JPH10314779A - Method for biological treatment of organic solid-containing wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To remove efficiently organic matter solid contained in wastewater by a method wherein a microbe fixing carrier is filled in a treating tank for treating organic solid containing wastewater, and brought in contact with treating water. SOLUTION: A wastewater treating device 10 is used for treatment of organic solid containing wastewater, and prinipally composed of a precipitation separation tank 11, a contact aeration tank 12, and an aerobic digestion tank 13. The aerobic digestion tank 13 is so constituted that an inside of the tank is kept in an aerobic atmosphere with air blown out from an diffuser 131 provided to a tank bottom part, and the solid in solid concentrated wastewater 112 is principally treated by decomposition with action of the aerobic microbe. When cellulose carriers of about 5 mm side cube 3...3 are filled in the aerobic digestion tank 13 herein, microbes are solidified by sticking or the like inside those carriers 3...3 or both of the surface and the inside. Thereby, a growth concentration of the microbe is raised in the aerobic digestion tank 13, and a decomposition rate of the solid and material difficult to be decomposed can be raised.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a biological treatment method for wastewater containing organic solids generated in food processing factories, restaurants, houses, and the like.

[0002]

2. Description of the Related Art In Japan, where most of the population is concentrated in a narrow urban area, the problem of garbage has been highlighted as a very serious social problem, and interest in reducing and recycling garbage is increasing.

[0003] Among them, garbage generated in food processing factories, restaurants, houses, etc., which accounts for about one-third of combustible garbage, emits a bad smell and is difficult to recycle. Most are collected separately and disposed of by incineration or burial.

[0004] Such a processing method requires a great deal of labor for transporting, collecting and processing, and in the case of burial processing, a large site is required, and further, adverse effects on the surrounding environment such as odor and leachate are serious. It has been taken up as a major social issue.

[0005] For this reason, each maker is working on the development of a method and an apparatus for treating garbage in units of discharge points. Among them, there is a method of fermenting garbage by the action of microorganisms, reducing the volume and composting, recycling it as compost in vegetable gardens, etc.Also, after crushing garbage, perform processing such as dehydration and compression to reduce the volume There is a method of reducing the amount of garbage, and a method of anaerobically or aerobically treating garbage with wastewater after crushing the garbage with a disposer (crusher).

[0006]

Among the above-mentioned methods, the method of composting garbage requires a space for installing the apparatus and has a problem of bad smell. In an apartment house or the like that does not have a field or a garden, some can be used as compost, but most of them cannot be used, and a new treatment method must be adopted.

[0007] In the processing methods such as dehydration and compression, the installation space of the apparatus is similarly required, and the processed garbage must be similarly separated and recovered as garbage or combustible refuse. .

On the other hand, in the method of treating garbage together with wastewater by the action of living organisms, garbage (organic solid matter) crushed by a disposer can be decomposed and removed. Although there are restrictions on the above, if the concentration of pollutants in the wastewater is reduced below a certain reference value, the wastewater can be discharged to the sewerage system, and there is no new treatment problem related to decomposition product treatment. In addition, the treatment tank is buried underground, and no special installation space is required on the ground.

Although the method of treating garbage together with the wastewater is superior to other methods,
The garbage wastewater crushed by the disposer contains a large amount of organic solids, and the solids need to be decomposed in a larger amount in a short time.

The literature (Journal of the Japan Society of Water Treatment Biology Vol. 29, No. 2-11, 1993) describes the anaerobic and aerobic decomposition characteristics of ground food solids. It is recognized that the decomposition of the organic solid requires a longer time than the decomposition of the organic substance. The proportion of non-degradable solids also varies depending on the type of food, but some of them show a considerable proportion.

Therefore, many techniques for efficiently decomposing pollutants such as organic solids by biological treatment have been proposed. As one example, Japanese Patent Application Laid-Open No. 58-20291 discloses a processing apparatus having both a precipitation action and an aeration action.

This publication describes that organic solids are converted into water-soluble organic substances by the action of microorganisms by aeration and the solids are completely removed from the processing tank.
In most cases, garbage coexists with hard-to-decompose solids such as fibers and inorganic solids such as sand.When sedimentation is used, these substances are concentrated and accumulated in the treatment tank. In practice, it is necessary to extract sludge during use.

