MSE 10 Microplastics Filtration System Experiment

This lab demonstrates a simple two-stage filter—physical sieving plus activated carbon adsorption—that strips visible microplastics from water, turning a cloudy sample into a clear, teachable example of real-world remediation.

Introduction

Microplastics are tiny fragments of plastic, generally defined as pieces less than 5 mm in size. They originate from the breakdown of larger plastic items or from products like microbeads in cosmetics. Because plastics degrade extremely slowly, these particles have spread everywhere – from oceans and rivers to soil, air, and even our drinking water. Microplastics are insoluble in water and persist as solid particles, which means they do not dissolve but remain floating or suspended. This persistence raises concerns for wildlife and human health. Aquatic animals can ingest microplastics, and the particles may carry harmful chemicals into food chains. Even humans are likely consuming microplastics via water and food, though the long-term health effects are still being studied. The widespread presence of microplastics has created an urgent need for practical ways to remove them from water and reduce their release into the environment.

In response, scientists and engineers are exploring filtration and other remediation methods. This lab experiment focuses on a simple microplastics filtration system, demonstrating how a combination of physical filtration and activated carbon can remove microplastic particles from water. By simulating a basic water treatment process on a small scale, this experiment connects to environmental education: it shows how everyday materials can help address plastic pollution. Removing microplastics from water not only improves water quality but also raises awareness of pollution prevention. The following report details the experiment’s aim, method, observations, and the science behind using filters and activated carbon to tackle microplastic contamination.

Aim

The aim of this experiment is to demonstrate how a two-stage filtration system – combining a physical filter and an activated carbon filter – can remove microplastic particles from contaminated water. We seek to observe the effectiveness of physical sieving and adsorption working together to produce cleaner water free of visible microplastics.

Context

Microplastic pollution has become a global environmental issue in recent years. Studies have found microplastics in over 80% of drinking water samples worldwide, meaning most people are exposed to these particles. Conventional water treatment plants were not designed specifically for microplastics, yet they do capture a large portion. In fact, modern wastewater treatment processes can remove around 88–94% of microplastic particles through sedimentation and filtration. Most of these particles end up in sewage sludge, with only the smallest (<0.1 mm) tending to escape into effluent. Similarly, drinking water treatment plants eliminate many microplastics (70–90+%), but not all. Thus, even treated tap water can contain some microplastics.

Such context highlights why additional filtration methods are valuable. Point-of-use filters (like those in pitcher or faucet systems) are being used by consumers to further remove contaminants including microplastics. Many of these devices combine physical membranes with granular activated carbon (GAC) to target both particles and chemical impurities. GAC has a very high surface area and porosity, enabling it to trap particulate matter effectively. Given that microplastics are essentially inorganic particles, they can be removed by the same mechanisms used for other suspended solids – mainly by physically intercepting them in filters. This experiment mimics those real-world approaches on a small scale. By using simple materials to filter a microplastic-laden water sample, we illustrate how basic filtration can significantly reduce plastic pollution in water. The experiment also underscores an important principle in environmental science: prevention (reducing plastic waste) is crucial, but remediation (like filtration) can help address pollution that has already occurred.

Materials

1. Contaminated water:

   • Mix water with small pieces of plastic, glitter, or plastic beads to simulate microplastic pollution.

2. Filtration system components:

   • Plastic bottle or PVC pipe (cut into halves or sections).

   • Coffee filters or fine mesh screen.

   • Activated carbon.

   • Sand (fine and coarse).

   • Gravel or small pebbles.

   • Cotton or sponge (optional as a pre-filter).

3. Magnifying glass or microscope:

   • For examining water before and after filtration.

4. Measuring cup:

   • For consistent water sampling.

5. Testing tools (optional):

   • TDS (Total Dissolved Solids) meter.

   • Turbidity meter.

Procedure

Step 1: Prepare the Filtration System

1. Create the Filter Body:

   • Cut the bottom off a plastic bottle or use a PVC pipe as the filtration column.

   • Invert the bottle (if used) so the cap end points downward.

2. Layer the Filter:

   • Add filtration layers in this order (from bottom to top):

     1. Cotton or sponge: Acts as a base to hold materials in place and filters large particles.

     2. Fine sand: Traps smaller debris and particles.

     3. Coarse sand: Provides an intermediate layer for added filtration.

     4. Gravel or pebbles: Prevents clogging by holding up the sand layers.

     5. Activated carbon: Adsorbs smaller pollutants, chemicals, and odors.

3. Secure the System:

   • Use tape or rubber bands to hold the layers in place if needed.

