A microalgae-enhanced artificial wetland carbon reduction and denitrification system and its operation process

Abstract

The present invention discloses a microalgae-enhanced artificial wetland carbon reduction and denitrification system and its operation process. The system comprises an inlet pipe (1), a microalgae acclimation system (2), an artificial wetland purification system (3), and an outlet pipe (4). Sewage enters the mixing tank of the microalgae acclimation system through the inlet pipe. Microalgae and return water are added according to the quality of the inlet water. After the three are fully mixed and prepared, they enter the floating body acclimation device. The microalgae are enhanced to purify the sewage through an aeration pipe and a venting device. The sewage then passes through a filter screen and enters a collection tank. The collection tank is connected to the water distribution pipe of the artificial wetland purification system. The sewage enters the water distribution pipe and is acted upon by the roots of the artificial wetland plants and microorganisms. The wastewater is then discharged through the outlet pipe. It is determined whether it needs to enter the return device according to its concentration. The water in the return device and the microalgae in the microalgae mixing tank are circulated and supplied, ultimately achieving carbon cycle and denitrification. The system has the characteristics of high efficiency, energy saving, and environmental protection, and is suitable for the fields of urban sewage treatment, industrial wastewater treatment, etc.

Description

Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to a microalgae-enhanced artificial wetland carbon reduction and denitrification system and an operation process thereof. Background Art

[0002] Currently, water pollution and nitrogen and carbon emissions have become one of the serious environmental problems facing the world. Traditional wastewater treatment methods have problems such as high energy consumption and limited treatment effects. Therefore, there is a need to seek an efficient and low-energy water pollution control technology. At the same time, microalgae are microorganisms that can absorb large amounts of carbon dioxide (CO2) through photosynthesis. During their growth process, they can effectively remove organic pollutants such as nitrogen and phosphorus from water bodies. Therefore, using microalgae to treat sewage and reduce carbon and denitrify has become an environmental protection technology that has attracted much attention. However, existing microalgae treatment technologies have some problems in the sewage treatment process. For example, the growth of microalgae is limited by the water quality and oxygen supply of the influent, and the treatment effect is unstable. In addition, the harvesting and recycle of microalgae also face certain technical challenges. Therefore, a novel technology is needed to solve the problems of existing microalgae treatment technologies and provide an efficient microalgae-enhanced artificial wetland carbon reduction and denitrification system and method.

[0003] Patent application number CN201720071848, "A Solar Aerated Vertical Flow Constructed Wetland System for Enhanced Denitrification," provides a solar aerated vertical flow constructed wetland system for enhanced denitrification. The system comprises a gravel layer, a packing layer, and a fine sand protective layer, arranged in sequence within the tank. A water distribution pipe is located above the gravel layer, a water collection pipe is laid on the fine sand protective layer, and an aeration pipe is located in the middle of the packing layer. Several corundum microporous aerators are connected to the aeration pipes, and the aeration blower is a DC blower powered by an on-site solar power generation system. This invention can form long-term, stable aerobic and anoxic zones within the packing layer, creating a long-term, stable environment for the corresponding microorganisms. As water flows through the aerobic and anoxic zones, aerobic biochemical reactions, including nitrification and denitrification, and anoxic / anaerobic biochemical reactions, occur sequentially. However, the system uses a solar power generation system for power supply, which can be an environmentally friendly and sustainable solution in areas with abundant sunlight. However, in rainy weather or at night, the power supply of the solar power generation system may be limited, causing the aeration equipment to fail to work properly, thereby affecting the stability and treatment efficiency of the system.

[0004] Patent application number CN201820586249, "An Efficient Constructed Wetland Wastewater Treatment System," discloses an efficient constructed wetland wastewater treatment system, including a pool body with an outlet provided on the side of the pool body. The pool body includes, from top to bottom, a soil layer, a fine sand layer, a zeolite layer, and a gravel layer. A composite material structure layer is provided within the gravel layer, which separates the gravel layer into an upper gravel layer and a lower gravel layer. The composite material structure layer includes a fly ash ceramsite layer, a solid carbon source layer, and a composite layer. The fly ash ceramsite layer, the solid carbon source layer, and the composite layer are arranged in sequence from top to bottom. The composite layer includes a number of fly ash ceramsite strips and a number of solid carbon source strips, and the fly ash ceramsite strips and the solid carbon source strips are arranged in an interlaced manner. However, this system provides a solid carbon source layer within the composite material structure layer to treat organic carbon substances in wastewater. However, compared with the biological adsorption and conversion capacity of microalgae, the treatment efficiency of the solid carbon source layer may be lower, especially for the degradation and treatment capacity of complex organic matter in wastewater, which may be limited.

