JP2001120909A - Flocculating and settling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To most suitably control the properties of floc to be settled in a settling tank and the flow of water to be treated containing the floc just before flowing into the settling tank without substantially causing size increase of the whole device and with simple improvement, and to obtain treated water of excellent quality even at a high treating rate. SOLUTION: In a flocculating and settling device provided with a flocculating tank in which suspended material in raw water is coagulated as floc by adding a flocculating agent and particulate matter and the settling tank in which the floc in the water to be treated from the flocculating tank is settled to separate the same to the floc and the treated water, a means for controlling contained floc by which flow and/or size of the floc contained in the water to be treated can be controlled (for instance, a flowstraightening means and a floc developing means) is provided at a part where the water to be treated flows in the settling tank.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a coagulation sedimentation apparatus for separating suspended substances in raw water into sludge and treated water by coagulation sedimentation.

[0002]

2. Description of the Related Art Substances suspended in raw water (hereinafter referred to as SS
Sometimes called [Suspended Solid]. Is known. S in conventional raw water
As a coagulation sedimentation apparatus for removing S, an apparatus is known which simply adds a coagulant to raw water to precipitate coagulation, pulls out the coagulation as sludge, and discharges treated water from the upper part. .

In such a general coagulation / sedimentation apparatus, it takes a long time to settle the coagulates, and an extremely large sedimentation tank is required. A coagulating sedimentation apparatus has been proposed.

[0004] For example, in French Patent No. 1411172, in a coagulation tank, raw water is mixed with a coagulant together with a particle size of 1;
Granules (typically, sand) of about 0 to 200 μm are added, and SS in the raw water is coagulated as relatively large flocs containing granules having a large specific gravity. There is disclosed a coagulation sedimentation apparatus which sediments flocs in treated water and separates them from treated water. The sediment floc pulled out of the sedimentation tank is separated into sludge and particulate matter by a separator such as a cyclone, and the separated particulate matter is returned to the flocculation tank and used for circulation.

[0005] Such a coagulating sedimentation apparatus is, for example, shown in FIG.
Can be configured as shown in FIG. In the apparatus shown in FIG. 8, an inorganic coagulant 102 is injected into raw water 101 and introduced into a coagulation tank 103. In the coagulation tank 103, a polymer coagulant 104 and particulate matter 105 are added, and the mixture is stirred by a stirrer 106. Flock grows. The water to be treated containing the grown flocs is introduced into the sedimentation tank 108 through the sedimentation tank inlet 107, where it is separated into sedimented flocs and treated water 109 as a reversing ascending flow. Treated water 109
Is discharged to the outside through, for example, an inclined plate 110 arranged at the upper part in the precipitation tank 108. The settled sludge is withdrawn by a sludge withdrawing pump 111 and separated into sludge 113 and particulate matter to be circulated by a separator 112 such as a cyclone.

In the coagulating sedimentation apparatus as described above, flocs flocculated together with the particulate matter have a very high sedimentation speed due to their higher density than flocs containing no particulate matter, and the LV in the sedimentation tank is obtained. (Linear velocity) is 50
Processing at a high flow rate of m / h or more is also possible.

However, in general, it is difficult to uniformly form particulate matter and raw water SS as flocs in the flocculation tank, and the density of the formed flocs varies because the amount of particulate matter in the flocs is not constant. In addition, since the particle size of the floc also varies, the sedimentation rate ranges from extremely high sedimentation velocity to low sedimentation velocity. In order to improve the quality of treated water in the presence of such variations, it is necessary to install an inclined plate in the sedimentation tank as described above or to determine the flow velocity of the sedimentation tank in accordance with the floc having a low sedimentation speed. Was.

Further, in the inflow part of the sedimentation tank (flow flowing from the coagulation tank to the sedimentation tank), when flocs having a high sedimentation speed rapidly fall into the water regulating area below the sedimentation tank, a density flow is generated around the same. Vortices cause destruction of the flocs and / or winding of relatively small flocs from the falling flocs, which deteriorates the water quality by flowing toward the inclined plate and outlet at the top of the settling tank. There was a problem of letting it.

