Pulse electrochemical crystallization coupling composite constructed wetland system

Abstract

The invention discloses a pulse electrochemical crystallization coupled composite constructed wetland system which comprises an energy system, a pulse electrochemical crystallization pond and a composite constructed wetland system, and the energy system supplies energy to the pulse electrochemical crystallization pond and the composite constructed wetland system. Aquaculture wastewater firstly enters a pulse electrochemical crystallization pond, struvite (MAP) sediment is formed through electrochemical crystallization, ammonia nitrogen and phosphate in the wastewater are efficiently removed, and partial removal of organic matter is achieved. Then the wastewater enters a composite artificial wetland system, and the wastewater is deeply purified under the action of filler filtration / adsorption, microbial assimilation / conversion and plant absorption. The pulse electrochemical crystallization coupled composite constructed wetland system is compact in structure, and the defects of high energy consumption of direct-current electrochemical crystallization and low purification efficiency of a traditional constructed wetland are overcome through physical-chemical-biological multi-path coupling enhanced culture wastewater treatment.

Description

Technical Field

[0001] The invention relates to the treatment of aquaculture wastewater, sewage or sludge, and in particular to a pulse electrochemical crystallization coupled composite artificial wetland system. Background Art

[0002] With the large-scale development of livestock and poultry breeding industry, the amount of breeding wastewater is increasing day by day. Livestock and poultry breeding wastewater has the characteristics of high organic matter concentration, strong biodegradability, high nitrogen and phosphorus content, etc. Improper treatment can easily lead to water environment safety problems such as eutrophication, black odor, and corruption.

[0003] The main purpose of aquaculture wastewater treatment methods is solid-liquid separation, organic matter degradation, and nitrogen and phosphorus removal, and can be roughly divided into physicochemical methods and biochemical methods. Among the physicochemical methods, the struvite (MAP) precipitation method based on electrochemical crystallization can not only effectively remove nitrogen and phosphorus from wastewater, but also recycle these nutrients to prepare slow-release fertilizers, which is in line with the sustainable development concept of environmental protection and resource recovery. However, the formation of MAP is a complex process, and the existing crystallization MAP method has the main defects of high operating energy consumption, unstable treatment effect, and low resource recovery rate.

[0004] Compared with other aquaculture wastewater treatment technologies, artificial wetlands have low construction and operation costs, simple operation and maintenance, significant ecological and environmental benefits, and certain economic benefits, landscape benefits and ornamental value. In recent years, they have been widely valued and applied in sewage / wastewater treatment at home and abroad. However, traditional artificial wetlands have poor adaptability to high-concentration aquaculture wastewater, high energy consumption of sewage lifting pumps and aeration processes, weak phosphorus removal performance, and it is difficult to achieve the aerobic-anoxic-anaerobic alternating oxygen environment required for biological denitrification within the wetland system. These problems have greatly limited the application of artificial wetland technology in livestock and poultry aquaculture wastewater treatment. Summary of the invention

[0005] In view of this, the main purpose of the present invention is to provide a pulse electrochemical crystallization coupled composite artificial wetland system, which can solve the problems in the prior art of high energy consumption of DC electrochemical crystallization, poor adaptability of traditional artificial wetlands to high-concentration aquaculture wastewater, high energy consumption of sewage lifting pumps and aeration processes, and weak phosphorus removal performance.

[0006] To achieve the above object, the technical solution of the present invention is achieved as follows:

[0007] A pulse electrochemical crystallization coupled composite artificial wetland system, comprising: an energy system, a pulse electrochemical crystallization pool and a composite artificial wetland system; the energy output end of the energy system is connected to the pulse electrochemical crystallization pool and the energy input end of the composite artificial wetland system for energy supply, and the pulse electrochemical crystallization pool is connected to the composite artificial wetland system through a pipeline;

[0008] The pulse electrochemical crystallization tank comprises: a first sewage inlet pipe, a cathode electrode, an anode electrode, a first sewage outlet pipe and a tank body;

[0009] The first sewage inlet pipe is arranged at the upper part of the tank body and is connected to the tank body, the first sewage outlet pipe is arranged at the lower part of the tank body and is connected to the tank body, and the cathode electrode and the anode electrode are fixed at the center of the tank body;

[0010] The cathode electrode and the anode electrode are cylindrical, the diameter of the cathode electrode is larger than the diameter of the anode electrode, and the anode electrode is located in the cavity of the cathode electrode.

[0011] The cathode electrode and the anode electrode are connected to the energy system via a pulse power supply, and the energy system provides pulse current to the cathode electrode and the anode electrode via the pulse power supply.

[0012] Preferably, the pulse electrochemical crystallization cell further comprises: a stirrer, the stirrer being fixed at the bottom of the cell body;

[0013] Preferably, the pulse current frequency is 3000-4000 Hz.

[0014] Preferably, the cathode electrode is made of aluminum alloy, and the anode electrode is made of magnesium alloy.

