64 



Dr. G. Reid. 



[May 7, 



at the same time, such a record, considered in conjunction with that of the 

 suspended solids, is useful for comparative purposes. 



For convenient reference, I have shown in the form of a diagram the 

 percentage reduction in free ammonia, albuminoid ammonia, and oxygen 

 absorbed at different stages, the figures for the sewage being taken at 100, 

 and also the actual nitric nitrogen figures in parts per 100,000. 



75 



*S' 



Percentage 

 reduction of 



Free Ammonia 

 Albuminoid D9 

 Oxygen absorbed 

 . in 4 hours at 8o°F. 



mR 



n 



n 



Nitric Nitrogen 

 in Parts per 100,000. 



Sewage 



Detritus 

 tank 



Septic 

 tank 



1 foot 



z feet 



3 feet 



4-5feet 



So much, then, for the detailed results of the working of this plant. 

 Whether what has been proved to be possible in this case will be found to be 

 equally possible in other cases remains to be seen, and if the answer be in the 

 affirmative, it is unnecessary to point out that the resulting economy in the 

 construction of filters would be very material. Personally I am extremely 

 optimistic regarding future possibilities in this direction, and only the other 

 day I had an opportunity of practically applying this recent experience with, 

 so far, most gratifying results, in the case of a stronger sewage and one which 

 contains a considerable amount of brewery waste. 



In this case the authority had some years ago constructed works which 

 provided for the nitrification of the sewage by means of " contact " beds, and, 

 being lately threatened with proceedings on account of pollution, on the 

 advice of their engineer an experimental plant was constructed, with the 

 view of determining whether better results could be obtained by means of 

 *' percolating " filters. Having worked these filters for about seven months, 

 the engineer came to the conclusion that he might safely recommend the 

 adoption of a scheme on similar lines, but with 5-ft. 6-in. filters, to dispose of 



