Question

If the diameter of particles entering the basin is 1.5 ?m, and the number of particles, N0, is 107 /mL, what is N, or the number of particles leaving the flocculation basin. Assume a = 0.9, Q = 0.8 MGD, power is 195 kW, and ?floc basin is 1 hr.

Answer 1

Given data: Diameter of the particles entering the basin, d = 1.5mu m Number of particles, N_0 = 10^7/mL Collision efficiency factor, a = 0.9 Discharge, Q = 0.8MGD Power, P = 195kW Detention time, t = 1hr Assumed date: Dynamic viscosity of water, mu = 0.00145kg/m-s State the conversion factor 1MGD = 0.0438m^3/s Calculate the volume of tank. V = Q times t Substitute the values. V = (0.8times 0.0438) times (3600) = 126.144m^3 Calculate the velocity gradient G = squareroot P/mu V Substitute the values G = squareroot 195times 10^3/(0.00145)(126.144) = 1032.52 s^-1 Calculate the floc volume concentration. Ohm = pi d^3N_0/6 Substitute the values. Ohm = pi times(1.5times 10^-6)(10^7)(10^6)/6 = 1.767times 10^-5 Consider the mass balance equation QN_0 = QN+a4Ohm GVN/pi N_0/N = 1+a4Ohm GV/pi Q Substitute the values N_0/N = 1+4(1.767times 10^-5)(0.9)(1032.52)(126.144)/pi (0.8times 0.0438) 10^7/N = 76.264 N = 1.311times 10^5/mL Hence, the number of particles leaving the flocculation basin is[1.311times 10^5 m/L]