JP5874360B2 - Method and apparatus for flocculation treatment of silt-containing water - Google Patents

Description

  The present invention relates to a method and apparatus for aggregating silt-containing water such as river water, and in particular, aggregating silt-containing water using an inorganic flocculant, a cationic polymer flocculant, and an anionic polymer flocculant. Then, the present invention relates to a method and apparatus for solid-liquid separation.

  Aggregation and solid-liquid separation of suspended water (SS) -containing water such as river water, lake water, sewage, industrial effluent, etc. is generally necessary to remove SS contained in SS-containing water. After adding a suitable inorganic flocculant, a pH adjuster is added to adjust the pH to a suitable level for the flocculant treatment to form a flock, and solids are separated by sedimentation separation, flotation separation, filtration separation, etc. to remove solids It is done by doing. In this agglomeration treatment, a polymer flocculant is used in combination with an inorganic flocculant in order to increase the solid-liquid separation property by coarsening the formed floc, and Patent Document 1 discloses agglomeration of various suspensions. In the treatment, a method has been proposed in which the polymer flocculant is added in two stages before and after, an anionic polymer flocculant is added in the former stage, and a cationic polymer flocculant is added in the latter stage.

In addition, when a precipitation tank is used as the solid-liquid separation means of the flocculated water, the supernatant water separated in the precipitation tank may be further processed with a filter.
In addition, the solid-liquid separated water may be further desalted by a reverse osmosis (RO) membrane separation apparatus depending on the application.

JP 2008-114142 A

  According to the study by the present inventors, the floc formed is formed in the aggregation treatment in which the anionic polymer flocculant is added first and then the cationic polymer flocculant is added when the high-concentration silt-containing water is subjected to the aggregation treatment. It has been found that the flocs are brittle and easily collapse due to excessive coarsening. In other words, silt is a fine soil particle, and it is difficult to float and settle in water. Water containing such silt at a high concentration can be satisfactorily agglomerated even if the usual SS agglomeration method is applied. Can't get frock.

  When the floc collapses and a fine floc occurs, the turbidity of the supernatant water of the sedimentation tank increases due to the fine floc, the quality of the treated water deteriorates, and the subsequent filter is easily clogged. The frequency of backwashing of the filter increases. Furthermore, when the RO membrane separation device is provided in the subsequent stage, this RO membrane separation device is also easily clogged and there is a problem that the differential pressure increases.

  Also, if the flocs become too coarse, the porosity in the flocs and between the flocs will increase, and the sludge interface of the settling tank will rise, so in order to maintain this sludge interface in an appropriate position, the amount of sludge extraction should be reduced. There is a need to do more.

  The present invention solves the above-mentioned conventional problems, improves the solid-liquid separability by forming flocs with high density and high sedimentation in the coagulation treatment of high-concentration silt-containing water, thereby improving the treatment water with high water quality. It is an object of the present invention to provide a flocculation treatment method and apparatus for silt-containing water.

  As a result of intensive studies to solve the above-mentioned problems, the present inventors have described in Patent Document 1 as a procedure for adding a polymer flocculant used in combination with an inorganic flocculant in the flocculation treatment of high-concentration silt-containing water. Contrary to the method described above, when the cationic polymer flocculant is added first and then the anionic polymer flocculant is added, the SS is firmly bonded by the action of the inorganic flocculant and the cationic polymer flocculant. Although the floc diameter is small, a floc that is dense and sufficiently tightened is formed, and then by adding an anionic polymer flocculant, the floc remains in a high-density state, and further It has been found that flocs are formed which become coarse, are not easily broken, and have excellent sedimentation properties.

  The present invention has been achieved on the basis of such findings, and the gist thereof is as follows.

[1] In the method for treating silt-containing water having a coagulation step of adding an aggregating agent to the silt-containing water and coagulating, and then a solid-liquid separation step of performing solid-liquid separation, the coagulation step includes the silt-containing water. in the step of adding an inorganic flocculant and a cationic polymer flocculant, followed by adding an anionic polymer flocculant, was closed, the inorganic coagulant to the first reaction vessel or the first reaction vessel It is added to the silt-containing water to be introduced, the cationic polymer flocculant is added to the first reaction tank, and the effluent water of the first reaction tank is separated from the first reaction tank. And aggregating treatment of silt-containing water, wherein the anionic polymer flocculant is added to the second reaction tank or the second reaction tank inflow water, wherein the residence time of the first reaction tank and the second silt containing the residence time of the reaction vessel and wherein 10~30min der Rukoto Water coagulation method.

