Artificial wetland system and method for treating low-carbon high-nitrate-nitrogen wastewater

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to an artificial wetland system and a method for treating low-carbon high-nitrate-nitrogen wastewater. Comprising a system main body, and a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer and a supporting layer are sequentially arranged in the system main body from top to bottom in the height direction of the system main body; the aerobic layer is formed by taking first sludge biochar as a carrier and loading domesticated aerobic microorganism sludge; the anaerobic layer is formed by taking second sludge biochar as a carrier and loading domesticated anaerobic microorganism sludge. The litter layer is used as a supplementary carbon source, aerobic microorganisms are valued through the aerobic layer, anaerobic microorganisms are valued through the anaerobic layer, and an aerobic-anaerobic synergistic environment is constructed through the litter layer, the aerobic layer, the facultative anaerobic layer, the anaerobic layer and the supporting layer, so that the synchronous nitrification-denitrification efficiency is improved, and the denitrification capacity of the low-carbon high-nitrate-nitrogen wastewater is remarkably improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of wastewater treatment, and particularly relates to an artificial wetland system and a method for treating low-carbon and high-nitrate wastewater. Background Art

[0002] Low-carbon and high-nitrate wastewater is a type of wastewater with a high concentration of nitrate nitrogen (NO3 - -N) but extremely low organic carbon content, commonly found in agricultural runoff, industrial wastewater, and the tail water of some municipal sewage treatment. If such wastewater is directly discharged without effective treatment, it will lead to water eutrophication, triggering ecological disasters such as algal blooms and depletion of dissolved oxygen. However, its characteristics of low carbon and high nitrate nitrogen pose severe challenges to traditional biological nitrogen removal processes - the denitrification process relies on sufficient organic carbon as an electron donor, and the lack of carbon source directly restricts the nitrogen removal efficiency, making it difficult for the total nitrogen in the effluent to meet the standard stably, becoming a difficult problem in water pollution control.

[0003] There are multiple bottlenecks in the existing technology for treating such wastewater. First, the carbon-nitrogen ratio is imbalanced: denitrifying bacteria need to use organic carbon as an electron donor to reduce nitrate nitrogen, but the lack of carbon source in the wastewater forces traditional processes to rely on the addition of exogenous carbon (such as methanol), which not only increases the operating cost but also easily causes secondary pollution. Second, the microbial function is limited: conventional artificial wetlands rely on naturally enriched microbial communities, and the abundance and activity of their nitrogen removal functional bacteria (such as denitrifying bacteria and nitrifying bacteria) are low, making it difficult to achieve efficient simultaneous nitrification-denitrification (SND) under low-carbon conditions. In addition, the filler adaptability is poor: the specific surface area of traditional fillers such as single gravel is limited, the microbial colonization efficiency is low, the system startup period is long (usually 2 to 3 months), and the biofilm is prone to shedding during long-term operation, resulting in insufficient stability. Finally, the problem of greenhouse gas emissions: incomplete denitrification during the nitrogen removal process easily leads to the escape of N2O (a powerful greenhouse gas), which is contrary to the goal of green treatment. The above problems are intertwined, severely restricting the treatment efficiency of the existing technology for low-carbon and high-nitrate wastewater. Summary of the Invention

[0004] To solve the above problems, the present invention provides an artificial wetland system and a method for treating low-carbon and high-nitrate wastewater. Using the litter layer as a supplementary carbon source, aerobic microorganisms are colonized in the aerobic layer, and anaerobic microorganisms are colonized in the anaerobic layer. An aerobic-anaerobic synergistic environment is constructed through the litter layer, aerobic layer, facultative anaerobic layer, anaerobic layer, and support layer, thereby improving the simultaneous nitrification-denitrification efficiency and significantly enhancing the nitrogen removal ability of low-carbon and high-nitrate wastewater.

[0005] The present invention solves the above technical problems through the following technical solutions.

[0006] One of the objectives of the present invention is to provide an artificial wetland system, which includes a system main body. Along the height direction of the system main body, a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer and a support layer are sequentially arranged from top to bottom in the system main body; the aerobic layer is formed by using a first sludge biochar as a carrier and loading domesticated aerobic microbial sludge; the anaerobic layer is formed by using a second sludge biochar as a carrier and loading domesticated anaerobic microbial sludge.

[0007] Furthermore, the preparation method of the aerobic layer includes the following steps: Step 1: Using the sludge in the aeration tank of a sewage treatment plant as the aerobic zone strain, inoculating Hyphomicrobium into the aerobic zone strain, and carrying out domestication culture. During the domestication culture process, the dissolved oxygen is 2 mg / L to 4 mg / L, and domesticated aerobic microbial sludge is obtained.

[0008] Step 2: Adding the domesticated aerobic microbial sludge to the first sludge biochar, and culturing to obtain aerobic packing material, which is the aerobic layer.

[0009] Furthermore, the Hyphomicrobium is Hyphomicrobium sp., the inoculation amount is 5×10 5 cfu / g to 1×10 6 cfu / g, and the time for carrying out domestication culture is 15 d to 25 d.

[0010] Furthermore, the mass ratio of the domesticated aerobic microbial sludge to the first sludge biochar is 4 to 9:1, the culturing time is 3 d to 5 d, and the particle size of the first sludge biochar is 6 mm to 10 mm.

[0011] Furthermore, the preparation method of the anaerobic layer includes the following steps: Step 1: Using the sludge in the upflow anaerobic sludge bed of a sewage treatment plant as the anaerobic zone strain, and inoculating Thauera, Azospirillum and Pseudomonas into the anaerobic zone strain, and carrying out domestication culture. During the domestication culture process, the dissolved oxygen is 0 mg / L to 1 mg / L, and domesticated anaerobic microbial sludge is obtained.

[0012] Step 2: Adding the domesticated anaerobic microbial sludge to the second sludge biochar, and culturing to obtain anaerobic packing material, which is the anaerobic layer.

[0013] Furthermore, the Thauera is Thauera sp., the Azospirillum is Azoarcus sp., the Pseudomonas is Pseudomonas sp., the inoculation amounts of Thauera, Azospirillum and Pseudomonas are all 5×10 5 cfu / g to 1×10 6 cfu / g, and the time for carrying out domestication culture is 15 d to 25 d.

[0014] Furthermore, the mass ratio of the domesticated anaerobic microbial sludge to the second sludge biochar is 4-9:1, the cultivation time is 3d-5d, and the particle size of the second sludge biochar is 6mm-10mm.

[0015] Furthermore, the height ratio of the litter layer, aerobic layer, facultative anaerobic layer, anaerobic layer and support layer is 8-10:30-35:10-15:30-35:10.

[0016] Furthermore, the facultative anaerobic layer is the first gravel layer, the particle size of the first gravel in the first gravel layer is 6mm-10mm, the support layer is the second gravel layer, and the particle size of the second gravel in the second gravel layer is 20mm-40mm.

