Liquid purification or separation – Plural chambers with movement of granules therebetween
Reexamination Certificate
2001-11-19
2004-08-24
Cintins, Ivars C. (Department: 1724)
Liquid purification or separation
Plural chambers with movement of granules therebetween
C210S268000, C210S269000, C210S276000
Reexamination Certificate
active
06780312
ABSTRACT:
BACKGROUND OF THE INVENTION
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
Cintins Ivars C.
Finnegan Henderson Farabow Garrett & Dunner LLP
Nihon Genryo Co., Ltd.
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