A reactor suitable for Lemna minor suspension culture

Abstract

This utility model discloses a reactor suitable for the suspension culture of *Lysimachia christinae*, relating to the field of aquaculture, aiming to solve the problems of low water utilization and difficulty in algae-water separation in traditional *Lysimachia christinae* cultivation. The reactor includes a sphere, and a conical tube and an air inlet pipe integrally connected to the top and bottom of the sphere, respectively. The bottom of the sphere has a circular plane, and the top has an opening in the center. The conical tube is wider at the top and narrower at the bottom, with the opening at the bottom; its side wall is connected to an outlet pipe, and the inner end of the outlet pipe has an annular protrusion for holding a filter screen. The air inlet pipe is connected to the bottom side wall of the sphere, and its top is higher than the outlet pipe, and is connected to an aeration device. The key dimensions, such as the radius R of the sphere and the diameter D1 of the circular plane, are in the ratio of 6.5:5:6:4:6. This reactor uses aeration to cause the *Lysimachia christinae* to rotate and suspend, improving water utilization and nitrogen and phosphorus absorption efficiency, while simultaneously achieving efficient algae-water separation, making it suitable for aquaculture wastewater purification.

Description

Technical Field

[0001] This utility model relates to aquaculture, specifically to a reactor suitable for the suspension culture of duckweed. Background Technology

[0002] Aquaculture has made significant contributions to food security and economic development. However, modern aquaculture, due to its intensive nature, generates large amounts of wastewater containing high levels of nutrients, organic matter, and other pollutants. Discharging untreated or inadequately treated aquaculture wastewater into natural water bodies leads to environmental degradation, including eutrophication, dissolved oxygen depletion, and loss of biodiversity.

[0003] Using aquatic plants to purify aquaculture wastewater is environmentally friendly. Firstly, aquatic plants absorb carbon dioxide through photosynthesis using their chloroplasts, synthesizing organic matter and releasing oxygen. This process not only produces nutrients like starch for the plants themselves but also provides abundant oxygen to the water. Secondly, aquatic plants can directly absorb nutrients like nitrogen and phosphorus from the water and sediment through their leaves, roots, and other tissues, reducing the concentration of nitrogen and phosphorus in the water, and their resource consumption is lower than that of physical and chemical treatment methods. While constructed wetlands have advantages such as low cost, low energy consumption, and ecological benefits, they require a large area and rely on natural purification processes (such as microbial decomposition and plant absorption), requiring a large surface area to ensure sufficient wastewater retention and treatment. They are generally suitable for rural or suburban areas with abundant land resources, and their application in cities is limited. Especially in economically developed areas, land costs may offset their low construction cost advantage. Compared to constructed wetlands, microalgae reactors have advantages such as high space efficiency and fast treatment speed. However, its disadvantage is that the microalgae have small particle size and low concentration, which makes algae-water separation difficult and increases the need for further resource utilization of biomass produced during wastewater purification.

[0004] Duckweed (Wolffia arrhiza) is a perennial floating plant belonging to the Araceae family and the Wolffia genus. It is also known as rootless duckweed, gourd-shaped duckweed, and grain duckweed. Its thallus is ovoid-hemispherical, green and flat on the upper surface with stomata, and convex and pale green on the lower surface. The epidermal cells are pentagonal to hexagonal, and it lacks veins and roots. Duckweed is as small as sand (commonly 500-1500 micrometers in diameter). As an aquatic floating plant, it is the smallest seed plant in the world, with a size and particle size between common aquatic plants and microalgae (commonly 5-10 micrometers in diameter). It has good water treatment effects and can be easily separated from treated wastewater to obtain high-value-added products, such as biodiesel (oil) for energy utilization and feed (starch, protein) for animal feed utilization.

[0005] However, duckweed typically grows and floats on the water surface, leading a floating lifestyle and resulting in low water utilization. If large-scale wastewater purification is required, a significant water surface area is still needed to support the duckweed. This invention has discovered that aeration or mechanical agitation of the water flow can suspend the duckweed in the water, allowing it to continue growing and reproducing normally, purifying and absorbing nitrogen and phosphorus nutrients from the water. Utility Model Content

[0006] This invention aims to solve at least one of the technical problems existing in the prior art or related technologies. This invention uses a duckweed reactor instead of a microalgae reactor, which reduces the footprint while solving the problem of difficult algae-water separation; it uses water flow to suspend the duckweed in the water, increasing the utilization rate of water per unit area; and it enhances the growth of duckweed and the purification capacity of aquaculture wastewater through suspended growth.