[0017] The second object of the present invention is to provide a method for treating low-carbon and high-nitrate wastewater, which is carried out by using the above artificial wetland system, and includes the following steps: Along the height direction of the system main body, a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer and a support layer are sequentially loaded into the system main body from top to bottom. The continuous flow operation mode of upper inlet and lower outlet is adopted, and the wastewater to be treated is injected into the system main body for simultaneous nitrification and denitrification nitrogen removal. During the simultaneous nitrification and denitrification nitrogen removal process, the hydraulic retention time is 2.5d-3.5d, and the time for simultaneous nitrification and denitrification nitrogen removal is 25d-35d.

[0018] The present invention has the following beneficial effects compared with the prior art: (8) The artificial wetland system provided by the present invention constructs an aerobic-anaerobic synergistic environment in a layered manner with a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer and a support layer, realizes simultaneous nitrification-denitrification (SND), and the total nitrogen and nitrate nitrogen removal rates are significantly improved compared with the traditional system. Among them, the litter layer can provide an active carbon source for the aerobic layer and the anaerobic layer, enhance the metabolic activity of denitrification functional bacteria (such as denitrifying bacteria), and the porous structure of the biochar provides numerous attachment sites for the aerobic microorganisms domesticated from aerobic microbial sludge and the anaerobic microorganisms domesticated from anaerobic microbial sludge, thereby accelerating the formation rate of the biofilm. Through the synergistic effect of the sludge biochar and the litter layer, the adsorption capacity of the biochar can intercept the dissolved organic matter (such as humus) released by the litter, extend its utilization period, and reduce the loss of carbon source. The facultative anaerobic layer provides a transition environment, coordinates the aerobic and anaerobic processes, can flexibly switch the metabolic mode, and stabilizes the treatment efficiency.

[0019] (9) The present invention uses biochar as a carrier for aerobic and anaerobic microbial sludge. The porous structure of biochar provides numerous attachment sites for aerobic microorganisms domesticated from aerobic microbial sludge and anaerobic microorganisms domesticated from anaerobic microbial sludge, thereby accelerating the formation rate of biofilms. At the same time, a litter layer is introduced as a slow-release carbon source. Through the synergistic effect of the litter layer, domesticated aerobic microorganisms and anaerobic microorganisms, the constructed wetland can be rapidly started, and the efficiency of treating low-carbon and high-nitrate wastewater by the constructed wetland can be significantly enhanced. Moreover, the litter layer accurately supplements the carbon source, solving the problem of carbon-nitrogen ratio imbalance, avoiding the cost of external carbon addition, and preventing the accumulation of N2O due to insufficient carbon source during denitrification.

[0020] (10) The present invention inoculates Hyphomicrobium in aerobic microbial sludge and Thauera, Azospirillum and Pseudomonas in anaerobic microbial sludge. By introducing highly active strains into the sludge, an efficient nitrifying flora can be rapidly constructed. Combining the hierarchical construction of an aerobic-anaerobic synergistic environment (including an aerobic layer, a facultative anaerobic layer, and an anaerobic layer), the constructed wetland can be rapidly started, shortening the time for the wetland to reach operational stability. In addition, the in-situ slow-release carbon source of the litter layer solves the problem of insufficient carbon source during the denitrification of low-carbon wastewater, significantly enhancing the synchronous nitrification-denitrification (SND) efficiency of the constructed wetland. Moreover, the complete denitrification process reduces the emission of greenhouse gases (such as N2O). By recycling waste resources of sludge biochar and plant litter, not only the raw material cost is reduced and the pressure of waste disposal is reduced, but also secondary pollution caused by external carbon addition is avoided, achieving the green cycle goal of "treating waste with waste". BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a schematic structural diagram of the constructed wetland system of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS: 1. System main body, 2. Litter layer, 3. Aerobic layer, 4. Facultative anaerobic layer, 5. Anaerobic layer, 6. Support layer, 7. Distribution tank, 8. Driving device, 9. Wetland plants, 11. Monitoring tube. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0023] The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0024] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. Unless otherwise specifically stated, various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be obtained through market purchase or prepared by existing methods.

[0025] It should be noted that the professional terms used in the present invention are only for the purpose of describing specific embodiments and are not intended to limit the protection scope of the present invention. In the present invention, certain terms are used to refer to specific components. Those skilled in the art should understand that technicians may use different terms to refer to the same component.

[0026] The present invention provides an artificial wetland system, as Figure 1 shown, including a system main body 1. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5 and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom; the aerobic layer 3 is formed by using a first sludge biochar as a carrier and loading domesticated aerobic microbial sludge; the anaerobic layer 5 is formed by using a second sludge biochar as a carrier and loading domesticated anaerobic microbial sludge.

[0027] It should be noted that the artificial wetland system provided by the present invention uses biochar as a carrier to direct aerobic microbial sludge and anaerobic microbial sludge. The porous structure of the biochar provides numerous attachment sites for the aerobic microorganisms domesticated by the aerobic microbial sludge and the anaerobic microorganisms domesticated by the anaerobic microbial sludge, thereby accelerating the formation rate of the biofilm. At the same time, a litter layer 2 is introduced as a slow-release carbon source. Through the synergistic effect of the litter layer 2, domesticated aerobic microorganisms and anaerobic microorganisms, the artificial wetland can be quickly started and the efficiency of treating low-carbon and high-nitrate wastewater by the artificial wetland can be significantly enhanced. Moreover, the litter layer accurately supplements the carbon source, solves the problem of carbon-nitrogen ratio imbalance, avoids the cost of external carbon source addition, and avoids the accumulation of N2O due to insufficient carbon source during denitrification. In addition, the present invention constructs an aerobic-anaerobic synergistic environment in layers by setting the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5 and the support layer 6, realizes simultaneous nitrification-denitrification (SND), and the total nitrogen and nitrate nitrogen removal rates are significantly improved compared with the traditional system. The system startup period is shortened to within 1 month, and the emission of N2O is significantly reduced compared with the conventional startup method system. And through the synergistic effect of the sludge biochar and the litter layer, the adsorption capacity of the biochar can intercept the dissolved organic matter (such as humus) released by the litter, extend its utilization period, and reduce carbon source loss. At the same time, the continuous decomposition of the litter provides an active carbon source for microorganisms, enhances the metabolic activity of denitrifying functional bacteria (such as denitrifying bacteria), and has the advantages of high-efficiency denitrification, green emission reduction and economy, providing a sustainable solution for the treatment of low-carbon and high-nitrate wastewater.

[0028] In some specific embodiments, the preparation method of the aerobic layer 3 includes the following steps: Step 1: Use the sludge in the aeration tank of the sewage treatment plant as the aerobic zone strain, inoculate Hyphomicrobium into the aerobic zone strain, and carry out acclimation cultivation. During the acclimation cultivation process, the dissolved oxygen is 2 mg / L to 4 mg / L to obtain acclimated aerobic microbial sludge.

