slow sand filter


slow sand filter

[′slō ′sand ‚fil·tər] (civil engineering) A bed of fine sand 20-48 inches (151-122 centimeters) deep through which water, being made suitable for human consumption and other purposes, is passed at a fairly low rate, 2,500,000 to 10,000,000 gallons per acre (23,000 to 94,000 cubic meters per hectare); an underdrain system of graded gravel and perforated pipes carries the water from the filters to the point of discharge.