Water Purification Plants: Definition, Function & Their Importance In Industries


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Water purification plants are essential facilities that ensure clean and safe drinking water for communities. These plants use various methods and technologies to remove impurities and contaminants from water sources, such as rivers, lakes, or groundwater. The process typically involves several stages, including coagulation, sedimentation, filtration, and disinfection.

In today’s fast-paced and modern world, it’s easy to take clean and safe water for granted. However, with pollution and contaminants on the rise the need for water purification has become increasingly crucial. Water purification is the process of removing impurities and harmful substances from water, ensuring its safety for consumption and other purposes.

From bacteria and viruses to heavy metals and chemicals, untreated water can pose serious threats to our well-being. By investing in water purification systems, we not only protect ourselves and our families but also contribute to the overall well-being of our communities. Purified water also offers a multitude of benefits beyond drinking, such as improved taste, odor, and appearance, making it a desirable choice for various household and industrial applications. 

What Are Water Purification Plants?

Water purification plants (often called water filtration plants) are essential facilities that ensure the supply of clean and safe drinking water (municipal water) to communities. 

For example, the Britannia Water Purification Plant in the City of Ottawa is one of two treatment plants that supplies drinking water to approximately 1,000,000 people living in that area that meets the US drinking water standards.

The primary goal of water purification plants is to provide clean water that meets the standards and regulations set by health authorities. These plants are equipped with advanced technologies and monitoring systems to ensure that every drop of water that leaves the plant is free from contaminants and safe for consumption.

What Type Of Water Goes Through A Water Purification Plant?

The most common type of water filtered is groundwater. Groundwater comes from infiltration from water, runoffs from the Earth’s surface, and water extracted from wells. Groundwater is typically filtered through layers of soil and rocks, however, it requires further filtering before it can be used by humans. 

Water also comes from surface water such as lakes, rivers, and reservoirs. Surface water must be filtered to remove bacteria, algae, and harmful contaminants that degrade the water quality

How Does A Water Purification Plant Work?

Water purification plants use a combination of physical, chemical, and biological processes to purify water:

  • Coagulation
  • Flocculation
  • Sedimentation
  • Filtration
  • Disinfection
  • Carbon Adsorption/Oxidation
  • Fluoridation

Coagulation & Flocculation

The first step in the purification process is typically coagulation and flocculation. In this stage, chemicals are added to the raw water to bind the suspended particles and impurities, allowing them to form larger clumps called flocs. These flocs then settle down at the bottom of the water.


During sedimentation, the water is left undisturbed for a certain period, allowing the flocs to settle at the bottom of the tanks. This sedimentation process helps in separating the solid impurities from the water.


Filtration is a critical step in water purification as it removes harmful bacteria, viruses, and other pathogens that can cause diseases. The water passes through different types of filters made of layers of sand, gravel, charcoal, or membrane filters. 

Rapid & Slow Sand Filters

Rapid sand filters are designed to provide a quick and efficient filtration process. They work by passing water through a bed of coarse sand at a high flow rate. The sand acts as a physical barrier, trapping any solid particles and impurities present in the water. As the water flows through the filter, it undergoes a series of chemical and biological processes that further enhance its quality. 

Rapid sand filters are commonly used in large-scale water treatment plants and are capable of processing a high volume of water in a short amount of time.

On the other hand, slow sand filters offer a more natural and gradual purification process. The slow flow rate allows for more contact time between the water and the sand, promoting the growth of beneficial microorganisms that help eliminate harmful bacteria and pathogens. Slow sand filters are often used in smaller-scale water treatment systems, such as individual households or small communities.

Both rapid and slow sand filters have their advantages and disadvantages. Rapid sand filters are efficient and can handle large amounts of water, but they require regular maintenance to prevent clogging. Slow sand filters, although slower in operation, are easier to maintain and provide better removal of bacteria and viruses. 

Gravel Filters

Gravel filters are made up of layers of different-sized gravel, and are incredibly effective at removing impurities from water. The concept is simple yet brilliant – as water passes through the gravel layers, the gravel acts as a physical barrier, trapping and filtering out any contaminants. This makes gravel filters an excellent choice for both residential and industrial use. Plus, they are relatively low-cost and easy to maintain. 

Carbon Filters

Carbon filters work by using activated carbon, which has a high surface area and a porous structure. As water passes through the carbon filter, the impurities and contaminants in the water are attracted to the carbon and are trapped in its pores. This process effectively removes chlorine, heavy metals, chemicals, and other harmful substances from the water. Carbon filters are not only efficient in purifying water, but they are also easy to use and maintain.

