Sewage Treatment — How It Is 

 Accomplished 1 



By C. E. Keefer 



Assistant Bureau Engineer, Sewers 

 Bureau of Sewers, Baltimore, Md. 



[With 6 plates] 



Man's desire to enjoy the amenities of urban life has brought with 

 it many difficult problems that demand prompt and adequate solutions. 

 One of these, which up to about 100 years ago had remained unsolved, 

 related to the satisfactory treatment and disposal of municipal sewage. 

 Many factors were instrumental in directing the attention of legis- 

 lators, sanitarians, and engineers to this problem. Among these 

 factors were the increased use of water, which served as a means to 

 transport municipal wastes to the nearest watercourse, the phenomenal 

 growth of our cities with its concomitant increase in the volume of 

 municipal sewage, the growth of our knowledge of water-borne dis- 

 ease, and an aroused public opinion that clean watercourses are con- 

 ducive to the general welfare of the public. 



WHAT IS SEWAGE? 



The purpose of this discussion is to indicate the various methods 

 that are used to treat municipal sewage so that 85 or 90 percent of 

 the organic and suspended materials and at least 99 percent of the 

 bacteria can be removed at a reasonable cost. To understand how the 

 various treatment processes function it is desirable to know what 

 municipal sewage is and how it is collected. 



Sewage has been defined as "the spent water supply of a community, 

 together with those human and household wastes that are removed 

 by water carriage, supplemented in some instances by street washings 

 and industrial wastes." Sewage consists of the liquid discharge from 



1 This paper gives a brief description of the more important facilities found 

 in modern sewage-treatment plants. No attempt has been made to describe all 

 of the means available for treating sewage. Those facilities that have been out- 

 moded, that are little used, or that as yet have not become well-established 

 processes have not been discussed. 



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