JP2012200695A - Method of treating organic wastewater - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method of treating organic wastewater capable of remarkably reducing the generation of surplus sludge using a simple facility and without adding high pressure gas or chemical.SOLUTION: In the method of biologically treating organic wastewater using active sludge, a portion of the active sludge in a biological treatment tank is sheared and refined in a solubilization tank, fine air bubbles are generated and dispersed in the active sludge, and thereafter, the active sludge is used again for biological treatment.

Description

  The present invention relates to a method for treating organic wastewater such as domestic wastewater, livestock wastewater, fishery processing wastewater, or various industrial wastewater. More specifically, the present invention relates to a reduction in the amount of activated sludge that increases in such treatment.

  Conventionally, as an organic wastewater biochemical treatment method, an activated sludge method in which organic wastewater is treated with activated sludge containing aerobic microorganisms has been employed. There exists a process as shown in FIG. 9 as a process of a general activated sludge method. As shown in FIG. 9, after drainage is homogenized in the flow rate adjustment process, the organic wastewater is introduced into the biological treatment process, and the pollutant components in the organic wastewater are decomposed by the activated sludge within the biological treatment process. Let the purification process. However, a large amount of activated sludge is newly generated in the activated sludge method. Therefore, after the wastewater treated in the biological treatment process is transferred to the treated water separation process, the precipitated activated sludge is separated, and only the amount of the separated activated sludge necessary for the purification treatment of organic wastewater is returned to the living organism. It is returned to the treatment process and the rest is discarded as excess sludge. Disposable surplus sludge is difficult to handle due to its high water content and poor dewaterability, and its disposal costs are high.When organic wastewater is purified by the activated sludge method, there is always a problem with how to treat surplus sludge. It becomes.

  As a method for reducing excess sludge, a reduction method as shown in FIG. 10 is known (see, for example, Patent Document 1). In this method, organic wastewater is treated by activated sludge treatment in the activated sludge treatment tank 101, and carbon dioxide in a high-pressure state is added to a return sludge suspension that is part of the activated sludge separated in the settling tank 102. Is dissolved as microbubbles. The return sludge suspension is brought into contact with carbon dioxide in a high pressure state in the carbon dioxide treatment apparatus 103, and microorganisms in the return sludge are efficiently killed. In the carbon dioxide treatment apparatus 103, carbon dioxide having a pressure that does not deactivate the residual enzyme is made to have a particle size of 1000 μm or less using a stirrer, a static mixer, a microfilter, or the like. After contacting the return sludge with carbon dioxide in a high-pressure state, the return sludge suspension from which carbon dioxide has been removed is returned to the activated sludge treatment tank 101, and the activated sludge treatment is performed again. The activated sludge generated in the activated sludge treatment tank 101 is reduced.

JP 2005-246287 A

  However, in the method of Patent Document 1, there is a safety concern because high pressure carbon dioxide is used. In order to ensure the safety of the equipment, it is necessary to make the carbon dioxide treatment device, the surrounding piping system, etc. have a high pressure resistance specification. In addition, it is necessary to consider the equipment design, operation, maintenance management method, etc. for abnormal pressure rise or leakage of carbon dioxide. Although used carbon dioxide is collected and reused after pressurization, there is a problem in that the facility becomes complicated and large because the pressurization facility and the storage facility are also required here.

  The present invention has been made in view of the problems as described above, and can add a large amount of excess sludge using simple equipment without adding high-pressure gas or chemicals. It aims at providing the processing method of waste water.

The organic wastewater treatment method of the present invention is a biological treatment of organic wastewater with activated sludge in a biological treatment tank, and an organic wastewater treatment method in which activated sludge is newly generated by the biological treatment,
A part of the activated sludge in the biological treatment tank is taken out and sheared and refined, fine bubbles are generated and dispersed in the activated sludge, and then transferred to the biological treatment tank. The following configuration is preferable Including as an aspect.

