Method for jointly controlling growth of cylindrotheca by using allelochemicals and modified clay flocculant

Abstract

The invention relates to the technical field of water treatment, and discloses a method for jointly controlling growth of cylindrotheca by using an allelochemical and a modified clay flocculant, which comprises the following steps: adding a plant-derived allelochemical into a water body containing cyanobacteria, stirring and standing; and adding a modified clay flocculant into the water body after standing, and stirring for flocculation to inhibit the generation of algal bloom. The allelopathic effect of the natural allelopathic substance and the flocculation effect of the modified clay flocculant are utilized to fully inhibit the diffusion and growth of the cylindrotheca algal bloom and continuously prevent the recurrence and regeneration of the cylindrotheca algal bloom, so that the method has the characteristics of environment friendliness, quick effect and low cost, and is suitable for popularization and application. The method has an extremely high application value for the problem of water bloom of the cylindrocarpon in a plateau lake water body.

Description

Technical Field

[0001] The present invention relates to the technical field of water treatment, and particularly to a method for jointly controlling the growth of Cylindrospermopsis raciborskii by using allelochemicals and modified clay flocculants. Background Art

[0002] With climate change and economic development, cyanobacterial blooms have become an important environmental pollution problem. Cylindrospermopsis raciborskii is one of the cyanobacteria causing blooms that has received extensive attention in recent years. It is distributed in lakes in Guangdong, Fujian, Taiwan, Yunnan and other places in China. The algal toxins produced by it have liver and kidney toxicity. Moreover, it can have an obvious allelopathic inhibitory effect on other algae in the same lake, so as to achieve the rapid expansion and outbreak of Cylindrospermopsis raciborskii, which has a serious impact on the water ecological environment.

[0003] Since Cylindrospermopsis raciborskii has a small algal body (filament length 40–310 μm, width 2–4 μm) and strong dispersibility in water. Common algal control technologies include: physical algal control technology, chemical algal control technology and biological algal control technology. Among them, physical algal control technology refers to separating and removing or inhibiting the reproduction of algae from water by physical means, so as to achieve the purpose of controlling the growth of algae; chemical algal control technology refers to killing algal cells with chemical drugs, mainly by adding specific chemical reagents to the water body and directly killing algal cells by oxidation or other reactions. Biological algal control technology is a technology that uses natural enemies of algae and the growth inhibitory substances they produce to inhibit and kill algae. Among these methods, physical technology is often costly, chemical technology has a large environmental cost, and biological algal control technology using allelochemicals to remove algae is considered a fast-acting, low-cost and low-ecological-risk algal control technology. Summary of the Invention

[0004] The purpose of the present invention is to provide a method for jointly controlling the growth of Cylindrospermopsis raciborskii by using allelochemicals and modified clay flocculants, so as to solve the problem that the existing algicides have poor flocculation effect on the removal of filamentous algae.

[0005] The solution of the present invention is as follows:

[0006] A method for jointly controlling the growth of Cylindrospermopsis raciborskii by using allelochemicals and modified clay flocculants, comprising the following steps:

[0007] 1) Put plant-derived allelochemicals into the water body containing cyanobacteria, stir, and let stand;

[0008] 2) Put modified clay flocculants into the water body after standing, stir and flocculate to inhibit the occurrence of algal blooms.

[0009] By adding allelochemicals, the Cylindrospermopsis raciborskii in the water body is lysed and killed. The modified clay is compounded with a polymer flocculant to improve the floc structure of a single polymer flocculant, and the particulate organic carbon in the water body is reduced by flocculation.

[0010] As a preferred technical solution, the Cyanophyta includes Cylindrospermopsis.

[0011] As a preferred technical solution, the standing time is 24 to 48 h.

[0012] As a preferred technical solution, the plant allelochemical is one or more of gallic acid, ellagic acid or salicylic acid.

[0013] As a preferred technical solution, the plant allelochemical is processed to obtain a derivative allelochemical.

[0014] As a preferred technical solution, the modified clay flocculant includes modified clay and a polymer flocculant.

[0015] As a preferred technical solution, the preparation method of the modified clay flocculant includes the following steps:

[0016] S1. The clay is subjected to a modification treatment, and after the modification treatment, it is dried, ground and sieved to obtain modified clay;

[0017] S2. The modified clay and the polymer flocculant are uniformly mixed to obtain the modified clay flocculant.

[0018] As a preferred technical solution, the clay is any one or more of kaolin, montmorillonite and bentonite; the modification treatment is any one or more of ultrasonic modification treatment, thermal modification treatment, acid modification treatment and alkali modification treatment; the polymer flocculant is any one or a combination of two or more of polyacrylamide and polyaluminum chloride.

