THE WASHINGTON FILTRATION PLANT
华盛顿过滤厂由29个慢砂过滤器组成，每个过滤器都有英亩的过滤区域。它们位于三个公开法庭上，在三个公开法庭上，它们的安排是用沙子洗涤和储存的，在这些方面是滤波器的调节，在这些方面是几种构成工厂必不可少的管道和排水系统的系统，plant is located just south of the Soldiers’ Home grounds, between the Washington city or McMillan Park reservoir and North Capitol street. The normal level of water on the lilters is some 25 ft., more or less, above the level of this reservoir, and, therefore, a pumping station is necessary to lift the water from the reservoir to the filters. The plant includes a filtered water reservoir, to which the water flows from the various filters, and from which it flows to the District of Columbia highservice pumping station and the gravity supply. It includes, also, an office building, in which are located the offices and the laboratories, where chemical and bacteriological examinations of the water are being made every day, in order properly to observe and control the operation of the filters. The pumping station will lift something more than 250,000 tons per day through a comparatively small vertical distance of 25 ft., more or less. The equipment consists briefly of the following: i’our 200-h. p. Babcock and Wilcox boilers, with Roney automatic stokers and Green economisers; three 36-in. centrifugal pumps, each one direct-connected to a Harrisburg engine— fTeming four-valve; two 2,500,000-gal. tandem, compound pumps for the sand-washer system; electric lighting equipment of one 50-K.W. and one 25-K.W. generator, direct-connected to vertical, compound steam engine; coal pocket to hold about four months’ supply. The water is discharged from the pumps into a rising main 72-in. in diameter of riveted steel, coated with asphalt and imbedded in concrete. Outside the pumping station the main branches are a 72-in. branch feeding 19 filters, and a 54-in. branch for the ten that remain. On each main branch is a Venturi meter, and from them 20-in. cast iron branches lead to the individual filters. The normal position of tne gates on these 20-in. branches, when the filters are in operation, is wide open. The water-level on the filters is, therefore, maintained practically constant, simply by holding a constant head on the pumps, and no regulating apparatus for this purpose is necessary. In the typical filter, the shell containing the filtering medium is of concrete masonry. It consists of a floor of inverted groined arches, carrying piers and partition and side-walls. Upon these is supported the roof, of groined arches of ellipical section. Under the floor is the main central underdrain, built of 24-in. tile pipe, reinforced with concrete, with the floor laid over it. Through the floor, in the centre of each bay through which the main underdrain passes, are openings for the discharge of water from the laterals into the main underdram. The flow through these openings is controled by orifices. At right angles to the main underdrains, between each two rows of piers, and on top of the inverted-arch floor are the laterals, which collect the water from the gravel layers and conduct it to the main underdrain. These are of tile, 6-in. at the outer edge of the filter, and increasing to 12-in. towards the centre. The smaller tile have the bell sliced off, in order to rest flat upon the floor; the larger ones are split. They are not perforated, but laid with open joints. Over the laterals is placed crushed stone, trap or granite, 12-in. thick midway between the piers, and decreasing to 3-in. at the piers, three grades being used. The lower layer 7-in. thick, is of such size that it will be retained on a i-in. screen, and but a small part of it on a 2-in. screen. The second is of a size to pass a i-in. screen and be retained upon a Jfs-in. screen. The third and upper is of a size to pass a K-in. screen; it is coarser than the ordinary sand and entirely free from fine material. The function of this gravel layer is twofold—to support the sand and prevent its passage down into the underdrains, and to afford a free passage for the water from all points of the lower surface of the sand layer to the underdrains. Great care is necessary in placing the different layers to maintain the continuity of each grade; but, when this is properly done, no sand ever passes down through the gravel into the underdrains. The sand—the filtering medium—is placed upon the gravel. It was furnished from a bank of sand and clay some 15 or 20 miles from the city. Clay was present in prohibitively large quantities and had to be removed from the sand by washing. The contractor for the sand built a plant tor this purpose, consisting of coarse grating, coarse and tine screens, link-belt elevators for handling the material, pug-mills and washing-boxes. After some experience with the plant, a product was obtained which fully met the requirements of the specifications. These specifications required the sand to contain not more than 0.5% smaller than .13 mm. diameter; not more than 8.0.% smaller than.26 mm. diameter; at least 7.0% smaller than .34 mm. diameter; at least 70.0% smaller than .83 mm. diameter; at least 90.0% smaller than 2.10 mm. diameter; at least 100.0% smaller than 5.70 mm. diameter; and not more than 0.2% of clay, before being tried. The sand was placed in the filters by means of carts, through the numerous manholes in the filter-tops. In the corner of each filter are the gates for controling the inflow.of unfiltered water and the outflow to the sewer, when the filter is drained from above the sand. The gates are below the sand level in a quadrantshaped well, whose wall breaks the force of the inflowing water and prevents the disturbance of the sand. Brass orifices as already mentioned control the flow from the laterals of the underdrainage system to the main central underdrain. They form a series placed in the openings where the laterals of the underdrainage system discharge into the main central underdrain below the floor. These problems were so designed that at any point the total loss of head, or resistance to the passage of the water, through the sand, through the gravel and underdrains, through the orifices and thence through the central underdrain to the outlet of the filter, would not differ appreciably from the corresponding total