Drainage treatment device and drainage treatment method

Abstract

The system is designed to treat wastewater by performing denitrification and nitrification using relatively simple equipment. The wastewater treatment device controls the amount of aeration in the wastewater treatment path to form, in order from upstream, a front aerobic zone, a front combined zone where nitrification and denitrification proceed, a denitrification zone, a rear combined zone where nitrification and denitrification proceed, and a rear aerobic zone, and generates a pair of first and second swirling flows. Additionally, the wastewater treatment device controls the amount of aeration in the front aerobic zone and the front combined zone based on nitrate nitrogen concentration, and controls the amount of aeration in the rear combined zone and the rear aerobic zone based on ammonia nitrogen concentration. The first swirling flow rises in the front combined zone, descends near the center of the denitrification zone from the water surface side of the denitrification zone toward downstream, and moves upstream from the bottom of the denitrification zone; the second swirling flow rises in the rear combined zone, descends near the center of the denitrification zone from the water surface side toward upstream, and moves downstream from the bottom of the denitrification zone.

Description

Technology Field

[0001] The present disclosure relates to a wastewater treatment device and a wastewater treatment method. Background Technology

[0002] In a method for treating wastewater such as sewage, ammoniacal nitrogen contained in the wastewater is converted into nitrate nitrogen by the action of nitrifying bacteria in an aerobic zone where aeration treatment is performed, and this nitrate nitrogen is discharged as nitrogen gas by the action of denitrifying bacteria in a denitrification zone where aeration treatment is not performed (for example, see Patent Document 1). Prior art literature

[0003] [Patent Document 1] Patent Publication No. 2008-221162 The problem to be solved

[0004] However, in the technology of the above-mentioned patent document 1, partition plates or stirring blades were required, which resulted in equipment costs. means of solving the problem

[0005] The wastewater treatment device of the present disclosure comprises a tank having an inlet for wastewater, a flow path where wastewater treatment is performed, and an outlet for treated water; an aeration device having a plurality of aeration sections arranged at the bottom of the flow path along the flow path of the tank; a first detection device for detecting the nitrate nitrogen concentration of the wastewater; a second detection device provided downstream of the first detection device for detecting the ammonia nitrogen concentration of the wastewater; and a control device for controlling the amount of aeration from the plurality of aeration sections of the aeration device, and forming a front aeration zone, a front combined zone where both nitrification and denitrification proceed, a denitrification zone, a rear combined zone where both nitrification and denitrification proceed, and a rear aeration zone in order from the upstream side along the flow path, and further, generating a pair of first and second swirling flows in the flow path. The above control device controls the amount of aeration in the overall aerobic zone and the overall combined zone based on the nitrate nitrogen concentration detected by the first detection device, and controls the amount of aeration in the latter combined zone and the latter aerobic zone based on the ammonia nitrogen concentration detected by the second detection device; the first swirling flow rises in the overall combined zone, descends near the center of the denitrification zone towards the downstream side of the denitrification zone, and is a swirling flow that moves upstream from the bottom of the denitrification zone; the second swirling flow rises in the latter combined zone, descends near the center of the denitrification zone towards the upstream side of the denitrification zone, and is a swirling flow that moves downstream from the bottom of the denitrification zone.

[0006] The wastewater treatment method of the present disclosure is a wastewater treatment method performed in a wastewater treatment device having a tank having a wastewater inlet, a flow path where wastewater treatment is performed, and a treated water outlet; an aeration device having a plurality of aeration sections arranged at the bottom of the flow path along the flow path of the tank; a first detection device for detecting the nitrate nitrogen concentration of the wastewater; and a second detection device provided downstream of the first detection device for detecting the ammonia nitrogen concentration of the wastewater. The method comprises controlling the amount of aeration from the plurality of aeration sections of the aeration device, and forming, in order from the upstream side along the flow path, a general aerobic zone, a general combined zone where both nitrification and denitrification proceed, a denitrification zone, a secondary combined zone where both nitrification and denitrification proceed, and a secondary aerobic zone, and further, a process of generating a pair of first and second swirling flows in the flow path, and in the process of generating the first and second swirling flows, controlling the amount of aeration in the general aerobic zone and the general combined zone based on the nitrate nitrogen concentration detected by the first detection device, and The process has a method for controlling the amount of aeration in the second-half combined area and the second-half aerobic area based on the ammonia nitrogen concentration detected by the second detection device, wherein the first swirling flow rises in the first-half combined area, descends near the center of the denitrification area towards the downstream side of the denitrification area, and is a swirling flow that moves upstream from the bottom side of the denitrification area, and the second swirling flow rises in the second-half combined area, descends near the center of the denitrification area towards the upstream side of the denitrification area, and is a swirling flow that moves downstream from the bottom side of the denitrification area. Brief explanation of the drawing

[0007] FIG. 1 is an explanatory diagram illustrating one embodiment of the processing apparatus of the present disclosure. FIG. 2 is an explanatory diagram illustrating the configuration of an aeration device of the processing apparatus of the present disclosure. Figure 3 is an explanatory diagram illustrating the details of the control performed in the main body of the control device. Figure 4 is a diagram illustrating a flowchart of the operation processing by the main body of the control device. FIG. 5 is a graph showing the change in BOD concentration at the first and last leaching outlets when wastewater treatment is performed using the treatment device of the present disclosure. FIG. 6 is a graph showing the change in TN concentration at the first and last leaching outlets when wastewater treatment is performed using the treatment device of the present disclosure. FIG. 7 is a graph showing the change in TP concentration at the first and last leaching outlets when wastewater treatment is performed using the treatment device of the present disclosure. Specific details for implementing the invention

[0008] Hereinafter, embodiments of the present disclosure are described with reference to the drawings. However, such description should not be interpreted in a limiting sense and is not intended to limit the subject matter described in the claims. Furthermore, various modifications, substitutions, or alterations may be made without departing from the spirit and scope of the present disclosure. Additionally, other embodiments may be appropriately combined.

