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J. WALDO SMTIH,
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WATER PURIFICATION
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l.iWiU'.'iliiil Umml Engineering News
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Si|\i\.il l^iinlnooi- AiwrionEngTKi
\\\ 111.' W.lU\MV Joufnal Coal Age
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.1. 1
WATER PURIFICATION
BY
JOSEPH W. ELLMS,
Member Ambbican Socibtt Civil Enoineebs. Ambbioan Chemical
SociETT. Amebican Public Health AssociATioif and New
England Water Works Association.
F1B8T Edition
McGraw-Hill book company, inc.
239 WEST 39TH STREET. NEW YORK
U)SDOS: HILL PUBLLSIIIXG CXJ.. Ltd.
« 4 8 B^Jl'VERIE 8T., E. C.
1917
THE HEW TOU
PUBLIC UBRARTI
764885 A
COPTRIQHT, 1917, »T THK
Mc-llHAw<HiLi. Book Comtakt, Ixc
A
^
PREFACK
In writing this book the object has been to provJrl/5 Dm r<?mktr
with a fairly complete account of the developnKjnt tjl i\m hri r/f
water purification. As a knowled|;e <jf ilm phyMJ/;al, r^U'rrii^^al
and biological characteristics of natural waUrrn is a \nt^^'t\H\n\\M
to the proper understanding of purificatirm in<H*Atmimf a iumnuU^t^
tion of the properties of various clause of wat^s \im \m*^i il^/UK^/t
advisaUe. The relation of polluted puMic wat^ Mupf/ii^ Uf
water-borne diseases has received especial atteriii/;n l>^/rafM^ //(
its importance. The vsltumm vUifm in p«jrifi/;at«/;fi prr/^?^!**^*,
sQch as i^ain sedimentation^ coagtilati/^ri, fiitrati/^i arid fUnutl^^^^
tion, are described in eonidderabk; d^daiL H^^^rial chaf/t^ii a/^
dcToted to water wfA\emx$%^ aiid to tte r*rw#//ral ^>f ir^/ri a/,d
manganese from ground wat^r ir.*jppik3t.
The rapid progress made in th^ art of -^lAnf /,r.^ ar.d lr*f»!/,f,$c
turfcfd waters in the UiaVrd .S^at/=«t <: /Hr-g tw: psi^rt '| *Ar*>r '^ a
cettTry, has been i^^aa'ta^. Ttjh *rf'? r.or. 0/ ♦r^ f%;A'S »<%?,^
fiher from its ende l^c-r-r-ci V> >.* p«r**^rr.it ^^-^'Vr/'-V/^yt
^"* for p-irifriE45 watVr^ of tr-.* *7?^' -s* ':.'^.'./^.*/ *r^ ?*:»-,.^ //
:h work oiLO^^.aitt: c ^,t^^ u^ *A,':r ^/trt '/ ♦'.* ;^ry^
b w*i tie a*r:iy>r'i fr</i f^rr ..vt */> ^av^ '^^^, ^Vr*.^ ■>/; »,^r,
been a.'.tift' v, fcsl'^w >.* tot ;rrf.',c ♦,:/>«' 7 .i 4a-* -.^ ;r*^"^i*>, ''^ 'V^r^"-'
CCS lilt wif'^tie j^TjVi,
:^ ■»^,* t;jr '^^^-'i/Vi* ->->*--';•,.''» •/ '*-:;v*- *^ ^ • '^
'/ *'j»: vr.-i i,- ' V. r.-<-: ::<*'' ..-*-'' v >^- ^ >-- ^
30
viii PREFACE
used in filter plant construction, who have loaned original draw-
ings and photographs for reproduction.
The author desires to acknowledge especially the contribution
of the subject matter in the appendices written by Mr. C. N.
Miller, Assoc. M. Am. Soc. C. E., dealing with the hydraulics
of the flow of water through filters, and with the discharge* of
water from waste-water troughs in the operation of rapid sand
filters. The author is also imder special obligation to Mr.
S. J. Hauser, Chemist and Bacteriologist of the Cincinnati
Water Purification Plant, for his kindly assistance in reading
the proof of the book and in preparing the index.
Cincinnati, Ohio,
March 1, 1917.
CONTENTS
. Paob
Pbeface vii
Chapteb
I. Introduction 1
II. Classification of Natural Waters 8
III. Transmission of Disease Through Drinking Water . 22
IV. The Effect of Improved Water Supplies upon Health . 34
V. Objects and Methods of Water Purification .... 43
VI. Sedimentation 50
VII. Types of Settling Reservoirs AND Coagulation Basins . 60
VIII. Practical Efficiencies of Settling and Coagulation
Basins 80
IX. Filtration of Water 89
X. Preliminary Treatment of Water for Slow Sand
Filters 97
XI. System of Slow Sand Filtration 116
XII. System of Slow Sand Filtration (Continued) 134
XIII. Efficiency and Cost of Operation of Slow Sand Filters . 150
XIV. Rapid Sand Filtration 159
XV. General Arrangement of Rapid Sand Filter Plants . . 173
XVI. Details OF Rapid Sand Filter Plant Construction. . . 183
XVII. Details of Rapid Sand Filter Plant Construction
(Continued) 200
XVIII. Details of Rapid Sand Filter Plant Construction
(Continued) 211
XIX. Regulating, Measuring and Indicating Devices for
Rapid Sand Filter Plants 220
XX. Regulating, Measuring and Indicating Devices for
Rapid Sand Filter Plants (Continued) 238
XXI. Equipment for the Handling and Storing of Chemicals
AND For the Preparation of Solutions 256
XXII. Apparatus and Methods for Applying Chemicals and the
Preparation of Solutions 274
XXIII. Power Plant, Pumping Machinery, Air Compressors,
Air Tanks, Wash Water Tank and Miscellaneous
Equipment 290
XXIV. The Cost of Constructing Rapid Sand Filters. . . . 305
XXV. Rates of Filtration, Loss of Head and Washing of Rapid
Sand Filters 312
ix
X CONTENTS
Chaptsr Paqs
XXVI. The Physical and Chemical Changes Produced by the
Application op Chemical Coagulants, and by the Sub-
sequent Filtration op the Treated Water 331
XXVII. Eppiciency and Cost op Operation op Rapid Sand Filters 347
XXVIII. Disinfection op Water Supplies 367
XXIX. DisiNPECTioN OP Water Supplies {Continued) 395
XXX. The Removal op Dissolved Mineral Matter prom Water 410
XXXI. The Removal op Dissolved Mineral Matter prom Water
(Continued) 437
XXXII. The Control op Water Purification Processes. . . . 452
Appendix A. — The Flow op Water Through Rapid Sand Filters . 461
Appendix B. — An Approximate Formula for Calculating the
Discharging Capacity op Rapid Sand Filter Wash Water
Troughs 465
Tables. — Nos. 1 to 12 inclusive 468
Index 479
WATER PURIFICATION
CHAPTER I
INTRODUCTION
Water purification may be broadly defined as the art of remov-
ing foreign and polluting substances from solution and suspen-
sion in water. The character and amount of these impurities,
and the object for which their removal is undertaken, naturally
leads to the treatment of this subject under the following heads:
1. Rendering impure water potable and hygienically safe for
drinking piu poses, and suitable for industrial uses.
2. Removing putrescible organic matter and disease-produc-
ing organisms from the fouled water supply or sewage of a
commimity.
In the following pages it is intended to treat only of the first
division of this subject, since the second covers too broad a
field to bring it within the scope of this volume.
Both the kind and the amount of impurities in a polluted water
aflfect the methods which can be employed for its purification,
and this is so peculiarly true of sewage that its treatment has
become an art in itself. Those waters which are to be purified
for di inking purposes demand that a degree of purity shall be
produced which is not possible and usually imnecessary in the
case of sewage. The purification of the latter is, as a rule, quite
incomplete as compared with that required for a safe drinking
water, and obviously the object to be attained is quite different.
In the case of waters to be treated for making them suitable for
steam-boiler purposes, or for general industrial uses, a slightly
different object is sought. The softening of hard waters or the
removal of compounds of iron or manganese may be an integral
part of the purification of a public drinking water supply, in which
case it is combined with those processes utilized for making a
water hygienically safe. Of course it is quite possible to carry
on purification for industrial purposes independently of the more
refined methods used for drinking water, and frequently this
course is piu^ued in connection with manufacturing plants.
1
WATER PURIFICATION
HISTORICAL
Ancient Systems of Water Supply. — Good water for drinking
purposes has doubtless been appreciated by the human race
from time immemorial, for it does not take a very high degree
of intelligence to discriminate between a clear, colorless and
odorless drinking water, and one that does not possess these
outward attractive physical properties. Among primitive
peoples the question of water supply was never of pressing im-
portance, except in arid and semi-arid regions. In these latter
countries provision for securing and storing a supply of water
was usually necessary. Consequently, springs were sought for,
wells were dug, and cisterns constructed in order that a supply
of water might at all times be available.
Wells were common in ancient Egypt, Greece, Assyria, Persia
and India, and from the sanitary point of view they probably
furnished a safer drinking water than could be obtained from the
surface waters in the rivers and lakes. Wells of great antiquity
may be found today in Egypt and India. Joseph's well at Cairo
in Egypt is one of the most famous ancient weUs, and was
excavated in solid rock to a depth of 297 ft. The Chinese were
familiar with the driving of artesian wells and pursued methods
similar to those now in vogue in sinking them.
Where turbid surface waters had to be employed for drink-
ing, domestic filters of unglazed earthenware or of sandstone
were known to have been used by the ancient Egyptians and
by the Japanese. Clarification of muddy water by the siphoning
of the liquid from one vessel to another by the capillary action
of porous material, such as a strip of cloth, and the consequent
separation of the water from the suspended matter, was well
known to the ancients.
As population became more dense and people began to congre-
gate in cities, the need for larger volumes of water, than could
be suppUed by springs and wells, became urgent. Works for
the collection, storage and conveyance of water were built for
suppljdng many of the ancient cities, and the ruins of some of
these works yet remain.
The ancient water tanks of Aden in Arabia for the collection
of surface water from the gorges of the volcanic crater, at the
bottom of which the old city was located, afford an example of
early impounding reservoirs of an elementary type. These
INTRODUCTION 3
tanks may have been built by Persian engineers as early as 600
B*C., or possibly by the Romans; but they without doubt
antedate the Christian era.
The infiltration galleries for collecting ground water at Athens
in Greece were probably constructed over 2,000 years ago, and
the same method is stiU pursued to obtain a pure and satisfactory
water supply. The rain-water cisterns of ancient Carthage
(160 B.C.) were devised into several storage compartments, two
of which were apparently used for settling or possibly filtering
the water. Historians state that the city of Laodicea in Asia
Minor obtained its supply from the River Caprus. The latter
had its origin in springs. The water was conveyed to the city
through a masonry aqueduct over 4 miles in length. A set-
tling tank with double compartments formed a part of this
water-works system. In Jerusalem underground cisterns were
constructed, which were supplied through masonry conduits.
Probably no more elaborate system of public water supply
was provided for any ancient city than that for Rome. Until
312 B.C., the Romans took their supply from the River Tiber
and from springs and wells in the vicinity of the city. The
increasing pollution of the river water, as well as the need for
a greater volume of water, evidently induced the Romans to
seek elsewhere for a supply. In consequence, three groups of
springs in the volcanic plain on the left bank of the Tiber were
made use of, and the water from them conveyed by aqueducts
to the city. A fourth group of springs was also used which were
located in the mountains of limestone formation somewhat more
distant than the three other groups. This latter group furnished
the best quality of water with which the city was supplied.
E. H. D'Avigdor, in his "Water Works of Ancient Rome"
{Engineering t xxi, p. 403), interestingly describes the character
of the Roman water supply as follows: "The Romans possessed
three almost independent water services, for which they used
water of different degrees of purity. The least clear and most
loaded with sand, such as the Anio aqueduct supplied, was used
for pubUc baths and the watering of streets; the clearer water
from Tepula and Alsietina served for tanks, fountains and wash-
ing troughs; while the very best (Virgo, Marcia and Claudia)
was confined to drinking purposes, and these springs were
undefiled even after the heaviest rains."
Rome was supplied with water from the above-mentioned
4 WA TER PURIFICA TION
four groups of springs through nineteen aqueducts, which were
built between 321 B.C. and 305 A.D. The aggregate length
of these aqueducts was 381 miles.
There can be said to have been no real distribution system
for the water entering Rome through the system of aqueducts.
The aqueduct water flowed through small tanks in whic^i the
heaviest sand and gravel were deposited. To a limited extent
the small distributing reservoirs (castella) near the city served
a like purpose. From these reservoirs the water was distributed
to cisterns, pubUc fountains and private residences.
During the Middle Ages,^ when disease played such havoc with
the people of Europe, polluted water undoubtedly assisted in
conveying infection. At the time of the fall of the Roman Em-
pire many of the aqueducts built by the Romans at Rome and
in the provinces were either destroyed or fell into disuse. The
Moors in Spain during the ninth century constructed some
important works, as well as repairing in the twelfth century
some old Roman works.
Until 1183 A.D. Paris obtained its entire supply of water from
the River Seine. As late as 1550, Paris used only 1 qt. of water
per capita per day, and at the end of the seventeenth century
was using but 2}4 Qt. per capita per day. With such small
amounts of water being used one can easily imagine what sanitary
conditions must have been.
LfOndon was first supplied in small quantities with spiing water
conducted through lead pipes, and masonry conduits. In 1582
a pump was erected on London Bridge to take water from the
River Thames, and to deliver it through lead pipes to the city.
By the invention of the steam engine, pumping machinery of
adequate capacity and power was made possible. The growth
and development of water-works plants in reality dates from
the eighteenth century. However, not until the latter half of
the nineteenth century was very rapid progress made. The use
of cast-iron pipe became general in about the year 1800, and
gra4ually replaced the wooden mains formerly used.
Development of Modem Purification Plants. — The methods
employed in securing and maintaining pure water supplies have
been in a large measure governed by topographical and geological
conditions. In different countries, where like physical condi-
tions prevailed, similar lines of development have not always
^ TuRNBAURE and Russel: "Public Water Supplies.'*
INTRODUCTION 6
been followed. Mr. Allen Hazen, in his book on "Filtration of
Public Water Supplies," points out that "it is really marvellous
how each country has met its problems of water supply from its
own resources, and often without much regard to the methods
which had been found most useful elsewhere. England has
secured a whole series of magnificent supplies by impounding
the waters of small streams in reservoirs holding enough water
to last through dry periods, while on Continental Europe such
suppUes are hardly known. Germany has spent millions upon
millions in purifying turbid and polluted river waters, while
France and Austria have striven for mountain-spring waters
and have built hundreds of miles of costly aqueducts to secure
them. In the United States an abundant supply of some Uquid
has too often been the objective point, and the eflforts have been
most successful, the American works being entirely unrivalled
in the volumes of their supplies. I do not wish to imply that
quaUty has been entirely neglected in our country, for many
cities and towns have seriously and successfully studied their
problems, with the result that theie are hundreds of water sup-
plies in the United States which will compare favorably upon
any basis with suppUes in any part of the world; but on the other
hand, it is equally true that there are hundreds of other cities,
including some of the largest in the country, which supply their
citizens with turbid and unhealthy waters which cannot be
regarded as anything else than a national disgrace and a menace
to our prosperity."
Since the above quotation was written, nearly two decades
ago, many of the cities of the United States have done much to
redeem the bad reputation which they had because of polluted
and unwholesome water suppUes. There is still much that can
be done, however, toward improving present conditions, and as
time goes on and population becomes more dense, the danger
from polluted water increases.
Those impurities in water which render it turbid, and which
for the most part are in suspension, make it unattractive as a
drinking water. It was probably noted at an early period, that
a muddy water, if allowed to remain quiescent for a short time,
lost more or less of its suspended matter by settlement. In
storing muddy waters for irrigation purposes this phenomenon
could hardly have failed to have been noticed.
The appearance of a muddy water was obviously improved by
6 WA TER PURIFICA TION
settlement, and its suitability as a drinking water enhanced.
If clear spring waters could not be obtained for a public supply,
resorting to surface waters was a necessity. Hence, we find
evidence that in some of the ancient water-works systems pro-
vision was made for settlement of muddy waters in tanks or
settling basins. The ''castellse" and piscinse of the Roman
aqueduct system evidently performed the function of settling
tanks, whether originally intended for that purpose or not. In
other ancient systems the evident purpose of tanks for settling
purposes is more pronounced. Some of these works have been
cited in the preceding pages.
These early devices for improving the quality of a water supply
were crude and imperfect, and can only be recorded as the
beginnings from which the really modern art of water purification
sprang.
While sedimentation for the clarification of water may be
looked upon as the earliest step in the art, nevertheless, it can
only be regarded in most cases as preliminary to more complete
methods. The straining action of sand and gravel was doubt-
less also noted by keen observers at an early date, in the same
way that the clarification effected by settling tanks had been
observed. The application of this principle to the public water
supply of LfOndon was made in 1829. Filters of sand and gravel
were also constructed for many of the Continental cities, more
especially in Germany, wheie the principles underlying the action
of filters of this type were carefully studied.
Mr. Allen Hazen has divided the history of water purification
in the United States into three epochs, the first beginning with
James P. Kirkwood's report on the "Filtration of River Waters"
in 1866, resulting from his study of European practice; the
second epoch commencing with the work of the Massachusetts
State Board of Health at its Lawrence Experiment Station in
1887; and the third with the experiments on very turbid waters
beginning at LouisviUe, Ky., in 1896, and continued at Pitts-
burgh and Cincinnati during the 3 or 4 years following. To
these three epochs the author would add a fourth, which was
introduced in 1908 by the experiments at Chicago and at Boon-
ton, N. J., on the disinfection of water with hypochlorite of lime.
The use of this latter compound has become widespread in the
past 5 years throughout the United States, and its usefulness as
a practical, efficient and economical agent in water purification,
INTRODUCTION 7
under certain conditions, has been fully demonstrated. The
sterilization of water with chlorine and its compounds, as well
as the action of ozone and ultra-violet light, have been carefully
studied diu'ing the past few years, especially in Europe. This
phase of water purification is well established, and marks an
important stage in the practical development of the art.
References
1. L. F. Vernon-Harcout: "Sanitary Engineering/' 1907.
2. Bolton: "Ancient Methods of Filtration." Pop. Sci. Mo.^ 16, 496.
3. Arthur S. Riggs: "Ancient Water Tanks of Aden, Arabia." Eng,
News, 52, 25, 1904.
