JPH04337453A - Method for quickly measuring bod and microorganism electrode to be used therefor - Google Patents

Abstract

PURPOSE:To obtain the method for measuring BOD in the liquid to be measured accurately, quickly and easily, and provide microorganism electrode to be used therefor. CONSTITUTION:In a method for measuring BOD quickly, a microorganism electrode comprising the microorganism film 11, which is formed by adhering multiple kinds of microorganism 17 belong to at least any one of bacillus genus, pseudomonas genus, Escherichia genus, streptmyces genus, mycobacterium genus to a single layer or two layers of porous film 12 made of high molecular material such as cellulose nitrate or polyvinylidene fluoride so that organic suspended matter and organic decomposed component are also to be the base, is used.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rapid BOD measurement method and a microbial electrode used therein, and more particularly, to a method for rapidly measuring BOD and a microbial electrode used therein. The present invention relates to a rapid BOD measurement method that can accurately, simply and quickly measure the BOD (biochemical oxygen demand) of a liquid to be measured, and a microbial electrode used therein. [Prior Art] Regarding the BOD measurement method, Japanese Industrial Standards (Industrial Wastewater Test Method JIS K 0102-198)
6) is specified in detail. [0003] This method measures the decrease in dissolved oxygen after leaving wastewater at 20°C for 5 days, and it takes 5 days to determine whether or not the wastewater is within standards before the measurement results are known. Until then, the wastewater had to be stored strictly as is (hereinafter referred to as the "official 5-day method"). [0004] Furthermore, in the case of this official 5-day method,
The BOD in the sample water is predicted so that the amount of consumed oxygen used for assimilation by bacteria during 5 days will be 40 to 70% of the initial dissolved oxygen of the dissolved oxygen saturated in the sample water. It is necessary to prepare the concentration in advance. For this purpose, the saturated dissolved oxygen concentration of water must be 8.84 mg at 20°C.
/g, so in order to reduce the amount of oxygen consumed to 40-70%, it must be diluted to about 3.5-6.2 mg/liter, which poses operational difficulties. In order to improve measurement accuracy, a skilled measurer is required, and furthermore, since it is a batch method, automation is impossible. [0005] Therefore, in order to solve the above-mentioned problems found in the official 5-day method, a microbial electrode was used to measure BOD.
A variety of methods have been proposed to rapidly measure . One of these rapid BOD measurement methods involves flowing a neutral buffer solution into a measurement cell equipped with a microbial electrode to maintain neutral conditions, and also blowing air into the measurement cell to maintain a neutral condition. The solution to be measured is supplied under oxygen-saturated conditions, and the amount of dissolved oxygen decreased in the measurement cell corresponding to the BOD component in the solution to be measured, that is, the amount of dissolved oxygen consumed by microbial metabolism. The amount of oxygen is detected as the output of the diaphragm type oxygen electrode, and the current or voltage output when a standard solution with a known BOD is supplied instead of the liquid to be measured is used as a reference, and the output and BOD are measured at each predetermined measurement step. This is done by calibrating a calibration curve with FIG. 11 shows an example of a system configuration of an apparatus used to carry out the above BOD rapid measurement method. According to the figure, a liquid to be measured 50, a plurality of types of standard liquids 51 whose BODs are known, and cleaning water 52 for suppressing slime generation are transferred to a roller pump via a valve switching means 22. 23, the liquid is selectively supplied into the thermostatic chamber 26 from one pipe line 24 side. [0009] The neutral buffer solution 53 is also used in the roller pump 23.
, the other pipe 25 is directly supplied into the thermostatic chamber 26 , and the one pipe 24 and the other pipe 25 are joined within the thermostatic chamber 26 , and the inside The liquid to be measured is saturated with oxygen by the air pump 27 in the presence of a neutral buffer solution, and is then measured via the microbial electrode 31 disposed within the measurement cell 28 . The liquid is discharged outside the main body 21 of the apparatus. [0010] Furthermore, the output from the microorganism electrode 31 is
