1. Field of the Invention
The present invention relates to a filtration apparatus that filters liquids such as water.
2. Description of the Related Art
Conventional water purification processes at large scale water treatment plants involve adding chemicals to untreated water drawn from rivers, lakes, ponds, or wells to consolidate the suspended matter therein to a size that causes said consolidated matter to deposit on the bottom. The supernatant water is skimmed and sent to a filtration reservoir, where it is passed through filtration media such as filtration sand to remove the finer suspended matter. This water is then disinfected with chlorine.
However, if water is filtered utilizing filtration media in this manner over a long period of time, the filtering efficiency decreases due to the pollutants in the water (contaminants such as sludge, hereinafter referred to as contaminants) attaching to the filtration media, among other reasons. Therefore, it becomes necessary to periodically cleanse the filtration media. As cleansing methods of filtration media, surface cleaning, which washes the surface of a sand layer by hitting it with water sprayed from a nozzle, and backwash, which forces purified water into a filtration reservoir from a lower pressure compartment, thereby floating the filtration sand grains, causing them to scrub against each other, were in common use.
However, the surface cleaning and backwash methods described above utilize the effects of stream shear, and cannot cleanse the filtration media with satisfactory efficacy. Problems arise from repeated use over a period of time such as: the reduction of space among the filtration media due to the progressive thickening of particle size from contaminant accumulation thereon, clogging due to the separation of materials that had been attached to the filtration media, and the leaking of the contaminants themselves.
Conventionally these problems were dealt with by, for example, increasing the frequency of the backwash process. However, if the backwash process is repeated over a long period of time, the water pressure thereof influences even the gravel layer which supports the filtration media, creating areas of different thickness in said layer, which is optimally flat and of an even thickness. In this case, it is necessary to perform a regeneration process, which involves: ceasing the total operation of the filtration reservoir, removing the filtration media, correcting the discontinuities in thickness of the gravel layer), replacing the filtration media with new filtration media, or with the polluted filtration media which has been cleansed. However, the regeneration process is extremely costly, and as during said process the filtration reservoir is not operating, it leads to a decrease in water treatment efficiency, there is a strong demand on the part of the water treatment plant to space the intervals between regeneration processes as long as possible.
The applicant of the present invention, in order to meet this demand, has developed and proposed a sand cleansing apparatus which cleanses polluted filtration media in a shorter time and with a higher degree of cleansing ability (Japanese Unexamined Patent Publication Nos. 10(1998)-109051 and 11(1999)-057526), which has been utilized and praised by those in the field. This sand cleansing apparatus comprises: a sand receiving opening for receiving filtration media drawn from a filtration reservoir in its upper portion; a cleansing tank which stores sand and cleansing water having a sand extraction opening; a agitating tank erected within said cleansing tank having openings on the upper and lower ends thereof; and a screw conveyor which rotates within said agitating tank. The grains of sand are brought upward by the screw conveyor along with the cleansing water. As they are being conveyed upward, said grains of sand rub against each other, and the scrubbing action thereof effectively removes the contaminants that are attached or coated thereon.
As opposed to a large scale water treatment plant as has been described above, filtration systems such as those installed in the filtration tanks of small scale simple plumbing or factories have within a container a filtration tank which holds the filtration media as well as the water to be purified by said filtration media. These filtration systems are structured to expel the water that has been purified by said filtration media from the filtration tank through a filtration floor to the outside of the container. It is common practice to utilize the surface washing or backwash methods for the filtration media of these filtration systems, and they have similar problems as those of the filtration reservoir; that is, the consumption of a large amount of purified water in the backwash process, and that the cleansing effectiveness is insufficient.
Further, as the filtration media in a filtration system is housed within a small container, the contamination thereof progresses at a higher rate than that of a filtration reservoir. Still further, as they perform high-speed filtration, contaminants are more likely to leak, so it can be said that said filtration media is operated under harsher conditions than that of a filtration reservoir. Therefore, it is necessary to replace or regenerate said filtration media on a shorter cycle.
