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There are many different best practices involved in the treatment of water at your commercial or industrial site. Two of the most common are flocculation and coagulation water treatments. Both methods are aimed at removing solids from water during the treatment phase, and leaving behind water that can either be used safely in applications such as cooling towers or disposed of responsibly.

But which one is the best option here? Let’s explore flocculation vs. coagulation in a little more detail so that you can gain a better picture of which one represents the best option for you and your business.

What is coagulation and how is it used in water treatment?

Coagulation is the process of adding specific chemicals to untreated water in order to destabilize the particles within the water. In most cases, aluminum sulfate or ferric chloride is added to achieve this. These particles have positive charges that are opposite to the negative charges of suspended particles within the water.

The process results in the formation of non-suspended solids. The solids have a neutral charge and can begin to collect together into clumps. They may also begin to settle at the bottom of the chamber or float on the surface, where they can be removed via filtration.

Electrocoagulation can also be used to speed up the process. There are a number of advantages and disadvantages to electrocoagulation, but this tends to be a more expensive and resource-intensive process.

Advantages of coagulation

  • Works to treat particles that are suspended in the water — not just those which have already formed non-suspended solids.
  • Forms clumps or flocs that can be removed from the water relatively simply.
  • Cost-effective, as the chemicals required in coagulation are not difficult or expensive to obtain.
  • Coagulation is a quick process that may take only three minutes to complete.

Disadvantages of coagulation

  • Once the clumps or flocs have been formed, it is difficult to encourage further clumping together of particles into larger clusters through coagulation alone.
  • Following coagulation, sophisticated separation and filtration techniques may be required to remove the clumps of solids from the water after treatment.
  • While the coagulation process may be completed in only three minutes, there is more work to be done in treating the water after this point.

What is flocculation and how is it used in water treatment?

Flocculation is the process of encouraging the formation of flocs, or small clumps, from solids in the water. The water is mixed and activated slowly, allowing movement of particles and micro solid throughout the waste water treatment chamber. The aim is to encourage the moving particles to interact with one another and form larger flocs, which are then easier to remove from the water.

The mixing process continues for as long as it is required — only 15 to 20 minutes in some cases or more than an hour in others. The process is complete once the floc has reached its optimal dimensions in terms of size and mass and is structurally sound. At this point, the solids can be separated using the chosen method, which may be separated by sedimentation, floatation, or filtration.

At the beginning of the flocculation phase, there will be destabilized solids in the water-solid mix. These neutrally charged micro flocs will already have begun to join together into clumps. During flocculation, the mixing action will make these clumps grow larger and more structurally sound. As flocculation continues, additional chemicals can be added to begin the bridging phase — i.e., the formation of bonds between these separate micro flocs. Eventually, these micro flocs join together, growing in size and getting closer and closer to the optimal dimensions.

Advantages of flocculation

  • Leaves far larger particle clumps behind that are relatively easy to remove via filtration.
  • In most cases, the process will not take too long to complete — between 15 minutes and one hour in the majority of instances.
  • As the mixing motion is gentle, your facility does not require too much power to operate this kind of process, making flocculation cost-effective.

Disadvantages of flocculation

  • While flocculation is useful for creating larger flocs that can easily be removed, it does not work on small particles suspended in the water.
  • Getting the best results from flocculation may also require a preliminary phase of destabilization.
  • This may make the entire process somewhat longer than one hour in some cases.

Deploying coagulation and flocculation together in sequence

Where coagulation is found to be lacking — i.e., in creating large macro flocs that can be easily filtered and removed — flocculation can help. In areas where flocculation is inadequate by itself — for example, in targeting the particles that are suspended within the untreated water — coagulation is useful. Because of the convenient, complementary relationship that exists between these two processes, many facility owners choose to deploy both together.

The most common way to deploy the two processes together is to do them in sequence. Coagulation is the first process in the sequence, and it is this procedure that is used to destabilize the suspended solids and to create neutrally charged micro flocs. Rather than heading straight to an expensive process of filtration or separation, facility managers can follow up the coagulation process with a flocculation procedure. Flocculation will grow the size of the flocs to make them easier to deal with and remove.

Filtration, separation, or other removal procedures will still be required after flocculation is complete. However, these processes will be made far easier, more reliable, and more cost-effective, as the flocs will be at the optimal size and level of structural integrity for removal.

Achieve effective water treatment without excessive cost

It’s not always a case of flocculation vs. coagulation or of selecting the best individual option for your facility. For some highly specialized applications, it may be suitable to deploy a process of flocculation or a coagulation water treatment in isolation. Most will find that the best course of action is to put these two water treatment options to work together in sequence.

The mechanical action of flocculation does not require too much of an investment in terms of energy or resources, while the coagulating agents — as well as the chemicals that are added to aid flocculation — are not expensive to procure. Businesses will find that it is possible to put both processes to work without stretching their budget or their resources.