GATE Civil Engineering (CE) 2020 Shift 2 Solved Paper

Two identically sized primary settling tanks receive water for Type-I settling (discrete particles in dilute suspension) under laminar flow conditions. The Surface Overflow Rate (SOR) maintained in the two tanks are $30{\mathit{m}}^3/{\mathit{m}}^2.\mathit{d}$ and $15{\mathit{m}}^3/{\mathit{m}}^2.\mathit{d}$. The lowest diameters of the particles, which shall be settled out completely under SORs of $30{\mathit{m}}^3/{\mathit{m}}^2.\mathit{d}$ and 15 ${\mathit{m}}^3/{\mathit{m}}^2/\mathit{d}$ are designated as ${\mathit{d}}_{30}$ and ${\mathit{d}}_{15}$, respectively. The ratio, ${\mathit{d}}_{30}/{\mathit{d}}_{15}$ (round off to two decimal places), is