Microplastics, tiny plastic particles less than five millimeters long, are a widespread environmental concern. They enter water sources from the breakdown of larger plastic debris, industrial discharges, and synthetic fibers shed from clothing. Microbeads, small manufactured plastic spheres, also contribute. Their presence in tap and bottled water has increased public awareness.
How Filtration Addresses Microplastics
Water filtration systems address microplastics through physical mechanisms. Physical straining, or size exclusion, is one method where particles are too large to pass through a filter’s pores. The filter acts as a physical barrier, effectively separating contaminants from water.
Adsorption is another mechanism, where microplastic particles adhere to the filter material. Some microparticles are trapped within the filter’s porous structure, while others are bound to the filter material. A filter’s effectiveness depends on its pore sizes and materials.
Filtration Methods and Their Effectiveness
Various filtration technologies target microplastics with differing effectiveness.
Reverse osmosis (RO) systems remove very small contaminants. They force water through a semi-permeable membrane with extremely fine pores (0.0001 to 0.001 microns), blocking most microplastics. RO systems achieve high removal rates, often up to 99.9%.
Activated carbon filters primarily adsorb chemicals that affect water’s taste and odor. Their effectiveness against microplastics is more limited, generally capturing larger particles due to the pore size and surface area of the carbon. Carbon block filters can remove particles down to 0.5 microns, while granular activated carbon (GAC) typically filters particles 5 microns and larger.
Membrane technologies like ultrafiltration (UF) and nanofiltration (NF) offer advanced solutions. Ultrafiltration membranes (0.01 to 0.1 micrometers) remove smaller microplastic particles, bacteria, and some viruses. Nanofiltration provides finer filtration, removing dissolved organic compounds and even smaller microplastics. Both UF and NF are highly efficient for microplastic removal, with UF achieving rates as high as 95.6%.
Mechanical filters, often sediment filters, serve as a preliminary stage. They physically remove larger particles like sand, silt, and rust, and are effective for microplastics larger than 5 microns. Their efficiency decreases with smaller microplastic particles.
Home Water Filtration Options
For household use, several water filtration systems offer varying microplastic removal capabilities. Pitcher filters commonly utilize activated carbon, providing limited effectiveness against microplastics and typically only removing larger ones. Faucet-mounted filters, also using activated carbon, have similar limitations.
Under-sink filtration systems vary in design and effectiveness. Many incorporate advanced methods like reverse osmosis or specialized mechanical filtration for enhanced microplastic removal. Whole-house systems offer broad protection, depending on the installed filter cartridges. These range from sediment filters to advanced RO or UF technology.
When selecting a home water filter, check for certifications like NSF/ANSI Standard 401 for microplastic reduction. This certification indicates a filter has been independently tested to reduce microplastics between 0.5 and 1 micrometer by at least 85%. Some advanced systems are certified to remove 100% of tested contaminants, including microplastics.
Current Limitations in Microplastic Removal
Despite filtration advancements, complete microplastic removal remains challenging. Nanoplastics, particles less than one micrometer in size, some as minute as 0.0001 millimeters, are a significant hurdle. They often pass through advanced filtration membranes and are difficult to detect.
The diversity in microplastic shape, size, and type (fibers, fragments, beads) complicates developing a single, universally effective filter. Current methods are not designed to remove dissolved plastic components or leached chemicals. Some processes might inadvertently break larger microplastics into smaller fragments, increasing nanoplastic concentration. Research is ongoing to overcome these limitations.