Christian Baresel

Microplastics (MPs) and nanoplastics (NPs) have emerged as significant anthropogenic pollutants. They are garnering increasing scientific and public scrutiny due to their pervasive presence in the environment, drinking water, and food, which raises serious concerns regarding their effects on ecological systems and human health. The complexity and heterogeneity of these particles in size, shape, density, polymer type, and surface characteristics complicate this task. Addressing the rapid technical innovation and the surge of new methods, this review consolidates recent advances in chemical and hybrid remediation of MPs and NPs and furnishes a thorough discussion on the recent advancements in the remediation techniques of MPs and NPs, targeting chemical processes for their capture and degradation. Chemical approaches include electrochemical, photochemical, and thermal methods of treatment, and each of them is presented with a basic understanding and a critical analysis of their effectiveness. Additionally, the review stresses the development of integrated processes for synergistic MP/NP removal efficiency of multiple methods applied in tandem. Finally, an assessment of the currently existing knowledge gaps and prospective future perspectives for the development of MP/NP remediation and management has been conducted, identifying challenges and opportunities that lie ahead. Key identified knowledge gaps include material–plastic interactions under varying environmental conditions, reliance on controlled laboratory experiments, and operational issues such as catalyst optimization, nanomaterial aggregation, recovery difficulties, and emission risks in waste‐to‐energy processes. Also, the potential secondary toxicity from degradation by‐products remains largely unassessed. Future research should prioritize scalable, environmentally safe treatment technologies validated under realistic conditions. Advancing standardized global protocols, shared data infrastructures, and interdisciplinary approaches supported by AI tools will be critical for improving monitoring, technology optimization, and policy development to mitigate MP/NP pollution.

To meet future nitrogen removal targets, Henriksdal wastewater treatment plant (WWTP) will require external carbon addition, estimated at 8 tons COD/day by 2040, due to low influent BOD/TN ratios, precipitation chemical use, and low temperatures. Methanol, the projected option, is fossil-based and contributes to indirect greenhouse gas emissions. This study evaluated a volatile fatty acid (VFA)-based fermentate produced from primary sludge and food waste in a 2 m3 mesophilic fermenter as a carbon source for denitrification. The filtrated fermentate was tested as carbon source in both batch denitrification tests and pilot-scale MBR (4.5 m3/h), where it was dosed for 70 days, replacing glycerol currently used at Henriksdal and Henriksdals WWTP. In batch tests, the fermentate achieved a 40% higher denitrification rate than glycerol. Pilot trials showed a 30% higher denitrification rate and 50% lower carbon consumption while maintaining effluent concentration below 3 mg NO3- -N/L. Microbial analysis revealed no significant community changes with the carbon source transition, indicating effective VFA uptake by existing microorganisms. Full-scale projections suggested that replacing methanol would require 10% of the plant's primary sludge plus food waste. Although this sludge use would reduce biogas production, methane potential tests showed that recycling of the fermentate solid fraction would result in only 2% lower biogas production, representing a minor trade-off.

Pharmaceuticals have been detected in water and wastewater, resulting in increasing research attention towards the elimination of these substances from aqueous environments. Due to the limitations of conventional processes in wastewater treatment plants (WWTPs) to fully eliminate these compounds, more research is needed on complementary advanced treatment technologies. This study aims to examine the removal efficiency for 24 selected pharmaceuticals and the fate of their 7 main metabolites including several oxidation transformation products by various technique combinations applied on the effluent from a full-scale WWTP. Investigated treatment options include ozonation (O₃) combined with either granular activated carbon (GAC), two different types of biochar, and anion exchange (AIX) in a continuously operated laboratory-scale system. The average removal of analyzed pharmaceuticals ranged between 8.8–97% with an O₃ dose of 0.28 g O₃/g DOC (dissolved organic carbon), whereas it ranged from 86–99% for higher O₃ dosages (0.96 and 2.17 g O₃/g DOC). Overall, the investigated metabolites of pharmaceuticals exhibited lower removal efficiency (between −33 and 99%) with ozone compared to the parent compounds at all O₃-dosages. Concentrations of oxidation transformation products such as citalopram N-oxide were increased after ozone treatment, whereas it was decreased after the columns at different rates. The bromate concentrations during all three O₃-dosages (0.28, 0.96 and 2.17 g O₃/g DOC) were below 5 μg L⁻¹. GAC was the best performing sorbent among all materials, where even after two weeks of continuous operation, nearly all compounds were removed below quantification levels. Although biochar 1 showed better performance (30–89%, mean = 68%) than biochar 2 (8.5–82%, mean = 38%), both sorption materials showed reduced sorption capacity over the time period of two weeks for most of the target compounds. On the other hand, AIX had lower removal rates ranging between 2–55% (mean = 20%). Regarding the combination of O₃ with the individual sorbent materials, GAC was the most successful combination with O₃ for the removal of pharmaceuticals (>99%) and oxidation transformation products (>60%). The combination of O₃ with biochar 1 was more successful (mean = 91%) than the combination with biochar 2 (mean = 79%), where the combination of O₃ with AIX showed the lowest removal rates (mean = 58%).

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.

Membrane bioreactors (MBRs) have gained attraction in municipal wastewater treatment because of their capacity to meet strict water quality standards and support water reuse. Despite this, their operational sustainability is often compromised by high resource consumption, especially regarding the use of chemicals for membrane cleaning. This study explores innovative membrane-cleaning strategies to enhance the sustainability of MBR processes. Through long-term pilot trials at Stockholm’s largest wastewater treatment plant, this study showed that alternative cleaning strategies can reduce chemical use by up to 75% without sacrificing treatment performance. The results further suggest that these alternative strategies could result in cost reductions of up to 70% and a reduction in environmental impacts by as much as 95% for certain indicators. Given that MBRs play a crucial role in addressing increasing treatment demands and advancing circular water management, the outcomes of this study are beneficial for the broader adoption of MBR processes. These results also have implications for existing installations, offering a pathway to more sustainable wastewater treatment. Moreover, the presented cleaning strategies provide significant opportunities for lowering operational costs and reducing the environmental footprint of new and existing MBR installations.