阅读说明：本技术 一种快速检测水体bod的微流控微生物电化学传感器及应用 (Micro-fluidic microbial electrochemical sensor for rapidly detecting BOD (biochemical oxygen demand) of water body and application ) 是由 黄津辉 肖楠 庞纳巴勒姆拉维赛奥维格纳珀菲 于 2019-09-05 设计创作，主要内容包括：一种快速检测水体BOD的微流控微生物电化学传感器的设计和应用,具有检测速度快(BOD常规检测是5天,COD是2-3小时),便携,易操作免维护,可以实现实时在线监测,制作成本及操作维护成本极低的特点。本发明通过合理的结构设计,制作出微升体积的BOD微生物反应器,用于水质生化需氧量的传感与测试,该传感器响应周期最短缩至1-5分钟,大大降低了测试时间。本设计适合大规模生产,由于其较宽的监测范围和极低的制作运行维护成本,适合大范围和大面积的应用。在污水厂的运行管理和地表/地下水监测包括垃圾渗滤液监测等领域有很好的应用前景。(The design and application of the micro-fluidic microbial electrochemical sensor for rapidly detecting the BOD of the water body have the characteristics of high detection speed (the conventional BOD detection is 5 days, and the COD is 2-3 hours), portability, easy operation, maintenance-free performance, capability of realizing real-time online monitoring, and extremely low manufacturing cost and operation and maintenance cost. The invention manufactures the BOD microbial reactor with microliter volume through reasonable structural design, is used for sensing and testing the biochemical oxygen demand of water quality, and the response period of the sensor is shortened to 1-5 minutes to greatly reduce the testing time. The design is suitable for large-scale production, and is suitable for large-scale and large-area application due to the wider monitoring range and the extremely low manufacturing, operating and maintaining cost. The method has good application prospect in the fields of operation management of sewage plants and ground surface/underground water monitoring including landfill leachate monitoring and the like.)

1. A micro-fluidic microbial electrochemical sensor for rapidly detecting BOD of a water body is characterized in that: the sensor comprises an anode chamber (1), an ion exchange membrane (d), a cathode chamber (2), an anolyte inlet (3), an anolyte outlet (4), a catholyte inlet (5), a catholyte outlet (6), an anode lead (7) and a cathode lead (8); the anode chamber (1) is separated from the cathode chamber (2) by an ion exchange membrane (d);

the anode chamber (1) is formed by overlapping an anode layer (a), an anode carbon cloth layer (b) and an anode chamber layer (c); the cathode chamber (2) is formed by superposing a cathode layer (g), a platinum film layer (f) and a cathode chamber layer (e);

the anolyte inlet (3) and the anolyte outlet (4) are formed by two round holes on the anolyte layer (a) and adhering PDMS three-dimensional blocks (9); the catholyte inlet (5) and the catholyte outlet (6) are formed by sticking PDMS three-dimensional blocks (9) on the other two round holes on the anode layer (a); the PDMS three-dimensional block (9) is penetrated by a silica gel conduit and corresponds to the round hole;

the anode layer (a) and the anode chamber layer (c) correspondingly penetrate through four round holes to form an anolyte channel; the anode layer (a), the anode chamber layer (c), the ion exchange membrane (d) and the cathode chamber layer (e) are correspondingly penetrated by 8 circular holes to form a cathode liquid channel;

the anode lead (7) is contacted with the anode carbon cloth layer (b) and penetrates through the elliptical small hole in the anode layer (a); the cathode lead (8) sequentially penetrates through elliptical small holes on the other sides of the cathode chamber layer (e), the ion exchange membrane (d), the anode chamber layer (c) and the anode layer (a);

the anode carbon cloth layer (b) is placed in an inverted structure, namely, microorganisms grow on the lower surface of the anode carbon cloth layer.

2. The microfluidic microbial electrochemical sensor of claim 1, wherein: the effective reaction volume of the anode chamber (1) is 0.72-4.5 uL.

