JP3333127B2 - Organic wastewater treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a process for treating organic wastewater by biological digestion, such as a sewage treatment process such as a sewage treatment plant and a human waste treatment plant, and a wastewater treatment process such as a food factory and a chemical factory.

[0002]

2. Description of the Related Art Conventionally, as a method for treating such organic wastewater, an aerobic biological treatment method called an activated sludge method is most commonly practiced. In this method, as shown in FIG. 7, organic wastewater such as sewage introduced from the organic wastewater storage tank 1 to the aeration tank 5 is an oxidative decomposition reaction by microorganisms under aerobic conditions in the aeration tank 5. This is a method of decomposing into inorganic substances such as carbon dioxide or water by biological oxidation. The wastewater treated in the aeration tank 5 is solid-liquid separated into treated water C and sludge D in the sedimentation tank 7, and a part of the sludge D is returned to the aeration tank 5 as a microbial source, and the remaining sludge is removed. Sludge is generally treated as excess sludge E.

However, in this case, the precipitated solid concentrate (sludge) containing the organic solid separated in the sedimentation tank 7 is:
Since the treatment is performed through steps such as concentration, digestion, dehydration, composting, and incineration, such treatment is troublesome and costly and is not preferable.

[0004] For this reason, as a treatment method that generates as little sludge as possible, a long-term aeration method in which the residence time of the sludge is extended, or a catalytic oxidation method in which a large amount of sludge is retained in a reaction tank by attaching the sludge to the surface of the contact material. The law has been proposed and put into practical use (published by the Japan Sewerage Association, supervised by the Sewerage Department, Urban Bureau, Ministry of Construction, Sewerage Facility Planning and Design Guideline and Commentary, 1994). However, these methods require a large installation area to increase the residence time, and the long-time aeration method causes sludge dispersion when the load is reduced, which hinders solid-liquid separation. . Further, the catalytic oxidation method is not preferable in that clogging of sludge occurs when the load increases. Furthermore, in order to solve these problems, a method of temporarily storing excess sludge, reducing the volume of sludge by anaerobic digestion to reduce the amount of sludge, and reducing the burden of disposal treatment has also been proposed. However, in this method, the processing time is as long as 20 to 30 days,
It is hard to say that the volume reduction rate of organic sludge is about 30 to 50%, which is sufficient.

Japanese Patent Application Laid-Open No. 6-2060888 discloses a method for reducing excess sludge by subjecting an organic waste liquid to aerobic treatment and then subjecting the solid-liquid separated sludge to oxidation treatment in an ozone oxidation tower. I have. However, in this method, handling of the ozone oxidation tower requires skill, there is a problem of treating residual ozone, and the decomposition rate of excess sludge in the ozone oxidation tower is still not a satisfactory value.

[0006] In the activated sludge treatment method for treating organic wastewater, Japanese Patent Application Laid-Open No. 9-10791 discloses an activated sludge treatment method capable of extremely reducing the amount of excess sludge generated. After the aerobic biological treatment in, the treatment liquid treated by the aeration treatment device is solid-liquid separated into treated water and sludge by the sedimentation device, and a part of the sludge separated by the sedimentation device is passed through the circulation route. And returned to the aeration treatment device.The excess sludge of the sludge separated by the sedimentation device is solubilized at high temperature by the solubilization treatment device, and the treatment solution solubilized by the solubilization treatment device is aerated via the return route. Activated sludge treatment method, wherein the method is returned to a treatment apparatus ". However, in the method described in this publication, the load on the aeration treatment device increases due to the treatment liquid returned from the solubilization treatment device to the aeration treatment device, and thus the quality of treated water may deteriorate.

[0007] The present invention has been made in view of such problems of the prior art, and its object is to deteriorate the quality of treated water even if the treated solution after solubilization is returned to the aeration tank. It is an object of the present invention to provide a method for treating organic wastewater that does not require any treatment.

