JP2013226508A - Treatment method of nitrogen-containing wastewater and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a treatment method of a nitrogen-containing wastewater which is provided for solving a problem, can prevent the generation of a denitrification reaction in a sedimentation tank, and can prevent a rise of an interface in the sedimentation tank.SOLUTION: A treatment method of nitrogen-containing wastewater comprises: a raw water flow-in step of making the nitrogen-containing wastewater flow into a denitrification tank 7; a denitrification treatment step of subjecting the raw water to denitrification with active sludge in the denitrification tank 7; an organic matter adding step of adding a nutrient source of the active sludge to the denitrification tank 7; an organic matter decomposing step of subjecting a remaining organic matter to oxidation decomposition in an aerating tank 11; and a solid/liquid separation step of subjecting treated water to solid-liquid separation after the organic matter decomposing process by a sedimentation tank 13. The organic matter adding step comprises: an organic matter adding amount calculation step of calculating an adding amount of the organic matter on the basis of the nitrogen density and a flow-in rate of the raw water; and an organic matter adding amount correction step of correcting a result of the calculation on the basis of an organic matter amount and the nitrogen density of the treated water before flowing into the sedimentation tank 13.

Description

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

Nitrogen components contained in wastewater from food factories and sewage treatment facilities cause eutrophication of the discharge basin and worsen the surrounding environment, so the amount is controlled to be less than the amount regulated by local government regulations. It is obliged to do.
Examples of nitrogen-containing wastewater include nitric acid-containing wastewater that is generated in pickling processes such as stainless steel. The treatment methods for such nitric acid-containing wastewater include physicochemical methods such as ion exchange and adsorption, and activated sludge. A biological denitrification method using methane is used, but biological treatment is mainly used from the viewpoint of cost.

Biological treatment of nitric acid-containing wastewater is usually conducted by removing harmful elements (such as Cr) whose emissions are regulated by a coagulation sedimentation method, etc., and then guided to a denitrification tank. Is reduced to nitrogen gas, and removal of the nitrogen source is achieved.
At this time, since the microbial nutrient source (organic carbon source) necessary for denitrification tends to be insufficient, it is generally performed to add an organic carbon source (hydrogen donor) such as methanol from outside the system. Yes.
The denitrified nitric acid-containing wastewater is then aerated and the remaining COD components such as untreated organic carbon sources are aerobically treated, and then solid-liquid separated into sludge and supernatant water in the final sedimentation basin. Clear water is discharged as treated water.
If the nitrogen component contained is ammoniacal nitrogen rather than nitrate nitrogen, ammonia is oxidized to nitrate nitrogen by the action of ammonia-oxidizing bacteria and nitrite-oxidizing bacteria in the subsequent aeration process, and then removed from the former stage. Nitrogen is removed by converting it to nitrogen gas by returning it to the nitrogen tank.

  In an actual apparatus that biologically denitrifies such nitrogen-containing wastewater, swelling of sludge, called bulking, and solid-liquid separation obstacles are problems. Bulking is a phenomenon in which filamentous bacteria with low sedimentation predominate in sludge, and the sedimentation of sludge, which is an aggregate of microorganisms, extremely deteriorates. When this bulking occurs, the solid-liquid separability in the settling tank deteriorates, and in severe cases, sludge is discharged together with the supernatant water (this phenomenon is called carry-over). In addition to the incomplete treatment due to the mixing of sludge in the treated water, the activated sludge in the treatment tank cannot be sufficiently secured if the treatment is prolonged, and the treatment capacity of the equipment itself is also reduced.

This sludge sedimentation problem can be said to be an eternal problem of activated sludge treatment, and generally a flocculant or the like is added. In addition, various bulking suppression methods have been proposed so far.
For example, Patent Document 1 discloses that a fine granular solid (fine powder of blast furnace granulated slag) having a particle size of 100 μm or less is added to the activated sludge floc.
Further, in Patent Document 2, the water to be treated is caused to flow so that the solid BOD is 60% or more of the BOD in the whole water to be treated among the biological oxygen demand (BOD) of the water to be treated. It is disclosed.
Further, Patent Document 3 discloses that control is performed from each measurement value using a simulation model.
In Patent Document 4, it is disclosed that the amount of excess sludge extracted and the amount of returned sludge are controlled based on inflow BOD data, water temperature change data, DO data, and the like.
Furthermore, Patent Document 5 discloses that a selector tank is provided in the drainage inflow portion, and an organic substance concentration adjusting step for adjusting the organic substance concentration in the selector tank based on the value of the sludge volume index (SVI) is disclosed. .

Japanese Patent Laid-Open No. 3-178395 JP 2007-44604 A JP 2001-252691 A Japanese Patent Laid-Open No. 2002-126679 JP 2011-16076 A

In the methods disclosed in the above patent documents, the deterioration of the solid-liquid separation property of sludge (bulking) is caused by the fact that filamentous bacteria with low sedimentation predominate in sludge, or the sedimentation property of sludge The target is bulking that can be judged by the sludge volume index (SVI).
However, as a result of intensive studies by the present inventors, in the nitrogen-containing wastewater treatment facility, even when filamentous bacteria do not grow and SVI does not deteriorate, the sludge interface height increases in the sedimentation basin. In the worst case, it was found that sludge may flow out of the sedimentation basin (carry over).
Therefore, the methods disclosed in the above patent documents cannot cope with the increase in the sludge interface height in the settling basin as described above.

The inventors investigated the cause of the increase in the sludge interface height in the sedimentation basin even though the growth of filamentous bacteria was not observed and the SVI did not deteriorate.
Fig. 6 is a graph showing the change over time in the nitrogen inflow load immediately before the three periods in which the sludge interface rises during the survey period. The time lapse (h) until sludge ascending when the point in time is zero is shown.
As shown in the graph of FIG. 6, it was found that the inflow load fluctuation occurred such that the nitrogen load once lowered again rises immediately before the sludge interface rises.
At this time, the sludge before flowing out from the aeration tank and into the final sedimentation basin was sampled, and after solid-liquid separation, the concentration of nitrate nitrogen remaining in the supernatant was measured. It was found that the nitric acid contained in the wastewater was not completely removed before the final sedimentation basin.
In addition, even if the design load of the facility was not exceeded, it was confirmed that residual nitric acid would temporarily flow into the final settling basin if there was a change from a sudden drop in nitrogen load to an increase.

From these facts, as shown in FIG. 6, when there is a sudden change such as a decrease in nitrogen load and an increase, sludge activity cannot follow the increase in nitrogen load and does not exceed the design load of the facility. Even in this case, it is considered that a situation that could not be processed occurred.
In such a case, the hydrogen donor (microbial nutrient source) is not consumed, and the hydrogen donor (microbial nutrient source) flows into the final sedimentation basin together with the untreated residual nitric acid.
For this reason, the denitrification reaction was activated in the final sedimentation basin, and fine bubbles of nitrogen gas were generated.

