Wastewater treatment device and wastewater treatment method

Abstract

The present invention makes it possible to treat wastewater by performing denitrification and nitrification with comparatively simple equipment. This wastewater treatment device controls an air diffusion amount in a flow path for wastewater treatment, forms, in order from upstream, a first-half aerobic region, a first-half shared region where nitrification and denitrification progress, a denitrification region, a second-half shared region where nitrification and denitrification progress, and a second-half aerobic region, and generates a pair of first and second swirl flows. Furthermore, the wastewater treatment device controls the air diffusion amount in the first-half aerobic region and the first-half shared region on the basis of a nitrate nitrogen concentration, and controls the air diffusion amount in the second-half shared region and the second-half aerobic region on the basis of an ammoniacal nitrogen concentration. The first swirl flow rises in the first-half shared region, heads downstream on the water surface-side of the denitrification region, falls near the center of the denitrification region, and heads upstream on the bottom side of the denitrification region. The second swirl flow rises in the second-half shared region, heads upstream on the water surface-side of the denitrification region, falls near the center of the denitrification region, and heads downstream on the bottom side of the denitrification region.

Description

[Technical 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, ammonia nitrogen contained in the wastewater is converted to nitrate nitrogen by the action of nitrifying bacteria in an aerobic zone where aeration treatment is performed, and this nitrate nitrogen is then discharged as nitrogen gas by the action of denitrifying bacteria in a denitrification zone where aeration treatment is not performed (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2008-221162 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the technique of Patent Document 1 requires a partition plate and stirring blades, which increases the equipment costs. [Means for solving the problem]

[0005] The wastewater treatment device of the present disclosure comprises: a tank having an inlet for wastewater, a flow path through which wastewater treatment is performed, and an outlet for treated water; an aeration device having multiple aeration units arranged at the bottom of the flow path of the tank along the flow path; a first detection device that detects the nitrate nitrogen concentration of the wastewater; a second detection device that is arranged downstream of the first detection device and detects the ammonia nitrogen concentration of the wastewater; and a control device that controls the amount of air diffused from the multiple aeration units of the aeration device, and forms, in order from upstream along the flow path, a first aerobic region, a first dual-purpose region in which both nitrification and denitrification proceed, a denitrification region, a second dual-purpose region in which both nitrification and denitrification proceed, and a second aerobic region, and further generates a pair of first and second swirling flows in the flow path. The control device controls the amount of air diffused in the first aerobic region and the first dual-use region based on the nitrate nitrogen concentration detected by the first detection device, and controls the amount of air diffused in the second dual-use region and the second aerobic region based on the ammonia nitrogen concentration detected by the second detection device, the first swirling flow is a swirling flow that rises in the first dual-use region, heads downstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and heads upstream on the bottom side of the denitrification region, and the second swirling flow is a swirling flow that rises in the second dual-use region, heads upstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and heads downstream on the bottom side of the denitrification region. The wastewater treatment method of the present disclosure is a wastewater treatment method carried out in a wastewater treatment device including: a tank having a wastewater inlet, a flow path through which wastewater treatment is performed, and a treated water outlet; an aeration device having a plurality of aeration units arranged at the bottom of the flow path of the tank along the flow path; a first detection device that detects the nitrate nitrogen concentration of the wastewater; and a second detection device that is provided downstream of the first detection device and detects the ammonia nitrogen concentration of the wastewater. The method controls the amount of air diffused from the plurality of aeration units of the aeration device to form, in order from upstream along the flow path, a first aerobic region, a first dual-purpose region where both nitrification and denitrification proceed, a denitrification region, a second dual-purpose region where both nitrification and denitrification proceed, and a second aerobic region, and further generates a pair of first and second swirling flows in the flow path. and in the step of generating the first and second swirling flows, controlling the amount of air diffused in the first aerobic region and the first dual-use region based on the nitrate nitrogen concentration detected by the first detection device, and controlling the amount of air diffused in the second dual-use region and the second aerobic region based on the ammonia nitrogen concentration detected by the second detection device, wherein the first swirling flow is a swirling flow that rises in the first dual-use region, heads downstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and heads upstream on the bottom side of the denitrification region, and the second swirling flow is a swirling flow that rises in the second dual-use region, heads upstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and heads downstream on the bottom side of the denitrification region. [Brief explanation of the drawings]

[0006] [Figure 1] 1 is an explanatory diagram illustrating an embodiment of a processing apparatus according to the present disclosure. [Figure 2] FIG. 2 is an explanatory diagram showing the configuration of an air diffuser of the treatment device of the present disclosure. [Figure 3] FIG. 2 is an explanatory diagram illustrating details of control performed by the control device main body. [Figure 4] FIG. 4 is a flowchart showing an operation process performed by the control device main body. [Figure 5] 1 is a graph showing the change in BOD concentration at the initial settling outlet and the final settling outlet when wastewater treatment is performed using the treatment device of the present disclosure. [Figure 6] 1 is a graph showing the change in TN concentration at the initial settling outlet and the final settling outlet when wastewater treatment is performed using the treatment device of the present disclosure. [Figure 7] 1 is a graph showing the change in TP concentration at the initial settling outlet and the final settling outlet when wastewater treatment is performed using the treatment device of the present disclosure. DETAILED DESCRIPTION OF THE INVENTION

[0007] Hereinafter, embodiments of the present disclosure will be described with reference to the drawings. However, such descriptions should not be interpreted in a limiting sense, and do not limit the subject matter described in the claims. Furthermore, various changes, substitutions, and modifications can be made without departing from the spirit and scope of the present disclosure. Furthermore, different embodiments can be combined as appropriate.

