WO2023207134A1

WO2023207134A1 - Organic wastewater bod test device and method, and application

Info

Publication number: WO2023207134A1
Application number: PCT/CN2022/139061
Authority: WO
Inventors: 郏建波; 杨倩; 赖明阳; 张钧源; 张杨; 徐晓龙; 刘长宇
Original assignee: 五邑大学
Priority date: 2022-04-25
Filing date: 2022-12-14
Publication date: 2023-11-02
Also published as: CN114894863A

Abstract

Disclosed in the present invention are an organic wastewater BOD test device and method, and an application. The device comprises a microbial fuel cell reactor comprising an anode chamber, a cathode chamber, and a wire; a cathode material and a cathode electron acceptor are provided in the cathode chamber, and the cathode electron acceptor comprises potassium ferricyanide; an anode material, microorganisms enriched on the anode material and an anode nutrient solution are provided in the anode chamber, and the anode nutrient solution comprises glucose, glutamic acid, a pH buffer system, mineral elements and vitamins; the anode material and the cathode material are both carbon felts; pretreatment steps for the carbon felts comprises: modifying the carbon felts by using strong oxidizing acid, then washing using water, and neutralizing until the washing liquid is neutral, and burning. The device can stably run for months, the measurement data has good reproducibility, and the stability is remarkably superior to that in conventional microbial electrode method and BOD5 assay method.

Description

An organic wastewater BOD detection device and its application and method

Technical field

The invention belongs to the technical field of water quality monitoring, and specifically relates to an organic wastewater BOD detection device and its application and method.

Background technique

Organic pollutants are a major aspect of water pollution. Biochemical oxygen demand (BOD) is a comprehensive indicator that reflects the content of organic pollutants in water. It is also a key indicator for measuring water quality to ensure environmental safety and human health. The current national standard method is the traditional five-day biochemical method. However, this method is a time-consuming and labor-intensive technology, which consumes a lot of time in the response process. In addition, cumbersome operations, low reproducibility, high maintenance costs, and the generation of large amounts of waste have also become its limiting factors. Therefore, this method is not suitable for process control and real-time monitoring of the water environment in daily wastewater (such as urban wastewater, domestic sewage and groundwater) treatment. Vigorously develop technologies that can be directly applied to water environment on-site and real-time biochemical oxygen demand monitoring to promote Current wastewater treatment methods and methods that help conserve water resources are of great significance.

The automatic online monitoring based on real-time biochemical oxygen demand values developed in recent years can effectively reflect the water quality change process and measure water quality conditions, which is more ideal than the traditional BOD detection process. A number of BOD biosensors aimed at shortening measurement times have been developed, including those based on bacterial respiration, immobilized bacterial oxygen consumption, enzymatic reactions in dead cells, and bioluminescence. These biosensors measure BOD over a short period of time, approximately 15 minutes to 1 hour, and show high correlation with BOD. However, most of these methods are complex, and the measurements are performed out of situ and cannot reflect real-time changes in water quality. Therefore, it is urgent to develop a new technology that is easy to operate, saves time, and has strong universal applicability to monitor BOD in water samples in real time. Among them, the research on BOD sensors based on the working principle of microbial fuel cells (MFCs) has also become the focus of researchers in recent years.

Microbial fuel cells (MFCs) are a type of device that uses microorganisms as anode catalysts to directly convert chemical energy into electrical energy. MFCs can directly degrade organic matter in water or sludge and convert the electrons generated by organic matter during microbial metabolism into electrical signals to obtain electrical energy. MFCs biosensors have obvious advantages compared to other types of biosensors; they are small in size, fast in response, high in accuracy, have good repeatability, can achieve continuous online monitoring, and usually do not require sample pretreatment, etc. The entire determination process is simple and fast, and automatic analysis is realized. These advantages are all realized in MFCs biosensing technology. At the same time, MFCs biosensors can use electrical signals for biosensing, making full use of the weak electrical energy generated by MFCs and realizing real-time online monitoring of organic wastewater, which has certain practical application value. Therefore, MFCs biosensing technology has good comprehensiveness, stability and energy recovery, and has broad application prospects.

Many studies in related technologies have shown that the BOD concentration in wastewater has a linear relationship with the output electrical signal of MFCs within a certain range. However, BOD detection devices in related technologies have many shortcomings such as poor stability and low accuracy, making them unable to meet the requirements for fast and accurate BOD detection in actual wastewater monitoring and treatment processes.

Contents of the invention

The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes an organic wastewater BOD detection device, which has excellent stability and high accuracy.

The invention also proposes the application of the above device.

The invention also proposes a detection method using the above device.

According to one aspect of the present invention, an organic wastewater BOD detection device is proposed, including a microbial fuel cell reactor. The microbial fuel cell reactor includes an anode chamber, a cathode chamber and wires. The anode chamber and the cathode chamber pass through the Wire connection;

Wherein, the cathode chamber is provided with a cathode material and a cathode electron acceptor, and the cathode electron acceptor includes potassium ferricyanide;

The anode chamber is provided with anode material, microorganisms enriched on the anode material and an anode nutrient solution. The anode nutrient solution contains glucose, glutamic acid, pH buffer system, mineral elements and vitamins. The pH buffer The system is used to adjust the pH of the anode nutrient solution to 6.0~8.0;

The anode material and the cathode material are both carbon felts. The pretreatment steps of the carbon felts include: modifying the carbon felts with a strong oxidizing acid; then washing with water, neutralizing until the washing liquid is neutral, and burning.

