JP6691019B2 - Treatment apparatus and treatment method for wastewater containing ammoniacal nitrogen - Google Patents

Description

  The present invention relates to a treatment device and a treatment method for wastewater containing ammoniacal nitrogen.

  Ammoniacal nitrogen contained in waste water causes eutrophication in rivers, lakes and oceans when it flows into the environment. In addition, for example, in Japan, the discharge amount is severely restricted by the drainage standards of the Ministry of the Environment. In other words, the removal of ammoniacal nitrogen contained in wastewater is a problem to be solved from both an environmental standpoint and a legal standpoint.

  Conventionally, wastewater generated from anaerobic digested sludge or the like, which contains a high concentration of ammonia nitrogen, and contains a low concentration of organic matter, oxidizes ammonia nitrogen to nitrate nitrogen through nitrite nitrogen, After that, it has been treated by a nitrification denitrification method of reducing and converting to nitrogen gas. However, this method has been problematic in that it requires the addition of an organic substance such as methanol in the denitrification step, which increases the operating cost.

  On the other hand, as an example of a denitrification method that does not require the addition of an organic substance, an anaerobic ammonium oxidation method called an anammox method using an anammox bacterium which is an autotrophic bacterium has been attracting attention in recent years. In the denitrification reaction by anammox bacteria, the reduction of nitrite nitrogen oxidizes almost the same amount of ammonia nitrogen, whereby nitrogen gas is generated and nitrogen is removed from the wastewater. Therefore, unlike the reaction in which nitrate nitrogen is reduced by organic matter and nitrogen gasification, which is performed by general denitrifying bacteria that are heterotrophic bacteria, the Anammox method requires the addition of organic matter in the reaction process. The feature is not to do. Further, in the treatment using anammox bacteria, when oxidizing the ammoniacal nitrogen in the pretreatment stage, it is sufficient to oxidize almost half of the whole to nitrite nitrogen, so compared with the conventional nitrification denitrification method. The amount of aeration air in the pretreatment process can be small.

By the way, it is considered that the denitrification process (anammox treatment process) by anammox bacteria generally follows the following chemical reaction formula (1). As shown in the formula, in the anammox method, it is a technical problem to keep the ratio of the ammonia nitrogen concentration and the nitrite nitrogen concentration of the wastewater entering the anammox treatment step to an appropriate value (1: 1.32). Is. Therefore, in the anaerobic ammonia oxidation method, as a pretreatment for the denitrification process by the anammox bacteria represented by the following formula (1), a part of the ammonia nitrogen (NH ₄ ⁺ ) in the waste water is converted to nitrite (NO ₂ ⁻ ). Process to convert to. Then, thereafter, nitrogen is removed by performing an anaerobic ammonia oxidation treatment for converting ammoniacal nitrogen and nitrous acid in the wastewater into nitrogen gas.
1.0NH ₄ ⁺ + 1.32NO ₂ ⁻ + 0.066HCO ₃ ⁻ + 0.13H ⁺ → 1.02N ₂ + 0.26NO ₃ ⁻ + 0.066CH ₂ O _0.5 N _0.15 + 2.03H ₂ O (1)
The anaerobic ammonia oxidation technology using Anammox bacteria described above is disclosed in Patent Documents 1 and 2, for example.

  FIG. 9 is a system diagram showing the configuration of the anaerobic ammonia oxidation treatment system (anammox treatment system) disclosed in Patent Document 1. In the anaerobic ammonia oxidation treatment system 100, after the wastewater is supplied from the raw water tank 114 to the distribution tank 115, a part thereof passes through the nitrite tank 116 to the adjusting tank 117, and the rest passes through the raw water bypass waterway. It is supplied to the adjusting tank 117. After that, the wastewater introduced into the adjustment tank 117 is supplied to the anaerobic ammonia oxidation tank 118 and denitrified.

As described above, in the anaerobic ammonia oxidation treatment system 100, a part of the waste water is bypassed through the raw water bypass channel to bypass the nitrite tank 116. Then, a fully is nitrous oxide waste water by mixing the waste water untreated, the ratio of the nitrite nitrogen (NO 2 _-N) concentration and the ammonium nitrogen (NH 4 _-N) concentration suitable Is kept at a reasonable value.

Further, FIG. 10 is a configuration diagram of the nitrogen removing device disclosed in Patent Document 2. In the nitrogen removal device 200, the entire amount of wastewater is guided to the nitrification tank 212, and a part of the ammoniacal nitrogen (NH ₄ —N) in the wastewater is converted to nitrite nitrogen (NO ₂ —N) by using ammonia oxidizing bacteria. It is partially oxidized. Next, in the denitrification tank 218, ammoniacal nitrogen is anaerobically oxidized by nitrite nitrogen using anammox bacteria, and treated in the form of nitrogen gas.

Japanese Unexamined Patent Publication No. 2012-20262 (Published February 2, 2012) Japanese Patent Laid-Open No. 2003-212177 (Published July 29, 2003)

  In the anaerobic ammonia oxidation treatment system 100 shown in FIG. 9, the nitrite can be easily controlled by controlling the ratio of the amount of waste water introduced into the nitrite tank 116 and the amount of waste water flowing through the raw water bypass channel. The ratio of neutral nitrogen and ammoniacal nitrogen can be controlled to a theoretical value of about 1: 1.32. However, in order to bring the ratio of nitrite nitrogen and ammonia nitrogen close to the theoretical value, the amount of wastewater introduced into the nitrite tank 116 is 0.57 (≈1.32 / 1/1 + 1.32). )) At this time, the amount of alkalinity available for nitrite oxidation by the ammonia-oxidizing bacteria is limited to about half (57%) of the total amount of waste water flowing out from the distribution tank 115. Therefore, the amount of alkalinity required to generate the ideal amount of nitrite nitrogen is relatively large compared to the amount of alkalinity contained in the wastewater. When the alkalinity derived from the waste water is exhausted in the tank, the effect of buffering hydrogen ions generated by the nitrite oxidation by the ammonia-oxidizing bacteria is reduced. Then, there is a problem that the amount of the alkaline chemicals added to compensate for the decrease in pH caused by the decrease in the buffering effect increases.

  Further, in the nitrogen removing device 200 of Patent Document 2 shown in FIG. 10, since the entire amount of the waste water is introduced into the nitrification tank 212, the carbon dioxide component and the like contained in the total amount of the wastewater is changed due to the nitrite oxidation by the ammonia oxidizing bacteria. The resulting alkalinity can be used to the maximum extent. Therefore, the amount of the alkaline chemical added as the pH adjuster can be suppressed to a relatively small amount. On the other hand, it is difficult to control the ratio of nitrite nitrogen to ammonia nitrogen to a theoretical value of about 1: 1.32 by various settings in the nitrification tank.

  As described above, in the conventional wastewater treatment system, the ratio of nitrite nitrogen to ammonia nitrogen can be easily controlled to be close to the theoretical value of 1: 1.32, and the nitrite is added to the nitrite tank. It is difficult to reduce the amount of alkaline chemicals used.

  The present invention has been made in view of the above problems, and an object thereof is to facilitate the adjustment of the ratio between the nitrite nitrogen concentration and the ammonia nitrogen concentration, and include in the ammonia nitrogen-containing wastewater. It is intended to provide a processing apparatus and a processing method capable of maximally utilizing a carbonic acid component corresponding to the alkalinity.

  The inventors of the present invention can solve the above problems by arranging two or more nitrite tanks in parallel and varying the flow rate of the ammoniacal nitrogen-containing wastewater flowing into each nitrite tank. Heading out, the present invention was reached.

  That is, in order to solve the above problems, the treatment device of the present invention is a treatment device having a partial nitrite reactor for performing partial nitrite treatment of ammoniacal nitrogen-containing wastewater, wherein the partial nitrite reactor is Is a plurality of nitrite tanks arranged in parallel with each other, a confluence facility for converging the partial nitrite water flowing out from each of the plurality of nitrite tanks, and partial nitrites confluent by the confluence facility. A variable inflow water supply mechanism for changing the flow rate of the ammonia-nitrogen-containing wastewater between the plurality of nitrite tanks so that the concentration of nitrite nitrogen in the fossilized water becomes a predetermined multiple of the concentration of ammonia nitrogen. It is characterized by having and.

