Chemical treatment of wastewater uses chemical reactants to break down pollutants. It is ideal for wastewaters with high chemical toxin contents, such as the wastewaters from chemical or pharmaceutical manufacturing, pump and paper mills, laboratories and textile manufacturers
When referring to coagulants, positive ions with high valence are preferred. Coagulation is very dependent on the doses of coagulants, the pH and colloid concentrations. To adjust pH levels Ca(OH)2 is applied as co-flocculent. Doses usually vary between 10 and 90 mg Fe3+/ L, but when salts are present a higher dose needs to be applied.
To promote the formation of flocs in water that contains suspended solids polymer flocculants (polyelectrolytes) are applied to promote bonds formation between particles. These polymers have a very specific effect, dependent upon their charges, their molar weight and their molecular degree of ramification. The polymers are water-soluble and their molar weight varies between 105 and 106 g/ mol.
There can be several charges on one flocculent. There are cationic polymers, and anionic polymers.
A defoamer or an anti-foaming agent is a chemical additive that reduces and hinders the formation of foam in industrial process liquids. The terms anti-foam agent and defoamer are often used interchangeably.