In 2019, the Syndicat Mixte du Bourdary, which includes the town of Aubenas in the Ardèche, called on Naldeo to help it replace its outdated wastewater treatment plants. The town's ambition was to equip itself with a modern facility, exemplary in terms of water resource treatment, respect for the environment and climatic impact.
Right from the design phase, Naldeo incorporated several innovative features into the project. Firstly, a sludge methanization unit produced biomethane to supply local town gas, while reducing the volume of sludge to be disposed of. Secondly, a sand washing unit has been installed to enable sand to be reused in public works, notably for backfilling trenches. In addition, advanced technologies such as variable frequency drives, screw aeration boosters and heat pumps have been installed on the treated water to generate energy savings. In addition, part of the treated water is reused for the plant's own needs. Finally, tertiary wastewater treatment was integrated into the design process.
Since its commissioning at the end of 2022, the plant has achieved remarkable results. It injects 200,000 m³ per year of biomethane into the municipal gas network, equivalent to the consumption of 200 homes. What's more, it has reduced the amount of sludge to be transported and treated by over 60%. Finally, it discharges water that meets bathing water quality criteria, even when the flow of the Ardèche is low.
The community now has a modern, high-performance, environmentally friendly facility capable of treating the effluent of 49,000 inhabitants. Representing an investment of 17.5 million euros, the plant is designed to meet the syndicate's needs for the next 30 years.
The Naldeo group is a leading engineering and consulting firm specializing in the climatic and environmental transition of industries and local communities.