JP7430470B2 - Inclined sedimentation device - Google Patents

Description

The inclined sedimentation device of the present invention is mainly used in gravity type sedimentation tanks (hereinafter referred to as sedimentation tanks) in water purification treatment facilities and industrial wastewater treatment facilities. A sedimentation tank is a device that continuously separates and clarifies suspended substances in a liquid using the principle of gravity sedimentation, and there are horizontal flow types and upward flow types. Used in flow-type sedimentation tanks. Table 1 shows the principles of the horizontal flow type and upward flow type. Further, FIG. 2 shows an example of application of the upward flow type inclined sedimentation apparatus of the present invention.
In the horizontal flow type, the water to be separated flows horizontally into the tilting device and flows out, whereas in the upward flow type, the water to be separated flows in from below the tilting device and flows out upward. In either method, the separated suspended solids settle below the tilting device and accumulate at the bottom of the tank.

The inclined sedimentation device applies the principle of horizontally partitioning the sedimentation tank into layers, reducing the distance over which suspended solids settle and reducing the time required for separation.
Therefore, the size of the settling tank can be reduced in proportion to the reduction in size, which greatly contributes to reducing the construction cost of the settling tank.

In order to ensure continuity in the sedimentation separation operation of the inclined sedimentation device, the bottom surface on which the suspended solids settle is sloped, and the separated suspended solids are constantly discharged out of the device by rolling or sliding.
As shown in FIG. 5(a), when the bottom surface is tilted to a height H, the sinking distance is h, and the sinking performance is increased by a factor of H/h compared to the case without a tilting device. (Non-Patent Document 1) A similar description is found on page 196, lines 19-27 of Water Supply Design Guidelines 2000.

The angle of inclination is practically 45 degrees to 70 degrees with respect to the horizontal plane, with 60 degrees being the most common.
An integral three-dimensional structure of a large number of inclined partition walls (hereinafter referred to as inclined partition walls (50)) is called an inclined sedimentation device.
As mentioned above, there are two types of inclined sedimentation devices: the horizontal flow type, which is installed in the horizontal part of the sedimentation tank, and the upward flow type, which is installed in the upward flow part. The inclined sedimentation device of the present invention is an upward flow type inclined sedimentation device A0.
A typical example is shown in Figure 1, and an example of its use is shown in Figure 2. Note that a typical example of an inclined sedimentation device is also shown in FIG. 1, 1/3 of Patent Document 1.

As shown in Table 1, the upflow type sedimentation device A0 is located below the water surface of the settling tank, and is installed between the raw water on the inflow side below the device and the treated water on the outflow side above the device.
The inclined sedimentation device used in the upward flow type basically has one stage, and there is no multi-stage type with stacked layers like the horizontal flow type.

The upflow type inclined sedimentation device A0 is further divided into the inclined pipe type and the inclined plate type as shown in Table 2, and the inclined pipe (60) and the inclined partition wall (50) are provided with finely divided width direction b on the inclined partition wall (50). The device using partitioned tubular members is referred to as the inclined tube settling device A10, and the device using an inclined flat plate (hereinafter referred to as the inclined plate (51)) as the inclined partition wall (50) is referred to as the inclined plate settling device A20. It is an inclined plate sedimentation device.
The inclined plate settling device A20 does not have a side wall (40) that constitutes the inclined tube settling device, and both ends of the inclined plate (51) are free.
The inclined plate is a thin flat plate with reinforcing ribs of various shapes to increase its rigidity. There are many sizes of flat plates, from 1 meter square to 1 meter wide and 2 meters long, but there is no standard size.
A large number of inclined plates are arranged horizontally at equal intervals and fixed to a support frame or the like to form an inclined plate settling device. The length L or height H of each inclined plate is the same, and the heights of the top side (30) and bottom side (31) are the same in order to maximize the sedimentation performance.