According to a preferred embodiment of the present invention, it has at least the following beneficial effects: Aiming at the shortcomings of existing microbial fuel cell-based BOD sensors such as high cost and low performance, the present invention proposes a new low-cost mediator-free dual sensor. Organic wastewater BOD rapid detection device for microbial fuel cells. This device uses potassium ferricyanide as the cathode electron acceptor, making full use of the characteristics of potassium ferricyanide with high redox potential, strong stability, and no by-products in the reaction. It improves the performance of the BOD sensor and can realize the detection of wastewater with high BOD concentration. Rapid detection, while the electrons gained from potassium ferricyanide are reduced to potassium ferrocyanide, and the cathode solution changes from yellow-green to colorless. The solution will cause less pollution to the diaphragm, which can ensure that the device can operate stably for a longer period of time. The carbon felt is modified by soaking it in a strong oxidizing acid, which improves the hydrophilicity of the electrode surface, thereby improving the electrochemical activity. At the same time, the wettability of the carbon felt surface can be significantly improved after acidification treatment with a strong oxidizing acid; after ignition After burning, the carbon felt is loose and porous. The carbon felt pretreated by the scheme of the present invention increases the specific surface area, porosity and oxygen-containing functional groups on the surface of the carbon felt, and has good stability, excellent conductivity, high specific surface area, Excellent electrochemical activity, and the surface can be pre-oxidized; using carbon felt as an electrode material can not only reduce costs, but at the same time, the carbon felt pretreated by the scheme of the present invention has a loose and porous structure with more voids inside. It increases the specific surface area of the electrode to a certain extent, allowing more microorganisms to attach and grow. It has high electrochemical activity, shortens the response time, and can achieve real-time online detection of BOD while also improving the accuracy of the detection results. (the actual domestic wastewater detection results have an error of less than 5% compared with the traditional five-day biochemical method), and its structure is also relatively stable, making the detection effect more stable and reliable. The start-up time of the BOD detection device using the solution of the present invention does not exceed 192 hours; it not only has a higher detection upper limit, but also has a wider linear range, and can accurately measure organic wastewater with a BOD concentration below 500 mg/L without dilution. There is a good linear relationship between BOD concentration and voltage in the range of 50 to 500mg/LBOD (linear correlation coefficient R ² =0.9967), which can achieve accurate quantification; response can be achieved within 5min to 3h, which has good application prospects in actual online monitoring. It breaks through the traditional BOD detection device that can only stay in the experimental stage; the device can run stably for several months, and the measurement data has good reproducibility, and its stability is significantly better than the traditional microbial electrode method and BOD ₅ determination method.

In some preferred embodiments of the present invention, the strongly oxidizing acid modification treatment is soaking treatment with a strong oxidizing acid, and the soaking time is 3 to 6 hours; preferably about 4 hours.

In some preferred embodiments of the invention, the strong oxidizing acid is nitric acid.

In some preferred embodiments of the present invention, the mass concentration of nitric acid is 30 to 40%.

In some preferred embodiments of the present invention, the mass concentration of nitric acid is approximately 34%.

In some preferred embodiments of the present invention, the nitric acid is prepared by diluting commercially available concentrated nitric acid in a volume ratio of about 1:1.

In some preferred embodiments of the present invention, the carbon felt is first dried and then burned.

In some preferred embodiments of the present invention, the drying process is constant temperature vacuum drying.

In some preferred embodiments of the present invention, the drying treatment temperature is 75 to 85°C.

In some preferred embodiments of the present invention, the drying process temperature is about 80°C.

In some preferred embodiments of the present invention, the drying treatment time is 10 to 14 hours.

In some preferred embodiments of the present invention, the drying treatment time is about 12 hours.

In some preferred embodiments of the present invention, the burning temperature is 580-620°C, and the burning time is 1.5-2.5 hours.

In some more preferred embodiments of the present invention, the burning temperature is about 600°C, and the burning time is about 2 hours.

In some preferred embodiments of the present invention, the heating rate of the burning is 1 to 3°C/min.

In some preferred embodiments of the present invention, the heating rate of the burning is about 2°C/min.

In some preferred embodiments of the present invention, the porosity of the carbon felt is not less than 90%.

In some more preferred embodiments of the present invention, the porosity of the carbon felt is between 90% and 98%.

In some more preferred embodiments of the invention, the carbon felt has a porosity of about 95%.

In some preferred embodiments of the present invention, the length, width and thickness of the carbon felt are 1.5-2.5cm, 1.5-2.5cm, and 0.5-1.5cm, respectively.

In some more preferred embodiments of the present invention, the length, width and thickness of the carbon felt are 2cm, 2cm, and 1cm in order.

In some preferred embodiments of the present invention, the working area of the carbon felt is 10 to 15 cm ² .

In some preferred embodiments of the present invention, the working area of the carbon felt is approximately 12 cm ² .

In some preferred embodiments of the present invention, the thickness of the carbon felt is 8 to 12 mm.

In some preferred embodiments of the present invention, the thickness of the carbon felt is approximately 10 mm.

In some preferred embodiments of the present invention, the distance between the carbon felts used as cathodes and anodes is 1 to 3 cm.

In some preferred embodiments of the invention, the distance between the carbon felts serving as cathode and anode is approximately 2 cm.

In some preferred embodiments of the present invention, in the startup phase, the microorganism is inoculated on the anode material through an inoculum solution. The preparation process of the inoculation solution includes the following steps: taking anaerobic activated sludge and mixing it with a pretreatment solution , sealed, shaken at constant temperature for 20 to 28 hours, and then deoxygenated; the pretreatment liquid contains glucose, glutamic acid, pH buffer system, mineral solution and vitamin solution. Using pre-treated inoculum solution for inoculation, the start-up time of the device can be as low as 96 hours. Using mixed strains in anaerobic activated sludge as the inoculum source of electrochemically active microorganisms has a wider range of use and linear range than microbial electrodes that use a single strain, and can measure multiple species within a larger concentration range. samples or samples with complex components.

In some preferred embodiments of the present invention, the oscillation at constant temperature is oscillation at 34-36°C and at a speed of 80-120 rpm.

In some more preferred embodiments of the present invention, the shaking at constant temperature is at about 35°C and at a speed of about 100 rpm.

In some preferred embodiments of the present invention, the BOD value of the pretreatment liquid is about 500 mg/L.

In some preferred embodiments of the present invention, a resistor is externally connected to the wire, and the resistance of the resistor is approximately 1000Ω. The output power density first increases with the increase of resistance. When the external resistance reaches 1000Ω, it reaches the maximum power density of 68mW/m ² , and then the power density begins to decrease as the external resistance further increases. This may be because the high external resistance limits the absorption of electrons through the circuit. Therefore, the present invention selects the external resistance to be 1000Ω to ensure the maximum output power density of MFCs. The external resistor when the MFCs output power is maximum can improve the accuracy of BOD detection.

In some preferred embodiments of the present invention, the pH buffer system in the anode nutrient solution is used to adjust the pH of the anode nutrient solution to 6.5-7.5.

In some preferred embodiments of the present invention, the pH buffer system in the anode nutrient solution is used to adjust the pH of the anode nutrient solution to about 7.0.

In some preferred embodiments of the present invention, the concentration of glucose in the anode nutrient solution is 0.3-0.4g/L.

In some preferred embodiments of the present invention, the concentration of glucose in the anode nutrient solution is approximately 0.375g/L.

