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.