  The present invention has been made to solve the problems based on such assumptions, and a method for treating nitrogen-containing wastewater that prevents the denitrification reaction from occurring in the settling tank and prevents the interface from rising in the settling tank. And to obtain a device.

In general, the idea of adding a hydrogen donor (microbe nutrient source) according to the inflow nitrogen load is based on the amount of organic matter used for the growth of microorganisms in addition to the theoretical amount necessary to remove nitrate nitrogen. In theory, the minimum amount required is determined according to the inflow nitrogen load.
However, even if the inflowing nitrogen load is the same, the microbial nutrient source is because the sludge carcasses, etc. become BOD components, the sludge activity varies depending on the water temperature and other factors, and the amount of nutrients consumed also varies. As a result, the required addition amount varies and becomes different from the above theoretical addition amount.
For this reason, conventionally, a hydrogen donor (microbe nutrient source) is added slightly more than the theoretical addition amount, and the hydrogen donor (microbe nutrient source) remaining without being consumed is decomposed in an aeration tank. Although the method had to be adopted, as described above, when there was an abrupt load change that could not be followed by the treatment of activated sludge, the above-described problem occurred.
Therefore, from the viewpoint of suppressing the interfacial rise in the final sedimentation basin of sludge, the hydrogen donor (microorganism nutrient source) is slightly larger than the theoretically required amount depending only on the inflow nitrogen load that has been performed so far. Control alone is not sufficient.
Therefore, as described above, a method for preventing the denitrification reaction from being activated in the final sedimentation basin even when there is a sudden change such as a decrease in the nitrogen load and an increase in the nitrogen load was studied.

Even if residual nitric acid flows into the final sedimentation basin, the denitrification reaction does not occur unless a hydrogen donor (a microbial nutrient source) is present.
Therefore, the inventors did not perform the “addition more than necessary and sufficient amount” which has been conventionally performed with respect to the addition of the hydrogen donor (microbe nutrient source), but only the minimum necessary amount. By adding, it was thought that the flow of hydrogen donor (microbe nutrient source) into the final sedimentation basin could be suppressed and the activation of the denitrification reaction in the final sedimentation basin could be prevented.

Furthermore, in order to reliably cope with a sudden change such as a decrease in the nitrogen load and an increase as shown in FIG. 6, the nitrogen load such as the nitrogen concentration of the treated wastewater flowing into the raw water tank rapidly increases. Even if there was a sudden change in the load, it was considered to be able to reduce the load on the equipment due to the load change.
In addition, activated sludge sedimentation tends to depend on the water temperature, and the tendency generally seen in activated sludge treatment facilities, where sedimentation is more likely to deteriorate in winter than in summer, is also applicable to nitrogen-containing wastewater treatment methods. I also found out.
The present invention has been made based on such various findings, and specifically comprises the following configurations.

(1) The nitrogen-containing wastewater treatment method according to the present invention includes a raw water inflow process in which the nitrogen-containing wastewater stored in the raw water tank flows into the denitrification tank, and the inflowing raw water is biologically desorbed by activated sludge in the denitrification tank. A denitrification treatment step for nitriding treatment, an organic matter addition step for adding organic matter as a nutrient source for the activated sludge to the denitrification tank, and the remaining organic matter not used in the denitrification treatment step are activated in the aeration tank. An organic matter decomposition step that biologically oxidatively decomposes and converts to CO ₂ and water by sludge, and a solid-liquid separation step that causes the treated water after the organic matter decomposition step to flow into the precipitation tank and separates into solid and liquid in the precipitation tank A nitrogen-containing wastewater treatment method comprising:
The organic matter addition step calculates the addition amount of the organic matter based on a predetermined standard based on the total nitrogen (TN) or nitrate nitrogen (NOx-N) concentration of the raw water and the amount of treated water flowing into the denitrification tank. Organic substance addition amount calculation process, chemical oxygen demand (COD) or biological oxygen demand (BOD) of treated water before flowing into the precipitation tank, total nitrogen (TN) concentration or nitrate nitrogen (NOx) -N) Concentration detected, total nitrogen (TN) and nitrate nitrogen (NOx-N) not detected, and chemical oxygen demand (COD) or biological oxygen demand (BOD) detected In such a case, an organic substance addition amount correcting step for correcting the organic substance addition amount in the organic substance addition amount calculating step is provided.

(2) In the above (1), the amount of raw water flowing into the denitrification tank and the total nitrogen (TN) concentration or nitrate nitrogen (NOx-N) concentration in the organic substance addition amount correction step The amount of change over time of the load is calculated based on the above, and when the amount of change over time of the load exceeds a predetermined value, the amount of inflow of nitrogen-containing wastewater into the denitrification tank in the raw water inflow step is reduced. It is what.

(3) In the above (1) or (2), the organic substance addition amount correcting step detects total nitrogen (TN) and nitrate nitrogen (NOx-N), and requires chemical oxygen. When the amount (COD) or the biological oxygen demand (BOD) is not detected, the organic substance addition amount in the organic substance addition amount calculation step is corrected to be increased.

(4) Moreover, in the thing in any one of said (1) thru | or (3), in the said denitrification process process and / or the said organic substance decomposition | disassembly process, the fluctuation range is 20-37 degreeC. It has a drainage temperature adjustment process that adjusts within 5 ° C.

(5) Moreover, the thing as described in said (4) WHEREIN: The said waste_water | drain temperature adjustment process utilizes the waste heat which generate | occur | produces in a steelworks.

(6) A nitrogen-containing wastewater treatment apparatus according to the present invention includes a raw water inflow pump that causes nitrogen-containing wastewater stored in a raw water tank to flow into the denitrification tank, and a denitrification treatment that biologically denitrifies the inflowed raw water using activated sludge. A nitrogen addition tank, an organic substance addition device for adding an organic substance as a nutrient source for the activated sludge to the denitrification tank, and a biological oxidative decomposition treatment of the remaining organic substance without being used in the denitrification tank with activated sludge. ₂ and an aeration tank to be converted into water, a precipitation tank in which the treated water treated in the aeration tank is introduced and solid-liquid separated, and a chemical oxygen demand (COD) of the treated water before flowing into the precipitation tank Alternatively, biological oxygen demand (BOD), first detection means for detecting total nitrogen (TN) concentration or nitrate nitrogen (NOx-N) concentration, and total nitrogen in raw water stored in the raw water tank ( Second detection to detect TN) concentration or nitrate nitrogen (NOx-N) concentration A wastewater treatment apparatus including nitrogen, wherein the organic substance addition apparatus includes the total nitrogen (TN) or nitrate nitrogen (NOx-N) concentration of the raw water detected by the second detection means and the desorption. An organic substance addition amount calculation means for calculating the addition amount of the organic substance based on a predetermined standard based on the amount of treated water flowing into the nitrogen tank, and total nitrogen (TN) and nitrate nitrogen (NOx-N) by the first detection means If no chemical oxygen demand is detected and chemical oxygen demand (COD) or biological oxygen demand (BOD) is detected, the amount of organic matter added is corrected so as to reduce the amount of organic matter added in the organic matter addition device. A correction means is provided.

