JP2016077954A - Biological nitrogen removal method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological nitrogen removal method where, in the case the inhibitory substance of anaerobic ammonia oxidation reaction caused by anammox bacteria is contained in ammonia nitrogen-containing waste water, only by removing the inhibitory substance by a simple method, denitrification is performed more stably, using anammox bacteria.SOLUTION: Provided is a biological nitrogen removal method where ammonia nitrogen-containing waste water including a substance checking anaerobic ammonia oxidation reaction caused by anammox bacteria is treated, in which, in a nitritation step where the ammonia nitrogen-containing waste water is contacted with ammonia oxide bacteria to oxidize a part of the ammonia nitride into nitrite nitrogen, in the tank, using a nitritation tank including a fixed bed or a fluidized bed in which the amount of biological sludge per carrier surface area is 1.6 to 8.0 g-VSS/m, in the nitritation tank, the ammonia nitrogen is oxidized into nitrogen nitrate, and further, inhibiting substance is removed by biological sludge held to the carrier.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a biological nitrogen removal method, and more particularly, a substance that inhibits anaerobic ammonia oxidation reaction by autotrophic denitrifying microorganisms contained in ammoniacal nitrogen-containing wastewater is a part of ammoniacal nitrogen. A biological process that uses biological sludge to reduce the nitritation process to oxidize nitrite to nitrite nitrogen (hereinafter simply referred to as the “nitrite-type nitrification process”), thereby improving its treatment efficiency. The present invention relates to a nitrogen removal method.

A technique for purifying nitrogen-containing wastewater using autotrophic denitrifying microorganisms (hereinafter referred to as “anammox bacteria”) is known. This technology oxidizes a part of ammonia nitrogen (NH ₄ -N) in nitrogen-containing wastewater to nitrite nitrogen (NO ₂ -N) in the nitrite type nitrification process, and then uses anammox bacteria Anammox process that performs anaerobic ammonia oxidation reaction (hereinafter referred to as “anammox reaction”) has been introduced. Compared with conventional nitrification denitrification, the amount of aeration is reduced, the amount of organic substances such as methanol is reduced, and surplus It is said that sludge can be reduced (Patent Document 1).

Here, in order to efficiently and stably denitrify in the anammox process, ammonia nitrogen (NH ₄ -N) and nitrite in the treated water are treated in the nitrite type nitrification process from the following anammox reaction formula. It is known that the ratio of nitrogen (NO ₂ —N) is preferably 1: 1.32 (0.43: 0.57).

On the other hand, conventionally, as a method for controlling the ratio of ammonia nitrogen and nitrite nitrogen in the effluent from the nitritation tank, an effluent from the nitrification tank is used by using an NH ₄ -N concentration measuring device. Is used to automatically sample the total nitrogen concentration and ammonia nitrogen (NH ₄ -N) concentration, and use this to control the nitrite type nitrification step so that the above-mentioned ratio becomes the optimum concentration ratio Has been proposed (Patent Document 2).

JP 2003-33784 A Japanese Patent No. 5006849

However, anammox bacteria are known to be inferior in resistance to other bacteria and the countermeasures are considered. However, as a result of detailed investigations by the present inventors, phenols contained in wastewater Biological activities are inhibited by organic substances such as organic substances and heavy metals, and the effects of these inhibitors are not negligible. As described later, wastewater treated by anammox bacteria, which has been considered difficult in the past Even if the ratio of ammonia nitrogen (NH ₄ -N) and nitrite nitrogen (NO ₂ -N) is optimized, it is not sufficient, and these substances are reduced in advance so that the anammox reaction is not affected If not, it has been found that efficient biological treatment cannot be expected.