4. "Ancient Water Supply of Athens." Engineer^ 101, 215, 1906.
5. Crobs: "The Water Works of Carthage." Eng. Record, 25, 8, 1892.
6. Edward Wegmann: "The Water Works of Laodicea, Asia Minor."
Eng. Record, 40, 354.
7. Edward Wegmann: "Ancient and Modem Water Works." Eng.
Record, 65, June, 1912.
8. E. H. D'Avigdor: "Water Works of Ancient Rome." Engineering
21, 403, 1876.
9. Geo. Higginb: "The Old Water Supply of Seville." Proc. Inst.
C. E., 38, 334.
10. TuRNEAURE and Russel: "Public Water Supplies."
11. Allen Hazen: "Filtration of Public Water Supplies."
12. W. P. Mason: "Water Supply."
CHAPTER II
CLASSIFICATION OF NATURAL WATERS
In order to understand intelligently the methods employed in
water-purification processes, it is necessary to have a knowledge
of the composition of the various classes of natxiral waters which
require treatment. Although all the water which is now flowing
on the surface of the ground, as well as that which is found in
the ground, has a common origin, nevertheless, this water has
acquired varied characteristics, which have been derived from
the substances with which it has come into contact.
Rainfall. — From the water surfaces of the earth the sun is
constantly evaporating enormous volumes of water, which are
again condensed and precipitated upon the land and water
surfaces as rain, snow or ice. That which falls upon the land
surfaces of the earth is disposed of in diflferent ways. Some of
the water is evaporated again; some is absorbed by growing
vegetation; some flows directly over the ground into the rivers
and lakes; and some sinks into the soil to become the subter-
ranean water of the earth. The amount of water precipitated
on the surface of the earth in any particular region depends upon
a number of factors. Warm air which is saturated with water
in the form of vapor will only precipitate this moisture when
sufficiently cooled. Air currents may be cooled by coming into
contact with the cold surfaces of the earth, or by being forced
upward by mountain ranges into colder air currents, or by
mingUng directly with colder air currents at lower levels. Pre-
cipitation of water will take place under these conditions.
The water thus precipitated is as near pure water as may be
found under natural conditions. It probably will contain minute
quantities of nitrogen compounds, such as ammonium salts, and
some organic matter consisting of plant spores and bacteria.
It will also contain in solution small quantities of the gases,
oxygen and carbon dioxide.
As the descending rain or snow approaches the earth, it washes
out of the atmosphere suspended particles of dust and thus puri-
fies the air. These impurities will, of course, be found in the
8
CLASSIFICATION OF NATURAL WATERS 9
rain water if collected before reaching the ground. Rain water
caught in or near our large cities is much more impure than that
collected in the open country. The impurities swept from the
air are relatively in smaU amounts as compared with those
acquired by the water after reaching the earth; but they are the
first of the dissolved and suspended constituents to be taken
up by the water, and are soon increased in amount and kind after
the water reaches the ground.
SXIRFACE WATERS
Flowing Surface Waters. — The character of the land surfaces
upon which rain or snow is precipitated naturally influences the
proportion of the volume of water which finds its way over the
top of the ground into the streams and lakes, and that which
sinks into the ground to become a part of the underground water
of the earth. If the land is mountainous, the rain rapidly runs
oflf the steep slopes into the valleys, and quickly enters the
rivers. If the soil is easily washed away, the water will carry
with it large volumes of sediment, the composition of which will
depend upon the geological characteristics of the denuded sm*-
faces. On the other hand, if the precipitation occurs in a flat
level country, a much larger proportion of the water will per-
colate into the soil. If vegetation is abundant, some of this
water will be retained by the growing plants, and may sensibly
retard the discharge of surface water into the natural water
courses. In water which has been subjected to such conditions
there will be found those dissolved salts with which the water
has come into contact, as well as organic matter derived from
vegetation.
Flowing surface waters may be characterized, therefore, as
those which contain relatively small amounts of dissolved mineral
compounds, more or less of suspended matter, depending upon
topographical and geological conditions, and variable amounts
of organic matter, likewise modified by the flora of the region.
Impounded Surface Waters. — Natural lakes and ponds are
composed of water which has found its way directly through
surface streams into the depressions in which these bodies of
water lay, and of the water which has percolated for some distance
through the ground and reappears as a surface water at lower
smface levels. In a like manner the low-water flow of streams
10 WA TER PURIFICA TION
is very largely maintained by the ground-water flow from higher
levels.
In consequence, these lake waters are virtually mixtures of
surface and ground waters, and their composition is, in a large
measure, intermediate between them. Obviously local topog-
raphy and the very important factor of sedimentation will
materially affect their composition. They also have an im-
portant influence in rendering streams flowing from them more
uniform in their discharge on account of the storage for water
which they afford.
UNDERGROUND WATERS
The water which sinks into the ground does not all imme-
diately pass through the subsoil to underground channels. Some
is held by the surface soil, and in hot countries may soon be
evaporated into the air; some of the water is absorbed by the
growing plants; and the remainder sinks slowly or quickly through
the ground depending upon the porosity of the latter.
The movement of this ground water is governed exclusively
by the character of the strata with which it comes into contact.
Impervious formations wiU block or divert the flow, while per-
meable strata will soon become filled and form the channel along
which the underground stream moves. The velocity of flow is,
of course, low, and depends upon the porosity of the soil in which
the water is moving.
All of these factors have a bearing upon the dissolved constitu-
ents which will be found in an underground water. The sus-
pended matter of the surface water will have been filtered out,
whether in a relatively coarse form like sand and silt, or in a
finer or colloidal condition like finely divided clay. On the other
hand, the solution of mineral compounds containing sodium,
potassium, calcium, magnesium, iron, aluminum, silica, etc.,
will have begun, and will continue as long as the water does not
become supersaturated, and until '* a chemical system of balanced
values"^ is attained for the various salts with which the water is
in contact.
CONTABflNATION OF WATER
Natural Impurities. — For convenience the impurities in water
may be divided into classes according to the sources from which
* Chase Palmer: **The Geochemical Interpretation of Water Analyses."
U. S. Geological Survey B\ill. 479.
CLASSIFICATION OF NATURAL WATERS 11
they are derived. As has been previously noted water in the
course of its flow over the surface or through the ground dis-
solves more or less material as well as carrying varying amounts
in suspension. Provided no contact with the wastes of human
life or activity has occurred, the acquired impurities might be
designated as natural impurities, in distinction from those
derived from sewage or manufacturing wastes. Water polluted
from the latter sources is unfit for human consumption without
purification as wiU be shown in a later chapter. Water which
h^ not been subjected to such contamination may or may not
be fit for drinking, depending entirely on the nature of the
dissolved and suspended impurities which it may contain.
Dissolved Impurities. — The solvent action of water upon the
seemingly insoluble constituents of the earth's crust is enormous,
aside from its erosive action. The surface and subsoil, as well
as the deeper rock strata, are all subjected to the decomposing
action of the water with which they come into contact. Erosion
assists the solution of the mineral compounds composing the
various strata by reducing them to a finely divided state.
Disintegration of minerals Uke orthoclase, for example, is
able to supply the bases sodium and potassium; dolomitic lime-
stones may furnish calcium and magnesium; and clay ironstone
and pyrite may give up iron, aluminum and silica. The acids
with which the above bases are usually associated are carbonic,
hydrochloric and sulphuric acids. These latter are derived from
the disintegration of the minerals in the rock strata the same as
are the bases. More or less carbonic acid is obtained directly
from the air and from the oxidation of carbonaceous compounds
in the breaking down of organic matter. Minute quantities of
nitric acid may be derived directly from the air, and from oxida-
tion of nitrogenous compounds. The oxidation of sulphur in
minerals supplies sulphuric acid in many cases. Sulphates,
chlorides, nitrates, carbonates and silicates exist as such in the
earth's crust in enormous amounts, and whenever they come into
contact with water are dissolved directly, and in amounts
depending upon the supply available and the solubility of the
salt being acted upon.
A classification of natural waters with respect to their dissolved
constituents, which is based upon the chemical nature and the
proportional amounts of the radicles present in solution, has been
suggested by Mr. Chase Palmer in a paper entitled "The Geo-
12 WATER PURIFICATION
chemical Interpretation of Water Analyses" (U. S. Geological
Survey BvU. 479, 1911). He states that:
"Nearly all terrestrial waters have two general properties, sfi^inity and
alkalinity, on whose relative proportions their fundamental characters
depend. Salinity is caused by salts that are not hydrolyzed; alkalinity
is attributed to free alkaline bases produced by the hydrolytic action
of water on solutions of bicarbonates and on solutions of salts of other
weak acids."
According to his classification waters may possess five special
properties as follows:
1. Primary salinity; that is salinity caused by the sulphates
and chlorides of the alkalies sodium and potassium.
2. Secondary salinity; that is salinity produced by the sul-
phates and chlorides of the alkaline earths calcium and mag-
nesium, or in other words permanent hardness.
3. Tertiary salinity; that is in reality an "acidity" arising from
an excess of saline compounds over and above that due to primary
and secondary salinity.
4. Primary alkalinity; that is an alkalinity produced by car-
bonates and bicarbonates of sodium and potassium, or in other
words permanent alkalinity.
5. Secondary alkalinity; that is the property caused by alkaline
earth bicarbonates such as those of calcium and magnesium, or
in other words temporary hardness.
By various combinations of these properties five well-defined
classes of waters are possible and are found in nature.
Class 1. Waters characterized by properties 1, 4 and 5 as
stated above.
Class 2. Those showing properties numbered 1 and 5.
Class 3. Those exhibiting properties niunbered 1, 2 and 5.
Class 4. Those marked by properties numbered 1 and 2.
Class 5. Those possessing properties numbered 1, 2 and 3.
"Surface waters appear to belong chiefly to the first three
classes, class 4 is represented by sea water and brines, class 5
is exemplified by mine (acid) waters and waters of volcanic
origin."
Suspended Impurities. — Intermediate between a solution, as
it is commonly understood, and a suspension of finely di\aded
particles, like sand for example, there may be so-called colloidal
suspensions of certain substances in water which possess
peculiar properties, and which are of considerable importance
CLASSIFICATION OF NATURAL WATERS 13
in connection with water purification problems. For example,
silica is found in this state in many natural waters, especially
those showing primary alkalinity, t.c, waters containing sodium
and potassiiim carbonates. The sDica compounds characteristic
of the clays show a marked tendency toward the colloidal state,
and render the problem of the purification of turbid waters of
this class almost a problem in itself.
The enormous amount of the heavier sediment carried by
many rivers consists largely of sand and clay. Any reduction
in the velocity of flow of the water laden with such sediment
causes it to be deposited on the bed of the stream. Gravel and
sand bars are thus formed in river beds, which may be shifted
from one point to another by any sudden increase in the velocity
of the current, such as might be produced by a flood. Lighter
material like clay is more slowly deposited and more quickly
moved again by any change in the rate of flow of the water. It
thus happens that almost all surface waters carry varying
amounts of suspended material in them which depend upon the
velocity of the currents of water and on the character of the
bottom and shores. The action of the wind on large bodies of
water Uke the Great Lakes, for example, may stir up the sediment
on the bottom and render the water, near the shore especially,
quite turbid.
Compounds of iron and of manganese are not infrequently met
with in the colloidal state in natural waters, and offer some of the
most interesting phases of water-purification work. Organic
matter found in natural waters is probably always present in this
form to a greater or less degree. Vegetable stain produced by
humic substances is a marked characteristic of a very large class
of natural surface waters, and as such has received considerable
attention in the study of purification problems.
How the removal of these impurities, whether in solution or in
suspension, is effected will be discussed under the description
of the various methods of purification now employed, rather than
in this place. It is only desired to emphasize the varied classes
of impurities which may be found in natural waters, and which
are virtually "natural impurities,'^ as distinguished from those
derived from sewage and manufacturing wastes. This waste
material may furnish similar classes of polluting compounds to
those derived naturally, but their origin usually justifies their
consideration separately.
14 WATER PURIFICATION
Whether the dissolved salts usually found in natural waters
are objectionable depends upon the use to which the water is
to be put. A certain amount of the chlorides, sulphates and
carbonates of sodium, potassium, calcium and magnesium are
by no means deleterious, and may possibly be beneficial in a
drinking water. On the other hand, if too great amounts are
present these dissolved salts render the water unfit for domestic
and industrial uses, and actually cause financial losses of no small
amount to those obliged to use them. Compounds of iron or of
manganese are especially objectionable, and not infrequently
have caused waters containing them to be abandoned as sources
of supply. Excessive amounts of the fixed alkalies either as
salts of the strong acids like hydrochloric and sulphuric, or of
the weak acids like carbonic, make a water unsuitable as a public
supply.
Microscopic Plant and Animal Life. — In many of our natural
waters a luxuriant growth of algse and diatoms is found at certain
seasons of the year. The character of the mineral and organic
constituents of the water, as well as the conditions of light and
temperature materially affect the extent of these growths. They
occur in both still and running water. Accompanying the growth
and also the decay of certain of these organisms bad odors and
tastes are not infrequently developed, and where this occurs
in public water supplies, they become a nuisance entirely out of
proportion to their number and size. Certain microscopic
animal forms may also produce troubles of this same character.
The odor of growth appears to be due to secretions of an oil-
like character which they produce, and is usually somewhat
characteristic of the special organism producing it. When the
organisms are in large enough numbers they are capable of giving
an odor to large volumes of water, and not infrequently spoil
the taste and odor of the whole of a public water supply. Odors
of decomposition are usually very oflfensive, and notably so in
the case of the "blue green algae '^ or Cyanophyceae.
It is not probable that impurities of this nature in natural
waters produce disease in human beings, when swallowed in
drinking water. They are very objectionable if they produce
a marked odor, and in such cases are most frequently com-
plained of in public water supplies.
Bacteria. — Even lower in the scale of plant life than the
diatoms and the algae are found the bacteria. They are present
CLASSIFICATION OF NATURAL WATERS 15
in all natural waters, being the more numerous in surface waters,
and much less so in ground waters. By far the larger niunber of
the various species of bacteria play a beneficent r61e in the
economy of nature, and appear absolutely essential to many of
the normal processes of development of both plants and animals.
A few species, however, are associated with disease in animals
and in human beings. So far as the contamination of water is
concerned, it is only the organisms capable of producing patho-
logic conditions in man that are of interest. These virulent
forms usually reach our natural waters through the medium of
domestic sewage and manufacturing wastes. This class of
impurities is considered in more detail in the next section.
IMPURITIES DERIVED FROM WASTE MATERIAL
Sewage. — The water carriage of waste material of human and
animal origin has become, in those countries which pay any atten-
tion to problems of sanitation, the most common method for
its transfer to some point of ultimate disposal. Wherever
public water supplies are installed, a system of sewers will of
necessity follow. Hence the disposal of large volumes of fouled
water has become a problem of great diflBculty, and one that yet
awaits a completely satisfactory solution.
It is obvious that some method, even though it is not entirely
satisfactory, must be used to get rid of this polluted water or
sewage, and the easiest way has been to turn it into the natural
water courses. In this manner much of the surface water on
thickly settled land areas has become polluted with material
dangerous to the health of human beings, who unwittingly or of
necessity drink the water thus contaminated. Since disease has
been found to originate so largely from specific plant and animal
forms, microscopic in size, which, having produced the disease,
are discharged from the body chiefly in the excreta and the urine,
the conveyance of disease through sewage to water has been
pretty definitely proven.
Ground waters as well as surface waters may become polluted
by sewage. The discharge of sewage on the surface of the ground
or into cesspools, or the leakage or overflow of vaults, may furnish
the dangerous pollution to well and spring waters by direct
percolation through fissures in the rock strata, or by more
indirect routes through the soil itself.
16 WATER PURIFICATION
Manufacturing Wastes. — In many industries there remains
after the manufactured product has been completed, a great
deal of waste material, which for economic reasons it is not worth
while to work over. Much of this material is in suspension and
solution in relatively large volumes of water. Its disposal by
the easiest method is to dump it into the nearest body of water.
Water fouled with such material is totally unfit for human con-
sumption. Frequently tl^e material renders even the best
methods for the purification of domestic sewage inadequate, and
its proper disposal becomes a special problem in almost every
case.
The waste liquids from textile works, dye works, straw board
factories, paper mills, abattoirs, meat packing establishments,
dairies, etc., furnish material which is obviously difficult to
dispose of, and which must pollute in the foulest manner any
natural water into which they may be turned.
NATURAL METHODS OF PURIFICATION
Sedimentation. — Some of the impurities which a natural water
acquires in the course of its flow, may be lost uader certain favor-
able conditions. For example, a water laden with suspended clay
or fine sand will deposit this material as soon as the velocity of
the water is sufficiently retarded as was previously explained.
This process of sedimentation is one of the most important of
the natural methods of purification, and plays an important part
in our artificial methods as well. In flowing streams the deposi-
tion of sediment is intermittent, being active during low stages
of the stream when the rate of flow is relatively low, and much
diminished or practically nil in flood periods. At such times the
scouring action of the current causes much that has been de-
posited to be again placed in suspension, and thus carried further
toward its ultimate disposal in the sea. In this way the immense
deltas at the mouths of rivers like the Mississippi and the Nile
are formed.
Effect of Sunlight. — The purifying action of sunlight on certain
vegetable compounds in colloidal suspension, such as the brown
coloring matter in many of the streams and lakes in the north
central and northeastern parts of the United States,) is worth
mentioning in this connection. A certain amount of bleaching
out of this coloring matter is apparently effected when this class
CLASSIFICATION OF NATURAL WATERS 17
of waters are impounded in natural lakes or artificial reservoirs.
Oxidation of the carbonaceous matter probably occurs, and
sedimentation in the quiet water undoubtedly assists in the
clarification.
Precipitation of Compounds from Solution. — Dissolved salts
are not usually readily removed once they have gone into solu-
tion. The chlorides, sulphates and nitrates of either sodium,
potassiiun, ammonium, calcium or mi.gnesium will be retained
on accoimt of their great solubility. Carbonates and bicar-
bonates of the fixed alkalies, as well as of ammonia, are also
very soluble. On the other hand, the bicarbonates of the
alkaline earths have a rather limited solubility and may be
deposited from solution if the excess of carbon dioxide, which is
necessary for their retention in solution, is in anyway removed.