In some preferred embodiments of the present invention, the concentration of glutamic acid in the anode nutrient solution is 0.3-0.4g/L.

In some preferred embodiments of the present invention, the concentration of glutamic acid in the anode nutrient solution is about 0.375g/L.

In some preferred embodiments of the present invention, the pH buffer system is a phosphate buffer system.

In some preferred embodiments of the present invention, the concentration of phosphate in the phosphate buffer system is 0.08-0.12 mol/L.

In some preferred embodiments of the present invention, the concentration of phosphate in the phosphate buffer system is about 0.1 mol/L.

In some preferred embodiments of the present invention, the mineral elements are added to the anode nutrient solution in a volume ratio of 1:70 to 90 through a mixed solution containing the following components:

In some preferred embodiments of the present invention, the vitamin is added to the anode nutrient solution in a volume ratio of 1:100 to 300 through a mixed solution containing the following ingredients:

In some preferred embodiments of the present invention, the concentration of potassium ferricyanide is 40-60 mmol/L.

In some preferred embodiments of the present invention, the concentration of potassium ferricyanide is about 50 mmol/L.

In some preferred embodiments of the present invention, the wire is titanium wire. As the wire that contacts the solution, the titanium wire has good corrosion resistance. During the operation of MFCs, the titanium wire is not easily corroded by the solution, will not enter the solution, and will not have a toxic effect on microorganisms, thus ensuring the safety of MFCs. stability.

In some preferred embodiments of the present invention, the diameter of the titanium wire is 0.5-1.5 mm.

In some preferred embodiments of the present invention, the diameter of the titanium wire is approximately 1 mm. Choose titanium wire with a diameter of 1mm as the wire in contact with the solution. The corrosion resistance of the titanium wire is good. During the operation of MFCs, the titanium wire is not easily corroded by the solution, will not enter the solution, and will not have a toxic effect on microorganisms, thus The stability of MFCs can be ensured.

In some preferred embodiments of the present invention, the microbial fuel cell reactor further includes a cation exchange membrane (CEM) for separating the cathode chamber and the anode chamber. The use of cation exchange membranes instead of expensive proton exchange membranes greatly reduces production costs. At the same time, it effectively ensures that there is no interference between the two reaction chambers, the device performance is more stable, and the data results are more reproducible. For real-time detection of wastewater BOD more advantageous.

In some preferred embodiments of the present invention, the cation exchange membrane is selected from CMI-7000 cation exchange membrane.

In some preferred embodiments of the present invention, the cation exchange membrane is pretreated through the following steps:

Hydrogen peroxide soaking treatment;

High temperature water immersion treatment;

Nitric acid high temperature soaking treatment;

High temperature water immersion treatment;

Store in a moisturized state until later use.

In some preferred embodiments of the present invention, the temperature of the high-temperature soaking treatment is 75-85°C.

In some preferred embodiments of the present invention, the temperature of the high-temperature soaking treatment is about 80°C.

In some preferred embodiments of the present invention, the time of the high-temperature soaking treatment is 0.5 to 1.5 hours.

In some preferred embodiments of the present invention, the time of the high-temperature immersion treatment is about 1 hour.

In some preferred embodiments of the present invention, during the pretreatment process of the cation exchange membrane, the mass concentration of hydrogen peroxide is 4 to 8%.

In some preferred embodiments of the present invention, during the pretreatment process of the cation exchange membrane, the mass concentration of hydrogen peroxide is about 5%.

In some preferred embodiments of the present invention, during the pretreatment process of the cation exchange membrane, the mass concentration of nitric acid is 8 to 12%.

In some preferred embodiments of the present invention, during the pretreatment process of the cation exchange membrane, the mass concentration of hydrogen peroxide is about 10%.

In some preferred embodiments of the present invention, the working area of the cation exchange membrane is 6 to 10 cm ² .

In some preferred embodiments of the present invention, the working area of the cation exchange membrane is approximately 7 cm ² .

In some preferred embodiments of the present invention, the volume of the microbial fuel cell reactor is 24-32 ml, in which the anode chamber and the cathode chamber are each 12-16 ml. The reactor volume of the solution of the present invention is only 28 ml, which is easy to carry and use.

In some preferred embodiments of the present invention, the volume of the microbial fuel cell reactor is 28 ml, in which the anode chamber and the cathode chamber are each 14 ml. The reactor volume of the solution of the present invention is only 28 ml, which is easy to carry and use.

According to another aspect of the present invention, the application of the above device in online BOD monitoring of organic wastewater is proposed.

The application according to a preferred embodiment of the present invention has at least the following beneficial effects: the solution of the present invention has good application prospects in online monitoring of BOD of organic wastewater.

According to another aspect of the present invention, an organic wastewater BOD detection method is proposed, including the following steps:

Add the water sample to be tested to the above-mentioned detection device, measure the output voltage generated by the detection device, and substitute the voltage value into the linear equation to calculate the BOD value.

The method according to a preferred embodiment of the present invention has at least the following beneficial effects: BOD is calculated directly based on the voltage value. Compared with the traditional method that requires converting voltage into electricity, the detection method of the present invention is simpler.

Description of the drawings

The present invention will be further described below in conjunction with the accompanying drawings and examples, wherein:

Figure 1 is a schematic structural diagram of the device according to Embodiment 1 of the present invention;

Figure 2 is a physical diagram of the microbial fuel cell reactor in Embodiment 1 of the present invention;

Figure 3 is a side view of the microbial fuel cell reactor of Embodiment 1 of the present invention;

Figure 4 is a diagram showing the start-up time test results of the device according to Embodiment 1 of the present invention;

Figure 5 is a diagram showing the open circuit voltage test results of the device according to Embodiment 1 of the present invention;

Figure 6 is a schematic diagram of the working principle of the microbial fuel cell reactor in Embodiment 1 of the present invention;

Figure 7 is a standard curve diagram measured in Example 2 of the present invention;

Figure 8 is a linear relationship diagram of simulated sample test data in Embodiment 2 of the present invention;

Figure 9 is a graph showing the test results of microbial activity under different BOD concentrations in Example 2 of the present invention;

Figure 10 is a graph showing voltage and power output results under different external resistances in Embodiment 2 of the present invention;

Figure 11 is a diagram showing the voltage and power output results under different pH in Example 2 of the present invention;

Figure 12 is a graph of stability test results in Example 3 of the present invention;

Figure 13 is a diagram showing the stability test results in Comparative Example 2 of the present invention.