(7) Further, in the above-mentioned (6), the load time change amount is calculated based on the detection value of the second detection means and the raw water inflow amount, and the load time change amount is a predetermined value. In the case of exceeding, the raw water inflow pump control device for controlling the raw water inflow pump so as to reduce the amount of the raw water flowing into the denitrification tank is provided.

(8) Further, in the above (6) or (7), the organic substance addition amount correction means detects total nitrogen (TN) and nitrate nitrogen (NOx-N), and requires chemical oxygen. When the quantity (COD) or the biological oxygen demand (BOD) is not detected, the organic substance addition amount in the organic substance addition apparatus is modified to increase.

(9) Moreover, in the thing in any one of said (6) thru | or (8), the fluctuation range is within 5 degrees C between 20-37 degrees C of the temperature of the treated water of the said denitrification tank and / or the said aeration tank. It is characterized by having a waste water temperature adjusting device for adjusting to the above.

(10) Further, in the above-mentioned (9), the waste water temperature adjusting device uses exhaust heat generated in an ironworks.

  In the nitrogen-containing wastewater treatment method according to the present invention, chemical oxygen demand (COD) or biological oxygen demand (BOD) of treated water before flowing into the precipitation tank, total nitrogen (TN) concentration or nitric acid Concentration nitrogen (NOx-N) concentration is detected, total nitrogen (TN) and nitrate nitrogen (NOx-N) are not detected, and chemical oxygen demand (COD) or biological oxygen demand (BOD) Is detected, decrease the amount of organic matter added based on a predetermined standard based on the total nitrogen (TN) or nitrate nitrogen (NOx-N) concentration of raw water and the amount of treated water flowing into the denitrification tank. As a result, the organic matter added as a nutrient source is used for the growth of microorganisms in addition to the minimum amount necessary for the removal of nitrate nitrogen at that time. The minimum amount of addition that is theoretically derived considering the organic matter content) Ri, organic matter as a nutrient source is prevented from flowing into the sedimentation tank, inhibiting the activation of denitrification in the sedimentation tank, it is possible to prevent the floating of the sludge by the nitrogen gas resulting from the denitrification.

It is explanatory drawing explaining the nitrogen-containing waste water treatment apparatus which concerns on Embodiment 1 of this invention. It is explanatory drawing explaining the nitrogen-containing waste water treatment equipment which concerns on Embodiment 2 of this invention. It is explanatory drawing explaining the nitrogen-containing waste water treatment equipment which concerns on Embodiment 3 of this invention. It is explanatory drawing explaining the effect of Example 1. FIG. It is explanatory drawing explaining the effect of Example 3. FIG. It is explanatory drawing for demonstrating the subject which this invention tends to solve.

[Embodiment 1]
As shown in FIG. 1, a nitrogen-containing wastewater treatment apparatus 1 according to an embodiment of the present invention includes a raw water inflow pump 5 that causes the nitric acid-containing wastewater stored in the raw water tank 3 to flow into the denitrification tank 7 and the raw water that has flowed in. A denitrification tank 7 for biologically denitrifying the activated sludge, an organic substance addition device 9 for adding an organic substance (hereinafter simply referred to as “organic substance”) as a nutrient source of the activated sludge to the denitrification tank 7, and a denitrification tank The aeration tank 11 which biologically oxidatively decomposes the remaining organic matter without being used in 7 by activated sludge to convert it into CO ₂ and water, and the treated water treated in the aeration tank 11 flows into the solid-liquid separation. The first detection means 15 for detecting the biological oxygen demand (BOD) of the treated water before flowing into the settling tank 13, the nitrate nitrogen (NOx-N) concentration, and the raw water tank 3 Second test to detect total nitrogen (TN) concentration in raw water stored in A nitrogen-containing wastewater treatment apparatus 1 having a TN meter 17 as means.
The organic substance addition device 9 calculates the organic substance addition amount based on a predetermined standard based on the total nitrogen (TN) of the raw water detected by the TN meter 17 and the amount of treated water flowing into the denitrification tank 7. When nitrate nitrogen (NOx-N) is not detected by calculation means 19 and first detection means 15 and biological oxygen demand (BOD) is detected, the amount of organic matter added in organic matter addition device 9 The organic substance addition amount correcting means 23 for correcting so as to decrease is provided.
Hereinafter, each configuration will be described in detail with reference to FIG.

<Raw water tank>
The raw water tank 3 is for temporarily storing nitric acid-containing wastewater generated at a steel mill or the like.
The nitric acid-containing wastewater is generated in a pickling process of stainless steel, for example, in an ironworks. The nitric acid-containing wastewater is subjected to coagulation precipitation and filtration, and then stored in the raw water tank 3 as raw water. At this point, the total nitrogen concentration is about 50 to 150 mg / L, most of which is nitrate nitrogen. On the other hand, the organic substance which becomes a hydrogen donor has a drainage property that hardly exists. The raw water is pumped up by the raw water inflow pump 5 and is fed to the denitrification tank 7 through the raw water feed pipe 25 connecting the raw water tank 3 and the denitrification tank 7.

<Denitrification tank>
The denitrification tank 7 stores the nitric acid-containing wastewater supplied from the raw water tank 3 and performs a denitrification process. Activated sludge for performing denitrification treatment exists in the denitrification tank 7, and the activated sludge performs denitrification treatment (biological denitrification treatment) using organic matter added from the organic matter addition device 9 as a nutrient source. .
In the denitrification tank 7, a stirrer 27 for agitating the inside of the tank to promote the denitrification reaction is provided.

<Aeration tank>
The aeration tank 11 is for aeration of the wastewater supplied from the denitrification tank 7, and biologically oxidatively decomposing organic matter remaining in the wastewater with activated sludge to convert it into CO ₂ and water. .
The aeration tank 11 has an aeration device 29 that generates bubbles for aeration. A blower 31 for sending air to the air diffuser 29 is connected to the air diffuser 29.

<Settling tank>
The sedimentation tank 13 is for storing the wastewater supplied from the aeration tank 11 and separating it into a supernatant and sludge.
The sedimentation tank 13 has a return sludge conduit 33 for extracting a part of the sludge and returning it to the denitrification tank 7.

<First detection means>
The first detection means 15 is a sampling tank 15a for sampling and storing the treated water before flowing into the settling tank 13 for solid-liquid separation, and a nitrate nitrogen (NOx-N) concentration in the sampled treated water. The NOx-N meter 15b for measuring the BOD and the BOD meter 15c for measuring the biological oxygen demand (BOD).
Although the method of solid-liquid separation in the sampling tank 15a can be considered, such as gravity sedimentation, filtration, and centrifugation, any method may be used.
The NOx-N meter 15b can be replaced with a TN meter. The TN meter also measures nitrogen that is not nitrate nitrogen, such as sludge carcasses. Therefore, when a TN meter is used, the value of the TN meter when the nitrate nitrogen is not detected and is operated stably is previously grasped as a baseline.
In addition, when the nitrogen component contained is not nitrogen nitrate but ammonia nitrogen, a TN meter is used.
The BOD meter 15c can be replaced with a COD meter. Also in this case, grasp the baseline and the correlation between BOD and COD.