[0015] Preferably, the composite artificial wetland system comprises: a second sewage inlet pipe, a gravel support layer, a microporous aeration device, an elastic filler biological reinforcement layer, a functional filler physicochemical reinforcement layer, a quartz sand layer, a plant stem tissue layer, aquatic plants and a second sewage discharge pipe;

[0016] The gravel support layer, the microporous aeration device, the elastic filler biological reinforcement layer, the functional filler physicochemical reinforcement layer, the quartz sand layer and the plant stem tissue layer are laid in sequence from bottom to top, the aquatic plants are planted on the quartz sand layer and the upper side of the plant stem tissue layer, and the second sewage discharge pipe is located below the plant stem tissue layer;

[0017] Preferably, the energy system comprises: a photovoltaic module wind turbine, a chopper, a rectifier, a grid bus, a transformer and a battery;

[0018] The grid bus is connected to the electrical equipment of the composite artificial wetland system and the agitator in the pulse electrochemical crystallization pool, and the transformer is connected to the cathode electrode and the anode electrode of the pulse electrochemical crystallization pool through a pulse power supply;

[0019] A chopper is arranged between the photovoltaic assembly and the grid bus, a rectifier is arranged between the wind turbine and the grid bus, the storage battery is connected to the grid bus, and a transformer is arranged between the storage battery and the grid bus.

[0020] Preferably, the gravel support layer is formed by piling up coarse gravel, the coarse gravel particle size is 20-50 mm, and the gravel support layer height is 20-50 cm.

[0021] Preferably, the elastic filler bioreinforcement layer is made of polypropylene, the particle size of the polypropylene filler in the elastic filler bioreinforcement layer is 15-25 mm, the height of the elastic filler bioreinforcement layer is 20-50 cm, and heterotrophic nitrification-aerobic denitrifying bacteria (HN-ADB) are attached to the elastic filler bioreinforcement layer.

[0022] Preferably, the functional filler physicochemical strengthening layer is a strong adsorption PO4 3― -P functional filler, the particle size of the functional filler is 10-15mm, the height of the physicochemical strengthening layer of the functional filler is 20-50cm, the functional filler is made of Ca / Al-based sludge, sponge iron powder, calcium carbonate and bentonite, water is added at a set ratio for granulation, and after drying in the shade, it is calcined at a high temperature of 800-1200℃ for 2-4h.

[0023] Preferably, the quartz sand particle size in the quartz sand layer is 2-10 mm, and the quartz sand layer height is 20-50 cm.

[0024] The pulse electrochemical crystallization coupled composite artificial wetland system of the present invention has the following beneficial effects: the pulse electrochemical crystallization coupled composite artificial wetland system comprises an energy system, a pulse electrochemical crystallization pool and a composite artificial wetland system. The energy system supplies energy to the pulse electrochemical crystallization coupled composite artificial wetland system for deep treatment of aquaculture wastewater. After the aquaculture wastewater enters the pulse electrochemical crystallization pool, the electrochemical crystallization precipitation forms struvite to achieve large-scale removal of nitrogen and phosphorus in the wastewater and partial degradation of organic matter. The treated aquaculture wastewater enters the composite artificial wetland system, and the aquaculture wastewater is deeply treated through filler filtration / adsorption, microbial assimilation / conversion and plant absorption of the composite artificial wetland.

[0025] The pulse electrochemical crystallization coupled composite artificial wetland system has a compact structure, multiple treatment pathways, good purification effect and stable performance. The introduction of a pulse electrochemical crystallization device before the composite artificial wetland not only improves the biodegradability of aquaculture wastewater, but also significantly reduces the nitrogen and phosphorus concentrations in livestock and poultry wastewater and achieves partial removal of organic matter, reducing the pollutant load of the subsequent wetland treatment system. The struvite (MAP) precipitate formed in the pulse electrochemical crystallization pool is rich in phosphorus, magnesium and nitrogen, three macronutrients required for crop growth, and is not easily washed away or lost by rainwater in the soil. Therefore, it can be used as a slow-release fertilizer in agriculture to reduce environmental pollution problems caused by excessive fertilization. The electrode plate in the pulse electrochemical crystallization device is a cylindrical hollow body structure, which increases the effective contact and reaction area of ​​the electrochemical electrode plate, thereby accelerating the crystallization process and reducing the passivation of the electrode plate; the introduced pulse current technology provides more stable current and voltage, reduces energy consumption, and further improves the working efficiency of the electrode and the recovery rate of nitrogen and phosphorus resources; the Al ionized by the aluminum alloy cathode 3+ , enhancing the chemical flocculation effect on the removal of pollutants. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0027] Figure 1 A schematic diagram of the structure of a pulse electrochemical crystallization coupled composite artificial wetland system according to an embodiment of the present disclosure;

[0028] Figure 2 A structural block diagram of an energy system according to an embodiment of the present disclosure;

[0029] Figure 3 A schematic diagram of the structure of a pulse electrochemical crystallization system according to an embodiment of the present disclosure;

[0030] Figure 4 A schematic diagram of a cross-sectional structure of a composite artificial wetland according to an embodiment of the present disclosure;

[0031] Figure 5 This is a test diagram comparing electrode stability and energy consumption of direct current electrochemical crystallization and pulse electrochemical crystallization according to an embodiment of the present disclosure;

[0032] Figure 6 According to one embodiment of the present disclosure, the functional filler adsorbs PO4 3- -P isothermal static adsorption simulation results;

[0033] Figure 7 An experimental diagram of the ratio between the adsorption amount and the initial saturated adsorption amount of a functional filler in a cyclic adsorption-desorption-re-adsorption process according to an embodiment of the present disclosure.

