Problem 4 (30 points): The Blue Ox Tannery has asked you to assist them in preparations to file for a NPDES permit to discharge wastewater into the Zmellsbad River. The water quality criterion for Zmellsbad River is 5.00 mg/L of DO. They have you the following questions: What is the critical DO and where does it occur downstream? [Use Saturation DO concentration as 10.15 mg/L] Parameter Blue Ox wastewater Zmellsbad River Flow, m3/s 1.5 6.5 BOD5 at 15 C, mg/L 85 N/A Ultimate BOD at 15 C, mg/L N/A 7.66 DO, mg/L 1.00 6.00 Temperature, C 15 15 k at 20 C, d-1 0.3 N/A Speed, m/s N/A 0.3 Depth, m N/A 3.5 Bed-activity coefficient N/A 0.300