Treatment for drinking water production involves the removal of contaminants from raw water to produce water that is pure enough for human consumption without any short term or long term risk of any adverse health effect. Substances that are removed during the process of drinking water treatment include suspended solids, bacteria, algae, viruses, fungi, and minerals such as iron and manganese.

The processes involved in removing the contaminants include physical processes such as settling and filtration, chemical processes such as disinfection and coagulation and biological processes such as slow sand filtration.

Measures taken to ensure water quality not only relate to the treatment of the water, but to its conveyance and distribution after treatment. It is therefore common practice to have residual disinfectants in the treated water in order to kill any bacteriological contamination during distribution.

World Health Organization (WHO) guidelines are a general set of standards intended to be applied where better local standards are not implemeted. More rigorous standards apply across Europe, the USA and in most other developed countries. followed throughout the world for drinking water quality requirements.

Empty aeration tank for iron precipitation

Tanks with sand filters to remove precipitated iron (not working at the time)
A combination selected from the following processes is used for municipal drinking water treatment worldwide:

Pre-chlorination for algae control and arresting biological growth
Aeration along with pre-chlorination for removal of dissolved iron and manganese
Coagulation for flocculation or slow-sand filtration
Coagulant aids, also known as polyelectrolytes – to improve coagulation and for thicker floc formation
Sedimentation for solids separation, that is removal of suspended solids trapped in the floc
Filtration to remove particles from water
Disinfection for killing bacteria viruses and other pathogens.
Technologies for potable water treatment are well developed, and generalized designs are available that are used by many water utilities (public or private). In addition, a number of private companies provide patented technological solutions. Automation of water and waste-water treatment is common in the developed world. Capital costs, operating costs available quality monitoring technologies, locally available skills typically dictate the level of automation adopted.