A screening method for aluminum salt coagulants

Abstract

This invention relates to a method for screening aluminum salt coagulants, comprising the following steps: S1: Selecting P candidate coagulants; S2: Conducting coagulation tests on the same raw water with each candidate coagulant, measuring the removal effect of each candidate coagulant, and determining the optimal dosage of each candidate coagulant based on its turbidity removal effect; S3: Selecting the candidate coagulants under the corresponding optimal dosage conditions as primary screening coagulants, measuring the removal effect of each primary screening coagulant, and ranking each primary screening coagulant according to its organic matter removal effect, with the one having the best organic matter removal effect being the optimal primary screening coagulant; S4: Measuring the dissolved residual aluminum content in the supernatant of the water sample after coagulation tests with the primary screening coagulants, obtaining the test value, and judging whether the test value meets the limit requirements starting from the optimal primary screening coagulant, until the first test value that meets the limit requirements is the optimal coagulant.

Description

Technical Field

[0001] This invention relates to the field of tap water treatment technology, and in particular to a method for screening aluminum salt coagulants. Background Technology

[0002] In drinking water treatment, coagulation is a key step in removing suspended solids, colloids, and some dissolved impurities from the water. Its core principle is that the added coagulant neutralizes the charge and adsorbs and bridges the water, causing the tiny particles that are difficult to settle to aggregate into larger flocs, which eventually settle under gravity, thus achieving separation from the clear water.

[0003] Coagulants are mainly divided into two categories: inorganic coagulants and organic polymeric coagulants. Inorganic coagulants primarily include aluminum salt coagulants such as aluminum sulfate and polyalumina. Aluminum salt coagulants are currently the most widely used and consumed mainstream water treatment agents in China.

[0004] However, in actual production, the composition of substances in water varies due to different water sources or different time periods of the same water source. If the same coagulant is used and a fixed dosage is applied, the concentration of dissolved residual aluminum in the effluent may increase. High levels of particulate aluminum can affect the subsequent solid-liquid separation process, leading to increased turbidity. The residue of aluminum flocs may coat the surface of unremoved microorganisms, affecting the disinfection process, causing a decrease in disinfection efficiency, and leading to an increase in disinfection byproducts, especially chloroform. This could result in the effluent water quality exceeding drinking water standards. Summary of the Invention

[0005] Based on this, the purpose of the present invention is to overcome the defects or deficiencies of the prior art and provide a screening method for aluminum salt coagulants, which can determine the optimal coagulant type and optimal dosage for different raw water characteristics, effectively control the turbidity, organic matter and residual dissolved aluminum in the effluent after coagulation, and improve the economy and safety of drinking water treatment.

[0006] A method for screening aluminum salt coagulants, comprising the following steps:

[0007] S1: Select P candidate coagulants, where P≥2; S2: Take each candidate coagulant and conduct coagulation tests on the same raw water to measure the turbidity removal effect of each candidate coagulant on the raw water. Based on the obtained turbidity removal effect of each candidate coagulant, determine the optimal dosage of each candidate coagulant. S3: Take each candidate coagulant under the corresponding optimal dosage condition as the primary screening coagulant, measure the removal effect of each primary screening coagulant on the organic matter in the raw water, and rank each primary screening coagulant according to the obtained organic matter removal effect of each primary screening coagulant. The one with the best organic matter removal effect is the primary screening optimal coagulant. S4: Measure the dissolved residual aluminum content in the supernatant of the water sample after coagulation test of the raw water with the primary screening coagulant, and obtain the test value. According to the ranking of the primary screening coagulants, starting from the optimal primary screening coagulant, determine whether the test value of the dissolved residual aluminum content in the effluent of each primary screening coagulant meets the limit requirement, until the test value meets the limit requirement. The primary screening coagulant corresponding to the first one that meets the limit requirement is the optimal coagulant.

[0008] Compared with existing technologies, the aluminum salt coagulant screening method of the present invention selects core indicators for water treatment effect evaluation such as "turbidity" and "organic matter content" and core indicators for safety evaluation such as "dissolved residual aluminum content in effluent" as screening indicators. By analyzing the coagulation performance of different candidate coagulants on the same raw water, the optimal coagulant type and its optimal dosage for a specific raw water can be screened to achieve the best coagulation effect, while ensuring that the dissolved residual aluminum content in the effluent meets safety standards.

[0009] In one embodiment, step S2 specifically involves: setting a dosage gradient for each candidate coagulant, conducting coagulation tests on the same raw water according to the dosage gradient, and obtaining the turbidity removal rate of each candidate coagulant under different dosage conditions; based on the obtained turbidity removal rate of each candidate coagulant under different dosage conditions, determining the minimum dosage required for each candidate coagulant to meet the preset conditions as the optimal dosage of that candidate coagulant.

[0010] In one embodiment, in step S2, the preset condition is: turbidity removal rate ≥ 95%, or turbidity removal rate < 95% and closest to 95%.

[0011] In one embodiment, step S2, the coagulation test of the same raw water according to the dosage gradient, includes the following steps: Turbidity removal sample groups were prepared using the same raw water, each corresponding to one of the candidate coagulants described in P. Each turbidity removal sample group included m water samples, and m dosage gradients were set for each candidate coagulant, where m ≥ 2. The candidate coagulants with different dosages were added to a single water sample of the corresponding turbidity removal sample group, and coagulation tests were conducted. Then, the turbidity removal rate of each candidate coagulant under different dosage conditions was calculated.

[0012] In one embodiment, step S3 specifically involves: taking each candidate coagulant under the corresponding optimal dosage condition as the primary screening coagulant, taking the supernatant of the water sample corresponding to each primary screening coagulant, and measuring the TOC in each supernatant to obtain the TOC value corresponding to each primary screening coagulant. Based on the TOC value corresponding to each primary screening coagulant, sorting each primary screening coagulant in ascending or descending order, with the one with the smallest TOC value being the optimal primary screening coagulant.