  That is, in the biological nitrogen removal method in which wastewater containing ammonia nitrogen and nitrite nitrogen is denitrified using anammox bacteria, there is an inhibitor against anammox bacteria in the wastewater to be treated. The anammox reaction does not proceed in a good state, and there is a problem that stable nitrogen removal cannot be performed. More specifically, the growth of anammox bacteria is extremely slow, and once the cells are damaged by the inhibitor, it takes a long time to recover, so anammox bacteria are used against wastewater containing the inhibitor. It was found that it is difficult to apply a biological nitrogen removal method that denitrifies and to perform a stable treatment. Here, examples of the inhibitor include heavy metals such as zinc, phenols, cyans, and thiocyans. On the other hand, the actual wastewater contains many of the above-mentioned inhibitors, and the problem of inhibitors is an important issue that cannot be avoided in practical use. It was a big issue when putting the wastewater treatment method to practical use, and it came to recognition that finding the solution was an urgent task.

As described above, in order to further increase the treatment efficiency of wastewater treatment using anammox bacteria, nitrogen-containing wastewater to be treated in the anammox process is separated from ammonia nitrogen (NH ₄ -N) and sub- It is desirable that the ratio to nitrate nitrogen (NO ₂ —N) is reliably optimized. Therefore, in the technique described in Patent Document 2 described above, by measuring the ammonium nitrogen (NH ₄ -N) concentration in the waste water, whereby ammonia nitrogen wastewater treatment with (NH ₄ -N) nitrous It is assumed that the concentration ratio with nitrate nitrogen (NO ₂ —N) is optimized. On the other hand, the ammoniacal nitrogen (NH ₄ -N) measuring device currently on the market is not for continuous measurement, but automatically samples the water to be measured, and then adjusts the sampled liquid to a strongly alkaline pH of 12. Since this is a method of measuring the adjusted liquid, there is a time lag until the measured value comes out, the control is not in line with the current situation, the actual wastewater is more efficient In order to handle well, there are also points to be improved on this point. For this reason, in order to stabilize the treatment in the Anammox process, it is necessary to develop means that can reduce the inhibitory substances contained in the wastewater treated in the Anammox process to a level that does not affect the treatment. In addition, in order to improve the treatment efficiency compared to the conventional method and stabilize the treatment efficiency, ammonia nitrogen (NH ₄ -N) and nitrite nitrogen (NO) in actual wastewater treated with anammox bacteria in the anammox process are used. It is desirable to be able to optimize the _2- N) ratio more reliably without time lag. Furthermore, in order to put the biological nitrogen removal method described above into practical use, there is a requirement that the means must be able to be achieved by a simpler method.

  Therefore, the object of the present invention is to prevent the inhibitory activity of these inhibitors in advance by a simple method when the ammonia nitrogen containing wastewater contains inhibitors of the anammox reaction by anammox bacteria. The purpose is to establish a biological nitrogen removal method that can reduce denitrification and enable denitrification treatment using more stable and efficient anammox bacteria. In addition to the above, the object of the present invention is to realize stable oxidation of ammoniacal nitrogen in wastewater treated with anammox bacteria to nitrite nitrogen at a desired ratio, It is to provide a nitrite type nitrification method of ammoniacal nitrogen-containing wastewater that can enable more efficient denitrification treatment. The final object of the present invention is to solve the above-mentioned problems. Conventionally, although it is an excellent technique, it has been considered difficult to put it to practical use due to unique problems caused by using anammox bacteria. The aim is to develop a method for purifying nitrogen-containing wastewater using the anammox reaction into an efficient and stable treatment technique that can be industrially put into practical use.

