JPH11147088A - Dephosphorization of waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a waste water dephosphorizing method with reduced treatment cost, not generating a troublesome flocculated precipitate and allowing reutilizing adsorbed phosphorine as resources. SOLUTION: After waste water is subjected to membrane separation treatment by a membrane separator 1 having a filter membrane unit 2, this membrane transmitted water is sent to a receiving tank 7 provided at a position higher than a phosphorus adsorbing tower 9. Subsequently, the membrane transmitted water is supplied to the phosphorus adsorbing tower 9 from the receiving tank 7 in a constant flow rate by a flow rate automatic adjusting valve 8 so that the water passing condition in the phosphorus adsorbing tower 9 becomes LV = about 150 (cn/h) and SV = about 3(1/h). The pH of the membrane separated treated water at the inlet of the phosphorus adsorbing tower is 6.5-7.5 and the total phosphoric acid ions of the membrane separated treated water at the inlet of the phosphorus adsorbing tower are 7-8 (mg-p/1). The phosphorus adsorbing tower 9 is packed with a phosphorus adsorbing agent 21 up to the height about half from the tower bottom. A head having height about three times the diameter of the tower is provided to an adsorbent filling part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to wastewater from various factories such as the chemical, food, pharmaceutical, and fertilizer industries,
The present invention relates to treatment of wastewater from treatment facilities such as sewage treatment plants and human waste treatment plants, and more particularly to a method for removing phosphorus contained in wastewater in the form of orthophosphate ions, polyphosphate ions, organic phosphate ions, and the like. Things.

[0002]

2. Description of the Related Art Conventionally, to remove phosphorus from wastewater, aluminum salts such as aluminum sulfate (sulfuric acid band) and polyaluminum chloride (PAC) as a coagulant, and ferrous sulfate and ferric chloride such as ferric chloride are used. A method of coagulating and precipitating phosphorus using an iron salt was generally used.

[0003]

However, in the above-mentioned conventional method, a large amount of coagulant is used continuously, so that the treatment cost is high, and a large amount of sediment is generated from the coagulant as sludge, and There was a problem of difficulty in treatment or management, and it was difficult to recycle sludge.

[0004] In view of the above, the present invention provides a method for removing phosphorus from wastewater, which can reduce the processing cost, does not generate troublesome coagulated precipitates, and can recycle adsorbed phosphorus. The purpose is to provide.

[0005]

A first method for removing phosphorus according to the present invention is characterized in that waste water is subjected to membrane separation treatment, and then to phosphorus absorption treatment with a phosphorus adsorbent containing zirconium ferrite hydrate as a constituent material. How to

[0006] The pH of the membrane separation treatment water is preferably 5.8 to
8.6, more preferably in the range of 6.5 to 7.5, to improve the performance of the phosphorus adsorbent.

Further, the pH of the membrane separation treatment water is adjusted to 1.0 to 6.
It is also preferable to adjust the pH to 5 and adjust the pH of the phosphorus adsorption treatment water to 5.8 to 8.6. In this case, the phosphorus adsorption capacity of zirconium ferrite hydrate greatly increases. As the pH adjusting agent, a general acidic aqueous solution such as sulfuric acid or hydrochloric acid, or a general alkaline aqueous solution such as caustic soda or caustic potash is used.

[0008] The water flow conditions in the phosphorus adsorption tower are linear velocity (L
V), preferably 50 to 500 (cm / h), more preferably 100 to 250 (cm / h), space velocity (SV)
1 to 10 (1 / h), more preferably 2 to 5 (1 / h).
h).

It is preferable that the membrane separation treatment water is once received in a receiving tank located at a position higher than the adsorption tower. Thus, water can be continuously supplied from the receiving tank to the adsorption tower even during the intermittent operation of the membrane separation device.