[0013] In one embodiment, step S4 specifically involves: based on the TOC value ranking of each primary screening coagulant, starting with the optimal primary screening coagulant, sequentially measuring the effluent dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant, obtaining test values. For each primary screening coagulant, the effluent dissolved residual aluminum content test value is compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the next lowest TOC value is taken, and the steps of measuring the effluent dissolved residual aluminum content and comparing the test value with the limit value are repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant. Alternatively, the dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant is measured to obtain a test value. Based on the TOC value ranking of each primary screening coagulant, starting from the optimal primary screening coagulant, the effluent dissolved residual aluminum content test value of each primary screening coagulant is compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the next lowest TOC value is selected, and the step of comparing the effluent dissolved residual aluminum content test value with the limit value is repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant.

[0014] In one embodiment, step S3 specifically involves: taking each candidate coagulant under the corresponding optimal dosage condition as the primary screening coagulant, taking the supernatant of the water sample corresponding to each primary screening coagulant, performing three-dimensional fluorescence spectral scanning on each supernatant to obtain the fluorescence intensity integral value of each primary screening coagulant, and sorting each primary screening coagulant in ascending or descending order according to the fluorescence intensity integral value of each primary screening coagulant, wherein the one with the smallest fluorescence intensity integral value is the optimal primary screening coagulant.

[0015] In one embodiment, step S4 specifically involves: based on the ranking of each primary screening coagulant according to its fluorescence intensity integral value, starting with the optimal primary screening coagulant, sequentially measuring the effluent dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant, obtaining test values, and comparing the test values ​​with the limit values. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded, and the next smallest fluorescence intensity integral value is taken, and the steps of testing the effluent dissolved residual aluminum content and comparing the test sample with the limit value are repeated until the effluent dissolved residual aluminum content test value is lower than the limit value. The primary screening coagulant corresponding to the first test value lower than the limit value is the optimal coagulant. Alternatively, the dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant is measured to obtain a test value. Based on the ranking of each primary screening coagulant according to the fluorescence intensity integral value, starting from the optimal primary screening coagulant, the effluent dissolved residual aluminum content test value of each primary screening coagulant is compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the second lowest fluorescence intensity value is selected, and the step of comparing the effluent dissolved residual aluminum content test value with the limit value is repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant.

[0016] In one embodiment, the fluorescence intensity integral value is obtained by the following method: performing a three-dimensional fluorescence spectrum scan on the supernatant of the water sample after coagulation test of each primary screening coagulant within a preset wavelength range, and calculating the fluorescence intensity integral value of each primary screening coagulant within the spectral scanning range by integrating the fluorescence regions.

[0017] In one embodiment, if two or more primary screening coagulants have the same and optimal organic matter removal effect in step S3, step S3 further includes the following steps: measuring the effluent dissolved residual aluminum component in the supernatant of the water sample after coagulation test of the raw water by the primary screening coagulants with the same and optimal organic matter removal effect, obtaining the effluent dissolved residual aluminum speciation distribution of the primary screening coagulants, and ranking the primary screening coagulants with the same and optimal organic matter removal effect according to the obtained proportion of effluent dissolved residual aluminum speciation >100kDa, wherein the one with the largest value is the optimal primary screening coagulant.

[0018] To better understand and implement this invention, the following detailed description is provided in conjunction with the accompanying drawings. Attached Figure Description

[0019] Figure 1 The image shows the turbidity removal effect of different candidate coagulants in Example 1 of the screening method for aluminum salt coagulants of the present invention. Figure 2 This is a graph showing the residual TOC content of different candidate coagulants under the optimal dosage condition in Example 1 of the screening method for aluminum salt coagulants of the present invention. Figure 3 Three-dimensional fluorescence images of different candidate coagulants under optimal dosage conditions in Example 1 of the screening method for aluminum salt coagulants of the present invention: Figure 3 A: Three-dimensional fluorescence effect image after AlCl3 treatment; Figure 3 B: Three-dimensional fluorescence effect image of the product after PACl treatment; Figure 3 C: PACl 10 Processed 3D fluorescence effect image; Figure 3 D: PACl 20Processed 3D fluorescence effect image; Figure 3 E:Al 13 Processed 3D fluorescence effect image; Figure 4 This is a graph showing the residual aluminum content in effluent under optimal dosage conditions for different candidate coagulants in Example 1 of the aluminum salt coagulant screening method of the present invention. Figure 5 This is a diagram showing the residual aluminum composition of effluent under optimal dosage conditions for different candidate coagulants in Example 1 of the aluminum salt coagulant screening method of the present invention. Figure 6 Example 1 of the adaptability verification test of the screening method for aluminum salt coagulants of the present invention: Al 13 Images showing the turbidity removal effect of PACl on products; Figure 7 Example 1 of the adaptability verification test of the screening method for aluminum salt coagulants of the present invention: Al 13 Image showing the algae removal effect of PACl concentration in commercial products; Figure 8 The image shows the turbidity removal effect of different candidate coagulants in Example 2 of the screening method for aluminum salt coagulants of the present invention. Figure 9 This is a graph showing the residual TOC content of different candidate coagulants under the optimal dosage condition in Example 2 of the screening method for aluminum salt coagulants of the present invention. Figure 10 Three-dimensional fluorescence images of different candidate coagulants under optimal dosage conditions in Example 2 of the screening method for aluminum salt coagulants of the present invention: Figure 10 A: Three-dimensional fluorescence effect of the effluent after AlCl3 treatment; Figure 10 B: Three-dimensional fluorescence effect image of the product after PACl treatment; Figure 10 C: PACl 10 Processed 3D fluorescence effect image; Figure 10 D: PACl 20 Processed 3D fluorescence effect image; Figure 10 E:Al 13 Processed 3D fluorescence effect image; Figure 11 This is a graph showing the residual aluminum content in effluent under optimal dosage conditions for different candidate coagulants in Example 2 of the aluminum salt coagulant screening method of the present invention. Figure 12 This is a diagram showing the residual aluminum composition of effluent under optimal dosage conditions for different candidate coagulants in Example 2 of the aluminum salt coagulant screening method of the present invention. Figure 13 Example 2 of the adaptability verification test of the aluminum salt coagulant screening method of the present invention. 13 Images showing the turbidity removal effect of PACl on products; Figure 14 Example 2 of the adaptability verification test of the aluminum salt coagulant screening method of the present invention. 13 The image shows the algae removal effect of PACl concentration used in the product. Detailed Implementation

[0020] Aluminum salt coagulants have good coagulation effects and are therefore widely used in water treatment. However, in the actual production process of water treatment, if the type and dosage of aluminum salt coagulant are not selected properly, it will directly lead to an increase in the residual aluminum concentration. The increase in the residual aluminum concentration in the water will affect the treatment effect of subsequent treatment processes, resulting in the risk that the effluent water quality exceeds drinking water standards.