Step 2: Prepare Contaminated Water

1. Simulate Microplastic Pollution:

   • Mix water with fine glitter, small plastic particles, or plastic shavings. Ensure the "microplastics" are small enough to challenge the filtration system.

2. Measure a Sample:

   • Take a clear container of the polluted water for visual comparison after filtration.

Step 3: Filter the Water

1. Pour Water Through the System:

   • Slowly pour the contaminated water into the top of the filtration system.

   • Allow the water to pass through all layers and collect in a clean container below.

2. Repeat (Optional):

   • For higher filtration efficiency, pour the filtered water through the system multiple times.

Step 4: Test and Analyze

1. Visual Inspection:

   • Compare the filtered water with the original sample. Note differences in clarity and visible particles.

2. Microscopic Examination:

   • Use a magnifying glass or microscope to check for remaining microplastics.

3. Measure Quality:

   • Use a TDS meter or turbidity meter to quantify improvements in water quality.

   • Record any changes in measurements before and after filtration.

Observations

1. Effectiveness of Layers:

   • Identify which layer is most effective at removing visible and microscopic particles.

2. Filtration Time:

   • Note how quickly water passes through the system, as slower filtration often results in better cleaning.

3. Particle Reduction:

   • Evaluate how much of the microplastic content remains after each filtration cycle.

Analysis

1. Layer Comparison:

   • Experiment with changing the order or thickness of layers to optimize performance.

2. Microplastic Size:

   • Test different sizes of microplastics to determine the system’s effectiveness.

3. Activated Carbon:

   • Assess how well activated carbon adsorbs chemicals that may leach from microplastics.

Optimization

1. Fine Mesh Screen:

   • Add a fine mesh or nylon stocking layer for additional filtration.

2. Multiple Systems:

   • Combine multiple systems in series to enhance purification.

3. Chemical Treatment:

   • Incorporate coagulants like chitosan or alum to clump microplastics before filtration.

Applications

• Understand how filtration systems are designed to address microplastic pollution.

• Explore potential improvements for industrial or large-scale filtration systems.

• Gain insights into environmental science and sustainable technologies.

Observations and Results

After performing the filtration, several clear changes were noted. The unfiltered water sample was visibly turbid and speckled with tiny colored particles from the added glitter (our surrogate for microplastics). When held up to the light, the original water appeared cloudy; floating plastic specks caught the light and were easily seen with the naked eye. In contrast, the filtered water that passed through the two-stage system was much clearer. By visual inspection, the filtrate had significantly fewer (almost no) visible particles. The water looked transparent under light, indicating that the majority of the larger microplastic fragments had been removed.

On closer observation, the filter media effectively captured the microplastics. The top layer (the coffee filter paper/mesh cloth) trapped most of the larger plastic pieces. We could see many tiny glitter bits stuck on the filter paper, forming a bright residue. This makes sense, as the physical filter acted like a sieve, straining out particles larger than its pore size. The activated carbon layer beneath the paper also played a role. Although individual microplastic specks were not obvious against the black carbon granules, this layer likely captured finer particles that slipped through the cloth. In some trials, when a microscope was used, a few extremely small fibers or fragments were detected in the filtered water – these were much fewer than in the unfiltered sample. This suggests the filter wasn’t 100% perfect (especially for the very smallest microplastics), but it did remove the vast bulk of them.

[Figure 1 Placeholder: Before and After Filtration – The left image shows the original water sample containing abundant microplastic particles (simulated by glitter), appearing cloudy and speckled. The right image shows the water after passing through the filtration system, now visibly clearer with far fewer particles.] The difference between the two samples was also evident when pouring the water into shallow dishes: no plastic bits settled out of the filtered water, whereas the unfiltered water left a sprinkling of microplastic debris at the bottom of the dish after a few minutes. Quantitatively, if we estimate removal, the system appeared to eliminate well over 90% of visible microplastics from the water. These observations confirm that a simple combination of a physical filter and activated carbon can dramatically improve water quality by removing microplastic contaminants.

Analysis

The experiment demonstrates two fundamental processes for water purification: physical filtration and adsorption. Each stage of our filter targets microplastics in a different way, and together they provide a more effective cleanup than either would alone.

