JP2017087090A - Water treatment method and water treatment equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a water treatment method and water treatment equipment capable of suppressing inflow of bubbles into a flocculent settling tank, and preventing decline of treatment water quality.SOLUTION: An inorganic coagulant is added into water to be treated and line-mixed, and bubbles are removed from the line-mixed water to be treated, and an anionic polymer is added into the water to be treated from which bubbles are removed. Then, the water to be treated is introduced from a lower part of a sludge blanket formed in the flocculent settling tank, and allowed to pass the sludge blanket, to thereby obtain treatment water.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a water treatment method and a water treatment apparatus for agglomerating and separating fine suspended substances and the like from water to be treated.

  It is known that an inorganic flocculant is added to raw water (treated water) such as factory waste water and sewage, and then an anionic polymer flocculant and a cationic polymer flocculant are added to perform solid-liquid separation. Patent Document 1 discloses a line mixing device for adding an inorganic flocculant, a cationic polymer flocculant and an anionic polymer flocculant to raw water containing fine SS, and a structure provided on the downstream side of the line mixing device. A water treatment apparatus comprising a granulated coagulation sedimentation tank is disclosed.

  In such a conventional water treatment apparatus, bubbles from raw water may flow into the line mixing apparatus. In addition, the addition of an inorganic flocculant may lower the pH and generate bubbles due to decarboxylation. When bubbles enter / generate into the line mixing device, the bubbles flow into the coagulation sedimentation tank, and the bubbles adhere to the flocs of the sludge blanket in the coagulation sedimentation tank. There was a problem that the flocs to which bubbles were attached easily floated and the quality of treated water was lowered.

  Moreover, in the conventional water treatment apparatus, the flow-type pH meter was installed in the line mixing apparatus, and the pH adjuster was added so that the pH of raw | natural water might become the value of the predetermined range. However, poor pH measurement may occur due to blockage of the piping or insufficient cleaning of the electrodes of the pH meter. Moreover, electrode wear due to SS particles in the raw water may occur, and the maintenance frequency of the pH meter may increase.

International Publication No. 2014/038537

  The present invention has been made in view of the above-described conventional situation, and an object thereof is to provide a water treatment method and a water treatment apparatus capable of suppressing the inflow of bubbles into a coagulation sedimentation tank and preventing deterioration of treated water quality. To do.

  The water treatment method of the present invention (first invention) is a water treatment in which treated water is introduced into a lower portion of a sludge blanket formed in a coagulation sedimentation tank, and the treated water is obtained by passing the sludge blanket in an upward flow. In this method, a flocculant is added to the water to be treated, line-mixed, air bubbles are removed from the water to be treated mixed with the line, and the water to be treated from which bubbles have been removed is introduced to the lower portion of the sludge blanket. It is a feature.

  The water treatment method according to one aspect of the first invention is characterized in that an antifoaming agent is added to the water to be treated.

  The water treatment method according to one aspect of the first invention is characterized in that an anionic polymer is added to the water to be treated from which bubbles have been removed or the water to be treated in which bubbles are being removed, and introduced into the lower portion of the sludge blanket. .

  The water treatment method according to one aspect of the first invention is characterized in that the flocculant is an inorganic flocculant and / or a cationic polymer.

  In the water treatment method according to one aspect of the first invention, the treated water mixed in the line is supplied from the upper part of a defoaming pipe installed in the vertical direction outside the coagulating sedimentation tank, and the treated water from which bubbles are removed is obtained. It discharges | emits from the lower part of this defoaming pipe | tube, and introduce | transduces into the said coagulation sedimentation tank, The descent | fall flow rate of the to-be-processed water in this defoaming pipe | tube is 0.1 m / s or less.

  In this case, the pH of the water to be treated may be measured using an immersion pH meter in the defoaming tube, and a pH adjuster may be added to the water to be treated that is line-mixed based on the measurement result.

  Furthermore, the electrode part of the probe of the immersion type pH meter is positioned lower than the treated water supply port of the defoaming tube, and the vertical distance h between the electrode part and the treated water supply port, You may arrange | position to the position where the diameter D of a defoaming tube is the same, or h / D becomes 1-3, and may measure pH of to-be-processed water.

