Immobilized microalgae coupling iron-carbon artificial wetland system

Abstract

The invention relates to the technical field of wastewater treatment, and particularly discloses an immobilized microalgae coupled iron-carbon artificial wetland system which is characterized in that a microalgae bioreactor is connected with an artificial wetland through a second connecting pipeline, and the artificial wetland is connected with a sedimentation tank through a first connecting pipeline; a traditional constructed wetland is converted into an iron-carbon constructed wetland, the mode of heterotrophic denitrification in the traditional constructed wetland depending on an external carbon source is changed into autotrophic denitrification providing electrons through iron carbon, dependence on the external carbon source is greatly eliminated, and an iron-carbon internal electrolysis technology and a constructed wetland technology are organically combined; the denitrification efficiency of the constructed wetland on the sewage with the low C / N ratio can be obviously improved. The denitrification efficiency of the iron-carbon constructed wetland is improved by 20-30% compared with that of a common constructed wetland, the denitrification efficiency of the system can be further improved by adding microalgae into the system, and the method for treating the aquaculture tail water through the iron-carbon constructed wetland and the method for treating the aquaculture tail water through the microalgae are coupled; and a novel microalgae type iron-carbon constructed wetland is constructed.

Description

Technical Field

[0001] The invention relates to the technical field of wastewater treatment, in particular to an immobilized microalgae coupled iron-carbon artificial wetland system. Background Art

[0002] Constructed wetlands are ecological systems that use the physical, chemical and biological synergistic effects of substrates, plants and microorganisms to achieve sewage treatment. They are a water treatment technology with dual functions of sewage treatment and ecological improvement. They have the advantages of good pollutant removal, simple operation and maintenance, low cost, strong resistance to shock loads and good environmental benefits. They are widely used in various types of sewage treatment. In constructed wetlands, nitrogen removal is mainly achieved through substrate adsorption, plant absorption and microbial transformation. Studies have shown that the role of substrates in the denitrification process of constructed wetlands includes direct adsorption and providing a stable attachment surface for microorganisms to grow and reproduce to form biofilms for conversion and denitrification. The role of plants in the denitrification process of constructed wetlands includes direct absorption of nitrogen during plant growth and its indirect effect of affecting denitrification by changing wetland microorganisms. Although substrates and plants in wetland systems can remove some nitrogen, they do not occupy an important position. Microorganisms play a core role, contributing more than 90% to wetland denitrification. The organic combination of iron-carbon internal electrolysis technology and artificial wetland technology can significantly improve the denitrification efficiency of artificial wetlands for low C / N ratio sewage. There are relatively few studies on the mechanism of denitrification in iron-carbon artificial wetlands. The applicant has previously constructed an iron-carbon artificial wetland and pioneered the use of iron-carbon artificial wetland technology to treat marine aquaculture tailwater. The study found that the denitrification efficiency of iron-carbon artificial wetlands is 20-30% higher than that of wetlands without iron-carbon. The wetland system containing 33% v / v iron-carbon can achieve a relatively high denitrification efficiency, and the average removal rate of total inorganic nitrogen is 63.40±12.11%.

[0003] Artificial wetlands have also begun to be used in aquaculture as a treatment process for aquaculture tailwater, which can effectively reduce nitrogen-containing pollutants in tailwater. However, most of them are concentrated on the treatment of freshwater aquaculture tailwater, and there are relatively few studies on the treatment of marine aquaculture tailwater. The traditional artificial wetland treatment system limits the denitrification efficiency due to the high salinity and low C / N ratio of marine aquaculture tailwater. Salt has an inhibitory effect on the denitrification process. The high salinity (10-30‰) of marine aquaculture tailwater increases the osmotic pressure of the solution. In an environment with high osmotic pressure, the enzyme activity of bacteria is inhibited, and the denitrification efficiency is reduced. The denitrification effect of iron-carbon artificial wetlands on marine aquaculture tailwater needs to be further strengthened, and microalgae require a large amount of nitrogen and phosphorus elements during their growth. Studies have shown that the application of algae can significantly improve the denitrification efficiency of iron-carbon artificial wetlands on marine aquaculture tailwater. However, when microalgae exist alone in artificial wetlands, due to their suspended growth characteristics, it is very easy to cause the loss of microalgae in the system. Existing microalgae all grow in suspension, and the microalgae cannot be evenly distributed in the wastewater treatment equipment, resulting in poor nitrogen removal effect on the wastewater. For this purpose, an immobilized microalgae coupled iron-carbon artificial wetland system is provided. Summary of the invention

[0004] The purpose of the present invention is to provide an immobilized microalgae coupled iron-carbon artificial wetland system to address the defects of the prior art and solve the problems raised by the above-mentioned background technology.

