Raw sewage enters the first compartment of a two-compartment septic tank (concrete, fiberglass, or plastic) that provides about 48 hours of retention at the rated capacity. This compartment provides primary treatment; settleable solids accumulate on the bottom and floatable solids accumulate on the surface.
Effluent from the clear layer flows into the second compartment of the tank, which provides about 16 hours of retention at the rated capacity and contains media to provide additional surface area for BOD reduction. The liquid effluent from the septic tank mixes with the percolate from the filter media in the reservoir below the media. When enough water enters the reservoir, a float activates the treatment process.
During the trickling filter processing, wastewater is repeatedly sprayed over and trickles through the filter media. Air from the outside is drawn in during the recirculation process through the air intake snorkel. Sloughed biomass, made up of organisms and other solid material, is washed out of the media pillows and into the bottom of the processor. A portion of the treated effluent is recycled to the septic tank to enhance the removal of nitrogen by reduction of the nitrate under anoxic conditions in the septic tank. The solids are periodically returned to the first compartment of the septic tank by a dedicated sludge return pump. After treatment, the effluent flows to a decant chamber for pumping to the dispersal system.