JP2003126886A - Biological denitrification method and device of the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a biological denitrification method capable of easily obtaining a high-quality treated water at a low cost and a device of the same. SOLUTION: In a method that a wastewater containing an ammoniacal nitrogen is biologically nitrified and denitrified, wherein there are provided the biological denitrification method and the device of the same that the wastewater is treated in a first denitrification process that the ammoniacal nitrogen, a nitrite nitrogen and/or a nitrate nitrogen in the wastewater are partially denitrified as nitrogen gas while the ammoniacal nitrogen is allowed to stay behind in the presence of a mycology of independent nutritious nitrifying bacteria and independent nutritious denitrifying bacteria under a microaerophilic condition and/or an intermittent aeration condition and in a second denitrification that the ammoniacal nitrogen, the nitrite nitrogen and/or the nitrate nitrogen in the effluent of the first denitrification process are denitrified as nitrogen gas in the presence of the mycology of the independent nutritious denitrifying bacteria capable of utilizing a bound oxygen.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a biological nitrogen removal method and apparatus for biologically purifying wastewater containing ammoniacal nitrogen.

[0002]

2. Description of the Related Art Ammoniacal nitrogen contained in sewage is one of the causative substances of eutrophication in rivers, lakes and oceans, and it is desired to be efficiently removed in the sewage treatment process. In general, ammoniacal nitrogen in wastewater is decomposed into nitrogen gas by a nitrification process and a denitrification process. Specifically, in the nitrification step, ammoniacal nitrogen is oxidized to nitrite nitrogen by an autotrophic bacterium, an ammonia-oxidizing bacterium under aerobic conditions, and the nitrite nitrogen is an autotrophic bacterium, a nitrite-oxidizing bacterium. Is oxidized to nitrate nitrogen. In the next denitrification step, these nitrite nitrogen and nitrate nitrogen are decomposed into nitrogen gas under anaerobic conditions by the denitrifying bacterium, which is a heterotrophic bacterium, while utilizing organic substances as electron donors.

In such a conventional biological nitrogen removal method, a large amount of oxygen is required in the nitrification step for oxidizing ammoniacal nitrogen to nitrite nitrogen and nitrate nitrogen, and denitrification which is a heterotrophic bacterium is required. In the denitrification process using nitrifying bacteria,
Since it is necessary to add a large amount of an organic substance such as methanol as an electron donor, the running cost is increased.

By the way, recently, under anaerobic conditions, ammonia nitrogen is used as an electron donor and nitrate nitrogen is used as an electron acceptor to react with each other to produce nitrogen gas. Nitrogen treatment technology is being developed.

For example, in Japanese Unexamined Patent Publication No. 8-192185, after the partial nitrification step of partially nitrifying wastewater containing ammoniacal nitrogen in a nitrification tank to leave a part of the ammoniacal nitrogen, the effluent of the partial nitrification step is Ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen are removed by reacting with the autotrophic microorganism group in the combined oxygen denitrification process. However, in such a method, there is a problem that the treatment is extremely unstable due to the following phenomenon, nitrogen removal is insufficient, and practicability is poor. That is, the nitrification reaction is generally set in a state in which almost no ammonia nitrogen remains, and DO and MLSS (sludge) can be used to make nitrite nitrogen or nitrate nitrogen while leaving ammonia in the partial nitrification process. It is necessary to adjust (concentration) with extremely high accuracy according to the raw water conditions. In the combined oxygen denitrification step, if the amount of ammonia nitrogen remains excessively, the amount of nitrite nitrogen and nitrate nitrogen is equal to or more than the equivalence ratio, and as a result, ammonia nitrogen remains. On the contrary, when the amount of ammoniacal nitrogen is small and the amounts of nitrite nitrogen and nitrate nitrogen exceed the equivalent ratio, nitrite nitrogen and nitrate nitrogen remain.

Further, in Japanese Patent Laid-Open No. 2000-104992,
Part of the wastewater is introduced into the nitrite tank, mixed with the biological sludge containing ammonia-oxidizing bacteria in the tank, and aerated from the air diffuser, and the ammonia-oxidizing bacteria oxidize the ammoniacal nitrogen to nitrite nitrogen. . The nitrite solution in the nitrite tank is introduced into the autotrophic denitrification tank, and at the same time, another part of the wastewater is introduced from the bypass wastewater channel and mixed with the biological sludge containing the autotrophic denitrifying bacteria in the tank. , A method of denitrifying under anaerobic conditions is disclosed. However, both in this method and in the nitrite tank, depending on the aeration time and pH conditions,
The reaction of ammonia nitrogen in sewage proceeds to nitrification,
As a result, denitrification by autotrophic denitrifying bacteria was often insufficient under anaerobic conditions, and the treatment was not stable and there was a problem in practicality.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to propose a method for removing biological nitrogen, which is low in cost and can easily obtain high treated water quality. Another object of the present invention is to provide a biological nitrogen removing apparatus that can easily obtain high quality of treated water at low cost.

