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Article

Upstream Microplastic Removal in Industrial Wastewater: A Pilot Study on Agglomeration-Fixation-Reaction Based Treatment for Water Reuse and Waste Recovery

by
Anika Korzin
,
Michael Toni Sturm
,
Erika Myers
,
Dennis Schober
,
Pieter Ronsse
and
Katrin Schuhen
*
Wasser 3.0 gGmbH, Neufeldstr. 17a–19a, 76187 Karlsruhe, Germany
*
Author to whom correspondence should be addressed.
Clean Technol. 2025, 7(3), 67; https://doi.org/10.3390/cleantechnol7030067
Submission received: 3 July 2025 / Revised: 29 July 2025 / Accepted: 1 August 2025 / Published: 6 August 2025
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Abstract

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.

1. Introduction

Freshwater scarcity—when demand exceeds availability, from a lack of supply or infrastructure, or when poor water quality limits use—is an increasing global challenge with direct impacts on water security, socioeconomic development, and ecosystem and human health. Climate change further exacerbates the issue of regional water availability [1,2]. It contributes to higher water temperatures, glacier melt and reduced snowpack, and an intensification of the water cycle, including more frequent floods and droughts, often with disproportionate impacts on arid and semi-arid regions already vulnerable to water stress [3]. The resulting water shortages can result in ecosystem degradation, negative health impacts, and destruction of livelihoods [4].
Over half of the world’s population already experiences severe water scarcity during part of the year, and challenges related to global water scarcity are expected to increase substantially—almost half of the world’s large cities are estimated to be in water-scarce regions by 2050 [5,6,7]. This accounts for an increase of 0.99 billion people facing urban water scarcity, with 4.6% of this increase attributed to reduced water availability due to climate change [7].
Globally, water consumption has been increasing at twice the rate of population growth over the last century. While agriculture accounts for the highest freshwater withdrawals globally (70%), industrial (~20%), and domestic (~12%) uses are the predominant drivers of increasing water demand [8]. The proportion of use varies across different regions; in the EU, industry is the largest water consumer, with an average consumption of 55%, ranging from 49–96%, with the highest level in Estonia, whereas in South Asia, industry accounts for only 7% with agriculture responsible for 91% of freshwater usage [9]. Domestic, urban, and industrial water demands are expected to increase by 50–80% over the next 30 years. It has also been projected that water demands for manufacturing industries alone may rise by 400% by 2050 [1,10].
The most water-intensive industries also generate the most significant volumes of wastewater. Each year in Europe, 25,500 million m3 of industrial wastewater are produced; currently, only 2.5% of treated wastewater is reused in Europe [11,12,13]. Among 22 countries reporting industrial wastewater data globally, only 38% of industrial wastewater was reported as treated, and only 27% was safely treated [14].
The pollution emitted in industrial wastewater discharge may contain chemical additives, microplastics (MPs), and organic pollutants [15,16].
Microplastic pollution has emerged as a pervasive environmental pollutant in both freshwater and marine ecosystems. In addition to industrial effluents, they originate from a variety of sources, including the breakdown of larger plastic debris, microbeads in personal care products, synthetic textiles, and tire abrasion. Studies report highly variable MP concentrations across aquatic environments, with reported concentrations in marine environments ranging from 0.002 to 62.50 items/m3, with a mean abundance of 2.76 particles/m3 [17], and MP levels in freshwater systems ranging from 0.01 to 2559 particles/m3 [18]. Other studies have found that MP levels in freshwater systems range over six orders of magnitude (from 0 to 4,275,800 particles/m3) [18]. But levels of MPs are difficult to compare, as the sampling and detection methods have a large influence on the abundance of MPs measured [19].
This widespread MP contamination poses ecological risks through ingestion by aquatic organisms, potential bioaccumulation in food webs, and the transport of persistent organic pollutants and pathogenic microorganisms, along with risks of ecosystem degradation and to human health, particularly in regions with insufficient wastewater treatment infrastructure [20,21]. The persistence and complex behavior of microplastics in aquatic environments underscore the urgent need for improved monitoring, source mitigation, and standardized assessment methodologies. Various methods have been tested to remove MPs from wastewater, as outlined in Table 1, but industry faces significant hurdles in implementing these solutions, particularly cost and scalability [22]. Further, understanding the interplay between water usage, waste generation, and environmental risks is crucial for developing holistic sustainability strategies for industrial sectors [11].
One promising approach to mitigating industrial water consumption and pollution is the adequate treatment and reuse of process water within manufacturing cycles in a circular economy approach. Industrial water reuse has the potential to significantly reduce freshwater withdrawals, lower operational costs, and limit pollutant discharge and brings many environmental, economic, and social benefits [25]. This has direct implications on achieving the UN’s Sustainable Development Goals, specifically SDG 6, Clean Water and Sanitation, and SDG 12, Responsible Consumption and Production [26]. Additionally, targeting the removal of pollutants such as MPs upstream at industrial sources is much more effective at minimizing the amount of pollutants and MPs released into the environment, and removes the financial and technical burdens from municipal treatment plants, so that municipalities are not bearing most of the treatment costs for such pollutants, adhering to a polluter pays principle [27].
However, technical, economic, and regulatory challenges continue to hinder the widespread adoption of advanced treatment for pollutant removal and the reuse of process waters. These include concerns about process water quality, potential impacts on product quality, high upfront investment costs, and the complexity and costs of the operations. In many cases, advanced treatment costs outweigh the benefits, particularly in areas where water is inexpensive and abundant [27,28,29]. Thus, without strong drivers such as financial benefits, water scarcity, or regulatory pressure, industries may not prioritize water reuse.
There is a necessity to determine sustainable and circular solutions for industrial wastewater treatment that enable process water reuse, consider waste as a resource, and ultimately consider the cost-benefit trade-offs of advanced treatment systems—including potential savings on freshwater procurement and wastewater discharge fees—so that industries can better align economic objectives with environmental and health objectives [25].
This study investigates an automated and scalable pilot plant to remove MPs from industrial wastewater in the plastic packaging-producing industry. The technology is based on organosilane-based MP removal, which initiates agglomeration fixation on the basis of the water-induced sol–gel process [30,31]. Through the agglomeration-fixation reactions, MPs are collected in agglomerates through physical interaction with the agglomeration reagent and the MP surface. The agglomerates are then fixed by a chemical, water-induced reaction of the agglomeration reagent, which gives them a high degree of stability. Since the innovation lies in the development of the organosilane-based removal process, the advantage of this process is its ease of application in a low-tech process. Only a tank with a stirrer and a dosing pump for the agglomeration process, followed by a simple filtration unit for separating the agglomerates, is required (Figure 1). This makes the process simple, low-maintenance, and cost-effective.
This novel process was applied and tested for the first time in municipal wastewater in 2023 and in industrial wastewater in 2024 [32,33]. The current case study investigates its performance in a long-term application for wastewater from the plastic packaging industry to validate stability and effectiveness in this application over 5 weeks. In plastic industries, MPs can be generated by pellet loss but also by plastic processing as cutting, drilling, polishing, fragmentation, abrasion etc. [34]. Further, the pilot plant is installed as a sustainable upgrade that enables the reuse of the process water and reuse of the collected waste material that would otherwise be discharged into the connected municipal wastewater treatment plants. This sustainable process design combines economic and environmental benefits and thus an incentive to implement an advanced treatment method.

