Full-scale quaternary treatment of municipal wastewater using granular activated carbon: long-term removal of organic micropollutants

ABSTRACT To meet future demands for cleaner water and comply with the revised Urban Wastewater Treatment Directive (UWWTD), many European wastewater treatment plants (WWTPs) will need quaternary treatment to reduce emissions of organic micropollutants (OMPs). Quaternary treatment based on granular activated carbon (GAC) is a promising solution, yet long-term, full-scale operational data remain scarce. This study presents operational experiences from Kivik WWTP in southern Sweden – one of the first full-scale municipal installations in Europe using GAC for OMP removal. The system has treated the full plant flow for over four years, corresponding to more than 50,000 bed volumes. Thirteen of the 15 analyzed OMPs were detected, including six UWWTD indicators. Results show >80% removal of several key compounds, even under highly variable flow conditions. However, flow variability – especially during wet seasons – complicates performance assessment due to dilution and reduced effective contact time. Weakly adsorbing compounds were most affected, while compounds with strong GAC affinity exhibited stable removal throughout the year. The findings highlight the importance of long-term monitoring when evaluating GAC performance and provide valuable input for future design, regulatory compliance and cost estimation of quaternary treatment systems.