[0019] As a preferred technical solution, the modification treatment is ultrasonic modification treatment, which is carried out at a frequency of 20 to 40 kHz by using ultrasonic waves, the power range is 100 to 500 W, the treatment time is 10 to 60 minutes, the ultrasonic-modified clay is dried at 60 to 120 °C, and then it is sieved by using a sieve to obtain uniform modified clay.

[0020] As a preferred technical solution, the mass ratio of the modified clay to the polymer flocculant is 1:3 to 10.

[0021] As a preferred technical solution, the uniform mixing treatment in step S2 is one of mechanical stirring or high-speed mixing.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] The present invention uses mineral clay modified by ultrasound as a carrier to obtain a polymer flocculant, and allelochemicals are applied in combination. By adding the allelochemical pyrogallol, the cylindrospermopsis raciborskii in the lake is lysed and killed. The ultrasound-modified clay is compounded with the polymer flocculant to improve the floc structure of the single polymer flocculant, and the particulate organic carbon in the water body is reduced by flocculation. The combined algal control technology of the allelochemicals and the modified clay flocculant shows excellent algicidal performance, especially has a significant killing effect on filamentous algae such as cylindrospermopsis raciborskii. Moreover, the allelochemical component and the clay component are significantly bio-friendly and will not harm the water body ecosystem, which is a green and efficient algicidal means. Description of the Drawings

[0024] Figure 1 It is a comparison chart of the algae removal rates of different types of clay, flocculant and their compound in Experiment 1 of the present invention;

[0025] Figure 2 It is a comparison chart of the algae removal rates of the modified flocculants obtained from different compounding ratios of clay and polyacrylamide in Experiment 2 of the present invention;

[0026] Figure 3 It is a comparison chart of the algae removal rates obtained with different dosages of the modified clay flocculant in Experiment 3 of the present invention;

[0027] Figure 4 It is a chart of the density change of algal cells after being treated with allelochemicals at different concentrations in Experiment 4 of the present invention;

[0028] Figure 5 It is an inhibition effect chart of pyrogallol on cylindrospermopsis raciborskii under different pH environments in Experiment 5 of the present invention;

[0029] Figure 6 It is a floc morphology chart of the flocs without and with the addition of allelochemicals under a forty-fold microscope in Experiment 6 of the present invention;

[0030] Figure 7 It is a chart of the change of the removal rate of cylindrospermopsis raciborskii cells in two pools within seven days after adding drugs in Experiment 7 of the present invention;

[0031] Figure 8 It is a chart of the change of the density of cyanobacteria in three pools within two months after adding drugs in Experiment 7 of the present invention. Detailed Embodiments

[0032] In order to make the technical means, creative features, achieved purposes and functions of the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

[0033] Embodiment

[0034] Take 250 mL of algal solution, and add 100 mg of clay of different materials (sieved through a 0.064 mm sieve before dosing). First, stir at 500 r / min for 5 min, then reduce the rotation speed to 200 r / min, keep it for 10 min and then let it stand. After sampling, observing and counting, calculate the removal rate. The formula is:

[0035]

[0036] IR in the formula represents the algal cell removal rate, N0 represents the algal cell density of the blank control group, and Nx represents the algal cell density of the experimental treatment group. The unit of all is cells / L.

[0037] Experiment 1

[0038] Comparative experiment on the effect of compound flocculant and single flocculant.

[0039] Take 250 mL of algal solution, and mix and add and add alone three kinds of clays (bentonite, montmorillonite and kaolin) and two kinds of polymer flocculants (polyaluminum chloride and polyacrylamide) respectively. After stirring and flocculating and standing in the same way, sample and calculate the removal rate.

[0040] The results are shown in Figure 1 , generally speaking, after the clay is compounded with the flocculant, the flocculation effect on the algae is better than adding clay or polymer flocculant alone. The main reason is that after the compound addition, the internal voids of the formed flocs are smaller and the structure is more compact. For the two flocculants, the clay compounded with polyacrylamide generally has better flocculation performance than the clay.

[0041] Experiment 2

[0042] Test the flocculation effect of the ratio of modified clay flocculant. Add the clay to 100 mL of ultrapure water (ultrasonic frequency 40 kHz) and ultrasonic for 20 min, let it stand and precipitate, pour out the supernatant, dry it overnight at 60 °C, and grind it through a 0.064 mm sieve after drying to obtain the modified clay. The mass ratio of modified clay: flocculant (polyacrylamide) is 1:1, 1:3, 1:5, 1:7. Obtain the modified clay flocculant, where the clay is bentonite and montmorillonite respectively;

[0043] After adding 100 mg of the modified clay flocculant into 250 ml of algal solution, first set the rotation speed to 300 r / min and keep it for 1 min, then adjust the rotation speed to 100 r / min and stir for 5 min. At the same time, in order to observe the change of the algal cell number in the algal solution in time, adjust the sampling time to 30 min after the end of stirring, and still use a microscope for observation and counting.

