JP2016131928A - Method and apparatus for denitrifying nitrogen-containing waste water - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for denitrifying nitrogen-containing waste water which allow a treatment apparatus to be downsized and can stably and efficiently perform partial nitritation and anaerobic oxidation treatment in the same reaction vessel.SOLUTION: A method for denitrifying nitrogen-containing waste water includes: a step (S11) of supplying nitrogen-containing waste water into a reaction vessel accommodating microorganism carriers containing ammonia-oxidizing bacteria and anaerobic ammonia oxidizing bacteria or accommodating the microorganism carriers and activated sludge; steps (S12, S13) of sequentially supplying a gas containing oxygen and a gas containing no oxygen into the reaction vessel to agitate the nitrogen-containing waste water in the reaction vessel and denitrifying the nitrogen-containing waste water by action of the ammonia-oxidizing bacteria and the anaerobic ammonia oxidizing bacteria; and steps (S14, S15) of separating the microorganism carriers, or the microorganism carriers and the activated sludge from treated water and discharging the treated water from the reaction vessel.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a denitrification method and denitrification apparatus for nitrogen-containing wastewater, and in particular, dewatered separation liquid of sewage digested sludge, leachate, methane fermentation dehydrated separation liquid of livestock waste liquid, concentrated dewatered separation liquid of human waste and septic tank sludge, food The present invention relates to a denitrification method and a denitrification apparatus for nitrogen-containing wastewater suitable for denitrification treatment of wastewater from chemical plants and chemical plants.

In recent years, the anaerobic ammonia oxidation method, which is more energy-saving than conventional dependent denitrification, has attracted attention. The anaerobic ammonia oxidation method uses an autotrophic microorganism having NH ₄ -N as an electron donor and NO ₂ -N as an electron acceptor, and directly reacts NH ₄ -N and NO ₂ -N in an anaerobic state. And converted to nitrogen gas. For this reason, addition of organic substances such as methanol from the outside is unnecessary, and the chemical cost can be greatly reduced. Moreover, since it is the process using an autotrophic microorganism, it also has the advantage that the amount of sludge generation is extremely small.

  In order to stably obtain the denitrification reaction by the anaerobic ammonia oxidation method, nitrogen of the water to be treated, generally a part of ammonia nitrogen, is converted into nitrite nitrogen in advance, that is, partial nitritation. It is necessary to carry out the process. For example, in Patent Document 1 (Japanese Patent Laid-Open No. 2012-24707), as shown in FIG. 1, an example of a processing apparatus configured by a two-tank system including a nitritation tank and an anaerobic ammonia oxidation tank is described. . A polymer gel carrier is added into the anaerobic ammonia oxidation tank, and anaerobic ammonia oxidation bacteria are adhered and fixed on the surface of the carrier to keep the bacterial concentration in the anaerobic ammonia oxidation tank high.

  In recent years, a method of performing partial nitritation and anaerobic ammonia denitrification in the same reaction tank has also been proposed. For example, Patent Document 2 (Japanese Patent Application Laid-Open No. 2014-36959) describes a denitrification method in which partial nitritation and anaerobic ammonia oxidation are simultaneously performed in the same reaction tank. Patent Document 3 (Japanese Patent No. 5347221) also describes a denitrification method in which partial nitritation and anaerobic ammonia oxidation are simultaneously performed in the same reaction tank.

JP 2012-24707 A JP 2014-36959 A Japanese Patent No. 5347221

  However, when partial nitritation treatment and anaerobic ammonia oxidation treatment are simultaneously performed in the same reaction tank as described in Patent Documents 2 and 3, the control of the amount of aeration air and DO (dissolved oxygen) to the reaction tank is partial. Greatly affects nitritation and anaerobic ammonia oxidation performance. For example, when the aeration air volume is large and the DO is high, the nitritation performance of the ammonia-oxidizing bacteria attached to the outside of the carrier is increased, but oxygen permeation to the anaerobic ammonia-oxidizing bacteria inside the ammonia-oxidizing bacteria occurs, Denitrification performance is greatly reduced. For this reason, in the present processing apparatus and processing method, it is extremely difficult to appropriately control DO in the reaction tank, and it is difficult to stably achieve both partial nitritation and anaerobic oxidation treatment. Furthermore, in the techniques of Patent Documents 2 and 3, it is difficult to make the carrier flow in the reaction tank uniform while controlling the amount of aeration air.