3. The microfluidic microbial electrochemical sensor of claim 1, wherein: the number of the anode chamber layers (c) and the cathode chamber layers (e) is 1-5.

4. The design of a micro-fluidic microbial electrochemical sensor for rapidly detecting BOD of a water body is characterized in that: the preparation process of the micro-fluidic microbial electrochemical sensor is as follows:

aligning, compacting and bonding 1-5 anode chamber layers and an ion exchange membrane into a whole;

stacking the anode layer and the carbon cloth, and leading an anode lead to be in contact with the carbon cloth and penetrate through the corresponding elliptical small holes before compaction to obtain a complete anode chamber;

pasting the cathode chamber layer to the lower layer of the ion exchange membrane, wherein the holes are in one-to-one correspondence, and the thickness of the cathode chamber is adjusted by adjusting the number of the cathode chamber layers;

and (3) correspondingly sticking the cathode layer and the cathode material to the lower surface of the cathode chamber layer from top to bottom, penetrating out the cathode lead through elliptical small holes which penetrate through the cathode chamber layer (e), the ion exchange membrane (d), the anode chamber layer (c) and the anode layer (a) in sequence, and completing the assembling process of the whole reactor after compacting.

5. Use of a microfluidic microbial electrochemical sensor according to any of claims 1 to 3, wherein: the microfluidic microbial electrochemical sensor is used for constructing a microfluidic microbial electrochemical sensor test system; the microfluidic microbial electrochemical sensor test system comprises a microfluidic sample introduction module, a sensor module, an electric signal test module and a data acquisition module.

6. Use of a microfluidic microbial electrochemical sensor according to any of claims 1 to 3 for BOD detection, wherein: the detection steps are as follows:

1) starting of micro-fluidic microbial electrochemical sensor and culturing of anode biological membrane

Introducing a bacterial liquid and a culture solution into the anode chamber, observing the change of a current signal value, adding a new culture solution when a current value is increased and then decreased to be stable, and finishing the culture of the biomembrane after the final peak value is stable, namely successfully starting the sensor;

2) test of performance of microfluidic microbial electrochemical sensor

Adopting a microfluidic microbial electrochemical sensor test system, sequentially and simultaneously adding solutions to be tested and catholyte with different concentrations into an anode chamber and a cathode chamber, and recording time from the beginning of sample injection until a new peak value appears as response time; the BOD value is taken as an abscissa, and the current value and the response time are taken as two ordinates to obtain a linear relation between the current value and the BOD; and the anolyte and the catholyte keep synchronous sample injection at the same flow velocity.

7. Use of a microfluidic microbial electrochemical sensor according to claim 6 in BOD detection, characterized in that: the detection range of the BOD is 20-450mg/L, and the response time is 1-5 min.

8. Use of a microfluidic microbial electrochemical sensor according to claim 6 in BOD detection, characterized in that: the test adopts a sequential batch mode or a continuous flow mode.

Technical Field

The invention belongs to the field of microbial electrochemical sensors, and particularly relates to a method for rapidly evaluating biochemical oxygen demand of water quality by a micro-fluidic microbial electrochemical sensor prepared by a micro-machining technology.

Background

The real-time monitoring of the water quality index of the sewage, especially the biochemical oxygen demand of the water body, not only can provide real-time water quality information, but also can play a core role in the surface/underground water management and the operation of sewage treatment plants, the timely feedback of the water quality index can effectively reduce the potential safety hazard of drinking water, can effectively improve the operation management and sewage treatment efficiency of the sewage treatment plants, and reduce the operation and maintenance cost so as to meet the requirements of the self-purification capacity and policy and regulation of the environmental ecosystem. The five-day biochemical oxygen demand method of the national standard test method has long time consumption and large error, and can not meet the requirement of timely feedback of water quality information.

