XI, B, 2 



Gabel: Examinations of Swimming Pools 



81 



well and would probably show greater uniformity if a larger 

 number of tests had been made or a greater number of pools 

 could have been examined. 



By comparing the bacterial counts of pools I and III in Tables 

 VIII, IX, and XI, it is noticeable, especially in the last table, 

 that the calcium hypochlorite seemed to have less disinfecting 

 power in pool III than in pool I. This was true for both B. coli 

 and total counts. In seeking a possible explanation, we find that 

 it was not due to the difference in the number of bathers, as 

 the daily average, during these weeks, of the people who used 

 pool I was 19, whereas it was only 17 for pool III. The probable 

 reason seems to be that the latter pool was open at the sides, 

 admitting an abundance of light which caused a deterioration 

 of the disinfectant. That light hastens the decomposition of 

 the hypochlorite has already been mentioned. 



During weeks VIII and IX the same water was used with 

 the daily addition of 0.5 part of available chlorine from calcium 

 hypochlorite per million parts of water. However, on the inter- 

 vening Sunday no disinfectant was added. The effect was 

 readily observable by the sudden increase of the bacterial count 

 on the following day. 



RELATION OF TURBIDITY AND BACTERIAL CONTENT 



As the strength of a bacterial emulsion is often judged from 

 its turbidity, it was thought that possibly some relation might 

 exist between the turbidity of a swimming-pool water and its 

 bacterial content. However, in this case, besides the physical 

 suspension of bacteria, new chemical compounds are formed by 

 the addition of disinfectants. Table XIV is presented to show 

 how these factors compare. 



Table XIV. — Comparison of turbidity and bacterial content of water in 



swimming pools. 



[Average of 25° and 37° C. count.] 

 POOL I. 



Affe of water in 

 dayB. 



VII. No disin- 

 fectant. 



v. One part per 

 million copper sul- 

 phate. 



VI. Two parts per 

 million copper sul- 

 phate. 



IV. Two parts per 

 million chlorine 

 from calcium hypo- 

 chlorite. 



Turbi- 

 dity. 



Bacteria 

 per cc. 



Turbi- 

 dity. 



Bacteria 

 per cc. 



Turbi- 

 dity. 



Bacteria 

 per cc. 



Turbi- 

 dity. 



Bacteria 

 per cc. 



1 



13.5 

 8.5 



280 



9,300 



14,000 



270, 000 



90,000 



550, 000 



11.5 



10.6 

 10.7 

 10.5 

 10.5 

 9.7 



46 



1,850 



46,500 



230,000 



450,000 



165,000 



12.8 



13 



12 



18.5 



12.4 



660 



23,000 



195,000 



2, 300, 000 



6, 700, 000 



17, 500, 000 



13 



16 



10 



10.5 



13.5 



3,500 



660 



6 



11,500 



1,850,000 



175,000 



2... 



3- 



4 



8.4 

 8.4 

 8.8 



6 - 



6 