[0021] Based on this, the present invention provides a screening method for aluminum salt coagulants. The method involves conducting coagulation tests on the same raw water with each candidate coagulant. First, the turbidity removal effect of each candidate coagulant is measured, and the optimal dosage of each candidate coagulant is determined based on the turbidity removal effect. Then, the organic matter removal effect of each candidate coagulant under the optimal dosage condition is measured, and the candidate coagulants are ranked according to the organic matter removal effect to initially determine the optimal coagulant. Finally, the effluent dissolved residual aluminum content of the candidate coagulant under the optimal dosage is measured. Starting from the optimal coagulant in the initial screening, the obtained effluent dissolved residual aluminum content test value is compared with the limit requirement, and the effectiveness of the initial screening is determined based on the comparison result. If ineffective, the comparison of the effluent dissolved residual aluminum content test value with the limit requirement is repeated until the first one that meets the requirement is identified as the optimal coagulant. This invention selects core indicators for evaluating water treatment effectiveness, such as "turbidity" and "organic matter content," as well as core indicators for evaluating safety, such as "dissolved residual aluminum content in effluent," as screening indicators to analyze the coagulation performance of different candidate coagulants on the same raw water. In this way, the optimal type of coagulant and its optimal dosage for a specific raw water can be selected to achieve the best coagulation effect while ensuring that the dissolved residual aluminum content in the effluent meets safety standards.

[0022] Based on the above-mentioned preparation design concept, the aluminum salt coagulant screening method of the present invention will be described in detail below.

[0023] The aluminum salt coagulant screening method of the present invention, in one embodiment, includes the following steps: S1: Select P candidate coagulants, where P≥2; S2: Take each candidate coagulant and conduct coagulation tests on the same raw water to measure the turbidity removal effect of each candidate coagulant on the raw water. Based on the obtained turbidity removal effect of each candidate coagulant, determine the optimal dosage of each candidate coagulant. Specifically, a dosage gradient was set for each candidate coagulant, and then turbidity removal tests were conducted on the same raw water according to the dosage gradient to obtain the turbidity removal rate of each candidate coagulant under different dosage conditions. The turbidity removal test of the same raw water according to the dosage gradient already includes the following steps: First, use the same raw water to prepare turbidity removal sample groups corresponding to the P candidate coagulants. Each turbidity removal sample group includes m water samples, and set m dosage gradients for each candidate coagulant, where m≥2. Then, candidate coagulants with different dosages were added to individual water samples of the corresponding turbidity removal sample groups for coagulation tests, and the turbidity removal rate of each candidate coagulant under different dosage conditions was calculated.

[0024] The specific procedure for the coagulation test is as follows: Take a certain volume of raw water, mix it rapidly at a set speed, add a predetermined amount of coagulant, first stir at a higher speed to form initial flocs, then switch to a lower speed to promote floc growth, and finally allow it to settle. After completion, the turbidity removal rate can be calculated by measuring the turbidity in the water samples before and after coagulation.

[0025] Based on the turbidity removal rates of each candidate coagulant under different dosage conditions, the minimum dosage required for each candidate coagulant to meet preset conditions is determined as the optimal dosage for that candidate coagulant. The preset conditions are: turbidity removal rate ≥ 95%, or turbidity removal rate < 95% but closest to 95%. Specifically, the turbidity removal rates of the obtained candidate coagulants under different dosage conditions are compared, and the minimum dosage with a turbidity removal rate ≥ 95% is taken as the optimal dosage for that candidate coagulant. If the turbidity removal rate of the candidate coagulant is < 95% under all dosage conditions, then the minimum dosage with a turbidity removal rate closest to 95% is taken as the optimal dosage for that candidate coagulant.

[0026] S3: Take each candidate coagulant under the corresponding optimal dosage condition as the primary screening coagulant, measure the removal effect of each primary screening coagulant on the organic matter in the raw water, and rank each primary screening coagulant according to the obtained organic matter removal effect of each primary screening coagulant. The one with the best organic matter removal effect is the primary screening optimal coagulant. Specifically, the primary screening coagulant is a candidate coagulant under its own optimal dosage conditions. The following uses TOC (Total Organic Carbon) to characterize the removal effect of the primary screening coagulant on organic matter in the raw water, and includes the following steps: Take the same raw water used in step S2 to prepare water samples corresponding to P types of primary screening coagulants. Add each primary screening coagulant to the corresponding water sample and conduct the same coagulation test as in step S2. Then, measure the TOC in the supernatant of the water sample after the coagulation test using a total organic carbon analyzer to obtain the TOC value corresponding to each primary screening coagulant. The smaller the TOC value after coagulation, the better the organic matter removal effect of the primary screening coagulant. Then, based on the obtained TOC values ​​of each primary screening coagulant, sort the primary screening coagulants in order of increasing or decreasing TOC value. The one with the smallest TOC value is the optimal primary screening coagulant. Alternatively, the TOC in the supernatant of the water sample corresponding to the candidate coagulant (i.e., the primary screening coagulant) under the optimal dosage conditions in step S2 can be measured directly. In this way, there is no need to perform an additional coagulation test.

