JPS63119818A - Upward stream filtrating device - Google Patents

Abstract

PURPOSE:To secure the reliability of treating capacity of a device by providing a fixed lattice body in a specified position in a filtration layer. CONSTITUTION:The fixed lattice body consisting of grids such as plane plates arranged in parallel is provided in such a position in the filtration layer that the head loss in the filtration layer is not increased in the case of filtrating operation and the position is in the downstream. As a result, the filter medium near the fixed lattice body receives underwater weight of the filter medium of higher position than the fixed lattice body, and accordingly it ensures bridge effect which surely prevents the floating-up of a filtration layer 17 by the fixed lattice body. Consequently, the critical range for break-through is largely improved, the stability of operation is increased, and the reliability of treating capacity of the device is secured.

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to an upward flow filtration device that filters a treatment fluid by passing it upwardly through a filter layer, and particularly relates to an upflow filtration device that filters a treatment fluid by passing it upwardly through a filter layer.
The present invention relates to an upward flow filtration device suitable for use in subsequent processing.

(Prior Art) This type of conventional device will be explained with reference to FIG. 5.

The polluted water flows into the bottom of the filter tank 1, and is passed through the water diversion device 2,
The water passes through the supporting gravel layers 3 and 4, the upper filtration layer 5 and the upper filtration layer 6 in order, and is collected at the upper part of the filtration tank 1. Note that the a filter layer 7 is filtered by the lower WHjl filtration R5 and the upper layer filtration WJ6.
is formed.

By the way, as filtration continues, suspended matter in the polluted water is trapped in the linear layer 7, and as this retention increases, the head loss in the filter layer increases with the amount of water in the filter medium constituting the filter layer 7. I feel hazy. Furthermore, as the filtration continues, the head loss in the a-layer becomes larger, a part of the filter layer 7 becomes floating, and the trapped suspended matter flows out into the filtrate water. This phenomenon is called a breakthrough, and once this breakthrough occurs, the filtration function is lost.

Conventionally, in order to prevent this breakthrough, as shown in the figure, in 81117, the filtration M7 is below the surface, in other words, above the Jli filtration 1i! A grid 8 is fixedly provided below the surface of 6. With this grid 8, the sand of the filtering medium that constitutes the uiH7 is interlocked between the grids of the grid 8, creating a reverse bridge, and the sand transmits a force greater than its own weight to the grid, resulting in a breakthrough due to the so-called bridge effect. Preventing.

The grid 8 is a steel grid in which flat plates with a thickness of 6 to 9 nm and a width of 15 to 20 CI are arranged at intervals of 15C1, and the upper end surface thereof is set to be the filtration layer 7 surface 0ag. The filter material for layer 6 is silica sand, and its thickness is 1
．． When the distance is 5 to 1.7 m, it is recognized that almost no breakthrough occurs until the head loss within 1 lIH is about 31 m.

(Problem to be solved by the invention) However, in reality, the grid 8 is
Even if it is provided, it is unstable against breakthroughs. For example, due to factors such as insufficient cleaning of the Ill7, insufficient compaction of the filter layer 7, or even slight fluctuations in the filtration rate, breakthrough may occur at a given I1m.
A head loss of 70 to 80% of the W4 internal head loss often occurs, resulting in a problem that the reliability of the throughput of the device is impaired.

The present invention has been made to solve these problems.

(Means for Solving the Problems) In order to achieve the above-mentioned object, the upflow filtration device according to the present invention, in the above-mentioned device, is configured to reduce the loss within the #Ii layer due to filtration. This system is characterized in that the fixed grid is provided at a position on the lower side where almost no change in water head occurs.

(Function) By providing the fixed grid at the position described above,
The underwater weight of the filtration material above the fixed lattice is sufficiently applied to the filtration material constituting Ill around the fixed lattice. As a result, the filtering media are compacted, and the meshing between the filtering media between the grids of the fixed grid body and the meshing between the grids and the filtering media become extremely strong, and a bridging effect can be fully expected.

Therefore, lifting of the dlm can be reliably prevented by the fixed grid.