As a method for solving this problem, Japanese Patent No. 2,634,230 discloses that an intermediate tank 123 is provided between a flocculation tank 121 and a precipitation tank 122 as shown in FIG. Has proposed a method of aging flock. However, in this method, a new power for stirring in the intermediate tank 123 is required, and the intermediate tank 123 needs to be specially installed as compared with the apparatus shown in FIG. However, there is a problem that the number increases.

[0010]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to substantially eliminate the increase in the size of the entire apparatus, and
With simple improvements, the properties of flocs to be settled in the sedimentation tank and the flow of the water to be treated containing the flocs can be optimally controlled just before flowing into the sedimentation tank. Another object of the present invention is to make it possible to obtain treated water having excellent water quality.

[0011]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a coagulation-sedimentation apparatus according to the present invention comprises: a coagulation tank for coagulating a suspended substance in raw water as flocs by adding a coagulant and particulates; In a coagulation sedimentation apparatus including a sedimentation tank for sedimenting floc in the water to be treated from the tank and separating the floc into treated water and floc, the floc contained in the water to be treated is supplied to the inflow part of the water to be treated into the sedimentation tank Characterized in that it is provided with a contained floc control means capable of controlling the flow and / or size of the flow.

The contained floc control means has a rectifying means extending along the flow direction of the water to be treated, or extends in a direction inclined with respect to the flow direction of the water to be treated, and rolls the flocs on its surface. Having floc growth means capable of growing floc by causing
Furthermore, it can be configured to have both of these.
As the flock growth means, a configuration in which flock temporary damming fins extending in a direction intersecting (for example, a direction orthogonal to) the flow direction of the water to be treated can be employed. A relatively small flock temporarily blocked,
While being blocked, it rotates at that position and combines with other flocs that flow later, and when it grows into a relatively large floc, it is sent downstream over the fins.

The contained floc control means can be formed in a plate shape or a tubular shape, and a plurality of them, for example, can be arranged in parallel, in a lattice, or concentrically.

In the coagulating sedimentation apparatus according to the present invention, the flow of the floc contained in the water to be treated, in fact, the flow of the water to be treated containing the floc is controlled by rectification by the contained floc control means. Or the size of the floc contained in the water to be treated is controlled, or both controls are performed, this control being performed at the inlet to the settling tank.

When the flow is rectified, for example, the flow of the water to be treated containing relatively large flocs and the flow of the water to be treated containing relatively small flocs are rectified so that the flow is large. The generation of vortices due to the density flow of the floc-containing flow is suppressed, and the vortices prevent the flocculated flocs from being crushed and small flocs from entering the flow of the treated water. As a result, a stable sedimentation behavior of the floc is obtained, and the quality of the treated water is improved.

When the growth of flocks is promoted by the floc growing means, the small flocs are temporarily blocked, combined with the flocs coming later, grown to a sufficient size, and then sent downstream. Thus, the variation in the size of the flocks can be suppressed to be small. As a result, fine flocs, which are unlikely to settle, are prevented from entering the stream of the treated water, and the quality of the treated water is improved.

If both of the rectifying means and the floc growing means are provided, both of the above-mentioned effects can be obtained, and more excellent water quality can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. In each embodiment described below, the addition of an inorganic flocculant or a polymer flocculant, the addition of particulate matter (eg, sand), the extraction of sludge from a sedimentation tank, and the separation of sludge and particulate matter in the extracted sludge are described. May be adopted in the same manner as that shown in FIG. 8 or FIG. 9. Therefore, a description will be mainly given of a configuration example from the flocculation tank to the sedimentation tank.