The above object is achieved by the present invention described below. That is, the present invention treats an ammoniacal nitrogen-containing wastewater containing at least one of heavy metals, phenols, thiocyans, and cyanes that inhibits anaerobic ammonia oxidation reaction by autotrophic denitrifying microorganisms. A biological nitrogen removal method comprising contacting an ammonia-containing nitrogen-containing wastewater with an ammonia-oxidizing bacterium, which is provided before a denitrification step in which an anaerobic ammonia oxidation reaction is performed by contacting an autotrophic denitrifying microorganism. In the nitritation step of oxidizing a part of ammonia nitrogen to nitrite nitrogen, the fixed bed or the amount of biological sludge per carrier surface area is 1.6 to 8.0 g-VSS / m ² in the tank, or Using a nitritation tank having a fluidized bed, the ammonia nitrogen is oxidized to nitrite nitrogen in the nitritation tank, and the inhibition is performed by the biological sludge held on the carrier. Removing the quality, to provide a biological nitrogen removal method characterized by reducing the inhibitor of the vessel to the extent not affecting the anaerobic ammonium oxidation reactions.

  In addition to the above-described configuration, the biological nitrogen removal method of the present invention preferably further includes the following configuration. The biological sludge concentration in the nitritation tank is 200 to 1000 mg-VSS / L; when the inhibitor contained in the ammoniacal nitrogen-containing wastewater is heavy metal and the concentration is 1.0 mg / L or more Adjusting the pH of the nitritation tank to 8.0 to 9.0; when the concentration of each inhibitor contained in the ammoniacal nitrogen-containing wastewater is phenols, 10 mg / L or more, In the case of thiocyans, it is 10 mg / L or more, and in the case of cyanides, it is 0.01 mg / L or more; it is mentioned that the carrier is a sponge made of polyurethane or polyolefin.

As a more preferable form of the biological nitrogen removal method of the present invention, in addition to the above-described structure, the following structure is also preferable. Furthermore, each using an ammonia measuring device using a free ammonia gas-selective diaphragm type electrode, the free ammonia (NH ₃ ) concentration a of the ammoniacal nitrogen-containing wastewater that is the inflow water to the nitritation tank, free ammonia nitrite reduction vessel (NH ₃₎ concentration b or free ammonia in the effluent water from the nitritation tank (NH ₃₎ concentration b were measured continuously, resulting free ammonia (NH ₃₎ based on the measured values of the density to calculate the concentration of ammonia nitrogen (NH ₄ -N), respectively, the concentration of free ammonia (NH ₃₎ ammonium nitrogen which is calculated based on the concentration a (NH ₄ -N) Assuming that A is the concentration of ammonia nitrogen (NH ₄ -N) calculated based on the free ammonia (NH ₃ ) concentration b, B is ammonia nitrogen (NH ₄ ) at each time point. _The amount of aeration in the nitritation tank is controlled by a control device so that the concentration ratio B / A of _4- N) falls within the target range; the target ammoniacal nitrogen (NH ₄ -N) ) In the range of the concentration ratio B / A is 0.28 to 0.58.

  According to the present invention, when an ammonia nitrogen-containing wastewater contains an inhibitor against an anammox reaction by anammox bacteria, these inhibitors are removed by a simple method, and the treatment by the anammox reaction is affected. There is provided a biological nitrogen removal method capable of more stable and efficient treatment that achieves a reduction to a certain extent. Further, according to a preferred embodiment of the present invention, in addition to the above, it is possible to stably oxidize ammonia nitrogen in the influent water to nitrite nitrogen at a desired ratio, thereby achieving anammox It is possible to provide a biological nitrogen removal method that enables more efficient denitrification treatment by bacteria. According to the present invention, there is provided a method for purifying nitrogen-containing wastewater using an anammox reaction, which has been considered difficult to put into practical use, due to peculiar problems resulting from the use of anammox bacteria while being an excellent technique. Therefore, it is possible to develop an efficient and stable processing technique that can be industrially put into practical use.

It is a figure which shows typically the basic flow of the biological nitrogen removal method of this invention using the nitritation tank which has a fixed bed. It is a figure which shows typically the basic flow of the biological nitrogen removal method of this invention using the nitritation tank which has a fluidized bed. The basic flow of the control device to constantly optimize the concentration ratio of ammonia nitrogen (NH ₄ -N) and nitrite nitrogen (NO ₂ -N) is a diagram schematically showing.

