JP2002355506A - Flocculating and settling equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a flocculating and settling equipment in which a sludge separated by a separator is concentrated more efficiently when concentrated by using a concentrating means such as a floatation separation column so that the concentrated sludge sent from the concentrating means can be treated efficiently in a concentrated sludge storage tank and a dehydrator, and the capacity of sludge storage tank and the pomp for the dehydrator can be restrained from being large-sized. SOLUTION: This flocculating and settling equipment provided with a flocculating tank for flocculating the suspended matter in raw water as flocks by adding a granular material and a flocculant, a settling tank for settling the flocks in the water introduced from the flocculating tank and separating the flock-containing water into the treated water and slurry, the separator for separating the slurry withdrawn from the settling tank into sludge and the granular material and returning the separated granular material to the flocculating tank, is characterize in that a concentrating means for furthermore separating the sludge separated by the separator into the concentrated sludge and the treated water for circulation and returning the treated water for circulation to the raw water side in provided and a macromolecular flocculant adding means is additionally arranged between the separator and the concentrating means.

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 a suspended substance in raw water into sludge and treated water by coagulation sedimentation by adding a particulate matter and a coagulant, and in particular, sludge separated by coagulation sedimentation. The present invention relates to a coagulation-sedimentation apparatus capable of efficiently and further concentrating the water.

[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 and sedimentation apparatus, it takes a long time to settle the coagulates, and an extremely large sedimentation tank is required. Therefore, the coagulation and sedimentation is more efficiently performed. A device has been proposed.

For example, as a coagulating sedimentation apparatus for removing SS in raw water, a particulate matter (sand) having a particle size of about 10 to 200 μm and a polymer flocculant are added to raw water to remove SS in raw water.
A flocculation tank for forming flocs together with the floc, a sedimentation tank for separating the flocs flowing out of the floc formation tank (coagulation tank) from the treated water, and a separator for separating the sedimented flocs (slurry) drawn from the sedimentation tank into sand and sludge ( (Cyclone) is known.

[0004] In such a coagulating sedimentation apparatus, the sludge discharged from the upper outlet of the cyclone has a relatively low concentration, and it is difficult to smoothly perform the sludge concentration treatment in the subsequent process. In order to promote the reaction by the inorganic coagulant used for the treatment,
A structure in which a classification tower is installed in a sludge line from the upper exit of the cyclone has been proposed (Japanese Patent Laid-Open No. 2000-317).
No. 220).

[0005] For example, as shown in FIG.
The inorganic coagulant 103 is added to the raw water 102 introduced into the raw water 01 and stirred by the stirrer 104.
05 is added to the flocculation tank 106 and stirred by the stirrer 107 to form flocs 108 together with the particulate matter (sand) 115. The water to be treated is introduced into the settling tank 109 to settle and separate sludge. The treated water 111 is obtained from above through the inclined plate 110. The slurry is drawn from the lower part of the settling tank 109 by a sludge drawing pump 112,
3, is sent to a cyclone 114 as a separator to separate sludge and particulate matter, and the separated particulate matter 115 is returned to the flocculation tank 106. Separated sludge is sent from the upper outlet of the cyclone 114 to the classification tower 116, where the concentrated sludge 117 and the circulated water 11
8 and the circulated treated water 118 is returned to the raw water side. In the proposed apparatus, the sludge separated by the cyclone is further classified into concentrated sludge and circulating treated water returned to the raw water side, and the concentrated sludge is sent to a subsequent sludge concentration step.

Although the application has not yet been published, the present applicant has previously provided a flotation / separation tank which separates the concentrated sludge and circulating treated water by the flotation of air bubbles instead of the classification tower. Has also been proposed (Japanese Patent Application No. 2000-27902).
No. 0). In the proposed apparatus, when SS in raw water is a component that is unlikely to settle, such as biological sludge, it is possible to more efficiently concentrate sludge discharged from the cyclone.

[0007]

However, in the above-mentioned coagulating sedimentation apparatus, the sludge (slurry) containing the particulate matter (sand) drawn from the sedimentation tank is transferred by a sludge drawing pump, and the sludge and sand are separated by a cyclone. When separated into sludge, the sludge is vigorously stirred, resulting in destruction and miniaturized flocs.
The sludge concentration property in the classification tower and the flotation tank becomes poor, and the concentration of the concentrated sludge sent to the subsequent sludge storage tank becomes thin. As a result, it becomes necessary to increase the capacity of the sludge storage tank and the size of the pump for transferring the concentrated sludge to the dehydrator, and further increase the amount of the polymer flocculant added to the concentrated sludge in the sludge storage tank. Is left.