<Second detection means>
The second detection means is for detecting the total nitrogen (TN) concentration in the raw water stored in the raw water tank 3, and includes a TN meter 17.
Instead of the TN meter 17, a NOx-N meter that detects the concentration of nitrate nitrogen (NOx-N) in the raw water may be used. It can be selected as appropriate in view of drainage properties and the like.

<Organic substance addition device>
The organic substance adding device 9 is for adding an organic substance as a nutrient source of activated sludge to the denitrification tank 7.
The addition amount is calculated by the organic substance addition amount calculation means 19 based on the inflow nitrogen load flowing into the denitrification tank 7, and the calculated addition amount is calculated based on the state of the treated water before flowing into the precipitation tank 13. The amount is corrected and determined by the addition amount correcting means 23.
The organic substance addition device 9 is connected to the TN meter 17, the flow meter 21, the NOx-N meter 15b, and the BOD meter 15c in order to acquire the inflow nitrogen load and the state of the treated water before flowing into the settling tank 13. .
The organic substance addition amount calculating unit 19 and the organic substance addition amount correcting unit 23 will be described in detail below.

≪Method for calculating the amount of organic substances added≫
The organic matter addition amount calculation means 19 flows in based on the nitrate nitrogen (NOx-N) concentration of raw water measured by the TN meter 17 and the amount of treated water flowing into the denitrification tank 7 measured by the flow meter 21. The nitrogen load is calculated, and the amount of organic matter added is calculated based on the calculated inflow nitrogen load according to a predetermined standard described later.
The amount of organic matter added according to the inflow nitrogen load is determined in consideration of the amount of organic matter used for the growth of microorganisms in addition to the theoretical amount necessary for removal of nitrate nitrogen (denitrification treatment). . Therefore, the addition amount of the organic matter calculated by the organic matter addition amount calculating means 19 is a necessary and sufficient amount.

<< Organic substance addition amount correction means >>
The organic substance addition amount correcting means 23 is configured to treat the nitrate nitrogen (NOx-N) concentration measured by the NOx-N meter 15b and the biological concentration measured by the BOD meter 15c in the treated water before flowing into the precipitation tank 13. Based on the oxygen demand (BOD), the addition amount calculated by the organic substance addition amount calculation means 19 is corrected.
Although a specific correction method will be described later, by providing the organic substance addition amount correction means 23, the addition amount of the organic substance continues to maintain the necessary and sufficient amount in that state at that time. This can prevent the denitrification reaction from occurring in the precipitation tank 13. If this correction means is not provided, it will be controlled only by the nitrogen load flowing into the denitrification tank 7, and as the time passes, the state of microorganisms and the degree of growth will change. It becomes impossible to follow.

A method for correcting the addition amount of the organic substance by the organic substance addition amount correcting means 23 will be described below.
The correction method depends on the combination of high and low nitrate nitrogen concentration and biological oxygen demand. Table 1 shows patterns of combinations of high and low nitrate nitrogen concentration and biological oxygen demand, wastewater treatment conditions, and correction methods according to the treatment conditions.

Pattern 1 shows the case where neither nitrate nitrogen concentration nor biological oxygen demand is detected. This is because organic substances are added without excess or deficiency, and a good denitrification process is performed. Further, when there are extra organic substances that have not been used in the denitrification process, the organic substances are all decomposed in the aeration tank 11. It means that.
In this case, since the addition amount calculated by the organic substance addition amount calculation unit 19 is an ideal amount, correction by the organic substance addition amount correction unit 23 is unnecessary.

  Pattern 2 is when the nitrate nitrogen concentration is high while the biological oxygen demand is hardly detected. This means that the denitrification treatment in the denitrification tank 7 is not sufficiently performed because the amount of organic matter added is insufficient. In this case, the organic substance addition amount correction means 23 corrects the addition amount calculated by the organic substance addition amount calculation means 19 so as to increase.

Pattern 3 is when the nitrate nitrogen concentration is hardly detected while the biological oxygen demand is high. This means that the amount of the organic substance added is excessive, there is an extra organic substance that was not used for the denitrification treatment, and the extra organic substance could not be completely decomposed in the aeration tank 11. As described above, in the conventional method, the organic substance is added in a larger amount than the theoretically necessary amount, so that the pattern 3 is often obtained.
In this case, the organic substance addition amount correction means 23 corrects the addition amount calculated by the organic substance addition amount calculation means 19 so as to decrease. By this correction, the amount of organic substance added becomes the minimum necessary value at that time, and this can prevent the denitrification reaction from occurring in the precipitation tank 13.

Pattern 4 is a case where both the nitrate nitrogen concentration and the biological oxygen demand are high, and it can be determined that the denitrification treatment could not be completed within the residence time. In this case, there is a concern about inflow of nitrogen load exceeding the design value, rapid fluctuation of inflow nitrogen load (rapid increase after decrease in inflow nitrogen load), reduction in processing speed due to some damage to activated sludge.
In such a case, by sending some warning to the operation manager, the operation manager can detect the malfunction of the process in advance and take measures according to the situation, so that the deterioration of the treated water is minimized. Can be suppressed.
In this sense, it is preferable to provide an alarm transmission means for transmitting an alarm to the operation manager when the situation of pattern 4 occurs.

  By performing the control as described above, it is possible to approach an ideal state in which both the nitrate nitrogen concentration and the biological oxygen demand as shown in pattern 1 are hardly detected. By doing so, it is possible to realize a treatment with almost no residual nitrogen in the treated water without raising the sludge interface.

Next, a method for treating nitric acid-containing wastewater will be described together with the operation of the nitric acid-containing wastewater treatment apparatus 1 using the nitric acid-containing wastewater treatment apparatus 1 of the present embodiment configured as described above.
First, the nitrogen-containing wastewater stored in the raw water tank 3 is caused to flow into the denitrification tank 7 by operating the raw water inflow pump 5 (raw water inflow process).
The nitric acid-containing wastewater fed from the raw water tank 3 is stored in the denitrification tank 7, and organic substances are added to the denitrification tank 7 in an organic substance addition step described later. Then, the activated sludge existing in the denitrification tank 7 decomposes nitric acid in the nitric acid-containing wastewater using organic matter as a nutrient source (denitrification process).

Next, the waste water supplied from the denitrification tank 7 is stored in the aeration tank 11, bubbles are generated using the air diffuser 29 having the blower 31, and aeration is performed using the bubbles. By doing so, it converts the denitrification process CO ₂ and water is treated biologically oxidize and decompose organic substances remaining without being used by the activated sludge in the aeration tank 11 in the step (organic decomposition step).
Next, the treated water after the organic matter decomposition step is allowed to flow into the precipitation tank 13 and solid-liquid separation is performed in the precipitation tank 13. A part of the sludge is pulled out and returned to the denitrification tank 7 through the return sludge conduit 33. The remaining sludge is processed as excess sludge (solid-liquid separation process).

