A method for determining the dilution multiple of BOD detection and a monitor for implementing the method

Abstract

The present application relates to the technical field of environmental protection, and discloses a BOD detection method for determining dilution multiple and a monitoring instrument for realizing the method. The method provided by the present application can determine whether the dilution multiple of a diluted water sample is within a range before detecting the BOD concentration of the diluted water sample, so as to determine whether the concentration of the diluted water sample is within a detection range. When the dilution multiple of the diluted water sample is within the range, the BOD concentration of the diluted water sample is detected. When the dilution multiple of the diluted water sample is too large or too small, the diluted water sample is prepared again until the dilution multiple is within the range, and then subsequent detection is performed. The invalid process of detection is reduced, the efficiency of detection is improved, and the accuracy of detection is ensured. The monitoring instrument provided by the present application can realize automatic detection.

Description

Technical Field

[0001] This invention relates to the field of environmental protection technology, and in particular to a method for determining the dilution factor of BOD and a monitoring instrument for implementing the method. Background Technology

[0002] BOD (Biochemical Oxygen Demand) refers to the amount of dissolved oxygen consumed by microorganisms during the biochemical process of decomposing biodegradable organic matter in water under certain conditions. It is an important physicochemical parameter in water quality analysis and testing, and is one of the essential indicators for surface water, domestic sewage, and most industrial wastewater. It not only characterizes the biodegradability and pollution intensity of the water sample but also provides a reference for the design of water treatment structures. Since any BOD concentration detection method has a certain analytical range, when the concentration of the water sample exceeds this range (too high or too low), the analytical results will be inaccurate. Therefore, it is generally necessary to dilute the sample before measurement. However, existing BOD detection methods do not determine whether the concentration of the diluted water sample is within the range during the detection process. The determination of whether the concentration of the diluted water sample is within the range can only be made after the test is completed. If the concentration of the diluted water sample is found to be outside the range after testing, retesting is required, which undoubtedly increases the testing process. Summary of the Invention

[0003] The technical problem to be solved by the present invention is a method for detecting BOD that can determine whether the dilution ratio of a diluted water sample is within the specified range.

[0004] To address the aforementioned technical problems, this invention provides a method for determining BOD by dilution factor, comprising the following steps: S1: Prepare a diluted water sample with a dilution factor of n using the water sample to be tested and a blank water sample, where the dilution factor n is the reciprocal of the ratio of the volume of the water sample to be tested measured during preparation to the volume of the diluted water sample obtained during preparation. S2: The diluted water sample is continuously passed through the microbial membrane reactor, and the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor is detected at first set time intervals. ; S3: Any three consecutive measurements The values ​​are respectively , and ,when and The difference and and When the difference is greater than 0.1 mg / L, then... The detection time is recorded as the first moment. ; S4: Continue to pass the diluted water sample through the microbial membrane reactor from the first moment. After one minute, the dissolved oxygen content of the diluted water sample was measured three times sequentially after passing through the microbial membrane reactor. , and ,in and The detection interval and and The detection intervals are equal; S5: Calculate △ ={( - ) + ( - )} / 2; S6: If 0.5 mg / L ≤ △ If the concentration is ≤2.0 mg / L, the dilution factor of the diluted water sample is deemed to meet the requirements. Subsequently, the BOD concentration of the diluted water sample is measured, and the measured BOD concentration is multiplied by the dilution factor n to obtain the BOD concentration of the water sample to be tested. If △ If the concentration is <0.5 mg / L, the dilution factor of the diluted water sample is determined to be too large. Then, the diluted water sample is prepared again, and the dilution factor is reduced. Then, S2-S5 are repeated until the dilution factor of the diluted water sample meets the requirements. If △ If the concentration is >2.0 mg / L, the dilution factor of the diluted water sample is determined to be too small. The diluted water sample is then prepared again with a higher dilution factor. S2-S5 are then repeated until the dilution factor of the diluted water sample meets the requirements.

[0005] As a preferred embodiment of the present invention, in S6, the BOD detection method of the diluted water sample includes the following steps: Step 1: First, calibrate the microbial membrane reactor to detect the microbial membrane reaction coefficient K of the microbial membrane reactor; Step 2: Continuously pass a blank water sample through the microbial membrane reactor. Once the dissolved oxygen content of the blank water sample after passing through the reactor stabilizes, detect and record the dissolved oxygen content of the blank water sample after passing through the reactor. ; Step 3: Continuously pass the diluted water sample through the microbial membrane reactor. Once the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor has stabilized, detect and record the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor. ; Step 4: Calculate the dilution water sample = ( ) / K, thus obtaining the water sample to be tested. *n.

[0006] In a preferred embodiment of the present invention, in step one, a blank water sample is continuously passed through the microbial membrane reactor. Once the dissolved oxygen content of the blank water sample after passing through the microbial membrane reactor is measured to be stable, the dissolved oxygen content of the blank water sample after passing through the microbial membrane reactor is detected and recorded. Then, a standard solution with a BOD concentration of C is passed through the microbial membrane reactor. After the dissolved oxygen content of the standard solution stabilizes after passing through the microbial membrane reactor, the dissolved oxygen content of the standard solution after passing through the microbial membrane reactor is detected and recorded. Subsequently, the microbial film coefficient of the microbial film reactor was calculated to be K, K=( - C.

