TREATMENT OF CITY SEWAGE. 79 



gregate together, this method becomes objectionable, and finally 

 impossible. The treatment of city sewage has become a problem 

 involving the ingenuity of the expert sanitary engineer. It cannot 

 be said that any wholly satisfactory method has yet been devised 

 for handling this difficult problem. 



In the first place it is evident that sewage contains material that 

 is very valuable if it can be used upon the soil. The large amounts 

 of nitrogen in the urea alone from a large city would be worth mil- 

 lions of dollars yearly if it could be utilized. The nitrogen was taken 

 originally from the soil by the crops, and the continued fertility of 

 the soil is dependent upon its being in some way replaced. It re- 

 quires no argument to show the wastefulness of throwing this valu- 

 able material away without attempting to utilize it. In China 

 careful attention is paid to prevent the loss of such material, and as a 

 result the soil remains fertile; while in our country a constantly 

 decreasing fertility has followed the practice of wasting it. The only 

 methods yet devised of utilizing city sewage on a large scale is by 

 what is called sewage farming. 



Sewage Farming. This method of disposing of sewage has 

 been established in the last thirty years as a means of at once dis- 

 posing of and utilizing the sewage of large cities. These farms, 

 necessarily located as near as possible to the city, receive its sewage 

 and distribute it over the fields by conduits, thus furnishing the crops 

 at the same time with nourishment and water. Upon such soils 

 crops are raised, mostly garden crops, since these are sure of a ready 

 market in the city. This plan of utilizing sewage has been very 

 vigorously urged, and many such farms have been organized in 

 England, in continental Europe, and some in this country. Enor- 

 mous sewage farms are cultivated near the cities of Paris and Berlin, 

 the latter city having thousands of acres under cultivation. In some 

 of the arid western sections of United States, where water is es- 

 pecially valuable, sewage farming has also become very profitable. 



There can be no doubt that this method of disposing of sewage is, 

 theoretically, the proper one. It has two distinct advantages: 

 i. Economic. It puts back into the soil the great quantities of 

 nitrogen and other materials taken from it by the crops. 2. Sani- 



