A composition for controlling the release of phosphorus from the sediment of coastal rivers and lakes and the enrichment of phosphorus-dissolving bacteria, a preparation method and uses thereof

Abstract

This invention discloses a composition, preparation method, and uses for controlling phosphorus release and phosphorus-solubilizing bacteria accumulation in coastal river and lake sediments. The composition contains four components: calcium oxide, magnesium chloride, ferric chloride, and aluminum sulfate. A reagent containing the composition is also disclosed. Both the composition and the reagent are effective in controlling phosphorus release and phosphorus-solubilizing bacteria accumulation in coastal river and lake sediments.

Description

Technical Field

[0001] This invention relates to the field of phosphorus pollution, and more particularly to a composition, preparation method and use of a phosphorus-controlling composition for controlling phosphorus release and phosphorus-solubilizing bacteria accumulation in coastal river and lake sediments. Background Technology

[0002] Phosphorus pollution is a crucial control target for river and lake water quality protection. Especially in recent years, with the continuous strengthening of external pollution control measures, internal pollution has gradually become the main factor restricting water quality improvement. Internal phosphorus pollution mainly originates from the re-release of phosphorus accumulated in bottom sediments. To effectively control internal pollution, there are generally two technical approaches: one is to excavate and treat bottom sediments in situ to remove the main source of phosphorus; the other is to use in-situ treatment technology, which involves adding phosphorus-controlling agents to inhibit the release of phosphorus from the sediments. This method is more widely used for rivers and lakes that are difficult to dredge. Phosphorus-controlling agents can quickly lock phosphorus in the bottom sediments through chemical reactions or physical actions, thereby reducing its migration and release into the overlying water.

[0003] Currently, phosphorus control agents can be mainly divided into two types based on their composition: lanthanide agents and calcium-based agents. Lanthanide agents, due to their high chemical affinity and stability for phosphate, are considered highly efficient phosphorus-locking agents. However, their high cost severely limits the feasibility of large-scale application. In contrast, calcium-based agents have attracted widespread attention due to their low cost, and under certain conditions, they can react with phosphate in sediment to form stable calcium phosphate compounds. However, the high pH issue generated during the application of calcium-based agents has become a significant limiting factor, as national surface water standards clearly stipulate that the pH level of water bodies should be maintained between 6 and 9. Therefore, to overcome the shortcomings of single calcium-based agents, composite agents, through the synergistic effect of multiple components, are feasible for controlling the pH within an ecologically safe range while ensuring effective phosphorus locking. Furthermore, the scouring effect of water flow in the sediment environment can also lead to agent loss and a decrease in fixation capacity. By rationally combining calcium, magnesium, iron, and aluminum agents, the physical strength of the agents can be enhanced to a certain extent, thereby improving their stability in water bodies. However, the combination methods for these four agents are still in the exploratory stage. How to achieve a balance between pH control and agent stability while maintaining a high phosphorus-locking effect remains a technical problem that urgently needs to be solved.

[0004] Traditional research on phosphorus control agents primarily focuses on chemical phosphorus locking, mainly concentrating on reducing phosphorus release through the reaction of the agent with phosphate ions to form insoluble compounds. However, these studies generally overlook the profound impact of microorganisms on the phosphorus cycle, particularly the potential negative effect of phosphate-solubilizing bacteria on the efficacy of phosphorus control agents. Phosphate-solubilizing bacteria are microorganisms capable of converting insoluble phosphorus compounds into soluble phosphate ions. Their activity can lead to the re-release of phosphorus fixed in sediment, thereby weakening the persistence and overall effectiveness of phosphorus control agents. Therefore, effectively inhibiting the activity of phosphate-solubilizing bacteria and reducing their interference with phosphorus control efficacy is a crucial issue to consider in the research and application of phosphorus control agents. However, existing patents and related technology research lack a systematic discussion on the enrichment of phosphate-solubilizing bacteria by phosphorus control agents, indicating a significant research gap in this area.

