410 



SCIENCE 



[N. S. Vol. XXXVin. No. 977 



and on one occasion in 1/1000 c.c. The entire 

 significance of this relation will be fully deter- 

 mined only by further study. It further was 

 found that the bacterial content of the city water 

 during periods of pollution was different from 

 that during periods of relative purity. Bacillus 

 coli comprised 55 per cent, of all organisms iso- 

 lated during the period of relative purity, while 

 during the period of pollution it comprised only 

 25 per cent, of organisms present. At this latter 

 time, however, several new forms made their ap- 

 pearance, such as lactis aerogenes, intermediate 

 group, attenuated forms and "liquefying fer- 

 menters. ' ' During little more than a year now it 

 has been possible to observe the effect of hypo- 

 chlorite of lime and later of alum on the bacterial 

 flora of the city water. In the main the bacterial 

 count has been greatly reduced under the chemical 

 treatment, the counts practically always being less 

 than 500 organisms per cubic centimeter. ISTot- 

 withstanding this, however, the degree of fer- 

 mentation has remained practically the same, i. e., 

 1/10 and 1/100 c.c. of the water giving positive 

 tests in the Smith tube. The typhoid fever during 

 this period of chemical treatment has been slightly 

 reduced. However, the reduction was not at all 

 striking, which makes us believe that perhaps the 

 greater part of our typhoid fever may not be 

 water-borne or, on the other hand, if water-borne, 

 the specific organisms of pollution have not been 

 removed from the water by the chemical treatment 

 in the usual strengths of available chlorine. 

 Some Results of the HypocTilorite Disinfection of 

 the Baltimore City Water Supply: J. Boslet 

 TOMAS and Edgab. A. Sandman, Baltimore City 

 Water Department. 



Stokes and HaehteP have reported the result 

 obtained by the hypochlorite disinfection of the 

 Baltimore city water supply during a period ex- 

 tending from the institution of the treatment on 

 June 15, 1911, to October 30, 1911. They exam- 

 ined samples taken from the untreated water in 

 the impounding reservoir and from the treated 

 water after it had passed through each of two 

 storage reservoirs. The result of their examina- 

 tion showed bacterial reduction varying between 

 94.5 and 99 per cent. They also showed average 

 reduction in the colon bacillus from 57.5 per cent, 

 positive tests with 0.1 c.c. of untreated water to 

 12 per cent, positive tests with 0.1 c.c. of treated 

 water, and from 89 to 40 per cent, with 1 c.c. 

 The greatest reductions were obtained with one 

 ^ Am. Jour. Buh. Health, April, 1912. 



part per million of available chlorin, when there 

 were shown reductions from 86 per cent, positive 

 tests with 0.1 c.c. of treated water, and from 100 

 per cent, to 37 per cent, with 1 c.c. The period 

 covered by the following report extends from 

 January to December, 1912. In addition to the 

 places sampled by Stokes and Haehtel we obtained 

 samples at the influent of the first storage reser- 

 voir, after the water had passed through seven 

 miles of tunnel subsequent to treatment. The 

 time required for the water to pass through this 

 tunnel varies between 4.9 and 12.2 hours. While 

 allowing sufiicient time for effective disinfection, 

 the taking of samples just before the water enters 

 the first storage reservoir permits of counts being 

 obtained before any after-growths are likely to 

 have occurred. The amount of available chlorin 

 applied during the period covered by the report 

 of Stokes and Haehtel was raised from 0.4 parts 

 per million applied at the start on June 15, to 

 0.6 on June 23 and to 1 on October 15. On July 

 15, 1912, the amount was again raised, by order 

 of the Commissioner of Health, to 1.5 parts per 

 million, and this amount has been maintained until 

 the present time. From January 11 to November 

 12 aluminum sulfate, in amounts varying between 

 0.610 and 1.05 grains per gallon, was applied to 

 the water as it entered the first storage reservoir. 

 Shortly after the period covered by the report of 

 Stokes and Haehtel after-growths in the storage 

 reservoir caused excessive bacterial counts. These 

 conditions maintained during the first five months 

 of the year, but about the middle of May the 

 counts showed a marked diminution, and no fur- 

 ther after-growths were observed, excepting during 

 the few days in September. The monthly averages 

 of the results in bacterial counts and B. coli tests, 

 shown in the accompanying table, are taken from 

 daily analyses. The counts during the first six 

 months were obtained on standard agar at 20°, 

 and during the remainder of the year at 37°. The 

 B. coli averages were obtained from tests made 

 on portions of water varying by a multiple of ten 

 from 0.001 c.c. to 100 c.c, sufficient number of 

 tubes being used in each ease to secure at least 

 one negative and one positive test, excepting when 

 no fermentation was obtained with 100 c.c. The 

 average number of B. coli per cubic centimeter for 

 each month was estimated by considering the 

 number of positive and negative tests in each 

 dilution and following the method described by 

 Phelps before the American Public Health Asso- 

 ciation in 1907. Lactose bile was used as an 



