Wastewater Treatment System

Abstract

Provided is a wastewater treatment system including a preceding treatment part and a succeeding treatment part for treating the water treated by the preceding treatment part. The preceding treatment part comprises N (N is an integer of 1 or larger) water treatment chambers including a first treatment chamber in which water is treated without aeration. The succeeding treatment part comprises: M (M is an integer of 2 or larger) water treatment chambers including a second treatment chamber, in which water is treated without aeration, and a succeeding aerobic treatment chamber in which the water treated in the second treatment chamber is treated; a first transfer device for transferring either the water inside the succeeding aerobic treatment chamber or the water treated in the succeeding aerobic treatment chamber to the first treatment chamber or to a position located more upstream than the first treatment chamber; and a second transfer device for transferring either the water inside the succeeding aerobic treatment chamber or the water treated in the succeeding aerobic treatment chamber to the second treatment chamber or to a portion of the succeeding treatment part which is located more upstream than the second treatment chamber.

Description

[Technical Field]

[0001] The present specification relates to a technique for treating wastewater. [Background technology]

[0002] Conventionally, wastewater from facilities such as ordinary homes and stores has been treated by wastewater treatment systems such as septic tanks. When the concentration of organic matter in the wastewater is high, a treatment section for aerobic treatment of the organic matter may be added to the septic tank. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 4-45890 Summary of the Invention [Problem to be solved by the invention]

[0004] Various water quality standards can be applied to wastewater treatment systems. For example, standards for nitrogen concentration (total nitrogen concentration (TN) etc.) can be applied. However, there is room for improvement in reducing nitrogen concentration.

[0005] This specification discloses a technique for reducing the nitrogen concentration in water. [Means for solving the problem]

[0006] The techniques disclosed in this specification can be implemented in the following application examples.

[0007] [Application example 1] A wastewater treatment system comprising: a pre-processing unit; a post-treatment section for treating water treated by the pre-treatment section; Equipped with The pre-treatment unit includes N water treatment chambers (N is an integer of 1 or more) including a first treatment chamber that treats water without aeration, The post-processing unit includes: M (M is an integer of 2 or more) water treatment chambers including a second treatment chamber that treats water without aeration and a downstream aerobic treatment chamber that treats water already treated by the second treatment chamber; A first transfer device that transfers the water in the downstream aerobic treatment chamber or the water treated by the downstream aerobic treatment chamber to the first treatment chamber or upstream of the first treatment chamber; A second transfer device that transfers the water in the downstream aerobic treatment chamber or the water treated by the downstream aerobic treatment chamber to the second treatment chamber or a portion of the downstream treatment unit upstream of the second treatment chamber; wastewater treatment systems, including:

[0008] With this configuration, the first transfer device transfers the water in the downstream aerobic treatment chamber or water treated by the downstream aerobic treatment chamber to the first treatment chamber or upstream of the first treatment chamber, thereby promoting denitrification in the first treatment chamber. Furthermore, the second transfer device transfers the water in the downstream aerobic treatment chamber or water treated by the downstream aerobic treatment chamber to the second treatment chamber or a portion of the downstream treatment section upstream of the second treatment chamber, thereby promoting denitrification in the second treatment chamber. As a result, the wastewater treatment system can reduce the nitrogen concentration in the treated water.

[0009] [Application example 2] The wastewater treatment system according to Application Example 1, The number N of water treatment chambers in the pre-treatment section is 2 or more, The N water treatment chambers include a preliminary aerobic treatment chamber that treats water that has been treated by the first treatment chamber, The pre-processing unit further comprises: A third transfer device is provided to transfer the water in the preliminary aerobic treatment chamber or the water treated by the preliminary aerobic treatment chamber to the first treatment chamber or to a portion of the preliminary treatment unit upstream of the first treatment chamber. Wastewater treatment system.

[0010] According to this configuration, in the pre-treatment section, the third transfer device transfers the water in the pre-aerobic treatment chamber or the water treated by the pre-aerobic treatment chamber to the first treatment chamber or to a portion of the pre-treatment section upstream of the first treatment chamber, thereby further promoting denitrification in the first treatment chamber. As a result, the wastewater treatment system can further reduce the nitrogen concentration in the treated water.

[0011] [Application example 3] The wastewater treatment system according to Application Example 1 or 2, further comprising: a pre-stage tank accommodating the pre-stage treatment unit; a downstream tank that accommodates the downstream processing unit and is separated from the upstream tank; A wastewater treatment system comprising:

[0012] According to this configuration, the upstream tank and downstream tank are separated, which improves the degree of freedom in installing the wastewater treatment system.

[0013] [Application example 4] The wastewater treatment system according to Application Example 3, further comprising: a pump tank that temporarily stores water flowing out of the preceding tank and has a pump that transfers the stored water to the subsequent tank; The pump is configured to start transferring water when the water level in the pump tank exceeds a first water level, and to stop transferring water when the water level in the pump tank drops to a second water level that is lower than the first water level; L (L is an integer of 1 to M) water treatment chambers out of the M water treatment chambers of the downstream tank include a water level fluctuation region between a reference water level, which is a stable water level when the first transfer device is stopped and no water flows into the downstream tank, and a high water level higher than the reference water level, and in which the water level fluctuates according to the flow of water into the downstream tank; A first difference in the amount of water in the pump tank between the first water level and the second water level is equal to or less than a second difference in the amount of water in the L water treatment chambers of the rear tank between the reference water level and the high water level. Wastewater treatment system.

[0014] With this configuration, the pump tank transfers water flowing out of the previous tank to the next tank, improving the flexibility of the arrangement of the previous and next tanks. Also, since the first difference in the amount of water in the pump tank between the first and second water levels is equal to or less than the second difference in the amount of water in the next tank between the reference water level and the high water level, the possibility of the water level in the next tank exceeding the high water level due to the transfer of water by the pump tank is reduced.

[0015] [Application example 5] The wastewater treatment system according to any one of Application Examples 1 to 4, further comprising: A wastewater treatment system including a phosphorus removal device that removes phosphorus from the water.

[0016] According to this configuration, the wastewater treatment system can reduce the phosphorus concentration in addition to the nitrogen concentration in the treated water.

[0017] The technology disclosed in this specification can be realized in various forms, for example, in the form of a wastewater treatment method and system, a downstream tank for a wastewater treatment system, etc. [Brief explanation of the drawings]

[0018] [Figure 1] 1 is a block diagram showing a wastewater treatment system according to an embodiment of the present invention; [Figure 2] 1A is a diagram showing the schematic configuration of the downstream tank 800 as seen from the side, and FIG. 1B is a diagram showing the schematic configuration of the downstream tank 800 as seen from below. [Figure 3] 1A is a diagram showing an example of the configuration of a pump tank 700. FIG. 1B is a diagram showing a schematic configuration of a downstream tank 800. [Figure 4] (A) and (B) are tables showing the measurement results of water quality in the wastewater treatment system. DETAILED DESCRIPTION OF THE INVENTION

[0019] A. First Example: FIG. 1 is a block diagram showing a wastewater treatment system according to one embodiment. The wastewater treatment system 1000 purifies wastewater from facilities (such as homes, stores, and offices). The wastewater treatment system 1000 of this embodiment includes an upstream tank 500, a pump tank 700, and a downstream tank 800. The upstream tank 500 is a wastewater treatment device that houses a upstream treatment unit 500p. The upstream treatment unit 500p includes multiple water treatment chambers 510-550 and a circulation air lift pump 580. The downstream tank 800 is a wastewater treatment device that houses a downstream treatment unit 800p. The downstream treatment unit 800p includes multiple water treatment chambers 810-850, a circulation air lift pump 880, a transfer air lift pump 890, and a phosphorus removal unit 860. A flow path 400 is connected upstream of the upstream tank 500. Wastewater flows into the upstream tank 500 via the flow path 400. The water treated in the upstream tank 500 flows into the pump tank 700. The pump tank 700 temporarily stores the water from the upstream tank 500 and transfers the stored water to the downstream tank 800 using a pump. The water treated in the downstream tank 800 is discharged outside the downstream tank 800 (and thus outside the wastewater treatment system 1000).

