JP2005193106A - Wastewater treatment apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wastewater treatment apparatus which can perform an efficient solid-liquid separation with a separation membrane module, and a stable wastewater treatment. <P>SOLUTION: In the wastewater treatment apparatus 10, wastewater is mixed with activated sludge in a biological treatment tank 12 to be biologically treated under an aerobic condition, and the mixture is subjected to solid-liquid separation with the separation membrane module 14. At this time, a coarse bubble diffusion pipe 16 diffuses air fed from a blower, and bubbles of the diffused air are brought into contact with the separation membrane module 14. A fine bubble diffusion pipe 18 diffuses ozone gas fed from an ozone gas generator 22, or air fed from the blower 20 so that the diffused bubbles are not brought into contact with the separation membrane module 14. A controller 24 is connected to an activated sludge densitometer 27, an air supply valve 38, and an ozone supply valve 40, and switching of the diffusion through the fine bubble diffusion pipe 18 is controlled from the measured values sent from the activated sludge densitometer 27. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a wastewater treatment apparatus, and more particularly to a wastewater treatment apparatus in which solid-liquid separation using a separation membrane is used in combination with a biological treatment tank for biologically treating wastewater.

  Conventionally, biological treatments in which wastewater and sewage are treated with microorganisms are widely employed because of their relatively low cost. Since the treated water treated by this biological treatment is mixed with activated sludge containing microorganisms, means for solid-liquid separation of the activated sludge is required before discharging the treated water out of the system.

  As one of the solid-liquid separation means, membrane treatment using a separation membrane module or the like is employed. However, when wastewater with high turbidity is treated, there is a disadvantage that the suction force is lowered due to the deposits on the membrane surface, and the entire wastewater treatment capacity is lowered.

As a countermeasure, a method of providing a diffuser below the separation membrane module and aerating a gas such as air to the separation membrane module as in the wastewater treatment device of Patent Document 1 is adopted. By switching to ozone gas aeration, the cleaning effect on the surface of the separation membrane module can be enhanced.
Japanese Patent Laid-Open No. 11-77044

  By the way, in general, the larger the gas bubbles to be diffused, the better the cleaning power. Therefore, in the air diffuser of Patent Document 1, air is diffused with relatively coarse bubbles.

  However, when performing membrane cleaning with ozone gas, it is difficult for ozone gas to dissolve in the wastewater when air is diffused with large bubbles, and the separation membrane module deteriorates in contact with the dissolved ozone. There was a problem that only a separation membrane could be used.

  Also, in membrane cleaning that always diffuses with air, the amount of dissolved oxygen in the biological treatment tank increases, so that microorganisms in the activated sludge grow and the amount of activated sludge increases, and the activated sludge enters the separation membrane module. There was the fault that it became easy to adhere.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a wastewater treatment apparatus that can efficiently perform solid-liquid separation by a separation membrane module and can stably treat wastewater.

  According to a first aspect of the present invention, in order to achieve the above object, in a wastewater treatment apparatus for treating wastewater by biological treatment in a biological treatment tank, it is immersed in the wastewater in the biological treatment tank and is solid-liquid by membrane treatment. A separation membrane module for performing separation, a coarse bubble diffusing means that is installed at a position directly below the separation membrane module at the bottom of the biological treatment tank, and diffuses air with coarse bubbles, and a bottom of the biological treatment tank. Fine bubble diffusing means that is installed at a position other than directly below the separation membrane module and diffuses air or ozone gas with fine bubbles, and air diffusion switching means for switching the air diffused by the fine bubble diffusing means to air or ozone gas And.

  According to the present invention, by installing a coarse bubble diffusing means directly below the separation membrane module and diffusing air with coarse bubbles to the separation membrane module, activated sludge or the like adheres to the membrane surface. And the cake layer adhering to the separation membrane module can be efficiently removed. Thereby, the efficient waste water treatment which reduced the fall of membrane treatment efficiency can be performed.

  Also, air or ozone gas can be efficiently dissolved in the wastewater in the biological treatment tank by installing a fine bubble diffusing means at the bottom of the biological treatment tank and diffusing air or ozone gas with fine bubbles. it can. And aeration according to a situation can be performed by switching aeration in fine bubble aeration means by aeration switching means. In other words, by switching to air during normal operation, air can be easily dissolved in the wastewater with fine bubbles, so the amount of dissolved oxygen in the wastewater is increased and the efficiency of wastewater treatment with activated sludge is improved. it can. On the other hand, when the amount of activated sludge increases, the aeration of the fine bubble aeration means is switched to ozone gas by the aeration switching means, so that the ozone gas is efficiently dissolved in the waste water, and the activated sludge microorganisms are made available by the dissolved ozone. Solubilization and decomposition of organic substances can be promoted. Further, since the fine bubble diffusing means is disposed at a position where the diffused bubbles do not contact the separation membrane module, the deterioration of the separation membrane module due to the strong oxidizing power of ozone can be reduced.

