Artificial wetland system of iron-containing sludge biochar and method for reinforcing Feammox reaction denitrification

Abstract

The invention belongs to the technical field of wastewater treatment, and particularly relates to an artificial wetland system of iron-containing sludge biochar and a method for reinforcing Feammox reaction denitrification. Comprising a system body, the top end of the system body is open, the bottom end of the system body is closed, a supporting layer and a matrix mixing layer are vertically stacked in the system body in the height direction of the system body, and the height ratio of the supporting layer to the matrix mixing layer is 1: (5-7); the supporting layer is a first gravel layer, and the matrix mixing layer is prepared by mixing iron-containing sludge biochar and second gravel according to the volume ratio of 1: (2.5-5). According to the constructed artificial wetland system, the rich porous structure and the high specific surface area of the iron-containing sludge biochar provide an ideal adhesion matrix for microorganisms, slowly-released iron ions not only provide necessary nutritional ingredients for the microorganisms, but also further excite the activity of the microorganisms by adjusting the oxidation-reduction potential and enhancing electron transfer, so that the biological activity of the microorganisms is improved. The denitrification reaction is promoted.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to an artificial wetland system containing iron sludge biochar and a method for enhancing Feammox reaction denitrification. Background Art

[0002] With the acceleration of population growth and industrialization, nitrogen pollution has become one of the major threats facing the global aquatic ecosystem. Excessive accumulation of nitrogen in water bodies will cause eutrophication, leading to the massive reproduction of algae, consuming oxygen in the water body, causing water quality deterioration and endangering the living environment of aquatic organisms. This chain reaction not only affects the ecological balance, but also aggravates the problem of water resource pollution, posing a serious challenge to human life and the ecosystem. Traditional methods of nitrogen pollution removal mainly rely on nitrification-denitrification processes, but this process consumes a lot of carbon sources and oxygen, and has high treatment costs. It is difficult to effectively deal with nitrogen pollution problems in low-carbon or carbon-free environments. Anaerobic ammonia oxidation (Anammox) technology is an efficient denitrification method developed in recent years. It uses autotrophic microorganisms to convert ammonia nitrogen (NH4 + -N) into nitrogen (N2), significantly reducing dependence on organic carbon sources. However, Anammox is limited in its application in low-carbon or carbon-free environments due to its slow reaction rate, which generally makes it difficult to achieve high denitrification efficiency.

[0003] In recent years, iron-coupled anaerobic ammonium oxidation (Feammox) has gradually attracted attention. This process promotes the oxidation of ammonia nitrogen to nitrogen gas under anaerobic conditions by using iron as an electron acceptor. Feammox is not only suitable for low-carbon environments, but also can effectively reduce nitrogen pollution in water bodies. For example, Kadam et al. Magnetite addition reduces nitrite requirement for efficient anaerobic ammonium oxidation by facilitating mutualism of ANAMMOX and FEAMMOX bacteria. Sci. Total. Environ. 946, 174497. pointed out that in the ANAMMOX reactor, the introduction of magnetite can significantly promote the occurrence of Feammox reaction and effectively reduce the nitrogen load of water bodies. However, due to the low reaction rate of Feammox and limited electron transfer efficiency, it faces many challenges in practical applications. Summary of the Invention

[0004] In order to solve the above problems, the present invention provides an artificial wetland system of iron-containing sludge biochar and a method for strengthening Feammox reaction denitrification. An artificial wetland system is constructed with iron-containing sludge biochar and a second gravel as a matrix layer and a first gravel as a support layer. The rich porous structure and high specific surface area of ​​the iron-containing sludge biochar provide an ideal attachment matrix for microorganisms. The slowly released iron ions not only provide the necessary nutrients for microorganisms, but also further stimulate the activity of microorganisms by regulating the redox potential and enhancing electron transfer, thereby improving the stability and activity of the microbial community, further promoting the denitrification reaction, providing sufficient electron donors for the Feammox reaction, and significantly enhancing the efficiency of the iron-coupled anaerobic ammonia oxidation (Feammox) reaction. The participation of iron ions effectively accelerates the conversion of ammonia nitrogen (NH4 + The conversion process of nitrogen (N) to nitrogen (N2) greatly improves the denitrification effect, especially in low-carbon or carbon-free environments. This method significantly reduces the dependence on external carbon sources, making the denitrification process more efficient and sustainable.

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

[0006] One of the purposes of the present invention is to provide an artificial wetland system of iron-containing sludge biochar, comprising a system main body, the top of the system main body is open and the bottom is closed, and a support layer and a matrix mixed layer are stacked up and down in the system main body, wherein the height ratio of the support layer and the matrix mixed layer is 1:5~7; the support layer is a first gravel layer, and the matrix mixed layer is prepared by mixing iron-containing sludge biochar and a second gravel in a volume ratio of 1:2.5~5.

[0007] Furthermore, the particle size of the first gravel in the first gravel layer is 20 mm to 40 mm, the particle size of the iron-containing sludge biochar is 8 mm to 15 mm, and the particle size of the second gravel is 8 mm to 15 mm.

[0008] Furthermore, the method for preparing the iron-containing sludge biochar comprises the following steps:

[0009] S1. Using dehydrated activated sludge from a wastewater plant as the matrix, but under a protective gas atmosphere, pyrolysis at 600℃~800℃ was performed to obtain activated sludge biochar;

[0010] S2, soak the activated sludge biochar in water containing Fe 3+ In the solution, Fe 3+ The iron-containing sludge biochar was obtained by loading it on activated sludge biochar.

[0011] Furthermore, activated sludge biochar and Fe 3+ The mass ratio of the solution is 1:6~8, containing Fe 3+ Fe in solution 3+The concentration is 0.3mol / L~0.5mol / L, containing Fe 3+ The solution is one of ferric sulfate, ferric nitrate, and ferric chloride. The soaking temperature is room temperature and the soaking time is 15h to 28h.