[0020] The upstream tank 500 and the downstream tank 800 may each be various types of wastewater treatment devices. For example, the upstream tank 500 and the downstream tank 800 may each be a wastewater treatment device configured to treat wastewater from a facility (such as a home, a store, or an office) individually. In this embodiment, by using the upstream tank 500 and the downstream tank 800 connected in series, it is possible to accommodate high loads and various water quality standards (for example, standards for total nitrogen concentration and standards for total phosphorus concentration).

[0021] FIG. 1 shows an example of a pre-stage tank 500 and an example of a post-stage tank 800. In this embodiment, the pre-stage tank 500 houses an impurity removal chamber 510, an anaerobic filter bed chamber 520, a contact filter bed chamber 530, a treated water chamber 540, and a disinfection chamber 550. Wastewater that flows into the pre-stage tank 500 is treated sequentially in the impurity removal chamber 510, the anaerobic filter bed chamber 520, the contact filter bed chamber 530, the treated water chamber 540, and the disinfection chamber 550, and then flows out of the pre-stage tank 500. A blower B5 is connected to the pre-stage tank 500. The pre-stage tank 500 performs a purification process using an oxygen-containing gas (here, air) supplied by the blower B5.

[0022] The impurity removal chamber 510 separates impurities from the wastewater. The impurity removal chamber 510 has a solid-liquid separation means such as an inlet baffle (not shown). The water from which the impurities have been separated flows into the anaerobic filter bed chamber 520. The anaerobic filter bed chamber 520 performs anaerobic treatment using anaerobic microorganisms. The anaerobic filter bed chamber 520 has a filter medium to which the anaerobic microorganisms adhere (not shown). Organic matter in the water is decomposed by the anaerobic treatment. The water treated by the anaerobic filter bed chamber 520 flows into the contact filter bed chamber 530.

[0023] The contact filter bed chamber 530 performs aerobic treatment using aerobic microorganisms. The contact filter bed chamber 530 has components (e.g., contact material, filter material, etc.) to which the aerobic microorganisms adhere and an air diffuser (not shown). Air is supplied to the air diffuser by a blower B5. The air diffuser supplies oxygen-containing air bubbles to the water in the contact filter bed chamber 530. The aerobic microorganisms use the oxygen to decompose organic matter in the water. Furthermore, ammonium ions in the water are oxidized by the action of nitrifying bacteria contained in the aerobic microorganisms to produce nitrite ions and then nitrate ions (a process called nitrification). The water containing nitrate ions (also called nitrified solution) is transferred to the impurity removal chamber 510 by a circulating air lift pump 580 (described later). The nitrified solution flows into the anaerobic filter bed chamber 520 through the impurity removal chamber 510. The impurity removal chamber 510 and the anaerobic filter bed chamber 520 treat water without aeration. In these water treatment chambers, anaerobic treatment by anaerobic microorganisms proceeds. The anaerobic filter bed chamber 520 has a filter medium (not shown) for the anaerobic microorganisms to adhere to, thereby facilitating anaerobic treatment. In anaerobic treatment, the action of denitrifying bacteria contained in the anaerobic microorganisms reduces nitrate ions contained in the nitrification liquid to produce nitrogen gas, which is then released into the air (so-called denitrification). The water treated in the contact filter bed chamber 530 flows into the treated water chamber 540.

[0024] The treated water chamber 540 temporarily stores the water flowing in from the contact filter bed chamber 530 and allows solids in the water (e.g., sludge, suspended solids, etc.) to settle and separate. The treated water chamber 540 is provided with a circulating air lift pump 580. The circulating air lift pump 580 uses gas supplied by the blower B5 to suck water containing settled solids from the bottom of the treated water chamber 540 and transfers it to the impurity removal chamber 510. The treated water in the treated water chamber 540 flows into the disinfection chamber 550. The disinfection chamber 550 is configured to disinfect the water using a disinfectant (not shown). In this embodiment, the treated water in the upstream tank 500 is further treated in the downstream tank 800. Therefore, disinfection in the disinfection chamber 550 may be omitted. For example, the disinfectant may be omitted from the disinfection chamber 550. The water from the disinfection chamber 550 flows out of the upstream tank 500. In this embodiment, the upstream tank 500 is connected to a pump tank 700. Water from the upstream tank 500 flows into the pump tank 700.

[0025] The pump tank 700 transfers the water that has flowed into the pump tank 700 to the downstream tank 800 by a pump.

[0026] In this embodiment, the downstream tank 800 houses an impurity removal chamber 810, an anaerobic filter bed chamber 820, a contact filter bed chamber 830, a treated water chamber 840, and a disinfection chamber 850. The impurity removal chamber 810 is provided with a phosphorus removal device 860. Wastewater that flows into the downstream tank 800 is treated sequentially in the impurity removal chamber 810, the anaerobic filter bed chamber 820, the contact filter bed chamber 830, the treated water chamber 840, and the disinfection chamber 850, before flowing out of the downstream tank 800. A blower B8 is connected to the downstream tank 800. The downstream tank 800 performs a purification process using an oxygen-containing gas (here, air) supplied by the blower B8. The functions of the impurity removal chamber 810, anaerobic filter bed chamber 820, contact filter bed chamber 830, treated water chamber 840, and disinfection chamber 850 are similar to those of the impurity removal chamber 510, anaerobic filter bed chamber 520, contact filter bed chamber 530, treated water chamber 540, and disinfection chamber 550 in the upstream tank 500, respectively. The treated water chamber 840 is provided with a circulation air lift pump 880 and a transfer air lift pump 890. The circulation air lift pump 880 uses gas supplied by the blower B8 to suck water containing settled solids from the bottom of the treated water chamber 840 and transfer it to the impurity removal chamber 810. The transfer air lift pump 890 uses gas supplied by the blower B8 to transfer water from the treated water chamber 840 to the flow path 400. The flow path 400 may have various configurations for transferring water. The flow path 400 may include, for example, a pipe. In addition to pipes, the flow path 400 may include various devices other than pipes, such as a raw water pump tank, a cleaning port, and a bucket (e.g., an invert bucket or a trap bucket). The destination of water transferred by the transfer air lift pump 890 may be any part of the flow path 400 (e.g., a part of the pipes in the flow path 400, or a device other than the pipes in the flow path 400). The bucket forms an opening for observing the inside of the flow path. The opening formed by the bucket is normally covered with a lid. The bucket may be provided midway along a single pipe, or at a point where multiple pipes converge. The device forming the cleaning port is a type of bucket.

[0027] Fig. 2(A) is a diagram showing the schematic configuration of the downstream tank 800 as seen from the side. Fig. 2(B) is a diagram showing the schematic configuration of the downstream tank 800 as seen from below. In these figures, the Z direction indicates the vertically upward direction, the X direction indicates the longitudinal direction (horizontal direction) of the downstream tank 800, and the Y direction indicates the direction (horizontal direction) perpendicular to both the X direction and the Z direction. Hereinafter, the X direction side will also be referred to as the "+X side," and the side opposite the X direction will also be referred to as the "-X side." The same applies to the Y direction and the Z direction.

[0028] The subsequent tank 800 has a tank body 801 that forms the outer surface of the subsequent tank 800. The tank body 801 is provided with an inlet 804 and an outlet 805. Two partition walls 802 and 803 that are aligned in the X direction are provided inside the tank body 801. The partition walls 802 and 803 divide the tank body 801 perpendicularly to the X direction.

[0029] The space on the -X side of partition wall 802 (here, the space surrounded by partition wall 802 and tank body 801) forms impurity removal chamber 810. The space between partition walls 802 and 803 (here, the space surrounded by partition wall 802, partition wall 803, and tank body 801) forms anaerobic filter bed chamber 820.

[0030] 2(B), side walls 843, 842, and 844, which are arranged in a substantially U-shape when viewed from above, are fixed to the +X side of the partition wall 803. The space surrounded by the side walls 843, 842, and 844 and the partition wall 803 forms a treated water chamber 840. Of the space on the +X side of the partition wall 803 (here, the space surrounded by the partition wall 803 and the tank body 801), the portion outside the side walls 843, 842, and 844 forms a contact filter bed chamber 830.