[0005] Coastal river and lake environments present unique salinity disturbances compared to inland water bodies. Salinity significantly impacts the effectiveness of phosphorus control agents. On one hand, the types and concentrations of dissolved ions in high-salinity environments may competitively react with the active components in the agent, weakening its phosphorus-locking efficiency. On the other hand, salinity can alter the interaction between the agent and sediment particle surfaces, leading to increased agent loss. Furthermore, salinity can also have complex effects on the actual application of phosphorus control agents by changing the structure of sediment microbial communities and the activity of phosphate-solubilizing bacteria. Therefore, developing phosphorus control agents that maintain high phosphorus-locking performance under high-salinity conditions is crucial for adapting to the unique environment of coastal rivers and lakes. Summary of the Invention

[0006] To address the aforementioned challenges, this invention proposes a method for controlling phosphorus release and phosphate-solubilizing bacteria accumulation in coastal river and lake sediments. The core strategy of this method is to develop a comprehensive mixed agent based on four components: calcium oxide (A), magnesium chloride (B), ferric chloride (C), and aluminum sulfate (D). Through a reasonable component ratio, this agent can achieve efficient fixation of phosphorus in the sediment while maintaining the water pH within an ecologically safe range. This solves the problem of calcium-based single agents easily causing pH exceedances in environmental water. Furthermore, it promotes a synergistic solidification reaction between calcium oxide and other components upon contact with water, forming a gel that effectively enhances the physical bond between agent particles, thereby improving erosion resistance. Simultaneously, the pH of the agent is controlled within an appropriate range to inhibit phosphate-solubilizing bacteria.

[0007] Furthermore, based on the above steps, this invention further introduces silica as a modifying material. By coating and modifying the surface of the agent particles, the stability and persistence of the agent under high-salt conditions are improved. This method, while achieving efficient phosphorus control, can also effectively inhibit the activity of phosphate-solubilizing bacteria and reduce the secondary release of phosphorus, thus providing a novel technical solution for the treatment of endogenous pollution in coastal rivers and lakes.

[0008] To achieve the above objectives, the present invention provides a composition for controlling phosphorus release and phosphorus-solubilizing bacteria accumulation in coastal river and lake bottom sediments. The composition is characterized by containing four components: calcium oxide, magnesium chloride, ferric chloride, and aluminum sulfate. Preferably, the weight ratio of these four components is 35%-40%, with magnesium chloride at 5%-10%, ferric chloride at 10%-20%, and aluminum sulfate at 30%-45%.

[0009] The present invention also provides an agent for controlling the release of phosphorus and the accumulation of phosphate-solubilizing bacteria in the bottom sediments of coastal rivers and lakes, characterized in that it contains the aforementioned composition.

[0010] Furthermore, the agent is modified with silica.

[0011] Furthermore, the modification of the agent with silica refers to the process of using tetraethyl orthosilicate or sodium silicate as the silicon source, hydrolyzing it under alkaline conditions to form a uniform silica sol; then, uniformly dispersing the agent particles in the silica sol and ultrasonically stirring to promote the deposition reaction of the silica sol on the particle surface; and then drying and sintering at low temperature to form a dense silica thin-layer coated particles.

[0012] Furthermore, the pH of the alkaline conditions is 8.5-9.2.

[0013] Furthermore, the ultrasonic stirring frequency is 20–40 kHz, and the stirring conditions are 100–300 rpm.

[0014] Furthermore, the deposition reaction takes 10-40 minutes.

[0015] Furthermore, the drying refers to drying at 60-80℃ for 5-8 hours, and the low-temperature sintering refers to sintering at 300-500℃ for 1-3 hours.

[0016] This invention also protects the composition and the agent described herein from having the effect of controlling the release of phosphorus from coastal river and lake bottom sediments and enriching phosphorus-solubilizing bacteria.

[0017] This invention aims to address the problems of phosphorus release from river and lake sediments and poor phosphorus control in high-salt environments during endogenous pollution control. With the core objectives of achieving efficient phosphorus control, stabilizing environmental pH, and enhancing salt tolerance, it proposes a method based on the combination optimization of multi-component agents and silica coating modification. Through a combination of comprehensive experiments and theoretical models, this invention optimizes agent ratios and long-term performance. Furthermore, considering the unique impact of high-salt environments in coastal rivers and lakes on agent performance, this invention further proposes a method based on silica coating modification. Silica sol is prepared using the sol-gel method, with tetraethyl orthosilicate or sodium silicate as the silicon source, and hydrolyzed under alkaline conditions to form a homogeneous silica sol solution. Then, the optimized agent particles are uniformly dispersed in the silica sol, and the deposition reaction of the silica sol on the particle surface is promoted by heating or ultrasonic stirring. After drying at 60-80℃ and sintering at a low temperature of 300-500℃, dense silica thin-layer coated particles are formed. This modification method effectively enhances the stability and salt resistance of the agent. This coating can reduce the direct competitive interference of sodium and potassium ions on the active components of the drug in a high-salt environment, while providing additional phosphate adsorption sites to further enhance the phosphorus fixation capacity. Attached Figure Description

[0018] Figure 1 This is a pH level response diagram of the overlying water under the application of traditional calcium-based phosphorus removal agents.