[0008] In the present disclosure, examples of wastewater include sewage and industrial wastewater, but the wastewater treatment device of the present disclosure (hereinafter referred to as the treatment device as appropriate) is particularly suitable for treating sewage.

[0009] Wastewater such as sewage is introduced into a primary sedimentation tank (not shown), where primary sludge is separated by settling, and the resulting 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 human waste, etc. The treatment device of the present disclosure reduces the nitrogen concentration in the wastewater and performs nitrification / denitrification treatment on the wastewater so that the ammoniacal nitrogen concentration is reduced to an acceptable concentration or below so that the wastewater can be discharged.

[0010] One embodiment of the treatment device of the present disclosure is shown in Figures 1 and 2. Treatment device 100 for treating wastewater in Figure 1 includes a treatment tank (hereinafter referred to as tank) 200 for treating wastewater, an aeration device 300 for supplying oxygen-containing gas (hereinafter referred to as air) into 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 device is an apparatus that simultaneously performs the above-mentioned nitrification and denitrification in a single tank (i.e., a single tank), and is also called a single-tank nitrification / denitrification apparatus.

[0011] The tank 200 has a gravity flow tank structure, has an inlet 201 for wastewater at one end, an outlet 202 for treated water at the other end, and has a wastewater flow path 203 extending from the inlet 201 to the outlet 202.

[0012] In this embodiment, a partition wall 204 is disposed midway along the flow path 203 near the inlet 201, and wastewater flowing in from the inlet 201 flows into an anaerobic zone 205 separated by the partition wall 204. The anaerobic zone 205 mixes wastewater introduced through a primary sedimentation tank (not shown) with returned sludge and, under anaerobic conditions, releases phosphorus contained in the organic matter in the wastewater and the returned sludge. This phosphorus is then absorbed into the activated sludge in the subsequent aerobic zone, thereby reducing the phosphorus content in the wastewater. However, in the present invention, the partition wall 204 and the anaerobic zone 205 are not essential, and the tank 200 may be one without the partition wall 204 and the anaerobic zone 205. Furthermore, in the present disclosure, a "single tank" means that the portion excluding the anaerobic zone 205 forms a single tank without a partition wall.

[0013] The air diffusion device 300 includes a plurality of air diffusion units 306. The plurality of air diffusion units 306 are arranged at the bottom (lower part) of the flow path 203 of the tank 200 along the flow path 203. In this embodiment, the device includes a first blower 301, a second blower 302, and piping 303 connected thereto. The piping 303 is connected to the tank 200 via a first electric valve 304 and a second electric valve 305. The plurality of air diffusion units 306 are installed at the bottom of the tank 200 along the flow path 203. A pressure detection device 308 is attached to the flow path of the piping 303 leading to the first electric valve 304. In this embodiment, two blowers, the first blower 301 and the second blower 302, are provided, but the number of blowers may be one or three or more.

[0014] 2, the piping 303 that passes through the first electric valve 304 and the second electric valve 305 branches into multiple branches, which are connected to each of the air diffusion units 306 via manual valves 307. Therefore, by adjusting the output of the first blower 301 and the second blower 302, the opening degree of the first electric valve 304 and the second electric valve 305, and the opening degree of the manual valve 307 connected to each of the air diffusion units 306, the amount of air diffused from each of the air diffusion units 306 can be adjusted. The manual valve 307a is a valve located at the boundary between the regions described below.

[0015] 2, in the remaining area of ​​the flow path 203 of the tank 200 past the partition wall 204, the amount of air diffused from the air diffuser 306 of the air diffuser 300 is adjusted, and thereby, from the side closest to the inlet 201, the first aerobic region 206, the upstream first combined region 209f, the denitrification region 207, the downstream second combined region 209b, and the second aerobic region 208 are formed. Here, the first aerobic region 206 and the first combined region 209f located downstream thereof constitute a region related to the first aerobic region. In addition, the second combined region 209b located downstream of the denitrification region 207 and the second aerobic region 208 located downstream thereof constitute a region related to the second aerobic region. There are no partition walls in the portions of the flow path 203 where the first-half aerobic region 206, the first-half dual-use region 209f, the denitrification region 207, the second-half dual-use region 209b, and the second-half aerobic region 208 are arranged, and these regions are formed by adjusting the amount of air diffused. For convenience, the first-half dual-use region 209f and the second-half dual-use region 209b are omitted from the illustration in Figure 1. Furthermore, the first-half dual-use region 209f and the second-half dual-use region 209b may be collectively referred to as the dual-use region 209.

[0016] The aeration sections 306 arranged in the first aerobic region 206, the first dual-use region 209f, the downstream second dual-use region 209b, and the second aerobic region 208 diffuse air when the corresponding manual valves 307, 307a are open, and the aeration section 306 arranged in the denitrification region 207 does not diffuse air or the amount of air diffused is reduced when the corresponding manual valves 307, 307a are closed or throttled.

