JP2006272161A - Method and apparatus for treating nitrate nitrogen-containing waste water - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To secure denitrification performance for a long time by preventing fixing of a material by fluidizing a denitrification material by an economic method of reutilizing to circulate nitrogen gas generated by a denitrification reaction. <P>SOLUTION: In a method for treating nitrate nitrogen in waste water by bringing the denitrification material containing sulfur and a carbonate of an alkaline earth metal into contact with the waste water containing the nitrate nitrogen, gas comprising nitrogen generated by the denitrification reaction as a main component is circulated by a compressor 10 to make a gas-liquid mixed fluid to distribute and circulate continuously or intermittently at one to twice the rate of a fluidizing start rate of a packed bed through a bed packed with the denitrification material 7 by a pump 2 for circulating the waste water. It is preferable that a volume ratio (gas/waste water) of the gas of a mixed fluid to the waste water is in the range of 0.05 to 0.8. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a denitrification apparatus and a treatment method capable of maintaining denitrification activity when biochemically removing nitrate nitrogen from wastewater containing nitrate nitrogen using a denitrification material.

  Wastewater treatment using a denitrification material containing sulfur and an alkaline earth metal carbonate has been performed by introducing a wastewater to be treated containing a dilute nitrate ion solution into a tank filled with the denitrification material. As a charging method, there were a pouring method and a batch method. The pouring method is a method in which a denitrification material is filled in a container, and the waste water to be treated is continuously poured into the container and treated while overflowing. In this system, when the liquid volume and nitrate ion concentration were low, the amount of nitrogen produced by the reaction was small and continuous operation was possible. The batch system is a system in which a fixed amount of liquid is intermittently stored in a container and the processed liquid is discharged when the processing is completed. In both methods, the denitrification material and the wastewater to be treated come into contact with each other, so that bacteria present in the denitrification material or on the surface cause a denitrification reaction to perform the treatment. When this system is applied to wastewater treatment with high concentration and large capacity, it is necessary to effectively remove the generated nitrogen.

  Moreover, gypsum is likely to precipitate in wastewater containing a large amount of calcium ions, such as wastewater to which slaked lime is added for the purpose of neutralizing wastewater or treating heavy metals. The effect of the bio-coating on the gypsum and denitrification material that is generated causes the denitrification material to stick locally, preventing effective contact between the denitrification material and the drainage, and the nitrogen gas stays locally, There was a problem of significantly reducing the performance of the nitrogen material. Various methods such as a method of applying mechanical vibration to the denitrification material, a method of applying ultrasonic vibration, a method of circulating water, and a method of extracting gas by reducing the pressure of the apparatus have been tried as methods for extracting nitrogen gas. (See Patent Document 1).

  The method of applying mechanical vibration to the denitrification material is, for example, a method in which the device is struck with a hammer from the outside, and the device is vibrated to give an impact to the denitrification material in the device to extract gas. The method of applying ultrasonic vibration is a method of removing a gas by applying an impact from the outside of the apparatus using ultrasonic waves. The water circulation method is a method in which water is allowed to flow inside the apparatus and gas is extracted by the water flow. The method of extracting the gas by reducing the pressure of the device is a method of reducing the pressure in the device and extracting the gas by the pressure difference. Each method has a problem that gas cannot escape effectively and is expensive in cost, especially in a large apparatus.

  Moreover, there was no effective method regarding the problem that the denitrification material in the apparatus sticks. As a result, the load of the denitrification material is reduced and the denitrification materials are not brought into close contact with each other. Therefore, the filling height of the denitrification material cannot be increased, and is about 1,000 mm. Therefore, when the filling amount is large, the apparatus area becomes large, and there is a problem that a large apparatus cost and required area are required.

  In addition, as the denitrification reaction proceeds, the denitrification material is consumed, resulting in fine particles, but these particles are present between the denitrification material, helping to fix the denitrification material, and releasing the gas. There has been a problem of obstructing.

JP 2003-334590 A JP 2004-174328 A

  As a method for solving these problems, in Patent Document 2, the bulk density of the denitrification material is reduced to 0.2 to 0.7, and the generated nitrogen gas is effectively extracted by a method of flowing or floating the material by a water flow or air flow. The method of taking is proposed. However, although a water flow and an air flow are disclosed as a flowing method, it does not teach flow rate conditions that can be operated while stably maintaining the activity for a long period of time, and the gas used for the air flow is also the nitrogen gas generated in the denitrification tank. I don't tell you to reuse it.