[0012] Furthermore, the protective gas is nitrogen or inert gas, the heating rate during the pyrolysis process is 8°C / min to 12°C / min, the pyrolysis time is 1.8h to 2.2h, and the water content of the dehydrated activated sludge is 70% to 80%.

[0013] Furthermore, the artificial wetland system further comprises:

[0014] A water distribution tank connected to the bottom end of the system body via a water inlet pipe, wherein the water inlet pipe is provided with a power mechanism;

[0015] Wetland plants are arranged at the top of the system body. The top side wall of the system body is provided with a wastewater outlet, the bottom side wall is provided with a wastewater inlet, the wastewater inlet is connected to the water inlet pipe through an inlet valve, and the water outlet is provided with a water outlet valve;

[0016] The monitoring pipe has a lower end arranged in the system body and an upper end portion passing through the wetland plants.

[0017] A second object of the present invention is to provide a method for enhancing Feammox reaction denitrification, which is carried out using the above-mentioned artificial wetland system containing iron sludge biochar, comprising the following steps:

[0018] In step 1, the sludge in the wastewater aeration tank is used as the bacterial strain in the aerobic zone and is domesticated to obtain aerobic activated sludge, and the sludge in the wastewater upflow anaerobic sludge bed is used as the bacterial strain in the anaerobic zone and is domesticated to obtain anaerobic activated sludge.

[0019] Step 2: The system body is provided with an anaerobic zone and an aerobic zone. The anaerobic zone is located at the lower end of the aerobic zone along the height direction of the system body. An intermittent operation mode of top-in and bottom-out is adopted. The anaerobic activated sludge and wastewater are first mixed and then added to the anaerobic zone of the system body to form an anaerobic activated sludge layer by forming a biofilm. Then, the aerobic activated sludge and wastewater are mixed and added to the aerobic zone of the system body to form a biofilm to form an aerobic activated sludge layer.

[0020] Step 3: Inject the wastewater to be treated into the main body of the system in a continuous flow manner of upstream flow to carry out enhanced Feammox reaction denitrification.

[0021] Furthermore, the aerobic zone bacterial strain is domesticated in the following manner: the aerobic zone bacterial strain is added to the reactor, wastewater is added and stirred to adjust the dissolved oxygen concentration of the reactor to 1 mg / L to 3 mg / L, and cultured for 15 to 20 days to obtain the domesticated aerobic zone bacterial strain, wherein the water is changed every 24 hours.

[0022] Furthermore, the method of acclimating the anaerobic zone bacteria is as follows: adding the anaerobic zone bacteria to the reactor, adding wastewater and stirring to adjust the dissolved oxygen concentration of the reactor to <1 mg / L, culturing for 15 to 20 days to obtain the acclimated anaerobic zone bacteria, wherein the water is changed every 24 hours during the culturing process.

[0023] Furthermore, the volume ratio of the anaerobic zone to the aerobic zone is 1:1-3, the volume ratio of the anaerobic activated sludge or aerobic activated sludge to the wastewater is 1:350-450, and during the enhanced Feammox reaction denitrification process, the hydraulic retention time is 2.5d-3.5d, and the time for enhanced Feammox reaction denitrification is 25d-35d.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] (1) The present invention uses iron-containing sludge biochar and the second gravel as the matrix layer and the first gravel as the support layer to construct an artificial wetland system. The rich porous structure and high specific surface area of ​​the iron-containing sludge biochar provide an ideal attachment matrix for microorganisms. The slowly released iron ions not only provide the necessary nutrients for microorganisms, but also further stimulate the activity of microorganisms by regulating the redox potential and enhancing electron transfer, thereby improving the stability and activity of the microbial community, further promoting the denitrification reaction, providing sufficient electron donors for the Feammox reaction, and significantly enhancing the efficiency of the iron-coupled anaerobic ammonia oxidation (Feammox) reaction. The participation of iron ions effectively accelerates the denitrification of ammonia nitrogen (NH4 + The conversion process of nitrogen (N) to nitrogen (N2) greatly improves the denitrification effect, especially in low-carbon or carbon-free environments. This method significantly reduces the dependence on external carbon sources, making the denitrification process more efficient and sustainable.

[0026] (2) The artificial wetland system of the present invention uses iron-containing sludge biochar and the second gravel as the matrix layer to carry out enhanced Feammox reaction denitrification, thereby achieving low-energy green and environmentally friendly wastewater treatment. The Feammox reaction does not rely on exogenous organic carbon, so no additional energy is required to supply the carbon source, which significantly reduces the energy consumption in the treatment process. In addition, as a low-energy, naturally driven treatment device, the artificial wetland system further reduces energy demand by combining iron-containing sludge biochar, achieving low-energy green and environmentally friendly wastewater treatment, thereby making the method more sustainable and economical in practical applications. At the same time, by adopting sludge biochar, not only industrial waste (such as sludge) is effectively utilized, but also the recycling of solid waste in the wastewater treatment process is promoted, which helps to realize the resource utilization of waste and meets the requirements of environmental protection and sustainable development.

[0027] (3) The iron-containing sludge biochar used in the present invention can provide a more suitable environment for the growth of anaerobic bacteria such as Geobacter during the enhanced Feammox reaction denitrification process. The abundance of Geobacter in the artificial wetland system is 9.19%. In the Feammox reaction process, Geobacter can reduce the Fe 3+ Fe 2+ , providing electrons to promote NH4 + -N is converted into N2, thereby achieving NH4 + -N removal, the iron-containing sludge biochar-based artificial wetland system provided by the present invention strengthens the Feammox reaction denitrification, and removes NH4 + The removal rates of -N and TN reached 98.56% and 94.13%, respectively, and the TN removal load was 0.128 kgN·m -3 ·d -1 .

[0028] (4) The iron-containing sludge biochar-based artificial wetland system provided by the present invention can effectively reduce the emission of N2O from the wetland. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 This is a schematic structural diagram of the artificial wetland system of iron-containing sludge biochar according to the present invention.

