CEE 370

Spring 1996


Exam #1


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.

    1. What is the 5-day BOD at 20 C?
    2. How much oxygen is utilized between the end of day 2 and day 4 (20 C)?
    3. What is the 5-day BOD if the temperature were 25 C?
    4. What is the ultimate BOD if the temperature were 25 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

    1. What is meant by the indicator organism concept (e.g., coliform organisms)?
    2. Why (under what circumstances) would nutrients (N and P) be a water quality concern?
    3. What is vector transmission?
    4. What are chemosynthesis and photosynthesis?