  Therefore, the present invention is intended to solve these problems, by preventing the material from sticking by fluidizing the denitrification material by an economical method of reusing and circulating the nitrogen gas generated by the reaction, The gas generated by the reaction is effectively removed so that the fine particles after the reaction can be separated from the denitrification material. Furthermore, the filling height of the denitrification material can be increased based on the present invention.

  The present invention is a treatment apparatus for treating nitrate nitrogen in wastewater by contacting a denitrification material containing sulfur and an alkaline earth metal carbonate with wastewater containing nitrate nitrogen, Means to circulate and circulate a mixed fluid composed of wastewater and a gas mainly composed of nitrogen generated by the denitrification reaction at a rate of 1.0 to 2.0 times the fluidization start speed of the packed bed in the bed filled with the denitrifying material. It is the processing apparatus of nitrate nitrogen characterized by having.

  The present invention also relates to a method for treating nitrate nitrogen in waste water by contacting a denitrification material containing sulfur and an alkaline earth metal carbonate with waste water containing nitrate nitrogen. The mixed fluid consisting of waste gas and nitrogen-based gas produced by the denitrification reaction at a rate 1.0 to 2.0 times the fluidization start rate of the packed bed is circulated continuously or intermittently in the packed bed. This is a method for treating nitrate nitrogen.

  Here, a preferable example of the shape of the processing apparatus is a processing apparatus having a vertical packed bed. In addition, in the treatment method, 1) the denitrification material that has become fine as the reaction progresses is suspended and discharged from the packed bed, and 2) the mixed fluid is circulated and circulated at a rate 1.3 to 1.7 times the fluidization start rate. It is more preferable to suspend the denitrification material or to satisfy any one or more of 3) the volume ratio (gas / drainage) of the mixed fluid gas to the wastewater within the range of 0.05 to 0.8. It becomes.

  Here, the fluidization start speed means the speed of the mixed fluid when it starts to move and starts floating in a state where the denitrification material is not fixed. The circulation rate is defined as 1.0 to 2.0 times the fluidized bed flow rate of the mixed fluid. If the flow rate is less than 1.0 times, the denitrification material does not fluidize, so the denitrification materials can be sufficiently prevented from sticking to each other. If the ratio exceeds 2.0 times, the flow of the denitrification material is too intense, and the material wear due to friction between the materials is large, and the power is also large, which is not economical. Furthermore, 1.3 to 1.7 times the fluidization start speed is more preferable in terms of equipment and economy.

  A denitrification material containing sulfur and a carbonate of an alkaline earth metal such as calcium carbonate or magnesium carbonate used in the present invention is known from Patent Documents 1 and 2 above. Usually, a powder of alkaline earth metal carbonate such as sulfur and limestone is combined with a binder, or the sulfur is once melted and combined by a binding action when it solidifies into a granular or massive shape Is used. In addition, if necessary, fibers, iron oxides and porous materials can be included. Usually, it contains 20 to 80 wt% sulfur and 80 to 20 wt% alkaline earth metal carbonate.

  A preferred denitrification material is a denitrification material (Bacilace: registered trademark) manufactured by Nippon Steel Chemical Co., Ltd., having a bulk density of 0.9 to 1.1 and a diameter of sulfur, calcium carbonate, magnesium carbonate and other alkaline earth metal carbonates. Are of the same cylindrical shape but different lengths. Although there are various lengths in the initial stage, the diameter and length become smaller as the denitrification material itself is consumed as the denitrification reaction proceeds. Accordingly, the particle size and length of the denitrification material are not particularly limited, but those having a diameter of about 5 mm and a length of about 2 to 9 mm are preferable.

