JP2008194620A - Wastewater treatment method and apparatus - Google Patents

Abstract

[PROBLEMS] To prevent clogging of a screen and improve processing efficiency.
[Solution]
An anaerobic reaction tank 12 that performs anaerobic ammonia oxidation reaction by contacting waste water containing ammonia nitrogen and an entrapping immobilization support 24 containing anaerobic ammonia oxidizing bacteria under anaerobic conditions, and an upper part of the anaerobic reaction tank 12 And a screen which is provided inside the anaerobic reaction tank 12 so as to incline and drains the treated waste water and separates the entrapping immobilization support 24 and the waste water, and is substantially parallel to the screen 14 inside the screen 14. A guide plate 16 that forms a flow path 17 between the surface of the screen 14 and a nitrogen gas ejection nozzle 18 that is provided below the screen 14 and ejects nitrogen gas toward the screen 14. Prepared.
[Selection] Figure 1

Description

  The present invention relates to a wastewater treatment method and apparatus, and more particularly to a wastewater treatment method and apparatus using a carrier containing anaerobic ammonia oxidizing bacteria using ammonia and nitrous acid as substrates.

  There is a need to remove nitrogen in wastewater that causes eutrophication in closed waters. Nitrogen is contained mainly in the form of ammonia nitrogen in sewage and various industrial wastewaters.

  As a method for removing ammonia nitrogen in wastewater, there is generally a method of removing nitrogenous gas by converting it into nitrogen gas using nitrifying bacteria and denitrifying bacteria. However, in recent years, nitrogen removing method by anaerobic ammonia oxidation method Has attracted attention (for example, Patent Document 1).

  The anaerobic ammonia oxidation method is a method in which ammonia in nitrogen-containing water to be treated is used as an electron donor and nitrous acid is used as an electron acceptor for simultaneous denitrification by anaerobic ammonia oxidizing bacteria according to the following formula.

NH ₄ ⁺ +1.32 NO ₂ ⁻ +0.066 HCO ₃ ⁻ + 0.13H ⁺
→ 1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O
... (Formula 1)
Anaerobic ammonia-oxidizing bacteria have a slower growth rate than denitrifying bacteria and the like, so it is necessary to prevent them from flowing out of the treatment tank. For example, Patent Document 1 proposes a method of removing nitrogen by introducing a fluid carrier in which anaerobic ammonia-oxidizing bacteria are entrapped and immobilized into a treatment tank.

  Usually, in wastewater treatment using such a microbial carrier, a screen is provided in the vicinity of the outlet in the treatment tank in order to prevent the microbial carrier from flowing out together with the treated water. However, there is a problem that the microbial carrier tends to clog the screen.

  On the other hand, in patent document 3, in the aerobic processing tank which suppresses that a fixed support | carrier adheres by giving the flow of the treated water parallel to a screen member to a screen surface, the to-be-processed water which passed the screen member There has been proposed a method for preventing clogging of the screen by providing a backflow means for backflowing a part of the screen.

Moreover, in order to perform wastewater treatment efficiently, the inside of the treatment tank is usually stirred or aerated, but this requires running costs. On the other hand, Patent Document 4 proposes a method of circulating biogas generated in the process of methane fermentation of organic waste and using it as stirring power in order to reduce the stirring power of the methane fermentation tank. Yes.
JP 2004-275997 A JP 2005-161257 A JP 2003-71481 A JP 2001-314839 A

  However, in Patent Documents 1 and 2, a large amount of nitrogen gas is generated from the inside of the carrier due to the anaerobic ammonia oxidation reaction, so fine bubbles are attached to the surface of the carrier, and the specific gravity of the carrier is smaller than that of the treated water. For this reason, there is a problem that the carrier floats and clogs occur by filling the gaps of the screen.

  In addition, if fine bubbles adhere to the surface of the carrier, the waste water is less likely to diffuse inside the carrier, which may reduce the activity of the carrier.

  Moreover, since the said patent documents 3 and 4 do not assume the gas generated from the carrier itself, no measures for suppressing the floating of the carrier have been taken, and clogging of the screen could not be reliably prevented. .

