JP2012236122A - Method for denitrification treatment of ammonium nitrogen and calcium-containing wastewater, and treatment apparatus for the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for denitrification treatment of ammonium nitrogen and calcium-containing wastewater capable of stably attaching and fixing an ammonium oxidizing bacterium to a carrier and capable of carrying out stable nitritation treatment; and to provide an apparatus for the same.SOLUTION: (1) The method for denitrification treatment of ammonium nitrogen and calcium-containing wastewater includes: a calcium concentration controlling step of controlling the calcium concentration in the ammonium nitrogen and calcium-containing wastewater according to the operation condition of the nitritation step; a nitritation step of fixing an ammonium oxidation bacterium to the carrier and for nitrating the wastewater in the presence of the wastewater obtained in the calcium concentration controlling step; and a denitrification step of denitrification of the wastewater containing nitrous acid and ammonium nitrogen obtained in the nitritation step. (2) The apparatus for denitrification treatment of the ammonium nitrogen and calcium-containing wastewater, carrying out the denitrification treatment of the ammonium nitrogen and calcium-containing wastewater of (1) and used for the calcium concentration controlling step, includes: an device for measuring the calcium concentration of the wastewater; a device for eliminating calcium; and a tank having a device for measuring an M-alkalinity concentration and an NH-N concentration. A device used in the nitritation step includes: a neutralizing agent-adding quantity-controlling device communicating with the device for measuring the M-alkalinity concentration and the NH-N concentration; and a nitritation tank having a neutralizing agent-injecting device communicating with the neutralizing agent-adding quantity-controlling device. A device used for the denitrification step includes a denitrification tank.

Description

  The present invention relates to a denitrification method and treatment apparatus for ammonia nitrogen and calcium-containing wastewater, and more particularly to nitrogen removal from ammonia and nitrogen-containing organic and inorganic waste liquids. It is related to nitrogen removal from waste leachate with high concentration, wastewater from semiconductor factories and chemical factories.

Generally, NH ₄ -N is high as a feature of leachate, and the concentration of organic substances such as BOD is low. Conventionally, a biological nitrification denitrification method is often used as a nitrogen removal method for such leachate. The biological nitrification denitrification method is usually composed of a nitrification process and a denitrification process. In the nitrification process of the first process, ammoniacal nitrogen in raw water is first oxidized to nitrite nitrogen by ammonia-oxidizing bacteria in an aerobic reaction tank, commonly called a nitrification tank, and then nitrite-nitrogen by nitrite-oxidizing bacteria. Is oxidized to nitrate nitrogen. In the denitrification process after the nitrification process, the treatment liquid (nitrification liquid) from this nitrification tank is introduced into an anaerobic reaction tank, commonly known as a denitrification tank, and nitrate nitrogen and nitrite nitrogen in the nitrification liquid are heterotrophic. The denitrifying bacteria are reduced to harmless nitrogen gas by the electron donor. As this electron donor, an organic substance in the liquid to be treated is usually used. When the amount of organic substances is small, it is necessary to add methanol as an electron donor from the outside.

  In this biological nitrification denitrification treatment, ammonia nitrogen in the inflow raw water is finally oxidized into nitrate nitrogen via nitrite nitrogen in the nitrification tank. For this reason, it is necessary to supply oxygen necessary for ammoniacal nitrogen oxidation to the nitrification tank. The required amount of oxygen is 4.57 times higher than that of raw water ammonia nitrogen, and the supply power cannot be ignored. Further, in the denitrification tank, an organic substance that becomes an electron donor is required in a dependent denitrification reaction in which nitrate nitrogen becomes an electron acceptor. When the organic water is small in the raw water, it is necessary to add methanol as an electron donor necessary for denitrification. In order to obtain stable denitrification performance, the amount of methanol added is usually required to be about 2.5 to 3 times the amount of nitrate nitrogen flowing into the denitrification tank. Thus, the aeration power of the nitrification process and the amount of methanol added in the denitrification process are enormous, and the running cost is high. These reductions are a major issue that must be solved to disseminate the nitrification denitrification process.

In recent years, a denitrification treatment method using an autotrophic denitrifying bacterium that is completely different from the conventional denitrifying mechanism using the heterotrophic denitrifying bacterium has been disclosed (for example, Patent Document 1). This uses an autotrophic microorganism that uses ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, and reacts ammonia nitrogen and nitrite nitrogen in an anaerobic state to convert them into nitrogen gas. And an ammonia ammonia oxidation process, a nitrogen removal method using a so-called ANAMX reaction, or an ammonia denitrification method. The following formula (1) shows a reaction formula of ammonia denitrification. As shown in the formula (1), in the case of ammonia denitrification, ammonia nitrogen and nitrite nitrogen directly react with each other, so that addition of organic substances such as methanol is unnecessary, and the chemical cost is greatly reduced. In addition, since the denitrification reaction is performed at a ratio of 1.32 mol of NO ₂ -N to 1 mol of NH ₄ -N, the ammonia nitrogen in the raw water to be treated is completely nitrite-like as in the conventional nitrification process. There is no need to oxidize to nitrate nitrogen, and a part of it may be oxidized to nitrite nitrogen. If 57% of the raw water NH ₄ —N is oxidized to nitrite nitrogen from the ammonia denitrification reaction, the NO ₂ —N / NH ₄ —N ratio of the ammonia denitrified raw water becomes 1.32. A reaction as shown is obtained, and it is possible to eliminate both NH ₄ —N and NO ₂ —N in the treated water.
1NH 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)

As described above, as a denitrification process using ammonia denitrification, it is necessary to first oxidize a part of ammonia nitrogen in the inflow raw water to nitrite nitrogen in the nitrification process. In order to obtain a high rate of denitrification performance by the ammonia denitrification reaction, it is desired that 57% of the raw water NH ₄ —N is changed to NO ₂ —N and 43% NH ₄ —N is left. In this case, the NO ₂ —N / NH ₄ —N ratio of nitrite-treated water is 1.32, which matches the NO ₂ —N / NH ₄ —N ratio required for the ammonia denitrification reaction shown in Formula (1). To do.