The activated sludge is sheared and refined, and the generation and dispersion of the fine bubbles are simultaneously performed as a fine dispersion treatment by one means,
1 to 10 times the amount of activated sludge newly generated in the biological treatment tank is taken out, subjected to the fine dispersion treatment and transferred to the biological treatment tank.

Means for shearing and refining the activated sludge and generating and dispersing the fine bubbles in the activated sludge,
In the activated sludge, rotate the stirring blade provided with an intake pipe with one end opened at the center of rotation,
The activated sludge and the outside air are sucked into the rotation center by the negative pressure generated at the rotation center,
The activated sludge and the outside air are refined by the shearing force and stirring force generated by the rotation of the stirring blade.

  The outside air is a gas containing any one of air, ozone or carbon dioxide, and the fine bubbles to be generated and dispersed in the activated sludge are made of the gas.

Said amount of fresh air sucked into the rotation center portion, the solid content concentration of excess sludge 1 m ³ per 0.06~1.2m ³ / h of 7,000~30,000g / m ^3.

At least the inflow process, the flow rate adjustment process, the dispersion process, the biological treatment process, the treated water separation process, and
A part of the activated sludge taken out from the biological treatment tank is sheared and refined, and after generating and dispersing fine bubbles in the activated sludge, including a step of transferring to the biological treatment tank,
The dispersion step is a step of generating and dispersing fine bubbles in the organic waste water while shearing and refining insoluble substances in the organic waste water in a step before the biological treatment step.

  Here, in the present invention, the fine dispersion treatment means that insoluble substances in activated sludge or organic waste water are sheared and refined, and fine bubbles are generated and dispersed in activated sludge or organic waste water.

The present invention has the above-described configuration, and the following excellent effects can be obtained.
(1) The activated sludge taken out from the biological treatment tank is sheared and refined, and further, the activated sludge is solubilized by generating and dispersing fine bubbles in the activated sludge. By returning to the treatment tank and using it again for biological treatment, excess sludge can be reduced.
(2) Excess sludge can be reduced by a simple device under a mild condition at normal temperature and pressure without requiring addition of high-pressure gas or chemical solution.

It is the process flowchart which showed the 1st Embodiment of this invention. It is the block diagram which showed the 1st Embodiment of this invention. It is a schematic diagram which shows the solubilization tank used for the 1st Embodiment of this invention. It is a schematic diagram which shows the space near the stirring blade of the solubilization tank of FIG. It is a schematic diagram which shows the other solubilization tank used for the 1st Embodiment of this invention. It is a schematic diagram which shows the other solubilization tank used for the 1st Embodiment of this invention. It is the process flowchart which showed the 2nd Embodiment of this invention. It is the block diagram which showed the 2nd Embodiment of this invention. It is the processing flowchart which showed the processing method of the organic waste water of a prior art. It is the block diagram which showed the processing method of the other organic waste_water | drain of prior art.

  Hereinafter, although an embodiment of the present invention is described with reference to drawings, it cannot be overemphasized that the present invention is not limited to this embodiment.

[First Embodiment]
Based on FIG. 1 thru | or FIG. 6, the processing method of the organic waste_water | drain which is the 1st Embodiment of this invention is demonstrated. FIG. 1 is a process flowchart of the first embodiment of the present invention, and FIG. 2 is a block diagram. As shown in FIG. 1, the treatment process in the present invention includes an inflow process, a flow rate adjustment process, a biological treatment process, a treated water separation process, a sludge return process, a solubilization process, and a solubilization transfer process.

