Activated carbon was discovered by Scheele in 1773, and was initially used for medical applications. Only in 1862 did Lipscombe first use activated charcoal for the purification of water.
Filtration Technology
How Carbon Based Water Filtration Works
7 min read
- 01 | Pros & Cons of Carbon Filtration
- 02 | In a Nutshell: How Carbon Filtration Works
- 03 | What Is Activated Carbon and How Does It Attract Contaminants?
- 04 | The Problem with Chlorine
- 05 | How Carbon Filtration Works
- 06 | What Carbon Filters Remove
- 07 | What Carbon Filters Do Not Remove
- 08 | Are All Carbon Filters Equally Effective?
- 09 | Types of Carbon Filtration
- 10 | Different Carbon Filter Designs
- 11 | Advanced Features for Carbon Filters
Carbon, a.k.a. charcoal, has a knack for absorbing toxins and impurities.
Swallow a charcoal pill, and it’ll detox your gut.
Use a carbon filter, and it’ll detox your water.
Keep reading to learn more about how carbon based water filtration works and to decide if it’s the right fit for your home...
Pros
- Improves taste and odor
- Reduces chlorine and other disinfection by-products (DBPs)
- Reduces the risk of waterborne illnesses
- Enhances other water treatment systems, like reverse osmosis (RO)
Cons
- Does not remove dissolved solids
- Does not remove most dangerous pollutants, like lead and arsenic
- Doesn't remove “hard” minerals, like calcium and magnesium
- Doesn't protect your pipes from limescale and calcification
- Filters need to be changed often
CHEAT CODE: If you think your water might contain dangerous contaminants like lead, arsenic, and nuclear waste, install a reverse osmosis system instead.
Carbon filtration removes contaminants through two unique processes:
Process #1: Organic compounds stick to carbon like Velcro through a process called adsorption.
Process #2: Chlorine and disinfection by-products are removed through a chemical process called catalytic reduction.
At the end of the day, your water will taste better and be safer to drink.
In a sec, we’ll take a closer look at these two processes in action...
Activated carbon is a special type of charcoal that attracts and traps a range of contaminants.
It has a slight electro-positive charge and acts like a magnet to attract negatively-charged pollutants.
The combination of electro-magnetism and a large, porous surface makes activated carbon an ideal filtration medium.
Most people buy carbon filters to improve the taste of their water by removing chlorine.
Chlorine and other disinfectants, like chloramine, are added by water treatment plants to prevent outbreaks—the problem is that they leave a bad taste.
Even worse, when chlorine mixes with organic matter in water, it produces toxins called disinfection by-products (DBPs).
Research shows that long-term exposure to DBPs can cause cancer and cognitive impairment, especially in developing babies and young children.
Chloramine isn’t much better…
Although it’s a small upgrade from chlorine, it still leaves a bad taste and causes severe skin irritation in some individuals.
Fortunately, the right carbon filter can remove both, but more on that later...
Next, let’s take a more in-depth look at carbon filtration in action...
Like we touched on earlier, the two principal mechanisms at work are adsorption (sticky Velcro) and catalytic reduction (chemical rearranging).
Let’s dive in!
According to the World Health Organization (WHO), the consumption of chlorinated tap water has been found to specifically increase the risk of bladder cancer. This was found in a population-based study, which was conducted over half of the lifetimes of each participant.
You’re probably familiar with the term absorption (soak up like a sponge), but what about adsorption?
Adsorption causes organic compounds to stick to carbon like pieces of tape.
Carbon has a large, porous surface that’s ideal for trapping a wide range of contaminants.
But when carbon is “activated,” that’s when it really becomes powerful...
Activated carbon has a positive charge and it attracts negatively-charged compounds like mini magnets.
As the water flows through the activated carbon, organic compounds easily stick to the surface.
Carbon filtration removes chlorine and DBPs through catalytic reduction.
In this chemical process, chlorine molecules are literally transformed into chloride. POOF! The threat is eliminated.
Chloramine removal works much the same way, except that it requires an upgraded type of carbon called catalytic carbon.
Because chloramine is more stable, regular activated carbon just won’t cut it.
Catalytic carbon, however, gets the job done fast.
Before you start shopping for filters, test your water for chloramine so you know what you’re up against.
Some upgraded carbon filters will work just fine, but another option is a reverse osmosis filter. They’re guaranteed to remove chloramines, chlorine, and up to 99.9% of all other dangerous contaminants.
Carbon filters remove or reduce a range of contaminants, including:
- Volatile organic chemicals (VOC)
- Pesticides and herbicides
- Chlorine
- Benzene
- Disinfection by-products (DBP)
- Solvents
- Radon
Depending on the design, some filters also remove chloramine, hydrogen sulfide, heavy metals, and pathogens like Giardia and Cryptosporidium.
Many are fitted with a sediment pre-filter to improve discoloration and remove dirt and debris.
Although carbon filters are good at removing chlorine and organic compounds, they don’t stand a chance against the biggest and baddest pollutants on the block.