[0034]

Main component symbol description

[0035] 1. Energy system;

[0036] 10. Photovoltaic module; 11. Wind turbine; 12. Chopper; 13. Rectifier;

[0037] 14. Grid bus; 15. Transformer; 16. Battery;

[0038] 17. Electrical equipment;

[0039] 2. Pulse electrochemical system;

[0040] 20. First sewage inlet pipe; 21. Aluminum alloy cathode electrode;

[0041] 22. Magnesium alloy anode electrode; 23. Electric rotor;

[0042] 24. First sewage discharge pipe; 25. Cylindrical electrode plate;

[0043] 3. Artificial wetlands;

[0044] 30. Second sewage inlet pipe; 31. Gravel support layer; 32. Microporous aeration device;

[0045] 33. Bioelastic filler layer; 34. Wetland physicochemical functional filler layer; 35. Quartz sand layer;

[0046] 36. Tissue layer on plant stem; 37. Aquatic plants; 38. Second sewage discharge pipe. DETAILED DESCRIPTION

[0047] The method of the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments of the present invention.

[0048] It should be noted that, in the absence of conflict, the embodiments and features in the embodiments of the present application can be combined with each other. The present invention will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0049] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit the exemplary embodiments according to the present application. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprise" and / or "include" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0050] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the data used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0051] For ease of description, spatially relative terms such as "above", "above", "on the upper surface of", "above", etc. may be used here to describe the spatial positional relationship between a device or feature and other devices or features as shown in the figure. It should be understood that spatially relative terms are intended to include different orientations of the device in use or operation in addition to the orientation described in the figure. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Thus, the exemplary term "above" can include both "above" and "below". The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatially relative descriptions used here are interpreted accordingly.

[0052] See also Figure 1-Figure 7 , the present invention provides a technical solution:

[0053] A pulse electrochemical crystallization coupled composite artificial wetland system for deep treatment of aquaculture wastewater comprises: an energy system 1, a pulse electrochemical crystallization pool 2, and a composite artificial wetland system 3; the energy output end of the energy system 1 is connected to the pulse electrochemical crystallization pool 2 and the energy input end of the composite artificial wetland system 3 for energy supply, and the pulse electrochemical crystallization pool 2 is connected to the composite artificial wetland system 3 through a pipeline; the aquaculture wastewater enters the pulse electrochemical crystallization pool 2 by gravity flow, and the carbon, nitrogen, and phosphorus in the aquaculture wastewater are simultaneously removed by forming struvite and electrochemical degradation in the pulse electrochemical crystallization pool, and the refractory macromolecular organic matter is oxidized and electrolyzed into small molecular organic matter with higher biodegradability for subsequent biochemical treatment; the aquaculture wastewater treated by the pulse electrochemical crystallization pool 2 enters the composite artificial wetland system 3 by gravity flow, and is filtered / adsorbed by fillers, assimilated / converted by microorganisms, and absorbed by plants by the composite artificial wetland system 3, so as to achieve efficient, stable, and deep removal of pollutants such as carbon, nitrogen, and phosphorus in the aquaculture wastewater.

[0054] The pulse electrochemical crystallization cell 2 comprises: a first sewage inlet pipe 20, a cathode electrode 21, an anode electrode 22, a first sewage outlet pipe 24 and a cell body 25;

[0055] The first sewage inlet pipe 20 is arranged at the upper part of the tank body 25 and is conductively connected to the tank body 25. The aquaculture wastewater flows into the hollow cavity of the tank body 25 under the action of gravity through the first sewage inlet pipe 20. The first sewage discharge pipe 24 is arranged at the lower part of the tank body 25 and is conductively connected to the tank body 25. The cathode electrode 21 and the anode electrode 22 are fixed at the center of the tank body 25. The aquaculture wastewater is in the cavity of the tank body 25 and is discharged from the first sewage discharge pipe 24 through the electrochemical crystallization effect between the cathode electrode 21 and the anode electrode 22.

[0056] The cathode electrode 21 and the anode electrode 22 are cylindrical, and the diameter of the cathode electrode 21 is larger than the diameter of the anode electrode 22. The anode electrode 22 is located in the cavity of the cathode electrode 21. The cylindrical cathode electrode 21 and the anode electrode 22 effectively increase the effective reaction area of ​​the electrode plate during the electrochemical reaction, thereby accelerating the crystallization process and reducing the passivation of the electrode plate.

[0057] The cathode electrode 21 and the anode electrode 22 are connected to the energy system 1 via a pulse power supply 26. The energy system 1 provides pulse current to the cathode electrode 21 and the anode electrode 22 via the pulse power supply 26. The use of pulse current reduces energy consumption while further improving the working efficiency of the electrodes and the recovery rate of nitrogen and phosphorus resources.

[0058] The high concentration of organic matter in aquaculture wastewater is treated by a pulse electrochemical crystallization tank, which converts the difficult-to-biodegrade macromolecular organic matter in the wastewater into easily biodegradable small molecular substances. The formation of struvite through electrochemical crystallization can simultaneously reduce the nitrogen and phosphorus concentrations in the wastewater, thereby reducing the pollutant treatment load of the subsequent composite wetland system.