  Hereinafter, the present invention will be described in more detail with reference to preferred embodiments. As described above, the present inventors have a problem in carrying out the stable treatment in order to make the denitrification treatment using anammox bacteria industrially practical. Recognized that it is important to reduce the inhibitory substances contained in the wastewater to be treated to a concentration that does not inhibit the reaction of anammox by simple means. . As a result of intensive studies to solve the above-mentioned problems, the present inventors, for actual wastewater containing an inhibitor in an amount that affects the activity of anammox bacteria, By applying a very simple treatment of passing through a fixed bed or fluidized bed carrying biological sludge placed in the tank, the inhibitor present in the wastewater is brought to a concentration that does not inhibit the activity (reaction) of anammox bacteria. The inventors have found that it is possible to achieve a reliable reduction until the present invention.

  Further, according to the study by the present inventors, examples of inhibitors against the activity of anammox bacteria include heavy metals such as zinc, phenols, cyans, and thiocyans. In any case, the method of the present invention is used. By carrying out, the influence on the activity of the anammox bacteria resulting from these inhibitors can be reduced. According to the study by the present inventors, the concentration of these inhibitors, which are clearly shown to inhibit the activity of anammox bacteria, in wastewater is 1.0 mg / L in the case of heavy metals such as zinc. The concentration of these substances is 10 mg / L or more in the case of phenols, 10 mg / L or more in the case of thiocyans, and 0.01 mg / L or more in the case of cyans. In order to perform efficient processing, it is effective to reduce the number.

More specifically, in the present invention, the treatment is stabilized by excluding the influence on the anammox reaction caused by the presence of the above-described inhibitory substances in the wastewater by the following configuration. . First, in the anammox reaction, which is attracting attention as an innovative method for removing nitrogen that does not use organic matter, which is used in the present invention, in order to increase the treatment efficiency, an ammonia nitrogen-containing wastewater is added before the anammox reaction. There is a need for a nitritation step that contacts ammonia-oxidizing bacteria to oxidize some of the ammoniacal nitrogen to nitrite nitrogen. In the present invention, the amount of biological sludge (activated sludge) per surface area of the carrier is 1.6 to 8.0 g-VSS / m ² , more preferably in the treatment tank (nitritation tank) used in this nitritation step. Removes the inhibitory substances present in the wastewater to be treated to a level that does not affect the reaction, and reduces by arranging a fixed bed or fluidized bed of 4.0 to 8.0 g-VSS / m ² To be configured. That is, in the present invention, the function as an inhibitor removal tank is further added to the nitritation tank used in the nitritation step required when performing efficient denitrification treatment using anammox bacteria. Although it is an excellent method in principle, the denitrification treatment using anammox bacteria, which has a problem in practical use, can be made more stable by an extremely simple configuration of having the structure.

  The material of the fixed bed or fluidized bed carrying biological sludge disposed in the treatment tank used in the nitritation process characterizing the present invention is not particularly limited, and any of activated carbon, various plastic carriers, sponge carriers, etc. Can also be used. Among them, it is preferable to use a sponge carrier or a porous carrier, particularly a sponge carrier because biological sludge can be carried at a high concentration. Further, according to the study by the present inventors, in particular, when a sponge carrier is used, it is more effective for removing the inhibitory substance intended by the present invention. The sponge material used in the present invention is not particularly limited, but is preferably made of polyurethane or polyolefin. Among these, those made of polyurethane are preferred. Although there is no restriction | limiting in particular also as the quantity of the support | carrier to arrange | position, Generally, it is about 20-50% by the apparent capacity | capacitance (ratio at the time of dense packing) with respect to the tank capacity of a biological treatment reaction tank, Especially about 30-40% It is preferable that

  Further, according to the study by the present inventors, the biological sludge concentration in the nitritation tank in which the fixed bed or the fluidized bed carrying the biological sludge made of the material as described above is 200 to 1000 mg-VSS / L, more preferably about 500 to 1000 mg-VSS / L. The concentration of ammoniacal nitrogen in the wastewater is not particularly limited, but when treating wastewater with a low nitrogen concentration (300 mg / L or less) at a high load, the biological sludge concentration can be maintained high by a fixed bed or fluidized bed. Makes it possible to produce nitrite nitrogen.

