Method for monitoring concentration of trace particulate matters in tap water
By measuring the absorbance change rate of filter membrane during tap water filtration, combined with linear fitting and standard curves, the concentration of trace particulate matter in tap water is achieved inexpensively and easily monitored, solving the problems of expensive equipment and complex operations in the prior art, and providing a cost-effective detection solution.
Patent Information
- Application Number
- CN202510459256.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-04-14
- Publication Date
- 2025-07-18
AI Technical Summary
The prior art is difficult to monitor the concentration of trace particulate matter in tap water inexpensively and easily, especially in low concentrations. Conventional methods such as turbidity detection cannot accurately measure particulate matter concentration, and online particle counter equipment is expensive and precise.
The tap water sample is filtered by a filter membrane, and a laser emission and detection device is set up in the vertical direction of the membrane filter surface. By measuring the change of the absorbance of the filter membrane with the volume of the filter water sample, combined with linear fitting and standard curves, the detection of the concentration of trace particles is achieved.
It provides an inexpensive and easy method that accurately monitors the concentration of trace particulate matter in tap water, overcomes the limitations of turbidity detection, simplifies the operation process and reduces costs.
Smart Images
Figure CN120334079A_ABST
Abstract
Description
Technical Field
[0001] The invention relates to the technical field of water quality monitoring, and in particular to a method for monitoring the concentration of trace particles in tap water. Background Art
[0002] Tap water refers to water that meets the corresponding standards and is produced after being purified and disinfected by a water treatment plant for people's living and production use. Domestic water is mainly drawn from rivers, lakes, groundwater, and surface water through the water plant's water intake pump station. The water plant is treated by sedimentation, disinfection, filtration and other process flows in accordance with the "National Hygiene Standards for Drinking Water", and finally delivered to each user through a water distribution pump station. Turbidity is a conventional indicator that reflects the physical properties of natural water and drinking water. It is used to indicate the clarity or turbidity of water and is an important sensory indicator of water quality. The USEPA or ISO scattering turbidity measurement method is used for detection. The scattering turbidity meter detects the intensity of scattered light at 90 degrees to the light source, and the quantitative turbidity value is obtained by comparison with the turbidity standard. The turbidity value is the result of the scattering effect of all substances in the water sample. The substances that affect the turbidity of tap water mainly include inorganic or organic particles, microorganisms and other insoluble substances in the water.
[0003] Compared with turbidity, the concept of particles is very intuitive, representing insoluble substances in water. During the entire process of tap water production, the particles contained in the water mainly include inorganic / organic particles brought in by the raw water, flocculation residues, quartz or activated carbon particles leaked from the filter tank, and microorganisms in the water. In particular, for the shedding of biofilm on the inner wall of the pipe in the tap water network, there are often low-concentration biofilm fragments, which may contain potential pathogens and may pose a threat to drinking water safety.
[0004] Water quality testing is an indispensable part of the drinking water treatment technology field. Existing conventional and simple water quality test indicators such as turbidity are widely used because of their economic and convenient advantages. However, when the number concentration of particles in water is small, turbidity is often difficult to measure the concentration of particles in water. The particle concentration in tap water is detected using an online particle counter, which can generally monitor the particle size and corresponding number of multiple channels at the same time. It uses the principle of light obstruction and can monitor particles with a particle size range of 2-400um. It is usually used in conjunction with an online turbidity meter to better manage the operation of tap water. However, online particle counter equipment is expensive and precise, and there is an urgent need to develop a cheap and simple method for monitoring low-concentration particles. Summary of the invention
[0005] The purpose of the present invention is to provide a cheap and simple method for monitoring the concentration of trace particles in tap water.
[0006] In the present invention, the water sample to be measured is filtered with a filter membrane, and a visible light emission and detection device is arranged in the vertical direction of the membrane filtration surface. On the filter membrane after filtering the water sample, due to the continuous formation and growth of the filter cake, the detected transmembrane absorbance keeps changing. A suitable laser wavelength is selected, the transmembrane absorbance corresponding to different volumes of the filtered water sample when the light of the selected wavelength passes through the water sample is measured, and the data is linearly fitted to obtain the change rate of the filter membrane absorbance with respect to the volume of the filtered water sample; then, according to the correlation between the concentration of particulate matter in the water and this change rate, the detection of the concentration of trace particulate matter in the water sample to be measured is realized.
