Water spray filter bed system and water spray filter bed method

Abstract

The present invention comprises: a tank that is filled with a carrier on which a microorganism is supported, and in which biological treatment is performed on water to be treated by the microorganism; a water spray pipe that sprays the water to be treated on the carrier; a first supply unit that supplies air containing oxygen to the tank; and a second supply unit that supplies, to the tank, at least a portion of an exhaust gas that is discharged from the tank and contains a nitrogen oxide generated by the biological treatment.

Description

Trickling filter system and trickling filter method

[0001] The present disclosure relates to trickling filter systems and trickling filter methods.

[0002] In a water treatment system (hereinafter simply referred to as a water treatment system) that treats water to be treated, such as sewage (hereinafter simply referred to as water to be treated), organic pollutants (hereinafter simply referred to as organic matter) and nitrogen compounds contained in the water to be treated are biologically treated by using, for example, a trickling filter (see Patent Document 1).

[0003] Meanwhile, when treating water containing nitrogen compounds (mainly ammoniacal nitrogen) through biological treatment, nitrogen oxides (e.g., nitrous oxide) are generated as reaction by-products. Nitrous oxide is a greenhouse gas and is also known as an ozone-depleting gas that destroys the ozone layer in the stratosphere (see Patent Document 2).

[0004] JP 2017-051922 A JP 2013-150970 A

[0005] In the water treatment system described above, it is desirable to reduce the amount of nitrogen oxides (for example, nitrous oxide) that are generated in conjunction with the biological treatment of organic matter and nitrogen compounds.

[0006] The trickling filter system of the present disclosure comprises a tank filled with carriers carrying microorganisms and in which the microorganisms carry out biological treatment of the water to be treated, a spray pipe that sprays the water to be treated onto the carriers, a first supply unit that supplies oxygen-containing air to the tank, and a second supply unit that supplies at least a portion of the exhaust gas that is discharged from the tank and contains nitrogen oxides and is produced by the biological treatment to the tank.

[0007] The trickling filter system and trickling filter method disclosed herein make it possible to reduce the amount of nitrogen oxides generated during biological treatment of organic matter and nitrogen compounds.

[0008] FIG. 1 illustrates an example configuration of a water treatment system 1000 in a first embodiment. FIG. 2 illustrates an example configuration of a trickling filter bed system 900 in a comparative example. FIG. 3 illustrates an example configuration of a trickling filter bed system 100 in the first embodiment. FIG. 4 illustrates an example configuration of a trickling filter bed system 200 in a second embodiment. FIG. 5 illustrates an example configuration of a trickling filter bed system 300 in a third embodiment. FIG. 6 is a diagram illustrating the function of a control device 50. FIG. 7 is a diagram illustrating the hardware configuration of the control device 50. FIG. 8 is a flowchart illustrating opening adjustment control in the third embodiment.

[0009] 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.

[0010] [Water Treatment System 1000 According to First Embodiment] First, a configuration example of a water treatment system 1000 according to a first embodiment will be described. Fig. 1 is a diagram illustrating a configuration example of a water treatment system 1000 according to the first embodiment.

[0011] As shown in FIG. 1, the water treatment system 1000 includes, for example, a trickling filter bed system 100, a filtration device 700 provided in a stage preceding the trickling filter bed system 100, and a filtration device 800 provided in a stage following the trickling filter bed system 100.

[0012] The filtration device 700 removes suspended solids (SS) and the like contained in the water to be treated by filtering the water to be treated supplied from an upstream facility (e.g., a grit chamber) via a line L1. The line L1 is, for example, a pipe connecting the upstream facility and the filtration device 700.

[0013] Specifically, the filtration device 700 removes suspended solids and the like from the water to be treated, for example, by using a carrier filled in a tank (not shown). The filtration device 700 then supplies the water to be treated, from which suspended solids and the like have been removed, to the trickling filter bed system 100 via line L2. Line L2 is, for example, a pipe connecting the filtration device 700 and the trickling filter bed system 100.

[0014] The trickling filter bed system 100 decomposes and removes organic matter contained in the water to be treated, for example, supplied via line L2, through biological treatment. The trickling filter bed system 100 then supplies the water to be treated that has undergone biological treatment to the filtration device 800, for example, via line L3. The line L3 is, for example, a pipe connecting the trickling filter bed system 100 and the filtration device 800.

[0015] The filtration device 800 removes suspended matter contained in the treated water (for example, suspended matter that was not removed by the filtration device 700 or suspended matter that has peeled off from the filtration device 700) by filtering the treated water supplied from the trickling filter bed system 100 via line L3, for example.

[0016] Specifically, filtration device 800 removes suspended solids and the like from the water to be treated, for example, by using a carrier filled in a tank (not shown). Filtration device 800 then supplies the water to be treated, from which suspended solids and the like have been removed, to downstream equipment (for example, a sterilization tank for sterilizing the water to be treated) via line L4, for example. Line L4 is, for example, a pipe connecting filtration device 800 to the downstream equipment.