The anode of the BOD microbial sensor is attached with electrogenesis microbes to generate current while metabolizing organic matters, so the BOD microbial sensor has potential for being used in the application of rapidly determining the biochemical oxygen demand of the water body. However, factors such as high manufacturing cost and relatively long response time restrict large-area popularization and application of the sensor, and the micro-volume microbial sensor has the characteristics of low manufacturing cost, fast response time, convenience in on-line monitoring and the like, and is an effective measure for solving the problem.

The BOD microbial sensor is basically in the laboratory research stage, and the main reasons for restricting the practical production and application of the BOD microbial sensor are that the equipment manufacturing process is complex, the cost is high, the response time to the water quality biochemical oxygen demand is relatively slow, and the BOD microbial sensor cannot make a timely and reliable response to the water quality change. And the reduction of the volume of the microbial electrochemical sensor is an effective measure for improving the performance of the biosensor and reducing the response time. However, although common micro-fabrication methods based on the micro-fluidic technology, including the photolithography technology, the soft lithography technology, the laser ablation technology, and the like, can effectively reduce the volume of the reactor to the microliter (uL) level and have high precision, these technologies often require specific precision instruments, sterile operating environments, and good professional training, often cannot achieve mass production, and have high operating thresholds. Therefore, a micro-manufacturing technology with low cost, short manufacturing period and simple operation needs to be found and applied to the design and manufacture of the microbial electrochemical sensor, and is finally used for the construction of the water quality sensor, and indexes such as response time, test range and the like are considered, so as to further realize productization and popularization in practical application.

Disclosure of Invention

In order to solve the problems in the technology, the invention provides a micro-manufacturing technology which is simple to operate, low in manufacturing cost, short in period and suitable for batch production, and a microbial electrochemical reactor with microliter volume is manufactured through reasonable design and is used for sensing and testing water Biochemical Oxygen Demand (BOD) to evaluate the applicability and application prospect of the reactor.

In order to achieve the purpose, the invention is obtained by the following technical scheme:

a micro-fluidic microbial electrochemical sensor for rapidly detecting BOD of a water body comprises an anode chamber 1, an ion exchange membrane d, a cathode chamber 2, an anolyte inlet 3, an anolyte outlet 4, a catholyte inlet 5, a catholyte outlet 6, an anode lead 7 and a cathode lead 8; the anode chamber 1 is separated from the cathode chamber 2 by an ion exchange membrane d;

the anode chamber 1 is formed by stacking an anode layer a, an anode carbon cloth layer b and an anode chamber layer c; the cathode chamber 2 is formed by overlapping a cathode layer g, a platinum film layer f and a cathode chamber layer e;

the anolyte inlet 3 and the anolyte outlet 4 are formed by two round holes on the anolyte layer a and adhered with PDMS three-dimensional blocks 9; the catholyte inlet 5 and the catholyte outlet 6 are formed by sticking PDMS three-dimensional blocks 9 on the other two round holes on the anode layer a; the PDMS three-dimensional block 9 is penetrated by a silica gel conduit and corresponds to the round hole;

the anode layer a and the anode chamber layer c correspondingly penetrate through round holes to form an anolyte channel; the anode layer a, the anode chamber layer c, the ion exchange membrane d and the corresponding through round holes on the cathode chamber layer e form a cathode liquid channel;

the anode lead 7 is contacted with the anode carbon cloth layer b and penetrates through the elliptical small hole in the anode layer a; the cathode lead 8 sequentially penetrates through elliptical small holes which penetrate through the cathode chamber layer e, the ion exchange membrane d, the anode chamber layer c and the other side of the anode layer a;

as shown in fig. 8, the anode carbon cloth layer b is placed in an inverted structure, that is, the microorganisms grow on the lower surface of the anode carbon cloth layer, that is, the microorganisms completely grow and are planted on the surface of the anode by the self-adhesive force of the microorganisms.

Further, the effective reaction volume of the anode chamber 1 is 0.72-4.5 uL. The effective reaction volume can also be adjusted according to the required surface area of the anode and the number of the chamber layers, for example, the surface area of the anode is set to be 4mm × 4mm, and the effective reaction volume is 0.72uL when the anode chamber layers are 3 layers.

