PAPERS OX CHEMISTRY AND PHYSICS 147 



CHEMISTRY OF SEWAGE TREATMENT 



A. M. Bus well. Chief, Illinois State Water Survey 



and Professor of Sanitary Chemistry, 



University* of Illinois 



A recent conversation between an eminent scientist 

 and a successful business man, which the speaker chanced 

 to overhear, will serve to introduce the subject of this 

 paper and to emphasize the need for greater general en- 

 lightenment in educated circles. Asked the scientist, ''Is 

 it possible to purify sewage?" "Oh yes." the business 

 man replied, "We are building a sewage treatment plant 

 for our town. I think it is to be some sort of an in- 

 cinerator ! ' ' 



Almost every chemical graduate has a general notion 

 of how leather, rubber or Portland cement is manu- 

 factured, and even high school students of chemistry are 

 likely to know how gas is produced and how water may be 

 softened. These and other chemical processes are dis- 

 cussed both in the elementary and advanced texts on in- 

 dustrial chemistry. But the treatment of human and in- 

 dustrial wastes, while essentially a chemical process, is 

 almost wholly neglected. Xaturally. therefor* 1 , the sci- 

 entifically trained student knows nothing about sewage 

 treatment unless he has taken a special elective course. 



In introducing the subject of sewage treatment I want 

 therefore to say a few words about the amount and com- 

 position of sewage. Sewage may be defined as the com- 

 bined water carried wastes of a city or community. In 

 addition to the human and household wastes it may con- 

 tain the by-products from almost any variety of indus- 

 try : it may contain the washing from streets, and unless 

 separate drains are provided it will include the surface 

 run-off during rain. 



In amount, the sewage includes the ordinary water 

 consumption plus what is contributed from rain and other 

 sources. The dry weather flow usually approximates 

 rather closely the water consumption. This amount va- 

 ries greatly between different localities. In Europe the 

 sewage flow in dry weather will run from 20 to -iO gal- 

 lons per capita per day. In this country it will be from 



