If you live in an incorporated area such as a city or town, your home is probably connected to a centralized waste-treatment, or sewer, system. The Environmental Protection Agency estimates that, as of 2007, 80 percent of homes in the United States have this type of service. If you are not connected to a centralized system, the best septic solution for you will depend upon how much land you have available, the type of soil you have, and your feelings about using the system to benefit the environment.
Mound Systems
The National Small Flows Clearinghouse at West Virginia University describes a mound system as having a septic tank for initial sewage treatment, a pump or dosing chamber, and a system of distribution pipes that flow through trenches of sand and gravel covered by a mound of soil. Mound systems are good choices for locations with high water tables, porous bedrock, or soils that permeate too quickly or slowly to provide adequate effluent filtering.
With a mound system, waste flows to a septic tank, separating into solids, liquids, and floating solids like grease or lighter waste. The liquid flows from the septic tank to the pump or dosing chamber, which controls the further flow of liquids through the perforated distribution pipes to ensure the mound and surrounding ground is not flooded. The effluent is filtered through sand and gravel before returning to the soil. The mound is usually overplanted with grass or groundcover to prevent erosion.
Lagoon Systems
According to the University of Missouri Extension, a lagoon system can operate effectively for up to 30 years, making it a low-maintenance septic solution. Wastewater flows from the home to a septic tank for separation, and liquids flow down a watertight pipe to a lagoon or pond. Once in the pond, the effluent is treated by wind, sunlight, temperature and microscopic plants and animals that feed on and digest the effluent, creating a natural method for processing household wastewater. Lagoons can be self-contained, with no run-off, or they may discharge liquid onto a grassy area that uses it for moisture and nutrients. The lagoon's size varies, depending upon average rainfall, evaporation rates, and water usage; however, lagoon depths will be around 3 feet to allow for adequate sunlight penetration.
Aerobic Systems
Aerobic systems use pumped air and a greater variety of bacteria to hasten the decomposition of liquid effluents and solids, according to the Idaho Department of Environmental Quality. Aerobic septic tanks usually have two chambers. The first chamber filters out some solids to improve the efficiency of the bacteria in the second chamber. The second chamber contains the bacteria, a mixing rotor that moves through solids deposited in this chamber, and an air pump. Once the wastewater has been treated, it can flow to a drain field or be used through a spray system that distributes the water over lawns, making aerobic systems a good choice for reuse of domestic wastewater.
References
- Environmental Protection Agency: Septic Systems Fact Sheet
- National Small Flows Clearinghouse, West Virginia University: Mounds-A Septic System Alternative
- University of Missouri Extension: Residential Sewage Lagoon Systems
- Idaho Department of Environmental Quality: Aerobic Treatment Systems and Drainfields
- US Inspect: Septic Systems Overview: Common "Alternative" Systems
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