[0009] In the present disclosure, examples of drainage include sewage and factory drainage, but the drainage treatment device of the present disclosure (hereinafter appropriately described as a treatment device) is particularly suitable for sewage treatment.

[0010] Wastewater, such as sewage, is introduced into an initial sedimentation pond that is not shown, where the first sedimentation sludge is separated by settling, and the supernatant is introduced into the treatment device of the present disclosure as water to be treated. This water to be treated (the "wastewater" to be treated by the wastewater treatment device of the present disclosure) contains nitrogen components such as ammonia derived from manure, etc. In the treatment device of the present disclosure, the wastewater is subjected to nitrification and denitrification treatment so that the nitrogen concentration in the wastewater is reduced and the ammoniacal nitrogen concentration is reduced to below the allowable concentration so that it can be discharged.

[0011] FIGS. 1 and FIGS. 2 illustrate an embodiment of the treatment apparatus of the present disclosure. The treatment apparatus (100) for treating wastewater of FIG. 1 comprises a treatment tank (hereinafter appropriately referred to as a tank) (200) for treating wastewater, an aeration device (300) for supplying an oxygen-containing gas (hereinafter appropriately referred to as air) to the wastewater, a control system (400) for controlling the aeration device (300), a first detection device (403), and a second detection device (404). The wastewater treatment apparatus is a device that performs the above-mentioned nitrification and denitrification simultaneously in a single tank (i.e., a single tank), and is also called a single-tank type nitrification and denitrification device.

[0012] The tank (200) has a tank structure of a natural flow method, has a drainage inlet (201) at one end and a treated water outlet (202) at the other end, and has a drainage path (203) extending from the inlet (201) to the outlet (202).

[0013] In this embodiment, a partition wall (204) is placed in the middle of the flow path (203) near the inlet section (201), and the wastewater flowing in from the inlet section (201) is directed to flow into an anaerobic zone (205) separated by the partition wall (204). The anaerobic zone (205) mixes the wastewater introduced through the initial sedimentation pond (not shown) with the return sludge and serves to release organic matter in the wastewater or phosphorus contained in the return sludge under anaerobic conditions. This phosphorus enters the activated sludge through the subsequent aerobic zone, thereby reducing the phosphorus content in the wastewater. However, in the present invention, providing the partition wall (204) and the anaerobic zone (205) is not mandatory, and the tank (200) may be made without the partition wall (204) and the anaerobic zone (205). In addition, in the present disclosure, a single tank means that the portion excluding the anaerobic area (205) forms a single tank without partition walls.

[0014] The aeration device (300) is equipped with a plurality of aeration sections (306). The plurality of aeration sections (306) are arranged at the bottom (lower) of the flow path (203) along the flow path (203) of the tank (200). In the case of this embodiment, there is a first blower (301), a second blower (302), and a pipe (303) connected thereto, and the pipe (303) is connected to the tank (200) through a first electric valve (304) and a second electric valve (305). Additionally, a plurality of aeration sections (306) are installed along the flow path (203) at the bottom of the tank (200). Furthermore, a pressure detection device (308) is installed in the middle of the flow path leading to the first electric valve (304) of the pipe (303). In addition, in this embodiment, there are two blowers such as the first blower (301) and the second blower (302), but there may be one blower or three or more blowers.

[0015] And, as shown in FIG. 2, the piping (303) passing through the first electric valve (304) and the second electric valve (305) is branched into multiple branches and connected to each aeration unit (306) through a manual valve (307). Accordingly, the amount of aeration ejected from each aeration unit (306) can be adjusted by adjusting the output of the first blower (301) and the second blower (302), the degree of opening of the first electric valve (304) and the second electric valve (305), or the degree of opening of the manual valve (307) connected to each aeration unit (306). In addition, the manual valve (307a) is a valve located at the boundary of each area described later.

[0016] Referring to FIG. 2, in the remaining area that passes through the partition wall (204) of the flow path (203) of the tank (200), by adjusting the amount of aeration from the aeration section (306) of the aeration device (300), the front aeration area (206), the upstream front combined area (209f), the denitrification area (207), the downstream rear combined area (209b), and the rear aeration area (208) are formed from the side closer to the inlet section (201). Here, the front aeration area (206) and the front combined area (209f) located downstream therefrom form the area corresponding to the front aeration area. In addition, the rear combined area (209b) located downstream of the denitrification area (207) and the rear aeration area (208) located downstream therefrom form the area corresponding to the rear aeration area. In the section where the front aerobic area (206), front combined area (209f), denitrification area (207), rear combined area (209b), and rear aerobic area (208) of the Euro (203) are arranged, there are no partition walls, and these areas are formed by adjusting the amount of aeration. Additionally, in FIG. 1, the front combined area (209f) and the rear combined area (209b) are omitted for convenience. Also, the front combined area (209f) and the rear combined area (209b) are collectively referred to as the combined area (209).

[0017] The aeration unit (306) located in the front aeration area (206), the front combined area (209f), the downstream second combined area (209b), and the second aeration area (208) is configured so that aeration is performed by opening the corresponding manual valve (307, 307a), and the aeration unit (306) located in the denitrification area (207) is configured so that aeration is not performed or the amount of aeration is reduced by closing or tightening the corresponding manual valve (307, 307a).

[0018] Herein, referring to the arrows (U1, U2, R1, R2, L1, L2, D) of FIG. 2, a process (step) comprising a control device (400) controlling the amount of aeration from an aeration unit (306) to generate a pair of first and second swirling flows is described in the present disclosure. The first swirling flow is a flow indicated by the arrows (U1, R1, D, L2), and the second swirling flow is a flow indicated by the arrows (U2, L1, D, R2). Here, arrows (U1 and U2) indicate an upward flow, arrow (R1) indicates a forward flow on the surface, arrow (R2) indicates a forward flow on the bottom, arrow (L1) indicates a reverse flow on the surface, arrow (L2) indicates a reverse flow on the bottom, and arrow (D) indicates a downward flow.