  On the other hand, in the processing apparatus described in Patent Document 1, since it is necessary to prepare two reaction vessels, the equipment is larger than when the same reaction vessel is used. Furthermore, in Patent Document 1, a mechanical stirring method using an impeller is adopted in the anaerobic ammonia oxidation tank. When the carrier is caused to flow using such a mechanical stirring method, anaerobic ammonia on the surface of the carrier is used. It was found that the adhesion rate and amount of oxidized bacteria were greatly influenced by the stirring strength, impeller material, shape, amount of carrier added, and the like. That is, when the stirring strength is too strong and the impeller material is too hard, the anaerobic ammonia oxidizing bacteria adhering to the surface of the carrier are separated by mechanical friction, and the separated ammonia oxidizing bacteria rise and flow out of the reaction tank. Occurs. As a result, it may be difficult to always hold a certain amount or more of microorganisms in the reaction tank, and it may be difficult to perform a stable treatment.

  In view of the above-described problems, the present invention is capable of reducing the size of a treatment apparatus, and removing nitrogen-containing wastewater capable of performing partial nitritation and anaerobic ammonia oxidation treatment stably and efficiently in the same reaction tank. A nitriding method and a denitrification apparatus are provided.

  As a result of intensive studies by the present inventors in order to solve the above problems, oxygen-containing gas or oxygen-free gas is sequentially supplied to the same reaction tank, and partial nitritation and anaerobic ammonia oxidation treatment are performed in the same reaction tank. In addition, it was found that it is possible to perform the denitrification treatment of nitrogen-containing wastewater more efficiently while reducing the size of the apparatus by batch processing.

  The present invention completed on the basis of the above knowledge, in one aspect, supplies nitrogen-containing wastewater into a microbial carrier containing ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria or a reaction tank containing a microbial carrier and activated sludge. Supplying oxygen-containing gas or non-oxygen-containing gas into the reaction tank in order, stirring the nitrogen-containing wastewater in the reaction tank, and removing nitrogen-containing wastewater by the action of ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria. There is provided a method for denitrifying nitrogen-containing wastewater, comprising a step of nitriding, a step of separating a microbial carrier or a microbial carrier and activated sludge from the treated water, and discharging the treated water from the reaction vessel.

  The nitrogen-containing wastewater denitrification method according to the present invention is, in one embodiment, before denitrifying the nitrogen-containing wastewater, the M-alkalinity (mg / L) relative to the TN concentration (mg / L) of the nitrogen-containing wastewater. ) Includes pre-adjusting the M-alkalinity of the nitrogen-containing wastewater so that it becomes 3.5 to 4.5 times.

  In another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, the step of denitrifying the nitrogen-containing wastewater supplies oxygen-containing gas into the reaction tank and stirs the nitrogen-containing wastewater in the reaction tank Aerobic stirring step including oxidizing a part of ammonia nitrogen contained in the nitrogen-containing wastewater to nitrite nitrogen by the action of ammonia-oxidizing bacteria, and stopping the supply of oxygen-containing gas, By supplying a gas that does not contain oxygen in the reactor and stirring the nitrogen-containing wastewater in the reaction tank, nitrogen gas is removed from the ammonia nitrogen and nitrite nitrogen contained in the nitrogen-containing waste water by the action of anaerobic ammonia-oxidizing bacteria. Anaerobic stirring step including generating.

  In another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, after the anaerobic stirring step, an additional aerobic reaction is performed in which the oxygen-containing gas is supplied into the reaction tank and the nitrogen-containing wastewater in the reaction tank is stirred. A stirring step is further provided.

  In yet another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, when supplying the oxygen-containing gas into the reaction tank, the dissolved oxygen concentration in the reaction tank is determined by ammonia oxidizing bacteria. While monitoring the pH of the nitrogen-containing wastewater in the reaction tank while controlling the dissolved oxygen concentration range necessary for partial nitritation treatment, if the pH of the nitrogen-containing wastewater falls below a predetermined value, oxygen into the reaction tank Including stopping the supply of the contained gas.

  In still another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, the supply of the gas not containing oxygen is performed by circulating nitrogen gas generated in the reaction vessel into the reaction vessel.

  In another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, the treated water discharged from the reaction vessel is aerated, and the aerated liquid is solid-liquid separated to obtain a supernatant, and by solid-liquid separation. It further includes returning the obtained concentrated sludge to the reaction tank.

  In yet another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, the microorganism carrier is treated with ammonia oxidizing bacteria and anaerobic ammonia on the surface of the hydrophilic polymer carrier as the treatment progresses in the reaction vessel. This is a combined microbial carrier obtained by gradually attaching oxidizing bacteria.

  In yet another embodiment of the method for denitrifying nitrogen-containing wastewater according to the present invention, the activated sludge contains ammonia oxidizing bacteria.

  In another aspect of the present invention, a supply unit for supplying nitrogen-containing wastewater, a nitrogen-containing wastewater, a microorganism carrier containing ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria, or a microorganism carrier and activated sludge are accommodated. A reaction tank for denitrifying nitrogen-containing wastewater by sequentially supplying oxygen-containing gas or oxygen-free gas, and a reaction tank by sequentially supplying oxygen-containing gas or oxygen-free gas into the reaction tank. An aeration means for stirring the nitrogen-containing wastewater in the inside, a switching means connected to the aeration means for switching the supply of oxygen-containing gas or gas not containing oxygen, and a treatment liquid obtained by denitrification treatment as microorganisms There is provided a denitrification apparatus for nitrogen-containing wastewater comprising a carrier or a microorganism carrier and activated sludge separated from treated water and discharged to the outside of the reaction tank.