[0029] Step 2: Add the acclimated aerobic microbial sludge to the first sludge biochar and cultivate to obtain aerobic packing, which is the aerobic layer 3.

[0030] The Hyphomicrobium used in the present invention is Hyphomicrobium sp., purchased from Wuhan Huizao Biotechnology Co., Ltd. The present invention uses the sludge in the aeration tank of the sewage treatment plant as the aerobic zone strain, adds it to the aerobic acclimation reactor, and directionally inoculates Hyphomicrobium. The inoculation amount of Hyphomicrobium is 5×10 5 cfu / g to 1×10 6 cfu / g, and add water containing the basic nutrients required for microbial growth for acclimation. A sludge stirrer and a dissolved oxygen detector are set in the aerobic acclimation reactor. The dissolved oxygen (DO) in the aerobic zone needs to be maintained at 2 mg / L to 4 mg / L to ensure the activity of nitrifying bacteria. Cultivate for 15 d to 20 d to obtain the acclimated aerobic zone strain. During the cultivation process, water is changed every 24 h to obtain Hyphomicrobium in the acclimated aerobic microbial sludge, and a highly efficient nitrifying bacteria group is quickly constructed by introducing highly active strains into the sludge.

[0031] In some specific embodiments, the mass ratio of the acclimated aerobic microbial sludge to the first sludge biochar is 4 to 9:1, the cultivation time is 3 d to 5 d, and the particle size of the first sludge biochar is 6 mm to 10 mm.

[0032] In some specific embodiments, the preparation method of the anaerobic layer 5 includes the following steps Step 1: Use the sludge in the upflow anaerobic sludge bed of the sewage treatment plant as the anaerobic zone strain, and inoculate Thauera, Azospirillum, and Pseudomonas into the anaerobic zone strain for acclimation cultivation. During the acclimation cultivation process, the dissolved oxygen is 0 mg / L to 1 mg / L to obtain acclimated anaerobic microbial sludge.

[0033] Step 2: Add the acclimated anaerobic microbial sludge to the second sludge biochar and cultivate to obtain anaerobic packing, which is the anaerobic layer 5.

[0034] The Thauera used in the present invention is Thauera sp., the Azospirillum is Azoarcus sp., and the Pseudomonas is Pseudomonassp., all purchased from Wuhan Euglena Biotechnology Co., Ltd. In the present invention, the sludge in the upflow anaerobic sludge bed of the sewage treatment plant is used as the anaerobic zone strain, which is added into the anaerobic acclimation reactor, and Thauera, Azospirillum and Pseudomonas are inoculated directionally. The inoculation amounts of Thauera, Azospirillum and Pseudomonas are all 5×10 5 cfu / g~1×10 6 cfu / g, and water containing the basic nutrients required for microbial growth is added for acclimation. A sludge stirrer and a dissolved oxygen detector are arranged in the anaerobic acclimation reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 0 mg / L~1 mg / L to ensure the activity of denitrifying bacteria. After culturing for 15 d~20 d, the acclimated anaerobic zone strain is obtained. Among them, water is changed every 24 h during the culturing process to obtain acclimated anaerobic microbial sludge. A highly efficient nitrifying bacteria group is rapidly constructed by introducing highly active strains into the sludge.

[0035] In some specific embodiments, the mass ratio of the acclimated anaerobic microbial sludge to the second sludge biochar is 4~9:1, the culturing time is 3 d~5 d, and the particle size of the second sludge biochar is 6 mm~10 mm.

[0036] It should be noted that the first sludge biochar or the second sludge biochar adopted in the present invention is prepared by a conventional method, including the following steps: using the dewatered activated sludge of the wastewater treatment plant as the matrix, pyrolyzing at 600℃~800℃ under the atmosphere of protective gas to obtain the activated sludge biochar. The heating rate during the pyrolysis process is 8℃ / min~12℃ / min, the pyrolysis time is 1.8 h~2.2 h, and the water content of the dewatered activated sludge is 70%~80%. In a preferred embodiment, the preparation method of the sludge biochar includes the following steps: taking the dewatered activated sludge from the wastewater treatment plant with a water content of 80%, making the activated sludge into mud balls with a diameter of 30 mm through a mold, placing them outdoors for air drying for 2 d, and pulverizing and screening them after drying until the sludge particle size is 10 mm; sealing the screened sludge with aluminum foil paper and placing it in a muffle furnace, with a heating rate of 10℃ / min, pyrolyzing the sludge under the N2 atmosphere, with a pyrolysis temperature of 700℃ and a pyrolysis time of 2 h; obtaining the sludge biochar.

[0037] In some specific embodiments, the height ratio of the litter layer 2, aerobic layer 3, facultative anaerobic layer 4, anaerobic layer 5, and support layer 6 is 8-10:30-35:10-15:30-35:10. It should be noted that the present invention constructs an aerobic-anaerobic synergistic environment in the form of the litter layer 2, aerobic layer 3, facultative anaerobic layer 4, anaerobic layer 5, and support layer 6. Among them, the litter layer 2 can provide an active carbon source for the aerobic layer 3 and anaerobic layer 5, enhancing the metabolic activity of denitrifying functional bacteria (such as denitrifying bacteria). The porous structure of biochar provides numerous attachment sites for aerobic microorganisms domesticated from aerobic microbial sludge and anaerobic microorganisms domesticated from anaerobic microbial sludge, thereby accelerating the formation rate of biofilms. Through the synergistic effect of sludge biochar and the litter layer, the adsorption capacity of biochar can intercept dissolved organic matter (such as humus) released by the litter, extend its utilization cycle, and reduce carbon source loss. The facultative anaerobic layer 4 provides a transitional environment to coordinate the aerobic and anaerobic processes, including: 1. Oxygen gradient regulation: By consuming residual oxygen or releasing metabolites, maintaining the oxygen concentration gradient between the upper and lower layers, and avoiding direct conflict between the aerobic layer and the anaerobic layer; 2. Resistance to load fluctuations: When the concentration of influent pollutants or hydraulic load changes, the microorganisms in the facultative anaerobic layer can flexibly switch their metabolic modes to stabilize the treatment efficiency.

[0038] It should be noted that the present invention uses sludge biochar as a carrier to load aerobic microbial sludge or anaerobic microbial sludge. Due to its high specific surface area and pore structure, it can be used as an ideal carrier for microbial attachment, significantly increasing the colonization density and stability of functional bacteria. The organic matter (such as humus) adsorbed on its surface can also slowly release carbon sources, alleviating the bottleneck of insufficient carbon sources in wastewater and supporting the metabolism of denitrifying bacteria.

[0039] In some specific embodiments, the facultative anaerobic layer 4 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 6 mm - 10 mm. The support layer 6 is the second gravel layer, and the particle size of the second gravel in the second gravel layer is 20 mm - 40 mm.

