The Effect of Increasing Grain Size in Biosand Water Filters in Combination with Ultraviolet Disinfection
Journal Article - Open Access
United States Air Force Academy Air Force Academy United States
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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 BSFs 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.
- Water Pollution and Control