JPH07136664A - Dephosphorization of waste water - Google Patents

Abstract

PURPOSE:To easily add a necessary amt. of a dephosphorizing chemical agent to waste water, in a waste water treatment apparatus having a contact aeration tank, by solidifying the dephosphorizing chemical agent by a soluble binder and charging the solidified chemical agent in the aeration tank to solubilize the same. CONSTITUTION:A dephosphorizing chemical agent such as fibrous iron is solidified by a soluble binder to form a solidified chemical agent 1 and the solubilizing amt. thereof is controlled by adjusting the properties of the soluble binder. This solidified chemical agent l is received in a holding net 6 and the holding net 6 is attached to an aeration tank 4 by a hook 10 so as to be positioned above the surface of the internal liquid 7 of the aeration tank 4. When the internal soln. 7 of the aeration tank 4 is aerated and stirred by ejecting air sent by a blower 8 from an air diffusion pipe 9, the solidified chemical agent 1 is dissolved at a constant speed and reacted with a phosphate ion to form a hardly soluble salt and this hardly soluble salt is removed from the internal soln. 7 of the aeration tank in a mode incorporated in sludge.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for dephosphorizing wastewater in wastewater treatment, and more particularly to a method for injecting a dephosphorizing agent.

[0002]

2. Description of the Related Art Conventionally, a biological dephosphorization method, a coagulant addition method, an adsorption method, a crystallization dephosphorization method and the like have been used for removing phosphorus in waste water. However, the biological dephosphorization method, the coagulant addition method, the adsorption method, the crystallization dephosphorization method, etc. are all difficult to control when there is a load fluctuation in the wastewater, and frequent maintenance is required. There was a point.

There is also a method of immersing an iron plate, a steel round bar or the like in an anaerobic filter bed tank, an aeration tank, a settling tank, a sludge storage tank or the like. In this method, iron in a steel plate or the like is dissolved, phosphorus in waste water is made insoluble as an iron compound, and phosphorus is taken into sludge and removed. Therefore, it is an excellent method of simply immersing iron material or steel material in the liquid without incurring the troublesome expense of injecting chemicals such as metal salts in proportion to the amount of wastewater each time to remove phosphorus. Is.

[0004]

The dephosphorization method of immersing an iron plate is an excellent method that is easy to maintain and economically inexpensive. On the other hand, the amount of iron dissolved in the liquid depends on the water load. There was a problem that it was difficult to adjust. Further, since the dissolution rate of iron content is slow and the specific surface area of the iron plate is small, it is necessary to install a considerable amount of the iron plate. further,
There was a problem that as the number of days of treatment after immersion of the iron plate increased, a corrosion-resistant coating was formed in a slime shape on the surface area of the iron plate, the elution of iron ions gradually diminished, and the phosphorus removal rate decreased daily.

The present invention not only provides easy maintenance and economically inexpensive, but also provides a method for removing phosphorus in wastewater by adding a dephosphorizing agent to wastewater in a required amount at a constant rate. To aim.

[0006]

In order to achieve the above object, the method according to the present invention is to immerse a solidifying agent instead of immersing an iron plate. They took advantage of the fact that they were easy to maintain and economically cheap. However, in addition to being easy to maintain and economically inexpensive, the solidifying agent must dissolve in the wastewater at a constant rate and a certain amount of the agent must be added to the wastewater. Therefore, by solidifying the dephosphorizing agent with a soluble binder, the dephosphorizing agent can be effectively solidified by simply immersing it in the waste water. The dephosphorization agent of the solidifying agent is any one or a combination of sand iron, fibrous iron, lime, aluminum powder, fibrous aluminum, aluminum foil, ferric chloride solution, and aluminum sulfate solution. Is. When dissolved, the dephosphorizing agent binds to phosphorus in the water to be treated and becomes insoluble. The soluble binder for solidifying the dephosphorization agent is a mixture of fatty acid ester and the like. In this case, the dephosphorization drug is evenly distributed in the entire volume of the solidified drug, but preferably the concentration of the drug is increased near the center of the solid. This is because the area for maintaining the drainage becomes smaller as the solidifying agent dissolves. As a countermeasure against such a change in the contact area, if several solidifying agents are put in one holding net and replaced one by one at regular time intervals, the sum of the one having a large surface area and the one having a small surface area becomes close to a constant value.

The dissolution rate of the solidified drug is controlled by the type and properties of the soluble binder. By installing this solidifying agent in the aeration tank and dissolving it in the water to be treated, an appropriate amount of the agent can be added. The dephosphorization method aimed at by the present invention can be achieved by adding the dephosphorization agent to the water to be treated by the above-mentioned addition method. Further, the installation location of the solidifying agent may be any of the following.

[0008] The anaerobic filter bed inflow pipe, which is the transfer route of sewage, the transfer pipe from the anaerobic filter bed to the contact aeration tank, the transfer pipe from the aeration tank to the settling tank, and the settling tank to the tertiary treatment device Any one or more of the transfer pipes.

Any of a circulation pipe from a contact aeration tank to an anaerobic filter tank, which is a transfer route of circulating water, a circulation pipe from a precipitation tank to an aeration tank, and a circulation pipe from a tertiary treatment device to an aeration tank. One place

Any one or more of an anaerobic filter bed tank, a sedimentation tank, and a sludge storage tank.