[0017] Here, with reference to arrows U1, U2, R1, R2, L1, L2, and D in Figure 2, this disclosure will explain the aeration control, which includes a process (step) in which control device 400 controls the amount of aeration from aeration unit 306 to generate a pair of first and second swirling flows. The first swirling flow is the flow indicated by arrows U1, R1, D, and L2, and the second swirling flow is the flow indicated by arrows U2, L1, D, and R2. Here, arrows U1 and U2 indicate an upward flow, arrow R1 a forward flow at the water surface, arrow R2 a forward flow at the bottom, arrow L1 a reverse flow at the water surface, arrow L2 a reverse flow at the bottom, and arrow D a downward flow. In the regions related to the first aerobic region (first aerobic region 206 and first dual-use region 209f) and the regions related to the second aerobic region (second dual-use region 209b and second dual-use region 208), aeration generates an upward flow (see arrows U1 and U2), raising the water surface. Therefore, at the downstream end of the regions related to the first aerobic region (first aerobic region 206 and first dual-use region 209f) and the upstream end of the regions related to the second aerobic region (second dual-use region 209b and second dual-use region 208), flows toward the denitrification region 207 are generated on the water surface (see arrows R1 and L1). These flows become downward flows near the center of the denitrification region 207 (see arrow D), and then flow outward toward each other at the bottom of the denitrification region 207 (see arrows R2 and L2). Then, dual-use areas 209 in which both nitrification and denitrification proceed are formed outside the denitrification area 207 adjacent to the area related to the first half aerobic area (first half aerobic area 206 and first half dual-use area 209f), and outside the denitrification area 207 adjacent to the area related to the second half aerobic area (second half dual-use area 209b and second half aerobic area 208).

[0018] In the treatment device 100, the dual-use region 209 serves as a buffer region, so that even without a partition plate, situations in which wastewater with a high dissolved oxygen concentration in the first aerobic region 206 mixes with wastewater with a low dissolved oxygen concentration in the denitrification region 207 due to the push flow, or wastewater with a high dissolved oxygen concentration in the second aerobic region 208 mixes with wastewater with a low dissolved oxygen concentration in the denitrification region 207 due to a flow counter to the push flow, which would impair the anoxic or hypoxic state in the denitrification region 207, can be effectively avoided, allowing the denitrification reaction to proceed sufficiently. Furthermore, since denitrification treatment can be performed in the dual-use region other than the denitrification region, and nitrification treatment is also performed in the dual-use region, the denitrification region can be expanded without reducing the aerobic region, making it possible to increase the denitrification treatment amount that can be targeted with the same tank capacity, or to reduce the tank capacity while maintaining the same denitrification treatment amount.

[0019] In the treatment device 100, wastewater flowing in from the inlet 201 flows from upstream to downstream along the flow path 203 of the tank 200, and is mainly a push flow in which treated water flows out from the outlet 202. However, near the denitrification zone 207, due to the above-mentioned swirling flow, a mixed flow is also generated in which wastewater with a high dissolved oxygen concentration from the first aerobic zone 206 and the second aerobic zone 208 mixes with wastewater with a low dissolved oxygen concentration from the denitrification zone 207, to the extent necessary to form the dual-use zone 209. Furthermore, since there are a pair of swirling flows, the mixed flow does not diffuse, and the dual-use region 209 is maintained in a stable state.

[0020] In addition, as wastewater treatment progresses, activated sludge is formed, which contains microorganisms such as BOD-oxidizing bacteria, nitrifying bacteria (ammonia-oxidizing bacteria, nitrite-oxidizing bacteria, etc.), and denitrifying bacteria that break down organic matter in each area.This activated sludge floats in the wastewater and flows along with the flow of wastewater, and depending on the environmental conditions such as the oxygen concentration in each area, the activity of nitrifying bacteria or the activity of denitrifying bacteria increases, resulting in nitrification and denitrification.

[0021] The treated water flowing out from the outlet 202 of the tank 200 is stored in a final settling tank where the sludge is separated. A portion of the separated sludge is returned to the inlet 201 as returned sludge, and the excess sludge is removed as excess sludge.

[0022] 1, the control system 400 is provided to control the aeration device 300 and adjust the amount of air diffused from the aeration units 306 arranged in the anaerobic region 205, the first aerobic region 206, the first dual-use region 209f (omitted in FIG. 1), the denitrification region 207, the second dual-use region 209b (omitted in FIG. 1), and the second aerobic region 208. The control system 400 includes a control device main body 401, a terminal computer 402 connected to the control device main body 401 by wire or wirelessly, and a first detection device 403 and a second detection device 404 arranged in the tank 200.

[0023] The first detector 403 is disposed downstream of the first aerobic region 206, preferably at a position closer to the denitrification region 207 than the middle of the flow path of the first aerobic region 206, and more preferably immediately upstream of the dual-use region 209 formed downstream of the first aerobic region 206. The first detector 403 is a device that detects the concentration of nitrate nitrogen consisting of NOx such as NO2 and NO3 in the wastewater. The detected value may be the concentration of NOx itself, or the concentration of nitrogen derived from NOx.

[0024] The second detector 404 is disposed downstream of the latter aerobic region 208, preferably at a position closer to the outflow section 202 than the middle of the flow path of the latter aerobic region 208, and more preferably near the downstream end of the latter aerobic region 208 (a position returned upstream from the downstream end by an amount necessary to maintain sensor accuracy). The second detector 404 is a device that detects the concentration of ammoniacal nitrogen such as NH4OH in the wastewater. The detected value may be the concentration of NH4OH itself, or the concentration of nitrogen derived from NH4OH.

[0025] The control device main body 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 control device main body 401 includes, for example, an electronic circuit. An example of such an electronic circuit is a computer (PC) configured with a CPU (Central Processing Unit), storage media such as ROM (Read Only Memory) and RAM (Random Access Memory), and a storage medium such as a hard disk, or an FPGA (Field-Programmable Gate Array) or ASIC (Application Specific Integrated Circuit).