[0008]

According to the present invention, in order to achieve the above object, a part or all of organic wastewater is subjected to anaerobic treatment and then aeration treatment, so that the load on the aeration tank is reduced and solubilization is achieved. Even if the treated liquid after the treatment is returned to the aeration tank, the quality of the treated water does not deteriorate.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention provides a method for biologically treating organic wastewater, which reduces the load on the aeration tank.
To reduce the amount of organic wastewater, anaerobic treatment of the organic wastewater in an anaerobic tank is performed, followed by aerobic biological treatment in an aeration tank, and then the treatment liquid treated in the aeration tank is treated with treated water by a solid-liquid separator. Solid-liquid separation into sludge, part of the sludge separated by the solid-liquid separation device is returned to the aeration tank, and excess sludge of the sludge separated by the solid-liquid separation device is removed by thermophilic bacteria in the solubilization tank. The first invention is a method for treating organic wastewater, wherein the treatment liquid is solubilized and returned to the anaerobic tank or the aeration tank, and the organic wastewater is biologically treated. in the process, 曝
In order to reduce the load on the air tank, the organic wastewater was subjected to anaerobic treatment in an anaerobic tank, and then a portion of the treatment liquid was subjected to aerobic biological treatment in an aeration tank, and then treated in an aeration tank. The liquid is separated into treated water and sludge by a solid-liquid separator, and a part of the sludge separated by the solid-liquid separator is returned to the aeration tank, and the excess sludge is separated from the sludge separated by the solid-liquid separator. And the excess sludge from the anaerobic tank is solubilized by a thermophilic bacterium in the solubilizing tank, and the treated liquid solubilized in the solubilizing tank is returned to the anaerobic tank or the aeration tank. The treatment method as the second invention, in a method of biologically treating organic wastewater,
In order to reduce the load on the aeration tank, part of the organic wastewater is subjected to anaerobic treatment in an anaerobic tank, and the treated liquid after anaerobic treatment and the remaining organic wastewater are subjected to aerobic biological treatment in an aeration tank. And then
The treatment liquid treated in the aeration tank is solid-liquid separated into treated water and sludge by a solid-liquid separation device, and a part of the sludge separated by the solid-liquid separation device is returned to the aeration tank, and the solid-liquid separation device Excess sludge among the separated sludge is solubilized by thermophilic bacteria in a solubilization tank,
The third invention is a method for treating organic wastewater, which comprises returning the treatment solution solubilized in the solubilization tank to the anaerobic tank or the aeration tank, and a method for biologically treating the organic wastewater. among the plurality of organic wastewater with different concentration of organic substances, 曝
In order to reduce the load on the air tank, organic wastewater with high organic matter concentration is subjected to anaerobic treatment in an anaerobic tank, and the treated liquid after anaerobic treatment and organic wastewater with low organic matter concentration are treated with aerobic organisms in an aeration tank. Then, the treatment liquid treated in the aeration tank is solid-liquid separated into treated water and sludge by a solid-liquid separation device, and a part of the sludge separated by the solid-liquid separation device is returned to the aeration tank, Excess sludge of the sludge separated by the solid-liquid separator is thermophilic bacteria in the solubilization tank.
A fourth invention provides a method for treating organic wastewater, wherein the treatment solution is solubilized in the solubilization tank, and the treatment liquid solubilized in the solubilization tank is returned to the anaerobic tank or the aeration tank.

According to the present invention configured as described above,
Since aeration treatment is performed after part or all of the organic wastewater is subjected to anaerobic treatment, the load on the aeration tank is reduced, and even if the treated liquid after solubilization is returned to the aeration tank, the treated water quality will not deteriorate. Absent.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. (1) Embodiment 1 FIG. 1 is a schematic configuration diagram of an embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

