JP2000317217A - Flocculating and settling device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve efficiency of separating flocks from treated water by installing a precipitation promoting means extending vertically with respect to an open part of an inlet passage of raw water in a settling tank, which is provided together with a flocculating tank in the titled device, for separating the flocks from the treated water by precipitating the flocks in the raw water fed from the flocculating tank. SOLUTION: This flocculating and settling device 1 is provided with the flocculating tank 2 and the settling tank 3. The raw water 5 is supplied to the tank 2 through a raw water supply line 4, and an inorganic flocculating agent 6 and a polymeric flocculating agent are injected to the line 4. In the tank 3, the flocks in the introduced water are precipitated on the bottom and separated from the upper treated water 14. Such a precipitation promoting means 23 being a cylindrical type (settling pipe) is installed by plural numbers in parallel in the tank 3, as extends vertically with respect to the open part 22 of the inlet passage 21 so that they are disposed near the wall 24 forming the inlet passage 21.

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 matter in raw water by coagulation sedimentation into sludge and treated water. The present invention relates to a coagulation / sedimentation apparatus capable of improving water quality and performing high-speed treatment.

[0002]

2. Description of the Related Art Substances suspended in raw water (hereinafter referred to as SS
Sometimes called [Suspended Solid]. Is known. As a conventional coagulation sedimentation device for removing SS in raw water, a device that simply adds a coagulant to raw water to precipitate coagulated material, pulls out the coagulated material as sludge, and draws out treated water from the upper part. well known.

For example, as shown in FIG. 6, for example, a coagulant is injected into a raw water by a line, and the raw water flows into a coagulation cylinder 102 from a raw water inlet 101, and the inflowing water to be treated is settled through a lower opening of the coagulation cylinder 102. There is known a coagulation sedimentation apparatus in which floc 104 containing flocculated SS is caused to flow down into a tank 103 and sedimented down, and separated treated water 105 is taken out from an upper treated water outlet 106.

In such a general coagulation / sedimentation apparatus, it takes a long time to settle the agglomerate, and an extremely large sedimentation tank is required. There has been proposed a coagulation sedimentation apparatus in which a particulate material (typically, sand) is used together with a coagulant for coagulation.

For example, French Patent No. 1411172 discloses that in a coagulation tank, raw water and coagulant together with a coagulant have a particle diameter of 1%.
Granules (sand) of about 0 to 200 μm are added, and the SS in the raw water is agglomerated as relatively large flocs containing granules having a large specific gravity, and flocs in the water to be treated introduced from the flocculation tank in the sedimentation tank are removed. A coagulation sedimentation device for sedimentation and separation from treated water is disclosed. 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.

However, in reality, it is difficult to grow the floc to an optimum size and specific gravity in the next precipitation step by stirring in the flocculation tank, so that the floc can be settled only in a state where the precipitate can be quickly and efficiently separated. It was difficult to do. Therefore, in actual operation, the linear velocity of the water treatment in the settling tank can be achieved only about 6 to 8 m / h, and it is difficult to achieve a linear velocity of a higher flow velocity.

[0007] Japanese Patent No. 26342 discloses such a situation.
Japanese Patent No. 30 discloses a coagulation / sedimentation apparatus in which an intermediate tank provided with a stirrer is provided between the coagulation tank and the precipitation tank, thereby enabling processing at a high flow rate linear velocity.

In this coagulation sedimentation apparatus, sand as particulate matter is added to raw water together with, for example, an inorganic coagulant and a polymer coagulant, and the SS in the raw water is stirred by a stirrer in a coagulation tank.
Are agglomerated, and the water to be treated is introduced into the intermediate tank, and is further agitated by a stirrer to further promote the growth of flocs. Since the water to be treated containing the grown sand-containing flocs is introduced into the settling tank, the flocs can settle more efficiently and quickly, and can be separated from the treated water in a shorter time. The floc settled at the bottom of the settling tank is drawn out as sludge, separated into sludge and sand by a separator made of cyclone or the like, and the separated sand is returned to the flocculation tank for circulating use. Patent No. 2634
According to Japanese Patent Publication No. 230, it is described that this coagulation-sedimentation apparatus enables processing at a linear velocity of 30 to 60 m / h, and even at a high flow rate of 90 m / h.