It is conceivable to utilize the above-described sand cleansing apparatus by the present applicant (Japanese Unexamined Patent Publication Nos. 10(1998)-109051 and 11(1999)-057526) to cleanse the filtration media drawn from the filtration systems. However, compared to the amount of filtration media in a filtration reservoir, the amount of filtration media in a filtration system is extremely small, and the operational scale of same is also small. Therefore, it is inefficient and impractical to secure the space required to install the above-described sand cleansing apparatus, as well as expending costs for its installation and removal, to cleanse such a small amount of filtration media. As a practical matter, it is generally the case that the filtration media is replaced with new filtration media, as opposed to being reused after cleansing.
However, the filtration media to be disposed after being replaced must be dealt with as industrial waste, and the cost of such disposal is high. It is also preferable from an ecological viewpoint to switch from the easy trend of consume-then-dispose to a direction in which resources are recycled and reused.
In view of these points, there are known filtration apparatuses which have a filtration media cleansing mechanism provided within the filtration tank, such as the filtration devices disclosed in Japanese Patent No. 31491 and Japanese Utility Model Publication No. 63(1988)-98704. In the former filtration device, a central pipe is suspended from above a filtration compartment and positioned so that a lower opening of said pipe communicates with the interior of said compartment. Within the upper portion of the central pipe is provided a propulsion device in the form of a propeller. Higher still than said propulsion device is disposed a tube having a spray opening slightly above the central pipe, facing a lateral side thereof. The tube is linked to the propulsion device so that it rotates therewith, and sprays cleansing fluid at high speed from its spray opening by centrifugal force. To cleanse the filtration media, the propulsion device is rotated, thereby drawing the filtration sand into the central pipe through its lower opening. The filtration sand that has been propelled upward is expelled to the side of the central pipe by the cleansing fluid discharged from the spray opening of the tube. By this, the filtration sand is cleansed by the separation of the contaminants therefrom.
As to the latter filtration device, a pump pipe is suspended from above a tank so that it is positioned therein, and within this pipe is provided a rotatable spiral water pump. This filtration device is configured to perform a normal filtration operation by discharging untreated water into the filtration sand by an untreated water distribution tube placed within the filtration sand. This water travels upward through the filtration sand, is filtered thereby, and the resultant processed water is expelled from above said filtration sand. This filtration device is further configured to perform a cleansing operation by rotating the spiral water pump, raising the filtration sand which has acquired contaminants thereon, separating the contaminants from the filtration sand by the centrifugal separation phenomenon, and the resultant cleansed filtration sand is excelled through a filtration sand expulsion opening provided in the upper portion of the pump pipe.
Further, in the former filtration device, a normal filtration operation is performed by filtering untreated water provided from above through filtration sand placed on an apertured false bottom. The central pipe in this device has an open bottom; therefore it is always in the state that filtration sand is inside said pipe. However, the device is not constructed so that water flows into said central pipe and aggressively filtered therethrough. Further, to perform the cleansing operation, it is necessary to rotate the propulsion device at a rather high speed in order to draw up the filtration sand; therefore there is a fear that the filtration sand will be crushed upon impact with the propulsion device.
As to the latter filtration device, as it is of a upward flow type, that is, the filtration is performed by directing the stream of water from beneath the filtration sand upward, if the filtration speed is increased, the small grains of filtration sand are caused to float, increasing the space between said grains of filtration sand. As a result, contaminants, especially small particles thereof are insufficiently filtered, thereby decreasing the filtering performance. Also, when performing a cleansing operation, as a spiral water pump (screw) is rotated at high speed, the cleansing effect is low, and there is a fear that the filtration sand will be crushed upon impact with the spiral water pump as it rotates at high speed.
The present invention has been made in view of the above-described circumstances, and it is an object of the present invention to provide a filtration apparatus possessing both a high filtration performance property and a high cleansing performance property. Another object of the present invention is to provide a filtration apparatus that effectively cleanses filtration media without requiring the installation and removal of a cleansing apparatus each time that filtration media is to be cleansed.
The filtration apparatus of the present invention has a filtration media cleansing mechanism installed within the filtration tank. By utilizing said mechanism to cleanse the filtration media in the filtration apparatus, obviates the need to provide a specific space for a separate cleansing apparatus, as well as the need to install and remove such apparatus, while cleansing said filtration media in a short amount of time with a sufficiently high degree of cleansing.
