Method and device for in-situ salvage of blue-green algae and separation of algae and water

Abstract

The invention discloses a method and device for in-situ blue-green algae salvage and algae-water separation, and belongs to the technical field of blue-green algae salvage. The device designed by the invention can efficiently intercept blue-green algae and take the blue-green algae out of the water surface, and meanwhile, the algae filtering belt can also perform gravity dehydration to prevent the blue-green algae from being remained on the algae filtering belt due to the acting force of the blue-green algae and water to reduce the algae removal efficiency. Moreover, the device prolongs the time of separating the blue-green algae from the water body by controlling the speed of the algae filtering belt, and further dehydrates and dries the blue-green algae by means of environmental factors such as sunlight, wind power and high temperature to form an algae paste layer which is easier to strip, so that the removal rate of the blue-green algae is improved. By adopting the method and the device, a filter pressing process is not needed, secondary pollution caused by blue-green algae rupture and intracellular substance release cannot be caused, manual work can be reduced to the maximum extent, and the fishing speed and efficiency can be adjusted according to site conditions.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of cyanobacteria salvage, and relates to a method and device for salvaging cyanobacteria in situ and separating algae from water. BACKGROUND

[0002] Since the 20th century, with the development of human society, a large amount of nitrogen and phosphorus nutrients have entered natural water bodies, leading to water eutrophication and triggering cyanobacterial blooms. Superimposed with the influence of climate warming, cyanobacterial blooms exist widely in freshwater lakes around the world, with significantly increased outbreak intensity and frequency. The outbreak of cyanobacterial blooms greatly changes the lake ecosystem, and through the destruction of water habitats during the growth and decline of cyanobacterial blooms, it leads to a decrease in biodiversity and a decrease in the stability of the ecosystem, and many other problems; at the same time, cyanobacterial blooms also pose a great challenge to human production and life, and the cyanotoxins produced by cyanobacteria threaten human health, and the outbreak of cyanobacterial blooms pollutes water bodies and seriously affects human water safety.

[0003] Cyanobacteria have a small cell density and are often suspended in water, making it difficult to harvest cyanobacteria. The use of traditional flocculation sedimentation, centrifugal separation, filtration, air flotation and other harvesting methods to remove cyanobacteria usually consumes a lot of time and effort, and the removal efficiency is also low. For example, in the salvage method using a rotating filter algae belt system, the filter algae belt is always wet, and cyanobacteria are more likely to remain on the filter algae belt. When the filter algae belt re-contacts the water surface, cyanobacteria are released back into the water, resulting in a decrease in cyanobacterial removal efficiency. Similar problems exist in patents CN222715940U (a device for automatically salvaging river surface cyanobacteria), CN203975162U (a device ship for removing lake cyanobacteria) and CN202323910U (a water surface cyanobacterial cleaning device).

[0004] Harvesting cyanobacteria on the filter algae belt by scraping is a method to improve cyanobacterial removal efficiency and can be used to solve the problem of cyanobacterial collection difficulty. For example, the scraper design mentioned in patent CN120132432A (a fixed cyanobacterial bloom collector), but the patent still lacks an overall design of the scraper and the filter algae belt, so there may be a general scraping effect and the cyanobacteria cannot be completely stripped. In addition, if not careful during scraping, the cyanobacterial cells may be broken, causing the release of intracellular toxins (cyanotoxins), which may have unexpected negative effects. SUMMARY

[0005] TECHNICAL PROBLEM

[0006] Conventional cyanobacterial removal methods (flocculation sedimentation, centrifugal separation, filtration) have the problems of time and effort consumption, low removal efficiency and intracellular toxin release, so a simple, convenient, time and labor saving method that does not cause cyanobacterial cell breakage is needed.

[0007] Technical solutions

[0008] In view of the above technical problems, the present application aims to provide a device for salvaging and separating algae from water in situ. The device can be installed at the algae gathering point in a lake or other water body, and can efficiently and automatically separate the blue algae from the water continuously. The device does not require a filter pressing process, and thus will not cause the rupture of blue algae and the release of intracellular substances. The device can minimize manual labor, and the salvaging speed and efficiency can be adjusted according to the on-site conditions.