As NH ₄ —N in raw water is oxidized to NO ₂ —N, M-alkalinity is consumed. The M-alkalinity consumed by nitrification of 1 mg / L NH ₄ -N is 7.1 mg / L. If M- alkalinity ratio _NH 4 -N raw water is low, the raw water _NH 4 -N is low nitrification ratio of the treated water _NO 2 -N / _NH 4 -N ratio well below the 1.3 target value It becomes. Conversely, when the M-alkalinity of the raw water with respect to NH ₄ -N is high, nitrification proceeds, the residual amount of the treated water NH ₄ -N decreases, and the treated water NO ₂ -N / NH ₄ -N ratio is a target value of 1 .3 will be greatly exceeded. Therefore, it is necessary to set the M-alkalinity / NH ₄ -N ratio in the raw water to an appropriate value in advance. Usually, it is important to prepare such that M-alkalinity / NH ₄ —N is 3.7 to 4.4.

On the other hand, in recent years, the ratio of incineration ash and incineration residue among the waste landfilled in the landfill site has increased. Along with this, the calcium concentration (Ca concentration) in the leachate is increasing. If the Ca concentration is high, it precipitates as insoluble CaCO _{3 due} to the reaction with carbonate ions (CO ₃ ²⁻ ) in the leachate. In water treatment facilities, this insoluble CaCO ₃ precipitation causes clogging of the treated water piping, clogging of the diffuser, and the like, which is a major cause of equipment trouble. In order to cope with this, generally, a softening treatment device for removing Ca in advance is provided for leachate having a high Ca concentration.

The softening treatment method for removing Ca generally includes adding sodium carbonate (Na ₂ CO ₃ ) to the water to be treated, and increasing the pH to about 10 or more by adding an alkali, so that Ca ions in the water to be treated are insoluble CaCO. ₃ Remove as sludge. In this softening treatment, the added amount of Na ₂ CO ₃ theoretically requires 2.65 times Na ₂ CO ₃ with respect to the concentration of the liquid Ca to be treated as shown in the reaction formula (2). Generally, when the treated water Ca concentration is 100 mg / L or less, Ca scale precipitation is suppressed, and therefore, the target value of the treated water Ca concentration for the softening treatment is often set to 100 mg / L or less. In the actual treatment, in order to make the Ca concentration of treated water 100 mg / L or less, the amount of Na ₂ CO ₃ added is 1.05 to 1.1 times the theoretical value, that is, 2. Addition of 8 to 2.9 times is required.
Ca ²⁺ + Na ₂ CO ₃ = CaCO ₃ ↓ + 2Na ⁺ (2)

It is disclosed that, as a conventional Ca and nitrogen removal method, water removal treatment with high Ca and nitrogen is performed in the order of softening treatment of Ca removal → nitrification denitrification. As disclosed in FIG. 1 of Patent Document 2, carbonate is added to the water to be treated in a pretreatment tank, and CO ₃ ²⁻ reacts with Ca ^{2+ in the} water to be treated to precipitate as insoluble CaCO _3. It is clearly stated that Furthermore, it is disclosed that the supernatant water after removing Ca is neutralized and introduced into a biological nitrification denitrification tank in the subsequent stage to perform nitrogen removal by a conventional biological denitrification treatment.

  In recent years, instead of conventional nitrogen removal in Ca removal + nitrogen removal, a treatment method has been disclosed that applies denitrification by the above-mentioned autotrophic denitrifying bacteria, that is, denitrification by the ANAMMOX method.

  In Patent Document 3, as shown in FIG. 1, Ca and nitrogen are removed from the water to be treated in the order of a Ca removal device + a nitritation reaction tank + an ANMOX reaction tank.

  On the other hand, in the nitritation treatment process, a carrier system in which a biological carrier to which nitrifying bacteria can adhere has been recently added to a nitritation tank (for example, Patent Document 4).

Japanese Patent No. 3460745 JP 2002-355695 A JP 2007-125484 A JP 2010-253404 A

In the case of an actual machine, in the Ca removal softening treatment method, measurement of the water to be treated Ca is not usually performed frequently, and the amount of Na ₂ CO ₃ added is often determined based on the planned Ca concentration. In the case of leachate, the Ca concentration varies depending on the amount of rainfall. When the amount of Na ₂ CO ₃ added is excessive, the M-alkalinity of the softened water is increased. For these reasons, a predetermined amount of Na ₂ CO ₃ is often added to the initially planned Ca concentration, and excessive addition is often the case. When the amount of Na ₂ CO ₃ added is excessive, the M-alkalinity of the softened water is increased. There is a problem that a large amount of carbonic acid remains in the softened water, and decarboxylation by acid addition is performed as necessary, which increases Lancos.

Further, since the M-alkalinity of leachate is usually high, the carbonate source derived from the M-alkalinity of leachate also reacts with Ca in the high pH region to become insoluble CaCO _3. That is, when the required amount of Na ₂ CO ₃ was added without considering the carbonic acid source, there was a problem that the amount added was further excessive, resulting in an increase in Lancos.

In the above prior art, as one of the Ca removing means, a method of depositing and removing insoluble CaCO _{3 by} adding sodium carbonate or sodium bicarbonate as a carbonate is shown. In addition, by setting the treated water Ca concentration to 100 mg / L or less, there is no scale deposition due to Ca, and stable treatment is obtained. However, an appropriate injection method that can cope with the concentration fluctuation of raw water Ca or the like is not shown for the amount of carbonate added. Therefore, if the amount of carbonate added is excessive, the carbonate remains in the treated water, resulting in an increase in M-alkalinity. In particular, since there are many dissolved carbonates as typified by M-alkalinity in the leachate, a necessary amount of carbonate is taken into account in removing Ca from the leachate without considering the carbonate source derived from M-alkalinity. There was a problem that the carbonate in the treated water remained largely and the M-alkalinity increased.

On the other hand, in the nitritation treatment for the softened water after removing Ca, in order to set the NO ₂ —N / NH ₄ —N ratio of the treated water to 1.32 which is optimal for the ammonia denitrification reaction in the subsequent stage. It is necessary to adjust the M-alkalinity concentration of the softened treated water to be 3.7 to 4.4 times the NH ₄ -N concentration. Therefore, there is also a problem that the amount of acid addition necessary for adjustment increases as the amount of carbonate remaining in the softened water increases and the M-alkalinity increases.

In addition, the nitrification performance depends on the amount of adhering nitrifying bacteria on the surface of the carrier when a carrier is added to the nitrification tank and nitrifying bacteria adhere to the surface of the carrier. In the nitrification tank in which the carrier and the activated sludge are mixed, the inventors found that when raw water with a high Ca concentration flows into the nitrification tank, the nitrifying bacteria are increased in the activated sludge, while the nitrifying bacteria ratio due to CaCO ₃ precipitation decreases. Further, the present inventors have found a problem that nitrifying bacteria are hardly adhered to the carrier.