[0059] In order to make the electrochemical reaction of the pulse electrochemical crystallization pool sufficient, the pulse electrochemical crystallization pool 2 also includes a stirrer 23. The stirrer 23 is a submersible stirrer fixed at the bottom of the pool body 25 to stir the aquaculture wastewater in the pool body 25 so that the wastewater undergoes a sufficient electrochemical reaction.

[0060] The pulse current frequency is 3000-4000Hz, preferably 3500Hz, and the current density is 2-4mA·cm 2 , preferably 3 mA·cm 2 The distance between the cathode electrode 21 and the anode electrode 22 is 2-6 cm, preferably 4 cm, and the duty cycle is 20%-40%, preferably 30%.

[0061] The cathode electrode 21 is made of aluminum alloy, and the anode electrode 22 is made of magnesium alloy. Compared with other electrode plates, aluminum alloy and magnesium alloy are cheaper and easier to obtain. 3+ As an excellent flocculant, it can enhance the removal of suspended solids and organic matter in wastewater by flocculation and sedimentation; Mg ionized from magnesium alloy 2+ It can provide a stable magnesium source for the electrochemical crystallization process and promote the efficient removal of nitrogen and phosphorus in wastewater.

[0062] The composite artificial wetland system 3 includes: a second sewage inlet pipe 30, a gravel support layer 31, a microporous aeration device 32, an elastic filler biological reinforcement layer 33, a functional filler physical and chemical reinforcement layer 34, a quartz sand layer 35, a plant stem tissue layer 36, aquatic plants 37 and a second sewage discharge pipe 38;

[0063] A gravel support layer 31, a microporous aeration device 32, an elastic filler biological reinforcement layer 33, a functional filler physical and chemical reinforcement layer 34, a quartz sand layer 35 and a plant stem tissue layer 36 are laid in sequence from bottom to top, aquatic plants 37 are planted on the upper sides of the quartz sand layer 35 and the plant stem tissue layer 36, and a second sewage discharge pipe 38 is located below the plant stem tissue layer 36;

[0064] Wastewater flows out of the pulse electrochemical crystallization pool 2 and enters the composite artificial wetland system 3 through the second sewage inlet pipe 30. The wastewater first flows through the gravel support layer 31, and the suspended pollutants in the wastewater are removed by physical filtration and interception; then it enters the elastic filler biological enhancement layer 33, and the carbon, nitrogen, phosphorus and other pollutants in the wastewater are effectively removed by microbial assimilation / conversion; a microporous aeration device 32 is provided under the elastic filler layer 33, which provides oxygen for the growth of aerobic bacteria such as BOD oxidizing bacteria and heterotrophic nitrification-aerobic denitrifying bacteria (HN-ADB) through aeration, solving the problem that the aerobic-anoxic-anaerobic alternating oxygen environment is difficult to achieve in the traditional biological denitrification process; the functional filler physicochemical enhancement layer 34 is provided with a self-made functional filler that can strongly adsorb phosphate, which can further effectively remove PO4 in the wastewater under the combined action of physical adsorption and chemical adsorption. 3- -P, and the physical and chemical adsorption is less affected by environmental conditions; a quartz sand layer 35 is provided above the functional filler physical and chemical strengthening layer 34, and the quartz sand layer 35 performs deep filtration on the wastewater to reduce the turbidity of the effluent; the quartz sand layer 35 is covered with wetland plant stem tissue harvested in winter to form a plant stem tissue layer 36. The wetland plant stem tissue is naturally air-dried and crushed into plant tissue with a length of 20-30 mm, which can be regarded as an external slow-release carbon source to promote the denitrification process in the biological denitrification of wastewater, and at the same time help the wetland to keep warm; aquatic plants 37 are planted on the upper side of the quartz sand layer 35 and the plant stem tissue layer 36. The aquatic plants 37 mainly include plants such as reeds and cattails, which further remove pollutants in the wastewater through plant absorption and improve the landscape effect and ornamental value of the composite artificial wetland system;

[0065] The composite artificial wetland system adopts an upward vertical flow distribution method with bottom-in and top-out. The livestock and poultry breeding wastewater passes through the gravel support layer, elastic filler biological enhancement layer, functional filler physical and chemical enhancement layer, quartz sand layer, and plant stem tissue layer respectively. The suspended pollutants are removed through the filtration effect of the filler particle grading between different particle sizes. The self-made functional filler has a large specific surface area and pore volume and is rich in calcium, magnesium, aluminum, and iron. It can effectively remove phosphates in the wastewater through physical-chemical adsorption. The elastic filler layer is inoculated with heterotrophic nitrification-aerobic denitrification functional bacteria (HN-ADB) that are screened, domesticated, and enriched and cultivated, and a microporous aeration device is provided below it to provide oxygen for the growth of functional bacteria. While effectively removing ammonia nitrogen, nitrite nitrogen, nitrate nitrogen, and organic matter in the breeding wastewater, it solves the problem that the aerobic-anoxic-anaerobic alternating oxygen environment required for traditional nitrification-denitrification biological denitrification is difficult to achieve during the operation of the wetland.