[0026] In the control device main body 401, a predetermined program capable of executing the wastewater treatment method and control method described below is stored on a recording medium. As will be described in detail later, the control device main body 401 outputs a control signal in accordance with 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. In this way, the control device main body 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 air diffused from the air diffusion unit 306 arranged in each area.

[0027] The terminal computer 402 is connected to the control device main body 401 by wire or wirelessly and is used to operate the control system 400 from a remote location and to grasp the operating status of the processing device 100 using electronic data transmitted from the control system 400.

[0028] As described above, the dual-use region 209, in which both nitrification and denitrification proceed, is formed outside the denitrification region 207 adjacent to the first aerobic region 206 and outside the denitrification region 207 adjacent to the second aerobic region 208. The position of this dual-use region 209 can be set to a desired position or changed by selecting the aeration section 306 that diffuses air by opening and closing the manual valve 307. Depending on the position of the dual-use region 209, the length and capacity along the flow path 203 of each of the first aerobic region 206, denitrification region 207, and second aerobic region 208 are set.

[0029] Next, with reference to FIGS. 3 and 4, details of the control performed by the control system 400 (control device main body 401) of the processing device 100 will be described.

[0030] 3, the control device main body 401 includes an air volume calculation unit 401a and a machine learning DB (database) 401b. As will be described in detail later, 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 inflow water flowing into the tank 200 is input to the air volume calculation unit 401a.

[0031] The air volume calculation unit 401a then calculates the air diffusion rates C and D from this input information. When calculating the air diffusion rates C and D, it may refer to information acquired by machine learning past data stored in the machine learning DB 401b. The numerical values ​​of the air diffusion rates C and D vary depending on factors such as the water temperature, the TN (total nitrogen) load of the wastewater, and the HRT (hydraulic residence time), but by referencing this information, it is possible to automatically determine optimal parameters for calculating the air diffusion rates C and D. This allows the treatment device 100 to stabilize the water quality while reducing the burden of tuning the air diffusion rate.

[0032] The air diffusion rates C and D calculated by air volume calculation unit 401a are sent to first blower 301 and second blower 302. First blower 301 and second blower 302 are equipped with air volume control units 301a and 302a, respectively. Air volume control units 301a and 302a control the outputs of first blower 301 and second blower 302, respectively, so that the air diffusion rates C and D are obtained.

[0033] Furthermore, the control device main body 401 controls the valve openings of the first electric valve 304 and the second electric valve 305 to adjust the air diffusion amounts C and D. To this end, the air volume calculation unit 401a transmits valve opening / closing information to the first electric valve 304 and the second electric valve 305.

[0034] Next, a flowchart of the operation process performed by the control device main body 401 of the control system 400 will be described with reference to FIG.

[0035] First, the first detector 403 measures the nitrate nitrogen concentration A in the latter half of the first aerobic zone 206 (STEP 10). Then, the amount of aeration C is calculated from the target nitrate nitrogen concentration A1 required to achieve the target denitrification amount (concentration) and the nitrate nitrogen concentration A in the latter half of the first aerobic zone 206 (STEP 20).

[0036] Specifically, the concentration A is compared with the target nitrate nitrogen concentration A1, and the nitrate nitrogen concentration A when passing through the first aerobic region 206 is equal to the target nitrate nitrogen concentration A1. nitric acidity The amount of air diffused C in the first aerobic region 206 and the first dual-use region 209f is calculated, for example, by the following (Equation 1) so that the nitrogen concentration reaches A1. C=P×(A1-A)…(Formula 1) Here, P is a coefficient determined from the relationship between the amount of aeration and the nitrification rate in the first aerobic region 206, and can be determined experimentally in advance.

[0037] P can also be calculated using multiple parameters p1, p2, p3... determined by treatment conditions such as water temperature, TN (total nitrogen) load of the wastewater, HRT (hydraulic retention time), etc. Optimal values ​​for these parameters p1, p2, p3... can be determined using the machine learning DB 401b described above.

[0038] Next, the outputs of the first blower 301 and the second blower 302 and the opening of the first electric valve 304 are controlled so that the amount of air diffused in the first aerobic region 206 and the first dual-use region 209f becomes the above-mentioned amount of air diffused C (STEP 30).

[0039] Next, the second detector 404 measures the ammoniacal nitrogen concentration B in the latter region of the latter aerobic region 208 (STEP 40). After that, the amount of aeration D is calculated from the ammoniacal nitrogen concentration B in the latter region of the latter aerobic region 208 and a target ammoniacal nitrogen concentration B1 that is allowed to remain in the treatment liquid that flows out through the latter aerobic region 208 (STEP 50).

[0040] Specifically, the concentration B is compared with the target ammoniacal nitrogen concentration B1, and the amount of aeration D in the latter aerobic region 208 and the latter dual-use region 209b is calculated, for example, by the following (Equation 2) so that the ammoniacal nitrogen concentration in the treated water that has passed through the latter aerobic region 208 is equal to or lower than the target ammoniacal nitrogen concentration B1. D=Q×(B-B1)…(Formula 2) Here, Q is a coefficient determined from the relationship between the amount of aeration and the nitrification rate in the latter aerobic region 208, and can be determined experimentally in advance.

[0041] Q can also be calculated using multiple parameters q1, q2, q3... determined by treatment conditions such as water temperature, TN (total nitrogen) load of the wastewater, HRT (hydraulic retention time), etc. Optimal values ​​for these parameters q1, q2, q3... can also be determined by using the machine learning DB 401b described above, taking external factors into consideration.

