PREFACE TO THE ENGLISH TRANSLATION SINCE the recognition of their significance in the promotion of the public health, methods of water purification and sewage disposal have earned a steadily increasing importance. Consequently, these branches of industry have enjoyed the most zealous attention of the scientist and of the engineer. I have endeavoured in the present monograph to give a survey, short perhaps, but as complete as possible, of the present position in regard to Water Purification and Sewage Disposal. Owing to the wide range of this subject . particular processes could only be treated shortly in the space at disposal. One chapter, which is very fully treated in the present volume, though slightly elsewhere, is the disposal of industrial sewage. Many of the processes of purification are of quite recent date, and fresh experience is being obtained daily and reported upon in the most diverse publications. I have endeavoured to collect such information. In the translation some small changes and additions have been made in the chapters on sand filtration, the removal of manganese, and Travis and Emscher wells. The extensive literature supplied in the German original, which served as the basis in the composition of the book, has not been printed in the English translation, as it treats in the main of German literature. October, 1912 as, the author points out, is thc classic country for sewage disposal. As a consequence, the translation of a book on the subject of water purification and sewage disposal from the German point of view, might at first sight seem unnecessary. It is to be hoped, however, that a study of the present volume will prove that view to be incorrect. The carefulattention which has been paid by the German authorities during the past few decades to the provision of suitable water supplies and the adequate disposal of sewage, renders the present critical survey of modern methods at once interesting and useful to the English reader. Especially should this be true of the chapter on the disposal of industrial sewage. I have to express my thanks to the author, Dr. Tillmans, for a revision of the present text, and to Messrs. Hubers and Mond. I desire also to record my indebtedness to my friends Mr. J. W. Yates, MSc., and Mr. A. Shacklady, B. Sc., for valuable guidance and assistance in the correction of the proofs. HUGH S. TAYLOR. LIVERPOOL, October, 191 2. TABLE OF CONTENTS WATER PURIFICATION. GROUND-WATER, SPRING-WATER, SURFACE-WATER. PAGE . l. Purijication o f W tzfefro r Dri zkiq Puq5oses . . 2 Bacteria and disease germs in water ., . . . 2 i Filtration Processes . 4 a Slow sand filtration . . . . . . Preparation, composition, and workink of the filter. . Uniformity of the sand, filtration pressure, covered and uncovered filters . . . . . . . . Washing and renewal of the sand . . . . . Filter film, filtration pressure, Frankel and Pielkes fundamental investigations, double filtraiio., according to Gotze, and preliminary filtration, PuechXhabal system . . . . . . . . Cost control by estimation of the germ-content . . . b Percolating sand filters . . . . c Mechanical filters . Nature and control of the mechanical filter, old and new l systems. . . . . . . . The Jewell Export Mechanical Filter . Experience with the Jewell Export Mechanical Filler . d Artificia. preparation of ground-water from surface-water Natural bank filtration, infiltration .Application of the process in various towns . ...