JP7520779B2 - Slurry circulation type high-speed coagulation and sedimentation device and water purification method - Google Patents

Description

The present invention relates to a slurry circulation type high-speed coagulation and sedimentation device and a water purification method, and in particular to a slurry circulation type high-speed coagulation and sedimentation device and a water purification method suitable for water purification.

The coagulation sedimentation equipment used in water purification is a treatment device that uses a coagulant to coagulate impurities, mainly turbidity, in the raw water to form flocs, and then separates the flocs (solids) from water (liquid) mainly using gravity. Such coagulation sedimentation equipment is broadly divided into horizontal flow coagulation sedimentation tanks and high-speed coagulation sedimentation equipment. High-speed coagulation sedimentation equipment is equipment that enables high-speed coagulation treatment by utilizing slurry (also called mother flocs) held within the system, and is broadly divided into slurry circulation type high-speed coagulation sedimentation equipment in which the slurry circulates within the equipment, and blanket type high-speed coagulation sedimentation equipment in which the slurry does not circulate within the equipment.

In addition, ultra-high-speed coagulation and sedimentation equipment, which uses sand with a majority of particle size over 100 μm as ballast material, is mainly used for industrial water. This equipment differs from high-speed coagulation and sedimentation equipment in that it circulates ballast material instead of a slurry made from turbidity components derived from raw water and coagulants.

For example, Japanese Patent No. 6082209 (Patent Document 1) describes a slurry circulation type high-speed coagulation and sedimentation device. Patent Document 1 describes an example of a high-speed coagulation and sedimentation device that includes a truncated cone-shaped skirt plate that divides the inside of a circular settling tank into a stirring chamber and a separation chamber, a high-speed agitator that stirs the flocs and forms a circulating flow in the settling tank, a first drive unit that rotates the high-speed agitator, a concentrator in which the flocs settle, a low-speed agitator that stirs the flocs that have accumulated at the bottom of the settling tank, and a second drive unit that rotates the low-speed agitator.

JP 2009-247957 A (Patent Document 2) describes an example of a water treatment method in which solid particles of a specific particle size are added to raw water with a turbidity of 10 degrees or less using a slurry circulation type high-speed coagulation and sedimentation device, and the solid particles are stirred under specific stirring conditions to form flocs with high settling properties.

JP 2019-171309 A (Patent Document 3) describes an example of a coagulation and sedimentation method that uses a slurry circulation type high-speed coagulation and sedimentation device to return at least a portion of the slurry to one or more locations downstream of the addition location of the organic polymer coagulant to circulate the flocs and improve the settling properties of the flocs.

Patent No. 6082209 JP 2009-247957 A JP 2019-171309 A

However, although all of the above conventional techniques have been effective in increasing the number of collisions of flocs and improving the settling properties of flocs to a certain extent, there is still room for improvement in terms of further increasing the strength and settling properties of flocs using polymer flocculants and achieving more efficient solid-liquid separation.

In view of the above problems, the present invention provides a slurry circulation type high-speed coagulation and sedimentation device and a water purification method that can increase the strength and sedimentation properties of flocs and perform efficient solid-liquid separation.

As a result of intensive research conducted by the inventors to solve the above problems, it was discovered that it would be useful to provide an injection section for injecting a polymer flocculant into the slurry in the concentrator of a slurry circulation type high-speed flocculation and settling device.

The embodiment of the present invention, which was completed based on the above findings, is, in one aspect, a slurry circulation type high-speed coagulation and settling device that includes a stirring chamber that performs coagulation treatment on raw water to which an inorganic coagulant has been added in the presence of a slurry, a separation chamber that separates the slurry into solid and liquid, an outlet section that discharges the treated water after solid-liquid separation to the outside, a concentrator that concentrates the slurry after solid-liquid separation, an agitator that forms a stirring flow to circulate the slurry between the stirring chamber, the separation chamber, and the concentrator, and an injection section that is provided in the concentrator and injects a polymer coagulant into the slurry in the concentrator.

According to one embodiment of the present invention, the injection section is provided above the slurry circulation port provided between the concentrator and the mixing chamber.

According to another embodiment of the present invention, the concentrator includes a dispersion mechanism for dispersing the polymer flocculant within the concentrator and a baffle plate provided on the upper portion of the concentrator.

According to yet another embodiment of the present invention, the dispersion mechanism includes an agitator disposed above the injection section and generating a liquid flow below the concentrator.

According to yet another embodiment of the present invention, the dispersion mechanism includes a pump device having a discharge pipe, the outlet of the discharge pipe is disposed above the injection section, and the outlet of the discharge pipe is directed horizontally or below the horizontal direction within the concentrator.

According to yet another embodiment of the present invention, the dispersion mechanism includes a pump device having a suction pipe, a discharge pipe, and a pump body connected to the suction pipe and the discharge pipe, the pump body is disposed above the water surface of the slurry circulation type high-speed coagulation and sedimentation device, the discharge port of the discharge pipe is disposed in the injection section, and an injection point for injecting a polymer coagulant is provided in at least one of the suction pipe and the discharge pipe.

According to yet another embodiment of the present invention, the stirring chamber comprises a first stirring chamber provided below the stirrer and a second stirring chamber provided above the stirrer, the dispersion mechanism includes a pump device having a pump body connected to a suction pipe and a discharge pipe, the pump device comprises a supply pipe connected to the pump body and capable of supplying a slurry containing a polymer flocculant into the first stirring chamber, and a supply pipe connected to the pump body and capable of supplying a slurry containing a polymer flocculant into the second stirring chamber, and the second stirring chamber comprises an auxiliary stirring blade for stirring the second stirring chamber.