  Further, according to the study by the present inventors, when the inhibitor against anammox bacteria contained in the ammoniacal nitrogen-containing wastewater is a heavy metal such as zinc, a fixed bed or fluidized bed carrying the biological sludge is disposed. In addition to using the nitritation tank, it has been found effective to adjust the pH in the treatment tank to 8.0 to 9.0. In this way, it is possible to reduce the amount of heavy metals in the wastewater when the concentration of heavy metals in the wastewater, which is clearly affected by the anammox reaction, is 1.0 mg / L or more. The anammox reaction becomes stable.

Furthermore, in a preferred embodiment of the present invention, in addition to the above, by configuring as described below, the measured value of free ammonia (NH ₃ ) concentration that can be continuously measured is skillfully used, and anammox is used. In the nitrite type nitrification process performed prior to the process, the amount of aeration is adjusted as appropriate to partially oxidize a part of ammonia nitrogen (NH ₄ —N) to nitrite nitrogen (NO ₂ —N), and the anammox process The ratio of ammonia nitrogen (NH ₄ -N) and nitrite nitrogen (NO ₂ -N) in the wastewater introduced into the reactor can be reliably controlled within a desired range with high accuracy.

Specifically, in the nitrite type nitrification process, continuous measurement of the free ammonia concentration of the inflow water to the nitritation tank and the nitrification liquid in the nitritation tank or the outflow water from the nitritation tank, The concentration ratio of the ammonia nitrogen in the nitrification liquid in the nitrification tank or the effluent from the nitrification tank and the ammonia nitrogen concentration of the inflow water to the nitrification tank calculated based on the measured value is the target value. Thus, the amount of aeration in the nitritation tank is controlled by the control device. By doing so, the ratio of ammonia nitrogen (NH ₄ -N) and nitrite nitrogen (NO ₂ -N) in the wastewater introduced into the anammox process is surely stable so as to be within a desired range. To be controlled. That is, according to the study by the present inventors, an existing free ammonia measuring device is used in a nitrite type nitrification method for wastewater containing ammoniacal nitrogen that oxidizes ammoniacal nitrogen in the influent water to nitrite nitrogen at a desired ratio. , And continuously measuring the free ammonia (NH ₃ ) concentration with the apparatus, and using these values to control the amount of aeration in the nitritation tank, ammonia nitrogen (NH ₄ − The ratio of N) to nitrite nitrogen (NO ₂ —N) is stably maintained with high accuracy within a desired range optimum for the anammox process.

FIG. 3 schematically shows the basic flow of the above nitrite type nitrification method. Referring to FIG. 3, an ammoniacal nitrogen measuring device 1a is used, and in the illustrated example, the free ammonia (NH ₃ ) concentration a in the raw water tank 3 serving as inflow water is continuously measured, and the information is controlled by the control device. The concentration A of ammonia nitrogen (NH ₄ —N) is continuously calculated by the apparatus. In parallel with this, in the illustrated example, the free ammonia (NH ₃ ) concentration b of the nitrification liquid in the nitrification tank (nitrite type nitrification tank) 4 is continuously measured using the ammoniacal nitrogen measuring device 1a ′. Then, the information is sent to the control device 2, and the concentration B of ammoniacal nitrogen (NH ₄ -N) is continuously calculated by the device. Then, the control device 2, and the concentration A of the obtained in ammonia nitrogen at each time point (NH ₄ -N), calculates the ratio between the concentration B of ammonia nitrogen (NH ₄ -N), is the ratio A signal is sent from the control device 2 to the aeration device 5 of the nitritation tank 4 so as to be within the set target value range, and the aeration amount is controlled.

