JP2008086980A - Raw water treatment method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce a residual turbidity of treated water by reducing the consumption of a flocculant even in the case where the turbidity of raw water is low while reducing the dissolving amount of the flocculant. <P>SOLUTION: A flocculation accelerating member is provided in a mixing basin, and the flocculant and raw water are supplied to the mixing basin to treat raw water. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for treating raw water in a water purification plant, an industrial water treatment plant or the like.

  In the early stages of water treatment technology, the raw water hardness and turbidity are high in Europe and the United States, and the concentration tends to be interference sedimentation. It was. This technology was introduced by Japan, but the raw water was low in both turbidity and hardness, so that it was extremely difficult to maintain and form aggregated flocs.

  Japan's river water quality is mostly low turbidity, low water temperature, low alkali raw water, and it is difficult to form agglomeration flocs and operation maintenance is difficult, and agglomeration failure is likely to occur, but the agglomeration technology has not been improved. The treatment with a single-sink inclined plate type cross-flow sedimentation basin, which is easy to maintain, is adopted exclusively.

  As described above, the water source in Japan is difficult to agglomerate because of its low turbidity, low water temperature, and low alkali throughout the year. As a result, it has conventionally caused excessive injection of a flocculant and an alkali agent. Residual substances derived from coagulants such as Alzheimer's disease due to residual ions, residual turbidity and increased filtration loss water head, increased washing frequency, and re-elution of residual ions in water purification ponds are contained in tap water. As a result of increasing the redox value, various problems that make it difficult to produce delicious water have not been solved. (Non-Patent Documents 1 and 2). This is because the flocculant is added to the raw water and floc formation is performed, but due to poor aggregation, the residual material remains until the end.

Non-Patent Document 1 “Water Supply Association Magazine” November 2004, Vol. 73, No. 11 (No. 842), pages 2 to 10)
Non-Patent Document 2 The 55th National Waterworks Research Presentation (issued on May 10, 2004) pp. 322-323

  Therefore, the present inventor has conducted various studies to eliminate these conventional drawbacks, and even when the turbidity of the raw water is low, the amount of the flocculant used is reduced, and the amount of the flocculant (especially aluminum) in the purified water is reduced. It came to complete the raw water processing method which can measure concentration.

  According to the method of the present invention, the amount of coagulant used is reduced, the head of filtration loss is reduced (filter closure), the mold odor is prevented due to poor aggregation when a large amount of algae are generated, and the concentration of the coagulant (especially aluminum) in clean water is low. Various effects are obtained such as slagging, increasing sludge concentration, reducing the total amount of dewatering treatment, and reducing the amount of generated soil.

The present invention is a raw water treatment method characterized in that a coagulation promoter is provided in a mixing pond, and the coagulant and raw water are supplied to the mixing pond for treatment.
Next, the present invention will be described with reference to the drawings, but the present invention is not limited to the following description.

FIG. 1 is an example of a treatment apparatus schematically showing the raw water treatment method of the present invention.
1 is a mixing pond, 2 is an agglomeration accelerator, 3 is a floc formation pond, 4 is a sedimentation basin, 5 is a flash mixer, 6 is a paddle type stirring device, and 7 is a water flow inclined plate.
The flash mixer 5 in the mixing basin 1 rotates rapidly to stir the raw water and the flocculant. The paddle type stirring device 6 in the flock formation pond 3 is driven to perform slow stirring.
In the mixing basin 1, the shaft of the aggregation promoting body is pivotally supported by the stay 8 at the upper part thereof, and is supported so as to be fixed and freely rotatable. When a stopper (not shown) provided at the support portion of the stay 8 is tightened, the stopper is fixed and loosened, so that the agglomeration promoting body 2 rotates manually, electrically, or by a water flow. The aggregation promoter 2 in FIG. 1 is a flow resistor in the mixing basin 1 and is a plate-type wing formed of a flat plate or a non-linear (spiral) twist of a flat plate. The body shown in FIG. 2 is provided with a resistor 9 at the edge of the plate body, the blade is corrugated as shown in FIG. 3, the brush body is shown in FIG. 4, and the body is shown in FIG. Such a non-linearly twisted plate portion, a round blade shape shown in FIG. 6, a limbon blade shape shown in FIG. 7, a double round blade shape shown in FIG. 8, a face blade shape shown in FIG. 10 and the paddle blade shape shown in FIG. 11 can be used.
FIG. 12 shows a case where the mixing basin 1 and the floc-forming pond 3 are formed as an up-down diverted water channel 10, and the mixing pond 1 and the flock-forming pond 3 are equipped with the aggregation accelerator 2, and the flash mixer 5 and the paddle in FIG. This is an example of a raw water treatment device that is not equipped with a rotational drive, such as the type stirring device 6, and rapidly and slowly stirs the raw water and the flocculant by the flow of water.

