Two identical complete-mix activated sludge units are connected in series; one-half of the sludge recycle flow rate, QR, is recycled to the primary effluent pipeline which handles a flow rate Q, and the other half is recycled to the effluent line from the first tank. The total flow from the primary settling tank (QT = Q + QR/2) is split into two streams, each one of which entering each tank. The following is a plant schematic. Find the rate of biological growth, rg (mg VSS/L.d), in each reactor.
Use the following design parameters: Q = 3.785 x 106 L/d; QR = 7.57 x 105 L/d; XR= 8000 mg VSS/L; X= 3000 mg VSS/L; V = 3785 m3.