JP2018047403A - Biological treatment apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological treatment apparatus which can dissolve a large amount of oxygen in a reaction tank with low power consumption and exhibits good contact efficiency between sewage and microbes.SOLUTION: Multiple stages of oxygen permeable membrane modules 2a to 2c are arranged in a reaction tank 3. An oxygen-containing gas flows from a blower B through the oxygen permeable membrane modules 2a to 2c sequentially via pipes 4, 5, 6, and exits from a pipe 7. The reaction tank 3 has a water depth of 6 m or more, and at least part of the oxygen permeable membrane modules 2a to 2c is arranged at or below the water depth of 6 m. The pressure of the blower is less than a hydraulic pressure caused by the water depth in the reaction tank 3. The oxygen permeable membrane modules 2 have hollow fiber membranes.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an aerobic biological treatment apparatus for organic waste water.

  Since aerobic biological treatment is inexpensive, it is frequently used as a treatment method for organic wastewater. In this method, it is necessary to dissolve oxygen in the water to be treated, and aeration with a diffuser is usually performed.

  Aeration with a diffuser has a low dissolution efficiency of about 5-20%. In addition, it is necessary to aerate at a pressure higher than the water pressure applied to the water depth where the diffuser pipe is installed, and a large amount of air is blown at a high pressure, so the power cost of the blower has been a problem. Usually, more than 2/3 of the power cost in aerobic biological treatment is used for oxygen dissolution.

  The deep aeration tank has been widely used as a biological treatment apparatus in factories and urban areas where the site area is small because the required area of the apparatus can be reduced and the dissolution efficiency of oxygen is high. However, the deep aeration tank for biological treatment having a water depth of 5 m or more, for example, about 10 m has a drawback that a high-pressure blower is required when aeration is performed from the bottom, and the efficiency of the blower is poor and the power cost is high. In addition, a general-purpose medium-pressure blower may be used to aerate from the middle of the aeration tank, and the entire tank may be stirred and mixed by a swirling flow. However, in this method, the oxygen dissolution efficiency is lower than that of full aeration, and the power cost is higher.

  In the system using a high-pressure blower, the efficiency of the high-pressure blower is low, so the power cost is high. The general-purpose blower swirling method uses a large amount of power because of low oxygen dissolution efficiency.

  The membrane aeration bioreactor (MABR) can dissolve oxygen without generating bubbles. In MABR, it is only necessary to ventilate air having a pressure lower than the water pressure applied to the water depth, so that the required pressure of the blower is low and the dissolution efficiency of oxygen is high. However, since MABR does not generate bubbles, it is difficult to mix and agitate the liquid. As a result, the contact between the microorganism and the substrate is deteriorated, and the processing efficiency is lowered.

  In order to improve this, the microorganisms and the substrate are usually brought into contact with each other by aeration intermittently (for example, 1 to 5 minutes every 10 to 30 minutes) to mix and stir the liquid. However, a large blower is required for aeration. Moreover, since the stirring efficiency of the blower is low, the power consumption is increased.

JP-A-11-162

  An object of the present invention is to provide a biological treatment apparatus capable of dissolving a large amount of oxygen in a reaction tank with low power consumption and having good contact efficiency between waste water and microorganisms.

  The biological treatment apparatus of the present invention is a biological reaction apparatus of a deep reaction tank type, and supplies an oxygen-containing gas to a reaction tank, an oxygen permeable membrane module installed in the reaction tank, and the oxygen permeable membrane module. An oxygen-containing gas supply means, and the oxygen permeable membrane module includes a non-porous oxygen permeable membrane. The membrane allows oxygen in the supplied oxygen-containing gas to pass through the tank and In the method, bubbles are not generated.

  In the biological treatment apparatus of one embodiment of the present invention, the reaction tank has a water depth of 6 m or more.

  In the biological treatment apparatus of one aspect of the present invention, the oxygen permeable membrane module is installed in the tank so that at least a part of the membrane has a water depth of 6 m or more.

  In the biological treatment apparatus of one aspect of the present invention, the oxygen permeable membrane module is installed in the tank so that the entire membrane has a water depth of 6 m or more.