Further, the number of the anode chamber layer c and the cathode chamber layer e is 1-5. Can be flexibly set to 1 layer or more according to the required chamber volume.

The design of a micro-fluidic microbial electrochemical sensor for rapidly detecting BOD of a water body is characterized in that: the preparation process of the micro-fluidic microbial electrochemical sensor is as follows:

aligning, compacting and bonding 1-5 anode chamber layers and an ion exchange membrane into a whole;

stacking the anode layer and the carbon cloth, and leading an anode lead to be in contact with the carbon cloth and penetrate through the corresponding elliptical small holes before compaction to obtain a complete anode chamber;

pasting the cathode chamber layer to the lower layer of the ion exchange membrane, wherein the holes are in one-to-one correspondence, and the thickness of the cathode chamber is adjusted by adjusting the number of the cathode chamber layers;

and (3) correspondingly sticking the cathode layer and the cathode material to the lower surface of the cathode chamber layer from top to bottom, penetrating out the cathode lead through elliptical small holes which penetrate through the cathode chamber layer e, the ion exchange membrane d, the anode chamber layer c and the anode layer a in sequence, and compacting to complete the assembly process of the whole reactor.

The application of the micro-fluidic microbial electrochemical sensor for rapidly detecting the BOD of the water body is characterized in that the micro-fluidic microbial electrochemical sensor is used for constructing a micro-fluidic microbial electrochemical sensor test system; the microfluidic microbial electrochemical sensor test system comprises a microfluidic sample introduction module, a sensor module, an electric signal test module and a data acquisition module.

The microfluidic microbial electrochemical sensor test system is shown in fig. 1, and is a test platform established in a laboratory and used for detecting the response of a sensor to the concentration of organic matters (generally biochemical oxygen demand) in a water body. And a large amount of practical detection applied to the field or sewage plant in the future can correspondingly simplify the device or realize data wireless transmission by utilizing the technology of the internet of things. The whole test system comprises: the device comprises a micro-flow sample introduction module, a sensor module, an electric signal testing module and a data acquisition module. The micro-flow sample injection module mainly comprises two injectors which are respectively used for completing the sample injection process of the anolyte and the catholyte, when the sensor adopts the 'sequencing batch mode' test, a sample to be tested and the catholyte need to be manually and slowly injected, and when the sensor adopts the 'continuous flow mode' test, the injectors can be connected to a micro-flow injection pump to complete the sample injection of continuous flow. The mode can be flexibly switched according to the actual test requirement. The sensor module consists of the microbial electrochemical sensor and the effluent collecting device. The electric signal testing module is mainly formed by connecting a lead, an external resistor and a constant potential device in series. The data acquisition module mainly comprises a display and data acquisition software and is used for recording and storing electric signal data, the current data acquisition and recording of the test system are realized, the acquisition frequency is set to be 10 data per minute, and the data acquisition module is visually displayed in the display in real time so as to adjust the test process according to the real-time data response condition.

An application of a microfluidic microbial electrochemical sensor in BOD detection specifically comprises the following detection steps:

1) actuation of microfluidic microbial electrochemical sensors

Introducing a bacterial liquid and a culture solution into the anode chamber, observing the change of a current signal value, adding a new culture solution when a current value is increased and then decreased to be stable, and finishing the culture of the biomembrane after the final peak value is stable, namely successfully starting the sensor;

2) testing of microfluidic microbial electrochemical sensors

Adopting a microfluidic microbial electrochemical sensor test system, sequentially adding solutions to be tested and catholyte with different concentrations into an anode chamber and a cathode chamber, and recording time from sample injection until a new peak value appears as response time; the BOD value is taken as an abscissa, and the current value and the response time are taken as two ordinates to obtain a linear relation between the current value and the BOD.