  1 and 2, the organic wastewater that has flowed into the facility in the inflow process is adjusted in flow rate in the flow rate adjustment process and sent to the biological treatment process. In the biological treatment process, the organic waste water is biologically treated in the membrane separation activated sludge tank 1 by the activated sludge method. The membrane-separated activated sludge tank 1 is provided with a membrane 2 in which activated sludge for biological treatment is placed in the treatment tank, and the treated water discharged outside the equipment through a disinfection process (not shown) is separated. Therefore, the process water separation process is also performed in the membrane separation activated sludge tank 1. Part of the activated sludge in the membrane-separated activated sludge tank 1 is discarded outside the facility as surplus sludge through a concentration storage step (not shown). Moreover, the remainder of activated sludge is sent to the solubilization transfer process as return sludge, and is solubilized in the solubilization process in the solubilization transfer process. In the solubilization step, the activated sludge 3 is sheared and refined by the disperser 5 in the solubilization tank 4, and the fine bubbles generated by the disperser 5 are dispersed in the activated sludge 3. The activated sludge 3 that has been finely dispersed and solubilized in the solubilization tank 4 is transferred to a biological treatment process and used for biological treatment in the membrane separation activated sludge tank 1. In addition, a part of the returned sludge is sent to the sludge return process without passing through the solubilization process through the concentration storage process, and may be transferred to the biological treatment process. In this case, the concentration storage step may be performed together with excess sludge to be discarded. Further, when the activated sludge can be reduced sufficiently, the excess sludge to be discarded may be eliminated, and the entire activated sludge may be returned.

  FIG. 3 is a diagram showing a configuration example of the solubilization tank 4 of FIG. In FIG. 3, an introduction pipe 6 for introducing the activated sludge 3 taken out from the membrane separation activated sludge tank 1 into the solubilized tank 4 is disposed above the solubilized tank 4. Below the solubilization tank 4, a water supply pipe 7 for supplying the treated activated sludge 3 to the membrane separation biological treatment tank 1 is provided. In the solubilization tank 4, a disperser 5 including a stirring blade 8, a drive unit 9, and an intake pipe 10 is disposed. Both ends of the intake pipe 10 are open, one end is disposed outside the solubilization tank 4, and the other end is disposed at a position serving as a central part of the negative pressure generated when the stirring blade 8 is rotated by the drive unit 9. .

  With the configuration described above, the disperser 5 has the following action. The activated sludge 3 introduced into the solubilization tank 4 from the introduction pipe 6 is stirred by the rotation of the stirring blade 8, and is sheared and refined. At this time, the activated sludge 3 in the vicinity of the stirring blade 8 moves in a direction away from the stirring blade 8 and moves to the vicinity of the water surface as an upward flow along the side wall 11 of the solubilization tank 4. On the other hand, the central part of the stirring blade 8 generates a negative pressure when the activated sludge 3 moves toward the side wall 11 and sucks the activated sludge 3 from above. Then, the activated sludge 3 that has moved to the vicinity of the water surface descends again and passes through the stirring blade 8. In this way, the activated sludge 3 circulates in the solubilization tank 4 by the rotation of the stirring blade 8 and is sheared and refined by the stirring blade 8 every time it passes through the stirring blade 8.

  Further, since the intake pipe 10 is disposed at a position where the negative pressure is generated in the central portion of the stirring blade 8, air (outside air) is sucked from the outside of the solubilization tank 4 and discharged to the central portion of the stirring blade 8. The The discharged outside air reaches the stirring blade 8 together with the activated sludge 3, and is sheared by the stirring blade 8 to become fine bubbles 12. The generated fine bubbles 12 circulate in the solubilization tank 4 together with the activated sludge 3 that has been sheared and refined, and are uniformly dispersed in the activated sludge 3 by being stirred by the stirring blades 8. The activated sludge 3 is solubilized by the self-crushing effect of the fine bubbles 12 dispersed in the activated sludge 3.

  In the present invention, the crushing refers to a phenomenon in which the fine bubbles 12 existing in the liquid gradually shrink and disappear due to natural dissolution of the gas contained in the fine bubbles 12. When the fine bubbles 12 are crushed, free active groups having extremely strong oxidizing power are generated, solubilizing the activated sludge 3.