[0042] Next, the outputs of the first blower 301 and the second blower 302 and the opening of the second electric valve 305 are controlled so that the amount of air diffused in the latter aerobic region 208 and the latter dual-use region 209b becomes the above-mentioned amount of air diffused D (STEP 60). This completes the series of operation processes by the control device main body 401, but by repeating each of the above processes, the control device main body 401 can diffuse the desired amount of air in each region of the tank 200.

[0043] Next, a nitrification / denitrification method using the treatment device 100 of the present disclosure will be described.

[0044] Wastewater such as sewage passes through a primary settling tank (not shown) and is introduced into the anaerobic zone 205. Return sludge returned from a sludge recovery section (not shown) is also introduced into the anaerobic zone 205. Because the anaerobic zone 205 is maintained in an anaerobic state, phosphorus contained in the return sludge is released under anaerobic conditions. This phosphorus is taken up by microorganisms in the subsequent first half aerobic zone 206, denitrification zone 207, and second half aerobic zone 208, and is removed from the wastewater as sludge.

[0045] After being treated for a predetermined time in the anaerobic region 205, the wastewater flows through a notched opening below the partition wall 204 and into the first-half aerobic region 206. In the first-half aerobic region 206, the amount of aeration is controlled to be the amount calculated by the above-mentioned (Equation 1), so that nitrifying bacteria become active and nitrify the ammoniacal nitrogen contained in the wastewater to produce nitrate-nitrogen, thereby increasing the nitrate-nitrogen concentration. In other words, the nitrate-nitrogen concentration (NOx-N) increases from the first-half aerobic region 206 to the denitrification region 207 (denitrification region, inlet).

[0046] At this time, the amount of air diffused in the first-half aerobic region 206 and the first-half dual-use region 209f is controlled by the above-mentioned (Equation 1), so the nitrate nitrogen concentration (NOx-N) in the denitrification region 207 (inlet portion) becomes a concentration that reaches the target nitrate nitrogen concentration A1. However, in order to maintain an anaerobic state in the subsequent denitrification region 207, the amount of air diffused in the first-half aerobic region 206 and the first-half dual-use region 209f is controlled to be an amount sufficient to reach the target nitrate nitrogen concentration A1, but not excessive.

[0047] The wastewater that has passed through the first-half aerobic region 206 passes through the first-half dual-use region 209f and is introduced into the denitrification region 207, where the amount of air diffused from the aeration unit 306 is controlled by the control device main body 401 and the denitrification region 207 is maintained in an anaerobic or reduced-oxygen state, allowing denitrification by denitrifying bacteria. At this time, the nitrate nitrogen formed in the first-half aerobic region 206 at a concentration that reaches the target nitrate nitrogen concentration A1 is denitrified, and nitrogen equivalent to the target amount of denitrification is removed from the wastewater.

[0048] Next, the wastewater that has passed through the denitrification region 207 passes through the latter combined region 209b and is introduced into the latter aerobic region 208. The amount of air diffused from the aeration unit 306 in the latter aerobic region 208 is controlled by the control device main body 401, and the latter aerobic region 208 is again in an aerobic state, so that ammoniacal nitrogen remaining in the wastewater is nitrified into nitrate nitrogen. The amount of air diffused in the latter aerobic region 208 and the latter combined region 209b is controlled to be the amount of air diffused calculated by the above (Equation 2), so that the ammoniacal nitrogen concentration in the wastewater that has passed through the denitrification region 207 becomes equal to or less than the target ammoniacal nitrogen concentration B1 that is allowed to remain in the treated water.

[0049] In this way, the treated water that has passed through the latter aerobic region 208 has not only a reduced ammonia nitrogen concentration but also a reduced overall nitrogen concentration, becoming more highly detoxified treated water. This treated water will undergo normal treatment such as chlorination before being discharged into a river or the like.

[0050] As described above, the treatment device 100 compares the target nitrate-nitrogen concentration A1 required to achieve the target denitrification amount (concentration) with the nitrate-nitrogen concentration A in the latter half of the former aerobic region 206, and controls the amount of air diffused C in the former aerobic region 206 and the former dual-purpose region 209f so that the nitrate-nitrogen concentration after passing through the former aerobic region 206 reaches the target nitrate-nitrogen concentration A1. Therefore, nitrate nitrogen can be formed in the former aerobic region 206 so as to ensure the amount of denitrification required to reduce the nitrogen concentration in the wastewater to a predetermined value or below, while maintaining an anoxic or reduced-oxygen state in the denitrification region 207. As a result, the nitrogen concentration in the wastewater can be reduced to a predetermined value or below in the denitrification region 207, thereby achieving the target denitrification amount.

[0051] Furthermore, the ammoniacal nitrogen concentration B in the latter region of the latter aerobic region 208 is compared with the target ammoniacal nitrogen concentration B1 that is allowed to remain in the treatment liquid, and the amount of aeration D in the latter aerobic region 208 and the latter dual-use region 209b is controlled so that the ammoniacal nitrogen concentration in the treatment water that has passed through the latter aerobic region 208 is equal to or less than the target ammoniacal nitrogen concentration B1, thereby reducing the ammoniacal nitrogen concentration remaining in the treatment water to equal to or less than the target ammoniacal nitrogen concentration B1.

[0052] In the nitrification-denitrification method of the present disclosure, as shown by the arrows in Figure 2, in the first aerobic region 206 and the second aerobic region 208, an upward flow is generated by aeration, raising the water surface, resulting in the generation of the pair of swirling flows described above, and dual-use regions 209, in which both nitrification and denitrification proceed, are formed outside the denitrification region 207 adjacent to the first aerobic region 206 and outside the denitrification region 207 adjacent to the second aerobic region 208.

