Do Water Filters Remove Algae?

Algae are a group of aquatic plant-like organisms which can sometimes find their way into our water sources. While algae themselves might not pose a direct health risk, their presence can indicate potential issues with water quality. You may therefore be wondering if water filters are capable of removing algae from your drinking water.

Water filters that use reverse osmosis, ultrafiltration, activated carbon adsorption and sometimes mechanical filtration techniques can remove algae. Reverse Osmosis systems are the most effective at removing algae, while those relying solely upon mechanical filtration may not always be 100% effective.

In this post, we will be discussing whether some popular forms of water filters can remove algae from our drinking water. We will also provide you information on what algae is, how to detect its presence, the drawbacks of consuming water with algae, and the various mechanisms by which different types of water filters address this concern.

Let’s begin!

What is Algae?

Although you will often find algae described as plants, they form an entire ‘Kingdom’ of their own in the classification of lifeforms, known as ‘Protista’. As such, you can understand algae as simple, unicellular, plant-like organisms that thrive in aquatic environments. 

Freshwater algae can be microscopic in size.

They contain chlorophyll – the green pigment that is found in plants – so they are capable of producing their own food/nutrition. They also (usually) appear green like other plants. However, they lack true roots, stems or leaves.

While there are a few rare species of algae that can be toxic to humans, The vast majority of algae are harmless. Some, however, can produce compounds that impart an unpleasant taste and odor to water. Additionally, water with excessive algae can appear greenish or cloudy. 

It is therefore essential to note that the presence of algae doesn’t necessarily mean that the water is unsafe to drink, but it does raise concerns about the water quality.

Do Water Filters Remove Algae?

How Do Water Filters Remove Algae?

Water filters employ various methods to remove impurities, including algae, from water. Let’s explore these common filtration methods and their approaches to tackling algae contamination:

Mechanical Filtration

The majority of water filter pitchers, bottles, and faucet filters utilize mechanical filtration to extract larger particles, including algae. These filters typically consist of a porous material that physically captures impurities as water flows through them.

While this method can be effective in removing larger algae particles, it might not be as efficient against smaller or microscopic forms of algae.

Reverse Osmosis

Reverse osmosis (RO) systems use a semipermeable membrane to remove a wide range of impurities, including algae. 

The membrane’s minute pores obstruct contaminants, permitting only water molecules to pass through. RO systems can effectively remove over 99% of algae and other particles from water.


Activated carbon serves as a favored filtering element in various water filters. Although primarily designed to remove chemical impurities, activated carbon is highly effective at eliminating up to 99% of the toxins produced by harmful algae.

At times, activated carbon can also reduce the nutrients, such as phosphate, required by algae to survive, thus preventing further algal growth in your water.


Ultrafiltration is another advanced method of water filtration that can remove up to 99% of algae from water. This is achieved by directing water through a fibrous membrane containing microscopic pores, allowing only water to pass through.


Distillation involves heating water to create steam, which is then condensed back into liquid form. This process effectively separates water from most types of contaminants, including algae.

While not practical for purifying water for an entire house, distillers provide economical options for purifying drinking water.

Effectiveness of Different Water Filters in Removing Algae

Now, let’s assess various filters that utilize one or more of these methods:

1. Water Filter Pitchers and Bottles

Water filter pitchers and bottles typically employ a combination of activated carbon and mechanical filtration. While effective at improving taste and removing some contaminants, their capability to remove algae can vary.

They excel at removing larger algae particles and sediment but may not be as efficient at capturing smaller or microscopic algae. For areas with significant algae concerns, consider more advanced filtration methods.

2. Reverse Osmosis (RO)

RO systems rank among the most effective methods for eliminating algae from water. The semipermeable membrane’s microscopic pores can block even the tiniest particles, ensuring >99.9% removal of algae.

RO systems also eliminate potential toxins produced by algae, rendering the water safe for consumption.

3. Undersink Filters

Undersink filters often use a combination of filtration technologies, including activated carbon, mechanical filtration, and sometimes even additional stages like RO. 

Their effectiveness varies among different models and brands, but in general, they are reliable in removing algae and enhancing overall water taste and clarity, especially if they incorporate RO elements.

4. Faucet Filters

Faucet filters are similar to water filter pitchers but are installed directly onto the faucet. 

A vast majority of faucet filters use mechanical and activated carbon filtration to remove impurities.

While they can improve water taste and clarity by removing some larger algae particles, their efficiency in removing algae might be limited compared to more advanced methods.

5. Shower Filters

Shower filters are primarily designed to remove chlorine and other chemicals from shower water to protect the skin and respiratory system. They are not intended for producing drinkable water and are often ill-equipped to handle algae-contaminated water.

While some shower filters may include basic filtration components for reducing sediment and particles, their primary purpose is not algae removal. They may offer some assistance, particularly with larger algae particles, but are not suitable for dedicated drinking water filtration.

Potential Risks Of Drinking Water With Algae

Most algae that we are likely to encounter are not inherently harmful. However, water with an excess of algae can have several drawbacks. Some of them are as follows:

  1. The most noticeable is the alteration of taste and odor, making the water less pleasant to drink. 
  2. The water appears green or cloudy, making it look unappetising.
  3. Presence of algae suggests that the water you are drinking has been exposed to the environment. This means the water could possibly contain other contaminants, like harmful bacteria. 
  4. Additionally, some forms of algae (usually marine forms) can release toxins into the water, which could lead to adverse health effects if consumed in large quantities. These toxins are known as algal toxins, and can cause gastrointestinal issues, skin irritation, and other health concerns including neuro-behavioral abnormalities

Therefore, it is essential to address any concerns related to algae in your water supply.

Detecting Algae In Water

We will not go into great detail of how you can detect algae in your water in this post, but the following general methods are helpful:

  1. The first method is visual inspection. If your water has a noticeable green color, taste, or odor issue, there’s a chance that algae could be the culprit. 
  2. Consider the source of the water. If you are drawing water from a natural source like a well or a pond, the risk of algae contamination is higher. 
  3. If you suspect algae in your water, there are at-home testing kits available. These usually show if there are any toxins from blue-green algae, or cyanobacteria. 
  4. Finally, the most reliable method is to contact your local water authority, who can observe the water under a microscope and run more sophisticated tests to ensure the exact type, concentration and health effects of the algae in your water.  

A Note On Harmful Algal Blooms

Sometimes, when they receive just the right conditions, algae may grow or ‘bloom’ in an uncontrolled fashion, known as ‘Harmful Algal Bloom’, or HAB. 

This can be harmful because of the various toxins they may produce, or because of the fact that they consume most of the oxygen in water, leaving little for other aquatic plants and animals to survive. 

Because of potential health risks, people are advised not to drink water in an area with HAB, and even freshwater fish or shellfish obtained from that region is to be strictly avoided. 

You can read more on HABs on this page from the National Oceanic and Atmospheric Administration. 

Theresa Orr

Theresa Orr is an Earth Scientist who specializes in determining past climates from rocks using geochemistry. Her passion for clean water drives her to breakdown the science to provide easy to understand information that everyone can read.

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