The organic substance adding step is a step of adding an organic substance serving as a nutrient source for the activated sludge to the denitrification tank 7 using the organic substance adding device 9.
As described above, the addition amount is calculated based on the inflow nitrogen load flowing into the denitrification tank 7 (organic substance addition amount calculation step), and the calculated addition amount is the state of the treated water before flowing into the precipitation tank 13. To correct based on (organic substance addition amount correction step). From the organic substance adding device 9, the minimum necessary amount of organic substance after the correction is added.
A specific processing flow of the organic substance addition amount calculation step and the organic substance addition amount correction step will be described below.

  The organic matter addition amount calculation means 19 monitors the total nitrogen (TN) concentration of the raw water using the TN meter 17 and the amount of treated water flowing into the denitrification tank 7 using the flow meter 21, and the addition amount of organic matter is Calculate according to a predetermined standard based on these measured values (organic matter addition amount calculation step)

On the other hand, the organic substance addition amount correction means 23 uses the NOx-N meter 15b and the BOD meter 15c to treat the biological oxygen demand (BOD) of the treated water before flowing into the settling tank 13 and nitrate nitrogen (NOx- N) The concentration is monitored.
At this time, when nitrate nitrogen (NOx-N) is not detected and biological oxygen demand (BOD) is detected, the organic substance addition amount in the organic substance addition amount calculation step is corrected to be reduced. To do.
On the contrary, when nitrate nitrogen (NOx-N) is detected and the biological oxygen demand (BOD) is not detected, the organic substance addition amount in the organic substance addition amount calculating step is corrected to be increased. (Organic substance addition amount correction process)

  As described above, in the present embodiment, by correcting the addition amount of the organic substance calculated by the organic substance addition amount calculation unit 19 using the organic substance addition amount correction unit 23, it is always the minimum necessary amount without excess or deficiency. Organic substances can be added, and the biological oxygen demand (BOD) of the treated water in the precipitation tank 13 and the nitrate nitrogen (NOx-N) concentration can be hardly detected. This can prevent the denitrification reaction in the precipitation tank 13 from occurring.

[Embodiment 2]
As explained in the above-mentioned pattern 4 (see Table 1), depending on the operation status of the ironworks, the generation of inflow nitrogen load exceeding the design range and sudden fluctuation of nitrogen load (rapid increase after inflow nitrogen load decrease) May occur.
For this reason, in the first embodiment, an alarm is issued to notify the operation manager, and the operation manager responds according to the situation so that the deterioration of the treated water can be minimized.

In the second embodiment, in addition to the above measures, the amount of time change of the inflowing nitrogen load is calculated, and when the amount of time change of the inflowing nitrogen load exceeds a predetermined value, the raw water is supplied to the denitrification tank 7. By controlling the raw water inflow pump so as to reduce the amount of inflow to control the nitrogen load fluctuation flowing into the denitrification tank 7, the above problem can be solved more reliably.
Hereinafter, the nitrogen-containing wastewater treatment apparatus 51 that performs control for slowing the inflow nitrogen load as described above in the present embodiment will be described with reference to FIG.

As shown in FIG. 2, the nitrogen-containing wastewater treatment apparatus 51 according to the present embodiment is provided with a raw water inflow pump control device 53 in the nitrogen-containing wastewater treatment apparatus 1 of the first embodiment. In FIG. 2, the same components as those in the nitrogen-containing wastewater treatment apparatus 1 are denoted by the same reference numerals, and the description thereof is omitted.
The raw water inflow pump control device 53 will be described in detail.

<Raw water inflow pump control device>
The raw water inflow pump control device 53 calculates the time variation of the inflow nitrogen load based on the total nitrogen (TN) concentration in the raw water stored in the raw water tank 3 and the inflow amount of the raw water, and When the amount of time change exceeds a predetermined value, the raw water inflow pump 5 is controlled so as to reduce the inflow amount of the raw water into the denitrification tank 7. At this time, the water level in the raw water tank 3 is also monitored so that the raw water does not overflow from the raw water tank 3 or is not depleted.
As shown in FIG. 2, the raw water inflow pump control device 53 includes a TN meter 17 for measuring the total nitrogen (TN) concentration of raw water, a flow meter 21 for measuring the raw water inflow amount, and the raw water tank 3. It is connected to a water level meter 55 that measures the water level.

Specifically, the control is performed as follows.
When the total nitrogen (TN) concentration in the raw water tank 3 is high, the pumping amount of the raw water is reduced, and when it is low, it is increased. By taking such a method, the inflow nitrogen load can be averaged as much as possible.
Furthermore, when the amount of time change of the total nitrogen (TN) concentration in the raw water tank 3 exceeds a predetermined value, the pumping amount of the raw water is reduced.

  In controlling the pumping amount of the raw water, the water level in the raw water tank 3 is also monitored using the water level meter 55. If the water level is rising, the pumping amount is increased by gradually increasing the total load, and if the water level is decreasing, the pumping amount is decreased by decreasing the total load. By taking such a measure, the load fluctuation is suppressed to a gentle one, and the situation of excessive inflow of organic matter into the settling tank 13 and accompanying interface rise due to activation of denitrification reaction in the settling tank is avoided. be able to.

  In addition, when the raw | natural water tank 3 is small and there is no room as a storage tank, you may add the adjustment tank which stores raw | natural water other than the raw | natural water tank 3. FIG. Further, when some wastewater flows into the raw water tank 3, a method may be adopted in which the inflow nitrogen load is individually controlled for wastewater having a large influence before the raw water tank 3 flows.

As described above, in the present embodiment, the inflow nitrogen load can be averaged, and the nitrogen load inflow exceeding the design value can be prevented. In addition, it is possible to prevent a sudden inflow nitrogen load fluctuation and to suppress the load fluctuation to a gradual one.
For this reason, it is possible to avoid a situation such as an excessive inflow of organic matter into the precipitation tank 13 and an accompanying interface rise due to activation of a denitrification reaction in the precipitation tank.
In addition, if the process according to the present embodiment is performed, even if the process is incomplete (see pattern 4 in Table 1 above), the cause is that the activated sludge has failed (the activated sludge has been damaged in some way). Since it is almost limited to a reduction in processing speed, there is also an effect that it can be expected that the response is performed easily and promptly.