Detailed ways

The concept of the present invention and the technical effects produced will be clearly and completely described below with reference to the embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without exerting creative efforts are all protection scope of the present invention. Unless otherwise stated, the test methods used in the examples are conventional methods; unless otherwise stated, the materials and reagents used are commercially available reagents and materials.

In the description of the present invention, unless otherwise explicitly limited, words such as connection should be understood in a broad sense. Those skilled in the art can reasonably determine the specific meaning of the above words in the present invention in combination with the specific content of the technical solution.

In the description of the present invention, reference to the terms "one embodiment," "some embodiments," "illustrative embodiments," "examples," "specific examples," or "some examples" is intended to be in conjunction with the description of the embodiment. or examples describe specific features, structures, materials, or characteristics that are included in at least one embodiment or example of the invention. In this specification, schematic representations of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials or characteristics described may be combined in any suitable manner in any one or more embodiments or examples.

In the description of the present invention, unless otherwise specified, the meaning of "about" means plus or minus 2%.

Example 1

This embodiment provides an organic wastewater BOD detection device and its application, as shown in Figure 1, including a microbial fuel cell reactor, a liquid supply system, a liquid drainage system and a signal acquisition device (a computer equipped with KickSart software). The fuel cell reactor (shown in Figures 2 and 3) includes an outer shell (made of plexiglass, with a volume of 28 ml) and an anode chamber located inside the outer shell (a cylindrical structure with a diameter of 3 cm, a height of 2 cm, and a volume of approximately 14 ml). type), cathode chamber (cylindrical configuration with a diameter of 3cm, a height of 2cm, and a volume of about 14ml), a cation exchange membrane that separates the anode chamber and the cathode chamber (working area of ^7cm2 ), and wires connecting the cathode chamber and the anode chamber. And a rheostat box externally connected to the wire; among them, the cathode chamber is equipped with cathode material (carbon fiber felt, referred to as carbon felt, 10mm (thickness) × 20mm × 20mm, working area 12cm ² ) and 50mmol/L iron as the electron acceptor Potassium cyanide solution; the anode chamber is equipped with anode material (carbon fiber felt, referred to as carbon felt, 10mm (thickness) 20mm × 20mm, working area 12cm ² ), microorganisms (electricity-producing bacteria) enriched on the anode material and anode nutrient solution .

Anodic nutrient solution, also known as anolyte or artificial wastewater (AWW). It serves as a nutrient for microorganisms during the start-up phase of MFCs, and as a liquid to be tested during the BOD detection phase.

In this example, artificial sewage is used as the anode nutrient solution. Each liter of artificial sewage contains: 0.375g/L glucose, 0.375g/L glutamic acid, 0.1mol/L phosphate buffer solution (0.1M PBS, pH 7.0), 12.5mL/L trace mineral solution and 5mL/L vitamin solution (the formulas of phosphate buffer solution, trace mineral solution and vitamin solution are shown in Table 1-3).

Table 1 Recipe of phosphate buffer solution

Table 2 Recipe of Trace Mineral Solution

Table 3 Recipe of vitamin solution

The prepared anodic nutrient solution is packed in a conical bottle, sealed with aluminum foil and placed in an autoclave for 30 minutes at a sterilization temperature of 121°C. The sterilized anodic nutrient solution is stored in the refrigerator at -4°C for later use.

The total volume of the MFCs reactor is 28 mL, and the volumes of the anode chamber and cathode chamber are both 14 mL. The separator uses CMI-7000 cation exchange membrane (CEM), and the working area of the membrane is 7 cm ² . The cathode and anode electrode materials are treated carbon felt with a thickness of 10mm, a porosity of 95%, and a working area of 12cm ² . The wire is made of titanium wire with a diameter of 1 mm, and the electrode carbon felt is connected through the titanium wire. The electrode distance between the anode and the cathode is 2 cm. There are two circular hole channels with a diameter of 10mm at the upper end of the cathode (anode) chamber, connected by silicone tubes, for the addition and discharge of fuel. The wires are connected to the resistance box (range: 0~9999Ω) and the Keithley multimeter to form a complete circuit. The Keithley multimeter is connected to the computer, and the data is continuously recorded through the KickSart software. All reactors were operated in a constant-temperature water bath at 35°C.

The electrode material is carbon felt, which is pretreated through the following steps:

First, soak the 10mm×20mm×20mm carbon felt in 1+1 nitric acid solution (commercially available concentrated nitric acid solution and water diluted 1:1 (vol/vol)) for 4 hours, and then modify it by soaking it in strong oxidizing acid. properties, improve the hydrophilicity of the electrode surface, thereby improving the electrochemical activity. At the same time, the wettability of the carbon felt surface can be significantly improved after nitric acid acidification treatment.

Then remove the carbon felt soaked in acid and clean it with deionized water, then soak it in 1.0 mol/L NaOH solution for 4 hours to neutralize the adsorbed acid, and finally wash it thoroughly with deionized water until the pH is neutral. . The cleaned carbon felt was dried in a constant temperature vacuum drying oven at 80°C for 12 hours.

Finally, seal the crucible and place it in a muffle furnace to burn for 2 hours at 600°C and a heating rate of 2°C/min. After cooling, it is used as an electrode material for MFCs.

The carbon felt pretreated by the above operations has excellent electrical conductivity, high specific surface area and superior electrochemical activity, and can be pre-oxidized on the surface; this not only increases the specific surface area, porosity and oxygen content of the carbon felt Functional groups, and make the carbon felt have good stability in the electrolyte.

The cation exchange membrane used in the above operation is pretreated through the following steps:

The two-chamber separator of MFCs uses CMI-7000 cation exchange membrane. First, soak the cation exchange membrane in 5wt% H ₂ O ₂ and keep it in a constant temperature water bath of 80°C for 1 hour to oxidize and clean the surface impurities of the cationic membrane; take out the membrane and place it in deionized water, and keep it in a constant temperature water bath of 80°C for 1 hour; then take out the membrane and place it in a constant temperature water bath of 80°C for 1 hour. 10wt% nitric acid solution, the same 80°C constant temperature water bath for 1 hour; finally placed in deionized water, 80°C constant temperature water bath for 1 hour; the processed cation exchange membrane was placed in ultrapure water for storage until later use.