[0007] This utility model is achieved through the following technical solution:

[0008] A reactor suitable for suspension culture of duckweed.

[0009] The reactor is equipped with a sphere and a conical tube and an air inlet pipe integrally connected to the top and bottom of the sphere, respectively;

[0010] The sphere has a circular flat surface at its bottom and an opening in the center of its top.

[0011] The tapered tube is wider at the top and narrower at the bottom, with the bottom connected to the opening. A water outlet pipe is connected to the side wall of the tapered tube. One end of the water outlet pipe extends into the inside of the tapered tube and has an annular protrusion protruding from the inner wall of the tapered tube. The annular protrusion is used for the detachable installation of the filter screen.

[0012] An air inlet pipe is connected to the bottom side wall of the sphere, and the top of the air inlet pipe is higher than the water outlet pipe and connected to the aeration device.

[0013] The ratio of the sphere radius R, the circular plane diameter D1, the top opening diameter D2 of the conical tube, the bottom opening diameter D3 of the conical tube, and the height H of the conical tube satisfies: R:D1:D2:D3:H=6.5:5:6:4:6.

[0014] Furthermore, the sphere, conical tube, and air intake pipe are integrally molded from glass or transparent plastic.

[0015] Furthermore, the air intake pipe is an L-shaped pipe, with the horizontal pipe of the L-shaped pipe connected to one side wall of the bottom of the sphere, and the vertical pipe extending vertically upward. The top of the vertical pipe is equipped with a cone-shaped nozzle that is narrow at the top and wide at the bottom, which is connected to the aeration device.

[0016] The middle side wall of the sphere is fixedly connected to the vertical tube by a connecting rod.

[0017] Furthermore, the air inlet pipe and water outlet pipe are located on opposite sides of the sphere.

[0018] Furthermore, the radius R of the sphere is 6.5 cm, and the diameter D1 of the circular plane is 5 cm.

[0019] The top opening, bottom opening, and height of the tapered tube are 6cm, 4cm, and 6cm, respectively.

[0020] The inner diameter of the water outlet pipe is 1-3cm;

[0021] The inner diameter of the air intake pipe is 0.5-2cm.

[0022] Furthermore, the effective volume of the sphere is 0.2-50L, and can be further enlarged under appropriate conditions;

[0023] The outer wall of the sphere is provided with volume scale lines.

[0024] Furthermore, the filter screen is made of 80-100 mesh silk.

[0025] The advantages of this utility model are:

[0026] 1) The bottom of the sphere has a circular plane, which avoids the dead water area at the bottom of the traditional reactor, and ensures that the rotating water flow generated by aeration is evenly distributed in the entire sphere, promoting the suspended growth of duckweed in the whole water body and improving the utilization rate of water per unit volume.

[0027] 2) The bottom of the conical tube is connected to the opening of the sphere to form a gradual flow channel, which guides the purified water to flow from the top to the bottom, preventing duckweed from being discharged directly with the water; the side wall is connected to the water outlet pipe, and the end of the pipe extends into the interior and is provided with an annular protrusion protruding from the inner wall, which facilitates the detachable installation of an 80-100 mesh silk screen to achieve efficient duckweed-water separation and obtain purified wastewater at the same time.

[0028] 3) The air inlet pipe adopts an L-shaped design. The horizontal part of the L-shaped pipe is connected to the bottom side wall of the sphere, and the top part is higher than the water outlet pipe and connected to the aeration device. The L-shaped design achieves single-sided bottom aeration, generating a directional rotating water flow, which makes the duckweed evenly suspended rather than sinking or floating, thus improving the nitrogen and phosphorus absorption efficiency. The L-shaped vertical pipe is fixed to the middle side wall of the sphere by a connecting rod to prevent the air inlet pipe from breaking.