[0017] [Trickling filter bed system 900 in comparative example] Next, a comparative example (hereinafter also simply referred to as comparative example) corresponding to the trickling filter bed system 100 in the first embodiment will be described. Figure 2 is a diagram illustrating an example of the configuration of the trickling filter bed system 900 in the comparative example.

[0018] The trickling filter system 900 includes, for example, a trickling filter device 10 as shown in FIG.

[0019] The trickling filter bed device 10 includes, for example, carriers 11 having microorganisms attached thereto, a packed tank 12 (hereinafter simply referred to as tank 12) filled with the carriers 11, a sprinkler pipe 13 for sprinkling the water to be treated onto the carriers 11, a support member 14 for supporting the carriers 11 packed in the packed tank 12 from below, and a storage tank 15 for temporarily storing the water to be treated that has been biologically treated in the carriers 11. The carrier 11 is made of, for example, natural stone or resin.

[0020] The sprinkler pipe 13 is installed, for example, in a space (hereinafter also referred to as the space section 12a) above the space in the filling tank 12 where the carrier 11 is filled (hereinafter also referred to as the filling section 12b), and sprinkles the water to be treated onto the carrier 11 from above.

[0021] Specifically, the water to be treated supplied to the line L2 is supplied to the sprinkler pipe 13 by, for example, a pump P1 provided on the line L2. Then, the water to be treated supplied to the sprinkler pipe 13 is sprinkled onto the carrier 11, for example.

[0022] Thereafter, organic matter contained in the water to be treated that has been sprayed onto the carrier 11 is decomposed and removed, for example, by microorganisms attached to the carrier 11 as the water to be treated passes through the carrier 11. The water to be treated after the organic matter has been decomposed and removed is then supplied to the storage tank 15, for example, via a plurality of holes 14a provided in the support member 14, and temporarily stored therein. Furthermore, the water to be treated (water to be treated W in the example shown in FIG. 2 ) stored in the storage tank 15 is sequentially discharged, for example, via line L3 to the filtration device 800.

[0023] That is, in the packed tank 12, for example, the water to be treated supplied by the sprinkler pipe 13 flows downward and passes through the carrier 11, whereby organic matter contained in the water to be treated is decomposed and removed.

[0024] In addition, when the water to be treated is supplied to the sprinkler pipe 13 by gravity flow due to a water level difference, the line L2 may not be provided with the pump P1, for example. In this case, the water to be treated may be temporarily stored in a storage tank (not shown) provided upstream of the trickling filter bed device 10, and supplied to the sprinkler pipe 13 from the storage tank.

[0025] Further, the packed tank 12 is attached with, for example, a line L11 that supplies air (outside air) to the space 12a in the packed tank 12. The line L11 is, for example, a pipe that connects the outside of the trickling filter bed device 10 with the space 12a.

[0026] Specifically, the air supplied to the line L11 is supplied to the space 12a by, for example, a pump P3 provided on the line L11, and then is supplied to the charging section 12b by descending within the charging tank 12. The air that has passed through the charging section 12b is then supplied to the storage tank 15 via, for example, a plurality of holes 14a. Hereinafter, the line L11 and the pump P3 will also be collectively referred to as the first supply section 21.

[0027] In addition, a line L12 that discharges air supplied from the filling section 12b to the outside is attached to the storage tank 15. The line L12 is, for example, a pipe that connects the storage tank 15 to the outside of the trickling filter bed device 10, and an induction fan F that draws air into the storage tank 15 is attached to the line L12.

[0028] Specifically, the air supplied from the filling section 12b to the storage tank 15 is discharged to the line L12 (outside the trickling filter bed device 10) by, for example, an induced draft fan F. Hereinafter, the air discharged from the storage tank 15 is also referred to as exhaust gas.

[0029] That is, in the filling tank 12, for example, air supplied to the upper part (space 12a) of the filling section 12b via the line L11 is drawn by the induction fan F provided on the line L12, thereby forming a downward air flow in the filling section 12b. Therefore, in the filling tank 12, for example, oxygen (oxygen contained in the air supplied from the line L11) is supplied to the microorganisms attached to the carrier 11.

[0030] Further, the storage tank 15 is attached with, for example, a line L3 for supplying the water to be treated (water to be treated W) stored in the storage tank 15 to the filtration device 800 .

[0031] Specifically, the water to be treated (water to be treated W) stored in the storage tank 15 is supplied to the filtration device 800 by, for example, a pump P2 provided in the line L3.

