Calcium salt-based microcystic algicide and method for removing algae

Abstract

The present invention belongs to the field of removal of Microcystis in water, and specifically relates to a method based on Ca 2+ With C2O4 2‑ The application of the formed crystal system in removing Microcystis from water, and the application of the crystal system containing Ca 2+ and C2O4 2‑ The algaecide of the salt of these two crystal-forming ions. The present invention focuses on protecting Ca 2+ With C2O4 2‑ The formed crystal system is used to remove Microcystis from water bodies, that is, the CaC2O4 crystals are used to remove Microcystis from water bodies. The present invention also protects algaecides containing CaC2O4 crystals and their uses. Over 30 days, the overall removal rate for Microcystis aeruginosa was maintained at over 95%, the overall removal rate for Microcystis whitney was maintained at over 99%, and the overall removal rate for Microcystis blooms was maintained at over 96%, demonstrating that the CaC2O4 crystals are excellent and stable in removing Microcystis.

Description

TECHNICAL FIELD

[0001] The present application belongs to the field of removal of microcystis in water body, and particularly relates to a Ca 2+ and C2O4 2- crystalline system formed in removal of microcystis in water body, and an algicide containing a salt of the two crystal-forming ions. 2+ and C2O4 2- crystal-forming ions. BACKGROUND

[0002] Cyanobacterial bloom is one of the most common water blooms in freshwater water area, which usually refers to that under suitable environmental conditions and eutrophication state of water body, cyanobacterial cells in the water body multiply in large quantities and accumulate in the surface layer of the water body to form a special blue-green "film", thus causing the water body to become blue-green. Common cyanobacteria mainly include Microcystis, Anabaena, Oscillatoria and Aphanizomenon, etc., which have the characteristics of the most widely distributed, the most influential and the most serious harm. Under the background of global warming, the degree, range and frequency of cyanobacterial bloom are increasing year by year, which brings great harm to the aquatic ecological environment. It has a considerable influence on human health, aquatic ecosystems, aquaculture industry, sightseeing tourism industry and other industries, therefore, the prevention and control of cyanobacterial bloom has become an urgent environmental pollution problem to be solved.

[0003] As for the treatment method of cyanobacterial bloom, some documents disclose that calcium chloride is used to kill algae. For example, a certain proportion of liquid calcium chloride is put into water to inhibit the growth of algae. In the above method, since calcium chloride has a certain toxicity, it cannot be used in excess, otherwise it will affect the aquatic ecological environment. Moreover, calcium chloride can only kill algae, but cannot completely remove algae in water, so it is necessary to regularly check the water quality and use different prevention and control methods for different types of algae. Moreover, through experiments, it is proved that the removal effect of microcystis by adding calcium ions alone is limited.

[0004] Some documents also disclose the research on calcium carbonate crystallization algae removal effect and mechanism in tap water. The document uses CaCO3 crystalline to remove algae. However, the calcium carbonate coagulation method for removing algae still has the following problems: first, the effect is unstable for different algae; second, the effect is not ideal for natural water body with rich DOM. SUMMARY

[0005] In order to solve the above technical problems, the present application provides a Ca 2+ and C2O4 2-The method for removing microcystis by forming a crystalline system takes into account that DOM is also present in the water body containing microcystis, and therefore, the influence of DOM on the removal of the algae is investigated through specific experiments. The results prove that the overall removal rate of microcystis can be maintained at more than 95% by using the method of the present application, and the removal efficiency of CaC2O4 crystals on microcystis is not affected by humic acid over time.

[0006] The present application focuses on the use of Ca 2+ and C2O4 2- to form a crystalline system in the removal of microcystis in water bodies.

[0007] The above-mentioned microcystis refers to any one of Microcystis aeruginosa, Microcystis wesenbergii, and Microcystis flos-aquae, but is not limited to the above-mentioned several species. Blue-green algae blooms with similar characteristics to the above-mentioned microcystis can also be removed by the method of the present application.

[0008] In the above-mentioned application, specifically, a salt containing Ca 2+ and C2O4 2- is added to the water body containing microcystis, so as to achieve the purpose of inhibiting the growth of algae or removing algae.

[0009] As a preferred mode, after Ca 2+ and C2O4 2- are added, glucose or a substance containing glucose can be added to the water body.

[0010] The calcium salt-based microcystis algae removal agent containing a salt of Ca 2+ and C2O4 2- which is resistant to DOM is also the focus of the present application.

[0011] Preferably, the above-mentioned algae removal agent contains CaC2O4 crystals.

[0012] The method for removing microcystis by using the above-mentioned algae removal agent includes the following steps:

[0013] (1) preparing CaCl2 solution and Na2C2O4 solution;

[0014] (2) pouring the prepared CaCl2 solution and Na2C2O4 solution into the water body containing microcystis, and standing and precipitating; the concentration of Ca 2+ in the water body is maintained at 6-8 mM, and the molar ratio of C2O4 2- to Ca 2+ in the CaCl2 solution in (1) is 0.25-1:1.

[0015] Preferably, before the CaCl2 solution and the Na2C2O4 solution are put in, hydrogen peroxide is added to the water body in a direct addition method at a ratio of 0.5 mL of hydrogen peroxide per 200 mL of water body, and then the water body is left to stand for 2-3 hours, and then the CaCl2 solution and the Na2C2O4 solution are added to the water body.

[0016] The CaC2O4 crystal is applied to the removal of microcystis, and the effect is excellent, and possible reasons and mechanisms are analyzed as follows: (1) adsorption electric neutralization theory: the surface of the microcystis cell is negatively charged, most of the CaC2O4 crystal is positively charged, adsorption electric neutralization is generated between the two, the electrostatic repulsion between the algae cells is reduced, the algae cells are more easily combined and aggregated, and the settlement of the algae cells is promoted;

[0017] (2) net capture and sweeping theory: a large amount of crystal ions in the algae liquid are distributed around the algae cells, form positively charged crystal products, and attract negatively charged algae cells to accumulate to form an aggregate, when the crystal products shrink and settle, the algae cells in the water are captured and swept down;

[0018] (3) co-flocculation: under the driving action of external force, the algae cells and the crystal products with similar particle sizes collide and aggregate with each other to form larger precipitates which are separated from the aqueous solution, so that the algae cells and the crystal products are co-precipitated.