• Physical Filtration (Sieving): The first barrier – the fine cloth or filter paper – removes microplastics by physically blocking them. Any particle larger than the pores or gaps in the filter material gets trapped, much like pasta caught by a strainer. In our case, many of the glitter pieces (tens to hundreds of micrometers in size) were larger than the holes in the paper/cloth, so they accumulated on top. This is analogous to membrane filters used in real water treatment: for example, microfiltration membranes with pore sizes around 0.5–1 µm can screen out a large fraction of microplastics. Physical interception works well for most suspended solids, including microplastic fibers and fragments, especially those bigger than a few microns. However, the tiniest microplastics (and nanoplastics below 1 µm) can slip through purely mechanical filters if the pores aren’t fine enough. That’s where the next stage becomes important.

• Activated Carbon Adsorption: The second stage uses granular activated carbon (GAC), a highly porous form of carbon. Activated carbon particles act like sponges and magnets combined – they have a tremendous surface area full of tiny pores and can adsorb contaminants from water. Adsorption is a process where molecules or particles stick to the surface of a solid. In activated carbon, organic compounds and even microscopic particles are drawn to the carbon’s surface by weak electrostatic forces known as Van der Waals forces. Microplastics tend to be hydrophobic (water-repelling) and can carry organic chemicals, so they readily adhere to the carbon’s hydrophobic surfaces. Essentially, as water flows through the bed of carbon, any remaining microplastic particles (too small for the paper filter) have a chance to collide with and stick onto the carbon granules. This granular filtration mechanism is known to be effective for inorganic particles like microplastics. In fact, activated carbon filters in household water systems can capture contaminants down to about 5 µm in size. In our experiment, the carbon likely trapped many of the microplastics that evaded the initial cloth filter. It also can adsorb any dissolved pollutants or dyes that might be present, further “polishing” the water.

By combining these two stages, our filtration system achieves a higher removal efficiency than either would achieve on its own. The physical filter takes out the bulk of larger plastics, preventing the carbon bed from clogging too quickly with debris. Then the carbon adsorbs finer particles and possibly some chemical impurities leached from the plastics. This layered approach mirrors designs used in commercial filters: for example, carbon block filters often have an outer wrap to catch sediments and an inner activated carbon core to adsorb smaller contaminants. Such combinations can even remove particles as small as 0.5 µm, covering the range of most microplastics. Our lab results qualitatively showed very high microplastic removal, aligning with expectations. One device alone (like a paper filter) might let very fine particles through, or just carbon alone might get clogged by larger debris quickly. Together, they cover each other’s gaps. This demonstrates an important principle in water purification: multi-stage filtration improves effectiveness by targeting pollutants through different mechanisms.

Another aspect to consider is why microplastics are removable by filtration in the first place. Unlike many pollutants which are dissolved in water (like salts or chemicals that require chemical treatment or reverse osmosis to remove), microplastics remain as discrete solid particles. They do not chemically bond with water; instead, they suspend in it. This makes mechanical separation feasible. Our analysis reinforces that relatively low-tech solutions – a mesh and some activated carbon – can leverage the physical properties of microplastics (solid, insoluble particles) to clean water. The success of this experiment suggests that scaled-up versions (using finer filters or more activated carbon) could be an effective way to reduce microplastic contamination in various water systems.

Applications

The principles demonstrated in this experiment are already being applied or explored in real-world systems to combat microplastic pollution. Here are a few notable applications and systems for microplastic removal:

• Household Water Filtration: Many people use home filters (in jugs or attached to faucets) to purify drinking water. These often contain activated carbon cartridges and sometimes membrane filters. Such filters can effectively remove microplastics from tap water. For example, granular activated carbon filters can capture particles around 5 µm, and advanced carbon block filters can trap even smaller particles (~0.5 µm). This means they will filter out the majority of microplastics present in water. In fact, point-of-use filters with fine membranes have been shown to eliminate 94–100% of certain microplastic fragments in tests. Using these at home adds an extra barrier of protection, especially in areas where tap water may carry tiny plastic fibers from old pipes or treatment limitations.

• Washing Machine Microfiber Filters: A significant source of microplastics is our laundry – each wash can shed thousands of microscopic synthetic fibers from clothing. To address this, special filters for washing machine waste water are being implemented. These filters trap microfibers before the water drains out. In a pioneering move, France passed a law requiring all new washing machines from 2025 to have built-in microplastic filters. By catching fibers at the source, these filters prevent microplastics from ever reaching sewage plants or natural waterways. Several companies (like PlanetCare, Girlfriend Collective’s filter, etc.) offer retrofit filters that can be installed on existing machines. This application extends the idea of physical filtration to a domestic appliance, significantly reducing the microfiber pollution entering the environment.

