GATE Civil Engineering (CE) 2015 Shift 1 Solved Paper

Consider a primary sedimentation tank (PST) in a water treatment plant with Surface Overflow Rate (SOR) of 40 m³/m²/d. The diameter of the spherical particle which will have 90 percent theoretical removal efficiency in this tank is _______________ μm. Assume that settling velocity of the particles in water is described by Stokes’s Law.
Given: Density of water = 1000 kg/m³; Density of particle = 2650 kg/m³; g = 9.81 m/s²; Kinematic viscosity of water= 1.1x 10^-6 m²/s