As the inorganic coagulant to be added, for example, polyaluminum chloride (PAC), ferric chloride and ferric sulfate can be used. As the polymer coagulant, for example, nonionic, anionic or amphoteric can be used. A polymeric flocculant can be used. Examples of the anionic polymer coagulant include a polymer of acrylic acid or a salt thereof, a copolymer of acrylic acid or a salt thereof and acrylamide, and a copolymer of acrylamide and 2-acrylamido-2-methylpropanesulfonic acid salt And a tertiary copolymer of acrylic acid or a salt thereof, acrylamide and 2-acrylamido-2-methylpropanesulfonate, and a partial hydrolyzate of polyacrylamide, but are not particularly limited thereto. A typical nonionic polymer flocculant includes polyacrylamide, but is not particularly limited thereto. Examples of the amphoteric polymer flocculant include at least one cationic monomer such as a tertiary salt and a quaternary salt of dimethylaminoethyl (meth) acrylate (eg, a methyl chloride salt), acrylic acid and a salt thereof. (A salt such as sodium and calcium), a copolymer of at least one anionic monomer such as 2-acrylamido-2-methylpropanesulfonate (a salt such as sodium and calcium), or at least one of Examples include tertiary or quaternary copolymers of at least one kind of cationic monomer and at least one kind of anionic monomer and at least one kind of nonionic monomer such as acrylamide, It is not particularly limited to these. The range of the molecular weight of the polymer flocculant is not particularly limited, but is preferably in the range of 5,000,000 to 20,000,000. These polymer flocculants can be used alone or as a mixture. The addition amount of the polymer flocculant is generally about 0.3 to 2 mg / l from an economic viewpoint.

In the coagulation tank, sand as a granular material is added. The addition amount is initially added so that the concentration of sand in the coagulation tank is equal to or higher than a predetermined concentration, and the shortage is replenished regularly or irregularly so that the sand used for circulation can maintain the predetermined concentration. Is done. The particle size of the sand used may be appropriately selected, for example, from the range of 10 to 200 μm.

FIG. 1 shows a coagulation / sedimentation apparatus 1 according to a first embodiment of the present invention, and particularly shows main components from a coagulation tank 2 to a sedimentation tank 3.

In FIG. 1, raw water 4 is supplied from the lower part of the flocculation tank 2 in this embodiment, and SS in the raw water is mixed with the flocculant and the granular material while being stirred by the stirrer 5 in the flocculation tank 2. Addition of a substance (sand) causes the floc to coagulate. The coagulation tank 2 and the sedimentation tank 3 are partitioned by the coagulation tank partition plate 6, and the water to be treated in the coagulation tank 2 is introduced into the sedimentation tank 3 over the upper end of the coagulation tank partition plate 6 by overflow. It has become so. A settling tank partition plate 7 is provided at the entrance to the settling tank 3, and a space between the coagulation tank partition plate 6 and the settling tank partition plate 7 flows from the treated water inflow portion 8 into the settling tank 3. Formed on the road.

In the sedimentation tank 3, the flocculated floc 9 contained in the water to be treated is settled, and the treated water separated from the flocculated floc 9 is sent upward by a reverse ascending flow, and the supernatant water overflowing from the water surface 10. Is discharged as treated water 11. An inclined plate similar to that shown in FIGS. 8 and 9 may be disposed in the upper part of the precipitation tank 3 (not shown).
The precipitated sludge 12 is, as shown in FIGS. 8 and 9,
The sludge is extracted by a sludge extraction pump, and separated into sludge and particulate matter used for circulation by a separator such as a cyclone.

The configuration so far is substantially the same as the configuration shown in FIG. However, in the present invention, the precipitation tank 3
Is provided with a floc control means capable of controlling the flow and / or size of the floc contained in the water to be treated. In the present embodiment, the contained floc control means is provided on the rectifying plate 13 as rectifying means extending along the flow direction of the water to be treated. The current plate 13 includes a plurality of (two in the illustrated example) current plates extending in the flow direction of the to-be-treated water, in the present embodiment, in the vertical direction, and at intervals.

In the coagulation / sedimentation apparatus 1 according to the first embodiment thus configured, the water to be treated containing the flocculated floc 9 from the coagulation tank 2 passes through the water to be treated inflow section 8 and the sedimentation tank 3 Flows into. At this time, as shown in FIG.
Since the relatively large flocculated floc 9 starts to settle immediately after climbing over the upper end of the flocculating tank partition plate 6, the water to be treated containing the relatively large flocculated floc 9 is mainly
The water to be treated, which descends through the flow path defined and partitioned between the coagulation tank partition plate 6 and the closest straightening plate 13 and contains other relatively small coagulation flocs, is mainly discharged from the coagulation tank partition plate 6. Descends the flow path formed by being partitioned at a position away from the flow path. That is, the to-be-treated water inflow portion 8 into the settling tank 3
In the flow path, immediately before reaching the settling tank 3, the water to be treated is divided into a flow of the water to be treated containing relatively large flocculated flocs and a flow of the water to be treated containing relatively small flocculated flocs. While being separated, both flows are rectified along the rectifying plate 13. Moreover, while the two flows are flowing along the current plate 13, the two flows do not interfere with each other.