  In addition, it is preferable that the diameter of the bubble diffused from the fine bubble diffuser is in the range of 0.1 to 2.0 mm. Thereby, since air or ozone gas can be efficiently dissolved in the waste water, the amount of activated sludge and the biological treatment capacity can be adjusted only by switching by the air diffusion switching means.

  Claim 3 of the present invention controls the activated sludge measuring means for measuring the activated sludge concentration in the biological treatment tank of claim 1 or 2, and controls the aeration switching means based on the measured value of the activated sludge measuring means. And a control means for controlling the measured value of the activated sludge measuring means to be 10 to 20% from the set value when the preset value of the activated sludge concentration is set to 100%. When the increased value exceeds a certain value, the aeration of the fine bubble diffusing means is switched to ozone gas, and when the value is less than the certain value, the aeration of the fine bubble diffusing means is switched to air. And

  According to claim 3, in the wastewater treatment apparatus, the amount of activated sludge in the biological treatment tank always changes depending on the quality of the wastewater. Therefore, the activated sludge concentration in the biological treatment tank is measured by the activated sludge measuring means, the preset set value is set to 100%, and if the measured value exceeds a certain value between 10 to 20% from the set value, the control is performed. The means controls the switching of the aeration in the aeration switching means. This allows air or ozone gas to be diffused according to the amount of activated sludge in the biological treatment tank, so that it can always be maintained at an appropriate amount of activated sludge, and solid-liquid separation by the separation membrane module is stable. Therefore, efficient wastewater treatment can be stably performed.

  As described above, according to the wastewater treatment apparatus of the present invention, the coarse bubble diffusing means is installed below the separation membrane module immersed in the biological treatment tank, and the diffused bubbles are formed in the separation membrane module. By installing fine bubble diffusing means in a non-contact position and switching the air diffused in the fine bubble diffusing means to air or ozone gas with the air diffusing means, efficient membrane separation can be achieved and the amount of excess sludge generated Therefore, stable and efficient wastewater treatment can be performed.

  Hereinafter, preferred embodiments of the waste water treatment apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic configuration diagram of a wastewater treatment apparatus 10 according to an embodiment of the present invention, which is an example of aerobic biological treatment.

  The wastewater treatment apparatus 10 is mainly composed of a biological treatment tank 12, a separation membrane module 14, a coarse bubble diffusing pipe 16 that is a coarse bubble diffusing means, a fine bubble diffusing pipe 18 that is a fine bubble diffusing means, and a blower 20. And an ozone gas generator 22 and a controller 24 as control means.

  In the biological treatment tank 12, the wastewater flowing in from the inflow pipe 26 disposed above is mixed with the activated sludge in the biological treatment tank 12 and biologically treated. Moreover, the activated sludge concentration meter 27 which is an activated sludge measuring means is installed in the bottom part of the biological treatment tank 12, and the amount of activated sludge in the biological treatment tank 12 is measured from turbidity.

  The separation membrane module 14 is disposed in a state of being immersed in the biological treatment tank 12, and a separation membrane capable of filtering contaminants such as activated sludge is used. Further, an outflow pipe 28 provided with a pump 30 is provided above the separation membrane module 14, and a suction force is applied to the separation membrane module 14 by driving the pump 30, so that solid-liquid separation is performed by membrane treatment. Water is discharged out of the system from the outflow pipe 28.

  A coarse bubble diffusing tube 16 is installed at the bottom of the biological treatment tank 12 so as to be positioned directly below the separation membrane module 14. The coarse bubble diffusing pipe 16 is a pipe having a plurality of holes (not shown), and each hole is arranged so that the diffused bubbles are in contact with the outer surface of the separation membrane module 14. The coarse bubble diffusing pipe 16 is connected to the blower 20 via the air supply pipe 32, and air is supplied from the blower 20 so as not to affect the membrane processing ability of the separation membrane module 14.

