JP2019217448A - Water treatment apparatus and water treatment method - Google Patents

Abstract

To provide a water treatment apparatus and a water treatment method capable of increasing a sedimentation rate of suspended matter.SOLUTION: A water treatment apparatus includes: a coagulation unit; a particle size distribution control unit; and a solid-liquid separation unit. The coagulation unit causes the suspended mater and a coagulating agent to be coagulated with each other to produce coagulant by mixing the coagulating agent to treatment water containing the suspended matter. The particle size distribution control unit causes the surface of the coagulant to become a spherical surface and narrows a particle size distribution of the coagulant. The solid-liquid separation unit separates the coagulant from the treatment water.SELECTED DRAWING: Figure 1

Description

  Embodiments of the present invention relate to a water treatment apparatus and a water treatment method.

In the fields of water supply and sewerage, wastewater treatment, and water supply, various methods have been devised and implemented to purify water. The water purification method is a method of removing unnecessary substances and substances that cannot be discharged to a subsequent process, among solid substances and dissolved substances in water.
As a general method for purifying water, a water tank is set up, water to be treated is retained therein, and sedimentation separation or floating separation in which solids are separated by a specific gravity difference and gravity, and water in which air is dissolved by pressurization. Is brought into contact with a solid material, and fine air bubbles are adhered to the solid material and floated by pressure.

  When the water to be treated contains oil, organic substances, a large amount of suspended substances (hereinafter referred to as “turbidity”), colloids (fine turbidity), etc., the solid matter is utilized by utilizing the specific gravity difference. Is difficult to separate. In this case, in addition to sedimentation separation and flotation separation, a coagulation treatment for adding a chemical such as a coagulant or a coagulant to the water to be treated to coarsen solids and then separating them is used in combination. In addition, membrane separation by filtration using porous ceramics or resin, an activated sludge method in which microorganisms prey on organic substances and the like may be used.

  Among such separation methods, sedimentation separation is widely used as compared with other methods because it has few consumable parts and has excellent maintainability.

The problem in the sedimentation separation includes, for example, the size of the installation area. Since the sedimentation separation utilizes the difference in specific gravity, the volume of the sedimentation tank increases according to the flow rate of the water to be treated and the sedimentation speed of the aggregates. If the separation speed can be increased, the equipment can be downsized.
The sedimentation rate depends on the density and size of the aggregate. However, the aggregate is a mixture of a gel-like flocculant containing a large amount of water and a turbid substance.If the flocculant is increased to increase this, the density and strength decrease, resulting in sedimentation. It is difficult to increase speed.

JP-A-2005-85252

  The problem to be solved by the present invention is to provide a water treatment apparatus and a water treatment method capable of improving the sedimentation speed of suspended matter.

  The water treatment device according to the embodiment has a coagulation device, a particle size distribution control device, and a solid-liquid separation device. The aggregating device aggregates the turbidity and the aggregating agent by mixing the aggregating agent with the water to be treated containing the turbidity to form an aggregate. The particle size distribution control device makes the surface of the aggregate a spherical surface and narrows the particle size distribution of the aggregate. The solid-liquid separation device separates aggregates from the water to be treated.

The schematic diagram which shows the water treatment apparatus of embodiment. FIG. 3 is a schematic diagram showing a suspended substance and a gel-like flocculant. FIG. 4 is a schematic diagram illustrating an aggregate containing a turbid substance and an aggregating agent in the aggregation step of the water treatment method of the embodiment. FIG. 4 is a schematic diagram showing aggregates in the course of a particle size distribution control step of the water treatment method according to the embodiment. The schematic diagram which shows the aggregate in the state where the particle size distribution control process of the water treatment method of embodiment was completed. The schematic diagram which shows the solid-liquid separation process of the water treatment method of embodiment. The figure which shows the sedimentation velocity ratio in the solid-liquid separation process of the water treatment method of embodiment.

Hereinafter, a water treatment apparatus and a water treatment method of an embodiment will be described with reference to the drawings.
The water treatment apparatus 100 shown in FIG. 1 is schematically composed of a coagulation device 1, a particle size distribution control device 2, and a solid-liquid separation device 3. These devices are provided in this order along the direction in which the water to be treated is transferred.
The water treatment apparatus 100 may have a treated water storage tank 5 and a flocculant storage tank 6, as shown in FIG. These components are connected by a flow path composed of a pipe or the like.