[0040] In some specific embodiments, as Figure 1 shown, the constructed wetland system further includes: Wetland plants 9, which are arranged at the top of the system main body 1; a wastewater discharge outlet is provided on the top side wall of the system main body 1, and a wastewater inlet is provided at the bottom; a distribution pool 7, which is connected to the wastewater inlet through an inlet pipe 10, and a driving device 8 is provided on the inlet pipe 5; a monitoring pipe 11, the lower end of which is arranged inside the system main body 1, and the upper end part passes through the wetland plants 9.

[0041] The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. The material of the system main body 1 is acrylic glass. Inside the system main body 1, there are 5 layers arranged from top to bottom along the height direction, which are the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5, and the support layer 6 in sequence.

[0042] The water distribution tank 7 is connected to the wastewater inlet at the top of the system main body 1 through the inlet pipe 10. The inlet pipe 10 is integrated with a driving device 8 to regulate the water flow transportation. The side wall at the top of the inlet pipe 10 is provided with a wastewater discharge outlet and an outlet valve, and the side wall at the bottom is provided with a wastewater inlet and an inlet valve. The water flow control is realized through the inlet pipe 10 and the drainage pipe respectively. In addition, the lower end of the monitoring pipe 11 extends into the system main body 1, and the upper end penetrates through the wetland plants 9 and is exposed to the external environment, which is used to monitor the internal operation parameters of the system in real time.

[0043] The wastewater inlet at the top of the system main body 1 is located 4 cm from the top along its axis, and the wastewater outlet at the bottom is located 4 cm from the bottom along the axis. The treated wastewater is discharged through the water outlet controlled by the outlet valve, and the drainage volume can be accurately controlled by adjusting the outlet valve. The wastewater in the water distribution tank 7 is transported to the system main body 1 through the inlet pipe 10. The inlet pipe 10 is equipped with a peristaltic pump 8 as the driving unit, and the inlet flow rate can be dynamically adjusted through the inlet valve. Aquatic wetland plants 9, such as calamus, are planted on the top of the system main body 1 to enhance the ecological purification function. The monitoring pipe 11 is made of PVC material. Its lower end extends into the system main body 1, and the upper end is exposed outside the plant layer, which can monitor the dissolved oxygen (DO), pH, temperature and other physicochemical parameters in real time in-situ, providing data support for the operation of the system.

[0044] In addition, the present invention also provides a method for treating low-carbon high-nitrate wastewater, which is carried out by using the above artificial wetland system, and includes the following steps: Along the height direction of the system main body 1, there are a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 arranged from top to bottom in the system main body 1 in sequence. The continuous flow operation mode of "inlet at the top and outlet at the bottom" is adopted, and the wastewater to be treated is injected into the system main body for synchronous nitrification and denitrification nitrogen removal.

[0045] In some specific embodiments, the hydraulic retention time is 2.5 d to 3.5 d, and the time for synchronous nitrification and denitrification nitrogen removal is 25 d to 35 d.

[0046] It should be noted that the artificial wetland system of the present invention is inoculated with Hyphomicrobium sp., Thauera sp., Azospirillum sp., and Pseudomonas sp. Hyphomicrobium sp. Thauera sp. Azoarcus sp. Pseudomonassp.), combined with the hierarchical construction of an aerobic-anaerobic coenvironment (including an aerobic layer, a facultative anaerobic layer, and an anaerobic layer), can quickly start the constructed wetland and shorten the time for the wetland to reach operational stability. By in-situ slow-release of carbon sources through the litter layer (such as dry iris litter), the problem of insufficient carbon sources in the denitrification process of low-carbon wastewater is solved, significantly enhancing the synchronous nitrification-denitrification (SND) efficiency of the constructed wetland. Moreover, the complete denitrification process reduces the emission of greenhouse gases (such as N2O). By recycling waste resources from sludge biochar and plant litter, not only the raw material cost is reduced and the pressure of waste disposal is decreased, but also secondary pollution caused by external carbon addition is avoided, achieving the green cycle goal of "treating waste with waste".

[0047] The following is further illustrated by specific examples.

[0048] Example 1 A constructed wetland system, as Figure 1 shown, includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged from top to bottom in the system main body 1.

[0049] The material of the litter layer 2 is dry iris litter.

[0050] The aerobic layer 3 uses sludge biochar with a particle size of 8 mm as a carrier, and loads domesticated aerobic microbial sludge to form aerobic packing, obtaining the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0051] Step 1, using the sludge in the aeration tank of the sewage treatment plant as the aerobic zone strain, adding it into the aerobic domestication reactor, and then inoculating Hyphomicrobium Hyphomicrobium sp., the inoculation amount of Hyphomicrobium is 5×10 5 cfu / g, adding water containing the basic nutrients required for microbial growth for domestication, and setting a sludge stirrer and a dissolved oxygen detector in the aerobic domestication reactor. The dissolved oxygen (DO) in the aerobic zone needs to be maintained at 3 mg / L through the dissolved oxygen detector added to the aerobic domestication reactor. During the cultivation process, water is changed every 24 h, and it is cultured at room temperature for 15 d to obtain domesticated aerobic microbial sludge.

[0052] Step 2, adding the domesticated aerobic microbial sludge to the sludge biochar, and culturing at room temperature for 3 d to obtain aerobic sludge biochar, which is the aerobic layer 3.

[0053] The facultative anaerobic layer 4 is a gravel layer, and the gravel in the gravel layer has a particle size of 10 mm.

[0054] The anaerobic layer 5 uses sludge biochar with a particle size of 8 mm as a carrier, and the domesticated anaerobic microbial sludge is loaded to form anaerobic packing, thus obtaining the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0055] Step 1: The sludge from the upflow anaerobic sludge bed of the sewage treatment plant is used as the anaerobic zone strain and added into the anaerobic domestication reactor. Then, Thauera sp., Azospirillum sp., and Pseudomonas sp. are inoculated in sequence. The inoculation amounts of Thauera sp., Azospirillum sp., and Pseudomonas sp. are all 5×10 cfu / g. Then, water containing the basic nutrients required for microbial growth is added for domestication. A sludge stirrer and a dissolved oxygen detector are set in the anaerobic domestication reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, water is changed every 24 h, and after 15 days of cultivation, the domesticated anaerobic microbial sludge is obtained. Thauera sp., Azospirillum Azoarcus sp. and Pseudomonas Pseudomonas sp. The inoculation amounts of Thauera sp., Azospirillum sp., and Pseudomonas sp. are all 5×10 5 cfu / g. Then, water containing the basic nutrients required for microbial growth is added for domestication. A sludge stirrer and a dissolved oxygen detector are set in the anaerobic domestication reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, water is changed every 24 h, and after 15 days of cultivation, the domesticated anaerobic microbial sludge is obtained.

