SEWAGE DISPOSAL 191 



requires no purification and, if conducted through the 

 tank, would necessitate one of too large dimensions. 

 Moreover, the large amount of cold water needed for 

 cooling milk and cream would cool the contents of the 

 tank too much for a rapid decomposition of the material 

 within. 



Size of Tank. This must necessarily depend upon the 

 amount of sewage run into it. In general it should have 

 capacity sufficient to hold all of one day's waste in the 

 smallest section (C). It will be noticed from the cut 

 that section A is considerably larger than either of the 

 other two. The reason for this is that nearly all of the 

 inorganic matter remains in the bottom of this part of the 

 tank, while the organic matter, as already stated, gradu- 

 ally accumulates at the surface in this section, in spite 

 of constant decomposition. Where the tank receives the 

 sewage from both the dairy and the dwelling, a tank 

 12 feet square by 4^2 feet deep will be large enough, 

 provided the water used for cooling is not run into it. 

 It is well to remember, however, that the larger the tank 

 used the better the results that may be expected from it. 



Flow of Sewage Through Tank. Four-inch tile, 

 carefully laid, may be used to conduct the sewage from the 

 creamery to the tank. A trap is placed near the creamery 

 to shut off the odors coming from the drain. At the 

 point at which the sewage enters the tank it is desirable 

 to attach an elbow with an arm sufficiently long to keep 

 the lower end always in the sewage. This prevents un- 

 due mixing of the incoming sewage with that already 

 in the tank, a matter of importance in the successful 

 operation of the tank. 



When the sewage in section A has reached the dotted 

 line, it begins to discharge into section B through three- 



