Reverse osmosis (RO) systems frequently are used to reduce the levels of total dissolved solids and suspended particles within water. These systems remove a variety of ions and metals as well as certain organic, inorganic, and bacterial contaminants. In general, the process of reverse osmosis can effectively remove high percentages of dissolved ions such as: Arsenic, Antimony, Aluminum, Barium, Beryllium, Cadmium, Calcium, Chloride, Chromium, Copper, Fluoride, Iron, Lead, Magnesium, Manganese, Mercury, Nitrate, Potassium, Selenium, Silver, Sodium, Sulfate, Thallium, and Zinc; radionuclides like Radium and Uranium; select pesticides like Endrin, Heptachlor, Lindane, and Pentachlorophenol; and particles like cysts, oocysts, and asbestos fibers.
There are some contaminants not removed from water by RO systems. Reverse osmosis units do not effectively remove most organic compounds, bacterial microorganisms, chlorine by-products, or dissolved gases like carbon dioxide, methane, and radon. Therefore, it is necessary to address the presence of dissolved gases that may impact the water chemistry prior to the reverse osmosis process. The reverse osmosis process is not particularly effective at selecting specific anions or cations to remove from the water so there can be a tendency for reverse osmosis water to have a low pH and to be slightly more corrosive than the untreated water. This can be addressed by using a post-treatment remineralization filter. The RO membrane's efficiency in reducing the amount of contaminants in the water depends on the contaminant concentration, chemical properties of the contaminant, the membrane type and condition, and operating conditions. Reverse osmosis is considered an ultrafiltration process; it is also expensive.
The RO membrane alone may not be an effective method for total removal of these contaminants but a properly designed system may be effective in reducing these contaminants to safe levels. Contaminant removal by the system may vary depending on operating conditions and equipment. Reverse osmosis can significantly reduce the microorganism population in the water, but because these microbes may regrow on the membrane and cause the formation of bio-slimes or cause the membrane to prematurely fail, it is recommended that the water be properly disinfected prior to RO treatment. RO treatment systems have a few system components:
- 1 | Prefilter - Typically a particle filter to remove particles, rust, and other debris.
- 2 | Possibly a water softener if the total hardness is elevated along with a smaller-diameter particle filter to remove particles that are greater than 1 to 5 microns, i.e., large clay to silt-size particles and larger.
- 3 | The RO pressure pump, line-pressure and pump pressure gauges, and a flow regulator.
- 4 | RO treatment unit will have a treated-water storage tank, a product line, a membrane, a flush-to-waste line, and a dispenser. The RO treatment unit should specify the typical or nominal cation and anion rejection rates for the thin film membrane which would be either a cellulose acetate membrane or a cellulose triacetate membrane.
- 5 | Most treatment systems have an activated-carbon pre-filter and post-filtration that may include a remineralization cartridge, a UV disinfection system, and a 0.22 to 0.45 micron (submicron) filter.
The ROtreatment system requires pretreatment that most likely includes Particle Filtration, UV Disinfection, Chemical or Ion Exchange, and other pretreatment to prevent scale formation or bio-slime regrowth/growth. Because of all the pretreatment, these are typically point-of-use units and not whole-house treatment systems. ROSystems are commonly used when the water contains elevated levels of salts, such as chloride, Nitrate, Total Hardness, and Sodium.
Reverse osmosis unit performance is measured by a combination of the membrane rejection rate, see above, and the recovery rate for the system. The membrane rejection rate is the percentage of the contaminant that is not permitted to pass through the filter. The rejection rate can be used to predict the effectiveness of the treatment process and the feasibility of the approach. For example, if there were two water sources that required treatment and one water source (source A) had an arsenic level of 2000 ppb and the other source (source B) had a concentration of 50 ppb and the membrane had a 90 % rejection rate, then:
Source A 2000 ppb * 0.90 = 1800 ppb of the arsenic is captured and diverted to waste, but 200 ppb of arsenic would pass through the filter. This concentration exceeds the recommended USEPA drinking water standard of 10 ppb for arsenic.
Source B 50 ppb * 0.90 = 45 ppb of the arsenic is captured and diverted to waste, but 5 ppb of arsenic would pass through the filter. This concentration is below the USEPA drinking water standard of 10 ppb for arsenic, but would be at the drinking water limit for some states.
Recently, the recovery rates for reverse osmosis units have significantly increased by the addition of booster pumps and a permeate pump. The reverse osmosis booster pump increases the water pressure in the feed line, while the permeate pump does not increase pressure, but helps the reverse osmosis unit waste less water.