[0007] In a preferred embodiment of the present invention, after continuously passing the liquid through the microbial membrane reactor, the dissolved oxygen content of the liquid after passing through the microbial membrane reactor is detected at second predetermined time intervals. Any three consecutive measurements The values ​​are respectively , and ,when and The difference and and When the difference between the values ​​is less than 0.02 mg / L, it is determined that the dissolved oxygen content of the liquid is stable after passing through the microbial membrane reactor.

[0008] As a preferred embodiment of the present invention, when the dissolved oxygen content of the liquid after passing through the microbial membrane reactor is determined to be stable, the value at this time is calculated. , and The average value is taken as the value of the dissolved oxygen content after the liquid passes through the microbial membrane reactor and stabilizes.

[0009] As a preferred embodiment of the present invention, in S1, the water sample to be tested is continuously passed through the microbial membrane reaction tube, so that a microbial membrane is formed on the inner wall of the microbial membrane reaction tube, thereby forming a microbial membrane reactor.

[0010] Meanwhile, the present invention also provides a monitoring instrument for implementing the above-mentioned method for determining the dilution factor of BOD detection: comprising a constant temperature water bath device, a sampling cup, a water sample container, a reagent bottle, a microbial membrane reaction tube, a flow container, a dissolved oxygen electrode, and a controller. The constant temperature water bath device is equipped with a tap water inlet pipe, which has a first valve. The constant temperature water bath device is also equipped with a drain outlet and a first liquid level sensor for detecting the liquid level within the constant temperature water bath device. A second valve is located at the drain outlet. The sampling cup is equipped with an inlet, an outlet, and a liquid level sensor for detecting the liquid level within the sampling cup. The second liquid level sensor is located at the position. The infusion port is connected to the constant temperature water bath device through an infusion tube. A third valve is provided on the infusion tube. The inlet is connected to the water sample bucket through a first pump. The reagent bottle is connected to the constant temperature water bath device through a second pump. One end of the microbial membrane reaction tube is located inside the constant temperature water bath device. The flow container is provided with a detection port, an inlet, and an outlet. The dissolved oxygen electrode is inserted into the detection port. The inlet is connected to the other end of the microbial membrane reaction tube. The outlet is connected to the third pump. The controller is electrically connected to the dissolved oxygen electrode.

[0011] As a preferred embodiment of the present invention, the monitoring instrument further includes an oxygenation pump, the output end of which is connected to the internal structure of the constant temperature water bath device.

[0012] As a preferred embodiment of the present invention, the detector further includes a refrigerator, and the reagent bottle is disposed inside the refrigerator.

[0013] As a preferred embodiment of the present invention, the inner wall of the constant temperature water bath device is provided with a plurality of spirally arranged tube clamps, and the microbial membrane reaction tube is clamped on the tube clamps.

[0014] This invention provides a method for determining the dilution factor for BOD detection and a monitoring instrument for implementing the method. Compared with the prior art, the advantages of this method are as follows: The method provided by this invention can determine whether the dilution factor of the diluted water sample is within the range before detecting the BOD concentration of the diluted water sample, thereby determining whether the concentration of the diluted water sample is within the detection range. Only when the dilution factor of the diluted water sample is within the range can the BOD concentration of the diluted water sample be detected. If the dilution factor of the diluted water sample is too large or too small, the diluted sample is re-prepared until its dilution factor is within the range before subsequent detection is performed. This reduces invalid detection steps, improves detection efficiency, and ensures detection accuracy. The monitoring instrument provided by this invention can achieve automated detection. Attached Figure Description

[0015] Figure 1 This is a schematic diagram of the monitoring instrument provided by the present invention; Figure 2 yes Figure 1 A structural diagram of the flow container in the middle; In the diagram, 1. Constant temperature water bath device; 11. Tap water inlet pipe; 111. First valve; 12. First liquid level sensor; 13. Drain outlet; 131. First valve; 14. Heater; 15. Temperature sensor; 16. Pipe clamp; 17. Oxygen pump; 2. Sampling cup; 21. Infusion port; 211. Infusion tube; 212. Third valve; 22. Inlet; 23. Second liquid level sensor; 3. Water sample container; 31. First pump; 4. Reagent bottle; 41. Second pump; 42. Refrigerator; 5. Microbial membrane reaction tube; 6. Flow container; 61. Water inlet; 62. Water outlet; 63. Detection port; 64. Third pump; 65. Rinse cup; 7. Dissolved oxygen electrode; 8. Controller. Detailed Implementation

[0016] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0017] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., used to indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," and "third" are used for descriptive purposes only and should not be construed as indicating or implying relative importance.