Carbon filters do not remove:
- Total dissolved solids (TDS)
- “Hard” minerals, like calcium and magnesium
- Inorganic contaminants
- Arsenic
- Asbestos
- Barium
- Cadmium
- Chromium
- Copper
- Fluoride
- Mercury
- Nickel
- Nitrates and nitrites
- Sulfate
- Radionuclides
Most of these contaminants will slip right through your carbon filter.
In order to remove them, you’ll either need a either a reverse osmosis (RO) system or distiller instead.
No, not all carbon filters are created equal.
Their effectiveness depends on a few key features, like:
- Carbon particle size
- Amount of carbon
- Type of carbon
Carbon particle size has the greatest effect on removal rate.
Activated carbon particles range from 20 microns (least effective) all the way down to 0.5 microns (most effective).
The smaller the particles, the better the removal rate.
A typical carbon filter contains 12 to 24 ounces of activated carbon.
More carbon equals greater surface area and better removal rate.
At the same time too much carbon can make the water flow too slowly, so it’s all about balance!
The most common types of activated carbon are:
- Wood-based
- Bituminous
- Coconut shell
Coconut shell carbon is the most effective and the most eco-friendly.
Here’s a quick breakdown of the three main types of carbon filtration, from least effective to most effective:
- Faster flow rate
- But more contaminants sneak through
GAC filters contain loose granules of activated carbon.
The water flows more easily, but this also means that it’s in contact with the carbon for less time (a.k.a. bad for filtration).
Plus, faster flow rate and larger granules can cause channeling, where the water cuts a path through the carbon and allows more contaminants to slip through.
At the same time, GAC does not remove sediment particles very well.
Only consider buying a GAC filter if it includes a sediment pre-filter to remove sediment and protect your carbon from clogging.
- Slower flow rate
- Up to 10 times the surface area of GAC filters
- More effective at removing sediment and pathogens
Carbon block filters contain finer carbon granules than GAC filters—sometimes as small as 0.5 microns. That’s small enough to remove pathogens like Giardia and Cryptosporidium.
Carbon block filters are also more resistant to channeling than GAC filters.
- Greater flow rate
- Lower pressure drop
- Higher surface area
- Removes contaminants more thoroughly
- Removes some pathogens
- Longer filter life
Radial flow carbon filters combine the best of both worlds—they have the surface area of a carbon block filter and the flow rate of a GAC filter.
The secret is in the design...
Rather than removing contaminants in a single pass, the water flows back and forth in a zig-zag pattern several times: up the side, across the middle, up the side, and over again and again.
This means more carbon contact time, faster flow rate, and better contaminant removal.
Carbon filters are most commonly used as pre- and post-filters for advanced systems like reverse osmosis, ultrafiltration, and ultraviolet systems.
It’s their job to protect the system from unnecessary wear and tear and to remove disinfectants like chlorine.
You can also buy carbon filters as a self-contained unit in a variety of designs:
- Faucet filters
- Pitcher filters
- Whole house filters
- Under-sink filters
Faucet filters attach directly to the kitchen faucet or shower head.
It’s one of the simplest and most affordable ways to improve the taste of your tap water and protect your family from chlorine.
Chlorine was first used in WWI for chemical warfare. When you take a nice, steamy chlorine shower, it’s basically like being on the battlefield.
Luckily, faucet filters keep you safe.
Pitcher filters are a portable water filter that you can store in your fridge.
#1: Fill it from the top with regular tap water.
#2: Wait 2-15 minutes for it to filter gradually (gravity-fed)
#3: Enjoy delicious, chlorine-free drinking water
NOTE: Pitcher filters are one of the least effective filter designs. Chances are your water will still contain trace amounts of chlorine.
Whole house (point-of-entry) filters treat water before it even enters the house.
They typically use finer granules, have a faster flow rate, and are more effective than pitcher or faucet filters.
Although they can be expensive, you’ll be protected from chlorine in your kitchen, your shower, and literally every square inch of your home.
Under-sink (point-of-use) filters are basically smaller versions of whole house filters---the difference being they only protect your drinking water and the kitchen sink.
When you’re shopping around, look for advanced features like catalytic carbon, KDF-55, and silver-enhanced carbon.
Catalytic carbon is one of the few filtration mediums that can remove chloramine from drinking water.
KDF-55 (Kinetic Degradation Fluxion) is designed to reduce iron. It chemically converts iron from a dissolved state to a solid state, making it easier to remove.
And for a bacteria-killing boost, look for silver-enhanced carbon.
Although these features can work pretty well, they still won’t compare to the heavy-hitting power of reverse osmosis RO filters.
Cloud Water Filters fit right under the kitchen sink and remove 99.9% of all contaminants, including the most dangerous ones like arsenic, lead and nuclear waste.
Plus, they use built-in software that monitors your water quality 24/7 and automatically ships replacement filters right to your door.
Click here to learn more.
