Wastewater treatment device

Abstract

To provide a wastewater treatment apparatus capable of performing maintenance in a short time.SOLUTION: There is provided a wastewater treatment apparatus 1, including: a storage tank 30 for storing water to be treated, which is a treatment target; a plurality of carriers 51 stored in the storage tank 30 and carrying at least microorganisms; and oxygen supply means 40 for mixing micro-nano bubbles containing oxygen into the water to be treated introduced from the storage tank 30 by the action of pumps 47, 47' to suck in the water to be treated and supplying a mixture into the storage tank 30, in which the suction sides of the pumps 47, 47' are provided with strainers 8, 8' having pores 8a for preventing the passage of the carrier 51. The wastewater treatment apparatus 1 also includes backwashing means 60 for introducing fluid into flow paths 48, 48' between the pumps 47, 47' and the strainers 8, 8' to wash the strainers 8, 8'.SELECTED DRAWING: Figure 7

Description

Technical Field

[0001] The present invention relates to a wastewater treatment apparatus for treating wastewater containing organic wastewater discharged from power plants such as thermal power plants, composite facilities in collaborative operations, food, chemical, paper, automobile factories, and the like.

Background Art

[0002] In the case of wastewater containing organic wastewater discharged from various industrial facilities, food, chemical, paper, automobile factories, and the like, a wastewater treatment apparatus that sterilizes bacteria contained in the wastewater and decomposes and removes organic substances and oil and fat components contained in the wastewater is used. In particular, it is known that biological treatment using microorganisms is effective for decomposing and removing organic substances and oil and fat components contained in wastewater.

[0003] For example, as shown in Patent Document 1, a wastewater treatment apparatus that performs biological treatment using microorganisms includes a storage tank into which treated water is introduced, a plurality of carriers introduced into the treated water in the storage tank, and oxygen supply means for supplying oxygen to the treated water. The carrier is composed of a synthetic resin using a mineral as a raw material, and mainly aerobic microorganisms are supported in the pores of the carrier. The oxygen supply means includes a water absorption pump that absorbs the treated water in the storage tank and a micro-nano bubble generation nozzle attached to the downstream side of the water absorption pump. The treated water sucked by the water absorption pump is mixed with ultrafine bubbles when passing through the micro-nano bubble generation nozzle and returned to the biological treatment tank.

[0004] In this way, the treated water in the storage tank is biologically treated by coming into contact with the carrier carrying aerobic microorganisms. In addition, oxygen is supplied to the treated water at any time by the oxygen supply means, so that aerobic microorganisms can be activated to exhibit a high aerobic decomposition ability.

Prior Art Documents

Patent Documents

[0005]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0006] In the wastewater treatment apparatus of Patent Document 1, the wastewater in the storage tank is agitated by suction and discharge by a suction pump and the buoyancy of micronano bubbles, so that oxygen and moisture necessary for the growth of aerobic microorganisms can be sufficiently supplied. However, in such a wastewater treatment apparatus, the carrier introduced into the wastewater may be sucked in by the suction pump, resulting in damage to the suction pump, blockage of the flow path, or damage to the carrier. Therefore, it is conceivable to use a filter in front of the suction pump, but clogging occurs over time, and the filter must be removed and cleaned, forcing the wastewater treatment apparatus to stop for a long time.

[0007] The present invention has been made paying attention to such problems, and an object thereof is to provide a wastewater treatment apparatus capable of performing maintenance in a short time.

Means for Solving the Problems

[0008] In order to solve the above problems, the wastewater treatment apparatus of the present invention includes a storage tank for storing wastewater to be treated, a plurality of carriers stored in the storage tank and carrying at least microorganisms, and oxygen supply means for mixing micronano bubbles containing oxygen into the wastewater introduced from the storage tank by the action of a pump for sucking the wastewater and supplying the mixture to the storage tank, a strainer having pore portions for preventing passage of the carriers is provided on the suction side of the pump, The wastewater treatment apparatus is characterized by comprising backwashing means for introducing fluid into the flow path between the pump and the strainer to wash the strainer. According to this feature, it is possible to prevent the carrier from being sucked into the pump of the oxygen supply means by the strainer. Further, by temporarily sending out the fluid to the flow path between the pump and the strainer by the backwashing means, it is possible to eliminate the clogging of the carrier in the pore portion of the strainer in a short time.

[0009] The backwashing means is characterized in that the water to be treated introduced through the strainer is introduced into the flow path. According to this feature, since the water to be treated passing through the strainer is used for backwashing, the amount of the water to be treated does not increase due to the backwashing operation.

[0010] The wastewater treatment apparatus has at least two oxygen supply means having a strainer on the suction side of the pump, and is characterized in that the water to be treated introduced through one strainer by one pump is introduced into the flow path between the other pump and the other strainer. According to this feature, since backwashing can be performed using the pump of the oxygen supply means, a pump for backwashing is not required, and the wastewater treatment apparatus can have a simple structure.

[0011] The oxygen supply means has a mixing section for mixing micro-nano bubbles containing oxygen. It is characterized in that a branch path is provided that branches from between the mixing section of the one oxygen supply means and the one pump to the flow path between the other pump and the other strainer. According to this feature, since the water to be treated can be introduced between the other pump and the other strainer without passing through the mixing section, the other strainer can be efficiently backwashed.

[0012] The one pump and the other pump are characterized in that the water to be treated is discharged in the same turning direction in the storage tank. According to this feature, since the discharge flow of one pump and the discharge flow of the other pump do not interfere with each other, the stirring force of the water to be treated is high.

[0013] The upper surface of the strainer is inclined obliquely. According to this feature, the stacking of the carrier on the upper surface of the strainer is suppressed.

