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Water Purification: Different Water Filtration Methods Explained

Did you know that at least 2 billion people in the world right now, only have access to drinking water that’s contaminated with faeces?

It is heart-breaking that the basic necessity of living beings is capable of putting our lives at risk. What’s more sad is it’s not easy to figure out if the water we use everyday is polluted.

So, it is fair that people are willing to spend so much money on water filtration systems because one can’t put a price on clean and pure water.

A proper filtration process leaves you with not just clean water but also water that’s free from any bad odors or taste.

But before you buy a random water filter, it’s better to have a clear understanding of the filtration process for your health and safety.

So, let’s look at everything there is to know about the water filtration process so that you can choose the most suitable filter for you.

Difference between Physical and Chemical filtration

Water filtration methods usually follow one of two methods: physical or chemical filtration.

Physical filtration involves straining water or using a filter to remove larger impurities. This method of filtration acts like a sieve that targets heavier contaminants.

Chemical filtration involves passing water through an active material. The adsorption properties of this material can remove a variety of pollutants. The various filtration processes that we are about to discuss below cover both these types of filtration.

Types of water filtration methods:

Different water filtration methods remove the many kinds of sediment, taste or odor.

Depending on the type of impurity, these methods can provide better-tasting and pure drinking water or prevent any scale build-up by providing soft water.

To get a better idea, feel free to go through our list of the six different commonly used water filtration methods.

1. Distillation

Distillation is a filtration method that has been around for generations. This process starts by heating water until it’s at a boiling point.

The water vapor that rises during this process is further condensed and cooled. Then, the pure water is collected as the heavier contaminants stay behind in the original container.

The heat helps to take care of the majority of the bacteria. However, as the water boils at 100°C (212 °F), this method is not feasible for impurities that have the same or lower boiling point. So, any volatile organic compounds such as herbicides, pesticides, and more cannot be removed. They can actually become more potent via distillation.

But, Distillation is best at removing heavier contaminants. This method can get rid of almost 99.5% of the impurities that include nitrates, bacteria, dissolved solids, lead, sodium, and most organic compounds. The high effectiveness of Distillation is one of the reasons why this filtration method stands out from the crowd.

Advantages and Disadvantages of Distillation

Advantages Disadvantages
Can remove a wide range of contaminants It requires careful maintenance.
It is reusable. It requires a large amount of energy.
It is feasible for heavier contaminants. The resulting water can have a flat taste.
It is not very space-efficient.

2. Reverse Osmosis (RO)

Reverse osmosis is a process that utilizes a semi-permeable membrane.

Water passes through this membrane so that any larger impurities are left behind. The membrane here acts as an excellent filter as the water flows through with some amount of pressure.

The name of this method may sound complicated, but the actual process is pretty easy to understand.

Generally, Osmosis involves two solutions with different concentrations. The thin porous membrane then balances these solutions until they are both equally concentrated.

In simple terms, Reverse Osmosis means that water goes from being very concentrated to less concentrated. Since this process involves pushing the impure water against its natural direction, it requires more energy. So, this filtration process needs powered pumps to function. The thin membrane retains most salts and sugars, which helps it prevent at least 95% of the impurities.

This process is best for removing chemical contaminants such as chloride, copper, sodium, lead, and chromium. It also effectively reduces substances like arsenic, sulfate, calcium, potassium, nitrate, fluoride, and phosphorus.

But, it does not remove dissolved gases like hydrogen sulfide, some pesticides, and herbicides. Most modern Reverse Osmosis systems come paired with a carbon filter to target these impurities specifically.

Advantages and Disadvantages of Reverse Osmosis

Advantages Disadvantages
It effectively targets a wide range of impurities. The flow rate limits the filtration process.
It provides economical filtration. It usually needs carbon filtration to deliver the best results.
It is mostly low-maintenance. It requires high water pressure to function well.

