58 



ELEMENTS OF WATER BACTERIOLOGY 



September 21, 1898, and January 25, 1899, while 

 the average content of the effluent from the Jewell 

 filter was 400. Data with regard to the operation of 

 mechanical niters are now abundant, since all over the 

 world the operation of these plants is controlled by 

 bacteriological methods. Recently Johnson (1907) has 

 reported some interesting results from the far East. 

 At Osaka, Japan, an average of 200 bacteria per c.c. in 

 the raw water of the Yodo River was reduced, in 1905, 

 to an average of 25 by slow sand niters; at Bethmangala, 

 India, in 1906, mechanical niters treated the water of the 

 'Palar River, containing 4350 bacteria per c.c., and 

 yielded an effluent with only 13 per c.c. (Johnson, 1907). 

 The average monthly results obtained with the new 

 mechanical filter plant at Harrisburg, Pa., are included 

 in the table below for comparison with the figures 



REMOVAL OF BACTERIA BY NATURAL SAND FILTERS 

 AND MECHANICAL FILTERS. BACTERIA PER C.C. IN 

 APPLIED WATER AND EFFLUENT. MONTHLY AVER- 

 AGES 