  In the biological treatment apparatus of one aspect of the present invention, the oxygen supply means includes a blower, and the pressure of the blower is smaller than the water pressure generated by the water depth of the reaction tank.

  In the biological treatment apparatus of one aspect of the present invention, the membrane is a hollow fiber membrane, and the oxygen permeable membrane module includes a header in which end portions of the hollow fiber membrane are continuous.

  In the biological treatment apparatus of the present invention, the water depth of the reaction tank is 6 m or more, and since the oxygen permeable membrane module is used, oxygen is efficiently dissolved in water by membrane permeation. In this invention, a blower pressure can be made low compared with the case where oxygen-containing gas is blown in water.

It is a longitudinal cross-sectional view of the biological treatment apparatus which concerns on embodiment. (A) is a side view of an oxygen supply permeable membrane module, (b) is a perspective view of an oxygen supply permeable membrane module. It is a front view of a hollow fiber membrane module. It is a longitudinal cross-sectional view of the biological treatment apparatus which concerns on embodiment. It is a perspective view explaining the arrangement | sequence of a hollow fiber membrane. It is a perspective view explaining the arrangement | sequence of a hollow fiber membrane. It is a disassembled perspective view of a hollow fiber membrane module. It is a perspective view of a hollow fiber membrane module. (A) is a side view which shows the arrangement | sequence of the hollow fiber membrane in a hollow fiber membrane module, (b) is the top view. It is a side view of a hollow fiber membrane module. It is a side view of a hollow fiber membrane module. It is a graph which shows oxygen dissolution efficiency. It is a graph which shows a general oxygen transfer coefficient.

  Hereinafter, the present invention will be described in more detail with reference to the drawings.

  The biological treatment apparatus of the present invention is an aerobic biological treatment apparatus suitable for treating organic wastewater such as sewage, paper pulp, chemistry, food, and automobile manufacturing process, and oxygen permeation into a deep tank type reaction tank. A membrane module is arranged. 1A to 1D are longitudinal sectional views showing biological treatment apparatuses 1A to 1D according to an example of the present invention. Each of the biological treatment apparatuses 1A to 1D includes a plurality of oxygen permeable membrane modules 2 arranged in multiple stages in a deep tank type reaction tank 3. In this embodiment, the oxygen permeable membrane module 2 is installed in three stages, but the oxygen permeable membrane module 2 is preferably installed in two to eight stages, particularly in two to four stages.

  The reaction vessel 3 preferably has a water depth of 6 m or more, for example 6 to 100 m, especially 10 to 20 m. It is preferable that at least a part of the oxygen permeable membrane module 2, particularly the upper end of the oxygen permeable membrane module 2, be installed so as to have a water depth of 6 m or more, for example, 10 to 20 m. When a plurality of oxygen permeable membrane modules 2 are provided, it is preferable that the upper end of at least one oxygen permeable membrane module 2 is installed so as to have a water depth of 6 m or more, for example, 10 to 20 m.

  In the biological treatment apparatuses 1A to 1D, raw water may be supplied to the upper part of the reaction tank 3, the treated water may be taken out from the lower part of the reaction tank 3, and the raw water is supplied to the lower part of the reaction tank 3, The treated water may be taken out from the upper part of 3. The raw water may be supplied to the lower part of the reaction tank 3 by a distributor, and in this way, an upward flow of the plug flow is easily formed.

  The oxygen permeable membrane module 2 includes a non-porous oxygen permeable membrane, and oxygen that has permeated through the membrane is dissolved in the water to be treated in the reaction tank 3, so that no bubbles are generated in the reaction tank 3.

  In FIG. 1 (a), oxygen-containing gas such as air from the blower B is supplied to the upper part of the lowermost oxygen permeable membrane module 2c by the pipe 4, flows out from the lower part of the oxygen permeable membrane module 2c, and passes through the pipe 5 Then, it is supplied to the upper part of the second oxygen permeable membrane module 2b from the top, flows out from the lower part of the oxygen permeable membrane module 2b, and is supplied to the upper part of the uppermost oxygen permeable membrane module 2a via the pipe 6. The gas flowing out from the lower part of the oxygen permeable membrane module 2b is discharged through the pipe 7.

