WO2023206930A1 - Method for treating polluted water body by using water quality regulator - Google Patents

Abstract

Disclosed in the present invention is a method for treating a polluted water body by using a water quality regulator. The water quality regulator comprises acidic calcium sulfate. Pollutants in polluted water bodies comprise blue-green algae, green algae, moss or spirogyra. The acidic calcium sulfate has great safety; and, at a use dilution ratio of 1/3000, an alga removing effect can be achieved just after half an hour, and blue-green algae obviously settle and die after one hour. The water quality regulator is remarkably better than several commonly-used chemical algaecides currently on the market. The water quality regulator causes no secondary pollution, is non-corrosive, has low cost, can be widely used, and is easy to use, thereby being very suitable for emergency treatment and control of blue-green alga outbreak.

Description

A method of using water quality regulator to control polluted water bodies (1) Technical field

The present invention relates to the treatment of polluted water bodies, and in particular to a method of treating polluted water bodies by utilizing a water quality conditioner named acidic calcium sulfate.

(2) Background technology

Lake eutrophication and cyanobacteria blooms are one of the major environmental problems currently facing the world. Cyanobacteria bloom is a natural ecological phenomenon caused by the excessive and rapid proliferation of Cyanobacteria algae caused by eutrophication of water bodies. It is also a kind of secondary pollution. The apparent characteristic is the accumulation of algae on the surface of the water body or the suspension of algae particles in the water body. In the context of global warming, as human activities increasingly impact the surrounding environment, algal blooms have become more frequent and serious. The scale of cyanobacteria outbreaks in my country's Taihu Lake, Chaohu Lake, Dianchi Lake and other lakes is getting larger and larger, the outbreak period is getting longer and longer, and the damage and losses caused are getting more and more serious.

The outbreak of cyanobacteria blooms can cause great damage to aquatic ecosystems, and can also cause many problems such as environmental pollution and water quality safety, and have adverse effects on fisheries, industry, agriculture, tourism, and daily life. Cyanobacteria blooms can release odors and algal toxins, causing the death of fish and other aquatic animals. The algae decompose after death, making the water black and smelly. In 2007, a large outbreak of cyanobacteria in Taihu Lake triggered a drinking water crisis in Wuxi City and posed a huge threat to the water safety of local people. In response to the increasingly serious large-scale blue-green algae outbreaks, efficient and large-scale emergency algae removal measures are more urgently needed. In April 2020, the Ministry of Ecology and Environment emphasized improving emergency response capabilities when deploying algae bloom prevention and control work in key lakes and reservoirs. Emergency management technology should be a core component of cyanobacteria bloom prevention and control capabilities.

At present, conventional algae removal methods mainly include chemical, physical, biological and other technologies. Chemical algaecides use oxidants (hydrogen peroxide, ozone, chlorine dioxide, sodium hypochlorite, potassium persulfate, etc.), algaecides (copper sulfate, isothiazolinone, etc.), antibiotics, etc. to directly kill algae cells. Existing chemical algaecides can reduce the concentration of algae in water bodies in a short time, and are easy to operate and have obvious effects. However, existing chemical algaecides are not very safe and require large dosages, which can cause damage to microorganisms, animals and plants in the water body, and can easily cause secondary pollution. In addition, long-term use of certain algaecides can easily cause algae to develop resistance. Copper ions can destroy intracellular substances such as chloroplasts, leading to the reduction or death of algal cells. However, metal ions themselves have certain toxicity, and excessive dosage can easily cause the concentration of copper ions in the water to exceed the biosafety warning line, causing damage to the water ecosystem. As a new algaecide, chlorine dioxide is more efficient than Cl ₂ , but it still produces the risk of exceeding standards such as Cl ^- , and such substances are also potentially toxic to mammals.

