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UNIVERSITY OF CALIFORNIA
FOREWORD
Refer to FM 5-5, FM 5-10, FM 5-35, AR 100-5, Tables of Basic Allowances,
TM 5-400, TM 5-405, TM 5-410 and TM 3-215.
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UNIVERSITY OF CALIFORNIA
TECHNICAL lilANUAL
WATER SUPPLY AND -PURpipATION
Changes I (* ^^^W A] J^ft^ARTMEKT,
^ J Washington^, ''d. C., 20 November 1943.
TM 5-295, 1942, is changed as f olloiys j *
u.
36. General.
A * • • * * *
h. Rescinded.
c. Rescinded.
(A. G. 300.7 (23 Aug 43).] (C 1, 20 Nov 43.)
36.1. (Added.) Chemical warfare agents in water. — a. Water
supplies may be contaminated directly by chemical warfare agents
placed in the water or indirectly by the use of toxic gases in the air ( see
par. 14). It is difficult to contaminate a large quantity of water,
particularly a fast-moving stream ; small, motionless bodies of water
such as wells and ponds are more easily contaminated. When a con-
taminated source is encoimtered, reconnaissance is made to find an-
other source because in most areas it is practically impossible to poison
all water sources. In a still body of water, the chemical agents may
be heavy enough to sink to the bottom, leaving the water near the sur-
face less contaminated. By testing at various intervals and depths
in a pond or other still water, it may be possible to locate usable
water.
h. Chlorine does not neutralize poisonous chemical agents in water.
However, it may reveal the presence of certain chemical warfare agents
which react very quickly with chlorine and immediately increase the
chlorine demand of the water. When the addition of 6.0 parts per
million of chlorine to water fails to leave a residual of at least 2.0 parts
per million, at the end of 2 minutes chemical warfare agents may be
present.
c. Another indication of possible chemical warfare contamination
of water is a low pH value. pH tests are routine control tests run by
engineer water supply personnel at all water points. When the pH
drops below 6.0, chemical warfare agents may be present. In some
areas the natural pH of the water is below 6.0 In such areas, the pH
test alone is not conclusive.
*The indiTidnal itema in this change will be cut apart and paated oyer the specific paragrapha
or subparagraphs affected.
M173.--4. M574532
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TM 5-295
' C 1 WATER SUPPLY AND WATER PURIFICATION
d. Use of the simple test kit illustrated in figures 9.1 and 9.2 de-
termines whether water contains chemical warfare agents (kit, field,
water testing, screening, for chemical warfare agents). This kit con-
tains equipment for making the tests for pH and chlorine demand men-
tioned in & and c above as well as for other more comprehensive tests.
All these tests are rough qualitative tests only, not sufficiently accurate
for any control purpose other than determining the presence of tlie
chemical agents. Each kit is issued with the complete instructions for
its use. These instructions are tentative as of 1 September 1943, and.
are subject to changes resulting from continuing experiments. Tests
which can be made with it are as follows :
Figure 9.1. — Kit for testing presence of chemical warfare agents. All vials are lettered to
assist identification.
, [A. G. 300.7 (23 Aug 43).] (C 1, 20 Nov 43.)
(1) Turbidity and color . — Place water in a test tube and note the
presence or absence of turbidity and color.
(2) pH test . — Dip a strip of nitrazine test paper into the water and
compare the resulting color of the paper with the color chart. En-
gineer water supply personnel may determine the pH with a com-
parator instead of with the nitrazine test paper. A pH below 6.0
indicates possible contamination.
(3) Arsenic test (for lewisite and other agents containing ar-
senic). — {a) Fill pot P up to mark with water to be tested.
(6) Place two pellets from vial A into the pot. Shake it to dissolve
pellets.
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TM 5-295
WATER SUPPLY' AND WATER PURIFICATION C 1
Figure 9.2. — Contents of water-testing kit (kit, field, water testing, screening, for chemical
warfare agents). Left to right: (1) vial A, KHSO 4 tablets; (2) vial B, arsenic test
papers ; (3) vial C, zinc pellets ; (4) vial D, RA tablets ; (5) vial E, RB tablets ; (6) vial
F, water purification tablets; (7) nitrazine strips for pH test; (8) ortholidine testing
tablets ; (9) pot P with tube H assembled for arsenic test ; (10) test tubes. Wire brush,
pipe cleaners, and color chart are not shown.
[A. G. 300.7 (23 Aug 43 ) . ] (C 1, 20 Nov 43. )
(<?) From vial B take a test strip by the top end. Carefully insert
the strip into tube H as shown in figure 9.3. Bend the strip near the
top so it will remain in tube with bent end hanging over the edge of
the tube. In handling the strip touch the top end only and keep the
strip dry.
(d) When pellets from vial A have dissolved, add five pellets from
vial C to the contents of the pot.
(e) Promptly fit the test paper assembly (e above) into the pot, as
indicated in figure 9.3, so that the gases released will rise up past the
test paper.
(/) If the pot is cold, warm it with the hand. Keep the test paper
assembly in the pot for 20 minutes.
(g) Remove the test strip and note the length of the resulting yel-
low or brown stain. A stain of % inch or more indicates a positive
test ; a stain less than ^ inch is negative.
(4) Mustards test {for nitrogen mustards). — {a) Rinse a test tube
with the water to be tested and fill it to a depth of ^ inch with
suspected water.
(&) Add one tablet from vial D.
(c) Shake for at least 3 minutes.
{d) During cold weather warm the tube in the hand or in a pocket
for 5 minutes.
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C 1 WATER STJPPLY AND WATTER FUEIFICATION
\
{e) Break in half one tablet from vial E and add both halves to th.e
water being tested. Shake the test tube until the tablet is dissolved.
While shaking watch for a blue color to appear.
(/) Observe the tube for % minute against a white background.
Any trace of blue (mainly in curd form) indicates a positive test for
mustards. White or gray indicates a negative test. Yellow indicates
cyanogen chloride.
(5) Chlonne-demand test (see h above). — {a) Fill a canteen vs^itB
water to within 1 inch of the top.
(6) Add three water purification (halazone) tablets from vial F.
Place the cap on the canteen and shake it until the tablets dissolve.
(c) After 5 minutes, test for chlorine residual. (Five minutes is
necessary to allow tablets to dissolve. Reaction of chlorine with,
chemical warfare agents is practically instantaneous.) This may be
done with orthotplidine testing tablets (par. 108<^(2)); or, water-
supply personnel may use the comparator. A positive test is indicated
by a residual of less than 1.0 part per million ; this means chlorine de-
mand is greater than 4. A negative test is indicated by a residual
of 1.0 part per million or greater.
Figure 9.3. Arsenic-test assembly.
[A. G. 300.7 (23 Aug 43).] (C 1, 20 Nov 43.)
(6) Taste and odor. — {a) If the tests for color and turbidity, ar-
senic, mustards, and chlorine demand all are negative, carefully smell
and taste the suspected water.
(&) A positive test is indicated by an odor that makes the eyes
smart or stings the nose ; a biting, peppery, or strongly objectionable
taste ; or any taste or odor of a known war gas.
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WATEE SUPPLY AND WATER PURIFICATION C 1
(<?) Absence of taste or odor indicates a negative test, but does not
iTecessarily mean water is safe. A, negative test also is indicated if the
only odors and tastes are those normally characteristic of natural
'water.
e. The test given in <?(4) above detects nitrogen mustards in con-
centrations greater than 8.0 parts per million. Since concentrations
below 8.0 parts per million may incapacitate consumers, complete re-
liance cannot be placed on this one test by itself. ^
f. A more comprehensive kit than the type discussed above is under
development. It will permit qualitative analysis of water and will
detect nitrogen mustards in concentrations below 8.0 parts per million.
[A. G. 800.7 (23 Aug 43). 1 (C 1, 20 Nov 43.)
36.2. (Added.) Responsibility for detection of chemical war-
fare agents in water. — a. A water testing kit of the simple type
discussed in paragraph 36.1<^ is issued to the medical officer of each
battalion or similar unit. One kit also is issued with each engineer
water purification set. The more comprehensive kit for both quanti-
tative and qualitative analysis is available to higher echelons.
6. If as a result of an excessive chlorine demand, a low pH value,
an intelligence report, or for any other reason water supply personnel
suspect that water may be contaminated by chemical warfare agents,
tests are made with the simple water test kit. If any single test gives
a positive result the water point is shut down and an attempt is made
to locate an uncontaminated source. The proper S-2, medical officer,
and water control officer are notified at once. The water control
officer, or other qualified officer, analyzes the contaminated water with
the comprehensive kit to determine the steps necessary for purification.,
c. Where a consuming organization obtains water locally instead
of from a water distributing point the organization commander, with
the assistance of the organization medical officer, is responsible for
the purity of the water. When water is suspected of being contami-
nated with chemical warfare agents, the proper officers are notified
as in 6 above.
[A. G. 300.7 (23 Aug 43).] (Cl, 20 Nov 43.)
36.3. (Added.) Bone oil and fish oil. — ^Enemy troops may at-
tempt to make ]vater sources, particularly wells, unfit for use by con-
taminating them with fish oil or bone oil. These oils give water such
a disagreeable^ nauseating taste and odor that personnel cannot use
it. For methods of removal, s^e paragraph 83.1.
[A. G. 300.7 (23 Aug 43).] (C 1, 20 Nov 43.)
5
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WATER SUPPLY AKTU WATER PURarrCATTON C 1
39. Quality variation during distribution.
» ♦ ♦ ♦ « * •
h. Where water is ♦ * * t<5 the troops. Dangerous contami-
nation may be introduced by careless handling or by dipping
water from cans with unclean cups or other receptacles. The
nse of other purpose containers for water is objectionable. If
it becomes necessary to use gasoline containers or hose for
transporting water, they must be cleaned adequately as de;
scribed in paragraph 73.1; otherwise the water becomes un-
safe and requires special purification.
« ******
[A. G. 300.7 (23 Aug 43).] (C 1, 20 Nov 43.)
73.1. (Added.) Removing gasoline from containers and from
water. — Gasoline containers which have been used for leaded gaso-
line can be cleaned effectively and made safe as containers for water
to be consumed by troops. The methods for doing so are described
below. Even after careful cleaning, water stored in gasoline con-
tainers may be contaminated with objectionable quantities of lead
and gasoline retained in the scale, rough surfaces, and cracks and
joints in the material of the container. Such contamination usually
is delayed, and may be avoided by limiting the time of storage. The
odor of gasoline increases during storage of the water and precedes
a rise in lead content which sometimes exceeds the allowable limit of
0.1 part per million. The odor, therefore, is an indicator of the
potability of the water. A definite odor of gasoline is an indication
that cleaning was incomplete, or that safe storage time has been
exceeded. Whenever gasoline odor is detected in water drawn from
cleaned epntainers, it must be treated before being used for drinking,
cooking, and bathing purposes. Methods of treatment are given in
f below.
a. Precanitions against -fire and explosion. — ^Keep all open flames
and portable electric motors away from all openings such as pouring
spouts, outlet valves, manholes, and domes in cans, drums, and tanks
previously used for gasoline. All such containers retain gasoline
vapor even though all liquid gasoline has been removed. This vapor
is highly inflammable and explosive. Hence, when starting to clean
gasoline containers to convert them to use for water, all fire precau-
tions must be observed and continued in effect until the cleaning
process has removed all trace of gasoline vapors. Men must never
enter empty tanks until after the vapor is removed. For additional
details, see paragraph 16?, TM 3-260.
J. Cleaning 6-gallon gasoline cans. — (1) Choose new cans with
bright interiors.
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TH 5-295
WATER STJPPLT AND WATER FURIFICATION C 1
(2) . Allow the can to drain for 10 to 15 minutes to remove as much
gasoline as possible.
(3) Half fill the can with water, add 1 ounce of powdered soap,
and shake for 5 minutes. If soap is not available, 3 ounces of activated
carbon may be used instead.
( 4) Drain, refill with 2 to 3 gallons of water, and shake.
( 6 ) Drain and fill to overflowing with water. Drain.
(6) Fill with drinking water. This water should be used within
a few days. Since the can rusts rapidly, it should be cleaned before
each filling to remove as much rust as possible.
c. Gleaning 56-gcJlon gasoUtie drvms. — (1) Choose drums whose
interiors show no scale, are bright, or have galvanized coatings clearly
discernible. Drain out any remaining gasoline.
(2) If steam is available, steam for ^ to 1 hour and proceed with
steps (5) to (8) below.
(3) If no steam is available, blow for 16 minutes with compressed
air, or fill to overflowing with water to displace remaining gasoline.
Drain.
(4) Add 10 to 20 gallons of water and 1 pound of powdered soap,
and shake by rolling the drum back and forth for 15 minutes. Drain.
(5) Put in 10 to 20 gallons of water, ^ pound of powdered activated
carbon, and repeat the rolling operations. Drain.
(6) Remove residual carbon by rinsing repeatedly with a little
water.
(7) If time permits and sufficient water is available, fill drum to
overflowing. Drain.
(8) Fill drum with drinking water.
d. Gleaning gasoline tank trucks. — (1) Drain gasoline from com-
partments as completely as possible.
(2) Steam each compartment for not less than 90 minutes.
(3) Flush out loose scale with a pressure water hose.
(4) Fill to overflowing with water to displace remaining
gasoline.
(5) Drain to gauge level. Storage should not exceed 18 hours.
(6) Soap or activated carbon is not used in cleaning tank trucks.
Trucks once cleaned and placed in water service improve with use
so far as odor and lead content are concerned, but are flushed with
a hose before each filling to remove scale and rust which otherwise will
color the water after only a short period of storage.
e. Gleaning gasoline tank cars. — (1) Drain out any remaining gaso-
line and ventilate the tank by opening the dome.
(2) Steam for not less than 6 hours. This requires locomotive or
powerhouse boiler steam.
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WATEiR SUPPLY AND WATTER PURIFICATION C 1
(3) Have a man enter the tank car to flush away all loose surface
scale with a hose and stream of water under pressure. As a precau-
tionary measure, this man must be equipped with mask and safety
belt or harness and rope, with two attendants outside the car for
rescue or resuscitation purposes.
(4) Fill with water to overflowing, to displace any remaining
gasoline.
(5) Drain water to level of dome. Storage should not exceed 25
hours. Soap or activated carbon is not used in cleaning tank cars.
/. Treating stored water . — Two metho'ds of treatment can be em-
ployed to remove from water any remaining gasoline odors derived
from containers or hose.
(1) Garhon treatment . — ^Enough activated carbon to remove the
odors is added to the water. This amount varies according to the con-
centration of the contamination, but usually is less than 15 grains per
gallon, or about 1 cupful per 55-gallon drum. More can be used, if
necessary. After the carbon is added to the cans or drums, they are
agitated for approximately 5 minutes. Much of the carbon can be
removed prior to use by straining the water through a flannel cloth
or blanket. Water from tank trucks and tank cars is transferred
to 3,000-gallon canvas tanks before adding the carbon. The water
and carbon are thoroughly agitated in the canvas tanks. The carbon
can then be removed by filtration. As, much as 0.40 part per million
of lead, together with well-defined gasoline odors, can be removed in
this manner.
(2) -Pmification with standard mohUe or 'portable unit . — This treat-
ment reduces the gasoline odor and lead content and also removes
color and sediment that the water may have picked up. Activated
carbon should be employed in conjunction with purification through
the imit.
g. Water transported or stored in the above containers must meet
the usual requirements as to chlorination.
[A. a 300.7 (23 Aug 43).] (C 1, 20 Nov 43.)
. 83.1. (Added.) Removal of bone oil or fish oil from water. —
Both fish oil and bone oil contain water soluble chemicals and have
a specific gravity less than that of water. A well contaminated with
these oils (see par. 36.3) is not used unless absolutely necessary. If the
water rrmst be used, the well is pumped to waste for 30 minutes to 1
hour or until its odor is less objectionable. Then water is pumped
into storage tanks and allowed to stand for 1 hour. Water which
is carefully withdrawn from the bottom of the tank without disturbing
the surface film has a much less objectionable odor and taste. It is
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WATEB STJPFLT AND WATEB PUEIFICATION C 1
safe to drink if it has been treated properly to eliminate bacterial
contamination and provided tests show it free from chemical warfare
agents. Activated carbon, available in water supply equipment sets
and in engineer depots, may be used as an absorbing agent for further
removal of objectionable taste and odor.
(A. G. 300.7 (23 Aug 43).] (C 1, 2C Nov 43.)
108. Basic. — a. Water supply in its simplest form is illustrated
by an individual soldier on an isolated mission filling his canteen
from a spring or brook and disinfecting it by adding water-puri-
fication tablets or by boiling the water for 1 minute.
h. Lyster hag chlorination.
m ♦ ♦ ♦
(5) After the calcium ♦ * * onto the ground. Then fill a
clean canteen cup to a depth of Vi inch with water from the same
faucet.
*******
c. (Added.) Water purification tablets {Hdlcizone), — ^Water puri-
fication tablets are issued primarily for the purification of small quan-
tities of water. Two 4-milligram tablets are added to one canteen of
water if the water is clear, four if it is turbid or colored. The water
should not be consumed for 30 minutes after the tablets have dissolved.
To speed dissolving of the tablets, the canteen is shaken vigorously.
Water may be treated in larger containers by addition of the appro-
priate number of tablets. Thus a 10-gallon container requires 40
times as many tablets as a 1-quart canteen.
d. (Added-) Additional tests for chlorine residual. — ^In addition
to the liquid orthotolidine test covered in 6(6) above, the following
tests may be used to determine chlorine residual.
(1) Comparator. — Engineer water purification sets all are equipped
with pH and chlorine comparator kits. The comparator is the fastest
and most accurate method for determining chlorine residual.
(2) Orthotolidine tablets. — These tablets are issued in a small vial
which fits inside a larger vial in which the test is made. Eemove the
inner vial. Fill the outer vial up to the bottom of the colored band
with water to be tested. From the inner vial take one orthotolidine
testing tablet ; drop it into the water, shake, and note the color pro-
duced. The result is measured as follows :
(a) Equal or darker yellow than the colored band — satisfactory
chlorination. The chlorine residual is about 1.0 part per million.
(6) Lighter yellow than the colored band — ^insufficient chlorina-
tion. Add more calcium hypochlorite to the water being treated;
wait 10 minutes and retest.
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WATER SUPPLY AN>D WATER PURIFICATION C 1
(<?) Orange color — the water is overchlorinated. Add more water
to the water being treated ; wait 10 minutes and retest.
[A. Q. 300.7 (23 Sept 43).] (C 1. 20 Nov 43.)
110. Iodine sterilization. — Eescinded.
[A. O. 300.7 (23 Aug 43 ) . ] (C 1, 20 Nov 43. )
111. Boiling. — If tubes of calcium hypochlorite or water purifi-
cation tablets are not available, water may be purified by boiling
for 1 minute. Care must be taken to see that the water actu-
ally boils for this period of time. This method is not used by the
individual soldier, if avoidable. The water should be boiled under
supervision in comparatively large quantities, and then distributed
to the troops. Water may be boiled in galvanized iron cans.
[A. G. 300.7 (23 Aug 43).] (C 1, 20 Nov 48.)
Appendix I
19. Field test for pH and free chlorine.
*******
c. Comparator.
«***««*
(3) (Added.) Two indicator solutions are issued for use with the
comparator in determining pH. One is bromthymol blue which covers
pH values ranging from 7.6 to 6.0. The other is bromcresol purple-
green which covers values from 6.0 to 4.4.
* *
[A. G. 300.7 (23 Aug 43 ) . ] (C 1, 20 Nov 43. )
Bt order op the Secretary or War :
G. C. MARSHALL,
Chief of Staff.
OrnciAL:
J. A. ULIO,
Major General.^
The Adjutant General.