As a result, the generation of a vortex which is particularly likely to occur due to the density flow of the water to be treated containing relatively large flocculated flocs is suppressed, and the flocculated flocs are crushed or the relatively small flocculated flocs are wound up. The inconvenience of climbing up the flowing water is avoided. Therefore, as shown by the arrow in FIG. 1, the flocculated floc 9 is smoothly settled without causing disturbance in the direction along the flocculating tank partition plate 6 (floc flow 14), and the inverted water flow separated from the floc is treated. As water, it rises smoothly without involving flocks (processed water flow 15). The flocculated flocs 9 are efficiently separated from the treated water, and the quality of the treated water is improved.

FIG. 2 shows a coagulation / sedimentation apparatus 21 according to a second embodiment of the present invention. In the present embodiment, the first
Compared to the embodiment, the contained floc control means provided in the treated water inflow portion 22 to the settling tank 3 extends in a direction inclined with respect to the flow direction of the treated water, and can roll the floc on that surface. Inclined plate 2 as possible floc growth means
3. In the present embodiment, the inclined plate 23 is
It is formed on a settling tank inlet inclined plate disposed below the treated water inflow section 22, and is constituted by a plurality of inclined plates extending in parallel with each other at intervals.

In the coagulating sedimentation apparatus 21 according to the second embodiment, when the water to be treated containing flocculated flocs flows into the sedimentation tank 3 through the water to be treated inflow portion 22, the sedimentation is performed. When passing through the tank entrance inclined plate 23, the contained flocculated flocks roll on the inclined plate 23, and during this rolling, the flocs coming later are rolled up and joined to form a larger flocculated floc. And grow. Particularly fine flocs grow into larger flocculated flocs.
Therefore, a large variation in the size of the flocculated floc is suppressed from occurring immediately before flowing into the precipitation tank 3, and in particular, a large amount of too small floc is suppressed. As a result, the size of the flocculated floc to be settled is naturally adjusted to a certain level or more, a high settling speed is secured, the processing speed in the settling tank 3 is improved, and the entrapment of the fine floc in the treated water is suppressed. The quality of the treated water is improved. Further, since the inclined plates 23 shown in FIG. 2 are arranged in parallel with each other at intervals, they have the same function as the rectifying plate shown in FIG. The effect of the rectifying action is also exerted, and it is possible to achieve a higher processing speed and a higher quality of the treated water.

In the case where the above-mentioned inclined plates 23 are provided, as shown in FIG. 3, a direction (arrow direction) intersecting the flow direction of the water to be treated (arrow direction) is further provided on each inclined plate 23. For example, it is preferable that a flock temporary damming fin 24 extending in a direction perpendicular to the projection is provided in a protruding manner. The floc temporary damming fins 24 temporarily dampen the fine flocculated flocs 25 and entangle and combine the subsequent flocculated flocs while rotating by the water flow at the damped position, thereby forming larger flocs. When it grows and grows to a certain large floc,
It is sent downstream over the flock temporary damming fins 24. Therefore, the protrusion height of the flock temporary damming fins 24 may be set according to the target size for growing the fine aggregated flocs 25. By providing the floc temporary damming fins 24 in this manner, the size of the flocculent floc to be settled is more naturally adjusted to a certain level or more, a high settling speed is secured, and the processing speed in the settling tank 3 is improved. As well as
Entrapment of the fine flocs in the treated water is suppressed, and the quality of the treated water is improved.