[0029] 4) The air inlet pipe and water outlet pipe are located on both sides of the sphere to avoid air bubbles interfering with the water outlet path and to ensure that aeration does not affect the separation process;

[0030] 5) Precise proportions ensure fluid matching between the sphere and the conical tube. The sphere provides suspension space, and the conical tube enhances separation, realizing a closed loop of water flow from bottom air intake → rotation and suspension inside the sphere → water outlet at the top, maximizing the exposure of duckweed to light and nutrients. Attached Figure Description

[0031] To more clearly illustrate the technical solutions in the embodiments of this utility model, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a structural diagram of a reactor suitable for suspension culture of duckweed according to the present invention;

[0033] Figure 2 This is a schematic diagram of the cylindrical flask structure used in Example 2. Detailed Implementation

[0034] In the following description, numerous specific details are set forth in order to provide a more thorough understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be practiced without one or more of these details. In other instances, certain technical features well-known in the art have not been described in order to avoid confusion with the present invention.

[0035] To fully understand this utility model, detailed steps and structures will be presented in the following description to illustrate the technical solution of this utility model. Preferred embodiments of this utility model are described in detail below; however, in addition to these detailed descriptions, this utility model may have other embodiments.

[0036] Reference Figure 1 As shown, this utility model provides a reactor suitable for suspension culture of duckweed. The reactor is provided with a sphere 1 and a conical tube 4 and an air inlet pipe 7 integrally connected to the top and bottom of the sphere 1, respectively.

[0037] In an optional embodiment, the effective volume of the sphere 1 is 0.2-50L; volume scale lines are provided on the outer wall of the sphere 1. The bottom of the sphere 1 is provided with a circular plane 2, and the top of the sphere 1 is provided with an opening 3 in the center.

[0038] The conical tube 4 is wider at the top and narrower at the bottom, with its bottom connected to an opening. A water outlet pipe 5 is connected to the side wall of the conical tube 4. One end of the water outlet pipe 5 extends into the conical tube 4 and has an annular protrusion 6 protruding from the inner wall of the conical tube 4. The annular protrusion 6 is used for the detachable installation of a filter screen to prevent duckweed from flowing out with the water, thus achieving duckweed-water separation. Preferably, the filter screen is made of 80-100 mesh silk, with an annular elastic band sewn onto it. The elastic band holds the silk screen onto the annular protrusion 6.

[0039] An air inlet pipe 7 is connected to the bottom side wall of the sphere 1. The top of the air inlet pipe 7 is higher than the water outlet pipe 5 and is connected to an aeration device (not shown in the figure). The air inlet pipe 7 and the water outlet pipe 5 are located on opposite sides of the sphere 1 to prevent air bubbles from interfering with the water outlet path and to ensure that aeration does not affect the separation process.

[0040] The ratio of the radius R of sphere 1, the diameter D1 of circular plane 2, the diameter D2 of the top opening of conical tube 4, the diameter D3 of the bottom opening of conical tube 4, and the height H of conical tube 4 satisfies: R:D1:D2:D3:H = 6.5:5:6:4:6. Preferably, the radius R of sphere 1 is 6.5cm, and the diameter D1 of circular plane 2 is 5cm. The top opening, bottom opening, and height of conical tube 4 are 6cm, 4cm, and 6cm, respectively. The inner diameter of water outlet pipe 5 is 1-3cm. The inner diameter of air inlet pipe 7 is 0.5-2cm.

[0041] In an optional embodiment, the sphere 1, the conical tube 4, and the air inlet pipe 7 are integrally molded from glass or transparent plastic. This integral molding can stably maintain the aeration pressure, ensure uniform diffusion of bubbles to suspend the duckweed, and prevent leakage of aquaculture wastewater, thus ensuring the airtightness of the cultivation environment and operational safety. The glass or transparent plastic allows for direct observation of the duckweed suspension state (such as density and growth morphology) and water quality changes (such as turbidity and pollutant sedimentation) within the sphere. Aeration intensity and light parameters can be adjusted in real time without disassembling the reactor, reducing operational complexity and facilitating experimental monitoring and production control.

