How Do Water Filters Work? (Process Explained) – WaterFiltersAdvisor

Water system diagram

We can now discuss the most critical aspect of water filtration. How do water filters work? So far, we mentioned adsorption, sediment filtration, reverse osmosis, and distillation, among others. You may have already heard about carbon filtration and other technical terms.

It is important to understand that some technologies can be present in other types of filters. This can range from the smallest water filter straw to the most extensive systems for your entire home. Here, we can discuss the different filtering technologies to choose from.

Common Types of Water Filtration Technologies

As mentioned, there are many different types of filtering technology. Some are even used in combination with others. Here, we can see the different types of filtering technology, how they work, and their best applications. 

1. Sediment Filtration

This is the most straightforward and basic water treatment. This type of filter is present across industrial, commercial, and residential filtration systems. 

A sediment filter consists of a washable screen. These screens are usually made from polypropylene (PP) or pleated polyester with a micron rating that can range from 1 to 100.

You can find standalone sediment water filters as a POE whole home filter. The most frequent application of sediment water filters is in combination with carbon filters or Reverse osmosis filters. This pairing provides more efficient filtration. The sediment filter works as a pre-filter to prevent the clogging of carbon filters or reverse osmosis membranes.

How Sediment Filter Works

Imagine a flour sifter. When water passes through a sediment filter with a 5 microns rating, it will sift all particles of 5-microns or larger. This leaves water containing contaminants smaller than 5 microns will flow through the screen and reaching your tap.

Advantages and Disadvantages

Pros Cons
Affordable Does not remove chemicals, toxins, or other contaminants smaller than 1 micron
Easy to use and replace It has to join another (more complex) water filtration system for clean water
Efficient against large particles  
A broad range of microns rating  
Pairs well with other types of filtration technologies  

2. Adsorption

You may know adsorption in the context of water filter systems as carbon filtration. However, adsorption is the process/technology used for the carbon filtration of water.

Adsorption is by far the most common filter technology on the market today. You will find large home units using this technology. These filters usually go together with carafe-size or even pencil-size water filters in the shape of filter water pitchers and filtered water bottles.

How Adsorption Water Filters Work

Imagine a sponge. Adsorption is the consequence of surface energy. As the water comes through the pipes, it meets the adsorption filters. The filtration occurs as the atoms, the gas ions, or molecules of a liquid or dissolved solid adhere to the adsorbing surface and cannot move forward to reach your tap. All the contaminants in water’s various micron sizes remain as a film on the surface of the adsorbent medium.

When it comes to adsorption water filtering, you can get one of two principal water filters: Activated Carbon Block filtration (ACB) and Granular Activated Carbon filtration (GAC). In commercial filters, you will meet this filtering process as Activated Carbon (AC), but you can know the differences between the two carbon water filters.

2. Activated Carbon Block Water Filters (ACB)

One of the most straightforward types of carbon filters, ACB filters consist of a fine carbon powder and a binding agent holding it together and making it stay static.

The powder features high porosity, resulting in a larger adsorbing area that can block a large number of particles, preventing water from channeling as well. The pore size of ACB filters is tiny, making them able to block small-sized contaminants. It also has high bacterial resistance.

ACB filters adsorb the contaminants and impurities in the water that have sizes larger than the filter’s pores. ACB filter systems also feature positively-charged carbon molecules that attract all negatively charged chemicals in the water. This way, with active carbon block filters, you can remove chlorine and the bad odor & taste in your water.

ACB filters are efficient in the removal and reduction of contaminants such as chlorine, bad taste and smell, VOCs, some chemicals, and cysts.

Advantages and Disadvantages 

Pros Cons
Efficient in removing bad taste and odors in the water For increased efficiency, they require a sediment filter for pre-filtration
Efficient in removing chlorine Can not remove hazardous contaminants such as viruses
Versatile and customizable for a wide range of water filters designs and applications Can not remove excess dissolved solids, minerals, and other smaller contaminants
Do not filter out essential minerals in the water  
Easy to use in pair with other water filtration technologies and systems  
Eco-friendly water filtration  
Long filter life  
Do not alter water flow rates  
Resilient to bacterial growth  

You can find ACB block filters in residential or commercial areas. Common applications include whole house filters, as the first-stage filtration in reverse osmosis. Smaller applications include countertop water filters and more.