As shown in FIG. 1, raw wastewater A stored in an organic wastewater storage tank 1 is introduced into an anaerobic tank 3 via a path 2, and a treated liquid subjected to anaerobic treatment is passed through a path 4 to an aeration tank 5
The raw wastewater, which is organic wastewater, is subjected to aerobic biological treatment in the aeration tank 5. In addition, aerobic biological treatment means that organic substances are decomposed into inorganic substances such as carbon dioxide or water by biological oxidation, and the aerobic microorganisms used are gram-negative or gram-positive bacilli used in the activated sludge method for sewage purification. For example, Pseudomonas (Pseu
domonas) and Bacillus, the inoculum of which is obtained from a conventional sewage purification plant. In this case, the temperature of the aeration tank 5 is 10
The operation is performed at a temperature of 50 ° C., usually 20 to 30 ° C., but a higher temperature is preferable for more efficient treatment. For example, when a mesophilic bacterium separated from sewage excess sludge is used, , Operating in the range of 35-40 ° C. In any case, an optimal temperature condition is selected and operated from the above temperature range so that the oxidative decomposition reaction by the microorganism can efficiently and sufficiently occur. In addition, as an apparatus for aerobic microbial decomposition in the aeration tank 5,
It is not particularly limited, and in short, any device provided with an air diffuser can be used. In this case, as the aeration tank, either a batch type or a continuous type can be used.

Next, the treated water B thus treated in the aeration tank 5 is introduced into the sedimentation tank 7 through the path 6 and is separated into solid and liquid. The supernatant liquid C separated into solid and liquid is discharged to the discharge destination. According to the standards, if necessary, a tertiary treatment such as nitrification denitrification or ozone treatment is performed, and the wastewater is used as river discharge or landscape water.

On the other hand, part of the sludge D separated in the sedimentation tank 7 joins the path 4 via the path 8 and is introduced into the aeration tank 5 together with the anaerobic treatment liquid. The amount of sludge sent through the route 8 is determined by the amount of microorganisms held in the aeration tank 5.

Further, the remaining excess sludge E separated in the sedimentation tank 7 is introduced into the solubilization tank 10 via the path 9. In the solubilization tank 10, the organic sludge is anaerobically or aerobically solubilized under high temperature conditions. In this case, the inoculum of the anaerobic or aerobic microorganism (thermophilic bacterium) used under high temperature conditions is obtained, for example, by culturing the microorganism from a conventional anaerobic or aerobic digestion tank. Further, the optimum temperature of the solubilization tank 10 is preferably
The operation is performed under the condition of a temperature range of 50 to 90 ° C., but the temperature varies depending on the type of thermophilic bacterium that decomposes the organic solids contained in the excess sludge E to be treated at a high temperature. In the case of thermophilic bacteria separated from excess sludge, the temperature at high temperature conditions must be such that both the solubilization reaction by microorganisms (thermophilic bacteria) and the physicochemical thermal decomposition by heat can be performed efficiently and sufficiently. Is operated in the range of 55-75C, preferably about 65C. In any case, 50 to 90 ° C. depending on the type of microorganism so that both the solubilization reaction by the microorganism (thermophilic bacterium) and the physicochemical thermal decomposition by heat can be efficiently and sufficiently generated simultaneously.
The temperature may be set so as to be within the temperature range.

As a device for aerobically decomposing microorganisms in the solubilization tank 10, a device provided with a conventional air diffuser, and an anaerobic device for decomposing microorganisms include:
Active microorganisms and sludge to be treated, such as a method of stirring by circulating the liquid in the tank, a method of stirring by circulating aeration of the generated gas, a method of installing a stirrer such as a stirring blade, and a method having an active microorganism fixing means, etc. Any device can be used as long as it has a means for efficiently contacting. In this case, as the solubilization tank, either a batch type or a continuous type can be used.

As described above, the processing solution F solubilized in the solubilizing tank 10 joins the path 4 via the path 11 and is introduced into the aeration tank 5 together with the processing liquid after the anaerobic treatment to perform the aerobic biological treatment. Will be Thereafter, the above-described processing cycle is repeated.