  The present invention has been made in order to solve the above problems, and the problem is that ammonia nitrogen capable of stably adhering and fixing ammonia-oxidizing bacteria to a carrier and stable nitritation treatment and An object of the present invention is to provide a denitrification method and apparatus for calcium-containing wastewater.

1) A denitrification method for wastewater containing ammoniacal nitrogen and calcium, comprising the following steps.
Calcium concentration control process: A process for controlling the calcium concentration in ammonia nitrogen and calcium-containing wastewater according to the operating conditions of the nitritation process. Nitrite process: Ammonia in the carrier in the presence of wastewater obtained in the calcium concentration control process. A process of immobilizing oxidizing bacteria and nitrifying the wastewater Denitrification process: A process of denitrifying wastewater containing nitrous acid and ammonia nitrogen obtained in the nitritation process 2) Ammonia of 1) above An apparatus for performing a denitrification method of nitrogen and calcium-containing wastewater, the apparatus used in the calcium concentration control step is an apparatus for measuring the calcium concentration of the wastewater, an apparatus for removing calcium, and an M-alkalinity concentration , And a tank equipped with a device for measuring the NH ₄ -N concentration, and the device used for the nitritation step comprises the M-alkaliness concentration, And a neutralizing agent addition amount control device in communication with a device for measuring the NH ₄ -N concentration, and a nitrification tank equipped with a neutralizing agent injection device in communication with the neutralizing agent addition amount control device. The apparatus used in the nitriding process is a denitrification apparatus for wastewater containing ammonia nitrogen and calcium, including a denitrification tank.

The present invention controls calcium concentration (Ca concentration) in ammoniacal nitrogen (NH ₄ -N) and calcium-containing wastewater according to the operating conditions of the nitritation process using a carrier that immobilizes ammonia oxidizing bacteria. The greatest feature is that a concentration control step is provided.
It has been found that one of the reasons why nitrifying bacteria cannot adhere to the carrier is that nitrifying bacteria are difficult to adhere due to CaCO ₃ deposition on the surface of the carrier. Particularly in a nitrification tank, in order to proliferate ammonia-oxidizing bacteria preferentially during start-up operation, if the Ca concentration is lowered, there is almost no risk of CaCO ₃ precipitation, and the ammonia-oxidizing bacteria stabilize on the surface of the carrier. It was found that it can adhere.
On the other hand, after steady operation where ammonia-oxidizing bacteria adhered and fixed to the carrier and nitrification became nitrite-type nitrification, even if the Ca concentration increased in the nitrite tank, there was no Ca precipitation on the carrier, and ammonia-oxidizing bacteria were not It was confirmed experimentally that it was stably adhered.

According to the present invention, when water to be treated containing Ca and ammonia nitrogen is subjected to nitrogen removal by a treatment process that combines nitritation treatment using a carrier and ammonia denitrification treatment, If Ca is removed in advance, ammonia oxidizing bacteria can adhere and be fixed to the carrier in the nitritation tank in a short period of time, and stable partial nitritation performance can be obtained. In addition, in the Ca removal softening treatment, the amount of carbonate added can be reduced by adding the necessary amount of carbonate in consideration of the carbonate concentration in the water to be treated. By optimizing the amount of carbonate added, there is no increase in M-alkalinity due to residual carbonate in the softened treated water, and the M-alkalinity / NH ₄ -N ratio of the treated water is stabilized for partial nitritation treatment. Since it can be set within the required numerical range, partial nitritation treatment can be obtained stably. Furthermore, after ammonia-oxidizing bacteria adhere and fix to the carrier and shift to partial nitritation type nitrification, even if the Ca concentration of the softening water is set high under the nitritation treatment conditions based on the M-alkali degree, the carrier surface In addition, there is no scale generation due to CaCO ₃ precipitation, and ammonia oxidizing bacteria can be stably adhered and fixed, so that the amount of chemical addition and sludge generation accompanying the softening treatment can be greatly reduced.

It is explanatory drawing showing the structure of the method and apparatus which concerns on embodiment of this invention.

Hereinafter, the present invention will be described in detail.
First, the Ca concentration control process will be described.
The Ca concentration control step is a step of controlling the Ca concentration in the ammoniacal nitrogen and calcium-containing waste water (hereinafter also simply referred to as raw water) according to the operating conditions of the nitritation step.
Here, the Ca concentration is a value measured by any one of a calcium analysis pack test, an electrode-type Ca concentration meter, a chelate enemy method, a flame atomic absorption method, and an ICP emission spectroscopic method manufactured by Kyoritsu Riken. means.
In this step, the Ca concentration is controlled according to the measured Ca concentration and the operating conditions of the nitritation step. In the present invention, the control includes only measurement of the Ca concentration of the raw water, and there is no need for softening treatment when the measured value is not more than a predetermined value. The raw water treated in this step is also called softened treated water. However, the raw water that has not been softened is also included in the softened water for convenience.
When the operation condition is a start-up operation process of the nitritation process, control is performed so that the Ca concentration is lowered. When the Ca concentration is less than or equal to a predetermined value, there is no need for softening treatment. On the other hand, in the steady operation step of the nitritation step, the Ca concentration can be kept high and the load of the softening treatment can be reduced.
The softening treatment is not particularly limited as long as a control means for lowering the Ca concentration is used. For example, aggregation precipitation, aggregation-membrane separation, crystallization, ion exchange, electrodeionization, electrophoresis and the like can be mentioned.

In the present invention, in the softening treatment, Na ₂ CO ₃ addition amount C ₀ (mg / L) is calculated from the following formula (3) and added to the raw water to perform coagulation precipitation of calcium carbonate to control the Ca concentration of the raw water. The treatment is preferably
_{C 0 = (C in -C out} ) × a-C 2 /1.06 (3)
Here, C _in (mg / L): raw water Ca concentration, C _out (mg / L): raw water target Ca concentration (for example, start-up operation step, steady operation step), C ₂ (mg / L): M-alkalinity concentration of raw water, a is a coefficient. In the present invention, the M-alkalinity concentration means a value measured by a titration method for determining alkali consumption at pH 4.8.
This softening treatment can effectively use carbonate in raw water for Ca removal. As a result of experimentally examining the relationship between the M-alkalinity of leachate and the concentration of added carbonate (converted to Na ₂ CO ₃ ), the inventors were able to clarify that the relational expression shown in the above equation (3) can be obtained. It was.
The coefficient a is slightly different depending on the pH of the softening treatment, but a suitable pH for removing Ca is 9 to 10, preferably 9.0 to 9.5. The coefficient a is 2.6 to 2.9 at pH 9.0 to 10.0, and 2.8 to 2.9 at pH 9.0 to 9.5, so that stable Ca concentration control can be performed. Stable target water quality can be obtained.