[0009] To achieve the above-mentioned purpose, the present application provides the following technical solutions:

[0010] The first aspect of the present application is to provide a device for separating blue algae from water in situ, which comprises an upper roller 1, a lower roller 2, an algae filter belt 3, a scraper 4, an algae collection tank 5, and a driving motor 6.

[0011] As an embodiment of the present application, the upper roller 1 is a driving cylinder fixedly installed on land, and the lower roller 2 is a driven cylinder fixedly installed below the water surface at a certain distance from the land. The algae filter belt 3 is wound around the upper roller 1 and the lower roller 2, and the lower middle part of the algae filter belt 3 is immersed in the water body, and the other part is above the water surface. The scraper 4 is fixedly installed below the side of the upper roller 1, and one end is fixed and the other end is pressed on the algae filter belt 3 through a spring piece. The algae collection tank 5 is fixedly connected below the scraper 4. The driving motor 6 is connected with the upper roller 1 through a belt or a chain and drives the upper roller 1 to rotate.

[0012] As an embodiment of the present application, the algae filter belt 3 is a strip that can permeate water but can intercept microalgae. The material has a microporous structure with a pore size of 20-100 μm, which can be made of one or several materials such as polyester (polyester), polypropylene, polyamide (nylon), aramid, and stainless steel wire, and the moisture absorption rate is 0.5-15%.

[0013] As an embodiment of the present application, the length of the algae filter belt is 5-45 m, and the width is 1.5-8 m. The inclination angle β after installation is 5-30°.

[0014] As an embodiment of the present application, the material of the scraper 4 can be one of stainless steel, MnV alloy steel, steel-plastic composite material, polyurethane rubber, ultra-high molecular weight polyethylene, nylon, and polyformaldehyde (POM). The inclination angle α of the scraper 4 is 120-175°.

[0015] As an embodiment of the present application, the driving motor 6 can change the speed, and thus the speed of algae-water separation can be changed according to the algae gathering condition.

[0016] As an embodiment of the present application, the spring sheet is pressed against the algae filter belt 3 with a pressure of 2-15 N.

[0017] The second aspect of the present application provides a method for in-situ cyanobacteria salvage and algae-water separation, which uses the device for in-situ separation of cyanobacteria from water body as described above, and comprises the following steps:

[0018] The device is placed on land, and the lower roller 2 and the algae filter belt 3 are immersed in the water body containing cyanobacteria;

[0019] When salvaging cyanobacteria, the driving motor 6 drives the upper roller 1 to rotate, and with the rotation of the roller, the algae filter belt 3 separates the algae in the water from the water body. In the conveying process, water flows back into the water body from below through the algae filter belt 3, and the algae attached to the top of the algae filter belt 3 are transported to the scraper 4 and scraped off from the algae filter belt 3, and then flow into the algae collection tank 5 along the scraper 4.

[0020] As an embodiment of the present application, the part of the algae filter belt immersed in the water body accounts for 10-65% of the total belt length.

[0021] As an embodiment of the present application, the linear speed of the algae filter belt is 0.01-0.5 m / s.

[0022] The working principle of the device for in-situ separation of cyanobacteria from water body of the present application is as follows:

[0023] The driving motor drives the upper roller fixed to the land to rotate through the transmission mechanism, and then drives the algae filter belt wound between the upper roller and the underwater lower roller to circulate. When the algae filter belt moves at a linear speed of 0.01-0.5 m / s, the middle and lower sections immersed in the water pass through the algae-rich water body, and the microporous structure (pore size 20-100 μm) woven with hydrophobic materials such as polyester and polypropylene traps cyanobacterial groups (particle size > 20 μm), while allowing water to pass through the micropores to flow back to the lake, realizing in-situ primary separation of algae water. The algae attached to the surface of the algae filter belt are transported upward along with the inclined belt body (inclination angle 5-30°), and form an algae paste layer with a moisture content of 80-95% under the action of gravity dehydration and sunlight, wind, and high temperature (generally, the weather environment with strong sunlight and high temperature is the one in which the algae proliferate massively). When the algae paste is transported to the top of the device, the fixed and installed elastic scraper lightly presses the surface of the algae filter belt with a contact angle of 120-175°, and applies a continuous pressure of 2-15 N through the spring sheet, and only breaks the adhesion between the algae paste and the filter belt without damaging the algae cells, so as to strip the intact algae paste layer. The stripped algae paste slides into the algae collection tank along the inclined surface of the scraper, and finally obtains the algae residue with a moisture content of 80-95% and zero release of intracellular toxins. This principle realizes the efficient in-situ separation of cyanobacteria and the immediate purification of the water body through the synergistic mechanism of "trapping-gravity dehydration-elastic stripping", and avoids the risk of cell rupture in the traditional pressure filtration process.

[0024] Compared with the prior art, the present application has the beneficial effects that:

[0025] (1) The design of the filter algae belt material in the present application enables it to efficiently trap cyanobacteria and carry them out of the water surface, and the filter algae belt can also be gravity dewatered to prevent cyanobacteria from remaining on the filter algae belt due to the action of water, thereby reducing the algae removal efficiency.

[0026] (2) The present application prolongs the time for cyanobacteria to separate from the water body by controlling the speed of the filter algae belt, and further uses environmental factors such as sunlight, wind power, and high temperature to cause the cyanobacteria to further dewater and dry, thereby forming an algae paste layer that is more easily peeled off, and improving the removal rate of cyanobacteria.

[0027] (3) The device for separating cyanobacteria from a water body in situ designed in the present application has a simple structure and is easy to operate, and has excellent cyanobacteria removal effect, and at the same time, will not cause the rupture of cyanobacteria cells, avoiding the leakage of intracellular toxins. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 is a schematic diagram of the device for separating cyanobacteria from a water body in situ of the present application; wherein 1 is an upper roller, 2 is a lower roller, 3 is a filter algae belt, 4 is a scraper, 5 is an algae collection tank, and 6 is a driving motor. DETAILED DESCRIPTION

[0029] The present application will be further described below in conjunction with the drawings and examples.

[0030] As shown in Figure 1 , a device for separating cyanobacteria from a water body in situ comprises an upper roller 1, a lower roller 2, a filter algae belt 3, a scraper 4, an algae collection tank 5, and a driving motor 6.

[0031] The upper roller 1 is a driving cylinder fixedly installed on land, and the lower roller 2 is a driven cylinder fixedly installed below the water surface at a certain distance from the land; the filter algae belt 3 is wound around the upper roller 1 and the lower roller 2, the lower middle part of the filter algae belt 3 is immersed in the water body, and the other part is above the water surface; the scraper 4 is fixedly installed below the side of the upper roller 1, one end is fixed, and the other end is lightly pressed on the filter algae belt 3 through a spring piece; the algae collection tank 5 is fixedly connected below the scraper 4; and the driving motor 6 is connected with the upper roller 1 through a belt or a chain and drives the upper roller 1 to rotate.

[0032] The filter algae belt 3 is a strip that can permeate water but can trap microalgae, and its material can be one or several materials such as polyester (polyester), polypropylene, polyamide (nylon), aramid, spandex, etc. hydrophobic material and stainless steel wire, which is made of fiber, and its moisture absorption rate is 0.5-15%.

[0033] The length of the algae filtering belt is 5-45m, the width is 1.5-8m, and the installation inclination angle β is 5-30°.

[0034] The material of the scraper 4 can be one of stainless steel, MnV alloy steel, steel-plastic composite material, polyurethane rubber, ultra-high molecular weight polyethylene, nylon, polyoxymethylene (POM), etc.; the inclination angle α of the scraper 4 is 120-175°.

[0035] The position of the scraper 4 can be adjusted, so that algae of different thicknesses can be scraped.

[0036] The driving motor 6 can change the rotating speed, so that the algae-water separation speed can be changed according to the algae aggregation condition.