The filtration apparatus of the present invention comprises: a container that houses a filtration tank which holds therein filtration media as well as the liquid to be filtered by said media; a filtration media cleansing mechanism having a hollow cleansing tank for cleansing the filtration media inside the filtration tank; wherein said filtration media cleansing mechanism is provided with a contaminant expulsion means for expelling the contaminants that have been separated from the filtration media to the outside of the container and also expels the liquid that has been purified by the filtration media to the outside of the container. Said cleansing tank is a hollow body erected within said filtration tank; has lower openings that are closed during a filtering operation and opened during a cleansing operation; has an upper opening at a level at least higher than the upper surface of the filtration media in the filtration tank; has provided therein a screw conveyor which conveys the filtration media as well as the liquid which flows into the cleansing tank upwards from the lower openings to the upper opening thereof while scrubbing said filtration media and said fluid. The rotation of said screw conveyor conveys the filtration media upwards, and discharges said media as well as the contaminants separated therefrom by the scrubbing action from the upper opening into the filtration tank.
Here, the liquid to be poured into the container is generally water to be purified by filtration, but it is not limited to this. For instance, waste oil of cutting lubricant may be used. Further, when water is used as the liquid, it is preferable to utilize filtration sand as the filtration media, but it is not limited to this. Many different materials may be used as the filtration media.
As the filtration media and the liquid is conveyed upwards by the screw conveyor, the filtration media is fluidized, the grains of the filtration media rub against each other, and the scrubbing action thereof effectively removes the contaminants that are attached or coated thereon. The contaminants removed in this manner floats in the liquid being conveyed upward, is discharged into the filtration tank from the upper opening of the cleansing tank, and is expelled outside the container by the contaminant expulsion means.
As the contaminant expulsion means, it is preferable to utilize a backwash mechanism that discharges filtered or clean liquid during a state when the lower openings of the cleansing tank are closed by the opening/closing means. The discharge of liquid by said backwash mechanism causes the contaminants, which are floating in the liquid surface layer within the filtration tank to be expelled through an overflow expulsion means. It is possible to effectively expel the contaminants, which have been separated from the filtration media, that remaining the filtration tank by utilizing the backwash mechanism equipped on the filtration apparatus to cleanse the filtration media therein.
Further, if the filtration media cleansing mechanism is of the type that does not have a water retention means to retain the liquid that has been poured into the container within the filtration tank, it is preferable to provide a retention means with a water retaining function. This is because it is possible to perform efficient cleansing utilizing only the retained water.
With regard to the filtration apparatus of the present invention, it is preferable to provide a switching mechanism for switching between the operations of xe2x80x9ccleansingxe2x80x9d by the filtration media cleansing mechanism and xe2x80x9cfilteringxe2x80x9d of liquids. This is because it is possible to efficiently perform each of these operations by switching the switching mechanism to xe2x80x9cfilteringxe2x80x9d when filtration of the liquid is to be performed, which precludes xe2x80x9ccleansingxe2x80x9d from being performed, and by switching the switching mechanism to xe2x80x9ccleansingxe2x80x9d when cleansing is to be performed, which precludes filtration from being performed.
As to the switching mechanism, it is preferable to utilize one that is equipped with a door that is of a sufficient size to close the lower openings of the cleansing tank and an opening/closing means for opening and closing same. This is because by the opening and closing operation of said door, it is possible to allow the filtration media and liquid to flow into the cleansing tank during a cleansing operation, and to positively prevent the filtration media from flowing into the cleansing tank during a filtration operation, thereby positively switching between the two operations (filtration and cleansing). Further, the screw conveyor and the lower and upper openings formed in the cleansing tank combine to provide the effect that the filtration media within the filtration tank progressively circulate within the filtration tank and the cleansing tank. This circulation makes thorough cleansing of the filtration media possible in a short time.
It is preferable to utilize a door, which is movable along an outer or inner periphery of the outer wall of the cleansing tank. This is to reduce the resistance of the filtration media accumulated within the filtration tank during an opening/closing operation. Similarly, it is also preferable to utilize a structure for the opening/closing means that easily overcomes the resistance of the filtration media. For example, a structure may be utilized such that a worm wheel is fixed on the outer peripheral surface of the door, and a motor or the like rotates the worm that engages said worm wheel. By this structure, the rotation of the worm scrapes out the filtration media, which had entered the spaces between the teeth of the worm wheel, and the resistance of the filtration media can be reduced during an opening/closing operation.