  This invention is made | formed in view of such a subject, and it aims at providing the waste-water-treatment method and apparatus which can improve processing efficiency while preventing clogging of a screen.

  In order to achieve the above object, claim 1 of the present invention performs anaerobic ammonia oxidation reaction by contacting waste water containing ammoniacal nitrogen and a entrapping immobilization support containing anaerobic ammonia oxidizing bacteria under anaerobic conditions. A treatment tank, a screen provided at an upper portion of the treatment tank and inclined to the inside of the treatment tank, and discharges the treated waste water and separates the entrapping immobilization support and the waste water; and A guide plate which is provided on the inner side so as to be substantially parallel to the screen and forms a flow path between the screen and a nitrogen gas which is provided below the screen and which blows out nitrogen gas toward the screen There is provided a wastewater treatment apparatus characterized by comprising ejection means.

  According to the first aspect of the present invention, the nitrogen gas blowing means for maintaining anaerobicity is provided below the screen, and the nitrogen gas is supplied toward the screen. As a result, the nitrogen gas bubbles rise due to the guidance of the guide plate, forming a water flow along the screen surface, and impacting the carrier adhering to the screen and the carrier floating on the liquid surface. As a result, fine bubbles adhering to the surface of the carrier can be removed, and the carrier adhering to the screen and the carrier that has floated can be lowered. Therefore, the contact efficiency between the waste water and the carrier can be increased, the processing efficiency can be improved, and clogging of the screen by the carrier can be suppressed.

  A second aspect of the present invention according to the first aspect is characterized in that the lower part of the screen surface is made of a shielding member from which the waste water does not flow out.

  According to the second aspect, since the screen surface on which the carrier collides with the waste water is constituted by the shielding member from which the treated water does not flow out, the nitrogen gas ejected from the nitrogen gas ejecting means escapes from the lower portion of the screen and is wasted. Therefore, the waste water and the carrier can be reliably collided with the screen surface even with a small nitrogen gas ejection amount. By this impact, fine bubbles adhering to the surface of the carrier can be removed, and the carrier adhering to the screen or floating on the water surface can be lowered. Therefore, the processing efficiency of the carrier can be improved, and clogging of the screen by the carrier can be suppressed.

  A third aspect of the present invention is the method according to the first or second aspect, wherein the nitrogen gas collecting section is defined in the upper part of the processing tank and collects nitrogen gas generated by a reaction in the processing tank, and the nitrogen gas collecting section. And a circulation line that communicates with the nitrogen gas blowing means in the treatment tank and circulates the collected nitrogen gas in the treatment tank.

  According to the third aspect of the present invention, the nitrogen gas collecting part for collecting the nitrogen gas generated from the carrier surface is provided, and the collected nitrogen gas is circulated in the treatment tank. Thereby, not only can the inside of the treatment tank be maintained in a highly anaerobic state, but also nitrogen gas generated by the anaerobic ammonia oxidation reaction can be effectively used to prevent clogging of the screen.

  A fourth aspect of the present invention is the method according to the third aspect, wherein the nitrogen gas collecting portion is a lid plate disposed on an upper surface of the processing tank, and a flow that is suspended from the lid plate and formed on an upper side surface of the processing tank. A partition plate for partitioning the upper cross-section of the inlet and the outlet and being partitioned into an upper portion in the treatment tank, and a tip of the partition plate is positioned below the surface of the wastewater flowing in or out. It is characterized by.

  Thereby, a nitrogen gas collection part can be formed in the upper part in a processing tank by simple composition.

  A fifth aspect of the present invention is the method according to the third or fourth aspect, wherein the circulation line communicates the buffer tank that stores the nitrogen gas collected in the nitrogen gas collection section, the nitrogen gas collection section and the buffer tank, An introductory pipe for introducing the collected nitrogen gas into the buffer tank communicates with the buffer tank and a nitrogen gas supply port in the processing tank, and at least a part of the collected nitrogen gas is in the processing tank. A circulation pipe that circulates to the buffer tank, and a discharge pipe that communicates with the buffer tank and discharges the remaining nitrogen collected into the atmosphere.