[0044] Through Figure 2It can be seen that different compounding ratios have a relatively significant impact on the flocculation effect of clay. The flocculation effect of the compounded ultrasonic bentonite is better than that of the montmorillonite after ultrasonic modification at any compounding ratio. In addition, among various compounding ratios, the modified ultrasonic bentonite with a mass ratio of modified clay to flocculant (polyacrylamide) of 1:5 has a flocculation algae removal rate of 98% within 15 minutes, achieving the best effect. Considering economic factors, it is considered that the compounding ratio of 1:5 can maximize the flocculation ability.

[0045] Experiment 3

[0046] This experiment compared the algae cell removal effects obtained with different dosages of flocculants;

[0047] 25 mg, 50 mg, 75 mg, and 100 mg of modified clay flocculant were respectively added to 250 mL of algae solution, and the mass ratio of modified clay to polyacrylamide in the modified clay flocculant was 1:5. Among them, a dosage of 50 mg could achieve an algae removal rate of 97% within 15 minutes, and the algae removal rate after 30 minutes reached 99%, enabling the effective removal of Cylindrospermopsis raciborskii. Therefore, a dosage of 100 mg could achieve an almost 100% removal rate within 15 minutes, with the best removal effect.

[0048] Experiment 4

[0049] Comparison of the algae-killing effects of different dosages of allelochemicals (pyrogallic acid) added

[0050] Different dosages of allelochemicals added will significantly affect the growth of Cylindrospermopsis raciborskii when exposed to pyrogallic acid. Combining the actual situation and comprehensively considering economic and efficiency factors, five concentration gradients were selected to study the impact of the one-time exposure amount of allelochemicals.

[0051] In this experiment, 0.1 ppm, 0.5 ppm, 1 ppm, and 2 ppm of pyrogallic acid were respectively selected and added to the inoculated algae solution at one time, and then cultured in an incubator at a normal temperature of 20 °C. Keeping other factors unchanged, the culture was carried out for 72 hours, and samples were taken every 24 hours to record and analyze the data.

[0052] As Figure 4 shown, when the initial algae cell density was relatively low, around 3.5×10 9 cells / L, the experimental group with a pyrogallic acid concentration of 2 ppm could achieve the best inhibitory effect compared to the 0.1 ppm, 0.5 ppm, and 1 ppm experimental groups, and could remove all algae cells. Moreover, different concentration experimental groups showed a trend that as the dosage of allelochemicals added increased, the inhibition rate also increased.

[0053] Experiment 5

[0054] This experiment provides a comparison of the algae removal effects of allelochemical dosages under different pH conditions.

[0055] There were significant differences in the number of algal cells among different pH treatment groups. From pH = 6 to pH = 9, the number of algal cells decreased with the increase of pH, and the inhibition rate of Cylindrospermopsis raciborskii gradually increased. When pH = 9, all the algal cells exposed to pyrogallic acid for 24 hours died, showing an obvious inhibitory effect, and the inhibition rate of Cylindrospermopsis raciborskii reached 100% (see Figure 5 ).

[0056] Experiment 6

[0057] This experiment compares the algae removal effects of adding allelochemicals alone, flocculants alone, and the combined addition of allelochemicals and flocculants.

[0058] For the algae solution completely inactivated by allelochemicals, flocculants were added continuously. After adding the flocculants, the turbid liquid became clear. Comparing the flocs observed under a microscope before inactivation without adding allelochemicals, filamentous algal cells were clearly visible in the flocs under a 40× objective lens. Similarly, observing the flocs flocculated after complete inactivation by adding allelochemicals under a 40× objective lens, the flocs formed into clusters, and only granular broken residues of Cylindrospermopsis raciborskii were visible inside the clusters (see Figure 6 ).

[0059] Experiment 7

[0060] This example provides the application of the combined algae control technology of allelochemicals and modified clay flocculants of the present invention in the treatment of algal blooms in a plateau lake in Yunnan Province.

