Water treatment chemicals play a significant role in various water treatment processes, especially coagulants and flocculants. Coagulation is an important physicochemical treatment technology and is a key separation process in the water treatment, chemical and mineral processing industries. Especially in the water treatment process, coagulation is an essential step either as the main clarification process, or as a pretreatment or post-treatment enhancement of biochemistry, as well as a means of pretreatment of membranes. When it comes to water quality that is not identical, the choice of water treatment agent becomes a challenging issue since there is no quantitative link between the amount of water treatment agent dosed in the coagulation process and the colloid or pollutant. This book describes in detail the mechanism of coagulation, production process, quality index, use characteristics, application conditions, application process control of various coagulants and flocculants, and provides a comprehensive discussion of the domestic and international market situation. We hope that this book will be useful for water treatment engineering designers, water treatment agent researchers and production engineers.