  According to the fifth aspect, the nitrogen gas collected in the nitrogen gas collecting section is introduced into the buffer tank, and at least a part of the nitrogen gas is circulated in the processing tank. While suppressing mixing, the pressure fluctuation in a processing tank can be made small. Thereby, the inside of a processing tank can be maintained in a high anaerobic state, without newly providing the apparatus for supplying nitrogen gas.

  A sixth aspect of the present invention provides the method according to the fifth aspect, wherein the pressure measuring means for measuring the gas pressure in the nitrogen gas collecting section and the control for controlling the amount of nitrogen gas to be circulated in the processing tank based on the measurement result of the pressure measuring means. Means.

  According to the sixth aspect, the collected nitrogen gas pressure is measured, and the amount of nitrogen gas to be circulated in the treatment tank is controlled based on the measurement result. It can be maintained in an anaerobic state. Moreover, the reaction state in a processing tank can also be detected by measuring the amount of nitrogen gas.

  A seventh aspect is characterized in that, in the fifth or sixth aspect, an oxygen concentration measuring means for measuring an oxygen concentration of the nitrogen gas to be circulated is provided.

  Thus, by detecting the oxygen concentration in the nitrogen gas to be circulated, it is possible to stop the circulation of the nitrogen gas in the treatment tank or to judge the reaction state in the treatment tank.

  In order to achieve the above object, claim 8 of the present invention is anaerobic by contacting waste water containing ammonia nitrogen and a entrapping immobilization carrier containing anaerobic ammonia oxidizing bacteria in a treatment tank under anaerobic conditions. In the wastewater treatment method for performing an ammonia reaction and separating the entrapping immobilization support from the wastewater flowing to the outlet by a screen provided in the vicinity of the outlet of the treatment tank, nitrogen gas generated by the anaerobic ammonia reaction is captured. A collecting step for collecting, a circulating step for circulating the collected nitrogen gas below the screen, a nitrogen gas ejecting step for ejecting the circulated nitrogen gas toward the screen, and the ejected nitrogen A wastewater treatment method comprising: a bubble raising step for raising gas bubbles along the screen.

  A ninth aspect of the present invention provides the method according to the eighth aspect, wherein a gas pressure measuring step for measuring a pressure of the nitrogen gas collected in the collecting step and a nitrogen gas amount to be circulated below the screen are controlled based on the measurement result. And a control process.

  A tenth aspect of the present invention is the method according to the eighth or ninth aspect, further comprising an oxygen concentration measuring step of measuring an oxygen concentration of the nitrogen gas to be circulated.

  According to the present invention, clogging of the screen can be prevented and processing efficiency can be improved.

  Hereinafter, preferred embodiments of a wastewater treatment method and apparatus according to the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a schematic cross-sectional view illustrating a configuration as an example of a wastewater treatment apparatus according to the present invention.

  As shown in FIG. 1, the wastewater treatment apparatus 10 mainly includes an anaerobic reaction tank 12 (treatment tank) that performs anaerobic ammonia oxidation treatment on wastewater containing ammoniacal nitrogen, and the vicinity of the outlet of the anaerobic reaction tank 12. A screen 14 for separating the entrapping immobilization carrier from the waste water, a guide plate 16 provided substantially parallel to the screen 14 and forming a flow path between the screen 14 and a lower portion of the screen 14. And a nitrogen gas ejection nozzle (nitrogen gas ejection means) 18 for supplying nitrogen gas into the anaerobic reaction tank 12.

  The anaerobic reaction tank 12 has an inlet 20 through which waste water containing ammonia nitrogen flows in and an outlet 22 through which waste water after being treated in the anaerobic reaction tank 12 flows out at the upper part of the side surface. Others are almost sealed. In the anaerobic reaction tank 12, a plurality of entrapping immobilization carriers 24 (hereinafter also referred to as “carriers 24”) immobilizing anaerobic ammonia-oxidizing bacteria are introduced, and ammonia nitrogen flowing from the inlet 20 is removed. Nitrogen in the wastewater can be removed by contacting with the wastewater containing. A stirrer 26 is provided at the bottom of the anaerobic reaction tank 12 to stir the waste water containing the carrier.

  The method of the stirrer 26 is not particularly limited, and stirring with a propeller, gas stirring with a blower, stirring with an aquater, or the like can be used.