Groimd waters in particular may become heavilj'- charged with
bicarbonates and, on being brought to the surface where the
pressure is diminished, will lose some of their free carbon dioxide
and deposit their monocarbonates, which are much less soluble.
This is particularly true of calcium carbonate. Magnesium
carbonate, however, is considerably more soluble.
Oxidizable salts like ferrous sulphate, ferrous carbonate, and
corresponding salts of manganese occurring in ground waters
may be deposited from solution on exposure to the air. Such
purification can be hastened by aeration and thus render some
unsuitable deep well waters entirely acceptable as a source of
water supply.
"Acid mine waters" are usually contaminated with dissolved
iron compounds, which not infrequently find their way into sur-
face streams. As much of this iron may be in an unoxidized
state, the exposure to the oxygen of the air, and to that dissolved
in the surface water, soon converts the iron to the form of the
insoluble ferric oxide. Organic matter in colloidal suspension
may retard the precipitation of the iron, and cause the latter to
assume a colloidal state itself.
In waters in which the alkalinity is due to sodium and potas-
sium' carbonates, colloidal solutions of silica and alumina are
sometimes found, and on account of their slight solubility may
be deposited, should this "primary alkalinity" be diminished.
Such a diminution can be effected if waters of this class come
into contact with chlorides and sulphates of lime and magnesia.
These latter salts will react with the fixed alkaline carbonates,
18 WATER PURIFICATION
forming carbonates of lime and magnesia and the chlorides and
sulphates of sodiiun and potassium. The latter salts are without
power to assist in holding the silica in solution.
Filtration. — The natural filtration of water through the soil
effects a high degree of purification provided the ground is of the
right character. Sand and gravel, when not too coarse, afford
an excellent purifying medium. Suspended impurities, organic
matter and oxidizable salts are removed as a result of the strain-
ing action, and the chemical and biological changes induced
during filtration. The action of both sedimentation and filtra-
tion in* purifying natural waters is perfectly noiinal, and one
which is constantly going on. To these agencies we owe the
potability of most of our ground waters, and by a study of the
principles underlying these natural processes we have been able
to design and operate our modem water-purification plants.
PURIFICATION BY MEANS OF IflNUTE PLANT AND ANIMAL
ORGANISMS
Thus far in considering natural methods of purification only
those agencies have been especially noted which are effective
without the intervention of organized plant and animal life.
In the cycle through which inert mineral matter passes into
organized matter, and then back again into inorganic compounds,
life in some of its most marvellous forms plays an important and
essential part. These forms belong both to the animal and
vegetable kingdom, and for the most part are microscopic in
size. The borderland between plant and animal, in these almost
invisible organisms, is extremely ill-defined; but no matter
how classified their importance in the economy of nature is
fundamental.
All living organisms which float about in water between the
surface and the bottom are designated by biologists as "plank-
ton." They are moved about by the currents and the wind
chiefly, although they have slight powers of locomotion. They
also possess the peculiar ability to remain suspended in the water
with little effort on their part. The plankton can be divided
into two general classes:
"the food producers or plants, which assimilate inorganic matter and
build up organic compounds by means of their chromophyll coloring
matter; and the food consumers or animals, such as the microscopic
protozoa, rotifera, etc., together with the larger ones up to the fishes/'
CLASSIFICATION OF NATURAL WATERS 19
In the lecture from which the above quotation was cited, Dr.
Marsson^ concisely epitomizes the relations of these two groups
by stating that the
''vegetable component of the plankton is the fundamental food supply
or condition of existence for all aquatic life. It comes from the prod-
ucts of the decomposition of the albumen which finds its way into the
•water from decaying am'mals and plants, as well as from sewage. The
self-purif3ring power of natural waters is merely the maintenance
of the proper equilibrium between retrogressive and progressive
metamorphosis.''
The groups of microscopic plant forms known as the algae,
diatoms, fungi and bacteria exist in enormous numbers in all
natural surface waters, and to some extent in ground waters.
The algffi and diatoms through their peculiar cellular structure
are living laboratories in which light is the energy which tears
the carbon from carbonic acid, and the nitrogen from its simpler
compoimds and converts them into starch, sugar and albumen.
Thus oxygen is liberated and becomes available for oxidizing
organic matter and preventing putrefactive changes.
The fungi and bacteria find their nutriment in dead organic
matter, and are the primary agents for its decomposition into
simpler compounds. Bacterial activity is associated with the
using up of large amounts of oxygen, where the latter is available;
and in such cases non-putrefactive disposal of contaminating
impurities in water is in process in distinction to putrefactive
changes where the oxygen is not Resent.
The bacteria are the natural food for many of the microscopic
animal organisms. The latter include the protozoa, infusoria
and metazoa, and where these organisms are found in abundance,
bacteria and food for bacteria will also be present. They thus
become indexes of pollution in water, quite as indicative as the
bacteria themselves. When the food supply is gone they must
die also.
Since the smaller plant and animal organisms are the source
of food for the fishes, and they in tiuu for hiunan beings, the
cycle of matter from man through human wastes to mineralized
^ Max Marsson: ''The Significance of Flora and Fauna in Maintaining
the Purity of Natural Waters, and How They are Affected by Domestic
Sewage and Industrial Wastes." Eng, News, Aug. 31, 1911. Trans, by
Emil Kuichling.
20 WATER PURIFICATION
compounds and back again to man is complete. The natural
methods of self-purification of water are going on ceaselessly and
effectively, but the agencies ordained for this purpose must have
time and opportunity to do their work.
References
1. United States Geological Survey:
(o) Water Supply Papers :
"Conservation of Water Resources." No. 234, 1909.
Herman Stabler: "Some Stream Waters of the Western United
States." No. 274, 1911.
R. B. Dole: "The Quality of Surface Waters in the United States."
No. 236.
Herman Stabler and Gilbert H. Pratt: "The Purification of Some
TextUe and Other Factory Wastes." No. 235, 1909.
(6) Water Supply and Irrigation Papers :
D. D. Jackson: "The Normal Distribution of Chlorine in the Natural
Waters of New York and New England." No. 144, 1905.
Herman Stabler: "Prevention of Stream Pollution by Distillery
Refuse." No. 179, 1906.
Herman Stabler: "Stream Pollution by Acid Iron Wastes." No.
186, 1906.
(c) Bulletins:
Chase Palmer: "The Geochemical Interpretation of Water Analyses."
BuU. 479, 1911.
2. United States Department of Agriculture :
Office of Public Roads:
A. S. Cushman: "A Study of Rock Decomposition Under the Action of
Water." Circular 38.
Bulletins: •
A. S. Cushman: "The Effect of Waters on Rock Powders." BuU.
92, 1905.
Bureau of Chemistry :
J. K. Haywood and B. H. Smith: "Mineral Waters of the United
States." BuU. 91, 1907.
3. Mass. State Board op Health Report tor 1892:
T. M. Drown: "On the Mineral Constituents of Some Natural Waters
in Massachusetts."
4. Engineering News:
Dr. Max Marsson: "The Significance of Flora and Fauna in Main-
taining the Purity of Natural Waters, and How They Are Affected by
Domestic Sewage and Industrial Wastes." Aug. 31, 1911. Trans, by
Emil Kuichling. J. D. Watson: "Pollution of the River Taine."
Feb. 8, 1912.
5. Journal New England Water-wctrks Association:
G. C. Whipple and D. D. Jackson: " Asterionella : Its Biology, Its
Chemistry and Its Effect on Water SuppHes." Vol. 14, No, 1.
CLASSIFICATION OF NATURAL WATERS 21
F. S. HoLLis and H. N. Parker: '^Chlamydomonas in Spot Pond
(Mass.)." Vol. 14, No. 1.
R. S. Weston: " The Occurrence of Cristatella in the Storage Reservoirs
at Henderson, N. C." Vol. 13, No. 1.
T. M. Drown: "Odor and Color of Surface Waters." Vol. 2, No. 3,
1888.
6. Transfictions American Microscopical Society:
D. D. Jackson: "A New Species of Crenthroix (C. Manganifera)."
Vol. 23, May, 1902.
G. C. WmppLE and H. N. Parker: "On the Amount of Dissolved
Oxygen and Carbonic Acid Dissolved in Natural Waters, and the
Effect of These Gases upon the Occurrence of Microscopic Organ-
isms.'' Vol. 24, May, 1902.
H. N. Parker: "Notes on the Growth of Synura in Lake Cochituate,
Mass." Vol. 30, No. 2, April, 1911.
7. American Naturalist:
D. D. Jackson: "Movements of Diatoms and Other Microscopic
Plants." Vol. 23, No. 461, 1905.
8. Technology Quarterly:
D. D. Jackson and J. W. Ellms: "Odors and Tastes of Surface Waters
with Especial Reference to Anabaena." Vol. 10, No. 4, December,
1897.
9. Geo. C. Whipple: "Microscopy of Drinking Water."
10. Surveyor:
"AlgfiB and Water Supplies." Aug. 25, 1911.
James Scott: " The Chara : A Water-purifying Plant." Aug. 25, 191 1 .
11. Proceedings Engineers Society op Western Pennsylvania*
T. P. Roberts: "Acids in the Monongahela River." November, 1911.
12. Engineering and Contracting:
Tborndyke Saville: "The Nature of Color in Water." January
10, 1917.
CHAPTER III
TRANSMISSION OF DISEASE THROUGH DRINKING
WATER
The discharge of sewage and waste material of all kinds into
the streams and lakes obviously affords ample opportunity for
disease-producing organisms to enter the sources of most of our
public water supplies. Those diseases peculiar to the intestinal
tract of the human body are the ones most likely to be dis-
seminated in consequence of this common practice; and hence,
typhoid fever, cholera, dysentery and gastro-intestinal disturb-
ances have come to be regarded as derived in a large measure
from polluted drinking water, wherever these diseases are endemic
or even epidemic. Anyone or all of these diseases may be trans-
mitted in other ways, but where they are widespread, some com-
mon carrier of infection is generally found to be the source, and
a common drinking-water supply usually offers the most favorable
opportunity, for transmitting the disease.
Probably most of the diseases transmitted by water are of
bacterial origin. The ''spirillum cholerae" of Asiatic cholera,
the ''bacillus typhosus" of typhoid fever, and the "bacillus
dysenteriae" of dysentery have all been found in contaminated
drinking water. Pathogenic protozoa may also produce certain
diseases, and in the case of one form of dysentery, an amoeba
is known to be the cause. If the theory advanced by Sedgwick
and MacNutt, that inflammatory diseases of the respiratory
organs may be also to some extent water-borne, is accepted, then
polluted water supplies are chargeable with another group of
diseases particularly prevalent among all classes of people.
The virility of disease-producing organisms upon their entrance
to a water is of importance with respect to the real danger which
they possess. This ability to live and retain their vitality in a
medium foreign to their natural habitat is also of consequence,
for if the power to reproduce the disease is soon diminished and
eventually destroyed, then the length of time before their vitality
is lost is of the utmost importance. Much experimental work
has been done to determine the period elapsing before certain
pathogenic organisms die, when placed in water under varying
22
TRANSMISSION OF DISEASES 23
conditions. Laboratory experiments throw some light on this
problem, but are not usually conclusive, because of the artificial
conditions imposed. In almost all the experimental work the
niunber of organisms diminish in time, and usually very rapidly.
This may be the result of a decreasing food supply, or to toxic
compounds eliminated in the course of growth or decay, which
kill off rapidly the less resistant organisms.
The presence of pathogenic forms in a drinking-water supply
denotes, of course, all the possibilities of dangerous infection.
Nevertheless, sanitarians have of late regarded the number of
such organisms, and the length of time which they may have
been in the supply, as factors of much importance in the epi-
demiology of disease. This quantitative feature is of consider-
able significance in connection with the quality of a water
obtained by the methods commonly employed in the purification
of polluted waters.
SpiiiUum Cholerse and Bacillus Typhosus. — The chojera
spirillum and the typhoid bacillus are the pathogenic organisms
which have been most studied in water-borne diseases. It is
very doubtful whether either of these organisms will multiply
outside the body, or in impure water. The cholera spirillum
is not very resistant to adverse conditions outside the human
body. It is killed in 10 min. by a temperature of 60°C., easily
destroyed by chemical disinfectants, and does not long retain
its vitality in association with the ordinary saprophytic bacteria
in the water.
The typhoid bacillus is probably more resistant than the
cholera organism to outside influences. Laboratory experiments
have demonstrated that the typhoid bacillus will live in sterile
water in glass vessels for 3 months, and in unsterilized ground and
surface waters for several weeks. Jordan* showed by his experi-
ments with typhoid cultures placed in sacks of collodion and
parchment and suspended in flowing water, that they would
retain their vitality under natural conditions for at least 4 or
5 days. Mr. Geo. A. Johnson's experiments at Columbus,
Ohio,* in which he modified Prof. Jordan's technique, showed
that the ability of the bacteria to pass through the walls of the
parchment sacks, might indicate that conclusions drawn from
the disappearance of the bacteria in Jordan's experiments, were
^ Jordan, Russel and Zbit: Jour, Infect. Diseiises, 1904, 1, p. 641.
< Eng. Record, vol. 52, Sept. 23, 1905.
24 WATER PURIFICATION
somewhat misleading. If the organisms actually escaped from
the sacks, failure of samples withdrawn from the latter to
develop typical cultures, did not necessarily mean that the
typhoid bacilli had died. Jordan concludes,^ that:
"It is possible that water may continue to be the vehicle of infection
during a much longer period (than 4 or 5 days), but the available data
point to a comparatively short duration of life of the specific germ in
the water of flowing streams."
Houston' has shown that samples of Thames River water
inoculated with a typhoid emulsion and stored at temperatures
ranging from 32°F. to 98.6°F., developed negative tests for
typhoid in 9 weeks at the low temperature, and in 2 weeks at
the highest temperature. Intermediate temperatures gave nega-
tive results in conformity with the results stated above, viz.,
the higher the temperature of the water, the shorter the period
of life of the organism. The history of typhoid epidemics tends
to confirm in a measure the data obtained in these experiments.
It emphasizes the protective value of ample periods of sedimenta-
tion and storage of polluted waters used as public supplies.
Isolation of Cholera and Typhoid Organisms from Water. —
The actual isolation of these two organisms from polluted water
has been accomplished only in a comparatively few well-authenti-
cated cases. In the case of cholera the organism is discharged
from the intestines in enormous numbers, but not in the urine.
Its appearance in sewage and polluted water would, therefore,
be expected, and has been demonstrated. In 1892 Dunbar
isolated the spirillum of cholera from the polluted water of the
Elbe, during the epidemic in Hamburg. Koch^ also reports its
isolation from the water of two Altona reservoirs supplied also
from the Elbe.
The isolation of the typhoid bacillus from natural waters also
offers a great deal of difficulty, although it probably is more
virile and capable of living longer in natural water than the
cholera organism. The bacilli of typhoid fever are discharged
from the human body both in the urine and the feces. From
9 to 14 days after infection has taken place are required before
the disease fully develops. This characteristic feature of typhoid
fever makes the tracing of infection through natural waters much
^ E. O. Jordan: "Greneral Bacteriology."
* Eng, Record, vol. 65, June 1, 1912, p. 608.
* Zeit. fUr hygiene und I fifed. Krank,, 14.
TRANSMISSION OF DISEASES 25
more difficult, for although the bacilli may have been present
and caused the disease, they will have probably disappeared
before suspicion is thoroughly aroused as to their possible presence
in the water. Comparatively few cases have been recorded,
therefore, in which the bacillus has been isolated and shown to
have been the probable cause of a case of typhoid fever.
The work of Mr. D. D. Jackson and his associates in improving
methods^ of technique for the differentiation of the colon-typhoid
group of bacilli offers considerable hope that the isolation of the
typhoid fever bacillus may yet be accomplished with more cer-
tainty and ease. Mr. Jackson states that he has isolated B.
typhosus from a river water used as a source of water supply,
from a local private water supply and from two points in the
Hudson River.
Other Water-borne Diseases. — Intestinal diseases and some
gastric troubles may be and probably frequently are caused by
organisms found in water. Among infants this perhaps is truer
than with adults. Epidemics of diarrhea and dysentery are not
imcommon and have been traced to impure drinking water.
The possible infection of a water supply by anthrax (B. anthracis)
derived from animals sick with the disease produced by this
organism is rather remote, but not impossible. It is of more
theoretical interest than practical that the pathogenic organisms
B. anthracis and B. tetani* have both been isolated from river
water by Zeit and Fiitterer; but it goes to show the possibilities
of water-borne infection. Sewage-polluted, waters may contain
all known pathogens as well as saprophytes, and what rdle the
latter forms may play in disease is by no means a settled question.
The relation between pneumonia, bronchitis and other inflam-
matory diseases affecting the respiratory organs and polluted
drinking water has been noted above. The ascertainable facts
relating to this phase of water-borne diseases are few and difficult
to satisfactorily classify. The data already collected by Dr.
W. T. Sedgwick and his associates are extremely valuable, and
further confirmation of their deductions is hoped for.
* D. D. Jackson and T. W. Melia: " Differential Methods for Detecting
the Typhoid Bacillus in Infected Water and Milk." Jour. Infect. Diseases,
vol. 6, No. 2, April 1, 1909.
'"Report of the Sanitary Investigation of the Ilhnois River and Its
Tributaries." 111. State Board Health, 1900, p. 85.
26 WATER PURIFICATION
EPIDEMICS OF WATER-BORNE DISEASES
Cholera
Probably no disease is more truly characterized as a "filth
disease" than is cholera. In certain parts of India it may be
said to be endemic. Explosive outbreaks are not uncommon, and
the spreading of the disease by contact is probably constantly
going on. The insanitary nature of the personal habits of the
lower classes of natives affords ample opportunity for trans-
mitting infection, and the streams and lakes frequently serve
as carriers.
In 1817 a violent epidemic of cholera broke out in Jessore in
Bengal, which rapidly spread over a larger part of British India.
It continued unabated for 3 years, and then began to spread into
China and Persia. In 1823 the disease had reached Asia Minor
and Russia. For the next 7 years it did not advance westward
any further, but a fresh outbreak in 1830 in Russia caused the
disease to spread all over the latter country and into northern
Europe and the British Isles. During the next 5 years it spread
southward, invading northern Africa.
Another epidemic started in India and China in 1841, reaching
Europe in 1847; another began in 1850 and entered Europe in
1853, and was carried across the Atlantic to North and South
America, where it was particularly severe. The epidemic of
1865-66 was less extensive than its predecessors. Since 1832
eight epidemics of cholera have occurred in the United States,
the last being in 1873.