[0005] Patent application number CN202210057821, "A device and method for decarbonization and denitrification of a MEC-type downward vertical flow artificial wetland with a rapid start-up microbial electrolysis cell," discloses a device and method for decarbonization and denitrification of a MEC-type downward vertical flow artificial wetland with a rapid start-up microbial electrolysis cell, comprising an artificial wetland tank body, wherein the artificial wetland tank body is provided with a top water distribution pipe, a top non-conductive filler layer, an anode conductive filler layer and an artificial bacteria introduction pipe and an exhaust pipe, a non-conductive filler isolation layer, a cathode conductive filler layer and an artificial bacteria introduction pipe and an exhaust pipe, a bottom non-conductive filler layer and a water outlet pipe from top to bottom. The anode conductive filler layer in the artificial wetland tank body is respectively connected to the top non-conductive filler layer and the non-conductive filler isolation layer, and the cathode conductive filler layer is respectively connected to the bottom non-conductive filler layer and the non-conductive filler isolation layer. However, this system involves the process of introducing artificial bacteria to achieve decarbonization and denitrification. The introduction of artificial bacteria requires special treatment and management, which increases the complexity and difficulty of system operation. Compared with microalgae, the introduction of artificial strains may not be as stable and sustainable as the natural growth process of microalgae.

[0006] The patent "Aerobic-Anaerobic Three-Phase Pulsed Cascade Water Inlet Wetland System" with application number CN202011503254 provides an aerobic-anaerobic three-phase pulsed cascade water inlet wetland system, wherein a water distribution structure and a cascade water inlet pipe are arranged on the top and side of the wetland system, and a water outlet is arranged at the bottom of the wetland system to be connected to a siphon drain pipe. The top of the siphon drain pipe is lower than the height of the top of the wetland system to form a pressure difference for periodic siphon drainage, so that the area of the wetland system above the L-shaped vent pipe on the siphon drain pipe is the upper aerobic zone, and the area below it is the lower anaerobic zone. The position of the L-shaped vent pipe can regulate the ratio of the two. However, since the system involves the connection between the siphon drain pipe and the L-shaped vent pipe, there is a potential risk of leakage. Leakage problems may cause the system to operate in a reduced efficiency and cause pollution to the surrounding environment. Summary of the Invention

[0007] Purpose of the invention: In response to the problems existing in existing artificial wetland systems in treating carbon and nitrogen substances in sewage, the present invention provides a microalgae-enhanced artificial wetland carbon reduction and denitrification system and its operating process. It is based on the biological adsorption and nitrogen conversion characteristics of microalgae, combined with the working principle and operation mode of the artificial wetland system, and effectively purifies water quality through an innovative system configuration and operation method. Through the introduction of a microalgae domestication system and an innovative method of microalgae enhanced treatment, the present invention fully utilizes the advantages of microalgae in carbon adsorption and nitrogen conversion, thereby improving the treatment effect of the artificial wetland system. At the same time, through reasonable system configuration and operation mode, the efficient degradation and removal of carbon and nitrogen substances in sewage are achieved, achieving the dual goals of environmental protection and resource utilization.

[0008] Technical solution: A microalgae-enhanced artificial wetland carbon reduction and denitrification system, comprising an inlet pipe, a microalgae acclimation system (2), an artificial wetland purification system (3), and an outlet pipe connected in sequence, wherein the outlet of the outlet pipe is free to discharge or connected to an outlet return device of the microalgae acclimation system (2); wherein:

[0009] an inlet pipe (1) for introducing influent sewage into the microalgae acclimation system;

[0010] The microalgae acclimation system (2) comprises: a blending tank (2-2) and a microalgae dosing device (2-1), which are used to supplement microalgae and return a certain proportion of effluent to the blending tank through an effluent return device (2-3); a rectifying pipe (2-4) connecting the blending tank and the float acclimation device, which is used to introduce sewage into the float acclimation device; the float acclimation device (2-5), which comprises an aeration pipe (2-10) and a venting device (2-8), which strengthens the growth of microalgae through aeration and activates the venting device when the capacity exceeds a preset value; a collecting pipe (2-7) connecting the float acclimation device and the collecting tank (2-6), which is used to introduce sewage treated by the float acclimation device into the collecting tank (2-6); an output end of the collecting tank (2-6) is connected to a filter screen (2-9), which is used to filter the sewage; and the treated water is filtered through the filter screen and then output to the artificial wetland purification system (3).

