JP2009291719A - Biological wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To achieve the volume reduction of surplus sludge and the improvement in the quality of treated water. <P>SOLUTION: A biological treatment tank 1 is structured to have three layers, namely an aerobic area A, a facultative anaerobic area B and an anaerobic area C, arranged from top to bottom, thereby enabling decomposition of all biodegradable organic substances in organic wastewater, introduced into the tank 1, according to the three layers A, B, and C, and enabling cooperation of microorganisms different in property to achieve the volume reduction of surplus sludge and the improvement of the quality of treated water. The organic wastewater is introduced into the biological treatment tank 1 from its bottom through an organic wastewater introduction part 6, which supplies the organic substances sufficiently to anaerobic sludge on the bottom to sufficiently maintain the activity of the anaerobic sludge, thereby maintaining the anaerobic area C to maintain the three layers A, B, and C. As a result, further a volume reduction of the surplus sludge and improvement of the quality of the treated water can be achieved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a biological wastewater treatment apparatus for treating organic wastewater with microorganisms.

The activated sludge method often used for organic wastewater treatment such as sewage treatment is a typical biological wastewater treatment method, in which organic wastewater is introduced into an aeration tank (reaction tank) that is a biological treatment tank and aerated. Then, the organic matter in the organic wastewater is decomposed by aerobic microorganisms, the treated water from this aeration tank is settled and separated in the subsequent settling tank (final settling tank), and a part of the settled sludge is returned to the aeration tank. At the same time, the remainder is discharged as excess sludge (see, for example, Non-Patent Document 1).
Supervision of Sewerage Department, City Bureau, Ministry of Construction “Sewerage Facilities Planning and Design Guidelines and Explanation, Part 1994” Japan Sewerage Association, Chapter 5 Water Treatment Facilities, p14

  However, in the above activated sludge method, there is a lot of excess sludge, and a great amount of cost is required for the disposal of this excess sludge, so that volume reduction of the sludge is required. In addition, improvement of treated water quality is further demanded.

  The present invention has been made to solve such problems, and an object of the present invention is to provide a biological wastewater treatment apparatus capable of reducing the volume of excess sludge and improving the quality of treated water.

  A biological wastewater treatment apparatus according to the present invention includes a biological treatment tank having three layers of an aerobic region, a facultative anaerobic region, and an anaerobic region in a tank from the top to the bottom, and the biological treatment tank. And an organic drainage introduction section for introducing organic drainage from the bottom side.

  According to such a biological wastewater treatment apparatus, the biological treatment tank has three layers of an aerobic region, a facultative anaerobic region, and an anaerobic region from top to bottom. All the biodegradable organic substances in the introduced organic wastewater can be decomposed according to the three layers. For example, ammonia nitrogen produced by protein decomposition in the aerobic region is further oxidized to nitrite nitrogen, It becomes nitrate nitrogen and these nitrogen oxides are reduced to nitrogen in the facultative anaerobic region, and a large amount of excess sludge generated in the aerobic region can be decomposed in the anaerobic region. As a result, it becomes possible to reduce the volume of excess sludge and improve the quality of treated water. In addition, since organic wastewater is introduced from the bottom side of the biological treatment tank by the organic wastewater introduction part, organic matter is sufficiently given to the anaerobic sludge at the bottom, and the activity of the anaerobic sludge is sufficiently maintained. As a result of maintaining the anaerobic region and maintaining the three layers, it is possible to further reduce the volume of excess sludge and improve the quality of treated water. In addition, when organic wastewater is introduced from the upper side of the biological treatment tank, organic matter is almost decomposed in the aerobic region, and organic matter is not satisfactorily given to the anaerobic sludge. It becomes difficult to maintain.

  Here, an impeller that stirs the organic wastewater in the tank by rotation in order to form a three-layer structure that can rotate around the vertical axis, and the introduction direction of the organic wastewater by the organic wastewater introduction unit is If the direction is in accordance with the direction of rotation of the impeller, the direction of introduction substantially coincides with the direction of swirling of organic wastewater due to the rotation of the impeller, and the organic wastewater is like an extruded flow (piston flow) upward from the bottom. As a result of flowing and flowing upward so that the layers formed in the vertical direction do not mix so much, it is possible to maintain three layers, further reducing the volume of excess sludge and improving the quality of treated water.

  Thus, according to the present invention, it is possible to reduce the volume of excess sludge and improve the quality of treated water.

  Hereinafter, a preferred embodiment of a biological wastewater treatment apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a biological wastewater treatment apparatus according to an embodiment of the present invention, and FIG. 2 is a plan view showing an organic wastewater introduction state by an organic wastewater introduction unit in FIG.