[0018] A preferred embodiment of the present invention provides a method for determining BOD by dilution factor, comprising the following steps: S1: Prepare a diluted water sample with a dilution factor of n using the water sample to be tested and a blank water sample. The dilution factor n is the reciprocal of the ratio of the volume of the water sample to be tested measured during preparation to the volume of the diluted water sample obtained. That is, when preparing the diluted water sample, the sum of the volumes of the water sample to be tested and the blank water sample measured is divided by the volume of the water sample to be tested. S2: The diluted water sample is continuously passed through the microbial membrane reactor, and the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor is detected at first set time intervals. The formation process of the microbial membrane reactor is as follows: under a constant temperature of 37°C and air saturation, the water sample to be tested is continuously passed through the microbial membrane reaction tube. The microorganisms in the water sample grow layer by layer on the inner wall of the tube to build the microbial membrane reactor. The material of the microbial membrane reaction tube is at least one of carbon fiber, graphene, glass, polyethylene, polyvinyl chloride, polytetrafluoroethylene, polyurethane, nylon, quartz, and silicone. Its inner diameter is 3-30 mm and its length is 4-400 cm. S3: Any three consecutive measurements The values ​​are respectively , and ,when and The difference and and When the difference is greater than 0.1 mg / L, then... The detection time is recorded as the first moment. Because when the diluted sample passes through the microbial membrane reactor, the microorganisms in the reactor utilize the dissolved oxygen in the diluted water sample to degrade the organic matter in the diluted water sample, thereby consuming the dissolved oxygen in the diluted water sample. and The difference and and When the difference between the values ​​is greater than 0.1 mg / L, it can be considered that the microorganisms in the microbial membrane reactor have begun to contact the diluted water sample and produce a response. S4: Continue to pass the diluted water sample through the microbial membrane reactor from the first moment. After one minute, the dissolved oxygen content of the diluted water samples was measured three times sequentially after passing through the microbial membrane reactor. , and ,in and The detection interval and and The detection intervals are equal, allowing the microorganisms in the biofilm reactor to perform a preliminary degradation reaction on the diluted water sample within this minute. The difference in dissolved oxygen before and after the reaction can be used to preliminarily determine the biodegradation efficiency of the biofilm and thus determine whether the dilution ratio meets the requirements. S5: Calculate △ ={( - ) + ( - )} / 2, this value represents the dissolved oxygen content before and after the microbial degradation of the diluted water sample in the microbial membrane reactor. This difference can reflect the biodegradation efficiency. If the difference is large, it indicates that the biodegradation efficiency is high, which means that the BOD concentration of the diluted water sample is high. Conversely, if the difference is small, it indicates that the biodegradation efficiency is low, which means that the BOD concentration of the diluted water sample is low. This difference can be used to preliminarily determine whether the dilution ratio is appropriate. If it is not appropriate, it is necessary to choose to continue dilution or increase the volume of the water sample to be tested to avoid repeated measurements. S6: If 0.5 mg / L ≤ △ If the concentration is ≤2.0mg / L, it indicates that the BOD concentration of the diluted water sample is appropriate. Therefore, the dilution factor of the diluted water sample is deemed to meet the requirements. At this point, the measurement procedure is continued to detect the BOD concentration of the diluted water sample. The measured BOD concentration of the diluted water sample is then multiplied by the dilution factor n to obtain the BOD concentration of the water sample to be tested. If △ If the BOD concentration is <0.5 mg / L, it indicates that the BOD concentration of the diluted water sample is too low. Therefore, the dilution factor of the diluted water sample is determined to be too large. Subsequently, the diluted water sample is prepared again, increasing the proportion of the water sample to be tested, thereby reducing the dilution factor (relative to the previously prepared diluted water sample). Then, S2-S5 are repeated until the BOD concentration of the diluted water sample is appropriate (i.e., the dilution factor of the diluted water sample meets the requirements) to ensure the accuracy of the test results. If △ A BOD concentration >2.0 mg / L indicates that the diluted water sample has an excessively high concentration. Therefore, the dilution factor of the diluted water sample is determined to be too low. Subsequently, a new diluted water sample is prepared, increasing the proportion of the blank water sample to increase the dilution factor. This process is repeated from S2 to S5 until the dilution factor of the diluted water sample meets the requirements, ensuring that the BOD concentration of the diluted water sample is appropriate and thus guaranteeing the accuracy of the test results.

[0019] This detection method first prepares a diluted water sample, then continuously passes the diluted water sample through a microbial membrane reactor (BMRT). The dissolved oxygen content of the diluted water sample after passing through the BMRT is periodically measured using a dissolved oxygen electrode. When the difference between the first two measurements and the difference between the last two measurements are all greater than 0.1 mg, it indicates that the microorganisms in the BMRT have begun to contact the diluted water sample and respond. After one minute, the dissolved oxygen content of the diluted water sample after passing through the BMRT is measured three times sequentially. The difference in dissolved oxygen content before and after the diluted water sample flows through the BMRT is calculated. This difference is used to determine whether the dilution factor of the diluted water sample is within the acceptable range. If the dilution factor is within the acceptable range, the detection continues to determine the BOD concentration of the diluted water sample, and... The BOD concentration of the water sample to be tested is calculated based on the dilution factor of the diluted water sample. If the dilution factor is too low or too high, the diluted water sample is prepared again and adjusted according to the previous dilution factor. Then, the test is performed again until the dilution factor of the diluted water sample is within the range. This method can determine whether the concentration of the diluted water sample is within the detection range before testing the BOD concentration. Only when the dilution factor of the diluted water sample is within the range will the BOD concentration of the diluted water sample be tested. If the dilution factor of the diluted water sample is too high or too low, the diluted water sample is prepared again until its dilution factor is within the range before subsequent testing. This reduces invalid steps in the test, improves the efficiency of the test, and ensures the accuracy of the test.

