CEE 330 Homework #1
Problem 1. (a) During drinking water treatment, 17 lb. of chlorine (Cl) are added daily to
disinfect 5 million gallons of water. What is the aqueous concentration of chlorine in mg/L? (b)
The chlorine demand is the concentration of chlorine used during disinfection. The chlorine
residual is the concentration of chlorine that remains after treatment so the water maintains its
disinfecting power in the distribution system. If the residual concentration is 0.20 mg/L, what is
the chlorine demand in mg/L?
Solution:
a) 17 lb. chlorine added to 5 million gallons of water. Chlorine dosage in mg/L:
17 lb / day
454 g 1000 mg 1 gal



 0.41 mg / L
6
5  10 gal / day 1 lb
1g
3.78 L
b) Chlorine demand:
0.41 mg / L  0.20 mg / L  0.21 mg / L
Problem 2. Coliform bacteria (for example, E. coli) are excreted in large numbers in human and
animal feces. Water that meets a standard of less than one coliform per 100 mL is considered
safe for human consumption. Is a 1 L water sample that contains 9 coliforms safe for human
consumption?
Solution
Standard requires < 1 coliform/100 mL, or 10 coliform/1 L
9 coliforms
L

 0.9 coliforms / 100 mL
L
10 coliforms (100 mL)
This value is < 1 coliform/100 mL; therefore, water is safe.
Problem 3. What is the concentration in (a) ppmv, and (b) percent by volume, of carbon
monoxide (CO) with a concentration of 103 µg/m3? Assume a temperature of 25°C and pressure
of 1 atm.
Solution:
a)
R = 0.08205 L-atm/mole-oK.
g RT
1


106  ppmv
3
m
P MW
3

5 m  atm 
 8.205 10
  (298 K )
mole  K 
103  g 106 g 
1



106 
3
m
g
1atm
28 g / mole
 8.9 102 ppm
1
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b)
[CO] 
8.9  102 mg
 100 %  0.0000089 %
106 mg
Problem 3 (2.13 from e-book)
Mirex (MW = 540) is a fully chlorinated organic pesticide that was manufactured to control fire
ants. Due to its structure, mirex is very unreactive; thus, it persists in the environment. Lake Erie
water samples have had mirex measured as high as 0.002 µg/L and lake trout samples with 0.002
µg/g. (a) In the water samples, what is the aqueous concentration of mirex in units of (i) ppbm,
(ii) pptm, (iii) µM? (b) In the fish samples, what is the concentration of mirex in fish in (i) ppmm,
(ii) ppbm?
Solution:
a)
i)
0.002  g
1 mg
1 L 1000 million



 0.002 ppb
L
1000  g 1 kg
1 billion
ii)
0.002  g
1 mg
1 L 1, 000, 000 million



 2 ppt
L
1000  g 1 kg
trillion
iii)
0.002  g 1 mole

 3.7  106  M
L
540 g
b)
i)
0.002  g
 0.002 ppm
g
ii)
In solids, ppb = g/kg
0.002  g 1000 million

 2 ppb
g
1 billion
Problem 4. Formaldehyde is commonly found in the indoor air of improperly designed and
constructed buildings. If the concentration of formaldehyde in a home is 0.7 ppmv and the inside
volume is 800 m3, what mass (in grams) of formaldehyde vapor is inside the home? Assume T =
298 K, P = 1 atm. The molecular weight of formaldehyde is 30.
Solution:
2
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g
P
 g 
6
 ppmv 
 MW 
  10 
3
m
RT
 mole 
g 

0.7 ppmv   30
 1 atm
g
mole 


106 
3
3
m

5 m  atm 
 8.205 10
  298 K
mole  K 

 858.9 106
g 106  g
g

 858.9 3
3
m
g
m
The mass of formaldehyde equals
858.9  g
g
 800 m3  6
 0.7 g
3
m
10  g
Problem 5 (first edition). Polycyclic aromatic hydrocarbons (PAHs) are a class of organic
chemicals associated with the combustion of fossil fuels. Undeveloped areas may have total
PAH soil concentrations of 5 µg/kg, while urban areas may have soil concentrations that range
from 600 µg/kg to 3,000 µg/ kg. What is the concentration of PAHs in undeveloped areas in
units of ppmm?
Solution:
In soil mg/kg = ppm
5
g
kg