[0019] In the areas corresponding to the front aerobic zone (front aerobic zone (206) and front combined zone (209f)) and the areas corresponding to the rear aerobic zone (rear combined zone (209b) and rear aerobic zone (208)), an upward flow (see arrows (U1, U2)) is generated by aeration, causing the water level to rise. Therefore, at the downstream end of the area corresponding to the front aerobic zone (front aerobic zone (206) and front combined zone (209f)) and at the upstream end of the area corresponding to the rear aerobic zone (rear combined zone (209b) and rear aerobic zone (208)), a flow is generated from the water level side toward the denitrification zone (207) (see arrows (R1, L1)). This flow becomes a downward flow near the center of the denitrification zone (207) (see arrow (D)), and further, at the bottom side of the denitrification zone (207), it flows outward from each other (see arrows (R2, L2)).

[0020] Additionally, a combined area (209) in which both nitrification and denitrification proceed is formed on the outer side of the denitrification area (207) adjacent to the area according to the general aerobic area (general aerobic area (206) and general combined area (209f)), and on the outer side of the denitrification area (207) adjacent to the area according to the latter aerobic area (secondary combined area (209b) and secondary aerobic area (208)).

[0021] In the treatment device (100), the combined area (209) becomes a buffer area, so that even without providing a partition plate, the wastewater with a high dissolved oxygen concentration in the overall aerobic area (206) is mixed with the wastewater with a low dissolved oxygen concentration in the denitrification area (207) by the extrusion flow, or the wastewater with a high dissolved oxygen concentration in the latter aerobic area (208) is mixed with the wastewater with a low dissolved oxygen concentration in the denitrification area (207) by the flow opposite to the extrusion flow, thereby effectively avoiding the situation where the anaerobic or low oxygen state in the denitrification area (207) is damaged, and it becomes possible to sufficiently carry out the denitrification reaction. Furthermore, since denitrification treatment can be performed in the combined area in addition to the denitrification area, and nitrification treatment is also performed in the combined area, the denitrification area can be expanded without reducing the aerobic area, making it possible to increase the target denitrification treatment amount with the same tank capacity or to reduce the tank capacity while maintaining the same denitrification treatment amount.

[0022] In the treatment device (100), the wastewater introduced from the inlet (201) flows from the upstream side to the downstream side along the flow path (203) of the tank (200), and the discharge flow is based on the discharge flow that becomes treated water and is discharged from the outlet (202). However, near the denitrification area (207), a mixed flow is also generated in which the wastewater with a high dissolved oxygen concentration in the front aerobic area (206) or the rear aerobic area (208) and the wastewater with a low dissolved oxygen concentration in the denitrification area (207) are mixed with each other by the swirling flow described above, to the extent necessary for the formation of the combined area (209).

[0023] In addition, since there is a pair of swirling flows, the mixed flow is not spread, and the combined area (209) is maintained stably.

[0024] In addition, activated sludge containing microorganisms such as BOD-oxidizing bacteria, nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, etc.), and denitrifying bacteria is formed in conjunction with wastewater treatment, and these activated sludges flow together with the flow of wastewater while suspended in the wastewater, and depending on environmental conditions such as the oxygen concentration in each area, the activity of nitrifying bacteria or the activity of denitrifying bacteria is increased, thereby nitrifying and denitrifying occur.

[0025] The treated water discharged from the outlet (202) of the tank (200) is stored in the final sedimentation pond, where the sludge is separated. A portion of the separated sludge is returned to the inlet (201) as return sludge, and the excess sludge is discharged as excess sludge.

[0026] As illustrated in FIG. 1, a control system (400) is provided to control an aeration device (300) to adjust the amount of aeration from an aeration unit (306) placed in an anaerobic area (205), a general aerobic area (206), a general combined area (209f) (omitted in FIG. 1), a denitrification area (207), a secondary combined area (209b) (omitted in FIG. 1), and a secondary aerobic area (208). The control system (400) is provided with a control device body (401), a terminal computer (402) connected to the control device body (401) via wired or wireless connection, and a first detection device (403) and a second detection device (404) placed in a tank (200).

[0027] The first detection device (403) is positioned downstream of the general aerobic zone (206), preferably at a location closer to the denitrification zone (207) than the middle of the flow path of the general aerobic zone (206), and more preferably at the upstream of the combined zone (209) formed downstream of the general aerobic zone (206). The first detection device (403) is a device for detecting the concentration of nitrate nitrogen consisting of NOx, such as NO2 and NO3, in the wastewater. In addition, the detection value may be the concentration of NOx itself or the concentration of nitrogen derived from NOx.

[0028] Additionally, the second detection device (404) is positioned downstream of the second aeration area (208), preferably at a location closer to the outlet (202) than the middle of the flow path of the second aeration area (208), and more preferably at a location near the downstream end of the second aeration area (208) (a location returned upstream from the downstream end as much as is necessary to maintain the precision of the sensor). The second detection device (404) is a device for detecting the concentration of ammoniacal nitrogen, such as NH4OH, in the wastewater. Furthermore, the detection value may be the concentration of NH4OH itself or the concentration of nitrogen derived from NH4OH.

[0029] The main body of the control device (401) is electrically connected to each of the first blower (301), the second blower (302), the pressure detection device (308), the first electric valve (304), the second electric valve (305), the first detection device (403), and the second detection device (404). The main body of the control device (401) includes, for example, an electronic circuit. Examples of such electronic circuits include, for example, a computer (PC) configured with a CPU (Central Processing Unit), a memory medium such as ROM (Read only memory) or RAM (Random access memory), and a recording medium such as a hard disk, or a field-programmable gate array (FPGA) or an application specific integrated circuit (ASIC).