[0013] In addition, microorganisms that degrade hard-to-degrade solids have a slow growth rate, and if drainage is discharged out of the treatment tank, the concentration in sludge will be low. Gets worse. Therefore, in order to maintain good decomposition performance, it is necessary to lengthen the residence time in the processing tank,
The capacity of the processing tank becomes large, so that a large installation space is required.

The present invention has been made in view of such circumstances, and it is possible to efficiently remove organic solids contained in wastewater, and to reduce the size of a wastewater treatment tank. Another object of the present invention is to provide a biological treatment method for wastewater containing organic solids.

[0015]

SUMMARY OF THE INVENTION To achieve the above object, the present invention is a method for decomposing organic solids contained in wastewater by biological treatment. In the processing tank to be filled, the microorganism-immobilized carrier is filled,
Characterized by contact with treated wastewater.

As described above, when the carrier for immobilizing microorganisms is filled in the treatment tank, the microorganisms are immobilized on the inside of the carrier or on both the surface and the inside by adhesion or the like. As a result, the growth amount of the microorganisms in the treatment tank increases, and the decomposition rate of the organic solid contained in the wastewater increases.

Also, by filling the carrier, microorganisms capable of decomposing hardly decomposable substances grow at a high density.
The decomposition rate of the hardly decomposable substance also increases. Here, the biological treatment method of the present invention is preferably applied to a separation tank for separating organic solid matter-containing wastewater into solid matter concentrated wastewater and separated wastewater, and a solid matter concentrated wastewater and a separated wastewater separated by the separation tank. When implemented in a wastewater treatment device equipped with a digestion tank and a wastewater treatment tank that are treated by aerobic biological treatment means, if the digestion tank is filled with a microorganism-immobilized carrier, it is difficult to decompose organic solids. The decomposition rate of the insoluble substance is increased, and accumulation of the insoluble substance in the digestion tank can be prevented.

As the microorganism-immobilized carrier used in the biological treatment method of the present invention, microorganisms such as organic synthetic polymer materials, natural polymer materials, and inorganic materials can be grown inside the carrier or both on the surface and inside. Any material can be used as long as it has good fluidity in a liquid having a specific gravity of about 1.

Examples of the organic synthetic polymer carrier include polyvinyl alcohol, polyethylene glycol, polyester, polyolefin such as polyethylene and polypropylene, polyurethane, polyacrylamide and epoxy resins.

As the natural polymer carrier, cellulose,
Carrageenan, calcium alginate and the like can be mentioned. Examples of the inorganic carrier include activated carbon, anthracite, zeolite, quartz sand, pumice, cristobalite and the like.

These carriers may be subjected to intermolecular cross-linking, intramolecular cross-linking, etc. in order to further increase strength, durability and the like.
The microorganisms to be immobilized on these carriers are, for example, pure cultures of bacteria, actinomycetes, yeasts, molds, microalgae, etc., cultured in wastewater containing organic solids from garbage and isolated. It may be cultured. Further, activated sludge such as sewage and industrial wastewater having an activity of decomposing organic solids-containing wastewater of garbage may be used.

As a method for immobilizing microorganisms on a carrier, a comprehensive immobilization method in which microorganisms are incorporated into a fine lattice structure in the carrier,
Alternatively, any of the binding immobilization methods for attaching or retaining microorganisms may be used.

Examples of the shape of the carrier include a cube, a rectangular parallelepiped, a sphere, a solid cylinder, a hollow cylinder and the like, and irregularities may be provided to increase the surface area. Further, a foamed one may be used.

One side of a cubic or cuboid carrier is 10 mm
It is preferably about 30 mm. Further, it is preferable that the average diameter of the sphere, the columnar body, and the cylindrical body is also about 10 mm to 30 mm.

The packing ratio of the carrier into the processing tank is as follows.
The range is suitably from 50% to 50%, preferably from 5% to 30%.