According to yet another embodiment of the present invention, the stirring chamber comprises a first stirring chamber provided below the stirrer and a second stirring chamber provided above the stirrer, the dispersion mechanism is disposed between the concentrator and the second stirring chamber, and comprises an air lift capable of supplying the polymer flocculant to the injection section or the second stirring chamber, and comprises an auxiliary stirring blade in the second stirring chamber for stirring the inside of the second stirring chamber.

In another aspect, the embodiment of the present invention is a water purification method for coagulating and sedimenting raw water using a slurry circulation type high-speed coagulation and sedimentation device that includes a stirring chamber that performs coagulation treatment of raw water to which an inorganic coagulant has been added in the presence of a slurry, a separation chamber that separates the slurry into solid and liquid, an outlet section that discharges the treated water after solid-liquid separation to the outside, a concentrator that concentrates the solid-liquid separated slurry, and an agitator that forms an agitation flow for circulating the slurry between the stirring chamber, the separation chamber, and the concentrator, the water purification method includes a step of supplying a polymer coagulant into the concentrator and bringing the slurry in the concentrator into contact with the polymer coagulant.

The present invention provides a slurry circulation type high-speed coagulation and sedimentation device and a water purification method that can increase the strength and sedimentation properties of flocs and perform efficient solid-liquid separation.

1 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation device according to an embodiment of the present invention. FIG. 2 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a first modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to the embodiment of the present invention. FIG. 11 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a second modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to the embodiment of the present invention. FIG. 11 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a third modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to the embodiment of the present invention. FIG. 13 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a fourth modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to the embodiment of the present invention. FIG. 13 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a fifth modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to the embodiment of the present invention. FIG. 13 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a sixth modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to an embodiment of the present invention. FIG. 13 is a schematic diagram showing an example of a slurry circulation type high-speed coagulation and sedimentation apparatus according to a seventh modified example of the slurry circulation type high-speed coagulation and sedimentation apparatus according to an embodiment of the present invention.

The following describes an embodiment of the present invention with reference to the drawings. In the following description of the drawings, identical or similar parts are given identical or similar reference numerals. Note that the following embodiment is an example of an apparatus and method for embodying the technical idea of this invention, and the technical idea of this invention does not specify the structure, arrangement, etc. of the components as described below.

(Slurry circulation type high-speed coagulation and settling equipment)
As shown in FIG. 1, a slurry circulation type high-speed coagulation and sedimentation apparatus 1 according to an embodiment of the present invention includes stirring chambers 11 and 12 for coagulating raw water to which an inorganic coagulant has been added in the presence of a slurry, a separation chamber 13 for separating the slurry into solid and liquid, an outlet section 16 for discharging the treated water after solid-liquid separation to the outside, a concentrator 15 for concentrating the slurry after solid-liquid separation, an agitator 2 for forming a stirring flow for circulating the slurry among the stirring chambers 11 and 12, the separation chamber 13, and the concentrator 15, and an injection section 5 provided within the concentrator 15 for injecting a polymer coagulant into the slurry in the concentrator 15.

The slurry circulation type high-speed coagulation and sedimentation device 1 is equipped with an agitator 2 in the center, and a cylindrical inner draft tube 43a is arranged around the agitator 2. A ring plate 42 is arranged at the lower end of the inner draft tube 43a, and a conical skirt plate 4 whose diameter increases toward the bottom is arranged on the outer circumferential surface of the inner draft tube 43a. This skirt plate 4 divides the mixing chambers 11, 12 and the separation chamber 13.

A first stirring chamber 11 is provided below the agitator 2. A cylindrical outer draft tube 43b is disposed above the agitator 2, and a second stirring chamber 12 is provided inside the outer draft tube 43b. Raw water is supplied into the raw water supply chamber 10 through a raw water inlet pipe 21 connected to the raw water supply chamber 10 partitioned between the skirt plate 4, the ring plate 42, and the inner draft tube 43a. An annular gap is formed between the skirt plate 4 and the ring plate 42, and the raw water supplied into the raw water supply chamber 10 is introduced into the first stirring chamber 11 through this annular gap.

The raw water inlet pipe 21 is provided with an injection point 8 for injecting an inorganic coagulant into the raw water, and it is preferable from the viewpoint of miniaturization of the device that the inorganic coagulant is injected at an injection rate according to the turbidity of the raw water. The injection of the inorganic coagulant is not limited to the embodiment shown in FIG. 1, and may be performed by providing a separate mixing tank or the like. For example, an aluminum-based coagulant or an iron-based coagulant can be used as the inorganic coagulant. Polyaluminum chloride (PAC) or aluminum sulfate (aluminum sulfate) can be used as the aluminum-based coagulant. Ferric sulfate (polyferric) or ferric chloride can be used as the iron-based coagulant. Since the inorganic coagulant is acidic, the optimal coagulation pH range of the slurry circulation type high-speed coagulation sedimentation device 1 may be exceeded when the inorganic coagulant is injected into the raw water. In such a case, it is preferable to further add an alkaline agent such as slaked lime or caustic soda. It is preferable that the injection rate of the inorganic coagulant is adjusted to the optimal injection rate according to the retention time and turbidity related to the flow rate of the raw water by a jar test or the like.

