Iron & Manganese Removal Using Manganese Dioxide Filter Media
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Welcome to Episode 11 of Clean Water Made Easy Podcast
In today's episode, our host Gerry Bulfin, a water treatment contractor and WQA Certified Master Water Specialist, discusses iron filter media, particularly manganese dioxide filter media, for removing iron and manganese from well water.
Manganese dioxide is a natural filter media that effectively removes iron, manganese, and sulfur odors from well water. There are different types of manganese dioxide filter media, and Gerry discusses the advantages of the various kinds and what to look for when using this filter media.
Filter media is what is inside a filter tank and removes iron and manganese.
Manganese Dioxide Filter Media for Well Water
Items We Cover in This Episode:
- What is manganese dioxide filter media, and how is it used?
- What are the benefits and advantages of using manganese dioxide to remove iron, manganese, and odors from well water?
- What is the difference between greensand, birm, and other coated and solid manganese dioxide media such as Pro-OX, Filox, Pyrolox, and Birm?
- Under what conditions does manganese dioxide media work best?
- Importance of water chemistry and flow rate, such as how many gallons or liters your pump puts out per minute
Transcript of Episode 11
Iron & Manganese Removal Using Manganese Dioxide Filter Media
You’re listening to the Clean Water Made Easy Podcast Episode 11
Hello, and thanks so much for tuning in to the Clean Water Made Easy podcast. Gerry Bulfin here again. I’m a Water Treatment Contractor and WQA-Certified Master Water Specialist. I hope you’re having a fine day wherever you are listening.
In this series, I’ve been providing useful, easy-to-follow tips and information about well water, well water treatment systems, and how to improve the quality of your well water. I appreciate the emails and feedback I’ve been getting. If you’re using iTunes, it would be great if you went over to iTunes and rated it and maybe left a short review of the podcast. That helps the podcast a lot; I appreciate it.
In today’s episode, we will talk about iron and manganese media. Specifically manganese dioxide filter media. Media is the word that we use. It looks like sand. It’s a granular type of filter media that goes inside a filter tank. In this context, we are talking about back-washing iron filters. So the water flows in down through the filter media, iron and manganese are removed, and then after a while, they’re usually automatic, it turns on, backwashes and cleans this media.
There are many different kinds of filter media, and we are going to discuss them. Manganese dioxide media is probably the most common type of filter media used for iron and manganese removal.
If you want to see pictures of what the media looks like and iron filter tanks, please go to our website, cleanwaterstore.com/blog/podcast. You can also email me directly at gerrybulfin@cleanwaterstore.com. I spell my name with a G E R R Y, and then B U L F I N.
Topics in this Episode
Anyway, today the items we’re going to cover are: what is manganese dioxide, how is it used, what are the benefits and the advantage of using manganese dioxide for removing iron, manganese, odors from well water, and what’s the difference between the coded type of media such as greensand or Birm where there’s a thin layer of manganese dioxide coating on a different type of mineral element underneath it. And the solid manganese dioxide media where it’s a solid granular like a solid chunk of the manganese dioxide. You see different brand names for that, such as Pro-OX, which is one we sell, or Filox and Pyrolox; those are all brands of the manganese dioxide media.
We’re going to discuss under what conditions manganese media work the best and the importance of water chemistry and flow rate. I discussed this before in episode 2, when we discussed how to test your flow rate. In episode 5, we covered basic iron treatment, but here, I’m going to talk specifically about manganese dioxide. I get a lot of questions about it, so it should be interesting.
If you’re listening to this, you already know this, but iron is a serious problem. Many folks all over the world have problems with iron in their wells. It’s now a problem in the US and Canada, but we see a lot of iron and manganese problems in Mexico and South America. We’ve even seen some folks in Europe have this problem, and we know there are different parts of Europe that have a problem with it, as well as in the Middle East and Asia, of course.
So, generally, you should see .3 parts per million or less with iron and .05 parts per million or less with manganese. If it’s a very small amount over that level, it causes stains. Water can become red, brown, or yellow and stain laundry fixtures.
