KR20040023170A - Dipping sensor for real-time BOD monitoring of the water - Google Patents

Abstract

PURPOSE: A dipping sensor for real-time BOD monitoring of water is provided, thereby directly contacting water with the cathode, and improving sensitivity of the sensor using polymer electrolytic membrane-electrode assembly(MEA) and platinum as catalyst. CONSTITUTION: The dipping sensor for real-time BOD monitoring of water comprises a biological fuel cell(10) consisting of the cathode(10a) and anode(10b); a pretreating device(11) for inhibiting introduction of floating matter to the cathode(10a); a rain and dust protecting cover(14) for inhibiting introduction of floating matter to the biological fuel cell(10); a buoy(15); a sensor direction correcting wing(18) connecting to the backside of the biological fuel cell(10) for correcting the installation direction of the fuel cell(10); a data receiving and transmitting device(19) for transmitting data to a data receiving device; and a sinker(16) connected to the biological fuel cell(10) for fixing the position of the fuel cell(10).

Description

Dipping sensor for real-time BOD monitoring of the water

The present invention relates to a buoy sensor for real-time BOD measurement of water quality for measuring in real time the biochemical oxygen demand of the water quality (hereinafter referred to as BOD).

Generally, the water quality measurement items of the stream are 26 items such as biochemical oxygen demand (COD), suspended solids (SS), and total phosphorus (TP), taking into account the items necessary to understand the water quality standards of the river and the quality of the water. (Water Pollutant Monitoring and Application in Water Treatment Systems, 1999, Korea Institute of Science and Technology).

The BOD is an important indicator of water pollution and generally measures the amount of dissolved oxygen required for the biochemical oxidation of organic compounds (Standard Methods for the examination of water and wastewaters, 1995, 19th Edition). However, this method requires the experience and skill of the measurer and has an uncertainty of 15-20% (Wilfrid et al ., 2001, On-line monitoring of wastewater quality: a review, J. Chem. Technol. Biotechnol., 76: 337-348). Moreover, since it requires a long time of 5 days, there is a limit that it is not possible to cope with the BOD change of the water quickly.

The general type of BOD sensor developed so far has been to measure the oxygen consumption rate in a sample by attaching a membrane to which a specific microorganism is fixed to the dissolved oxygen measuring electrode. However, this BOD sensor has a disadvantage in that the microorganisms are fixed to the porous membrane, and thus the porous membrane must be frequently exchanged and an electron transfer medium and a separate transducer must be attached (a monitoring technique and phenomenon of water pollutants, 1998, Korea Institute of Science and Technology, 88-89).

Recently, a mediator-free biofuel cell has been developed and can be enriched with microorganisms having electrochemical activity using activated sludge as inoculum. The current generated in the enriched biofuel cell was directly proportional to the concentration of organic material supplied (Kim, Byung-Hong et al., 1999, Microbial fuel cell without medium, microorganism and industry , 25 (2), 7-). 10). Applicant has developed and commercialized BOD measuring instruments (model names: HABS-2000 and HABS-2001) by applying this principle.

In Korea, the first automatic water quality meter was installed in Noryangjin and Ttukseom water sources in Seoul in 1974. Since then, automatic meters have been distributed to major water supply reserves and intake stations in Korea. Chemical oxygen demand (COD), Cd, Pb, Cu, etc. are continuously measured, and harmful substances are measured as needed (water pollutant monitoring and application research in water treatment systems, 1999, Korea Institute of Science and Technology).

In January 1994, the Ministry of Environment continuously measured and monitored the water quality of major water sources and vulnerable areas of pollution throughout the Nakdong River water pollution incidents. have. The automatic water quality measurement network is an integrated technology business that includes design installation, operation management, maintenance, and quality control of the unmanned remote monitoring system room.It was installed in 20 places at the National Institute of Environmental Research from 1995 to 2000. The Environmental Management Corporation is promoting it as a private agency project. By 2005, 36 additional automatic water quality monitoring networks will be installed to prepare for water pollution accidents.

Therefore, the demand for a sensor capable of measuring BOD, which is a representative measurement item among water quality measurement items, in real time is expected to increase.

Recently, a study has been reported that BOD concentration and current value are correlated when BOD of artificial wastewater is measured in real time continuous mode using a biofuel cell (ISChang et al ., 2001, Continuous determination of BOD in wastewater using microbial fuel cell type of novel biosensor, Proceedings of the International Sensor Conference , 125-126, Seoul, Korea).