  A fine bubble diffusing tube 18 is installed at a position other than just below the separation membrane module 14 at the bottom of the biological treatment tank 12. The fine bubble diffusing pipe 18 is a pipe provided with a plurality of holes (not shown), but is smaller than the holes of the coarse bubble diffusing pipe 16, and the diameter of the bubbles to be diffused is in the range of 0.1 to 2.0 mm. The size of each hole (not shown) is set so that The fine bubble diffusing pipe 18 is connected to the ozone gas generator 22 via the ozone gas supply pipe 34, and the ozone gas generated by the ozone gas generator 22 is supplied to the fine bubble diffusing pipe 18.

  The air supply pipe 32 and the ozone gas supply pipe 34 are connected by a connection pipe 36, and an air supply valve 38 serving as a diffuser switching unit is installed in the connection pipe 36. Opening and closing the air supply valve 38 adjusts the supply of air to the fine bubble diffusing tube 18. The ozone gas supply pipe 34 is also provided with an ozone gas supply valve 40, which is also a diffuser switching means, at a position downstream of the connection location with the connection pipe 36. The ozone gas supply valve 40 is opened and closed to adjust the supply of ozone gas to the fine bubble diffusing tube 18.

  The controller 24 is connected to the activated sludge concentration meter 27, the air supply valve 38, and the ozone gas supply valve 40. Based on the measured value transmitted from the activated sludge concentration meter 27, the controller 24 opens and closes the air supply valve 38 and the ozone gas supply valve 40. To control.

  Next, the operation of the waste water treatment apparatus 10 according to the embodiment of the present invention configured as described above will be described.

  In the wastewater treatment apparatus 10, wastewater such as sewage flows into the biological treatment tank 12 through the inflow pipe 26 and is mixed with activated sludge to be biologically treated under aerobic conditions. The biologically treated waste water is solid-liquid separated from the activated sludge by the separation membrane module 14 by the suction force of the pump 30, and flows out of the system as treated water from the outflow pipe 28.

  At this time, in the coarse bubble diffusing pipe 16, since a certain amount of air supplied from the blower 20 is always diffused in the form of coarse bubbles, the upward flow generated by the diffused air is generated on the surface of the separation membrane module 14. Works. Thereby, it is possible to suppress the adhering substances such as activated sludge from adhering and fixing on the surface of the separation membrane module 14 by the suction force, so that the membrane treatment in the separation membrane module 14 can be performed efficiently.

  In addition, by constantly diffusing a certain amount of air from the coarse bubble diffusing tube 16, the wastewater in the biological treatment tank 12 can be efficiently stirred and mixed with the activated sludge, and the amount of dissolved oxygen in the wastewater can be increased. Therefore, aerobic biological treatment can be performed efficiently and stably in the biological treatment tank 12.

  In the wastewater treatment apparatus 10, the amount of activated sludge in the biological treatment tank 12 is likely to fluctuate due to external factors such as the quality of the wastewater, and the wastewater treatment capacity of the wastewater treatment apparatus 10 is improved in proportion to the amount of activated sludge. However, if the amount of activated sludge increases too much, activated sludge tends to adhere to the separation membrane module 14 no matter how much air is diffused from the coarse bubble diffusing tube 16. For this reason, the capacity of the separation membrane module 14 is reduced, and thus the processing capacity of the waste water treatment apparatus 10 as a whole is reduced. Therefore, in order to perform an efficient wastewater treatment with the wastewater treatment apparatus 10, it is necessary to maintain the activated sludge in the biological treatment tank 12 in an appropriate amount.

  Therefore, an activated sludge concentration meter 27 that measures the amount of activated sludge in the biological treatment tank 12 is installed, and the measured value is transmitted to the controller 24. Based on the measured value transmitted by the controller 24, the air supply valve 38 and The opening and closing of the ozone gas supply valve 40 was controlled. That is, the controller 24 sets an arbitrary value in advance, sets the set value as 100%, and closes the air supply valve 38 when the measured value exceeds a certain value increased by 10 to 20% to the set value. Then, the ozone gas supply valve 40 is opened, and when the measured value falls below a certain value, the air supply valve 38 is opened and the ozone gas supply valve 40 is closed. The reason why the controller 24 is managed in the range of 10 to 20% of the set value is that the amount of activated sludge does not change linearly, and therefore it is easier to manage by giving a wide range to the set value.

  At this time, a preferable range when the range of 10 to 20% increase from the set value is viewed as an absolute value of the activated sludge concentration is a range of 15 to 20 g / L. For example, if the activated sludge concentration exceeds 20 g / L, it is fine. It is preferable to switch the air diffuser of the bubble diffuser 18 to ozone gas, and to switch the air diffuser to air when it is 20 g / L or less.