2. Materials and Methods

2.1. Description of the Pilot Plant

The Wasser 3.0 PE-X® technology is a (waste)water treatment unit for the removal of MPs through agglomeration fixation [30,31]. This pilot plant consists of two main components: the reactor unit for particle agglomeration and the inclined belt filter with filter fleece for the separation of wastewater and agglomerates (Figure 1).
The pilot plant can operate fully automated in 200 L batches. Untreated wastewater can be stored in a storage tank. In the first step, the wastewater to be treated is filled into a 200 L reactor containing a mechanical stirrer. After filling the reactor and starting the agitation process, 140 mL of agglomeration reagent (abcr eco Wasser3.0 PE-X®, industrial waste water AB930006, abcr GmbH, Karlsruhe, Germany) is added using a dosing pump. The MP agglomerates formed are separated from the treated wastewater by an inclined belt filter with a filter fleece (FIV12-1067, Leiblein GmbH, Hardheim, Germany, material: polyester, pore size: 70–80 μm).

2.2. Test Site

The test site was a medium sized German company that processes plastic packaging. The wastewater originates from a washing plant. The Wasser 3.0 PE-X® pilot plant is fed with the effluent water of the packaging washing plant.

2.3. Test Runs and Sampling

There was a total of five test series. Each test series was performed in one week with five working days. Each working day is considered a test run. On each test run, two samples were taken, resulting in 10 samples per test series. The samples were taken from the influent and effluent of the same 200 L batch, so one batch per day was sampled.
On average, 680 L of wastewater were treated per day, with a minimum of 400 L/day and a maximum of 1200 L/day, depending on the amount of wastewater generated. The pilot plant can treat a maximum of 800 L/hour.
Samples were taken at two different sampling points (Figure 1).
1: Untreated wastewater—reactor unit before dosing of agglomeration agent;
2: Treated wastewater—after Wasser 3.0 PE- X® treatment in the water collection basin of the belt filter.
The samples were stored at 5 °C. After five days, this resulted in 10 samples for shipment and further analysis. The samples were sent by cooled express shipping to the research center Wasser 3.0 gGmbH in Landau, Germany and stored in a refrigerator at 5 °C until analysis.

2.4. Analytics

Six parameters were analyzed for each sample: pH value, chemical oxygen demand (COD), microplastics (MPs), total suspended solids (TSSs), turbidity, and photometric TSS.

2.4.1. pH Value

The pH value of the samples was measured using a Dostmann pH 50 VioLab Set digital benchtop pH meter.

2.4.2. COD

The COD was measured using Macherey-Nagel’s tube test nanocolor COD 4000–10,000 (Macherey-Nagel GmbH & Co. KG, Düren, Germany). The procedure complies with DIN ISO 15705-H45 (water quality—determination of chemical oxygen demand (ST-CSB)—cuvette test) [35].
The round cuvette was either swirled/shaken or the sample was pipetted directly into the cuvette. The cuvette as then shaken with a safety vessel. In the Thermoblock (model: Thermoblock NANOCOLOR VARIO C2, single block), the round cell was heated at 160 °C for 30 min or at 148 °C for 2 h. The round cell was removed from the thermoblock, let sit for 10 min, and then shaken for 20 s. After the round cell had cooled down to room temperature, the COD content was measured using the NANOCOLOR UV/VIS II, 190–1100 nm spectrophotometer from Macherey-Nagel.

