CHAS. E. FOWLEK. 285 



98 per cent. In the matter of water purification by this 

 method of filtration Germany is in advance of all other 

 countries. In 1894 the German government adopted a 

 set of rules regulating the filtration of surface waters 

 used for public water supplies. Among other require- 

 ments is that of daily bacteriological examinations of the 

 filtrate from each single filter; and every city in the em- 

 pire is requested to make a quarterly report of their 

 working results (bacteriologically) to the Imperial Board 

 of Health. 



A sand filter bed is a very efficient but highly sensi- 

 tive appliance. When in good order and properly 

 operated the results obtained are most satisfactory. 

 When the conditions are changed the eflSciency rapidly 

 deteriorates. My observation of the working of our 

 own filter beds has been that, while unfavorable condi- 

 tions greatly reduce the efficiency no condition has ever 

 existed by which the effluent water was rendered loorse 

 than the applied river water but always better. The 

 appearance of the water always indicates this and all the 

 chemical and biological examinations made, without an 

 exception, show this to be the case. 



Our beds were designed to filter at a much more rapid 

 rate than the established rate before stated. The total 

 area of filtering surface is 29,300 square feet, or about 

 two-thirds of an acre. The quantity filtered was intend- 

 ed to be 3,000,000 gallons in 24 hours, giving an area of 

 one acre to 4,500,000 gallons in 24 hours, or less than 

 half that above mentioned. The quantity filtered fre- 

 quently considerably exceeds 3,000,000 gallons in 24 

 hours, in fact, adding the leakage, the quantity passing 

 through the sand is nearly 4,000,000 gallons in 24 hours. 



In the practical management of filter beds many 

 difficulties, not apparent to the casual observer, are 

 encountered. In most cases they are open to the 

 weather, their great area rendering any method of cover- 



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