JPH10290997A - Device for detecting ammoniacal nitrogen concentration - Google Patents

Abstract

PROBLEM TO BE SOLVED: To precisely detect the ammoniacal nitrogen concn. in a short time even if the ammoniacal nitrogen concn. of a liq. sample ranges widely from low to high concn. SOLUTION: A carrier 1 immobilizing nitrifying bacteria is held in a vessel 3, a fixed amt. of treated water, etc., is introduced as a liq. sample from a nitrification tank 8 for removing nitrogen from waste water by a sampling pump 9, and air is supplied by an air pump 4 through an air flow controller 5. The ammoniacal nitrogen concn. is reduced and detected by an arithmetic unit 7 based on the value (dissolved oxygen concn.) measured by a dissolved oxygen densitometer 6 and changing as the batch reaction proceeds in the vessel 3. When the detection is finished, the following liq. sample is introduced by the pump 9, and the measured liq. sample is simultaneously discharged from a return pipeline 10. The detection of ammoniacal nitrogen concn. is repated in this way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for biologically detecting the concentration of ammonia nitrogen in a liquid or treated water in a denitrification tank or a nitrification tank in a wastewater treatment process.

[0002]

2. Description of the Related Art Among biological treatment methods for wastewater, a nitrogen removal method utilizing a nitrification and denitrification reaction by activated sludge microorganisms has been put to practical use as a method for simultaneously removing BOD and nitrogen. This method comprises a nitrification step of oxidizing ammonium nitrogen (NH ₄ -N) to nitrite or nitric acid by the action of nitrifying bacteria in activated sludge under aerobic conditions, and a nitrite treatment by the action of denitrifying bacteria under anaerobic conditions. It consists of a denitrification step of reducing nitric acid to nitrogen gas and removing it from wastewater. In this method, the growth rate of the nitrifying bacteria responsible for the nitrification reaction is slow, and since it is easily affected by water temperature, etc., in order to obtain a stable nitrogen removal performance, it is necessary to perform a sufficient nitrification reaction in the nitrification step. It is necessary to properly manage operating conditions. For that purpose, including the detection of the concentration of ammonia nitrogen remaining in the liquid and treated water in the nitrification reaction tank, the detection of the concentration of ammonia nitrogen in the liquid in the denitrification reaction tank located at the preceding stage, and the nitrification reaction tank takes charge It is necessary to know the nitrogen load.

Japanese Patent Application Laid-Open No. 61-100657 discloses an apparatus for detecting the concentration of ammonia nitrogen in the liquid in the reaction tank and the treated water in the nitrogen removal process of waste water. Disclosed is an apparatus provided with a means for measuring a consumption rate, in which a part of activated sludge of a reaction tank for actually treating wastewater is introduced into a small aeration tank and the reaction is continued batchwise. Has been proposed. In this method, a nitrification inhibitor is added to one small aeration tank, and aeration treatment is performed without adding a nitrification inhibitor to the other small aeration tank, and a difference in oxygen consumption measured from the aeration exhaust gas is obtained as an integrated value. This is converted to an ammonia nitrogen concentration. With this apparatus and method, it is not necessary to filter the activated sludge in the reaction tank, and the ammonia nitrogen concentration can be detected online. However, in this method, not only the effect of temperature on the growth of nitrifying bacteria is large, but also in the case of a batch reaction in a small aeration tank, it is necessary to perform two operations, that is, the case where the nitrification inhibitor is not injected and the case where the nitrification inhibitor is injected. Yes, the equipment and operation method become complicated. Therefore, a method for detecting the concentration of ammoniacal nitrogen with a simple apparatus and one operation without using a nitrification inhibitor is desired.

