# Approaching Breakthrough: Resource-Efficient Micropolitan Removal with MBR-GAC Configuration
###### Abstract  
The removal of micropollutants from municipal wastewater is crucial to mitigate negative environmental impacts on aquatic ecosystems. However, existing advanced treatment techniques often require extensive fossil resources to achieve the targeted removal of a broad range of micropollutants. This study presents the combination of Membrane bioreactors (MBRs) and subsequent Granular Activated Carbon (GAC) filters as a resource-efficient solution. Based on long-term pilot studies at a municipal WWTP in Stockholm, Sweden, this investigation explores the MBR-GAC configuration as a sustainable alternative for quaternary treatment at WWTPs. Results from over three years demonstrate a high removal efficiency of over 80% for targeted pharmaceuticals and other organic micropollutants, such as per- and polyfluoroalkyl substances (PFASs), from the WWTP inlet to the outlet. The synergy between MBR and GAC technologies provides this high removal efficiency with considerably lower resource consumption and cost compared to traditional GAC installations. No breakthrough of micropollutants has been observed to date indicating even better resource efficiency than presented in this paper. micropollutants; membrane bioreactor; activated carbon 2024, 14, 7759. [[https://doi.org/10.3390/app1417759](https://doi.org/10.3390/app1417759)]([https://doi.org/10.3390/app1417759](https://doi.org/10.3390/app1417759))  
Footnote †: journal: Applied Sciences  
been proposed and evaluated in recent years (e.g., [16; 17; 18; 19]). Today, ozone oxidation and activated carbon filtration (in the shape of granules, GAC, or powder, PAC) are the most well-established quaternary treatment techniques, as indicated by installations at WWTPs in Switzerland, which have been the foundation for the Urban Wastewater Treatment Directive [20]. However, ozonation, despite being cost-efficient for removing pharmaceutical residues even at high doses and long contact times, cannot remove PFASs from wastewater on its own [21; 22; 23], necessitating the use of activated carbon or other technologies. The new requirements for OMP removal according to the sewage directive are based on the entire treatment process at WWTPs. Therefore, the total efficiency at a WWTP for OMP removal can benefit from complementary and synergistic treatment processes, especially secondary, tertiary, and quaternary treatment steps. Membrane bioreactors (MBRs) are gaining increasing popularity in municipal wastewater treatment, with an exponential increase in the number and scale of MBR facilities [24; 25; 26; 27]. This popularity is due to MBRs' low footprint, robust operation, and ability to meet high-quality demands on treated water. Recent research indicates that the sustainability of the MBR process can be further optimized [28], and the costs and environmental impact of the MBR process are already considered competitive with conventional activated sludge (CAS) processes (e.g., [29]). While standard MBR processes have no significant impact on OMP removal alone compared to CAS [30], the combination of the MBR process and activated carbon has been investigated by [31]. Recent studies have further explored the potential benefits of MBR-GAC systems for efficient removal of pharmaceuticals and as facilitator for water reuse schemes [32; 33; 34]. This study aims to provide results from a unique, long-term, and ongoing evaluation of the MBR-GAC configuration at a Swedish WWTP for the removal of OMPs. The presented results provide insights into the potential to reduce resource consumption and costs for OMP removal at WWTPs by this technology combination. The pilot trials are conducted in preparation for a potential and pre-designed full-scale implementation of the process in one of Stockholm's WWTPs and thus are directly relevant for full-scale implementation.