  Denitrification reaction is always performed in the part where the denitrification material and waste water are in contact, and sulfate such as gypsum is produced by sulfate ions generated by the reaction and alkaline earth metal ions present in the denitrification material. To do. In normal operation, the concentration of gypsum etc. is kept within the solubility, but the inside of the device is not completely uniform concentration, and it can completely prevent the local high concentration and low concentration. Absent. Therefore, a solid such as gypsum precipitates at a locally high concentration, and the denitrification material is fixed. As a result, a portion where the denitrification material cannot act effectively is formed, and the reaction rate is lowered. When the fixing portion is formed, the flow path of the drainage is obstructed and a drift occurs, and even in a portion where the fixing does not occur, a sufficient contact time cannot be obtained and the reaction rate is lowered. In addition, the deposited gypsum or the like covers the surface of the denitrification material, preventing contact between the denitrification bacteria that inhabit the denitrification material and the waste water, thereby inhibiting the denitrification reaction. In addition, nitrogen gas is generated as a result of the denitrification reaction. However, if the denitrification material is fixed, the gas is prevented from being discharged, and the gas becomes bubbles and accumulates in the gaps of the denitrification material. Due to the bubbles, contact between the waste water and the denitrification material is hindered, and the nitrate nitrogen treatment capacity is reduced.

Nitrate nitrogen (NO ₃ , NO ₂ ) in the wastewater is reduced to nitrogen gas by sulfur-oxidizing bacteria that live in the denitrification material, and sulfur in the denitrification material is oxidized to sulfate ions. It reacts with the alkaline earth metal carbonate in the denitrification material to form an alkaline earth metal sulfate. Therefore, by continuing the waste water treatment, the denitrification material is consumed and pulverization gradually proceeds.

  The denitrification material is preferably packed in a packed tower or the like, and the drainage is allowed to flow upward into the packed bed for continuous drainage treatment. In this case, if the generated nitrogen gas adheres to the surface of the denitrification material, the contact between the denitrification material and the drainage is hindered, and the denitrification does not proceed sufficiently. Further, denitrification does not proceed sufficiently even if a slime-like substance including powdered material or gypsum adheres to the surface of the denitrification material.

  Therefore, in the present invention, a mixed fluid composed of a gas mainly composed of nitrogen generated by drainage and denitrification reaction at a rate of 1.0 to 2.0 times the fluidization start speed of the packed bed in the layer filled with the denitrification material. A processing device equipped with means for circulation is used. Then, by continuously or intermittently carrying out this circulation, the coating such as gas and adhesive substance adhering to the surface of the denitrification material is efficiently removed.

  The treatment device circulates and circulates a mixed fluid comprising a tank having an appropriate shape such as a tower shape provided with a packed bed filled with a denitrification material, and a gas mainly composed of nitrogen generated by drainage and denitrification reaction. Means.

In order to circulate the mixed fluid through the packed bed and fluidize the denitrification material, the mixed fluid is circulated and circulated at a speed of 1.0 to 2.0 times the fluidization start speed of the packed bed. Here, the flow start speed varies depending on the mixing ratio of the liquid and the gas in the mixed fluid, and the mixed fluid containing the liquid and the gas may be smaller in speed than the liquid alone fluid. Therefore, by using the mixed fluid, it is possible to reduce the pump power for circulating the fluid. A suitable mixing ratio is in the range of 0.05 to 0.8 in volume ratio (gas / liquid). When the volume ratio is less than 0.05, nitrogen gas is hardly circulated, and the effect of circulating the gas is almost lost. On the other hand, if the volume ratio exceeds 0.8, the gas flow rate becomes too high, which is not economical. The fluidization start speed of the packed bed has the same meaning as described above. This is the gas / liquid ratio of the mixed fluid, the true specific gravity and shape of the denitrification material, the height of the packed bed, and the tank provided with the packed bed. It depends on the shape of the. Therefore, it is preferable to obtain the fluidization start speed in advance for a processing apparatus including a packed bed to be used by flowing several mixed fluids having different gas / liquid ratios. This can be obtained by providing a packed bed in a transparent container or a container having a window, flowing a mixed fluid through the packed bed, and measuring the speed at which the packed bed starts to fluidize. The fluidization start speed varies depending on the shape and specific gravity of the material to be fluidized. For example, when a material having a diameter of 5 mm, a length of 2 mm to 9 mm, and a bulk density of 0.95 is filled and fluidized, the fluidization start speed is 3 Although it is about ˜8 cm / s, it is generally preferable to set the range of about 1 to 10 cm / s in order to prevent damage and outflow of the normal shape denitrification material. The numerical value of the fluidization start speed here is calculated by dividing the amount of mixed fluid to be circulated (cm ³ / s) by the cross-sectional area (cm ² ) of the packed bed.

