JP3290621B2 - Method and apparatus for treating organic wastewater - 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 organic wastewater, an aerobic biological treatment method called an activated sludge method is most commonly practiced. In this method, as shown in FIG. 5, organic wastewater such as sewage introduced from the organic wastewater storage tank 1 to the aeration tank 3 is an oxidative decomposition reaction by microorganisms under aerobic conditions in the aeration tank 3. 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 3 is solid-liquid separated into treated water C and sludge D in the sedimentation tank 5, and a part of the sludge D is returned to the aeration tank 3 as a microorganism source, and the remaining sludge is removed. Sludge is generally treated as excess sludge E.

In this case, however, the precipitated solid concentrate (sludge) containing the organic solid separated in the sedimentation tank 5 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 ".

When the same amount of solids is treated for a certain period of time, if the concentration of sludge in the sedimentation tank (the concentration of sludge at the inlet of the solubilization tank) decreases, the amount of sludge to be treated in the solubilization tank increases. When the concentration of sludge in the sedimentation tank increases, the amount of sludge to be treated in the solubilization tank needs to be reduced. in this case,
The method described in the above publication has the following disadvantages because the amount of sludge treated in the solubilization tank is constant even when the concentration in the settling tank fluctuates. That is,
The sludge concentration in the sedimentation tank (concentration of sludge at the inlet of the solubilization tank) is now C
₀ (kg / m ³ ), and the amount of sludge treated in the solubilization tank is L ₀
(M ³ / day). At this time, the sludge concentration C _{1 in the} settling tank
Is lower than C _{0, the} amount of sludge L _{1 to be} treated in the solubilization tank is L ₁
Must be increased from L _0, the residence time of the sludge in the solubilization tank is shortened, and the sludge is not sufficiently solubilized. On the other hand, the sludge concentration C _{2 in the} settling tank
Is higher than C _{0, the} amount of sludge L _{2 to be} treated in the solubilization tank
Despite the fact that the amount of sludge flowing into the solubilization tank remains large despite the fact that it should be reduced from L ₀ , the volume of sludge more than necessary is reduced, and the activated sludge concentration in the aeration tank decreases. Therefore, there is a possibility that the treatment efficiency is reduced, and as a result, the quality of the treated water is deteriorated.

The present invention has been made in view of such problems of the prior art, and an object of the present invention is to provide an organic solvent capable of efficiently treating sludge without deteriorating treated water quality. It is an object of the present invention to provide a method and a device for treating a wastewater.

[0009]

In order to achieve the above-mentioned object, the present invention provides a method for treating excess sludge in a solubilization tank corresponding to the concentration of sludge separated in a sedimentation tank so that a predetermined treatment time can be secured. By adjusting the amount of sludge, the quality of the treated water does not deteriorate, and the organic wastewater can be treated efficiently.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention relates to a method for biologically treating organic wastewater, wherein the organic wastewater is subjected to aerobic biological treatment in an aeration tank and then treated in an aeration tank. The liquid is solid-liquid separated into treated water and sludge by a solid-liquid separator,
A part of the sludge separated by the solid-liquid separator was returned to the aeration tank, and excess sludge among the sludge separated by the solid-liquid separator was solubilized in the solubilization tank and solubilized in the solubilization tank. In the method of treating organic wastewater that returns the treatment liquid to the aeration tank, the same
Solid-liquid fraction so that the solid content can be solubilized in a certain time
When the concentration of excess sludge separated by the separation device increases
Reduce the amount of excess sludge to be solubilized in the solubilization tank,
When the concentration of excess sludge separated by the separation device is low
The first invention is a method of treating organic wastewater characterized by increasing the amount of excess sludge to be solubilized in the solubilization tank .
BACKGROUND ART In an apparatus for biologically treating organic wastewater, an aeration tank for aerobic biological treatment of organic wastewater, and a solid solution for solid-liquid separation of the treatment liquid treated in the aeration tank into treated water and sludge. A liquid separator, a route for returning a part of the sludge separated by the solid-liquid separator to the aeration tank, and a solubilization for solubilizing excess sludge of the sludge separated by the solid-liquid separator. An organic wastewater treatment device having a tank and a path for returning a treatment liquid solubilized in the solubilization tank to an aeration tank, wherein a concentration of sludge separated by the solid-liquid separation device is measured. the sludge concentration measuring apparatus for providing one of the same solid content
The solubilization tank is set up so that the solubilization process can be performed in a fixed time.
The excess sludge concentration measured by the sludge concentration measuring device is high.
If it becomes unnecessary, reduce the amount of excess sludge to be solubilized and
The excess sludge concentration measured by the sludge concentration measuring device is low.
If so, increase the amount of excess sludge to be solubilized.
In addition, a second aspect of the present invention is an organic wastewater treatment apparatus, which is a solubilization tank having a variable capacity.