2.4.3. Microplastics—Particle Counting

MP detection was conducted using fluorescent staining in combination with fluorescent microscopy and software-based particle counting (Figure 2) [36,37,38]. Since only plastic is used in the industrial process, all particles in the wastewater are MPs. This makes sample processing for the reduction in non-plastic particles, such as chemical degradation or density separation, obsolete.
For fluorescence staining, the fluorescence dye abcr eco Wasser 3.0 detect mix MP-1 (AB930015, abcr GmbH, Karlsruhe, Germany) was used. A total of 0.5 mg/L dye was added to 100 mL of the sample, swiveled until evenly distributed, and stored for 24 h at RT. Subsequently, the sample was filtered on a black filter membrane. (Metricel® Black PES Membrane Disk Filters, 0.80 µm pore size, Pall Cooperation, Dreieich, Germany).
Fluorescent imaging was conducted using a ZEISS Axio Zoom.V16. The microscope was operated with Zen Blue Software (Zen Blue 3.8; Carl Zeiss Microscopy Deutschland GmbH, Oberkochen, Germany). The microscope was equipped with a ZEISS Axiocam 712 mono camera and a PlanNeoFluar Z 1×/0.25 objective, yielding a spatial resolution of 1 μm per pixel. Image acquisition was performed for five tiles of 3.9 × 3.9 mm per filter.
The automated particle counting was performed using the particle counting add in of the Zen Blue 3.8 software. MPs were identified by a brightness threshold, which was set to 3500. The total particle concentration (particles/L) was calculated by extrapolating the counted particles based on the total filter surface area and the volume of filtered water.
As the samples were highly contaminated with MPs, which hindered filtration and particle counting to achieve a more even distribution of MP particles on the filter, the individual samples were diluted with demineralized water to reach a volume of 100 mL. Due to the high contamination, a dilution of 1:1000 was selected for untreated samples and 1:100 for the treated samples. The dilution was performed after the fluorescent staining and before the filtration.

2.4.4. Photometric-TSS and Turbidity

The turbidity and Photometric-TSS were also measured using the NANOCOLOR UV/VIS II, 190–1100 nm spectrophotometer from Macherey-Nagel (Macherey-Nagel GmbH & Co. KG, Düren, Germany). Empty reaction tubes with an outer diameter of 16 mm from Macherey-Nagel are required. A total of 10 mL of the sample was pipetted into the reaction tube, shaken homogeneously with or without further dilution depending on the degree of contamination, and placed in the spectrophotometer. As the TSS of the untreated wastewater exceeded the measurement range of 400 NTU, the samples were diluted by 1:10.
Photometric TSS does not follow any DIN standard and is therefore not as reliable as gravimetric TSS. However, it can be measured within a short time of approximately 1 min per sample without sample preparation, and thus, it is significantly faster and requires less effort compared to gravimetric TSS following the DIN standard. The goal is to compare the data from gravimetric TSS according to the DIN standard with photometric TSS, to see if it can be used as a fast and low-cost alternative for process validation.

2.4.5. Gravimetric-TSS

The quantitative determination of the total suspended solids is carried out in accordance with DIN 38 409-H2-2 (German standard method for water, wastewater, and sludge analysis; summary effect and substance characteristics (Group H); determination of filterable substances and residue on ignition). A total of 125 mm round filters (MN 640 w, retention capacity 7–12 μm, Macherey-Nagel GmbH & Co. KG, Düren, Germany) were used in a vacuum filtration process. First, the round filters were rinsed with 100 mL of demineralized water and dried for 2 h at 105 °C. The dry and empty round filters are weighed, and 1 L of the sample is filtered. The round filters are dried again for 2 h at 105 °C and weighed. The difference between the full and empty round filters in relation to the sample volume is the result of the filterable substances.

2.5. Agglomerate Analytics

Two agglomerate samples of the pressed agglomerates were taken and sent to Limbach Analytics GmbH, Labor Mannheim, Germany for analytics Parameters according to the German Landfill Ordinance [39,40]. The used analytic methods and DIN norms can be found in Collection of methods for waste analysis—Version 3.0 from the Länderarbeitsgemeinschaft Abfall (LAGA) [41].

2.6. Reuse Concepts—MP Agglomerates and Further Inclusion of Parameters

In the course of the work, additional parameters were determined for the economic–ecological assessment of the overall process. These include energy consumption, quantities of abcr eco Wasser3.0 PE-X®, industrial wastewater used, unpressed and pressed agglomerates, waste streams, and recycling concepts.
The MP particles present in the wastewater are agglomerated and fixed by adding abcr eco Wasser3.0 PE-X®, industrial wastewater, and separated from the treated wastewater by the inclined belt filter. Each day, the agglomerates were weighed (unpressed) from the collecting tray and then placed in a fruit press. The water was pressed out with the help of a manually operated press and weighed again. The pressed agglomerates were dried at 60 °C in a drying cabinet. This allowed the dry weight and water content to be determined.

3. Results

3.1. Microplastics Removal by TSS

As the production process only works with plastic-based products, all TSS are MPs. The average reduction is 97.4%, which demonstrates high removal efficiency. The lowest reduction is 96.4%, the highest reduction is 99.5% (Figure 3). The fluctuations are therefore minimal, which indicates a high reproducibility of the treatment. The concentrations of TSS after treatment are all below 160 mg/L. The results show a consistently high reduction in the TSS across all five test series.
In the untreated wastewater, the TSS ranged from 1019 mg/L to 2572 mg/L, with an average of 1725 ± 377 mg/L. After the wastewater treatment, the average TSS content was 46 ± 23 mg/L, with values ranging from 0.6 mg/L to 121 mg/L. The reduction is statistically significant (t-test, two-sided, paired, p < 0.001). On average, 1.7 kg of TSS (MPs) are removed per m3 of water.

