226 Microbes and You 



but only if such water has not been filtered. The amoebae cannot 

 pass a sand filter, but they can withstand the usual concentrations 

 of chlorine employed in water purification. 



SMALL VOLUMES OF WATER 



Campers, unless they carry their own drinking water, are faced 

 with the problem of finding water near the camp site and treating 

 this water to make it fit for consumption. Other methods being 

 unavailable, water can be vigorously boiled for ten minutes and 

 the usual enteric pathogens will be inactivated. The higher the 

 altitude, the lower will be the boiling point of water in an open 

 container. But even on the highest peak in the United States, the 

 boiling point will be sufficiently high to insure killing undesirable 

 organisms within the prescribed ten minute period. 



During World War I the Army Medical Corps advocated the 

 use of two drops of tincture of iodine for each quart of water to 

 make it safe for human consumption. A thirtv-minute waiting 

 period, however, is required for insuring this disinfection. The use 

 of tablets containing available chlorine was a recommended prac- 

 tice in the army during the second World War. Two such tablets 

 for each canteen (about one quart) of water will disinfect this 

 volume in thirty minutes, but if the water is very muddy, four 

 tablets are required to allow for the affinity the chlorine has for 

 organic matter. 



WELLS IN RURAL AREAS 

 Water from newly constructed wells will normally have a very 

 high bacterial count which will not "settle down" for a matter of 

 weeks or even months unless the supply is treated to reduce the 

 bacterial population that found its way into the water during 

 construction operations. A common treatment is to dissolve the 

 contents of a freshly opened one pound can of chloride of lime in 

 two quarts of water. After the insoluble lime has settled, introduce 

 into the well two ounces of the clear supernatant solution for every 

 estimated one hundred gallons of water. This concentration of 

 chlorine is high enough to be detected by smell. Allow the 