With a better idea of the true cause for this disease in par-
ticular, and with improved methods for combating infection and
contagious diseases in general, cholera has not been widely
prevalent in Europe or the United States for a great many years.
Constant vigilance is required for its suppression, however, and
only by prompt action, where sporadic cases are discovered, have
the health authorities prevented epidemics. How many of these
epidemics have been directly transmitted through drinking water,
it is impossible to know; but that water acted as a carrier to a
greater or less extent in many of them is extremely probable.
In the period from 1831 to 1873, 373,000 people died in Prussia
of Asiatic cholera, and in 1886 alone 114,000. In 1892, 1,634
persons died from this disease in Prussia, and from the Hamburg
TRANSMISSION OF DISEASES 27
epidemic in this same year 8,616 deaths resulted. In 1910
Germany had but 10 cases of cholera.^
Circumstantial evidence of a very convincing character has
been collected, which proves that some cholera epidemics were
water-borne, and probably no discussion of this subject is com-
plete without mentioning the disastrous Hamburg epidemic which
occurred in 1892-93. This city was using unfiltered water from
the River Elbe, which was contaminated by the sewage of over
800,000 people. During the fall of 1892, 17,000 cases developed,
resulting in 8,600 deaths. In fact, wherever the drinking-water
supply was either filtered or obtained from some source other
than the river, few or no cases resulted.
In 1887 the city of Messina, Sicily, suffered from an epidemic
of cholera, during which 6,000 cases and 2,200 deaths resulted.
An investigation showed that water purposely diverted from a
conduit, conveying water to the city, ran into pools, which were
used for washing soiled clothing by the Messina washerwomen.
Much of this water found its way back into the open conduit,
and passed into the city. It was also found that the unglazed
tile used to distribute the water in the city were broken, and that
leakage from joints was conunon. Sewers laid on top and parallel
with the water mams were in a Uke condition and ofifered ex-
cellent opportunity for further contamination. After a supply
of pure water, carried in tank ships from the mainland, was
provided for drinking water, the epidemic ceased at once.^
A similar outbreak of cholera in 1884 in Cuneo, Italy, which
resulted in 3,344 cases, was traced to a like cause, viz., washing
infected linen in a brook emptying into a public water supply.*
Typhoid Fever
The prevalence of typhoid fever in civilized countries, where
no little attention is paid to matters of sanitation, seems at first
thought surprising. But not until 1880 was the organism which
causes this disease discovered by Eberth in the spleen of persons
dying from typhoid fever. Since it seems doubtful that this
disease, as it develops in human beings, can be reproduced in
animals, the evidence that the Eberth bacillus is the true cause
^ Dr. Arthur Lederer: "The Modern Sewage and Water Problem."
Cliniquef August, 1912.
« W. P. Mason: "Water Supply."
28 WATER PURIFICATION
for the disease has been only slowly accumulating. Another
factor only recently discovered is that persons showing no clinical
symptoms of the disease are genuine "culture factories" for
producing the bacillus and for its dissemination.
Epidemics resulting from these "typhoid carriers" have been
satisfactorily traced. The existence of such persons explains in
some measure the continuance of the disease, and its persistence.
The transmission by direct contact, by flies, by milk and by water
has been proven in scores of cases.
While there may be some extenuating circumstances for the
continued presence of typhoid fever to the extent to which it still
exists in the United States, nevertheless it constitutes a national
disgrace, of which our sanitary authorities and people as a whole
should be heartily ashamed. Typhoid fever has been practically
stamped out in Europe as the following table will show.*
Unit of comparison ] ^^S^n
Deaths per
100.000 from
t3rphoid fever,
1910
Thirty-three principal European cities in Russia, j
Sweden, Norway, Austria-Hungary, Germany, •
Denmark, France, Belgium, Holland, England, .
Scotland and Ireland 31,590,000
Fifty American cities of 100,000 inhabitants or |
over , 20,250,000
Excess of deaths, typhoid fever in American cities
per 100,000 population
6.5
25.0
18.5
In three-fifths of the population of the United States included
in the registration area for mortality statistics as compiled by
the Census Bureau, there occurred 12,673 deaths from typhoid
fever in 1910, or a death rate of 23.5 per 100,000 of population.
Assuming the same proportion of deaths in the unregistered
sections as in the registered, then there were 21,120 deaths from
this disease, representing probably 200,000 cases.
The following diagram (Fig. 1) illustrates the prevalence of this
disease in the United States as compared with certain countries
in Europe.
* Allan J. McLaughlin: "Sewage Pollution of Interstate and Inter-
national Waters." Public Health and Marine Hospital Service, Hygienic
Lab. BuU. 83, March, 1912.
TRANSMISSION OF DISEASES 29
Dr. J, F. Anderson' concludes from his study of typhoid fever
epidemics due to contaminated water, that they are characterized
by:
(a) A general distribution of cases throughout the area
supplied by a particular water.
(6) By the explosive onset of the outbreaks.
(c) By the trouble occurring in the late winter or spring.
(d) By the comparative freedom from the disease of persons
not using the suspected water.
(e) By evidences of sources of infection found by an inspection
of the watershed.
(/) By the outbreak beginning or ending after a change in the
water supply.
(ff) And by indications of the pollution of the water when
analyzed.
TYPHOtD FEVER
OCATH RATE
PER
100.000 OF TOPULATION
uy
1 .. 1
m
Fio. 1, — Typhoid fever death rate in various countries.
As an illustration of one or more of the above features of
typhoid fever epidemics, the one which came under the author's
personal observation, may be cited as quite characteristic. A
town located on the Ohio River was supplied, together with
two other communities, with water from a tributary of the Ohio
River. This tributary flows into the Ohio River a short distance
above the town. The water supply was treated with sulphate
of iron and lime, and settled in a series of basins, from which
the water flowed by gravity to the service pipes of the three
communities. On account of a fire the pumping station was par-
tially disabled, and the town located on the Ohio River was cut
off from this supply for a period of about 5 weeks; but the two
other communities continued to receive water from this same
'"A Symposium on Typhoid Fever." Amer. Jour. Public Hygierte,
May, 1909.
30 WATER PURIFICATION
source. In order to obtain a supply of water for this town, a
pumping station which had been out of service for some time,
and which drew its supply of water from the Ohio River, was
started, and pumped Ohio River water into the service pipes for
35 days, covering parts of the months of October and November.
Just above the intake of this pumping station is a small creek,
which drains a ravine. Along this ravine and just above the
pumping station were located quite a number of houses, about
which the sanitary conditions were bad. While this pumping
station was in service, a small artificial pond, located near the
head of this ravine and connected with a sununer amusement
resort, was emptied. This water was discharged into the Ohio
River just above the pumping station intake.
An epidemic of typhoid fever began in the town supplied with
Ohio River water about the middle of November. The author
was not called in until about one month later, and at that time
135 cases had been reported.
An examination of the milk supply showed insanitary condi-
tions about many of the dairies, but cases of typhoid were not
found to be confined to any particular milk route, but were
general all over the town. The milk supply was evidently
not the source of the infection. The town had many wells, but
the distribution of the cases was too uniform to attribute the
infection to any particular locality in the town.
At the time the author was making the investigation, the Ohio
River supply of water had been stopped, and a return to the
supply formerly used had been made. It was not, therefore,
possible to obtain much chemical or bacteriological evidence of
the character of the water which had been taken from the Ohio
River. It was ascertained, however, that no epidemics of
typhoid had occurred in the two other conmiunities which had
continued to receive their regular supply of partially purified
water. Neither was there known to have been any more than
the usual number of cases in a town on the opposite side of the
Ohio River, and taking its supply from the latter stream.
The logical cause for the epidemic seemed to be, therefore, the
temporary pumping of a polluted water from the Ohio River,
which rapidly infected many of the persons who drank it. More-
over, on account of the explosive character of the outbreak, the
pollution^of the water was probably quite direct. The 'germs
may have been washed into the Ohio River, and from thence
TRANSMISSION OF DISEASES
31
passed into the intake of the pumping station at the time the
pond in the summer resort was emptied, or following a flushing
out of the creek by rains. The insanitary conditions along the
creeky and the negative evidence obtained in investigating the
milk supply, all led to the conclusion that it was a water-borne
epidemic of typhoid fever that had occurred.
A somewhat similar water-borne infection, which caused an
epidemic of typhoid fever in Columbus, Ohio, in 1903-04, resulting
in 1,606 cases and 162 deaths in 3 months, probably originated
from the pollution of the public water supply drawn from the
Scioto River. ^ Cases of typhoid fever at the State Hospital
were known to have existed 10 days prior to the outbreak in
Columbus. The sewage from this institution entered the Scioto
River not far from the Columbus water-works intake. The
suddenness of the outbreak is shown by the following table:
Typhoid Fevbr Epidemic, Columbus, Ohio
Cases
Deaths
Rate per 100.-
000 of
population
December, 1903
January, 1904. . ,
February, 1904,
March, 1904. ...
40
725
798
83
4
35
94
33
34
300
805
283
Some of the more important typhoid fever epidemics which
have been traced to infected water are listed below :
Caterham, England
Plymouth, Pa
Tees River Valley, England
Lowell, Mass
Lawrence, Mass
Worthing, England
Grand Forks, N. D
Maidstone, England
Ithaca, N. Y
Butler, Pa
1879
5,000
352
1885
8,000
1,104
1890-91
251,976
1,330
1890-91
77,696
2,855
1890-91
44,654
1,792
1893
16,000
1,411
1893-94
6,000
1,245
1897
33.830
1,928
1903
18,000
1,350
1903
13,000
1,348
21
114
100
217
137
168 (Wells)
96
150 (Springs)
82
111
* Jour. Mass. Assoc. Boards of Health, vol. 14, May, 1904.
32 WA TER PVRIFICA TION
Comparatively recent outbreaks of water4x>me typhoid fever,
or a gradually increasing prevalence of this disease, which forced
the authorities to provide remedial measures, have occurred at
Erie, Pa., Niagara Falls, X. Y., Evanston, Dl., Coatesville, Pa.,
Ironton, Ohio, Winnipeg, Canada, Rockford, Dl., Memphis,
Tenn., Council Bluffs, Iowa, and Omaha, Neb.
The pollution of the Great Lakes in the United States by the
cities built upon their shores is to a large extent local; but since
these communities draw their water supply from the same source,
the problem of preventing the drinking water from becoming
contaminated, and still obtain a satisfactory disposal of the
sewage, is a troublesome one. The ccMnmon remedy of extend-
ing the water supply intakes out from 3 to 5 miles from the shore
has been resorted to with fair success, and with marked decreases
in the typhoid death rate in most cases. The City of Chicago
has diverted a large part of its sewage through a drainage canal
into the Illinois River, thus keeping a constantly increasing
volume of sewage from polluting the lake water farther and
farther from the shore line. Other lake cities are contemplating
partial purification of their sewage in order to conserve the purity
of their water supplies.
The effect of the wind on these large bodies of water in causing
currents, the influence which the shore lines may have on these
currents, and the movement of ice polluted with sewage from the
shore out into the lake in the spring months are all factors which
may at times be the cause for water-borne epidemics.'
Even ground-water supplies, which through carelessness or
ignorance are not properly protected from pollution after being
drawn to the surface, are not infrequently the distributors of
infectious material. A rather remarkable case was recently
described as occurring at Lincoln, Neb.,* in which a water from a
well 60 ft. in depth became contaminated by leakage of sewage
from a broken sewer. The escaping sewage found its way into
the ground and into an abandoned pipe which had been forgotten
and which connected directly with the well.
An outbreak of typhoid fever occurred during September,
October and November of 1911, from which six deaths resulted.
* D. D. Jackson: "Chlorination at Cleveland, O." Eng. Record^ vol.
65, June 15, 1912.
« "A Polluted Well at Lincoln, Neb." Eng. Record, vol. 65, June 15, 1912,
- 614.
TRANSMISSION OF DISEASES 33
About the middle of December a severe outbreak of bowel
trouble, during which there were several thousand cases, took
place. This was followed about Dec. 20 by a second epidemic
of typhoid fever, during which 300 cases were reported.
References
1. ''Report of the Sanitary Investigations of the Illinois River and Its
Tributaries." Illinois State Board of Health, 1900, p. 85.
2. Vitality and Isolation of Cholera and Typhoid Organisms:
(o) Jour. Infect. Diseases j 1904, 1, p. 641.
(6) Eng. Record^ vol. 52, Sept. 23, 1905.
(c) Eng. Record^ vol. 65, June 1, 1912.
(d) Zeit. far Hygiene und Infect Krank.f 14.
(e) E. O. Jordan: "General Bacteriology."
3. D. D. Jackson and T. W. Melia: "Differentiation Methods for
Detecting the Typhoid Bacillus in Infected Water and Milk."
Jour. Infect Diseases^ vol. 6, No. 2, Apr. 1, 1909.
4. "A Symposium on Typhoid Fever" (8 papers). Am. Jour. Public
Hygiene, May, 1909.
5. "Epidemic of Typhoid Fever at Columbus, Ohio." Jour. Mass.
Assoc. Boards of Health, vol. 14, May, 1904.
6. Allan J. McLaughlin: "Sewage Pollution of Interstate and Inter-
national Waters." Public Health and Marine Hospital Service. Hy-
gienic Lab. Bull 83, March, 1912.
7. D. D. Jackson: "Chlorination at Cleveland, O." Eng. Record, vol.
65, June, 15, 1912.
8. " A Polluted Well at Lincohi, Neb." Eng. Record, vol. 65, June 1, 1912.
9. Typhoid Fever Epidemics and Statistics:
(o) Eng. Record, vol. 65, February, 1907, p. 131.
(6) Eng. Record, vol. 58, October, 1908, p. 444.
(c) Eng. Record, vol. 61, March, 1910, p. 263, 677.
id) Eng. Record, vol. 62, December, 1910, p. 630.
(c) Eng. Record, vol. 63, June, 1911.
(f) Eng. Record, vol. 65, pp. 254, 300, 591 and 601.
(g) Eng. Record, vol. 66, July, 1912, p. 95.
{h) Eng. News, vol. 67, June 13, 1912.
10 Charles B. Boldrean: "Typhoid Fever in New York City, etc."
Am. Jour. Public Health, vol. 2, 1912.
11. H. de B. Parsons: "Our Typhoid Streams." Stevens Inst., Janu-
ary, 1911.
12. Nicholas S. Hill, Jr. and Leon R. Whitcomb: "The Relation of a
Pure Water Supply to Chronic Intestinal Tract Infection." Eng.
News, vol. 69, No. 5, Jan. 30, 1913.
13. George A. Johnson: "The Typhoid Toll." Jour. Am. Water-works
Assn., June, 1916.
CHAPTER IV
THE EFFECT OF IMPROVED WATER SUPPLIES UPON
HEALTH
As the relation between impure water and disease becomes
better understood and appreciated, more attention is being given
to the quality of public water supplies. Sometimes the method
pursued is to seek a purer water from some uncontaminated
source, or to render a polluted supply better by some process of
purification. By substituting a piu*e drinking water supply for
an impiu*e one, the reduction in the death rate from water-borne
diseases has been notable, and the improved health of the com-
mimity has usually been demonstrated beyond question.
In the United States the typhoid fever death rates imdoubtedly
furnish the best indicators of the quality of public water supplies.
The following table taken from Dr. Geo. M. Kober's paper on
the "Conservation of Life and Health by Improved Water Sup-
ply" sununarizes the statistics of 61 cities in the United States for
the years 1902-06.1
Mean Typhoid Fever Death Rate from 1902-06 per 100,000 of
Population for Cities Using Various Classes of Water
4 cities using ground water from large wells 18 . 1
18 cities using impounded water and conserved rivers
or streams 18. 5
8 cities using water from small lakes 19. 3
7 cities using water from the Great Lakes 32 . 8
5 cities using both surface and underground water. . . 45 . 7
19 cities using polluted river water 61 . 1
From the same paper is reproduced a diagram (Fig. 2) showing
in more detail the typhoid fever death rates in different cities
according to the character and the source of their water supply.
Spring waters, groimd waters from wells, and filtered waters
evidently furnish the safest supplies. Surface waters, whether
from streams or lakes, may furnish safe drinking water, but they
are much more likely to be^poUuted.
Probably the most striking effects in reducing typhoid fever
have come from the purification of polluted supplies. By filter-
^Eng. Record, vol. 57, June, 1908.
34
IMPROVED WATER SUPPLIES 35
iDg an impure water supply marked reductions in water-boroe
diseases have almost invariably resulted. Jlven where the
0 10 » 30 « H n nnu iMUOiw
Pia. 2. — Typhoid fever death rste according ti
community has beeo only partially supplied with purified water,
the efifect on the typhoid death rate has been noticeable.
36
WATER PURIFICATION
Ttphoid Dkath Ratbs pbb 100,000 of Population fob Citibs Chanoinq
FBOM POLLUTBD TO FlTBtFIBD WaTEB SuPPUBS
1907
1908
1909
1910
ColumbuB. Ohio
38.3
55.5
67.9
130.8
60.7
110.5
33.1
44.2
46.6
35.5
20.0
28.4
42.0
24.0
22.3
18.1
New Orleans, La
31.5
liOMisville, FlY
31.7
PittsbuFKh, Pa
27.8
Philadelphia, Pa
17.5
The filter plant for the City of Columbus, Ohio, was started
in August, 1908; the high rate[for this year was due to an epidemic
in the early part of the year. The filter plants in New Orleans
Fig. 3.
yw i^ui liWi i*a iWM jyu6 jyo6 lyo; iyrt> lyoy laio
Typhoid death rate by years for city of Pittsburgh, Pa.
and Louisville were start txi in 1909. In Pittsburgh and Philadel-
phia filter plants were placed in operation in 1907 and 1908,
respectively; but in neither city was the entire population sup-
plied with the purified water.
IMPROVED WATER SUPPLIES
37
Fig. 3 from Dr. Allan J. McLaughlin's paper on "Sewage
Pollution of Interstate and International Waters," which was
previously referred to, is of especial interest in this connection, in
showing how pronounced a reduction in the death rate followed
the introduction of even a limited volume of purer water.
From the typhoid fever statistics of Cincinnati, Ohio, a most
convincing argument for the purification of a polluted water
supply can be presented.