  The screen 14 has a structure in which a large number of wedge wires are arranged in a vertical direction at intervals in which a carrier does not pass through a rectangular frame, and inclines toward the bottom in the vicinity of the outlet 22 of the anaerobic reaction tank 12. It is provided as follows. The opening of the screen 14 such as a wedge wire is set in relation to the size of the carrier 24. For example, when the size of the carrier 24 is 1.5 to 4 mm, the opening is 0.5 to 1.5 mm. The degree is preferred.

  Further, a shielding plate 28 (shielding member) through which waste water does not pass is provided at the lower portion of the screen 14, and the guide plate 16 is disposed in parallel to the surface of the screen 14. The shielding plate 28 may be disposed on either the inside or the outside (FIG. 1) of the screen 14, but is preferably disposed on the inside. Thereby, the flow path 17 along the screen 14 is formed by the lower part (substantially lower half) of the guide plate 16 and the shielding plate 28. Further, a nitrogen gas ejection nozzle 18 is disposed immediately below the screen 14.

  As a result, the nitrogen gas bubbles ejected from the nitrogen gas ejection nozzle 18 hit the shielding plate 28 and then rise up the flow path 17 while maintaining a certain rate of rise. The rising bubbles collide with the surface of the screen 14 (portion where the shielding plate 28 is not present) and the carrier 24 floating on the surface of the water with fine bubbles adhering to the surface and giving an impact. Due to this impact, the carrier 24 clogged in the screen 14 is removed from the screen 14, and fine bubbles adhering to the carrier surface can be removed from the carrier 24.

  Further, due to the air lift effect when the bubbles of nitrogen gas ascend the flow path 17, an upward flow of wastewater is formed in the flow path 17, and the upward flow reaching the water surface is directed downward, as indicated by a broken line. It is converted into a downward flow toward the bottom of the anaerobic reaction tank 12. Accordingly, the carrier 24 having a specific gravity greater than that of the waste water after the fine bubbles are removed flows along the downward flow and flows from the vicinity of the outlet to the central portion of the anaerobic reaction tank 12. By the flow of the carrier 24, the contact efficiency between the waste water and the carrier 24 is increased, and the processing performance is improved.

  Further, by providing the shielding plate 28 at the lower part of the screen 14, the bubbles of nitrogen gas ejected from the nitrogen gas ejection nozzle 18 hit the shielding plate 28, so that the bubbles do not escape from the screen 14 and are wasted. . Thereby, a large number of bubbles rising along the screen 14 can be formed with a small amount of nitrogen gas. Here, the size of the bubbles needs to be larger than the fine bubbles generated by the anaerobic ammonia oxidation reaction (the size of the fine bubbles is about 0.01 mm to 0.5 mm), for example, 0.1 mm. About ~ 20 mm particle size is preferred.

  The distance L between the surface of the screen 14 and the surface of the guide plate 16 is not particularly limited, but is set so that a rising water flow can be formed by impacting the surface of the screen 14 and the carrier 24 can pass through. Specifically, the distance L is preferably 20 to 100 cm.

  The wastewater treatment apparatus 10 includes a nitrogen gas collection unit 30 that collects nitrogen gas generated in the anaerobic reaction tank 12, and a circulation line 32 that circulates the collected nitrogen gas into the anaerobic reaction tank 12. It is equipped with.

  The nitrogen gas collection unit 30 includes a cover plate 12 a disposed on the upper surface of the anaerobic reaction tank 12, and a partition plate 40 that hangs down from the cover plate 12 a and partitions the upper cross-section of the outlet 22 of the anaerobic reaction tank 12. Are provided. The front end of the partition plate 40 is provided so as to be located below the surface of the outflowing wastewater. The lid plate 12a is supported on the anaerobic reaction tank 12 by a support member (not shown).

  The circulation line 32 includes a buffer tank 34 for storing the collected nitrogen gas, an introduction pipe 36 for introducing the nitrogen gas into the buffer tank 34, and a part of the collected nitrogen gas in the anaerobic reaction tank 12. A circulation pipe 38 that circulates in the wastewater and a discharge pipe 39 that discharges the remaining portion of the collected nitrogen gas to the outside of the apparatus are provided.