  In the water treatment method according to one aspect of the first invention, a center column extends vertically in the center of the coagulation sedimentation tank, and the water to be treated supplied to the upper part of the center column is fed from the lower part of the center column. The sludge blanket is designed to be introduced into the lower part of the sludge blanket. A center well having a diameter larger than that of the center column is provided at the upper part of the center column, and bubbles are removed by the center well. The descending flow rate of water is set to 0.1 m / s or less.

  In this case, the pH of the water to be treated may be measured using an immersion pH meter in the center well, and a pH adjuster may be added to the water to be treated that is line-mixed based on the measurement result.

  Further, the center well may be formed in a cylindrical shape having a cylinder axis in the vertical direction, and water to be treated may be supplied to the center well to form a swirling flow along the peripheral wall of the center well.

  The water treatment apparatus of the present invention (second invention) is a water treatment apparatus comprising a coagulation sedimentation tank for introducing treated water into a lower portion of a sludge blanket and obtaining treated water by passing through the sludge blanket. A line mixing device for adding a flocculant to the water and mixing the lines; and a defoaming unit for removing bubbles from the water to be treated that has been mixed by line. It is characterized by being introduced into a tank.

  A water treatment apparatus according to one aspect of the second invention is a water treatment apparatus comprising a coagulation sedimentation tank for introducing treated water into a lower part of a sludge blanket and passing the sludge blanket in an upward flow to obtain treated water. The defoaming treated water from the defoaming unit is provided with a line mixing device that adds a flocculant to the treated water and performs line mixing, and a defoaming unit that removes bubbles from the treated water subjected to the line mixing. Is introduced into the coagulation sedimentation tank.

  In this case, you may further provide the antifoamer addition means provided in the upstream of the said line mixing apparatus which adds an antifoamer to the said to-be-processed water.

  Further, an anionic polymer addition means for adding an anionic polymer to the treated water from which bubbles are removed or to the treated water from which bubbles are being removed, the treated water to which the anionic polymer has been added is provided in the sludge blanket. It may be introduced to the lower part.

  The flocculant may be an inorganic flocculant and / or a cationic polymer.

  In the water treatment apparatus according to one aspect of the second invention, the defoaming section is a defoaming pipe provided in the vertical direction on the upstream side of the coagulation sedimentation tank.

  In this case, the defoaming tube may be provided with an immersion pH meter that measures the pH of the water to be treated.

  Further, the electrode part of the probe of the immersion type pH meter is positioned lower than the treated water supply port of the defoaming tube, and the vertical distance h between the electrode part and the treated water supply port, You may arrange | position in the position where the diameter D of a defoaming tube is the same, or h / D becomes 1-3.

  In the water treatment apparatus according to one aspect of the second invention, the coagulation sedimentation tank has a center column extending in the vertical direction at the center, and the treated water supplied to the upper part of the center column is below the center column. To the lower part of the sludge blanket, a center well having a diameter larger than that of the center column is provided at the upper part of the center column, and the anionic polymer addition means is provided in the center well. An anionic polymer is added.

  In this case, the center well may be provided with an immersion pH meter for measuring the pH of the water to be treated.

  Further, the center well may have a cylindrical shape with a cylinder axis in the vertical direction, and the water to be treated may be supplied to the center well so as to form a swirling flow along the peripheral wall of the center well. .

  In the present invention, an anionic polymer is added to the water to be treated from which bubbles have been removed, and introduced into the lower part of the sludge blanket in the coagulation sedimentation tank, so that bubbles are prevented from flowing into the sludge blanket and floating. , Can prevent deterioration of treated water quality.

It is a flowchart which shows the water treatment method which concerns on embodiment. It is the schematic of the water treatment apparatus by a 1st aspect. It is the schematic of the water treatment apparatus by a 2nd aspect. It is the schematic of the water treatment apparatus by a 3rd aspect.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. As shown in FIG. 1, the water treatment device according to this embodiment includes a line mixing device 2, a defoaming unit 4, and a coagulation sedimentation tank 6. Raw water (treated water) containing fine SS is passed through a pipe 1 to a line mixing device (line mixer) 2 by a raw water pump 10.

  In the pipe 1, an antifoaming agent is added to the raw water. The raw water to which the antifoaming agent is added is added with an inorganic flocculant, a pH adjuster and a cationic polymer in the line mixing device 2. The pH of the raw water is adjusted to about 6-8 with a pH adjuster.

