JP2021133298A - Treatment method of ammoniac nitrogen-containing waste water and treatment apparatus - Google Patents

Abstract

To provide a treatment method of ammoniac nitrogen-containing waste water capable of stably performing nitrite treatment and hydrophobic ammonia oxidation treatment while suppressing generation of scale, and a treatment apparatus.SOLUTION: In a treatment method of ammoniac nitrogen-containing waste water, a treatment step of ammoniac nitrogen-containing waste water comprises: a calcium removing step for removing calcium in the ammoniac nitrogen-containing waste water containing calcium; a nitrite step for nitrite treating part of ammoniac nitrogen in the ammoniac nitrogen-containing waste water after the calcium removing step to nitrite nitrogen; and a nitrification step including an anaerobic ammonia oxidation step for anaerobic ammonia oxidation treating the treated water of the nitrite treatment using anaerobic ammonia oxidation bacteria. Carbonate for removing calcium and carbonate for refilling inorganic carbon necessary in the nitrite step are added in the calcium removing step.SELECTED DRAWING: Figure 1

Description

The present invention relates to a method and an apparatus for treating ammoniacal nitrogen-containing wastewater.

It is known that leachate _{has a high NH 4-} N and a low concentration of organic substances such as BOD. As a nitrogen removal method for such leachate, a biological nitrification denitrification method is generally often used. Biological nitrification denitrification methods usually consist of a nitrification process and a denitrification process. In the nitrification process, ammonia nitrogen in raw water is first oxidized to nitrite nitrogen by ammonia-oxidizing bacteria in an aerobic reaction tank, commonly known as nitrification tank, and then nitrite nitrogen is converted to nitrate nitrogen by nitrite-oxidizing bacteria. Oxidizes in. 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, to make nitrate nitrogen and nitrite nitrogen in the nitrification liquid dependent nutrients. It is reduced to harmless nitrogen gas by the denitrifying bacteria. As the electron donor in this denitrification reaction, an organic substance in the liquid to be treated is usually used. When the amount of organic matter is small, it is necessary to add methanol as an electron donor from the outside.

In this biological nitrification denitrification treatment, ammoniacal nitrogen in the inflow raw water is finally oxidized to nitrate nitrogen through the nitrite nitrogen in the nitrification tank. Therefore, it is necessary to supply oxygen necessary for ammoniacal nitrogen oxidation to the nitrification tank. The oxygen requirement is 4.57 times higher than that of raw water ammoniacal nitrogen, and its supply power cannot be ignored. Further, in the denitrification tank, an organic substance as an electron donor is required in the dependent denitrification reaction in which nitrate nitrogen becomes an electron acceptor. When the raw water is low in organic matter, it is necessary to add methanol, which is an electron donor required for denitrification. In order to obtain stable denitrification performance, the amount of methanol added is usually about 2.5 to 3 times the amount of nitrate nitrogen flowing into the denitrification tank. As described above, 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 major issues that must be resolved in order to popularize the nitrification denitrification process.

In recent years, a denitrification treatment method using an autotrophic denitrifying bacterium, which is completely different from the conventional denitrification mechanism by the heterotrophic denitrifying bacterium, has been disclosed. It uses an autotrophic microorganism that uses ammoniacal nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, and reacts ammoniacal nitrogen and nitrite nitrogen in an anaerobic state to convert them into nitrogen gas. This is a method for removing nitrogen by a so-called ANAMMOX reaction, which is an anammonia oxidation process.

The following formula (1) shows the reaction formula of anaerobic ammonia oxidation. As shown in the formula (1), since the ammoniacal nitrogen and the nitrite nitrogen react directly with each other, it is not necessary to add an organic substance such as methanol, and the chemical cost is greatly reduced. In the denitrification reaction, NH _4- N reacts at a ratio of 1 mol to NO _2- N at a ratio of 1.32 mol. Therefore, all the ammoniacal nitrogen in the raw water to be treated is nitrite as in the conventional nitrification process. It is not necessary to oxidize to sex and 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 anammoxic ammonia oxidation reaction, _{the NO 2-} N / NH _4- N ratio of the ammonia denitrified raw water becomes 1.32, and the formula (1) The reaction shown in is obtained, _{and both NH 4-} N and NO _2- N of the treated water can be removed.
^{_{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)

For the denitrification treatment using anaerobic ammonia oxidation as described above, it is first necessary to oxidize a part of ammonia nitrogen in the inflow raw water to nitrite nitrogen in the nitrification process. At this time, in order to obtain a high rate of denitrification performance in the anaerobic ammonia oxidation reaction, it is desirable to change _{57% of the raw water NH 4-} N to NO _2- N and leave 43% NH _4-N. Is done. As a result, nitrous acid treatment water NO ₂ -N / NH ₄ -N ratio 1.32, and the in NO ₂ -N / NH ₄ -N ratio required anaerobic ammonium oxidation shown in equation (1) Match.

In general, in the nitrification process, as shown in the following formulas (2) and (3), NH _4- N in raw water undergoes an ammonia oxidation reaction and a nitrite reaction under aerobic conditions. Eventually it becomes nitrate nitrogen (NO _3- N). Since both reactions occur almost at the same time, it is usually difficult to proceed only with ammonia oxidation, and the amount of nitrification should be controlled so as to match the _{required NO 2-} N / NH _{4-N ratio as described above.} In addition, it is necessary to devise a control so that the nitrification reaction itself stops at nitrite nitrogen.
^{_{NH 4 + + 1.5O 2 → NO}} 2 - + H 2 O + 2H + (2)
^{_{NO 2 - + 0.5O 2 → NO}} 3 - (3)

In recent years, the ratio of incineration ash and incineration residue of wastes landfilled in landfills has increased. Along with this, the calcium concentration (Ca concentration) in the leachate water is increasing. When the Ca concentration is high, _{insoluble CaCO 3} is precipitated by the reaction with _{carbonate ions (CO 3} ^{2-) in the leachate.} In water treatment facilities, this insoluble CaCO ₃ precipitation causes clogging of treated water pipes and clogging of air diffusers, which is a major cause of equipment troubles.

In order to deal with this, a softening treatment device for removing Ca in advance is generally provided for leachate having a high Ca concentration. Generally, the softening treatment method for removing Ca is _{to add sodium carbonate (Na 2} CO ₃ ) to the water to be treated and raise the pH to about 10 or more by adding alkali to make Ca ions in the water to be treated insoluble CaCO. _{3 It} is removed as sludge. Amount of Na ₂ CO ₃ in the softening process is theoretically to-be-treated liquid Ca concentration, it is necessary to 2.65 times the Na ₂ CO _3. Generally, when the Ca concentration of the treated water is 100 mg / L or less, Ca scale precipitation is suppressed, so that the target value of the Ca concentration of the treated water for the softening treatment is often set to 100 mg / L or less.

For example, in Japanese Patent No. 4703370, wastewater containing nitrogen and calcium is reduced to 100 mg / L or less in calcium concentration in the wastewater, and carbonate ion or hydrogen carbonate ion is supplied for pH adjustment in the ammonia oxidation step. However, a method for treating nitrogen-containing wastewater, which is denitrified by the ANAMMOX reaction in the anammox tank in the subsequent stage, is described.

Further, in Japanese Patent No. 5727291, the calcium concentration, the M-alkali concentration, and the ammoniacal nitrogen concentration in the waste water are measured, the amount of sodium carbonate added is calculated based on a predetermined formula, and the calculated addition amount is calculated. A method is described in which an amount of sodium carbonate is added to waste water to obtain softened treated water, and then the softened treated water is treated by an anaerobic ammonia oxidation treatment method.

Japanese Patent No. 4703370 Japanese Patent No. 5727291

In the invention described in Patent Document 1, after reducing the calcium concentration in wastewater containing nitrogen and calcium to 100 m / L or less, carbonate ion or hydrogen carbonate ion is supplied for pH adjustment in the ammonia oxidation step. It is stated that it should be done. However, when carbonate ion or hydrogen carbonate ion is used for the purpose of pH adjustment, the amount of addition required for pH adjustment increases, and it cannot be said that the treatment is always efficient. In addition, when the quality of raw water changes abruptly, the calcium concentration in the wastewater cannot be completely reduced, and the subsequent partial nitrite step and ammonia oxidation step may become unstable.

