CN1293368A - Biological sensor of oxygen amount needed biochemically - Google Patents

Abstract

The invention belongs to the technical field of environmental monitoring and consists of a measurement chamber, immobilized cells, a dissolved oxygen electrode, a magnetic stirrer and a magnetic stirrer, a micro aeration device and an aeration tube; wherein the magnetic stirrer is placed at the bottom of the measurement chamber; The aeration tube of the aeration device is fixed next to the dissolved oxygen electrode: the dissolved oxygen electrode is placed in the center of the measurement chamber; the measurement chamber is filled with buffer solution. The invention has the advantages of low dependence on high-precision dissolved oxygen meter, low price, improved mass transfer, expanded linear measurement range, biosensitive materials can be produced in batches, and can be reused, and can be used for field measurement requirements and can increase the weight of measurement. advantages such as presentness.

Description

Biochemical Oxygen Demand Biosensor

The invention belongs to the technical field of environmental monitoring, in particular to the structural design of a biochemical oxygen demand (BOD) rapid measurement and analysis instrument in water quality pollution monitoring.

A sensor is a device or device that can sense a specified measured substance and convert it into a usable signal (mainly an electrical signal) according to a certain rule. It usually consists of a sensitive element, a conversion element, and a corresponding mechanical structure and electronic circuit. Sensors in which biological components (enzymes, antibodies, antigens, hormones) or organisms themselves (cells, organelles, tissues) are used as sensitive elements are called biosensors.

The biosensor for rapid determination of biochemical oxygen demand (BOD) in water pollution monitoring is mainly composed of microorganisms and oxygen electrodes. Its measurement principle is: when there is no organic oxygen-consuming substance in the measurement chamber, the oxygen electrode outputs a steady-state voltage, which represents the endogenous respiration level of the sensor microorganisms. After adding the water sample for measurement, the biodegradable organic matter in the water sample makes the microorganisms quickly switch to exogenous respiration, consume dissolved oxygen, and the output voltage of the oxygen electrode drops to another low level steady state. There is a linear relationship between the difference between the two steady states and the BOD concentration of the measured water sample within a certain range, so that the rapid measurement of BOD can be carried out.

The typical type of BOD biosensor is sandwich method. Its structure is shown in Fig. 1, is that the porous membrane (14) that has adsorbed microorganism (13) is fixed on the surface of oxygen electrode (11) polytetrafluoroethylene membrane (12) with O-ring (15). In this way, microorganisms are sandwiched between the porous membrane (14) and the polytetrafluoroethylene membrane (12), so it is called the interlayer method.

This structure has the following two problems:

First, the oxygen electrode in the sensor does not measure the real dissolved oxygen content in the test water sample, but the amount of oxygen diffused through the biofilm, which weakens the electrical signal by 3-6 orders of magnitude. Therefore, this kind of instrument not only needs a good measurement environment, but also needs the support of an extremely accurate dissolved oxygen instrument, which makes the price of the overall sensor rise, reaching more than 10,000 US dollars.

Second, the measurement range of this BOD measuring instrument is not only restricted by the metabolism of the microorganism itself, but also largely controlled by the mass transfer of the porous membrane in which the microorganism is embedded, resulting in a low measurement linear range, generally only a few tens of milligrams /L, lower than the BOD level of urban sewage, it can only be measured after dilution.

The purpose of the present invention is to overcome the deficiencies of the prior art, and propose a biochemical oxygen demand (BOD) biosensor, which has low dependence on high-precision dissolved oxygen meters, low price, can improve mass transfer, and expand Linear measurement range, bio-sensitive materials can be produced in batches, and can be used repeatedly, can be used for field measurement requirements and can improve the reproducibility of measurement and other advantages.

A kind of BOD biosensor that the present invention proposes, its composition as shown in Figure 2, by exposure measurement chamber (26), immobilized cell (27), dissolved oxygen electrode (21), magnetic stirrer (29) and magnetic stirrer Sub (28), trace aerator (211) and aeration pipe (210) form. Among them, the magnetic stirring bar is placed at the bottom of the measurement chamber; the aeration hose of the micro aeration device is fixed next to the dissolved oxygen electrode; the dissolved oxygen electrode is placed in the center of the measurement chamber; at the beginning of each measurement, a certain Volume buffer solution, which acts as a dilution of the water sample to be tested, and can adjust the pH value to protect microorganisms. The buffer solution can be water or aqueous solution free of organic pollutants and biological toxic substances, such as phosphate aqueous solution, deionized water, distilled water and the like.

The invention may also comprise a thermostat in which said measuring chamber is placed. The function of the constant temperature device is to ensure that the measurement is carried out at a stable temperature and improve the stability of the measurement.

Features and effects of the present invention

The main feature of the invention is that the mixed solution of immobilized microbial particles and buffer solution or buffer solution and water sample to be tested is used in the sensor to achieve rapid mass transfer and dissolved oxygen balance through magnetic stirring and micro aeration. This measurement method improves the shortcomings of the original sensor and achieves very good results.

