Sewage treatment device

Abstract

Provided is a sewage treatment device comprising an inexpensive flow rate adjustment tank having a low probability of failure and high reliability.　This sewage treatment device 100 comprises: a sewage inflow passage 4; biological treatment tanks 7, 8 for purifying sewage flowing in from the sewage inflow passage 4; and a flow rate adjustment tank 5 for adjusting the amount of sewage flowing into the biological treatment tanks 7, 8 from the sewage inflow passage 4. The sewage inflow passage 4 has a first outflow port 43 through which sewage flows into the biological treatment tanks 7, 8 and a second outflow port 44 through which sewage flows into the flow rate adjustment tank 5. The height of the first outflow port 43 is set to be at a lower level than the height of the second outflow port 44.

Description

Sewage treatment equipment

[0001] The present invention relates to a wastewater treatment device.

[0002] Patent Document 1 discloses a wastewater treatment device that employs a membrane separation activated sludge method, in which a membrane separation device that separates the activated sludge mixed liquid in a biological treatment tank that biologically treats wastewater with activated sludge is immersed in the tank.

[0003] In the membrane bioreactor, the amount of wastewater that can be treated is proportional to the area of ​​the membrane installed. Therefore, if the amount of influent wastewater fluctuates, it is necessary to install a membrane with an area large enough to accommodate the peak amount of influent wastewater.

[0004] However, membranes are relatively expensive equipment and have high running costs, including power consumption. Therefore, introducing membranes large enough to handle peak inflow volumes of wastewater results in high running costs, and energy conservation is desired.

[0005] Therefore, a design that minimizes the required membrane area by installing a flow adjustment tank to absorb fluctuations in the inflowing wastewater and make the amount of wastewater sent to the biological treatment tank uniform is adopted as standard in small-scale sewage treatment plants (see Figure 7 and paragraph

[0072] of Patent Document 1).

[0006] Japanese Patent Application Laid-Open No. 2018-34077

[0007] There are two types of flow equalization tanks: an in-line type that receives all of the wastewater at once, and a side-line type that receives all or part of the wastewater as needed. As shown in Figure 4, in an in-line type flow equalization tank 5, the wastewater is pumped up by a wastewater pump P1, and after impurities have been removed by a fine screen 3, the entire amount of wastewater is temporarily stored in the flow equalization tank 5. The wastewater stored in the flow equalization tank 5 is then pumped up by a pump P2 and transferred to a wastewater distribution tank 12 via a wastewater inlet 4. The wastewater, adjusted to a constant flow rate by the wastewater distribution tank 12, is then transferred to the biological treatment tanks 7 and 8.

[0008] As shown in Figure 5, in a sideline-type flow equalization tank 5, sewage is pumped by a sewage pump P1, and after impurities have been removed by a fine screen 3, it is transferred to a sewage distribution tank 12 via a sewage inlet conduit 4. The sewage, adjusted to a constant flow rate by the sewage distribution tank 12, is then transferred to the biological treatment tanks 7 and 8. When the water levels in the biological treatment tanks 7 and 8 reach a predetermined upper water level, excess sewage is stored in the flow equalization tank 5 via a branch conduit 4D branching off from the sewage inlet conduit 4. When the water levels in the biological treatment tanks 7 and 8 drop below the upper water level, sewage is again supplied to the sewage distribution tank 12 via the sewage inlet conduit. When the amount of sewage flowing into the biological treatment tanks 7 and 8 decreases, the sewage stored in the flow equalization tank 5 is pumped by a pump P2 and transferred to the sewage distribution tank 12 via a sewage inlet conduit 6. The sewage inlet conduit 4 and the branch conduit 4D are provided with electromagnetic valves V1 and V2 for switching the flow path.

[0009] Compared to inline types, sideline flow equalization tanks are superior in terms of energy conservation because they reduce the amount of water that needs to be re-pumped. However, fluctuations in the amount of wastewater generated are difficult to predict, and adopting sideline flow equalization tanks in small-scale sewage treatment plants that require patrol management requires the adoption of automatic water control equipment such as electrically operated weirs and electrically operated valves for switching flow paths, which increases costs. If the automatic water control equipment does not function properly due to a malfunction, sewage may overflow from the tank or an accident may occur where untreated water is discharged. Therefore, a backup mechanism is essential for automatic water control equipment, but installing redundant electrically operated weirs and electrically operated valves to prepare for malfunctions would increase costs even further and make it difficult to implement.

[0010] In view of the above-mentioned problems, an object of the present invention is to provide a sewage treatment device having a flow adjustment tank that is inexpensive, highly reliable, and has a low probability of failure.

