XI, A, 1 Heise: Water Supply of Manila 13 



SUMMARY AND CONCLUSIONS 



The present water supply of Manila, although insufficient in 

 amount during dry seasons of long duration, is a vast improve- 

 ment over the old supply. 



Chemically the water is satisfactory for domestic use, but its 

 bacterial content makes artificial purification necessary. Pre- 

 liminary experiments indicate that the self-purification of the 

 water in the reservoir was about 90 per cent, although the 

 average storage period was only a little over three days. 



Chlorination effected a bacterial reduction of less than 70 per 

 cent. Turbidity, temperature, and especially chlorine-consum- 

 ing capacity are the factors probably accounting for the low 

 efficiency of the treatment. 



The oxygen consumption seems to be the chemical factor which 

 gives the best indication of fluctuations in quality of the water 

 and which shows the greatest similarity with bacteriological 

 data. 



Of the procedures discussed, it appears obvious that a daily 

 determination of the oxygen-consuming capacity, supplemented 

 by a bacteriological colony count and a test for the presence or 

 absence of B. coli, furnishes the most reliable data concerning 

 the quality of the water. In addition, the frequent determina- 

 tion of chlorine-consuming capacity is of great help in fixing 

 the amount of chloride of lime that will be most effective. 