The design and operation principle of the microfluidic microbial electrochemical sensor is as follows:

the structure design principle of the microfluidic microbial electrochemical sensor is derived from the reaction mechanism of the traditional double-chamber microfluidic BOD microbial sensor. Fig. 3 is a schematic diagram showing the cross section and names of various components of the sensor, and the right side is a partially non-isometric enlarged schematic diagram, wherein the materials and names shown in the diagram correspond to those shown in fig. 2 one by one. The schematic cross-sectional view shows the flowing direction of the anolyte, i.e. the anolyte flows in from the left circular hole and flows out from the right circular hole, and the catholyte flows in from the direction perpendicular to the paper. Along with the inflow of the anolyte, the organic matters contained in the anolyte are metabolized and utilized by electrogenic microorganisms attached to and grown on the surface of the anode, electrons and protons are generated, the protons pass through the ion exchange membrane and reach the cathode chamber, and the electrons pass through an external circuit and reach the cathode chamber to be combined with the protons and oxygen molecules to generate water molecules. Therefore, theoretically, the higher the organic matter content in the anode liquid is, the more electrons generated by the metabolism of the electrogenic microorganisms are, the higher the corresponding electric signal value is, so that the content of the organic matters in the water body can be responded according to the detected electric signal, namely the working principle of the microfluidic BOD microorganism sensor. The design reduces the risk of micro-channel blockage caused by excessive growth of the biological membrane, and the efficient selectivity formed by inversion can preferentially attach microorganisms with high metabolic activity, strong electrogenesis capability and strong attachment capability to the surface of the anode, and the microorganisms with poor metabolic activity or poor attachment capability can flow out of the system along with the anolyte, so that the remaining biological membrane has strong electrogenesis capability and robustness and is more suitable for high-strength detection and relatively severe growth environment.

Micro-fluidic microbial electrochemical sensor test process

The sensor of the invention tests the chemical oxygen demand in the water body and comprises the following steps: firstly, the preparation of the microfluidic microbial electrochemical sensor is mainly divided into the design of a cavity and a liquid channel (the size of the cavity can be reasonably changed according to different requirements, the effective reaction volume can be controlled), the preparation and cutting of materials, and the assembly and fixation of a reactor; and secondly, culturing the anode biomembrane of the reactor by two processes of bacterial liquid inoculation and nutrient substance culture. And finally, testing the performance of the sensor, namely testing the artificial wastewater with different concentrations (the BOD value is generally adjusted by the concentration of sodium acetate) to obtain a standard curve of the relation between the BOD concentration and the electric signal. In the test process, sequencing batch sample introduction can be adopted, namely, a sample to be tested is added into the anode chamber and then reacts automatically, the current response condition is observed, the reaction is complete when the current peak value is reached, and the current peak value and the consumed time are recorded as response time. In addition, continuous flow can be used to test the performance of the sensor, i.e. a microfluidic injection pump is used to continuously inject the sample into the sensor, and the specific operation depends on the size of the sensor and the detection requirement to be met (according to our earlier research experience, the larger the flow rate, the faster the response time and the longer the response time with higher BOD concentration).

The invention has the beneficial effects that:

(1) the microfluidic microbial electrochemical sensor prepared by the invention has low manufacturing cost and high efficiency. The price of the required material is low, the required equipment is only one industrial cutting machine, the 1.8 microliter reactor with the anode size of 4mm multiplied by 10mm is taken as an example, the manufacturing cost is only 2.5 yuan RMB, and the preparation process is only 10 minutes.

(2) The invention places the anode upside down, is beneficial to efficiently screening the electrogenesis microorganisms with high metabolic activity and strong anode adhesion capacity, and avoids the occurrence of the blockage problem of the microchannel while improving the performance of the sensor.

(3) By utilizing the characteristic of small reaction volume of the sensor, the detection time of the biochemical oxygen demand of the water body is further shortened to 1 minute by optimizing the operation mode, and the detection range is 20-450mg/L BOD value, so that the microfluidic microbial electrochemical sensor has the fastest reaction and the largest detection range.