[0037] A cyanobacteria salvaging method based on the above device, specifically comprising the following steps:

[0038] The device is placed on land, and the lower roller 2 and part of the algae filtering belt 3 are immersed in the water body containing cyanobacteria, so that the part of the algae filtering belt immersed in the water body accounts for 10-65% of the total belt length;

[0039] Then the driving motor 6 drives the upper roller 1 to rotate, and with the rotation of the roller, the algae filtering belt 3 is driven to separate the algae in the water from the water body at a linear speed of 0.01-0.5m / s. In the conveying process, water flows back into the water body from below through the algae filtering belt 3, the algae attached to the top of the algae filtering belt 3 are transported to the scraper 4, and are scraped off from the algae filtering belt 3, and flow into the algae collection tank 5 along the scraper 4.

[0040] Example 1

[0041] In a simulated water tank with length × width × height = 4m × 1.2m × 1.5m, an artificial algal bloom water body (mainly Microcystis aeruginosa) is configured, and the algae concentration gradient (1×10 5 -5×10 8 cells / mL) is maintained by an aeration system to simulate the natural algal bloom accumulation state.

[0042] The device is scaled down by 1:5. The algae filtering belt is woven with dacron monofilament (pore size 25μm), with a size of 1.8m × 0.4m and an inclination angle β = 10°; the scraper is made of polyoxymethylene (POM) material, with an inclination angle α = 160° and a spring sheet pressure of 2.5N; the driving motor is a miniature stepping motor (adjustable at 0.1-1.2r / min); and the monitoring system uses an online chlorophyll fluorescence probe (accuracy ±0.1μg / L).

[0043] In the algal bloom outbreak stage, high-concentration algae liquid is injected into the water tank, so that the local algae concentration reaches 3.2×10 7cells / mL (Chlorophyll a = 95.6 μg / L), the device was started at 0.8 r / min. The filter belt was submerged 20 cm below the water surface, and the filter belt trapped algae to form a 2.3 mm thick layer of algal sludge, with a water permeability rate maintained at 205 L / (m 2 ·min). The scraper peeled off the algal sludge at a 160° contact angle, and microscopic examination showed that the algal cell rupture rate was only 0.4% (n = 500). The algal sludge collected in the tank had a moisture content of 84.7% (determined by oven drying at 105°C).

[0044] When the algae solution was re-injected after stopping operation (initial concentration 2.5 x 10 7 cells / mL), the device reduced the algae concentration to 12% of the initial value within 120 min, demonstrating its sustained control capability. The extracellular microcystin content of the peeled algal sludge was <0.001 mg / kg (detected by HPLC-MS), which was significantly lower than that of the pressed algal sludge (0.83 mg / kg). The energy consumption per ton of algae was 7.8 kWh, which was only 28% of that of the centrifugal process for the same processing capacity.

[0045] The results showed that the device still maintained a 94% retention rate at an ultra-high algae concentration (>3 x 10 7 cells / mL), overcoming the problem of traditional screen clogging. After scaling down the device, the algal sludge yield per unit filter belt area (1.02 kg dry algae / m 2 ·h) was highly consistent with that of a large-scale engineering device (Example 1: 0.98 kg / m 2 ·h). High-speed camera recordings showed that the elastic scraper caused the algal sludge to be peeled off in continuous sheets (non-fragmented state) with zero leakage of intracellular substances.

[0046] Example 2

[0047] A large-scale blue-green algal bloom occurred in Meiliang Bay in the northern part of Lake Taihu, with a peak algae concentration of 1.8 x 10 8 cells / mL (mainly Microcystis), and an algal bloom coverage area of about 12 km 2 . The device was installed in the near-shore algal bloom accumulation area (water depth 1 m), with the lower roller fixed 50 cm below the water surface. The filter algae belt used an 8 m x 1 m polypropylene-stainless steel composite woven mesh (inclination β = 20°), and the scraper was made of ultra-high molecular weight polyethylene (inclination α = 155°). After starting, the driving motor was dynamically adjusted according to the real-time algae concentration.

