Does Reverse Osmosis Remove Manganese from Water?
Written by: Alexandra Uta // Last Updated: Apr 5, 2023
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Many water sources contain manganese (Mn), putting users at risk of harmful health effects and causing damage to plumbing fixtures.
Reverse osmosis is the go-to filtration method for a lot of people, as it removes a broad range of contaminants from water. But does reverse osmosis also remove manganese?
Prepare for an informative ride as we explore the science behind reverse osmosis and its ability to clear out manganese!
Contents
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Key Takeaways
- Reverse osmosis removes up to 99% of manganese from water.
Does Reverse Osmosis Remove Manganese from Water?
So, does reverse osmosis remove manganese from water?
Yes, manganese is one of the many contaminants that reverse osmosis water filtration removes.
How Effective Is Reverse Osmosis At Removing Manganese from Water?
Reverse osmosis is very effective; it removes up to 99% of manganese from water.
How? At the heart of any reverse osmosis system lies the RO membrane, which is semipermeable. This means that the membrane allows certain matter to diffuse through but rejects other.
Manganese in its various forms (particulate, colloidal, organic, dissolved) that occur in water is one of the elements that get rejected. Simply put, it’s too large to pass through the membrane’s tiny pores – they have a size of about 0.0001 micron – and gets washed down the drain in the wastewater stream.
Purified, manganese-free water continues its journey through the reverse osmosis system, often getting stored in a tank before being dispensed through the RO faucet.
Other Treatment Methods to Remove Manganese
Besides reverse osmosis, other water treatment methods can be trusted to remove manganese.
However, the effectiveness of these methods depends on the form of manganese present. In water, manganese mainly exists in its solid state (manganic manganese) or soluble form (manganous manganese). We’ll explain more as we go on.
Oxidation
Oxidation involves adding an “oxidant” to water to remove contaminants. The oxidant reacts with the chemical impurities like manganese removing its electrons. As a result, manganous manganese turns into manganic manganese and precipitates out, and can then be removed via mechanical filtration
There are different ways to oxidize manganous manganese. We’ve discussed three of them below:
“Regular” Manganese Filter
There are whole house water filters specifically designed to remove manganous manganese from water without relying on pre-oxidation. These filters use greensand or Birm, for example, as their filter media.
When water flows through the media, soluble manganese oxidizes and becomes insoluble. The filter media can then easily trap the solid manganese and removes it from the water.
To maintain a manganese filter, you must backwash it regularly to flush out accumulated manganese. If you don’t backwash your filter, it eventually clogs up and stops working as it should.
Remember that manganese filters are usually whole house systems, so you’ll have them installed at the point of entry to remove manganese from all the water coming into your home.
Air Injection
Air injection is a less expensive way to pre-oxidize manganese in water. With air injection, your water is fed into a tank with an air pocket. As the system mixes the air into the water, soluble manganese oxidizes and becomes insoluble.
The insoluble manganese separates and stays within the system (in the media bed) while clean water flows out.
Like regular manganese filters, air injection systems also require backwashing after some time. Air injection is affordable, effective, and works well for other contaminants like iron and sulfur, too.
Chemical Oxidation + Manganese Filter
Oxidizing chemicals (like ozone, chlorine, and hydrogen peroxide) can be combined with manganese filters to give a more satisfying filtration result.
After applying the chemicals causing manganese to take on its insoluble form, the water flows through greensand or an alternative manganese filter media where it gets trapped.
Chemical oxidation is an excellent option if your water contains manganese and harmful bacteria because the chemicals also kill those bacteria. Another upside here is that chemical oxidation works even when manganese levels in water are very high.
On the downside, this method is only effective if the chemicals remain in the water for a long-enough time. In addition, it may leave chemical residues, making post-filters necessary.
Ion Exchange Water Softener
Water softeners can also remove manganese from water. But first, two conditions must be met.
- Your water must contain only soluble manganese in low amounts (3-5 ppm max).
- Second, your water’s pH must be over 6.7.
If your water meets these conditions, an ion exchange water softener will effectively remove manganese from it. This ion exchange water softener works by using resin beads to replace manganese ions with sodium ions.
Ensure your water does not pass through any oxidizers before getting to the softener. If it does, the dissolved manganese will convert to manganic manganese, which a softener cannot remove (manganic manganese could even damage the system). Also, you must backwash a softener regularly if you’re using it for manganese removal.
Distillation
In distillation, the distiller boils water until it vaporizes completely, then cools the gas into a purified liquid, and stores it in a collection tank.
Since manganese has a higher boiling point than water, water evaporates first, leaving manganese behind in the boiling chamber. This effectively separates manganese from pure water.
Distillation works for both dissolved and solid manganese. However, it’s a slow process, and it’s not ideal for large-scale applications (like whole house filtration). Distillation is only practical for point-of-use manganese removal, where it purifies only the water at a sink or faucet.
What Is Manganese and How Does It Enter Our Water Supplies?
Manganese is a naturally-occurring mineral found in rocks, water, and air. It is an essential nutrient for human health, but excessive levels of manganese in drinking water can cause health problems.
Manganese can enter our water supplies from natural geological sources, like rocks and soil, that contain high levels of the mineral. When rainwater or snowmelt percolates through the ground, it can dissolve manganese from these sources and carry it into underground aquifers and surface waters.
Manganese could also enter our water supplies through industrial discharge, mining operations, and agricultural runoff. These activities can release manganese into nearby water bodies, spreading to other water sources. In addition, corroding old water mains and plumbing systems can also leach manganese into water supplies.
Further Reading:
How to Test for Manganese in Water
The best way to test for manganese is to take your water sample to an accredited laboratory. They’ll do the testing and provide a result that shows the quantity of manganese in your water.
Alternatively, you could request a water quality report from your public water provider. This report contains the contaminants in your water and details the amount of pollutants present.
The Most Common Signs of Manganese in Water
If you’ve noticed these signs, there’s a high chance that your water contains manganese:
- Brown or orange stains on kitchen sinks, faucets, and other similar surfaces
- Metallic-smelling and tasting water
- Water discoloration (brown or rusty color)
- Brown or black stains on washed clothing
Also, if you’ve confirmed that your water contains iron, it likely contains manganese too. Manganese does not stay alone in water; it’s commonly found along with iron.
Health Risks
Manganese affects water taste, making it metallic. It also leaves ugly, brown stains on plumbing fixtures, laundry, faucets, and sinks. But that’s not all. Drinking high levels of manganese in water poses health risks like:
- Cognitive issues: The Minnesota Department of Health mentions that people who drink water with high manganese levels may have memory, attention, and motoric skill issues.
- Development problems: Kids who drink manganese water may suffer from learning and behavioral issues.
- Toxicity: Manganese toxicity causes sleeping problems, depression, appetite loss, and headaches.
Safe Levels of Manganese in Drinking Water
Manganese is not always dangerous in drinking water. If the manganese level in your water is within the safe level, there’s nothing to worry about. The Environmental Protection Agency (EPA) sets a secondary maximum contaminant level of 0.05 mg/L for manganese.
Since it’s only a secondary level from the EPA, public water supplies are not legally bound by it. The manganese content in public water supplies may sometimes exceed 0.05 mg/L.
If you have any thoughts about the question, does an RO system remove manganese, please don’t hesitate to leave a comment below!
About the Author Alexandra Uta
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