  By fluidizing the denitrification material by an economical method in which the nitrogen gas generated by the reaction is recycled and circulated, the material can be prevented from sticking and a long-term denitrification performance can be ensured. Furthermore, according to the present invention, the nitrate nitrogen in the waste water is treated by contacting a denitrification material comprising a carbonate of a group II element such as sulfur, calcium carbonate, magnesium carbonate and the waste water containing nitrate nitrogen. In this method, the drainage and gas are circulated in the bed filled with the denitrification material at a speed equal to or higher than the fluidization start speed of the packed bed, the denitrification material is floated, and sticking due to gypsum etc. generated as a result of the reaction is prevented. The nitrogen gas produced as a result of the reaction can be effectively separated from the denitrification material, and the denitrification material having various sizes after the reaction can be classified by fluidization to collect fine particles upward. This makes it possible to increase the filling height of the denitrification material, and to provide an apparatus that can reduce the installation space without increasing the size of the apparatus for processing. Further, by classifying fine particles, stable processing can be performed without blocking the inside of the apparatus. The application of the present invention is large in terms of wide industrial benefits.

Hereinafter, although embodiment of this invention is shown, it is not limited to these.
FIG. 1 is a conceptual diagram showing an example of an apparatus suitable for carrying out the present invention. The treatment tank 1 has a drainage inlet 5 and a circulation water inlet 3 in the lower part, a circulation water outlet 4 and a treatment drainage outlet 6 in the upper part, and the tank is filled with a denitrification material 7. The waste water from the treatment waste water outlet 6 is configured to be discharged out of the system. The circulation gas inlet 8 is provided at the lower part of the treatment tank, and the circulation gas outlet 9 is provided above the treatment drainage outlet 6. This circulating gas is used because nitrogen produced by the denitrification reaction is accumulated in the upper space of the tank. The upper space has a volume that allows a circulating gas to flow at a desired circulation speed, and is preferably not in communication with the outside air, or structured so that a large amount of outside air does not flow in due to a valve or the like during circulation. Then, the circulating gas and the circulating water are mixed in the lower part of the treatment tank 1 to become a mixed fluid, circulate through the packed bed, and fluidize the denitrification material.

  The amount of denitrification material 7 filled in the treatment tank 1 can be changed depending on the amount and concentration of waste water. Since this denitrification material is consumed and pulverized by the progress of the denitrification reaction, when the denitrification material is fluidized, the refined denitrification material is floated, and the treatment drain outlet It is preferable to take out together with the waste water from 6. In addition, when stopping the inflow / outflow of drainage at the time of circulation, the denitrification material floating after the end of circulation is taken out together with the drainage. Moreover, since the denitrification material is consumed, it is preferable to replenish or replace the denitrification material in a timely manner.

  In order to make the denitrification material 7 flow, the water flow made by the circulation pump 2 and the gas flow mainly made of nitrogen gas made by the compressor 10 are mixed and flowed through the packed bed. Circulation pump 2 has the ability to circulate the waste water at a speed more than the speed at which the flow of the packed bed can be started with the flow of the liquid alone (referred to as the liquid single fluidization start speed), preferably about twice that speed. It should be a thing. The compressor 10 should be capable of supplying gas at a rate of about 1/20 or more, preferably 1/10 or more of the liquid speed for circulating the waste water. Further, if the circulation pump 2 and the compressor 10 are not used and an ejector pump is used instead, the apparatus is simple. Even when an ejector pump is used, the amount of liquid and the amount of gas required for fluidization may be the same as when the circulation pump 2 and the compressor 10 are used.

  Here, the fluidization start speed of the packed bed means the speed of the mixed fluid when the denitrification material of the packed bed starts to fluidize in a gas-liquid mixed state. Further, the liquid single fluidization start speed means the liquid speed at the start of fluidization of the denitrification material in the packed bed in the liquid only state. Note that “being fluidized” also means the speed of the liquid when the denitrification material in a non-adhered state starts to move and a part starts to float.