  In the softening treatment, the Ca concentration is preferably controlled to 100 mg / L or less, or from 100 mg to 500 mg / L. When the Ca concentration is controlled to 100 mg / L or less, it is possible to promote adhesion and fixation of ammonia-oxidizing bacteria to the carrier in the start-up operation process of the nitritation process. Moreover, by controlling to 100 mg or more and 500 mg / L or less, the steady operation process of a nitritation process can be performed stably, and the chemical | medical agent of a softening process can be reduced.

The apparatus used for the Ca concentration control process of the present invention includes a tank equipped with an apparatus for measuring the Ca concentration of raw water, an apparatus for removing calcium, an M-alkalinity concentration, and an apparatus for measuring NH ₄ -N concentration. . Each of the above devices can be in communication with a control device. In the present invention, the NH ₄ -N concentration means a value measured by any of the pack test for assumption of ammonium nitrogen, NH ₄ -N electrode measurement method, and neutralization titration method manufactured by Kyoritsu Riken. .
The apparatus used for the Ca concentration control step may be independently provided with a tank for measuring Ca concentration and softening treatment, and a tank for measuring M-alkalinity concentration and NH ₄ -N concentration. It is good also as a tank. In the latter case, the measurement of M-alkalinity concentration and NH ₄ -N concentration is preferably performed after the softening treatment.
The device for removing calcium can be equipped with an injection device that is used also as a tank for performing the softening treatment and injects a chemical for precipitating calcium as calcium carbonate into the tank. Moreover, you may make this injection | pouring apparatus contact the control apparatus connected with the apparatus which measures Ca density | concentration. For example, the result of calculating the chemical amount by the control device using the above formula (3) can be communicated to the injection device, and the same amount can be put into the tank from the injection device.

Next, the nitritation step will be described.
In the nitrification step, ammonia-oxidizing bacteria are immobilized on the carrier in the presence of the waste water obtained in the calcium concentration control step (that is, in the presence of the softening treatment water obtained in the Ca concentration control step), and the softened treatment water is sublimated. This is the step of nitrating. Here, the softened water obtained in the Ca concentration control step refers to treated water obtained by performing the softening treatment, or water that has not been subjected to the softening treatment. Moreover, the treated water obtained in this nitritation process is also called nitritation treated water.
The nitritation step preferably includes a start-up operation step and a steady operation step, and the Ca concentration of the softened treated water is controlled as described above.
Moreover, nitrous acid step, it is preferable to control the M- alkalinity / _NH 4 -N ratio of softening treatment water from 3.7 to 4.4.

In the start-up operation process, in order to adhere and fix ammonia oxidizing bacteria on the carrier, the pH in the reaction tank is generally increased and the free NH ₃ (hereinafter referred to as FA) concentration is maintained high. Usually, if the FA in the nitrification tank is maintained at 1 to 10 mg / L, preferably 2 to 10 mg / L, ammonia oxidizing bacteria preferentially adhere and fix to the carrier in a short period of time, so stable nitritation Processing is obtained. FA greatly depends on changes in pH, NH ₄ -N concentration, and water temperature in the reaction vessel. Since FA increases as pH increases, the pH may be increased to about 8 at the initial stage of the start-up operation process. Under these conditions, if the Ca concentration is 100 mg / L or less, there is almost no fear of CaCO ₃ precipitation, and ammonia oxidizing bacteria can adhere stably on the surface of the carrier.

  On the other hand, in a steady operation process in which ammonia-oxidizing bacteria adhere and fix to the carrier and nitrification becomes nitrite-type nitrification, partial nitritation treatment with M-alkalinity rate control proceeds in the nitritation tank, and the pH is 7 Near or below 7 Under these conditions, even when the Ca concentration in the nitritation tank reaches 500 mg / L at the maximum, there is no Ca precipitation on the carrier, and ammonia oxidizing bacteria adhere to the carrier stably and are maintained.

In the nitrous acid treatment using the carrier as described above, the FA concentration is high if the softened water Ca concentration is, for example, 100 mg / L or less in the start-up operation process until the ammonia-oxidizing bacteria adhere and fix to the carrier. Even at a pH of about 8 that can be maintained, there is no scale adhesion due to CaCO ₃ precipitation on the surface of the carrier, and ammonia oxidizing bacteria can be stably adhered and fixed. When ammonia-oxidizing bacteria once adhere and fix and proceed to nitrite type nitrification, it becomes a steady operation step, and the pH of the nitrite tank decreases to around 7 with M-alkali rate control. Under this pH condition, there is almost no possibility of CaCO ₃ precipitation even when the maximum Ca concentration in the nitritation tank is 500 mg / L. That is, in the Ca removal softening treatment process, the amount of carbonate added can be greatly reduced as shown in the equation (3), and the amount of sludge deposited on CaCO ₃ is also greatly reduced.

The apparatus used for the nitritation process of the present invention includes a neutralizer addition amount control apparatus in communication with an apparatus for measuring the M-alkaliness concentration and NH ₄ -N concentration of softened treated water, and the neutralizer addition It includes a nitritation tank equipped with a neutralizing agent injection device in communication with a volume control device. The neutralizer addition amount control device processes the information on the M-alkalinity and NH ₄ -N concentration of the softened treated water to calculate the amount of neutralizer added to the nitritation tank, It can be configured to communicate with the sump injection device and to have the function of injecting the same neutralizing agent addition amount into the same tank from the injection device.