[0032] Here, the microorganisms attached to the carrier 11 include, for example, organic matter-oxidizing bacteria, which are aerobic bacteria that decompose and remove organic matter, as well as ammonia-oxidizing bacteria, which are aerobic bacteria that oxidize (nitrify) ammonia, and nitrite-oxidizing bacteria, which are aerobic bacteria that oxidize nitrite. Hereinafter, ammonia-oxidizing bacteria and nitrite-oxidizing bacteria will be collectively referred to simply as ammonia-oxidizing bacteria, etc. The microorganisms attached to the carrier 11 also include, for example, denitrifying bacteria, which are anaerobic bacteria that denitrify nitrogen components.

[0033] Therefore, in the packed tank 12, for example, ammonia contained in the water to be treated sprayed by the spray pipes 13 is oxidized to nitrite by ammonia-oxidizing bacteria, and the nitrite oxidized by the ammonia-oxidizing bacteria is further oxidized to nitrate by nitrite-oxidizing bacteria, thereby performing two-stage nitrification. Also, in the packed tank 12, for example, denitrifying bacteria that assimilate organic matter use nitric acid or the like as an oxygen source, thereby denitrifying the nitrogen components contained in the water to be treated.

[0034] However, for example, if the nitrification of ammonia and nitrite (hereinafter simply referred to as nitrification) in the filling tank 12 is not carried out sufficiently, or if the denitrification of nitrogen components (hereinafter simply referred to as denitrification) in the filling tank 12 is not carried out sufficiently, the trickling filter system 900 may generate nitrous oxide (dinitrogen oxide), which causes the greenhouse effect, etc., and the generated nitrous oxide may be discharged outside the trickling filter device 10 via line L12.

[0035] Therefore, in the trickling filter system 100 of this embodiment, for example, at least a portion of the exhaust gas discharged from the trickling filter device 10 is supplied again to the trickling filter device 10 via line L12, thereby further denitrifying the nitrous oxide generated in the filling tank 12.

[0036] As a result, the trickling filter bed system 100 of this embodiment can suppress, for example, the amount of nitrous oxide emitted from the trickling filter bed device 10. The trickling filter bed system 100 of the first embodiment will be described below.

[0037] [Trickling filter bed system 100 in the first embodiment] Figure 3 is a diagram illustrating an example of the configuration of the trickling filter bed system 100 in the first embodiment. Below, differences from the trickling filter bed system 900 described in Figure 2 will be described.

[0038] As shown in FIG. 3, the trickling filter system 100 includes, for example, valves V1 and V2 in addition to the components of the trickling filter system 900.

[0039] The valve V1 is, for example, a valve provided in the line L21. The line L21 is, for example, a pipe that connects the line L12 and the space 12a.

[0040] Valve V2 is, for example, a valve provided on line L12 downstream of the position where line L12 communicates with line L21. Hereinafter, line L12, line L21, induced draft fan F, valve V1, and valve V2 will also be collectively referred to as second supply unit 22.

[0041] That is, in the trickling filter system 100 of this embodiment, for example, by adjusting the opening degree of at least one of the valves V1 and V2, at least a portion of the exhaust gas (e.g., exhaust gas containing nitrous oxide) discharged from the storage tank 15 is returned to the space 12a. Hereinafter, the exhaust gas (at least a portion of the exhaust gas discharged from the storage tank 15) returned to the space 12a is also referred to as circulating gas. Then, in the trickling filter system 100 of this embodiment, for example, the circulating gas returned to the space 12a descends within the packed tank 12, thereby again denitrifying the nitrous oxide contained in the circulating gas.

[0042] Thus, the trickling filter bed system 100 of this embodiment includes, for example, a packed tank 12 filled with carriers 11 carrying microorganisms and in which the microorganisms perform biological treatment on the water to be treated, and a sprinkler pipe 13 that sprinkles the water to be treated onto the carriers 11. The trickling filter bed system 100 of this embodiment also includes, for example, a first supply unit 21 that supplies oxygen-containing air to the packed tank 12. The trickling filter bed system 100 of this embodiment also includes, for example, a second supply unit 22 that supplies at least a portion of the exhaust gas that is discharged from the packed tank 12 and contains nitrogen oxides (e.g., nitrous oxide) generated by the biological treatment to the packed tank 12.

[0043] Specifically, in the trickling filter bed system 100 of this embodiment, the first supply unit 21 supplies air, for example, to the space 12 a above the upper end position of the carrier 11 packed in the packed tank 12 .

[0044] In addition, in the trickling filter system 100 of this embodiment, the second supply unit 22 supplies circulating gas, for example, to the space 12 a above the upper end position of the carrier 11 packed in the packed tank 12 .

[0045] As a result, the trickling filter bed system 100 in this embodiment can, for example, reduce the amount of nitrous oxide contained in the exhaust gas discharged from line L12.

[0046] In the above example, the trickling filter bed system 100 has been described as having valves V1 and V2, but this is not limited thereto. Specifically, the trickling filter bed system 100 may have, for example, either valve V1 or valve V2. In addition, the trickling filter bed system 100 may adjust the opening degree of either valve V1 or valve V2, for example.

