XI, B, 2 Gabel: Examinations of Swimming Pools 67 



part per million made the water practically sterile. It appeared 

 that the effect of the hypochlorite lasted only about three days, 

 after which there was a considerable increase in bacteria. 



When unchlorinated, the water at the University of Pennsyl- 

 vania showed a continued increase in numbers of bacteria." 

 The tank has a capacity of 155,000 gallons, and city water was 

 used. After adding alum as a coagulant, the water was filtered 

 before it entered the tank. Fifteen hundred gallons were 

 allowed to flow through the tank daily. Every Sunday the tank 

 was emptied, scrubbed, and refilled. Bacillus pyocyaneus was 

 frequently isolated from the water. Part of the results obtained 

 is appended herewith. 



Bacteria per cubic centimeter found in University of Pennsylvania swimming 



tank. 



[Grown 24 hours on agar.] 

 BACTBRIA m UNCHLORINATED WATER, 



DV. 



Colonies 

 percc. 



1 85 



2 340 



3 428 



4 3,000 

 6 7,090 

 6 50,000 



On Thursday approximately 0.5 part of available chlorine per million 

 parts of water was added to the water, giving the following results: 



BACTERIA IN CHLORINATED WATER. 



Colonies 

 per cc. 



Before adding chlorine 50,000 



15 minutes after adding chlorine 250 



2 hours after adding chlorine 



24 hours after adding chlorine 160 



Some of the conclusions drawn from the work just mentioned 

 were that pathogenic organisms may readily find entrance to 

 the water and possibly cause disease; that small amounts of 

 chlorine added to the water in the tank every morning quickly 

 destroy the microorganisms present; that accumulations of hair 

 and other debris at the bottom of the tank should be removed 

 daily by small hand pumps, as they are less readily disinfected 

 than the water. 



There are many factors influencing the sterilizing action of 

 chlorine and hypochlorites on water, and a great part of the 

 conflicting evidence found in the literature relative to quantity 



"W. J. Lyster, Joum. Am. Med. Assoc. (1911), 57, 1992. 



