Algae treatment method based on far ultraviolet light irradiation

Abstract

The invention discloses an algae treatment method based on far ultraviolet light irradiation. The method uses far ultraviolet light to irradiate the treated algae-containing raw water. Compared with an existing ultraviolet light irradiation technology, the method has the advantages that the illumination intensity is low, and algae cells can be greatly inactivated in a short time. Algal toxins can be degraded through far ultraviolet light irradiation, and the total toxin reduction trend is presented on the whole. And meanwhile, the algae inactivated by far ultraviolet irradiation cannot grow again, so that the effect of inhibiting the re-outbreak of algal blooms is achieved. Besides, the used far ultraviolet light is harmless to a human body, the illumination intensity is low, the treatment time is short, the method is simple to operate, the algae can be thoroughly inactivated, meanwhile, the energy consumption is reduced, the treatment efficiency is improved, and the harm to workers is avoided.

Description

Technical Field

[0001] The invention belongs to the technical field of algae treatment, and in particular relates to an algae treatment method based on far ultraviolet light irradiation. Background Art

[0002] In recent years, with the increasing degree of eutrophication of water bodies, cyanobacteria blooms have frequently occurred in rivers, lakes and other water bodies, and have become one of the biggest threats to surface water bodies around the world. Microcystis aeruginosa is the main dominant algae species in cyanobacteria blooms. Its massive proliferation not only pollutes drinking water and landscape water bodies, increases the cost of water treatment and maintenance, but also causes an imbalance in the water ecological environment. At the same time, Microcystis aeruginosa can produce and release microcystins into water bodies. Microcystins can be enriched in aquatic organisms through food chains and food webs, and have toxic effects on organisms in the aquatic environment. In addition, microcystins can enter the human body through various pathways, causing health risks such as tumors.

[0003] At present, the treatment methods of algae are mainly divided into three categories: physical method, chemical method and biological method. The physical method treats algae through filtration, flotation, adsorption and other means, which has a significant effect, but during the outbreak of blue algae blooms, the amount of coagulant needs to be doubled, which increases the treatment cost. Chemical treatment technologies such as adding ozone, sodium hypochlorite, potassium permanganate, etc., have a quick oxidation effect, but long-term addition of agents will cause secondary pollution, inevitably causing environmental pollution and ecological imbalance. Biological treatment technology uses algae pathogens, viruses, etc. to inhibit the growth of algae cells. It has low cost investment and can continuously reduce nutrients in the water body, but it still faces technical challenges and is difficult to implement. Summary of the invention

[0004] The purpose of the present invention is to provide a more efficient inactivation method, namely, an algae treatment method based on far ultraviolet light irradiation, in view of the unsatisfactory treatment efficiency of the existing drinking water treatment plant water purification process, so as to overcome the shortcomings of the existing water treatment technology. The algae treatment in the present invention specifically refers to the inactivation of algae cells, inhibition of regeneration and degradation of algae toxins.

[0005] The present invention provides an algae treatment method based on far-ultraviolet light irradiation, and the treatment process is: use far-ultraviolet light with a wavelength of 200 nm to 230 nm to irradiate the treated algae-containing raw water. The irradiation time is greater than or equal to 5 min. The wavelength of far-ultraviolet light can directly act on biological macromolecules such as proteins and phospholipids, triggering lipid peroxidation, thereby causing cell membrane damage and significantly reducing cell activity. In addition, the algae-containing raw water after far-ultraviolet light irradiation will generate hydroxyl radicals, which can directly react with biological macromolecules such as proteins, nucleic acids, fatty acids and cytochromes, thereby affecting their functions and further causing algae cell death.

[0006] Preferably, the wavelength of the far ultraviolet light is 222 nm.

[0007] Preferably, the ultraviolet intensity of the irradiated algae-containing raw water is 0.1 mW·cm -2 ~0.4 mW·cm -2 .

[0008] Preferably, the far-ultraviolet light irradiation time is greater than or equal to 5 min.

[0009] Preferably, the far-ultraviolet light irradiation time is 7 min to 45 min.

[0010] Preferably, the algae in the algae-containing raw water are cyanobacteria; the wavelength of far-ultraviolet light is just absorbed by DNA and RNA, causing additional collisions and damage. This wavelength energy will damage the genome of cyanobacterial cells and hinder their replication and reproduction capabilities.

[0011] Preferably, the algae cells in the algae-containing raw water are Microcystis aeruginosa cells.

[0012] Preferably, the algae-containing raw water is continuously stirred during the far-ultraviolet light irradiation process.

[0013] As a preferred method, the algae cell density in the algae-containing raw water is 5×10 5 cells / mL~1×10 6 cells / mL.

[0014] Preferably, during the far-ultraviolet light irradiation, the temperature of the algae-containing raw water is maintained at 25°C.

[0015] Compared with the prior art, the present invention has the following advantages and positive effects: (1) Compared with traditional chemical treatment methods, the algae treatment method based on far-ultraviolet light irradiation provided by the present invention does not require the addition of chemical agents and does not produce chemical residues or toxic byproducts. This makes it more environmentally friendly in water treatment and does not pollute water resources and the surrounding environment. At the same time, the operation and maintenance of the far-ultraviolet system are relatively simple. Once installed, the system can operate almost automatically without frequent human intervention.