[0047] In the above example, the case where the filling tank 12 and the storage tank 15 are integrated has been described, but this is not limiting. Specifically, the filling tank 12 and the storage tank 15 may be, for example, separate tanks.

[0048] In the above example, the trickling filter system 100 has been described as having one trickling filter device 10, but is not limited to this. Specifically, the trickling filter system 100 may have, for example, multiple trickling filter devices 10 that treat the water to be treated supplied from the filtration device 700 in parallel.

[0049] The trickling filter bed system 100 may also have, for example, a plurality of trickling filter bed devices 10 arranged in series. Specifically, the trickling filter bed device 10 may have, for example, a trickling filter bed device 10 (hereinafter also referred to as the first trickling filter bed device 10) and another trickling filter bed device 10 (hereinafter also referred to as the second trickling filter bed device 10) installed downstream of the first trickling filter bed device 10. In this case, for example, the space 12a of the second trickling filter bed device 10 may be sprinkled with the water to be treated discharged from the first trickling filter bed device 10, and the exhaust gas discharged from the first trickling filter bed device 10 may be supplied. Furthermore, in this case, for example, the space 12a of the first trickling filter bed device 10 may be supplied with the circulating gas returned from the second trickling filter bed device 10.

[0050] In addition, the trickling filter bed apparatus 10 may be configured to circulate at least a portion of the water to be treated. Specifically, in the trickling filter bed apparatus 10, for example, at least a portion of the water to be treated discharged from line L3 (hereinafter also referred to as circulating water) may be returned to line L2. In addition, in the trickling filter bed apparatus 10, for example, the circulating water supplied from line L3 may also be sprinkled from the sprinkler pipe 13.

[0051] In addition, in the trickling filter bed device 10, for example, hot air or high-concentration oxygen may be supplied to the space portion 12a from the line L11.

[0052] Furthermore, the trickling filter bed device 10 may be configured to supply, for example, hot air or high-concentration oxygen to the circulating water before it is returned to the line L2.

[0053] [Trickling filter bed system 200 in second embodiment] Figure 4 is a diagram illustrating a configuration example of a trickling filter bed system 200 in a second embodiment. Below, differences from the trickling filter bed system 100 described in Figure 3 will be described.

[0054] 4, the line L11 in this embodiment, for example, connects the outside of the trickling filter bed apparatus 10 with the filling section 12b in the filling tank 12. That is, unlike the line L11 in the trickling filter bed system 100, the line L11 in this embodiment is, for example, a pipe that supplies air to the filling section 12b.

[0055] Specifically, the line L11 in this embodiment communicates with, for example, a predetermined position between the upper end and the lower end of the filling section 12b (hereinafter also simply referred to as the predetermined position).

[0056] On the other hand, the line L21 in this embodiment supplies circulating gas to the space 12a, for example, similar to the line L11 in the trickling filter bed system 100.

[0057] That is, in the trickling filter bed system 200 of this embodiment, for example, air supplied from outside the trickling filter bed apparatus 10 is supplied to a predetermined position in the filling section 12b, and the air supplied from outside the trickling filter bed apparatus 10 forms a downward flow in the filling tank 12. Therefore, a space where oxygen is not sufficiently supplied (hereinafter also referred to as an anaerobic section 12b2) is formed in the portion of the filling section 12b above the predetermined position. On the other hand, a space where oxygen is sufficiently supplied (hereinafter also referred to as an aerobic section 12b1) is formed in the portion of the filling section 12b below the predetermined position. In other words, in the filling section 12b, not only is an aerobic section 12b1, which is a space where aerobic bacteria such as ammonia-oxidizing bacteria can easily grow, but also an anaerobic section 12b2, which is a space where anaerobic bacteria such as denitrifying bacteria can easily grow, is formed.

[0058] In the trickling filter bed system 200 of this embodiment, for example, the circulating gas returned via line L22 is supplied to the anaerobic section 12b2, thereby further promoting denitrification of the nitrogen components contained in the circulating gas.

[0059] Thus, in the trickling filter bed system 200 of this embodiment, the first supply section 21 supplies air to a predetermined position, for example, between the upper end position (upper end position in the filling section 12b) and the lower end position (lower end position in the filling section 12b) of the carrier 11 filled in the filling tank 12.

[0060] In addition, in the trickling filter bed system 200 of this embodiment, the second supply unit 22 supplies circulating gas, for example, to the space 12 a above the upper end position of the carrier 11 packed in the packed tank 12 .

[0061] As a result, the trickling filter bed system 200 of this embodiment can further promote denitrification of nitrogen components contained in the circulating gas returned via line L22. Therefore, the trickling filter bed system 200 of this embodiment can further reduce the amount of nitrous oxide contained in the exhaust gas discharged to the outside of the trickling filter bed device 10 via line L12.