Therefore, in Japanese Patent Application Laid-Open No. 8-281288, a measurement vessel having a water sampling port that can be opened and closed is immersed in a nitrification tank without using a nitrification inhibitor. And a method of detecting the concentration of ammoniacal nitrogen by one batch reaction operation has been proposed. The batch reaction involving the consumption of oxygen in the container is divided into the following two reactions. (A) Nitrification reaction of ammoniacal nitrogen in the sample solution by nitrifying bacteria, and (b) Oxidation reaction of organic matter and sludge accumulated organic matter in the sample solution by BOD oxidizing bacteria. Of these, the amount of organic matter related to the reaction of (b) In detail, the concentration of soluble BOD in the nitrification tank of the nitrogen removal process such as sewage is several mg / L, whereas the amount of accumulated sludge is usually 100 to 300 mg / L, which is much higher. When the activated sludge mixture in each tank is collected in a container and aeration is continued, the change in the amount of accumulated sludge organic matter (BOD amount) is expressed by the following equation. By the way,
The same applies to the activated sludge mixture in the denitrification tank. A = Ao.exp (-kt) k = 0.105exp (0.0655 (T-20)) Here, A is the amount of sludge accumulated organic matter after time t (mg-BO).
D / g-SS), Ao is the initial amount of accumulated sludge organic matter (mg)
-BOD / g-SS), k means metabolic rate constant of sludge accumulated organic matter (l / h), t means time (h), and T means water temperature (° C).

That is, a substantially constant metabolic rate constant can be obtained at each water temperature, and if the aeration time is about 30 minutes to 1 hour at, for example, 20 ° C., 90 to 95% of the sludge accumulated organic matter remains. There is no significant change in the oxidation reaction rate. Therefore, during the period of 30 minutes to 1 hour, the oxygen consumption rate accompanying the reaction (b) generally changes at a constant value, and the change in only the oxygen consumption rate accompanying the nitrification reaction (a) is a batch reaction. In the overall oxygen consumption rate at Therefore, it is possible to convert the initial ammonia nitrogen concentration and the nitrification rate of the sample liquid from the time-dependent change of the oxygen concentration until the ammonia concentration in the sample liquid is completely nitrified and the oxygen concentration shows a steady value. It becomes possible.

However, detecting the ammonia nitrogen concentration by this method has the following problems. When the nitrification rate of the sample solution is low and the concentration of ammonia nitrogen is high, and it takes one hour or more to complete the nitrification reaction in the container, the reaction of (b) cannot be ignored. The accuracy of density detection is reduced. In addition, it becomes difficult to be an index for appropriately managing the operating conditions in real time in a nitrification tank in which the inflow load varies in units of time. By the way, 30 minutes or 1
The range of the ammonia nitrogen concentration of the sample liquid that can be detected by time is as shown by the hatched portion in the diagram shown in FIG. 8 at each nitrification rate. However, in a normal nitrification tank using only suspended sludge, it is difficult to obtain a nitrification rate of 10 mg / L · h or more. Therefore, it has been difficult to detect the concentration of ammonia nitrogen in treated water which contains almost no liquid having a high concentration of ammonia nitrogen or a mixture of microorganisms and has a very low nitrification rate.

[0007]

DISCLOSURE OF THE INVENTION The present invention solves the above-mentioned problems of the prior art, and in the process of removing nitrogen from wastewater, a sample mixture of microorganisms and treated water in each reaction tank such as a denitrification tank and a nitrification tank is sampled. Liquid, and the ammoniacal nitrogen concentration of the sample solution can be varied over a wide range from low to high.
An object of the present invention is to provide an ammonia nitrogen concentration detecting device capable of detecting an ammonia nitrogen concentration accurately and in a short time by a simple device and operation without adding a chemical.

[0008]

SUMMARY OF THE INVENTION According to the present invention, a sample solution is sampled by an external take-out system, and a nitrifying bacteria-immobilized carrier is held in a measuring container installed outside a reaction tank. In addition to increasing the capacity to cope with high ammonia nitrogen concentration, the amount of carrier held in the container is varied according to the ammonia nitrogen concentration of the sample solution to change the ammonia nitrogen concentration of the sample solution from low to high. The above object has been achieved by making it possible to cope with a wide range of concentrations. That is, the ammonia nitrogen concentration detecting device of the present invention comprises a container holding a carrier on which nitrifying bacteria are immobilized and a sample solution, a sample solution sampling means connected to the container, and a container from the air supply device. The apparatus is characterized by comprising a flow rate adjusting device for air blown into the apparatus, a dissolved oxygen concentration meter, an arithmetic device for calculating an ammonia nitrogen concentration from a measured value of the concentration meter, and a sample liquid return pipe.

