Massachusetts Wastewater Practice Exam

Which of the following is not classified as a physical method of wastewater treatment?

1. Sedimentation

2. Ultrafiltration

3. Electrodialysis

4. Air stripping

The correct answer is: Electrodialysis

Electrodialysis is not classified as a physical method of wastewater treatment; instead, it is considered a chemical method. This technique uses a combination of electrical potential and ion-selective membranes to separate ions from wastewater, which requires a chemical understanding of ion behavior rather than merely relying on the physical properties of the substances involved. In contrast, sedimentation, ultrafiltration, and air stripping all utilize physical processes. Sedimentation involves the gravitational settling of solids, ultrafiltration relies on membrane technology to filter particles based on size, and air stripping removes volatile contaminants from water by transferring them to the air. Each of these methods leverages physical forces or changes in state rather than chemical reactions, thus differentiating them from electrodialysis, which is more dependent on electrochemical principles.