Putting construction groundwater to good use is goal of volunteer group


Did you know that construction sites pump up groundwater that then just flows into the sewer? A new non-profit group is trying to get city services to use it

Use it or lose it

The idea for the project came to them in the summer of 2018, when Brussels – much like the rest of the country – was in the middle of a dry and crushing heatwave.

The handful of locals behind Buumplanters, a group of volunteers working to improve the city’s biodiversity, needed to water the trees they’d planted throughout the city – trees that had been thirsting for rain for some time.  

One of the volunteers, Yoeri Bellemans, came across a local construction site and saw an installation pumping up gallons of water. It disappeared into a sewer drain.

Wouldn’t it be possible to use that water to water the trees they’d planted, he wondered? Eighteen months later, and Bellemans, 37, has been able to interest major water and building companies as well as city services that his plan is a viable one.

Groundwater sharing

Opensource.Brussels, the project that Bellemans launched with two other locals, aims to create a marketplace for groundwater. It works to connect city services in need of water with building companies actively pumping it out of the ground.

Construction workers pump up groundwater from building sites because the upward pressure would otherwise jeopardise the building’s stability. This pumped water is almost always discharged into sewage.

Even though such groundwater is not drinkable, it doesn’t make any sense to let it go to waste, Opensource.Brussels says, particularly in times of growing water scarcity. They now want to develop an app that will create a marketplace for such groundwater.

Almost everywhere in Brussels, and also in Flanders, streets are systematically cleaned with pure drinking water

- Yoeri Bellemans of Opensource.Brussels

Many of the city’s services in fact use drinking water for a variety of applications when they could be using groundwater. “Almost everywhere in Brussels, and also in Flanders, streets are systematically cleaned with pure drinking water,” says Bellemans. “What you’re using to cook your spaghetti is what they’re using to water trees.”

No-one knows just how much groundwater is currently being drained to sewers – from where it goes onward to wastewater treatment plants before being released into surface water like rivers.

But a proof-of-concept test Opensource.Brussels conducted a couple of months ago offers some idea. During this test, various city services together filled up 15 vehicles with pumped water from a construction site at Tour & Taxis.

From left: Gil Duarte de Cruz, Lieve De Witte and Yoeri Bellemans of Opensource.Brussels

“The capacity was approximately 1,000 cubic metres per day, so that means that one million litres of water is pumped up and discharged into sewage every day,” Bellemans explains, contrasting the amount of water to that held by an Olympic pool. “That means with a pump like that, you can fill such a pool in two-and-a-half days. And you should know that some pumping installations run for up to a year or even 18 months.”

An added problem is that public treatment plants are designed to clean dirty water – the water from our showers, toilets, cooking and so on. The fact that so much fairly uncontaminated groundwater is directed toward these plants lowers their efficiency.

“A public treatment plant actually requires dirty water to function properly,” says Bellemans. “So diverting the water to treatment plants via sewage means that they are able to function much less efficiently.”

There’s an app for that

The goal of Opensource.Brussels is to create an app that will direct every city worker in the Brussels-Capital Region to the nearest construction site with an active pumping installation, where they can fill up their water tank. “They’ll have a real-time overview showing where water is available in the area in which they’re working,” he explains. “We’ll try to send the drivers to the nearest unit that has water of a quality that meets their needs.”

It’s such a genius, let alone simple, concept that it seems surprising that the project still hasn’t gotten off the ground since that summer of 2018. That’s because developing a digital platform, building prototypes for the standard water tanks that will be used on construction sites, and hiring and paying engineers and developers to do all that costs money – hundreds of thousands of euros.

They’ll have a real-time overview of where water is available in the area in which they’re working

- Yoeri Bellemans

Opensource.Brussels applied for a subsidy from Brussel Leefmilieu, the Brussels-Capital Region's environmental agency, in May of last year. It’s not yet clear when they’ll find out whether they got the money, but Bellemans says that they’ll continue working to make their vision of a “blue network” a reality, even if they don’t get the grant.

They’ve also gotten financial pledges from several private companies who want to help them develop the app. But, Bellemans says, public funds would be the preferable option because the government is a key player in all this water spillage.

In any case, the city workers who drive all those sweeping vehicles, who water municipal flower beds are already game, he says. “When we talk to people on the ground, to the people who’ve tested our proof-of-concepts … all these people say: ‘Yes, we want this. It makes sense that we would do it this way’.”

Photo top: A test last autumn saw a construction project at Tour & Taxis offering pumped up groundwater to Schaarbeek’s municipal services
©Photos courtesy Opensource.Brussels