SUMMARY OF THE INVENTION An object of the present invention is to provide a buoyancy sensor for real-time biometric measurement of water quality in which a conventional biofuel cell is modified to measure the BOD concentration of water quality in real time based on the research results and social needs as described above. have.

1 is a schematic diagram of a buoy sensor.

2 is a schematic diagram of a cathode and an anode of a buoy sensor.

3A is a three-dimensional view of the pretreatment device.

3B is a plan view of the side of the pretreatment device.

4 is a schematic diagram of a data transmission and reception system.

Figure 5 is a graph showing the change in current value for each concentration of artificial wastewater.

6 is a graph showing the relationship between the concentration of artificial wastewater and the average current value.

7 is a graph showing the relationship between the concentration of artificial wastewater and the maximum current value.

Figure 8a is a graph showing the coulomb produced by the concentration of the artificial waste water in the area.

Figure 8b is a graph showing the relationship between the coulomb produced by the concentration of artificial wastewater.

9 is a graph showing the change in the current value when applied to the sample per arm.

(Explanation of symbols for the main parts of the drawing)

10 biofuel cell 10a negative electrode

10b: anode 11: pretreatment device

12 negative electrode sample outlet 14 non-dust dust

15: buoy 16: weight

17: weight fixing thread 18: sensor direction correction blade

19: Data collection and transmission device 20: Acrylic cylinder

21: cathode sample inlet 22: electrode (cathode)

24a: anode part acrylic cylinder 24b: upper open tube

25 polymer electrolyte membrane electrode assembly 26 platinum wire

27: silicone rubber 28: plastic screw

31 plate 32: hole

41: voltmeter 42, 46: signal converter

43 transmitter 44 data receiving device

45 receiver 47 data interpreter

An object as described above includes a biofuel cell having a cathode through which an organic material is oxidized by a concentrated electrochemically active microorganism and an anode through which electrons generated at the cathode are transferred; A rain / dust shield provided on an upper portion of the biofuel cell to prevent rain and dust from entering the biofuel cell; A buoy provided to the biofuel cell such that the biofuel cell floats in water; A sensor direction correction vane connected to a rear portion of the biofuel cell to correct an installation direction of the biofuel cell; A data collecting / transmitting device provided on said biofuel cell for transmitting and receiving the measured value sensed by said biofuel cell, and transmitting data to a data receiving device arranged at a far distance; It can be achieved by a buoy sensor for real-time biometric measurement of water quality according to the invention, characterized in that it comprises a weight connected to the biofuel cell to fix the position of the biofuel cell floating in water.

In the above, the cathode is disposed in the direction in which water flows to directly react with the organic material and the electrochemically active microorganisms present in the sample.

The negative electrode and the positive electrode are separated by a polymer electrolyte membrane, and a polymer electrolyte membrane-electrode assembly is applied to improve efficiency.

In addition, since the anode is exposed to the atmosphere, oxygen in the atmosphere is used as an oxidant, and is composed of a catalyst layer and a support for supporting the catalyst layer.

In the anode, platinum (Pt) serves as a catalyst in the reduction reaction of oxygen, the support on which this reaction occurs is a water-repellent porous carbon body.

The pretreatment apparatus is formed of a cylindrical body, and a plurality of plates are provided on the upper and lower portions of the cylindrical body so as to cross each other at an angle of 45 ° in a direction opposite to the flow direction of water, while a plurality of holes are formed adjacent to the plate.

In the above, the data collection / transmission apparatus transmits a voltmeter for measuring the voltage of the current generated by the biofuel cell, a signal converter for converting the measured voltage for wireless transmission, and a signal converted for wireless transmission. A transmitter for; The data receiving device analyzes a receiver for receiving data transmitted from the data collecting / transmitting device, a signal converter for converting the received signal into a voltage value of a specific method, and a voltage value converted into a voltage value of a specific method. It includes a data interpreter for outputting the BOD.

Hereinafter, preferred embodiments of the present invention will be described in more detail with reference to the accompanying drawings.

The buoyancy sensor for real-time biometric measurement of water quality according to the present invention flows into the cathode 10a through the pretreatment device 11 of the biofuel cell 10 (buoy sensor) shown in FIG. , It flows out through the negative electrode sample outlet 12. The upper part of the anode 10b of the biofuel cell 10 is opened so that oxygen in the atmosphere can be used as an oxidant, so that no separate oxidant injection is required. At this time, the rain / dust film 14 is provided on the upper part of the anode 10b of the biofuel cell 10 to prevent dust, rain, and the like from flowing into the anode 10b. The biofuel cell 10 can float on the water by the buoy 15 provided on the anode 10b, and the data collection / transmission device 19 for collecting and transmitting data on the upper part of the buoy 15 is provided. Is provided.

