168 



REPOKT — IS71. 



Tho sewage, after passing through the tank and pump, contains more sohd 

 matters in solution hut much less in suspension than the sewage as it comes 

 from the town ; the agitation causes some of the suspended matter to pass 

 into solution ; and it will be noticed that the amoimt of albuminoid ammonia 

 in solution is nearly doubled, showing that a considerable amount of nitro- 

 genous organic matter formerly in a state of suspension has been dissolved. 



This sewage is very much stronger than the average summer sewage, 

 which only contains from 2-5 to 4 parts of actual ammonia in 100,000 ; and 

 so one would hardly expect it to be so satisfactorily purified (especially, con- 

 sidering the extreme frost and the want of growth) as the sewage was 

 during the summer. 



Nevertheless the purification was very satisfactory indeed ; for the effluent 

 water only contained 0-143 of actual ammonia, instead of 5-628, while the 

 albuminoid ammonia was reduced from 0-524 to 0-059. 



Prom this we see that very little nitrogen passes away in the form of 

 ammonia or of organic nitrogen, even in winter, when vegetation has least 

 to do with the purification. 



Some of it passes away, however, in the form of nitrates and nitrites ; but 

 the amount which is thus lost is very little greater in the winter than in the 

 summer, being 1-208 part in winter and about 1-106 part in summer in 

 100,000 parts. 



Thus it appears that, with an underdrained soil, the sewage being obliged 

 to pass through several feet of soil before it escapes, (1) oxidation goes on in 

 ■winter as well as in summer, and almost all nitrogen lost is lost in an oxidized 

 and inoffensive form, and (2) this loss is very slightly greater in winter with 

 a very strong sewage than in summer with a weaker one ; so that sewagiug 

 in the winter would appear to entail no extra loss of manure. 



2. Beddington Farm, Croydon. 



Three samples of Croydon sewage, taken from Beddington Fields, 3rd Jan- 

 uary, 1871. 



The analyses show that the sewage applied to this farm contained on 

 January 3rd, 1871, just about the same quantity of ammonia as that applied 

 to Breton's Farm on tho da}^ before. 



The effluent water contained 0-744 part of ammonia, or between five and 

 six times as much as that at Breton's Farm ; the albuminoid ammonia was 

 less in actual amount in the effluent Avater; but the reduction -was from 0-188 

 to 0-045, or to one fourth of the original amount ; while in the last case it 

 was_ from 0-524 to 0-059, or to betM-een one eighth and one ninth of the 

 original amount contained in the scAvage as pumped on to the land. The 

 nitrates and nitrites in the effluent Avatcr were in insignificant amount, thus 