  As a material constituting the aggregation promoter 2, any of a rigid material made of metals, hard synthetic resin, or the like, or a flexible material made of rubber, soft synthetic resin, or the like can be used.

  The agglomeration promoter 2 may be coated or contained with tourmaline such as drabite or tourmaline. By applying or containing tourmaline such as drabite and tourmaline, water molecules can be finely divided (clustered) by electromagnetic waves. This increases the hydrogen ion concentration, lowers the oxidation-reduction potential of the raw water, increases the affinity of substances such as flocculants and turbidity, enhances miscibility, and achieves good aggregation.

  One or two or more of these aggregation promoters 2 can be installed in the mixing basin 1, and the installation method may be provided in a plurality of rows in parallel. These agglomeration promoters 2 may be fixed or forcibly rotated by appropriate driving means such as manual operation or electric drive. Furthermore, depending on the structure of the agglomeration promoter 2, rotation may be caused by the flow of water. It can also be made.

By moving the agglomeration promoting body 2, it is possible to easily wash the particles deposited and deposited without stopping the operation of the mixing basin 1.
Furthermore, in order to assist the stirring of the mixing basin 1, the aggregation promoter 2 can be forcibly rotated.

  Further, as other embodiments of the aggregation promoter, there are plate-like bodies such as a net-like flat plate and a slid-like flat plate, which are arranged in a row or so as to move (slide) in the lateral direction and the oblique direction in the mixing pond. Multiple rows may be installed. Further, an agglomeration promoter having a structure that shakes or vibrates can be suitably used.

Next, the processing method of the present invention will be described with reference to FIG.
In order to promote aggregation and to form favorable flocs, the elements in which particles are present are indispensable for aggregation. By supplying the flocculant and the raw water to the mixing basin 1 provided with the aggregation accelerator 2, the flocs that have formed are stagnating in the vicinity of the aggregation accelerator 2 while interfering with sedimentation, even if the raw water turbidity is low. It shows the same effect as turbidity in water. The remaining flocs of particle mutual interference due to the attractor (retraction) region stagnate before and after the aggregation accelerator 2, so that floc formation and flocculation with turbidity are fast, resulting in good flocs.

  This is because the aggregation promoter 2 that enhances the stirring effect of the mixing basin 1 produces different flows in the aggregation promoter 2 installed in the mixing pond 1 near the central part of the stirrer of the flash mixer 5 and the wall surface. It was found that the environment where some turbidity exists in the vicinity of the aggregation promoter 2 in the mixing basin 1 can be formed even if the concentration is different, the seed floc drifts in the vicinity of the aggregation promoter 2 and the raw water turbidity is low. .

  The aggregation promoter 2 is a flow resistor in the mixing basin 1 and, unlike the flow in the central portion of the mixing basin 1, various flows are generated in the vicinity of the resistor in a chaotic manner. Diverse flows collect the turbidity of raw water and formed flocs, and contact and adhere to each other, resulting in good flocs. This good floc becomes a seed floc and floats in the raw water, promoting the removal of Cryptosporidium and diatoms.

  The aggregation promoter 2 can also create a turbulent flow region by providing it in a water channel in flowing water, the mixing pond 1, the flock formation pond 3, etc., and can increase the concentration by interfering with the flock. By providing the aggregation promoter 2 in this way, the particles that have been contact-settled by conventional one-pass have the effect of recontacting and adhering with the aggregation promoter 2.

  Conventionally, only the stirrer was operated with only the strength of the speed, but according to the method of the present invention, the aggregation and contact of the agglomerated particles are in the flow stirring field, so that the particles are stagnated due to particle adhesion or attractor. As a result, a good flocculation floc can be formed, and the clarification and separation effect which is the initial purpose can be obtained.