Brief Description of the Drawings

[0014]

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Mode for Carrying Out the Invention

[0015] A mode for carrying out the wastewater treatment apparatus according to the present invention will be described below based on examples.

Example

[0016] The wastewater treatment apparatus according to Example 1 will be described with reference to FIGS. 1 to 8. First, reference numeral 1 in FIG. 1 is the wastewater treatment apparatus to which the present invention is applied. This wastewater treatment apparatus 1 is installed in a food factory in this example, and is a device that purifies wastewater containing organic components such as oil and fat discarded from the factory as raw water before discharging it into a river or the like. The wastewater treatment apparatus 1 that can be directly discharged into a river, a waterway, a sea area, etc. without providing a sedimentation tank or a membrane treatment means is unprecedented.

[0017] As shown in FIG. 1, the wastewater treatment apparatus 1 is connected to a raw water tank 4 that collects wastewater discharged from inside the factory 2 to the outside on its upstream side. Note that the wastewater treatment apparatus according to the present invention is not limited to the food factory of this example, and can be widely applied to general wastewater such as domestic wastewater from apartment houses such as condominiums, and complex buildings for business use, power plants such as thermal power plants, chemical factories, etc., hospitals, hotels, restaurants, etc. containing organic wastewater, or can also be operated at a sewage treatment plant.

[0018] In addition, the wastewater treatment apparatus 1 is connected to a drain pipe 39 that discharges the treated wastewater on its downstream side, and the purified wastewater is discharged into a river or the like (not shown) through the drain pipe 39.

[0019] The wastewater treatment apparatus 1 mainly includes an ozone reaction tank 10 for performing ozone treatment, a biological treatment tank 30 as a storage tank into which the ozone-treated water to be treated is introduced for performing biological treatment, an ozone bubble generator 20 as ozone supply means, oxygen (air) bubble generators 40, 40' as oxygen supply means, and a backwashing means 60 for eliminating clogging of strainers 8, 8' described later. Hereinafter, each component of the wastewater treatment apparatus 1 will be described in detail.

[0020] The raw water tank 4 is a substantially rectangular tank in plan view into which the wastewater collected from the factory 2 is introduced through the wastewater channel 3. In the raw water tank 4, a raw water pump 5 for transferring the water to the next ozone reaction tank 10 and a float 6 as a water level sensor are installed. In this embodiment, the internal capacity of the raw water tank 4 is approximately 2 tons, but in practice, it is transferred to the next ozone reaction tank 10 by float control with a storage amount of less than 1 ton.

[0021] Next, the ozone reaction tank 10 is a substantially cylindrical tank into which the water to be treated from the raw water tank 4 is introduced through a transfer pipe 7 connected to the raw water pump 5. In the ozone reaction tank 10, a suction pump 27 constituting the ozone bubble generator 20, a transfer pump 15 for transferring the water to the next biological treatment tank 30, and a float 16 as a water level sensor are installed. In this embodiment, the internal capacity of the ozone reaction tank 10 is approximately 2.7 tons. Further, outside the ozone reaction tank 10, an ozone generator 29 constituting the ozone bubble generator 20 is installed and connected to a micro-nano bubble generation nozzle (not shown) through a connection pipe 26.

[0022] The ozone generated by the ozone generator 29 installed outside the ozone reaction tank 10 and sucked through the connection pipe 26 connected to this ozone generator 29 becomes ultra-fine bubbles, that is, micro-nano bubbles of ozone, when passing through the micro-nano bubble generation nozzle, and is ejected into the ozone reaction tank 10.

[0023] In the ozone reaction tank 10, ozone treatment using micro-nano-bubbled ozone (hereinafter simply referred to as ozone treatment) is performed. Specifically, ozone (O3) having a strong oxidizing power is bubbled into micro-nano level fine diameters, generating a large amount of OH groups (OH - ) and physically decomposing the organic substances contained in the water to be treated. In this way, since the organic substances are physically decomposed by ozone (O3), it becomes easier for microorganisms to prey on them in the biological treatment tank 30 described later.

[0024] Next, as shown in FIGS. 1 and 2, the biological treatment tank 30 will be described. The biological treatment tank 30 is a substantially cylindrical water tank into which the water to be treated from the ozone reaction tank 10 is introduced via a transfer pipe 17 connected to a transfer pump 15. Inside the biological treatment tank 30, there are water inlets 30b, 30b' communicating with oxygen (air) bubble generators 40, 40', bubble outlets 30c, 30c' for discharging oxygen (air) micro-nano-bubbles (hereinafter sometimes simply referred to as oxygen (air) bubbles), an outlet 30d that is openably and closably connected to a drain pipe 39 via an on-off valve 38, and a float 36 as a water level sensor is installed.

[0025] In this embodiment, the internal volume of the biological treatment tank 30 is approximately 54 tons, that is, approximately 20 times the volume of the ozone reaction tank 10, and the height in the vertical direction is formed to be longer than the inner diameter in the planar direction. In this way, in the biological treatment tank 30 having a larger internal volume, by flowing oxygen (air) micro-bubbles over a wide range, it is possible to promote biological treatment and chemical changes to reduce residual ozone. Also, the bubble outlets 30c, 30c' are connected to oxygen (air) bubble generators 40, 40' installed outside and communicating with the biological treatment tank 30 and a backwashing means 60. Incidentally, hereinafter, the entire biological treatment tank 30, oxygen (air) bubble generators 40, 40' and backwashing means 60 may also be referred to as a biological treatment apparatus 300.