[0008]

The present invention solves the above problems by a biological nitrogen removing method and apparatus having the following constitution. (1) In a method for biologically nitrifying and denitrifying wastewater containing ammoniacal nitrogen, the wastewater is treated under a slightly aerobic condition and / or
Alternatively, under intermittent aeration conditions, in the presence of an autotrophic nitrifying bacteria and an autotrophic denitrifying bacteria group, while leaving ammoniacal nitrogen, ammoniacal nitrogen and nitrite nitrogen and / or nitrate nitrogen are converted into nitrogen. A first nitrogen removal step of partially denitrifying as a gas, and an effluent of the first nitrogen removal step in the presence of an autotrophic denitrifying bacteria group capable of utilizing bound oxygen. A method for removing biological nitrogen, which comprises performing a second nitrogen removal step of denitrifying nitrogen and nitrite nitrogen and / or nitrate nitrogen as nitrogen gas.

(2) The method for removing biological nitrogen according to (1) above, wherein a microbial carrier and activated sludge are present in the first nitrogen removing step and the second nitrogen removing step. (3) In the first nitrogen removing step, the dissolved oxygen concentration is constantly set to 1
An oxygen-containing gas is aerated so as to be less than mg / liter, or intermittently aerated so that the dissolved oxygen concentration is 0.2 mg / liter or less at a time of 1 mg / liter or more. (1) or (2)
The method for removing biological nitrogen according to 1. (4) The soluble BOD is removed so that the BOD of the inflowing wastewater becomes 1/2 or less of the inflowing ammoniacal nitrogen, and the soluble BOD is removed. Biological nitrogen removal method.

(5) In a device for biologically nitrifying and denitrifying sewage containing ammoniacal nitrogen, the sewage is subjected to autoaerobic nitrifying bacteria and autotrophs under microaerobic conditions and / or intermittent aeration conditions. A first nitrogen removing device for partially denitrifying ammoniacal nitrogen and nitrite nitrogen and / or nitrate nitrogen as nitrogen gas while leaving the ammoniacal nitrogen in the presence of a group of denitrifying bacteria; 1 The effluent of the nitrogen removal device is used in the presence of an autotrophic denitrifying bacteria group capable of utilizing bound oxygen, with ammonia nitrogen and nitrite nitrogen and / or nitrate nitrogen in the effluent as nitrogen gas. A second nitrogen removal device for denitrification, a solid-liquid separation device for separating the effluent of the second nitrogen removal device into treated water and settling sludge, and a part of the settling sludge as return sludge to the first nitrogen removal device It has a pipe for returning Biological nitrogen removal system to.

The following are preferred embodiments of the present invention. (6) In the first nitrogen removal step, the autotrophic denitrifying bacteria group is prioritized by placing it under conditions of pH 7.5 or higher, or the autotrophic denitrifying bacteria that have been subjected to increased culture under the conditions. The above (1) to characterized in that a group is added.
(4) The biological nitrogen removal method as described above. (7) In the first nitrogen removing step and the second nitrogen removing step, a plurality of reaction tanks are provided, (1)
~ The biological nitrogen removing method according to any one of (4) and (6). (8) The biological nitrogen removing device according to (5), wherein a microbial carrier and activated sludge are allowed to coexist in the first nitrogen removing device and the second nitrogen removing device. (9) The first nitrogen removing device keeps the dissolved oxygen concentration at 1
An air diffuser that aerates oxygen-containing gas to less than mg / liter, or an aerator that intermittently aerates so that the dissolved oxygen concentration is 0.2 mg / liter or less when there is 1 mg / liter or more. The biological nitrogen removing apparatus according to (5) or (8) above, which further comprises: (10) The first nitrogen removing device and the second nitrogen removing device are provided with a plurality of reaction tanks, and the above (5) and (8) to (9) are included. Biological nitrogen removal equipment.

In the present invention, "denitrification" means denitrification by autotrophic denitrifying bacteria unless otherwise specified. The sewage to be treated in the present invention is sewage containing ammoniacal nitrogen and may contain organic matter, nitrite nitrogen, and other impurities. Sewage containing organic nitrogen compounds,
Although it may be directly used for the present invention, it may be used for the present invention after converting an organic nitrogen compound into ammonia nitrogen by anaerobic treatment or aerobic treatment. Also, BOD
Although the concentration of the present invention is not limited, in order to increase the abundance of the autotrophic denitrifying bacteria group, only BOD was biologically treated in advance to reduce the BOD to ½ or less with respect to ammoniacal nitrogen. It is effective to use it. Examples of wastewater to be treated in the present invention include human waste, sewage, anaerobic digester desorption liquid, leachate leachate, fertilizer factory wastewater, and the like.

The biological nitrogen removal of the present invention is carried out in the presence of autotrophic nitrifying bacteria and autotrophic denitrifying bacteria under aerobic conditions and / or intermittent aeration of sewage containing ammoniacal nitrogen. First, a first nitrogen removing step of partially denitrifying the ammonia nitrogen and the nitrite nitrogen and / or nitrate nitrogen as nitrogen gas while leaving the ammonia nitrogen remaining, and the outflow of the first nitrogen removing step. A second nitrogen that denitrifies the liquid as nitrogen gas using ammonia nitrogen and nitrite nitrogen and / or nitrate nitrogen in the effluent in the presence of an autotrophic denitrifying bacteria group capable of utilizing bound oxygen It is a biological treatment method characterized by treatment in a removal step.

