The pervasive use of plastic has created the widespread contamination of water supplies with microscopic plastic fragments. Concerns about water safety have grown as scientific studies confirm the ubiquitous presence of these pollutants in freshwater sources and the ocean. As people seek ways to protect their health, a common question arises regarding the effectiveness of household water purification methods. Understanding whether a common home filtration system, like Reverse Osmosis (RO), can successfully remove these tiny plastic particles is important for making informed decisions about drinking water quality.
Defining Microplastics and Particle Size
Microplastics are plastic particles measuring less than five millimeters in diameter. Their origin is twofold, arising either as primary sources, like microbeads, or more commonly as secondary sources. Secondary microplastics form when larger plastic items, such as water bottles and synthetic textiles, degrade due to weathering and physical abrasion. The size range of these fragments is extensive, presenting a challenge for filtration technologies. Particles less than one micrometer (0.001 millimeters) are classified as nanoplastics, which are the most difficult to capture. The effectiveness of any water purification method depends on its ability to physically block particles across this wide spectrum of sizes.
How Reverse Osmosis Filtration Works
Reverse Osmosis is a membrane-based water treatment process that relies on applied pressure to overcome natural osmotic forces. Water is forced across a synthetic semipermeable membrane, allowing only the smallest molecules, primarily water, to pass through while leaving behind dissolved and suspended solids. Residential RO membranes typically have a pore size of about 0.0001 microns, or 0.1 nanometers. This minute pore size enables the system to reject the vast majority of contaminants based on physical size and molecular weight. Contaminants that cannot pass through the membrane are collected in a concentrated stream and flushed away, which is why RO systems require a drain connection. This mechanism is effective for removing larger physical particles.
RO Efficiency for Microplastic Removal
Reverse Osmosis systems are highly effective at removing microplastics due to the substantial size difference between the plastic particles and the membrane pores. Microplastics, even the smaller fragments measured in the micron range, are physically blocked from passing through this barrier. Scientific testing consistently shows that RO filtration systems achieve an exceptionally high removal rate for microplastics. Removal efficiencies are typically cited at 99.9% or even 99.99% for particles in the relevant size range. This efficacy is maintained across the entire spectrum of microplastic sizes. The rejection mechanism is purely mechanical, ensuring that the plastic material cannot penetrate the membrane structure.
Comparing Other Common Water Filtration Methods
The high efficiency of Reverse Osmosis stands out when compared to other common household filtration technologies.
Granular Activated Carbon (GAC) Filters
Granular Activated Carbon (GAC) filters, frequently found in pitcher filters or refrigerator systems, primarily work through adsorption. These filters are highly effective at removing contaminants that cause taste and odor issues, such as chlorine, and can capture some larger microplastic particles. However, GAC filters are not designed to physically block the smallest microplastic and nanoplastic fragments, making their removal capability incomplete.
Ultrafiltration (UF)
Ultrafiltration (UF) is another membrane-based method that operates with a larger pore size than RO, typically in the range of 0.01 to 0.1 microns. UF is effective at removing virtually all bacteria, viruses, and most microplastics, offering a significant advantage over GAC filters. While Ultrafiltration is an excellent barrier against most microplastic contaminants, its larger pore size means it is less comprehensive than RO when dealing with the absolute smallest nanoplastic fragments. Therefore, for the broadest protection against the full range of plastic particles, the Reverse Osmosis system’s extremely tight membrane provides the most robust physical rejection capability.