[0062] In addition, the first supply section 21 may, for example, supply air to above the upper end position of the carrier 11 filled in the filling tank 12, and to a predetermined position between the upper end position and the lower end position of the carrier 11 filled in the filling tank 12.

[0063] [Trickling filter bed system 300 in the third embodiment] Figures 5 and 6 are diagrams illustrating an example of the configuration of a trickling filter bed system 300 in the third embodiment. Below, differences from the trickling filter bed system 100 described in Figure 3 will be described.

[0064] As shown in Figures 5 and 6, the trickling filter bed system 300 has, for example, in addition to the components of the trickling filter bed system 100, a measuring device M1, a measuring device M2, a measuring device M3, and a control device 50.

[0065] The measuring device M1 is, for example, a concentration meter that is set upstream of the branch point of line L12 with line L21 and measures the oxygen concentration in the exhaust gas discharged from the trickling filter bed device 10 (exhaust gas moving within line L12).

[0066] The measuring device M2 is, for example, a concentration meter that is set downstream of the branch point of line L12 with line L21 and measures the concentration of nitrous oxide in the exhaust gas discharged from the trickling filter bed device 10 (exhaust gas moving within line L12).

[0067] The measuring device M3 is, for example, a concentration meter that is set on the line L2 and measures the concentration of ammonia in the water to be treated that is supplied to the sprinkler pipe 13 (the water to be treated that moves within the line L2).

[0068] The trickling filter system 300 may include, for example, a storage container (not shown) for temporarily storing the exhaust gas flowing through the line L12. At least one of the measuring device M1 and the measuring device M2 may measure, for example, the concentration of oxygen or nitrous oxide in the exhaust gas stored in the storage container.

[0069] The control device 50 controls the amount of circulating gas returned to the filling tank 12 (space portion 12a) via line L21 by performing control (hereinafter also referred to as opening adjustment control) to adjust the opening of at least one of valves V1 and V2 based on, for example, at least one of the measurement results by measuring device M1, the measurement results by measuring device M2, and the measurement results by measuring device M3.

[0070] Specifically, for example, when the concentration measured by the measuring device M1 (oxygen concentration in the exhaust gas discharged from the trickling filter bed device 10) is less than a threshold value (hereinafter also referred to as the first threshold value), the control device 50 reduces the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to reduce the opening of valve V1 and control to increase the opening of valve V2.

[0071] That is, when the concentration measured by the measuring device M1 is less than the first threshold value, it means, for example, that the amount of oxygen in the filling tank 12 may be insufficient compared to the amount of organic matter, ammonia, or nitrite in the filling tank 12. In this case, it can be determined that the quality of the treated water in the line L3 in the filling tank 12 may be deteriorating.

[0072] Therefore, in this case, the control device 50 controls the ratio of the amount of oxygen to the amount of organic matter, ammonia, etc. in the filling tank 12 to increase by, for example, reducing the amount of circulating gas returned to the space 12a via line L21, in other words, by increasing the amount of exhaust gas discharged to the outside of the trickling filter bed device 10 via line L12, thereby maintaining the removal performance of organic matter, ammonia, etc., and thereby maintaining good water quality of the treated water.

[0073] Then, for example, after performing at least one of control to reduce the opening of valve V1 and control to increase the opening of valve V2, if the concentration measured by measuring device M1 becomes equal to or greater than the first threshold value, control device 50 performs at least one of control to increase the opening of valve V1 and control to reduce the opening of valve V2, thereby again increasing the amount of circulating gas returned to filling tank 12 via line L21.

[0074] In addition, when the concentration measured by the measuring device M2 (the concentration of nitrous oxide in the exhaust gas discharged from the trickling filter bed device 10) is equal to or greater than a threshold value (hereinafter also referred to as the second threshold value), the control device 50 increases the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2.

[0075] In other words, when the concentration measured by the measuring device M2 is equal to or higher than the second threshold value, it means that, for example, an increase in ammonia and the like in the filling tank 12 due to a change in the water quality of the water to be treated or a decrease in the activity of ammonia-oxidizing bacteria and the like has prevented sufficient nitrification of ammonia by ammonia-oxidizing bacteria and the denitrification of nitrogen components by denitrifying bacteria in the filling tank 12, potentially resulting in an increase in the amount of nitrous oxide generated in the filling tank 12.

[0076] Therefore, in this case, the control device 50 controls the nitrification of ammonia by ammonia-oxidizing bacteria and the denitrification of nitrogen components by denitrifying bacteria in the filled tank 12 to be more efficient by, for example, increasing the amount of circulating gas returned to the space 12a via line L21, in other words, reducing the amount of exhaust gas discharged to the outside of the trickling filter bed device 10 via line L12, thereby suppressing the amount of nitrous oxide generated in the filled tank 12.