In the second nitrogen removing step, about 1/3 to 1/2 amount of the ammoniacal nitrogen in the wastewater is oxidized to nitrite nitrogen or nitrate nitrogen, and at the same time, the nitrous acid produced by the remaining ammoniacal nitrogen. Nitrogen or nitrate nitrogen is denitrified. The reaction formulas are as shown in formulas (1) to (4). 1) Generation of nitrite nitrogen NH ₄ ⁺ + 3 / 2O ₂ → NO ₂ ⁻ + 2H ⁺ + H ₂ O (1) 2) Generation of nitrate nitrogen NO ₂ ⁻ + 1 / 2O ₂ → NO ₃ ^- ............ (2) 3) denitrification with ammonia nitrogen and autotrophic denitrification bacteria group using nitrous acid bound oxygen ^{_{NH 4 + + NO 2 - →}} N _{2 + 2H 2 O ·········· (3} ) 4) denitrified by ammonia nitrogen and nitrate bound oxygen autotrophic denitrifying bacteria group using the reaction ^{_{NH 4 + + 2 / 3NO 3}} - → 5 / 6N ₂ + 2H ₂ O ... (4)

In the first nitrogen removing step of the present invention, the reactions (1) and (3) are predominantly the mainstream, and the reactions (2) and (4) are extremely unlikely to occur. Furthermore, the trigger for the reactions of (1) and (3) is that the first nitrogen removal step generally has about 1
The presence of more than 1 mg / l, preferably 3 mg / l of free ammonia. In order to allow free ammonia to exist, it is preferable to adjust the water temperature and / or pH depending on the inflowing ammoniacal nitrogen.
Equations (5) and (6) show the standard calculation formulas. [NH3-N] = {[NH4 ⁺ -N] [10 ^pH ]} / {(Kb / Kw) +10 ^pH } (5) (Kb / Kw) = exp (6334 / (273 + T)) (6) Here, [NH ₃ -N] is the free ammonia concentration (mg
-N / l), a [NH ₄ ⁺ -N] of ammonia nitrogen concentration (mg-N / L), T is temperature (° C.).

In the biological treatment, it is general to stabilize the treatment by dilution. Even when a few thousand mg / liter of ammoniacal nitrogen is introduced, the reaction tank contains at most several hundred mg / liter of ammoniacal nitrogen. It is a concentration.
Therefore, it is preferable to set the water temperature and / or the pH to be slightly higher than the value obtained by the equation (5). Furthermore, p
The reaction in the first nitrogen removal step is also promoted by adding the above-mentioned autotrophic denitrifying bacteria group, which has been subjected to increased culture under conditions of H7.5 or higher.

According to the results of long-term experiments conducted by the present inventors, the water temperature is 10 ° C to 80 ° C, preferably 20 ° C to 60 ° C, and the pH is 7.5 or more, preferably 7.5 to 9.5. By setting it, the amount of free ammonia was about 1 mg / liter or more, and the reactions (1) and (3) predominantly proceeded in the first nitrogen removal step. At pH 7 or less, free (gaseous) ammonia is 1.0 mg / liter or less, but at 7.5 or more, it is 3 mg / liter or more, and the growth of nitrite-oxidizing bacteria that convert nitrite nitrogen to nitrate nitrogen is increased. It is largely suppressed, and most of the ammoniacal nitrogen is terminated by nitrite nitrogen.

Further, in this first nitrogen removing step,
Long-term experiments have revealed that DO (dissolved oxygen) concentration in the process is an important operating condition. That is,
As shown in the formulas (1) and (2), do not convert all of the ammoniacal nitrogen into nitrite nitrogen as well as nitrate nitrogen, and restrict the supply of DO for denitrification of the converted nitrite nitrogen. It has been revealed that this is an important factor for stabilizing the treatment. Therefore, this first
In the nitrogen removal step, the oxygen-containing gas is aerated so that the dissolved oxygen concentration is always less than 1 mg / liter, and the condition is slightly aerobic, or when the dissolved oxygen concentration is 1 mg / liter or more, the dissolved oxygen concentration is 0.2 mg. It is important to perform intermittent aeration so that there is a time zone of 1 / liter or less, preferably 0 mg / liter. In case of intermittent aeration, DO concentration is 0.2m
It is preferable to take the time of g / liter or less longer than the time of 0.2 mg / liter or more. The DO supply method may be a combination of slightly aerobic and intermittent aeration.

Further, in the present invention, the activated nitrogen sludge (floating microorganisms) alone can grow the autotrophic denitrifying bacteria group and the autotrophic nitrifying bacteria, and the reaction in the first nitrogen removing step is possible, but the first nitrogen is removed. When a microbial carrier is added to the removal step, biofilms of autotrophic denitrifying bacteria and autotrophic nitrifying bacteria are formed on this surface, and the reaction is promoted. Since the numbers of bacteria on the activated sludge and the surface of the microbial carrier are slightly different, the mutual effects exert each other, so that not only the reaction time in the first nitrogen removal step is shortened, but also ammonia nitrogen in the wastewater can be supported. Processing is extremely stable. Further, by making the inside of the first nitrogen removal step multistage, it is possible to select an appropriate pH and sludge concentration according to the ammonia nitrogen concentration in the wastewater, and a more stable first nitrogen removal treatment becomes possible. Specifically, it is possible to set a lower pH on the inflow end side of the wastewater, lower the MLSS to increase the nitrogen load, and set a higher pH on the outflow side of the process to raise the MLSS.

