JPH07136500A - Cod component removing material and method and production of cod component removing material - Google Patents

Abstract

PURPOSE:To obtain a COD component removing material low in lining cost and capable of removing COD up to low concn. by fixing fine particles of iron hydroxide to granular matter having a three-dimensional reticulated structure by an org. polymeric gel. CONSTITUTION:An aq. ferric chloride soln. is neutralized with caustic soda to produce amorphous iron hydroxide. This amorphous iron hydroxide is dried to obtain powdery fine particles 2 of amorphous iron hydroxide. These fine particles 2 of this powdery iron hydroxide are added to an aq. sodium alginate soln. to prepare a suspension. Next, polyurethane foam 1 with a reticulated pore size of 2-2.5nm is immersed in the suspension to infiltrate the suspension in the meshes of the polyurethane foam 1. Thereafter, the polyurethane foam 1 is taken out of the suspension to be immersed in an aq. calcium chloride soln. to form a calcium alginate gel 3 in the polyurethane reticulated structure 2 and polyurethane foam granules are taken out of the aq. calcium chloride soln.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a technique for effectively removing COD components contained in sewage, night soil and biologically treated water thereof, various industrial wastewaters, raw water for tap water and the like, particularly COD which is difficult to decompose. It is provided.

[0002]

2. Description of the Related Art Sewage, various industrial wastewater, organic wastewater such as human waste are usually purified by a biological treatment such as an activated sludge method and then discharged into a public water area. BOD and SS can be sufficiently removed by the biological treatment, but biodegradable C
OD is not removed by biological treatment and remains in treated water. As a technique for removing COD remaining in the treated water, an activated carbon adsorption method and a coagulation sedimentation method have been conventionally known. However, when COD is removed to a low concentration by the activated carbon adsorption method, the activated carbon reaches the equilibrium adsorption amount in a short time, so the activated carbon must be replaced frequently, and the running cost is too expensive. In addition, the coagulation-sedimentation method has a serious drawback that a large amount of sludge is produced as a result of the treatment, and therefore, the activated carbon adsorption method or the coagulation-sedimentation method is rarely actually carried out.

RO (reverse osmosis) membranes have recently been studied as a method for removing COD at a high rate, but an efficient method for treating a concentrated liquid generated by membrane separation is a concern. Also, as the COD concentration of the concentrated liquid increases,
There is also a drawback that the D concentration also rises, and there remains a problem to be solved for practical application of the RO film.

[0004]

DISCLOSURE OF THE INVENTION The present invention provides an excellent COD component removing material which can solve the drawbacks of the conventional COD removing method with existing equipment and can remove COD to a low concentration at a low running cost. CO in water using the removal material
It is an object of the present invention to provide a method for removing the D component, and further to provide a production method for producing the removal material.

[0005]

The object of the present invention, which provides the COD component removing material and the method for removing the COD component using the removing material, has been achieved by the removing material and the removing method according to the present invention. That is, (1) succeeded in developing a COD component removing material in which fine particles of iron hydroxide are immobilized on a granular material having a three-dimensional network structure by an organic polymer gel, (2)
It was achieved by a method of removing the COD component in water by filling the fixed bed with the COD component removing material or in contact with raw water in a floating state. As a result of earnest research, the present inventor found that
It has been found that COD can be effectively removed by bringing fine particles of iron hydroxide, particularly amorphous iron hydroxide, immobilized on a granular solid by an organic polymer gel into contact with water containing COD. Is.

Further, the object of the present invention for producing a COD component removing material in which iron hydroxide fine particles are immobilized on an organic polymer gel is achieved by the following production method. That is, (3) 1) a step of preparing a suspension in which fine particles of iron hydroxide are dispersed in an aqueous solution of a water-soluble organic polymer,
2) Step of immersing the three-dimensional network structure granules in the suspension to allow the suspension to penetrate into the network structure of the three-dimensional network structure granules. 3) Take out the three-dimensional network structure granules from the suspension. After that, it is immersed in an aqueous solution of a gelling agent to form a gel of the organic polymer, 4) a manufacturing method comprising a step of taking out the three-dimensional network structure granules from the aqueous solution of the gelling agent and washing with water. It can be manufactured.