[0007] The solution adopted by the present invention to achieve the purpose is as follows: A method for detecting the concentration of trace particulate matter in tap water, comprising the following steps: (1) Take a certain volume of tap water and filter it with a filter membrane, then use a spectrometer to measure the spectrum of the absorbance of the filter membrane to be measured changing with the wavelength, and select an appropriate wavelength as the detection wavelength; (2) Continuously filter the tap water sample with a filter membrane, and at the same time arrange a laser emission and detection device in the vertical direction of the filter membrane to measure the absorbance of the filter membrane corresponding to different volumes of the filtered water sample; (3) Linearly fit the obtained filter membrane absorbance and the corresponding volume of the filtered water sample to obtain a linear curve of the filter membrane absorbance with respect to the volume of the filtered water sample, and the slope of the linear curve is the change rate of the filter membrane absorbance; (4) Take tap water samples with various particulate matter concentrations, measure their particulate matter concentrations with a particle counter, and measure the change rate of their filter membrane absorbance with steps (2) and (3), and then make a standard curve between the change rate of the filter membrane absorbance and the particulate matter concentration according to the relationship between the particulate matter concentration and the change rate of the filter membrane absorbance; (5) In actual monitoring, detect the change rate of the filter membrane absorbance of the tap water sample to be measured relative to the volume of the filtered water sample, and then obtain the particulate matter concentration in the water sample to be measured according to the standard curve in step (4).
[0008] Preferably, in step (1), a spectrometer is used to measure the spectrum of the absorbance of the water sample to be measured changing with the wavelength, the scanning wavelength range used is from 400 to 800 nm, and the scanning step size is not greater than 5 nm. And finally, 600 nm is selected as the detection wavelength.
[0009] Preferably, in step (2), the microfiltration membrane is a transparent etched microfiltration membrane with a pore size of 0.1 - 1 μm and a uniform pore size distribution. When filtering with the filter membrane, the water sample to be measured is driven by a constant flow pump, the filtration mode is dead-end filtration, and the filtration flux is 5 - 20 L / (m 2 ·h).
[0010] Preferably, in the water quality detection method, it is characterized in that the measurement of the absorbance of the filter membrane is carried out in a dark environment or under light-shielding conditions.
[0011] Preferably, in the water quality detection method, the water sample to be measured can be continuously fed for detection.
[0012] Preferably, in the water quality detection method, the filtration method can be used for the enrichment sampling of other trace substances.
[0013] The present invention has the following advantages and beneficial effects: The method of the present invention utilizes the good retention effect of the membrane on particulate matter, colloidal substances, and microbial particles in the water sample, overcoming the problem of difficulty in characterizing ultra-low concentration substances by turbidity in water quality detection; by combining the filter cake layer generated by water sample filtration with the filter membrane absorbance detection technology, it overcomes the problems of complex operation, long time consumption, and poor economy in the conventional detection methods of trace substances, and develops a water quality detection method that cannot be measured by turbidity and is convenient and economical.
[0014] The present invention applies the filter cake layer generated by water sample filtration to water quality detection, performs spectral scanning on the concentrated particulate matter in multiple filtered water samples to measure the absorbance, and selects a suitable wavelength; filters the water sample to be measured with a filter membrane, and at the same time sets a laser emission and detection device in the vertical direction of the membrane filtration surface, measures the absorbance of the filter membrane corresponding to different filtration volumes when the laser of the selected wavelength passes through the water sample, and transmits the signal to a computer for linear fitting to obtain the slope of the filter membrane absorbance with respect to the filtration volume; then, according to the negative correlation between the water quality and the slope, the water quality detection of the water sample to be measured is realized. Description of the Drawings
[0015] Figure 1 Schematic diagram of the water quality detection device using filter membrane pollution in Example 1; Figure 2 Spectrum diagram of the change of the filter cake absorbance of the water samples M and N to be measured with the laser wavelength measured by a spectrometer; Figure 3 For the filter cake absorbance corresponding to the water samples M and N in Example 1: A M , A N and the filtration volume V M , V N are linearly fitted, and the correlation coefficient R 2 is calculated to obtain the corresponding linear regression equation; Figure 4 Standard curve between the change rate of filter membrane absorbance and particulate matter concentration; Figure 5 For Figure 3 Comparison chart of the two linear regression equations in Detailed Description of the Invention
[0016] For a better understanding of the present invention, the following embodiments further illustrate the present invention, but the content of the present invention is not limited to the following embodiments only. Embodiment
[0017] A water quality detection method using membrane fouling includes the following steps: (1) Perform spectral scanning on multiple tap water samples to be measured, and select a suitable laser wavelength As Figure 1 shown, filter the water samples to be measured M and N with a filter membrane, and at the same time set a laser emission and detection device in the vertical direction of the membrane filtration surface. After filtering a certain volume of water sample, use a spectrometer to measure the spectral diagram of the absorbance of the filter membranes of the water samples to be measured M and N changing with the wavelength. The scanning range is from 250 to 750 nm, and the scanning step size is 1 nm. The result is as Figure 2 shown. In the selection of the detection wavelength, give priority to the wavelength with a large absorbance, and at the same time ensure that the change of the absorbance with the wavelength is not too drastic. The result measured by such a wavelength is more sensitive, and the detection conditions are easy to control. The selection of the wavelength when measuring the absorbance is easy for those skilled in the art. In the above spectral diagram, within the range where the average slope of the filter membrane absorbance with respect to the laser wavelength is less than 0.2, select the laser wavelength λ = 600 nm.
