A BOD test is run using 100 mL of treated wastewater mixed with 200 mL of pure water. The initial DO of the mix is 9.0 mg/L. After 5 days, the DO is 3.5 mg/L. After a long period of time, the DO is 2.0 mg/L, and it no longer seems to be dropping. Assume nitrification has been inhibited so the only BOD being measured is carbonaceous. Required:
a. What is the five-day BOD of the wastewater?
b. Assuming no nitrification effects, estimate the ultimate carbonaceous BOD.
c. What would be the remaining BOD after five days have elapsed?
d. Estimate the reaction rate constant k (day−1).