Brussels' outdoor swimming pool Flow closed due to water quality

Brussels outdoor swimming pool Flow has had to temporarily close, just a few days after opening for the summer season, after a water quality test provided results not in line with their strict standards aimed at protecting people with lower immune systems.

“We have received the results of the first water quality tests by Brulabo, an independent laboratory,” Flow announced on its website.

“For one important parameter, the values are too high. We do not want to take any risks and, together with the laboratory, have decided to close Flow to the public.”

According to Paul Steinbrück of Pool is Cool - an organisation for promoting outdoor swimming in Brussels, which launched the project - the cause lies with the new purification system.

Since this year, the pool's water has been biologically purified using plants and microorganisms, as is done in many outdoor swimming ponds in Belgium.

Brulabo will conduct a second test to verify the results and Flow will also look at possible measures to address the issue. After that, a decision on reopening will be made.

“This was not the start of the season we had hoped for; however, we were aware of the possibility that hiccups might occur when a new infrastructure is put to use for the first time,” Flow said in an announcement.

“A natural swimming pool is an ecosystem that consists of the swimming pool basin, the different stages of the biological filters and all the living beings in it: from microorganisms that treat the water up to the swimmers in the water. Such an ecosystem can not simply be switched on like a machine but needs some time to develop.”

In coordination with its technical partners, Flow decided to limit this time to the days from filling the pool with clean tap water at the end of June until the opening on Wednesday 5 July – “an ambitious but not impossible plan given the small size of Flow and the specific concept of the filter system.”

Brulabo was asked to do the necessary tests to verify the water quality before the opening.

“Due to internal circumstances at Brulabo we were informed only on Friday morning about the values that were too high for one biological parameter,” Flow explained.

“We then immediately took the necessary steps in coordination with Brulabo and closed Flow, to our personal disappointment, for the days to come until the water quality has returned to normal.”

Flow came about from a grassroots movement for outdoor swimming opportunities in Brussels and is the only open-air summer swimming pool in the capital.

“Flow must still be seen as a prototype – a project that is set up every year again almost from scratch,” its announcement explained.

“We can not rely on a technical infrastructure that has already stood the test of time, every season is a new beginning. You might remember that last year we had to close Flow already on the second day because of a malfunctioning pump of the classical chemical water treatment system.”

The pump was immediately replaced the day after, but this time, Flow said, “given the involvement of biological processes, a prediction of the progress is more difficult. This is a challenge that often comes with ecological approaches.”

Brulabo will conduct tests twice a week with the aim of reopening the swimming pool as quickly as possible.