Number op Cases and Deaths from Typhoid Fever
Unfiltered water from old works
Filtered water from new works
Year
1904
1005
1906
ToUl
for 3
years
1908
1909
1910
ToUl
for 3
years
Cases
1,646
270
746
155
1,940
239
4,332
664
235
67
218
45
183
21
636
Defttrht?
133
The figures for the year 1907 are omitted because water from
both the old and the new works was supplied to the city.
.If the above figures are expressed as cases and deaths per
100,000 of population, a better comparison may be made with
other statistics.
Number op Cases and Deaths per 100,000 op Population
For 3 years before introducing
filtered water
For 3 years after introducing
filtered water
Average
1908
1909
1910
Cases
417
64
Percentage r<
67
19
Auction from
84
70
62
13
the average.
85
80
50.0
Deaths
5.7
Cases
88.0
Deaths
91.0
Tn a report on the purification of the Montreal water supply
Messrs. Hering and Fuller present a table showing the effect of
purification by filtration on the death rate from typhoid fever in
a number of American citie.s
The relation between impure water supplies and certain intes-
tinal diseases other than typhoid fever, is more or less obscure.
38
WATER PURIFICATION
Death Rates from Ttphoid Feveb pbb 100,000 Population in Ambbican
Cities Using Filtered Water
City
Year
plant WM
com-
pleted
Before
filtra-
tion
After
filtra-
tion
Yean averaged
Before
filtra-
tion
After
filtra-
tion
Death rate
Sand filters
Albany, N. Y. . .
Lawrence, Mass.
Pittsburgh, Pa. .
1899
10
9
90
1893
7.
15
114
1907
8
1
133
22
25
47»
Mechanical filters
Binghamton, N. Y 1907
Cincinnati, Ohio
Columbus, Ohio
Paterson, N. J
Watertown, N. Y
York, Pa
Hoboken, N. J
1907
5
5
47
1908
4
1
50
1908
11
1
78
1902
5
7
32
1904
5
5
100
1899
2
8
76
1905
7
4
19
15
16
20
10
38
22
14
Infant mortality from diarrhea and enteritis is probably both
directly and indirectly the result of drinking impure water,
although other causes contribute more frequently to death.
About 85 per cent, of the deaths listed under "diarrhea and
enteritis" in the United States census mortality statistics occur
in children under 2 years of age. Dr. A. J. McLaughlin* in
discussing this subject says:
"Instead of one disease designated under different names we are
probably considering several diseases with common factors of trans-
mission. Whatever the real relation between typhoid fever and enteritis
or diarrhea of children may be, one fact is clear, the same causes operate
to cause excessive prevalence of both. It is probable that cases of
typhoid in children under 2 years in many cities are often incorrectly
diagnosed as enteritis. It must be remembered, however, that the
causative agent of bacillary dysentery is transmitted in the same way
and by the same media as that of typhoid. There are too many cases
of fatal illness in children under 2 years classed as diarrhea and enteritis,
and an exhaustive investigation should be made to establish the real
^ Including Allegheny, supplied with un filtered water.
• Public Health and Marine Hospital Service. Hygienic Lab., Bxdl.
83, March, 1912.
IMPROVED WATER SUPPLIES
39
cause of death in enteritis and diarrhea of children. Without such an
investigation it is impossible to assign the real cause of the excessive
child mortality from diarrhea and enteritis. In cities of less than 50,000
population without slums and which are not 'mill' towns an enteritis
rate in children under 2 years above 100 deaths per 100,000 indicates
prevalence of an acute intestinal disease preventable by the same
measures that prevent typhoid fever. It is probable that in such cities
proper enforcement of prophylactic measures against typhoid fever
would reduce the enteritis rate below 40 deaths per 100,000. Enforce-
ment of prophylactic measures would include the installation of pure
water supplies and proper sewerage systems, coupled with a vigorous
campaign against the insanitary outdoor privy and the equally dangerous
shallow well."
Dr. McLaughlin gives the following table which emphasizes
the complexity of the problem.
City
Tjrphoid
death rate
lOOOOO.
average for
10 years.
1000-1900
Character
of water
supply
Death raU
enteritis,
average
for 5 years.
1004-1908
»
Remarks
Rochester, N. Y
Syracuse, N. Y
Albany, N. Y
Binghamton, N. Y
Utica, N. Y
Schenectady, N. Y. . . .
Amsterdam, N. Y
Yonkers, N.Y
echoes, N.Y
13.7
14.8
21.9
20.9
17.3
22.4
18.6
9.5
83.8
129.1
148.5
27.0
Good
Good
Good
Good
Good
Good
Good
Good
PoUuted
Polluted
Polluted
Polluted
89.5
105.5
80.0
104.7
133.7
164.7
150.7
207.7
170.9
173.2
175.0
151.6
Sanitary conditions
good.
Mill and factory
towns; bad sanitary
conditions.
Sanitary conditions,
' exchisive of water»
good. Mill and f ac-
' tory towns.
NiagaraFalls, N. Y...
Ogdensburg, N. Y
Bufifalo, N.Y
The following mortality statistics taken from reports of the
Health Department of Cincinnati, Ohio, point pretty plainly
to the fact that a change from an impure water supply to a
purified supply made a marked difference in the number of
deaths from dysentery, diarrhea and enteritis in persons over 2
years of age.
The following figures show a reduction in deaths from dysen-
tery for 3-year periods before and after the introduction of
filtered water of 64.3 per cent, and for diarrhea and enteritis
of 55.1 per cent.
40
WATER PURIFICATION
Unfilterbd Water from Old
Works.
Filtered Water from
New Works.
Year
1904
27
152
1905
1906
Total
for 3
years
1
1908
1909
1910
Total
for 3
years
Dysenterv
21 22
70
493
1
1
9
90
11 ' ^
25
Diarrhea and enteritis over 2
years of ace
167
174
60
71
221
N. B. The year 1907 is omitted because water was supplied to the
city both from the old works and from the new works.
THE MILLS-REINCKE PHENOMENON AND HAZEN'S THEOREM
The available evidence clearly proves that cholera, typhoid
fever, dysentery and gastro-intestinal troubles are commonly
transmitted by infected drinking water, and that there is reason
to believe that other diseases are also conveyed in the same
manner. The effect of purifying a polluted water supply, in
decreasing the deaths from diseases other than cholera and
typhoid, has been studied recently by W. T. Sedgwick and J.
Scott MacNutt. They point out that in 1893-94, Messrs.
Hiram F. Mills, C. E., of Lawrence, Mass., and Dr. J. J. Reincke
of Hamburg, Germany, respectively, noted independently a
decline in the general death rate of each of these cities as a result
of improving their water supplies. Prof. Sedgwick and his asso-
ciate have collected numerous mortality statistics in a paper^
on this subject, and have termed the coincidence between a
lowered death rate and a purified water supply as the '^Mills-
Reincke Phenomenon." In 1904 Mr. Allen Hazen in a paper
read before the International Engineering Congress held in St.
Louis, gave a quantitative expression for the phenomenon by
stating that: ** Where one death from typhoid fever has been
avoided by the use of better water a certain number of deaths,
probably two or three, from other causes have been avoided."
Sedgwick and MacNutt have called this expression **Hazen*s
theorem," and have concluded from the studies which they have
made, that the statement appears sound and conservative, but
^ W. T. Sedgwick and J. Scott MacNutt: "On the Mills-Reincke
Phenomenon and Hazen *8 Theorem Concerning the Decrease in Mortality
from Diseases Other than Typhoid Fever Following the Purification of
Public Water Supplies." Jour. Inject. Diseases, vol. 7, 1910.
IMPROVED WATER SUPPLIES
41
not necessarily precise. The ratios they worked out varied
widely. For example^ at Hamburg, Germany, for every death
less from typhoid fever after filtration, there were 15.8 deaths
less from other causes; at Lawrence, Mass., the ratio was 1 to
4.4, at Lowell, Mass., 1 to 6.0, at Albany, N. Y., 1 to 4.1, and at
Binghamton, N. Y., 1 to 1.5.
A cS S S oi o cS
S 1^ ^ ^ .^ ^ ^
Pig. 4. — Growth of water filtration and decrease in typhoid fever death
rate in the registration cities of the United States.
From the data which they compiled with respect to diseases
of the respiratory organs, the evidence in many cases is striking
and warrants a more extended study. Factors not specifically
related to an improved water supply may have been potent in
reducing the death rate in the cities studied. Greater knowledge
of methods for the prevention of disease must have played its part
42 WATER PURIFICATION
in diminishing mortality, and in extending the length of the
average life. On the other hand, the real causes for many dis-
eases are still unknown, and the probability that some of them
can be transmitted through polluted drinking water is by no
means imreasonable.
The elimination of disease germs from a water supply would be
a direct cause for a decrease in the death rate, while an indirect
cause could come from an increased vital resistance produced by
the use of a purer drinking water. Probably both of these factors
are instrumental in bringing about a lowered death rate.
The accompanying diagram (Fig. 4) from Mr. George A.
Johnson's paper "The Typhoid ToU," in the Journal of the
American Water-works Association for Jime, 1916, is a striking
graphic presentation of the effect which water purification has had
in reducing typhoid fever in the United States.
References
1. Geo. M. Kober: "Conservation of life and Health by Improved
Water Supply." Eng. Record^ vol. 57, June, 1908.
2. Arthur Lederer: "The Modem Sewage and Water Problem."
CliniquCf August, 1912.
3. E. Bonjean: "Les eaux d'alimentation publique observations g^n^rales
sur leur rdle 6pid6miologique; leur choix; ^tat actuel de I'^puration."
Rev, Scient, 49, An 5, pp. 138-146.
4. W. T. Sedgwick and J. Scott MacNutt: "On the Mills-Reincke Phe-
nomenon and Hazen's Theorem ([Concerning the Decrease in Mortality
from Diseases Other than Typhoid Fever Following the Purification of
Public Water Supplies.^' Jour. Infect. Diseases, vol. 7, 1910.
6. Geo. A. Johnson: "The Typhoid Toll." Jour. Amer. W. W. Assoc.^
June, 1916.
CHAPTER V
OBJECTS AND METHODS OF WATER PURIFICATION
The purpose of purifying a drinking water is obviously to make
it more pleasant'and more wholesome to drink. The removal of
suspended sediment and of vegetable coloring matter, in order to
convert a dirty water into a clear and colorless one, commends
itself if for no other reason than that the water becomes more
acceptable to the senses of taste, smell and sight. If in addition
to improving its appearance, it is possible to reduce materially
or eliminate entirely the bacteria, some of which may be capable
of producing disease, a second important reason for the purifica-
tion of a drinking water can be advanced. By rendering a water
hygienically safe for drinking purposes, sickness and death, as
well as economic losses of no small magnitude are avoided. It is
not difficult to show that a pure and wholesome water supply is a
sanitary investment which pays in dollars and cents, as well as in
health and happiness.
For industrial purposes many waters are entirely unfitted for
use without purification. Usually the dissolved salts which pro-
duce hardness make a water unsuitable for use in steam boilers.
The softening of hard waters is a method of purification which
has long been practised, and which could be even more exten-
sively employed today to the financial advantage of users of
boiler scale-forming waters. In general, soft waters are more
desirable for niost iildustrial purposes. In such industries as
brewing, distilling, starch and sugar manufacturing, the bacterial
content of the water is of some importance, since certain organ-
isms may produce fermentations which are undesirable. Waters
containing iron in solution or suspension are especially objection-
able for domestic purposes and for such industries as dyeing,
paper making and bleaching.
General Methods of Purification. — The impurities in water
which it is necessary to remove are in suspension and solution, and
purification methods fall naturally into two classes in consequence.
For the removal of matter in suspension two processes are em-
ployed, namely, sedimentation and filtration. These processes
43
44 WATER PURIFICATION
occur normally in nature, but being uncontrolled produce re-
sults of varying degrees of excellence. When artificially controlled ,
sedimentation and filtration, properly carried out, are able to
purify waters of very poor quality, and with a degree of certainty
that have established these methods upon a scientific basis.
Mineral matter in suspension can be entirely removed, as well as
practically all of the organic matter, which latter includes the
bacteria. Chemical reagents may or may not be employed to
facilitate either or both of these processes. The chemical com-
pounds used in this connection are mechanical agents exclusively,
and merely assist and hasten thebringingtogetherof finely divided
suspended particles into larger masses, which will settle and filter
out with greater ease.
For the removal of dissolved impurities, such as salts of lime
and magnesia, chemical reagents are usually resorted to. A pre-
cipitation of the bases in an insoluble form, and their subsequent
removal by sedimentation and filtration, constitute the usual
methods of purification. In the case of easily oxidizable soluble
salts, such as those of iron, aeration is effective in breaking down
the ferrous compounds by the removal of dissolved carbon dioxide,
and the introduction of suflScient oxygen to bring about the oxida-
tion of thejerrous to the insoluble ferric compounds.
Filtration usually follows the process of sedimentation, and is
carried out in various ways. Sand, gravel, coke, charcoal, coal,
porous tile and sponges are some of the materials which have been
and are still used as filtering media. Only the first two media,
viz., sand and gravel, are commonly employed in large filtration
plants.
Purification methods which do not fall under any of the above-
mentioned classes, are those of distillation and sterilization by
chemical or physical agents. In the case of distillation all dis-
solved and suspended impurities are removed, as well as the
bacteria being killed. It is obviously the most perfect method of
purification, but not necessarily the most desirable. Its cost
makes it prohibitive for all practical purposes so far as large
supplies are concerned.
Disinfection and sterilization present the most advanced
phases of water purification, and furnish methods of great prac-
tical value for supplementing other methods, as well as in some
cases, furnishing themselves all the purification needed.
The action of these agents is primarily upon the readily oxidiz-
WATER PURIFICATION 45
able matter which may be in a water, whether it be of organic or
of mineral origin. The bacteria being a low form of plant life are
thus attacked, and are either destroyed or their vitality so im-
paired that they no longer are able to reproduce themselves.
The effect of these agents is not selective, except in so far as they
react first with the more easily oxidized material. If not ex-
hausted on the latter, they will react slowly upon the more re-
sistant matter, but may fail to effect a complete oxidation or to
hinder vital processes. Those bacteria which are capable of form-
ing spores, and which may be in this stage, are sometimes not
affected, on account of their well-known resistance to injurious con-
ditions. The effect of these disinfectants upon the pathogenic
forms is the same as upon the non-disease-producing bacteria
which may be present in a water. If practically all the bacteria
are destroyed, therefore, the water is rendered hygienically safe.
The agents used for disinfecting water are the hypochlorites of
calcium and sodium, piu'e chlorine gas, ozone, copper sulphate,
and the rays of ultra-violet light. Other chemical compounds
have been suggested and experimented with, and the use of the
electric current has frequently been tried. None of these agents
is of much practical value excepting chlorine and its compounds
in the form of the hypochlorites, ozone gas and the ultra-violet
light. All of the chemical disinfectants are used in very minute
amounts in water-purification work; nevertheless, they are ex-
tremely effective when properly applied. The relative merits of
these various agents will be discussed in a later chapter.
The use of copper sulphate as an agent for killing off growths
of algae and diatoms in water supplies is of practical importance,
and of much value. The troublesome character of these growths
in the operation of water- works, and even of purification plants
will be considered in detail later.
Statistics of Purification Plants. — Fifty years ago in the United
States no plants for the purification of a public water supply were
in existence. In Europe plants which clarified the water were
in use, and incidentally effected a certain degree of bacterial puri-
fication. They were operated upon an empirical basis and with
no true understanding of the scientific principles underlying the
art. In fact, the modern theory of the cause for many diseases
was unknown, and the part played by minute vegetable and
animal organisms in the dissemination of disease was undreamed
of. By the wonderful investigations and deductions of Pasteur
46
WATER PURIFICATION
and Koch, the relation between polluted waters and the trans-
mission of certain diseases became apparent and furnished
a rational basis upon which methods of purification could be
constructed.
According to statistics first compiled by Mr. Allen Hazen for
the International Engineering Congress held in St. Louis in 1905,
and brought up to 1910 by Mr. Geo. C. Whipple in a paper read
before the Congress of Technology held in Boston in 1911, over
10,000,000 people in the United States are now supplied with
water purified by filtration. Mr. Whipple presents some tables
which clearly indicate how rapid the growth in the construction
of purification plants has been.
PopuLATioNB Supplied with Filtered Water at Different Dates
Year
Total urban popu*
lation in U. S.,
places of more
than 2,600 inhabi-
tants
Population i
Sand filters
supplied with filtered water
Mechajucal ^otal
i
Per cent, of
urban popu-
lation sup-
plied
1870
1
None
30,000
35,000
360,000
3,883,221
None None
0.00
1880
1890
1900
1910
13,300,000
21,400,000
29,500,000
38,350,000
275,000
1,500,000
6,922,361
30,000
310,000
1,860,000
10,805,582
0.23
1.45
6.30
28.20
In 1870 water supplies in the United States which were purified
by filtration were practically unknown, while today probably
30 per cent, at least of communities of more than 2,500 inhabi-
tants are drinking filtered water. Mr. Whipple estimates that:
*' If the cities of more than 25,000 inhabitants are considered alone,
it will be found that our 228 cities have a total population of 28,508,000.
Of these, about 8,098,000 are supplied with water that does not need
filtration, or at least will not for a long time. This leaves about
20,311,000 people that are using water from sources subject to contami-
nation. Of these 8,402,000 or 42 per cent, are adequately protected by
the filtration of the water. Filters are under construction or have been
authorized for 648,000 more, thus raising the percentage to 45 per cent.
Filter? have been officially recommended for 3,541,000; 7,720,000 people
are still using water of questionable quality, although in some of these
cases filtration has been seriously considered by sanitarians."
A summary of statistics of population supplied with filtered
water in the United States is given by Mr. Whipple in another
table, which is well worth quoting.
WATER PURIFICATION
47
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48 WA TER PIRIFICA TION
A recent compflation of the rapid sand or mechanical filter
plants now in operation in America, together with their daily
capacities is shown in the following table:
Ratid SA?n> OR Mechanical Filter Plants
Harinc daily
10 MC 3 M.G. to Lms Uab
or oT«r 10 M.G. 3 M.G.
Total
Kumbcr of pljuit5 29 112 365 506
MillioDs ol gallons
Total dtthr capftritT as grouped. . $92 520 332 1,844
Mr. George A. Johnson, in his recent paper on the ** Typhoid
ToU."^ estimates that the total population of the cities of the
United States making returns of vital statistics is 34,230,000.