3.2. Microplastics Removal by Particle Count

The MP removal by particle count (Figure 4) demonstrates an average removal of 99.1%, ranging from 97.7% to 99.7% in the single test runs. This exceeds the removal measured by TSS.
Looking at the contamination of the wastewater, the untreated wastewater is contaminated with 673 ± 183 mio MPs/L, ranging from 38 mio to 1112 mio MPs/L. This underscores the extremely high contamination of the wastewater, suggesting severe environmental impact when not removed sufficiently in wastewater treatment. Also, the data shows the fluctuation of MP contamination in wastewater. Despite the wide range of contamination, the MPs could be removed in all test runs reliably.
The concentrations in the treated wastewater averages, 5.8 ± 2.8 mio MPs/L, ranging from 14.1 mio MPs/L to 2.7 mio MPs/L, which is significantly lower than the untreated water (t-test, two-sided, paired, p < 0.001).
Looking at the size distribution (Table 2), the particle sizes range from 2.9 µm to 417 µm in the untreated and 571 µm in the treated samples. A total of 2.9 µm represents the lowest detectable particle size due to the resolution of the microscope, and the minimum pixels for particle detection is set to four pixels. Thus, it is unclear how many MPs smaller than 2.9 µm are contained in the samples.
The particle distribution also reveals that the average particle size of the treated samples, with 10.2 µm, is smaller than in the untreated sample, with 22.7 µm. This can also be seen in Figure 5. It is also notable that 95% of the particles are smaller than 62.3 µm in the untreated sample, while in the treated sample, 95% of the particles are smaller than 22.1 µm.

3.3. COD Removal

In all test series, the COD value was significantly reduced by wastewater treatment, on average by 78.8% (Figure 6). The highest reduction was achieved in test series 4, with 83.4%. The lowest reduction was in test series 2, with 72.0%.
Between 1257 mg/L and 2243 mg/L COD, with an average of 1577 ± 427 mg/L, remain in the wastewater after treatment, which could be relevant for discharges to the wastewater treatment plant or reuse, depending on the threshold. The initial COD of the untreated wastewater ranges from 5410 mg/L to 10,200 mg/L with an average of 7570 ± 1339 mg/L. The t-test confirms the statistical significance (t-test, two-sided, paired, p < 0.001).
The removal process focuses on MP removal; COD removal is an additional benefit. Since COD is related to the amount of dissolved and particulate oxidizable matter, the removal of MP particles reduces COD to the amount of dissolved matter [33,42]. Per m3 treated water, 1.69 kg TSS and respective particulate matter, are removed from the water, resulting in the reduction of 5.99 kg COD per m3 water. The remaining COD can be allocated to dissolved organic chemical compounds. Typical for the plastic packaging industry are residues of inks (binders, pigments, solvents, additives) and glues [43,44,45]. Further, the washing process introduces surfactants [46].

3.4. Turbidity Removal

The turbidity of all samples (Figure 7) was measured to determine whether it was suitable as an easily measured process control parameter. The untreated wastewater is milky white and contains white and black particles. The untreated samples have high turbidity values, between 1124 NTU and 3000 NTU, with an average of 1926 ± 462 NTU. By treatment, the turbidity is reduced to an average of 112 ± 88 NTU, ranging from 21 NTU to 290 NTU.
In test series 3, 4, and 5, a reduction of over 97% was achieved, while in test series 1 and 2, the reduction was lower, reaching 89.3% and 87.9%, respectively. The average reduction corresponds to 92.3 ± 6.6%. The reduction is statistically significant (t-test, two-sided, paired, p < 0.001).

3.5. pH Value Analytics

The average pH of the untreated samples was 8.76 ± 0.36, with values ranging from 8.16 to 9.42. After treatment, the average pH was 8.52 ± 0.47 with a minimum of 7.72 and a maximum of 9.57.
In all five test series, the pH value of the treated samples is lower than that of the untreated samples (Figure 8). The effect is most visible in test series 4 (difference of 0.39 pH units). The data indicates an effective pH-regulating measure, the effect of which remains stable across all test series. The t-test confirms the statistical significance of the difference (t-test, two-sided, paired, p = 0.002)
The pH value of the untreated processed water should be higher than 9, due to the washing process the water originates from. Due to a malfunction of the washing plant between test series 2 and 3, the pH of untreated wastewater was lower than 9 in the following test series. The experiments showed no effect on the MP removal efficiency.

3.6. Correlation Analysis

A correlation analysis (Figure 9) is conducted to identify potential relationships between the measured parameters, providing insights into how the variables interact and if easily measurable and cost-effective parameters such as turbidity or photometric TSS can be used for process control. Similar approaches are discussed in advanced wastewater treatment using the SAC-254 [47].
The correlation analysis shows that all parameters are well correlated, with all Pearson correlation coefficients between 0.97 and 0.99. As TSS and turbidity are mainly caused by dispersed MPs, they are directly related and correlated. Further, the COD is caused by the particulate, oxidizable MPs dispersed in the water, which leads to a direct correlation. It is also notable that photometrically measured TSS is well correlated with gravimetrically measured TSS. This would make it possible to replace the more labor-intensive TSS measurements with simple and fast photometric TSS measurements.
It should be noted that the treated samples show a much lower variance or scatter for all measured parameters than the untreated samples, which is why it influences the correlation much more than the treated samples. However, this is of minor relevance for the application of process control of MP removal, and is therefore deemed negligible.