The inclined tube type has an inclined channel (11) closed in a tubular shape with a side wall (40) and an inclined partition wall (50), while the inclined plate type has no side wall (40) and is partitioned in parallel by an inclined plate (51). The water to be separated rises through the inclined channel (11).
The pitch at which the inclined plates (51) are arranged in parallel is generally in the range of 70 mm to 150 mm. A narrow pitch is advantageous because it provides greater sedimentation performance, but there are concerns about blockage due to turbidity. Furthermore, if the diameter is widened, the sedimentation performance will deteriorate, and to compensate for this, it is necessary to increase the size of the device.
Furthermore, the material of the inclined plate (51) has lower rigidity than that of the inclined pipe (60) and is easily bent, so the pitch cannot be made as narrow as that of the inclined pipe (60).

Published practical application No. 137704, Showa 56, 1/3 Figure 1 Patent No. 6653203 Page (11) Figure 14

Water Supply Design Guidelines 2000 Pages 194-199 "5.5.4 Inclined Plate (Pipe) Type Sedimentation Tank", Pages 199-202 "5.5.5 High Speed Coagulation Sedimentation Tank" Published March 31, 2000 Japan Water Works Association

First, the problem of blockage that occurs in the upflow inclined sedimentation apparatus A0 will be described.

When the upward flow type sedimentation device A0 is operated for a long period of time in the sedimentation tank B, dirt adheres to the outflow end (22) of the slope sedimentation device A0, obstructing the flow and significantly reducing the separation performance.
Most of the components of dirt are turbid flocs (3) of several millimeters in size, which are made by adding an alum-based flocculant to the liquid to agglomerate suspended substances in order to improve separation efficiency.
The adhesion of dirt is due to a small amount of turbid flocs (3) remaining without being completely separated in the upflow channel re-sedimenting on the upper surface of the inclined sedimentation device A0 and depositing at the outflow end (21). Occur.
Since the inclined plate settling device A20 does not have a partition wall compared to the inclined tube settling device A10, blockage is less likely to occur, but blockage cannot be completely prevented.

In order to maintain good separation performance of the upflow tilted sedimentation device A0, regular cleaning and maintenance of the device is essential.

In particular, depending on the nature of the suspended solids, suspended flocs (3) may settle and accumulate on the outflow end (22) of the device, and if left for a long period of time, they may form a mat-like layer (hereinafter referred to as mat layer (4)). There have also been many reports of cases in which occlusion has occurred.

FIG. 3 shows a schematic diagram showing the behavior of the outflow end of the inclined plate sedimentation device A20 leading to blockage. FIG. 3(a) is a plan view of the outflow end of the inclined plate, and FIG. 3(b) is a side sectional view of the same. From the initial state of the sedimentation equipment installation, to the state in which turbid flocs (3) have been deposited due to long-term operation, and the state in which a mat layer (4) is formed as a result of being left unused for a long time without regular cleaning, leading to blockage. show.
When a blockage condition occurs, the flow flowing into the tilting device becomes non-uniform, and a short circuit flow occurs in a part, which significantly reduces the separation efficiency.

Second, we will describe conventional blockage prevention measures.

In order to prevent the turbid flocs (3) deposited at the outflow end (21) of the upflow type inclined plate sedimentation device A20 from growing and forming a mat layer (4), the inclined flow path (11) is Expansion is required.

For example, measures have been taken to increase the diameter of the inclined pipe (60) of the inclined tube settling device A10 from 50 mm square to 100 mm square, or in the case of the inclined plate settling device A20, the pitch (spacing) of the inclined plates (51) has been changed, for example. Measures will be taken to expand the diameter from 100mm to 200mm.

FIG. 4 is a schematic cross-sectional view of the outflow end side of the inclined plate sedimentation device A20 that takes measures to prevent blockage. FIG. 4(a) is a schematic diagram of inclined partition walls (50) or inclined plates (51) arranged at a pitch p that have been adopted in the past, before taking measures to prevent blockage. FIG. 4(b) is a schematic diagram of a conventional blockage prevention measure in which the interval p between the inclined plates (51) is doubled. FIG. 4(c) is a schematic diagram showing the countermeasure of the present invention.
The turbid flocs (3) deposited at the outflow end (21) of the inclined plate sedimentation device A20 gradually aggregate and form a mat layer (4) if left alone. The mat layer (4) is fragile, and as the distance between the opposite sides increases, that is, the channel cross section expands, the strain ε in the center of the layer increases during the formation of the mat layer, and when the strain ε exceeds a certain limit ε _mx , turbidity occurs. The matte flocs (3) lose their cohesion and break, and the mat layer (4) is not formed, resulting in no blockage.