Predetermined data processing is performed via the data processing means 30 and recorded as measurement data. In this case, as shown in FIG. 12, the microbial electrode 31 includes an anode electrode 35 and a cathode electrode 36 which are disposed in a cylinder 33 and immersed in an electrolytic solution 34, and which are in close contact with the cathode electrode 36. A diaphragm-type dissolved oxygen electrode 32 consisting of a diaphragm 37 that covers one open end surface of a cylindrical body 33, and a microbial membrane 38 disposed in close contact with the diaphragm 37 in this diaphragm-type dissolved oxygen electrode 32. has been done. FIG. 13 shows an example of the conventional structure of the microbial membrane 38 constituting the microbial electrode 31.
Trichosporon (Tri) is present in the space between the two porous membranes 39 and 41 that are spaced apart via the ring spacer 44.
A microorganism 43 consisting of a single yeast cell belonging to the genus Chosporon is encapsulated therein, and the porous membranes 39 and 41 in this case have a pore diameter of 0.45 to 0.
It has many holes of 6 μm and has a thickness of 120 to 150
μm Teflon membrane, nylon membrane, cellophane membrane,
A membrane made of cellulose acetate is used. FIG. 14 is an explanatory diagram schematically showing the relationship between the porous membranes 39 and 41 in the microbial membrane 38 and the encapsulated microorganisms 43.
A single bacterial cell of yeast belonging to the genus Chosporon (for example, about 100 to 2000 μm in length and 5 to 500 μm in width)
The microorganisms 43 consisting of pores of about 10 μm have a pore size of 0.
It is sealed and fixed in such a size that it cannot pass through porous membranes 39 and 41 having pores 40 and 42 of 45 to 0.6 μm. [0014] By the way, in the BOD rapid measurement method using the microorganism electrode 31 having the above structure, as is clear from the structure of the microorganism film 38 shown in FIG. 43 will be separated by porous membranes 40 and 42. [0015] Therefore, the microorganisms 43 are exposed to the porous membrane 40,
Even if an attempt is made to assimilate suspended solids in the liquid to be measured that are sufficiently larger than the pore diameter of 42, the porous membranes 40 and 42 prevent direct contact with the suspended solids, and the assimilation is not possible. Can not. Moreover, yeasts belonging to the genus Trichosporon, which are single bacteria (for example, Trichosporonctaneum IF
Microbial membrane 38 (O-10466) formed using
When using a microbial electrode 31 equipped with a "single bacterial membrane" (hereinafter referred to as a "single bacterial membrane"), among the organic substances that may exist in the liquid to be measured, apart from components that can undergo sufficient decomposition, For example, it has been difficult to assimilate insoluble components such as proteins, starches, and fats, making it impossible to accurately measure them. [0017] In this way, in the conventional BOD rapid measurement method, among the organic components of the liquid to be measured, only those that can be assimilated in a short time are the components to be measured (J
IS K3602-1990, page 9, “Scope of Application”), especially in liquids to be measured containing organic suspended matter, the accuracy may further decrease and in some cases the BO
There were inconveniences such as making D measurement impossible. This is due to the assimilation effect on the microbial film 38 constituting the microbial electrode 31 for organic substances, especially organic suspended matter, present in the liquid to be measured. This is due to the fact that there are limits. [Means for Solving the Problems] In view of the above-mentioned problems observed in conventional methods, the present invention has been developed to solve the above-mentioned insoluble organic components, which are excluded from the measurement target according to the above-mentioned JIS standards because they are difficult to assimilate in a short period of time. In particular, by incorporating suspended solids and persistent components into the measurement target, accurate BO that corresponds to the measurement results using the official 5-day method for organic components present in the liquid to be measured can be obtained.
