Is Reverse Osmosis Sustainable: RO Sustainability

Reverse Osmosis: Is It Sustainable and Eco-Friendly?

Are you concerned about the environmental sustainability of your reverse osmosis filter? If so, you may be asking is reverse osmosis sustainable.

Reverse osmosis is one of the most effective methods of purifying drinking water. It can remove more than 99% of most contaminants from tap water, making it safe for drinking and cooking. By treating your water with reverse osmosis, you can eliminate thousands of plastic water bottles. These benefits make RO a very green way of filtering your drinking water.

In this article, we explore the overall sustainability of reverse osmosis, how you can minimize its undesirable waste of resources, and much more.

Is Reverse Osmosis Sustainable

Bear in mind – reverse osmosis has several unsustainable drawbacks. It wastes a lot of water as it removes impurities – as much as 4 gallons for every gallon purified!

In addition, the reverse osmosis membrane is a single use filter that must be disposed of when it becomes spent. RO systems also require pre-treatment with sediment and carbon filters that are not reusable. Most of these filters must be replaced several times a year.

As this technology becomes more widely adopted, many people have begun questioning just how sustainable and eco-friendly reverse osmosis is. Ideally, your RO filter will not only waste less water but last longer as well.

How Does Reverse Osmosis Work

How does reverse osmosis work
Reverse osmosis uses a membrane to filter out impurities from contaminated water.

Reverse osmosis, also known as RO, is a process that uses pressure to force water through an ultra-fine membrane. This results in clean, pure drinking water on the other side of the filter, while dirty water remains behind. This treatment process is very effective at removing a long list of contaminants from water.

The RO membrane is a plastic film that is semipermeable. It has thousands of tiny holes, called pores, that are designed to filter out the impurities. The pores allow water molecules to pass through, while blocking larger particles and contaminants.

Osmosis systems

The membrane is placed in a housing unit, which is connected to the water supply. It can be installed at your faucet (called a POU system) or where the water comes into your house (called a POE system).

When you turn on the tap, water enters the RO system and is forced under pressure through the membrane. The water that comes out on the other side is clean and pure, while the dirty water remains behind. This dirty water is called brine – because it contains highly concentrated contaminants that are filtered out. The brine is dumped down the drain as a waste.

It is this wasted water that causes a lot of concern among environmentalists. They point out that having clean drinking water is important but using a process that wastes a precious resource like water is not sustainable.

Reverse osmosis filter system

I installed this reverse osmosis filter in my home to remove PFAS. It works great and is easy to maintain. I recently tested my water and found that my RO filter removes 100% of the contaminant!

You may want a similar reverse osmosis filter for your home.

Check Amazon

How Much Water Does RO Waste

If you have an RO filter, you know that it dumps some of your water down the drain as a waste. You may not know exactly how much water it wastes.

The amount of water that is wasted depends on the type of RO system you have. A typical POU system will waste about three gallons for every gallon of purified water. A POE system wastes less water because it has a larger membrane and is made to be more efficient than an under-sink unit.

For older RO systems, the technology is extremely wasteful and does not contribute to sustainability. These osmosis systems require more energy and water than conventional sediment filters do.

Despite these drawbacks, reverse osmosis is a greener alternative to using harmful chemicals. On whole, this wastewater treatment approach is very simple yet equally effective process.

Let’s review the RO process and the amount of water that these filters waste.

Wasted water in RO process

Industrial RO filter
Industrial-scale RO filters waste significantly less water than residential systems.

All reverse osmosis filters waste some amount of water. This is an inherent part of the process.

Some RO filters waste a lot of water – as much as 4 gallons are dumped for every 1 gallon of drinking water produced. This is especially true of point-of-use filters that are installed under your sink. This type of filter has a single pass membrane where the water only goes through the filter one time.

You can find reverse osmosis filtration systems that waste less water. A whole-house RO filter, also known as a point-of-entry system, generally wastes 2 to 3 gallons of water per gallon of clean water. This is better than a POE filter but is still very wasteful.

