Water Purification Meaning, Facts, Steps, and Importance Explained

Water purification is any process which involves the reduction or removal of unwanted and potentially harmful materials from water.

As part of issues involved in achieving sustainable development, water purification is a very important topic in the world today. This article discusses water purification from the following perspectives;

-What is Water Purification?

-Facts about Water Purification

-Reasons for Water Purification

-Factors that Affect Water Quality

-Steps in Water Purification







What is Water Purification?

Water purification refers to the process by which unwanted and harmful materials are removed from water.


purified water distribution
Purified Water Distribution (Credit:  Courtesy of Armed Forces of the Philippines 2013).


These unwanted and harmful materials may include solid, liquid and gaseous substances that occur in the water, and which affect its quality [2]. The unwanted materials may be referred to as contaminants or pollutants, depending on how they affect the composition of the water. Contaminants mainly alter the natural composition, without necessarily rendering the water harmful, while pollutants render the water harmful for various (especially domestic) purposes.

Another way we can define water purification, is a process by which water is made suitable for specific uses [9]  Most often, water purification is carried out to make the water potable (suitable for human consumption). Other reasons for water purification include chemical, pharmacological, industrial and medical uses [4].


Facts about Water Purification

1). Water purification systems are capable of removing between 90-95 percent of contaminants in water

2). In addition to removing unwanted materials, filtration method of water purification helps to improve the taste and odor of water

3). The technologies used in water purification are mainly three, including distillation, de-ionization, reverse osmosis

4). The process of producing bottled water releases large quantities of carbon dioxide into the atmosphere, thereby contributing to global warming and climate change.

5). Recycling of plastics used for packaging and sale of water, is at a generally low rate, and this has negative effects on the environment

6). Water filtration is a cost-saving method which produces water with better quality in general, than most bottled water products.

This implies that it is safer and more economical to use a water filtration system at home than tp purchase bottled water. Various water filtration systems are available, varying in the specifications, to meet the existing need.

As we have stated earlier, properly-filtered water has a better taste; and no odor, making it suitable for consumption.

7). The use of disinfectants like chlorine for water purification, can have negative effects on the taste and odor of water. To prevent these effects, such chemicals should be used moderately

8). Water purification helps to preserve human health. This is mainly by removing harmful and unwanted substances and additives like arsenic, lead, iron, and chlorine

9). Various water filtration products exist, and they can be categorized into; ion-exchange filters, reverse-osmosis filters, and mechanical filters [1].

10). More than 80 percent of wastewater on Earth is released into the environment without proper treatment

11). Ultraviolet radiation can destroy contaminants in water, through a process called ultraviolet germinal irradiation [7]

12). The number of deaths caused by consumption of unsafe water around the world, is greater than the number of deaths caused by all forms of violent conflict [11]

13). A constant supply of clean water is essential to maintain human health

14). Many contaminants in water cannot be detected by physical inspection

15). For water contaminated by arsenic and uranium, filtration and purification can be done using a filter bed composed of crushed animal bones

16). Boiling can be a very effective method for removing biological contaminants and microorganisms in water. However, it is not effective for removing chemical contaminants

17). In all parts of the United States, metallic contaminants like arsenic, copper and lead occur in tap water

18). The World Health Organization (WHO) estimates that more than 94% of diarrhea cases within the human population, can be prevented

19). Municipal water treatment was introduced in the Nineteenth Century by a number of countries as part of measures to enforce the human right to safe water [10]. One of the first countries to implement this measure was Scotland

20). Water purification technology was greatly advanced by the advent of microscopic studies, after the invention of the microscope, which made it possible to observe some insoluble contaminants in water

21). Chromium, arsenic and other common chemical contaminants in tap water, can cause hormonal imbalance in the body

22). Water is highly vulnerable to contamination, because it is the liquid with the highest capability of dissolving foreign substances


Reasons for Water Purification

Water purification is usually carried out for one or more of the following reasons;

1). To make the water potable and suitable for domestic use

2). To alter the chemical composition of the water for industrial purposes

3). To make the water safe for medical use

4). To get distilled water for both consumption and chemical processes

5). To make it possible for the water to be discharged into the environment (may be into larger water bodies like rivers and the ocean)

6). To remove specific contaminants that have been identified

7). To meet the requirements of a particular water quality standard

8). To eliminate taste and/or odor in water

9). As part of general environment remediation

10). To prevent water-related illnesses within the human population

11). To save costs that may be incurred when resolving problems caused by polluted or contaminated water


Factors that Affect Water Quality

As we have already stated, water purification is carried out for the ultimate purpose of improving the quality of water. If this is so, it implies that the quality of water can be affected, and degraded or reduced.