[2] Oite to [1], wherein the inorganic coagulant is Fe-based flocculant, flocculation treatment method silt-containing water, characterized in that 5 to 6 the pH of the aggregation step.

[3] [1] or Oite in [2], in the turbidity of the silt-containing water above 100 NTU, aggregation treatment method silt-containing water, wherein the SS concentration is 200 mg / L or more.

[ 4 ] A first reaction vessel into which silt-containing water is introduced, a silt-containing water introduced into the first reaction vessel, or an inorganic flocculant addition means for adding an inorganic flocculant to the first reaction vessel; Cationic polymer flocculant addition means for adding a cationic polymer flocculant to one reaction tank, a second reaction tank into which effluent water from the first reaction tank is introduced, and an inflow to the second reaction tank possess a solid-liquid separation means for solid-liquid separation effluent anionic polymer coagulant adding means and the second reaction vessel to add the anionic polymer flocculant in water or second reaction vessel, said 1 reactor and the residence time in the second reaction vessel coagulation treatment apparatus 10~30min der Ru silt-containing water.

[ 5 ] In [ 4 ], a silt-containing water coagulation treatment apparatus is provided, wherein pH adjusting means for adjusting the pH of the first reaction tank and the second reaction tank to 5 to 6 is provided.

According to the present invention, in the flocculation treatment of the high-concentration silt-containing water, since it is possible to form a coarse floc that is high in density, excellent in sedimentation properties, and is not easily broken, Treated water can be obtained.
Further, in the case of solid-liquid separation in a sedimentation tank, it is possible to suppress an increase in supernatant turbidity and an increase in the sludge interface in the tank, and to reduce the amount of sludge extraction for maintaining the sludge interface, The frequency of backwashing of the filter provided in the latter stage can be reduced, and high quality filtered water can be obtained. Further, even when the RO membrane separation device is provided in the subsequent stage, an increase in the differential pressure of the RO membrane separation device can be suppressed.
Even when a membrane separation device or a filter is provided as the solid-liquid separation means, the increase in the differential pressure can be prevented and the frequency of backwashing can be reduced.
In addition, when a floating separation tank is used as the solid-liquid separation means, it is possible to prevent the scum from being damaged, and clear treated water can be obtained.

  In the present invention, the aggregation treatment is preferably performed in the range of pH 5 to 6 in order to obtain high-quality treated water from which SS has been sufficiently removed. Since the aggregation treatment is performed under such pH conditions, the inorganic flocculant is used. It is preferable to use an Fe-based flocculant.

It is a systematic diagram which shows an example of embodiment of the aggregation processing method and apparatus of the silt containing water of this invention.

  Hereinafter, embodiments of a method and apparatus for aggregating silt-containing water according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 is a system diagram showing an example of an embodiment of the silt-containing water coagulation treatment method and apparatus of the present invention. In FIG. 1, raw water (silt-containing water) is introduced into the first reaction tank 1, An inorganic flocculant, a cationic polymer flocculant (hereinafter referred to as “cationic polymer”) and, if necessary, a pH adjuster are added and subjected to an agglomeration treatment, and then introduced into the second reaction tank 2 to be anionic. A polymer flocculant (hereinafter referred to as “anionic polymer”) and, if necessary, a pH adjuster are added for aggregation treatment. The outflow water of the second reaction tank 2 is solid-liquid separated in the precipitation tank 3, and the supernatant water (separated water) is taken out as treated water.

  The silt-containing water to be agglomerated in the present invention is water containing clayey substances (silt) that are fine soil particles having a particle size of about 0.002 to 0.02 mm, such as surface water of rivers and lakes. The present invention is a high-concentration silt having a turbidity of 100 NTU or more, such as 100 to 10000 NTU, and an SS concentration of 100 mg / L or more, such as about 100 to 3000 mg / L. Effective for contained water.

