8 



The Philippine Journal of Science 



1916 



At this latter concentration the odor of the city water was 

 marked, and complaints were so numerous that it was deemed 

 inadvisable further to increase the addition rate. 



The effects of different quantities of chlorine are shown in 

 Tables V to IX, inclusive. 



Table V. — Effect of 0.5 part available chlorine per million parts of water.* 



Date. 



Reservoir. 



San Juan. 



Reduc- 

 tion. 



Colony 

 count. 



Test for B. 

 coli group. •> 



Colony 

 count. 



Test for B. 

 coli group. •> 



1914. 

 June 1 . 



110 



350 



180 



38 



60 



210 



120 



48 



34 



14 



10 



128 



Dn less tha 



Positive .— 

 Negative... 

 Positive .... 



......do 



do 



do 



do 



do 



do 



do ...... 



do 



do 



n . 



80 



80 



120 



26 



36 



190 



360 



36 



26 



18 



8 



36 



Positive .... 



Negative... 



Positive . — 



Negative 



do 



do 



Positive 



Per cent. 

 27 

 77 

 33 

 32 

 40 

 10 











June 6 



June 7 .. . 



June 8 . 



do 



Negative 



Positive 



25 

 24 



June 9 



June 10 



June 27 



Negative... 

 do 



20 



72 



50 



June 28 



Average reducti< 











» Examination by O. Schobl, bacteriologist. Bureau of Science. 



1> In 2 cubic centimeter samples. Bacillus coli removed six out of eleven times = 56 per cent. 



The next series, representing the addition of 0.56 part of 

 chlorine per million, is probably not conclusive because of the 

 uniformly low bacterial content of the water during the time 

 of examination and because of the small number of observations; 

 it is included, however, for the purpose of comparison. 



Table VI. — Effect of 0.56 part available chlorine per million of ivater.^ 



Date. 



Reservoir. 



San Juan. 



Reduc- 

 tion. 



Colony 

 count. 



Test for B. 

 coli group, h 



Colony 

 count. 



Test for B. 

 coli group, b 



1914. 

 June 11 . - 



70 

 4 



48 

 46 



Positive 



do 



do 



do 



18 

 12 

 18 

 16 



Negative... 

 . . do 



Per cent. 

 74 



June 12 ... . . 



June 13 



do 



do 



63 

 65 



June 14 





" Examination by O. Schobl, bacteriologist. Bureau of Science. 



* In 2 cubic centimeter samples. Bacillus coli removed three out of three times. 



Another set of observations was made while 0.625 part of 

 chlorine per million parts of water was being added, and as this 



