A BOD real-time online monitoring device

Abstract

The application discloses a BOD real-time online monitoring device and relates to the technical field of water quality monitoring.The device comprises two monitoring units, each of which comprises a water inlet pump, a biological reactor and a water outlet pump which are sequentially connected through pipelines; the biological reactor is a microbial electrolysis cell; the biological reactor comprises a closed shell, a cylindrical cathode and an anode which is arranged in the cathode are arranged in the shell, and an electroactive biofilm is grown on the anode; the water inlet pump is communicated with a water inlet of the shell, and the water outlet pump is communicated with a water outlet of the shell; a data acquisition module is electrically connected with the cathode and the anode; a data processing module is electrically connected with the data acquisition module; a display screen is electrically connected with the data processing module; and a power supply is used for supplying power to the cathode, the anode, the data acquisition module and the display screen. The application realizes real-time online monitoring of BOD.

Description

Technical Field

[0001] This invention relates to the field of water quality monitoring technology, and in particular to a real-time online BOD monitoring device. Background Technology

[0002] Whether from the perspective of strengthening supervision and reducing regional carbon emissions, or from the perspective of upgrading processes and realizing wastewater resource utilization, the real-time and accurate acquisition of key pollution indicators in water bodies is essential.

[0003] Biochemical oxygen demand (BOD) refers to the level of organic matter in water that can be utilized by microorganisms. It can be used to directly reflect carbon emissions and also largely reflects the potential for wastewater resource recovery. For wastewater treatment processes such as nitrification and denitrification, BOD is also one of the important process parameters affecting treatment efficiency.

[0004] However, traditional BOD testing methods require dilution and inoculation of collected water samples. The resulting diluted inoculum then needs at least five days for organic matter to be degraded by microorganisms. During this period, instruments such as dissolved oxygen meters, differential pressure gauges, and spectrometers are required to obtain the dissolved oxygen difference before and after biodegradation of the test solution, and finally convert it into the BOD value. The entire testing process is time-consuming, the monitoring system is complex, the land investment is large, and the measurement process is greatly affected by the operators and operating conditions, making it impossible to meet the process control and in-situ real-time online monitoring needs of the water environment in wastewater treatment. Summary of the Invention

[0005] The purpose of this invention is to provide a real-time online BOD monitoring device to solve the problems existing in the prior art and realize real-time online monitoring of BOD.

[0006] To achieve the above objectives, the present invention provides the following solution:

[0007] This invention provides a real-time online BOD monitoring device, comprising:

[0008] Two monitoring units are provided, each of which includes an inlet pump, a bioreactor, and an outlet pump connected in sequence by pipelines. The bioreactor is a microbial electrolysis cell, which includes a closed shell containing a cylindrical cathode and an anode inserted into the cathode. An electroactive biofilm grows on the anode. The inlet pump is connected to an inlet on the shell, and the outlet pump is connected to an outlet on the shell.

[0009] A data acquisition module is provided, wherein the cathode and the anode are electrically connected to the data acquisition module, and the data acquisition module is used to acquire the current generated on the anode.

[0010] A data processing module, which is electrically connected to the data acquisition module, is used to automatically calculate the BOD of the water sample in the bioreactor based on the current.

[0011] A display screen, electrically connected to the data processing module, is used to display the BOD;

[0012] A power supply is provided to power the cathode, the anode, the data acquisition module, and the display screen.

[0013] Preferably, it also includes an automatic control system, which includes a PLC programmable controller, and all the water inlet pumps and all the water outlet pumps are electrically connected to the PLC programmable controller.

[0014] Preferably, it also includes a housing, the middle of which is provided with a horizontal partition that divides the space inside the housing into an upper housing and a lower housing; the bioreactor is located in the lower housing, and the inlet pump, the outlet pump, the data acquisition module, the display screen and the power supply are located in the upper housing.

