Michael Toni Sturm

Understanding microplastic (MP) transport dynamics in river systems requires spatially and temporally resolved monitoring to disentangle localized point sources from diffuse catchment inputs. This study investigated MP contamination across two contrasting Central European catchments: the heavily impounded, industrialized Neckar (n = 136; June 2026) and the transboundary Lusatian Neisse (n = 102; March and May 2026). A standardized monitoring campaign collected 0.5 L grab samples across both rivers and at the Neckar–Rhine confluence in Mannheim, including an inland port area, where 12 sites were sampled on four dates between January and April 2026. Samples underwent hydrogen peroxide digestion, fluorescent staining with a MP-specific dye mixture (particles > 10 µm), automated fluorescence microscopy, and geospatial analysis incorporating land cover and wastewater infrastructure metrics. Microplastic concentrations were significantly higher in the Neisse than in the Neckar (median 22.5 vs. 5.0 MP L⁻¹; Cliff’s delta = 0.44). Because the two rivers were sampled in different months and at different water levels, seasonal and hydrological contributions to this difference cannot be excluded. In the Mannheim port area, the highest site mean was recorded upstream of a lock structure (544 MP L⁻¹) with pronounced temporal variability at this site (5 to 1591 MP L⁻¹). Neither local land use nor wastewater treatment plant (WWTP) metrics showed a detectable association with MP abundances in either river under the present design, which could reliably detect only moderate to strong associations. These results indicate that immediate land cover and WWTP proximity left no detectable signal in surface-water MP concentrations, possibly because point-source signals are masked by diffuse inputs, hydrological dynamics and temporal variation. Concentrations in the Neisse decreased from the upper to the lower reaches; whether this reflects the secondary WWTPs of the upper catchment or other longitudinal differences (e.g., flow conditions) could not be resolved.

The accurate quantification of microplastics (MPs) in aquatic environments remains challenging due to the heterogeneous distribution of MPs in different environments, making representative sampling difficult, as well as methodological variabilities in sampling, sample processing, and detection. This study examined measurement fluctuations for MP analysis across four distinct water matrices: wastewater treatment plant (WWTP) effluent, tap water (TW), combined sewer overflow (CSO), and surface water (SW). Two sampling strategies were compared: grab sampling (0.5 L, n = 5) and large-volume filtration using a particle sampling unit (PSU; 100 L, 10 µm mesh, subsampled). Samples were processed through oxidative digestion, stained with fluorescent dye, and analyzed via fluorescence microscopy with automated particle counting. Recovery experiments using polyamide (PA) reference particles (357 ± 60 µm) were conducted to assess method accuracy. PSU sampling demonstrated higher precision (mean R.S.D. 41 ± 17%) compared to grab sampling (mean R.S.D. 64 ± 19%), despite additional variability introduced by subsampling. Recovery rates reached 93 ± 7% for grab samples and 88 ± 23% for PSU samples with complete filter analysis. Statistical modeling revealed that achieving a ±25% margin of error (95% CI) required 21 PSU samples versus 51 grab samples. The quadratic relationship between the margin of error and required sample size underscores the importance of methodological optimization for cost-effective monitoring. These findings provide practical guidance for designing MP monitoring campaigns and demonstrate that fluorescent labeling combined with large-volume sampling offers a reliable approach for MP quantification in diverse aquatic environments.

This study evaluated the performance of a pilot unit for the combined removal of microplastics and total suspended solids at the municipal wastewater treatment plant of Mykonos, Greece. The pilot unit was installed downstream of the two-stage conventional activated sludge line and operated in semi-continuous mode to demonstrate its function under real effluent conditions. Across five experimental loops, influent microplastics concentrations ranged from 633 to 5843 microplastics/L, while effluent values were reduced to 96–263 microplastics/L, corresponding to an average removal efficiency of 86 ± 8%. In parallel, total suspended solids decreased by 95 ± 3%, turbidity by 93 ± 7%, and chemical oxygen demand by 70 ± 20%, while pH and conductivity remained stable. Influent water showed pronounced variability in chemical oxygen demand, total suspended solids, and turbidity due to irregular wastewater deliveries, yet the pilot consistently stabilized the effluent quality. A correlation analysis revealed strong associations between turbidity, total suspended solids, and chemical oxygen demand in the influent, while effluent data indicated close links between microplastics removal and particulate reduction. These findings confirm the robustness of the organosilane-based agglomeration process and highlight its potential as an advanced treatment stage to reduce MP emissions, improve effluent stability, and mitigate environmental risks in receiving environments such as the Mediterranean Sea.