[0042] In an optional embodiment, the air inlet pipe 7 is an L-shaped pipe. The horizontal pipe 71 of the L-shaped pipe is connected to one side wall of the bottom of the sphere 1, and the vertical pipe 72 extends vertically upward. The top of the vertical pipe 72 is provided with a tapered nozzle 74 that is narrower at the top and wider at the bottom, which is connected to the aeration device. The middle side wall of the sphere 1 and the vertical pipe 72 are fixedly connected by a connecting rod 73 to prevent the air inlet pipe 7 from breaking. The water flow is rotated by aeration at one bottom, causing the duckweed to grow in suspension. Preferably, the water flow rotation speed is adjusted to 6-12 cm / s by controlling the aeration volume of the air inlet pipe.

[0043] In use, this invention involves adding a growth regulator into the reactor to improve the adaptability of aquaculture wastewater to duckweed.

[0044] The growth regulator is prepared according to the following composition and ratio: each 1000 mL (aqueous solution) of the growth regulator contains 98.4 mg of magnesium sulfate heptahydrate, 217.2 mg of calcium nitrate tetrahydrate, 52 mg of potassium dihydrogen phosphate, 0.75 mg of boric acid, 0.86 mg of manganese chloride tetrahydrate, 0.15 mg of zinc sulfate heptahydrate, 0.05 mg of sodium molybdate dihydrate, 0.05 mg of copper sulfate pentahydrate, 6.05 mg of ferrous sulfate heptahydrate, and 15.00 mg of disodium ethylenediaminetetraacetate.

[0045] The initial density of *Lysimachia christinae* inoculated into the reactor is 2-8 g / L. A full-spectrum light source is preferably used to provide illumination for both the *Lysimachia christinae* and the reactor, with a light intensity of 6000-10000 lux; the darkness period is 0-6 hours and the light period is 18-24 hours within a 24-hour period.

[0046] Harvest duckweed to obtain purified aquaculture wastewater. After 12-120 hours of cultivation and purification, when the density of duckweed in the suspended growth reactor reaches above 16 g / L, discharge the suspended growth mixture from the reactor outlet by adding new aquaculture wastewater or by direct discharge. Filter the duckweed through an 80-100 mesh screen to obtain purified aquaculture wastewater, reducing the density of duckweed in the reactor to below 8 g / L, and begin the next cycle of duckweed cultivation and wastewater purification.

[0047] Example 1

[0048] Four 1.1L suspended growth reactors for *Dendrobium nobile* were used. The reactors were made of glass and consisted of a sphere and a frustum at the top. The ratio of the sphere's radius, bottom diameter, top diameter of the frustum, bottom diameter of the frustum, and height was 6.5:5:6:4:6. An air inlet pipe with an opening at the bottom on one side of the sphere and an inner diameter of 0.5cm was included. An outlet with an inner diameter of 1cm was located at the top of the frustum. See the attached diagram for a detailed dimensional example of the *Dendrobium nobile* suspended growth reactor. Figure 1 .

[0049] Add 1.1 L of modified Hoagland medium and 2 mL of growth regulator to each *Pleurotus ostreatus* suspension growth reactor. The growth regulator is prepared according to the following composition and ratio: per 1000 mL (aqueous solution) of growth regulator, there are 98.4 mg of magnesium sulfate heptahydrate, 217.2 mg of calcium nitrate tetrahydrate, 52 mg of potassium dihydrogen phosphate, 0.75 mg of boric acid, 0.86 mg of manganese chloride tetrahydrate, 0.15 mg of zinc sulfate heptahydrate, 0.05 mg of sodium molybdate dihydrate, 0.05 mg of copper sulfate pentahydrate, 6.05 mg of ferrous sulfate heptahydrate, and 15.00 mg of disodium ethylenediaminetetraacetate.

[0050] Each reactor was initially inoculated with 4 g / L of *Alopecurus aequalis*, illuminated by full-spectrum lamps at an intensity of 8000 lx, with a photoperiod of 12 L:12 D. During operation, continuous aeration was achieved via an air inlet connected to an air pump, and the water flow rate was controlled at 8 cm / s using an air valve. Every 3 days, a water change was performed, and water samples were taken for water quality testing (ammonia nitrogen and phosphate). After weighing the fresh weight of the *Alopecurus aequalis*, 4 g / L of *Alopecurus aequalis* was inoculated back into the *Alopecurus aequalis* growth reactor.