In the present invention, nitrous acid _step, it is preferable to control the _PO 4 -P concentration 0.1 to 1 mg / L.
For example, in the case of leachate or factory wastewater, if the raw water contains little phosphorus, it is preferable to add phosphorus necessary for microbial growth to the nitritation tank. When the phosphorus concentration is low in the nitritation tank, it tends to be difficult to attach and fix ammonia oxidizing bacteria to the carrier.
According to the results of the experimental study by the inventors, if the phosphorus concentration of the softened water is 0.1 mg / L or more, preferably 0.2 mg / L or more as PO ₄ -P, It was confirmed that all of the activities were stable. On the other hand, since the Ca concentration is about 100 mg / L in the treated water, when PO ₄ -P is high, the insoluble water is mainly composed of hydroxyapatite (hereinafter referred to as HAP) due to the reaction between Ca and PO ₄ -P in the high pH region. Solid matter precipitates and adheres to the carrier, which inhibits stable adhesion of ammonia-oxidizing bacteria. For this reason, it is calculated | required to adjust phosphorus addition amount to an appropriate value. If the softened water is 1 mg / L or less, preferably 0.5 mg / L or less as PO ₄ -P, there is no HAP precipitation in the long term, and stable nitritation treatment performance can be obtained.

As means for controlling the PO ₄ -P concentration of nitrite-treated water to 0.1 to 1 mg / L, nitrite-treated water is used in the nitrite treatment step or before the denitrification step. A device for measuring the concentration of PO ₄ -P can be provided and communicated with the phosphorus infusion device and control device in the same manner as described above. For example, the PO ₄ -P concentration can be communicated by the control device, and a phosphorous substance having a predetermined PO ₄ -P concentration can be supplied from the injection device to the softened water or nitritation tank.

Next, the denitrification process will be described.
The denitrification step of the present invention is a step of denitrifying waste water containing nitrous acid and ammonia nitrogen obtained in the nitritation step (ie, nitritation water).
In the nitrite-treated water, NH ₄ -N in the nitrite-treated water becomes an electron donor and NO ₂ -N becomes an electron acceptor, and is denitrified by ammonia denitrifying bacteria. The treated water obtained by this denitrification treatment is also called ammonia denitrification treatment water.
It is preferable that the apparatus used for the denitrification step includes a denitrification tank for denitrifying the nitritation water.

Hereinafter, the present invention will be described in detail with reference to the drawings illustrating an example of an embodiment. However, the present invention is not limited to this.
FIG. 1 is a flow sheet illustrating an example in which leachate from a landfill final disposal site is used as raw water, and the raw water is treated according to the present invention.
As shown in FIG. 1, raw water 1 is introduced into a softening treatment tank 2, and Ca is removed using the formula (3). Additive chemicals 3 such as carbonates, alkalis and coagulation polymers necessary for Ca removal are sequentially added to the softening tank, and Ca in the raw water is precipitated and concentrated as sludge containing insoluble CaCO ₃ to discharge the concentrated sludge. 4 is discharged outside the system.
The softening treatment of Example 1 described later was a batch type in which agglomeration, mixing reaction and solid-liquid separation were sequentially performed in one softening treatment tank, but generally a softening treatment tank in which agglomeration reaction was performed by adding carbonate and adjusting pH. The same effect can be obtained by continuous treatment in the order of a mixing tank for forming sludge flocs by addition of a polymer and a sedimentation tank for solid-liquid separation.
In the softening treatment tank 2, an injection device 21 for injecting the additive chemical 3 into the raw water 1, a stirring device 2b for mixing and stirring the additive chemical 3 in the raw water 1, a pH measuring device 2c for measuring the pH of the raw water, A concentration measuring device for measuring Ca concentration, M-alkalinity concentration, and the like can be provided.

The supernatant from the softening tank 2 is introduced into the raw water tank 6 as softening water 5. The softened water 5 is introduced into the nitritation tank 8 as nitritation tank raw water 7. The raw water tank 6 is not necessarily required, and the raw water tank may not be provided particularly when the water quality fluctuation is small or when a stable inflow amount is obtained. In addition, since the pH of the softened water is usually high, it is desirable to adjust the pH by adding an acid as necessary.
The raw water tank 6 includes a device 6 a for measuring the M-alkaliness concentration and the NH ₄ -N concentration, and a stirring device 6 b for mixing a desired additive chemical into the softened water 5.

The carrier immediately after addition to the nitrification tank 8 has no ammonia-oxidizing bacteria attached and fixed, so the raw water 7 is supplied in a state where seed sludge containing nitrifying bacteria is added, and is provided with a blower 8d1 and an air diffuser 8d2. The aeration operation is performed by the aeration device 8d, and the start-up operation for attaching and fixing ammonia oxidizing bacteria is performed. If the raw water 7 flowing into the nitritation tank 8 in this start-up operation, that is, the Ca of the softened water 5 is controlled to 100 mg / L or less, even if the pH and water temperature in the nitritation tank fluctuate greatly, CaCO ₃ There is no precipitation, and ammonia-oxidizing bacteria can be stably adhered and fixed on the surface of the carrier in a short period of time. In this start-up operation, in order to increase the FA concentration to 1 to 10 mg / L, when the water temperature is set to 20 ° C. or higher, preferably 25 ° C. to 40 ° C., ammonia oxidizing bacteria adhere in several days. If the pH is set to 7.0 or higher, preferably 7.5 to 8.5, ammonia-oxidizing bacteria can proliferate preferentially and adhere and be fixed to the carrier. Thus, nitrification becomes nitrite type, NO 3 _-N generation of almost eliminated. When the water-passing treatment is carried out for several days under the above startup operation conditions for a maximum of about two weeks, ammonia oxidizing bacteria close to a steady state can adhere to the carrier.

When ammonia-oxidizing bacteria adhere stably, the nitrification rate increases, and ammonia nitrogen in the raw water 7 flowing into the nitritation tank 8 is converted to NO ₂ -N by the action of the ammonia-oxidizing bacteria. Along with that, M-alkalinity is consumed and pH is lowered. Since the M-alkalinity / NH ₄ -N ratio of the raw water 7 was adjusted to 3.7 to 4.4 in advance, even if the M-alkalinity decreased to 100 mg / L or less, nitrite-treated water NO ₂ the -N / _NH 4 -N approximately 1.0 to 1.5. Since there is little residue of M-alkalinity, nitrification hardly proceeds any more, and NO ₂ —N / NH ₄ —N remains approximately 1.0 to 1.5.
Thus, when the partial nitrite type nitrification proceeded stably, since NO 2 _-N also increases with nitritation bath pH lowered free nitrous acid (hereinafter FNA) Concentration of nitrite reduction vessel increases. The higher the FNA, the more ammonia-oxidizing bacteria grow. Therefore, the dominant growth of the ammonia-oxidizing bacteria is maintained by controlling the pH to 7.5 or lower, preferably 6.0 to 7.2.

