Chemical Science Test - 6

Pretreatment may include a sand or grit channel or chamber, where the velocity of the incoming sewage is adjusted to allow the settlement of sand, grit, stones and broken glass.

Coagulation can be carried out by passing ozone through waste water.

In primary treatment, large sized particles are filtered through screens and residual water is subjected to sedimentation.

Secondary treatment involves aerobic digestion of the organic waste.

In tertiary treatment, the waste water is treated with lime to remove phosphate followed by coagulation.