146 



Mr. Harry Grimshaw on the 



efficiently purify, under the conditions of flow, &c, in the 

 main tanks, and the trial was commenced on Monday, 

 June 1 2 th, 1890. 



Careful inspection of the results during the next day's 

 working made it evident that the quantities of precipitants 

 were not sufficient to produce a good result, and althougli 

 during the next day or two every possible variation was 

 made within the limit of quantity desired by the Salford 

 Committee, by allowing for the known rate of flow and 

 varying composition of the sewage during different periods 

 of the 24 hours, these variations all tended to show that 

 the quantities of precipitant whilst quite sufficient for the 

 night sewage, were inadequate for the kind of sewage 

 prevalent during the working day. 



That this was the case is shown by the following table 

 of the amount and percentage of albumenoids removed on 

 the first three days' working. The effluent showed by its 

 turbid appearance that it was not completely precipitated. 



Table II. 



Result of treatment of Salford Sewage, about 10,000,000 gallons 

 per day, with Basic Persulphate of Iron at the rate of one ion 

 per million gallons, together with 5 cwt. of lime per million 

 gallons. Albumenoid Ammonia per 100,000 percentage of 

 purification is on settled Sewage, and represents % of soluble 

 impurity removed. 



1893. 



Crude Sewage. 



Effluent. 



Effluent filtered. 



Shaken. 



Settled. 



Alb. Amm. 



% of puri- 

 cation. 



Alb. Amm. 



% of puri- 

 fication. 



June 13 



." I4 



r6o 



071 

 71 

 •54 

 '54 

 •51 

 •51 



0-58 

 *49 

 •48 

 •40 

 •41 

 •38 



18 

 30 

 II 

 26 

 20 

 25 



O'l 



o"i8 



31 

 63 



* Sewage after precipitation collected in special tank, and allowed to 

 subside before running off. 