3. Granular Activated Carbon Water Filters (GAC)

Granular Activated Carbon water filters (GAC) perform the same functions as Activated Carbon Blocks (ACB). However, their construction is different. They contain loose carbon granules larger in size than the powder you encounter in ACB filters. This difference results in weaker contaminant removal but higher filtration rates.

You will find GAC filters as part of more complex water filters. They usually come in the shape of pre-filters or first-stage filtration. This is because of their ability to remove large contaminant particles.

They also remove bad odor and taste in water, along with chlorine reduction. One of the best things about CAC filters is that they allow high water flow rates. You will find them in POE applications like home filtration units or reverse osmosis under-sink water filters.

They absorb all the contaminants in the water whose particles are bigger than their pores. The positive-negative attraction is present here as well. It makes the GAC water filter some of the best solutions when it comes to eliminating chlorine, bad taste, color, and smells in your water.  

Advantages and Disadvantages 

Pros Cons
Excellent water filtration capabilities and flow rates Do not remove viruses
Affordable Do not remove excess dissolved solids or minerals
Very effective against chlorine, lousy water taste, and smell Cannot remove water contaminants of small sizes
Long filter life The loose carbon granules can lead to water channeling
Pairs well with other water filtration technologies and applications  
Widely available in various types of water filters  
Eco-friendly water filtration technology  
Does not remove essential minerals in the water  
Good filtration capabilities against most common water pollutants  

 Some of the most common applications of Granular Activated Carbon water filters are:

  • Whole house water filters;
  • Countertop water filters;
  • Water filter pitchers;
  • Refrigerator water filters;
  • Faucet water filters;
  • Filtered water bottles.

Keep in mind that most GAC filters come in a combination of multi-stage water filters featuring other filtration technologies.

4. Reverse Osmosis Filtration (RO)

Diagram of reverse osmosis filtration

Reverse Osmosis is a filtration system based on semi-permeable membranes. RO membranes split the water into two streams. One stream contains all the contaminants that cannot pass through the membrane. The other is the clean water you get on your tap.

Reverse osmosis is one of the most efficient filtration systems. It is capable of removing up to 99.9% of all water contaminants.

How do Reverse Osmosis Water Filters Work?

Reverse osmosis is a process based on water pressure. The RO system forces the water flowing in your pipes to pass through a semi-permeable membrane. The membrane turns the concentrated solution (as it contains contaminants) into a less concentrated one (lacking contaminants). The main advantage of RO systems is that their membranes can block particles that are as small as 0.0001 microns.

While these units are highly effective in removing bacteria, you cannot rely on them alone. RO filters alone are not able to remove most VOCs, some pesticides, some solvents, and chlorine.

The pollutants in your water adhere to the surface of the membrane. The RO system flushes away in the drain of the stream of contaminated water to preserve the efficiency and lifespan of the RO filter.

The system also usually comes with a tank to store the filtered clean water for later use. This is the reason behind its slow filtration rate.

One of the problems with reverse osmosis filters was their environmental burden and high operational costs. It is not efficient to consume 4 gallons of water to obtain 1 gallon of clean, water and pour the rest down the drain.

Another issue of the past was concern regarding reverse osmosis filters. They remove essential minerals from the water, leaving it dull, with no nutritional value, and flat-tasting.

Now, the Reverse osmosis filters feature multiple stages of filtration, feature wastewater-to-filtered-water ratios of 1:1, and come with additional re-mineralization steps. In other words, modern reverse osmosis systems put back the essential minerals in the water, making it mineral safe while still maintaining eco-friendly operations. 

Advantages and Disadvantages
Pros Cons
Offers the most efficient water filtration against most water contaminants It does not remove chlorine, some VOCs, some pesticides, etc.
Produces the cleanest water of all POU water filtration systems May interfere with the water flow rate in your home
Lowers the TDS value in your water Requires maintenance
Long lifespan of the membranes Expensive
Modern RO water filters re-mineralize the water with balanced levels of good minerals for nutrition  
Moderate to low environmental impact  
Available for a wide range of industrial, commercial, and residential applications  

RO filters are the answer to the question, “how do I filter well water? Moreover, the technology is available most commonly in under-sink filters.

