What Water Filtration Method Removes Viruses?

Infectious viruses can readily spread through water and cause illnesses. Some ailments caused by viruses include cholera, typhoid, flu, hepatitis, conjunctivitis, gastroenteritis, and meningitis. It is of utmost importance to use a water filter that will get rid of viruses to prevent contracting such ailments.

Do Viruses Pass Through Bacteriological Filters?

Viruses are hundreds of times smaller than bacteria, with most varying between 0.004 and 0.1 microns. They are also extraordinarily tough organisms that can live through extreme cold and hot temperatures. With a filter size of 0.3 microns or less, you can achieve moderate effectiveness in removing bacteria from water. However, this range of filter size is not effective in removing viruses at all and they easily pass through.

Do Charcoal Filters Remove Viruses?

Charcoal filters have been in use both for point-of-use and municipal water treatment. However, their viral filtration capacity is quite negligible. To improve them, they are usually coated or mixed with oxides or hydroxides of metals such as calcium, iron, aluminum, and magnesium to make them positively charged. In this way, they can hold onto the negatively charged viruses electrostatically.

Pure charcoal filters can only remove between 50% to 90% of viruses and only when the viruses are coagulated together or bound to other larger particles. On the other hand, positively charged adsorptive filters can remove 90 to 99% of viruses. The downside to modified charcoal filters is that the technical expertise needed can be too involving and expensive for household use. Because of that, they are often mainly used for community or municipal water treatment operations.

Does RO Remove Viruses?

Reverse Osmosis Systems are very highly effective at eliminating viruses and work by pumping water through semi-porous membranes, from the highly contaminated source to a region of low contamination. They usually contain more than one filter for pre-and post-filtration, with pore sizes as tiny as 0.0001 microns.

Viruses are the hardest to filter out among all microbial pathogens due to their small sizes (between 0.02 and 0.4 microns). Since the pore sizes of RO membranes are much smaller than these typical viral sizes, they can entirely remove viruses by size exclusion alone. The membranes need careful and regular monitoring because any slight faults in their structure can result in the passage of contaminated water into the product side.

Does Boiling Water Remove Viruses?

According to the Centre for Disease Control (CDC), bringing water to a rolling boil for at least one minute is highly effective in killing viruses. So, if you do not have a water filter, you can achieve the same results by boiling your water for a couple of minutes. Research has shown that many viruses get killed almost 100% when subjected to temperatures above 64°C for more than 3 minutes.

Do water filters kill viruses?

Filters do not kill viruses or any other biological contaminants found in water. They are, instead, designed to work like sieves that allow the smaller particles like water molecules to pass through while blocking particles that are larger than their pore size. However, many typical filters have pores 0.2 microns in diameter, which is large enough for viruses to pass through. For that reason, simply filtering water is not a sure way of making it safe for drinking.

Which Filters Cannot Remove Viruses?

All microfiltration filters such as ceramic, sediment, charcoal, activated carbon, fabric, and paper filters with pore sizes ranging from 0.05 to 5 microns cannot remove viruses. Also, ultrafiltration filters such as membrane filters with pore sizes between 0.001 and 0.05 micron cannot remove viruses significantly.

In addition, many viruses are way too small and light to be removed by simply settling using gravitational sedimentation filters unless they are attached to bigger and heavier particles. Removal of viruses by sedimentation hardly ever exceeds 90%.

Granular media and rapid rate depth filters like sand, gravel, diatomaceous earth, coal, and other minerals have low effectiveness. Vegetable and animal-derived depth filters such as coal, sponge, charcoal, and cotton, among others, have moderate effectiveness.

Chemical filters like the ion exchange technology that bind contaminants to the surface of the filter do not trap viruses. Iodine resins used in point-of-use systems can inactivate viruses substantially.

However, it is difficult to dissolve iodine in water and, it can also lead to undesirable health effects. None of the other chemical agents suggested and occasionally used to disable pathogens are considered safe for prolonged use in disinfecting drinking water. 

For example, copper and silver are also difficult to dissolve in water and are mainly bacteriostatic. The silver concentrations used in point-of-use treatment systems cannot inactivate viruses.

On the other hand, quaternary ammonium compounds (QACs) are rare, expensive, and ineffective against viruses. For these reasons, therefore, these chemical filter agents are not approved to be used for routine household water disinfection.

Why Can’t Some Filters Remove Viruses?

Fabric, paper, membrane, canvas filters, and their likes such as cloth, other woven fabric, synthetic polymers, wick siphons have high to low effectiveness depending on pore size and composition.

Nonetheless, many such filters have low efficacies since their pores are much larger than the diameters of viruses. However, some membrane and fiber filters have pore sizes between 0.01 and 0.001 micrometers (ultrafilters), which are tiny enough to remove viruses efficiently.

Ordinary fabric, paper, monofilament nylon, or filters of similar nature have no endorsement to be used for the general treatment of household water. It is because the pore sizes of these filters are too large to tangibly retain free viruses, which are not associated with large particles or organisms.           

Ceramic and other porous cast filters made of clay or other minerals too have effectiveness that varies from high to low depending on pore size and ceramic filter quality. Many of these filters consist of media that can adsorb viruses and should be able to attain high virus retention rates.

But, due to competition for adsorption sites with other contaminants, the efficiency of adsorbing viruses often decreases with increased use. It becomes necessary to restore the adsorption sites through physical or chemical cleaning processes.

Commercial ceramic filters, especially those manufactured in the UK and US, are highly tested for their microbial removal efficiencies, and most have certified performance ratings. Some of these filters are rated to remove viruses by at least 99.99%, as required by the United States Environmental Protection Agency (USEPA) for point-of-use microbial water filtration. Body feed and septum filters like diatomaceous earth and other fine earth media also exhibit moderate removal effectiveness.

Final Thoughts

Viruses are one of the most dangerous microbial contaminants found in water. They are highly infectious, more than bacteria, and limited contact with them is enough to cause illnesses and life-threatening health conditions. It is necessary that water used for drinking, cooking, or washing fruits and utensils be free of these pathogens. The surest way of doing this is to use water filters that have been tried, tested, and certified to rid water of viruses according to the highest available standards. That’s why you need a reverse osmosis filter that deploys a combination of water treatment technologies to give you the safest drinking water you can trust. When it comes to viruses, not just any filter will do.