1.a completely mixed activated sludge plant is to treat 10,000 m^3\day.the wastwater has a BOD5 of 1200 mg\liter that must be reduced to 200 mg\liter.if the mean cell residence time 5 days and suspended solids concentration of 5000 mg\liter and Y 0.7 kg\kg and kd 0.03 \day determine sludge recycle ratio R?
2.A steel rod of 1/8 inch diameter is bent into a loop 10 feet in diameter. Determine the maximum flexural stress in the rod
3.Determine the allowable moment about the horizontal neutral axis that a timber beam with nominal size 50 X 100 can resist without exceeding the allowable stress of 10 MPa. The dressed size is 38.1 X 88.9 mm, I = 0.00000223m^4, and S = 0.0000502 m^3.
Please show all steps and work.