[0053] As a result, in the nitrification-denitrification method of the present disclosure, an anaerobic or hypoxic state can be maintained in the denitrification region 207 without the need for a partition plate, allowing the denitrification reaction to proceed. Furthermore, denitrification treatment can also be performed in the dual-use region 209 other than the denitrification region 207, and nitrification treatment is also performed in the dual-use region 209. Therefore, the denitrification region can be expanded without reducing the aerobic region, and the target denitrification treatment amount can be increased with the same tank capacity. Furthermore, there is no need to install a partition wall in the tank 200, reducing equipment costs.

[0054] Furthermore, in the treatment device 100, when the amount of wastewater treatment or the organic matter concentration fluctuates depending on the weather or season, the position of the dual-use region 209 can be changed by changing the open / close state of the manual valve 307a located at the boundary between each region, thereby changing the capacity and length of the first aerobic region 206, the denitrification region 207, and the second aerobic region 208. Furthermore, the device is configured so that the position of the first detection device 403 can be moved in accordance with the change in the position of the dual-use region 209.

[0055] As a result, for example, when the amount of wastewater or the load of organic matter in the wastewater increases, the manual valve 307a can be switched so that the capacity and length of the first aerobic region 206 and the second aerobic region 208 are increased, thereby making it possible to maintain the ammoniacal nitrogen concentration remaining in the treated water at or below the target ammoniacal nitrogen concentration B1.

[0056] Furthermore, by comparing the difference (A1-A) between the target nitrate nitrogen concentration A1 required to achieve the target denitrification amount (concentration) in (Equation 1) and the nitrate nitrogen concentration A in the latter half of the first-aerobic region 206, and the difference (B-B1) between the ammonia nitrogen concentration B in the latter half of the latter-aerobic region 208 and the target ammonia nitrogen concentration B1 that is allowed to remain in the treatment liquid that flows out through the latter-aerobic region 208 in (Equation 2), the position of the dual-use region 209 can be changed by operating the manual valve 307a to achieve a more balanced region distribution.

[0057] In this case, in the above embodiment, all the valves controlling the individual aeration sections 306 are manual valves 307, but the manual valves 307a located adjacent to each region may be changed to motor-operated valves, and the capacity and length of each region may be changed by changing the opening degree of the motor-operated valves.

[0058] The amount of air diffused from the air diffuser 306 in the denitrification area 207 can be set to 0, but it is also possible to diffuse a small amount of air so that the sludge in the wastewater continues to float and is prevented from settling. Denitrification area 207 This eliminates the need to provide stirring blades or the like, thereby further reducing equipment costs.

[0059] As described above, the control device 401 controls the amount of air diffused from the multiple air diffuser sections 306 of the air diffuser 300, and forms, in order from the upstream side along the flow path 203, the first aerobic region 206, the first dual-use region 209f in which both nitrification and denitrification proceed, the denitrification region 207, the second dual-use region 209b in which both nitrification and denitrification proceed, and the second aerobic region 208, and further executes a process (step) of generating a pair of first and second swirling flows in the flow path 203.

[0060] In this process, the control device 401 controls the amount of air diffused in the first-half aerobic region 206 and the first-half dual-use region 209f based on the nitrate nitrogen concentration detected by the first detection device 403, and controls the amount of air diffused in the second-half dual-use region 209b and the second-half aerobic region 208 based on the ammonia nitrogen concentration detected by the second detection device 404. The first swirling flow rises in the first-half dual-use region 209f (see arrow U1), flows downstream on the water surface side of the denitrification region 207 (see arrow R1), falls near the center of the denitrification region 207 (see arrow D), and flows upstream on the bottom side of the denitrification region 207 (see arrow L2), which is a swirling flow. In addition, the second swirling flow rises in the latter combined region 209b (see arrow U2), moves upstream on the water surface side of the denitrification region 207 (see arrow L1), descends near the center of the denitrification region 207 (see arrow D), and moves downstream on the bottom side of the denitrification region 207 (see arrow R2), which is a swirling flow.

[0061] According to the treatment device 100, the dual-use region 209 acts as a buffer region, making it less susceptible to the effects of the oxygen-rich forward flow from the first aerobic region 206 and the oxygen-rich upstream flow from the second aerobic region 208, and maintaining a low-oxygen state in the denitrification region 207, thereby achieving a sufficient denitrification treatment rate despite the absence of a partition plate. Furthermore, because a partition plate is not required, it is possible to avoid expensive capital investment.

[0062] Furthermore, since denitrification treatment can be performed in the dual-use area 209 other than the denitrification area 207, and nitrification treatment is also performed in the dual-use area 209, the denitrification area 207 can be expanded without reducing the aerobic area, thereby meeting the demands of increasing the denitrification treatment amount with the same tank capacity, or reducing the tank capacity while maintaining the same denitrification treatment amount.

[0063] Furthermore, by controlling the amount of air diffused in the area related to the first aerobic area 206 based on the nitrate nitrogen concentration measured by the first detection device 403 located downstream of the first aerobic area 206, the nitrate nitrogen concentration in the wastewater flowing into the denitrification area 207 can be adjusted so that a sufficient amount of denitrification can be obtained in the denitrification area 207, and by controlling the amount of air diffused in the area related to the second aerobic area 208 based on the ammonia nitrogen concentration measured by the second detection device 404 located downstream of the second aerobic area 208, nitrification can be sufficiently carried out in the second aerobic area 208, and the concentration of remaining ammonia nitrogen can be treated to fall within an acceptable range.