[0026] In addition, a large number of biofilters 50, 50,... are placed inside the biological treatment tank 30, and these biofilters 50, 50,... are used as beds for aerobic microorganisms and facultative anaerobic microorganisms. The biofilters 50, 50,... are composed of substantially rectangular parallelepiped carriers 51, 51,... having long sides and short sides and can move freely inside the biological treatment tank 30. By forming the carriers 51, 51,... in a substantially rectangular parallelepiped shape in this way, not only can the fluidity of the carriers 51, 51,... floating in the water to be treated be enhanced, but also the occurrence of chipping of the carriers 51, 51,... accompanying the flow can be suppressed. The biofilter 50 is formed from a synthetic resin using a mineral having a plurality of pores as a raw material. Further, not only aerobic microorganisms and facultative anaerobic microorganisms but also activated carbon 58 produced in powder form as described later is added to these biofilters 50, 50,... (see Fig. 5), but not limited to this, a neutralizing agent, an odor inhibitor, etc. can also be added.

[0027] In the biological treatment tank 30, an inlet 17a that opens at the tip of the transfer pipe 17 described above is provided at the upper part of the biological treatment tank 30, and an outlet 30d that communicates with the drain pipe 39 via an opening / closing valve 38 is provided near the bottom surface of the lower part of the biological treatment tank 30. Therefore, the water to be treated introduced into the biological treatment tank 30 from the inlet 17a of the transfer pipe 17 descends while being biologically treated. According to this, since the water to be treated introduced from the upper part of the biological treatment tank 30 flows until it reaches the lower part of the biological treatment tank 30, the time for biological treatment in the biological treatment tank 30 can be lengthened. The drain pipe 39 is once raised to the water surface level of the biological treatment tank 30, and the same amount of water as the amount of water flowing in from the inlet 17a flows down naturally and is discharged as it is.

[0028] Furthermore, since the bubble discharge port 30c opens in the circumferential direction of the inner peripheral wall 30a of the biological treatment tank 30, when micronano bubbles are discharged from the bubble discharge port 30c, a circulating flow is generated in the cylindrical biological treatment tank 30. The micronano bubbles adhere to the biofilters 50, 50,... and are moved upward by the circulating flow while enhancing buoyancy. As the micronano bubbles are crushed or detached over time, they are dropped downward again. Therefore, biological treatment can be effectively performed.

[0029] In addition, a stirring plate or the like for stirring the biofilter beds 50, 50,... may be provided on the inner peripheral surface of the biological treatment tank 30. By doing so, when the inside of the biological treatment tank 30 is rotationally driven, the biofilter beds 50, 50,... are moved upward by the above-described stirring plate and dropped downward again, so that biological treatment can be effectively performed.

[0030] Further, as shown in FIGS. 2 and 3, substantially cylindrical strainers 8, 8' each having a plurality of pore portions 8a are attached to the water suction ports 30b, 30b' which are the suction sides of the water suction pumps 47, 47' (only the strainer 8 is shown here). In the present embodiment, the pore portions 8a are formed on the entire surface of the strainers 8, 8', but the present invention is not limited to this. For example, the pore portions 8a may be formed only on the side surfaces of the strainers 8, 8'.

[0031] The pore portions 8a are formed to have openings smaller than the biofilter beds 50 (carriers 51), and the biofilter beds 50, 50,... cannot pass through. According to this, the biofilter beds 50, 50,... are prevented from being sucked into the water suction pumps 47, 47' of the oxygen (air) bubble generators 40, 40'. In the present embodiment, mesh-like strainers 8, 8' are illustrated, but the present invention is not limited to this. For example, if it has pore portions 8a formed to have openings smaller than the carrier 51, it may be composed of punching metal or the like. Furthermore, the strainers 8, 8' may be provided as a part of connection pipes 48, 48' described later which are the suction sides of the water suction pumps 47, 47'.

[0032] Also, each upper surface 8b of these strainers 8, 8' is inclined so as to become lower from the outer diameter side of the biological treatment tank 30 toward the central portion. According to this, since the biofilter beds 50, 50,... fall from each upper surface 8b of the strainers 8, 8, the biofilter beds 50, 50,... are prevented from being stacked and staying on the upper surface 8b of the strainer 8.

[0033] Next, as shown in FIGS. 1 and 4, the oxygen (air) bubble generators 40, 40' will be described.

[0034] The oxygen (air) bubble generator 40 mainly comprises a water suction pump 47 that sucks the liquid in the biological treatment tank 30 disposed outside the biological treatment tank 30, a connection pipe 48 as a flow path connecting a water suction port 30b opened near the bottom surface of the lower part of the biological treatment tank 30 and the water suction pump 47, a micro-nano bubble generation nozzle 45 as a mixing part connected to a bubble discharge port 30c opened near the bottom surface of the lower part of the biological treatment tank 30, and a connection pipe 49 connecting the water suction pump 47 and the bubble discharge port 30c.

[0035] Also, the oxygen (air) bubble generator 40’ mainly comprises a water suction pump 47’, a connection pipe 48’ as a flow path, a micro-nano bubble generation nozzle 45’, and a connection pipe 49’. Since the configurations of the various members of the oxygen (air) bubble generator 40’ are substantially the same as those of the various members of the oxygen (air) bubble generator 40, the following will only describe the specific configuration of the oxygen (air) bubble generator 40, and the description of the specific configuration of the oxygen (air) bubble generator 40’ will be omitted.

[0036] The water suction pump 47 is adapted to suck the liquid inside the biological treatment tank 30 through the strainer 8 (see FIGS. 2 and 3) and the water suction port 30b of the biological treatment tank 30.

[0037] The micro-nano bubble generation nozzle 45 is attached to a connection pipe 49 extending downstream from the water suction pump 47, and the liquid sucked by the water suction pump 47 is supplied to the micro-nano bubble generation nozzle 45 and blown out.

