JP5754649B2 - Depth filtration equipment - Google Patents

Description

  The present invention relates to a downflow filtration apparatus for treating sewage and industrial wastewater generated in a sewage treatment plant, or purifying lakes, rivers, etc. The present invention relates to a depth filtration device that captures foreign matter inside.

Conventionally, sand filtration devices are well known, and it is also known to use granular activated carbon and garnet in combination with sand filtration devices. For example, sand or garnet having a particle size of 0.45 to 0.8 mm, or a first filter medium layer filled with sand and garnet as a multilayer, and a granular activated carbon having a particle size of 0.9 to 1.6 mm on the support above it. Alternatively, Patent Document 1 discloses a filtration device that forms a second filter medium layer filled with anthracite and performs a filtration process in a downward flow. And the filtration apparatus which performs solid-liquid separation and biological treatment using a resinous filter medium, a fiber filter medium, etc. is also well known. For example, as a primary treatment device for wastewater using a resinous filter medium, an upward flow solid-liquid in which a filter medium layer in a treatment tank is filled with a small cylindrical filter medium having a porosity of 70% or more and a specific gravity of 1.0 or less. A separation apparatus is disclosed in Patent Document 2. In addition, as a flowable filler used in aeration chambers for biological treatment, a water treatment filler having a large surface area with a specific gravity of 0.800 to 0.999 and a substantially spherical outer ring is also patented. It is disclosed in Document 3.

As a fiber filter medium for separating suspended substances contained in sewage, a water filter fiber filter medium is disclosed in Patent Document 4 in which a thread filter is wound around a twisted core thread and a presser thread and heat treated to form a mall filter medium. Applicant has proposed. Moreover, as a filter medium layer in which two types of granular filter media are mixed, a filter medium made of expanded polystyrene and having a specific gravity of 0.1 and a particle diameter of 0.6 mm and a filter medium having a specific gravity of 0.1 and a particle diameter of 2.8 mm are stirred and mixed. Patent Document 5 discloses a flotation filtration method in which two types of flotation filter particles are mixed without being separated and have a long-time pressure loss and a large SS trapping amount.

(JP 2001-38107 A) (Japanese Laid-Open Patent Publication No. 64-7920, Example FIGS. 1 and 2) (Patent No. 3730441, claim 1 and paragraph number 0031, FIGS. 1 to 12) (Patent No. 3994392, claims and paragraph number 0010, FIG. 3 and FIG. 4) (Japanese Patent Laid-Open No. 7-232007, claim 1 and paragraph number 0017)

Conventional high-speed filtration devices such as sand filtration devices and fiber filtration devices are deep-layer filtration devices that form a filter medium layer with a certain thickness and trap suspended substances inside the filter medium layer. If the suspended solids flow out and the filter medium layer is too dense, surface filtration is performed. Although it is necessary to select a filter medium according to the properties of raw water and treatment conditions, it is difficult to prepare many types of filter medium. For this reason, the filter medium which can respond | correspond to raw | natural water of standard properties, such as discharge water of a sewage, is needed. With this standard filter medium, raw water that is prone to surface layer filtration, such as coagulation filtration, cannot use the entire filter medium layer, shortens the filtration duration, increases the frequency of washing, and does not exhibit a sufficient function as depth filtration. It is necessary to develop and adapt a special filter medium. Even if only one type of special filter medium that is different from the standard filter medium is developed to cope with this problem, it cannot be said that the filter medium is optimal when the surface layer is easily filtered. In addition, in the case of highly turbid raw water such as river water immediately after rainy weather, it is necessary to develop and adapt a dedicated coarse filter medium in order to cope with the optimum material. When the configuration of the filter medium layer deviates from the optimum condition, the filter medium is operated with a processing amount lower than the standard performance of the filter device or the frequency of cleaning the filter medium is increased. However, depending on the situation, the performance may be greatly reduced.

In the conventional sand filtration apparatus, a technique for forming a deep filter medium layer using a filter medium having a small particle diameter from several kinds of coarse particle diameter is widely used in water purification treatment and the like. As described in Patent Document 1, two or more types of filter media having different particle sizes and specific gravity are used in combination, and each filter media constitutes each filter media layer. A conventional sand filtration device that uses two or more types of filter media in combination captures a part of the particles inside the filter media layer in a stepwise manner for each particle size of suspended solids contained in raw water. The suspended matter in the raw water is not captured over the entire thickness of the filter medium layer. A sand filtration device using a multilayer filter medium layer captures relatively large particles with a filter medium layer of filtration particles that form large voids, and captures relatively small particles with a filter medium layer of filtration particles that form small voids.