[0066] The energy system 1 comprises: a photovoltaic module 10, a wind turbine 11, a chopper 12, a rectifier 13, a grid bus 14, a transformer 15 and a battery 16; the grid bus 14 is connected to the microporous aeration device 32 of the electrical equipment in the composite artificial wetland system 3 and the agitator 23 in the pulse electrochemical crystallization tank 2, the chopper 12 is arranged between the photovoltaic module 10 and the grid bus 14, the light irradiated on the solar panel of the photovoltaic module 10 is converted into electrical energy and connected to the grid bus 14 through the chopper 12, the rectifier 13 is arranged between the wind turbine 11 and the grid bus 14, the wind turbine 11 absorbs wind energy and converts it into alternating current and then converts it into direct current through the rectifier 13 and then merges it into the wind turbine 11. The battery 16 is connected to the grid bus 14, and a transformer 15 is arranged between the battery 16 and the grid bus 14. The excess electricity in the grid bus 14 can be stored in the battery through the transformer 15. When the wind and light are relatively weak, the battery 16 releases electricity and reaches the electrical equipment 17 through the grid bus 14. The transformer 15 is connected to the cathode electrode 21 and the anode electrode 22 of the pulse electrochemical crystallization cell 2 through the pulse power supply 26.

[0067] The photovoltaic module 10 and the wind turbine 11 can operate independently or simultaneously, which is in line with the environmental characteristics of the north, where the sunlight is strong during the day and the wind is strong at night, the light intensity is strong and the wind is weak in summer, and the wind is strong and the light intensity is weak in winter and spring. The energy system uses the photovoltaic module 10 and the wind turbine 11 simultaneously to make up for the unstable power generation defect of separate wind power generation or solar photovoltaic power generation.

[0068] The gravel support layer 31 is formed by the accumulation of coarse gravel, the particle size of the coarse gravel is 20-50 mm, and the height of the gravel support layer 31 is 20-50 cm. The gravel support layer 31 can be used as a support layer, and the wastewater can pass through the gravel support layer 31, and the suspended pollutants in the wastewater can be effectively removed by physical filtration and interception.

[0069] The elastic filler biological reinforcement layer 33 is made of polypropylene, the particle size of the filler in the elastic filler biological reinforcement layer 33 is 15-25mm, and the height of the elastic filler biological reinforcement layer 33 is 20-50cm. The microorganisms attached to the elastic filler biological reinforcement layer 33 are heterotrophic nitrification-aerobic denitrification bacteria (HN-ADB). After enrichment and biofilm formation of heterotrophic nitrification-aerobic denitrification functional bacteria screened and domesticated from river and lake bottom mud, the elastic filler biological reinforcement layer 33 can simultaneously achieve effective removal of pollutants such as carbon, nitrogen, and phosphorus in wastewater under aerobic conditions. A microporous aeration device 32 is set on the lower side of the biological elastic filler layer 33, which provides oxygen for the growth of heterotrophic nitrification-aerobic denitrification functional bacteria (HN-ADB) through aeration, solving the problem that the aerobic-anoxic-anaerobic alternating oxygen environment in the traditional biological denitrification process is difficult to achieve.

[0070] Functional filler physical and chemical strengthening layer 34 is a strong adsorption PO4 3- -P functional filler. The particle size of the functional filler is 10-15mm, the height of the functional filler physicochemical strengthening layer 34 is 20-50cm, and the functional filler physicochemical strengthening layer 34 has a great influence on the PO4 3- -P has the dual effects of physical adsorption and chemical adsorption. After adsorption saturation, the functional filler of the functional filler physical and chemical strengthening layer 34 can be desorbed and regenerated using 2-4mmol / L citric acid to ensure the stability and recyclability of the functional filler during wetland operation. The functional filler of the functional filler physical and chemical strengthening layer 34 is made of dehydrated Ca / Al-based sludge, sponge iron powder, calcium carbonate and bentonite as raw materials. Water is added to granulate at a set ratio, and after curing and drying in the shade, it is calcined at a high temperature of 800-1200℃ to form pores. The obtained physical and chemical functional filler has a large specific surface area, rich pores and channels, and is very effective in treating PO4 in aquaculture wastewater. 3- -P has excellent adsorption performance, which solves the problem of difficult effective resource utilization of wastewater plant sludge and avoids the occupation of land resources by solid waste landfill. 3- -P has excellent adsorption performance, which can improve the wetland's ability to absorb PO4 in aquaculture wastewater 3- -P purification efficiency is different from the traditional biological enhancement method which is greatly affected by the season. The physical and chemical enhancement method is more stable and efficient.

[0071] The quartz sand in the quartz sand layer 35 has a particle size of 2-10 mm and a height of 20-50 cm. The quartz sand layer 35 can effectively reduce the turbidity of the effluent. The quartz sand layer is covered with wetland plant stem tissue harvested in winter, which can be regarded as an external slow-release carbon source, promoting the denitrification process in the biological denitrification of wastewater and helping the wetland to keep warm.

[0072] Example 1

[0073] In one embodiment, the pulse current frequency is 3500 Hz, the gravel support layer 31 is 35 cm high, the biological strengthening layer 33 is 30 cm high, the functional filler physical and chemical strengthening layer 34 is 30 cm high, and the functional filler is made of Ca / Al-based sludge, sponge iron powder, calcium carbonate and bentonite, which are granulated with water at a ratio of 5:1:1:2, dried in the shade and calcined at 1000°C for 2 hours. The quartz sand layer is 35 cm high.

