Question

You are tasked with conducting BOD studies for a waste treatment facility and its discharge to a nearby river. You are told that the facility removes 93% of the BOD in total with a discharge rate of 1.0 m3 /s. you sample the receiving water and find that it has a 0.5 mg/L deficit from saturation concentration (saturation is at 9.7 mg/L) and a BOD5 content of 10 mg/L. The river flows at a speed of 0.25 m/s and has a flow rate of 9.0 m3 /s. The reaeration constant is known to be 0.49 d-1 , and the deoxygenation constant for the river is 0.20 d-1 .

a. In a 5-day BOD test of untreated wastewater in a 300 mL bottle, you measure an initial DO of 9.7 mg/L and a final DO of 3.4 mg/L. If the dilution factor was 0.025, what is the BOD concentration in the influent wastewater?

b. What is the largest volume of treated wastewater that you can use to test the BOD in the effluent, if you must have at least 2.0 mg/L of DO in the bottle after 5 days?

c. Assuming complete and instantaneous mixing, estimate the ultimate BOD of the river just downstream of the outfall.

d. If the stream has a cross-section that is approximately constant, flowing at a fixed speed, estimate the BOD remaining in the stream at a distance of 25 km downstream.

e. Estimate the oxygen deficit in the river just downstream of the outfall (assume the wastewater is aerated to saturation).

f. How far downstream will the DO reach a minimum?

g. What is the largest DO deficit that can be expected in the stream?

Answer #1

[ * First line of the above page which is incomplete:

**Final DO of the BOD bottle = 2 mg/L
(given)**]

You are tasked with conducting BOD studies for a waste treatment
facility and its discharge to a nearby river. You are told that the
facility removes 93% of the BOD in total with a discharge rate of
1.0 m3 /s. you sample the receiving water and find that it has a
0.5 mg/L deficit from saturation concentration (saturation is at
9.7 mg/L) and a BOD5 content of 10 mg/L. The river flows at a speed
of 0.25 m/s and has...

8. A wastewater has a dissolved oxygen concentration of 2.0 mg/L
and a discharge rate of 1.1 m3/s. The river into which it is being
discharged has DO equal to 8.3 mg/L, a flow rate of 1.4 m3/s and a
temperature of 200C. Assuming complete and instantaneous mixing,
estimate the initial dissolved oxygen deficit of the mixture of
wastewater and river water just downstream from the discharge
point. The saturated valued of DO at 200C is 9.1 mg/L.

A waste stream has a dissolved oxygen concentration of 1.5 mg/L,
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is running at 2.2 m3 /s at a saturated DO, a temperature of 12°C,
and an ultimate BOD of 1.6 mg/L.
A) Calculate the mixing (a) temperature and (b) ultimate BOD for
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Find the reaction rate K, for the treated wastewater.
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A wastewater
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stream flow rate =
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The water quality
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A beverage manufacturer has recently commissioned a 500 m3
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A paper mill generates
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(a) Determine the BOD
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a) 1066
b) 533
c) 333
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A wastewater treatment plant disposes of its effluent in a
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What will be the dissolved oxygen concentration in the stream
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What will be the lowest dissolved oxygen concentration as a
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Parameter
Wastewater
Stream
Flow, m3/s
0.2
5.0
Dissolved Oxygen, mg/L
1.0
8.0
Temperature, o C
15.0
20.2
BOD5 at 20oC, mg/L
100
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