It is preferable that the flow rate from the receiving tank to the phosphorus adsorption tower be adjusted by a flow rate control valve or a combination of a submersible pump and a measuring device having a triangular weir. It is preferable that the flow control valve be an automatic flow control valve, and that the submersible pump be one with an anti-spin function. The above-mentioned measuring device supplies water to the adsorption tower at a constant flow rate by the function of the triangular weir, and the weir plate of the triangular weir is slidable up and down, so that the supply amount can be changed.

In supplying the treated water to the phosphorus adsorption tower, a head having a height of preferably 0.5 to 5 times the diameter of the tower is provided at the top of the adsorption tower. In this case, in the phosphorus adsorption tower, water is passed by a weight filtration method using a head pressure.

It is also preferable to disperse the membrane separation treatment water at the top of the phosphorus adsorption tower. This dispersion is performed using, for example, a flat dispersion plate orthogonal to the flow direction of the treated water. By this dispersion, the water for membrane separation treatment can be uniformly supplied into the adsorption tower, and sufficient phosphorus adsorption treatment can be performed.

The phosphorus adsorbent used in the first dephosphorization method is
It is based on zirconium ferrite hydrate. For example, "Seventor P" manufactured by Takeda Pharmaceutical Co., Ltd. is preferably used. This is to selectively adsorb and remove phosphate ions by utilizing the ion exchangeability derived from the surface hydroxyl groups possessed by zirconium ferrite hydrate. Agent.

The average particle diameter of the phosphorus adsorbent used in the first phosphorus removal method is preferably 0.1 to 4.0 mm, more preferably 0.2 to 1.5 mm.

[0015] The first dephosphorization method reaches a breakthrough point when it is carried out for a certain time. After the breakthrough, in order to wash the phosphorus adsorbent in the phosphorus adsorption tower with a chemical solution, it is preferable to supply a detergent from the chemical supply line to the phosphorus adsorption tower. The drug supply line is connected to a supply line for the liquid to be subjected to the adsorption treatment. As the cleaning agent, an aqueous alkali solution such as caustic soda is preferable. This washing removes phosphate from the phosphorus adsorbent. Next, in order to activate the adsorbent, an acid such as sulfuric acid or hydrochloric acid is passed from the drug supply line to the adsorbent filling section to regenerate the phosphorus adsorbent.

The phosphorus adsorption tower is preferably one in which a cartridge comprising a plurality of columns filled with a phosphorus adsorbent is replaceably incorporated in the phosphorus adsorption tower. The use of cartridges makes it easy to replace the adsorbent,
Also, maintenance of the phosphorus adsorption tower is easy.

It is also preferable to provide an overflow line from the receiving tank to the discharge tank. Even if the membrane of the membrane separation device is damaged for any reason and suspended matter flows out of the device and the phosphorus adsorption tower is clogged, the overflow of the receiving tank flows out to the discharge tank by the same line and the adsorption tower Water can be prevented.

In a second method for removing phosphorus according to the present invention, a phosphorus adsorbent containing zirconium ferrite hydrate as a constituent material is charged into a raw water side of a membrane in a membrane separation apparatus, and the wastewater is subjected to a phosphorus adsorption treatment. This is a method characterized by performing a membrane separation treatment.

It is preferable that the bottom of the membrane separation device is formed in a hopper shape. It is also preferable to diffuse air into the membrane separation device. By the aeration, the phosphorus adsorbent is uniformly stirred in the membrane separation device, and the phosphorus removal treatment is efficiently performed. Sludge and adsorbent deposited from the bottom of the membrane separator are usually withdrawn intermittently. Thereby, the replacement of the adsorbent can be easily performed.

The pH of the waste water in the membrane separation device is preferably in the range of 5.8 to 8.6, more preferably in the range of 6.5 to 7.5.

Further, the pH of the waste water in the membrane separation device is adjusted to 1.0
~ 6.5 and adjust the pH of the phosphorus adsorption treated water to 5.8 ~
Adjustment to 8.6 is also preferable. The selection of the pH value is performed in consideration of the acid resistance of the membrane in the membrane separation device and the activated sludge in the wastewater. As the pH adjusting agent, a general acidic aqueous solution such as sulfuric acid or hydrochloric acid, or a general alkaline aqueous solution such as caustic soda or caustic potash is used.

