Sewer-to-tap recycling water project to launch in west France

A pioneering environmental project in western France is to start sending water recycled from sewers into domestic taps next year.

Using existing filtration, reverse osmosis and disinfecting techniques, the system will recycle 25% of water flowing from the town of Les Sables-d’Olonne in the Vendée.

The water will be taken from an existing sewage plant which cleans it to standards good enough for sea discharge. In a new plant, it will then be thoroughly cleaned, before being sent through 25km of pipes to a specially constructed marshland, where it will pass into a river feeding a drinking water reservoir.

Water from the reservoir is then treated normally before feeding into household taps.

Up and flowing

“We had to do something to boost our water supply because we realised that, even in good rainfall years, we will have a significant deficit by 2030,” Caroline Rautureau of Vendée Eau told The Connexion.

“Various solutions were looked at and costed, including desalination of seawater, but they were far too expensive, both in terms of cash and damage to the environment.

“The system we developed, with techniques used elsewhere in the world, made the most sense.”

Team members studied a plant in Namibia, which cleans water up to drinking standards, before deciding on the final design.

The new plant was completed in 2023 and will run for a year sending the ultra-clean water to the sea to make sure quality standards remain constant.

Then, from next year, water will be diverted into the recycling system.

“So far, all the tests on water from the new plant have been absolutely fine. You can drink the water without any problems as it comes out of the unit,” said Ms Rautureau.

One of the reasons the clean water has to pass through the artificial swamp before going into the river upstream of the dam, is that the treatment leaves it demineralised, and the swamp returns some minerals to it.

The system started before the government promised new laws and decrees to make recycling water in France easier. At the moment, only 1% of all tap water is reused in the country, with many health authorities imposing a blanket ban on any reuse.

Elsewhere in Europe most countries have systems which allow an average of 10% of water to be reused, mainly for watering parks and sports grounds.

The Vendée project is now running under local exceptions to rules, for a fixed trial period which finishes in 2027.

Ms Rautureau said the company was confident that the €24.5million scheme will be allowed to continue, with a temporary extension of the 2027 deadline if needed.

Half of the money came from the company, and the rest from government and local government grants.

“This system is planned from the start to allow the water to be drinkable, which is not common,” said Ms Rautureau.

“Since we started publicising it there has been enormous interest from all over the country, and I expect some other coastal towns will copy it, especially if there is government action on recycling rules,” she said.

“In Vendée we have three other coastal towns where similar plants could be built.”

Rainfall shortage

Vendée, the second sunniest part of France after the Mediterranean departments, is also one of the driest, with average rainfall of around 880mm a year.

Added to the low rainfall is a very deep water table, which means that boreholes, used as the main water source in most of France, are not practical.

Rivers, lakes and dams account for 90% of drinking water in the department.

“Our reliance on surface water means the system is only suitable for seaside towns because, inland, all the water treated in sewage plants is put back in the rivers, which would otherwise dry up,” said Ms Rautureau.

She said the company had ensured the public was informed about the project from the start.

“This has meant there is very little opposition to it,” she said.

“People know the situation we are in with water and see that it makes sense.”