  According to the above configuration, the partial nitrite reactor comprises a plurality of nitrite tanks arranged in parallel with each other, and the total amount of the ammoniacal nitrogen-containing wastewater flows into each of the plurality of nitrite tanks. It is composed. And, by the inflow water amount variable supply mechanism, so that the nitrite nitrogen concentration of the partial nitrite water joined by the joining facility is a predetermined multiple of the ammonia nitrogen concentration, flow into each of the plurality of nitrite tanks By controlling the flow rate ratio of the wastewater containing ammoniacal nitrogen, the amount of nitrite nitrogen produced in each of the plurality of nitrite tanks is controlled. Therefore, as compared with the conventional wastewater treatment system (eg, the system shown in FIG. 10) that performs partial nitrite treatment in one partial nitrite tank, nitrite nitrogen and ammonia in partially nitrite water are reduced. It becomes possible to easily optimize the ratio with the neutral nitrogen.

  Further, according to the above configuration, the alkalinity in the ammoniacal nitrogen-containing wastewater is consumed by the ammonia-oxidizing bacteria in each of the plurality of nitrite tanks. As described above, according to the above configuration, unlike the conventional wastewater treatment system that bypasses the ammoniacal nitrogen-containing wastewater (for example, the system shown in FIG. 9), the ammoniacal nitrogen-containing wastewater is consumed due to consumption by the ammonia-oxidizing bacteria. The alkalinity contained in the total amount of waste water can be used without waste. Therefore, the amount of the alkaline chemicals added for pH adjustment can be suppressed to a low level, as compared with the conventional wastewater treatment system that bypasses the ammoniacal nitrogen-containing wastewater.

  As described above, according to the above configuration, it is easy to adjust the ratio between the nitrite nitrogen concentration and the ammonia nitrogen concentration, and it is possible to maximize the alkalinity contained in the ammonia nitrogen-containing wastewater. The processing device can be realized.

  In the treatment apparatus of the present invention, it is preferable that each of the plurality of nitration tanks includes an ammoniacal nitrogen concentration meter and a nitrite nitrogen concentration meter.

  According to the above configuration, the ammoniacal nitrogen concentration and the nitrite nitrogen concentration can be easily measured.

  It is preferable that the treatment apparatus of the present invention includes a switching unit that switches between communication and shielding between the plurality of nitrite oxidization tanks.

  According to the above configuration, since a switching unit that switches between communication and shielding between the plurality of nitrite tanks is provided, for example, there is a difference in the nitrite nitrogen generation capacity between the plurality of nitrite tanks. When it occurs, the nitrite nitrogen producing capacity among the plurality of nitrite tanks can be homogenized by opening the switching unit.

  In the treatment apparatus of the present invention, each of the plurality of nitrite tanks is provided with a fluid carrier carrying a group of ammonia-oxidizing bacteria, and movement and separation of the fluid carrier between the plurality of nitrite tanks are switched. It is preferable to include a switching unit.

  According to the above configuration, the movement of the fluid carrier carrying the group of ammonia-oxidizing bacteria is smooth between the plurality of nitrite tanks, so that nitrite nitrogen generation between the plurality of nitrite tanks is generated. When there is a difference in the capacities, it is possible to efficiently homogenize the nitrite nitrogen producing capacity among the plurality of nitrite tanks by opening the switching unit.

  In the treatment apparatus of the present invention, the partial nitrite reactor preferably includes two nitrite tanks having the same capacity.

  This facilitates the adjustment of the flow rate ratio by the inflow water amount variable supply mechanism.

  In order to solve the above problems, the treatment method of the present invention is a method for treating ammoniacal nitrogen-containing wastewater using the above-mentioned treatment device, wherein nitrite in the partially nitrite-containing water joined by the joining facility is When the concentration of neutral nitrogen exceeds a predetermined multiple of the concentration of ammonia nitrogen, the inflow water amount variable supply mechanism causes the first nitrite tank of one of the plurality of nitrite tanks to While supplying the ammoniacal nitrogen-containing wastewater so that the ammoniacal nitrogen contained in the partially nitrated water flowing out of the first nitrite tank does not remain, the second nitrite except the first nitrite tank is supplied. The feature is that the remaining wastewater containing ammoniacal nitrogen is supplied to the tank.

  With the above configuration, it is possible to realize a treatment method that facilitates the adjustment of the ratio between the nitrite nitrogen concentration and the ammoniacal nitrogen concentration, and can maximize the alkalinity contained in the ammoniacal nitrogen-containing wastewater.

  In the treatment method of the present invention, when the nitrite nitrogen concentration in the partially nitrated water joined by the joining facility becomes equal to or less than a predetermined multiple of the ammonia nitrogen concentration, the inflow water amount variable supply mechanism causes the plurality of It is preferable that the ammonia-containing nitrogen-containing wastewater is supplied to each of the nitrite tanks so that the inflow rates are all equal.

  In the treatment method of the present invention, in each of the plurality of nitrite tanks, a partial nitrite treatment is carried out by a fluidized carrier carrying a group of ammonia-oxidizing bacteria, and the treatment device is the plurality of nitrites. A switching unit that switches the movement and separation of the fluidized carrier between the tanks is provided, and when a difference occurs in the nitrite nitrogen producing capacity between the plurality of nitrite tanks, by opening the switching unit, It is preferable that the fluidized carrier is homogenized between the plurality of nitrite tanks, and the nitrite nitrogen producing capacities of the plurality of nitrite tanks are averaged.

  According to the present invention, it is possible to facilitate the adjustment of the ratio between the nitrite nitrogen concentration and the ammonia nitrogen concentration, and to maximize the use of the alkalinity contained in the ammonia nitrogen-containing wastewater.

It is a schematic diagram which shows the schematic structure of the processing apparatus which concerns on one Embodiment of this invention. It is a schematic diagram which shows schematic structure of the partial nitrite reactor with which the processing apparatus which concerns on one Embodiment of this invention was equipped. It is a schematic diagram for demonstrating the 1st operating method of the partial nitrite reactor with which the processing apparatus which concerns on one Embodiment of this invention was equipped. It is a schematic diagram which shows the state before implementing the 2nd operating method of the partial nitrite reactor with which the processing apparatus which concerns on one Embodiment of this invention was equipped. It is a schematic diagram for demonstrating the 2nd operating method of the partial nitrite reactor with which the processing apparatus which concerns on one Embodiment of this invention was equipped. It is a schematic diagram for demonstrating the 3rd operating method of the partial nitrite reactor with which the processing apparatus which concerns on one Embodiment of this invention was equipped. FIG. 7 is a schematic diagram for explaining a method of determining a lower limit value of the flow rate of the ammoniacal nitrogen-containing wastewater flowing into the partial nitrite tank on the flow rate reducing side in the second operation method of the partial nitrite reactor. It is a flowchart which shows an example of the processing method of the ammoniacal nitrogen containing wastewater using the processing apparatus which concerns on one Embodiment of this invention. FIG. 6 is a system diagram showing a configuration of an anaerobic ammonia oxidation treatment system (anammox treatment system) disclosed in Patent Document 1. It is a block diagram of the nitrogen removal apparatus disclosed by patent document 2.

  First, terms used to describe the present invention will be defined.

As used herein, the term "ammonia nitrogen" is intended the nitrogen present as ammonia (NH ₃₎ or ammonium ion (NH 4 ^₊₎ in water. As used herein, the term “nitrite nitrogen” intends nitrogen present in water as nitrite (HNO ₂ ) or nitrite ion (NO ₂ ⁻ ). As used herein, the term “nitrate nitrogen” intends nitrogen present in water as nitric acid (HNO ₃ ) or nitrate ion (NO ₃ ⁻ ).

  The ammonia nitrogen concentration, the nitrite nitrogen concentration, and the nitrate nitrogen concentration are measured by known methods.

  The process of nitrite in wastewater treatment is roughly divided into "total nitrite" that nitrite all ammoniacal nitrogen, and "partial nitrite" that nitrite only part of ammoniacal nitrogen. To be done. The ammoniacal nitrogen-containing wastewater partially nitrided by the treatment apparatus or the treatment method of the present invention is suitable as the partially nitrite water to be introduced into the anammox treatment step.

In the present specification, the term “alkalinity” means an alkali content such as hydrogen carbonate, carbonate or hydroxide contained in water. The alkalinity is expressed in terms of the concentration of calcium carbonate (CaCO ₃ ) corresponding to the alkali content, and serves as an index of the ability of water as a sample to neutralize the acid.

