106 '^he Philippine Journal of Science isie 



I, II, and III, are of slightly varying depths and dimensions. 

 Each of installations I and II has a capacity of about 200 cubic 

 meters, and III has a capacity of about 225 cubic meters. Each 

 is between 18 and 19 meters (60 feet) long, and has a depth of 

 about 2.5 meters (8 feet) in the deepest portion. Installations 

 I and II are situated indoors. Installation III, although covered 

 by a roof and surrounded by a low, light wall of sawale (woven 

 bamboo) , is practically outdoors. Owing to building operations 

 at III, the tank was not in continuous operation and foreign 

 material fell into it, causing discrepancies in the results. These 

 discrepancies, however, were not great enough to affect the 

 general conclusions obtained. 



The same water, direct from the Manila city supply system, 

 was used in all three tanks. This is a river water, which is 

 kept in storage for three days and treated, before it enters the 

 city distribution system, with chloride of lime at a rate cor- 

 responding to an addition of 0.5 part of available chlorine per 

 million parts of water. 



As it leaves the pipes it is a slightly turbid water with a 

 greatly fluctuating bacterial content. Its turbidity, due to very 

 finely divided clay, varies from 7 to 15 parts per million, as 

 measured by the United States Geological Survey turbidity-rod 

 method. Its temperature, which shows slight variations at 

 different seasons of the year, is usually between 27° C. and 30° C. 

 A typical analysis of this water is shown in Table I. 



Table I. — Analysis of water from Manila supply system." 

 [Results expressed as parts per million.] 



Total solids 



154 



Alkalinity (as CaCOs) 



100 



Silica (SiOs) 



24 



Iron and aluminium oxides (FejOa+AUOs) 



1.7 



Calcium (Ca) 



31 



Magnesium (Mg) 



6 



Sodium (Na) 



13 



Potassium (K) 



2 



Normal carbonates (CO3) 



0-10 



Bicarbonates (HCO3) 



100-120 



Sulphates (SO4) 



14 



Chlorides (CI) 



4 



Nitrates (N) 



0.046 



Nitrites (N) 



trace 



Free ammonia (N) 



0.03 



Albuminoid ammonia (N) 



0.116 



« Analysis by V. Q. Gana, chemist. Bureau of Science. 



The problem of maintaining a swimming pool in Manila in a 

 sanitary and attractive condition is rather complicated. The 