In the present invention, the solubilization step needs to be performed by removing the activated sludge from the membrane separation activated sludge tank 1. This is because when the treatment using the disperser 5 is performed in the biological treatment process, the activated sludge 3 that has been sheared and dispersed causes sedimentation failure in the treated water separation process. The solid content concentration of the activated sludge 3 in the solubilization step is preferably 7,000 to 30,000 g / m ³ . In order to efficiently shear and refine the activated sludge, the solid content concentration of the activated sludge 3 is preferably 7,000 g / m ³ or more, and 30 for the disperser 5 to be processed without clogging with excess sludge. 000 g / m ³ or less is preferable. Hereinafter, description will be made on the assumption that the solubilization treatment is performed at such a concentration.

  In the present embodiment, the amount of activated sludge 3 that is finely dispersed by the disperser 5 in the solubilization tank 4 is preferably 1 to 10 times the amount of activated sludge generated in the membrane separation activated sludge tank 1. In order to finely disperse and sufficiently solubilize the activated sludge 3 with the disperser 5, it is preferable to treat it for 2.4 hours or more. In addition, in order to effectively reduce the amount of activated sludge 3 generated in the membrane separation biological treatment tank 1 by sending the activated sludge 3 that has been finely dispersed and solubilized to the membrane separation biological treatment tank 1, The amount is preferably one or more times the amount of activated sludge generated in the membrane separation activated sludge tank 1. Therefore, specifically, the solubilization tank 4 capable of treating the activated sludge newly generated in the day in the membrane separation activated sludge tank 1 is prepared, and the membrane separation activated sludge tank 1 is treated for 2.4 to 24 hours. It is preferable to repeat the step of transferring to

In the present invention, the amount of the outside air sucked by the agitation of the stirring blade 8 for activated sludge 1 m ³ of the solid content concentration 7,000~30,000g / m ^3, often at least 0.06 m ³ / h 0.06 to 1.2 m ³ / h is preferable. 0.06m microbubbles 12 in the activated sludge 3 in order to efficiently disperse the amount of outside air is solid concentration with respect to activated sludge 1 m ³ of 7,000~30,000g / m ^{3 3} / h The above is preferable. Further, in order to prevent the activated sludge 3 from being re-synthesized using the organic components solubilized by the fine bubbles 12, and to efficiently reduce the activated sludge generated in the membrane separation activated sludge tank 1, the amount of outside air the following are preferred 1.2 m ³ / h with respect to activated sludge 1 m ³ of solid concentration 7,000~30,000g / m ^3.

  In the present invention, “outside air” means gas existing outside the activated sludge 3.

  In the present invention, the ratio of the volume of outside air existing in the volume of the space A near the stirring blade 8 and the volume of the activated sludge 3 is preferably 0.3 to 6%. Here, the volume of the space A in the vicinity of the stirring blade 8 has the same center as the stirring blade 8 and has a height 1.0 to 1.5 times that of the stirring blade 8 as shown in FIG. The volume of the cylindrical space A having a radius 1.0 to 3 times the radius of the stirring blade 8. The volume of the outside air existing in the volume of the space A near the stirring blade 8 is preferably 0.3% or more of the volume of the activated sludge 3 in order to efficiently disperse the fine bubbles 12 in the activated sludge 3. In order to refine the air to such an extent that the self-crushing effect is obtained, it is preferably 6.0% or less of the volume of the activated sludge 3.

  In the present invention, by reducing the depth of the activated sludge 3 in the solubilization tank 4 and increasing the number of revolutions of the stirring blade 8, the activated sludge 3 near the water surface above the rotation center of the stirring blade 8 is also reliably secured. It can be drawn toward the stirring blade 8. Further, when a plurality of dispersers 5 are used as shown in FIG. 5, it is effective to provide a partition plate 13 in the solubilization tank 4. Further, as shown in FIG. 6, the drive unit 9 of the disperser 5 may be taken out of the solubilization tank 4 and the draft tube 14 may be provided above the stirring blade 8. If it does in this way, while the maintenance check of the drive part 9 becomes easy, when activated sludge 3 circulates in the solubilization tank 4, an upflow and a downflow can be divided. Thereby, the residence of the activated sludge 3 near the side wall 11 of the solubilization tank 4 can be prevented. As described above, the activated sludge 3 can be finely dispersed efficiently by appropriately selecting the shape and specifications of the solubilization tank 4 and the disperser 5.

