CHAPTER XXVII 

 BACTERIA or WATER AND SEWAGE 



Introduction. Water always contains bacteria. It was 

 supposed some years ago that such waters as distilled water 

 and that from deep wells were sterile, but since Burbon Sander- 

 son, in 1871, showed that many bacteria existed in distilled 

 water, it has been recognized that there are always bacteria 

 present in a water supply. Many of these bacteria are per- 

 fectly harmless so far as man is concerned, and exist in the 

 water composing a natural flora. None of the bacteria found 

 normally in water are harmful to man. Some of these, how- 

 ever, may cause trouble by growing in the water pipes, rilling 

 them up, as in the case of the Crenothrix. Certain bacteria 

 that cause a good deal of difficulty may also get into the water, 

 especially from human sewage. One of the great problems 

 of sanitation is to protect the water supplies from sewage con- 

 tamination, or in case they become contaminated to purify 

 them. 



Number of Bacteria in Water. The number varies from 

 a very few bacteria per cubic centimeter in the water from 

 deep wells or springs to a very great many in a surface water, 

 especially if this is contaminated with sewage. A good idea 



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