In the second nitrogen removing step, an autotrophic denitrifying bacterium capable of utilizing the combined oxygen by combining the ammoniacal nitrogen and the nitrite nitrogen and / or nitrate nitrogen in the effluent of the first nitrogen removing step of the preceding stage. This is a step of denitrifying as nitrogen gas in the presence of the group. In this step, under anaerobic conditions, the DO concentration is preferably 0.2 mg / liter or less, whereby the denitrification reaction proceeds efficiently and the inflowing ammoniacal nitrogen is almost completely denitrified. In the present invention, since the DO is controlled in the first nitrogen removing step in the former stage as described above, it is possible to easily set the anaerobic condition without using a special method. In the first nitrogen removing step, B
The OD is 50 mg / liter or less, which is an environment suitable for the growth of autotrophic denitrifying bacteria. Since the alkalinity increases in the denitrification process, it is possible to circulate this alkalinity in the first nitrogen removing step in the preceding stage.

Further, by adjusting the internal sludge in the second nitrogen removing step to a plurality of stages and adjusting the returned sludge, the same as in the first nitrogen removing step, the concentration of ammonia nitrogen and nitrite nitrogen / nitrate nitrogen in the inflow water is adjusted. You can select the appropriate pH and sludge concentration.
A more stable denitrification process becomes possible. When a microbial carrier is added to the second nitrogen removal step, biofilms of autotrophic denitrifying bacteria and autotrophic nitrifying bacteria are formed on this surface, and the reaction is promoted. Since the numbers of bacteria on the activated sludge and the surface of the microbial carrier are slightly different, in order to exert mutual effects,
Not only the reaction time of this process is shortened, but also fluctuation of ammonia nitrogen in the wastewater can be dealt with and the treatment is extremely stable.

The first nitrogen removing device and the second nitrogen removing device 2 constituting the biological nitrogen removing device of the present invention are not limited to the above-mentioned activated sludge type, activated sludge + microbial carrier addition type, and biological filtration type. Any of (floating filter media and immersion filter media) can be used. Further, by making the insides of the first nitrogen removal device and the second nitrogen removal device multi-stage, it is possible to select an appropriate pH and sludge concentration according to the ammonia nitrogen concentration in the wastewater, and a more stable denitrification treatment can be performed. It will be possible. As the solid-liquid separation device, not only a sedimentation tank but also a hollow fiber membrane separation device and a dynamic filtration device can be adopted.

The first nitrogen removing device suppresses the activity of the ammonia-oxidizing bacteria to be high and the activity of the nitrite-oxidizing bacteria to be low, and at the same time, the autotrophic denitrifying bacteria group uses ammonia nitrogen to deoxidize the bacteria. Be suffocated. In addition, it is a device that does not convert all ammoniacal nitrogen into nitrite nitrogen as well as nitrate nitrogen. That is, the water temperature is 10 ° C-
The temperature is 80 ° C, preferably 20 ° C to 60 ° C, and the pH is 7.
It is set to 5-10.5, preferably 7.5-9.5.
Furthermore, the oxygen-containing gas is aerated so that the dissolved oxygen concentration is constantly less than 1 mg / liter, and the condition is slightly aerobic, or when the dissolved oxygen concentration is 1 mg / liter or more, the dissolved oxygen concentration is 0.2 mg / liter or less, Preferably 0 mg /
It is important to perform intermittent aeration so that there are liter hours. In the case of intermittent aeration, it is preferable to take the time when the DO concentration is 0.2 mg / liter or less longer than the time when the DO concentration is 0.2 mg / liter or more. Nitrogen load is 3kg-N / m ³
・ Control so that it is less than or equal to day.

The second nitrogen removing device which constitutes the biological nitrogen removing device of the present invention removes ammoniacal nitrogen and nitrite nitrogen and / or nitrate nitrogen in the effluent of the first nitrogen removing step of the preceding stage. It is denitrified as nitrogen gas in the presence of a group of autotrophic denitrifying bacteria that can utilize bound oxygen. With this device,
Under anaerobic conditions, the denitrification reaction proceeds efficiently, and the inflowing ammoniacal nitrogen is almost completely denitrified. That is, the water temperature is 10 ° C to 80 ° C, preferably 20 ° C to 60 ° C, and the pH is 7.5 to 10.5, preferably 7.5 to 9.
Set to 5. The nitrogen load is controlled so as to be 1 kg-N / m ³ · day or less.

[0025]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail with reference to the drawings, but the present invention is not limited to these drawings. In all the drawings for explaining the embodiments and examples, constituent elements having the same function are designated by the same reference numerals.