[0030] In the main body of the control device (401), a predetermined program capable of executing the drainage processing method or control method described later is stored in a recording medium. Although details will be described later, the main body of the control device (401) outputs a control signal according to the stored program based on measurement value data input from the pressure detection device (308), the first detection device (403), and the second detection device (404). Accordingly, the main body of the control device (401) controls the first blower (301), the second blower (302), the first electric valve (304), the second electric valve (305), etc., to control the amount of aeration from the aeration unit (306) placed in each area.

[0031] A terminal computer (402) is connected to the main body of the control device (401) via a wired or wireless connection and is used to operate the control system (400) from a remote location or to determine the operating status of the processing device (100) by means of electronic data transmitted from the control system (400).

[0032] As described above, a combined area (209) in which both nitrification and denitrification proceed is formed on the outer side of the denitrification area (207) adjacent to the front aerobic area (206) and on the outer side of the denitrification area (207) adjacent to the rear aerobic area (208). However, the location of this combined area (209) can be set or changed to a desired location by selecting the aeration section (306) where aeration takes place by opening and closing the manual valve (307). Depending on the location of the combined area (209), the length or capacity according to the direction of the flow path (203) of each area of ​​the front aerobic area (206), the denitrification area (207), and the rear aerobic area (208) is set.

[0033] Next, with reference to FIGS. 3 and FIGS. 4, the details of the control performed in the control system (400) (control device body (401)) of the processing device (100) will be explained.

[0034] As illustrated in FIG. 3, the main body of the control device (401) is equipped with an air volume calculation unit (401a) and a machine learning DB (database) (401b). Although details will be described later, the air volume calculation unit (401a) receives information such as the nitrate nitrogen concentration (A) detected by the first detection device (403), the ammonia nitrogen concentration (B) detected by the second detection device (404), and the amount of water flowing into the tank (200).

[0035] Then, the air volume calculation unit (401a) calculates the aeration amount (C) and the aeration amount (D) from these input information. When calculating the aeration amount (C, D), information obtained by machine learning past data stored in the machine learning DB (401b) may be referenced. Although the values ​​of the aeration amount (C, D) fluctuate due to factors such as water temperature, the TN (total nitrogen) load of wastewater, or HRT (hydraulic retention time), the optimal parameters for calculating the aeration amount (C, D) can be automatically determined by referring to the relevant information. Accordingly, the treatment device (100) can achieve water quality stabilization while reducing the burden of tuning the aeration amount.

[0036] The air aeration amount (C, D) calculated by the air aeration calculation unit (401a) is transmitted to the first blower (301) and the second blower (302). The first blower (301) and the second blower (302) each have an air aeration control unit (301a, 302a). The air aeration control unit (301a, 302a) controls the output of the first blower (301) and the second blower (302) respectively so that the air aeration amount (C, D) is obtained.

[0037] Additionally, the control device body (401) controls the opening of the first electric valve (304) and the second electric valve (305) to adjust the amount of air (C, D) to be obtained. Therefore, the air volume calculation unit (401a) transmits valve opening / closing information to the first electric valve (304) and the second electric valve (305).

[0038] Next, with reference to FIG. 4, a flowchart of the operation processing by the control device body (401) of the control system (400) will be explained.

[0039] First, the nitrate nitrogen concentration (A) in the latter part of the overall aerobic zone (206) is measured by the first detection device (403) (STEP 10). Then, the target nitrate nitrogen concentration (A1) required to achieve the target demass (concentration) and the aeration amount (C) are calculated from the nitrate nitrogen concentration (A) in the latter part of the overall aerobic zone (206) (STEP 20).

[0040] Specifically, by comparing the concentration (A) with the target nitrate nitrogen concentration (A1), the amount of aeration (C) in the general aerobic zone (206) and the general combined zone (209f) is calculated, for example, by the following (Equation 1), so that the nitrate nitrogen concentration (A) when passing through the general aerobic zone (206) reaches the target nitrate nitrogen concentration (A1).

[0041] C=P×(A1-A)… (Equation 1)

[0042] However, P is a coefficient obtained from the relationship between the amount of aeration and the nitrification rate in the overall aerobic zone (206), and can be determined experimentally in advance.

[0043] In addition, P can be calculated using multiple parameters (p1, p2, p3…) obtained by treatment conditions such as water temperature, TN (total nitrogen) load of wastewater, or HRT (hydraulic retention time). These parameters (p1, p2, p3…) can be determined using the machine learning DB (401b) described above to determine optimal values.

[0044] Next, the output of the first blower (301) and the second blower (302) and the opening degree of the first electric valve (304) are controlled so that the amount of aeration in the general aeration area (206) and the general combined area (209f) becomes the amount of aeration (C) (STEP30).

[0045] Next, the ammonia nitrogen concentration (B) in the latter part of the latter aerobic region (208) is measured by the second detection device (404) (STEP 40). Then, the amount of ammonia (D) is calculated from the ammonia nitrogen concentration (B) in the latter part of the latter aerobic region (208) and the target ammonia nitrogen concentration (B1) that is allowed to remain in the treatment liquid flowing out through the latter aerobic region (208) (STEP 50).

[0046] Specifically, by comparing the concentration (B) with the target ammonia nitrogen concentration (B1), the amount of aeration (D) in the latter ammonia zone (208) and the latter combined zone (209b) is calculated, for example, by the following (Equation 2), so that the ammonia nitrogen concentration in the treated water passing through the latter aerobic zone (208) becomes less than or equal to the target ammonia nitrogen concentration (B1).

