Sewage treatment plant

Abstract

Provided is a sewage treatment device having a flow regulating tank that is low in probability of failure, high in reliability, and inexpensive. A sewage treatment device (100) has: a sewage inflow path (4); a biological treatment tank (7, 8) that purifies sewage flowing in from the sewage inflow path (4); and a flow regulating tank (5) that regulates the amount of sewage flowing from the sewage inflow path (4) to the biological treatment tank (7, 8), wherein a first outflow (43) that causes sewage to flow to the biological treatment tank (7, 8) and a second outflow (44) that causes sewage to flow to the flow regulating tank (5) are formed on the sewage inflow path (4), and the height of the first outflow (43) is set at a position lower than the height of the second outflow (44).

Description

Technical Field

[0001] This invention relates to a wastewater treatment device. Background Technology

[0002] Patent document 1 discloses a wastewater treatment device using membrane separation activated sludge process. In this membrane separation activated sludge process, a membrane separation device for solid-liquid separation of activated sludge mixture in the tank is impregnated in a biological treatment tank that uses activated sludge to biologically treat wastewater.

[0003] Since the amount of wastewater that can be treated by the membrane separation activated sludge process is directly proportional to the area of ​​the membrane installed, when the amount of wastewater flowing in changes, a membrane with an area that can handle the peak amount of wastewater flowing in is required.

[0004] However, membranes are relatively expensive equipment with high operating costs, including electricity consumption. Therefore, if membranes capable of handling peak sewage inflows are introduced, the operating costs will be too high, and thus energy saving is expected.

[0005] Therefore, in small-scale wastewater treatment plants, the standard approach is to use a flow regulating tank to absorb the fluctuations in the inflow of wastewater and make the amount of wastewater fed into the biological treatment tank uniform, thereby controlling the required membrane area to a minimum (see Figure 7,

[0072] of Patent Document 1).

[0006] Existing technical documents

[0007] Patent documents

[0008] Patent Document 1: Japanese Patent Application Publication No. 2018-34077 Summary of the Invention

[0009] The problem the invention aims to solve

[0010] However, flow regulating tanks can be either in-line type, which temporarily receives all the wastewater, or side-line type, which receives all or part of the wastewater as needed.

[0011] like Figure 4 As shown, in the online flow regulating tank 5, the entire amount of sewage pumped by sewage pump P1 and after impurities are removed by micro screen 3 is temporarily stored in the flow regulating tank 5. The sewage stored in the flow regulating tank 5 is pumped by pump P2 and transferred to sewage distribution tank 12 via sewage inflow path 4. After the sewage distribution tank 12 is adjusted to a constant flow rate, the sewage is transferred to biological treatment tanks 7 and 8.

[0012] like Figure 5As shown, in the bypass flow regulating tank 5, wastewater pumped by wastewater pump P1 and after impurities are removed by the micro screen 3 is transferred to the wastewater distribution tank 12 via the wastewater inflow path 4. The wastewater, after being regulated to a constant flow rate by the wastewater distribution tank 12, is then transferred to the biological treatment tanks 7 and 8. When the water level in the biological treatment tanks 7 and 8 reaches the specified upper limit, the remaining wastewater is stored in the flow regulating tank 5 via the branch path 4D branching from the wastewater inflow path 4. When the water level in the biological treatment tanks 7 and 8 drops below the upper limit, the wastewater is again supplied to the wastewater distribution tank 12 via the wastewater inflow path. When the amount of wastewater flowing into the biological treatment tanks 7 and 8 decreases, the wastewater stored in the flow regulating tank 5 is pumped by pump P2 and transferred to the wastewater distribution tank 12 via the wastewater inflow path 6. Solenoid valves V1 and V2 are installed in the wastewater inflow path 4 and the branch path 4D for switching flow paths.