According to the present invention configured as described above,
By adjusting the amount of excess sludge treated in the solubilization tank in accordance with the concentration of sludge separated in the sedimentation tank, the amount of sludge treated in the solubilization tank can be arbitrarily adjusted to follow the change in the concentration of inflow sludge. Since a predetermined residence time in the solubilization tank can be secured, it is possible to maintain the treated water quality at a constant level and efficiently treat sludge.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment) 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 aeration tank 3 via a path 2, and the raw wastewater as organic wastewater is aerobic in the aeration tank 3. Biologically treated. 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
And Bacillus, the inoculum of which is obtained from a conventional sewage purification plant. In this case, the temperature of the aeration tank 3 is 10 to 50C,
Usually, the operation is performed so as to be in a temperature range of 20 to 30 ° C. However, for more efficient treatment, a higher temperature is preferable.
For example, when using mesophilic bacteria separated from sewage excess sludge, the operation is performed in the range of 35 to 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. The device for aerobic and microbial decomposition in the aeration tank 3 is not particularly limited, and in short, any device provided with a 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 3 is introduced into the sedimentation tank 5 through the path 4 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, a part of the sludge D separated in the sedimentation tank 5 joins the path 2 via the path 6 and is introduced into the aeration tank 3 together with the raw wastewater A. The amount of sludge sent via the route 6 is determined by the amount of microorganisms held in the aeration tank 3.

Further, the remaining excess sludge E separated in the sedimentation tank 5 is introduced into the solubilization tank 8 via the path 7. Then, the capacity of the solubilization tank 8 is made variable in accordance with the concentration of the sludge measured by the concentration meter 9 so that a predetermined treatment time in the solubilization tank 8 can be secured. The solubilization tank 8 is configured so that the amount can be adjusted.

In the solubilization tank 8, 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 optimal temperature of the solubilization tank 8 is preferably operated under the condition of a temperature range of 50 to 90 ° C., but decomposes organic solids contained in the excess sludge E to be treated at a high temperature. It differs depending on the type of thermophilic bacteria. For example, in the case of thermophilic bacteria separated from excess sewage sludge, both effects of solubilization by microorganisms (thermophilic bacteria) and physicochemical thermal decomposition by heat are used. At the same time, the temperature under the high temperature condition is set to 55 to
It is intended to operate in the range of 5 ° C, preferably at about 65 ° C. In any case, depending on the kind of the microorganism, 5 so that both the solubilization reaction by the microorganism (thermophilic bacterium) and the action of physicochemical thermal decomposition by heat can be generated efficiently and sufficiently simultaneously.
What is necessary is just to set so that it may become the temperature range of 0-90 degreeC.

As a device for aerobic microbial decomposition in the solubilization tank 8, a device provided with a conventional air diffusion tube, and an anaerobic and microbial decomposition device for the microbial decomposition are provided in the tank. Efficiency of active microorganisms and sludge to be treated, such as a method of stirring by circulating the liquid, a method of stirring by circulating aeration of the generated gas, a method of installing a stirrer such as a stirring blade, a method having an active microorganism fixing means, etc. Any device can be used as long as it is provided with a means for bringing into contact therewith. In addition,
In this case, either a batch type or a continuous type can be used as the solubilization tank.

As described above, the treatment liquid F solubilized in the solubilization tank 8 joins the path 2 via the path 10 and is introduced into the aeration tank 2 together with the raw wastewater A to perform aerobic biological treatment.
Thereafter, the above-described processing cycle is repeated.

Next, in order to confirm the effects of the present invention, a square tank made of a transparent vinyl chloride resin having a sectional area of 800 cm ² and a height of 60 cm and an effective volume of 40 liters was used as an aeration tank. It was ventilated at 0.3 vvm. Further, a sedimentation tank having a shape as shown in FIG. 2 was used. FIG.
In the figure, 11 is a motor, 12 is a rotating shaft rotated by the motor 11, and a large number of round bars 13 made of stainless steel are attached to the rotating shaft 12 like an arrow. The concentration of sludge discharged from the sedimentation tank was changed by changing the number of rotations of the rotating shaft 12. As a solubilizing tank, a glass cylinder having an inner diameter of 13 cm and a height of 25 cm and an effective volume of 2 liters as shown in FIG. 3 or FIG. 4 was used, and this tank was ventilated with 0.5 vvm. In FIG. 3, reference numeral 14 denotes a handle rotatable in accordance with the indicated value of the concentration meter 9 for measuring the concentration of sludge. The handle 14 is screwed to a support rod 15 threaded on the outer surface. When the support rod 15 screwed to the handle 14 which rotates in accordance with the indicated value of 9 moves up and down, the telescopic tube 16 moves up and down integrally therewith, as shown in FIG. 3 (a) or (b). it is possible to change the liquid level L ₁ or L _2. That is, when the sludge concentration is low, the liquid level can be raised, and when the sludge concentration is high, the liquid level can be lowered to change the amount of treated sludge in the solubilization tank. In FIG. 4, reference numeral 17 denotes a motor which rotates in accordance with the indicated value of the densitometer 9. The winch 19 fitted to the motor shaft 18 is rotated one or the other to wind or wind the wire 20. By returning, the telescopic tube 16 moves up and down integrally with the wire 20, and FIG.
Alternatively, the liquid level can be changed to L ₁ or L ₂ as shown in (b). That is, when the sludge concentration is low, the liquid level can be raised, and when the sludge concentration is high, the liquid level can be lowered to change the amount of treated sludge in the solubilization tank.