The present invention aims to provide a rapid BOD measurement method capable of performing D measurement and a microbial electrode used therein. Among these, the structural feature of the BOD rapid measurement method according to the present invention is that oxygen is removed in the presence of a neutral buffer solution in a measurement cell equipped with a microbial electrode consisting of a diaphragm-type dissolved oxygen electrode and a microbial membrane. A BOD that measures the BOD of the liquid to be measured by supplying a liquid to be measured in a saturated state and comparing the output detected by the microbial electrode with the reference output when supplying a standard solution containing organic matter with a known BOD. In the rapid measurement method, the microbial membrane constituting the microbial electrode is a single-layer or double-layer porous membrane made of a polymeric material that contains microorganisms containing organic suspended matter and organic persistent components. The purpose is to use a material that is formed by adhering it so that it can also be coated. [0021] In the present invention, the liquid to be measured may be supplied into the measurement cell after a pretreatment step of adding an enzyme that decomposes organic substances that may be present in the liquid to be measured, or may be homogenized in advance. Further, the microorganism may be Bacillus (Bacillus).
lus), Pseudomonas
s) Genus Escherichia, Genus Streptomyces, Genus Mycobacterium
) A plurality of types belonging to at least one of the genuses can be suitably used. [0022] Furthermore, the structural feature of the microbial electrode used in this BOD rapid measurement method is that it is a diaphragm-type dissolved oxygen electrode in which a microbial membrane is closely fixed to the diaphragm. Bacillus produces enzymes that decompose and solubilize turbid suspended matter and persistent components.
illus), Pseudomonas
nas) genus, Escherichia
Genus, Streptomyces
) genus, Mycobacterium
m) It is formed by attaching a plurality of types of microorganisms belonging to at least one of the genus to a single-layer or double-layer porous membrane made of a polymeric material such as cellulose nitrate or polyvinylidene fluoride. [Embodiments] Hereinafter, embodiments of the present invention will be described with reference to the drawings. The system configuration of the device used for implementing the BOD rapid measurement method according to the present invention is shown in FIG.
1, and hereinafter, the same constituent members will be described using the same reference numerals. FIGS. 1 to 3 show a microbial electrode 3 according to the present invention.
1 shows an example of the structure of the microbial membrane 11 in No. 1, all of which are Bacillus that produces enzymes that decompose and solubilize suspended floaters and difficult-to-decompose components.
The porous membrane 12 made of a polymeric material such as cellulose nitrate or polyvinylidene fluoride contains a plurality of types of microorganisms 17 belonging to at least one of the genera Pseudomonas, Pseudomonas, and Escherichia. It is formed by being deposited in the pore structure. The porous membrane 12 of the present invention made of a polymeric material such as cellulose nitrate or polyvinylidene fluoride is
It maintains about 10 to 1000 times more microbial adhesion than Teflon membranes, nylon membranes, cellophane membranes, and cellulose acetate membranes used in conventional porous membranes 39 and 40. Among these, the microbial membrane 11 shown in FIG.
4 and a porous membrane material 13 disposed on the side in contact with the liquid to be measured, and a diaphragm shown in FIG. It is formed by attaching microorganisms 17 to each of the pores 13 and 16 of a two-layered porous membrane 12 comprising a porous membrane material 15 disposed on the side in contact with the membrane 37. The microbial membrane 11 shown in FIG. 2 also includes a porous membrane material 13 having a large number of pores 14 with a pore diameter of 2.5 to 10.0 μm and disposed on the side in contact with the liquid to be measured. , a porous membrane material 15 having a large number of pores 16 with a pore diameter of 0.2 to 0.5 μm and disposed on the side in contact with the diaphragm 37;
The pores 14 in the porous membrane 12 having a two-layer structure consisting of
microorganisms 17 are attached to each of them. Furthermore, the microbial membrane 11 shown in FIG.
Microorganisms 17 are attached to each of the pores 14 of a porous membrane 12 having a single layer structure. The selection of the microorganisms 17 (species) used in the microbial membrane 11 of the present invention, the material and shape of the porous membrane 12, and the method of attaching the microorganisms 17 to the porous membrane 12 determine the BO.
Regarding the D measurement method, even though it should be considered a different indicator from the official 5-day method, the BO of this official 5-day method