A small cylindrical filter medium as described in Patent Document 2 of the prior art forms a filter medium layer with a plastic small cylindrical filter medium having a porosity of 70% or more and a specific gravity of 1.0 or less, and is passed in an upward flow. . The small cylindrical filter media has an extremely high porosity, and suspended substances are not trapped only on the lower surface of the filter medium layer, but are trapped three-dimensionally by the entire filter medium layer, increasing the retention capacity of suspended substances and enabling long-term operation. It becomes. Sand filtration equipment, such as secondary treatment water at sewage treatment plants, has a high removal rate of suspended solids and a high filtration rate with low-concentration wastewater, but exhibits excellent capacity when used as primary treatment water. Therefore, the filter sand surface that forms the filter medium layer is blocked in a short time.

As described in Patent Document 3, a conventional water treatment filler having a substantially spherical outer ring is mainly used in a septic tank for biological treatment. In the septic tank that fills the aeration chamber and performs the water treatment, the bacteria can be effectively decomposed by supporting a large number of bacteria with a large surface area of the filler. The substantially spherical water treatment filler also has a feature that it is difficult to cause clogging by moving between fillers with respect to suspended substances contained in raw water.

A conventional high-speed filter using fiber filter media is a deep filter that forms a filter medium layer with a certain thickness and traps suspended substances in raw water inside the filter medium layer. The trapping zone gradually advances along the flow direction of the raw water. If the filtration pressure loss accompanying the trapping of the suspended solid does not reach a predetermined pressure, the trapping zone proceeds to the deep part of the filter medium layer, and finally a breakthrough phenomenon occurs in which a large amount of the suspended solid flows out. The turbidity of the treated water is monitored to detect a breakthrough and the filtration process is terminated, and the filter medium cleaning process is started, or the cleaning process is started with a timer every predetermined time.
Further, if the filtration pressure loss accompanying the trapping of the suspended solids reaches a predetermined pressure before the breakthrough, the filtration process is terminated without using up all of the filter medium layer, and the filter medium cleaning process is started.
For example, if the water filter fiber filter described in Patent Document 4 is used as the molding filter medium to be filled in the filtration tank, the gaps between the filter media in the filtration layer are efficiently and averagely filled to reduce the gaps between the filter media. The filter medium layer of the filter medium layer formed in the filtration tank can easily disperse and develop the trapped portion of the suspended matter, and can separate and drop the trapped particles between the flocked fibers with extremely small energy.

The flotation filtration method using two types of filter media described in Patent Document 5 forms a filter media layer in which two types of flotation filter media particles are mixed without separation, and has a small pressure loss during filtration over a long period of time. Increase the amount of capture. For the filter media layer in which filter media with different filter media sizes and specific gravity are mixed, filter media with different particle sizes are dispersed to reduce coarse passages. Passing members (coarse filter media) and filter media (fine filter media) ) Is not divided into a filter medium layer and water is passed through the filter medium layer.

The filter medium constituting the filter medium layer of the depth filtration device of the present invention uses a filter medium having a function of trapping suspended substances and a filter medium having a water passing function, and disperses the filter medium having different functions in the filter medium layer. A part of the suspended matter is passed through the depth of the filter medium layer, and suspended substances are captured in the entire filter medium layer. The mixing ratio of the filter medium with different functions is adjusted according to the raw water condition and processing conditions. The present invention relates to the improvement of a depth filtration device that optimizes the function.

The gist of the present invention is that the particulate filter medium is stored in the filtration tank, the raw water is supplied from the upper part of the filter tank, and the separated liquid is extracted from the bottom part of the filter tank. And adjusting the mixing ratio of the flow aid to pass the suspended solids, mixing the granular filter medium and the flow aid to form a deep filter medium layer, and evenly dispersing the granular filter medium and the flow aid However, the granular filter medium that forms the deep filter medium layer causes the suspended matter of the suspended solids contained in the raw water to gradually move from the surface layer along the flow direction of the raw water, The suspended substance is passed through the filter medium layer as it is, and the suspended substance is captured by the granular filter medium that forms the rear filter medium layer, and solid-liquid separation can be performed by utilizing the function of the entire deep filter medium layer.