Filtered water was supplied to 48 per cent, of the population
of these cities in 1913, or in other words to a peculation of
16,500,000 persons. This latter figure represents 17 per cent, of
the total estimated population of the United States.
The purification of water supplies by disinfection with calcium
hypochlorite, either continuously or intermittently, has gone for-
ward by leaps and bounds within the past 5 years. Today it is
estimated *'that 300 to 350 cities in the United States alone use
this process.*'^ The use of disinfecting agents in water supplies is
also increasing in Europe.
The investment represented by purification plants mounts into
many millions of dollars, but the ciniservation of life effected by
them, measured in dollars, is ver>- many times more than their
first cost. Efficiency of these plants is of the utmost importance
both from the hygienic and ei^onomic standpoint, and is becoming
more and more appreinateii by communities owning them. To
the technical problem of purification much study has been given
in the past, and is still Ix^ine given at present: but the art as a
whole is on a thoroushly scientific and practical basis, as the
beneficial results of water purification amply testify.
* y .' w. A***, W J^it -- v-* " ^"s't . t s.^ 't . , Ju lie, 1 9 1 rt.
^ C. A- Jennings: '' iivpxvh'orite Sttnlization of Water Supplies."
fTv- /vc.v'i, vui- w>, S<p:. 14. 19r-\
WATER PURIFICATION 49
References
1. Allen Hazen: "Filtration of Public Water Supplies." Appendix IV.
2. "Water Purification in the United States." Eng, News, 47, p. 310.
3. Ridbal: "Water and Its Purification."
4. G. C. WmppLE: "The Present Status of Water Purification in the
United States, etc." Proc, Congress of Technology, Boston, 1911.
5. Engineering Record:
(a) Geo. W. Fuller: "Importance of Proper Operation of Water
and Sewage Purification Plants." Vol. 68, p. 498, 1908.
(6) George C. Whipple: "Policy of Water Filtration." Vol. 60, p.
718, 1909.
(c) Rudolph Herino and George W. Fuller: "History of Devel-
opment of Water Purification — Report on Montreal Supply." Vol.
62, p. 539, 1910.
CHAPTER VI
SEDIMENTATION
The removal of suspended mineral and organic matter from
water supplies is most easily accomplished by settling in reser-
voirs. The clarification and purification eflfected by settling in
this manner is usually spoken of as plain sedimentation. By the
addition of certain chemical compounds to naturally turbid
waters, an artificial fiocculation or coagulation of the suspended
particles is produced whereby they settle out more rapidly.
This process is termed ''sedimentation after coagulation" or
"precipitation with chemicals."
PLAIN SEDIMENTATION
Turbid surface waters flowing into impounding reservoirs be-
come partially clarified in passing slowly through or in standing
imdisturbed in them. This result is produced because the veloc-
ity of flow of the water, which has maintained these minute par-
ticles in suspension, is lessened or reduced to practically zero.
The reduction in the velocity of flow permits the sediment to
gravitate toward the bottom of the reservoir, and to be finally
deposited thereon. Provided the wind does not set up surface
currents, nor temperature changes produce vertical currents, the
sooner will the deposition of the sediment be effected. For ob-
vious reasons a perfectly quiescent condition of the water can not
be produced, and complete clarification, therefore, is not usually
practicable.
The ponds and lakes are, as a rule, natural settling reservoirs,
in so far as the turbid surface waters which may flow into them
are concerned. The water in them is, therefore, usually quite
clear. The factors tending to disturb the water and to retard
settlement are of course active at times.
Artificial settling reservoirs and coagulation basins form a
most important part of purification plants treating clay-bearing
waters. As a preliminary treatment for filtration they are
absolutely essential for eflSciently and economically handling
these turbid waters. They may be also of much assistance in
60
SEDIMENTATION 51
purifying waters which are only turbid during portions of the
year. In water softening, settling basins are 'essential to obtain-
ing a well-clarified effluent.
Theory of Sedimentation. — The very practical importance of
sedimentation in water purification has caused the conditions
which influence the phenomena to be carefully studied. Much of
the experimental work has of necessity been empirical in charac-
ter, because of the number of factors which are involved. Some
investigators, however, have approached the problem from a
theoretical standpoint, and many of their deductions are valuable
and suggestive. The early work of Brewer, Durham, Hunt,
Barus and Seddon is of interest in connection with this general
subject. The more recent paper of Mr. Allen Hazen,' however,
has a more practical bearing on sedimentation, although discuss-
ing in a theoretical manner certain important factors.
From the simple assumption, ''that whenever a particle of sus-
pended matter hits the bottom, it remains where it strikes, and
is never carried forward on the bottom, or picked up again;
second, that all the sediment in the water is of the same hydraulic
value, that is to say that every particle settles through the water
at the same rate as every other particle," Mr. Hazen proceeds to
develop mathematically fifteen special propositions. He dis-
cusses the velocity with which particles of sediment settle
through still water, and the effect of temperature, flocculation
and coagulation upon the rate of settlement.
The minute size of the particles, their very slow subsiding
velocities, and the mixing action produced by surface and vertical
currents, all tend to maintain the finest particles in practically
constant suspension. Mr. Hazen gives a table of the subsiding
velocities of various-sized particles which is reproduced on the
following page.
Mr. Hazen's r4sum6 of the deductions and conclusions at the
close of the paper is clearly and concisely stated as follows:
Resume
"The fundamental proposition, in clearing water by sedimentation,
seems to be that every particle of sediment moves downward through
the water at a velocity depending upon its size and weight and upon
the viscosity of the water. Particles of sediment are generally so far
apart that they do not influence each other; and, while there is no doubt
» Trans. Am. See. C. E., vol. 53, p. 46, 1904.
jQ
WATER PVRIFICATIOS
Vu.*vmHt AT vmca Pabticlks or Scwiixsrr Fall ts Snu. Watcb
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SEDIMENTATION 63
accounted for this distribution of sediment by the constant mixing
of the water from top to bottom, and to the sustaining power of vortex
motions in the water. These motions he thought arose from the internal
motion of the water at the time of entrance, and from wind, and from
temperature changes.
''The writer has taken Seddon's development of the case as his
starting point, and has carried the discussion further. He believes thai
while the internal motions keep the water mixed, and with nearly the
same density of sediment from top to bottom, the tendency of the
particles of sediment to settle is nevertheless an unbalanced force always
acting to take the particles to the bottom, and the number of particles
that hit the bottom in a given time is proportional, first, to the velocity
at which the individual particles settle, and second, to the density of
sediment in the water immediately above the bottom.
"With these fundamental relations in mind, it is easy to compute
and to express by simple formulas the proportions of particles of sedi*
ment of a given hydraulic value which will hit the bottom under given
conditions and which, therefore, presumably will be removed.
"The fundamental propositions may be very concisely expressed.
They are: First, that the results obtained are dependent upon the
area of bottom surface exposed to receive sediment, and that they
are entirely independent of the depth of the basin; and second, that the
best results are obtained when the basins are arranged so that the
incoming water containing the maximum quantity of sediment is kept
from mixing with water which is partially clarified. In other words,
the best results are obtained where any given lot of water goes through
the basin with the least mixing with the water which enters after it.
This is practically accomplished by dividing the basins into consecutive
apartments by baffles or otherwise.
"Thus far, the discussion is easy and apparently certain. The next
step is a more difficult one. It relates to bottom velocities, and has to
do with the question whether these velocities are such as to allow the
particles to remain on the bottom when they get there, or whether
they will be taken up again and be kept in motion with the body of the
water. This is a point upon which further experimental data are
needed. The problem of securing such data seems to be difficult.
The observations must be made at the bottom of a layer of liquid of
considerable thickness, where the conditions of observation are not
favorable. The observations, further, must be made on very low
velocities and on particles so small as to be practically microscopic.
"Whatever view may be taken of the second part of the problem, or
whatever researches upon it may show, the arrangements of basins
most favorable to taking particles to the bottom should stand."
54 WA TER PURIFICA TION
of Sediment. — The collection of minute particles
of suspended matter into larger aggregates is a process which
appears to occur only to a limited extent in natural waters, al-
though it may be artificially produced by the addition of certain
chemical compounds. Since the deposition of these finely divided
particles greatly facilitates sedimentation and subsequent filtra-
tion, when the latter forms a part of the purification process, the
phenomenon is of much practical interest and importance in
water purification.
CoUoidal Character of Sediment — ^The analc^y between the
physical properties of liquid suspensions of certain chemical com-
pounds, and those of turbid clay-bearing waters is so marked that
some description of their properties will be of interest. In a paper^
published some years ago by the author attention was called to
Dr. A. A. Noyes'^ classification of colloidal mixtures, in which he
defined non-viscous, non-gelatinixing, but readily coagulable
mixtures as ''colloidal suspensions." He regarded them as
really suspensions of minute particles and not true solutions. He
differentiates further by designating mixtures in which the par-
ticles may be visible under the microscope as '' microscopic sus-
pensions," reserving the term ''colloidal suspensions" for those
containing particles beyond the limit of microscopic visibility.
Physical and Electrical Properties. — Natural waters furnish
many examples of colloidal suspensions. Most turbid waters in
their natural condition may be considered as mixtures of "mi-
croscopic and colloidal suspensions." A beam of li^t passed
through Ohio River water, even after the water has stood for
many weeks, is plainly visible, in the same manner as when a sun-
beam passes through dusty air. This is a fairly good proof of the
presence of minute particles in suspension, which reflect the light
from their surfaces. Colloidal suspensions of gold and arsenious
sulphide artificially prepared act in a similar manner to a ray of
Ught.
Another property of colloidal and microscopic suspensions,
apparently depending on the presence of electric charges upon
them, is seen in the migration of the colloidal particles by the
passage of an electric current through the mixture. Thus the
particles of a colloidal suspension of ferric hydroxide or aluminum
*"The Coagulation and Precipitation of Impurities in Water Pmifica-
tion.*' Eng. Record, vol. 51, May 13, 1905.
* Jaur. Am. Chem. Soc.^ vol. 27, No. 2.
SEDIMENTATION 55
hydroxide migrate with the positive current toward the cathode,
while kaolin and other similar colloidal or microscopic particles
migrate with the negative current toward the anode. The col-
loidal suspension of clay particles characteristic of turbid Ohio
River water act in a precisely similar manner to those of kaolin.
Experiments by the author with slightly turbid Ohio River water
produced an average rate of travel of the particles toward the
anode of 0.29 cm. per hour for a potential gradient of 4 volts per
centimeter. These results are of the same order of magnitude as
were obtained by Whitney and Blake for the migration of par-
ticles in a colloidal suspension of silicic acid.^ Silica doubtless
formed the larger proportion of the particles in the sample of
Ohio River water with which the above experiments were made.
The clearing of the water at the cathode and the movement of the
particles toward the anode indicated them to be negatively
charged.
Coagulation with Chemicals. — Turning now to another impor-
tant property of colloidal suspensions in general, viz., their coagula-
tion, we find that turbid natural waters possess similar properties
to colloidal suspensions artificially prepared. Non-electrolytes
do not have the power of coagulating colloidal suspensions;
but all electrolytes will do so with a proper degree of concentration
of the latter, and a sufficient length of time. Acids, bases and
salts, therefore, will coagulate colloidal suspensions, all being
more or less dissociated in aqueous solution and capable of con-
veying an electric current. In a similar manner hydrochloric acid,
caustic soda, caustic Ume or an ordinary salt solution will each, if
of the proper concentration, coagulate the coUoidal clay of a natu-
rally turbid water like that in the Ohio River. It should always
be borne in mind in dealing with natural waters that we are work-
ing with extremely dilute solutions of salts, even in those waters
which we commonly speak of as high in soluble compounds. In
other words the concentration of the electrolytes is very low.
In a number of modern purification plants in which lime is used
to soften the water, in addition to the employment of sulphate of
iron or aluminum sulphate to effect clarification, the action of the
caustic alkaU is virtually that of a coagulant, especially if the lime
is added in sufficient amounts to produce a slightly caustic con-
dition. Some quite extensive experiments undertaken on a large
scale some years ago, clearly proved that by rendering the Ohio
* Jour, Amer, Chem, Soc, October, 1904.
66 WATER PURIFICATION
River water caustically alkaline with lime, the suspended clay
could be coagulated, and could be subsequently removed by
rapid filtration through sand. The explanation of the phenom-
enon seems to be that the introduction of the base calcium hy-
drate in excess, furnished an electrolyte of sufficient concentration
in the water to effect coagulation of the colloidal clay.
The similarity between artificially prepared colloidal suspen-
sions and the very small suspended particles characteristic of tur-
bid waters as above described, seems to warrant the classification
of the latter mixtures with the former. If we seek further analo-
gies in the co-precipitation or absorption by colloids of other sub-
stances in solution and suspension with them when these colloids
are coagulated, the true character of turbid waters seems even
more apparent.
When a turbid water containing carbonates of lime and mag-
nesia in solution is treated with sulphate of alumina, for example,
a reaction results setting free aluminum hydroxide. The Uber-
ated aluminum hydroxide absorbs or mechanically traps the
finely divided material in suspension, and in the course of time
the finer particles come together to form larger particles which
settle out readily. This process of coagulation of the colloidal
clay suspension and co-precipitation of the larger suspended par-
ticles, appear to be started by the coagulation of the aliuninum
hydroxide. It is evident, as Dr. Noyes points out in the paper
referred to, 'Hhat the mechanism of this coagulation is not yet
understood," although it appears, **that it is the ion with a charge
opposite to that of the colloid particles that is mainly responsible
for their coagulation." It is also probable that it is the electric
charge upon the particle which tends to hold it in suspension.
Time Required for Coagulation. — The time factor in the
coagulation of turbid waters is an important one. The length of
time required to bring about the proper degree of coagulation
varies with dififerent waters. It is apparently influenced by the
character of the suspended colloids, by the kind and amount of
salts in solution, by the quantity of the coagulating chemical
applied, by the temperature of the water, and by the agitation to
which the mixture is subjected. The presence of much organic
matter may retard the formation of the floe. An ordinary clay
suspension is usually quickly coagulated. Complete flocculation
and partial clarification may take place under favorable condi-
tions in as short a time as 10 or 15 min.; on the other hand, the
SEDIMENTATION 67
author has seen a water which was not affected at the end of 4
hrs. This water had only a slight turbidity. Two hours after
appl3ring the coagulating chemical to this water it could be passed
through a sand filter without removing the suspended matter or
all of the coagulant. The large amount of soluble organic
matter present in the water evidently produced a colloidal sus-
pension with the aluminum hydroxide, formed by the decomposi-
tion of the aluminum sulphate which was added, and was only
slowly precipitated.
Under ordinary conditions a period of 3 to 5 hrs. is sufficient to
properly coagulate and settle a turbid water. Of course a proper
arrangement of basins, inlets, outlets and baffles is requisite for
bringing about effective coagulation and clarification. The con-
struction of typical coagulation and settling basins will be de-
scribed in a succeeding chapter.
Loss of Chemical by Adsorption. — Another phenomenon
common to the coagulation of turbid waters is the adsorption of
the applied chemical compound by the flocculent material pro-
duced by the reaction and the associated suspended matter. The
particular significance of this fact in water purification was pointed
out by Mr. George W. Fuller in his report on the experiments
on Ohio River water made at Louisville, Ky., some years ago.
While adsorption or concentration of a liquid on the contact-
surface of the particles is not alone peculiar to colloids, but is
characteristic of all solid precipitates, it has a practical bearing
on coagulation in that there is some loss of chemical on account
of this property. The amount of chemical thus lost is probably
proportional to the surface area of the particles of the precipitate,
and is a function of the nature of the solid and dissolved bodies,
and of the concentration of the latter.
Natural Colloids. — The ''schmutzdecke," which forms on the
top of slow sand filters, is doubtless a true colloid, and by its
adsorptive power removes the organic and inorganic suspended
matter. The difference between the appearance of the sand in
the beds of slow sand filters receiving water carrying considerable
dissolved and suspended organic matter, and those which receive
water holding more or less clay in suspension, as pointed out by
Mr. George W. Fuller in his discussion of Mr. Allen Hazen's
paper " On Sedimentation, '' previously quoted from, may possibly
be explained by a difference in the character of the colloids pro-
duced or carried by the two types of water. The colloid formed
58 WATER PURIFICATION
by the soluble and suspended organic matter in a water has prob-
ably the[characteristic of a true colloid, i.e., a viscous, gelatinizing
compound not coagulated by salts, like gelatine for example. On
the other hand clay-bearing waters produce or carry a colloid
which is non-viscous and non-gelatinizing, but whichjmay be
readily coagulated by compoimds like aluminum sulphate or
sulphate of iron. Bacterial activity very likely aids in the forma-
tion of the natural scums foimd on slow sand filters.
In the absence of any artificially applied coagulant like alumi-
num hydrate the "granular appearance'' of sand beds receiving
clay-bearing waters indicates the formation of a colloid whose
ability to prevent the passage of finely divided suspended matter
is limited. The colloidal particles pass deeper into the sand than
would a true gelatinous colloid, and their power of adsorption is
soon exhausted. The "ripening" of the sand beds of both slow
sand and rapid sand filters, is, therefore, probably a process of the
formation and deposition of colloidal particles upon the sand
grains, by which their adsorptive power is slowly increased.
It is, therefore, in the character of the colloid formed that one
must seek for the explanation of the phenomena connected with
the coagulation and filtration of natural waters. It is evident
that much more Ught is needed on a great many of these prob-
lems, but that some of them are associated in some way with the
colloidal state of the clay, of the organic matter and of the artifi-
cially applied coagulants, is self-evident. While the above points
may at first sight appear to be only of scientific interest, they
are in reality intimately associated with the most efficient de-
sign of purification plants. The size of coagulation basins, the
mixing and the agitation of the raw water with the coagulant, the
ability to vary the period of coagulation for any given water, the
best chemical compoimds to use for the proper coagulation of the
suspended matter in the water, the advisability of providing
for plain sedimentation before attempting coagulation and the
size and character of the sand grains composing the filter bed are
all factors entering into the practical design of water-purifica-
tion plants. The poor results often obtained in the operation
of plants is quite as frequently the result of improper design as
of faulty methods of handling the plant.
