Water treatment describes those processes used to make water more acceptable for a
desired end-use. These can include use as drinking water, industrial processes, medical
and many other uses. The goal of all the water treatment process is to remove existing
contaminants in the water, or reduce the concentration of such contaminants so the water
 becomes fit for its desired end-use. One such use is returning water that has been used
 back into the natural environment without adverse ecological impact.The processes involved
 in treating water for drinking purpose may be solids separation using physical processes
such as settling and filtration, and chemical processes such as disinfection and coagulation.
 Biological processes are also employed in the treatment of wastewater and these processes
 may include, for example, aerated lagoons, activated sludge or slow sand filters.