Chemical Conditioning

Chemical conditioning is associated principally along with mechanical sludge dewatering systems. It decreases the moisture content of incoming sludge from 90-99 per cent to 65-85 per cent through causing solids to coagulate, so in which the absorbed water is released. Both organic and inorganic chemicals are used for this reason. The two most general used inorganic conditioners are ferric chloride and lime. Upon being added, ferric chloride forms positively charged soluble iron complexes in which neutralize the negatively charged sludge solids, causing them to aggregate. Ferric chloride also reacts along with the bicarbonate alkalinity in the sludge to form hydroxides which cause flocculation. Lime, for its element, is ordinarily used along with ferric iron salts. It reacts in the sludge to generate calcium carbonate, therefore creating a granular structure that increases sludge porosity and decreases sludge compressibility. Organic polymers are also hugely used in sludge conditioning. Organic polyelectrolytes dissolve in water to form solutions of varying viscosity.

The electrolytes adhere to the surface of the sludge particles, causing desorption of bound surface water, charge neutralization, and agglomerization through bridging among particles.