FIG. 1 shows an example of a flow sheet according to the processing method of the present invention. The structure of the processing apparatus of the present invention comprises a first nitrogen removing apparatus 1, a second nitrogen removing apparatus 2, and a solid-liquid separation apparatus 3. Hereinafter, sewage containing ammoniacal nitrogen is referred to as raw water. The entire amount of raw water 4 is supplied to the first nitrogen removing device 1.
At that time, the first nitrogen removing device 1 is also supplied with the return sludge 6 which has been subjected to solid-liquid separation by the solid-liquid separating device 3. The amount of raw water input is controlled so that the nitrogen load is 3 kg-N / m ³ · d or less. The first nitrogen removing device 1 uses the air diffuser 10, and the air 9 is intermittently supplied. The air supply timing is 0/2 m when DO is 0.2 mg / liter or less.
It is longer than the time of g / liter or more, and 0
It is controlled so that it has a time of mg / liter. Further, the pH inside the apparatus is adjusted to 7.5 to 10.5, preferably 7.5 to 9 by adding an alkali using the pH control apparatus 11.
It is controlled within the range of 5. In the first nitrogen removing apparatus 1, 1/3 to 1/2 of the ammoniacal nitrogen in the raw water 4 is oxidized to nitrite nitrogen and some is oxidized to nitrate nitrogen, and in parallel with this reaction, the ammoniacal nitrogen in the raw water 4 is At this, nitrite nitrogen and nitrate nitrogen react and denitrify as nitrogen gas.

The entire amount of the first nitrogen removing device effluent 7 flows into the second nitrogen removing device 2, and the remaining ammoniacal nitrogen reacts with nitrite nitrogen and nitrate nitrogen to become nitrogen gas, and the gas is discharged. It is discharged from the pipe 14 to the outside of the device. The nitrogen load is controlled to be 1 kg-N / m ³ · d or less. Also in the second nitrogen removing device 2, the pH in the device is adjusted to 7.5 to 10.5, preferably 7.5 by using the pH control device 12.
It is controlled to 9.5. Since the first nitrogen removing device 1 controls the pH and the second nitrogen removing device 2 has a small pH fluctuation, the pH control in the second nitrogen removing device 2 can be omitted. The second nitrogen removal device effluent 8 is introduced into the solid-liquid separation device 3 and separated into sludge and treated water 5. The separated sludge is returned to the first nitrogen removing device 1 as return sludge 6. The treated water 5 is discharged outside the system. In addition, a part of the sludge that has been solid-liquid separated is discharged outside the system as excess sludge 13.

In FIG. 1, the first nitrogen removing device 1 and the second nitrogen removing device 2 show an addition system of activated sludge containing a carrier 17 and a microorganism carrier. Any of the sludge system and the biofilm filtration system (floating filter medium or immersion filter medium) can be used. Further, by making the insides of the first nitrogen removing device 1 and the second nitrogen removing device 2 multi-staged, an appropriate pH and sludge concentration can be selected according to the ammonia nitrogen concentration in the wastewater, and a more stable denitrification process can be performed. Is possible. As the solid-liquid separation device, not only a sedimentation tank but also a hollow fiber membrane separation device and a dynamic filtration device can be adopted.

[0029]

The present invention will be described in more detail below with reference to examples, but the present invention is not limited to these examples.

Example 1 In this example, waste leachate was treated according to the flow shown in FIG. The capacity of each device is as follows: first nitrogen removing device 1; 10 liters, second nitrogen removing device 2; 10
It consists of liters. First, Table 1 shows the water quality of the waste leachate, which is Raw Water 4. In this case, BOD is 20 mg / liter, ammoniacal nitrogen is 390 mg / liter,
BOD was less than 1/2 of ammoniacal nitrogen.
In each table, ammoniacal nitrogen is represented by NH ₄ —N, nitrite nitrogen is represented by NO ₂ —N, and nitrate nitrogen is N 2.
It is represented by O ₃ -N. The same applies to FIGS.

[0031]

[Table 1]

Raw water 4 is supplied to the first nitrogen removing device 1,
Nitrogen was removed. Table 2 shows the operating conditions of the first nitrogen removing apparatus 1. 5 mm x 5 mm x for the first nitrogen removing device 1
A 5 mm sponge carrier was added at 10 v / v% of the device volume, and continuous stirring was performed using a stirrer. DO control was performed by aeration for 1 minute and intermittent aeration for 5 minutes. pH control is p
When using H controller and it becomes higher than 8.7 H ₂ S
This was done by adding NaOH when O ₄ , below 8.5. The consumption of NaOH is 1.8-2.5g
/ D, H ₂ SO ₄ was hardly consumed.

[0033]

[Table 2]

The entire amount of the first nitrogen removing device effluent 7 was introduced into the second nitrogen removing device 2. Table 3 shows the operating conditions of the second nitrogen removing device 2. 5 mm x 5 m for the second nitrogen removal device
A m × 5 mm sponge carrier was added at 10 v / v% of the apparatus volume, and continuous stirring was performed using a stirrer in a sealed state. Aeration with air was not performed, DO was always 0.2 mg / liter or less, pH was 8.6, and pH control was unnecessary.

[0035]

[Table 3]

Table 4 shows the water quality at the inlet and outlet of each device. In the first nitrogen removing device 1, the amount of ammonia nitrogen is about 90
%, And increases in nitrite nitrogen and nitrate nitrogen were observed. In the second nitrogen removing device 2, almost 100% of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen are removed,
The amount of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the treated water was 1 mg / liter or less, and the nitrogen was almost completely removed.

