A septic tank is an underwater sedimentation tank used for wastewater treatment as a result of biological decomposition and drainage. Septic tanks can come in all different shapes and sizes. Older tanks may be brick built or concrete, modern ones are made of reinforced plastic. Septic tanks differ to cesspits as they are not sealed. Bacteria inside the tank breaks down the solid waste decomposing it more rapidly allowing the liquids to separate.
Septic tanks don’t have any mechanical parts or perform any treatment of the waste. The process is:
- Waste enters the tank.
- Waste separates into three different layers.
- Middle layer of separated waste water leaves the tank via soakaway system.
- Solids are broken down due to the bacteria.
WHAT IS A SOAKAWAY?
A soakaway system is a network of slotted or perforated pipes typically built to reduce standing surface water. They consist of a large hole or pit that receives surface rainwater via a drainage pipe, which then percolates through the soil. Designed to store a large volume of water, a soakaway slowly releases water into the ground (i.e. in a heavy downpour) to help prevent high volumes of runoff entering the main sewer system and overwhelming it. By installing a soakaway the risk of flooding is reduced.
Soakaways can also be used to dispose of the effluent from septic tanks. As part of a septic tank system, the soakaway treats the effluent, allowing waste water to percolate through the sub soils via a drainage field – designed to add additional treatment to the water. Remaining contents of the tank are removed at regular intervals by a tank emptying company.
WHAT IS A DRAINAGE FIELD?
A drainage field is a system of infiltration pipes placed in trenches to safely discharge effluent to the ground. Sewage effluent, even from a sewage treatment plant, contains bacteria and viruses. These must be digested by the aerobic natural soil bacteria, which cannot live lower than 1 metre below ground, due to the lack of air. The field must be constructed in a certain way that allows for the effluent to be treated in the soil through aerobic digestion.
WHAT IS A CESSPIT/ CESSPOOL?