If you’ve stumbled across this article, you’re either annoyed that your tap water gives off a metallic taste or worried about all those black stains on your sink. Take a breath—you probably have high manganese content in your water, and it’s fairly easy to diagnose and remove.
Manganese and iron are often found together in groundwater, and they are more prevalent in private wells than in municipal water. Even in small amounts, these pesky metallic pollutants can destroy your water’s color, taste, and smell—ruining your drinking experience and staining your laundry and fixtures.
Let’s get into how you can identify manganese and what treatment methods you can use to bring it down to safe levels.
What Is Manganese?
Manganese is one of the many metallic minerals found naturally on our planet in soil, rocks, groundwater, and surface water. Unfortunately, human activities, such as mining, steel production, and unmindful waste disposal, also release manganese into the environment in excessive amounts.
According to the basics of chemistry, iron (Fe) and manganese (Mn) are alike in many respects, and they usually, if not always, originate from the same sources. So, if you have manganese in water, there is a high chance you have iron as well because they occur together in nature.
Who would have thought the innocent “Mn” in your chemistry class periodic table would come to annoy you again in the future?
One study says that almost 2.6 million private-well owners in the US consume high levels of manganese in their drinking water. The same research also suggests that manganese is mainly found near shallow rivers and lakes where the soil is contaminated with fertilizers and organic matter.
In deep and old wells, aquifers come in prolonged contact with manganese rocks, which is why private wells are more prone to this contamination. But this doesn’t mean city water folks never face manganese contamination. How badly your water is contaminated, whether well or municipal, largely depends on your location and the mineral makeup of the groundwater.
Just like ferrous iron, manganous manganese (Mn2O) appears clear in water but changes its color to brown and black as the molecules oxidize in the air and form manganic manganese (H2MNO4). In some extreme cases, manganese pairs up with materials like tannins in deep wells to form colloidal manganese or black tint.
Health Effects of Manganese on Water Supply
Manganese is a vital mineral for your body and is found in many fruits and vegetables. Although it’s needed in only trace amounts that a balanced diet can easily fulfill, it’s responsible for the normal functioning of the brain, regeneration of tissues, calcium absorption, and regulation of enzymatic activity.
Manganese deficiency is rare, and there are no established studies discussing its repercussions. But there is solid evidence that high doses of manganese, also called manganese toxicity, can damage your health. You can easily fulfill the daily requirement of this mineral through your regular diet. That’s why consuming manganese in contaminated water might lead to overconsumption and health problems.
Here are a few ways that high manganese in your drinking water can affect your health:
Excessive manganese exposure may cause clinical neurodegenerative disorders, such as Parkinson’s. Manganese toxicity can also develop manganism, which is associated with symptoms such as loss of appetite, insomnia, depression, weakness, body tremors, spasms, and fever.
Studies suggest that taking high doses of magnesium through drinking water for long periods of time can halt the development of the brain in both children and adults. It can cause memory issues and attention deficit hyperactivity disorder (ADHD). Infants taking in too much manganese may develop learning and behavioral issues as they grow up.
Another issue with consistently taking in too much manganese is that it can disturb the absorption of iron in your body and lead to anemia. Since iron and manganese are structurally similar, their absorptive pathways are also the same. Presence of greater amounts of manganese can inhibit iron absorption in the body. Conversely, excess iron can hinder manganese absorption in the organs.
Impacts on food and drink
Aside from direct health issues, manganese can indirectly affect your health by changing the taste and quality of your food and water. You see, dissolved manganese generates an off-putting bitter, metallic taste that can destroy the flavor of any beverage and food you cook in this water.
In addition, manganese tends to react with organic matter in food, like the tannins naturally present in coffee and tea, to form black sludge. You definitely don’t want black slimy stuff floating in your cup of tea.
Household Problems Caused by Manganese in Water
Not only is manganese terrible as drinking water, but it can also wreak havoc on your home in myriad ways.
Manganese can damage your plumbing components by forming a nasty brown coating that erodes and flows out of faucets as black precipitates. You may find yourself dealing with this issue—called encrustation—even at concentrations as low as 0.2 PPM.
The brownish-black stains caused by manganese on white porcelain fixtures, utensils, and laundry don’t come off easily with soap. Instead, soap can make the stains even worse.