  The order of addition of the inorganic flocculant, pH adjuster and cationic polymer is preferably this order or simultaneous. The positive charge of the inorganic flocculant and the cationic polymer acts on the negative charge of the SS to neutralize the charge, and the polymer chains of the cationic polymer are entangled by hydrogen bonds, resulting in a small particle size but high density and firmness. A floc is formed.

The mixing intensity of the line mixer 11 is preferably about 50 to 500 s ⁻¹ in terms of G value (average velocity gradient value), and the total residence time with the defoaming section 4 is about 20 to 120 seconds, particularly about 20 to 60 seconds. It is preferable that

  The raw water to which the inorganic flocculant, the pH adjuster and the cationic polymer are added in the line mixing device 2 is supplied to the defoaming section 4 through the pipe 3. The defoaming unit 4 removes bubbles from the raw water.

  An anionic polymer is added to the raw water from which bubbles have been removed in the defoaming section 4. The raw water to which the anionic polymer is added is introduced into the bottom of the granulation type coagulation sedimentation tank 6. In the coagulation sedimentation tank 6, a sludge blanket is formed in which aggregates (pellets) having a very high sedimentation rate are held. In addition to supplying pellets from the outside of the system at the initial stage of operation, a sludge blanket holding pellets can be formed by growing agglomerates by performing granulation-type aggregation precipitation. When the raw water introduced into the bottom of the coagulation sedimentation tank 6 passes through a sludge blanket (hereinafter sometimes simply referred to as a blanket) in an upward flow, flocs are adsorbed by the pellets in the blanket and are separated into solid and liquid. Only clear water (for example, SS concentration of 20 mg / L or less, particularly 10 mg / L or less) flows out as treated water.

  Agitation blades may be provided in the coagulation sedimentation tank 6. The stirring blade applies a shearing force to the blanket, thereby promoting mechanical dehydration of the floc and forming granulated pellets. When water containing an anionic polymer and flocs passes through the blanket, the flocs are firmly bonded to the pellets, so that suspended substances are removed and the pellets are hard to break by shearing force. The granulated pellet (granulated sludge) is drawn out from the coagulation sedimentation tank 6. Since dehydration from floc is promoted during the pellet formation process, the granulated sludge has a high density.

The stirring strength of the blanket in the coagulation sedimentation tank 6 is preferably ¹ to 150 s ^−1, particularly 2 to 50 s ⁻¹ in terms of G value. The SS concentration of the blanket is preferably 5000 to 60000 mg / L, particularly 10,000 to 30000 mg / L. Moreover, it is preferable that the water flow LV of the coagulation sedimentation tank 6 is 4 to 30 m / hr, particularly 6 to 20 m / hr.

  After the anionic polymer is added to the raw water, it is necessary to introduce the raw water into the coagulating sedimentation tank 6 in a mixed state with the coagulated floc without sufficiently coagulating, so immediately after the addition of the anionic polymer (for example, 0.5 to 60 seconds in particular) It is preferable to introduce raw water into the coagulation sedimentation tank 6 (lower blanket) at 1 to 30 seconds).

  In the present embodiment, bubbles are removed by the defoaming unit 4 from the raw water to which the antifoaming agent is added. Since an anionic polymer is added to the raw water from which bubbles have been removed and introduced into the lower part of the blanket, it is possible to prevent bubbles from flowing into the blanket of the coagulation sedimentation tank 6, to prevent the flocs from rising, and to prevent deterioration of the treated water quality.

[Raw water]
The raw water (treated water) is not particularly limited as long as it is water containing fine suspended substances such as river water, rain water, factory waste water, or water containing heavy metals, fluorine, or phosphoric acid. In addition, when suspended substance containing water is to-be-processed water, Preferably the SS density | concentration is 20-10000 mg / L especially 20-5000 mg / L. In addition, when the fluorine-containing water is a treatment target, the fluorine concentration is preferably about 20 to 1500 mg / L, and when the phosphoric acid-containing water is a treatment target, the phosphoric acid concentration is preferably about 10 to 1000 mg / L.

[Flocculant]
The inorganic flocculant is preferably one that forms hydroxide such as PAC, polyiron (polyferric sulfate), salt iron (ferric chloride), or sulfate band. In fluorine-containing water and phosphoric acid-containing water, calcium compounds such as slaked lime can also be used as the inorganic flocculant. The amount of the inorganic flocculant added is preferably 20 to 2000 mg / L, particularly about 50 to 1500 mg / L.