In the invention described in Patent Document 2, the theoretically optimum amount of sodium carbonate added is calculated based on the calcium concentration, M-alkalinity and ammoniacal nitrogen concentration in the waste water, and the calcium concentration in the waste water is reduced. After that, ammonia denitrification treated water is obtained by nitrification and denitrification treatment. However, when the wastewater fluctuates abruptly, the amount of sodium carbonate added may not be properly controlled. As a result, the high-concentration calcium-containing effluent flows into the nitrite step and the denitrification step, impairs the stability of the nitrite and ammonia oxidation treatment, and may cause scale to be generated in the subsequent treatment tank.

In view of the above problems, the present invention provides a method and a treatment apparatus for ammonia nitrogen-containing wastewater capable of more stably performing nitrite treatment and anaerobic ammonia oxidation treatment while suppressing the generation of scale. do.

As a result of diligent studies by the present inventors in order to solve the above problems, in the calcium removal step of removing calcium contained in ammonia nitrogen-containing wastewater, not only the carbonate for removing calcium is added but also thereafter. It was found that it is effective to add a carbonate for supplementing the inorganic carbon required in the nitrification step of the above in the calcium removal step.

One aspect of the embodiment of the present invention completed based on the above findings is a calcium removing step of removing calcium in the ammoniacal nitrogen-containing wastewater containing calcium and an ammoniacal nitrogen-containing wastewater after the calcium removal step. An anaerobic ammonia oxidation step in which a part of the ammonia nitrogen in the nitrite is nitrite-treated to nitrite nitrogen and the treated water in the nitrite treatment is anaerobic ammonia oxidation treatment using anaerobic ammonia-oxidizing bacteria. In the nitration step including, and in the treatment step of the ammoniacal nitrogen-containing wastewater containing, the carbonate for removing calcium and the carbonate for supplementing the inorganic carbon required in the nitration step are added in the calcium removal step. It is a method for treating ammoniacal nitrogen-containing wastewater including addition.

In one embodiment, the method for treating ammoniacal nitrogen-containing wastewater according to the embodiment of the present invention includes adding caustic soda as a pH adjuster for the nitrite treatment in the nitrite treatment step.

In another embodiment of the method for treating ammoniacal nitrogen-containing wastewater according to the embodiment of the present invention, the calcium removal step includes the calcium concentration, alkalinity, and ammoniacal nitrogen concentration in the ammoniacal nitrogen-containing wastewater. It involves the addition of carbonates to replenish the inorganic carbon required in the nitrite step, based on the relationship with the target ammoniacal nitrogen concentration in the nitrite step.

In still another embodiment of the method for treating ammoniacal nitrogen-containing wastewater according to the embodiment of the present invention, the nitrite treatment adheres ammonia-oxidizing bacteria to the nitrite tank for treating the ammoniacal nitrogen-containing wastewater. It involves flowing the immobilized carrier.

In still another embodiment of the method for treating ammoniacal nitrogen-containing wastewater according to the embodiment of the present invention, the nitrite treatment causes floating sludge to coexist in the nitrite tank for treating the ammoniacal nitrogen-containing wastewater. Including that further.

In still another embodiment of the method for treating ammoniacal nitrogen-containing wastewater according to the embodiment of the present invention, the nitrite treatment performs intermittent aeration in the nitrite tank for treating the ammoniacal nitrogen-containing wastewater. include.

In another aspect, the embodiment of the present invention is a softening treatment tank for softening calcium-containing ammoniacal nitrogen-containing wastewater to remove calcium, and an ammoniacality contained in the softened ammoniacal nitrogen-containing wastewater. An nitrite tank that nitrites a part of nitrogen to nitrite nitrogen, and an anaerobic ammonia oxidation tank that anaerobic ammonia oxidation treatment of the treated water for nitrite treatment using anaerobic ammonia-oxidizing bacteria. Ammonia-nitrogen provided with a carbonate-adding means for adding the carbonate necessary for the nitrite treatment and the anaerobic ammonia oxidation treatment to the softening treatment tank based on the calcium concentration and alkalinity in the ammoniacal nitrogen-containing wastewater. It is a treatment device for contained wastewater.

According to the present invention, it is possible to provide a method and a treatment apparatus for ammonia nitrogen-containing wastewater capable of more stably performing nitrite treatment and anaerobic ammonia oxidation treatment while suppressing the generation of scale.

It is a schematic diagram which shows an example of the treatment apparatus of the ammoniacal nitrogen-containing wastewater which concerns on 1st Embodiment. It is a schematic diagram which shows an example of the treatment apparatus of the ammoniacal nitrogen-containing wastewater which concerns on 2nd Embodiment. It is a graph which shows the relationship between the operation time ratio by intermittent aeration and the required nitrification amount. It is a graph which shows the time-dependent change of _{the NO 2-} N / NH _4- N ratio in the nitrite tank when the partial aeration tank is intermittently aerated and when it is continuously aerated. It is a graph which shows the time-dependent change of _{the NO 2-} N / NO _x- N ratio in a partial nitrite tank. It is a graph showing the nitrogen removal rate of the treated water obtained from the anaerobic ammonia oxidation tank when the indirect aeration according to the present example and the continuous aeration according to the comparative example are performed.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. The embodiments shown below exemplify devices and methods for embodying the technical idea of the present invention, and the technical idea of the present invention specifies the structure, arrangement, etc. of components as follows. It's not something to do.

(First Embodiment)
As shown in FIG. 1, the ammoniacal nitrogen-containing wastewater treatment apparatus according to the first embodiment of the present invention includes a softening treatment tank 1, a settling tank 13, a relay tank 14, a nitrite tank 2, and a settling tank 3. The anaerobic ammonia oxidation tank 4, the settling tank 5, the water quality measuring means 11, 21, 24, the carbonate adding means 12, the aeration / pH adjusting means 22, the flow rate adjusting means 23, and the controlling means 100 are provided.

As the raw water, calcium-containing ammoniacal nitrogen-containing wastewater is used. Although not limited to the following, as the ammoniacal nitrogen-containing wastewater, for example, wastewater containing organic matter such as leachate from a landfill, calcium, and ammoniacal nitrogen can be used. Typically, the organic matter concentration of the raw water is 0 to 1,000 mg / L as BOD, preferably 0 to 500 mg / L, and more preferably 0 to 300 mg / L.

The calcium concentration of the raw water is 100 to 3,000 mg / L, typically 100 to 2,000 mg / L, and more typically 150 to 1,800 mg / L. The ammoniacal nitrogen concentration of the raw water is 50 to 2,000 mg / L, preferably 100 to 1,000 mg / L, and more preferably 200 to 500 mg / L.

In the softening treatment tank 1, a calcium removing step (softening treatment) is performed to remove calcium (Ca) which is a hardness component contained in the ammoniacal nitrogen-containing wastewater which is the raw water. The softening treatment tank 1 is connected to a water quality measuring means 11 for measuring the quality of raw water and a carbonate adding means 12 for adding carbonate to the softening treatment tank 1. By arranging the softening treatment tank 1, it is possible to suppress the generation of scale of the treatment apparatus in the subsequent stage of the softening treatment tank 1.

The calcium removal step is not particularly limited as long as it is a method capable of lowering the Ca concentration, and for example, aggregation precipitation, aggregation-membrane separation, crystallization, ion exchange, electrosalting, electrophoresis and the like can be used. In the present embodiment, it is preferable to remove calcium from the raw water by adding a carbonate to the softening treatment tank 1 and performing a coagulation precipitation treatment. As the carbonate, sodium carbonate (Na ₂ CO ₃ ), sodium hydrogen _{carbonate (Na HCO 3} ) and the like can be used. In the calcium removal step, it is preferable to reduce the Ca concentration in the raw water to 100 mg / L or less, preferably 50 mg / L or less, and more preferably 30 mg / L or less.

