able to remove more than 4log10 of MS2 viruses.