[0056] Step 2: The domesticated anaerobic microbial sludge is added to the sludge biochar and cultivated for 3 days to obtain anaerobic sludge biochar, which is the anaerobic layer 5.

[0057] The support layer 6 is a gravel layer, and the gravel in the gravel layer has a particle size of 30 mm.

[0058] Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom. The height ratio of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5, and the support layer 6 is 8.5:35:11.5:35:10, thus obtaining the system main body 1.

[0059] Example 2 An artificial wetland system, as Figure 1 shown, includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom.

[0060] The material of the litter layer 2 is dry iris litter.

[0061] The aerobic layer 3 uses sludge biochar with a particle size of 6 mm as a carrier, and the domesticated aerobic microbial sludge is loaded to form aerobic packing, thus obtaining the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0062] Step 1: Use the sludge in the aeration tank of the sewage treatment plant as the aerobic zone bacteria, add it to the aerobic acclimation reactor, and then inoculate Hyphomicrobium Hyphomicrobium sp. The inoculation amount of Hyphomicrobium is 8×10 5 cfu / g. Then add water containing the basic nutrients required for microbial growth for acclimation. Install a sludge stirrer and a dissolved oxygen detector in the aerobic acclimation reactor. Control the dissolved oxygen (DO) in the aerobic zone to be maintained at 4 mg / L through the dissolved oxygen detector added to the aerobic acclimation reactor. During the cultivation process, change the water every 24 h and cultivate at room temperature for 15 d to obtain the acclimated aerobic microbial sludge.

[0063] Step 2: Add the acclimated aerobic microbial sludge to the sludge biochar. The mass ratio of the acclimated aerobic microbial sludge to the sludge biochar is 4:1, and cultivate at room temperature for 3 d to obtain the aerobic sludge biochar, which is the aerobic layer 3.

[0064] The facultative anaerobic layer 4 is a gravel layer, and the particle size of the gravel in the gravel layer is 15 mm.

[0065] The anaerobic layer 5 uses sludge biochar with a particle size of 6 mm as the carrier, and loads the acclimated anaerobic microbial sludge to form anaerobic packing to obtain the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0066] Step 1: Use the sludge in the upflow anaerobic sludge bed of the sewage treatment plant as the anaerobic zone bacteria, add it to the anaerobic acclimation reactor, and then inoculate Thauera Thauera sp., Azospirillum Azoarcus sp. and Pseudomonas Pseudomonas sp. The inoculation amounts of Thauera, Azospirillum and Pseudomonas are all 8×10 5 cfu / g. Then add water containing the basic nutrients required for microbial growth for acclimation. Install a sludge stirrer and a dissolved oxygen detector in the anaerobic acclimation reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 0 mg / L during cultivation. Change the water every 24 h during the cultivation process and cultivate for 15 d to obtain the acclimated anaerobic microbial sludge.

[0067] Step 2: Add the acclimated anaerobic microbial sludge to the sludge biochar and cultivate for 3 d to obtain the anaerobic sludge biochar, which is the anaerobic layer 5.

[0068] The support layer 6 is a gravel layer, and the particle size of the gravel in the gravel layer is 20 mm.

[0069] Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5 and a support layer 6 are successively arranged in the system main body 1 from top to bottom. The height ratio of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5 and the support layer 6 is 8:30:15:30:10 to obtain the system main body 1.

[0070] Example 3 An artificial wetland system, as Figure 1 shown, includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged from top to bottom in the system main body 1.

[0071] The material of the litter layer 2 is dry iris litter.

[0072] The aerobic layer 3 uses sludge biochar with a particle size of 10 mm as a carrier, and the domesticated aerobic microbial sludge is loaded to form aerobic packing, obtaining the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0073] Step 1, using the sludge in the aeration tank of the sewage treatment plant as the aerobic zone bacteria, adding it into the aerobic domestication reactor, and then inoculating Hyphomicrobium Hyphomicrobium sp., the inoculation amount of Hyphomicrobium is 1×10 6 cfu / g, adding water containing the basic nutrients required for microbial growth for domestication, and setting a sludge stirrer and a dissolved oxygen detector in the aerobic domestication reactor. The dissolved oxygen (DO) in the aerobic zone is controlled to be maintained at 4 mg / L through the dissolved oxygen detector added to the aerobic domestication reactor. During the cultivation process, water is changed every 24 h, and it is cultivated at room temperature for 20 d to obtain the domesticated aerobic microbial sludge.

[0074] Step 2, adding the domesticated aerobic microbial sludge to the sludge biochar. The mass ratio of the domesticated aerobic microbial sludge to the sludge biochar is 9:1, and it is cultivated at room temperature for 3 d to obtain the aerobic sludge biochar, which is the aerobic layer 3.

[0075] The facultative anaerobic layer 4 is a gravel layer, and the gravel in the gravel layer has a particle size of 10 mm.

[0076] The anaerobic layer 5 uses sludge biochar with a particle size of 8 mm as a carrier, and the domesticated anaerobic microbial sludge is loaded to form anaerobic packing, obtaining the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0077] Step 1, using the sludge in the upflow anaerobic sludge bed of the sewage treatment plant as the anaerobic zone bacteria, adding it into the anaerobic domestication reactor, and then sequentially inoculating Thauera Thauera sp., Azospirillum Azoarcus sp., and Pseudomonas Pseudomonas sp., the inoculation amounts of Thauera, Azospirillum, and Pseudomonas are all 1×10 6cfu / g, and then add water containing the basic nutrients required for microbial growth for domestication. A sludge stirrer and a dissolved oxygen detector are set in the anaerobic domestication reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, the water is changed every 24 hours, and after 20 days of cultivation, domesticated anaerobic microbial sludge is obtained.

[0078] Step 2: Add the domesticated anaerobic microbial sludge to the sludge biochar. The mass ratio of the domesticated anaerobic microbial sludge to the sludge biochar is 9:1, and cultivate at room temperature for 3 days to obtain anaerobic sludge biochar, which is the anaerobic layer 5.

[0079] The support layer 6 is a gravel layer, and the particle size of the gravel in the gravel layer is 40 mm.

[0080] Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom. The height ratio of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5, and the support layer 6 is 10:35:10:35:10, and the system main body 1 is obtained.

[0081] Comparative Example 1 An artificial wetland system includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom.

[0082] The material of the litter layer 2 is dry iris litter.

[0083] The aerobic layer 3 uses sludge biochar with a particle size of 8 mm as a carrier, and loads domesticated aerobic microbial sludge to form aerobic packing material to obtain the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0084] Step 1: Use the sludge in the aeration tank of the sewage treatment plant as the aerobic zone strain, add it to the aerobic domestication reactor, and then add water containing the basic nutrients required for microbial growth for domestication. A sludge stirrer and a dissolved oxygen detector are set in the aerobic domestication reactor. The dissolved oxygen (DO) in the aerobic zone is controlled by the dissolved oxygen detector added to the aerobic domestication reactor to be maintained at 3 mg / L. During the cultivation process, the water is changed every 24 hours, and after 15 days of cultivation at room temperature, domesticated aerobic microbial sludge is obtained.