[0015] Preferably, an insulation shell and a heating plate are sequentially attached to the inner wall of the lower housing, and a cooling fan and a temperature sensor are installed in the lower housing; the heating plate, the cooling fan and the temperature sensor are electrically connected to the PLC programmable controller.

[0016] Preferably, the cathode is a titanium-based cathode; the anode is a carbon fiber brush anode.

[0017] Preferably, the housing is also provided with a manual switch for each of the water inlet pumps and each of the water outlet pumps, and each of the manual switches is electrically connected to the PLC programmable controller.

[0018] The present invention achieves the following technical effects compared to the prior art:

[0019] The BOD real-time online monitoring device of the present invention realizes real-time online monitoring of BOD. Attached Figure Description

[0020] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0021] Figure 1 This is a schematic diagram of the structure of the real-time online BOD monitoring device of the present invention;

[0022] Figure 2 This is a schematic diagram of the structure of the real-time online BOD monitoring device of the present invention;

[0023] Figure 3 This is a schematic diagram of the structure of the real-time online BOD monitoring device of the present invention;

[0024] Figure 4 This is a schematic diagram of the bioreactor in the real-time online BOD monitoring device of the present invention;

[0025] The components include: 1. Upper housing; 2. Display screen; 3. Lower housing; 4. Main drain pipe; 5. Second water inlet pipe; 6. First water inlet pipe; 7. Upper movable door; 8. Lower movable door; 9. Main power supply line; 10. Cooling fan; 11. Data acquisition module; 12. Data processing module; 13. Power supply; 14. First water inlet pump; 15. First drain pump; 16. Second water inlet pump; 17. Second drain pump; 18. Insulation shell; 19. Heating plate; 20. PLC programmable controller; 21. First bioreactor; 22. Second bioreactor; 23. First overflow pipe; 24. Second overflow pipe; 25. Water collection tank; 26. Temperature sensor; 27. Water inlet; 28. Cathode; 29. ​​Anode; 30. Overflow outlet; 31. Drain outlet; 32. Support leg. Detailed Implementation

[0026] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0027] The purpose of this invention is to provide a real-time online BOD monitoring device to solve the problems existing in the prior art and realize real-time online monitoring of BOD.

[0028] To make the above-mentioned objects, features and advantages of the present invention more apparent and understandable, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] like Figures 1-4 As shown, this embodiment provides a real-time online BOD monitoring device, including a housing, an automatic control system, a constant temperature system, a data acquisition module 11, a data processing module 12, a display screen 2, a power supply 13, and two monitoring units.

[0030] The box has a horizontal partition in the middle, which divides the space inside the box into an upper box 1 and a lower box 3. The upper box 1 has an upper movable door 7, and the lower box 3 has a lower movable door 8.

[0031] The two monitoring units are designated as a first monitoring unit and a second monitoring unit. The first monitoring unit includes a first inlet pump 14, a first bioreactor 21, and a first outlet pump 15 connected in sequence by pipelines. The second monitoring unit includes a second inlet pump 16, a second bioreactor 22, and a second outlet pump 17 connected in sequence by pipelines. Both the first bioreactor 21 and the second bioreactor 22 are microbial electrolysis cells. Both the first bioreactor 21 and the second bioreactor 22 include a closed shell, within which a cylindrical cathode 28 and an anode 29 inserted into the cathode 28 are disposed. An electroactive biofilm grows on the anode 29. An overflow port 30 is provided at the top of the shell, and multiple support legs 32 are provided at the bottom of the shell for supporting the shell. The overflow port 30 of the shell of the first bioreactor 21 is connected to the first overflow pipe 23, and the overflow port 30 of the shell of the second bioreactor 22 is connected to the second overflow pipe 24. The outlet of the first drainage pump 15, the outlet of the second drainage pump 17, the first overflow pipe 23, and the second overflow pipe 24 are all connected to the water collection tank 25, and a main drain pipe 4 is provided at the bottom of the water collection tank 25. The inlet port 27 on the shell is connected to the outlet of the corresponding water inlet pump, and the drain port 31 on the shell is connected to the suction port of the corresponding water inlet pump. The first water inlet pump 14 is connected to the first water inlet pipe 6, and the second water inlet pump 16 is connected to the second water inlet pipe 5. The cathode 28 is a titanium-based cathode, and the anode 29 is a carbon fiber brush anode.