When the start-up operation of the above-described nitrite-type nitrification is completed, then, for example, the following steady operation is performed. In the treatment stage in which the pH is lowered to 7.5 or less due to the rate of M-alkalinity, the softened treated water Ca concentration is increased from 100 mg / L or less to 100 to 500 mg / L during the start-up operation, particularly pH 6 of the nitritation tank 8. In the case of 0 to 7.2, even if the Ca concentration of the softened treated water is set to 300 to 500 mg / L, there is no CaCO ₃ generation, so that the nitrification performance does not deteriorate due to Ca scale adhesion to the carrier, and a stable treatment can be obtained. As a result, the amount of carbonate added in the softening treatment and the amount of sludge generated due to CaCO ₃ precipitation are greatly reduced, resulting in a reduction in treatment costs.

As described above, the M-alkalinity / NH ₄ -N ratio of the raw water 7 introduced into the nitritation tank 8 is controlled in advance so as to be 3.7 to 4.4 necessary for the partial nitritation treatment. It is desirable to prepare. Since the amount of carbonate corresponding to the Ca and M-alkalinity of raw water is added in the softening treatment, there is almost no excess of M-alkalinity. In some cases. The same effect can be obtained by adding a predetermined amount of the neutralizing agent 9 to the raw water tank or directly adding it to the nitritation tank.
The addition amount of the neutralizing agent is usually 2000 mg / L or less in terms of M-alkalinity although it depends on the M-alkalinity concentration of the softened water.
As the neutralizing agent 9, sodium bicarbonate, sodium carbonate, or sodium hydroxide can be used. Further, adjustment by adding an acid such as sulfuric acid or hydrochloric acid is also possible as required.
The nitritation tank 8 includes a neutralizer addition amount control device 8a in communication with a device 6a for measuring the M-alkaliness concentration and NH ₄ -N concentration of the softened treated water provided in the raw water tank 6, and the neutralization A neutralizer injection device 8b communicated with the agent addition amount control device 8a is provided. The neutralizer addition amount control device 8a calculates the addition amount of the neutralizer 9 to the nitritation tank by processing information on the M-alkalinity and NH ₄ -N concentration of the softened treated water. The result is communicated to the neutralizing agent injection device 8b, and the addition amount of the neutralizing agent 9 is injected from the injection device into the tank 8. The neutralizing agent injection device 8b can be composed of a pump and a neutralizing agent solution tank. Moreover, the nitritation tank can be provided with a device 8e for measuring the amount of dissolved oxygen (DO) in the tank and a device 8f for measuring the pH in the tank.

In the nitritation tank 8, a part of the inflow NH ₄ -N is oxidized to NO ₂ -N by the action of the ammonia oxidizing bacteria adhering carrier 10 in the tank and the ammonia oxidizing bacteria in the activated sludge. After the treatment, the mixed solution in the nitritation tank is separated by the nitritation tank separation screen 8c, and 8 g of the nitritation tank mixture flows into the sedimentation tank 11, and after the sludge sedimentation separation, the supernatant is sublimed. Nitrated water 12 is obtained. A part of the concentrated sludge 11a from the sedimentation basin is returned to the nitritation tank as the return sludge 11b, and the remainder is the surplus sludge 11c.

  The nitrite-treated water 12 may be directly introduced into the ammonia denitrification tank 13, but an intermediate adjustment tank 14 is provided to adjust the amount of water and pH, and to add a carbonic acid source and nutrients necessary for ammonia denitrification. When the additive chemical 15 is added to and mixed with the nitrite-treated water from the injection device 14a, the amount of water and the water quality are made more uniform.

When the effluent water from the intermediate adjustment tank 14 is introduced into the ammonia denitrification tank 13 as the ammonia denitrification raw water 16, the NH ₄ -N of the inflow raw water becomes an electron donor, NO ₂ by the ammonia denitrification bacteria attached and fixed to the carrier 17. -N becomes an electron acceptor and is denitrified. The treatment liquid from which the carrier 17 has been separated from the mixed liquid after the denitrification treatment by the separation screen 131 becomes the ammonia denitrification treated water 18.
The ammonia denitrification tank 13 includes a device 13b for measuring the oxidation-reduction potential (orp) amount in the tank, a device 13c for measuring the pH in the tank, a stirring device 13d, and an additive chemical injection device 13e. Can do.

As the carrier 10 capable of adhering and fixing ammonia-oxidizing bacteria to the nitritation tank 8, if the polymer carrier is filled, the ammonia-oxidizing bacteria can be stably adhered, so that stable nitritation performance can be obtained in the nitritation tank. . Gels using synthetic polymers such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyacrylamide, and photocurable resin, and polymers such as carrageenan and sodium alginate as the polymer carrier to be filled in the nitritation tank Examples of the carrier include a carrier, polyethylene, polyurethane, and polypropylene.
As the shape of the carrier, any of a spherical shape, a square shape and a cylindrical shape can be used, and the effective diameter is preferably 3 to 10 mm which can be stably separated from the screen at the outlet of the aeration tank. The specific gravity of the carrier is preferably 1.01 to 1.05, which allows the carrier to flow uniformly in the aerated state. Further, it is desirable that the carrier filling amount is 10 to 30% by volume (V%) that enables uniform mixing and flow.

As the carrier 17 capable of adhering and fixing ammonia denitrifying bacteria to the ammonia denitrifying tank 13, if the polymer carrier is filled, the ammonia denitrifying bacteria can be stably adhered, so that stable denitrification performance can be obtained in the ammonia denitrifying tank 13. Examples of the polymer carrier filled in the ammonia denitrification tank include fluid carriers made of the same materials as those used for nitritation.
As the shape of the carrier, any of a spherical shape, a square shape and a cylindrical shape can be used, and the effective diameter is preferably 3 to 10 mm which can be stably separated from the screen at the denitrification tank outlet. A carrier having a large number of fine pores on the surface, a sponge having a hollow inside, and a material having innumerable irregularities on the surface can quickly attach and fix ammonia denitrifying bacteria, and high denitrification performance can be obtained in a short period of time. Furthermore, since the ammonia denitrifying bacteria in the denitrification tank can be maintained at a high concentration for a long period of time, stable denitrification performance can be obtained.
The specific gravity of the carrier is preferably 1.01 to 1.10 which can flow uniformly by stirring in an anaerobic state. The carrier filling amount is desirably 10 to 30 V% so as not to cause local deposition in the denitrification tank.