  According to the present invention, a denitrification method for nitrogen-containing wastewater capable of reducing the size of a treatment apparatus and performing stable and efficient partial nitritation and anaerobic ammonia oxidation treatment in the same reaction tank and A denitrification device can be provided.

It is the schematic showing an example of the denitrification apparatus which concerns on embodiment of this invention. It is a flowchart which shows an example of the denitrification method which concerns on embodiment of this invention. It is the schematic showing an example of the denitrification apparatus which concerns on the modification of embodiment of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The following embodiments exemplify apparatuses and methods for embodying the technical idea of the present invention, and the technical idea of the present invention specifies the structure, arrangement, etc. of components as follows. Not what you want.

  An example of a denitrification apparatus suitable for the denitrification process according to the embodiment of the present invention is shown in FIG. As shown in FIG. 1, the denitrification apparatus according to the present invention includes a reaction tank 7 for treating nitrogen-containing wastewater and a reaction tank 7 by sequentially supplying oxygen-containing gas or oxygen-free gas into the reaction tank 7. 7 is provided with an air diffuser 12 for stirring the nitrogen-containing wastewater in 7 and a switching means 5 for switching the supply of the oxygen-containing gas or the gas not containing oxygen to the reaction tank 7.

  A supply unit (supply port) 6 for supplying nitrogen-containing wastewater is provided in the upper part of the reaction tank 7. From the supply unit 6, an amount of nitrogen-containing wastewater necessary for one treatment in the reaction tank 7 is supplied. As shown in FIG. 1, at least a microbial carrier 10 carrying ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria is accommodated in the reaction tank 7. In the present embodiment, “ammonia oxidizing bacteria” means microorganisms for oxidizing a part of ammonia nitrogen contained in nitrogen-containing wastewater to nitrite nitrogen. “Anaerobic ammonia-oxidizing bacteria” means microorganisms for converting ammonia nitrogen and nitrite nitrogen contained in nitrogen-containing wastewater into nitrogen gas in an anaerobic state.

  As the microbial carrier 10 charged into the reaction tank 7, in order to stably maintain the ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria in the tank, the ammonia oxidizing bacteria and the It is preferable to use a bound microbial carrier obtained by gradually attaching anaerobic ammonia-oxidizing bacteria. The “bound microbial carrier” means a bound and immobilized carrier in which microorganisms are immobilized mainly by a binding and immobilization method in which microorganisms adhere or grow on the surface of a hydrophilic polymer carrier. In this case, an anaerobic ammonia-oxidizing bacterium is first bound and immobilized on the surface of the carrier, and then a double-layer biofilm that adheres and immobilizes the ammonia-oxidizing bacterium on the surface can be formed. By using the bound microbial carrier, a microbial carrier more suitable for the properties of the inflowing nitrogen-containing wastewater can be used, and the treatment can be made more efficient than when the microbial carrier is produced outside the apparatus. On the other hand, when using the entrapping immobilization carrier which is another immobilization method, it is preferable to entrap and fix anaerobic ammonia-oxidizing bacteria inside the carrier and to adhere and fix aerobic ammonia-oxidizing bacteria on the surface.

  Examples of the material for the hydrophilic polymer carrier include polyvinyl alcohol (PVA), polyethylene glycol (PEG), polyacrylamide, a gel polymer using a polymer such as photocurable resin, a polymer such as carrageenan and sodium alginate, polyethylene A carrier made of polyurethane, polyurethane, polypropylene or the like is preferably used.

  As the shape of the hydrophilic polymer carrier, any of a spherical shape, a square shape, and a cylindrical shape can be used, and the effective diameter thereof is preferably 1 to 20 mm which is easily separated when the treated water and the carrier are separated later. A carrier having a large number of fine pores on the surface and a carrier having innumerable irregularities on the surface can quickly attach and fix ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria, and high denitrification performance can be obtained in a short period of time.

The specific surface area of the hydrophilic polymer carrier is preferably 200 to 30000 m ² / m ³ , more preferably 200 to 20000 m ² / m ³ , still more preferably 200 to 10000 m ² / m ³ . The specific gravity of the carrier is 1.01 to 1.15, more preferably 1.01 to 1.10, and further preferably 1.01 to 1.05, which can flow more uniformly by gas stirring in the reaction vessel 7. Are preferred.

  The filling amount of the microbial carrier 10 into the reaction tank 7 is preferably 5 to 30 V%, more preferably 10 to 30 V%, and further preferably 10% by which gas can be mixed and flowed uniformly in the reaction tank 7. Is 10-20V%.