The present invention further comprises an oxygen dissolving tank, a vessel for holding a carrier on which nitrifying bacteria are immobilized, and circulating means for circulating a sample liquid between the oxygen dissolving vessel and the vessel. Means for sampling the sample liquid connected to the tank, a device for adjusting the flow rate of air blown into the container from the air supply device, a dissolved oxygen concentration meter, and calculate the ammonia nitrogen concentration from the measured value of the concentration meter. It is an object of the present invention to provide an ammonia nitrogen concentration detecting device comprising an arithmetic unit and a sample liquid return pipe.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the detection apparatus of the present invention, a carrier on which nitrifying bacteria are immobilized may be held in a container, but a nitrification tank using the immobilized carrier for actual wastewater treatment is used. In the case of a target, an immobilization carrier can be collected in a container together with a mixed liquid (sample liquid) containing suspended sludge in a nitrification tank and used for the nitrification reaction of the container. When the treated water is used as the sample liquid, the immobilized carrier must be held in the container in advance. In the present invention, immobilizing nitrifying bacteria means attaching or entrapping the nitrifying bacteria to the surface or inside of the carrier. The carrier used for immobilization is not particularly limited, for example, polyethylene glycol, a polymer gel such as polyacrylamide, a polymer resin,
And inorganic substances. The carrier on which the nitrifying bacteria are immobilized is usually used in the form of a cube, a column, or a pellet.

The magnitude of the metabolic rate constant k value of the organic matter in the immobilized carrier is equal to or less than that of the activated sludge, and until the ammonia nitrogen of the sample liquid is completely nitrified and the oxygen concentration shows a steady value. If the time is adjusted within 1 hour, preferably within 30 minutes, the amount of change in the oxygen consumption rate due to the oxidation of organic matter is negligible. Usually, the distribution amount of the flowing carrier is small near the water surface of the nitrification tank,
In the apparatus described in JP-A-8-281288, in which the apparatus is immersed near the water surface of a nitrification tank and a sample solution is collected from a water sampling port on the side, a carrier having nitrifying bacteria immobilized in the nitrification tank is used. However, a sufficient amount of the carrier could not enter the container from the water sampling port.

When the amount of the immobilized carrier in the container is increased in accordance with the high ammonia nitrogen concentration and the low ammonia nitrogen concentration is detected in a state where the nitrification rate is increased, the rate of change of the oxygen concentration in the container is increased. It became clear that the measurement with a dissolved oxygen concentration meter caused a time delay, and as a result, the detection accuracy of the ammonia nitrogen concentration was reduced. for that reason,
When a low ammonia nitrogen concentration is measured using the detection device of the present invention, it is preferable to change the amount of the carrier held in the container according to the ammonia nitrogen concentration of the sample solution. At that time, it is desirable to change the oxygen supply rate in accordance with the amount of the immobilized carrier held, and to supply oxygen in accordance with the nitrification rate of the entire container. In this case, the carrier holding amount and the oxygen supply rate in the container are changed in accordance with the initial ammonia nitrogen concentration of the sample solution, until the ammonia nitrogen of the sample solution is completely nitrified and the oxygen concentration shows a steady value. Time 1
Adjust within hours, preferably within 30 minutes.