[0038] As shown in FIG. 4, the micro-nano bubble generation nozzle 45 is a nozzle member having a substantially cylindrical shape (straight pipe shape) having a supply part 21 connected to the connection pipe 49 and supplied with liquid from the water suction pump 47, a compression part 22 (passage part) through which the liquid supplied from the supply part 21 passes while being compressed, and a blowing part 23 from which the liquid that has passed through the compression part 22 is blown out.

[0039] The inner diameter of the supply unit 21, which is the inlet of the liquid, is substantially parallel to the compression unit 22, and the inner diameter of the blowing unit 23 is enlarged from the compression unit 22. That is, the inner diameter of the compression unit 22 is the smallest, and the liquid supplied from the supply unit 21 passes through the compression unit 22, and the flow rate increases. Due to the Venturi effect, the flow rate of the sewage becomes high and is blown out from the blowing unit 23.

[0040] Air containing oxygen, which is sucked into the micronano bubble generation nozzle 45 from the atmosphere through the intake pipe 46, is ejected into the compression unit 22 through the plurality of branched branch pipes 24. The bubbles ejected from the branch pipe 24 into the compression unit 22 become ultrafine bubbles and are mixed with the liquid in the compression unit 22. Then, these ultrafine bubbles are ejected as micronano bubbles of oxygen (air) from the blowing unit 23 into the biological treatment tank 30 through the bubble discharge port 30c.

[0041] That is, the micronano bubble generation nozzle 45 of oxygen (air) is disposed in the connection pipe 49 and blows out the liquid containing micronano bubbles into the water through the bubble discharge port 30c.

[0042] Next, the backwashing means 60 will be described. Returning to FIG. 1, the backwashing means 60 of this embodiment mainly includes the water suction pumps 47, 47', the conduit 41 connecting the connection pipe 49 and the connection pipe 48', the conduit 42 connecting the connection pipe 49' and the connection pipe 48, and the valves V1 to V8 provided in the connection pipes 48, 48', 49, 49' and the conduits 41, 42, respectively.

[0043] The conduit 41 functions as a branch path that branches from between the micronano bubble generation nozzle 45 and the water suction pump 47 in the connection pipe 49 to between the water suction pump 47' and the strainer 8'. The conduit 42 functions as a branch path that branches from between the micronano bubble generation nozzle 45' and the water suction pump 47' in the connection pipe 49' to between the water suction pump 47 and the strainer 8.

[0044] That is, the connecting pipe 49, the conduit 41, and the connecting pipe 48' are flow paths that communicate the water suction pump 47 and the strainer 8', and the connecting pipe 49', the conduit 42, and the connecting pipe 48 are flow paths that communicate the water suction pump 47' and the strainer 8.

[0045] The valves V1 to V8 are on-off valves that can change the communication state of the two flow paths. The valve V1 is disposed at a position closer to the water suction pump 47 than the communication point with the conduit 42 in the connecting pipe 48. The valve V2 is disposed at a position closer to the micro-nano bubble generation nozzle 45 than the communication point with the conduit 41 in the connecting pipe 49. The valve V3 is disposed at a position closer to the water suction pump 47' than the communication point with the conduit 41 in the connecting pipe 48'. The valve V4 is disposed at a position closer to the micro-nano bubble generation nozzle 45' than the communication point with the conduit 42 in the connecting pipe 49'.

[0046] The valve V5 is disposed near the communication point with the connecting pipe 49 in the conduit 41. The valve V6 is disposed near the communication point with the connecting pipe 48' in the conduit 41. Note that neither of these valves V5 and V6 needs to be disposed in the conduit 41. For example, only one valve may be disposed at a substantially central portion of the conduit 41. The valve V7 is disposed near the communication point with the connecting pipe 49' in the conduit 42. The valve V8 is disposed near the communication point with the connecting pipe 48 in the conduit 42. Note that neither of these valves V7 and V8 needs to be disposed in the conduit 42. For example, only one valve may be disposed at a substantially central portion of the conduit 42.

[0047] These valves V1 to V8 are flow path switching means for switching the flow paths on the discharge sides of the water suction pumps 47 and 47'. The switching of the flow paths by the valves V1 to V8 will be described in detail later.

[0048] Hereinafter, the fungus bed 50 will be described with reference to FIG. 5. Here, the fungus bed 50 is obtained by inoculating aerobic microorganisms and facultative anaerobic microorganisms on the carrier 51, and the carrier 51 means a state in which no microorganisms are inoculated. In addition, the synthetic resin made from minerals constituting the carrier 51 excludes natural resins such as plant resins and means a material that is not decomposed by aerobic microorganisms.

[0049] Regarding the inoculation on the carrier 51, by operating the wastewater treatment apparatus 1 according to the present invention, natural soil bacteria derived from nature are naturally inoculated to generate the fungus bed 50.

[0050] The fungus bed 50 is composed of a carrier 51 made of a synthetic resin using a mineral having a plurality of pores 52, and at least a part of the plurality of pores formed in the carrier 51 carries aerobic microorganisms and facultative anaerobic microorganisms, and a predetermined amount of an enzyme that activates the activities of the aerobic microorganisms, and contains activated carbon 58 produced in a fine powder form. The pores 52 include those in which at least a part thereof communicates with other pores and those that do not communicate with other pores. The size of the pores 52 is about 50 μm to about 800 μm, and pores 52 of various sizes are almost uniformly dispersed in the carrier 51. In addition, the pores 52 carry the enzyme 53 and contain powdered activated carbon 58, and the pores 52 serve as nests for aerobic microorganisms and facultative anaerobic microorganisms (not shown).

