During what stage of water treatment does the addition of coagulants typically occur?

The addition of coagulants is a crucial step in the water treatment process, occurring before filtration. During this stage, substances such as aluminum sulfate or iron salts are introduced to the water. Coagulants help to aggregate suspended particles, such as dirt and organic matter, creating larger clumps known as flocs. This process is essential because it facilitates the removal of these particulates during subsequent filtration.

By effectively grouping the impurities together, coagulants enhance the efficiency of subsequent treatment processes, including sedimentation and filtration. This ensures that the water is clearer and more purified before moving on to disinfection and chlorination stages, where the focus shifts to eliminating pathogens rather than removing particulate matter. Therefore, the timing of coagulant addition is strategically placed before filtration to maximize its effectiveness in improving water quality.