Before proceeding with our discussion of water purification, it is necessary to identify some of the factors that can affect water quality, some of which are listed below;

1). Acidity or pH

2). Runoff

3). Sedimentation

4). Dissolved solids

5). Dissolved oxygen

6). Temperature

7). Pesticides

8). Erosion

9). Decayed biological materials

10). Inorganic waste materials

11). Unwanted chemical substances

Some of these factors, such as chemical substances, dissolved solids, pH, dissolved oxygen, and temperature, are used to evaluate the quality of water. These factors may also be referred to as criteria or parameters for water quality assessment [8].

Steps in Water Purification

Various methods exist by which these pollutants and contaminants can be removed from water. Some of these methods may also be arranged in a definite order, to form the basic steps involved in water purification. They include;

1). Flocculation, Ion Exchange, and Coagulation

Flocculation, ion exchange and coagulation, constitutes the first step in the process of water purification.

The purpose of using these methods, is to remove chemical substances in the water that cause hardness, as well as other unwanted elements like heavy metals [3].

Flocculation and coagulation involve adding a chemic substance which has a net positive charge, to the water. An example of such a substance is Alum. When added to water, the minerals that cause hardness are caused to precipitate, alongside some other unwanted elements. The precipitated substances are often called flocs, which ultimately settle at the bottom of the water column, from whence they can be removed.

2). Sedimentation

The process of sedimentation in water purification. simply involves the settling of flocs at the bottom of the water column [6].

Flocs are caused to move to the bottom of the water column, and settle, mainly due to their own weight. In most water purification equipment, sediment filters occur, which help to trap the particles as they settle.

3). Filtration as a Step/Method of Water Purification

After the floc has settled by the process of sedimentation, a series of filters are used to remove residual, dissolved particles from the water. These particles may include biological matter and dust.

The filters usually have different compositions and pore sizes. They often consist of gravel, charcoal, or sand, among other materials.  


water filtration
Water Filtration Showing Various Filter Layers


Filtration is carried out for the primary reason of removing any particles in the water that have not been eliminated by coagulation, flocculation and sedimentation.

In filtration, the various filter beds (gravel, sand. charcoal) are usually arranged in a sequence of layers. Activated carbon (charcoal) helps to remove chemic pollutants while the other layers mainly eliminate physical pollutants.

4). Disinfection

Disinfection is yet another important step in water purification, which helps mainly with eliminating biological pollutants like viruses and bacteria [5].

Through disinfection, the diseases caused by these microorganisms can be prevented, thereby protecting the consumers of the water.

In order to carry out disinfection, a disinfectant like chlorine is often added to the water. Other disinfectants include ultraviolet radiation. and chloramine.

5). Distillation as a Step/Method of Water Purification

Distillation is a step in water purification, which involves boiling water and collecting the steam in a separate vessel [12]. It is a very efficient and relatively cheap method of water purification, that eliminates both dissolved and undissolved; solid and liquid; physical, chemical and biological pollutants.


water distillation
Water Distillation

6). pH Adjustment

Water purification usually includes a step in which the pH of the water is adjusted.

The reason for carrying out this step is because, water with high pH may affect the pipes used to channel their flow. This is because alkaline water (high pH) can cause deterioration or corrosion of (especially metal) pipelines. In other cases, alkaline water causes scales to form in pipelines, and thereby reduces their efficiency and capability to allow the passage of water through them.

pH adjustment helps to prevent some human illnesses. In the absence of pH water treatment, metal poisoning of water is likely to occur. This involves the introduction of large concentrations of lead, copper and any other metallic element, into the water.

The symptoms of metal poisoning include;

-Muscle and joint pain

-High blood pressure

-Abdominal pain




7). Reverse Osmosis as a Step/Method of Water Purification

Reverse Osmosis is often the last step in the process of water purification.