  It is preferable that the activated sludge 3 is sheared and refined, and the fine bubbles 12 are generated and dispersed in the activated sludge 3 at the same time. By doing so, not only can the solubilization tank 4 be prevented from becoming complicated and large, but also the fine bubbles 12 are uniformly dispersed in the activated sludge 3 that has been sheared and refined, and the activated sludge 3 can be effectively dispersed. Can be solubilized.

  In this embodiment, although the thing by the stirring blade 8 was shown as the disperser 5, as long as the activated sludge 3 can carry out the fine dispersion process, what kind of apparatus may be sufficient as it. For example, a static mixer such as a device using ultrasonic waves, a submersible pump, or a line mixer can be used, and is not particularly limited. In the solubilization tank 4, the activated sludge 3 is finely dispersed and solubilized using the disperser 5, so that it is not necessary to add high-pressure gas or chemical solution, etc. Excess sludge can be reduced.

  In the present invention, the outside air sucked by the stirring of the stirring blade 8 includes oxygen, carbon dioxide, ozone, etc. in addition to air, and is not particularly limited. When a gas having a strong oxidizing power such as ozone gas is used, solubilization of the activated sludge 3 is promoted.

  In the present embodiment, the membrane separation activated sludge system, which is a treatment system in which the biological treatment process and the treated water separation process are performed in one tank, has been shown, but the biological treatment process and the treated water separation process are performed in separate tanks. A method may be used and is not particularly limited.

[Second Embodiment]
A second embodiment of the present invention will be described with reference to FIGS. The second embodiment differs from the first embodiment in the treatment process and the biological treatment tank. In the processing step of the second embodiment, a dispersion step is provided after the flow rate adjustment step. Moreover, about the biological treatment tank, in the first embodiment, the biological treatment process and the treated water separation process are performed in the membrane separation biological treatment tank 1, but in the second embodiment, the biological treatment process and the treated water separation are performed. The process is performed in separate tanks. In the present embodiment, the same components as those in the first embodiment are denoted by the same reference numerals, and differences from the first embodiment will be mainly described below.

  FIG. 7 is a processing flow of the second embodiment, and FIG. 8 is a configuration diagram. As shown in FIG. 7, the treatment process of the second embodiment is composed of an inflow process, a flow rate adjustment process, a dispersion process, a biological treatment process, a treated water separation process, a sludge return process, a solubilization process, and a solubilization transfer process. Is done.

  7 to 8, the organic wastewater that has flowed into the facility in the inflow process is sent to the flow rate adjustment process, the flow rate is adjusted in the flow rate adjustment process, and sent to the dispersion process. In the dispersion step, the solid matter in the organic waste water is sheared and refined using the disperser 5 in the dispersion tank 15. Further, the fine bubbles 12 generated by the disperser 5 are dispersed in the organic waste water. Since the structure of the dispersion tank 15 and the disperser 5 is the same as that of the disperser 5 arrange | positioned in the solubilization tank 4 and the solubilization tank 4 of 1st Embodiment, description is abbreviate | omitted. The organic wastewater finely dispersed in the dispersion process is sent to the biological treatment process. In the biological treatment process, the organic wastewater is biologically treated in the biological treatment tank 16 by the activated sludge method. The biologically treated organic waste water is sent to the treated water separation step, and is separated into activated sludge and treated liquid in the settling tank 17. Since other configurations of the second embodiment are the same as those of the first embodiment, description thereof is omitted.

