Treatment method for organic drainage and treatment device for organic drainage

Abstract

The present invention provides a method for treating organic wastewater by biologically treating the organic wastewater in an aerobic condition using a reaction tank (12) having a carrier (44), wherein the biological treatment is carried out by maintaining the dissolved phosphorus concentration in the reaction tank (12) at 0.5 mg / L or less and maintaining the dissolved nitrogen concentration in the reaction tank (12) at 3 mg / L or more.

Description

Technical Field

[0001] The present invention relates to a method for treating organic wastewater and a treatment apparatus for organic wastewater. Background Art

[0002] The treatment of organic wastewater generally uses the activated sludge method, but the BOD volume load is about 0.5 to 1.0 kg / m 3 / day, so a large floor area is required. On the other hand, the biological treatment method using a carrier can achieve a high load of 1.5 kg / m 3 / day or more, and can reduce the floor area.

[0003] For example, Patent Document 1 discloses a treatment method: in a biological treatment method using a carrier for treating organic wastewater in which the amounts of nitrogen and phosphorus relative to BOD are less than the weight ratio of BOD: nitrogen: phosphorus of 100:5:1, in order to make the amounts of nitrogen and phosphorus in the raw water become BOD: nitrogen: phosphorus weight ratio of 100:5:1 or more, while adding insufficient nitrogen and / or phosphorus to the raw water, while measuring the number of bacteria relative to the volume load of the carrier, and after the number of bacteria on the carrier becomes substantially constant, reducing the amount of nitrogen and / or phosphorus added to the raw water to BOD: nitrogen: phosphorus weight ratio of 100:2.5:0.5 or less.

[0004] Prior Art Documents

[0005] Patent Documents

[0006] Patent Document 1: Japanese Patent Application Laid-Open No. 2001-149974 Summary of the Invention

[0007] (Problems to be Solved by the Invention)

[0008] However, in the biological treatment method using a carrier, the problem is that the amount of excess sludge generated is large. In addition, if the amount of excess sludge generated is to be suppressed, the problem is that the BOD removal rate will decrease significantly.

[0009] Therefore, an object of the present invention is to provide a method for treating organic wastewater and a treatment apparatus for organic wastewater that biologically treat organic wastewater using a carrier, suppressing the amount of excess sludge generated and suppressing a significant decrease in the BOD removal rate.

[0010] (Technical Solution for Solving the Problems)

[0011] (1) The present invention relates to a method for treating organic wastewater, which is a method for biologically treating organic wastewater by using a reaction tank with a carrier under aerobic conditions. The biological treatment is carried out by maintaining the dissolved phosphorus concentration in the reaction tank at 0.5 mg / L or less and the dissolved nitrogen concentration in the reaction tank at 3 mg / L or more.

[0012] (2) Based on the method for treating organic wastewater described in (1) above, the reaction tank is composed of two or more reaction tanks connected in series. In at least one of the two or more reaction tanks connected in series, the biological treatment is carried out by maintaining the dissolved phosphorus concentration at 0.5 mg / L or less and the dissolved nitrogen concentration at 3 mg / L or more.

[0013] (3) The present invention relates to a method for treating organic wastewater, which is a method for biologically treating organic wastewater by using a reaction tank with a carrier under aerobic conditions. The BOD: nitrogen weight ratio of the organic wastewater flowing into the reaction tank is 100:1 or more. A nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more to carry out the biological treatment.

[0014] (4) Based on the method for treating organic wastewater described in (3) above, preferably, the reaction tank is composed of two or more reaction tanks connected in series. In at least one of the two or more reaction tanks connected in series, the BOD: nitrogen weight ratio of the organic wastewater flowing into the reaction tank is 100:1 or more. A nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more to carry out the biological treatment. In addition, in the present invention, the BOD: nitrogen weight ratio of the organic wastewater being 100:1 or more means that for 100 parts by weight of the BOD of the organic wastewater, the nitrogen is 1 part by weight or more.

[0015] (5) Based on the method for treating organic wastewater described in any one of (1) to (4) above, preferably, the reaction tank is a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is 1.5 kg / m 3 / day or more.

[0016] (6) The present invention relates to a treatment device for organic wastewater, which biologically treats the organic wastewater in an aerobic condition by using a reaction tank with a carrier. The treatment device for the organic wastewater maintains the dissolved phosphorus concentration in the reaction tank at 0.5 mg / L or less and maintains the dissolved nitrogen concentration in the reaction tank at 3 mg / L or more to perform the biological treatment.

[0017] (7) Based on the treatment device for the organic wastewater described in the above (6), preferably, the reaction tank is composed of two or more reaction tanks connected in series. In at least one of the two or more reaction tanks connected in series, the dissolved phosphorus concentration is maintained at 0.5 mg / L or less and the dissolved nitrogen concentration is maintained at 3 mg / L or more to perform the biological treatment.

[0018] (8) The present invention relates to a treatment device for organic wastewater, which biologically treats the organic wastewater in an aerobic condition by using a reaction tank with a carrier. The weight ratio of BOD to nitrogen of the organic wastewater flowing into the reaction tank is 100:1 or more. A nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more to perform the biological treatment.

[0019] (9) Based on the treatment device for the organic wastewater described in the above (8), preferably, the reaction tank is composed of two or more reaction tanks connected in series. In at least one of the two or more reaction tanks connected in series, the weight ratio of BOD to nitrogen of the organic wastewater flowing into the reaction tank is 100:1 or more. A nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more to perform the biological treatment.

[0020] (10) Based on the treatment device for the organic wastewater described in any one of the above (6) to (9), preferably, the reaction tank is a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is 1.5 kg / m 3 / day or more.

[0021] (Advantages of the Invention)

[0022] According to the present invention, a treatment method and a treatment device for organic wastewater that biologically treat the organic wastewater using a carrier can be provided, which can inhibit the generation amount of excess sludge and inhibit a significant decrease in the BOD removal rate. Description of the Drawings

[0023] Figure 1It is a schematic diagram showing an example of the configuration of an organic wastewater treatment device according to this embodiment.

[0024] Figure 2 It is a schematic diagram showing another example of the configuration of an organic wastewater treatment device according to this embodiment.

[0025] Figure 3 It is a schematic diagram showing another example of the configuration of an organic wastewater treatment device according to this embodiment.

[0026] Figure 4 It is a schematic diagram showing another example of the configuration of an organic wastewater treatment device according to this embodiment. Detailed Embodiment

[0027] Hereinafter, embodiments of the present invention will be described. This embodiment is an example of implementing the present invention, and the present invention is not limited to this embodiment.