As described above, from the following anammox reaction formula, the ratio of ammonia nitrogen (NH ₄ -N) and nitrite nitrogen (NO ₂ -N) in the wastewater to be treated introduced into the anammox process is: It is desirable to set it as 1: 1.32 (0.43: 0.57). Therefore, to set as the target in the present invention, a concentration A of ammonium nitrogen (NH ₄ -N), as the ratio B / A between the density B of the ammonium nitrogen (NH ₄ -N) is 0.28～ A range of 0.58 is preferable. According to the study by the present inventors, when the target value is set in such a range, ammonia nitrogen in actual waste water (inflow water) is stably oxidized to nitrite nitrogen at a desired ratio. Is realized. Furthermore, by controlling in this way, it confirmed that the denitrification process by anammox bacteria performed after that could be performed more efficiently and stably.

Hereinafter, the present invention will be described in more detail with reference to Examples and Comparative Examples.
Example 1
Processing was performed by the apparatus shown in FIG. Using a 50-liter nitritation tank installed with a fixed bed made of vinyl chloride at a filling rate of 60% in the tank, after introducing activated sludge derived from sewage sludge, artificial wastewater having the composition shown in Tables 1 to 3 Was supplied as raw water.

The treatment was controlled so that the HRT was 3.0 hrs, the pH was 7.6, and the water temperature was 30 to 33 ° C. And it was acclimatized for about 4 weeks, and it confirmed that the biofilm was adhering to the support | carrier surface. The biological sludge concentration in the tank thus adjusted was 500 mg-VSS / L. And it processed, adjusting aeration amount suitably so that about 57% of ammonia nitrogen of raw | natural water might turn into nitrite nitrogen. The nitrogen load at this time is 1.0 kg-N / m ³ / day.

After acclimatization of the nitritation tank, 2 L of anammox granule is introduced into the 4 liter anammox tank shown in FIG. 1 and the pH of the nitritation water is adjusted to 7.2. The inflow of waste water as described above was started. The treatment was performed at a water temperature of 30 ° C. to 33 ° C. and a nitrogen load of 10 kg-N / m ³ / day. Table 4 shows the analysis results of the raw water, the treated water after the nitritation treatment, and the treated water in the anammox tank.

(Example 2)
In this example, the treatment was carried out by the apparatus using the fluidized bed shown in FIG. Specifically, using a 50-liter nitritation tank filled with 20% apparent volume of a fluidized bed made of polyurethane sponge (10 mm square) in the tank, the activity derived from sewage sludge was the same as in Example 1. After introducing the sludge, artificial wastewater having the composition shown in Tables 1 to 3 was supplied as raw water.

The treatment conditions were controlled so that the HRT was 2.0 hrs, the pH was 7.6, and the water temperature was 30 to 33 ° C. And it was acclimatized for about 4 weeks, and it confirmed that the biofilm was adhering to the support | carrier surface. Thus, the biological sludge density | concentration in the tank adjusted was high compared with the fixed bed of Example 1, and was 700 mg-VSS / L. And it processed, adjusting aeration amount suitably so that about 57% of ammonia nitrogen of raw | natural water might turn into nitrite nitrogen. The nitrogen load at this time is 1.0 kg-N / m ³ / day. Table 5 shows the analysis results of the raw water, the treated water after the nitritation treatment, and the treated water in the anammox tank.

(Comparative example)
The raw water in which the nitrogen component composition of the artificial wastewater described in Table 1 was changed to 236 mg / L ammonium sulfate and 246 mg / L sodium nitrite was not directly treated in the nitritation tank of the apparatus shown in FIG. I let you. The treatment was performed in the same manner as in Example 1 under the anammox water passage conditions. Table 6 shows the analysis results of the raw water and the treated water in the anammox tank.

