JPH0618474A - Batch continuous method for measuring ammonia in water - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a batch continuous water ammonia measuring method for on-line measuring the concentration of ammonia nitrogen contained in water.

[0002]

2. Description of the Related Art In a biological denitrification process, in order to monitor the process, ammoniacal nitrogen (hereinafter referred to as NH
_It is necessary to measure the concentration of ( _3- N). On the other hand, the importance of NH ₃ —N is known as an index of pollution of raw water in water purification plants. From this point of view, it is pointed out that there is a need for an apparatus capable of measuring NH ₃ —N concentration, particularly on-line for a long time and automatically analyzing.

In order to meet the above needs, a method for analyzing ammonia in water is known from Japanese Patent Laid-Open No. 63-165751 proposed by the present applicant. The gist of the above-mentioned prior invention is as follows. A gas phase is formed in the measuring cell to let the sample water flow, and an alkali is added to this sample water to add p.
After H11 or more, NH ₃ —N is present as dissolved ammonia gas. Then, the sample water in the measurement cell is gently stirred. In this case, since the ammonia gas concentration in the gas phase portion is proportional to the NH ₃ -N concentration in the sample water, the ammonia gas electrode in the gas phase portion is detected by the ammonia gas electrode, and the NH _3- Determine the N concentration.

At this time, while changing the mixing ratio of the standard solution having a known ammonia concentration into the sample water at a constant cycle, the moving average and the moving average of the ammonia gas electrode output over a time corresponding to an integral multiple of the mixing ratio switching cycle are changed. The NH ₃ —N concentration in the sample water is obtained by using the past ammonia gas electrode output value for a time corresponding to ½ of the average time.

[0005]

Since the above-mentioned method for measuring ammonia in water is of the continuous flow type, alkali is always injected and the standard solution is mixed, resulting in a large amount of chemicals used. In particular, the scale generated by the reaction with alkali may be accumulated in the pipe and the pipe may be blocked.

Since the precision of the measuring instrument cannot follow the precision of mixing the standard solution, it lacks stability. The amount of drainage increases. It takes time to stabilize the output of the ammonia gas electrode. The response is slow, and it is not possible to respond to sudden changes in concentration. There are problems such as.

In order to solve the above problems, the present applicant proposed a batch continuous automatic ammonia measuring method in Japanese Patent Laid-Open No. 3-61856, but proposes another method. An object of the present invention is to provide a batch continuous ammonia measuring method for water, which has a short response time, a small amount of chemicals, is easy to maintain, and can be stably measured for a long period of time.

[0008]

In order to solve the above-mentioned problems, according to the present invention, a batch continuous type ammonia measuring method according to the present invention forms a gas phase part in a measuring cell housed in a constant temperature bath to form a constant amount. Pour the sample water of, and at the same time add alkali
After making H11 or more, the sample water is kept at a constant temperature and stirred, the ammonia in the sample water is gasified and transferred to the gas phase part, and the ammonia gas in this gas phase part is detected by the diaphragm type ammonia gas electrode. The ammonia concentration in the sample water shall be quantified based on the calibration curve prepared in advance from the obtained output.

[0009]

Ammonia in the sample water exists as dissolved ammonia gas by adding an alkali to a fixed amount of the sample water injected by forming a gas phase portion in the measuring cell in a batch method to adjust the pH to 11 or more. In this state, if the sample water is kept at a constant temperature and stirred, the dissolved ammonia is gasified and transferred to the gas phase part. Therefore, the ammonia gas transferred to the gas phase portion is detected by the diaphragm type ammonia gas electrode to obtain the electrode output.

By thus obtaining the calibration curve in advance, it is possible to quantify the ammonia concentration in the sample water from the electrode output based on this calibration curve.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A batch continuous method for measuring ammonia in water according to an embodiment of the present invention will be described below with reference to the drawings.
FIG. 1 is a system diagram of a batch continuous type aqueous ammonia measuring device when the method for measuring aqueous ammonia according to the present invention is adopted. In FIG. 1, a batch continuous type ammonia measuring device 1 has a measuring cell 6 as a main part, which forms a gas phase part 3 and holds a fixed amount of sample water, and includes a stirrer 5 having a stirrer 4.
A diaphragm type ammonia gas electrode 7 for detecting the ammonia gas transferred to the gas phase part 3 of the measurement cell 6, and a sample water to be injected into the measurement cell 6 via a water sampling pump 8 and a pinch valve 9. A water tank 10, an alkali tank 12 for storing alkali to be injected into the sample water in the measurement cell 6 via an alkali pump 11, and pinch valves 13, 14 in the measurement cell 6.
And a zero liquid tank 16 and a span liquid tank 17 for storing standard solutions of known different ammonia concentrations supplied via the water sampling pump 8, a pinch valve 18 for overflowing the sample water from the measurement cell 6, and a pinch valve for draining the sample water. 19
A solenoid valve 20 for introducing air into the measurement cell 6, a heater 22 and a temperature controller 23 for maintaining the temperature of the sample water in the measurement cell 6 at a predetermined constant temperature, and an output of the ammonia gas electrode 7 And an arithmetic controller 25 for controlling various pinch valves, pumps and the like according to a sequence program stored in advance. Reference numeral 24 is a first stage amplifier.