[0016] (2) The algae treatment method of far-ultraviolet light irradiation provided by the present invention can efficiently degrade algae toxins and significantly reduce toxicity by destroying their chemical structure, thereby ensuring water safety. In contrast, traditional physical treatment methods, such as filtration and sedimentation, mainly remove algae and suspended particles and cannot effectively degrade algae toxins. (3) Compared with existing ultraviolet light sources, the far-ultraviolet light source provided by the present invention not only has low light intensity, but also can significantly inactivate algae cells in a short period of time. The power of traditional ultraviolet lamps decreases with the increase of usage time, and its inactivation effect also decreases accordingly. In contrast, the light intensity required for far-ultraviolet light is low and the treatment time is short, so its service life and inactivation effect can be further improved.

[0017] (4) The far-ultraviolet light irradiation technology provided by the present invention can destroy the genome of algae cells, so the algae cells in the treated algae-containing raw water will not be able to grow again, which has an inhibitory effect on the re-outbreak of algae blooms.

[0018] (5) Compared with the existing ultraviolet wavelengths, the far-ultraviolet wavelengths provided by the present invention can directly cause the photolysis of proteins and lipids, resulting in cell membrane damage, thereby causing cell shrinkage, depression and permeability changes. At the same time, these wavelengths can also induce lipid peroxidation, significantly reducing cell activity. Under far-ultraviolet irradiation, the algae liquid system will generate hydroxyl radicals, further increasing the inactivation rate and inactivation rate of algae cells.

[0019] (6) The far-ultraviolet light used in the present invention has a relatively long wavelength and can effectively kill bacteria, viruses and other microorganisms in water. It also has a significant algae inactivation effect, but it cannot penetrate the surface cells of human or other mammalian skin, greatly reducing the potential risk to human health. Therefore, far-ultraviolet light can be used in water treatment systems of various sizes, including drinking water, industrial water and water parks. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 It is a comparison chart of the inactivation rate of algae cells at different light intensities in Examples 1-3 of the present invention.

[0021] Figure 2 It is a comparison chart of the algae cell inactivation rates of Example 2 of the present invention and Comparative Examples 1 and 2.

[0022] Figure 3 This is a comparison chart of the effects of algae toxins in Example 2 of the present invention and Comparative Example 1.

[0023] Figure 4 This is a comparison diagram of the submicroscopic structure of algae cells in Example 2 of the present invention and Comparative Example 1 at 45 minutes.

[0024] Figure 5 This is a diagram showing the regrowth of algae cells in Example 2 of the present invention. DETAILED DESCRIPTION

[0025] The technical solution of the present invention is further described below by means of specific embodiments: Example 1 A method for treating algae based on far-ultraviolet light irradiation, the process is as follows: first, obtain algae-containing raw water, and then irradiate it with far-ultraviolet light to achieve the effect of quickly inactivating algae cells. During the far-ultraviolet light irradiation process, magnetic stirring is performed throughout the process to ensure that the solution is fully uniform. In this embodiment, the emission wavelength of the far-ultraviolet light source is 222 nm; the ultraviolet intensity is 0.126 mW·cm -2 .

[0026] In this embodiment, the algae cells in the algae-containing raw water are Microcystis aeruginosa in the cyanobacteria. The initial cell density of Microcystis aeruginosa is 7.5×10 5 cells / mL, and the system temperature was maintained at 25°C.

[0027] Example 2 The main difference between this embodiment and embodiment 1 is that the intensity of far-ultraviolet light irradiation is different; in this embodiment, the ultraviolet intensity is 0.276 mW·cm -2 .

[0028] Example 3 The main difference between this embodiment and embodiment 1 is that the light intensity of far-ultraviolet light irradiation is different; in this embodiment, the ultraviolet intensity is 0.387 mW·cm -2 .

[0029] like Figure 1 As shown, in Examples 1-3, after 3 minutes of far-ultraviolet irradiation, the inactivation rates of algae cells were 17.0%, 39.0% and 81.1%, respectively. The results show that the inactivation rate of algae cells significantly increases with the increase of far-ultraviolet light intensity. When the illumination time is extended to 5 minutes, the algae cells in Examples 2 and 3 are completely inactivated; when the illumination time is extended to 7 minutes, the algae cells under the three light intensities are completely inactivated, proving the effectiveness of far-ultraviolet light irradiation in inactivating algae. By performing linear fitting analysis on the inactivation rate of algae cells and the light intensity at three minutes, it is found that the linear relationship between the inactivation rate of algae cells (y) and the light intensity (x) is y = 240.18 x-17.465 (R 2 = 0.9319). That is, when the light intensity exceeds 0.468 mW·cm -2 The inactivation rate of algae cells can exceed 95% within three minutes.

[0030] Comparative Example 1 The invention discloses an algae treatment method, which obtains raw water containing Microcystis aeruginosa without any treatment.