[0019] As for the above-mentioned mechanism, the present application does not conduct in-depth verification, but all the experimental data show that the CaC2O4 crystal is applied to the removal of microcystis, and the effect is remarkable.

[0020] The present application has the following beneficial effects:

[0021] (1) In the present application, it is verified by experiments that the total removal rate of the copper green microcystis in the microcystis contaminated water body can finally be maintained at more than 95% by putting the CaC2O4 crystal into the water body, the total removal rate of the Whistler microcystis can finally be maintained at more than 99%, and the total removal rate of the water bloom microcystis can finally be maintained at more than 96%, which shows that the CaC2O4 crystal has excellent and stable removal effect on the microcystis, and is almost not affected by the DOM in the process of removing the microcystis, that is, the CaC2O4 crystal has strong tolerance to the DOM.

[0022] (2) The CaC2O4 crystal is used to remove the microcystis, and it is found for the first time that the algal-removal effect of oxalate + calcium salt is more excellent, and good effects are obtained on the three kinds of microcystis water bloom, especially the Whistler microcystis with thick and difficult-to-remove jelly sheath, and it is proved by the DOM experiment that even in the case that the types of the DOM are many and the content of the DOM is rich, the sustained algal-removal effect (the effect in 30 days) is still very stable. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1 Removal effect of CaCl2 on Microcystis aeruginosa alone;

[0024] Figure 2 Removal effect of CaCl2 on Microcystis wesenbergii alone;

[0025] Figure 3 Removal effect of CaCl2 on Microcystis flos-aquae alone;

[0026] Figure 4 Influence of CaCl2 on water pH value alone;

[0027] Figure 5 Influence of different NaC2O4:CaCl2 ratios on removal efficiency of Microcystis aeruginosa;

[0028] Figure 6 Influence of different NaC2O4:CaCl2 ratios on removal efficiency of Microcystis wesenbergii;

[0029] Figure 7 Influence of different NaC2O4:CaCl2(w:w) ratios on removal efficiency of Microcystis flos-aquae;

[0030] Figure 8 Influence of different NaC2O4:CaCl2 ratios on water pH value;

[0031] Figure 9 XRD pattern of CaC2O4 crystal;

[0032] Figure 10 IR pattern of CaC2O4 crystal;

[0033] Figure 11 Influence of single component DOM on removal of Microcystis aeruginosa by CaC2O4;

[0034] Figure 12 Influence of single component DOM on removal of Microcystis wesenbergii by CaC2O4;

[0035] Figure 13 Influence of single component DOM on removal of Microcystis flos-aquae by CaC2O4;

[0036] Figure 14 Influence of single component DOM on water pH value by CaC2O4;

[0037] Figure 15 Influence of multi-component DOM on removal of Microcystis aeruginosa by CaC2O4 crystal;

[0038] Figure 16 Influence of multi-component DOM on removal of Microcystis wesenbergii by CaC2O4 crystal;

[0039] Figure 17 The effect of multi-component DOM on the removal of Microcystis algae by CaC2O4 crystallization;

[0040] Figure 18 The effect of DOM on the removal of Microcystis by CaC2O4 crystallization within 30 days;

[0041] Figure 19 is the XRD pattern of CaC2O4 crystalline sediment;

[0042] Figure 20 This is the IR diagram of CaC2O4 crystals. DETAILED DESCRIPTION

[0043] In order to enable those skilled in the art to better understand the present invention, the present invention will be further explained in conjunction with specific embodiments.

[0044] In this application, common algae species of water blooms were selected as experimental subjects. Microcystis aeruginosa, Microcystis whitney, and Microcystis blooms were purchased from the freshwater algae species bank of the Institute of Hydrobiology, Chinese Academy of Sciences (Wuhan), and the algae species numbers were FACHB-315, FACHB-908, and FACHB-1028, respectively.

[0045] Example 1

[0046] 1.1 Cultivation of Microcystis: Microcystis aeruginosa, Microcystis huiyi, and Microcystis aquae were cultured using BG-11 medium. The specified amounts of each reagent were added to a conical flask and diluted with deionized water. The flask was then sealed with sealing film. The sealed culture medium was transferred to a high-temperature steam pressure sterilizer for sterilization (121°C for 30 min). After sterilization, the culture medium was removed. After the culture medium cooled, the algae solution was added and the culture medium was transferred to an intelligent incubator for cultivation (culture conditions: 25 ± 1°C, 3000 Lux light intensity, 12:12 hour day / night ratio, and shaking three times daily, morning, noon, and evening). Algal cell growth was monitored using a hemocytometer under a microscope. Algae in the exponential growth phase (absorbance A680 between 0.25 and 0.45) were selected for the experiment.

[0047] 1.2 Investigating the algae removal effect of CaC2O4 crystals

[0048] 1.2.1 Study on the effect of adding CaCl2 alone to remove Microcystis

[0049] The removal effects of different concentrations of CaCl2 on Microcystis aeruginosa, M. wesenbergii and M. flos-aquae were explored. The CaCl2 dosage concentration gradient was set as 0, 2, 4, 6, 8, 10 mmol / L. After 4 h of static precipitation, the water sample at 3 cm below the liquid surface was taken to detect the absorbance (A680nm) at 680 nm, determine the concentration of chlorophyll (Chl-a), and measure the pH value. The experimental results are shown in 680 , Figure 1 , Figure 2 , Figure 3 , Figure 4 .