[0064] The air diffusion device 300 has a plurality of air diffusion sections 306 that can be opened and closed along the flow path 203, and is configured so that the position of either the first combined area 209f or the second combined area 209b can be changed by selecting the air diffusion section 306 that will diffuse the air, and is also configured so that the position of either the first detection device or the second detection device can be moved in accordance with the change in position. Here, examples of "a plurality of air diffusion sections that can be opened and closed" include a plurality of air diffusion sections that can switch between limited aeration and aeration using an electric valve, for example.

[0065] According to this configuration, the aeration device 300 can change the position of the dual-use area 209 by selecting the aeration section 306 that will diffuse the air, so that the position of the dual-use area 209 can be changed and the length of each area can be adjusted to an appropriate length by selecting the aeration section 306 that will diffuse the air in accordance with the treatment conditions of the facility to which it is applied and fluctuations in the wastewater load due to weather and seasonal changes. Also, since the configuration allows the position of the first detection device 403 to be moved in accordance with changes in the position of the dual-use area 209, the first detection device 403 can always be positioned downstream of the first aerobic area 206 even if the length of the first aerobic area 206 changes.

[0066] The control device 401 is configured to control the amount of air diffused into the first aerobic region 206 and the first dual-use region 209f based on the difference between the target nitrate nitrogen concentration in the first aerobic region 206 and the nitrate nitrogen concentration detected by the first detection device 403, which is set so that the amount of denitrification necessary to reduce the nitrogen concentration in the wastewater to a predetermined value or below can be ensured in the denitrification region 207 and so that a predetermined anaerobic or reduced-oxygen state can be formed in the denitrification region 207, and to control the amount of air diffused into the second dual-use region 209b and the second aerobic region 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.

[0067] According to the above embodiment, the amount of air diffused in the area related to the first aerobic area 206 is controlled based on the difference between the target nitrate-nitrogen concentration A1 in the first aerobic area 206 and the nitrate-nitrogen concentration A detected by the first detection device 403 so that the nitrate-nitrogen concentration approaches the target nitrate-nitrogen concentration A1, thereby ensuring a sufficient nitrate-nitrogen concentration in the wastewater flowing into the denitrification area 207 and ensuring the required amount of denitrification. In addition, the amount of air diffused in the area related to the second aerobic area 208 is controlled 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 acceptable to remain in the treated water, thereby reducing the ammonia-nitrogen concentration to below the target ammonia-nitrogen concentration that is acceptable to remain in the treated water. [Example]

[0068] <Test Example 1> 1 and 2, sewage was treated while controlling the amount of air diffused by the air diffuser 300 using the control system 400. The results are described below.

[0069] (1) The quality and treatment volume of sewage after discharge from the primary sedimentation tank are as follows: Total nitrogen (TN) 30mgN / L NH4-N (ammonia nitrogen concentration) 23mgN / L ·Water volume 26,740m3 / day / system ·TN load amount 802.2kgN / day / system HRT 10.3hr (2) The water quality and treatment volume of returned sludge are as follows: ·NOx-N (nitrate nitrogen concentration) 10.3mgN / L Return rate 50% Sludge volume: 13,370m3 / day / system ·NOx-N load amount 138.16kgN / day / system (3) Water quality at the end of the first half of the aerobic zone NH4-N 10.3mgN / L NOx-N 5mgN / L Water volume + sludge volume 40,110m3 / day / system ·NOx-N load amount 200.6kgN / day / system (4) Water quality at the edge of the denitrification zone (denitrification zone) NH4-N 10.3mgN / L NOx-N 0mgN / L Water volume + sludge volume 40,110m3 / day / system ·NOx-N load amount 0kgN / day / system (5) Water quality at the end of the latter half of the aerobic zone NH4-N 0.0mgN / L NOx-N 10.3mgN / L Water volume + sludge volume 40,110m3 / day / system ·NOx-N load amount 414.5kgN / day / system (6) Water quality at the final settling outlet TN (total nitrogen) 12mgN / L NOx-N 10.3mg / L ·Water volume 26,740m3 / day / system ·TN load amount 320.9kgN / day / system ·TN removal rate 60% (7) Excess sludge ·N content 10% MLSS (activated sludge suspended solids) 4000mg / L Sludge volume: 376m3 / day / system Load: 150.4 kgN / day / system As shown in the above results, the treated water had a TN (total nitrogen) removal rate of 60% and ammonia of 0.0 mgN / L.

[0070] <Test Example 2> Using the treatment device 100 shown in Figures 1 and 2, sewage was continuously treated while controlling the amount of air diffused by the air diffuser 300 using the control system 400. The BOD (biochemical oxygen demand) concentration, TN (total nitrogen) concentration, and TP (total phosphorus) concentration at the initial settling outlet and final settling outlet were then measured periodically, and changes in these concentrations were investigated.

[0071] The BOD concentration was measured using the method described in Section 21, Chapter 1, Part 2 of the Sewage Testing Methods (2012 Edition), 1. Biochemical Oxygen Demand (BOD). The TN concentration was measured using the method described in JIS K 0170-3 based on Section 13, Chapter 5, Part 1 of the Sewage Testing Methods (2012 Edition). The TP concentration was measured using the method described in JIS K 0170-4 based on Section 13, Chapter 5, Part 1 of the Sewage Testing Methods (2012 Edition).

[0072] The results of measurements taken over more than a year of continuous test operation are shown in Figure 5 for BOD concentration, Figure 6 for TN concentration, and Figure 7 for TP concentration. The dashed lines in each figure indicate the target reduction values ​​for each.