  With the configuration as described above, the following operation occurs in the second embodiment. The organic wastewater that has flowed into the dispersion process from the flow rate adjustment process is sheared and refined in the dispersion tank 15 by the disperser 5. Further, the fine bubbles 12 are dispersed in the organic waste water. Organic wastewater often contains insoluble substances (for example, gelled substances such as fats and oils, proteins, starches, etc.), and by providing a dispersion process before the biological treatment process, The insoluble material can be made to have a particle size suitable for biological treatment. Insoluble substances in organic wastewater are often physically separated and removed by the pressure flotation method, etc., but biological treatment of finely dispersed organic wastewater eliminates the need for large-scale equipment and processes. In addition, the biological treatment can be efficiently performed in the biological treatment tank 16. In addition, by treating the organic wastewater treated in the dispersion process and the activated sludge 3 treated in the solubilization process in the biological treatment process, biological treatment can be performed in a short time and the activated sludge is reduced. A synergistic effect can be obtained. Since other operations of the second embodiment are the same as those of the first embodiment, description thereof is omitted.

[Examples 1-6, Comparative Example 1]
In the solubilization step of the present invention, the influence of the amount of outside air sucked by the disperser 5 on the solubilization of the activated sludge 3 was evaluated by the following test method.

As shown in FIG. 3, a disperser 5 is disposed in a solubilization tank 4 having a volume of 4 × 10 ⁻³ m ³ containing 2 × 10 ⁻³ m ³ of activated sludge, and an intake pipe having both ends opened. The test equipment 10 was arranged at one end at the outside of the solubilization tank 4 and at the other end at the position where it becomes the central part of the negative pressure generated when the stirring blade 8 was rotated by the drive unit 9. The activated sludge 3 is previously taken out from the membrane separation biological treatment tank 1 and has a solid content concentration of 12,000 g / m ³ . Air was used as the outside air. The disperser 5 is operated at a predetermined rotational speed while adjusting the amount of air sucked by the intake pipe 10 per hour for 1 m ³ of activated sludge 3 to a predetermined amount, and the processing time is set to 6 hours. Distributed processing was performed. And the solid content density | concentration of the activated sludge in the solubilization tank 4 before and behind a process was compared, and the solubilization rate was computed according to the following [1] formula.
Solubilization rate (%) = (1- (solid content concentration after treatment / solid content concentration before treatment)) × 100 [1]

  The amount of air sucked from the intake pipe 10 was changed as shown in Table 1, and the influence of the amount of air on the solubilization of the activated sludge 3 was evaluated. The results are shown in Table 2.

As shown in Table 1, it was confirmed that the comparative example 1 in which the activated sludge 3 was sheared and refined only by stirring with the stirring blade 8 without sucking air showed a solubilization rate of less than 10%. In Example 1, it was confirmed that the solubilization rate was greatly improved by sucking even a small amount of air, generating fine bubbles 12 and dispersing them in the activated sludge 3. Further, in Examples 2 to 3, the solubilization rate increases when the amount of air sucked is increased, but the solubilization rate of Examples 3 and 4 in which the air amount with respect to 1 m ³ of activated sludge exceeds 0.3 m ³ / h. It has been confirmed that it has reached its peak and gradually decreases. Furthermore, it was confirmed that in Examples 5 and 6 in which the amount of air with respect to 1 m ³ of activated sludge was 1.8 m ³ / h or more, the solubilization rate rapidly decreased.

In Examples 5 and 6, the cause of the decrease in the solubilization rate is that the activated sludge 3 solubilized by the fine bubbles 12 has been re-synthesized, or the amount of air to be sucked becomes too large, resulting in fine bubbles. It can be considered that the self-crushing effect cannot be obtained because it cannot be generated. From these results, in order to disperse the fine bubbles 12 in the activated sludge 3 and effectively solubilize the activated sludge 3, the solid content concentration of the activated sludge 3 is about 12,000 g / m ^{3 for} 1 hour. air 0.06~1.2m ³ / h it was found that it is preferable to suck the intake pipe 10 to the activated sludge 3 of 1 m ³ per.