[0037]

[Table 4]

Example 2 In the same flow as in Example 1, the same treatment of raw water 1 as in Example 1 was performed without adding a carrier to the first nitrogen removing device 1 and the second nitrogen removing device 2. The operating conditions were the same as in Example 1 except that no carrier was added. Table 5 shows the water quality at the inlet and outlet of each device. In the first nitrogen removing apparatus 1, about 90% of ammonia nitrogen was removed, and an increase in nitrite nitrogen and nitrate nitrogen was observed. The nitrate nitrogen concentration was higher than that in Example 1. In the second nitrogen removing device 2, almost 100% of ammonia nitrogen and nitrite nitrogen are removed, about 25% of nitrate nitrogen is also removed, and the amount of ammonia nitrogen and nitrite nitrogen of the treated water is 1 mg / liter or less. But
The nitrate nitrogen was 24 mg / liter, which was higher than that in Example 1.

[0039]

[Table 5]

Example 3 In this example, human waste treatment was carried out according to the flow shown in FIG. BOD by catalytic oxidizer 19
Was reduced prior to biological nitrogen removal. The capacity of each device is as follows: catalytic oxidizer 19; 10 liters, first nitrogen remover 1; 10 liters, second nitrogen remover 2; 10
It consists of liters. First, Table 6 shows the water quality of diluted raw sewage, which is raw water 4. In this case, BOD is 860 mg / liter, ammoniacal nitrogen is 385 mg / liter,
BOD was about 2.2 times that of ammoniacal nitrogen.

[0041]

[Table 6]

The raw water 4 is also supplied to the catalytic oxidizer 19 B
OD removal was performed. The operating conditions of the catalytic oxidation device 19 are
Shown in the table. 50 × 50 × 80 mm for the catalytic oxidizer 19
The honeycomb-structured filter medium 21 was immersed and continuously aerated.

[0043]

[Table 7]

The operating conditions of the first nitrogen removing device 1 and the second nitrogen removing device 2 were the same as in Example 1. Table 8 shows the water quality at the inlet and outlet of each device. The catalytic oxidizer 19 removed about 80% of BOD. Contact oxidizer effluent 20
Is BOD 180 mg / liter, ammoniacal nitrogen 3
It was 65 mg / liter, and the BOD was about 1/2 of that of ammoniacal nitrogen. In the first nitrogen removing apparatus 1, the amount of ammonia nitrogen was reduced by about 90%, and the increase of nitrite nitrogen and nitrate nitrogen was recognized. In the second nitrogen removing apparatus 2, almost 100% of ammonia nitrogen and nitrite nitrogen were removed, and about 40% of nitrate nitrogen was removed. By providing the catalytic oxidation device 19 in front of the first nitrogen removal device 1 to remove the BOD, the denitrification treatment by the autotrophic denitrifying bacteria in the first nitrogen removal device 1 is preferentially advanced. It was

[0045]

[Table 8]

Comparative Example 1 Biological nitrogen removal was performed by injecting methanol, which is a conventional nitrification denitrification method. The flow is shown in FIG. The size and arrangement of the tank were the same as in Example 1, the first nitrogen removing device 1 was continuously aerated, and a normal nitrification tank was used without pH control, and the second nitrogen removing device 2 was a denitrification tank. I drove. First
Table 9 shows the operating conditions of the nitrogen removing apparatus 1. A 5 mm × 5 mm × 5 mm sponge carrier was charged into the first nitrogen removing device at 10 v / v% of the device volume, and continuous stirring was performed using a stirrer. The second nitrogen removing device 2 was continuously stirred and the injection amount of methanol was set to 0 g / d.

[0047]

[Table 9]

Table 10 shows the water quality at the inlet and outlet of each device. In the first nitrogen removing apparatus 1, the amount of ammonia nitrogen is 10
0% nitrification, almost converted to nitrate nitrogen. Also, p
Since H control was not performed, the value decreased to 6.5. Second
Nitrate nitrogen was hardly removed by the nitrogen removing device 2. In addition, sludge floated due to denitrification in the sedimentation tank, making sludge management difficult. The nitrogen removal rate of both the first nitrogen removal apparatus 1 and the second nitrogen removal apparatus 2 was 21%, which resulted in a very low removal rate as compared with Examples 1 and 2.

[0049]

[Table 10]

Comparative Example 2 As in Comparative Example 1, biological nitrogen removal by injecting methanol, which is a conventional nitrification denitrification method, was performed. The flow is shown in FIG. The size and arrangement of the tank were the same as in Example 1, the first nitrogen removing device 1 was continuously aerated, and operated as an ordinary nitrification tank without controlling the pH, and the second nitrogen removing device 2 was used.
For the denitrification tank, 8.0 g / d of methanol was added and continuously stirred to make a denitrification tank. Since there was residual methanol, a 3 liter re-aeration tank was installed in front of the sedimentation tank for operation.