[0020] For example, in S6, the method for detecting BOD in a diluted water sample includes the following steps: Step 1: First, calibrate the microbial membrane reactor to detect its biofilm reaction coefficient K. Specifically, continuously pass a blank water sample through the reactor. Once the dissolved oxygen content of the blank water sample after passing through the reactor stabilizes, measure and record the dissolved oxygen content. Then, a standard solution with a BOD concentration of C is passed through a microbial membrane reactor. After the dissolved oxygen content of the standard solution stabilizes after passing through the reactor, the dissolved oxygen content of the standard solution after passing through the reactor is measured and recorded. Subsequently, the microbial film coefficient of the microbial film reactor was calculated to be K, K=( - C. Since the response of microorganisms in the microbial reactor to the same concentration of standard solution changes little in a short period of time, this calibration step can be performed before determining whether the dilution factor of the diluted water sample meets the requirements. Step 2: Continuously pass the blank water sample through the microbial membrane reactor. Once the dissolved oxygen content of the blank water sample after passing through the reactor stabilizes, measure and record the dissolved oxygen content of the blank water sample after passing through the reactor. It should be noted that this step can be performed before determining whether the dilution ratio of the diluted water sample meets the requirements; Step 3: Continuously pass the diluted water sample through the microbial membrane reactor. Once the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor has stabilized, measure and record the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor. ; Step 4: Calculate the dilution of the water sample = ( ) / K, thus obtaining the water sample to be tested. *n.

[0021] In the above steps, after the liquid is continuously passed through the microbial membrane reactor, the dissolved oxygen content of the liquid after passing through the microbial membrane reactor is detected every second set time interval. Any three consecutive measurements The values ​​are respectively , and ,when and The difference and and When the difference is less than 0.02 mg / L, the dissolved oxygen content of the liquid is considered stable after passing through the microbial membrane reactor. At this point, the calculation... , and The average value is taken as the value of the dissolved oxygen content after the liquid passes through the microbial membrane reactor and stabilizes.

[0022] At the same time, such as Figure 1-2As shown, the present invention also provides a monitoring instrument for implementing the above-mentioned method for determining the dilution factor of BOD detection: it includes a constant temperature water bath device 1, a sampling cup 2, a water sample container 3, a reagent bottle 4, a microbial membrane reaction tube 5, a flow container 6, a dissolved oxygen electrode 7, and a controller 8. The constant temperature water bath device 1 is provided with a tap water inlet pipe 11, which is provided with a first valve 111. After opening the first valve 111, tap water (i.e., blank water sample) will be delivered into the constant temperature water bath device 1. The constant temperature water bath device 1 is provided with a drain outlet 13 and a first liquid level sensor 12 for detecting the liquid level in the constant temperature water bath device 1. A second valve 131 is provided at the drain outlet 13. When the second valve 131 is opened, the liquid in the constant temperature water bath device 1 can be discharged through the drain outlet 13. The sampling cup 2 is provided with an infusion port 21, an inlet port 22, and a second liquid level sensor 23 for detecting the liquid level in the sampling cup 2. The infusion port 21 is connected to an infusion tube. 211 is connected to the constant temperature water bath device 1. A third valve 212 is installed on the infusion tube 211. The inlet 22 is connected to the water sample container 3 via a first pump 31. The first pump 31 can pump the water sample from the water sample container 3 into the sampling cup 2. After opening the third valve 212, the water sample in the sampling cup will be transported into the constant temperature water bath device 1. The reagent bottle 4 is connected to the constant temperature water bath device 1 via a second pump 41. One end of the microbial membrane reaction tube 5 is located inside the constant temperature water bath device 1. The flow container 6 is equipped with… It has a detection port 63, an inlet 61, and an outlet 62. The dissolved oxygen electrode 7 is inserted in the detection port 63. The inlet 61 is connected to the other end of the microbial membrane reaction tube 5. The outlet 62 is connected to the third pump 64. The controller 8 is electrically connected to the dissolved oxygen electrode 7. The first liquid level sensor 12, the second liquid level sensor 23, the first pump 31, the second pump 41, the third pump 64, the first valve 111, the second valve 131, and the third valve 212 are all electrically connected to the controller 8.

[0023] In this monitoring instrument, tap water inlet pipe 11 can deliver tap water (blank water sample) to constant temperature water bath device 1. First pump 31 can deliver water sample in water sample bucket 3 to water sample cup, and then water sample in water sample bucket 3 can be delivered to constant temperature water bath device 1. The delivery volume of water sample and tap water is controlled by first liquid level sensor 12 and second liquid level sensor 23, thereby realizing the preparation of diluted water sample with specified dilution ratio. The inner wall of microbial membrane reaction tube 5 can generate microbial membrane by passing in the water sample to be tested, thereby forming a microbial membrane reactor. Second pump 41 can deliver standard solution in reagent bottle 4 to constant temperature water bath device 1. Third pump 64 can deliver liquid in constant temperature water bath device 1 to microbial membrane reaction tube 5 and flow container 6 in sequence, and finally discharge it. Dissolved oxygen electrode 7 can detect the dissolved oxygen content of liquid in flow container 6 in real time and feed it back to controller 8, thereby realizing real-time monitoring of dissolved oxygen content of liquid after passing through microbial membrane reaction tube 5. Through controller 8, automated detection can be realized.

