462 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 



HIGH NITRIFICATION OF SEWAGE EFFLUENTS. 



With Simple Methods of Obtaining them for Horticulture. 



By W. D. Scott- Moncrieff, F.R.H.S. 



[Lecture delivered January 20, 1909.] 



Our knowledge regarding the natural processes that reduce organic 

 matter to its original inorganic elements is of recent date. There is 

 a distinction between the contributions of those who have made more 

 or less speculative suggestions and the pioneers who have not only 

 taken up a theory but have succeeded by actual experiments to positive 

 proof. Although Cagniard de la Tour and Schwamm in the beginning 

 of the last century demonstrated that yeast was a living plant, and that 

 putrefaction was due to something in the air that could be destroyed 

 by heat, the catalytic theory, so fiercely advocated by Liebig and his 

 followers, delayed the acceptance of the germ theory for more than 

 thirty years, and it is to the illuminating genius of Pasteur that we 

 are indebted for having proved the connection of microscopic life and 

 all forms of putrefaction without an exception of any kind. The 

 suggestions made by Dupre in 1886 that sewage discharged into a river 

 might be purified by the cultivation of low organisms on a large scale 

 may very well have emanated from the labours of the great Frenchman, 

 but the vagueness of the proposal shows how little was really known of 

 these vast natural processes even twenty years ago. 



The first application in this country of the knowledge of bacteriologists 

 that certain organisms had the power of liquefying organic matters was 

 made by myself in 1891 in what are known as the Ashtead experiments, 

 in which there was a tank, of a peculiar construction, filled with large flints 

 that provided surfaces for the propagation of the organisms contained in 

 the sewage from a household of about ten persons. 



The process referred to was a purely putrefactive one, and the results 

 obtained were due to the work of anaerobic organisms and their ferments, 

 which break down the organic matter into simpler molecular forms, and 

 so prepare the polluted liquid for the further purification carried on by 

 different kinds of organisms working under highly aerobic conditions. 

 My efforts to solve the second half of the problem, involving the 

 oxidation of the substances that may be spoken of as being on the 

 way to final mineralization, were not rewarded with much success, and 

 it was not until 1897 that I devised a very simple apparatus that 

 produced results far in excess of any other process. The arrangement 

 is shown on the accompanying diagram (fig. 102), and consists of a series 

 of superimposed trays, each containing suitable filtering material, so that 

 the liquid could drip from one to the other, with an ample provision of 

 air in the spaces between the trays. 



