Since last Thursday, five pumpers have been reasoning around the Nakache outdoor swimming pool in Toulouse, one of the largest outdoor pools in Europe with its 150 meters long and 50 wide. Every day, tank trucks and vans equipped with tanks take turns around the site built in 1931 and which this summer welcomed no less than 127,000 visitors.
But unlike previous seasons, the emptying of the 6,100 m3 of water will not end up in the wastewater network. This year, for the first time, the town hall has taken the initiative to recycle it, using it to water its green spaces, supply its ornamental ponds in the parks or for cleaning public roads. “Drought and global warming are pushing us to ask new questions that we did not ask ourselves before. The idea came at the end of the summer and we wondered if we could not recover this water, ”explains Jean-Luc Moudenc, the mayor of the Pink City.
Already 500 m3 reused
Before it could be used elsewhere, it had to be left to rest. “We stopped the public reception system on August 29. It took the next day for the treatment to end, then a little over two days for the chlorine level to naturally evaporate on contact with the air. Chlorine and PH levels were measured daily to ensure water quality was fit for reuse. We let time do its thing, ”explains Olivier Perez from the technical department at the city’s sports department.
This Tuesday, nearly 500 m3 of water had already been pumped. And several thousand liters will still be there by the end of the week. But certainly not beyond, because afterwards, the algae that develops in the pool should make it unsuitable for use.
To be able to make this operation effective, the city had to hire water tankers, which, financially, certainly compensates for the water savings that are made during these days. Above all, this makes it possible to provide a solution for irrigating the young trees recently planted and to ensure the survival of the fish and the biotope of the water points of the public gardens, the replenishment of which was prohibited by prefectural decree due to the drought.
A first experience that could be repeated over the next few years. Consideration of extending it to other outdoor pools is also under consideration, even if their size makes the operation less interesting, not to mention their more complex access.
In Bourg-lès-Valence, in the Drôme, the town hall offered residents to recover used water from their private swimming pools in order to water the green spaces. An idea that could also be emulated in the long term.