The phosphorus adsorbent used in the second dephosphorization method also includes
It is based on zirconium ferrite hydrate. For example, "Seventor P" manufactured by Takeda Pharmaceutical Co., Ltd. is preferably used.

The average particle size of the adsorbent used in the second dephosphorization method is preferably from 0.1 to 4.0 mm, more preferably from 0.2 to 1.5 mm.

[0024]

Next, the present invention will be specifically described based on examples. Note that the same components and portions are denoted by the same reference symbols throughout the drawings, and redundant description will be omitted.

Embodiment 1 In FIG. 1, a filtration membrane unit (2) having a plurality of hollow flat membrane modules is arranged in a tank of a membrane separation device (1). Although not shown, each flat membrane module is composed of two flat membranes arranged in opposition, and a frame-shaped spacer arranged between the peripheral portions of both flat membranes. A suction tube is connected to each flat membrane module so as to communicate with the inside of the hollow portion,
All suction pipes are connected to one suction pump (3). Note that, as the filtration membrane unit (2), a module using a hollow fiber membrane can be applied instead of a flat membrane module using a flat membrane. A plurality of air diffusion tubes (4) are arranged below the filtration membrane unit (2), and air is sent into the air diffusion tubes (4) by a blower (5). The lower end of the membrane separation device (1) is shaped like a hopper tapered downward, and a drain pipe (6) is provided at the bottom.

After treating the wastewater by the membrane separation device (1) having the above structure to remove activated sludge and the like, the membrane permeated water is collected by a suction pump (3) at a position higher than the phosphorus adsorption tower (9).
Send to (7). Next, the membrane permeated water is supplied from the receiving tank (7) by the automatic flow rate regulating valve (8) so that the water passing condition in the phosphorus adsorption tower (9) is LV = about 150 (cm / h) and SV = about 3 (1). / H)
Is supplied to the phosphorus adsorption tower (9) at a constant flow rate.
The pH of the membrane separation treatment water at the inlet of the phosphorus adsorption tower is 6.5 to 7.
5 The total phosphate ions in the membrane separation treatment water at the inlet of the phosphorus adsorption tower are 7 to 8 (mg-P / liter).

The phosphorus adsorption tower (9) is filled with a phosphorus adsorbent (21) to a height of about half from the bottom of the tower, and a dephosphorized water line (10) is arranged at the bottom. Dephosphorization treatment water line (10)
Goes up the outside of the column from the bottom of the column to the top of the column, and then reaches the discharge tank (11) so that a head of about three times the diameter of the column is formed above the adsorbent packed section.

As the phosphorus adsorption tower (9), there is provided one in which a cartridge comprising a plurality of columns filled with a phosphorus adsorbent is exchangeably incorporated in the phosphorus adsorption tower, and the necessity of replacing the adsorbent arises. When replacing the cartridge.

As the adsorbent (21), "Seventor P" manufactured by Takeda Pharmaceutical Co., Ltd. based on zirconium ferrite hydrate is used. This adsorbent has an average particle size of about 1
mm granulated product.

When the dephosphorization treatment is carried out for the above-mentioned flow rate for a certain time, the breakthrough point is reached. This is shown in the graph of FIG. The breakthrough point is defined as total phosphate ion outlet concentration / total phosphate ion inlet concentration = 0.1.

The phosphorus adsorbent used in the method of the present invention has a property that it selectively adsorbs a large amount of phosphate ions in the pH range of about 1 to 7, but hardly adsorbs phosphate ions on the alkali side. Therefore, using this adsorbent,
After performing a phosphate ion adsorption operation in a liquid in an acidic to neutral range of 8.6, phosphate ions are desorbed with an alkaline aqueous solution, and then the adsorbent is treated with an acidic aqueous solution to regenerate. be able to. For example, when the present adsorbent having adsorbed phosphate ions is immersed in a 5% by weight aqueous sodium hydroxide solution for several hours, the adsorbed phosphate ions are desorbed. This is washed with water and immersed in a 0.5% sulfuric acid aqueous solution for several hours, whereby the adsorbent is reactivated and the initial adsorption performance is restored. The alkaline aqueous solution used for desorption is
An aqueous solution containing another alkali such as potassium hydroxide may be used. The alkali concentration of the alkaline aqueous solution is 0.1
It may be about 20% by weight. The acidic aqueous solution used for the activation may be an aqueous solution containing an acid such as hydrochloric acid or nitric acid.
The concentration of the acid may be about 0.1 to 10% by weight.

