The filtration of public water-supplies / Third edition, revised and enlarged.

by Allen Hazen

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 MuddyWaters	[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 ofMechanical 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 ofSurface-waters Used For Public Water-supplies	[221]
II.	Extracts from “Bericht Des Medicinal-inspectorats Des HamburgischenStaates 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 acre daily	0.9354	meter in depth 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.