  The alkalinity is measured by, for example, a known method defined as "acid consumption" in JIS standard "JIS K 0102-15.1".

Here, in the anammox method, the wastewater introduced into the nitrite tank contains alkalinity derived from carbonate, hydrogencarbonate or the like as a component having a buffering action for maintaining pH. Specific examples of the treatment apparatus of the present invention and the ammonia-nitrogen-containing wastewater applicable to the treatment apparatus that satisfy such conditions include anaerobic digestion of sludge generated in a sewage treatment plant (for example, initial sludge, surplus sludge). A dehydrated separated liquid obtained by extracting water from the anaerobic digested sludge obtained by the above is mentioned. For example, when the wastewater is a digested dehydrated separated liquid containing 1000 mgN / L of ammoniacal nitrogen (“mgN / L” is a nitrogen concentration in terms of organic nitrogen), generally, the wastewater contains 3000 to 4000 mg / L (CaCO ₃ (Conversion) alkalinity is included.

As used herein, the term “anammox reaction” intends a reaction for converting ammoniacal nitrogen and nitrite nitrogen into nitrogen gas (N ₂ ) under anoxic conditions. As used herein, the term “anammox bacterium” intends a group of autotrophic bacteria exhibiting an anammox reaction (for example, 5 genera such as Canditaus. Brocade, Canditaus. Kueneia, etc. are proposed). As used herein, the term “anammox treatment” means a treatment that utilizes anammox bacteria to remove nitrogen contained in wastewater. In general, when effluent is anammox-treated, a nitrite-oxidizing step is required as a preceding step.

  Next, an embodiment of an apparatus and method for treating wastewater containing ammoniacal nitrogen according to the present invention will be described with reference to the drawings.

[Processing device]
One embodiment of the present invention will be described based on FIG. FIG. 1 is a schematic diagram showing a schematic configuration of a processing device 50 according to this embodiment.

  The treatment device 50 is a device for anammox-treating and denitrifying the wastewater containing ammoniacal nitrogen. The treatment device 50 includes at least a partial nitrite reactor 10 into which waste water containing ammoniacal nitrogen is introduced, and an anammox reactor 20 into which the partial nitrite water discharged in the partial nitrite reactor 10 is introduced. ing. A treated water tank 30 that stores the denitrification treated water discharged from the anammox reactor 20 may be provided at the subsequent stage of the anammox reactor 20.

  When the wastewater is introduced into the partial nitrite reactor 10, part of the ammoniacal nitrogen in the wastewater is converted into nitrite nitrogen by the ammonia oxidizing bacteria. Ammonia-oxidizing bacteria are aerobic autotrophic bacteria, and examples thereof include the genus Nitrosomonas. In the partial nitrite reactor 10, the water temperature in the reactor is maintained at 30 ° C. or higher and the pH is maintained at about 7.8 in order to suppress the conversion of nitrite nitrogen into nitrate nitrogen. Further, due to the anammox treatment in the anammox reactor 20 in the subsequent stage, in the partial nitrite reactor 10, the ratio of ammoniacal nitrogen to nitrite nitrogen in the discharged partial nitrite water is around 1: 1.32. Is controlled. In the anammox reactor 20, anammox treatment of partially nitrite water is performed. That is, under anaerobic conditions, anammox bacteria convert ammonia nitrogen and nitrite nitrogen in the partially nitrite water into nitrogen gas and denitrify.

  As shown in FIG. 1, the partial nitrite reactor 10 according to the present embodiment has a configuration in which two nitrite tanks 1A and 1B are arranged in parallel. In the partial nitrite reactor 10, wastewater containing ammoniacal nitrogen is introduced into each of the nitrite tanks 1A and 1B. Then, the partially nitrite water discharged from each of the nitrite tanks 1 </ b> A and 1 </ b> B joins and is introduced into the anammox reactor 20.

  FIG. 2 is a schematic diagram showing a schematic configuration of the partial nitrite reactor 10 according to the present embodiment. As shown in FIG. 2, the partial nitrite reactor 10 includes two nitrite tanks 1A and 1B arranged in parallel with each other, an air diffuser 3, a variable inflow water supply mechanism 4, a confluence pipe 5 (a confluence facility). ), An opening / closing gate 6, a carrier outflow prevention mechanism 7, an alkaline chemical supply facility 8, and an in-tank water quality detection unit 9. The merging pipe 5 is a pipe for merging the partially nitrite water discharged from each of the nitrite tanks 1A and 1B.

  The nitrite tank 1A and the nitrite tank 1B are processing tanks having the same capacity, and the fluid carrier 2 is put in each tank. Further, each of the nitrite tanks 1A and 1B is provided with an air diffuser 3, a carrier outflow prevention mechanism 7, an alkaline chemical supply facility 8, and a tank water quality detection unit 9.

  The fluid carrier 2 is a microbial carrier that holds a group of ammonia-oxidizing bacteria (nitrite bacteria), and is configured to flow in the nitrite tanks 1A and 1B. Examples of the fluid carrier 2 include the biological treatment carrier disclosed in JP-A-10-180278, in which a fiber bundle is formed by heat fusion. The material of the fluid carrier 2 is not limited to fiber bundles, and may be any material that easily retains microorganisms and has a high porosity, and may be, for example, a resin material or a gel carrier.

  The air diffuser 3 is installed at the bottom of each of the nitrite tanks 1A and 1B, supplies oxygen necessary for the nitrite reaction by the ammonia-oxidizing bacteria group, and causes the fluidized carrier 2 to flow. Further, the carrier outflow prevention mechanism 7 is provided so as to cover the outlet of the partially nitrite water. The carrier outflow prevention mechanism 7 prevents the fluidized carrier 2 from flowing out from the nitrite tanks 1A and 1B.

  The in-tank water quality detection unit 9 includes a measuring device for monitoring the water quality in the nitrite tanks 1A and 1B. The in-tank water quality detection unit 9 includes, for example, a pH sensor 9a, a nitrite nitrogen concentration meter 9b, and an ammonia nitrogen concentration meter 9c. In the nitrite tanks 1A and 1B, the pH in the tank needs to be maintained at 7.8 (about). The pH sensor 9a is a sensor for monitoring the pH in the nitrite tanks 1A and 1B and determining whether to start or stop the supply of the alkaline chemical according to the control value. Further, the nitrite nitrogen concentration meter 9b is a device equipped with an ion electrode for measuring the concentration of nitrite nitrogen in the nitrite tanks 1A and 1B, and the ammonia nitrogen concentration meter 9c is a nitrite tank. It is an apparatus equipped with an ion electrode for measuring the concentration of ammonia nitrogen in 1A and 1B. The pH sensor 9a, the nitrite nitrogen concentration meter 9b, and the ammonia nitrogen concentration meter 9c are not particularly limited as long as they are conventionally known measuring instruments. The arrangement of the in-tank water quality detection unit 9 in the partial nitrite reactor 10 is not limited as long as the water quality in the nitrite tanks 1A and 1B can be detected. For example, the in-tank water quality detection unit 9 may be arranged in a pipe between each of the nitrite tanks 1A and 1B and the confluent pipe 5.

  Further, the in-tank water quality detection unit 9 does not necessarily have to include the nitrite nitrogen concentration meter 9b and the ammonia nitrogen concentration meter 9c. When the in-tank water quality detection unit 9 does not include the nitrite nitrogen concentration meter 9b and the ammonia nitrogen concentration meter 9c, a sample of the treated water in the nitration tanks 1A and 1B is sampled, and the ammoniacal It is also possible to measure the concentrations of nitrogen and nitrite nitrogen. In addition, except that both the nitrite nitrogen concentration meter 9b and the ammonia nitrogen concentration meter 9c are used, under the premise that nitrate nitrogen is not generated, the value indicated by the ammonia nitrogen concentration meter 9c is used to calculate the nitrite nitrogen concentration. The concentration may be calculated. In the processing apparatus 50 according to the present embodiment, the concentration of ammonia nitrogen and the concentration of nitrite nitrogen do not change abruptly, so samples may be taken and the respective concentrations may be investigated.

  The alkaline chemical supply equipment 8 is provided in each of the nitrite tanks 1A and 1B, and when the pH in the nitrite tanks 1A and 1B is lower than 7.8 (about), the nitrite tank 1A and It is configured to add an alkaline drug to 1B. The alkaline chemical is not particularly limited as long as it is a strong alkaline solution, and examples thereof include caustic soda.

