primary treatment mechanically removes solid matter Secondary treatment uses bacteria to break down dissolved organic matter. Tertiary treatment uses chemicals to remove additional contaminants.

Water treatment describes the processes used to make water more acceptable for a desired end-use. These can include use as drinking water, for use in industrial processes or to allow discharge into the environment without adverse ecological impact. These processes may be physical such as settlement, chemical such as disinfection or coagulation or biological such as lagooning, slow sand filtration or activated sludge.