In the calcium removal step, addition of a carbonate necessary for the calcium removal treatment and a carbonate in consideration of nitrification, that is, carbonic acid for supplementing the inorganic carbon required in the nitrite formation step and the anaerobic ammonia oxidation step. Salt and salt are added to the softening treatment tank 1. In this way, to the softening treatment tank 1, a carbonate is added in advance in consideration of not only the purpose of removing calcium from the raw water but also the amount of inorganic carbon required for nitrite, that is, the inorganic carbon is added. By adding more than the amount, the reaction pH can be raised and the carbonate ion concentration can be maintained high, so that the reaction efficiency becomes high, and as a result, the Ca concentration in the treated water can be reduced more than usual, and nitrite formation. The conventional work of adding inorganic carbon in the tank 2 can be omitted. Further, even when the calcium concentration in the raw water suddenly increases, the calcium concentration can be stably reduced because the carbonate is already excessively added to the softening treatment tank 1. Further, by adding an excessive amount of carbonate to the softening treatment tank 1, it is possible to suppress scale adhesion to the piping, the air diffuser, the carrier, etc. in the subsequent stage of the softening treatment tank 1.

-Amount of carbonate added to remove calcium-
As a method for calculating the amount of carbonate added to remove calcium from ammoniacal nitrogen-containing wastewater, for example, the case where _{Na 2} CO _{3 is used as the carbonate will be described below.}

In the present embodiment, the amount _{of Na 2} CO _{3 added for calcium removal C 0} (mg / L) is calculated by the following formula (4), and Na ₂ CO ₃ is added to the raw water based on the calculation result. Calcium carbonate is aggregated and precipitated to control the Ca concentration.
C ₀ = (C _in- C _out ) x a-C _ALK-in /1.06 (4)
(Here, C _in (mg / L): Ca concentration of raw water, C _out (mg / L): Target Ca concentration of softened treated water, a: Coefficient, _CALK-in : Alkaliity of raw water (mg-CaCO) ₃ / L) is shown.)

The coefficient a is slightly different depending on the pH of the softening treatment, but the pH suitable for the calcium removal treatment in the present embodiment is 9 to 10, and more preferably 9.0 to 9.5. The coefficient a can be 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. The target calcium concentration C _out can be appropriately set to be 100 mg / L or less, preferably 50 mg / L or less, and more preferably 30 mg / L or less. The control means 100 controls the amount of carbonate to be added by the carbonate adding means 12 for removing calcium from the raw water based on the measurement result of the Ca concentration and the alkalinity of the raw water by the water quality measuring means 21. The water quality measurement by the water quality measuring means 21 and the carbonate addition control by the carbonate adding means 12 may be continuously performed or may be performed every time a predetermined time elapses.

By determining the amount of carbonate added to remove calcium based on the formula (4), the optimum _{amount of Na 2} CO ₃ added is determined based on the Ca concentration and alkalinity of the raw water in the softening treatment tank 1 It is possible to control the Ca concentration in a stable manner according to the quality of the raw water, and a stable target water quality can be obtained while optimizing the amount of _{Na 2} CO _{3 added.}

-Amount of carbonate added in consideration of nitrification (1)-
In this embodiment, not only the amount of carbonate added according to the quality of the raw water is optimized, but also the nitrification treatment in the nitrite tank 2 and the anaerobic ammonia oxidation tank 4 described later after the softening treatment tank 1 is further performed. In consideration, the amount of carbonate added when the inorganic carbon required in the nitrification step is added to the softening treatment tank 1 is determined. Both the nitrifying bacteria and the anaerobic ammonia bacteria used in the nitrite tank 2 and the anaerobic ammonia oxidation tank 4 are autotrophic bacteria, and inorganic carbon is required for their growth. Based on the amount of inorganic carbon required for the treatment in the nitrite tank 2 and the anaerobic ammonia oxidation tank 4, the addition of Na ₂ CO _{3 for the softening treatment to be added to the softening treatment tank 1 to replenish the inorganic carbon.} By calculating the amount, it becomes possible to stabilize the ability to remove calcium and maintain good biological treatment in the subsequent stage.

The reaction by anaerobic ammonia-oxidizing bacteria is as shown in formula (1), but the nitrification reaction from ammonia to nitrite nitrogen by ammonia-oxidizing bacteria is represented by the following formula (5) including cell synthesis. Will be done.
^{_{1NH 4 + + 1.38O 2 + 1.98HCO}} 3 -
_{→ 0.018C 5 H 7 O 2 N} + 0.98NO 2 - + 1.04H 2 O + 1.89H 2 CO 3 (5)

From the formula (5), the nitrite step requires 0.077 mg-C / L of inorganic carbon (= 0.68 mg-Na ₂ CO ₃ / L) per 1 mg-N / L of ammoniacal nitrogen. Further, according to the formula (1), 0.057 mg-C / L of inorganic carbon (0.50 mg-Na ₂ CO ₃ / L) is required for 1 mg-N / L of ammoniacal nitrogen in the anaerobic ammonia oxidation step. I understand.

_{When the formula (5) is included in the formula (4), the amount of Na 2} CO ₃ added is C _{0, which} takes into consideration the amount of carbonate added for nitrification in addition to the amount of carbonate added for removing calcium. (Mg / L) can be calculated by the following formula (6).
C ₀ = (C _in- C _out ) x a + (C _N-in- C _N-out ) x 1.18-C _{ALK-in /} 1.06 (6)
(Here, C _N-in : Ammonia nitrogen concentration in raw water (mg-N / L), C _N-out : Target ammonia nitrogen concentration (mg-N / L) in the nitrite treatment tank. .)

In this way, considering the quality of the raw water and nitrification in the nitrite tank 2 and the anaerobic ammonia oxidation tank 4, the softening treatment tank 1 is required not only for the purpose of removing carbon from the raw water but also for nitrification. By adding a carbonate in consideration of inorganic carbon to the softening treatment tank 1 in advance, the work of adding inorganic carbon, which was conventionally required in the nitrite tank 2, can be omitted. In addition to being able to simplify the above, it is possible to stably reduce the calcium concentration even when the fluctuation of raw water is large, and to suppress scale adhesion to the piping, air diffuser, carrier, etc. in the subsequent stage of the softening treatment tank 1. Can be done. _{In addition, since a large amount of Na 2} CO ₃ can be added in the Ca removal step by the amount of the second term: (CN _{-in −C N-out} ) × 1.18 in the formula (6), the reaction between calcium and carbonate ions. Can be promoted efficiently.

-Amount of carbonate added in consideration of nitrification (2)-
As the amount of carbonate added in consideration of nitrification, it is also possible to determine the amount of carbonate added from the viewpoint of the alkalinity required for nitrification. Alkalinity necessary for nitrification of ammonium nitrogen 1 mg-N / L in the nitrification step is _{7.14mg-CaCO 3 /L(=7.57mg-Na 2 CO 3} / L), to which (4) _{Including, the Na 2} CO ₃ addition amount C ₀ (mg / L), which takes into consideration the addition amount of carbonate required for nitrification in addition to the addition amount of carbonate for removing calcium, is calculated by the following formula (1). It can be obtained by 7).
C ₀ = (C _{in −} C _out ) × a + (CN _{-in −C N-out} ) × 7.57-C _ALK-in /1.06+C _ALK-out /1.06 (7)

_CALK-out is the target alkalinity of the nitrite tank 2, and is determined by the relationship between the pH and alkalinity of the nitrite tank 2. For example, when the target pH of the nitrite-treated water in the nitrite tank 2 is 7.8 and the alkalinity at this time is 500 mg / L, the _CALK-out is 500 mg / L. The relationship between the pH and alkalinity of the nitrite-treated water can be obtained by drawing a neutralization titration curve.

Comparing Eqs. (6) and (7), Eq. (6) _{requires less Na 2} CO ₃ addition, but when controlling the addition of carbonate based on Eq. (6), the latter stage It is necessary to add alkali separately in the nitrite tank 2. In this case, in order to adjust the alkalinity of the nitrite tank 2, by using caustic soda, pH control can be facilitated as compared with the case of using carbonate or the like, and more efficient treatment can be performed. Can be done. _{On the other hand, when Na 2} CO ₃ is added to the softening treatment tank 1 based on the equation (7), it is not necessary to add alkali in the nitrite tank 2 in the subsequent stage, so that the control becomes easier and the control becomes easier. The process can be simplified. However, since the pH of the raw water flowing into the biological treatment may increase, it is preferable to take care not to inactivate the microorganisms.