The biofuel cell 10 is composed of a cathode 10a and an anode 10b in which organic substances and electrochemically active microorganisms in a sample react directly with each other, and the cathode 10a has a flow direction of water so that the sample can be easily introduced therein. It is arranged toward. A polymer electrolyte membrane-electrode assembly is applied as the cathode 10a and the anode 10b of the biofuel cell 10, and a platinum catalyzed electrode (Korean Patent Application No. 2001-75259, filed by the present applicant) Biofuel cells using a polymer electrolyte membrane-electrode assembly). The negative electrode 10a of the biofuel cell 10 functions as a sensor by oxidizing organic matter by the concentrated electrochemically active microorganism, and generating electrons transferred to the positive electrode 10b to generate a current.

The anode 10b of the biofuel cell 10 is exposed to the atmosphere so that oxygen in the atmosphere is used as an oxidant, and is composed of a support for supporting the catalyst layer and the catalyst layer. As the catalyst material, platinum (Pt), which serves as a catalyst for the reduction reaction of oxygen, is mainly used, and a porous carbon body such as water repellent porous carbon paper or carbon cloth can be used as the support. These can satisfy conditions such as electrical continuity of Pt / C, smooth movement of oxygen into electrode pores filled with thin H ₂ O film, and smooth movement of H-ion to Pt catalyst. The reaction proceeds smoothly, resulting in high performance.

2 shows in more detail a biofuel cell 10 used in a buoy sensor for real-time biometric measurement of water quality in accordance with the present invention. As shown in FIG. 2, the cathode 10a includes an acrylic cylinder 20 having a sample inlet 21 on which the pretreatment device 11 is mounted, and an electrode 22 positioned in the cylinder 20. In the sample inlet 21 of the negative electrode 10a of the biofuel cell 10, a pretreatment device 11 is installed to filter out suspended substances in the sample, as shown in FIG. 1. A clogging phenomenon of the negative electrode 10a due to the suspended matter in the sample can be prevented. The sample introduced into the cathode 10a through the pretreatment device 11 reacts by being in direct contact with the electrode 22 to oxidize the organic material in the sample by the electrochemically active microorganisms concentrated on the electrode 22. ) And the sample reacted to the outside through the outlet (12).

In addition, the anode 10b made of an acrylic plate includes an acrylic cylinder 24a and an upper opening tube 24b positioned at an upper center of the cylinder 24a, as shown in FIG. External atmospheric oxygen may be supplied to the electrode 25 (the anode electrode (platinum catalyzed carbon) in the MEA) through 24b). A polymer electrolyte membrane-electrode assembly (MAA) 25, which is a constituent of the biofuel cell 10, and a leak-proof silicon rubber 27 are disposed between the negative electrode 10a and the positive electrode 10b. Is assembled firmly by acrylic or plastic screws 28. By using platinum-catalyzed electrodes on the anode 10b of the biofuel cell 10 used in the present invention, chemical reactions at the electrodes are smooth and the internal resistance of the sensor itself is low. The polymer electrolyte membrane-electrode assembly 25 is disposed between the cathode 10a and the anode 10b as shown in FIG. 2 and has one of a pair of platinum wires 26 having a diameter of about Φ = 0.5 mm. Is connected to the electrode 22 of the cathode 10a and the other is connected to the anode portion of the polymer electrolyte membrane-electrode assembly 25. The electrons generated at the cathode 10a through oxidation of organic matter in the sample are platinum wires. The current is generated by flowing through the 26 to the anode 10b.

On the other hand, the sample flowing into the biofuel cell 10 is introduced into the cathode 10a through the pretreatment device 11, which is formed in a cylindrical body as shown in Figs. 3a and 3b. The upper and lower portions of the cylindrical body are provided with a plurality of plates 31 staggered with each other at an angle of 45 ° in a direction opposite to the flow direction of water, while a plurality of holes 32 are formed adjacent to the plate 31. Float introduced into the pretreatment device 11 together with water is filtered by the plates 31 arranged to cross each other, and the filtered float is discharged to the outside through the holes 32. As described above, the sample (water) from which the suspended matter is filtered by the pretreatment device 11 flows into the cathode 10a.

