what is gray water, this solution for watering fields?

The subject of water, with possible restrictions, was raised on Monday February 27 by the Minister for Ecological Transition Christophe Bechu and the prefects who manage the water resource in the country. The reuse of wastewater is one of the solutions, even if it remains very marginal in France. However, the water that comes out of treatment plants represents more than a billion cubic meters of water, mostly discharged into nature or into rivers.

Water coming out of sewage treatment plants

There are about 150 irrigation projects with gray water. Since the 1990s, almost Clermont-Ferrand, around fifty of farmers irrigate 750 hectares of crops with the water that comes out of the city’s wastewater treatment plant. In Noirmoutier, the early potatoes are watered with the water that comes out of the treatment plant. This water undergoes a bacterial treatment, then it is subjected to the rays of the sun in tanks. It is regulated and the health thresholds are not the same for vegetables or fruit: they are more demanding for consumption without cooking.

In 2022, the government took a first step towards expanding uses, authorizing the experimental use of this water to wash cars and roads. A decree is currently before the council ofEstate for “to soften and clarify certain things”, According to the latest statements from Marc Fesneau, the Minister of Agriculture. AT Paris, a system has been tested since 2019 by the town hall to use wastewater to heat buildings.

More expensive water

According to specialists, there is an accumulation of brakes. The first is cultural because, before the drought of last summer, offering fruit and vegetables watered with water that comes out of a treatment plant was not a selling point. The second obstacle is financial. Treating water with sanitary standards increases the price of water compared to what a farmer can spend to draw from a river or underground.

Some specialists therefore propose to separate upstream, in homes, toilet water from kitchen or bathroom water to limit the cost of treatment. France now has an objective for the use of this resource. It should triple the volume within two years, which will remain relatively marginal.