What Is Purified Water? | The Chemistry Blog (2023)

As you might expect, purified water is exactly what it says – water that has been purified to varying degrees. It can be made via many different processes, and is used in a range of industries. From purified bottled water to water that is pure enough for laboratory applications, this article will discuss the science behind purified water.

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Purified Water: A Brief Overview

Purified water isn’t necessarily 100% pure. Regular tap water, for example, must undergo a process of purification in order for it to become drinkable. This is not just done naturally, like when water passes through springs or underground aquifers, but involves a series of mechanical filtrations and chemical treatments. These purify the water from harmful amounts of mineral residues, heavy metals, and soil particles. Purification also removes pathogens, such as bacteria, viruses, fungi, amoeba, microscopic worms, and even parasitic eggs from water.

Municipal water undergoes several steps of purification before it becomes potable and is distributed to the public. Here are the four steps:

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  • Step 1 – Coagulation and flocculation: At this stage, negatively charged particles in water are filtered out by adding in positively charged chemicals. The particles then coagulate into larger particles called floc.
  • Step 2 – Sedimentation: The larger and heavier particles that clumped into flocs settle to the bottom of the water supply treatment facility. They’re then easily separated from the water.
  • Step 3 – Filtration: The water then passes through several filtration systems that consist of sand, charcoal, and gravel. This process removes microscopic contaminants, such as bacteria and chemicals.
  • Step 4 – Disinfection: Chemical disinfectants like chlorine are added to the purified water in order to kill any pathogens in it.
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Different Grades Of Water

Water can be purified to either completely, or partially, remove organic and inorganic impurities. This makes it suitable for a wide variety of uses, depending on which purification method is used. To gauge the level of purity, water is classified into grades.

For laboratory applications, the International Organisation for Standardisation (ISO) has specified three grades of water: Grade 1, which is the purest, Grade 2, and Grade 3, which is the least pure. Each of these grades of water has its own specifications, according to ISO 3696:1987:

  • Grade 1: Otherwise known as ultrapure water, this is the purest grade of water. As such, it’s used in very sensitive laboratory procedures, such as culturing mammalian cells.
  • Grade 2: Commonly known as purified water, this is used in general laboratory applications, such as preparing buffers, where the purity level is important, but not crucial.
  • Grade 3: Also called primary grade water, this is used in procedures that are considered to be non-critical, like rinsing laboratory glass equipment or feeding autoclaves.

What Methods Are Used To Purify Water?

There are many methods that are used to purify water. The most common method is simply boiling it, which kills bacteria and viruses. While this method is effective for purifying ordinary drinking water, it’s nowhere near effective enough to be used in laboratory or medical applications.

When higher purity water is needed, distillation tends to be the go-to method of purification. Distillation has been used since ancient times to purify the alcohol content in fermented alcoholic liquids, transforming it into spirits. Nowadays, distilled water is the most common form of purified water on an industrial scale. The process basically involves boiling water in one container and allowing it to precipitate and condense in another.

Aside from distillation, the other methods of purifying water include:

  • Deionisation
  • Reverse osmosis
  • Carbon filtering
  • Microfiltration
  • Ultrafiltration
  • Ultraviolet oxidation
  • Electrode ionisation

Commercially available purified water is processed using combinations of two or more of these purification methods. As a result, it’s now possible to have water that has barely any contaminants in it – they can be so low, in fact, that they can’t be measured in parts per billion, or even parts per trillion.

Reagent grade or laboratory grade purified water has several applications. In terms of large-scale applications, highly purified water is mainly used in the production of medicines. Meanwhile, the industrial production of lower-grade purified water is largely used in the beverage industry.

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What Is Purified Water? | The Chemistry Blog (2)

What Is The Process Of Purifying Water Called?

The process of purifying water goes by many names, some which we’ve just mentioned, like distillation, deionisation, and ultrafiltration. What the purification process is called depends on what method is being used.

Although there are various processes and steps involved in purifying water, the main mechanisms function in the same way: they remove impurities from the water. The various steps involved in water purification can be classified into four categories:

  • Physical processes: These include filtration in various stages, sedimentation, and water distillation. One, or a combination of various processes, are used here.
  • Biological processes: These involve the removal of organic and biological contaminants in water. Sand filters and biologically active carbon are also used in the process.
  • Chemical processes: Some examples of chemical processes are chlorination and flocculation, wherein chemicals are applied to remove or kill contaminants.
  • Radiation exposure processes: During these types of processes, water is irradiated to kill pathogens like bacteria and viruses. The most common method used is ultraviolet light exposure.