[0051] Comparative Example 1

[0052] Four cylindrical beakers (6.5 cm radius, 15 cm height, with a water surface area equal to the maximum circular cross-sectional area of ​​the reactor in Example 1) with a working volume of 1.1 L were used. The beakers were made of glass, and a specific dimension example is shown in the figure. Figure 2 .

[0053] Add 1.1 L of Hoagland medium and 2 mL of growth regulator to each cylindrical beaker. The growth regulator is prepared according to the following composition and ratio: per 1000 mL (aqueous solution) of growth regulator, there are 98.4 mg of magnesium sulfate heptahydrate, 217.2 mg of calcium nitrate tetrahydrate, 52 mg of potassium dihydrogen phosphate, 0.75 mg of boric acid, 0.86 mg of manganese chloride tetrahydrate, 0.15 mg of zinc sulfate heptahydrate, 0.05 mg of sodium molybdate dihydrate, 0.05 mg of copper sulfate pentahydrate, 6.05 mg of ferrous sulfate heptahydrate, and 15.00 mg of disodium EDTA.

[0054] Each cylindrical beaker was initially inoculated with 4 g / L of duckweed and illuminated by a full-spectrum lamp at an intensity of 8000 lx, with a light cycle of 12 L:12 D. Every 3 days, the water was changed and water samples were taken for water quality testing (ammonia nitrogen and phosphate). After weighing the fresh weight of the duckweed, it was inoculated back into the duckweed growth reactor with 4 g / L of duckweed.

[0055] As a result, in all cultivation and purification cycles, the suspended growth of *Lysimachia christinae* (Example 1) showed a high removal rate of ammonia nitrogen, exceeding 90%. However, the suspended growth of *Lysimachia christinae* (Example 1) showed a higher removal rate of phosphate than the floating growth of *Lysimachia christinae* (Comparative Example 1), exceeding 80%, and the former also had a higher biomass growth rate than the latter.

[0056] Table 1-1 Water purification capacity of *Lysimachia christinae* under suspension growth in Example 1 (nutrient solution conditions)

[0057]

[0058]

[0059] Table 1-2 Biomass growth of *Lysimachia christinae* under suspension growth in Example 1 (nutrient solution conditions)

[0060]

[0061] Table 1-3 shows the water purification capacity of floating duckweed in Comparative Example 1 (under nutrient solution conditions).

[0062]

[0063]

[0064] Table 1-4 Biomass growth of floating duckweed in Comparative Example 1 (under nutrient solution conditions)

[0065]

[0066] Example 2

[0067] Four 1.1L suspended growth reactors for *Dendrobium nobile* were used. The reactors were made of glass and consisted of a sphere and a frustum at the top. The ratio of the sphere's radius, bottom diameter, top diameter of the frustum, bottom diameter of the frustum, and height was 6.5:5:6:4:6. An air inlet pipe with an opening at the bottom on one side of the sphere and an inner diameter of 0.5cm was included. An outlet with an inner diameter of 1cm was located at the top of the frustum. See the attached diagram for a detailed dimensional example of the *Dendrobium nobile* suspended growth reactor. Figure 1 .

[0068] Add 1.1L of aquaculture wastewater (wastewater from tilapia farming) and 20mL of growth regulator to each *Pterocarya stenoptera* suspension growth reactor. The growth regulator is prepared according to the following composition and ratio: per 1000mL (aqueous solution) of growth regulator, there are 98.4mg of magnesium sulfate heptahydrate, 217.2mg of calcium nitrate tetrahydrate, 52mg of potassium dihydrogen phosphate, 0.75mg of boric acid, 0.86mg of manganese chloride tetrahydrate, 0.15mg of zinc sulfate heptahydrate, 0.05mg of sodium molybdate dihydrate, 0.05mg of copper sulfate pentahydrate, 6.05mg of ferrous sulfate heptahydrate, and 15.00mg of disodium ethylenediaminetetraacetate.

[0069] Each reactor was initially inoculated with 6 g / L of *Alopecurus aequalis*, illuminated by full-spectrum lamps at an intensity of 8000 lx, with a photoperiod of 12 L:12 D. During operation, continuous aeration was achieved via an air inlet connected to an air pump, and the water flow rate was controlled at 12 cm / s using an air valve. Every 3 days, a water cycle was performed, with water samples taken for water quality testing (ammonia nitrogen and phosphate). After weighing the fresh weight of the *Alopecurus aequalis*, 6 g / L of *Alopecurus aequalis* was inoculated back into the *Alopecurus aequalis* growth reactor.

