Started in 1993, the reconstruction of the Joinville plant, in order to comply with new health standards, was awarded to Veolia Water Solutions & Technologies by EAU DE PARIS, a subsidiary of the City of Paris, in order to upgrade the existing biological treatment process.
This system was chosen to address a major concern : the need to maintain a consistent quality of water with respect to the environment. Low doses of chemicals are used and sludge production is minimised.
At Joinville, more than half a day is spent on water treatment that could be produced in less than one hour using physico-chemical processes.
Slow biological reaction of this type ensures that the water produced is of a high quality.
Specific pretreatment has been incorporated to meet the seasonal characteristics of the water from the Marne: very large quantities of algae, considerable turbidity after periods of storms.
Pretreatment, upstream of slow sand filtration, is modular and can be adapted according to the quality of the raw water :
- for good or average quality water from the Marne :contact coagulation, filter coagulation;
- in the event of planktonic flooding : preozonation, flotation with a low dose of chemicals, contact coagulation, filter coagulation;
- during high turbidity peaks : settling, filter coagulation.
The pretreated water is directed towards the slow biological filtration stage.