According to the present embodiment, the addition of carbonate to be added to the softening treatment tank 1 based on the calcium concentration, ammoniacal nitrogen concentration, alkalinity, and alkalinity or target ammoniacal nitrogen concentration of the nitrite tank 2 of the raw water. The amount can be controlled. That is, in consideration of the water quality of the raw water and nitrification in the nitrite tank 2, not only the purpose of removing calcium from the raw water but also the inorganic carbon necessary for the nitrite treatment is added in advance to the softening treatment tank 1. By doing so, it is possible to omit the work of adding the inorganic carbon, which was conventionally required in the nitrite tank 2, so that the apparatus and the treatment can be simplified. Further, even when the calcium concentration in the raw water suddenly increases, the calcium concentration can be stably reduced because the carbonate is excessively added. It is also possible to suppress scale adhesion to the piping, the air diffuser, the carrier, etc. in the subsequent stage of the softening treatment tank 1.

As will be described in detail below, in the present embodiment, intermittent aeration may be performed in the nitrite tank 2 in the subsequent stage. At that time, if the calcium removal in the raw water is insufficient, the phenomenon that scale is generated in the air diffuser pores or the scale is likely to adhere to the carrier may become remarkable during the aeration stop period of the nitrite tank 2. .. By appropriately performing the softening treatment in the softening treatment tank 1 based on the equations (6) and (7), it is possible to prolong the life of the air diffuser and the carrier.

In the present embodiment, the Ca concentration can be measured by any one of a calcium analysis pack test manufactured by Kyoritsu Institute of Physical and Chemical Research, an electrode type Ca concentration meter, a chelate titration method, a frame atomic absorption method, and an ICP emission spectroscopic analysis method. When the measured value of the calcium concentration in the raw water is lower than the target Ca concentration of the softened water, it is not necessary to add carbonate for the softening treatment.

In the subsequent stage of the softening treatment tank 1, a settling tank 13 for precipitating and separating _{CaCO 3} produced in the softening treatment and a relay tank 14 for storing the ammoniacal nitrogen-containing wastewater after the _{CaCO 3 is settled and separated are arranged.} A water quality measuring means 21 for measuring the quality of the treated water in the relay tank 14 and the nitrite tank 2 is connected to the relay tank 14 and the nitrite tank 2. Normally, the softened water obtained after the calcium removal step has a pH of about 8.5 to 9.5. Therefore, a pH adjusting step is provided after the softening treatment tank 1, and the inflow water to the biological treatment is pH 7.5. It is necessary to neutralize to about 8.5. In the treatment apparatus according to the first embodiment, the settling tank 13 and the relay tank 14 are provided so that the residence time of the nitrite tank 2 can be adjusted and the wastewater flowing into the nitrite tank 2 is sub-nitrite. Since it can be retained for a predetermined period in the settling tank 13 and the relay tank 14 before flowing into the nitrite tank 2, the softened treated water can be flowed into the subsequent treatment without providing a neutralization step. Become. Therefore, according to the method for treating ammoniacal nitrogen-containing wastewater according to the first embodiment, the acid required for neutralization and the alkali, nitrification, and inorganic carbon required for anaerobic ammonia oxidation are required. Processing can be performed efficiently while reducing consumption. The relay tank 14 may be omitted.

The total residence time of the raw water in the settling tank 13 and the relay tank 14 is preferably 2 days or more, preferably 5 days or more, and more preferably 10 days or more with respect to the planned treated water amount. The relay tank 14 may be agitated. As for the agitation of the relay tank 14, it is desirable to use mechanical agitation because nitrification may proceed in the raw water tank 10 if aeration agitation is performed.

The nitrite tank 2 is a treatment tank that accommodates ammonia nitrogen-containing wastewater and nitrites a part of ammonia nitrogen contained in the ammonia nitrogen-containing wastewater into nitrite nitrogen. The nitrite tank 2 is connected to an aeration / pH adjusting means 22 that appropriately controls the free ammonia concentration in the nitrite tank 2 and adjusts the aeration operation time and the amount of aeration.

In the nitrite tank 2, about 57% of the ammoniacal nitrogen in the raw water is nitrified to nitrite nitrogen using microorganisms. As the nitrification using microorganisms, for example, an activated sludge method, a fluidized carrier method, a fixed bed method (contact oxidation method) and the like can be used. In order to more stably perform the partial nitrite treatment that stops the nitrification reaction of ammoniacal nitrogen by the production of nitrite nitrogen, a carrier to which ammonia-oxidizing bacteria are adhered and fixed is flowed in the nitrite tank 2. It is more preferable to use the fluid carrier method.

The carrier used in the nitrite tank 2 is not particularly limited, but by filling the polymer carrier, ammonia-oxidizing bacteria can be stably attached, so that more stable nitrite formation in the nitrite tank 2 can be achieved. Performance is obtained. As the polymer carrier to be filled in the nitrite tank 2, a synthetic polymer carrier such as polyethylene glycol (PEG), polyvinyl alcohol (PVA), polyacrylamide, or a photocurable resin, or a polymer such as carrageenan or sodium alginate is used. Examples thereof include a gel carrier that has been used, a carrier made of polyethylene, polyurethane, polyporopylene, and the like.

As the shape of the carrier, any of spherical, quadrangular, and cylindrical shapes can be used. The effective diameter of the carrier is preferably 3 to 10 mm, which can be stably separated by a screen for separating the carrier. ^{The specific gravity of the carrier shall be 1.00 to 1.10 g / cm 3} which enables quick and uniform flow in the nitrite tank 2 even when intermittent aeration is performed in the nitrite tank 2. Is preferable, and more preferably 1.01 to 1.05 g / cm ³ . The filling amount of the carrier is preferably 5 to 40% by volume (V%) so that the carrier can be uniformly mixed and flowed in the nitrite tank 2, and further is 10 to 30% by volume (V%). Is preferable. By setting the nitrogen load of the nitrite tank 2 to, for example, 0.01 to 2.0 kg-N / m ³ / d, the nitrite treatment can be stably performed.

In the nitrite treatment, the nitrification reaction of ammonia nitrogen contained in the raw water is stopped by the production of nitrite nitrogen, and the concentration of ammonia nitrogen in the treated water flowing out from the nitrite tank 2 to the anaerobic ammonia oxidation tank 4 is dealt with. It is necessary to control the ratio of nitrite nitrogen concentration (NO _2- N / NH _4- N ratio) to approach about 1.32, which is an appropriate target ratio for treatment in the anaerobic ammonia oxidation tank 4. ..

In this embodiment, the free ammonia (FA) in the nitrite tank 2 is based on the water quality information of the raw water in order to control it so as to approach about 1.32, which is suitable for the treatment in the anaerobic ammonia oxidation tank 4. It is preferable to control the pH and intermittent aeration of the nitrite tank 2 so that the concentration becomes a predetermined target concentration.

-PH control-
According to the study by the present inventors, the free ammonia concentration of the ammoniacal nitrogen-containing wastewater in the nitrite tank 2 should be maintained at 1.0 to 10 mg / L, more preferably 2.0 to 10 mg / L. It was found that by adjusting the pH, the ammonia-oxidizing bacteria could be preferentially attached to the carrier while suppressing the growth of the nitrite-forming bacteria, whereby a stable nitrite-forming treatment could be obtained.

The free ammonia concentration can be calculated according to the following formula (8).

（８）式からわかるように、遊離アンモニア濃度は、ｐＨ、ＮＨ₄−Ｎ濃度、水温の変化の影響を受ける。

As can be seen from Eq. (8), the free ammonia concentration is _{affected by changes in pH, NH 4-} N concentration, and water temperature.

