180 ANNUAL REPORT 



The difficulty of applying the Aylesbury plan to London and other 

 great cities, is that the immense proportion of inert mineral matter 

 in the sludge reduces its value for manure out of all proportion to cost 

 of handling. 



To lessen this difficulty a combination of the systeras of simple 

 subsidence and chemical precipitation has been proposed by a Maj. 

 Gen. Scott, of England, who appears to be acknowledged as an ex- 

 pert in sanitary matters. 



This plan proposes to flow the liquid sewage from the mains first 

 into great settling tanks, where the mineral matters in suspension are 

 to be allowed to subside. It is calculated that two-thirds of the solid 

 matter, nearly all mineral, will settle. Naturally some organic matter 

 will be carried down. From these settling tanks the sewage water, 

 bearing little but organic matter and that in solution, is to flowioto a 

 secQud set of tanks, when some defecating process, such as the lime pro- 

 cess of precipitation, is to be applied to it. This is expected to yield 

 a sludge so rich in organic matter that the manufacture of a fertilizer 

 will be profitable. It is further proposed to enrich this organic sludge 

 with superphosphates. The sludge of the settling tanks must be removed 

 by barges or wagons, and may serve for filling low lands; if not, it 

 must go out to sea. The effluent water, nearly pure, may be dis- 

 charged^s may be found convenient. 



4 MECHANICAL FILTRATION. 



This system, nowhere in operation except in an experimental way, 

 is interesting because it is a Yankee invention, and because I believe 

 it to point towards a simplification of the sewage problem. 



Not many years ago a Mr. Hyatt, of Newark, N. J., invented an 

 apparatus for filtering ou a great scale water for house use and manu- 

 facturing purposes. An example was shown in the Minneapolis In- 

 dustrial Exposition of 1886. This apparatus forces the water, treated 

 with a solution of alum, through a filter bed of pulverized coke and 

 clean sand. The novel feature is that of cleaning the filter bed by 

 simply reversing the current for a very short time, once in say twen- 

 ty-four hours. There can be no doubt of the efficiency of the Hyatt 

 apparatus, on a moderate scale, for cleansing waters. A thousand 

 towns and cities are already using it. 



The claim is now made that this apparatus will filter liquid sewage 

 effectually, and deliver the water purer than most unfiltered drinking 

 water. As an instance: An experimental apparatus set up in Chi- 

 cago has, it is alleged, delivered water purer than that of Lake Mich- 