[0024] For example, the monitor also includes an oxygenation pump 17, the output of which is connected to the interior of the constant temperature water bath device 1. The oxygenation pump 17 ensures that the liquid in the constant temperature water bath device 1 is saturated with air and that the liquid temperature in the constant temperature water bath device 1 is more uniform, so as to ensure the accuracy of the detection.

[0025] For example, the detector also includes a refrigerator 42, in which the reagent bottle 4 is placed. The refrigerator 42 is like a small refrigerator, which can keep the reagent bottle 4 at a low temperature.

[0026] For example, the inner wall of the constant temperature water bath device 1 is provided with a plurality of spirally arranged tube clamps 16, and the microbial membrane reaction tube 5 is clamped on the tube clamps 16, that is, the microbial membrane reaction tube 5 is located inside the constant temperature water bath device 1.

[0027] In this embodiment, the total volume of the constant temperature water bath device 1 is 2.5L. Two first liquid level sensors 12 are provided, arranged vertically. When the lower first liquid level sensor 12 just detects liquid, the volume of liquid in the constant temperature water bath device 1 is 1L; when the higher first liquid level sensor 12 just detects liquid, the volume of liquid in the constant temperature water bath device 1 is 2L. One second liquid level sensor 23 is provided, vertically adjustable on the sampling cup 2. By adjusting the position of the second liquid level sensor 23, the volume of liquid in the sampling cup 2 when it detects liquid can be adjusted. In other embodiments, multiple second liquid level sensors 23 can be provided, arranged vertically, to determine the volume of liquid in the sampling cup 2. This configuration allows the monitor to prepare diluted water samples with a dilution ratio of 3-40 times, and can measure approximately 0-800mg / L. The BOD concentration samples basically cover all actual water samples. In this embodiment, the constant temperature water bath device 1 is equipped with a heater 14 and a temperature sensor 15 for detecting the temperature inside the constant temperature water bath device 1. The temperature control target of the constant temperature water bath device 1 is preferably set to 36.5-37.0℃. The first pump 31 and the third pump 64 are peristaltic pumps, the second pump 41 is a micro pump, the flow rate of the third pump 64 is set to 2.7-4ml / min, and the flow rate of the first pump 31 is set to 10-250ml / min.

[0028] Example 1 of the monitoring instrument of the present invention is a detection example for calibrating a microbial membrane reactor.

[0029] In this testing example, a microbial membrane reactor was pre-cultured inside the microbial membrane reaction tube. The reactor was calibrated first, with the following steps: First, the first valve was opened, and tap water (i.e., a blank water sample) was supplied to the constant temperature water bath via the tap water inlet pipe. When the lower first liquid level sensor just detected the liquid, the first valve was closed. Then, the heater and oxygenation pump were turned on, and the target water bath temperature was set to 37.0℃. When the temperature sensor inside the constant temperature water bath detected that the water bath temperature reached 36.0℃... At ℃, the third pump is started. The third pump sequentially delivers tap water from the constant temperature water bath to the microbial membrane reaction tube and the flow container, finally draining into the rinsing cup 65. The flow rate of the third pump is set to 3.0 ml / min. At this time, the dissolved oxygen electrode continuously monitors the dissolved oxygen content of the tap water after passing through the microbial membrane reaction tube and feeds it back to the controller. The controller records the detection value every 15 seconds. To improve accuracy, the controller continuously takes the dissolved oxygen content measured by ten dissolved oxygen electrodes each time it records, calculates the average value, and records it as the detection value for that reading. In this detection example... During the test, at 8 minutes, the controller recorded a value of 6.77 mg / L; at 8 minutes and 15 seconds, the controller recorded a value of 6.76 mg / L; and at 8 minutes and 30 seconds, the controller recorded a value of 6.76 mg / L. It can be seen that in the three consecutive test records at 8 minutes, 8 minutes and 15 seconds, and 8 minutes and 30 seconds, the difference between the first two recorded values ​​and the difference between the last two recorded values ​​were all less than 0.02 mg / L, indicating that the dissolved oxygen content of the tap water after passing through the microbial membrane reactor had stabilized. At this point, the average of the three test values ​​was taken as 6.76 mg / L and recorded as... ; The second pump (with metering function) is then activated to transfer the standard solution (GGA = 5000 mg / L) from the reagent bottle to the constant temperature water bath. A diluted standard solution (relative to the standard solution in the reagent bottle) is prepared in the water bath to achieve a BOD concentration of 10 mg / L. Then, the 10 mg / L BOD standard solution from the water bath is sequentially passed through the microbial membrane reaction tube and flow container via the third pump and discharged into the rinsing cup 65. The controller records the detection value every 15 seconds. In this example, after 18 minutes of testing, the controller recorded a value of 4.96 mg / L. At 18 minutes and 15 seconds, the controller recorded a detection value of 4.97 mg / L; at 18 minutes and 30 seconds, the controller recorded a detection value of 4.96 mg / L. It can be seen that in the three consecutive detection records at 18 minutes, 18 minutes and 15 seconds, and 18 minutes and 30 seconds, the difference between the first two recorded values ​​and the difference between the last two recorded values ​​are all less than 0.02 mg / L. This indicates that the dissolved oxygen content of the standard solution with a BOD concentration of 10 mg / L has stabilized after passing through the microbial membrane reactor. At this point, the average of the three detection values ​​is taken as 4.96 mg / L and recorded as... The controller calculated K = (6.76 - 4.96) / 10 = 0.18, meaning the microbial film coefficient of the microbial film reactor in this test example is 0.18. Afterwards, the heater and aeration pump of the constant temperature water bath were shut off, and the third pump was set to high-speed reverse operation at a flow rate of 8.0 ml / min. After 5 minutes, the third pump was shut off, and then the second valve was opened to drain the constant temperature water bath. It is understood that if no test is performed for a long time after calibration, recalibration is required before the next test.