[0009] However, the above-mentioned Patent No. 2634230
In the apparatus proposed in No. 2, it is necessary to provide an intermediate tank with agitation between the flocculation tank and the precipitation tank, which leads to an increase in equipment cost, power consumption, and installation area. .

[0010] Therefore, although the application has not yet been published,
According to the present applicant, without first providing the intermediate tank as described above, the sedimentation tank is disposed adjacent to the coagulation tank, and the formation of flocs in the coagulation tank is performed more optimally, so that the linear velocity is reduced An agglomerated sedimentation apparatus that can be processed at a high flow rate of 30 to 100 m / h and can be configured small and inexpensively as a whole has been proposed (Japanese Patent Application No. 11-13097).
6, Japanese Patent Application No. 11-130977, Japanese Patent Application No. 11-13
0978).

[0011]

However, the following problems still remain in the coagulation / sedimentation apparatus previously proposed by the present applicant.

That is, by optimizing the flocculation of the floc containing the particulate matter in the flocculation tank, a flocculation floc suitable for the next precipitation step can be formed. Therefore, a conventional general flocculation and precipitation apparatus as shown in FIG. In comparison with this, the sedimentation process can be performed at a much higher speed.However, in response to this high-speed process, there is a possibility that the inflow speed of the raw water containing coagulated flocs flowing into the sedimentation tank may be increased. As compared with the conventional general coagulating sedimentation apparatus as shown in FIG.
It may be more than twice as fast. At such a high inflow rate, for example, as shown in FIG.
There is a possibility that a short path to the treated water outflow side may be generated in the settling tank 111 in the flow of the raw water 113 flowing through the inlet flow path 112. When a short path occurs, it becomes difficult to effectively use the inside of the precipitation tank 111, and accordingly, the separation efficiency between the treated water and the flocculated floc is reduced,
The processing speed can be kept low, and the quality of the treated water may deteriorate.

At a high inflow speed, the inlet flow path 11
2 and the flow of the raw water 113
Due to the relationship with the flow in the sedimentation tank 111 along the wall surface forming the turbulence 12, the vortex 114 is likely to be generated in a portion immediately after the opening of the inlet channel 112. When the vortex is generated, the flocs entrained in the vortex cannot escape from the vortex and are mixed into the treated water, causing a deterioration in the quality of the treated water. Since the vortex is more likely to be generated as the flow rate becomes higher, the improvement of the separation efficiency is hindered, and the processing speed is suppressed to be lower.

SUMMARY OF THE INVENTION It is an object of the present invention to increase the efficiency of separating floc and treated water in a sedimentation tank, particularly in a coagulation sedimentation apparatus capable of efficiently forming a flocculent floc in a coagulation tank using a particulate material together with a coagulant. Another object of the present invention is to provide a coagulation / sedimentation apparatus capable of obtaining excellent treated water quality even at a high treatment speed.

[0015]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, an agglomeration and precipitation apparatus according to the present invention comprises an aggregating tank for aggregating suspended substances in raw water as flocs by adding an aggregating agent and particulate matter; Coagulating sedimentation apparatus having a sedimentation tank for sedimenting floc in raw water from the raw water and separating the floc into treated water and floc. It comprises a means for promoting precipitation.

The above-mentioned precipitation accelerating means includes:
It is preferable that it is arranged near the wall forming the inlet flow path of the raw water to the settling tank. The inlet flow path of the raw water to the settling tank is configured, for example, so that the raw water flowing into the settling tank is substantially a downward flow.