[0013]

Next, the present invention will be described in more detail with reference to the drawings. FIG. 1 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a first embodiment of the present invention. The apparatus shown in FIG. 1 has a container 3 for holding a carrier 1 on which nitrifying bacteria are immobilized and a sample solution 2 containing ammoniacal nitrogen, an air pump 4 for supplying air to the container, and a constant flow rate of air. Flow rate adjusting device 5 for measuring the dissolved oxygen concentration in the sample liquid
And an arithmetic unit 7. A part of the activated sludge mixed liquid or a part of the treated water which does not contain activated sludge is introduced into the container by the sampling pump 9 as a sample liquid from the nitrification tank 8 in the nitrogen removal process of the wastewater by the sampling pump 9 in some cases. Dissolved oxygen concentration meter 6 that changes with the batch reaction in vessel 3
Based on the measurement value (dissolved oxygen concentration), the arithmetic device 7 converts and detects the ammonia nitrogen concentration. When the detection operation is completed, the next sample liquid is introduced by the sampling pump 9 and, at the same time, the measured sample liquid is led out from the return pipe 10. In this way, the operation for detecting the concentration of ammonia nitrogen is repeated. In this embodiment, the carrier 1 is always held in the container by the screen 11 and is sufficiently fluidized by air. In the case where the nitrifying bacteria-immobilized carrier 18 is used for actual wastewater treatment in the nitrification tank 8, only treated water containing suspended sludge from the outside of the screen 19, or only treated water is used when suspended sludge is not used. It is introduced into the container 3.

FIG. 2 shows the dissolved oxygen concentration value of the dissolved oxygen concentration meter 6 in the operation of detecting the concentration of ammonia nitrogen when the suspended sludge is collected from the nitrification tank and used as a sample liquid in the first embodiment of the present invention. FIG. 3 is a graph showing the change over time in the oxygen consumption rate obtained by calculation from the dissolved oxygen concentration value shown in FIG. The oxygen consumption rate Rr (mg / Lh) is calculated from the overall oxygen transfer capacity coefficient KLa (l / h) by air supply to the container 3 according to the following equation. Rr = KLa (Cs-C) -dC / dt Here, Cs is a saturated oxygen concentration (mg / L), C is a dissolved oxygen concentration value (mg / L) measured at each time, dC / dt.
Means a time change (mg / L · h) of the dissolved oxygen concentration value.

The graphs shown in FIGS. 2 and 3 show that the amount of the carrier in the container is 10% of the volume of the container, the water temperature is 20 ° C., the KL
a is 16.0 (l / h), the dissolved oxygen concentration value is measured every 20 seconds, and the time change dC of the dissolved oxygen concentration value is measured.
/ Dt was determined. As can be seen from these graphs, the time when the sample solution was introduced into the container 3 was time 0, and nitrification progressed in the subsequent batch reaction, and as the concentration of ammonia nitrogen remaining in the sample solution decreased, The nitrification rate and the accompanying oxygen consumption rate gradually decrease, and the concentration of dissolved oxygen in the vessel increases. Eventually, after about 20 minutes, the ammonia nitrogen is completely nitrified, and the dissolved oxygen concentration and the oxygen consumption rate show constant values. As described above, the constant value of the oxygen consumption rate is mainly associated with the oxidation reaction of organic substances, and it can be considered that this value does not significantly change within 30 minutes to 1 hour. That is, the area of the shaded area above the certain value shown in FIG. 3 is the oxygen consumption due to the nitrification reaction, and from this, it is possible to convert the concentration of ammonia nitrogen that initially remained in the sample solution. it can.

In the above experimental example, 1.3 mg / L was obtained as the detected value of the ammonia nitrogen concentration. With the nitrification of ammonia nitrogen at this time, the ratio (yield) of ammonia nitrogen used for the synthesis of nitrifying bacteria has been reported to be as small as about 2%. When sewage is used as wastewater, NH ₄ —N is almost nitrified to NO ₃ —N, and stoichiometrically 4.57 times as much oxygen is consumed. From these facts, it is determined that it is appropriate to use a value of about 4.5 as the conversion coefficient. Note that KLa by supplying air to the container 3 can be easily obtained by an unsteady method or a steady method in which the oxygen consumption rate of a sample solution containing a carrier is separately measured.