[0013] Compared to online systems, bypass flow regulating tanks reduce the amount of water pumped back, making them superior in terms of energy efficiency. However, the fluctuations in wastewater generation are difficult to predict. In small-scale wastewater treatment plants relying on routine inspections, the use of bypass flow regulating tanks necessitates the adoption of automatic water control equipment such as electrically movable weirs and electric valves for flow path switching, increasing costs. If the automatic water control equipment malfunctions, wastewater may overflow from the tank or result in untreated discharge. Therefore, backup mechanisms are indispensable in automatic water control equipment. However, repeatedly installing backup electrically movable weirs and electric valves to prevent malfunctions further increases costs and is impractical.

[0014] The purpose of this invention is to provide a wastewater treatment device with a flow regulating tank that has a low probability of failure, high reliability, and low cost, in view of the above-mentioned problems.

[0015] means for solving problems

[0016] To achieve the above objectives, a first characteristic structure of the wastewater treatment apparatus according to the present invention is that it is a wastewater treatment apparatus comprising: a wastewater inflow path; a biological treatment tank for purifying wastewater flowing in from the wastewater inflow path; and a flow regulating tank for regulating the amount of wastewater flowing from the wastewater inflow path into the biological treatment tank, wherein a first outlet for allowing wastewater to flow into the biological treatment tank and a second outlet for allowing wastewater to flow into the flow regulating tank are formed on the wastewater inflow path, the height of the first outlet is set at a position lower than the height of the second outlet, and the upper limit water level of the biological treatment tank is determined by the height of the second outlet.

[0017] Wastewater flowing into the wastewater inlet path can be transferred from the first outlet to the biological treatment tank, and from the second outlet to the flow regulating tank. Since the height of the first outlet is set lower than that of the second outlet, when the water level in the biological treatment tank is lower than the height of the second outlet, the wastewater transferred via the wastewater inlet path flows directly out of the biological treatment tank through the first outlet. Furthermore, as the inflow of wastewater increases, when the water level in the biological treatment tank reaches or exceeds the level corresponding to the height difference between the first and second outlets, wastewater exceeding the volume of activated sludge or treated water flowing out of the biological treatment tank will flow from the second outlet to the flow regulating tank. Subsequently, when the inflow of wastewater decreases and the water level in the biological treatment tank falls below the level corresponding to the height difference between the first and second outlets, the entire amount of inflowing wastewater will again flow out of the biological treatment tank through the first outlet. Therefore, since there is no need for water control mechanisms that could cause malfunctions, such as electric valves or electronic control devices that switch whether the wastewater transferred via the wastewater inflow path flows out into the biological treatment tank or the flow regulation tank, a highly reliable wastewater treatment device can be achieved.

[0018] Its second feature is that, based on the first feature, the height of the first outlet is set at a position lower than the height of the second outlet, and the upper limit water level of the biological treatment tank is determined by the height of the second outlet.

[0019] Because the biological treatment tank is allowed to generate water level changes corresponding to the height difference between the first and second outlets, even if there is a sharp increase in the inflow of sewage that exceeds the treatment capacity of the biological treatment tank, the outflow to the flow regulating tank can be suppressed by temporarily storing the water in the biological treatment tank, thereby minimizing the power consumption required to pump sewage to the sewage inflow path.

[0020] Its third feature is that, based on the first feature, the first outlet is formed at a position downstream of the sewage inflow path than the second outlet.

[0021] Wastewater flowing into the sewage inlet flows out through the second outlet to the flow regulating tank, while activated sludge from the biological treatment tank does not flow out through the first outlet to the flow regulating tank.

[0022] Its fourth feature structure is that, based on the first feature structure mentioned above, it also has a sewage pump well, which is equipped with a sewage pump that transfers sewage to the sewage inflow path, and the sewage treatment device has a sewage pump control unit. When the sewage level in the sewage pump well exceeds the first starting water level, the sewage pump is made to operate intermittently, and when the sewage level in the sewage pump well exceeds the second starting water level which is higher than the first starting water level, the sewage pump is made to operate continuously.