Polyvinyl alcohol (PVA) is increasingly encountered in wastewater, yet reliable quantification and effective removal remain challenging. A colorimetric method for PVA quantification was validated, demonstrating excellent linearity and recoveries of 100.6 ± 2.8%. Limits were established at a limit of detection (LOD) of 1.28 mg/L and a limit of quantification (LOQ) of 1.8 mg/L. Accuracy was influenced by the PVA type, with errors reaching up to 42% due to variations in molecular weight and degree of hydrolyzation affecting the color complex. Consequently, polymer-specific calibration is advised. Analytical precision required strict temperature control and exact reaction times, and potential matrix interferences in wastewater should be assessed prior to application. PVA removal was evaluated using an AOP process based on hydrogen peroxide (H₂O₂) and UV-C irradiation. Increasing the H₂O₂/PVA ratio beyond 1:1 provided only marginal improvements, whereas increasing the UV-C dose was more impactful. A 1:1 H₂O₂/PVA ratio was sufficient even at PVA concentrations up to 5 g/L. Optimal UV-C doses were 7.5–12.5 kJ/m²; higher doses yielded only marginal additional removal. The colorimetric method was suitable for laboratory trials. A pilot-scale treatment of industrial wastewater applied microplastic agglomeration with organosilanes followed by granular activated carbon (GAC) treatment, which reduced PVA from an average of 24.2 mg/L to 7.4 mg/L, achieving ~65% removal, while microplastic removal reached 99.1%.

Microplastic (MP) contamination in riverine systems poses a growing environmental challenge, and their spatial and temporal variability complicates proper assessments. This study investigated MP concentrations (≥10 µm) across three German rivers using fluorescent staining-based detection. The results reveal highly heterogeneous distributions ranging from 4 to 1761 MP/L. The Rehbach displayed the highest mean MP concentration (540 ± 476 MP/L), whereas the Alb had the lowest (98 ± 54 MP/L). Long-term monitoring underscored pronounced temporal fluctuations linked to changing inputs, weather events, and hydrodynamics. To capture these fluctuations, monitoring campaigns must consider an appropriate temporal sampling framework. Further, to address detection challenges, the study compared 0.5 L grab sampling with 100 L pump sampling (PSU) and observed that the PSU yielded 4.7 times higher MP concentrations with improved reproducibility (27 ± 25% vs. 49 ± 33%). These results highlight the critical need for standardized protocols and scalable, cost-effective methods for reliable MP quantification and hotspot identification in freshwater environments.

This pilot study investigated an automated pilot plant for removing microplastics (MPs) from industrial wastewater that are generated during packaging production. MP removal is based on organosilane-induced agglomeration-fixation (clump & skim technology) followed by separation. The wastewater had high MP loads (1725 ± 377 mg/L; 673 ± 183 million particles/L) and an average COD of 7570 ± 1339 mg/L. Over 25 continuous test runs, the system achieved consistent performance, removing an average of 97.4% of MPs by mass and 99.1% by particle count, while reducing the COD by 78.8%. Projected over a year, this equates to preventing 1.7 tons of MPs and 6 tons of COD from entering the sewage system. Turbidity and photometric TSS measurements proved useful for process control. The approach supports water reuse—with water savings up to 80%—and allows recovery of agglomerates for recycling and reuse. Targeting pollutant removal upstream at the source provides multiple financial and environmental benefits, including lower overall energy demands, higher removal efficiencies, and process water reuse. This provides financial and environmental incentives for industries to implement sustainable solutions for pollutants and microplastic removal.