[0070] Comparative Example 2

[0071] Four cylindrical beakers (6.5 cm radius, 15 cm height, with a water surface area equal to the maximum circular cross-sectional area of ​​the reactor in Example 1) with a working volume of 1.1 L were used. The beakers were made of glass, and a specific dimension example is shown in the figure. Figure 2 .

[0072] Add 1.1L of aquaculture wastewater (wastewater from tilapia farming) and 20mL of growth regulator to each cylindrical beaker. The growth regulator is prepared according to the following composition and ratio: per 1000mL (aqueous solution) of growth regulator, there are 98.4mg of magnesium sulfate heptahydrate, 217.2mg of calcium nitrate tetrahydrate, 52mg of potassium dihydrogen phosphate, 0.75mg of boric acid, 0.86mg of manganese chloride tetrahydrate, 0.15mg of zinc sulfate heptahydrate, 0.05mg of sodium molybdate dihydrate, 0.05mg of copper sulfate pentahydrate, 6.05mg of ferrous sulfate heptahydrate, and 15.00mg of disodium EDTA.

[0073] Each cylindrical beaker was initially inoculated with 4 g / L of duckweed and illuminated by a full-spectrum lamp at an intensity of 8000 lx, with a light cycle of 12 L:12 D. Every 3 days, the water was changed and water samples were taken for water quality testing (ammonia nitrogen and phosphate). After weighing the fresh weight of the duckweed, it was inoculated back into the duckweed growth reactor with 4 g / L of duckweed.

[0074] As a result, in all cultivation and purification cycles, the suspension growth of *Lysimachia christinae* (Example 2) showed a high removal rate of ammonia nitrogen, reaching over 89%. However, the removal rate of phosphate by suspension growth of *Lysimachia christinae* (Example 2) was higher than that by floating growth of *Lysimachia christinae* (Comparative Example 2).

[0075] Table 2-1 Water purification capacity of floating duckweed in Example 2 (under aquaculture wastewater conditions)

[0076] Table 2-2 Biomass growth of suspended *Lysimachia christinae* in Example 2 (under aquaculture wastewater conditions)

[0077]

[0078] Table 2-3 shows the water purification capacity of floating duckweed in Comparative Example 2 (under aquaculture wastewater conditions).

[0079] Table 2-4 Biomass growth of floating duckweed in Comparative Example 2 (under aquaculture wastewater conditions)

[0080]

[0081]

[0082] Example 3

[0083] Twenty suspended growth reactors of *Lysimachia christinae* were used. Referring to Example 1, the reactor dimensions were scaled up to a working volume of 30L. The 20 reactors were divided into 5 groups (4 replicates per group). Each group was initially fed with *Lysimachia christinae* at concentrations of 0.5, 1, 2, 4, and 8 g / L, respectively. Each group was designated as "Suspension 0.5" group, "Suspension 1" group, "Suspension 2" group, "Suspension 4" group, and "Suspension 8" group.

[0084] Each reactor was supplemented with 30L of aquaculture wastewater (wastewater from tilapia farming) and 600mL of growth regulator. Cultivation conditions were controlled as follows: 6000Lx light intensity, 12L:12D photoperiod, and 25℃. During operation, continuous aeration was achieved via an air inlet connected to an air pump, with the water flow rate controlled at 6cm / s using an air valve. The cultivation and purification period was 7 days, with no water changes during this time. Water samples were taken every 12 hours for water quality testing (ammonia nitrogen and phosphate). At the end of the experimental period, the fresh weight of the duckweed was measured. The results are shown in the table below.

