Investigation of E. coli and Virus Reductions Using Replicate, Bench-Scale Biosand Filter Columns and Two Filter Media

One Liner: 
Reductions of E.coli, MS2 and PRD-1 increases as filtration rate declines. Biosand filters using crushed granite as the filtration media has superior virus reductions than using Accusand silica as the filtration media, only when the media is not backwashed. E. coli reduction did not differ significantly between the two types of filter media.
TitleInvestigation of E. coli and Virus Reductions Using Replicate, Bench-Scale Biosand Filter Columns and Two Filter Media
Publication TypeJournal Article
Year of Publication2015
AuthorsElliott, M, Stauber, C, DiGiano, F, de Aceituno, A, Sobsey, M
JournalInternational Journal of Environmental Research and Public Health
Volume12
Issue9
Pagination10276 - 10299
Date PublishedJan-09-2015
AbstractThe biosand filter (BSF) is an intermittently operated, household-scale slow sand filter for which little data are available on the effect of sand composition on treatment performance. Therefore, bench-scale columns were prepared according to the then-current (2006–2007) guidance on BSF design and run in parallel to conduct two microbial challenge experiments of eight-week duration. Triplicate columns were loaded with Accusand silica or crushed granite to compare virus and E. coli reduction performance. Bench-scale experiments provided confirmation that increased schmutzdecke growth, as indicated by decline in filtration rate, is the primary factor causing increased E. coli reductions of up to 5-log10. However, reductions of challenge viruses improved only modestly with increased schmutzdecke growth. Filter media type (Accusand silica vs. crushed granite) did not influence reduction of E. coli bacteria. The granite media without backwashing yielded superior virus reductions when compared to Accusand. However, for columns in which the granite media was first backwashed (to yield a more consistent distribution of grains and remove the finest size fraction), virus reductions were not significantly greater than in columns with Accusand media. It was postulated that a decline in surface area with backwashing decreased the sites and surface area available for virus sorption and/or biofilm growth and thus decreased the extent of virus reduction. Additionally, backwashing caused preferential flow paths and deviation from plug flow; backwashing is not part of standard BSF field preparation and is not recommended for BSF column studies. Overall, virus reductions were modest and did not meet the 5- or 3-log10 World Health Organization performance targets.
URLhttp://www.mdpi.com/1660-4601/12/9/10276/
DOI10.3390/ijerph120910276
Short TitleIJERPH