4. Treatment plants for groundwater or deep water

4.1 Main problems encountered in groundwater intended for drinking water supply

For groundwater, quality can be :

• excellent ;

• naturally deteriorated by episodic turbidity (water in karstic zones), by microorganisms, by iron, manganese, ammonia, arsenic, selenium, fluorine, or too "hard" to be distributed;

• deteriorated by anthropogenic activities leading to the presence of nitrates, pesticides and metabolites, chlorinated solvents or other known or emerging micropollutants.

The corresponding processes are described schematically below, with a few examples of drinking water production plants in France.