ABSTRACT
In the field of chemistry, most authors follow the lead of LaMer, who defines coagulation as destabilization produced by compression of the electric double layers surrounding small particles, and flocculation as destabilization produced by the formation of long-chain molecular bridges between particles. Besides lime, alum, and iron salts, the only other materials in common use are activated silica and magnesium hydroxide, which like alum form polymers and/or floes under the conditions of use. All these materials, except lime, possess some properties of flocculation as well as coagulation. All "simple" flocculants in use are relatively high molecular weight organic compounds. Flocculants may be conveniently separated into three types according to the overall charge on the molecule. These are anionic, cationic, and nonionic. Most anionic flocculants are based on the polyacrylamide structure, with a few percent carboxyl groups dispersed among the predominant amides.
