Transcriber’s Notes:
The spelling, hyphenation, punctuation and accentuation are as the
original, except for apparent typographical errors which have been
corrected.
Italic text is denoted _thus_.
Bold text is denoted =thus=.
See further notes at the end of the book.
[Illustration: GENERAL VIEW OF FILTERS AT HAMBURG.
[_Frontispiece._]
]
THE FILTRATION
OF
PUBLIC WATER-SUPPLIES.
BY
ALLEN HAZEN,
MEMBER OF THE AMERICAN SOCIETY OF CIVIL ENGINEERS, THE BOSTON SOCIETY
OF CIVIL ENGINEERS, THE AMERICAN WATER-WORKS ASSOCIATION, THE NEW
ENGLAND WATER-WORKS ASSOCIATION, THE AMERICAN CHEMICAL SOCIETY, THE
AMERICAN PUBLIC HEALTH ASSOCIATION, ETC.
_THIRD EDITION, REVISED AND ENLARGED._
SECOND THOUSAND.
NEW YORK:
JOHN WILEY & SONS.
LONDON: CHAPMAN & HALL, LIMITED.
1905.
Copyright, 1900,
BY
ALLEN HAZEN.
ROBERT DRUMMOND, ELECTROTYPER AND PRINTER, NEW YORK.
PREFACE TO FIRST EDITION.
The subject of water-filtration is commencing to receive a great deal
of attention in the United States. The more densely populated European
countries were forced to adopt filtration many years ago, to prevent
the evils arising from the unavoidable contaminations of the rivers
and lakes which were the only available sources for their public
water-supplies; and it has been found to answer its purpose so well
that at the present time cities in Europe nearly if not quite equal in
population to all the cities of the United States are supplied with
filtered water.
Many years ago, when the whole subject of water-supply was still
comparatively new in this country, filtration was considered as a means
for rendering the waters of our rivers suitable for the purpose of
domestic water-supply. St. Louis investigated this subject in 1866,
and the engineer of the St. Louis Water Board, the late Mr. J. P.
Kirkwood, made an investigation and report upon European methods of
filtration which was published in 1869, and was such a model of full
and accurate statement combined with clearly-drawn conclusions that, up
to the present time, it has remained the only treatise upon the subject
in English, notwithstanding the great advances which have been made,
particularly in the last ten years, with the aid of knowledge of the
bacteria and the germs of certain diseases in water.
Unfortunately the interest in the subject was not maintained in
America, but was allowed to lag for many years; it was cheaper to use
the water in its raw state than it was to purify it; the people became
indifferent to the danger of such use, and the disastrous epidemics
of cholera and typhoid fever, as well as of minor diseases, which so
often resulted from the use of polluted water, were attributed to other
causes. With increasing study and diffusion of knowledge the relations
of water and disease are becoming better known, and the present state
of things will not be allowed to continue; indeed at present there is
inquiry at every hand as to the methods of improving waters.
The one unfortunate feature is the question of cost. Not that the cost
of filtration is excessive or beyond the means of American communities;
in point of fact, exactly the reverse is the case; but we have been so
long accustomed to obtain drinking-water without expense other than
pumping that any cost tending to improved quality seems excessive, thus
affording a chance for the installation of inferior filters, which by
failing to produce the promised results tend to bring the whole process
into disrepute, since few people can distinguish between an adequate
filtration and a poor substitute for it. It is undoubtedly true that
improvements are made, and will continue to be made, in processes of
filtration; so it will often be possible to reduce the expense of the
process without decreasing the efficiency, but great care must be
exercised in such cases to maintain the conditions really essential to
success.
In the present volume I have endeavored to explain briefly the nature
of filtration and the conditions which, in half a century of European
practice, have been found essential for successful practice, with a
view of stimulating interest in the subject, and of preventing the
unfortunate and disappointing results which so easily result from the
construction of inferior filters. The economies which may possibly
result by the use of an inferior filtration are comparatively small,
and it is believed that in those American cities where filtration is
necessary or desirable it will be found best in every case to furnish
filters of the best construction, fully able to do what is required of
them with ease and certainty.
PREFACE TO THIRD EDITION.
There have been several distinct epochs in the development of water
purification in the United States. The first may be said to date
from Kirkwood’s report on the “Filtration of River Waters,” and the
second from the inauguration of the Lawrence Experiment Station by
the Massachusetts State Board of Health, and the construction of
the Lawrence city filter, with the demonstration of the wonderful
biological action of filters upon highly polluted waters.
The third epoch is marked by the experiments at Louisville, Pittsburg
and Cincinnati, which have greatly increased our knowledge of the
treatment of waters containing enormous quantities of suspended matter,
and have reduced to something like order the previously existing
confused mass of data regarding coagulation and rapid filtration.