[0028] Figure 1 It is a schematic diagram showing an example of the configuration of an organic wastewater treatment device according to this embodiment. Figure 1 The shown treatment device 1 includes a raw water tank 10, a reaction tank 12, a treatment water tank 14, a control device 16, a raw water pump 18, detectors 20a, 20b, an inflow pipeline 22, and a treated water pipeline 24. In addition, Figure 1 The shown treatment device 1 includes a nitrogen source supply device for supplying a nitrogen source to the reaction tank 12, a phosphorus source supply device for supplying a phosphorus source to the reaction tank 12, and a flocculant supply device for supplying a flocculant to the raw water tank 10. Figure 1 The shown nitrogen source supply device includes a nitrogen source tank 26 for containing a nitrogen source such as ammonium chloride, a nitrogen source addition pipeline 28, and a nitrogen source addition pump 30 provided in the nitrogen source addition pipeline 28. Figure 1 The shown phosphorus source supply device includes a phosphorus source tank 32 for containing a phosphorus source such as phosphoric acid, a phosphorus source addition pipeline 34, and a phosphorus source addition pump 36 provided in the phosphorus source addition pipeline 34. Figure 1 The shown flocculant supply device includes a flocculant tank 38 for containing a flocculant such as PAC or ferric chloride, a flocculant addition pipeline 40, and a flocculant addition pump 42 provided in the flocculant addition pipeline 40.

[0029] One end of a flocculant addition pipeline 40 is connected to the raw water tank 10, and the other end of the flocculant addition pipeline 40 is connected to the flocculant tank 38. One end of an inflow pipeline 22 is connected to the raw water outlet of the raw water tank 10, and the other end of the inflow pipeline 22 is connected to the inlet of the reaction tank 12. A raw water pump 18 is provided in the inflow pipeline 22. In addition, one end of a nitrogen source addition pipeline 28 is connected to the inflow pipeline 22, and the other end of the nitrogen source addition pipeline 28 is connected to the nitrogen source tank 26. In addition, one end of a phosphorus source addition pipeline 34 is connected to the inflow pipeline 22, and the other end of the phosphorus source addition pipeline 34 is connected to the phosphorus source tank 32. One end of a treated water pipeline 24 is connected to the outlet of the reaction tank 12, and the other end of the treated water pipeline 24 is connected to the inlet of the treated water tank 14. The control device 16 is electrically connected to each pump and each detector respectively, for example.

[0030] A carrier 44 for holding microorganisms is filled in the reaction tank 12. The carrier 44 is not particularly limited, and examples thereof include plastic carriers, sponge-like carriers, and gel-like carriers.

[0031] An aeration device 46 is provided at the bottom of the reaction tank 12. For example, a blower (not shown) is connected to the aeration device 46, and the air supplied from the blower is supplied into the reaction tank 12 from the aeration device 46.

[0032] Detectors 20a and 20b are provided in the reaction tank 12. The detector 20a is a device for detecting the dissolved nitrogen concentration in the reaction tank 12. In addition, the detector 20b is a device for detecting the dissolved phosphorus concentration in the reaction tank 12. The detectors 20a and 20b can be provided in the treated water tank 14 or the treated water pipeline 24. Moreover, the dissolved nitrogen concentration and the dissolved phosphorus concentration of the treated water measured by the detectors 20a and 20b can be set as the dissolved nitrogen concentration and the dissolved phosphorus concentration in the reaction tank 12. In addition, the dissolved nitrogen is, for example, nitrogen derived from the nitrogen source supplied from the nitrogen source supply device, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, etc. originally contained in the drainage. In addition, the dissolved phosphorus is, for example, phosphorus derived from the phosphorus source supplied from the phosphorus source supply device, phosphorus compounds originally contained in the drainage, etc.

[0033] The control device 16 is composed of, for example, a microcomputer and an electronic circuit constituted by a CPU that performs operations on a program, a ROM and a RAM that store the program and the operation result, reads out a given program stored in the ROM, etc., and executes the program to control the operation of the processing device 1. For example, the control device 16 controls the operation and stop of the raw water pump 18. In addition, for example, the operation and stop of the nitrogen source addition pump 30 are controlled according to the dissolved nitrogen concentration detected by the detector 20a. In addition, for example, the control device 16 controls the operation and stop of the phosphorus source addition pump 36 and the flocculant addition pump 42 according to the dissolved phosphorus concentration detected by the detector 20b.

[0034] Next, the operation of the processing device 1 shown below will be described. Figure 1 The organic drainage in the raw water tank 10 passes through the inflow pipeline 22 and is supplied to the reaction tank 12 when the control device 16 operates the raw water pump 18. Moreover, air is supplied from the aeration device 46 to the reaction tank 12, and under aerobic conditions, the organic matter in the organic drainage is biologically treated (biological treatment process) by microorganisms attached to the carrier 44 in the reaction tank 12. The treated water treated by the reaction tank 12 passes through the treatment water pipeline 24 and is supplied to the treatment water tank 14.

[0035] However, phosphorus and nitrogen in the organic drainage are taken into the cells of microorganisms as nutrient sources for the microorganisms in the reaction tank 12. Therefore, from the aspects of promoting the proliferation of microorganisms in the reaction tank 12 and even the decomposition of organic matter, it is preferable to add a phosphorus source and a nitrogen source to the organic drainage. As a result of intensive research by the inventors of the present invention, the following recognition was obtained: if the dissolved phosphorus concentration in the reaction tank 12 is high, the amount of excess sludge generated along with the decomposition of organic matter will increase. For this reason, through further repeated research, the following recognition was obtained: by maintaining the dissolved phosphorus concentration in the reaction tank 12 at an exhausted state, specifically at 0.5 mg / L or less, preferably at 0.1 mg / L or less, the amount of excess sludge generated can be suppressed. On the other hand, if the dissolved nitrogen concentration in the reaction tank 12 is in an exhausted state, the BOD removal rate will decrease significantly. Therefore, by maintaining the dissolved nitrogen concentration in the reaction tank 12 at a residual state, specifically at 3 mg / L or more, preferably at 5 mg / L or more, a significant decrease in the BOD removal rate can be suppressed.

[0036] Therefore, in the processing device 1 shown below, although the control device 16 can operate the nitrogen source addition pump 30 and the phosphorus source addition pump 36 to introduce the nitrogen source and the phosphorus source into the reaction tank 12, the control device 16 controls the supply amounts of the nitrogen source and the phosphorus source according to the dissolved phosphorus concentration and the dissolved nitrogen concentration measured by the detectors 20a and 20b, so as to maintain the dissolved phosphorus concentration in the reaction tank 12 at 0.5 mg / L or less and the dissolved nitrogen concentration at 3 mg / L or more.

[0037] Therefore, in Figure 1 the processing device 1 shown below, although the control device 16 can operate the nitrogen source addition pump 30 and the phosphorus source addition pump 36 to introduce the nitrogen source and the phosphorus source into the reaction tank 12, the control device 16 controls the supply amounts of the nitrogen source and the phosphorus source according to the dissolved phosphorus concentration and the dissolved nitrogen concentration measured by the detectors 20a and 20b, so as to maintain the dissolved phosphorus concentration in the reaction tank 12 at 0.5 mg / L or less and the dissolved nitrogen concentration at 3 mg / L or more.

[0038] In addition, when the phosphorus concentration in the organic wastewater introduced into the raw water tank 10 is high and the dissolved phosphorus concentration measured by the detector 20b exceeds 0.5 mg / L, the control device 16 operates the coagulant addition pump 42 to add a coagulant to the raw water tank 10, thereby reducing the dissolved phosphorus concentration in the organic wastewater and maintaining the dissolved phosphorus concentration in the reaction tank 12 at 0.5 mg / L or less. In addition, when the phosphorus concentration in the organic wastewater introduced into the raw water tank 10 is low and the dissolved phosphorus concentration measured by the detector 20b is 0.5 mg / L or less even without supplying a phosphorus source to the organic wastewater, a phosphorus source can still be supplied to the organic wastewater so that the dissolved phosphorus concentration in the reaction tank 12 is within a range not exceeding 0.5 mg / L.

