Filler

( Special.) A composition for filling small holes or pores in wood to prepare it for painting or varnishing. -n. pl . Lower grades of tobacco used in the manufacture of plug-tobacco and for the inside of cigars. Fill'more, in Nebraska , a S. E. co.; area, 576 sq. m. Rivers. W. Fork of Big Blue river, and Turkey creek. Surface, nearly level, and soil fertile. Cap . Geneva. Pop . (1890) 16,022. Filtration of Water. ( Sanitary Eng .) The water which was long furnished to many cities for drinking purposes, and which is still supplied in various instances, was and is unsuited for the purpose intended, being in some cases actually poisonous from the deleterious character of its contents. Originally, as a rule, it carried nothing more injurious to health than the mineral ingredients washed down from its sources and held in solution. But as the area of settlement grew, and towns and villages arose on the banks of streams supplying water to cities lower down, sewage and the liquid waste of manufactories became mingled with the water, and it grew more and more dangerous to drink, largely from the germs of certain epidemic diseases which it bore. As an example of this evil, it will suffice to mention the cholera epidemic at Hamburg (1892), which was traced very directly to the use of impure river water. How best to overcome this unsafe state of affairs is one of the leading problems in modern city management. Few cities can wait upon the slow proce of reservoir subsidence, even if that could be trusted to remedy the evil. To bring water from new and pure sources at great distances is a costly proce , with the danger of after-contamination of these sources. This being the case, filtration is looked to as the quickest, cheapest and most practical method of overcoming the difficulty; and, in consequence, many cities have provided themselves with filtering plants on a scale sufficient for the purpose. The methods of filtration resorted to are practically two in number-sand filtration and iron filtration-the character of each of which may be briefly described. In advance, it may be said, that deposition and filtration, if properly conducted, give us clearer and purer water than can ordinarily be had from natural sources; for not only is the suspended matter removed, but it is now known that filtration removes from water most and in some instances all of its pathogenic germs. Sand Filters. In the construction of a sand filter bed, the kind ordinarily used, a water-tight tank of some 12 feet in depth is provided, of an area in accordance with the quantity of water to be treated, an acre being sufficient for about 2,000,000 gallons a day. In the method now employed in London, Berlin, and some other cities, the concrete floor of the tank is covered with round tiles of three to four inches diameter, laid closely together. These are covered with about a foot of coarse gravel or broken stone, above which is a layer of sand 3 or 4 feet deep. Above the sand the water to be filtered stands at a depth of three or four feet. The bottom of the tank slopes downward in all directions toward a draw-off outlet. Through this the filtered water pa es at the speed nece ary to carry the water through the sand at the required rate, this being controlled by devices for adjusting the "head" at which the water flows off. The rate varies considerably in different cases, a good average being 50 gallons per sq. foot in 24 hours. The quantity pa ing per foot being known, it is easy to calculate the area nece ary to filter any fixed volume of water, though an extra filtering area must be provided to permit an occasional removal and washing of the upper layer of sand. Experiment has shown that it is in this upper layer that the most e ential duty of the filter is performed. There gradually gathers upon it a deposit which has a remarkable power of preventing the pa age of microbic germs. Investigation has shown that from 96 to 99 per cent. of the bacteria disappear. By this removal from the water of its mechanical impurities and its organic and microbic contents, it is left clear, pure, and wholesome for drinking purposes. Where available, the water should first stand in a subsiding reservoir until it has deposited the bulk of its coarser materials, and then be drawn or pumped to the filter bed for the final proce of cleansing. Iron Filtration . The first employment of iron as a filtering agent was by Prof. Bischof, who combined sand and iron filtration in the following manner: Under a layer of sand, for the removal of mechanical impurities, was placed a mixture of 3 parts of gravel to 1 of iron. When this was examined, after employment as a filter, no discoloration was visible in the sand except near the iron, where it became thickly coated and mixed with a reddish, slimy product. Lower down the mixture was of a black color. The slimy coating was removed and washed every six months. This method of using iron has since been considerably improved upon. The iron is now placed in a large, slowly revolving cylinder, suspended on horizontal trunnions, through one of which the water enters, escaping through the other. The iron commonly used consists of the burrs or punch ings from plates, about 2 tons being needed to treat a million gallons a day. Inside of the cylinder are curved shelves, which scoop up the iron and shower it through the water as they revolve. In this case no slimy product gathers, it being washed off as it forms, and the iron kept bright. A small quantity of the iron is di olved, forming ferrous hydrate at the expense of a part of the di olved oxygen. After leaving the cylinder the water regains the oxygen it had lost and the ferrous hydrate is further oxidized to ferric hydrate. This, being insoluble, settles, carrying with it most of the suspended organic matter. It is probable that a small portion of the organic impurities may be attacked chemically, but the chief action seems to be mechanical; the gelatinous precipitate entangling the germs and other foreign contents of the water and settling with them to the bottom. The purified water now pa es to a sand filter, on whose surface a film of oxide is deposited, which seems to have the power to retain microbes. One advantage of the employment of the iron filter is that this layer is formed immediately; while in the case of ordinary sand filtration, days pa before the layer is fully formed and the work of purification grows complete. The first employment of iron filters on a large scale was in 1881, at the Antwerp water-works, to deal with the highly contaminated water of the river Nethe. It here proved very succe ful, converting this liquid filth into a transparent and pure drinking water. It has since been employed in other parts of Europe, in the U.S., and India. Other methods of filtration have been employed, alum being one of the ingredients used; but sand filtration is the method most commonly adoted, and, wherever properly tested, with highly fav rable results. The one chief difficulty in the way is the considerable area needed to filter the water for a large city. The subject is still in the experimental stage, and new experience is being annually gained concerning it Fin de siecle ( făng deh se- ākl '). [Fr., end of the century.] (Used adjectively.) Appropriate to the period; up to date; advanced; progre ive.