June 7, 1900J 



NATURE 



131 



The experience obtained from several years' experi- 

 mental bacterial treatment of sewage at several of our 

 largest cities has recently been published. 



In 1893 the London County Council constructed an 

 acre coke-bed about three feet in depth at the Barking Out- 

 fall of the North London Sewage. This bed has been 



Impression preparation from a gelatine plate 

 culture. X 1000. 



receiving screened and sedimented sewage up to the 

 present time, the process of sedimentation having been 

 assisted by the addition of a small proportion of solutions 

 of lime and of ferrous sulphate. Two years ago the bed 

 was deepened to about six feet. Its purifying action, as 

 measured by the amount of oxidisable matter present in 



\entericus. Sewage variety E 

 from a 20 hours' agar culture at ; 



Microscopic preparation 

 C. X 1000. 



[the raw sewage and in the clear efifluent, amounts to 

 I92 per cent., and if the purification is calculated from the 

 |clear sewage and efifluent, it amounts to 84 per cent, 

 "lore recent experiments have proved that the treatment 

 " raw, roughly-screened sewage in such coke-beds is 

 Uisfactory, but that the capacity of the bed becomes 



NO. 1597, VOL. 62] 



continuously reduced by the deposition upon the coke of 

 mineral matter from road detritus, of particles of straw, 

 chaff and woody matter from the horse-traffic and from 

 the wood pavements. It was, therefore, evident that these 

 matters must be deposited by sedimentation before the 

 sewage was brought into the coke-beds. A comparatively 



—B. enteritidis sporogenes (Klein). Microscopic double-stained 

 preparation, from a serum culture, showing spores. X 3000. 



rapid process of sedimentation suffices to remove these 

 matters, since even the cellulose matters arrive in the 

 sewage in a heavy and waterlogged condition. 



It was found advantageous to use coke in comparatively 

 large fragments, about the size of walnuts, since this 

 facilitated the rapid draining of the liquid from the coke. 



Fig. 9. — Proteus vulgaris, x 1000. 



and at the same time increased the sewage capacity of 

 the bed and promoted its efficient aeration. The depth 

 of the beds has been augmented from 4 to 13 feet, and the 

 increase of depth seems to be attended with increase of 

 efficiency. The 13-foot bed has for long periods given a 

 purification from dissolved oxidisable matter of over 