[0030] The second example of the monitoring instrument of the present invention is an example of testing a water sample to be tested.

[0031] It should be noted that in this testing example, the microbial film has been calibrated, and its biofilm reaction coefficient K is 0.18. In this testing example, the dissolved oxygen content of the blank water sample after passing through the microbial film reactor was first measured. The specific process is the same as in Detection Example 1. The detection process is the same. In this detection example, the detection record was obtained at 7 minutes and 30 seconds. The concentration was 6.56 mg / L. Then, a diluted water sample was prepared. The specific process was as follows: the first pump was turned on to pump the water sample from the sample container into the sampling cup. The second liquid level sensor was set to a height of 52.5 ml in the sampling cup. When the second liquid level sensor just detected liquid, the first pump was turned off, and then the third valve was opened to transfer the water sample from the sampling cup into a constant temperature water bath. A diluted water sample was then prepared in the constant temperature water bath, with a dilution factor of (1000 + 52.5) ​​ / 52.5 = 20.0 times. Then, the diluted water sample from the constant temperature water bath was pumped through the microbial membrane reactor and the flow container via the third pump and discharged into the rinsing cup 65. Finally, the diluted water sample was analyzed. The procedure for checking if the dilution ratio is within the acceptable range is as follows: The controller continuously monitors the dissolved oxygen concentration of the dilution water sample flowing out of the biofilm reactor and records the detection value every 10 seconds. In this detection example, at 15 minutes, the controller recorded a value of 6.51 mg / L; at 15 minutes and 10 seconds, the controller recorded a value of 6.38 mg / L; and at 15 minutes and 20 seconds, the controller recorded a value of 6.19 mg / L. It can be seen that in the three consecutive detection records at 15 minutes, 15 minutes and 10 seconds, and 15 minutes and 20 seconds, the difference between the first two recorded values ​​and the difference between the last two recorded values ​​are all greater than 0.1 mg / L. Therefore, 15 minutes and 20 seconds is recorded as the first moment. At this point, the third pump continues to pass the dilution water sample through the microbial membrane reactor. One minute later, the controller sequentially detects and records the dissolved oxygen content of the dilution water sample after passing through the microbial membrane reactor three times. The interval between the first two detection records is the same as the interval between the last two detection records. In this example, at 16 minutes and 20 seconds, the controller records a value of 6.05 mg / L; at 16 minutes and 35 seconds, the controller records a value of 5.83 mg / L; and at 16 minutes and 50 seconds, the controller records a value of 5.89 mg / L. It can be seen that at 16 minutes and 20 seconds, 16 minutes and 35 seconds, and 16 minutes and 50 seconds, the difference between the first two recorded values ​​and the difference between the last two recorded values ​​are all less than 0.5 mg / L. Therefore, it is determined that the dilution ratio of the dilution water sample is too high, and the dilution water needs to be prepared again. Next, the first pump is turned on again to pump the water sample from the water sample container into the sampling cup. The first pump is turned off just as the second liquid level sensor detects the liquid. The second liquid level sensor is located at a height of 52.5 ml in the sampling cup. Then, the third valve is opened, and the water sample in the sampling cup is transferred to the constant temperature water bath. At this time, the dilution factor of the diluted water sample in the constant temperature water bath is (1052.5+52.5) / (52.5+52.5) ​​= 10.5 times (the discharge of the constant temperature water bath was small before, so it can be ignored, and its error is within the allowable range). Then, the operation of determining whether the diluted water sample is within the range is performed again. The process is the same as described above, so it will not be repeated. This time, it is determined that the dilution factor of the diluted water sample is within the range, so the next step is to detect the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor. The specific process is as follows: While the third pump continues to discharge the diluted water sample from the constant temperature water bath through the microbial membrane reaction tube and flow container into the rinsing cup 65, the controller continuously monitors the dissolved oxygen concentration of the diluted water sample flowing out of the microbial membrane reactor and records the detection value every 15 seconds. In this detection example, at 25 minutes and 5 seconds, the controller recorded a detection value of 4.87 mg / L; at 25 minutes and 20 seconds, the controller recorded a detection value of 4.86 mg / L; and at 25 minutes and 35 seconds, the controller recorded a detection value of 4.87 mg / L. It can be seen that at 25 minutes and 5 seconds, 25 minutes and 20 seconds, and 25 minutes and 35 seconds, the difference between the first two recorded detection values ​​and the difference between the last two recorded detection values ​​are all less than 0.02 mg / L. Therefore, the average of the three detection values ​​is taken as 4.87 mg / L and recorded as... Then, the BOD of the diluted water sample was calculated as (6.56-4.87) / 0.18=9.4. Therefore, the BOD concentration of the water sample to be tested was 9.4*10.5=98.7mg / L. Finally, the heater and oxygenation pump of the constant temperature water bath were turned off, and the third pump was turned off at high speed in reverse. The reverse flow rate of the third pump was set to 8.0ml / min. After 5 minutes, the third pump was turned off, and then the second valve was opened to drain the constant temperature water bath.