  The pH condition in the flocculation treatment of such silt-containing water is preferably in the range of pH 5-6, and high quality treated water can be obtained by flocculation treatment within this pH range. Therefore, in FIG. 1, an acid or alkaline pH adjuster is added to the first reaction tank 1 and the second reaction tank 2 as necessary so that the pH of the liquid in the tank is 5-6. Is preferred.

  In addition, since the pH during the flocculation treatment is preferably set to 5 to 6 as described above, an Fe-based inorganic flocculating agent having a high flocculating effect in the range of pH 5 to 6 is used as the inorganic flocculating agent to be added to the raw water. For example, one or more of ferric chloride, iron polysulfate and the like can be used. Fe-based flocculants have a relatively heavy specific gravity and are effective in improving the sedimentation of flocs formed.

  The amount of the inorganic flocculant added to the raw water varies depending on the quality of the raw water and the type of the inorganic flocculant used, but in the normal case, it is preferably about 40 to 500 mg / L.

  The cationic polymer to be added to the first reaction tank is not particularly limited. For example, polydiallyl quaternary ammonium salt, poly (meth) acrylic acid amino ester, poly (meth) acrylic acid amino ester copolymer, polyethyleneimine, Polyamide polyamines, dihaloalkane polyalkylene polyamine polycondensates, polyacrylamide Mannich modified products, polyacrylamide Hofmann degradation products, poly (meth) acrylate polyalkylene polyamines, cationized starch, chitosan, etc. Two or more kinds can be used.

  If the amount of the cationic polymer added is too small, a sufficiently dense floc cannot be formed, and if it is too much, it may leak and clog the filter or the RO membrane. It is preferable to do.

  In order to form a sufficiently dense floc in the first reaction tank 1, it is preferable to perform the treatment so that the residence time of the first reaction tank 1 is 10 to 30 minutes.

  The anionic polymer to be added to the second reaction tank 2 is not particularly limited. For example, a partial hydrolyzate of polyacrylamide, a copolymer of polyacrylamide and sodium acrylate, a copolymer of acrylamide and sodium vinyl sulfonate And terpolymers of acrylamide, sodium acrylate, and sodium 2-acrylamido-2-methylpropanesulfonate, and one or more of these can be used.

  If the amount of the anionic polymer added is too small, the floc cannot be sufficiently coarsened, and if it is too large, it will leak like the cationic polymer and may clog the filter or the RO membrane. It is preferable to set the degree.

  In addition, in the 2nd reaction tank 2, in order to fully coarsen a floc, it is preferable to process so that the residence time of the 2nd reaction tank 2 may be 10-30 min.

  The precipitation tank 3 for solid-liquid separation of the agglomerated treated water in the second reaction tank 2 is preferably operated under conditions of about LV1 to 5 m / hr.

  FIG. 1 shows an example of an embodiment of the present invention, and the present invention is not limited to the form of FIG. 1 as long as the gist thereof is not exceeded.

For example, the inorganic flocculant may be added to the first reaction tank 1 or the raw water introduction pipe to the first reaction tank 1, and added to both the introduction pipe and the first reaction tank 1. May be.
In addition to the addition of the anionic polymer to the second reaction tank 2, the effluent water of the first reaction tank 1 may be added to the pipe introduced into the second reaction tank 2. You may add to both the tanks 2.

  The solid-liquid separation means is not limited to a precipitation tank, and may be a filter, an ultrafiltration membrane separation apparatus, a microfiltration membrane separation apparatus, or a floating separation tank. A membrane separation device may be provided. Furthermore, you may process solid-liquid separation water with a RO membrane separator.

  Hereinafter, the present invention will be described more specifically with reference to examples, comparative examples, and experimental examples.