The properties of the organic wastewater (raw wastewater) are as follows: peptone: glucose: yeast extract = 4: 4: 1
With a load of 0.4 kg BOD / m ³ / day,
The amount of sludge passing through the passage 6 is adjusted so that the concentration of sludge in the aeration tank 3 shown in FIG. 1 becomes about 3000 mg / L, and the number of revolutions of the rotating shaft 12 of the settling tank 5 is changed to discharge from the settling tank. The sludge concentration is changed to two types, high and low, and if the sludge concentration is high, the amount of sludge treated in the solubilization tank is relatively reduced. If the sludge concentration is low, the sludge is solubilized. The amount of sludge to be treated in the tank was relatively increased, and a predetermined treatment time was ensured at any concentration to obtain a constant level of treated water quality. Here, 1 vvm means “5 liter air volume / 5 liter reactor volume / min.”. Further, in the above-described 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. (2) Comparative Example For comparison, in the apparatus shown in FIG. 1, when the amount of treated sludge in the solubilization tank 8 cannot be changed, the sludge in the aeration tank 3 was subjected to the same load using organic wastewater. The operation was performed by adjusting the amount of sludge passing through the route 6 so that the concentration was about 3000 mg / L.

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

[0023]

[Table 1]

The following points are evident from Table 1.

According to this embodiment, the volume of the solubilization tank and the amount of sludge to be treated are changed in accordance with the concentration of sludge discharged from the sedimentation tank, so that a predetermined treatment time in the solubilization tank is secured. It is possible to maintain a constant quality of treated water without removing excess sludge.

However, in the case where the capacity of the solubilization tank is fixed as in the comparative example, the residence time is about 20% shorter in the case of low sludge concentration than in the case of high sludge concentration. Insufficiently deteriorates the treated water quality as compared with the examples, and the volume reduction of the sludge is inadequate.
Some sludge withdrawal was required to maintain 0 (mg / l).

[0027]

Since the present invention is configured as described above, it is possible to provide an organic wastewater treatment method and a treatment apparatus capable of efficiently treating treated water without deteriorating treated water quality. .

[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 side sectional view of one embodiment of a settling tank.

FIG. 3 is a side sectional view of one embodiment of the solubilization tank of the present invention.

FIG. 4 is a side sectional view of another embodiment of the solubilization tank of the present invention.

FIG. 5 is a schematic configuration diagram of a conventional organic wastewater treatment apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Organic wastewater storage tank 2, 4, 6, 7, 10 ... Route 3 ... Aeration tank 5 ... Sedimentation tank 8 ... Solubilization tank 9 ... Concentration meter

────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Akira Akashi 2014 Nishi-Futami, Futami-cho, Akashi-shi, Hyogo 15 B703 (72) Inventor Takahiro Fukui 1-10-20 Nitta, Kawanishi-shi, Hyogo (56) Reference Document JP-A-9-136097 (JP, A) JP-A-9-122679 (JP, A) Japan Industrial Water Association, Water treatment test method, Corona, September 20, 1977, 266 (58) Field surveyed (Int. Cl. ⁷ , DB name) C02F 11/02

Claims (2)

(57) [Claims] In a method for biologically treating organic wastewater, the organic wastewater is subjected to an aerobic biological treatment in an aeration tank, and then the treated liquid treated in the aeration tank is subjected to solid-liquid separation. Solid-liquid separation into treated water and sludge, a part of the sludge separated by the solid-liquid separator is returned to the aeration tank, and excess sludge of the sludge separated by the solid-liquid separator is solubilized in the solubilization tank. In the method of treating organic wastewater, in which the treatment liquid solubilized in the solubilization tank is returned to the aeration tank, the same amount of solids is solubilized in a fixed time.
Of excess sludge separated by a solid-liquid separator
Excess solubilization in solubilization tank when concentration increases
Excess sludge separated by solid-liquid separator with reduced sludge volume
If the concentration of
A method for treating organic wastewater, comprising increasing the amount of excess sludge . 2. An apparatus for biologically treating an organic wastewater, comprising: an aeration tank for aerobic biological treatment of the organic wastewater; and a treatment liquid treated in the aeration tank being solidified into treated water and sludge. A solid-liquid separator for separation, a route for returning part of the sludge separated by this solid-liquid separator to the aeration tank, and solubilization of excess sludge among the sludge separated by the solid-liquid separator And a route for returning the processing solution solubilized in the solubilization tank to the aeration tank, wherein the sludge separated by the solid-liquid separation device is provided. A sludge concentration measuring device for measuring the concentration of
In order to be able to solubilize the same amount of solids in a certain time,
The solubilization tank is the surplus measured by the sludge concentration measuring device described above.
Excess sludge to be solubilized when the concentration of sludge increases
Reduce the amount and use the surplus
Excess sludge to be solubilized when the sludge concentration becomes low
An organic wastewater treatment apparatus characterized in that it is a solubilization tank whose capacity is variable so as to increase the amount .