Since the inclined plate as shown in FIG. 2 also has a rectifying function as described above, it can be disposed over substantially the entire length of the inflow portion of the water to be treated. For example, as shown in FIG. 4 showing a coagulating sedimentation apparatus 31 according to a third embodiment of the present invention, the shape of the treated water inflow section 32 into the sedimentation tank 3 is devised, and A plurality of portions 32 can be provided so as to extend over the entire length of the portion 32. With such a configuration, it is possible to obtain a more excellent rectifying action while obtaining the floc growth action of the inclined plate 33, and it is possible to achieve a higher processing speed and an excellent quality of the treated water. It is preferable that the inclined plate 33 is also provided with a flock temporary damming fin as shown in FIG.

Further, the contained floc control means according to the present invention may be formed in a plate shape as shown in each of the above embodiments, or may be formed in a tubular shape. For example, as shown in FIG. 5, a coagulating sedimentation apparatus 41 according to a fourth embodiment of the present invention, a sedimentation tank inlet inclined pipes 43 are arranged vertically and horizontally (in a grid) at a treatment water inflow part 42 into the sedimentation tank 3. May be. Instead of the inclined tube structure, a straightening tube structure extending in the vertical direction may be used. In the case of forming the inclined tube 43, it is possible to provide a flock temporary damming fin as shown in FIG. 3 on the inner surface thereof. With such a settling tank inlet inclined pipe 43 configuration or straightening pipe configuration, the same operation and effect as the configuration shown in FIGS. 2 and 4 or the same operation and effect as the configuration shown in FIG. 1 can be obtained. Is possible.

Further, the contained floc control means according to the present invention can also be applied to a treatment water inflow portion into a cylindrical settling tank. For example, as shown in FIG. 6 showing a coagulating sedimentation apparatus 51 according to a fifth embodiment of the present invention, a sedimentation tank inlet rectification cylinder is provided inside a treated water inflow cylinder 53 provided at the center of a cylindrical sedimentation tank 52. 54 can be arranged concentrically.
With such a configuration, for example, the flow into the sedimentation tank inlet rectifying cylinder 54 at the center is the flow of the water to be treated containing relatively large flocculent floc, and the flow path is formed by being divided around the flow. Rectifying and separating both streams as a stream of water to be treated containing relatively small flocculated flocs,
It is possible to suppress the generation of vortices due to the density flow of the flow containing the relatively large agglomerated flocs, and to suppress the agglomerated flocs from being crushed or the small flocs being rolled up by the vortices. Therefore, such a cylindrical settling tank 5
The present invention is also applicable to No. 2, and the functions and effects targeted by the present invention can be obtained. further,
It is also possible to incline the wall of the settling tank inlet straightening cylinder 54 partially or over the entire length, and it is also possible to add the function and effect of the above-mentioned inclined plate.

In each of the above-described embodiments, the rectifying plate, the inclined plate, and the rectifying tube provided side by side extend linearly in a certain direction with respect to the flow direction of the water to be treated, but extend in a zigzag manner. It is also possible to set up. For example, as shown in FIG. 7, the rectifying plates 61 or inclined plates or rectifying cylinders provided side by side can be formed in a zigzag shape in the flow direction of the water to be treated (the direction of the arrow). With this configuration, by appropriately setting the degree of zigzag, the rectification effect and the flock rolling effect by the inclined structure can be optimized without canceling each other.

The following experiment was conducted to confirm the effect of the present invention. PAC was added as an inorganic coagulant to the artificial turbid water to which kaolin was added as a suspended substance, this was supplied to a coagulation tank, and granular materials and a polymer coagulant (polymer) were injected. The turbidity of the treated water was measured (in the experiment, the apparatus shown in FIGS. 1 and 2 was used). [Experimental equipment] Coagulation tank: 500 mm □ × 3000 mmH Precipitation tank: 500 mm □ × 3000 mmH [Operating conditions] Raw water flow rate: 17.5 m ³ / h (Sedimentation tank LV = 70 m / h) PAC injection amount: 20 mg / liter Kaolin addition amount : 20 mg / l Polymer addition amount: 0.7 mg / l (polyacrylamide) Granular material addition amount: 10 kg (silica sand)