By installing the aggregation promoter 2 in the mixing basin 1, the flock formation pond 3, the sedimentation basin 4, the up-and-down diverted water channel 10, the meandering diverted water channel, and the flowing water channel, the agglomerated flocs gather at the interference sedimentation concentration. In this case, the entire amount does not flow down, but a part of the stagnation stays behind the agglomeration promoting body 2 and remains as active floc in the mixing basin 1 or the floc formation basin 3, the sedimentation basin 4, the flow path, etc. .
This is a proof that cohesion is easy if there is turbidity in the raw water.

The reason why the particles are concerned is that the treated water in the sedimentation basin 4 before filtration has a turbidity of 1 mg / l or less, and a chemical injection of 2 mg / l to 3 mg / l is performed on the water. Although it is so fine as to say, Cryptosporidium, diatoms, etc. are removed by filtration with anthracite, silica sand, or gravel on the filter bed, because the flocculant has adhered to the particle surface of the filter bed. It is.
Thus, the flocculant adheres to the surface of the solid particles and generates floc.

Examples of the flocculant used in the present invention include aluminum flocculants such as a sulfate band, iron flocculants such as ferric sulfate and iron chloride, polymer type flocculants such as polyaluminum chloride (hereinafter referred to as PAC), and polysilica iron. In addition to inorganic flocculants such as polyiron sulfate, CMC (carboxymethylcellulose sodium / carboxylmethylcellulose calcium), which is widely used in the fields of foods, pharmaceuticals and cosmetics, is often highly viscous and highly etherified. However, by adding CMC having a low viscosity and a low degree of etherification, cross-linking agglomeration occurs, and a cross-linking aggregating agent that increases the precipitation rate due to the increase in flocs is used. A plurality of these flocculants may be used in combination.
For example, when PAC is used as the concentration of these flocculants, those containing 10% to 11% as aluminum oxide (Al ₃ O ₂ ) can be used. The mixing ratio of these flocculant solution and raw water depends on the turbidity of the raw water, but generally it is preferable to mix the flocculant solution with the raw water at a ratio of 10 mg / l to 100 mg / l.

As another embodiment of the method of the present invention, an aqueous solution (hereinafter referred to as a slurry) containing fine particles that have settled and flocked in a sedimentation basin is used, and a mixture of the slurry and a flocculant and raw water are supplied for treatment. Can also be adopted.
As described above, a small amount of slurry and a coagulant are directly mixed to produce a simulated active aggregate (hereinafter referred to as preflock), and this preflock and raw water are supplied and processed. The slurry has a small amount of moisture mother and a high particle density. Compared to the mixing ratio of the flocculant and raw water, the slurry has a high concentration of flocculant while the particle density is high by directly mixing the flocculant with the flocculant. It exists, and physical and electrochemical simulated agglomeration occurs instantaneously to generate pre-floc.
The use ratio of the slurry and raw water is preferably 2 mg / l to 500 mg / l of fine particles contained in the slurry with respect to the raw water. The concentration of fine particles in the slurry is usually in the range of 0.03% to 10% by weight, particularly 0.1% to 5% by weight. The use ratio of the flocculant and the raw water is generally preferably 10 mg / l to 100 mg / l of the flocculant solution with respect to the raw water.
In the present invention, a method of adding water to a mixture of powder or granule particles and a powder or granule flocculant and supplying the mixture to raw water can also be employed. Examples of powder or granule particles include zeolite, bentonite, kaolin, calcined drabite, calcium carbonate, slaked lime, lime, powdered titanium oxide, powdered shell, sand, and sun-dried sludge. This particle may be used alone.

  As another embodiment of the method of the present invention, a method of supplying a raw water and treating it with a mixture of warm water and a flocculant can also be employed. In cold regions, the lower the raw water temperature, the more difficult it is to form agglomeration flocs, which makes it difficult to maintain and manage, making it difficult for agglomeration to occur. (Hereinafter referred to as simulated flock), and this simulated flock and raw water are supplied and processed. The temperature of the hot water used is preferably in the range of 14 ° C to 50 ° C.