What’s The Difference Between Purified And Filtered Water?

Generally speaking, filtered water is one type of purified water. However, its purity depends on the level of filtration that has been used and how many contaminants have been filtered out. Remember, it doesn’t count as purified water if the level of contaminants are not within the standard range.

The main difference is that filtration is typically used to remove solid particles, while purification is used to eliminate all forms of contaminants. For example, muddy water can be filtered in various ways, such as through reverse osmosis and sand-carbon filtration. But if some sediment or other particles still remain, it’s not yet purified. Water has to undergo various stages of filtration and purification before it’s considered pure.

What Is The pH Of Purified Drinking Water?

The pH level of purified water depends on its type and the processes it’s undergone. Here’s a list of the various types of purified water and their corresponding pH levels:

  • Tap water has an average pH of 7.5
  • Common bottled water has a pH of between 6.5 to 7.5
  • Bottled water marketed as alkaline water has a pH between 8 and 9
  • Water from distilled reverse osmosis has a pH of between 5 and 7

It’s a misconception that water that has been properly purified, either through distillation or deionisation, has a neutral pH of exactly 7. While these purification methods do remove most pH swayers, like ions, minerals and other contaminants, the water they yield will have a slightly acidic pH. This is because it absorbs carbon dioxide from the atmosphere, which brings its pH down to a comfy 5.8 or 5.5.

What Is Purified Water? | The Chemistry Blog (3)

Social Impact Of Water Purification

Water purity is a serious issue that is directly related to health and environmental sustainability. Contaminated water is very dangerous because it carries pathogens, such as the bacterium species that causes cholera. Other diseases contaminated water results in include:

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  • Dysentery
  • Typhoid fever
  • Schistosomiasis
  • Polio (infantile paralysis)

Globally, it’s estimated that around 780 million people don’t have access to clean drinking water. Many natural sources of freshwater, such as rivers, ponds, and lakes, are unfortunately not suitable for drinking due to pollution. Even water that comes from springs and aquifers can be contaminated by pathogens and toxic substances that need to be filtered out.

Many communities simply do not have the resources to process contaminated water into drinking water, and commercially available bottled water products are sometimes too expensive for many people living in impoverished counties. However, the process of purifying water can be made more affordable for communities and households that need it the most. For instance, the water filter straw could potentially have a significant impact on the lives of millions of people in third world countries.


The blog on chemicals.co.uk and everything published on it is provided as an information resource only. The blog, its authors and affiliates accept no responsibility for any accident, injury or damage caused in part or directly from following the information provided on this website.We do not recommend using any chemical without first consulting the Material Safety Data Sheet which can be obtained from the manufacturer and following the safety advice and precautions on the product label.If you are in any doubt about health and safety issues please consult the Health & Safety Executive (HSE).

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What is purified water in chemistry? ›

Purified water is water that has been filtered or processed to remove impurities like chemicals and other contaminants. It is usually produced using groundwater or tap water. Through purification, many types of impurities are removed, including ( 1 ): Bacteria. Algae.

How is water purified explain? ›

There are several methods used in the water purification process, which include: (1) physical processes, such as filtration, sedimentation, or distillation; (2) biological processes, such as sand filters, active carbon; (3) chemical processes, such as flocculation, chlorination, the use of ultraviolet light.

What is purified water called? ›

Purified water, according to the U.S. Food and Drug Administration, is "produced by distillation, deionization, reverse osmosis or other suitable processes" and also may be called "demineralized water, deionized water, distilled water or reverse osmosis water."

What is purified water in pharmaceutical industry? ›

What Is Purified Water? Purified Water is a grade of pharmaceutical water used as an excipient in the production of non-parenteral preparation for pharmacology including tests and analyses.

Why is purified water important? ›

Water purification can not only help remove harmful containment but also improve the taste, smell and visual appearance of your drinking water. It reduces the amount of chlorine, soil residue, and organic and inorganic substances.