Membrane Filters

Membrane filters work by utilizing a semi-permeable barrier that allows water molecules to pass through while trapping larger particles, such as bacteria, viruses, and chemicals. This process ensures that the water is thoroughly cleansed, making it suitable for drinking, cooking, and other household uses. 


Next comes the disinfection stage. water purification plants also use disinfection methods to kill any remaining bacteria and viruses in the water. The most commonly used disinfectant is chlorine, which is added to the water in controlled amounts to ensure it is safe for consumption.

Carbon Adsorption/Oxidation

Water purification plants also take into consideration the removal of chemical contaminants from the water. This can involve additional treatment processes such as activated carbon adsorption or oxidation. These processes help remove chemicals like pesticides, heavy metals, and organic compounds that may be present in the raw water. In areas that have high agricultural use, this is usually necessary due to surface runoff of pesticides and herbicides. 


Before the purified water is distributed to households or industries, it undergoes a final step called fluoridation and is processed for quality assurance. Fluoride is added to the water in controlled amounts to help prevent tooth decay and improve dental health. Water samples are regularly collected and analyzed to ensure that it meets the required standards for drinking water. If any issues are detected, adjustments are made to the treatment processes to maintain water quality.

How Do Water Purification Plants Improve Drinking Water Supplies?

In addition to overall water quality such as removing contaminants, water purification plants also focus on removing any unpleasant taste or odor from the water. This is achieved through additional treatment processes like aeration or activated carbon adsorption. These processes help to remove any dissolved gases or organic compounds that may affect the taste or smell of the water.

Water Purification Plants & Wastewater

In addition to treating drinking water, water purification plants also play a vital role in treating wastewater. Wastewater is treated to remove harmful pollutants before it is discharged back into the environment. This helps to protect our rivers, lakes, and oceans from contamination and maintain a healthy ecosystem.

Alternative Purification Methods

Another popular method of water purification is distillation, which involves boiling water and then condensing the steam to remove impurities. This process effectively kills bacteria and removes heavy metals, resulting in clean and pure water.

Another purification method that is gaining popularity is reverse osmosis (RO). This process involves forcing water through a semipermeable membrane. The membrane only allows water molecules to pass through, trapping contaminants and purifying the water. Reverse osmosis is highly effective in removing dissolved salts, heavy metals, and other harmful substances from the water. RO systems are often used in households with high levels of mineral content in their water supply.

UV radiation is probably the newest water purification method that has gained popularity in recent years. This method uses ultraviolet light to kill bacteria and other microorganisms present in the water. UV radiation disrupts the DNA of these microorganisms, preventing them from reproducing and therefore, causing them to die off. UV purification is particularly effective against bacteria like E.coli and Salmonella, making it an excellent choice for disinfecting water where water sanitation is an issue.

One more method of water purification is chlorination. Chlorine is added to the water to kill bacteria and other harmful microorganisms. It is a widely used method of disinfection as it is effective in killing most pathogenic organisms present in the water. However, excessive chlorine can have adverse health effects, so it is crucial to ensure proper dosing and monitoring.

Measuring Water Quality At Water Purification Plants

At water purification plants, a range of instruments are used to measure and monitor the quality of the water being treated. 


A turbidimeter measures the clarity of the water by measuring the amount of suspended particles or solids (total dissolved solids: TDS) in it. By doing so, it can detect any abnormalities or impurities that may be present in the water. This is important because high levels of turbidity can indicate the presence of harmful bacteria or other contaminants that could pose a risk to public health.

Chlorine Analyzer

It is crucial to maintain the right balance of chlorine, as too much can be harmful to human health while too little may not effectively kill all the microorganisms. 

Chlorine analyzers accurately measure the concentration of chlorine in the water, allowing plant operators to adjust and maintain optimal levels for disinfection.

pH Meters

pH meters are also instrumental in water quality measurement at purification plants. pH is a measure of how acidic or alkaline a substance is, with a pH of 7 being neutral. In water treatment, maintaining the correct pH level is crucial for various reasons. Firstly, it affects the efficiency of disinfection processes, as certain microorganisms are more vulnerable to disinfection at specific pH levels. 

Secondly, pH can influence the taste and odor of water, so maintaining an optimal pH ensures that the treated water is palatable to consumers.

pH meters provide accurate readings of the water’s acidity or alkalinity, enabling operators to make necessary adjustments to ensure water quality meets regulatory standards.


Water purification plants are vital facilities that treat raw water to provide safe drinking water to communities and industries. Through a series of processes such as coagulation, filtration, disinfection, and chemical removal like chlorination, these plants remove contaminants and impurities from the water. They play a crucial role in maintaining public health by ensuring access to clean and safe drinking water.

If you have any questions regarding purification methods or what water quality measuring instruments we have, do not hesitate to contact the world-class team at Atlas Scientific

pH Probes & Sensors

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