Wastewater treatment
Gamechanger for Clean Water: First Micropollutant Post-Treatment
A few years ago, Aquafin gave the starting signal, and today Flanders ranks among the European frontrunners with the first full-scale quaternary treatment. The installation not only improves the quality of local waterways, such as the Grote Struisbeek, but also provides valuable insights for future applications both domestically and internationally.
The well-being of ecosystems and humans directly depends on the quality of our surface water. Clean waterways are indispensable for drinking water, recreation, and biodiversity. Given the increasing concerns about micropollutants – think of residues from medicines, pesticides, and other harmful substances – improving our water treatment systems is crucial.
- Client
- Aquafin
- Location
- Aartselaar
- Expertise
- Feasibility study, preliminary design, permit application, tender documents, execution supervision, process design, electromechanics, civil engineering, electricity, automation, and infrastructure
New Milestone in Water Purification
At Aquafin’s wastewater treatment plant (WWTP) in Aartselaar, the first full-scale quaternary facility in Flanders has been installed. It removes micropollutants from the effluent (purified wastewater) of a classic biological water treatment plant. Micropollutants are indeed difficult to break down and can accumulate.
Sweco was responsible for the feasibility study, preliminary design, permit application, preparation of tender documents, and execution supervision, and managed the disciplines of process design, electromechanics, civil engineering, electricity, automation, and infrastructure.
Innovative Pilot Project Launched
Through the Interreg project ‘Schone Waterlopen door O3G’, Ozonation (O3) in combination with Granular Activated Carbon (GAC) is being used at WWTPs. This innovative, efficient, and cost-effective post-treatment technique aims to improve the surface water quality in Flanders and the Netherlands. With ozone, a part of the micropollutants is broken down, and activated carbon adsorbs the remaining micropollutants. In this way, the water is made as pure as possible.
The WWTP in Aartselaar serves as a pilot project for Flanders. The installation or post-treatment consists of disc filters to remove the remaining suspended solids, an ozonation reactor to oxidize and break down the micropollutants, and then a final treatment with activated carbon filters. The official opening of the full post-treatment facility took place on May 23, 2025, in the presence of Jan Goossens, CEO of Aquafin, and Bernard De Potter, Director-General of the Flemish Environment Agency.
© Frederik Beyens // Aquafin
Towards Healthy Waterways in Flanders
The quaternary treatment follows a primary mechanical, secondary biological, and tertiary (phosphorus and nitrogen removal) treatment step. Annually, it will treat 75% of all wastewater arriving at the Aartselaar WWTP.
At this point, it is still unclear how many WWTPs in Flanders will require quaternary treatment. But at least the six largest (Ghent, Bruges, Ostend, Antwerp-South, Deurne, and Leuven), with one expected to be operational by 2033 and four more by 2039. For smaller installations, a risk analysis is still needed to determine whether they discharge into vulnerable areas.
By the end of 2030, Flanders must have a list of WWTPs in this category that require quaternary treatment. This first installation in Aartselaar gives us the opportunity to gain extensive knowledge and experience with the techniques used, both in terms of efficiency and cost. It’s no coincidence we chose this location, where our research hall is based and our R&D team conducts practical tests.
Jan Goossens, CEO Aquafin
Smart Monitoring for Clean Water
The Aartselaar WWTP discharges its treated wastewater into the Grote Struisbeek. No less than 50% of the water in this stream consists of treated wastewater from the WWTP. To assess the impact of the quaternary treatment on this watercourse, the Flemish Environment Agency (VMM) is conducting a large-scale monitoring campaign and studying the evolution of water quality. Finally, this additional treatment step also brings the reuse of treated wastewater a step closer, given the higher water quality. In a water-scarce region like Flanders, treated wastewater has great potential as a stable alternative water source.
“By measuring smartly, we make visible how post-treatment purifies wastewater of micropollutants and thus reduces the ecotoxicological impact on the watercourse.”
Bernard De Potter, Director-General VMM