[0031] As shown in FIG. 2(B), side wall 843 is the side wall on the +Y side of the treated water chamber 840, side wall 842 is the side wall on the +X side of the treated water chamber 840, and side wall 844 is the side wall on the -Y side of the treated water chamber 840. The lower portions of side wall portions 843, 842, and 844 have a so-called hopper structure. As shown in FIG. 2(A), the lower ends of side wall portions 843, 842, and 844 are spaced from the bottom surface of the tank body 801 and form an opening 836 that connects the bottom of the contact filter bed chamber 830 and the bottom of the treated water chamber 840. The disinfection chamber 850 is located above the treated water chamber 840.

[0032] Wastewater from inlet 804 flows into impurity removal chamber 810. Impurity removal chamber 810 has inlet baffle 812 and phosphorus removal device 860. Inlet baffle 812 separates impurities from the water. After the impurities have been separated, the water flows into anaerobic filter bed chamber 820 through opening 814 in partition wall 802. The phosphorus removal device 860 will be described later.

[0033] The anaerobic filter bed chamber 820 is provided with an inflow baffle 821, a filter medium 822 for anaerobic microorganisms to adhere to, and a scum baffle 829. The filter medium 822 may have various shapes, such as a plate or a mesh. Water that flows into the anaerobic filter bed chamber 820 through the opening 814 is guided below the filter medium 822 by the inflow baffle 821. The filter medium 822 is not provided within the inflow baffle 821, but is arranged outside the inflow baffle 821. The water guided below the filter medium 822 passes through the filter medium 822 from bottom to top. The water that moves above the filter medium 822 flows into the contact filter bed chamber 830 through an opening 824 provided in the partition wall 803.

[0034] 2(A) shows the reference water level LWL and the high water level HWL. As will be described later, the reference water level LWL indicates the stable water level when there is no water transfer from the downstream tank 800 by the transfer air lift pump 890 and no water flows into the downstream tank 800. When water flows into the downstream tank 800, the water level may temporarily rise from the reference water level LWL. In this embodiment, the water level may rise to the high water level HWL. When the flow of water into the downstream tank 800 stops, the water level drops to the reference water level LWL.

[0035] The opening 824 extends from a height below the reference water level (LWL) to a height above the high water level (HWL). As shown in FIG. 2(B), the scum baffle 829 divides the water surface of the anaerobic filter bed chamber 820 (excluding the interior of the inlet baffle 821) into a first water surface portion WS1 continuous with the opening 824 and the remaining second water surface portion WS2. As shown in FIG. 2(A), the scum baffle 829 extends from a height between the filter medium 822 and the reference water level (LWL) to a height higher than the high water level (HWL). The scum baffle 829 reduces the possibility of solids floating on the second water surface portion WS2 migrating through the opening 824 to the contact filter bed chamber 830.

[0036] As shown in FIG. 2(A), the contact filter bed chamber 830 includes an air diffuser 834, an aerobic filter medium 833 disposed on the air diffuser 834, and a contact material 832 disposed on the aerobic filter medium 833. The aerobic filter medium 833 and the contact material 832 are intended for aerobic microorganisms to adhere to. These components 834, 833, and 832 are provided on the +Y side and the -Y side of the treated water chamber 840 (FIG. 2(B)), respectively. The contact material 832 and the aerobic filter medium 833 may have portions of various shapes, such as plate portions and mesh portions. The contact material 832 may, for example, include multiple plates. The aerobic filter medium 833 may, for example, include a mesh portion.

[0037] Air is supplied to the air diffuser 834 by a blower B8 (FIG. 1). In this embodiment, the air diffuser 834 is configured using a pipe with multiple holes (not shown) on the bottom surface. A large number of bubbles are discharged from the multiple holes in the air diffuser 834. The large number of bubbles pass through the aerobic filter material 833 and the contact material 832 and reach the water surface WL. The movement of the bubbles creates a water current, which agitates the water in the contact filter bed chamber 830. In addition, the large number of bubbles supplies oxygen to the water. Aerobic microorganisms attached to the members 832 and 833 use the oxygen to perform aerobic treatment. The water treated in the contact filter bed chamber 830 flows into the treated water chamber 840 through an opening 836 at the bottom of the contact filter bed chamber 830.

[0038] Water temporarily stagnates in the treated water chamber 840. Solids in the water (e.g., sludge, suspended solids, etc.) may settle to the bottom of the treated water chamber 840. A circulating air lift pump 880 is provided in the treated water chamber 840. An intake port 882 of the circulating air lift pump 880 is located at the bottom of the treated water chamber 840. The circulating air lift pump 880 transfers water containing solids that have settled to the bottom of the treated water chamber 840 to the impurity removal chamber 810 (specifically, the phosphorus removal device 860).

[0039] The phosphorus removal device 860 includes a support base 862 fixed to the inflow baffle 812 and multiple cells 865 supported by the support base 862. Each cell 865 includes two iron electrodes 865f and a cell base 865b that supports the two iron electrodes 865f spaced apart from each other. The two iron electrodes 865f are immersed in water. That is, the two iron electrodes 865f include portions positioned lower than the reference water level (LWL). Power is supplied to the two iron electrodes 865f by a power source (not shown). Divalent iron ions are eluted from the iron electrode 865f, which corresponds to the anode. The circulation air lift pump 880 transports water from the treated water chamber 840 to the vicinity of the two iron electrodes 865f. The divalent iron ions are oxidized by oxygen contained in the water transported by the circulation air lift pump 880 and converted to trivalent iron ions. The trivalent iron ions react with phosphate ions contained in the water in the impurity removal chamber 810 to form iron phosphate, which is a solid and is separated from the water and stored by the impurity removal chamber 810 or the anaerobic filter bed chamber 820. In this way, phosphorus is removed from the water.

[0040] The water transferred by the circulation airlift pump 880 contains nitrified liquid produced by aerobic treatment in the contact filter bed chamber 830. The nitrified liquid flows into the anaerobic filter bed chamber 820 through the impurity removal chamber 810. In the impurity removal chamber 810 and the anaerobic filter bed chamber 820, denitrification is carried out by anaerobic microorganisms.

[0041] The treated water chamber 840 is also provided with a transfer air lift pump 890. An intake port 892 of the transfer air lift pump 890 is located near the water surface in the treated water chamber 840. The transfer air lift pump 890 transfers the water in the treated water chamber 840 to the flow path 400 (FIG. 1). The water transferred to the flow path 400 flows into the upstream tank 500. Nitrate ions contained in the water transferred by the transfer air lift pump 890 flow into the anaerobic filter bed chamber 520 through the impurity removal chamber 510. In the impurity removal chamber 510 and the anaerobic filter bed chamber 520, denitrification is carried out using water from the downstream tank 800.

[0042] The disinfection chamber 850 is located above the treated water chamber 840. In this embodiment, the disinfection chamber 850 has a discharge air lift pump 870. An inlet 872 of the discharge air lift pump 870 is located at the same height as the reference water level LWL in the treated water chamber 840. An outlet 874 of the discharge air lift pump 870 is located in the upstream portion of the disinfection chamber 850. The discharge air lift pump 870 uses gas supplied by the blower B8 to gradually transfer water (water from which solids have been separated) near the water surface WL in the treated water chamber 840 to the disinfection chamber 850. When the water level in the treated water chamber 840 is higher than the reference water level LWL, the discharge air lift pump 870 draws water from the inlet 872 and transfers the drawn water to the disinfection chamber 850. When the water level in the treated water chamber 840 drops to the reference water level LWL, the discharge air lift pump 870 cannot draw water from the intake port 872 and does not transfer water. Thus, the reference water level LWL is the stable water level when the transfer of water by the transfer air lift pump 890 has stopped and no water is flowing into the downstream tank 800.

[0043] When a large amount of water temporarily flows into the downstream tank 800 (e.g., during peak inflow), the water levels in the water treatment chambers 810, 820, 830, and 840 upstream of the discharge air lift pump 870 may temporarily rise above the reference water level LWL. In this embodiment, the water level may rise to the high water level HWL. When the water level exceeds the high water level HWL, water is transferred from the treated water chamber 840 to the disinfection chamber 850 through an overflow opening (not shown) in the disinfection chamber 850. Thus, under normal operating conditions, the highest water level is the high water level HWL. The high water level HWL can be considered the highest design water level. When the amount of inflow water per unit time exceeds the expected range, the water level may temporarily rise above the high water level HWL.

