Septic tank
The septic tank (also septic tank, septic tank , lavatory pit, septic tank, septic tank with flow, septic tank for sewage, septic tank ) is, in contrast to the manure or slurry pit, a pit for the makeshift cleaning of small amounts of sewage for individual houses that are not connected to the public sewer system. It is the oldest and structurally simplest form of wastewater treatment . Their operation has been prohibited in Germany since 2016 (except as a drainless cesspool , see below) for reasons of environmental protection.
A septic tank with no drainage and permeable walls and floor is called a septic tank .
Construction and function
A septic tank works on the principle of sedimentation. According to this, it consists of a pit with a container in which the non-water components of the wastewater, which are heavier, sink under their own weight in the standing water and are deposited on the bottom as sewage sludge (sedimentation). The excess water is either regularly sucked off by a suction vehicle , diverted into a body of water or seeps into the ground.
More elaborate septic tanks consist of three chambers. In such a modern three-chamber septic tank, the wastewater is decomposed anaerobically . Therefore there are no remains of faeces or toilet paper ; these pits can almost keep up with small sewage treatment plants in their cleaning performance, apart from the nitrate content of the treated wastewater.
Efficiency of wastewater treatment
The waste water is clarified through the sedimentation, but many harmful substances remain in the water. The nitrogen dissolved in the water caused by putrefaction is particularly problematic . Nitrogen and bacteria, which multiply strongly in the course of the decomposition processes of the organic material, pollute the soil and waters into which they are discharged.
The modern three-chamber septic tanks were a bit more effective than the older single-chamber septic tanks, which mostly only had one overflow. A thorough and sufficiently environmentally friendly cleaning could not be achieved with these septic tanks either.
distribution
Before 1990, the septic tank was a common form of wastewater treatment in many small towns in East Germany . After German reunification, the aim was to connect as many properties as possible to the public sewer system, as the public sewage treatment plants enable more thorough wastewater treatment . Until the turn of the millennium, septic tanks were only found in remote locations or in buildings outside of built-up areas where the construction of a connection to the public sewer system would be too costly or not possible for topographical reasons.
Although the water quality has improved significantly again since the 1980s, the EU has been promoting water protection in European rivers and lakes since 2001. Wastewater should no longer be discharged into rivers and lakes, which would lead to severe changes in the water balance and threaten the natural flora and fauna in the water. In 2015, the ban on septic tanks came into force.
Since then, only so-called sewer-free sewage collection pits have been permitted in Germany, the contents of which are pumped out by a disposal company at regular intervals and transported to the sewage treatment plant. In order to avoid the costly disposal, which can only be carried out by special companies with the appropriate permit, many homeowners convert to a modern small sewage treatment plant or plant-based sewage treatment plant . Collecting pits must be checked regularly for their tightness so that no sewage can seep into the ground.