Here, the measuring cell 6 and the ammonia gas electrode 7 are housed in a constant temperature bath 26 in order to eliminate the influence of the outside temperature. The procedure for measuring the ammonia concentration in the sample water with such a configuration is performed as follows.
Sample water is injected from the water sampling tank 10 into the measurement cell 6 by the water sampling pump 8. At this time, the pinch valves 9, 18, 19 are open, and the pinch valves 13, 14 are closed. In this state, the sample water injected into the measurement cell 6 overflows via the pinch valve 18 and is drained via the pinch valve 19 to be discharged to the measurement cell 6
Wash the inside of the. After the cleaning is completed, the pinch valve 19 is closed, the sample water in the measuring cell 6 is overflowed to a fixed amount, and then the pinch valves 9 and 18 are closed to stop the water sampling pump 8. Then, the alkali pump 11 is driven to inject the alkali from the alkali tank 12 into the measurement cell 6, and the sample water is adjusted to pH 11 or higher. At the same time, the sample water is heated by the heater 22, kept at a constant temperature by the temperature controller 23, stirred by the stirrer 4 of the stirrer 5, and the dissolved ammonia in the sample water is gasified and transferred to the gas phase part 3.

The ammonia gas electrode 7 detects the ammonia gas transferred to the gas phase portion 3, and the arithmetic controller 25 quantifies the ammonia concentration of the sample water according to a calibration curve prepared in advance based on the electrode output generated by the ammonia gas. Such measurement of the ammonia concentration is continuously performed in a batch system, and a calibration curve is periodically obtained by the following procedure.

After cleaning the inside of the measuring cell 6 and the like to empty the inside of the measuring cell 6 as described above, the pinch valve 13 is opened and the sampling pump 8 is used to remove a known ammonia concentration from the zero liquid tank 16. Zero solution is injected into the measuring cell 6 and allowed to overflow to maintain a constant amount. Then, in the same manner as described above, the alkali is added from the alkali tank 12 to adjust the pH to 11 or more, and the heater 22 is used to heat the mixture to a constant temperature.
After stirring with the stirrer 4, the electrode output obtained by detecting with the ammonia gas electrode 7 when stable is stored in the arithmetic controller 25.

After the above operation is completed, the zero liquid in the measuring cell 6 is drained by opening the pinch valve 19 and washed as described above, and then the inside of the measuring cell 6 is emptied. And span liquid tank 1
The sump liquid containing ammonia having a concentration different from that of the zero liquid from 7 is injected into the measurement cell 6 by the same procedure as in the case of the zero liquid, and the ammonia gas transferred to the gas phase part 3 by heating and stirring is added to the ammonia gas electrode. Detected by 7,
The obtained electrode output is stored in the arithmetic controller 25. Then, a calibration curve is created from the different outputs of the ammonia gas electrodes obtained by detecting the different ammonia concentrations of the zero liquid and the sump liquid by the arithmetic controller 25.

Here, it is desirable that the ammonia concentrations of the zero liquid and the sump liquid are near the lower and upper limits of the measuring range of the measuring device, respectively. The electromagnetic valve 20 is opened together with the pinch valve 19 when the sample water or the like in the measuring cell 6 is discharged. Here, in order to measure the ammonia concentration in water in a batch continuous manner by injecting sample water after cleaning in the measurement cell 6 and detecting the ammonia gas concentration at the ammonia gas electrode 7 and periodically creating a calibration curve. Pinch valve 9,1
3, 14, 18, 19, the opening and closing of the solenoid valve 20, the start and stop of the water sampling pump 8, the alkaline pump 11 are the arithmetic and control unit 25.
Is performed according to the sequence program stored in.

[0017]

As is apparent from the above description, according to the present invention, the method for measuring the ammonia concentration in water described above is a batch method, so that alkali is constantly injected to make the pH of the sample water 11 or more. Also, since no standard solution is mixed, the amount of chemicals used and the amount of drainage are reduced. Further, since the ammonia concentration is quantified by preparing a calibration curve instead of mixing the standard solution as in the conventional case, the injection accuracy of the standard solution is not required. In addition, the batch type output stabilizes the output of the ammonia gas electrode quickly, shortens the overall response, reduces the amount of chemicals used, and reduces fouling due to pipe scales, etc. It is possible to stably measure the ammonia concentration in water.

[Brief description of drawings]

FIG. 1 is a system diagram of a batch continuous type aqueous ammonia measuring device when the method for measuring aqueous ammonia according to an embodiment of the present invention is adopted.

[Explanation of symbols]

 1 Batch Continuous Type Ammonia Measuring Device 3 Gas Phase Section 4 Stirrer 5 Stirrer 6 Measuring Cell 7 Ammonia Gas Electrode 10 Water Collection Tank 12 Alkaline Tank 16 Zero Liquid Tank 17 Span Liquid Tank 22 Heater 23 Temperature Controller 25 Calculation Controller 26 Constant temperature bath

Claims (1)

[Claims] 1. A vapor phase part is formed in a measuring cell housed in a constant temperature bath to inject a fixed amount of sample water, and at the same time, alkali is added to adjust the pH to 11 or more, and then the sample water is kept at a constant temperature. Agitation to gasify the ammonia in the sample water, transfer it to the gas phase, and detect the ammonia gas in the gas phase with the diaphragm type ammonia gas electrode. A batch continuous method for measuring ammonia in water, which comprises quantifying the ammonia concentration in water.