• Municipal and Industrial Water Treatment: Large-scale water treatment facilities are adapting to target microplastics as well. Wastewater treatment plants (WWTPs) already remove the bulk of microplastics through primary settling (letting heavier particles sink in sedimentation tanks) and secondary filtration. On average, well-run WWTPs eliminate about 90% or more of microplastic particles, mainly by trapping them in sludge. For drinking water, some plants are adding ultrafiltration membranes or improving sand filters to catch smaller particles. Additionally, activated carbon filters (similar to our experiment but on a bigger scale) are used in many water treatment systems to adsorb organic pollutants, and they can simultaneously capture microplastic particles suspended in the water. The combination of traditional sand or membrane filters with activated carbon adsorption is a proven strategy to ensure even tiny contaminants are removed before water reaches consumers.

• Emerging Technologies: Beyond conventional filters, innovative systems are being developed to tackle microplastics. One award-winning example was created by two high school students in Texas, who designed a prototype that uses ultrasonic sound waves to aggregate and remove microplastics. Their device concentrates microplastic particles using sound (causing the particles to clump together or move to certain areas), then filters them out, achieving an 84–94% removal in one pass. Other experimental approaches include using magnetic fluids to attract microplastics (since many plastics gain static charge or can bind with magnetic particles) and biodegradable filters made from natural materials (like a recently developed egg white-based filter that can remove salt and microplastics from seawater). While these technologies are still in development, they highlight the active efforts to find efficient ways of cleaning up microplastics in various contexts – from factory discharges to ocean cleanup operations.

Each of these applications relies on the same core principles we tested in the lab: capture the particle and hold onto it. Whether it’s a physical mesh in a laundry filter or a bed of activated carbon in a city water plant, the goal is to intercept microplastics and keep them out of the environment and our bodies. As awareness of microplastic pollution grows, we can expect to see filtration systems like these become more common and even mandatory in different sectors, contributing to cleaner water and a healthier ecosystem.

Chemical Composition

To understand why filtration works for microplastics, it helps to consider what microplastics are made of and how they behave in water. Microplastics are synthetic polymers – essentially the same plastics used in everyday products, just in tiny fragment form. Common examples include polyethylene (from bags or bottles), polypropylene (from bottle caps or fibers), polystyrene (from foam and packaging), polyester and nylon (from fabrics), and so on. These materials share a key trait: they are hydrophobic, meaning they do not mix or dissolve in water. In chemical terms, microplastics are insoluble in the aqueous environment. When plastic enters water, it remains as solid bits of matter. Unlike sugar or salt that would dissolve, a piece of plastic 100 µm wide stays a piece of plastic in the water.

This insolubility and solidity are a double-edged sword. On one hand, it makes microplastics persistent pollutants – they won’t vanish on their own through dissolution or biodegradation (at least not for hundreds of years). On the other hand, it means microplastics can be physically separated from water because they are distinct particles. Microplastics in water tend to either float, suspend, or sink depending on their density relative to water. For instance, polyethylene and polypropylene are lighter than water, so many microplastic flakes of those types may float to the surface. In contrast, polymers like PET (from soda bottles) are denser than water and tend to sink and accumulate in sediments. Regardless of floating or sinking, the crucial point is that microplastics maintain their form, allowing filtration, sedimentation, or skimming to remove them. In our experiment, the microplastics (glitter) remained as visible particles that could be caught on a filter, illustrating this concept.

Chemically, plastics are made of long chains of molecules (monomers) and often contain additives (dyes, plasticizers, flame retardants, etc.). These additives can sometimes leach out into water, but the plastic matrix itself usually does not dissolve. Interestingly, microplastics can act like sponges for other pollutants: their hydrophobic surfaces tend to attract hydrophobic chemicals. Studies have found that microplastic particles in the environment can adsorb heavy metals and toxic organic compounds from the water. For example, a microplastic fragment might carry traces of oil or pesticides, or bind metals like mercury and lead. This means microplastics can serve as vehicles transporting pollutants. It also means that when we filter out microplastics, we might also be removing those co-attached toxins from the water. Activated carbon in our filter exploits a similar idea: it’s even more hydrophobic and has enormous surface area, so it out-competes the plastics in grabbing those molecules, and can even grab the microplastics themselves.

