Method for rapid detection of BDOC in water supply network based on electrochemical impedance spectrum

Abstract

A method for rapid detection of BDOC in water supply networks using biofilm sensing based on electrochemical impedance spectroscopy is disclosed, relating to the field of BDOC detection as a water quality biological stability indicator. This invention aims to achieve rapid, in-situ, and non-destructive detection of BDOC in water, thereby reflecting the biological stability of pipeline water quality. The method is based on the linear relationship between the Ct ratio and the concentration of biodegradable dissolved organic matter (BDOC) in water. This relationship can be used to plot a curve fitting equation. Following the same measurement process, the capacitance of the biofilm growing in the actual water sample is measured, and the BDOC concentration in the water sample is calculated by substituting this value into the curve fitting equation. This method enables rapid BDOC measurement; secondly, it uses biofilm capacitance to more comprehensively reflect BDOC and water quality biological stability; and it can be used in water supply networks to achieve in-situ, non-destructive online monitoring of BDOC in water supply networks using electrochemical impedance spectroscopy.

Description

Technical Field

[0001] This invention belongs to the field of BDOC detection, a biological stability index of water quality, and specifically relates to a method for rapid detection of BDOC in water supply networks based on biofilm sensing using electrochemical impedance spectroscopy. Background Technology

[0002] Biological stability of water quality is crucial to drinking water safety. Biofilms in drinking water distribution systems contain pathogens, and infectious diseases caused by pathogens such as bacteria, viruses, and protozoa are the most common and widespread health risks associated with drinking water. These risks can be minimized by controlling the nutrient matrix in drinking water. Biodegradable dissolved organic carbon (BDOC) is an important indicator for evaluating the biological stability of drinking water. Currently, there are various methods for determining BDOC, including suspension culture, bioreactor methods, dynamic circulation methods, and activated biosand methods. These methods are all based on the principle of calculating BDOC by measuring the change in dissolved organic carbon (DOC) before and after inoculation with microorganisms. These methods require long measurement times, lack timeliness, and their detection limits are limited by the TOC analyzer. In addition, because these methods utilize single cultures of non-native bacteria or batch methods of highly domesticated bacteria, they cannot represent the dynamic local bacterial communities found in most water and distribution systems.

[0003] Electrochemical impedance spectroscopy (EIS) applies small-amplitude potentials or currents to an electrode system, causing it to produce an approximately linear response. Based on the impedance spectrum of the electrode system obtained over a wide frequency range, it analyzes electrode process kinetics and interface structure information, finding wide applications in metal corrosion and battery performance research. EIS has also been extensively used to study microbial attachment and biofilm development; its non-destructive nature makes it highly advantageous for real-time monitoring of biofilm development. Summary of the Invention

[0004] The purpose of this invention is to achieve rapid, in-situ, and non-destructive detection of BDOC in water, thereby reflecting the biological stability of pipeline water quality. This invention provides a method for rapid detection of BDOC in water supply networks based on biofilm sensing using electrochemical impedance spectroscopy.

[0005] This invention provides a method for rapid detection of BDOC in water supply networks using biomembrane sensing based on electrochemical impedance spectroscopy. The method comprises the following steps:

[0006] S1. Prepare the sensing electrode by placing it in drinking water containing the concentration of BDOC to be detected, so that a biofilm forms on its surface.

[0007] S2. Measure the electrochemical impedance spectroscopy of electrodes with biofilms attached to their surfaces at a fixed culture time;

[0008] S3. Based on the electrochemical impedance spectrum of the electrode with attached biofilm, the parameters of each device in the equivalent circuit model are identified to obtain the electrochemical capacitance value.

[0009] S4. Microbial detection is performed on electrodes with biofilms attached to their surfaces at a fixed incubation time;

[0010] S5. Collect the biofilm on the electrode surface, prepare a cell suspension, and use a flow cytometer to count the microbial parameters, including cell density.