Notes:
- 1 | Please keep in mind that standard reverse osmosis units may waste 3 gallons of water for every gallon of drinking water produced or 75 % of the water is wasted. That now more heavily contaminated waste water must be appropriately disposed of. The addition of a permeate pump can reduce this wastewater volume by about 85 %.
- 2 | If the water is not chlorinated and there are no trace levels of organics, it would not be advisable to install a granular-activated-carbon pre-filter. If a GAC filter is installed as a pre-filter on a source that is not chlorinated, it is likely that bacteria may regrow on the filter and membrane; it may be wise to install the GAC filter as a post filtration unit. A GAC filter is needed for systems that have chlorinated water and the RO unit is using a thin-film composite membrane.
Table 1 | Common Types of System Fouling (Cause and Approach)
| Common Types of Fouling | The Primary Cause | Pretreatment Approach |
| Disinfectant or Strong oxidizer | Potassium Permanganate, Chlorine Residual, Peroxide, and Ozone | Granular-Activated-Carbon or Oxygen Scavenger |
| Particles | Large particles in water, "rust" flakes from the piping or corrosion, or aquifer particles, such as: large clay, silt, sand, and fine stone, | Filtration with at least a 1 to 5 micron pre-filter |
| Biological Material | Bacteria, Total Coliform, E. coli, Nuisance Bacteria, and Heterotrophic Plate Count | Chlorination, UV disinfection, Ozonation, Hydrogen Peroxide |
| Scaling or Mineral Fouling | The presence of Barium, Calcium, Magnesium, or Strontium with the dominant anion being bicarbonate or sulfate. | Prefiltration and then Post filtration with 0.22 micron filter |
Follow the Path to Clean Water
We recommend that, prior to installing a Reverse Osmosis System, you Get Informed by gathering as much information as possible and Get Tested by conducting multiple levels of testing depending on your needs: Level 1 Observational Testing using our Self Test Web App, Level 2 Do-It-Yourself Testing, Level 3 Informational Lab Testing and, if needed, Level 4 Certified Testing conducted by a water professional.
If you have any questions please Contact the KnowYourH2O team.
FAQs
Yes, reverse osmosis is indeed effective in removing forever chemicals from water. Numerous scientific studies and findings support the efficacy of RO systems in significantly reducing or eliminating per- and polyfluoroalkyl substances (PFAS), commonly referred to as forever chemicals, from drinking water.
Does reverse osmosis remove forever chemicals in PFAS? ›
According to the EPA, reverse osmosis separation is up to 99% effective at removing certain PFAS. Think of it like keeping bugs out of a house with a window screen.
Are PFOS and PFAS the same? ›
What are PFOA and PFOS? Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) are part of a large group of lab-made chemicals known as perfluoroalkyl and polyfluoroalkyl substances (PFAS). Some of these chemicals have been in commercial use since the 1940s.
What water filters remove PFAS and PFOS? ›
The most common in-home water filters that remove PFAS are activated carbon and reverse osmosis. Dual stage filters (activated carbon + reverse osmosis) are also an option. REVERSE OSMOSIS FILTERS REMOVE PFAS BETTER THAN ACTIVATED CARBON FILTERS.
What chemicals are not removed by reverse osmosis? ›
For example, some common contaminants that can slip through the average RO filter are:
- Pesticides.
- Herbicides.
- Many other agricultural treatment products like fungicides.
- Some dissolved gasses, like hydrogen sulfide.
- Certain organic compounds.
Where are PFAS found?
- Cleaning products.
- Water-resistant fabrics, such as rain jackets, umbrellas and tents.
- Grease-resistant paper.
- Nonstick cookware.
- Personal care products, like shampoo, dental floss, nail polish, and eye makeup.
- Stain-resistant coatings used on carpets, upholstery, and other fabrics.
At ZeroWater, we believe you should have zero doubt about your drinking water. Our 5-stage filters not only remove 94.9% of PFOA and PFOS, but other contaminants like lead and pesticides. And you can conveniently get your water from ZeroWater pitchers or dispensers.
Do Brita filters remove forever chemicals? ›
While Brita filters were not designed—and do not claim to—remove PFAS (per- and polyfluoralkyl substances), they use the same processes that the U.S. Environmental Protection Agency (EPA) says is effective in reducing PFAS. These include using activated carbon and an ion exchange treatment.
How do I remove PFAS from my drinking water? ›
Filters containing activated carbon or reverse osmosis membranes have been shown to be effective at removing PFAS from water supplies. All water treatment units require regular maintenance to work properly.