Examples of the present invention will be described below, but are not limited to the following.
Example 1
Denitrification treatment of ammonia nitrogen and calcium containing wastewater was performed according to the method and apparatus configuration shown in FIG.
Table 1 shows the conditions for the softening treatment in Example 1. As described above, the softening treatment was performed by a batch method in which aggregation, mixing reaction, and solid-liquid separation were sequentially performed in one softening treatment tank.

The conditions for the softening treatment corresponded to the start-up operation period and the steady operation period of the subsequent nitritation treatment. Table 1 shows the average value of each period.
The pH and HRT for the softening treatment were 9.0 and 20 minutes, respectively, and were the same for any treatment period. In the start-up operation period, the target value of the softened treated water Ca concentration was 100 mg / L, and the amount of Na ₂ CO ₃ added obtained from the above equation (3) was 2040 mg / L. On the other hand, in the steady operation period after nitritation treatment start-up operation, the Ca concentration target value of softened water is changed to 300 mg / L, so the amount of Na ₂ CO ₃ added is 1480 mg / L, which is higher than that during start-up operation. Reduced by 560 mg / L.

Table 2 shows the conditions of the nitritation tank. Table 3 shows the treatment conditions for ammonia denitrification.
In the start-up operation of the nitritation treatment, the water temperature was 30 ° C., the pH was 7.5 to 8.0, the NH ₄ —N load was averaged 1.0 kg / m ³ / d, and continuous water flow was performed for 15 days.
During the steady operation period after the start-up operation, the water temperature was 20 to 30 ° C., the pH was 6.0 to 7.5, the NH ₄ —N load was 2.5 kg / m ³ / d on average, and continuous water treatment was performed for 180 days. .

The nitrite treatment tank was filled with 20 V% of a PEG carrier having an average particle size of 4.2 mm. M-alkalinity / NH ₄ -N ratio is determined in advance for raw water 7 (softening-treated water), and a predetermined amount of NaOH aqueous solution is added to nitrous acid so that M-alkalinity / NH ₄ -N is about 4.0. It was injected into the chemical bath. The output of the blower was adjusted so that the DO in the nitritation tank was 4 mg / L or more.
The ammonia denitrification tank was controlled by injecting sulfuric acid so that the pH was 7.5 or less. The denitrification tank was filled with 20 V% of a PVA carrier having an average particle diameter of 4 mm. Further, since inorganic carbon nitrite treatment water flowing into the ammonia denitrification had little, was added Na ₂ CO ₃ to about 250 mg / L nitrite treatment water as an inorganic carbon source.
Table 4 shows an example of the quality of raw water, softened water, nitrified water, and ammonia denitrification water during the 180-day steady operation period after the nitritation treatment start-up operation in Example 1.

In the softening treatment, ammonia oxidizing bacteria had already adhered to the PEG carrier in the nitritation tank during the start-up operation period shown in Tables 1 and 2, and therefore the Ca concentration of the softening treated water was 250 mg, which is a target value of 300 mg / L or less. / L.
In the nitritation treatment, since the M-alkalinity / NH ₄ -N ratio of the softened water was adjusted to 4.0 by NaOH injection into the nitritation tank, about 56 NH ₄ -N was obtained. % Is nitritized, NO ₂ —N of nitrite-treated water is 140 mg / L, and the NO ₂ —N / NH ₄ —N ratio is 1.22, which is close to the ammonia denitrification required amount of 1.32. Obtained. The NO ₂ —N ratio to NO _X —N of the nitritation water was 98.6%, and a stable nitritation treatment was obtained.

In the ammonia denitrification treatment, the NO ₂ —N / NH ₄ —N ratio of nitrite-treated water is 1.22, which is close to the ratio required for the ammonia denitrification reaction. As a result, the denitrification treated water NH ₄ -N and NO ₂ -N are both low at 12.3 mg / L and 8.9 mg / L, respectively. TN became 52.2 mg / L and the removal rate with respect to raw | natural water TN was obtained 83.3%.

In Example 1, a predetermined amount of alkaline agent was continuously added to the nitritation tank 8 in order to replenish the insufficient M-alkalinity of raw water. Note that the same effect can be obtained by adding an alkali agent directly to the raw water tank 6. The same effect can be obtained by using any one of NaOH, Na ₂ CO ₃ and NaHCO ₃ as the alkali agent. In this example, the nitrite-treated water was once introduced into the intermediate adjustment tank, the water amount and pH were adjusted, and the carbonic acid source and nutrients necessary for ammonia denitrification were added and mixed, and then introduced into ammonia denitrification. Even if it is directly introduced into the ammonia denitrification tank, the same effect can be obtained.

(Comparative Example 1)
The same raw water as in Example 1 was used, and the treatment was performed directly in the order of nitritation treatment and ammonia denitrification treatment without performing Ca softening treatment. The amount of treated water was 540 L / d with the same amount of water as in the steady operation period of Example 1 shown in Table 2, and the NH ₄ —N load was also 2.5 kg / m ³ / d.
Table 5 shows an example of the raw water and treated water quality results of Comparative Example 1.
As shown in Table 5, since there was no Ca removal from the raw water, the inflow raw water Ca was as high as 1200 mg / L and the nitrite-treated water Ca was 1050 mg / L, which was about 150 mg / L lower than the raw water. This is due to the formation of CaCO ₃ in the nitritation tank, and scale deposition derived from CaCO ₃ was observed on the surface of the support. As a result, NH ₄ —N of nitritation water was as high as 230 mg / L, and the NO ₂ —N / NH ₄ —N ratio was as low as 0.2, indicating that the nitritation capacity was low.
As described above, stable nitritation treatment cannot be performed in the nitritation tank, NH ₄ -N of nitritation water is high, and nitrification performance is low. _4- N was as high as 205 mg / L, and the treated water TN was 242 mg / L, almost the same as the raw water TN, and the nitrogen removal rate was only about 18%.

(Comparative Example 2)
The raw water was the same as in Example 1. In this comparative example, the carbonate source derived from the M-alkalinity in the raw water was not considered in the softening treatment, and about 2.8 times as much sodium carbonate (Na ₂ CO ₃ ) as Ca concentration was added. Other processing conditions were the same as in Example 1.
Table 6 shows an example of the quality of raw water and softened water in the softening treatment.
The amount of added Na ₂ CO _{3 for the} softening treatment is 3360 mg / L, which is 1880 mg / L higher than 1480 mg / L in Example 1. As a result, the treated water Ca was as low as 50 mg / L, but the M-alkalinity was as high as 1850 mg / L and a large amount of carbonate remained. The M-alkalinity / NH ₄ -N ratio was 6.1 times, and a large amount of acid was required to adjust to 4.0, which is necessary for the partial nitritation treatment. In addition, the amount of sludge containing CaCO ₃ is 500 mg / L higher than that in Example 1.