[0027] S4: Measure the dissolved residual aluminum content in the supernatant of the water sample after coagulation test of the raw water with the primary screening coagulant, and obtain the test value. According to the ranking of the primary screening coagulants, starting from the optimal primary screening coagulant, determine whether the test value of the dissolved residual aluminum content in the effluent of each primary screening coagulant meets the limit requirement, until a test value meets the limit requirement. The primary screening coagulant corresponding to the first one to meet the limit requirement is the optimal coagulant.

[0028] Specifically, based on the ranking of each primary screening coagulant according to its organic matter removal effect, starting with the optimal primary screening coagulant, each primary screening coagulant is sequentially used to conduct coagulation tests on the raw water used in step S2. Then, the dissolved residual aluminum content in the supernatant of the water sample after the coagulation test is measured to obtain the effluent dissolved residual aluminum content test value of the primary screening coagulant. The effluent dissolved residual aluminum content test value of the primary screening coagulant is compared with the limit value. If the test value is lower than the limit value, the primary screening is effective, and the optimal primary screening coagulant is the optimal coagulant. If the test value is higher than the limit value, the primary screening is ineffective, and the optimal primary screening coagulant is excluded. Then, the coagulant with the second best organic matter removal effect is selected, and the steps of measuring the effluent dissolved residual aluminum content and comparing the obtained test value with the limit value are repeated until a test value is lower than the limit value. The coagulant that first meets the condition of having a test value lower than the limit value is the optimal coagulant.

[0029] Of course, in step S4, the dissolved residual aluminum content in the supernatant of the raw water sample after coagulation can also be measured at once using all the primary screening coagulants. Then, based on the ranking of each primary screening coagulant according to its organic matter removal effect, starting with the optimal primary screening coagulant, the test value of the dissolved residual aluminum content in the effluent corresponding to the optimal primary screening coagulant is compared with the limit value. If the test value is lower than the limit value, the primary screening is effective, and the optimal primary screening coagulant is the optimal coagulant. If the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the test value of the coagulant with the second best organic matter removal effect is taken, and the step of comparing the obtained test value of dissolved residual aluminum content in the effluent with the limit value is repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the one whose test value is lower than the limit value first is the optimal coagulant.

[0030] Similar to step S3, when measuring the effluent dissolved residual aluminum content of the candidate coagulant under optimal conditions, water samples corresponding to each initial screening coagulant in step S2 can be taken and the effluent dissolved residual aluminum content in the supernatant of the water sample can be directly measured, thus eliminating the need for an additional coagulation test.

[0031] In other embodiments, the removal effect of the primary screening coagulant on organic matter in the raw water can also be characterized by the fluorescence intensity integral value of three-dimensional fluorescence. When the fluorescence intensity integral value of three-dimensional fluorescence is used to characterize the organic matter removal effect of the primary screening coagulant, the specific steps include: Coagulation tests were conducted on the same raw water used in step S2 using various primary screening coagulants. A three-dimensional fluorescence spectrophotometer was used to scan the supernatant of the water sample after the coagulation test within a preset wavelength range. The fluorescence intensity integral (FRI) was calculated to represent the total integral value of fluorescence intensity within the spectral scanning range, thus characterizing the content of residual dissolved organic matter in the supernatant. A smaller FRI value indicates a better organic matter removal effect of the primary screening coagulant. The primary screening coagulants were then sorted in ascending or descending order based on the obtained FRI values. Alternatively, a three-dimensional fluorescence spectrophotometer could be directly used to scan the supernatant of the water sample corresponding to each primary screening coagulant in step S2 to calculate the FRI value, thus eliminating the need for an additional coagulation test.

[0032] Correspondingly, in step S4, based on the ranking of each primary screening coagulant according to the fluorescence intensity integral value, starting from the primary screening coagulant corresponding to the minimum fluorescence intensity, the dissolved residual aluminum content in the supernatant of the water sample after coagulation test of the raw water by each primary screening coagulant is measured in sequence to obtain the test value. For each primary screening coagulant, the effluent dissolved residual aluminum content test value is obtained and compared with the limit value. If the test value is lower than the limit value, the primary screening is valid, and the optimal primary screening coagulant is the optimal coagulant, and the test ends. If the test value is higher than the limit value, the primary screening is invalid, and the optimal primary screening coagulant is excluded. Then, the next smallest fluorescence intensity value is taken, and the effluent dissolved residual aluminum content is measured again and the test value is compared with the limit value, until the obtained effluent dissolved residual aluminum content test value of the primary screening coagulant is lower than the limit value. The primary screening coagulant corresponding to the first effluent dissolved residual aluminum content test value lower than the limit value is the optimal coagulant. Alternatively, the effluent dissolved residual aluminum content of all primary screening coagulants can be measured at once. Then, based on the ranking of each primary screening coagulant according to its organic matter removal effect, the test value of each primary screening coagulant is compared with the limit value one by one to determine whether the primary screening is effective. This continues until a test value is lower than the limit value. The primary screening coagulant corresponding to the first one whose test value is lower than the limit value is the optimal coagulant.

[0033] When measuring the organic matter removal effect of each primary screening coagulant, if two or more primary screening coagulants have the same and smallest TOC value or three-dimensional fluorescence intensity integral value, it means that there are two or more optimal primary screening coagulants. To further determine which one is the optimal coagulant, step S3 also includes the following steps: The dissolved residual aluminum components in the supernatant of the water sample after coagulation test of the raw water with the primary screening coagulant with the same and best organic matter removal effect are measured to obtain the residual aluminum speciation distribution of the two or more primary screening coagulants. According to the obtained residual aluminum speciation >100kDa ratio, the primary screening coagulants with the same and best organic matter removal effect are ranked, and the one with the highest value is the optimal primary screening coagulant.

[0034] Therefore, when the optimal coagulant cannot be selected using organic matter removal efficiency (TOC removal rate or fluorescence intensity integral value of three-dimensional fluorescence), the primary coagulants with the same and optimal organic matter removal efficiency are further ranked and screened based on the distribution of dissolved residual aluminum speciation in the effluent. A high proportion of dissolved residual aluminum speciation with a value >100kDa in the effluent is beneficial for coordinating with subsequent filtration and sedimentation processes after coagulation treatment to further reduce the dissolved residual aluminum content in the effluent and achieve better treatment results.

