A city’s sewage outfall flows 40 ft3 /s of sewage with a BOD concentration of 30 mg/L and a DO of 1.5 mg / L into a small river that has a flow rate of 280 ft3 /s and a velocity of 1.1 ft /s. The river has a natural BOD of 3.5 mg/L and at this time of year the DO level is 7 mg/L. Given the water temperature this time of year the DO saturation is 8.5 mg / L. Given a deoxygenation coefficient of 0.59 day-1 and a rearation coefficient of 0.70 day-1, answer the following: a. what is the basic assumption we make regarded the mixing of waste into the river? b. calculate Do amd Lo just downstream from the outfall c. calculate the tiem and distance when DO is a minimum d. calculate the minimum DO e. Find the DO 10 miles downstream.
A city’s sewage outfall flows 40 ft3
/s of sewage with a BOD concentration of 30 mg/L and
a DO of 1.5 mg / L into a small river that has a flow rate of 280 ft3
/s and a velocity of 1.1 ft /s.
The river has a natural BOD of 3.5 mg/L and at this time of year the DO level is 7 mg/L. Given
the water temperature this time of year the DO saturation is 8.5 mg / L. Given a deoxygenation
coefficient of 0.59 day-1 and a rearation coefficient of 0.70 day-1, answer the following:
a. what is the basic assumption we make regarded the mixing of waste into the river?
b. calculate Do amd Lo just downstream from the outfall
c. calculate the tiem and distance when DO is a minimum
d. calculate the minimum DO
e. Find the DO 10 miles downstream.
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