  The buffer tank 34 is a hollow tank that communicates with the nitrogen gas collection unit 30 through the introduction pipe 36, and can introduce the collected nitrogen gas. The buffer tank 34 has a circulation pipe 38 for circulating a part of the collected nitrogen gas into the waste water in the anaerobic reaction tank 12, and a discharge pipe 39 for discharging the remaining collected nitrogen gas to the outside of the apparatus. Are communicated with each other via valves 42 and 44, respectively. The valve 42 adjusts the amount of nitrogen gas circulated to the anaerobic reaction tank 12, and the valve 44 can adjust the amount of nitrogen gas released from the buffer tank 34 to the outside of the apparatus.

  In order to prevent gas other than nitrogen gas from entering the anaerobic reaction tank 12, the volume of the buffer tank 34 is preferably as large as possible without increasing the size of the apparatus, and specifically, the volume of the anaerobic reaction tank 12. 1/1000 to 1/10. By comprising in this way, even when gas other than nitrogen gas mixes in the buffer tank 34, gas concentrations other than nitrogen gas can be diluted, and it becomes anaerobic ammonia oxidation bacteria in the anaerobic reaction tank 12. Can be minimized. Note that an adsorbent or the like that adsorbs components other than nitrogen gas may be introduced into the buffer tank 34.

  The introduction pipe 36 is provided with a gas pressure gauge 46 (pressure measurement means) for measuring the gas pressure in the anaerobic reaction tank 12. Based on the measurement result of the gas pressure gauge 46, the controller 48 (control means) controls the valve 42 so that the amount of nitrogen gas circulated in the anaerobic reaction tank 12 can be adjusted. The gas pressure gauge 46 is not particularly limited, and a known one can be used. The gas pressure in the anaerobic reaction tank 12 is preferably −1 to 3 MPa. Further, from the viewpoint of promoting the anaerobic ammonia oxidation reaction, it is more preferable to maintain the inside of the anaerobic reaction tank 12 slightly under reduced pressure.

  In this way, by monitoring the gas pressure in the anaerobic reaction tank 12 with the gas pressure gauge 46, it is possible to detect abnormalities such as negative and positive pressures due to clogging of the screen and to take measures such as stopping the apparatus.

  The circulation pipe 38 is provided with a blower 50 as a driving force for supplying nitrogen gas. A nitrogen gas injection nozzle 18 for supplying nitrogen gas from below the screen 14 of the anaerobic reaction tank 12 is formed at the tip of the circulation pipe 38.

Specifically, when the waste water volume in the anaerobic reaction tank 12 is 10 m ³ and the denitrification rate is 3 kg-N / m ³ / day, the amount of nitrogen gas circulated in the anaerobic reaction tank 12 is 18 L / Minutes.

The nitrogen gas pressure supplied into the anaerobic reaction tank 12 needs to be within a range sufficient to remove bubbles adhering to the surface of the carrier and to remove and lower the carrier 24 attached to the surface of the screen 14. is there. Specifically, when the denitrification rate in the anaerobic reaction tank 12 is 3 kg-N / m ³ / day, and about 1 to 5% of the charged carrier floats up, the rate is 1 to every 30 to 60 minutes. Nitrogen gas is supplied for 5 minutes. At this time, when the inner diameter of the circulation pipe 38 is 10 cm, the nitrogen gas pressure supplied into the anaerobic reaction tank 12 is 0.2 MPa (0.01 to 1 MPa).

  The discharge pipe 39 is preferably as long as possible in order to avoid mixing of gases other than nitrogen gas from the outside of the apparatus, and is preferably 1 m or more from the buffer tank 34. Although the discharge pipe 39 is formed in a straight line in the embodiment of FIG. 1, it is also possible to reliably prevent the introduction of a gas other than nitrogen gas from the outside by making it into a curved line. Further, by providing a backflow prevention valve (not shown) in the discharge pipe 39, it is possible to more reliably prevent gas other than nitrogen gas from being mixed from the outside.