Accurate estimation of the D value is achieved by using the bacterial species group used in the official 5-day method, and by using the method shown in Figure 1 above, which can fully contact and assimilate suspended solids and persistent components in the sample to be measured. - This can be achieved by using the structure shown in FIG. [0029] The bacterial cells used as the microorganism 17 are not those found in natural soil or activated sludge, but are formed using a bacterial preparation that always contains the same amount of bacterial species. Since the microbial film 11 is always prepared under the same conditions, it is possible to produce the microbial film 11 under the same conditions. Regarding the shelf life of the microbial film 11 formed in this way, if it is an unused product, it can be stored in a sterilized plastic petri dish with a lid and stored in a cool, dark place in a desiccator for at least 6 months. It can be saved without. [0031] Furthermore, once the microbial membrane 11 has been moistened, if it is stored in a neutral buffer solution without contamination from the outside, it can be stored under good conditions at room temperature for 1 to 6 months. can do. On the other hand, the method of adhering the microorganisms 17 to the porous membrane 12 when forming the microbial film 11 is as follows: First, it is necessary to extract the microorganisms from the bacterial preparation without damaging them, so The amount is suspended in a neutral buffer solution, and the bacterial cells are separated and extracted while being washed several times using a centrifuge. [0033] This extracted microbial cell group is applied to the pores 14 of the porous membrane 12 made of a polymeric material having an area necessary for adhering to the surface of the cathode electrode 36 of the diaphragm-type dissolved oxygen electrode 32 of the microbial electrode 31. The microorganisms 17 are attached by a method such as vacuum filtration. This film is formed as a two-layer or single-layer microbial film 11 as shown in FIGS. 1 to 3, and this microbial film 1
By using a porous membrane 12 made of a polymeric material having a large number of pores 14 with a pore diameter of 2.5 μm or more on the surface in contact with the liquid to be measured in 1, a group of bacterial cells as microorganisms 17 is introduced into the liquid to be measured. must be brought into direct contact. By the way, the microbial membrane 11 of the present invention is produced by identifying several bacterial cell groups effective for BOD measurement from among the bacterial species contained in activated sludge, and using bacterial cells obtained from a bacterial preparation of the same species. Therefore, the previous JIS K 360
2-1990, as in the case of using activated sludge, the microbial flora changes over time, resulting in large changes in its responsiveness over time, making it different from the official 5-day method. However, this does include problems such as the inability to obtain a satisfactory correlation. However, in the present invention, the microbial membrane 11
The above-mentioned drawbacks can be solved and stable measurements can be performed by acclimatizing the sample for several hours to more than ten hours with aeration in a liquid to be measured to which neutral buffer solution 53 has been added, or a liquid of the same kind. be able to. On the other hand, when using a "single bacterial membrane" which is the conventional microbial membrane 38, there are the following disadvantages. [0038] In other words, the component contained in the liquid to be measured is not limited to just one type, but rather it usually contains many types of components, whereas fungi oxidize all the components in the same manner. Oxidation does not necessarily depend on the rate. For this reason, it is natural that a measurement method that shows a BOD value close to the BOD value by the official 5-day method for a liquid to be measured containing multiple components with different oxidation rates is the BOD value by the official 5-day method. It is possible to take a value close to , with good correlation. Table 1 below shows the BO according to the official 5-day method.
This shows an example of simulation estimation obtained assuming that the D measurement value is set at 100 mg/liter. "BOD5" in the table is the official 5-day method, and "mixed bacterial film" is the one shown in Figures 1 to 3. The microbial membrane 11 of the present invention shown in FIG. [Table 1] [0042] According to the above table, in the case of the "mixed bacterial membrane" which is the microbial membrane 11 of the present invention, in all samples, the BOD value measured by the official 5-day method was 5%. Whereas there was only a difference of about 10%, in the case of the conventional type of microbial film 38, ``single bacterial film'', there was a difference of 20 to 50% compared to the BOD measured value by the official 5-day method, depending on the sample.
%, and this also explains why the BOD measurement value using the microbial membrane 11 of the present invention is different from the BOD measured using the official 5-day method.
