526 



The Storage of Farmyard Manure 



There was therefore considerable breaking down of organic matter. 

 Much of the nitrogenous matter was decomposed with formation of 

 ammonia, the gain in ammoniacal nitrogen being : 



Exeter 

 Ammoniacal nitrogen in sewage (lbs.) ... ... 14,711 



„ „ „ septic tank liquor ... 16,452 



Increase in ammoniacal nitrogen 



Percentage increase ... ... ... •... 



But there was no loss of nitrogen ; the total amount remained prac- 

 tically unchanged: 



1,741 



11-8 



Uford 

 8,311 

 9,020 



709 



8-5 



Under aerobic conditions, however, a loss of nitrogen sets in. This 

 is shown in an experiment made by the Sewage Commission at Accring- 

 ton^ in which sewage was run by means of a rotating sprinkler from the 

 septic tank on to a percolating filter made of clinker. The persistence of the 

 aerobic conditions is demonstrated by the fact that the effluent remained 

 saturated with dissolved oxygen. The experiment continued altogether 

 for three years, and was divided into five periods; the results of all 

 show considerable agreement so that it is not necessary for us to tran- 

 scribe more than two. The figures are stated as parts per 100,000, 

 but as the volume of sewage remained approximately constant they 

 are proportional to the total weights. 



Loss of nitrogen in aerobic decomposition of seivage. 



Nitrogen as complex compounds 

 „ „ ammonia 

 „ „ nitrate 

 Nitrogen lost 



Total 



Percentage loss of nitrogen 



612 



612 6-06 606 



30-6 — 34-2 



It will be observed that the loss of nitrogen now exceeds 30 %, 

 whereas in the preceeding experiments it was nil. 

 ^ McGowan and Frye, ibid. pp. 52-72. 