  In the reaction tank 7, coexistence of the microorganism carrier 10 and activated sludge (floating activated sludge) is desirable. Coexistence of suspended activated sludge enables averaging by activated sludge treatment even if the quality of the nitrogen-containing wastewater varies, and a stable partial nitritation treatment is obtained. The activated sludge preferably contains ammonia oxidizing bacteria.

  The air diffuser 12 is provided at the bottom of the reaction vessel 7. A blower 11 is connected to the upstream side of the air diffusion means 12 via a pipe or the like. A water trap 13 is disposed in the upstream pipe of the blower 11, and nitrogen gas generated in the reaction tank 7 is supplied to the water trap 13, and the pipe connected to the water trap 13, the blower 11, and the aeration means. 12 can be internally circulated to the reaction tank 7 as a gas not containing oxygen.

  By circulating the nitrogen gas generated in the reaction tank 7 in the reaction tank, the nitrogen gas generated in the reaction tank 7 can be used effectively, as compared with the case where a gas not containing oxygen is introduced from the outside of the apparatus. Productivity is improved. Of course, when a sufficient supply amount of nitrogen gas cannot be obtained by internal circulation, a gas not containing oxygen can be supplied from the outside of the apparatus.

  A supply unit (not shown) for supplying an oxygen-containing gas (for example, air) is connected to the upstream pipe of the blower 11 in FIG. The switching means 5 performs an oxygen-containing gas and a gas not containing oxygen (nitrogen gas from the reaction tank 7) according to the processing state of the reaction tank 7. For example, when it is desired to advance the partial nitritation treatment preferentially in a batch manner in the reaction tank 7, the oxygen-containing gas is supplied from the aeration means 12 by the switching means 5. When the anaerobic ammonia oxidation treatment is desired to proceed preferentially in a batch manner, the supply of oxygen-containing gas is stopped by the switching means 5 so that a gas not containing oxygen is supplied from the aeration means 12.

  The reaction vessel 7 is provided with a DO meter 2, a pH meter 3, and an ORP meter 4, and can measure the dissolved oxygen concentration (DO), pH, and oxidation-reduction potential (ORP) of the nitrogen-containing wastewater in the reaction vessel 7. It has become. With the DO meter 2, the pH meter 3, and the ORP meter 4, it is possible to determine the end point of the reaction when the partial nitritation treatment and the anaerobic ammonia oxidation treatment are performed in a batch process. The reaction tank 7 may be provided with an exhaust port 14 through which exhaust gas generated in the reaction tank 7 can be discharged to the outside of the reaction tank 7. The treated water finally obtained by denitrification treatment in the reaction tank 7 is separated from the microorganism carrier 10 and activated sludge through the discharge part 15 and discharged to the outside.

  Next, an example of the denitrification method according to the present embodiment will be described using the flowchart shown in FIG. The denitrification method according to this embodiment is a step of supplying nitrogen-containing wastewater into a microbial carrier containing ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria, or a reaction tank 7 containing the microbial carrier and activated sludge. (S11) and an oxygen-containing gas or a gas not containing oxygen are sequentially supplied into the reaction tank 7 to stir the nitrogen-containing wastewater in the reaction tank 7, and nitrogen is contained by the action of ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria. Steps for denitrifying wastewater (S12, S13), supply of oxygen-containing gas or oxygen-free gas into the reaction tank 7 is stopped, and the microbial carrier (and activated sludge) is separated from the treated water (S14). ) And discharging the treated water from the reaction tank 7 (S15).

  In the step of supplying nitrogen-containing wastewater into the reaction tank 7 (S11), an amount of nitrogen-containing wastewater necessary for one treatment in the reaction tank 7 is supplied into the reaction tank 7. Nitrogen-containing wastewater includes sewage digestion sludge dewatered separation liquid, leachate, livestock wastewater methane fermentation dewatered separation liquid, human waste and septic tank sludge concentrated dewatered separation liquid, food and chemical factory wastewater, inorganic discharged in semiconductor manufacturing processes Chemical waste water is used.

  This nitrogen-containing wastewater has a M-alkaliness (mg / L) of 3.5 to 4.5 times the TN concentration (mg / L) of the nitrogen-containing wastewater before denitrification treatment in the reaction tank 7. It is preferable to adjust the M-alkalinity of the nitrogen-containing wastewater in advance so that it is more preferably 3.7 to 4.4 times, and even more preferably 3.9 to 4.1 times. Adjustment of the M-alkalinity / TN concentration ratio of nitrogen-containing wastewater is performed by adding an acid such as sulfuric acid or hydrochloric acid or an alkali such as sodium hydroxide, sodium carbonate or sodium bicarbonate according to the properties of the nitrogen-containing wastewater. Adjustment is possible. The adjustment of the M-alkalinity / TN concentration ratio of the nitrogen-containing wastewater may be performed in advance before being supplied to the reaction tank 7 or may be added directly to the reaction tank.