In summary, there is currently a lack of algae removal technologies and products on the market that are safe, efficient, fast-acting, widely used, convenient, and free of secondary pollution. Therefore, it is necessary to develop new, efficient, safe, environmentally friendly, and free of secondary pollution algae removal technologies and products. Algaecides that can be used on a large scale are particularly urgent.

Acidic Calcium Sulfate (ACS) is a new type of slightly soluble Group IIA complex (AGIIS) acidic or low pH solution developed by American Mionix Company (US25348299, CN100490684C). Its main applications include: cleaning , food production, disinfection, biological decontamination, agricultural applications, medical applications and detoxification of substances. ACS is a generally recognized safe ingredient (Generally Recognized as Safe, GRAS for short) and has a strong bactericidal effect.

However, the research and application of ACS in the treatment of polluted water bodies such as cyanobacteria has not yet been discovered and reported. The present invention aims to provide a new solution for treating polluted water bodies containing cyanobacteria and the like.

(3) Contents of the invention

The purpose of the present invention is to provide a method for treating polluted water bodies using a water quality conditioner to solve the problems of low efficiency, poor safety of existing cyanobacteria bloom control technology, and no effective method to deal with sudden outbreaks of high-concentration cyanobacteria.

The technical solution adopted by the present invention is:

The present invention provides a method for treating polluted water bodies using a water quality conditioner. The water quality conditioner includes acid calcium sulfate (ACS). The pollutants in the polluted water bodies include cyanobacteria, green algae, moss or spirogyra.

Preferably, the method is to add a water quality conditioner into the polluted water body to destroy the pollutants.

Preferably, the cyanobacteria include Microcystis spp., Anabaena spp., Aphanizomenon spp., Dolichospermum spp., Cylindrospermopsis raciborskii ), Spirogyra spp., Planktothrix spp., Pandorina spp., Euglena spp., Aulacoseira spp., Fragilaria ( Fragilaria spp.), Hydrodictyon spp. or Cladophora spp. are common algae that pollute water bodies.

Preferably, the volume ratio (V:V) of the added amount of the water quality conditioner (especially acidic calcium sulfate, equivalent concentration is 16.0N) to the polluted water body is 1:100~1000000, and the usage concentration and needs under different conditions It is related to the degree of controlled cyanobacteria blooms, moss, spirogyra and other pollutants.

Preferably, based on the inhibition rate ≥50%, when the cyanobacterial cell density in the polluted water to be treated is ≤1.0×10 ³ cells·mL ^-1 , the application volume ratio of ACS is one hundred thousandth, that is, ACS:water (V:V)＝1:100000;

When the density of cyanobacterial cells in the polluted water to be treated is 1.01×10 ³ to 1.0×10 ⁵ cells·mL ^-1 , the application volume ratio of ACS is one ten thousandth, that is, ACS:water (V:V)=1 :10000;

When the density of cyanobacterial cells in the polluted water to be treated is 1.01×10 ⁵ to 1.0×10 ⁷ cells·mL ^-1 , the application volume ratio of ACS is one-thousandth, that is, ACS:water (V:V) = 1:3000;

When the density of cyanobacterial cells in the polluted water to be treated is ≥1.01×10 ⁷ cells·mL ^-1 , the application volume ratio of ACS is 1/2000, that is, ACS:water (V:V)=1:(100~ 2000).

Preferably, the water quality conditioner of the present invention also includes a mixture of one or more of the following auxiliaries: organic acids, inorganic acids, organic alcohols, and oxidants; the organic acids include acetic acid; the organic alcohols include ethanol, The oxidizing agent includes hydrogen peroxide.