[0031] 1. System body, 2. Support layer, 3. Matrix mixing layer, 4. Water distribution tank, 5. Water inlet pipe, 6. Power mechanism, 7. Wetland plants, 8. Monitoring pipe. DETAILED DESCRIPTION

[0032] The following will provide a clear and complete description of the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts shall fall within the scope of protection of the present invention.

[0033] 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 scope of protection of the present invention. Unless otherwise specified, the various raw materials, reagents, instruments and equipment used in the following embodiments of the present invention can be purchased from the market or prepared by existing methods.

[0034] 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 scope of protection of the present invention. Certain terms are used in the present invention to refer to specific components. Those skilled in the art will understand that technicians may use different terms to refer to the same component.

[0035] The present invention provides an artificial wetland system containing iron sludge biochar, such as Figure 1 As shown, it includes a system body 1, the top of the system body 1 is open and the bottom is closed, and a support layer 2 and a matrix mixed layer 3 are stacked up and down in the system body 1, wherein the height ratio of the support layer 2 and the matrix mixed layer 3 is 1:5-7; the support layer 2 is the first gravel layer, and the matrix mixed layer 3 is prepared by mixing iron-containing sludge biochar and the second gravel in a volume ratio of 1:2.5-5.

[0036] It should be noted that in recent years, the sludge biochar matrix has achieved good results in water purification due to its advantages in applicability, adsorption, availability and stability. The present invention uses iron-containing sludge biochar and the second gravel as the matrix layer and the first gravel as the support layer to construct an artificial wetland system. The rich porous structure and high specific surface area of ​​the iron-containing sludge biochar provide an ideal attachment matrix for microorganisms. The slowly released iron ions not only provide the necessary nutrients for microorganisms, but also further stimulate the activity of microorganisms by regulating the redox potential and enhancing electron transfer, thereby improving the stability and activity of the microbial community, further promoting the denitrification reaction, providing sufficient electron donors for the Feammox reaction, and significantly enhancing the efficiency of the iron-coupled anaerobic ammonia oxidation (Feammox) reaction. The participation of iron ions effectively accelerates the denitrification of ammonia nitrogen (NH4 + The conversion process of nitrogen (N) to nitrogen (N2) greatly improves the denitrification effect, especially in low-carbon or carbon-free environments. This method significantly reduces the dependence on external carbon sources, making the denitrification process more efficient and sustainable.

[0037] In some specific embodiments, the particle size of the first gravel in the first gravel layer is 20 mm to 40 mm, the particle size of the iron-containing sludge biochar is 8 mm to 15 mm, and the particle size of the second gravel is 8 mm to 15 mm. The present invention uses the first gravel layer as the support layer 2. The gravel has good mechanical strength and is not easily compressed or deformed. It can maintain the physical structure of the wetland matrix during long-term operation and reduce the risk of reaction blockage in the artificial wetland system. The iron-containing sludge biochar and the second gravel form a matrix mixed layer 3. On the one hand, the second gravel provides a stable structural layer for the iron-containing sludge biochar, preventing the iron-containing sludge biochar from being subjected to long-term compression and deformation. On the other hand, the second gravel can provide sufficient reaction channels for the iron-containing sludge biochar, thereby improving the stability and activity of the microbial community and further promoting the denitrification reaction.

[0038] In some specific embodiments, the method for preparing iron-containing sludge biochar comprises the following steps:

[0039] The activated sludge biochar is obtained by pyrolysis at 600℃~800℃ under protective gas atmosphere using dehydrated activated sludge from wastewater plants as the matrix;

[0040] Activated sludge biochar was soaked in Fe 3+ In the solution, Fe 3+ The iron-containing sludge biochar was obtained by loading it on activated sludge biochar.

[0041] The present invention uses iron-containing sludge biochar to provide an attachment matrix for microorganisms, increase the reaction surface area, and gradually release iron ions, providing additional electron acceptors for the Feammox reaction. In addition, the iron-containing sludge biochar, with its porous structure and high specific surface area, can further promote the growth of anaerobic microorganisms and improve the efficiency of anaerobic ammonia oxidation. Therefore, using iron-containing sludge biochar to enhance the Feammox reaction under low-carbon conditions can enhance the denitrification effect, improve the microbial environment, reduce carbon source demand, and improve the stability and pollution resistance of the wetland, thereby achieving efficient and sustainable water purification.

[0042] In some embodiments, activated sludge biochar and Fe 3+ The mass ratio of the solution is 1:6~8, containing Fe 3+ Fe in solution 3+ The concentration is 0.3mol / L~0.5mol / L, containing Fe 3+ The solution is one of ferric sulfate, ferric nitrate, and ferric chloride. The soaking temperature is room temperature and the soaking time is 15h to 28h.

[0043] In some specific embodiments, the protective gas is nitrogen or an inert gas, the heating rate during the pyrolysis process is 8° C. / min to 12° C. / min, the pyrolysis time is 1.8 h to 2.2 h, and the water content of the dehydrated activated sludge is 70% to 80%.

[0044] In some specific embodiments, the activated sludge dehydrated from the wastewater plant is first made into mud balls with a diameter of 20 mm to 30 mm through a mold, and then placed outdoors for air drying for 2 to 3 days. After drying, the sludge is crushed and sieved to a sludge particle size of 8 mm to 15 mm, and then sealed with aluminum foil and placed in a muffle furnace for pyrolysis.

[0045] In a specific embodiment, after soaking, the biochar is repeatedly washed with deionized water to remove unreacted iron salts and impurities, and then the iron-containing sludge biochar is dried to a constant weight to finally obtain the iron-containing sludge biochar.

[0046] In some specific embodiments, Figure 1 As shown, the artificial wetland system also includes:

[0047] A water distribution tank 4 is connected to the bottom end of the system body 1 through an inlet pipe 5, and a power mechanism 6 is provided on the inlet pipe 5; wetland plants 7 are arranged at the top of the system body 1, and a wastewater outlet is provided on the top side wall of the system body 1, and a wastewater inlet is provided on the bottom side wall. The wastewater inlet is connected to the inlet pipe 5 through an inlet valve, and an outlet valve is provided on the water outlet; a monitoring pipe 8, the lower end of which is arranged in the system body 1, and the upper end part passes through the wetland plants 7.

