TJie Purification and Utilization of Sewage. 



297 



is passed through wooden screens, containing 

 2 feet of charcoal, into the small chamber, 

 which contains about 5 feet 6 inches of rough 

 charcoal, through which the sewage percolates 

 into ^ smaller tank, thus completing the first 

 stage of filtration. The suspended matters 

 are partly arrested by the wooden and char- 

 coal screens ; and there is a further deposit in 

 the small chamber, which is usually cleared 

 once in six months. From the second tank 

 the sewage, after again passing through a screen 

 containing 6 inches of rough charcoal, is con- 

 veyed by a 12-inch pipe to the "deodorizers," 

 which are three in number. The first and 

 largest has a surface area of nearly 200 square 

 feet, and contains a depth of 5 feet 6 inches of 

 rough charcoal ; the second has an area of 

 about 70 square feet, and contains 2 feet 6 

 inches of charcoal of smaller size ; the last is a 

 small box containing 4 feet of fine charcoal, 

 supplemented by layers of flannel and filter 

 cloth. This completes the process, the effluent 

 water being discharged into a small well, from 

 which samples were taken for analysis. Wood 

 charcoal was used at the time of the inspection, 

 but it was stated that it was proposed to use 

 peat charcoal. The practice is to remove the 

 "spent" charcoal from the last deodorizer to 

 the second, from the second to the first, and 

 from the first to the first tank. 



The flow of effluent water for the period of 

 twenty-four hours amounted to only about 2000 

 gallons, as against 5000 gallons of sewage re- 

 ceived into the first tank during the same period. 

 The deposit removed from the tanks, with the 

 refuse of the establishment, is utilized upon a 

 farm belonging to the union, and cultivated 

 entirely by the inmates. Complete analysis of 

 the sewage and effluent water are appended, 

 f.nd the Committee observe that the general 

 result is to remove the suspended matter and 

 much to reduce the quantity of ammonia and 

 organic nitrogen. No oxidation occurs, and 

 the effluent water is to all intents and purposes 

 merely diluted sewage. 



The second section of the Report dealt with 

 processes in use at Ealing, namely, upward fil- 

 tration and the method of General Scott. The 

 Committee declare that upward filtration is 

 absolutely worthless, and with regard to General 

 Scott's process they say that by it the suspended 

 matters are precipitated very completely, but 

 that the effluent water was shown by analysis to 

 contain rather more than two-thirds of the 

 chlorine and of the dissolved nitrogen of the 

 sewage. They remark, however, that the dis- 



solved nitrogen appears in a different way in 

 the effluent water and in the sewage, the actual 

 ammonia is reduced to one-quarter of its origi- 

 nal amount, and the organic nitrogen, doubtless 

 from a solution of some of the suspended nitro- 

 genous matters, is nearly doubled. Some oxida- 

 tion has also occurred, by which nitrates appear 

 in the solution. Such water would be at once 

 too valuable to be wasted, and too impure to be 

 discharged into a river. It is not pretended that 

 the process is capable of purifying the sewage ; 

 its object being merely the separation and 

 deodorization of the sludge (which in the 

 majority of cases must be removed in some 

 way before the sewage can be applied to agri- 

 cultural purposes), and its ultimate employment 

 as fuel for the manufacture of cement. On the 

 whole, the process, when perfected, promises 

 well as a means of treating one of the difficulties 

 of the sewage question. 



The third section contains an account of 

 visits to the Earlswood and Tunbridge Wells 

 Farms. The Earlswood Farm was found to be 

 in much the same state as when reported on last 

 year — that is to say, that the sewage flows over 

 it, instead of percolating through it, from 

 saturation of the soil for want of deep drainage. 

 At Tunbridge Wells the sewage was very offen- 

 sive, but the effluent water was running away 

 tolerably pure. Here, also, however, an evidence 

 of the value of subsoil drainage in connexion 

 with sewage irrigation was afforded by the 

 marked contrast between the state of a bean 

 crop in the drained and the undrained portion 

 of the same field. 



The fourth section describes the results of an 

 arrangement first suggested and tried as a labora- 

 tory experiment by the Rivers Pollution Com- 

 mission, and first carried into actual practice by 

 the authorities of Merthyr Tydfil at the neigh- 

 bouring village of Troedyrhiw. The method is 

 known as that of " intermittent downward filtra- 

 tion ; " and consists essentially in the substitu- 

 tion of depth of soil for area as a purifying agent, 

 with especial reference to conditions under 

 which extent of area cannot be obtained. The 

 Rivers Commissioners stated that an acre of 

 filtering material 6 feet deep would cleanse the 

 sewage of 3300 people ; but they expressed an 

 opinion that, while successful from a remedial 

 point of view, the system would be very waste- 

 ful as not utilizing the valuable manurial pro- 

 perties of sewage, and for this reason it was 

 only to be recommended on a small scale, 

 or where circumstances rendered other 

 processes difficult and expensive. In 186S 