In addition, the particulate filter medium is stored in the filter tank, the raw water is supplied from the upper part of the filter tank, and the separated liquid is extracted from the bottom part of the filter tank. Adjust the mixing ratio of the water flow aid to pass the substance, mix the granular filter medium and water flow aid to form a deep filter medium layer, and make the water flow aid (5) the surface layer side of the deep filter medium layer (2) The water flow aid disperses a lot of suspended substances and passes them through the deep filter medium layer, and flows into the back while capturing the suspended substances in the granular filter medium layer. The function of the entire deep filter medium layer can be exhibited.

The depth filtration apparatus according to the present invention uses a particulate filter medium that traps suspended substances, and a flow aid that allows the suspended substances to pass downstream of the filter medium layer. The mixing ratio of the particulate filter medium and the water flow aid can be adjusted, and the function of the filter medium layer can be optimized according to the raw water condition and processing conditions. And the filter medium layer which exhibits the function of depth filtration can be formed also in the coagulation filtration etc. which are easy to become surface layer filtration. In addition, the filter medium layer can be adjusted and adapted by selecting a water flow aid for special purposes such as high turbidity raw water and pools that require high clarity.

It is a conceptual diagram of the deep filter medium layer formed in the filtration tank of the deep filter apparatus which concerns on this invention. Similarly, it is a longitudinal cross-sectional view of a depth filtration apparatus. Similarly, it is an external view of a cylindrical water flow auxiliary material constituting a water flow auxiliary material having a water flow function. Similarly, it is an external view of the cylindrical water flow assistant of another Example. Similarly, it is the external view of the spherical water flow auxiliary material which comprises a water flow auxiliary material. Similarly, it is an outline view of a mall-shaped water flow aid constituting the water flow aid. Similarly, it is an enlarged view of the surface layer part of the depth filter medium layer which shows the filtration state of a depth filter. Similarly, it is a conceptual diagram of a filtration tank in which filter sand and a mole filter medium are mixed to form a filter medium layer. It is a comparison table of the comparison test of the filtration pressure and the filtration continuation time of the filter media layer formed only by the conventional filter sand, and the filter media layer formed by mixing the filter sand of the invention of this application and a mole filter media.

The depth filtration apparatus according to the present invention will be described in detail with reference to the drawings. FIG. 1 is a conceptual diagram of a filter medium layer formed in a filtration tank, and the depth filter medium layer 2 formed in the filtration tank 1 has a water passage hole. 3. Adjust the mixing ratio of the particulate filter medium 4 that captures suspended substances contained in the raw water and the water passage aid 5 that allows the suspended substances to pass through, and mix the particulate filter medium 4 and the water passage aid 5 with each other. A thick deep filter medium layer 2 is formed. The granular filter medium 4 having a filtration function for trapping suspended substances in the gaps between the filter medium and the water flow assistant 5 having a water flow function allowing the raw water containing the suspended substances to pass through the inside have a specific gravity of 1.0. It is set to -3.0. The raw water supplied from the upper part of the filtration tank 1 is made into the downflow type filtration apparatus which capture | acquires suspended solids in the deep filter medium layer 2, and extracts the treated water solid-liquid-separated from the bottom part of the filtration tank 1. The granular filter medium 4 gradually advances the trapping substance trapping zone from the surface layer along the flow direction of the raw water, and the water passage aid 5 allows a part of the suspended substance to pass through the deep filter medium layer 2 as it is, A deep layer filtration device 6 is configured which can capture suspended substances between the granular filter media 4 at the rear and can perform solid-liquid separation by utilizing the function of the entire depth filter media layer 2.

FIG. 2 is a longitudinal sectional view of the depth filtration apparatus. The depth filtration apparatus 6 has a raw water supply pipe 7 connected to the upper part of the filtration tank 1 forming the depth filter medium layer 2 and a treated water pipe 8 connected to the bottom of the filtration tank 1. A treated water chamber 9 from which suspended substances are removed is formed below the support bed 3, and an upper portion of the deep filter medium layer 2 is a raw water chamber 10. The particulate filter medium 4 for trapping suspended solids can be used in combination with filter sand, garnet, or anthracite alone or in combination, and the water flow aid 5 through which the suspended solids pass is a cylindrical member, spherical water flow aid. Materials or mall filter media can be used. The filter medium forming the deep filter medium layer 2 can be obtained by dispersing the granular filter medium 4 having a filtration function and the water flow aid 5 having a water flow function evenly to form the deep filter medium layer 2. It can be. Moreover, if the water flow aid 5 is dispersed and mixed with a high density on the surface layer side of the deep filter medium layer 2, the water flow aid 5 allows many suspended substances to pass through the deep filter medium layer 2, and the granular filter medium 4. ... the suspended solids are trapped in between and flowed into the inner part, and the function of the entire deep filter medium layer 2 can be exhibited.