The ACS of the present invention is made by mixing calcium hydroxide, calcium sulfate, sulfuric acid and water as raw materials to produce a concentration greater than 0.1N; the ACS is added to cyanobacteria-containing water bodies that need to be treated, and can be added preferentially to areas where cyanobacteria occur densely and locally. Key areas with high concentrations; the waters to be treated and cyanobacteria blooms include composite harmful organisms other than common algae, such as filamentous algae such as Spirogyra and other aquatic pollutants such as moss; the ACS application volume ratio can also be based on Adjust appropriately according to different seasons, water temperatures, algae growth potential, etc. In severe cases such as sudden outbreaks, increase the frequency of use or increase the concentration; the ACS can be used alone, or organic acids, inorganic acids, ethanol, and peroxide can be added. It can also be used in combination with other physical algae control and algae removal measures; the algae density and occurrence severity of the cyanobacteria waiting to be treated can also be measured based on the volume concentration of the algae (for example, the volume concentration of the algae in the water is 100 ml /L), it can also be carried out based on chlorophyll concentration (for example, 5000 μg/L) or algae cell density.

Preferably, the acidic calcium sulfate is prepared as follows: add sulfuric acid dropwise into a reaction kettle filled with deionized water, stir, slowly add calcium sulfate, and cool to 8-12°C; mix the calcium compound with deionized water. Mix, stir, and add to the reaction kettle in batches, control the temperature between 8 and 12°C, and complete the addition; continue to keep stirring for 3-6 hours (preferably 4 hours); discharge and filter to obtain acidic calcium sulfate; the sulfate 98% concentrated sulfuric acid is preferred; the calcium compound is calcium hydroxide, calcium oxide, calcium carbonate or calcium bicarbonate, more preferably calcium hydroxide; the calcium sulfate and concentrated sulfuric acid feeding mass ratio is 1:200~210, so The feeding mass ratio of the calcium compound and concentrated sulfuric acid is (0.075-0.75): 1; the total volume of deionized water is 120-150L/Kg based on the mass of calcium sulfate.

Compared with the existing technology, the beneficial effects of the present invention are mainly reflected in:

1. ACS has high security. ACS is a "generally recognized as safe substance (GRAS)" announced by the U.S. Food and Drug Administration (FDA). "GRAS" is determined by the food industry based on relevant laws and regulations, public scientific evidence or long-term use history, and Decisions must be made based on careful evaluation of their safety under specific conditions of use. Therefore, its safety can be absolutely guaranteed. At present, the substance has been widely used in the fields of cleaning, food production, disinfection, biological decontamination, agricultural applications, medical applications and detoxification of substances. This is an advantage that no other chemical algaecide currently has;

2. Efficiency. When the application volume ratio of ACS is one-thousandth, that is, ACS: water body (V:V) = 1:3000), the algae removal effect can be observed after 0.5 hours. After 1 hour, obvious settlement and death of cyanobacteria were observed. The high efficiency of ACS is also reflected in its ability to effectively treat high-concentration cyanobacteria blooms, which is significantly better than several commonly used chemical algaecides currently on the market;

3. No secondary pollution and non-corrosive. ACS is a highly structured complex inorganic acid. After algae removal, its original structure disintegrates and forms algal sludge with the inactivated cyanobacteria and sinks to the bottom of the water;

4. Low cost. The raw materials for manufacturing ACS are widely sourced, cheap and easy to obtain, the preparation process is simple, and the manufacturing cost is low;

5. It can be used in a wide range and is easy to apply. Very suitable for emergency treatment and management of blue-green algae outbreaks.

(4) Description of drawings

Figure 1. Relationship curve between alkali-acid ratio and acidic calcium sulfate equivalent concentration.

Figure 2. Temporal effect of chlorophyll a concentration changes in Microcystis aeruginosa under the action of different concentrations of acidic calcium sulfate.

Figure 3. Time effect diagram of changes in the percentage of complete cells of Microcystis aeruginosa under the action of different concentrations of acidic calcium sulfate.

Figure 4. Time effect diagram of the turbidity change of Microcystis aeruginosa under the action of different concentrations of acidic calcium sulfate.

Figure 5. Comparative photos before and after treating cyanobacteria with acid calcium sulfate (ACS) in Example 4. A and B are both untreated controls, and C is the treated group.