The sludge inoculated with electrogenic microorganisms is the sludge from the anaerobic section of the secondary sedimentation tank of a sewage treatment plant in Jiangmen City (the anaerobic sludge is in a black granular state, and the sludge retrieved in a plastic bucket is stored in the 105 laboratory of the College of Continuing Education for sealed storage) . During the start-up phase of MFCs, artificial wastewater containing the above-mentioned anode nutrient solution and a BOD concentration of 500 mg/L was used as the inoculum solution. Put the anaerobic sludge and inoculation solution into a conical flask at a volume ratio of 1:1, and seal it with plastic wrap. It was pretreated by the following steps: place it in a constant-temperature shaker at 100 rpm and 35°C for 24 hours. The shaken mixture is used for inoculation. Before injecting into the anode chamber of MFCs, nitrogen gas needs to be passed to remove excess dissolved oxygen, and a peristaltic pump is used intermittently. Inject the inoculum solution into the anode chamber of MFCs in a certain manner. After the inoculum solution fills the anode chamber, the injection is paused, and the sample is injected again after the microorganisms have consumed the organic matter in the anode chamber (that is, the voltage first rises to the maximum value, and then the voltage slowly decreases. reaches the baseline value, replace the anode nutrient solution again, and perform the second cycle measurement). During the start-up period, the electron acceptor used in the cathode of MFCs is K ₃ [Fe(CN) ₆ ]. The cathode potassium ferricyanide solution is replaced once a day, and the potassium ferricyanide solution is freshly prepared and used every time. The size of the external resistor is 1000Ω. Continuously record the voltage generated by MFCs, as well as the maximum and average voltages every day. When the maximum and average voltages in each cycle reach stability and there is no significant change in the starting voltage curve, it means MFC _S starts successfully, that is, enough electricity-producing microorganisms have been enriched on the anode carbon felt. The specific testing process is as follows:

MFCs are inoculated with anaerobic activated granular sludge and fed with artificial wastewater as the nutrient solution. After each replacement of the MFCs anode inoculation solution, due to sufficient nutrients in the early stage, the electricity-producing microorganisms convert chemical energy into electrical energy during the degradation of organic matter. MFCs The voltage gradually rises to the peak; with the gradual reduction of nutrients and the continuous accumulation of metabolites, the voltage of MFCs shows a sharp downward trend; finally, the nutrients are slowly consumed, and the voltage value slowly drops to the baseline. The voltage peak of each cycle of MFCs is shown in Figure 4. As can be seen from Figure 4, as the startup time increases, the voltage peak of MFCs gradually increases and gradually becomes stable, with the peak voltage of the startup being approximately 550mV. At 96 hours, the starting voltage of MFCs basically reached a stable value, indicating that the carbon felt in the anode chamber was enriched with enough electricity-producing microbial communities, and the MFCs device was successfully started. Since the nutrients in the artificial sewage are sufficient, the injected anaerobic sludge and the artificial sewage are fully mixed evenly after shaking under constant temperature conditions, and the inoculation solution is replaced in time in each cycle. Therefore, the device according to the invention can be started successfully in 96 hours (if Inoculation with microorganisms without pretreatment requires 192h).

The open circuit voltage of MFCs is one of the important indicators to measure battery performance. After the MFCs reactor is started successfully, disconnect the external resistor to change the device from closed loop to open circuit state, and keep it in the open circuit state for 1 hour. Then use the electrochemical workstation to measure the open circuit voltage. During the measurement process, the working electrode clamps the anode. , the reference electrode and the auxiliary electrode sandwich the cathode, the time is set to 3600s, the sampling interval is 10s, and the open circuit voltage of the MFCs is measured 96 hours after startup. The results are shown in Figure 5. As can be seen from Figure 5, the open circuit voltage of the MFCs reactor tends to be stable in about 20 minutes, and the open circuit voltage is about 624mV, indicating that the MFCs start-up is successful and the device stability is good.

In the above device, the working principle of the microbial fuel reactor is shown in Figure 6:

MFCs are devices that use microorganisms as anode catalysts and can directly convert the chemical energy of degradable organic matter in wastewater into electrical energy. The device consists of loaded microorganisms (mainly electrogenic bacteria), anodes and cathodes. Its working process can be summarized as follows: the anode organic matter produces protons and electrons under the oxidation and decomposition of microorganisms, and the electrons are combined with NAD ⁺ through respiratory enzymes (NADH). It is transmitted within the cell, and then reaches the anode through extracellular electron transfer mechanisms such as wires, membrane protein contacts or electron mediators, and reaches the cathode through the external circuit. At the same time, the protons in the electrolyte are driven by the electric field force and concentration difference and are transferred from the anode chamber to the cathode. In the cathode chamber, electrons and protons undergo reduction reactions with the electron acceptor [Fe(CN) ₆ ] ^3- at the cathode.

The theoretical potential of microbial fuel cells is as follows:

Anode: C ₆ H ₁₂ O ₆ +6H ₂ O＝24e ^- +24H ⁺ +6CO ₂ E ⁰ ＝-0.428V (Formula 1-1)

Cathode: [Fe(CN) ₆ ] ^3- +e ^- =[Fe(CN) ₆ ] ^4- E ⁰ =0.361V (Formula 1-2)

By optimizing the types of microorganisms and the configuration of the reactor in the MFCs type BOD detection device, the present invention reduces the volume of the reactor to 14 ml, shortens the electrode spacing to 2 cm, uses carbon felt as the electrode material instead of expensive metal catalysts, and uses titanium wire as the conductor. Better corrosion resistance and reduced impact on microbial activity, thus obtaining a MFCs-type BOD detection device with high sensitivity, high stability and wide monitoring range, which can be used to measure BOD values in organic wastewater online or offline, greatly Improved monitoring levels.

This embodiment also provides the application of the above device in online or offline organic wastewater BOD monitoring. In online or offline organic wastewater BOD monitoring, the devices structured according to the embodiments of the present invention have good application effects. By optimizing the configuration of the device, selecting low-cost electrode materials and membrane materials, reducing the use of precious metal catalysts, rationally processing electrode materials and membrane materials, using potassium ferricyanide as the cathode electron acceptor, and using anaerobic granular sludge as the inoculation The liquid is enriched with electroactive microorganisms, shortening the start-up time of MFCs, achieving high stability and wide applicability of the MFCs-type BOD detection device, and realizing real-time online monitoring of organic wastewater BOD.

Example 2

This embodiment provides a method for detecting BOD of organic wastewater. The device constructed in the above embodiment is used for detection. The specific process is: adding the water sample to be tested into the anode chamber of the above detection device, and measuring the output generated by the detection device. Voltage, substitute the voltage value into the linear equation to calculate the BOD value.