The agitator 2 is equipped with an agitator blade 2a that agitates the slurry in the first agitation chamber 11, and a circulation blade 2b that creates an upward flow from the first agitation chamber 11 to the second agitation chamber 12. The agitator 2 is connected to a rotating shaft 31 that extends above the water surface of the slurry circulation type high-speed coagulation and sedimentation device 1. The rotation of the agitator blade 2a and the circulation blade 2b is driven by a drive device 3 that drives the rotation shaft 31. The slurry in the first agitation chamber 11 is agitated by driving the agitator blade 2a, and the slurry in the first agitation chamber 11 flows into the second agitation chamber 12 by driving the circulation blade 2b.

Above the separation chamber 13, there is provided a supernatant section 14 that contains the supernatant water obtained by solid-liquid separation, and an outlet section 16 equipped with an overflow weir or the like for discharging the supernatant water outside the device as treated water. Below the separation chamber 13, there is provided a concentrator 15 that further concentrates the slurry that has settled due to solid-liquid separation in the separation chamber 13. Multiple concentrators 15 are installed within the slurry circulation type high-speed coagulation and sedimentation device 1, and the required number of concentrators can be operated according to the required amount of sludge discharged.

The concentrator 15 can be equipped with a dispersion mechanism 6 that disperses the polymer flocculant in the concentrator 15, and a baffle plate 7 provided on the top of the concentrator 15. In the example of FIG. 1, a supply pipe 25 for supplying the polymer flocculant is inserted from the side of the slurry circulation type high-speed flocculation and sedimentation device 1, and an example is described in which the polymer flocculant is supplied to the injection part 5 of the concentrator 15 via the supply pipe 25. However, the manner in which the polymer flocculant is supplied into the concentrator 15 is not limited to the example shown in FIG. 1, and various configurations can be adopted.

For example, instead of the supply pipe 25, a supply pipe (not shown) for supplying the polymer flocculant is arranged so as to extend from the injection part 5 of the concentrator 15 to above the water surface of the slurry circulation type high-speed flocculation and sedimentation device 1. Then, the polymer flocculant may be injected on the upper side of the slurry circulation type high-speed flocculation and sedimentation device 1, and the polymer flocculant may be supplied from above via the supply pipe to the injection part 5.

The polymer flocculant supplied to the concentrator 15 is not particularly limited. For example, any one or more selected from the group consisting of polyacrylic acid, sodium polyacrylate, potassium polyacrylate, ammonium polyacrylate, polymethacrylic acid, sodium polymethacrylate, potassium polymethacrylate, and ammonium polymethacrylate can be used as the polymer flocculant, with sodium polyacrylate being preferred. The polyacrylamide polymer flocculant is a copolymer of polyacrylamide and poly(meth)acrylate, and commercially available products can be used as anionic polymer flocculants.

The rate at which the polymer flocculant is injected into the concentrator 15 may be adjusted in advance using a jar test or the like so that the optimal injection rate is obtained according to the retention time and turbidity related to the flow rate of the raw water. Alternatively, the turbidity of the raw water is measured, and the sludge concentration of the slurry generated in the concentrator 15 is predicted according to the measurement results. It is then preferable to optimize the amount of polymer flocculant to be added by determining the amount based on the weight of the sludge in the concentrator 15.

Although not limited to the following, the addition rate of the polymer flocculant can typically be, for example, 0.005 to 1.0 wt% to SS, and preferably 0.01 to 0.5 wt% to SS. If the addition rate of the polymer flocculant is less than 0.005 wt% to SS, the polymer flocculant in the concentrator 15 will be insufficient, and the strength and sedimentation of the flocculant generated may not be sufficient. Conversely, if the addition rate of the polymer flocculant exceeds 1.0 wt% to SS, the polymer flocculant in the concentrator 15 will be excessive, and highly viscous flocculant may be generated. If the slurry containing the highly viscous flocculant is circulated to the first stirring chamber 11, the dispersibility of the flocculant in the first stirring chamber 11 will decrease, and the flocculant settling effect of the first stirring chamber 11 and the second stirring chamber 12 connected to the first stirring chamber 11 may not be significantly obtained.

The injection section 5 refers to the area (injection point) where the polymer flocculant and the slurry come into contact in the concentrator 15. In the embodiment shown in FIG. 1, it is located at the tip of the supply pipe 25 that supplies the polymer flocculant into the concentrator 15, and refers to the area where the concentration of the polymer flocculant is higher than the surrounding area. This injection section 5 is preferably provided above the circulation port 15b that is provided between the concentrator 15 and the first stirring chamber 11 and supplies the slurry to be circulated from the concentrator 15 to the first stirring chamber 11 to the first stirring chamber 11. This makes it possible to obtain the injection effect of the polymer flocculant more effectively. As shown in FIG. 1, typically, an opening/closing valve 41 for controlling the circulation of the slurry is often provided at the circulation port 15b, so that the injection section 5 is preferably provided above the opening/closing valve 41.

If the height of the injection section 5 is too high, the sludge interface at the top of the concentrator 15 may flow due to the flow of the polymer flocculant supplied to the injection section 5, and the slurry in the concentrator 15 may flow back into the separation chamber 13. On the other hand, if the height of the injection section 5 is too low, the highly concentrated slurry (sludge) may become even more viscous, and such a slurry may not be sufficiently dispersed in the stirring chamber 11 when circulated to the first stirring chamber 11. In addition, if the injection section 5 is buried under the concentrated sludge interface concentrated in the concentrator 15, it may cause blockage of the supply pipe 25 that supplies the polymer flocculant to the injection section 5, corrosion of the dispersion mechanism 6 adjacent to the injection section 5, or adhesion of the slurry. Although not limited to the following, typically, the injection section 5 is positioned at a height of 2/3 to 1/3 when the bottom of the concentrator 15 is set to a height of 0 and the height of the straightening plate 7 at the top of the concentrator 15 is set to 1. In this embodiment, the height of the injection section 5 refers to the height of the center of the tip of a supply pipe or an air lift pipe through which the polymer flocculant is supplied.

