142 



HKPOKT 1872. 



mixture, effected only a very slight purification of the sewage, which left in the 

 filters stiU a sewage of average strength ; it was not even clarified. AVith 

 regard to General Scott's i^rocess, it would appear that by it the suspended 

 matters are precipitated very completely : as to tlie more important consti- 

 tuents of the sewage, it is seen from the analyses that the effluent water 

 contained rather more than two thirds of the chlorine, and three fourths of 

 the dissolved nitrogen of the sewage ; but it must be remarked that the 

 dissolved nitrogen appears in a different way in the effluent water and in 

 the sewage ; the actual ammonia is reduced to one quarter of its amount, 

 while the organic nitrogen, doubtless from solution of some of the nitrogenous 

 suspended matters, is nearly doubled in amount in the effluent water. Some 

 oxidation, too, has taken place by which nitrates appear in the solution. Such 

 water would be much too impure to be sent into a river, and too valuable to 

 bo wasted ; indeed it is not pretended that the process is capable oi purifijinjj 

 the liquid sewage, its object is merely the separation and deodorization of 

 the sludge (which, in the majority of cases, must necessarily be removed before 

 the sewage can be utilized), and its ultimate use as fuel in the manufacture 

 of cement. 



Sectiox III. 



A process known as " Whitthread's Patent " having been brought under 

 the notice of the Committee, has been investigated by a preliminary experi- 

 ment on a sufflcicntly large scale, although it is not at present in operation 

 anywhere, the supporters agreeing to pay the expense of the necessary 

 analyses. 



The process consists in the addition of a mixture of dicalcic and mono- 

 calcic phosphate containing, it was stated, two equivalents of dicalcic to one of 

 monocalcic phosphate (the latter being added as commercial superphosphate), 

 and then afterwards a little milk of lime. In the experiment referred to 100 

 gallons of sewage, taken from the Eomford sewer before it joins the tanks 

 on Ereton's Farm, were operated on, one pound of the mixture being stirred 

 up in a little water, and added after the addition of a little milk of lime. 

 The precipitation was very rapid, and the supernatant water remained very 

 nearly clear and quite inoffensive. 



The accompanying Table shows the result of the analyses of the raw 

 sewage, the supernatant water, and the precipitate : — 



Ecsults giYc;i in parts per 100,000. 