  The coagulation device 1 is a device that mixes a coagulant with the water to be treated containing turbidity and forms an aggregate in the water to be treated. The coagulation device 1 has a treatment tank 7 for containing the water to be treated containing turbid matter. As the aggregating device 1, a stirring device equipped with a general stirring blade is used. In the aggregating apparatus 1, stirring in a general aggregating process is performed in order to agglomerate turbid substances in the water to be treated into aggregates. That is, in the aggregating apparatus 1, by inputting energy to the water to be treated containing the turbid substance, the turbid substance and the aggregating agent are mixed, and the substances collide with each other to be coarsened to form an aggregate. Agglomerates are mixtures of turbids and flocculants.

Next, the particle size distribution control device 2 has a stirring tank 8. The particle size distribution control device 2 is a device for stirring the water to be treated discharged from the aggregating device 1 in a stirring tank 8 with a stirring force (G) defined by the following equation (1). It is preferable that the stirring force (G) is 1000 or more and 5000 or less.
G = (P / (V · μ)) ^1/2 (1)
(Where P is the energy (W) input to the particle size distribution control device, V is the capacity (m ³ ) of the stirring tank 8 provided in the particle size distribution control device and contains the water to be treated, and μ is the viscosity coefficient of water. (Kg / m · s)

  In the particle size distribution control device 2, the surface of the aggregate formed in the aggregation device 1 is made spherical, and the particle size distribution of the aggregate is narrowed. When the stirring force (G) is 1,000 or more and 5,000 or less, the surface of the aggregate can be made spherical, and the particle size distribution of the aggregate can be narrowed. The energy P (W) input to the particle size distribution control device 2 can be confirmed by a power meter or the like provided in the particle size distribution control device 2.

  In the particle size distribution control device 2, the agitation for spheroidizing the surface of the aggregate formed in the water to be treated is performed by applying energy to the water to be treated containing the aggregate, and the agitation between the aggregates is performed. The surface of the aggregate is made spherical by a shear force, collision between substances, collision of the substance with the inner wall surface of the stirring tank 8, and the like.

  In addition, in the particle size distribution control device 2, the stirring for narrowing the particle size distribution of the aggregate formed in the water to be treated means that energy is supplied to the water to be treated containing the aggregate having a spherical surface. Thus, the particle size distribution of the aggregates is narrowed by the shear force between the aggregates, collision between the substances, collision between the substances and the inner wall surface of the stirring tank 8, and the like.

  In the particle size distribution control device 2, an operation of making the surface of the aggregates spherical and narrowing the particle size distribution of the aggregates is performed at one time. For this purpose, the stirring time in the particle size distribution control device 2 is preferably set in the range of 10 seconds to 10 minutes.

  The particle size distribution control device 2 is preferably at least one selected from the group consisting of a stirring device, a dispersion device and an emulsification device. One of these devices may be used alone, or two or more of them may be used in combination. By using these devices, the unevenness of the aggregate can be removed and the particle size distribution of the aggregate can be narrowed.

  The solid-liquid separation device 3 is a device in which water to be treated containing aggregates is allowed to stand, and solid-liquid separation is performed into aggregates and treated water. The solid-liquid separation device 3 is specifically a sedimentation separation tank.

The to-be-treated water storage tank 5 is connected to the flocculation apparatus 1 and the industrial facility 200 via a flow path composed of a pipe or the like.
The treated water storage tank 5 is a tank that stores the treated water (wastewater) discharged from the industrial facility 200 and supplies the treated water to the flocculation device 1.

The flocculant storage tank 6 is connected via a flow path composed of a pipe or the like in the middle of the flow path connecting the water-to-be-treated water storage tank 5 and the flocculation apparatus 1 and immediately before the flocculation apparatus 1 in the flow path. ing.
The coagulant storage tank 6 is a tank for adding a coagulant to the water to be treated immediately before being supplied from the water to be treated storage tank 5 to the coagulation device 1.

  In FIG. 1, the coagulant storage tank 6 is connected in the middle of a flow path connecting the water-to-be-treated storage tank 5 and the coagulation device 1, and the coagulant storage tank 6 is connected to the water-to-be-treated in the middle of the flow path. Although the case where the coagulant is added to is described as an example, the present embodiment is not limited to this. In the present embodiment, the flocculant storage tank 6 may be directly connected to the flocculation apparatus 1, and the flocculant may be directly added from the flocculant storage tank 6 to the treated water in the flocculation apparatus 1.

(Water treatment method)
An example of a water treatment method using the water treatment device 100 will be described with reference to FIGS. 1 to 7, and the operation of the water treatment device 100 will be described.
In the water treatment apparatus 100 according to the embodiment, the water to be treated is, for example, industrial wastewater containing oil, organic matter, solid matter, and turbid matter such as colloid discharged from the industrial facility 200.
The water to be treated is transferred from the water tank 5 to be treated to the flocculation device 1 by a pump or the like.

