BACTERIAL PURIFICATION 



211 



listinguished from the bacterial changes in the chemical con- 

 stitution was to some extent lost sight of, and it has required 

 [subsequent writers to accentuate the proposition that the cata- 

 lytic theory of Liebig was true in the sense that the reduction 

 »f the organic matter from a sewage in a contact-bed was 

 )rimarily due to absorption, and that this mechanical removal 

 >f organic matter was determined by the bacterial surfaces in 

 the bed independent of their vital activity.^ 



In the further experiments with a i-acre coke-breeze filter at 



[Barking it was found, as at Massachusetts, that continuous 



running resulted in clogging and a foul effluent, and that it was 



iibest to commence with small quantities of liquid, the filter 



^(3 feet of coke breeze and 3 inches of gravel) being at first 



lerely filled and emptied twice a day, with a view to producing 



m active bacterial bed. The following are averages computed 



From the daily analyses : 



Average Analyses from i-Acre Filter (Dibdin). 

 Parts per 100,000. 



The highest efficiency reached was 83 per cent, purification, 

 with 1,000,000 gallons daily and a shorter time of rest. The 

 filter was finally worked on the system considered to be the 

 best at Barking, Exeter, and Sutton — namely, alternate filling, 

 resting full, and emptying, with a periodical entire rest empty 

 for complete aeration. At Barking the filling occupied two 

 hours, the standing full one hour, the emptying five hours, so 

 that three cycles of eight hours were completed each day. 



_ ^ See, further, Dunbar, Vierteljahrsschf. Med. u. offentl. Sanitdlswesen, 3 Folge, 

 xix. ; Kattein u. ]nh'beri, Gesundheits-Ing, 1903; Jones and Travis, Proc. I.C.E.] 

 1905-1906 ; Fermi, Z. Spirit, ind., 1906, xxix., 221. 



14—2 



