Method for detecting content of suspended matter in water

Abstract

This invention relates to the field of water quality testing technology, specifically to a method for detecting suspended solids content in water, comprising at least the following steps: S1, collecting a water sample and obtaining a filter membrane carrying suspended solids through suspended solids separation; S2, drying and cooling the filter membrane to constant weight, and then using a beta-ray particulate matter analyzer to obtain the mass concentration Δ of suspended solids trapped on a unit area of ​​the filter membrane. mS S3. The mass concentration of suspended solids in the water sample is calculated using a formula. The detection method used in this application can effectively analyze suspended solids in the range of 0.05-1000 mg / L, and the analytical method is stable and reliable, with high accuracy of analytical results, short detection time for single samples, and high detection efficiency.

Description

Technical Field

[0001] This invention relates to the field of water quality testing technology, specifically to a method for detecting the content of suspended solids in water. Background Technology

[0002] The content of suspended solids in water is one of the core physicochemical indicators for water quality monitoring and water environment assessment. Its content directly reflects the turbidity, pollution level and ecological environment of the water body. Therefore, establishing accurate and efficient methods for detecting suspended solids in water is of great practical significance for water quality monitoring.

[0003] Currently, the mainstream method for detecting suspended solids in the industry is the classical gravimetric method. This method separates suspended solids through a filter membrane, and after multiple drying, cooling, and weighing to constant weight, the concentration of suspended solids is calculated by the ratio of the filter membrane weight gain to the sample volume. For example, Chinese invention patent application CN121324180A. This method serves as an industry benchmark and its test results are highly reliable. However, it suffers from a core flaw: a high detection limit. It cannot accurately quantify low-concentration suspended solids in water samples, making it unsuitable for monitoring surface water, drinking water, and other water bodies with low suspended solids content. This significantly limits its applicability to water quality testing. Furthermore, its detection efficiency is low; the complete testing cycle for a single sample using the traditional gravimetric method typically exceeds 24 hours, failing to meet the needs of continuous testing of large batches of water samples and rapid on-site monitoring. Summary of the Invention

[0004] To address the aforementioned technical problems, a first aspect of the present invention provides a method for detecting the content of suspended solids in water, comprising at least the following steps: S1. After collecting water samples, a filter membrane carrying suspended solids is obtained through suspended solids separation. S2. After drying and cooling the filter membrane to constant weight, the mass concentration Δ of suspended matter trapped on the filter membrane per unit area is obtained using a β-ray particulate matter analyzer. mS The unit is mg / cm³ 2 ; S3. Calculate the mass concentration of suspended solids in the water sample using the formula; The formula is: in, ρ This refers to the concentration of suspended solids, expressed in mg / L. V nd The sample volume is in mL.

[0005] This invention uses a portable beta-ray particulate matter analyzer to directly measure the beta-ray transmittance before and after filtration to obtain the mass of suspended solids captured on a unit area of ​​the filter membrane. The mass concentration of suspended solids in the water sample can then be calculated in real time based on a formula. The attenuation of beta rays penetrating suspended solids is proportional to their mass; by directly converting the transmittance into mass, the accumulated error caused by repeated drying and cooling in traditional weighing methods is avoided. Simultaneously, digital processing eliminates human reading errors, improving data reliability. The relative error of the detection results is ≤±2%, and the single-sample detection cycle is ≤2 hours.

[0006] In some embodiments, the method for collecting water samples includes: washing a polyethylene bottle or hard glass bottle with detergent and rinsing it with water, then washing it three times with the water sample to be tested, and extracting the water sample to be tested using a quantitative sampling pump.

[0007] Optionally, the water is tap water or distilled water.

[0008] In some embodiments, the sampling volume of the collected water sample is 10-100 mL and the sampling flow rate is 5-10 mL / min.

[0009] In some embodiments, the suspended solids separation step includes: filtering the water sample using a filter membrane with a pore size of 0.45 μm at a filtration pressure of 0.1-0.3 MPa.

[0010] This invention controls the pore size of the filter membrane to 0.45 μm and the filtration pressure to 0.1-0.3 MPa, which can improve the integrity of suspended particles and avoid particle size distribution distortion caused by particle breakage; at the same time, the filtration efficiency is improved and there is no risk of filter membrane clogging. The pore size design can effectively trap suspended matter without destroying the particle morphology; low-pressure filtration avoids particle breakage caused by high pressure, ensuring that β-ray attenuation only reflects the true mass of suspended matter, rather than the pseudo-mass after breakage.

[0011] In some embodiments, the filter membrane is made of glass fiber, quartz, or a mixture of cellulose esters.

[0012] In some embodiments, the filter membrane is dried in an oven at 103~105°C for 0.5-1h before use, and then removed and cooled to room temperature in a desiccator.