[0074] The above-mentioned pulse electrochemical crystallization coupled composite artificial wetland system was used to treat aquaculture wastewater, and some data were measured. The results are as follows:

[0075] 1) Pulse electrochemical removal rate of pollutants such as COD, ammonia nitrogen, phosphate, TN, TP, turbidity, etc. in wastewater

[0076] The actual chemical oxygen demand (COD), ammonia nitrogen (NH4 + -N), phosphate (PO4 3- -P), total nitrogen (TN), total phosphorus (TP) and turbidity concentrations were 1503.59±10.52mg / L,

[0077] 291.62±2.53mg / L, 15.98±0.12mg / L, 291.70±2.83mg / L, 17.26±0.19mg / L and 14.99±0.11NTU. After being treated by the pulse electrochemical crystallization coupled composite constructed wetland system disclosed in the present invention, the analysis results are shown in Table 1. The COD and NH4 + -N, PO4 3- -P, TN, TP and turbidity concentrations were 268.39±2.16mg / L, 36.89±0.34mg / L, 2.72±0.02mg / L, 43.23±0.52mg / L, 3.18±0.05mg / L, 3.52±0.07NTU, respectively, and the corresponding removal rates were 82.15%, 87.35%, 82.98%, 85.18%, 81.58% and 76.53%, respectively. It can be seen that the pulse electrochemical system can significantly reduce the concentrations of carbon, nitrogen and phosphorus pollutants in aquaculture wastewater.

[0078] Table 1 Removal effect of pulse electrochemical crystallization pool on various indicators in livestock and poultry wastewater

[0079]

[0080] 2) Electrode stability and energy consumption test

[0081] In order to verify the stability and energy consumption of the pulse electrochemical electrode, a direct current electrochemical crystallization device (DC-MAP) was added for comparison and a series of cycle tests were carried out. Figure 5 As shown in the figure, with the increase of cycle number, the phosphate removal efficiency decreased from the initial 83.71% to 79.35% under the DC electrochemical crystallization condition, and the energy consumption decreased from the initial 11.4 kWh·m -3 Increased to 13.45 kWh m -3 Under the condition of pulse electrochemical crystallization, the phosphate removal rate was stable at 82.98±1.16%, and the energy consumption was only 0.91±0.02 kWh·m -3 It can be seen that the pulse electrochemical crystallization electrode mentioned in this application greatly weakens the phenomenon of electrode passivation and has good stability and low energy consumption.

[0082] 3) Denitrification performance of HN-ADB

[0083] The domesticated strain HN-ADB was cultured in enriched medium (EM) until OD600 was 1.0. The bacterial solution was centrifuged and the separated bacteria were washed with sterile saline and inoculated into heterotrophic nitrifying culture NM (initial NH 4+ -N concentration was 150 mg / L) and aerobic denitrification medium DM (initial NO 3- -N was 150 mg / L) and cultured in an aerobic environment (15°C, 120 rpm) for 48 h. Samples were taken every 8 h to measure the nitrogen concentration in the reaction bottle. Three parallel experiments were set up. Samples were collected regularly to measure the NH4 + -N and NO3 - -N concentration, evaluate the denitrification performance of HN-ADB, as shown in Table 2, after 48h, NH4 + -N, NO3 - -N concentration dropped from 150mg / L to 0.03mg / L and 0.08mg / L respectively, which is much higher than the limit of Class III standard for surface water (Surface Water Environmental Quality Standard, GB4848-2002). It can be seen that HN-ADB has excellent denitrification performance and can achieve synchronous and efficient removal of ammonia nitrogen and nitric nitrogen in wastewater under aerobic conditions.

[0084] Table 2 Changes of ammonia nitrogen and nitrate nitrogen concentrations over time under the action of HN-ADB (mg / L)

[0085]

[0086] 4) Functional filler for PO4 3- -P adsorption performance and desorption regeneration

[0087] (1) Investigate the effect of functional fillers on PO4 3- -P adsorption performance, comprising the following steps:

[0088] A) Use KH2PO4 to configure the initial PO4 3- -P solutions with phosphorus concentrations of 5 mg / L, 10 mg / L, 20 mg / L, 30 mg / L, 40 mg / L, 50 mg / L, 60 mg / L, 70 mg / L, 80 mg / L and 100 mg / L respectively.

[0089] B) The pH value of the solution was adjusted to 7.0±0.2 using 0.1 mol / L NaOH and HCl, and the functional filler was added at a dosage of 20 g / L, and the mixture was oscillated at a constant temperature of 25±0.5° C. and 120 rpm for 24 hours.

[0090] C) After the reaction, the solution was centrifuged at 5000 rpm for 10 min, and the supernatant was passed through a 0.45 μm cellulose acetate membrane to measure the residual PO4 in the solution. 3- -P concentration.

[0091] The experimental results were fitted using the Langmuir and Freundlich isotherm adsorption models, respectively.

[0092] Figure 6 For the functional filler after calcination, PO4 3- -P isothermal adsorption model. It can be seen from the figure that the simulation results of the adsorption process by the two adsorption models are R 2 The values ​​are all greater than 0.9, with a high degree of fit. This shows that the functional filler prepared in this application has good 3- The adsorption process of -P involves both a chemical adsorption process based on the monolayer adsorption theory and a physical adsorption process based on the multilayer adsorption theory, and the corresponding saturated adsorption capacity is 42.01 mg / g.