  By fluidization, a space is created between the individual denitrification materials, and sticking can be prevented. In addition, the denitrifying materials can be rubbed together by fluidization to remove the coating such as gypsum on the surface of the material, and the gas adhering to the surface can be effectively separated to restore the activity of the denitrifying material. it can.

  Since the denitrification material in the apparatus exists in various sizes as described above, the denitrification material of various sizes is densely packed, making it difficult for gas to escape. Accordingly, the denitrification material having various sizes can be classified by fluidization, and fine particles can be collected above the packed bed and large particles can be collected below the packed bed.

  When fine particles that are discharged from the packed bed on the water stream are classified by fluidization, the fine particles are taken out of the apparatus system and can be processed separately. At that time, by providing an apparatus for solid-liquid separation of fine particles, scaling and clogging of the reaction apparatus can be prevented.

  FIG. 2 is a conceptual diagram showing a modification based on the above. The treatment tank 1a includes a drainage inlet 5a and a circulating water inlet 3a at the lower part and a treatment drainage outlet 6a at the upper part, and the tank is filled with a denitrification material 7a for each room. Waste water from the treated waste water outlet 6a is connected to the solid-liquid separator 10a, and the liquid and solid separated by the solid-liquid separator 10a are discharged from the waste water outlet 11 and the solid outlet 12, respectively. A part of the liquid in the solid-liquid separator 10a is sent to the treatment tank 1a from the circulating water outlet 4a by the circulation pump 2a. As the circulating gas, nitrogen gas accumulated in the upper space of the processing tank 1a is sucked from the circulating gas outlet 9a by the ejector 8a. The inside of the processing tank 1a is divided into several rooms, and the switching valve 13 is configured to supply liquid and gas to each room. In the apparatus as shown in FIG. 2, even when the fluidization start speed of the denitrification material 7a is high, the capacity of the circulation pump 2a can be kept small by dividing the inside of the treatment tank 1a. At that time, one circulation pump 2a is not required for each room, but the number of pumps can be greatly reduced by providing the switching valve 13 in each room. The switching valve 13 only needs to be sequentially switched by a timer (not shown) or the like, and can be freely designed and selected depending on the amount and type of waste water to be treated.

  Fluidization is sequentially performed in each chamber by the circulating flow of the mixed fluid generated in the circulation pump 2a and the ejector 8a, so that bubbles generated by the reaction do not accumulate, and a decrease in nitrate nitrogen treatment capacity can be prevented. During this circulation, the fine particles of the denitrification material 7a are sent to the solid-liquid separator 10a that continues from the treatment wastewater outlet 6a. The solid-liquid separator 10a is not particularly limited, and it is more effective to use a commonly used filter or the like. By providing an apparatus for separating the solid and liquid, the fine particles can be taken out from the apparatus system and processed separately. In addition, scaling and blockage in the treatment tank can be prevented.

  The operation of circulating and fluidizing the mixed fluid may be carried out continuously, but since a good denitrification reaction proceeds for a while after the initial stage of the reaction and the fluidization operation, every half day to every few days. It is better to perform the fluidizing operation. The operation time is about 1 minute to 1 hour, preferably about 2 to 10 minutes.

Examples are shown below. The present invention is not limited thereby.
Reference example 1
Using a device as shown in FIG. 1, the liquid and nitrogen gas produced by the denitrification reaction were added to flow the denitrification material 7 in the treatment tank 1. That is, a denitrification material 7 (sulfur-calcium carbonate system, diameter 5 mm, length) is added to the transparent plastic cylindrical treatment tank 1 (filling tower diameter 154 mm, filling cylinder height 4,600 mm, volume 154 L) in FIG. 2 kg to 9 mm) and 20 kg (1,000 mm at the filling height) were randomly packed (in a state where particles having different sizes are mixed in the treatment tank). Artificial drought drainage A (potassium nitrate aqueous solution is used in this treatment tank 1 and the concentration of nitrate nitrogen is adjusted to 1000 mg-N / L, and slaked lime is added as a condition for easy precipitation of gypsum, and the calcium concentration is 1100 mg / L. 144 L) was added, and the fluidization start speed of the packed bed by the mixed fluid in which nitrogen gas was blended at various ratios was measured using the circulation pump 2 and the compressor 10. The fluidization start speed of the packed bed when supplying 0.3 volume times nitrogen gas amount to the liquid was 4.55 cm / s.