(Example) Next, a specific example of the upflow filtration device according to the present invention will be described with reference to the drawings.

In Fig. 1, a filtration tank 11 made of metal such as a steel plate, concrete, etc. has a water diversion function that evenly distributes water during filtration or washing from the bottom to the top. Device 12, lower gravel layer 1@13 consisting of gravel with a diameter of 30 to 50 nm as support material, upper layer of gravel 14 consisting of gravel with a diameter of 8 to 20 nm, - upper layer of filtration consisting of gravel with a diameter of 2 to 3 nm as filter material 1!1715, and an upper filtration layer 16 made of silica sand having a diameter of 1 to 2 nm as a filter material. A filter rim 17 is formed by the lower 11111 filtration R15 and the upper filtration H16. The thickness of the support shoulder consisting of the lower and upper gravel layers 13 and 14 is approximately 25CI+, and the lower and upper filtration layers 15 and 14 have a thickness of approximately 25CI+.
The thickness of 16 is 25ci11 and about 110ci, respectively.
It is.

In this example, the thickness of the filter @111 was made thin in order to examine the resistance against breakthrough, but the thickness of the upper layer filtration wJ16 is usually about 150 ai.

A grid 18 is provided in the center of the upper filtration layer 16 by being fixed to the filtration tank 11 by a well-known means such that its upper end surface is located below 50C11 from the surface of the upper H filtration layer 16. . The structure of this grid 18 is
As shown in FIG. 2, the thickness A 6 a.

It is a lattice body made of steel or synthetic resin, etc., in which flat plates with a width of 315 am are arranged parallel to each other with an interval of C15 CIll.

Raw water as well as secondary treated sewage water, etc. are introduced from the bottom of the filter tank 11, separated by a water diversion device 12', and are directed upward to a support layer consisting of a lower layer and an upper gravel layer 13, 14, and a lower layer and l1 filter layer 1 consisting of 15 and 16 filter layers
7 successively, the water is collected at the upper part of the filtration tank 11, and taken out as clear treated water.

Next, l! of the grid 18! The position within the filter layer 7 will be explained in detail. FIG. 3 shows the m layer 17 and this filter m
The head loss distribution in 17 is shown for initial and final losses at filtration rates of 300 m/day and 400 m/day, respectively. In the figure, Xa is a line representing the initial loss at a filtration rate of 300 m/day, xb is a line representing the final loss, ya is a line representing the initial loss at a filtration rate of 400 ra/day, and Yb is the final loss. It shows the lines that represent it.

The lines Xa, Xb, Ya, Yb representing the losses are
If it is located below the straight line Z indicating the underwater weight due to the laminated load of the filtration material of the cline 17 (in FIG. 3, the underwater weight is expressed in terms of head loss), The weight of the filter material underwater is greater than the pressure from below, making it safe from breakthrough. Conversely, the line Xa.

If Xb, Ya, and Yb are located above the straight line Z, the state is unstable with respect to breakthrough. The grid 18 is for absorbing the difference in water head pressure when the water head loss of the filter 11117 exceeds the submerged base of the filter medium, so its position is determined by the filtration with respect to the final loss mentioned above. The location will be selected at a location where the weight of the wood in the water will not be exceeded.

On the other hand, the function of preventing lifting of [1l17] by the grid 18 is due to the supporting force against lifting due to the thickness of the flat plate constituting the lattice of the grid 18, as well as the engagement between the filter media between the grids, and the engagement between the grid and the filter material. This is to prevent lifting due to reverse bridges caused by The bridging effect due to this reverse bridge is
As the compaction of the 'a layer 17 around the grid 18, specifically the silica sand which is the filtering material of the upper filtration layer 16, progresses, the density of the silica sand increases, and the stronger the aforementioned interlocking, the larger the Become. Therefore, the cline 11 of the grid 18
The prevention force due to the bridging effect against floating increases as the thickness of 11117 on the grid 18 increases and as the density of the silica sand around the grid 18 increases due to the underwater weight of the silica sand due to this thickness.

