Collected in the sewerage system, domestic and industrial wastewater is brought to the treatment plants.
Domestic wastewater is divided into black water (from toilets) and grey water (from sinks, showers, kitchen, washing machines, etc.).
The wastewater that arrives at the treatment plant contains :
• Organic materials,
• Suspended matter (various wastes, sands) and oils,
• Mineral materials.
The treatment of wastewater takes place in 3 stages: (See diagram) :
• Pre-treatment: Removal of large solid debris, sand and grease by “screening” and “oil and sand removal”.
• A primary treatment: separation by decantation of the solid matters still contained in the water.
• Biological treatment: elimination of organic sludge.
Sludge is often recovered to produce biomethane or heat when incinerated.