[0032] It should be noted that the electroactive biofilm in this embodiment is formed by enriching and growing one or more genera of bacteria capable of extracellular electron transfer. The preferred embodiment is that the electroactive biofilm contains the genus *Geobacter anodireducens*. Electroactive biofilms are existing technology, but the actual cultivation methods vary. The electroactive biofilm in this embodiment must be pre-cultured in the laboratory, formed by inoculation with electrolyte from a pre-acclimated microbial electrolysis cell and alternating anaerobic and aerobic culture. The electrode arrangement in the electrolytic cell used for pre-acclimation and cultivation of mature microorganisms is the same as that in the bioreactor, but the volume of the electrolytic cell used for pre-acclimation and cultivation of mature microorganisms is larger. The criteria for determining the completion of supplementary cultivation are: ① After inoculation of the electroactive biofilm, second-generation 16S rRNA gene sequencing shows that the relative abundance of microorganisms capable of extracellular electron transfer in the electroactive biofilm, such as *Geobacter metalireducens*, *Geobacter lovleyi*, and *Geobacter anodireducen*, is >90%, with *Geobacter anodireducens* being the preferred option; ② After inoculation, the anaerobic and aerobic environments are switched at a frequency of 12–24 h / time, and during cultivation in a nutrient solution with BOD5 = 200 mg / L for 5–7 days, the maximum volumetric current density collected by the device is >350 A / m³. 3 (Peak current divided by the effective volume of the bioreactor shell).

[0033] In this embodiment, the first bioreactor 21 and the second bioreactor 22 are fixed in the lower housing 3, and the first inlet pump 14, the first outlet pump 15, the second inlet pump 16 and the second outlet pump 17 are all located in the upper housing 1. The constant temperature system is located in the lower housing 3, and the constant temperature system specifically includes an insulation shell 18, a heating plate 19, a cooling fan 10 and a temperature sensor 26. The main body of the lower housing 3 is the insulation shell 18, the heating plate 19 is attached to the inner wall of the insulation shell 18, the temperature sensor 26 is located in the lower housing 3, and the cooling fan 10 is located on the side wall of the lower housing 3. When the cooling fan 10 is turned on, it can exhaust the high-temperature air in the lower housing 3, thereby dissipating heat for the lower housing 3. The heating plate 19, the cooling fan 10 and the temperature sensor 26 are electrically connected to the PLC programmable controller 20. After the PLC programmable controller 20 obtains the actual temperature signal in the lower housing 3 measured by the temperature sensor 26, it compares it with the preset design temperature value. If the actual temperature value is greater than the design temperature value, the cooling fan 10 is turned on to dissipate heat. If the actual temperature value is less than the design temperature value, the heating plate 19 is turned on to heat. If the actual temperature value is equal to the design temperature value, the cooling fan 10 and the heating plate 19 do not need to be turned on.

[0034] The cathode 28 and anode 29 are electrically connected to the data acquisition module 11, which is used to acquire the current generated on the anode 29. The data processing module 12 is electrically connected to the data acquisition module 11, which is used to automatically calculate the BOD of the water sample in the bioreactor based on the current. The display screen 2 is electrically connected to the data processing module 12, which is used to display the BOD calculated by the data processing module.

[0035] The two bioreactors (i.e., the first bioreactor 21 and the second bioreactor 22) have different residence times. One operates in continuous flow mode, continuously outputting a changing current signal, while the other operates in intermittent flow mode, renewing the internal water sample when the current signal change caused by sample injection returns to the initial level. The interval between two sample injections in the intermittent flow bioreactor is 5–30 min, and the flow rate in the continuous flow bioreactor is 5–20 mL / min.