[0048] When the algae concentration in the dense algal bloom area was >1.2 x 10 8 cells / mL, the motor was accelerated to 2.2 r / min (filter belt speed 0.2 m / s), and a 1-5 mm thick layer of algal sludge was formed on the surface of the filter belt, with a water permeability rate still maintained at 180 L / (m 2 ·min).

[0049] The elastic scraper peeled off the algae mud with 6N pressure, and the algae cell rupture rate was only 0.7% (microscopic counting method) after detection. The peeled algae mud entered the collection tank along the flow guide groove, and the moisture content was stable at 83-88%.

[0050] After 72 hours of continuous operation, the algae concentration in the water area with a radius of 50m around the device decreased to 2.5×10 6 cells / mL.

[0051] The results show that the salvaging efficiency of the device is 5-8 times higher than that of artificial ships; the combination of hydrophobic filter belt and elastic scraper ensures that the moisture content of the algae mud is ≤90% and the cells are intact, avoiding the release of algae mud toxins (<0.01mg / kg) caused by traditional pressure filtration; after the operation of the device, the algal bloom regeneration rate is reduced by 40-65% (compared with the same period in the unmanaged area), and the in-situ separation mechanism blocks the spread of algae species.

[0052] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Although the present application has been described in detail with reference to the foregoing embodiments, those skilled in the art can modify the technical solutions described in the foregoing embodiments or make equivalent replacements to some technical features. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A device for in-situ separation of cyanobacteria from water, characterized in that: The device comprises an upper drum, a lower drum, an algae filtering belt, a scraper, an algae collecting tank and a driving motor; The upper roller is a driving roller and is fixedly installed on land; The lower drum is a driven drum, which is fixedly installed below the water surface at a certain distance from the land; The algae filter belt is wound around the upper drum and the lower drum, with the middle and lower parts of the algae filter belt immersed in the water body and the other parts above the water surface; The scraper is fixed on the lower side of the upper drum, with one end fixed and the other end pressed on the algae filter belt through a spring sheet; The algae collecting tank is fixedly connected below the scraper; The driving motor is connected to the upper roller via a belt or a chain and drives the upper roller to rotate.

2. The device according to claim 1, characterized in that The algae filter belt is a water-permeable strip that can intercept microalgae; the material of the algae filter belt is made of one or more materials selected from polyester, polypropylene, polyamide, aramid, spandex, and stainless steel wire with a microporous structure with a pore size of 20 to 100 μm; the moisture absorption rate of the material is 0.5 to 15%.

3. The device according to claim 1, characterized in that The length of the algae filtering belt is 5 to 45 meters, and the width is 1.5 to 8 meters; the tilt angle β after installation is 5 to 30 degrees.

4. The device according to claim 1, characterized in that The scraper is made of one of stainless steel, MnV alloy steel, steel-plastic composite material, polyurethane rubber, ultra-high molecular weight polyethylene, nylon, and polyoxymethylene; the inclination angle α of the scraper is 120-175°.

5. A method for in-situ cyanobacteria salvage and algae-water separation, characterized in that: The method uses the device for in-situ separation of cyanobacteria from water according to any one of claims 1 to 4, comprising the following steps: The device is placed on land, and the lower drum and the filter belt are immersed in a body of water containing cyanobacteria; When salvaging blue algae, the driving motor drives the upper drum to rotate. As the drum rotates, it drives the filter belt to separate the algae in the water. During the transportation process, water flows back into the water body from the bottom through the filter belt. The algae attached to the filter belt are transferred to the scraper, scraped off the filter belt, and flow into the algae collection tank along the scraper.

6. The method according to claim 5, characterized in that The portion of the filter algae belt submerged in the water body accounts for 10 to 65% of the total belt length.

7. The method according to claim 5, characterized in that The linear speed of the algae filter belt is 0.01 to 0.5 m / s.

8. The method according to claim 5, characterized in that The spring sheet presses on the algae filter belt with a pressure of 2 to 15N.

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