  In the biological treatment apparatus of FIG. 1 (b), the oxygen-containing gas from the blower B is supplied to the upper part of the lowermost oxygen permeable membrane module 2c through the pipe 4, flows out from the lower part thereof, and comes into two stages from the lower part. It is supplied to the lower part of the oxygen permeable membrane module 2b of the eye, flows out from the upper part thereof, is then supplied to the lower part of the uppermost oxygen permeable membrane module 2a, and is discharged from the upper part through the pipe 7.

  In the biological treatment apparatus of FIG. 1 (c), the oxygen-containing gas from the blower B is supplied to the lower part of the lowermost oxygen permeable membrane module 2c through the pipe 4, flows out from the upper part, and comes into two stages from the lower part. It is supplied to the lower part of the oxygen permeable membrane module 2b of the eye, flows out from the upper part thereof, is then supplied to the lower part of the uppermost oxygen permeable membrane module 2a, and is discharged from the upper part through the pipe 7.

  In the biological treatment apparatus of FIG. 1 (d), the oxygen-containing gas flows in parallel to the oxygen permeable membrane modules 2a to 2c. That is, the oxygen-containing gas from the blower B is supplied to the upper part of each oxygen permeable membrane module 2 a, 2 b, 2 c through the pipe 4, flows out from the lower part of each, and is discharged through the pipe 7.

  As shown in FIGS. 1A and 1B, the oxygen-containing gas is supplied to the upper part of the lowermost oxygen permeable membrane module 2c, flows out from the lower part of the oxygen permeable membrane module 2c, and then the upper oxygen permeable membrane. In the biological treatment apparatus configured to flow sequentially to the modules 2b and 2a, the condensed water in the oxygen permeable membrane module is easy to escape.

  As shown in FIG. 1C, when the oxygen-containing gas is configured to flow upward in the oxygen permeable membrane modules 2a to 2c, the condensed water in the oxygen permeable membrane module easily evaporates. In particular, by flowing a gas with high dryness as the oxygen-containing gas, the condensed water is easily evaporated.

  As shown in FIGS. 1A to 1C, in a biological treatment apparatus in which an oxygen-containing gas is circulated sequentially from the lowermost oxygen permeable membrane module 2c to the upper oxygen permeable membrane modules 2b and 2a. By making the flow of water to be treated in the tank 3 into an upward flow plug flow, more oxygen is supplied to the water to be treated on the raw water side having a higher BOD concentration. be able to.

  As shown in FIG. 1D, when the oxygen-containing gas is circulated in parallel to each of the oxygen permeable membrane modules 2a to 2c, the pressure loss of the oxygen-containing gas is small and energy is saved. In FIG. 1D, the oxygen permeable membrane module disposed on the raw water side (for example, when the water to be treated is an upward flow, the oxygen permeable membrane module on the lower stage side) increases the oxygen-containing gas flow rate. By doing so, the oxygen supply amount according to the load can be obtained.

  In any of FIGS. 1A to 1D, the oxygen permeable membrane module on the downstream side in the flow direction of the water to be treated may have a smaller membrane area or a lower membrane packing density. .

  The oxygen permeable membrane of the oxygen permeable membrane module 2 may be any of a hollow fiber membrane, a flat membrane, and a spiral membrane, but a hollow fiber membrane is preferable. As the material of the film, silicon, polyethylene, polyimide, polyurethane and the like which are usually used for MABR can be used, but silicon is preferable. A composite film having a high strength and a porous hollow fiber coated with a nonporous polymer may be used.

  The hollow fiber membrane preferably has an inner diameter of 0.05 to 4 mm, particularly 0.2 to 1 mm, and a thickness of 0.01 to 0.2 mm, particularly 0.02 to 0.1 mm. If the inner diameter is smaller than this, the aeration pressure loss is large, and if it is larger, the surface area becomes smaller and the oxygen dissolution rate decreases. When the thickness is smaller than the above range, the physical strength is reduced and the film is easily broken. On the other hand, when the thickness is larger than the above range, the oxygen permeation resistance increases and the oxygen dissolution efficiency decreases.