[0047] D=Q×(B-B1)… (Equation 2)

[0048] However, Q is a coefficient obtained from the relationship between the amount of aeration and the nitrification rate in the later aerobic region (208), and can be determined experimentally in advance.

[0049] In addition, Q can be calculated using multiple parameters (q1, q2, q3…) obtained by treatment conditions such as water temperature, TN (total nitrogen) load of wastewater, or HRT (hydraulic retention time). For these parameters (q1, q2, q3…), the optimal value considering external factors can be determined using the machine learning DB (401b) described above.

[0050] Next, the output of the first blower (301) and the second blower (302) and the opening degree of the second electric valve (305) are controlled so that the amount of aeration in the second aeration area (208) and the second combined area (209b) becomes the amount of aeration (D) (STEP 60). Thus, a series of operation processes by the control device main body (401) are terminated, and by repeating each of the above processes, the control device main body (401) can perform the intended aeration in each area of ​​the tank (200).

[0051] Next, a nitrification denitrification method using the treatment apparatus (100) of the present disclosure is described.

[0052] Wastewater and other wastewater are introduced into the anaerobic zone (205) via a primary sedimentation pond not shown. Additionally, return sludge from a sludge recovery unit not shown is also introduced. Since the anaerobic zone (205) is maintained in an anaerobic state, phosphorus contained in the return sludge is released under anaerobic conditions. This phosphorus enters the microorganisms in the subsequent primary aerobic zone (206), denitrification zone (207), and secondary aerobic zone (208), and is removed from the wastewater as sludge.

[0053] Wastewater treated for a predetermined time in the anaerobic zone (205) flows through an empty notch-shaped opening below the partition wall (204) and enters the general aerobic zone (206). In the general aerobic zone (206), the amount of aeration is controlled to be the amount calculated by the above (Equation 1), so nitrifying bacteria become active, nitrify the ammoniacal nitrogen contained in the wastewater to produce nitrate nitrogen, and increase the nitrate nitrogen concentration. That is, the nitrate nitrogen concentration (NOx-N) increases while moving from the general aerobic zone (206) to the denitrification zone (207) (denitrification zone, inlet).

[0054] At this time, since the amount of aeration in the general aerobic zone (206) and the general combined zone (209f) is controlled by the above (Equation 1), the nitrate nitrogen concentration (NOx-N) in the denitrification zone (207) (inlet) becomes a concentration that reaches the target nitrate nitrogen concentration (A1). However, in order to maintain an anaerobic state in the subsequent denitrification zone (207), the amount of aeration in the general aerobic zone (206) and the general combined zone (209f) is controlled so that it is sufficient to reach the target nitrate nitrogen concentration (A1) but not excessive.

[0055] The wastewater passing through the general aerobic zone (206) is introduced into the denitrification zone (207) via the general combined zone (209f). The denitrification zone (207) is maintained in an anaerobic or oxygen-reduced state by controlling the amount of aeration from the aeration unit (306) by the main body of the control device (401), thereby allowing denitrification by denitrifying bacteria to occur. At this time, nitrate nitrogen at a concentration reaching the target nitrate nitrogen concentration (A1) formed in the general aerobic zone (206) is denitrified, thereby removing nitrogen equivalent to the target amount of denitrification from the wastewater.

[0056] Next, the wastewater that has passed through the denitrification zone (207) passes through the second-half combined zone (209b) and is introduced into the second-half aerobic zone (208). Since the amount of aeration from the aeration unit (306) in the second-half aerobic zone (208) is controlled by the main body of the control device (401) and is restored to an aerobic state, the ammoniacal nitrogen remaining in the wastewater is nitrified and becomes nitrate nitrogen. Since the amount of aeration in the second-half aerobic zone (208) and the second-half combined zone (209b) is controlled to be the amount of aeration obtained by the above (Equation 2), the concentration of ammoniacal nitrogen in the wastewater that has passed through the denitrification zone (207) becomes less than or equal to the target ammoniacal nitrogen concentration (B1) that is allowed to remain in the treated water.

[0057] In this way, the treated water that passes through the latter aerobic zone (208) has not only a reduced concentration of ammoniacal nitrogen but also a reduced overall nitrogen concentration, resulting in highly harmless treated water. This treated water is discharged into a river or the like after undergoing conventional treatment such as chlorine disinfection.

[0058] As described above, according to the treatment device (100), the target nitrate nitrogen concentration (A1) required to achieve the target denitrification amount (concentration) is compared with the nitrate nitrogen concentration (A) in the latter part of the general aerobic area (206), and the amount of aeration (C) in the general aerobic area (206) and the general combined area (209f) is controlled so that the nitrate nitrogen concentration when passing through the general aerobic area (206) reaches the target nitrate nitrogen concentration (A1). Therefore, nitrate nitrogen can be formed in the general aerobic area (206) so that the denitrification amount required to reduce the nitrogen concentration contained in the wastewater to below a predetermined value can be secured while maintaining an oxygen-free state or an oxygen-reduced state in the denitrification area (207). As a result, the target denitrification amount can be achieved by reducing the nitrogen concentration contained in the wastewater to below a predetermined value in the denitrification area (207).

[0059] In addition, by comparing the ammonia nitrogen concentration (B) in the latter part of the latter aerobic region (208) with the target ammonia nitrogen concentration (B1) that is allowed to remain in the treatment liquid, and controlling the amount of aeration (D) in the latter aerobic region (208) and the latter combined region (209b) so that the ammonia nitrogen concentration in the treated water passing through the latter aerobic region (208) becomes less than or equal to the target ammonia nitrogen concentration (B1), the ammonia nitrogen concentration remaining in the treated water can be reduced to less than or equal to the target ammonia nitrogen concentration (B1).