Industrial-scale RO filters waste a lot less water because they use multiple filters in series to maintain high contaminant removal rates without wasting as much water. It is possible to get filters that only waste 1/2 gallon of water for every gallon of drinking water made. Unfortunately, this type of efficient filter is very expensive to purchase and is only available to large-scale users like municipalities and manufacturing plants.

Efficiency of RO filters varies

For people interested in sustainability, there are a few options available if you need to filter your drinking water. Look for the RO filter efficiency. This is the ratio of water that is wasted to clean water produced. You’ll see a number that looks like 4:1 which means the unit discharges 4 gallons of brine for every 1 gallon of clean water produced.

All of our RO filter reviews include a measurement of the amount of water they waste. This is an important criterion and we spend a lot of time discussing it.

Reverse osmosis and wastewater treatment

Some manufacturers (although not very many) will provide this information with the specifications of their RO filters. If it is available, you can use it as a guide in your buying decision.

If the information is not provided by the manufacturer, you should assume it was intentionally omitted because their filter wastes a lot of water.

  • A POU RO filter will have an efficiency ranging between 3:1 to 6:1. This means an under-sink RO filter will waste 3 to 6 gallons of water for every gallon of drinking water produced.
  • A typical POE RO system has an efficiency of 2:1 to 4:1. A whole-house reverse osmosis filter wastes between 2 and 4 gallons of water for every gallon of water it purifies.

Here are some of the reverse osmosis filter reviews we have prepared with information about their efficiencies. Check them out if you want to learn more about them.

APEC water countertop filter

Express water countertop filter

Sustainable Aspects of Reverse Osmosis Water Purification

Reverse osmosis is a water treatment process that removes contaminants from water. It sounds eco-friendly since it takes contaminated water and turns it into pure H2O for people to consume. However, the reality of the situation is much more complicated than that.

RO water treatment provides many “green” and sustainable benefits to you and society as a whole. The eco-friendly benefits of reverse osmosis include:

  1. Eliminates bottled water. If your water is contaminated, you have to either spend a lot of money on bottled water or invest in an RO filter. Having access to clean drinking water can save you hundreds of dollars per year.
  2. Provides clean, safe water. The primary reason we use RO filters is to remove impurities and have clean water for drinking and cooking. By allowing us to drink water that would otherwise be unsafe, we avoid wasting a precious resource.
  3. Less wasteful than distillation. For some contaminants like pharmaceuticals, RO and distillation are the only treatment options available. In this situation, reverse osmosis is the most sustainable method for having safe drinking water.

Unsustainable Properties of RO Water Filtration

reverse osmosis membrane cartridge
Spent RO filter cartridges become a waste that often ends up in landfills.

Although reverse osmosis is a very effective water treatment method, it has several unsustainable properties that need to be considered.

  1. RO wastes a lot of water. Reverse osmosis wastes as much as 4 gallons of water for every gallon of drinkable water it produces. This is because the wastewater from the RO filter (referred to as brine) is high in salt and other contaminants.
  2. RO requires a lot of energy. The membranes used in an RO filter require pressure to remove impurities, and this pressure comes from electric pumps.
  3. RO produces concentrated waste. Reverse osmosis does not destroy the contaminants, it merely filters them out of the water. The brine that is left behind contains very high concentrations of the impurities that are often more toxic than the untreated water.
  4. Pre-treatment creates waste. All RO filters require sediment filters and activated carbon filters to pre-treat the water. When these filters are spent, they are thrown away.
  5. RO membranes not recycled. Eventually, all RO membranes must be replaced. Most membrane cartridges are not designed to be recycled which produces significant amount of waste.

Can RO Waste Water Be Reused?

A typical reverse osmosis filter for residential use wastes up to 4 gallons of water to purify one gallon for drinking and cooking. What happens to those 4 gallons of water? In most cases, it’s just dumped down the drain and wasted.

