Method for monitoring acid-alkali wastewater through sediment microbial fuel cell sensor matrix

Abstract

The invention discloses a method for monitoring acid-alkali wastewater by using a sediment microbial fuel cell sensor matrix, which comprises the following steps of: arranging the sediment microbial fuel cell sensor matrix in a water body to be detected, and recording the voltage, the conductivity and the dissolved oxygen of each sediment microbial fuel cell sensor in real time and on line through a monitoring terminal; the pH value of the water body at the monitoring position of each sediment microbial fuel cell sensor is calculated through a formula, and a heat map is drawn to display the dynamic change of the pH along with time, so that the diffusion range of the acid-alkali wastewater is monitored, and pollutants are traced. According to the method, the pH and the diffusion range of the sewage can be remotely monitored online in real time, the source tracing of acidic and alkaline sewage is realized, the monitoring result is intuitively presented in a dynamic heat map form, the sensor is light, the labor is saved, the cost is low, and the monitoring process is pollution-free.

Description

Technical Field

[0001] The present invention belongs to the technical field of ecological environmental protection, and particularly relates to a method for monitoring the diffusion range of acid-base wastewater by using a sediment microbial fuel cell sensor matrix. Background Art

[0002] Acidic and alkaline wastewater has the characteristics of diverse pollutants, high treatment difficulty, and great potential hazards. In acid-base wastewater pollution incidents, understanding the diffusion range of wastewater can trace the flow path of sewage and determine the location of the pollution source, which is crucial for pollution source tracing, hazard range assessment, and formulation of response measures. In traditional water pollution monitoring, due to the time-consuming and laborious on-site sampling and analysis, and the limitation of remote sensing technology by weather and light, in practice, the method of setting up an automatic monitoring station equipped with a sensor network in water bodies such as rivers, lakes, and wetlands is often used to achieve real-time automatic monitoring. The types of pH sensors used in the monitoring station are electrochemical (metal electrode) sensors, glass electrode sensors, ion-selective electrode sensors, and optical pH sensors. These instruments have their respective advantages, but these electrodes have disadvantages such as being easily polluted, fragile, requiring regular calibration, high price, and high maintenance cost in the complex hydrological environment of wetlands.

[0003] Electricity-producing bacteria are generally present in soil and wetland sediment. Through the sediment microbial fuel cell (SMFC) constructed in the wetland, electricity-producing microorganisms are enriched on the anode to decompose organic matter to generate electrons, and the electrons are conducted to the cathode to react with hydrogen ions and dissolved oxygen in water to generate H 2 O, thereby generating current and voltage in the circuit. Existing research has found that adding acidic wastewater to the overlying water of the wetland can promote the cathode reaction, causing the voltage of the SMFC to increase and appear a voltage peak; while adding alkaline wastewater inhibits the cathode reaction, causing the voltage to drop (Electroanalysis, 2024, 36, e202300394). Therefore, the SMFC can be used as an acid-base sensor, and its voltage change can reflect the pH of the sewage discharged into the wetland water body; however, a single SMFC acid-base sensor cannot monitor the diffusion range of acidic or alkaline wastewater, nor can it easily trace the sewage, and the voltage signal of the SMFC acid-base sensor is also affected by the salinity of the sewage and the dissolved oxygen in the water body. In addition, the reported SMFC acid-base sensors rely on wired transmission to save data on a computer, making it difficult to be widely applied in the field.

[0004] Therefore, the present invention designs and constructs a sediment microbial fuel cell sensor matrix for wireless data transmission to the cloud, and through the calculation formula of the sensor voltage and the pH, conductivity, and dissolved oxygen of the wetland water body, thereby realizing the tracing of acidic or alkaline wastewater discharged into the wetland water body and the monitoring of the diffusion range. Summary of the Invention

[0005] The object of the present invention is to provide a method for monitoring acidic and alkaline wastewater by using a sediment microbial fuel cell sensor matrix. A matrix of sediment microbial fuel cell sensors is arranged in the water body to be measured, and the voltage, conductivity, and dissolved oxygen of each sediment microbial fuel cell sensor are recorded in real time and online by a monitoring terminal. The pH value of the water body at the monitoring position of each sediment microbial fuel cell sensor is calculated through a formula, and a heat map is drawn to display the dynamic change of pH over time, so as to realize the monitoring of the diffusion range of acidic and alkaline wastewater and trace the pollutants;

[0006] The formula is one of the following:

[0007] (1) When the wastewater is acidic wastewater, the formula is U = -26.6pH + 1.6DO + 0.5EC + 6.4Ub + 60.5,

[0008] (2) When the wastewater is alkaline wastewater, the formula is U = -32.5pH - 1.6DO + 0.5EC - 6.0Ub + 330.0,

[0009] where U is the voltage, DO is the dissolved oxygen, EC is the conductivity, and U b is the baseline voltage.