In the present embodiment, the target ammonia nitrogen concentration calculated from the ammonia nitrogen concentration of the raw water ammonia-containing nitrogen-containing wastewater (hereinafter _{, also referred to as “raw water NH 4-} N”) (hereinafter, also referred to _{as “target NH 4-N”).} ) And the water temperature in the nitrite tank 2, the target pH is determined so that the free ammonia concentration in the nitrite tank 2 becomes 1.0 to 10 mg / L according to the formula (8). The target NH _4- N can be calculated according to the following equation (9).
Target NH _4- N = Raw water NH _4- N × (1 / 2.3) (9)
For example, when the ammoniacal nitrogen concentration of the raw water is 100 mg-N / L, the target ammoniacal nitrogen concentration of the nitrite tank 2 is about 43 mg-N / L.

Next, the pH in the nitrite tank 2 is set based on the relationship between the water temperature of the nitrite tank 2, the target ammoniacal nitrogen concentration and the free ammonia concentration. For example, a table for calculating the relationship between the target pH, the target ammoniacal nitrogen concentration, and the free ammonia concentration is prepared in advance using Eq. The target pH in the nitrite tank 2 can be set by determining the pH range such that the ammonia concentration satisfies 1.0 to 10 mg / L. For example, when the target ammoniacal nitrogen concentration of the nitrite tank 2 is about 43 mg-N / L and the water temperature is 30 ° C., the pH range in which the free ammonia concentration is 1.0 to 10 mg / L is 7.5 to 8. It becomes 4.

After the pH range is set, an acid or alkali is added so that the inside of the nitrite tank 2 is within the pH range. As the acid added to the nitrite tank 2, for example, sulfuric acid, hydrochloric acid and the like can be used. As the alkali added to the nitrite tank 2, caustic soda, sodium carbonate, sodium hydrogen carbonate and the like can be used. In particular, in this embodiment, it is preferable to use caustic soda, which is a strong alkali whose pH can be easily adjusted, rather than using sodium carbonate or sodium hydrogen carbonate as the alkali. As a result, the pH in the nitrite tank 2 can be optimized at an early stage with a small amount of chemical solution, and the free ammonia concentration in the nitrite tank 2 can be optimized. In addition, by using caustic soda, there are secondary advantages that the running cost can be suppressed as compared with sodium carbonate and sodium hydrogen carbonate, and clogging due to scale generation in the chemical injection pipe is less likely to occur.

-Intermittent aeration control-
As a result of the examination by the present inventors, the amount of nitrification from ammonia nitrogen to nitrite nitrogen in the nitrite tank 2 is the aeration air volume and the aeration time ratio between the aeration operation time and the aeration stop time (On / ( It was found to be proportional to On + Off)). Therefore, the amount of nitrification is calculated by analyzing either the aeration air volume at a certain point in time, the ammonia concentration of the raw water and the nitrite-treated water obtained in the nitrite tank 2 during the aeration operation time, or the nitric acid or nitrite concentration. Therefore, it is preferable to set the aeration air volume and the aeration operation time for maintaining an appropriate NO _2- N / NH _{4-N ratio.}

In the present embodiment, the target ammonia nitrogen concentration is determined from the equation (9) based on the water temperature and the ammonia nitrogen concentration of the raw water ammonia-containing nitrogen-containing wastewater. Then, the required nitrification amount at which the ratio of the nitrite nitrogen concentration produced in the nitrite tank 2 to the target ammonia nitrogen concentration (NO _2- N / NH _4- N ratio) becomes the target ratio is determined. Based on the required nitrification amount, the operation time ratio between the aeration operation time and the aeration stop time in the nitrite treatment is adjusted.

For example, the target ammonia nitrogen concentration and the target pH are determined based on the formulas (8) and (9) from the ammonia nitrogen concentration of the raw water and the water temperature of the ammonia nitrogen-containing wastewater flowing into the nitrite tank 2. NS. Then, based on the amount of treated water in the nitrite tank 2 and the tank capacity of the nitrite tank 2, the _{required nitrification amount at which the NO 2-} N / NH _4- N ratio becomes the target ratio of 1.32 is determined. .. Since the operating time ratio and the required vitrification amount are in a proportional relationship as described above, a table (see Table 3) or a figure (see Fig. 3) showing the relationship between the operating time ratio and the required vitrification amount is prepared in advance, and the figure or table is prepared. Is used to set an operating time ratio that satisfies a certain required vitrification amount based on the relationship between the operation time ratio and the required vitrification amount.

When controlling the aeration air volume, in the control using an inverter, there may be a limit to the lower limit of control due to the discharge pressure, or an air volume above a certain level may be required to flow the carrier or activated sludge. Therefore, precise control may not be possible. Therefore, in the present embodiment, it is preferable that the aeration / pH adjusting means 22 that aerates the nitrite tank 2 is used to provide an aeration blower connected to the nitrite tank 2 with a timer to perform intermittent aeration. Finer adjustment of the time ratio is possible.

When adjusting the operation time ratio using a timer, if both the on (aeration operation) time and the off (aeration stop) time are set to less than 1 minute, the blower will be burdened and stable operation for a long period of time may be performed. It can be difficult. In order to reduce the burden on the blower that aerates the nitrite tank 2 and to stably treat the treated water obtained by the nitrite treatment so as to be in a suitable state by the anaerobic ammonia oxidation treatment. The off time is preferably 5 minutes or more.

The off time is preferably set to a condition in which the progress of nitrification can be stopped more reliably by setting the dissolved oxygen amount (DO) in the nitrite tank 2 to 0.5 mg / L or less. For example, although it depends on the capacity of the blower and the size of the nitrite tank 2, the DO in the nitrite tank 2 is set to 0 by setting the off time more preferably 10 minutes or more, further preferably 15 minutes or more. It is possible to reduce the dose to 5.5 mg / L or less to provide a period during which nitrifying bacteria are inactive.

On the other hand, if the off time is set too long, scale tends to adhere to the air diffuser, the carrier, etc. in the nitrite tank 2 during the aeration stop period. The aeration stop time in the nitrite treatment is 60 minutes or less, more preferably 45 minutes or less, still more preferably 30 minutes or less.

There is no particular limitation as long as the on-time is 1 minute or more. In the on-time, the DO is preferably 1 mg / L or more, and more preferably 2.5 mg / L or more when a fluidized carrier is used. As long as the residence time of the softening tank 1 and the off time in the nitrite tank 2 are observed, the inside of the nitrite tank 2 may or may not be agitated by the stirrer during the off time. ..

The alkalinity in the nitrite tank 2 is preferably 100 mg / L or more, more preferably 150 mg / L or more, still more preferably 200 mg / L or more for the good progress of the nitrification treatment. .. From the viewpoint of preventing scale adhesion, it is preferably 800 mg / L or less, more preferably 700 mg / L or less, and further preferably 500 mg / L or less. The water temperature is 15 ° C. or higher, more preferably 20 ° C. or higher, still more preferably 25 ° C. or higher, and preferably 35 ° C. or lower. Alkaliity can be measured by a titration method using an acid such as hydrochloric acid or sulfuric acid, a pack test manufactured by Kyoritsu Rikagaku Kenkyusho Co., Ltd., an analysis kit manufactured by HACH, or the like.

The nitrite treated water obtained in the nitrite tank 2 is subjected to the precipitation treatment of suspended sludge (suspended activated sludge) in the settling tank 3, and a part of the precipitated sludge is returned to the nitrite tank 2 as floating sludge. The remaining sludge is treated as excess sludge. By providing the settling tank 3, SS-like foreign substances in the treated water obtained in the nitrite tank 2 can be removed. Therefore, even if the raw water fluctuates, the treated water flowing into the anaerobic ammonia oxidation tank 4 can be removed. The properties can be maintained in a stable state at all times. Further, since the suspended sludge in the settling tank 3 is returned to the previous stage of the nitrite tank 2, the fluidized carrier and the suspended sludge coexist in the nitrite tank 2. Due to this coexistence, even if the quality of the raw water flowing into the nitrite tank 2 fluctuates, it can be averaged by activated sludge treatment, so that there is almost no effect on the carrier of ammonia-oxidizing bacteria adhesion, and stable nitrite. Can be processed. The settling tank 3 may be omitted depending on the quality of the raw water. The settling tank 3 may be omitted.

