Treatment of Sewage with Basic Per-Salts of Iron. 143 



On the Treatment of Sewage with Basic Per-Salts of 

 Iron under varying conditions. By Harry Grimshaw, 

 F.CS. 



(Received February 6th, 1894..) 



The object of the present paper is to present the 

 conclusions arrived at from the treatment on the working 

 scale of large volumes of the sewage of a manufacturing 

 town in relation to the chemical problem involved, and 

 the practical conditions under which the trials were 

 carried out. 



In a paper read before the Manchester Literary and 

 Philosophical Society on May 4th, 1890, and printed in the 

 Memoirs of the Society, the results of the treatment for a 

 period of a month, of 100,000 gallons per day, of the 

 Salford Sewage are given, and the further results which are 

 given in the present paper are from the application of the 

 Basic Persulphate of Iron to the whole of the sewage of 

 that town. 



The preliminary experiments upon the 100,000 gallons 

 per day were conducted in a set of experimental tanks at 

 the Salford Sewage Works, which are constructed to 

 contain exactly one hundredth part of the volume held by 

 the main tanks, which are used to treat an average of nearly 

 10 million gallons per day of 24 hours. 



The minimum daily flow of the Salford Sewage is about 

 six million gallons upon the Sunday when, owing to the 

 manufactories not being at work, the sewage approximates 

 to that of an ordinary residential town. The maximum is 

 some thirteen or fourteen millions during the middle of the 

 week and during wet weather. From about 6 a.m. on the 