Therefore, conventional measures have been taken to prevent the formation of the matte layer (4) by increasing the distance between adjacent inclined plates.

Third, we will discuss the problems with conventional blockage prevention measures.

As a measure to prevent blockage, enlarging the inclined flow path (11) increases the size of the inclined plate sedimentation device A20, which increases the manufacturing cost and also enlarges the sedimentation tank B that accommodates the inclined sedimentation device A20, leading to an increase in construction costs. It turns out.
Furthermore, the enlargement of the inclined flow path (11) tends to cause turbulence in the flow path, which has the disadvantage of lowering the separation efficiency.

First, the enlargement of the inclined plate sedimentation device A20 and its problems will be explained.

The sedimentation and separation performance of the inclined plate sedimentation device A20 decreases in inverse proportion to the distance between the two inclined plates (51).
That is, as shown in FIG. 5(a), sedimentation separation performance is proportional to the number of deepest perpendicular lines h between two inclined plates (51) of height H, and is expressed as H/h times. If the interval p between the inclined plates (51) is doubled to 2p to prevent blockage, the separation performance will be increased by H/2h times as shown in FIG. 5(b), and the separation performance will be reduced to one-half. In order to compensate for this, the length of the inclined partition wall (50) must be doubled.
If the length L of the inclined plate (51) is doubled, the height H of the inclined plate settling device A20 becomes 1.73 times higher, H=2Lsin60=1.73L when the inclination angle is 60 degrees. In this method, the inclined plate settling device A20 becomes large, and the manufacturing cost of the inclined plate settling device A20 and the construction cost of the settling tank B in which the inclined plate settling device A20 is housed increase significantly.

Next, the decrease in separation efficiency will be explained.

By expanding the inclined channel (11), turbulent flow is likely to occur within the inclined channel, resulting in a decrease in separation performance and deterioration in separation efficiency. The degree of rectification, which greatly affects the efficiency of sedimentation separation performance, is expressed by the Reynolds number, and the lower the number, the higher the degree of rectification.
It is an absolute condition that the sedimentation separation operation be performed within a rectified region, and the Reynolds number is a very important factor.

Reynolds number is a dimensionless numerical value that expresses the degree of rectification of flow, Re=ρvD _e /μ Re: Reynolds number, ρ: fluid density, v: fluid velocity, D _e : wetted wall area D _e =4×cross-sectional area/ Calculated by immersion length, μ: fluid viscosity. In the field of sedimentation separation technology, a Reynolds number of 500 or less is considered a laminar region, and a Reynolds number of 2,500 or more is considered a turbulent region, but in practice, a value of 200 or less is used.

Assuming that the velocity of the flow in the inclined plate is constant, the wetted wall area is an important factor that changes the Reynolds number.If the flow path diameter is small, the wetted wall area D _e will also be small, and the Reynolds number will also be proportionally small.
The Reynolds number required for an inclined sedimentation device is said to be from several tens to two hundred, which is preferably as low as possible under conditions where there is no risk of clogging by turbid flocs (3).

As a countermeasure to prevent blockage, in the prior art, a measure is taken to enlarge the inclined channel (11), but this method has the disadvantage that the Reynolds number increases and sedimentation separation performance deteriorates.
In the inclined plate sedimentation device A20, compared to the inclined tube sedimentation device A10, there is no side wall (40) and it is an open channel, so the wetted wall area D _e is larger, and the Reynolds number is several times to several tens of times larger.
Therefore, increasing the distance between adjacent inclined plates may greatly impair sedimentation separation performance.