  Further, the opening / closing gate 6 (switching unit) communicates between the nitrite tank 1A and the nitrite tank 1B, and by switching the opening and closing, the flow between the nitrite tank 1A and the nitrite tank 1B. It is a gate that adjusts the movement (movement) of the carrier 2. That is, the opening / closing gate 6 is a switching unit that switches between movement and separation of water in the nitrite-containing tank containing the fluid carrier 2 between the nitrite-containing tanks 1A and 1B. In the partial nitrite reactor 10, the opening / closing gate 6 is closed during normal operation.

  The opening / closing gate 6 as a switching unit has a function of switching between communication and shielding between the nitrite tanks 1A and 1B. In other words, the opening / closing gate 6 combines the opening / closing switching operation and the operation of the inflow water amount variable supply mechanism 4 so that the ratio of ammonia nitrogen load / amount of nitrite bacteria between the nitrite tanks 1A and 1B is different. Or to have a uniform ratio.

  The inflow water amount variable supply mechanism 4 adjusts the nitrite tank 1A so that the nitrite nitrogen concentration of the partial nitrite water joined by the joining pipe 5 becomes 1.32 ± 0.10 times the ammonia nitrogen concentration. And 1B, the flow rate of the ammoniacal nitrogen-containing wastewater is changed and supplied. The inflow water amount variable supply mechanism 4 determines the flow rate of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A according to the concentration of nitrite nitrogen in the partial nitrite water joined by the joining pipe 5, and the nitrite The flow rate ratio with the flow rate of the ammoniacal nitrogen-containing wastewater flowing into the tank 1B is adjusted.

  Examples of the configuration of the variable inflow water supply mechanism 4 include a configuration including a flow meter and a valve. In the case of this configuration, the flowmeter has piping at a position before branching the ammonia nitrogen-containing wastewater into the nitrite tank 1A and the nitrite tank 1B, and 2 pipes after branching to the nitrite tanks 1A and 1B, respectively. At least two of the three pipes are provided. Further, the valve is provided in at least one location of the two pipes after branching to the nitrite tanks 1A and 1B, respectively. In such a configuration, the flow rate to each of the nitrite tanks 1A and 1B is controlled by the opening degree of the valve. If, for example, an electromagnetic flow meter and a motor-operated valve are used as the flow meter and valve of the variable inflow water supply mechanism 4, the opening degree of the valve can be automatically adjusted to obtain the set flow rate.

  In the partial nitrite reactor 10, the ammoniacal nitrogen-containing wastewater is supplied to the nitrite tanks 1A and 1B at a predetermined flow rate ratio via the inflow water amount variable supply mechanism 4. Then, the partially nitriding water treated in each of the nitrite tanks 1 </ b> A and 1 </ b> B joins at the joining pipe 5 and is sent to the anammox reactor 20. The anammox reactor 20 is not particularly limited as long as it has a conventionally known configuration. For example, there may be mentioned a reactor described in JP-A 08-238495, in which a fixed bed formed by molding a mat-shaped nonwoven fabric is filled.

  In the partial nitrite reactor 10, the fluid carrier 2 is used to carry ammonia-oxidizing bacteria. Here, in addition to the method of using the fluid carrier 2, there are two methods of accumulating ammonia-oxidizing bacteria, a floating sludge method in which the bacteria themselves form flocs, and a method of using a fixed carrier (fixed bed). The method for accumulating the ammonia-oxidizing bacteria is not particularly limited, but in the processing device 50 having the opening / closing gate 6, the accumulation method using the fluid carrier 2 that can freely move between the nitrite tanks by opening the opening / closing gate 6. Is preferably used. When accumulating ammonia-oxidizing bacteria by the floating sludge method, the treatment device 50 is provided with a sedimentation tank for precipitating the suspended sludge between the partial nitrite reactor 10 and the anammox reactor 20. The configuration is such that it is returned to the partial nitrite reactor 10. However, since the treatment device 50 of the present invention is provided with two or more nitrite tanks, the floating sludge method is not preferable because the operation becomes complicated.

〔Processing method〕
Here, the ammoniacal nitrogen-containing wastewater flowing into the partial nitrite reactor 10 has an alkalinity mainly composed of a carbonic acid component (CO ₃ ²⁻ ). This carbonic acid component has a buffering effect for maintaining the pH in the wastewater and is also a carbon source consumed by the ammonia-oxidizing bacteria. More specifically, the group of ammonia-oxidizing bacteria (nitrites) consumes 7.14 g of alkalinity (calculated as CaCO ₃ ) to produce 1 g of nitrite nitrogen from ammoniacal nitrogen. Therefore, in the nitrite tanks 1A and 1B, the alkalinity is consumed by the nitrite oxidation by the ammonia-oxidizing bacteria and the pH buffering action is reduced. As a result, in the nitrite tanks 1A and 1B, the pH decreases due to the production of nitrite by the ammonia-oxidizing bacteria. Therefore, in the nitrite tanks 1A and 1B, an alkaline chemical is added from the alkaline chemical supply facility 8 in order to maintain the pH in the tank within an appropriate range.

  The amount of alkali chemicals added depends on the difference between the alkalinity required for ammonia-oxidizing bacteria to produce an ideal amount of nitrite nitrogen and the alkalinity in the wastewater contained in the nitrite tank. ,growing.

  In the partial nitrite reactor 10, the entire amount of the ammoniacal nitrogen-containing wastewater flows into the nitrite tanks 1A and 1B, respectively. Then, by controlling the flow rate ratio between the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A and the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1B by the variable inflow water supply mechanism 4, The amount of nitrite nitrogen produced in each of the chemical tanks 1A and 1B is controlled. Therefore, as compared with the conventional nitrogen removing apparatus 200 shown in FIG. 10, it becomes possible to easily optimize the ratio of nitrite nitrogen to ammonia nitrogen in the partially nitrite water.

  Further, in the partial nitrite reactor 10, the alkalinity in the ammoniacal nitrogen-containing wastewater is consumed by the ammonia oxidizing bacteria in each of the nitrite tanks 1A and 1B. Thus, in the partial nitrite reactor 10, unlike the conventional anaerobic ammonia oxidation treatment system 100 shown in FIG. 9, the alkali contained in the total amount of the ammoniacal nitrogen-containing wastewater is consumed by the ammonia oxidizing bacteria. You can use your time without waste. Therefore, as compared with the conventional anaerobic ammonia oxidation treatment system 100 shown in FIG. 9, the amount of the alkaline chemicals added for pH adjustment can be suppressed low.

  Hereinafter, a method for treating ammoniacal nitrogen-containing wastewater using the partial nitrite reactor 10 (that is, a method for operating the partial nitrite reactor 10) will be described with reference to FIGS. FIG. 3 is a schematic diagram for explaining the first operation method of the partial nitrite reactor 10. The first operation method is the operation of the partial nitrite reactor 10 when the concentration of nitrous nitrite in the partial nitrite water passing through the confluent pipe 5 is 1.32 times or less than the concentration of ammonia nitrogen. Is the way. The term "1.32 times" as used herein means "1.32 times" within the measurement limits of the nitrite nitrite concentration and the ammoniacal nitrogen concentration, and is 1.32 ± 0.10 times. is there.

In the state shown in FIG. 3, the partially nitrite water passing through the confluent pipe 5 lacked nitrite nitrogen from the ideal nitrite nitrogen concentration / ammoniacal nitrogen concentration ratio with respect to the anammox reaction. It is in a state. That is, assuming that the ammoniacal nitrogen concentration of the ammoniacal nitrogen-containing wastewater flowing into the partial nitrite reactor 10 is C,
Concentration of nitrite nitrogen in partially nitrite water passing through confluent pipe 5 ≤0.57C
Ammonia nitrogen concentration of partially nitrite water passing through confluent pipe 5 ≧ 0.43C
Is.

