262 



MICROBIOLOGY OF WATER AND SEWAGE 



Upland Surface Waters. — There are few bacteria in upland sur- 

 face waters draining barren uplands. Cultivation, grazing of animals, 

 and human habitation produce other conditions. In pure waters, 

 50 to 300 per c.c. by the gelatin and i to 10 by the agar count are found. 



Rivers.— The greatest variation in the number of bacteria exists 

 in river waters. Many factors, such as sewage contamination, tempera- 

 ture, rain fall, vegetable debris, etc., influence the microbial popu- 

 lation. A few figures may be given for illustration. 



Bacteriological Examination of Rivers at and below Large Sources of 

 Pollution {Boyce and Co-woekers) 



In the Chicago drainage canal, Jordan found 1,245,000 bacteria 

 per c.c. at Bridgeport; 650,000 at Lockport, twenty-nine miles below; 

 and 3,660 at Averyville, 159 miles below. Below where the sewage of 

 Peoria enters, the number rises to 758,000 at Wesley City, and decrease 

 to 4,800 at Kampsville, 123 miles from Peoria. 



The River Rhone contains an average of 75 bacteria per c.c. above 

 Lyons and 800 below. The Dee, 88 above Braemar and 2,829 P^r c.c. 

 below. Many more similar results are found in the literature. 



Lakes. — ^The water of lakes is generally much purer than river 

 water. Near the shore, the bacterial corjtent is higher than farther 

 out, showing the contaminating influence of habitation. Thus Lake 

 Gdneva contains as many as 150,000 bacteria per c.c. near the shore, 

 and further out only 38 per c.c. Other figures are as follows: Loch 

 Katriner, 74 per c.c. Lake Lucerne, 8 to 51 per c.c, Lake Champlain, 

 82 per c.c. 



Sea Water. — There are few bacteria in sea water remote from 

 the coast; but near the shore and in the neighborhood of seaports 

 there may be large numbers. 