[0077] Then, for example, if the concentration measured by the measuring device M2 becomes less than the second threshold value after performing at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2, the control device 50 again reduces the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to decrease the opening of valve V1 and control to increase the opening of valve V2.

[0078] In addition, when the concentration measured by the measuring device M3 (the concentration of ammonia in the treated water supplied to the trickling filter bed device 10) is equal to or greater than a threshold value (hereinafter also referred to as the third threshold value), the control device 50 increases the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2.

[0079] That is, it can be determined that the concentration of ammonia contained in the water to be treated supplied to the trickling filter bed apparatus 10 has a correlation (hereinafter also simply referred to as a predetermined correlation) with, for example, the concentration of nitrous oxide contained in the flue gas discharged from the trickling filter bed apparatus 10. The predetermined correlation is, for example, a relationship in which, when the concentration of ammonia contained in the water to be treated supplied to the trickling filter bed apparatus 10 increases, the concentration of nitrous oxide contained in the flue gas discharged from the trickling filter bed apparatus 10 also increases. Furthermore, the predetermined correlation is, for example, a relationship in which, when the concentration of ammonia contained in the water to be treated supplied to the trickling filter bed apparatus 10 decreases, the concentration of nitrous oxide contained in the flue gas discharged from the trickling filter bed apparatus 10 also decreases.

[0080] Therefore, the case where the concentration measured by measurement device M3 is equal to or greater than the third threshold, similar to the case where the concentration measured by measurement device M2 is equal to or greater than the second threshold, may occur when, for example, the circulation of circulating gas between the packed tank 12, line L12, and line L21 increases the amount of ammonia and other substances in the packed tank 12, thereby preventing sufficient nitrification of ammonia by ammonia-oxidizing bacteria and denitrification of nitrogen components by denitrifying bacteria in the packed tank 12, thereby increasing the amount of nitrous oxide generated in the packed tank 12. Therefore, in this case, the control device 50 controls the amount of circulating gas returned to the space 12a via line L21, for example, by increasing the amount of circulating gas returned to the space 12a via line L21, in other words, by reducing the amount of exhaust gas discharged to the outside of the trickling filter device 10 via line L12, thereby increasing the amount of nitrification of ammonia by ammonia-oxidizing bacteria and denitrification of nitrogen components by denitrifying bacteria in the packed tank 12 and suppressing the amount of nitrous oxide generated in the packed tank 12.

[0081] Then, for example, if the concentration measured by the measuring device M2 becomes less than the third threshold value after performing at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2, the control device 50 again reduces the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to decrease the opening of valve V1 and control to increase the opening of valve V2.

[0082] Note that the control device 50 may be configured to wait until a predetermined time (hereinafter simply referred to as the predetermined time) has elapsed after reducing the amount of circulating gas returned to the space 12a via the line L21 by, for example, at least one of controlling the valve V1 to decrease the opening degree and the valve V2 to increase the opening degree. Then, the control device 50 may be configured to, for example, at least one of controlling the valve V1 to increase the opening degree and the valve V2 to decrease the opening degree in response to the elapse of the predetermined time, thereby again increasing the amount of circulating gas returned to the filling tank 12 via the line L21.

[0083] Similarly, the control device 50 may be configured to wait until a predetermined time has elapsed after increasing the amount of circulating gas returned to the space 12a via line L21, for example, by at least one of controlling the valve V1 to increase the opening degree and the valve V2 to decrease the opening degree. Then, the control device 50 may be configured to again reduce the amount of circulating gas returned to the filling tank 12 via line L21 by at least one of controlling the valve V1 to decrease the opening degree and the valve V2 to increase the opening degree in response to the predetermined time having elapsed.

[0084] In the above example, the trickling filter bed system 300 has been described as having each of the measuring devices M1, M2, and M3, but this is not limited thereto. Specifically, the trickling filter bed system 300 may have, for example, some of the measuring devices M1, M2, and M3 (for example, any one of the measuring devices M1, M2, and M3). In this case, the control device 50 may perform opening adjustment control based on the measurement results of some of the measuring devices M1, M2, and M3. The control device 50 in the third embodiment will be described below.

[0085] [Control Device 50 in Third Embodiment] FIG. 7 is a diagram illustrating the hardware configuration of the control device 50. As shown in FIG.

[0086] 7, the control device 50 is, for example, an electronic device having an electronic circuit. Specifically, the control device 50 is, for example, a computer device having a CPU 501 which is a processor, a memory 502, a communication device 503, and a storage medium 504. Each unit is connected to each other via, for example, a bus 505.

[0087] The storage medium 504 has, for example, a program storage area (not shown) for storing a program 510 for performing the opening degree adjustment control. The storage medium 504 also has, for example, an information storage area 530 for storing information used when performing the opening degree adjustment control. The storage medium 504 may be, for example, a hard disk drive (HDD) or a solid state drive (SSD).

