The disposal of the city garbage and refuse has resolved itself into a question of vital importance confronting various municipalities of any size, and one that is proving hard to solve. Owing to the unsanitary features combined in the disposition of this material by dumping on waste land, or the transportation of it many miles to sea, such methods of disposal are becoming obsolete. It has been found that, even after dumping this refuse thirty miles at sea, it returned to shore and caused much annoyance. There is no doubt that many epidemics of disease are caused by such antiquated methods of disposal. Aside from the sanitary side of the question, it has been found that the citv-waste can be reduced to valuable commercial by-products, and in this age of enlightenment and progress, it seems truly criminal to destroy that which, by proper utilisation, can contribute so materially to the wealth of the country. Plants for disposal of garbage can be classified in a general way under two heads, namely, Incineration and Reduction. The first-named burns the material to an ash, and the last reduces to commercial by-products. Incineration does not appeal to me, from the fact that nothing remains but the ash, which contains but a small percentage of potash, of very little value. Bv reason of my connection with the reduction plant at Toledo as receiver, the past year, it has been my privilege to become familiar with the reduction system in vogue there. It is known as the Edson system, and the commercial products obtained are garbage-grease and garbage-tankage. Phe tankage produced is used byfertiliser manufacturers in the manufacture of commercial fertilisers, and is worth on an average about $9 per ton f. o. b. cars at plant. The grease is sold to soapmakers for use in the manufacture of soaps, and commands a price of about $80 per ton f. o. b. cars at plant. I shall confine myself to the general operation of this system, without going into minute details. The apparatus used in the process consists of hermetically sealed digestors, dryers and grease-extractors. Two digestors and one dryer constitute what is known as a unit of capacity, and are supposed to be capable of treating twenty tons of raw garbage every twenty-four hours. In the plant with which I am familiar there are three units—consequently, giving it a total capacity of sixty tons of garbage in twenty-four hours. The delivery of garbage to the plant during the summer months averages about forty-five tons daily, and during the winter months, about thirty tons daily, and, consequently, the plant has never been forced to its full capacity. The raw garbage is delivered in steel wagonboxes, so constructed that a box can be picked up with an electric crane, hoisted to the fourth, or charging-floor, and there dumped into bins of concrete construction. The box is then thoroughly cleansed and cleaned by hot steam and re turned to the wagon, the whole operation consuming less than five minutes. The next step is to charge the digestors with this raw material, which is done through galvanised iron pipes running from the charging-floor into the digestors on the floor below. When the digestors are filled, they are sealed up; the steam is turned on; and the mass of garbage undergoes sterilisation and disintegration for a period of about nine hours. During this time, the heat is regulated by air pressure upon the surface of the material, and no boiling occurs within. A valve is nowopened, and the mass is dropped through a sleeve into the drier waiting to receive it. It is dried by an external steam-pressure, and the maintenance internally of a vacuum during the drying process, which consumes about twelve hours’ tune. The original mass of material is now dry, and is dis charged automatically from the dryer in the form of unpercolated tankage, or, in other words, tank age from which the grease has not been extracted. It must be borne in mind, that during this entire process until now, this material has been under steam-pressure, and not once exposed to the air. All foul gases that arise during the operation arcpassed through a deodoriser for that purpose, thence into the combustion chambers under the boilers and destroyed. The unpercolated tankage is nowconveyed by means of elevators and conveyors to the third floor of the grease-extracting department, where it is ready to be put through the percolating process, which consists of cold nitration, using naphtha as a solvent. The material is fed through a galvanised iron pipe into the percolators, of which there are tw-o, each having a capacity’ of about five tons of unpercolated material every twelve hours. The percolator being filled, it is then sealed, and naphtha pumped into it until the material is entirely flooded. It is allowed to stand for a certain length of time, and the naphtha and grease together are pumped out and into separating tanks, which are provided with mushrooms heated to a degree of heat necessary to vaporise the naphtha, which is con ducted through vapor-lines to the condensing tank, changed into liquid form and used again. The grease is then pumped into storage tanks. Tinprocess is repeated until the whole mass of ilia terial in the percolator is thoroughly percolated and the grease removed. The material is now ready to dry, which is accomplished in the same receptacle by an external steam-pressure, tlior ough agitation and the maintenance of a vacuum. The dry tankage is now discharged automatically from the percolator, taken by means of elevator and conveyors to the storage room, where it is ready to lie shipped out for use in the manufacture of fertilisers. The percolating process con suming from six to seven hours time, the drying, from four to five hours. Using as a basis, the class of garbage we have been operating on, which is not the best, the percentage of finished tankage from raw garbage is about seventeen per cent.; of grease, about three per cent. This system, in addition to garbage, will handle dead animals, bones and anything in the way of or ganic matter.
•Paper read at the convention of the Central Waterworks association, Wheeling, W. Va., September, 1907.