[0048] The system body 1 is a cylindrical cavity with an open top and a closed bottom. The height of the cylindrical cavity is 320 mm and the diameter is 140 mm. The cylindrical volume is approximately 4.92 L and the effective volume is approximately 1.85 L. The system body 1 is made of acrylic glass and is wrapped with black plastic cloth. The height of the support layer 2 is 40 mm and the height of the matrix mixing layer 3 is 240 mm.

[0049] The axial distance between the wastewater outlet and the top of the system body 1 is 4 cm. The treated wastewater flows out from the outlet. The outlet is equipped with an outlet valve, and the discharge volume is controlled by the outlet valve. The axial distance between the wastewater inlet and the bottom of the system body 1 is 4 cm. The water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow is controlled by the water inlet valve. The wetland plant 7 is an aquatic plant, such as calamus. The power mechanism 6 is a peristaltic pump, and the monitoring tube 8 is a PVC tube, the lower end of which is set in the system body 1 for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0050] In addition, the present invention also provides a method for enhancing Feammox reaction denitrification, which is performed using the above-mentioned artificial wetland system containing iron sludge biochar, comprising the following steps:

[0051] In step 1, the sludge in the wastewater aeration tank of the sewage treatment plant is used as the bacterial strain in the aerobic zone, and is domesticated to obtain aerobic activated sludge. The sludge in the wastewater upflow anaerobic sludge bed of the sewage treatment plant is used as the bacterial strain in the anaerobic zone, and is domesticated to obtain anaerobic activated sludge.

[0052] Step 2: The system body is provided with an anaerobic zone and an aerobic zone. The anaerobic zone is located at the lower end of the aerobic zone along the height direction of the system body. An intermittent operation mode of top-in and bottom-out is adopted. The anaerobic activated sludge and wastewater are first mixed and then added to the anaerobic zone of the system body to form an anaerobic activated sludge layer by forming a biofilm. Then, the aerobic activated sludge and wastewater are mixed and added to the aerobic zone of the system body to form a biofilm to form an aerobic activated sludge layer; until the system body operates stably.

[0053] In step 3, the continuous flow mode of the above upstream flow is adopted, the hydraulic retention time is set, and then the wastewater to be treated is injected into the main body of the system for enhanced Feammox reaction denitrification.

[0054] The artificial wetland system of the present invention uses iron-containing sludge biochar and the second gravel as the matrix layer to carry out enhanced Feammox reaction denitrification, thereby achieving low-energy green and environmentally friendly wastewater treatment. The Feammox reaction does not need to rely on exogenous organic carbon, so no additional energy is required to supply the carbon source, which significantly reduces the energy consumption in the treatment process. In addition, as a low-energy, naturally driven treatment device, the artificial wetland system further reduces energy demand by combining iron-containing sludge biochar, achieving low-energy green and environmentally friendly wastewater treatment, thereby making the method more sustainable and economical in practical applications. At the same time, by adopting sludge biochar, not only industrial waste (such as sludge) is effectively utilized, but also the recycling of solid waste in the wastewater treatment process is promoted, which helps to realize waste resource utilization and meets the requirements of environmental protection and sustainable development.

[0055] During the Feammox reaction of iron-containing sludge biochar, a more suitable environment can be provided for the growth of anaerobic bacteria such as Geobacter. During the Feammox reaction, Geobacter can reduce Fe 3+ Fe 2+ , providing electrons to promote NH4 + -N is converted into N2, thereby achieving NH4 + -N removal.

[0056] In some specific embodiments, the method for acclimating the aerobic zone strain is: adding the aerobic zone strain to the reactor, adding water and stirring to adjust the dissolved oxygen concentration of the reactor to 1 mg / L to 3 mg / L, and culturing for 15 to 20 days to obtain the acclimated aerobic zone strain, wherein the water is changed every 24 hours during the cultivation process.

[0057] In some specific embodiments, the method for acclimating the anaerobic zone bacteria is as follows: adding the anaerobic zone bacteria to a reactor, adding water and stirring to adjust the dissolved oxygen concentration of the reactor to <1 mg / L, and culturing for 15 to 20 days to obtain the acclimated anaerobic zone bacteria, wherein the water is changed every 24 hours during the culturing process.

[0058] It should be noted that during the aerobic zone or anaerobic zone bacterial acclimation process, basic nutrients required for microbial growth must be added during water adjustment to ensure normal growth and metabolism of the microorganisms in the activated sludge. Activated sludge is acclimated using artificial water addition to quickly adapt the microorganisms in the sludge to growth, resulting in activated sludge.

[0059] In some specific embodiments, the volume ratio of the anaerobic zone to the aerobic zone is 1:1-3, the volume ratio of anaerobic activated sludge or aerobic activated sludge to wastewater is 1:350-450, and during the enhanced Feammox reaction denitrification process, the hydraulic retention time is 2.5d-3.5d, and the time for enhanced Feammox reaction denitrification is 25d-35d.

[0060] The following is further described through specific examples.

[0061] Example 1

[0062] The present invention provides an artificial wetland system containing iron sludge biochar, comprising:

[0063] System body 1, the top of the system body 1 is open and the bottom is closed, the height is 320mm, the diameter is 140mm, the cylindrical volume is about 4.92L, and the effective volume is about 1.85L; the system body 1 is wrapped with black plastic cloth.

[0064] A support layer 2 and a matrix mixing layer 3 are stacked up and down in the system body 1. The height of the support layer 2 is 40 mm, and the height of the matrix mixing layer 3 is 240 mm. The support layer 2 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 30 mm. The matrix mixing layer 3 is prepared by mixing iron-containing sludge biochar and the second gravel in a volume ratio of 3:10. The particle size of the iron-containing sludge biochar is 10 mm, and the particle size of the second gravel is 10 mm.

[0065] The water distribution tank 4 is connected to the bottom end of the system body 1 through a water inlet pipe 5, and a peristaltic pump is provided on the water inlet pipe 5.

