17 Jul Activated carbon filters for water
Carbon is the stuff that’s been around a long, long time that makes your water taste better.
Back in the ancient Egyptian times in fact, they figured out that carbon made the water taste better so there are places in the history books that talks about how they used it.
Today we use it in a variety of spaces, not just for water. It’s used to clean up the air. It’s used to put in your insoles to make your shoes smell better and I’ve heard that some companies actually put it in your undershorts to make, well you know.
Carbon is used everywhere because the advantage and the function of carbon is awesome for taking out tastes and odors from water, odors from the air and many municipalities use it in their treatment process.
How does activated carbon filter water work?
Carbon functions through a process called adsorption. That’s not what a sponge does. A sponge works through a process called absorption with a B. If I put a sponge in water the water runs up into the pores of the sponge but when I squeeze the sponge the water runs right back out. That’s different than what carbon does.
When organics bond with the surface area of carbon it sticks. I can squeeze it, I can twist it, it’s not comin’ off and that’s how carbon is so good at getting rid of the things that cause taste and odors.
Where does carbon come from?
It is derived from a variety of sources. In the water filtration business, it’s primarily from coconut shell, from wood, or from bituminous coal.
We don’t use bituminous coal quite as much these days because there’s been arsenic, trace elements of arsenic found in the mining process of the bituminous coal.
Coconut shell is widely used for a couple of reasons.
First, it is a very renewable resource and two, it lends itself very well for water filtration.
Wood products, they’re used but not quite as much in our business.
The filters come in a variety of forms. They come in a granular form which gives us the advantage of flow rate.
A granular carbon filter has just like it sounds, granular carbon inside. The beauty of that is water can flow through that without a lot of resistance.
The other type is carbon block and this one has a little more capacity than the granular because we’ve ground it down to a real fine grain of carbon but because it’s in a block form the water flow has some resistance.
So the water flow is a little bit restricted as opposed to a granular carbon but we gain a lot more surface area.
So the capacity of a block is quite a bit higher than a granular filter in the same configuration.
Radial flow carbon filter
From there we go to a radial flow carbon which is kind of a mix between the two. Typically a granular filter, the water has to flow all the way to the bottom and up through the media inside the cartridge and it flows out the top where a carbon block, the water flows through the media all the way down. This is called a radial flow.
Well imagine if we can create a filter that combines the granular capacity and flow rate benefits of granular with the radial flow of a block. This gives us a lot more capacity than a typical granular and it gives us a flow rate benefit.
Now this is only available in a big blue 4-1/2-inch in a 20 or a 10 inch but it has so many advantages over the standard configurations.
Carbon, when it’s first ground, has a certain amount of surface area and then we go through an activation process by using heat or steam that opens up the pores of that carbon granule.
A one gram actually has 500 to 1,000 square feet of surface area.
That’s enormous and the finer you grind the carbon the more surface area is created.
This particular capacity would be like the parking lot down at the mall but it’s only got one floor.
Now we’re gonna add and grind it even finer and we’re gonna compress it into a block. We’ve just added about four floors to that parking structure and expanded the capacity. The interesting thing about carbon capacity, however, is it has only so many parking spots.
If, like at Christmas time, when you go to the mall and you drive around and around and around and never find a place to park, well you just pull back out on the street and you go on about your business. Same things happen with carbon.
If all of the surface areas is exhausted and there’s a car parked in every one of those spaces, the stuff you’re hoping to filter out will travel right on through.
So it’s very important with carbon capacity that you make sure you change the filter or you change the media before it totally runs out.
What can carbon remove from water?
It’s a pretty big list. It takes care of things that are organic in nature, things like volatile organic compounds.
The biggest one is chlorine. Carbon is used more widely for chlorine reduction than anything else.
Now a lot of municipalities have started to go to chloramine for disinfection. It takes a little bit more contact time with carbon to get chloramine out. The chloramine is a chlorine-ammonia compound and it takes a long time with carbon to separate that so that they can get each independent element out.
So we use a product called catalytic carbon and this carbon has like a coating on it that enhances the adsorption function and it’s really good for getting out chloramines.
But the list goes on. Volatile organic compounds, a lot of chemical things that get put in the water from pesticides or herbicides fall into those lists.
Now there are some things will not get out, for example lead.
It takes a little bit of a blended material, blended in with it, to reduce lead and as long as that formula is in there they can be quite good at getting lead out of the water. Things like arsenic, not so much. Dissolved inorganic minerals, not so much. Those things sail right through the carbon without any reduction whatsoever. But carbon on its own can do so much, it does a lot but to get out certain other elements that fall into the mineral category, it needs a little help and that comes in a manner of a blend that goes in with the carbon.
Sediment and carbon
A carbon filter typically does not make a good sediment filter and a sediment filter, it doesn’t have anything to do with taste and odor reduction. So if you have a sediment problem use a sediment filter to protect your carbon so that the carbon capacity can get used up the way it’s supposed to.
Granular filters don’t act as a good sediment filter either. A whole house carbon, upflow carbon or a backwashing carbon is gonna have about a mesh of 25 microns. It’ll capture some dirt and debris but that’s not the good purpose, that’s not the best application for carbon.
Filter systems with carbon?
It’s all over the place. Carbon is used in every reverse osmosis system, residential that is.
It is used on ultrafiltration systems. There are a variety of places to use a carbon filter.
The refrigerator door or the refrigerator filter you have has got carbon in it, I’ll guarantee ya.
So all over the place, we’re using carbon to filter drinking water. When used in a system like reverse osmosis or like ultrafiltration it’s doing a multiple of things. It’s getting rid of chemicals, it’s getting rid of chlorine to protect downstream like in reverse osmosis, it’s protecting that membrane.
If the membrane sees chlorine it’ll get destroyed. So the carbon plays a big, big role in that type of a system.
In a UF system or ultrafiltration, the carbon is doing a couple of things. It’s helping get rid of chlorine to protect the membrane, it’s also where lead gets reduced as some of these systems are rated for lead reduction. That carbon is doing that with the blend, that additive blend. And then the ultrafiltration membrane, which is typically a tiny little hollow fiber, kinda like a microscopic noodle, that’s gonna mechanically filter all of the dirt and debris that gets down to .025 micron.
So carbon is used with a conjunction in all kinds of different systems almost across the board in water filtration.
How often do I replace the filters?
You should always replace them at least once a year and here’s why.
The carbon, with all of its parking places, is collecting these organics and overtime as those parking places get, they get occupied there’s gonna be a time when there’s no more place for an organic to set down and it could possibly start to break pieces off that have been parked there for quite some time and the end result of that is you have water coming out of that filter that’s actually worse than the water going in. So it’s very important that carbon filters get replaced on an adequate basis, and that adequate basis is gonna be based on several variables but check with the manufacturer, take a look at the specs on the filter to give you the idea of how frequently it should be changed.
Is a carbon filter worth it?
And that’s really in a pro and con look at carbon filtration the pro is it does enormous, wonderful things to reduce tastes and odors. The con is if ya don’t replace it adequately enough it no longer becomes a good thing and quite frankly it could become a bad thing. So each application can present its own calculation on how long a filter should last.
So if I have a little bit, a little pitcher and I have a little bitty carbon filter I’m gonna have to replace that fairly frequently because it doesn’t have a lot of capacity. If I have a bigger filter and I’m using it in a lower fashion, then I might not have to replace it quite as frequently, and lower fashion would be I’m not putting quite as much water through it.