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Emulsion polymers are the most widely used type of polymer products for most small and medium sized applications. Emulsions are suspensions of polymer hydrogels in an oil. They generally contain 25 to 50% of active material. The hydrogel – a hydrated polymer – is in the form of micro spheres with an average diameter of 1 µm. These micro spheres are dispersed in the oil and protected from agglomeration by surfactants.

One of the main benefits is that all types of polymer can be made into an emulsion product, including the highly branched and cross-linked versions, which are not available as dry products.

Emulsion polymers generally has an active content of 20-50%.

Emulsion must be prepared into a 0,2-0,6% solution using Polymer make-down equipment (link til polymerenheder)

This type of liquid polymer is also referred to as dewatered or distilled polymers. This alternative process consists in distilling the emulsions to remove the water. The result is a higher concentration of active polymer, thereby reducing the packaging and transport costs, good stability over time (longer lifetime) high fluidity (easier to mix into the sludge) and easy handling. The process does however increase the cost and there is a slight loss of efficiency because of the heating during distillation.

The active content for these products are generally 50%.

Dispersion polymers can be fed directly to some applications, but it is generally recommended to use a polymer make-down unit.

This type of polymer is a type where the polymer is in a water dispersion. This makes the polymer product free of solvents and surfactants.

The range is limited, but the polymers are comparable to emulsion polymers in performance.

The polymers are very easily dispersible and can be dosed neat to the process.

Natural polymer products are becoming available, f.ex based on starch, but these cannot be produced with the same diversity in charge, structure and molecular weight. These products are somewhat in between a coagulant and a flocculant. As such, their ability to form the very strong flocs needed in sludge dewatering is weak and their use for this application is very limited.

However, they find an increased use in applications where very strong and dense flocs are not needed, and where acrylamide-based polymers can’t be used.

Powders are produced by gel polymerisation, a basic production process where monomers are polymerized in liquid form, then ground and then dried. The quality obtained by this process, particularly with regard to solubility, is exceptionally good and the molecular weight can be very high.

The powders have a particle size of 0 to 1mm and may be dissolved in 30 to 240 minutes depending on the type and the molecular weight. A good dry polymer make-down unit should be used to avoid undissolved residues (fisheyes) in the prepared solution.

Because of the very high molecular weight they find good use in sludge dewatering processes, where high shear forces are used (like centrifuge applications).

Also, because of the more or less 100% active content, this is the most economical type of polymer to use in large applications.