3.7. Avoided MP Emissions and Agglomerate Production

During the pilot study, a total of 85 batches of 200 L wastewater were treated, which means that a total of 17 m3 of wastewater was treated in the five test weeks, and thus, five test series (Table 3). The piloted company had a yearly wastewater discharge of 1016 m3 in 2024, resulting in an average of 4.2 m3 per day operating 240 days a year.
For every 200 L of wastewater to be treated, 140 mL of abcr eco Wasser3.0 PE-X®, industrial wastewater AB930006 was dosed, which means a total consumption of 0.7 L/m3. This would result in a yearly consumption of 711 L abcr eco Wasser3.0 PE-X®, industrial wastewater, and 1422 kWh of electricity.
This prevents the emission of 1.7 kg MPs/m3 or 670 billion MP particles/m3, corresponding to the retention of 1.7 t MPs/year and 680 trillion MPs/year, that is prevented from entering the wastewater streams. Also, a COD emission of 6.0 kg/m3 and 6.1 t/year is avoided.
During the entire test period, 100.4 kg of unpressed agglomerates were produced. After pressing the fruit by hand, 74.0 kg of pressed agglomerates remained, meaning that 26.0 L of water was drained. The mass of dried agglomerates produced in the trials was 32.3 kg.
The MP agglomerates are collected for later reuse, and the treated wastewater is to be returned to the production cycle for a circular process, with an estimated four times reuse, saving 80% of the processed water. The reuse is enabled by the removal of the MPs from the process water, as well as a reduction in the COD. Thus, not only is water saved, but also process chemicals in the water (e.g., surfactants) are reused, which is a further sustainability upgrade to the approach.

3.8. Agglomerate Analytics Results

The agglomerate analysis according to landfill regulations concludes that the agglomerates are not suitable for landfill, and should be sent for thermal recycling, i.e., waste incineration or incineration in cement plants.
The high mineral oil hydrocarbons (MOH) (sample 1, 245,700 mg/kg DR; sample 2, 267,300 mg/kg DR), the high amount of organic content according to LOI at 550 °C (sample 1, 99.5%; sample 2, 98.8%), the high amount of extractable lipophilic substances (sample 1, 32.9%; sample 2, 16.3%) and the Total Organic Carbon content (sample 1, 79.5%; sample 2, 73.1%) are decisive for the non-landfill ability [39,40]. Also, it is notable that an elevated Extractable Organic Halogens value was found in sample 2 with 14 mg/kg DR. The other agglomerate parameters (heavy metals, polyaromatic hydrocarbons, volatile halogenated hydrocarbons, BTXE) are unremarkable and below the limit values.
As discussed in the COD section (Section 3.3), typical dissolved substances in plastic packaging wastewater are ink and glue residues, including their solvents and additives [44,45]. Further, the washing process introduces surfactants [46]. It is important to note that these hazardous substances are removed from the wastewater during the treatment process and do not remain in the wastewater. If these hazardous substances were not removed with the agglomerates, they would be released with wastewater and potentially be released into the environment via the sewage sludge or the treated wastewater. Controlled disposal is possible within the agglomerates.
Previous studies have also shown that the organosilanes added for agglomeration fixation react in the water-induced sol–gel process and are bound as solids in the agglomerates. Dissolved residues could no longer be detected by Inductively Coupled Plasma Optical Emission Spectrometry [31].
The high calorific values of 38.6 MJ/kg DR for sample 1 and 28.6 MJ/kg DR for sample 2 mean that the agglomerates are ideally suited for combustion in energy production. This exceeds the calorific value of wood (18–19 MJ/kg) and is in the range of hard coal (29–35 MJ/kg) [48]. The disadvantage of this method is the CO2 release.
A more sustainable reuse alternative would be a filter for asphalt materials, which would require further leaching tests and material property analysis (e.g., tensile strength, water sensitivity, dynamic stiffness, and creep rate) [49,50].

4. Discussion

4.1. Microplastic Removal Performance of the Pilot Plant

The data from the pilot study shows that the system can effectively remove MPs from wastewater and, as a positive side effect, also significantly reduce COD. The cleaning performance measured by the MP particle count is consistently above 98.8%, and if measured by the MP weight, consistently above 96.4%, with a COD reduction of 72.0–83.4 %. This not only significantly reduces emissions into the wastewater system but also enables the wastewater to be reused. The weekly test series shows clear fluctuations in the untreated wastewater for MPs (TSS and particle count), as well as COD, which can be seen in the standard deviation (Figure 3, Figure 4 and Figure 6). Those are caused by a combination of changing production batches and a variable washing process, depending on the production batches. Despite these variations, the pilot plant showed a stable removal performance.
Other studies using the Wasser 3.0 PE-X® method in pilot trials in plastic processing companies achieved similar removal performances. In these studies, a removal of 98.0 ± 1.1% by mass and 99.9987 ± 0.0007% by particle count [51], respectively, 98.26 ± 2.15%, measured by mass, and 97.92 ± 2.31% measured by particle count were reached [32].
Alternative technologies for MP removal that are often discussed include sand filtration, membrane filtration, or dissolved air flotation [24]. Sand filtration can effectively reduce the MPs from municipal and industrial wastewater and is a simple and cost-effective method [52,53]. However, drawbacks include a high area requirement, limited effectiveness for small particles without pretreatment, and the need for regular backflushing to clear out the filtered particles. Membrane filtration is a highly effective method for the removal of particles and MPs in wastewater [54,55]. But its primary drawback is the high maintenance demand, especially due to membrane fouling and scaling, and high energy consumption due to the high pressure required. Dissolved air flotation is also often discussed but has exhibited a low effectiveness in scientific studies as well as a high energy demand for the air supply [56,57]. In the scientific literature, chemical degradation, e.g., Advanced Oxidation Processes, is often discussed, but is not applied at a large scale, as they are only effective if very high doses and exposure times are applied [58,59].
Flocculation and coagulation were also tested in various studies, but showed to have often insufficient removal performance, depending on the polymer types and the wastewater composition [60,61]. Comparing the organosilane-based physical–chemical agglomeration to common flocculation and coagulation methods, the biggest advantage is the large flock size and the chemical fixation, which leads to higher stability of the agglomerates [31,60]. In the pilot trials, the method was also stable for the different wastewaters that were tested and for different polymers [33,61].
One advantage of the Wasser 3.0 PE-X® technology is its simple applicability with low technical effort, as it only needs a tank for mixing and agglomeration formation and a filtration device: in this application, a band filter. A disadvantage is that the physical chemical process, based on sol–gel chemistry, can potentially be disturbed by substances dissolved in water. However, until now, this has not yet been observed, so the process appears to be robust against such influences [31,33,61]. Further, the process requires abcr eco Wasser3.0 PE-X® as a consumable.

