Hydraulic Loading Rate Effect on Removal Rates in a BioSand Filter: A Pilot Study of Three Conditions

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(Caution: This study did not have replicates) Reducing the initial flow rate in Hydraid filters, by modifying the outlet pipe, did not significantly improve E.coli reduction.
TitleHydraulic Loading Rate Effect on Removal Rates in a BioSand Filter: A Pilot Study of Three Conditions
Publication TypeJournal Article
Year of Publication2012
AuthorsKennedy, TJ, Hernandez, EA, Morse, AN, Anderson, TA
JournalWater, Air, & Soil Pollution
Pagination4527 - 4537
Date PublishedJan-09-2012
AbstractSafe drinking water is a luxury to approximately 800 million people worldwide. The number of people without access to clean water has been reduced, thanks to technologies like the biosand filter (BSF), an intermittently operated household scale slow sand filter. The BSF outlet (control diameter 0.5″) was modified in this study by reducing the outlet diameter (0.37″ and 0.25″) to determine the effects of hydraulic retention time on removal rates. Filters were dosed with 20 L of spiked lake water daily and observed for pH, dissolved oxygen (DO), fecal coliforms (FC), turbidity, nitrate, nitrite, sulfate, and ammonia until initial flow rates dropped below 0.2 L/min. Consistent with previous studies, the average turbidity was reduced to below 1 NTU; the average DO was reduced by 45 %. No significant difference was observed between the modified BSFs and the control BSF. Removal efficiency of FC was not significantly different between the modified BSFs (93.3 % and 91.9 %) and the control BSF (89.6 %). Mean FC reduction during the startup period (17 days) was significantly greater in the modified 0.25″ BSF when compared with the control during the same time period. After the first 17 days of the experiment, the average reduction efficiency of all filters was >97 %. While source water was below guideline values for nitrate, nitrite, ammonia, and sulfate during the course of the experiment, total nitrogen reduction was observed. The reduction indicates that the plastic BSF is capable of accomplishing limited denitrification during the filtering process.
Short TitleWater Air Soil Pollut
Refereed DesignationRefereed