  The biological wastewater treatment apparatus 100 is, for example, a biological treatment tank 1 in which organic wastewater such as sewage is introduced to biologically treat the organic wastewater, and treated water from the biological treatment tank 1 is introduced to purify sludge. A solid-liquid separation device 2 for solid-liquid separation into water, a sludge return line L1 for connecting the solid-liquid separation device 2 and the biological treatment tank 1 and returning the sludge of the solid-liquid separation device 2 to the biological treatment tank 1, Is provided.

The biological treatment tank 1 is configured, for example, in a circular shape, a rectangular shape, or the like, accommodates microorganisms, and biologically treats organic wastewater. Here, the amount of wastewater introduced into the biological treatment tank 1 is 200 m ³ / d, and the volume is 200 m ³ .

  An impeller 3 is attached to the biological treatment tank 1. The impeller 3 is a stirring blade that can rotate around an axis in the vertical direction for aeration and stirring, and is arranged so as to be immersed in the organic waste water R introduced into the tank 1. . The impeller 3 is configured to rotate in accordance with the driving of the rotary driving source and further to move up and down in accordance with the driving of the lifting / lowering driving source. The state in the tank 1 due to the vertical movement and rotation of the impeller 3 will be described later.

  Here, the solid-liquid separation device 2 is a sedimentation tank, and by separating the treated water containing the sludge generated by the biological treatment in the biological treatment tank 1, the solid-liquid separation apparatus 2 is separated into the precipitated sludge and the supernatant water. Then, this settled sludge is returned to the biological treatment tank 1 by the sludge return line L1, while the supernatant water is discharged to the subsequent stage as purified water.

  Here, particularly in the present embodiment, a state detector 4 for detecting the state in the biological treatment tank 1 is provided for the biological treatment tank 1, and based on the detection result of the state detector 4, The impregnation degree and rotation of the impeller 3 in the organic drainage R so that three layers of an aerobic region A, a facultative anaerobic region B, and an anaerobic region C are formed in the tank 1 from top to bottom. Control means 5 for controlling the speed is provided.

  The aerobic region A here is a region where the treatment with the aerobic microorganism is performed in the presence of oxygen, and the anaerobic region C is the product of the anaerobic microorganism without oxygen, nitric acid / nitrous acid. The facultative anaerobic region B is a transition region between the aerobic region A and the anaerobic region C, and is a facultative anaerobic microorganism (denitrifying microorganism) in the absence of dissolved oxygen. ) Is a region where processing is performed.

  And the said control means 5 controls the raising / lowering drive regarding the impeller 3, controls the immersion degree with respect to the organic waste_water | drain R of the impeller 3, and controls the rotational speed of the impeller 3 by controlling the rotational drive regarding the impeller 3. Control.

  In addition, although the immersion degree with respect to the organic waste_water | drain R of the said impeller 3 is controlled by controlling the vertical motion of the impeller 3 here, the height of the overflow dam of the biological treatment tank 1 is adjusted. Thus, the water surface height of the organic waste water R may be raised and lowered, and thereby the degree of immersion of the impeller 3 in the organic waste water R may be controlled.

  Here, in the impeller 3, when the immersion degree is lowered (when the impeller 3 is raised), a small stirring force is applied to the drainage R in the tank 1, and when the immersion degree is raised (the impeller 3 is lowered). And a large stirring force for the drainage water R in the tank 1, while exhibiting a large stirring force in the vicinity of the water surface, but a small stirring force at the bottom of the tank. .

  Therefore, in view of such characteristics of the impeller 3, in the present embodiment, in order to form the aerobic region A, the sludge (aerobic microorganism agglomerates) is sufficiently stirred to form the organic waste water near the water surface. While making it contact with dissolved oxygen, in order to form the anaerobic area | region C in the bottom part in a tank, the immersion of the impeller 3 so that it may become a water flow (flow velocity 1-5 cm / s) of a grade which does not wind up sludge. Control the degree.

  More specifically, the impregnation degree of the impeller 3 is increased (the impeller 3 is lowered) to create a state where the entire tank is agitated, and then the state detector 4 is used as a velocimeter as shown in the tank. It is thrown into the inner bottom, and the degree of immersion is lowered (the impeller 3 is raised) until the flow velocity at the inner bottom of the tank reaches about 10 cm / s. And since a flow rate falls with sedimentation of sludge, it controls so that the flow rate of a tank inner bottom part may finally become 1-5 cm / s.