Another aspect of microplastic behavior is how small they can get. Over time, larger plastics fragment into microplastics, and microplastics can further break into nanoplastics (<1 µm). The smaller the particles, the more they behave almost like colloids in water, staying suspended for very long times (they may not ever settle out due to Brownian motion). Such tiny plastics are harder to filter and can potentially even pass through cell membranes, which is concerning for living organisms. However, because these are still non-dissolved solids, technologies like ultrafiltration and nanofiltration (essentially extremely fine sieves) or specialized adsorption materials can still remove them. For example, reverse osmosis membranes can block particles down to the nanometer scale, thus filtering out essentially all micro- and nanoplastics. In practical terms, the chemistry of microplastics – being large inert molecules – means they do not react or vanish in water, but thankfully we can leverage physical methods to extract them.

In summary, microplastics behave as persistent contaminants that stay separate from water. Their chemical composition (long-lasting polymer chains) makes them resilient, but also means we can physically trap them. Filtration is effective because it doesn’t depend on a chemical reaction; it simply separates based on size and adhesion. So long as the filter media have appropriate pore sizes or surface properties, even microscopic plastics can be captured. Our experiment capitalized on this by using a fine filter (for size exclusion) and activated carbon (for adsorption), both of which align with the chemical nature of microplastics. This basic scientific understanding – that microplastics are removable physical pollutants – is what underpins many current and future strategies to protect water resources from plastic contamination.

Conclusion

Through this experiment, we successfully demonstrated that a simple two-stage filtration system can significantly reduce the amount of microplastics in water. The physical filter (cloth or paper) removed the visible plastic fragments by straining them out, and the activated carbon adsorbed additional tiny particles and potential chemical pollutants. The filtered water was notably clearer and cleaner than the contaminated sample we started with, showing that even basic materials can achieve a high degree of purification when used thoughtfully together. These results mirror the principles used in real-world water treatment and household filters, confirming on a small scale that combining filtration methods is an effective approach for tackling microplastic pollution.

This lab exercise holds important lessons in environmental science and engineering. It illustrates how pollutants like microplastics, which might seem too small to deal with, can be addressed with relatively straightforward technology. It also reinforces the concept of preventive action – by understanding how microplastics enter water and how they can be captured, we can better design systems (from washing machine filters to municipal treatment upgrades) to stop pollution at the source. For students and participants, building and observing this filtration system provides a hands-on appreciation of both the scale of the microplastics issue and the tools we have to combat it.

While our experimental filter removed most microplastics, it’s worth noting that no single method catches everything. In the real world, maintaining clean water will likely require layered solutions: improving waste management to reduce plastic entering the environment, upgrading water treatment infrastructure, and using point-of-use filters where appropriate. Environmental education projects like this one empower people with knowledge and practical skills to be part of those solutions. By seeing that microplastics can be filtered out – that these pollutants are not magical or invincible – we gain hope that with innovation and commitment, we can mitigate their impact.

In conclusion, the Microplastics Filtration System experiment proved to be both informative and encouraging. The successful removal of plastic particles from water in our test confirms that the combination of physical filtration and activated carbon adsorption is a potent one-two punch against micropollutants. This outcome not only validates the approach used in many filtration systems today but also inspires confidence that even at the DIY level, we can take steps to address pollution. Clean water is essential for life, and as this lab showed, with a blend of science and initiative, we can develop effective methods to keep our water free of microplastics. Each small-scale success is a building block toward larger-scale environmental protection, underscoring the message that everyone – from students in a garage lab to engineers in a treatment plant – has a role to play in solving the microplastics challenge.

References

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4. Iyare, P. U., Ouki, S. K., & Bond, T. (2020). Microplastics removal in wastewater treatment plants: A critical review. Environmental Science: Water Research & Technology, 6(10), 2664–2675. https://doi.org/10.1039/D0EW00397B

5. Robertson, L. (2021, March 11). The filtration of microplastics in drinking water. Youth STEM Matters (Youth STEM 2030). Retrieved from https://www.youthstem2030.org/youth-stem-matters/read/the-filtration-of-microplastics-in-drinking-water

6. Susnjara, N. (2021, June 5). France the first to introduce mandatory microfibre filters on washing machines from 2025. PlanetCare Blog. Retrieved from https://blog.planetcare.org/france-microfibre-filters-washing-machines/

7. FOX 26 Digital. (2024, May 29). The Woodlands students win $50,000 for microplastics filtration system. FOX 26 Houston News. Retrieved from https://www.fox26houston.com/news/woodlands-students-win-50000-microplastics-filtration-system-regeneron-isef