JP2685310B2 - BOD measuring device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a BOD measuring device. For more details B
The present invention relates to a continuous BOD measuring device capable of efficiently measuring OD using a microbial electrode.

(B) Conventional technology Various devices for continuously measuring BOD using a microbial electrode have been proposed. As one of these, in a flow cell equipped with a microbial electrode, a neutral buffer solution is flown to maintain a neutral condition and air is blown in to maintain a substantially air-saturated condition. The amount of decrease in dissolved oxygen in the cell corresponding to the BOD component in the sample diluted with buffer solution, that is, the amount of dissolved oxygen consumed by the metabolism of microorganisms is detected and measured as the output of the diaphragm oxygen electrode. The device is known. There is known a device controlled by a sequence controller so that these can be automatically measured.

In such a device, the normally intended BOD value of the test water is based on the output when the cleaning liquid (usually water) is supplied as the liquid to be measured, whereas the BOD value of the organic liquid containing the known BOD is 2 or more. Calibration of output-concentration conversion is performed from the output when the standard solution (for example, three standard solutions A, B, and C in which the organic substance concentration is doubled sequentially) is supplied, and then the sample water is supplied. ing. The supply of each standard solution and the test water is performed through the cleaning solution supply process.

However, when the device is driven, or when the device is restarted after the suspension or after the microbial membrane exchange of the microbial electrode, the microbial activity is not sufficient or the microbial activity does not become constant, and the BOD measurement is substantially performed. Can't do.

Therefore, in such a BOD measuring device, when driving or re-driving the device, first, as shown in FIG. 2, a plurality of standard solutions (eg, standard solutions A, B, C) are washed for a short time (eg, 15 minutes). ) (That is, increasing the cumulative time for introducing the standard solution) to sequentially introduce into the flow cell and repeat this for 1 to 2 days to rapidly activate the microorganisms.
After stabilization, a plurality of standard solutions are sequentially introduced into the flow cell through a long washing step (for example, 50 minutes) as shown in FIG. 3, and the flow is switched to a second solution sending mode in which this is repeated. After the output of the microbial electrode in the liquid sending mode of 2 is stabilized, sequence control is performed in which the sample water is introduced into the flow cell as an interrupt process (for example, about 10 minutes) based on a command from the external measurement key.

The first liquid transfer mode is so-called warm-up operation, and the second liquid transfer mode is BOD.
It is called standby operation, which means a measurable state.

(C) Problems to be Solved by the Invention However, in the conventional BOD measuring device, switching from the first liquid feeding mode to the second liquid feeding mode is performed manually by judging from the output chart of the microbial electrode. It was being appreciated.

Therefore, when the person in charge is absent on holidays and the like, it is often the case that the liquid transfer in the first liquid transfer mode, which consumes a large amount of the standard liquid per hour, is performed longer than necessary. There is an inconvenience which causes wasteful consumption and eventually an increase in running cost.

In addition, even in the second liquid transfer mode, it is necessary to introduce the test water after the person in charge determines whether the output is stabilized from the output chart, which is complicated and is one factor that causes a measurement error. It was.

The present invention has been made under such circumstances, and in particular, it is possible to automatically switch from the first liquid sending mode to the second liquid sending mode, which results in a large consumption of the standard liquid.
It is possible to minimize the liquid transfer in the liquid transfer mode to the required minimum, and automatically perform BOD without the need to judge the suitability when introducing the test water.
The present invention is intended to provide a BOD measuring device capable of performing continuous measurement of.

(D) Means for Solving the Problems Thus, according to the present invention, (a) a microbial electrode formed by combining a diaphragm-type oxygen electrode and a microbial membrane, and (b) a liquid inlet and a liquid outlet and A flow cell arranged on the microbial electrode so that a liquid passing between the two can come into contact with the microbial membrane, and (c) a buffer for washing liquid, a plurality of standard liquids having different organic matter contents, and test water. A solution to be measured which is diluted with a solution and selectively introduced, and (d)
An air supply unit that continuously supplies aeration air to the flow cell, and (e) a first liquid transfer mode in which the plurality of standard solutions are sequentially introduced into the flow cell through a short cleaning step and then repeated. , A drive control unit for controlling the measured liquid introducing means so as to select and execute any one of the second liquid transfer modes in which the liquid is sequentially introduced into the flow cell through a long washing step and is repeated. f) The first liquid transfer mode is selected, the output of the microbial electrode for any of the standard liquids in this liquid transfer mode is monitored, and when the output value exceeds a predetermined value, the liquid transfer mode is set to the first mode. A first arithmetic and control unit for controlling to switch to the second liquid sending mode; and (g) monitoring the output of the microbial electrode in the second liquid sending mode, and varying the repetitive output of any of the standard solutions and the standard solution. Calculate the output ratio between And, when the fluctuation value and the output ratio falls within a predetermined range, the second calculation control section for controlling to introduce test water into the flow cell on the basis of an external input signal,
There is provided a BOD measuring device comprising:

It is suitable that the introduction time of each standard solution in the first liquid feeding mode and the second liquid feeding mode of the present invention is about 5 to 60 minutes. Here, the introduction of the standard solution in the first liquid transfer mode is performed through a short cleaning step, and this cleaning step is
Usually, it is performed by introducing a washing solution for about 10 to 20 minutes. On the other hand, the introduction of the standard solution in the second liquid transfer mode is performed through a long washing step, and this washing step usually takes 20 to
It is performed by introducing a cleaning solution for about 80 minutes. In addition,
The concentration of the standard solution to be introduced is not particularly limited, but usually,
It is suitable from the viewpoint of measurement accuracy to use about 3 kinds of aqueous solutions with different organic substance concentrations within the range of 500 mg /, which is a multiple difference series of concentration (for example, 25 mg /, 50 mg / and 100 mg /
It is preferable to use the above-mentioned.

In the first arithmetic control unit of the present invention, the output of at least one of the standard solutions is compared with the predetermined value. As a predetermined value that serves as this reference, it is suitable to set an output value that is 60% or more of the normal output that can occur with the same standard solution when the microorganism is activated, and particularly an output value of 70 to 80%. It is preferable to set it in the point of quick switching to the second liquid transfer mode. On the other hand, the fluctuation value in the second arithmetic control unit is calculated for at least one standard solution, and it is suitable that the predetermined range is ± 3% of the average output. Similarly, the output ratio is repeatedly measured for at least two types of standard solutions. For example, when a plurality of standard solutions of a multiple difference series are used, the standard range is a standard solution with a predetermined concentration and a standard solution with a concentration twice that of the standard solution. It is suitable to set the output ratio for the liquid in the range of 1: 1.5 to 1: 2.5.

The introduction of the test water may be configured to be performed in response to the input of the measurement key, and may be further program-controlled so that the introduction of the test water can be introduced at every predetermined synchronization in the second liquid transfer mode.

(E) Action When the BOD measuring device is driven or re-driven, the first arithmetic control unit controls the drive control unit to select the first liquid transfer mode, and thus the first liquid transfer mode is executed. But
In this liquid transfer mode, when the output value of the standard liquid exceeds a predetermined value, the first arithmetic control unit automatically switches the liquid transfer mode to the second liquid transfer mode, and the liquid transfer time of the first liquid transfer mode is changed. Keep it to a minimum. On the other hand, the second arithmetic control unit calculates the fluctuation value and the output ratio of the output of the standard solution during the liquid transfer in the second liquid transfer mode, judges whether or not the measurement is possible based on the calculated fluctuation value, and outputs the external input signal to the external input signal. Introduce and measure the test water based on this.

Therefore, continuous measurement of BOD can be efficiently and smoothly performed without any complicated operation and without wasteful consumption of the standard solution.

(F) Embodiment 1 FIG. 1 is a structural explanatory view showing a BOD measuring device according to an embodiment of the present invention.

In the figure, 2 is a diaphragm type oxygen electrode and a microbial membrane (Trichosp
orn cutaneum), and a flow cell 3 having a liquid inlet and a liquid outlet is attached to the lower part thereof, and the liquid introduced into the flow cell comes into contact with the microbial membrane. Here, the electrode 2 is kept in a constant temperature water tank at a constant temperature (about
30 ℃). A liquid introducing passage 4 made of a vinyl tube is connected to the liquid inlet, and a peristaltic pump 9, branch passages 10 and 11, open / close valves 12 and 12 are provided upstream of the liquid introducing passage 4.
Through 12 ..., a standard solution introducing means for diluting the three kinds of standard solutions 5A, 5B, 5C, test water 6, and washing solution 7 with the buffer solution 8 and selectively introducing them into the flow cell 3 is connected. Further, an air pump 13 is connected to the liquid introduction path 4. Reference numeral 14 denotes a control unit, which is configured to control the drive of the peristaltic pump 9, the opening / closing valves 12, 12, ..., And the air pump 13 in the liquid to be measured introducing means according to the liquid sending mode. Reference numeral 15 is an input key, and 16 is a display unit.

In this example, the buffer solution is a neutral phosphate buffer solution, and the standard solutions 5A, 5B, and 5C are each a BOD concentration of 2
5 mg /, 50 mg /, and 100 mg / three standard solutions A, B, and C are used, water is used as the cleaning solution, and the flow rates of the buffer solution, the standard solution, and the cleaning solution when driving the peristaltic pump 9 are both 1.5 ml / min. And In addition, the Pt-Al type (electrolyte KC
1 saturated liquid, 95% ethylene glycol) was used.