[0011] The artificial wetland purification system (3) includes a water distribution pipe (3-5), a supporting layer (3-1), a filter layer (3-2) and a purification layer (3-3). The sewage is evenly distributed in the artificial wetland purification system through the water distribution pipe, and the dissolved oxygen concentration in the filter bed is maintained through the bottom aeration pipe (3-6).

[0012] The outlet pipe is used to achieve the discharge of sewage in compliance with the standards.

[0013] The operating process of the microalgae-enhanced artificial wetland carbon reduction and denitrification system of the present invention comprises the following steps:

[0014] Step 1: Influent wastewater enters the microalgae acclimation system through the inlet pipe. In the blending tank, microalgae are added through the microalgae dosing device, and a certain proportion of effluent return water is blended according to the influent water quality. The effluent return water enters the blending tank through the return device. The volume ratio of influent water to return water from the return device is 1: (0.3-1).

[0015] Such a configuration can ensure that the microalgae can fully grow and reproduce in the acclimation pond and increase the microalgae's ability to adsorb carbon sources in sewage. The microalgae dosage is calculated as shown in formula (1), formula (2), formula (3) and formula (4).

[0016]

[0017]

[0018] M1=C1×V1 Formula (4)

[0019] In the above formula

[0020] - Nitrate nitrogen concentration after ammonia nitrogen is converted to nitrate nitrogen, mg / L;

[0021] - Background concentration of nitrate nitrogen in influent, mg / L;

[0022] The conversion rate of α-ammonia nitrogen to nitrate nitrogen is dimensionless and is generally taken as 0.7-0.9;

[0023] -Influent ammonia nitrogen concentration, mg / L;

[0024] C c -Required carbon source concentration, mg / L;

[0025] C1-dosed microalgae concentration, mg / L;

[0026] β-microalgae utilization rate, dimensionless, generally taken as 0.8-0.95;

[0027] M1-mass of added microalgae, mg;

[0028] V1-microalgae acclimation system operating volume, L.

[0029] Step 2: Sewage enters the floating acclimation system through a rectifier pipe. Aeration pipes at the bottom of the system enhance microalgae growth, with an aeration intensity of 1:5 to 1:8. A venting device is also installed at the bottom of the system. When the actual volume V1 exceeds 40% of the set volume V, the venting device activates. When V1 drops to ≤40% of the set volume V, the venting device deactivates, and the microalgae acclimation pond resumes normal operation.

[0030] Such a setup can maintain a suitable growth environment for microalgae, preventing excessive accumulation and deterioration of wastewater quality.

[0031] Step 3: After being treated by the floating acclimation device, the wastewater first flows through a collection pipe into a collection tank, where it is filtered through a filter screen before entering the constructed wetland purification system. This step further removes suspended matter and solid particles from the wastewater, providing a clean water environment for subsequent microalgae-enhanced treatment.

[0032] Step 4: Wastewater from the microalgae acclimation system enters the constructed wetland purification system through the distribution pipes. The distribution pipes are uniformly perforated, distributing the wastewater evenly throughout the constructed wetland purification system. The wastewater passes through the support layer, filtration layer, and purification layer in sequence. Within the constructed wetland, microalgae participate in the purification process. By adjusting the composition of each layer of filter media and maintaining a supply of dissolved oxygen, the microalgae's growth environment is effectively controlled, guiding their continued growth and metabolism, maintaining their purification function. Aeration pipes are installed at the bottom of the constructed wetland purification system to provide oxygen and maintain the dissolved oxygen concentration in the filter bed, which is conducive to the growth of microorganisms and microalgae.

[0033] Step 5: The sewage treated by the artificial wetland purification system is discharged through the outlet pipe for testing. When the effluent ammonia nitrogen concentration is greater than the discharge ammonia nitrogen standard concentration but does not meet the discharge standard, that is, C2>C0, the reflux device is turned on and the water intake is stopped at the same time. The sewage enters the step 1 circulation purification through the reflux device; when the effluent ammonia nitrogen concentration is less than the discharge ammonia nitrogen standard concentration but meets the discharge standard, that is, C2≤C0, the reflux device is turned on and water is intaken at the same time, and part of the purified water that meets the standard is returned to the blending tank, ultimately achieving effective purification of the water quality.

