ABSTRACT
The importance of coagulation and flocculation processes in conventional water treatment is discussed in this chapter. The different coagulants and coagulant aids commonly used are presented. Chemical reactions between coagulant and alkalinity are presented. The stoichiometric requirements of the chemicals are explained with the help of solved example problems. In addition, the consumption of alkalinity and changes in the chemical nature of the coagulated water are also discussed. Zero-order and first-order chemical reactions as they influence the time of reaction for both completely mixed flow reactors and plug flow reactors are explained with the help of example problems. Factors affecting coagulation and flocculation are discussed in detail. The term velocity gradient as used in the design and operation of flocculation tanks is explained and a design example problem is presented. The jar test for determining the optimum dose of coagulants and other tests performed to optimize the process are also detailed.
