Coagulants and flocculants are essential chemicals used in water and wastewater treatment to remove suspended solids, colloids, and other contaminants by promoting the aggregation of small particles into larger, more easily settleable or filterable flocs. Coagulants, such as aluminum and iron-based compounds, neutralize the electrical charges of suspended particles, while flocculants, including anionic, cationic, and non-ionic polymers, help bridge the gaps between flocs to create larger and more stable aggregates. These chemicals are used in various applications, including drinking water treatment, wastewater treatment, sludge dewatering, industrial process water treatment, and stormwater treatment. Factors such as water quality, pH, temperature, and contaminants should be considered when selecting coagulants and flocculants, and their dosage is optimized through jar testing to achieve the desired water quality while minimizing treatment costs.