[Embodiment 3]
In the activated sludge, the type of bacteria constituting the activated sludge changes depending on the change in the temperature of the treated water, and the sedimentation property may deteriorate.
In this case, it can be dealt with by keeping the temperature of the treated water in the denitrification tank or aeration tank constant, but in the case of normal wastewater treatment such as sewage, the treatment amount is enormous, and all the enormous inflow water in the neighborhood is appropriate. In most cases, there is no heat source to maintain a stable water temperature, and it has never been thought of to heat the treatment tank.
On the other hand, ironworks have a wide variety of heat sources, including a blast furnace that reaches as high as 2000 ° C. The waste heat from these heat sources is used in wastewater treatment to keep the entire tank at a constant temperature. Therefore, it is possible to improve the sludge settling and to treat the waste water while suppressing bulking.
In addition, the temperature required for the wastewater treatment is up to 100 ° C. at the upper limit as long as the treatment is performed at atmospheric pressure. Therefore, low-temperature exhaust heat of 400 ° C. or less, which has been difficult to use, can also be used.

In the present embodiment, the present invention relates to a nitrogen-containing wastewater treatment apparatus 61 that can maintain the water temperature of treated water in each treatment tank using the exhaust heat as described above, and this apparatus is based on FIG. I will explain.
As shown in FIG. 3, the nitrogen-containing wastewater treatment device 61 is provided with a wastewater temperature adjusting device 63 in the denitrification tank 7 and the aeration tank 11 of the nitrogen-containing wastewater treatment apparatus 1 of the first embodiment. In FIG. 3, the same components as those in the nitrogen-containing wastewater treatment apparatus 1 are denoted by the same reference numerals, and the description thereof is omitted.
Hereinafter, the drainage temperature adjusting device 63 will be described.

<Drain temperature control device>
The drainage temperature adjusting device 63 uses the exhaust heat generated at the ironworks to adjust the temperature of the treated water in the denitrification tank 7 and the aeration tank 11 between 20-37 ° C. so that the fluctuation range is within 5 ° C. Is.
The exhaust heat includes steam, gas, hot water, etc. Any exhaust heat can be used as long as it has a function of adjusting the temperature in the treatment tank.
For example, if it is a vapor | steam and gas, these can be utilized by blowing directly in each tank. In this case, it is desirable to analyze the contained components in advance and confirm that they are not toxic to living organisms. In particular, in the denitrification tank 7, the denitrification treatment needs to keep the inside of the tank anaerobically, but by blowing steam or gas into the denitrification tank 7, the inside of the tank does not become anaerobic and denitrification occurs. If not, the heat added to the denitrification tank 7 may be reduced or may be omitted in some cases.

In the case of hot water, a predetermined amount may be added to the denitrification treatment. In this case, since the treatment amount in the tank is diluted and the residence time is decreased depending on the addition amount, it is preferable to start with a small amount at first and increase the amount while observing the situation.
As described above, when problems such as biological activity or treatment efficiency are confirmed by directly exchanging steam, gas, or hot water with the treated water in each tank, It is also possible to indirectly exchange heat by installing appropriate equipment.

  A predetermined effect can be obtained by keeping the water temperature within a range of 5 ° C. within a range of 20 to 37 ° C., preferably 25 to 35 ° C. In addition, as shown in FIG. 3, if the water temperature meter 65 is installed in the denitrification tank 7 and the amount of heat added is controlled according to the measured water temperature, sludge is hardly applied to the operation manager at the site. Activated sludge treatment with no fear of sedimentation deterioration and sludge outflow can be realized.

  As described above, in the present embodiment, by using the exhaust heat, it becomes possible to keep the entire tank at a substantially constant temperature, further improving the sedimentation property of the sludge and suppressing the bulking. Processing can be performed.

  In the above description, the nitrogen-containing wastewater treatment apparatus 1 according to the first embodiment is described as an example in which the wastewater temperature adjusting device 63 is provided. However, the nitrogen-containing wastewater treatment apparatus 51 according to the second embodiment may be provided. .

Experiments were conducted to confirm the operational effects of the nitrogen-containing wastewater treatment apparatus 1 shown in Embodiment 1, particularly the operational effects of providing the organic substance addition amount correcting means 23.
In the experiment, an experimental apparatus corresponding to the nitric acid-containing wastewater treatment apparatus 1 of the above embodiment was created.
In the experimental apparatus, the capacity of each tank was a denitrification tank 5L, an aeration tank 3L, and a precipitation tank 7L. A pH sensor and an acid / alkali addition device were installed in both the denitrification tank and the aeration tank to control to a predetermined pH. Sludge was collected from actual nitrogen-containing wastewater treatment equipment. Methanol was added as an organic substance.

  The nitric acid-containing wastewater to be treated was collected from the actual equipment that performs the stainless steel pickling process in the steelworks. Table 2 shows the properties of this nitric acid-containing wastewater.

The TN in the wastewater containing nitric acid was almost all NO ₃ -N. Also, during the experiment, the nitrogen concentration varied between 50 and 200 mg / L. In addition, Ca, Mg, Al, etc. were contained as trace elements. The COD as an indicator of organic matter was 5 mg / L.

An experimental method performed using the above experimental apparatus will be described.
The experiment method is to supply nitric acid-containing wastewater at 10L / day and control the amount of methanol added using an organic substance addition device (organic substance addition amount calculation means, organic substance addition amount correction means) to treat nitric acid-containing wastewater treatment for 15 days. The sludge interface of the sedimentation tank (effective volume 7L, (depth about 350mm)) during the experiment was evaluated by measuring the depth from the water surface.
Prior to the experiment, dilute the raw water according to the concentration, or add sodium nitrate separately to keep the raw water nitric acid concentration constant for about one month, and the activated sludge is in a steady state. The experiment was conducted after confirming that

The amount of methanol to be added is calculated based on the measured value of the raw water nitrogen concentration every hour and the value of the flow meter, and the amount of added nitrogen is calculated using the organic matter addition amount calculation means according to the inflow nitrogen load. Calculated.
Sampling was performed twice a day, sludge was collected from the aeration tank, and NOx-N and COD were measured for the filtered filtrate. Based on these measured values, the calculated addition amount was corrected using the organic substance addition amount correction means so that the residual COD was minimized within a range where NOx-N was not detected. Specifically, it is as follows. When NOx-N was not detected and residual COD was detected, the coefficient of the equation for deriving the methanol addition amount from the inflowing nitrogen load was changed and adjusted to reduce the addition amount. Conversely, when NOx-N was detected and the residual COD was near the minimum value, the amount of methanol added was increased.

  As a comparative example, an experimental apparatus similar to the above experimental apparatus is prepared separately except that the organic substance addition amount correction means is not provided. Using this experimental apparatus, the methanol addition amount is calculated using only the organic substance addition amount calculation means. Except for the calculation, the same nitrogen-containing wastewater treatment as described above was performed.

The result of the experiment will be described with reference to FIG. Fig. 4 shows the sludge interface of the sedimentation tank (effective volume 7L, (depth of about 350mm)) during the experiment in terms of depth from the water surface. The vertical axis represents the interface depth (cm) and the horizontal axis. Indicates elapsed days. In FIG. 4, if the plot position is high, it means that the sedimentation property is poor.
In the comparative example, as shown in Fig. 4, the interface is very unstable, especially the sludge interface rises greatly with the increase in inflow nitrogen load, and the sludge carryover is also short 4 days and 9 days after the start of the experiment. Observed in time.
On the other hand, although the interface rise corresponding to the rise of the inflow load was also observed in the example, the amount of the rise was much smaller than that of the comparative example, and stable treatment could be performed.