This series of desorption and activation operations can be performed while the column is filled with the adsorbent. That is, the regeneration can be easily performed by passing an alkaline aqueous solution and an acidic aqueous solution through the column in order after the adsorption operation to the column filled with the adsorbent. In this case, the flow direction may be either an upward flow or a downward flow.

In this regeneration operation, a washing operation can be performed using water or air to prevent clogging and the like. The washing water is returned to the treated raw water.

The phosphate ions desorbed in this regeneration operation can be recovered in the form of phosphate. For example, phosphate ions desorbed with sodium hydroxide can be recovered as sodium phosphate crystals by using a commonly used crystallization method. This can be reused as a valuable phosphorus resource.

To wash the phosphorus adsorbent in the phosphorus adsorption tower, a caustic soda aqueous solution is flowed into the adsorption tower from a chemical supply line (13) provided in the supply line of the liquid to be subjected to the adsorption treatment, and the phosphorus is removed from the adsorbent. The acid salt is eliminated. Thereafter, sulfuric acid is passed through the chemical supply line to activate the adsorbent, and the adsorbent is regenerated.

Dephosphorized water discharged from the bottom of the phosphorus adsorption tower (9) is sent to a discharge tank (11) by a line (10). Also,
The chemical solution used for washing the adsorbent is withdrawn from the bottom of the column by the line (14).

An overflow line (12) is provided from the receiving tank (7) to the discharge tank (11). As a result, even if the membrane of the membrane separation device is damaged for some reason and suspended matter flows out of the device and the phosphorus adsorption tower (9) is clogged, overflow of the receiving tank (7) is performed by the line. The discharge tank
The water is discharged to (11) to prevent overflow of the adsorption tower.

The phosphorus removal rate of the treated water obtained by the above treatment is shown in the graph of FIG. From this graph, it was confirmed that the phosphorus removal method according to the present invention exhibited an excellent phosphorus removal effect.

Embodiment 2 In FIG. 2, in this embodiment, the flow rate from the receiving tank (7) to the phosphorus adsorption tower (9) is controlled by the submersible pump (15)
And a measuring device (16) having a triangular weir. The measuring device (16) supplies water to the phosphorus adsorption tower (9) at a constant flow rate by the function of the triangular weir, and the weir plate of the triangular weir is slidable up and down, so that the supply amount can be changed. it can. Excess water is received from the measuring device (16)
Returned to (7).

At the end of the line from the measuring device (16) to the phosphorus adsorption tower (9), a disc-shaped dispersion plate (1
7) is disposed so as to face the liquid level of the phosphorus adsorption tower (9). As shown in FIG. 4, the dispersion plate (17) has four dispersion holes (20) on the lower surface. Thereby, the permeated water is dispersed and supplied to the phosphorus adsorption tower (9) at a uniform flow rate over the entire liquid surface.
Other points are the same as the first embodiment.

Embodiment 3 Referring to FIG. 8, in this embodiment, a sulfuric acid aqueous solution is added to the membrane permeated water from the acid aqueous solution tank (22) by the feed pump (23) in the receiving tank (7). Adjust the pH to 3.0. Further, in the discharge tank (11), an aqueous caustic soda solution is added to the dephosphorized water from the alkaline aqueous solution tank (24) by the liquid supply pump (25), and the pH of the dephosphorized water is adjusted to 7.0. Other points are the same as the first embodiment.