[0066] Wetland plant 7, the wetland plant is calamus, which is arranged at the top of the system body 1, the axial distance between the wastewater outlet of the system body 1 and the top is 4 cm, the treated wastewater flows out from the outlet, the outlet is provided with an outlet valve, the discharge volume is controlled by the outlet valve, the axial distance between the wastewater inlet and the bottom of the system body 1 is 4 cm, the water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow rate is controlled by the water inlet valve;

[0067] The monitoring tube 8 has its lower end disposed in the system body 1 and its upper end partially passing through the wetland plants 7 and is used for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0068] The method for preparing iron-containing sludge biochar comprises the following steps:

[0069] S1. Dehydrated activated sludge with a water content of 80% was taken from a wastewater plant. The activated sludge was formed into 30 mm diameter mud balls using a mold. The balls were then air-dried outdoors for 2 days. After drying, the sludge was crushed and sieved to a particle size of 10 mm.

[0070] S2. Seal the sieved sludge with aluminum foil and place it in a muffle furnace with a heating rate of 10℃ / min. Pyrolyze the sludge in a N2 atmosphere at a pyrolysis temperature of 700℃ and a pyrolysis time of 2h. After stopping the heating, take out the sludge-made biochar and place it in a dryer to cool to room temperature for 2d. Then soak the sludge biochar in a 0.4mol / L FeCl3 solution for 24h. The mass ratio of sludge biochar to iron salt solution is 1:8, so that the iron ions are fully adsorbed on the surface of the biochar. Then wash it repeatedly with deionized water to remove unreacted iron salts and impurities. Then dry the iron-rich sludge biochar to constant weight to finally obtain iron-containing sludge biochar.

[0071] Example 2

[0072] The present invention provides an artificial wetland system containing iron sludge biochar, comprising:

[0073] System body 1, the top of the system body 1 is open and the bottom is closed, the height is 320mm, the diameter is 140mm, the cylindrical volume is about 4.92L, and the effective volume is about 1.85L; the system body 1 is wrapped with black plastic cloth.

[0074] A support layer 2 and a matrix mixing layer 3 are stacked up and down in the system body 1. The height of the support layer 2 is 40 mm, and the height of the matrix mixing layer 3 is 240 mm. The support layer 2 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 30 mm. The matrix mixing layer 3 is prepared by mixing iron-containing sludge biochar and the second gravel in a volume ratio of 3:10. The particle size of the iron-containing sludge biochar is 10 mm, and the particle size of the second gravel is 10 mm.

[0075] The water distribution tank 4 is connected to the bottom end of the system body 1 through a water inlet pipe 5, and a peristaltic pump is provided on the water inlet pipe 5.

[0076] Wetland plant 7, the wetland plant is calamus, which is arranged at the top of the system body 1, the axial distance between the wastewater outlet of the system body 1 and the top is 4 cm, the treated wastewater flows out from the outlet, the outlet is provided with an outlet valve, the discharge volume is controlled by the outlet valve, the axial distance between the wastewater inlet and the bottom of the system body 1 is 4 cm, the water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow rate is controlled by the water inlet valve;

[0077] The monitoring tube 8 has its lower end disposed in the system body 1 and its upper end partially passing through the wetland plants 7 and is used for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0078] The method for preparing iron-containing sludge biochar comprises the following steps:

[0079] S1. Dehydrated activated sludge with a water content of 80% was taken from a wastewater plant. The activated sludge was formed into 30 mm diameter mud balls using a mold. The balls were then air-dried outdoors for 2 days. After drying, the sludge was crushed and sieved to a particle size of 10 mm.

[0080] S2. Seal the sieved sludge with aluminum foil and place it in a muffle furnace with a heating rate of 10℃ / min. Pyrolyze the sludge in a N2 atmosphere at a pyrolysis temperature of 700℃ and a pyrolysis time of 2h. After stopping the heating, take out the sludge-made biochar and place it in a dryer to cool to room temperature for 2d. Then soak the sludge biochar in a 0.3mol / L FeCl3 solution for 24h. The mass ratio of sludge biochar to iron salt solution is 1:8, so that the iron ions are fully adsorbed on the surface of the biochar. Then wash it repeatedly with deionized water to remove unreacted iron salts and impurities. Then dry the iron-rich sludge biochar to constant weight to finally obtain iron-containing sludge biochar.

[0081] Example 3

[0082] The present invention provides an artificial wetland system containing iron sludge biochar, comprising:

[0083] System body 1, the top of the system body 1 is open and the bottom is closed, the height is 320mm, the diameter is 140mm, the cylindrical volume is about 4.92L, and the effective volume is about 1.85L; the system body 1 is wrapped with black plastic cloth.

[0084] A support layer 2 and a matrix mixing layer 3 are stacked up and down in the system body 1. The height of the support layer 2 is 40 mm, and the height of the matrix mixing layer 3 is 240 mm. The support layer 2 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 30 mm. The matrix mixing layer 3 is prepared by mixing iron-containing sludge biochar and the second gravel in a volume ratio of 3:10. The particle size of the iron-containing sludge biochar is 10 mm, and the particle size of the second gravel is 10 mm.

[0085] The water distribution tank 4 is connected to the bottom end of the system body 1 through a water inlet pipe 5, and a peristaltic pump is provided on the water inlet pipe 5.

[0086] Wetland plant 7, the wetland plant is calamus, which is arranged at the top of the system body 1, the axial distance between the wastewater outlet of the system body 1 and the top is 4 cm, the treated wastewater flows out from the outlet, the outlet is provided with an outlet valve, the discharge volume is controlled by the outlet valve, the axial distance between the wastewater inlet and the bottom of the system body 1 is 4 cm, the water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow rate is controlled by the water inlet valve;

[0087] The monitoring tube 8 has its lower end disposed in the system body 1 and its upper end partially passing through the wetland plants 7 and is used for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0088] The method for preparing iron-containing sludge biochar comprises the following steps:

[0089] S1. Dehydrated activated sludge with a water content of 80% was taken from a wastewater plant. The activated sludge was formed into 30 mm diameter mud balls using a mold. The balls were then air-dried outdoors for 2 days. After drying, the sludge was crushed and sieved to a particle size of 10 mm.