The first edition of this book represented the earlier epochs
before the opening of the third. In the five years since it was
written, progress in the art of water purification has been rapid
and substantial. No apology is needed for the very complete revision
required to treat these newly investigated subjects as fully as were
other matters in the earlier editions.
In the present edition the first seven chapters remain with but few
additions. Experience has strengthened the propositions contained
in them. New data might have been added, but in few cases would the
conclusions have been altered. The remaining chapters of the book have
been entirely rewritten and enlarged to represent the added information
now available, so that the present edition is nearly twice as large as
the earlier ones. In the appendices, also, much matter has been added
relating to works in operation, particularly to those in America.
NEW YORK January, 1900.
CONTENTS.
PAGE
Chapter I. INTRODUCTION. 1
II. CONTINUOUS FILTERS AND THEIR CONSTRUCTION 5
Sedimentation-basins 8
Size of Filter-beds 10
Form of Filter-beds 11
Covers for Filters 12
III. FILTERING-MATERIALS 20
Sand 20
Sands Used in European Filters 24
Effect of Size of Grain Upon Efficiency of Filtration 30
Effect of Grain Size Upon Frequency of Scraping 32
Selection of Sand 33
Thickness of the Sand Layer 34
Underdraining 35
Gravel Layers 35
Underdrains 39
Depth of Water on Filters 45
IV. RATE OF FILTRATION AND LOSS OF HEAD 47
Effect of Rate Upon Cost of Filtration 48
Effect of Rate Upon Efficiency of Filtration 50
The Loss of Head 52
Regulation of the Rate and Loss of Head in the
Older Filters 52
Apparatus For Regulating the Rate and Loss of Head 55
Apparatus For Regulating the Rate Directly 57
Apparatus For Regulating the Height of Water Upon
Filters 59
Limit to the Loss of Head 60
V. CLEANING FILTERS 68
Frequency of Scraping 72
Quantity of Sand to Be Removed 74
Wasting the Effluents After Scraping 74
Sand-washing 76
VI. THEORY AND EFFICIENCY OF FILTRATION 83
Bacterial Examination of Waters 93
VII. INTERMITTENT FILTRATION 97
The Lawrence Filter 100
Chemnitz Water-Works 107
Application of Intermittent Filtration 111
VIII. TURBIDITY AND COLOR, AND THE EFFECT OF MUD UPON
SAND FILTERS 113
The Measurement of Color 114
Amount of Color in American Waters 115
Removal of Color 117
Measurement of Turbidity 117
Relation of Platinum-wire Turbidities to Suspended
Matters 122
Source of Turbidity 123
The Amounts of Suspended Matters in Water 129
Preliminary Processes to remove Mud 133
Effect of Mud upon Sand Filters 137
Effect of Turbidity Upon the Length of Period 137
Power of Sand Filters to Produce Clear Effluents
from Muddy Water 139
Effect of Mud Upon Bacterial Efficiency of Filters 141
Limits to the Use of Subsidence for the Preliminary
Treatment of Muddy Waters 142
IX. COAGULATION OF WATERS 144
Substances used for Coagulation 145
Coagulants Which Have Been Used 150
Amount of Coagulant required to remove Turbidity 150
Amount of Coagulant required to remove Color 153
Successive Applications of Coagulant 154
The Amount of Coagulant which Various Waters will
receive 155
X. MECHANICAL FILTERS 159
Providence Experiments 159
Louisville_Experiments 161
Lorain Tests 161
Pittsburg Experiments 162
Wasting Effluent After Washing Filters 163
Influence of Amount of Sulphate of Alumina on
Bacterial Efficiency of Mechanical Filters 165
Influence of Degree of Turbidity upon Bacterial
Efficiency of Mechanical Filters 167
Average Results Obtained with Various Quantities of
Sulphate of Alumina 171
Types of Mechanical Filters 172
Efficiency of Mechanical Filters 179
Pressure Filters 180
XI. OTHER METHODS OF FILTRATION 181
Worms Tile System 181
The Use of Asbestos 181
Filters Using High Rates of Filtration Without
Coagulants 182
Household Filters 183
XII. REMOVAL OF IRON FROM GROUND-WATERS 186
Amount of Iron Required to Render Water Objectionable 186
Cause of Iron in Ground-waters 187
Treatment of Iron-containing Waters 189
Iron-removal Plants in Operation 192
XIII. TREATMENT OF WATERS 197
Cost of Filtration 200
What Waters Require Filtration 207
XIV. WATER-SUPPLY AND DISEASE—CONCLUSIONS 210
Appendix I. RULES OF THE GERMAN GOVERNMENT IN REGARD TO THE
FILTRATION OF SURFACE-WATERS USED FOR PUBLIC
WATER-SUPPLIES 221
II. EXTRACTS FROM “BERICHT DES MEDICINAL-INSPECTORATS
DES HAMBURGISCHEN STAATES FÜR DAS JAHR 1892” 226
III. METHODS OF SAND-ANALYSIS 233
IV. FILTER STATISTICS 241
Statistics of Operation of Sand Filters 241
Partial List of Cities Using Sand Filters 244
List of Cities and Towns Using Mechanical Filters 247
Notes Regarding Sand Filters in the United States 251
Capacity of Filters 254
V. LONDON’S WATER-SUPPLY 255
VI. THE BERLIN WATER-WORKS 261
VII. ALTONA WATER-WORKS 265
VIII. HAMBURG WATER-WORKS 269
IX. NOTES ON SOME OTHER EUROPEAN WATER-SUPPLIES 272
The Use of Unfiltered Surface-waters. 275
The Use of Ground-water. 276
X. LITERATURE OF FILTRATION 277
XI. THE ALBANY WATER-FILTRATION PLANT 288
Description of Plant. 289
Capacity of Plant and Means of Regulation. 308
Results of Operation. 314
Cost of Construction. 314
INDEX 317
UNITS EMPLOYED.
