Flocculation: How It Works & How It Differs from Coagulation

In wastewater treatment, there is one important process that removes impurities in water, namely flocculation. Flocculation is a water treatment method of clumping particles into flocs, or big groups of particles.

This article discusses flocculation and how it works. Thus, to learn more about the method, read this article thoroughly!

What Is Flocculation?

Flocculation is a process of gathering small particles in water to become bigger ones called flocs. Collected flocs in water will float or sink, making them easier to collect. This process is crucial because water often contains tiny particles that cannot be filtered out, leading to contamination even after treatment.

By pouring in chemicals that act as flocculants, the particles clump together and more easily removed from the water. Various flocculants that can be used are natural flocculants (chitosan), inorganic flocculants (alum), and organic flocculants (polymers).

Flocculation occurs naturally in some cases, such as in the sedimentation process. This method is frequently used in wastewater treatment, drinking water purification, and the management of rainwater or melted snow.

Some benefits of flocculation are increasing water clarity, removing pollutants from water, reducing the need for filtration, and disinfecting water.

Although flocculation can make water clearer, it also has some limitations, such as the process tending to be long, potentially requiring chemicals, being difficult to control, and creating too many flocs that can clog filters.

However, this technique is safe for improving the quality of water and wastewater, making it widely used in various industries.

How Flocculation Works

Flocculation begins with adding flocculant to water, clumping the particles, and making them float or sink. Below are the steps of flocculation you should know:

Flocculant addition: Adding flocculants, such as alum or others, to gather and clump particles, creating filterable flocs.
Stirring: The water will be stirred continuously and mixed well to trigger optimal interactions between water and flocculants.
Clumping: Particles clump and form flocs that grow bigger as the process runs.
Floc sedimentation: The floc formed will be precipitated and separated from the water or solution. Some of the precipitation methods used are filtration and sedimentation.

Types of Flocculation

In general, flocculation is divided into two categories: natural and chemical flocculation. Here is the complete information:

1. Chemical Flocculation

Chemical flocculation uses chemically synthesized flocculants and comes from different monomers. Yet, chemical flocculants are very toxic because the resulting sludge contains many metal hydroxides, which are harmful to living things.

2. Natural Flocculation

Natural flocculation is considered more environmentally friendly, which makes it frequently used for wastewater treatment. This process uses plant seeds, such as moringa, to make the process more efficient. In addition, natural products such as starch can also be used as flocculants.

This type of flocculation is claimed to be more efficient and environmentally friendly since it does not pollute the environment and endanger living things. However, natural flocculants are often not long-lasting.

Factors Affecting the Flocculation Process

Flocculation is one of the water treatment processes effective in removing particles and contaminants in water. Yet, its effectiveness depends on several factors, such as:

1. Bioflocculant Concentrations

The first factor is bioflocculant concentrations. Bioflocculants must have a stable concentration because when it is too high, the resulting floc will be bigger and harder to separate. On the other hand, if the concentration is too low, the particles will be hard to clump and hinder the entire flocculation process.

2. Ion Addition

In the flocculation process, ions will be added to neutralize the charge of the particles. Therefore, the particles can clump together and form flocs easily. The ions used also depend on the particles contained in the water.

3. The Initial pH of the Solution

The initial pH of the solution affects the process significantly because if it is too low or too high, it can neutralize the particles. As a result, flocculation fails to happen. Thus, make sure to pay attention to the pH during flocculation.

4. Temperature

The next factor is temperature stability. Temperature can affect the effectiveness since higher temperatures can break the floc, and lower temperatures can slow the process.

5. Stirring Speed

Stirring time and speed also determine the effectiveness of flocculation. Stirring speed is expressed by the velocity gradient. A large velocity gradient (300-1000 s⁻¹) over 60 seconds is used in fast stirring.

Meanwhile, a small velocity gradient (20-100 s⁻¹) for 10–60 minutes is used for slow stirring. This speed should be continuously monitored because if stirred for too long, flocculation may not be effective.

Not only that, the velocity gradient should be lowered gradually to ensure that the resulting flocs do not break and can form sizable clumps.

6. Pollutant Content

Contamination content in water also influences the effectiveness and duration of flocculation. Typically, the more contaminants in water, the more flocculants are needed, and the process will take more time.

7. Types and Number of Flocculants

The types and number of flocculants depend on the water. If you put in too many flocculants, the water will be murkier, while putting in too few can halt the process.

The Difference between Flocculation and Coagulation

Flocculation and coagulation are two techniques widely used to remove contaminants in water. Coagulation uses chemicals called coagulants that clump particles. The clumping particles are called aggregates.

In contrast, flocculation gathers aggregates to become bigger clots named flocs. This can happen with the help of flocculants.

Overall, it may be concluded that coagulation is the initial process of particle clumping to form an aggregate. Yet, the aggregate is still too small to be filtered. Therefore, you carry out flocculation to unite the aggregates into bigger particles that are filterable.

That is the information about flocculation you must know. Flocculation is the process of producing cleaner and clearer water. Then, the water can be processed for other purposes.

If you need wastewater treatment for your company, you can entrust it to Krakatau Tirta Industri (KTI). KTI treats wastewater in a standard manner and makes sure that the wastewater is safe and environmentally friendly.

So, make sure to entrust your industrial water and wastewater treatment needs to Krakatau Tirta Industri!