146 



CREAMERY BUTTER MAKING 



I. Sewage. The disposal of waste or sewage from 

 creameries is often a serious problem, especially with 

 those creameries that cannot discharge their sewage into 

 flowing water. The best means at our disposal at the 

 present time is the method of sewage purification. This 

 consists essentially of a septic tank, or germ incubator. 



^ O^JL 



Fig. 42.— Septic tank. 



in which the waste is oxidized or decomposed by the 

 action of bacteria. This scheme is illustrated in Fig. 42. 

 The tank, A and B, is divided by a water-tight parti- 

 tion which extends to within six inches of the top, making 

 in reality a double tank. It is located in the ground 

 below the frost line and may be constructed of brick, 

 stone, or cement, with capacity sufficient to hold all 

 of one day's waste in division A. Here the larger 

 portion of the organic matter is oxidized or decomposed 

 by the action of bacteria. When the next day's waste 

 begins to flow into the tank, the partially decomposed 

 sewage flows through the discharge pipe into tank B, 

 \\here the purification is completed by further oxidation. 



