We illustrate in Fig. 2 the Hyatt plant at the Long Branch (N. J.) Water-Works, having a capacity of treating 2,000,000 gals. per day. This consists of 8 cisterns, each 10 ft. in diameter, and connected with a common inlet and outlet pipe: "The water having first been aiirated and coagulated, flows from the main supply-pipe to and into the filters above the surface of the filter-beds, and in passing downward is relieved of all objectionable constitu ents, issuing through a series of wire-bound outlet screens into a common delivery-pipe, and being carried by the continuous pressure to the various consumers. At stated periods (ordi narily once each day) the arrested impurities are thrown off from the beds of filtering material into a waste-pipe leading to the sea, each filter being renovated independently while the others are performing their work of purification. During this operation the intake-pipe to the filter undergoing the operation is cut off from the main inlet,, and water passes through a central vertical pipe connecting with a horizontal radial pipe at the bottom of the bed. The water issuing through this horizontal pipe saturates the bed immediately around and above it, the arrested impurities being detached and carried off by the current. While this current is flowing through the horizontal washing-pipe, the latter is gradually moved by means of a lever outside of the filter, and by the time it has passed all round the interior, agitating and scouring the mass in succession until it has arrived back to its original position, the entire filter-bed will have become cleansed, and the process of filtering is then resumed. This operation occupies usually about 10 min., but where the water treated yields an extraordinary amount of tenacious sediment a somewhat longer scouring may be necessary. The automatic aeration is accomplished before the water reaches the pumps. After leaving these it flows through the main inlet to the filters, and thence to the consumers. The plant at Atlanta, Ga., differs in construction front that at Long Branch, in the fact of having two stories or chambers, one above the other, the upper comprising the washing-chamber, separated from the lower compartmencor filter proper, by means of a partition or diaphragm, this partition being indented with funnel-shaped depressions to facilitate the return-flow by gravitation of the filtering material to the lower chamber. The unpurified water enters at a point just below the diaphragm, flows downward through the filter-bed, issues at the bottom through a series of valves all connected in one system, and is delivered into a clear-water basin, from which it is pumped by the Holly system of pumps directly to consumers. The principles of coagulation and as exemplified in this plant, are precisely the same as at Long Branch, the difference in construction consisting in the method of renovating or washing the beds. In this case the beds are washed by means of vertical pipes, through which the entire contents of the lower chamber are forced up by ordinary water-pressure and deposited in the upper or washing-chamber. The combined effect of attrition in passing through these pipes and violent contact with the water contained in the upper chamber causes a complete separa tion of the filtering material from the impurities, which flow with the current out through the pipe leading from the upper chamber, thence to a sewer or other outlet. This operation having been accomplished, the filtering material is permitted to return to the lower chamber by gravity through the conical apertures in the dividing partition. When thus restored to its original position all openings are closed, excepting the inlet and outlet, and the process of filtration is immediately resumed." The report of the Board of Water Commissioners of Atlanta for the year 1890 shows that the filters used 02,390 lbs. of alum during the preceding year, equal to •G17 grain to the gal., and that the cost of filtration per million gals. was $3.83.
The Warren Filter (Fig. 3) was invented in 1885 by Mr. John E. Warren, of S. D. Warren & Co., paper manufacturers. The invention was the outcome of the necessity of a filter which would purify the large amount of water used in the Cumberland Mills of the above firm, this being now the largest mechanical filter-plant in existence, having a daily capacity of 12,000.000 gals. The chief merit claimed for this filter is the mechanical rake or agitator. By its use the sand composing the filter-bed is thoroughly scoured, and the filtered water is only used to rinse off the dirt thus loosened. As a result of this method of procedure, the filter can be rtipidly and thoroughly cleaned with the minimum consmnption of water. Experiments also pointed to the fact that insufileient clone was usually allowed for the reaction of the alum or other coagulant used in the water ; hence. in the Warren system, the coagulant, in the form of a solution of definite strength, is pumped into the water as it passes to a settling-basin or tank so proportioned in size as to allow each particle of water to remain in contact with the coagulant the length of time found neces sary for the chemical reaction. In this way it is claimed that a greater economy of the coagulant is obtained, and the possibility of its passing into the filtrate is removed— a point of much value where the water is used for domestic purposes. The filter, by Mau bin ing coagulation, sedimeil tation, and filtration. by the use of an open filter-bed so arranged as to be quickly and mechani cally freed from the intercepted Matter. and by the use of a light pressure never exceeding % lb. per sq. in.. is intended to
unite all desirable features with a compar atively inexpensive form of construction.