Table 11 shows the water quality at the inlet and outlet of each device. Ammoniacal nitrogen was 100% nitrified and almost converted to nitrate nitrogen. In addition, the pH was lowered to 6.5 because the pH was not controlled. In the second nitrogen removing device 2, denitrification proceeded by adding methanol, and nitrate nitrogen was removed by 90%. The nitrogen removal rate of both the first nitrogen removal device 1 and the second nitrogen removal device 2 is about 90%, and in the case of the conventional nitrification denitrification method, methanol was added to the amount of nitrogen of 3.4.
Despite the double addition of 8.0 g / d, the quality of the treated water was worse than that of Example 1.

[0052]

[Table 11]

Confirmation Experiment 1 First nitrogen removing apparatus 1 and second nitrogen removing apparatus 2 of Example 1
In order to confirm that the reduction of ammonia nitrogen and nitrite nitrogen by autotrophic denitrifying bacteria has occurred, denitrification with ammonia nitrogen and nitrite nitrogen was performed using activated sludge mixture and carrier. Batch processing was performed. As raw water for batch treatment, NaNO ₂ and NaNO ₃ were added to the leachate used in the continuous experiment so that nitrite nitrogen and nitrate nitrogen were 400 mg / liter. BOD of raw water is 1
It was 0 mg / liter or less.

(1) In the case of activated sludge alone The nitrogen removal rate of the activated sludge was measured by adding 60 mg / min of the above-mentioned raw water to the activated sludge mixed solution with ammoniacal nitrogen and nitrite nitrogen.
Liter, nitrate nitrogen of 50 mg / liter, BOD of 5 mg / liter or less, and MLSS of 3000 mg / liter were placed in a closed container and continuously stirred to react. DO in the tank is always 0 mg / liter, pH is 8.5-
It was 8.6. The behaviors of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the case of the first nitrogen removing device 1 are shown in FIG. After treatment for 10 hours, the ammonia nitrogen is almost 100
% And nitrite nitrogen were reduced by 83%. The removal rate of ammoniacal nitrogen obtained from this result was 2.0 mg-N /
gMLSS / h, removal rate of nitrite nitrogen is 1.7 mg
It was -N / g-MLSS / h. Nitrate nitrogen is 17%
The rate of removal of nitrate nitrogen is 0.3mg-N
/ G-MLSS / h. The removal rate of nitrate nitrogen was lower than that of ammonia nitrogen and nitrite nitrogen.

(2) When the carrier alone is used: The removal rate of the carrier is measured by mixing the carrier, treated water and the above-mentioned raw water, and the carrier is 20 v / v% and the amount of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen is 60 mg / Liter, BOD1
The mixture was placed in a closed container so that the concentration became 0 mg / liter, and the reaction was carried out by continuously stirring. DO in the tank was always 0.2 mg / liter or less, and pH was 8.5 to 8.7. The behavior of ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen in the case of the first nitrogen removing apparatus 1 is shown in FIG. After treatment for 7.5 hours, the amount of ammonia nitrogen was reduced by almost 100% and the amount of nitrite nitrogen was reduced by 86%. The removal rate of ammoniacal nitrogen determined from these results was 36 mg-N / liter-carrier.h, and the removal rate of nitrite nitrogen was 32 mg-N / liter-carrier.h. Nitrate nitrogen was reduced by 14%, and the removal rate of nitrate nitrogen was 5.3 mg-N / liter-carrier-h. The removal rate of nitrate nitrogen was lower than that of ammonia nitrogen and nitrite nitrogen. The results of the first nitrogen removing device 1 and the second nitrogen removing device 2 were almost the same. From the above results,
In the first and second nitrogen removing devices 2, the presence of denitrifying bacteria capable of denitrifying nitrite nitrogen with ammonia nitrogen was recognized in both the carrier and the activated sludge.

Confirmation Experiment 2 The same confirmation was performed for the first nitrogen removing apparatus 1 and the second nitrogen removing apparatus 2 of Comparative Example 1. (1) In the case of activated sludge alone FIG. 6 shows the behavior of ammoniacal nitrogen, nitrite nitrogen, and nitrate nitrogen in the case of the first nitrogen removing device 1. After the treatment for 10 hours, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen were hardly reduced. The removal rate obtained from these results was 0.07 mg-N / g-MLS of ammonia nitrogen.
S / h, nitrite nitrogen 0.07 mg-N / g-MLS
S / h, nitrate nitrogen 0.03mg-N / g-MLSS
Was / h.

(2) When the carrier is used alone The behavior of ammoniacal nitrogen, nitrite nitrogen, and nitrate nitrogen in the case of the first nitrogen removing device 1 is shown in FIG. After the treatment for 10 hours, ammonia nitrogen, nitrite nitrogen, and nitrate nitrogen were hardly reduced. The removal rate obtained from these results was as follows: ammoniacal nitrogen 0.4 mg-N / liter-carrier-h, nitrite nitrogen 0.4 mg-N / liter-carrier-h, nitrate nitrogen 0.2 mg-N / liter. -Carrier h. The results of the first nitrogen removing device 1 and the second nitrogen removing device 2 were almost the same. From the above, the first of Comparative Example 1
In the nitrogen removing device 1 and the second nitrogen removing device 2, a carrier,
The presence of denitrifying bacteria capable of denitrifying nitrite nitrogen with ammoniacal nitrogen in activated sludge was virtually nonexistent.