[0050] As can be seen from the Figures 1-3 , the removal rates of algal cells and Chl-a vary with the CaCl2 dosage, and the removal rate of Chl-a is higher than that of algal cells. With the increase of CaCl2 dosage, the removal rates of algal cells and Chl-a of M. aeruginosa, M. wesenbergii and M. flos-aquae all increase, but the removal effects of algal cells and Chl-a are very limited. When the CaCl2 dosage reaches 10 mmol / L, the removal rates of algal cells and Chl-a are the highest, but the removal rates of Chl-a in the three algae are less than 15%, 10% and 20%, respectively. The experiment proves that the improvement effect of increasing the CaCl2 concentration on the removal rate of M. aeruginosa is very limited when low-concentration CaCl2 is added alone to remove M. aeruginosa, M. wesenbergii and M. flos-aquae. Therefore, low-concentration CaCl2 alone is not considered to remove M. aeruginosa.

[0051] As can be seen from the Figure 4 , adding CaCl2 alone to remove microcystis can reduce the pH value of the water body, and the lower the CaCl2 dosage, the greater the degree of reduction of the pH value of the water body, and the lower the pH value of the water body. When the CaCl2 dosage reaches 10 mmol / L, the pH value of the water body is the lowest. Compared with the pH value of the algal stock solution, the degree of reduction of the pH value of the water body is M. aeruginosa: 0.55, M. wesenbergii: 0.68, and M. flos-aquae: 0.58, all less than 1. The degree of reduction of the pH value of the water body by CaCl2 is M. wesenbergii > M. flos-aquae > M. aeruginosa. Therefore, the effect of low-concentration CaCl2 alone on the removal of microcystis on the pH value of the water body is small.

[0052] 1.2.2 Effect of different NaC2O4:CaCl2 conditions on the removal of microcystis

[0053] The effects of different NaC2O4:CaCl2 (w:w) molar ratios on the removal efficiency of three kinds of microcystis under the optimal CaCl2 dosing concentration of Microcystis aeruginosa, Microcystis wesenbergii and Microcystis flos-aquae were explored. The dosing concentration of CaCl2 was 6 mmol / L for Microcystis aeruginosa, 8 mmol / L for Microcystis wesenbergii and 8 mmol / L for Microcystis flos-aquae. The dosing molar ratio of NaC2O4 to CaCl2 (w:w) was 0.25:1, 0.5:1 and 1:1, respectively. After 6 h of static precipitation, the water sample at 3 cm below the liquid surface was taken to detect the absorbance at 680 nm (A680), determine the concentration of chlorophyll-a (Chl-a), measure the turbidity and determine the pH value. The experimental results are shown in 680 , Figure 5 , Figure 6 , Figure 7 , Figure 8 .

[0054] The detection methods of each index are as follows: (1) Turbidity determination: Turbidity is one of the important standards for measuring the water quality of water body. The turbidity of the supernatant of water body was determined by a portable electromagnetic (WZB-170) turbidimeter.

[0055] (2) pH value determination: The pH value of the water sample was determined by a electromagnetic PHS-25 pH acidity meter.

[0056] (3) Algal cell number determination: The blood cell counting method was used in the early stage of algal counting. The function relationship between the algal density obtained by the blood cell counting method and the absorbance obtained by the absorbance method was established, and the curve between the algal number and the absorbance was drawn. After the algal cells were fixed on the blood cell counting plate, the optical microscope was used to observe and record the number of algal cells, and the average value of the number of algal cells calculated by three repeated experiments was taken as the final calculation result.

[0057] (4) Algal density determination: The absorbance value of the algal liquid at a wavelength of 680 nm was selected to determine the algal density of the solution, which was represented by A680; the removal rate of algal cells (R) = (initial A680 - supernatant A680) / initial A680 x 100%; the absorbance of water body was directly determined by a ultraviolet-visible spectrophotometer (Q-6). The experimental results showed that the algal cell density had a good linear relationship with the A680 of the algal-containing water, and the relationship was as follows: Microcystis aeruginosa: y = 0.1187x - 0.018, R2 = 0.9992; Microcystis wesenbergii: y = 0.0224x + 0.0054, R2 = 0.9992; Microcystis flos-aquae: y = 0.0169x + 0.005, R2 = 0.9992. 680 680 680 680 680 2 2 2 ​​​​​​​= 0.9999, so A 680 as a measure of algal cell density.

[0058] (5) Measurement of chlorophyll concentration (μg / L): The measurement of chlorophyll (Chl-a) was directly measured using a phytoplankton classification fluorometer (PPAB0168).

[0059] According to Example 1, the removal effect of algal cells and chlorophyll was very limited when CaCl2 was added alone to remove Microcystis aeruginosa, but the algal removal effect was significantly enhanced when CaC2O4 crystals were used to remove algae, as shown in Figure 5 (a). Figure 5 It can be seen from (a) that when the molar ratio of NaC2O4 to CaCl2 was 0.25:1, 0.5:1, and 1:1, the removal rates of algal cells and Chl-a were all above 95%. When the molar ratio of NaC2O4 to CaCl2 was 0.25:1, the removal rates of algal cells and Chl-a were 97.0% and 95.7%, respectively. When the molar ratio of NaC2O4 to CaCl2 was 0.5:1, the removal rates of algal cells and Chl-a were 97.9% and 96.7%, respectively. When the molar ratio of NaC2O4 to CaCl2 was 1:1, the removal rates of algal cells and Chl-a were 98.9% and 97.0%, respectively. However, as the molar ratio of NaC2O4 to CaCl2 increased, the removal effect of algal cells and Chl-a did not significantly improve, and the removal rates were basically the same under the three molar ratios.