[0085] Table 3-1 Water purification capacity of *Duckweed* at different initial inoculation amounts in Example 3

[0086]

[0087] Table 3-2 Biomass growth of *Lysimachia christinae* at different initial inoculation amounts in Example 3

[0088]

[0089]

[0090] Example 4

[0091] Twenty suspended growth reactors of *Lysimachia christinae* were used, and the reactor dimensions were scaled down according to Example 1 to achieve a working volume of 30L. The 20 reactors were divided into 5 groups (4 replicates per group). The water flow rotation speed (maximum water flow speed close to the flask wall) of each group was controlled to be 4, 6, 8, 12, and 16 cm / s, respectively. Each group was designated as "Flow Rate 4 Group", "Flow Rate 6 Group", "Flow Rate 8 Group", "Flow Rate 12 Group", and "Flow Rate 16 Group".

[0092] Each reactor was supplemented with 30 L of aquaculture wastewater (wastewater from tilapia farming) and 600 mL of growth regulator, initially inoculated with 2 g / L of *Lemna minor*. The cultivation conditions were controlled as follows: 10000 Lx light, 6 hours of darkness and 18 hours of light within a 24-hour period; temperature 25℃. The cultivation and purification period was 7 days, with no water changes during this time. Water samples were taken every 12 hours for water quality index testing (ammonia nitrogen and phosphate). At the end of the experimental period, the fresh weight of the *Lemna minor* was measured. The results are shown in the table below.

[0093] Table 4-1 Water purification capacity of *Duckweed* at different water flow velocities in Example 4

[0094]

[0095] Table 4-2 Growth of *Lysimachia christinae* biomass under different water flow velocities in Example 4

[0096]

[0097]

[0098] The preferred embodiments of this utility model have been described above. It should be understood that this utility model is not limited to the specific embodiments described above. Devices and structures not described in detail herein should be understood as being implemented in a conventional manner within the art. Any person skilled in the art can make many possible variations and modifications to the technical solutions of this utility model using the disclosed methods and techniques, or modify them into equivalent embodiments with equivalent changes, without departing from the scope of the technical solution of this utility model. This does not affect the essential content of this utility model. Therefore, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of this utility model, without departing from the content of the technical solution of this utility model, still fall within the protection scope of the technical solution of this utility model.

Claims

1. A reactor suitable for suspension culture of *Lysimachia christinae*, characterized in that: The reactor is equipped with a sphere and a conical tube and an air inlet pipe integrally connected to the top and bottom of the sphere, respectively; The sphere has a circular flat surface at its bottom and an opening in the center of its top. The tapered tube is wider at the top and narrower at the bottom, with the bottom connected to the opening. A water outlet pipe is connected to the side wall of the tapered tube. One end of the water outlet pipe extends into the inside of the tapered tube and has an annular protrusion protruding from the inner wall of the tapered tube. The annular protrusion is used for the detachable installation of the filter screen. An air inlet pipe is connected to the bottom side wall of the sphere, and the top of the air inlet pipe is higher than the water outlet pipe and connected to the aeration device. The ratio of the sphere radius R, the circular plane diameter D1, the top opening diameter D2 of the conical tube, the bottom opening diameter D3 of the conical tube, and the height H of the conical tube satisfies: R:D1:D2:D3:H=6.5:5:6:4:

6.

2. The reactor according to claim 1, characterized in that: The sphere, conical tube, and air intake pipe are made of glass or transparent plastic in one piece.

3. The reactor according to claim 1, characterized in that: The air inlet pipe is an L-shaped pipe. The horizontal tube of the L-shaped pipe is connected to the side wall of the bottom of the sphere, and the vertical tube extends vertically upward. The top of the vertical tube is equipped with a cone-shaped nozzle that is narrow at the top and wide at the bottom, which is connected to the aeration device. The middle side wall of the sphere is fixedly connected to the vertical tube by a connecting rod.

4. The reactor according to claim 3, characterized in that: The air inlet pipe and water outlet pipe are located on both sides of the sphere.

5. The reactor according to claim 1, characterized in that: The radius R of the sphere is 6.5cm, and the diameter D1 of the circular plane is 5cm. The top opening, bottom opening, and height of the tapered tube are 6cm, 4cm, and 6cm, respectively. The inner diameter of the water outlet pipe is 1-3cm; The inner diameter of the air intake pipe is 0.5-2cm.

6. The reactor according to claim 1, characterized in that: The effective volume of the sphere is 0.2-50L; The outer wall of the sphere is provided with volume scale lines.

7. The reactor according to claim 1, characterized in that: The filter screen is made of 80-100 mesh silk.

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