Chapter XVI 



— 183 — 



Sanitary Aspects 



In experiments designed to simulate natural conditions in polluted sea 

 water, Beard and Meadowcroft (1935) noted a rapid diminution in 

 numbers of both Ehcrtliella typhosa and Escherichia colt, although some 

 of each survived for more than a month. Representative findings are 

 summarized in Table XXXVIII. The bacteria were suspended in freshly 

 collected unfiltcred water from San Francisco Bay in semipermeable mem- 

 brane cells which were immersed in the bay. The rate of death of the 

 bacteria was invariably higher in unfiltered water than in similar water 

 which was sterilized by passage through an L-3 Chamberland candle. 



Table XXX\TII. — Number of enteric bacteria in filtered and unfiltered sea water in 

 semipermeable cells immersed in the sea (from Beard and Meadowcroft, igjs): — 



Similar results were obtained by ZoBell (1936), who suspended sew- 

 age bacteria in different kinds of water in the sea in semipermeable tubes 

 prepared by impregnating porous porcelain filter candles with collodion: 



The "natural" sea water was unfiltered and unheated. The "filtered" 

 sea water was passed through a Berkefeld-W candle. A continuation of 

 the experiment summarized above showed that, while 99.9 per cent of the 

 sewage organisms were killed after two days suspension in sea water, a 

 few survived for nearly a month. Carpenter et al. (1938) found that 

 natural sea water killed 80 per cent of the organisms in sewage within 

 half an hour. 



Porcelain or diatomaceous earth filters may remove marine sapro- 

 phytes with which the terrestrial organisms cannot successfully compete, 

 or may adsorb bactericidal substances from sea water. Kiribayashi and 

 AiDA (1934) found that Vibrio comma lived much longer in boiled or ster- 

 ilized sea water than in comparable raw sea water. The average survival 

 time of this organism in harbor water of Kellung, Formosa, was 10 days. 

 Gelarie (191 6) estimated that Vibrio comma could be eliminated by the 

 natural flora and other adverse conditions in New York harbor water 

 within 48 hours. 



Water from the Black Sea was found by Krassilnikov (1938) to be 

 germicidal for terrestrial bacteria until boiled. Passing the water through 



