Have you ever wondered how clean water gets to your taps? Water treatment plants use the process of coagulation to clean water and make it safe for consumption and use. What is coagulation exactly? Take a look:
Coagulation Definition: Water treatment plants add chemicals to wastewater to cause clumps of suspended solids to bind together and sink to the bottom of the treatment chamber. This process is called coagulation.
The coagulation process will remove certain contaminants from the water in conjunction with sedimentation, disinfection, and filtration processes.
High-quality water is essential for economic, social, and health development. However, as the world’s population keeps growing, clean water supply is continually becoming a challenge.
To curb this problem, processes like water coagulation are implemented. However, UN-Water’s research shows that 50% of household water is not treated safely.
In this blog, we will look at what coagulation is (a water treatment method), its importance, and the contaminants eliminated during the process.
The Importance of Water Treatment
Shortages in drinking water brought about water treatment. Research shows that about 0.4% of the 2.5% of freshwater is unsafe for drinking. Therefore, water is treated mainly to eliminate contaminants so that the water is fit for drinking.
Water treatment entails different operations — among them is coagulation. They can either be physiochemical, chemical, or physical.
What Is a Coagulant?
A coagulant is defined as an organic or inorganic chemical that initiates the congealing process during water treatment. Coagulants are used during the coagulation process, and they aid in cleaning the water and removing contaminants. Examples of coagulants used in water treatment include iron and aluminum salts like ferric chloride, aluminum sulfate, and ferric sulfate.
These chemicals aid in the removal of suspended solids from drinking water. They neutralize the water as they are made of positively charged molecules, and the suspended particles are negatively charged.
Before we discuss how the coagulation process works, let’s explore the different types of coagulants and the forms in which they are used.
Organic and Inorganic Coagulants in Water Treatment
To understand what coagulation is and how it works, you need to know there are two types of coagulants: organic and inorganic. Here’s a brief description of each so you can understand their pros and cons:
Organic Coagulants
These include polyamines, polytannate, and poly DADMAC. They do not contain metal or hydroxide, and they can remove organic matter, making the disinfection process safer as fewer harmful byproducts are produced during this stage of water treatment. Finally, they do not affect the water’s pH levels.
While they come with many benefits, it’s important to note that organic coagulants are more expensive per unit, produce low-density floc (clumps of suspended solids) and must be used in higher dosages.
Inorganic Coagulants
These include forms of aluminum and iron coagulants. Like organic coagulants in water, these chemicals can remove organic particles, improving the disinfection process. They also enhance the formation of micro-flocs and are extremely affordable and readily available.
Before adding an inorganic coagulant to water, water treatment plants must recognize that the floc produced will have a high metal content and will need to be disposed of carefully. Additionally, inorganic coagulants affect water’s pH, requiring the use of pH control in addition to the coagulant.
Here Are 4 Common Types of Coagulants Used in Water Treatment
- Sodium Aluminate
- Ferric chloride
- Ferric sulfate
- Aluminum sulfate
Sodium Aluminate
This coagulant is a combination of aluminum oxide and sodium oxide. When it is in solid form, it contains 70-80% sodium illuminate, and in liquid form, it has 30% sodium aluminate.
Aluminum Sulfate
Aluminum sulfate can be used in a block, kibbled, or ground form during water treatment. When added to alkaline water containing calcium bicarbonate, it produces aluminum hydroxide floc.
Ferric Sulfate
If aluminum sulfate is not available, ferric sulfate is the best alternative. It is often used with chlorine, and it produces a denser floc than its counterpart, aluminum sulfate. However, the hydroxide sludge produced by ferric sulfate is heavier.
Ferric Chloride
This is a great alternative to ferric sulfate, but it is less popular because, when the water has more chlorine, the corrosivity also increases.
How Do You Choose a Coagulant for Water Treatment?
Water treatment facilities usually select a coagulant based on its availability and affordability. Aluminum sulfate is the most affordable and readily available among all the coagulants.
Metal, biopolymer, and synthetic coagulants are also used. Natural biopolymer coagulants made from animals, fungi, and other plant sources can produce less sludge and are non-toxic.
A Look at the Coagulation Process in Wastewater Treatment
To truly understand coagulation, you need to know how it is used during water treatment. Coagulation is usually done before filtration and sedimentation. The coagulant is added to the water and evenly distributed to enhance water treatment.
Like the name, this process entails the addition of a coagulant that contains positive charges. The positive charges of the coagulant will then be neutralized by the negative charges of the suspended solids; hence, the water is neutralized.
The suspended solids in the water will then coagulate or bind together to form clumps known as flocs. They will then sink to the bottom of the treatment chamber. From here, the flocs will be filtered out. Various filtration processes, such as microfiltration or ultrafiltration via a medium filter or a membrane, can be used.