It involves the use of a semi-permeable membrane to remove impurities that may be present in water after the main purification process has been completed. The semi-permeable membrane mainly helps to eliminate dissolved contaminants in the water.

8). Odor and Taste Control

One of the common problems of impure water is the presence of an unpleasant taste and/or odor. Such characteristics may often remain even after the entire process of water purification.

In many cases, odor and taste do not pose any potential health problems. However. because they make the water generally unpleasant for use, additional steps are often taken to eliminate these characteristics.

The removal of unpleasant odor and taste from water is usually done by adding chemicals to the water (chemical treatment). In the final stages of water purification. fluoride may also be added to the water, to prevent tooth decay for its consumers.



This article has highlighted some important issues with respect to the meaning, and methods of water purification.

Among the reasons for water purification, we have discussed its importance toward preserving and protecting human health. Asides this, water purification makes the water suitable for specific processes, and standards.

The typical steps involved in water purification, which we have also discussed, include;

1). Flocculation, Ion Exchange, and Coagulation

2). Sedimentation

3). Filtration

4). Disinfection

5). Distillation

6). pH Adjustment

7). Reverse Osmosis

8). Odor and Taste Control



1). Bourland, L. (2021). “Choosing the Best Water Filter for Your Home.” Available at: https://www.buildwithrise.com/stories/choosing-a-water-filtration-system-for-your-home. (Accessed 19 December 2021).

2). Chaudhry FN, Malik MF (2017) Factors Affecting Water Pollution: A Review. J Ecosyst Ecography 7: 225. doi: 10.4172/2157-7625.1000225. Available at: https://www.omicsonline.org/open-access/factors-affecting-water-pollution-a-review-2157-7625-1000225.php?aid=87940. (Accessed 18 December 2021).

3). Dongre, R. S. (2020). “Lead: Toxicological Profile, Pollution Aspects and Remedial Solutions.” Available at: https://www.intechopen.com/chapters/72652. (Accessed 19 December 2021).

4). Ecologix (2018). “Water Purification.”Available at: https://www.ecologixsystems.com/library-water-purification/. (Accessed 18 December 2021).

5). Ishaq, S. M.; Khan, A. A.; Khan, A. (2018). “Disinfection Methods.” Available at: https://www.intechopen.com/chapters/63788. (Accessed 19 December 2021).

6). Lee U-J, Hyeong K-S, Cho H-Y. (2020). Estimation of Settling Velocity and Floc Distribution through Simple Particles Sedimentation Experiments. Journal of Marine Science and Engineering; 8(7):500. https://doi.org/10.3390/jmse8070500. Available at: https://www.mdpi.com/2077-1312/8/7/500/htm?__cf_chl_managed_tk__=DAd4yR8glAk0uzJNCgxlqbkefDC44ehM_uJOIjtPJ3M-1639885742-0-gaNycGzNCGU. (Accessed 19 December 2021).

7). Linden, K. (2008). “Ultraviolet Irradiation: An Age-Old Emerging Technology for Water Treatment” National Academy of Engineering. Frontiers of Engineering: Reports on Leading-Edge Engineering from the 2007 Symposium. Washington, DC: The National Academies Press. doi: 10.17226/12027. Available at: https://www.nap.edu/read/12027/chapter/23. (Accessed 19 December 2021).

8). Omer, N. H. (2019). “Water Quality Parameters.” Available at: https://www.intechopen.com/chapters/69568. (Accessed 19 December 2021).

9). Sciencedaily (2021). “Water purification.” Available at: https://www.sciencedaily.com/terms/water_purification.htm. (Accessed 18 December 2021).

10). Tulchinsky, T. H. (2018). “John Snow, Cholera, the Broad Street Pump; Waterborne Diseases Then and Now.” Available at: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7150208/. (Accessed 19 December 2021).

11). United Nations (2010). “Unsafe water kills more people than war, Ban says on World Day.” Available at: https://news.un.org/en/story/2010/03/333182-unsafe-water-kills-more-people-war-ban-says-world-day. (Accessed 19 December 2021).

12). Woodard, J. (2019). “What is a Water Distiller and How Does It Work?” Available at: https://www.freshwatersystems.com/blogs/blog/what-is-a-water-distiller-and-how-does-it-work. (Accessed 19 December 2021).

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