1919] RURAL ENGINEERING. 589 



of the Miles acid process is ineluded in counectiou with chemical treatment. 

 New chapters have been added treating of the newer processes of two-story 

 tank treatment and purification by means of activated sludge. New chapters 

 have also been added which discuss, respectively, the broad principles under- 

 lying the selection, design, and operation of a sewage treatment plant and the 

 disposal of excretal wastes from houses and institutions which are not con- 

 nected with sewernge systems. 



A new form of septic tank, DeW. H. Wyatt (Dom. Engin., 87 {1919), No. 9, 

 pp. 379, 380, fig. 1). — A new form of septic tank for private sewage disposal in 

 rural districts is described and diagranimatically illustrated which is made 

 entirely of vitrilied pipe shapes. 



Grease interception from house sewage, H. J. Belmont {Dom. Engin., 88 

 {1919), No. 6, pp. 249-251, 285, figs. 5). — Information is given on the construc- 

 tion of grease traps, togetlier with drawings of approved types. 



Treatment and disposal of creamery wastes, E. B. Phelps {Puh. Health 

 Rpis. [U. S.}, 33 {1918), No. 49, pp. 2169-2174, pi. i).— Experiments conducted 

 in cooperation with the Dairy Division of the U. S. Department of Agriculture 

 on the purification and disposal of creamery sewage are reported. This sewage 

 consisted of wastes from washing cans and cleaning and rinsing churns, 

 together with a small amount of milk, cream, and buttermilk spilled on the 

 fiooi*. The experimental disposal plant as used consisted of a septic tank and 

 two sand filters. 



" In May, 1916, the plant was put in operation, the sand filter being operated 

 at a nominal rate of 25,000 gal. per acre per day, and the septic tank on the 

 basis of a 12-hour storage period. The results of the operation were excellent 

 almost from the start. During July the nominal rate of filtration gradually in- 

 ■creased to approximately 70,000 gal. per acre per day, at about which point it 

 was maintained throughout the investigation. With the advent of cold weather 

 a noticeable reduction occurred in the degree of nitrification, and a somewhat 

 less marked effect was .shown by the relative stability and oxygen demand val- 

 ues. The degree of purification was always satisfactory for discharge into a 

 comparatively small volume of diluting water in cold weather, and the spring of 

 1917 brought with it increased biological activity and resulting improvement 

 in quality of the effluent. A noticeable and quite unexpected result was the 

 complete neutralization of the characteristic acidity of the settled wastes, 

 the average values for 18 months being 226 parts per million of acidity in the 

 settled vraste and 3.56 parts per million of bicarbonate alkalinity in the filter 

 effluent." 



" The results of this investigation indicate the entire feasibility of satisfac- 

 torily treating creamery wastes." " It has been demonstrated that plain sedi- 

 mentation is a satisfactory tank treatment preliminary to sand filtration, and 

 that ... a disposal plant may readily be designed for satisfactory treatment 

 of creamery wastes." 



On the basis of these experiments brief specifications for a disposal plant 

 are given as follows : 



" The settling tank should have a net capacity of about one day's output of 

 the creamery. It should have one or more hopper bottoms with side slopes of 

 45" and a sludge outlet pipe rvmning nearly to the bottom. The total depth 

 from water line to sludge outlet should be about 12 ft. There should be a 

 vertical bottom baffle extending 3 ft. above the upper edge between each two 

 hoppers, and scum baffles extending 5 ft. into the liquid over the center of 

 each hopper. The entire tank should be covered with a tight board cover. The 

 effluent from the tank should overflow to a siphon chamber having a capacity 