[0044] During peak inflows, the water levels in the multiple water treatment chambers 810, 820, 830, and 840 temporarily rise, thereby mitigating the increase in the outflow rate per unit time from the contact filter bed chamber 830. As a result, the possibility of untreated water outflowing from the contact filter bed chamber 830 can be reduced. The discharge air lift pump 870 operates as a mechanism (also called a "peak shaving mechanism") that mitigates the increase in the outflow rate per unit time from the contact filter bed chamber 830 caused by peak inflows.

[0045] The sterilization chamber 850 has a chemical cylinder 854 filled with a disinfectant (e.g., a solid chlorine agent). In the sterilization chamber 850, the water comes into contact with the disinfectant and is disinfected. The disinfected water is discharged to the outside of the subsequent tank 800 through the outlet 805.

[0046] FIG. 3(A) is a diagram showing an example of the configuration of the pump tank 700. In this embodiment, the pump tank 700 has two pumps 710, 720 and two water level sensors SH, SL. The pump tank 700 temporarily stores water flowing out from the upstream tank 500. The pumps 710, 720 of the pump tank 700 then transfer the stored water to the downstream tank 800. The first water level sensor SH detects whether the water level in the pump tank 700 is equal to or higher than a predetermined first water level HWL7. The second water level sensor SL detects whether the water level in the pump tank 700 is equal to or lower than a predetermined second water level LWL7. The water level sensors SH, SL may each be, for example, a float switch. The pumps 710, 720 are configured to use power supplied from a power source (not shown) to start transferring water when the water level in the pump tank 700 exceeds a first water level HWL7 and to stop transferring water when the water level in the pump tank 700 drops to a second water level LWL7 that is lower than the first water level HWL7. For example, the pumps 710, 720 may be provided with an electric circuit that drives the pumps 710, 720 as described above in accordance with the detection results of the water level sensors SH, SL. The electric circuit may be configured to alternately drive the pumps 710, 720.

[0047] 3(A) shows a first difference V7. The first difference V7 indicates the difference in the amount of water in the pump tank 700 between the first water level HWL7 and the second water level LWL7. In other words, the first difference V7 is the difference between the amount of water in the pump tank 700 when the water level in the pump tank 700 is the first water level HWL7 and the amount of water in the pump tank 700 when the water level in the pump tank 700 is the second water level LWL7.

[0048] 3(B) is a diagram showing a schematic configuration of the downstream tank 800. The diagram shows a second difference V8. The second difference V8 indicates the difference in the amount of water in the downstream tank 800 between the reference water level LWL and the high water level HWL. In other words, the second difference V8 is the difference between the amount of water in the downstream tank 800 when the water level in the downstream tank 800 is the high water level HWL and the amount of water in the downstream tank 800 when the water level in the downstream tank 800 is the reference water level LWL.

[0049] In this embodiment, the first difference V7 is equal to or less than the second difference V8. The reason for this is as follows: The amount of water transferred per unit time by the pumps 710, 720 of the pump tank 700 is greater than the amount of normal drainage per unit time. When the pumps 710, 720 transfer water so that the water level drops from the first water level HWL7 to the second water level LWL7, water equivalent to the first difference V7 flows into the downstream tank 800 in a short period of time. If the first difference V7 is greater than the second difference V8, the water level in the downstream tank 800 may exceed the high water level HWL. If the first difference V7 is equal to or less than the second difference V8, the possibility of the water level exceeding the high water level HWL is reduced.

[0050] B. Evaluation Results: Figures 4(A) and 4(B) are tables showing the measurement results of water quality for the wastewater treatment systems. Figure 4(A) shows the average water quality for the three wastewater treatment systems. All three wastewater treatment systems treat wastewater from stores. The upstream tanks used were septic tanks stipulated in Article 31, Paragraph 2 of the Building Standards Act (each system treated 30 people). The upstream tank configuration differs from the upstream tank 500 shown in Figure 1. However, like the upstream tank 500 shown in Figure 1, the upstream tank includes an anaerobic treatment chamber (here, an anaerobic filter bed tank) that treats water without aeration, and an aerobic treatment chamber (here, either a carrier reaction tank or a carrier fluidized bed tank) that aerobically treats water treated by the anaerobic treatment chamber. A downstream tank was added after the upstream tank. The downstream tank used was a wastewater treatment system obtained by adding a transfer airlift pump 890 (Figures 1, 2(A), and 2(B)) to a CRXII wastewater treatment system manufactured by Fuji Clean Industries Co., Ltd. The configuration of the downstream tank was the same as that of the downstream tank 800 in Figures 1, 2(A), 2(B), and 3(B). The transfer air lift pump 890 was configured to transfer water to a flow path connected upstream of the upstream tank. The flow path upstream of the upstream tank in one wastewater treatment system included a raw water pump tank. The transfer air lift pump 890 was configured to transfer water to the raw water pump tank. The flow path upstream of the upstream tank in the other two wastewater treatment systems had a cleanout port. The transfer air lift pump 890 was configured to transfer water to a portion of the flow path forming the cleanout port. In this way, a pipe transferring water from the transfer air lift pump 890 was connected to the raw water pump tank or the portion forming the cleanout port of the flow path connected upstream of the upstream tank. The raw water pump tank and the cleanout port (more generally, a bucket) form openings exposed to the ground surface, making it easier to process new pipes than underground pipes. The number of people to be treated in the rear tank was determined according to the amount of wastewater from the store. Two wastewater treatment systems were fitted with a CRXII-10 (10-person tank), and one was fitted with a CRXII-5 (5-person tank). In addition, in one wastewater treatment system equipped with a CRXII-10, a sufficient height difference between the front and rear tanks could be ensured, so the rear tank was directly connected to the front tank without using a pump tank 700 (Figure 1).The other two wastewater treatment systems were equipped with a pump tank 700 connecting the upstream tank and the downstream tank.

[0051] The "average water consumption" in Figure 4(A) is the average water consumption per day, which is 2.1 m 3 / day. This value is the average of the three average water usage volumes of the three wastewater treatment systems. "Average water quality of pre-treated water" indicates the average water quality of treated water from the pre-tank before the post-tank was added (here, the average of the three wastewater treatment systems). "Average water quality of post-treated water" indicates the average water quality of treated water from the post-tank approximately 10 months after the post-tank was added (here, the average of the three wastewater treatment systems). Water quality measurements included BOD (Biochemical Oxygen Demand), TN (Total Nitrogen), TP (Total Phosphorus), and SS (Suspended Solids) (all units are mg / L).

[0052] As shown in the figure, the addition of the post-stage tank reduced the average BOD from 159 to 12.9. This is presumably because organic matter was decomposed by aerobic treatment in the contact filter bed chamber 830 of the post-stage tank (FIGS. 1, 2(A), and 2(B)).

[0053] The average TN decreased from 55.7 to 18.7. This is presumably because denitrification using nitrification liquid transported by circulating airlift pump 880 is carried out in anaerobic filter bed chamber 820 of the downstream tank, and denitrification using nitrification liquid transported by transport airlift pump 890 is carried out in the anaerobic treatment chamber of the upstream tank.

[0054] The average TP was reduced from 10.9 to 4.5, presumably because phosphorus was removed from the water by the phosphorus removal device 860 in the downstream tank.

[0055] The average SS was reduced from 90.0 to 3.1. This is presumably because solids in the water were captured by the water treatment chambers in the subsequent tanks (e.g., impurity removal chamber 810 and anaerobic filter bed chamber 820).