[0060] However, in the nitrification and denitrification method of the present disclosure, as shown by the arrow in FIG. 2, an upward flow is generated by aeration in the front aerobic area (206) and the rear aerobic area (208), causing the water level to rise, and thus a pair of swirling flows are generated, and a combined area (209) in which both nitrification and denitrification proceed is formed on the outer side of the denitrification area (207) adjacent to the front aerobic area (206) and on the outer side of the denitrification area (207) adjacent to the rear aerobic area (208).

[0061] Accordingly, in the nitrification denitrification method of the present disclosure, it is possible to maintain an oxygen-free or low-oxygen state in the denitrification zone (207) without providing a partition plate, thereby enabling the denitrification reaction to proceed. In addition, denitrification treatment can be performed in a combined zone (209) other than the denitrification zone (207), and nitrification treatment can also be performed in the combined zone (209). Therefore, the denitrification zone can be expanded without reducing the aerobic zone, and the target amount of denitrification treatment can be increased with the same tank capacity. In addition, equipment costs can be reduced without the need to provide a partition wall in the tank (200).

[0062] In addition, in the treatment device (100), when the amount of wastewater or the concentration of organic matter fluctuates due to climate or season, the position of the combined area (209) can be changed by changing the open / closed state of the manual valve (307a) at the boundary of each area, and the capacity or length of the front aerobic area (206), denitrification area (207), and rear aerobic area (208) can be changed. In addition, the device is configured so that the position of the first detection device (403) can be moved in conjunction with the change in the position of the combined area (209).

[0063] Accordingly, when, for example, the volume of wastewater or the load of organic matter in the wastewater increases, the manual valve (307a) is switched so that the capacity or length of the front aerobic zone (206) or the rear aerobic zone (208) increases, thereby maintaining the ammoniacal nitrogen concentration remaining in the treated water at or below the target ammoniacal nitrogen concentration (B1).

[0064] In addition, the position of the combined area (209) can be changed by operating the manual valve (307a) to achieve a more balanced area distribution by comparing the difference (A1-A) between the target nitrate nitrogen concentration (A1) required to realize the target demass (concentration) in the above (Equation 1) and the nitrate nitrogen concentration (A) in the latter part of the front aerobic area (206), the ammonia nitrogen concentration (B) in the latter part of the rear aerobic area (208) in the above (Equation 2), and the difference (B-B1) between the target ammonia nitrogen concentration (B1) allowed to remain in the treatment liquid discharged through the rear aerobic area (208).

[0065] In this case, in the above embodiment, the valves controlling each individual diffuser (306) are all manual valves (307), but the manual valve (307a) located adjacent to each area may be changed to an electric valve to change its opening degree, thereby allowing the capacity or length of each area to be changed.

[0066] In addition, the amount of aeration from the aeration unit (306) in the denitrification zone (207) may be zero, but a small amount of aeration may be performed to the extent that the sludge in the wastewater continues to float and prevents settling. By doing so, there is no need to provide stirring blades, etc. in the denitrification zone (207), and thus equipment costs can be further reduced.

[0067] As described above, the control device (401) controls the amount of aeration from a plurality of aeration sections (306) of the aeration device (300), and forms a front aeration area (206), a front combined area (209f) where both nitrification and denitrification proceed, a denitrification area (207), a rear combined area (209b) where both nitrification and denitrification proceed, and a rear aeration area (208) in order from the upstream side along the flow path (203), and further, performs a process (step) of generating a pair of first and second swirling flows in the flow path (203).

[0068] The control device (401) controls the amount of aeration in the overall aerobic zone (206) and the overall combined zone (209f) based on the nitrate nitrogen concentration detected by the first detection device (403) in this process, and controls the amount of aeration in the latter combined zone (209b) and the latter aerobic zone (208) based on the ammonia nitrogen concentration detected by the second detection device (404). Additionally, the first swirling flow is a swirling flow that rises in the overall combined zone (209f) (see arrow (U1)), moves downstream from the water surface side of the denitrification zone (207) (see arrow (R1)), descends near the center of the denitrification zone (207) (see arrow (D)), and moves upstream from the bottom side of the denitrification zone (207) (see arrow (L2)). Additionally, the second swirling flow rises in the rear combined area (209b) (see arrow (U2)), moves upstream from the water surface side of the denitrification area (207) (see arrow (L1)), descends near the center of the denitrification area (207) (see arrow (D)), and moves downstream from the bottom side of the denitrification area (207) (see arrow (R2)).

[0069] According to the treatment device (100), the combined area (209) becomes a buffer area, and the oxygen-rich forward flow from the front aerobic area (206) and the oxygen-rich backward flow from the rear aerobic area (208) are difficult to influence, thereby maintaining a low-oxygen state in the denitrification area (207), so that a sufficient amount of denitrification treatment is obtained even without a partition plate. In addition, since the partition plate is unnecessary, it is possible to avoid high-cost equipment investment.

[0070] In addition, denitrification treatment can be performed in the combined area (209) other than the denitrification area (207), and since nitrification treatment is also performed in the combined area (209), the denitrification area (207) can be expanded without reducing the aerobic area, and it is possible to meet the desire to increase the denitrification treatment amount with the same tank capacity or the desire to reduce the tank capacity while maintaining the same denitrification treatment amount.

[0071] Furthermore, by controlling the amount of aeration in the area according to the overall aerobic area (206) based on the nitrate nitrogen concentration measured by the first detection device (403) placed downstream of the overall aerobic area (206), the nitrate nitrogen concentration in the wastewater flowing into the denitrification area (207) is adjusted so that a sufficient amount of denitrification is obtained in the denitrification area (207), and by controlling the amount of aeration in the area according to the latter aerobic area (208) based on the ammonia nitrogen concentration measured by the second detection device (404) placed downstream of the latter aerobic area (208), sufficient nitrification is performed in the latter aerobic area (208), so that the concentration of the remaining ammonia nitrogen is treated to fall within an allowable range.