[0060] It can be seen from (b) that the turbidity of the algal stock solution without CaC2O4 crystal removal was 51.4 NTU, and the turbidity of the water body after CaC2O4 crystal removal was greatly reduced. When the molar ratio of NaC2O4 to CaCl2 was 0.25:1, 0.5:1, and 1:1, the turbidity of the water body after algal removal was reduced to 3.8, 8.4, and 17.3 NTU, respectively. As the molar ratio of NaC2O4 to CaCl2 increased, the turbidity of the water body increased. Therefore, while ensuring the effect of CaC2O4 crystal in removing Microcystis aeruginosa, the effect of CaC2O4 crystal on water turbidity was considered. It was considered that the CaC2O4 crystal had a good algal removal effect when the concentration of CaCl2 was 6 mmol / L and the molar ratio of NaC2O4 to CaCl2 was 0.25:1. Figure 5 Similarly,

[0061] Figure 6 ​The "system" refers to the microcystis algae liquid cultured in Example 1, and in the actual water treatment process, the "system" refers to the water body in which the microcystis blooms exist. When the molar ratio of NaC2O4 to CaCl2 is 0.25:1, 0.5:1 and 1:1, respectively, the removal rates of algal cells are 41.5%, 50.0% and 70.2%, respectively, and the removal rates of Chl-a are 34.6%, 51.3% and 74.6%, respectively. After the H2O2 pre-oxidation treatment, when the molar ratio of NaC2O4 to CaCl2 is 0.25:1, 0.5:1 and 1:1, respectively, the removal rates of algal cells are 64.0%, 70.5% and 75.0%, respectively, and the removal rates of Chl-a are 57.4%, 76.7% and 86.3%, respectively. According to the experimental results, the removal rates of algal cells and Chl-a are improved after the H2O2 pre-oxidation treatment, and the removal effect of algal cells and Chl-a is significantly improved as the molar ratio of NaC2O4 to CaCl2 increases. From the above experimental results, it can be seen that the removal effect of algal cells and Chl-a is significantly improved after the H2O2 pre-oxidation treatment, and the removal effect of algal cells and Chl-a is significantly improved as the molar ratio of NaC2O4 to CaCl2 increases. Figures 3-6 (b)It can be seen that the turbidity of the algal stock solution after the H2O2 pre-oxidation treatment but without CaC2O4 crystallization algal removal is 42.8 NTU, and the turbidity of the water body after the CaC2O4 crystallization algal removal is greatly reduced. When the molar ratio of NaC2O4 to CaCl2 is 0.25:1, 0.5:1 and 1:1, respectively, the turbidity of the water body after the algal removal is 18.7, 16.0 and 14.8 NTU, respectively. As the molar ratio of NaC2O4 to CaCl2 increases, the turbidity of the water body slightly decreases. Therefore, while ensuring the effect of CaC2O4 crystallization on removing the microcystis, the influence of CaC2O4 crystallization on the turbidity of the water body is considered. It is considered that the CaC2O4 crystallization algal removal effect is better when the CaCl2 addition concentration reaches 8 mmol / L and the molar ratio of NaC2O4 to CaCl2 (w:w) is 1:1.

[0062] Figure 7 It is shown that the removal effect of algal cells and chlorophyll is very limited for the water bloom microcystis, but the algal removal effect is significantly enhanced when the CaC2O4 crystallization is used for algal removal, as shown in Figure 7 Figure 7 ​(a) It can be seen that when the molar ratio of NaC2O4 to CaCl2 is 0.25:1, 0.5:1 and 1:1, the removal rates of algal cells and Chl-a can reach more than 70% and more than 80%, respectively. When the molar ratio of NaC2O4 to CaCl2 is 0.25:1, the removal rates of algal cells and Chl-a are 72.7% and 80.8%, respectively. When the molar ratio of NaC2O4 to CaCl2 is 0.5:1, the removal rates of algal cells and Chl-a are 84.5% and 88.9%, respectively. When the molar ratio of NaC2O4 to CaCl2 is 1:1, the removal rates of algal cells and Chl-a are 74.7% and 83.0%, respectively. However, with the increase of the molar ratio of NaC2O4 to CaCl2, the removal effect of algal cells and Chl-a first increases and then decreases. From the above results, it can be seen that the removal effect of CaC2O4 crystallization on algal cells and Chl-a is the best when the molar ratio of NaC2O4 to CaCl2 is 0.5:1. Figure 7 (b) It can be seen that the turbidity of the algal stock solution without CaC2O4 crystallization is 55.5 NTU, and the turbidity of the water body after CaC2O4 crystallization is greatly reduced. When the molar ratio of NaC2O4 to CaCl2 is 0.25:1, 0.5:1 and 1:1, the turbidity of the water body after algae removal is 25.3, 12.7 and 25.5 NTU, respectively. With the increase of the molar ratio of NaC2O4 to CaCl2, the turbidity of the water body first decreases and then increases. Therefore, in order to ensure the effect of CaC2O4 crystallization on removing Microcystis aeruginosa, and considering the influence of CaC2O4 crystallization on the turbidity of the water body, it is considered that when the molar ratio of NaC2O4 to CaCl2 is 0.5:1 and the dosage of CaC2O4 is 8 mmol / L, the effect of CaC2O4 crystallization on removing algae is better. 2+ (b) It can be seen that the turbidity of the algal stock solution without CaC2O4 crystallization is 55.5 NTU, and the turbidity of the water body after CaC2O4 crystallization is greatly reduced. When the molar ratio of NaC2O4 to CaCl2 is 0.25:1, 0.5:1 and 1:1, the turbidity of the water body after algae removal is 25.3, 12.7 and 25.5 NTU, respectively. With the increase of the molar ratio of NaC2O4 to CaCl2, the turbidity of the water body first decreases and then increases. Therefore, in order to ensure the effect of CaC2O4 crystallization on removing Microcystis aeruginosa, and considering the influence of CaC2O4 crystallization on the turbidity of the water body, it is considered that when the molar ratio of NaC2O4 to CaCl2 is 0.5:1 and the dosage of CaC2O4 is 8 mmol / L, the effect of CaC2O4 crystallization on removing algae is better.

[0063] From the above results, it can be seen that the removal effect of CaC2O4 crystallization on algal cells and Chl-a is the best when the molar ratio of NaC2O4 to CaCl2 is 0.5:1. Figure 8 From the above results, it can be seen that the removal effect of CaC2O4 crystallization on algal cells and Chl-a is the best when the molar ratio of NaC2O4 to CaCl2 is 0.5:1.

