Sewage- Disposal lOd 



immediately begin to decompose, because of the pres- 

 ence in the air and water of certain bacteria that 

 find the organic matter in the sewage proper food for 

 their development. 



Sewage can be made entirely harmless only by the 

 destruction of its organic matter, as- well as by the 

 destruction of the disease germs contained in it. Since 

 the destruction of the organic matter is almost exclu- 

 sively a bacteriological process, whether taking place 

 naturally in the self-purification of streams, or more or 

 less artificially in sewage-purification plants and sewage- 

 farms, it is evident that the matter, to be properly under- 

 stood, should be regarded from the bacteriological 

 rather than the chemical standpoint. 



Growth of the problem. — The problem of sewage- 

 disposal, like that of water-supply, has grown in magni- 

 tude within the last few decades. The gathering of 

 vast numbers of people on comparatively small areas, 

 and the diversified interests of the city with its human 

 and manufacturing wastes, are rendering the proper 

 solution of this problem more and more difficult. Like 

 a dread specter, threatening disease and destruction, 

 it has disturbed the peace of inland cities. Notwith- 

 standing the progress of modern sanitation, it still 

 continues to be the subject of careful inquiry. Even 

 communities like that of Greater New York, favored 

 in their situation on the ocean coast, are not entirely 

 free from the care and anxiety of rendering their sewage 

 harmless to human health and comfort. 



Inland communities and sewage-disposal. — Away from 

 the coast, the problem of sewage-disposal is rendered 