The units used in this work are uniformly those in common use in
America, with the single exception of data in regard to sand-grain
sizes, which are given in millimeters. The American units were not
selected because the author prefers them or considers them particularly
well suited to filtration, but because he feared that the use of the
more convenient metric units in which the very comprehensive records
of Continental filter plants are kept would add to the difficulty of
a clear comprehension of the subject by those not familiar with those
units, and so in a measure defeat the object of the book.
TABLE OF EQUIVALENTS.
Unit. Metric Equivalent. Reciprocal.
Foot 0.3048 meter 3.2808
Mile 1609.34 meters 0.0006214
Acre 4047 square meters 0.0002471
Gallon[1] 3.785 liters 0.26417
1 million gallons 3785 cubic meters 0.00026417
Cubic yard 0.7645 cubic meters 1.308
1 million gallons per } { meter in depth }
acre daily } 0.9354 { of water daily } 1.070
ACKNOWLEDGMENT.
I wish to acknowledge my deep obligation to the large number of
European engineers, directors, and superintendents of water-works, and
to the health officers, chemists, bacteriologists, and other officials
who have kindly aided me in studying the filtration-works in their
respective cities, and who have repeatedly furnished me with valuable
information, statistics, plans, and reports.
To mention all of them would be impossible, but I wish particularly to
mention Major-General Scott, Water-examiner of London; Mr. Mansergh,
Member of the Royal Commission on the Water-supply of the Metropolis;
Mr. Bryan, Engineer of the East London Water Company; and Mr. Wilson,
Manager of the Middlesborough Water-works, who have favored me with
much valuable information.
In Holland and Belgium I am under special obligations to Messrs. Van
Hasselt and Kemna, Directors of the water companies at Amsterdam and
Antwerp respectively; to Director Stang of the Hague Water-works; to
Dr. Van’t Hoff, Superintendent of the Rotterdam filters; and to my
friend H. P. N. Halbertsma, who, as consulting engineer, has built many
of the Dutch water-works.
In Germany I must mention Profs. Frühling, at Dresden, and Flügge, at
Breslau; Andreas Meyer, City Engineer of Hamburg; and the Directors of
water-works, Beer at Berlin, Dieckmann at Magdeburg, Nau at Chemnitz,
and Jockmann at Liegnitz, as well as the Superintendent Engineers
Schroeder at Hamburg, Debusmann at Breslau, and Anklamm and Piefke at
Berlin, the latter the distinguished head of the Stralau works, the
first and most widely known upon the Continent of Europe.
I have to acknowledge my obligation to City Engineer Sechner at
Budapest, and to the Assistant Engineer in charge of water-works,
Kajlinger; to City Engineer Peters and City Chemist Bertschinger at
Zürich; and to Assistant Engineer Regnard of the Compagnie Générale des
Eaux at Paris.
On this side of the Atlantic also I am indebted to Hiram F. Mills,
C.E., under whose direction I had the privilege of conducting
for nearly five years the Lawrence experiments on filtration; to
Profs. Sedgwick and Drown for the numerous suggestions and friendly
criticisms, and to the latter for kindly reading the proof of this
volume; to Mr. G. W. Fuller for full information in regard to the
more recent Lawrence results; to Mr. H. W. Clark for the laborious
examination of the large number of samples of sands used in actual
filters and mentioned in this volume; and to Mr. Desmond FitzGerald
for unpublished information in regard to the results of his valuable
experiments on filtration at the Chestnut Hill Reservoir, Boston.