Manganese and other metals that leave stains, instead of rust stains like iron, leave a brown stain. That, again, is standard for anything over .05 ppm. So if you have an effective iron and manganese filter to reduce the level below 0.05 ppm, it’s not going to cause stains. Iron and manganese are not really health threats, but they taste pretty terrible if they're high enough, and some people are affected. Manganese can affect the stomach, and some people have problems with too much iron in their diet, so that’s another problem. But generally, it’s more of an aesthetic issue.
So, we use a few different methods to remove iron and manganese from well water. Generally, iron and manganese are usually found in groundwater dissolved. Now that is, the water looks clear, but if you taste it, it tastes terrible, tastes like rust or has a bad taste from the manganese, but the water looks clear. But if your water has been exposed to lots of air or there’s dissolved oxygen present and/or sometimes iron bacteria, then you get rusty water coming right out of the ground. But usually, it’s clear water.
So the reason I brought that up is that’s how manganese dioxide works. What happens is that the water comes out of the ground clear, but when the iron and the manganese hit the manganese dioxide media, the iron and manganese oxidize. That is, they turn from a dissolved form to a solid form. In other words, they’re ferrous iron and turn into ferric iron, which is trapped in the filter media. Then once or twice a week or more often, it turns on in the middle of the night, typically this is for homes, and backwashes all that rusty water out. It removes rust particles, and the filter media is good to go for another run. This can last years, hopefully they do last many years.
So you’ve got this situation where you need to oxidize the iron and manganese. Traditionally, and still used quite a bit, you can use just plain sand and anthracite. So, for instance, it’s a special type of filter sand, but basically, it’s just sand, and then the water is injected with chlorine or ozone, or it’s aerated in a very strong way, but it’s typically chlorine. Then the water flows into these sand filters, and if all the iron is a hundred percent oxidized just right, then the sand filter will eventually start to remove the iron over time.
The reason that this was a hassle is that it required very careful operation. It didn’t always work well, you had to have an operator present, you’d had adjust the chlorine levels based on different water conditions. Sometimes, you’d use other chemicals to help with the process. So generally, it’s not that effective. So for homes and small communities, it’s not used that much, but it’s cheap. So that’s one reason it was used a lot. But you can’t just get a standalone sand filter, just like you can’t use a standalone cartridge filter, expect it to remove all the iron and rust in the well water. The iron is largely dissolved in the water, so you need to find a way to oxidize it.
Types of Filter Media
So, there are various types of filter media. The main types of manganese dioxide media that we’re going to talk about here are coated and high purity, like a solid chunk of the manganese dioxide. So they both work well, but they have different advantages and disadvantages. I’m mainly going to talk about manganese dioxide, but first, we’ll talk a little bit about oxidation because it relates to the type of manganese dioxide you might use.
A very common method for homes is to use either aeration or chlorination. Chlorine has the advantage of killing iron bacteria and working really well with manganese dioxide. It primes the water or increases its oxidation capacity. You don’t need to inject enough air, chlorine, or ozone to get the iron to completely turn to rust.
The idea is that you want to increase the potential of the water for oxidation so when it hits the manganese dioxide media, a catalytic reaction takes place right in the media, and boom, you get all these great formations of iron floc happening right in the media. Usually, if it’s a tank, say it’s a standard tank for a home, it might be 3 or 4 feet tall or maybe 5 feet tall. Most of this oxidation process will occur right on the media's top layer. But the idea is that you’re using some oxidizer ahead of the manganese dioxide. That’s the best way to go.
I’ll talk about it, but there are some conditions where you don’t need any oxidation if your water chemistry is right. You can use the manganese dioxide system by itself without any aeration. But generally, that’s a rare case, or that’s a smaller percentage of the cases that we at least see in North America. Perhaps if you get into the borehole wells in Africa or somewhere else where there are shallow wells and there’s a lot of oxidation going on anyway, then you use a standalone filter system. But usually, you’re combining the manganese dioxide with some oxidation. So chlorine, air, or ozone works well, or hydrogen peroxide.