[0031] Comparative Example 2 A method for treating algae. The difference between this comparative example and Example 2 is that the algae-containing raw water is irradiated with ultraviolet light having a wavelength of 254 nm. The intensity of the ultraviolet light having a wavelength of 254 nm is 0.336 mW·cm -2 .

[0032] Based on Example 2, comparative experiments were conducted on Examples 1 and 2; 3 replicates were set for each experimental group, and water samples were collected at different times of raw water treatment to determine the inactivation rate of algae cells, the determination of microcystin, the observation of the submicroscopic structure of algae cells, and the observation of the regrowth of algae cells. The results are as follows: Figure 2 , Figure 3 , Figure 4 , Figure 5 shown.

[0033] like Figure 2 As shown, after 3 minutes of far-ultraviolet light irradiation in Example 2, the inactivation rate of algae cells reached 21.2%; at 7 minutes, the inactivation rate rapidly increased to 91.6%; in the following 15 minutes, the inactivation rate reached 99.9%, that is, almost all algae cells were inactivated after 15 minutes of far-ultraviolet light irradiation. The inactivation rate of algae cells in Comparative Example 1 remained basically unchanged within 30 minutes, maintaining at 1.0%. In contrast, the inactivation rate of algae cells in Comparative Example 2 did not change much, and only rose to 3.3% after 30 minutes of ultraviolet light irradiation. At the same time, the far-ultraviolet light intensity of Example 1 was lower than that of Comparative Example 2. This shows that the algae treatment method of far-ultraviolet light irradiation of the present invention has a more significant algae cell inactivation rate and inactivation rate compared with ultraviolet light irradiation.

[0034] like Figure 3 As shown, the algae cell toxin content of Example 2 did not change much within seven minutes of far-ultraviolet light irradiation; it decreased significantly at 20 minutes, with a decrease rate of 25.9%. As the far-ultraviolet light irradiation time increased, the algae cell toxin content further decreased, and the decrease rate increased to 66.2% at 45 minutes. This shows that the algae treatment method based on far-ultraviolet light irradiation of Example 2 can significantly reduce the toxin content of algae cells.

[0035] like Figure 4 As shown, compared with Comparative Example 1, after 45 minutes of far-ultraviolet light treatment in Example 2, the algae cells showed slight overflow around them, the nuclear cavity enlarged, and the arrangement of the organelles became more chaotic. This indicates that far-ultraviolet rays can damage the internal structure and genome of Microcystis aeruginosa, thereby preventing the normal growth and reproduction of algae cells.

[0036] like Figure 5As shown in the figure, the algae cells lost their regeneration ability after 7 minutes of far-ultraviolet light irradiation, which proves that the algae treatment method of the present invention by far-ultraviolet light irradiation can effectively inhibit the re-emergence of algae blooms.

[0037] In the above experiment, the process of determining the inactivation rate of algae cells is as follows: the inactivation rate of algae cells after far-ultraviolet light irradiation is evaluated using flow cytometer.

[0038] The determination process of microcystin is as follows: the algae liquid treated with far-ultraviolet light is filtered through a filter membrane and then collected, and extracted using a C18 solid phase extraction column. A high performance liquid chromatography is used to determine the microcystin.

[0039] The observation process of the submicroscopic structure of algae cells is as follows: the algae solution treated with far-ultraviolet light is double-fixed with glutaraldehyde and osmium acid, and then dehydrated with gradient ethanol and acetone. The algae are then observed under a transmission electron microscope through penetration, embedding, sectioning, staining and other steps.

[0040] The observation process of algae cell regrowth is as follows: the algae-containing raw water exposed to different far-ultraviolet light times is left to stand for a period of time and its growth status is recorded.

[0041] The present invention is described above by way of example in conjunction with the accompanying drawings. This specific embodiment is merely an explanation of the present application, but the present invention is not limited by the above embodiment. As long as various non-substantial improvements are made using the method concept and technical solution of the present invention; or the above concept and technical solution of the present invention are directly applied to other occasions without improvement, they are all within the scope of protection of the present invention.

Claims

1. A method for treating algae based on far ultraviolet light irradiation, characterized in that: The algae-containing raw water to be treated is irradiated with far ultraviolet light having a wavelength of 200 nm to 230 nm.

2. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: The wavelength of far-UVC is 222 nm.

3. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: The UV intensity of the algae-containing raw water is 0.1 mW·cm -2 ~0.4mW·cm -2 .

4. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: The far-ultraviolet light exposure time is greater than or equal to 5 min.

5. The algae treatment method based on far ultraviolet light irradiation according to claim 4, characterized in that: The far-ultraviolet light irradiation time is 7 min to 45 min.

6. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: The algae in algae-containing water are cyanobacteria.

7. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: The algae cells in the treated raw water are Microcystis aeruginosa cells.

8. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: During the far-UVC light irradiation, the algae-containing raw water was continuously stirred.

9. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: The density of algae cells in algae-containing raw water is 5×10 5 cells / mL~1×10 6 cells / mL.

10. The algae treatment method based on far ultraviolet light irradiation according to claim 1, characterized in that: During the far-ultraviolet light irradiation process, the temperature of the algae-containing raw water was maintained at 25°C.

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