[0088] The CPU 501 performs opening adjustment control by executing a program 510 loaded into the memory 502 from the storage medium 504, for example.

[0089] The communication device 503 accesses an operation terminal (not shown) through which an operator inputs necessary information, for example, via a network (not shown) such as the Internet.

[0090] The control device 50 may include, for example, a Field Programmable Gate Array (FPGA) or an Application Specific Integrated Circuit (ASIC). The control device 50 may also include, for example, a Peripheral Interface Controller (PIC). The opening adjustment control may be performed by, for example, the FPGA or the ASIC.

[0091] [Opening degree adjustment control in the third embodiment] Next, the opening degree adjustment control in the third embodiment will be described with reference to Fig. 8, which is a flow chart illustrating the opening degree adjustment control in the third embodiment.

[0092] 8, the control device 50 waits until it is time to acquire the measurement results of at least one of the measurement devices M1, M2, and M3 (hereinafter simply referred to as the acquisition timing) (NO in step S1 in FIG. 8). The acquisition timing may be, for example, a regular interval such as every minute.

[0093] Then, when the acquisition timing arrives (YES in step S1 of FIG. 8), the control device 50 acquires the measurement results of at least one of the measurement devices M1, M2, and M3, for example (step S12 of FIG. 8).

[0094] Next, the control device 50 determines whether or not the measurement result acquired in step S12 satisfies a condition (step S13 in FIG. 8), for example.

[0095] As a result, for example, if it is determined that the measurement results obtained in step S12 satisfy the conditions (YES in step S13), the control device 50 controls at least one of the opening degree of valve V1 and the opening degree of valve V2 (step S14 in Figure 8).

[0096] Specifically, for example, if the measurement result obtained in step S12 is the concentration measured by the measuring device M1 (oxygen concentration in the exhaust gas discharged from the trickling filter bed device 10) and the concentration is less than the first threshold value, the control device 50 reduces the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to reduce the opening of valve V1 and control to increase the opening of valve V2.

[0097] Furthermore, for example, if the measurement result obtained in step S12 is the concentration measured by the measuring device M2 (the concentration of nitrous oxide in the exhaust gas discharged from the trickling filter device 10) and the concentration is equal to or greater than the second threshold value, the control device 50 increases the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2.

[0098] Furthermore, for example, if the measurement result obtained in step S12 is the concentration measured by the measuring device M3 (the concentration of ammonia in the treated water supplied to the trickling filter bed device 10) and the concentration is equal to or greater than the third threshold value, the control device 50 increases the amount of circulating gas returned to the filling tank 12 via line L21 by performing at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2.

[0099] As such, the trickling filter bed system 300 in this embodiment includes, for example, a measuring device M1 that measures the concentration of oxygen contained in the exhaust gas discharged from the packed tank 12, and a control device 50 that controls the amount of circulating gas supplied by the second supply unit 22 to the packed tank 12 in accordance with the concentration measured by the measuring device M1.

[0100] The trickling filter system 300 in this embodiment also has a measuring device M2 that measures the concentration of nitrogen oxides (e.g., nitrous oxide) contained in the exhaust gas discharged from the packed tank 12. In this case, the control device 50 in this embodiment controls the amount of circulating gas supplied to the packed tank 12 by the second supply unit 22, for example, in accordance with the concentration measured by the measuring device M2. Hereinafter, the oxygen and nitrogen oxides contained in the exhaust gas discharged from the packed tank 12 will also be simply referred to as components.

[0101] The trickling filter system 300 in this embodiment also has a measuring device M3 that measures the concentration of ammonia contained in the water to be treated that is supplied to the packed tank 12. In this case, the control device 50 in this embodiment controls the amount of circulating gas that the second supply unit 22 supplies to the packed tank 12, for example, in accordance with the concentration measured by the measuring device M3. Hereinafter, the ammonia contained in the water to be treated that is supplied to the packed tank 12 will also be simply referred to as a component.

[0102] This allows the trickling filter bed system 300 of this embodiment to adjust the amount of circulating gas returned via line L22, for example. Therefore, the trickling filter bed system 300 of this embodiment can further reduce the amount of nitrous oxide contained in the exhaust gas discharged to the outside of the trickling filter bed device 10 via line L12, while maintaining good quality of the treated water discharged via line L3.

[0103] In addition, the control device 50 in this embodiment may, for example, control the amount of exhaust gas supplied by the second supply unit 22 to the filling tank 12 in accordance with each of the concentrations measured by the measuring device M1 and the concentrations measured by the measuring device M2.

