JP3872883B2 - High sensitivity BOD sensor and high sensitivity measurement method of BOD using the sensor - Google Patents

Description

【００２２】
実施例及び相関試験例 (河川水に関する BOD 値の実測)
実際の河川水を渡良瀬川に関して 1 箇所及び鬼怒川に関して 2 箇所から採取して被検試料水とし、本発明による測定法と従来の希釈法とを利用して BOD を 測定し、又希釈法による BOD 値を 100% とした場合における本発明方法による 測定値の占める割合を調べた。
結果は下記の表 2 に示されている通りであり、両方法による測定値は極めて 近接しており、従って本発明による測定法は実際の測定に適用可能であることが判明した。
【００２３】
【表２】

【００２４】
【発明の効果】
本発明による BOD の測定法は、従来の測定法と比較した場合に、操作が簡便 で熟練を必要とせず、測定所要時間も従来法の 5 日間程度に対して 1 - 10 分 間であって極めて短く、然も本発明方法は、これを実施するために使用される好気性微生物であるシュードモナス・プチーダ 10G の呼吸活性は塩化物イオンや 重金属イオンの影響を殆ど受けず、検出限界も 0.25 ppm 程度なので塩分が存在する河川水や重金属が存在する河川水・湖沼水等を試料水とすることができ、実用性が極めて高い。
【図面の簡単な説明】
【図１】本発明による BOD 測定装置を示す概略図である。
【図２】 BOD 値と電流の変化量との関係を示すグラフであり、検量線として使用し得るグラフである。
【図３】試料水中の塩化物イオン濃度と電流の変化量との関係を示すグラフである。
【符号の説明】
10 : BOD 測定装置、
12 : BOD センサー、
14 : 試料水収容用の容器、
16 : 記録装置、
S : 試料水。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a highly sensitive BOD (Biochemical Oxygen Demand) sensor, particularly a BOD sensor using an aerobic microorganism, and a highly sensitive measurement method of BOD using the sensor.
[0002]
[Prior art]
BOD has been widely used as an effective index for judging the degree of water pollution since ancient times. This BOD is nothing but the amount of dissolved oxygen in the sample water that is consumed by respiration of the microorganisms until the organic matter present in the sample water is decomposed and stabilized by the aerobic microorganisms.
[0003]
For the measurement of BOD, a dilution method is generally employed. In this method, the sample water is diluted with a dilution water containing a sufficient amount of dissolved oxygen and then kept in a sealed container. The amount of dissolved oxygen consumed when left for a day is expressed in ppm. As a method for determining dissolved oxygen, there are a Winker-sodium azide modified method (JIS K0102), a modified Miller method, and a diaphragm electrode method.
[0004]
[Problem to be Solved by the Invention]
The conventional BOD measurement method is basically a dilution method, and this method has problems in that sample water must be pretreated and a long culture period of 5 days is required. Use diluted water whose oxygen consumption during the 5-day culture period is 0.2 mg O / l or less, and when using diluted plant water, the oxygen consumption during the 5-day culture period is 3.5- Use a value in the range of 6.2 mg O / l, (D1-D2) x 100 / D1 = 40-70 (%), and calculate BOD.
In the above formula,
D1: Dissolved oxygen amount before culture of diluted seed solution
D2: The amount of dissolved oxygen before culturing of the diluted seed solution Therefore, this dilution method has a problem in that it is complicated.
[0005]
The Winker-sodium azide modified method is more sensitive than the Miller modified method. However, it requires two days to prepare sodium thiosulfate as a reagent and there are processes such as titration. There is a problem in that it requires.
[0006]
On the other hand, the diaphragm electrode method overcomes the deficiencies of the above-mentioned methods that require maneuver and is extremely simple when compared with the dilution method, but was originally developed for measuring BOD for industrial wastewater. Therefore, there is a problem that low concentrations of BOD (less than about 5 ppm) such as those in river water and lake water cannot be measured. This is because there are persistent organic substances in river water and lake water, and these substances cannot be decomposed within a predetermined measurement time, and therefore cannot respond to these substances.
[0007]
Therefore, the object of the present invention can be applied to river water and lake water having a low BOD value, there is no complicated pretreatment, no skill is required, and no organic solvent is required. It is to provide a BOD measurement method that is excellent in environmental chemistry, and to provide a BOD sensor that enables the measurement method to be carried out.
[0008]
[Means to solve the problem]
There are a wide variety of organic substances that cause water pollution in rivers and lakes, but pollutants in rivers with low BOD values are mainly persistent organic substances. In particular, domestic wastewater and municipal sewage have a high content ratio of components such as humic acid, lignin, tannic acid, cellulose (gum arabic), and surfactant, which are biologically slow to decompose. Such persistent organic substances cannot be treated at sewage treatment plants or purification facilities and are often discharged into rivers as secondary treated water, which is thought to cause water pollution.
[0009]
Therefore, if an aerobic microorganism having an excellent resolution with respect to the above-mentioned hardly decomposable organic matter is searched and isolated from activated sludge etc. in a sewage treatment plant, and the microorganism and the oxygen electrode are combined, the conventional method is not possible. It should be possible to measure BOD for river water and lake water with low BOD values. This is because a microorganism membrane in which aerobic microorganisms are immobilized is arranged on the cathode side of the oxygen electrode, and the oxygen electrode is immersed in a dissolved oxygen-saturated aqueous solution that does not contain organic substances. Oxygen diffuses into the microbial membrane, part of which is consumed by microbial respiration, and the remaining oxygen permeates through the microbial membrane and is reduced on the cathode of the oxygen electrode, where the microbial respiratory activity is nearly constant. Therefore, the current value is in a steady state. Subsequently, when sample water containing organic matter is added, the respiration activity of the microorganism increases due to utilization of the organic matter, and as a result, the amount of oxygen reaching the electrode decreases, and thus the current value decreases rapidly. However, since the diffusion of the organic matter to the microbial membrane thereafter becomes a steady state, the oxygen consumption amount due to the respiration of the microorganism becomes a steady state, and thus the current value also becomes a steady state. It is recognized that there is a correlation between the steady-state current value and the amount of organic matter in the sample water. By using this principle, the BOD of the sample water can be measured. .
[0010]
Accordingly, the present inventors have included an oxygen-containing composition containing 25.76% by weight of humic acid, 14.72% by weight of lignin, 25.33% by weight of tannic acid, 28.48% by weight of gum arabic, and 5.71% by weight of a surfactant, which are persistent organic substances. Prepare artificial sewage (added the above composition so that the total organic matter content is 16.485 mg / l) by adding to distilled water and having a BOD value of 3.77 ppm according to the conventional dilution method, and supply it from the sewage treatment plant As a result of searching for microorganisms having a high resolution with respect to hardly decomposable organic substances from various activated sludges that have been subjected to the above, microorganisms with extremely high omnivorous properties were found, and thus the present invention was basically completed. This microorganism was named Pseudomonas putida 10G ( Pseudomonas putida 10G) and deposited with the Institute of Biotechnology, Institute of Industrial Science and Technology (Accession Number: FERM P-16457).