(Aggregation step)
In the aggregating step, the agglomerator apparatus 1 aggregates the turbid substance 310 with a coarse gel-like aggregating agent 320 as shown in FIG. 2 to form an aggregate 330 as shown in FIG. More specifically, the coagulant 320 is added from the coagulant storage tank 6 to the water to be treated being transferred from the water storage tank 5 to the coagulation device 1. The position at which the coagulant 320 is added is immediately before the coagulation device 1 in the example of FIG. 1, but is not limited to this.

  By stirring the water to be treated containing the turbidity 310 and the flocculant 320 by the agitation force of the flocculation device 1, the turbidity 310 and the flocculant 320 are brought into contact with each other, and the flocculant 330 I do. The addition amount of the flocculant 320 is not particularly limited, and is appropriately adjusted based on the content of the turbid substance 310 in the water to be treated.

  As the coagulant 320, an iron coagulant or an aluminum coagulant is used. Examples of the iron-based coagulant include polyiron and ferric chloride. Examples of the aluminum-based coagulant include aluminum sulfate (sulfuric acid band), polyaluminum chloride (PAC), and the like.

  As shown in FIG. 3, the aggregates 330 formed in the aggregation device 1 are gel-like, have an indeterminate shape in which the interface with the water to be treated is unclear, have a low density, and their sizes are not constant. And the distribution width of the particle size distribution is relatively large. For this reason, the specific gravity difference with respect to water is small and sedimentation and separation are difficult. In addition, one aggregate 330 incorporates a plurality of turbid substances 310.

  Next, the water to be treated including the aggregates 330 is transferred from the aggregation device 1 to the particle size distribution control device 2 by a pump or the like.

(Particle size distribution control step)
In the particle size distribution control step, the surface of the aggregate 330 is made spherical by the particle size distribution control device 2 as shown in FIG. 4, and further, the particle size of the aggregate 330 is made uniform as shown in FIG. 5. By adjusting, the particle size distribution of the aggregates 330 in the water to be treated is narrowed. More specifically, by stirring the water to be treated by the stirring force of the particle size distribution control device 2, the surface of the aggregate 330 is made spherical and the particle size distribution of the aggregate 330 is narrowed.

  As shown in FIG. 4, when the surface of the aggregate 330 becomes spherical from an irregular shape, the fluid resistance of the aggregate 330 decreases. When the fluid resistance of the aggregates 330 decreases, a decrease in the sedimentation velocity can be suppressed. Further, the density of the aggregates is improved. In addition, as shown in FIG. 5, if the range of the particle size distribution of the aggregates 330 becomes narrow and the size of the aggregates 330 becomes relatively uniform, the sedimentation speed of the aggregates 330 becomes uniform. Thereby, the difference in specific gravity with respect to water is increased, and the sedimentation speed is improved.

  In the particle size distribution control step, the stirring power when stirring the water to be treated including the aggregates 330 is, as described above, 1000 to 5000 in the stirring power (G) defined by the above formula (1). Is preferred. If the stirring power (G) is less than 1,000, the surface of the aggregate 330 cannot be made spherical and the particle size distribution of the aggregate 330 cannot be narrowed. On the other hand, if the stirring force (G) exceeds 5000, the stirring force is too strong, so that the particle size of the aggregates 330 is significantly reduced, the fluid resistance of the aggregates 330 is increased, and the sedimentation speed is reduced.

  In the particle size distribution control step, the stirring time when stirring the water to be treated including the aggregates 330 is preferably 10 seconds to 10 minutes as described above. If the stirring time is less than 10 seconds, the surface of the aggregate 330 cannot be made spherical and the particle size distribution of the aggregate 330 cannot be narrowed. On the other hand, if the stirring time exceeds 10 minutes, the particle size of the aggregate 330 is significantly reduced, the fluid resistance of the aggregate 330 is increased, and the sedimentation speed is increased.

  Next, the water to be treated including the aggregates 330 is transferred from the particle size distribution control device 2 to the solid-liquid separation device 3 by a pump or the like.

After the particle size distribution control step, it is preferable to measure the particle size of the aggregate in order to confirm the shape and the particle size of the aggregate. That is, the measurement of the particle size of the aggregate is preferably performed between the particle size distribution control step and the solid-liquid separation step. As a method of measuring the shape and particle size of the aggregate, a general measurement method such as laser diffraction, dynamic light scattering, and image processing is used. The shape of the aggregate is determined by a circularity (a value obtained by dividing a peripheral length by a peripheral length of a circle having an area equal to the particle area) calculated from an aggregate image obtained by image processing or the like. The particle size distribution is determined by a CV value (a value obtained by dividing a standard deviation by an average diameter of an aggregate).

  When the particle size of the aggregates is out of the predetermined range, the stirring force (G) and the stirring time may be adjusted by feeding back the particle size distribution control device 2 to obtain an appropriate particle size.