[0104] Specifically, for example, when the concentration measured by measuring device M2 (the concentration of nitrous oxide in the exhaust gas discharged from trickling filter bed device 10) is equal to or greater than a second threshold value, control device 50 may perform at least one of control to increase the opening of valve V1 or control to decrease the opening of valve V2 within a range in which the concentration measured by measuring device M1 (the concentration of oxygen in the exhaust gas discharged from trickling filter bed device 10) is equal to or greater than a first threshold value, thereby increasing the amount of circulating gas returned to filling tank 12 via line L21.

[0105] In addition, the control device 50 in this embodiment may control the amount of exhaust gas supplied by the second supply unit 22 to the filling tank 12, for example, in accordance with the concentration measured by the measuring device M1 and the concentration measured by the measuring device M3.

[0106] Specifically, for example, when the concentration measured by measuring device M3 (the concentration of ammonia in the treated water supplied to trickling filter bed device 10) is equal to or greater than a third threshold, control device 50 may perform at least one of control to increase the opening of valve V1 and control to decrease the opening of valve V2 within a range in which the concentration measured by measuring device M1 (the concentration of oxygen in the exhaust gas discharged from trickling filter bed device 10) is equal to or greater than a first threshold, thereby increasing the amount of circulating gas returned to filling tank 12 via line L21.

[0107] In addition, in the trickling filter bed system 300 of this embodiment, the line L11 may not be provided with the pump P3, for example. In this case, the induced draft fan F may, for example, both draw the air supplied to the packed tank 12 via line L11 and the circulating gas returned to the packed tank 12 via line L21. That is, the amount of air supplied to the packed tank 12 via line L11 (amount per unit time) may vary depending on, for example, the amount of circulating gas returned to the packed tank 12 via line L21. Specifically, the amount of air supplied to the packed tank 12 via line L11 may decrease depending on, for example, the amount of circulating gas returned to the packed tank 12 via line L21. The amount of air supplied to the packed tank 12 via line L11 may increase depending on, for example, the amount of circulating gas returned to the packed tank 12 via line L21. Therefore, in this case, for example, when the concentration measured by the measuring device M1 (oxygen concentration in the exhaust gas discharged from the trickling filter bed device 10) is less than the first threshold value, the control device 50 may directly increase the amount of air supplied to the filling tank 2 from the line L11 by reducing the amount of circulating gas returned to the filling tank 12 via the line L21, thereby suppressing the amount of nitrous oxide generated in the filling tank 12.

[0108] 10: Trickling filter bed device 11: Carrier 12: Filled tank 12a: Space portion 12b: Filled portion 13: Trickling pipe 14: Support member 14a: Hole 15: Storage tank 21: First supply portion 22: Second supply portion 50: Control device 100: Trickling filter bed system 101: CPU 102: Memory 103: Communication device 104: Storage medium 105: Bus 110: Program 130: Information storage area 200: Trickling filter bed system 300: Trickling filter bed system 700: Filtration device 800: Filtration device 900: Trickling filter bed system 1000: Water treatment system F: Induced draft fan L1: Line L2: Line L3: Line L4: Line L11: Line L12: Line L21: Line P1: Pump P2: Pump P3: Pump W: Water to be treated

Claims

1. A trickling filter system having: a tank filled with carriers carrying microorganisms, in which the microorganisms carry out biological treatment of water to be treated; a sprinkler pipe that sprinkles the water to be treated onto the carriers; a first supply unit that supplies oxygen-containing air to the tank; and a second supply unit that supplies at least a portion of the exhaust gas that is discharged from the tank and contains nitrogen oxides and is produced by the biological treatment to the tank.

2. A trickling filter bed system as described in claim 1, wherein the first supply unit supplies the air to at least one of a position above the upper end of the carrier filled in the tank and a predetermined position between the upper end and a lower end of the carrier filled in the tank, and the second supply unit supplies the exhaust gas above the upper end.

3. The trickling filter system of claim 1, further comprising: a measuring device for measuring the concentration of components contained in the exhaust gas; and a control device for controlling the amount of exhaust gas supplied by the second supply unit to the tank in accordance with the concentration measured by the measuring device.

4. The trickling filter system of claim 1, further comprising: a measuring device for measuring the concentration of components contained in the treated water; and a control device for controlling the amount of exhaust gas supplied to the tank by the second supply unit in accordance with the concentration measured by the measuring device.

5. A trickling filter method in a trickling filter system having a tank filled with carriers carrying microorganisms and in which the microorganisms perform biological treatment on the water to be treated, a spray pipe that sprays the water to be treated onto the carriers, a first supply unit that supplies air containing oxygen to the tank, a second supply unit that supplies to the tank at least a portion of the exhaust gas containing nitrogen oxides that is discharged from the tank and generated by the biological treatment, and a measuring device that measures the concentration of oxygen contained in the exhaust gas, wherein the trickling filter method controls the amount of exhaust gas supplied to the tank by the second supply unit in accordance with the concentration measured by the measuring device.

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