Does Reverse Osmosis Remove Sulfur (Smell) from Water?
Written by: Gene Fitzgerald // Last Updated: Apr 4, 2023
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Have you ever been lucky enough to encounter that sulfur smell? The one that is just like rotten eggs? It is pretty awful, and your water supply at home is the last place you want it coming from. Ick!
Unfortunately, it does happen, making the thought of staying hydrated seem really unappealing.
Using a reverse osmosis system may be something you have considered to deal with the issue. Let’s see if that would be effective or not.
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Key Takeaways
- Reverse osmosis does remove two forms of sulfur from water: Sulfites and sulfates.
- But if the sulfur in water is in the form of hydrogen sulfide, it will not be removed by a reverse osmosis membrane.
- A reverse osmosis system, including the activated carbon filters, may remove small amounts of hydrogen sulfide.
Does Reverse Osmosis Remove Sulfur from Water?
First of all, does reverse osmosis remove sulfur from water?
It depends on what chemical form the sulfur is. Sulfite or sulfate will be removed, but hydrogen sulfide will not be. Hydrogen sulfide is a dissolved gas that has molecules that are small enough to pass through the reverse osmosis membrane without being filtered. So no, usually, RO membranes cannot remove all sulfur from water.
However, the other components of a reverse osmosis system may be able to – think pre or post-filtration steps. If your water has an odor, and your reverse osmosis system removes that, it is probably due to an activated carbon filter.
What About Hydrogen Sulfide?
As mentioned, hydrogen sulfide is the gas form of sulfur. If your water smells like rotten eggs, this is the culprit. Hydrogen sulfide has a really small molecular size and low weight, so it will easily pass through a reverse osmosis membrane’s pores.
Does a Reverse Osmosis System Remove Sulfur?
The activated carbon filters often included in a reverse osmosis filtration system can remove some hydrogen sulfide when present at low levels (around 0.3 ppm). However, if the sulfide concentration in the water is higher than this, then most of it will remain.
Challenges with Sulfur and RO Systems
If your water contains hydrogen sulfide of a level above 0.3 ppm, then it is best to remove it another way before running that water through your reverse osmosis system. Why? Because it can cause slime and buildup on the reverse osmosis membrane, which will reduce the effectiveness of the membrane itself.
Other, More Effective Ways to Remove Sulfur from Water
Don’t worry, though; there are some more effective ways to remove sulfur from your water supply. You can utilize one of several methods, including oxidation or anion exchange.
Oxidation Followed By Mechanical Filtration
Oxidation followed by mechanical filtration is one of the most reliable and also cost-effective ways to get sulfur out of your water. Exposing hydrogen sulfide to oxygen in this process separates the sulfur, which becomes solid and can then be filtered out through carbon and other filters.
Hydrogen peroxide makes a cheap and effective oxidizer, or you can use aeration or an oxidizing filter.
Anion Exchange
When sulfur oxidizes, it turns into sulfuric acid, and the sulfate and sulfite ions can be removed with anion exchange. This process can be performed with a potassium permanganate filter, which works similarly to a water softener, but instead of removing the calcium and magnesium from the water, it removes sulfur odors.
Does Activated Carbon Remove Sulfur?
Yes, it can remove some of the hydrogen sulfide, but not all of it. Activated carbon will only remove hydrogen sulfide in levels lower than 0.3 ppm. If the sulfide in your drinking water is higher than this, activated carbon will not be able to remove the odor.
Does a Water Softener Remove Sulfur?
The particular kind of ion exchange used for water softening and hydrogen sulfide removal are different. The latter requires anion exchange. Water softeners are based on cation exchange, though.
In water softening, sodium ions are exchanged with calcium and magnesium. While this may remove some low levels of sulfur odor, it won’t be enough.
What Is Sulfur/Hydrogen Sulfide Gas?
The 5th most common element on Earth, sulfur, is naturally found around us, usually in the form of sulfide and sulfate. It is used to make fertilizers, fungicides, and pesticides (which can get into groundwater if you live in an agricultural area). It is also used in the pharmaceutical industry and for food preservation.
Hydrogen sulfide gas is another form of sulfur and one that smells like rotten eggs. At high levels, it can be toxic. It is used in industries such as oil and gas refineries, paper processing, and mining, and you can also find it naturally in sewers, well water, and manure pits.
How Does Sulfur Enter Water Supplies?
There are several ways that sulfur can enter your water supply. The most common are:
- Sulfur bacteria growing in a water heater
- Sulfur bacteria growing in water pipes
- Something rotting in your water supply (decaying soil, rocks, and matter all contain sulfur)
- Acid rainfall
- Pollution of groundwater from nearby industries using hydrogen sulfide gas.
Further Reading:
Is Water with Sulfur Safe to Drink?
Sulfur is not considered dangerous at low levels, and while it might not smell or taste pleasant, if it is only a tiny amount causing that rotten egg odor, it is still safe to consume. Water with as little as 0.5 ppm can cause a noticeable smell.
Sulfur Levels Considered Safe for Health
The EPA sets no listed maximum contaminant level for hydrogen sulfide in drinking water. The rotten egg odor will be noticeable at 1-2 ppm of hydrogen sulfide.
Sulfate, on the other hand (the form that doesn’t smell), is set at 250 ppm.
How to Test for Sulfur in Water
The most effective way to test for sulfur in the water is by using a specific water testing kit or having your water analyzed at the laboratory.
A TDS test is insufficient to indicate the presence of sulfur in the water supply. You can also perform some inspections yourself at home:
- Check for changes in the color of your water, black, grey, red/brown, and white. This could indicate the presence of bacterial slime.
- Look for black stains on silverware and appliances that use water.
- The smell of rotten eggs in the water.
- The plumbing could be corroding.
If you have any thoughts about the question, will reverse osmosis remove sulfur smell, please don’t hesitate to leave a comment below!
About the Author Gene Fitzgerald
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