Coagulation is a chemical process involving charge neutralistion, which causes the colloidal particles to accumulate in microflocs.
Coagulants are used as the first part of the precipitation process. They react with dissolved and suspended substances and form these microflocs. With the use of polymers, the microflocs can be gathered into large flocs, which can be separated from the water phase and dewatered.
Coagulants are divided into two main groups: organic and inorganic coagulants. Special mixtures of inorganic and organic coagulants are gaining more and more ground, as in some applications they produce a better result than standard coagulants do individually.
Norlex Chemicals manufactures its own PAC and sodium aluminate, which is produced at the Norlex Group’s plant in Kalundborg, Alumichem.
Amines and polyDADMAC are the most commonly used. They are widely used in the industry and potable water treatment, where inorganic coagulants do not produce the same result.
Tannin-based products have a more limited use but are an attractive alternative due to their green profile. Today, they are used in the fishing industry in particular.
Most mixtures are based on PAC and amines, but products containing iron chloride (either iron (II) or iron (III)) and magnesium also have applications where they generate a noticeable effect.
Wastewater may contain substances that are not captured during the normal precipitation process with coagulants. For example, the content of heavy metals may be too high. For this purpose, special precipitation products are used that form insoluble complexes with these substances, which precipitate as small particles. These are caught in the flocculation process and bound into the sludge