I will talk about hydrogen peroxide in its dedicated episode coming up. But while peroxide can be used as an oxidizer before the manganese dioxide filters, it’s not as effective as chlorine, especially if you have manganese. The peroxide is not that effective for manganese. It’s counter-intuitive because we have peroxide, and sometimes you put it on your skin to clean a cut or whatever, so you think, “Oh, it’s going to kill bacteria”. But when we have it in the water, it’s considered a very weak biocide. So it’s not an effective disinfectant at the levels we’re using. It’s more of an oxidizer.
So anyway, it works great if you have iron if you’re looking for iron removal with a manganese dioxide filter. But if you have manganese in the water, then you’re better off using chlorine or ozone.
Aeration can work, too, but you have to raise the pH. I’m going to talk about pH in a minute here, too. But the pH is critical. It needs to be between 7.5 and 8. If you’re using some very weak coated media, you have to get a pH of over 8.2 for manganese to work, and those media, such as Birm, are not as effective for manganese removal in our experience.
Okay, so we talked about oxidation, but now, what type of filter media should we use? We talked about the sand and anthracite media, it is not the best option generally for iron treatment especially for homes on standard wells. It is better to use manganese dioxide because manganese dioxide is a catalyst. So when there is a tiny bit of dissolved oxygen in the water, and the iron and manganese in the water come in contact with the manganese dioxide, you get that catalytic reaction, and the iron and manganese are filtered out of the water. It is the same with hydrogen sulfide. If there’s enough oxidation in the water, then when the hydrogen sulfide and water flow through the manganese dioxide media, it basically converts the hydrogen sulfide into an insoluble particle that then gets trapped in the media, and the odor is gone.
Several different types of manganese dioxide-coated filter media are used. Birm is a very popular one. It’s a Clack Corporation trademark. It’s been used for many years. It’s cheaper and light, but it has a very thin coating of manganese dioxide on it and is a bit unstable. You can’t use chlorine with it. It strips the coating. If hydrogen sulfide is in the water, the rotten egg odor doesn’t work well for that.
We’re in California, and for some reason, we can’t sell it here because of the proposition where there’s a warning against it. From what we heard, the backwash has a little bit of chromium, so it’s basically banned. But anyway, a lot of people have used it for many years, and it works well if you have just a small amount of iron and the right conditions for it. The Clack will tell you the operation conditions.
But it has a very thin coating, probably 1%. You can talk about coatings in terms of the percentage of manganese dioxide in them. So Birm and maybe a couple of others are very low, like 1%. Greensand and some of the different Greensand-type coated media are slightly higher, around 5%. Some are as high as 10%. There’s one that can even go up to 18%, which is very high for the coated media.
That means that they’ve been able to put a coating of this manganese dioxide material over some other kind of cheaper and lighter substrate, usually silica. One company uses dolomite, which also helps raise the pH, but it’s sacrificial, so it doesn’t last as long.
And then there are a couple of different types of substrate or inner core that they coat with manganese dioxide. So, historically, greensand filters were cleaned and regenerated with potassium permanganate, this purple chemical. You can also inject potassium permanganate into the pipe before the greensand filter, and you can do this as well with the manganese dioxide filters. But this intermittent regeneration regenerates the media intermittently, which is perhaps less effective than continuous regeneration, where you inject chlorine or ozone into the water ahead of the greensand filter. And now what you get is the media doesn’t ever get exhausted. This media can only run so long before it needs to be regenerated, usually with potassium permanganate or chorine. You can also inject that into the water ahead of it. But it needs something; these coated systems don't work well on their own without any oxidation. They usually need some oxidation or water that already has a lot of dissolved oxygen.
So, the other media type we have already discussed is solid manganese dioxide. The solid type means that it is an ore that they have mined, so it’s a natural material, and they’ve carefully grated it into a fine particle. It’s not coated, and it’s not really treated at all. All it is is that they mine this pure manganese dioxide ore, grind it, grate it, and wash it so you get a very high-quality filter media. So the advantage is it’s natural, and. there are no chemicals in it.