[0039] In addition, when the nitrogen concentration in the organic wastewater introduced into the raw water tank 10 is high and the dissolved nitrogen concentration measured by the detector 20a is 3 mg / L or more even without supplying a nitrogen source to the organic wastewater, a nitrogen source for the organic wastewater can still be supplied. However, considering the discharge standard, etc., the upper limit of the dissolved nitrogen concentration in the reaction tank 12 is preferably maintained at 20 mg / L or less, and more preferably maintained at 10 mg / L or less.

[0040] Regarding the dissolved phosphorus concentration and the dissolved nitrogen concentration in the reaction tank 12, on-line analysis by a detector is preferred. However, in the case where no detector is provided, manual analysis by an operator is also possible.

[0041] In addition, for example, the detectors 20a and 20b can be arranged in the raw water tank 10, and the dissolved phosphorus concentration and the dissolved nitrogen concentration in the reaction tank 12 can be estimated based on the dissolved phosphorus concentration and the dissolved nitrogen concentration of the organic drainage. In this case, for example, a graph (or arithmetic expression, table, etc.) showing the correlation between the dissolved phosphorus concentration of the organic drainage and the dissolved phosphorus concentration in the reaction tank 12 and a graph (or arithmetic expression, table, etc.) showing the correlation between the dissolved nitrogen concentration of the organic drainage and the dissolved nitrogen concentration in the reaction tank 12 are prepared in advance through experiments or the like and stored in the control device 16. Then, the control device 16 substitutes the dissolved phosphorus concentration and the dissolved nitrogen concentration of the organic drainage measured by the detectors 20a and 20b into the above-mentioned graph or the like to estimate the dissolved phosphorus concentration and the dissolved nitrogen concentration in the reaction tank 12. When the estimated dissolved phosphorus concentration in the reaction tank 12 exceeds 0.5 mg / L, the flocculant addition pump 42 is operated to add a flocculant to the raw water tank 10. When it is 0.5 mg / L or less, no phosphorus source is added, or the phosphorus source addition pump 36 is operated in such a way that the phosphorus source is added within a range where the dissolved phosphorus concentration in the reaction tank 12 does not exceed 0.5 mg / L. In addition, when the estimated dissolved nitrogen concentration in the reaction tank 12 is less than 3 mg / L, the nitrogen source addition pump 30 is operated to supply a nitrogen source to the reaction tank 12. When it exceeds 3 mg / L, no nitrogen source is added, or the nitrogen source addition pump 30 is operated to add a given amount of nitrogen source.

[0042] The method for reducing the dissolved phosphorus concentration of the organic drainage is preferably the method of adding a flocculant to the organic drainage. However, for example, it can also be the method of diluting the organic drainage by supplying the treated water in the treatment tank 14 to the raw water tank 10.

[0043] Figure 2 It is a schematic diagram showing another example of the configuration of the organic drainage treatment device according to the present embodiment. In Figure 2 the treatment device 2, the same reference numerals are given to the same configurations as those of Figure 1 the treatment device 1, and the description thereof is omitted. Figure 2 The treatment device 2 includes a reaction tank group having a first reaction tank 12a and a second reaction tank 12b. The reaction tank group is configured such that the first reaction tank 12a is the pre-stage, the second reaction tank 12b is the post-stage, and the first reaction tank 12a and the second reaction tank 12b are arranged in series. In addition, the reaction tank group can be configured to have three or more reaction tanks arranged in series.

[0044] One end of an inflow pipeline 22a is connected to the raw water outlet of the raw water tank 10, and the other end of the inflow pipeline 22a is connected to the inlet of the first reaction tank 12a. One end of an inflow pipeline 22b is connected to the outlet of the first reaction tank 12a, and the other end of the inflow pipeline 22b is connected to the inlet of the second reaction tank 12b. One end of a treated water pipeline 24 is connected to the outlet of the second reaction tank 12b, and the other end of the treated water pipeline 24 is connected to the inlet of the treated water tank 14. In addition, one end of a nitrogen source addition pipeline 28a is connected to the inflow pipeline 22a, and the other end of the nitrogen source addition pipeline 28a is connected to the nitrogen source tank 26a. In addition, one end of a phosphorus source addition pipeline 34a is connected to the inflow pipeline 22a, and the other end of the phosphorus source addition pipeline 34a is connected to the phosphorus source tank 32a. In addition, one end of a nitrogen source addition pipeline 28b is connected to the inflow pipeline 22b, and the other end of the nitrogen source addition pipeline 28b is connected to the nitrogen source tank 26b. In addition, one end of a phosphorus source addition pipeline 34b is connected to the inflow pipeline 22b, and the other end of the phosphorus source addition pipeline 34b is connected to the phosphorus source tank 32b.

[0045] Next, the operation of the treatment device 2 shown in Figure 2 will be described.

[0046] The raw water pump 18 is operated by the control device 16, and the organic drainage water in the raw water tank 10 passes through the inflow pipeline 22a and is supplied to the first reaction tank 12a. Moreover, air is supplied from the aeration device 46 to the first reaction tank 12a, and under aerobic conditions, the organic matter in the organic drainage water is biologically treated (first biological treatment process) by microorganisms attached to the carrier 44 in the first reaction tank 12a. The first treated water treated by the first reaction tank 12a passes through the inflow pipeline 22b and is supplied to the second reaction tank 12b. Moreover, air is supplied from the aeration device 46 to the second reaction tank 12b, and under aerobic conditions, the organic matter in the first treated water is biologically treated (second biological treatment process) by microorganisms attached to the carrier 44 in the second reaction tank 12b. The treated water treated by the second reaction tank 12b passes through the treated water pipeline 24 and is supplied to the treated water tank 14.

[0047] Here, when the reaction tank is composed of two or more stages, in at least one of the reaction tanks, the dissolved phosphorus concentration is maintained in a depleted state, specifically, maintained at 0.5 mg / L or less, preferably maintained at 0.1 mg / L or less, and the dissolved nitrogen concentration is maintained in a residual state, specifically, maintained at 3 mg / L or more, preferably maintained at 5 mg / L or more. Thereby, the amount of excess sludge generated can be suppressed, and a significant decrease in the BOD removal rate can be suppressed. In Figure 2In the treatment apparatus 2 shown, for example, the control device 16 controls the operations of the nitrogen source addition pump 30a, the phosphorus source addition pump 36a (or the flocculant addition pump 42) based on the dissolved phosphorus concentration and the dissolved nitrogen concentration measured by the detectors 20a and 20b provided in the first reaction tank 12a, so as to maintain the dissolved phosphorus concentration in the first reaction tank 12a at 0.5 mg / L or less and the dissolved nitrogen concentration at 3 mg / L or more. Similarly for the second reaction tank 12b, the operations of the nitrogen source addition pump 30b, the phosphorus source addition pump 36b (flocculant addition pump 42) can be controlled based on the dissolved phosphorus concentration and the dissolved nitrogen concentration measured by the detectors 20a and 20b provided in the second reaction tank 12b, so as to maintain the dissolved phosphorus concentration in the second reaction tank 12b at 0.5 mg / L or less and the dissolved nitrogen concentration at 3 mg / L or more. Further, when the reaction tank is composed of two or more stages, it is preferable to make the dissolved phosphorus in a depleted state and the dissolved nitrogen in a remaining state in the first-stage reaction tank. In this case, since most of the organic matter is removed in the first-stage reaction tank, the amount of organic matter to be removed in the second-stage reaction tank becomes less. Therefore, even if the control of the remaining phosphorus state is not performed in the reaction tanks after the second stage, the amount of excess sludge in the entire system can be suppressed.