5. Distillation Technology

Distillation works through the process of condensation. A distiller boils the water. It then captures the cooled and condensed vapors and transfers the purified water into a separate compartment.

How Water Distillers Work

Distillation is a very simple process. Distillers use electricity to heat up the unit. The water then starts to evaporate. The distiller collects the steam and condenses it into liquid form. The distillation technology discards contaminants together with the essential minerals.

Water distillers work well against most contaminants. However, some pollutants reach the boiling point before the water. This allows them to remain in the distilled compartment. This applies to the case of volatile organic compounds (VOCs). Their boiling point is lower than 212 F (100℃). This means that they will vaporize and condense faster than water. So they will end up in the distilled water compartment.

The entire distillation process is relatively slow. It produces limited volumes of filtered water at a time. While most applications are industrial, you can find a wide range of distillation machines for residential use. Their performance and output capacity may vary depending on the size of the unit. 

Advantages and Disadvantages

Pros Cons
Excellent water purification capacity Time-consuming with low output
Removes bacteria, most water contaminants, and dissolved solids from the water Removes essential minerals from the water without putting them back as RO systems do
You don’t have to replace filter cartridges The water tastes flat
Affordable Cannot remove any contaminant with a boiling point lower than 212℉ (100℃)
Present in commercial water distillers Requires careful maintenance

Many people wonder if it is safe to drink distilled water. The simple answer is yes. But as the chart presents above, you will want to be aware of the taste. Distillers do not usually support re-mineralization features. This can leave your water with a flat taste. 

6. Ion Exchange Water Filter Technology (IX)

Ion exchange water filter technology installation

Ion-Exchange filtration is present in softeners as commercial IX technology goes. The process allows the capture and replacement of positively charged hardness minerals (calcium and magnesium ions) in the water with sodium ions.

The IX filtration technology is capable of exchanging both positively charged ions (cations) and negatively charged ions (anions). It means that in some industrial settings, the IX process can remove fluoride, nitrate, arsenic, sulfate, and others, as they represent negatively charged ions.

How Ion Exchange Works

When it comes to water softening, you have an ion-exchange resin with positively charged sodium ions that captures the ions responsible for harness and limescale buildup. In exchange for these ions, the resin bed releases sodium into the water.

The resin bed in a softener has a limited lifespan. For this reason, it has to go through a process of regeneration that restores the initial efficient conditions of the IX resin. The restoration works by using softener salts. These salts usually contain sodium chloride solution and Hydrochloric acid.

Ion-exchanging filtration can remove some contaminants in the. But it is not the same thing as filtration alone. In your home, IX technology is present only in conventional water softeners.

Keep in mind that if you have contaminated water, you can always pair a softener with whole house filters.  Activated carbon technology and RO filters are also good alternatives. Keep in mind that softeners cannot remove organic contaminants, waterborne pathogens, and other common pollutants.

Advantages and Disadvantages

Pros Cons
The best solution against hard water Cannot remove sediment, organic contaminants, microorganisms, and other hazardous water pollutants
Effective against most dissolved inorganics contaminants Massive units for home water softening
  Moderate to high maintenance
  Moderate to high operational costs
  High environmental impact

When it comes to the best water softeners on the market, you can know that they do a terrific job as POE devices. 

You will want to make sure you check our guide on more modern water treatment techniques against hardness. You can also find information regarding conventional softeners, electronic water descalers, or Template Assisted Technology.

7. Ultraviolet Water Filters (UV)

UV filters usually come with more complex filters. Many reverse osmosis systems feature UV disinfection as a bonus.  You can also purchase standalone UV filters to install along with your Reverse Osmosis filter, Carbon Activated whole house filter, and even water softeners.

UV filters have the ability to kill 99.99% of bacteria and viruses present in your city or well tap water. They can remove the following microorganisms: 

How UV Water Filters Work

A UV filter usually consists of a system encased in a chamber. The UV lamp (mercury vapors) lies in a glass quartz sleeve. It emits UV-C radiation to kill microorganisms by penetrating the transparent glass sleeve, reaching the water, and disinfecting it.

Since water and electricity do not work well together, it is crucial to have the system encased in a quartz glass container. Usually, O-rings hold together the entire device.  

