XI. A, 1 



Heise: Water Supply of Manila 



ally reported. Clliates, flagellates, and amoebae are frequently 

 present, but it is doubtful whether these are objectionable, es- 

 pecially as Walker " has shown that the amoebae normally present 

 in water do not cause dysentery, and that the dysenteric amoebae 

 rapidly die in water. 



However, in view of the great fluctuation in bacteria count 

 and the occasional presence of organisms of the B. coli group, 

 it is evident that the water should be subjected to some sort 

 of purifying treatment before it is used for domestic supply. 

 The combination of turbidity and high bacterial content would 

 point to filtration as the most logical method of treatment. At 

 the present time large numbers of small fishes, shrimps, and 

 quantities of other foreign substances find their way into the 

 distribution system and give rise to troubles, most of which 

 would be eradicated by filtration. 



SELF-PURIFICATION AT THE RESERVOIR 



Although the Manila city reservoir has only a little over three 

 days' capacity, a surprisingly great degree of bacterial purifica- 

 tion seems to be effected during the brief storage period. As 

 the water is often decidedly turbid when it arrives at the res- 

 ervoir, it is probable that the improvement is due in a great 

 measure to sedimentation. None but preliminary observations 

 on bacterial self -purification have been made, and these only at 

 one season of the year, so that the results are hardly conclusive ; 

 however, they show good agreement and probably give a good 

 indication of the magnitude of the purifying action. Samples 

 were taken daily both at the inlet and at the outlet of the 

 reservoir. The average temperature of the water was 26° C. 

 at the inlet and 27° C. at the outlet. The experimental data are 

 given in Table III. 



Table III.— 



Self -purification of water 



in reservoir.^ 



Date. 



Inlet. 



Outlet. 



Reduc- 

 tion. 



Colony 

 count. 



Test for 

 B. coli. b 



Colony 

 count. 



Test for 

 B. coli. b 



1914. 

 July 16 .— 



2,900 



2,800 



425 



625 



750 



jn 



Positive 



do 



do 



do 



do 



48 

 400 

 24 

 48 

 90 



Positive 



do 



do 



do 



An 



Per cent. 

 98 

 86 

 94 

 92 

 88 

 92 



July 21.- 



July 22 — 



July 23 



July 30 



Average reducti( 









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

 b In 2 cubic centimeter samples. 



'This Journal, Sec. B (1911), 6, 259; (1913), 8, 253. 