(Example 2)
The same raw water as in Example 1 was used, and processing was performed in the same processing flow as in Example 1 shown in FIG. In Example 2, the nitritation treatment was gradually started by adding PO ₄ -P to about 0.8 mg / L with respect to softening-treated water having almost no phosphorus. Table 7 shows an example of raw water and treated water during steady operation after the start of nitritation treatment.
As shown in Table 7, with respect to softened treated water, PO ₄ -P was adjusted to about 0.8 mg / L by adding phosphoric acid, and the nitrite treating solution PO ₄ -P became 0.6 mg / L. . As a result, stable ammonia-oxidizing bacteria could adhere to the nitrification tank PEG carrier, so that NH ₄ -N of nitrite-treated water decreased to 140 mg / L and NO ₂ -N increased to 171 mg / L. did. The NO ₂ —N / NH ₄ —N ratio was 1.22, which was close to the optimum value of 1.32 for ammonia denitrification. Further, NH ₄ -N and NO ₂ -N decreased to 12.3 mg / L and 8.9 mg / L, respectively, and TN became 52.2 mg / L in ammonia denitrification treated water, and good denitrification performance was gotten.

(Comparative Example 3)
In Comparative Example 3, the same raw water and treatment flow as in Example 2 were used. However, the difference from Example 2 was that the concentration of phosphoric acid added to the softened water was higher than that of Example 2 and was about 3.0 mg / L as PO ₄ -P. Table 8 shows an example of the quality of raw water and various treated water in Comparative Example 3.
The PO ₄ -P added to the softened water was as high as 3.0 mg / L, and a scale that seems to be mainly HAP was generated on the PEG carrier in the nitrite treatment tank due to the influence of Ca residue and high pH. As a result, good nitritation treatment performance cannot be obtained, the treated water NH ₄ —N is as high as 240 mg / L, and the NO ₂ —N is as low as 45 mg / L. As a result, NH ₄ —N of ammonia denitrification treated water was as high as 205 mg / L, and TN was 244 mg / L.

By knowing the M-alkaliness and NH ₄ —N concentration in the softened water in advance in the Ca concentration control step, it is possible to appropriately control the amount of neutralizing agent added to the softened water in the nitritation step.

DESCRIPTION OF SYMBOLS 1 ... Raw water, 2 ... Softening processing tank, 2a ... Injection | pouring apparatus, 2b ... Stirring apparatus, 2c ... pH measuring device, 3 ... Additive chemical, 4 ... Discharged sludge, 5 ... Softening processing water, 6 ... Raw water tank, 6a ... M -Apparatus for measuring alkalinity concentration and NH ₄ -N concentration, 6b ... Stirrer, 7 ... Raw water for nitritation tank, 8 ... Nitrite tank, 8a ... Control device for adding neutralizing agent, 8b ... Neutralization Agent injection device, 8c ... separation screen, 8d ... aeration device, 8d1 ... blower, 8d2 ... aeration tube, 8e ... DO measurement device, 8f ... pH measurement device, 8g ... mixed liquid of nitritation tank, 9 ... neutralizing agent DESCRIPTION OF SYMBOLS 10 ... Carrier, 11 ... Sedimentation basin, 11a ... Concentrated sludge, 11b ... Return sludge, 11c ... Excess sludge, 12 ... Nitrite treatment water, 13 ... Ammonia denitrification tank, 13a ... Separation screen, 13b ... Orp amount measuring device , 13c ... pH measuring device, 13d ... Stirrer, 13e Added chemical injection device, 14 ... intermediate adjustment tank, 14a ... added chemical injection device, 15 ... adding chemicals, 16 ... ammonia de 窒原 water, 17 ... carrier, 18 ... ammonia denitrifying water.

Claims (7)

A denitrification method for wastewater containing ammoniacal nitrogen and calcium, comprising the following steps.
Calcium concentration control process: A process for controlling the calcium concentration in ammonia nitrogen and calcium-containing wastewater according to the operating conditions of the nitritation process. Nitrite process: Ammonia in the carrier in the presence of wastewater obtained in the calcium concentration control process. A process of immobilizing oxidizing bacteria and nitrifying the wastewater Denitrification process: A process of denitrifying wastewater containing nitrous acid and ammonia nitrogen obtained in the nitritation process   The denitrification method according to claim 1, wherein the nitritation step includes a start-up operation step and a steady operation step. The denitrification treatment of ammonia nitrogen and calcium-containing wastewater according to claim 1 or 2, wherein the calcium concentration control step calculates the amount of Na ₂ CO ₃ addition C ₀ (mg / L) from the following formula and adds it to the waste water. Method.
_{C 0 = (C in -C out} ) × a-C 2 /1.06
Here, C _in (mg / L): Calcium concentration of the waste water, C _out (mg / L): Target calcium concentration of the waste water, C ₂ (mg / L): M-alkalinity concentration of the waste water, a Is a coefficient. 4. The denitrification of ammonia nitrogen and calcium-containing wastewater according to claim 1, wherein the nitritation step controls the M-alkalinity / NH ₄ -N ratio to 3.7 to 4.4. Processing method.   5. The denitrification method for ammonia nitrogen and calcium-containing wastewater according to claim 1, wherein the nitritation step controls the calcium concentration to 100 mg / L or less, or 100 mg to 500 mg / L or less. The denitrification process according to any one of claims 1 to 5, wherein the nitritation step controls the PO ₄ -P concentration to 0.1 to 1 mg / L. It is an apparatus which implements the denitrification method of ammonia nitrogen and calcium containing wastewater of any one of Claims 1-6, Comprising: The apparatus used for the said calcium concentration control process measures the calcium concentration of this wastewater. Including an apparatus, an apparatus for removing calcium, an apparatus for measuring M-alkalinity concentration, and an apparatus for measuring NH ₄ -N concentration, and the apparatus used in the nitritation step includes the M-alkalinity concentration, and A denitrification tank comprising a neutralizer addition amount control device in communication with a device for measuring the NH ₄ -N concentration, and a nitritation tank equipped with a neutralizer injection device in communication with the neutralization agent addition amount control device. The apparatus used in the process is a denitrification apparatus for wastewater containing ammonia nitrogen and calcium, including a denitrification tank.

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