FIG. 4 shows the ammonia nitrogen concentration detected in the first embodiment and the sample liquid No. The relationship with the analysis value when the filtrate of 5A filter paper was analyzed according to JIS K0102 is shown. High correlation was obtained between the detection value and the analysis value. In these detection experiments, the amount of the carrier held in the container was 10% of the volume of the container. The nitrification rate of the entire container including the sample liquid and the carrier is 8 to 20 mg-N / L · h, and the dissolved oxygen concentration and the oxygen consumption rate show constant values, and the nitrification rate is determined until the detection of the ammonia nitrogen concentration is completed. The time was about 20 to 40 minutes in each plot.

FIG. 5 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a second embodiment of the present invention. In this embodiment, the nitrification tank 8 also uses the immobilizing carrier 18 for nitrifying bacteria for actual wastewater treatment. In this case, the carrier 18 can be collected simultaneously with the suspended sludge (sample liquid) from the inside of the screen 19 and introduced into the container 3. This makes it possible to detect the concentration of ammonia nitrogen using the nitrification ability of the actual immobilization carrier for wastewater treatment. In this embodiment, in order to collect a sufficient amount of the carrier 18, the carrier 18 is configured to be collected not from near the water surface of the nitrification tank 8 but from a place where the amount of the carrier distribution is large. The screen 11 used in the first embodiment of the present invention shown in FIG. 1 is not required here.

FIG. 6 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a third embodiment of the present invention. In this embodiment, an oxygen dissolving tank 12 is provided separately from the container 3 holding the carrier 1 and the sample liquid 2 therein, and the sample liquid is first introduced into the oxygen dissolving tank 12, where air is supplied and the sample liquid is supplied. The solution in this tank is circulated to the container 3 by the circulation pump 13 to supply dissolved oxygen to the carrier 1 and the sample solution 2. The carrier 1 is filled in the container 3 or is flowed so as not to flow out of the container 3. This embodiment is a further improvement of the following points in the first embodiment. In the first embodiment, the nitrification rate in the container is several mg-N /
When the flow rate is as low as L · h or less, the operation needs to be performed with a reduced amount of supplied air. When the amount of the support is about 10% (volume ratio), the flowability of the support by air becomes unstable. As a result, the value of KLa required for calculating the oxygen consumption rate may not be stable. When the amount of the carrier exceeds 20%, the value of KLa may not be stable because the bubble diameter of air becomes unstable. It is difficult to automatically check the KLa value.

On the other hand, in a third embodiment of the present invention,
Since the oxygen dissolving tank 12 for supplying air to the sample liquid is provided separately from the container 3 holding the carrier, a stable KLa value can be obtained. In addition, since the amount of the carrier can be held to nearly 40% of the total amount of the oxygen dissolving tank 12 and the container 3, a higher ammonia nitrogen concentration can be detected. further,
During each detecting operation of the ammonia nitrogen concentration, the KLa value is periodically and automatically confirmed by the following operation, and the KLa value used for calculating the oxygen consumption rate can be corrected. That is, the sample liquid 2 is collected into the container 3 from a reaction tank 15 such as a denitrification tank or a nitrification tank, and once circulated by the air pump 4 for a short time while being circulated by the circulating pump 13 so that the dissolved oxygen concentration value becomes a predetermined value. Up to. Thereafter, the air supply is stopped, and the subsequent change in the dissolved oxygen concentration value is recorded. From the decreasing rate of the dissolved oxygen concentration value, the oxygen consumption rate of the sample solution containing the carrier is determined. Furthermore, the same sample solution is collected again, and a stable value of the dissolved oxygen concentration appearing at the beginning of the batch reaction can be obtained in a normal operation for detecting the concentration of ammoniacal nitrogen which continuously supplies air. KLa can be calculated from the oxygen consumption rate and the stable value of dissolved oxygen by a steady method. In addition, by making the sample liquid used for confirmation of KLa have an ammonia nitrogen concentration of about 3 mg / L or more, the dissolved oxygen concentration value when the air supply is stopped decreases linearly, and the air is continuously supplied. The duration of the stable value of the dissolved oxygen concentration appearing at the beginning of the batch reaction is relatively long, and KLa can be calculated with high accuracy.