4.2. Benefits of Upstream Removal of Microplastics

In the current operation, the wastewater is discharged untreated into the sewer system and treated by a municipal wastewater treatment plant. To assess the optimal point of MP removal using Wasser 3.0 PE-X® along the wastewater effluent chain, three scenarios can be considered (Figure 10):
1.
Status quo, i.e., no MP removal;
2.
Removal of MP from municipal wastewater effluent;
3.
Removal of MP from industrial wastewater effluent.
For all scenarios, the industrial effluent is estimated to contain 700 million MPs/L, with an average of 4.2 m3 treated per day, based on values from the pilot plant in this study. To determine the overall MP release, the industrial effluent flow (calculated without water reuse) into a medium-sized conventional municipal WWTP is considered, with an estimated treated volume of 10,000 m3/day. This results in a 1:1000 dilution of the industrial wastewater effluent concentration once it enters the municipal WWTP (additional MP sources are excluded for the estimations, and dilution of industrial MPs within municipal wastewater streams is likely significantly higher).
By determining the resulting amount of MPs that would enter the environment in each scenario, Scenario 2 has the greatest impact on the final MP concentration released into the environment, with 2.8 million MPs/day, compared to 28 million MPs/day if the MP removal unit is installed at the municipal WWTP. It is important to note that once water reuse is considered, the industrial effluent flow is reduced by 80%, resulting in significantly lower MP release to the WWTP and thus the environment, with only 560,000 MPs entering surface waters per day. This highlights another large environmental benefit of water re-use and reduced effluent flows. Additional benefits of upstream removal include the following:
  • Less total wastewater to be treated with a higher overall removal efficiency.
  • Less energy and time required.
  • Water can be reused in industrial processes, reducing freshwater demand.
  • Adheres to the polluter pays principle, relieving the financial and technical burden from the municipality.
Targeting pollutant, specifically MP, removal at point sources, such as industrial wastewater effluents, offers clear environmental and economic advantages over downstream treatment and enables effective industrial water reuse, a key strategy to address growing water scarcity under climate change [8,62]. If untreated at the source, these pollutants dilute in larger municipal wastewater streams, making removal more energy-intensive, costly, and technically challenging [28].
Economically, treating pollutants at the source allows for targeted, smaller-scale processes, reducing energy use and treatment costs per unit of contaminant removed [29]. In contrast, downstream removal requires treating larger water volumes with higher operational costs and greater technical complexity. Moreover, delayed treatment often results in higher indirect costs due to environmental restoration, biodiversity loss, and impacts on human health [63].
Upstream treatment also allows the waste to be used as a resource and supports circular economy strategies [29,63]. Despite these benefits, high upfront investments for advanced treatment technologies, operational complexity, and a lack of clear regulatory or financial incentives often remain barriers for the industry to implement removal processes [63]. It is therefore important to find solutions with a positive cost-benefit ratio, through, for example, the re-use of water and waste materials.
As industrial water demand is expected to rise by up to 400% by 2050, integrating pollutant removal with reuse strategies is no longer optional but increasingly necessary to align with global climate adaptation and water security goals [8]. Upstream treatment is therefore both a pollution prevention strategy and a water security measure in the face of worsening climate impacts, as demonstrated with the Wasser 3.0 PE-X® pilot plant.

5. Conclusions

The pilot study demonstrated the suitability of the Wasser 3.0 PE-X® pilot plant to remove MPs from this specific industrial wastewater that originates from plastic packaging. The wastewater showed high MP contamination with an average of 1725 ± 377 mg/L and 673 ± 183 mio MPs/L by particle count. In addition, the average COD was 7570 ± 1339 mg/L.
In 25 test runs over 25 working days, the process could deliver stable removal performances. An average MP removal of 97.4 % by particle mass and 99.1 % by particle count was achieved. In addition, the COD could be reduced, on average, by 78.8 %. Extrapolated to a one-year period, the emission of 1.7 t of MPs by weight and 680 trillion MPs by particle count, as well as 6 t of COD into the sewage system, can be avoided. This enables a reuse of the water with an overall estimated water saving of 80%. The produced agglomerates can be used in energy generation due to their high calorific value.
Further, a correlation analysis showed that photometric TSS measurement or turbidity measurement are applicable parameters for process control.

