Which of the following processes helps to remove oils from wastewater?

The process that effectively helps to remove oils from wastewater involves primary pre-aeration. This step occurs early in the treatment process and is designed to physically agitate the wastewater, facilitating the separation of light materials, including oils and greases, from the denser liquid components.

During pre-aeration, air is introduced into the wastewater, causing the oils to form bubbles. These bubbles rise to the surface, where the floating oil can be skimmed off. This process is particularly effective because oils are less dense than water, allowing them to concentrate at the surface for easy removal.

In contrast, primary screening, grit removal, and comminution primarily address different types of solids and particles in wastewater. Primary screening targets larger solids to prevent damage to the treatment equipment. Grit removal focuses on heavier inorganic materials like sand and gravel. Comminution is the process of shredding or breaking down large solids into smaller pieces to prevent clogs in downstream processes. All of these processes do not specifically target the removal of oils, making primary pre-aeration the correct choice for oil removal in wastewater treatment.