10
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UNIVERSITY OF CALIFORNIA
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TM 5-295
•C 2
r
'^SULkUdLuilr
TECHNICAL MANUAL
WATER SUPPLY AND WATER PURIFICATION
ChanoesI WAR DEPARTMENT,
No. 2 j Wabhington 25, D. 0.,
TM 5-295, 1942, is changed as follows :
37.1. (Added.) Schistosomiasis. — a. In sub-
tropical countries, a disease caused by worm/|:|az^si^ mown IJ^Awbod ^
flukes may be contracted from contact with wat^r con^fer^ ttie minut^^
larval stages. This disease is called schistosomiasis. The organj^ii^
which cause it usually enter the body by penetj^i^g|Jh^^l4n^kire
one is wading or bathing in contaminated water, -^ore rarely the
disease may be contracted through drinking water. The principal
areas in which schistosomiasis occurs are located in China, Japan,
Africa, northern South America, and certain of the West Indies. In
areas in which the disease is prevalent, wells and springs which are
not subject to contamination by drainage and surface wash should
be used in preference to natural bodies of surface water such as ponds
and sluggish streams.
6. The Medical Department is responsible for determining whether
or not these blood flukes are present in water which is being used for
drinking or bathing. Where the presence of these organisms is in-
dicated the following safety measures will be taken by engineer water-
supply personnel :
(1) Sedimentation (see par. 115). — Settling tanks must be placed
between the point at which chemicals are added to the water and the
filter. The coagulant dosage should produce a heavy, rapidly settling
floe. The sedimentation period should be at least 60 minutes.
(2) Filtration (see pars. 128 and 133). — The filter rate must not
exceed 6 gallons per minute per square foot of sand area. This means
that the maximum filter rate with the portable unit will be 10 gallons
per minute ; with the mobile unit, 60 gallons per minute.
(3) Disinfection (see par. 71 ) . — or proper purification the chlorine
content after 30 minutes of contact with the water must be at least one
part per million. In making the test for chlorine residual, the read-
ing is taken within 1 minute after the orthotolidine has been added.
(4) Use of 'portable bathing 'umt (see par. 163) . — The best available
source of water should be used with the portable bathing unit. Prior
indiTidoal Items In this change will be cut apart and pasted orer the specific paragraphs
at snbparagraphs affected.
57ffl42* — 44
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WATER SUPPLY AND PXTRIFICATION
TM 5->295
c a
to use in the unit the water should be treated by one of the following
methods :
(a) Treat water as given in (1), (2), and (3) above.
(&) Place a dosage of 10 parts per million of copper sulphate in
water. In a large body of water, this may be done by trailing behind
a boat a small cloth sack filled with copper sulphate crystals. The
water should not be used for at least 48 hours after the addition of
the copper sulphate. This method of treatment is applicable to still
bodies of water only ; it cannot be used in fast-moving streams.
(5) Protection of water supply personnel. — Personnel operating
water supply points should wear rubber gloves and rubber boots when
they are required to place their hands in or wade in untreated water.
[A. G. 300.7 (2 Dec 43).] (C 2, 18 Feb 44.)
128. To Start the Mobile Unit in Operation.
* * * <: * * *
q. When the effluent * * ♦ pump discharge pipe. Open the
valve in the filter discharge pipe slowly, as long as the effluent remains
clear and until the the flow is just sufficient for the requirements over
the period available, but not more than 75 gallons per minute, as indi-
cated by the manometer. The plant is now in complete operation, and
purified water is being delivered.
[A. O. 300.7 (2 Dec 43).] (C 2, 18 Feb 44.)
By order of the Secretary of War ;
G. C. MARSHALL,
GUef of Staff.
Official:
J. A. ULIO,
Major General.,
The Adjutant General.
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WATER SUPPLY AND WATER PURIFICATION
Table of Contents
0
CHAPTER 1. GENERAL
Paragraph Page
The Purpose and Scope 1 1
The Problem of Water Supply 2 1
Importance 3 2
Responsibility 4 2
Duties of Engineers 5 3
Definitions 6 3
CHAPTER 2. SOURCES OF WATER AND ITS IMPURITIES
Classification of Water Sources 7 5
Rainwater 8 5
Dew Ponds 9 6
Surface Water 10 6
Physical and Bacterial Impurities in Surface Water 11 6
Dissolved Impurities 12 7
Pollution of Surface Water 13 8
Chemical Warfare Agents in Surface Water 14 8
Ground Water 15 8
Wells 16 12
Springs 17 16
Sea Water 18 17
Choice of a Water Supply Source 19 18
CHAPTER 3. DEVELOPMENT OF WATER SOURCES
General 20 19
Surface Water Intakes 21 20
Pump Location 22 * 23
Substream-bed Sources 23 23
Intakes in Lakes and Ponds 24 23
Sea Water Intakes 25 25
Permanent Intakes 26 26
By-passes 27 27
Development of Ground Waters 28 27
Development of Springs 29 29
Dug Wells 30 29
Infiltration Galleries 31 30
Bored Wells 32 31
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CHAPTER 3. DEVELOPMENT OF WATER SOURCES (CONT’D.)
Paragraph
Driven Wells 33
Drilled Wells 34
Capacity 35
CHAPTER 4. WATER QUALITY AND EFFECT OF SUBSTANCES
DISSOLVED AND SUSPENDED IN WATER
General 36
Impurities Found in Water Supplies 37
Selection of Sources and Equipment to be Used 38
Quality Variation During Distribution 39
Effect of Impurities on Animals 40
Non-bacterial Impurities 41
Body Irritants 42
Saline Water 43
Hardness, Iron and Manganese 44
Other Dissolved Mineral Substances 45
Corrosion of Lead, Copper, and Brass 46
Constituents Affecting Boiler and Heater Operation 47
Attractiveness 48
Color 49
Suspended Matter 50
Temperature 51
Odor 52
Taste 53
Habituation to Tastes and Odors 54
Corrosion by Gases 55
Effect of Ammonia on Copper and of Alkalies on Brass 56
Effect of Chlorine on Metals 57
Difficulties in Photo Processing 58
CHAPTER 5. WATER PURIFICATION
General
Self Purification
Pre-Sedimentation
Aeration
Coagulation
Chemicals Used in Coagulation
Mixing Basins
Sedimentation
Settling Basins
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CHAPTER 5. WATER PURIFICATION (CONT’D.)
Paragraph Page
Filtration 68 67
Types of Rapid Sand Filters 69 69
Washing 70 70
Disinfection 71 71
Activated Carbon 72 74
Iron and Manganese Removal 73 74
Water Softening 74 75
Softening with Lime or Lime and Soda Ash 75 77
Recarbonation 76 81
Softening by Ion Exchange 77 81
Chemical Feeds 78 83
Neutralization 79 87
Deareation 80 87
Distillation 81 88
Addition of Salt to Water 82 88
Boiler Compound 83 88
CHAPTER 6. STORAGE, DISTRIBUTION, AND MEASUREMENT
OF WATER
Storage Location 84 89
Types of Storage 85 89
Transportation of Water 88 96
Pumps 87 96
Plunger Pumps 88 98
Rotary Pumps 89 99
Centrifugal Pumps 90 99
Priming Centrifugal Pumps 91 100
Pump Characteristics 92 102
Comparison of Pump Types 93 102
Air Lift 94 103
Strainers 95 103
Effect of Temperature and Elevation on Suction Lift 96 103
Pipe Friction 97 104
Power Required 98 104
Estimating Power, Capacity, Lift and Efficiency
of Pumps 99 105
Kinds of Pipe 100 106
Effect of Temperature on Pipe 101 107
Standard Pipe Sizes 102 107
Rate of Laying Pipe 103 109
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CHAPTER 6. STORAGE, DSTRIBUTION, AND MEASUREMENT
OF WATER (CONT’D.)
Paragraph
Pipe Distribution Systems 104
Railroad Tank Car Distribution 105
Motor Vehicle Distribution 106
Measurement of Water 107
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CHAPTER 7. OPERATION
Section I. General
Basic 108 113
Emergency Chlorination 109 114
Iodine Sterilization 110 115
Boiling 111 119
Installations 112 119
Water Supply Points 113 119
Section II. Coagulation and Sedimentation
Determination of Optimum pH Range for Coagulation 114 121
Sedimentation 115 124
Section III. Mobile Water Purification Unit M-3, Model 1940
Description 116 125
Flow 117 127
Truck Body 118 127
Pump and Engine 119 127
Three-Position Valve 120 127
Filter 121 127
Alum Pot 122 128
Soda Pot 123 128
Venturi Tube and Manometer 124 128
Test Set 125 128
Piping and Connections 126 128
Chlorinator 127 130
To Start the Mobile Unit in Operation 128 131
To Wash 129 133
Special Notes 130 133
Servicing Chlorinator 131 134
Section IV. The Portable Water Purification Unit
Description 132 141
Filter 133 145
Chlorinator 134 145
Operating Procedure 135 145
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CHAPTER 7. OPERATION (CONT’D.)
Paragraph Page
Section V. Rotary Drill Rig
Rotary Drill Rig 136 147
Crew 137 154
Procedure 138 154
Testing For Strata 139 157
Section VI. Percussion Well Rig
Description 140 159
Drilling Tools and Equipment 141 161
Crew 142 164
Procedure 143 164
Testing and Completion 144 165
General Information 145 165
Instructions For Dressing and Hardening Drill Bits 146 167
What A Drill Bit Does 147 168
Drilling in Hard Limestone 148 168
Drilling in Soft Limestone 149 169
Drilling in Quartzite or Granite 150 169
Drilling in Soft Formations 151 169
Section VII. Drive Point (Driven) Wells
Typical Locations 152 170
Equipment 153 174
Operation 154 174
Development and Testing 155 176
Pulling the Well 156 178
Section VIIL Jetted Wells 157 178
Section IX. Screening, Testing, and Development of Wells
Well Screens 158 178
Testing and Developing the Well 159 181
Cementing (Grouting) 160 182
Increasing Yield of Wells 161 183
Protection of Wells 162 185
Section X. Portable Field Bathing Unit
Description 163 185
Section XI, Portable Distillation Units
The 50 GPH (1000 Gallons Per Day) Unit 164 188
The 100 GPH (2000 Gallons Per Day) Unit 165 196
To Shut Down (Either 50 or 100 GPH Unit) 166 204
Fusible Plug (Either 50 or 100 GPH Unit) 167 204
Improvised Distillation Setup 168 204
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APPENDIX
I. Water Analysis
II. Useful Chemical Data Relating to Water
III. Water Reconnaissance Report Form
IV. Engineer Water Supply Chests
V. Useful Tables
VI. Bibliography
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WATER SUPPLY
AND
TM 5-295
WATER PURIFICATION
Chapter 1
GENERAL
1. The Purpose and Scope. — The purpose of this manual is to pro-
vide technical information concerning water supply and water purifi-
cation and to assist Engineer troops in fulfilling their water supply
functions. It discusses those basic principles of water supply and water
treatment which pertain to both civilian and military practice and in
addition, the expedients necessary in the field.
2. The Problem of Water Supply. — a. Water is normally procured
from local sources when practicable. Permanent installations, stations,
and camps may find it necessary to develop water supplies. It will often
be necessary to operate and extend civilian water supply facilities in oc-
cupied territory. Treatment of the water may or may not be required.
b. The first consideration in all water supply problems is the quan-
tity of water available. If an adequate amount of water is not procurable
locally, it must be transported by truck, tank car, or pipe line.
c. Where there are several sources from which the necessary quan-
tity of water may be obtained, the supply with the most desirable charac-
teristics is selected. To determine which of several sources is to be chosen
on the basis of water quality, the characteristics of water should be con-
sidered in the following order:
(1) Safety.
Freedom from bacteria — especially pathogenic types — patho-
genic protozoa, parasitic worms, other objectionable organ-
isms and physiologically active chemical substances.
(2) Palatability.
Acceptable taste, odor, and temperature.
(3) Attractiveness.
Freedom from noticeable color and turbidity.
(4) Mineral characteristics affecting convenience of use.
Iron, manganese, hardness, soluble salts, and acidity or alka-
linity.
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d. Few water supplies are entirely satisfactory, as found in nature,
but any source which can yield enough water should be given considera-
tion. Appropriate treatment can alter almost any natural water, so as
to permit its use for military purposes. If, however, the required treat-
ment is complicated or difficult, another source should be sought, even if
it is necessary to transport water from a more suitable supply located
at a distance.
e. The quality of military water supplies in the field need not meet
the standards of municipalities, but when the tactical situation war-
rants, it should be progressively improved until the quality compares
favorably with municipal supplies.
3. Importance. — a. Water supply is vital to the accomplishment
of the tactical mission. Men can go longer without food than without
water. More casualties, both permanent and temporary, can be brought
about by water than by any other single cause. A mistake in the pro-
curement or treatment of water can immobilize an entire command.
h. Consumption of impure water results in widespread violent
diarrhea which promptly reduces troop efficiency. These diarrhea epi-
demics may be followed in a week or ten days by outbreaks of serious
intestinal disease. Whereas diarrhea may incapacitate a command very
suddenly, but only temporarily, the more serious intestinal disorders may
require the hospitalization of large numbers of men, and result in serious
depletion of the effective strength of the organization.
4. Responsibility. — a. The Corps of Engineers is responsible for
the supply of water for all purposes to all major units of the army in the
field down to and including the division, and to smaller units if practi-
cable.
h. The responsibility of the Medical Department in connection with
water supply is covered in AR 40-205, which reads, in part, as follows:
“The Medical Department is charged with the duty of investigat-
ing the sanitary condition of the Army and making recommendations
in relation thereto, of advising with reference to the quality
of water supply and purification and the execution of all
measures for conferring immunity from disease on military person-
nel.’’
c. In general, responsibility for the quality of water supplied to
troops in the theater of operations to include delivery to the point where
it is distributed to consuming organizations rests with the engineers,
assisted as may be necessary for laboratory examination by Medical De-
partment personnel. The handling of water in organization water con-
tainers, in sterilizing bags, and in the canteen of the individual soldier
is a responsibility of the organization commander, acting with the advice
and assistance of attached medical personnel.
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5. Duties of Engineers. — Engineers have the following general du-
ties in connection with water supply:
a. Reconnaissance and collection of data.
h. Development of sources.
c. Purification.
d. Construction and operation of establishments.
e. Transportation to distributing points.
For a discussion of engineer water supply operations in higher units see
FM 5-5.
6. Definitions. — pH is a measure of the degree of acidity or alka-
linity of a solution.
An Indicator is a substance which has different colors in different
pH ranges.
Alkalinity in water practice consists of all those substances which
impart a straw yellow color to methyl orange indicator, usually bicarbon-
ates, carbonates and hydroxides.
Acidity in water is divided into two kinds; viz., mineral acidity,
which consists of all substances which impart a red color to methyl
orange indicator, and carbon dioxide aridity, which does not impart a
red color to methyl orange but causes phenolphthalein indicator to change
from pink to colorless.
A Coagulant is a substance which forms a gelatinous precipitate cap-
able of attracting other particles to itself.
A Floe is the gelatinous precipitate formed by the action of a coag-
ulant with the alkalinity in water.
Coagulation is the process of gathering together finely divided par-
ticles suspended in water and consists of feeding a coagulant, reaction of
the coagulant and alkalinity, the formation of the fioc particles, increas-
ing the size of the particles, and attraction of the suspended matter to
them.
Turbidity consists of particles suspended in water which give it a
“muddy” appearance.
Color consists of finely dispersed particles which impart color to
water.
Hardness consists of calcium, magnesium, and iron salts which de-
stroy soap and form incrustations on heated surfaces.
A Filter is an apparatus for the removal of solids from liquids or
gases.
Head is the depth of a column of water. Pressure head is the pres-
sure equivalent to that exerted by a column of water of a certain depth.
2.3 feet depth of water exerts a pressure of 1 pound per square inch.
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Suction lift is the difference in elevation from the surface of a body
of water to the centerline of a pump.
Static lift is the difference in elevation from the centerline of a pump
to the point to which the water must be raised.
Friction loss is the reduction in pressure to overcome the friction
or drag of the pipe material on the water.
Equivalent loss is the loss in pressure in passing through a valve or
fitting, expressed in terms of the equivalent length of straight pipe which
would be required to produce the same loss in pressure.
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Chapter 2
SOURCES OF WATER AND ITS IMPURITIES
7. Classification of Water Sources. (Fig. 1). — Water is classified
as to source as follows:
a. Rainwater
b. Surface water
c. Ground water
d. Sea water (Used only as a last resort)
8. Rainwater. — a. Rainwater is normally collected on a roof or
other surface, such as a bare rock area, and drained to a reservoir. Rain-
water is not an important source of military water supply except under
special conditions, such as on small islands, on isolated headlands, or in
other places where ground waters are brackish or salty and surface
waters disappear too quickly to be useful. If the number of persons to be
served is very small, and the minimum annual rainfall expected is rela-
tively large, the water collected from the roofs of buildings may be suffi-
cient. Extensions to the roof area may be constructed to augment the
volume of water to a limited extent. Larger quantities of rainwater may
be collected, as at Gibraltar, by constructing concrete collecting surfaces,
or by baring and preparing rock surfaces to drain the water into under-
ground storage cisterns.
h. Rainwater generally contains some- dissolved matter. In falling
it has washed the air through which it passed. It has dissolved carbon
dioxide, salts, and other soluble substances, and picked up dust from the
air. Rainwater frequently contains molds, yeasts, and bacteria which
multiply in cisterns and reservoirs. It varies somewhat in character
according to the locality where it is collected, the amount of smoke in
the air, and the recentness of dust storms or strong convection currents.
The smaller the amount of dissolved substances in rainwater the stronger
the tendency to dissolve materials with which it comes into contact;
that is, it will be corrosive to those materials.
c. If the areas on which rainwater is collected are not kept clean,
the impurities therefrom will be washed into the collecting cisterns.
Dust, leaves, and feces are the usual polluting substances.
d. Subterranean cisterns usually help to keep rainwater cool. In
some areas rainwater is collected in barrels and small elevated tanks.
Water in these is likely to attract mosquitoes, midges, and other insects
which lay their eggs on a water surface. This egg-laying is not usually
regarded as pollution of the water, but the worm-like larvae are notice-
able and breeding of mosquitoes may be objectionable. They are a nuis-
ance and may be associated with the spread of yellow fever, malaria,
dengue and other diseases.
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9. Dew Ponds. — In some localities water condensed on vegetation,
rocks, or purposely laid masses of stone, drains into a pond and accumu-
lates an excess over the losses due to percolation, evaporation and use by
plants. Such ponds are known as dew ponds and in some localities con-
tribute to the local available water resources.
10. Surface Water. — a. When rainwater falls on the ground and
runs across the surface to collect in brooks, streams, or lakes, it becomes
surface water. Surface water is a very important source of water espec-
ially for communities of large size. Small communities frequently find
surface waters more satisfactory than ground waters in those areas
where the ground waters are hard and heavily mineralized.
b. From the military standpoint, the fact that surface waters can
be easily located by maps and aerial or ground reconnaissance, and that
the necessary work for development may be estimated quickly, make them
the chief source of temporary water supplies.
11. Physical and Bacterial Impurities in Surface Water. — a. The
character of the earth’s surface on which rain or snow falls determines
the character of the surface water which may be collected in that locality.
If the surface is rock or relatively insoluble, the water running from it
will probably differ little from the rainwater in the amount of dissolved
and suspended matter it contains. If there is a large quantity of the
fine products of rock weathering, if the rock surface is covered by soil
and wind-blown clay, and especially if the land is tilled, more or less insol-
uble matter will be picked up by the water, the amount varying with
weather conditions, the slope of the earth’s surface and the volume of rain-
fall. When the earth’s surface is frozen, the fine earth particles are held
in place and the runoff will be low in turbidity, but as soon as the fine
surface material begins to thaw, it is easily displaced by running water
and the turbidity in the runoff increases. Later, when the earth is com-
pletely thawed out, its capacity for absorbing water is increased and
minor rains may be absorbed completely without any apparent runoff.
Vegetation on the earth’s surface has an important effect in retaining
earth particles and in reducing the turbidity of the runoff.