It can be confirmed that there is a good correlation with the measured values. Next, a BOD rapid device equipped with a "mixed bacterial membrane" which is the microbial membrane 11 of the present invention, and a "single bacterial membrane" which is a conventional type of microbial membrane 38 using a single bacterium Trichosporonctaneum. Table 2 shows the results of measurements conducted using a BOD rapid device equipped with a BOD system equipped with a BOD rapid device, and introducing a sample from a certain sewage treatment plant as the liquid to be measured, and the BOD value according to the official 5-day method. [Table 2] [0045] According to the above table, the measured value of the official 5-day method is 1
00%, for influent sewage, 83% has a "mixed bacterial film" and 37% has a "single bacterial film", and for sewage from which suspended suspended solids (SS components) have been removed, it has a "mixed bacterial film". 89% were ``membranes,'' 34% were ``single bacterial membranes,'' and furthermore,
For runoff water with low suspended solids (SS components),
``Mixed bacterial membrane'' accounted for 100%, and ``single bacterial membrane'' accounted for 63%. [0046] As a result, the "single bacterial membrane" includes the three types of measurement samples mentioned above, including not only suspended solids but also ultrafine suspended solids of 1 μm or less that pass through a glass fiber filter (GFP). It is also found that the reactivity of the components is weak. [0047] In addition, when estimating the BOD value by the official 5-day method from the results of the "mixed bacterial film" which gives a measurement value close to the BOD value by the official 5-day method, it is relatively easy to estimate the BOD value by the official 5-day method. It turned out that it can be done. Note that FIG. 4 shows a graph diagram regarding Table 2. Table 3 below shows the results of sewage samples from a certain sewage treatment plant: a "mixed bacterial membrane" which is the microbial membrane 11 of the present invention, and a "single bacterial membrane" which is the conventional type microbial membrane 38. FIG. 5 is a graph showing a comparison of the BOD values according to the results. [Table 3] According to this, the BOD value of "single bacterial membrane" is
It was confirmed that there was no big difference in either of the results with filtered water, but there was a big difference in the "mixed bacterial membrane". [0051] This fact suggests that the "mixed bacterial membrane" reacted with the SS component (suspended suspended solids component) in the influent raw sewage.
The difference between 21.1mg/liter and 10.7mg/liter in P filtered water
It is assumed that mg/liter is the BOD value of the SS component in the influent raw sewage. However, in the case of the "single bacterial membrane", no significant difference could be found between the influent raw sewage and 1 μm GFP-filtered water, and the measured values themselves were also lower than those of the "mixed bacterial membrane". was also very low, suggesting that there was almost no reaction with the SS components in the inflowing raw sewage. Next, BOD according to the present invention is carried out using the apparatus shown in FIG. 11 in which the microorganism electrode 31 having the structure shown in FIG.
The rapid measurement method will be explained. That is, the measurement cell 2 is equipped with a microbial electrode 31 consisting of a diaphragm-type dissolved oxygen electrode 32 and a microbial membrane 11.
8, a test solution brought into an oxygen-saturated state in the presence of a neutral buffer solution 53 is supplied, and at this time, the output detected by the microbial electrode 31 and the standard for supplying the organic matter-containing standard solution 51 with a known BOD are supplied. This is done by comparing the output and measuring the BOD of the liquid to be measured. In this case, a stirrer is provided in each of the liquid tank for the standard solution 51 and the liquid tank for the measured liquid 50, and the liquid is fed to the measurement cell 28 while stirring the content liquid. If so, it is possible to quickly stabilize the calibration curve and the measured values of the liquid to be measured. In this case, the microbial membrane 11 constituting the microbial electrode 31 suspends the microorganisms 17 in the porous membrane 12 made of a polymeric material such as cellulose nitrate or polyvinylidene fluoride. A material that is formed by adhering to it and capable of assimilating suspended solids and persistent components is used. In this case, if the liquid to be measured contains a high concentration of