890 EXPERIMENT STATIOX RECORD. 



large lumps of suspeuded curd. . . . The inlet tu the tauk should, consist of a 

 6-in. pipe ending in a*tee supported by IJ-in. gas pipes set in the concrete wall 

 of the tank so that the inlet will be submerged. A wooden baffle placed across 

 the end of the tank and extending about 2 ft. below the surface of the sewage 

 will distribute the liow across the tank and will reduce to a minimum the dis- 

 turbance due to the entering water. At the outlet end of the tank the discharge 

 t;ik<'s iiliice in a thin sheet flowing over a weir, which may be made of angle 

 iron set on the top of the concrete wall. ... A wooden baffle similar to the one 

 at the inlet end should be placed about* 6 in. from the weir wall to prevent the 

 scum from passing over or clogging the weir. Preferably the tank should be 

 divided into two or three compartments by baffle walls iierforated with a num- 

 ber of holes, so arranged as to distribute the flow uniformly throughout the 

 cross section of the tank." 



Openings are provided in the baflle walls by placing a number of drain tiles 

 through the forms. " To prevent scum from going through, the upper row of 

 openings should be IS in. below the surface and to be above the level of the 

 sludge the lower row should be about 2 ft. above the bottom. The walls should 

 have an opening under them near the center for the purr)ose of flushing the 

 sludge to the sludge drain." 



The depth of the tank, it is stated, should be great enough to provide for a 

 considerable depth of scum and .sludge and still leave room for the passage of 

 the wastes at a very slow rate, which will require a depth of from 4 to 7 ft. 

 below the level of the water surface. The dimensions of the tank should be so 

 proportioned as to make the length two to three times the width. 



A filter bed should be provided for final treatment of the sewage after it 

 comes from the tank. The depth of filter should not be less than 30 in. and 

 preferably from 36 to 48 in., and the area should be such that the rate of appli- 

 cation of the settled wastes will not exceed 25.000 gal. per acre in twenty-four 

 hours. A dosing chamber fitted with an automatic siphon for intermittent dis- 

 charge is considered an essential part of the septic tank. 



A two-story sedimentation tank of the Imhoff type in which the solid mntter 

 in the sewage drops through slots in the floor of the sedimentation chamber into 

 the lower compartment is described and illustrated as being a suitable device 

 for the digestion of creamery sewage. 



For the suppression of odors from tlie filters the addition of chlorid of lime 

 to the tank effluent about an hour before it is discharged from the dosing 

 chamber is recommended. The necessary amount will vaiy with the seasons, but 

 it is stated that from 1 to 5 lbs. of chlorid of lime to 1.000 gal. of tank effluent 

 will ordinarily be sufficient. 



Design of two residential sewage treatment plants, including settling' 

 tanks of Imhoff type, S. A. Greeley {Engin. and Contract.. 42 (1914). ^o. 25, 

 pp. 565-567, figs. 5). — One of these plants, designed for twenty-five people, con- 

 sists of a settling tank, covei'ed sprinkling filter, and a small secondary set- 

 tling basin. A tipping bucket drops the dose vmto a splash plate, thence to the 

 filter. The second plant consists of a settling tank and a subsurface irriga- 

 tion system in sandy soil. 



RTJRAL ECONOMICS. 



[Needs of American farm women] (U. ^. Dcpt. Agr. Rpts.. 1915, Xos. 103, 

 pp. 100; 104, PP- 100; 105, pp. 88; 106, pp. ^00).— These four reiwrts consist 

 mainly of extracts from about 2,0(X) letters receive<l from farm women in re- 

 sponse to an inquiry from the Secretary of Agriculture as to how this depart- 

 ment could better meet the needs of the farm housewives. 