[0011] S6. At a fixed incubation time, the BDOC concentration of the standard solution with the sensing electrode is detected to obtain the BDOC concentration.

[0012] S7. Based on the formula relating cell density and BDOC concentration, plot a curve and fit the equation.

[0013] The formula relating the microbial parameter cell density to BDOC concentration is as follows:

[0014]

[0015] Where tK1 is a constant under the condition of fixed reaction time, S is the single limiting substrate concentration, and N... t N is the number of cells attached to the electrode at time t, and N0 is the number of cells attached to the electrode at the initial time.

[0016] The aforementioned curve is used to fit an equation formula:

[0017]

[0018] Where K is the half-saturation constant, S is the single limiting substrate concentration, and C... t The ratio of the double-layer capacitor, where b is a constant; the C t The calculation formula is as follows:

[0019] C t =K2N t +b.

[0020] Where K2 is the half-saturation constant, N t Let be the number of cells attached to the electrode at time t, and b be a constant;

[0021] S8. Measure the capacitance of the biofilm growing in the actual water sample, substitute it into the curve fitting equation, and calculate the concentration of BDOC in the water sample.

[0022] Furthermore, the sensing electrode is made of stainless steel, and the geometric dimensions of the stainless steel electrode are 100mm in length and 5mm in diameter.

[0023] Furthermore, the sensing electrode is pretreated and then placed in drinking water containing the BDOC concentration to be detected. The pretreatment involves immersing the electrode in a sodium hypochlorite solution for 1 hour, followed by immersing the electrode in fresh ultrapure water for 30 minutes three times consecutively, and then placing the electrode in an oven at 75°C for 48 hours to remove any residual chlorine. The total chlorine concentration of the sodium hypochlorite solution is 20 mg / L.

[0024] Furthermore, in step S2, the fixed culture time refers to measuring once every 1 day, specifically at intervals of 0d, 1d, 2d, 3d, 4d, 5d, 6d, and 7d.

[0025] Furthermore, in step S3, the parameter identification of each device in the equivalent circuit model based on the electrochemical impedance spectrum of the electrode with attached biofilm is performed at an AC voltage of 10mV, between 10mHz and 100KHz.

[0026] Furthermore, the equivalent circuit model described in step S3 includes: a solution resistance Rs, a double-layer capacitor C, and a charge transfer resistor Rct connected in parallel and then connected in series with a diffusion electrochemical element W.

[0027] Furthermore, in step S4, the fixed culture time refers to measuring once every 1 day, specifically at intervals of 0d, 1d, 2d, 3d, 4d, 5d, 6d, and 7d.

[0028] Furthermore, the temperature for microbial detection in step S4 is 25°C.

[0029] Furthermore, the formula for calculating K1S is μ = K1S, where μ is the specific growth rate of the microorganism.

[0030] Furthermore, the specific growth rate μ of the microorganism is formulated as follows: Where μ max The maximum specific growth rate of microorganisms.

[0031] The present invention has the following beneficial effects:

[0032] Biofilm growth encompasses the formation process of bacterial biofilms, including the adhesion phase, growth phase, maturity phase, and dispersal phase. The present invention is based on the linear relationship between the Ct ratio and the concentration of biodegradable dissolved organic matter (BDOC) in water. This relationship can be used to plot a curve fitting equation. Following the same measurement procedure, the capacitance of the biofilm growing in the actual water sample is measured, and the BDOC concentration in the water sample is calculated by substituting the measured value into the curve fitting equation. The method of this invention enables rapid BDOC measurement by indirectly obtaining BDOC through biofilm capacitance measurement. Secondly, using biofilm capacitance to reflect BDOC and water quality biological stability more comprehensively avoids the drawbacks of traditional methods involving single-species inoculation and long measurement times. Finally, it can be used in water supply networks to achieve in-situ, non-destructive online monitoring of BDOC in water supply networks using electrochemical impedance spectroscopy. Attached Figure Description

[0033] Figure 1 The equivalent circuit model diagram used in this invention;

[0034] Figure 2 Simulated curves and their fitted equations;

[0035] Figure 3 Simplified design diagram of the device. Detailed Implementation

[0036] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the spirit of the contents disclosed in the present invention will be described in detail below. After understanding the embodiments of the present invention, any person skilled in the art can make changes and modifications based on the technology taught in the present invention without departing from the spirit and scope of the present invention.