FIG. 7 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a fourth embodiment of the present invention. In this embodiment, the flow of the sample liquid into the oxygen
a or 14b, and when the liquid in the oxygen dissolving tank 12 is circulated to the container 3 by the circulation pump 13,
The position of the circulating fluid flowing into the container 3 is determined by the valves 17a and 17b.
To switch to one of two locations. According to this embodiment, even if the ammonia nitrogen concentration of the sample liquid changes greatly each time the sample is collected, the operation of detecting the ammonia nitrogen concentration can be performed within 1 hour, preferably 30 minutes by switching the circulating fluid flow path. The processing is completed within a period of time so that accurate detection can be performed.

In this embodiment, the activated sludge mixed liquid in the nitrification tank 8 and the denitrification tank 16 in the nitrogen removal process of wastewater can be alternately sampled. When the sample liquid is collected from the denitrification tank 16 having a high ammonia nitrogen concentration, the valve 14a and the valve 17a are opened, and the sample liquid 2 in the oxygen dissolution tank 12 is discharged from the bottom of the packed bed of the carrier 1 in the container 3. Inflow. On the other hand, when the sample liquid is collected from the nitrification tank 8 having a low ammonia nitrogen concentration, the valve 14b and the valve 17
b is opened, and the sample liquid 2 flows from the intermediate portion of the packed bed of the carrier in the container 3. Therefore, a high concentration of ammonia nitrogen is nitrified at a high carrier loading, and a low concentration of ammonia nitrogen is nitrified at a low carrier loading. For example, when sewage is targeted as wastewater, the ammonia nitrogen concentration in the nitrification tank is usually about 2 mg / L or less, and the ammonia nitrogen concentration in the denitrification tank is about 5 to 20 mg / L. The filling rate (volume%) of the carrier is 5 to 10% (for the volume of the circulating liquid passage portion) for the ammonia nitrogen in the nitrification tank with respect to the total volume of the circulating liquid passage portion of the oxygen dissolving tank 12 and the container 3. The nitrification rate with respect to the total is about 5 to 10 mg-N / L · h, and about 20 to 30% for ammonia nitrogen in the denitrification tank (also about 20 to 3%).
By setting to about 0 mg-N / Lh, the operation of detecting the concentration of ammonia nitrogen is completed within about 30 minutes.

Incidentally, when the sample solution of low-concentration ammonia nitrogen is nitrified at a high carrier filling rate, the change rate of the dissolved oxygen concentration accompanying the nitrification of ammonia nitrogen is large, and the response of the dissolved oxygen concentration meter can follow. However, the detection accuracy may be reduced, which is not appropriate. In this embodiment, the flow path of the circulating liquid can be selected so that nitrification is performed at an appropriate carrier filling rate in accordance with the ammonia nitrogen concentration of the sample liquid. Further, it is desirable to adjust the air flow controller 5 so that the amount of air supplied to the oxygen dissolving tank 12 increases according to the nitrification rate when the carrier filling rate is high and decreases when the carrier filling rate is low.

In the fourth embodiment, the nitrification tank 8 and the denitrification tank 16
Activated sludge mixed liquids are sampled alternately as sample liquids, and the ammonia nitrogen concentration in both tanks can be detected, so that the nitrogen removal process of wastewater can be suitably controlled. In addition, the concentration of ammonia nitrogen in the denitrification tank is extremely high,
When detection within minutes to 1 hour becomes impossible, for example, half of the activated sludge mixed solution in the denitrification tank and that in the nitrification tank with a low ammonia nitrogen concentration are simultaneously sampled to obtain a sample solution, After detecting the ammonia nitrogen concentration, it is also possible to convert the ammonia nitrogen concentration in the denitrification tank from the ammonia nitrogen concentration in the nitrification tank.