[0005] To achieve the above object, the present invention provides the following technical solution: an immobilized microalgae coupled iron-carbon artificial wetland system, comprising a microalgae bioreactor, an artificial wetland, and a sedimentation tank, wherein the microalgae bioreactor is connected to the artificial wetland through a second connecting pipe, and the artificial wetland is connected to the sedimentation tank through a first connecting pipe;

[0006] The four corners of the top of the microalgae bioreactor are all equipped with hydraulic cylinders, a lifting top plate is installed on the top of the hydraulic cylinder, a plurality of reduction boxes are installed on the top of the lifting top plate, a stainless steel pipe is provided in the middle of the reduction box, a microalgae condensate bead feeding hopper is connected to the top of the stainless steel pipe, a plurality of arc pipes are connected to the bottom of the stainless steel pipe, a plurality of microalgae condensate bead storage cages are connected to the bottom of the arc pipe, a second solenoid valve is installed on the connecting pipe between each microalgae condensate bead storage cage, a bearing is connected to the bottom pipe of the microalgae condensate bead storage cage, a plurality of microalgae supplementary light tubes are installed inside the microalgae bioreactor, and transparent lampshades are installed on the four side walls inside the microalgae bioreactor;

[0007] Each microalgae condensate bead storage cage contains microalgae condensate beads, wherein the microalgae condensate beads are condensate beads containing Chlorella made of sodium alginate;

[0008] A microalgae condensate delivery pipe is installed on the top of the lifting top plate through a support frame, a plurality of feed pipes are arranged at the bottom of the microalgae condensate delivery pipe, a first solenoid valve is installed on the feed pipe, and a solar panel is also installed on the top of the lifting top plate through a support frame.

[0009] As a preferred technical solution of the present invention, a water outlet pipe is connected to the top of one side of the microalgae bioreactor, and a first valve is installed on the water outlet pipe. A second valve is installed on the second connecting pipe connected to the bottom of the other side of the microalgae bioreactor. The first valve and the second valve are used to adjust the flow rate of inlet and outlet water.

[0010] As a preferred technical solution of the present invention, a reduction gearbox is installed at one end of the microalgae condensate bead feeding pipe, a second motor is installed on one side of the reduction gearbox, an auger is connected to the reduction gearbox, and a feeding hopper is provided on the top of the microalgae condensate bead feeding pipe.

[0011] As a preferred technical solution of the present invention, the stainless steel pipe is installed on the reduction box through a bearing, and a gear is installed on the stainless steel pipe and meshes with the gear on the main shaft of the first motor.

[0012] As a preferred technical solution of the present invention, the stainless steel pipe is welded to the arc pipe, the microalgae condensate bead feeding hopper is connected to the arc pipe through the stainless steel pipe, the arc pipe is connected to the microalgae condensate bead storage cage, the microalgae condensate bead storage cage is made of transparent PP material, and a plurality of through holes are evenly arranged on the microalgae condensate bead storage cage.

[0013] As a preferred technical solution of the present invention, a lamp pole is arranged inside the microalgae supplementary light tube, and the lamp pole is a quadrangular prism, and LED modules are installed on the four sides of the lamp pole; an LED light board is installed inside the transparent lampshade.

[0014] As a preferred technical solution of the present invention, a water level sensor and a temperature sensor are installed inside the microalgae bioreactor. The temperature sensor is electrically connected to an electric heating device through a controller. The electric heating device is an electric heating rod.

[0015] As a preferred technical solution of the present invention, the artificial wetland is provided with pebbles, iron carbon and zeolite in sequence from bottom to top, and a central tube is provided in the middle of the artificial wetland, and a plurality of through holes are provided on the central tube.

[0016] As a preferred technical solution of the present invention, a liquid inlet is provided on the top of one side of the sedimentation tank, a filter screen is provided inside the sedimentation tank, a sedimentation tank is provided on one side of the filter screen, and a mud discharge pipe is provided at the bottom of the sedimentation tank.