(Processing results of Examples 1 and 2 and Comparative Example)
As is apparent from the results of Tables 4 and 5, when wastewater is treated by the treatment method of Example 1 or Example 2, that is, raw water containing an inhibitor is sublimated with a fixed bed or fluidized bed. Treatment in a nitration tank clearly reduced the concentration of inhibitor in the tank. In particular, the nitritation tank using the fluidized bed of Example 2 has a high biological sludge concentration, and can be operated with a shorter HRT than the nitritation tank using the fixed bed of Example 1. It was revealed that the nitrogen treatment ability and the ability to remove inhibitory substances were higher. On the other hand, from the results of Table 6, when raw water containing an inhibitory substance was directly introduced into the anammox tank, as in the comparative example, ammonia nitrogen (NH ₄ -N) and nitrite nitrogen ( Even if the concentration ratio with NO ₂ -N) was optimized, the processability of anammox was clearly reduced as compared with Examples 1 and 2. This means that the influence on the anammox treatment caused by including the inhibitor could be reduced.

(Example 3)
In this example, the artificial wastewater described in Table 1 was changed to phenol of 500 mg / L and thiocyan was changed to 100 mg / L, and raw water with increased concentrations of these inhibitors was prepared. 2 and 2, respectively. As a result, in both treatments, the phenol concentration and the thiocyan concentration in the nitritation tank treated water were less than 10 mg / L. That is, even when wastewater containing these inhibitory substances is in a high concentration region, the effect on the anammox treatment can be reduced by treating the wastewater in a nitritation tank provided with a fixed bed or fluidized bed as defined in the present invention. It was confirmed that the inhibitor concentration could be reduced to the level.

Example 4
Zinc sulfate was added to the artificial waste water shown in Table 1 as Zn at 5 mg / L, and this was used as raw water, and by using an apparatus having a fixed bed in the nitritation tank shown in FIG. The treatment was carried out by adjusting the pH to 7.5 to 9.5. The operation was performed under the same conditions as in Example 1 except for the pH conditions of this nitritation tank. Table 7 shows the raw water, the zinc concentration of the treated water after the nitritation treatment, and the nitrogen removal rate (%) of the anammox tank.

  From the treatment results shown in Table 7, in the raw water containing a large amount of zinc as an inhibitor, the zinc concentration of the treated water is reduced to 1 mg / L or less when the pH control condition of the nitritation tank is 8.0 or more. It became clear that it was preferable. And when the pH of the nitritation tank was made into the range of pH 8.0-9.0 especially, it turned out that the nitrogen removal rate of anamox is high. However, when the pH is adjusted to 9.5, the activity of ammonia oxidizing bacteria in the nitritation tank is reduced due to the influence of pH, so the amount of nitrite produced is reduced, and ammonia nitrogen and nitrite nitrogen that are optimal for anammox As a result, it was found that the nitrogen removal rate of Anammox tends to decrease. On the other hand, it was found that when the pH condition was 7.5, only about half of the zinc concentration was removed, and the nitrogen removal rate of Anammox was low. From this result, it was confirmed that it was effective to adjust the pH of the nitritation tank to 8.0 to 9.0 when zinc was contained as an inhibitory substance.

