March 11, 1996
Each problem is worth 20 points.
1.The ultimate BOD (BODU) of a wastewater is 300 mg/L; K=0.25 days-1 at 20 C.
2. Two input streams are joined in a mixing box as shown below:
What is the flowrate of stream 2 if the output concentration (Cout) = 150 mg/L?
3. For the same situation as problem three, what would Cout be if conversion occurred in the mixing box and C were converted to a product? Assume that a first order reaction is applicable (with K = 0.25 hrs-1), that the reactor is completely mixed, and the reactor retention time is 2 hours.
4. Sketch an oxygen-sag curve and label Do, Dc, DOmin and td. Also indicate on the curve:
5. Short Answers