The data transmission / reception system of the buoy-type sensor having the configuration as described above is schematically shown in FIG. The biofuel cell 10 is provided with a data collection / transmission device 19 as shown in FIG. 4, and the data collection / transmission device 19 measures the voltage of the current generated by the biofuel cell 10. A voltmeter 41, a signal converter 42 for converting the measured voltage for wireless transmission, and a transmitter 43 for transmitting the converted signal for wireless transmission.

The biofuel cell 10 connects a resistance of 500 Ω between the positive electrode 10b and the negative electrode 10a and the voltage between the positive electrodes is measured by the voltmeters 41 and DDV-032. The voltage measured by the voltmeter 41 is converted for wireless transmission by the signal converter 42 (RS-232S method, which is self-made), and the data receiving device 44 separated from the apparatus by the transmitter 43 (RATA 10V). Is sent).

The data receiving device 44 includes a receiver 45 (RATA 10V) for receiving data transmitted from the data collecting / transmitting device 19 attached to the buoy sensor, and a signal converter 46, RS for converting the received signal. -232S system), and a data analyzer 47 for outputting the BOD by analyzing the converted voltage value.

Data transmitted from the data collection / transmission device 19 via the transmitter 43 is received by the data reception device 44 through the receiver 45. The signal received through the receiver 45 is converted into a voltage value by the signal converter 46 by the RS-232S method, which is the same as the data collection / transmission device 19, and the BOD value by the data analyzer 47. Converted to, outputs BOD. Using this tele-meter system (TMS), the user can monitor the BOD concentration of water quality in the office in real time.

<Example 1>

This embodiment looks at the change in the current value generated when an artificial wastewater of various concentrations is injected into the buoy sensor according to the present invention. In order to enrich the culture with electrochemically active microorganisms, artificial wastewater was continuously injected using sludge for wastewater treatment of Jungnang sewage treatment plant as an inoculum.

The resistance in the biofuel cell 10 was 500 Ω, and the voltage generation amount in the cell 10 was received by converting the voltage signal measured by the voltmeter (DDV-032) using the RS-232S method. Voltage values were measured at intervals. A buoy-type sensor was installed in a 120 × 60 × 100 (cm) tank, and the artificial wastewater was adjusted by adjusting the BOD concentration to 10, 20, 40, and 50 ppm using glucose and glutamic acid. It was to be locked, and the current value generated at this time was measured (see FIG. 5). When a new concentration of artificial wastewater was injected into the tank containing the buoy-type sensor, the current value gradually increased and reached the maximum current value.

The relationship between the average current value generated for about 17 hours and the BOD concentration of the artificial wastewater is shown in the graph of FIG. 6. As a result of the regression, the linear linear relationship was shown and the regression coefficient (r ² ) was about 0.98, indicating a high proportional relationship.

7 is a graph showing the relationship between the maximum current value generated for each concentration of artificial wastewater. The BOD concentration and the maximum current generation of artificial wastewater tended to be proportional to the BOD concentration of about 40 ppm or less, but did not increase to about 1㎃ at the BOD concentration of about 40-50 ppm or more. .

The cumulative current value generated by BOD concentration of artificial wastewater for a certain period of time (about 17 hours) was accumulated (see Fig. 8a) and compared to a coulomb value. 50 coulombs at 50 ppm and about 58 coulombs at 50 ppm. The regression coefficient (r ² ) was about 0.98, indicating a first-order proportional relationship (see FIG. 8B).

<Example 2>

In this embodiment, the BOD concentration of the water quality was measured through the current value generated when the buoy sensor was applied to the field. In order to enrich and culture the electrochemically active microorganism on the buoy-type sensor negative electrode, artificial wastewater was continuously injected in the same manner as in Example 1 using the sludge for wastewater treatment of Jungnang sewage treatment plant as an inoculation source.

The buoyancy sensor after the thickening culture was installed near the upstream of Paldang Dam, a water source protection zone, to observe the change in the current value (see FIG. 9). At this time, the voltage generation amount was received by converting the voltage signal measured by the DDV-032 voltmeter using the RS-232S method, the voltage value was measured at intervals of 120 seconds. BOD measurement results are summarized in Table 1. As a result of applying a sample having a BOD ₅ concentration of 3.8 ± 0.5 ppm, an average current of 0.52 mA and a coulombic value generated for about 17 hours were 31.04 coulombs. The BOD value of the sample per arm was 3.47 ppm calculated by applying the above coulomb value to the regression result of FIG. The BOD value measured using HABS-2000 (Biosystem, Korea), a BOD meter using the biofuel cell (10), was 3.5 ± 0.1 ppm. Could. The difference was about 0.3 ppm from the BOD ₅ value, which is also within the error range. These results indicate the field applicability of buoyancy sensors.