  Under the condition shown in FIG. 3, it is necessary to arrange the reaction conditions between the nitrite tanks 1A and 1B to promote the nitrite reaction in both the nitrite tanks 1A and 1B at the same time. Therefore, the flow rate ratio is adjusted by the inflow water amount variable supply mechanism 4 so that the supply amount of the ammoniacal nitrogen-containing wastewater to the nitrite tanks 1A and 1B becomes equal to 0.5Q. Furthermore, the nitrate nitrogen producing reaction by the nitric acid bacteria group in the nitrite tanks 1A and 1B is suppressed by a method such as controlling the water temperature to 30 ° C. and the pH to 7.8 (about). By the above treatment method, the nitrite nitrogen concentration becomes 1.32 times the ammonia nitrogen concentration (that is, the nitrite nitrogen concentration of the partially nitriding water passing through the confluent pipe 5 = 0.57C). Control).

  FIG. 4 is a schematic diagram showing a state before the second operation method of the partial nitrite reactor 10 is carried out. FIG. 5 is a schematic diagram for explaining the second operating method of the partial nitrite reactor 10.

  For example, by continuing the operation method shown in FIG. 3, it is possible to determine that the concentration of nitrite nitrite in the partially nitrite water passing through the confluent pipe 5 exceeds 1.32 times the concentration of ammonia nitrogen. Become.

That is, as shown in FIG. 4, the partial nitrite water passing through the confluent pipe 5 has the ammonia nitrogen concentration of the ammoniacal nitrogen-containing wastewater flowing into the partial nitrite reactor 10 as C, and the confluent pipe 5 is Assuming that the concentration of nitrite nitrogen in the partially nitriding water passing through is c,
Concentration of nitrite nitrogen in partially nitrite water passing through confluent pipe 5 c> 0.57C
Ammoniacal nitrogen concentration C-c <0.43C of partially nitrite water passing through the confluence pipe 5.
Becomes The second operation method of the partial nitrite reactor 10 is the partial nitrite when the concentration of nitrous acid in the partial nitrite water passing through the confluent pipe 5 is higher than 1.32 times the concentration of ammoniacal nitrogen. It is a method of operating the chemical reactor 10.

  As shown in FIG. 5, in the second operation method of the partial nitrite reactor 10, the inflow amount of the ammoniacal nitrogen-containing wastewater to be supplied to the nitrite tank 1A is a portion discharged from the nitrite tank 1A. In order to prevent ammoniacal nitrogen in the nitrite water from remaining, it is reduced from 0.5Q to q by the variable inflow water supply mechanism 4. As a result, in the nitrite tank 1A, the entire amount of ammonia nitrogen in the inflowing ammoniacal nitrogen-containing wastewater is converted into nitrite nitrogen. Therefore, the nitrite nitrogen concentration of the partially nitrite water discharged from the nitrite tank 1A becomes equal to the ammonia nitrogen concentration C of the inflowing ammoniacal nitrogen-containing water. As a result, the amount of nitrite nitrogen produced in the nitrite tank 1A is C * q (“*” is synonymous with “x”). Here, "there is no residual ammoniacal nitrogen in the partially nitrite water" means that the ammoniacal nitrogen is not detected within the detection limit of the ammoniacal nitrogen, and the detected ammoniacal nitrogen concentration is 15 mg / L or less. Say.

  Further, in the second operation method of the partial nitrite reactor 10, the remaining ammoniacal nitrogen-containing wastewater is caused to flow into the nitrite tank 1B. That is, the inflow amount of the ammoniacal nitrogen-containing wastewater supplied to the nitrite tank 1B increases from 0.5Q to Qq. The amount of nitrite nitrogen produced in the nitrite tank 1B is determined by the amount and activity of the ammonia-oxidizing bacteria group carried on the fluid carrier 2. Therefore, the amount of nitrite nitrogen produced does not change in a short period of time (about 1 to 2 days although it varies depending on various conditions). Therefore, the amount of nitrite nitrogen produced in the nitrite tank 1B does not change from the state before performing the second operation method (that is, the state of FIG. 4) and is c * 0.5Q.

  Here, the flow rate q of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A is such that the ratio of the nitrite nitrogen concentration / ammoniacal nitrogen concentration of the partial nitrite water passing through the confluent pipe 5 is 1.32. Is adjusted to The method of calculating the flow rate q will be described below.

First, since the nitrite nitrogen concentration A in the partially nitrite water passing through the confluent pipe 5 is (the amount of nitrite nitrogen produced in each of the nitrite tanks 1A and 1B) / total flow rate, the following formula (2)
A = (C * q + c * 0.5Q) / Q (2)
Represented by

In the case of an ideal nitrite nitrogen concentration / ammonia nitrogen concentration ratio, the nitrite nitrogen concentration A is 0.57C. By substituting into the equation (2), the flow rate q is given by the following equation (3)
q = Qx (0.57C-0.5c) / C (3)
q: Flow rate of ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A after flow rate adjustment Q: Flow rate of ammoniacal nitrogen-containing wastewater flowing into the partial nitrite reactor 10 C: Flow into the partial nitrite reactor 10 Ammoniacal Nitrogen Concentration of Wastewater Containing Ammoniacal Nitrogen c: Calculated based on the nitrite nitrogen concentration of the partial nitrite water discharged from the nitrite tank 1B immediately before the flow rate adjustment.

  In the second operating method of the partial nitrite reactor 10, when the concentration of nitrite in the partial nitrite water passing through the confluent pipe 5 exceeds 1.32 times the concentration of ammoniacal nitrogen, The flow rate ratio of the ammoniacal nitrogen-containing wastewater between the chemical tanks 1A and 1B is changed by the inflow water amount variable supply mechanism 4. At this time, by setting the flow rate q flowing into the nitrite tank 1A on the side of decreasing the inflow amount according to the above equation (2), partial nitrite water suitable for the anammox treatment step can be obtained without trial and error. Obtainable. Further, in the second operating method of the partial nitrite reactor 10, the entire amount is supplied to the nitrite tanks 1A and 1B without bypassing the ammoniacal nitrogen-containing wastewater. Therefore, since the alkalinity contained in the ammoniacal nitrogen-containing wastewater can be utilized to the maximum for the nitrite reaction by the ammonia-oxidizing bacteria, the amount of the alkaline chemicals to be added can be reduced.

  FIG. 6 is a schematic diagram for explaining a third operating method of the partial nitrite reactor 10. For example, if the second operation method is continued for a long time (about one month), the ammonia-oxidizing bacteria group existing in the nitrite tank 1A in which the inflow amount of the ammoniacal nitrogen-containing wastewater is reduced is decreased, while the ammonia-oxidizing bacteria group is decreased. It is considered that the group of ammonia-oxidizing bacteria existing in the nitrite tank 1B in which the inflow amount of the nitrogen-containing wastewater is increased is increased. For this reason, there is a difference in the nitrite nitrogen generation capacity of the fluid carrier 2 between the nitrite tank 1A and the nitrite tank 1B. The third operating method of the partial nitrite reactor 10 is a method of dealing with the case where there is a difference in the nitrite nitrogen producing capacity between the nitrite tank 1A and the nitrite tank 1B in this way.

  As shown in FIG. 6, in the third operating method of the partial nitrite reactor 10, by opening the opening / closing gate 6, the fluid carrier 2 is provided between the nitrite tank 1A and the nitrite tank 1B. Move to each other. As a result, the group of ammonia-oxidizing bacteria comes to be evenly distributed between the nitrite tank 1A and the nitrite tank 1B, and the ability to generate nitrite nitrogen becomes uniform.

  The opening / closing gate 6 may be configured so that the fluid carrier 2 existing in each of the nitrite tanks 1A and 1B can move between the nitrite tanks 1A and 1B. Preferably, the opening / closing gate 6 is provided at least at one location, preferably at two locations, in each of the nitrite tanks 1A and 1B.

  Next, in the second operating method of the partial nitrite reactor 10, the lower limit value of the flow rate q of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A will be described.

  In the third operation method, the opening / closing gate 6 is opened to make the nitrite nitrogen producing capacity uniform between the nitrite tanks 1A and 1B. As a result, in the partial nitrite reactor 10, the nitrite nitrogen concentration and ammonia are It is desirable to ensure the ability to generate nitrite nitrogen that can achieve a suitable ratio with the concentration of nitrous acid. When the flow rate q flowing into the nitrite tank 1A is extremely small, the nitrite nitrogen generation capacity in the nitrite tank 1A becomes extremely low. For this reason, even if the opening / closing gate 6 is opened by the third operating method, there is a possibility that nitrite nitrogen is not generated enough to achieve a suitable ratio between the nitrite nitrogen concentration and the ammonia nitrogen concentration.