The control unit 14 functions as the drive control unit, the first arithmetic control unit and the second arithmetic control unit of the present invention, and is program-controlled by the microcomputer.
A system chart of the control unit 14 is shown in FIG. In the figure, 17 is a CPU, 18A is a liquid feeding program for setting the first liquid feeding mode and the second liquid feeding mode, 18B is a liquid feeding mode switching program corresponding to the first arithmetic control unit, and 18C is a second arithmetic control. A measurement program corresponding to each part is shown, 19 is a bus line, and 20 is a driver of the measurement introducing means. Then, in the liquid transfer program 18A, the second
A program for executing a sequence step of either the first liquid sending mode or the second liquid sending mode as shown in FIGS. 3 and 4 is stored, while 18B and 18C store the fifth program.
As shown in the figure, a program for switching the liquid-sending mode and determining whether or not to introduce the test water is linked and stored based on the output of the microbial electrode. In this embodiment, the switching from the first liquid feeding mode to the second liquid feeding mode is performed when the output of the standard liquid C (100 mg /) becomes 0.6 μA or more (70% or more of the output at the normal time). The fluctuation range serving as a reference in the second calculation control unit is ± 3% for the standard solution C, and the output ratio is calculated for the standard solution A and the standard solution B, and the standard range is 1: 1.5. It is set to ~ 2.5.

In the BOD measuring device 1, at the time of driving or re-driving, firstly, the drive control unit is first controlled by the command of the first calculation unit.
The liquid transfer mode is executed, and as shown in FIG. 2, the standard solutions A, B, and C are sequentially introduced into the flow cell through a short washing step (15 minutes), and this is repeated. And of these, the standard solution C
The output of the above is compared in real time with the first operation unit to determine whether it exceeds 0.6 μA. When it exceeds 0.6 μA, the liquid feeding mode is switched to the second liquid feeding mode, and a long washing process (50 minutes)
The standard solutions A, B, and C are sequentially introduced into the flow cell via, and this is repeated. Then, the fluctuation X of the output value of each of the outputs of the standard solution C at each synchronization and the output ratio Y of the standard solutions A and B
Is calculated, and when X is within ± 3% and Y is in the range of 1 to 1.5 to 2.5 (measurement enable signal is issued), the measurement key is input to introduce and measure water. To do. After the measurement, the second liquid transfer mode is set again and the standby state is maintained.

When BOD continuous measurement of the wastewater of a certain heavy electric factory was actually performed using the BOD measuring device 1, the same measurement result as the conventional manual operation could be obtained.

(G) Effect of the Invention According to the BOD measuring device of the present invention, it is possible to perform BOD measurement without performing a complicated liquid transfer mode switching operation and proper judgment at the time of measurement, and without wasteful consumption of the standard solution. It can be carried out efficiently and continuously. Therefore, it becomes possible to perform completely unmanned operation, and its usefulness is extremely great.

[Brief description of the drawings]

FIG. 1 is a structural explanatory view showing a BOD measuring device according to an embodiment of the present invention, FIGS. 2 and 3 are flow charts showing two liquid transfer modes selectively executed by a drive controller, and FIG. Is also a system chart of the control unit, 5th
The figure is a flow chart showing the control steps by the first arithmetic control unit and the second arithmetic control unit. 1 ... BOD measuring device, 2 ... Microbial electrode, 3 ... Flow cell, 4 ... Liquid introduction path, 5A-5C ... Standard solution, 6 ... Test water, 7 ... Washing solution, 8 ... Buffer solution, 9 ... Perista pump, 10,11 ... Branch flow path, 12 ... Open / close valve, 13 ... Air pump, 14 ... Control section, 15 ... Input key, 16 ... Display section, 17 ... CPU, 18A ... … Liquid delivery program, 18B… Liquid delivery mode switching program, 18C… Measurement program, 19… Bus line, 20… Driver.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yasuo Onuma 1739 Motoyoshida Town, Mito City, Ibaraki Prefecture Hiranuma Industrial Co., Ltd. In-house (56) Bibliographic Reference Sho 60-23754 (JP, U)

Claims (1)

(57) [Claims] 1. A microbial electrode comprising (a) a combination of a diaphragm type oxygen electrode and a microbial membrane, (b) a liquid inlet and a liquid outlet, and a liquid passing between them contacts the microbial membrane. A flow cell disposed on the microbial electrode so that (c) a liquid to be measured is selectively introduced into the flow cell by diluting with a buffer solution one of a washing solution, a plurality of standard solutions having different organic substance contents, and test water. Means, (d) an air supply unit for continuously supplying aeration air to the flow cell, and (e) the plurality of standard solutions are sequentially introduced into the flow cell through a short washing step and repeated. The measured liquid introducing means is controlled to select and execute one of the liquid sending mode 1 and the second liquid sending mode in which the flow cell is sequentially switched and introduced through the same long washing step and repeated. A drive control unit, f) The first liquid transfer mode is selected, the output of the microbial electrode for any of the standard liquids in this liquid transfer mode is monitored, and when the output value exceeds a predetermined value, the liquid transfer mode is set to the first mode. The first control to switch to the second liquid transfer mode
And (g) monitoring the output of the microbial electrode in the second liquid transfer mode, calculating the fluctuation value of the repeated output of any standard solution and the output ratio between the standard solutions, and calculating the fluctuation value and A BOD measurement device comprising: a second calculation control unit that controls so as to introduce a sample water into the flow cell based on an external input signal when the output ratio falls within a predetermined range.