Flocculants are essential chemical additives in industrial wastewater treatment that support the flocculation process by aggregating finely dispersed particles in the water into larger flocs. These larger flocs can be more easily separated by CP (sedimentation ) or flotation plants and contribute significantly to improving solids separation and compliance with legal limits. The effectiveness of flocculants depends on the composition of the wastewater and the specific properties of the particles. Flocculants are therefore available in different forms and with specific properties that are suitable for various industrial applications.

Technical background to flocculation

The flocculation process consists of two main phases:

1. Coagulation: By adding precipitants such as iron or aluminium salts, the dissolved substances are destabilized and the finest particles are converted into the smallest flocs (primary flocs) by ion accumulation or chemical bonding.
2. Flocculation: The primary flocs are aggregated by flocculants to form larger, more stable flocs, which can then be effectively separated by mechanical processes.

Types of flocculants and their functions

1. Anionic polymers

   • Properties and function: Anionic flocculants carry negative charges and are therefore particularly suitable for flocculating particles with a positive charge. They act primarily by bridging between the particles and improve the agglomeration of the primary flocs.
   • Areas of application: Anionic polymers are widely used in wastewater treatment in the food and beverage industry, in the paper and pulp industry and in the textile industry. They support the separation of organic substances and facilitate the removal of solids.

2. Cationic polymers

   • Properties and function: Cationic flocculants have positive charges and are ideal for treating negatively charged particles. Due to the electrostatic attraction, they combine with the particles in the wastewater, which leads to the formation of larger and more stable flocs.
   • Areas of application: These flocculants are frequently used in the metal processing and electroplating industries as well as in sludge treatment, where the removal of heavy metals and inorganic substances is the main focus.

3. Non-ionic polymers

   • Properties and function: Non-ionic flocculants do not carry an electrical charge and are therefore particularly suitable for flocculation in wastewater with fluctuating pH values or particles that do not have a specific charge. Their effect is mainly based on bridging and physical attachment to particle surfaces.
   • Areas of application: They are used in the petrochemical industry, paper production and in processes with high organic loads, as they offer a versatile solution for wastewater with different compositions.

4. Organic flocculants (polyacrylamides)

   • Properties and function: Polyacrylamides are synthetic polymers that are available in various ionic forms (anionic, cationic and non-ionic). They offer high flexibility in application and are particularly effective in the formation of large, stable flocs by bridge flocculation.
   • Applications: They are used in many industries, including food processing, chemical industry and mining. Polyacrylamides offer efficient flocculation with low chemical consumption and are suitable for wastewater with a high solids content.

5. Inorganic flocculants

   • Properties and function: These include precipitants such as ferric chloride, aluminum sulfate and lime, which are used not only for coagulation but also as flocculants. Inorganic flocculants increase the density of the flocs and improve the sedimentation and filtration properties.
   • Areas of application: They are often used in phosphate elimination in the food industry and in the removal of heavy metals in electroplating, as they bind poorly soluble solids and promote the settling of flocs.

6. Organic, natural flocculants

   • Properties and function: These flocculants, such as chitosan and guar gum, are biodegradable and sustainable. They have good flocculation properties and are used in special environmentally friendly applications.
   • Areas of application: These natural flocculants are particularly popular in the food industry and in the treatment of drinking water, as they are more environmentally friendly and less toxic than synthetic alternatives.