[0037] The illustrative embodiments and descriptions of the present invention are used to explain the present invention, but are not intended to limit the present invention.

[0038] This embodiment presents a method for rapid detection of BDOC in water supply networks using biomembrane sensing based on electrochemical impedance spectroscopy.

[0039] S100: Prepare a sensing electrode by placing the sensing electrode in drinking water with a known BDOC concentration to form a biofilm on its surface;

[0040] S200: Electrochemical impedance spectroscopy of an electrode with a biofilm attached to its surface measured at a fixed culture time;

[0041] S300: Based on the electrochemical impedance spectrum of the electrode with attached biofilm, the parameters of each device in the equivalent circuit model are identified to obtain the electrochemical capacitance value.

[0042] S400: Microbial detection of electrodes with biofilms attached to their surfaces at a fixed incubation time;

[0043] S500: Remove the biofilm from the electrode surface, prepare a cell suspension, and use a flow cytometer to count and obtain the microbial parameter cell density;

[0044] The microbial parameter cell density is shown in the table below:

[0045] Group <![CDATA[Cell density (cells / cm 2 )]]> BDOC value (mg / L) 1 474 - 2 1077 0.048 3 2305 0.125 4 2907 0.14 5 18530 0.284 6 32716 0.359 7 41225 0.443

[0046] S600: BDOC detection is performed on a standard solution with a sensing electrode placed at a fixed incubation time;

[0047] S700: By using cell density as an intermediate parameter, the capacitance is correlated with BDOC concentration, a curve is plotted, and an equation is fitted. (See...) Figure 2 ;

[0048] S800: Following the above measurement process, measure the capacitance of the biofilm growing in the actual water sample, substitute it into the curve fitting equation, and calculate the concentration of BDOC in the water sample. If the concentration of BDOC in the water sample is less than 0.2 mg / L, it basically proves that the biological stability of the water quality is high.

[0049] The basic principle of this embodiment is as follows:

[0050] Heterotrophic bacteria can utilize dissolved organic matter in water as a carbon source, and their reaction kinetics can be expressed as follows:

[0051]

[0052] Where: μ - specific growth rate of microorganisms;

[0053] μ max - Maximum specific growth rate of microorganisms;

[0054] K S - The half-saturation constant is given when μ = μ max Substrate concentration at / 2;

[0055] S - Single limiting substrate concentration.

[0056] The water supply network is located in an oligotrophic environment, with very low concentrations of biodegradable dissolved organic matter (BDOC) in the water, i.e., S < 0.05. <K S At this point, microbial growth follows a first-order reaction, and the concentration of the organic substrate becomes the controlling factor for microbial growth. The S value in the denominator of the equation can be ignored, and the reaction kinetic equation can be simplified to:

[0057]

[0058]

[0059] μ=K1S (3)

[0060] Specific growth rate:

[0061]

[0062] Where: N—number of cells

[0063] The relationship between cell number and the concentration of biodegradable soluble organic matter (BDOC) can be derived.

