Which of the following is the process of removing oil and grease from sewage in a wastewater treatment plant?

The correct answer is "Skimming." In a wastewater treatment plant, the process of removing oil and grease from sewage is called skimming. Skimming is a physical process that removes floatable solids and liquids, such as oil and grease, from the surface of the wastewater. Skimming is usually the first step in the treatment process, and it is followed by other processes, such as aeration, filtration, and disinfection.

After skimming, the wastewater is sent to the aeration tank, where aerobic bacteria break down some of the contaminants. In the aeration tank, oxygen is added to the wastewater to support the growth of bacteria, which help to break down organic matter.

Filtration is the process of passing the wastewater through a filter to remove suspended particles, while screening involves the use of a mechanical screen to remove large solids such as sticks, rags, and plastic from the wastewater. These processes are used to further treat the wastewater after skimming and aeration.