CHAPTER IX 



BACTERIAL PURIFICATION 



History of the idea and of early experiments — Mueller's process 

 — Mouras' automatic scavenger — Massachusetts — London — 

 Sutton — Oswestry — Leeds — Triple filtration or contact. 



It had been proved early in the nineteenth century that natural 

 destruction of organic matter was due to living organisms, and 

 that these were the actual cause of decay and putrefactive 

 change ;^ but the powerful advocacy of Liebig and his school of 

 the so-called '* Catalytic " theory delayed the general acceptance 

 of the " germ theory " for more than thirty years. " Catalysis " 

 meant that some organic substances, in the act of undergoing 

 decomposition, possessed the power of causing the alteration 

 and decay of other organic substances in contact with them, 

 and this mechanical, as distinct from a biological, explanation 

 survived until Pasteur re-proved that fermentation and putre- 

 faction did not take place in the absence of living organisms. 

 He divided them into aerobic, or thriving in presence of oxygen, 

 and anaerobic, or growing without it, and their life-history and 

 character were elaborated by a number of observers. The 

 purifying action of soil was still regarded as partly mechanical 

 straining and partly chemical oxidation, and the necessity of 

 the co-operation of life in the processes was hardly taken into 

 account, more especially as in the important action of nitrifica- 

 tion no causal organism had been then discovered. The Berlin 

 Sewerage Commission, however, reported in 1872 that sewage 

 matter was converted into nitrates, not by a simply molecular 

 process, but by organisms present in natural sewage and soil, 

 and many observers demonstrated in various ways how the 

 purification of sewage was accomplished by bacterial action. 



^ On the history of the subject see J. T. Wood, Journal of the Society of Chemical 

 Industry, February 15, 1906, p. 109; Sims Woodhead, "Bacteria and their 

 Products," p. 49. 



