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Flocculant Chemical Metering

Flocculants are polymers that promote flocculation by formation of links between themselves and thus enable suspended particles to aggregate. When the suspended particles are flocculated into larger ones, they are settled in devices like thickeners and clarifiers and removed with the underflow. The flocculants accelerate the settling process, which leads to the potential use of smaller thickeners. Flocculants can also be used to aid filtration.

Flocculation is employed for a variety of applications from mineral processing to purification of drinking water.
This includes:
• Concentrate and Tailings thickeners in the mining industry
• Water treatment plants
• Filtration aid
• Sewage applications
• Treatment of industrial waste water streams
• Clarification processes


Requirements of flocculant polymers are that they be strongly adsorbed onto the particles and that they are capable of spanning the gap between the particles. Synthetic polymers of high molecular weight are long enough for one end of a single molecule to adsorb onto one particle and the other end onto a second particle. Higher molecular weight polymers can adsorb on several particles at once, forming a three-dimensional matrix.

In general, the higher the molecular weight the better the flocculation and the faster the sedimentation rate. In the case of filtration, however, the lower molecular weight products can be more effective. This is because the flocs formed with high molecular weight products are relatively large, trapping water within the structure and increasing the final moisture content of the filter cake.

Most synthetic flocculants are based on polyacrylamide and its derivatives. Flocculants generally carry either a positive (cationic) or a negative (anionic) charge. Polyacrylamide itself essentially is nonionic and the desired ionic character is produced by copolymerisation with other monomers. Anionic polyacrylamides are produced by copolymerisation with acrylic acid, while for cationic polymers one of several cationic monomers will be used. These charges serve two purposes; they provide a means of adsorption onto the particle surfaces by electrostatic attraction and they cause the polymer molecule to extend and uncoil due to charge repulsion along the polymer chain.

AquFlow provides pumps and automatic controls to ensure optimal flocculation for maximum effectiveness of separation and filtration. We have pumps with flow rates ranging from just a few milliliters per hour to several hundred gallons per hour. For polymers that are viscous or have slurry, AquFlow offers a tubular diaphragm pump to give clog free performance.

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