[0013] Residual moisture on the filter membrane can cause positive interference. Pretreatment and drying can eliminate the influence of background moisture on the filter membrane, ensure the stability of the initial β-ray count, and improve the consistency of the detection baseline.

[0014] In some embodiments, the separation of suspended solids further includes washing the filtered membrane three times with distilled water.

[0015] The washing step can effectively remove soluble salts and microbubbles remaining on the surface of the filter membrane. These impurities can adhere to the surface of suspended matter or occupy the pores of the filter membrane, interfering with the penetration path of beta rays and causing deviations in quality measurement.

[0016] In some embodiments, the amount of distilled water used is 10 mL each time. Precisely controlling the amount of water used for washing can ensure the washing effect while avoiding excessive washing that could lead to the loss of suspended solids. The amount of 10 mL per wash can remove impurities while retaining the maximum amount of trapped suspended particles.

[0017] In some embodiments, the drying and cooling in S2 includes: transferring the filter membrane into an oven and drying it at 103~105°C for 1-1.5 hours, and then transferring it into a dryer to cool it to room temperature.

[0018] In some embodiments, the criterion for determining constant weight in S2 is: repeatedly performing the drying and cooling steps until the difference in filter membrane weight between two adjacent weighings is ≤0.4mg.

[0019] In this application, the filter membrane is kept at a constant weight (with a water content of 0) by repeated drying and cooling. This ensures that when β rays penetrate the filter membrane, their attenuation is determined only by the actual mass of the suspended matter, avoiding false mass signals caused by residual moisture, thereby ensuring the accuracy of subsequent β ray measurements.

[0020] Beneficial effects: 1. This invention uses a portable beta-ray particulate matter analyzer to directly measure the beta-ray attenuation of the dried filter membrane to obtain the suspended matter mass, replacing the traditional method of repeated drying and weighing. The single-sample testing time is reduced from over 24 hours to within 2 hours, increasing efficiency by 12 times and significantly improving environmental monitoring efficiency.

[0021] 2. This invention directly quantifies the mass of suspended solids by measuring the attenuation of β-rays, avoiding the influence of residual moisture and mechanical weighing errors. The relative error is controlled within ±2%, which is 60% more accurate than the traditional gravimetric method (5%) and 75% more accurate than the light scattering method (8%). This ensures high accuracy and reliability of the detection data, meeting the needs of monitoring scenarios with strict accuracy requirements, such as drinking water and surface water, and providing accurate basis for water quality safety assessment.

[0022] 3. This invention uses a filter membrane with a pore size of 0.45μm, combined with a low-pressure filtration process of 0.1-0.3MPa, to effectively avoid the breakage of suspended particles and ensure that the β-ray attenuation is strictly linearly correlated with the mass of suspended matter. The detection range is extended to 0.05-1000mg / L. This method fully covers the full concentration range of drinking water, industrial wastewater, etc., and completely solves the detection bottleneck of traditional gravimetric method in that it cannot detect low-concentration samples and is saturated in high-concentration samples, realizing the applicability of water quality monitoring in all scenarios.

[0023] 4. By optimizing the sampling volume (10-100mL) and sampling flow rate (5-10mL / min), this invention significantly reduces the requirement for water sample volume, greatly alleviating the burden of field sampling. At the same time, the small volume of water sample combined with low-pressure filtration further ensures the uniform distribution of suspended particles on the filter membrane, reduces the deviation of β-ray measurement caused by particle accumulation, and improves the stability of low-concentration sample detection. Detailed Implementation

[0024] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are only for explaining the invention and are not intended to limit the invention. Experimental methods not specifying specific conditions in the embodiments were performed under conventional conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available conventional products.

[0025] Example The first aspect of this example provides a method for detecting suspended solids in water, including the following steps: S1. After collecting water samples, a filter membrane carrying suspended solids is obtained through suspended solids separation. S2. After drying and cooling the filter membrane to constant weight, the mass concentration Δ of suspended matter trapped on the filter membrane per unit area is obtained using a portable β-ray particulate matter analyzer. mS The unit is mg / cm³ 2 ; S3. Calculate the mass concentration of suspended solids in the water sample using the formula; The formula is: in, ρ This refers to the concentration of suspended solids, expressed in mg / L. V nd The sample volume is in mL.

[0026] The water sample collection volume was 100 mL, and the sampling flow rate was 8 mL / min.

[0027] The suspended solids separation step includes: filtering the water sample using a CN-CA filter membrane (nitric acid-acetic acid mixed cellulose ester) with a pore size of 0.45 μm and a filtration pressure of 0.2 MPa.

[0028] The separation of suspended solids also includes washing the filtered membrane three times with distilled water, with 10 mL of distilled water used each time.

[0029] Before use, the filter membrane is dried in an oven at 104°C for 0.5 hours, then removed and cooled to room temperature in a desiccator.