[0035] The following describes in detail the aluminum salt coagulant screening method of the present invention through the process of screening coagulants for raw water from two water supply plants.

[0036] Example 1 This embodiment describes the screening of aluminum salt coagulants for the raw water supplied by Water Plant A. The raw water of Water Plant A is taken from a river-type water source, and its water quality characteristics are: turbidity 17.7 NTU, TOC 4.54 mg / L, pH 7.71, and water temperature 18℃.

[0037] First, take AlCl3 (aluminum chloride), commercial PACl (polyaluminum chloride), and PACl... 10 (Polyaluminum chloride with a basicity of 1.0), PACl 20 (Polyaluminum chloride with a basicity of 2.0) and Al 13 (Nano-polymerized aluminum) as a candidate coagulant; Next, nine dosage gradients were set for each candidate coagulant: 0.005 mmol / L, 0.010 mmol / L, 0.015 mmol / L, 0.020 mmol / L, 0.025 mmol / L, 0.030 mmol / L, 0.035 mmol / L, 0.040 mmol / L, and 0.045 mmol / L, and the following coagulation and sedimentation tests were conducted for each: Take 500 mL of raw water and pre-stir at 250 r / min for 30 seconds. Add a candidate coagulant of a specific concentration and stir rapidly at 200 r / min for 9 seconds to form flocs. Then stir slowly at 40 r / min for 10 minutes to promote floc growth. Finally, let it stand and settle for 30 minutes to complete solid-liquid separation. Measure the turbidity of the water sample after coagulation and calculate the turbidity removal rate of the candidate coagulant at that concentration. Figure 1 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 The turbidity removal effect of five candidate coagulants under different concentration conditions.

[0038] like Figure 1 As shown, Al 13 At 0.020 mmol / L, the turbidity removal rate first exceeds 95%, then Al 13 The optimal dosage is 0.020 mmol / L. PACl 20 PACl 10 At concentrations of 0.030 mmol / L and 0.045 mmol / L, respectively, the turbidity removal rate first exceeded 95%, indicating that PACl... 20 The optimal dosage is 0.030 mmol / L, PACl 10 The optimal dosage is 0.045 mmol / L. Commercially available PACl and AlC... l3Neither PACl nor AlC achieved a turbidity removal rate exceeding 95% under the specified concentration conditions. However, at 0.045 mmol / L, the turbidity removal rate was closest to 95%. Therefore, PACl and AlC... l3 The optimal dosage is 0.045 mmol / L.

[0039] Each candidate coagulant under the corresponding optimal dosage condition is selected as the primary screening coagulant. Then, the supernatant of the water sample corresponding to each primary screening coagulant is taken, and the TOC value in each supernatant is measured. The primary screening coagulants are ranked according to the obtained TOC values, and the primary screening coagulant with the maximum TOC value is determined as the optimal primary screening coagulant. Figure 2 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 The removal efficiency of five candidate coagulants on organic matter under optimal dosage conditions. Figure 2 As shown, under optimal dosage conditions, the five coagulants, ranked from best to worst in terms of organic matter removal efficiency, are: Al 13 PACl 20 PACl 10 >Commercial PACl>AlC l3 .

[0040] While measuring the TOC values ​​of each primary screening coagulant, a three-dimensional fluorescence spectrometer (EEM) was used to scan the supernatant of the water sample. The excitation wavelength (Ex) scanning range was set to 220-400 nm, and the emission wavelength (Em) scanning range was set to 200-550 nm. Fluorescence regional integration (FRI) was used to calculate the overall integral value of fluorescence intensity within the spectral scanning range, obtaining the fluorescence intensity integral value of each primary screening coagulant. The primary screening coagulants were then ranked according to the obtained fluorescence intensity integral values. Figure 3 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 Three-dimensional fluorescence spectra of five candidate coagulants under optimal dosage conditions. Figure 3 As shown, the fluorescence intensity of the supernatant from the initial screening water sample decreased significantly, and the organic matter content decreased significantly. It showed a significant removal effect on proteins (Ex220-250 Em220-380), fulvic acid humic substances (Ex220-250 Em220-380), and dissolved microbial metabolites (Ex250-360 Em220-380), with the removal effect on proteins being the most significant. Therefore, it is evident that, regardless of whether the initial screening coagulants are ranked based on TOC value or the fluorescence intensity integral value of three-dimensional fluorescence, Al... 13Optimal, therefore Al can be 13 It was initially determined to be the optimal coagulant in the preliminary screening.

[0041] Finally, the dissolved residual aluminum content in the supernatant of the water sample corresponding to the optimal coagulant AlCl3 was measured. Figure 4 The figure shows the dissolved residual aluminum content in the supernatant of the initial screening water sample of AlCl3. For example... Figure 4 As shown, the residual aluminum content in the effluent from AlCl3 under optimal dosage conditions is less than 0.2 mg / L (the limit for residual aluminum concentration in domestic water in GB5749-2022), indicating effective initial screening. Therefore, AlCl3 can be used for initial screening. 13 It was determined to be the optimal coagulant, with an optimal dosage of 0.020 mmol / L.

[0042] Furthermore, before measuring the dissolved residual aluminum content in the effluent corresponding to the primary screening coagulant, the distribution of residual aluminum speciation in the supernatant of the water sample corresponding to each primary screening coagulant was measured. Figure 5 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 Distribution of aluminum speciation in five primary screening coagulants. Figure 5 As shown, the proportions of residual aluminum forms >100 kDa in the supernatant of the water samples corresponding to the five primary screening coagulants, ranked from largest to smallest, are: Al 13 PACl 20 PACl 10 >Commercial PACl>AlC l3 Although no two or more primary screening coagulants showed the same or optimal organic matter screening effect during the above screening process, the measurement of the proportion of primary screening coagulants with residual aluminum forms >100kDa further confirmed the presence of Al. 13 It is indeed the optimal coagulant.