  Using this treatment tank 1, a circulating fluid 2 and a compressor 10 are used to feed a mixed fluid of artificial dredged drainage A and nitrogen gas (nitrogen gas / drainage flow rate ratio = 0.3) 1.3 times the fluidization start speed of the packed bed. The operation of circulating at a speed was performed once a day for 5 minutes.

Reference example 2
Using the treatment equipment of Reference Example 1, similarly, filling with denitrification material, charging artificial dredging pseudo drainage A, and using mixed fluid of drainage and nitrogen gas (nitrogen gas / drainage flow rate ratio = 0.3) in the packed bed The operation of circulating at a speed 0.6 times the fluidization start speed was performed once a day for 5 minutes.

Reference example 3
Using the treatment equipment of Reference Example 1, similarly, filling with denitrification material, charging artificial dredging pseudo drainage A, and using mixed fluid of drainage and nitrogen gas (nitrogen gas / drainage flow rate ratio = 0.3) in the packed bed The operation of circulating at a speed 2.1 times the fluidization start speed was performed once a day for 5 minutes.

Reference example 4
Using the treatment apparatus of Reference Example 1, similarly, the denitrification material is filled, artificial artificial simulated waste water A is charged, the waste water is circulated at a rate 1.0 times the liquid single fluidization start speed of the packed bed, nitrogen gas Was not circulated, and the operation of fluidizing the packed bed was performed once a day for 5 minutes. In this case, the liquid single fluidization start speed was 7.3 cm / s.

The results are summarized in Table 1. Here, the liquid superficial velocity and the nitrogen gas superficial velocity are numerical values obtained by dividing the liquid or gas amount cm ³ / sec circulated to the treatment layer by the cross-sectional area cm ² of the treatment layer. The gas-liquid circulation speed is the sum of both speeds. The symbols have the following meanings. ◎: Large effect, ○: Slightly effective, ×: Little effect.

  According to Table 1, it was confirmed that the product gas was removed and the material was prevented from sticking well by circulating the mixed fluid at a fluidization start speed or higher of the packed bed. In addition, it was confirmed that the consumption rate of the material due to friction after 30 days of operation is small and the required power can be reduced. On the other hand, when the mixed fluid was circulated at 0.60 times the fluidization start speed of the packed bed, it was confirmed that the material was fixed, although it was effective in removing the generated gas. Furthermore, when the mixed fluid is circulated at 2.10 times the fluidization start speed of the packed bed, it is possible to remove the generated gas and prevent material sticking well, but the material consumption rate due to friction after 30 days of operation is large. It was confirmed that the required power was large and it was not economical. In addition, when only the waste water of Reference Example 4 was circulated, both the removal state of the produced gas and the prevention of sticking of the denitrification material were good.

Example 1
Using a device as shown in FIG. 1, a denitrification treatment experiment was conducted using artificial dredging drainage B (using a potassium nitrate aqueous solution and adjusted to a nitrate nitrogen concentration of 300 mg-N / L). That is, 82 kg (4,000 mm at the filling height) of the denitrification material 7 (sulfur-calcium carbonate system, diameter 5 mm, length 2 mm to 9 mm) is filled in the treatment apparatus of Reference Example 1, Then, 113 L was added, and then artificial dewatering waste water B was supplied by a pouring method in which 15 L per hour was continuously supplied from the lower portion with a metering pump to perform denitrification treatment.
An operation that circulates a mixed fluid of artificial dredged drainage B and nitrogen gas (nitrogen gas / drainage flow rate ratio = 0.3) at a rate 1.3 times the fluidization start speed of the packed bed with the circulation pump 2 and the compressor 10 for one day. Once for 5 minutes.

Comparative Example 1
In the same experiment as in Example 1, waste water treatment was performed under the same conditions as in Example 1 except that the circulation operation for 5 minutes was not performed once a day.

Comparative Example 2
In the same experiment as in Example 1, except that the mixed fluid of artificial dredged drainage B and nitrogen gas (nitrogen gas / drainage flow rate ratio = 0.3) was circulated as 0.6 times the fluidization start speed of the packed bed, Waste water treatment was carried out under the same conditions as in Example 1.