difficult-to-decompose components such as proteins, starches, and fats, the microbial membrane 38 as a "single bacterial membrane" used in the conventional method may Assimilation is impossible, and furthermore, even with the "mixed bacterial membrane" that is the microbial membrane 11 of the present invention, there may be a portion that is not assimilated in a short time and may not be measured. An enzyme that decomposes organic substances that can be used, for example, at least one of the genera Bacillus, Pseudomonas, Escherichia, Streptomyces, and Mycobacterium. It is preferable that the enzyme is supplied into the measurement cell 28 after a pretreatment process in which an enzyme produced by the enzyme is added. In this case, the assimilation ability of the microbial film 11 is increased by adding the following enzyme selected in consideration of the conditions described below to the liquid to be measured, and moreover, It becomes possible to measure values very close to those measured by the method. Examples of enzymes selected in this case are shown below.・Enzyme example■ Proteolytic enzyme Microbial ser
ine proteinase enzyme source Bacill
genus us, genus Escherichia, Pseudmo
nas genus, etc. ■ Starch degrading enzyme α-Amylase
Enzyme source Bacillus genus (e.g. Bacillus
us subtilis), etc.■ Starch-degrading enzymes
β-Amylase enzyme source Bacillus sp., P
Seudmonas genus, Streptmyces genus, etc. ■ Lipolytic enzyme Phospholipase
A2 enzyme source Escherichia sp., Myco
Bacterium genus, etc. ■ Lipolytic enzyme Ly
sophospholipase enzyme source Esc
Herichia genus [0060] The liquid to be measured 50 supplied to the device main body 21 side of the BOD rapid measuring device used for carrying out the method of the present invention is produced by a group of bacterial species attached to the porous membrane 12, One or more water-solubilized or hydrated enzymes that decompose proteins, starches, and fats are added to the sample in advance, and the amount added is extremely small, but the amount required for the reaction is used. Even if the amount is several times more than that, it has almost no effect on the obtained measured value; on the contrary, an undersized amount tends to be smaller than an appropriate measured value. Further, the appropriate addition amount can be determined without much effort by dividing the addition amount into several stages and performing rapid BOD measurement. An example of an experiment in which BOD measurement was performed by adding an enzyme is shown below. First, Table 4 below shows the difference between the "mixed bacterial membrane" which is the microbial membrane 11 of the present invention and the conventional type microbial membrane when an enzyme is added to a skim milk solution containing particulate protein as a constituent component. BO with “single bacterial membrane” which is 38
The D values are compared, and FIG. 6 is a graph thereof. [Table 4] Since the skim milk solution has very little SS component, the BOD value of the "single bacterial membrane" is higher than that of the "mixed bacterial membrane" in the absence of enzyme addition. higher than [0065] This suggests that the "single bacterial membrane" reacts more easily to dissolved skim milk than the "mixed bacterial membrane," but it is still significantly different from the measured value by the official 5-day method. It fell short. . It was also confirmed that when enzymes were added, the BOD values increased for both the "single bacterial membrane" and the "mixed bacterial membrane." However, for the "mixed bacterial membrane", no change was observed in the BOD value even if 1.0 mg/liter or more of the enzyme was added, and measurement results that were very close to those obtained by the official 5-day method were obtained. was confirmed. On the other hand, with regard to the "single bacterial membrane", if an excessive amount of enzyme was added, the BOD value greatly exceeded the official 5-day method, and it was found that there was a difficulty in having to adjust the amount added. let [0069] Table 5 below compares the BOD value of the "mixed bacterial membrane" which is the microbial membrane 11 of the present invention when enzymes are added to bonito flakes with the values measured by the official 5-day method. Yes, and FIG. 7 is a graph thereof. [Table 5] [0071] According to this, regarding the "mixed bacterial membrane",
It was confirmed that by adding 2.0 mg/liter of enzyme, a BOD measurement value that was extremely close to the measurement value of the official 5-day method could be obtained. On the other hand, if the suspended solids (solid matter) contained in the liquid to be measured 50 are relatively large compared to the size of the microorganisms 17 in the microorganism film 11,