[0064] 1.2.3 Investigation of sediment characteristics

[0065] (1) XRD analysis

[0066] XRD determination is a research method that determines the material composition, molecular structure and morphology, and crystal structure of the material by performing X-ray diffraction on the sample and analyzing its diffraction pattern. CaC2O4 crystallinity analysis: relative crystallinity calculation formula: ε=I c / (I c +I a )×100%(where: I c is the integrated intensity of the crystallization peak in the XRD pattern, I a is the integrated intensity of the amorphous peak in the XRD pattern).

[0067] Table 1 Analysis of relative crystallinity of CaC2O4 crystals

[0068]

[0069]

[0070] By XRD analysis of pure CaC2O4 crystals, it was found that there were crystal peaks at the interplanar spacings d = 0.591, 0.364, 0.296, 0.235 and 0.197 nm, which were respectively attributed to calcium oxalate monohydrate (COM) (020) (130) and Crystal planes, such as Figure 9 As shown, the results show that COM is generated. And compared Figure 9 The three pictures in the figure show that Figure 9 The peak value of the crystallization peak of the pure substance in (b) is the highest. Figure 9 The peak value of the crystallization peak of the pure substance in (c) is second, Figure 9 The peak value of the crystallization peak of the pure substance in (a) is the lowest. The results show that as the ratio of the amount of NaC2O4 to CaCl2 increases, the peak value of the crystallization peak of the CaC2O4 crystal increases accordingly. And according to the calculation formula of relative crystallinity ε, the relative crystallinity ε of the pure substance of CaC2O4 crystal is calculated in combination with the XRD pattern, as shown in Table 1. The results show that when the ratio of the amount of NaC2O4 to CaCl2 added reaches 0.25:1, 0.5:1, and 1:1, respectively, the relative crystallinity ε of the CaC2O4 crystal is 91.88%, 93.80%, and 96.99%, respectively. As the ratio of the amount of NaC2O4 to CaCl2 increases, the relative crystallinity ε of the pure substance of CaC2O4 crystal increases accordingly. In addition, after the algae removal test using CaC2O4 crystals, the peak value of the crystallization peak and the relative crystallinity ε of the CaC2O4 crystals are reduced, as shown in Table 1. Figure 9 As shown in Table 1, the results show that in the process of algae removal using CaC2O4 crystals, algae cells inhibit the crystallization process of CaC2O4 and reduce the relative crystallinity ε of CaC2O4 crystals.

[0071] (2) IR analysis

[0072] IR analysis is to analyze the functional groups carried in the object to be measured. By comparing the characteristic wave number of the chemical bond of the sample with that in the standard spectrum, the type of chemical bond is analyzed to determine the variety of the compound. The sample to be measured is pressed into a transparent thin sheet and subjected to infrared measurement by an infrared spectrometer (Vertex 70).

[0073] Figure 10 It can be seen that, by IR detection analysis of the pure substance of CaC2O4crystal, it is detected that when the molar ratio of NaC2O4to CaCl2is 0.25:1, the infrared absorption peak is mainly concentrated in the wavelength of 3464cm-1, 1320-1650cm-1, 510-920cm-1; when the molar ratio of NaC2O4to CaCl2is 0.5:1, 3060-3440cm-1, 1310-1620cm-1, 510-960cm-1; when the molar ratio of NaC2O4to CaCl2is 1:1, 3060-3490cm-1, 1310-1620cm-1, 510-960cm-1; by IR detection analysis of the substance after CaC2O4crystal experiment, it is detected that when the molar ratio of NaC2O4to CaCl2is 0.25:1, the infrared absorption peak is mainly concentrated in the wavelength of 3431cm-1, 1060-1650cm-1, 510-920cm-1; when the molar ratio of NaC2O4to CaCl2is 0.5:1, 3060-3440cm-1, 1320-1620cm-1, 510-890cm-1; when the molar ratio of NaC2O4to CaCl2is 1:1, 3060-3440cm-1, 1320-1620cm-1, 510-950cm-1. By comparing the absorption peaks of the pure substance of CaC2O4crystal in -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 -1 Figure 10 Figure 10 (a-1) and the absorption peaks of the pure substance in Figure 10 (b-1).​​​​​​​​​​​​​​​​​​​Figure 10 (c-1) pure substance in the absorption peak of two, respectively, in 3060cm -1 and 3440cm -1 , the results show that, with the different amount of substance ratio of NaC2O4 and CaCl2, will cause the absorption peak position of CaC2O4 crystal change. Comparison Figure 10 of CaC2O4 crystal pure substance in the experiment after the absorption peak of the substance, the peak value of each absorption peak position of the substance after the experiment and CaC2O4 crystal pure substance peak value basically flat, the results show that, in the process of using CaC2O4 crystal algae, algae cells basically no change CaC2O4 crystal internal functional group composition and chemical bond activity.

[0074] Example 2

[0075] Because of the management of microcystis bloom, DOM in the environment is an external factor affecting the management of microcystis bloom, which will have a certain influence on the management effect of microcystis bloom. DOM will compete with the negatively charged algal cells for cationic flocculants, hinder the flocculation process, and reduce the removal efficiency; it will react with oxidants, reduce the oxidation of oxidants, and reduce the removal efficiency; it can be a special light induced factor involved in the process of photosensitization, which will participate in the indirect photodegradation process of algal toxins, and have a positive influence on the degradation of algal toxins.

[0076] In this embodiment, three different types of DOM (humic acid, glucose, amino acid) and their mixtures are added to the algal liquid, and the influence of CaC2O4 crystal system on the removal efficiency of three kinds of microcystis under the condition of DOM is studied. By changing the type and concentration of DOM in the reaction system, the influence of CaC2O4 crystal on the removal rate of algal cells in algal water under the condition of different types and concentrations of DOM is investigated, and the CaC2O4 crystal algal removal efficiency is evaluated.