[0072] Additionally, the aeration device (300) has a plurality of aeration sections (306) that can be opened and closed according to the flow path (203), and is configured so that the position of either the front combined area (209f) or the rear combined area (209b) can be changed by selecting the aeration section (306) where aeration takes place, and is also configured so that the position of either the first detection device or the second detection device can be moved according to the change in position. Here, as "a plurality of aeration sections that can be opened and closed," for example, a plurality of aeration sections that can switch between restricted aeration and aeration by means of an electric valve are envisioned.

[0073] According to this configuration, the aeration device (300) can change the position of the combined area (209) by selecting the aeration section (306) where aeration takes place. Therefore, depending on the treatment conditions of the applied facility or the fluctuation in the load of drainage due to changes in climate or seasons, the position of the combined area (209) can be changed by selecting the aeration section (306) where aeration takes place, and the length of each area can be adjusted to an appropriate length. In addition, since the device is configured to move the position of the first detection device (403) according to the change in the position of the combined area (209), the position of the first detection device (403) can always be placed on the downstream side of the general aeration area (206) even if the length of the general aeration area (206) changes.

[0074] The control device (401) is configured to control the amount of aeration in the overall aerobic area (206) and the overall combined area (209f) based on the difference between the target nitrate nitrogen concentration in the overall aerobic area (206), which is set to form a predetermined anoxic state or an oxygen reduction state in the denitrification area (207), and the nitrate nitrogen concentration detected by the first detection device (403), and simultaneously control the amount of aeration in the latter combined area (209b) and the latter aerobic area (208) based on the difference between the ammonia nitrogen concentration detected by the second detection device (404) and the target ammonia nitrogen concentration that is allowed to remain in the treated water.

[0075] According to the above embodiment, by controlling the amount of aeration in the area according to the overall aerobic zone (206) to approach the target nitrate nitrogen concentration (A1) based on the difference between the target nitrate nitrogen concentration (A1) in the overall aerobic zone (206) and the nitrate nitrogen concentration (A) detected by the first detection device (403), the nitrate nitrogen concentration in the wastewater flowing into the denitrification zone (207) is sufficiently secured, thereby securing the required amount of denitrification. In addition, by controlling the amount of aeration in the area according to the latter aerobic zone (208) based on the difference between the ammonia nitrogen concentration (B) detected by the second detection device (404) and the target ammonia nitrogen concentration (B1) that is allowed to remain in the treated water, the ammonia nitrogen can be reduced to be below the target ammonia nitrogen concentration allowed to remain in the treated water.

[0076] Examples

[0077] <Test Example 1>

[0078] Using the treatment device (100) illustrated in FIGS. 1 and 2, wastewater was treated while controlling the amount of aeration of the aeration device (300) by the control system (400). The results are described below.

[0079] (1) The water quality and treatment volume of the sewage after the first sedimentation pond runoff are as follows.

[0080] ·TN (Total Nitrogen) 30 mgN / L

[0081] ·NH4-N (Ammonia nitrogen concentration) 23 mgN / L

[0082] · Quantity 26,740 m³ / day / total

[0083] · TN load 802.2 kgN / day / total

[0084] ·HRT 10.3hr

[0085] (2) The water quality and treatment volume of the returned sludge are as follows.

[0086] · NOx-N (Nitrate Nitrogen Concentration) 10.3 mgN / L

[0087] · Return rate 50%

[0088] · Sludge volume 13,370 m³ / day / total

[0089] · NOx-N load 138.16 kgN / day / total

[0090] (3) Water quality at the end of the overall aerobic zone

[0091] ·NH4-N 10.3mgN / L

[0092] ·NOx-N 5mgN / L

[0093] · Water + Sludge Amount 40,110 m³ / day / total

[0094] · NOx-N load 200.6 kgN / day / total

[0095] (4) Water quality at the end of the denitrification zone

[0096] ·NH4-N 10.3mgN / L

[0097] ·NOx-N 0mgN / L

[0098] · Water + Sludge Amount 40,110 m³ / day / total

[0099] · NOx-N load 0 kgN / day / total

[0100] (5) Water quality at the end of the aerobic zone in the latter half

[0101] ·NH4-N 0.0mgN / L

[0102] ·NOx-N 10.3mgN / L

[0103] · Water + Sludge Amount 40,110 m³ / day / total

[0104] · NOx-N load 414.5 kgN / day / total

[0105] (6) Water quality at the last leaching outlet

[0106] ·TN (Total Nitrogen) 12 mgN / L

[0107] ·NOx-N 10.3mg / L

[0108] · Quantity 26,740 m³ / day / total

[0109] ·TN load 320.9 kgN / day / total

[0110] · TN removal rate 60%

[0111] (7) Excess sludge

[0112] ·N content 10%

[0113] · MLSS (Activated Sludge Suspended Solids) 4000 mg / L

[0114] · Sludge volume 376 m³ / day / total

[0115] · Load 150.4 kgN / day / total

[0116] As shown in the results above, the treated water was able to achieve a TN (total nitrogen) removal rate of 60% and an ammonia level of 0.0 mg N / L.

[0117] <Test Example 2>

[0118] Using the treatment device (100) illustrated in FIGS. 1 and 2, sewage was continuously treated while controlling the amount of aeration of the aeration device (300) by the control system (400). Then, the concentrations of BOD (Biochemical Oxygen Demand), TN (Total Nitrogen), and TP (Total Phosphorus) at the first and last leachate outlets were measured periodically, and the changes were investigated.

[0119] In addition, BOD concentration was measured by the method of Section 21, Chapter 1, Part 2 of the Sewage Test Methods -2012 Edition-. TN concentration was measured by the method of JIS K 0170-3 based on flow analysis in Section 13, Chapter 5, Part 1 of the Sewage Test Methods -2012 Edition-. TP concentration was measured by the method of JIS K 0170-4 based on flow analysis in Section 13, Chapter 5, Part 1 of the Sewage Test Methods -2012 Edition-.