By supplying the liquid to be measured into the measurement cell 28 after the solid substance has been previously pulverized using an ultrasonic homogenizer, the decomposition power of the enzyme and the assimilation power of the microbial film 11 can be improved. An example of an experiment in which a liquid to be measured was micronized using an ultrasonic homogenizer will be shown below. First of all, Table 6 below shows that after a sewage sample collected from a certain sewage treatment plant has been micronized using an ultrasonic homogenizer, the "mixed bacterial membrane" which is the microbial membrane 11 of the present invention and the conventional type The BOD value is compared with the "single bacterial membrane" which is the microbial membrane 38, and FIG. 8 is a graph thereof. [Table 6] [0076] According to this, it was confirmed that for both "mixed bacterial membrane" and "single bacterial membrane," the BOD value increases as the homogenization time increases. On the other hand,
It was also found that there was no significant numerical change after 10 minutes. Therefore, if homogenization is not performed for at least 10 minutes, BO according to the official 5-day method will not be processed.
It seems likely that it will not approach the D value. Furthermore, as explained earlier in Table 3 and FIG. The results of this experiment showed a large difference between the BOD value of the bacterial membrane and the fact that the mixed bacterial membrane reacted more with the SS components in the influent sewage than the single bacterial membrane. It is supported. Table 7 below shows that after the bonito flakes were pre-pulverized using an ultrasonic homogenizer, the "mixed bacterial membrane" which is the microbial membrane 11 of the present invention, and the "single bacterial membrane" which is the conventional type microbial membrane 38. FIG. 9 is a graph of the comparison. [Table 7] According to this, BOD due to "single bacterial membrane"
The measured value is after 9 minutes of homogenization processing time.
It is gradually increasing. On the other hand, the BOD measurement value for the "mixed bacterial membrane" shows almost no change when the homogenization time exceeds 9 minutes. [0083] On the other hand, the "single bacterial membrane" has 3 to 9
Homogenization time of 3 minutes did not allow sufficient assimilation, and
It takes 0 minutes of homogenization time to reach the same level of assimilation as when the "mixed bacterial membrane" has been homogenized for 3 minutes. This shows that even if the SS component is considerably refined, the "single bacterial membrane" has a significantly inferior assimilation ability. [0084] That is, the BOD value itself is higher for the "mixed bacterial membrane", and from this, the BOD value of the "mixed bacterial membrane" is higher.
It can be seen that the D value is deeply related to the assimilation ability of SS components. Furthermore, FIG. 10 shows that the SS component of inflowing sewage from a certain sewage treatment plant was 126 (
Fig. 3 is a graph obtained by measuring the BOD value using a "mixed bacterial membrane" for a treatment solution with an SS component of 98 (mg/liter) after homogenization for 9 minutes. According to the same figure, by using the "mixed bacterial membrane", the BOD can be achieved which almost matches the BOD measurement value by the official 5-day method, simply by atomizing the solid matter using an ultrasonic homogenizer for the inflowing sewage. I was able to get the value. Effects of the Invention As described above, according to the present invention, a porous membrane is used which has superior microbial adhesion properties compared to conventionally used acetyl cellulose membranes. , it is possible to attach microorganisms under conditions where they can directly contact the suspended solids and persistent components in the liquid to be measured. It is possible to perform BOD measurement with a small difference between them, and BOD can be measured quickly and accurately while maintaining correlation with the official 5-day method. [0088] Furthermore, in the case where an enzyme produced by a group of bacterial species attached to a porous membrane is added to the test liquid in the method of the present invention, the assimilation ability of the microbial membrane can be improved; In the case of using a liquid to be measured in which the solid matter has been made fine through a pre-modification treatment, the decomposition power of enzymes and the assimilation ability of microbial membranes can be further improved.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram schematically showing the basic structure of a microbial membrane constituting a microbial electrode according to the present invention.