[0043] The above screening method determines the optimal dosage of each candidate coagulant by its turbidity removal effect. Then, it determines the optimal coagulant by the organic matter removal effect of each candidate coagulant under the optimal dosage condition (in some cases, the results of the effluent dissolved residual aluminum component of each candidate coagulant under the optimal dosage condition can also be combined). Finally, the optimal coagulant in the initial screening is subjected to a safety test on the effluent dissolved residual aluminum content to confirm the validity of the initial screening results and ensure that the optimal coagulant finally selected has the best coagulation performance while meeting the water quality safety requirements.

[0044] Adaptability Validation To verify the performance of the optimal coagulant selected through the above screening method, the optimal coagulant Al was... 13Compared with the existing commercial PACl coagulant used in water supply A, at their respective optimal dosages (Al) 13 The optimal dosage for [the product] is 0.020 mmol / L, and the optimal dosage for commercial PACl is 0.045 mmol / L. The following adaptability verification tests were conducted: (1) Prepare two sets of water samples with different turbidity gradients, each with 6 gradients: 10 NTU, 20 NTU, 30 NTU, 40 NTU, 50 NTU, and 60 NTU. Add 0.020 mmol / L of Al to one set of water samples with different turbidity gradients. 13 Another set of turbidity gradient water samples were treated with 0.045 mmol / L of commercial PACl, and the turbidity of the effluent was measured and the turbidity removal rate was calculated. Figure 6 Al was shown 13 The turbidity removal effect of PACl on products. Figure 6 As shown, as the initial turbidity increased from 10 NTU to 60 NTU, the turbidity removal rate of PACl dropped sharply from 90% to 70%; while the turbidity removal rate of Al13 decreased from 93% to 85% within the same density range, showing higher stability compared to commercial PACl.

[0045] (2) Configure two sets of algal concentrations (OD) 680 Water samples with varying algal concentrations were used, employing *Microcystis aeruginosa* solution. Each group had six concentration gradients: 0.10, 0.15, 0.20, 0.25, 0.30, and 0.40. 0.020 mmol / L of Al was added to one of the algal concentration gradient water samples. 13 Another group of water samples with varying algae addition rates were treated with 0.045 mmol / L of commercial PACl. The algae density in the effluent was measured, and the algae removal rate was calculated. Figure 6 Al was shown 13 The algae removal effect of PACl used in commercial products. For example... Figure 7 As shown, as the initial algae density increased from 0.10 to 0.40, the algae removal rate of commercial PACl dropped sharply from nearly 90% to 70%; Al 13 The removal rate decreased from approximately 93% to 83% within the same density range, demonstrating greater stability.

[0046] The results of the above adaptability verification tests show that the coagulants screened by the screening method of the present invention have better coagulation performance and higher stability.

[0047] Example 2 This embodiment describes the screening of aluminum salt coagulants for the raw water supplied by Water Plant B. The raw water of Water Plant B is taken from a river-type water source, and its water quality characteristics are: turbidity 10.94 NTU, TOC 9.68 mg / L, pH 7.39, and water temperature 16℃.

[0048] First, take AlCl3, commercial PACl, and PACl... 10 PACl 20 And Al 13 As a candidate coagulant; Next, six dosage gradients were set for each candidate coagulant: 0.005 mmol / L, 0.015 mmol / L, 0.025 mmol / L, 0.035 mmol / L, 0.040 mmol / L, and 0.045 mmol / L, and coagulation and sedimentation tests were conducted for each. The specific steps of the coagulation and sedimentation test have been described in Example 1, so they will not be repeated here.

[0049] Figure 8 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 The turbidity removal effects of five candidate coagulants under different concentration conditions. Figure 8 As shown, Al 13 At 0.025 mmol / L, the turbidity removal rate first exceeds 95%, then Al 13 The optimal dosage is 0.025 mmol / L. PACl 20 PACl 10 Commercial PACl and AlC l3 The turbidity removal rates of all samples did not exceed 95%, but the closest turbidity removal rate was observed at 0.045 mmol / L. Therefore, PACl... 20 PACl 10 Commercial PACl and AlC l3 The optimal dosage for all cases was 0.045 mmol / L.

[0050] Each candidate coagulant under the corresponding optimal dosage condition is selected as the primary screening coagulant. Then, the supernatant of the water sample corresponding to each primary screening coagulant is taken, and the TOC value in each supernatant is measured. The primary screening coagulants are ranked according to the obtained TOC values, and the primary screening coagulant with the maximum TOC value is determined as the optimal primary screening coagulant. Figure 8 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 The removal efficiency of five candidate coagulants on organic matter under optimal dosage conditions. Figure 2 As shown, under optimal dosage conditions, the five coagulants, ranked from best to worst in terms of organic matter removal efficiency, are: Al 13 PACl 20 PACl 10 >Commercial PACl>AlC l3 .

[0051] While measuring the TOC values ​​of each primary screening coagulant, a three-dimensional fluorescence spectrophotometer (EEM) was used to scan the supernatant of the water sample. The excitation wavelength (Ex) scanning range was set to 220-400 nm, and the emission wavelength (Em) scanning range was set to 200-550 nm. Fluorescence regional integration (FRI) was used to calculate the overall integral value of fluorescence intensity within the spectral scanning range, obtaining the fluorescence intensity integral value of each primary screening coagulant. Based on the obtained fluorescence intensity integral values, the primary screening coagulants were ranked. Figure 10 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 Three-dimensional fluorescence spectra of five candidate coagulants in the 220-500 nm range under optimal dosage conditions. Figure 10 As shown in A-10E, the effluent after AlCl3 treatment ( Figure 10 A) High fluorescence intensity within the spectral scanning range indicates a high organic content in the water; effluent treated with PACl (commercial) Figure 10 B) Fluorescence intensity decreased within the same spectral scanning range, but a significant fluorescence signal was still present; PACl 10 The treated effluent ( Figure 10 C) The fluorescence intensity further decreased, indicating a better organic matter removal effect; PACl 20 The treated effluent ( Figure 10 D) Lower fluorescence intensity indicates that it is more effective in removing organic matter; Al 13 The treated effluent ( Figure 10 E) The lowest fluorescence intensity within the spectral scanning range indicates the best organic matter removal effect. The overall integral value of fluorescence intensity within the spectral scanning range is calculated by integrating the fluorescence region, yielding the fluorescence intensity integral value for each primary screening coagulant. The primary screening coagulants are then ranked according to their obtained fluorescence intensity integral values, with Al having the smallest fluorescence intensity integral value. 13 Therefore, it can be seen that whether ranking the initial screening coagulants based on TOC value or the fluorescence intensity integral value of three-dimensional fluorescence, Al 13 Optimal, therefore Al can be 13 It was initially determined to be the optimal coagulant in the preliminary screening.