SEDIMENTATION 59
References
Thbobies of Sbdimbntation:
1. Brbwbr: Proc, Nat. Acad. Sciences, November, 1883.
2. Durham: Chem. News, 30, p. 67, 1874; ibid., 37, p. 47, 1878.
3. Hunt: Proc, Boston Soc. Natural Hbtory, February, 1874.
4. Barus: Bull U. S. Geological Survey, No. 36, 1886.
5. Seddon: Jour, Assoc, Eng, 8oc,f p. 477, 1889.
6. Hasbn: 7*ran<. Amer. Soc. C. E., vol. 53, p. 45, 1904.
7. Lonolet: Eng, Record, vol. 57, pp. 793, 813.
Coagulation:
1. Ellms: Eng, Record, vol. 51, p. 552, 1905.
2. Eng, Record, vol. 54, pp. 439, 475, 1906.
3. Eng, Record, vol 58, p. 292, 1908.
4. Eng,' Record, vol. 61, pp. 176, 215, 247, 599, 1910.
5. Eng. Record, vol. 64, p. 476, 1911.
General Experimental Data:
1. Fuller: "Report on Water Purification at Louisville, Ky."
2. Fuller: "Report on Water Purification at Cincinnati, Ohio."
3. Weston: "Report on Water Purification at New Orleans, La."
4. "Report of Filtration Commission of Pittsburgh, Pa."
5. George F. Catlbtt: "Colloidal Theories Applied to Colored Water."
Eng, Record, June 3, 1916.
6. Thorndtke Saville: "The Nature of Color in Water." Engineering
and Contracting, January 16, 1917.
CHAPTER VII
TYPES OF SETTLING RESERVOIRS AND COAGULATION
BASINS
The design of reservoirs and basins for efficient sedimentation
has received considerable attention in water-purification work,
but not as much as the subject deserves. The complexity of the
problem has not alwayB been appreciated, and too frequently this
portion of the plant has been made to accommodate itself to other
features of the design instead of being properly coordinated with
them.
A certain amount of flexibility in the design of these reservoirs
is quite possible without materially sacrificing efficiency. Never-
theless, it is the author's opinion that much more of the work of
clarification should be thrown on this part of the purification
plant than is now the practice. They are by far the least com-
plicated portions of the works, and the least expensive to operate.
Their tendency to make more uniform the operation of the filters
strongly commends them to the operators of such plants. It is
believed that in designing settling reservoirs of all kinds more con-
sideration should be given to obtaining efficient sedimentation
and to making them as large as good engineering practice will
permit, due regard being had for other portions of the plant, in
order to produce a well-balanced design.
Impounding Reservoirs. — Impounding reservoirs built pri-
marily for storing water are, of course, to be considered from a
somewhat different standpoint than those especially designed
for sedimentation purposes. The depositing of suspended sedi-
ment in storage reservoirs is an incident rather than the object of
their operation. However, considerable purification is effected
in them, and the influences which lead to such results will be
discussed in another section.
Settling Reservoirs. — Storage of turbid waters for purposes of
plain sedimentation, in reservoirs especially constructed for this
purpose, is undoubtedly good practice, but is not always provided
for. Usually such supplies are drawn from turbid streams in
which the water may at times be loaded with sediment. Pro-
vided the reservoirs are relatively large in proportion to the con-
60
RESERVOIRS AND COAGULATION BASINS 61
sumption of water, quite a number of days of settlement may be
possible before the water is drawn off. The relative positions of
the inlet and outlet of these reservoirs is obviously of great im-
portance in even approximating theoretical displacement of the
water if they are used continuously. The tendency of the
water currents to seek the shortest path between the inlet and
outlet, and thereby render more or less ineffective certain parts
of the reservoir, is a commonly observed condition. Baffling
undoubtedly has the effect of breaking up "short-circuiting
currents of water, " but is not always employed in plain sedi-
mentation basins.
Cleaning out the sediment deposited in this class of reservoirs
is greatly facilitated by smooth and hard linings to the reservoirs,
by sufficient slope to the sides and bottom and by an adequate
system of gutters and drains. Proper facilities for flushing out
the mud by streams of water under pressure, or by scraping the
mud to the gutters assisted by a flow of water which is not under
pressure, are necessary in all well-designed basins.
In all settling basins the sand and heavier portions of the silt
will be found deposited close to the inlet. In some cases the
amount of sediment dropped near the inlet is very great, especially
where the turbid stream supplying the water carries a good deal of
sand and silt, and where the pumping from the stream is practi-
cally continuous.
Cincinnati Storage and Settling Reservoirs. — Combined stor-
age and settling reservoirs are in operation at Cincinnati, Ohio,
(Fig. 5) in which Ohio River water undergoes plain sedimentation
before being coagulated with chemicals and filtered. These two
reservoirs hold approximately 392,000,000 gal. of water, and
were designed with the idea of their being operated on the fill-and-
draw plan. This method of operation, however, has never been
followed. The water flows continuously through them in parallel.
The inlets to the reservoirs are between 500 and 600 ft. from the
outlets. The latter consist of movable pipes (Figs. 6 and 7)
with their mouths held about 4 ft. under the surface of the water
by means of floats. The water is thus continuously skimmed
from the surface. The depth of water in the reservoirs varies
from 35 to 50 ft.
The irregular shape of these reservoirs (Fig. 8) is accounted for
by the desire in construction to make the excavations equal the
embankments as nearly as possible. As it was intended that
62 WATER PURIFICATION
they should be operated by Erst fiUmg with water, then allowing
the latter to stand and deposit its sediment for a day or so, and
finally drawing off the settled water, it was of no particular conse-
quence if the inlet was close to the outlet. Since they are not
Fio. 5. — (^cinnati settling raaerroiis.
Fi'i. 6.— Cincir.naCi setrLng reservoire, effluent Boat tubtt.
Utilized in thia manner, but are operated continuously, their
efRcienny La iindrjiihr.iH'ily somewhat reduced because of their
irret^ilair odtline, and the short distance between the inlet and
ouf let. The appariinfly d-^ad spaces in these reser%"oir5, however.
RESERVOIRS AND COAGULATION BASINS 63
are by no meaaB UBeless, since experience bKowb that diffusion of
the sediment causes a much more uniform deposition of the latter
than would be supposed. The depth of mud in the lobes of these
Fio. 7. — Cinciiuuiti settling
lire, profile showing float tubes.
SECTION ON LINE A-B
Fio. 8. — Cincinnati settling reservoirs, plan and cross section,
reservoirs will probably run from 35 to 40 per cent, of the average
depth in the portions of the reservoirs where more active sedimen-
tation is in progress.
64 WATER PURIFICATION
Louisville Settling Reservoirs. — The two Crescent Hill reser-
voirs at Louisville, Ky., perform a similar service to those at
Cincinnati. They cover an area of 750,000 sq. ft., and hold, when
filled to a depth of 20 ft., a little over 100,000,000 gal. of water.
Originally the water as it was pumped from the Ohio River was
delivered into the gate house at the end of the division wall sepa-
rating these two basins. It passed over a weir above the 20-ft.
level into the first basin, and was drawn off at a point diagonally
opposite at the bottom through a conduit 5 ft. in diameter.
Through this conduit the water passed to the corresponding cor-
ner of the second basin, where it entered at tl\,e bottom. It was
drawn off at the diagnonally opposite corner through the gate
house.
Delivering the muddy water at the surface of these reservoirs
and drawing off at the bottom has been recently changed, so that
the water now enters from the gate house at the bottom of the
first basin, and is withdrawn over a weir tower built to enclose the
inlet end of the conduit. After passsing through the latter to the
bottom of the second basin, it is skimmed off at the top of this
basin at the gate house from which it flows to the coagulation
basins.
Mr. George W. Fuller observed, when these reservoirs as origi-
nally arranged, were drawn off to be cleaned, that with the ex-
ception of the coarser material piled up near the inlet, the depth
of sediment was substantiaUy uniform over the entire bottom.
Mr. Allen Hazen has noted the same condition in other reservoirs,
and accounts for it by the mixing action by which water in all
parts of the reservoir is made substantially of the same quality.
New Orleans Grit Reservoirs. — For removing the heavy silt
and sand of a normally turbid water, relatively small grit reser-
voirs have been used. In the New Orleans purification plant two
such reservoirs are in service. Each reservoir is 75 by 150 ft. in
area, and has outer walls 20 ft. high. These reservoirs are pro-
vided with a center baffle which causes the water to travel up one
side of the reservoir and down the opposite side to the outlet. At
the normal capacity of the plant a sedimentation period of about
1 hr. is obtained with one basin in service. The heaviest sedi-
ment settles nearest the inlet, and grows much lighter as the out-
let is approached (Fig. 9).
Albany Settling Reservoir. — The settling basin designed to be
used in conjunction with the slow sand filtration plant at Albany,
RESERVOIRS AND COAGULATION BASINS
65
^¥ .JJiiam
aioAMMH J^I^Ak '■*10 Mn^nj
i
s
o
a
o
a
c8
d
o
C
S
O
o
66 wateh purification
N. Y., was intended to be operated continuously. The basin has
an area of 228,000 sq. ft. and a depth of 9 ft. It holds 14,600,000
gal. of water. Provision was made to aUow the water entering
the reservoir to discharge through 11 inlet pipes, which rise 4 ft.;
above the water line. By discharging into the basin in this
manner aeration of the water was produced. The water was with-
drawn through 11 outlets.
At the present time the water is not^erated as it enters the
reservoir through two l8-in. perpendicular and one 36-in. hori-
zontal inlets. At the present rate of consumption a 17-hr. period
of subsidence is obtained. .
COAGITLATION BASINS
The bringing together of finely divided particles of suspended
sediment in natural waters by means of the action of certain
chemical compounds is termed coagulation. Basins, in which
this action may take place and the flocculated sediment settle out,
are commonly provided in connection with rapid sand filter |
plants. They may also form a part of slow sand filter plants'
where the sediment in the water settles out slowly and is liable to
clog the sand in the filters.
Mixing Channels. — The introduction and uniform distribution
in the water to be treated of chemical solutions of the strengths
usually employed in water purfication offers some mechanical
difficulties. Since the efficiency of the coagulating compound
depends upon the formation of a large and well-defined floe, the
size and character of which is directly influenced by the tempera-
ture of the water and the nature of the salts and colloids in solu-
tion and suspension, a thorough mixing of the water with the
solution is of the utmost importance.
By sending the water through relatively narrow channels at a
velocity of 1.5 to 2.0 ft. per second, and allowing the travel
through these channels to take about 1 hr., a thorough mixing and
a complete coagulation is effected, which produces rapid sedimen-
tation in the coagulation basins into which the water discharges.
The eddies formed in the channels by reversing the direction of
flow or by baffles or by projecting portions of the concrete con-
struction in the channels, assist materially in bringing about a
thorough mixing.
In New Orleans mixing channels are provided for applying a
5 per cent, milk of lime in the manner described above. In this ,
RESERVOIRS AND COAGULATION BASINS 67
plant duplicate reservoirs 75 by 320 ft. each with outer walls 19
ft. high, are divided into 16 rectangular double-decked passages
with a cross-sectional area of over 60 sq. ft. each, and an aggror
gate length of about 5,120 ft. When passing 40,000,000 gal. of
water in 24 hrs., the flow of the water through the channels
requires about 1 hr.
Iron sulphate for coagulation purposes, and soda ash for re-
ducing the permanent hardness of the water, may be both intro-
duced in these channels, but provision is also made for applying
a coagulant at various points in the flow of the water, through the
coagulation basins proper.
Obviously, mixing channels may become settling chambers un-
less the velocity of flow is sufficient to retain the flocculated sedi-
ment in suspension. This does take place, but corrects itself by
reducing the cross-section of the channel by deposition of sedi-
ment until the velocity is sufficient to maintain a scouring action
through the passage. On the other hand, too great a velocity
may break up the floe and thereby diminish its ability to settle
rapidly, as well as failing to entrap the very fine suspended sedi-
ment for which the coagulating chemical was added. Provided
a very thorough mixing action is obtained in the channels, it is
evident that the coagulation basins themselves may be made
smaller than they otherwise could be.
A more recent design is found in the Grand Rapids, Mich.,
plant, where the water after passing through a grit chamber hold-
ing about a 26.5-min. supply at a normal rating of 20,000,000 gal.
per day, enters a mixing chamber 44 ft. wide by 160 ft. long. The
chamber holds 732,000 gal., or about a 53-min. supply at normal
rating. The basin is provided with wooden baffles of " around the
end type, " spaced 3 ft. apart for the full length of the chamber.
Mr. J. W. Armstrong who designed this plant, as well as the
plant at New Orleans, states this type of baffle permits the opera-
tion of the plant with varying heads of water, and offers reason-
ably good facilities for cleaning and inspection.
Settlement After Coagulation. — The deposition of coagulated
sediment should take place rapidly if the proper amount of
chemicals have been added to the wat^r, a thorough mixing of the
water with the chemicals has been effected, and temperature con-
ditions are favorable. The same general principles governing the
deposition of sediment in plain sedimentation basins, as previously
discussed, apply here, except that the suspended particles are
68 WATER PURIFICATION
larger and should gravitate toward the bottom more rapidly.
A velocity of flow of 1.0 to 1.5 ft. per minute can probably be
safely maintained in most cases without carrying too much of
the finest material forward to the outlets of the basins. Baffles will
probably be found advantageous in most basins of this type. A
uniform and even distribution of flow across the entire cross-
section of the basin is desirable between the inlets and outlets.
Skimming from the surface at the outlets is the proper method
for the withdrawal of the settled water. Provision for secondary
application of the coagulating chemicals as the water flows
through the basins for the purpose of correcting the original
treatment, should never be omitted in any well-designed plant.
If possible, an auxiliary basin for getting the benefit of this
secondary treatment ought to be installed, otherwise too much
coagulated material is liable to be carried through the outlets to
the filters.
The primary coagulation basins are usually constructed in
duplicate in order to be able to clean one of them at a time
without interrupting the operation of the whole plant. An ade-
quate number of sumps and drains ought to be provided, so
that the deposit when ready to be cleaned out does not have to
be moved too far. The size of the drains should be ample to
prevent clogging, and plenty of water should be available for
flushing purposes.
St Louis Settling Basins. — The six original settling basins of
this water-works plant (Fig. 10) were constructed as plain sedi-
mentation basins. For a number of years since the chemical
coagulants sulphate of iron and caustic lime have been used to
clarify the water, they have become coagulation basins. They
originally consisted of six rectangular masonry tanks 670 by 400
ft. in plan, and placed side by side. The walls are of masonry but
the bottoms are of concrete. They were intended to be operated
in parallel, but since coagulants have been used the walls dividing
adjoining basins have been cut down, so that the water now
passes through them in series, entering through four 3 by 3 ft.
openings at the end of one of the basins. The water is withdrawn
through a masonry conduit at the end of the sixth basin after
having passed through the preceding five basins. Sluice gates in
each basin, connected with both the inlet and outlet conduits,
make it possible to withdraw basins from service for cleaning,
and to provide for emergency conditions.
RESERVOIRS AND COAGULATION BASINS 69
Two additional basins, covering together an area 400 ft. wide
by 1,660 ft, long have been constructed of concrete. The two
basins are separated by a division wall, and are each 400 by 800
ft. in plan, and have an average depth of about 21 ft. Their
combined capacity is 75,000,000 gal. This makes the total
capacity of the eight basins 255,000,000 gal. These are the
Fio. 10.^ — St. Louis settling basins.
largest coagulation basins known to the author, and they handle
effectively a very turbid water. The effluent from these basins
is now filtered.
Fio. 10a.— -St. Louis filtration plant.
Cincinnati Coagulation Ba^s. — A good example of coagulation
basins which are effective, but which are unprovided with batHes,
are the three basins of the Cincinnati plant (Pigs. 11 and 12). A
lined basin or reservoir 400 by 400 ft. in plan is divided by a con-
crete wall into two basins, each ofwhich may be operated independ-
ently, but which are usually operated together in parallel. The
depth of these basins is about 21 ft. The water enters the two
70
WATER PURIFICATION
basins through sluice gates at the bottom of a gate bouse at one
end of the division wall. It flows into the bottom of the basins
through two reinforced-concrete conduits on either side of the
above-mentioned gate house. These conduits are 7 ft. in diame-
Fio. 11. — Cincinnati coagulatioi:
m
^
|i| — g
T^^r-
Fio. 12. — Ciacinnati coagulation basins, plan and cross section.
ter and have set in the top of each of them twenty-one 20-in. tees.
Each of these tees discharges through the two openings in line
with each other, and in parallel with the line of flow through the
body of the conduit. In this manner the velocity of the counter-
RESERVOIRS AND COAGULATION BASINS 71
currenta of water tend to oppose each other, and to produce a
uniform and quiet inflow. The water then passes across to the
opposite side of the basins, and is skimmed off at the surface by
openings into a steel conduit which conveys the settled water to
either a third basin for secondary treatment, or directly to the
filters. Two mud valves hydraulically operated are placed in the
bottom of each basin. The slope of the bottom toward the
sumps of these valves is approximately 2 per cent. The sides
have a slope of 1.75 to 1. These basins have a concrete lining
covered with hard-burned brick which are grouted in place so as
to form a smooth hard surface for flushing out the deposited mud.
The third basin is 400 by 80 ft. and about 16 ft. deep. It is
used in series with the two larger basins, and although operated
Pio. I2a. — Cincinnati filtered water reservoir.
continuously to obtain the maximum period of sedimentation, was
originally intended for settling the water after a secondary appli-
cation of chemicals, when the first application had been found
insufficient. Whenever it is necessary to make a second applica-
tion of chemicals, which is rarely the case, the third basin is used
as originally intended.
The two large basins havea capacity of 10,000,000 gal. each, and
the small baain a capacity of 2,000,000 gal. At the maximum
output of this plant a period of 4 to 5 hr. for settlement is possible
in these basins.
Grand Rapids Coagulation Basins (Fig. 13). — As an example
of well-baffled coagulation basins those at Grand Rapids, Mich.,'
may be cited. There are two covered coagulation basins in this
plant. The smaller basin is 88 ft. 6 in. by 118 ft. 9 in., and holds
' "The Municipal Water Purification Plant at Grand Rapida, Mich." Eng.
Record, vgl. 64, p. 379, 1911.
72
WATER PURIFICATION
1,134,000 gal. of water, which is about 1 hr. and 22 min. supply
at the normal rating of 20,000,000 gal. per day. The larger basin
is 118 ft. 6 in. by 118 ft. 9 in., and holds 1,452,000 gal., or about
1 hr. and 44 min. supply at the normal rating. The basins may
be operated in series or in parallel.