[0048] Hereinafter, the operating conditions and the like of the treatment apparatus of the present embodiment will be described.

[0049] From the aspects such as the cultivation of microorganisms, the pH in the reaction tank is preferably adjusted to weakly acidic to weakly alkaline, and more preferably adjusted to the range of pH 6 to 8.

[0050] The dissolved oxygen concentration in the reaction tank is preferably 0.5 mg / L or more, and more preferably 1 mg / L or more.

[0051] A solid-liquid separation device can be provided at the subsequent stage of the reaction tank. Especially when discharging the treated water into a river, it is preferable to provide a solid-liquid separation device at the subsequent stage of the reaction tank. The solid-liquid separation device is a conventionally well-known device or the like, and examples include sedimentation tanks, pressurized flotation devices, turbidity removal membrane devices, MBRs, etc.

[0052] The reaction tank can be either a fixed-bed type in which the carrier does not flow or a fluidized-bed type in which the carrier flows. The fluidized-bed type has advantages such as being less likely to have short passes of the raw water, excellent maintainability, and low introduction cost.

[0053] In addition, the BOD volume load of the reaction tank (in the case of a reaction tank group, it is the BOD volume load of all reaction tanks) is preferably 1.5 kg / m 3 / day or more, and more preferably 2.0 kg / m 3 / day or more.

[0054] As the nitrogen source, as long as it is a nitrogen compound, there is no particular limitation. For example, ammonium chloride, ammonium sulfate, diammonium hydrogen phosphate, urea, etc. can be cited. Residual ammonium sulfate, etc. generated by factories can also be applicable.

[0055] As the phosphorus source, as long as it is phosphoric acid and phosphorus compounds, there is no particular limitation. For example, dipotassium phosphate, disodium phosphate, monopotassium phosphate, monosodium phosphate, ammonium phosphate, etc. can be cited.

[0056] Nutrient salts and trace elements other than the nitrogen source and phosphorus source can be added to the raw water. For example, calcium, magnesium, iron, copper, zinc, manganese, etc. can be cited.

[0057] Examples of the carrier include plastic carriers, sponge-like carriers, gel-like carriers, etc. Among them, from the aspects of cost and durability, sponge-like carriers are preferred.

[0058] From the aspect of improving the treatment speed of biological treatment, the number of units of the carrier (the number of pores) is preferably 30 pieces / 25 mm or more, more preferably 30 pieces / 25 mm or more and 100 pieces / 25 mm or less, further preferably 40 pieces / 25 mm or more and 100 pieces / 25 mm or less, and particularly preferably 46 pieces / 25 mm or more and 100 pieces / 25 mm or less. The number of units of the carrier is obtained, for example, based on JIS K 65400-1 (Appendix 1).

[0059] From the aspect of improving the treatment speed of biological treatment, the surface area of the carrier is preferably 3000 m 2 / m 3 or more, more preferably 3500 m 2 / m 3 or more, further preferably 4000 m 2 / m 3 or more, and particularly preferably 4500 m 2 / m 3 or more. The upper limit of the surface area of the carrier can be determined by considering the number of units, the size of the carrier, etc., and there is no particular limitation.

[0060] From the aspect of improving the treatment speed of biological treatment, the biological attachment amount of the carrier is preferably 500 mg / L or more, more preferably 1000 mg / L or more. The more the biological attachment amount of the carrier, the better, and there is no particular upper limit. The upper limit is, for example, 5000 mg / L.

[0061] The shape of the carrier is not particularly limited, and examples include tetrahedral shapes such as cubic shapes, granular shapes, spherical shapes, particulate shapes, cylindrical shapes, fibrous shapes, film shapes, etc.

[0062] The size of the carrier is not particularly limited and can be appropriately set according to the size of the reaction tank, the shape of the carrier, etc. For example, if it is cube-shaped, the length of one side is preferably in the range of 3 to 20 mm, and if it is spherical, the diameter is preferably in the range of about 0.5 to 20 mm. The size of the carrier can be measured using a vernier caliper or a microscope, etc.

[0063] In order to form a flow state inside the reaction tank, the specific gravity of the carrier is at least greater than 1.0. As the true specific gravity, it is preferably 1.1 or more, or as the apparent specific gravity, it is preferably 1.01 or more.

[0064] The input amount of the carrier into the reaction tank is preferably in the range of 10 to 70% with respect to the volume of the reaction tank. If the input amount of the carrier is less than 10% with respect to the volume of the reaction tank, the reaction rate may decrease. If it exceeds 70%, the following may occur: the carrier becomes difficult to flow, and sludge may cause blockage during long-term operation, resulting in short-circuit flow of the raw water and deterioration of the treated water quality.

[0065] Figure 3 It is a schematic diagram showing another example of the configuration of the treatment apparatus for organic wastewater according to the present embodiment. Figure 3 The treatment apparatus 3 shown includes a raw water tank 10, a reaction tank 12, a treatment tank 14, a control device 16, a raw water pump 18, detectors 20a, 20b, an inflow pipeline 22, and a treated water pipeline 24. In addition, Figure 3 The treatment apparatus 3 shown includes a nitrogen source supply device for supplying a nitrogen source to the reaction tank 12 and a phosphorus source supply device for supplying a phosphorus source to the reaction tank 12. Figure 3 The nitrogen source supply device shown includes a nitrogen source tank 26 for accommodating a nitrogen source such as ammonium chloride, a nitrogen source addition pipeline 28, and a nitrogen source addition pump 30 provided in the nitrogen source addition pipeline 28. Figure 3 The phosphorus source supply device shown includes a phosphorus source tank 32 for accommodating a phosphorus source such as phosphoric acid, a phosphorus source addition pipeline 34, and a phosphorus source addition pump 36 provided in the phosphorus source addition pipeline 34.

[0066] One end of the inflow pipeline 22 is connected to the raw water outlet of the raw water tank 10, and the other end of the inflow pipeline 22 is connected to the inlet of the reaction tank 12. A raw water pump 18 is provided in the inflow pipeline 22. In addition, one end of the nitrogen source addition pipeline 28 is connected to the inflow pipeline 22, and the other end of the nitrogen source addition pipeline 28 is connected to the nitrogen source tank 26. In addition, one end of the phosphorus source addition pipeline 34 is connected to the inflow pipeline 22, and the other end of the phosphorus source addition pipeline 34 is connected to the phosphorus source tank 32. One end of the treated water pipeline 24 is connected to the outlet of the reaction tank 12, and the other end of the treated water pipeline 24 is connected to the inlet of the treatment tank 14. The control device 16 is electrically connected to each pump and each detector, respectively.