  Here, the degree of immersion of the impeller 3 is controlled based on the flow rate at the bottom of the tank, but is not limited to the flow rate at the bottom of the tank. It is preliminarily converted into a flow velocity at another position such as a position corresponding to the region A and a position corresponding to the facultative anaerobic region B in the middle part of the tank, and the control is performed based on the flow velocity at the position. May be. Moreover, the measurement position of the flow velocity is not limited to a single position, and may be a plurality.

  Further, the above-described control of the rotational speed of the impeller 3 is specifically performed by an inverter or a mechanical transmission. Here, the impeller 3 has a characteristic that when the rotational speed is lowered, the supply amount of oxygen decreases, and when the rotational speed is increased, the supply amount of oxygen increases.

  Therefore, in view of such characteristics of the impeller 3, in the present embodiment, in order to form the aerobic region A, oxygen is sufficiently supplied to the sludge (aerobic microbial conglomerate) floating near the water surface. In order to form the facultative anaerobic region B and the anaerobic region C, in the middle and bottom, the impeller 3 is configured so that oxygen is sufficiently consumed by the sludge floating near the water surface and dissolved oxygen is not supplied. Control the rotation speed.

  Here, the rotational speed of the impeller 3 is controlled based on the oxidation-reduction potential and the amount of dissolved oxygen. In this case, the standard of the aerobic region A is 0 to 3 mg / L of dissolved oxygen, redox potential 0 to 100 mV, and the standard of the facultative anaerobic region B is 0 mg / L of dissolved oxygen, redox. A potential of −100 to 0 mv and an anaerobic region C are set to a dissolved oxygen amount of 0 mg / L and a redox potential of −400 to −100 mv.

  Specifically, a reduction potentiometer is inserted into the tank 1 as another state detector, and for example, the impeller 3 is set so that the oxidation-reduction potential at an intermediate position in the height direction of the biological treatment tank 1 is −50 mV. To control the rotation speed. In addition, a dissolved oxygen meter is put into the tank as another state detector. For example, the dissolved oxygen amount at the height of 1/3 from the bottom of the tank is set at the height of 0 mg / L and 2/3. The rotational speed of the impeller 3 is controlled so that the amount of dissolved oxygen becomes 0.1 mg / L or more.

  Of course, the oxidation-reduction potential and dissolved oxygen amount corresponding to the two regions and the oxidation-reduction potential and dissolved oxygen amount corresponding to the three regions may be measured, and based on this, the rotational speed of the impeller 3 may be controlled. .

  Incidentally, since the influence of the impregnation degree and the rotation speed of the impeller 3 on the stirring force and the oxygen supply amount is not completely independent, the adjustment of the immersion degree and the rotation speed may need to be repeated several times. Moreover, since such adjustment changes with changes in the sludge concentration, it is preferable to make fine adjustments about once a week. If the target value is not reached even after such adjustment is repeated several times, the impeller 3 may be intermittently operated by a timer.

  In particular, in the present embodiment, the organic waste water is introduced from the bottom side of the biological treatment tank 1 by the organic waste water introduction unit 6. Specifically, as shown in FIG. 1 and FIG. 2, the organic waste water introduction section 6 is an organic waste water that enters the tank 1 from approximately the center of the bottom of the biological treatment tank 1 and into which the organic waste water flows. A line La and a plurality of introduction pipes 7 connected to the upper end portion of the organic drainage line La and branch off are provided.

  As shown in FIG. 2, the number of the introduction pipes 7 is three here, and extends along the bottom surface of the biological treatment tank 1 (see FIG. 1). A plurality of openings 7a are introduced into the tank 1, and the opening direction of the organic waste water from the openings 7a (arrow in FIG. 2) is the rotation direction of the impeller 3 (clockwise in this case). Is provided in the introduction pipe 7 so as to be in a direction conforming to (so as to substantially coincide).

  According to such a biological waste water treatment apparatus 100, organic waste water is introduced into the biological treatment tank 1 via the organic waste water line La, and the organic waste water R of the impeller 3 that can rotate around the vertical axis. By controlling the degree of immersion and the rotation speed, the three layers of the aerobic region A, the facultative anaerobic region B, and the anaerobic region C are formed in the tank 1 from top to bottom. For this reason, all the biodegradable organic substances can be decomposed according to the three layers A, B, and C, and the ammonia nitrogen generated by the protein decomposition in the aerobic region A is further oxidized to nitrite nitrogen. It is possible to convert nitrate nitrogen into nitrogen in the facultative anaerobic region B, or a large amount of excess sludge generated in the aerobic region A to be decomposed in the anaerobic region C. It is possible to collaborate with microorganisms with different properties. Therefore, the volume of excess sludge can be reduced and the quality of treated water can be improved.

