Slow Sand Filtration and the Impact of Schmutzdecke

Abstract The use of sand media to filter drinking water dates to the early nineteenth century; and rural areas are the primary benefactors of slow sand technology due to the passive nature of the treatment process and the availability of large tracts of land necessary for filter construction. The source water flows by gravity through the filter column, and biomass forms at the sand/water interface (schmutzdecke) that provides an effective layer for removing pathogenic microorganisms. Although source water quality is an important design consideration when communities consider this technique as a treatment method, slow sand filtration is one of the oldest drinking water treatment techniques and is still a viable method of biological water treatment best suited for raw water sources low in turbidity and suspended solids.