[0067] The reaction tank 12 is filled with a carrier 44 for holding microorganisms. The carrier 44 is not particularly limited, and examples thereof include plastic carriers, sponge-like carriers, and gel-like carriers.

[0068] An aeration device 46 is provided at the bottom inside the reaction tank 12. For example, a blower (not shown) is connected to the aeration device 46, and the air supplied from the blower is supplied into the reaction tank 12 from the aeration device 46.

[0069] Detectors 20a and 20b are provided in the reaction tank 12. The detector 20a is a device for detecting the dissolved nitrogen concentration inside the reaction tank 12. In addition, the detector 20b is a device for detecting the dissolved phosphorus concentration inside the reaction tank 12. The detectors 20a and 20b can be provided in the treatment water tank 14 or the treatment water pipeline 24. Moreover, the dissolved nitrogen concentration and the dissolved phosphorus concentration of the treated water measured by the detectors 20a and 20b can be used as the dissolved nitrogen concentration and the dissolved phosphorus concentration inside the reaction tank 12. In addition, the dissolved nitrogen is, for example, nitrogen derived from the nitrogen source supplied from the nitrogen source supply device, ammonia nitrogen, nitrate nitrogen, nitrite nitrogen, etc. originally contained in the drainage. In addition, the dissolved phosphorus is, for example, phosphorus derived from the phosphorus source supplied from the phosphorus source supply device, phosphorus compounds, etc. originally contained in the drainage.

[0070] The control device 16 is composed of, for example, a microcomputer and an electronic circuit constituted by a CPU that performs operations on a program, a ROM and a RAM that store the program and the operation results, reads out a given program stored in the ROM, etc., and executes the program to control the operation of the treatment device 1. For example, the control device 16 controls the operation and stop of the raw water pump 18. In addition, for example, according to the BOD in the organic drainage and the dissolved nitrogen concentration detected by the detector 20a, etc., it controls the operation and stop of the nitrogen source addition pump 30. In addition, for example, the control device 16 controls the operation and stop of the phosphorus source addition pump 36 according to the dissolved phosphorus concentration detected by the detector 20b.

[0071] Next, Figure 3 The operation of the treatment device 3 shown in the figure will be described. The organic drainage to be treated by the treatment device 3, that is, the organic drainage put into the raw water tank 10, is organic drainage with a weight ratio of BOD of the organic drainage to nitrogen less than 100:1.

[0072] When the control device 16 operates the raw water pump 18, the organic drainage in the raw water tank 10 passes through the inflow pipeline 22 and is supplied to the reaction tank 12. Moreover, air is supplied from the aeration device 46 to the reaction tank 12, and under aerobic conditions, the organic matter in the organic drainage is biologically treated (biological treatment process) in the reaction tank 12 by microorganisms attached to the carrier 44, etc. The treated water treated by the reaction tank 12 passes through the treatment water pipeline 24 and is supplied to the treatment water tank 14.

[0073] However, phosphorus and nitrogen in the organic drainage are taken into the cells of the microorganisms in the reaction tank 12 as nutrient sources for the microorganisms. Therefore, from the aspects of promoting the proliferation of the microorganisms in the reaction tank 12 and even the decomposition of organic substances, it is preferable to add a phosphorus source and a nitrogen source to the organic drainage. As a result of intensive research by the inventors of the present invention, the following knowledge was obtained: The amount of excess sludge generated accompanying the decomposition of organic substances depends on the dissolved nitrogen concentration and the dissolved phosphorus concentration in the reaction tank 12. For this reason, through further repeated research, the following knowledge was obtained: From the aspect of suppressing a significant decrease in the BOD removal rate, it is necessary to add a nitrogen source to the organic drainage so that the weight ratio of BOD: nitrogen in the organic drainage is 100:1 or more. However, if the nitrogen source is added excessively, the amount of excess sludge generated will increase. Therefore, the dissolved nitrogen concentration in the reaction tank 12 is maintained at 5 mg / L or less, preferably maintained at 3 mg / L or less. By adding a nitrogen source to the organic drainage, the amount of excess sludge generated can be suppressed. On the other hand, if the dissolved phosphorus concentration in the reaction tank 12 is in a depleted state, the biosynthesis of the microorganisms is restricted and the consumption of nitrogen will decrease. Therefore, it is difficult to maintain the dissolved nitrogen concentration in the reaction tank 12 at 5 mg / L or less. For this reason, as a result of intensive research by the inventors of the present invention, the following knowledge was obtained: If it is desired to stably maintain the dissolved nitrogen concentration in the reaction tank 12 at 5 mg / L or less, it is necessary to maintain the dissolved phosphorus concentration in the reaction tank 12 at 0.1 mg / L or more, preferably maintained at 0.5 mg / L or more. Hereinafter, examples of controlling the dissolved nitrogen concentration and the dissolved phosphorus concentration will be described.

[0074] In Figure 3 In the treatment device 3 shown, the control device 16 operates the nitrogen source addition pump 30 to introduce the nitrogen source into the reaction tank 12. At this time, the control device 16 calculates the supply amount of the nitrogen source based on the BOD of the organic drainage and a specified weight ratio specified in a range where the weight ratio of BOD: nitrogen in the organic drainage is 100:1 or more, and controls the nitrogen source addition pump 30 to supply the calculated supply amount of the nitrogen source to the reaction tank 12. The measurement of the BOD of the organic drainage is performed, for example, in accordance with the method specified in JIS K 0102. The measurement of the BOD based on this method takes time, so it is desirable to perform it in advance before the operation of the treatment device 1. In addition, for example, the TOC of the organic drainage can be detected, and the BOD can be estimated based on the detected TOC. Since the TOC can be measured quickly, by the method of estimating the BOD based on the TOC, the BOD of the organic drainage can be obtained at any time while the treatment device 3 is operating. For calculating the supply amount of the nitrogen source, the measured BOD is stored in the control device 16. In addition, if necessary, the nitrogen amount of the organic drainage can be measured. For calculating the supply amount of the nitrogen source, the measured nitrogen amount can be stored in the control device 16.

[0075] Moreover, if the dissolved nitrogen concentration measured by the detector 20a is 5 mg / L or less, the control device 16 controls, for example, the nitrogen source addition pump 30 to maintain the supply amount of the nitrogen source calculated above. Additionally, when the dissolved nitrogen concentration measured by the detector 20a exceeds 5 mg / L, the control device 16 restricts the output of the nitrogen source addition pump 30 to reduce the supply amount of the nitrogen source within a range where the weight ratio of BOD: nitrogen in the organic wastewater is 100:1 or more.

[0076] In addition, when the phosphorus concentration in the organic wastewater is low and the dissolved phosphorus concentration measured by the detector 20b is less than 0.1 mg / L, the control device 16 operates the phosphorus source addition pump 36 to introduce the phosphorus source into the reaction tank 12. Additionally, even when the phosphorus concentration in the organic wastewater is high and the dissolved phosphorus concentration measured by the detector 20b exceeds 0.1 mg / L, the phosphorus source addition pump 36 can be operated to introduce the phosphorus source into the reaction tank 12. However, considering the discharge standard, etc., the upper limit of the dissolved phosphorus concentration in the reaction tank 12 is preferably maintained at 8 mg / L or less, and more preferably maintained at 4 mg / L or less.