[0052] Finally, the dissolved residual aluminum content in the supernatant of the water sample corresponding to the optimal coagulant AlCl3 was measured. Figure 11 The figure shows the dissolved residual aluminum content in the supernatant of the initial screening water sample of AlCl3. For example... Figure 11 As shown, the residual aluminum content in the effluent from AlCl3 under optimal dosage conditions is less than 0.2 mg / L (the upper limit for residual aluminum concentration in GB5749-2022), indicating effective initial screening. Therefore, AlCl3 can be used for initial screening. 13 It was determined to be the optimal coagulant, with an optimal dosage of 0.025 mmol / L.

[0053] Furthermore, before measuring the dissolved residual aluminum content in the effluent corresponding to the primary screening coagulant, the distribution of residual aluminum speciation in the supernatant of the water sample corresponding to each primary screening coagulant was measured. Figure 12 AlCl3, commercial PACl, and PACl are shown. 10 PACl 20 And Al 13 Distribution of aluminum speciation in five primary screening coagulants. Figure 12 As shown, the proportions of residual aluminum forms >100 kDa in the supernatant of the water samples corresponding to the five primary screening coagulants, ranked from largest to smallest, are: Al 13 PACl 20 PACl 10 >Commercial PACl>AlC l3 The measurement of the proportion of residual aluminum forms >100 kDa in the initial screening of coagulants further confirmed the Al content. 13 It is indeed the optimal coagulant.

[0054] Adaptability Validation To verify the performance of the optimal coagulant selected through the above screening method, the optimal coagulant Al was... 13 Compared with the existing commercial PACl coagulant used in water supply A, at their respective optimal dosages (Al) 13 The optimal dosage is 0.025 mmol / L (the optimal dosage for commercial PACl is 0.045 mmol / L). The following adaptability verification tests were conducted: (1) Prepare two sets of water samples with different turbidity gradients, each with 6 gradients: 10 NTU, 20 NTU, 30 NTU, 40 NTU, 50 NTU, and 60 NTU. Add 0.020 mmol / L of Al to one set of water samples with different turbidity gradients. 13 In another group of turbidity gradient water samples, 0.045 mmol / L of commercial PACl was added to conduct coagulation and sedimentation tests, and the turbidity of the effluent was measured and the turbidity removal rate was calculated. Figure 13 Al was shown 13 The turbidity removal effect of PACl on products. Figure 13As shown, the turbidity removal rate of PACl gradually decreased with increasing initial turbidity, from approximately 92% at an initial turbidity of 10 NTU to approximately 75% at an initial turbidity of 60 NTU. 13 The turbidity removal rate was approximately 95% at an initial turbidity of 10 NTU, gradually decreasing to approximately 86% at 60 NTU as the initial turbidity increased. Although the removal rate also decreased, Al... 13 Its removal performance was consistently better than PACl across the entire turbidity range, with a smaller decrease.

[0055] (2) Configure two sets of algal concentrations (OD) 680 Water samples with varying algal concentrations were used, employing *Microcystis aeruginosa* solution. Each group had six concentration gradients: 0.10, 0.15, 0.20, 0.25, 0.30, and 0.40. 0.025 mmol / L of Al was added to one of the algal concentration gradient water samples. 13 Another group of water samples with varying algae addition rates were treated with 0.045 mmol / L of commercial PACl, and the algae density in the effluent was measured to calculate the algae removal rate. As the initial algae density increased, the algae removal rate of PACl decreased sharply, from approximately 97% at an initial algae density of 0.10 to less than 80% at an initial algae density of 0.40. 13 The algae removal rate was approximately 98% at an initial algae density of 0.10, decreasing to approximately 90% as the density increased to 0.40. Despite this decrease in removal rate, Al... 13 Its removal performance was consistently better than PACl across the entire density range, with a smaller decrease.

[0056] The results of the above adaptability verification tests show that the coagulants screened by the screening method of the present invention have better coagulation performance and higher stability.

[0057] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to limit the embodiments of this application. The singular forms “a,” “the,” and “the” used in the embodiments and claims of this application are also intended to include the plural forms, unless the context clearly indicates otherwise. It should also be understood that, unless otherwise stated, “a plurality” means two or more; the terms “first,” “second,” “third,” etc., are used only to distinguish and not to describe a particular order or sequence, nor should they be construed as indicating or implying relative importance. The term “and / or” as used herein refers to and includes any or all possible combinations of one or more associated listed items. When the above description relates to drawings, unless otherwise indicated, the same numbers in different drawings represent the same or similar elements. In the description of this application, those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0058] The embodiments described above are merely examples of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements all fall within the scope of protection of the present invention.

Claims

1. A screening method for aluminum salt coagulants, characterized by, The method comprises the following steps: S1: selecting P candidate coagulants, wherein P≥2; S2: taking each candidate coagulant to conduct coagulation test on the same raw water, measuring the turbidity removal effect of each candidate coagulant on the raw water, and determining the optimal dosage of each candidate coagulant according to the obtained turbidity removal effect of each candidate coagulant; S3: taking each candidate coagulant under the corresponding optimal dosage as a primary screening coagulant, measuring the organic matter removal effect of each primary screening coagulant on the raw water, and ranking each primary screening coagulant according to the obtained organic matter removal effect of each primary screening coagulant, wherein the primary screening coagulant with the optimal organic matter removal effect is the primary screening optimal coagulant; S4: measuring the dissolved residual aluminum content in the supernatant of the water sample after the coagulation test of the primary screening coagulant on the raw water to obtain a test value, and starting from the primary screening optimal coagulant, judging whether the test value of the dissolved residual aluminum content of the primary screening coagulant meets the limit value requirement one by one until the test value meets the limit value requirement, and the primary screening coagulant corresponding to the first one that meets the limit value requirement is the optimal coagulant.