Figure 6. Photomicrographs before and after treatment of cyanobacteria with acid calcium sulfate (ACS) in Example 4; A: Untreated cyanobacteria cells, intact. B: Cells ruptured and died after ACS treatment for 1 hour.

Figure 7. Comparative photos of the algae removal effects of different algaecides in Example 4, 1-1 chlorine dioxide, 2-1 hydrogen peroxide, 3-1 potassium hydrogen persulfate, 4-1 ACS, 5-1 sodium hypochlorite (containing active Chlorine 5.2%).

Figure 8. Photos before and after acid calcium sulfate (ACS) treatment of cyanobacteria bloom ponds.

(5) Specific implementation methods

The present invention will be further described below with reference to specific examples, but the protection scope of the present invention is not limited thereto: the room temperature mentioned in the present invention refers to 22 to 25°C.

Example 1, Preparation of 16.0N acid calcium sulfate (ACS)

Add 1050Kg of 98% concentrated sulfuric acid dropwise into a 2000-liter reaction kettle containing 380Kg of deionized water, stir, slowly add 5Kg of calcium sulfate, and cool to 8°C. Mix 182Kg of calcium hydroxide powder (food grade, purity above 98%) and 260Kg of deionized water, stir, and add to the reactor in batches. Control the temperature between 8 and 12°C and complete the addition. Continue to keep warm and stir for 4 hours. Discharge, filter, and take the filtrate to obtain 16.0N acid calcium sulfate (ACS for short).

Adjust the material ratio of calcium hydroxide and concentrated sulfuric acid (i.e., different alkali-acid ratios) to obtain acidic calcium sulfate (ACS) with different equivalent concentrations, as shown in Figure 1. It can also be diluted with deionized water to form the required equivalent concentration. of acid calcium sulfate.

Example 2. Algaecidal effect of acidic calcium sulfate on Microcystis aeruginosa

1. Experimental materials

The experimental algae species is Microcystis aeruginosa, which comes from the freshwater algae species bank of the National Aquatic Germplasm Resource Bank of the Institute of Hydrobiology, Chinese Academy of Sciences.

2. Experimental methods

Add 300 mL of BG11 medium (Gibco ^TM BG-11 Media) to a 1L Erlenmeyer flask, and inoculate Microcystis aeruginosa so that the algae cell concentration is between 1*10 ⁷ cells·mL ^-1 and 1.3*10 ⁷ cells·mL ^-1 between, as Microcystis aeruginosa algal fluid. Take 150 mL of Microcystis aeruginosa algae solution and add it to a 250 mL cell culture bottle, and then add 16.0N acidic calcium sulfate prepared by the method of Example 1 in the amount of 0, 0.2, 0.3, and 0.5 mL/L, and observe continuously for 168 hours at room temperature. The algae liquid treated with different amounts of acidic calcium sulfate was obtained, and the algae liquid was taken for sample analysis.

3. Sample analysis

(1) Use the four-band measurement method to detect the concentration of chlorophyll a (Chlorophyll a, Chl-a): take 5mL of algae liquid and filter it with GF/C glass fiber filter membrane (Whatman, diameter 47mm, pore size 1.2μm), and filter the The filter cake and filter membrane were soaked in 8 mL of 90% ethanol aqueous solution, placed at room temperature and in the dark for 24 hours, and then centrifuged at 3500 rpm for 15 min. Carefully absorb the supernatant and measure its absorbance values at 750, 663, 645 and 630 nm. , violent shaking of the sample should be avoided during the entire extraction and measurement process. The chlorophyll a concentration was measured according to the four-band measurement method of the national environmental protection standard "Spectrophotometric method for the determination of water quality chlorophyll a (HJ 897-2017)". The results are shown in Figure 2. Figure 2 shows that after 72h treatment with 0.5mL/L ACS , the chlorophyll a concentration is reduced to about 0.26mg/L, and the algae removal effect is significant.