[0093] (2) Investigate the effect of functional fillers on PO4 3- -P desorption regeneration, comprising the following steps:

[0094] A) Weigh a certain mass of functional filler that is saturated with adsorption and drained of water, place it in a 250 mL conical flask, and use 100 mL of NaOH, KCl, HCl with a molar concentration of 0.1 mol / L and 2 mmol / L citric acid to desorb it.

[0095] B) Place the conical flask in a constant temperature shaker at 25±0.5℃ and 120rpm for 24h, take the supernatant and filter it through a 0.45um filter membrane to determine the residual PO4 in the filtrate. 3- -P concentration, after calculation, the best functional filler desorption liquid is selected.

[0096] Table 3 Desorption rate of different desorption liquids on functional fillers after adsorption saturation

[0097]

[0098] From the results in Table 3, we can see that compared with strong acids, strong bases, and strong acid and strong base salts such as HCl, NaOH, and KCl, 2mmol / L citric acid has the best desorption effect on the functional filler after adsorption saturation, and the desorption rate can reach 93.52%. Figure 7 It can be seen that after five cycles of adsorption-desorption-re-adsorption after citric acid desorption, the adsorption amount is still 86.85% of the initial saturated adsorption amount. This shows that the functional filler has strong adsorption-desorption-re-adsorption stability, which can ensure its cyclic regeneration during use, and the use of low-concentration organic acid for desorption has the least impact on the ecosystem of the composite constructed wetland during actual operation.

[0099] 5) Water purification by composite wetlands

[0100] Composite artificial wetland influent COD, NH4 + -N, PO4 3- -P, TN, TP concentrations and turbidity were 268.39 mg / L, 36.89 mg / L, 2.72 mg / L, 43.23 mg / L, 3.18 mg / L and 3.52 NTU, respectively. As shown in Table 4, the corresponding concentrations of the effluent were 29.98 mg / L, 10.21 mg / L, 0.32 mg / L, 12.17 mg / L, 0.37 mg / L and 0.06 NTU, and the corresponding removal rates were 88.83%, 72.32%, 88.24%, 71.85%, 88.36% and 98.29%, respectively. The concentrations of pollutants such as TN, TP and COD in the effluent of the composite wetland can reach the Class A standard in the Pollutant Discharge Standard for Urban Sewage Treatment Plants (GB18918-2002). It can be seen that the composite artificial wetland proposed in this paper has high purification performance, and the functional filler introduced has strong phosphorus removal performance.

[0101] Table 4 Pollutant concentrations in the inlet and outlet water of the composite constructed wetland

[0102]

[0103] 6) Purification effect of coupling system

[0104] Actual aquaculture wastewater COD, NH4 + -N, PO4 3- -P, TN, TP concentrations and turbidity were 1503.59±10.52mg / L, 291.62±2.53mg / L, 15.98±0.12mg / L, 291.70±2.83mg / L, 17.26±0.19mg / L and 14.99±0.11NTU, respectively. After being treated by the pulse electrochemical crystallization coupled composite constructed wetland system proposed in this paper, the continuous monitoring results are shown in Table 5, indicating that the effluent COD and NH4 + -N, PO4 3- -P, TN, TP concentrations and turbidity were reduced to 29.98±0.26mg / L, 10.21±0.11mg / L, 0.32±0.008mg / L, 12.17±0.15mg / L, 0.37±0.009mg / L and 0.06±0.001NTU respectively, far exceeding the "Pollutant Emission Standard for Livestock and Poultry Breeding Industry" GB18596-2001 and "Farmland Irrigation Water Quality Standard"

[0105] GB5084-2021 and Level A standard of "Pollutant Discharge Standard for Urban Wastewater Treatment Plants" (GB18918-2002).

[0106] Table 5 Removal effect of coupling system

[0107]

[0108] In summary, the present invention uses an energy system to power the pulse electrochemical crystallization pool and the composite artificial wetland system. After the aquaculture wastewater enters the pulse electrochemical crystallization pool, it undergoes electrochemical crystallization to form struvite (MAP) precipitation, removes ammonia nitrogen and phosphates in the wastewater, and partially removes organic matter, thereby improving the biodegradability of the aquaculture wastewater and reducing the pollutant load of the subsequent wetland treatment unit. The use of pulse electrochemical crystallization technology has greatly reduced the operating energy consumption of the traditional direct current electrochemical process for purifying aquaculture wastewater. By designing a cylindrical hollow electrode plate, the effective reaction area of ​​the electrode plate in the electrochemical process is increased, the crystallization process is accelerated, the passivation of the electrode plate is reduced, and the stability of the device is improved. On the basis of traditional wetlands, self-made functional fillers with strong phosphate adsorption and elastic fillers using heterotrophic nitrification-aerobic denitrification functional bacteria for biofilm formation are introduced. The carbon, nitrogen, and phosphorus in the wastewater are simultaneously and deeply purified through filler filtration / adsorption, microbial assimilation / conversion, and plant absorption. The pulse electrochemical crystallization coupled composite artificial wetland system for deep treatment of aquaculture wastewater has a compact structure and strengthens the treatment of aquaculture wastewater through physical, chemical and biological multi-pathway coupling. The introduced HN-ADB solves the problem that the aerobic-anoxic-anaerobic alternating oxygen environment is difficult to achieve in the traditional biological denitrification process, reducing the process cost. The composite artificial wetland makes up for the defect of low purification efficiency of traditional artificial wetlands. The pulse electrochemical crystallization system has low operating energy consumption and the struvite formed by electrochemical crystallization can be used as a slow-release fertilizer to achieve resource recovery, which is in line with the sustainable development concept of resource recycling.