Note that of the filtration apparatus of the present invention, the filtration media cleansing mechanism and the switching mechanism that switches between xe2x80x9ccleansingxe2x80x9d of the filtration media by the cleansing mechanism and xe2x80x9cfilteringxe2x80x9d as necessary provided in the filtration tank of the filtration apparatus, can be provided as an after market cleansing apparatus. By this, it becomes possible to customize an existing filtering apparatus to a filtering apparatus of the present invention, having the function of cleansing the filtration media, thereby controlling the installation cost.
Further, the filtration apparatus of the present invention comprises: a container that houses a filtration tank which holds therein filtration media as well as the liquid to be filtered by said media; a filtration media cleansing mechanism having a hollow cleansing tank for cleansing the filtration media inside the filtration tank, wherein said mechanism is provided with a contaminant expulsion means for expelling the contaminants that have been separated from the filtration media to the outside of the container; and a means for expelling the liquid that has been purified by the filtration media to the outside of the container. Said cleansing tank is a hollow body erected within said filtration tank; has lower openings that are open at all times; has an upper opening at a level at least higher than the upper surface of the filtration media in the filtration tank; has a plurality of lateral surface openings that extend in a vertical direction on a lateral surface thereof; said lateral surface openings having lateral surface doors opened and closed by a plurality of drive means. Said cleansing tank further has filtration media housed therein at all times; has provided therein a screw conveyor which conveys the filtration media as well as the liquid which flows into the cleansing tank upwards from the lower to the upper opening thereof while scrubbing said filtration media and said fluid. The rotation of said screw conveyor conveys the filtration media upwards, and discharges said media as well as the contaminants separated therefrom by the scrubbing action from the upper opening into the filtration tank.
With regard to the contaminant expulsion means, it may be of the type that utilizes a backwash mechanism. The backwash mechanism discharges filtered or clean water from the filtration floor into the filtration tank to float the filtration media during a closing operation of the lateral surface doors, performed in order for the screw conveyor to agitate the filtration media.
Further, during rotation of the screw conveyor, it is preferable that the lateral surface doors are closed.
The backwash mechanism of the contaminant expulsion means is structured to discharge filtered or clean liquid from the filtration floor into the filtration tank during an opening operation of the lateral surface doors, performed when the agitating operation is completed. Further, the contaminant expulsion means can be equipped with an overflow expulsion means that expels the contaminants caused to float in the liquid surface layer by the discharge of liquid by said backwash mechanism within the filtration tank to be expelled therethrough.
The filtration media cleansing mechanism can also be equipped with a retention means for retaining the liquid poured into the filtration tank therein.
When the filtration tank is filled with liquid, the liquid becomes pressurized. It is also possible to filter said pressurized liquid through the cleansing tank, as the filtration media is housed in the cleansing tank at all times.
The filtration apparatus of the present invention is equipped with a backwash mechanism that discharges filtered or clean liquid into the filtration tank through the filtration floor. During a cleansing operation, it is preferable that the lateral surface doors be closed after the filtration media is caused to be in a suspended state by said backwash mechanism.
Further, the contaminant expulsion means described above can be configured to expel the contaminants caused to float in the surface layer of the liquid by the discharge of filtered or clean liquid by the backwash mechanism after the agitating operation is complete and the lateral surface doors are opened.
Still further, the filtration media cleansing mechanism may be equipped with a retention means for retaining the liquid poured into the container. The agitating, scrubbing, and expelling operations may be performed using solely said retained liquid.
According to the filtration apparatus of the present invention, the cleansing tank is a hollow body having a plurality of lower openings, which are closed during a filtering operation and opened during a cleansing operation of filtration media as well as an upper opening that is positioned above the upper surface of the filtration media within this cleansing tank is equipped a screw conveyor that conveys the filtration media as well as the liquid upward through said tank from the lower openings to the upper opening thereof, while scrubbing the filtration media. As the cleansing tank is structured so that the rotation of the screw conveyor conveys the filtration media upward while scrubbing same, and said filtration media along with the contaminants separated therefrom are discharged into the filtration tank from an upper opening thereof, the following effects are obtained.