As the dispersion mechanism 6 for dispersing the polymer flocculant in the concentrator 15, it is preferable to use various devices that generate a liquid flow in the concentrator 15, including, for example, an agitator, a pump device, etc. However, a device that generates an upward flow in the concentrator 15, such as an aeration device, may hinder the thickening and settling of the slurry in the concentrator 15. Therefore, when distributing the dispersion mechanism 6, it is preferable to use a dispersion mechanism 6 that generates a slow downward flow from the top to the bottom of the concentrator 15 so as not to hinder the thickening and settling of the slurry in the concentrator 15. In order not to hinder the thickening and settling of the slurry in the concentrator 15, it is preferable to adjust the downward flow generated by the dispersion mechanism 6 to, for example, 2 m/s or less, more typically 0.1 to 1.5 m/s.

For example, as shown in FIG. 1, the dispersion mechanism 6 is preferably an agitator equipped with an agitating blade 60 that is disposed above the injection section 5 in the concentrator 15 and generates a liquid flow downward from the concentrator 15. The shape of the agitating blade 60 is not particularly limited, and blades of various shapes can be used. Baffle plates, granulation plates, etc. may also be disposed around the agitating blade 60 to promote a downward flow.

Furthermore, it is preferable that a baffle plate 7 consisting of multiple inclined plates is disposed on the upper part of the concentrator 15. The baffle plates 7 are arranged at equal intervals along the radial direction of the slurry circulation type high-speed coagulation and sedimentation device 1, and are disposed perpendicular to the radial direction of the slurry circulation type high-speed coagulation and sedimentation device 1 when viewed from above.

The straightening plate 7 is preferably inclined in the same direction as the inclined surface of the skirt plate 4. In other words, by inclining the straightening plate 7 radially inward of the slurry circulation type high-speed coagulation and sedimentation device 1 with respect to the vertical direction, the slurry can be smoothly flowed into the concentrator 15 along the inclination of the skirt plate 4. The straightening plate 7 is preferably disposed over the entire upper part of the concentrator 15 as much as possible. The straightening plate 7 is preferably made of metal from the viewpoint of durability and material costs, but plastic material or carbon fiber may also be used.

When the slurry separated by solid-liquid separation from the separation chamber 13 flows into the concentrator 15, the flow is straightened by the straightening plate 7, so that the stirring up of sludge in the concentrator 15 is suppressed. Furthermore, by disposing the straightening plate 7 on the top of the concentrator 15, even if a liquid flow is generated by the dispersion mechanism 6, it is possible to suppress the slurry from flowing back from the concentrator 15 into the separation chamber 13, so that the concentration of the slurry in the concentrator 15 can be efficiently increased.

The concentrator 15 preferably further includes a sludge discharge section 23 consisting of a pipe or a sludge pit for discharging the slurry in the concentrator 15 to the outside as excess sludge. When processing is continued in the slurry circulation type high-speed coagulation and sedimentation device 1, the amount of slurry (solid amount) in the system increases. For this reason, an on-off valve 41 for controlling the circulation of the slurry and a sludge discharge section 23 for discharging the slurry to the outside are provided in the concentrator 15. The concentration of the slurry in the system can be stably maintained within a certain range by the operator operating the on-off valve 41 as necessary, or by periodically discharging the sludge from the concentrator 15. When the on-off valve 41 of the concentrator 15 is closed, the circulation flow of the slurry is interrupted and the slurry is concentrated, and when it is opened, the slurry flows from the concentrator 15 to the first mixing chamber 11.

The opening and closing control of the on-off valve 41 is preferably controlled by a control device not shown in FIG. 1. For example, while the polymer flocculant is being supplied to the injection section 5 in the concentrator 15, the control device outputs a control signal to close the on-off valve 41 so that the polymer flocculant is sufficiently dispersed in the concentrator 15. When the slurry concentrated in the concentrator 15 is circulated to the first stirring chamber 11, the control device outputs a control signal to open the on-off valve 41, thereby adjusting the amount of slurry to be circulated. The excess sludge that accumulates at the bottom of the slurry circulation type high-speed flocculation and settling device 1 can be discharged from the sludge discharge section 22 connected to the bottom of the slurry circulation type high-speed flocculation and settling device 1.

Polymer flocculants coarsen flocs through their adsorption and bridging action, increasing their strength and sedimentation properties, enabling efficient solid-liquid separation. The characteristics of polymer flocculants include that they only require an injection rate of about 1/100 of that of inorganic flocculants, which means that they do not need to track fluctuations in raw water turbidity like inorganic flocculants, they do not consume alkali like inorganic flocculants, so there is no need to add and control alkali such as caustic soda, and they make operation and management in water purification treatment easier. For these reasons, it is preferable to use polymer flocculants in water purification treatment as coagulation aids to improve response to raw water fluctuations, operation and management, and filtration treatment (water quality).