Test example To confirm the effect, a jar tester was used, and the raw water was added with a flocculant, and a small amount of slurry was mixed and stirred directly with the flocculant, and then added to the raw water. Stirring, the turbidity after 2 minutes and 10 minutes of standing, and the aluminum concentration after 10 minutes of standing are measured.
Furthermore, the treated water after 10 minutes of standing is filtered, and turbidity and aluminum concentration are measured.
Rapid stirring is a test method that reproduces the mixing pond at 120 rpm for 2 minutes, slow stirring is a test method that reproduces the floc-forming pond at 60 rpm for 10 minutes, a test method that reproduces the inside of the sedimentation basin after 2 minutes of standing, The treated water after 10 minutes is a test method that reproduces the settling basin treated water. Filtration was a natural equilibrium type and adopted a two-layer filtration system of anthracite and sand to obtain filtered water.
The beaker is tested with and without the aggregation promoter having the shape shown in FIG. Samples with a coagulation promoter attached to a beaker were sampled after 2 minutes and 10 minutes of standing, and the supernatant of the beaker and the back of the coagulation promoter were siphoned. The supernatant water in the center of the beaker was sampled with a siphon after 2 minutes and 10 minutes after placing.
Aggregation promoters were 60 cm ² and three were attached.
Test 1
Prepare 3 l of raw water (turbidity 5 mg / l) in a beaker equipped with a coagulation accelerator, add 20 mg / l of PAC, perform rapid stirring, and then perform slow stirring. After slow stirring, sample the water supply after 2 minutes of standing and measure the turbidity. Further, 10 minutes after standing, sampling is performed in the same manner to measure turbidity and aluminum concentration. The supernatant water in the center of the beaker after standing for 10 minutes is filtered to measure turbidity and aluminum concentration.
Test 2
Prepare 3 l of raw water (turbidity 10 mg / l) in a beaker equipped with the same aggregation promoter as used in Test 1, mix and stir 20 mg / l of slurry with PAC 20 mg / l, add to the stock solution, perform rapid stirring, Subsequently, slow stirring is performed. After slow stirring, sample the water supply after 2 minutes of standing and measure the turbidity. Further, 10 minutes after standing, sampling is performed in the same manner to measure turbidity and aluminum concentration. The supernatant water in the center of the beaker after 10 minutes of standing is filtered to measure turbidity and aluminum concentration.
Test 3 (Comparative example of Test 1)
Prepare 3 l of raw water (turbidity 5 mg / l) in a beaker without a coagulation promoter, add 20 mg / l of PAC, stir rapidly, and then slowly stir. After slow stirring, sample the water supply after 2 minutes of standing and measure the turbidity. Further, 10 minutes after standing, sampling is performed in the same manner to measure turbidity and aluminum concentration. The supernatant water in the center of the beaker after 10 minutes of standing is filtered to measure turbidity and aluminum concentration.
Next, the measurement results of the turbidity of treatment water and the aluminum concentration (hereinafter referred to as Al concentration) are as follows.

試験の結果では、試験１と試験３を比べると凝集促進体を装着した方が、処理水の清澄化に優れ濁度およびアルミニウム濃度が低く、凝集促進体の背面部に凝集フロック粒子が停滞し濁度及びアルミニウム濃度が高い。
凝集促進体を設置することで、原水濁度が低くても、凝集促進体近くに濁質や凝集フロック粒子が干渉沈降しながら停滞し接触付着し、凝集フロック粒子を肥大化し、均一化させ、良好なフロックを作り、沈澱池において沈降を促進し、清澄化に優れている。

As a result of the test, comparing the test 1 and the test 3, when the coagulation accelerator is attached, the clarification of the treated water is excellent and the turbidity and the aluminum concentration are low, and the aggregated floc particles are stagnated on the back surface of the coagulation promoter. High turbidity and aluminum concentration.
By installing an agglomeration promoter, even if the raw water turbidity is low, turbidity and agglomerated floc particles are stuck and contacted while interfering with sedimentation near the agglomeration promoter, and the aggregated floc particles are enlarged and homogenized. Creates good flocs, promotes sedimentation in the sedimentation basin and excels in clarification.

The longitudinal cross-sectional view which showed an example of the processing apparatus for performing the processing method of this invention Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter Side view of aggregation promoter The longitudinal cross-sectional view which showed an example of the processing apparatus for performing the processing method of this invention

Explanation of symbols

1 Mixing Pond 2 Aggregation Promoter 3 Flock Formation Pond 4 Sedimentation Pond

Claims (3)

  A raw water treatment method comprising: providing a coagulation promoter in a mixing pond and supplying the coagulant and raw water to the mixing pond.   The processing method according to claim 1, wherein a flocculant mixed with the slurry is used.   The processing method according to claim 1, wherein the aggregation promoter is fixed or rotatable.

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