  Next, by supplying an oxygen-containing gas into the reaction tank 7 and stirring the nitrogen-containing wastewater in the reaction tank 7, a part of ammonia nitrogen contained in the nitrogen-containing wastewater is sublimated by the action of the ammonia oxidizing bacteria. An aerobic stirring step including oxidation to nitrate nitrogen is performed (step S12).

  Specifically, the blower 11 of FIG. 1 is activated, the switching means 5 is switched to open the air intake port so as to take in the oxygen-containing gas, and the oxygen is supplied into the reaction tank 7 through the air diffuser means 12. The aeration of the reaction tank 7 and the carrier flow are performed by causing a liquid flow in the nitrogen-containing wastewater in the tank 7. Thereby, the partial nitritation process which oxidizes a part of ammonia nitrogen contained in nitrogen-containing wastewater to nitrite nitrogen by the action of the ammonia oxidizing bacteria proceeds.

The aeration air volume of the oxygen-containing gas is preferably 5 to 100 L / m ³ / min, more preferably 5 to 50 L / m in order to allow the microorganism carrier 10 and activated sludge to flow sufficiently in the reaction tank 7. ³ / min, more preferably 5 to 20 L / m ³ / min.

  In step S12, in order to perform partial nitritation stably and to avoid oxygen inhibition to anaerobic ammonia oxidizing bacteria adhering to the microbial carrier, the degree of aeration is adjusted by appropriately adjusting the degree of opening and closing of the air intake. It is important to control the dissolved oxygen concentration (DO) of the nitrogen-containing wastewater in the reaction tank 7 to the dissolved oxygen concentration range necessary for the partial nitritation treatment by ammonia oxidizing bacteria by adjusting

  Specifically, while confirming with the DO meter 2 in FIG. 1, it is preferable to control the DO of nitrogen-containing wastewater in the reaction tank 7 to 0.3 to 2.0 mg / L, more preferably 0.5 to Control to 1.0 mg / L.

  The reaction time in step S12 can be controlled by the pH of the nitrogen-containing wastewater in the reaction tank 7. By adjusting the ratio of M-alkalinity to the TN concentration (or soluble TN concentration) of the nitrogen-containing wastewater to 3.5 to 4.5 times in advance, the pH is around 7 or When it falls below that, it can be set as the completion | finish time of partial nitritation treatment reaction.

  Therefore, in step S12, the dissolved oxygen concentration in the reaction vessel 7 is set to a dissolved oxygen concentration range (DO = 0.3 to 2.0 mg / L) necessary for partial nitritation treatment with ammonia oxidizing bacteria. 1, the pH of the nitrogen-containing wastewater is monitored by the pH meter 3 in FIG. 1, and the pH of the nitrogen-containing wastewater is not more than a predetermined value (7.5 or less, more preferably 6.5 to 7.5, still more preferably In the case of 6.5 to 7.0), it is preferable to stop the supply of the oxygen-containing gas into the reaction vessel 7 and end the step S12.

  After the supply of the oxygen-containing gas is stopped, ammonia-containing nitrogen and nitrous acid contained in the nitrogen-containing wastewater are supplied by supplying a gas not containing oxygen into the reaction tank 7 and stirring the nitrogen-containing wastewater in the reaction tank. An anaerobic stirring step including generating nitrogen gas from the functional nitrogen by the action of anaerobic ammonia oxidizing bacteria is performed (step S13).

The supply amount of the gas not containing oxygen is preferably 5 to 100 L / m ³ / min in order to sufficiently flow the microorganism carrier 10 and the activated sludge in the reaction tank 7 as in step S12. Preferably it is 5-50 L / m < ³ > / min, More preferably, it is 5-20 L / m < ³ > / min.

  The reaction in step S13 can be appropriately and stably performed by controlling the pH and ORP of the nitrogen-containing wastewater in the reaction tank 7. That is, as the anaerobic ammonia oxidation treatment proceeds, the pH increases, so when the pH in the reaction tank 7 increases according to the detection result of the pH meter 3, sulfuric acid or hydrochloric acid is injected. Thus, the pH in the reaction vessel 7 is controlled to 8.5 or less, preferably 8.0 or less.

  Furthermore, it is preferable to monitor the ORP of the nitrogen-containing wastewater by the ORP meter 4. When the ORP rises to 50 mV or more, the activity of the anaerobic ammonia oxidizing bacteria may be reduced. Therefore, ORP is 50 mV or less, preferably 20 mV or less by mixing organic additives in the reaction tank 7 temporarily. More preferably, it can be maintained at 0 mV or less. Alternatively, the ORP may be lowered by increasing the amount of internal circulation of a gas not containing oxygen (nitrogen gas). Alternatively, the denitrification processing time may be lengthened before the ORP decreases by a predetermined value. Examples of organic substances to be added include methanol, ethanol, acetic acid, sodium acetate, glucose, peptone, organic sludge and the like.

