Chapter 1 focuses on “Water and Coagulation”. First, in the section “Composition and Properties of Natural Water”, it introduces the distribution of water, the composition of natural water bodies, the properties of natural water, and also elaborates on pollutants in water, especially the relevant situations of toxic pollutants. Then, in the section “Chemical Treatment and Coagulation Process”, the coagulation process and coagulation principle are explained. Next, in the section “Hydrolysis Mechanism of Aluminum and Iron Salts”, coagulant agents are classified first, and then the hydrolysis mechanism of aluminum and iron salts is emphasized. After that, the section “Coagulation Kinetics” involves coagulation kinetics and coagulation parameters and other contents. The section “Influencing Factors of Coagulation” discusses the relevant factors affecting coagulation. Finally, the section “Determination Method of Zeta Potential” describes Zeta potential and precipitation, Zeta potential and flotation process, as well as the improvement of Zeta potential analysis methods and other improvements in water quality characteristics.