loss of head for any other point. In this plant the compensating orifices permitted the use of 24-in. pipe for the main central underdrains instead of 36-in., which effected a saving in cost of construction, $14,500. The filtered water flows out through the main central underdrain to the regulatorhouse in the court, in which are the gates and devices for the control of the flow. The massive concrete foundation is divided into one large central well and six smaller wells. One of the six small ones is reserved as a dry chamber for the indicating apparatus. Each of the other five serves as the gate-chamber, or regulating well, for a single filter. The central well communicates through an open cast iron pipe with the filtered water reservoir and serves as a main collector and discharge for all filters converging in that house. The water flowing from a filter reaches its proper gatechamber in the regulator-house, after passing through the 20-in. outlet pipe, on which is located a Venturi meter. The flow is controled by the gate on the end of this pipe, the work being done entirely and satisfactorily by hand. Between the gate-chamber and the main central well is a gate which is open during normal operation and shut at all other times. In the bottom of the gate-chamber is a sewer-discharge which is normally closed. Between adjoining gate-chambers there is a gate to permit the passage of filtered water from one filter backwards into the underdrains of the other, as there are marked advantages in filling the filter in this way from below, after it has been drained for cleaning. The exterior drainage system is made in two distinct parts. One part communicates with the filters above the sand and with the regulator-houses, in such a way as to permit the occasional return to the McMillan Park reservoir of certain portions of the water which are not as good as the filtered water, but still no worse than the unfiltered water. The other part collects all other drainage and liquid wastes, including the dirty water from the sand-washers, and conveys it to the city sewers. From the regulator-house the water flows through an open pipe to the filtered water reservoir—a converted basin of the same type of construction as the filters, only on a larger scale. The water flows into the basin at several points from the various .regulator-houses. The capacity of the basin in round numbers, is 14,000,000 gal. With a consumption of (10,000,000 to 65,000,000 gal. a day, this is obviously a compensating reservoir, to permit a fluctuating draught at different hours of the day, while maintaining a practically constant rate on the filters. The flow-line in the filtered water reservoir, besides being fluctuating, is considerably higher, at times, than the floor of the gatehouse controling the flow to the District pumping station. Some means is, therefore, necessary to maintain the outflow below this level. This is effected by a balanced-valve arrangement at the outlet of this reservoir. By proper adjustment, the water level below the floats may be prevented from rising above a certain elevation.
华盛顿过滤厂由29个慢砂过滤器组成，每个过滤器都有英亩的过滤区域。它们位于三个公开法庭上，在三个公开法庭上，它们的安排是用沙子洗涤和储存的，在这些方面是滤波器的调节，在这些方面是几种构成工厂必不可少的管道和排水系统的系统，plant is located just south of the Soldiers’ Home grounds, between the Washington city or McMillan Park reservoir and North Capitol street. The normal level of water on the lilters is some 25 ft., more or less, above the level of this reservoir, and, therefore, a pumping station is necessary to lift the water from the reservoir to the filters. The plant includes a filtered water reservoir, to which the water flows from the various filters, and from which it flows to the District of Columbia highservice pumping station and the gravity supply. It includes, also, an office building, in which are located the offices and the laboratories, where chemical and bacteriological examinations of the water are being made every day, in order properly to observe and control the operation of the filters. The pumping station will lift something more than 250,000 tons per day through a comparatively small vertical distance of 25 ft., more or less. The equipment consists briefly of the following: i’our 200-h. p. Babcock and Wilcox boilers, with Roney automatic stokers and Green economisers; three 36-in. centrifugal pumps, each one direct-connected to a Harrisburg engine— fTeming four-valve; two 2,500,000-gal. tandem, compound pumps for the sand-washer system; electric lighting equipment of one 50-K.W. and one 25-K.W. generator, direct-connected to vertical, compound steam engine; coal pocket to hold about four months’ supply. The water is discharged from the pumps into a rising main 72-in. in diameter of riveted steel, coated with asphalt and imbedded in concrete. Outside the pumping station the main branches are a 72-in. branch feeding 19 filters, and a 54-in. branch for the ten that remain. On each main branch is a Venturi meter, and from them 20-in. cast iron branches lead to the individual filters. The normal position of tne gates on these 20-in. branches, when the filters are in operation, is wide open. The water-level on the filters is, therefore, maintained practically constant, simply by holding a constant head on the pumps, and no regulating apparatus for this purpose is necessary. In the typical filter, the shell containing the filtering medium is of concrete masonry. It consists of a floor of inverted groined arches, carrying piers and partition and side-walls. Upon these is supported the roof, of groined arches of ellipical section. Under the floor is the main central underdrain, built of 24-in. tile pipe, reinforced with concrete, with the floor laid over it. Through the floor, in the centre of each bay through which the main underdrain passes, are openings for the discharge of water from the laterals into the main underdram. The flow through these openings is controled by orifices. At right angles to the main underdrains, between each two rows of piers, and on top of the inverted-arch floor are the laterals, which collect the water from the gravel layers and conduct it to the main underdrain. These are of tile, 6-in. at the outer edge of the filter, and increasing to 12-in. towards