6. Surface waters which come in contact with peat, humus or de-
composing organic substances tend to take on a yellowish, or brownish
appearance due to the substances which the water extracts and holds in
solution or colloidal dispersion. The effect produced by the extracted
matter is to give the water a color ranging from a light green to the
color of strong tea. This color is called the “true color’’, and should be dif-
ferentiated from the apparent color of water which is the “true color’’
modified by the color of materials in suspension. Thus, a water which is
turbid from coal dust will be grayish; one which contains iron oxide or
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red earth will be reddish; one which contains fine silica or undissolved
air will have a milky appearance. When the turbidity is removed, the
true color, or stain, in the water will be seen.
c. Some forms of turbidity may be irritating if present in sufficient
amount and may produce a type of diarrhea. Water having brownish
stains is not usually considered objectionable.
d. Greenish colors in water are also produced by the color of the
bodies of minute organisms, such as algae and protozoa. These organ-
isms grow best in clear waters exposed to sunlight, but they appear in
large numbers only when temperatures, alkalinity, and the concentration
of oxygen, carbon dioxide and dissolved mineral substances are such as
to give them the necessary stimulus. Heavy growths of these and other
aquatic organisms, such as duck-weed, may make surface scums on waters
of ponds and streams. When the organisms are removed, the color dis-
appears.
e. Growths of algae and aquatic protozoa are objectionable chiefly
because they sometimes give offensive odors and tastes to the water. It
has been claimed that blue-green algae belonging to the family nostocaceae
may produce poisonous growths under certain conditions.
/. The gravest dangers associated with the use of surface waters
are due to pathogenic bacteria, parasitic protozoa and certain types of
higher organisms, including parasitic worms.
g. Large numbers of bacteria, mostly non-pathogenic, live in the
surface earth where oxygen, moisture and the organic debris on which
they live are abundant. These organisms are washed into surface collec-
tions of water with the fine particles of material which make up the sus-
pended matter. With these bacteria may go pathogenic organisms de-
rived from the feces of man and other higher animals. Animal parasites
such as certain protozoa, and the eggs, larvae, and even the adults of
some disease-producing worms, may also be carried into surface waters.
Consequently, surface waters need careful purification to remove the
turbidity and the living organisms which might cause consumers to suf-
fer from simple diarrhea or more serious diseases such as typhoid fever
and amebic dysentery.
12. Dissolved Impurities. — The mineral characteristics of surface
waters vary with the mineral character of the mantle rock and of the
soils over which they pass. Some are hard; others are almost as free
from dissolved mineral substances as distilled water. Limestone and
dolomite are among the more soluble rocks which contribute to the hard-
ness of surface waters. During the winter, when surface runoff is neg-
ligible, due to the retention of the water as ice, streams and ponds are fed
mostly by springs and seeps. This spring or seepage water is really
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ground water escaping from the formations in which it has been held.
Such water is often hard and has the characteristics of the ground water
of the region. In the warm months the surface runoff dilutes water from
the springs and seeps and the influence of the ground waters upon the
composition of the water in streams and ponds is correspondingly reduced.
13. Pollution of Surface Water. — a. Pollution of streams by sew-
age and industrial waste is to be expected in inhabited areas. The degree
of pollution will vary with the density of population, the development of
industry in the vicinity, and the flow of the stream. If treatment of the
wastes is completely or partially provided for, reduction in the pollution
load upon the stream may be expected.
h. Nuisances such as floating sludge and bad odors are apt to de-
velop in polluted streams. These are greatest during hot weather. In
the summer, the violence of bacterial action reduces the oxygen con-
tent of the water and gives rise to the evolution of hydrogen sulflde and
foul odors. Fish are killed by lack of oxygen in the stream water. In
the winter a similar effect is produced because the ice-covered surface of
the water prevents reaeration and the action of the bacteria, though
slower on account of the lowered temperature, ultimately exhausts the
natural oxygen supply. The need for oxygen may result in the removal
of oxygen from unstable compounds. Thus, removal of oxygen from the
oxides of manganese in the silt of the stream bottom will result in the
formation of troublesome manganese salts. Black deposits of the oxides
of manganese may form when these manganous salts are acted upon by
the chlorine used in the sterilization of the filtered stream water.
14. Chemical Warfare Agents in Surface Water. — Surface water
supplies may be exposed to contamination by chemical warfare agents
distributed over the watersheds on which water is collected. The serious-
ness of the contamination depends upon the amount of the chemical agent
spread, where and how it is distributed, and the character of the chemical
agent itself. Each chemical agent has its own solubility, toxicity, and
rate of hydrolysis and decomposition. Chemical agents on the water-
shed at a point distant from that where the water is taken for use may
be expected to undergo decomposition more completely, and to be less
dangerous to the consumers than the same agent, in equivalent amount,
at the water intake. Odors and tastes of non-toxic decomposition pro-
ducts of the chemical agents may also be undesirable.
15. Ground Water. — a. If the surface water seeps down into the
earth it becomes ground water, and is recovered from wells or collecting
galleries. The surface water which enters the ground by percolation soon
changes its characteristics with the environment. The part which flows
into sinkholes, fissures, and other openings leading directly into the under-
ground consolidated rock retains many of the more objectionable charac-
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teristics of surface waters, such as the turbidity and high bacterial con-
tent, and is slow to alter in character. It remains essentially surface
water and without purification is correspondingly undesirable for drink-
ing.
h. As the water starts to penetrate the earth, it carries with it
suspended matter, including many bacteria, and it contains oxygen and
some carbon dioxide. Bacteria are numerous in the superficial layers of
the earth, but as greater depth is reached, the number of bacteria in
the soil rapidly decreases — unless the earth has been disturbed by man
or burrowing animals. One of the reasons for this decrease is the deple-
tion of oxygen in the soil air and its conversion to carbon dioxide through
the life and activities of the bacteria, algae, molds, protozoa and higher
organisms. Turbidity and bacteria are also reduced by the filtering out
of these suspended matters by their absorption on the surfaces of the
grains of the soil. The great increase in carbon dioxide brought about
by the utilization of oxygen by the organisms in the earth makes the
ground water much more active in the solution of carbonate rocks (lime-
stone and dolomite) and thus brings about the increase in the hardness
of the water which is observed where rock formations of this sort are
found. If other soluble substances are present in the earth and in the
underlying rocks, they too will go into solution. In the absence of oxy-
gen, and the presence of carbon dioxide, iron and manganese oxides are
converted into the soluble bicarbonates.
c. Ground water may be hard and contain iron, manganese, and
enough carbon dioxide to have a corrosive effect, but it is generally clear
when drawn and low in bacterial content. If ground water is not low in
bacterial content and hence is to be suspected of contamination and doubt-
ful or dangerous quality for domestic uses, it is practically certain that
the condition is due to the entrance of surface waters into the ground
water source. Usually, the pollution will enter at the top of the well,
though occasionally it will be due to sub-surface drainage within the first
eight or ten feet of the surface. In areas where sink-holes, fissures and
caverns exist, the pollution may enter a rock formation some distance,
even miles, from the source of the supply and be carried through pas-
sages in the rock to the spring or well from which the water is taken.
d. Ground waters continue their downward percolation through
unconsolidated earth until they reach a saturated zone, the upper surface
of which is commonly called the water table. When the water table has
been built up to a certain height by the addition of water from above, the
water begins to flow laterally toward an outlet, or to approach a static
condition. The greater the difference in the elevation of the water table
between two points and the greater the porosity of the intervening ma-
terial, the more rapid is the lateral movement toward the lower point.
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e. In the course of this lateral movement, the ground water may
pass underneath an impervious layer of clay, shale or rock, or a layer
which is so much less porous than the formation in which the water is
traveling, that it is essentially impervious. If the ground surface at a
point where the water-bearing formation, or aquifer, is to be reached by
a well, or where the aquifer comes to the surface, is below the water
table, a static pressure will exist. If struck at that depth, the water will '
flow toward the surface, producing an artesian well. An artesian spring
is similarly produced by a fault or other outlet to the surface.
/. The water table rises and falls according to the replenishment
of water from the surface by rainfall and the escape of water from the
area. When the water table drops below the bottom of a shallow well,
the well goes dry. When replenishment of the ground water by rains
takes place, the water rises and the well begins to yield water again.
g. If a well is called upon to yield water in large amount, the de-
mand may exceed the rate at which it can be replenished by the water
from the surrounding earth and the water surface in the well will be
drawn down below the surface of the water table. The distance from
this new level to the water table is called the “draw-down” of the well
for that particular rate of yield. The draw-down of the well is influenced
by the porosity of the earth. (See Fig. 2)
WELL
, GROUND
^STATIC LEVEL OF WELL
yUATPR TARI P
t
c3nE OF
^ INFLUENCE
CONE OF ^
INFLUENCE
*
DRAWDOWN
OPERATING LEVEL
OF WELL
Figure 2. Drawdown and cone of influence.
h. In unconsolidated material a depression will be formed in the
water table in the vicinity of the well. This depression will become less
as the distance from the well increases. This produces around each well
a “cone of influence” (Fig. 2), within which water will not be obtained
by other wells. The actual slope of this “cone” of influence is a para-
bolic curve, but for practical purposes it may be considered to be a
straight line. The base of the cone is sometimes called a “circle of in-
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fluence.” Wells within the circle of influence will have their water levels
lowered according to their position within the cone of influence. The slope
of the cone of influence may be experimentally determined by sinking
a series of wells on a radiating line from the yielding well and taking the
draw-down values for the other wells. If there is variation in the porosity
of the earth within the circle of influence, that area may not be truly
circular. Obviously, wells should be located far enough apart so that
when they are yielding their maximum quantities of water, the cones
of influence will not intersect.
i. When wells secure their water from beneath an impervious layer,
there can be no cone of influence reaching the earth’s surface. Never-
theless, there may be a reduction in the yield of nearby wells when one
well is pumped heavily. If a number of wells are pumped heavily in one
locality for a period of time, the draw-down of all of these wells may be
progressively increased. Discontinuance of pumping permits the return
of the draw-down of the wells to the original value by the normal replen-
ishment.
j. The flow of water in any water-bearing formation is presumably
in the direction of the dip of the strata. Therefore, it is not desirable to
locate wells along the dip line. It is better to locate the wells along a
line at right angles to the dip of the strata. This line is called the strike
of the strata. If the direction of the strike is known, the wells should
be placed along this line far enough apart so that one will not affect the
other’s yield. If faults, dykes, or other irregularities occur, they may
complicate the situation.
k. Ground waters will escape laterally from formations whenever
it is possible. The rate depends upon the porosity of the water bearing
material and the slope of the ground water table. In stream valleys,
at the foot of cliffs, and in general wherever the surface dips sharply,
escape of ground water may occur. If there is a definite current pro-
duced by the escaping water, a spring is formed. If the flow is so diffuse
or so small that no definite current is observed, seeps are produced.
1. In general, it may be expected that wells will decrease in yield,
rather than increase, over a period of years. In addition to the deple-
tion factor, there is often a movement of fine particles of sandy matter
toward the well bore, with the result that the interstices between the
coarse particles become packed with the smaller grains. The flow from
the surrounding earth is correspondingly reduced. Deposits of calcium
carbonate, and the oxides of iron or other relatively insoluble matter on
well screens and coarse gravelly materials surrounding the well bore may
cause a similar loss of water yield. Turbidity from the falling of earth
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from the roof of a cavern may cause this clogging and in addition, the
roof may collapse and produce a sink-hole which will cause pollution by
the surface runoff.
16. Wells. — a. Wells are classified in numerous ways, depending
on their depth, artesian or non-artesian character, the method of their
construction, and, sometimes, the character of the water delivered.
b. Depth. — Based on their depth, wells are classified roughly as
shallow or deep. To the geologist a deep well is one which derives its
water from beneath an impervious stratum. Since it is often impossible
to learn about the geological conditions encountered when a well is sunk,
and hence also impossible to learn whether or not an impervious stratum
was passed through, it has become customary to define a deep well, arbi-
trarily, as any well which is 100 feet or more in depth.
c. Artesian character. — The geologist considers an artesian well
to be one in which the water rises toward the surface under a static pres-
sure. The flow does not need to reach the surface according to this defi-
nition.
d. Method of construction. — There are a number of variations in
the methods of penetrating to a water-bearing formation in well construc-
tion and each method has a name. This discussion concerns only four of
the construction types: the dug well, the bored well, the driven well, and
the drilled well. Each type has its own peculiar advantages and disad-
vantages, based on diameter, depth, limitations as to formations which
can be penetrated, character of the casings used, and the ease with which
the well can be safeguarded against pollution. In general, wells of large
diameter have the advantage of greater storage capacity and the ability
to utilize the water of formations which yield only small amounts of
water in a given period of time. However, their larger perimeter makes
them more difficult to protect against the entrance of polluting materials
and more difficult to case. Bored and driven wells cannot be sunk in con-
solidated rock or, except in fortunate locations, in boulder-bearing ma-
terials. Dug wells may be put down through such hard materials, at
the expense of large amounts of labor and explosives. Drilled wells are
adapted to great depth and hard rocks, but on account of their small di-
ameter, have limited storage. They are so readily protected against sur-
face pollution however, that water from them is usually safe.
e. Character of water delivered. — Wells are often spoken of as
mineral wells. This term commonly means that the water produced is
high in mineral salts, but strangely enough is sometimes used to indicate
water which is particularly pure, or low in solid content. Mineral waters
have been minutely subdivided into types on the basis of the kinds of
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SINGLE CASING
DOUBLE CASING
WATER TROUGH
DRAIN PIPE
OUTSIDE
CASING
CONCRETE
CURB
CASING
v-'9P
( L\
DROP PIPE ~ZI:^
^ 7-^'i nr^/ ,
soil
ROCK
fe^=,CLAY
BOTTOM
INSIDE CASING,
WATER LEVEL^^== ==i.
BOTTOM
OF CASING
WELL ROD
CYLINDER
PUMP
CYLINDER
PISTON
INSIDE CASING
TOP SOIL
BOTTOM OF OUTSIDE
CASING SEALED IN
ROCK
FISSURE REACHING
TOPSOIL AND THRU
WHICH WATER FLOWS-
WATER SUBJECT TO
POLLUTION.
WATER LEVEL
■BED ROCK
FISSURE IN ROCK THRU
WHICH UNPOLLUTED
WATER FLOWS.
OOT VALVE
STRAINER
Figure 5. Drilled well.
dissolved substances contained and their supposed physiological action
on the human body. Waters which contain hydrogen sulphide are often
high in public esteem as mineral waters in spite of their offensive odor.
Waters high in sodium chloride are usually objectionable to most per-
sons when they first drink them, but familiarity and continued use fre-
quently cause these waters to be preferred, if the chloride content is just
at the concentration where a definite taste is imparted.
/. The characteristics of the four principal types of wells, based
on construction procedure, are shown in Table Number I.
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TABLE NO. I
GENERAL CHARACTERISTICS
OF WELLS
Type of
Well
Normal
Diameter
Normal
Depth
Method of Construction
Remarks
Dug
Fig. 3
3-6 feet
20-40 ft
Pick and shovel usually. Drill
and explosives. Windlass and
bucket to raise materials. Stone,
brick, or wood casings.
Most common in old wells.
Usually restricted to loose
materials.
Bored
2-12 in.
(but up
to 24")
20-100 ft
Hand or power-driven augers.
Clay, cement, metal, or wooden
casing.
Cannot be constructed in
consolidated rock, large
gravel, or boulders.
Driven
Fig. 4
1-6 in.
10-200 ft
Pipes, with driving shoe, sunk
by pile-driver, water jet or a
combination or with screen and
drive point, using sledge, maul,
or drive monkey.
Cannot be constructed in
consolidated rock or large
boulders. Better results ob-
tained if well is equipped
with a sand screen. May be
gravel -packed.
Drilled
Fig. 5
3-20 in.
100 ft or
more
Power-driven percussion or rota-
ry drilling machines.
Can be constructed in nearly
any kind of rock in which
water is found. Capable of
reaching great depths. For
military use, wells over 1000
ft. deep or in very hard rock
are unlikely.
17. Springs. — a. Springs are commonly classified as follows:
Class I — ^The water in its lateral movement comes to the sur-
face at a point where a porous stratum overlies a relatively impervious
stratum. This is probably the commonest type of spring. Flow may or
may not persist in times of deficient rainfall. The porous stratum may
be sand, gravel, till, or porous rock and the underlying stratum may be
clay, shale, or any relatively impervious rock.
Class II — This class of spring derives its water from a pervious
collecting stratum which passes under an impervious stratum of some
sort, so that an artesian type of flow is produced when the impervious
cover is broken through in some manner. A fault, or a joint plane in
consolidated rocks, may supply the opportunity for the water to escape,
or the covering material may be eroded away by the action of water,
disturbed by man, or otherwise weakened until the water of the spring
breaks through to the surface. This type of spring is sometimes called
an artesian spring.
Class III — ^This type of spring is a mere overflow of ground
water and consequently is highly variable in its delivery. It occurs
whenever the ground water level, or water table, intersects the earth sur-
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face and the formation is sufficiently porous to allow the water to escape
with the rapidity necessary to produce a flow having a distinct current.
As the volume of water falls off, the flow decreases in velocity and ulti-
mately the spring becomes a seep. There is no impervious cover involved
and the impervious substrata may be considerably below the point of
emergence of the water.
h. The yield of springs is often variable in volume. Frequently
there is a marked increase in flow after heavy rains due to the building
up of the slope of the ground water table and the more rapid, lateral move-
ment of water toward the outlet. If turbidity accompanies the increase
in yield, it suggests that surface waters are gaining access to passages
in the rocks from which the spring derives its water, and if this is so, the
bacterial condition of the water will probably be bad.
18. Sea Water. — a. The surface water streams and the flow of
ground waters from springs and seeps along the shore or in the sea bot-
tom, contribute water to the sea, as does the fall of rain water. The
salinity of the sea water is due to evaporation and the abandonment of
soluble salts.
b. Sea water is used only as a last resort in water supply. It is
very high in its dissolved salt content, and frequently contains living
organisms and suspended matter. In order for sea water to be usuable,
the concentration of the salts must be greatly reduced. Ground waters
and surface waters vary greatly in their salt content, ranging from a
purity approaching that of rain water to salt concentrations even greater
than that of sea water. While the salt content of sea water is approxi-
mately 37,000 parts per million, most surface and ground waters which
are used for drinking purposes will contain less than 500 parts per million
of dissolved solids.
c. It is desirable to Alter sea water prior to distillation and to select
carefully the intake site so as to reduce the organic content of the water
taken for treatment. Sedimentation (Fig. 6) should be provided to per-
mit separation of sand from the sea water and the incidental rise of oil
to the surface. Intakes near beaches are likely to pick up both sand and
oil. Jetted drive point wells on the beach can often be used to advantage
instead of intakes in the sea.
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TO RECEIVINO VESSEL. DO NOT PLACE ANY
STATIC WATER HEAD ON DISCHARGE FROM STILL
PLAN
NO SCALE
Figure 6. Suggested lay out — sea water distillation point for
either a 250 gal per hour or 50 gal per hour unit.
d. It is possible to secure water of reduced salt content by digging
infiltration gallery trenches near the shore, thereby intercepting ground
waters from the land as a part of the supply. Water that filters through
the sands from the sea into the infiltration gallery, will also be reduced
in its content of organic matter.
19. Choice of a Water Supply Source. — a. The first consideration
in any water problem as already noted, is the securing of an adequate
volume of water. It may be necessary to use several sources in order to
secure the required amount. But where a selection may be made among
several water supplies which offer an adequate volume of water, quality,
ease of procurement, distance between source and point of use, and num-
erous other matters enter into the final selection.
h. There will be occasions when time will be available for thorough
study of several possible sources and for the balancing of considerations
to determine the most advantageous source. In the majority of cases
time is not likely to be available for consultation, study, securing hydro-
logical records, and the investigation of alternate sources. However,
even the most temporary water supplies require consideration to avoid
undesirable waters when it is possible to secure better sources in the
time available, with the equipment at hand and within the designated
area. A hasty estimate of quality and adequacy may be all that is pos-
sible and the controlling geological and hydrological factors which deter-
mine continuity will not be determined. Under these conditions, the
needs of the moment, not other seasonal and demand requirements, will
determine the actual point at which to begin work.