  Therefore, the lower limit value of the flow rate q of the nitrite nitrating tank 1A that reduces the flow rate is determined under the following conditions. The lower limit value of the flow rate q is that the nitrite rate after performing the homogenizing operation of the fluidized carrier 2 between the nitrite tanks 1A and 1B in the third operation method is required in the subsequent anammox reaction. The condition is that the nitrite nitrogen concentration is a value capable of producing nitrite nitrogen.

  Here, as a result of the flow rate adjustment in the second operation method, the nitrous acid capacity in the nitrite nitrating tank 1B on the flow rate increasing side becomes the maximum value, while the nitrite property in the nitrite nitrating tank 1A on the flow rate decreasing side is maximized. Assume that the nitrogen generation capacity is at its minimum value. Here, the nitrite nitrogen generation capacity is that the ammonia nitrogen concentration of the inflowing ammoniacal nitrogen-containing wastewater does not become the rate-determining factor (ammonia nitrogen is detected from the partially nitrite water treated in the nitrite tank. Nitrite rate. That is, in the nitrite tank 1B on the flow rate increasing side where ammoniacal nitrogen always remains, the nitrite nitrogen generation capacity is always equal to the nitrite rate. On the other hand, in the nitrite tank 1A, which is premised on the treatment in which ammoniacal nitrogen does not remain due to the whole amount of nitrite, the nitrite nitrogen producing capacity may be higher than the nitrite rate. The state in which the nitrite nitrogen generation capacity is the minimum value means that the ammonia nitrogen inflow load to the nitrite tank 1A and the nitrite nitrogen generation capacity of the nitrite tank 1A become equal, Ammoniacal nitrogen is only slightly detected.

  Further, in order to carry out the second operation method, the lower limit value of the flow rate q, when the fluidized carrier 2 is homogenized between the nitrite tanks 1A and 1B from the state assumed as described above, It is desirable to be determined on the condition that the nitrite nitration rate by the homogenized fluid carrier 2 produces nitrite nitrogen at a concentration equal to or higher than the nitrite nitrogen concentration required in the subsequent anammox reaction. . In addition, the above condition is always obtained when the nitrite treatment is performed at the nitrite velocity obtained by homogenizing the fluid carrier 2 in a state where the nitrite capacity in the nitrite tank 1B on the flow rate increasing side becomes the maximum value. , Means that nitrite nitrogen is not insufficient in the latter-stage anammox reaction.

  Hereinafter, a method of determining the lower limit value of the flow rate q will be described with reference to FIG. 7. FIG. 7 is a schematic diagram for explaining the method of determining the lower limit value of the flow rate q, and as a result of the flow rate adjustment in the second operating method, the nitrite nitrating rate in the nitrite nitrating tank 1B on the flow rate increasing side is the maximum. On the other hand, it shows the state where the nitrite nitrogen generation capacity in the nitrite tank 1A on the flow reduction side becomes the minimum value.

First, the maximum value of the nitrite nitrating capacity of the nitrite nitrating tank 1B on the flow rate increasing side depends on the maximum amount of the ammonia-oxidizing bacteria group that the fluid carrier 2 can hold. Therefore, the value is almost constant regardless of the flow rate condition of the inflowing ammoniacal nitrogen-containing wastewater. That is, the nitrite nitrogen generation rate in the nitrite tank 1B may gradually increase as the ammonia nitrogen load increases, but finally converges to a constant value. The value varies depending on the surface area and material of the fluidized carrier 2 and the addition rate of the fluidized carrier 2 to the partial nitrite reactor 10, but is generally within the range of 1 to 2 kgN / m ³ -tank / day, and is unique to the tank. Is defined as the value (μ _i ).

  On the other hand, in the nitrite tank 1A, the entire amount of ammoniacal nitrogen is always nitrite (also referred to as complete nitrite). Therefore, the nitrite tank 1A is operated with an ammonia nitrogen load that is smaller than the nitrite nitrogen generation capacity originally possessed by the nitrite tank 1A. As a result, the nitrite nitrogen production capacity of the nitrite tank 1A may gradually decrease in accordance with the reduction of the ammonia nitrogen load by adjusting the flow rate of the inflow water amount variable supply mechanism 4. Therefore, under the condition that the entire amount of ammoniacal nitrogen can be maintained in the nitrite tank 1A, ammoniacal nitrogen is slightly detected in the partial nitrite water flowing out from the nitrite tank 1A. The state in which the minimum value of the nitrite nitrating ability is obtained is the state in which it is present.

Referring to FIG. 7, the minimum value μ _d of the nitrite nitrogen generation capacity in the nitrite tank 1A is represented by the following formula (4), where V is the capacity of the nitrite tanks 1A and 1B.
μ _d = q × C / V (4)
Represented by

Further, the maximum value μ _i of the nitrite nitrating ability of the nitrite tank 1B is a constant value.

The nitrite rate μ in the nitrite tanks 1A and 1B after the fluidized carrier 2 is homogenized by the opening / closing gate 6 is the arithmetic mean of the nitrite capacity of the nitrite tanks 1A and 1B, (5)
μ = (μ _d + μ _i ) / 2 = (q × C / V + μ _i ) / 2 (5)
Represented by

Then, for the nitrite rate μ represented by the formula (5), if the condition that nitrite nitrogen is generated at a concentration equal to or higher than the nitrite nitrogen concentration required in the subsequent anammox reaction is applied, (6)
μ ≧ 0.57Q × C / 2V (6)
Is established.

From the equations (5) and (6), the following equation (7) is obtained for the flow rate q.
q ≧ 0.57Q−V × μ _i / C (7)
Is obtained. From the equation (7), the minimum value q _min of the flow rate q is as follows: the flow rate Q of the ammoniacal nitrogen-containing wastewater and the ammoniacal nitrogen concentration C, the capacity V of the nitrite tanks 1A and 1B, and the nitrite tank 1B. It is possible to calculate a unique value from the maximum value of the nitrification rate μ _i .

For example, the ammoniacal nitrogen-containing wastewater flowing into the partial nitrite reactor 10 has a flow rate Q of 200 m ³ / day, an ammoniacal nitrogen concentration C of 1.00 kgN / m ³ , and a nitrite nitrite production in the nitrite tank 1B. When the maximum velocity value (μ _i ) is 1.50 kgN / m ³ −tank · day, from equation (7),
q ≧ 0.57 × 200-50 × 1.50 ÷ 1 = 39 (m ³ / day)
The condition is obtained, and the lower limit value q _min of the flow rate q becomes 39 m ³ / day.

Therefore, under the above-mentioned conditions, as long as the total amount of nitrite is carried out in the nitrite tank 1A, even if the flow rate q is reduced to 39 m ³ / day, the fluid carrier 2 is removed by the third operating method. If it is made uniform, there will be no shortage of nitrite nitrogen concentration. On the other hand, when the flow rate q is reduced below 39 m ³ / day, there is a possibility that the nitrite nitrogen concentration may be insufficient even if the fluidized carrier 2 is made uniform by the third operation method. In this state, it takes time for the ammonia-oxidizing bacteria to grow again.

  In the method for treating ammoniacal nitrogen-containing wastewater using the treatment device 50 according to the present embodiment, in order to obtain partially nitriding water necessary for the anammox reaction, the above-described first to first depending on the nitrite nitrogen concentration. The third operating method is appropriately selected. FIG. 8 is a flowchart showing an example of the processing method according to this embodiment.

  In the treatment method shown in FIG. 8, first, the same amount of raw water (wastewater containing ammoniacal nitrogen) is treated with a carrier homogenized between two nitrite tanks (step S1). Specifically, in step S1, the above-described first operating method is performed.

  Then, as a result of continuing step S1, if the nitrite nitrogen concentration in the partially nitrated water after the two tanks merge is excessive (becomes greater than 1.32 times the ammoniacal nitrogen concentration), in step S2. There is a difference in the flow rate of raw water flowing between the two nitrite tanks. Specifically, in step S2, the second operating method described above is performed.