However, in conventional high-speed slurry circulation coagulation and settling equipment, the use of polymer coagulants is not anticipated, and injection points are often not provided within the equipment. In conventional high-speed slurry circulation coagulation and settling equipment, an inorganic coagulant is generally injected into the raw water inlet pipe, but simultaneous injection of an inorganic coagulant and a polymer coagulant may result in a decrease in coagulation treatment performance. It is possible to provide a coagulation stirring tank for the inorganic coagulant and a coagulation tank for the polymer coagulant separately, but this increases the installation space, and depending on the existing facility, there may be cases where the space is insufficient to install them. Furthermore, when the turbidity of the raw water is relatively low, the coagulation and settling effect of adding a polymer coagulant may not be sufficient.

According to the slurry circulation type high-speed coagulation and sedimentation device 1 according to the embodiment of the present invention, an injection section 5 is provided in the concentrator 15, where the slurry in the concentrator 15 comes into contact with the polymer coagulant. Since the slurry in the concentrator 15 has a higher sludge concentration than the slurry in the first stirring chamber 11 and the second stirring chamber 12, the effect of improving the strength and settling properties of the flocs by the polymer coagulant can be obtained more efficiently than when the slurry in the first stirring chamber 11 and the second stirring chamber 12 comes into contact with the polymer coagulant.

In addition, by returning the slurry containing flocs whose strength and settling properties have been improved by the polymer coagulant to the first stirring chamber 11, the returned flocs become the core of the coagulation process in the first stirring chamber 11, and the coagulation process in the first stirring chamber 11 can be carried out more efficiently. According to the slurry circulation type high-speed coagulation and sedimentation device 1 of the embodiment of the present invention, there is no need to install dedicated equipment for mixing the polymer coagulant with the raw water outside the slurry circulation type high-speed coagulation and sedimentation device 1, so installation space can be saved and the device as a whole can be made more compact.

The amount of polymer flocculant injected is smaller than that of inorganic flocculants, and dispersion by stirring may be required in the injection section 5. According to the slurry circulation type high-speed flocculation and settling device 1 according to the embodiment of the present invention, since it is equipped with a dispersion mechanism 6 that disperses the polymer flocculant in the concentrator 15, the polymer flocculant injected into the concentrator 15 can be efficiently dispersed within the concentrator 15.

Furthermore, by providing a straightening plate 7 at the top of the concentrator 15, even if an upward liquid flow occurs in the concentrator 15 due to the dispersion mechanism 6, the straightening plate 7 suppresses the upward liquid flow and prevents the slurry in the concentrator 15 from flowing back toward the top of the separation chamber 13, thereby efficiently increasing the concentration of the slurry in the concentrator 15.

(Water purification method)
Next, an example of a water purification method using the slurry circulation type high-speed coagulation and sedimentation apparatus 1 according to the embodiment of the present invention will be described. Raw water containing suspended solids is added with an inorganic coagulant in a raw water inlet pipe 21 having an injection point 8 for injecting the inorganic coagulant, and then introduced into a raw water supply chamber 10 of the slurry circulation type high-speed coagulation and sedimentation apparatus 1 shown in Fig. 1 and flows into a first stirring chamber 11. In the first stirring chamber 11 and the second stirring chamber 12, the inflow raw water is coagulated in the presence of a slurry containing mother flocs, and the flocs are coarsened. The slurry containing the coarsened flocs is subjected to solid-liquid separation in a separation chamber 13. The separated supernatant water passes through a supernatant part 14 above the separation chamber 13 and is taken out of the system from an outlet part 16 equipped with an overflow weir.

The solid-liquid separated slurry flows from the separation chamber 13 into the concentrator 15 through the baffle plate 7 located at the top of the concentrator 15. In the concentrator 15, a polymer flocculant is injected through the supply pipe 25, and the slurry and the polymer flocculant are mixed in the injection section 5, improving the strength and settling properties of the flocs contained in the slurry in the concentrator 15. The slurry containing the flocs that have been concentrated in the concentrator 15 and whose strength and settling properties have been improved by the addition of the polymer flocculant is recirculated from the circulation port 15b to the first stirring chamber 11 to continue the flocculation and settling process.

As the coagulation and sedimentation process continues, the amount of slurry (solids) increases in the slurry circulation type high-speed coagulation and sedimentation device 1. If the amount of slurry increases too much, the operator can manually, or a control device (not shown) can automatically, close the on-off valve 41 and open the sludge discharge sections 22 and 23, thereby discharging the slurry in the concentrator 15 and the sludge that has settled to the bottom of the first mixing chamber 11 outside the system.

The water purification method according to the embodiment of the present invention includes a step of supplying a polymer flocculant into the concentrator and contacting it with the slurry in the concentrator, thereby increasing the strength and settling properties of the flocs and enabling more efficient solid-liquid separation.

The present invention has been described by the above embodiment, but the descriptions and drawings forming part of this disclosure should not be understood as limiting this invention. Various alternative embodiments and operating techniques will become apparent to those skilled in the art from this disclosure.

(First Modification)
For example, as shown in FIG. 2, a slurry circulation type high-speed coagulation and sedimentation apparatus 1a according to a first modified example of the present invention has a dispersion mechanism 6 including a pump device equipped with a discharge pipe 61 immersed in a concentrator 15, and it is preferable that a discharge port 61a of the discharge pipe 61 is disposed above the injection section 5 and that the discharge port 61a of the discharge pipe 61 is directed horizontally or downwardly relative to the horizontal direction within the concentrator 15.