In addition to raw water with standard properties such as sewage effluent, granular filter media 4 and special applications such as flocculated sludge that easily becomes surface filtration, high turbidity raw water, or pools that require high clarity If the depth filter medium layer 2 is formed by adjusting the mixing ratio of the water flow aid 5, the function of the depth filtration can be sufficiently exhibited. The function of the deep filter medium layer 2 can be optimized by adjusting the mixing ratio of the granular filter medium 4 and the water flow aid 5 according to the raw water condition and processing conditions. Further, when the deep filter medium layer 2 is clogged, if the wash water is supplied from the treated water pipe 8 to the treated water chamber 9 and the wash water is injected from the water passage holes of the support floor 3 to flow the deep filter medium layer 2. Then, the suspended substance captured by the particulate filter medium 4 is separated and floated on the raw water chamber 10, and the washing waste water is discharged from the raw water supply pipe 7. In addition, you may utilize an ultrasonic transmitter for the filter medium washing | cleaning of the deep filter medium layer 2. FIG.

The granular filter medium 4 for capturing the suspended solids has a specific gravity of 1.0 to 3.0, and the specific gravity of the water passing aid 5 for passing the suspended solids to the depth of the deep filter medium layer 2 is 1. It is approximated to 0-3.0. FIG. 3 is an external view of a cylindrical water flow aid having a water flow function. In the embodiment of the present invention, a resin adjusted to have a specific gravity of 1.0 to 3.0 and mainly PP (polypropylene) Φ5 mm × It is composed of a 15 mm cylindrical water passage aid 11. FIG. 4 is an external view of a cylindrical water flow aid of another embodiment, and is a resin adjusted to a specific gravity of 1.0 to 3.0 with resin fibers, and mainly made of PET (polyethylene terephthalate), Φ5 mm × 15 mm. If the cylindrical water flow aid 12 is configured, the water flow aid 5 having a filtration function on the outer peripheral surface is obtained.

The depth filter medium layer 2 formed in the depth filtration apparatus 6 shown in FIG. 2 includes the water passage aid 5 composed of cylindrical water passage aids 11 and 12, and the granular filter medium 4 and the cylindrical water passage aids 11 and 12. If the mixing ratio is 0.9 to 0.5: 0.1 to 0.5, the trapped SS amount of the entire filter medium layer can be maintained while preventing the breakthrough phenomenon. FIG. 5 is an external view of a spherical water-assisting material having a water-permeable function according to another embodiment, and the water-assisting material 5 that allows the suspended substance to pass through the deep filter medium layer 2 has a specific gravity of 1.0 to It is made of PET adjusted to 3.0, and the outer ring is constituted by a spherical water passage aid 13 having a spherical shape of Φ5 mm. The depth filter medium layer 2 formed in the depth filtration apparatus 6 shown in FIG. 2 comprises the water passage aid 5 with the spherical water passage aid 13 and the mixing ratio of the granular filter medium 4 and the spherical water passage aid 13 is 0.9. If it is set to -0.5: 0.1-0.5, the whole filter medium layer can be utilized, preventing a breakthrough phenomenon.

FIG. 6 is an outline view of a mall-shaped water-assisting material having a water-permeable function according to another embodiment. The water-assisting material 5 is a core material 14a made of stainless steel having a specific gravity of 7.7 or aluminum having a specific gravity of 2.7. A PET-made thread 14b is bonded to the outer periphery, and a molding water passage aid 14 adjusted to a specific gravity of 1.0 to 3.0 with an outer diameter of 5 mm and a length of 5 mm is formed. The mall-shaped water passage aid 14 may be formed of glass fiber. If the molding water passage aid 14 is made of coarse fibers with a reduced number of the flower yarns 14b, the voids of the suspended substance will be increased, and if the molding yarn passage aid 14 is made dense, the filtration function will be achieved. Can be provided. The depth filter medium layer 2 formed in the depth filtration apparatus 6 shown in FIG. 2 is configured such that the water passage aid 5 is composed of the mall-shaped water passage aid 14, and the mixing ratio of the granular filter medium 4 and the mall-shaped water passage aid 14 is 0. .8 to 0.4: If it is set to 0.2 to 0.6, the suspended substance can be caused to flow into the deep part, and the function of the entire deep filter medium layer 2 can be exhibited. Cylindrical water flow aids 11, 12, spherical water flow aids 13 and mall-shaped water flow aids 14 constituting the water flow aid 5 having a water flow function can also inhabit biological treatment microorganisms. It is.