[0026]

FIG. 1 is a diagram showing an example of a wastewater treatment apparatus to which the biological treatment method of the present invention is applied. The wastewater treatment apparatus 10 shown in FIG. 1 is an apparatus used for treating organic solid matter-containing wastewater generated from a detached house in a sewerage maintenance area.
Precipitation separation tank 11, contact aeration tank 12, and aerobic digestion tank 1
3 mainly.

The sedimentation / separation tank 11 is a device for separating wastewater containing organic solids into solid wastewater and separated wastewater. The wastewater is used to collectively discharge the disposer wastewater and kitchen wastewater generated at the sink of a detached house. Tube 1 is connected. The solids separated in the sedimentation separation tank 11 are transferred to the aerobic digestion tank 13 together with the surrounding liquid by the air lift pump 14 as solids concentrated wastewater 112.

The aerobic digestion tank 13 has a structure in which the inside of the tank is maintained in an aerobic atmosphere by air jetted from a diffuser 131 provided at the bottom of the tank. Decomposes solids mainly.

On the other hand, the separated drainage 111 from which solids have been removed in the sedimentation separation tank 11 is led to the contact aeration tank 12. The contact aeration tank 12 is also a tank for performing aerobic biological treatment. The inside of the tank is maintained in an aerobic atmosphere by air ejected from an air diffuser 121 at the bottom of the tank, and the separated wastewater 111 is separated by aerobic microorganisms. Decompose the soluble pollutants.

In the above arrangement, the disposer drain and the kitchen drain flow into the sedimentation separation tank 11 through the drain pipe 1,
The solids-concentrated wastewater 112 separated in the sedimentation separation tank 11
Is transferred to the aerobic digestion tank 13 by the air lift pump 14, in which the solids contained in the solids concentrated wastewater 112 are decomposed by the action of the aerobic microorganisms. Then, in the aerobic digestion tank 13, the treated water in which the solids have been sufficiently decomposed is discharged into the solids concentrated wastewater 1 in the tank.
At the time of inflow of 12, a part thereof flows out of the tank due to overflow, and the effluent water 114 is guided to the contact aeration tank 12 through the drainage supply pipe 2. On the other hand, the separated wastewater 111 from which solids have been removed in the sedimentation separation tank 11 flows into the contact aeration tank 12, where the soluble pollutants are decomposed by the action of aerobic microorganisms, and the treated water 113 The separated wastewater is discharged outside the tank due to overflow when the separated wastewater flows into the tank.

As described above, in the wastewater treatment apparatus shown in FIG. 1, since the solid matter and the soluble pollutant are treated in the individual treatment tanks, the capacity of each of the tanks 12 and 13 can be optimized. Thus, the entire apparatus can be compactly assembled.

Here, in the wastewater treatment apparatus shown in FIG.
The solid matter is decomposed in the aerobic digestion tank 13, and the solid matter contains a hardly decomposable substance such as fiber, and the decomposition rate is low. Therefore, the aerobic digester 13
It is necessary to prolong the residence time of the treated water in the process, and there remains a problem that the hardly decomposable substance is not sufficiently decomposed and accumulates in the digestion tank.

Therefore, in the present embodiment, as shown in FIG. 1, an aerobic digestion tank 13 is filled with a cubic cellulose carrier 3... The above-mentioned problem has been solved by increasing the growth density of microorganisms and increasing the decomposition rate of solids and hardly decomposable substances.

If the aerobic digestion tank 13 is filled with the cellulose carriers 3 in this way, even if the treated wastewater flows out of the digestion tank, the microorganisms are transferred to the cellulose carriers 3. Since it can be stopped in the tank by adhesion or the like, the concentration of microorganisms does not decrease, and good decomposition performance can be maintained. As a result, even if the capacity of the digestion tank is reduced and the hydraulic residence time in the tank is shortened, the concentration of pollutants in the treated wastewater is maintained at a level below the reference value that can be discharged to the sewer. be able to.