[0061] The modified clay flocculant was prepared according to the following method:

[0062] Weigh 2.5 g of clay, add 100 mL of ultrapure water (ultrasonic frequency 40 kHz), sonicate for 20 min, let it stand for precipitation, pour out the supernatant, dry it overnight at 60 °C, and grind it after drying and pass it through a 0.064 mm sieve to obtain modified clay. Take a certain amount of polyacrylamide and mix it evenly with the clay. The mass ratio of modified clay to polyacrylamide is 1:5. The clay is bentonite.

[0063] To a certain amount of lake water with algal blooms that was extracted and stored, first add a certain amount of allelochemical pyrogallic acid, and after fully removing the algae, then add the modified clay flocculant and conduct mechanical stirring. Among them, 20 mg / L of pyrogallic acid was added to Pool No. 1, and 40 mg / L of pyrogallic acid was added to Pool No. 2. The dosage of the modified clay flocculant in both pools was 300 mg / L.

[0064] The monitoring results of the inhibition rate of Cylindrospermopsis raciborskii in the test pools within 7 days showed (see Figure 7), the quantity of Cylindrospermopsis raciborskii in the two experimental pools was effectively inhibited, and the inhibition rate of Cylindrospermopsis raciborskii in both pools reached 99%. The long-term monitoring results for two months showed (see Figure 8 ), a dosage of 40 mg / L pyrogallic acid and 300 mg / L modified clay flocculant could continuously inhibit the density of cyanobacteria in the long term, and the inhibition rate reached 94% at two months.

[0065] In summary, the combined algae control technology of the allelochemical and the modified clay flocculant of the present invention has a strong killing effect on Cylindrospermopsis raciborskii, and its algae removal rate can reach 100%, which is an efficient means for combined bloom control.

[0066] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited by the above embodiments. What is described in the above embodiments and the specification only illustrates the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention will have various changes and improvements, and these changes and improvements fall within the scope of the present invention claimed. The scope of the present invention claimed is defined by the appended claims and their equivalents.

Claims

1. A method for controlling the growth of Pseudocylospora by using allelochemicals and modified clay flocculants, characterized in that: The following steps are involved: 1) Add plant-derived allelopathic substances into water containing cyanobacteria, stir, and let stand; 2) Add modified clay flocculant into the water after standing, stir and flocculate to inhibit the formation of algal bloom.

2. A method for controlling the growth of Pseudocylospora using allelochemicals and modified clay flocculants as claimed in claim 1, characterized in that: The Cyanobacteria include the genus Pseudocylindrospermum.

3. A method for controlling the growth of Pseudocylindrospermum using allelochemicals and modified clay flocculants as claimed in claim 1, characterized in that: The standing time is 24 to 48 hours.

4. A method for controlling the growth of Pseudocylospora by combining allelochemicals with modified clay flocculants as claimed in claim 1, characterized in that: The plant-derived allelopathic substances are one or more of gallic acid, ellagic acid or salicylic acid.

5. A method for controlling the growth of Pseudocylospora by combining allelochemicals with modified clay flocculants as claimed in claim 4, characterized in that: The plant-derived allelopathic substances are processed to obtain derived allelopathic substances.

6. A method for controlling the growth of Pseudocylindrospermum using allelochemicals and modified clay flocculants as claimed in claim 1, characterized in that: The modified clay flocculant comprises modified clay and a polymer flocculant.

7. A method for controlling the growth of Pseudocylindrospermum using allelochemicals and modified clay flocculants as claimed in claim 6, characterized in that: The modified clay flocculant preparation method is as follows: S1, modifying the clay, drying, grinding and sieving to obtain modified clay; S2. Mixing the modified clay and the polymer flocculant to obtain a modified clay flocculant.

8. A method for controlling the growth of Pseudocylindrospermum using allelochemicals and modified clay flocculants as claimed in claim 7, characterized in that: The clay is one or more of kaolin, montmorillonite and bentonite; the modification treatment is one or more of ultrasonic modification treatment, thermal modification treatment, acid modification treatment and alkali modification treatment; the polymer flocculant is one or a combination of polyacrylamide and polyaluminium chloride.

9. A method for controlling the growth of Pseudocylospora by combining allelochemicals with modified clay flocculants as claimed in claim 7, characterized in that: The mass ratio of the modified clay to the polymer flocculant is 1:3-10.

10. A method for controlling the growth of Pseudocylindrospermum using allelochemicals and modified clay flocculants as claimed in claim 8, characterized in that: The modification treatment is an ultrasonic modification treatment, which uses ultrasonic waves at a frequency of 20 to 40 kHz, a power range of 100 to 500 W, and a treatment time of 10 to 60 minutes. The ultrasonically modified clay is dried at 60 to 120° C. and then sieved with a sieve to obtain uniform modified clay.

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