[0011] In order to achieve the above-mentioned object, the first characteristic configuration of the sewage treatment device according to the present invention is a sewage treatment device comprising a sewage inlet conduit, a biological treatment tank that purifies the sewage flowing in from the sewage inlet conduit, and a flow rate adjustment tank that adjusts the amount of sewage flowing from the sewage inlet conduit into the biological treatment tank, wherein the sewage inlet conduit is formed with a first outlet through which sewage flows into the biological treatment tank and a second outlet through which sewage flows into the flow rate adjustment tank, the height of the first outlet is set 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.

[0012] Sewage flowing into the sewage inlet conduit can be transferred to the biological treatment tank through the first outlet and to the flow equalization tank through the second outlet. Because the height of the first outlet is set lower than the height of the second outlet, when the water level in the biological treatment tank is lower than the height of the second outlet, sewage transferred through the sewage inlet conduit flows exclusively into the biological treatment tank through the first outlet. Then, as the amount of inflowing sewage increases and the water level in the biological treatment tank exceeds the water level corresponding to the difference in elevation between the first and second outlets, any amount of sewage exceeding the volume of activated sludge or treated water flowing out of the biological treatment tank flows out through the second outlet to the flow equalization tank. Then, as the amount of inflowing sewage decreases, when the water level in the biological treatment tank falls below the water level corresponding to the difference in elevation between the first and second outlets, all of the inflowing sewage flows back into the biological treatment tank through the first outlet. Therefore, there is no need to provide a water control mechanism that may cause malfunctions, such as an electric water control device such as an electric valve that switches whether the sewage transported through the sewage inlet is discharged into the biological treatment tank or the flow rate adjustment tank, or an electronic control device that controls the electric water control device, so a highly reliable sewage treatment device can be realized.

[0013] The second characteristic configuration has the same features as the first characteristic configuration described above, in that the height of the first outlet is set 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.

[0014] The water level in the biological treatment tank is allowed to fluctuate only by an amount corresponding to the difference in elevation between the first and second outlets. Even if there is a sudden increase in the amount of wastewater inflow that exceeds the treatment capacity of the biological treatment tank, the water can be temporarily stored in the biological treatment tank to prevent it from flowing out into the flow adjustment tank, and the power consumption required to pump wastewater into the wastewater inlet can be minimized.

[0015] The third characteristic feature of the present invention is that, in addition to the first characteristic feature described above, the first outlet is formed downstream of the second outlet in the sewage inlet channel.

[0016] Sewage flowing into the sewage inlet channel flows out from the second outlet into the flow rate equalization tank, and activated sludge in the biological treatment tank does not flow out from the first outlet into the flow rate equalization tank.

[0017] The fourth characteristic configuration is that, in addition to the first characteristic configuration described above, the system further includes a sewage pump well in which a sewage pump is installed that transports sewage to the sewage inlet conduit, and a sewage pump control unit that operates the sewage pump intermittently when the sewage water level in the sewage pump well exceeds a first starting water level, and operates the sewage pump continuously when the sewage water level exceeds a second starting water level that is higher than the first starting water level.

[0018] By operating the sewage pump intermittently until the sewage level in the sewage pump well exceeds the second activation level, which is higher than the first activation level, a sudden increase in the amount of sewage flowing into the sewage inlet can be suppressed.As a result, the amount of sewage flowing out from the sewage inlet to the flow adjustment tank can be reduced, and the power consumption required to pump sewage by the sewage pump can be minimized.

[0019] The fifth characteristic feature of the present invention is that, in addition to any one of the first to fourth characteristic features described above, the biological treatment tank employs a membrane separation activated sludge method.

[0020] By absorbing fluctuations in the amount of sewage flowing into the sewage inlet and stabilizing the amount of sewage sent to the biological treatment tank, it is possible to realize a sewage treatment system with a reliable, inexpensive flow adjustment tank, while suppressing the increase in membrane area and reducing initial and running costs.

[0021] As described above, according to the present invention, it is possible to provide a sewage treatment device equipped with a flow adjustment tank that is inexpensive, has a low probability of failure, and is highly reliable.

[0022] FIG. 1 is an explanatory diagram of a sewage treatment device. FIG. 2A is an explanatory diagram of the operation of the sewage treatment device. FIG. 2B is an explanatory diagram of the operation of the sewage treatment device. FIG. 3A is an explanatory diagram of a sewage treatment device showing another embodiment. FIG. 3B is an explanatory diagram of a sewage treatment device showing another embodiment. FIG. 4 is an explanatory diagram of a conventional inline type flow equalization tank. FIG. 5 is an explanatory diagram of a conventional sideline type flow equalization tank.

[0023] The sewage treatment device according to the present invention will now be described. Figure 1 shows a sewage treatment device 100 that is installed in a sewage treatment plant or industrial wastewater treatment plant and employs a membrane bioreactor. The sewage treatment device 100 includes a sewage pump well 1 for storing sewage, a fine mesh screen 3, a side-line flow equalization tank 5, biological treatment tanks 7 and 8, and a membrane separation device 9. Reference numeral 7 denotes an anoxic tank that constitutes part of the biological treatment tank, and reference numeral 8 denotes an aerobic tank that also constitutes part of the biological treatment tank.