From Fig. 3. which clearly exhibits the internal mechanism, the operation of this filter will be understood.
During filtration, the unfiltered water, entering through the valve, passes up into the filter-tank, thence downward through the filter-bed, supported by the perforated plate, and through the filtered water-main, by which it is carried to the mill. When it becomes necessary to cleanse the filter bed the valves are adjusted to allow the water in the tank to pass into the sewer. When the water in the tank has been drawn off, the agitator is set in motion, and driven down into the bed by means of the screw shown, while at the same time a slight amount of filtered water is allowed to flow back up through the bed, in order to rinse away the dirt which has been loosened by the scouring action of the revolving agitator. When the flow of water up through the bed becomes clear the agitator is raised. the waste-gate closed. and by the opening of the valves filtration is resumed.
The Nalion.al —This filter, manufac tured by the National Water-Purifying Co, of New York, is represent ed in section in Fig. 4. The filter proper is about two thirds filled with in thstruet ible fine quartz sea sand, lm the top of the filter-ease is shown a device for supplying a minute quantity of chemical solution to the water when it is very may or turbid or im pregnated e11h sewage. the effeet of the eliemi cal being 10 precipitate the impurities in solu tion and srl+frOnsiWW, while 11 , chmnient it set f is retained with the impurit les it precipi tates upon filo I op of the filtering materil, so that lin tries of it (even by anidysistriptwars in the filtered water. In the bottom of the filter are shown the brass tub ular strainers for preventing the sand passing out with the filtered water. These strainers are filled with gravel, and are half imbedded in cement—up to the line of perforation—which prevents any filth and disease-germs from settling below them, where they could not be reached and dislodged by the reverse current when washing the filter. They are also so pro portioned and constructed that in washing the filter they insure a complete reverse-current in every part of the bed, which does away with the necessity of any mechanical appliance for stirring the bed when washing. The water to be purified is admitted under pressure to the filter at A above the sand filter-bed, and where, if necessary, it is mixed with a minute quan tity of chemical solution as above described ; it then passes down through the sand, brass strainers, and outlet-pipe E back into the service-pipe, leaving the commingled impurities and chemical (if used) on the surface of the filtering material at the top of the filter. Once a day the water should be shut off from the inlet, above the filtering material, and be allowed to enter the filter in the reverse direction, from the bottom at E. It will then pass up through the filtering material, which it thoroughly loosens and scours, carrying the commingled im purities and chemical on the surface of the filter-bed off through the waste outlet B, which connects with the sewer. This operation only takes 10 min. time, when the water is again admitted at the inlet at top of the filter as before, and filtering recommences. The waste B (at some point close to the filter) should be left exposed by means of a trough or funnel, so that the condition of waste washing-water will show when the filter-bed has been thoroughly cleansed. The National filtering system is in use in Chattanooga, Tenn., 6,000,000 gals. daily capacity: Terre Haute, Ind., 3,000,000 gals. daily capacity ; and in various other cities of the United States.
Small Filters and Fillers for Special Purposes.—The Jewett filter, made by the John C. Jewett Manufacturing Co., of Buffalo, embodies a cup containing sponge and a vessel con taining gravel, through both of which the water passes into a settling receptacle. After over flowing the latter it proceeds through the filtering-bed proper, which consists of layers of gravel, sand, and decarbonized charcoal.
A Filler-Press for Porcelain Clay, devised by M. P. Faure. of Limoges, France, and described in Engineering, January 17, 1890, possesses many novel features. The clay and water are mixed to the consistence of cream, and are pumped into the filter-press. The mixed clay and water are not allowed to come in contact with the plunger of the pump, an elastic diaphragm being interposed, the vibrating movement of which forces the material into the press; the pump-cylinder has two plungers, one working within the other, and so arranged that the smaller one can be put in operation when it is desired to increase the pressure in the filter-press. The last-named apparatus has a east-iron frame, on the longitudinal bars of which are hung a series of cast-iron rings covered with iron gauze ; between the frames thus formed canvas bags are placed, so arranged that the liquid which is delivered by the pump to a central opening in one end of the press, receives it, and allows the water to pass freely. The series of frames and bags are held together by the end screw, and the pressure that can be exerted within the filter by the pump varies from 120 lbs. to 150 lbs. per sq. in.; the clay freed from the water that held it remains in the form of compressed cakes in the bags, and about 500 lbs. of clay ready for the edge-runners can be turned out from one of these presses per hour.