[0017] Compared with the prior art, the beneficial effects of the present invention are: transforming the traditional artificial wetland into an iron-carbon artificial wetland, changing the heterotrophic denitrification mode in the traditional artificial wetland that relies on external carbon sources to autotrophic denitrification with electrons provided by iron-carbon, greatly getting rid of the dependence on external carbon sources, and organically combining the iron-carbon internal electrolysis technology with the artificial wetland technology, which can significantly improve the denitrification efficiency of artificial wetlands for low C / N ratio sewage. The denitrification efficiency of the iron-carbon artificial wetland has increased by 20-30% compared with ordinary artificial wetlands, and adding microalgae to the system can further improve the denitrification efficiency of the system;

[0018] The present invention utilizes the characteristic of microalgae in efficiently absorbing nitrogen in water, couples the method of treating aquaculture tail water with an iron-carbon artificial wetland and the method of treating aquaculture tail water with microalgae, and constructs a novel microalgae-type iron-carbon artificial wetland.

[0019] The present invention connects an iron-carbon artificial wetland and a microalgae bioreactor together, and wastewater is treated in the iron-carbon artificial wetland and then enters the microalgae bioreactor for treatment. In the microalgae bioreactor, beads containing microalgae are placed in a rotatable storage cage, which can not only prevent the loss of microalgae, but also allow the microalgae to fully contact with the wastewater, thereby increasing the amount of nitrogen absorbed from the water body. In addition, the microalgae bioreactor of the present invention can realize automatic material replacement of the microalgae beads, provide sufficient light for the microalgae beads in the storage cage, and use outdoor solar power generation to supply energy for light, thereby achieving the purpose of energy saving, and allowing the microalgae beads inside the microalgae bioreactor to receive light more evenly, thereby increasing the survival rate of the microalgae and thus improving the nitrogen removal effect. The present invention utilizes sodium alginate to fix microalgae through its gelation characteristics. Sodium alginate is a natural polysaccharide. When it contacts a solution containing divalent cations, ionic crosslinking will occur to form a stable gel network. Microalgae cells are wrapped in this gel network, thereby achieving immobilization. This immobilization method can not only protect microalgae cells from mechanical damage and predator infringement, but also improve cell density, enhance microalgae adsorption and utilization efficiency of nutrients, thereby improving its efficiency in applications such as sewage treatment. In the immobilization process, the higher the concentration of sodium alginate, the denser the gel network formed, and the better the mechanical protection of microalgae cells. The concentration of the crosslinking agent and the crosslinking time are key factors for controlling gel stability and pore structure. These characteristics are crucial for maintaining the metabolic activity of microalgae cells. By optimizing the crosslinking conditions, it can be ensured that the pore structure of the gel can provide enough space for microalgae cells to maintain their activity and promote the effective removal of pollutants. Therefore, appropriate crosslinking agent concentration and crosslinking time will not only not affect the metabolic activity of microalgae cells and the removal efficiency of pollutants, but can enhance these properties, thereby improving the processing capacity of the entire system. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1It is a schematic diagram of the system structure of the present invention;

[0021] Figure 2 It is a schematic diagram of the structure of the microalgae bioreactor of the present invention;

[0022] Figure 3 It is a schematic diagram of the structure of the artificial wetland of the present invention;

[0023] Figure 4 It is a structural schematic diagram of the sedimentation tank of the present invention;

[0024] Figure 5 This is the effect of coupled microalgae on the removal of ammonia nitrogen by iron-carbon constructed wetlands in Experiment 2 of Example 2 of the present invention;

[0025] Figure 6 This is the effect of coupled microalgae on the removal of nitrate and nitrogen by iron-carbon artificial wetlands in Experiment 1 of Example 2 of the present invention;

[0026] Figure 7 This is the effect of coupled microalgae on total nitrogen removal by iron-carbon constructed wetlands in Experiment 3 of Example 2 of the present invention.