[0034] Compared with the prior art, the present invention has the following advantages:

[0035] (1) Efficient degradation of carbon and nitrogen substances: By introducing a microalgae domestication system and microalgae enhanced treatment methods, the advantages of microalgae in carbon adsorption and nitrogen conversion are fully utilized. Microalgae can absorb organic carbon in water, reducing carbon source pollution to water bodies. At the same time, through nitrogen conversion, it effectively removes nitrogen substances in water, achieving efficient degradation and removal of carbon and nitrogen.

[0036] (2) Improve treatment effect: The introduction of microalgae acclimation system and microalgae enhanced treatment method can improve the system's treatment effect on sewage. Microalgae are fully grown and reproduced in the acclimation pond, which increases the microalgae's ability to adsorb carbon sources in sewage. At the same time, microalgae produce oxygen through photosynthesis, providing oxygen supply for microbial respiratory metabolism, further promoting the degradation of organic matter and nitrogen in sewage. However, unlike the natural microalgae environment, microalgae purification is carried out under controlled conditions.

[0037] (3) Resource Utilization and Environmental Protection: The present invention utilizes the carbon source adsorption and conversion properties of microalgae to achieve resource utilization of organic carbon and nitrogen substances in wastewater. Microalgae absorb carbon dioxide during their growth process and can effectively convert organic carbon in wastewater into useful biomass, thus achieving the recycling of carbon resources in wastewater. At the same time, the conversion of nitrogen substances by microalgae can reduce nitrogen emissions and reduce pollution to the water environment, thus having a good environmental protection effect.

[0038] (4) Wide application and sustainability: The microalgae-enhanced artificial wetland carbon reduction and denitrification system and method are applicable to wastewater treatment in a variety of fields, including urban sewage treatment and agricultural aquaculture wastewater treatment. The system has a simple structure and convenient operation. It can be combined with existing artificial wetland systems to improve the overall treatment effect and has a wide range of application prospects. In addition, because microalgae can grow and reproduce independently, they have good sustainability and the system operating costs are low, which is conducive to achieving long-term and stable wastewater treatment effects. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 Schematic diagram of the connection relationship of the microalgae-enhanced artificial wetland carbon reduction and nitrogen removal system;

[0040] Figure 2 Front view of the microalgae-enhanced constructed wetland carbon reduction and nitrogen removal system;

[0041] Figure 3 yes Figure 2 Top view of .

[0042] In the figure: 1-water inlet pipe; 2-microalgae acclimation system; 2-1-microalgae dosing device; 2-2-mixing tank; 2-3-water reflux device; 2-4 rectifier pipe; 2-5 floating body acclimation device; 2-6-collecting tank; 2-7-collecting pipe; 2-8-venting device; 2-9-filter screen; 2-10-aeration pipe; 3-artificial wetland purification system; 3-1 supporting layer; 3-2-filtration layer; 3-3-purification layer; 3-4-plants; 3-5-water distribution pipe; 3-6-aeration pipe; 4-water outlet pipe. DETAILED DESCRIPTION

[0043] The technical solutions of the present invention are further described through the following specific embodiments.

[0044] Example 1: Assume a city's domestic sewage treatment system, which adopts the microalgae-enhanced artificial wetland carbon reduction and nitrogen removal system described in the patent.

[0045] Step 1: The influent sewage enters the microalgae acclimation system through the inlet pipe. In the blending tank, microalgae are added through the microalgae dosing device, and a certain proportion of effluent return is blended according to the influent water quality. The effluent return enters the blending tank through the return device, and the ratio of influent to return device is 1:1. This configuration can ensure that the microalgae can fully grow and reproduce in the acclimation system and increase the microalgae's ability to adsorb carbon sources in the sewage. The relevant calculations are shown in Equations (1), (2), (3) and (4).

[0046]

[0047] M1=C1×V1 Formula (4)

[0048] In the above formula

[0049] - Nitrate nitrogen concentration after ammonia nitrogen is converted to nitrate nitrogen, mg / L;

[0050] -Influent nitrate nitrogen background concentration, mg / L, take 5;

[0051] The conversion rate of α-ammonia nitrogen to nitrate nitrogen is dimensionless and is taken as 0.7;

[0052] -Influent ammonia nitrogen concentration, mg / L, take 10;

[0053] C c-Required carbon source concentration, mg / L;

[0054] C1-dosed microalgae concentration, mg / L;

[0055] β-microalgae utilization rate, dimensionless, taken as 0.8;

[0056] M1-mass of added microalgae, mg;

[0057] V1-microalgae acclimation pond operating volume, L, take 40.