Further, the more preferred COD component removing material of the present invention is: (4) The iron hydroxide is amorphous iron hydroxide, the water-soluble organic polymer is sodium alginate, and the three-dimensional network is It can be produced by the method for producing a COD component removing material as described in (3) above, wherein the granular structure-like particles are polyurethane foam particles, and the gelling agent is calcium chloride. COD-containing water and COD of the present invention
In order to bring the component removing material into contact with the COD removing material, a method of passing the raw water through a packed tank in which the COD removing material is packed in a fixed bed or in a floating state is effective.

[0008]

[Function] In order to obtain amorphous iron hydroxide, an aqueous solution of ferric chloride or ferric polysulfate generally called polyiron is neutralized with an alkaline agent such as NaOH or Ca (OH) _2. Then, it is preferable to neutralize the pH to an acidic side, for example, pH 4 to 6, and precipitate iron hydroxide from the aqueous solution. It has been found that when iron hydroxide is deposited at an alkaline pH, the COD removal ability is inferior to that when deposited at an acidic pH. In addition, crystalline iron hydroxide (α, β, γ and FeOO
H) was inferior in COD removal ability to amorphous iron hydroxide. Further, it was also confirmed that aluminum hydroxide has a significantly lower COD removing ability than the amorphous iron hydroxide.

The COD removing material of the present invention comprises amorphous iron hydroxide, calcium alginate, chitosan, agarose,
It is immobilized on a granular solid with an organic polymer gel such as hydroxyethyl cellulose, CMC, modified starch, polyacrylic acid, PVA, and a copolymer of vinyl acetate and methacrylic acid. In particular, organic polymer gels made of calcium alginate, chitosan, polyacrylic acid, PVA, etc. are suitable. More particularly, a gel from calcium alginate is the most suitable immobilizing gel.

As the three-dimensional network structure granular material, a granular material having a three-dimensional network structure such as polyurethane foam and polyethylene foam is suitable for the present invention. Particularly, a granular material having a three-dimensional network structure made of polyurethane foam is most suitable for the present invention. COD of the present invention
A typical example of the method for producing the removing material is a cubic polyurethane foam having a pore diameter of about 2 mm and having a three-dimensional network shape (sponge shape) as a material for fixing amorphous iron hydroxide, and calcium alginate as an organic polymer gel. The case where a gel is used will be described. However, the present invention is not limited to the following description.

Step 1: A suspension in which fine particles of amorphous iron hydroxide are dispersed in a sodium alginate solution is prepared. Step 2: Immerse the polyurethane foam granules in the suspension to penetrate the suspension into the polyurethane foam mesh. Step 3: After removing the polyurethane foam granules from the suspension, they are immersed in an aqueous solution of calcium chloride to gel the sodium alginate as calcium alginate. Step 4: If the polyurethane foam granules are taken out of the calcium chloride aqueous solution and washed with water, the COD of the present invention can be obtained.
A removal material is produced.

FIG. 1 is an enlarged schematic view showing a state in which fine particles of amorphous iron hydroxide are fixed in a mesh structure of polyurethane foam particles by a calcium alginate gel.
It was shown to. In practice, the calcium alginate gel does not necessarily need to be all continuous, and small holes may be formed in the network structure. As a material for immobilizing the fine particles of the amorphous iron hydroxide of the present invention by a gel, the optimum particle diameter of the three-dimensional network material is preferably about 10 to 50 mm. Further, the shape thereof is preferably a square shape because of the ease of molding and the size of the porosity when packed in a fixed bed, but other shapes such as a spherical shape and an ellipsoidal shape may be used. The pore size of the mesh is an important factor, and it is preferably about 0.5 to 4 mm. If the pore size of the mesh is too small, it is difficult for the amorphous iron hydroxide to penetrate inside. Also, if the mesh pore size is too large,
The network structure becomes sparse, and the gel is easily peeled off when the amorphous iron hydroxide is immobilized by the gel.

With the COD removing material as described above, C
In order to remove the OD, the COD-removing material of the present invention may be contacted with the COD-containing water for an appropriate time. When the secondary treated water of the sewage is used as the raw water, the treated water of 5 to 6 mg / liter can be stably obtained for a long time by passing the raw water through the COD removing material. In the present invention,
When the raw water contains phosphoric acid in addition to COD, there is a secondary effect that phosphoric acid can be removed at the same time. For example, since COD and phosphoric acid are contained in the secondary treated water of sewage,
By applying the COD removing material of the present invention, COD and phosphoric acid can be removed from the sewage secondary treated water all at once.

