TECHNICAL AND SANITARY PROBLEMS 1081 



Ground waters normally do not contain microscopic organisms, 

 and when these are found in ground waters a natural inference is 

 that a ground water has been contaminated with surface water. 

 Thus the microscopical examination of ground water is sometimes 

 useful in determining questions of pollution. 



Organisms in Pipes of Water Systems. When surface water 

 which contains algae and other microscopic organisms is allowed to 

 flow 'through pipes, as in the distribution systems of public water 

 supplies, it frequently happens that the pipes become more or less 

 choked with what is popularly called pipe-moss. Sometimes this 

 pipe-moss acquires a thickness of several inches and forms a mat 

 upon the inside of the pipes which materially reduces their carrying 

 capacity. The organisms which give trouble of this character 

 are chiefly the Polyzoa, Plumatella, Paludicella, and Pectinatella. 

 Fresh- water sponges are also found in pipes and masonry aqueducts. 

 Snails, worms, and various Crustacea may be found associated with 

 these moss growths. Dr. Thresh of London has described the 

 occurrence of fresh-water mussels in a thirty-six inch pipe which 

 attained such a growth that the bore was reduced to nine inches. 



It is evident that the pipe dwelling organisms depend upon the 

 plankton for their food supply. The above-mentioned growths 

 do not occur in pipes which carry water which has been filtered or 

 ground water, which contains no microscopic organisms. 



There is another organism sometimes found in ground waters 

 which contain salts of iron and magnesia, namely Crenothrix. 

 There are three distinct varieties of this organism. One of these 

 deposits manganese in its gelatinous sheath, another deposits iron, 

 while the other deposits alumina. All of them grow best in waters 

 somewhat deficient in dissolved oxygen. Crenothrix grows on 

 the walls of the pipes in tufts of filaments. The filaments become 

 attached and are found in the water discharged from the faucets. 

 The iron which impregnates the gelatinous sheaths that surround the 

 cells causes trouble in laundries. Clothes washed in such water 

 acquire rusty stains difficult to remove. Crenothrix is sometimes 

 found associated with the pipe-moss above mentioned. 



Pipe-moss may be removed from a distribution system of a water 

 supply by flushing, but the best practice is to prevent the growths 



