240 Microbes and You 



are meeting the challenge of waste disposal quite satisfactorily. It 

 is important that such privies be provided with self-closing lids to 

 minimize the entrance and the multiplication of flies and other 

 insects capable of disseminating enteric pathogens. The filthy hab- 

 its of flies, which lay their eggs in human and other animal wastes 

 and then fly to places where food is being prepared for human 

 consumption, create a potential health hazard. More will be said 

 in a later chapter relative to insects and their possible role in the 

 transmission of disease. Suffice it to say at this point that flies 

 should be denied access to human wastes, which might contain 

 enteric pathogens. 



When sanitary privies fill up to within a few feet of the soil 

 surface, the wastes should be properly covered with dirt after 

 first pouring oil on the material to minimize opportunities for 

 insects to breed in the excrement. As was mentioned in the 

 previous chapter on water bacteriology, sewage outlets should 

 never be placed nearer than fifty feet from water supplies, and 

 drainage of sewage should be in the opposite direction from that of 

 water sources. If the soil conditions do not favor adequate de- 

 composition of sewage, fifty feet may not be sufficient distance 

 between the sewage outlet and the water supply. Each case is an 

 individual problem. 



CESSPOOLS 



Disposal of sewage on a small scale, such as from a private 

 home, is oftentimes accomplished by means of a cesspool, which 

 can be described as a hole in the ground with walls constructed 

 of stone or bricks piled up without the use of mortar. Such con- 

 struction allows seepage of sewage into the surrounding soil. 

 Solids drop to the bottom of the cesspool where they undergo 

 decomposition, principally anaerobic, and pathogens are eventually 

 destroyed through the antagonistic action of saprophytes. Unless 

 the ground around the cesspool is rather porous to permit proper 

 drainage, however, cesspools mav fill up and overflow, with un- 

 pleasant results. Manv properlv constructed cesspools have been 

 in operation for years requiring little or no attention. 