Since the inclined plate sedimentation device has a large channel width, the Reynolds number must necessarily be large, and is generally around 300. Therefore, the efficiency of inclined plate sedimentation equipment is estimated to be around 70%.
In the case of inclined plate sedimentation equipment, if the width of the channel is expanded to prevent blockages, a significant drop in sedimentation performance is unavoidable.

Table 3 shows an example of Reynolds number comparison. A comparison was made between a sloped plate with a channel width of 100mm, which has been used in the past and has a good track record, and a sloped plate with a width of 200mm, which is newly provided as a measure to prevent blockage.
Comparing the Reynolds numbers for channel widths a 100 mm and b 200 mm in Table 3, they are 308 and 616, respectively, which is twice as large. Therefore, by doubling the channel width, the Reynolds number increases significantly and the separation efficiency significantly decreases beyond the laminar region.
Therefore, it is understood that a significant decrease in separation performance due to the enlargement of the inclined channel (11) is unavoidable.

An inclined plate sedimentation device A20 is required that has measures to prevent blockage without changing the interval between the inclined channels (11), and by providing a step z at the outflow end (21) of the adjacent inclined plate (51), We have invented a method that can achieve results equal to or better than those achieved by increasing the spacing between channels (11).

Patent Document 2 has already been devised as an inclined sedimentation device with steps.

Patent Document 2 is an inclined tube settling device A10, which has a side plate (referred to as a side wall (40) in the present application), and is significantly different in structure from the inclined plate settling device A20 of the present application which does not have a side wall.

Therefore, the circumstances leading to the blockage and the preventive measures are also different.

The process and assembly method of the conventionally used inclined plate sedimentation device A21 has been partially changed to prevent the outflow of the inclined plate (51) without increasing the diameter of the inclined channel (11) and while maintaining separation performance. By providing steps z alternately in the front and rear directions of the edge (22), it is possible to prevent blockage by turbid flocs (3), extend the period until cleaning maintenance, and maintain separation performance. To provide a sloped plate sedimentation device A22 with steps.

Except in special cases, the adhesion of turbid flocs (3) occurs only at the outflow end (21) of the inclined plate settling device A20, so there is no need to take measures for the entire inclined plate settling device. Measures should be taken only at the outflow end (21).

The basic principle of the present invention will be explained using FIG. 4. FIG. 4(a) is a schematic diagram of a side cross section of the outflow section of a conventional inclined plate sedimentation device. Figure 4(b) shows the distance p between the inclined plates (51) doubled and the distance between the outflow ends (21) expanded to prevent blockage, and Figure 4(c) shows the distance p between the inclined plates (51). A step z is provided at the outflow ends (21) of adjacent inclined plates (51) while maintaining the same.
In the conventional inclined plate sedimentation device shown in Fig. 4(a), the suspended solids attached to the outflow end (21) grow and coalesce with adjacent suspended solid masses to form a mat layer (4), causing blockage. In the state shown in FIG. 4(b), the distance between the outflow ends is doubled to 2p, and the attached suspended solids collapse beyond the strain limit ε _mx without forming a mat layer (4). In Figure 4(c), the distance between the outflow ends at the same height is 2p, so no matte layer (4) is formed, but turbid agglomeration does not occur even at the outflow end (21), which has a step below. Therefore, the mat layer (4) is not formed unless the lower turbidity aggregate is combined with the upper turbidity aggregate.

In this case, the size of the step z must be such that the turbidity agglomerate generated at the lower outflow end grows and collapses before coming into contact with the upper turbidity agglomerate. It must also be avoided that the turbid conglomerates that grow at both ends of the upper outflow end (21) are supported by the lower outflow end (21). In other words, the condition is that the strain limit ε _mx or more is exceeded. Below the strain limit ε _mx , the mat layer (4) growing from both ends is supported by the lower outflow end (21) and does not collapse.

From the above, it is understood that the same effect as when widening the interval between the inclined plates (51) can be obtained without widening the interval.

