Membrane filtration is among the newer strategies for tackling tiny pollutants
Concerns about microplastic pollution in water are mounting, prompting the search for effective removal strategies. As we celebrate Earth Day on April 22 with the theme Planet vs. Plastics, we focus on microplastics in water and the challenges of removing these tiny pollutants.
Microplastics are tiny plastic particles, typically less than 5 millimeters in size. They are either manufactured — for example, microbeads used in personal care products, microfibers in textiles, or pellets used in plastic production ─ or they are formed when larger plastic items break down with exposure to sunlight, heat, or mechanical abrasion.
Environmental and Human Health Impacts
Microplastics pose significant environmental challenges because of their widespread distribution, persistence in the environment, and potential to harm ecosystems. Their small size allows them to be easily transported by currents and winds, or to pass through soil to contaminate groundwater. As a result, microplastics are found in water bodies worldwide, including oceans, rivers, lakes, and even groundwater, as well as water bodies that are drinking water sources.
Aquatic organisms including fish, seabirds, and marine mammals can ingest microplastics directly, or indirectly through the food chain, leading to physical harm, digestive blockages, and the transfer of harmful plastic chemicals.
Microplastics can adsorb and concentrate impurities such as heavy metals, persistent organic pollutants, and pathogens from their surrounding environment. When ingested, these pollutants can be released, causing harmful effects. As a result, there is growing concern about the possible health impacts of microplastics on humans, particularly through ingesting contaminated food and water.
There is evidence to suggest that exposure to microplastics causes skin problems, digestive disorders, endocrine disruption, neurological issues, liver damage, and cancer. Removing microplastics from water and wastewater can help minimize the environmental impact and human exposure to these potentially harmful particles.
In honor of Earth Day 2024 and its theme, Planet vs. Plastics, Seven Seas’ Tampa employees dedicated time to a park and shoreline cleanup at R.E. Olds Park.
Removing microplastics from water presents several challenges because of their size, ubiquity, and diverse sources of contamination. Municipal water and wastewater treatment plants primarily rely on physical processes such as filtration and sedimentation to remove microplastics. However, advanced treatment methods like membrane filtration, including microfiltration and ultrafiltration, are increasingly being employed to capture smaller microplastic particles. Some of the more common methods include:
Coagulation and Flocculation — Coagulation involves adding chemical coagulants to water to destabilize colloidal particles, including microplastics, by neutralizing their surface charges. When coagulants are added to water, they form insoluble precipitates called flocs, which trap suspended particles, including microplastics, and facilitate their removal through additional processes such as sedimentation or filtration.
The coagulated water is then gently mixed, or flocculants are added, to encourage the destabilized particles to bind together to form larger flocs. This step enhances the removal efficiency of microplastics by increasing the size and density of the flocs, making them easier to settle out of suspension or capture through filtration. Coagulation and flocculation can be integrated into conventional water treatment systems, such as sedimentation basins or filtration units, making them potentially cost-effective and practical for large-scale microplastic removal.
Filtration — Both conventional and advanced filtration methods are commonly used to remove microplastics. Some processes typically employed include:
- Sand Filtration: It relies on the physical trapping of microplastics as water passes through layers of sand or other porous materials. The sand acts as a filter, capturing particles based on size and density.
- Activated Carbon Filtration: These filters can effectively adsorb organic compounds, including microplastics, from water. The porous structure of activated carbon provides a large surface area for adsorption, trapping microplastics as water flows through the filter.
- Granular Filtration: This involves the use of granular materials such as activated carbon, sand, or anthracite coal as filter media. These materials can physically trap and adsorb microplastics and other pollutants.
- Membrane Filtration: This process involves passing water through a membrane with a pore size small enough to capture microplastics while allowing clean water to pass through. Ultrafiltration and nanofiltration membranes with pore sizes in the range of 0.001 to 0.1 microns are typically used.
- Biological Filtration: Here, living organisms such as bacteria, algae, or biofilms degrade or metabolize microplastics in water. While still in the early stages of development, biological filtration shows promise as a sustainable and environmentally friendly method for removing microplastics from water and wastewater.
Combining filtration methods or integrating them into existing treatment systems can enhance the efficiency of microplastic removal. However, it’s important to consider factors such as cost, energy requirements, maintenance, and the specific characteristics of the water source when selecting the most suitable filtration method.
While a multifaceted approach to microplastic removal can help significantly reduce levels of this contaminant in water, complete removal remains a challenge, and further research and innovation are needed.
Removing microplastics presents a formidable challenge in water and wastewater treatment. Take action with us to combat microplastics by exploring our sustainable water treatment solutions, including reverse osmosis solutions. Let’s work together to safeguard water quality and protect our planet’s precious resources for future generations. Contact Seven Seas to learn more.
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