The drawing process of the above linear equation (BOD standard curve) is as follows:

Prepare GGA solutions with different standard BOD concentrations (50, 100, 200, 300, 500mg/L) (commercially available, diluted and prepared with 0.1MPBS (pH 7.0) solution), use the MFCs reactor to detect the BOD concentration, and record them respectively. Output voltage (U) and response time (T), and linearly fit the voltage peak and BOD concentration of artificial sewage to obtain the corresponding linear equation, which is the BOD standard curve, as shown in Figure 7. As can be seen from Figure 7, the linear equation is y=0.9635x+52.1914, R ² =0.9967.

The above-mentioned water samples to be tested are simulated samples, specifically artificial sewage with different BOD concentrations (50, 100, 200, 300, 500, 1000 mg/L) (refer to the above concentration preparation: each liter of artificial sewage contains: 0.375g/L Glucose, 0.375g/L glutamic acid, 0.1mol/L phosphate buffer solution (0.1M PBS, pH 7.0), 12.5mL/L trace mineral solution and 5mL/L vitamin solution (phosphate buffer solution, The formulas of trace mineral solutions and vitamin solutions are shown in Table 1-3).

The test results of the simulated sample of 50-500 mg/L BOD are shown in Figure 8. It can be seen from Figure 8 that when AWW with different BOD concentrations is injected into the anode chamber, the electricity-producing microorganisms on the anode electrode quickly begin to degrade organic matter to generate voltage. , and the voltage value rises to the maximum value in a short period of time; as the BOD concentration increases, more organic matter can be degraded by microorganisms, resulting in a larger voltage value. When the BOD concentration is >500mg/L, the maximum voltage value gradually deviates from the linear relationship and is lower than the theoretical value. When the concentration of organic matter exceeds the needs of microorganisms, the number of microorganisms on the anode carbon felt and the limitation of the cation exchange membrane area make the proton transfer efficiency no longer increase linearly; at the same time, the continued increase in BOD concentration may cause metabolites such as organic acids in the system. The accumulation of ions leads to acidification of the anode chamber, resulting in a huge concentration difference, causing the electron acceptors of the cathode to reach the anode through the cation exchange membrane, thereby affecting the activity of the electricity-producing microorganisms on the anode carbon felt, reducing the electron transfer rate between the cathode and the anode, resulting in The maximum voltage gradually decreases. Therefore, when the wastewater BOD concentration is between 50 and 500 mg/L, the maximum voltage generated by MFCs can be used to detect the wastewater BOD concentration. Organic wastewater with a BOD concentration below 500 mg/L can be accurately measured without dilution. It only requires a simple injection operation. The output voltage signal value of the device is directly read through the program-controlled software connected to the multimeter. According to the linearity of the BOD standard curve obtained The BOD mass concentration of the sample to be tested can be calculated using the equation.

In order to verify the detection conditions, different detection conditions were verified:

1) Effect of BOD concentration of anode nutrient solution on microbial activity: Cyclic voltammograms (CV) were used to perform curve scanning on anaerobically cultured electrogenic bacteria during the voltage stabilization period to evaluate the electrochemical activity of the electrode biofilm. . In this study, CV curve scanning was performed on anode test solutions with different concentrations. The test found that the oxidation peak and reduction peak obtained by CV curve scanning became more obvious as the concentration of the test liquid increased. When it exceeded a certain concentration, the peak value did not change significantly. The test results of 50~500mg/LBOD are shown in Figure 9. It can be seen from Figure 9 that different concentrations of the test solution have a greater impact on the activity of anode electrogenic bacteria. The higher the solution concentration, the greater the area of the CV curve. The larger it is, the greater the amount of electron transfer, the stronger the electron transfer capability of the electrode, and the stronger the microbial activity. It also illustrates that when the concentration of the anolyte is within the range of the solution of the present invention, the obtained curve shows that the electrogenic bacteria enriched on the anode carbon felt have good electrochemical activity and can be used to conduct the next experiment.

2) The impact of different sizes of external resistance on the detection effect:

The external resistor when the MFCs output power is maximum can improve the accuracy of BOD detection. Measure the output voltage (U) of MFCs under the conditions of connecting different external resistors (Rext). Use GGA solution with a BOD concentration of 300 mg/L as the MFCs anolyte. Calculate the different external resistors according to the following formula (the external resistance values are 100 and 200 respectively. , 330, 510, 680, 1000, 1200 and 1500Ω) power density (P) of MFCs:

P＝U ² /Rext*A

In the formula: A is the surface area of the anode carbon felt electrode.

The test results are shown in Figure 10. It can be seen from Figure 10 that the power density first increases with the increase of resistance. When the external resistance reaches 1000Ω, it reaches the maximum power density of 68mW/m ² , and then the power density begins to decrease as the external resistance further increases. This may be because the high external resistance limits the absorption of electrons through the circuit. Therefore, the external resistance is preferably 1000Ω to ensure the maximum output power density of MFCs.

3) The impact of different pH on detection results:

By changing the BOD concentration of the anode nutrient solution and the pH of the anolyte, the impact on the performance of MFCs was explored, and the optimal detection conditions and detection range of BOD were determined.

The pH value is an important factor in biochemical reactions. If it is too high or too low, it will affect the microbial activity in the anode chamber and lead to the failure of the MFCs reactor. At the same time, during the process of microorganisms decomposing organic matter, organic acids and other substances will be produced, reducing the pH value of the solution. Therefore, a certain concentration of buffer solution should be added to the water sample to control the pH value of the solution. Using a GGA solution with a BOD of 300 mg/L as the anolyte and an external resistance of 1000Ω, the effect of a GGA solution with a pH value of 3.0 to 10.0 on the output voltage and power density of the MFCs reactor was investigated. The test results are shown in Figure 11. As can be seen from Figure 11, when the pH value is 7.0, the output voltage of MFCs is the highest, the power density is also the largest, and the signal stabilization time is the longest, which is most beneficial to the detection results. Therefore, during the later detection process, the pH value of the solution should be adjusted to about 7.0, which is most conducive to the growth of microorganisms.