Mr. J. W. Armstrong in describing this plant notes that in
basins having but few baffles, that there is a tendency for the
Drmfty
R
CmrMuuBoam
f\
I
"It
»C5f
\--4oh^
■\
lAi.
^GrrfCAomh0r
T
^ .vaob^-.. J
PUn of Works.
Pio. 13. — Grand Rapids water purification plant, general plan.
water to short-circuit, and for the floe to settle out unevenly in
different parts of the reservoir. In order to overcome this diffi-
culty and to maintain a more even distribution of the floe, the
baffles in these basins are placed closer than usual, being 15 ft.
apart on centers.
CLEANING SETTLING AND COAGULATION BASINS
The method of removing the sediment deposited in settling and
coagulation basins should always receive careful consideration in
'^ign. Where large amounts of sediment must be removed,
RESERVOIRS AND COAGULATION BASINS 73
adequate means for handling the accumulated mud are necessary
in order not to keep a basin out of service for too long a period.
In small plants the time factor is not of so much importance,
although even here great inconvenience may arise from limited
facilities for handling the accumulated sediment. Basins ought
always to be in duplicate, in order that one at a time may be with-
drawn from service for cleaning. Where the sediment accumu-
lates rapidly, frequent cleaning appears preferable to allowing a
large amount to acciunulate, which would require a considerable
time to remove.
Concrete or concrete- and brick-lined basins form the best sur-
faces from which to wash off the mud. Drains should be of
ample size, and there should be a good slope toward them. The
general method of cleaning employed will depend on the slope of
the sides and bottom toward the siunps, and on the distance the
mud must be moved. Where the deposit is washed out by
streams of water under pressure, the author has found that slopes
of less than 1 in 20 greatly retarded the process of cleaning. One
and 2 per cent, grades are not enough when cleaning by this
method. On such grades the semi-fluid deposit has to be re-
peatedly pushed forward toward the sumps, thereby losing much
time and requiring large volumes of water.
Where scraping is employed to assist the flushing with water,
the latter need not be under much pressure, but a considerable
voliune of water is needed to give a semi-fluid consistency to the
mud. At the St. Louis plant horse-drawn scrapers are employed
made from 2-in plank 10 in. wide and 12 ft. long. Men follow
the teams with hand scrapers, cleaning the bottom as they go and
arranging gutters so as to confine the flushing water used to a
narrow strip nearest the teams and to prevent its being wasted
over the cleaned bottom.
The St. Louis basins have a comparatively flat bottom with a
gutter running through the center. This gutter runs lengthwise
of the basin and has a 1 per cent, slope to the sewer into which it
discharges. No trouble is experienced in moving the mud along
the gutter. More difficulty is encountered with the heavy silt
and sand which settles near the inlets, and which requires teaming
and much water to move.
It has been the experience of the author that sand and silt
deposits are easily moved on 8 and 10 per cent, slopes, provided
the deposit is first disintegrated by a stream of water under a
WATER PURIFICATION
e of 70 to 75 lb. per square inch. The mud banks in such
cases need not be entirely liquefied; but if they are undermined
by a stream of water (Figs. 14 and 15) from a nozzle 1 in. or even
Fia. 14. — Cleaning CincinnBti settling
Fia. 15. — Cleaning Cincinnati settling
% in. in diameter and under the above-mentioned pressure, they
can be readily floated away to the sump. On the other hand,
the gelatinous clay deposits usually have to be well liquefied be-
fore they can be moved, although on slopes of 10 or 12 per cent.
RESERVOIRS AND COAGULATION BASINS 75
the mud can be floated to the sump in larger pieces than when the
grades are less. These observations apply particularly to the
kind of silt and clay carried by the water of the Ohio River, and
to handling large amounts of sediment in large settling reservoirs.
Nevertheless, they are believed to be generally true, although
the original character of the sediment must necessarily influence
the general properties of the deposit. In coagulation basins the
applied chemicals or the products of the reactions, such as hy-
drates of iron, almninum, magnesium, and carbonate of lime,
must of necessity modify the nature of the deposit.
Cost of Cleaning Settling and Coagulation Basins. — The cost
of cleaning basins will necessarily vary with the kind and amount
of deposit to be removed. This has been found to be the case
both at St. Louis and at Cincinnati. At St. Louis the cost seems
more dependent on the amount of sand in the deposit than in
the amount to be moved. The following table compiled from
the records of the Cincinnati Water Department shows the cost
of cleaning one of its large plain sedimentation reservoirs.
ToUl coat
Eatimated cost
per cubic yard of
sediment
removed
Labor $1,100.45
Supplies 440.23
Power j 154. 44
Value of water used in cleaning 62 . 82
Value of water wasted in draining 183. 13
Total $1,941.07
$0.0267
0.0107
0.0037
0.0015
0.0044
$0.0470
N.B. The cost of cleaning per million gallons of water settled was $0,056-
The cost of cleaning settling basins at St. Louis, Mo., in
which coagulated sediment is precipitated is shown by the fol-
lowing table compiled from the annual reports of the Water
Commissioner.
Cost op Cleaning Chain op Rocks' Basins
1908
1900
1910
1911
Cubic yards sediment
removed
Total cost
Cost per cubic yard . . .
135,108 I 129,035 182,500 I 144,200
$2,631.85 I $2,947.26 $3,159.11 | $2,158.39
$0.0195, $0.0228 $0.0173 $0.0150
76 WATER PURIFICATION
The costs given for cleaning the Chain of Rocks' basins are
for labor and teams, for furnishing and keeping in repair all tools,
boots, etc., used in cleaning, and for moving such apparatus to
and from the basins before and after cleaning. It does not in-
clude the cost of the water lost by draining or used in cleaning
the basins.
In April, 1908, 700 cu. yd. of mud were removed from the
Baden storage reservoir at St. Louis, at a cost of $149, or $0,213
per cubic yard. The basins at Bissell's Point were cleaned in
August of the same year at a cost of $0,133.
Cost op Cleaning Cincinnati Coaqulation Basins in 1911
Labor $89.67
Power 24. 75
Value of water lost in draining and used in cleaning. 76.52
$190.94
N.B. Cost per cubic yard of mud estimated to have been removed,
$0,024.
For cleaning these basins twice in 1910, when 15,600 cu. yd. of
mud were estimated to have been removed, the total cost was
found to be $468, or a cost of $0.03 per cubic yard. If the value
of the water lost in draining, and that used in cleaning is deducted
from this total cost, the cost per cubic yard is practically one-
half that given above or $0,015. This latter figure is the one to
be compared with those costs obtained in cleaning the Chain of
Rocks' basins in St. Louis, since there no charge for the value of
the water lost by draining or that used in cleaning is included.
The cost of cleaning reservoirs, passages, and chambers of the
Carrollton plant of the New Orleans water purification plant is
of interest, on account of the completeness of the detailed list of
cost items. The following table is taken from the Report of the
Sewerage and Water Board for the year 1911:
Total amount of wet mud removed from reservoirs 45,000 cu. yd.
Total amount of dry material removed from reservoirs 18,000 cu. yd.
Total amount of water treated during year 5,274 M. gal.
Total amount of filtered water required, 4 M. gal., value.. . $62.40
Total amount of treated water used and wasted, 17 M. gal.,
value 174.59
Total amount of raw water used and wasted, 12 M. gal.,
value 47 . 62
Total amount of labor required, value 302 . 05
RESERVOIRS AND COAGULATION BASINS 77
Cost of labor for cleaning per million gallons water treated. 0. 053
Cost of water for cleaning per million gallons water treated. 0. 049
$0,102
Total estimated cost of cleaning per cubic yard of dry
material removed 0. 033
Value of raw water taken at $3.96 per million gallons.
Value of treated water taken at $10.27 per million gallons.
Value of filtered water taken at $15.55 per million gallons.
The cost of cleaning based on the wet mud removed is S0.013
per cubic yard, and is comparable with the figures given for clean-
ing the Chain of Rocks, basins at St. Louis or the coagulation
basins at Cincinnati.
Cost of Clearing Water by Settling. — Mr. S. Bent Russell in a
paper^ discussing the cost of clearing water by sedimentation in
reservoirs gives some interesting data on the costs obtained at St.
Louis in operating the BisselFs Point basins between 1881 and
1894. These basins were operated as plain sedimentation basins
on the intermittent-flow plan. The head lost by this method of
operation was 14 ft., and the cost of the increased lift is figured
in the following table as one of the six items of cost chargeable
against the clarification of the water.
Analysis of Cost op Sedimentation in Bissell's Point Basins at St.
Louis, Mo., between 1881 and 1894.
Itema
Coat per million
gsUona settled
1. Interest
2. Depreciation.
3. Repairs
4. Operating —
5. Cleaning
6. Increased lift
Total
$2,820
0.790
0.054
0.281
0.198
0.329
$4,472
Cost per year in per
cent, of first cost
5.000
1.400
0.068
0.340
0.230
0.585
7.623
Mr. Russell concludes that:
"The cost of clearing is dependent upon the quantity of water handled
and the proportion of sediment removed. The area or dimensions of
the floors will influence the cost. The inclination of floor and drains,
etc., are important factors, and the character of the sediment must be
considered. This item is of some importance, where there is much
> Eng. Record, vol. 60, Oct. 16, 1909.
78 WATER PURIFICATION
sediment, and to keep the cost within proper limits we are justified in
adding considerably to the first cost of the plant."
The cost of plain sedimentation, as shown by the operation
costs of the Cincinnati, Ohio, settling reservoirs, was S0.20 per mil-
lion gallons of water settled in both 1909 and 1910; in 1911 the
cost was S0.19, and in 1912 $0.42 per million gallons of water
settled. These costs do not include fixed charges, but are the
entire cost of operating and maintaining the reservoirs and the
grounds about them which are quite extensive. They include
in the years 1909 and in 1912, respectively, the cost of cleaning
one reservoir. Probably on an average 50 per cent, of the fore-
going costs at Cincinnati are chargeable to the upkeep of grounds
about the reservoirs, and should not properly be made a part of
the cost of sedimentation.
In 1912 labor costs were greater than in 1909, and this to-
gether with certain changes made in drainage valves during the
cleaning of the reservoir in that year accounts in part for the
increased cost. The cost of upkeep of the grounds about the re-
servoirs in 1912 was over 40 per cent, of the total.
First Cost of Settling Reservoirs. — The first cost of construct-
ing settling reservoirs naturally varies with their size, manner of
construction and the general topography of the locality. Reser-
voirs formed by the damming of a valley and having the land to
be flowed stripped of its surface soil, have been found to cost
from $135 to $600 per million gallons of capacity. Reservoirs
formed by an earth embankment damming a natural ravine, and
lined with concrete and brick, like those at Cincinnati, cost nearly
$4,000 per million gallons of capacity; while the coagulation
basins built principally in embankment and lined with concrete
and brick cost nearly $14,000 per million gallons of their hold-
ing capacity. On the other hand, masonry-walled basins like
those at St. Louis cost from $6,000 to $6,500 per million gaUons
capacity.
The cost of the coagulation basins of the Toledo, Ohio, water
purification plant was $2,500 per million gallons of the daily
rated capacity of the plant. The coagulation basins of the Cin-
cinnati plant mentioned above when estimated in a similar man-
ner cost about $2,700 per million gallons of daily capacity. The
settling basins of the Columbus, Ohio, purification plant cost
$5,630 per million gallons of daily capacity, while the large mix-
ing tanks cost $1,470 per million gallons of daily capacity.
RESERVOIRS AND COAGULATION BASINS 79
These figures are given merely to show ranges of cost rather
than to make any comparisons, since the local topographical
conditions, general type of plant and style of construction are so
varied that a strict comparison of costs is improper and may be
misleading.
References
1. F. B. Leopold: "The Water Filtration Works at Anderson, Ind."
Eng. Recordy vol. 51, p. 125, 1905.
2. "The Revised Plans for the Purification of the Pittsburgh Water
Supply." Eng. Record, vol. 51, p. 133, 1905.
3. "A Concrete Settling Reservoir at McKeesport, Pa." Eng, Record,
vol. 51, p. 597, 1905.
4. "The Water Filtering and Softening Works at Columbus, Ohio."
Eng. Record, vol. 53, p. 202, 1906.
5. J. H. Gregory: "The Improved Water and Sewage Works at Colum-
bus, Ohio." Discussion of paper in Proc. Amer. Soc. C. E., vol. 36,
No. 3, 1910.
6. "The Water Filtration Plant at Moline, HI." Eng. Record, vol. 55,
p. 705, 1907.
7. "The New Settling Basins and Other Improvements to the St. Louis,
Mo., Water Supply System." Eng. Record, vol. 56, p. 13, 1907.
8. "Water Filtration Plant at Sandusky, Ohio." Eng. Record, vol. 60,
p. 431, 1909.
9. "Sedimentation Basin Cleaning at Poughkeepsie, N. Y." Eng. Record,
vol. 63, p. 329, 1911.
10. "The Use of Coagulants with Slow Sand Filtration." Eng. Record,
vol. 64, p. 476, 1911.
11. S. Bent RusseIll: "The Cost of Clearing Water by Sedimentation."
Eng. Record, vol. 60, Oct. 16, 1909.
12. "New Reinforced Concrete Reservoir at Council Bluffs, la." Er^f.
Record, vol. 67, p. 39, 1913,
13. Annual reports of the Water Departments of New Orleans, La., Louis-
ville, Ky., St. Louis, Mo., and Cincinnati, Ohio, for the years 1911
and 1912.
CHAPTER VIII
PRACTICAL EFFICIENCIES OF SETTLING AND COAGU-
LATION BASINS
The practical efficiency of settling basins in the removal of
sediment from turbid waters is variable, and depends upon a
number of factors which have been discussed in the preceding
two chapters. The manner in which the basins are operated,
either as a result of unintelligent methods of handling, or because
of the demands upon the plant which the operator must meet,
are conditions contributing to their inefficiency. How great a
percentage of the sediment is removed in the different types of
basins is best illustrated by actual examples.
The very finely divided clay sediment in the Allegheny River
at Pittsburgh, Pa., is difficult to settle out. The sedimentation
basins hold approximately 120,000,000 gal. of water. On the
basis of 90,000,000 gal. daily consmnption there is a theoretical
storage of 32 hr. It has been concluded, however, that the water
frequently passes through the basins in as short a time as 11 or
12 hr. The following table compiled from the 1910 report of
the Bureau of Water of Pittsburgh indicated a yearly average
removal of but 28.2 per cent., and ranged from zero to nearly 49
per cent.
At Cincinnati, Ohio, the sediment in the Ohio River water is
possibly somewhat more easily removed by settling. In the set-
tling reservoirs there is provided a considerably longer period of
storage, than at Pittsburgh, which probably accounts for the
larger percentage of sediment removed.
In the Cincinnati reservoirs there is a theoretical storage for
6.6 days if based on a consumption of 50,000,000 gal. per day and
an available storage capacity of 330,000,000 gal. From obser-
vations made it has been concluded that the water actually
passes through these basins in as short a time as 40 to 48 hr. The
relative positions of the inlets and outlets in these reservoirs,
as previously described, obviously make complete displacement
impossible.
80
SETTLING AND COAGULATION BASINS
81
Turbidity or Allegheny River Water at Ross Pumping Station and
OF Water after Settling
Averages of 2-hr. readings in 1910-1911
River water
Settled water
Year.
1910
Average
Maxi-
mum
Mini-
mum
Average
February . .
March ....
April
May
June
July
August —
September
October . . .
November
December .
1911
January . . .
Average
38
65
44
24
27
17
18
50
19
35
54
78
388
366
300
53
147
27
29
158
56
105
833
328
7
14
18
10
13
8
12
6
9
13
8
16
39
22
58
29
18
21
15
17
40
20
29
28
40
28
Maxi-
mum
Mini-
mum
Percent-
reduc-
tion
110
8
42.1
200
14
10.8
110
11
34.1
38
8
25.0
110
10
22.3
25
8
11.7
23
12
5.5
140
6
20.0
80
11
60
13
17.1
270
7
48.1
100
16
48.7
28.2
Average Percentage Removal of Sediment by Plain Sedimentation
in Cincinnati Settling Reservoirs
Average turbidity
Percentage removal
Month
River water
1911 I
Settled water
1912
1911
1912
January. . .
February . .
March
April
May
June
July
August . . . .
September
October . . ,
November
December.
Average
6
240
190
140
160
55
76
50
64
410
257
148
128
159
Parts per million
122
226
360
291
202
100
712
385
328
60
76
87
245
1911
1912
85
54
105
83
62
190
57
105
18
97
24
20
24
190
27
170
119
140
102
13
40
16
36
25
58
92
1
64.6
55.7
44.7
63.2
55.7
47.5
64.4
64.0
67.3
52.1
68.4
79.9
52.0
73.4
57.8 1
55.8
71.0 1
57.3
60.3
78.3
73.0
79.0
71.9
71.3
63.5 ,
62.5
82 WATER PURIFICATION
At the New Orleans purification plant the turbid Mississippi
River water is pumped directly into so-called grit reservoirs, and
flows from the latter into mixing channels, where the water re-
ceives the lime and such small amounts of coagulant as are used
at this plant. It then flows to the settling basins, and from
thence to the filters. The following table taken from the 1911
report of the Sewerage and Water Board of New Orleans indi-
cates the reduction in turbidity effected at various stages of the
process.
Turbidities of Mississippi River Water and £>fluentb of Grit Reser-
voirs AND COAQULATION RESERVOIRS AT NeW ORLEANS
Purification Plant
River wmter Efflaent grit r«.
1909 1910 1911 1909 1910 1911
EflBaent come*
rei.
1909 » 1910 !
1
1911
Parts per million
Maximum . . .
Minimum . . .
Average
1,600 1,700 1,400 1,550 1,450, 1,250
80 55 150 75 55 130'
525 550 500 475 450 425.
' 1
340 1 525
1 2
44 ; 32
280
5
32
It will be noted that the reduction in the turbidity of the river
water after passing through the grit reservoirs ranges from 8 to
18 per cent, on an average, while the reduction after passage
through the coagulation reservoirs averages over 90 per cent.
In all probability the grit reservoirs really remove considerably
more sediment by actual weight than is indicated by the turbid-
ity readings. They are to be regarded as settling chambers for
the removal of the coarse silt and sand only, and not for deposit-
ing the finer clay particles.
The purification plant at St. Louis, Mo., offers some interest-
ing data on the removal of sediment by co
…[truncated]