Lafayette College
Department of Civil and Environmental Engineering
CE 425: Water Supply and Pollution Control
Spring 2007
Homework #3
Due Date: Wednesday, 10/17/07
1) Design Considerations for a Water Treatment or Wastewater Treatment Plant.
a) Name at least eight participates that would be considered essential in the design
process.
b) Provide three reasons that would help justify a 20-year design period vs. a 30year design period for a typical WWTP or WTP.
c) In the predesign phase design standards are established; name 10 important
considerations.
d) Name at least eight non-industry wastewater sources that could impact the
design. Provide a brief explanation detailing the impact of each non-industry
consideration.
2) Define the following terms
a) Septage
b) Septic
c) Septic Tank
d) Sewage
e) Sewer
f) Sewerage
3) Show the typical path (draw sketches - plan view) of a drop of water through:
a) A water treatment plant.
b) A wastewater treatment plant.
c) Briefly discuss the various processes involved.
d) What do you think would happen to the contaminate perchlorate (OCl4-) in a
water treatment plant and why? (i.e., describe the fate and transport of
perchlorate)
4) Find a maximum reservoir storage requirement if a uniform draft of 726,000 gpd/mi 2
from a specific stream is to be maintained. Perform both a graphical and tabular
analysis. Explain any differences in your final storage requirement between the two
methods. The following record of average monthly runoff values is given:
Mo*
A
M
J
J
A
S
O
N
D
J
F
M
A
M
J
RO** 97 136 59 14
6
5
3
7
19 13 74 96 37 63 49
*
MO = Month
** RO = Runoff (mgal/mi2)
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5) Problem 4.2 - Reynolds/Richards (Note: since the data for Part a is limited, consider
the population increase based on a ratio of the years that are available)
6) A community has experienced the growth in population and water use shown.
Estimate the population per capita water use, and total average daily water demand
in the year 2010.
Year
1950
1960
1970
1980
1990
Population
8,000
8,990
11,300
14,600
18,400
3
Average daily flow, m
2,270
2,720
3,630
4,790
6,600
7) Discuss how you would go about collecting data for an analysis of the water budget
of a region. What agencies would you contact? What other sources of information
would you seek out?
8) A community has a population of 200,000 in 1995 and it is expected that this will
increase to 260,00 by 2010. The water treatment capacity in 1995 was 43 mgd. A
survey showed that the average per capita water use rate was 180 gpcd. Estimate
the community’s water requirements in 2010 assuming (a) no change in use rate
and (b) a reduced rate of 160 gpcd. Will expanded treatment facilities be needed by
2010 for condition (a)? For condition (b)?
9) A population of spotted wolves lives on the mountain Hesperides. There were 26
wolves in the year 2054 and 54 wolves counted in 2079. Assuming exponential
growth, what is the net growth rate constant?
10) For Problem 9, what will be the population of wolves in 2102?
11) Using the data presented in Problem 9, the Derived Logistic S Method, a net growth
rate of 0.04 year-1 and a carrying capacity of 159, what will be the predicted
population of wolves in the year 2102?
12) Using the General Logistic S Method and the Declining Rate of Growth Method
determine the population in the year 2180 using the data on the following page.
Provide comment on each method. SHOW ALL WORK!
2
Year
1900
1910
1920
1930
1940
1950
1960
1970
1980
1990
2000
2010
2020
2030
2040
2050
2060
2070
2080
2090
2100
Population
50000
55000
60000
70000
85000
105000
120000
150000
180000
230000
280000
330000
390000
460000
540000
640000
760000
860000
950000
1030000
1100000
3