[0073] As shown in FIGS. 5, 6 and 7, the nitrification and denitrification method using the treatment device 100 of the present invention was able to stably reduce BOD, TN and TP for more than one year. [Explanation of symbols]

[0074] 100... treatment device, 200... tank, 201... inlet section, 202... outlet section, 203... flow path, 204... partition wall, 205... anaerobic region, 206... first half aerobic region, 207... denitrification region, 208... second half aerobic region, 209... dual-use region, 209f... first half dual-use region, 209b... second half dual-use region, 300... air diffuser, 301... first blower, 301a... air volume control section, 302... second blower, 302a... air volume control section , 303...piping, 304...first electric valve, 304a...valve opening / closing control unit, 305...second electric valve, 305a...valve opening / closing control unit, 306...aeration unit, 307...manual valve, 307a...manual valve, 308...pressure detection device, 400...control system, 401...control device main body, 401a...air volume calculation unit, 401b...machine learning DB, 402...terminal computer, 403...first detection device, 404...second detection device.

Claims

1. a tank having an inlet for wastewater, a flow path for wastewater treatment, and an outlet for treated water; an air diffusion device in which a plurality of air diffusion units are arranged at the bottom of the flow path along the flow path of the tank; a first detection device for detecting a nitrate nitrogen concentration in the wastewater; a second detection device provided downstream of the first detection device and configured to detect the ammonia nitrogen concentration of the wastewater; a control device that controls the amount of air diffused from the plurality of air diffuser sections of the air diffuser, and forms, in order from the upstream side along the flow path, a first aerobic region, a first dual-purpose region in which both nitrification and denitrification proceed, a denitrification region, a second dual-purpose region in which both nitrification and denitrification proceed, and a second aerobic region, and further generates a pair of first and second swirling flows in the flow path, the first detection device is provided downstream of the first aerobic region, the second detection device is provided downstream of the latter aerobic zone, The control device Based on the nitrate nitrogen concentration detected by the first detection device, Controlling the amount of air diffused in the first aerobic region and the first dual-use region; controlling the amount of air diffused in the latter dual-use area and the latter aerobic area based on the ammonia nitrogen concentration detected by the second detection device; the first swirling flow is a swirling flow that rises in the first combined use region, moves downstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and moves upstream on the bottom side of the denitrification region, In the wastewater treatment device, the second swirling flow is a swirling flow that rises in the latter combined region, flows upstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and flows downstream on the bottom side of the denitrification region.

2. 2. The wastewater treatment device according to claim 1, wherein the air diffusion device has a plurality of air diffusion sections that can be opened and closed along the flow path, and is configured to be able to change the position of either the first half combined area or the second half combined area by selecting the air diffusion section that diffuses the air, and is configured to be able to move the positions of the first detection device and the second detection device in accordance with the change in position.

3. The control device controls the amount of air diffused in the first aerobic region and the first dual-use region based on a difference between a target nitrate nitrogen concentration in the first aerobic region and the nitrate nitrogen concentration detected by the first detection device, the difference being set so that the amount of denitrification necessary to reduce the nitrogen concentration in the wastewater to a predetermined value or less can be ensured in the denitrification region and a predetermined hypoxic state can be formed in the denitrification region; and 3. The wastewater treatment device according to claim 1, wherein the amount of aeration in the latter dual-use region and the latter aerobic region is controlled based on a difference between the ammoniacal nitrogen concentration detected by the second detection device and a target ammoniacal nitrogen concentration that is allowed to remain in the treated water.

4. A wastewater treatment method carried out in a wastewater treatment device comprising: a tank having an inlet for wastewater, a flow path through which wastewater treatment is performed, and an outlet for treated water; an aeration device having a plurality of aeration units disposed at a bottom of the flow path of the tank along the flow path; a first detection device that detects the nitrate nitrogen concentration of the wastewater; and a second detection device that is provided downstream of the first detection device and detects the ammonia nitrogen concentration of the wastewater, a step of controlling the amount of air diffused from the plurality of air diffuser units of the air diffuser device to form, in order from the upstream side along the flow path, a first aerobic region, a first dual-purpose region in which both nitrification and denitrification proceed, a denitrification region, a second dual-purpose region in which both nitrification and denitrification proceed, and a second aerobic region, and further generating a pair of first and second swirling flows in the flow path; the first detection device is provided downstream of the first aerobic region, the second detection device is provided downstream of the latter aerobic zone, In the step of generating the first and second swirling flows, the method includes a step of controlling the amount of air diffused in the first aerobic region and the first dual-use region based on the nitrate nitrogen concentration detected by the first detection device, and controlling the amount of air diffused in the second dual-use region and the second aerobic region based on the ammonia nitrogen concentration detected by the second detection device, the first swirling flow is a swirling flow that rises in the first combined use region, moves downstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and moves upstream on the bottom side of the denitrification region, a second swirling flow that rises in the latter combined-use region, flows upstream on the water surface side of the denitrification region, descends near the center of the denitrification region, and flows downstream on the bottom side of the denitrification region.

5. 5. The wastewater treatment method according to claim 4, wherein in the step of generating the first and second swirling flows, the air diffuser has a plurality of air diffuser sections that can be opened and closed along the flow path, and the position of at least one of the first combined region and the second combined region is changed by selecting the air diffuser section that diffuses the air in accordance with the load amount of the wastewater, and the position of at least one of the first detection device and the second detection device is moved in accordance with the change in position.

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