JP3289522B2 - BOD measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a biochemical oxygen demand (BOD) which is a measure of organic matter contamination in wastewater from sewage treatment plants, factories, offices, and the like, and in sample water in environmental waters such as rivers and lakes. The present invention relates to an apparatus for measuring the above (1), in particular, correction of errors in measured values and means for detecting a cleaning time.

[0002]

2. Description of the Related Art BOD represents the amount of oxygen consumed by aerobic microorganisms at 20 ° C. for 5 days in mg / l, and is extremely important as the most representative index of water pollution. The BOD is usually measured as an official method by a factory drainage test method (JIS K 0102) specified in Japanese Industrial Standards (JIS) or a sewage test method. A method for measuring BOD using a microbial sensor to which a microbial membrane is applied is disclosed in, for example,
No. 7258, and the like.

FIG. 4 is a schematic sectional view showing an example of the configuration of a main part of a conventional BOD measuring device. In FIG. 4, a cleaning solution is stored in a container 1, a calibration solution is stored in a container 2, a calibration solution having different concentrations is stored in a container 3, a test solution is stored in a container 4, and a buffer solution is stored in a container 5. Switching valves 7 to 10 provided in the respective solution flow paths of
One of a cleaning solution, a calibration solution having two concentrations, and a measurement test solution is selected, and this is mixed with the buffer solution in the container 5 using the liquid sending pumps 11 and 12, and the air pump 13 is used.
To saturate the dissolved oxygen in the liquid feed.

The calibration solution used at this time is a BOD standard solution defined by the JIS manual analysis method and the sewage test method, and is used for preparing a calibration curve of the microorganism sensor 14 . Also,
The cleaning liquid is used for cleaning the piping system and for returning the output of the microorganism sensor 14 to the standard state. The cleaning liquid is supplied and washed every time another solution is supplied. The microorganism sensor 14 includes a microorganism membrane 15 in which microorganisms are immobilized on a porous membrane, and a dissolved oxygen electrode 1.
6 and a flow cell 17, and together with a heat exchanger 18 for keeping the temperature of the solution constant, are incorporated in a thermostat 19 whose temperature is controlled to a set temperature.

[0005] The mixed solution saturated with dissolved oxygen passes through a heat exchanger 18 in a thermostat 19 together with air, is kept at a set temperature, is sent to a microorganism sensor 14 , and is subjected to microorganisms immobilized on the membrane 15. Then, the amount of dissolved oxygen (respiration) consumed when assimilating the organic matter in the fed solution is output as an electric signal (voltage or current). At this time, the amount of dissolved oxygen is proportional to the concentration of organic matter in the solution. Therefore, a calibration curve was prepared by measuring two types of BOD standard solutions with known concentrations in advance, and the measured water was measured. The control device 6 compares and calculates the output signals of the above to calculate the BOD concentration of the measured test water, and prints a series of data.

The program of the control device 6 is as follows. First, in order to set the output of the microorganism sensor 14 to a standard state, the valve 7 is opened so as to send out the cleaning liquid. When the standard condition is reached, or when the standard condition has already been reached, valves 8, 7, 9 and 7 are opened in sequence to send two types of calibration solutions, and after calibration, the origin and two calibration values Create a calibration curve using and print the data. Next, the measurement sample is sent, and the concentration of the sample with unknown concentration is calculated from the calibration curve to print the data. Calibration is started again when the set number of water sample measurements has been completed and the sensor output has reached the standard state. Settings such as the operating time of each valve and the number of times of water measurement can be easily changed.

BOD using the microorganism sensor as described above
The measuring device can measure the BOD in the waste water in about 20 to 40 minutes, and is an effective BOD measuring method.
Year Japanese Industrial Standards: adopted in [JIS K3602 biochemical oxygen consumption by microbial electrode "BOD _5" instrument, already put into practice.

[0008]

However, the conventional BOD measuring device using a microorganism sensor has the following problems. It is a continuous measurement for a long time,
Biological contamination such as propagation of various bacteria occurs in the piping system and heat exchanger, and some of the organic matter in the test sample is consumed by the bacteria that propagated before reaching the immobilized microorganism membrane. The output decreases and a measurement error occurs.

