18 



Appendices to Tv:enty-sio:th Annual Report 



there is no real distinction between purification by bacterial filters 

 and purification on land. In each case the oxidation of the 

 organic matter is almost entirely brought about by living 



organisms. 



The fact that organic matter can be purified on land has, of 

 course, been known for many years, but there are many localities 

 where it is not practicable to obtain a sufficient area of land which 

 is suitable for the purification of the sewage or trade refuse which 

 has to be dealt with, and it is therefore of considerable importance 

 to ascertain the value of other methods of treatment. 



At the invitation of the Earl of Iddesleigh, Mr. W. E. Archer, of 

 the English Board of Agriculture and Fisheries, and I, attended a 

 conference of the Sewage Commission to discuss the question of 

 the purification of distillery refuse, with special reference to 

 Salmon Fisheries. Dr. Cowie, of the Mortlach Distillery at Duff- 

 town, had carried out a number of experiments for the purpose of 

 ascertaining whether distillery refuse could be properly purified by 

 bacterial filters. The results of these and other experiments 

 caused the Commission to think that, with certain modifications, 

 distillery refuse might be adequately purified by treatment on 

 bacterial filters. 



A special plant, which the Commission designed, was erected at 

 the Coleburn Distillery, some five miles from Elgin, early in 

 1906, and has since been in regular use for the treatment of pot 

 ale and steep water. 



It may be explained that in the process of whisky-making as 

 practised in Strathspey and neighbourhood, two distillations take 

 place. After the malting, which forms the essential commence- 

 ment, the first distillation results in low-wine, with pot ale as the 

 bye-product. The second distillation results in whisky and spent 

 lees. The pot ale which has to be got rid of after the first 

 distillation has in the past given rise to a great amount of trouble 

 in the Spey district, where distilleries are now very numerous. 

 The case of Lady Seajield v. Bodeiick Kemp was referred to at some 

 length in these reports (17th Ann. Kep., Part II., Append. IV.), 

 and as a result the distillers have attempted many methods of 

 purification, and in addition have had, in certain cases, to meet 

 proceedings for interdict against continued pollution. So far as I 

 have been able to ascertain, the processes of purification have been 

 not only costly in application but only partial in result. Pot ale 

 is the highly toxic substance which in all cases has formed the 

 chief source of difficulty. It is extremely complex in chemical com- 

 position, is highly putrescibie, absorbs oxygen rapidly, and forms 

 a characteristic and most disagreeable fungus which gives off great 

 quantities of lactic acid. I understand that the toxic properties 

 are estimated to be about fifty times as great as those of mixed 

 sewage of such cities as Manchester or Glasgow, or, put in another 

 form, that the poison-ratio of mixed sewage to pot ale is as 14 to 

 400. From experiment I have found that a salmon par put into 

 pot ale dies in two minutes. 



By means of the treatment by bacterial filtration now employed 

 by the Commissioners, an effluent is obtained which is non- 



