In water treatment coagulation is the destabilization of colloidal particles by neutralizing their charge with an added chemical, called a coagulant.
In dirty water there are - in order of decreasing size - three groups of substances: suspended solids, colloidal particles and soluble particles. Colloidal or suspended particles are less than 1 micron in diameter, have a negative charge and are stable in water. They don't settle. By adding coagulants such as trivalent iron or trivalent alumium the negative charge of colloidal particles is neutralized by the positive charge of the metal ions of iron or aluminum. This charge neutralization will ensure that the colloidal particles no longer repel each other but can clump together. The agglomerated particles will setlle or float and can easily been removed from the water. By adding flocculants this process can be accelerated.

Besides inorganic coagulants such as iron and aluminum salts,  also organic coagulants can be used. The most popular coagulants are FeCl3 (iron trichloride) and PAC (Poly Aluminum Chloride)

By the means of dosing pumps these liquid chemicals can be dosed in the desired concentration.

  • Diaphragm metering pumps with an electromagnetic drive
  • Diaphragm metering pumps with a motor drive
The dosage of chemicals should best be done correctly.  This is necessary for optimal process conditions, for environmental purposes and from an economic point of view as well. Using a combination of a flow meter on the treated water stream and possibly on the coagulant flow, an optimal dose can be obtained. The dosing pumps are activated via a 4-20 mA signal or pulse contacts depending on the wastewater flow. The operator can still manually adjust the dosage per m³ of wastewater as its composition can vary in function of time.

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Primary TreatmentPrimary Treatment
Effluent polishingEffluent polishing

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