[0011]
Therefore, the high-sensitivity BOD sensor according to the present invention has a support on which the aerobic microorganism Pseudomonas putida 10G is immobilized arranged on the cathode side of the oxygen electrode, and the amount of change in the output current from the oxygen electrode is measured. It is characterized by measuring .
[0013]
On the other hand, the highly sensitive measurement method for BOD according to the present invention is prepared in advance by placing a microbial membrane on which Pseudomonas putida 10G is immobilized on the cathode side of an oxygen electrode and measuring the amount of change in the output current from the oxygen electrode. It is characterized by matching with a standard curve.
[0014]
Any commercially available oxygen electrode can be used, and examples of the carrier material for microbial fixation include nitrocellulose, polyacrylonitrile, photocurable resins (polyvinyl alcohol, etc.), polyurethane, carrageenan, calcium alginate gel can do.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Next, a BOD measuring apparatus equipped with a BOD sensor according to the present invention will be described with reference to the drawings, and examples of preliminary test examples using standard sample water and actual test examples of river water will be described.
[0016]
FIG. 1 shows an outline of a BOD measuring apparatus 10, which contains the BOD sensor 12 according to the present invention, the sample water S, and the above BOD sensor so that the lower part is immersed in the sample water. A container 14 and a recording device 16 containing an ammeter are provided. The BOD sensor 12 includes a commercially available Clark-type oxygen electrode and an immobilized microbial membrane disposed on the cathode side of the oxygen electrode. This microbial membrane is made of nitrocellulose. The microbial suspension is poured onto one side of a porous membrane with a pore size of 0.4 μm and suction filtered, and then the same porous nitrocellulose membrane is also applied to the microbial layer side. It was created by putting the microbial layer in a sandwich state. In addition, 40 mg of microorganisms in wet weight are fixed to the above cellulose membrane, and 50 ml of sample water is used.
[0017]
The operation of the BOD measuring apparatus 10 will be described. First, an electrolytic solution is introduced into the oxygen electrode, the BOD sensor 12 is set in the container 14, and the oxygen electrode is connected to a power source. Next, a buffer solution (0.05M phosphate buffer, pH 9.0) is introduced into the container 14, and the current value is stabilized while monitoring the voltage ammeter of the recording device 16, and if the current value is stabilized, Record this. Thereafter, sample water containing an organic substance is introduced into the container 14 to replace the buffer solution with the sample water. When the sample water comes into contact with the immobilized microbial membrane, the organic matter in the sample water is assimilated by the microorganisms, and the respiratory activity of the microorganisms increases, so the amount of dissolved oxygen in the sample water decreases and the current value increases accordingly. Decrease. Since the amount of decrease in current depends on the BOD value of the sample water, a calibration curve should be created in advance using a standard sample water with a known BOD value, and the measured current variation should be verified against the calibration curve. For example, the BOD value of sample water whose BOD value is unknown can be measured.
[0018]
Preliminary test example 1
A composition containing 25.76% by weight of humic acid, 14.72% by weight of lignin, 25.33% by weight of tannic acid, 28.48% by weight of gum arabic and 5.71% by weight of surfactant was added to distilled water containing oxygen to give a BOD value of 10 by the dilution method. Various types of artificial sewage were prepared up to ppm (as described above, when the total organic matter content is 16.485 mg / l, the BOD value by the conventional dilution method is 3.77 ppm. (Adjust the amount of composition in the above). Using these artificial sewage and the apparatus as shown in FIG. 1, the amount of change in current was measured in the manner described in connection with the figure. The results are as shown in Fig. 2. It was found that there was a very good correlation between the response value and the BOD value (correlation coefficient: 0.994). The measurement was performed five times for the same sample water, but the regression equation was y = 4.4939e-2 + 0.14417x, and the reproducibility was very good. Therefore, the graph shown in Figure 2 can be used as a calibration curve. The detection limit is 0.25 ppm for BOD, and this sensitivity means that it can be used for BOD measurement of river water in Japanese first-class rivers that are 3 ppm or less. 1-10 minutes, depending on the BOD value.
[0019]
Preliminary test example 2 (effect of chloride ion on measurement)
The BOD measurement method according to the present invention is mainly intended for river water and lake water. In particular, in the case of river water, sample water collected in a catchment where salinity goes up is also measured. Therefore, the amount of change in current was measured using sample water with a known BOD value and sample water in which various amounts of sodium chloride were added to this sample water to change the chloride ion concentration. The results of comparing the results are shown in Fig. 3. It was found that there was almost no effect on the measurement until the chloride ion concentration reached 1000 ppm. Therefore, the BOD measurement method according to the present invention is sufficiently applicable even when the salt-containing water is used as the sample water.
[0020]
Preliminary test example 3 (effect of heavy metal ions on measurement)
Although river water and lake water targeted by the BOD measurement method according to the present invention may contain heavy metals, heavy metals are generally considered to inhibit the respiratory activity of microorganisms. Therefore, using the composition described in Preliminary Test Example 1 and oxygen-containing distilled water, artificial sewage (control) with a BOD of 1 ppm was prepared, and this artificial sewage was added to the device shown in Fig. 1. On the other hand, chromium, manganese, iron, copper, or zinc ions were added to the above control to 1 ppm, and the current change was measured in the same manner. The effect of heavy metal ions on the measurement was examined using a relative value where the amount of change in current was 100. The results are shown in Table 1 below. Manganese, iron, copper and zinc ions did not affect the measurement, and the effects of chromium ions were very slight.
[0021]
[Table 1]