Author Contributions

Conceptualization, A.K., D.S. and K.S.; methodology, A.K., M.T.S., D.S. and K.S.; validation, A.K., M.T.S. and K.S.; formal analysis, A.K., M.T.S. and K.S.; investigation, A.K. and P.R.; resources, K.S.; data curation, A.K., M.T.S. and K.S.; writing—original draft preparation, A.K., M.T.S., E.M. and K.S.; writing—review and editing, A.K., M.T.S., E.M. and K.S.; visualization, A.K., E.M. and M.T.S.; supervision, K.S.; project administration, K.S.; funding acquisition, K.S. All authors have read and agreed to the published version of the manuscript.

Funding

This project has received co-funding from the European Union’s Horizon Europe innovation program under grant agreement 101093964. This publication reflects the views only of the author, and the European Commission cannot be held responsible for any use that may be made of the information contained therein.

Data Availability Statement

All data is available from the corresponding author at reasonable request.

Acknowledgments

The authors thank the REMEDIES consortium partners for the collaboration.

Conflicts of Interest

The authors Anika Korzin, Michael Toni Sturm, Erika Myers, Dennis Schober, Pieter Ronsse and Katrin Schuhen were employed by the company Wasser 3.0 gGmbH. The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Abbreviations

The following abbreviations are used in this manuscript:
BTXEBenzene, Toluene, Ethylbenzene, Xylenes
CODChemical oxygen demand
DRDry Residue
LOILoss on Ignition
MOHMineral oil hydrocarbons
MPsMicroplastics
S.D.Standard deviation
SDGSustainable Development Goal
TSSTotal suspended solids

