Final answer:
Primary (physical) treatment is used to remove floating fats, oils, greases, and settleable inorganic and organic material during wastewater treatment.
Step-by-step explanation:
The type of treatment used to remove floating fats, oils, greases, and settleable inorganic and organic material during wastewater treatment is primary (physical) treatment. During this stage, wastewater is stored in a basin where settleable solids can sink to the bottom and lighter substances such as fats, oils, and greases can rise to the top. These layers are then removed before the remaining liquid is sent to secondary treatment. Specialized structures, often referred to as sedimentation tanks or primary clarifiers, facilitate this process by allowing enough retention time for separation to occur. The covering is composed of lighter materials, such as grease and oil, is skimmed from the surface, and the sludge consisting of heavier solids settles at the bottom and is subsequently pumped out.
Secondary treatment follows, which removes dissolved and suspended biological matter, predominantly through the action of aerobic bacteria. Tertiary treatment may be applied afterwards for further purification, especially if the water is being discharged into a sensitive ecosystem or used for specific applications.