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connection with city water supplies, in sewers, near dung heaps, and 

 in various places containing decaying organic matter. 



The equipment of the Thirty-ninth Street Sewage Testing Sta- 

 tion is as follows: a "grit chamber", 20X4X3 feet, with a capacity of 

 1,500 gallons at flow depth; three tanks, each 40 feet long, 7 to 9 

 feet deep and yYz feet wide, total capacity 19,000 gallons, flow 17,000 

 gallons, tank "A" being an open septic tank with a nominal eight-hour 

 period, tank "B" a closed septic tank, and tank "C" an open settling 

 tank; an Imhoff or Emscher tank, jYi feet in diameter and 17 feet 

 deep ; a modified Dortmund tank, 7^ feet in diameter and 9 feet deep ; 

 five sprinkling filters in cylindrical wooden tanks connected with the 

 settling and septic tanks, four being open and one covered ; various 

 settling basins; and a sludge digestion tank 29X7X6 feet, with a 

 total capacity of 8,900 gallons. The following diagram will indicate 

 the relation of these various tanks and filters to each other. 



Shallow Seltlind 

 Basin 



To Final Disposal 



Sludge Digestion Jink 



To Fm&l Disposal 



To Final Disposal 



The one important thing to note in connection with the data which 

 is to follow is the nature of the effluents of the various settling and 

 septic tanks. In brief, the aim of modern sewage disposal involves 

 two distinct steps : the disposal of the small amount of suspended mat- 