  The cationic polymer (cationic polymer flocculant) is preferably an acrylamide type, and the cationic group ratio is preferably 10 to 50 mol%, particularly 15 to 40 mol%, and more preferably 15 to 30 mol%. The weight average molecular weight of the cationic polymer flocculant is preferably about 12 million to 25 million, particularly about 15 million to 22 million. The addition amount of the cationic polymer flocculant is preferably 0.1 to 3 mg / L, particularly 0.5 to 2 mg / L.

  As such a cationic polymer, for example, a copolymer of a cationic monomer and acrylamide can be suitably used. Specific examples of the cationic monomer include dimethylaminoethyl acrylate and dimethylaminoethyl methacrylate (hereinafter, both compounds may be referred to as “dimethylaminoethyl (meth) acrylate”) or a quaternary ammonium salt thereof. Dimethylaminopropylacrylamide, dimethylaminopropylmethacrylamide (hereinafter, both compounds may be referred to as “dimethylaminopropyl (meth) acrylamide”) or their quaternary ammonium salts are preferably used. Yes, but not limited to this.

  The product form of the cationic polymer is not particularly limited, such as a powder product, a W / O type emulsion, or a dispersion in which cationic polymer flocculant particles are dispersed in an aqueous medium having a high salt concentration. It is applicable to the general circulation for waste water agglomeration treatment.

  The anionic polymer (anionic polymer flocculant) is preferably an acrylamide type, and the anionic group ratio is preferably 5 to 30 mol%, particularly 5 to 20 mol%. The weight average molecular weight of the anionic polymer is preferably 9 million to 20 million, particularly about 10 million to 18 million. The addition amount of the anionic polymer flocculant is preferably 0.2 to 8 mg / L, particularly 0.5 to 6 mg / L.

  As such an anionic polymer, for example, a copolymer of an anionic monomer and acrylamide, or a hydrolyzate of polyacrylamide can be used. As a specific example of the anionic monomer, acrylic acid or a salt thereof can be suitably used. Polymers copolymerized with acrylamide using 2-acrylamido-2-methylpropanesulfonic acid or a salt thereof together with acrylic acid or a salt thereof as an anionic monomer are particularly useful in that they can be used stably over a wide pH range. It can be used suitably.

  The product form of the anionic polymer is not particularly limited, such as a powder product, a W / O type emulsion, or a dispersion in which anionic polymer flocculant particles are dispersed in an aqueous medium having a high salt concentration. Those generally circulated for wastewater agglomeration treatment can be applied.

  The cationic group ratio is a molar ratio of the cationic monomer in the total molar amount of the nonionic monomer and the cationic monomer to be copolymerized. Anionic group ratio is the molar ratio of anionic monomer to the total molar amount of nonionic monomer and anionic monomer to be copolymerized (in the case of polyacrylamide hydrolyzate, nonionic repeating unit and anionic repeating unit Molar ratio).

For example, in the case of a cationic polymer flocculant obtained by copolymerizing 80 mol of acrylamide and 20 mol of quaternary ammonium salt of dimethylaminoethyl acrylate, the ratio of the cation group is 20 mol% as follows.
Cationic group ratio [mol%] =
[Molar ratio of cationic monomer / (molar ratio of cationic monomer + molar ratio of nonionic monomer)] × 100
= [20 / (20 + 80)] x 100 = 20 [mol%]

[Timing of addition of coagulant, addition amount and addition means]
The cationic polymer is added to the water to be treated (raw water) together with the inorganic flocculant, or immediately after the addition of the inorganic flocculant (for example, 1 second to 1 minute, particularly 5 seconds to 30 seconds) or later. The Thereafter, the anionic polymer is added after 30 seconds to 2 minutes.

  The ratio Ac / Aa between the addition amount Ac of the cationic polymer and the addition amount Aa of the anionic polymer is preferably from 0.1 to 1, particularly from 0.4 to 0.8.

It is preferable that the addition amount Am of the inorganic flocculant, the addition amount Ac of the cationic polymer, and the addition amount Aa of the anionic polymer satisfy the following formula.
0.1 <(Am / 100 + Ac) / Aa <2
The flocculant is added by a chemical injection pump or the like.