If you want to be “green” and not waste a resource as precious as water, you can collect the brine and use it in a beneficial way. I divert my RO filter waste water discharge to a holding tank and use it for non-potable purposes.

Here are five ways you can reuse the waste water brine from your reverse osmosis water filter.

  1. Flushing toilets. With a little plumbing, you can use the wasted water from your RO filter to flush your toilets.
  2. Househole cleaning. The brine discharge from your RO system can be used to mop your floors, wash windows, and other cleaning tasks that require water.
  3. Washing cars. The wasted water from RO filtration can be used to wash your cars. The contaminants won’t hurt your car’s paint and is a great way to reuse water.
  4. Watering plants. The water from the RO filter is perfect for watering your plants. Because of the low efficiency of RO filtration, the minerals and other impurities aren’t too concentrated for your plants.
  5. Laundry pre-rinse. I use my RO filter discharge water to remove stains and spots from my family’s laundry before putting them in the washer. You have to be careful with some fabrics to avoid problems with the high salt concentration, but most clothes do fine.

Remember, if your drinking water contains impurities like PFAS or lead, RO can help purify it.

What Should You Do?

Having clean and safe water to drink and cook with is your top priority. It wouldn’t make sense to stop treating contaminated water for the sake of sustainability. If you use reverse osmosis to treat your drinking water, what can you do to be more eco-friendly?

The most sustainable solution to safe drinking water is to avoid contaminating it in the first place. This requires a national solution in which we avoid using dangerous and toxic chemicals. Fortunately, there are green and sustainable manufacturing processes, and many industries are moving in this direction.

If you have hard water, you can use a water softener to remove some of the minerals that make your RO filter work harder. This will remove the impurities that cause scaling while minimizing the amount of water you waste.

You can write letters to elected officials and manufacturers, asking them to consider green and sustainable alternatives to harmful processes. You can also vote with your dollars by supporting companies who have made the commitment to sustainability.

If every person took these small steps, we would see a big change in the direction of our country and world. We need to be proactive in preserving our resources for future generations, and it starts with each of us.

If you have a reverse osmosis water filter, don’t just dump the waste water down the drain. There are many ways to reuse it so that we can all do our part in preserving our earth’s resources.

You can also purchase the RO filters that have high efficiencies. Check out my reviews and other resources to find the most sustainable treatment systems available. Make smart purchasing decisions and you can make a difference within your own home.

Final Take on RO Sustainability

Reverse osmosis is a water purification process that has both sustainable and unsustainable aspects. It eliminates the need for bottled water and can be used as an alternative to distillation which requires a significant amount of electricity to evaporate and then condense water.

RO also wastes 1 to 4 gallons of precious water for every gallon you can drink. It also concentrates toxins in the waste product streams which are then dumped down the drain. This just transfers your problem to someone else to deal with. The sediment filter and activated carbon filters are all single-use components that are thrown away when spent.

Does reverse osmosis waste some amount of water? Yes, it produces reject water that has very limited beneficial uses. Outside of sewage treatment, it is still one of the best alternatives available to homeowners looking for clean, safe drinking water.

On whole, using reverse osmosis to purify your drinking water is a beneficial and important part of your health and worth the environmental “cost”. You should be mindful of the inefficient aspects of this treatment method and make decisions to minimize the negative impact you have on the planet. In my opinion, having clean and safe drinking water is the most important consideration and is a good justification for using reverse osmosis to have pure water for you and your family.

Boch Richard

Richard Boch is a chemical engineer responsible for designing water filtration systems for industrial and residential customers. He has more than 20 years of experience with ion exchange, activated carbon, and reverse osmosis. Richard's expertise has made him a go-to source for municipalities and businesses looking to improve their water quality. When he's not working, Richard enjoys spending time with his wife and two young children. You can also follow him on LinkedIn, Twitter and Facebook.

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