  The retention form of the anaerobic ammonia-oxidizing bacteria in the anaerobic reaction tank 12 is not particularly limited, but the immobilization of an adhesion-immobilizing carrier in which anaerobic ammonia-oxidizing bacteria are adhered and fixed to a plastic carrier or the like, a monomer material, a prepolymer material, etc. A entrapping immobilization carrier immobilized in an immobilization material by mixing the material and anaerobic ammonia-oxidizing bacteria and polymerizing the mixed solution is preferred. As anaerobic ammonia oxidizing bacteria, pure microorganisms of anaerobic ammonia oxidizing bacteria or mixed microorganisms such as activated sludge containing anaerobic ammonia oxidizing bacteria can be used.

  The shape of the entrapping immobilization carrier 24 includes a square shape, a spherical shape, a cylindrical shape, and the like, and is not particularly limited. The size of the entrapping immobilization carrier 24 is preferably 1 to 10 mm. The filling rate of the entrapping immobilization support 24 containing anaerobic ammonia oxidizing bacteria into the anaerobic reaction tank 12 is preferably 20 to 50% by volume.

  The waste water used in the present invention is preferably one having an ammoniacal nitrogen concentration in the range of 50 to 200 mg / L. In addition, in the anaerobic ammonia oxidation reaction, nitrous acid is required to treat ammonia nitrogen, so the nitrous acid concentration in the wastewater is in the range of 1 to 1.5 times the ammonia nitrogen concentration. It is preferable.

Denitrification rate in the anaerobic reactor 12 is preferably in at 0.5~20kg-N / ^{m 3} / day, more preferably it is 0.5~5.0kg-N / ^{m 3} / day. The residence time (HRT) in the anaerobic reaction tank 12 is preferably 2 to 24 hours.

  Next, the operation of the wastewater treatment apparatus 10 according to the present invention will be described.

  Waste water containing a lot of ammonia nitrogen flows into the anaerobic reaction tank 12 from the inlet 20. In the anaerobic reaction tank 12, the carrier 24 containing anaerobic ammonia-oxidizing bacteria and the waste water come into contact with each other in an anaerobic state of nitrogen gas, and ammonia nitrogen in the waste water is removed. The waste water after being treated in the anaerobic reaction tank 12 flows out from the outlet 22 after the carrier 24 is separated by passing through the screen 14.

  In this anaerobic ammonia oxidation treatment, since nitrogen gas is generated from inside the carrier, fine nitrogen gas bubbles adhere to the surface of the carrier and the specific gravity decreases. For this reason, the carrier 24 rises and the screen 14 is easily clogged.

  In the present invention, nitrogen gas for maintaining anaerobic properties is ejected from below the screen 14 toward the screen 14 surface. As a result, the nitrogen gas bubbles ejected from the nitrogen gas ejection nozzle 18 hit the shielding plate 28 and then rise up the flow path 17 while maintaining a certain rate of rise. The rising bubbles collide with the surface of the screen 14 (portion where the shielding plate 28 is not present) and the carrier 24 floating on the surface of the water with fine bubbles adhering to the surface and giving an impact. By this impact, the carrier 24 clogged in the screen 14 can be removed from the screen 14, and fine bubbles adhering to the carrier surface can be removed from the carrier 24.

  Further, due to the air lift effect when the bubbles of nitrogen gas ascend the flow path 17, an upward flow of wastewater is formed in the flow path 17, and the upward flow reaching the water surface is directed downward, as indicated by a broken line. It is converted into a downward flow toward the bottom of the anaerobic reaction tank 12. Accordingly, the carrier 24 having a specific gravity greater than that of the waste water after the fine bubbles are removed flows along the downward flow and flows from the vicinity of the outlet to the central portion of the anaerobic reaction tank 12. By the flow of the carrier 24, the contact efficiency between the waste water and the carrier 24 is increased, and the processing performance is improved.

  The nitrogen gas generated from the inside of the carrier 24 is collected by the nitrogen gas collection unit 30, and at least a part of the nitrogen gas is supplied to the wastewater in the anaerobic reaction tank 12 through the circulation pipe 38. Thereby, in addition to the effect mentioned above, the inside of the anaerobic reaction tank 12 can be maintained in a high anaerobic state without newly providing nitrogen gas jetting means outside.