The presence of this pollutant also gives rise to manganese bacteria that feed off metallic ions and form slime and sludge in toilet rings and sinks.
Reduced water pressure
Manganese scale, like iron scale, may clog up pipes, water heaters, water softeners, pressure tanks, and ion-exchange units, disturbing the water pressure throughout your house.
High household costs
All these problems from manganese in your water supply can be a burden on your household maintenance budget. Replacing damaged components and appliances can cost you a lot of money. And low water pressure and clogged pipes can increase your water bill.
Safe Limits Set by the EPA
According to the United States Environmental Protection Agency (EPA), drinking water must not exceed 0.3 parts per million (PPM) of manganese ions. But here’s the deal about iron and manganese: they start imparting a foul smell and metallic taste and staining your toilets and fixtures even at low concentrations of 0.1 PPM.
So, the EPA has further set a Secondary Maximum Contaminant Level (SMCL) similar to Canada’s “aesthetic objective” that defines the threshold as 0.050 PPM, after which manganese starts affecting the appearance, smell, and taste of water.
If you want your clothes to come out clean, instead of having multiple black and brown dots all over, and your drinking water to smell and taste fresh, you need to keep the manganese concentration in your water strictly below 0.050 PPM.
How to Test for Manganese in Well Water
The easiest method to figure out if there’s any manganese in your water supply is to fill a clear glass with tap water and leave it overnight. Manganese oxidizes in the air to form manganic manganese that appears as solid, black flakes in water. But keep in mind that manganese in small amounts will not precipitate enough to be seen through the naked eye. Plus, this is the least accurate method to judge the presence of manganese in the water. Even if you can identify black manganese flakes, there’s no way to tell its concentration in water.
Other telltale signs include the smell and staining of your wash basins and washed clothes. Or, if you’re up for it, you can channel your inner detective and use a flashlight to find black slime or dense coating in corners or crevices of your faucets, toilets, plumbing pipes, or dishwasher.
Another way to test manganese at home is to use well-water testing kits or strips. Dip one strip in a cupful of tap water and match the developed color with the standard color scale given on the package. Don’t rely on testing strips too much though. This technique is only good enough for gaining a general idea of the presence of manganese in the water.
The best and only accurate way of finding out what’s lurking in your well or local tap water down to the last contaminant is to get it tested in an accredited laboratory. It will send you detailed reports about the pollutants and their concentration in your sample within a week. Your state probably sponsors at least one of these labs, and the test should not cost more than $100.
Iron and Manganese Removal Methods
Once you confirm the culprit behind the metallic taste and brown color is manganese, it’s time to remove it from your water. There are several purification systems that you can install in your home to get rid of manganese for good. Since manganese and iron are usually present together, you should invest in a system that can treat both of these dissolved metals simultaneously.
Oxidation followed by filtration
The most common methods of iron and manganese removal involve oxidizing them with a strong oxidant to form solid precipitates, which can later be filtered out through mechanical filtration. You’ll find a variety of purification systems that use air, chlorine, ozone, or potassium permanganate as oxidants to pretreat manganese and iron.
Air injection oxidizing (AIO) filters
AIO filters work by oxidizing metallic ions in water in an air pocket just above the tank. This water then passes through an in-built AIO filter-media bed that captures the solid oxidized particles. Such filters require periodic backwashing to flush the captured pollutants into the drain. Nowadays, high-quality filters come with automatic backwash and regeneration operations that you can control through your smartphone from anywhere around the house. AIO filters are available within the range of $200–$1500.
These filters are a good way of removing iron, manganese, and hydrogen sulfide odors from your private well or city water.
Ozone filtration systems use ozone as an oxidant to convert dissolved iron and manganese into precipitates. This type of filtration uses an ozone generator to produce fresh ozone continuously and is slightly expensive, costing you anywhere between $900 and $3,000. But the good thing about this filter is that it treats bacteria and viruses along with metallic ions. The solid oxidized compounds can then be easily removed through any kind of mechanical filtration.
Some filters come with built-in sediment filters, while others require the installation of a separate sediment filter. Certain catalytic-carbon filters also work great with ozone filters to remove manganese and iron.
Chemical injection of chlorine and potassium permanganate
If you’re low on budget, you can perform the good ol’ shock chlorination of your well water. This method works best if your well has a combined concentration of 10 mg/L of iron and manganese and a pH of 8–8.5. People also use hydrogen peroxide and potassium permanganate solution in place of chlorine to precipitate metal ions.