[0032] The third example of the monitoring instrument of the present invention is another example of testing a water sample.

[0033] It should be noted that in this testing example, the microbial film has been calibrated, with a biofilm reactivity coefficient K of 0.18. In this testing example, the dissolved oxygen content of the blank water sample after passing through the microbial film reactor was measured. The specific procedures for preparing the diluted water sample, as well as the procedures for determining whether the dilution ratio of the diluted water sample is within the acceptable range, are the same as the corresponding procedures in Test Example 2. In this test example, the test record was obtained at 7 minutes and 40 seconds. The concentration was 6.88 mg / L. A diluted water sample was prepared using a constant temperature water bath with a dilution factor of 20. At 15 minutes and 40 seconds, it was determined to be the first moment. Then, at 16 minutes and 40 seconds, the controller recorded a detection value of 5.25 mg / L; at 16 minutes and 55 seconds, the controller recorded a detection value of 2.87 mg / L; and at 17 minutes and 10 seconds, the controller recorded a detection value of 0.75 mg / L. It can be seen that at 16 minutes and 20 seconds, 16 minutes and 35 seconds, and 16 minutes and 50 seconds, the difference between the first two recorded values ​​and the difference between the last two recorded values ​​were all greater than 2.0 mg / L. Therefore, it was determined that the dilution factor of the diluted water sample was too small, and a new diluted water sample needed to be prepared. Then, the first valve was opened again, and water was added to the constant temperature water bath. Tap water is supplied until the highest level sensor just detects the liquid. The first valve is then closed, at which point the volume of liquid in the constant-temperature water bath is 2L. The dilution factor of the diluted water sample in the constant-temperature water bath is approximately 2000 / 52.5 ≈ 38.1 times (ignoring the previous discharge from the constant-temperature water bath, the error is within the allowable range). The process of determining whether the diluted water sample meets the range is then repeated, as described above. Since the dilution factor is now within the range, the next step is to detect the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor. The specific process is as follows: The dilution water sample from the constant temperature water bath is discharged into the rinsing cup 65 after passing through the microbial membrane reactor and the flow container via the third pump. The controller continuously monitors the dissolved oxygen concentration of the dilution water sample flowing out of the microbial membrane reactor and records the detection value every 15 seconds. In this detection example, at 28 minutes and 25 seconds, the controller recorded a detection value of 4.87 mg / L; at 25 minutes and 20 seconds, the controller recorded a detection value of 5.37 mg / L; and at 28 minutes and 45 seconds, the controller recorded a detection value of 5.38 mg / L. It can be seen that at 28 minutes and 25 seconds, 28 minutes and 40 seconds, and 28 minutes and 55 seconds, the difference between the first two recorded detection values ​​and the difference between the last two detection values ​​are all less than 0.02 mg / L. At this time, the average of the three detection values ​​is taken as 5.38 mg / L and recorded as... Then, the BOD of the diluted water sample was calculated as (6.88-5.38) / 0.18=8.3 mg / L, and the BOD concentration of the diluted water sample was 8.3*38.1=316.23mg / L. Finally, the heater and oxygenation pump of the constant temperature water bath were turned off, and the third pump was turned on in reverse at high speed. The reverse flow rate of the third pump was set to 8.0ml / min. After 5 minutes, the third pump was turned off, and then the second valve was opened to drain the constant temperature water bath.

[0034] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and substitutions can be made without departing from the technical principles of the present invention, and these improvements and substitutions should also be considered within the scope of protection of the present invention.

