Septic tank
- Slovak term: Slovenský termín
- Watertight chamber for the retention, partial treatment, and discharge for further treatment, of sewage (WHO 1992).
- An underground tank that passively treats wastewater by a combination of solids settling and anaerobic digestion. The effluents may be discharged or may overflow into soak pits or small-bore sewers (WHO 2006).
Explanation
A septic tank is a water tight tank, usually located just below ground, with one or two compartments. Waste is flushed into the tank by water from a pipe that is connected to the toilet. It functions as a storage tank for settled solids and floating materials (e.g. oils and grease). Some of the solids float on the surface, where they are known as scum, while others sink to the bottom where they are broken down by bacteria to form a deposit called sludge. The storage time of the wastewater in the tank is usually between 2 and 4 days. The overflow from a septic tank is directed to a leach pit or trench. The liquid effluent flowing out of the tank is as dangerous to health as raw sewage and should be disposed of, normally by soaking it into the ground through a soakaway, or by connecting the tank to sewer systems (WHO 1992).
A septic tank is used to dispose of sewage when a building is isolated from or cannot be connected to a sewerage system, the sewage being liquefied and purified by active bacteria where an anaerobic digestion takes place. The excess or overflowing liquid is known as the effluent (Standards New Zealand 1998).
Example
A septic tank is usually rectangular or cylindrical in shape and made of concrete, concrete blocks, or of a plastic material. It is buried underground on the property of the dwelling it serves. Alternatives are available including aerobic wastewater treatment systems, aerobic sand filters, composting toilets, reed beds and other systems utilising wastewater treatment technologies. Connection to a community disposal scheme may also be an alternative where available (World Plumbing Council Working Group 2008).
References
- WHO (1992) A guide to the development of on-site sanitation
- WHO (2006) Guidelines for the safe use of wastewater, excreta and greywater
- Standards New Zealand (1998) Glossary of Building Terms NZMP 4212:1998
Links
- WHO — The Health and Environment Lexicon
- WHO (2002) Healthy villages: a guide for communities and community health workers
- WHO (2003) Linking technology choice with operation and maintenance in the context of community water supply and sanitation: A reference document for planners and project staff
- UNEP (1997) Water pollution control: a guide to the use of water quality management principles
