Clean watercourses through ozonation and granular activated carbon – O3G

Wastewater treatment plants (WWTPs) treat wastewater, mainly originating from households, before it is discharged as effluent into surface water. Although the quality of the effluent has significantly improved in recent years ─ particularly in terms of nutrients ─ organic micropollutants (OMPs), such as pharmaceutical residues and pesticides, remain a major challenge. Most WWTPs are currently unable to sufficiently remove these OMPs, posing risks to water quality. With the goal of achieving cleaner watercourses in Flanders and the Netherlands, a cross-border collaboration has been established to test ozonation (O₃) combined with granular activated carbon (GAC) adsorption as a post-treatment technique for WWTPs at laboratory, pilot and full-scale. Given the stricter requirements for OMP removal in the revised European Urban Wastewater Directive, this project provides valuable insights for future practical applications.

The choice for these technologies is based on previous research in both Flanders (e.g., at Ghent University) and The Netherlands. In these studies, ozonation emerged as one of the most successful technologies. However, ozone dosing requires careful consideration. High ozone concentrations can lead to the formation of undesirable by-products, such as bromate, as well as inefficient use of energy. To maximize the removal efficiency of OMPs while minimizing these adverse effects, ozonation can be combined with activated carbon filtration (adsorption).    

Ghent University is investigating on a lab scale ─ but with a focus on full-scale applications ─ how pre-treatment steps (e.g., coarse filtration) can remove unwanted scavengers of reactive species in order to optimize ozone consumption. Post-treatment of the ozonated effluent with activated carbon helps in the removal of by-products and persistent OMPs, providing an effective overall solution. In this process, we conduct in-depth research to determine the optimal conditions for combining ozone and activated carbon to remove various micropollutants. Additionally, advanced analytical methods are being developed to detect a wide range of OMPs and gain more insights into their removal. Ghent University is also investigating whether online surrogate measurements such as UV-VIS absorbance and fluorescence can make monitoring and controlling ozone-based treatment processes more efficient, potentially leading to operational cost savings of 10-20%.

Other partners within the consortium are investigating aspects such as the ecotoxicity and the effect of biodegradation on OMP removal (University of Antwerp), process optimization through 3D simulations (AM-Team), and sustainability assessment through life cycle analysis (HZ University). Within the project, tests are also conducted on the new ozone-GAC full-scale installation at Aquafin (Aartselaar; 4000 m³/d) and on the pilot installations built at Waterschap De Dommel by aid of PureBlue. The acquired project knowledge is disseminated by the project coordinator VITO Kennispunt Water with the support of CAPTURE, to maximize its practical impact.

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