Reverse osmosis (RO) is a widely used water purification technology designed to remove a broad spectrum of impurities from water.
How Reverse Osmosis Works
Reverse osmosis operates by forcing water through a semi-permeable membrane under pressure. This membrane features extremely small pores, which act as a barrier, allowing water molecules to pass through while blocking larger dissolved solids and contaminants. The process essentially reverses natural osmosis. By applying pressure greater than the natural osmotic pressure, RO systems push water from a more contaminated side to a less contaminated side, producing purified water.
The system separates the incoming water into two streams: the purified water, known as permeate, and a concentrated waste stream containing the rejected impurities. This concentrated stream is then flushed away. The effectiveness of reverse osmosis relies heavily on the membrane’s ability to physically block particles based on their size.
Does Reverse Osmosis Remove Viruses?
A properly functioning reverse osmosis system is highly effective at removing viruses from water. The primary reason for this effectiveness lies in the extremely small pore size of RO membranes. These membranes typically have pores ranging from 0.0001 to 0.001 microns (0.1 to 1 nanometer).
In comparison, viruses are significantly larger than these membrane pores. Most viruses generally measure between 0.02 and 0.4 microns (20 to 400 nanometers) in size. This substantial size difference means that viruses are physically unable to pass through the tight structure of the RO membrane. It is akin to trying to push a beach ball through a pinhole.
Consequently, RO systems can achieve a very high rate of viral removal. While reverse osmosis effectively removes viruses, it is important to note that it physically blocks them rather than inactivating or killing them. For an additional layer of protection, especially in situations with high microbial concern, RO systems can be paired with other disinfection methods such as ultraviolet (UV) treatment.
Other Contaminants Removed by Reverse Osmosis
Beyond viruses, reverse osmosis systems are capable of removing a wide array of other contaminants. The semi-permeable membrane effectively filters out larger biological contaminants like bacteria and protozoa, which are typically larger than viruses.
RO technology also excels at rejecting dissolved inorganic solids, including salts, minerals, and heavy metals. Common examples of contaminants removed include lead, arsenic, fluoride, nitrates, and sulfates. Many chemical contaminants, such as chlorine, pesticides, herbicides, and emerging contaminants like PFAS, are also significantly reduced or eliminated by RO systems.
Maintaining Your Reverse Osmosis System for Optimal Performance
Regular maintenance is important to ensure a reverse osmosis system continues to operate effectively and maintain its high contaminant removal efficiency. This maintenance involves the timely replacement of pre-filters and post-filters. Pre-filters, typically sediment and carbon filters, protect the delicate RO membrane by removing larger particles like sand, silt, and rust, as well as chlorine, which can damage the membrane.
If pre-filters are not replaced regularly (typically every 6-12 months), they can become clogged, leading to reduced water flow and potentially allowing contaminants to reach and foul the RO membrane. Membrane fouling, which is the accumulation of unwanted substances, can decrease the system’s performance, reduce water quality, and shorten the membrane’s lifespan. The RO membrane itself generally requires replacement every 3-5 years, depending on water quality and usage. Annual cleaning and sanitization of the entire system, including the storage tank, also contribute to optimal performance and longevity.