A septic tank is the most common onsite sewage treatment system in use in Missouri. Nearly 30 percent of all housing units in Missouri use onsite wastewater treatment systems. For at-risk areas, connecting to an adequate public sewer system is generally the best alternative for disposing of domestic sewage from private residences. Where access to a public sewer system is impractical or too expensive, proper siting and design of an onsite sewage system is critical to avoid its premature failure. Misuse of individual sewage systems results not only in water quality problems and nuisance conditions, but also in costly repairs to rehabilitate a failing system. Failing systems include both those that you can see and smell and those that seep effluent, or waste liquids, into groundwater supplies before the soil can properly remove disease-causing pathogens.
A septic tank system consists of three major components: the septic tank, a distribution device and an absorption field. A septic tank is a large, watertight, corrosion-resistant, buried container that receives raw sewage from the plumbing drains of the home. In it, solids are separated out of the raw sewage and are partially digested by anaerobic (oxygen-lacking) bacteria. After primary treatment in the septic tank, the liquid effluent flows through the distribution device, which ensures that equal quantities of effluent go to each pipe in the absorption field. The absorption field is a subsurface leaching area within the soil that receives the liquid effluent from the distribution device and distributes it over a specified area where it is allowed to seep into the soil. The filtering action of the soil, combined with further bacterial action, removes disease organisms and treats the harmful material in the effluent, completing the treatment process so that the water is recycled to the surface or groundwater source.