  Then, as a result of continuing the step S2, the difference in the nitrite nitrogen producing capacity between the two tanks becomes large, and the nitrite nitrogen concentration in the partially nitriding water after joining the tanks becomes insufficient (ammonia nitrogen concentration of 1 .32 times or less), one of the following two processes is performed. The first process is a process in which the opening / closing gate is opened to make the fluidized carrier uniform (that is, the above-described third operation method is performed), and then step S1 is performed. The second process is a process of performing step S3. In step S3, the flow rate difference between the two tanks is reduced within the range where the nitrite tank on the flow rate reduction side is completely nitrided. More specifically, in step S3, in the second operation method described above, the flow rate is reduced by the inflow water amount variable supply mechanism 4 within a range in which the total amount of ammonia nitrogen is nitrite in the nitrite tank 1A. The difference between the flow rate q of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A on the side and the flow rate Qq of the ammoniacal nitrogen-containing wastewater flowing into the flow rate increasing side nitrite tank 1B is reduced.

Moreover, as a result of continuing the step S2, when the nitrite nitrogen concentration in the partially nitriding water after the tank confluence becomes excessive, the step S4 is performed. In step S4, the flow rate difference between the two tanks is increased (within a range in which the flow rate q to the tank on the flow reduction side does not become smaller than the lower limit value q _min ). More specifically, in step S4, in the second operation method described above, the inflow water amount is variable within a range in which the flow rate q of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A does not become smaller than the lower limit value q _min. With the supply mechanism 4, a flow rate q of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A on the flow rate decreasing side and a flow rate Qq of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1B on the flow rate increasing side. Increase the difference between.

  As a result of continuing step S3, if the nitrite nitrogen concentration in the partially nitrite water after the tank confluence is insufficient, step S3 is performed again. Further, as a result of continuing step S3, if the nitrite nitrogen concentration in the partially nitriding water after the tank confluence becomes excessive, step S4 is performed.

  Further, as a result of continuing step S4, when the difference in the nitrite nitrogen generation capacity between the two tanks becomes large and the nitrite nitrogen concentration in the partially nitriding water after the tank merges is insufficient, step S3 is performed. Alternatively, the opening / closing gate is opened to homogenize the fluidized carrier (that is, the third operation method described above is performed), and then step S1 is performed. Further, as a result of continuing step S4, when the nitrite nitrogen concentration in the partially nitriding water after the tank confluence becomes excessive, step S4 is performed again.

[Comparison by simulation]
The following simulation 1 and simulation 2 compare the processing method according to the present embodiment with the conventional processing method.

<Simulation 1: Comparison with the method using bypass>
In the simulation 1, the required amount of alkaline chemicals was compared between the treatment method according to the present embodiment and the treatment method using the bypass (for example, the treatment method shown in FIG. 9).

In this simulation, the total amount (Q) of the ammoniacal nitrogen-containing wastewater supplied is 200 m ³ / day, the ammoniacal nitrogen concentration (C) of the ammoniacal nitrogen-containing wastewater is 1000 mgN / L, and the alkalinity is 3000 mg / L. . In this case, the load of ammonia nitrogen flowing into the partial nitrite reactor is 200 kgN / day, and the load of alkalinity is 600 kgCaCO ₃ / day. The nitrite nitrogen concentration in the partially nitrided water after the confluence is 1.32 times the ammonia nitrogen concentration. That is, the amount of nitrite nitrogen produced is 114 kgN / day.

[In the case of the processing method according to this embodiment]
The simulation will be described below again with reference to FIG. In this simulation, the inflow amount of the ammoniacal nitrogen-containing wastewater into the nitrite tanks 1A and 1B is 0.5Q = 100 m ³ / day / tank. Assuming that the volume (V) of the nitrite tanks 1A and 1B is 50 m ³ , the nitrite nitrogen production rate required to achieve the above-mentioned nitrite nitrogen production amount is 1 in both the nitrite tanks 1A and 1B. 14 kgN / m ³ · day (m ³ in the unit of nitrite nitrogen generation rate represents per 1 m ³ of nitrite tank capacity). With this nitrite nitrogen production rate, nitrite nitrogen of 50 × 1.14 = 57 kgN / day, 114 kgN / day in total, is produced from the nitrite tanks 1A and 1B.

  Here, in this simulation, the alkalinity consumed for the production of nitrite nitrogen is defined as the amount of nitrite nitrogen × 7.14. Therefore, 814 kg / day of alkalinity is consumed in the production of nitrite nitrogen. Of this, 600 kg / day is contained in the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A or 1B, so it is necessary to supplement the alkalinity of 214 kg / day by introducing an alkaline chemical.

[Bypass method]
For example, in the system shown in FIG. 9, the capacity of the nitrite tank 116 is V = 100 m ³ . The nitrite rate in the nitrite tank 116 is 1.14 kgN / m ³ · day, which is the same as in the treatment method according to this embodiment. Under these conditions, if the flow rate of the ammoniacal nitrogen-containing wastewater into the nitrite tank 116 is 114 m ³ / day and the wastewater amount of the ammoniacal nitrogen-containing wastewater into the raw water bypass channel is 86 m ³ / day, the above-mentioned nitrite nitrogen generation is generated. Amount can be achieved. At this time, 114 kgN / day of ammonium nitrogen flows into the nitrite tank, while the nitrite nitrogen production capacity of the nitrite tank is 1.14 × 100 = 114 kgN / day, which is ideal. A high nitrite nitrogen production of 114 kg N / day can be achieved.

  In this case, the amount that can be used as the alkalinity contained in the ammoniacal nitrogen-containing wastewater is 342 kg / day contained in the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 116. It is necessary to make up for it by adding drugs.

  Therefore, according to the processing method of the present embodiment, it is possible to reduce the amount of the alkaline chemical input to be half or more as compared with the method using the bypass.

<Simulation 2: Comparison with the method with one nitrite tank>
In the simulation 2, between the treatment method according to the present embodiment and the conventional method (for example, the treatment method shown in FIG. 10) in which the nitrite tank is one, The recovery process was compared.

In this simulation, the total amount of the ammoniacal nitrogen-containing wastewater (Q) supplied is 200 m ³ / day, the ammoniacal nitrogen concentration (C) of the ammoniacal nitrogen-containing wastewater is 1000 mgN / L, and the alkalinity is 3000 mg / L. . In this case, the total amount of ammoniacal nitrogen is 200 kgN / day, and the total amount of alkalinity is 600 kg / day. The ideal nitrite nitrogen concentration in the partially nitrided water after joining is 1.32 times the ammonia nitrogen concentration. That is, the ideal amount of nitrite nitrogen produced is 114 kgN / day.

In this simulation, the initial nitrite rate is 1.30 kgN / m ³ · day. In this case, 130 kgN / day of nitrite nitrogen, which is more than the ideal 114 kgN / day, is generated.

[In the case of the processing method according to this embodiment]
The simulation will be described below with reference to FIG. 5 again. The volume (V) of the nitrite tanks 1A and 1B is 50 m ³ . The flow rate q of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1A (flow rate decrease side) is 49 m ³ / day, and the flow rate of the ammoniacal nitrogen-containing wastewater flowing into the nitrite tank 1B (flow rate increase side) is Adjust to 151 m ³ / day. Then, 49 kgN / day is generated from the nitrite tank 1A, and 65 kgN / day of nitrite nitrogen is generated from the nitrite tank 1B, which is an ideal nitrite nitrogen production amount of 114 kgN / day. Is achieved.

  In this case, since the alkalinity of 600 kg / day contained in the ammoniacal nitrogen-containing wastewater can be utilized for the nitrite nitration step, it is necessary to supplement the alkalinity of 214 kg / day by introducing an alkaline chemical.

[In the case of the method in which there is one nitrite tank]
When there is only one nitrite tank, it is difficult to return the nitrite nitrogen concentration to a suitable state while continuing to introduce the entire amount of the ammoniacal nitrogen-containing wastewater into the nitrite tank. One of the simplest means is to bypass a part of the ammoniacal nitrogen-containing wastewater. In this case, when an ammoniacal nitrogen-containing wastewater of 114 m ³ / day is flowed into the nitrite tank and 86 m ³ / day of water is flowed into the bypass, an ideal nitrite nitrogen generation amount is achieved. At this time, 114 kgN / day of ammonium nitrogen flows into the nitrite tank, while the nitrite nitrogen producing capacity of the nitrite tank is 1.30 × 100 = 130 kgN / day, so the total amount of nitrite is Is converted to convert all ammoniacal nitrogen to nitrite nitrogen.

  In this case, of the alkalinity contained in the ammoniacal nitrogen-containing wastewater, only 342 kg / day flowing into the nitrite tank can be used for the nitrite nitration step, so the alkalinity must be supplemented with 472 kg / day of alkalinity. .

