Q1: In primary sedimentation, the 0.2 mm inorganic solids get separated if specific gravity is

ANS:D - 2.65

A specific gravity of 2.65 indicates that the density of the substance is 2.65 times that of water. In the context of sedimentation, substances with higher specific gravity tend to settle more effectively in water. When we consider primary sedimentation processes in wastewater treatment, the objective is to separate suspended solids from wastewater effectively. These suspended solids include organic and inorganic particles of various sizes and densities. For particles as small as 0.2 mm, which are typically fine inorganic solids, a specific gravity of 2.65 would be suitable for effective separation. This means that the density of these solids is 2.65 times that of water. The sedimentation process relies on gravity to settle out the suspended solids. As the wastewater flows into the sedimentation tank, the velocity of the water decreases, allowing gravity to take effect. Suspended particles, including the inorganic solids with higher specific gravity, settle to the bottom of the tank under the influence of gravity, forming a sludge layer. A specific gravity of 2.65 ensures that the inorganic solids have sufficient density to settle out effectively within the detention time provided by the sedimentation tank. This allows the clear water to be decanted or siphoned off the top of the tank, leaving the settled solids behind. Therefore, a specific gravity of 2.65 would facilitate the separation of 0.2 mm inorganic solids efficiently during primary sedimentation in wastewater treatment.