BACTERIAL PURIFICATION 



203 



Among them Hatton investigated^ the conditions under which 

 oxygen was absorbed and CO2 and H produced by bacteria ; 

 he also examined the effect of adding nitre to putrescent 

 organic liquids, and concluded that '* during the reduction of 

 nitrates by sewage COg is generated in the liquid, and perhaps 

 free N given off, while O is absorbed." 



Sorby, in 1883, remarked on the very large proportion of the 

 detritus of faeces which was lost in the river Thames, owing to 

 the action of larger organisms. Dupre, in a report to the Local 

 Government Board in 1884 on his experiments on aeration, 

 stated that " the consumption of oxygen from the dissolved 

 air of a natural water is due to the presence of growing 

 organisms, and that in the complete absence of such organisms 

 little or no oxygen would be thus consumed."^ Notwith- 

 standing this knowledge, the Royal Commission of 1882-1884, 

 after deciding against the discharge of crude sewage into any 

 portion of the Thames, prescribed " some process of deposition 

 or precipitation, the solid matters to be applied to the raising 

 of low-lying ground, or to be burnt, or dug into land, or carried 

 away to sea." The latter course was chosen as the only one 

 available for London. In i8g6 Dupre proposed " to cultivate 

 the low organisms on a larger scale, and to discharge them 

 with the effluent into the river, as the power these lower 

 organisms had was remarkable "; and at the Sanitary Congress, 

 Bolton, in 1887, he said, " Whatever scheme may be adopted, 

 except destruction of the sewage material by fire, the agents 

 to which the ultimate destruction of sewage is due are living 

 organisms (not necessarily micro-organisms), either vegetable 

 or animal. Our treatment should be such as to avoid the 

 killing of these organisms, or even hampering them in their 

 actions, but rather to do everything to favour them in their 

 beneficial work." 



Meanwhile, Emich in Germany was experimenting on the 

 changes which occurred in water and sewage on exposure to 

 and after agitation with air; also the behaviour of sterilized 



^ Chemical Society's journal, May, 1881, " Action of Bacteria on Gases," and 

 *' Reduction of Nitrates by Sewage." 



'^ The Second Report of the Royal Commission on Sewage^ 1902, p. 9, shows that 

 when sewage is sterilized either by chemicals or heat its oxidation, either by 

 filter or aeration, is almost prevented. The average percentage purification 

 obtained in the experiments was— with sterile filters, 15 ; with normal filters, 42. 

 The average nitrification was — nitrous nitrogen, sterile trace; normal, o'oiy ; 

 nitric nitrogen, sterile, 0-027 '• normal, 0-452. 