2. The method for screening aluminum salt coagulants according to claim 1, wherein: Step S2 is specifically: a dosage gradient is set for each candidate coagulant, coagulation test is conducted on the same raw water according to the dosage gradient, and the turbidity removal rate of each candidate coagulant under different dosages is obtained; the minimum dosage required by each candidate coagulant to meet a preset condition is determined as the optimal dosage of the candidate coagulant according to the obtained turbidity removal rate of each candidate coagulant under different dosages.

3. The method for screening aluminum salt coagulants according to claim 2, wherein: in step S2, the preset condition is that the turbidity removal rate is ≥95% or the turbidity removal rate is <95% and is closest to 95%.

4. The method for screening aluminum salt coagulants according to claim 2, wherein: in step S2, the coagulation test on the same raw water according to the dosage gradient comprises the following steps: a turbidity removal sample group corresponding to each of the P candidate coagulants is prepared from the same raw water, each turbidity removal sample group comprises m water samples, and m dosing gradients are set for each candidate coagulant, wherein m≥2; the candidate coagulants with different dosages are added into the single water samples of the corresponding turbidity removal sample groups respectively, coagulation test is conducted, and then the turbidity removal rates of the candidate coagulants under different dosages are calculated.

5. The method for screening aluminum salt coagulants according to claim 1, wherein: Step S3 is specifically: each candidate coagulant under the corresponding optimal dosage is taken as a primary screening coagulant, the supernatant of the water sample corresponding to each primary screening coagulant is taken, the TOC in each supernatant is measured to obtain the TOC value corresponding to each primary screening coagulant, and each primary screening coagulant is ranked in ascending or descending order according to the TOC value corresponding to each primary screening coagulant, wherein the primary screening coagulant with the minimum TOC value is the primary screening optimal coagulant.

6. The method for screening aluminum salt coagulants according to claim 5, wherein: Step S4 is as follows: Based on the TOC value ranking of each primary screening coagulant, starting with the optimal primary screening coagulant, the dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant is measured sequentially to obtain the test value. For each primary screening coagulant, the effluent dissolved residual aluminum content test value is compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the next lowest TOC value is taken, and the steps of measuring the effluent dissolved residual aluminum content and comparing the test value with the limit value are repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant. Alternatively, the dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant is measured to obtain a test value. Based on the TOC value ranking of each primary screening coagulant, starting from the optimal primary screening coagulant, the effluent dissolved residual aluminum content test value of each primary screening coagulant is compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the next lowest TOC value is selected, and the step of comparing the effluent dissolved residual aluminum content test value with the limit value is repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant.

7. The screening method for aluminum salt coagulants according to claim 1, characterized in that: Step S3 is as follows: Each candidate coagulant under the corresponding optimal dosage condition is selected as the primary screening coagulant. The supernatant of the water sample corresponding to each primary screening coagulant is taken, and three-dimensional fluorescence spectroscopy is performed on each supernatant to obtain the fluorescence intensity integral value of each primary screening coagulant. According to the fluorescence intensity integral value of each primary screening coagulant, the primary screening coagulants are sorted in ascending or descending order, and the one with the smallest fluorescence intensity integral value is the optimal primary screening coagulant.

8. The screening method for aluminum salt coagulants according to claim 7, characterized in that: Step S4 is as follows: Based on the ranking of each primary screening coagulant according to its fluorescence intensity integral value, starting with the optimal primary screening coagulant, the dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant is measured sequentially. The test value is obtained and compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. At the same time, the second smallest fluorescence intensity integral value is taken, and the test of dissolved residual aluminum content in the effluent is repeated, and the test sample is compared with the limit value, until the test value of dissolved residual aluminum content in the effluent is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant. Alternatively, the dissolved residual aluminum content in the supernatant of the water sample after coagulation testing of the raw water by each primary screening coagulant is measured to obtain a test value. Based on the ranking of each primary screening coagulant according to the fluorescence intensity integral value, starting from the optimal primary screening coagulant, the effluent dissolved residual aluminum content test value of each primary screening coagulant is compared with the limit value. If the test value is lower than the limit value, the optimal primary screening coagulant is the optimal coagulant; if the test value is higher than the limit value, the optimal primary screening coagulant is excluded. Then, the second lowest fluorescence intensity value is selected, and the step of comparing the effluent dissolved residual aluminum content test value with the limit value is repeated until a test value is lower than the limit value. The primary screening coagulant corresponding to the first test value to be lower than the limit value is the optimal coagulant.

9. The screening method for aluminum salt coagulants according to claim 7, characterized in that: The fluorescence intensity integral value is obtained by the following method: Three-dimensional fluorescence spectroscopy was performed on the supernatant of water samples after coagulation tests of each primary screening coagulant within a preset wavelength range. The fluorescence intensity integral value of each primary screening coagulant within the spectral scanning range was calculated by integrating the fluorescence regions.

10. The screening method for aluminum salt coagulants according to claim 1, characterized in that: In step S3, if two or more primary screening coagulants have the same and optimal organic matter removal effect, step S3 further includes the following steps: The dissolved residual aluminum components in the supernatant of the water sample after coagulation test of the raw water with the primary screening coagulant with the same and optimal organic matter removal effect were measured to obtain the effluent dissolved residual aluminum speciation distribution of the primary screening coagulant. Based on the obtained proportion of effluent dissolved residual aluminum speciation >100kDa, the primary screening coagulants with the same and optimal organic matter removal effect were ranked, and the one with the largest value was the optimal primary screening coagulant.

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