[0027] In the figure: 1, microalgae bioreactor; 2, artificial wetland; 3, sedimentation tank; 4, first connecting pipeline; 5, second connecting pipeline; 6, sampling tube;

[0028] 101, hydraulic cylinder; 102, lifting top plate; 103, reduction gearbox; 104, stainless steel pipe; 105, arc pipe; 106, microalgae condensate storage cage; 107, microalgae condensate feed hopper; 108, first motor; 109, microalgae condensate delivery pipe; 110, feed hopper; 111, reduction gearbox; 112, second motor; 113, feed pipe; 114, solar panel; 115, first solenoid valve; 116, auger; 117, bearing; 118, second solenoid valve; 119, microalgae supplementary light tube; 120, electric heating equipment; 121, transparent lampshade; 122, water outlet pipe; 123, first valve; 124, second valve;

[0029] 201, pebbles; 202, iron-carbon; 203, zeolite; 204, central tube;

[0030] 301. Filter screen plate; 302. Liquid inlet; 303. Sedimentation tank; 304. Mud discharge pipe. DETAILED DESCRIPTION

[0031] The preferred embodiments of the present invention are described in detail below in conjunction with the accompanying drawings so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby making a clearer and more definite definition of the protection scope of the present invention.

[0032] Example 1: Please refer to Figure 1-3The present invention provides a technical solution: an immobilized microalgae coupled iron-carbon artificial wetland system, including a microalgae bioreactor 1, an artificial wetland 2, and a sedimentation tank 3. The microalgae bioreactor 1 is connected to the artificial wetland 2 through a second connecting pipe 5, and the artificial wetland 2 is connected to the sedimentation tank 3 through a first connecting pipe 4. The wastewater is first precipitated through the sedimentation tank 3, and then filtered through the filter screen 301 in the sedimentation tank 3 before being sent to the artificial wetland 2 by a pump. The artificial wetland 2 adopts an iron-carbon artificial wetland, which can change the mode of heterotrophic denitrification in traditional artificial wetlands that relies on external carbon sources into autotrophic denitrification that provides electrons through iron-carbon, greatly getting rid of the dependence on external carbon sources, and organically combining the iron-carbon internal electrolysis technology with the artificial wetland technology, which can significantly improve the artificial wetland's ability to resist low-carbon. The C / N ratio of the sewage denitrification efficiency is first treated in the artificial wetland 2 and then transported to the microalgae bioreactor 1 through the second connecting pipe 5. The microalgae condensate storage cage 106 in the microalgae bioreactor 1 rotates, thereby driving the microalgae condensate storage cage 106 to contact the wastewater. The microalgae condensate is a microalgae cell that is wrapped in a gel network to achieve immobilization. The use of condensate can not only protect the microalgae cells from mechanical damage and predator invasion, but also increase cell density and enhance the microalgae's adsorption and utilization efficiency of nutrients. The microalgae condensate storage cage 106 allows the condensate containing microalgae to be set at any position of the microalgae bioreactor 1, so that the condensate is more evenly distributed in the microalgae bioreactor 1, so that the microalgae can absorb nitrogen more efficiently.

[0033] like Figure 2 As shown: hydraulic cylinders 101 are installed at the four corners of the top of the microalgae bioreactor 1, a lifting top plate 102 is installed on the top of the hydraulic cylinder 101, and a plurality of reduction boxes 103 are installed on the top of the lifting top plate 102. A stainless steel pipe 104 is provided in the middle of the reduction box 103. A microalgae condensate feeding hopper 107 is connected to the top of the stainless steel pipe 104, and a plurality of arc pipes 105 are connected to the bottom of the stainless steel pipe 104. A plurality of microalgae condensate storage cages 106 are connected to the bottom of the arc pipe 105. A second solenoid valve 118 is installed on the connecting pipe between each microalgae condensate storage cage 106, and a bearing 117 is connected to the bottom pipe of the microalgae condensate storage cage 106. A plurality of microalgae supplementary light tubes 119 are installed inside the microalgae bioreactor 1, and transparent lampshades 121 are installed on the four side walls inside the microalgae bioreactor 1.