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Figure 1. Schematic drawing of the Wasser 3.0 PE-X® wastewater treatment technology and its sampling points (red circle).
Figure 1. Schematic drawing of the Wasser 3.0 PE-X® wastewater treatment technology and its sampling points (red circle).
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Figure 2. Example images and process for MP detection by fluorescence microscopy. The images shown are the untreated wastewater from test series 1, test run 1 with a dilution of 1:1000, and 100 µL sample, respectively. Thus, the MPs in the image of 3.9 × 3.9 mm represents the MPs in a volume of 1.3 µL untreated wastewater. Orange fluorescence was used, detected particles are marked in light blue.
Figure 2. Example images and process for MP detection by fluorescence microscopy. The images shown are the untreated wastewater from test series 1, test run 1 with a dilution of 1:1000, and 100 µL sample, respectively. Thus, the MPs in the image of 3.9 × 3.9 mm represents the MPs in a volume of 1.3 µL untreated wastewater. Orange fluorescence was used, detected particles are marked in light blue.
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Figure 3. TSS values in five test series, in each case for the untreated samples and the samples after treatment with abcr eco Wasser3.0 PE-X®, industrial wastewater. The percentage reduction in TSS values per test series and the mean value before and after treatment are also shown.
Figure 3. TSS values in five test series, in each case for the untreated samples and the samples after treatment with abcr eco Wasser3.0 PE-X®, industrial wastewater. The percentage reduction in TSS values per test series and the mean value before and after treatment are also shown.
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Figure 4. MPs by particle count in five test series, in each case for the untreated samples and the samples after wastewater treatment with abcr eco Wasser3.0 PE-X®, industrial wastewater. The percentage reduction in MP count per test series and the mean value before and after treatment are also shown.
Figure 4. MPs by particle count in five test series, in each case for the untreated samples and the samples after wastewater treatment with abcr eco Wasser3.0 PE-X®, industrial wastewater. The percentage reduction in MP count per test series and the mean value before and after treatment are also shown.
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Figure 5. Histogram of particle size (ferret maximum) frequency and probability, in each case for the untreated samples and the samples after treatment with abcr eco Wasser3.0 PE-X®, industrial wastewater. The analysis refers to the five tiles recorded and analyzed of the filter of test series 1, test run 1. Extrapolated with the sample volume, this results in the sample volume indicated in the legend.
Figure 5. Histogram of particle size (ferret maximum) frequency and probability, in each case for the untreated samples and the samples after treatment with abcr eco Wasser3.0 PE-X®, industrial wastewater. The analysis refers to the five tiles recorded and analyzed of the filter of test series 1, test run 1. Extrapolated with the sample volume, this results in the sample volume indicated in the legend.
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Figure 6. Comparison of COD values for the five test series, including their mean values. Two values are shown for each test series, untreated wastewater and after treatment with Wasser 3.0 PE-X®, industrial wastewater. The percentage reductions before and after treatment are also shown.
Figure 6. Comparison of COD values for the five test series, including their mean values. Two values are shown for each test series, untreated wastewater and after treatment with Wasser 3.0 PE-X®, industrial wastewater. The percentage reductions before and after treatment are also shown.
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Figure 7. Comparison of turbidity values for the five test series, including their mean values. Two values are shown for each test series: untreated wastewater and after treatment with Wasser 3.0 PE-X®, industrial wastewater. The percentage reductions before and after treatment are also shown.
Figure 7. Comparison of turbidity values for the five test series, including their mean values. Two values are shown for each test series: untreated wastewater and after treatment with Wasser 3.0 PE-X®, industrial wastewater. The percentage reductions before and after treatment are also shown.
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Figure 8. The comparison of pH values between untreated and treated samples over five test series, including their mean values.
Figure 8. The comparison of pH values between untreated and treated samples over five test series, including their mean values.
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Figure 9. Correlation plot between MP Count, COD, gravimetric TSS, photometric TSS, and turbidity. Yellow = untreated samples, green = treated samples. The numbers represent the Pearson correlation coefficients, the stars (***) represent a highly significant correlation (p < 0.001).
Figure 9. Correlation plot between MP Count, COD, gravimetric TSS, photometric TSS, and turbidity. Yellow = untreated samples, green = treated samples. The numbers represent the Pearson correlation coefficients, the stars (***) represent a highly significant correlation (p < 0.001).
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Figure 10. Assessment of the benefits of upstream removal of MPs before entering the wastewater streams. Assumptions receiving wastewater treatment plant with an average of 10,000 m3/day and 95% of MP removal.
Figure 10. Assessment of the benefits of upstream removal of MPs before entering the wastewater streams. Assumptions receiving wastewater treatment plant with an average of 10,000 m3/day and 95% of MP removal.
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Table 1. Overview of different microplastic removal methods and the associated advantages and disadvantages [22,23,24].
Table 1. Overview of different microplastic removal methods and the associated advantages and disadvantages [22,23,24].
MethodPrincipleProsCons
Physical Separation
Screening and FiltrationPhysical barrier (meshes, membranes)High removal for various sizes (esp. fine membranes); establishedFouling (clogging); high energy/cost for fine membranes
SedimentationGravity settling (heavier particles)Simple, low cost for larger/denser MPs; common primary stepIneffective for small/light MPs; needs large tanks; generates sludge
Flotation (DAF)Air bubbles lift MPs to surfaceGood for buoyant MPs; fast; high efficiency (with flocculants)Less effective for dense MPs (without chemicals); energy use; creates sludge
CentrifugationCentrifugal force separates particlesEffective for various sizes/densities; fastHigh cost (capital/operating); not for large volumes; complex maintenance
Chemical/Physico-Chemical
Coagulation/FlocculationChemicals clump MPs for easier removalBoosts removal for small MPs; enhances other methods; widely usedChemical use/cost; more sludge; variable effectiveness
Advanced Oxidation Processes (AOPs)Strong oxidizers degrade some MPsCan break down polymers, effective for various organicsHigh cost (energy/chemicals); may form small byproducts; complex control
AdsorptionMPs stick to adsorbent materialEffective for specific MP types; removes other organicsAdsorbent disposal/regeneration issues; limited capacity; variable effectiveness
Biological (Indirect)
Activated Sludge
Process		Microbes entrap MPs in biological flocsPart of standard wastewater treatment; incidental MP removalMPs concentrated in sludge; re-release risk if sludge is mismanaged
Table 2. Size distribution and mean size of MPs in treated and untreated samples. The size relates to the feret maximum. PX stands for the percentiles, e.g., P5 is the 5th percentile.
Table 2. Size distribution and mean size of MPs in treated and untreated samples. The size relates to the feret maximum. PX stands for the percentiles, e.g., P5 is the 5th percentile.
UnitUntreatedTreated
Meanµm22.710.2
S.D.µm 23.539.5
Min.µm 2.92.9
Max.µm 416.8571.2
P5µm 3.72.9
P25µm 8.33.7
P50 (Median)µm 16.25.2
P75µm 29.48.1
P95 µm 62.322.1
Table 3. Extrapolation of avoided emissions and agglomerate production.
Table 3. Extrapolation of avoided emissions and agglomerate production.
UnitPer m3Pilot StudyPer Day *Per Year *
Wastewater treatedm31174.21016
Agglomerates (wet)kg5.9100.524.75976
Agglomerates (pressed)kg4.474.018.34423
Agglomerates (dry)kg1.932.37.91912
Avoided MP masskg1.728.57.11706
Avoided MP particlesn6.7 × 10111.1 × 10132.8 × 10126.8 × 1014
Avoided CODkg6.0101.925.26089
abcr eco Wasser3.0 PE-X®, industrial wastewater usedkg0.711.92.9711
Energy usedkWh1.423.85.91422
* 240 working days per year for the company in this case study.
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Korzin, A.; Sturm, M.T.; Myers, E.; Schober, D.; Ronsse, P.; Schuhen, K. Upstream Microplastic Removal in Industrial Wastewater: A Pilot Study on Agglomeration-Fixation-Reaction Based Treatment for Water Reuse and Waste Recovery. Clean Technol. 2025, 7, 67. https://doi.org/10.3390/cleantechnol7030067

AMA Style

Korzin A, Sturm MT, Myers E, Schober D, Ronsse P, Schuhen K. Upstream Microplastic Removal in Industrial Wastewater: A Pilot Study on Agglomeration-Fixation-Reaction Based Treatment for Water Reuse and Waste Recovery. Clean Technologies. 2025; 7(3):67. https://doi.org/10.3390/cleantechnol7030067

Chicago/Turabian Style

Korzin, Anika, Michael Toni Sturm, Erika Myers, Dennis Schober, Pieter Ronsse, and Katrin Schuhen. 2025. "Upstream Microplastic Removal in Industrial Wastewater: A Pilot Study on Agglomeration-Fixation-Reaction Based Treatment for Water Reuse and Waste Recovery" Clean Technologies 7, no. 3: 67. https://doi.org/10.3390/cleantechnol7030067

APA Style

Korzin, A., Sturm, M. T., Myers, E., Schober, D., Ronsse, P., & Schuhen, K. (2025). Upstream Microplastic Removal in Industrial Wastewater: A Pilot Study on Agglomeration-Fixation-Reaction Based Treatment for Water Reuse and Waste Recovery. Clean Technologies, 7(3), 67. https://doi.org/10.3390/cleantechnol7030067

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