[0024] When the sewage stored in the sewage pump well 1 reaches either of the preset starting water levels HWL1 or HWL2, the sewage pump P1 is started and the sewage is pumped into the lifting pipe 2. After impurities are removed by the fine screen 3, the sewage is transferred to the anoxic tank 7 via the sewage inlet conduit 4. The sewage transferred to the anoxic tank 7 is mixed with the activated sludge in the tank and transferred through the lower opening of the partition wall 10 to the aerobic tank 8 where ammonia nitrogen is nitrified, and a portion of the sewage is returned to the anoxic tank 7 for denitrification. The sewage that has been nitrified in the aerobic tank 8 and has had organic components decomposed and removed is suction-filtered as treated water by the membrane separation device 9, and the treated water extracted from the suction pipe 11 is subjected to sterilization and other treatments before being released into a river or used as on-site treated water.

[0025] The end of the sewage transport pipe 41 that constitutes the sewage inlet channel 4 is branched in two directions by a branch pipe 42, and at one end is formed a first outlet 43 through which sewage flows into the anoxic tank 7, which is a biological treatment tank, and at the other end is formed a second outlet 44 through which sewage flows into the flow rate adjustment tank 5.

[0026] The height H1 of the first outlet 43 (height from the bottom of the anoxic tank 7) is set lower by ΔH than the height H2 of the second outlet 44 (height from the bottom of the flow rate adjustment tank 5), and the upper water level limit of the anoxic tank 7 is determined by the height H2 of the second outlet 44. Specifically, the distal end of the wastewater transport pipe 41 hangs downward and branches into a horizontally positioned branch pipe 42. One end of the branch pipe 42 forms the first outlet 43 that opens on the anoxic tank 7 side, and the other end of the branch pipe 42 bends upward, with its tip forming the second outlet 44 that opens on the flow rate adjustment tank 5 side.

[0027] In other words, the wastewater flowing into the wastewater inlet channel 4 through the fine screen 3 can be transported from the first outlet 43 to the anoxic tank 7, and from the second outlet 44 to the flow rate adjustment tank 5.

[0028] As shown in Figure 2A, the height H1 of the first outlet 43 is set ΔH lower than the height H2 of the second outlet 44, so when the water level in the anoxic tank 7 is lower than the height of the second outlet 44, the sewage transported through the sewage transport pipe 41 flows into the anoxic tank 7 exclusively through the first outlet 43.

[0029] When the water level in the anoxic tank 7 reaches or exceeds the level corresponding to the elevation difference ΔH between the first outlet 43 and the second outlet 44, the flow of wastewater from the first outlet 43 to the anoxic tank 7 stops, and the wastewater flowing into the wastewater transport pipe 41 begins to flow out from the second outlet 44 to the flow rate adjustment tank 5, as shown in Figure 2B.

[0030] Thereafter, as biological treatment progresses, the treated water is suction filtered in the membrane separation device 9, and when the water level in the biological treatment tanks 7, 8 falls below the water level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, the wastewater again flows out into the anoxic tank 7 through the first outlet 43.

[0031] Therefore, there is no need to provide a water control mechanism that may cause malfunctions, such as an electric water control device such as an electric valve that switches whether the sewage transported through the sewage inlet line 4, which is the sewage transport pipe 41 and branch pipe 42, flows out into the biological treatment tanks 7, 8 or the flow rate adjustment tank 5, or an electronic control device that controls the electric water control device, so a highly reliable sewage treatment device can be realized.

[0032] 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 the biological treatment tanks 7 and 8 is determined by the height of the second outlet 44, and the steady-state water level NWL of the biological treatment tanks 7 and 8 is set slightly above the height of the first outlet 43.

[0033] The water level in the biological treatment tanks 7, 8 is allowed to fluctuate by an amount corresponding to the difference in elevation between the first outlet 43 and the second outlet 44, and even if there is a sudden increase in the amount of wastewater inflow that exceeds the treatment capacity of the biological treatment tanks 7, 8, the water can be temporarily stored in the biological treatment tanks 7, 8 to prevent it from flowing out to the flow adjustment tank 5. In other words, the power consumption required for the wastewater pump P1 to pump wastewater into the wastewater inlet conduit 4 can be kept to a minimum.

[0034] When the amount of wastewater pumped into the wastewater inlet 4 by the wastewater pump P1 decreases and the water level in the biological treatment tanks 7 and 8 drops below, for example, the steady-state water level NWL, the wastewater stored in the flow rate adjustment tank 5 is transferred to the biological treatment tanks 7 and 8 by the pump P2 provided in the flow rate adjustment tank 5.