[0051] Next, the state during normal operation of the biological treatment apparatus 300 will be described. As shown in FIG. 6, during normal operation of the biological treatment apparatus 300, the oxygen (air) bubble generators 40, 40' are operating.

[0052] Specifically, during the normal operation of the biological treatment device 300, valves V1 to V4 are in the open state, valves V5 to V8 are in the closed state, and the water suction pumps 47 and 47' are in the ON state. Therefore, the fluid in the biological treatment tank 30 is sucked by the water suction pump 47 through the strainer 8, the water suction port 30b, and the connecting pipe 48 in the bubble generator 40, and then returned into the biological treatment tank 30 through the connecting pipe 49 and the micro-nano bubble generation nozzle 45. Also, the fluid in the biological treatment tank 30 is sucked by the water suction pump 47' through the strainer 8', the water suction port 30b', and the connecting pipe 48' in the bubble generator 40', and then returned into the biological treatment tank 30 through the connecting pipe 49' and the micro-nano bubble generation nozzle 45'.

[0053] When the oxygen (air) bubble generators 40 and 40' operate for a long time, clogging may occur in the pore portions 8a of the strainers 8 and 8' due to the biofilms 50, 50,..., and the discharge pressure of the water suction pumps 47 and 47' may decrease. In such a case, the normal operation is temporarily interrupted, and the following backwashing operation of the strainers 8 and 8' is performed. Note that this backwashing operation may be performed regularly, such as before the start of the daily operation or after the end of the operation, or may be performed irregularly when the discharge pressure of the water suction pumps 47 and 47' is constantly detected and the pressure drops below a predetermined value.

[0054] First, the state of the biological treatment device 300 during the backwashing operation of the strainer 8' will be described. As shown in FIG. 7, during the backwashing operation of the strainer 8', valves V1, V5, and V6 are in the open state, valves V2, V3, and V8 are in the closed state, the water suction pump 47 is in the ON state, and the water suction pump 47' is in the OFF state. At this time, valves V4 and V7 may be in the open state or the closed state.

[0055] Therefore, the fluid in the biological treatment tank 30 first passes through the strainer 8 and returns into the biological treatment tank 30 through the connecting pipe 48, the conduit 41, the connecting pipe 48', and the strainer 8' without accompanying the carrier 51. In this way, as the fluid moves from the space S1' inside the strainer 8' (the downstream side of the strainer 8' during normal operation) to the inside of the biological treatment tank 30 outside the strainer 8' (the upstream side of the strainer 8' during normal operation) in a direction opposite to that during normal operation, the carrier 51 that had blocked the pore portion 8a of the strainer 8' is removed, that is, the clogging is eliminated.

[0056] Next, the state of the biological treatment apparatus 300 during the backwashing operation of the strainer 8 will be described. As shown in FIG. 8, during the backwashing operation of the strainer 8, the valves V3, V7, and V8 are in the open state, the valves V1, V4, and V6 are in the closed state, the water suction pump 47 is in the OFF state, and the water suction pump 47' is in the ON state. Incidentally, at this time, the valves V2 and V5 may be in the open state or the closed state.

[0057] Therefore, the fluid in the biological treatment tank 30 first passes through the strainer 8' and returns into the biological treatment tank 30 through the connecting pipe 48', the conduit 42, the connecting pipe 48, and the strainer 8 without accompanying the carrier 51. As the fluid moves from the space S1 inside the strainer 8 (the downstream side of the strainer 8 during normal operation) to the inside of the biological treatment tank 30 outside the strainer 8 (the upstream side of the strainer 8 during normal operation) in a direction opposite to that during normal operation, the carrier 51 that had blocked the pore portion 8a of the strainer 8 is removed, that is, the clogging is eliminated.

[0058] As described above, strainers 8 and 8' each having a plurality of pore portions 8a through which the carrier 51 cannot pass are provided at the water inlets 30b and 30b' of the oxygen (air) bubble generators 40 and 40'. By means of these strainers 8 and 8', it is possible to prevent the carrier 51 from being sucked into the oxygen (air) bubble generators 40 and 40'. As a result, it is possible to prevent the carrier 51 from clogging the water suction pumps 47 and 47' of the oxygen (air) bubble generators 40 and 40' and causing malfunctions, or the carrier 51 from being damaged when sucked into the water suction pumps 47 and 47' and the quantity of the carrier 51 in the biological treatment tank 30 from decreasing, and so on.

[0059] Further, when the carrier 51 clogs the strainers 8 and 8', the normal operation of the biological treatment apparatus 300 is stopped, and the clogging of the carrier 51 in each pore portion 8a of the strainers 8 and 8' can be eliminated in a short time by temporarily sending a fluid between the water suction pumps 47 and 47' and the strainers 8 and 8' by means of the backwashing means 60. As a result, it is possible to prevent the discharge pressure of the water suction pumps 47 and 47' from decreasing.

[0060] In addition, since the backwashing means 60 introduces the water to be treated introduced through the strainers 8 and 8' between the water suction pumps 47 and 47' and the strainers 8 and 8' to perform the backwashing operation of the strainers 8 and 8', the water to be treated in the biological treatment tank 30 does not increase due to the backwashing operation.

[0061] Also, the treated water introduced through one strainer 8 by one water suction pump 47 is introduced between the other water suction pump 47' and the other strainer 8' to backwash the other strainer 8', and the treated water introduced through the other strainer 8' by the other water suction pump 47' is introduced between one water suction pump 47 and one strainer 8 to backwash one strainer 8. That is, since backwashing can be performed using the water suction pumps 47, 47' of the oxygen (air) bubble generators 40, 40', there is no need to separately prepare a pump for backwashing, and the wastewater treatment apparatus 1 can have a simple structure. Further, when performing the backwashing operation of one strainer 8, 8', since the treated water that has passed through the other strainer 8', 8 is introduced, there is no risk of mixing the carrier 51 into the inside of the strainer 8, 8' for which the backwashing operation is being performed.