  The length of the hollow fiber membrane is preferably about 0.5 to 3 m, particularly preferably about 1 to 2 m. If the hollow fiber membrane is too long, when a large amount of biofilm adheres, problems such as breakage, solidification into a dumpling, a decrease in surface area, a decrease in oxygen dissolution efficiency, and an increase in pressure loss occur. If the hollow fiber membrane is too short, the cost increases. For the same reason, the length of the flat membrane and the spiral membrane is preferably 0.5 to 1.5 m.

  FIG. 2 shows an example of the oxygen permeable membrane module 2. This oxygen permeable membrane module 2 uses a hollow fiber membrane 12 as an oxygen permeable membrane. In this embodiment, the hollow fiber membranes 12 are arranged in the vertical direction, and the upper end of each hollow fiber membrane 12 is connected to the upper header 10 and the lower end is connected to the lower header 11. The inside of the hollow fiber membrane 12 communicates with the upper header 10 and the lower header 11, respectively. Each of the headers 10 and 11 is a hollow tube, and a plurality of headers 10 and 11 are arranged in parallel in a substantially horizontal direction. Even when a flat film or a spiral film is used, they are arranged in the vertical direction.

  One end or both ends of each header 10 are preferably connected to the manifold 13, and one end or both ends of each header 11 are preferably connected to the manifold 14. When oxygen-containing gas is supplied to the upper part of the oxygen permeable membrane module 2 and discharged from the lower part of the oxygen permeable membrane module 2, the oxygen-containing gas flows from the upper header 10 through the hollow fiber membrane 12 to the lower header 11, Oxygen permeates through the hollow fiber membrane 12 and dissolves in the water in the reaction vessel 3. Conversely, when oxygen-containing gas is supplied to the lower part of the oxygen permeable membrane module 2 and discharged from the upper part, the oxygen-containing gas is supplied to the lower header 11 and discharged from the upper header 10 through the hollow fiber membrane 12. .

  FIG. 3 is a front view showing an example of the oxygen permeable membrane module 2 arranged in the frame 15. The frame 15 includes four pillars 15a erected at the four corners, an upper beam 15b erected between the upper ends of the pillars 15a, and a lower erection between lower parts of the pillars 15b. It has the beam 15c and the base plate 15d attached to the lower end surface of each pillar 15a. By holding the manifolds 13 and 14 of the oxygen permeable membrane module 2 on the frame 15, the oxygen permeable membrane module 2 is installed in the frame 15.

  The oxygen permeable membrane module 2 provided with the frame 15 can be easily installed in the reaction tank 3 in upper and lower stages. That is, the upper oxygen permeable membrane module 2 can be disposed on the frame 15 of the lower oxygen permeable membrane module 2 so that the bottom seat plate 15d of the upper oxygen permeable membrane module 2 is placed thereon.

  In one aspect of the present invention, a hollow fiber membrane module in which hollow fiber membranes are arranged in the vertical direction is a membrane module having a low height of about 1 to 2 m, and is laminated in two or more stages, preferably four or more stages. To do.

  In this way, oxygen can be dissolved at a low pressure by stacking hollow fiber membrane modules in which the length of the hollow fiber membrane is shortened and the height is lowered in multiple stages.

  The pressure of the oxygen-containing gas blown to the hollow fiber membrane is preferably a pressure slightly higher than the pressure loss of the hollow fiber membrane, for example, about 5 to 20% higher from the viewpoint of cost.

  The pressure supplied to the hollow fiber membrane may be determined regardless of the water depth. Since a normal air diffuser requires a pressure higher than the water depth, the present invention is more advantageous as the water depth of the reaction vessel is deeper.

  In addition, the influence of the carbon dioxide gas melt | dissolved in a film | membrane from the condensed water in a film | membrane or a biological tank changes with piping connection of the module of an up-down direction. Therefore, it is preferable to adopt a pipe connection structure that takes pressure loss, condensed water, and carbon dioxide into consideration.

