1. A food processing plant produces waste with a high level of BOD. Typically they have to aerate their waste onsite before discharging into the nearby stream so as to not deplete all of the oxygen in the natural waterway. An accident occurred and some of their wastewater was released before it was able to be treated. Their wastewater contains a BOD of 200mg/L and they estimate it leaked for several days at a rate of 10m3/min. Assuming the stream has a flow rate of 2m3/s, a velocity of 0.1m/s, and its own BOD of 10mg/L answer the following questions.
a. (10pts)What will be the L0 of the stream in mg/L (i.e. the BOD where the waste and stream mix)?
b. (10pts) What will be the BOD 1km downstream? What will be the BOD 5km downstream? (Deoxygenation rate constant is 0.20/day)
c. (10pts) If your answer from part ‘a’ is the ultimate carbonaceous oxygen demand and the TKN (total Kjeldahl nitrogen) is measured to be 1.78mg/L, what is the nitrogenous oxygen demand and what is the total BOD?
2. Calculate the BOD5 for an unseeded lab sample using a full 300mL BOD bottle containing 20mL of wastewater. The initial dissolved oxygen concentration was 10mg/L. Five days later the DO was measured again and was found to be 4 mg/L. Assume a decay rate of k=0.01/hra. (10pts) What is the BOD5 for this sample?b. (10pts) What is the ultimate carbonaceous oxygen demand (L0)?
3. (30 pts) Create a list of equations from the lectures so far that may be helpful for you on the mid-term. (Label the equations as needed). (For full points you should include all of the equations you have used for the homework and any other equations you think may be helpful).
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