Water scarcity has pushed utilities across Europe to look past traditional groundwater and surface water sources. In Flanders, De Watergroep and its sister utility Farys have gone a step further, turning treated wastewater effluent into a genuine drinking water source. Chief Executive Hans Goossens spoke to the Exec Exchange about the Hofstade direct potable reuse plant, the technology behind it, and what it took to bring the public along.

From Effluent to Drinking Water

The project began when Flanders launched its Blue Deal, encouraging utilities to explore wastewater effluent as an alternative water source. Farys, which serves the Aalst region, approached De Watergroep to combine expertise under a joint initiative called Waterunie. The result is a plant treating effluent through nanofiltration, reverse osmosis, activated carbon, and a final chlorination barrier, producing water clean enough for direct supply.

Aquifer Storage as a Seasonal Buffer

Rather than feeding treated water straight into distribution year-round, De Watergroep injects surplus capacity into an aquifer during lower-demand winter months and recovers it in summer when demand peaks. This aquifer storage and recovery step has proven more complex than the treatment process itself, with the utility still refining how to maintain water quality in underground storage over extended periods.

Scaling Up Quickly

Operational since mid-2025, Hofstade started at 1,000 cubic meters per day and is now doubling to 2,000 cubic meters per day. Goossens described performance as going well, with the treatment technology itself proving more predictable than the storage component.

What It Actually Costs

Goossens was direct about the economics. Groundwater remains the cheapest source at roughly 20 cents per cubic meter, while advanced surface water treatment runs 80 to 90 cents depending on investment and depreciation schedules. Hofstade sits just above that range, but not dramatically so, and remains considerably cheaper than desalination once energy costs are factored in.

Monitoring in Real Time

A recurring concern with reuse schemes is microbial risk, particularly E. coli, where conventional lab testing can take 48 hours to return results. Farys and De Watergroep addressed this with continuous online monitoring using flow cytometry technology from Swiss company bNovate, alongside a maintained sampling regime and a final chlorination barrier as a further safeguard.

Building Public Trust

Rather than running a single awareness campaign, De Watergroep committed to ongoing, transparent communication with both the public and technical specialists. Goossens framed Hofstade as a living lab, designed to demonstrate that reuse as a water source is proven and carefully tested rather than a sudden shift in practice.

Hofstade also sits within a longer-term structural story: De Watergroep and Farys are working toward a full merger by 2032, when the intermunicipal agreement underpinning Farys comes to an end. Projects like this one, Goossens noted, reinforce the case for combining the two organizations.