What is the method of removing floating grease or scum from the surface of sewage in a tank called?

The correct answer pertains to the specific function of a septic tank. A septic tank is designed to treat sewage by utilizing natural processes of sedimentation and anaerobic digestion. One of the critical functions of a septic tank is to separate solids, liquids, and floating substances such as grease or scum from the sewage. The lighter materials, including grease, rise to the surface and form a layer of scum. This characteristic allows for the easy removal of scum during routine maintenance, ensuring that the tank operates efficiently and that the treatment process remains effective.

The other options listed serve different functions in wastewater treatment. For example, a squeegeeing pond does not specifically address the removal of grease or scum; it refers to a broader method of surface cleaning. Intermittent sand filters are used for filtering wastewater rather than for separating floating substances. An aeration tank is primarily for promoting the aerobic digestion process and does not focus on the removal of floating materials like scum.