In the anaerobic ammonia oxidation tank 4, the ammonia nitrogen contained in the nitrite treatment liquid flowing from the nitrite tank 2 and the nitrite nitrogen are reacted according to the formula (1) to proceed the denitrification reaction. Is. The anaerobic ammonia oxidation tank 4 is connected to a flow rate adjusting means 23 for adjusting the flow rate of the nitrite-treated water flowing into the anaerobic ammonia oxidation tank 4. Further, a water quality measuring means 24 capable of measuring the water temperature, ammonia nitrogen concentration, alkalinity, calcium concentration and the like in the anaerobic ammonia oxidation tank 4 is connected to the anaerobic ammonia oxidation tank 4.

As a method for retaining anaerobic ammonia-oxidizing bacteria in the anaerobic ammonia-oxidizing tank 4, a granule method using the self-granulation function of microorganisms, a fluid bed method for immobilizing anaerobic ammonia-oxidizing bacteria on a carrier, and a fixed bed. There is a law. In the present embodiment, particularly by adopting the fluidized bed method, it is possible to prevent the outflow of anaerobic ammonia-oxidizing bacteria and maintain an appropriate biomass amount in which the inside of the anaerobic ammonia-oxidizing tank 4 is not blocked.

The carrier is not particularly limited, and examples of a carrier capable of stably immobilizing anaerobic ammonia-oxidizing bacteria include a fluid carrier made of a polymer material similar to that used in the above-mentioned nitrite step. As the shape of the carrier, any of spherical, quadrangular, and cylindrical shapes 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 anaerobic ammonia oxidation tank 4. As a carrier, a carrier having many fine pore diameters on the surface, a sponge having a hollow inside, and a carrier having innumerable irregularities on the surface can quickly adhere and fix anaerobic ammonia-oxidizing bacteria, and high denitrification performance can be obtained in a short period of time. The specific gravity of the carrier 1.00~1.10g / cm ³ can be uniformly fluidized than stirred at anaerobic conditions, and more preferably to 1.01~1.05g / cm ^3. The filling amount of the carrier is preferably 5 to 40% by volume (V%), more preferably 10 to 30% by volume (V%) so as not to have a local volume.

When starting up the anaerobic ammonia oxidation tank 4, the start-up period can be shortened by adding sludge on which anaerobic ammonia-oxidizing bacteria have accumulated or a carrier (seed carrier) to which the anaerobic ammonia-oxidizing bacteria have adhered. In particular, when the fluidized bed method is adopted for the anaerobic ammonia oxidation tank 4, the contact efficiency between the seed carrier and the new carrier to which no microorganisms are attached is increased by adopting the same carrier as the input carrier. The period can be further shortened. The ratio of seed carriers is efficiently 1 to 30% by volume (V%), preferably 5 to 20% by volume of all carriers in the tank. The seed carrier is cultivated using tap water, industrial water, or artificial wastewater in which the concentrations of nitrite and ammonia are adjusted with reagents based on actual wastewater.

In order to maintain the flow of the carrier during stirring, the number and position of stirring blades so that the flow velocity in the tank is 0.03 m / s or more, preferably 0.07 m / s or more, and more preferably 0.1 m / s or more. , Shape, and rotation rate are desirable. The number and position of the stirring blades are not particularly limited. For example, by providing the stirring blades in the upper and lower two stages and setting the lower stage stirring blades to about 300 to 700 mm from the bottom of the tank, the flow velocity in the tank can be increased at a small rotation speed. Can be kept. In order to maintain the activity of anaerobic ammonia-oxidizing bacteria, it is desirable to add iron and trace elements such as zinc, cobalt, manganese, copper, molybdenum, and nickel into the anaerobic ammonia oxidizing tank 4. The anaerobic ammonia oxidation treated water obtained in the anaerobic ammonia oxidation tank 4 is subjected to solid-liquid separation treatment in the settling tank 5 to obtain treated water.

As the control means 100, a general-purpose computer or the like for controlling each device based on the predetermined algorithm shown in the present embodiment can be used, and the water quality measuring means 11, 21, 24, the carbonate adding means 12, and the aeration can be used. The pH adjusting means 22 and the flow rate adjusting means 23 can be configured to output a predetermined control signal.

Ammonia-nitrogen-containing wastewater can be treated using the ammonia-nitrogen-containing wastewater treatment apparatus shown in FIG. That is, the method for treating ammoniacal nitrogen-containing wastewater according to the first embodiment of the present invention includes a calcium removal step for removing calcium in calcium-containing ammoniacal nitrogen-containing wastewater and an ammoniacality after the calcium removal step. An anaerobic step of nitriding a part of ammoniacal nitrogen in nitrogen-containing wastewater to nitrite nitrogen and anaerobic ammonia oxidation treatment of treated water for nitrite treatment using anaerobic ammonia-oxidizing bacteria. In the nitrification step including the ammonia oxidation step and the treatment step of the ammonia nitrogen-containing wastewater including the ammonia nitrogen-containing wastewater, the carbonate for removing calcium and the carbonate for supplementing the inorganic carbon required in the nitrification step are provided. Includes addition in the calcium removal step.

According to the ammonia nitrogen-containing wastewater treatment apparatus and treatment method according to the first embodiment of the present invention, considering the water quality of raw water and nitrification in the nitrite tank 2 and the anaerobic ammonia oxidation tank 4, the nitrification is taken into consideration. A carbonate is added to the softening tank 1 in advance, taking into consideration not only the purpose of removing calcium from the raw water but also the inorganic carbon required for nitrification. As a result, the work of adding inorganic carbon, which was conventionally required in the nitrite tank 2, can be omitted, and the apparatus and work can be simplified. Further, even when the raw water fluctuates, the excess carbonate is supplied to the softening treatment tank 1, so that the calcium concentration can be stably reduced, and the piping and the powder in the subsequent stage of the softening treatment tank 1 can be dispersed. It is also possible to suppress scale adhesion to an air device, a carrier, or the like. As a result, it is possible to provide a method and a treatment apparatus for ammonia nitrogen-containing wastewater capable of more stably performing nitrite treatment and anaerobic ammonia oxidation treatment while suppressing the generation of scale.

(Second Embodiment)
As shown in FIG. 2, the ammoniacal nitrogen-containing wastewater treatment apparatus according to the second embodiment of the present invention is a BOD oxidation tank 15 instead of the relay tank 14 in the previous stage of the nitrite tank 2 shown in FIG. Is provided, and an aerobic tank 6 and an anaerobic tank 7 for treating the treated water of the settling tank 5 are further provided, which is different from the treatment apparatus shown in FIG. Others show substantially the same configuration as the processing apparatus according to the first embodiment, and thus duplicate description will be omitted.

The BOD oxidation tank 15 is a treatment tank for oxidizing and removing easily decomposable organic matter in wastewater after calcium removal by a microbial reaction when the raw water contains easily decomposable organic matter. By arranging the BOD oxidizing tank 15, it is possible to prevent the easily decomposable organic matter from flowing into the nitrite tank 2 and the anaerobic ammonia oxidizing tank 4 to proliferate the BOD oxidizing bacteria and destabilize the treatment.

The organic substance removing treatment performed in the BOD oxidation tank 15 is not particularly limited as long as a means for lowering the concentration of easily decomposable organic substances is used. For example, the standard activated sludge method, the fluidized carrier method, the fixed bed method (contact oxidation method), the rotary disk method, the sprinkling filter method and the like can be mentioned. If the concentration of organic matter in the raw water is expected to fluctuate as in leachate treatment, use the fluidized carrier method or fixed bed method in which microorganisms are immobilized on the carrier and the aeration air volume can be adjusted. Is desirable.

In the BOD oxidation step, it is desirable to control so that the nitrification of ammonia in the raw water does not proceed. Specifically, easily decomposable organic substances, ammoniacal nitrogen concentration, nitrate nitrogen concentration, and nitrite nitrogen concentration in the raw water and the softened water flowing into the BOD oxidation tank 15 are appropriately measured, and aeration is performed in a range where nitrification does not proceed. Control the air volume. Examples of the aeration air volume control method include air volume control by an inverter, operation time control by a blower timer, and the like.