FIG. 7 is an enlarged view of the surface layer part of the deep filter medium layer showing the filtration state, and is included in the raw water in the surface layer part of the deep filter medium layer 2 in which the granular filter medium 4. It shows a state where suspended solids are trapped. When raw water is supplied from the raw water supply pipe 7 of the filtration tank 1 shown in FIG. 2 to the raw water chamber 10, a large suspended substance contained in the raw water is trapped between the granular filter media 4... In the surface layer portion of the deep filter medium layer 2. The The raw water containing suspended solids that have passed through the water flow aid 5 dispersed in the surface layer portion captures the suspended solids in the granular filter media 4 of the deep filter medium layer 2, while the water flow aid 5 And flows into the deep filter medium layer 2. The trapping zone is gradually advanced along the flow direction of the raw water from the surface layer part forming the deep filter medium layer 2, and the remaining suspended substance is refined while trapping the suspended substance in the granular filter medium 4. The flow aid 5 ... passes a part of the suspended substance as it is to the back of the deep filter medium layer 2 and traps the suspended substance with the granular filter medium 4 ... that forms the deep deep filter medium layer 2. The solid-liquid separation can be performed by utilizing the function of the entire deep filter medium layer 2. The treated water from which suspended substances have been removed flows into the treated water chamber 9 from the water passage hole of the deep filter medium layer 2 support floor 3 and is extracted from the treated water pipe 8 of the filtration tank 1.

The deep bed filtration device 6 in which the granular filter media 4... And the flow aid 5 are dispersed is not subjected to surface filtration by sand filtration, and suspended matter contained in the raw water is the entire depth filter media layer 2. It is captured three-dimensionally and exerts the function of depth filtration to increase the retention capacity of suspended solids, enabling long-time operation and less frequent washing. The mixing ratio of the water passing aid 5 having different functions from that of the granular filter medium 4 is adjusted according to the raw water condition and processing conditions, and the depth filtration device 6 that optimizes the function of the depth filter medium layer 2 is obtained. Although the mixing ratio varies depending on the shape of the water flow function member, the water flow aid cylindrical or water flow aid 13 which does not give the water filtration function member a filtration function is 10 to 30% mixed. A ratio is desirable. The mall-shaped water passage aid 14 that imparts a filtration function to the water flow member is about 20 to 60%.

FIG. 8 is a conceptual diagram of a filtration tank in which filter media is formed by mixing filter sand and Mole filter media. Specifically, the flow aid 5 is heavily concentrated on the upstream side of the deep filter medium layer 2, and it is possible to prevent an increase in the filtration pressure near the surface layer where the granular filter medium 4 is likely to be clogged. Suspended substances can be captured by flowing raw water into the deep filter medium layer 2.

A comparative test was conducted with a filter medium layer formed by mixing a conventional filter medium layer formed only with filter sand, a particulate filter medium 4 for capturing suspended substances according to the present invention, and a water passage aid 5 for passing suspended substances. .
The granular filter medium, the water flow aid, and the filtration tank were tested according to the following specifications.
Raw water: Pond water added with flocculant, or pond water granular filter medium containing algae: Filtration sand water passing aid: Made of PET with a specific gravity of 1.38, thick Φ5mm × 5mm long yarn fiber, less number Mall-shaped water passage aid body tank height: 4000 mm
Body tank inner diameter: Φ600mm
Water flow speed: 20m / h

FIG. 9 is a comparison table of filtration pressure and filtration duration, with the vertical axis representing the filtration pressure (kPa) and the horizontal axis representing the filtration duration (h), and the results of the comparative test are displayed.
When the filtration pressure rises to 15 kPa as a result of the comparative test, it is necessary to wash the filter medium in order to remove clogged suspended substances from the filter medium layer. In the filter medium layer formed with conventional filtration sand, the filtration pressure rises to 15 kPa in 8 hours. This indicates that the filter medium needs to be cleaned every 8 hours. On the other hand, in the deep filter medium layer 2 formed by mixing the filtration sand 4a of the present invention and the molding water flow aid 14 of the water flow aid 5, the time until the filtration pressure rises has been remarkably increased.
Specifically, in the filter medium layer 2 in which 80% of the filtration sand 4a and 20% of the molding water passage aid 14 were mixed, the filtration pressure increased only to 4.5 kPa after 8 hours. The filtration pressure rose to 15 kPa after 13 hours.
In addition, the SS density | concentration in the treated water which passed the filter-medium layer 2 after 13 hours did not have a difference in the conventional sand filtration apparatus and the filtration tank of this invention.
In addition, in the filter medium layer 2 in which the filtration sand 4a was mixed uniformly at a ratio of 70% and the molding water passage aid 14 was 30%, it took 16 hours for the filtration pressure to rise to 15 kPa. However, after 10 hours, the SS concentration in the treated water after the filtration treatment was increased, and a breakthrough phenomenon was confirmed.

