Question

BOD is naturally consumed in rivers. A stream (flowing at 3 MGD with no BOD) has a point source of pollution (untreated sewage outfall) flowing at 2 MGD that has 300 mg/l of BOD. How will this affect the stream quality? Answer the questions below. You will need to use both mass balance and kinetic equations. Also: stream velocity = distance / time (= 3 miles / hr). Show all work.

Determine the flow rate of the stream downstream of the outfall - My answer is 5 MGH

Determine the BOD concentration of the stream just downstream of the outfall - My answer is 120 Mg/L

Using the data below, determine if the natural rate of BOD consumption is a zero, 1st or 2nd order reaction rate - My answer is 1st order with a line slope of 0.1067.

How much BOD will be left in the stream after it has flowed for 24 hours (assume no more dilution)? Please explain the formal to figure out the answer. Thanks for the help.

Data |
BOD |

t(hr) |
mg/l |

0 |
120 |

5 |
75 |

10 |
40 |

15 |
25 |

Answer #1

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...

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...

Consider a lake that is fed by mix of two streams: one stream
has a flow rate of N m3/s and BOD concentration of 10 mg/L. The
other is a sewage outfall that discharges 0.6 m3/s and a BOD
concentration of 40 mg/L. Assuming the pollution is completely
mixed in the stream, find the resulting BOD concentration

Problem #3: Biochemical Oxygen Demand (BOD) and Stream
Quality
A wastewater
treatment plant designed for a community of 45,000 people has a
flow of 100 gal/person/day and a BOD5 loading of 0.2
lb/person/day. The upstream characteristics of the receiving waters
are:
stream flow rate =
20 cfs and BOD5 = 2 mg/L
The water quality
standards require the in-stream BOD5 to be less than 7
mg/L in this stretch of the river.
The minimum BOD
removal efficiency that the treatment...

A paper mill generates
0.087 m3/s of wastewater which has an ultimate BOD of
720 mg/L. The reaction rate constant at 20 °C was determined to be
6.48 hr-1.
(a) Determine the BOD
exerted in the water after 5 days at 20 °C (units: mg/L)
a) 1066
b) 533
c) 333
d)720
(b) Determine the BOD
exerted in the water after 5 days at 10 °C (units:
mg/L)
a)533
b) 227
c)...

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