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Slow Sand Filter Basics. The sand provides a large surface area for “good” micro-organisms to attach and be retained in the filter (high biomass retention time ).
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Slow Sand Filter Basics • The sand provides a large surface area for “good” micro-organisms to attach and be retained in the filter (high biomass retention time). • Influent dissolved organic matter (DOM) is removed by microbial mineralization (CO2 and H2O) by the good bacteria (reducing color and odor). • Influent particles are removed by attachment to (collection on) the large surface area (reducing turbidity). • The top Schmutzdeckelayer enhances both filtration and mineralization of particles and DOM. • Slow sand filters can be operated as continuous flow or batch reactors. • The long hydraulic retention time (8 hrs) allows for complete mineralization, and reduces biomass growth that would clog the filter.