[0077] 2.1 Study on the influence of single component DOM on the CaC2O4 crystal algal removal efficiency

[0078] The influence of different concentrations of humic acid, glucose, tryptophan and tyrosine on the CaC2O4 crystal removal efficiency of Microcystis aeruginosa, M. wesenbergii and M. flos-aquae is explored. The concentration gradient of humic acid and glucose is set as 0, 2, 4, 6, 8, 10 mg / L, and the concentration gradient of tryptophan and tyrosine is set as 0, 0.4, 0.8, 1.2, 1.6, 2 mg / L. After 6 h of static precipitation, the water sample at 3 cm below the liquid surface is taken for detection of absorbance (A 680 ) at 680 nm, determination of chlorophyll (Chl-a) concentration and determination of pH value. The experimental results are shown in Figure 11 , Figure 12 ,Figure 13 、 Figure 14 .

[0079] Depend on Figure 11 It can be seen that the addition of different types of DOM (humic acid, glucose, tryptophan, tyrosine) alone inhibited the removal of Microcystis aeruginosa by CaC2O4 crystallization, and the inhibitory effect became greater with the increase of DOM concentration. When the dosage of humic acid reaches 10 mg / L, the removal rate of algal cells reaches more than 62%, the removal rate of Chl-a reaches more than 69%, and the inhibition effects of humic acid are 32% and 25% respectively; when the dosage of glucose reaches 10 mg / L, the removal rate of algal cells reaches more than 91%, the removal rate of Chl-a reaches more than 92%, and the inhibition effects of glucose are 4% and 4% respectively; when the dosage of tryptophan reaches 2 mg / L, the removal rate of algal cells reaches more than 93%, the removal rate of Chl-a reaches more than 94%, and the inhibition effects of tryptophan are 2% and 1% respectively; when the dosage of tyrosine reaches 2 mg / L, the removal rate of algal cells reaches more than 82%, the removal rate of Chl-a reaches more than 84%, and the inhibition effects of tyrosine are 11% and 9% respectively. Analysis of the above experimental results shows that the main DOM components in water that affect the removal of Microcystis aeruginosa by CaC2O4 crystallization are humic acid and some types of amino acids, which show an inhibitory effect, and the other components have little effect on the removal of Microcystis aeruginosa by CaC2O4 crystallization.

[0080] Depend on Figure 12It is known that the addition of different types of DOM (humic acid HA, tryptophan Trp, tyrosine Tyr) alone has an inhibitory effect on the removal of Microcystis wesenbergii by CaC2O4crystallization, and the inhibitory effect increases with the increase of DOM concentration. The inhibitory effect of humic acid is greater than that of tryptophan and tyrosine. The addition of glucose alone has a promoting effect on the removal of Microcystis wesenbergii by CaC2O4crystallization, and the promoting effect increases with the increase of DOM concentration. When the dosage of humic acid reaches 10 mg / L, the removal rate of algal cells is more than 56%, and the removal rate of Chl-a is more than 72%, and the inhibitory effect of humic acid is 25% and 13% respectively. When the dosage of glucose reaches 10 mg / L, the removal rate of algal cells is more than 91%, and the removal rate of Chl-a is more than 92%, and the promoting effect of glucose is 2% and 1.5% respectively. When the dosage of tryptophan reaches 2 mg / L, the removal rate of algal cells is more than 68%, and the removal rate of Chl-a is more than 83%, and the inhibitory effect of tryptophan is 11% and 6.5% respectively. When the dosage of tyrosine reaches 2 mg / L, the removal rate of algal cells is more than 71%, and the removal rate of Chl-a is more than 83%, and the inhibitory effect of tyrosine is 9% and 7% respectively. Based on the analysis of the above experimental results, it is considered that the main DOM components affecting the removal of Microcystis wesenbergii by CaC2O4crystallization in water body are humic acid and amino acid, which have an inhibitory effect, and the effect of glucose (Glu) on the removal of Microcystis wesenbergii by CaC2O4crystallization is small.

[0081] By Figure 13It can be seen that the addition of humic acid alone has an inhibitory effect on the removal of Microcystis blooms by CaC2O4 crystallization, and as the DOM concentration increases, the inhibitory effect becomes greater. The addition of different types of DOM (glucose, tryptophan, tyrosine) alone has a promoting effect on the removal of Microcystis blooms by CaC2O4 crystallization, and as the DOM concentration increases, the promoting effect becomes greater. The promoting effect is: glucose>tryptophan>tyrosine. When the dosage of humic acid reached 10 mg / L, the removal rate of algal cells reached more than 65%, the removal rate of Chl-a reached more than 76%, and the inhibitory effects of humic acid were 6% and 5% respectively; when the dosage of glucose reached 10 mg / L, the removal rate of algal cells reached more than 89%, the removal rate of Chl-a reached more than 92%, and the promoting effects of glucose were 8% and 11% respectively; when the dosage of tryptophan reached 2 mg / L, the removal rate of algal cells reached more than 84%, the removal rate of Chl-a reached more than 86%, and the promoting effects of tryptophan were 5.5% and 4.5% respectively; when the dosage of tyrosine reached 2 mg / L, the removal rate of algal cells reached more than 84%, the removal rate of Chl-a reached more than 85%, and the promoting effects of tyrosine were 5.5% and 4% respectively. Analysis of the above experimental results shows that the main DOM components in water that affect the removal of Microcystis blooms by CaC2O4 crystallization are humic acid and glucose. Humic acid exhibits an inhibitory effect, glucose exhibits a promoting effect, and amino acids have little effect on the removal of Microcystis blooms by CaC2O4 crystallization.

[0082] like Figure 14 As shown in the figure, the curve shows that the addition of humic acid to CaC2O4 crystallization to remove Microcystis will reduce the pH value of the water body. The reduction degrees for Microcystis aeruginosa, Microcystis whitney, and Microcystis blooms are 0.1, 0.4, and 0.3, respectively. The addition of glucose to CaC2O4 crystallization to remove Microcystis has basically no significant effect on the pH value of the water body. The addition of tryptophan and tyrosine to CaC2O4 crystallization to remove Microcystis will increase the pH value of the water body. The increase degrees for Microcystis aeruginosa, Microcystis whitney, and Microcystis blooms are 0.3 and 0.2, respectively. The degree of influence of humic acid, glucose, tryptophan, and tyrosine on the pH value of the water body during CaC2O4 crystallization to remove Microcystis is humic acid > tryptophan > tyrosine > glucose.