3. Activated carbon

Carbon filtration is a method commonly used in many home water filtrations. It involves utilizing the active absorption capabilities of carbon in reducing impurities and also removing any bad odors and tastes. It mainly targets chemicals and gases but is effective against bacteria as well.

The activated carbon used is a very porous form of carbon, based on charcoal. Since there is a reduced oxygen supply during its formation, it behaves like a sponge with a large internal surface area. It also creates many crevasses into the molecules. As a result, this process can trap a variety of impurities using adsorption. Instead of solids dissolving into liquids, this process works by solids or liquids capturing liquids or gases.

Activated carbon filtration is excellent for removing impurities such as chlorine-based chemicals and some pesticides, and industrial solvents. However, it is not ideal for removing any hardness out of water or treating heavy metals such as sodium, fluorine, or nitrates. There are special carbon filters dedicated to treating some heavy metals, but it might come with additional costs.

The effectiveness of this system largely depends on the kind of carbon used. Additionally, the diameter of the pores formed into the carbon filter and the diffusion rate of the impurities also affect the adsorption process. So, people usually use this method alongside different treatment processes for maximum efficiency.

Advantages and Disadvantages of Activated Carbon

Advantages Disadvantages
Excellent removal of chlorine and dissolved organic chemicals Need to replace the carbon filter every time it clogs up
Simple to use Need to choose the correct carbon filter for different impurities

4. Ion exchange

This filtration process mostly works to soften the water, which means it targets limescale by splitting the atoms of any contaminants into ions. The ions are then trapped and released to purify the water. In simple words, this process is “ion-exchange.”

This process generally prepares the hard, impure water for RO treatment. There are certain beads in place made from a substance called Zeolite, which contains sodium ions. They further help in exchanging two sodium ions for every calcium or magnesium ion that is removed.

How this works is that the ion-exchange filter effectively splits apart the compounds around it. The beads then attract the impurities that create hard water: calcium and magnesium. It thus traps all the incoming impure ions and fills the gap by releasing its own sodium ions.

Once the process reduces or removes the impurities, the water instantly becomes softer. However, it simply replaces the contaminants with sodium. So, you will still need to go through further filtration to be able to drink this water.

Advantages and Disadvantages of Ion Exchange

Advantages Disadvantages
Well-suited for the treatment of hard water Resulting sodium water might not be suitable for people on low-sodium diets.
Highly effective to be paired with RO filters for best results The filters need to be recharged periodically with sodium ions.

5. Activated Alumina

This method targets fluoride in drinking water. It also removes arsenic and thallium.

Many fluoride removal plants across the United States still have this effective filtration method.

The filter, in this case, is of aluminum oxide. It more or less has the same mineral make-up that is commonly found in rubies and sapphires but without any of the coloring impurities. The only concern for this filter is that much like the ion exchange method, it might add aluminum to your water. While a small amount of aluminum is bound to leak into your water system, it is mostly harmless.

Advantages and Disadvantages of Activated Alumina

Advantages Disadvantages
Highly effective in removing fluoride It can leak aluminum into the water in small amounts.
Very Affordable

6. UV Filtration

Ultraviolet water filtration disinfects the water of microorganisms.

In this process, water passes through a chamber. The UV rays of the UV lamp/bulb present inside the chamber kills off any bacteria, parasites, and viruses. The UV light can be scorching hot of upto 104°F.

But since this process usually only purifies water, it can't remove mineral contaminants.

Advantages and Disadvantages of UV Filtration

Advantages Disadvantages
Effectively kills bacteria, viruses, and parasites It does not remove mineral contaminants, ions or lead.
It might decrease resistivity.


There is a wide variety of filtration methods that target various impurities.  But, no method, in particular, is the one-size-fits-all of water filtration.

Most of these filtration techniques give the best results when you combine multiple methods.

So when you are looking for a filtration system, keep in mind what kind of impurities you want to target.

Make sure to check how much maintenance each method requires.