Environmental Engineering Reference
In-Depth Information
BOD of the wastewater: 20 mg/L
C
O
2
,w
in the wastewater: 2 mg/L.
Obtain the following: (a) the dissolved oxygen profile in the stream as
a function of distance downstream from the discharge point; (b) the
maximum oxygen deficit and its location; and (c) the concentration of
the waste (BOD) 15 miles downstream of the discharge point (outfall).
De-oxygenation coefficient,
k
d
is 0.2 d
−
1
.
6.20
2
Consider the University lake system in Baton Rouge, Louisiana, which has
a potential water quality problem resulting from waste discharged into the
nearby Crest Lake. From the following data determine what nutrient level
(phosphorus) is to be expected at steady state in the Crest Lake, which is
a completely mixed unstratified system.
Mean depth: 1.5 m
Surface area: 3.4
×
10
4
m
2
Mean settling velocity: 10 m/y
Mean detention time: 561 d
Phosphorus concentration in the waste: 10 mg/L.
Assume no losses due to volatilization or other reactions of P in the lake.
What reduction in discharge level should be accomplished so that the P
concentration is reduced to
<
0.2 mg/L at which no fish kills are observed
in the lake?
6.21
3
Consideratwo-levelsystemcomprisingthebasefoodchainphytoplankton
that forms the food for a fish. They are both exposed to a pollutant (a
PCB) in the aqueous phase. Consider the fish population to be in two age
classes: 0-3 years and 4-6 years. Using the data given below, obtain a plot
of PCB concentration in the fish at steady state as a function of the age
(year).
Age Class
Parameter
0-3 Years
4-6 Years
μ
i
(d
−
1
)
Growth rate,
0.002
0.0005
W
γ
e
ρ
t
Respiration rate:
R
= β
e
vu
(g/g d)
β =
0.05
γ =−
0.2
ρ =
0
◦
C
−
1
ν =
0.01 s/cm
Swim speed,
u
(cm/s):
ω
W
δ
e
φ
T
ω =
1
δ =
0.1
φ =
0EC
−
1
Food assimilation efficiency 0.8
PCB assimilation efficiency 0.35
K
B
(
μ
g/kg/
μ
g/L) 4
×
10
5
Dissolved PCB concentration (ng/L) 5
Weight of fish (g)
0.5
3
Lipid fraction (kg lipid/kg weight)
0.1
0.1
6.22
2
Determinethehalf-lifeand90%removaltimeforthefollowingcompounds
from a well-mixed lake surface water: (a) pyrene, (b) 1,2-dichloroethane,
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