Further, the precipitation accelerating means is preferably formed in a cylindrical shape or a U-shaped cross section, but may be formed in a simple flat plate shape. In such a sedimentation promoting means, the upper end is located higher than the opening of the inlet flow path, and the lower end is located lower than the opening of the inlet flow path. Is preferably located 0.4 to 1 m below the opening of the inlet flow path of the raw water. In addition, only one settling accelerator may be provided, or a plurality of settling accelerators may be arranged in parallel according to the size of the settling accelerator or the size of the opening of the inlet channel.

As the granular material used for the coagulation in the coagulation tank, sand can be typically used, and those having a uniform particle size are particularly preferable. Also, as a coagulant, usually,
Inorganic and polymeric flocculants can be used. The inorganic flocculant can efficiently flocculate the suspended substance in the raw water, and the polymer flocculant grows fine flocculated flocs generated by the inorganic flocculant into larger flocs by further entanglement of the polymer. Granules made of sand or the like having a large specific gravity are mixed in the grown flocks, and flocs having a large specific gravity (density) and easy to precipitate are formed as a whole. Raw water containing flocs that have grown to such a shape that is easy to sediment flows into the sedimentation tank, and the sedimentation promoting means according to the present invention is utilized to separate the floc to be precipitated and treated water satisfactorily.

In the coagulating sedimentation apparatus according to the present invention as described above, the raw water that has flowed into the sedimentation tank via the inlet passage collides with the sedimentation promoting means extending vertically with respect to the opening of the inlet passage. The flow velocity of the water stream in the settling tank is reduced. Further, a vortex in the horizontal direction is generated on the downstream side of the sedimentation promoting means to attenuate the kinetic energy of the water flow. As a result, the flow velocity of the flow that is going to be short-passed upward is significantly reduced, and as a result, the short-pass flow is favorably suppressed. Therefore, the flocculated floc in the raw water is well separated from the treated water and settled downward, and the quality of the treated water separated from the floc is improved.

Further, since the sedimentation promoting means extends in the vertical direction, it also functions as a guide means for the sedimented flocs in the downward sedimentation direction. The flocculated flocs trapped in the vortex generated on the downstream side of the precipitation promoting means are guided downward along the precipitation promoting means and settle quickly. The lower end of the sedimentation promoting means is located at a proper distance below the opening of the inlet channel, and the sedimentation promoting means is formed to be appropriately long downward and guided along the sedimentation promoting means. Can be guided to the lower still water area. Since the floc guided to the still water area no longer rides on the water flow toward the treated water side, it is more reliably settled to the bottom of the settling tank. Therefore, the separation efficiency between flocs and treated water is further enhanced, and the quality of treated water is further improved.

As described above, the short path flow is suppressed well, and the floc and the treated water are separated well, so that a good treated water quality can be obtained even at a high treating speed, and 30 to 100 m / H and an improvement in the quality of the treated water are simultaneously achieved.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a coagulation / sedimentation apparatus 1 according to one embodiment of the present invention. The coagulation / sedimentation apparatus 1 includes a coagulation tank 2 and a sedimentation tank 3 disposed adjacent thereto. The coagulation tank 2 has a raw water supply line 4
The raw water 5 is supplied via the, and in the present embodiment, the inorganic coagulant 6 and the polymer coagulant 7 are injected in a line. Downstream of the injection position of the inorganic flocculant 6, a mixer 8 such as a static mixer is interposed so that the injected flocculant can be mixed well with the raw water. However,
These coagulants can be directly charged into the coagulation tank 2.

