344 ^^^6 Philippine Journal of Science 1914 



1912. It was demonstrated in the laboratory that, in order to 

 safeguard the supply against cholera vibrios, the addition of cop- 

 per sulphate in the ratio of 1 part per 150,000 of water (a 

 strength considered undesirable for drinking purposes), acting 

 over a period of four hours, would be required. 



Calcium hypochlorite. — During the past few months the water 

 entering the Manila city main has been treated with an amount 

 of calcium hypochlorite representing an addition of from 1 part 

 of available chlorine in 3,000,000 parts of water to 1 part in 

 1,200,000. Unfortunately, the city is using unfiltered surface 

 water, leaving the ultimate success of chlorination in considerable 

 doubt. A rather extensive investigation of the purification of 

 Manila water is being carried on, and is to be reported more fully 

 later. The water is chlorinated at the reservoir just as it enters 

 the main leading to the city. At San Juan Bridge, about 3 kilo- 

 meters below the chlorination station, the water shows a much 

 lo'wer bacterial count than the water entering the reservoir from 

 the dam or pumped into the old Spanish reservoir from Mari- 

 quina River at Santolan, indicating a high efficiency for the 

 chlorination process. 



The velocity in the city main is relatively low. The mains 

 were designed for a daily consumption of 25,000,000 gallons 

 which would produce a velocity of almost 1 meter per second. As 

 they usually carry less than half that amount, there is insufficient 

 scouring of the pipe to carry off sediment. Considerable quan- 

 tities of fragments of leaves, wood, and other organic matter are 

 carried by the water into the mains, where they lodge and form 

 culture media for bacterial growth. There seems to be no doubt 

 that bacteria multiply rapidly in the pipes within the city, for 

 the bacterial count from the taps at the Bureau of Science is 

 usually higher than that at either San Juan Bridge or even at 

 the intake of the city mains. This is further substantiated by 

 the significant fact that, although bacteria of the B. coli group 

 were usually absent in 2 cubic centimeter samples of water taken 

 daily for a period of several weeks at San Juan Bridge, they are 

 generally found in samples taken from the taps at the Bureau 

 of Science. The forced flushing of the mains with sufficient 

 water to scour the pipes would be beneficial, but this measure 

 is impracticable during the dry months, when the amount of 

 water available is so small that it is either inadequate or barely 

 sufficient for the city's needs. 