How do you purify water chemistry? ›

Purifying water
  1. Sedimentation – the water is stored in a large tank or a reservoir. ...
  2. Filtration – the water is sprayed onto specially-prepared layers of sand and gravel. ...
  3. Chlorination – chlorine gas is injected into the water to sterilise it.

What is used to purify water? ›

Chlorine and chloramine are the major disinfectants used in public water systems.

What are the characteristics of purified water? ›

It contains no chloride, calcium, or sulfate, and is essentially free of ammonia, carbon dioxide, heavy metals, and oxidizable substances. Total solids content will be no more than 10 ppm, pH will be 5–7, and the water will contain no coliforms.

How can we purify water short answer? ›

Here are some of the most effective water purification methods that have stood the test of time:
  1. Boiling. The simplest method to purify water is to boil it for a good time. ...
  2. Water Purifier. ...
  3. Reverse Osmosis. ...
  4. Water Chlorination. ...
  5. Distillation. ...
  6. Iodine Addition. ...
  7. Solar Purification. ...
  8. Clay Vessel Filtration.

What is the most purified water? ›

Icelandic Water, marketed as the purest tasting water on Earth, possesses a pH of 8.14, which is significantly higher than tap water and its bottled water competitors.

Is purified water pure water? ›

As its name suggests, purified water is some of the purest water you can drink because purified water is a designation that refers to the actual quality of the water. Water can become purified through many different processes, each leaving the resulting drink with varying levels of minerals and flavors.

What is the FDA definition of purified water? ›

Purified Water – Water that has been produced by distillation, deionization, reverse osmosis, or other suitable processes and that meets the definition of “purified water” in the United States Pharmacopeia.

What is the difference between water and purified water? ›

Put simply, purified water is water that's been mechanically filtered or processed to remove chemicals and impurities, according to Carpenter. The purification process removes contaminants including bacteria, chemicals, and toxins from tap water or ground water.

How safe is purified water? ›

Purified water is perfectly safe for consumption, as it contains no harmful chemicals, pathogens, and contaminants that could otherwise pose a health risk to you or your household members.

What is the conclusion of water purification? ›

Water purification can remove all the unnecessary bacteria and viruses from the water that is hazardous for our health. Water purification may also improve the flavor and appearance of water. It removes the unpleasant odor.

How is purified water purified? ›

Purified water usually comes from groundwater or tap water. It's treated in a water processing plant to remove impurities and contaminants. You can also purchase in-home filters to purify your tap water.

What are the effects of purified water? ›

Put simply, purified drinking water provides a better way for people to stay hydrated. Among its many benefits, it aids in digestion, boosts athletic performance, detoxifies the body, and promotes clearer skin.

What pH is purified water? ›

Pure water has a pH of 7 and is considered “neutral” because it has neither acidic nor basic qualities.

How does water purify naturally? ›

In nature, water is filtered through layers of soil, sand, rock, and other natural materials like leaves. Surfaces where water can penetrate are called permeable surfaces. Impervious surfaces, like rooftops and paved roadways, are surfaces where water cannot penetrate.

How many ways are there to purify water? ›

The methods used include physical processes such as filtration, sedimentation, and distillation; biological processes such as slow sand filters or biologically active carbon; chemical processes such as flocculation and chlorination; and the use of electromagnetic radiation such as ultraviolet light.

How do you purify drinking water? ›

Make Your Water Safe by:
  1. Boiling. If water is cloudy, allow to settle, then skim the clean water above the sediment. ...
  2. Disinfect by using: Unscented household chlorine bleach or iodine (useful against most, but not all, harmful viruses or bacteria. ...
  3. Filtering.

What is the safest purified water to drink? ›

Best Overall: Essentia Ionized Water

It's safe, clean, tastes great, and has all the right certificates. It's a supercharged and ionized alkaline water that's filtered through a proprietary process that purifies Essentia's water, making it 99.9% pure.

What is the world's healthiest water? ›

What Is The Healthiest Water To Drink? When sourced and stored safely, spring water is typically the healthiest option. When spring water is tested, and minimally processed, it offers the rich mineral profile that our bodies desperately crave.

What is the healthiest way to purify water? ›

Purifying by boiling

If your tap water is unsafe, boiling is the best method to kill disease-causing organisms.