[0120] Thus, the measurement results of BOD concentration measured by continuously conducting test operations for more than one year are shown in FIG. 5, the measurement results of TN concentration are shown in FIG. 6, and the measurement results of TP concentration are shown in FIG. 7. The dashed lines in each figure represent the respective target reduction values.

[0121] As shown in FIGS. 5, 6, and 7, according to the nitrification denitrification method using the treatment device (100) of the present invention, BOD, TN, and TP could be stably reduced over a period of more than one year. Explanation of the symbols

[0122] 100 : Processing unit 200 : Unit 201: Inlet 202: Outlet 203 : Euro 204 : Partition wall 205: Anaerobic zone 206: General aerobic zone 207: Denitrification zone 208: Later aerobic zone 209 : Combined area 209f : General combined area 209b : Rear combined area 300 : Aeration device 301: 1st blower 301a: Air volume control unit 302: Second blower 302a: Air volume control unit 303: Piping 304: First electric valve 304a: Valve opening / closing control unit 305: Second electric valve 305a: Valve opening / closing control unit 306: Diffusion unit 307: Manual valve 307a: Manual valve 308 : Pressure detection device 400 : Control system 401: Control unit main body 401a: Air volume calculation unit 401b: Machine learning DB 402: Terminal computer 403: First detection device 404: Second detection device

Claims

Claim 1 A tank having an inlet for wastewater, a channel for wastewater treatment, and an outlet for treated water; an aeration device having a plurality of aeration units arranged at the bottom of the channel along the channel of the tank; a first detection device for detecting the nitrate nitrogen concentration of the wastewater; a second detection device provided downstream of the first detection device for detecting the ammonia nitrogen concentration of the wastewater; and a control device that controls the amount of aeration from the plurality of aeration units of the aeration device to form, in order from the upstream side along the channel, a general aerobic zone, a general combined zone where both nitrification and denitrification proceed, a denitrification zone, a secondary combined zone where both nitrification and denitrification proceed, and a secondary aerobic zone, and further, a control device that generates a pair of first and second swirling flows in the channel, wherein the control device controls the amount of aeration in the general aerobic zone and the general combined zone based on the nitrate nitrogen concentration detected by the first detection device, and in the secondary combined zone and the secondary aerobic zone based on the ammonia nitrogen concentration detected by the second detection device A drainage treatment device that controls the amount of aeration, wherein the first swirling flow rises in the overall combined area, descends near the center of the denitrification area toward downstream from the water surface side of the denitrification area, and is a swirling flow that heads upstream from the bottom side of the denitrification area, and the second swirling flow rises in the latter combined area, descends near the center of the denitrification area toward upstream from the water surface side of the denitrification area, and is a swirling flow that heads downstream from the bottom side of the denitrification area. Claim 2 In claim 1, the aeration device is configured such that it has a plurality of aeration sections that can be opened and closed according to the flow path, and by selecting an aeration section where aeration is performed, the position of either the front combined area or the rear combined area can be changed, and furthermore, the position of the first detection device and the second detection device can be moved according to the change in position. Claim 3 A wastewater treatment device configured such that, in claim 1 or 2, the control device can secure a denitrification amount necessary to reduce the nitrogen concentration contained in the wastewater in the denitrification area to a value or less, and also controls the aeration amount of the overall aerobic area and the overall combined area based on the difference between the target nitrate nitrogen concentration in the overall aerobic area, which is set to form a predetermined low-oxygen state in the denitrification area, and the nitrate nitrogen concentration detected by the first detection device, and simultaneously controls the aeration amount of the latter combined area and the latter aerobic area based on the difference between the ammonia nitrogen concentration detected by the second detection device and the target ammonia nitrogen concentration that is allowed to remain in the treated water. Claim 4 A wastewater treatment method performed in a wastewater treatment device comprising: a tank having a wastewater inlet, a flow path where wastewater treatment is performed, and a treated water outlet; an aeration device having a plurality of aeration sections arranged at the bottom of the flow path along the flow path of the tank; a first detection device for detecting the nitrate nitrogen concentration of the wastewater; and a second detection device provided downstream of the first detection device for detecting the ammonia nitrogen concentration of the wastewater; wherein the amount of aeration from the plurality of aeration sections of the aeration device is controlled to form, in order from the upstream side along the flow path, a general aerobic zone, a general combined zone where both nitrification and denitrification proceed, a denitrification zone, a secondary combined zone where both nitrification and denitrification proceed, and a secondary aerobic zone; furthermore, a process of generating a pair of first and second swirling flows in the flow path; and in the process of generating the first and second swirling flows, the amount of aeration in the general aerobic zone and the general combined zone is controlled based on the nitrate nitrogen concentration detected by the first detection device, and the amount of aeration detected by the second detection device A wastewater treatment method having a process for controlling the amount of aeration in the second-half combined area and the second-half aerobic area based on the ammonia nitrogen concentration, wherein the first swirling flow rises in the first-half combined area, descends near the center of the denitrification area towards the downstream side of the denitrification area, and is a swirling flow that moves upstream from the bottom side of the denitrification area, and the second swirling flow rises in the second-half combined area, descends near the center of the denitrification area towards the upstream side of the denitrification area, and is a swirling flow that moves downstream from the bottom side of the denitrification area. Claim 5 A drainage treatment method according to claim 4, wherein in the process of generating the first and second swirling flows, the aeration device has a plurality of aeration sections that can be opened and closed according to the flow path, and by selecting an aeration section where aeration is performed according to the load of the drainage, the position of at least one of the first combined area and the second combined area is changed, and at the same time, the position of at least one of the first detection device and the second detection device is moved according to the change in position.

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