That is, considering two adjacent inclined channels (11) as a pair, the height of the outlet end (21) of the inclined plate (51) located in the middle of the channel is set to the height of the outlet end (21) on the other opposite side. This is a sloped plate sedimentation device A22 with a step, which is lower than the height and provided with a step z.

Furthermore, since the pitch p of the inclined plate (51) is maintained, the Reynolds number, which affects separation efficiency, does not change, and performance does not deteriorate.

The size of the step z is better as the distance k between the opposing outflow ends is greater than the pitch p.
This will be explained using the analysis diagram of the step z in FIG. A, B, and C are the outflow ends of the conventional inclined plate (51) (hereinafter referred to as the longitudinal inclined plate (51a)), and B1 is the outlet end of the stepped inclined plate (hereinafter referred to as the short inclined plate 51b), which is the inclined flow path. (11) is cut at a right angle, B3 is also the outflow end of the short inclined plate, the position of the inclined flow path (11) is cut at an inclination angle θ, and the position B2 is half the pitch p. A circular arc having a radius of 1 is the position on the short inclined plate (51b) that is in contact with the line AB.
α refers to the inner angle that a straight line connecting the outflow end of the longitudinal inclined plate (51a) to the outflow end of the short inclined plate (51b) makes with the longitudinal inclined plate (51a). Generally, the inclination angle θ of the inclined plate (51) is 60 degrees, the position of B is α = 120 degrees, the position of B1 is α = 90 degrees, the position of B2 is α≒85 degrees, and the position of B3 is α =θ=60 degrees.
The growth of aggregated turbid flocs (mat layer) at the outflow ends A, B, and C is schematically shown by a circle whose radius is the midpoint M between A and B. When the circles touch each other, a bridge occurs and occlusion begins.
There are outflow ends A, B, and C, and the pitch of the partition walls is p. When the step is zero, the distance between the outflow ends is pitch p, but until the step reaches _B3 , the distance k1 between the outflow ends starting at A becomes narrower than the pitch p, and below B3 it expands. . On the contrary, the distance k2 between the outflow ends starting from C becomes larger than p after B where there is no step.
If the midpoint between B3 and A is N, then the curve MN shows the position where the circle at each step is closest to A, and the circle at each step is closer to point B1, which is a cross section of the inclined flow path (11) at right angles, and the circle is closest to A. The step B of the shape cut at the angle θ becomes equal to M at the three points N, and then expands.

That is, from M to N, it can be said that the space between the outflow ends becomes narrower, leading to blockage more easily than in the case where there is no step z, and the necessary step must be below B3.
However, considering the mechanism in which the bridge of agglomerated turbid flocs becomes weaker and more likely to collapse due to the difference in level, B1 to B3 can be expected to be effective, but the difference in level from B to B1 does not have a significant blockage prevention effect. I can't get it.

Figure 7 shows the outflow ends A and B of the inclined flow path (11) cut horizontally, A and B1 cut at right angles, and A and B3 cut at an inclination angle of 60 degrees. The turbid flocs (3a) that aggregate at each position grow in a circular shape as shown in the figure, and the outline of their growth is shown by diagonal lines on the right.
In reality, it is rarely observed that suspended matter adheres to the lower right corner of the circle, but it is represented as a circle to simplify the analysis.

When the circles with diagonal lines on the right overlap, a bridge occurs and a blockage state occurs.
The overlapping portion increases until the step z reaches B1, the overlapping portion begins to decrease below B1, and the overlapping portion disappears at B3. Below B3, there are no adjacent agglomerated flocs, so blockage does not occur.
However, it is not recommended below B3 because the length of the inclined plate (51b) becomes shorter and the decrease in sedimentation performance cannot be ignored.

From the above, it is better to set the step z below B3 if the expansion between the outflow ends is important, but considering the practical effect of preventing the formation of a mat layer, the step z necessary to prevent blockage is B1. It can be said that below B3 is sufficient.

