365 



Sewage Disposal. 



Charles Brossmann, Consulting Engineer, Indianapolis. 



Civilization and education has been accompanied by a wonderful 

 growth of cities and has made the problem of sewage disposal one of civic, 

 state and national importance. 



Sanitation becomes of greater importance as communities become 

 more congested. 



It is only of late years that this question has received proper atten- 

 tion, the greatest progress having been made in tbe last few decades. The 

 combined efforts of the scientist, chemist and engineer have been called 

 upon to help solve this problem of ever-increasing importance. 



Improper disposal of sewage has caused directly or indirectly a large 

 percentage in the typhoid mortality rate. 



Tbe gathering of large numbers of people calls for additional safe- 

 guards and means of sanitation. In some instances sewage can be dis- 

 posed of by dilution, discharging direct into large bodies of running water; 

 but most streams are as a rule not of sufficient size, or are already so 

 polluted that additional sewage would increase the burden already too 

 large. 



fyenerally sewage is diluted with the entire water supply of a city and 

 is a dirty appearing water, containing a greater or less percentage of 

 organic matter. There is usually enough organic matter present to make 

 it disagreeable and to cause odors. The presence of various disease germs 

 also make it a source of pollution to water bodies. 



In general all methods of sewage treatment employ the principal of 

 reduction through microscopic organisms. Bacteria of various kinds at- 

 tack the organic compounds reducing them to simpler forms, doing so 

 through successive stages. Reduction takes place through two classes of 

 bacteria, namely aerobic (thriving in the presence of oxygen), and anae- 

 robic (thriving in the absence of oxygen). These two processes occur in 

 septic, Imhoff or other tanks and in various forms of filters. 



The most prevalent form of getting rid of sewage is by dilution. 

 Where the stream is sufficient in size to allow proper oxidation the sewage 