Factors Affecting Coagulation
It’s not enough for a water treatment plant to add coagulant chemicals to wastewater; the engineers must take into account an array of factors. In fact, the effectiveness of coagulation in the water treatment process depends on numerous elements:
- pH Levels: The pH level of the water significantly influences the coagulation process. Each coagulant has an optimal pH range where it works most effectively.
- Temperature: Higher temperatures generally enhance the coagulation process, while lower temperatures can slow it down.
- Dosage of Coagulant Chemicals: The amount of coagulants added to the water must be carefully controlled. Too little may not be effective, while too much can lead to other issues.
- Nature of Contaminants: The type and concentration of suspended particles and organic compounds in the water can affect coagulation. Some contaminants are more challenging to coagulate than others.
- Mixing Intensity: Proper mixing of coagulants is crucial to ensure uniform distribution.
Is Coagulation Always Needed in Water Treatment?
After learning about the definition of coagulation as it pertains to water treatment, many people naturally wonder if this process is always necessary. The short answer is no. Not every water treatment plant uses the process of coagulation to purify water. However, creating coagulated water is a critical step in wastewater treatment. These plants will follow this necessary step to create potable water.
With that said coagulants are not always used during the treatment of drinking water. Some drinking water supplies come from groundwater sources and are naturally filtered as the water flows over rocks and soil. In some of these cases, using coagulation to treat groundwater isn’t always necessary. You can contact your local water treatment plant to determine which processes they use to treat wastewater and drinking water.
What Contaminants Are Removed During Coagulation?
Various things are removed during the coagulation process before the water becomes clear. However, the main particles removed are suspended solids and organic matter (Natural Organic Matter and Dissolved Organic Carbon) like bacteria, protozoa, iron, clay, algae, sand, and gravel. When these contaminants are in the water in large amounts, they make the water have an unpleasant taste, and the color of the water becomes either orange or brown.
However, the coagulation process does not remove all contaminants in a specific time frame. For this reason, other processes have to be incorporated during water treatment. For example, contaminants like sand and gravel take about two minutes to be neutralized, while others, like protozoa, clay, and algae, may take up to 2 hours.
Did you know that it takes up to 8 days for bacteria and algae of 1 micron to coagulate and collect at the bottom of the water? Viruses with 0.1 microns may take up to 2 years to coagulate.
Because of these challenges, disinfection is used to kill the microorganisms before the coagulation process. The remaining pathogens will attach themselves to the coagulated particles and will be removed during filtration.
Remember that coagulation in water treatment does not guarantee the water is safe, but it is crucial. When the suspended solids are removed, it is easier to disinfect the water and add chlorine.
Coagulation is a vital process in water treatment, but it cannot work alone. Other processes that should be done are disinfection, sedimentation, and filtration. These ensure that your water is safe for drinking and general consumption.
Hire Serv-All Water Conditioning to Treat Your Water
While coagulation is a vital process for treating wastewater and drinking water and does a fantastic job alongside sedimentation and filtration, it may not be enough. Water can still pick up contaminants from the moment it leaves the treatment plant to the time it pours through your faucets. For this reason, it’s often beneficial to look into residential water treatment solutions.
Do you live in Las Vegas and want to find a reliable water treatment contractor? Your search has come to an end. Serve-All Water Conditioning is a team of professional water treatment contractors specializing in water conditioning systems, including repairs and installations of residential water softeners. We also repair and install reverse osmosis systems and water filters.
Do you want a free estimate on new equipment or a service call on all your existing systems? Contact the professionals at Serv-All Water Conditioning today!
Additional Questions About Coagulation
What is the most common coagulant in water treatment?
Aluminum sulfate, commonly known as alum, is the most widely used coagulant in water treatment. Alum is favored due to its effectiveness in removing a wide range of contaminants, including suspended solids, organic compounds, and microorganisms. It is also relatively inexpensive and readily available.
What is the difference between coagulation and flocculation?
While coagulation and flocculation are often mentioned together in the context of water and wastewater treatment, they refer to different processes:
- Coagulation: This is the initial chemical process where coagulant chemicals are added to the water to destabilize and neutralize the suspended particles and organic compounds. The result is the formation of small, sticky particles called microflocs.
- Flocculation: The flocculation process follows coagulation and involves gentle mixing of the water to encourage the microflocs to collide and stick together, forming larger, more easily removable particles known as flocs.
Why is filtration necessary after coagulation?
Filtration is a critical step following coagulation and flocculation. Even after water and wastewater treatment operations, there are still small particles and impurities in the water. Filtration helps to remove these residual particles, ensuring the water meets safety and quality standards.
How does coagulation prepare drinking water for residential filtration?
By reducing the quantity of impurities, coagulation enhances the efficiency and effectiveness of residential filtration systems, such as activated carbon filters and reverse osmosis units. This preparation also helps ensure that the water delivered to homes is of the highest quality, free from harmful substances and safe for consumption.
