ON THE TREATMENT AND UTILIZATION OF SEWAGE. 



169 



sho-wing that the nitrogen that is lost on this farm is lost for the most pcart 

 in the form in which it came on to the land, and that mere surface-action 

 (which is relied upon here) is not sufficient to cause the oxidization of the 

 ammonia and organic matters contained in the sewage. At the same time 

 the amount of purification effected was certainly very considerable. 



3. N'orwood Parm. 



Samples of sewage and effluent water collected from N'orwood Fields on 

 January 5th, 1871. 



The sewage employed on this farm was very strong, containing as much 

 as 7*42 parts of ammonia in the 100,000. 



It will be seen that more than two parts of actual ammonia escaped as 

 such in the effluent water, while nearly one fourth of the albuminoid am- 

 monia also escaped unaltered. At the same time a considerable amount of 

 nitrogen was lost as nitrates and nitrites, showing that a certain amount of 

 oxidizing action was going on. 



Thus there was a considerable loss of nitrogen, both in its original forms 

 and also as nitrates and nitrites. 



It must be remembered that this sewage was very strong, and that in this, 

 as in the other two cases, the samples were taken under the most disadvanta- 

 geous conditions during a very severe frost, when growth was at its minimum. 



The purification is in every case very considerable ; but these comparative 

 results speak volumes in favour of underdraining sewage-farms, and of so 

 obliging aU the sewage to pass through the soil. 



Some interesting results were observed as regards the temperature of the 

 sewage and effluent water. 



At Breton's Farm in the winter the temperature of the sewage was 46° F., 

 that of the effluent water 40° F. = 4°-4 C, a reduction of 5° or 6° only ; while 

 at Beddington Farm the temperature of the sewage was 42° F., and that of 

 the effluent water 34° F.=l°-1 C, a reduction of 8°. 



Thus with percolation through the soil the reduction is during the winter 

 much less than with surface-flow. 



On the other hand, we have observed that sewage is always cooled (sco 

 Table, Section II.) during the hottest weeks in summer by percolation 

 through the soil, and almost always heated (sometimes considerably so) by a 

 surface-flow during the summer. 



These results are favourable to percolation through the soil as opposed to 

 mere surface-flow, both in summer and winter. 



Percolation causes a considerable cooling in the summer, while in winter 

 it does not cool the effluent water so much as suiface-flow does. 