For solubilization, other than thermophilic bacteria can be used. For example, a method of bringing into contact with ozone, a method of electrolyzing sludge into an acidic sludge and an alkaline sludge, a method of neutralizing by soaking again after solubilization, a method of solubilizing at a high temperature, a method of heating after adding an alkali, A method of adding an enzyme, a method of ultrasonic treatment, and the like can be used. (2) Embodiment 2 FIG. 2 is a schematic configuration diagram of another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention. The difference from the apparatus of FIG. 1 is that the processing liquid F returned from the solubilization tank
And is introduced into the anaerobic tank 3 together with the raw wastewater A via the route 2. (3) Embodiment 3 FIG. 3 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention. The difference from the apparatus of FIG. 1 is that a part of the processing liquid processed in the anaerobic tank 3 is transferred to the path 4.
, And the excess sludge G from the anaerobic tank 3 is introduced into the solubilization tank 10 via the path 13 together with the excess sludge E from the path 9. (4) Embodiment 4 FIG. 4 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention. The difference from the apparatus of FIG. 1 is that a part of the organic wastewater is treated in the anaerobic tank 3, and the remaining H of the organic wastewater and the treatment liquid I subjected to the anaerobic treatment are treated via the path 14 from the path 11. It is introduced into the aeration tank 5 together with the liquid F and the sludge from the passage 8. (5) Example 5 FIG. 5 is a schematic configuration diagram of still another example of an organic wastewater treatment apparatus suitable for carrying out the method for treating organic wastewater of the present invention. Here are some cases. The difference from the apparatus of FIG. 1 is that raw wastewater having a high concentration of organic matter stored in an organic wastewater storage tank 1 is treated in an anaerobic tank 3 and raw water having a low concentration of organic matter stored in an organic wastewater storage tank 1 ′ is processed. Wastewater J and anaerobic treatment liquid K
The point is that the treatment liquid F from the path 11 and the sludge from the path 8 are introduced into the aeration tank 5 via the path 14.

Next, in order to confirm the effects of the present invention, an anaerobic tank having an effective volume of 4 cm having an inner diameter of 10 cm and a height of 80 cm was used.
Using a liter jacket type vinyl chloride resin cylinder, the aeration tank has a cross-sectional area of 400 cm ² and a height of 60 cm.
Of a transparent vinyl chloride resin tank having an effective volume of 20 liters, and aeration of 0.3 vvm through this aeration tank, as a sedimentation tank, an effective volume 1 having a cross-sectional area of 400 cm ² and a height of 40 cm.
A lower pyramid-shaped square tank made of 0 liter transparent polyvinyl chloride resin is used, and the solubilization tank is 13 cm in inner diameter and 25 cm in height.
Using a glass cylinder having an effective volume of 2 liters and passing 0.3 vvvm through this solubilization tank, the properties of organic wastewater (raw water) are peptone: glucose: yeast extract =
4: 4: 1, and the sludge concentration in the aeration tank 5 is about 30
The amount of sludge flowing into the route 8 was adjusted to be 00 mg / L, and the BOD of the raw water was adjusted to 2250 mg / L for the examples shown in FIGS. 1, 2 and 3, and FIG. For the example shown, the BOD of the raw water was 2250 mg / L
5 L / day anaerobic treatment, and the treated liquid after the anaerobic treatment and 2 L / day raw water were aerated, and
For the examples shown in the table, high-concentration waste liquid (7500 mg /
L) was subjected to anaerobic treatment at 2 liters / day, and the treated liquid after the anaerobic treatment and a low-concentration waste liquid (500 mg / L) at 6 liters / day
And aeration was performed. In addition, 1vvm means
"5 liter air volume / 5 liter reaction tank volume / mi
n. It means. Further, in the above embodiment, the sedimentation tank is used for solid-liquid separation, but it goes without saying that an apparatus usually used for solid-liquid separation such as a membrane separation apparatus can be used. (6) Comparative Example For comparison, as shown in FIG. 6, for an organic wastewater treatment apparatus having no anaerobic tank, the sludge concentration in the aeration tank 5 was reduced by using the organic wastewater and the BOD load. The operation was performed by adjusting the amount of sludge flowing into the route 8 so as to be about 3000 mg / L.

As a result, the results shown in the following Table 1 were obtained.

[0021]

[Table 1]

The following points are clear from Table 1. According to the present example, treated water having water quality equal to or higher than that of the comparative example can be obtained. However, the quality of water treated by the method of the comparative example is inferior to that of the present example. Further, according to the present embodiment, the amount of sludge treated in the solubilization tank is 1/2 or less of that of the comparative example, and the solubilization tank can be made compact.