Accordingly, an object of the present invention is to pay attention to the above problems, and to concentrate the sludge separated by the separator with a concentration means such as a classification tower or a flotation tank more efficiently. Accordingly, it is an object of the present invention to provide an agglomerated sedimentation apparatus capable of easily and efficiently treating a concentrated sludge sent from a concentration means in a sludge storage tank and a dehydrator and suppressing an increase in the size thereof. .

[0009]

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 particulate matter and a coagulant; A sedimentation tank for sedimenting flocs in the introduced water from the tank and separating the treated water and slurry, a separator for separating the slurry extracted from the sedimentation tank into sludge and particulate matter, and returning the separated particulate matter to the flocculation tank; In the coagulating sedimentation apparatus provided with, a sludge separated by the separator is further separated into concentrated sludge and circulating treated water, and a concentrating means for returning the circulating treated water to the raw water side is provided. And a means for adding a polymer flocculant.

The concentrating means is, for example, a classifying means as shown in FIG. 3 for classifying into concentrated sludge and circulating treated water by gravity, or a floating separation for separating into concentrated sludge and circulating treated water by floating air bubbles. Consisting of means.

As the flocculant to be added by the polymer flocculant adding means, any of anionic, nonionic, cationic flocculants and the like can be used. In the case of nonionic properties, when a cationic polymer flocculant is used, it reacts more densely because of its ionicity, so that the concentration property is further improved.

[0012] Such a coagulating sedimentation apparatus according to the present invention comprises:
This is particularly effective when floc that is difficult to concentrate is generated, such as when the amount of the inorganic coagulant is larger than the SS content of the raw water or when alkali coagulation and precipitation of heavy metals is performed.

[0013] In the coagulating sedimentation apparatus according to the present invention as described above, the sludge separated by the separator is sent to the concentration means and further concentrated to be concentrated sludge. Since the polymer flocculant is added in between, the floc broken and miniaturized by the sludge drawing pump or the separator is reagglomerated by the polymer flocculant, and the floc grows large and densely, thereby improving the concentrating property. Therefore, the sludge separated by the concentration means after the addition of the polymer flocculant becomes a sufficiently thick concentrated sludge. As a result, the capacity of the sludge storage tank provided at the subsequent stage of the concentrating means and the increase in the size of the pump for transferring the concentrated sludge to the dehydrator are avoided, and the processing and transfer are easily performed efficiently without increasing the cost. It becomes possible. Also, since this concentrated sludge is sufficiently thick, even when a polymer flocculant is added before the dehydrator,
It is possible to reduce the amount added.

[0014]

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 according to a first embodiment of the present invention. In FIG. 1, the coagulation / sedimentation apparatus 1 includes a coagulation tank 2 and a sedimentation tank 3 disposed adjacent thereto. The raw water 5 is supplied to the pre-coagulation tank 7 via the raw water supply line 4, where the inorganic coagulant 6 is added. The pre-coagulation tank 7 has a motor 8
Is provided, and after being stirred by the stirrer 9, the polymer flocculant 10 is further injected when it is sent to the flocculation tank 2.

In the coagulation tank 2, sand 11 as a granular material is added. The flocculation tank 2 is provided with a stirrer 13 driven by a motor 12, and the suspended substance in the raw water is stirred by the stirrer 13 to form a floc containing the inorganic coagulant 6, the polymer coagulant 10, and the sand 11. Aggregated and grown.

In this flocculation, the inorganic flocculant 6 flocculates the suspended substance to form fine flocs, and the polymer flocculant 10 becomes entangled to grow into larger flocs, and the grown flocs have specific gravity. It contains sand 11 as a large granular material, and grows into a relatively large floc having a high specific gravity and easy to settle as a whole.

The water to be treated including the grown floc 14 is introduced into the sedimentation tank 3 through the overflow weir 15. In the settling tank 3, the flocs in the introduced water are settled downward, and the settled flocs are separated from the treated water 16 above. A plurality of inclined plates 17 are arranged in the upper part in the settling tank 3 so as to prevent the floc from flowing out together with the treated water 16.

The bottom of the settling tank 3 is connected to a drawing line 18 for drawing out settled flocs, and a sludge drawing pump 19 draws out sludge slurry containing settled flocs. The extracted slurry is sent to a cyclone 20 as a separator, and is separated into sludge 21 and sand 11 by centrifugation in the cyclone 20. The separated sand 11 is returned from the lower outlet 22 of the cyclone 20 to the flocculation tank 2 again, and is circulated and reused.