[0035] The sewage pump P1 installed in the sewage pump well 1 is operated intermittently at a predetermined time interval by the sewage pump control unit when the sewage water level in the sewage pump well 1 exceeds a first starting water level HWL1, and is operated continuously when the sewage water level exceeds a second starting water level HWL2, which is higher than the first starting water level HWL1. It goes without saying that the pump's stop water level is set at a position lower than the first starting water level HWL1.

[0036] When the amount of sewage stored in the sewage pump well 1 is not enough to cause overflow, that is, until 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 prevent a sudden increase in the amount of sewage flowing into the sewage inlet conduit 4.As a result, the amount of sewage flowing out from the sewage inlet conduit 4 to the flow rate adjustment tank 5 can be reduced, and the energy used to pump sewage by the sewage pump P1 can be effectively utilized.

[0037] For example, if the pumping capacity of the sewage pump P1 is 1.2 m ３ / min, and the processing capacity of the membrane filtration equipment is 0.76 m ３ / min, processing capacity shortage 0.44m ３ / min, the biological treatment tanks 7 and 8 (water surface area is 60 m ２ By ensuring a fluctuation range of 0.3 m (BMW-NWL) in the water level of the wastewater treatment plant, the time that wastewater can be accepted with treatment stopped is 18 m. ３ ÷0.44 m ３ / min = 40 min, and the flow rate adjustment function for 40 minutes can be ensured.

[0038] In the above-described embodiment, the sewage inlet channel 4 is configured as a pipe, but the 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 shown in Figures 3A and 3B, the sewage inlet channel 4 may be configured as a water channel 41. The first outlet 43 formed in the water channel 41 is formed downstream of the second outlet 44 in the flow path of the sewage inlet channel 4.

[0039] In this case, as shown in Figure 3A, when the water level in the anoxic tank 7 is lower than the height of the second outlet 44, the wastewater transported through the waterway 41 flows into the anoxic tank 7 exclusively through the first outlet 43.

[0040] When the water level in the anoxic tank 7 reaches or exceeds the level corresponding to the elevation difference ΔH between the first outlet 43 and the second outlet 44, as shown in Figure 3B, the atmospheric pressure acting on the wastewater surface in the anoxic tank 7 causes the flow of wastewater from the first outlet 43 to the anoxic tank 7 to stop, and the wastewater flowing into the waterway 41 begins to flow out from the second outlet 44 to the flow rate adjustment tank 5.

[0041] Therefore, when wastewater flowing into the waterway 41 flows out from the second outlet 44 into the flow rate adjustment tank 5, the activated sludge in the biological treatment tanks 7 and 8 does not flow out from the first outlet 43 into the flow rate adjustment tank 5.

[0042] In the above-described embodiment, a wastewater treatment device 100 employing a membrane bioreactor in the biological treatment tank has been described. However, the present invention is also applicable to a wastewater treatment device employing a standard activated sludge process in which wastewater biologically treated in the biological treatment tank is introduced into a settling tank for solid-liquid separation, and the supernatant liquid is extracted as treated water.

[0043] The above-described embodiment is one aspect of the present invention, and the present invention is not limited to this description. It goes without saying that the specific configuration of each part can be appropriately modified and designed within the scope of the effects of the present invention.

[0044] 1: Sewage pump well 2: Lifting pipe 3: Fine screen 4: Sewage inlet 41: Sewage transport pipe (sewage inlet) 42: Branch pipe (sewage inlet) 43: First outlet 44: Second outlet 5: Flow rate adjustment tank 7: Anoxic tank (biological treatment tank) 8: Aerobic tank (biological treatment tank) 9: Membrane separation device 10: Partition wall 11: Suction pipe

Claims

1. A sewage treatment apparatus comprising a sewage inflow path, a biological treatment tank for purifying sewage flowing in from the sewage inflow path, and a flow rate adjustment tank for adjusting the amount of sewage flowing from the sewage inflow path into the biological treatment tank, wherein a first outlet through which sewage flows into the biological treatment tank and a second outlet through which sewage flows into the flow rate adjustment tank are formed in the sewage inflow path, and the height of the first outlet is set lower than the height of the second outlet.

2. The sewage treatment apparatus according to claim 1, wherein the upper limit water level of the biological treatment tank is defined by the height of the second outlet.

3. The sewage treatment apparatus according to claim 1, wherein the first outlet is formed on the downstream side of the sewage inflow path from the second outlet.

4. The sewage treatment apparatus according to claim 1, further comprising a sewage pump well in which a sewage pump for transferring sewage to the sewage inflow path is installed, and a sewage pump control unit that intermittently operates the sewage pump when the sewage water level in the sewage pump well exceeds a first activation water level and continuously operates the sewage pump when the sewage water level exceeds a second activation water level higher than the first activation water level.

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

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