[0056] Figure 4(B) shows the water quality of another wastewater treatment system, different from the three wastewater treatment systems shown in Figure 4(A). This wastewater treatment system treats wastewater from a store. A septic tank stipulated in Article 31, Paragraph 2 of the Building Standards Act was used as the upstream tank (treating 30 people). The upstream tank's configuration differs from that of the upstream tank 500 shown in Figure 1. However, like the upstream tank 500 shown in Figure 1, the upstream tank has an anaerobic treatment chamber (an anaerobic filter bed tank in this case) that treats water without aeration, and an aerobic treatment chamber (a carrier fluidized bed tank in this case) that aerobically treats water already treated in the anaerobic treatment chamber. A downstream tank was added after the upstream tank. The downstream tank was a wastewater treatment system obtained by adding a transfer airlift pump 890 (Figures 1, 2(A), and 2(B)) to a CRXII wastewater treatment system manufactured by Fuji Clean Industries Co., Ltd. The configuration of the rear tank is the same as that of the rear tank 800 in Figures 1, 2(A), 2(B), and 3(B). The transfer air lift pump 890 was configured to transfer water to the part of the flow path connected to the upstream side of the front tank that forms the cleaning port. The number of people to be treated by the rear tank was determined based on the amount of wastewater from the store (here, a tank for 10 people). The front tank and rear tank were connected via a pump tank 700.

[0057] The "water consumption" in Figure 4(B) is the average water consumption per day, which is 1.7 m 3 / day. "Pre-treated water quality" indicates the quality of treated water from the pre-tank before the post-tank was added. "Post-treated water quality (no transfer)" indicates the quality of treated water from the post-tank approximately 10 months after the post-tank was added. During this approximately 10-month period, water transfer from the post-tank to the pre-tank by the transfer air lift pump 890 (Figure 1) was stopped. After this, water transfer by the transfer air lift pump 890 began. "Post-treated water quality (with transfer)" indicates the quality of treated water from the post-tank approximately 3 months after water transfer by the transfer air lift pump 890 began. Water quality measurements included BOD, TN, TP, and SS (all in mg / L).

[0058] As shown in the figure, the BOD was reduced from 140 to 47.3 (without transfer) by adding the subsequent tank. The reason for this is presumably because organic matter was decomposed by aerobic treatment in the contact filter bed chamber 830 of the subsequent tank (FIGS. 1, 2(A), and 2(B)). Furthermore, by transferring water using the transfer air lift pump 890, the BOD was reduced from 47.3 (without transfer) to 42.1 (with transfer). The reason for this is presumably because aerobic treatment is carried out in the aerobic treatment chamber of the previous tank using water transferred by the transfer air lift pump 890.

[0059] By adding the subsequent tank, TN was reduced from 121 to 70.2 (without transfer). This is presumably because denitrification is carried out in the anaerobic filter bed chamber 820 of the subsequent tank using nitrification liquid transferred by the circulation air lift pump 880. Furthermore, by transferring water using the transfer air lift pump 890, TN was reduced from 70.2 (without transfer) to 34.2 (with transfer). This is presumably because denitrification is carried out in the anaerobic treatment chamber of the previous tank using nitrification liquid transferred by the transfer air lift pump 890.

[0060] By adding the latter-stage tank, the TP was reduced from 11.4 to 9.2 (without transfer). This is presumably because phosphorus was removed from the water by the phosphorus removal device 860 in the latter-stage tank. Furthermore, by transferring water using the transfer air lift pump 890, the TP was reduced from 9.2 (without transfer) to 7.7 (with transfer). This is presumably because phosphate ions in the water were removed by the formation of iron phosphate as the water transferred by the transfer air lift pump 890 flowed between the former and latter-stage tanks.

[0061] The SS was reduced from 112 to 2.0 (without transfer) by adding the subsequent tank. This is presumably because solids in the water were captured by the water treatment chambers of the subsequent tank (e.g., impurity removal chamber 810 and anaerobic filter bed chamber 820). Furthermore, by transferring water using the transfer air lift pump 890, the SS increased from 2.0 (without transfer) to 11.5 (with transfer). The reason for this is unclear, but an SS of 11.5 mg / L is within a good range.

[0062] As described above, the wastewater treatment system 1000 (FIG. 1) of this embodiment includes a pre-treatment unit 500p and a post-treatment unit 800p that treats water treated by the pre-treatment unit 500p. The pre-treatment unit 500p includes N water treatment chambers 510-550 (N is an integer greater than or equal to 1; in this embodiment, N is 5). The anaerobic filter bed chamber 520 is an example of a first treatment chamber that treats water without aeration (hereinafter, the anaerobic filter bed chamber 520 will also be referred to as the first treatment chamber 520). The post-treatment unit 800p includes M water treatment chambers 810-850 (M is an integer greater than or equal to 2; in this embodiment, M is 5). The anaerobic filter bed chamber 820 is an example of a second treatment chamber that treats water without aeration (hereinafter, the anaerobic filter bed chamber 820 will also be referred to as the second treatment chamber 820). The contact filter bed chamber 830 is an example of a downstream aerobic treatment chamber that treats water that has been treated by the second treatment chamber 820 (hereinafter, the contact filter bed chamber 830 is also referred to as the downstream aerobic treatment chamber 830). The downstream treatment unit 800p further includes a transfer air lift pump 890 that transfers water from the treated water chamber 840 to the flow path 400. The water in the treated water chamber 840 contains water that has been treated by the downstream aerobic treatment chamber 830. The flow path 400 is upstream of the first treatment chamber 520. The transfer air lift pump 890 is an example of a first transfer device that transfers water that has been treated by the downstream aerobic treatment chamber 830 upstream of the first treatment chamber 520 (hereinafter, the transfer air lift pump 890 is also referred to as the first transfer device 890). The downstream treatment unit 800p further includes a circulating air lift pump 880 that transfers water from the treated water chamber 840 to the impurity removal chamber 810. The circulating air lift pump 880 is an example of a second transfer device that transfers water treated by the downstream aerobic treatment chamber 830 to a portion of the downstream treatment section 800p upstream of the second treatment chamber 820 (here, the impurity removal chamber 810) (hereinafter, the circulating air lift pump 880 will also be referred to as the second transfer device 880).

[0063] According to this configuration, the first transfer device 890 can promote denitrification in the first treatment chamber 520 by transferring the water treated in the downstream aerobic treatment chamber 830 upstream of the first treatment chamber 520. Furthermore, the second transfer device 880 can promote denitrification in the second treatment chamber 820 by transferring the water treated in the downstream aerobic treatment chamber 830 to a portion of the downstream treatment section 800p that is upstream of the second treatment chamber 820. As described above, the wastewater treatment system 1000 can reduce the nitrogen concentration in the treated water.

[0064] The reduction in nitrogen concentration is also shown by the measurement results in Figures 4(A) and 4(B). As shown in Figure 4(A), the addition of the subsequent tank reduced TN from 55.7 to 18.7. As shown in Figure 4(B), the addition of the subsequent tank (stopping transfer by the first transfer device 890) reduced TN from 121 to 70.2 (without transfer). Furthermore, by transferring water by the first transfer device 890, TN reduced from 70.2 (without transfer) to 34.2 (with transfer). In this way, denitrification is promoted by the transfer of nitrification solution by the first transfer device 890. Furthermore, denitrification is promoted by the transfer of nitrification solution by the second transfer device 880.

[0065] Furthermore, the downstream aerobic treatment chamber 830 can decompose organic matter through aerobic treatment. As a result, the wastewater treatment system 1000 can reduce the concentration of organic matter (e.g., BOD) in the treated water. The reduction in organic matter concentration is also shown by the measurement results in Figures 4(A) and 4(B). As shown in Figure 4(A), the addition of the downstream tank reduced the average BOD from 159 to 12.9. Furthermore, as shown in Figure 4(B), the addition of the downstream tank (transfer by the first transfer device 890 was stopped) reduced the BOD from 140 to 47.3 (no transfer). In this way, the downstream aerobic treatment chamber 830 can reduce the concentration of organic matter.

[0066] As described above, the wastewater treatment system 1000 can reduce the concentration of nitrogen in addition to the concentration of organic matter.

