The Philippine journal of Science 



1916 



The constancy in quality is further indicated by the chlorine 

 content and oxygen-consuming capacity of the water in the 

 reservoir, as shown by determinations made during the rainy 

 season, at a time when the greatest variation in quality might 

 reasonably have been expected. 



Chlorine was determined by Mohr's method. The oxygen- 

 consuming capacity was measured by the method designated as 

 standard by the American Public Health Association, ^ except 

 that the sample was acidulated and heated to boiling before 

 the addition of the permanganate, and that the digestion was 

 made on a steam bath instead of in a bath of boiling water. 



Table II. — Daily variation in chlorine content and oxygen-consuming 

 capacity of the water at the reservoir. 



[Eesults expressed as parts per million.] 



Date. 



Chlo- 

 rine. 



Oxygen 



con- 

 sumed. 



Date. 



Chlo- 

 rine. 



Oxygen 



con- 

 sumed. 



1915. 



September 20... 

 September 21... 

 September 22... 

 September 23... 

 September 24... 

 September 25... 

 September 27... 

 September 28... 

 September 29... 

 September 30... 



October 1 



October 2 



October 4 



3.5 

 3.5 

 3.5 

 3.5 

 3.5 

 3.5 

 3.5 

 3.9 

 3.8 

 4.1 

 3.9 

 3.6 

 3.8 



0.67 



0.8 



0.8 



0.77 



0.85 



0.96 



0.71 



0.78 



1.01 



1.23 



1.30 



1.26 



1.01 



October 5 



October 6 



October 7 



October 8 



October 11- 16 a.. 



October 18 



October 19 



October 26 



October 27 



October 28 



October 29 



October 30 



November 1 



November 2 



3.7 

 3.5 

 3.4 

 4.1 

 3.9 

 3.5 

 3.0 

 3.6 

 3.4 

 3.5 

 3.6 

 3.1 

 3.3 

 3.3 



1.33 

 1.43 

 1.27 

 1.29 























• Composite sample. 



The constancy of the results in this table show the improve- 

 ment in the present water supply over that of the old Mariquina 

 system. Thus the chlorine content varied only from 3.5 to 4.1, 

 while that of the old supply (Table I) varied from 2.1 to 4.4; 

 the oxygen-consuming compacity of the former fluctuated be- 

 tween 0.67 and 1.4, that of the latter between 0.65 and 2.2. 



Bacteriologically the water shows the fluctuations naturally to 

 be expected from a surface water. After a heavy rain the 

 colony count of the Montalban supply sometimes reaches an 

 enormous figure, although the water as it leaves the reservoir 

 generally has a count below 1,000. Pathogenic organisms in 

 all probability are generally absent, although B. coli is occasion- 



' Standard methods of water analysis (1912), 29. 