[0022]
Examples and correlation test examples (measurement of BOD values for river water)
Actual river water was collected from one location on the Watarase River and two locations on the Kinugawa River as test sample water, and BOD was measured using the measurement method according to the present invention and the conventional dilution method. When the value was 100%, the ratio of the measured value according to the method of the present invention was examined.
The results are as shown in Table 2 below, and the measured values obtained by both methods are very close to each other. Therefore, it was found that the measuring method according to the present invention is applicable to actual measurement.
[0023]
[Table 2]

[0024]
【The invention's effect】
The BOD measurement method according to the present invention is simple and does not require skill when compared with the conventional measurement method, and the measurement time is 1 to 10 minutes compared to the conventional method of about 5 days. The respiration activity of Pseudomonas putida 10G, an aerobic microorganism used for carrying out this, is extremely short, and is hardly affected by chloride ions or heavy metal ions, and the detection limit is 0.25 ppm. Therefore, sample water can be used as sample water, such as river water with salt and river water with heavy metals.
[Brief description of the drawings]
FIG. 1 is a schematic view showing a BOD measuring apparatus according to the present invention.
FIG. 2 is a graph showing the relationship between the BOD value and the amount of change in current, and can be used as a calibration curve.
FIG. 3 is a graph showing the relationship between the chloride ion concentration in the sample water and the amount of change in current.
[Explanation of symbols]
10: BOD measuring device,
12: BOD sensor,
14: Container for holding sample water,
16: recording device,
S: Sample water.

Claims (2)

A highly sensitive BOD, characterized in that a carrier on which 10 g of aerobic microorganism Pseudomonas putida 10G is immobilized is arranged on the cathode side of the oxygen electrode and the amount of change in the output current from the oxygen electrode is measured. sensor.   BOD characterized by placing a microorganism membrane on which Pseudomonas putida 10G is immobilized on the cathode side of the oxygen electrode, measuring the amount of change in the output current from the oxygen electrode, and comparing it with a calibration curve prepared in advance. Sensitive measurement method.

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