[0083] 2.2 Study on the effect of multi-component DOM on the algae removal efficiency of CaC2O4 crystallization

[0084] The effect of mixed DOM on the removal of Microcystis aeruginosa, Microcystis whitney and Microcystis blooms by CaC2O4 crystallization was investigated. The dosages of humic acid, glucose, tryptophan and tyrosine were shown in Table 2. After settling for 6 h, water samples were taken 3 cm below the liquid surface and the absorbance at 680 nm (A 680detection and chlorophyll (Chl-a) concentration determination, the experimental results are shown in Figure 15 、 16 、17.

[0085] It can be seen from Figure 15 that the removal rates of CaC2O4 crystals on Microcystis aeruginosa cells and chlorophyll in each experimental group were lower than that in the blank control group. The inhibition effect of DOM mixed solution mainly containing HA on CaC2O4 crystals removing Microcystis aeruginosa was the most obvious, which indicated that HA was the key DOM substance to inhibit the effect of CaC2O4 crystals removing Microcystis aeruginosa.

[0086] It can be seen from Figure 16 that the removal rates of CaC2O4 crystals on Microcystis wesenbergii cells and chlorophyll in each experimental group were lower than that in the blank control group. The inhibition effect of DOM mixed solution mainly containing HA on CaC2O4 crystals removing Microcystis wesenbergii was the most obvious, which indicated that HA was the key DOM substance to inhibit the effect of CaC2O4 crystals removing Microcystis wesenbergii. However, a certain concentration of Glu could weaken the inhibition effect of other types of DOM on CaC2O4 crystals removing Microcystis wesenbergii.

[0087] It can be seen from Figure 17 that the removal rates of CaC2O4 crystals on Microcystis flos-aquae cells and chlorophyll in each experimental group were basically consistent with that in the blank control group, which indicated that the promotion effect of Glu, Trp and Tyr on CaC2O4 crystals removing Microcystis flos-aquae basically offset the inhibition effect of HA.

[0088] 2.2.1 Orthogonal experiment research

[0089] The effects of different concentrations of mixed DOM on the removal efficiency of CaC2O4 crystals on Microcystis aeruginosa, Microcystis wesenbergii and Microcystis flos-aquae were investigated. Three-factor and three-level orthogonal experiment was designed, and the dosages of humic acid, glucose, tryptophan and tyrosine were shown in Table 2. After 6h of static precipitation, the water sample at 3cm below the liquid surface was taken for A680 detection at 680nm. The experimental results were shown in Tables 2-4, and the obtained results were analyzed and compared by calculating the range.

[0090] Table 2 Results of three-factor and three-level orthogonal experiment (Microcystis aeruginosa)

[0091]

[0092] From the orthogonal experiment, it can be seen that the maximum range of HA is 0.082, followed by Trp+Tyr with a range of 0.044, and finally Glu with a range of 0.033. According to the size of the range R, the order of the influence of different types of DOM on the removal of Microcystis aeruginosa by CaC2O4 crystallization is HA concentration > Trp+Tyr concentration > Glu concentration. It can also be determined that the most unfavorable condition for the removal of Microcystis aeruginosa by CaC2O4 crystallization is HA concentration of 8 mg / L, Glu concentration of 8 mg / L, and Trp+Tyr concentration of 4 mg / L, with a removal efficiency of 74.65% for Microcystis aeruginosa cells.

[0093] Table 3 Results of three-factor three-level orthogonal experiment (Oocystis borgei)

[0094]

[0095] From the orthogonal experiment, it can be seen that the maximum range of HA is 0.033, followed by Glu with a range of 0.028, and finally Trp+Tyr with a range of 0.023. According to the size of the range R, the order of the influence of different types of DOM on the removal of Oocystis borgei by CaC2O4 crystallization is HA concentration > Glu concentration > Trp+Tyr concentration. It can also be determined that the most unfavorable condition for the removal of Oocystis borgei by CaC2O4 crystallization is HA concentration of 4 mg / L, Glu concentration of 4 mg / L, and Trp+Tyr concentration of 4 mg / L, with a removal efficiency of 71.97% for Oocystis borgei cells.

[0096] Table 4 Results of three-factor three-level orthogonal experiment (Microcystis flos-aquae)

[0097]

[0098] From the orthogonal experiment, it can be seen that the maximum range of HA is 0.021, followed by Trp+Tyr with a range of 0.017, and finally Glu with a range of 0.003. According to the size of the range R, the order of the influence of different types of DOM on the removal of Microcystis flos-aquae by CaC2O4 crystallization is HA concentration > Trp+Tyr concentration > Glu concentration. It can also be determined that the most unfavorable condition for the removal of Microcystis flos-aquae by CaC2O4 crystallization is HA concentration of 8 mg / L, Glu concentration of 8 mg / L, and Trp+Tyr concentration of 4 mg / L, with a removal efficiency of 86.19% for Microcystis flos-aquae cells.

[0099] 2.3 Influence of CaC2O4 crystallization on the removal efficiency of Microcystis within 30 days

[0100] The removal of M. aeruginosa, M. wensii and M. flos-aquae by CaC2O4 crystallization was investigated within 30 days. The DOM was added in the amount shown in Table 7, NaC2O4: CaCl2 (w:w) = 0.5:1. The water sample was taken at 3 cm below the liquid surface every 5 days during the experiment to detect the absorbance (A680) at 680 nm. The results are shown in Table 8. To avoid the randomness of the experimental results, each experiment was conducted three times, and the final results were averaged. 680 Figure 18

[0101] Table 5 Three-factor three-level orthogonal experiment

[0102]

[0103] The absorbance of the supernatant was measured continuously for 30 days. The efficiency of DOM on the removal of M. aeruginosa by CaC2O4 crystallization had no significant effect within 30 days. The overall removal rate of M. aeruginosa could be maintained above 95%, but the removal rate of M. aeruginosa cells showed a downward trend over time, especially for Glu. The overall removal rate of M. wensii could be maintained above 99%, and the removal rate of M. wensii cells showed an upward trend over time, which may be due to the persistent algal-killing effect of H2O2, which stabilized the removal effect of CaC2O4 crystallization on M. wensii cells. Within the first 25 days, the overall removal rate of M. flos-aquae showed a slight downward trend over time, and the removal rate of M. flos-aquae cells increased in the last 5 days. The overall removal rate could be maintained above 96%.