[0085] Step 2: Add the domesticated aerobic microbial sludge to the sludge biochar and cultivate at room temperature for 3 days to obtain aerobic sludge biochar, which is the aerobic layer 3.

[0086] The facultative anaerobic layer 4 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 10 mm.

[0087] The anaerobic layer 5 uses sludge biochar with a particle size of 8 mm as a carrier, and loads domesticated anaerobic microbial sludge to form anaerobic packing, obtaining the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0088] Step 1, Use the sludge from the upflow anaerobic sludge bed in the sewage treatment plant as the anaerobic zone strain, add it to the anaerobic domestication reactor, and then add water containing the basic nutrients required for microbial growth for domestication. Set a sludge stirrer and a dissolved oxygen detector in the anaerobic domestication reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, change the water every 24 hours and cultivate for 15 days to obtain domesticated anaerobic microbial sludge.

[0089] The support layer 6 is the second gravel layer, and the particle size of the third gravel in the second gravel layer is 30 mm.

[0090] Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom. The height ratio of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5, and the support layer 6 is 8.5:35:11.5:35:10, obtaining the system main body 1.

[0091] Comparative Example 2 An artificial wetland system includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom.

[0092] The material of the litter layer 2 is dry iris litter.

[0093] The aerobic layer 3 is formed by domesticated aerobic microbial sludge to form aerobic packing. The preparation method of the aerobic layer 3 includes the following steps:

[0094] Use the sludge from the aeration tank in the sewage treatment plant as the aerobic zone strain, add it to the aerobic domestication reactor, and then inoculate Hyphomicrobium Hyphomicrobium sp., The inoculation amount of Hyphomicrobium is 5×10 5cfu / g, and then add water containing the basic nutrients required for microbial growth for domestication. A sludge stirrer and a dissolved oxygen detector are set in the aerobic domestication reactor. The dissolved oxygen (DO) in the aerobic zone is controlled by the dissolved oxygen detector added to the aerobic domestication reactor and needs to be maintained at 3 mg / L. During the cultivation process, water is changed every 24 h, and it is cultivated at room temperature for 15 d to obtain domesticated aerobic microbial sludge, which is the aerobic layer 3.

[0095] The facultative anaerobic layer 4 is a gravel layer, and the gravel in the gravel layer has a particle size of 10 mm.

[0096] The anaerobic layer 5 is an anaerobic filler formed by domesticated anaerobic microbial sludge. The preparation method of the oxygen layer 5 includes the following steps:

[0097] Take the sludge from the upflow anaerobic sludge bed in the sewage treatment plant as the anaerobic zone strain, add it to the anaerobic domestication reactor, and then inoculate Thauera Thauera sp., Azospirillum Azoarcus sp. and Pseudomonas Pseudomonas sp. The inoculation amounts of Thauera, Azospirillum and Pseudomonas are all 5×10 5 cfu / g, and then add water containing the basic nutrients required for microbial growth for domestication. A sludge stirrer and a dissolved oxygen detector are set in the anaerobic domestication reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, water is changed every 24 h, and it is cultivated for 15 d to obtain domesticated anaerobic microbial sludge, which is the anaerobic layer 5.

[0098] The support layer 6 is a gravel layer, and the gravel in the gravel layer has a particle size of 30 mm.

[0099] Along the height direction of the system main body 1, a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer and a support layer are successively arranged in the system main body 1 from top to bottom. The height ratios of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5 and the support layer 6 are 8.5:35:11.5:35:10 to obtain the system main body 1.

[0100] Comparative Example 3 An artificial wetland system includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L; along the height direction of the system main body 1, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5 and a support layer 6 are successively arranged in the system main body 1 from top to bottom.

[0101] The aerobic layer 3 uses sludge biochar with a particle size of 8 mm as a carrier, and domesticated aerobic microbial sludge is loaded to form an aerobic filler to obtain the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0102] Step 1: Take the sludge in the aeration tank of the sewage treatment plant as the aerobic zone bacteria, add it into the aerobic acclimation reactor, then inoculate Hyphomicrobium Hyphomicrobium sp., the inoculation amount of Hyphomicrobium is 5×10 5 cfu / g, then add water containing the basic nutrients required for microbial growth for acclimation, and set a sludge stirrer and a dissolved oxygen detector in the aerobic acclimation reactor. Control the dissolved oxygen (DO) in the aerobic zone to be maintained at 3 mg / L through the dissolved oxygen detector added to the aerobic acclimation reactor. During the cultivation process, change the water every 24 h, and cultivate at room temperature for 15 d to obtain the acclimated aerobic microbial sludge.

[0103] Step 2: Add the acclimated aerobic microbial sludge to the sludge biochar and cultivate at room temperature for 3 d to obtain the aerobic sludge biochar, which is the aerobic layer 3.

[0104] The facultative anaerobic layer 4 is a gravel layer, and the particle size of the gravel in the gravel layer is 10 mm.

[0105] The anaerobic layer 5 uses sludge biochar with a particle size of 8 mm as a carrier, and loads the acclimated anaerobic microbial sludge to form an anaerobic filler to obtain the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0106] Step 1: Take the sludge in the upflow anaerobic sludge bed of the sewage treatment plant as the anaerobic zone bacteria, add it into the anaerobic acclimation reactor, and then inoculate Thauera Thauera sp., Azospirillum Azoarcus sp. and Pseudomonas Pseudomonas sp., the inoculation amounts of Thauera, Azospirillum and Pseudomonas are all 5×10 5 cfu / g, then add water containing the basic nutrients required for microbial growth for acclimation, and set a sludge stirrer and a dissolved oxygen detector in the anaerobic acclimation reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L during cultivation. Change the water every 24 h during the cultivation process and cultivate for 15 d to obtain the acclimated anaerobic microbial sludge.

[0107] Step 2: Add the acclimated anaerobic microbial sludge to the sludge biochar and cultivate for 3 d to obtain the anaerobic sludge biochar, which is the anaerobic layer 5.

[0108] The support layer 6 is a gravel layer, and the particle size of the gravel in the gravel layer is 30 mm.

[0109] Along the height direction of the system main body 1, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5 and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom. The height ratio of the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5 and the support layer 6 is 35:11.5:35:10 to obtain the system main body 1.

[0110] Comparative Example 4 An artificial wetland system includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are successively arranged from top to bottom in the system main body 1.

[0111] The material of the litter layer 2 is dry iris litter.