[0062] Also, the oxygen (air) bubble generators 40, 40' have micronano bubble generation nozzles 45, 45' for mixing micronano bubbles containing oxygen, and a conduit 41 that branches from between one micronano bubble generation nozzle 45 and one water suction pump 47 to between the other water suction pump 47' and the other strainer 8', and a conduit 42 that branches from between the other micronano bubble generation nozzle 45' and the other water suction pump 47' to between one water suction pump 47 and one strainer 8 are provided. According to this, since the treated water can be introduced between the water suction pumps 47, 47' and the strainers 8, 8' without passing through the micronano bubble generation nozzles 45, 45', the strainers 8, 8' can be efficiently backwashed.

[0063] Further, one water suction pump 47 and the other water suction pump 47' are configured to discharge the water to be treated in the same turning direction. Specifically, since the bubble discharge ports 30c and 30c' open in the same direction in the circumferential direction of the inner peripheral wall 30a of the biological treatment tank 30, the discharge flow of one water suction pump 47 and the discharge flow of the other water suction pump 47' do not interfere with each other, and in the cylindrical biological treatment tank 30, a circulation flow that turns counterclockwise in plan view is efficiently generated in this embodiment, and the stirring force of the water to be treated is high. By doing so, the contact opportunity between the micro-nano bubbles and the biofilms 50, 50,... can be increased, and biological treatment can be effectively performed.

[0064] Further, each upper surface 8b of these strainers 8 and 8' is inclined so as to be lower from the outer diameter side to the central portion of the biological treatment tank 30. According to this, since the biofilms 50, 50,... fall from each upper surface 8b of the strainers 8 and 8, it is possible to prevent the biofilms 50, 50,... from being laminated on the upper surface 8b of the strainer 8.

[0065] Also, during the backwashing operation of one strainer 8, one water suction pump 47 is in the OFF state and the other water suction pump 47' is in the ON state. During the backwashing operation of the other strainer 8', one water suction pump 47 is in the ON state and the other water suction pump 47' is in the OFF state. Since the suction and discharge of one water suction pump 47 and the suction and discharge of the other water suction pump 47' do not interfere with each other, the strainers 8 and 8' can be reliably backwashed.

[0066] In addition, in this embodiment, the valves V1 to V8 are exemplified in the form of on-off valves capable of changing the communication state of two flow paths, but the present invention is not limited thereto, and a three-way valve or the like capable of changing the communication state of three flow paths may be used.

Example

[0067] Next, the wastewater treatment apparatus according to Example 2 will be described with reference to FIGS. 9 to 12. In addition, the description of the configuration that is the same as that of the above-described example and overlaps is omitted.

[0068] As shown in FIGS. 9 and 10, the wastewater treatment apparatus 100 of this embodiment includes a filter plate 18 as a strainer having a plurality of pore portions 18a. The filter plate 18 is composed of a curved side surface portion 18b and an upper surface portion 18c that is continuous with the upper end of the side surface portion 18b and inclined upward. The outer edge of the filter plate 18 is welded across the inner surface 130a and the bottom surface 130b of the biological treatment tank 130. Further, the internal space partitioned by the filter plate 18 and the inner surface 130a and the bottom surface 130b of the biological treatment tank 130 is divided into two substantially equal parts, one space S10 and the other space S11, in a plan view by a partition plate 101.

[0069] Next, the oxygen (air) bubble generators 140, 140' will be described.

[0070] The oxygen (air) bubble generator 140 mainly includes a water suction pump 147, a connection pipe 148 on the suction side of the water suction pump 147, a connection pipe 149 on the discharge side of the water suction pump 147, and a micro-nano bubble generation nozzle 145 connected to the connection pipe 149. The discharge side end of the connection pipe 149 is disposed in the biological treatment tank 130 through the filter plate 18. Note that the discharge side end of the connection pipe 149 may be disposed in the biological treatment tank 130 without passing through the filter plate 18.

[0071] The oxygen (air) bubble generator 140' mainly includes a water suction pump 147', a connection pipe 148' on the suction side of the water suction pump 147', a connection pipe 149' on the discharge side of the water suction pump 147', and a micro-nano bubble generation nozzle 145' connected to the connection pipe 149'. The discharge side end of the connection pipe 149' is disposed in the biological treatment tank 130 through the internal space of the filter plate 18. Note that the discharge side end of the connection pipe 149' may be disposed in the biological treatment tank 130 without passing through the filter plate 18.

[0072] On the side of the water absorption pump 147 rather than the micro-nano bubble generation nozzle 145 in the connecting pipe 149, a valve V10 is provided. Also, between the valve V10 and the water absorption pump 147 in the connecting pipe 149, a conduit 141 communicating with the other space S11 is provided. A valve V11 is provided in the conduit 141.

[0073] On the side of the water absorption pump 147' rather than the micro-nano bubble generation nozzle 145' in the connecting pipe 149', a valve V13 is provided. Also, between the valve V13 and the water absorption pump 147' in the connecting pipe 149', a conduit 142 communicating with one space S10 is provided. A valve V14 is provided in the conduit 142.

[0074] During the normal operation of the wastewater treatment device 100, the oxygen (air) bubble generation devices 140, 140' operate, the valves V10, V13 are in the open state, and the valves V11, V14 are in the closed state. Therefore, the fluid in the biological treatment tank 130 is sucked by the water absorption pump 147 through the filter plate 18 and the connecting pipe 148 in the bubble generation device 140, and returned into the biological treatment tank 130 through the connecting pipe 149 and the micro-nano bubble generation nozzle 145. Also, the fluid in the biological treatment tank 130 is sucked by the water absorption pump 147' through the filter plate 18 and the connecting pipe 148' in the bubble generation device 140', and returned into the biological treatment tank 130 through the connecting pipe 149' and the micro-nano bubble generation nozzle 145'.