In the above embodiment, the oxygen consumption was determined from the change in the dissolved oxygen concentration in the sample solution measured using the dissolved oxygen concentration meter and converted to the ammonia nitrogen concentration. It is also possible to obtain the oxygen consumption from the change in the oxygen concentration. However, in this case, the difference between the dissolved oxygen concentration at the beginning and the end of the batch reaction of the sample solution, which results in an error in the amount of oxygen consumed, results in an error. Further, in the above embodiment, the case where the activated sludge mixed liquid in the reaction tank of the nitrogen removal process is used as the sample liquid has been described, but the treated water from which the activated sludge is separated, or the case where the organic matter concentration is low. It can also be applied to wastewater containing ammonia nitrogen.

[0026]

According to the apparatus for detecting the concentration of ammoniacal nitrogen in the present invention, in the process of removing nitrogen from wastewater, a mixed solution of microorganisms in each of the reaction tanks such as a denitrification tank and a nitrification tank and treated water can be used as a sample liquid. Thus, even in a wide range from a low concentration to a high concentration of ammonia nitrogen in a sample solution, the concentration of ammonia nitrogen can be accurately detected in a short time with a simple apparatus and operation method that does not require the addition of chemicals.

[Brief description of the drawings]

FIG. 1 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a change with time of a dissolved oxygen concentration in an operation for detecting an ammonia nitrogen concentration in the first embodiment of the present invention.

FIG. 3 is a graph showing the change over time of the oxygen consumption rate in the operation of detecting the concentration of ammoniacal nitrogen in the first embodiment of the present invention.

FIG. 4 is a relationship diagram between a detected value and an analytical value of the concentration of ammoniacal nitrogen according to the first embodiment of the present invention.

FIG. 5 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a second embodiment of the present invention.

FIG. 6 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a third embodiment of the present invention.

FIG. 7 is a system diagram of an ammonia nitrogen concentration detecting apparatus according to a fourth embodiment of the present invention.

FIG. 8 is an explanatory diagram showing a detectable range of the ammonia nitrogen concentration of the sample liquid at each nitrification rate of the sample liquid in the container.

[Explanation of symbols]

 Reference Signs List 1 carrier 2 sample liquid 3 container 4 air pump 5 air flow controller 6 dissolved oxygen concentration meter 7 arithmetic unit 8 nitrification tank 9 sampling pump 10 return pipe 11 screen 12 oxygen dissolution tank 13 circulation pump 15 reaction tank 16 denitrification tank 18 in nitrification tank Carrier 19 nitrification tank screen

Claims (5)

[Claims] 1. A container holding a carrier on which nitrifying bacteria are immobilized and a sample liquid, a sample liquid sampling means connected to the container, a device for adjusting the flow rate of air blown into the container from an air supply device, An apparatus for detecting the concentration of ammonia nitrogen, comprising: a dissolved oxygen concentration meter, an arithmetic device for calculating the concentration of ammonia nitrogen from the measured value of the concentration meter, and a return pipe for a sample liquid. 2. The ammonia nitrogen concentration detection according to claim 1, wherein a carrier holding the nitrifying bacteria is held in the container, and a screen for preventing the outflow of the carrier having the nitrifying bacteria fixed thereon is provided on the upper part of the container. apparatus. 3. An oxygen dissolving tank, a container for holding a carrier on which nitrifying bacteria are immobilized, and a circulating means for circulating a sample liquid between the oxygen dissolving tank and the container. A sample liquid sampling means connected to the tank, a flow rate adjusting device for air blown into the container from the air supply device, a dissolved oxygen concentration meter, and an arithmetic device for calculating the ammonia nitrogen concentration from the measured value of the concentration meter. And a sample liquid return pipe. 4. An inlet for a sample liquid from an oxygen dissolving tank to a container holding a carrier on which nitrifying bacteria are immobilized is provided at a bottom portion and an intermediate portion of the container, and one of them is provided depending on the ammonia nitrogen concentration of the sample solution. 4. The ammonia nitrogen concentration detecting device according to claim 3, further comprising an on-off valve for allowing a sample liquid to flow from an inlet of the ammonia gas. 5. The ammonia nitrogen concentration detecting apparatus according to claim 3, wherein the sample liquid sampling means includes a valve for switching sampling of the sample liquid in the denitrification tank and the nitrification tank.