- Wastewater of 30ft3/s with a biochemical oxygendemand (BOD) of 55mg/l, and dissolved oxygen (DO) of 3.3mg/l entersa river where the flow is 125ft3/s with an ultimate BODof 7.0 mg/l, and DO of 6.8mg/l. The downstream has an averagevelocity of 0.8ft/s.
i          Calculate the minimum DO level and its distance in miles downstreamusing the oxygen sag equation. Assume k1 = 0.046 per dayand k2 = 0.304 per day. The saturation DO = 8.5mg/l. (1mile = 5280ft)
ii         At whatdistance downstream would the DO level of the river be equal to6.10 mg/l?
iii     Howmuch should the wastewater DO be increased to maintain a minimum DOof 4.8mg/l anywhere along the river. Assuming that the BOD of thewastewater and the river flow remains the same?
