120 



SEWAGE AND ITS PURIFICATION 



Another filter effluent illustrates a usual rule — that while 



nitrosification is active nitrification is almost stationary ; but 



when the nitrites begin to decline the nitrates rapidly rise : 



November 10. November 18. December 2. 



Nitrous N 0*03 074 trace 



Nitric N 1*49 1-51 2-58 



In a septic tank effluent on November 10 the nitrate was 

 0*030, the nitrite none ; on December 2 the nitrate was o*o6o, 

 the nitrite excessive ; the nitrite had obviously been formed 

 from ammonia, and not by reduction of nitrate. An instance 

 of the transfer of oxygen by means of the oxidized nitrogen 

 compounds, resulting in a reduction of the organic carbon, 

 without a corresponding decrease in the amount of total 

 nitrogen, was given by my analyses of the Caterham effluents 

 in 1899, when kept for a short time in stoppered bottles partially 

 full. 



Samples. 



No. I. 



Jan. 26 Feb. i 



No. 2. 



Jan. 27 Feb 



No. 



Jan. 28 Feb. 1 



No. 



4. j 



No. 5. 



Jan. 30 Feb. i Jan. 31 Feb 



Ammoniacal N ... 

 Organic N 

 Nitrous N 

 Nitric N 



Total nitrogen 

 Oxidized nitrogen 

 Percentage of 



nitrification ... 



12-15 

 o-6i8 

 o'i48 

 7-68 



0"4I2 



0-074 

 9-0 



20-596 

 7-828 



38-0 



21-386 

 974 



45"S 



12-56 

 0-823 

 1-924 

 4-14 



12-1 12-35 

 1-03 o-6i8 

 1-702! 1-184 

 4-36 i 5-60 



"•54 

 0-41 

 1-40 

 6-46 



21-4 



1-23 



0-407 

 10-3 



I9'447 

 6-064 



31-0 



19-192 19752 

 6-062, 6-784 



32-0 34-5 



19-81 

 7-86 



39*6 



33"337 

 10-707 



32-0 



xygen consumed 3-32 

 ^hlorine j 18-5 



Percentage of re- 

 duction in the 

 oxygen consumed 



2-24 



6*27 

 197s 



4'43 4'i9 

 — 21-5 



3*47 



4-85 

 22-15 



32-5 — 



30-0 



[7-0 



20-6 , 23-8 



1-44 I 0-82 



0-41 I 0-59 



10-64 6-46 



33-09 131-67 

 1 1 05 I 7-05 



33'4 



2-78 



22-3 



4-52 

 24-35 



43 



0-666 



5'52 



19-5 



t 



The chief change seems to have been a transfer of the oxygen 

 of the air by means of the nitrous acid to the carbonaceous 

 matter. The nitrifying and nitrosifying changes appear to 

 have gone on continuously, the nitric being reduced to nitrous 



