198 Mode of extracting Manure from Sewage Water, 



Upon subjecting some of it to a chemical examination, I found 

 its composition to be as follows : — 



Water .. . 4*71 



Organic matters, containing 1* 125 grains of nitrogen 



(= 1 • 366 grs. of ammonia) . , . , 15 "91 



Salts of potash and soda, soluble in water , , a little 



Carbonate of lime with some carbonate of magnesia . 69 * 28 



Sulphate of lime . . . , . , 3*26 

 Earthy phosphates, containing 2*03 grs. of phospho-^ 



ric acid . . . . . . , , 4*10 



Silica and other insoluble matters . . . . 2*74 



100- 



Now, good farm-yard manure contains, as an average, according 

 to my own experiments, about '42 per cent, of nitrogen, and '65 

 per cent, of phosphoric acid. Hence, this defecated night-soil 

 may be said to possess between three and three and a half times 

 the value of farm-yard dung. 



On obtaining such favourable results, I applied to Mr. Woods, 

 the Governor of the Cardiff Gaol, for some account of the 

 method by which the manure is prepared, and was referred by 

 that gentleman to Mr. Higgs, of London, who kindly furnished 

 me with the subjoined information. Near the outfall or at any 

 convenient point of the sewer's course, a series of tanks are 

 erected into which the sewerage- water is conducted, being either 

 run into them from a higher level or raised by pumping. These 

 tanks are filled in succession, and as the sewage flows in, it is 

 mixed with the chemical agent (in most cases, milk-of-lime), 

 which is added in just sufficient quantity to effect the precipita- 

 tion of the faecal matters, &c. Tlie first tank having been filled, 

 it is allowed to remain at rest, whilst the same operation is being 

 carried on in the others. In the course of a few hours the 

 manure is completely deposited, at the bottom of the tank, in the 

 form of a pulp or paste. The supernatant water is then drawn 

 off, and the vessel is ready for the next charge. 



Whilst the operation is being performed, the cover of the tank, 

 which is air-tight, is kept shut down, and the air that is expelled 

 on the entrance of the sewage, together with any offensive and 

 pernicious gases that might be liberated by the action of the 

 caustic lime on the faecal m.atters, &c., escapes by a pipe and is 

 conducted into a chamber or purifier, where it is compelled to 

 pass over several layers of peat charcoal saturated with dilute 

 hydrochloric acid. This chamber is somewhat similar in con- 

 struction to those employed in the purification of coal-gas in 

 many manufactories, and presents a section like the annexed 

 diagram. 



