The Effect of Increasing Grain Size in Biosand Water Filters in Combination with Ultraviolet Disinfection
Abstract
We examined how sand grain size effects biological sand filtration and how the combination of biological sand filtration and ultraviolet (UV) disinfection effects water quality. Two biosand water filters were built: a control filter (d10 = 0.19, UC = 2.1) with maximum grain size of 0.70 mm in accordance with the Center for Affordable Water Technology (CAWST) guidance and an experimental filter (d10 =0.80, UC = 1.5) with grain sizes ranging from 0.70 mm to 2.0 mm. Untreated water was manufactured and passed through each biosand water filter (BSF); the effluent was placed in clear polyethylene terephthalate bottles under longwave monochromatic UV light (365 mn) for disinfection. Water quality indicators of escherichia coli( e. coli) and turbidity were measured at three stages: untreated water, BSF effluent, and post-UV disinfection. Results show e.coli and turbidity removal characteristics of the control and experimental BSFs were not significantly different from one another. Although e. coli reduction was over 98% for each BSF, the high initial bacteria population resulted in effluent levels above World Health Organization drinking water guidelines. UV disinfection further reduced e.coli from both BSF's effluent to levels that met those guidelines. Additionally, both BSFs produced water that met turbidity guidelines. The data indicate existing grain size guidelines used in BSF construction may be relaxed without compromising water quality.
Document Details
- Document Type
- Technical Report
- Publication Date
- May 14, 2013
- Accession Number
- AD1016723
Entities
People
- Andrew Munoz
- Matthew Scheie
- Timothy Frank
- Victoria Cachro
Organizations
- United States Air Force Academy