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Chapter 3
DEVELOPMENT OF WATER SOURCES
20. General. — a. In general, the development of entirely new water
supplies will be avoided, but where an entirely new source must be de-
veloped for temporary use, the steps in the development would usually
be based on the following scheme. (Assuming lack of exact geological
knowledge.)
(1) The first step would be to develop a surface water source
and treat the water with the usual water purification equipment of engi-
neer troops, unless it is heavily polluted, contains algae in excessive
amount, is contaminated by warfare chemicals, or is otherwise dangerous
or objectionable.
(2) If there is no suitable source of surface water, the next
effort would be to try boring, driving, jetting or washing down shallow
wells, or even to construct infiltration galleries in a stream bed a few
feet back from the water’s edge where overflow after a rain is not too
likely. (See Chapter 2) If the valley is narrow, sheet piling may be used
if necessary as a subsurface dam to hold back the shallow ground water.
Water of recently constructed wells is often turbid and contaminated and
will require passage through the usual purification apparatus. However,
reduction of particularly objectionable foreign substances in the water
as compared with the objectionable surface source should make treat-
ment of the ground water easier. Wells in the terraces along the stream
may be used, if overflow of wells at lower elevation seems likely to occur
at times of freshets. Multiple-well systems may be required.
(3) (a) If the shallow wells do not yield freely enough, it will
be necessary to go deeper for ground water. In the interest of economy,
it is desirable to go no deeper than necessary to get enough water, unless
the lower waters are known to be sufficiently better to make the use of
time, man-power and equipment worth while. The wells may be pumped
with ordinary suction pumps unless the lift is too great (22 feet is a safe
maximum). If the lift is greater than 22 feet, a suitable plan is to install
a central-type, air-lift pump (see Chapter 6) or to improvise such device,
and deliver the water by means of a sweep elbow into a tank from which
it may be pumped with the pump units of the portable or mobile water
purification apparatus. A maximum depth to reach is about 1000 feet,
but at this depth unless the water level rises more than half way, it is
unlikely that air-lift pumping will be possible with adequate efficiency.
Standard motorized air compressors are contemplated as sources of the
air for air-lift operation.
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(b ) In the field, the wells put down will be of small diameter
and the casing used as the eduction pipe. If time permits, wells of greater
diameter may be sunk by means of cable-tool (percussion) rigs, or wells
sunk by rotary methods may be reamed to greater diameter. Exploratory
drilling with core barrels of I’otary well rigs will permit the taking of
cores in solid rocks. Limestones, sandstones, and shales may usually be
penetrated readily. When hard rocks, such as trap rock and granite, are
struck by any method of well drilling, continuance of the drilling is us-
ually unprofitable.
b. Concrete basins or tarpaulins draining to storage cisterns, may
be used to collect rainfall. The rainfall in inches, the area of collecting
surfaces, and the storage provided determine the quantity of water which
will be available. Storage cisterns are usually constructed below ground
level for protection, for cooling, and for ease in providing the necessary
downward gradient from the collecting surfaces, but occasionally the
cisterns will be elevated or enclosed within the buildings to be served. In
any event, provision should be made to prevent pollution of the water by
wasting the first flushings of the collecting surfaces, by preventing the
entrance of surface water, and by covering the top of the cistern. It is
well to screen vents to prevent the entrance of adult mosquitoes and other
insects that lay their eggs on a water surface. This precaution is espec-
ially important in localities where malaria or yellow fever may be ex-
pected, Down-turned elbow vents can be covered with fine metallic
gauze,
21. Surface Water Intakes. — a. In selecting the point from which
surface water is to be drawn, it is necessary that the water be as little in-
fluenced by agitation of bottom deposits, organic pollution, and floating
debris as possible. It is necessary, however, that an adequate amount of
water be available and continue to be available throughout the period of
time the water will be withdrawn from the selected source. In temporary
installations the protection against violent weather conditions, move-
ments of the stream bed and other occasional difficulties, will not usually
receive the attention which they would merit in permanent installations.
The intake screen should not rest on the bottom, nor should it be sus-
pended so near the surface of the water that air and floating matter may
be drawn into the suction pipe. If the water is too shallow for these con-
ditions to be fulfilled, it will be necessary to increase the depth. This may
be done by digging a pit in the stream bed or by building a temporary dam
of sand bags, sheet piling, earth, stone, or logs and brush. (Fig. 7)
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PICKETS WIRED
TOGETHER
CORRUGATED
IRON SHEETS
.WOOD OR ANGLE
IRON PICKETS
4/1 SLOPE
WATER LEVEL
- BED OF STREAM
\ ‘
note;
FOR LOW DAMS A SINGLE ROW ^
OF SHEET PILING BETWEEN TWO \ \
ROWS OF WALING WITH CLAY \J
BACKING WILL SUFFICE IF WELL ^
DRIVEN.
Figure 7. Improvised dam.
b. More permanent reservoirs justify efforts to secure information
regarding expected rainfall, stream flow, evaporation, water losses, and
the rapidity of the collection of silt. Dams, spillways, delivery lines,
intake works will also require more careful design. In general, although
great variation may be expected, it will be unwise to expect to impound
for use more than 10 to 25 percent of the annual flow of the average
small stream.
c. The screen selected for the intake hose or pipe should have aper-
tures totaling in area about three times the cross-sectional area of the
pipe because there is a definite hydraulic entrance loss for each of the
apertures and because there will be an accumulation of obstructions on
the screen surface. It is not desirable to have to clean the screen fre-
quently during the pumping period. It is possible to locate the intake
so that debris will be carried away from it and so that the screens will
clog less frequently. The vertical position of the screen can be control-
led by attaching it to a float so that it will hang suspended in the water
or by surrounding it with a larger cage made of iron bars or strap-iron.
Flexible joints in the pipe line or the use of hose will permit the rise and
fall of the float-supported intake screen.
d. In most streams, particularly streams of considerable flow, it
will be found that the quality of the water across the section of the stream
will be variable. Below sources of pollution, such as sewer outfalls, it
may be found that the polluting matter has a definite thread of flow
which follows a pattern dependent upon the character of the stream bed,
the course of the stream, and the fall. In general, in long, straight sec-
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tions of a stream, the thread will follow the margin of the stream on the
side of entrance and the sewage, if warm, will float upon the cooler sur-
face. Where there is a curve in the bed, and the sewage flow enters on
the inner side of the curve, the thread of flow will tend to pass across
the stream toward the outer side of the bend. Then there will be a tend-
ency to submerge and cross back to the side on which it entered. In the
course of these crossings the thread of flow will broaden and the pollu-
tion will be more thoroughly distributed throughout the whole stream.
Where there are riffles, dams, or falls, or where the stream velocity is
great, the agitation and turbulence will accelerate the attainment of a
uniform composition.
e. If time permits, tests with floats are useful in determining the
character and direction of surface currents. Submerged vanes with sur-
face floats will help to indicate conditions at lower levels.
/. Tidal back-waters should be avoided when possible because of
the possibility of the back-flow bringing in pollution from lower por- |
tions of the stream. During high tides there may be more salt in the
water at the intake.
g. Low velocity of streams frequently means stagnation and the i
opportunity for dense growths of algae to accumulate and produce clog-
ging masses of odorous vegetation. High velocity prevents the settling
of suspended matter and increases the turbidity. The mud loads carried,
particularly near the bottom, are usually greater when the velocity is
high, and relatively coarse sedimentary matter may be carried.
h. Winter and ice conditions impose certain considerations upon
locating intakes for surface water. If the water surface is covered with
ice, a hole may be cut through which the intake line is dropped to the
desired depth, if the depth of the water below the ice permits. Unless
the water in the intake line is kept moving fast enough, the whole intake
line, being exposed, is likely to freeze.
i. Ice exists in several forms the most common of which is a sur-
face sheet. Two forms which cause trouble are anchor ice and frazil ice.
Anchor ice forms on the beds of streams, coating the rocks beneath the
water surface, and may clog bottom intakes. Frazil ice, or spicular ice,
consists of needle-like ice crystals which form throughout the mass of
the water and may also clog submerged intake screens.
j. Water plant operators must be particularly attentive to their
intakes in winter time. If the intake structures are permitted to freeze
into the ice, they may be lifted, torn loose, or carried away by the ice
of a rising stream. Winds may pile ice along the shore, buffeting, bat-
tering, and crushing exposed intake structures. At the time of spring
thaw, ice jams are likely to cause the flooding of low lands and to drive
masses of ice far up onto the shore.
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k. Certain physical conditions of the intake site merit considera
tion. It is advantageous to select a site which has an adjacent area for
the erection of the pumping equipment. Military conditions may impose
the necessity for concealment of the intake, the suction lines, the pump-
ing and purification equipment, and storage facilities. Submerged in-
takes, buried suction lines, overhead cover for the pumps, filters, and
tanks, and the avoidance of tracks of men and vehicles, may also be nec-
essary.
22. Pump Location. — It is advantageous to keep the pump which
lifts the untreated water as close to the intake point as possible. The
friction of the screen, intake, pipes, elbows and hose should be kept to
a minimum. The pump should be as near to the surface of the water as
possible in order to reduce the suction lift; if it can be put in a pump well
below the water surface, with a positive head on the pump suction, so
much the better. Friction in hose lines is reduced by keeping the lines as
nearly straight as possible and with a minimum of humps which intro-
duce friction dnd permit air pockets to form at the high points. It may
be necessary to install booster pumps, or to provide one or more stages
of lift from one tank to another if the distance from the intake to the
purification equipment and final storage is too great.
23. Substream-Bed Sources. — If the character of the stream water
is bad, if the quantity is insuflftcient, if off-shore conditions make location
of the intake difficult, if concealment is not readily provided or if a suit-
able location for the water point equipment cannot be found, it may be
desirable to exploit the ground water resources of the stream-bed sands
and gravels or those of the bank of the stream. Infiltration galleries, dug
wells, wash-down wells or driven wells may be used as sources of supply.
Several shallow wells may be manifolded together, if necessary, in order
to secure a sufficient amount of water to keep the pumps operating con-
tinuously.
24. Intakes in Lakes and Ponds. — a. Lakes and ponds sometimes
offer convenient sources of water in the field. Most of the considerations
which apply to the selection of intake sites on streams (Par. 21) also
apply to the intake sites on the shore of lakes and ponds. Of course the
water of lakes and ponds ordinarily is not continuously flowing by the
selected intake pipe, carrying debris and materials from the upper por-
tion of a watershed as in the case of streams. Except in the dry season,
there is always drainage from the shores into a lake or pond and the en-
trance of tributary streams which bring materials which may modify the
condition and composition of the water available in the collecting basin.
b. Lakes and ponds do have currents. Sometimes a lake has a defi-
nite inflow and outflow to produce the currents; sometimes the currents
are caused by winds or by temperature changes which modify the density
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of the water. Onshore winds have a tendency to produce on-shore cur-
rents, building up the level of the water with resultant off-shore or under-
tow movements of bottom water and outward beach scour. If the cur-
rents are driven by heavy winds, the violence of the effect is greatly in-
creased and a surf, or wave impact action is produced. Large waves may
stir up a lake to depths of thirty or forty feet. Off-shore winds push the
water away toward the distant side of the lake, tend to lower the level
of the water at the near shore line and bring up cooler, bottom waters,
sometimes in a state of partial oxidation.
c. Lakes and ponds frequently support considerable quantities of
algae and other aquatic vegetation. Dead vegetation falls to the bottom
and there it continues its decomposition under the action of bacteria and
other living organisms which require oxygen for their metabolic pro-
cesses. The oxygen is taken first from the water and thereafter from the
next easier sources, the more easily reducible compounds such as nitrates,
sulphates, and the hydrated oxides of manganese. Ammonia, sulphides,
and soluble manganese compounds result from such reducing effects.
Some organic compounds having musty tastes and earthy odors may be
produced. Under certain circumstances compounds which react with
chlorine to form chlorine-addition products of objectionable odor and
taste, may be developed. Intakes near the surface may avoid these com-
pounds, unless the whole lake or pond is stirred up.
d. Vertical circulation of many lakes and ponds may be expected
in the spring and fall due to seasonal temperature changes. Pure water
has a point of maximum density at 3.98° Centigrade (39.2° Fahrenheit).
Above the point of maximum density, the weight of a unit volume of
water decreases with temperature rise. Below the point of maximum
density the weight per unit volume also decreases with the temperature
fall until the temperature of 0° Centigrade, or 32° Fahrenheit, is reached.
Then, with the formation of ice, a further decrease in density and an ex-
pansion of the order of 9 or 10% takes place. This has an important bear-
ing on lakes in the temperate zones. In the fall, as the air temperature cools
the surface water toward the temperature of maximum density, there is
a progressive sinking of the heavier water toward the bottom, mixing
with and bringing toward the surface, the warmer water. This is the fall
overturn. Just before freezing takes place, the point of maximum density
is passed and colder, but now lighter, water remains at the surface and
freezes. In the spring, the surface ice melts and leaves a cold surface
water slightly above the temperature of maximum density. The water at
the bottom, in shallow lakes or ponds, has been warmed slightly by the
heat from the earth and the slow oxidation taking place. The surface
water exposed to the air is warmed to the point of maximum density and
sinks, bringing up the warmer water from the depths of the pond to take
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its place. This mixing continues until all of the water has reached the
temperature of maximum density. This is the spring overturn. Between
the periods of spring and fall overturn, or circulation, there are two qui-
escent periods which are sometimes called the summer and winter stag-
nation periods.
e. Intakes on large lakes should be located with some consideration
to protection from the direct action wind-driven waves. Otherwise they
may be subjected to a severe buffeting by waves and ice. If possible, the
intakes should be to windward, that is, on the side of the lake from which
the prevailing winds come.
25. Sea Water Intakes (Fig. 6). — a. Sea water intakes will usually
be located beyond the surf, off the beach, or in the deeper water of a
protected inlet. The quality of the water will differ according to loca-
tion. The water of estuaries may be influenced by the amount of fresh
water being poured into them from tributary streams. The estuary water
will usually be lower in its saline content than sea water, but it may con-
tain a considerable quantity of polluting materials and city drainage.
Water taken from the surf will usually contain flne sand and, at times,
oil which has been discharged from passing ships. Water from protected
inlets may contain more of the marine algae and other living marine or-
ganisms than the water from the open sea, and these organisms may con-
tain volatile compounds of a pronounced flshy odor and taste.
b. Shallow beach wells may be practical as a means of securing
water of lower salt content and freer from sand, oil and marine life.
They may also be sunk nearer the line of vegetation and thus assist in
the concealment of beach installations which must depend upon the use
of salt wdter and distillation.
c. Sea water intakes located on beaches must be carried out con-
siderable distances in order to take care of fluctuations in rise and fall
of the tide and at the same time have sufiicient submergence for the in-
take screens at all times. The action of the surf on such intake lines may
be violent. Strong means must be devised to hold the intake and its pipe
line firmly in position. Piles, jetties, rock, and rip-rap are used for this
purpose and for protection. On-shore winds, storms, tidal waves, and
wave tossed debris or ice may also endanger the beach intake.
d. The exposed position of a beach water supply intake is a mili-
tary disadvantage. Dispersion of water production facilities becomes
necessary and the concealment of equipment, pipe lines, storage tanks
and personnel must also receive attention. Protection of personnel and
equipment against cold winds from the sea may be secured by placing
them behind dimes, if they are available, or behind artificial barricades.
It will often be better to construct beach wells than to depend upon pipe
lines from the sea. Sea water will not enter into the normal military
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water supply problem; it will be provided only for emergency use, or
when it is not feasible to secure natural fresh waters in sufficient amount.
26. Permanent Intakes. — a. Engineer personnel will occasionally
be called upon to operate, modify, or plan and construct permanent sur-
face water intakes on streams, lakes, or artificial impounding reservoirs.
These intakes may be submerged or exposed. They may be simple or
elaborate structures and their exact locations may require extensive
study and a knowledge of river control procedures to insure the perma-
nence of an adequate depth and volume of water at the ports of the
intake.
b. Submerged intakes (single or multiple) may be simple screened
pipes carried out to deep water where they will offer little obstruction
to the flow of the stream, avoid ice scour during the spring break-up of
surface ice, and offer a minimum of obstruction to navigation. They may
be secured in position with cribbing, and sometimes given additional pro-
tecton by piles, rip-rap, rock, or concrete. Intake screens of submerged
intakes are usually relatively coarse, made up of bars of strap iron. The
area of the screen openings is about three times the cross sectional area
of the bore of the pipe and it is designed to have an intake velocity of
less than 0.5 foot per second in order to prevent clogging of the screen
by fish. At times in the past the screen area was required to provide at
least one square inch of opening for each gallon per minute of rated pump
capacity. This is about ten times the suction capacity of the average
steam pump that would be connected to the screen. If the water was of
low turbidity, a smaller screen, even half this size, might be satisfactory.
Finer screens to remove material not rejected by the coarse outer screen,
may be provided and placed where they can be cleaned more easily and
frequently than the submerged intake screens.
c. Exposed intakes are generally preferred for larger water plants
although they have the disadvantages of increased cost, increased inter-
ference with navigation, and increased difficulties with floating ice and
debris. Usually, however, they are less likely to become clogged, permit
choice of one or more levels from which to select the water, and are easier
to operate, inspect, and maintain. Exposed intakes usually take the form
of intake towers or intake boxes with inclined screens going down into the
water source. Calculations for the latter type of screen, since it is only
partially submerged, should include only the area beneath the water sur-
face. Box-type intakes are sometimes designed in such a way as to per-
mit the operator to divert a portion of the raw water through the intake
box to flush the normal intake screen, cleaning it of accumulated debris.
At other times a different scheme is used to produce a back flow to clean
the screen. Intake towers may be of either the wet-well or dry-well type.
The former is essentially a tower having various intake ports at which
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water may be admitted, with a delivery conduit leading to the plant. The
dry-well type of tower has the conduit pipes connected directly to the
intake ports, and these ports are controlled by valves in the pipes. The
entire tower of the dry-well type is accessible for operation and repair.
Both towers must be structurally stable, heavy enough to prevent floating
when unwatered, strong enough to withstand water, ice, and wind pres-
sures, and the forces due to earthquake shock. The intake ports are
usually placed on the down-stream side of the tower or at right angles
to the current to avoid clogging by debris. Various levels of ports pro-
vide for stream or lake height fluctuation and permit selection of the best
available water from time to time, based on depth.
d. When intake towers are installed in an impounding reservoir they
are usually placed at the deepest point, commonly near the dam which
forms the reservoir. This renders the maximum capacity of the reservoir
available,
e. The intakes should discharge by gravity into an adequate suction
well so constructed that the suction pipes of the pumps will always be
submerged. Since the suction lift of pumps is limited to about twenty
feet, pumps should be placed in a pit deep enough to permit them always
to draw water from the suction well, no matter how great the fluctuation
of the water supply source. If water level variation at the source is ex-
pected, the pumps should be mounted on a platform which can be raised
or lowered to insure their proper functioning. If a positive head of water
can be maintained on the suction port of the pump, priming difficulties
will be eliminated.
27. By-Passes. — Public health authorities will object if the con-
struction of the plant permits untreated water from the surface source
to be pumped around treatment equipment and into the mains of the com-
munity. The mere possibility of such passage of untreated water into the
distribution system will prevent the approval of the supply by the public
health authorities.
28. Development of Ground Waters. — a. Except in those places
where ground waters issue from the earth under artesian pressure, or
where they can be tapped at an elevation conveniently located so they can
be withdrawn by gravity, it will be necessary to make arrangements to
lift the water by means of a pump. When the water is near enough to
the surface, an ordinary pump located at ground level with a suction lift
of about twenty feet will be ample, but in many cases the depth of water
will require a lift greater than the capacity of a simple suction pump. It
will then be necessary either to use a deep well pump or to lower a pump
into the earth and to use a portion of the positive lift capacity to raise
the water to the desired elevation.
