How Does Activated Charcoal Filter Water & What Does It Remove?

how does activated charcoal filter water

How on earth does a stick of charcoal filter water?

It sounds like it shouldn’t work, but it does. In fact activated carbon is one of the most effective natural water filters out there.

Activated charcoal is a highly effective, natural, eco-friendly water filter. Using a charcoal filter can bring many benefits to water, including to the taste, the mineral content and removing impurities.

A simple activated charcoal stick can drastically reduce the reliance on plastic filters and single use bottles of water, making this simple water filter a fantastic, good for the environment, sustainable choice.

I live in a natural soft water area with tap water coming down from the Lake District. I’ve never felt the need to filter my tap water but having used an activated charcoal stick for a little while, I’ve genuinely noticed an improvement, even to the high quality tap water I have access to.

One of the best things from my perspective is that activated charcoal filters water naturally. So let’s find out how activated charcoal works and what it filters out of water.

Disclaimer: This post contains some affiliate links to the activated charcoal stick that I use. These may give me a small commission on the set price as a thanks from the seller. Please note I bought the filter with my own money and any views portrayed are genuine and honest.

What is a charcoal water filter?

A charcoal water filter is a piece, or several smaller pieces, of charcoal that has been specially treated to become ‘activated’.

The resulting activated charcoal is very porous with an incredibly large surface area, which gives the charcoal its fantastic water filtering and purifying abilities.

There are broadly two different types of charcoal water filter:

  • Solid block activated charcoal
  • Granular activated charcoal

As the name suggests, a solid block charcoal filter is one solid mass of activated charcoal. These are generally in the shape of a thick stick so they can fit nicely into a water bottle. This picture below shows my own activated charcoal stick bought from andkeep.com before it went into my stainless steel WAKEcup bottle.

A granular filter is where the activated charcoal has been crushed up into many small parts, which as a filter bed when the water passes through. Because granular activated charcoal is crushed up, it requires some form of porous encasing to keep it altogether.

The activated charcoal can come from a number of primary carbon sources, such as wood, coal, coconut shell or bamboo. The sources of activated charcoal should be 100% natural and organic.

The idea of an activated charcoal water filter first originated in Japan around the 17th century. This is why you might see the name Binchōtan charcoal water filter – binchōtan means ‘white charcoal’ in Japanese. In Japan, the charcoal source typical comes from the oak tree.

Can charcoal filter water?

Yes, absolutely charcoal can be used to filter water and does work very efficiently. There is one main prerequisite though: it has to be activated charcoal.

This means that no, you cannot just put a lump of barbecue charcoal into a jug and hope it filters the water.

According to the US Environmental Protection Agency, activated charcoal can remove at least 81 chemicals, reduce 52 others and remove a large number of pesticides and herbicides.

How is activated charcoal made?

There are two main ways to activate charcoal: one is through a physical activation and the other is through chemical activation.

During physical charcoal activation, the initial carbon source needs to undergo a process of superheating and oxygen addition.

The wood or carbon substance, hopefully coming from a sustainable produced source, is first put in a kiln and heated to a temperature of 600-900oC with an inert gas, such as argon, which stops the carbon from burning. This first stage creates a pure carbon source with no impurities.

Next, the carbon is heated to even higher temperatures but with the addition of oxygen or steam. This causes the carbon to fracture, creating millions of tiny micro-fractures, cavities and pores.

When this final step is complete, the charcoal is now said to be activated.

The resulting activated charcoal is non-toxic, odourless and tasteless.

How does activated charcoal filter water?

It’s the creation of the porous material with an extremely large surface area that makes activated charcoal such an effective water filter.

The huge number of tiny fractures and pores create a vast number of potential binding sites that attract the chemicals and contaminants present in tap water.

When a stick of activated charcoal is placed into a jug or a bottle of water, it is chemistry that works it’s magic to purify the water.

The porous structure of the activated charcoal is made up of carbon ions. These ions attract other ions, manner of which make up the contaminants and other compounds found in the water.

Once attracted, the chemicals fill up the pore and are bonded to the activated charcoal where they stay. This is known as adsorption and is how activated charcoal filters water so effectively.