[0023] Before the sewage level in the sewage pump well exceeds the second starting water level, which is higher than the first starting water level, the sewage pump can be operated intermittently to suppress the rapid increase in sewage flowing into the sewage inlet. As a result, the amount of sewage flowing out of the sewage inlet into the flow regulating tank can be reduced, and the power consumption required to pump sewage is kept to a minimum.

[0024] Its fifth characteristic structure is that, based on the characteristic structures of any one of the first to fourth items above, the biological treatment tank adopts the membrane separation activated sludge method.

[0025] By absorbing the fluctuations in the sewage flowing into the sewage inlet and stabilizing the amount of sewage fed into the biological treatment tank, a sewage treatment device with a highly reliable and inexpensive flow regulating tank can be realized while suppressing the increase of membrane area, thereby reducing initial and operating costs.

[0026] The effects of the invention

[0027] As described above, according to the present invention, it is possible to provide a wastewater treatment device having a flow regulating tank with low failure probability, high reliability and low cost. Attached Figure Description

[0028] Figure 1 This is an explanatory diagram of a wastewater treatment device.

[0029] Figure 2A This is a diagram illustrating the operation of a wastewater treatment device.

[0030] Figure 2B This is a diagram illustrating the operation of a wastewater treatment device.

[0031] Figure 3A An explanatory diagram illustrating another embodiment of a wastewater treatment apparatus.

[0032] Figure 3B An explanatory diagram illustrating another embodiment of a wastewater treatment apparatus.

[0033] Figure 4 This is an explanatory diagram of a traditional online flow regulating tank.

[0034] Figure 5This is an explanatory diagram of a conventional bypass flow regulating tank. Detailed Implementation

[0035] The wastewater treatment apparatus according to the present invention will now be described.

[0036] exist Figure 1 The image shows a wastewater treatment device 100, which is installed in a wastewater treatment plant or industrial wastewater treatment plant and employs the membrane separation activated sludge process.

[0037] The wastewater treatment device 100 includes: a wastewater pump well 1 for storing wastewater, a fine screen 3, a bypass flow regulating tank 5, biological treatment tanks 7 and 8, and a membrane separation device 9. Reference numeral 7 indicates an anoxic tank that forms part of the biological treatment tank, and reference numeral 8 indicates an aerobic tank that forms part of the biological treatment tank.

[0038] When the sewage stored in the sewage pump well 1 reaches either the preset start-up water level HWL1 or HWL2, the sewage pump P1 starts, pumping the sewage to the discharge pipe 2. After passing through the fine screen 3 to remove impurities, the sewage is transferred to the anoxic tank 7 via the sewage inflow path 4. The sewage transferred to the anoxic tank 7 mixes with the activated sludge in the tank and is transferred to the aerobic tank 8 through the lower opening of the partition wall 10, where ammonia nitrogen is nitrified. A portion of the sewage is returned to the anoxic tank 7 for denitrification. The sewage that has been nitrified and whose organic components have been decomposed and removed in the aerobic tank 8 is then filtered by the membrane separation device 9 as treated water. The treated water taken out from the suction pipe 11 is then discharged into a river after sterilization treatment, or used as in-plant treated water.

[0039] The end of the sewage conveying pipe 41 that constitutes the sewage inflow path 4 branches in two directions through the branch pipe 42. At one end, a first outlet 43 is formed for sewage to flow into the anoxic tank 7, which serves as a biological treatment tank, and at the other end, a second outlet 44 is formed for sewage to flow into the flow regulating tank 5.

[0040] The height H1 of the first outlet 43 (from the bottom of the anoxic tank 7) is set ΔH lower than the height H2 of the second outlet 44 (from the bottom of the flow regulating tank 5). The upper limit water level of the anoxic tank 7 is determined by the height H2 of the second outlet 44. Specifically, the end of the sewage conveying pipe 41 hangs downwards, branching into a horizontal branch pipe 42. One end of the branch pipe 42 becomes the first outlet 43 opening on the side of the anoxic tank 7, and the other end of the branch pipe 42 bends upwards, with its top becoming the second outlet 44 opening on the side of the flow regulating tank 5.