Table 1

Measurement method BOD concentration (ppm) BOD ₅ 3.8 ± 0.5 HABS-2000 3.5 ± 0.1 Buoy sensor 3.5

According to the present invention described above, since the cathode of the sensor is opened and the sample is in direct contact with the cathode, the BOD concentration of the field sample can be monitored in real time more easily than the current water quality monitoring system in which the sample is collected and analyzed.

In addition, by using an electrode catalyzed by a polymer electrolyte membrane-electrode assembly (MEA) and platinum, the chemical reaction of the electrode can be more active, and the sensitivity of the sensor can be increased. In addition, by opening the upper portion of the anode to use oxygen in the atmosphere as an oxidant, the use of an injection device such as water and air injected into the anode to maintain the potential difference can be eliminated, thereby making the structure simpler. .

In addition, the buoyant sensor can float in the water through the floating material and weight, while wings are installed in the opposite direction of the water flow, so that the BOD concentration of water quality can be stably maintained without being disturbed by the river flow. Can be monitored. In addition, by introducing an unmanned remote monitoring system (TMS) to the buoy type sensor, the user can monitor the BOD concentration of the water quality in the office in real time.

Claims (8)

A biofuel cell 10 having a cathode 10a that reacts to oxidize organic matter by the concentrated electrochemically active microorganism, and an anode 10b through which electrons generated at the cathode 10a are transferred; A rain and dust film (14) provided on an upper portion of the biofuel cell (10) to prevent rain and dust from entering the biofuel cell (10); A buoy (15) provided to the biofuel cell (10) so that the biofuel cell (10) can float on water; A sensor direction correction vane (18) connected to a rear portion of the biofuel cell (10) to correct the installation direction of the biofuel cell (10); A data collecting / transmitting device which is provided on the biofuel cell 10 to transmit and receive measured values sensed by the biofuel cell 10 and transmits data to a data receiving device 44 disposed at a long distance ( 19); And a weight (16) connected to the biofuel cell (10) to fix the position of the biofuel cell (10) floating in water. 2. The real-time video quality of water according to claim 1, further comprising a pretreatment device (11) installed in the inlet (21) of the cathode (10a) to filter out suspended matter in the sample flowing into the cathode (10a). Buoy sensor for measurement. The buoy sensor according to claim 1, wherein the cathode (10a) is disposed in a direction in which water flows so as to directly react with organic substances and electrochemically active microorganisms present in the sample. The buoy for measuring real-time video quality of water according to claim 1, wherein a polymer electrolyte membrane-electrode assembly (MEA) is applied to the negative electrode 10a and the positive electrode 10b to bond the polymer electrolyte membrane and the electrode. Type sensor. The buoy sensor according to claim 1, wherein the anode (10b) is exposed to the atmosphere so that oxygen in the atmosphere is used as an oxidant, and is composed of a catalyst layer and a support for supporting the catalyst layer. . [Claim 6] The buoy type sensor of claim 5, wherein the catalytic material serves as a catalyst in the reduction reaction of oxygen with platinum (Pt), and the support on which the reaction occurs is a porous carbon body that is water repellent. . The method of claim 2, wherein the pretreatment device 11 is formed of a cylindrical body, a plurality of plates 31 are installed on the upper and lower portions of the cylindrical body to be staggered with each other at an angle of 45 ° in the direction opposite to the flow direction of water, Buoy type sensor for real-time video measurement of water quality, characterized in that a plurality of holes (32) are formed adjacent to the plate (31). The data collection / transmission device 19 according to claim 1, wherein the data collection / transmission device 19 includes a voltmeter 41 for measuring the voltage of the current generated by the biofuel cell 10, and a signal for converting the measured voltage for wireless transmission. A converter 42, and a transmitter 43 for transmitting the converted signal for wireless transmission; The data receiving device 44 includes a receiver 45 for receiving data transmitted from the data collecting and transmitting device 19, a signal converter 46 for converting the received signal into a voltage value of a specific scheme, and And a data analyzer 47 for outputting a BOD by analyzing a voltage value converted into a voltage value of a specific method.