  In the present invention, as shown in FIG. 4, a vertical partition 20 is installed in the reaction tank 3, and a downward flow portion 21 and an upward flow portion 22 are provided in the reaction tank 3. You may install an oxygen permeable membrane module in the flow part 22, respectively. In FIG. 4, the oxygen permeable membrane modules 2 a to 2 c and 2 d to 2 f are installed in three stages in the downward flow part 21 and the upward flow part 22, respectively, but the number of installation stages is not limited to this.

  The oxygen-containing gas from the blower B is circulated sequentially from the uppermost oxygen permeable membrane module 2a in the downflow portion 21 to the oxygen permeable membrane modules 2b and 2c via the pipes 4, 4a and 4b, and the oxygen permeable membrane module 2c. Gas is supplied to the lowermost oxygen permeable membrane module 2d in the upward flow portion 22 through the pipe 4c. Then, the oxygen permeable membrane modules 2e and 2f are sequentially passed through the pipes 4d and 4e, and the outflow gas of the uppermost oxygen permeable membrane module 2f is discharged from the pipe 7. The raw water is supplied to the upper part of the downward flow part 21, descends in the downward flow part 21, goes around the lower end of the partition 20 and rises in the upward flow part 22, and treats water from the upper part of the upward flow part 22. Is taken out.

  In FIG. 4, the oxygen permeable membrane modules 2 a to 2 f in the downflow portion 21 and the upward flow portion 22 are connected in series, and the oxygen-containing gas is circulated to the oxygen permeable membrane modules 2 a to 2 f by one blower B. However, the oxygen-containing gas may be circulated from separate blowers to the oxygen permeable membrane modules 2a to 2c of the downflow portion 21 and the oxygen permeable membrane modules 2d to 2f of the upward flow portion 22.

  In FIG. 4, the lower end of the partition 20 is higher than the bottom surface of the reaction tank 3, and the upper end of the partition 20 protrudes upward from the water surface in the reaction tank 3, but conversely, the lower end of the partition 20 is the reaction tank 3. The upper end of the partition 20 may be lower than the water level of the reaction tank 3.

  In this case, the raw water is supplied to the lower part of the upward flow part, rises in the upward flow part, wraps around the upper side of the partition, flows into the downward flow part, and descends in the downward flow part to lower the lower flow part. Treated water is taken out of the water.

  Although illustration is omitted, a plurality of upward flow portions and downward flow portions are provided in the reaction tank 3, and the raw water is a downward flow portion → upward flow portion → downflow portion → upward flow portion or upward flow portion → The flow path length may be increased by causing the flow to flow in a downward flow portion → an upward flow portion → a downward flow portion.

  In the present invention, it is preferable to feed the raw water in an upward flow or a downward flow to form a plug flow. By using the flow of the plug flow to bring the liquid and the organism into contact, efficient biological treatment becomes possible. When raw water is supplied through a distributor, a plug flow is easily formed.

  In normal aerobic biological treatment, since aeration was performed, an upward flow or a downward flow plug flow could not be formed. However, since no bubbles are generated in MABR, there is no disturbance in the upper and lower liquids, and an upward flow or downward flow of plug flow is easily formed.

  The LV of the water to be treated in the reaction tank 3 is preferably 4 m / hr or more, for example 4 to 40 m / hr, regardless of the BOD concentration of the raw water, and if it becomes 8 m / hr or more, sufficient substrate and microorganisms are mixed. .

  In the above embodiment, as shown in FIGS. 2 and 3, the hollow fiber membrane 12 is set in the vertical direction, and the raw water (treated water) flows in the vertical direction along the hollow fiber membrane 12. As the oxygen permeable membrane module, an oxygen permeable membrane module having hollow fiber membranes 12a arranged in the horizontal X direction as shown in FIG. 5 and hollow fiber membranes 12b arranged in the horizontal Y direction perpendicular thereto is used. May be. In this case, in order to prevent sludge and the like from accumulating on the upper surface side of the hollow fiber membranes 12a and 12b, the raw water is preferably passed in an upward flow.