By directing the discharge port 61a of the discharge pipe 61 horizontally or downward from the horizontal direction, a downward flow can be generated in the concentrator 15 by the flow of the liquid discharged from the discharge port 61a of the discharge pipe 61. Furthermore, the direction of the discharge port 61a of the discharge pipe 61 is adjusted so that the flow of the liquid discharged from the discharge port 61a of the discharge pipe 61 hits the inclined surface of the skirt plate 4 diagonally downward, or the vicinity of the tip of the discharge pipe is arranged to rotate in the concentrator 15, and a swirling flow is generated toward the bottom of the concentrator 15. This generates a swirling flow in the concentrator 15, which can extend the contact time with the polymer flocculant, thereby further improving the strength and settling property of the flocs. The discharge rate of the liquid discharged from the discharge port 61a of the discharge pipe 61 is not limited to the following, but by setting it to, for example, 2 m/s or less, preferably 0.1 to 1.5 m/s, the effect of mixing the polymer flocculant and the slurry can be obtained without impeding the concentration in the concentrator 15.

(Second Modification)
3, in the slurry circulation type high-speed coagulation and settling apparatus 1b according to the second modified example of the present invention, the dispersion mechanism 6 includes a pump device equipped with a discharge pipe 61 immersed in the concentrator 15, and it is preferable that the discharge pipe 61 extends above the water surface of the slurry circulation type high-speed coagulation and settling apparatus 1, and that the discharge pipe 61 drawn out above the water surface of the slurry circulation type high-speed coagulation and settling apparatus 1 is equipped with an injection point 63 for adding a polymer coagulant. The discharge port 61a of the discharge pipe 61 extends to the injection section 5, and the slurry to which the polymer coagulant has been added is supplied to the injection section 5.

The slurry circulation type high-speed coagulation and sedimentation device 1b according to the second modified example of the present invention does not require the installation of a supply pipe 25 as shown in FIG. 1 inside the concentrator 15, which simplifies the installation work for adding the polymer coagulant and improves the workability during maintenance of the device.

(Third Modification)
As shown in Fig. 4, in the slurry circulation type high-speed flocculation and sedimentation apparatus 1c according to the third modified example of the present invention, the dispersion mechanism 6 preferably includes a pump device including a suction pipe 62, a discharge pipe 61, and a pump body 64 connected to the suction pipe 62 and the discharge pipe 61. The pump body 64 is disposed above the water surface of the slurry circulation type high-speed flocculation and sedimentation apparatus 1, and is disposed so that the discharge port 61a of the discharge pipe 61 reaches the injection section 5, and the suction port 62a of the suction pipe 62 is provided below the discharge port 61a. An injection point 63 for injecting a polymer flocculant is preferably provided in at least one of the suction pipe 62 and the discharge pipe 61.

According to the slurry circulation type high-speed coagulation and settling device 1c shown in FIG. 4, the pump body 64 is disposed above the water surface of the slurry circulation type high-speed coagulation and settling device 1c, so that the state of the pump body 64 can be easily checked from an inspection walkway (not shown) provided above the water surface of the slurry circulation type high-speed coagulation and settling device 1c. Therefore, maintenance work is easier than when the pump body 64 is immersed in water. Since the injection point 63 of the polymer coagulant is provided in the suction pipe 62 or the discharge pipe 61, it is not necessary to provide a hole for piping connection in the slurry circulation type high-speed coagulation and settling device 1 to supply the polymer coagulant into the concentrator 15. Therefore, the installation work for injecting the polymer coagulant is also easier, and the management of the injection point 63 is also easier than when the injection point 63 is provided in water. Furthermore, by providing the suction port 62a at the tip of the suction pipe 62 below the discharge port 61a at the tip of the discharge pipe 61, and controlling the flow rate so that the liquid flow around the injection part 5 is directed downward by the suction pipe 62 and the discharge pipe 61, it is possible to omit the installation of stirring equipment for stirring within the concentrator 15.

(Fourth Modification)
As shown in Figure 5, in a slurry circulation type high-speed coagulation and sedimentation apparatus 1d according to a fourth modified example of the present invention, the dispersion mechanism 6 includes a pump device having a pump body 64 connected to a suction pipe 62 and a discharge pipe 61, and the pump device further includes a supply pipe 66 connected to the pump body 64 and capable of supplying a slurry containing a polymer coagulant into the first stirring chamber 11, and a supply pipe 65 connected to the pump body 64 and capable of supplying a slurry containing a polymer coagulant into the second stirring chamber 12.

The pump body 64, suction pipe 62, discharge pipe 61 and supply pipes 65, 66 are connected to the control device 9, and in response to a control signal from the control device 9, it is possible to control switching between supplying the slurry containing the polymer flocculant into the concentrator 15, the first stirring chamber 11, or the second stirring chamber 12.

According to the fourth modified example of the slurry circulation type high-speed coagulation and sedimentation device 1d of the present invention, the slurry in the concentrator 15 is drawn out through the suction pipe 62, and the slurry into which the polymer coagulant has been injected from the polymer coagulant injection point 63 provided on the water surface can be supplied to the first stirring chamber 11 and the second stirring chamber 12 through the supply pipes 66 and 65 in addition to the injection section 5. This improves the strength and settling properties of the flocs contained in the slurry supplied to the first stirring chamber 11 and the second stirring chamber 12, and allows the coagulation process to be carried out more efficiently.