[0058] By calculation, we get C c =68.64mg / L; C1=298.19mg / L; M1=11732.45mg; that is, 11.73g of microalgae needs to be added, of which 20L is influent water and 20L is reflux water.

[0059] Step 2: Sewage enters the floating acclimation system through a rectifier pipe. Aeration pipes at the bottom of the system enhance microalgae growth, with an aeration intensity of 1:5 to 1:8. A venting device is also installed at the bottom of the system. The volume of the microalgae acclimation system is V = 100L, and the operating volume is V1 = 40L, accounting for 40% of the total volume, so there is no need to activate the venting device.

[0060] Step 3: After being treated by the floating acclimation device, the wastewater first flows through a collection pipe into a collection tank, where it is filtered through a filter screen before entering the constructed wetland purification system. This step further removes suspended matter and solid particles from the wastewater, providing a clean water environment for subsequent microalgae-enhanced treatment.

[0061] Step 4: Wastewater from the microalgae acclimation system enters the constructed wetland purification system through distribution pipes. The distribution pipes are uniformly perforated to distribute the wastewater evenly throughout the constructed wetland purification system. The wastewater passes through the support layer, filtration layer, and purification layer in sequence. Aeration pipes are installed at the bottom of the constructed wetland purification system to maintain the dissolved oxygen concentration in the filter bed, providing oxygen for the microorganisms' respiratory metabolism.

[0062] Step 5: The sewage treated by the system is discharged through the outlet pipe for testing. The effluent ammonia nitrogen concentration is detected to be C2=0.9mg / L, and the ammonia nitrogen emission standard concentration is C0=1mg / L, that is, C2≤C0. The effluent ammonia nitrogen concentration is less than the emission ammonia nitrogen standard concentration, meeting the emission standard. The reflux device is turned on and water is introduced at the same time, and part of the purified water that meets the standards is returned to the mixing tank, ultimately achieving effective purification of the water quality.

[0063] Example 2: α = 0.7; β=0.85; other parameters are the same as those in Example 1.

[0064] By calculation, we get C c =44.09 mg / L; C1 = 423.91 mg / L; M1 = 16566.4 mg; that is, 16.67 g of microalgae needs to be added.

[0065] After steps 2, 3 and 4, it is detected that the effluent C2 is 2 mg / L, that is, C2>C0, and the effluent ammonia nitrogen concentration is greater than the discharge ammonia nitrogen standard concentration and does not meet the discharge standard. The reflux device is turned on and the water inlet is stopped at the same time. The sewage enters step 1 for circulation purification through the reflux device.

[0066] Example 3: α = 0.9; β=0.9;V1=60L,other parameters are the same as those in Example 1.

[0067] By calculation, we get C c =68.94 mg / L; C1 = 382.23 mg / L; M1 = 22128.27 mg; that is, 22.13 g of microalgae needs to be added, of which 30 L is influent water and 30 L is reflux water.

[0068] The volume of the microalgae acclimation system is V=100L, and the operating volume is V1=60L, accounting for 60% of the total volume. When V1>40%V, the venting device is started. When V1≤40%V, the microalgae acclimation pond begins to operate normally.

[0069] After steps three and four, it is detected that the effluent C2 is 0.8 mg / L, that is, C2 < C0, and the effluent ammonia nitrogen concentration is lower than the discharge ammonia nitrogen standard concentration, meeting the discharge standard. The reflux device is turned on and water is introduced at the same time, and part of the purified water that meets the standards is returned to the mixing tank, ultimately achieving effective purification of the water quality.

