Sewage treatment apparatus

Abstract

To provide a sewage treatment apparatus equipped with an inexpensive flow adjustment tank that is highly reliable and has a low probability of failure.SOLUTION: A sewage treatment apparatus 100 includes a sewage inflow path 4, biological treatment tanks 7 and 8 for purifying sewage flowing from the sewage inflow path 4, and a flow rate adjustment tank 5 for adjusting an amount of sewage flowing from the sewage inflow path 4 to the biological treatment tanks 7 and 8. The sewage inflow path 4 is formed with a first outflow port 43 through which sewage flows into the biological treatment tanks 7 and 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 lower than the height of the second outflow port 44.SELECTED DRAWING: Figure 2

Description

Technical Field

[0001] The present invention relates to a sewage treatment apparatus.

Background Art

[0002] Patent Document 1 discloses a sewage treatment apparatus that employs a membrane separation activated sludge method in which a membrane separation device for solid-liquid separation of the activated sludge mixed liquor in a tank is immersed in a biological treatment tank for biologically treating sewage with activated sludge.

[0003] In the membrane separation activated sludge method, since the amount of sewage that can be treated is proportional to the membrane area to be installed, when the inflow sewage volume fluctuates, it is necessary to install a membrane with an area capable of coping with the peak inflow sewage volume.

[0004] However, since the membrane is a relatively expensive facility and the running cost including the power consumption is high, if a membrane of a scale capable of coping with the peak inflow sewage volume is introduced, the running cost becomes disproportionately high, and energy saving is desired.

[0005] Therefore, by installing a flow adjustment tank, absorbing the fluctuation of the inflowing sewage, and equalizing the amount of sewage sent to the biological treatment tank, a design that minimizes the required membrane area is standardly adopted in small-scale sewage treatment plants (see FIG. 7 and paragraph

[0072] of Patent Document 1).

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0007] By the way, the flow adjustment tank includes an in-line type that once accepts the entire amount of sewage, and a side-line type that accepts the entire amount or a part of the sewage as needed. As shown in FIG. 4, in the in-line type flow rate adjustment tank 5, the total amount of sewage pumped up by the sewage pump P1 and having impurities removed by the fine screen 3 is once stored in the flow rate adjustment tank 5. The sewage stored in the flow rate adjustment tank 5 is pumped up by the pump P2 and transferred to the sewage distribution tank 12 via the sewage transfer pipe 4. The sewage adjusted to a constant flow rate by the sewage distribution tank 12 is transferred to the biological treatment tanks 7 and 8.

[0008] As shown in FIG. 5, in the side-line type flow rate adjustment tank 5, the sewage pumped up by the sewage pump P1 and having impurities removed by the fine screen 3 is transferred to the sewage distribution tank 12 via the sewage transfer pipe 4. The sewage adjusted to a constant flow rate by the sewage distribution tank 12 is transferred to the biological treatment tanks 7 and 8. When the water levels of the biological treatment tanks 7 and 8 reach a predetermined upper limit water level, excess sewage is stored in the flow rate adjustment tank 5 via the branch pipe 4D branched from the sewage transfer pipe 4. When the water levels of the biological treatment tanks 7 and 8 drop below the upper limit water level, the sewage is again supplied to the sewage distribution tank 12 via the sewage transfer pipe. When the amount of sewage flowing into the biological treatment tanks 7 and 8 decreases, the sewage stored in the flow rate adjustment tank 5 is pumped up by the pump P2 and transferred to the sewage distribution tank 12 via the sewage transfer pipe 6. Electromagnetic valves V1 and V2 for switching the flow path are provided in the sewage transfer pipe 4 and the branch pipe 4D.

[0009] Compared with the in-line type, the side-line type flow rate adjustment tank is superior from the viewpoint of energy saving because it can reduce the amount of water to be re-pumped. However, it is difficult to predict the fluctuation of the sewage generation amount. When adopting the side-line type flow rate adjustment tank in a small-scale sewage treatment plant premised on patrol management, it is necessary to adopt automatic water control facilities such as an electric movable weir and an electric valve for flow path switching, which increases the cost. If the automatic water control facilities do not operate correctly due to a failure or the like, sewage may overflow from the water tank, or an untreated discharge accident may occur. Therefore, a backup mechanism is indispensable for the automatic water control facilities. However, installing redundant electric movable weirs and electric valves for backup in case of failure further increases the cost and makes it difficult to realize.

[0010] An object of the present invention is to provide a sewage treatment apparatus provided with a flow rate adjustment tank that has a low failure occurrence probability, is highly reliable, and is inexpensive in view of the above-described problems.

Means for Solving the Problems

[0011] In order to achieve the above object, the first characteristic configuration of the sewage treatment apparatus according to the present invention is a sewage treatment apparatus including a sewage inflow channel, a biological treatment tank for purifying sewage flowing in from the sewage inflow channel, and a flow rate adjustment tank for adjusting the amount of sewage flowing from the sewage inflow channel into the biological treatment tank. In the sewage inflow channel, 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, 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 defined by the height of the second outlet.