The agitator 2 provides sufficient agitation in the first agitation chamber 11 with the agitation flow from the agitator blade 2a, but since there is no agitator blade in the second agitation chamber 12, sufficient agitation flow may not be obtained. According to the slurry circulation type high-speed coagulation and settling device 1d shown in Figure 5, since it is equipped with an auxiliary agitator blade 2c that stirs inside the second agitation chamber 12, the discharge liquid containing the polymer coagulant discharged from the supply pipe 65 can be quickly dispersed inside the second agitation chamber 12.

(Fifth Modification)
6, in a slurry circulation type high speed coagulation and sedimentation apparatus 1e according to a fifth modified example of the present invention, the dispersion mechanism 6 can include a pump device having a pump body 64 connected to a suction pipe 62, a discharge pipe 61, supply pipes 66 and 65, and a withdrawal pipe 67. Although not shown in the figure, valves are provided in the suction pipe 62, the discharge pipe 61, the supply pipes 66 and 65, and the withdrawal pipe 67, respectively, and the valves can be switched by the control device 9.

According to the slurry circulation type high-speed coagulation and settling device 1e of the fifth modified example of the present invention, the injection point of the polymer coagulant can be set at any location by controlling the supply of the suction pipe 62, the discharge pipe 61, the supply pipes 66, 65, and the extraction pipe 67 according to the state of the slurry circulating inside the slurry circulation type high-speed coagulation and settling device 1e. This increases the strength and settling property of the flocs in the tank, making it possible to perform more efficient solid-liquid separation.

In the example shown in FIG. 6, when a slurry containing a polymer flocculant is supplied from the supply pipe 65 into the second stirring chamber 12, the discharge liquid containing the polymer flocculant discharged from the supply pipe 65 can be quickly dispersed into the second stirring chamber 12 using the auxiliary stirring blade 2c that stirs inside the second stirring chamber 12.

(Sixth Modification)
7, in a slurry circulation type high speed coagulation and settling apparatus 1f according to a sixth modified example of the present invention, the dispersion mechanism 6 is preferably arranged between the concentrator 15 and the second stirring chamber 12 and includes an air lift 68 capable of supplying the polymer coagulant into the injection part 5 or the second stirring chamber 12. One end of the air lift 68 is arranged in the injection part 5 in the concentrator 15, and the other end of the air lift 68 is provided in the second stirring chamber 12. In the second stirring chamber 12, an auxiliary stirring blade 2c for stirring the inside of the second stirring chamber 12 is provided.

According to the slurry circulation type high-speed coagulation and settling device 1f of the sixth modified example of the present invention, the slurry in the concentrator 15 can be pumped or the polymer coagulant can be supplied to the injection section 5 via the air lift 68, which has an extremely simple structure including a lift pipe (not shown) and an air supply pipe (not shown). Therefore, compared with a stirrer or pump device, the treatment can be performed stably for a long period of time with fewer breakdowns. Furthermore, according to the slurry circulation type high-speed coagulation and settling device 1f of the sixth modified example of the present invention, the suction force of the air lift 68 can be used to disperse the slurry in the concentrator 15, so that large disturbances in the liquid flow are unlikely to occur, and the installation area of the baffle plate 7 can be reduced or the installation can be omitted. Furthermore, by providing an auxiliary stirring blade 2c for stirring the second stirring chamber 12 in the second stirring chamber 12, the auxiliary stirring blade 2c can quickly stir the second stirring chamber 12.

(Seventh Modification)
As shown in FIG. 8, a slurry circulation type high-speed coagulation and sedimentation apparatus 1g according to the seventh modified example of the present invention preferably includes a dispersion mechanism 6 disposed between the concentrator 15 and the second stirring chamber 12, an air lift 68 capable of supplying the polymer coagulant into the injection section 5 or the second stirring chamber 12, and an air bubble removal tank 50 provided at the end of the air lift 68.

The air bubble removal tank 50 includes a receiving tank 51 that receives the air bubble-containing slurry sent from the concentrator 15 via the air lift 68, a slurry storage tank 52 that is continuous with the receiving tank 51 and stores the slurry from which the air bubbles have been removed, and an air bubble removal wall 53 that is disposed between the receiving tank 51 and the slurry storage tank 52 to separate the receiving tank 51 and the slurry storage tank 52 and removes air bubbles that rise to the water surface of the receiving tank 51. A supply pipe 54 is disposed at the bottom of the slurry storage tank 52, and the slurry in the slurry storage tank 52 is sent to the second mixing chamber 12 via the supply pipe 54.

According to the seventh modified example of the present invention, the slurry circulation type high-speed coagulation and sedimentation device 1g is provided at the end of the air lift 68, and the air bubbles are removed from the bubble-containing slurry supplied by the air lift 68 in the air bubble removal tank 50, thereby preventing the air bubbles from entering the second stirring chamber 12. This makes it possible to more efficiently carry out the coagulation and sedimentation process in the second stirring chamber 12.

As described above, according to the slurry circulation type high-speed coagulation and settling apparatus 1a-1g and the water purification method using the same according to the embodiment of the present invention, by providing an injection point (injection section 5) for the polymer coagulant in the concentrator 15 of the slurry circulation type high-speed coagulation and settling apparatus 1a-1g, it is possible to increase the strength and settling property of the flocs and perform efficient solid-liquid separation without using a coagulation tank dedicated to the polymer coagulant. Furthermore, even if the turbidity and SS of the raw water supplied suddenly change, by appropriately adding the polymer coagulant, it is possible to obtain clear treated water with a stably low turbidity compared to conventional methods that do not add a polymer coagulant.