  For the artificial wastewater B, the nitrate nitrogen concentration and reaction rate of the treated wastewater treated in Example 1 and Comparative Example 1 were measured as needed. Table 2 shows changes with time in nitrate nitrogen concentration and reaction rate. Further, FIG. 3 shows the change over time in the reaction rate.

  As shown in Table 2 and FIG. 3, it was confirmed that the reaction in Example 1 was performed stably for a long time as compared with Comparative Examples 1 and 2 (reaction rate was 1 kg of nitrate nitrogen per 1 kg of the treated material per day). (Mg-N / treated material kg · day). Moreover, in Comparative Example 1 and Comparative Example 2, fine particles exist between the denitrifying materials, and the denitrifying materials are closely packed, and partial adhesion was confirmed. It was confirmed that the fine particles were collected above the packed bed and discharged from the packed bed in a water stream.

Example 2
In the treatment apparatus of Example 1, the denitrification treatment was performed under the same conditions as in Example 1 except that artificial simulated drainage B was changed to artificial simulated drainage A and the supply amount of artificial simulated drainage was changed to 5 L per hour. And a circulation operation was carried out.

Comparative Example 3
In the same experiment as in Example 2, the experiment was performed under the same conditions as in Example 2 except that the circulation operation was not performed once a day for 5 minutes.

Comparative Example 4
In the same experiment as Example 2, except that the mixed fluid of artificial simulated drainage A and nitrogen gas (nitrogen gas / drainage flow rate ratio = 0.3) was circulated as 0.6 times the fluidization start speed of the packed bed, Waste water treatment was carried out under the same conditions as in Example 2.
The time course of nitrate nitrogen concentration and reaction rate is shown in Table 3. Further, FIG. 4 shows the change over time in the reaction rate.

  From Table 3 and FIG. 4, as compared with Comparative Examples 3 and 4, Example 2 confirmed a long-term stable denitrification reaction effect as in Example 1.

Schematic diagram showing an example of an apparatus for carrying out the present invention The conceptual diagram which shows the modification of the apparatus for implementing this invention Graph showing the relationship between processing time and reaction rate Graph showing the relationship between processing time and reaction rate

Explanation of symbols

1, 1a: Processing tank
2, 2a: Circulation pump
3, 3a: Circulating water inlet
4, 4a: Circulating water outlet
5, 5a: Drainage inlet
6, 6a: Waste water outlet
7, 7a: Denitrification material
8: Circulating gas inlet
8a: Ejector
9, 9a: Circulating gas outlet
10: Compressor
10a: Solid-liquid separator
11: Drain outlet
12: Solid outlet

Claims (6)

  A treatment device for treating nitrate nitrogen in waste water by contacting a denitrification material containing sulfur and an alkaline earth metal carbonate with waste water containing nitrate nitrogen, The packed bed is provided with means for circulating and circulating a mixed fluid composed of waste gas and a gas mainly composed of nitrogen generated by the denitrification reaction at a speed 1.0 to 2.0 times the fluidization start speed of the packed bed. Nitrate nitrogen treatment equipment.   The treatment apparatus for nitrate nitrogen according to claim 1, wherein the treatment apparatus has a vertical packed bed.   In a method of treating nitrate nitrogen in wastewater by contacting a denitrification material containing sulfur and an alkaline earth metal carbonate with wastewater containing nitrate nitrogen, a layer filled with the denitrification material is used. A mixed fluid composed of a gas mainly composed of nitrogen generated by drainage and denitrification at a rate 1.0 to 2.0 times the fluidization start rate of the packed bed is circulated continuously or intermittently. Treatment method for nitrate nitrogen.   4. The method for treating nitrate nitrogen according to claim 3, wherein the denitrification material that has become fine as the reaction proceeds is suspended and discharged from the packed bed.   The method for treating nitrate nitrogen according to claim 3 or 4, wherein the denitrified material is suspended by circulating the mixed fluid at a rate 1.3 to 1.7 times the fluidization start rate. A method for treating nitrate nitrogen.   A method for treating nitrate nitrogen according to any one of claims 3 to 5, wherein the volume ratio (gas / drainage) between the gas and drainage of the mixed fluid is in the range of 0.05 to 0.8. Of treatment of reactive nitrogen.

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