Claims

1. A method for determining BOD based on dilution factor, characterized in that: Includes the following steps: S1: Prepare a diluted water sample with a dilution factor of n using the water sample to be tested and a blank water sample, where the dilution factor n is the reciprocal of the ratio of the volume of the water sample to be tested measured during preparation to the volume of the diluted water sample obtained during preparation. S2: The diluted water sample is continuously passed through the microbial membrane reactor, and the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor is detected at first set time intervals. ; S3: Any three consecutive measurements The values ​​are respectively , and ,when and The difference and and When the difference is greater than 0.1 mg / L, then... The detection time is recorded as the first moment. ; S4: Continue to pass the diluted water sample through the microbial membrane reactor from the first moment. After one minute, the dissolved oxygen content of the diluted water sample was measured three times sequentially after passing through the microbial membrane reactor. , and ,in and The detection interval and and The detection intervals are equal; S5: Calculate △ ={( - ) + ( - )} / 2; S6: If 0.5 mg / L ≤ △ If the concentration is ≤2.0 mg / L, the dilution factor of the diluted water sample is deemed to meet the requirements. Subsequently, the BOD concentration of the diluted water sample is measured, and the measured BOD concentration is multiplied by the dilution factor n to obtain the BOD concentration of the water sample to be tested. If △ If the concentration is <0.5 mg / L, the dilution factor of the diluted water sample is determined to be too large. Then, the diluted water sample is prepared again, and the dilution factor is reduced. Then, S2-S5 are repeated until the dilution factor of the diluted water sample meets the requirements. If △ If the concentration is >2.0 mg / L, the dilution factor of the diluted water sample is determined to be too small. The diluted water sample is then prepared again with a higher dilution factor. S2-S5 are then repeated until the dilution factor of the diluted water sample meets the requirements.

2. The BOD detection method for determining dilution factor according to claim 1, characterized in that: In S6, the method for detecting BOD in the diluted water sample includes the following steps: Step 1: First, calibrate the microbial membrane reactor to detect the microbial membrane reaction coefficient K of the microbial membrane reactor; Step 2: Continuously pass a blank water sample through the microbial membrane reactor. Once the dissolved oxygen content of the blank water sample after passing through the reactor stabilizes, detect and record the dissolved oxygen content of the blank water sample after passing through the reactor. ; Step 3: Continuously pass the diluted water sample through the microbial membrane reactor. Once the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor has stabilized, detect and record the dissolved oxygen content of the diluted water sample after passing through the microbial membrane reactor. ; Step 4: Calculate the dilution water sample = ( ) / K, thus obtaining the water sample to be tested. *n.

3. The BOD detection method for determining dilution factor according to claim 2, characterized in that: In step one, a blank water sample is continuously passed through the microbial membrane reactor. Once the dissolved oxygen content of the blank water sample after passing through the reactor stabilizes, the dissolved oxygen content is measured and recorded. Then, a standard solution with a BOD concentration of C is passed through the microbial membrane reactor. After the dissolved oxygen content of the standard solution stabilizes after passing through the microbial membrane reactor, the dissolved oxygen content of the standard solution after passing through the microbial membrane reactor is detected and recorded. Subsequently, the microbial film coefficient of the microbial film reactor was calculated to be K, K=( - C.

4. The BOD detection method for determining the dilution factor according to claim 2, characterized in that: After continuously passing the liquid through the microbial membrane reactor, the dissolved oxygen content of the liquid after passing through the microbial membrane reactor is detected at second predetermined time intervals. Any three consecutive measurements The values ​​are respectively , and ,when and The difference and and When the difference between the values ​​is less than 0.02 mg / L, it is determined that the dissolved oxygen content of the liquid is stable after passing through the microbial membrane reactor.

5. The BOD detection method for determining dilution factor according to claim 4, characterized in that: When the dissolved oxygen content of the liquid after passing through the microbial membrane reactor is determined to be stable, calculate the value at this point. , and The average value is taken as the value of the dissolved oxygen content after the liquid passes through the microbial membrane reactor and stabilizes.

6. The BOD detection method for determining dilution factor according to claim 1, characterized in that: In S1, the water sample to be tested is continuously passed through the microbial membrane reaction tube, causing a microbial membrane to form on the inner wall of the microbial membrane reaction tube, thereby forming a microbial membrane reactor.

7. A monitoring instrument for implementing the BOD detection method for determining the dilution factor as described in claim 1, characterized in that: The system includes a constant temperature water bath, a sampling cup, a water sample container, a reagent bottle, a microbial membrane reaction tube, a flow container, a dissolved oxygen electrode, and a controller. The constant temperature water bath is equipped with a tap water inlet pipe with a first valve. The system also includes a drain outlet and a first level sensor for detecting the liquid level within the water bath. A second valve is located at the drain outlet. The sampling cup has an inlet, an outlet, and a second level sensor for detecting the liquid level within the sampling cup. The inlet is connected to a... The liquid tube is connected to the constant temperature water bath device. The infusion tube is equipped with a third valve. The inlet is connected to the water sample container through a first pump. The reagent bottle is connected to the constant temperature water bath device through a second pump. One end of the microbial membrane reaction tube is located inside the constant temperature water bath device. The flow container is equipped with a detection port, an inlet, and an outlet. The dissolved oxygen electrode is inserted into the detection port. The inlet is connected to the other end of the microbial membrane reaction tube. The outlet is connected to the third pump. The controller is electrically connected to the dissolved oxygen electrode.

8. The monitoring instrument according to claim 7, characterized in that: It also includes an oxygenation pump, the output of which is connected to the interior of the constant temperature water bath device.

9. The monitoring instrument according to claim 7, characterized in that: It also includes a refrigerator, inside which the reagent bottle is located.

10. The monitoring instrument according to claim 7, characterized in that: The inner wall of the constant temperature water bath device is provided with multiple spirally arranged tube clamps, and the microbial membrane reaction tube is clamped in the tube clamps.

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