[0041] That is, the sewage flowing into the sewage inflow path 4 through the micro-grid 3 can be transferred from the first outlet 43 to the anoxic tank 7, and can be transferred from the second outlet 44 to the flow regulating tank 5.

[0042] like Figure 2A As shown, since the height H1 of the first outlet 43 is set at a position ΔH lower than the height H2 of the second outlet 44, when the water level in the anoxic tank 7 is lower than the height of the second outlet 44, the sewage transferred through the sewage conveying pipe 41 flows out of the anoxic tank 7 through the first outlet 43.

[0043] Furthermore, when the water level in the anoxic tank 7 reaches or exceeds the water level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, such as Figure 2B As shown, the flow of sewage from the first outlet 43 to the anoxic tank 7 stops, and the sewage flowing into the sewage delivery pipe 41 will flow from the second outlet 44 to the flow regulating tank 5.

[0044] Subsequently, as biological treatment proceeds and the suction filtration of treated water in the membrane separation device 9 is advanced, when the water level in the biological treatment tanks 7 and 8 is lower than the water level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, the wastewater flows out again through the first outlet 43 into the anoxic tank 7.

[0045] Therefore, since there is no need for water control mechanisms that could cause malfunctions, such as electric valves or electronic control devices that switch between the sewage flowing through the sewage conveying pipe 41 and branch pipe 42 (which serve as the sewage inflow path 4) flowing out to the biological treatment tanks 7 and 8 or to the flow regulating tank 5, a highly reliable sewage treatment device can be achieved.

[0046] The height of the first outlet 43 is set lower than the height of the second outlet 44. The upper limit water level BWL of biological treatment tanks 7 and 8 is determined by the height of the second outlet 44. The steady-state water level NWL of biological treatment tanks 7 and 8 is set slightly above the height of the first outlet 43.

[0047] Because the biological treatment tanks 7 and 8 are allowed to generate water level changes corresponding to the height difference between the first outlet 43 and the second outlet 44, even if there is a sharp increase in the sewage inflow exceeding the treatment capacity of the biological treatment tanks 7 and 8, the outflow to the flow regulating tank 5 can be suppressed by temporarily storing the water in the biological treatment tanks 7 and 8. That is, the power consumption required to pump sewage to the sewage inflow path 4 using the sewage pump P1 can be minimized.

[0048] When the amount of sewage pumped by sewage pump P1 to sewage inflow path 4 decreases, and the water level in biological treatment tanks 7 and 8 is lower than, for example, the steady-state water level NWL, the sewage stored in the flow regulation tank 5 is transferred to the biological treatment tanks 7 and 8 by pump P2 installed in the flow regulation tank 5.

[0049] The sewage pump P1, installed in sewage pump well 1, is controlled by the sewage pump control unit. When the sewage level in sewage pump well 1 exceeds the first starting water level HWL1, it operates intermittently at specified time intervals; when it exceeds the second starting water level HWL2, which is higher than the first starting water level HWL1, it operates continuously. It should be noted that a stop water level for the pump is set at a position lower than the first starting water level HWL1.

[0050] When the sewage stored in the sewage pump well 1 does not reach the amount that would cause an overflow, that is, before the sewage level in the sewage pump well 1 exceeds the second starting water level which is higher than the first starting water level HWL1, the sewage pump can be operated intermittently to suppress the rapid increase in sewage flowing into the sewage inflow path 4. As a result, the amount of sewage flowing out of the sewage inflow path 4 into the flow regulating tank 5 can be reduced, thereby effectively utilizing the pumping energy of the sewage pump P1 to pump sewage.

[0051] For example, assuming the sewage pump P1 has a pumping capacity of 1.2m... 3 The membrane filtration unit has a processing capacity of 0.76m³ / min. 3 / min, insufficient processing capacity is 0.44m 3 At a rate of / min, through biological treatment tanks 7 and 8 (with the water surface area set to 60m²), 2 The water level is guaranteed to fluctuate within a range of 0.3m (BMW-NWL), and the wastewater can be received for 18m when treatment is stopped. 3 ÷0.44m 3 / min = 40min, which ensures 40 minutes of flow rate regulation function.