  FIG. 6 is a perspective view showing an example of an oxygen permeable membrane module including the hollow fiber membranes 12 (12a, 12b) in the X and Y directions. The oxygen permeable membrane module 30A includes a pair of parallel headers 31 and 31 extending in the Y direction, a pair of headers 32 and 32 extending in the X direction perpendicular to the header 31, and the hollow fiber membrane 12. Have. The X-direction hollow fiber membrane 12 a is constructed between the headers 31, 31, and the Y-direction hollow fiber membrane 12 b is constructed between the headers 32, 32. The hollow fiber membrane 12 a communicates with the header 31, and the hollow fiber membrane 12 b communicates with the header 32.

  By connecting the end portions of the headers 31 and 32 to each other, the headers 31 and 32 have a rectangular frame shape. However, closing members (not shown) such as end plugs are provided inside both ends of the headers 31 and 32. The headers 31 and 32 are blocked. The oxygen-containing gas is supplied to one header 31, passes through the hollow fiber membrane 12 a, and flows into the other header 31. The oxygen-containing gas is supplied to one header 32, passes through the hollow fiber membrane 12 b, and flows into the other header 32.

  In FIG. 6, the hollow fiber membranes 12a and 12b are simply overlapped as shown in FIG. 5, but as shown in FIGS. 7 (a) and 7 (b), the hollow fiber membrane 12a in the X direction and the hollow fiber in the Y direction. The membrane 12b may be braided into a plain weave.

  In FIG. 6, the oxygen permeable membrane module 30A includes the hollow fiber membranes 12a and 12b extending in two orthogonal directions, but the hollow fiber membrane 12 extending in parallel only in one direction as shown in FIG. An oxygen permeable membrane module 30 that is installed between the pair of headers 33 and 33 and is connected to both ends of the headers 33 and 33 by rod-shaped connecting members 34 to form a rectangular frame shape may be used.

  In this case, a plurality of oxygen permeable membrane modules 30 are stacked in the reaction tank so that the directions of the hollow fiber membranes 12 are alternately reversed. In FIG. 8, the oxygen permeable membrane module 30 at the odd-numbered stage (the uppermost stage and the third stage from the top) has the hollow fiber membrane 12 extending in the Y direction, and the even-numbered (second stage) oxygen-permeable membrane module. 30, the hollow fiber membrane 12 extends in the X direction. Although only three stages of oxygen permeable membrane modules 30 are shown in FIG. 8, two stages or four or more stages may be installed. Further, although the oxygen permeable membrane modules 30 are separated from each other in FIG. 8, the oxygen permeable membrane modules 30 are actually arranged closer to each other than illustrated, for example, so as to overlap each other.

  As shown in FIGS. 9 and 10, a plurality of oxygen permeable membrane modules 30 may be arranged in the frame 15 as a unit. In FIG. 9, in one frame 15, an oxygen permeable membrane module 30 with the hollow fiber membrane in the X direction (hereinafter referred to as an oxygen permeable membrane module 30 </ b> X) and an oxygen permeable membrane module 30 with the hollow fiber membrane in the Y direction. (Hereinafter referred to as the oxygen permeable membrane module 30Y) are alternately arranged in multiple stages.

In FIG. 10, the unit in which the oxygen permeable membrane module 30X is arranged in the frame 15 and the unit in which the oxygen permeable membrane module 30Y is arranged in the frame 15 are arranged so as to be stacked up and down. In FIG. 10, only two stages are shown, but three or more stages may be provided.
In addition, although these hollow fiber membranes are one by one in FIGS. 5 to 8, they may be bundles of several to 100.

  By disposing the hollow fiber membrane horizontally and in a mesh or lattice, the water to be treated rising from the lower part is agitated and mixed when passing through the mesh or lattice and comes into contact with microorganisms attached to the hollow fiber membrane. . As the water to be treated rises and every time it passes through the mesh or lattice, the water to be treated comes into contact with microorganisms and biological treatment proceeds. The same applies when descending from the top.