[0109] The above description is only a preferred embodiment of the present invention and is not intended to limit the protection scope of the present invention.

Claims

1. A pulse electrochemical crystallization coupled composite artificial wetland system, characterized in that: include: An energy system (1), a pulse electrochemical crystallization pool (2) and a composite artificial wetland system (3); the energy output end of the energy system (1) is connected to the energy input end of the pulse electrochemical crystallization pool (2) and the composite artificial wetland system (3) for energy supply, and the pulse electrochemical crystallization pool (2) is connected to the composite artificial wetland system (3) via a pipeline; The pulse electrochemical crystallization cell (2) comprises: a first sewage inlet pipe (20), a cathode electrode (21), an anode electrode (22), a first sewage outlet pipe (24) and a cell body (25); The first sewage inlet pipe (20) is arranged at the upper part of the tank body (25) and is electrically connected to the tank body (25); the first sewage outlet pipe (24) is arranged at the lower part of the tank body (25) and is electrically connected to the tank body (25); the cathode electrode (21) and the anode electrode (22) are fixed at the center of the tank body (25); The cathode electrode (21) and the anode electrode (22) are cylindrical, the diameter of the cathode electrode (21) is larger than the diameter of the anode electrode (22), and the anode electrode (22) is located in the cavity of the cathode electrode (21). The cathode electrode (21) and the anode electrode (22) are connected to the energy system (1) via a pulse power supply (26), and the energy system (1) provides pulse current to the cathode electrode (21) and the anode electrode (22) via the pulse power supply (26).

2. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1 is characterized in that: The pulse electrochemical crystallization cell (2) further comprises: a stirrer (23), wherein the stirrer (23) is fixed at the bottom of the cell body (25).

3. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1 is characterized in that: The pulse current frequency is 3000-4000 Hz.

4. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1 is characterized in that: The cathode electrode (21) is made of an aluminum alloy, and the anode electrode (22) is made of a magnesium alloy.

5. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1 is characterized in that: The composite artificial wetland system (3) comprises: a second sewage inlet pipe (30), a gravel support layer (31), a microporous aeration device (32), an elastic filler biological reinforcement layer (33), a functional filler physicochemical reinforcement layer (34), a quartz sand layer (35), a plant stem tissue layer (36), aquatic plants (37) and a second sewage discharge pipe (38); The gravel support layer (31), the microporous aeration device (32), the elastic filler biological reinforcement layer (33), the functional filler physicochemical reinforcement layer (34), the quartz sand layer (35) and the plant stem tissue layer (36) are laid in sequence from bottom to top, the aquatic plants (37) are planted on the upper sides of the quartz sand layer (35) and the plant stem tissue layer (36), and the second sewage discharge pipe (38) is located below the plant stem tissue layer (36).

6. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 2 is characterized in that: The energy system (1) comprises: a photovoltaic module (10), a wind turbine (11), a chopper (12), a rectifier (13), a power grid bus (14), a transformer (15) and a battery (16); The grid bus (14) is connected to the electrical equipment of the composite artificial wetland system (3) and the agitator (23) in the pulse electrochemical crystallization pool (2), and the transformer (15) is connected to the cathode electrode (21) and the anode electrode (22) of the pulse electrochemical crystallization pool (2) via a pulse power supply (26); A chopper (12) is arranged between the photovoltaic module (10) and the grid bus (14), a rectifier (13) is arranged between the wind turbine (11) and the grid bus (14), the storage battery (16) is connected to the grid bus (14), and a transformer (15) is arranged between the storage battery (16) and the grid bus (14).

7. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1, characterized in that: The gravel support layer (31) is formed by piling up coarse gravels, the particle size of the coarse gravels is 20-50 mm, and the height of the gravel support layer (31) is 20-50 cm.

8. The pulse electrochemical crystallization coupled composite artificial wetland system for deep treatment of aquaculture wastewater according to claim 1, characterized in that: The elastic filler bioreinforcement layer (33) is made of polypropylene, the particle size of the polypropylene filler in the elastic filler bioreinforcement layer (33) is 15-25 mm, the height of the elastic filler bioreinforcement layer (33) is 20-50 cm, and heterotrophic nitrification-aerobic denitrification bacteria (HN-ADB) are attached to the elastic filler bioreinforcement layer (33).

9. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1, characterized in that: The functional filler physical and chemical strengthening layer (34) is a strong adsorbent of PO4 3― -P functional filler, the particle size of the functional filler is 10-15mm, the height of the functional filler physicochemical strengthening layer (34) is 20-50cm, the functional filler is made of Ca / Al-based sludge, sponge iron powder, calcium carbonate and bentonite, water is added at a set ratio for granulation, and after drying in the shade, it is calcined at a high temperature of 800-1200℃ for 2-4h.

10. The pulse electrochemical crystallization coupled composite artificial wetland system according to claim 1, characterized in that: The quartz sand in the quartz sand layer (35) has a particle size of 2-10 mm and a height of 20-50 cm.

Images