[0030] The drying and cooling process in step S2 includes: transferring the filter membrane into an oven and drying it at 104°C for 1 hour, then transferring it into a dryer to cool it to room temperature.

[0031] The criterion for determining constant weight in S2 is: repeatedly perform the drying and cooling steps until the difference in filter membrane weight between two adjacent weighings is ≤0.4mg.

[0032] Comparative Example 1 The specific implementation method of this example is the same as that of Example 1, except that the filter membrane described in S2 of this example is dried and cooled until the water content of the filter membrane is 10%.

[0033] Comparative Example 2 The specific implementation method of this example is the same as that of Example 1, except that in Example S2, the filter membrane is dried and cooled until the water content of the filter membrane is 20%.

[0034] Comparative Example 3 The specific implementation method of this example is the same as that of Example 1, except that the filter membrane described in S2 of this example is dried and cooled to a moisture content of 30%.

[0035] Performance testing 1. Perform an accuracy test on the detection method provided in this embodiment: The detection method provided in this embodiment was used to determine the suspended solids in simulated wastewater with concentrations of 50 mg / L, 100 mg / L, and 500 mg / L. The relative errors were 2.0%, 0.7%, and 0.1%, respectively, which verified the accuracy of the method. The test data are shown in Table 1.

[0036] Table 1

[0037] 2. The detection methods provided in the various embodiments and comparative examples were used to determine the suspended solids concentration in simulated wastewater with a concentration of 100 mg / L. The test results are shown in Table 2.

[0038] Table 2

[0039] As can be seen from the table above, the accuracy of Comparative Examples 1 to 3 decreased significantly with the increase of the filter membrane moisture content, reaching 49%, 30%, and 11% respectively. This fully demonstrates that drying the filter membrane to constant weight (0% moisture content) before β-ray detection is a crucial step to ensure detection accuracy. Residual moisture will seriously interfere with the measurement of β-ray attenuation, resulting in a large negative deviation in the determination of suspended solids mass concentration.

[0040] 3. Detection limit test: The suspended solids concentrations in simulated wastewater at 0.05 mg / L, 0.10 mg / L, 500 mg / L, and 1000 mg / L were determined. The test results are shown in Table 3. Table 3

[0041] 4. The comparison results between the detection method provided in this example and the traditional gravimetric method and light scattering method are shown in Table 4: Table 4

[0042] The table above shows that the detection method provided in this application can effectively analyze suspended matter in the range of 0.05-1000 mg / L. The method is stable and reliable, with high accuracy, short detection time per sample, and high detection efficiency.

Claims

1. A method for detecting the content of suspended solids in water, characterized in that, At least the following steps are included: S1. After collecting water samples, a filter membrane carrying suspended solids is obtained through suspended solids separation. S2. After drying and cooling the filter membrane to constant weight, the mass concentration Δ of suspended matter trapped on the filter membrane per unit area is obtained using a β-ray particulate matter analyzer. mS The unit is mg / cm³ 2 ; S3. Calculate the mass concentration of suspended solids in the water sample using the formula; The formula is: in, ρ This refers to the mass concentration of suspended solids, expressed in mg / L. V nd The sample volume is in mL.

2. The detection method according to claim 1, characterized in that, The method for collecting water samples includes: washing polyethylene bottles or hard glass bottles with detergent and rinsing them with water, then rinsing them three times with the water sample to be tested, and then extracting the water sample to be tested using a quantitative sampling pump.

3. The detection method according to claim 2, characterized in that, The sampling volume of the collected water samples is 10-100 mL, and the sampling flow rate is 5-10 mL / min.

4. The detection method according to claim 1, characterized in that, The suspended solids separation step includes: filtering the water sample using a filter membrane with a pore size of 0.45 μm and a filtration pressure of 0.1-0.3 MPa.

5. The detection method according to claim 4, characterized in that, The filter membrane is made of materials including glass fiber, quartz, or a mixture of cellulose esters.

6. The detection method according to claim 4, characterized in that, Before use, the filter membrane is placed in an oven at 103~105℃ for 0.5-1h and then removed and cooled to room temperature in a desiccator.

7. The detection method according to claim 4, characterized in that, The separation of suspended solids also includes washing the filtered membrane three times with distilled water.

8. The detection method according to claim 7, characterized in that, The amount of distilled water used is 10 mL each time.

9. The detection method according to claim 1, characterized in that, The drying and cooling process in step S2 includes: transferring the filter membrane into an oven and drying it at 103~105℃ for 1-1.5 hours, and then transferring it into a dryer to cool it to room temperature.

10. The detection method according to claim 1, characterized in that, The criterion for determining constant weight in S2 is: repeatedly perform the drying and cooling steps until the difference in filter membrane weight between two adjacent weighings is ≤0.4mg.

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