The initial ultimate bod after mixing of the bergelmir river is 12.0 mg · l−1. the do in the bergelmir river after the wastewater and river have mixed is at saturation. the river temperature is 10◦ c. at 10◦ c, the deoxygenation rate constant (kd) is 0.30 day−1 , and the reaeration rate constant (kr) is 0.40 day−1 . determine the critical point (tc) and the critical do. tc = 2.88 days. critical do = 7.53 mg · l−1

the equation above shows how temperature f, measured in degrees fahrenheit, relates to a temperature c, measured in degrees celsius. based on the equation, which of the following must be true?

a temperature increase of 1 degree fahrenheit is equivalent to a temperature increase of

5

9

degree celsius.

a temperature increase of 1 degree celsius is equivalent to a temperature increase of 1.8 degrees fahrenheit.

a temperature increase of

5

9

degree fahrenheit is equivalent to a temperature increase of 1 degree celsius.

a) i only

b) ii only

c) iii only

d) i and ii only

answer: a

a is the answer