Soluble TOC (total organic carbon), COD _Mn , COD _{Cr and the} like can be used as an index of easily decomposable organic matter. Here, the solubility refers to the analytical value of the filtrate filtered through a membrane having a predetermined pore size (usually 1 μm). The organic matter concentration of the treated water can be determined by treating the softened treated water with a batch type activated sludge test and a carrier test. There are no particular restrictions on the method of analyzing ammonia nitrogen concentration, nitrate nitrogen concentration, and nitrite nitrogen concentration, but for example, sensors such as an ammonia sensor, nitric acid sensor, and nitrite sensor are provided, and Kyoritsu Institute of Physical and Chemical Research Co., Ltd. Manufactured pack test, HACH analysis kit, etc. can be mentioned as simple analysis methods.

The steps after the organic matter removal step in the BOD oxidation tank 15 depend on the biological reaction, and in particular, the reaction between the nitrite tank 2 and the anaerobic ammonia oxidation tank 4 is easily affected by the water temperature. Therefore, it is desirable to provide equipment for heating the inflow water into the BOD oxidation tank 15 and the treated water obtained in the BOD oxidation tank 15. At the time of heating, it is desirable to adjust the water temperature in the anaerobic ammonia oxidation tank 4 to be 20 to 35 ° C, preferably 25 to 30 ° C.

In the anaerobic ammonia oxidation tank 4, about 11% of the reacted nitrogen _{remains as NO 3- N as shown in the formula (1), and NO 2-} N / NH ₄ − in the partial nitrite tank. _{NO 2-} N or NH _4- N remains as much as the N ratio deviates from 1.32. Therefore, depending on the discharge standard, post-treatment for removing these residual nitrogen components may be required. In the treatment apparatus according to the third embodiment, as the post-treatment of the anaerobic ammonia oxidation treatment, the aerobic tank 6 and the anaerobic tank 7 are provided after the settling tank 5, so that the treated water satisfying the discharge standard is stabilized. Can be obtained.

The post-treatment method is not particularly limited, and for example, a nitrification endogenous denitrification method (Wuhrmann method) using a fixed bed carrier or a fluidized bed carrier, a nitrification-denitrification method (Bringmann method), a circulating nitrification denitrification method, or the like is used. be able to. If the raw water contains easily decomposable organic matter, it is necessary for denitrification by bypassing the BOD oxidation step, nitrite conversion step, and anaerobic ammonia oxidation step and directly charging the aerobic tanks 6 and 7. Organic matter can be reduced.

Although the present invention has been described in accordance with the above embodiments, the statements and drawings that form part of this disclosure should not be understood to limit the invention. This disclosure will reveal to those skilled in the art various alternative embodiments and operational techniques.

For example, in the above-mentioned nitration step and anaerobic ammonia oxidation step, if the PO _4- P concentration in the nitrite tank 2 and the anaerobic ammonia oxidation tank 4 is too low, ammonia oxidizers and anaerobic ammonia oxidizers are used as carriers. It may be difficult to adhere and fix. On the other hand, if PO _4- P is too high, Ca _{reacts with PO 4-} P in a high pH region to precipitate an insoluble solid substance mainly composed of hydroxyl apatite (HAP), which is used as a carrier. It adheres and tends to inhibit the stable adhesion of ammonia-oxidizing bacteria and anaerobic ammonia-oxidizing bacteria. Therefore, in the nitrite formation step and the anaerobic ammonia oxidation step, the PO _4- P concentration can be controlled to be 0.1 to 1.0 mg / L, more preferably 0.1 to 0.5 mg / L. More preferred. For example, when leachate or factory effluent is used as raw water, it is preferable to add phosphorus necessary for microbial growth to the nitrite tank 2 when the phosphorus content in the raw water is low.

_{In the above-mentioned softening treatment step, when Na 2} CO _{3 is} added according to the formulas (6) and (7), the pH of the treated water flowing into the nitrite tank 2 becomes 8.5 or more, and the microorganisms are lost. There is concern that it will be useful. _{Therefore, in the case of excessive addition of Na 2} CO ₃ for nitrification and anaerobic ammonia oxidation during the calcium removal treatment in the softening treatment step, the floating sludge and the carrier should be used together in the nitrite tank 2 in the subsequent stage. Therefore, it is desirable that microorganisms for removing organic substances and nitrifying bacteria coexist. By coexisting the microorganisms for removing organic matter and the nitrifying bacteria in this way, the alkalinity is consumed as the nitrification progresses, the pH is lowered, and the pH (6.0 to 8.5) suitable for removing organic matter by the microorganisms is obtained. It will be possible to maintain.

As described above, the present invention is represented by the matters specifying the invention within the scope of claims reasonable from the above disclosure, and at the implementation stage, it can be modified and embodied without departing from the gist thereof.

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

Ammonia nitrogen-containing wastewater treatment was carried out using the treatment apparatus shown in FIG. As the raw water, leachate after the softening process of the actual industrial waste disposal site was used. Table 1 shows the raw water condition during the test period. In Table 1, "average", "minimum", and "maximum" represent the average value, minimum value, and maximum value of each raw water quality during the test period.

-Softening tank-
_{Na 2} CO ₃ was added as a carbonate to the raw water.
_{In Example 1, Na 2} CO ₃ was added according to the formula (6), and NaOH necessary for pH adjustment was added in the nitrite tank.
_{In Example 2, Na 2} CO ₃ was added according to the formula (7), and NaOH necessary for pH adjustment was added in the nitrite tank. In Example 2, a neutralization titration curve is prepared using the treated water in the nitrite tank to investigate the relationship between alkalinity and pH, and the treated water pH in the nitrite tank becomes the set value. The alkalinity in the nitrite tank was set as described above, and Na ₂ CO ₃ was added according to the value.
_{In the comparative example, Na 2} CO ₃ was added according to the formula (5), and no alkaline source was added to the nitrite tank.

-Nitrite tank-
In the nitrite tank, 20 V% of PEG carrier having an average particle size of 4.2 mm was filled. PH of nitritation tank sets a target NH ₄ -N concentration of NH ₄ -N concentration of the relay tank is FA from the target ammonia nitrogen concentration and temperature of nitritation tank 1.0 to 10 mg / The target pH was set so as to be L, and acid and alkali were added for control.

In the nitrite tank, when the average ammonia concentration of raw water is 120 mg-N / L and the water temperature is 30 ° C, the target ammonia nitrogen concentration of the nitrite tank is set to 120 × 1 ÷ 2.3 = 52 mg-N / L. NS. At this target ammonia nitrogen concentration, when the water temperature is 30 ° C, the FA should be 1.0 to 10 mg / L, and at this time, the safety factor should be 2.7 to 4.7 mg / L. The pH was determined. Here, the target pH was set to 7.8 to 8.0, and caustic soda (NaOH) was added as a pH adjuster so as to maintain this target pH. For the aeration air volume, _{measure NH 4-} N and NO _2- N in the nitrite tank, and adjust the operating time of the blower by intermittent aeration so that the NO _2- N / NH _{4-N ratio approaches 1.32.} It was adjusted. Further, 1Q sludge was circulated from the settling tank in the latter stage of the nitrite tank to maintain activated sludge in the tank.

-Anaerobic Ammonia Oxidation Tank-
An anaerobic ammonia oxide tank was filled with 20 V% of a PVA carrier having an average particle size of 4 mm. At the time of starting up the anaerobic ammonia oxidation tank, 10% of the carrier was charged with the seed carrier pre-cultured in artificial wastewater. The amount of water flowing into the anaerobic ammonia oxidation tank _{was adjusted so that NH 4-} N and NO _2- N in the anaerobic ammonia oxidation tank were measured and adjusted to 50 mg-N / L and 20 mg-N / L, respectively. At the same time, the amount of treated water was gradually increased. In addition, iron and trace element (zinc, cobalt, manganese, copper, molybdenum, nickel) liquids were added to the anaerobic ammonia oxidation tank. Regarding the amount of water flowing into the anaerobic ammonia oxidation tank, the NO _2- N and NH _4- N concentrations of the anaerobic ammonia oxidation tank treated water were confirmed, and the treatment was good (both 20 mg-N / L or less). After confirming that, the amount of inflow water was repeatedly increased, and the nitrogen load was gradually increased to ^{2.0 kg-N / m 3.}

<Effect of carbonate addition in calcium removal process (softening treatment)>
Table 2 shows the comparison results of the water quality of the softened treated water and the ammoniacal nitrogen-containing wastewater in the nitrite tank in Example 1, Example 2 and Comparative Example after the treatment was carried out for 120 days.

