C14.3 - Treating waste water

Screening

Large objects removed from the sewage using a metal grid

Primary treatment

Solid sediments allowed to settle and the sludge is pumped to a storage tank. The effluent moves to the next tank

Secondary treatment

Useful bacteria added to break down harmful microorganisms aerobically

Final treatment

Useful bacteria allowed to settle and can be reused or put with sludge

It can be put through a bed of sand and sterilised with UV light or chlorine

Uses of sludge

Can be dried and used for:

• burn to generate electricity

• fertiliser