[0112] The aerobic layer 3 uses sludge biochar with a particle size of 8 mm as a carrier, and domesticated aerobic microbial sludge is loaded to form aerobic packing, obtaining the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0113] Step 1, using the sludge in the aeration tank of the sewage treatment plant as the aerobic zone strain, adding it into the aerobic domestication reactor, and then inoculating Nitrosomonas Nitrosomonas sp. (purchased from Wuhan Huizao Biotechnology Co., Ltd.), the inoculation amount of Nitrosomonas is 5×10 5 cfu / g, and then adding water containing the basic nutrients required for microbial growth for domestication. A sludge stirrer and a dissolved oxygen detector are set in the aerobic domestication reactor. The dissolved oxygen (DO) in the aerobic zone is controlled to be maintained at 3 mg / L through the dissolved oxygen detector added to the aerobic domestication reactor. Water is changed every 24 h during the cultivation process, and it is cultivated at room temperature for 15 d to obtain domesticated aerobic microbial sludge.

[0114] Step 2, adding the domesticated aerobic microbial sludge to the sludge biochar and cultivating at room temperature for 3 d to obtain aerobic sludge biochar, which is the aerobic layer 3.

[0115] The facultative anaerobic layer 4 is a gravel layer, and the gravel in the gravel layer has a particle size of 10 mm.

[0116] The anaerobic layer 5 uses sludge biochar with a particle size of 8 mm as a carrier, and domesticated anaerobic microbial sludge is loaded to form anaerobic packing, obtaining the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0117] Step 1, using the sludge in the upflow anaerobic sludge bed of the sewage treatment plant as the anaerobic zone strain, adding it into the anaerobic domestication reactor, and then successively inoculating Paracoccus Paracoccus sp. (purchased from Wuhan Huizao Biotechnology Co., Ltd.), the inoculation amount of Paracoccus is 5×10 5cfu / g, and then add water containing the basic nutrients required for microbial growth for acclimation. Set a sludge stirrer and a dissolved oxygen detector in the anaerobic acclimation reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, the water is changed every 24 hours, and after 15 days of cultivation, the acclimated anaerobic microbial sludge is obtained.

[0118] Step 2: Add the acclimated anaerobic microbial sludge to the sludge biochar and cultivate for 3 days to obtain the anaerobic sludge biochar, which is the anaerobic layer 5.

[0119] The support layer 6 is the second gravel layer, and the particle size of the third gravel in the second gravel layer is 30 mm.

[0120] Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom. The height ratio of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5, and the support layer 6 is 8.5:35:11.5:35:10, and the system main body 1 is obtained.

[0121] Comparative Example 5 An artificial wetland system, as Figure 1 shown, includes a system main body 1. The system main body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 350 mm, the diameter is 140 mm, the volume of the cylinder is about 5.40 L, and the effective volume is about 2.15 L. Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5, and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom.

[0122] The material of the litter layer 2 is dry iris litter.

[0123] The aerobic layer 3 uses sludge biochar with a particle size of 8 mm as a carrier, and loads the acclimated aerobic microbial sludge to form an aerobic filler to obtain the aerobic layer 3. The preparation method of the aerobic layer 3 includes the following steps:

[0124] Step 1: Use the sludge in the aeration tank of the sewage treatment plant as the aerobic zone strain, add it to the aerobic acclimation reactor, and then inoculate Hyphomicrobium Hyphomicrobium sp., and the inoculation amount of Hyphomicrobium is 5×10 5 cfu / g, and then add water containing the basic nutrients required for microbial growth for acclimation. Set a sludge stirrer and a dissolved oxygen detector in the aerobic acclimation reactor. Control the dissolved oxygen (DO) in the aerobic zone to be maintained at 3 mg / L through the dissolved oxygen detector added to the aerobic acclimation reactor. During the cultivation process, the water is changed every 24 hours, and after 15 days of cultivation at room temperature, the acclimated aerobic microbial sludge is obtained.

[0125] Step 2: Add the domesticated aerobic microbial sludge to the sludge biochar and culture it at room temperature for 3 days to obtain aerobic sludge biochar, which is the aerobic layer 3.

[0126] The facultative anaerobic layer 4 is a gravel layer, and the gravel in the gravel layer has a particle size of 10 mm.

[0127] The anaerobic layer 5 uses sludge biochar with a particle size of 8 mm as a carrier, and the domesticated anaerobic microbial sludge is loaded to form anaerobic packing, thus obtaining the anaerobic layer 5. The preparation method of the anaerobic layer 5 includes the following steps:

[0128] Step 1: Use the sludge from the upflow anaerobic sludge bed in the sewage treatment plant as the anaerobic zone strain, add it to the anaerobic domestication reactor, and then inoculate Azospirillum Azoarcus sp., Paracoccus Paracoccus sp. and Bacillus Bacillus sp. The inoculation amounts of Azospirillum, Paracoccus and Bacillus are all 5×10 5 cfu / g. Then add water containing the basic nutrients required for microbial growth for domestication, and set a sludge stirrer and a dissolved oxygen detector in the anaerobic domestication reactor. The dissolved oxygen (DO) in the anaerobic zone needs to be maintained at 1 mg / L for cultivation. During the cultivation process, the water is changed every 24 hours, and after 15 days of cultivation, the domesticated anaerobic microbial sludge is obtained.

[0129] Step 2: Add the domesticated anaerobic microbial sludge to the sludge biochar and culture it for 3 days to obtain anaerobic sludge biochar, which is the anaerobic layer 5.

[0130] The support layer 6 is a gravel layer, and the gravel in the gravel layer has a particle size of 30 mm.

[0131] Along the height direction of the system main body 1, a litter layer 2, an aerobic layer 3, a facultative anaerobic layer 4, an anaerobic layer 5 and a support layer 6 are sequentially arranged in the system main body 1 from top to bottom. The height ratio of the litter layer 2, the aerobic layer 3, the facultative anaerobic layer 4, the anaerobic layer 5 and the support layer 6 is 8.5:35:11.5:35:10, thus obtaining the system main body 1.

[0132] Using the artificial wetland systems of Example 1 and Comparative Examples 1 to 5 to treat low-carbon high-nitrate wastewater, including the following steps: Step 1: Along the height direction of the system main body 1, a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer and a support layer are sequentially arranged in the system main body 1 from top to bottom. Adopt the continuous flow operation mode of upflow and downflow, inject the wastewater to be treated into the system main body, and carry out simultaneous nitrification and denitrification for nitrogen removal.

[0133] Step 2: Add the wastewater to be treated into the mixing pool 7. The inlet pipe 10 conveys the wastewater in the mixing pool 7 to the system main body 1 through the power mechanism 8 via the wastewater inlet, and controls the influent flow rate through the inlet valve. The treated water is discharged through the wastewater discharge outlet provided on the top side wall of the system main body 1. The system main body 1 operates in a continuous flow mode of upward flow, where the hydraulic retention time is 3 days, and simultaneous nitrification and denitrification nitrogen removal is carried out.

