The dirty drain water containing urine and faeces which is carried from our homes by the underground pipes (called sewers) is called sewage.

Sewage is disposed off by treating it at the sewage treatment plant (or sewage works). The treatment of sewage produces clean water which is discharged into the river. The organic matter present in sewage is ‘digested’ in the digesters of sewage treatment plant to produce ‘sewage gas’ (which is kind of biogas) and manure.