The invention has low dependence on high-precision dissolved oxygen meter, low price, can improve mass transfer, expand linear measurement range, and can produce biologically sensitive materials in batches, and can be reused, can be used for field measurement requirements and can increase the weight of measurement. advantages such as presentness.

Experiments show that the standard curve obtained from the determination has a good linear relationship. For a group of BOD standard solutions of 0~200, the correlation coefficient R ² of this measurement method can reach more than 0.9.

This method also has good reproducibility. For the standard solution of BOD50mg/L, the maximum relative deviation was 10.7% when measured 8 times during the day, which was less than the 15% relative deviation of the 5-day BOD standard dilution method.

Brief description of the drawings

Fig. 1 Schematic diagram of the structure of the sandwich method BOD sensor.

Fig. 2 is a schematic structural diagram of the BOD sensor of the present invention.

Fig. 3 is a schematic structural diagram of a BOD sensor embodiment of the present invention.

An embodiment of a biochemical oxygen demand (BOD) biosensor proposed by the present invention, and a water pollution monitoring system based on the sensor as shown in Figure 3, is composed of a (BOD) sensor and a data recording and processing unit. Wherein, the biochemical oxygen demand (BOD) biosensor comprises: constant temperature water bath device (312) is placed on the top of TB-600 gradient stirrer (39), measurement chamber (36) (volume is 150ml) is placed in water bath device, magnetic A stirring bar (38) is placed at the bottom of the measuring chamber. The aeration hose (310) of the CTB-208 micro-aeration pump (311) is fixed next to the dissolved oxygen electrode (31) by an adhesive. The dissolved oxygen electrode is placed in the center of the measuring chamber.

At the beginning of each measurement, the measurement chamber is filled with a certain volume of buffer solution, which acts as a dilution of the water sample to be tested, and can adjust the pH value to protect microorganisms. The function of the constant temperature water bath device is to ensure that the measurement is carried out at a stable temperature and improve the stability of the measurement. A magnetic stirrer and a micro-aeration device are used to mix the solutions in the measurement chamber, reducing the measurement time.

The data recording and processing unit is mainly composed of a YSI-58 dissolved oxygen measuring instrument (313) and a data acquisition card (314). The YSI-58 dissolved oxygen measuring instrument (313) is connected with the dissolved oxygen electrode (31), receives the electrical signal output by the dissolved oxygen electrode, and can monitor the change of dissolved oxygen in the water body in the measurement chamber, and the change can represent the BOD value of the water sample. The data acquisition card (314) collects the electrical signal output by the dissolved oxygen meter (313), and stores it in the computer for subsequent processing. The computer stores programs required for data processing, which can convert the collected data into the measured BOD value.

Use this experimental device to measure the BOD concentration of standard seawater.

Experimental steps:

Polyvinyl alcohol gel embedding of the microorganism Trichosporon cutaneum was first carried out. Cells with a wet weight of 5 g were suspended in 5 mL of 0.9% NaCl and mixed with 12.5 mL of a mixed solution of 10% polyvinyl alcohol and 1% sodium alginate. Then use a 0.40mm ID syringe to drop it into the mixed solution of cooled saturated boric acid and 1% CaCl ₂ to form white spherical beads with a diameter of 2 mm, soak them for 24 hours, and then wash them with normal saline . The above ratio can ensure that the immobilized particles can withstand a certain intensity of stirring for a long time and meet the requirements of repeated use. The immobilized cells can be stored after being dried, and can be used for determination after putting them into nutrient solution and aerating and activating for 24 hours before use, so as to meet the requirements of mass production and field measurement.

The mixture of immobilized particles and 100mL deionized water was placed in an open 150mL measuring chamber, stirred and aerated with a magnetic stirrer and a micro-aeration tube, and the aeration intensity was 24L/h. The temperature of the mixed solution is set at 25°C and the pH is 5. After the dissolved oxygen is stabilized, 10 mL of the solution to be tested is added until the dissolved oxygen drops to a new stable state. The measurement time is 15 minutes and the recovery time is 30 minutes.

The BOD concentration measured by this group is 5, 10, 15, 20, 30, 40, 50, and the linear correlation coefficient achieved by the measurement is 0.94, which meets the requirements of actual seawater online measurement.

Claims (2)

1, a kind of BOD biosensor, it is characterized in that, by exposure measuring chamber (26), immobilized cell (27), dissolved oxygen electrode (21), magnetic stirrer (29) and magnetic stirrer (28), trace The aeration device (211) is composed of an aeration tube (210); wherein, the magnetic stirring bar is placed at the bottom of the measurement chamber; the aeration tube of the micro-aeration device is fixed next to the dissolved oxygen electrode; the dissolved oxygen electrode is placed in the center of the measurement chamber; The measuring chamber is filled with a buffer solution. 2. The BOD biosensor according to claim 1, further comprising a constant temperature device, and said measuring chamber is placed in the constant temperature device.

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