ON THE TREATMENT AND UTILIZATION OF SEWAGE. 443 



into the river. The sludge from the tanks is cli-awn. off from time to time, 

 partially dried by an hydraulic press, and then biu'nt in a kUn, no additional 

 fuel being necessary after the firo is once started, as the dried sludge con- 

 tains sufficient organic matter to burn the deposit. The result is the pro- 

 duction of cement. It was found that the sewage was rendered inodorous 

 while in the sewers, and that the whole process was inoffensive. 



The Committee considered that " on the whole this process, when per- 

 fected, promises well as a means of treating one of the difficiUties of the 

 sewage question — the disposal of the sludge precipitated from sewage. It 

 ■appears not only possible to destroy the solid matters by fire, but also to 

 secure some return from their use in the manufacture of cement." 



They found, however, that the efiiuent water contained organic matters in 

 solution as well as ammonia ; so that this process cannot be considered as suffi- 

 cient of itself for the purification of sewage, nor for its utilization, but only as 

 one for satisfactorily getting rid of the offensive sludge which otherwise accu- 

 mulates in the tanks. 



Filtration. 



Upward Filtration. — The process of upward filtration through gravel was 

 examined at Ealing when General Scott's process was in abeyance. It was 

 found that this process, whether accompanied or not by the addition of a 

 deodorizing mixture to the sewage in the sewers in the town, " effected only 

 a very slight purification of the sewage, which left the filter still a sewage of 

 average strength. It was not even clarified." This observation thus con- 

 firmed the results of experiments previously carried out by the Rivers' Pol- 

 lution Commissioners. 



Weares Process. — This process, which is employed at the "Workhouse at 

 ^toke-upon-Trent, where the water-supply is very scanty and the sewage 

 consequently remarkably strong, consists in the filtration of the sewage 

 through coarse ashes and charcoal contained in the tanks through which it 

 passes successively. It appeared to be considerably purified ; but still the 

 effluent water after passing through the deodorizing tanks is described by 

 Dr. RusseU as having a strong smell of sewage. It is also to be observed 

 that no nitrates were found in this water, thus showing that no oxidation 

 had taken place. Prom the fact that the flow of effluent water was only 

 about 2000 gallons as against 5000 gallons of sewage in the 24 hours, and 

 that the chlorine was reduced to nearly half its original amount, the reduc- 

 tion taking place almost entirely in the first or so-caUed frecal tank, it would 

 appear that a considerable dilution must in some way have taken place, 

 accompanied by a very considerable and unexplained escape, which amounted 

 even supposing there were no dilution, to three fifths of the total amount. 



Intermittent clownivarcl Filtration. 



This process was examined at Troedyrhyw, near ITerthyr Tidfyl, where an 

 area of about 20 acres has been converted into a filter-bed for the purifica- 

 tion of the sewage of the town of Merthyr Tidfyl. The soU consists chiefly 

 of gravel and sand, having a vegetable-mould on the surface. It is extremely 

 porous. The land is drained at a depth of less than 7 feet, the drains bein" 

 brought together at the lowest corner, where the effluent water is discharged 

 into an open drain leading to the river Taff. '•' The area is laid out in square 

 beds, intersected with roads and paths, along which are constructed the main 

 carriers which receive the sewage from the outfaU-sewcr, and distribute it 

 over the beds." 