As the inorganic coagulant 6, for example, polyaluminum chloride (PAC), ferric chloride, and ferric sulfate can be used. As the polymer coagulant 7, for example, a nonionic, anionic or amphoteric polymer can be used. Flocculants 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. (Salts such as sodium and calcium), 2-
A copolymer of at least one anionic monomer such as acrylamide-2-methylpropanesulfonate (salts such as sodium and calcium), or at least one of the above cationic monomers and at least one of the above 1
Ternary or quaternary or higher copolymers of at least one kind of anionic monomer and at least one kind of nonionic monomer such as acrylamide are exemplified, but not particularly limited thereto. 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 2, sand 9 as a granular material is added. The flocculation tank 2 is provided with a stirrer 11 driven by a motor 10, and the suspended substance in the raw water is stirred by the stirrer 11 to form a floc containing the inorganic coagulant 6, the polymer coagulant 7, and the sand 9. Agglomerated.

In this flocculation, the inorganic flocculant 6 flocculates the suspended substance to form fine flocs, and the polymer flocculant 7 becomes entangled to grow into larger flocs, and the grown flocs have specific gravity. It contains sand 9 as large particulate matter and grows into relatively large, high specific gravity flocculable flocs as a whole.

The raw water containing the grown floc 13 is
It is introduced into the precipitation tank 3 via an overflow weir 12. In the sedimentation tank 3, the flocs in the introduced water are sedimented downward, and the sedimented flocs are separated from the upper treated water 14.
A plurality of inclined plates 15 are arranged side by side in the upper part of the settling tank 3 to prevent the floc from flowing out together with the treated water 14.

The bottom of the settling tank 3 is connected to a drawing line 16 for drawing out the settled flocs, and a slurry containing the settled flocs is drawn out by a sludge drawing pump 17. The extracted slurry is
It is sent to cyclone 18 as a separator, and cyclone 1
The sludge 19 and the sand 9 are separated by the centrifugal separation in the inside 8. The separated sand 9 is returned to the flocculation tank 2 again and used for circulation.

In the coagulation / sedimentation apparatus 1 basically constructed as described above, between the coagulation tank 2 and the sedimentation tank 3, an inlet flow path of the raw water from the coagulation tank 2 leading to the sedimentation tank 3. 21
Is provided. The inlet flow path 21 is formed as a flow path that opens substantially downward into the sedimentation tank 3 so that the raw water flowing into the sedimentation tank 3 has a substantially downward flow. It is configured. However, the opening direction may be set so that the flow of the raw water flowing into the settling tank 3 has a horizontal flow component together with the downward flow. In the present embodiment, the inlet channel 21 is formed in a shape that expands in a tapered shape toward the opening 22.

The sedimentation tank 3 is provided with sedimentation promoting means 23 extending vertically with respect to the opening 22 of the inlet channel 21. In the present embodiment, the precipitation promoting means 23
As shown in FIG. 2, is formed in a cylindrical means (settling cylinder), and a plurality (two in this embodiment) are juxtaposed. These sedimentation promoting means 23 are arranged in the sedimentation tank 3 in the vicinity of the wall 24 forming the inlet channel 21. The upper end position of the precipitation promoting means 23 is located at the opening 2 of the inlet flow path 21.
There is no particular limitation as long as it is located above 2. It is preferable that the lower end position of the precipitation accelerating means 23 is located 0.4 m or more, preferably 0.4 m to 1 m below the opening 22 of the inlet channel 21. By extending the sedimentation promoting means 23 to such a lower end position, it becomes possible to guide the flocculated floc along the sedimentation promoting means 23 to a still water area generated below.

As the shape of the precipitation promoting means, in addition to the cylindrical shape shown in FIG. 2, for example, the precipitation promoting means 31 may have a U-shaped cross section as shown in FIG. However, it may be constituted by a simple flat plate member.

The arrangement of the precipitation accelerating means may be appropriately changed according to the shape of the inlet channel. For example, as shown in FIG. 4, when an inlet channel 42 is provided in the center of the settling tank 41, a settling promoting means 44 is appropriately provided around a cylindrical wall 43 forming the inlet channel 42. Numbers can be arranged.

