Closed tank in which sludge is in direct contact with domestic wastewater passing through the structure. Solid organic matter is partially decomposed by the action of anaerobic bacteria.
The digester-decanter receives all the domestic wastewater from the house and pretreats it. Composed of two compartments in which the decanting (faster than in a septic tank) and the digestion of the organic material present in the wastewater take place. Anaerobic bacteria, without oxygen, are responsible for metabolising organic matter by gasifying, hydrolysing and mineralising it.
These systems are considered to have a 35 % BOD5 performance and an 87% SS performance.
The system complies with European Standard EC annex ZA EN 12566-1 (SEPTIC TANKS).