[0104] 2.4 Sediment properties

[0105] At the time of sampling, BG-11 medium was added to the water from Qingshan Lake filtered through a 0.45 μm filter to dilute the algal cell stock solution for algal culture, which was used in the later CaC2O4 crystallization experiment. The addition of CaC2O4 and C2O4 to the water from Qingshan Lake reached the optimal algal removal concentration for M. aeruginosa, M. wensii and M. flos-aquae, respectively. The experimental period was 2 days, and the settling experiment was recorded during the experiment. After the experiment, the water sample was taken at 3 cm below the liquid surface to detect the absorbance (A680) at 680 nm, determine the concentration of chlorophyll (Chl-a) and turbidity. XRD analysis of the sediment after precipitation and analysis of the three-dimensional fluorescence characteristics and three-dimensional fluorescence spectrum index of DOM in natural water during the CaC2O4 crystallization process were also conducted. To avoid the randomness of the experimental results, each experiment was conducted three times, and the final results were averaged. 2+ 2- 680

[0106] (1) XRD analysis ​​​​​

[0107] Table 6 Analysis of relative crystallinity of CaC2O4 crystalline sediments

[0108]

[0109] By performing XRD analysis on CaC2O4 crystal deposits, Figure 19 As shown, the results show that compared with the control group, the crystal form of CaC2O4 crystals did not change significantly with HA, Glu, Trp, and Tyr, and the position of the crystallization peak of CaC2O4 crystals did not shift significantly. However, HA will cause the peak height of the CaC2O4 crystallization peak to decrease, Glu basically does not change the peak height of the CaC2O4 crystallization peak, and Trp and Tyr will cause the peak height of the CaC2O4 crystallization peak to increase. According to the calculation formula of relative crystallinity ε, the relative crystallinity ε of CaC2O4 crystal sediment was calculated in combination with XRD patterns. The results are shown in Table 6. The results show that during the CaC2O4 crystallization algae removal process, HA will reduce the relative crystallinity ε of CaC2O4 crystals and inhibit the nucleation of CaC2O4 crystals; Glu has basically no effect on the relative crystallinity ε of CaC2O4 crystals; Trp and Tyr will increase the relative crystallinity ε of CaC2O4 crystals and promote the nucleation of CaC2O4 crystals. The effects of HA, Glu, Trp, and Tyr on the nucleation of CaC2O4 crystals are Trp>Tyr>Glu>HA.

[0110] (2) IR analysis

[0111] The sediments after algae removal by CaC2O4 crystallization after adding DOM components were analyzed by IR and compared. Figure 10 The IR spectrum of the CaC2O4 crystal experimental group showed that the infrared absorption peak of CaC2O4 crystals was still mainly concentrated in the wavelength range of 3060-3490 cm -1 1310~1620cm -1 510~960cm -1 The results show that in the process of algae removal by CaC2O4 crystallization after adding DOM component, the DOM component basically does not change the composition and chemical bond activity of the functional groups inside the CaC2O4 crystals.

[0112] As can be seen from Example 1, when CaCl2 solution and Na2C2O4 solution are used together, the CaC2O4 crystals they form are much more effective in removing algae than CaCl2 solution. 2+ The result of a single action; and when C2O4 2- With Ca2+ molar ratio of 0.25-1:1, Ca 2+ The input concentration of Ca2+ is 6-8 mM, and the removal effect on algae is better.

[0113] As can be seen from Example 2, even if the DOM in the water body changes, the method of the present application will not be affected by external factors. The total removal rate of microcystis can finally be maintained at more than 96% when the water body is treated by the method of the present application for 30 days.

Claims

1. Ca 2+ with C2O4 2- application of the crystalline system formed in removing microcystis in water body.

2. Use according to claim 1, wherein The microcystis is any one of Microcystis aeruginosa, Microcystis wesenbergii and Microcystis flos-aquae.

3. The use according to claim 1, wherein The water containing Ca 2+ and C2O4 2- The salts of these two crystal-forming ions are added to the water containing microcystis.

4. The use according to claim 3, wherein the compound is ###0002### Ca 2+ and C2O4 2- After that, glucose or a substance containing glucose is added to the water body.

5. The use according to claim 3, wherein the compound is ###0002### The salt containing Ca 2+ is CaCl2, and the salt containing C2O4 2- is NaC2O4; the molar ratio of C2O4 2- to Ca 2+ is 0.25-1:1, and the input concentration of Ca 2+ is 6-8 mM.

6. A calcium salt-based microcystic algal control agent that is resistant to DOM, characterized in that, The algaecide contains Ca 2+ and C2O4 2- salts of these two crystallographic ions.

7. The algaecide of claim 6, wherein The alga removing agent contains CaC2O4 crystal.

8. A method for removing microcystis by using the alga removing agent of claim 6, comprising the following steps: (1) preparing CaCl2 solution and Na2C2O4 solution; (2) Pour the prepared CaCl2 solution and Na2C2O4 solution into the water body containing microcystis, stand, and precipitate; keep the concentration of Ca2+ in the water body at 6-8 mM, and the molar ratio of C2O4- to Ca2+ in the CaCl2 solution in (1) at 0.25-1:

1. 2+ 2- 2+ ​​​ 9. The method for removing microcystis according to claim 8, characterized in that, (2) before adding CaCl2 solution and Na2C2O4 solution, adding hydrogen peroxide into water body by direct adding method at a ratio of 0.5 mL hydrogen peroxide / 200 mL water body, standing for 2-3 hours, and then adding CaCl2 solution and Na2C2O4 solution into water body.

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