We buy ours from Pro-Ox. They’re one of the largest manganese producers in the world, and the vast majority of the manganese they find is not suitable for water treatment, and that’s true with other mines as well. So, most of the manganese is used for various industrial processes, such as steel and batteries. So, the vast majority- I don’t know what the percentage is, but I’ve heard that 97 to 98% of all manganese is not used in water treatment. But, what happens is that when they’re working in the mines and they find a relatively high grade, in cases that we use, it has to be greater than 80%, and the average is like 85% pure manganese dioxide, then they set that aside.
That’s what they use for water treatment, and it’s low in other contaminants, and ours is NSF certified. I’m pretty sure all the filter media that’s sold, unless it's imported or off-brand or something, is all NSF-certified. NSF is an independent organization, and they test it to make sure that there’s nothing contaminating the water. It's not adding lead or arsenic to the water or other weird stuff. It’s in a good form that doesn’t add anything to the water.
So, this solid manganese dioxide media is interesting. There are different strengths and different qualities. I know, for instance, that in some countries, like India and China, the solid manganese dioxide has very low purity. It’s maybe 20%, 25%, and it doesn’t work that well.
And so this stuff works really well, and like I said, there are different brands you can look for. We have Pro-OX, but Filox, Pyrolox, and other types exist. What it is is that the media is porous. So the higher the porosity of the solid manganese dioxide media, the better it is. Also, other structures inside it, like pyrolusite and nsutite structures, create this highly oxidative environment, so it basically works better. What we’ve gathered over dealing with thousands of these systems over the years is that you can get higher flow through it with a smaller filter.
The disadvantage is that it’s heavier than the coated type. So, a lot of people are turning against it because it requires a slightly higher backwash rate. It needs a higher flow rate, but it’s not huge—like two or three times—but it’s somewhere around 30% higher than, say, a greensand or other type of coated media.
But the advantage is that we feel is that, and it’s not to be a sales thing for our media, I’m trying to give you all the different advantage and disadvantages, but the advantage is that it lasts longer and generally it just seems to work better. It doesn’t fail quickly. Some of the coated media can fail within a few years. You get the media, and the coating gets worn off. It’s a fact that if there’s a low pH for a certain time, the media will be ruined.
But the Pro-OX just doesn’t get ruined. If it’s not backwashed or set up properly, it can start clumping together, but you can take it out of the tank or cut the tank in two and smash it up yourself and reuse it. We don’t say it’s permanent media because some people replace it after 10 years or so. But generally, it’s pretty permanent. I mean, it does last a long time because it’s a very light sacrificial medium. In other words, there’s a very small attrition. It can backwash many, many more times than the standard coated media, which is a manufactured media.
That’s the big difference. However, if you don’t have the flow rate to backwash it, you must use a different, lighter media, put it in a holding tank, or figure out another way to increase your flow rate.
I was talking about how the performance of the media is directly related to the purity of the manganese dioxide, the porosity of the granules, and the level of highly active sites on the structure. So you want to have one that’s higher purity and more porous, and strict particle sizing is important.
All the media now have a good, high uniform coefficient, which means that all the particles are the same size. That’s what you want to look at: You want to ensure the filter tank's media is very uniform. And so that’s a sign of high-quality media: It’s all very uniform in size. Solid manganese dioxide filters can also use intermittent or continuous regeneration. Generally, continuous regeneration works best when you're injecting chlorine ahead of it.
Now, there are situations where you can use the manganese dioxide media without any prior aeration. One way to figure that out is to measure the ORP. You can get a little ORP meter or go to a pool place and have them measure the ORP. Basically, it measures millivolts, and there are different kinds of laboratory types and other ones. But essentially, if you can raise the ORP over 200 millivolts, then the water has enough oxidizing capability on its own, and it doesn’t necessarily need a chemical regenerant or aeration ahead of it.
Generally, we recommend aeration for homes because your water might change over time. You may know what you’re dealing with at this point, but maybe over time, the iron can get worse, and the pH could change. So it’s important that aeration helps with the iron filter media work because it adds dissolved oxygen to the water. You can also use chlorine injection.