  Further, when the interface of the comparative example was elevated (4 days and 9 days after the start of the experiment), the sludge in each experimental apparatus of the example and the comparative example was observed with a microscope. At this time, sedimentation sludge volume index SVI (Sludge Volume Index) was also measured. As a result of microscopic observation, no abnormal growth such as filamentous bacteria was observed in any sludge. In addition, SVI did not change in the vicinity of 180 ml / g-MLSS in both Examples and Comparative Examples. During the experiment, the nitrate nitrogen concentration in the treated water was maintained at approximately 0 mg / L in both the examples and the comparative examples.

That is, in the comparative example, there was no occurrence of filamentous bacteria and SVI was not different from the example, but the sludge interface was raised and carry-over was also generated. This is probably because in the comparative example, the amount of methanol added was excessive, and methanol that was not used in the denitrification tank and the aeration tank flowed into the precipitation tank, where a denitrification reaction occurred, resulting in sludge levitation.
In this regard, in the examples, as described above, the methanol addition amount is minimized by using the organic substance addition amount correction means, and the nitrate nitrogen concentration and the biological oxygen demand amount as shown in the pattern 1 in Table 1 above. Both of them could be brought close to an ideal state where they were hardly detected, so that stable processing could be performed.

  From the above results, in the nitric acid-containing wastewater treatment apparatus 1, the amount of organic methanol added can be minimized, the activation of denitrification reaction in the sedimentation tank and the resulting sludge floating can be suppressed and stable. It was proved that it was possible to operate smoothly.

In order to confirm the effect of the nitrogen-containing wastewater treatment apparatus 51 shown in the second embodiment, a specific experiment was performed.
In the experiment, an experimental apparatus corresponding to the nitric acid-containing wastewater treatment apparatus 51 of the second embodiment was created. This experimental apparatus is the same as the first embodiment except for the capacity of each tank, the pH control method, the activated sludge used, etc., except that it has a raw water inflow pump control apparatus.
The nitric acid-containing waste water was also the same as that used in Example 1 above. Therefore, as explained using Table 2 above, the nitrogen concentration fluctuated between 50 and 200 mg / L during the experiment in the nitric acid-containing wastewater.

The experiment method was the same as in Example 1 above, after the activated sludge was brought to a steady state by trial operation, and then the nitric acid-containing wastewater was fed at 10 L / day, and the organic substance addition device (organic substance addition amount calculating means, organic substance addition amount) The amount of methanol added was controlled using correction means), and the nitric acid-containing wastewater treatment was carried out for 15 days.
Further, in this embodiment, when the nitric acid-containing wastewater treatment is performed, based on the nitrogen concentration of the TN meter in the raw water tank using the raw water inflow pump control device, the flow rate of the raw water pumping pump so that the inflow nitrogen load is almost constant. Adjusted. Also, the load fluctuation amount was controlled so as not to exceed a predetermined value. At this time, the water level in the raw water tank was monitored, and the total nitrogen load was gradually changed so that the raw water would not overflow or be depleted.
The evaluation of the experiment was performed by measuring the depth from the water surface of the sludge interface of the sedimentation tank (effective volume 7 L, (depth of about 350 mm)) during the experiment, as in Example 1.

  Further, as a comparative example, an experimental apparatus similar to the experimental apparatus described above is prepared separately except that the organic substance addition amount correcting means is not provided, and using this experimental apparatus, only the organic substance addition amount calculating means is calculated. In addition, the raw water pump was set at a constant flow rate, and the other nitrogen-containing wastewater treatment was performed in the same manner as above.

As a result of the experiment, no interface rise was observed in the examples, and stable treatment could be performed. In the comparative example, the unstable sludge interface behavior was repeated in the same manner as shown in FIG. 4, and when there was an inflow that exceeded the set load of the experimental equipment, the sludge flowed out and the treatment broke down.
On the other hand, in the examples, even if raw water that exceeds the load of the experimental equipment flows into the raw water tank, the flow rate of the raw water supply pump is reduced to slow down the inflow load fluctuation in the raw water tank, thereby There was no deterioration in processing, and good processing could be continued.

From the above results, in the nitric acid-containing wastewater treatment device 51, the inflow nitrogen load can be averaged, and the nitrogen load inflow exceeding the design value can be prevented. Further, it is possible to prevent a sudden inflow nitrogen load fluctuation (a sudden rise after the decrease) and suppress the load fluctuation to a moderate one.
For this reason, it has been demonstrated that it is possible to avoid situations such as excessive inflow of organic substances into the settling tank and accompanying interface rise due to the activation of denitrification reaction in the settling tank.

An experiment was conducted to confirm the effects of the nitrogen-containing wastewater treatment apparatus 61 of the third embodiment.
In the experiment, an experimental apparatus corresponding to the nitric acid-containing wastewater treatment apparatus 61 of Embodiment 3 was created. This experimental apparatus is significantly different from the first embodiment in that it has a waste water temperature adjusting device. In addition, each tank of the experimental device was covered with a heat insulating material and installed inside a simple building that could withstand wind and rain so that the temperature around the processing device was basically the same as the outside temperature.

  The nitric acid-containing wastewater to be treated was collected from the actual equipment that performs the stainless steel pickling process in the steelworks. Table 3 shows the properties of this nitric acid-containing wastewater.

The TN in the wastewater containing nitric acid was almost all NO ₃ -N, and the nitrogen concentration was 120 mg / L. The nitric acid-containing wastewater contained Ca, Mg, Al and the like as trace elements in addition to NO ₃ -N. The COD as an indicator of organic matter was 5 mg / L.
In addition, the capacity of each tank, the ph control method, the activated sludge used, and the like are the same as in the first embodiment.

  The experimental method is to feed nitric acid-containing wastewater at 10 L / day, and control the amount of methanol added using an organic substance addition device, while blowing steam obtained from an ironworks into an aeration tank using a wastewater temperature adjustment device. The nitric acid-containing wastewater treatment was carried out for about 7 months while maintaining the water temperature at 35 ° C.

  As a comparative example, an experimental device similar to the above experimental device was prepared separately except that it did not have a waste water temperature adjusting device, and the amount of methanol added was controlled using this experimental device, but temperature control was not performed. Nitrogen-containing wastewater treatment was performed. Because the temperature was not controlled, the water temperature fluctuated during the experiment, reaching about 35 ° C in the summer and about 25 ° C in the winter.