The results are shown in Table 1. As is clear from Table 1, compared to Comparative Example 1 in which the content floc control means was not provided at the inflow portion of the water to be settled into the sedimentation tank, Example 1 in which a rectifying plate was provided as content floc control means, an inclined plate was provided. In Example 2 and Example 3 in which an inclined plate with flock temporary damping fins was provided, the turbidity of the treated water could be significantly improved. In this experiment, the LV of the settling tank was evaluated in the same manner. However, when the turbidity of the treated water was almost the same, Comparative Example 1 was used.
In comparison, in Examples 1, 2, and 3, the processing speed can be greatly improved, and both the turbidity of the treated water and the processing speed can be both improved.

[0036]

[Table 1]

[0037]

As described above, according to the coagulation sedimentation apparatus of the present invention, the flow and properties (particularly the size) of the coagulation floc are provided by providing the content floc control means at the inflow portion of the water to be treated into the sedimentation tank. ) Can be optimized immediately before introduction into the settling tank, whereby an improvement in the treatment speed in the settling tank and an improvement in the quality of the treated water can be achieved.

Further, the content floc control means can be provided at the inflow portion of the water to be treated into the existing sedimentation tank, and can be simply improved without increasing the size of the entire apparatus.
Moreover, the present invention can be easily implemented without requiring new power, and can provide an extremely useful technique.

[Brief description of the drawings]

FIG. 1 is a main part configuration diagram of a coagulation / sedimentation apparatus according to a first embodiment of the present invention.

FIG. 2 is a main part configuration diagram of a coagulation / sedimentation apparatus according to a second embodiment of the present invention.

FIG. 3 is a partial configuration diagram of a finned inclined plate.

FIG. 4 is a main part configuration diagram of a coagulation / sedimentation apparatus according to a third embodiment of the present invention.

FIG. 5 is a main part configuration diagram of a coagulation / sedimentation apparatus according to a fourth embodiment of the present invention.

FIG. 6 is a main part configuration diagram of a coagulation / sedimentation apparatus according to a fifth embodiment of the present invention.

FIG. 7 is a partial configuration diagram of a zigzag plate.

FIG. 8 is an overall configuration diagram of a conventional content floc control means.

FIG. 9 is an overall configuration diagram of another conventional content floc control means.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1, 21, 31, 41, 51 Coagulation sedimentation apparatus 2 Coagulation tank 3 Sedimentation tank 4 Raw water 5 Stirrer 6 Coagulation tank partition plate 7 Precipitation tank partition plate 8, 22, 32, 42 Inflow part for treated water 9 Coagulation floc 10 Water surface 11 Treated water 12 Sludge 13 Rectifying plate as control means for containing floc 14 Flow of floc 15 Flow of treated water 23, 33 Precipitation tank entrance inclined plate 24 Flock temporary damming fin 25 Fine floc 43 Precipitation tank entrance inclined pipe 52 Cylindrical sediment Tank 53 Inflow cylinder for treated water 54 Rectification cylinder at inlet of sedimentation tank 61 Zigzag rectification plate

Claims (5)

[Claims] 1. A flocculation tank for flocculating suspended substances in raw water as flocs by adding a flocculant and particulate matter, and a sedimentation tank for sedimenting flocs in water to be treated from the flocculation tank and separating them into treated water and flocs. In the coagulation sedimentation device having
A flocculation / sedimentation apparatus characterized in that a floc control means capable of controlling the flow and / or size of flocs contained in the water to be treated is provided at the inflow portion of the water to be treated into the sedimentation tank. 2. The method according to claim 1, wherein the contained floc control means has a rectifying means extending along the flow direction of the water to be treated.
Coagulation sedimentation equipment. 3. A floc growth means extending in a direction inclined with respect to the flow direction of the water to be treated, and having a floc growing means capable of rolling the flocs on the surface thereof. Coagulation sedimentation equipment. 4. The coagulating sedimentation apparatus according to claim 3, wherein said floc growth means is provided with a floc temporary damming fin extending in a direction intersecting with the flow direction of the water to be treated. 5. The coagulation / sedimentation apparatus according to claim 1, wherein a plurality of content floc control means are arranged in parallel.