Determine the required reactor volume, in million gallons (MG), for a completely mixed, aerobic, activated sludge system which will treat 1 MGD of domestic wastewater. The waste water has an initial ultimate BOD of 200 mg/L. The effluent requirement is 10 mg/L of ultimate BOD. The first order degradation rate constant is K = 0.1 L/mg-day, i. e. the governing equation is q = KSe for calculating the specific substrate utilization rate (q) through kinetic parameters. Se is the effluent ultimate BOD (i. e. 10 mg/L). The mixed liquor volatile suspended solids (X) equals 3,000 mg/L. What is the reactor volume? a. 0.095 MG
b. 0.063 MG
c. 0.92 MG
d. 0.13 MG

Acommercial grade cubical freezer, 4 m on a side, has a composite wall consisting of an exterior sheet of 5.0-mm thick plain carbon steel (kst= 60.5 w/m k), an intermediate layer of 100-mm thick polyurethane insulation (kins 0.02 w/m k), and an inner sheet of 5.0- mm thick aluminium alloy (kal polyurethane insulation and both metallic sheets are each characterized by a thermal contact resistance of r 2.5 x 104 m2 k/w. (a) what is the steady-state cooling load that must be maintained by the refrigerator under conditions for which the outer and inner surface temperatures are 25°c and -5°c, respectively? (b) for power saving purpose, which wall material should be increased/reduced in. thickness in order to reduce 50% of the cooling load found in part (a)? redesign the thickness of the proposed material. 177 w/m-k). adhesive interfaces between the q=575.93 w