Conventional septic systems involve buried tanks that release wastewater and sewage into sand and gravel drain fields. Most of the 25 percent of American homes using on-site sewage treatment employ this method, according to Wellowner.org. But if a home's original septic system has failed or if the home is in an area where this type of sewage treatment isn't feasible, alternative waste disposal methods may be necessary.
When there is inadequate room for a drain field large enough to properly process waste products, additional filtering systems are an option. One such system involves a recirculating sand filter that passes liquid waste through sand filtration several times before releasing it into the drain field.
Peat filtration is also frequently used in conjunction with traditional septic systems. Before the waste flows into the drain field, it passes through a 3-foot stretch of sponge-like peat. The peat soaks up the waste and spreads it out more evenly. The waste breaks down as it works its way to the bottom of the peat layer to percolate through the soil.
The conventional septic tank breaks down pathogens in waste products with naturally occurring anaerobic--or no oxygen--bacteria. The partly treated material is then sent to the drain fields, where aerobic bacteria in the soil process it further.
Some homes are on soil that isn't permeable enough or is too permeable to allow this process to occur properly. An aerobic system--in which waste proceeds through an additional tank that hosts aerobic bacteria--helps break down pathogens before it delivers the waste to the drain fields. An aspirator is used to inject oxygen into the second tank to promote aerobic bacterial production.
Two alternatives to the conventional flush toilet/septic tank system are the composting toilet and the incinerating toilet. Both are well-suited to locations where the soil is not permeable enough for traditional drain fields, as well as areas where water is scarce. Both these options use little, if any, water for waste disposal.
Aerobic bacteria and fungi in a composting toilet system reduce human waste to only 30 percent of its original mass, according to the Environmental Protection Agency. Fans or heaters evaporate liquid waste, while solid waste decomposes into a nutrient-rich product called humus. This compost-like material can either be buried in the ground or carried away by professional disposal services. Composting toilet systems range in size from single units in each bathroom to whole-house units located in basements.
The incinerating toilet is often used in areas where an existing septic system has failed or where there is inadequate room for conventional drain fields. The incinerating toilet is a self-contained, free-standing unit that requires no water. Both electric and natural or bottled gas models require a vent to the home’s exterior. Both types use high heat to burn solid and liquid waste into clean ash that's easily disposed of.