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b. Where there are existing ground water supplies they should
be exploited to the utmost. Hand pumps may be removed from wells
and power-driven apparatus installed to elevate the water. Larger pumps
may be substituted for existing power units of small capacity. Surging,
acid washing, and other means (Chapter 7) may be used to increase de-
livery of the existing ground water sources. Deepening to reach more
productive strata or replacement of screens to reduce resistance and in-
crease yields may also be feasible.
c. (1) If the military situation demands the development of addi-
tional ground water supplies, speed will be important. The first water
that can be obtained may be required for the troops. The construction
work involved will almost invariably cause the water to be turbid or
muddy. It is very likely that there will be sandy material included with
the muddy or earthy suspended matter. It will probably be bacterially
contaminated and will require filtration and chlorination to render it ac-
ceptable as drinking water.
(2) Suspended matter in the water from the new source may en-
danger the pumping equipment unless it is specially adapted to the hand-
ling of the earthy and sandy materials. Turbine pumps, rotary pumps,
reciprocating pumps, and others with closely fitting moving parts are
quickly abraded and damaged by gritty matter. Certain other kinds of
water-lifting machinery are adapted to delivering the sandy water of
new sources. Such equipment includes the diaphragm pump, air-lift,
canvas-belt elevator, and open impeller centrifugal pumps. After the
well has been developed pumps which are affected by grit may be installed
with reasonable safety. By making this change-over the greater efficiency
of these pumping machines may be utilized.
d. Shallow' w'ells may be dug, driven, or otherwise sunk in places
where the surface contours suggest the presence of ground-water. Deep
wells may be drilled to relatively great depths if there is reason to think
that water bearing strata carry a sufficient amount of water to justify
the work involved. It will frequently be best to drill a relatively small-
diameter well as an exploratory measure and then enlarge it if it is suc-
cessful. Small diameter w^ells can be sunk and placed in production more
quickly than can larger wells. A number of small wells can be sunk if re-
quired. Later, when there is less urgency, the small wells can be reamed
to larger diameter or larger-dianieter wells can be sunk to the level of
aquifers already located. The screens and equipment of these larger
wells can be more accurately specified than can the apparatus for the
small, hastily-sunk sources. Since the time available for larger wells
will permit it, the development of the large wells may be carried to a
degree sufficient to eliminate the dangerous load of grit before the more
efficient pumping equipment replaces the air-lift used initially.
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e. All ground waters from new sources should be chlorinated until
their safety has been assured by repeated bacteriological examinations,
and continued until there is no possibility of contamination under any
circumstances. It usually takes several weeks to eliminate all of the
contamination incident to the new construction. The removal of the con-
tamination may often be hastened by chlorination of the source with
heavy doses of chlorine-yielding compounds if enough of the chemical
can be made to reach all those places within the well where objectionable
bacteria have lodged. The required treatment should be applied to all
waters until they have been proved safe and free from the possibility of
casual or intermittent contamination.
29. Development of Springs. — a. To pump spring water easily it
must be collected in a basin after it emerges from the earth unless the
flow from the spring is so tremendous that it forms a reasonably deep,
water-filled channel. A temporary basin may be prepared by boxing in
the area about the point of emergence by means of crude walls of sand-
bags or wooden planking, or by digging into the ground to a sufficient
depth to form a pool of the desired capacity. Such crude basins are al-
most certain to permit pollution of the water by surface wash and will
require careful treatment before use.
b. Covered concrete spring boxes, if properly designed and made to
extend back into the earth a sufficient distance, may exclude the polluting
surface waters. Hillside surface flows may be diverted from the box by
digging a V-shaped trench with the point of the V uphill and the sides
of the V straddling the spring box. The overflow from the spring box
should pass through a pipe far enough above the ground level that it is
unlikely that surface waters or small animals may enter through the pipe
and pollute the spring water within. It may be desirable to screen this
outlet pipe to exclude insects. The fiow of some springs may emerge
from channels in the limestone or other cavernous rocks of the region
which have sink-hole openings and permit the admixture of polluted sur-
face wash with the normal ground water collected by percolation. At-
tempts to develop springs to increase their yield may sometimes be un-
successful.
30. Dug Wells (Fig. 3). — a. Next to springs, dug wells repre-
sent man’s most prolific source of ground water. Licks discovered by
animals and natural water holes indicate potential well sites; these may
be exploited by digging. By deepening the excavation, increasing the dia-
meter, and adding a casing, wells of this type can be provided. Where
the water table is close to the surface, where the porosity of the earth
permits relatively free drainage of water into the excavation, and where
it is possible to sink and case the well without the walls caving in, dug
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wells may be a very satisfactory means of securing ground water in the
field, particularly if only elementary construction equipment is avail-
able.
b. Dug wells have the advantage of utilizing water from practically
all of the formations which they penetrate. They permit the storing of
considerable quantities of water because of their relatively large dia-
meters and the reservoir effect thus produced. However, on account of
the large opening and the large perimeter to be protected against the en-
trance of surface drainage, dug wells are subject to pollution by sur-
face wash, by windblown material and even by objects falling into the
opening. This pollution is readily overcome by treatment with the mobile
and portable water purification units or by chlorination in a Lyster bag.
c. Dug wells are seldom less than three feet in diameter and they
may be much larger. Usually they are 20 to 40 feet deep, although close
to a stream, water may be secured at lesser depths. Dug wells over 60
feet in depth are unusual. Since they are usually dug by hand, great care
must be taken to shore up the walls as a safety measure. They may also be
sunk by the use of a grab-bucket. Dug wells are ordinarily limited to un-
consolidated earth.
d. Particularly favorable locations for dug wells are in the flood
plains and alluvial terraces of streams, beside lakes and ponds, and, gen-
erally, in those places where high ground water levels may be expected.
31. Infiltration Galleries. — a. Infiltration galleries are essentially
long, horizontal, shallow, dug wells. Frequently they are sunk along the
banks of streams where they intercept water flowing toward the stream.
When the water in the stream is temporarily higher than the water table
in the flood plain, the direction of flow may be reversed.
b. In the field, infiltration galleries may take the form of trenches
beside streams, lined with plank sheathing on the inshore side, or unlined
and ditch-like. In municipal practice, infiltration galleries may take the
form of timbered tunnels or buried tile lines laid with open joints and
draining to a pump sump. By the nature of its source, the water resembles
that of a dug well or spring. In places where iron is likely to be de-
posited by ground waters, or where fine sands may pack around coarser
materials, the interstices of the earth may clog and reduce the yield
of infiltration galleries. Such a reduction in capacity may require a
period of years. Infiltration galleries are most suitable for localities
where the flood plains of streams contain coarse sediments of sand and
gravel. Under these conditions large quantities of water may be re-
covered. Large communities have been supplied by infiltration galleries.
The largest city known to be dependent entirely on infiltration galleries
in 1941 was the city of Des Moines, Iowa, with a population of about
150,000.
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32. Bored Wells. — a. Bored wells are wells which are sunk by
hand or power augers and cased with wooden planking, tile, or sheet metal.
They vary in diameter from 2 to 24 inches. They can be sunk only in
unconsolidated earth in which boulders are not large or numerous. Depths
of 100 feet may be reached, but depths over 40 feet are unusual.
b. The advantages and limitations of bored wells are essentially
those of the dug well. They have a smaller diameter than dug wells, and
consequently have less storage capacity. But the smaller diameter and
perimeter make it easier to protect the bored wells at the top. Fabri-
cated casing materials are usually available or may be readily impro-
vised.
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33. Driven Wells. — a. The term “driven well” is used to describe
a tubular well sunk by any one of several processes, but not to be con-
fused with the methods employed for hard-rock drilling. These pro-
cedures are, in general, limited to unconsolidated sedimentary deposits
relatively free from boulders, but in which the coarseness of the deposit
permits such a swift flow into the well that the rapid and continuous re-
moval of water by pumping is possible. Driven wells are of very small
diameter for the most part and consequently it is impossible for a large
volume of water to be stored within the casing.
b. The procedures which are most commonly used in sinking driven
wells are the following:
(1) The jetting, or tcash-down process. — In this process a string
of pipe is sunk into the ground by means of a jet of water which re-
moves the earth at the bottom and carries it out of the well. Sometimes
a special well screen with a valve designed to allow jetting is used at the
end of the pipe. Occasionally the well casing is open; gravel may be
dropped in to form a screen or a commercial well screen may be inserted
into the pipe and the pipe jacked up a short distance to permit the con-
tact of the sand of the formation with the well screen.
(2) Use of a casing with drive shoe and bailer. — In this process
a heavy iron drive shoe with a cutting edge is screwed to the end of a
drive pipe and the earth within the pipe is removed by suspending it in
water and lifting it out with a bailer. The bottom of the well may be
gravel-packed, or a well-screen may be lowered into the well and packed
in place after the drive pipe has been jacked up a few feet.
(3) The drive point process, (a) This type of well (see Figs.
4 and 8) comprises a series of lengths of pipe, joined by pipe couplings,
and fitted at the upper end with a pump and at the lower end with a point
and a sand screen through which water is admitted. The first, or point
section consists of a 4 to 5 foot length of perforated pipe, usually covered
with a screen, at the lower end of which is a mild steel point which serves
to break through thin layers of hard material and to push aside the
pebbles or rocks it encounters. After this section has been driven, the
next section is screwed into place and driven like the first, and so on, until
the water-bearing stratum is reached, or further progress prevented by
the resistance of the ground. Frequently the well is started with an auger
of small diameter and the drive point and screen inserted into the open-
ing before actual driving begins. These wells are commonly referred
to in British practice as Norton tube, or Abyssinian wells.
(b) The well is pumped until the muddy water has been re-
moved and clear water is delivered. If water is needed badly, the muddy
water can be collected in a tank and subjected to the usual purification
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procedures. It may be found to be bacterially contaminated and even
the clear water from the well will require chlorination. Usually the
quality of water from a drive point well becomes bacterially satisfactory
within a week or two, but chlorination must be continued until the water
is passed upon as satisfactory.
Figure 9. Drive Point well fitted with deep well lift pump with pump cylinder.
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(c) These wells usually range in diameter from to 2"
but they are also driven in sizes up to 4". The larger sizes, although
the casing is of greater weight and more difficult to drive, have the ad-
vantage that deep-well pumps can be fitted to them when necessary.
Consequently, they are generally employed when the water level is known
to lie at depths of more than 25 feet — beyond the reach of ordinary pumps.
The smaller well sizes, on account of the reduced weight and greater port-
ability of the screens and pipe, are valuable for proving the depth at which
the ground water lies, as well as for testing the yields of water at shallow
depths. In many cases it will be possible to supply a sufficient amount of
water from one or more wells of small diameter. In other cases it will
be easier to sink several of the small-diameter, shallow wells and connect
them to a single pump by means of a manifold.
(d) Where the water lies below the suction limit of the pump,
it may be possible to sink a shaft which will permit the placing of the
pump cylinder within reach of the water, and the plunger can then be
worked by means of a rod connected to the surface pump handle. (See
Fig. 9) The pump cylinder, which is larger in diameter than the well pipe,
is attached by removing the upper lengths of drive pipe and screwing the
new connection to the remaining lengths, or valves may be fitted into the
drive casing itself.
c. Driven wells have many advantages over dug wells, including
cheapness, simplicity, speedy sinking and withdrawal, ease of dealing
with unstable ground, and exclusion of undesirable surface and shallow
waters. The formations tapped must yield water readily. In suitable
circumstances a yield of 500 gallons per hour can be obtained from a
driven well inches in diameter, or 1000 gallons per hour from a well
2 inches in diameter. Pitcher pumps may be screwed directly to the
top of the drive-point well pipe.
d. Driven wells can be sunk by 3 to 5 men in unconsolidated sedi-
ments at a rate varying from 3 inches to a foot or more per minute. The
average time of driving wells 20 feet deep is usually less than an hour
and the job requires about 3 to 5 man-hours of work. Under favorable
conditions drive-point wells can be put down to depths of 50 to 70 feet,
and exceptionally to depths of 100 feet.
e. The driving of successful wells requires care and experience.
Failures may result from inexperienced operators. Success has frequently
attended persistent and well-directed efforts where only failure had previ-
ously been recorded.
/. Physical conditions . — The following conditions are essential to
success with driven wells:
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(1) The upper strata must not be so hard or dense as to resist the
penetration of a pointed pipe.
(2) There must be beds of sand and gravel with pores large
enough to admit water to the pipe as fast as it is removed by pumping.
(3) The water must be within 20 to 25 feet of the surface to use
a suction pump. If the water is found at a greater depth, some form of
deep well pump must be used.
34. Drilled Wells. — a. While wells of this type are being drilled
a log should be kept, recording the depth, thickness, and characteristics
of each formation encountered. This log should be filed for reference
in drilling other wells in the vicinity. There are two general methods
of drilling wells, the cable tool (percussion) rig and the rotary rig. (Chap-
ter 7, Sec. 3)
h. The cable tool rig is especially advantageous in hard formations.
It consists of a prime mover, derrick, wheels and spools for cable, and a
walking beam which raises the bit and allows it to drop into the hole.
The well is deepened by the drill bit striking and breaking the formation,
the broken material being removed by means of a bailer. The drill bit
should be large enough to permit casing to be introduced when the well
has been completed. (See Chapter 7)
c. The rotary method is gaining increasing recognition at the pres-
ent time because of its speed. The rig consits of a prime mover, derrick,
draw works, rotary table, and mud circulation pump. The draw works
consist of wheels, equipped with brakes and clutches, which allow trans-
mission and control of the power from the prime mover to the rotary
table. A drive chain or shaft from the draw works turns the rotary table.
The rotary table, located over the well and the drill stem, with the bit on
the bottom, is turned to give an auger effect. (See Chapter 7) The cut-
ting bit, either the rock type or fishtail shape, wears away the rock or
other material by downward pressure and grinding action. The drill stem is
hollow and drilling mud composed of water and either upper layers of
clay or commercial mud material is pumped into the drill stem at the top
and allowed to discharge near the cutting surface of the bit. This mud
serves to keep the bit cool and return the cuttings to the surface by fioat-
ation and overfiow, and to plaster the sides of the hole to prevent caving.
As the drilling mud may impede or cut off the fiow of water into the well,
great care is necessary in using rotary drills, especially where the depth
to the water-bearing formations is unknown.
d. Casing . — Well casing to prevent caving may be placed while
drilling with either rig. The usual procedure is to drill the well to the
water-bearing strata and then, if the water is satisfactory, place the
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casing. Wells should be cased at least down to the top of the water-bear-
ing formation and preferably to the bottom of the well. When the latter
practice is used the screens permit taking water only from the strata
desired.
e. Cementing . — The casing is cemented in place to prevent the en-
trance of water from strata that is not satisfactory. Cementing also pro-
tects the casing from corrosion.
NOTE : For detailed methods of casing and cementing, and for a dis-
cussion of “Increasing Yield of Wells,” “Protection and Sterilization of
Wells,” “Testing and Developing,” etc., see Chapter 7, “Operation”, Sec. 3.
35. Capacity. — The capacity of a well, expressed as the amount of
water which can be withdrawn in a stated period of time, depends upon
(1) the water available in the water-bearing strata, (2) the head or pres-
sure available to cause the water to flow into the well casing, and (3)
the friction loss which occurs when the water moves through the water-
bearing formation and into the well casing. Although the amount of
water actually present in the formation depends upon a number of factors,
such as the rainfall and the rate of percolation through the earth, the
quantity of water available to the well may be thought of as nearly con-
stant. It will be assumed that the well has been driven deep enough to
furnish sufficient pressure, or head, to cause the water to flow into the
well in the desired quantity. Other things being equal, the capacity of
the well then depends upon the friction loss which occurs when the water
moves through the formation and into the well. The friction loss, in
turn, depends upon the velocity with which the water moves. The velocity
is governed by the size of the openings through which the movement of
water takes place. Therefore, with larger openings, the velocity of flow
is less; the slower the velocities, the less the friction; and the less the
friction, the greater is the capacity. In other words, given a sufficient
depth of penetration into a saturated layer, the coarser the water-bearing
material, the greater will be the output of the well.
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Chapter 4
WATER QUALITY AND EFFECT OF SUBSTANCES DISSOLVED
AND SUSPENDED IN WATER
36. General. — a. The essential qualities to be sought in water sup-
plies for military purposes in the field are: primarily, safety for drink-
ing, cooking, and washing; secondarily, palatability in water which is to
be used for drinking. It is not to be expected, nor is it essential, that
the quality of water furnished for field use shall always be of the high
standards which would be demanded by civilian communities. The mili-
tary situation, the needs of the moment, and the difficulties of transpor-
tation of equipment, supplies, and the water itself limit the selection of
water sources and the extent of the treatment procedures applied. The
portable and mobile purification units, which are intended for use only
when other and better facilities are not available, are a compromise be-
tween mobility and good practice. The quality of the water supplied
must be as nearly satisfactory as circumstances permit, and the water
must, above all things, be rendered safe for use. When established mu-
nicipal and industrial facilities become available to the field forces, per-
mitting adherence to standard practice, they will be used to the fullest
extent.
b. Water that is contaminated with warfare gases should be avoided
if other supplies can be obtained. If not, contaminated water will be con-
sidered as potable provided it meets all of the following requirements:
(1) There is no odor of any chemical agent present in the water
before chlorination.
(2) There is no excessive cloudiness or discoloration present.
(3) The addition of five parts per million of chlorine (2 ampules
of calcium hypochlorite per Lister bag) produces a chlorine residual of
one part per million or more.
(4) The pH (acidity), see Appendix 1, of the water before chlo-
rination is above 5.0.
c. These tests apply to all known warfare gases that may contami-
nate water supplies.
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37. Impurities Found in Water Supplies. — The common impurities
may be divided as follows:
Solids —
Inorganic —
lead
copper
zinc
aluminum
calcium
magnesium
sodium
iron
manganese
arsenic
phosphorous
oxide
bicarbonate
chloride
sulphate
nitrate
fluoride
sulphide
I — Dissolved —
Organic —
vegetable matter
animal matter
Gases —
chlorine
ammonia
hydrogen sulphide
carbon dioxide
oxygen
nitrogen
— Suspended Solids —
Inorganic —
iron
silica
clay
silt
mud
Organic —
animal matter
vegetable matter
sewage
oil
38. Selection of Sources and Equipment to be Used. — Where per-
manent camps and establishments are to be supplied with water, more
time can be spent in the selection of sources and greater elaboration of
equipment and processes is justified. Existing equipment can be im-
proved after installation as time and availability of equipment permit,
and demand requires. Thus, the installations may approach in complete-
ness and efficiency those water treatment plants which have been designed
and erected in peace time. If the need arises, the water may be softened,
or treated in other ways for particular uses.
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39. Quality Variation During Distribution. — a. Changes may take
place in the temperature and the amount of gases and iron in a water
between the plant and the consumer. More important is the accidental
introduction of foreign matter such as salt, coloring matter, organic pol-
lution, and living parasitic or pathogenic organisms.
2>. Where water is distributed in vessels such as the organization
water cans, the relative cleanliness of the containers has an important
bearing upon the quality of the water delivered to the troops. The use
of the tanks and cans for any other materials except water must be prohib-
ited. The introduction of dirt in handling or through the dipping of water
from cans with unclean cups or other containers also introduces danger
of organic contamination capable of causing diarrhea or other intestinal
disorders.
c. Chlorine, which is the chief barrier against bacterial contami-
nation in field water treatment, is continuously lost from the treated water
by escape from the surface, or through aeration when the water is poured
from one vessel to another, or by combination with chlorine-consuming
substances in the water. When the free chlorine and its germicidal ad-
dition products have disappeared from a water, contamination introduced
thereafter is not destroyed, and living organisms will multiply if tem-
perture and food conditions permit. Time, therefore, is an important
factor affecting the quality of chlorine-treated waters. Consequently, in
any study of a water supply it is not only necessary to know the quality
of the water at the source and after treatment, but it is also essential to
have information concerning the quality of the water at the point of use.
