C14.3 - Treating Waste water

Screening

Removes large solids and grit from the water. The sewage travels through a large metal grid which traps the solids.

Primary Treating

Solids allowed to settle at the bottom

Large paddles push sludge towards the middle + it is taken for further treatment

Effluent flows into the next tank

Secondary treating

Useful bacteria feed on a remaining microorganisms, breaking them down aerobically

Final treatment

Useful bacteria settle down to the bottom of the tank where it can be reused/disposed of with sludge

The waste water can be put pack into the river but may also go through UV light sterilisation

Treating sewage sludge

Sewage sludge broken down anaerobically and dried

Could be fertiliser or burnt for energy