[0067] In this embodiment, the number N of water treatment chambers in the pre-treatment unit 500p is 2 or more (N is 5 in this embodiment). The N water treatment chambers 510-550 include a contact filter bed chamber 530. The contact filter bed chamber 530 is an example of a pre-aerobic treatment chamber that treats water treated by the first treatment chamber 520 (hereinafter, the contact filter bed chamber 530 will also be referred to as the pre-aerobic treatment chamber 530). The pre-treatment unit 500p further includes a circulating air lift pump 580 that transfers water from the treated water chamber 540 to the impurity removal chamber 510. The water in the treated water chamber 540 contains water treated by the pre-aerobic treatment chamber 530. The impurity removal chamber 510 is a portion of the pre-treatment unit 500p upstream of the first treatment chamber 520. The circulating air lift pump 580 is an example of a third transfer device that transfers water treated in the pre-aerobic treatment chamber to a portion of the pre-treatment unit 500p that is upstream of the first treatment chamber 520 (hereinafter, the circulating air lift pump 580 will also be referred to as the third transfer device 580). In this way, within the pre-treatment unit 500p, the third transfer device 580 transfers water treated in the pre-aerobic treatment chamber 530 to a portion of the pre-treatment unit 500p that is upstream of the first treatment chamber 520, thereby further promoting denitrification in the first treatment chamber 520. As described above, the wastewater treatment system 1000 can further reduce the nitrogen concentration of the treated water.

[0068] Furthermore, in this embodiment, the wastewater treatment system 1000 includes a front-stage tank 500 that houses a front-stage treatment unit 500p, and a rear-stage tank 800 that houses a rear-stage treatment unit 800p and is separate from the front-stage tank 500. Since the front-stage tank 500 and the rear-stage tank 800 are separated in this manner, the flexibility of installation of the wastewater treatment system 1000 can be improved. For example, an existing wastewater treatment device may be used as the front-stage tank. A rear-stage tank may then be added to form a wastewater treatment system. Forming a wastewater treatment system by adding a rear-stage tank can appropriately respond to changes in circumstances, such as changes in the quality of wastewater from facilities (e.g., increased load) and changes in water quality standards (e.g., the addition of a standard for total nitrogen concentration (TN)).

[0069] In this embodiment, the wastewater treatment system 1000 (FIG. 1) also includes a pump tank 700. The pump tank 700 (FIGS. 1 and 3(A)) is a tank that temporarily stores water flowing out from the upstream tank 500 and has pumps 710 and 720 that transfer the stored water to the downstream tank 800. As described with reference to FIG. 3(A), the pumps 710 and 720 are configured to start transferring water when the water level in the pump tank 700 exceeds a first water level HWL7 and to stop transferring water when the water level in the pump tank 700 drops to a second water level LWL7 that is lower than the first water level HWL7. As described with reference to FIG. 3(B), in L (L is an integer between 1 and M; in this embodiment, L is 4) water treatment chambers 810-840 out of the M water treatment chambers 810-850 in the downstream tank 800, the water levels can fluctuate between a reference water level LWL and a high water level HWL in response to the inflow of water into the downstream tank. The reference water level LWL is the stable water level when the first transfer device 890 is stopped and there is no water flowing into the downstream tank 800. The high water level HWL is a water level higher than the reference water level LWL. The water treatment chambers 810-840 include a water level fluctuation region WA, which is the region between the reference water level LWL and the high water level HWL. As described with reference to Figures 3(A) and 3(B), the first difference V7 in the pump tank 700 is less than the second difference V8 in the downstream tank 800. The first difference V7 is the difference in the amount of water in the pump tank 700 between the first water level HWL7 and the second water level LWL7. The second difference V8 is the difference in the amount of water in the downstream tank 800 between the reference water level LWL and the high water level HWL.

[0070] In this way, the pump tank 700 transfers water flowing out from the upstream tank 500 to the downstream tank 800, which improves the flexibility in the arrangement of the upstream tank 500 and the downstream tank 800. For example, an arrangement may be adopted in which the inlet 804 of the downstream tank 800 (FIG. 2(A)) is higher than the outlet (not shown) of the upstream tank 500 (FIG. 1). This high degree of freedom in the arrangement of the upstream tank and the downstream tank improves the flexibility in the arrangement of the downstream tank when a downstream tank is added later to an upstream tank that is an existing wastewater treatment device.

[0071] Furthermore, the first difference V7 of the pump tank 700 is equal to or smaller than the second difference V8 of the downstream tank 800. This reduces the possibility that the water level in the downstream tank 800 will exceed the high water level HWL due to the water transfer by the pumps 710 and 720. This also reduces the possibility that untreated water will flow out of the downstream tank 800.

[0072] In this embodiment, the wastewater treatment system 1000 is also provided with a phosphorus removal device 860 that removes phosphorus from the water. Therefore, the wastewater treatment system 1000 can reduce the phosphorus concentration of the treated water in addition to the nitrogen concentration of the treated water.

[0073] C. Variations: (1) The first treatment chamber included in the upstream treatment unit is not limited to the anaerobic filter bed chamber 520 (FIG. 1), but may be any of various water treatment chambers that treat water without aeration. Such a first treatment chamber is capable of denitrification. For example, the first treatment chamber may be a water treatment chamber that performs solid-liquid separation, such as a sedimentation chamber or an impurity removal chamber. Even when the filter medium is omitted, the first treatment chamber is capable of anaerobic treatment (including denitrification) using anaerobic microorganisms. In either case, to promote anaerobic treatment, the first treatment chamber is preferably configured to store anaerobic microorganisms (e.g., sludge). The above description of the first treatment chamber also applies to the second treatment chamber included in the downstream treatment unit. For example, the filter medium may be omitted from the second treatment chamber. In this case, the second treatment chamber is also capable of anaerobic treatment (including denitrification) using anaerobic microorganisms.

[0074] (2) The downstream aerobic treatment chamber included in the downstream treatment chamber is not limited to the contact filter bed chamber 830 (see FIG. 1, etc.) but may be any of various water treatment chambers for aerobic treatment (e.g., a contact aeration chamber, a carrier fluidized bed chamber, a membrane separation activated sludge chamber, etc.). In such downstream aerobic treatment chambers, nitrification can proceed through the action of nitrifying bacteria contained in the aerobic microorganisms. In either case, the downstream aerobic treatment chamber preferably has an aeration device (e.g., a pipe with multiple holes, a porous aeration device, etc.) for supplying oxygen-containing gas (e.g., air) to the water. The above description of the downstream aerobic treatment chamber also applies to the upstream aerobic treatment chamber included in the upstream treatment unit. For example, the upstream aerobic treatment chamber is not limited to the contact filter bed chamber 530 (see FIG. 1) but may be any other type of water treatment chamber.

[0075] (3) The configuration of the pre-treatment unit is not limited to the configuration of the pre-treatment unit 500p in FIG. 1 , and various configurations may be used, including a first treatment chamber that treats water without aeration. For example, an intermediate treatment chamber (e.g., a sedimentation separation chamber) may be provided between the first treatment chamber 520 and the aerobic pre-treatment chamber 530. In this case, the water flowing from the intermediate treatment chamber to the aerobic pre-treatment chamber 530 (i.e., water treated by the intermediate treatment chamber) is water treated by the first treatment chamber 520. The pre-treatment unit may include any number of water treatment chambers, including the first treatment chamber (i.e., the total number N of water treatment chambers included in the pre-treatment unit may be any integer greater than or equal to 1). For example, the aerobic treatment chamber that performs aerobic treatment may be omitted from the pre-treatment unit. The total number N may be 1. In other words, the pre-treatment unit may include only the first treatment chamber.

[0076] (4) The configuration of the downstream treatment unit is not limited to the configuration of the downstream treatment unit 800p shown in FIG. 1 and other figures, and may be various configurations, including a second treatment chamber that treats water without aeration and a downstream aerobic treatment chamber that treats water already treated by the second treatment chamber. An intermediate treatment chamber (e.g., a sedimentation separation chamber) may be provided between the second treatment chamber 820 and the downstream aerobic treatment chamber 830. In this case, the water flowing from the intermediate treatment chamber to the downstream aerobic treatment chamber 830 (i.e., water already treated by the intermediate treatment chamber) is water already treated by the second treatment chamber 820. The downstream treatment unit may include any number of water treatment chambers, including the second treatment chamber and the downstream aerobic treatment chamber (i.e., the total number M of water treatment chambers included in the downstream treatment unit may be any integer equal to or greater than 2). For example, the total number M may be 2. In other words, the downstream treatment unit may include only the second treatment chamber and the downstream aerobic treatment chamber.