  When the hollow fiber membranes are arranged only in the longitudinal direction, the hollow fibers are formed into a large bundle and a water passage through which water preferentially passes is formed, or a short path is likely to occur.

  By arranging the hollow fiber membranes horizontally and in a mesh shape, the hollow fiber membranes are prevented from becoming clumped by the slime of the grown microorganisms, and the contact efficiency is increased.

  In this invention, you may further provide the reaction tank through which to-be-processed water flows sideways. In this case, in order to make the flow of water to be treated into a plug flow, it is preferable that the reaction tank is elongated and the ratio of length to width is 20: 1 or more. In this case, the lateral linear velocity of the water to be treated is preferably 4 m / hr or more as in the case of the upward flow and the downward flow.

  When the water to be treated is flowed sideways in this way, as at least a part of the oxygen permeable membrane module, as shown in FIG. 11, the vertical hollow fiber membranes 12c and the horizontal hollow fiber membranes 12d are arranged in a lattice pattern. It may be configured so that raw water flows in the horizontal direction through the lattice. A network-like hollow fiber membrane module may be used instead of the lattice shape.

  Next, preferred examples of the oxygen-containing gas and blower used in the present invention will be described.

<Oxygen-containing gas>
The oxygen-containing gas may be a gas containing oxygen, such as air, oxygen-enriched air, or pure oxygen. It is desirable that the gas to be vented pass through a filter to remove fine particles.

  The amount of aeration is preferably about twice the amount of oxygen required for biological reactions. If it is less than this, BOD and ammonia will remain in the treated water due to insufficient oxygen, and if it is greater, the air flow will be unnecessarily increased and the pressure loss will be increased, so the economy will be impaired.

  The aeration pressure is desirably slightly higher than the pressure loss of the hollow fiber generated at a predetermined aeration amount.

<Blower>
As the blower, it is sufficient that the discharge wind pressure is equal to or lower than the water pressure coming from the water depth. However, it is necessary to be more than the pressure loss of piping. Usually, the pipe resistance is about 1 to 2 kPa.

  In the case of a water depth of 5 m, a general-purpose blower with an output of up to about 0.55 MPa is usually used, and a high-pressure blower has been used at a water depth higher than that.

  In the present invention, a general purpose blower having a pressure of 0.5 MPa or less can be used even at a water depth of 5 m or more, and a low pressure blower of 0.1 MPa or less is preferably used.

  The supply pressure of the oxygen-containing gas is required to be higher than the pressure loss of the hollow fiber membrane, lower than the water depth pressure, and further, the membrane should not be crushed by water pressure. Since the pressure loss of the flat membrane and the spiral membrane is negligible compared to the water pressure, the pressure is very low, about 5 kPa or more, water pressure or less, preferably 20 kPa or less.

In the case of a hollow fiber membrane, the pressure loss varies depending on the inner diameter and length. Since the amount of air to be aerated is ²⁰ mL to 100 mL / day per m ² of membrane, the amount of air doubles when the membrane length is doubled, and the amount of air is only doubled even when the membrane diameter is doubled. Don't be. Therefore, the pressure loss of the membrane is directly proportional to the membrane length and inversely proportional to the diameter.

  The value of pressure loss is about 3 to 20 kPa for hollow fibers having an inner diameter of 50 μm and a length of 2 m.

  According to the experiment of the present inventor, it was confirmed that the oxygen dissolution rate hardly changed as a result of changing the aeration pressure to 11 to 140 kPa and the aeration amount to 240 to 460 mL / min.

  In the present invention, the oxygen dissolution efficiency is preferably 30 to 100%, particularly 40 to 60%.

FIG. 12 shows a hollow fiber membrane module having a membrane area of 1.5 m ² , 12 g-O ₂ / m ² / day, and supplying air at a rate of 11 to 140 mBar at 70 mL / min. And it is a graph which shows an example of oxygen dissolution efficiency at the time of driving | running with 60% dissolution efficiency. The curve between 1/11 and 1/31 in FIG. 12 is attributed to the consumption of oxygen due to the attachment of the biofilm to the hollow fiber membrane. Variations in oxygen dissolution efficiency occur due to consumption by biofilms and fluctuations in BOD (COD) load.