Further, in order to prevent such an error from occurring, every certain period that differs depending on the properties of the measurement sample,
Maintenance such as replacement of pipes and cleaning of the heat exchanger is required, but the period can be known empirically. FIG. 5 is a diagram showing a measurement example in a BOD measuring device using a conventional microbial sensor, in which the vertical axis represents sensor measurement values and the horizontal axis represents elapsed days. In this example, the sensor output gradually decreases due to biological contamination in the piping system and the heat exchanger.
It is empirically known that cleaning is necessary every other day.

The present invention has been made in view of the above points, and its purpose is to cause biological contamination even if the piping system and the heat exchanger are subjected to biological contamination such as propagation of various bacteria. Correcting the measurement error to show the correct measurement value, and when biological contamination with different speeds due to the nature of the measurement sample progresses, accurately detect the maintenance time such as pipe replacement and cleaning of the heat exchanger, An object of the present invention is to provide a BOD measuring device capable of performing such automatic cleaning.

[0011]

Means for Solving the Problems In order to solve the above-mentioned problems, the BOD measuring device of the present invention is obtained by adding the following to a conventional BOD measuring device. 1. A dirt detection sensor consisting of a dissolved oxygen electrode and a flow cell that can independently measure the amount of oxygen consumed by germs that have propagated in the piping, independent of the amount of microorganisms immobilized on the porous membrane.

2. A three-way valve for switching the flow path between the drain and the drain that guides the flow path out of the system from the middle of the piping of the heat exchanger and the dirt detection sensor. 3． A container for storing the cleaning acid for the heat exchanger.

[0013]

Since the BOD measuring device of the present invention is constructed as described above, the amount of respiration of microorganisms immobilized on the membrane and the amount of oxygen consumed by various bacteria propagated in the piping system and the heat exchanger are independently controlled. By detecting, even if the inside of the piping system or the heat exchanger receives biological contamination such as propagation of various bacteria, not only can the measurement error due to the contamination be corrected, correct measurement values can be obtained, but also The cleaning period in the piping system and the heat exchanger with different cycles can be accurately detected and automatically cleaned in accordance with the measurement sample.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below based on embodiments. FIG. 1 is a schematic cross-sectional view showing a configuration of a main part of a BOD measuring apparatus according to the present invention, and the same parts as those in FIG. 4 are denoted by the same reference numerals. The basic configuration of the apparatus of FIG. 1 according to the present invention is the same as that of the apparatus shown in FIG. 4, except that FIG. 1 is different from FIG. 4 in that a porous membrane (not shown) is fixed in FIG. Dissolved oxygen electrode 20 and flow cell 2 incorporating the same
Blot detection sensor 22 consisting of 1, the three-way valve 23 to bypass acid wash vessel 24 to put the acid cleaning solution, and is a container 5 that additionally installed valves 25 provided in the flow path of (buffer solution). Therefore, based on FIG. 1, the operation of the apparatus and the operation thereof will be described mainly on the points different from FIG. 4.

In the apparatus shown in FIG. 1, a calibration solution or a measurement sample is
Mix with a buffer solution and dissolve the dissolved oxygen in the solution.
With the heat exchanger 18 in the thermostat 19
First, the dirt detection sensor22Sent to
Dissolved oxygen consumption by various bacteria bred in the pipe system and heat exchanger 18
Expense (DO₁) Is measured, and this value is determined by the control unit 6 for each measurement.
To be stored. Next, this same mixed solution is
Sensor14To the case of the BOD measuring device in FIG.
In the same manner as described above, the liquid is sent by the microorganisms immobilized on the membrane 15.
Of dissolved oxygen consumed when assimilating organic matter in the solution
(DO_Two) Is measured. And inside the piping system and heat exchanger 18
Oxygen Consumption (DO)₁) And the membrane
Organic in solution sent by microorganism immobilized on 15
Dissolved oxygen (DO)_Two)When
Is added for each measurement (DO₁+ DO _TwoBy doing
Microbial sensor for dissolved oxygen consumption by various bacteria14Output reduction
A small amount of correction becomes possible. Also, for example, DO₁And the concentration
DO when measuring the lower calibration solution_TwoIs equal to
Output a signal or display from the controller 6 when
By replacing the piping system, the heat exchanger 18
The cleaning time can be detected. Cleaning of heat exchanger 18
When the timing is detected, the three-way valve 23 controls the flow cell 2
Switch the flow path to 1 to the drain (bypass),
For a fixed period of time, flush the acid for washing to the heat exchanger 18 and further add piping
After replacing the washing acid remaining on the way with washing water,
Perform positive and measurements.