[0034] When it is necessary to automatically change the condensed beads in the microalgae condensed bead storage cage 106, firstly, all the second solenoid valves 118 are turned on by the control switch, and the lifting top plate 102 is lifted up by the hydraulic cylinder, so that the microalgae condensed bead storage cage 106 is raised to a suitable height, so that the pipe at the bottom of the microalgae condensed bead storage cage 106 can be pulled out from the bearing 117. When the microalgae condensed bead storage cage 106 rises, the condensed beads in the microalgae condensed bead storage cage 106 will flow out of the microalgae condensed bead storage cage 106 under the gravity of the water. When all the condensed beads in the microalgae condensed bead storage cage 106 are discharged, the second solenoid valve 118 on the bottom pipe of the bottom microalgae condensed bead storage cage 106 is closed, and the condensed beads containing microalgae and water are put into the feed hopper 110. By connecting the power of the first solenoid valve 115 and the second motor 112, the first solenoid valve 115 is opened, and the second motor 112 drives the gear in the reduction box 111 to rotate, thereby driving the auger 116 to rotate, so as to realize The gel and water are transported together and enter the stainless steel pipe 104 through the microalgae condensate bead feeding hopper 107, enter the arc pipe 105 through the stainless steel pipe 104, and finally enter the last microalgae condensate bead storage cage 106 through a plurality of microalgae condensate bead storage cages 106. Then, according to the above-mentioned operation steps, the second solenoid valve 118 is closed from the bottom in sequence to realize the condensate beads in each microalgae condensate bead storage cage 106 for loading operation. When each microalgae condensate bead storage cage 106 is loaded, the top plate 102 is slowly lowered by the hydraulic cylinder, so that the pipe at the bottom of the microalgae condensate bead storage cage 106 is inserted into the bearing 117, thereby improving the stability of the entire microalgae condensate bead storage cage 106 and completing the material change operation. Microalgae condensate beads are stored in each microalgae condensate bead storage cage 106. The microalgae condensate beads are condensate beads made of sodium alginate and containing Chlorella. The condensate beads are used to protect the microalgae. The microalgae condensate bead storage cage 106 allows the microalgae to move within a set range.

[0035] like Figure 2 As shown, a microalgae condensate delivery pipe 109 is installed on the top of the lifting top plate 102 through a support frame, a plurality of feed pipes 113 are arranged at the bottom of the microalgae condensate delivery pipe 109, a first solenoid valve 115 is installed on the feed pipe 113, and a solar panel 114 is also installed on the top of the lifting top plate 102 through a support frame. The solar panel 114 is used to generate electricity to provide electric energy to the microalgae bioreactor 1, thereby achieving the purpose of saving energy.

[0036] A water outlet pipe 122 is connected to the top of one side of the microalgae bioreactor 1, and a first valve 123 is installed on the water outlet pipe 122. A second valve 124 is installed on the second connecting pipe 5 connected to the bottom of the other side of the microalgae bioreactor 1. The first valve 123 and the second valve 124 are used to adjust the flow rate of inlet and outlet water. The first valve 123 and the second valve 124 can be set as electric valves, and the water level is detected by a water level sensor to automatically adjust the opening of the electric valve or the flow rate of the electric valve.

[0037] like Figure 2 As shown: a reduction box 111 is installed at one end of the microalgae condensate bead conveying pipe 109, a second motor 112 is installed on one side of the reduction box 111, an auger 116 is connected to the reduction box 111, and a feed hopper 110 is provided on the top of the microalgae condensate bead conveying pipe 109. The second motor 112 is used to drive the auger 116 to convey the condensate beads containing microalgae and water to the microalgae condensate bead feeding hopper 107 to prevent blockage. Water can also be used to directly drive the condensate beads for conveying.

[0038] like Figure 2 As shown: the stainless steel pipe 104 is installed on the reduction box 103 through the bearing, and the stainless steel pipe 104 is equipped with a gear and meshes with the gear on the main shaft of the first motor 108. The first motor 108 drives the gear to rotate, thereby driving the stainless steel pipe 104 to rotate around the bearing, thereby realizing the rotation of the microalgae condensate storage cage 106, so that the microalgae condensate in the microalgae condensate storage cage 106 is fully in contact with the sewage.

[0039] like Figure 2 As shown: the stainless steel pipe 104 is welded to the arc pipe 105, the microalgae condensate bead feeding hopper 107 is connected to the arc pipe 105 through the stainless steel pipe 104, and the arc pipe 105 is connected to the microalgae condensate bead storage cage 106, which is convenient for putting in the microalgae condensate bead. The microalgae condensate bead storage cage 106 is made of transparent PP material, and the transparent PP material allows light to shine on the microalgae. A number of through holes are evenly arranged on the microalgae condensate bead storage cage 106, which is convenient for the microalgae condensate bead in the microalgae condensate bead storage cage 106 to contact with sewage, and also allows light to enter and shine on the microalgae.