In addition, it is often desirable to have information about the quality
of the water at one or more intermediate points.
d. Important changes in the quality of water, from a sanitary stand-
point, may take place in the consumer’s own quarters through cross-con-
nections to less satisfactory water supplies or sewer lines, through unin-
tended piping hook-ups, or through back-siphonage.
40. Effect of Impurities on Animals. — Animals are susceptible to
some diseases which seldom or never attack man, and they are frequently
more sensitive than man to certain poisons in waters. At times animals
will drink freely of surface water which contains large amounts of blue-
green algae. A toxic substance, apparently arising from the growth of
these aquatic plants, has injured or even killed livestock. So far as is
known, man has not been affected by this particular toxic substance de-
rived from water. Since the droppings of animals frequently foul sur-
face streams, the organisms of bovine tuberculosis, anthrax, and probabh/
undulant fever, as well as the eggs, larvae, and adults of parasitic worms
may be swallowed by stock while consuming the water of these surface
streams or eating the algae vegetation growing therein.
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41. Non-bacterial Impurities. — a. In addition to pathogenic bac-
teria and animal organisms, there are dissolved and suspended substances
which are irritants or poisons.
b. There are also many substances which, in small amounts, are
essential to bodily welfare ; greater concentrations may act as undesirable
stimulants to some bodily function; and still larger concentrations have
an irritant effect upon some tissues, and may even act as poisons. The
substances which we think of as the poisons are merely substances which,
in small quantities, are able to produce a definite physiological effect.
These substances may be either inorganic or organic.
c. The inorganic poisons found in waters are the most easily detected
and estimated. Toxic organic substances are more numerous and more
difficult to detect. They are also among the most potent toxic agents.
Very little is known of many of these organic poisons except that they
usually seem to be degradation products of other organic substances pro-
duced by the digestive action of bacteria or certain living organisms.
Some poisonous organic substances appear to be synthesized in the life
activities of plants and animals. The more numerous these organisms,
the greater the concentration of the poisonous agent, called toxin, they
may be expected to produce.
d. It requires such an extremely minute amount of some of the tox-
ins to produce a physiological effect, that it is seldom possible for the
average water laboratory to separate it and detect it by a specific test.
Since mineral poisons are more easily detected, and their quantity more
easily determined in the laboratory, it is possible to establish safe lim-
its, usually containing a factor of safety, within which there need be no
fear of toxic action on consumers of water. However, some of the poison-
ous substances, notably lead, accumulate to a certain extent in the body
and act as cumulative poisons, but even lead is slowly eliminated.
e. While the permissible quantity of lead has remained fairly con-
stant at 0.1 part per million parts of water, the permissible quantity of
copper may be 2.0 parts per million because some copper is required in
nutrition and that amount in water would not raise the amount of copper
ingested to dangerous values. Much of the copper and lead found in water
supplies comes from pipes. The copper sulfate which is used in combatting
algae growths in reservoirs is completely converted into insoluble com-
pounds which precipitate and are removed by sedimentation, especially
in waters containing carbonate hardness.
/. Zinc, which may be dissolved from the galvanizing (zinc coating)
on iron pipes and from brass pipes, is also present in the natural waters
of areas where the ores of the metal are to be found. The permissible limit
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is 15 parts per million. However, natural waters containing up to fifty
parts per million zinc are reported to have been in continuous use without
ill effect.
g. Arsenic may be harmful in quantities even less than ten parts
per million if the water is habitually used, but more is necessary to pro-
duce poisoning by one drink. However, the maximum which can be safely
taken has not been determined for either condition. Arsenic and phos-
phorous are belived to be cumulative and to cause a progressive disinte-
gration of the boney structure of the jaw, resulting in “phossy jaw.”
h. Since a number of chemical warfare agents contain arsenic, this
matter becomes of military importance. The matter is further compli-
cated by the fact that the chemical warfare agents containing arsenic are
complex organic compounds and the arsenic does not react as it would
in inorganic compounds. However, the hydrolysis of the organic arseni-
cals may proceed through a series of reactions to the point where the
arsenic returns, more or less completely, to the inorganic state.
i. Other substances whose exact critical concentrations in drinking
water are unknown are selenium, vanadium, boron, and fiourine. Appar-
ently the fiourine which is present as flourides begins to produce a physio-
logical effect at a concentration somewhere in the vicinity of 1.0 ppm.
Habitual consumption by children between the ages of 5 and 10 of water
containing in excess of 1 ppm of fiourides produces mottled enamel of
the teeth, but smaller amounts are said to be beneficial to both children
and adults in the prevention of dental caries. The critical concentration
of selenium is believed to be somewhere above 0.1 parts per million.
42. Body Irritants. — a. Although some of the hving organisms,
such as the immature worms living in water, may attack the skin and
invade the body while wading, swimming, or washing, most of the danger
is from swallowing the water. Much of the damage which may follow
is due to action upon the digestive tract.
b. Certain inorganic salts, normally present in water, cause an irri-
tant effect on the body when taken internally. Continued use of a water
containing an irritant substance may habituate consumers to the irritant
so that in time they may be able to use the water without annoyance or
apparent ill effect. This is observed with waters high in magnesium sul-
fate. It acts as a laxative on newcomers, but does not bother the perma-
nent population of an area where such waters are used.
c. A case of water failing to supply the desirable traces of a sub-
stance which in larger amounts may be toxic, is found in the so-called
“iodine deficiency.” Lack of iodine is considered to be the chief cause
of simple goiter which is found to be most prevalent in the population of
areas where the water generally consumed contains practically no iodine.
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It is possible to supply the iodine deficiency by adding salt water fish or
iodine-containing substances to the diet. Iodized table salt is commonly
used for this purpose. In a few instances, the water supply of cities has
been treated at intervals with sodium iodide to rectify the iodine defi-
ciency. This practice is not considered desirable, however, because most
of the expensive iodine compound added to the supply is wasted by being
lost with flushing waters and because there are cases where iodine may
actually be harmful to an individual.
43. Saline Water. — Some natural waters contain so much dissolved
mineral substance that they cannot be used for drinking purposes. The
taste of the dissolved substance is offensive and sometimes produces a
physiological action of a laxative or diuretic nature. Sea water is an
extreme example of high mineralization since it contains approximately
37,000 parts per million of dissolved solids, but even sea water is lower
in total solids than are the waters of some lakes in which evaporation has
brought about great concentration of total solids. Highly mineralized
waters are not always hard waters.
44. Hardness, Iron and Manganese. — a. Waters which contain
calcium and magnesium salts are called hard and destroy soap by convert-
ing the sodium or potassium soap of commerce into an insoluble non-
detergent form. (No lather is formed.) Calcium soap is a white curdy
precipitate. Magnesium soap is also a white curdy precipitate, but is
decidedly sticky as compared with the calcium soap. Iron and manganese
also produce insoluble soaps, colored in shades of light brown, red, or
darker tints. These calcium, magnesium, iron, and manganese soaps pro-
duce the “ring in the bathtub,” cause the cloudiness of washing waters,
and, by destroying the soluble soap, force the use of larger quantities of
commercial soap in order to get a suds and cleansing action.
h. Brines cause the precipitation of soap, but this soap curd is
still a usable soap in ordinary soft water.
c. Hard water should not be used in a laundry without first soften-
ing it. The curd formed represents an operating loss of IV 2 lbs. of soap,
per grain per gallon of hardness, per 1000 gallons of water. This curd
sticks to the fibers of the fabric causing a grayish tinge, and picks up
dirt which decomposes, putrifies the fabric, and causes it to “rot.” Many
laundries use excessive quantities of bleach to overcome this grayness:
this increases the cost of operation and weakens the fabric.
d. Hardness also causes deposits in the radiators, passages, and
water jackets of water cooled engines. This causes the engines to
overheat, which in turn causes the lubricant to break down and burn, and
the pistons and bearings to seize. The greater the evaporation and re-
placement of water the more aggravated will be the difficulties encoun-
tered.
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e. Heating water containing appreciable amounts of calcium and
magnesium either in open vessels or in boilers, causes it to deposit solid
matter at the bottom of the vessel or on the heated metal surfaces. Iron,
manganese, silica and some other substances may also play a part in the
deposition. The character of the deposit is influenced not only by the
kind and concentration of the ions present but also by the temperatures
to which the liquid rises. Hard, dense scales, such as those of calcium
sulfate, are usually associated with considerable concentrations of cal-
cium ions, or high pressures and high temperatures.
/. Any of the waters which contain iron in the form of ferrous bi-
carbonate may deposit hydrated ferric oxide in the pipes, on bathroom
fixtures, and on textiles which have been wet with the iron-containing
water. Hydrated oxides of manganese are deposited from manganiferous
waters after chlorination, but they are not so readily deposited after aera-
tion or loss of free carbon dioxide as are similar compounds of iron. Iron
deposits also result from the corrosion of iron pipes and the production of
ferric hydrate. The critical value, beyond which deposition may be ex-
pected, is 0.1 parts per million for iron and manganese. The iron content
of natural waters may reach as high as 100 parts per million in extreme
cases, while 10.0 parts per million of manganese is unusual.
45. Other Dissolved Mineral Substances. — Some dissolved mineral
substances are capable of influencing the safety of water, not because
they themselves are harmful, but because they tend to facilitate the solu-
tion of other substances which are dangerous. Substances, such as ni-
trates and possibly some of the phosphates, may increase the solubility
of lead and therefore the quantity of lead dissolved from piping.
46. Corrosion of Lead, Copper and Brass. — High concentrations
of dissolved salts favor passage of electric currents, and the electrolysis
which results may introduce, into the water, metals derived from pipes
and fittings. On the other hand, waters which are relatively free of dis-
solved material are eager to dissolve substances with which they come
into contact, and for that reason distilled water is corrosive to metals.
Waters containing suspended solids are apt to erode the materials with
which they come into contact. In the first instance the longer the water
stands in the pipe the greater is the dissolving action, while in the latter
case, high velocities are most objectionable as they increase erosion.
Corrosive waters which have stood over night in lead or copper house
piping are more likely to be dangerous than water that has flowed direct
from a main through the house piping without a pause. It is therefore
advantageous where long lines of pipe carry waters of low mineralization,
to waste the first water drawn in the morning.
47. Constituents Affecting Boiler and Heater Operation. — a.
Waters which are corrosive, or which erode metals, obviously cause diffi-
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culty in boilers, heaters, valves, and fittings. Hard waters which produce
scale in boilers and heaters are also harmful to the units in another way.
The deposition of scale not only reduces the thermal efficiency of the
equipment by its insulating effect, but also causes its destruction by over-
heating.
b. Alkalinity has been claimed to accelerate the cracking of the
metal around rivet holes in boiler plate, while the presence of certain
other salts in given amounts inhibits the cracking.
c. As the water evaporates in a boiler or water still it leaves behind
its dissolved and suspended solids and is replaced with water containing
additional solids. Thus the solids concentrate, and when the concentra-
tion reaches a certain value, which varies with each type of boiler, mois-
ture begins to be carried over with the steam (foaming). As the concen-
tration continues to build up, the carryover increases until slugs of water
are carried over (priming). The concentration, therefore, must be main-
tained below the “maximum allowable concentration,” predetermined by
trial, by bleeding a sufficient amount of the concentrated boiler water
from the boiler intermittently, or preferably, continuously. This proce-
dure is called boiler blowdown, or blowoff. Blowing off continuously, in
addition to permitting closer control of boiler concentrations, makes pos-
sible recovery of the heat in the blowoff by transfer to the feedwater.
Continuous blowoff therefore effects a large economy of fuel.
48. Attractiveness. — The attractiveness of a water is primarily
determined by the lack of color and turbidity, although sometimes the
odor, which is also a consideration of palatability, is sufficiently pro-
nounced to affect the attractiveness of a water supply.
49. Color. — a. Color, as a descriptive term applied to water, is
more properly described as “stain,” since pure water is colorless. Us-
ually the yellow or brownish stains are derived from organic substances,
extracted from plants or from organic residues undergoing decom-
position. Sometimes iron enters into the composition of the coloring ma-
terials. Color is usually due to colloidal material, although the state
of aggregation and the particle size is variable. The addition of lime or
other alkalies to colored water will often “fix” the color and make removal
difficult. The probable effect of the alkali is to cause dispersion of the
colloidal coloring substances, producing smaller particles of the colored
matter, and making their subsequent absorption by flocculating chemi-
cals more difficult. Colors are usually most easily removed at pH values
below 6.0.
50. Suspended Matter. — a. The effect of the suspended material
in water on its appearance depends upon the color of the suspended parti-
cles, their opacity and light-scattering power, the size of the particles,
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and the number of these particles. The finer the particles, the greater is
the turbidity produced by a given weight of the substance and the greater
is their resistance to the forces which would tend to cause them to settle.
h. The number of parts per million of suspended matter is deter-
mined by separating the suspended particles from a definite volume of
water and then weighing the suspended matter removed. The measure
of turbidity is obtained by comparing the obscuring ability of the water
with that of a standard suspension, made by taking a definite weight of
a particular suspendable material and shaking it with a given volume of
water. The standard suspension may be diluted with water to bring it
to the same range of turbidity as the specimen being examined. The
result will be the concentration of the standard suspension which would
cause the same optical effect as the suspended matter in the sample. It
does not refiect the condition of the suspended matter in the specimen
examined.
c. The size of the suspended particles in water is important in the
estimate of the rate of settling of suspended matter, and also in predict-
ing the ease of clarification of the water by plain subsidence or by coag-
ulation with chemicals. The finer the material to be removed, the more
difficult and time-consuming is the clarification, and usually the more ex-
pensive is the process when chemicals are to be purchased.
d. Turbidity can be determined in the field with portable turbidime-
ters, but the determination of the amount of suspended solids requires
laboratory facilities. Consequently, the determination of suspended
solids is often omitted in the study of water quality. This practice is apt
to lead to confusion, not only when different supplies are being compared,
but also when a single water supply from an extensive watershed is being
studied over a period of time. This is because waters of identical turbid-
ity may fluctuate widely in their behavior as a result of the state of dis-
persion of the suspended matter. Colloidal matter, which includes some
of the coloring matter in surface waters, may also act as a “protective
colloid” and interfere with the sedimentation process. Protective col-
loids tend to prevent aggregation and hence influence the flocculation
on which chemical clarification depends.
e. In considering the effect of suspended matter as modifying the
quality of a water supply, we must consider the probable fluctuation in
the quantity and character of the earthy suspended matter, the effect of
the colloidal substances present, and the ease with which it will be pos-
sible to remove objectionable constituents.
/. Water will deposit suspended materials if there is sufficient
time and the flow is sufficiently slow. The deposits at the bottom of pipes
eddy into quiet points in a pipe system and are dislodged when any marked
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change in velocity of flow occurs. This is often observed when a fire
hydrant is first opened. If the suspended material lodges in an aperture
of small size, it may clog it. Suspended material may block the meters
and orifices through which small flows pass.
51. Temperature. — a. Cold water is refreshing. Its coldness pre-
vents the taste buds from detecting many odor and taste-producing sub-
stances, if their concentration is not too great. A temperature of 50
degrees F. is desirable for drinking water. At that temperature it does
not have some of the objectionable characteristics of ice water and can
be consumed without excessive temperature-shock, unless one is greatly
over-heated. Water which is much warmer than 50 degrees F. is less satis-
factory for drinking.
b. Water from wells with a depth of 50 to 75 feet is usually close
to the mean annual temperature of the air at the location of the well.
Water from shallower wells is affected by the temperature of the air, and
the water temperature tends to follow the air temperature, but with a
certain lag and over a narrower temperature range. The shallower the
well, the smaller is the lag and the nearer is the water temperature range
to that of the air. The water of surface streams reflects the temperature
variations of the air more closely than do ground waters, unless there
is an addition of water from thermal springs, large volumes of condenser
water, or other sources of heat or cold, such as water from snow or ice
fields. The temperature of waters from deep wells is higher than those
of the wells of 50 to 70 feet depth. The temperature rise with increased
depth is not uniform, even in the same well, but it amounts to 1 degree
F. for each additional 50 to 75 feet of depth, within the usual ranges.
c. Low temperature reduces the biological activities of bacteria,
protozoa and other living organisms in water, but most of the organisms
which disappear die off in spite of the low temperature, rather than be-
cause of it. Decomposition of organic wastes entering streams in the
winter time is retarded, and consequently the contamination is percep-
tible for longer distances below the point of pollution. Pathogenic organ-
isms in cool water will persist for longer periods.
d. The greater activity of warm water causes it to wet and swell
gelatinous films more readily than does cold water. This may introduce
difficulties in photographic processes which require the films to be washed
free of unchanged salts of silver and developing and fixing chemicals.
Films may soften unduly, change shape, or even slip from their supports
in warm water. Warm water, however, improves the action of detergents
such as soaps and the recently developed wetting agents.
52. Odor. — a. Musty odors and tastes accompany incomplete de-
composition of polluting matter. Sometimes the tastes and odors are
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grassy, fishy, or definitely foul. Odors are observed by the action of min-
ute particles of certain substances on the olfactory nerves. Most odors
are due to volatile matter carried to the sense organs by diffusion through
the air.
h. In general, both volatility and ease of perception increase with
rise in temperature. Increasing the concentration of the odorous parti-
cles, by increased volatility, usually amplifies the effect and makes the
odor easier to detect and identify. This is not always so, and prolonged
exposure to the odor-producing particles may dull the sense of odor-
perception so that a person may no longer be aware of their presence. There
is great variation among individuals in their sensitivity to odor stimuli
and to the rapidity with which odor-fatigue becomes apparent. Some
highly odorous substances (such as hydrogen sulfide, which has the fa-
miliar rotten-egg smell, and which is poisonous in large concentrations)
quickly produce odor-fatigue and become especially dangerous when they
are forgotten. An individual may also have a greater sensitivity to one
kind of odor than another or may find one type of odor more pleasant
or more offensive than some other type.
c. Palatability is affected by the character of the odor and its
concentration or strength. Since the sense of smell is a protective sense,
one of its major functions has been to warn of dangers in the environment.
We are naturally inclined to fear most those odors which are unfamiliar,
and to disregard those which, in our experience, have not been accom-
panied by injury.
d. Many of the odors which affect the palatability of a water come
from the growth of algae, protozoa and other living organisms which
produce odorous substances, in the same manner that flowers produce
their characteristic perfumes. The objectionable odor may also come from
decomposing organic matter or from industrial waste products. Gases,
particularly hydrogen sulfide, may contribute to the effect. Industrial
wastes vary widely in the odors they produce. Chlorinous odors (fre-
quently due to chloro-phenols) , iodoform odors (due to the chlorination
of certain salicyl compounds), and, in general, “drug store” odors are
among those to be expected in chlorinated supplies. Water treatment
sometimes accentuates these odors unless special means are taken to re-
move, eliminate, or chemically change the odorous matter.
e. It is difficult to evaluate the importance of specific odors in drink-
ing waters because of the variance of opinion among observers. Like-
wise, it is difficult to ascribe to any particular method of odor removal
an accurate estimate of its efficiency. Much difficulty has been caused
by doubt as to whether the change in the odor observed after treatment
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was due to the action of the process or to a change in water character
at the source. Odors observed in the immediate vicinity of an aerator
may or may not indicate the degree of removal of odor from the water
passed through it.
53. Taste. — a. The taste of water is due to the presence of gases,
mineral substances in solution, or organic substances, many of which
are volatile. Waters low in dissolved gases such as oxygen (air) or car-
bon dioxide are often described as “flat tasting.” Waters which contain
hydrogen sulflde have a taste in addition to the odor of rotten eggs.
h. Taste and odor are closely associated sensations. Volatile sub-
stances may affect both taste and odor senses and their removal is de-
sired to improve the palatability of the water. Near the point of com-
plete removal sometimes the taste and sometimes the odor is the more
perceptible. Like odor, the taste of water is affected by the concentra-
tion of the substance detected. The impression created is variable through
the range from trace to measurable concentration, not only as to strength
but also as to the characterization, or association with remembered tastes.