[0090] S2. Seal the sieved sludge with aluminum foil and place it in a muffle furnace with a heating rate of 10℃ / min. Pyrolyze the sludge in a N2 atmosphere at a pyrolysis temperature of 700℃ and a pyrolysis time of 2h. After stopping the heating, take out the sludge-made biochar and place it in a dryer to cool to room temperature for 2d. Then soak the sludge biochar in a 0.5mol / L FeCl3 solution for 24h. The mass ratio of sludge biochar to iron salt solution is 1:8, so that the iron ions are fully adsorbed on the surface of the biochar. Then wash it repeatedly with deionized water to remove unreacted iron salts and impurities. Then dry the iron-rich sludge biochar to constant weight to finally obtain iron-containing sludge biochar.

[0091] Comparative Example 1

[0092] An artificial wetland system containing iron sludge biochar, comprising:

[0093] System body 1, the top of the system body 1 is open and the bottom is closed, the height is 320mm, the diameter is 140mm, the cylindrical volume is about 4.92L, and the effective volume is about 1.85L; the system body 1 is wrapped with black plastic cloth.

[0094] A support layer 2 and a matrix mixing layer 3 are stacked up and down in the system body 1. The height of the support layer 2 is 40 mm, and the height of the matrix mixing layer 3 is 240 mm. The support layer 2 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 30 mm. The matrix mixing layer 3 is prepared by mixing the iron-containing sludge biochar and the second gravel in a volume ratio of 1:10. The particle size of the iron-containing sludge biochar is 10 mm, and the particle size of the second gravel is 10 mm.

[0095] The water distribution tank 4 is connected to the bottom end of the system body 1 through a water inlet pipe 5, and a peristaltic pump is provided on the water inlet pipe 5.

[0096] Wetland plant 7, the wetland plant is calamus, which is arranged at the top of the system main body 1. The axial distance between the wastewater outlet of the system main body 1 and the top is 4 cm. The treated wastewater flows out from the outlet. The outlet is provided with an outlet valve, and the drainage volume is controlled by the outlet valve. The axial distance between the wastewater inlet and the bottom of the system main body 1 is 4 cm. The water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system main body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow is controlled by the water inlet valve.

[0097] The monitoring tube 8 has its lower end disposed in the system body 1 and its upper end partially passing through the wetland plants 7 and is used for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0098] The method for preparing iron-containing sludge biochar comprises the following steps:

[0099] S1. Dehydrated activated sludge with a water content of 80% was taken from a wastewater plant. The activated sludge was formed into 30 mm diameter mud balls using a mold. The balls were then air-dried outdoors for 2 days. After drying, the sludge was crushed and sieved to a particle size of 10 mm.

[0100] S2. Seal the sieved sludge with aluminum foil and place it in a muffle furnace with a heating rate of 10℃ / min. Pyrolyze the sludge in a N2 atmosphere at a pyrolysis temperature of 700℃ and a pyrolysis time of 2h. After stopping the heating, take out the sludge-made biochar and place it in a dryer to cool to room temperature for 2d. Then soak the sludge biochar in a 0.4mol / L FeCl3 solution for 24h. The mass ratio of sludge biochar to iron salt solution is 1:8, so that the iron ions are fully adsorbed on the surface of the biochar. Then wash it repeatedly with deionized water to remove unreacted iron salts and impurities. Then dry the iron-rich sludge biochar to constant weight to finally obtain iron-containing sludge biochar.

[0101] Comparative Example 2

[0102] A sludge biochar artificial wetland system, comprising:

[0103] System body 1, the top of the system body 1 is open and the bottom is closed, the height is 320mm, the diameter is 140mm, the cylindrical volume is about 4.92L, and the effective volume is about 1.85L; the system body 1 is wrapped with black plastic cloth.

[0104] A support layer 2 and a matrix mixing layer 3 are stacked up and down in the system body 1. The height of the support layer 2 is 40 mm, and the height of the matrix mixing layer 3 is 240 mm. The support layer 2 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 30 mm. The matrix mixing layer 3 is prepared by mixing sludge biochar and the second gravel layer in a volume ratio of 3:10. The particle size of the sludge biochar is 10 mm, and the particle size of the second gravel is 10 mm.

[0105] The water distribution tank 4 is connected to the bottom end of the system body 1 through a water inlet pipe 5, and a peristaltic pump is provided on the water inlet pipe 5.

[0106] Wetland plant 7, the wetland plant is calamus, which is arranged at the top of the system body 1, the axial distance between the wastewater outlet of the system body 1 and the top is 4 cm, the treated wastewater flows out from the outlet, the outlet is provided with an outlet valve, the discharge volume is controlled by the outlet valve, the axial distance between the wastewater inlet and the bottom of the system body 1 is 4 cm, the water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow rate is controlled by the water inlet valve;

[0107] The monitoring tube 8 has its lower end disposed in the system body 1 and its upper end partially passing through the wetland plants 7 and is used for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0108] The method for preparing iron-containing sludge biochar comprises the following steps:

[0109] S1. Dehydrated activated sludge with a water content of 80% was taken from a wastewater plant. The activated sludge was formed into 30 mm diameter mud balls using a mold. The balls were then air-dried outdoors for 2 days. After drying, the sludge was crushed and sieved to a particle size of 10 mm.

[0110] S2. The sieved sludge was sealed with aluminum foil and placed in a muffle furnace. The temperature was raised at a rate of 10°C / min and the sludge was pyrolyzed in a nitrogen atmosphere at a temperature of 700°C for 2 hours. After stopping the heating, the sludge biochar was taken out and placed in a dryer to cool to room temperature for 2 days to obtain sludge biochar.