  In step S14, the supply of the oxygen-containing gas or the oxygen-free gas from the air diffuser 12 to the reaction tank 7 is stopped, and the microorganism carrier flowing in the nitrogen-containing wastewater in the reaction tank 7 and the activated sludge are removed. It separates from treated water by settling or floating. The separated treated water is discharged from the discharge unit 15 provided in the reaction tank 7 in step S15.

  In step S16, when there is no new treatment target (nitrogen-containing wastewater), the process is terminated. In step S16, when a new treatment target (nitrogen-containing wastewater) is supplied to the reaction tank 7 and it is desired to continue the denitrification treatment, the process returns to step S11 and steps S11 to 15 are repeated.

  According to the denitrification apparatus and the denitrification method according to the embodiment of the present invention, in the same reaction tank, the aeration process with oxygen-containing gas and the gas stirring by the internal nitrogen gas circulation are performed by the action of the microbial carrier or the microbial carrier and activated sludge. By performing this aeration step, the aerobic and anaerobic sections can be stably maintained, and the partial nitritation and the anaerobic ammonia oxidation reaction can be efficiently obtained. Therefore, the denitrification performance can be improved as compared with the conventional method.

  Furthermore, since both the aerobic stirring step (S12) and the anaerobic stirring step (S13) flow the carrier in the reaction tank 7 by the gas stirring method, there is almost no mechanical impact on the carrier and it is uniform. The anaerobic ammonia oxidizing bacteria and ammonia oxidizing bacteria can adhere to the surface of the microorganism carrier at a high concentration.

  Furthermore, in the reaction tank 7, the carrier and the activated sludge are stably held, so that ammonia oxidizing bacteria and anaerobic ammonia oxidizing bacteria can be simultaneously held, and the partial nitritation and the anaerobic ammonia oxidation reaction are performed. Obtained efficiently.

  Furthermore, when activated sludge is coexisted with the microorganism carrier in the reaction tank 7, oxygen consumption by activated sludge is mainly used in the aerobic aeration process in which oxygen gas is introduced. There is almost no oxygen transfer to the bacteria, and there is no concern about inhibition.

  In addition, after the step (S12, 13) of denitrifying the nitrogen-containing wastewater in the reaction tank 7 described above, the oxygen-containing gas is further supplied into the reaction tank 7 and the nitrogen-containing wastewater in the reaction tank 7 is stirred. An aerobic stirring step may be further provided. By performing the additional aerobic stirring step, nitrogen gas adhering to the microbial carrier or activated sludge can be removed by aeration, so that the microbial carrier and activated sludge can be stably separated from the treated water. .

  Alternatively, as shown in FIG. 3, the treated water discharged from the reaction tank 7 is guided to the aeration tank 9 and aerated, and the aerated liquid obtained in the aeration tank 9 is separated into a solid-liquid separation in the solid-liquid separation tank (sedimentation basin 17). Then, the supernatant is obtained as treated water, and the concentrated sludge obtained by solid-liquid separation is returned to the reaction tank 7 via the return line 16. Moreover, you may extract some concentrated sludge as the excess sludge 18 for reaction tank MLSS adjustment. Thereby, the effect that the reduction of the treated water SS by the stable separation of the activated sludge and the setting of the reaction tank MLSS concentration can be easily and highly maintained is obtained. If the reaction tank MLSS concentration can be maintained high, not only can the raw water quality of the processing target be changed, but also the partial nitritation reaction rate can be improved, and the partial nitritation step can be completed in a short time.

  Examples of the present invention will be described below together with comparative examples, but these examples are provided for better understanding of the present invention and its advantages, and are not intended to limit the invention.

Example 1
Nitrogen-containing wastewater (raw water) was treated as follows.
(1) One batch of raw water was introduced into the top-sealed reaction tank 7.
(2) The blower 11 is started, the air inlet is opened using the switching means 5 and the oxygen-containing gas (air) is taken in, so that the aeration in the reaction tank 7 and the carrier flow are performed through the air diffusion means 12. It was. This treatment step was performed for the purpose of oxidizing a part of the ammonia nitrogen in the raw water to nitrite nitrogen.
(3) While the blower 11 was operated, the switching means 5 was switched to continue aeration of gas stirring using the internal circulation gas, and the carrier flow was performed. This treatment step was performed for the purpose of nitrogen removal by the reaction of nitrite nitrogen and ammonia nitrogen obtained in step (2) to generate nitrogen gas. In the anaerobic ammonia oxidation reaction, inorganic carbonate is consumed and the pH rises. Therefore, at the start of step (3), an aqueous inorganic carbonate solution was added and pH control was performed by injecting an aqueous acid solution.
(4) Aeration was stopped, the carrier was allowed to settle or float, and the treated liquid after separation was discharged through the discharge unit 15.