[0010] Further, the sensor matrix includes at least three sensors, which are located near the sewage outlet, upstream of the sewage outlet, and downstream of the sewage outlet respectively.

[0011] Further, the sediment microbial fuel cell sensor includes an anode, a cathode, an external resistor, a data collector, a conductivity meter, a dissolved oxygen meter, a solar panel, a floating ring, and a fixing frame;

[0012] The anode is buried in the wetland sediment, and the cathode floats in the overlying water of the wetland through a floating ring; the anode, the cathode, and the external resistor are connected in series through a wire; the external resistor is connected to the data collector;

[0013] The conductivity meter and the dissolved oxygen meter are located in the overlying water, and the conductivity meter and the dissolved oxygen meter are respectively connected to the data collector;

[0014] The data collector is used to receive the voltage data at both ends of the external resistor, the data of the conductivity meter and the dissolved oxygen meter, and transmit them to the monitoring terminal;

[0015] The floating ring floats on the overlying water, the fixing frame is arranged on the floating ring, the fixing frame is used to install the data collector and the solar panel, and the solar panel provides electric energy for the data collector.

[0016] Further, the material of the anode is stainless steel, titanium, graphite, or carbon felt.

[0017] Further, the material of the cathode is stainless steel, titanium, graphite or carbon felt.

[0018] Further, the material of the fixing frame is plastic, aluminum alloy or stainless steel.

[0019] In the previous experimental research, the inventor constructed the sediment microbial fuel cell (SMFC) sensor of the present application in the water body, added acid-base pollution with a determined pH value to the sensor, and simultaneously recorded the dissolved oxygen (DO, mg / L) and conductivity (EC, mS / cm) of the water body, as well as the baseline voltage (U b , mV) and the voltage (U, mV) generated in response to acid-base pollution of the SMFC sensor, and performed regression fitting on a large amount of experimental data to obtain the calculation formulas for the sensor voltage and the pH, salinity, and dissolved oxygen of the wetland water body.

[0020] The present invention can monitor the source tracing and diffusion range of acidic / alkaline wastewater discharged into the wetland water body by constructing a matrix of SMFC sensors and combining the calculation formulas for the sensor voltage and the pH, conductivity, and dissolved oxygen of the water body.

[0021] The SMFC sensor and its matrix of the present invention have the following advantages: 1) The sensor does not need to cultivate microorganisms and directly uses the anaerobic electricity-producing bacteria existing in the bottom mud to provide electrical signals; 2) Simple maintenance, the materials of the anode and cathode of the sensor are stable and strong, not easily damaged, and can be monitored for a long time with one installation; 3) The sensor monitors acid-base pollution in real time and online, and can realize pollution source tracing and diffusion range monitoring.

[0022] The key of the present invention lies in arranging a sensor matrix in the water bodies upstream and downstream of the sewage outlet. By the change of the voltage signals of the sensors at different positions over time, the pH and diffusion range of the sewage can be judged, and the source tracing of acidic and alkaline sewage can be realized.

[0023] The method of the present invention can remotely monitor the pH and diffusion range of sewage in real time and online, realize the source tracing of acidic and alkaline sewage, and the monitoring results are visually presented in the form of a dynamic heat map. The sensor is portable, labor-saving, low-cost, and pollution-free during the monitoring process. Description of the Drawings

[0024] Figure 1 It is a schematic structural diagram of a single sediment microbial fuel cell sensor, where: anode 1, cathode 2, wire 3, external resistor 4, data collector 5, conductivity meter 6, dissolved oxygen meter 7, solar panel 8, floating ring 9, fixing frame 10.

[0025] Figure 2For the results of Example 1, the squares represent the pH values of the water body monitored by each sensor in the sensor matrix after 60 seconds (60s), 120 seconds (120s), 180 seconds (180s), 240 seconds (240s), and 300 seconds (300s) of acidic wastewater discharge.