[0035]

EXAMPLES Examples of the present invention will be described below together with comparative examples. <Example> Standard garbage (45 g of carrots, 45 g of cabbage, 25 g of banana peel) ground in a digester with a disposer
g, apple 25g, grapefruit skin 25g, chicken bone 20g, fish meat 25g, egg shell 5g, tea shell 10g, cooked rice 2
5g) 5 L of the pulverized liquid was added periodically to perform sufficient aeration to acclimate the sludge. A cubic cellulose carrier (manufactured by Biomaterials Co., Ltd.) having a side of about 5 mm was added thereto, and acclimated until the weight of the carrier became substantially constant. At this time, the flow rate of the microorganisms adhering to the carrier was 2.4 mg / carrier.

3 L of this microorganism-immobilized carrier was mixed with 25 L of S
It was added to 40 L of digestion tank A together with the acclimated sludge having an S (suspended substance) concentration of 3500 mg / L. Next, 2 L of standard garbage pulverized liquid pulverized so that the SS concentration became 40000 mg / L was added to digester A, and the SS concentration in the digester was measured periodically. The water temperature during the measurement period was 10 ° C.

From the results obtained as described above, FIG. 2 shows the relative change in the SS concentration with time when the value of the SS concentration at the start of the experiment is 1. <Comparative Example> SS concentration of 3500 m acclimated as in the example
g / L of sludge was added to digestion tank B and SS concentration was 40
2 L of standard garbage pulverized liquid pulverized to 000 mg / L was added, and the SS concentration in the digestion tank was measured periodically.
The water temperature during the measurement period was 10 ° C.

FIG. 2 similarly shows the results obtained. From the results in FIG. 2, SS up to 12 days after the start of measurement
The concentration change was almost the same in both digestion tanks A and B, but the SS concentration change after day 12 was larger in digestion tank B, and almost no change was observed after about day 50. Was. On the other hand, the digestion tank A showed a change in the SS concentration until about 80 days later.

From the above results, the rate of SS reduction in digester A with the microorganism-immobilized carrier was faster than in digester B with no carrier added, and the decomposition of organic solids in garbage was faster. It has been found.

Comparing the relative SS concentrations of digester A and digester B at the time when no change was observed in SS concentration, it was found that digester A with the carrier added was lower. It is considered that this result is due to the difference in the decomposition rate of the hardly decomposable substance contained in the organic solid.

[0041]

As described above, according to the biological treatment method of the present invention, the decomposition rate of organic solids contained in wastewater containing organic solids is high, so that the entire treatment tank can be made compact. Can be.

Furthermore, microorganisms capable of decomposing hardly decomposable substances contained in the organic solid can be grown on the carrier at high density. Also, even if the treated wastewater flows out of the digestion tank, the microorganisms can stop in the tank due to adhesion to the carrier, etc., so that the concentration of the microorganisms does not decrease,
Good decomposition performance can be maintained.

As a result, even if the capacity of the treatment tank is reduced and the hydraulic residence time in the tank is shortened, the reference value at which the concentration of pollutants in the treated wastewater can be discharged to the sewerage system. The following can be maintained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a wastewater treatment apparatus to which a biological treatment method of the present invention is applied.

FIG. 2 is a graph showing the change with time of the SS concentration in the example of the present invention and the change with time of the SS concentration of the comparative example.

[Explanation of symbols]

 Reference Signs List 10 wastewater treatment apparatus 11 sedimentation separation tank 12 contact aeration tank 13 aerobic digestion tank 14 air lift pump 121, 131 air diffuser 3.3 cellulose carrier (microorganism fixed carrier)

Claims (2)

[Claims] Claims: 1. A method for decomposing organic solids contained in wastewater by biological treatment, wherein a microorganism-immobilized carrier is filled in a treatment tank for treating organic solids-containing wastewater,
A biological treatment method for organic solid matter-containing wastewater, which is brought into contact with treated wastewater. 2. A separation tank for separating organic solid matter-containing wastewater into a solid matter concentrated wastewater and a separated wastewater, and the solid matter concentrated wastewater and the separated wastewater separated by the separation tank are separated by an aerobic biological treatment means. The organic solid according to claim 1, wherein the wastewater is treated using a wastewater treatment apparatus having a digestion tank to be treated and a wastewater treatment tank, wherein the digestion tank is filled with a microorganism-immobilized carrier. Biological treatment of wastewater containing waste.