[0014]

[Examples] Specific examples of the method for producing a COD removing material of the present invention and examples of application to secondary treated water of sewage will be described below. However, the present invention is not limited by the following description of specific examples of the manufacturing method and application examples to the treatment.

Example 1: Method for producing COD removing material 20% ferric chloride aqueous solution was adjusted to pH 5 with caustic soda.
Neutralized to ~ 5.5 to produce amorphous iron hydroxide. It was confirmed by X-ray diffraction that the iron hydroxide was amorphous. The amorphous iron hydroxide was dried to obtain powdery amorphous iron hydroxide. This powdered iron hydroxide was added to a sodium alginate aqueous solution having a sodium alginate concentration of 1.5% so that the weight% concentration was 30% to prepare a suspension. Next, a cube-shaped polyurethane foam having one side of 10 mm and having a mesh hole diameter of 2 to 2.5 mm was immersed in the suspension for 5 to 10 minutes to infiltrate the suspension into the mesh of the polyurethane foam.

After that, the polyurethane foam was taken out from the suspension and put in a 20% aqueous solution of calcium chloride.
After soaking for a minute, a calcium alginate gel is formed in the polyurethane foam network structure, and then the polyurethane foam granules are taken out from the calcium chloride aqueous solution and washed with water. The COD removing material of the present invention can be manufactured by the above operation. As is clear from the above description, C of the present invention
The OD removing material is easy to manufacture. Therefore, the manufacturing cost is low.

Example 2: COD removal test A performance test of the COD removal material of the present invention was conducted under the conditions shown in Table 1. (By column water flow test.) Table 2 shows the results of the COD removal treatment. As a comparative example, the same performance test was performed using granular activated carbon (particle diameter 2 mm). The results are shown in Table 3.

[0018]

[Table 1]

[0019]

[Table 2]

[0020]

[Table 3]

As is clear from the comparison of the results shown in Tables 2 and 3, the COD removing material of the present invention has an excellent COD removing effect, and stably provides a low COD-treated water for a long period of time. I was able to. Further, as can be seen from the results in Table 2, phosphorus was also highly removed at the same time by the COD removing material of the present invention.

[0022]

The COD removing material of the present invention has the following important effects. COD obtained by using low cost iron hydroxide
Scavengers have a much lower product price than activated carbon and are ideal for wastewater treatment where treatment costs should be kept as low as possible. Amorphous iron hydroxide is particularly suitable as the iron hydroxide used. Since the COD removing material has a large particle size, even when applied to raw water containing SS, the packed bed is not closed by SS. Since the COD removing material is lightweight, it is easy to handle. COD and phosphorus can be removed at the same time.

[Brief description of drawings]

FIG. 1 is an enlarged schematic view of a state where fine particles of amorphous iron hydroxide are fixed in a mesh structure of polyurethane foam by calcium alginate gel.

[Explanation of symbols]

 1 Polyurethane foam mesh 2 Amorphous iron hydroxide particles 3 Calcium alginate gel

Claims (4)

[Claims] 1. A COD component removing material, characterized in that fine particles of iron hydroxide are fixed to a granular material having a three-dimensional network structure by an organic polymer gel. 2. A method for removing COD components in water, which comprises filling the fixed bed with the COD component removing material or bringing the material into contact with raw water in a floating state. 3. A step of 1) a step of preparing a suspension in which fine particles of iron hydroxide are dispersed in an aqueous solution of a water-soluble organic polymer, 2) a three-dimensional network-structured granular material is dipped in the suspension to form a three-dimensional network. Step of infiltrating the suspension into the network structure of granular structure-like particles, 3) After taking out the three-dimensional network structure granular material from the suspension, immersing it in an aqueous gelling agent solution to form a gel of the organic polymer. And 4) a step of removing the three-dimensional network structure granular material from the gelling agent aqueous solution and washing with water, the method for producing a COD component removing material. 4. The iron hydroxide is amorphous iron hydroxide, the water-soluble organic polymer is sodium alginate, and the three-dimensional network structure granules are polyurethane foam granules. The method for producing a COD component removing material according to claim 3, wherein the agent is calcium chloride.