Therefore, by making the shape of the flow path on the outflow side of the inclined plate (51) into a shape with effective steps alternately, blockage can be prevented, and the flow path can be formed from an acute angle of 90 degrees or less. By having a shape cut at an inclination angle of θ or more, it is possible to provide an inclined plate settling device A22 that has a blockage prevention effect.

Assuming that the pitch of the inclined plate (51) is p, the step z ₍₁₎ in B1 and B3 is z ₍₁₎ = psin θ × cos θ, and the step z ₍₃₎ in B3 is z ₍₃₎ = It becomes 2psinθ×cosθ. When the facing distance of the inclined plate is d, the step z ₍₁₎ of B1 is z ₍₁₎ = d cos θ, and the step z ₍₃₎ of B3 is z ₍₃₎ = 2 d cos θ.
For example, if p = 80 mm, z ₍₁₎ ≒ 35 mm, z ₍₃₎ ≒ 70 mm. If p = 150mm, z ₍₁₎ = 65mm, z ₍₃₎ = 130mm.

The size of the step z is selected depending on the properties of the suspended solids and the installation situation of the tilting device.If the adhesiveness is weak and the turbid flocs (3) are small, a small step will be effective; If it is a strong and large turbid floc (3), a large step is required.
When the tilt angle is 60 degrees and p = 80 mm, which is typical for a tilted plate settling device, z ₍₁₎ = 35 mm, z ₍₃₎ = 70 mm, and a value between 35 and 70 mm is adopted as appropriate. If there is a concern about stickiness in the properties of suspended flocs, a value between z ₍₁₎ =50 mm and z ₍₃₎ =100 mm is adopted with d = 100 mm.

However, on the other hand, since the inclined plate (51) lacks a part of the length or height, a slight decrease in sedimentation performance cannot be avoided numerically. Therefore, let's calculate and compare the rate of decline in sedimentation performance.

Figure 8 shows a diagram of the principle for determining sedimentation performance. In FIG. 8, the upper ends of the inclined plates (51) arranged continuously at a pitch p are alternately cut by a length l or a height z. That is, it has a structure in which steps z are provided alternately in the pitch p direction at the outflow end (21).
For example, if the inclination angle θ of the inclined plate (51) is 60 degrees, the face-to-face distance d of the inclined plate is 70 mm, and the inclined plate height H is 800 mm, the pitch p=70/sin60≒80 mm, and the partition wall length L=H/sin60≒ It will be 920mm.
The required height z of the inclined plate (51) is 35 mm in the right angle cut shape and 70 mm in the 60 degree cut shape. If this is replaced with the length l of the notch of the inclined plate (51), it becomes 40 mm to 80 mm.
This becomes 8.7% from 4.3% of the length L of the inclined partition wall (50) = 920 mm, but since the step z is limited to half the number of inclined plates (51), the influence is from 2.2% to 4.4%.
Therefore, the decrease in sedimentation performance due to the lack of the inclined plate (51) by l is 2.2% to 4.4%, and if the efficiency of the inclined plate settling device of 70% is taken into account, it becomes 1% to 2%, which is a functional The effect on separation performance is almost negligible.

The efficiency of inclined plate settling equipment varies depending on the type of equipment, and is said to be around 70 to 90% of the calculated settling performance.
This is the domestic water facility design guideline.
On page 196, lines 7 to 16, there is no mention of the efficiency of the inclined plate sedimentation device, but the efficiency is included within the design standards, so there is no particular mention of efficiency. Old standards in similar documents set 70% for inclined plate sedimentation equipment and 90% for inclined pipe sedimentation equipment.

Now, we assumed that the decrease in sedimentation separation performance due to the difference in level can be ignored, but if we are looking for numerical consistency in separation performance, it is necessary to increase the height of the inclined sedimentation device by 2.2% to 4.4%. However, this is within the range that is included in the processing error of the inclined sedimentation device, and has little effect on the increase in manufacturing costs due to the provision of the step z.

The inclined plate sedimentation device A22 of the present invention uses a method in which the inclined plates (51) are alternately provided with slight steps z, instead of the conventional method of enlarging the inclined channels (11) of the inclined plates (51). To provide an inclined sedimentation device that takes effective anti-clogging measures, can withstand long-term use, and is easy to maintain.