Grassy and woody tastes, like grassy and woody odors, are often annoy-
ing and difficult to remove from surface waters.
c. Mineral substances in solution give a taste to water which is not
associated with an odor impression. Sodium chloride (common salt) and
many other salts give a taste to water which is commonly described as
salty, though taste differences often permit identification of the substan-
ces. Calcium chloride and magnesium sulfate have a more bitter taste
than common salt. Waters high in sodium carbonate and similar alka-
line substances are frequently described as having a “slick” taste. Waters
which contain the salts of iron have an inky, sweetish taste, and sewage
contamination is associated with a sweetish taste. Some waters are acid
and betray that fact by a sour taste. Acidity in natural water is due usu-
ally to sulfuric acid. If the acidity is high, the water may also have an
astringent, “puckery” taste.
d. Taste-producing mineral substances frequently have a physio-
logical action when present in water, and the effect, like the taste, is
rendered more noticeable when the concentration is increased. Some-
times the concentration, as in sea water and some highly mineralized
natural waters from wells and springs, is so great as to render the water
unfit for drinking.
54. Habituation to Tastes and Odors. — Persons who have been
accustomed to consume a particular kind of water become so accustomed
to its odor and taste characteristics that they may not notice either the
odor or the taste. They may become adjusted to the physiological effects
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of relatively large concentrations of such materials so that they no
longer experience any noticeable action. Thus, if given water from
another source, they may actually miss the familiar taste or odor, and
find that odorless or tasteless waters are unsatisfactory and do not satisfy
the thirst. However, they may quickly readjust themselves to the new
water.
55. Corrosion by Gases. — a. Oxygen in water causes corrosion of
certain metals such as iron, steel, copper, and aluminum, while carbon
dioxide (carbonic acid) accelerates corrosion. This is true especially in
hot water systems or steam boilers. While these gases are not the sole
cause of corrosion, their importance makes it desirable to eliminate them
before allowing the water to act on piping systems or boilers. Special
linings of zinc, cement, tars, and bitumens are used to prevent the action
of corrosive gases when it is not feasible to inhibit corrosion by chemical
or other means.
h. Iron has a natural tendency to dissolve in water to a certain ex-
tent in the presence of oxygen, setting hydrogen free and ultimately cov-
ering the surface of the iron with a passivating layer of hydrogen which
effectively stops further solution until it is removed or broken. The dis-
solved iron forms ferric hydrate, or rust (also called hydrated ferric ox-
ide), represented either as 2Fe(OH)3 or as Fe20s.3H20. This rust forms
tubercles, or nodules, on the metal surfaces, or drops to the bottom to
be carried along and deposited elsewhere by currents. The process is
self-limited unless the hydrogen layer is disturbed. The introduction of
free acids or carbon dioxide, which combines with water to form carbonic
acid and lowers the pH, permits hydrogen of the protective layer to
escape as a gas. This removes the restraint on solution of the iron, and
speeds corrosion. The addition of alkalies to the water will neutralize
the acid, stop the evolution of hydrogen, and even render the water less
corrosive than it was. Another way of explaining this type of corrosion
is to say that the free carbon dioxide reacts with water to form carbonic
acid which attacks the iron, forming ferrous carbonate. This is acted
upon by the oxygen in the water to produce the ferric hydrate and release
carbon dioxide to repeat the process of corrosion. Alkalies combine with
with the free carbon dioxide and stop the action.
c. Gases other than oxygen and free carbon dioxide have an action
on pipes and structures. Hydrogen sulphide is decidedly destructive. It
forms a brittle ferrous sulphide on the surface of iron exposed to it. It
can also attack concrete by destroying its coherence and strength so it
can be scratched away with a knife blade or finger nail. However, hydro-
gen sulphide requires considerable oxygen for this action, and it is most
effective where pipes run partially full, as in sewer lines or flumes. The
action may be explained by saying that the hydrogen sulphide combines
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with the calcium of the cement in the concrete to form calcium sulphide
which, with the help of water and oxygen, forms gypsum (calcium sul-
phate). This acts as a wedge because the molecule of calcium sulphate
occupies more space than the calcium sulphide. The pressure produced
causes the concrete surface to break down and soften.
56. Effect of Ammonia on Copper and of Alkalies on Brass. — If
considerable ammonia is present in an alkaline water, it will be volati-
lized by heat and corrode copper and the copper in brass and bronze.
This corrosion is particularly undesirable on valve seats, discs, plugs, or
steam radiator valves. Highly alkaline waters dissolve the zinc in brass.
This process is known as dezincification.
57. Effect of Chlorine on Metals. — Chlorine is used in water treat-
ment, and is a corrosive gas. However, the amount of free chlorine pres-
ent in the treated water is so small and it is usually so rapidly consumed
by organic matter in the water, that the corrosion of water supply equip-
ment by chlorine is much less than is frequently presumed.
58. Difficulties in Photo Processing. — a. Technical difficulties with
water which may be encountered in photographic processes may be sum-
marized as follows:
(1) Temperature, and temperature-dissolved gas relationship.
(2) PH (see Appendix I) variations in the water.
(3) Opaque suspended materials or turbidity.
(4) Presence of iron and manganese.
(5) Presence of the calcium and magnesium salts responsible
for the hardness of water.
(6) Separation of particles when softeners are added to the water.
h. Solution of atmospheric gases in water is facilitated by low tem-
perature and by pressures above atmospheric pressure. Raising the tem-
perature or lowering the pressure causes the release of dissolved gases.
When cold water is introduced into a pressure distribution system and
allowed to warm before drawing, the sudden release of pressure when the
tap is opened is followed by the immediate separation of gas in the form
of minute bubbles. These bubbles give the water a milky appearance
which clears upward from the bottom. In photographic development,
these bubbles may adhere to the surface of the film as a scum. When
minute film bubbles are broken they produce a beaded appearance resem-
bling that due to a half-tone screen. Much of the details of the photograph
may be lost in this way. Storage tanks with open water surfaces at atmos-
pheric pressure permit the escape of gases and stabilization of the water
before use.
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c. In many of the chemical processes used in photographic and litho-
graphic work the reaction of the solutions, as measured in pH (see Appen-
dix I) units, has an important bearing upon the character of results
obtained. For example, the dampening water used in lithographic pro-
cesses should be kept within the narrow range of pH from 4.2 to 4.4, for
best results. This requires the addition of acid, since natural waters of
this range are unusual, the correct amount of acid to be used varying
with the water supply.
d. Waters which contain much free calcium bicarbonate, associated
with free carbon dioxide as is common in the states of the Middle West,
resist pH changes more than waters which contain less of these substan-
ces and related compounds. Such waters will require more acid to re-
duce the pH to the desired point than will softer waters with the same
original pH value. Similarly, more alkali will be required to raise the
pH an equivalent amount above the original value if an alkaline medium
is desired. Adjustment of water to a specified pH value, therefore, re-
quires testing of the treated water to see if the desired pH value has
been obtained and that the so-called “buffer action” of the dissolved salts
has not affected the result too much. This pH adjustment should be made
after the regular treatment of the water has been completed if a range
outside 5.6 to 8.6 is desired. Above a pH of 8.6 or below a pH of 5.6
there will be interference with the clarifying action of the ammonium
aluminum sulfate (or ammounia alum) regularly employed in water
treatment (Chapters 5 and 7). Consequently, the final pH value of the
treated water must be adjusted to the needs of the photographic or litho-
graphic process. Simple colorimetric testing sets should be used to check
the final pH value (Appendix I) .
e. If the presence of free chlorine in the water, as required for
drinking waters, is objectionable in photographic or lithographic work,
it can be destroyed by the use of a small amount of sodium thiosulfate
(photographer’s hypo). If the hardness of the water is objectionable,
one of the approved water softening processes may be used.
/. Iron and manganese, which are sometimes encountered in natural
waters, especially those of ground water type, stain negatives and prints
with rusty and brown stains. Iron must therefore be removed (Par. 73).
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CLEAR
DILUTION
a TYPICAL CONVENTIONAL CONCRETE GRAVITY FILTER PLANT WITH
CONSTANT RATE DRY CHEMICALS FEEDS
10 a
bu TYPICAL MODERATE SIZE COAGULATION OR LIME SODA
SOFTENING PLANT WITH SOLUTION FEEDS, SLUDGE
BLANKET TYPE SETTLING TANK AND PRESSURE
FILTERS.
lOb
CHEMICAL POTS-7 STORAGE TANK-
.^CHLORINATOR
PUMPING SECTION — 7/ IbEING^ FILLED \'^^TER IN CANVAS TANK
^ ^ HAVING SETTLED,
IS FILTERED
DESLUDGING VALVES
STRAINER
AUXILIARY PUMP OF
WATER SUPPLY SET
vA\7//> 'mm
FILTER SECTIOM
c. TYPICAL FIELD SETUP FOR PORTABLE OR
MOBILE WATER PURIFICATION EQUIPMENT
10 c
Figure 10.
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Chapter 5
WATER PURIFICATION
59. General. — a. To establish a background for a thorough under-
standing of the principles upon which water purification is based, para-
graphs 2, 3, 4, 5, 7, 11, 13, 14, 15, 20, 21, 22, 23, 27, 29, 34, 35, and 42-91
of TM 3-215, “Military Chemistry and Chemical Agents” should be re-
viewed.
h. Figure 10 illustrates the various steps in water purification and
shows typical water purification plants. The shapes of the various pieces
of apparatus shown are only symbolic and represent but one type of the
apparatus.
60. Self-purification. — While organic contamination of stream water
is naturally reduced by so-called self-purification while it is fiowing, the
reduction is less rapid and less dependable than many people suppose.
It is a common saying that “all streams purify themselves in seven miles
of flow.” Unfortunately, experience shows that this is untrue. Bacterial
and protozoic action, sedimentation, oxidation, and other agencies assist
in the destruction of contamination, but at the same time, runoff from
the shore, additions of farm, city, and industrial drainage, and other cir-
cumstances continue to prevent the water from reaching a state of purity.
Stream and surface waters in inhabited areas must always be considered
unsafe for drinking purposes, and even those encountered in uninhabited
areas must be regarded as of doubtful safety, unless they have been
treated by approved methods of water purification.
61. Pre-sedimentation. — a. Where the turbidity of a water supply
consists mainly of heavy suspended matter which settles readily without
a coagulant, it is advisable to remove most of this material by presettling
as this lightens the load on the coagulation, settling, and filtration pro-
cesses and saves coagulant chemicals. It will be shown in the discussion
of coagulation that it is not advisable to remove all of this heavy ma-
terial by pre-sedimentation as it has a value as an aid to the coagulation
of the finer suspended and colloidal particles.
h. Pre-sedimentation can be effected in continuous settling basins
or tanks, or by the batch method. Continuous settling basins or tanks
are designed so the water will fiow from the inlet to the outlet without
short circuiting and without dead spaces. The design should be such that
the entire body of the water moves as uniformly as possible from inlet
to outlet. The velocity of flow should be not less than three quarters of
a foot per second nor more than one and one-half feet per second.
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FLOAT
-TANK
Figure 11. Floating outlet and sludge valve
in batch sedimentation tank.
c. In the batch method a tank is filled with the dirty water and
allowed to stand while a second tank is being filled. When the second
tank is filled, the flow of raw water is directed to a third tank while the
water in the first tank is being drawn off for further treatment. In draw-
ing off, the water at the top of the tank should be drawn first. This can
be effected by means of a floating outlet pipe as shown in Figure 11.
d. The time of retention in either the batch tanks or the continuous
settling tank or basin will vary for different water supplies from one to
six hours. An excellent estimate can be made by noting how fast the
material will settle out in a milk bottle or other similar container. If,
for example, it settles at a rate of about one-half foot per minute and
the tank available for sedimentation is 30 feet deep, one hour would be
the minimum retention period, but since water supplies vary, a conser-
vative estimate as to the retention period would be 2 hours. Of course, if
time for the required retention period is not avaliable but a shorter time
is, pre-sedimentation should be permitted for as long a time as possible.
e. Some means for desludging, that is, removal of the mud which
settles to the bottom of the tank, should be provided. This can take the
form of a perforated pipe grid in the bottom (Fig. 10a), connected with
the outside and discharging through one or more quick-opening valves,
or, if the tank is elevated, a quick opening valve can be located in the
bottom. (Fig. 16) If the tank is not elevated the valve can be located
in the side at the bottom. If none of these methods are feasible the tank
can be emptied periodically and the mud removed manually.
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WATER INLET
BAFFLES
AIR OUTLET-
AIR STACKS
INLET CHAMBER
DISTRIBUTOR NIPPLES
STAGGERED SLAT
TRAYS
AIR INLET
BLOWER
DRAIN VALVE
AIR PRESSURE
WATER OUTLET
1 ^
1
1 _
HMS:
Figure 12. Closed forced draft aerator.
62. Aeration. — (Figs. 12 to 14) a. Aeration is a process in which
water is brought in intimate contact with air. This can be accomplished
in a number of ways such as blowing large volumes of air through a con-
tainer filled with water or by spraying the water from a grid system fitted
with ferrules, sprays or other atomizing devices into the air, over a catch
basin. The object is to break up the water as finely as possible and to
insure that a sufficient amount of continuously changing air comes in
contact with the water. Other devices employ beds of broken stone or
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coke, nests of wood slats, and the most modern practice is to allow water
to trickle over wood slats in a closed rectangular or cylindrical container
as air is blown up from the bottom.
DISTRIBUTING TRAY-
T
12
1 — 1
1 1
1 1
1 1
1 1
1 1
1 i
1 1
1 T
j j-
1
1
i
1
I
1
1
1
* ■
1 1
j
M
-OPENING
SPLASH
APRONS
5'-0"
6 - 0 "'
OUTLET
Figure 13 Coke aerator.
h. Aeration is used to free the water of objectionable gases and to
oxidize ferrous iron in the water and convert it to the insoluble ferric
form. Aeration is also used at times to eliminate part of the flat taste
in distilled water, and in many municipal plants to improve the taste of
water which has not been distilled.
c. Figures 12 to 14 illustrate a number of typical aerator designs
including an expedient for the field.
d. One of the most objectionable dissolved gases is hydrogen sul-
phide, which can usually be removed by aeration. This constituent causes
the “rotten egg” odor and taste in water, but this taste is also caused
by salts of hydrogen sulphide such as sodium sulphide and calcium sul-
phide. When these salts cause the odor it is often necessary to carbonate
the water by spraying it in an atmosphere of flue gas (which contains
carbon dioxide), and then aerating in the usual way. It is believed that
carbonating with carbon dioxide converts the salts of hydrogen sulphide
to hydrogen sulphide gas which can be removed by aeration. A two-com-
partment adaption of the aerator shown in figure 12 is best suited to this
purpose.
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STRAINER -MOUNT AS HIGH AS POSSIBLE
Figure 14. Field aerator made entirely of parts of engineer water supply set.
63. Coagulation. — a. The purpose of coagulation is to gather to-
gether small suspended particles so that they can be disposed of by sedi-
mentation and/or filtration. This process is made possible by the peculiar
properties of a group of chemicals known as coagulants, of which alumi-
num sulphate is the most common. When aluminum sulphate dissolves in
water, it reacts to form a gelatinous precipitate, which entraps small
particles of suspended matter. This combination of precipitate and sus-
pended matter, called “fioc”, can then be settled out or removed by a
sand filter.
h. The condition for greatest precipitation, or “optimum pH”, gen-
erally occurs somewhere between pH values of 4.0 and 7.6, depending
upon the type of water being purified. Colored waters containing only
a small amount of dissolved solids generally coagulate best between pH
values of 4.0 and 6.6, while turbid waters coagulate best between 6.0 and
7.6. These pH values are given only as indications, because there is only
one optimum pH for any given water. During coagulation, therefore, it
is essential to maintain the water at the optimum value. Floe will pre-
cipitate at pH values near the optimum but it takes a longer time for the
floe to form and a smaller amount will be formed. If, after the addition
of the coagulant, the water is not at the optimum pH, the pH value can be
adjusted by adding either acid or alkali. (The most common method for
obtaining the optimum pH for coagulation is known as the jar test,
which is described in Sec. 2 Chapter VII.)
c. In order to obtain the maximum amount of precipitation in the
minimum time, it is necessary to accelerate the rate of floe formation by
mechanical agitation of the water. This is best accomplished by a gentle
stirring motion. In order to remove a substantial amount of floe by sedi-
mentation, it is necessary to agitate the water for about 30 minutes; if,
on the other hand, the water is to be filtered only, floe particles wiil
be large enough to be retained in the filter after about 5 minutes of agi-
tation.
d. In the mobile and portable units, no provision is made for floe
formation. The coagulating chemicals are added to the water about 1
minute before it starts to pass through the sand. Some waters will not
coagulate in this short time, particularly if the water is not at the opti-
mum pH. It is essential, therefore, to provide additional time for floe
formation. This is best done in the field by utilizing a canvas tank for
coagulation and sedimentation (Fig, 10c) as described in Chapter 7,
“Operation”.
e. Water of low turbidity and alkalinity, especially colored water,
is often difficult to coagulate ; the pH range for good coagulation is narrow
and the floe forms with difficulty. Upon addition of clay and similar
materials which provide neuclei for the floe formation, the precipitation
of the coagulant is improved and the particles of floe formed are larger.
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The optimum pH range undergoes a small, apparent broadening. The
range can also be broadened by the addition of bivalent or trivalent nega-
tive irons such as sulphates or phosphates.
64. Chemicals Used in Coagulation. — a. The chemicals commonly
used in the coagulation are described below. The coagulants are given
first and are followed by the chemicals used for pH adjustment.
(1) Alum, (a) Filter alum or aluminum sulphate Al2(S04)3.18 H2O
weighs about thirty-nine pounds per cubic foot. It is available either in
the lump, granular, or powdered form. The material is an acid salt and
hence is corrosive to most metals. It is readily soluble in water and is
easily applied as a solution or as dry material.
(b) Reactions between alum and the natural consituents of
various waters are influenced by many factors, so that it is impossible to
determine accurately the amount of alum which will be required. The
amount of various forms of alkalinity which react with one grain per
gallon of aluminum sulphate are as follows:
One grain per gallon of alum react with:
0.45 grains per gallon natural alkalinity, expressed as CaCOs;
0.30 grains per gallon of 85 per cent quick lime as CaO;
0.35 grains per gallon of 95 per cent hydrated lime as Ca-
(0H)2;
0.48 grains per gallon of soda ash.
The above approximate amounts of added alkali are those required with
alum for the formation of aluminum hydroxide floe where the alkalinity
of the treated water is not changed. That is, water treated with 1.0 gr.
p.g. of alum and either 0.35 gr.p.g. hydrated lime or 0.48 gr.p.g. soda ash
would have approximately the same alkalinity as the raw water. If no
alkali be added, then 1.0 gr.p.g. of filter alum will lower the natural alka-
linity of the raw water by about 0.45 gr.p.g., or 7.7 p.p.m.
(2) Bloch alum. This phrase is applied to filter alum which con-
tains powdered activated carbon in quantities of 2 to 5 per cent by weight.
Black alum, therefore, is used to secure coagulation with taste and odor
reduction with a single compound, which can be fed by a single chemical
feeder. Independent adjustment of alum and carbon doses is not possible.
However, activated carbon may have to be added separately to remove all
the tastes and odors from some waters.
(3) Ammonium Alum. Ammonium alum (Ah (804)3. (NH4)2S04-
.24 H2O) should not be confused with filter alum (aluminum sulphate)
discussed above. It is the alum used in mobile and portable purification
units. It is used because it is much less soluble than filter alum, and,
therefore, will dissolve more slowly when placed in alum pots, and its
controlled application over an appreciable period of time is facilitated.