[0077] Regarding the dissolved phosphorus concentration and the dissolved nitrogen concentration in the reaction tank 12, it is preferable to perform on-line analysis by the detector. However, in the case where no detector is provided, it can also be manually analyzed by the operator.

[0078] In addition, for example, the detector 20b can be provided in the raw water tank 10, and the dissolved phosphorus concentration in the reaction tank 12 can be estimated based on the dissolved phosphorus concentration of the organic wastewater. In this case, for example, a graph (or arithmetic formula, table, etc.) representing the correlation between the dissolved phosphorus concentration of the organic wastewater and the dissolved phosphorus concentration in the reaction tank 12 is prepared in advance through experiments, etc., and stored in the control device 16. Then, the control device 16 substitutes the dissolved phosphorus concentration of the organic wastewater measured by the detector 20b into the above graph, etc., to estimate the dissolved phosphorus concentration in the reaction tank 12. When the estimated dissolved phosphorus concentration in the reaction tank 12 is less than 0.1 mg / L, the control device 16 operates the phosphorus source addition pump 36 and introduces the phosphorus source into the reaction tank 12.

[0079] In addition, for example, the detector 20a can be disposed in the raw water tank 10, and the dissolved nitrogen concentration in the reaction tank 12 can be estimated based on the dissolved nitrogen concentration of the organic wastewater. In this case, for example, a graph (or arithmetic expression, table, etc.) showing the correlation between the dissolved nitrogen concentration of the organic wastewater and the dissolved nitrogen concentration in the reaction tank 12 is prepared in advance through experiments or the like and stored in the control device 16. Then, the control device 16 substitutes the sum of the dissolved nitrogen concentration of the organic wastewater measured by the detector 20a and the dissolved nitrogen concentration obtained based on the supply amount of the nitrogen source set in the range where the BOD: nitrogen weight ratio of the organic wastewater is 100:1 or more into the above-mentioned graph or the like to estimate the dissolved nitrogen concentration in the reaction tank 12. When the estimated dissolved nitrogen concentration in the reaction tank 12 exceeds 5 mg / L, the control device 16 restricts the output of the nitrogen source addition pump 30 and reduces the supply amount of the nitrogen source in the range where the BOD: nitrogen weight ratio of the organic wastewater is 100:1 or more.

[0080] Figure 4 is a schematic diagram showing another example of the configuration of the organic wastewater treatment device according to the present embodiment. In Figure 4 treatment device 4, the same reference numerals are given to the same configurations as those in Figure 3 treatment device 3, and the description thereof is omitted. Figure 4 treatment device 4 includes a reaction tank group having a first reaction tank 12a and a second reaction tank 12b. The reaction tank group is configured such that the first reaction tank 12a is the pre-stage, the second reaction tank 12b is the post-stage, and the first reaction tank 12a and the second reaction tank 12b are connected in series. In addition, the reaction tank group may be configured to connect three or more reaction tanks in series.

[0081] One end of the inflow pipeline 22a is connected to the raw water outlet of the raw water tank 10, and the other end of the inflow pipeline 22a is connected to the inlet of the first reaction tank 12a. One end of the inflow pipeline 22b is connected to the outlet of the first reaction tank 12a, and the other end of the inflow pipeline 22b is connected to the inlet of the second reaction tank 12b. One end of the treated water pipeline 24 is connected to the outlet of the second reaction tank 12b, and the other end of the treated water pipeline 24 is connected to the inlet of the treatment water tank 14. In addition, one end of the nitrogen source addition pipeline 28a is connected to the inflow pipeline 22a, and the other end of the nitrogen source addition pipeline 28a is connected to the nitrogen source tank 26a. In addition, one end of the phosphorus source addition pipeline 34a is connected to the inflow pipeline 22a, and the other end of the phosphorus source addition pipeline 34a is connected to the phosphorus source tank 32a. In addition, one end of the nitrogen source addition pipeline 28b is connected to the inflow pipeline 22b, and the other end of the nitrogen source addition pipeline 28b is connected to the nitrogen source tank 26b. In addition, one end of the phosphorus source addition pipeline 34b is connected to the inflow pipeline 22b, and the other end of the phosphorus source addition pipeline 34b is connected to the phosphorus source tank 32b.

[0082] Next, the operation of the processing device 4 shown Figure 4 will be described.

[0083] The raw water pump 18 is operated by the control device 16, and the organic drainage in the raw water tank 10 passes through the inflow pipeline 22a and is supplied to the first reaction tank 12a. Moreover, air is supplied from the aeration device 46 to the first reaction tank 12a, and under aerobic conditions, the organic matter in the organic drainage is biologically treated by microorganisms attached to the carrier 44 or the like in the first reaction tank 12a (first biological treatment step). The first treated water treated by the first reaction tank 12a passes through the inflow pipeline 22b and is supplied to the second reaction tank 12b. Moreover, air is supplied from the aeration device 46 to the second reaction tank 12b, and under aerobic conditions, the organic matter in the first treated water is biologically treated by microorganisms attached to the carrier 44 or the like in the second reaction tank 12b (second biological treatment step). The treated water treated by the second reaction tank 12b passes through the treatment water pipeline 24 and is supplied to the treatment water tank 14.

[0084] Here, in the case where the reaction tank is composed of two or more stages, in at least one of the reaction tanks, the weight ratio of BOD: nitrogen of the organic drainage flowing into the reaction tank is 100:1 or more, and a nitrogen source is added to the organic drainage so that the dissolved nitrogen concentration in the reaction tank is maintained at 5 mg / L or less, preferably maintained at 3 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more, preferably maintained at 0.5 mg / L or more. Thereby, the amount of excess sludge generated can be suppressed, and a significant decrease in the BOD removal rate can be suppressed. In addition, in the case where the reaction tank is composed of two or more stages, the weight ratio of BOD: nitrogen of the organic drainage flowing into the first-stage reaction tank is 100:1 or more, and a nitrogen source is added to the organic drainage so that the dissolved nitrogen concentration in the first-stage reaction tank is maintained at 5 mg / L or less, and preferably the dissolved phosphorus concentration in the first-stage reaction tank is maintained at 0.1 mg / L or more. In this case, since most of the organic matter is removed in the first-stage reaction tank, the amount of organic matter to be removed in the second-stage reaction tank becomes smaller, so that the amount of excess sludge in the entire system can be suppressed even if the control to make the dissolved nitrogen concentration 5 mg / L or less is not performed in the reaction tanks after the second stage.

[0085] Hereinafter, the operating conditions and the like of the processing device of the present embodiment will be described.

[0086] From the aspects of culturing microorganisms and the like, the pH in the reaction tank is preferably adjusted to weakly acidic to weakly alkaline, more preferably adjusted to the range of pH 6 to 8.

[0087] The dissolved oxygen concentration in the reaction tank is preferably 0.5 mg / L or more, more preferably 1 mg / L or more, for example.

[0088] A solid-liquid separation device can be provided at the subsequent stage of the reaction tank. Especially when discharging the treated water into a river, it is preferable to provide a solid-liquid separation device at the subsequent stage of the reaction tank. The solid-liquid separation device is a conventionally well-known device, etc., and examples thereof include sedimentation tanks, pressurized flotation devices, turbidity removal membrane devices, MBRs, etc.

