# Approaching Breakthrough: Resource-Efficient Micropolitan Removal with MBR-GAC Configuration
## 3 Results
### Removal Efficiency for Pharmaceuticals  
Concentrations of pharmaceuticals (provided in Figure 15 in the Appendix A) indicate expected variations between the various sampling occasions and different levels for different substances. Variations in the incoming wastewater are explained by variations of wastewater flow and infiltration to the sewer system and consumption variations of various pharmaceuticals throughout seasons. Variations after the quaternary treatment may in addition be attributed to factors such as a varying EBCT in the GAC filters due to flow variations, which may imply varying adsorption, biological degradation, or desorption of certain substances. Substances such as paracetamol, naproxen, and ibuprofen show highest concentrations and variations in the incoming wastewater. These substances, however, are removed in the main treatment process, while the persistent pharmaceuticals remain unaffected. These pharmaceuticals are removed in the quaternary treatment with a general trend of increasing concentrations after both GAC filter lines over time. Figure 2 shows the removal efficiencies for pharmaceuticals across the main treatment process and the entire process, including quaternary treatment by the two GAC pilot lines. Results for each sampling occasion are shown in relation to the calendar week when sampling was performed and, in addition, for how many EBVs that have been treated in the GAC-filter lines at each sampling. As the second line (GAC L2) was put into operation some weeks later than GAC L1 due to a pump failure, treated EBVs are somewhat lower for this line compared to GAC L1. Removal efficiencies were only calculated for substances that could be quantified in the incoming wastewater. Concentration after treatment below level of detection (LOD) were considered as the LOD value and concentration below level of quantification (LOQ) as LOQ/2. Both diclofenac, identified as a significant risk substance for receiving water, and the average reduction of the sixteen most persistent substances are presented (including diclofenac, see also Table 15). The average removal of persistent substances serves as an indicator similar to the required average removal of various indicator substances according to the new wastewater directive, as these persistent substances are generally not removed by the main treatment process. Results indicate that the removal efficiency in the biological treatment stage of the process varied between sampling occasions but remained low, consistent with other studies. Negative removal rates in the MBR process for both diclofenac and other persistent pharmaceuticals were commonly observed. This is explained by the fact that substances are excreted as conjugates (e.g., glucuronide conjugates) that are deconjugated in the biological treatment, and the complex chemical matrix in incoming untreated wastewater suppresses signals during analysis. Both mechanisms result in a lower observed value in the raw wastewater than the actual concentration. Variations in removal efficiency over the MBRprocess cannot be explained by variations in incoming substance concentrations, although such variations were observed. For occasions with substantial negative removal in the main process, a lower treatment efficiency over the entire treatment were also observed, as the quaternary treatment cannot completely compensate for this (Figure 2). Except for these few samples, the removal of diclofenac and the persistent pharmaceuticals generally exceeded a potential target of 80%. This is also true after treating more than 50,000 EBVs in each line (>100,000 EBVs in each filter), corresponding to a dose of <10 g GAC/m\({}^{3}\), without any replacement of filter material yet. Removal efficiencies for at least four and two substances from categories 1 (amisulprid, citalopram, metoprolol, and venlafaxine) and 2 (benzotriazole and 4- and 6-methylbenzotriazole), respectively, according to the proposed sewage directive, were investigated in the last two sample campaigns.