1020] RURAL ENGINEERING. 47^ 



partk'ular reference to purifying equipment for the removal of acidity and the 

 consequent protection of metal parts of the system against excessive corrosion. 

 It is stated thai ordinarily the litmus test will serve to detect the least trace of 

 acidity in such waters. Primary treatment with a chalk filter followed by sand 

 fiUratir)n is recomniendwl. 



The sterilization of water by means of ultra-violet rays, W. L. Dkckeb 

 (Client. (1)1(1 Mctall. Kiujin., 22 (1920), Xo. Iff. pp. GS!l-(l'to, flya. 10).— The records 

 of work conducted on the adaptation of ultra-violet ray treatment to small 

 Isolated plant water sui^plies are reported, and the entire theory of the process 

 discus.sod in some detail. 



" Water, if clear, is practically as transparent as air to ultra-violet rays. 

 In many cases, however, ft must first be filtered to free it from suspended 

 matter and, if possible, also from colloidal matter, which would otherwise 

 retard the passnjie of the rays. Caivful observation of well-filtered water, 

 however, nearly always reveals the presence of a small amount of suspended 

 matter of a large enough size to allow microbes to be protected against the 

 rays. To sterilize such water with safety it was found advantageous to agitate 

 it while passing through the illuminated zone and to expose it several times 

 to the light of the same lamp. This stirring up is best accomplished by a proper 

 arrangement of baffles." 



It is noted that in the majority of analyses the water after passing through 

 the filters showed the presence of Bacillus coli. The sterilized water showed 

 that the violet-ray sterilizer functioned properly in killing all the B. coli germs 

 that were left afttr passing the filter. 



" An interesting development of the violet-ray apparatus is that the amount 

 of water that can be treated does not vary in arithmetical pi'ogression with the 

 number of units used." Recent tests have also developed the fact that water 

 treated with ultra-violet rays has a residual effect. When to a sample of water 

 that had been sterilized fresh bacteria were added, it was found tliat in an 

 hour's time 90 per cent of these added bacteria had succumbed. 



Copper sulphate treatment to counteract algie growths in large reser- 

 voirs (Knyin. and Contract., 53 (1920), No. 15, pp. -'{32, ^35).— An account is 

 given of recent experiments intended to free the Catskill water supply for the 

 city of New York from Asterionella. It was found that a continuous supply 

 of copper sulphate amounting to 625 lbs. daily in a flow of 380,000,000 gal. 

 substantially reduces the number of the microscopic organisms, the resulting 

 cost being about 13 cts. per million gallons. 



Running water in the farm home, C. A. Nouman (Purdue Agr. Ext. Bui. 

 91 (1920), pp. 12. figs. 7). — Brief popular information is given on systems for 

 farm water supply and sewage disposal. The water-supply systems include 

 the gravity, hydropneumatic, and pneumatic systems, the last of which has 

 been subject to considerable attack during the past from various sources. 



In the brief discussion of sewage disposal the statement is made that " the 

 septic tank provides a means for liquidifying and purifying sewage." 



Treatment of beet sugar plant sewage, L. Pearse and S. A. Gkeelky (.4»ier. 

 Jour. Pub. Health. 10 (1920), Xo. //, pp. 312-320, figs. 5).— A summary of data 

 on the subject, together with results of two years' experiments upon beet 

 sugar plant waste disposal, are reported. 



It was found that fine screening and se<limentation are necessary for any 

 type of treatment plant. The effluent of the settling tanks can be treated on 

 sprinkling filters. It is concluded that sprinkling filters for the crude con- 

 centrated sewage can be dosed at about 200,000 gal. per acre per 24 hours, 

 and sand filters at about 75,000 gal. per acre per 24 hours. Should the 