  If the oxygen concentration at the inlet of the hollow fiber membrane is 20% (in the air) and the oxygen concentration at the outlet is 10% (decreases by passing through the membrane), the oxygen dissolution efficiency is 50%. When the air volume is increased, a sufficient amount of oxygen is supplied, so that the dissolution efficiency decreases. Conversely, when the air volume is lowered, oxygen permeates through the inlet portion, and the dissolution efficiency approaches 100%.

  When setting the specifications of the biological treatment apparatus of the present invention, it is preferable to determine the water depth and blower pressure, then determine the dissolution efficiency, determine the membrane area commensurate with it, and determine the air volume. The determination of membrane area and air volume may be reversed.

  In general, kLa (overall oxygen transfer coefficient) is preferably higher. However, when an oxygen permeable membrane is used, even if the pressure is increased, it does not exceed the performance of the membrane. Therefore, it is necessary to control the amount of dissolution by changing the air volume or increase the membrane area.

  The upper graph of FIG. 13 shows kLa when a hollow fiber membrane module is installed in a water tank (substantially the same length of hollow fiber membranes are arranged vertically) at a water depth of 60 cm and the oxygen supply pressure is changed. The lower graph of 13 shows kLa when a hollow fiber membrane module in which a 60 cm hollow fiber membrane is vertically arranged is installed in a water tank having a water depth of 5 m and the oxygen supply pressure is changed.

  In any case, since oxygen permeates even at a pressure lower than the water depth, a blower supplied at a pressure lower than the water pressure can be used.

  Moreover, kLa hardly changes with the water depth.

  The straight line connecting the black squares in FIG. 13 is a theoretical line when using a diffuser plate, and indicates that kLa depends on the air volume and pressure. Therefore, bubbles do not come out from the diffuser tube into the tank unless pressure higher than the water depth is applied.

  In the case of deep aeration with a water depth of 5 m or more, it was necessary to use a high-pressure blower in the diffuser that generates normal bubbles, but when the water depth is shallow due to the effect of pressure loss (air leakage, etc.) In comparison with the above, the required pressure / water pressure gradient becomes larger.

  Therefore, by using a non-porous oxygen permeable membrane, it is possible to supply sufficient oxygen into the tank by using a low-pressure blower or a general-purpose blower even in deep layer aeration of 10 to 20 m or more. It is.

1A to 1E Biological treatment device 2, 30, 30A Oxygen permeable membrane module 10, 11, 31, 32, 33 Header 12, 12a to 12d Hollow fiber membrane 13, 14 Manifold 15 Frame 20 Partition 21 Downflow portion 22 Upflow portion 34 Connecting members

Claims (6)

A biological reactor of a deep reaction tank type,
A reaction vessel;
An oxygen permeable membrane module installed in the reaction vessel;
Oxygen-containing gas supply means for supplying an oxygen-containing gas to the oxygen permeable membrane module;
With
The oxygen permeable membrane module includes a non-porous oxygen permeable membrane, and the membrane permeates oxygen in the supplied oxygen-containing gas into the tank and does not generate bubbles in the tank. Biological treatment equipment.   The biological treatment apparatus according to claim 1, wherein the reaction tank has a water depth of 6 m or more.   The biological treatment apparatus according to claim 1 or 2, wherein the oxygen permeable membrane module is installed in a tank so that at least a part of the membrane has a water depth of 6 m or more.   The biological treatment apparatus according to claim 1 or 2, wherein the oxygen permeable membrane module is installed in a tank so that the entire membrane has a water depth of 6 m or more.   The biological treatment apparatus according to any one of claims 1 to 4, wherein the oxygen supply means includes a blower, and a pressure of the blower is smaller than a water pressure generated by a water depth of the reaction tank.   The biological treatment apparatus according to any one of claims 1 to 5, wherein the membrane is a hollow fiber membrane, and the oxygen permeable membrane module includes a header in which ends of the hollow fiber membranes are continuous.

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