Separated by cyclone 20, cyclone 2
The sludge 21 before concentration discharged from the upper outlet 23 of
It is sent to the concentration means 25 via the lead-out line 24. In this embodiment, the concentration means 25 is configured as a classification tower (classification means) for classifying the introduced sludge into the concentrated sludge 26 and the circulating water 27 by gravity. Thickened sludge 2
Numeral 6 is sent to a sludge storage tank at a later stage and further to a dehydrator via a sludge feed line 28 (not shown). The circulated treated water 27 is returned to the raw water side via the return line 29, and in this embodiment, to the pre-coagulation tank 7.

A polymer coagulant adding means 30 is provided between the upper outlet 23 of the cyclone 20 and the classification tower 25, and the sludge before being introduced into the classification tower 25 is supplied to the outlet line 2.
At 4, the polymer coagulant 31 is injected into the line.

FIG. 3 shows a coagulation / sedimentation apparatus 41 according to a second embodiment of the present invention. In the present embodiment, the first
Compared to the embodiment, the concentration means is provided with a flotation separation tank 42 (flotation separation means) which separates the concentrated sludge and the circulating treated water by the floating of bubbles. Upper exit 2 of cyclone 20
A floatation / separation water supply line 44 is joined to a sludge discharge line 43 from the tank 3 to the flotation / separation tank 42. In the present embodiment, the flotation tank 42 has an inner cylinder 45 and an outer cylinder 41, and the tank wall 47 of the flotation tank 42 is located outside the outer cylinder 45. The flotation / separation water supply line 44 joined to the sludge discharge line 43 is connected so as to face the inner cylinder 45, and bubbles for flotation / separation float in the inner cylinder 45. A scum 48 separated by a floating separation process is provided above the inner cylinder 45 and inside the outer cylinder 46.
Is collected and sent as a concentrated sludge 49 to a later-stage sludge storage tank and further to a dehydrator (not shown).

From the bottom of the flotation tank 42, the sludge 50 settled at the bottom is pulled out. This sludge 50
The condensed sludge 49 from the upper part of the flotation tank 42 may be combined with the concentrated sludge 49 and subjected to the subsequent treatment, or may be treated separately. Further, from the upper part between the outer cylinder 46 and the tank wall 47, the floatation / separation treatment water 51 as circulation treatment water separated from the sludge is returned to the preliminary flocculation tank 7 via the floatation / separation treatment water return line 52, It is intended to be recycled to the coagulation sedimentation system.

Air 53 for generating air bubbles for flotation is injected into the water supply line 44 for flotation, and is injected as pressurized air in this embodiment.
In addition, a pressurized pump 5
4 and a pressurized tank 55 are provided. After the injected air is pressurized to a predetermined pressurized state, when it is supplied into the inner cylinder 45, it is rapidly released to a reduced pressure state (atmospheric pressure state). Bubbles can be generated.

The water supplied to the flotation water supply line 44 can be collected from another system.
It is efficient to use a part of the treated water 16 by branching off from the line of treated water 16 from.

A polymer flocculant adding means 56 is provided between the upper outlet 23 of the cyclone 20 and the flotation tank 42, and the sludge in the sludge discharge line 43 is added before the flotation water supply line 44 joins the sludge. At the position, the polymer flocculant 57 is injected in a line.

The other structure is substantially the same as that of the first embodiment shown in FIG. 1, and the description thereof will be omitted by retaining the same reference numerals as in FIG.

In the coagulating sedimentation apparatuses 1 and 41 according to the first and second embodiments configured as described above, the sludge is removed before being introduced from the cyclone 20 into the classification tower 25 or the flotation tank 42. Since the polymer flocculants 31 and 57 are added, the floc is broken down by the sludge extraction pump 19 and the cyclone 20 and reagglomerated by the polymer flocculant to which the fine floc has been added, and the floc has grown greatly and densely. At the classification tower 25 and the flotation tank 42. Therefore, the sludge concentration in the classification tower 25 and the flotation tank 42 is greatly improved, and the concentration of the concentrated sludge discharged therefrom is greatly increased.

As a result, the capacity of the sludge storage tank provided at the subsequent stage can be small, and the pump for transferring to the dehydrator does not need to be large. In addition, when the polymer flocculant is added in the subsequent treatment, for example, when the polymer flocculant is added immediately before the dehydrator, the amount of the polymer flocculant added may be small.