[0111] Comparative Example 3

[0112] A biochar-containing artificial wetland system, comprising:

[0113] System body 1, the top of the system body 1 is open and the bottom is closed, the height is 320mm, the diameter is 140mm, the cylindrical volume is about 4.92L, and the effective volume is about 1.85L; the system body 1 is wrapped with black plastic cloth.

[0114] A support layer 2 and a matrix mixed layer 3 are stacked up and down in the system body 1. The height of the support layer 2 is 40 mm, and the height of the matrix mixed layer 3 is 240 mm. The support layer 2 is the first gravel layer, and the particle size of the first gravel in the first gravel layer is 30 mm. The matrix mixed layer 3 is prepared by mixing bamboo charcoal and the second gravel in a volume ratio of 1:10. The particle size of the bamboo charcoal is 10 mm, and the particle size of the second gravel is 10 mm.

[0115] The water distribution tank 4 is connected to the bottom end of the system body 1 through a water inlet pipe 5, and a peristaltic pump is provided on the water inlet pipe 5.

[0116] Wetland plant 7, the wetland plant is calamus, which is arranged at the top of the system body 1, the axial distance between the wastewater outlet of the system body 1 and the top is 4 cm, the treated wastewater flows out from the outlet, the outlet is provided with an outlet valve, the discharge volume is controlled by the outlet valve, the axial distance between the wastewater inlet and the bottom of the system body 1 is 4 cm, the water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow rate is controlled by the water inlet valve;

[0117] The monitoring tube 8 has its lower end disposed in the system body 1 and its upper end partially passing through the wetland plants 7 and is used for in-situ measurement of DO, pH, temperature and other physical and chemical parameters.

[0118] The method for enhancing Feammox reaction denitrification using the artificial wetland system of Example 1 and Comparative Examples 1 to 3 comprises the following steps:

[0119] Step 1: Sludge from a wastewater aeration tank of a sewage treatment plant is used as an aerobic zone strain, and the aerobic zone strain and the anaerobic zone strain are domesticated separately. The aerobic zone strain is added to a reactor, and water is added and stirred to adjust the dissolved oxygen concentration of the reactor to 2 mg / L. The culture is carried out for 20 days, and the water is changed every 24 hours to obtain aerobic activated sludge. Sludge from a wastewater upflow anaerobic sludge bed of a sewage treatment plant is used as an anaerobic zone strain, and the anaerobic zone strain is added to a reactor, and water is added and stirred to adjust the dissolved oxygen concentration of the reactor to less than 1 mg / L. The culture is carried out for 20 days, and the water is changed every 24 hours to obtain domesticated anaerobic activated sludge.

[0120] Step 2: The system body 1 is provided with an anaerobic zone and an aerobic zone. Along the height direction of the system body 1, the anaerobic zone is located at the lower end of the aerobic zone. The volume ratio of the anaerobic zone to the aerobic zone is 1:1. An intermittent operation mode of top-in and bottom-out is adopted. The anaerobic activated sludge and wastewater are first mixed at a volume ratio of 1:400, and then added to the anaerobic zone of the system body 1 to form an anaerobic activated sludge layer by forming a biofilm. Then, the aerobic activated sludge and wastewater are mixed at a volume ratio of 1:400, and then added to the aerobic zone of the system body 1 to form a biofilm to form an aerobic activated sludge layer.

[0121] In step 3, the wastewater to be treated is added to the water distribution tank 4. The water inlet pipe 5 transports the wastewater in the water distribution tank 4 to the system main body 1 through the wastewater inlet through the power mechanism 6, and the water inlet flow is controlled by the water inlet valve. The treated water is discharged through the wastewater outlet provided on the top side wall of the system main body 1. The system main body 1 performs an upward continuous flow mode to enhance the Feammox reaction denitrification.

[0122] Among them, the influent COD of the artificial wetland system of Example 1 and Comparative Examples 1 to 3 is 50±2 mg / L, NH4+ -N is 8±2mg / L, NO3 - -N was 9±2 mg / L, and TN was 17±2 mg / L. The results of enhanced Feammox denitrification under low carbon conditions are shown in Table 1.

[0123] Table 1 Denitrification results of enhanced Feammox reaction in artificial wetland system of Example 1 and Comparative Examples 1 to 3

[0124]

[0125] As shown in Table 1, the iron-containing sludge biochar-based artificial wetland system of the present invention strengthens the Feammox reaction denitrification, and the denitrification of NH4 + The removal rates of -N and TN reached 98.56% and 94.13%, respectively, and the TN removal load was 0.128 kgN·m -3 ·d -1 The present invention shows that 30% iron-containing sludge biochar has a great influence on NH4 + The removal of -N and TN has a significant strengthening effect. Under low carbon conditions, the iron-containing sludge biochar and the second gravel serve as the matrix layer. The rich porous structure and high specific surface area of ​​the iron-containing sludge biochar provide an ideal attachment matrix for microorganisms. The slowly released iron ions not only provide essential nutrients for microorganisms, but also further stimulate microbial activity by regulating the redox potential and enhancing electron transfer, thereby improving the stability and activity of the microbial community, further promoting the denitrification reaction, and conducting enhanced Feammox reaction denitrification. By combining the iron-containing sludge biochar, energy demand is further reduced, achieving low-energy green and environmentally friendly wastewater treatment.

[0126] The N2O emissions of the artificial wetland systems of Example 1 and Comparative Examples 1 and 2 were measured. The results are shown in Table 2.

[0127] Table 2 Comparison of N2O emissions of Example 1 and Comparative Examples 1-2

[0128]

[0129] As shown in Table 2, the N2O gas emitted by the iron-containing sludge biochar constructed wetland system in Example 1 of the present invention was reduced by 1.92 mg / m3 compared with the matrix layer formed by the iron-containing sludge biochar in Comparative Example 1. 3 , indicating that the mixing ratio of iron-containing sludge biochar and the second gravel has a significant impact on the N2O emissions from the wetland. The artificial wetland using 30% iron-containing sludge biochar in the present invention can effectively reduce the N2O emissions from the wetland.