4) Stability test:

Stability is one of the basic factors that must be considered when using the MFCs type BOD detection device for a long time. As shown in Figure 12, the stability of the MFCs-type BOD detection device is achieved by continuously operating 50, 100, 200, 300, and 500 mg/L BOD for more than 15 days. It can be seen from Figure 12 that during the test, the voltage output signal values of the MFCs type BOD detection device for different concentrations of BOD were stable. The average voltages corresponding to different concentrations of BOD were 101.27mV (50mg/L), 168.93mV (100mg/L), 241.67mV (200mg/L), 346.87mV (300mg/L) and 544.67mV (500mg/L), the standard deviations are ±5.31% (50mg/L), ±4.61% (100mg/L), ±4.80% ( 200mg/L), ±5.11% (300mg/L) and ±5.40% (500mg/L). In the following months, the test results remained relatively stable. It can be seen from this that the detection results of the device and detection conditions proposed by the present invention are stable and reliable.

During the test, it was also found that the electrical signal of the device according to the embodiment of the present invention responded quickly to the BOD concentration of organic wastewater (50-500mg/L), with the shortest response time of 5 minutes and the longest time not exceeding 180 minutes. The actual domestic wastewater detection results Compared with BOD ₅ , the relative error is within 5.0%. This result provides the possibility for the practical application of MFCs-type BOD biosensors in real-time measurement.

Example 3

This embodiment provides a method for detecting BOD of organic wastewater. The difference from Example 2 is that the water sample to be tested is actual organic wastewater (taken from four domestic sewage outfalls around a university in Jiangmen City).

Based on the MFCs type BOD detection device obtained in the above steps, the output voltage signal value of the artificial sewage is tested, and the BOD concentration of the actual organic wastewater is detected according to the standard curve drawn in Example 2.

Comparative example 1

This comparative example provides a BOD detection method for organic wastewater, which uses the traditional five-day biochemical method to detect and compare domestic wastewater from the same source.

The test results of Example 3 of the present invention and Comparative Example 1 are summarized in Table 4 below:

Table 4

As can be seen from the above table, using the traditional five-day biochemical method and the detection device constructed in the present invention, the relative deviations of the detection results are both <5%, indicating that the detection results of the two methods are basically consistent and can meet the requirements of BOD analysis accuracy. At the same time, It shows that the device of the embodiment of the present invention has high reliability and strong applicability.

Comparative example 2

This comparative example provides an organic wastewater BOD detection device. The difference from Example 1 is that: the anode chamber and the cathode chamber are hexahedral in shape and have a volume of 30 mL respectively; the anode nutrient solution does not contain glutamic acid and has a high concentration of 10 mmol/L. Potassium manganate is the cathode electron acceptor, both poles are made of graphite felt, and a proton exchange membrane (commercially available Nafion 117) is used as the separation membrane. The startup time was measured to be 240h and the response time was more than 10h. The stability data measured with reference to Example 2 is shown in Figure 13. It can be seen from Figure 13 that the operating stability of the device is poor.

The basic starting point of the device of the embodiment of the present invention is to improve the power generation capacity of MFCs and reduce the huge power consumption during wastewater treatment. At the same time, it shortens the BOD detection time and improves the BOD detection range. A double-chamber MFCs-type BOD without mediator was constructed using the anaerobic section activated granular sludge as the inoculation source, potassium ferricyanide solution as the cathode electron acceptor, and the cation exchange membrane instead of the expensive proton exchange membrane as the separator of the cathode and anode chambers. detection device, while also selecting and optimizing the measurement conditions of the MFCs-type BOD detection device. By optimizing the pH value of the anode nutrient solution, the size of the external resistance, and the concentration of the cathode potassium ferricyanide solution, the MFCs-type BOD detection device The measurement results are more accurate and reliable. Carry out BOD standard curve drawing and real-time online monitoring of actual organic wastewater BOD, compare the monitoring results of the MFCs type BOD detection device with the results obtained by the traditional BOD ₅ method, and test the reproducibility and accuracy of the measurement results of the MFCs type BOD detection device. . Compared with the existing technology, the solution of the present invention at least has the following advantages:

(1) By optimizing the microbial species and the configuration of the reactor in the MFCs type BOD detection device, the present invention reduces the volume of the reactor to 14 ml, shortens the electrode spacing to 2 cm, and uses carbon felt as the electrode material instead of expensive metal catalysts, while the membrane The material is a cation exchange membrane instead of the expensive proton exchange membrane. The cathode uses potassium ferricyanide solution as the catalyst and electron acceptor. There is no membrane pollution during operation. The dual-chamber MFCs reactor has real-time online continuous measurement function and is simple to operate. It has long continuous and stable working time, and the use and maintenance costs are relatively low. The conductor adopts titanium wire, which has better corrosion resistance and reduces the impact on the activity of microorganisms, thus obtaining an MFCs-type BOD detection device with high sensitivity, high stability and wide monitoring range, which can be used for online or offline measurement of organic wastewater. The BOD value greatly improves the monitoring level.

(2) The oxidation-reduction reaction of the dual-chamber MFCs type BOD detection device used in the present invention is usually carried out in a solution, with small reaction resistance and high output power; the dual-chamber MFCs have a simple structure, and the power generation conditions are easy to adjust, and two There is no interference between reaction chambers, the device performance is more stable, and the data results are more reproducible, which is more beneficial to the real-time detection of wastewater BOD.

(3) The MFCs type BOD detection device of the present invention uses potassium ferricyanide as the cathode electron acceptor, making full use of the characteristics of potassium ferricyanide with high redox potential, strong stability, and no by-products in the reaction, and improves the performance of the BOD sensor. performance, it can realize rapid detection of wastewater with high BOD concentration. At the same time, the electrons obtained by potassium ferricyanide are reduced to potassium ferrocyanide. The cathode solution changes from yellow-green to colorless. The solution has less pollution to the diaphragm, so the device can be guaranteed. Able to run stably for a longer period of time.

(4) The MFCs type BOD detection device of the present invention expands the detection limit of wastewater BOD to 500mg/L, which is significantly improved compared to other BOD sensors of the same type, and ensures the accuracy and reliability of the device monitoring results. Repeatability, the error of monitoring data is less than 5% compared with the traditional five-day biochemical method, indicating that the device has good stability and can be used to detect the concentration of BOD in wastewater in real time.

(5) The MFCs type BOD detection device of the present invention has a short response time, and the starting voltage reaches a stable value of about 545mV within a week. The treated anode carbon felt can enrich enough electricity-producing microorganisms in a short period of time, and starts The successful device has stable performance in later operations and can realize real-time online detection of BOD. Compared with the traditional BOD ₅ determination method, the response time of this device is shorter, and the determination can usually be completed within a few minutes to a few hours, and the response time of the reactor is proportional to the BOD mass concentration of the sample. At the same time, the signal response value of the MFCs type BOD detection device can be directly transmitted through the program-controlled software connected to the Keithley multimeter, thereby realizing real-time online detection of wastewater BOD.

