Loading Rate (gal/d/ac)
Filter Depth (in.)
Sand Size (mm)
Source: Data from the Massachusetts Board of Health (1912) and Mancl and Peeples (1991).
treated raw or primary effluent wastewater and produced an excellent effluent. A typical intermittent sand filter is shown in Figure 5.1. Intermittent sand filtration is capable of polishing pond effluents at relatively low cost and is similar to the practice of slow sand filtration in potable water treatment. Intermittent sand filtration of pond effluents is the application of pond effluent on a periodic or intermittent basis to a sand filter bed. As the wastewater passes through the bed, suspended solids and other organic matter are removed through a combination of physical straining and biological degradation processes. The particulate matter collects in the top 2 to 3 in. (5 to 8 cm) of the filter bed; this accumulation eventually clogs the surface and prevents effective infiltration of additional effluent. When this happens, the bed is taken out of service, the top layer of clogged sand is removed, and the unit is put back into service. The removed sand can be washed and reused or discarded.
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