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What Are Coagulants

Water treatment is an essential tool in protecting public and environmental health. Water needs to be properly treated, both before human use and after, when it is being returned to the source. This process helps ensure product quality and safety for people and proper balance for local ecosystems.

One of the most important steps in water treatment is coagulation. This process helps separate water from other particles suspended within it, including oils, metals, and solids, so that they can be disposed of properly. The challenge is getting the suspended particles to group together into flocs large enough to capture and remove.

To make coagulation possible, water treatment professionals rely on coagulants, or substances that cause particles to clump together via chemical reaction when added to the water. Coagulants find use during water pretreatment and wastewater treatment in various industries, including the food industry, oil refining, and manufacturing.

In this article you will learn:

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Organic Coagulants Versus Inorganic Coagulants

Inorganic coagulants are commonly used due to their low cost and ability to treat water with low turbidity. However, inorganic coagulants are required in higher doses to treat water. They also produce more sludge that must be removed after treatment and affect pH levels in the treated water.

Organic coagulants, by comparison, require smaller dosages, produce less sludge, and have reduced impact on pH levels, though they are most effective for separating liquids from solids and removing oil.

Differences in Coagulants

Coagulants are a category of products used to reduce water turbidity — in other words, to clarify water. They add cationic charges to neutralize the negative charges surrounding soluble particles, rendering them insoluble.

Different coagulants have been used to clarify water for many years. Today, we divide coagulants into two main categories: organic and inorganic. Each type has properties suited to different applications.

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Similarities in coagulants

Both inorganic and organic coagulants have their uses in water treatment. Some common coagulants in these categories include:

  • Aluminum salts: This category includes common inorganic coagulants such as
    aluminum chlorohydrate and aluminum sulfate, which are easy to handle and use during
    the treatment process.
  • Iron salts: Iron-based inorganic coagulants such as ferric sulfate, ferric chloride, and
    ferrous sulfate are effective coagulants but usually require added alkalinity.
  • Bio-polymers: Bio-polymers such as Brennfloc work in a range of pH levels and provide
    a more environmentally friendly alternative to some inorganic coagulants. This type of
    coagulant excels in separating oil from water.

    The type of coagulant you choose for your application will depend on what solids you are
    removing from the water and what environmental and health regulations you must follow.


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