The conventional inclined plate settling device A21 has the top side (30) and bottom side (31) of the inclined plate at the same height in order to maximize the performance of the settling device, but the inclined plate settling device A22 of the present invention has alternating steps in the height of the upper side.
By providing an effective level difference, a mat-like blockage state due to agglomeration of turbid flocs (3) can be avoided and operation can be continued for a long period of time.
Although the sedimentation performance decreases by about 1% by providing a step, this effect decreases and can be ignored as the height of the inclined plate increases.
Therefore, the size of the sedimentation device does not need to be changed from the conventional one.

The most emphasized effect of the present invention is that the Reynolds number, which affects sedimentation separation efficiency, is kept low and sedimentation separation performance is maintained as is.
Furthermore, it is no longer necessary to increase the size of the inclined plate settling device A22 by expanding the inclined flow path (11) as in the past, and the volume of the settling tank B that accommodates the inclined plate settling device A22 can be kept to a minimum. Increase in construction costs for B can also be avoided.
Further, the manufacturing cost of the inclined sedimentation device A22 of the present invention does not require any special process to form the step z, and the manufacturing cost is the same as that of the conventional method.

The inclined plate sedimentation device A22 of the present invention is also aesthetically superior.
Dirt found on the outflow edge (22) of the inclined plate settling device spoils the aesthetic appearance, but this is a significant improvement as the number of outflow edges (22) of the inclined plate settling device A22 of the present invention is reduced to one half. be done.
FIG. 9 shows a top pattern diagram of the outflow edge (22) of the inclined plate sedimentation device A20. (a) is a top pattern diagram of the conventional inclined plate sedimentation device A21, which has a large number of compartments, and (b) is a top pattern diagram of the inclined plate sedimentation device A2 of the present invention, which has a step, and the number of compartments is halved. is decreasing.

An assembled perspective view of the inclined plate sedimentation device of the invention Principle diagram of horizontal flow type inclined sedimentation device and upward flow type inclined sedimentation device Schematic cross-sectional diagram of the sedimentation tank side in an example of using an upflow type inclined sedimentation device Comparison diagram of measures to prevent blockage at the outflow end of inclined plate sedimentation equipment Principle diagram of inclined sedimentation device Analysis diagram of step z Plane and side cross-sectional schematic diagrams of the outflow end showing the mechanism of preventing matte layer formation Sedimentation performance calculation diagram Upper end pattern diagram of inclined plate sedimentation device

The basic form of the present invention is a stepped slope in which a plurality of longitudinal inclined plates (51a) and short inclined plates (51b) are alternately arranged at equal intervals with the lower sides of the inclined plates and the inflow end (20) having the same height. This is plate sedimentation device A22. As a result, a step z is created in the height of the top side of the inclined plate and the outflow end side (22), and the unevenness is repeated alternately.

The step z is set downward from the height of the outflow end (21) of the longitudinal inclined plate (51a), and its size varies depending on the pitch of the inclined plates (51) arranged at equal intervals.
The outflow end (21) of the longitudinal inclined plate (51a) and the outflow end (21) of the short inclined plate (51b) are connected with a straight line, and it is defined by the angle α formed with the longitudinal inclined plate (51a).
The angle α is selected depending on the properties of the turbid floc (3), and it is preferable that α = an acute angle of 90 degrees or less if little stickiness is observed, and α = θ (inclined angle) if stickiness is observed.
Note that the lower ends of both of the tilting plates (51a, 51b) are horizontal in accordance with the height of the tilting device.

Generally, plastic materials such as PVC resin, PET resin, and ABS resin are used for the materials that make up the stepped inclined plate sedimentation device A22, and in special cases, highly corrosion-resistant materials such as stainless steel are used. .
Note that various methods are used to assemble these members, such as joining with bolts or screws, sandwiching, adhesion, welding, and fitting, depending on the pitch.