  Further, the collected nitrogen gas is introduced into the buffer tank 34, and a part thereof is returned to the anaerobic reaction tank 12 through the circulation pipe 38 and the blower 50. Further, the remaining portion of the collected nitrogen gas is discharged from the buffer tank 34 through a discharge pipe 39 having a backflow prevention valve (not shown).

  Further, the gas pressure in the anaerobic reaction tank 12 is measured by the gas pressure gauge 46, and the opening degree of the valve 44 is adjusted by the controller 48 based on the measurement result. Then, the supply amount of nitrogen gas is adjusted so that the gas pressure in the anaerobic reaction tank 12 satisfies an appropriate range (−1 to 3 MPa) and a predetermined denitrification rate.

  Thereby, in addition to the above-described effects, it is possible to minimize the adverse effects on the anaerobic state due to mixing other than nitrogen gas and the effects on the toxicity in the process. Furthermore, since the gas pressure gauge 46 can monitor the negative / positive pressure state in the anaerobic reaction tank 12, troubles such as stopping the supply of nitrogen gas when the gas amount is abnormal can be prevented.

  FIG. 2 is a diagram for explaining another aspect of the wastewater treatment apparatus according to the present invention. The present embodiment is a method of detecting the oxygen concentration in the collected nitrogen gas and circulating the nitrogen gas in the anaerobic reaction tank 12 only when a predetermined or more anaerobic state is satisfied. In FIG. 2, members having the same functions as those in the above embodiment are given the same reference numerals, and detailed descriptions thereof are omitted.

  As shown in FIG. 2, the wastewater treatment apparatus 10 ′ further includes an oxygen concentration meter 52 that measures the oxygen concentration in the nitrogen gas in the buffer tank 34 or the circulation pipe 38, and nitrogen in the buffer tank 34 or the circulation pipe 38. A vent pipe 54 for venting gas to the outside, a valve 56 provided in the vent pipe 54, and a valve 56 so as to vent nitrogen gas from the buffer tank 34 or the circulation pipe 38 according to the measurement result of the oxygen concentration. 1 is substantially the same as that shown in FIG. 1 except that a controller 58 is provided.

  Thus, when a high oxygen concentration is detected in the nitrogen gas in the circulation pipe 38, the nitrogen gas in the circulation pipe 38 can be extracted outside and not supplied into the anaerobic reaction tank 12. Thereby, high anaerobic nitrogen gas can be supplied into the anaerobic reaction tank 12. The oxygen concentration meter 52 is not limited to the embodiment shown in FIG. 2, and may be provided in the middle of the nitrogen gas collection unit 30, the buffer tank 34, and the introduction pipe 36.

  As described above, by applying the wastewater treatment method and apparatus of the present invention, it is possible to prevent clogging of the screen and improve treatment efficiency.

  The preferred embodiments of the wastewater treatment method and apparatus according to the present invention have been described above. However, the present invention is not limited to the above-described embodiments, and various aspects can be adopted.

  For example, in each of the above embodiments, an example in which the entrapping immobilization support 24 containing anaerobic ammonia oxidation bacteria is used has been described. However, the present invention is not limited to this, and the adhesion immobilization is made by attaching anaerobic ammonia oxidation bacteria to a plastic support or the like. An activated carrier or activated sludge can also be used.

  In each of the above embodiments, the example in which the circulation amount of the collected nitrogen gas is controlled by using the gas pressure gauge 46 or the controller 48 has been described. However, these are not used, and the collected nitrogen gas is simply circulated and used. You can also. Moreover, the aspect which does not circulate and utilize the nitrogen gas collected by the nitrogen gas collection part 30 in the anaerobic reaction tank 12 is also employable.