The operation of the coagulation / sedimentation apparatus 1 constructed as described above will be described with reference to the apparatus shown in FIGS. 1 and 2.
In the flocculation tank 2, flocculated floc 13 containing inorganic flocculant 6, polymer flocculant 7 and sand 9 is flocculated and grown to a size suitable for the next precipitation step, and has a large specific gravity containing sand 9. The floc that has grown large is quickly settled in the sedimentation tank 3 and separated from the treated water 14, so that it can be treated at a high linear velocity.

The raw water containing the flocculated floc 13 from the flocculation tank 2 flows into the sedimentation tank 3 through the inlet channel 21. The raw water flowing into the sedimentation tank 3 as shown in FIGS. Into a stream 25 of water to be separated as treated water, which inverts upwards, and a stream 26 of sedimented floc separated from the treated water and settling down,
The separated flocs settle toward the bottom of the settling tank 3. At this time, the raw water flowing into the sedimentation tank 3 from the inlet channel 21 first collides with the sedimentation promoting means 23, and its flow velocity is reduced. On the downstream side of the sedimentation promoting means 23, a substantially horizontal vortex 27 is generated as shown in FIG. 5, and the vortex 27 also attenuates the kinetic energy of the inflowing raw water, thereby reducing the water flow. The flow rate is reduced. As a result, the occurrence of a short path flow to the upper treated water outflow side is suppressed, the amount of flocs mixed into the treated water is reduced, and the separation efficiency is improved.

The flow of the feed water containing flocs is generated through or along the cylindrical sedimentation promoting means 23, or along the sedimentation promoting means 31 having a U-shaped cross section. Therefore, the flocs to be settled are also guided along the flow. Since the sedimentation promoting means 23 extends downward in the sedimentation direction, flocs to be sedimented are appropriately guided in the sedimentation direction,
This also improves the efficiency of separating flocs from treated water. In particular, when the sedimentation promoting means 23 extends to the lower still water area, it is possible to guide the settling floc to the still water area, and the floc guided to the still water area becomes
Since it hardly gets on the rising water again, the separation efficiency is further improved.

As described above, the efficiency of separation of flocs from treated water is increased, and as a result, the quality of treated water is greatly improved.
In addition, as a result of improving the quality of the treated water, the treatment speed in the settling tank 3 is improved. That is, excellent treated water quality can be obtained while achieving a high treatment speed of 30 to 100 m / h.

In order to confirm the effect of the coagulation / sedimentation apparatus according to the present invention, the following experiment was conducted.

[Experiment] PAC as an inorganic coagulant was injected into artificial turbid water in which kaolin was added to raw water as a suspended substance, followed by line mixing, and a polymer as a high-molecular coagulant was injected. And the experiment was conducted under the following conditions, and the turbidity of the treated water was measured. The experiment was carried out according to the flow shown in FIG. 1, and the settling cylinder shown in FIG. In addition, the sedimentation cylinders having a length of 400 mm (Example 1) and 600 mm (Example 2) are prepared, and are set so that the upper end of the sedimentation cylinder is located 100 mm higher than the lower end of the raw water inlet channel wall. did.

Experimental machine: Coagulation tank capacity: 500 liters Precipitation tank: 500 mm □ × 3000 mmH Sedimentation cylinder: 100 mmφ × 2 ・ Operating conditions: Raw water flow rate: 15 m ³ / h (Sedimentation tank linear velocity [LV] = 60 m / h) ) PAC injection amount: 20 mg / l Polymer injection amount: 0.5 mg / l (polyacrylamide anionic polymer)

The results are shown in Table 1. From the comparison of the results of Comparative Example 1 and Examples 1 and 2, the water quality was improved when the sedimentation cylinder was installed in the sedimentation tank as compared with the case where the sedimentation cylinder was not installed. In addition, as a result of observation from a viewing window provided at the lower part of the sedimentation tank, the lower end of the sedimentation cylinder used in Example 2 was in the still water area below the sedimentation tank, and the short sedimentation cylinder used in Example 1 was extended to the still water area. It is more effective and reduces the quality of the treated water when the sedimentation cylinder extends to the still water area and does not extend to the static water area. It turns out that it can be improved.

