Ontario Operator-in-Training (OIT) Practice Exam

What mechanism is used in flocculation to facilitate the treatment of water?

1. Rapid mixing

2. Slow mixing

3. Filtration

4. Disinfection

The correct answer is: Slow mixing

Flocculation is a critical step in the water treatment process, where tiny particles in the water are agglomerated into larger flocs that can be more easily removed. The mechanism primarily involved in flocculation is slow mixing. During this phase, gentle agitation allows for the optimal interaction between the added coagulant and the suspended particles in the water. This slow mixing helps to promote the collision and binding of particles without breaking the flocs apart. It allows the microscopic particles to come together, creating larger aggregates that can be subsequently removed through sedimentation or filtration. While rapid mixing is an important preliminary step that facilitates the initial dispersion of coagulants and the beginning of the coagulation process, it is the slow mixing that is crucial for the formation and growth of flocs. Filtration and disinfection are subsequent stages in the water treatment process, focusing on the removal of these flocs and pathogens, respectively, but they do not play a direct role in the flocculation mechanism itself. Thus, understanding the role of slow mixing in flocculation is essential for effective water treatment practices, as it directly influences the efficiency and effectiveness of particle removal in the overall treatment process.