Ontario Operator-in-Training (OIT) Practice Exam

What is the purpose of Aluminum Sulphate in water treatment?

1. As a cooling agent

2. As a chemical coagulant

3. As an oxidizing agent

4. As a pH stabilizer

The correct answer is: As a chemical coagulant

Aluminum sulfate is primarily used in water treatment as a chemical coagulant. Its main function is to facilitate the process of coagulation, which involves the aggregation of small particles suspended in water into larger clusters, known as flocs. When aluminum sulfate is added to water, it dissociates into aluminum ions and sulfate ions. The aluminum ions have a positive charge, which helps neutralize the negative charges of suspended particles, allowing them to bind together more effectively. This aggregation process is crucial in water treatment because it aids in removing impurities such as suspended solids, organic matter, and pathogens from the water. The resulting larger flocs can be easily removed through sedimentation or filtration, leading to clearer and cleaner water. Other choices, like a cooling agent, oxidizing agent, or pH stabilizer, do not accurately describe the primary function of aluminum sulfate in the context of water treatment. While these substances have their own roles in various chemical processes or treatments, they do not encompass the coagulant property that aluminum sulfate is renowned for in the water treatment industry.