[0019] Figure 2 This is a graph showing the phosphorus release flux from sediment under different salinity conditions.

[0020] Figure 3 This is a weighted diagram of the influence of environmental factors.

[0021] Figure 4 This is a diagram showing the relative abundance of typical phosphate-solubilizing bacteria in sediment under conditions of no chemical treatment and chemical treatment.

[0022] Figure 5 This is a comparison chart of phosphorus control efficiency before and after reagent modification. Detailed Implementation

[0023] The embodiments of the present invention are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and intended to explain the present invention, and should not be construed as limiting the present invention. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in the art or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0024] Example 1

[0025] This invention uses four components—calcium oxide (A), magnesium chloride (B), ferric chloride (C), and aluminum sulfate (D)—as the basis. An experimental system was constructed using a central coincidence design method. The efficiency of phosphorus release control from the sediment and the pH level of the overlying water were used as key control factors. Thirty experimental protocols were developed and implemented. Through long-term monitoring (30 days), multiple sets of data on phosphorus release control efficiency and overlying water pH were obtained (see Table 1). Subsequently, analysis of variance was used to systematically evaluate the experimental data to determine a suitable model method for fitting the data relationships.

[0026] Table 1. 30 experimental schemes and their results

[0027]

[0028]

[0029] Based on the analysis and verification of the experimental data in Table 1, this invention establishes mathematical models for pH level and phosphorus release control efficiency, which are respectively...

[0030] pH=15.01*A+11.2*B+3.08*C+3.99*D;

[0031] Phosphorus release control efficiency = (93.27*A - 21.43*B + 35.45*C + 58.44*D) / 100.

[0032] Where A, B, C, and D are calcium oxide, magnesium chloride, ferric chloride, and aluminum sulfate, respectively, and all units are percentages (%) by mass; phosphorus release control efficiency is expressed in percent.

[0033] Based on the model, the experimental combination was optimized using a hill-climbing algorithm to determine the relatively optimal component ratio range. Specifically, the weight ratio of calcium oxide (A) was controlled at 35%-40%, magnesium chloride (B) at 5%-10%, ferric chloride (C) at 10%-20%, and aluminum sulfate (D) at 30%-45%. This optimized ratio effectively controls phosphorus release from the sediment, improves phosphorus fixation capacity, and maintains the pH level of the overlying water within the ecologically safe range (8.0-8.8), avoiding pH loss due to a single agent.

[0034] Based on this, this invention, combined with the activity studies of typical phosphate-solubilizing bacteria, further investigates the control requirements of the reagent components. Phosphate-solubilizing bacteria can convert insoluble phosphorus compounds into soluble phosphate, and their activity is significantly affected by environmental pH. The response characteristics of phosphate-solubilizing bacteria under different pH conditions are shown in Table 2. It was found that when the pH range is controlled above 8.0, actinomycetes and fungi are difficult to survive, and as the pH increases, the abundance of Pseudomonas and Bacillus species decreases significantly, thus potentially inhibiting the re-release of phosphorus from sediment. In conjunction with surface water control requirements, this invention proposes that the pH level of the reagent should be controlled between 8.0 and 8.8, giving the reagent comprehensive advantages in inhibiting phosphate-solubilizing bacteria activity, fixing sediment phosphorus, and maintaining the ecological safety of aquatic bodies.

[0035] Phosphate-solubilizing bacteria are a class of microorganisms capable of converting insoluble phosphorus compounds into soluble phosphates. Their activity may lead to the re-release of phosphorus fixed in sediment, thereby enhancing phosphorus release from the sediment. Phosphate-solubilizing bacteria rely on organic acids to dissolve phosphates, but an alkaline environment neutralizes these organic acids, reducing their effectiveness and thus hindering energy acquisition, resulting in an inhibitory effect. The research team found that when the relative abundance of the typical phosphate-solubilizing bacterium Bacillus is greater than 1.1%, there is a significant linear relationship between the relative abundance of this bacterium and phosphorus release. This relationship can be expressed by the following formula:

[0036] Y1 = 12.344562 * X + Y

[0037] Wherein, Y1 is the phosphorus release flux after coupling with phosphate-solubilizing bacteria information (unit: mg / kg / day), X is the relative abundance of Bacillus (unit: %), and Y is the phosphorus release flux obtained from the aforementioned environmental variables (unit: mg / kg / day).

[0038] The results are shown in Table 2 and Figure 1 .

[0039] Table 2. Relative abundance of Pseudomonas and Bacillus phosphate-solubilizing bacteria at different pH levels.

