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Develop an Excel spreadsheet that solves your mass balance model using Solver (picture of spreadsheet and explanation needed). Your model should give the substrate level (in mg BOD/L) and the biomass level (in mg VSS/L) at all key points around the circuit, as well as the required digester volume (in m^3), and the hydraulic and solids retention times (in days). Solving your model will require you to determine (or set) values for the circuit parameters alpha, beta. They determine the recycle activated sludge flowrate or RAS (ie alpha Q where Q is the feed flowrate to the circuit) and the wasted activated sludge flowrate or WAS (ie beta Q). Explain clearly your reasons for the values of alpha and beta chosen. Biomass balance: QX_0 + alpha QX_r = (1 + alpha) QX_m Substrate balance: QS_0 + alpha QS_r = (1 + alpha) QS_m Y (S_m - S_a) (1 + alpha) Q = r_x V Biomass balance: (1 + alpha) QX_m + r_x V = (1 + alpha) QX_a Substrate balance: (1 + alpha) QS_m - r_s V = (1 + alpha) QS_a Biomass balance: (1 + alpha) QXa = (alpha + beta) QX_r + (1- beta) QX_r + (1 - beta) QXe r_x V = (1 - beta) QX_e + beta QX_r r_x = 0.18 (S_a/100 +S_a) X_a - 0.0025 X_a Y = 0.6 = r_x/r_s gamma = X_r (alpha + beta) Q/X_a (1 + alpha) Q V = HRT times Q F:M = S_m (1 + alpha) Q/VX_a. SRT = (X_a V)/[beta Q X_r + (1 - beta) QX_e] Assume influent flow rate Q = 700 m^3/day, substrate loading 450mg/L. Perfect clarifier, gamma = 1. X_e=0. S_b = S_e = S_r = 5 mg/L. The substrate level in the effluent are strictly set as 5 mg/L as regulation required. Hydraulic retention time is between 4 hours to 24 hours Sludge retention time is in range of 4 to 24 days. F:M ratio is in range of 0.1 -0.5