  Next, the water to be treated including the aggregate transferred from the aggregation device 2 is separated into the aggregate and the treated water by the solid-liquid separation device 3.

(Solid-liquid separation process)
In the solid-liquid separation step, as shown in FIG. 6, in the solid-liquid separation device 3, the water to be treated 500 containing the aggregates 330 is allowed to stand to separate the aggregates 330. The supernatant water after the sedimentation is discharged to the outside of the solid-liquid separator 3. In this way, aggregates contained in the water to be treated are separated from the water to be treated to obtain treated water.

  FIG. 7 shows a sedimentation velocity ratio in a general water treatment method and the water treatment method of the present embodiment. A general water treatment method is a method in which a solid-liquid separation step is performed after the aggregation step. The sedimentation speed ratio is the sedimentation speed ratio when the sedimentation speed of the aggregate in the solid-liquid separation step of a general water treatment method is set to 100. Aggregates in the solid-liquid separation step of a general water treatment method are in the form shown in FIG. 3, and aggregates in the solid-liquid separation step of the water treatment method of the present embodiment are in the form shown in FIG. As shown in FIG. 7, it can be seen that the sedimentation speed is significantly improved in the water treatment method of the present embodiment as compared with a general method.

  According to the water treatment apparatus and the water treatment method of the present embodiment, in the particle size distribution control device or the particle size distribution control step, the surface of the aggregate is made spherical, and the particle size distribution of the aggregate is narrowed, so that the aggregate Reduction of fluid resistance due to surface spheroidization and uniform sedimentation speed of aggregates by narrowing particle size distribution of aggregates are achieved, and the sedimentation speed of aggregates in the solid-liquid separation device or solid-liquid separation process is reduced. The water treatment time can be greatly improved, and the water treatment time can be reduced.

  Further, according to the water treatment apparatus and the water treatment method of the present embodiment, in the particle size distribution control device or the particle size distribution control step, the water to be treated containing the aggregates is stirred for 10 seconds with a stirring force (G) of 1000 or more and 5000 or less. By stirring for 10 to 10 minutes, the surface of the aggregate can be made spherical, and the particle size distribution of the aggregate can be narrowed.

  According to at least one embodiment described above, the surface of the agglomerate is made spherical, and by having a particle size distribution control device that narrows the particle size distribution of the agglomerate, the sedimentation speed of the turbid matter can be improved. it can.

  While some embodiments of the invention have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. These embodiments can be implemented in other various forms, and various omissions, replacements, and changes can be made without departing from the spirit of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are also included in the invention described in the claims and equivalents thereof.

  DESCRIPTION OF SYMBOLS 1 ... Coagulation apparatus, 2 ... Particle size distribution control apparatus, 3 ... Solid-liquid separation apparatus, 8 ... Stirring tank, 100 ... Water treatment apparatus, 310 ... Suspension, 320 ... Coagulant, 330 ... Aggregate.

Claims (4)

By mixing a flocculant in the water to be treated containing a turbid substance, an aggregating apparatus for aggregating the turbid substance and the flocculant to form an aggregate.
A particle size distribution control device that makes the surface of the agglomerates spherical and narrows the particle size distribution of the agglomerates,
A solid-liquid separator for separating the aggregate from the water to be treated. The particle size distribution control device stirs the water to be treated containing the agglomerates with a stirring force (G) defined by the following formula (1) in a range of 1,000 to 5,000 in a stirring time of 10 seconds to 10 minutes. The water treatment device according to claim 1, wherein
G = (P / (V · μ)) ^1/2 (1)
(Where P is the energy (W) input to the particle size distribution control device, V is the capacity (m ³ ) of the stirring tank provided in the particle size distribution control device and contains the water to be treated, and μ is the viscosity coefficient of water ( kg / m · s).) An aggregating step of aggregating the turbidity and the aggregating agent into an aggregate by mixing the aggregating agent into the water to be treated containing the turbidity;
A particle size distribution control step of making the surface of the aggregate a spherical surface and narrowing the particle size distribution of the aggregate,
A solid-liquid separation step of separating the aggregate from the water to be treated. The particle size distribution control step is a step of stirring the water to be treated containing the agglomerates with a stirring force (G) defined by the following formula (1) of 1,000 to 5,000 and a stirring time of 10 seconds to 10 minutes. The water treatment method according to claim 3, wherein
G = (P / (V · μ)) ^1/2 (1)
(Where P is the energy (W) input to the particle size distribution control step, V is the capacity (m ³ ) of the stirring tank that contains the water to be treated in the particle size distribution control step, and μ is the viscosity coefficient of water (kg / m · Represents s)

Images