Chemical injection systems cost around $300–$1000. But if you perform chlorination yourself without any injection equipment, it can cost you as low as $100.
Once the chlorine solution is injected into the well through a chemical feed pump, let it sit for 12–24 hours. Iron and manganese immediately oxidize in the presence of chlorine and turn into flaky compounds that you can later remove using a mechanical filter. These filters must be backwashed every once in a while so they don’t clog with excess metal participates. It’s better to combine this system with an activated carbon filter to remove smelly chlorine by-products called tetrahalomethanes from your water.
If you want to get down to the nitty-gritty of shock chlorination, check out my article here.
Chlorine oxidation offers the additional benefit of killing all the microbial contamination in water.
Using manganese-based filter media
Manganese greensand filters are a great way of trapping soluble iron and manganese pollutants in water. The manganese greensand filter effectively captures metallic ions and catalyzes the oxidation process to convert them into solid precipitates. Once the manganese greensand filters reach their limit, the system must be backwashed using either potassium permanganate or chlorine. You can find a good quality greensand filter for $300–$800.
The good thing about oxidation filtration is that it oxidizes and filters the metallic ions in one place. You don’t need to attach a sediment filter separately to trap solid particles. However, one downside is that cleaning the filter media requires regular regeneration and backwashing. Moreover, potassium permanganate is toxic and must be stored carefully.
The Birm granular filter works on a similar principle except that it doesn’t require regeneration with potassium permanganate. Instead, such filters use the dissolved oxygen in the water to regenerate themselves. For Birm to be effective, your water must fulfill certain conditions, such as a pH higher than 6.8 and dissolved oxygen equal to 15% of the dissolved manganese and iron concentrations in water. Birm filter media will cost you $50–$150.
An ion-exchange filter uses the principle of replacing metal ions with other more desirable ions (usually sodium) with the same charge. Your water softener is a prime example of an ion-exchange filter. Although ion exchange is effective for removing the most common hardness-causing minerals—calcium and magnesium—it can also remove iron and manganese from water.
One thing to remember is that the ion-exchange process is good for only small amounts of iron and manganese, as excessive amounts can quickly clog up the system and render your equipment useless. In addition, if your water has some percentage of solid oxidized metallic ions, it can foul the filter bed. You’ll have to install a sediment filter before the ion-exchange filter to prevent solid particles from entering the water-softener resin bed. If your well water is infected with iron bacteria, make sure you treat it with chlorine or any other oxidizing agent beforehand. An average ion-exchange system will cost you around $700, in addition to the ongoing cost of water-softener salt for most models.
Once the resin bed reaches its maximum capacity, it must be regenerated and backwashed to flush out the captured metallic ions.
Water softeners can treat up to 5 mg/L of iron and manganese in the water.
Reverse-osmosis (RO) system
Reverse osmosis can remove almost 90% of the manganese and iron in your contaminated water supply. From bacteria and viruses to metallic and organic pollutants, the RO filter membrane can remove particles as small as 0.001 microns. It works by pushing water through a very fine semipermeable membrane that captures the contaminants. Depending on the quality, the filters must be replaced every two years.
Many RO filters can be attached with a combination of other filters, like activated carbon and sediment filters, to treat water down to the last pollutant. You’ll find RO systems between the price range of $250–$4000, depending on the size and design of the unit.
So, if you have more than one contaminant, take my advice and go for a good-quality RO system. Trust me, it’ll pay off greatly in the long run.
Manganese is present as a mineral ore in groundwater and can easily seep into your well or municipal water supply. Even as low as 0.05 PPM of this pollutant can make your water smell and taste metallic. What’s worse, it can stain your white fixtures, sinks, washbasins, and laundry with black and brown spots, clog your pipes, and damage your appliances.
Purification methods like ion exchange, chlorination, AIO, ozone oxidation, greensand, and reverse osmosis can easily remove manganese molecules from your water. Make sure you go for a system that can tackle both soluble (manganous) and insoluble (manganic) forms of manganese. And unless you remove it completely, it’s better to switch to another water source because manganese in large amounts can be dangerous to health.
It’s time to bid farewell to this annoying pollutant for good!