(Example 5)
As the water to be treated, actual raw water continuously treated with ammonia nitrogen (NH ₄ —N) concentration as described below was used, and the influence on the anammox treatment due to the inclusion of the inhibitory substance was confirmed. Specifically, as the water to be treated, an ammonia measuring device using a diaphragm-type electrode selective for free ammonia gas, and in parallel, the free ammonia (NH ₃ ) concentration a of water flowing into the nitritation tank, free ammonia nitrification liquid nitritation tank (NH ₃₎ free ammonia (NH ₃₎ of the effluent from the concentration b or nitritation tank and density b measured continuously, resulting free ammonia (NH ₃₎ based on the measured values of the density to calculate the concentration of ammonia nitrogen (NH ₄ -N) in each concentration of the free ammonia (NH ₃₎ ammonium nitrogen which is calculated based on the concentration a (NH ₄ -N) Is the concentration ratio of ammonia nitrogen (NH ₄ -N) at each time, where A is the concentration of ammonia nitrogen (NH ₄ -N) calculated based on the free ammonia (NH ₃ ) concentration b. B / A is 0. So as to be in the range of 8 to 0.58, using real raw water was continuously processed while controlling the aeration amount control device in the nitritation vessel. And when it processed on the conditions similar to Example 1, it was confirmed that a more stable process can be performed by using a control apparatus.

1a, 1a ': Ammonia nitrogen measuring device 2: Control device 3: Raw water tank 4: Nitrite tank 5: Aeration device

Claims (7)

Biological nitrogen removal method for treating ammonia nitrogen-containing wastewater containing at least one of heavy metals, phenols, thiocyans or cyanides, which inhibits anaerobic ammonia oxidation reaction by autotrophic denitrifying microorganisms Because
Ammonia nitrogen-containing wastewater is brought into contact with ammonia-oxidizing bacteria and placed in contact with autotrophic denitrifying microorganisms to perform denitrification by anaerobic ammonia oxidation reaction. In a nitritation step for oxidizing to basic nitrogen, a nitritation tank having a fixed bed or a fluidized bed in which the amount of biological sludge per carrier surface area is 1.6 to 8.0 g-VSS / m ² is used in the tank. In the nitrification tank, ammonia nitrogen is oxidized to nitrite nitrogen, and the inhibitor is removed by biological sludge held on the carrier, and the inhibitor in the tank is anaerobically ammonia oxidized. A biological nitrogen removal method, characterized in that the reaction is reduced to such an extent that the reaction is not inactivated.   The biological nitrogen removal method according to claim 1, wherein the biological sludge concentration in the nitritation tank is 200 to 1000 mg-VSS / L.   When the inhibitor contained in the ammoniacal nitrogen-containing wastewater is heavy metal and the concentration is 1.0 mg / L or more, the pH of the nitritation tank is adjusted to 8.0 to 9.0. The biological nitrogen removal method according to claim 1 or 2.   The concentration of each inhibitor contained in the ammonia-containing nitrogen-containing wastewater is 10 mg / L or more in the case of phenols, 10 mg / L or more in the case of thiocyans, 0.01 mg / L or more in the case of cyans, The biological nitrogen removal method according to any one of claims 1 to 3.   The biological nitrogen removal method according to any one of claims 1 to 4, wherein the carrier is a sponge made of polyurethane or polyolefin. Further, using an ammonia measuring device using a free ammonia gas-selective diaphragm electrode, free ammonia (NH ₃ ) concentration a of ammonia nitrogen-containing wastewater as inflow water to the nitritation tank, and the nitrous acid free ammonia (NH ₃₎ concentration b or free ammonia in the effluent water from the nitritation tank (NH ₃₎ concentration b were measured continuously in the reduction vessel, resulting free ammonia (NH ₃₎ concentration the concentration of ammonia nitrogen (NH ₄ -N) based on the measured values was calculated, the concentration of free ammonia (NH ₃₎ ammonium nitrogen which is calculated based on the concentration a (NH ₄ -N) and a , when the concentration of the free ammonia (NH ₃₎ ammonia is calculated based on the concentration b nitrogen (NH ₄ -N) is B, the ammonium nitrogen at each time point (NH ₄ -N) The biological nitrogen removal method according to any one of claims 1 to 5, wherein an aeration amount in the nitritation tank is controlled by a control device so that a degree ratio B / A is within a target range. . The biological nitrogen removal method according to claim 6, wherein the range of the target ammonia nitrogen (NH ₄ -N) concentration ratio B / A is 0.28 to 0.58.

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