This can be entered in the lower
To have easier numbers to work with
invert elevation column in row 16.
297.6 will be used.
This is entered
The upper invert elevation must be at
in the upper invert elevation column.
least 2 feet 4 inches below the
Using the invert elevation gives a
building elevation.
slope of 10.4 percent.
The results
are tabulated in row 16.
Invert
at
Bldg
D
=
300
-
2.33
=
297.67
EXERCISES
First requirement.
Multiple-choice
6. Trickling filters, used for
exercises 1 through 3 deal with the
secondary
treatment
of
sewage,
characteristics of sewage.
should have a 5- to 8-foot deep
layer of uniformly crushed stone
1. Which type of sewage is a
for best results.
The amount of
sewage collection system primarily
stone is determined by assuming a
designed for in the TO?
requirement of how many cubic yards
a. sanitary
c. storm
per capita?
b. industrial
d. infiltration
a. 0.15
c. 0.30
b. 0.23
d. 0.35
2. What percentage of sewage is
normally solid matter?
7. In the complete treatment of
a. 0.2
c. 1.4
sewage, what is the most common
b. 0.8
d. 2.1
method of effluent disposal?
a. dilution
c. irrigation
3. Biochemical
oxygen
demand
b. evaporation
d. drying
(BOD) is a measure of what, when
applied to sewage?
Third requirement.
Solve multiple-
a. composition
c. strength
choice exercises 8 and 9 to test your
b. volume
d. type
understanding
of
sewage
collection
systems.
Second requirement.
Multiple-choice
exercises 4 through 7 provide an
8. What minimum depth of cover in
opportunity for you to show that you
feet is normally required over
understand sewage treatment.
sewer pipes to protect them against
heavy truck traffic?
4. An Imhoff tank replaces what
a. 2
c. 4
two
separate
sewage
treatment
b. 3
d. 5
system components?
a. bar screen and drying bed
9. Manholes are required at the
b. drying bed and digestion tank
end of laterals and at each change
c. bar screen and settling tank
of direction, slope, or pipe size.
d. settling and digestion tanks
For sewers of less than 18-inches
diameter,
what
maximum
distance
5. Sludge
from
Imhoff
and
between
manholes
in
feet
is
digestion tanks can be dried in
specified if none of the above
lagoons.
The lagoons should have
conditions occur?
how many months' storage capacity?
a. 200
c. 400
a. 4
c. 8
b. 300
d. 500
b. 6
d. 12
4-25
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