METHODS OF DISPOSAL 367 



flowing streams, on account of their absorption of oxygen, tend to 

 purify themselves more rapidly than do slower ones. Cold water 

 holds more oxygen than does warm, and fresh than salt water; 

 hence, there is a greater tendency for oxidation in cold fresh waters 

 than in warm or salty waters. 



There is, however, a growing demand that sewage be treated 

 before it is thrown into streams or lakes. This may be done by 

 various methods, such as sedimentation, sub-surface irrigation, 

 broad irrigation and other means. For a description of each 

 together with its relative value the student is referred to any 

 of the standard works on sewage. 



REFERENCES. 



Whipple, George C.: Sewage Disposal. 

 Rosenau: Preventative Medicine and Hygiene. 

 Phelps, Earle B. : Microbiology of Sewage. 

 Marshall: Microbiology. 

 Folwell, A. Prescott: Sewerage. 

 Sam tee, E. M.: Farm Sewage. 

 Whipple, George C.: Typhoid Fever. 

 Fuller, George W. : Sewage Disposal. 