  As described above, the treatment method according to the present embodiment can achieve an ideal nitrite nitrogen generation amount while maximizing the alkalinity contained in the ammoniacal nitrogen-containing wastewater.

  In addition, in this embodiment, the structure in which the partial nitrite reactor 10 includes two nitrite tanks 1A and 1B has been described. However, the number of the nitrite tanks is not particularly limited as long as a plurality of the nitrite tanks are arranged in parallel.

  In the partial nitrite reactor 10, the opening / closing gate 6 whose position is always fixed was used as a switching unit for moving the fluid carrier 2 between the nitrite tanks 1A and 1B. However, the configuration of the switching unit of the partial nitrite reactor 10 in the present embodiment is not particularly limited as long as it has a function of switching communication and shielding between the nitrite tanks. For example, the switching unit can be a removable partition that can divide the nitrite tank at an arbitrary ratio (or at a preset ratio). In this case, the same effect as opening the opening / closing gate 6 can be obtained by removing the partition and making the nitrite tanks 1A and 1B into a single non-divided nitrite tank. In addition, in the configuration including the partition described above, it is possible to adjust the ammonia nitrogen load to each of the divided nitrite tanks by arbitrarily changing the tank volume instead of the flow rate ratio, so that it is fixed in addition to the fluid carrier. A carrier can also be preferably used.

  Further, the variable inflow water supply mechanism 4 adjusts the nitrite tanks 1A and 1B so that the nitrite nitrogen concentration of the partially nitrite waters joined by the joining pipe 5 becomes 1.32 times the ammonia nitrogen concentration. In between, the flow rate of the ammoniacal nitrogen-containing wastewater was changed and supplied. That is, the ratio of nitrite nitrogen concentration / ammonia nitrogen concentration was set to the optimum value of 1.32 for anammox reaction. However, the ratio of nitrite nitrogen concentration / ammonia nitrogen concentration is not limited to 1.32, and can be set to a predetermined ratio as appropriate according to the treatment technology of ammonia nitrogen-containing wastewater.

[Example: Adjustment of nitrite concentration]
Two 5 L water tanks equipped with an air diffuser (air stone) and a pH controller were prepared. In addition, caustic soda was used as an alkaline chemical for pH control. A fluid carrier (manufactured from fibers) in which activated sludge (collected from a sludge regeneration treatment center) was absorbed was charged into both water tanks by an apparent volume of 1.5 L each. These were made into the nitrite tank paralleled to two tanks.

  Ammonium chloride, potassium bicarbonate, and trace metals were dissolved in tap water, and a liquid having an ammoniacal nitrogen concentration of 1000 mgN / L and an alkalinity of 3000 mg / L was prepared as ammoniacal nitrogen-containing wastewater. The same amount of the ammonia-containing nitrogen-containing wastewater was constantly supplied to each nitrite tank, and the pH in the tank was controlled within the range of 7.9 ± 0.1.

  During the acclimatization period of 2 months, gradually increase the amount of ammonia nitrogen-containing wastewater supplied, and finally supply the amount of ammonia nitrogen-containing wastewater 6 L / day / tank, hydraulic retention time 20 hours, supply nitrogen load Was 1.2 g N / L · tank. At this point, the water quality of the partially nitrite water after the nitrite treatment in each nitrite tank has a small difference, the ammonia nitrogen concentration is 290 to 300 mgN / L, and the nitrite nitrogen concentration is 690 to 700 mgN. / L, and the nitrate nitrogen concentration was 10 mgN / L.

  Regarding the water quality of the partially nitrite water, nitrite nitrogen is excessive for the anammox reaction. Therefore, the flow rate q of the tank for reducing the flow rate was obtained according to the following equation (8) in which each value was substituted into equation (3).

q = 12 * (0.57 * 1000-0.5 * 700) /1000=2.64 (L / day) Formula (8)
The amount of the ammoniacal nitrogen-containing wastewater supplied to the nitrite tank for decreasing the flow rate is set to 2.64 L / day obtained by the formula (8), and the amount of the ammoniacal nitrogen-containing wastewater supplied to the nitrite tank for increasing the flow rate is set to 12 Each nitrite tank was operated at -2.64 = 9.36 L / day, and the obtained results are shown in Table 1.

  As shown in Table 1, the nitrite nitrogen concentration in the partially nitrite water after merging is 1.28 times the ammonia nitrogen concentration, and should be close to the ideal 1.32 times for the anammox reaction. I was able to.

  As described above, according to the treatment apparatus and the treatment method of the present invention, it is easy to adjust to an ideal nitrite nitrogen generation amount, particularly when nitrite nitrogen is excessively produced. In addition, the total amount of the ammoniacal nitrogen-containing wastewater flows into the partial nitrite reactor 10 and the alkalinity contained in the ammoniacal nitrogen-containing wastewater can be utilized to the maximum, so that the amount of the alkaline chemical input is reduced.

  INDUSTRIAL APPLICABILITY The present invention can be used for treating wastewater containing a high concentration of ammonia nitrogen.

1A, 1B Nitrite tank 2 Fluid carrier 3 Air diffuser 4 Variable inflow water supply mechanism 5 Combined piping (combining equipment)
6 Open / close gate (switching part)
7 Carrier Outflow Prevention Mechanism 8 Alkaline Chemical Supply Facility 9 Tank Water Quality Detector 10 Partial Nitrite Reactor 20 Anammox Reactor 50 Treatment Device

Claims (6)

A treatment device comprising a partial nitrite reactor for performing a partial nitrite treatment of ammoniacal nitrogen-containing wastewater,
The partial nitrite reactor is
A plurality of nitrite tanks arranged in parallel with each other,
A confluence facility that joins the partial nitrite water that has flowed out of each of the plurality of nitrite tanks,
The flow rate of the ammoniacal nitrogen-containing wastewater is changed between the plurality of nitrite tanks so that the nitrite nitrogen concentration of the partial nitrite water joined by the merging facility becomes a predetermined multiple of the ammonia nitrogen concentration. Inflow water amount variable supply mechanism for supplying
Equipped with
Each of the plurality of nitrite tanks comprises a fluid carrier carrying a group of ammonia-oxidizing bacteria,
A processing apparatus comprising a switching unit that switches between movement and separation of the fluidized carrier between the plurality of nitrite tanks .   The processing device according to claim 1, wherein each of the plurality of nitrite tanks comprises an ammoniacal nitrogen concentration meter and a nitrite nitrogen concentration meter.   The processing apparatus according to claim 1 or 2, further comprising a switching unit that switches between communication and shielding between the plurality of nitrite tanks. The said partial nitrite reactor is equipped with two nitrite tanks which are mutually equal in capacity, The processing apparatus in any one of Claims 1-3 characterized by the above-mentioned. A method for treating ammoniacal nitrogen-containing wastewater using the treatment apparatus according to any one of claims 1 to 4 ,
When the nitrite nitrogen concentration in the partially nitrated water joined by the joining facility becomes larger than a predetermined multiple of the ammonia nitrogen concentration, the inflow water amount variable supply mechanism,
To one of the plurality of nitrite tanks, which is the first nitrite tank, is used ammonia ammonia so that the ammoniacal nitrogen of the partial nitrite water flowing out from the first nitrite tank does not remain. While supplying nitrogen-containing wastewater,
The remaining ammoniacal nitrogen-containing wastewater is supplied to the second nitrite tank other than the first nitrite tank ,
In each of the plurality of nitrite tanks, partial nitrite treatment is carried out by a fluid carrier carrying a group of ammonia-oxidizing bacteria, and the treatment device is the fluid carrier between the plurality of nitrite tanks. Equipped with a switching unit that switches between moving and separating
When there is a difference in nitrite nitrogen producing capacity between the plurality of nitrite tanks, the switching unit is opened to homogenize the fluid carrier between the plurality of nitrite tanks, A method for treating wastewater containing ammoniacal nitrogen, which comprises averaging the nitrite nitrogen producing capacities of the respective nitrite tanks . When the nitrite nitrogen concentration in the partially nitriding water joined by the joining facility becomes a predetermined multiple or less of the ammonia nitrogen concentration, by the inflow water amount variable supply mechanism,
The method for treating ammoniacal nitrogen-containing wastewater according to claim 5 , wherein the ammoniacal nitrogen-containing wastewater is supplied to each of the plurality of nitrite tanks so that the inflow amounts thereof are all equal.

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