[0040] like Figure 2 As shown: a lamp pole is arranged inside the microalgae supplementary lighting tube 119, and the lamp pole is a quadrangular prism, and LED modules are installed on the four sides of the lamp pole; an LED light board is installed inside the transparent lampshade 121, and the LED light board and the lamp pole are used to provide sufficient light for the microalgae. When the microalgae condensate bead storage cage 106 rotates, the condensate beads are suspended and moved in the microalgae condensate bead storage cage 106, so that the light can irradiate the microalgae, thereby improving the survival rate of the microalgae.

[0041] A water level sensor and a temperature sensor are installed inside the microalgae bioreactor 1. The temperature sensor is electrically connected to the electric heating device 120 through a controller. The electric heating device 120 is an electric heating rod. The electric heating device 120 and the temperature sensor are used to achieve constant temperature in the microalgae bioreactor 1.

[0042] like Figure 3 As shown, the artificial wetland 2 is provided with pebbles 201, iron carbon 202, and zeolite 203 in sequence from the bottom to the top, and a central tube 204 is provided in the middle of the artificial wetland 2, and a plurality of through holes are provided on the central tube 204.

[0043] like Figure 4 As shown, a liquid inlet 302 is provided at the top of one side of the sedimentation tank 3, a filter screen plate 301 is provided inside the sedimentation tank 3, a sedimentation tank 303 is provided at one side of the filter screen plate 301, and a mud discharge pipe 304 is provided at the bottom of the sedimentation tank 303. The mud discharge pipe 304 is used to discharge the sludge in the sedimentation tank 303.

[0044] Example 2: The present invention constructs a composite aquaculture tailwater treatment system consisting of an iron-carbon artificial wetland, an immobilized microalgae bioreactor, and a sedimentation tank. The sedimentation tank is of a horizontal flow type, and 2.5 hours after the incoming water reaches the water level sensor of the sedimentation tank, the peristaltic pump is turned on to pump the water into the immobilized microalgae bioreactor.

[0045] Experimental verification:

[0046] The immobilized microalgae bioreactor is made of acrylic, with specifications of 500mm×300mm×500mm, and an effective tailwater treatment volume of 40L. It has two fixed-axis rotating racks built in, each of which is equipped with four microalgae condensate storage cages, two on each side, and a rotation speed of 60r / min. The fill light intensity is adjusted to 5000lx, and the temperature is controlled at 25℃. When the water level reaches the water level sensor at the 40L position, the peristaltic pump is turned on to pump water into the wetland system.

[0047] The shell of the iron-carbon artificial wetland is made of polytetrafluoroethylene, with specifications of 600mm×600mm×750mm (L×W×H). The fillers of the artificial wetland system are as follows from top to bottom: the upper layer is 300mm zeolite ( 8-12mm), middle layer 300mm iron-carbon matrix ( 5-10mm), bottom layer 100mm smooth pebbles ( 30-50mm). Five sampling ports were set on the side wall, with distances of 0, 150, 300, 450 and 600mm from the system surface. Each wetland system was planted with an average weight of 3.5±0.20g of seahorse teeth, with a planting density of about 133 plants / ㎡.

[0048] The microalgae beads storage cage contains seawater chlorella algae gel beads embedded with sodium alginate, with a density of about 5×10 6 cell·rubber ball -1 Each microalgae bead storage cage is approximately filled 2 / 3.

[0049] The system is equipped with pH detection components and dissolved oxygen detection components to monitor the system operation status and ensure stable operation of the system.

[0050] Immobilized microalgae embedding method:

[0051] Through the comparative experiment of algae treatment effect in the early stage, marine Chlorella was selected as the embedding species. The marine Chlorella strain was cultured in batches in a conical flask (1L) containing 500ml of f / 2 culture medium with a salinity of 16, at a temperature of 25±1℃, a light-dark ratio of 12:12, and a light intensity of 5000lx. The Chlorella density reached the logarithmic phase, and the algae solution was centrifuged at 20℃ for 10-15min to obtain microalgae cells. After washing with deionized water, it was mixed with a 6% sodium alginate solution, and a 0.1M calcium chloride solution was evenly dropped into it with a 50ml syringe to obtain a density of about 5×10 6 cell·rubber ball -1 , soak the gel balls in a calcium chloride solution for 12 hours to harden them; and obtain gel beads containing microalgae.