In any of the above methods, the processing and assembly for creating the step z are extremely simple, and the conventional manufacturing method can be followed as is, and there is no increase in manufacturing cost.

Now, the basic explanation above has been given using a single inclined plate sedimentation device, but in reality, the structure of a sedimentation tank is large and a large number of single units are used by arranging them in a plane. However, there is no limit to how they can be arranged.
The inclined plate settling device A20 is installed by hanging from above or by arranging it on a girder installed at the bottom of the device.
There is also a method of making the tilting device an independent structure by compositing and modularizing a large number of tilting plates (50), thereby maintaining strength and making the installation of the tilting plate settling device easier.

FIG. 1 shows an assembled perspective view of a stepped inclined plate settling device A22 according to the present invention.
The longitudinal inclined plates (51a) and the shorter inclined plates (51b) are arranged alternately to provide a step z.

The step z is such that the inner angle α between the straight line connecting the outflow end (21) of the longitudinal inclined plate and the outflow end (21) of the short inclined plate and the longitudinal inclined plate (51a) is an acute angle.
However, if blockage is likely to occur due to the properties of the turbid flocs (3), a larger step is required, and the angle of inclination θ is most recommended.

By providing the step, the pitch from the front longitudinal inclined plate (51a) to the next longitudinal inclined plate (51a) that has climbed over the short inclined plate (51b) is doubled, which greatly contributes to prevention of blockage.
However, since the pitch of the longitudinal inclined plate (51a) and the shorter inclined plate (51b) remains unchanged, the sedimentation performance in the sedimentation tank is maintained.

A practical example of step z is shown. The inclination angle of the inclined plate is 60 degrees, the pitch is approximately 75 mm to 150 mm, and when the pitch is p = 80 mm, the step z is selected between 35 mm and 70 mm.

As described above, the two inclined plates (51) fixed facing the support frame of the inclined plate settling device A21 are considered as a pair, and the height of the outflow end (21) of one inclined plate (51) is set to the height of the outflow end (21) of the other inclined plate. To provide an inclined plate sedimentation device A22 in which the height of the plate (51) is lower than that of the outflow end (21) and steps z are provided alternately.

B Sedimentation tank, C Water collection device, A0 Upward flow inclined sedimentation device, A10 Inclined tube sedimentation device, A20 Inclined plate sedimentation device, A21 Conventional inclined plate sedimentation device, A22 Stepped inclined plate sedimentation device

h Settling distance, H Height of inclined bulkhead, L Length of inclined bulkhead, l Notch length, p Pitch of inclined bulkhead, b Width of inclined bulkhead, d Face-to-face distance of inclined bulkhead or inclined pipe diameter, ε Strain, ε _mx limit Strain, z Step, θ Inclination angle of inclined bulkhead or inclined pipe, α Inner angle connecting the outflow end of the longitudinal inclined plate and the outflow end of the short inclined plate with a straight line

3 Suspended floc, 4 Mat layer, 11 Inclined channel, 20 Inflow end, 21 Outflow end, 22 Outflow end, 23 Inflow side, 24 Outflow side, 30 Inclined plate top side, 31 Inclined plate bottom side, 33 Top surface, 40 Side wall , 50 inclined bulkhead, 51 inclined plate, 51a longitudinal inclined plate, 51b short inclined plate, 53 corrugated inclined plate, 60 inclined pipe, 70 inclined plate support frame

Claims (1)

A large number of inclined partition walls below the water surface are lined up horizontally at equal intervals to form an inclined flow path, and the sides of the inclined flow path are free without partitions, and the inclined partition walls are composed of flat plate-shaped inclined plates that face each other. A pair of two inclined plates is made, the height of the outflow end of one is lower than the height of the outflow end of the other, steps are provided alternately, and the outflow end of the lower inclined plate is extended from the outflow end of the higher inclined plate. An inclined plate sedimentation device used in an upward flow sedimentation tank , characterized in that the inner angle between the connected straight lines and the higher inclined plate is 90 degrees or less and 60 degrees or more .

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