2. Malfunctions impacting reliability and performance

2.1 Reminders of water chemistry

The water available before treatment for use as make-up water has two different origins:

• surface water (rivers): in this case, coagulation-flocculation pre-treatment is essential;

• Borehole water (groundwater) or mains water: no pre-treatment required.

Natural surface waters contain suspended solids: solid particles of a mineral (sand, silt, clay) or biological (bacteria) nature. Fine particles smaller than 1 µm are the source of a phenomenon known as "fouling", which contributes to the creation of biofilm at the water-exchange surface interface between the surface water sampling point and the pre-treatment unit (softener, osmosis unit)....