[0018] (2) Run the filtration device and collect relevant data Continuously filter the water samples to be measured M and N with a filter membrane, measure the absorbance of the filter membrane corresponding to different filtration volumes of the water sample at the selected wavelength of the laser, and transmit the signal to a computer.
[0019] (3) Establish a linear regression equation to obtain the slope of the filter membrane absorbance with respect to the filtration volume; As Figure 3 shown, respectively perform linear fitting on the filter membrane absorbances: A M , A N corresponding to the water samples M and N and the filtration volumes V M , V N , and calculate the correlation coefficient R 2 , to obtain the corresponding linear regression equations: A M = 0.29V M + 0.2, R 2 = 0.999 and A N = 0.14V N + 0.004, R 2 = 0.999.
[0020] So K M = 0.29, K N= 0.14.
[0021] (4) Then, based on the negative correlation between the water quality and the slope, the water quality detection of the water sample to be measured is realized. Tap water samples with various particulate matter concentrations are taken, their particulate matter concentrations are measured with a particle counter, and the change rate of the absorbance of the filter membrane is measured using steps (2) and (3). Then, according to the relationship between the particulate matter concentration and the change rate of the absorbance of the filter membrane, a standard curve between the change rate of the absorbance of the filter membrane and the particulate matter concentration is made; as Figure 4 shown.
[0022] As Figure 5 shown, based on the negative correlation between the water quality of the water sample to be measured and the slope, combined with the standard curve shown in Figure 4 shown, the concentration of particulate matter in the water can be obtained.
[0023] The filter membrane used in this experiment is a 0.8 μm transparent etched microfiltration membrane.
[0024] During filtration, the water depth on both sides of the filter membrane is 0.5 cm. The water samples M and N to be measured are taken from tap water at different locations in Wuhan urban area, and their turbidities both fluctuate around 0.15 NTU, making it difficult to conveniently distinguish the different concentrations of particulate matter in the two water samples through turbidity.
Claims
1. A method for monitoring the concentration of trace particulate matter in tap water, characterized in that, It includes the following steps: (1) Take a certain volume of tap water and filter it with a filter membrane. Then use a spectrometer to measure the absorbance spectrum of the filter membrane to be measured as a function of wavelength, and select an appropriate wavelength as the detection wavelength; (2) Continuously filter the tap water sample with a filter membrane, and at the same time set up a laser emission and detection device in the vertical direction of the filter membrane to measure the absorbance of the filter membrane corresponding to different filtered water sample volumes; (3) Perform linear fitting on the obtained filter membrane absorbance and the corresponding filtered water sample volume to obtain a linear curve of the filter membrane absorbance against the filtered water sample volume, and the slope of the linear curve is the filter membrane absorbance change rate; (4) Take tap water samples with various particulate matter concentrations, measure their particulate matter concentrations with a particle counter, and measure their filter membrane absorbance change rates using steps (2) and (3). Then, according to the relationship between the particulate matter concentration and the filter membrane absorbance change rate, make a standard curve between the filter membrane absorbance change rate and the particulate matter concentration; (5) During actual monitoring, detect the change rate of the filter membrane absorbance of the tap water sample to be measured relative to the filtered water sample volume, and then obtain the particulate matter concentration in the water sample to be measured according to the standard curve in step (4).
2. The method according to claim 1, wherein: In step (1), use a spectrometer to measure the absorbance spectrum of the filter membrane enriched with particulate matter in the water sample to be measured as a function of wavelength. The scanning wavelength range used is from 400 to 800 nm, and the scanning step size is not greater than 5 nm.
3. The method according to claim 1, characterized in that: In step (2), the microfiltration membrane is a semi-transparent etched microfiltration membrane with a pore size of 0.1 - 1 μm and a uniform pore size distribution.
4. The method according to claim 1, characterized in that: In step (2), during the filtration of the filter membrane, the water sample to be measured is driven by a constant flow pump, the filtration mode is dead-end filtration, and the filtration flux is 5 - 20 L / (m 2 ·h).
5. The method according to claim 1, characterized in that: The measurement of the absorbance is carried out in a dark environment or under light-shielding conditions.
6. The method according to claim 1, wherein: The water sample to be measured can be continuously fed for continuous detection.
7. The method according to claim 1, wherein: The filtration method can be used for the enrichment sampling of low-concentration particulate matter in water.
8. The method according to claim 1, characterized in that: In step (1), the selected detection wavelength is 600 nm.