(2) Algal cell integrity: The combination of flow cytometry and fluorescent molecular probes provides the opportunity to evaluate the integrity of microbial cell membranes.

Take 5mL of algae liquid and centrifuge it at 1000*g (about 1000-2000rpm) for 5 minutes. Discard the supernatant, collect the cells, gently resuspend the cells in PBS and count. The PBS also plays a role in washing the cells while resuspending.

Take 50,000 to 100,000 resuspended cells, centrifuge at 1000*g for 5 minutes, discard the supernatant, and use the pellet to detect apoptosis using a cell apoptosis detection kit (SYTOX Green, Beyotime). First add 194 μL Annexin V-mCherry Binding Buffer and gently resuspend. Suspend the cells, then add 5μL Annexin V-mCherry and 1μL SYTOX Green, and mix gently. Incubate at room temperature (20-25°C) away from light for 10-20 minutes, then place in an ice bath. Use aluminum foil to protect from light. Cells can be resuspended 2 to 3 times during the incubation process to improve the labeling effect. The cell viability ratio was then measured using flow cytometry. The results are shown in Figure 3. Figure 3 shows that after 0.3mL/L ACS treatment for 12 hours, the percentage of intact cells decreased to 0.606%; after 0.5mL/L ACS treatment for 12 hours, the percentage of intact cells decreased to 0.316%, and the cell death rate was 99 % or above, the algae removal effect is significant.

(3) Measurement of turbidity: Use a turbidity meter (Hach 2100Q portable). After preheating for 30 minutes, put the "Calibration/Measurement" toggle switch to the measurement position; press the "Keyhead" key to select the appropriate range. . (In order to reduce the error, try to use a low range, but do not exceed the range); slowly inject 10mL of algae solution to be measured, wipe the sample cup with filter paper; place the sample cup smoothly into the colorimetric cell, and cover the inner cover of the colorimetric cell. Close the colorimetric cell cover. After the displayed data is stable, you can read the turbidity value of the solution being measured. During the sample measurement process, if the measured sample is not in the same range, press the "Range" key to switch the range. (Also: To ensure good measurement repeatability, the wide positioning bar of the sample cup must face the user). The results are shown in Figure 4. Figure 4 shows that after 12h treatment with 0.3mL/L ACS, the turbidity was reduced by more than 95%.

Example 3. Inhibitory effect of acidic calcium sulfate on several common aquatic algae

Using the method of Example 2, the dosage of ACS (16.0N) in Example 2 was changed to 0.3mL/L. After 12 hours of treatment, the inhibitory effect of ACS on several other common aquatic algae except Microcystis aeruginosa was detected. Changes in chlorophyll a concentration, percentage of intact cells, and turbidity were used as indicators for evaluation and comparison. The results are shown in Table 1.

Table 1. Treatment results of acid calcium sulfate on several algae

Algae species	Decline rate of chlorophyll a concentration	Percent of intact cells	Turbidity reduction rate (%)
Microcystis	67.3%	0%	96.4%
Anabaena	71.5%	0%	98.3%
Anophyllum	70.2%	0%	97.5%
Longispora	69.6%	0%	96.8%
Pseudocylindrosporum	68.3%	0%	97.5%
Spirogyra	70.6%	0%	97.2%

The experimental results show that ACS has a significant killing effect on the cells of the tested algal species, the chlorophyll a concentration is significantly reduced, and the turbidity removal rate is high.

Example 4. Comparison of the effects of different algaecides

1. ACS algae removal effect

Take 200 mL of algae water from a pond where cyanobacteria bloom under natural conditions in Xiaoshan District, Hangzhou City, Zhejiang Province. Add 16.0N acidic calcium sulfate prepared by the method of Example 1 according to a volume ratio of 1:2000. The effect will take effect after being left at room temperature for 1 hour, and algae sedimentation will occur. After 4 hours, it settled basically completely (Figure 5). Before and after ACS treatment for 1 hour, microscopic observation revealed that the cyanobacterial cells were ruptured and dead (Figure 6).