Claims

1. An operating process of a microalgae-enhanced constructed wetland carbon reduction and denitrification system, the microalgae-enhanced constructed wetland carbon reduction and denitrification system comprising: A water inlet pipe (1), a microalgae acclimation system (2), an artificial wetland purification system (3), and a water outlet pipe (4) are connected in sequence, wherein the outlet of the water outlet pipe (4) is freely discharged or connected to the water outlet return device of the microalgae acclimation system (2); wherein: A water inlet pipe (1), through which sewage is introduced into the microalgae domestication system; The microalgae acclimation system (2) comprises a blending tank (2-2) and a microalgae dosing device (2-1) for replenishing microalgae and returning a certain proportion of effluent to the blending tank through an effluent return device (2-3); a rectifying pipe (2-4) for introducing sewage into a floating body acclimation device; a floating body acclimation device (2-5) comprising an aeration pipe (2-10) and a venting device (2-8) for enhancing microalgae growth through aeration, purifying sewage with the aid of microalgae, and activating the venting device when the capacity exceeds a preset value; a collecting pipe (2-7) for introducing sewage treated by the floating body acclimation device into a collecting tank (2-6); a filter screen (2-9) for filtering sewage; the blending tank (2-2), the rectifying pipe (2-4), the floating body acclimation device (2-5), the collecting pipe (2-7), the collecting tank (2-6), and the filter screen are connected in sequence; The artificial wetland purification system (3) includes a water distribution pipe (3-5), a supporting layer (3-1), a filter layer (3-2) and a purification layer (3-3). The sewage is evenly distributed in the artificial wetland purification system through the water distribution pipe, the filter layer and the purification layer are used to purify the water body, and the dissolved oxygen concentration in the filter bed is maintained through the bottom aeration pipe (3-6); in the artificial wetland environment, microalgae continue to grow and metabolize, participating in the purification process; by adjusting the composition of the filter material in each layer and maintaining the supply of dissolved oxygen, the growth environment of the microalgae is effectively controlled, thereby guiding the microalgae to continuously play a purification role; An outlet pipe (4) is used to discharge the wastewater purified by the artificial wetland purification system in a manner that meets the standards; In the mixing tank, the volume ratio of the inlet water to the return water of the outlet return device is 1: (0.3 ~ 1); The aeration pipe of the floating body acclimation device has an aeration intensity of 1:5 to 1:8; It is characterized in that the steps are as follows: Step 1: Sewage enters the microalgae domestication system through the water inlet pipe; in the mixing tank, microalgae are added through the microalgae dosing device, and the effluent return is adjusted according to the inlet water quality, wherein the effluent return enters the mixing tank through the effluent return device; the volume ratio of the inlet water to the return water of the effluent return device is 1:(0.3-1); wherein, the microalgae dosage is obtained through calculation, specifically see formula (1), formula (2), formula (3) and formula (4): M1=C1×V1 Formula (4); In the above formula: - Nitrate nitrogen concentration after ammonia nitrogen is converted to nitrate nitrogen, mg / L; - Background concentration of nitrate nitrogen in influent, mg / L; The conversion rate of α-ammonia nitrogen to nitrate nitrogen is dimensionless and is taken as 0.7-0.9; -Influent ammonia nitrogen concentration, mg / L; C c -Required carbon source concentration, mg / L; C1-dosed microalgae concentration, mg / L; β-microalgae utilization rate, dimensionless, ranging from 0.8 to 0.95; M1-mass of added microalgae, mg; V1-microalgae acclimation system operating volume, L; Step 2: The wastewater enters the floating acclimation device through the rectifying pipe. Under the premise of controlling the amount of microalgae, the wastewater is purified by the microalgae. The aeration pipe at the bottom of the floating acclimation device is used to enhance the growth of microalgae. The bottom of the floating acclimation device is also equipped with an air venting device. Step 3: The sewage treated by the floating body acclimation device first enters the collection tank through the collection pipe, and then passes through the filter screen to remove suspended matter and solid particles in the sewage; Step 4: The wastewater treated by the microalgae domestication system is distributed to the artificial wetland purification system through the evenly opened holes of the water distribution pipe for purification; Step 5: The sewage treated by the artificial wetland purification system is discharged through the outlet pipe for testing; When the effluent ammonia nitrogen concentration C2 is greater than the discharge ammonia nitrogen standard concentration C0 and does not meet the discharge standard, the effluent return device is turned on and the water inlet is stopped at the same time. The sewage enters the blending tank through the effluent return device to achieve circulation purification; When the effluent ammonia nitrogen concentration C2 is less than the discharge ammonia nitrogen standard concentration C0 and meets the discharge standard, the effluent return device is turned on and water is introduced at the same time, and part of the purified water that meets the standard is returned to the blending tank, ultimately achieving effective purification of the water quality.

2. The operation process of the microalgae-enhanced artificial wetland carbon reduction and denitrification system according to claim 1 is characterized in that: In step 2, when the actual volume V1 is greater than 40% of the set volume V, the venting device is started; when V1 drops to ≤ 40% of the set volume V, the venting device is stopped and the floating body acclimation device starts to operate normally.

3. The operation process of the microalgae enhanced artificial wetland carbon reduction and denitrification system according to claim 1 is characterized in that: In step 4, holes are evenly opened in the water distribution pipes of the artificial wetland purification system, and the sewage is evenly distributed in the artificial wetland purification system through the holes; the sewage passes through the supporting layer, the filtration layer and the purification layer in sequence.

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