As a result, the further down the grid 18 is in l@17, the greater the bridging effect is obtained.

That is, the setting position of the grid 18 is preferably as low as possible.

From the above, it can be seen that the position of the grid 18 should be selected at a position where almost no change in head loss in the filter occurs due to filtration, and at a position as low as possible. In practice, since the normal filtration speed is about 400 m/day at maximum, the grid 18 is positioned as shown in FIGS. 1 and 3, where almost no head loss occurs, as described above. In this case, the upper filtration layer 16 in the a-filtration layer 11 is located near the vertical center of the upper filtration layer 16 so that its upper end surface is located below the surface of the cline layer 17.

In this example, the grid 18 is provided so that its upper end surface is located 50all below the surface of the 1N17 as described above (condition ①), and
Grid 18 such that its upper end surface is located below I+.
When we conducted a comparative experiment with the case where (Condition ■) was provided, we obtained the following results. In this experiment, the filtration rate was 30 h/day, and the inorganic turbidity (clay) was approximately 70 b/β in order to make the experimental conditions uniform.

The test was carried out using contaminated water injected with PAC30b/J2 until a breakthrough occurred, and this process was repeated 10 times.

Under the above condition (2), the total loss of the breakthrough filtrate H17 was 1.75 to 2.05 ra in water column, with an average of r 1.9 m. On the other hand, under the above condition (3), the total loss of the breakthrough cline 11 is 1.45 to 1.6 m in water column, and 1.5 m on average.
5 It was. Both have an average of 22% (=(1,9
A difference of > m −1,55 m ) / 1.55 m > was generated, and the worst operating result of condition (①) exceeded the good operating result of condition (③).

Taking one result of these experiments as an example, the relationship between the filtration time and the total loss such as turbidity of raw water (treated water) is shown in FIG. 4. In addition, the actual IJa, ,
b and C4 are the raw water turbidity under condition ■,
Showing the treated water turbidity and total loss, dotted line a2. b2# and C2 indicate the raw water turbidity, treated water turbidity, and total loss under condition (2), respectively. Additionally, when a breakthrough occurs, the turbidity of the treated water will exceed the turbidity of the raw water.

The flat plate of the grid 18 in this embodiment may be a flat plate with an uneven surface treatment, or a flat plate with sand or hard granules attached to the surface. Also, change it to a flat plate! A bar or the like may also be used. Further, the word lattice itself used in the specification includes not only cases where the grid has squares and rectangles, but also cases where the grids have shapes such as rhombuses and parallelograms.

(Effect of the invention) The underwater weight of the filter material above the fixed grid body is sufficiently added to the filter material around the fixed grid body, and a bridging effect can be fully expected. Uke can be stopped.

Therefore, the limit for breakthrough, which is the biggest problem in the operation of the device, can be significantly raised, stability is increased, and reliability of the processing ability of the device is ensured.

[Brief explanation of the drawing]

1 to 4 are drawings for explaining the upflow filtration device according to the present invention, in which FIG. 1 is a sectional view of the device, FIG. 2 is an enlarged perspective view of the grid, and FIG. Figure 4 is a diagram showing the relationship between filtration time and the turbidity of raw water (treated water) and total loss. , which corresponds to FIG. 1 for explaining the prior art. 16...Kamioka filtration WJ17...Cline 18...Grid patent applicant Nippon Insulators Co., Ltd. Figure 1

Claims (1)

[Scope of Claims] 1. In an upward flow filtration device that filters a treated fluid by passing it upward through a filter layer, there is a change in head loss within the filter layer that occurs within the filter layer and accompanying filtration. An upward flow filtration device characterized in that a fixed grid body is provided at a position on the lower side where almost no flow occurs. 2. The position where the head loss in the filter layer hardly changes due to filtration, and the lower position is near the center between the top and bottom of the upper filtration layer in the filter layer. An upward flow filtration device according to claim 1. 3. The upward flow filtration device according to claim 1 or 2, wherein the fixed grid body is a grid in which flat plates are combined in parallel or vertically and horizontally.