[0134] In addition, in Comparative Example 2, the aerobic layer and anaerobic layer are only domesticated aerobic microbial sludge and domesticated anaerobic microbial sludge. Therefore, before the simultaneous nitrification and denitrification nitrogen removal reaction, microbial film formation treatment is required. That is, after a litter layer, an aerobic layer, a facultative anaerobic layer, an anaerobic layer, and a support layer are sequentially arranged in the system main body 1 from top to bottom, an intermittent operation mode of upward inlet and downward outlet is adopted. First, anaerobic activated sludge and wastewater are mixed at a volume ratio of 1:400 and then added to the anaerobic zone of the system main body 1 to form an anaerobic activated sludge layer by film formation. Then, aerobic activated sludge and wastewater are mixed at a volume ratio of 1:400 and added to the aerobic zone of the system main body 1 to form an aerobic activated sludge layer by film formation.

[0135] Among them, the COD of the wastewater to be treated in Example 1 and Comparative Examples 1 - 5 is 50 ± 2 mg / L, NH4 + -N is 3 ± 2 mg / L, NO3 - -N is 14 ± 2 mg / L, and TN is 17 ± 2 mg / L. Nitrogen removal is carried out under low carbon conditions, and the results are shown in Table 1.

[0136] Table 1 Nitrogen removal results of the constructed wetland systems in Example 1 and Comparative Examples 1 - 5 As shown in Table 1, the effluent water quality of the constructed wetland system startup method of the present invention is stable. The COD removal efficiency is 94.82%, the NH4 + -N removal rate is 95.33%, the NO3 - -N removal rate is 96.43%, and the TN removal rate is 96.24%. Compared with the conventional startup methods of the constructed wetland systems in Comparative Examples 1 - 5, the sewage treatment effect is better.

[0137] Measure the N2O emissions of the constructed wetland systems in Example 1 and Comparative Examples 1 - 5. The results are shown in Table 2.

[0138] Table 2 Comparison of N2O emissions in Example 1 and Comparative Examples 1 - 5 As can be seen from Table 2, compared with the conventional startup method of the constructed wetland system, the N2O emissions of the constructed wetland system startup method of the present invention have a better emission reduction effect.

[0139] It should be noted that when the present invention involves a numerical range, it should be understood that both endpoints of each numerical range and any value between the two endpoints can be selected. Since the steps and methods adopted are the same as those in the embodiments, in order to avoid redundancy, the present invention describes the preferred embodiments. Although the preferred embodiments of the present invention have been described, those skilled in the art can make additional changes and modifications to these embodiments once they know the basic creative concept. Therefore, the appended claims are intended to be construed as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0140] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalent technologies, the present invention is also intended to include these changes and modifications.

Claims

1. An artificial wetland system, comprising a system main body (1), characterized in that, Along the height direction of the system main body (1), a litter layer (2), an aerobic layer (3), a facultative anaerobic layer (4), an anaerobic layer (5) and a support layer (6) are successively arranged in the system main body (1) from top to bottom; The aerobic layer (3) is formed by using the first sludge biochar as a carrier and loading domesticated aerobic microbial sludge; the anaerobic layer (5) is formed by using the second sludge biochar as a carrier and loading domesticated anaerobic microbial sludge.

2. The constructed wetland system according to claim 1, characterized in that, A preparation method of the aerobic layer (3) includes the following steps: Taking the sludge in the aeration tank of a sewage treatment plant as the aerobic zone strain, inoculating Hyphomicrobium into the aerobic zone strain, and carrying out acclimation culture. During the acclimation culture process, the dissolved oxygen is 2 mg / L to 4 mg / L to obtain domesticated aerobic microbial sludge; Adding the domesticated aerobic microbial sludge into the first sludge biochar, and culturing to obtain aerobic packing, which is the aerobic layer (3).

3. The constructed wetland system according to claim 2, wherein Mycelium Hyphomicrobium sp., the inoculum size was 5×10 5 cfu / g~1×10 6 cfu / g, and the acclimatization culture time is 15d to 25d.

4. The constructed wetland system according to claim 2, wherein, The mass ratio of the domesticated aerobic microbial sludge to the first sludge biochar is 4 to 9:1, the culture time is 3 d to 5 d, and the particle size of the first sludge biochar is 6 mm to 10 mm.

5. The constructed wetland system according to claim 1, characterized in that, The preparation method of the domesticated anaerobic microbial sludge includes the following steps: Taking the sludge in the upflow anaerobic sludge bed of a sewage treatment plant as the anaerobic zone strain, and inoculating Thauera, Azoarcus and Pseudomonas into the anaerobic zone strain, and carrying out acclimation culture. During the acclimation culture process, the dissolved oxygen is 0 mg / L to 1 mg / L to obtain domesticated anaerobic microbial sludge; Adding the domesticated anaerobic microbial sludge into the second sludge biochar, and culturing to obtain anaerobic packing, which is the anaerobic layer (5).

6. The constructed wetland system according to claim 5, wherein, Thauerbacteria is Thauera sp., Azotobacter is Azoarcus sp., Pseudomonas is Pseudomonas sp. The inoculation amounts of Thauerbacteria, Azotobacter and Pseudomonas are all 5×10 5 cfu / g to 1×10 6 cfu / g, and the domestication culture time is 15 d to 25 d.

7. The constructed wetland system according to claim 5, characterized in that, The mass ratio of the domesticated anaerobic microbial sludge to the second sludge biochar is 4 to 9:1, the culture time is 3 d to 5 d, and the particle size of the second sludge biochar is 6 mm to 10 mm.

8. The constructed wetland system according to claim 1, characterized in that, The height ratio of the support layer (6), the anaerobic layer (5) and the aerobic layer (3) is 10:30 - 35:30 - 35, the height ratio of the support layer (6) and the facultative anaerobic layer (4) is 10:10 - 15, and the height ratio of the support layer (6) and the litter layer (2) is 10:8 - 10.

9. The constructed wetland system according to claim 1, wherein The facultative anaerobic layer (4) is a first gravel layer, the particle size of the first gravel in the first gravel layer is 6 mm to 10 mm, the support layer (6) is a second gravel layer, and the particle size of the second gravel in the second gravel layer is 20 mm to 40 mm.

10. A method for treating low-carbon and high-nitrate wastewater, characterized in that, Using the constructed wetland system according to any one of claims 1 to 9, includes the following steps: Along the height direction of the system main body (1), the litter layer (2), the aerobic layer (3), the facultative anaerobic layer (4), the anaerobic layer (5) and the support layer (6) are successively loaded into the system main body (1) from top to bottom. Adopting an up - in and down - out continuous flow operation mode, injecting the wastewater to be treated into the system main body (1) for simultaneous nitrification and denitrification nitrogen removal. During the simultaneous nitrification and denitrification nitrogen removal process, the hydraulic retention time is 2.5 d to 3.5 d, and the time for simultaneous nitrification and denitrification nitrogen removal is 25 d to 35 d.

Images