Alum pots are not accurate feeding devices, even with ammonium alum,
but are more compact than other feeds and, therefore, more suitable for
mobile and portable equipment.
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(4) Sodium Aluminate. (a) Sodium aluminate (Na2Al204) is
a compound prepared by the action of sodium hydroxide on alunaina.
This coagulant is not used alone but with alum to secure special results.
Thus the failure of some very cold waters to coagulate with alum alone
may be corrected by adding about 0.2 gr.p.g. of sodium aluminate with
the alum. Another use of this coagulant is in connection with “double
coagulation” of highly colored water, whereby alum alone or alum and
sulphuric acid are added to the influent of the primary basin to coagulate
the highly colored water at the required low pH range (pH 4.4-5.0) . This
results, however, in the presence of undesirable concentrations of soluable
alumina (“free alum”) in the presettled water, so the alkaline sodium
aluminate, and also lime if needed, is added to increase the pH value, to
say 6.5. This secondary treatment results in the formation of aluminum
hydroxide floe, which settles in the secondary basin. A third use of sodium
aluminate is in conjunction with lime-soda softening of water, whereby
insoluble calcium aluminate floe is formed and coagulates the calcium
carbonate and magnesium hydroxide resulting from the softening reac-
tions.
(b) Sodium aluminate may be procured either as a solution
or as a solid and may be applied by conventional chemical feeders. The
cost of the material is high but the required doses are small so that the
treatment may be applied to advantage and at reasonable cost when
special local conditions justify.
(5) Copperas, (a) Ferrous sulphate (Fe SO4) ordinarily known
as copperas, is a granular, acid, compound which is shipped in bags, bar-
rels, or in bulk. The alkalinity and pH value of natural water are gen-
erally too low to react with copperas to form the desired ferric hydrox-
ide floe, because the reaction involves oxidation by the dissolved oxygen
in the water, which does not occur when pH value is less than about 8.5.
It is necessary, therefore, to add lime with copperas to secure coagulation.
Copperas and lime are very effective as a coagulant in lime-soda water
softening and in the coagulation of iron and manganese. The exact doses
of lime required to react with copperas can not be stated, but it is approx-
imately 0.27 gr.p.g. per each 1.0 gr.p.g. of copperas. Generally speaking, the
floe formed by the reaction of copperas and lime is feathery and fragile,
but it has a high specific gravity.
(h) While copperas is an acid salt, it is readily applied by
either solution or dry feed equipment, although there is a distinct tend-
ency for hygroscopic action to render the material moist and cause “arch-
ing” in the hoppers of the dry chemical feeders.
(6) Chlorinated Copperas. The oxidation of copperas by the dis-
solved oxygen of water under the conditions noted above, occurs only at
pH values exceeding about 8.5 and preferably over 9.0. Chlorine, how-
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ever, may be used to react with copperas irrespective of the pH value,
whereby ferric sulphate and ferric chloride are formed and in turn act
as coagulants Theoretically, one pound of chlorine reacts with 7.8 pounds
of copperas. Additional chlorine is added ordinarily to insure complete
reaction and also to disinfect the water being treated. Coagulation with
chlorinated copperas, therefore, is especially adaptable to conditions when
prechlorination is required and where coagulation by ferric chloride and
ferric sulphate over a wide range of pH values is an advantage because of
flexibility. As copperas is more readily applied to water than the ferric
coagulants, chlorinated copperas treatment may be used with conven-
tional chemical feeding equipment without modification.
(7) Ferric Sulphate. (Fe2 (804)3). ((i) Ferric sulphate was re-
cently introduced as a commercial coagulant in the form of an anhydrous
material which may be shipped and stored in wooden barrels. The ma-
terial will dissolve most readily in a limited quantity of warm water so a
special “solution pot” must be used with chemical feeders, whereby two
parts of water are used to dissolve each part of ferric sulphate, so as to
produce a solution of about 40 per cent strength. This is equivalent to
about three and one-third pounds of ferric sulphate per gallon of water.
(b) Ferric sulphate reacts with the natural alkalinity of the
water or with the lime added for the purpose and forms ferric hydroxide
floe. No intermediate oxidation reaction is involved as with copperas.
The required natural alkalinity, or the dose of lime, varies with different
waters Theoretically, however, the requirements are as follows:
1 gr.p.g. of ferric sulphate reacts with:
0.75 gr.p.g. natural alkalinity;
0.58 gr.p.g. 95 per cent hydrated lime.
(8) Ferric Chloride. (Fe CI3). (a) Three commercial forms
of ferric chloride are avaliable, namely, the liquid, the crystaline and the
anhydrous material. Liquid ferric chloride is very corrosive and is ship-
ped in rubber lined tank cars or twelve gallon glass carboys. The strength
varies from 31 to 45 per cent ferric chloride by weight, depending on the
temperature. The crystaline form of ferric chloride contains 60 per cent
ferric chloride by weight and is shipped in barrels holding about 435
pounds. Anhydrous ferric chloride is free from water of crystalization
and is shipped in steel drums holding about 100 pounds. The material re-
mains non-corrosive to the drums as long as moisture is excluded. The
drums must be left sealed therefore or their entire contents dissolved in
water at one time.
(b) Ferric chloride reacts with the natural alkalinity of the
water or with lime added for the purpose to form ferric hydroxide floe.
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Here again the concentration of the natural alkalinity or lime required
can not be definitely stated, but approximately is as follows:
Each gr.p.g. of ferric chloride requires:
0.92 gr. p.g. natural alkali;
0.72 gr.p.g, 95 per cent hydrated lime.
(9) Ferric Coagulants, (a) To summarize, chlorinated copper-
as, ferric chloride or ferric sulphate may give similar results when their
doses are compared in terms of iron content, although ferric sulphate
generally is a better coagulant than ferric chloride at low pH values re-
quired in the coagulation of highly colored water, because of the bene-
ficial influence of the sulphate ion or radical, as contrasted with the chlor-
ide ion.
(h) As in the case of coagulation with alum, the positively
charged floe, in this case ferric hydroxide, absorbs negatively charged
bacteria and the particles causing color and turbidity. There are a num-
ber of practical differences between alum and ferric coagulants, however,
which should be noted. Briefly, these are as follows:
1. Ferric hydroxide is formed at low pH values, so that
coagulation with ferric sulphate at pH values as low as 4.0 and
with ferric chloride pH values as low as 5.0 is possible.
2. Ferric hydroxide is insoluble over a wider range of pH
values than aluminum hydroxide except for the zone of 7.0 to
8.5. Chlorinated copperas, however, has been used with success
in this zone.
3. The floe formed with ferric coagulants, is heavier than
alum floe.
The ferric hydroxide does not re-dissolve at high pH
values.
5. Ferric coagulants may be used in color removal at the
high pH values required for the removal of iron and manga-
nese and in the softening of water.
(10) Clay, (a) Bentonite, Fullers earth, and other absorptive
clays have been utilized to some extent in recent years to assist in coag-
ulation. Clays assist in coagulation of relatively clear and colored waters
by supplying suspended matter as neuclei around which the floe forms.
Some of them “swell’ when added to water and produce a floe of them-
selves or with a limited dose of coagulant. In any case their use may
improve coagulation and reduce the coagulant cost. It is well, therefore,
to try them when difficulty is being experienced in coagulation.
(b) Some of the clays absorb taste and odor-producing sub-
stances, especially oily materials, so they may assist in the treatment of
waters polluted with trade wastes.
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(11) Sulphuric Acid. (H2SO4) (a) Sulphuric acid is of in-
terest only as an aid in the coagulation of soft colored water with alum,
where the use of acid is a more econimical means of producing the re-
quired low pH value than an equivalent dose of alum.
(h) The usual commercial strength of sulphuric acid is 66^
Beaume, which is equivalent to 93 per cent. The material is shipped in ten
gallon glass carboys or drums holding 50 to 500 pounds. The concen-
trated acid may be stored in iron tanks and conducted through wrought-
iron pipe, but the dilute acid is very corrosive to iron and must be stored
in glazed earthenware vessels, rubber lined steel tanks, or the like.
(12) Alkalies (a) Soda Ash. (Na 2 C 03 ) Soda ash, or sodium
carbonate, is a white powder very soluble in water so that little difficulty
is experienced in introducing this chemical into water to be treated. It
is used when waters do not contain natural alkalinity in sufficient quan-
tities to react with the coagulant. The reaction between alum and soda
ash produces about one-half the amount of carbon dioxide which is formed
when the natural alkalinity of water reacts with alum. No carbon dioxide
is formed, however, when an excess of soda ash is used, because the excess
combines with the carbon dioxide to produce sodium bicarbonate.
(b ) Soda ash is practically pure sodium carbonate, but never-
theless it should be procured by specification to contain at least 98 per
cent sodium carbonate. The use of this quality of soda ash has been as-
sumed in the calculation of chemical doses discussed in this manual. It
is readily apparent, for instance, that it is necessary to use about 102
pounds of 98 per cent commercial soda ash to provide 100 pounds of sod-
ium carbonate.
(c) Quick Lime. (CaO) Quick lime or calcium oxide may be
used with alum or copperas to provide artificial alkalinity when necessary.
It is used also in water softening. Quick lime varies in quality from
about 75 per cent to 99 per cent calcium oxide, so that the operators of
water treatment plants must know the quality of the lime they are using
before the doses can be calculated. The computations in this manual
are based on the use of 85 per cent quick lime. A high calcium lime should
be utilized, because of the ease with which it may be slaked.
(d) Hydrated Lime. (Ca(OH) 2 ) Slaked or hydrated lime, also
known as calcium hydroxide, is a white powder formed when quick lime
is slaked in water or in moist air. This material may be obtained in paper
or cloth bags in relatively small quantities. It does not deteriorate when
stored, does not have to be slaked, and contains fewer impurities than
most quick limes. This material may be mixed directly in solution tanks
and fed through orifice boxes into the water to be treated, or the chemical
can be fed in a dry form by the use of dry feed equipment. Lime is us-
ually fed as a suspension rather than as a solution because of its limited
solubility. Suspensions cannot be fed with the pots of either the mobile
or portable units.
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*G.P.G.=grain per gallon. One grain per gallon=17 . 1 parts per million. One grain per gallon=143 pounds per million gallons.
65. Mixing Basins. — a. A mixing basin serves both to mix the
chemical throughly with the water and to form a large floe in a minimum
length of time. A very rapid or violent mix is most suitable for the first
type of mixing, and is sometimes accomplished before water enters the
mixing tank. This type of mixing could be accomplished in a centrifugal
pump for example. When this initial mixing is done in the mixing tank,
it is often accomplished by a high variable speed propeller type agitator.
Flocculation is generally done with slow variable speed paddle type agi-
tators designed to give a gentle rolling motion to the water. Some tanks
have stationary blades, designed to accentuate the rolling motion, through
which the agitator blades pass.
h. Good floe formation is seldom accomplished in less than thirty
minutes. It is essential, therefore, to reduce “Short circuiting” through
the tank to an absolute minimum. The speed of the flocculating agitators
should be 0.5 to 2 feet per second and will vary with different waters. If
the speed is faster than this it will break up the large floe particles which
are essential to good settling. There is one type of a flocculating tank
which is really a combination of mixing and settling tank (Fig. 10b) . Floe
is formed in one section of the tank by agitating the incoming water and
chemicals in the presence of pre-formed floe. The water then passes into
another section where it moves upward through a bed of floe at a velocity
such that the bed is kept in suspension. As the water rises, the velocity
decreases, so that it is quite easy to prevent the suspended floe bed from
washing out of the tank. This floe bed is in effect a filter which removes
most of the particles formed in the flocculating chamber; the “floe filter’
also removes any particles from the water which escaped being caught
by floe in the agitating chamber. This sludge bed type of tank will ac-
complish in one hour what the usual mixing tank and settling basin will
in two to three hours. Several deviations from this method are possible,
varying from simple recirculation of sludge to the inlet of the basin, to
the arrangement in which the bulk of the water with its precipitates in
the tank is recirculated. (Figs. 17 & 18)
66. Sedimentation. — a. Sedimentation utilizes the force of gravity
to remove suspended particles. Because the ability of water to carry
suspended particles varies directly with the sixth power of the velocity,
the minimum practical velocity is used during sedimentation. If, however,
the velocity through the settling tank is coo low, currents caused by wind,
temperature differences, dissolved gas, etc. will materially interfere with
sedimentation. This instability can be prevented by increasing the veloc-
ity. The most efficient velocity in a settling tank is, therefore, the mini-
mum velocity which will maintain uniform flow conditions throughout
the tank.
h. The depth of the settling tank has little effect upon the removal
of floe because as a floe particle settles it picks up smaller particles, and,
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therefore, settles faster. The degree of removal depends upon the initial
particle sizes and the amount of flocculation which takes place during
settling. If the material to be removed is non-flocculating, then individ-
ual particles will retain their identity. In this type of a suspension, the
smallest particle that will be removed is one which will just settle to the
bottom of the tank in the detention period of the tank. For this type of
sedimentation, a shallow tank is most efficient. The detention period in
minutes for a tank is the volume of the tank in gallons divided by the
quantity of water in gallons per minute flowing into the tank. When a
volume of water passes through the tank in a time less than the detention
period, the tank is not operating efficiently. The most common cause for
this type of inefficiency is improper design of the inlet and outlet distri-
bution.
67. Settling Basins. — a. Settling basins are used to remove a sub-
stantial amount of the suspended matter in the water by utilizing the
force of gravity. The detention period for most tanks is from two to four
hours, some periods, however, are as long as twelve hours. Tanks may
have almost any shape, although circular and rectangular are the most
common. The best flow stability is obtained in long narrow rectangular
tanks. (Sewage has settling characteristics very similar to the settling
characteristics of floe particles in water.) In this type of tank it is easiest
to obtain good influent and effluent distribution. It is essential in any type
of tank, particularly circular and short tanks, to design the inlet so that
the water is distributed uniformly over the cross section of the tank and
so that the entrance velocities are completely dissipated before the water
has passed through 10% or less of the tank’s length. The collecting outlet
should be designed so that these same results are obtained in reverse. It
can be readily understood that if the entrance velocities extend for an
appreciable distance into the tank, part of the water will pass through
the tank in a time much less than the detention period.
b. After the sediment carried by the water is deposited in the tank,
the next problem is removing it from the tank. One method is to allow the
sludge to accumulate in the bottom of the tank for a month or two, and
then to drain the tank and wash the sludge out by hose, but this is waste-
ful of water and the sludge may putrify. Another method is to remove
the sludge continuously by a sludge removal mechanism which moves the
sludge to a sump at either end of a rectangular tank or at the center of a
circular tank. From this sump the sludge is removed by gravity or by
pumping. In the “floe filter’’ type of tank the sludge is removed contin-
uously by “bleeding” or draining off some of the bed.
68. Filtration. — a. Filtration is a process by which solids are re-
moved from liquids. Although there are many types of filters employed for
the filtration of water, among which are porous plates, paper, cloth, and
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other special types, the only types which are used on a large scale are those
known as sand filters. This term includes not only those employing sand
as the filter medium but also those employing anthracite coal, magnetite,
and certain other granular materials. In addition, calcite, zeolite, and
granular activated carbon are used in vessels which are essentially filters.
These special granular materials will be discussed further under their
specific application.
b. Slow Sand Filters. The original granular filters were known as
slow sand filters. No coagulant was used, but very often sedimentation
basins or reservoirs preceded them to remove the bulk of the material
which could settle out by its own weight during the long retention period
provided.
c. Slow sand filters employ a very slow filter rate. The sand which
acts as a filter medium is very much finer than the sand used in rapid
sand filters with which we are more familiar today. Slow sand filters,
since no coagulation or preliminary treatment is provided, depend on the
slow passage of the water over fine sand grains at a rate normally not in
excess of 3 to 4 million gallons per acre per day (0.016 gal. per sq. ft.
per minute.) In addition to the sand, a layer of the material removed from
the water is gradually built up on the sand grains, improving the filtra-
tion in a manner somewhat similar to that of the floe in the rapid sand
filter.
d. A slow sand filter will remove about 98% of the bacteria from
the water, almost all the other suspended solids, and when properly sea-
soned will absorb 30 to 40% of the coloring matter in the water. If the
raw water is very turbid the bed becomes clogged quickly. After a time,
the length of which depends on the amount of material removed by the
slow sand filter, the upper layer of the sand bed becomes sufficiently clog-
ged to reduce the flow appreciably. It is then necessary to scrape off the
upper few inches of sand and accumulated muck. After the bed is reduced
by repeated scrapings of this type to about one-half of its original depth,
new, clean sand is added to restore the bed to its original depth (usually
27 to 48 inches.) In slow sand filters the water always passes through
the bed by virtue of its own weight (gravity).
e. Rapid Sand Filters. By adding a coagulant, the size of the grains
and the rate of filtration can be increased. In municipal practice today
it is normal to use a filter rate one and one-half to two gallons per square
foot of filter area per minute. Depending largely upon its character, raw
water for industrial, swimming pool, and other such uses is filtered at
rates as high as 3 gallons per square foot per minute, and in emergencies
rates go as high as 4 gallons per square foot per minute for short periods.
In our mobile and portable water purification filters (Chapter 7) the maxi-
mum rate is set at 10 gallons per square foot per minute but this can
scarcely ever be attained, even if settling precedes filtration.
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/. The criterion in filtration, especially in mobile and portable units,
is to use only as high a rate as is absolutely necessary in order to produce
the quantity of water that will be required, utilizing the full time alloted,
and never exceeding a rate which fails to deliver clear water. When set-
tling is not practiced ahead of filtration in portable and mobile units, the
time available for the reaction of the coagulant with the natural or arti-
ficial alkalinity is very short. Settling should always be used in the trop-
ics, in other climates on every possible occasion, and always when the
water contains color or contains a turbidity over 50.
g. With rapid sand filters it is not necessary to remove the sand on
order to clean the filter. Cleansing is effected by reversing the fiow so
that the water enters the filter at the bottom, and rises, suspending the
sand and gravel, and causing the individual grains of sand to rub against
and scour each other. The wash water effluent leaves the filter at the top.
This process is called backwashing.
h. It is common to supplement the backwash with a water wash in
the surface. This is called surface wash, and is accomplished with rotat-
ing jets of water from a revolving distributor which impringe horizontally
on the surface. Surface wash is particularly useful where the formation
of mud balls on the surface of the filter bed occurs.
i. At times an air wash is employed instead of surface wash. The
filter is partially drained, and air is blown upward from the bottom of the
filter through a pipe grid to agitate the bed before the water wash has
begun, and continued for several minutes after the water wash begins.
Air wash is beneficial where the material filtered from the water is of a
sticky nature such as oil. Where oil is being removed, it is also beneficial
to give the bed of the filter a scour with a solution of caustic soda (sodium
hydroxide, NaOH) . This caustic scour is not given every time the unit is
backwashed, but at periodic intervals, say every 6 months or year.
69. Types of Rapid Sand Filters. — a. Gravity. (1) When water
is passed through rapid sand filters contained in vessels open to the
atmosphere, that is when no external pressure is applied, they are known
as gravity filters. The head necessary to overcome the friction in pass-
ing through the filter is furnished by maintaining a sufficient depth of
water over the sand bed. Gravity filters are built in open containers
of wood, steel, concrete, or similar material.
(2) The advantages of gravity filters are : the appearance of the
water being filtered, the sand bed, the effectiveness of washing, and the
degree of agitation during the washing process can be observed; it is
somewhat less difficult to replace the sand in gravity filters than in pres-
sure filters; and the rate of filtration is limited by the low heads available
and thus a careless operator is unable to exceed the rated capacity, as
with a pressure filter where the rate is limited only by the head available
at the inlet and the loss of head in the filter.
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b. Pressure Filters . — When water enters, passes through, and
leaves a filter under the influence of an external pressure without reduc-
ing that pressure any more than is necessary to. overcome the friction in
the filter and its bed, it is called a pressure filter. They are constructed in
closed vessels, usually of steel. The chief advantage of pressure filters
is that it is unnecessary to repump the filte
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