As shown in Table 2, the calcium concentrations of the softened water are, in ascending order, Example 2, Example 1, and Comparative Example, and by excessively adding the amount of _{Na 2} CO _{3 added during the calcium removal step (softening treatment).} It was confirmed that calcium can be stably removed even if the Ca concentration of raw water fluctuates. In addition, no difference was observed in the water quality of nitrogen in the partial nitrite tank in any of the methods. Furthermore, the Ca ratio in the carrier deposits of the nitrite tank at the end of the test decreased in the order of Comparative Example, Example 1 and Example 2, and in Comparative Example, the growth of calcium scale on the carrier was confirmed. It was confirmed that the production of calcium scale was suppressed in Examples 1 and 2. Further, in the comparative example, since the nitrification rate was lower than that in Examples 1 and 2 due to the scale adhesion to the carrier, nitrification did not proceed even if the operation was performed with the same aeration air volume as in Examples 1 and 2, and NO _2- N / The NH _4- N ratio decreased.

<Effect of indirect aeration>

In Example 1, NH _4- N and NO _2- N in the nitrite tank were measured, and the _{blower operating time was measured by intermittent aeration so that the NO 2-} N / NH _4- N ratio approached 1.32. Was adjusted. No intermittent aeration was performed in the comparative example. When the treated water volume is 30 L / d and the capacity of the nitrite tank is 70 L, the target ratio of _{each raw water NH 4-} N concentration and the NO _2- N / NH _{4-N ratio at that time is 1.32.} Table 3 shows the calculated values of the required nitrification amount, and FIG. 3 shows the relationship between the blower operating rate (On / (On + Off)) in intermittent aeration and the nitrification amount.

From Table 3, it can be seen that the required nitrification amount changes significantly when the concentration of _{raw water NH 4-N fluctuates.} Further, from FIG. 3, it can be seen that there is a linear relationship between the operating time ratio due to intermittent aeration and the required nitrification amount, and the operating time ratio can be adjusted according to the fluctuation of the raw water concentration. Using Table 3, for example, when the raw water NH _4- N is 125 mg-N / L, the required nitrification amount can be calculated as 2.1 g-N / d, and the operating time ratio is set to about 0.10. Turns out to be appropriate. From this result, for example, the operation time ratio can be adjusted such that the on time is 2 minutes and the off time is 18 minutes. In addition, after the day after the timer is set, check the water quality in the nitrite tank, and if the NO _2- N / NH _4- N ratio is higher than the target ratio of 1.32, extend the off time. However, when the NO _2- N / NH _4- N ratio was lower than 1.32, control was performed such as shortening the off time. After performing such intermittent aeration for 80 days, continuous aeration was performed under the same conditions as during intermittent aeration except for intermittent aeration for comparison.

_{Fig. 4 shows the change in the NO 2-} N / NH _4- N ratio (-) in the nitrite tank when the nitrite tank was exposed to intermittent air for 80 days and then continuously exposed to air. The changes in the elapsed treatment time and the NO _2- N / NO _x- N ratio (%) in the nitrite tank are shown in FIG. 5, and the nitrogen load and nitrogen removal rate in the raw water and anaerobic ammonia oxidation tank are shown. The change in (nitrogen removal rate / nitrogen load) is shown in FIG.

As shown in FIG. 4, in the nitrite formation step, the NO _2- N / NH _4- N ratio during the intermittent air exposure period is approximately 1.2 to 1.5, which is close to the target ratio of 1.32. On the other hand, when continuously exposed to air, the NO _2- N / NH _4- N ratio exceeded 3, and it can be seen that almost all of the ammoniacal nitrogen in the nitrite tank was nitrified. As shown in FIG. 5, the NO _2- N / NO _x- N ratio was almost 100% regardless of intermittent aeration and continuous aeration, and stable nitrite formation was obtained in both cases. As shown in FIG. 6, in the anaerobic ammonia oxidation tank, the nitrogen removal rate (nitrogen removal rate / nitrogen load) during the intermittent aeration period is as good as 80 to 100%, and it is stable even if the inflow water amount is gradually increased. However, the removal rate decreased to 10% or less during the continuous aeration period.

1 ... Softening treatment tank 2 ... Subnitration tank 3 ... Sedimentation tank 4 ... Anaerobic ammonia oxidation tank 5 ... Sedimentation tank 6 ... Aerobic tank 7 ... Anaerobic tank 11 ... Water quality measuring means 12 ... Carbonate adding means 13 ... Sedimentation tank 14 ... Relay tank 15 ... BOD oxidation tank 21 ... Water quality measuring means 22 ... Air exposure / pH adjusting means 23 ... Flow rate adjusting means 24 ... Water quality measuring means 100 ... Control means

Claims (7)

A calcium removal step for removing calcium in the ammonia-containing nitrogen-containing wastewater containing calcium, and a nitrite treatment of a part of the ammoniacal nitrogen in the ammoniacal nitrogen-containing wastewater after the calcium removal step into nitrite nitrogen. A nitrite step and a nitrification step including an anaerobic ammonia oxidation step of anaerobic ammonia oxidation treatment of the treated water of the nitrite treatment using an anaerobic ammonia-oxidizing bacterium, and a treatment step of ammonia nitrogen-containing wastewater including the anaerobic ammonia oxidation step. In
A method for treating ammoniacal nitrogen-containing wastewater, which comprises adding a carbonate for removing calcium and a carbonate for supplementing inorganic carbon required in the nitrification step in the calcium removing step. The method for treating ammoniacal nitrogen-containing wastewater according to claim 1, which comprises adding caustic soda as a pH adjuster for the nitrite treatment in the nitrite step. The calcium removal step
Inorganic carbon required in the nitrite step based on the relationship between the calcium concentration, alkalinity, and ammonia nitrogen concentration in the ammonia nitrogen-containing wastewater and the target ammonia nitrogen concentration in the nitrite step. The method for treating ammoniacal nitrogen-containing wastewater according to claim 1 or 2, which comprises adding the above-mentioned carbonate for supplementing. The one according to any one of claims 1 to 3, wherein the nitrite treatment involves flowing a carrier on which ammonia-oxidizing bacteria are adhered and fixed in a nitrite tank for treating the ammoniacal nitrogen-containing wastewater. A method for treating ammoniacal nitrogen-containing wastewater. The ammoniacal nitrogen-containing wastewater according to any one of claims 1 to 4, further comprising the coexistence of suspended sludge in the nitrite tank for treating the ammoniacal nitrogen-containing wastewater. Processing method. The method for treating ammoniacal nitrogen-containing wastewater according to any one of claims 1 to 5, wherein the nitrite treatment comprises intermittent aeration in the nitrite tank for treating the ammoniacal nitrogen-containing wastewater. A softening treatment tank that softens calcium-containing ammoniacal nitrogen-containing wastewater to remove calcium,
A nitrite tank that nitrites a part of the ammoniacal nitrogen contained in the ammoniacal nitrogen-containing wastewater after the softening treatment into nitrite nitrogen.
An anaerobic ammonia oxidation tank in which the treated water for nitrite treatment is treated with anaerobic ammonia oxidation using anaerobic ammonia-oxidizing bacteria,
A carbonate adding means for adding carbonate necessary for the nitrite treatment and the anaerobic ammonia oxidation treatment to the softening treatment tank based on the calcium concentration and alkalinity in the ammoniacal nitrogen-containing wastewater is provided. Ammonia nitrogen-containing wastewater treatment equipment.

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