the centre. The smaller tile have the bell sliced off, in order to rest flat upon the floor; the larger ones are split. They are not perforated, but laid with open joints. Over the laterals is placed crushed stone, trap or granite, 12-in. thick midway between the piers, and decreasing to 3-in. at the piers, three grades being used. The lower layer 7-in. thick, is of such size that it will be retained on a i-in. screen, and but a small part of it on a 2-in. screen. The second is of a size to pass a i-in. screen and be retained upon a Jfs-in. screen. The third and upper is of a size to pass a K-in. screen; it is coarser than the ordinary sand and entirely free from fine material. The function of this gravel layer is twofold—to support the sand and prevent its passage down into the underdrains, and to afford a free passage for the water from all points of the lower surface of the sand layer to the underdrains. Great care is necessary in placing the different layers to maintain the continuity of each grade; but, when this is properly done, no sand ever passes down through the gravel into the underdrains. The sand—the filtering medium—is placed upon the gravel. It was furnished from a bank of sand and clay some 15 or 20 miles from the city. Clay was present in prohibitively large quantities and had to be removed from the sand by washing. The contractor for the sand built a plant tor this purpose, consisting of coarse grating, coarse and tine screens, link-belt elevators for handling the material, pug-mills and washing-boxes. After some experience with the plant, a product was obtained which fully met the requirements of the specifications. These specifications required the sand to contain not more than 0.5% smaller than .13 mm. diameter; not more than 8.0.% smaller than.26 mm. diameter; at least 7.0% smaller than .34 mm. diameter; at least 70.0% smaller than .83 mm. diameter; at least 90.0% smaller than 2.10 mm. diameter; at least 100.0% smaller than 5.70 mm. diameter; and not more than 0.2% of clay, before being tried. The sand was placed in the filters by means of carts, through the numerous manholes in the filter-tops. In the corner of each filter are the gates for controling the inflow.of unfiltered water and the outflow to the sewer, when the filter is drained from above the sand. The gates are below the sand level in a quadrantshaped well, whose wall breaks the force of the inflowing water and prevents the disturbance of the sand. Brass orifices as already mentioned control the flow from the laterals of the underdrainage system to the main central underdrain. They form a series placed in the openings where the laterals of the underdrainage system discharge into the main central underdrain below the floor. These problems were so designed that at any point the total loss of head, or resistance to the passage of the water, through the sand, through the gravel and underdrains, through the orifices and thence through the central underdrain to the outlet of the filter, would not differ appreciably from the corresponding total loss of head for any other point. In this plant the compensating orifices permitted the use of 24-in. pipe for the main central underdrains instead of 36-in., which effected a saving in cost of construction, $14,500. The filtered water flows out through the main central underdrain to the regulatorhouse in the court, in which are the gates and devices for the control of the flow. The massive concrete foundation is divided into one large central well and six smaller wells. One of the six small ones is reserved as a dry chamber for the indicating apparatus. Each of the other five serves as the gate-chamber, or regulating well, for a single filter. The central well communicates through an open cast iron pipe with the filtered water reservoir and serves as a main collector and discharge for all filters converging in that house. The water flowing from a filter reaches its proper gatechamber in the regulator-house, after passing through the 20-in. outlet pipe, on which is located a Venturi meter. The flow is controled by the gate on the end of this pipe, the work being done entirely and satisfactorily by hand. Between the gate-chamber and the main central well is a gate which is open during normal operation and shut at all other times. In the bottom of the gate-chamber is a sewer-discharge which is normally closed. Between adjoining gate-chambers there is a gate to permit the passage of filtered water from one filter backwards into the underdrains of the other, as there are marked advantages in filling the filter in this way from below, after it has been drained for cleaning. The exterior drainage system is made in two distinct parts. One part communicates with the filters above the sand and with the regulator-houses, in such a way as to permit the occasional return to the McMillan Park reservoir of certain portions of the water which are not as good as the filtered water, but still no worse than the unfiltered water. The other part collects all other drainage and liquid wastes, including the dirty water from the sand-washers, and conveys it to the city sewers. From the regulator-house the water flows through an open pipe to the filtered water reservoir—a converted basin of the same type of construction as the filters, only on a larger scale. The water flows into the basin at several points from the various .regulator-houses. The capacity of the basin in round numbers, is 14,000,000 gal. With a consumption of (10,000,000 to 65,000,000 gal. a day, this is obviously a compensating reservoir, to permit a fluctuating draught at different hours of the day, while maintaining a practically constant rate on the filters. The flow-line in the filtered water reservoir, besides being fluctuating, is considerably higher, at times, than the floor of the gatehouse controling the flow to the District pumping station. Some means is, therefore, necessary to maintain the outflow below this level. This is effected by a balanced-valve arrangement at the outlet of this reservoir. By proper adjustment, the water level below the floats may be prevented from rising above a certain elevation.
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