Sand Filter

Constructed beds of sand or other suitable granular material usually two to three feet deep. The filter materials (called media) are sometimes contained in a liner made of concrete, plastic or other impermeable material. Depending on the design, the filter may be situated above ground, partially above ground or below ground, and the filter surface may be open or covered. Partially treated wastewater (e.g., from a septic tank) is applied to the filter surface and receives biological treatment as it slowly trickles through the media. In most sand filters, the wastewater then collects in an underdrain and flows to final treatment and dispersal. <