[0040]

[Table 1]

[0041]

As described above, according to the coagulating sedimentation apparatus of the present invention, when the raw water containing the floc containing particulate matter is introduced into the sedimentation tank, the raw water straddles the top and bottom of the inlet flow path opening in the sedimentation tank. By providing a settling accelerating means that extends, the short path of the water flow in the settling tank can be suppressed, and the flow rate can be appropriately reduced, so that the efficiency of separating flocculated floc and treated water can be significantly increased. Excellent treatment water quality can be achieved also at the treatment speed.

[Brief description of the drawings]

FIG. 1 is an overall configuration diagram of a coagulation / sedimentation apparatus according to an embodiment of the present invention.

FIG. 2 is a perspective view showing a flow state in a settling tank of the apparatus of FIG.

FIG. 3 is a perspective view showing a flow state in a settling tank of a coagulation settling apparatus according to another embodiment of the present invention.

FIG. 4 is a perspective view showing a flow state in a settling tank of a coagulation settling apparatus according to still another embodiment of the present invention.

FIG. 5 is a schematic perspective view showing a flow around a precipitation promoting means of the apparatus of FIG. 1;

FIG. 6 is an overall configuration diagram of a conventional general coagulation / sedimentation apparatus.

FIG. 7 is a schematic longitudinal sectional view showing a problem in a precipitation tank.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation apparatus 2 Coagulation tank 3, 41 Precipitation tank 4 Raw water supply line 5 Raw water 6 Inorganic coagulant 7 Polymer coagulant 8 Mixer 9 Granular sand 10 Motor 11 Stirrer 12 Overflow weed 13 Grown floc 14 Treatment Water 15 Inclined plate 16 Extraction line 17 Sludge extraction pump 18 Cyclone 19 as separator 19 Sludge 21, 42 Inlet channel 22 Opening 23, 31, 44 Precipitation promoting means 24 Wall forming inlet channel 25 Water flow 26 Flock Of flow 27 Vortex 43 Cylindrical wall forming inlet channel

Claims (11)

[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 precipitating flocs in raw water from the flocculation tank and separating them into treated water and flocs. Wherein the sedimentation accelerating means is provided in the sedimentation tank, the sedimentation promoting means extending up and down with respect to the opening of the inlet flow path of the raw water to the sedimentation tank. 2. The coagulating sedimentation apparatus according to claim 1, wherein the sedimentation promoting means is disposed in the sedimentation tank near a wall forming an inlet flow path of raw water to the sedimentation tank. 3. The coagulating sedimentation apparatus according to claim 1, wherein an inlet flow path of the raw water to the settling tank is configured such that the raw water flowing into the settling tank is substantially a downward flow. 4. The precipitation promoting means is formed in a cylindrical shape.
The coagulation sedimentation apparatus according to claim 1. 5. The coagulating sedimentation apparatus according to claim 1, wherein the precipitation accelerating means is formed in a U-shaped cross section. 6. The method according to claim 1, wherein the precipitation promoting means comprises a flat plate.
4. The coagulation sedimentation apparatus according to any one of claims 1 to 3. 7. The coagulation according to claim 1, wherein the lower end of the precipitation accelerating means is located 0.4 to 1 m below the opening of the raw water inlet passage to the precipitation tank. Precipitation equipment. 8. The coagulation / sedimentation apparatus according to claim 1, wherein a plurality of precipitation promotion means are provided in parallel. 9. The coagulation sedimentation apparatus according to claim 1, wherein the granular material is sand. 10. The coagulation / sedimentation apparatus according to claim 1, wherein the coagulant includes an inorganic coagulant and a polymer coagulant. 11. A settling tank is connected to a line for extracting settled flocs, and the extracting line is provided with means for separating the extracted flocs into sludge and particulate matter circulated to the flocculation tank. An apparatus according to any one of claims 1 to 10.