[0052] Experiment 1:

[0053] Two groups of iron-carbon artificial wetlands were selected, one of which was combined with microalgae, and artificially configured marine aquaculture wastewater with an ammonia nitrogen concentration of 30 mg / L, a nitrate concentration of 0, a C / N ratio of 1, and a salinity of 20 was introduced; the removal rate of ammonia nitrogen in the microalgae-coupled iron-carbon artificial wetland reached 27.57±3.82% in 12 hours, and the removal rate of ammonia nitrogen in 24 hours reached 65.58±5.94%. Figure 6 shown.

[0054] Experiment 2: Same as Experiment 1, the ammonia nitrogen concentration was 0, and the nitrate nitrogen concentration was 30 mg / L; the removal rate of nitrate nitrogen in 12 hours reached 96.81±1.35%, and the removal rate of nitrate nitrogen in 24 hours reached 99.49±0.13%. Figure 5 shown.

[0055] Experiment 3: Consistent with Experiment 1, the ammonia nitrogen concentration was 15 mg / L and the nitrate nitrogen concentration was 15 mg / L; the total nitrogen removal rate reached 81.98±3.38% in 12 hours and 95.05±2.21% in 24 hours. Figure 7 shown.

[0056] In summary: Through the above three experiments, it can be found that the coupling of microalgae and iron-carbon artificial wetlands is better than a single iron-carbon artificial wetland in removing ammonia nitrogen, nitrate nitrogen and total nitrogen.

[0057] It is concluded that microalgae coupled with iron-carbon constructed wetlands is an effective nitrogen removal technology, especially suitable for treating wastewater containing ammonia nitrogen and nitrate nitrogen. This system can not only effectively remove ammonia nitrogen, but also efficiently remove nitrate nitrogen, thereby significantly reducing the total nitrogen content in the water body. In addition, the removal efficiency of the system will gradually increase over time, showing good durability and stability.

[0058] The present invention designs a complete set of microalgae coupled iron-carbon artificial wetland systems for the purpose of more efficiently treating seawater aquaculture tailwater with a low carbon-nitrogen ratio. Seawater aquaculture tailwater contains a large amount of suspended particles formed by residual bait, feces, etc., including bioflocs formed by the combination of organic matter and microorganisms. A large amount of suspended particles and bioflocs directly enter the system without treatment, which will cause blockage of the system pipeline. Therefore, before treating the aquaculture tailwater, it is necessary to precipitate the suspended particles and bioflocs to avoid blockage of the subsequent system. Since a single iron-carbon artificial wetland has an excellent removal effect on nitrate nitrogen, but a poor removal effect on ammonia nitrogen, microalgae with high removal efficiency for ammonia nitrogen are added after the iron-carbon artificial wetland is removed for removal. Since microalgae are directly added to the artificial wetland, one is because the iron-carbon artificial wetland lacks sunlight and oxygen to meet the living environment of microalgae, and the other is because the microalgae will adhere to the matrix after entering the wetland system, which is difficult to collect. In the absence of sunlight, it will die quickly and release algae toxins, which is equivalent to adding additional pollution sources to the tailwater. Therefore, the present invention uses the immobilized microalgae embedding technology to embed the microalgae with sodium alginate, which can not only collect the microalgae more conveniently, but also accelerate the absorption of nitrogen and phosphorus elements in the tail water by utilizing the adsorption performance of the surface of the sodium alginate gel beads.

[0059] The technical pain point of the current treatment of seawater aquaculture tailwater is that the carbon-nitrogen ratio in the seawater aquaculture tailwater is low, and there is not enough carbon source to support the denitrification of microorganisms. Therefore, the efficiency of the traditional mode of seawater aquaculture tailwater treatment is very slow and the effect is not good. For this reason, iron and carbon are added during the treatment process to change the main denitrification of microorganisms from heterotrophic denitrification using the carbon source in the tailwater to autotrophic denitrification that obtains electrons from iron for nitrification, so that microorganisms do not need to rely on the carbon source in the tailwater during the treatment of tailwater. Based on this principle and traditional artificial wetland tailwater treatment technology, this iron-carbon artificial wetland system is designed. Because microorganisms will reduce part of the nitrate nitrogen to ammonia nitrogen when denitrifying, it is still insufficient to remove it only by a single iron-carbon artificial wetland. In order to make up for this deficiency, the present invention uses microalgae to make up for it and designs an immobilized microalgae reactor. The water treated by the iron-carbon artificial wetland is further treated.