[0012] The sewage flowing into the sewage inflow channel can be transferred from the first outlet to the biological treatment tank and from the second outlet to the flow rate adjustment tank. Since 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, the sewage transferred through the sewage inflow channel flows out exclusively through the first outlet into the biological treatment tank. Then, when the inflow water volume of the sewage increases and the water level in the biological treatment tank becomes higher than the water level corresponding to the height difference between the first outlet and the second outlet, the amount of sewage exceeding the volume of the activated sludge or treated water flowing out from the biological treatment tank flows out from the second outlet into the flow rate adjustment tank. Thereafter, when the inflow water volume of the sewage decreases and the water level in the biological treatment tank becomes lower than the water level corresponding to the height difference between the first outlet and the second outlet, again, the entire amount of the inflowing sewage flows out into the biological treatment tank through the first outlet. Therefore, there is no need to provide a water control mechanism such as an electric water control device such as an electric valve for switching whether the sewage transferred through the sewage inflow channel flows out into either the biological treatment tank or the flow rate adjustment tank, or an electronic control device for controlling the electric water control device, which may cause a failure, so that a highly reliable sewage treatment apparatus can be realized.

[0013] The second characteristic configuration is that, in addition to the first characteristic configuration described above, 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 defined by the height of the second outlet.

[0014] The water level fluctuation of the biological treatment tank is allowed only by the water level difference between the first outlet and the second outlet. Even if there is a sudden increase in the amount of sewage inflow exceeding the treatment capacity of the biological treatment tank, the outflow to the flow rate adjustment tank can be suppressed by temporarily storing water in the biological treatment tank, and the power consumption required for pumping the sewage into the sewage inflow path can be minimized.

[0015] The third characteristic configuration is that, in addition to the first characteristic configuration described above, the first outlet is formed on the downstream side of the sewage inflow path with respect to the second outlet.

[0016] The sewage flowing into the sewage inflow path flows out from the second outlet to the flow rate adjustment tank, and the activated sludge in the biological treatment tank does not flow out from the first outlet to the flow rate adjustment tank.

[0017] The fourth characteristic configuration is that, in addition to the first characteristic configuration described above, it further includes 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 level in the sewage pump well exceeds a first start-up level and continuously operates the sewage pump when it exceeds a second start-up level higher than the first start-up level.

[0018] By intermittently operating the sewage pump until the sewage level in the sewage pump well exceeds a second start-up level higher than the first start-up level, a sudden increase in the amount of sewage flowing into the sewage inflow path can be suppressed. As a result, the outflow volume of sewage from the sewage inflow path to the flow rate adjustment tank can be reduced, and the power consumption required for pumping the sewage by the sewage pump can be minimized.

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

[0020] By absorbing the fluctuations in the sewage flowing into the sewage inlet channel and stabilizing the amount of sewage sent to the biological treatment tank, it is possible to suppress an increase in the membrane area while suppressing the initial cost and running cost, and realize a sewage treatment apparatus equipped with a highly reliable and inexpensive flow rate adjustment tank.

Effect of the Invention

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

Brief Description of the Drawings

[0022]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Mode for Carrying Out the Invention

[0023] Hereinafter, the sewage treatment apparatus according to the present invention will be described. FIG. 1 shows a sewage treatment apparatus 100 installed in a sewage treatment plant or an industrial wastewater treatment plant and adopting the membrane separation activated sludge method. The sewage treatment apparatus 100 includes a sewage pump well 1 for storing sewage, a fine screen 3, a side-line type flow rate adjustment tank 5, biological treatment tanks 7 and 8, a membrane separation device 9, and the like. Reference numeral 7 is an anoxic tank, and reference numeral 8 is an aerobic tank.

[0024] When the sewage stored in the sewage pump well 1 reaches either of the preset start-up water levels HWL1 and HWL2, the sewage pump P1 is activated to pump the sewage into the lift pipe 2. After the fine debris is removed by the fine mesh screen 3, the sewage is transferred to the anoxic tank 7 through the sewage inlet channel 4. The sewage transferred to the anoxic tank 7 is mixed with the activated sludge in the tank and transferred from the lower opening of the partition wall 10 to the aerobic tank 8, where the ammonia nitrogen is nitrified. Part of it is returned to the anoxic tank 7 for denitrification treatment. The sewage that is nitrified in the aerobic tank 8 and has its organic components decomposed and removed is suction-filtered by the membrane separation device 9 as treated water. The treated water taken out from the suction pipe 11 is disinfected and then discharged into the river or used as on-site treated water.

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

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

[0027] That is, the sewage flowing into the sewage inlet channel 4 through the fine mesh screen 3 can be transferred from the first outlet 43 to the anoxic tank 7 and is configured to be transferable from the second outlet 44 to the flow adjustment tank 5.

[0028] As shown in Fig. 2(a), since the height H1 of the first outlet 43 is set 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 inflow channel 41 flows exclusively into the anoxic tank 7 through the first outlet 43.

[0029] And when the water level in the anoxic tank 7 reaches a level equal to or higher than the level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, as shown in Fig. 2(b), the flow of sewage from the first outlet 43 into the anoxic tank 7 stops, and the sewage flowing into the sewage inflow channel 41 flows out from the second outlet 44 into the flow rate adjustment tank 5.