[0064]

[0065]

[0066] Under the condition of a fixed reaction time, K1t is a constant, denoted by K;

[0067] Current research indicates that the number of cells N attached to the electrode has a strong linear relationship with the double-layer capacitance C, therefore:

[0068] C t =K2N t +b (7)

[0069] It can be concluded that

[0070]

Claims

1. A method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy using biomembrane sensing, characterized in that... The method is performed according to the following steps: S1. Prepare the sensing electrode by placing it in drinking water containing the concentration of BDOC to be detected, so that a biofilm forms on its surface. S2. Measure the electrochemical impedance spectroscopy of electrodes with biofilms attached to their surfaces at a fixed culture time; S3. Based on the electrochemical impedance spectrum of the electrode with attached biofilm, the parameters of each device in the equivalent circuit model are identified to obtain the electrochemical capacitance value. S4. Microbial detection is performed on electrodes with biofilms attached to their surfaces at a fixed incubation time; S5. Collect the biofilm on the electrode surface, prepare a cell suspension, and use a flow cytometer to count the microbial parameters, including cell density. S6. At a fixed incubation time, the BDOC concentration of the standard solution with the sensing electrode is detected to obtain the BDOC concentration. S7. Based on the formula relating cell density and BDOC concentration, plot a curve and fit the equation. The formula relating the microbial parameter cell density to BDOC concentration is as follows: Where tK1 is a constant under the condition of fixed reaction time, S is the single limiting substrate concentration, and N... t On the electrode The number of cells attached at time t, where N0 is the number of cells attached to the electrode at the initial time. The aforementioned curve is used to fit an equation formula: Where K is the half-saturation constant, S is the single limiting substrate concentration, and C... t The ratio of the double-layer capacitance, where b is a constant and C0 is the initial double-layer capacitance value; The C mentioned t The calculation formula is as follows: Where K2 is the half-saturation constant, N t Let be the number of cells attached to the electrode at time t, and b be a constant; S8. Measure the capacitance of the biofilm growing in the actual water sample, substitute it into the curve fitting equation, and calculate the concentration of BDOC in the water sample.

2. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy using biomembrane sensing, as described in claim 1, is characterized in that... The sensing electrode is made of stainless steel, and its geometric dimensions are 100mm in length and 5mm in diameter.

3. A method for rapid detection of BDOC in a water supply network based on electrochemical impedance spectroscopy using biomembrane sensing, as described in claim 1 or 2, characterized in that... The sensing electrode was pretreated and then placed in drinking water containing the concentration of BDOC to be detected. The pretreatment consisted of immersing the electrode in a sodium hypochlorite solution for 1 hour, then immersing the electrode in fresh ultrapure water for 30 minutes three times in succession, and placing the electrode in an oven at 75°C for 48 hours to remove any residual chlorine. The total chlorine concentration of the sodium hypochlorite solution was 20 mg / L.

4. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy and biomembrane sensing according to claim 1, characterized in that... In step S2, the fixed culture time refers to measuring once every 1 day, specifically at intervals of 0d, 1d, 2d, 3d, 4d, 5d, 6d, and 7d.

5. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy using biomembrane sensing according to claim 1, characterized in that... In step S3, the parameter identification of each device in the equivalent circuit model based on the electrochemical impedance spectrum of the electrode with attached biofilm is performed at an AC voltage of 10 mV, between 10 mHz and 100 kHz.

6. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy and biomembrane sensing according to claim 1, characterized in that... The equivalent circuit model described in step S3 includes: a solution resistance Rs, a double-layer capacitor C, and a charge transfer resistor Rct connected in parallel and then connected in series with a diffusion electrochemical element W.

7. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy and biomembrane sensing according to claim 1, characterized in that... In step S4, the fixed culture time refers to measuring once every 1 day, specifically at intervals of 0d, 1d, 2d, 3d, 4d, 5d, 6d, and 7d.

8. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy and biomembrane sensing according to claim 1, characterized in that... The temperature for microbial detection in step S4 is 25°C.

9. The method for rapid detection of BDOC in water supply networks based on electrochemical impedance spectroscopy and biomembrane sensing according to claim 1, characterized in that... The formula for calculating K1S is as follows: , where μ is rate.

10. The method for rapid detection of BDOC in a water supply network based on electrochemical impedance spectroscopy using biomembrane sensing, as described in claim 9, is characterized in that... The aforementioned The formula for the rate μ is: , where μ max speed, K s Defined as the half-saturation constant.

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