[0011]

The method for dephosphorizing wastewater according to the present invention comprises solidifying a dephosphorizing agent with a soluble binder to form a solidifying agent, immersing the solidifying agent in the wastewater, and adding the dephosphorizing agent. It is characterized by doing. The reason why the solidified drug is used in this way is that the dephosphorization drug is usually in a solid or liquid form and it is difficult to quantitatively add it. By solidifying the dephosphorizing agent with a soluble binder and adjusting the properties of the soluble binder, the amount of dissolution can be easily controlled. As a result, an appropriate amount of drug can be added. The dephosphorization agent solidified by the soluble binder is
Along with the dissolution of the soluble binder, for example, it is added to the aeration tank. The added dephosphorizing agent reacts with phosphate ions in the aeration tank to form a sparingly soluble salt. The sparingly soluble salt is removed from the water to be treated by being incorporated into sludge in the aeration tank or removed by the solid-liquid separation device in the next stage. Therefore, phosphorus in the water to be treated is removed. The type of the soluble binder is selected according to the type of the drug, the properties, the form of dissolution, and the required dissolution rate.

[0012]

Embodiments of the present invention will be described with reference to FIGS.

FIG. 1 is a conceptual vertical sectional view in which a solidified drug is installed in an aeration tank. The solidified chemical 1 is installed in the aeration tank 4 with a holding net 6. The holding net 6 is hung from the hook 10. The hook 10 is attached to the inner side wall of the aeration tank 4 and above the liquid level of the liquid 7 inside the aeration tank. Blower 8 provided outside the aeration tank 4
An air diffuser 9 for supplying more aeration air is installed in the aeration tank 4. The liquid 7 inside the aeration tank maintains a constant liquid level in the aeration tank 4.

FIG. 2 is a partially cut perspective view of the solidified drug 1. In this embodiment, the solidified drug 1 has a structure in which the dephosphorization drug 2 is solidified with a soluble binder 3 to have a diameter of 5 cm and a thickness of 3 cm.

In the embodiment shown in FIG. 1, the dephosphorizing agent 2 was fibrous iron, and the soluble binder 3 was a mixture of fatty acid ester and the like. When air is supplied from the diffuser pipe 9 to the aeration tank 4 in which the solidification agent 1 is installed by the air blower 8 installed outside, the aeration tank internal liquid 7 is agitated. The solidified drug 1 is gradually dissolved by the flow of the aeration tank internal liquid 7 (indicated by an arrow in FIG. 1), and the dephosphorization drug is supplied to the aeration tank internal liquid 7. The dephosphorization agent was dissolved at a constant rate and reacted with phosphate ions in the aeration tank 4 to form a sparingly soluble salt. The sparingly soluble salt was contained in the sludge in the aeration tank and was removed from the liquid 7 inside the aeration tank. As the dephosphorizing agent, sand iron, lime, aluminum powder, fibrous aluminum, aluminum foil, ferric chloride solution and aluminum sulfate solution were used in addition to fibrous iron, but similar results were obtained.

[0016]

Since the present invention is configured as described above, it has the following effects. (1) A dephosphorizing agent can be added to wastewater at a constant rate and in a fixed amount. (2) Since the addition of the dephosphorizing agent to the wastewater is stable, the dephosphorization in the wastewater is stable and can be performed efficiently. (3) Since the method for injecting the dephosphorizing agent is a convenient method of immersing the solidified agent in the waste water, the method according to the present invention is
It is easy to maintain and economically inexpensive. (4) The injection place of the dephosphorization drug may be any place where the solidified drug can be immersed. Therefore, a wide range of injection sites can be selected, and even if the injection sites are attached to a plurality of sites, the maintenance is easy and the cost is economical.

[Brief description of drawings]

FIG. 1 is a conceptual vertical sectional view in which a solidified drug of an example according to the present invention is installed in an aeration tank.

FIG. 2 is a partially cut perspective view of a graphic drug.

[Explanation of symbols]

 1 solidifying agent 2 dephosphorizing agent 3 soluble binder 4 aeration tank 6 retention net 7 aeration tank internal liquid 8 blower 9 aeration diffuser 10 hook

Claims (6)

[Claims] 1. A wastewater treatment apparatus having a contact aeration tank, wherein a dephosphorization agent is solidified with a soluble binder to give a solid agent, and the solidification agent is placed in an aeration tank and dissolved to remove the dephosphorization agent. A method for dephosphorizing waste water by adding a chemical for phosphorus. 2. The dephosphorizing agent is one or a combination of two or more of sand iron, fibrous iron, lime, aluminum powder, fibrous aluminum, aluminum foil, ferric chloride solution and aluminum sulfate solution. Claim 1
Dephosphorization of wastewater described in 3. An anaerobic filter bed inflow pipe, a transfer pipe from the anaerobic filter bed to a contact aeration tank, a transfer pipe from the contact aeration tank to a precipitation tank, which is a transfer path for the solidified chemical,
The method for dephosphorizing wastewater according to claim 1, wherein one or more of the transfer pipes from the settling tank to the tertiary treatment device are arranged. 4. The solidified chemical is circulated from a contact aeration tank which is a circulating water transfer path to an anaerobic filter bed, a precipitation tank to a contact aeration tank, and a tertiary treatment device. The method for dephosphorizing wastewater according to claim 1, wherein the method is arranged in any one of circulation pipes to the air tank. 5. The method for dephosphorizing wastewater according to claim 1, wherein the solidifying agent is placed in an anaerobic filter tank or a precipitation tank. 6. The method for dephosphorizing wastewater according to claim 1, wherein the solidifying agent is placed in a sludge storage tank.