FIG. 2 is an explanatory diagram schematically showing a modification of the microbial membrane shown in FIG. 1.

FIG. 3 is an explanatory diagram schematically showing another example of a microbial membrane constituting the microbial electrode according to the present invention.

FIG. 4 is a graph comparing the BOD values of the official 5-day method, mixed bacterial film method (invention), and single bacterial film method (conventional method), depending on the sample to be measured.

FIG. 5 is a graph comparing BOD values between a mixed bacterial film method (the present invention) and a single bacterial film method (conventional method) depending on the sample to be measured.

[Figure 6] Official formula 5 when enzyme is added to skim milk solution
Daily method, mixed bacterial film method (invention), and single bacterial film method (conventional method)
It is a graph diagram comparing BOD values with.

FIG. 7 is a graph comparing the BOD values between the official 5-day method and the mixed bacterial film method (invention) when enzymes are added to bonito flakes.

FIG. 8 is a graph comparing BOD values between a mixed bacterial film method (the present invention) and a single bacterial film method (conventional method) after homogenizing a sewage sample.

FIG. 9 is a graph comparing the BOD values of the mixed bacterial film method (invention) and the single bacterial film method (conventional method) after homogenizing bonito flakes.

FIG. 10 is a graph comparing the BOD values of the official 5-day method and the mixed bacterial film method (invention) for sewage samples before homogenization and after homogenization.

FIG. 11 is a schematic configuration diagram showing an entire system as an example of a BOD rapid processing device.

FIG. 12 is an explanatory diagram showing an example of the structure of a conventional microbial electrode.

13 is an explanatory diagram showing details of a microbial membrane constituting the microbial electrode of FIG. 12. FIG.

FIG. 14 is an explanatory diagram showing the detailed structure of the microbial membrane of FIG. 13.

[Explanation of symbols]

11 Microbial membrane 12 Porous membrane 13 Porous membrane material 14 Hole 15 Porous membrane material 16 holes 17 Microorganisms 21　Device body

Claims (8)

[Claims] Claim 1: A test liquid brought to an oxygen-saturated state in the presence of a neutral buffer is supplied into a measurement cell equipped with a microbial electrode consisting of a diaphragm-type dissolved oxygen electrode and a microbial membrane. In a BOD rapid measurement method, the BOD of the liquid to be measured is measured by comparing the output detected by the microbial electrode with the standard output when supplying a standard solution containing organic matter with a known BOD.
The microbial membrane constituting the microbial electrode has a single-layer or double-layer porous membrane made of a polymeric material that allows microorganisms to assimilate organic suspended matter and organic persistent components. A BOD characterized by using a BOD formed by adhering
Rapid measurement method. 2. The liquid to be measured is supplied into the measurement cell through a pretreatment operation of adding an enzyme that decomposes organic substances that may be present in the liquid to be measured.
The described BOD rapid measurement method. 3. The BOD rapid measurement method according to claim 1, wherein the liquid to be measured is supplied to the measurement cell after being subjected to a homogenization process for pulverizing solid matter in the liquid to be measured. 4. The microorganism is Bacillus.
lus), Pseudomonas
s) Genus Escherichia, Genus Streptomyces, Genus Mycobacterium
B according to any one of claims 1, 2, and 3, characterized in that the B is a plurality of types belonging to at least one of the genera B).
OD rapid measurement method. 5. A microbial electrode in which a microbial membrane is closely fixed to a diaphragm in a diaphragm-type dissolved oxygen electrode, wherein the microbial membrane contains an enzyme that decomposes and solubilizes organic suspended matter or persistent components. Bacillus that produces
llus), Pseudomonas
as) Genus, Escherichia
Genus, Streptomyces
Genus, Mycobacterium
) A microorganism characterized by being formed by adhering multiple types of microorganisms belonging to at least one of the following genera to a single-layer or double-layer porous membrane made of a polymeric material such as cellulose nitrate or polyvinylidene fluoride. electrode. 6. The microbial membrane has a pore size of 2.5 to 1.
A porous membrane material having a large number of pores with a diameter of 0.0 μm and disposed on the side in contact with the liquid to be measured, and a porous membrane material with a pore diameter of 2.5 to 10 μm.
It is characterized by being formed by attaching microorganisms to each of the pores of a two-layered porous membrane consisting of a porous membrane material having a large number of 0 μm pores and arranged on the side in contact with the diaphragm. The microbial electrode according to claim 3. 7. The microbial membrane has a pore size of 2.5 to 1.
A porous membrane material having a large number of pores with a diameter of 0.0 μm and arranged on the side in contact with the liquid to be measured, and a porous membrane material with a pore diameter of 0.2 to 0.5
microorganisms are attached to each of the pores of a two-layer porous membrane comprising a porous membrane material disposed on the contact side to the diaphragm and having a large number of pores of μm. The microbial electrode according to claim 3. 8. The microbial membrane has a pore size of 2.5 to 1.
4. The microorganism electrode according to claim 3, wherein the microorganism electrode is formed by adhering microorganisms to each of the pores of a single-layer porous membrane having a large number of 0.0 μm pores.