Pilot-scale study of catalytic wet peroxide oxidation (CWPO) in a continuous stirred-tank reactor with in-line magnetic catalyst recovery

The presence of emerging pollutants (EPs) in aquatic environments is a growing concern due to their potential environmental and health risks. Wastewater treatment plants (WWTPs) are key sources, as conventional processes are not designed to remove these pollutants, highlighting the need for the development of advanced and sustainable water treatment technologies. Catalytic wet peroxide oxidation (CWPO) using natural magnetite has shown high efficiency in degrading these pollutants, offering a cost-effective and environmentally friendly alternative. However, most research has been conducted under lab-scale batch conditions, with limited studies evaluating its performance in large-scale continuous operation. This study assesses CWPO at pilot scale using a slurry continuous stirred tank reactor (slurry CSTR) with in-line magnetic catalyst recovery for micropollutant removal. A mixture of azole pesticides was selected as target pollutants, and the effects of H 2 O 2 dose (6.7–23.5 mg L −1 ), catalyst concentration (2–6 g L −1 ), influent flow rate (25–100 mL min −1 ), and initial micropollutant concentration (100–500 μg L −1 ) were examined. Results showed that increasing the oxidant and catalyst enhanced degradation efficiency, but excessive amounts led to scavenging reactions. The system showed high stability, allowing complete catalyst recovery, maintaining activity, and minimizing iron leaching (0.02 % wt.). As proof of concept, the system effectively removed micropollutants even from secondary-treated WWTP effluent, although a higher H 2 O 2 dose was required to offset additional organic and inorganic matter competing for oxidation. Finally, an environmental impact assessment (ReCiPe-2016 method) and a preliminary techno-economic analysis confirmed the viability of the proposed system, with an operating cost of 0.16 € m −3 . • Continuous CWPO system with in-line magnetic recovery for EPs degradation. • Catalyst remained active after 5 consecutive runs (40 h on stream). • Over 75 % EPs removal achieved, even in real secondary WWTP effluent. • In-line magnetic catalyst separation (>97 %) allowed its reusability. • Pilot-scale CWPO proved technically and economically viable.