Wastewater treatment plants (WWTPs) are important point sources for microplastics (MPs) in the environment. For effective mitigation measures and regulations, it is important to monitor their release into the environment and understand the level of MPs in the WWTP effluents based on different treatment technologies. In this study, we compare the MP levels in the effluents of three different municipal WWTPs which each use a different treatment concept: a conventional three-stage WWTP, one with an additional fourth cleaning stage using powdered activated carbon, and a two-stage WWTP utilizing a membrane bioreactor (MBR). Long-term monitoring was performed on the WWTP effluents using the same standardized methods for sample collection, preparation, and detection, based on fluorescent staining. Despite the various advanced treatment processes, there are no significant differences in the resulting MP contamination in the investigation of WWTP effluents. The average MP concentrations in the effluents were 21.8 MPs/L for the conventional three-stage WWTP, 15.1 MPs/L for the four-stage WWTP, and 15.1 MPs/L for the MBR. Further, the MP contamination in all effluents shows a strong fluctuation over time. These findings highlight the need for standard MP monitoring at WWTPs, to gain a better understanding of the MP emission in different treatment processes. Further, it highlights the need for a fourth treatment stage that specifically targets MP removal to effectively prevent the MP release from WWTPs into the environment.

Microplastics (MPs) that are ubiquitous in aquatic environments and industrial wastewater streams have been identified as key hotspots of MP contamination. It is significantly more effective to remove MPs at these points before they enter municipal wastewater streams. This study is an environmental assessment of a novel pilot plant for the removal of MPs and the chemical oxygen demand (COD) from wastewater with a high MP contamination from a plastics manufacturer in Germany. MP removal is based on physical–chemical agglomeration–fixation by organosilanes. Formed agglomerates are separated using a belt filter. The COD is removed by an adsorption process. The resulting MP removal was 98.0 ± 1.1% by mass and 99.9987 ± 0.0007% by particle count, while the COD was reduced by 96 ± 2.7%. The system’s sustainability is evaluated using the Life Cycle Assessment methodology, evaluating system construction, operation, and end-of-life considerations. The current pilot plant is also compared to an optimized circular and sustainable upgrade, where drivers of environmental burdens are eliminated and collected MPs are reused. Significant reductions in environmental impact categories are achieved and the global warming potential is reduced by 96%. This study provides a sustainability assessment of a novel technology and circular solution to remove MPs from highly polluted industrial wastewater.

Wastewater treatment plants (WWTPs) have been identified as important point sources for microplastics (MPs) in the environment; monitoring MP emissions in the WWTP effluent is therefore essential for contamination control. The aim of this study is to acquire a large number of samples (320) over a period of two years and three months to determine the temporal variations in microplastic contamination in the outlet of the municipal WWTP Landau-Mörlheim. The effluent of the third cleaning stage is sampled with a 10 µm filter cartridge, processed in the laboratory using a hydrogen peroxide treatment, and MPs are then detected by fluorescence staining. The results show high temporal variations in the microplastic concentrations in the effluent of the WWTP. This indicates that high numbers of samples are necessary to obtain a representative assessment of the microplastic emissions; single samples are not representative. The average microplastic concentration in the effluent was 27.8 ± 29.8 MP/L, ranging from 0.6 MP/L to 194.0 MP/L. This leads to a yearly emission of 1.5 × 10¹¹ MP for the WWTP Landau-Mörlheim, corresponding to an emission of 2.8 × 10⁶ MP/inhabitant and year. Statistically significant seasonal variations could not be observed, although there is a trend towards lower MP concentrations in summer. Further, no correlations with other wastewater or weather parameters could be found.

Wastewater from plastic manufacturing or processing industries is often highly polluted with microplastics (MPs) and high levels of oxidizable organic matter, which results in a high chemical oxygen demand (COD). When industrial wastewater enters wastewater streams, the high microplastic load is a high burden for municipal wastewater treatment plants (WWTPs), as they are not sufficiently removed. To prevent MP from entering the WWTPs, an upstream prevention method is essential. This paper presents a pilot-scale plant study for the removal of MP and COD from industrial wastewater that was tested on-site at a plastic manufacturer in Germany. Eight test phases were performed over 3 months, with each test phase processing 1 m³ wastewater and four treatments. Per test phase, 12 samples were analyzed for 5 parameters: COD, total suspended solids (TSSs), particle count, pH, and turbidity. The results showed an average decrease in MP by 98.26 ± 2.15% measured by TSSs and 97.92 ± 2.31% measured by particle count. This prevents the emission of 1.1 kg MP/m³ water and an estimated 2.7 t MP/year. The COD was reduced efficiently by 94.3 ± 8.9%. Besides MP and COD, this treatment allows reuse of water and agglomerates, resulting in a reduction in the CO₂ footprint.