  The batch processing was basically repeated in the order of (1) → (2) → (3) → (4) → (1) as described above. If it is difficult to separate the sedimented carrier in step (4), after the completion of step (3), the switching means 5 is switched, the air intake is opened again and aerated, and the nitrogen gas adhering to the carrier is removed by aeration. Later, step (4) was performed again.

In the step (2), partial nitritation treatment was performed to convert a part of NH ₄ —N contained in the raw water into NO ₂ —N by the action of ammonia oxidizing bacteria adhering to the surface of the microorganism carrier. In order to stably perform this partial nitritation treatment and to minimize oxygen inhibition to anaerobic ammonia-oxidizing bacteria adhering to the microorganism carrier, the DO in the reaction vessel 7 was controlled. At the same time, the pH of the raw water in the reaction vessel 7 was monitored. The reaction time in step (3) was controlled by ORP and pH. While injecting sulfuric acid or hydrochloric acid into the reaction vessel 7, the reaction vessel pH was 8.5 or less, preferably 8.0 or less, and the ORP was controlled to 50 mV or less.

  Table 1 shows the processing conditions for carrying out the sewage digested sludge dewatered filtrate in the above processing flow. Table 2 shows the average water quality results of raw water and treated water that were treated for about 2 months continuously under the present treatment conditions.

In Example 1, batch processing was performed with a cycle of raw water introduction time 5 minutes, partial nitritation process time 3 h, anaerobic ammonia oxidation process time 3 h, re-aeration process time 15 minutes, and sedimentation separation time 15 minutes. The reaction tank 7 has an average diameter of 4 mm, a specific gravity of 1.01, and a polymer gel carrier mainly composed of polyvinyl alcohol (PVA) as insufficient alkali so that when raw water is introduced, the M-alkaline degree is 4 times that of TN. A fixed amount of Na ₂ CO ₃ aqueous solution was poured into the reaction tank together with raw water. In addition, after the partial nitritation step, a predetermined amount of Na ₂ CO ₃ aqueous solution was added as inorganic carbonic acid before the start of the anaerobic ammonia oxidation step. The injection was controlled with an aqueous H ₂ SO ₄ solution so that the pH during the anaerobic ammonia oxidation treatment was 8.0 or lower and ORP 50 mV or lower. As a result, as shown in Table 2, a stable denitrification performance with a TN removal rate of 84.8% was obtained.

(Example 2)
As shown in FIG. 3, as in Example 1, the raw water was batch-processed in the reaction tank 7 to perform the partial nitritation process and the anaerobic ammonia oxidation process, and then the treatment liquid separated from the reaction tank 7 by the carrier was treated with the aeration tank 9. The aerated liquid obtained in the aeration tank 9 is solid-liquid separated in the solid-liquid separation tank (sedimentation basin 17) to obtain the supernatant as treated water, and the concentration obtained by solid-liquid separation. The sludge was returned to the reaction tank 7. The treatment process was performed according to the following procedure and time. (1) Raw water introduction + sludge return 10 minutes → (2) Partial nitritation step 2h, (3) Anaerobic ammonia oxidation step 3h → (4) Reactor treatment liquid discharge + re-aeration 15 minutes. Batch processing was performed in the cycle of (1) → (2) → (3) → (4) → (1). Here, since the sedimentation basin 17 is separately installed, activated sludge can be settled and separated during batch processing, and a high-concentration return sludge was obtained. Table 3 shows the processing conditions of Example 2. In Example 2, the sewage digested sludge dehydrated filtrate was used as raw water in the same manner as in Example 1, and the M-alkalinity was adjusted in the same manner. A predetermined amount of Na ₂ CO ₃ aqueous solution was added as inorganic carbonic acid before the start of the anaerobic ammonia oxidation process. The injection was controlled with an aqueous H ₂ SO ₄ solution so that the pH during the anaerobic ammonia oxidation treatment was 8.0 or lower and ORP 50 mV or lower. Table 4 shows the average water quality of raw water and treated water treated continuously for about 2 months. As shown in Table 4, the TN removal rate averaged 83.8%, and stable denitrification performance was obtained.

(Comparative example)
The same reaction tank 7 as in FIG. 1 was used, and the amount of batch process water was set to 20 L as in Example 1, and a process of always performing partial nitritation treatment and anaerobic ammonia oxidation simultaneously by continuous aeration under aerobic conditions was performed. . The reaction vessel DO was controlled to 0.4 to 0.5 mg / L. The reaction vessel pH was set to 7.5. Other conditions were the same as in Example 1. Table 5 shows the average water quality of raw water and treated water treated continuously for about 2 months. As shown in Table 5, the TN removal rate relative to the raw water was only 52% on average, and stable denitrification performance was not obtained.

