From 10,000 MP/L to Filtered Water: Same-Sample Verification of Microplastic Removal Using EcoExposure™

Abstract

A preliminary same-sample experiment evaluated the EcoExposure™ optical computer-vision assay as a potential rapid verification method before and after microplastic filtration. A 1 L mixed-polymer suspension containing 10,000 particles/L of approximately 10–50 µm fragments was prepared. Approximately 400 mL was retained as the unfiltered sample. The remaining approximately 600 mL was gravity filtered through a LifeStraw system, and approximately 400 mL of filtrate was collected for testing. Both conditions were evaluated using the same EcoExposure workflow. The samples appeared visually similar at time zero, but separated optically after approximately 60 minutes: the unfiltered sample showed greater haze and reduced reference-pattern definition, whereas the filtrate remained comparatively clearer. Three anonymized computer-vision outputs also differed between conditions. Optical Metric A was 0.023 before filtration and 0.087 after filtration; Optical Metric B was 0.106 and 0.176; and Optical Metric C was 0.440 and 0.553, respectively. These preliminary findings support further evaluation of matched pre- and post-treatment measurement while preserving the proprietary definitions of the optical metrics.

  This paper is also available at :https://doi.org/10.5281/zenodo.23130615

Figure 1. Same-sample comparison before and after filtration. A 10,000 MP/L microplastic suspension and filtrate derived from the same starting sample were evaluated using EcoExposure™ before assay development and after 60 minutes. Complete results and metric comparisons are presented in the Results section.

IntroductionRapid evaluation of a treatment step benefits from measurements made before and after that step under otherwise matched conditions. This preliminary experiment tested whether the EcoExposure optical computer-vision assay could distinguish an unfiltered microplastic challenge suspension from filtrate derived from the same starting suspension. The same-sample design limits ambiguity introduced when unrelated water samples are compared and focuses interpretation on the intervening filtration step.

 

Materials and Methods

A 1 L mixed-polymer microplastic challenge suspension was prepared at 10,000 particles/L using approximately 10–50 µm fragments. The challenge mixture comprised PE, PET, PVC, PS, PP, and PU. Approximately 400 mL was retained as the unfiltered condition. The remaining approximately 600 mL was passed by gravity through a LifeStraw filtration system, and approximately 400 mL of the resulting filtrate was collected as the post-filtration condition.

Both conditions were evaluated with the same EcoExposure workflow. EcoExposure combines a plant-derived polysaccharide-based reagent, standardized optical imaging, and computer-vision analysis. The assay records optical characteristics associated with particulate interactions and aggregation, including haze, scattering, contrast, edge definition, and spatial texture. The metric definitions are proprietary and are reported here only as Optical Metric A, Optical Metric B, and Optical Metric C.

A second smartphone remained fixed throughout the experiment and continuously recorded sample handling, filtration, reagent addition, and imaging. This continuous recording provided visual provenance linking the starting suspension, filtration step, and subsequent assay images.

Figure 2. Filtration and assay workflow.(a) Introduction of the 10,000 microplastic particles/L challenge suspension into the LifeStraw filtration unit. (b) Gravity-driven filtration through the membrane filter. (c) Addition of the EcoExposure™ polysaccharide-based assay reagent to the post-filtration sample prior to standardized optical imaging and computer-vision analysis.

 

Results

At time zero, the unfiltered and post-filtration samples appeared visually similar. After approximately 60 minutes of assay development, the unfiltered 10,000 particles/L sample showed greater optical haze and reduced definition of the reference pattern. The post-filtration sample remained comparatively clearer.

Representative computer-vision outputs from the 60-minute images separated the two conditions as shown below.

 

Figure 1. Same-sample computer-vision response before and after filtration. The unfiltered 10,000 particles/L microplastic suspension and filtrate derived from the same starting suspension appeared visually similar before EcoExposure™ assay development. After 60 minutes, the unfiltered sample showed greater optical haze, while the filtrate remained comparatively clearer. Computer-vision analysis separated the two conditions: Optical Metric A, 0.023 versus 0.087 (3.78× higher in the filtrate); Optical Metric B, 0.106 versus 0.176 (+65.4%); and Optical Metric C, 0.440 versus 0.553 (+25.6%). Higher values indicate a clearer image, not a higher particle load.

DiscussionThe principal scientific value of this demonstration is the paired comparison. Both conditions originated from one starting suspension, so the experiment avoids uncertainty that would arise from comparing unrelated water samples with different particle loads or compositions. Within this design, the main procedural difference between the conditions was gravity filtration before the post-filtration assay.

The visual and computer-vision differences show that EcoExposure produced distinct responses for the unfiltered sample and its matched filtrate. This result supports continued study of a practical verification sequence: Measure → Treat/Remove → Measure Again → Verify. In that sequence, the assay would be used to compare a water sample with material derived from the same source after a removal step, rather than to infer treatment performance from a single isolated reading.

 

Limitations

This was a single preliminary proof-of-concept experiment. It does not establish a validated filtration-efficiency percentage, a detection limit, specificity for individual polymers, or performance across different water matrices, particle concentrations, filtration devices, or operating conditions. The findings are limited to the observed optical and anonymized computer-vision differences in this matched demonstration and require replication and controlled validation.

 

Conclusion

A 10,000 MP/L microplastic suspension and filtrate derived from that same starting sample produced visibly and quantitatively different EcoExposure™ responses after approximately 60 minutes. Because the two conditions came from a single prepared suspension and differed principally by the intervening filtration step, the same-sample design provides a clear and readily understandable demonstration of the assay’s ability to distinguish unfiltered water from its matched filtrate.

The separation observed across Optical Metrics A, B, and C supports further evaluation of EcoExposure as a rapid method for comparing water before and after filtration. This preliminary experiment does not establish complete microplastic removal or a validated filtration-efficiency percentage. It does, however, demonstrate the potential value of a straightforward approach in which the same water source is measured, filtered, measured again, and compared while the proprietary metric definitions remain protected.

Appendix:

Figure 3. Experimental setup and continuous video documentation.(a) EcoExposure™ filtration demonstration setup, including the optical imaging enclosure, reference target, microplastic challenge sample, filtration unit, and collection vessels. (b) Independent smartphone positioned on a fixed tripod to continuously video-record the experiment from sample preparation through filtration and post-filtration assay imaging, providing an additional provenance record.