Unlock document.
This document is partially blurred.
Unlock all pages and 1 million more documents.
Get Access
28. From Fig. 2.37, the Earth’s surface receives wavelengths of 0.3 mm
(300 nm) and above. Thus, only aniline will absorb sunlight and
potentially degrade by direct photodegradation; the anilinium ion
will not. A water treatment scheme using sunlight should therefore
favor the aniline form. From the acid-base reaction provided:
29. a. To calculate the maximum concentrations of Na
þ
and metham
downstream of the spill, the velocity of the Sacramento River must
be estimated from data on its discharge rate and average geometry:
Then, travel times to Dunsmuir and Shasta Lake can be
estimated:
e39CHAPTER 2 SOLUTIONS
At the town of Dunsmuir, the maximum concentration of Na
þ
will be:
At the point where the Sacramento River reaches Shasta Lake,
the maximum concentration of Na
þ
will be:
Metham concentration
Metham degrades by both acid and neutral hydrolysis
and by photolysis. To use Eq. (2.12), a combined, first-order
decay rate must first be estimated for these degradation
processes:
e40 SOLUTIONS MANUAL ONLINE
Using Eq. (2.12) and the results of the mass calculation performed
above (initial [Na
þ
]/m
2
equals initial [metham]/m
2
):
b. The effect of longitudinal dispersion can be seen from the
attenuation of the Na
þ
peak concentration between Dunsmuir and
Shasta Lake:
For hydrolysis of metham, the first-order decay rate is:
Peak attenuation due to hydrolysis alone can then be estimated
as:
e41CHAPTER 2 SOLUTIONS
Dunsmuir to Shasta Lake.
c. Using Eq. (1.21), the half-life for hydrolysis is:
d. The total load of metham depends on the total mass of metham in
the river, which is affected only by degradation reactions, not by
0:92 0:18 ¼0:16
Note that this is equivalent to summing the decay constants for
the two processes:
e42 SOLUTIONS MANUAL ONLINE
Shasta Lake.
One might ask whether metham at the tailing edge of the plume
has significantly more time to degrade than metham at the leading
edge of the plume. To determine this, consider how much the
metham plume has spread by the time it arrives at Shasta Lake.
From Eq. (2.7):
30. a. Using the Deffeyes diagram in Fig. 2.20, follow a vertical line from
C
of 410
4
mol/liter to where it intersects with a horizontal line
e43CHAPTER 2 SOLUTIONS
31. a. To estimate the reaeration coefficient, assume that the surface
renewal model is applicable to gas exchange in the stream. Then
the gas exchange coefficient for oxygen can be estimated from the
relationships:
b. Given the dimensionless Henry’s law constant of 0.02, resistance to
gas exchange in the stagnant air layer immediately above the water
c. First estimate the overall pseudo-first-order rate constant k
T
at the
stream pH of 8.5:
e44 SOLUTIONS MANUAL ONLINE
d. If volatilization is also considered as a loss mechanism, the overall
loss rate can be estimated as:
32. a. First estimate the river’s velocity using the Che
´zy-Manning
equation. For SI units, use Eq. (2.2b).
Using Eq. (2.4):
c. 95% of the chemical mass is contained within the portion of the
river lying within two standard deviations upstream and two
d. To estimate the reaeration coefficient, first estimate the rate at
which propane is being lost due to gas exchange with the
e45CHAPTER 2 SOLUTIONS
Assuming the surface renewal model is applicable, the
reaeration coefficient can be estimated as:
e. Equation (2.14) can be used to estimate the length of the transverse
mixing zone. To estimate the transverse dispersion coefficient,
assume that the uniform small river is a straight channel, and
therefore Eq. (2.16a) applies:
33. a. Under these conditions, the TCE is a pure phase liquid. First
estimate the TCE concentration just above the surface of the
e46 SOLUTIONS MANUAL ONLINE
Using Eq. (2.36) (or, alternatively, Eq. 2.35) to estimate the gas
exchange coefficient for air-side control:
b. Once the rain covers the TCE, the volatilization of TCE will be
controlled by the water side. Equation (2.34) can be used to
estimate the gas exchange coefficient:
34. a. First estimate the toluene concentration in the stream at the location
of the seep:
Use the stream depth to convert to a first-order loss coefficient:
e47CHAPTER 2 SOLUTIONS
Then use Eq. (1.20) to estimate the concentration of toluene at
point B:
b. Now consider that the chemical seeping from the ground is the
methyl ester of dichloroacetic acid. Neglecting volatilization and
acid-catalyzed hydrolysis, a pseudo-first-order loss rate can be
estimated based on neutral and base-catalyzed hydrolysis rates
and the stream pH:
35. a. First estimate the travel time to the municipal waterworks, using
Eq. (2.3a):
Then use Eq. (2.12) to estimate the maximum concentration
expected at the waterworks:
b. At the time of the peak organism concentration at the intake pipe,
the standard deviation of the cloud of organisms can be estimated
from Eq. (2.7):
c. If the organisms have a 10-hr half-life in the river, the maximum
concentration will be slightly decreased. First use Eq. (1.21) to
convert the half-life to a first-order decay rate:
e48 SOLUTIONS MANUAL ONLINE
m3
36.
a. At a peof 7 and a pH of 4.5:
b. Under sulfidic conditions, peis on the order of 4 (Fig. 2.28).
Therefore:
Pu
is the dominant plutonium species.
c. From Fig. 2.28, aerated water has a peon the order of 14. Therefore:
37. a. Given the Alk of 0.2 meq/liter and the pH of 7, use the Deffeyes
b. To estimate the pH of the wastewater after the organic matter has
been fully mineralized, the new C
T
and the new Alk must first be
e49CHAPTER 2 SOLUTIONS
b. When 510
5
mol HCl is added to the one liter sample, the
alkalinity decreases (see Eq. 2.41):
39. a. The benzene flux to the atmosphere will be controlled by the water
side. Assuming the thin film model applies to the pond, the gas
exchange coefficient for benzene can be estimated using Eq. (2.32):
b. Assuming volatilization is the only loss process for benzene in the
pond, Eq. (1.20) can be used to estimate the benzene concentration
e50 SOLUTIONS MANUAL ONLINE
Dividing both sides by volume and recognizing that (mass
benzene
/
volume) equals C
benzene
and (area/volume) equals (1/depth):
40. a. H2CO3
½þHCO3
½þCO32
¼0:001 mol=liter
From Eqs. (2.43) and (2.44):
b. Use Eq. (2.42) to determine if the lake is in equilibrium with the
atmosphere:
e51CHAPTER 2 SOLUTIONS
c. The reaction for calcium carbonate can be written as:
41. Assuming there has been no disturbance, the deepest sediments are
the oldest. PCB deposition began when the sediment now located at a
25 cm depth was first deposited.
42. a. If methane production is to begin immediately after the bioreactor
is filled, there must not be any other more energetically favorable
b. The first bubbles will consist of approximately 0.8 atm N
2
and
0.2 atm CH
4
, assuming total pressure of 1 atm in the bioreactor.
Use Eq. (1.25) to convert the partial pressure of CH
4
to a gas phase
concentration:
e52 SOLUTIONS MANUAL ONLINE