Do PFAS ever leave your body? ›
It takes nearly four years for the level in the body to go down by half. PFAS leave the body mainly through urine.
The Teflon brand revolutionized such products, but the use of PFAS is widespread across many nonstick cookware brands. PFAS are also often behind any product that boasts waterproof or stain-resistant properties. Such products include clothing, rainwear, furniture, outdoor equipment, tapes, and cosmetics.
What are the symptoms of PFAS in the body? ›
Can exposure to PFAS cause health problems? Some PFAS have been linked to some health problems in humans including higher cholesterol, lower birth weights, lower immune response to vaccines, kidney and testicular cancer, high blood pressure in pregnancy, and changes in liver function.
Does boiling water get rid of PFAS? ›
Boiling water does not remove the regulated PFAS and may concentrate PFAS into some foods. Consuming foods that contain PFAS increases your overall exposure as ingestion is the primary way PFAS enter the body.
Do all reverse osmosis systems remove PFAS? ›
Yes, reverse osmosis does remove PFAS, but you shouldn't rely on reverse osmosis alone. High-quality RO systems combine several types of filtration to make sure that every last bit of PFAS are kicked to the curb.
Does a fridge water filter remove PFAS? ›
Unfortunately, no. Refrigerator water filters reduce PFAS contaminants but do not remove them. These filters are designed to remove chlorine, taste, and odors from water. Consider a whole-home water filtration system if you're thinking about purchasing a water filter that removes PFAS from tap water.
Why you shouldn't use reverse osmosis? ›
RO water which doesn't contain enough minerals, when consumed, leaches minerals from the body. This means that the minerals being consumed in food and vitamins are being urinated away. Less minerals consumed plus more minerals being excreted causes serious negative side effects and big health problems.
Is it safe to drink RO water daily? ›
Experts warn against the prevailing belief that RO filtered water is healthiest, highlighting health risks due to mineral depletion. Maintaining TDS levels of 200-250 mg/L is crucial, retaining essential minerals. WHO and health professionals caution against excessive RO use.
What toilet paper doesn't have PFAS? ›
EcoHiny the PFAS-Free Toilet Paper
EcoHiny is your brand for buying sustainable and committing to eco-friendly practices.
What foods are high in PFAS? ›
Although the evidence is not as strong as for fish and shellfish, Eick said eggs, certain kinds of meat, especially liver and other organ meats and dairy products have also been found to have higher levels of longer chain PFAS in particular. EU scientists have also warned that fruit can contain elevated levels of PFAS.
What shampoos contain PFAS? ›
PFAS in one shampoo
In the test, the shampoo "Curl shampoo" from Living Proof contains the PFAS substance Octafluoropentyl methacrylate. PFAS is a group of substances that are particularly problematic for our environment and health.
Yes, water distillation does remove PFAS.
Do Brita filters remove PFAS? ›
Despite its cost-effectiveness, EWG's testing revealed that the standard Brita filter only achieved a modest 66% reduction rate for PFAS in water.
Which water filters remove forever chemicals? ›
Appendix: Full testing results (scroll left to right to see detected PFAS chemicals)
| Filter | Test | Percent reduction |
|---|
| Clearly Filtered | GenX and PFAS Water Test | 100% |
| Epic Water | GenX and PFAS Water Test | 98% |
| Seychelle pH2O | GenX and PFAS Water Test | 48% |
| Zero Water | GenX and PFAS Water Test | 100% |
8 more rowsJul 11, 2023
Toxic metals like lead or radioactive polonium, take months to halfway leave your blood. But PFAS surpass all of these other substances. Some of the PFAS that have been studied — PFOA, PFOS, and PFHS — can take over seven years to reduce by half in your bloodstream. It's no wonder they're called "forever chemicals."
How to get PFAS out of body? ›
How are PFAS excreted from the body? Some PFAS leave the body slowly over time, mostly through urine. People who have kidney disease may not excrete as much PFAS from their body through their urine as healthy individuals. Some PFAS routinely leave the body in blood during menstruation.
What eliminates PFAS? ›
Reverse osmosis is a membrane technology that only allows water and select compounds to pass through the membrane, while PFAS are blocked. This is commonly installed at the kitchen sink and has been found to be very effective at removing most PFAS in water.
Does a pur water filter remove forever chemicals? ›
There's also the possibility that the PUR filters simply don't contain enough activated carbon filter media to remove all PFAS, so while they might remove some forever chemicals, they don't offer removal rates that are worth boasting about.