1 mg
 5  103 mg / kg
1000  g
Problem 5 (e-book).
Ice resurfacing machines use internal combustion engines that give off exhaust containing CO
and NOx. Average CO concentrations measured in local ice rinks have been reported to be as
high as 107 ppmv and as low as 36 ppmv. How do these concentrations compare to an outdoorair-quality 1-h standard of 35 mg/m3? Assume the temperature equals 20°C.
Solution:
Convert the regulatory standard to ppmv and compare to stated values.
35 mg/m3 x 103 g/mg = 35,000 g/m3
3
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g  
L 

ppmv   28.0
  1000 3   1 atm 
mole  
m 

35, 000  g / m3 
L  atm 

 0.08205
  (293 K )
mole  K 

ppmv = 30; therefore, both are above the standard
Problem 6 (first edition).
In 2004, U.S. landfills emitted approximately 6,709 Gg of methane emissions and wastewater
treatment plants emitted 1,758 Gg of methane. How many Tg of CO2 equivalents did landfills
and wastewater plants emit in 2004? What percent of the total 2004 methane emissions (and
greenhouse gas emissions) do these two sources contribute (total methane emissions in 2004
were 556.7 Tg CO2e and total greenhouse gas emissions in 2004 were 7,074.4 TgCO2e).
Solution:
Tg
 167.7 Tg CO2e from landfills
1000 Gg
Tg
Tg CO2e  1758 Gg CH 4  25 
 43.95 Tg CO2e from WWTP
1000 Gg
Total CO2 e from both  167.7  43.95  211.65 Tg
Tg CO2e  6709 Gg CH 4  25 
% of total CH 4 emissions 
211.65 Tg
100%  38%
556.7 Tg
% of total greenhouse emissions 
211.65 Tg
100%  3%
7074.4 Tg
Note that if your book only asked for contribution from landfill only
167.7 Tg
% of total CH 4 emissions 
100%  30.1%
556.7 Tg
% of total greenhouse emissions 
167.7 Tg
100%  2.3%
7074.4 Tg
4
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Problem 6 (e-book).
2.25 The National Ambient Air Quality Standard (NAAQS) for sulfur dioxide (SO2) is 0.14
ppmv (24-hr average). (a) What is the concentration in µg/m3 assuming an air temperature of
25o C? (b) What is the concentration in moles SO2 per 106 moles of air?
Solution:
We actually need to calculate part b first before part a:
b) 0.14𝑝𝑝𝑚𝑣 = 0.14 𝑚3 SO2 /106 𝑚3 air solution × 1 𝑎𝑡𝑚 /(8.205 × 10−5 𝑚3 𝑎𝑡𝑚 /(𝑚𝑜𝑙𝑒 𝐾) ×
(25 + 273)K )= 𝟔. 𝟎 × 𝟏𝟎−𝟔 𝒎𝒐𝒍𝒆 𝐒𝐎𝟐 /𝟏𝟎𝟔 𝒎𝟑 𝐚𝐢𝐫
a) 6.0 × 10−6 𝑚𝑜𝑙𝑒 SO2 /106 𝑚𝑜𝑙𝑒 air × 64 𝑔SO2 / 𝑚𝑜𝑙𝑒 SO2 × 10 −6𝜇𝑔/ 𝑔 = 𝟑𝟖𝟒 𝝁𝒈/ 𝒎
Problem 7 (first edition).
The Department of Environmental Quality has determined that toxaphene concentrations in soil
that exceed 60 µg/kg can pose a threat to underlying groundwater. If a 100-g sample of soil
contains 10-5 g of toxaphene, what are the toxaphene soil and regulatory action level
concentrations reported in units of ppbm?
Solution:
a) In soil, ppb = g/kg
60
g
kg
 60 ppb
105 g toxaphene 1000 g 106  g
g


 100
 100 ppb
100 g  soil
1 kg
g
kg
Problem 7 (e-book).
What is the concentration in (a) ppmv, and (b) percent by volume, of carbon monoxide (CO) with
a concentration of 103 µg/m3? Assume a temperature of 25°C and pressure of 1 atm.
Solution:
a)
R = 0.08205 L-atm/mole-oK.
g  
L 

ppm   28.0
 1000 3   1 atm 

103  g CO
mole  
m 


 8.9  102 ppm
3
L  atm 
m

 0.08205
  (298 K )
mole  K 

b)
8.9  102 mg
[CO] 
 100 %  0.0000089 %
106 mg
5
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