It is a cross-sectional schematic diagram explaining the structure as an example of the wastewater treatment apparatus which concerns on this invention. It is a cross-sectional schematic diagram explaining another aspect of the waste water treatment apparatus which concerns on this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 10, 10 '... Waste water treatment apparatus, 12 ... Anaerobic reaction tank, 12a ... Lid plate, 14 ... Screen, 16 ... Guide plate, 17 ... Channel, 18 ... Nitrogen gas ejection nozzle, 24 ... Carrier (inclusive fixed support) ), 30 ... Nitrogen gas collecting part, 32 ... Circulation line, 34 ... Buffer tank, 36 ... Introduction pipe, 38 ... Circulation pipe, 39 ... Discharge pipe, 40 ... Partition plate, 42, 44, 56 ... Valve, 46 ... Gas pressure gauge, 48 ... controller, 50 ... blower, 52 ... oxygen concentration meter, 54 ... venting pipe, 58 ... controller

Claims (10)

A treatment tank that performs anaerobic ammonia oxidation reaction by contacting waste water containing ammonia nitrogen and an entrapped immobilization support containing anaerobic ammonia oxidizing bacteria under anaerobic conditions;
A screen that is provided at an upper portion of the treatment tank so as to be inclined to the inside of the treatment tank, and discharges the treated wastewater and separates the entrapping immobilization support and the wastewater;
A guide plate provided inside the screen so as to be substantially parallel to the screen, and forming a flow path between the screen surface;
A nitrogen gas jetting means provided below the screen and jetting nitrogen gas toward the screen;
A wastewater treatment apparatus characterized by comprising:   The wastewater treatment apparatus according to claim 1, wherein a lower portion of the screen surface is made of a shielding member from which the wastewater does not flow out. A nitrogen gas collection section that is partitioned in an upper portion of the treatment tank and collects nitrogen gas generated by a reaction in the treatment tank;
A circulation line for communicating the nitrogen gas collection part and the nitrogen gas jetting means in the treatment tank, and circulating the collected nitrogen gas in the treatment tank;
The wastewater treatment apparatus according to claim 1 or 2, characterized by comprising: The nitrogen gas collector is
A cover plate disposed on the upper surface of the treatment tank;
A partition plate that hangs down from the lid plate and partitions the upper cross-section of the inflow port and the outflow port formed in the upper side surface of the treatment tank;
It is divided into the upper part in the processing tank by providing,
The wastewater treatment apparatus according to claim 3, wherein a leading end of the partition plate is positioned below the surface of the inflowing or outflowing wastewater. The circulation line is
A buffer tank for storing the nitrogen gas collected in the nitrogen gas collecting section;
An introductory pipe for communicating the nitrogen gas collecting part and the buffer tank, and introducing the collected nitrogen gas into the buffer tank;
A circulation pipe for communicating the buffer tank and the nitrogen gas jetting means in the processing tank, and circulating at least a part of the collected nitrogen gas in the processing tank;
A discharge pipe that communicates with the buffer tank and discharges the remainder of the collected nitrogen into the atmosphere;
The wastewater treatment apparatus according to claim 3 or 4, further comprising: Pressure measuring means for measuring the gas pressure in the nitrogen gas collecting section;
Control means for controlling the amount of nitrogen gas to be circulated in the processing tank based on the measurement result of the pressure measuring means;
The wastewater treatment apparatus according to claim 5, comprising:   The wastewater treatment apparatus according to claim 5 or 6, further comprising oxygen concentration measuring means for measuring the oxygen concentration of the nitrogen gas to be circulated. In the treatment tank, the waste water containing ammonia nitrogen and the entrapping immobilization support containing anaerobic ammonia-oxidizing bacteria are brought into contact under anaerobic conditions to carry out an anaerobic ammonia reaction, and provided near the outlet of the treatment tank. In the wastewater treatment method for separating the entrapping immobilization support from the wastewater flowing to the outlet with a screen,
A collection step of collecting nitrogen gas generated by the anaerobic ammonia reaction;
A circulation step of circulating the collected nitrogen gas below the screen;
A nitrogen gas jetting step of jetting the circulated nitrogen gas toward the screen;
And a bubble raising step of raising the bubbles of the blown nitrogen gas along the screen. A gas pressure measuring step for measuring the pressure of the nitrogen gas collected in the collecting step;
A control step of controlling the amount of nitrogen gas to be circulated below the screen based on the measured result;
The wastewater treatment method according to claim 8, comprising:   The wastewater treatment method according to claim 8 or 9, further comprising an oxygen concentration measurement step of measuring an oxygen concentration of the nitrogen gas to be circulated.

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