[0052] In the above embodiment, the sewage inflow path 4 is described as being composed of a pipe; however, its specific form is not limited as long as the height of the first outlet is set lower than the height of the second outlet. Furthermore, as... Figure 3A , Figure 3B As shown, the sewage inflow path 4 can also be composed of a water path 41. The first outlet 43 formed in the water path 41 is located downstream of the flow path through the sewage inflow path 4, compared to the second outlet 44.

[0053] In this case, also as Figure 3A As shown, when the water level in the anoxic tank 7 is lower than the height of the second outlet 44, the sewage transferred via the waterway 41 flows out of the anoxic tank 7 through the first outlet 43.

[0054] Furthermore, when the water level in the anoxic tank 7 reaches or exceeds the water level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, such as Figure 3B As shown, affected by the atmospheric pressure acting on the surface of the wastewater in the anoxic tank 7, the flow of wastewater flowing out of the first outlet 43 into the anoxic tank 7 stops, and the wastewater flowing into the waterway 41 flows out of the second outlet 44 into the flow regulating tank 5.

[0055] Therefore, when the sewage flowing into waterway 41 flows out from the second outlet 44 into the flow regulating tank 5, the activated sludge in biological treatment tanks 7 and 8 will not flow out from the first outlet 43 into the flow regulating tank 5.

[0056] In the above embodiments, a wastewater treatment device 100 using membrane separation activated sludge process in biological treatment tank has been described. However, the present invention is also applicable to wastewater treatment devices using standard activated sludge process, in which wastewater that has undergone biological treatment in biological treatment tank is introduced into sedimentation tank for solid-liquid separation, and the supernatant is taken out as treated water.

[0057] The above-described embodiments are one aspect of the present invention. The present invention is not limited to this description. Obviously, the specific structure of each part can be appropriately modified within the scope of achieving the effects of the present invention.

[0058] Explanation of reference numerals in the attached figures

[0059] 1: Sewage pump well

[0060] 2: Water supply pipe

[0061] 3: Micro-grid

[0062] 4: Sewage flowing into the road

[0063] 41: Sewage delivery pipe (sewage inflow path)

[0064] 42: Branch pipe (sewage inflow path)

[0065] 43: First-class export

[0066] 44: Secondary exit

[0067] 5: Flow regulating tank

[0068] 7: Anoxic tank (biological treatment tank)

[0069] 8: Aerobic tank (biological treatment tank)

[0070] 9: Membrane separation device

[0071] 10: Partition wall

[0072] 11: Suction tube

Claims

1. A wastewater treatment device, wherein, The wastewater treatment device includes: a wastewater inflow path; a biological treatment tank for purifying wastewater flowing in from the wastewater inflow path; and a flow regulating tank for adjusting the amount of wastewater flowing from the wastewater inflow path into the biological treatment tank. A first outlet for sewage to flow into the biological treatment tank and a second outlet for sewage to flow into the flow regulating tank are formed in the sewage inflow path. The height of the first outlet is set to be lower than the height of the second outlet.

2. The wastewater treatment device according to claim 1, wherein, The upper limit water level of the biological treatment tank is determined by the height of the second outlet.

3. The wastewater treatment device according to claim 1, wherein, The first outlet is formed at a position downstream of the sewage inflow path than the second outlet.

4. The wastewater treatment device according to claim 1, wherein, It also includes a sewage pump well, which is equipped with a sewage pump to transfer sewage to the sewage inflow path. The wastewater treatment device includes a wastewater pump control unit, which causes the wastewater pump to operate intermittently when the wastewater level in the wastewater pump well exceeds a first starting water level, and causes the wastewater pump to operate continuously when the wastewater level in the wastewater pump well exceeds a second starting water level higher than the first starting water level.

5. The wastewater treatment apparatus according to any one of claims 1 to 4, wherein, The biological treatment tank uses the membrane separation activated sludge method.

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