[0026] Figure 3 For the results of Example 2, the squares represent the pH values of the water body monitored by each sensor in the sensor matrix after 60s, 120s, 180s, 240s, and 300s of alkaline wastewater discharge. Detailed implementation manners

[0027] The preferred implementation manners of the present invention will be described in detail below in conjunction with the embodiments. It should be understood that the following embodiments are given only for the purpose of illustration and are not used to limit the scope of the present invention. Those skilled in the art can make various modifications and substitutions to the present invention without departing from the purpose and spirit of the present invention.

[0028] The experimental methods used in the following embodiments are all conventional methods unless otherwise specified.

[0029] The materials, reagents, etc. used in the following embodiments can be obtained from commercial channels unless otherwise specified.

[0030] In the present invention, the data acquisition device, conductivity meter, dissolved oxygen meter, and solar panel are all commercially available products. For example, the data acquisition device can be EM9636B4 / USB (Zhongtai Research and Innovation), EM7660B (Zhongtai Research and Innovation), USB-3120 (Smacq), etc.; the conductivity meter can be 86031 (AZ), CT-2 (LICHEN), DDS-11A (Leici), etc.; the dissolved oxygen meter can be HQ1130 (HACH), AR8406 (Sima), JPB-607A (Leici), etc.; the solar panel can be SQ-JK4030 (Mingpin), 12V monocrystalline solar panel (Zhuyang), SWM-20W (MPPTSUN), etc. The resistance value of the external resistance is between 500 ohms and 20,000 ohms, and can be 1 / 6W (RISYM), 1 / 3W (TOUGLESY), 1 / 4W (ZAVE), etc.

[0031] Example 1

[0032] In the constructed wetland in the greenhouse of Xianlin Campus of Nanjing Normal University, a matrix composed of 16 sediment microbial fuel cell sensors was built. The sensors were arranged in a way of 4 sensors per row and 4 rows in total, with a spacing of 20 cm between adjacent sensors. The components and settings of a single sensor refer to Figure 1Among them, the anode of the sensor is a stainless-steel tube with a length of 10 cm, inserted 10 cm deep into the bottom mud. The cathode is a stainless-steel mesh, floating on the overlying water of the wetland through a floating ring, and the external resistance is 20,000 ohms.

[0033] After the voltage of the sensor stabilizes, an acidic buffer solution with a pH of 2.4 is added to a corner of the wetland at a flow rate of 1000 mL / min to simulate the discharge of acidic wastewater, and the discharge lasts for 300 s. Collect the voltage (U), conductivity (EC), dissolved oxygen (DO), and the baseline voltage (U b ) data before adding acid at the 60th s, 120th s, 180th s, 240th s, and 300th s after the start of the discharge. Calculate the pH value monitored by each sensor according to the formula U = –26.6pH + 1.6DO + 0.5EC + 6.4Ub + 60.5 (the voltage unit is mV, the dissolved oxygen unit is mg / L, and the conductivity unit is mS / cm), and draw a heat map to show the dynamic change of pH over time.

[0034] Since the SMFC sensor generates voltage as long as it is fixed in the bottom mud during operation, when used to monitor wastewater pollution, before the voltage of the sensor changes due to the wastewater, the stable voltage data detected by a single sensor in the sensor matrix is the baseline voltage.

[0035] Substitute the voltage (U), conductivity (EC), dissolved oxygen (DO), and baseline voltage (Ub) data of each sensor at the 60th s, 120th s, 180th s, 240th s, and 300th s of the acidic wastewater discharge into the above formula to calculate the pH of the overlying water where each sensor is located in the matrix. As Figure 2 shown, presented by the heat map, at the 60th s of the acidic wastewater discharge, the pH values of the water bodies where Sensor 1 and Sensor 2 are located reach pH 3.88 and pH 4.64 respectively; at the 120th s, the diffusion range of the acidic wastewater increases, and the pH values of the water bodies where Sensor 1, Sensor 2, Sensor 3, Sensor 6, and Sensor 7 are located reach 3.43, 4.90, 5.08, 5.61, and 5.80 respectively; at the 180th s, the diffusion range of the acidic wastewater increases to the water bodies where Sensor 5 and Sensor 11 are located; at the 240th s, the diffusion range of the acidic wastewater expands to the water body where Sensor 10 is located; at the 300th s, the diffusion range of the acidic wastewater does not increase further, but compared with the 240th s, the pH values of the water bodies where Sensor 6, Sensor 10, and Sensor 11 are located further decrease to pH 4.41, 3.64, and 3.92. By analyzing the diffusion range of the acidic wastewater at different time points, it can be traced that the acidic wastewater discharge outlet is located near the water bodies where Sensor 1 and Sensor 2 are located.

