Coagulation and flocculation processes are widely used in potable water treatment due to its high efficiency in turbidity removal. Egyptians discovered this method in 1500 BC by using alum to settle the suspended solids in the water. Today, the coagulation and flocculation processes are implemented with the purpose of agglomerate colloids and fine particles in water into larger particles, which is also known as floc. Therefore, reduction of turbidity and pollutants e.g. organic matter, inorganic matter, suspended solid, etc. can be achieved. This chapter covers the principle of coagulation and flocculation process which includes the charge neutralization and various binding mechanisms e.g. interparticle bridging, sweeping coagulation, and absorption. Besides, various types of coagulants and flocculants that have been discovered and their respective effectiveness in potable water treatment are discussed as well in this chapter. Polymer modifications to synthesize new coagulant/flocculant i.e. grafting and crosslinking are also included. â © 2020 by IGI Global. All rights reserved.