[0040] Bacillus 6.21％ 9.34％ 7.65％ 4.77％ 0.75％ 0.12％ 0.32％ Pseudomonas 11.20％ 4.56％ 8.23％ 5.21％ 0.87％ 0.57％ 0.14％

[0041] Example 2: Experiment on the effect of different salinities on phosphorus release flux in sediment

[0042] Sediment samples were collected from 46 monitoring points in a coastal lake / reservoir. The sampling process involved submerging the sediment sampler to the bottom of the water and then rapidly extracting the sample to maintain its original structure. After sampling, the sediment samples were stored in a low-temperature, sealed container to prevent the effects of oxygen and microbial degradation. Subsequently, laboratory tests were conducted on the 46 samples to determine the phosphorus release flux from the sediment in the salt-free overlying water. The study first used potassium dihydrogen phosphate to prepare phosphorus solutions ranging from 0.05 to 0.2 mg / L. Then, the samples were grouped according to a water-to-soil ratio of 90:1 (i.e., 45 mL: 0.5 g). Each group was separately mixed with the aforementioned sediment sample and the phosphoric acid solution, and after shaking at 25°C for 48 hours, the mixture was separated by centrifugation (10,000 rpm for 10 minutes). Subsequently, the supernatant was treated through a 0.45 μm fiber filtration membrane, and the total phosphorus concentration in the solution was determined according to the standard method "Determination of Total Phosphorus in Water Quality - Ammonium Molybdate Spectrophotometric Method (GB 11893-89)" in "Methods for Monitoring and Analysis of Water and Wastewater (4th Edition)". To investigate the effect of salinity on coastal lake reservoirs, the phosphorus release flux from the sediment in saline overlying water was measured for the aforementioned 46 sediment samples. In this process, solutions with salinity of 5-20‰ were prepared using sodium chloride; then, phosphorus solutions of 0.05-0.2 mg / L were prepared using both this solution and potassium dihydrogen phosphate. Based on a water-to-soil ratio of 90:1 (i.e., 45 mL: 0.5 g), sediment samples of different concentrations were mixed with phosphorus solution and grouped. After being shaken at 25°C for 48 hours, the samples were separated by centrifugation (10,000 rpm for 10 minutes). The supernatant was then extracted again through a 0.45 μm fiber filtration membrane. Finally, the total phosphorus concentration in the solution was determined according to the same standard method described above. The phosphorus release flux was obtained by dividing the phosphorus release by the mass after spectrophotometric analysis. Figure 2 This is a graph showing the phosphorus release flux from sediment under different salinity conditions. The vertical axis represents the sample number, and the horizontal axis represents the sample grouping. The image is a heatmap; the redder the color, the greater the release, and the bluer the color, the less the release.

[0043] The effect of salinity on phosphorus release was evaluated by combining variance inflation factor analysis with the Boruta algorithm. Results Figure 3 . Figure 3 This is a weighted graph of environmental factors. The vertical axis represents the environmental factors, and the horizontal axis represents the weight coefficients, used to compare the magnitude of the factor's influence. The larger the value, the greater the factor's influence. Figure 3 It can be seen that the presence of salinity significantly promotes phosphorus release, and its effect (0.01) is second only to the phosphorus concentration in the sediment (0.02).

[0044] Example 3: Preparation of the drug

[0045] Composition formulation: Calcium oxide 39%, magnesium chloride 8%, ferric chloride 15%, aluminum sulfate 38%. (weight percentage)

[0046] Preparation method:

[0047] Using tetraethyl orthosilicate or sodium silicate as the silicon source, a homogeneous silica sol is formed by hydrolysis under alkaline conditions (pH 8.5-9.2).

[0048] The particles of the above composition are uniformly dispersed in the above silica sol, and the silica sol is promoted to deposit on the particle surface by ultrasonic stirring (ultrasonic frequency of 20–40 kHz, stirring conditions of 100–300 rpm); the deposition reaction time is 10–40 minutes.

[0049] Re-drying: Dry at 60-80℃ for 5-8 hours.

[0050] Low-temperature sintering: Sinter at 300-500℃ for 1-3 hours.

[0051] This forms a dense silica thin-layer coating on the particles.

[0052] Comparative Example 1:

[0053] Composition formulation: Calcium oxide 39%, magnesium chloride 8%, ferric chloride 15%, aluminum sulfate 38%. (weight percentage)

[0054] Preparation method: Mix well, then dry at 60-80℃ for 1-3 hours.

[0055] Example 4: Preparation of the drug

[0056] Composition formulation: Calcium oxide 35%, magnesium chloride 10%, ferric chloride 10%, aluminum sulfate 45%. (weight percentage)

[0057] Preparation method: Same as in Example 3.