[0058]

According to the present invention, in the treatment of wastewater containing ammoniacal nitrogen, the wastewater is biologically removed by the first nitrogen removing device and the second nitrogen removing device whose DO and pH are controlled. By removing nitrogen, the required oxygen amount can be reduced as compared with the conventional method, and nitrogen can be denitrified to nitrogen gas without using an electron donor such as methanol. Be peeled off. Furthermore, the effect of accelerating the reaction between nitrite nitrogen and ammonia nitrogen while at the same time preferentially generating nitrite nitrogen is recognized, and nitrogen can be reliably removed by easy control.

[Brief description of drawings]

FIG. 1 is a flow chart showing a biological nitrogen removing apparatus of the present invention.

FIG. 2 is a flow chart showing a biological nitrogen removing device provided with the catalytic oxidation device of the present invention in the preceding stage.

FIG. 3 is a flow chart of a biological nitrogen removal apparatus by adding methanol, which is a conventional nitrification denitrification method.

4 is a batch test result of activated sludge in Example 1. FIG.

5 is a batch test result of the carrier in Example 1. FIG.

6 is a batch test result of activated sludge in Comparative Example 1. FIG.

7 is a batch test result of the carrier in Comparative Example 1. FIG.

[Explanation of symbols]

1st nitrogen removal device 2 Second nitrogen removal device 3 Solid-liquid separator 4 Raw water 5 treated water 6 Return sludge 7 First nitrogen removal device effluent 8 Second nitrogen removal device effluent 9 air 10 Air diffuser 11, 12 pH controller 13 Surplus sludge 14 gas exhaust pipe 15, 16 Stirrer 17 Carrier 18 Methanol addition device 19 Contact oxidizer 20 Outflow of catalytic oxidation equipment 21 Honeycomb structure filter media

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI Theme Coat (reference) C02F 3/08 C02F 3/08 Z 3/12 3/12 SV (72) Inventor Katsura Susumu Tokyo 11-1 Haneda Asahi-cho, Ota-ku, Ebara Corporation (72) Inventor Akira Yamaguchi 11-11 Haneda-Asahi-cho, Ota-ku, Tokyo (72) Inventor, Katsuyuki Kataoka Asahi Haneda, Ota-ku, Tokyo 11th Town No. 1 in Ebara Manufacturing Co., Ltd. (reference) 4D003 AA01 AA05 AA12 AB02 BA02 BA03 BA04 CA02 CA03 CA07 EA19 FA02 FA06 4D006 GA02 KA01 KB22 KB25 PA02 PB08 PC64 4D028 AB00 BB06 BC17 BC18 BD06 BD11 BD16 CC07 BD07 CA040 CA07 CA07 CA07 CA07 BB02 BB12 BB22 BB24 BB42 BB52 BB54 BB82 BB91

Claims (5)

[Claims] 1. A method for biologically nitrifying and denitrifying sewage containing ammoniacal nitrogen, comprising: treating the sewage under microaerobic conditions and / or intermittent aeration conditions with autotrophic nitrifying bacteria and autotrophic denitrification. In the presence of nitrogenous bacteria, ammoniacal nitrogen and nitrite nitrogen and /
Alternatively, in the presence of a group of autotrophic denitrifying bacteria capable of utilizing bound oxygen, a first nitrogen removing step of partially denitrifying nitrate nitrogen as nitrogen gas and an effluent of the first nitrogen removing step,
A method for removing biological nitrogen, which comprises performing a second nitrogen removing step of denitrifying ammoniacal nitrogen and nitrite nitrogen and / or nitrate nitrogen in the effluent as nitrogen gas. 2. The biological nitrogen removing method according to claim 1, wherein a microbial carrier and activated sludge are present in the first nitrogen removing step and the second nitrogen removing step. 3. In the first nitrogen removing step, the oxygen-containing gas is aerated so that the dissolved oxygen concentration is always less than 1 mg / liter, or when the dissolved oxygen concentration is 1 mg / liter or more, the dissolved oxygen concentration is 0.2 mg / liter. The method for biological nitrogen removal according to claim 1 or 2, wherein intermittent aeration is performed so that there is a time zone of liters or less. 4. The soluble BOD is removed so that the BOD of the inflowing wastewater becomes 1/2 or less with respect to the inflowing ammoniacal nitrogen, and the soluble BOD is removed. Biological nitrogen removal method. 5. An apparatus for biologically nitrifying and denitrifying sewage containing ammoniacal nitrogen, wherein the sewage is treated under microaerobic conditions and / or intermittent aeration conditions. Partial denitrification of ammonia nitrogen and nitrite nitrogen and / or nitrate nitrogen as nitrogen gas while leaving ammonia nitrogen in the presence of nitrogen bacteria group 1
The nitrogen removing device and the effluent of the first nitrogen removing device are used in the presence of an autotrophic denitrifying bacteria group capable of utilizing bound oxygen, and ammonia nitrogen and nitrite nitrogen and / or nitric acid in the effluent are provided. Nitrogen removal device for denitrifying organic nitrogen as nitrogen gas, a solid-liquid separation device for separating the effluent of the second nitrogen removal device into treated water and settling sludge, and a part of the settling sludge returning sludge And a pipe for returning it to the first nitrogen removing device as a biological nitrogen removing device.