As a result, the total phosphorus removal rate of the treated water was 90%.
The number of days required to reach the breakthrough is 45 days.
As can be seen from the comparison with Example 1, the number of days increased to about three times the number of days in Example 1.

Embodiment 4 In FIG. 3, in this embodiment, a phosphorus adsorbent (18) is directly charged into the raw water side of the filtration membrane unit (2) in the membrane separation device (1) to subject the waste water to a phosphorus adsorption treatment. Then, a membrane separation treatment is performed. The permeated water is discharged from the membrane separator (1) by the suction pump (3). As the adsorbent, "Seventor P" manufactured by Takeda Pharmaceutical Co., Ltd. based on zirconium ferrite hydrate is used as in Example 1. The amount of adsorbent used is approximately 2 for an effective volume of 60 liters of the membrane separation device.
500 g.

A plurality of air diffusion tubes (4) are arranged below the filtration membrane unit (2) in the tank of the membrane separation device (1). Air is blown into the air diffuser (4) by the blower (5). By the aeration, the phosphorus adsorbent is uniformly stirred in the membrane separation device, and the phosphorus removal treatment is efficiently performed.

The bottom of the tank of the membrane separation device (1) is formed in a hopper shape tapered downward.

When the phosphorus adsorbent exceeds the breakthrough point, the air diffusion is stopped. Since the phosphorus adsorbent (18) has a higher specific gravity than activated sludge, it precipitates preferentially. Pullout line at bottom of hopper (1
Take out the adsorbent together with a part of the sludge from 9) and add a new adsorbent from above. The removed adsorbent is regenerated and reused.

The pH of the waste water in the membrane separation device is preferably in the range of 5.8 to 8.6, more preferably in the range of 6.5 to 7.5.

Since the adsorption capacity of the adsorbent has been confirmed,
The phosphorus adsorption amount, breakthrough time, and the like are predicted in advance based on the amount of the adsorbent charged into the membrane separation tank.

FIG. 7 is a graph showing the phosphorus removal rate of the treated water obtained by the above treatment. From this graph, it was confirmed that the phosphorus removal method according to the present invention exhibited an excellent phosphorus removal effect. Example 5 In FIG. 9, in this example, acid was added to wastewater to be treated in the tank of the membrane separation device (1). Liquid supply pump from aqueous solution tank (22)
5. A sulfuric acid aqueous solution was added according to (23) to adjust the pH of the waste water to 6.
Adjust to 0. The permeated water is stored in the discharge tank (11) by the suction pump (3).
The pH of the dephosphorized water is adjusted to 7.0 by adding an aqueous solution of caustic soda with the feed pump (25). Other points are the same as the fourth embodiment.

As a result, the total phosphorus removal rate of the treated water was 90%.
The number of days required to reach the breakthrough is 22 days, as shown in FIG.
As is clear from the comparison with Example 1, the number of days in Example 4 was about 1.
It grew 5 times.

[0051]

According to the method for removing phosphorus from wastewater according to the present invention, the processing cost can be reduced, no troublesome aggregates are generated, and the adsorbed phosphorus can be recycled.

[Brief description of the drawings]

FIG. 1 is a flowchart showing Embodiment 1 of the present invention.

FIG. 2 is a flowchart showing a second embodiment of the present invention.

FIG. 3 is a flowchart showing a fourth embodiment of the present invention.

FIG. 4 is a bottom view showing a disk-shaped dispersion plate.

FIG. 5 is a graph showing a breakthrough curve.

FIG. 6 is a graph showing the total phosphorus removal rate.

FIG. 7 is a graph showing the total phosphorus removal rate.

FIG. 8 is a flowchart showing a third embodiment of the present invention.

FIG. 9 is a flowchart showing Example 5 of the present invention.