  Thereby, when the amount of activated sludge in the biological treatment tank 12 increases and the measured value of the activated sludge concentration meter 27 is a constant value, that is, the activated sludge concentration exceeds 20 g / L, the controller 24 closes the air supply valve 38. In addition, if the ozone gas supply valve 40 is opened, the ozone gas generated by the ozone gas generator 22 can be diffused from the fine bubble diffusing tube 18. Ozone gas is diffused in bubbles with a diameter of 0.1 to 0.2 mm, so it dissolves quickly in the waste water and reacts efficiently with activated sludge, promoting solubilization of microorganisms and decomposition of organic matter in activated sludge. be able to. Since the activated sludge solubilized and decomposed is biologically treated in the biological treatment tank 12 by self-digestion, the increased activated sludge can be decomposed and reduced in the biological treatment tank 12 without being discharged out of the system. it can.

  At this time, the diffused ozone gas immediately dissolves and reacts with the activated sludge, and the fine bubble diffuser 18 is disposed at a position where the diffused bubbles do not contact the separation membrane module 14. The deterioration of the separation membrane module 14 can be prevented.

  On the other hand, when the amount of activated sludge in the biological treatment tank 12 is reduced by ozone gas and the measured value of the activated sludge concentration meter 27 is a certain value or less, that is, the activated sludge concentration is 20 g / L or less, the controller 24 controls the air supply valve 38. And the ozone gas supply valve 40 is closed. At this time, in the fine bubble diffusing tube 18, air is diffused with bubbles having a diameter of 0.1 to 2.0 mm, so that dissolution of the air into the waste water can be promoted. Thereby, since the biological treatment capacity in the biological treatment tank 12 can be further improved, activated sludge whose solubilization / decomposition is promoted by ozone can be biologically treated efficiently.

  Thus, since the amount of activated sludge in the biological treatment tank 12 is automatically held by employing the wastewater treatment apparatus 10 of the present invention, stable wastewater treatment can be performed.

  In the wastewater treatment apparatus 10 described above, the number, shape, material, and the like of each member and apparatus used are not particularly limited. In the waste water treatment apparatus 10, although the biological treatment tank 12 which performs aerobic biological treatment was used, it does not specifically limit. If the upper surface of the biological treatment tank 12 is sealed and nitrogen is circulated instead of air, anaerobic denitrification treatment can be performed efficiently.

The schematic block diagram of the waste water treatment equipment which is embodiment of this invention

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10 ... Waste water treatment apparatus, 12 ... Biological treatment tank, 14 ... Separation membrane module, 16 ... Coarse bubble diffusing pipe, 18 ... Fine bubble diffusing pipe, 20 ... Blower, 22 ... Ozone gas generator, 24 ... Controller, 26 ... Inflow pipe 28 ... Outflow pipe, 30 ... Pump, 32 ... Air supply pipe, 34 ... Ozone gas supply pipe, 36 ... Connection pipe, 38 ... Air supply valve, 40 ... Ozone gas supply valve

Claims (3)

In wastewater treatment equipment that treats wastewater by biological treatment in biological treatment tanks,
A separation membrane module that is immersed in the wastewater in the biological treatment tank and performs solid-liquid separation by membrane treatment,
Coarse bubble diffusing means installed at a position directly below the separation membrane module at the bottom in the biological treatment tank, and diffusing air with coarse bubbles;
Installed in a position other than the bottom of the separation membrane module at the bottom of the biological treatment tank, and fine bubble diffusing means for diffusing air or ozone gas with fine bubbles;
Aeration switching means for switching the aeration of the fine bubble aeration means to air or ozone gas;
A wastewater treatment apparatus comprising:   The waste water treatment apparatus according to claim 1, wherein the diameter of the air bubbles diffused from the fine air bubble diffuser is in the range of 0.1 to 2.0 mm. An activated sludge measuring means for measuring the activated sludge concentration in the biological treatment tank, and a control means for controlling the aeration switching means based on the measurement value of the activated sludge measuring means,
The control means includes
When the set value of the activated sludge concentration set in advance is 100%, the measured value of the activated sludge measuring means exceeds a certain value in the range of 10 to 20% increased from the set value. The wastewater treatment apparatus according to claim 1 or 2, wherein the diffuser of the fine bubble diffuser is switched to ozone gas, and if the air bubble is less than the predetermined value, the diffuser of the fine bubble diffuser is switched to air.

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