DAIRY AND FARM SEWAGE 129 



MANNER OF DISPOSING OF SEWAGE 



The disposal of sewage is brought about by the decomposition 

 of the organic matter. All sewage is largely organic matter and 

 water. All organic matter decays. This decaying process is 

 simply the disintegrating action of minute organisms known as 

 bacteria upon the solid parts of the sewage, dividing the same 

 into such a form that it becomes fluid. The superficial layers of 

 soil from six to twelve inches are thoroughly inoculated with bac- 

 teria. The action of the bacteria upon any organic material is to 

 reduce the complex organic compounds into simpler compounds. 

 Hence, decay is the destruction of complex substances that have 

 been built up by growth. There are certain kinds of bacteria 

 that can penetrate organic substances to a slight extent only. 

 Some must have air, particularly oxygen, to decay a portion of the 

 mass, while there are other bacteria that have the power of de- 

 composing organic material without the presence of air or oxygen. 

 In the system herein described it is chiefly the last kind of bac- 

 teria with which we have to deal. The sewage discharges into a 

 receptacle that is air-tight, known as a "septic tank." This sew- 

 age is acted upon by these bacteria, which partially decomposes 

 and liquefies the same. Most of the disagreeable odors are 

 liberated by this process, and the liquid can then be discharged 

 into an open stream with a great bulk of the running water, or 

 into an irrigating system. 



The process of decomposition in this septic tank is greatly 

 aided by using a great quantity of water. This is an advantage 

 on dairy farms, for water is used in abundance for washing uten- 

 sils and cleaning the cow barns. 



PLAN OF DISPOSING OF SEWAGE AFTER LIQUEFYING 



As stated above, the sewage, after once being decomposed in a 

 septic tank, can be discharged into a running stream or river 

 without emitting offensive odors. This is the simplest way to dis- 

 pose the sewage, but there are many farms which are not located 

 so as to allow the sewage to be discharged into such a stream. 

 For such a farm, in fact for every farm where it can be adopted, 

 the disposal of sewage by irrigation is by far the best method. 

 There are two methods used for irrigation: the surface method 

 and the subsoil method. With the surface method liquid sewage 

 is drained through glazed tile to a piece of ground set apart for 

 this purpose. The ground is ridged and the sewage is allowed to 

 flow over the ground in shallow channels. The liquid slowly dis- 

 appears by filtering through the soil. Patches of ground that are 



