Slow Sand Filtration
A slow sand filter is merely a bed of sand, confined within a box, with appurtenances to deliver and remove water. Figure 13.1 illustrates the main elements of the process and technology.
Slow sand consists of a filter box with appurtenances that measure and control flows for operation, including inflow, filtered water drainage, backfilling after scraping, and headwater drainage. All of this is to support a bio-depthfiltration process within the filter bed, coupled with a
straining process by a schmutzdecke. Slow sand filtration may be characterized as a passive process in that it occurs without operator intervention.