2. Comparison of the algae removal effects of ACS and several commonly used chemical algaecides

(1) Observation on the algaecidal effects of five algaecides

Take 2L of algae water from a pond where cyanobacteria bloom under natural conditions in Xiaoshan District, Hangzhou City, Zhejiang Province, add 0.2mL of 16.0N acidic calcium sulfate prepared by the method of Example 1, and leave it at room temperature for 4 hours. See 4-1 in Figure 7 for the photo. .

Under the same conditions, replace ACS with equal volumes of chlorine dioxide (2%, liquid), hydrogen peroxide (30%), potassium hydrogen persulfate (0.1g added to 10mL water to make a solution), sodium hypochlorite (containing Active chlorine 5.2%), the volume ratio of each algaecide usage to the amount of algae water is 1:10000 (V:V). The results are shown in Figure 7, where 1-1, 2-1, 3-1, 4-1, and 5-1 are respectively chlorine dioxide, hydrogen peroxide, potassium hydrogen persulfate, acid calcium sulfate, and sodium hypochlorite (containing active chlorine 5.2%).

The results showed that after 4 hours of treatment, the effect of acidic calcium sulfate treatment was most obvious. The algae settled and broke, and the chlorophyll a content decreased.

(2) Determination of algae removal effect

Take the algae water from the pond where blue algae blooms under natural conditions in Xiaoshan District, Hangzhou City, Zhejiang Province. Each treatment volume is 300 mL. The 16.0N acidic calcium sulfate, copper sulfate (solid) and potassium hydrogen persulfate (solid) prepared by the method of Example 1 are respectively treated. The algaecidal effects of several algaecides including hydrogen peroxide (30%) and sodium hypochlorite solution (containing 5.2% active chlorine) were measured. Concentration gradients are set for each algaecide, ACS: 0, 0.2, 0.3, 0.5mL/L (16.0N ACS volume/algae water volume); copper sulfate: 0, 1.5, 3, 5mg/L; hydrogen persulfate Potassium: 0, 61.55, 123.1, 246.2mg/L; Hydrogen peroxide: 0, 10.2, 51, 102mg/L; Sodium hypochlorite (containing 5.2% active chlorine): 0, 2, 3, 4mg/L. Three parallels were set for each algaecide concentration, and samples were taken within each concentration gradient to measure changes in cell integrity, chlorophyll a concentration, and turbidity. Set the sampling time to 0, 0.1, 0.5, 1, 12, 24, 48, 72, 168h. The results in Table 2 show that 0.5mL/L ACS has a significant effect on cell destruction at 1h. When the ACS concentration was 0.3mL/L and 0.2mL/L, the chlorophyll a concentration in the sample decreased significantly as the contact time with the algaecide increased, the turbidity dropped by more than 90%, and no intact cells were found under the microscope. The optimal algaecide dose of ACS is 0.2mL/L, the optimal algaecide dose of copper sulfate is 1.5mg/L, the optimal algaecide concentration of potassium hydrogen persulfate is 123.1mg/L, and the optimal algaecide dose of hydrogen peroxide is It is 51 mg/L, and the optimal dose of sodium hypochlorite solution (containing 5.2% active chlorine) for algae removal is 3.0 mg/L. From the comprehensive analysis of reaction speed and algae control effect, ACS has the best effect (Table 2).

Table 2 Comparison of comprehensive algaecidal effects of several algaecides

algaecide	concentration	Effect time (h)
Acid Calcium Sulfate (ACS)	0.3mL/L	1～12
Potassium hydrogen persulfate	123.1mg/L	48
copper sulfate	1.5mg/L	12
hydrogen peroxide	51mg/L	12

Sodium hypochlorite solution (containing 5.2% active chlorine)

3mg/L

72

Example 5. Treatment of cyanobacteria in ponds with high concentrations of cyanobacteria.