[0075] As shown in FIG. 10, when the water to be treated containing micro-nano bubbles is discharged into the biological treatment tank 130, after moving along the bottom surface 130b of the biological treatment tank 130, it rises along the opposing inner surface 130a, and a circulating flow that swirls back from the water surface side to the filter plate 18 side is generated. Thereby, the contact opportunity between the micro-nano bubbles and the biofilms 50, 50,... is increased, and biological treatment can be effectively performed. Incidentally, a guide plate for promoting the circulating flow may be provided between the inner surface 130a and the bottom surface 130b of the biological treatment tank 130 facing the discharge ports of the connecting pipes 149, 149'.

[0076] In addition, since the connecting pipes 149 and 149' extend in parallel (see Fig. 9), the treated water containing micro-nano bubbles discharged from the connecting pipes 149 and 149' do not interfere with each other and can be discharged in the same direction. Therefore, an efficient circulating flow can be generated.

[0077] As shown in Fig. 11, during the backwashing operation on the space S11 side inside the filter plate 18, the valves V10 and V13 are in the closed state, the valve V11 is in the open state, the water suction pump 147 is in the ON state, and the water suction pump 147' is in the OFF state. Incidentally, at this time, the valve V14 may be in the open state or the closed state.

[0078] Therefore, the fluid in the biological treatment tank 130 first passes through the filter plate 18 and then returns to the biological treatment tank 130 through the connecting pipe 148, the conduit 141, and the filter plate 18 without accompanying the carrier 51. When the fluid moves from the space S11 inside the filter plate 18 to the inside of the biological treatment tank 130 outside the filter plate 18, the carrier 51 that has blocked the pore portion 18a of the filter plate 18 comes off, that is, the clogging on the space S11 side is eliminated.

[0079] As shown in Fig. 12, during the backwashing operation on the space S10 side of the filter plate 18, the valves V10 and V13 are in the closed state, the valve V14 is in the open state, the water suction pump 147 is in the OFF state, and the water suction pump 147' is in the ON state. Incidentally, at this time, the valve V11 may be in the open state or the closed state.

[0080] Therefore, the fluid in the biological treatment tank 130 is returned to the biological treatment tank 130 through the connecting pipe 148', the conduit 142, and the filter plate 18. When the fluid moves from the space S10 inside the filter plate 18 to the inside of the biological treatment tank 130, the clogging on the space S10 side of the filter plate 18 is eliminated.

Example

[0081] Next, the wastewater treatment apparatus according to Example 3 will be described with reference to Figs. 13 to 15. The description of the same configurations as those in the above examples will be omitted.

[0082] As shown in FIG. 13, the biological treatment tank 400 of the third embodiment is provided with water inlets 400a and 400b connected in parallel to the suction side of the water suction pump 401, and a bubble discharge port 400c connected to the discharge side of the water suction pump 401. Strainers 402 and 403 are respectively attached to the water inlets 400a and 400b.

[0083] The water inlet 400a and the water suction pump 401 are connected by a connecting pipe 404, and the water inlet 400b and the water suction pump 401 are connected by a connecting pipe 405. A valve V20 is provided in the connecting pipe 404, and a valve V21 is provided in the connecting pipe 405.

[0084] The water suction pump 401 and the bubble discharge port 400c are connected by a connecting pipe 406. The connecting pipe 406 includes a valve V22 and a micronano bubble generation nozzle 409 provided on the side of the bubble discharge port 400c with respect to the valve V22.

[0085] A part of the connecting pipe 404 on the side of the water inlet 400a with respect to the valve V20 and a part of the connecting pipe 406 on the side of the water suction pump 401 with respect to the valve V22 are connected by a conduit 407. Also, a part of the connecting pipe 405 on the side of the water inlet 400b with respect to the valve V21 and a part of the connecting pipe 406 on the side of the water suction pump 401 with respect to the valve V22 are connected by a conduit 408. A valve V23 is provided in the conduit 407, and a valve V24 is provided in the conduit 408.

[0086] During normal operation of the biological treatment apparatus of this embodiment, the valves V20, V21, and V22 are in the open state, the valves V23 and V24 are in the closed state, and the water suction pump 401 is in the ON state. Therefore, the fluid in the biological treatment tank 400 is sucked by the water suction pump 401 through the strainers 402 and 403, the water inlets 400a and 400b, and the connecting pipes 404 and 405, and is returned into the biological treatment tank 400 through the connecting pipe 406 and the micronano bubble generation nozzle 409.

[0087] As shown in FIG. 14, during the backwashing operation of one strainer 402, valves V21 and V23 are in the open state, valves V20, V22, and V24 are in the closed state, and the water suction pump 401 is in the ON state. Therefore, the fluid in the biological treatment tank 400 is sucked in by the water suction pump 401 through the strainer 403, the water suction port 400b, and the connecting pipe 405, and returned into the biological treatment tank 400 through the conduit 407 and the strainer 402, thus eliminating the clogging of the strainer 402.

[0088] As shown in FIG. 15, during the backwashing operation of the other strainer 403, valves V20 and V24 are in the open state, valves V21, V22, and V23 are in the closed state, and the water suction pump 401 is in the ON state. Therefore, the fluid in the biological treatment tank 400 is sucked in by the water suction pump 401 through the strainer 402, the water suction port 400a, and the connecting pipe 404, and returned into the biological treatment tank 400 through the conduit 408 and the strainer 403, thus eliminating the clogging of the strainer 403.