[Explanation of symbols]

 (1): Membrane separation device (7): Receiving tank (8): Automatic flow control valve (9): Phosphorus adsorption tower (11): Discharge tank (15): Submersible pump with anti-spin function (16): Triangular weir (17): Dispersion plate (19): Extraction line (18) (21): Adsorbent (22): Acid aqueous solution tank (24): Alkaline aqueous solution tank

 ──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Tomoki Matsumoto 1-7-89 Minami Kohoku, Suminoe-ku, Osaka-shi Inside Tachibana Shipbuilding Co., Ltd. issue

Claims (22)

[Claims] 1. A method for removing phosphorus from wastewater, comprising subjecting the wastewater to membrane separation treatment, and then subjecting the wastewater to a phosphorus adsorption treatment using a zirconium ferrite hydrate as a constituent material. 2. The method according to claim 1, wherein the pH of the membrane separation treatment water is adjusted to 5.8 to 8.6. 3. The method according to claim 2, wherein the pH of the membrane separation treatment water is adjusted to 6.5 to 7.5. 4. The method according to claim 1, wherein the pH of the membrane separation treatment water is adjusted to 1.0 to 6.5, and the pH of the phosphorus adsorption treatment water is adjusted to 5.8 to 8.6. Method. 5. The water passing condition in the phosphorus adsorption tower is 50 to 50 in LV.
The method according to claim 1, wherein the method is 500 (cm / h) and the SV is 1 to 10 (1 / h). 6. The water passing condition in the phosphorus adsorption tower is 100 at LV.
The method according to claim 5, characterized in that it is 250 to 250 (cm / h) and SV is 2 to 5 (1 / h). 7. The membrane separation treatment water is temporarily received in a receiving tank located at a position higher than the adsorption tower, and then sent to the phosphorus adsorption tower, and the flow to the adsorption tower is controlled by a flow control valve, or a submersible pump and a triangular weir are used. 7. The method according to claim 1, wherein the adjustment is carried out by means of a combination with a weighing device. 8. When the membrane separation treatment water is passed through the adsorbent filled section of the adsorption tower, a 0.5 mm diameter of the tower is placed on the adsorbent filled section.
2. A water head having a height of about 5 to 5 times is provided.
The method according to any one of claims 1 to 7. 9. The method according to claim 1, wherein the membrane separation treatment water is dispersed at the top of the phosphorus adsorption tower. 10. The method according to claim 1, wherein the phosphorus adsorbent in the phosphorus adsorption tower is washed with a chemical detergent. 11. The method according to claim 1, wherein a cartridge comprising a plurality of columns filled with the phosphorus adsorbent is replaceably incorporated in the phosphorus adsorption tower. 12. The phosphorus adsorbent has an average particle size of 0.1 to 4.
12. The method according to claim 1, wherein the distance is 0 mm.
The method described in the section. 13. The phosphorus adsorbent having an average particle size of 0.2 to 1.
13. The method according to claim 12, wherein the distance is 5 mm. 14. A raw water side of a membrane in a membrane separation device,
A method for removing phosphorus from wastewater, comprising introducing a phosphorus adsorbent containing zirconium ferrite hydrate as a constituent material, subjecting the wastewater to a phosphorus adsorption treatment, and then subjecting the wastewater to a membrane separation treatment. 15. The pH of wastewater in the membrane separation device is adjusted to 5.8 to
The method according to claim 14, wherein the control is performed at 8.6. 16. The pH of the waste water in the membrane separation device is adjusted to 6.5 to 16.
The method according to claim 15, wherein the control is performed at 7.5. 17. The method according to claim 14, wherein the pH of the waste water is adjusted to 1.0 to 6.5, and the pH of the phosphorus adsorption treated water is adjusted to 5.8 to 8.6. 18. The method according to claim 14, wherein the bottom of the membrane separation device is formed in a hopper shape. 19. The method according to claim 14, wherein air is diffused into the membrane separation device. 20. The sludge and the phosphorus adsorbent deposited from the bottom of the membrane separation device are withdrawn.
20. The method according to any one of claims 19 to 19. 21. The phosphorus adsorbent having an average particle size of 0.1 to 4.
21. The method according to claim 14, wherein the distance is 0 mm. 22. The phosphorus adsorbent having an average particle size of 0.2-1.
22. The method according to claim 21, wherein the distance is 5 mm.