You can have a situation where you have 100 percent iron with pure rust. In other words, a hundred percent oxidized iron. Theoretically, you could use a cartridge filter or, as I talked about before, sand and anthracite. But generally, the Pro-OX, the manganese dioxide media, will work better than just the cartridge because the iron will pass right through it.
Okay, so what are some things to look for? Well, one thing you want to look for is to check the water's pH. You know, 7 is neutral. pH has a scale of 1 to 14, so 7 is neutral. A pH below 7 is considered acidic. Above 7, alkaline. It depends on whether there’s manganese in the water, but generally, you want to see a pH for iron removal between 7 and 8. You can have a lower pH, and it won’t hurt the media. But it depends on how much iron is in the water, and it won’t work as well if the pH is much less than 7.
So there are ways you can deal with that, of course. If you have acidic water, you want to correct it anyway because you don’t want acidic water running into the home where it can corrode fixtures and fittings. Even if you have PEX pipe, you can still get corrosion problems on your water heater, etc. You can use another tank of crushed marble or other pH-raising filter media before the iron filter to raise or neutralize the pH. If you have a very low pH, say 5, in that range, then you might be better off injecting soda ash into the water, which comes in food-grade or potable water grade. You can also use sodium carbonate. And that all keeps a neutral pH, and then the manganese dioxide will work great. Most people don’t have acidic water, but we have quite a few people who drink it. They usually either use a tank before it, or they get a blend where 2/3 of the filter tank is manganese dioxide, and then 1/3 of it is calcite, crushed marble, or the less commonly used dolomite. But basically, you’ve got a mineral that will add a tiny bit of calcium and alkalinity into the water and neutralize the pH so your iron media will work.
Fortunately, the blends work well because the manganese dioxide media is much heavier, so it sits on the bottom, and then your calcite is on top. Then, if you have a one-tank system, you’ve got to add more calcite to it pretty regularly. So you might have to add it a couple of times a year, depending on how much water you’re using and what the pH is.
Okay, after pH, the next thing you want to check is manganese. A lot of folks think, “Oh, I’ve got rust stains” or “I got iron.” They don’t realize they also have manganese. So if you get a system and set it up so it only takes out the iron, then you’ll quickly realize that all the rust is gone, but now you’ve got black or tea-colored stains in the dishwasher, on sinks or fixtures, or in laundry.
So, for manganese, anything above 0.05 milligrams per liter causes stains. It’s a pretty low level, and manganese requires more oxidizing power. It has a slower reaction time than iron and requires a higher pH. So, in our experience, if you have manganese, it’s better to chlorinate it first or ozone it. Aeration will work too as long as the pH is higher, like 8 is good, 7.5 to 8 is good. And by chlorination, aeration, or ozonation, I mean an automatic or continuous system that injects a tiny bit of chlorine before the filter system.
Next, you want to check to see if you have iron and sulfur-related bacteria. There are various types of bacteria that live in water and that are very common in the environment. They metabolize the iron and manganese for their cell walls, and in the end, you end up with a stringy mass. You can usually see it in the flush tank of your toilet, where you’ll see it growing out from the sides, or maybe the water will be bubbly with clumps of slimy gelatinous material floating in it. That’s a good way to check because most people never clean their flush tank, and the iron bacteria living there go to town and create this slime. And so, if you have that, then the manganese dioxide works great; it’ll take out the iron, but it’s not going to take out iron bacteria or disinfect the water. So disinfection is a good idea if you can do it.
So it’s better to have a chlorinator, which is the cheapest way, or an ozone system ahead of the iron filter. Then you’ve got disinfected water, and the iron bacteria is removed along with the iron. However, there’s another way to do it, and that’s sort of semi-manual. Say you’re using an air injection iron filter, you’ve got your manganese dioxide filter, it’s working great, it’s taking out all the iron, Then once or twice a year or maybe more if you have a really bad problem, you sanitize the pipes and the well if you can with chlorine bleach. And so that kills the slime that’s growing in the pipes. For instance, if there’s no more iron in the water, that works pretty well. Because the thing is, those iron bacteria are not only a nuisance, but they can create odor. This can happen especially in pipes that aren’t used much.