[Example 1]
A silt-containing water having a turbidity of 100 NTU and an SS concentration of 200 mg / L was agglomerated and solid-liquid separated by the apparatus shown in FIG.
As the inorganic flocculant, ferric chloride (FeCl ₃ ) was used and added at 100 mg / L. In addition, 5 mg / L of “Zeta Ace (registered trademark)” manufactured by Kurita Kogyo Co., Ltd. is added as a cationic polymer, and 5 mg / L of “Cliff Rock (registered trademark)” manufactured by Kurita Kogyo Co., Ltd. is added as an anionic polymer. did. The residence time of the first reaction tank 1 is 10 min, the residence time of the second reaction tank 2 is 10 min, the water flow LV of the precipitation tank 3 is 4 m / hr, and the pH of the first reaction tank 1 is 5.5. A pH adjuster was added. The 2nd reaction tank 2 was maintaining pH5.5, without adding a pH adjuster.

  The turbidity of treated water (precipitation tank supernatant) obtained by this treatment was examined, and the results are shown in Table 1.

[Comparative Example 1]
In Example 1, the treatment was performed in the same manner except that the cationic polymer was not added to the first reaction tank 1, the turbidity of the obtained treated water (precipitation tank supernatant water) was examined, and the results are shown in Table 1. Indicated.

[Comparative Example 2]
In Example 1, it processed similarly except having added the anion polymer to the 1st reaction tank 1, and having added the cationic polymer to the 2nd reaction tank 2, and obtained process water (precipitation tank supernatant water) The turbidity was examined and the results are shown in Table 1.

  It can be seen from Table 1 that high-quality treated water can be obtained by adding the anionic polymer after the cationic polymer is added according to the present invention.

[Experimental Example 1]
In Example 1, the treatment was carried out in the same manner as in Example 1 except that a pH adjuster was added so that the solution pH in the first reaction vessel 1 was the value shown in Table 2. The turbidity of water (settlement tank supernatant) was examined, and the results are shown in Table 2 together with the results of Example 1.
The pH of the second reaction tank 2 was equivalent to the pH of the first reaction tank 1.

  From Table 2, it can be seen that the pH during the aggregation treatment is preferably in the range of 5-6.

1 First reaction tank 2 Second reaction tank 3 Precipitation tank

Claims (5)

In the method for treating silt-containing water, comprising a coagulation step of adding an aggregating agent to the silt-containing water and coagulating, and then a solid-liquid separation step of solid-liquid separation,
The aggregating step includes
Adding an inorganic flocculant and a cationic polymer flocculant to the silt-containing water;
Next, adding an anionic polymer flocculant;
I have a,
Adding the inorganic flocculant to the first reaction tank or the silt-containing water introduced into the first reaction tank;
Adding the cationic polymer flocculant to the first reaction vessel;
The outflow water from the first reaction tank is introduced into a second reaction tank separate from the first reaction tank, and the anionic polymer flocculant is added to the second reaction tank or the second reaction tank inflow water. A method for coagulating silt-containing water,
Coagulation treatment method silt containing water residence time of the residence time of the first reaction vessel and a second reaction vessel is characterized 10~30min der Rukoto. Oite to claim 1, wherein the inorganic coagulant is Fe-based flocculant, flocculation treatment method silt-containing water, characterized in that 5 to 6 the pH of the aggregation step. The flocculation treatment method for silt-containing water according to claim 1 or 2 , wherein the turbidity of the silt-containing water is 100 NTU or more and the SS concentration is 200 mg / L or more. A first reaction vessel into which silt-containing water is introduced;
Silt-containing water introduced into the first reaction tank or inorganic flocculant addition means for adding an inorganic flocculant to the first reaction tank;
A cationic polymer flocculant addition means for adding a cationic polymer flocculant to the first reaction tank;
A second reaction tank into which the effluent water from the first reaction tank is introduced;
An anionic polymer flocculant addition means for adding an inflow water to the second reaction tank or an anionic polymer flocculant to the second reaction tank, and a solid-liquid separation for solid-liquid separation of the effluent water of the second reaction tank It possesses the means,
First reactor and the residence time in the second reaction vessel coagulation treatment apparatus 10~30min der Ru silt-containing water. In Claim 4 , the pH adjustment means for setting pH of the said 1st reaction tank and the 2nd reaction tank to 5-6 is provided, The coagulation treatment apparatus of the silt containing water characterized by the above-mentioned.

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