That is, during a normal filtering operation, the lower openings of the hollow body are closed, preventing the entrance of water and filtration sand therein, thereby precluding the accumulation of untreated water therein, as well as the deterioration of water quality by filtration sand that is not used for filtering. Further, the filtration media is entrained in vortices caused by the opposing forces of the downward pull of gravity and the upward motion imparted thereon by the screw conveyor. These vortices cause the contaminated grains of the filtration media to frictionally engage, that is, scrub each other, thereby separating contaminants therefrom, so it is possible to effectively separate the contaminants from the filtration media without the crushing thereof.
If a switching mechanism is further provided and in the case that xe2x80x9cfilteringxe2x80x9d is selected by said mechanism, as the cleansing mechanism is not operated, a conventional filtering operation is secured. In the case that xe2x80x9ccleansingxe2x80x9d is selected, the cleansing mechanism is operated, and cleansing is performed utilizing only the water that is resident in the filtration tank, so the amount of water required is kept to a minimum. In addition, if as a final step, a backwash operation is performed to expel the contaminants which have been separated from the filtration media and remain in the filtration tank outside of the container, the filtration media can be cleansed more efficiently and with a higher degree of cleansing than by a conventional backwash operation.
As a result, the need to replace the filtration media with new filtration media is obviated; thereby suppressing the costs associated with the introduction of new filtration media. Also, the need to dispose of the used filtration media is obviated, and it becomes possible to maintain environmental protection standards (such as ISO14000) by the control of industrial waste, as well as reduce the costs associated with industrial waste disposal.
Further, as the intervals between the cleansing of the filtration media can be extended longer than with conventional systems, longer continuous filtration times can be secured, while decreasing the total time during which filtration is ceased for cleansing operations.
Still further, even if multiple cleansing operations are performed, contaminants do not accumulate within the filtration tank. Therefore, replacement of the filtration media and the cleaning of the filtration tank become unnecessary, thereby lowering the costs and labor associated with maintenance thereof.
Furthermore, as the filtration apparatus of the present invention is structured so that the cleansing tank houses therein filtration media at all times; said tank has a plurality of vertically extending lateral surface openings; said lateral surface openings have a plurality of lateral surface doors opened and closed by a plurality of drive means; the liquid poured into the filtration apparatus enters the cleansing tanks through said lateral surface openings, which are open in a normal operating state; and filtration occurs in the cleansing tank as well; then during a filtration operation, the filtration area is expanded, thereby improving the filtration efficiency. Also, as liquid flows into the cleansing tank at all times, stagnation of liquid therein is precluded. Therefore, contamination of liquid due to stagnation and the seeping out of said contaminated liquid from the cleansing tank into the filtered liquid and mixing therewith is prevented. Further, during a cleansing operation of the filtration sand, the lateral surface openings are closed, thereby allowing efficient circulation of the filtration sand between the cleansing tank and the container.
Further, in the case that the contaminant expulsion means is provided with a backwash mechanism that discharges filtered or clean water into the filtration tank through the filtration floor to cause the filtration media to float at the time when the lateral surface doors are closed in order for the screw conveyor to agitate the filtration sand, the opening and closing of the lateral surface doors is not prevented by the filtration media. That is, the lateral surface doors do not encounter much resistance by the filtration media, which eases the opening and closing operation, and the load on the drive means for opening and closing the lateral surface doors can be reduced.
Further, in the case that the lateral surface doors are closed during the time that the screw conveyor is rotating, agitating of the filtration media is efficiently performed.
In the case that the contaminant expulsion means is further provided with an overflow expulsion means that expels the contaminants caused to float within the surface layer of the liquid by the discharge of liquid from the backwash mechanism into the filtration tank through the filtration floor at the time when the lateral surface doors are opened at the completion of the agitating operation, not only is the opening of the lateral surface doors eased, but the contaminants can be efficiently discharged from the lateral surface doors as well.
In the case that the filtration media cleansing mechanism is further provided with a retention means for retaining the water poured into the container within the filtration tank, the effects of said means combine with those of the opening of the lateral surface doors to more efficiently cleanse the filtration media.
If the filtration apparatus is structured so that filtration media is housed in the cleansing tank at all times, the liquid under pressure by the filling of the filtration tank can also be filtered by the cleansing tank. In this case, because the liquid is under pressure, said liquid permeates the filtration media quickly, and because the filtration area is expanded, filtration is performed more efficiently.
The present invention, as has been described, is characterized by a cleansing mechanism being built in to a filtration tank so that both filtration and cleansing can be appropriately performed without sacrificing the performance of either.