2 ... DO meter 3 ... pH meter 4 ... ORP meter 5 ... switching means 6 ... supply unit 7 ... reaction tank 9 ... aeration tank 10 ... microbial carrier 11 .... Blower 12 ... Air diffuser 13 ... Water trap 14 ... Exhaust port 15 ... Discharge part 16 ... Return line 17 ... Sedimentation basin 18 ... Excess sludge

Claims (10)

Supplying nitrogen-containing wastewater into a microbial carrier containing ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria or into a reaction vessel containing the microbial carrier and activated sludge;
Oxygen-containing gas or oxygen-free gas is sequentially supplied into the reaction tank to stir the nitrogen-containing wastewater in the reaction tank, and the nitrogen-containing wastewater is acted upon by the ammonia oxidizing bacteria and the anaerobic ammonia oxidizing bacteria. A denitrification process,
Separating the microbial carrier or the microbial carrier and the activated sludge from the treated water, and discharging the treated water from the reaction tank.   Before denitrifying the nitrogen-containing wastewater, the M-alkaliness (mg / L) is 3.5 to 4.5 times the TN concentration (mg / L) of the nitrogen-containing wastewater. The method for denitrification of nitrogen-containing wastewater according to claim 1, comprising pre-adjusting M-alkalinity of the nitrogen-containing wastewater. The step of denitrifying the nitrogen-containing wastewater,
By supplying an oxygen-containing gas into the reaction tank and stirring the nitrogen-containing wastewater in the reaction tank, a part of ammonia nitrogen contained in the nitrogen-containing wastewater is converted to nitrous acid by the action of the ammonia oxidizing bacteria. An aerobic stirring step comprising oxidizing to basic nitrogen;
Stopping the supply of the oxygen-containing gas, supplying the gas not containing oxygen into the reaction tank, and stirring the nitrogen-containing wastewater in the reaction tank, thereby the ammoniac contained in the nitrogen-containing wastewater The method of denitrifying nitrogen-containing wastewater according to claim 1 or 2, further comprising an anaerobic stirring step including generating nitrogen gas from nitrogen and the nitrite nitrogen by the action of the anaerobic ammonia oxidizing bacteria.   The denitrification of nitrogen-containing wastewater according to claim 3, further comprising an additional aerobic stirring step of supplying an oxygen-containing gas into the reaction tank and stirring the nitrogen-containing wastewater in the reaction tank after the anaerobic stirring step. Method. When supplying the oxygen-containing gas into the reaction vessel,
The pH of the nitrogen-containing wastewater in the reaction tank is monitored while controlling the dissolved oxygen concentration of the nitrogen-containing wastewater in the reaction tank to a dissolved oxygen concentration range necessary for the partial nitritation treatment by the ammonia oxidizing bacteria. And the nitrogen-containing wastewater according to any one of claims 1 to 4, further comprising stopping the supply of the oxygen-containing gas into the reaction tank when the pH of the nitrogen-containing wastewater becomes a predetermined value or less. Denitrification method of waste water.   The nitrogen-containing wastewater denitrification according to any one of claims 1 to 5, wherein the supply of the oxygen-free gas is performed by circulating nitrogen gas generated in the reaction tank into the reaction tank. Method.   The method further comprises aeration of the treated water discharged from the reaction tank, solid-liquid separation of the aerated liquid to obtain a supernatant, and return of the concentrated sludge obtained by the solid-liquid separation to the reaction tank. Item 7. A method for denitrifying nitrogen-containing wastewater according to any one of Items 1 to 6.   The combined microbial carrier obtained by gradually attaching the ammonia oxidizing bacterium and the anaerobic ammonia oxidizing bacterium to the surface of the hydrophilic polymer carrier as the microbial carrier is treated in the reaction vessel. The method for denitrification of nitrogen-containing wastewater according to any one of claims 1 to 7.   The method for denitrifying nitrogen-containing wastewater according to any one of claims 1 to 8, wherein the activated sludge contains the ammonia-oxidizing bacteria. A supply section for supplying nitrogen-containing wastewater;
By containing the nitrogen-containing wastewater, a microbial carrier containing ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria or the microbial carrier and activated sludge, and supplying oxygen-containing gas or oxygen-free gas in order A reaction tank for denitrifying nitrogen-containing wastewater;
Aeration means for stirring the nitrogen-containing wastewater in the reaction tank by supplying the oxygen-containing gas or a gas not containing oxygen into the reaction tank;
Switching means connected to the aeration means for switching supply of the oxygen-containing gas or gas not containing oxygen;
A denitrification apparatus for nitrogen-containing wastewater, comprising: a treatment liquid obtained by the denitrification treatment, and a discharge unit that separates the microorganism carrier or the microorganism carrier and the activated sludge from treated water and discharges the treated liquid to the outside of the reaction tank.