Ontario Operator-in-Training (OIT) Practice Exam

What process is used for cleaning filters in water treatment?

1. Decantation

2. Backwashing

3. Filtration

4. Flocculation

The correct answer is: Backwashing

Backwashing is a critical process used to clean filters in water treatment systems. During this procedure, the flow of water is reversed through the filter media, dislodging trapped particles, debris, and contaminants that have accumulated. This reversal helps to restore the filter’s efficiency and prolong its operational life, ensuring that the water treatment plant continues to provide clean and safe drinking water. This process typically occurs at regular intervals or when the pressure differential across the filter reaches a specific threshold, indicating the filter is becoming clogged. The effectiveness of backwashing also depends on the type of filter media in question; for example, sand filters and cartridge filters may require different techniques or settings. In contrast to other processes mentioned, such as decantation, filtration, and flocculation, which serve distinct purposes within the water treatment process—decantation involves separating liquid from solids, filtration is the general process of removing particles from a liquid, and flocculation refers to the aggregation of fine particles—backwashing specifically addresses the maintenance and cleaning of filtration systems, making it essential for optimal filter performance.