[0023]

According to the method for treating organic wastewater of the present invention, the load on the aeration tank is reduced, and the quality of the treated water does not deteriorate even if the treated liquid after solubilization is returned to the aeration tank.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of an embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

FIG. 2 is a schematic configuration diagram of another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

FIG. 3 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

FIG. 4 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

FIG. 5 is a schematic configuration diagram of still another embodiment of an organic wastewater treatment apparatus suitable for carrying out the organic wastewater treatment method of the present invention.

FIG. 6 is a schematic configuration diagram of a conventional organic wastewater treatment apparatus.

FIG. 7 is a schematic configuration diagram of another conventional organic wastewater treatment apparatus.

[Explanation of symbols]

 1, 1 '... organic wastewater storage tank 2, 4, 6, 8, 9, 11, 12, 13, 14 ... route 3 ... anaerobic tank 5 ... aeration tank 7 ... sedimentation tank 10 ... solubilization tank

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Takahiro Fukui 1-10-20 Nitta, Kawanishi-shi, Hyogo Examiner Tadahiro Sanada (56) References JP-A-7-96297 (JP, A) JP-A-9 -122682 (JP, A) JP-A-5-15895 (JP, A) JP-A-4-293592 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) C02F 11/02 C02F 3/30 ZAB

Claims (4)

(57) [Claims] In the method for biologically treating organic wastewater , in order to reduce the load on the aeration tank, the organic wastewater is subjected to anaerobic treatment in an anaerobic tank and then to aerobic biological treatment in an aeration tank. Then, the treatment liquid treated in the aeration tank is solid-liquid separated into treated water and sludge by a solid-liquid separation device, and a part of the sludge separated by the solid-liquid separation device is returned to the aeration tank and solidified. Excess sludge of the sludge separated by the liquid separator is thermophilic bacteria in the solubilization tank.
A method for treating organic wastewater, wherein the treatment liquid is solubilized in the solubilization tank and the treatment liquid solubilized in the solubilization tank is returned to the anaerobic tank or the aeration tank. 2. In the method for biologically treating organic wastewater , in order to reduce the load on the aeration tank, the organic wastewater is subjected to anaerobic treatment in an anaerobic tank, and then a part of the treatment liquid is transferred to the aeration tank. Aerobic biological treatment, and then the treatment liquid treated in the aeration tank is solid-liquid separated into treated water and sludge by a solid-liquid separation device,
A part of the sludge separated by the solid-liquid separator is returned to the aeration tank, and the excess sludge separated from the sludge separated by the solid-liquid separator and the excess sludge from the anaerobic tank are solubilized in the solubilization tank by thermophilic bacteria. A method for treating organic wastewater, comprising solubilizing and returning a treatment solution solubilized in a solubilization tank to an anaerobic tank or an aeration tank. 3. A method for biologically treating organic wastewater, wherein part of the organic wastewater is subjected to anaerobic treatment in an anaerobic tank in order to reduce the load on the aeration tank. And aerobic biological treatment of the remaining organic wastewater in an aeration tank,
Next, the treatment liquid treated in the aeration tank is solid-liquid separated into treated water and sludge by a solid-liquid separation device, and a part of the sludge separated by the solid-liquid separation device is returned to the aeration tank, and solid-liquid separation is performed. Organic, characterized in that excess sludge among the sludge separated by the device is solubilized by thermophilic bacteria in a solubilization tank, and the processing solution solubilized in the solubilization tank is returned to an anaerobic tank or an aeration tank. Wastewater treatment method. 4. The method for biologically treating an organic wastewater, wherein the organic wastewater includes a plurality of organic wastewaters having different organic substance concentrations.
In order to reduce the load on the aeration tank, organic wastewater with high organic matter concentration is subjected to anaerobic treatment in the anaerobic tank, and the treated liquid after anaerobic treatment and the organic wastewater with low organic matter concentration are treated with aerobic organisms in the aeration tank. Then, the treatment liquid treated in the aeration tank is solid-liquid separated into treated water and sludge by a solid-liquid separation device, and a part of the sludge separated by the solid-liquid separation device is returned to the aeration tank, Excess sludge of the sludge separated by the solid-liquid separator is heated in the solubilization tank
A method for treating organic wastewater, comprising solubilizing bacteria and returning a treatment solution solubilized in a solubilization tank to an anaerobic tank or an aeration tank.