Sewage flowing into Brussels canal

Brussels has 37 storm basins and related buffer structures, but they aren’t being well-utilised during heavy rainfall as sewage is now flowing into the canal, according to Environment Minister Alain Maron (Ecolo).

Heavy rainfall in Brussels has taken its toll on the canal, Bruzz reports: in early June last year, the water was brown and there were dead rats floating on the surface after the city’s sewage system became overwhelmed.

The incident was not an isolated one, either. The sewage system overflowed into the canal near Sainctelette 19 times in 2019, according to the non-profit association Canal it Up.

In the river Senne, discharges are even more frequent. Every year, some 10 million cubic metres of water flow from the sewers into the watercourses in Brussels.

Buffer capacity isn’t being used during heavy rainfall

On paper, Brussels has a lot of buffer capacity with its 37 storm basins and other buffer volumes, which are intended to ensure that extra rainwater is collected during heavy storms.

But the storm drains are hardly used during heavy rainfall, Maron said when answering questions in the Brussels Parliament in response to an open letter from Canal it Up.

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“To reduce the volume of water that overflows into watercourses, we need to invest in dynamic management. The idea is to use a system of valves and sensors to ensure that the basins are filled with water from smaller rainfalls, which today cause overflow anyway,” Maron said.

This dynamic management has since been included in the water management plan, and water company Hydria will invest €4 million in the Maalbeek basin by 2025.

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Brussels also wants to disconnect the rainwater flow from the sewerage network more often and focus on integrated management of rainwater, taking an approach modelled after cities such as Copenhagen, whose once filthy canal is now clean enough for recreational swimming.