Carré de Réunion (Versailles) - France

The largest membrane treatment unit in Europe

OTV, subsidiary of Veolia Water Technologies, led the Carré de Réunion wastewater treatment plant project in Versailles (France).


The client’s needs

  • To improve the performance of the wastewater treatment in compliance with the Water Framework Directive (WFD).
  • To increase the plant's treatment capacity to meet demographic and environmental needs.
  • To reduce the nuisance of the activity to better preserve the residents’ living environment.


The solution

After pre-treatment, the water is sent to the biological treatment units where two efficient technologies are combined: biological treatment by activated sludge followed by Biosep® technology for filtration by submerged membranes.
Exelys®, a continuous thermal hydrolysis process, treats the sludge using thermal lysis by combining heating and pressurization. This increases the hygienization of the sludge and improves the quantity of biodegradable organic matter by destroying the cell walls present.

Air treatment
Two types of deodorization have been installed:

  • Aquilair™ treats the air of all the buildings (three towers  - acid, soda, bleach) to destroy malodorous molecules.
  • Biologically treats the air coming from the membrane cells thanks to natural support. An electronic nose ensures a permanent monitoring by continuously analyzing the odors of the site.

The advantages

  • Zero odor nuisance.
  • Energy control.
  • High quality of rejected water.

Key figures

  • Treatment capacity: 340,000 PE
  • Wastewater treatment volumes: 13,000,000 m3/year
  • Peak flow rate: 6,000 m3/h
  • Biogas production : 15 to 30% more
  • Sludge production: 20 to 40% less sludge produced