CHAPTER XXIX 



BACTERIOLOGY OF WATER 



All waters probably contain a greater or lesser num- 

 ber of bacteria, although those of the pathogenic variety 

 are found only wheif there is direct contamination from 

 human sources. The naked-eye appearance of any 

 sample of water is rarely indicative of its safety; some 

 very clear and sparkling water may be contaminated with 

 typhoid bacilli and constitute a serious menace, while a 

 turbid water may owe its lack of clearness and a possible 

 disagreeable taste and odor to the presence of minute 

 water plants and algse that are absolutely harmless. 



Pollution to be Guarded Against. — Rural communities 

 depend almost entirely on springs and wells for their 

 water supply, and great care is necessary to so locate cess- 

 pools, privies, drains, stable sinks, etc., that their dis- 

 charge or overflow may not contaminate the drinking- 

 water. Shallow wells, which are nearer the surface and 

 receive the local wash after a rainstorm, are naturally 

 richer in bacteria than deep wells, and in farming regions, 

 in pasture lands, may contain large numbers of intestinal 

 bacteria. 



For cities the supply of safe and pure water has be- 

 come a very important and serious problem. AMiere 

 mountain springs are abundant, within reasonable dis- 

 tance, the water may be allowed to collect in reservoirs 

 and be conducted to the city, often a distance of many 



.146 