Drawings

In order to make the purpose, technical scheme and beneficial effect of the invention more clear, the invention provides the following drawings for explanation:

FIG. 1 is a diagram of a microfluidic microbial electrochemical sensor test system;

FIG. 2 is a schematic structural diagram of a microfluidic microbial electrochemical sensor;

FIG. 3 is a schematic diagram of the design and operation of a microfluidic microbial electrochemical sensor;

FIG. 4 is a diagram of a microfluidic microbial electrochemical sensor;

FIG. 5 is a schematic diagram of the start-up of the microfluidic microbial electrochemical sensor;

FIG. 6 is an SEM image of an anode biofilm of the microfluidic microbial electrochemical sensor;

FIG. 7 is a diagram showing the result of the biochemical oxygen demand of a water body by the microfluidic microbial electrochemical sensor;

FIG. 8 is a schematic view of an inverted structure of an anode carbon cloth layer;

the electrochemical micro-fluidic microbial sensor comprises an anode chamber 1, an ion exchange membrane d, a cathode chamber 2, an anolyte inlet 3, an anolyte outlet 4, a catholyte inlet 5, a catholyte outlet 6, an anode lead 7, a cathode lead 8, a PDMS three-dimensional block 9, an anode layer a (containing round holes a1, a3, a4, a6, elliptical small holes a2 and a5), a carbon cloth layer b, a PDMS cube small block schematic diagram h, a schematic diagram i after the electrochemical micro-fluidic microbial sensor is assembled, an anode chamber layer c (containing round holes c1, c3, c4, c6 and elliptical small holes c2), an ion exchange membrane d (containing round holes d3, d4 and elliptical small holes d2), a cathode chamber layer e (containing round holes e3, e6 and elliptical small holes e2), and platinum cathode layers f and g.

Detailed Description

In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer.

Example 1

The structure of the microfluidic microbial electrochemical sensor is shown in fig. 2, the manufacturing process of the sensor is mainly completed by stacking and assembling, as shown in fig. 2(a-g), the microfluidic microbial electrochemical sensor is composed of seven structural parts, the anode layer a, the anode chamber layer c, the cathode chamber layer e and the cathode layer g are made of polyester plastic materials (PET plastics), and the single-layer thickness of the sensor is 125 μm; the thickness of the ion exchange membrane is 460 μm; the carbon cloth layer b takes carbon cloth as an anode material, and the thickness of the carbon cloth layer b is 330 μm; the platinum thin film layer f uses a thin film material of platinum metal as a cathode material, and is itself 60 μm thick. Before the reactor is assembled, except that electrode materials can be directly cut into required shapes by scissors, materials of other structural layers need to be cut into corresponding shapes according to designed patterns by a cutting and drawing machine which is commonly used in the field of micromachining and has simple operation, and the layers are vertically aligned, bonded and fixed. And then sticking 4 PDMS (polydimethylsiloxane) cubic small blocks which are prepared in advance and are provided with silica gel guide pipes to the upper surfaces of the 4 round small holes corresponding to the anode layer a through double-sided organic silicon adhesives to be used as water inlet and outlet channels of the anode liquid and the cathode liquid. The oval holes in the layers a, c, d, e in the figure eventually serve as anode and cathode lead channels. After the a-g layers are stacked and assembled, the d layers form an anode chamber, namely, the anode solution flows in through the PDMS and the conduit and flows only through one layer of the upper surface of the ion exchange layer and flows out from the other end, the e-g layers correspondingly form a cathode chamber, namely, the cathode solution also flows in through the PDMS and the conduit of the surface layer, but the inlet of the cathode solution directly penetrates through the two round holes of the ion exchange membrane to the lower surface layer and flows only through one layer of the lower surface of the ion exchange layer, and the outlet of the same cathode solution is arranged at the corresponding other end and is led out from the surface layer. The final product is schematically shown in fig. 2. And figure 4 shows an actual picture of 4mm x 10mm anode and cathode area for example, which uses 3 layers of polyester plastic for the anode layer and 2 layers of polyester plastic for the cathode layer during the manufacturing process. The effective reaction volume of the anode chamber was calculated to be 1.8 microliters.