[0058] Example 5: Preparation of the drug

[0059] Composition formulation: Calcium oxide 38%, magnesium chloride 5%, ferric chloride 17%, aluminum sulfate 40%. (weight percentage)

[0060] Preparation method: Same as in Example 3.

[0061] Example 6: Preparation of the drug

[0062] Composition formulation: 40% calcium oxide, 10% magnesium chloride, 20% ferric chloride, and 30% aluminum sulfate. (by weight)

[0063] Preparation method: Same as in Example 3.

[0064] Example 7 Effect Test

[0065] 1. A confirmatory analysis was conducted based on the model, and it was found that the model has good performance and can reflect the response change trend of phosphorus release control efficiency and overlying water pH.

[0066] Table 3 Comparison of Experimental Results

[0067]

[0068] Note: The prediction formula is pH = 15.01*A + 11.2*B + 3.08*C + 3.99*D;

[0069] Phosphorus release control efficiency = (93.27*A - 21.43*B + 35.45*C + 58.44*D) / 100.

[0070] It can be seen that the predicted results are close to the actual test results.

[0071] 2. After applying the above-mentioned components, the research team compared the relative abundance characteristics of typical phosphate-solubilizing bacteria in the sediment under conditions of no agent addition and agent addition (obtained in Example 3). The results are shown in [Figure 1]. Figure 4 See Table 4. The results showed that after the addition of the agent (the amount added was controlled at 500 g / m², and the determination was carried out 28 days after application), neither Aspergillus nor Penicillium was detected in the sediment, while Bacillus and Pseudomonas were significantly reduced after the addition of the agent compared with no agent. This result shows that the agent does have a significant ability to inhibit the accumulation of phosphate-solubilizing bacteria.

[0072] Table 4 Figure 4 Corresponding data table

[0073] Aspergillus 0.10％ 0 Penicillium 0.38％ 0 Bacillus 4.56％ 2.10％ Pseudomonas 7.93％ 3.44％

[0074] 3. Based on silica coating modification, the study found that the phosphorus control effect of the agent was slightly reduced in anhydrous water, but it still maintained a high degree of similarity to the unmodified agent, and the reduction in effect was not significant. However, as the salinity increased, the silica-coupled modification strategy played a significant role. Under salinity conditions of 10‰, 20‰, and 30‰, the phosphorus control efficiency of the silica-modified agent (obtained in Example 3) was 59.88%, 56.27%, and 57.22%, respectively, while the phosphorus control efficiency of the unmodified agent (obtained in Comparative Example 1) dropped significantly to 44.21%, 35.61%, and 33.32%, respectively. See Figure 5 .

[0075] Although embodiments of the present invention have been shown and described above, it is understood that the above embodiments are exemplary and should not be construed as limiting the present invention. Those skilled in the art can make changes, modifications, substitutions and variations to the above embodiments within the scope of the present invention without departing from the principles and spirit of the present invention.

Claims

1. A method for controlling phosphorus release and phosphate-solubilizing bacteria accumulation in coastal river and lake sediments, characterized in that, A reagent was used, which contains a composition consisting of four components: calcium oxide, magnesium chloride, ferric chloride, and aluminum sulfate; after the reagent was used, the pH of the overlying water was between 8.0 and 8.

8. The composition comprises 35%-40% calcium oxide, 5%-10% magnesium chloride, 10%-20% ferric chloride, and 30%-45% aluminum sulfate by weight.

2. The method as described in claim 1, characterized in that, The agent is modified with silica.

3. The method as described in claim 2, characterized in that, The modification of the agent with silica refers to the process of using tetraethyl orthosilicate or sodium silicate as the silicon source, hydrolyzing it under alkaline conditions to form a uniform silica sol; then, uniformly dispersing the agent particles in the silica sol and ultrasonically stirring to promote the deposition reaction of the silica sol on the particle surface; and finally drying and sintering at low temperature to form a dense silica thin-layer coated particles.

4. The method as described in claim 3, characterized in that, The pH of the alkaline conditions is 8.5-9.

2.

5. The method as described in claim 3, characterized in that, The ultrasonic stirring is performed at an ultrasonic frequency of 20–40 kHz and a stirring condition of 100–300 rpm.

6. The method as described in claim 3, characterized in that, The deposition reaction takes 10-40 minutes.

7. The method as described in claim 3, characterized in that, The drying refers to drying at 60-80℃ for 5-8 hours, and the low-temperature sintering refers to sintering at 300-500℃ for 1-3 hours.

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