  In addition, since the organic waste water is introduced from the bottom side of the biological treatment tank 1 by the organic waste water introduction part 6, organic matter is sufficiently given to the anaerobic sludge at the bottom, and the activity of the anaerobic sludge is sufficiently As a result of maintaining the anaerobic region C and maintaining the three layers A, B, and C, it is possible to further reduce the volume of excess sludge and improve the quality of treated water.

  In this embodiment, since the introduction direction of the organic waste water by the organic waste water introduction unit 6 is a direction according to the rotation direction of the impeller 3, the introduction direction is the turning of the organic waste water by the rotation of the impeller 3. It almost coincides with the direction. Therefore, the organic waste water flows like an extruding flow (piston flow) upward from the bottom, and flows upward so that the layers formed in the vertical direction do not mix so much. Three layers A, B, and C can be maintained, and the volume of excess sludge can be reduced and the quality of treated water can be further improved.

  In forming the three layers A, B, and C, it is more accurate and preferable to control both the immersion degree and the rotation speed of the impeller 3, but either the immersion degree or the rotation speed of the impeller 3 is preferable. The above three layers A, B, and C may be formed only by control.

  Although the present invention has been specifically described above based on the embodiment, the present invention is not limited to the above embodiment. For example, in the above embodiment, the impeller is controlled by the control means 5 as being particularly suitable. 3 is automatically controlled, but it may be controlled by manual operation by an operator.

  In the above embodiment, the three layers A, B, and C are formed by the rotation of the impeller 3 as being particularly preferable, but the three layers A, B, and C are formed without the rotation of the impeller 3. It can also be applied to biological treatment tanks.

  Moreover, in the said embodiment, although it is especially preferable, the introduction direction of organic waste water is made into the direction according to the rotation direction of the impeller 3, and it is hard to mix three layers A, B, C. It is also possible to introduce it vertically upward.

  Hereinafter, Example 1 and Comparative Examples 1 and 2 will be described.

(Example 1)
The biological wastewater treatment apparatus 100 shown in FIG. 1 is used to introduce organic wastewater from the bottom, and the biological treatment tank has an aerobic region A, a facultative anaerobic region B, and an anaerobic region C. It was set to 1. The amount of waste water to this biological treatment tank 1 is 200 m ³ / d, the volume is 200 m ^3, and the relationship between water depth, MLSS, dissolved oxygen amount, and oxidation-reduction potential is controlled by controlling the immersion degree and rotation speed of the impeller 3. It was like.

(Comparative Example 1)
Example 1 was the same as Example 1 except that the biological treatment tank 1 of FIG. 1 was used as an aeration tank and a so-called standard activated sludge system was adopted in which organic wastewater was introduced from above.

(Comparative Example 2)
It was the same as that of Example 1 except the point which introduce | transduced organic waste_water | drain from the upper part with respect to the biological treatment tank 1 of FIG.

  Table 2 shows the pH, SS, BOD, TN, and sludge generation amount of treated water in each of Example 1, Comparative Example 1, and Comparative Example 2.

  As shown in Table 2, in Comparative Example 2, the amount of excess sludge is reduced and the quality of the treated water is improved as compared with Comparative Example 1, but Example 1 is further more than Comparative Example 2. It can be seen that the amount of excess sludge is decreasing and the quality of the treated water is improved. In Comparative Example 1, the sludge was bulky (it was difficult to settle), and the tank sludge concentration (MLSS) could only be operated at 1000 to 3000 mg / L in the aerobic region. Moreover, the sedimentation property of the sludge has been remarkably improved, and the sludge concentration in the tank (MLSS) can be operated at 3000 to 6000 mg / L in the aerobic region.

It is a block diagram which shows the biological waste water treatment apparatus which concerns on embodiment of this invention. It is a top view which shows the introduction state of the organic waste_water | drain by the organic waste_water | drain introduction part in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Biological treatment tank, 3 ... Impeller, 6 ... Organic waste water introduction part, 7 ... Introduction pipe, 7a ... Opening, 100 ... Biological waste water treatment apparatus, A ... Aerobic area, B ... Facultative anaerobic area, C: Anaerobic region, La: Organic drainage line.

Claims (2)

In the tank, from the top to the bottom, a biological treatment tank having three layers of an aerobic region, a facultative anaerobic region, and an anaerobic region;
An organic wastewater introduction part for introducing organic wastewater from the bottom side of this biological treatment tank,
A biological wastewater treatment apparatus comprising: Comprising an impeller capable of rotating around an axis in the vertical direction and stirring the organic waste water in the tank by rotation in order to form the three layers;
2. The biological waste water treatment apparatus according to claim 1, wherein an introduction direction of the organic waste water by the organic waste water introduction unit is a direction according to a rotation direction of the impeller.

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