INAUGURATION OF THE WASTE WATER TREATMENT PLANT OF DERVAL (44)

The inauguration of the new plant of Derval was held on November 6th, 2009. Mr Trioulaire, subprefect of Chateaubriant and Mr Daniel, vice president of the council department, were present. The former plant using lagooning process didn't ensure anymore a correct treatment of raw water. In order to respect the strictest discharge standards (carbon - nitrogen and phosphorus), the town council has decided to have a new plant built, to conform with the national policy of surface water quality improvement.

The new plant is sized for treatment of 4 000 IE discharge. A 250 m³ storm water tank ensures control of flows. During low water season, treated water is discharged in existing lagoons and in the stream "Le Pas Guillaume".

This site was used to recover treated water from Derval's diary in the existing lagoons used for storage; treated water was then discharged in the farmers' lagoons for irrigation. Further to the closure of the diary, the process is still the same. A lifting station empties this storage and feeds farmers' lagoons.

Sludge are stabilized by mechanical thickening (draining table) and re-used in agriculture.

In the end, NDEI has supplied a new and modern plant conforming to current environmental standards.