Massachusetts Wastewater Practice Exam

Which element is commonly used in coagulation processes for its effectiveness in water treatment?

1. Aluminum

2. Iron

3. Calcium

4. Magnesium

The correct answer is: Aluminum

Aluminum is commonly used in coagulation processes due to its effectiveness in promoting the aggregation of suspended particles in water. Coagulation is a crucial step in water treatment, where coagulants are added to destabilize colloidal particles and allow them to clump together, forming larger aggregates that can then be removed through sedimentation or filtration. Aluminum salts, such as aluminum sulfate, are widely employed because they can efficiently reduce turbidity and improve water clarity. When aluminum is added to water, it reacts to form aluminum hydroxide, which acts as a “sticky” substance, capturing and binding with impurities. This makes the treatment process more efficient and helps to facilitate subsequent treatment steps, ensuring that water meets safety and quality standards. Iron can also be used in coagulation processes, but aluminum is often preferred due to its effectiveness and broader range of conditions under which it can work. Calcium is generally used in different contexts like lime softening, and magnesium, while useful in treating hardness, is not commonly associated with coagulation processes in water treatment.