[0036] For a bioreactor operating in intermittent flow, the precise BOD (mg / L) value of the previous sample is calculated using formula (1) during the time period from t0 to t0+t. Formula (1) is as follows:

[0037] Among them, BOD a The precise BOD value from the previous sampling is given in mg / L; I represents the current data collected at regular intervals in mA; V is the effective volume inside the bioreactor in L; t is the time interval between two water sample updates in seconds; F is the Faraday constant, 96500 C / mol; σ q The BOD conversion coefficient, dimensionless, is obtained from model training for a single reactor. The resulting It curve serves as the calibration curve over the time span t. For a bioreactor operating in intermittent flow, samples are injected at time t0, and measurements are taken at time t. The current data during this period is denoted as I. Based on the above formula, the BOD data of the sample at time t0 can be obtained at time t0+t. a The test takes time t. This process cycles continuously with a period of t. That is, at time t0+t, the sample is emptied and injected again for the next test with a duration of t. At time t0+2t, the sample BOD data at time t0+t is obtained, and so on.

[0038] In a continuous flow bioreactor, water samples continuously flow in and out. Therefore, the current data of a continuous flow bioreactor is continuously monitored for t0 + t + x (denoted as t). x For a water sample taken at time t0, let the intermittent current curve from time t0 to time t0+t be the calibration curve I0. Then, according to formula (2), t0+t+x (denoted as t) can be calculated. x The BOD value of the water sample at time ) is given by formula (2) as follows:

[0039]

[0040] Among them, BOD x For t x The real-time BOD value at time t is in mg / L; t is the test time for the intermittent flow reactor in seconds; I tx For t x The current value at time t, in mA; I represents the current data of the calibration curve, in mA; The integral of the current curve (calibration curve) of the intermittent flow reactor from time t0 to time t0+t, in mC; For I tx The time corresponding to the intersection with the calibration curve, in seconds; Represents t0 to The integral of the calibration curve I at time; V is the effective volume inside the bioreactor, in L; t is the time interval between two water sample updates, in s; F is the Faraday constant, 96500 C / mol; σ i This is a dimensionless real-time area correction factor.

[0041] The advantages of using the above calculation method to calculate BOD in this embodiment are:

[0042] (1) Compared with the standard curve method, this embodiment calculates the current-time integral every t time of intermittent flow, and directly correlates the integral, that is, the charge value, with the BOD value. This method can be calibrated in situ and according to national standards.

[0043] Existing BOD analyzers typically use the standard curve method for calculation: a parameter is selected, and each BOD standard concentration corresponds to a parameter value. Three to five such correspondences are used to form a standard curve. During actual testing, the measured parameter value is substituted into the standard curve to calculate the corresponding BOD value. However, this method requires a series (3-5) concentrations of BOD standard samples for calibration, and then the corresponding parameter values ​​at different standard concentrations are tested separately. The calibration process is complex and cannot be calibrated in situ.

[0044] In this embodiment, an intermittent flow reactor is set up, and an integral calculation method is used to calculate a current-time integral every t of time. The integral, i.e. the energy value, is directly related to BOD. In this method, during calibration, it is only necessary to use the national standard method to test the BOD standard value of the corresponding time period, and then compare it with the energy parameter calculated for the corresponding time period to modify and correct the parameter.

[0045] (2) In this embodiment, the real-time parameters obtained by continuous flow can be used to calculate the real-time BOD value. Compared with other testing methods, the testing time is shorter and in-situ online monitoring can be achieved.

[0046] Other methods require several processes, including strain domestication and cultivation, dissolved oxygen consumption, and dissolved oxygen measurement. The BOD values ​​calculated after such processes are relatively untimely. However, this embodiment can calculate BOD values ​​in real time.

[0047] (3) In this embodiment, the real-time current parameters measured by the continuous flow are correlated with the calibration curve of the intermittent flow to ensure the accuracy and reliability of the real-time BOD data.

