Water treatment refers to the process of improving water quality by removing undesirable physical, chemical, or biological matter.

There are specific water quality objectives to be met, whether for health reasons and/or aesthetic reasons or as a condition for an operating permit. More complex treatment can also condition the water for factors such as pH levels.

Two major types of water treatment for small water systems are:

• Filtration; removes matter from water by use of filter media, e.g. screens.
• Disinfection; kills or inactivates biological agents such as bacteria and protozoa.