[Examples 7 to 12, Comparative Example 2]
Next, the effect of the activated sludge 3 solubilized in the solubilization process on the reduction of the activated sludge generated in the biological treatment process was evaluated by the following test method.

As shown in FIG. 1, a biological treatment facility for organic waste water having a membrane separation activated sludge tank 1 with a volume of 65 m ³ , a disperser 5 and an intake pipe 10 and a solubilization tank 4 with a volume of 1 m ³ , A continuous test was conducted on the effect of the solubilized activated sludge 3 on the reduction of the activated sludge generated in the biological treatment process. 100m ³ of organic wastewater flows into the membrane separation activated sludge tank 1 on average per day, and about 1m ³ of activated sludge with a solid content concentration of 7,000 to 30,000g / m ³ is generated on average. Yes. The solid content concentration of the initial activated sludge in the membrane separation activated sludge tank 1 is 15,000 g / m ³ . 1 m ^{3 of} activated sludge 3 taken out from the membrane separation activated sludge tank 1 in advance is sent to the solubilization tank 4. The solid content concentration of the activated sludge 3 to be treated in the solubilization tank 4 is 15,000 g / m ³ , and the disperser 5 is operated at a predetermined number of revolutions, and approximately 1 hour for activated sludge 1 m ³ . It is adjusted so as to suck air of 0.3 m ³ / h. The test period of the continuous test is 1 month (30 days), and during this period, no activated sludge other than the activated sludge used for the solubilization treatment is taken out from the membrane separation activated sludge tank 1. In this test, the activated sludge used for the solubilization treatment is taken out from the membrane separation activated sludge tank 1 by 1 m ³ (solid content concentration: 15,000 g / m ³ ) at a time and sent to the solubilization tank 4. The timing of extraction is adjusted according to the amount of activated sludge to be solubilized per day, and newly activated sludge is taken out. At the same time, the activated sludge previously treated in the solubilization tank 4 is converted into a membrane-separated activated sludge tank. Transfer to 1. That is, if the amount of activated sludge to be solubilized per day is Am ³ (A is any one of 1, 2, 4, 8, 12, 24), the activated sludge is separated into activated sludge tanks A times a day. 1, treated in the solubilization tank 4 for (24 / A) time, and transferred to the membrane separation activated sludge tank 1. For Comparative Example 2, the activated sludge is not taken out, solubilized, or transferred.

  The solid content concentration of the activated sludge in the membrane separation activated sludge tank 1 was measured at the start of the test and after one month, respectively, and the increase amount of the activated sludge in the membrane separation activated sludge tank 1 was calculated.

This test was conducted at a wastewater treatment facility in a food factory. Therefore, in food factories, the amount of wastewater, biochemical oxygen demand (BOD) in the wastewater, and the concentration of suspended substances and starch may vary depending on the adjustment of the production item and the production amount. In addition, since the test period is monthly, the amount of wastewater treatment and the amount of activated sludge may vary depending on weather conditions and seasonal changes. Therefore, the amount of air sucked by the disperser 5 is basically set to 0.3 m ³ / h, and when the amount of wastewater treatment or activated sludge increases greatly, it is 0 according to the change of wastewater treatment status. It adjusted suitably in the range of 0.06-1.2m < ³ > / h.

As shown in Table 2, it was confirmed that the activated sludge increased in Comparative Example 2 in which the activated sludge 3 solubilized in the solubilization process was not sent to the biological treatment process. In Examples 7-12, the activated sludge which was solubilized by the disperser 5 in the solubilization process and sent the solubilized activated sludge 3 to the biological treatment process, compared with the comparative example 2 which did not send the activated sludge 3 It was confirmed that the increase in the number can be suppressed. Moreover, in Examples 7-10, when the amount of activated sludge 3 was increased, not only the increase in activated sludge was reduced, but it was confirmed that the amount of activated sludge can be significantly reduced compared with before performing biological treatment. It was. However, in Example 9 where the amount of activated sludge 3 exceeds 2 m ³ / day, the decrease in activated sludge peaked out, and in Example 10 where the amount of activated sludge exceeds 4 m ³ / day, it was confirmed that the amount of activated sludge decreased sharply. It was done. Furthermore, in Examples 11 and 12 in which the amount of activated sludge 3 to be solubilized was 12 m ³ / day or more, the activated sludge increased again, and as the amount of activated sludge 3 to be solubilized increased, membrane separation activated sludge tank 1 It was confirmed that the amount of activated sludge increased in Japan.