[Defoamer]
There is no restriction | limiting in particular as an antifoamer, For example, a hydrophobic organic solvent, a fatty acid polyvalent metal salt, hydrophobic inorganic powder, a nonionic surfactant etc. can be used.

  Examples of the hydrophobic organic solvent include paraffinic hydrocarbons, naphthenic hydrocarbons, and petroleum solvents. Examples of the fatty acid polyvalent metal salt include lauric acid, palmitic acid, stearic acid, oleic acid, erucic acid, and the like. And metal salts of fatty acids such as magnesium, aluminum, calcium, iron, zinc, nickel and barium.

  Examples of the hydrophobic inorganic powder include hydrophobic silica, alumina, and magnesium oxide. Examples of the nonionic surfactant include fatty acid esters such as glycerin fatty acid ester, sorbitan fatty acid ester, polyethylene glycol fatty acid ester, and polyethylene. Examples thereof include ether types such as glycol, polyoxyethylene polyoxypropylene (pluronic type / tetronic type), and polyoxyethylene alkyl ether.

  These antifoaming agents may be used individually by 1 type, and may be used in combination of 2 or more type.

<Water treatment apparatus according to the first aspect>
FIG. 2 is a schematic configuration diagram of a water treatment apparatus using a defoaming tube 40 as the defoaming unit 4. The defoaming tube 40 is formed of a tubular body having a tube axis in the vertical direction and opened upward. A supply port 41 to which the pipe 3 is connected is provided in the upper part of the defoaming pipe 40. The raw water to which the inorganic flocculant, the pH adjuster and the cationic polymer have been added in the line mixing device 2 is guided from the supply port 41 into the defoaming tube 40 via the pipe 3. The liquid level in the defoaming tube 40 is higher than the position of the supply port 41, and bubbles are not generated when the raw water is introduced into the defoaming tube 40.

  An antifoaming agent is added to the raw water supplied to the defoaming tube 40. Therefore, the bubbles of the raw water are gradually removed while descending the defoaming tube 40. A discharge port 42 is provided in the lower part of the defoaming tube 40 so that the raw water from which bubbles have been removed can be continuously discharged.

  The inner diameter D of the defoaming tube 40 is, for example, 200 to 600 mm and the length H is 600 to 1800 mm, but is not limited thereto.

  The water treatment apparatus includes an immersion type pH meter 12 that measures the pH of raw water in the defoaming tube 40. The probe 14 of the pH meter 12 is inserted into the raw water in the defoaming tube 40 through the upper opening 40a of the defoaming tube 40, and the pH of the raw water is measured. Thus, when the defoaming tube 40 is installed upstream from the addition position of the anionic polymer, the electrode 16 at the tip of the probe 14 is located at a position lower (deeper) than the supply port 41, In particular, it is preferable that the vertical distance h from the supply port 41 to the electrode 16 is substantially the same as the inner diameter D of the defoaming tube 40 or h / D is about 1 to 3. When h / D exceeds 3, since the supply port 41 and the electrode 16 are too far, the delay time of the feedback control signal from the pH meter 12 becomes large, and hunting may occur. When h / D is less than 1, since the supply port 41 and the electrode are too close, the electrode 16 is worn by SS and easily deteriorates.

  Based on the measurement result of the pH meter 12, the addition amount of the pH adjuster in the line mixing device 2 is controlled so that the raw water has a pH of about 6-8.

  The speed at which the raw water descends through the defoaming tube 40 (downflow velocity) is preferably 0.15 m / s or less, particularly preferably 0.1 m / s or less. The descending flow rate is preferably 0.04 m / s or more, particularly 0.06 m / s or more.

  When the descending flow rate is larger than 0.15 m / s, the residence time in the defoaming tube 40 of the raw water is short, and the bubbles may not be sufficiently removed. When the descending flow velocity is smaller than 0.04 m / s, an unnecessarily large defoaming tube is required, which leads to an increase in equipment size and an installation space.

  The raw water discharged from the discharge port 42 passes through the pipe 5 and is introduced into the bottom of the coagulation sedimentation tank 6A. In the pipe 5, an anionic polymer is added to the raw water.

  The raw water introduced into the bottom of the coagulation sedimentation tank 6 </ b> A passes through the sludge blanket in an upward flow. The sludge blanket is given a shearing force by the stirring blade 62 of the granulating stirrer 61, and the mechanical dehydration of the floc is promoted to form granulated pellets.