You don’t need to worry about these binding sites being used up over the short term. There are millions of pores in one stick of activated charcoal, which will take months of daily use before they are filled up.

three water bottles with activated charcoal
Source: Black + Blum

What does charcoal filter out of water?

We now know that activated charcoal is a very effective water filter, but what exactly does it filter out?

The activated charcoal doesn’t ‘know’ which chemicals and impurities we want filtering out. But thankfully it does a great job of attracting many things we don’t necessarily want to be drinking whilst leaving the salts and minerals that are beneficially to our bodies.

Activated charcoal can help produce healthier and tastier water. As mentioned, this all comes down to natural chemistry.

Activated charcoal can remove and filter out many chemicals and substances from water that we don’t want, such as chlorine, volatile organic compounds (VOCs) and even microplastics.

Just as a side note, chlorine is a common chemical used to disinfect water in public systems, such as the water the comes out of your tap. Chlorine isn’t especially harmful to us in small doses but it can affect the taste and quality of water.

Here’s a list of what activated charcoal can filter out of water:

  • Chlorine and chlorine by-products
  • Nitrate
  • Phosphate
  • Lithium
  • Lead
  • Microplastics

On its own, activated charcoal doesn’t remove every impurity present in water. It may be an excellent water filter, but it isn’t a bona fide miracle worker. Due to the chemical characteristics, some minerals and metals may pass through the filter and stay in the water.

However, activated charcoal filters allow most of the beneficial salts and minerals to stay in the water. The good minerals include magnesium, potassium, sodium and calcium.

Activated charcoal can even release extra beneficial minerals, such as calcium and magnesium, back into the water.

How to use charcoal to filter water?

Using a charcoal water filter couldn’t be much simpler.

It’s as easy as placing the fresh, sterilised activated charcoal straight into your water bottle or water jug.

The water and activated charcoal then need to be left for a while for the filtering to take place. Even after just one hour, a good level of filtering will have occurred. The longer the activated charcoal is left, the better the water quality will be.

It’s ideal if you can leave your water bottle in the fridge over night with the activated charcoal inside. When you wake up in the morning you’ll have lovely, cold, high quality water ready to drink.

I use my activated charcoal stick in my stainless steel water bottle and it works perfectly.

The great thing about an activated charcoal stick, such as this one from Black and Blum, is that is lasts a long time. In most cases, around 6 months.

For example, if you use a 750ml bottle of water and fill it up once a day, it will firstly last around 3 months. After this time, you’ll need to recharge your activated charcoal by boiling it in a pan for 10 minutes and let it dry, then it’s good to go for another 3 months.

How good and easy is that? Especially for the very small cost involved in buying one in the first place.

After 6 months, your charcoal water filter will need changing. Remember, when your charcoal stick filters the water, it chemically bonds the compounds to the charcoal permanently. This means over time the huge number of fractures and pores will now have been filled up.

How to reuse your activated charcoal filter?

After 6 months, just because your activated charcoal has finished being a water filter, it doesn’t mean you can’t use it elsewhere!

Those of you who care about the environment will be glad to know that activated charcoal is reusable in other places around the home.

There are a few places where you can reuse your charcoal filter:

  • In cupboards and wardrobes to reduce moisture and the potential for mould
  • Put in places with strong odours, such as fridges or shoes, to reduce smells
  • Crush up and put in soil or indoor house plants
  • Into your compost pile

As you can see activated charcoal is eco-friendly and extremely useful material. This website is all about the simple and sustainable – activated charcoal fits this criteria perfectly and gives you a fantastic opportunity to reduce plastic use.

It’s primary job is to filter water, which it does very effectively through its unique porous structure. It helps turn ordinary tap water into great tasting, healthy, high quality water. Even when your tap water comes from quality sources, such as the Lake District for me, an activated charcoal stick can still make a big, beneficial difference.

Even better, it also has many further re-uses when it’s filtered all the water it can, makes activated charcoal super substance in my eyes. If you are interested, I bought mine from the andkeep.com website and it’s brilliant.


You might be interested to read…