(6) The MFCs type BOD detection device of the present invention has a wide range of applications. This device uses mixed strains in the granular sludge from the anaerobic section of the sewage treatment plant as an inoculation source for electrochemically active microorganisms. Compared with microbial electrodes that use a single strain, it has a wider range of use and linear range, and can be used in a wider range of applications. Determine a variety of samples or samples with complex components within a wide concentration range.

(7) The MFCs type BOD detection device of the present invention has good stability. Potassium ferricyanide is used as the cathode electron acceptor, the cation exchange membrane is used as the intermediate membrane between the cathode and anode chambers, and a dual-chamber microbial fuel cell is used as the core component of the reaction. The device can operate stably for several months, and the measurement data has good reproducibility. It has better stability than the microbial electrode method and BOD ₅ determination method.

(8) The MFCs type BOD detection device of the present invention is simple to operate. Using the MFCs type BOD detection device of the present invention, organic wastewater with a BOD concentration below 500 mg/L can be accurately measured without dilution. It only requires a simple injection operation and the output voltage signal of the device is directly read through the program-controlled software connected to the multimeter. value, the BOD mass concentration of the sample to be tested can be calculated based on the linear equation of the BOD standard curve that has been obtained.

The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those of ordinary skill in the art, various modifications can be made without departing from the purpose of the present invention. Variety. In addition, the embodiments of the present invention and the features in the embodiments may be combined with each other without conflict.

Claims

An organic wastewater BOD detection device, characterized by: including a microbial fuel cell reactor, the microbial fuel cell reactor includes an anode chamber, a cathode chamber and wires, the anode chamber and the cathode chamber are connected through the wires;

Wherein, the cathode chamber is provided with a cathode material and a cathode electron acceptor, and the cathode electron acceptor includes potassium ferricyanide;

The anode chamber is provided with anode material, microorganisms enriched on the anode material and an anode nutrient solution. The anode nutrient solution contains glucose, glutamic acid, pH buffer system, mineral elements and vitamins. The pH buffer The system is used to adjust the pH of the anode nutrient solution to 6.0~8.0;

The anode material and the cathode material are both carbon felts. The pretreatment steps of the carbon felts include: modifying the carbon felts with a strong oxidizing acid; then washing with water, neutralizing until the washing liquid is neutral, and burning.
The organic wastewater BOD detection device according to claim 1, characterized in that: the carbon felt is first dried and then burned; preferably, the drying process is constant temperature vacuum drying; preferably, the drying process temperature is 75~85°C; preferably, the drying treatment time is 10~14h; preferably, the burning temperature is 580~620°C, and the burning time is 1.5~2.5h; preferably, the burning The heating rate is 1~3℃/min.
The organic wastewater BOD detection device according to claim 1, characterized in that: in the startup phase, the microorganisms are inoculated on the anode material through an inoculum solution, and the preparation process of the inoculation solution includes the following steps: taking anaerobic active wastewater The mud is mixed with the pretreatment liquid, sealed, shaken at constant temperature for 20 to 28 hours, and then oxygen is removed; the pretreatment liquid contains glucose, glutamic acid, pH buffer system, mineral solution and vitamin solution; preferably, the pretreatment liquid is The oscillation is at 34-36°C, at a speed of 80-120 rpm; preferably, the oscillation at constant temperature is at about 35°C, at a speed of about 100 rpm; preferably, the BOD value of the pretreatment liquid About 500mg/L.
The organic wastewater BOD detection device according to claim 1, characterized in that: a resistor is externally connected to the wire; preferably, the resistance of the resistor is about 1000Ω.
The organic wastewater BOD detection device according to claim 1, characterized in that: the pH buffer system in the anode nutrient solution is used to adjust the pH of the anode nutrient solution to 6.5-7.5; preferably, the pH buffer system in the anode nutrient solution The pH buffer system is used to adjust the pH of the anode nutrient solution to about 7.0; preferably, the concentration of glucose in the anode nutrient solution is 0.3~0.4g/L; preferably, the concentration of glucose in the anode nutrient solution is about is 0.375g/L; preferably, the concentration of glutamic acid in the anode nutrient solution is 0.3~0.4g/L; preferably, the concentration of glutamic acid in the anode nutrient solution is about 0.375g/L; preferably, The pH buffer system is a phosphate buffer system; preferably, the concentration of phosphate in the phosphate buffer system is 0.08-0.12 mol/L; preferably, the concentration of phosphate in the phosphate buffer system is about 0.1 mol/L; preferably, the mineral elements are added to the anode nutrient solution in a volume ratio of 1:70 to 90 through a mixed solution containing the following components:

Preferably, the vitamin is added to the anode nutrient solution in a volume ratio of 1:100 to 300 through a mixed solution containing the following components:
The organic wastewater BOD detection device according to claim 1, characterized in that: the concentration of potassium ferricyanide is 40-60mmol/L; preferably, the concentration of potassium ferricyanide is about 50mmol/L; preferably Ground, the wire is titanium wire.
The organic wastewater BOD detection device according to claim 1, characterized in that: the microbial fuel cell reactor further includes a cation exchange membrane for separating the cathode chamber and the anode chamber; preferably, the cation exchange membrane is selected from CMI-7000 cation exchange membrane; preferably, the cation exchange membrane is pretreated through the following steps:

Hydrogen peroxide soaking treatment;

High temperature water immersion treatment;

Nitric acid high temperature soaking treatment;

High temperature water immersion treatment;

Store in a moisturized state until later use.
The organic wastewater BOD detection device according to any one of claims 1 to 7, characterized in that: the volume of the microbial fuel cell reactor is 24-32 ml, wherein the anode chamber and the cathode chamber are each 12-16 ml; preferably Preferably, the volume of the microbial fuel cell reactor is 28 ml, in which the anode chamber and the cathode chamber are each 14 ml; preferably, the distance between the carbon felts used as the cathode and the anode is 1 to 3 cm.
Application of a device according to any one of claims 1 to 8 in online BOD monitoring of organic wastewater.
An organic wastewater BOD detection method is characterized by: including the following steps:

The water sample to be tested is added to the detection device as claimed in any one of claims 1 to 8, the output voltage generated by the detection device is measured, and the voltage value is substituted into the linear equation to calculate the BOD value.