Environmental Engineering Reference
In-Depth Information
the concentration of ammonia vapor 500 m from the accident. Is the con-
centration dangerous to the workers in the plant? The wind speed during
the period was nominal (3 m/s).
6.50 3 Ed Garvey determined that as water flows over hot spots in the Thom-
son Island pool of the Hudson River that its PCB concentration increases
rapidly. Data taken from 1993-1995 showed that the “hot-spot” sedi-
ments were responsible for about 1.5 pounds of PCBs (3 pounds during
the summer) moving into the water column. Because the flesh of most
Hudson River fish exceeds the FDA limit of 2 ppm for PCBs, various fish-
ing bans and advisories are in effect along the river, with children and
women of child-bearing age told to “eat none” (Rivlin, 1998). Use a com-
partmental box model to verify whether or not fish advisories or bans
are warranted. Assume: (a) no PCBs in the air, (b) no PCB upstream of
Thomson Island pool, and (c) fish in equilibrium with the PCBs in water.
The PCB data are evaporation mass transfer coefficient = 5.7 cm/h, log
K oc = 4.5. River data: surface area for evaporation = 2.3 × 10 5 m 2 ,river
flow = 4 × 10 5 L/s.
6.51 2 Benzene ( = 1), chlorobenzene ( = 2), methyl chloride ( = 3), and methane
( = 4)arecombustedinanewincineratordesignedforaresidencetimeof1 s
and a burner temperature of 1200 F. However, during the startup the con-
versionswereall < 20%whichisunacceptable.Asthecontactengineeryou
arepresentedwithtwooptions:(1)extendtheburnerchamber10-fold,thus
increasing the residence time to 10 s; or (2) increase the temperature from
1200to1400 F.Whichoptiongivesthehighestconversions?Whichwould
becheapesttoimplement?Whataretheconsequencesorconcernsofeach?
6.52 2 Heterogeneous reactions on polar stratospheric clouds (PSCs) are respon-
sible for the abnormal destruction of ozone in the Antarctic regions in the
springtime. The following series of reactions are shown to be occurring on
a surface, M:
k 1
−→ Cl 2 O 2 + M
2ClO + M
J 2
h ν
Cl 2 O 2
ClOO + Cl
k 3
−→ Cl + O 2 + M
ClOO + M
2 Cl + O 3
−→ ClO + O 2 .
k 4
ν
−→ 3O 2 . The first step in the above
scheme is the slowest reaction. Justify that d [ O 3 ] / d t =− k 1 [ ClO ]
h
Note that the overall scheme is 2O 3
2
[ M ] ,
10 44 m 6 /s at 190 K (stratospheric temperature).Assume
where k 1 =
8
×
10 24 m 3 and determine the mean concentration of
ClO responsible for the ozone destruction.
6.53 2 The SO 2 (g) from power plant smoke stacks dissolves in a surface cloud
(e.g.,fog)toproduceS(IV).TheresultingS(IV)thenreactswithadissolved
species A (aq) to give S(VI) in a fog droplet. The rate of the reaction is
given by r =− d [ S ( IV ) ] / d t = k [ A ] aq [ S ( IV ) ] aq . Rewrite the above equa-
tion to give the rate in terms of the liquid water content of the fog, θ L (see
an average
[ M ]=
3
×
 
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