ALLEN HAZEN.
BOSTON, April, 1895.
FILTRATION OF PUBLIC WATER-SUPPLIES.
CHAPTER I.
INTRODUCTION.
The rapid and enormous development and extension of water-works in
every civilized country during the past forty years is a matter which
deserves our most careful consideration, as there is hardly a subject
which more directly affects the health and happiness of almost every
single inhabitant of all cities and large towns.
Considering the modern methods of communication, and the free exchange
of ideas between nations, 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
supplies 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 liquid has too often been the objective point,
and the efforts have been most successful, the American works being
entirely unrivalled in the volumes of their supplies. I do not wish
to imply that quality has been entirely neglected in our country, for
many cities and towns have seriously and successfully studied their
problems, with the result that there are hundreds of water-supplies
in the United States which will compare favorably upon any basis with
supplies in any part of the world; but on the other hand it is equally
true that there are hundreds of other cities, including some among
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.
One can travel through England, Belgium, Holland, Germany, and large
portions of other European countries and drink the water at every city
visited without anxiety as to its effect upon his health. It has not
always been so. Formerly European capitals drank water no better than
that so often dispensed now in America. As recently as 1892 Germany’s
great commercial centre, Hamburg, having a water-supply essentially
like those of Philadelphia, Pittsburg, Cincinnati, St. Louis, New
Orleans, and a hundred other American cities, paid a penalty in one
month of eight thousand lives for its carelessness. The lesson was a
dear one, but it was not wasted. Hamburg now has a new and wholesome
supply, and other German cities the qualities of whose waters were open
to question have been forced to take active measures to better their
conditions. We also can learn something from their experience.
There are three principal methods of securing a good water-supply for a
large city. The first consists of damming a stream from an uninhabited
or but sparsely inhabited watershed, thus forming an impounding
reservoir. This method is extensively used in England and in the United
States. In the latter most of the really good and large supplies are so
obtained. It is only applicable to places having suitable watersheds
within a reasonable distance, and there are large regions where, owing
to geological and other conditions, it cannot be applied. It is most
useful in hilly and poor farming countries, as in parts of England and
Wales, in the Atlantic States, and in California. It cannot be used to
any considerable extent in level and fertile countries which are sure
to be or to become densely populated, as is the case with large parts
of France and Germany and in the Middle States.
The second method is to secure ground-water, that is, spring or well
water, which by its passage through the ground has become thoroughly
purified from any impurities which it may have contained. This was the
earliest and is the most widely used method of securing good water.
It is specially adapted to small supplies. Under favorable geological
conditions very large supplies have been obtained in this manner. In
Europe Paris, Vienna, Budapest, Munich, Cologne, Leipzig, Dresden, a
part of London, and very many smaller places are so supplied. This
method is also extensively used in the United States for small and
medium-sized places, and deserves to be most carefully studied, and
used whenever possible, but is unfortunately limited by geological
conditions and cannot be used except in a fraction of the cases where
supplies are required. No ground-water supplies yet developed in the
United States are comparable in size to those used in Europe.
The third process of securing a good water-supply is by means of
filtration of surface waters which would otherwise be unsuitable for
domestic purposes. The methods of filtration, which it is the purpose
of this volume to explain, are beyond the experimental stage; they
are now applied to the purification of the water-supplies of European
cities with an aggregate population of at least 20,000,000 people. In
the United States the use of filters is much less common, and most of
the filters in use are of comparatively recent installation.
Great interest has been shown in the subject during the last few
years, and the peculiar character of some American waters, which differ
widely in their properties from those of many European streams, has
received careful and exhaustive consideration. In Europe filtration has
been practised with continually improving methods since 1829, and the
process has steadily received wider and wider application. It has been
most searchingly investigated in its hygienic relations, and has been
repeatedly found to be a most valuable aid in reducing mortality. The
conditions under which satisfactory results can be obtained are now
tolerably well known, so that filters can be built in the United States
with the utmost confidence that the result will not be disappointing.
The cost of filtration, although considerable, is not so great as to
put it beyond the reach of American cities. It may be roughly estimated
that the cost of filtration, with all necessary interest and sinking
funds, will add 10 per cent to the average cost of water as at present
supplied.
It may be confidently expected that when the facts are better
understood and realized by the American public, we shall abandon the
present filthy and unhealthy habit of drinking polluted river and
lake waters, and shall put the quality as well as the quantity of our
supplies upon a level not exceeded by those of any country.