CEE 2300 – Environmental Engineering Principles
S08
1
Assignment 3 Solution
Due Date: Monday, February 25
Total Points: 100
Instructions
(20 pts)
:
You may work alone or in groups to complete the homework assignments,
but you should solve each problem yourself and turn in individual solutions. If you do work in
groups, write the names of the people you worked with at the top of the homework set.
Homework solutions are due at the start of class.
Problem 1
(5 pts)
.
Davis and Masten 51. Occupational hexavalent chromium exposure, Cr(VI)
Given:
concentration = 0.05 mg/m
3
in air; exposure: 8 h/d, 5 d/wk, 50 wk/yr, ages 18 to 65
Solution:
Exposure = (6518) = 47 years
Inhalation rate = 20 m
3
/day
Using the inhalation form of the equation in Table 58 (eq. 515)
CDI = (0.05 mg/m
3
) (20 m
3
/day) / (70 kg) x {(8x5x50x47 hr) / (70x365x24 hr)}
CDI = 0.0022 mg/kg/day
Problem 2
(5 pts)
.
Davis and Masten 57. Hexavalent chromium risk
Given:
concentration = 0.05 mg/m
3
in air; exposure: 8 h/d, 5 d/wk, 50 wk/yr, ages 18 to 65
Solution:
Slope factor for Cr(VI) from Table 55: 42 kg·day/mg
From Problem 51: CDI = 0.0022 mg/kg/day
Risk = (0.0022 mg/kg/day) (42 kg·day/mg) = 0.0924
Problem 3
(5 pts)
.
An epidemiologic study yields the results shown in the 2x2 table below. Do
the data support a positive association between the contaminant and the disease? Justify your
answer with a risk ratio.
With
disease
Without
disease
Exposed
121
225,000
Unexposed
320
775,000
RR = (121/225,121) / (320/775,320) = 1.3
> 1
Yes, data support a positive association between exposure to contaminant and disease
Problem 4
(5 pts)
.
Davis and Masten 712. World consumption rate of coal in 1991
Given:
world coal reserve will last 200 years
Solution:
Table 74: world coal reserves in 1998 = 25,700 EJ
Annual demand = 25,700 EJ / 200 years = 128.5 EJ/yr
(32% of current total demand)
Better: annual demand = 25,700 EJ / 193 years = 133.2 EJ/yr
(assuming an average coal heating value of 27.15 MJ/kg, 4733 Mt coal/yr)
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S08
2
Problem 5
(5 pts)
.
Davis and Masten 713. Coal exhaustion with improved efficiency
Given:
coal power plant at 33% efficiency, raise efficiency to 40%
Solution:
From Problem 712: annual consumption rate at 33% efficiency = 128.5 EJ/yr
Consumption rate at 40% efficiency = 128.5 EJ/yr x 0.33/0.40 = 106 EJ/yr
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 Spring '08
 SPAIN
 Coal, Fossil fuel power station, Environmental Engineering Principles, Engineering Principles S08

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