What is the most common way to purify water? ›

Three Ways To Purify Water
  1. Boiling. Bring the water to a rolling boil for 3-5 minutes. Let cool before drinking.
  2. Disinfect. You can use household liquid bleach (regular household bleach contains 5.25% sodium hypochlorite) to kill microorganisms. ...
  3. Distillation. Fill a pot halfway with water.

Can you drink 100% purified water? ›

Essentially, if you only drink ultra pure water, you would lose many important electrolytes. Pure water acts as sponge and soaks up what's around it, meaning that if you drank nothing but ultra pure water, the water would drink you back.

Is purified water just filtered water? ›

While these two get confused often, as we have seen, they are not the same. While both types are treated with filtration, purified water goes through an additional purification process. The result is pure water that has a higher purity rating than the filtered water.

Is boiled water the same as purified water? ›

Comparing boiled and filtered water

When looking at boiled vs filtered water, we found that boiling water isn't enough to completely purify water because it leaves harmful contaminants such as lead and chlorine.

Is purified water better than drinking water? ›

If you're talking about the purity of the water and you're talking about what you personally drink, then yes, purified water is BETTER than tap water. If you're talking about eliminating as many contaminants as you can from the water you drink, then, yes, purified water is BETTER than tap water.

What is purified water vs distilled water? ›

Purified water has had chemicals and contaminants removed but may contain minerals. Distilled water takes it one step further, with both contaminants and minerals removed.

What is the difference between distilled water and purified water? ›

Distilled water is a type of purified water that has had both contaminants and minerals removed. Purified water has had chemicals and contaminants removed, but it may still contain minerals.

What's the difference between purified and regular water? ›

Put simply, purified water is water that's been mechanically filtered or processed to remove chemicals and impurities, according to Carpenter. The purification process removes contaminants including bacteria, chemicals, and toxins from tap water or ground water.

What is the difference between purified or distilled water? ›

Both purified and distilled water are very healthy for you and are essentially the same. The main difference between the two is that purified water doesn't necessarily get rid of all of the healthy minerals that can be found in water, which isn't the case with distilled water.

What is the purest water to drink? ›

Distilled water is the PUREST drinking water possible.

Distilled water is the PUREST form of water. Many people are under the false impression that their tap water, and even bottled water and water produced by home filtration systems is "pure".

Why can't you drink distilled water? ›

Drinking distilled water creates health problems from the lack of essential nutrients and causes dehydration. Drinking distilled water is never a bad idea because the body cannot absorb dissolved minerals from water into the tissue.

What is the healthiest water to drink? ›

Conclusion. Mineral and pure spring water are some of the healthiest water you can drink because they're clean and contain all the essential minerals your body needs. There are still benefits of filtered water, even though they have no minerals.

What is purified water made of? ›

Purified water is water that has been mechanically filtered or processed to remove impurities like bacteria, viruses, chemical pollutants, and minerals like lead and copper (6). In most developed countries, including the United States and Canada, tap water is purified to ensure it's safe for consumption.

Is purified water safe to drink? ›

Purified water is perfectly safe for consumption, as it contains no harmful chemicals, pathogens, and contaminants that could otherwise pose a health risk to you or your household members.

Does purified water take minerals from your body? ›

Pure water removes the inorganic mineral deposits in your body. Organic minerals, on the other hand, are fully absorbed and remain in your tissues. According to many nutritionists minerals are much easier to assimilate when they come from foods.

Is purified water the healthiest? ›

Put simply, purified drinking water provides a better way for people to stay hydrated. Among its many benefits, it aids in digestion, boosts athletic performance, detoxifies the body, and promotes clearer skin.

Is purified water safer than tap water? ›

If you're talking about the purity of the water and you're talking about what you personally drink, then yes, purified water is BETTER than tap water. If you're talking about eliminating as many contaminants as you can from the water you drink, then, yes, purified water is BETTER than tap water.

Is boiled water distilled water? ›

No, they aren't the same. Boiled water is simply water that has had the temperature increased until it reaches its boiling point. This kills a host of bacteria that can make a person sick. Distilled water is water that has been stripped of all impurities, including minerals and microorganisms.

Is bottled water purified? ›

Truthfully, all drinking water is filtered. This includes all bottled water as well as tap water of any sort. Water—in order for it to be deemed appropriate for consumption—is filtered to some degree. For this reason, most bottled waters will say “filtered” on them.


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