[0030] After that, as biological treatment progresses and suction filtration proceeds as treated water in the membrane separation device 9, when the water levels in the biological treatment tanks 7 and 8 become lower than the level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, sewage again flows into the anoxic tank 7 through the first outlet 43.

[0031] Therefore, there is no need to provide a water control mechanism such as an electric valve for switching which of the biological treatment tanks 7 and 8 and the flow rate adjustment tank 5 the sewage transferred through the sewage inflow channels 41 and 42 flows into, or an electronic control device for controlling the electric water control device, which may cause a failure. Thus, 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 defined by the height of the second outlet 44, and the steady water level NWL of the biological treatment tanks 7 and 8 is set slightly above the height of the first outlet 43.

[0033] Only the water level corresponding to the height difference between the first outlet 43 and the second outlet 44 allows the water level in the biological treatment tanks 7 and 8 to fluctuate. Even if there is a sudden increase in the sewage inflow volume exceeding the treatment capacity of the biological treatment tanks 7 and 8, the outflow to the flow rate adjustment tank 5 can be suppressed by temporarily storing water in the biological treatment tanks 7 and 8. That is, the power consumption required for pumping sewage into the sewage inflow channel 4 by the sewage pump P1 can be minimized.

[0034] When the amount of sewage pumped into the sewage inflow channel 4 by the sewage pump P1 decreases and the water levels in the biological treatment tanks 7 and 8 drop below, for example, the normal water level NWL, the sewage 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 provided in the sewage pump well 1 is intermittently operated at a predetermined time interval when the sewage level in the sewage pump well 1 exceeds the first starting water level HWL1 by the sewage pump control unit, and is continuously operated when it exceeds the second starting water level HWL2 higher than the first starting water level HWL1. Needless to say, the pump 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 such that it overflows, that is, until the sewage level in the sewage pump well 1 exceeds the second starting water level higher than the first starting water level HWL1, by intermittently operating the sewage pump, a rapid increase in the amount of sewage flowing into the sewage inflow channel 4 can be suppressed. As a result, the outflow amount of sewage from the sewage inflow channel 4 to the flow rate adjustment tank 5 can be reduced, and the pumping energy of the sewage by the sewage pump P1 can be effectively utilized.

[0037] For example, when the pumping capacity of the sewage pump P1 is 1.2 m 3 / min, the treatment capacity of the membrane filtration device is 0.76 m 3 / min, and the insufficient treatment capacity is 0.44 m 3 / min, by ensuring a fluctuation range (BMW - NWL) of 0.3 m in the water levels of the biological treatment tanks 7 and 8 (the water surface area is 60 m 2 ).), the time during which sewage can be received in the state where the treatment is stopped is 18 m 3 ÷0.44 m 3 / min = 40 min, and a flow rate adjustment function for 40 minutes can be ensured.

[0038] In the above-described embodiment, the case where the sewage inflow path 4 is constituted by a pipeline has been described. However, as long as the height of the first outlet is set lower than the height of the second outlet, the specific form thereof is not limited. Further, as shown in FIGS. 3(a) and 3(b), the sewage inflow path 4 may be constituted by a water channel 41. The first outlet 43 formed in the water channel 41 is formed on the downstream side of the flow path through which the sewage flowing through the sewage inflow path 4 flows, as compared with the second outlet 44.

[0039] Also in this case, as shown in FIG. 3(a), when the water level in the anoxic tank 7 is lower than the height of the second outlet 44, the sewage transferred through the water channel 41 flows out exclusively to the anoxic tank 7 through the first outlet 43.

[0040] Then, when the water level in the anoxic tank 7 becomes equal to or higher than the water level corresponding to the height difference ΔH between the first outlet 43 and the second outlet 44, as shown in FIG. 3(b), the flow of the sewage flowing out from the first outlet 43 to the anoxic tank 7 stops due to the influence of the atmospheric pressure acting on the sewage water surface in the anoxic tank 7, and the sewage flowing into the water channel 41 flows out from the second outlet 44 to the flow rate adjustment tank 5.

[0041] Therefore, when the sewage flowing into the water channel 41 flows out from the second outlet 44 to 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 to the flow rate adjustment tank 5.

[0042] In the above-described embodiment, the sewage treatment apparatus 100 in which the membrane separation activated sludge method is adopted in the biological treatment tank has been described. However, the present invention is also applicable to a sewage treatment apparatus adopting a standard activated sludge method in which the sewage biologically treated in the biological treatment tank is led to a sedimentation tank for solid-liquid separation, and the supernatant liquid is taken out as treated water.

[0043] The above-described embodiment is one aspect of the present invention, and the present invention is not limited by the description. Needless to say, the specific configuration of each part can be appropriately changed and designed within the range in which the functions and effects of the present invention are achieved.

Explanation of reference numerals

[0044] 1: Sewage pump well 2: Lift pipe 3: Fine mesh screen 41: Sewage inlet channel 42: Branch path 43: First outlet 44: Second outlet 5: Flow adjustment tank 7: Anaerobic 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 with respect to 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 is installed in the sewage inflow path, 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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