  A receiving tank 69 is provided adjacent to the coagulation sedimentation tank 6A. The receiving tank 69 communicates with the coagulating sedimentation tank 6A through an outlet 69a provided in the middle part of the coagulating sedimentation tank 6A or slightly higher. When the interface of the sludge blanket reaches the height of the outlet 69a, pellets (granulated sludge) spill into the receiving tank 69. The sludge accumulated and concentrated in the receiving tank 69 is taken out from the bottom of the receiving tank 69.

  In this embodiment, bubbles are removed from the raw water by the defoaming tube 40 arranged on the upstream side of the coagulating sedimentation tank 6A, and then an anionic polymer is added to the raw water and introduced into the coagulating sedimentation tank 6A. Thereby, it can prevent that a bubble flows into a sludge blanket and a floc floats, and can prevent the fall of treated water quality.

  In this embodiment, the immersion type pH meter 12 is installed in the defoaming tube 40. Compared with the case where a flow-type pH meter is installed in the line mixing device 2, a pH measurement failure is less likely to occur, and the maintenance frequency can be suppressed.

  The granulating stirrer 61 and the stirring blade 62 may be omitted from the coagulating sedimentation tank 6A shown in FIG.

<Water treatment apparatus according to the second aspect>
3A is a schematic configuration diagram of a water treatment device that performs defoaming in the center well 65 of the coagulation sedimentation tank 6B, and FIG. 3B is a top view of the center well 65. FIG. A center column 64 extends in the vertical direction at the center of the coagulation sedimentation tank 6B. At the lower end of the center column 64, a distributor 67 is provided for uniformly supplying raw water into the coagulation sedimentation tank 6B. The distributor 67 is formed of a tubular body extending in the radial direction from the lower end of the center column 64.

  A center well 65 as a raw water receiving portion is provided on the upper portion of the center column 64. The center well 65 has a cylindrical shape in which the cylinder axis direction is the vertical direction. The center well 65 is an enlarged portion having a diameter larger than that of the center column 64. For example, the diameter D1 of the center well 65 is 250 to 1400 mm, the length in the vertical direction is 50 to 400 mm, the diameter d of the center column 64 is 200 to 1000 mm, and the length in the vertical direction is 1000 to 3000 mm. Not.

  The raw water to which the inorganic flocculant, the pH adjuster and the cationic polymer are added by the line mixing device 2 is supplied to the center well 65 through the pipe 3. Raw water is supplied from the pipe 3 in the tangential direction of the peripheral wall of the center well 65. Thereby, in the center well 65, as shown in FIG.3 (b), the swirl | vortex flow SF along a surrounding wall is formed.

  An antifoaming agent is added to the raw water on the upstream side of the line mixing device 2. Therefore, bubbles are gradually removed from the raw water at the center well 65. Defoaming is promoted by the swirling flow SF in the center well 65. The HRT (Hydraulic Retention Time) in the center well 65 is, for example, about 1 to 5 seconds.

  An anionic polymer is added to the raw water whose bubbles are being removed by the center well 65. The raw water from which bubbles are removed and to which the anionic polymer is added descends the center column 64 and is supplied from the distributor 67 into the sludge blanket.

  The speed at which the raw water descends through the center well 65 (downflow velocity) is preferably 0.15 m / s or less, particularly preferably 0.1 m / s or less. The descending flow rate is preferably 0.04 m / s or more, particularly 0.06 m / s or more.

  If the descending flow rate is greater than 0.15 m / s, the bubbles may not be sufficiently removed. When the descending flow velocity is smaller than 0.04 m / s, it is necessary to increase the inner diameter of the center column 64 by design, resulting in an increase in size of the equipment.

  The raw water introduced from the distributor 67 to the bottom of the coagulation sedimentation tank 6 </ b> B passes through the sludge blanket in an upward flow, fine SS and the like are filtered and separated, and clear treated water flows out from the trough 68. The settled floc is pulled out from the lower part of the coagulation sedimentation tank 6B.

  The probe 14 of the immersion type pH meter 12 is inserted into the raw water in the center well 65, and the pH of the raw water is measured. Based on the measurement result of the pH meter 12, the addition amount of the pH adjuster in the line mixing apparatus 2 is controlled.

