Prof. Woodhead, The results of Sterilisation, etc. 559 



The results of Sterilisation Experiments on the Cambridge 

 Water. By G. Sims Woodhead, M.A., Trinity Hall, Professor 

 of Pathology. 



[Received 20 July 1910.] 



Although the sterilisation of water has a special local interest 

 at the present time, it is bound to come into greater general 

 prominence as time goes on and as sources from which pure 

 drinking water may be obtained become restricted in number, 

 and as the collecting grounds for the present supplies are built 

 over and sewers are carried through them. Without entering 

 into any discussion as to the bacteriological purity of the Cam- 

 bridge water, a question on which, however, I hold a very strong 

 opinion, I may point out that in the interests of both consumers 

 and water company, in view of the report of the Local Govern- 

 ment Board* on the "potential danger" of contamination, it was 

 necessary to adopt some method of eliminating any such potential 

 danger by adapting or devising a method of sterilising the water 

 or, failing this, of having recourse to a new supply. 



Of the methods that have, from time to time, been suggested, 

 some five or six in number, one was soon proved to be unsatis- 

 factory — Clark's method of softening and sedimentation. 



Another, sand filtration, was also set down as unsatisfactory 

 and for the following reasons. The Cambridge water, beautifully 

 clear and bright, contains a very small amount of organic matter, 

 so little, indeed, that the formation of an organic filtering film 

 can go on very slowly and, as is now fully recognised, until such 

 film is formed on its surface no sand filter is reliable, that is, it 

 will not keep back the necessary proportion of microorganisms. 

 Experience has proved that filtration of chalk water, — unless such 

 water contains a fair amount of organic matter in suspension and 

 in solution, or argillaceous material in suspension, — is practically 

 useless. 



A third method, sterilisation by heat, though no doubt effica- 

 cious, appeared to involve too great expense and too large an 

 amount of apparatus to be entirely satisfactory. No doubt satis- 

 factory results could be obtained but it is impossible to test this 

 method without a very large preliminary outlay, an outlay which, 

 if the method were unsatisfactory or too costly to run, would of 

 course be entirely lost. 



* Thomson and Crosthwaite, Eeport to the Local Government Board on 

 Cambridge Water Supply, London, 1908. 