Example 2

FIG. 2 shows a schematic diagram of the structure of a BOD microbial sensor according to the present invention. The sensor is formed by mutually stacking an anode chamber, a cathode chamber and an ion exchange membrane. The ion exchange membrane separates the anode chamber from the cathode chamber and allows only positive ions to pass through. As is apparent from fig. 2, the anode layer a, the anode chamber layer c and the ion exchange membrane d are stacked to form an anode chamber; in the same way, the ion exchange membrane d, the cathode chamber layer e and the cathode layer g are superposed to form the cathode chamber, the carbon cloth layer b and the platinum film layer f are respectively used as the anode material and the cathode material, and the carbon cloth and the platinum metal are respectively used as the anode material and the cathode material. In the design, thin carbon fibers are used as lead materials, are contacted with a carbon cloth layer, penetrate out of an anode layer, are fixed by a copper foil adhesive tape (shown as A in figure 4), and are used as contact points to be connected with an external circuit for electrochemical analysis and test. The design can finally realize that the anolyte flows on the upper surface of the ion exchange membrane, and the catholyte flows on the lower surface of the ion exchange membrane, so that the anolyte and the catholyte do not interfere with each other. I in fig. 2 shows a schematic diagram after the fabrication is completed.

Example 3

Sensor activation

Fig. 5 shows the starting process of the microfluidic microbial electrochemical sensor of the invention, namely the culture process of the anode biofilm, which comprises a microbial inoculation stage and a culture stage. The inoculation process specifically introduces bacterial liquid and culture solution into the anode chamber. In the inoculation stage, bacterial liquid and culture liquid with the volume ratio of 1:1 are introduced into an anode chamber, the change of current signal values is observed, after an obvious process of increasing firstly and then decreasing, the fact that microorganisms are planted on the carbon cloth can be judged, then the culture stage is started, 3 periods are continuously introduced, the current value of each period is increased firstly and then decreased to be stable, and after the final peak value is stable, the culture of a biological film is considered to be finished, namely the sensor is started successfully. In order to observe the growth state of the biofilm, the cultured biofilm is observed by the SEM technology, and the result is shown in figure 6, wherein the phenomenon of microbial attachment is obvious.

Example 4

Sensor performance testing

This example describes the results of a sensor test in continuous flow mode. The specific operation is as follows:

the test system was set up as shown in fig. 1, where the microfluidic sample module was completed using a two-channel microfluidic syringe pump. The two injectors are respectively connected to the sample inlets of the anolyte and the catholyte of the microfluidic microbial electrochemical sensor with the cultured anodic biofilm through silica gel catheters, the corresponding effluent is respectively collected by two plastic beakers, an external circuit is connected in series with a constant value resistor and a constant potential device of 10 ohms and is connected with a display through data recording software, and the construction of the whole test system is completed (as shown in figure 1). According to the previous experimental results, a constant potentiometer is utilized to continuously apply a voltage of 1mV between the anode and the cathode in the testing process, so that a better testing effect can be achieved. In the testing process, the solution to be tested and the catholyte which are prepared in advance and have different BOD concentrations are sequentially introduced into the reactor, in order to maintain the air pressure balance of the two chambers, the catholyte and the anolyte are synchronously injected at the same speed, the time is recorded from the injection of the sample until a new peak value appears as the response time. The anolyte used in the embodiment is BOD (biochemical oxygen demand) concentrations of 49, 129, 321 and 492mg/L respectively obtained by adjusting the concentration of sodium acetate in the solution, and the test range is enough to meet the test requirements of daily sewage treatment plants. The whole test procedure was carried out in a laboratory at constant temperature (25 ℃) and 3 replicates were tested per sample, and finally the BOD value was plotted as abscissa and the current value and response time as two ordinates as a result as shown in fig. 7. It can be seen that there is a linear relationship between the current value and BOD and that the response time is only 1.1min when 49mg/L of sample is tested.