PROCEEDINGS 
OF THE 
Cambridge Philosophical Soctety. 
The oxygen content of the river Cam before and after recewing 
the Cambridge sewage effluent. By J. E. Purvis, M.A., Corpus 
Christi College, and E. H. Buack, M.B. (Kdin.). 
[Read 23 February 1914. | 
| The 8th Report (1912) of the Roya! Commission on Sewage 
Disposal, Vol. 1, deals with the standards to be applied 
to sewage and sewage effluents discharging into rivers and 
streams, and the tests which, in the opinion of the Commis- 
sioners, should be used in determining those standards. They 
discuss also the connection between the physical and the 
chemical conditions of streams receiving sewage liquids, the 
various tests which are now employed, such as the amount of 
ammoniacal nitrogen, the amount of oxygen absorbed from 
permanganate of potassium in four hours, and the amount of 
dissolved oxygen taken up in five days. Finally they selected 
‘the amount of dissolved oxygen which is consumed in five days at 
18° C. as the basis of a standard. 
| It is obvious that there are local and seasonal variations in 
the conditions of rivers and streams receiving sewage or sewage 
effluents ; but they conclude that if 100,000 c.c. of a river water 
do not normally take up more than 0-4 gram of dissolved oxygen 
in five days, the river will be free from signs of pollution; and 
jthat if the river gives a higher figure than this, it will show 
isigns of pollution, except perhaps in very cold weather. They 
therefore decided that this figure ought not to be exceeded by the 
mixture of the rivers and the polluting streams discharging into 
them. The experiments were carried out at 65° F. (183° C.), for 
when the five days’ test was carried out at the various tempera- 
jtures of different seasons, varying results were obtained. They 
also adopted the normal dry weather flow of the river. 
VOL. XVII. PT. V. 24 