The deep filter medium layer 2 formed only with the conventional filter sand 4a has a narrow gap between the filter sands 4a and 4a, and traps a large amount of suspended matter in the vicinity of the surface of the filter sand 4a forming the deep filter medium layer 2 in a short time. And accumulate. However, by trapping suspended substances in the surface layer portion of the filtration sand 4a, the filtration area of the filtration sand is reduced as the filtration device, and the filtration pressure is increased in a short time.
On the other hand, in the deep filter medium layer 2 formed by mixing the filter sand 4a and the mall-shaped flow aid 14, raw water flows through the gap between the mall-shaped flow filters 14 and flows into the deep filter medium layer 2. The
In particular, in the deep filter medium layer 2 containing 20% of the mall-shaped water aid 14, even if the suspended matter is captured by the filtration sand 4 a in the surface layer portion, the deep filter medium layer 2 is appropriately passed through the mall-shaped water aid 14. A passage for water to the back is secured. Then, the suspended water is captured by the filtered sand 4 a that forms the deep filter medium layer 2 on the downstream side of the molding water passage aid 14 in the raw water that is passed through the molding water passage aid 14. As a result, since the entire depth filter medium layer 2 is effectively used, the filtration area increases, and the increase in filtration pressure becomes gradual.
In addition, when the ratio of the mall-shaped water aid 14 of the water aid 5 is increased, many suspended substances are captured on the downstream side of the deep filter medium layer 2 and a breakthrough phenomenon is likely to occur. In addition, from the upstream to the downstream of the deep filter medium layer 2, the mall-shaped water passage aid 14 is connected to form a water passage, and the SS concentration in the treated water may increase.
The mixing ratio of the filtration sand 4a and the molding water passage aid 14 can be appropriately selected according to the properties of the raw water, the amount of treated water, and the filtration device.
Considering the rise time of the filtration pressure and the breakthrough phenomenon, the mixing ratio of the filtration sand 4a and the molding water passage aid 14 is preferably 0.8 to 0.4: 0.2 to 0.6.

The depth filtration apparatus according to the present invention is a mixture of a filter medium for trapping suspended solids and an auxiliary material for passing suspended substances in a filter medium layer formed in a filtration tank, A part of the filter media is passed through to the back of the filter media layer, and suspended substances are trapped in the entire filter media layer. The filter media layer functions by adjusting the mixing ratio of filter media with different functions according to the raw water condition and processing conditions. It becomes a depth filtration device that optimizes.
Therefore, it is most suitable for a down-flow type filtration device that treats sewage and industrial wastewater generated at a sewage treatment plant or purifies lakes and rivers.

DESCRIPTION OF SYMBOLS 1 Filtration tank 2 Deep filter medium layer 4 Granular filter medium 5 Water flow aid 11, 12 Cylindrical water flow aid 13 Spherical water flow aid 14 Mall-shaped water flow aid

Claims (2)

A particulate filter medium (4...) Is stored in the filtration tank (1), the raw water is supplied from the upper part of the filtration tank (1), and the separated liquid is extracted from the bottom part. Adjusting the mixing ratio of the particulate filter medium (4) to be passed and the water flow aid (5) through which the suspended substance passes, and mixing the granular filter medium (4) and the water flow aid (5) to form a deep filter medium layer (2 ) Is formed in the filtration tank (1), and the granular filter medium (4) and the water flow aid (5) are uniformly dispersed . A particulate filter medium (4...) Is stored in the filtration tank (1), the raw water is supplied from the upper part of the filtration tank (1), and the separated liquid is extracted from the bottom part. Adjusting the mixing ratio of the particulate filter medium (4) to be passed and the water flow aid (5) through which the suspended substance passes, and mixing the granular filter medium (4) and the water flow aid (5) to form a deep filter medium layer (2 ) Is formed in the filtration tank (1), and the water flow aid (5) is dispersed with a high density on the surface layer side of the deep filter medium layer (2) .

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