[0029]

EXAMPLE Using a tester having the same configuration as that shown in FIG. 1, an artificial turbid water in which kaolin was added as a suspending substance to raw water, and PAC (polyaluminum chloride) as an inorganic coagulant were used.
, And sand and a polymer flocculant were poured into the flocculation tank, and the experiment was performed under the following conditions. The concentration of the concentrated sludge extracted from the concentration means was adjusted, and the concentration at which the concentration of the concentrated sludge was maximized was measured. [Experimental equipment] Pre-coagulation tank capacity: 200 liter Coagulation tank capacity: 500 liter Precipitation tank: 500 mm □ × 3000 mmH (with inclined plate) Concentration tank (concentration means): 300 mmΦ × 2500 mmH [Operating conditions] Raw water flow rate: 10 m ³ / h Sludge withdrawal amount: 0.45 m ³ / h Flow rate from the cyclone upper outlet: 0.32 m ³ / h Kaolin addition amount: 20 mg / l The experimental results are shown in Table 1.

[0030]

[Table 1]

As shown in Table 1, in Examples 1 and 2,
Concentrated sludge concentration was higher than Comparative Examples 1 and 2,
The effect was greater when the amount of PAC added to S was larger. In Example 3, the amount of the polymer flocculant used was almost the same as that of Comparative Example 3, but the concentration of the concentrated sludge was high. In Example 4, the concentrated sludge concentration was higher than when the polymer flocculant added to the cyclone upper outlet side was an anionic polymer flocculant (Example 2).

The inorganic coagulant and polymer coagulant used in the present invention are not particularly limited,
Examples of the inorganic coagulant include polyaluminum chloride (PAC), ferric chloride, and ferric sulfate. Examples of the polymer coagulant include nonionic, anionic,
A cationic or nonionic and anionic, and a nonionic and cationic amphoteric polymer flocculant can be used. Representative examples of these polymer flocculants include polyacrylamide-based anionic or cationic polymer flocculants. 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.

[0033]

As described above, according to the coagulation / sedimentation apparatus of the present invention, a polymer flocculant is added before the sludge separated by the separator is concentrated by a concentration means such as a classification means or a flotation separation means. As a result, the concentrated sludge can be concentrated by the concentration means to a higher concentration sludge, so that the treatment in the subsequent stage can be facilitated, the capacity of the sludge storage tank can be reduced, and the transfer pump to the dehydrator etc. Can be reduced in size.

Further, since the concentration of the concentrated sludge is high, for example, when the polymer flocculant is added immediately before the dehydrator, the amount of the polymer flocculant can be reduced.

[Brief description of the drawings]

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

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

FIG. 3 shows a coagulation / sedimentation apparatus previously proposed by the present applicant (JP-A-2
000-317220).

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coagulation sedimentation apparatus 2 Coagulation tank 3 Precipitation tank 4 Raw water supply line 5 Raw water 6 Inorganic coagulant 7 Pre-coagulation tank 8 Motor 9 Stirrer 10 Polymer coagulant 11 Granular sand 12 Motor 13 Stirrer 14 Coagulation floc 15 Overflow 16 Treatment water 17 Inclined plate 18 Extraction line 19 Sludge extraction pump 20 Cyclone 21 as separator 21 Sludge before concentration 22 Lower exit of cyclone 23 Upper exit of cyclone 24 Sludge outlet line 25 Classification tower as concentration means 26 Concentrated sludge 27 Circulating treatment water 28 Sludge feed line 29 Return line 30 Polymer flocculant adding means 31 Polymer flocculant 41 Coagulant sedimentation device 42 Floating / separation tank as concentration means 43 Sludge lead-out line 44 Floating / separating water supply line 45 Inner cylinder 46 Outer cylinder 47 Tank wall 48 Scum 49 Condensed sludge 50 Settling sludge 51 Flotation treatment water 52 Flotation treatment water return line 53 Injected air 54 Pressurized pump 55 Pressurized tank 56 Polymer coagulant adding means 57 Polymer coagulant

Claims (3)

[Claims] 1. A flocculation tank for flocculating a suspended substance in raw water as a floc by adding a particulate matter and a flocculant, and a sedimentation tank for sedimenting floc in water introduced from the flocculation tank and separating it into treated water and slurry. In the coagulation sedimentation apparatus equipped with a separator that separates the slurry extracted from the sedimentation tank into sludge and particulate matter and returns the separated particulate matter to the coagulation tank, the sludge separated by the separator is further subjected to concentrated sludge and circulation treatment. Separated into water and
Concentration means to return the circulated treated water to the raw water side is provided,
A coagulation / sedimentation apparatus comprising a polymer coagulant adding means provided between the concentration means and the separator. 2. The coagulation sedimentation apparatus according to claim 1, wherein said concentration means comprises a classification means for classifying into concentrated sludge and circulating treated water by gravity. 3. The flotation means comprises flotation separation means for separating concentrated sludge and circulating treated water by flotation of bubbles.
The coagulation sedimentation device according to claim 1.