The evaluation of the experimental results was performed based on the measured SVI value of sludge during the experimental period.
The experimental results are shown in FIG. In FIG. 5, the vertical axis indicates SVI, and the horizontal axis indicates the measured date.
In the comparative example, as shown in FIG. 5, SVI deteriorated from the end of November when the temperature and water temperature decreased. In general, bulking has an SVI of 200 mL / g-MLSS or more, and in the comparative example, the SVI exceeded 200 until the end of February after the end of November. In addition, sludge levitation occurred irregularly and the treatment deteriorated.
On the other hand, in the example in which the water temperature in the treatment tank was kept constant, there was no change in SVI depending on the season, and SVI was maintained at almost 200 or less even in winter. In addition, no solid-liquid separation problems such as sludge levitation were observed during the experiment.

  From the above results, in the nitric acid-containing wastewater treatment device 3, the temperature of the treated water in the denitrification tank 7 and the aeration tank 11 is adjusted to within 5 ° C within 20 to 37 ° C using exhaust heat. As a result, it was demonstrated that wastewater treatment can be performed while improving sedimentation of sludge and suppressing bulking.

1 Nitrogen-containing wastewater treatment device 3 Raw water tank 5 Raw water inflow pump 7 Denitrification tank 9 Organic substance addition device 11 Aeration tank 13 Precipitation tank 15 First detection means 15a Sampling tank 15b NOx-N meter 15c BOD meter 17 TN meter 19 Calculation of organic substance addition amount Means 21 Flow meter 23 Organic substance addition amount correction means 25 Raw water supply conduit 27 Stirrer 29 Aeration device 31 Blower 33 Return sludge conduit 51 Nitrogen-containing wastewater treatment device 53 Raw water inflow pump control device 55 Water level meter 61 Nitrogen-containing wastewater treatment device 63 Waste water temperature control device 65 Water temperature gauge

Claims (10)

A raw water inflow process for flowing nitrogen-containing wastewater stored in the raw water tank into the denitrification tank, a denitrification process for biologically denitrifying the inflowing raw water with activated sludge in the denitrification tank, and the denitrification tank An organic substance addition step for adding an organic substance serving as a nutrient source for the activated sludge, and the organic matter remaining without being used in the denitrification treatment process is subjected to biological oxidative decomposition treatment with activated sludge in an aeration tank to produce CO ₂ A nitrogen-containing wastewater treatment method comprising: an organic matter decomposition step for converting into water; and a solid-liquid separation step for causing the treated water after the organic matter decomposition step to flow into the precipitation tank and solid-liquid separation in the precipitation tank,
The organic matter addition step calculates the addition amount of the organic matter based on a predetermined standard based on the total nitrogen (TN) or nitrate nitrogen (NOx-N) concentration of the raw water and the amount of treated water flowing into the denitrification tank. Organic substance addition amount calculation process, chemical oxygen demand (COD) or biological oxygen demand (BOD) of treated water before flowing into the precipitation tank, total nitrogen (TN) concentration or nitrate nitrogen (NOx) -N) Concentration detected, total nitrogen (TN) and nitrate nitrogen (NOx-N) not detected, and chemical oxygen demand (COD) or biological oxygen demand (BOD) detected In such a case, the nitrogen-containing wastewater treatment method further comprises an organic substance addition amount correction step for correcting the organic substance addition amount in the organic substance addition amount calculation step so as to decrease.   In the organic substance addition amount correction step, the amount of change in load over time is calculated based on the amount of raw water flowing into the denitrification tank and the total nitrogen (TN) concentration or nitrate nitrogen (NOx-N) concentration. 2. The nitrogen-containing wastewater treatment method according to claim 1, wherein when the amount of change over time exceeds a predetermined value, the amount of nitrogen-containing wastewater flowing into the denitrification tank in the raw water inflow step is reduced.   The organic substance addition amount correcting step is performed when total nitrogen (TN) and nitrate nitrogen (NOx-N) are detected, and chemical oxygen demand (COD) or biological oxygen demand (BOD) is not detected. The nitrogen-containing wastewater treatment method according to claim 1 or 2, wherein the organic substance addition amount is corrected so as to increase in the organic matter addition amount calculation step.   4. A waste water temperature adjusting step of adjusting the temperature of treated water within a range of 20 to 37 [deg.] C. within a variation range of 5 [deg.] C. in the denitrification treatment step and / or the organic matter decomposition step. The nitrogen-containing waste water treatment method as described in any one of these.   The nitrogen-containing wastewater treatment method according to claim 4, wherein the wastewater temperature adjustment step uses waste heat generated in an ironworks. A raw water inflow pump that causes the nitrogen-containing wastewater stored in the raw water tank to flow into the denitrification tank, a denitrification tank that biologically denitrifies the inflowed raw water with activated sludge, and a nutrient source for the activated sludge in the denitrification tank; An organic substance addition device for adding an organic substance, an aeration tank for biologically oxidatively decomposing the remaining organic substance without being used in the denitrification tank to convert it into CO ₂ and water, and an aeration tank A settling tank that allows the treated water to flow into a solid-liquid separation, a chemical oxygen demand (COD) or biological oxygen demand (BOD) of the treated water before flowing into the settling tank, and total nitrogen (TN) concentration or nitrate nitrogen (NOx-N) concentration first detection means and total nitrogen (TN) concentration or nitrate nitrogen (NOx-N) concentration in the raw water stored in the raw water tank A nitrogen-containing wastewater treatment device comprising a second detection means for detecting,
The organic substance adding device has a reference determined in advance based on the total nitrogen (TN) or nitrate nitrogen (NOx-N) concentration of the raw water detected by the second detection means and the amount of treated water flowing into the denitrification tank. The total amount of nitrogen (TN) and nitrate nitrogen (NOx-N) are not detected by the first detection means, and the chemical oxygen demand (COD) Alternatively, when a biological oxygen demand (BOD) is detected, the nitrogen-containing wastewater is characterized by comprising organic substance addition amount correcting means for correcting so as to reduce the organic substance addition amount in the organic substance addition device. Processing equipment.   A time change amount of the load is calculated based on the detection value of the second detection means and the raw water inflow amount. When the time change amount of the load exceeds a predetermined value, the raw water flows into the denitrification tank. The nitrogen-containing wastewater treatment apparatus according to claim 6, further comprising a raw water inflow pump control device that controls the raw water inflow pump so as to reduce an amount thereof.   The organic substance addition amount correcting means is used when total nitrogen (TN) and nitrate nitrogen (NOx-N) are detected and chemical oxygen demand (COD) or biological oxygen demand (BOD) is not detected. The nitrogen-containing wastewater treatment apparatus according to claim 6 or 7, wherein the organic substance addition apparatus is modified so as to increase an organic substance addition amount.   The drainage temperature adjusting device for adjusting the temperature of the treated water in the denitrification tank and / or the aeration tank between 20 to 37 ° C and a fluctuation range within 5 ° C is provided. The nitrogen-containing wastewater treatment apparatus according to one item.   The nitrogen-containing wastewater treatment apparatus according to claim 9, wherein the wastewater temperature adjustment device uses waste heat generated in an ironworks.

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