[0048] As can be seen from the calculation process, the time-current curve obtained from the most recent sampling test of the intermittent flow, which is the calibration curve, is used when calculating real-time BOD data. This calibration curve itself reflects the process of electroactive microorganisms consuming electrical energy to degrade organic matter in the bioreactor, and has practical physical significance. Using such a calibration curve in the calculation of real-time BOD data can shorten the BOD test time and improve the accuracy of BOD data.

[0049] The automatic control system includes a PLC programmable controller 20, and all inlet pumps and all outlet pumps are electrically connected to the PLC programmable controller 20.

[0050] Power supply 13 is used to supply power to cathode 28, anode 29, data acquisition module 11, data processing module 12, PLC programmable controller 20, water inlet pump, water outlet pump and display screen 2; power supply 13 is also connected to main power supply line 9, through which power supply 13 can be charged.

[0051] The first inlet pump 14, the first drain pump 15, the second inlet pump 16, the second drain pump 17, the data acquisition module 11, the data processing module 12, the display screen 2, and the power supply 13 are all housed in the upper housing 1. The housing also has manual switches for each inlet pump and each drain pump, and each manual switch is electrically connected to the PLC programmable controller 20. In this embodiment, the data processing module and the PLC programmable controller 20 can also connect wirelessly to terminals such as computers and mobile phones, allowing users to view data and perform remote control functions remotely.

[0052] Specific examples have been used to illustrate the principles and implementation methods of this invention. The descriptions of the above embodiments are only for the purpose of helping to understand the method and core ideas of this invention. Furthermore, those skilled in the art will recognize that, based on the ideas of this invention, there will be changes in the specific implementation methods and application scope. Therefore, the content of this specification should not be construed as a limitation of this invention.

Claims

1. A real-time online BOD monitoring device, characterized in that, include: Two monitoring units are provided, each of which includes an inlet pump, a bioreactor, and an outlet pump connected in sequence by pipelines. The bioreactor is a microbial electrolysis cell, which includes a closed shell containing a cylindrical cathode and an anode inserted into the cathode. An electroactive biofilm grows on the anode. The inlet pump is connected to an inlet on the shell, and the outlet pump is connected to an outlet on the shell. A data acquisition module is provided, wherein the cathode and the anode are electrically connected to the data acquisition module, and the data acquisition module is used to acquire the current generated on the anode. A data processing module, which is electrically connected to the data acquisition module, is used to automatically calculate the BOD of the water sample in the bioreactor based on the current. A display screen, electrically connected to the data processing module, is used to display the BOD; Power supply; the power supply is used to power the cathode, the anode, the data acquisition module and the display screen; It also includes an automatic control system, which includes a PLC programmable controller, and all the water inlet pumps and all the water outlet pumps are electrically connected to the PLC programmable controller. The system also includes a housing, with a horizontal partition in the middle dividing the internal space into an upper housing and a lower housing. The bioreactor is located in the lower housing, while the inlet pump, outlet pump, data acquisition module, display screen, and power supply are located in the upper housing. An insulation shell and a heating plate are sequentially attached to the inner wall of the lower housing, and a cooling fan and a temperature sensor are installed inside the lower housing. The heating plate, cooling fan, and temperature sensor are electrically connected to the PLC programmable controller. One bioreactor continuously receives and expels water samples, and is referred to as a continuous flow reactor. The other bioreactor periodically updates its water samples, and is referred to as an intermittent flow reactor. The data processing module calculates the accurate BOD value as a calibration curve based on the current-time integral within the update cycle of the intermittent flow reactor. The data processing module calculates the real-time BOD value of the continuous flow reactor based on the continuously collected real-time current values ​​and the calibration curve.

2. The BOD real-time online monitoring device according to claim 1, characterized in that: The cathode is a titanium-based cathode; the anode is a carbon fiber brush anode.

3. The BOD real-time online monitoring device according to claim 1, characterized in that: The housing is also equipped with manual switches for each of the water inlet pumps and each of the water outlet pumps, and each of the manual switches is electrically connected to the PLC programmable controller.

Images