[0036] Example 2

[0037] In the artificial wetland in the greenhouse of Xianlin Campus of Nanjing Normal University, a matrix composed of 16 sediment microbial fuel cell sensors was constructed according to the method of Example 1. After the sensor voltage was stabilized, an alkaline buffer solution with a pH of 13 was added to a corner of the wetland at a flow rate of 1000 mL / min to simulate the discharge of alkaline wastewater, and the discharge was ended after 300 s. The voltage (U), conductivity (EC), dissolved oxygen (DO), and the baseline voltage (U b ) data at the 60th s, 120th s, 180th s, 240th s, and 300th s after the start of the discharge were used to calculate the pH values monitored by each sensor according to the algorithm U = –32.5pH – 1.6DO + 0.5EC - 6.0Ub + 330.0 (the voltage unit is mV, the dissolved oxygen unit is mg / L, and the conductivity unit is mS / cm), and a heat map was made to show the dynamic change of pH. As Figure 3 shown, through the heat map presentation, at the 60th s of the alkaline wastewater discharge, the pH values of the water bodies where the 1st and 2nd sensors are located reached pH 11.15 and pH 12.21 respectively; at the 120th s, the diffusion range of the alkaline wastewater did not increase; at the 180th s, the diffusion range of the alkaline wastewater increased to the water body where the 5th sensor is located; at the 240th s, the diffusion range of the alkaline wastewater continued to expand to the water bodies where the 3rd, 7th, and 12th sensors are located; at the 300th s, the diffusion range of the alkaline wastewater further increased to the water bodies where the 4th, 6th, and 8th sensors are located. By analyzing the diffusion range of the alkaline wastewater at different time points, it can be traced that the alkaline wastewater discharge outlet is located near the water bodies where the 1st and 2nd sensors are located.

Claims

1. A method for monitoring acid-base wastewater using a sediment microbial fuel cell sensor matrix, characterized in that: A matrix of sediment microbial fuel cell sensors is arranged in the water body to be tested. The voltage, conductivity and dissolved oxygen of each sediment microbial fuel cell sensor are recorded online in real time through the monitoring terminal. The pH value of the water body at each sediment microbial fuel cell sensor monitoring position is calculated by formula, and a heat map is drawn to show the dynamic change of pH over time, so as to realize the monitoring of the diffusion range of acidic and alkaline wastewater and trace the source of pollutants. The formula is one of the following: (I) When the wastewater is acidic wastewater, the formula is U = -26.6pH + 1.6DO + 0.5EC + 6.4Ub + 60.5, (ii) When the wastewater is alkaline wastewater, the formula is U = -32.5pH-1.6DO+0.5EC-6.0Ub+330.0, where U is voltage, DO is dissolved oxygen, EC is conductivity, and U b is the baseline voltage.

2. The method according to claim 1, characterized in that The sensor matrix includes at least three sensors, which are respectively located near the sewage outlet, upstream of the sewage outlet and downstream of the sewage outlet.

3. The method according to claim 2, characterized in that The sediment microbial fuel cell sensor comprises an anode, a cathode, an external resistor, a data collector, a conductivity meter, a dissolved oxygen meter, a solar panel, a floating ring and a fixing frame; The anode is buried in the wetland bottom mud, and the cathode floats in the wetland overlying water through a floating ring; the anode, cathode and external resistor are connected in series through a wire; and the external resistor is connected to a data collector; The conductivity meter and the dissolved oxygen meter are located in the overlying water, and the conductivity meter and the dissolved oxygen meter are respectively connected to a data acquisition device; The data collector is used to receive the voltage data at both ends of the external resistor, the data of the conductivity meter and the dissolved oxygen meter, and transmit them to the monitoring terminal; The floating ring floats on the overlying water, and the fixing frame is arranged on the floating ring. The fixing frame is used for setting up a data collector and a solar panel, and the solar panel provides electric energy for the data collector.

4. The method according to claim 3, characterized in that The material of the anode is stainless steel, titanium, graphite or carbon felt.

5. The method according to claim 3, characterized in that: The cathode is made of stainless steel, titanium, graphite or carbon felt.

6. The method according to claim 3, characterized in that: The material of the fixing frame is plastic, aluminum alloy or stainless steel.

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