  For example, as shown in FIG. 3B, when raw water is supplied from the pipe 3 at the 9 o'clock position of the center well 65 to form a clockwise swirling flow SF, the position of the center well 65 at 12 o'clock. And an anionic polymer is added, and the probe 14 is placed at the 3 o'clock position. As a result, the raw water is not directly applied to the probe 14 and is in contact with a gentle swirling flow. Therefore, even if the electrode 16 of the probe 14 is located at the same height as the raw water supply port of the pipe 3, Deterioration can be suppressed.

  In this aspect, the center well 65 of the coagulation sedimentation tank 6B is used as a defoaming part to remove bubbles from the raw water. Thereafter, raw water is introduced from the distributor 67 into the sludge blanket. Thereby, it can prevent that a bubble flows into a sludge blanket and a floc floats, and can prevent the fall of treated water quality.

  In this embodiment, the pH of the raw water that gently turns in the center well 65 is measured using the immersion type pH meter 12. Compared with the case where a flow-type pH meter is installed in the line mixing device 2, a pH measurement failure is less likely to occur, and the maintenance frequency can be suppressed.

<Water treatment apparatus according to the third aspect>
As shown in FIG. 4, a mud collecting rake 81 along the inclined bottom surface of the coagulating sedimentation tank 6 </ b> C may be provided integrally with the distributor 67. The center column 64 is connected to the shaft 83 of the motor 82 and rotates slowly together with the mud collecting rake 81 and the distributor 67 together with the motor 82. The mud collecting rake 81 uses the rake action effect to discharge mud while concentrating the precipitated sludge.

Hereinafter, the present invention will be described more specifically with reference to examples.
[Example 1]
Treatment was performed using the water treatment apparatus shown in FIG. 2 using biologically treated water with an SS concentration of 50 mg / L as raw water. As an antifoaming agent, 1 mg / L of Kurita Kogyo "Kuriresu S115" was added. In the line mixing apparatus 2, 200 mg / L of polyferric sulfate was added as an inorganic flocculant. The pH was adjusted to 7 using 25% NaOH as a pH adjuster. As a cationic polymer, 1 mg / L of “Kuri Farm PC728” manufactured by Kurita Kogyo was added. The descending flow rate of the raw water in the defoaming tube 40 was 0.08 m / s.

  To the raw water discharged from the defoaming tube 40, 2 mg / L of “Kurifama PA465” manufactured by Kurita Kogyo was added as an anionic polymer. The diameter of the coagulation sedimentation tank 6A was 1000 mm and the height was 1500 mm. The SS concentration of the sludge blanket in the coagulation sedimentation tank 6A was 3000 mg / L.

  The SS concentration of the treated water flowing out from the trough 63 of the coagulation sedimentation tank 6A was 2 to 5 mg / L.

[Comparative Example 1]
In Example 1, the defoaming process in the defoaming tube 40 and the addition of the antifoaming agent were omitted. Other conditions were the same as in Example 1. The SS concentration of treated water was 5 to 15 mg / L.

  It was confirmed that the quality of the treated water was improved by adding an antifoaming agent and removing bubbles with the defoaming tube 40.

1, 3, 5 Piping 2 Line mixing device 4 Defoaming section 6, 6A, 6B, 6C Coagulation sedimentation tank 12 pH meter 14 Probe 40 Defoaming tube 64 Center column 65 Center well 67 Distributor

Claims (20)