[0089] The reaction tank can be either a fixed-bed type where the carrier does not flow or a fluidized-bed type where the carrier flows. The fluidized-bed type has advantages such as being less likely to have short-circuit flow of the raw water, excellent maintainability, and low introduction cost.

[0090] In addition, the BOD volume load of the reaction tank (in the case of a reaction tank group, it is the BOD volume load of all reaction tanks) is preferably 1.5 kg / m 3 / day or more, more preferably 2.0 kg / m 3 / day or more.

[0091] As the nitrogen source, as long as it is a nitrogen compound, there is no particular limitation, and examples thereof include ammonium chloride, ammonium sulfate, diammonium hydrogen phosphate, urea, etc. Residual ammonium sulfate waste generated in factories can also be applicable.

[0092] As the phosphorus source, as long as it is phosphoric acid and phosphorus compounds, there is no particular limitation, and examples thereof include dipotassium phosphate, disodium phosphate, monopotassium phosphate, monosodium phosphate, ammonium phosphate, etc.

[0093] Nutrient salts and trace elements other than the nitrogen source and phosphorus source can be added to the raw water, and examples thereof include calcium, magnesium, iron, copper, zinc, manganese, etc.

[0094] Examples of the carrier include plastic carriers, sponge-like carriers, gel-like carriers, etc. Among them, from the aspects of cost and durability, sponge-like carriers are preferred.

[0095] From the aspect of improving the treatment speed of biological treatment, the number of units of the carrier (the number of pores) is preferably 30 pieces / 25 mm or more, more preferably 30 pieces / 25 mm or more and 100 pieces / 25 mm or less, further preferably 40 pieces / 25 mm or more and 100 pieces / 25 mm or less, and particularly preferably 46 pieces / 25 mm or more and 100 pieces / 25 mm or less. The number of units of the carrier is obtained based on JIS K 65400-1 (Appendix 1), for example.

[0096] From the aspect of improving the treatment speed of biological treatment, the surface area of the carrier is preferably 3000 m 2 / m 3 or more, more preferably 3500 m 2 / m3 Above, more preferably 4000 m 2 / m 3 Above, particularly preferably 4500 m 2 / m 3 Above. The upper limit of the surface area of the carrier can be determined in consideration of the number of units, the size of the carrier, etc., and there is no particular limitation.

[0097] From the aspect of improving the treatment speed of biological treatment, the amount of biological attachment of the carrier is preferably 500 mg / L or more, more preferably 1000 mg / L or more. The more the amount of biological attachment of the carrier, the better, and there is no particular upper limit, and the upper limit is, for example, 5000 mg / L.

[0098] The shape of the carrier is not particularly limited, and examples include tetrahedral shapes such as cubic shapes, granular shapes, spherical shapes, particulate shapes, cylindrical shapes, fibrous shapes, film shapes, etc.

[0099] The size of the carrier is not particularly limited and can be appropriately set according to the size of the reaction tank, the shape of the carrier, etc. For example, if it is cubic, the length of one side is preferably in the range of 3 to 20 mm, and if it is spherical, the diameter is preferably in the range of about 0.5 to 20 mm. The size of the carrier can be measured using a vernier caliper or a microscope, etc.

[0100] In order to form a flow state inside the reaction tank, the specific gravity of the carrier is at least greater than 1.0, and as the true specific gravity, it is preferably 1.1 or more, or as the apparent specific gravity, it is preferably 1.01 or more.

[0101] The input amount of the carrier into the reaction tank is preferably in the range of 10 to 70% with respect to the volume of the reaction tank. If the input amount of the carrier with respect to the volume of the reaction tank is less than 10%, the reaction rate may decrease. If it exceeds 70%, there will be a situation where the carrier becomes difficult to flow, and sludge may cause blockage during long-term operation, resulting in short-circuiting of the raw water and deterioration of the treated water quality.

[0102] Examples

[0103] Hereinafter, examples and comparative examples will be listed to more specifically and detailedly illustrate the present invention, but the present invention is not limited to the following examples.

[0104] Under the test conditions shown below, the wastewater containing isopropanol was introduced into a single reaction tank for biological treatment.

[0105] <Common test conditions in examples and comparative examples>

[0106] Volume of the reaction tank: 2 L

[0107] Carrier: Sponge-like carrier made of hydrophobic polyurethane

[0108] Carrier filling rate: 20% of the loose volume is filled

[0109] Retention time: 6 hours

[0110] Drainage containing isopropanol: BOD is about 800 mg / L, N is 2 mg / L or less, and P is 0.1 mg / L or less

[0111] BOD volumetric load: about 3.2 kg / m 3 / day

[0112] Water temperature: about 20 °C

[0113] DO in the tank: 2 mg / L or more

[0114] pH in the tank: 6.5 - 8.0

[0115] <Comparative Example 1>

[0116] Ammonium chloride and phosphoric acid were added to the drainage containing isopropanol to make the N concentration 54 mg / L and the P concentration 9.6 mg / L, and then it was introduced into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 19 mg / L and the dissolved phosphorus concentration became 4.4 mg / L. As a result, the sludge production rate per BOD removal was 31%, and the BOD removal rate was 2.8 kg / m 3 / day.

[0117] <Example 1>

[0118] Ammonium chloride was added to the drainage containing isopropanol to make the N concentration 36 mg / L and the P concentration 0.012 mg / L, and then it was introduced into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 34 mg / L and remained in a nitrogen - remaining state, and the dissolved phosphorus concentration became 0.005 mg / L and was in a phosphorus - depleted state. As a result, the sludge production rate per BOD removal was 16%, and the BOD removal rate was 2.0 kg / m 3 / day.

[0119] <Example 2>

[0120] Ammonium chloride and phosphoric acid were added to the drainage containing isopropanol to make the N concentration 37 mg / L and the P concentration 2.6 mg / L, and then it was introduced into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 23 mg / L and remained in a nitrogen - remaining state, and the dissolved phosphorus concentration became 0.062 mg / L and was in a phosphorus - depleted state. As a result, the sludge production rate per BOD removal was 20%, and the BOD removal rate was 2.5 kg / m 3 / day.

[0121] <Example 3>

[0122] Ammonium chloride and phosphoric acid were added to the wastewater containing isopropanol to make the N concentration 14 mg / L and the P concentration 1.3 mg / L, and then it was fed into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 3.5 mg / L, remaining in a nitrogen residual state, and the dissolved phosphorus concentration became 0.056 mg / L, showing a phosphorus depletion state. As a result, the sludge production rate per BOD removal was 20%, and the BOD removal rate was 2.0 kg / m 3 / day.

[0123] <Comparative Example 2>

[0124] Phosphoric acid was added to the wastewater containing isopropanol to make the N concentration 1.4 mg / L and the P concentration 6.7 mg / L, and then it was fed into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 1.6 mg / L, remaining in a nitrogen depletion state, and the dissolved phosphorus concentration became 6.5 mg / L, remaining in a phosphorus residual state. As a result, the sludge production rate per BOD removal was 29%, and the BOD removal rate was 1.3 kg / m 3 / day.

