ABSTRACT
Coagulation includes several operations, and these operations are discussed because each of them involves different considerations. Different chemicals may be used in coagulation depending on the characteristics of the water being treated. In some waters, a combination of two or more chemicals produces better results than any one chemical alone. It is usually necessary to perform coagulation tests in the laboratory to decide which chemical or combination should be used. There are a number of chemical compounds which are used as water coagulants, but aluminum sulfate, commonly called alum, is most widely used. Control of flocculation basins consists of regulating the amount of coagulant that is added as well as the degree of agitation to secure the most effective floc formation with a minimum coagulant dosage. Belt-type gravimetric feeders span the capacity ranges of volumetric and loss-in-weight feeders and can usually be sized for all applications encountered in wastewater-treatment applications.