A water treatment method for introducing treated water into a lower portion of a sludge blanket formed in a coagulation sedimentation tank and passing the sludge blanket in an upward flow to obtain treated water,
Add flocculant to the water to be treated and mix the lines.
Remove air bubbles from the mixed water to be treated
A water treatment method comprising introducing treated water from which bubbles have been removed into a lower portion of the sludge blanket.   The water treatment method according to claim 1, wherein an antifoaming agent is added to the water to be treated.   3. The water treatment method according to claim 1 or 2, wherein an anionic polymer is added to the water to be treated from which bubbles have been removed or the water to be treated in which bubbles are being removed, and introduced into the lower portion of the sludge blanket.   The water treatment method according to any one of claims 1 to 3, wherein the flocculant is an inorganic flocculant and / or a cationic polymer. 5. The treated water mixed in the line according to claim 1, wherein the treated water mixed in the line is supplied from an upper part of a defoaming pipe installed vertically outside the coagulation sedimentation tank, and the treated water from which bubbles are removed is supplied to the treated water. Discharged from the lower part of the defoaming tube and introduced into the coagulation sedimentation tank,
A water treatment method, wherein a descending flow rate of water to be treated in the defoaming tube is 0.1 m / s or less.   6. The method according to claim 5, wherein the pH of the water to be treated is measured using an immersion type pH meter in the defoaming tube, and a pH adjuster is added to the water to be treated which is line-mixed based on the measurement result. Water treatment method.   In Claim 6, The electrode part of the probe of the said immersion type pH meter is a position lower than the to-be-processed water supply port of the said defoaming tube, and the distance h of the up-down direction of this electrode part and this to-be-processed water supply port And the diameter D of this defoaming tube is arrange | positioned in the position where h / D becomes 1-3, and the water treatment method characterized by measuring pH of to-be-processed water. 5. The coagulation sedimentation tank according to claim 1, wherein the coagulation sedimentation tank has a center column extending in the vertical direction at the center, and the water to be treated supplied to the upper part of the center column is supplied from the lower part of the center column. It is designed to be introduced to the bottom of the sludge blanket,
A center well having a diameter larger than that of the center column is provided on the center column,
Remove bubbles in the center well,
A water treatment method, wherein a descending flow rate of water to be treated in the center well is 0.1 m / s or less.   In Claim 8, pH of to-be-processed water is measured using the immersion type pH meter in the said center well, and a pH adjuster is added to the to-be-processed water currently line-mixed based on the measurement result. Water treatment method.   10. The center well according to claim 8, wherein the center well has a cylindrical shape with a cylinder axis in the vertical direction, and water to be treated is supplied to the center well to form a swirling flow along the peripheral wall of the center well. Water treatment method. A water treatment apparatus comprising a coagulation sedimentation tank for introducing treated water into a lower portion of a sludge blanket and passing the sludge blanket in an upward flow to obtain treated water,
A line mixing device for adding a flocculant to the water to be treated and mixing the lines;
A defoaming section for removing air bubbles from the water to be treated mixed in a line;
With
A water treatment apparatus, wherein defoamed water from the defoaming section is introduced into the coagulation sedimentation tank.   The water treatment apparatus according to claim 11, further comprising an antifoaming agent adding unit that is provided on an upstream side of the line mixing device and adds an antifoaming agent to the water to be treated. In Claim 11 or 12, further comprising an anionic polymer addition means for adding an anionic polymer to the water to be treated from which bubbles have been removed or the water to be treated in which bubbles are being removed,
A water treatment apparatus, wherein water to be treated to which the anionic polymer is added is introduced into a lower portion of the sludge blanket.   The water treatment apparatus according to claim 11, wherein the flocculant is an inorganic flocculant and / or a cationic polymer.   15. The water treatment device according to claim 11, wherein the defoaming portion is a defoaming tube provided in the vertical direction on the upstream side of the coagulation sedimentation tank.   The water treatment apparatus according to claim 15, wherein the defoaming pipe is provided with an immersion pH meter that measures the pH of the water to be treated.   In Claim 16, The electrode part of the probe of the said immersion type pH meter is a position lower than the to-be-processed water supply port of the said defoaming tube, and the distance h of the up-down direction of this electrode part and this to-be-processed water supply port And the diameter D of this defoaming pipe | tube, or h / D is arrange | positioned in the position used as 1-3, The water treatment apparatus characterized by the above-mentioned. In any one of Claims 11 thru | or 14, the said coagulation sedimentation tank has a center column extended in the up-down direction in the center part, and the to-be-processed water supplied to the upper part of this center column is from the lower part of this center column. It is designed to be introduced to the bottom of the sludge blanket,
A center well larger in diameter than the center column is provided at the top of the center column,
The water treatment apparatus, wherein the anionic polymer addition means adds an anionic polymer to the center well.   The water treatment apparatus according to claim 18, wherein the center well is provided with an immersion pH meter for measuring the pH of the water to be treated.   20. The center well according to claim 18 or 19, wherein the center well has a cylindrical shape with a cylinder axis in the vertical direction, and water to be treated is supplied to the center well so as to form a swirling flow along the peripheral wall of the center well. The water treatment apparatus characterized by the above-mentioned.

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