[0060] The above embodiments only express the implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention.

Claims

1. An immobilized microalgae coupled iron-carbon artificial wetland system, comprising a microalgae bioreactor (1), an artificial wetland (2), and a sedimentation tank (3), characterized in that: The microalgae bioreactor (1) is connected to the artificial wetland (2) via a second connecting pipe (5), and the artificial wetland (2) is connected to the sedimentation tank (3) via a first connecting pipe (4); Hydraulic cylinders (101) are installed at the four corners of the top of the microalgae bioreactor (1), a lifting top plate (102) is installed on the top of the hydraulic cylinder (101), a plurality of reduction boxes (103) are installed on the top of the lifting top plate (102), a stainless steel pipe (104) is provided in the middle of the reduction box (103), a microalgae condensate bead feeding hopper (107) is connected to the top of the stainless steel pipe (104), and a plurality of arc-shaped pipes (107) are connected to the bottom of the stainless steel pipe (104). 105), the bottom of the arc-shaped pipe (105) is connected to a plurality of microalgae condensate storage cages (106), a second solenoid valve (118) is installed on the connecting pipe between each microalgae condensate storage cage (106), the bottom pipe of the microalgae condensate storage cage (106) is connected to a bearing (117), a plurality of microalgae supplementary light tubes (119) are installed inside the microalgae bioreactor (1), and transparent lampshades (121) are installed on the four side walls inside the microalgae bioreactor (1); Each microalgae condensate bead storage cage (106) contains a plurality of microalgae condensate beads, wherein the microalgae condensate beads are condensate beads containing Chlorella and made of sodium alginate; A microalgae condensate delivery pipe (109) is installed on the top of the lifting top plate (102) through a support frame, and a plurality of discharge pipes (113) are arranged at the bottom of the microalgae condensate delivery pipe (109). A first solenoid valve (115) is installed on the discharge pipe (113). A solar panel (114) is also installed on the top of the lifting top plate (102) through a support frame.

2. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: A water outlet pipe (122) is connected to the top of one side of the microalgae bioreactor (1), and a first valve (123) is installed on the water outlet pipe (122). A second valve (124) is installed on a second connecting pipe (5) connected to the bottom of the other side of the microalgae bioreactor (1). The first valve (123) and the second valve (124) are used to adjust the flow rate of inlet and outlet water.

3. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: A reduction box (111) is installed at one end of the microalgae condensate bead conveying pipe (109), a second motor (112) is installed on one side of the reduction box (111), an auger (116) is connected to the reduction box (111), and a feed hopper (110) is provided at the top of the microalgae condensate bead conveying pipe (109).

4. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: The stainless steel pipe (104) is mounted on the reduction box (103) via a bearing. A gear is mounted on the stainless steel pipe (104) and meshes with a gear on the main shaft of the first motor (108).

5. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: The stainless steel pipe (104) is connected to the arc pipe (105) by welding, the microalgae condensate bead feeding hopper (107) is connected to the arc pipe (105) through the stainless steel pipe (104), the arc pipe (105) is connected to the microalgae condensate bead storage cage (106), the microalgae condensate bead storage cage (106) is made of transparent PP material, and a plurality of through holes are evenly arranged on the microalgae condensate bead storage cage (106).

6. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: The microalgae supplementary light tube (119) is provided with a lamp pole inside, the lamp pole is a quadrangular prism, and LED modules are installed on the four sides of the lamp pole; the transparent lampshade (121) is provided with an LED light board inside.

7. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: A water level sensor and a temperature sensor are installed inside the microalgae bioreactor (1); the temperature sensor is electrically connected to an electric heating device (120) via a controller; the electric heating device (120) is an electric heating rod.

8. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: The artificial wetland (2) is provided with pebbles (201), iron carbon (202), and zeolite (203) in sequence from the bottom to the top, and a central tube (204) is provided in the middle of the artificial wetland (2), and a plurality of through holes are provided on the central tube (204).

9. The immobilized microalgae coupled iron-carbon artificial wetland system according to claim 1, characterized in that: A liquid inlet (302) is provided at the top of one side of the sedimentation tank (3), a filter screen (301) is provided inside the sedimentation tank (3), a sedimentation tank (303) is provided at one side of the filter screen (301), and a mud discharge pipe (304) is provided at the bottom of the sedimentation tank (303).

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