In Examples 11 and 12, although the activated sludge 3 solubilized during the biological treatment process is sent, the cause of the activated sludge generated in the biological treatment process is that the amount of the activated sludge 3 increases. It is conceivable that the fine dispersion treatment time of 1 m ³ of activated sludge 3 was shortened. When the fine dispersion treatment time of the activated sludge 3 is shortened, the fine dispersion treatment of the activated sludge 3 is not sufficient, and it is considered that the activated sludge 3 cannot be sufficiently solubilized. From these results, in order to reduce the activated sludge in the biological treatment process by the activated sludge 3 that has been solubilized, the activated sludge 3 in an amount 1 to 10 times the amount of activated sludge newly generated in the biological treatment process is used. It is preferable to solubilize in the solubilization step and transfer to the biological treatment step.

1: membrane separation activated sludge tank, 2: membrane, 3: surplus sludge, 4: solubilization tank, 5: disperser, 6: introduction pipe, 7: water supply pipe, 8: stirring blade, 9: drive unit, 10: Intake pipe, 11: side wall, 12: fine bubbles, 13: partition plate, 14: draft tube, 15: dispersion tank, 16: biological treatment tank, 17: sedimentation tank

Claims (6)

In the organic wastewater biological treatment with the activated sludge in the biological treatment tank, and the organic wastewater treatment method in which activated sludge is newly generated by the biological treatment,
Taking out a part of the activated sludge in the biological treatment tank, shearing and refining it, generating and dispersing fine bubbles in the activated sludge, and then transferring the organic wastewater to the biological treatment tank Method. The activated sludge is sheared and refined, and the generation and dispersion of the fine bubbles are simultaneously performed as a fine dispersion treatment by one means,
2. The organic waste water according to claim 1, wherein 1 to 10 times the amount of activated sludge newly generated in the biological treatment tank is taken out, subjected to the fine dispersion treatment and transferred to the biological treatment tank. Processing method. Means for shearing and refining the activated sludge and generating and dispersing the fine bubbles in the activated sludge,
In the activated sludge, rotate the stirring blade provided with an intake pipe with one end opened at the center of rotation,
The activated sludge and the outside air are sucked into the rotation center by the negative pressure generated at the rotation center,
The method for treating organic waste water according to claim 2, wherein the activated sludge and the outside air are refined by a shearing force / stirring force generated by rotation of a stirring blade.   The organic waste water according to claim 3, wherein the outside air is a gas containing any one of air, ozone, and carbon dioxide, and the fine bubbles to be generated and dispersed in the activated sludge are composed of the gas. Processing method. Claims wherein the amount of outside air drawn into the rotation center portion, characterized in that the solids concentration of the activated sludge 1 m ³ per 0.06~1.2m ³ / h of 7,000~30,000g / m ³ Item 5. An organic wastewater treatment method according to Item 3 or 4. The organic wastewater treatment method comprises
At least the inflow process, the flow rate adjustment process, the dispersion process, the biological treatment process, the treated water separation process, and
A part of the activated sludge taken out from the biological treatment tank is sheared and refined, and after generating and dispersing fine bubbles in the activated sludge, including a step of transferring to the biological treatment tank,
In the step before the biological treatment step, the dispersing step is a step of shearing and refining insoluble substances in the organic waste water and generating and dispersing fine bubbles in the organic waste water. The processing method of the organic waste water of any one of Claims 1-5.

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