UV filters are point-of-entry devices. It means you can install them on your lines before the water enters your home. You find some UV filters as POU devices or some coming directly with a reverse osmosis system.

This sterilization process provided by UV filters does not add or remove particles from your water. It does not change your water from a chemical point of view as reverse osmosis systems do. The UV radiation at the 254 256 nm wavelength disrupts cells’ DNA.

A UV filter’s efficiency depends on the water flow in your home. The correct exposure to UV radiation, while it travels through the pipes, renders the system more or less efficient.In short, you need to make sure the flow rate in your home allows the UV filter to contact the water long enough. That way the radiation kills microorganisms.. Most UV systems operate efficiently with typical household pressures and flow rates.

Advantages and Disadvantages 

Pros Cons
They do not interact directly with the water Do not remove anything else from the water except for microorganisms
Easy to install with current water filtration systems Tend to heat the water
The quickest and most reliable method to remove microorganisms in the water  
Low operational costs and maintenance  
Low energy consumption  
One of the best water filtration solutions for well water when paired with other water filters  
One of the best lines of defense against natural disasters resulting in flooding and bacterial/viral spreading through water  

The most critical aspect you need to understand is that UV filters cannot remove different types of contaminants . Since tap water can contain plenty of pollutants, you need to use a UV filter with another filter. This can be a  reverse osmosis filter or another type of filtration system.

8. Water Ultrafiltration Technology (UF)

Ultrafiltration technology works more or less like reverse osmosis. It uses hydrostatic pressure to push the water through a semipermeable UF membrane made of a hollow fiber. The membrane’s pores range in size between 0.01 and 0.5 microns. This way, UF filtration technology is capable of removing most contaminants and pollutants with some caveats.

How Does Water Ultrafiltration Work

As the water flows against the hollow fiber medium, it leaves behind all impurities larger than 0.01 to 0.02 microns. One of the essential aspects of UF technology is that the membrane has high resilience against chlorine. For this reason, a UF filter does not require a supplemental AC system to act as a pre-filter.

Ultrafiltration technology is efficient against microorganisms. In comparison to reverse osmosis filtration, it does not block essential minerals in the water. Keep in mind that for a UF system to work efficiently, it needs to treat water that contains low levels of total dissolved solids (TDS).

Advantages and Disadvantages

Pros Cons
Excellent filtering capacity of contaminants down to 0.01 microns Does not remove chlorine, bad taste & odor in your water
Efficient in removing most waterborne pathogens Does not remove large dissolved solids like fluoride, salts, and more
Keeps the essential minerals in the water Not efficient against cysts or VOCs
Resistant against chlorine and other chemicals  
Does not affect the water flow rate  
Easy installation and low maintenance  

If you want clean drinking water, it is best to pair UF techs with other filtration systems. This can include carbon filtration (AC), sediment screens, and reverse osmosis.

9. Activated Alumina Water Filtration (AA)

Activated Alumina (AA) filtration is mostly standard in industrial settings namely, your city’s treatment plant. It is a rather niche filter technology, as the highly adsorptive porous aluminum oxide (bauxite) filter can only remove fluoride, arsenic, selenium, and thallium in water. For this reason, you will find fluoride using AA filtration.

Despite widespread concern and some myths, the aluminum in the activated alumina filter does not leach into the water, so you can not worry about filtering water of fluoride and drinking aluminum instead.

How Activated Alumina Water Filters Work

The activated alumina goes through a process of initialization before anything else. This process consists of the backwashing and the chemical treatment of the activated alumina filter.

The tap water coming to your tap through your pipes encounters the activated alumina medium. This filter then absorbs the fluoride, arsenic, selenium, and thallium onto the filter’s surface.

Advantages and Disadvantages

Pros Cons
Efficient in removing 99% of fluoride in your water Cannot remove most water contaminants
Also performant in removing arsenic, selenium, and thallium from the water Requires constant maintenance and regeneration
The filter can regenerate  

If you want to remove fluoride from your water, you can opt for a fluoride filter using AA filtration. However, it is best to pair your AA filter with another filter if you are dealing with other contaminants. Consider this option if you are dealing with the following:  chlorine, VOCs, heavy metals, and chemicals. It is best to pair AA filtration sediment, reverse osmosis, and even ion exchange filters.