In the slurry circulation type high-speed coagulation and settling apparatus 1a to 1g according to the embodiment of the present invention, it is also preferable to further provide a measuring device (not shown) for measuring the sludge concentration of the slurry in the injection section 5. The installation location of the measuring device for measuring the sludge concentration is not particularly limited. For example, the slurry in the injection section 5 may be sampled using a pipe or the like, and the sludge concentration of the slurry after sampling may be measured outside the slurry circulation type high-speed coagulation and settling apparatus 1a to 1g. By measuring the sludge concentration of the slurry in the injection section 5 and injecting an appropriate amount of polymer coagulant into the injection section 5 according to the sludge concentration, it is possible to more appropriately adjust the strength of the flocs and perform efficient solid-liquid separation.

Reference Signs List 1, 1a to 1g... Slurry circulation type high-speed coagulation and settling device 2... Agitator 2a... Agitator blade 2b... Circulation blade 2c... Auxiliary agitator blade 3... Drive device 4... Skirt plate 5... Injection section 6... Dispersion mechanism 7... Straightening vane 8... Injection point 9... Control device 10... Raw water supply chamber 11... First agitation chamber 12... Second agitation chamber 13... Separation chamber 14... Supernatant section 15... Concentrator 15b... Circulation port 16... Outflow section 21... Raw water inlet pipe 22... Sludge discharge section 23... Sludge discharge section 25...supply pipe 31...rotating shaft 41...on-off valve 42...ring plate 43a...inner draft tube 43b...outer draft tube 50...air bubble removal tank 51...receiving tank 52...slurry storage tank 53...air bubble removal wall 54...supply pipe 60...agitating blade 61...discharge pipe 61a...discharge port 62...suction pipe 62a...suction port 63...injection point 64...pump body 65...supply pipe 66...supply pipe 67...extraction pipe 68...air lift

Claims (9)

A mixing chamber in which raw water to which an inorganic coagulant has been added is coagulated in the presence of a slurry;
a separation chamber for separating the slurry into solid and liquid;
An outflow part for outflowing the treated water after solid-liquid separation to the outside;
a concentrator for concentrating the slurry obtained by the solid-liquid separation;
an agitator for forming an agitating flow for circulating the slurry among the agitation chamber, the separation chamber, and the concentrator;
an injection section provided within the concentrator for injecting a polymer flocculant into the slurry in the concentrator. The slurry circulation type high-speed coagulation and sedimentation device according to claim 1, wherein the injection section is provided above the slurry circulation port provided between the concentrator and the stirring chamber. The concentrator comprises:
a dispersion mechanism for dispersing the polymer flocculant in the concentrator;
3. The slurry circulation type high speed coagulation and sedimentation apparatus according to claim 1, further comprising a baffle plate provided on an upper portion of the concentrator. The dispersion mechanism comprises:
4. The slurry circulation type high speed flocculation and settling apparatus according to claim 3, further comprising an agitator disposed above said injection portion for generating a liquid flow below said concentrator. the dispersion mechanism includes a pump device having a discharge pipe;
4. A slurry circulation type high speed coagulation and sedimentation apparatus according to claim 3, characterized in that the discharge outlet of the discharge pipe is disposed above the injection part, and the discharge outlet of the discharge pipe is directed horizontally or downwardly below the horizontal direction within the concentrator. the dispersion mechanism includes a pump device including a suction pipe, a discharge pipe, and a pump body connected to the suction pipe and the discharge pipe;
the pump body is disposed above the water surface of the slurry circulation type high speed coagulation and sedimentation device, and the discharge port of the discharge pipe is disposed in the injection part,
4. The slurry circulation type high speed flocculation and settling apparatus according to claim 3, wherein an injection point for injecting the polymer flocculant is provided in at least one of the suction pipe and the discharge pipe. The stirring chamber includes a first stirring chamber provided below the stirrer and a second stirring chamber provided above the stirrer,
the dispersion mechanism includes a pump device having a pump body connected to a suction pipe and a discharge pipe;
The pump device further includes a supply pipe connected to the pump body and capable of supplying the slurry containing the polymer flocculant into the first stirring chamber, and a supply pipe connected to the pump body and capable of supplying the slurry containing the polymer flocculant into the second stirring chamber,
4. The slurry circulation type high speed coagulation and settling apparatus according to claim 3, further comprising an auxiliary stirring blade for stirring the inside of said second stirring chamber, said auxiliary stirring blade being provided in said second stirring chamber. The stirring chamber includes a first stirring chamber provided below the stirrer and a second stirring chamber provided above the stirrer,
The dispersion mechanism includes an air lift disposed between the concentrator and the second stirring chamber and capable of supplying the polymer flocculant to the injection portion or the second stirring chamber;
4. The slurry circulation type high speed coagulation and settling apparatus according to claim 3, further comprising an auxiliary stirring blade for stirring the inside of said second stirring chamber, said auxiliary stirring blade being provided in said second stirring chamber. A water purification method for subjecting raw water to coagulation and sedimentation treatment using a slurry circulation type high-speed coagulation and sedimentation device that includes a mixing chamber that performs coagulation treatment on raw water to which an inorganic coagulant has been added in the presence of a slurry, a separation chamber that separates the slurry into solid and liquid, an outlet that discharges the treated water after the solid-liquid separation to the outside, a concentrator that concentrates the slurry after the solid-liquid separation, and an agitator that forms an agitation flow for circulating the slurry between the mixing chamber, the separation chamber, and the concentrator, the water purification method comprising the steps of supplying a polymer coagulant into the concentrator and contacting the slurry in the concentrator with the polymer coagulant.