Coagulants
Coagulants are compounds that are used in water purification to change the microscopic molecular structure of the water, causing water molecules to join together and form larger particles. When water molecules become large enough, they settle out of the water, and the once-clear water is cloudy. Coagulants are also used to remove oils and suspended particles from water, allowing it to be purified for drinking, swimming, and other uses.
Coagulants come in many forms, from natural minerals to chemical compounds. Common coagulants such as aluminum sulfate, ferric chloride, and polymers are used around the world for water treatment. Natural coagulants such as bentonite and diatomaceous earth are also popular. All of these coagulants act by changing the electrostatic charge of the water molecules, causing them to attract and stick together.
Aluminum sulfate is one of the most popular coagulants due to its simplicity, low cost, and effectiveness. Aluminum sulfate works by binding to the negatively charged particles in the water, like bacteria and minuscule soil particles. These particles have an opposite charge than aluminum sulfate, so when the two come into contact, they bind together to form larger particles that settle out of the water. The most common method of applying aluminum sulfate is to drop pre-measured small doses directly into the water supply.
Ferric chloride is another popular coagulant, and it works very similarly to aluminum sulfate in that it binds to particles that have an opposite charge. However, ferric chloride is much more efficient at forming larger particles that can settle out of the water. This is why it is often used in industrial settings where very high water quality is necessary.
Polymers are also effective coagulants, but they differ from aluminum sulfate and ferric chloride in that they do not bind to particles. Instead, polymers change the molecular structure of the water itself to allow the particles to bind together more easily. Some polymers even cause these particles to form a gel-like texture that helps to remove particles and oils more quickly.
While all of these coagulants are effective at treating water, they all come with their own advantages and disadvantages. For example, aluminum sulfate is a cost-effective option, but it can cause the water to become acidic over time. Ferric chloride is much more efficient, but it can also leave behind iron content that may have adverse effects on certain aquatic organisms. Polymers are often the most expensive option, but they are also the safest because of their lack of metals and chemicals.
When selecting the appropriate coagulant for water treatment, it is important to consider the water quality, the level of water contamination, and the cost of treatment. Choosing the right coagulant will ensure that the water is safe to drink, swim in and use other activities. Ultimately, the right coagulant will provide safe, clean water that meets all government standards of clean water quality.