[0077] (5) The configuration of the first transfer device is not limited to the configuration of the first transfer device 890 shown in FIG. 1 and other figures, and various configurations are possible. The water transferred by the first transfer device may be water in the downstream aerobic treatment chamber or water treated by the downstream aerobic treatment chamber. In either case, the first transfer device can transfer nitrified liquid produced by aerobic treatment in the downstream aerobic treatment chamber. For example, the first transfer device 890 may acquire water from the downstream aerobic treatment chamber 830. The first transfer device 890 may acquire water from a portion of the downstream treatment section 800p downstream of the downstream aerobic treatment chamber 830 (e.g., water in the treated water chamber 840). In this case, the acquired water is water treated by the downstream aerobic treatment chamber 830. Furthermore, the destination of the water transferred by the first transfer device may be the first treatment chamber or any portion upstream of the first treatment chamber. In either case, the first treatment chamber can proceed with denitrification using the nitrified liquid transferred by the first transfer device. Here, the portion upstream of the first treatment chamber may be part of the wastewater treatment system, or alternatively, it may be outside the wastewater treatment system (for example, a flow path connected to the upstream side of the wastewater treatment system). For example, the first transfer device 890 may transfer water to a water treatment chamber (for example, the impurity removal chamber 510 or the first treatment chamber 520) included in the pre-treatment unit 500p. If the flow path connected to the upstream side of the wastewater treatment system 1000 includes a raw water pump tank or a bucket, the first transfer device 890 may transfer water to the raw water pump tank or the bucket. Furthermore, the first transfer device is not limited to an air lift pump, and may include various devices capable of transferring water (for example, an electric pump).

[0078] (6) The configuration of the second transfer device is not limited to the configuration of the second transfer device 880 shown in FIG. 1 and the like, and various configurations are possible. The water transferred by the second transfer device may be water in the downstream aerobic treatment chamber or water treated by the downstream aerobic treatment chamber. In either case, the second transfer device can transfer nitrified liquid produced by aerobic treatment in the downstream aerobic treatment chamber. For example, the second transfer device 880 may acquire water from the downstream aerobic treatment chamber 830. The second transfer device 880 may acquire water from a portion of the downstream treatment unit 800p downstream of the downstream aerobic treatment chamber 830 (for example, water in the treated water chamber 840). In this case, the acquired water is water treated by the downstream aerobic treatment chamber 830. Furthermore, the destination of the water transferred by the second transfer device may be the second treatment chamber or any portion of the downstream treatment unit upstream of the second treatment chamber. In either case, the second treatment chamber can proceed with denitrification using the nitrifying liquid transferred by the second transfer device. For example, the second transfer device 880 may transfer water to the second treatment chamber 820. Furthermore, the post-treatment section 800p may include a flow rate adjusting chamber located upstream of the second treatment chamber 820. The second transfer device 880 may transfer water to the flow rate adjusting chamber. Furthermore, the second transfer device is not limited to an air lift pump and may include various devices capable of transferring water (for example, an electric pump).

[0079] (7) The configuration of the third transfer device is not limited to the configuration of the third transfer device 580 shown in FIG. 1 and other figures, and various configurations are possible. The water transferred by the third transfer device may be water in the preliminary aerobic treatment chamber or water treated by the preliminary aerobic treatment chamber. In either case, the third transfer device can transfer nitrified liquid produced by aerobic treatment in the preliminary aerobic treatment chamber. For example, the third transfer device 580 may acquire water from the preliminary aerobic treatment chamber 530. The third transfer device 580 may acquire water from a portion of the preliminary treatment unit 500p downstream of the preliminary aerobic treatment chamber 530 (for example, water in the treated water chamber 540). In this case, the acquired water is water treated by the preliminary aerobic treatment chamber 530. Furthermore, the destination of the water transferred by the third transfer device may be the first treatment chamber or any portion of the preliminary treatment unit upstream of the first treatment chamber. In either case, the first treatment chamber can proceed with denitrification using the nitrifying liquid transferred by the third transfer device. For example, the third transfer device 580 may transfer water to the first treatment chamber 520. Furthermore, the pretreatment section 500p may include a flow rate adjusting chamber located upstream of the first treatment chamber 520. The third transfer device 580 may transfer water to the flow rate adjusting chamber. Furthermore, the third transfer device is not limited to an air lift pump and may include various devices capable of transferring water (for example, an electric pump).

[0080] (8) The second difference V8 described in Figures 3(A) and 3(B) may be less than the first difference V7. In this case, it is preferable to set the amount of water transferred per unit time by the pump tank 700 to a small value so that the water level in the downstream tank 800 does not exceed the high water level HWL due to the transfer of water by the pump tank 700.

[0081] The water level fluctuation region corresponding to the second difference V8 is a region in which the water level fluctuates in response to the inflow of water into the downstream tank. The water treatment chambers including such a water level fluctuation region may be any L (L is an integer between 1 and M) water treatment chambers out of the M water treatment chambers included in the downstream tank 800. For example, the downstream tank 800 (FIG. 3(B)) may be equipped with a transfer device that transfers water little by little from the anaerobic filter bed chamber 820 to the contact filter bed chamber 830. The water treatment chambers including the water level fluctuation region may be the water treatment chambers 810, 820 upstream of the contact filter bed chamber 830. The downstream tank may also include a flow rate adjustment chamber. The water treatment chamber having a water level fluctuation region may be the flow rate adjustment chamber alone.

[0082] In either case, the reference water level that defines the water level fluctuation region is not limited to the reference water level LWL in Figure 3(B) but may be any of various stable water levels when the first transfer device is stopped and no water flows into the downstream tank. Furthermore, the high water level that defines the water level fluctuation region is not limited to the high water level HWL in Figure 3(B) but may be any of various water levels higher than the reference water level. Here, the high water level is preferably a water level that prevents untreated water from flowing out of the downstream tank.

[0083] The first water level that determines the first difference V7 is not limited to the first water level HWL7 in Fig. 3(A) but may be any of various water levels configured to cause the pump in the pump tank to start transferring water when the water level in the pump tank exceeds the first water level. The second water level that determines the first difference V7 is not limited to the second water level LWL7 in Fig. 3(A) but may be any of various water levels configured to cause the pump in the pump tank to stop transferring water when the water level in the pump tank drops to a second water level (here, the second water level is lower than the first water level). The configuration for controlling the pump in this manner in response to the water level is not limited to an electric circuit including water level sensors SH and SL but may be any configuration (for example, the pump may be controlled by a control panel or a computer).

[0084] The water level fluctuation region may be omitted from the downstream tank. In this case, it is preferable to set the amount of water transferred per unit time by the pump tank to a small value so as to prevent untreated water from flowing out of the downstream tank.

[0085] The configuration of the pump tank is not limited to the configuration of pump tank 700 shown in Figures 1 and 3(A), and various configurations are possible, such as a tank that temporarily stores water flowing out from a previous tank and has a pump that transfers the stored water to a subsequent tank. For example, the total number of pumps provided in the pump tank may be any number greater than or equal to one. When the total number of pumps is two or more, the total number of pumps that transfer water simultaneously may be any number greater than or equal to one. For example, multiple pumps may transfer water one by one in turn.

[0086] If the upstream and downstream tanks are arranged so that the inlet of the downstream tank is lower than the outlet of the upstream tank, the water flowing out from the outlet of the upstream tank can be introduced into the inlet of the downstream tank without using a pump. In this case, the pump tank may be omitted.

[0087] (9) The phosphorus removal device 860 (FIGS. 2(A) and 2(B)) may be disposed in any portion of the wastewater treatment system through which water flows. For example, the phosphorus removal device 860 may be disposed in a water treatment chamber included in a subsequent tank (e.g., any one of the water treatment chambers 810, 820, 830, or 840). Alternatively, the phosphorus removal device 860 may be disposed in a water treatment chamber included in a subsequent tank (e.g., any one of the water treatment chambers 510, 520, 530, or 540). Furthermore, the phosphorus removal device 860 may be disposed midway through any one of the air lift pumps 580, 880, or 890, instead of in a water treatment chamber.