So we hear a lot of folks saying, “Yeah, I don’t know what the story is like. I don't have an odor problem in the house except for the upstairs bedroom that doesn’t get used” or “I have one part of the house that doesn’t get used, but the odor is terrible in that water. What’s the story?” Well, it’s because you have iron bacteria living in that pipe, happily undisturbed, so running chlorinated water through the pipes can kill that.
And I know I’ve referred to chlorine many times, which is covered in the other podcast on chlorination. But even though we’re chlorinating, most of our customers do not have a chlorine residual in their water in the house. So, there’s usually a carbon filter that removes it, or they’re using a contact tank, which gives time for the chlorine to degrade. After it goes through the manganese dioxide, it’s either gone or really low, and you can’t smell or taste it. Because you don’t want a high chlorine residual, you don't want a shower with high chlorine residual if you can avoid it. I mean, a lot of us grew up in city water where it has chlorine residual. But you know, the idea is that if you have a septic tank, you don’t want to run a bunch of chlorinated water down the septic tank. So better to remove it, and fortunately, it’s cheap and easy to do, so most folks do that. They chlorinate the water, run it through the contact tank, then the iron filter, and then the chlorine is removed when it goes into the house.
Okay, the next one after iron bacteria is the rotten egg odor. The terrible sulfur smell that’s so common. A lot of times, you’ll see specs that say it removes hydrogen sulfide. It doesn’t really remove hydrogen sulfide on its own for very long unless you use an oxidizer. You almost have to use an oxidizer if you’re using any manganese dioxide media, so chlorination is good. A combination of chlorination and aeration is good, but sometimes plain aeration is good as well. Ozone is really good, except for the price. However, chlorination and aeration are relatively low-cost ways to go.
I wanted to mention tannins, too. Water that contains high levels of tannin has a tea-colored look to it. If you’re drinking tea, you’re looking at the tannin color of the tea. It’s not extremely common, but it’s common in some areas of the country, and if you use a strong oxidizer such as chlorine in a contact tank and then have another filter tank with activated carbon, then low levels of tannin are not a problem.
It isn’t a problem for the manganese dioxide media, but if you have enough tannin in the water, you could still have weird-colored water even after you remove the iron and manganese. For example, if you fill the bathtub, it has a slightly tea-colored look to it. So there are different kinds of tannin filter systems out there as well, but that’s one thing you want to test if you suspect it—you know, how much tannins are in the water.
Last but not least is the flow rate. I talked about that a bit, but the flow rate is just how many gallons your well pump can pump in one minute. So, most homes in the US that are getting their water pressure from their submersible well pump are looking at somewhere between 5 and 20 gallons a minute. 8, 10, and 12 gallons a minute are pretty common. And then some folks with bigger homes or some agriculture used have higher flow rates. However, you need to know the flow rate because the manganese dioxide or even the coated type needs a certain minimal flow rate to clean that media out. So that’s a critical thing. If you don’t know the flow rate, you might make the mistake of buying two big iron filters, and you’re in trouble. It might work for a few months, and then it quits. So you want to ensure you have something that will work and actually remove the rust accumulated in the filter bed.
Okay, well, I’m going to wrap it up. This went out a little longer, but it’s a little more complicated subject. As I’ve said, if you have any questions, you can email me personally at gerrybulfin@cleanwaterstore.com or go to our website, cleanwaterstore.com, and get more information there.
To summarize, I talked about the best way to remove iron: oxidation and filtration. I also talked about how the coated media worked fine, but it is a thin layer that can generally wear off or out quicker. The solid manganese dioxide media are heavier but often have a higher throughput flow rate; that is, they work faster and require a smaller filter to do the same job as a coated type. I went over to make sure to check for pH, and you have to know your well pump flow rate and be on the lookout for iron bacteria and tannins in the well water.
Okay, well, thanks again for listening, and I hope you have a great day.