[0130] The anaerobic zone bacteria after the Feammox reaction denitrification in the iron-containing sludge biochar-based artificial wetland system in Example 1 were analyzed. The abundance of Geobacter reached 9.19%. The iron-containing sludge biochar had a significant promoting effect on the enrichment of Geobacter. Geobacter can reduce Fe in the environment by 3+ Fe 2+ , providing electrons to promote NH4 + -N is converted into N2, thereby achieving NH4 + -N removal.

[0131] It should be noted that when numerical ranges are mentioned in the present invention, it should be understood that both endpoints of each numerical range and any value between the two endpoints may be selected. Since the steps and methods used are the same as those in the embodiments, in order to avoid redundancy, the present invention describes preferred embodiments. Although preferred embodiments of the present invention have been described, those skilled in the art may make additional changes and modifications to these embodiments once they understand the basic inventive concepts. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0132] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. An artificial wetland system containing iron sludge biochar, characterized in that: The system body (1) comprises a system main body (1), the top of the system main body (1) is open and the bottom is closed, and a support layer (2) and a matrix mixed layer (3) are stacked up and down in the system main body (1) along the height direction of the system main body (1), wherein the height ratio of the support layer (2) to the matrix mixed layer (3) is 1:5-7; The support layer (2) is a first gravel layer, and the matrix mixed layer (3) is prepared by mixing iron-containing sludge biochar and second gravel in a volume ratio of 1:2.5-5.

2. The artificial wetland system of iron-containing sludge biochar according to claim 1, characterized in that: The particle size of the first gravel in the first gravel layer is 20 mm to 40 mm, the particle size of the iron-containing sludge biochar is 8 mm to 15 mm, and the particle size of the second gravel is 8 mm to 15 mm.

3. The artificial wetland system of iron-containing sludge biochar according to claim 1, characterized in that: The method for preparing iron-containing sludge biochar comprises the following steps: Using dehydrated activated sludge from a wastewater plant as the matrix, activated sludge biochar is obtained by pyrolysis at 600°C to 800°C under a protective gas atmosphere; Activated sludge biochar was immersed in Fe 3+ In the solution, Fe 3+ The iron-containing sludge biochar was obtained by loading it on activated sludge biochar.

4. The artificial wetland system of iron-containing sludge biochar according to claim 3, characterized in that: Activated sludge biochar and Fe 3+ The mass ratio of the solution is 1:6-8, containing Fe 3+ Fe in solution 3+ The concentration is 0.3mol / L~0.5mol / L, containing Fe 3+ The solution is one of ferric sulfate, ferric nitrate, and ferric chloride. The soaking temperature is room temperature and the time is 15h to 28h.

5. The artificial wetland system of iron-containing sludge biochar according to claim 3, characterized in that: The protective gas is nitrogen or inert gas, the heating rate during the pyrolysis process is 8°C / min to 12°C / min, the pyrolysis time is 1.8h to 2.2h, and the water content of the dehydrated activated sludge is 70% to 80%.

6. The artificial wetland system of iron-containing sludge biochar according to claim 1, characterized in that: The artificial wetland system also includes: A water distribution tank (4) connected to the bottom end of the system body (1) via a water inlet pipe (5), wherein a power mechanism (6) is provided on the water inlet pipe (5); Wetland plants (7) are arranged at the top of the system body (1); the top side wall of the system body (1) is provided with a wastewater outlet, the bottom side wall is provided with a wastewater inlet, the wastewater inlet is connected to the water inlet pipe (5) through a water inlet valve, and the water outlet is provided with a water outlet valve; The monitoring pipe (8) has a lower end disposed in the system body (1) and an upper end portion passing through the wetland plant (7).

7. A method for strengthening Feammox reaction denitrification, characterized in that: The artificial wetland system using the iron-containing sludge biochar according to any one of claims 1 to 6 comprises the following steps: The sludge in the wastewater aeration tank is used as the bacterial strain in the aerobic zone, and is domesticated to obtain aerobic activated sludge. The sludge in the wastewater upflow anaerobic sludge bed is used as the bacterial strain in the anaerobic zone, and is domesticated to obtain anaerobic activated sludge. The system body (1) is provided with an anaerobic zone and an aerobic zone. Along the height direction of the system body (1), the anaerobic zone is located at the lower end of the aerobic zone. An intermittent operation mode of top-in and bottom-out is adopted. The anaerobic activated sludge and wastewater are first mixed and then added to the anaerobic zone of the system body (1) to form an anaerobic activated sludge layer by forming biofilm. Then, the aerobic activated sludge and wastewater are mixed and then added to the aerobic zone of the system body (1) to form biofilm by forming an aerobic activated sludge layer. The wastewater to be treated is injected into the main body of the system (1) in a continuous flow manner in an upstream manner to carry out enhanced Feammox reaction denitrification.

8. The method for enhancing denitrification by Feammox reaction according to claim 7, characterized in that: The method of acclimatizing the aerobic zone strain is as follows: adding the aerobic zone strain to the reactor, adding water and stirring to adjust the dissolved oxygen concentration of the reactor to 1 mg / L to 3 mg / L, culturing for 15 days to 20 days to obtain the acclimated aerobic zone strain, wherein the water is changed every 24 hours during the culturing process.

9. The method for strengthening Feammox reaction denitrification according to claim 7, characterized in that: The method of taming the anaerobic zone strain is as follows: adding the anaerobic zone strain to the reactor, adding water and stirring to adjust the dissolved oxygen concentration of the reactor to <1 mg / L, culturing for 15 to 20 days to obtain the tamed anaerobic zone strain, wherein the water is changed every 24 hours during the culturing process.

10. The method for strengthening denitrification by Feammox reaction according to claim 7, characterized in that: The volume ratio of the anaerobic zone to the aerobic zone is 1:1-3, the volume ratio of the anaerobic activated sludge or aerobic activated sludge to the wastewater is 1:350-450, the hydraulic retention time in the enhanced Feammox reaction denitrification process is 2.5d-3.5d, and the time for enhanced Feammox reaction denitrification is 25d-35d.

Images