[0125] From the results of Examples 1 to 3 and Comparative Examples 1 to 2, it can be said that by setting the dissolved phosphorus concentration in the reaction tank to a depletion state and the dissolved nitrogen concentration in the reaction tank to a residual state, the amount of excess sludge generated can be inhibited, and a significant decrease in the BOD removal rate can be inhibited.

[0126] <Comparative Example 3>

[0127] Ammonium chloride and phosphoric acid were added to the wastewater containing isopropanol to make the N concentration 57 mg / L, the P concentration 9.9 mg / L, and BOD:N:P = 100:7.1:1.2, and then it was fed into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 26 mg / L, and the dissolved phosphorus concentration became 5.5 mg / L. As a result, the sludge production rate per BOD removal was 32%, and the BOD removal rate was 2.9 kg / m 3 / day.

[0128] <Example 4>

[0129] Ammonium chloride and phosphoric acid were added to the wastewater containing isopropanol to make the N concentration 8.3 mg / L, the P concentration 6.5 mg / L, and BOD:N:P = 100:1.0:0.81, and then it was fed into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 2.6 mg / L (ammoniacal nitrogen concentration 0.4 mg / L), and the dissolved phosphorus concentration became 5.3 mg / L. As a result, the sludge production rate per BOD removal was 21 - 26% (average 24%), and the BOD removal rate was 2.1 kg / m 3 / day.

[0130] <Example 5>

[0131] Ammonium chloride and phosphoric acid were added to the wastewater containing isopropanol to make the N concentration 15 mg / L, the P concentration 6.9 mg / L, and BOD:N:P = 100:1.9:0.86, and then it was introduced into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 1.0 mg / L (ammoniacal nitrogen concentration 0.2 mg / L), and the dissolved phosphorus concentration became 3.6 mg / L. As a result, the sludge production rate per BOD removal was 19 - 26% (average 23%), and the BOD removal rate was 2.4 kg / m 3 / day.

[0132] <Comparative Example 4>

[0133] Phosphoric acid was added to the wastewater containing isopropanol to make the N concentration 1.4 mg / L, the P concentration 6.7 mg / L, and BOD:N:P = 100:0.18:0.84, and then it was introduced into the reaction tank for biological treatment. As a result, the dissolved nitrogen concentration in the reaction tank became 1.6 mg / L, and the dissolved phosphorus concentration became 6.5 mg / L. As a result, the sludge production rate per BOD removal was 19 - 39% (average 29%), and the BOD removal rate was 1.3 kg / m 3 / day.

[0134] From the results of Examples 4 and 5 and Comparative Examples 3 and 4, it can be said that by making the weight ratio of BOD to nitrogen in the organic wastewater flowing into the reaction tank 100:1 or more, adding a nitrogen source to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and maintaining the dissolved phosphorus concentration in the reaction tank at 0.1 mg / L or more for biological treatment, the generation amount of excess sludge can be inhibited, and a large decrease in the BOD removal rate can be inhibited.

[0135] (Reference numeral description)

[0136] 1, 2, 3, 4 treatment devices, 10 raw water tank, 12 reaction tank, 12a first reaction tank, 12b second reaction tank, 14 treatment water tank, 16 control device, 18 raw water pump, 20a, 20b detectors, 22, 22a, 22b inflow pipelines, 24 treatment water pipelines, 26, 26a, 26b nitrogen source tanks, 28, 28a, 28b nitrogen source addition pipelines, 30, 30a, 30b nitrogen source addition pumps, 32, 32a, 32b phosphorus source tanks, 34, 34a, 34b phosphorus source addition pipelines, 36, 36a, 36b phosphorus source addition pumps, 38 flocculant tank, 40 flocculant addition pipeline, 42 flocculant addition pump, 44 carrier, 46 aeration device.

Claims

1. A method for treating organic wastewater is a method for biologically treating organic wastewater by using a reaction tank with a carrier under aerobic conditions, characterized in that the biological treatment is carried out by maintaining the dissolved phosphorus concentration in the reaction tank at 0.062 mg / L or less and maintaining the dissolved nitrogen concentration in the reaction tank at 3 mg / L or more.

2. The method for treating organic wastewater according to claim 1, characterized in that the reaction tank is composed of two or more reaction tanks connected in series, and in at least one of the two or more reaction tanks connected in series, the biological treatment is carried out by maintaining the dissolved phosphorus concentration at 0.062 mg / L or less and maintaining the dissolved nitrogen concentration at 3 mg / L or more.

3. A method for treating organic wastewater is a method for biologically treating organic wastewater by using a reaction tank with a carrier under aerobic conditions, characterized in that the weight ratio of BOD to nitrogen in the organic wastewater flowing into the reaction tank is 100:1 or more, a nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the biological treatment is carried out by maintaining the dissolved phosphorus concentration in the reaction tank at 0.1 mg / L or more.

4. The method for treating organic wastewater according to claim 3, characterized in that the reaction tank is composed of two or more reaction tanks connected in series, and in at least one of the two or more reaction tanks connected in series, the weight ratio of BOD to nitrogen in the organic wastewater flowing into the reaction tank is 100:1 or more, a nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the biological treatment is carried out by maintaining the dissolved phosphorus concentration in the reaction tank at 0.1 mg / L or more.

5. The method for treating organic wastewater according to any one of claims 1 to 4, characterized in that The reaction tank is a fluidized bed type reaction tank, and the BOD volume load of the reaction tank is 1.5 kg / m 3 / day or more.

6. An organic wastewater treatment device biologically treats organic wastewater by using a reaction tank with a carrier under aerobic conditions, characterized in that the organic wastewater treatment device carries out the biological treatment by maintaining the dissolved phosphorus concentration in the reaction tank at 0.062 mg / L or less and maintaining the dissolved nitrogen concentration in the reaction tank at 3 mg / L or more.

7. The organic wastewater treatment device according to claim 6, characterized in that the reaction tank is composed of two or more reaction tanks connected in series, and in at least one of the two or more reaction tanks connected in series, the biological treatment is carried out by maintaining the dissolved phosphorus concentration at 0.062 mg / L or less and maintaining the dissolved nitrogen concentration at 3 mg / L or more.

8. An organic wastewater treatment device biologically treats organic wastewater by using a reaction tank with a carrier under aerobic conditions, characterized in that The BOD: nitrogen weight ratio of the organic wastewater flowing into the reaction tank is 100:1 or more. A nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more to perform the biological treatment.

9. The treatment apparatus for organic wastewater according to claim 8, wherein the reaction tank is composed of two or more reaction tanks connected in series. In at least one of the two or more reaction tanks connected in series, the BOD: nitrogen weight ratio of the organic wastewater flowing into the reaction tank is 100:1 or more. A nitrogen source is added to the organic wastewater to maintain the dissolved nitrogen concentration in the reaction tank at 5 mg / L or less, and the dissolved phosphorus concentration in the reaction tank is maintained at 0.1 mg / L or more to perform the biological treatment.

10. The treatment apparatus for organic wastewater according to any one of claims 6 to 9, wherein The reaction tank is a fluidized bed type reaction tank, and the BOD volume loading of the reaction tank is 1.5 kg / m 3 / day or more.

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