FIG. 2 is a diagram showing a measurement example in the BOD measuring device of the present invention. The vertical axis of FIG. 2, a microorganism sensor 1
The measured value calculated from the output of No. 4 and the measured value calculated from the output of the dirt detection sensor 22 based on the oxygen consumption of various bacteria are shown on the same scale, and the horizontal axis is the number of elapsed days. In FIG. 2, the output of the microbial membrane is plotted with a circle (represented in FIG. 5), and the output due to various bacteria is plotted with a triangle. From the results shown in FIG. 2, by adding these two measured values, it is possible to correct the decrease in the output of the microorganism sensor 14 due to the consumption of dissolved oxygen by various bacteria.

FIG. 3 is a diagram showing the result after correction. The vertical axis in FIG. 3 is a measurement value (correction value) calculated by adding the output of the microorganism sensor 14 to the output of the dirt detection sensor 22 based on the oxygen consumption of various bacteria, and the horizontal axis is the elapsed days. FIG.
From this, it can be understood that stable measurement can be performed continuously for about 10 days by correction. As described above, according to the present invention, compared to the conventional BOD measurement device, the measurement system is less susceptible to measurement errors due to biological contamination in the piping system and the heat exchanger. The cleaning time in the heat exchanger can also be accurately detected in accordance with the measured water sample, and the cleaning can be automatically performed, so that the measurement can be performed stably and accurately for a long period of time.

[0018]

According to the BOD measuring device of the present invention, in addition to the conventional microbial sensor, a dirt detecting sensor is provided at the preceding stage.
Since the amount of respiration of microorganisms immobilized on the porous membrane and the amount of oxygen consumed by various bacteria that propagated in the piping system and heat exchanger can be detected independently, the piping system and the heat exchanger Correction of measurement errors due to biological contamination, correct measurement values were obtained, and biological contamination in pipe systems and heat exchangers with different speeds due to measurement water measurement, even when biological contamination such as propagation of various bacteria was received. Occasionally, it is possible to accurately detect the maintenance time such as replacement of piping and cleaning of the heat exchanger and perform automatic cleaning, so that the BOD in the test water can be measured accurately in a stable state for a long time. be able to.

[Brief description of the drawings]

FIG. 1 is a schematic cross-sectional view showing a main part configuration of a BOD measuring device of the present invention.

FIG. 2 is a diagram showing a measurement result before correction in the BOD measurement device of the present invention.

FIG. 3 is a diagram showing a measurement result after correction in the BOD measurement device of the present invention.

FIG. 4 is a schematic cross-sectional view showing a main part configuration of a conventional BOD measuring device.

FIG. 5 is a diagram showing a measurement result in a conventional BOD measurement device.

[Explanation of symbols]

Reference Signs List 1 container 2 container 3 container 4 container 5 container 6 control device 7 valve 8 valve 9 valve 10 valve 11 liquid supply pump 12 liquid supply pump 13 air pump 14 microorganism sensor 15 microbial membrane 16 dissolved oxygen electrode 17 flow cell 18 heat exchanger 19 constant temperature bath Reference Signs List 20 dissolved oxygen electrode 21 flow cell 22 dirt detection sensor 23 three-way valve 24 container 25 valve

Continuation of the front page (56) References JP-A-3-156360 (JP, A) JP-A-61-8662 (JP, A) JP-A-7-6757 (JP, U) JP-A-6-3322 (JP) , U) Hikaru 6-130031 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) G01N 33/18 105

Claims (1)

(57) [Claims] After saturating dissolved oxygen in a mixture of a test sample and a buffer solution, the solution is sent through a heat exchanger to a microbial sensor in a thermostat kept at a set temperature, based on a program of a predetermined control device. A BOD measurement device capable of outputting the dissolved oxygen amount of microorganisms consumed when assimilating organic substances in a mixed solution as an electric signal and washing a piping system using a washing solution when measurement is suspended, comprising: a. A dirt detection sensor which is disposed in front of the microorganism sensor and comprises a dissolved oxygen electrode and a flow cell, and outputs the amount of oxygen consumed by various bacteria propagated in the piping system; b. A drain that guides the flow path out of the system from somewhere in the piping of the heat exchanger and the dirt detection sensor. C. A three-way valve for switching a flow path to a dirt detection sensor and a drain; d. A container for storing a cleaning acid for a heat exchanger.