Q1: Removal of oil and grease from sewage, is known

ANS:B - skimming

Removal of oil and grease from sewage is known as skimming. Skimming is a common method used in wastewater treatment to remove oil and grease from sewage. It involves the use of skimmers or oil-water separators, which are devices designed to separate oil and grease from water. These devices utilize the differences in density and surface tension between oil, grease, and water to effectively separate them. During the skimming process, the oil and grease, which tend to float on the surface of the water, are physically skimmed off or collected using mechanical skimming mechanisms. This allows for the removal of oil and grease before the wastewater undergoes further treatment processes, preventing potential clogging of pipes, damage to equipment, and adverse environmental impacts. Therefore, the correct term for the removal of oil and grease from sewage is skimming.