Polymers and polyelectrolytes are mostly used as flocculation aids in wastewater treatment and for solid-liquid separation, e.g. sludge dewatering. The organic macromolecules bind small particles into large-volume, well-settling flocs and thus considerably increase the effectiveness of solid/liquid separations.

For most applications in wastewater treatment synthetic water-soluble organic polymers as flocculation aids are used in order to achieve sufficient floc stability for mechanical dewatering aggregates. Precise and adapted dosing is important here, because polymer overdosing can have negative effects on downstream processes. In the case of deammonification, polymer films can form on the biological granules, limiting the performance. With the EssDe^® deammonification process, these films are removed by shear forces in the hydrocyclones.


The polymers used in wastewater treatment are cationic or anionic polyelectrolytes. The flocculation effect of the polyelectrolytes is essentially determined by the molecular weight and the charge density of the polymers.
Typical examples of cationic polyelectrolytes are the condensation products of dimethylamine and epichlorohydrin, poly(diallyldimethylammonium chloride) (PDADMAC) and the copolymers of acrylamide and quaternary esters or amides of acrylic or methacrylic acid.
Anionic polyelectrolytes are mostly copolymers of acrylamide and acrylic acid.

Polymers based on acrylamide has been discussed in wastewater treatment for some time, as they are classified in different water hazard classes depending on their composition. Therefore, modified, natural polymers are increasingly being used. The basis for this can be starch, alginates and chitosan, among others.


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