Filtering Materials for Water Works

The present active interest in the question of filter materials for water work, coupled with some dissatisfaction with the present status of our knowledge and the standards in use, indicate the desirability of more extended consideration and research covering the relative effects of various characteristics of water works filter materials. A committee of the Sanitary Engineering Division of the American Society of Civil Engineers has been giving attention to filter materials for water works for the past several years as one phase of its activity. The objective of this paper is to indicate something of what has been undertaken and to outline briefly some of the factors and problems involved, to point out some lines of study which may be profitably developed and to call attention to the need and value of cooperative effort among the various investigators who are or may be conducting active studies. Mr. Armstrong and others to follow will present a number of pertinent data from several series of experimental work which will undoubtedly shed some light on certain of the problems involved. The more common filtering material for water works is a bed of well graded silica sand supported, generally, by a bed of gravel. Occasionally some other material is used for the filter media as, for instance, crushed coal at Denver. For the present discussion the filtering material is assumed to be graded sand.