[0088] The configuration of the phosphorus removal device is not limited to the configuration of the phosphorus removal device 860 shown in FIGS. 2(A) and 2(B), and various configurations capable of removing phosphorus from water may be used. For example, the electrode of the cell 865 may be an aluminum electrode instead of the iron electrode 865f. The phosphorus removal device may also include an addition device that adds a flocculant such as an iron salt or an aluminum salt instead of an electrode. The phosphorus removal device may also have an adsorbent that adsorbs phosphorus (e.g., a magnesia-based adsorbent, a titania-based adsorbent, a zirconium-based adsorbent, an alumina-based adsorbent, etc.). The phosphorus removal device may also include a phosphorus removal chamber using a biological phosphorus removal method. The phosphorus removal device may be omitted.

[0089] (10) The configuration of the wastewater treatment system is not limited to the configurations of the above-described embodiment and modified examples, and various configurations are possible. The wastewater treatment system may have a pre-tank that houses a pre-treatment unit and a post-tank that houses a post-treatment unit and is separate from the pre-tank, as in the embodiment of FIG. 1. Alternatively, the pre-treatment unit and the post-treatment unit may be housed in a single body. Furthermore, the multiple water treatment chambers of the wastewater treatment system may be housed in three or more separate bodies.

[0090] The above-described examples and modifications can be combined as appropriate. The above-described examples and modifications are provided to facilitate understanding of the present disclosure and are not intended to limit the present invention. The present invention may be modified or improved without departing from the spirit thereof, and the present invention includes equivalents thereof. [Industrial Applicability]

[0091] The present invention can be suitably used in wastewater treatment systems. [Explanation of symbols]

[0092] 400...flow path, 500...pre-stage tank, 500p...pre-stage treatment unit, 510...impurity removal chamber, 520...anaerobic filter bed chamber (first treatment chamber), 530...contact filter bed chamber (pre-stage aerobic treatment chamber), 540...treated water chamber, 550...disinfection chamber, 580...circulating air lift pump (third transfer device), 700...pump tank, 710, 720...pump, 800...post-stage tank, 800p...post-stage treatment unit, 801...tank body, 80 2...partition wall, 803...partition wall, 804...inlet, 805...outlet, 810...impurity removal chamber, 812...inlet baffle, 814...opening, 820...anaerobic filter bed chamber (second treatment chamber), 821...inlet baffle, 822...filter material, 824...opening, 829...scum baffle, 830...contact filter bed chamber (post-aerobic treatment chamber), 832...contact material, 833...aerobic filter material, 834...air diffuser, 836...opening , 840...treated water chamber, 842...side wall portion, 843...side wall portion, 844...side wall portion, 850...disinfection chamber, 854...chemical cylinder, 860...phosphorus removal device, 862...support stand, 865...cell, 865b...cell base, 865f...iron electrode, 870...discharge air lift pump, 872...intake port, 874...exhaust port, 880...circulation air lift pump (second transfer device), 882...intake port, 890...transfer Air lift pump (first transfer device), 892...suction port, 1000...wastewater treatment system, HWL7...first water level, LWL7...second water level, B5...blower, B8...blower, V7...first difference, V8...second difference, WA...water level fluctuation area, SH...first water level sensor, SL...second water level sensor, WL...water surface, WS1...first water surface portion, WS2...second water surface portion, LWL...reference water level, HWL...high water level

Claims

1. A wastewater treatment system comprising: a pre-processing unit; a post-treatment section for treating water treated by the pre-treatment section; Equipped with the pre-treatment unit includes N water treatment chambers (N is an integer of 1 or more) including a first treatment chamber that treats water without aeration; The post-processing unit includes: M (M is an integer of 2 or more) water treatment chambers including a second treatment chamber that treats water without aeration and a downstream aerobic treatment chamber that treats water already treated by the second treatment chamber; A first transfer device that transfers the water in the downstream aerobic treatment chamber or the water treated by the downstream aerobic treatment chamber to the first treatment chamber or upstream of the first treatment chamber; A second transfer device that transfers the water in the downstream aerobic treatment chamber or the water treated by the downstream aerobic treatment chamber to the second treatment chamber or a portion of the downstream treatment unit upstream of the second treatment chamber; Including, The number N of water treatment chambers in the pre-treatment section is 2 or more, The N water treatment chambers include a preliminary aerobic treatment chamber that treats water that has been treated by the first treatment chamber, The pre-processing unit further comprises: A third transfer device is provided to transfer the water in the preliminary aerobic treatment chamber or the water treated by the preliminary aerobic treatment chamber to the first treatment chamber or a portion of the preliminary treatment unit upstream of the first treatment chamber, The wastewater treatment system further comprises: a pre-stage tank accommodating the pre-stage treatment unit; a downstream tank that accommodates the downstream processing unit and is separated from the upstream tank; Equipped with The upstream tank is an existing wastewater treatment device, the latter-stage tank is a wastewater treatment device that is added to the former-stage tank later, The wastewater treatment system further comprises: a pump tank that temporarily stores water flowing out of the preceding tank and has a pump that transfers the stored water to the subsequent tank; the pump is configured to start transferring water in response to a water level in the pump tank exceeding a first water level, and to stop transferring water in response to the water level in the pump tank decreasing to a second water level lower than the first water level; L (L is an integer of 1 to M) water treatment chambers out of the M water treatment chambers of the downstream tank include a water level fluctuation region between a reference water level, which is a stable water level when the first transfer device is stopped and no water flows into the downstream tank, and a high water level higher than the reference water level, and in which the water level fluctuates in response to the flow of water into the downstream tank; A first difference in the amount of water in the pump tank between the first water level and the second water level is equal to or less than a second difference in the amount of water in the L water treatment chambers of the downstream tank between the reference water level and the high water level. Wastewater treatment system.

2. A wastewater treatment system comprising: a pre-processing unit; a post-treatment section for treating water treated by the pre-treatment section; Equipped with the pre-treatment unit includes N water treatment chambers (N is an integer of 1 or more) including a first treatment chamber that treats water without aeration; The post-processing unit includes: M (M is an integer of 2 or more) water treatment chambers including a second treatment chamber that treats water without aeration and a downstream aerobic treatment chamber that treats water already treated by the second treatment chamber; A first transfer device that transfers the water in the downstream aerobic treatment chamber or the water treated by the downstream aerobic treatment chamber to the first treatment chamber or upstream of the first treatment chamber; A second transfer device that transfers the water in the downstream aerobic treatment chamber or the water treated by the downstream aerobic treatment chamber to the second treatment chamber or a portion of the downstream treatment unit upstream of the second treatment chamber; Including, The wastewater treatment system further comprises: a pre-stage tank accommodating the pre-stage treatment unit; a downstream tank that accommodates the downstream processing unit and is separated from the upstream tank; a pump tank for temporarily storing water flowing out from the first tank, the pump tank having a pump for transferring the stored water to the second tank; Equipped with the pump is configured to start transferring water in response to a water level in the pump tank exceeding a first water level, and to stop transferring water in response to the water level in the pump tank decreasing to a second water level lower than the first water level; L (L is an integer of 1 to M) water treatment chambers out of the M water treatment chambers of the downstream tank include a water level fluctuation region between a reference water level, which is a stable water level when the first transfer device is stopped and no water flows into the downstream tank, and a high water level higher than the reference water level, and in which the water level fluctuates in response to the flow of water into the downstream tank; A first difference in the amount of water in the pump tank between the first water level and the second water level is equal to or less than a second difference in the amount of water in the L water treatment chambers of the downstream tank between the reference water level and the high water level. Wastewater treatment system.

3. The wastewater treatment system according to claim 2, The number N of water treatment chambers in the pre-treatment section is 2 or more, The N water treatment chambers include a preliminary aerobic treatment chamber that treats water that has been treated by the first treatment chamber, The pre-processing unit further comprises: A third transfer device is provided to transfer the water in the preliminary aerobic treatment chamber or the water treated by the preliminary aerobic treatment chamber to the first treatment chamber or to a portion of the preliminary treatment unit upstream of the first treatment chamber. Wastewater treatment system.

4. The wastewater treatment system according to any one of claims 1 to 3, further comprising: A wastewater treatment system including a phosphorus removal device that removes phosphorus from the water.

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