Example

[0089] Next, the wastewater treatment apparatus according to Example 4 will be described with reference to FIGS. 16 and 17. The description of the configurations that are the same as those in the above example and are duplicated will be omitted.

[0090] As shown in FIG. 16, in the biological treatment tank 500 of this Example 4, an immersion pump 501 and a strainer 502 surrounding the pump 501 are arranged. The water suction port 501a provided at the bottom of the main body of the pump 501 is arranged inside the strainer 502, and the discharge port 501b of the pump 501 is arranged outside the strainer 502 (i.e., inside the biological treatment tank 500) via the micronano bubble generation nozzle 503.

[0091] The wastewater treatment apparatus of Example 4 is provided with a backwash water tank 510 separately from the biological treatment tank 500. The backwash water tank 510 stores filtered water introduced through a screen or the like, or clean backwash fluid such as fresh water. Further, a backwash pump 511 is disposed in the backwash water tank 510, and the discharge port of the backwash pump 511 communicates with the inside of the strainer 502 through a conduit 512.

[0092] During normal operation of the biological treatment apparatus of this example, the pump 501 is turned on and the backwash pump 511 is turned off. Thereby, the fluid in the biological treatment tank 400 is sucked from the inside through the strainer 502 by the pump 501 and returned into the biological treatment tank 400 through the micronano bubble generation nozzle 503.

[0093] Also, as shown in FIG. 17, during backwashing of the strainer 502, the pump 501 is turned off and the backwash pump 511 is turned on. Thereby, the backwash fluid in the backwash water tank 510 is discharged into the inside of the strainer 502 through the conduit 512 by the backwash pump 511, passes through the strainer 502, and is discharged into the biological treatment tank 500 outside thereof. That is, when the fluid passes from the inside to the outside of the strainer 502, the clogging of the strainer 502 is eliminated.

[0094] As described above, the embodiments of the present invention have been described with reference to the drawings. However, the specific configuration is not limited to these embodiments, and modifications and additions within the scope not departing from the gist of the present invention are also included in the present invention.

[0095] For example, in the above embodiment, the backwashing of the strainer is performed using the pump of the oxygen supply means. However, the present invention is not limited to this, and the backwashing may be performed using the water to be treated by a pump different from the pump of the oxygen supply means. In this case, it is preferable that a strainer is provided on the suction side of the different pump.

[0096] In addition, in the above embodiment, a form in which backwashing of the strainer is performed using the water to be treated is exemplified. However, the present invention is not limited to this. For example, air may be introduced into the flow path between the pump and the strainer by a blower or a compressor, and backwashing may be performed using the bubbles.

[0097] In addition, in the above embodiment, a form in which two sets of a pump, a strainer, and an oxygen supply means are provided is exemplified. However, the present invention is not limited to this, and only one set of a pump, a strainer, and an oxygen supply means may be used. In this case, it is preferable that backwashing is performed by a pump different from the pump of the oxygen supply means.

[0098] In addition, three or more oxygen supply means may be provided. When backwashing the strainer of one oxygen supply means using the pump of another oxygen supply means, the oxygen supply means other than the one oxygen supply means and the other oxygen supply means may be in an operating state.

Explanation of Signs

[0099] 1 1 Wastewater treatment apparatus 8, 8’ Strainer 8a Pore part 8b Upper surface 18 Filter plate (strainer) 18a Pore part 30 Biological treatment tank (accommodation tank) 40, 40’ Oxygen (air) bubble generator (oxygen supply means) 41, 42 Conduit (branch path) 45, 45’ Micronano bubble generation nozzle (mixing part) 47, 47’ Suction pump (pump) 48, 48’ Connecting pipe (flow path) 51 Carrier 60 Backwashing means 100 Wastewater treatment apparatus 130 Biological treatment tank 140, 140’ Oxygen (air) bubble generator (oxygen supply means) 141, 142 Conduit (branch path) 142 Conduit 145, 145’ Micro-nano bubble generation nozzle (mixing section) 147, 147’ Water absorption pump 300 Biological treatment device V1 - V8 Valves V10 - V14 Valves

Claims

1. A wastewater treatment apparatus comprising: a storage tank for storing the water to be treated; a plurality of carriers accommodated in the storage tank and carrying at least microorganisms; and oxygen supply means for mixing micro-nano bubbles containing oxygen into the water to be treated introduced from the storage tank by the action of a pump that sucks the water to be treated, and supplying the mixture to the storage tank. A strainer having pore portions for preventing passage of the carriers is provided on the suction side of the pump. The wastewater treatment apparatus is characterized in that it comprises backwashing means for introducing fluid into the flow path between the pump and the strainer to wash the strainer.

2. The wastewater treatment apparatus according to claim 1, wherein the backwashing means introduces the water to be treated introduced through the strainer into the flow path.

3. The wastewater treatment apparatus has at least two oxygen supply means having strainers on the suction side of the pump, and is characterized in that the water to be treated introduced through one strainer by one pump is introduced into the flow path between the other pump and the other strainer.

4. The oxygen supply means has a mixing section for mixing micro-nano bubbles containing oxygen. The wastewater treatment apparatus according to claim 3 is characterized in that a branch path is provided that branches from between the mixing section of the one oxygen supply means and the one pump to the flow path between the other pump and the other strainer.

5. The wastewater treatment apparatus according to claim 3 or 4, wherein the one pump and the other pump discharge the water to be treated in the same turning direction in the storage tank.

6. The wastewater treatment apparatus according to any one of claims 1 to 5, wherein the upper surface of the strainer is inclined obliquely.

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