A pond in Hongshan Village, Xiaoshan District, Hangzhou City, Zhejiang Province (an area of about 1500m ² and a water depth of about 2m) has been polluted by cyanobacteria blooms every year in recent years. Blue algae occurred early in this pond, and the outbreak was serious in summer and autumn. The density of blue algae floating on the water surface was high and emitted a fishy smell. ACS treatment was used twice in 2020 and 2021, and significant algae control and algae removal effects were achieved.

In November 2020, when the blue algae broke out in the pond, 12.0N ACS was poured onto the water surface of the pond. The ACS dosage was 1L. After 1 week, the blue algae basically disappeared and the water surface became clear, as shown in Figure 8.

In July 2021, a large-scale blue-green algae outbreak occurred in the pond, which was severe. For treatment with ACS, 16.0N ACS prepared by the method of Example 1 was splashed on the water surface. The dosage in key areas was increased, and the total usage of ACS was 20Kg. After 10 days of treatment, blue-green algae were under control, and the amount of blue-green algae floating on the water surface was significantly reduced. After 14 days, it gradually disappeared, the water surface became clear, and other beneficial aquatic organisms, duckweed, began to appear on the water surface, and swimming fish were easy to see.

Example 6. Treatment of water bodies where Spirogyra occurs

In 2021, a natural water body in Huangshan City, Anhui Province was polluted by Spirogyra (algae belonging to the family Double Star Algae). Treated with 16.0N ACS prepared by the method of Example 1, the usage ratio is one ten thousandth of the water volume. After three days, the spirogyra disappeared and the green color faded. Spirogyra easily floats to the surface when encountering high temperatures and sunshine. It basically no longer floats after ACS treatment.

Claims (10)

1. A method of treating polluted water bodies using a water quality conditioner, characterized in that the water quality conditioner includes acid calcium sulfate.
2. The method of claim 1, wherein the pollutants in the polluted water include cyanobacteria, green algae, moss or spirogyra.
3. The method according to claim 1, wherein the cyanobacteria include Microcystis, Anabaena, Anocystis sp., Cylindrosporum algae, Pseudocylindrospora, Spirogyra, Planxonthora, and Enococcus, Euglena, Streptophyta, Fragilaria, Hydroticella or Cladophora.
4. The method according to claim 1, characterized in that the method is to add the water quality conditioner into the polluted water body to be treated to achieve the elimination of pollutants.
5. The method according to claim 4, characterized in that the addition amount of the acidic calcium sulfate is 1:100 to 1,000,000 based on the volume of polluted water.
6. The method according to claim 4, characterized in that when the density of cyanobacterial cells in the polluted water to be treated is ≤1.0×10 ³ cells·mL ^-1 , the volume ratio of acid calcium sulfate to the polluted water is 1:100000.
7. The method according to claim 4, characterized in that when the density of cyanobacterial cells in the polluted water to be treated is 1.01×10 ³ to 1.0×10 ⁵ cells·mL ^-1 , the volume ratio of acid calcium sulfate to the polluted water is 1:10000.
8. The method according to claim 4, characterized in that when the density of cyanobacterial cells in the polluted water to be treated is 1.01×10 ⁵ to 1.0×10 ⁷ cells·mL ^-1 , the volume ratio of acid calcium sulfate to the polluted water is 1:3000.
9. The method according to claim 4, characterized in that when the cyanobacteria cell density in the polluted water to be treated is ≥1.01×10 ⁷ cells·mL ^-1 , the volume ratio of acid calcium sulfate to the polluted water is 1:2000.
10. The method of claim 1, wherein the acidic calcium sulfate is prepared by mixing calcium hydroxide, calcium sulfate, concentrated sulfuric acid and water as raw materials to prepare a solution with a concentration greater than 0.1N.

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