A synchronous circulating ammonia and carbon fixation and sewage reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis and ammonia and carbon fixation method for sewage

Abstract

A synchronous circulating ammonia and carbon fixation device and sewage reduction method for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis, and a sewage ammonia and carbon fixation method, relate to an ammonia and carbon fixation device and sewage reduction method. The present invention aims to achieve circulating ammonia recovery in the cathode liquid in the microbial electrolysis system, utilizes step-by-step heat extraction to achieve water and ammonia resource recovery, and then utilizes a forward osmosis membrane to restore the cathode liquid conductivity with the help of water resources in the anode chamber sewage, so that the cathode liquid in the microbial electrolysis system can be regenerated and recycled. The wastewater treatment and energy conversion, continuous ammonia recovery, water recovery and sewage reduction of the microbial electrolysis system are achieved. The present invention realizes the efficient utilization of external energy and improves the overall resource and energy recovery rate of sewage for multiple resource components. It breaks the limitation of the continuous accumulation of non-ammonia cations in the cathode liquid on the efficient operation of the system and ammonia recovery, and avoids the loss of resource materials caused by the penetration of ammonium ions in the forward osmosis membrane.

Description

Technical Field

[0001] The present invention relates to a synchronous circulating ammonia and carbon fixation device and sewage reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis, and a sewage ammonia and carbon fixation method. Background Art

[0002] Since the Industrial Revolution, human activities have released large amounts of greenhouse gases, causing atmospheric concentrations to rise dramatically. This has led to an increasingly intensified greenhouse effect and a series of global climate challenges that are currently unpredictable. Energy consumption and carbon dioxide emissions are considered the primary drivers of the greenhouse effect. Due to increased energy demand, global energy-related carbon dioxide emissions increased by 1.7% in 2018, reaching a record high of 33.1 billion tons. As the world's largest energy consumer and carbon dioxide emitter, China has made significant efforts to reduce carbon emissions. Among its many industries, wastewater treatment is one of China's top ten energy-intensive sectors, contributing significantly to carbon emissions. Greenhouse gases generated during wastewater treatment account for 1.57% of global greenhouse gas emissions. Traditional wastewater treatment aims to remove carbon, nitrogen, phosphorus, and other pollutants (such as pathogens and suspended solids) to ensure that the effluent meets environmental standards, neglecting the requirements of low-carbon operation and energy conservation. Wastewater denitrification generally relies on microbial nitrification and denitrification processes. Nitrification is slow and requires high aeration levels, while denitrification consumes electron donors. Electron donors in wastewater treatment typically come from organic carbon sources, leading to further material consumption and carbon emissions. Simultaneously, with the advancement of science and technology and the development of my country's economy, numerous sectors, including industry, agriculture, and aquaculture, are constantly generating and discharging wastewater. Certain high-concentration, high-ammonia nitrogen wastewater (such as aquaculture wastewater, anaerobic digestion concentrate, and landfill leachate) contains ammonia nitrogen levels exceeding 500 mg / L. With the rapid development of the waste incineration industry, excessive emissions of incineration pollutants have also led to increasingly prominent neighborhood conflicts. Leachate generated from garbage dumps is characterized by high organic matter, high ammonia nitrogen content, high suspended solids content, high discharge volume, and complex composition. The unauthorized and indiscriminate discharge of this wastewater can lead to serious environmental pollution. Therefore, efficient treatment, coordinated resource utilization, and waste reduction are crucial.

[0003] Ammonia is a critical resource in wastewater containing high levels of ammonia nitrogen. In the national economy, 80% of ammonia is typically used to produce chemical fertilizers, while 20% serves as a raw material for other chemical products. Ammonia synthesis is a highly energy-intensive process requiring high temperatures and high pressures, accounting for approximately one percent of total global energy consumption. Effectively extracting and repurposing ammonia from wastewater would not only reduce energy consumption in the ammonia synthesis process but also further reduce the energy and material consumption required for denitrification.

[0004] Microbial electrochemical systems are devices that simultaneously treat organic pollutants in wastewater and utilize them for in-situ energy. Driven by the chemical energy released by organic matter metabolism at the anode, cations and anions can migrate in a directional manner within the electrolyte of the microbial electrochemical system, migrating toward the cathode and anode, respectively. Ammonia, typically present in wastewater as ammonium ions, migrates toward the cathode in the microbial electrochemical system. To effectively separate ammonia from the raw wastewater, microbial electrochemical systems are typically divided into anode and cathode compartments by a cation exchange membrane. While the anode compartment degrades organic matter in the wastewater, ammonia migrates from the anode to the cathode, facilitating its subsequent resource utilization. In microbial electrochemical systems in the form of electrolytic cells, applied electrical energy promotes directional ion migration within the system and effectively generates hydrogen at the cathode, achieving synergistic energy conversion from wastewater treatment. Hydrogen evolution at the cathode also raises the pH in the cathode compartment. While this reduces hydrogen evolution efficiency, it creates relatively favorable conditions for ammonia recovery. Ammonia accumulated in the cathode compartment can then be recovered through methods such as stripping. In addition, it has been reported that the anode chamber of the microbial electrolysis system can reduce nitrate into ammonia while degrading organic matter in sewage, thereby increasing the form of sewage ammonia recovery.

[0005] However, wastewater contains a variety of complex cations, and the cathode liquid accumulates other cations along with ammonia. The accumulation of multiple cations in the cathode liquid gradually leads to a stagnation of ammonia migration from the anode chamber and accumulation in the cathode chamber, making the ammonia recovery process unsustainable. Frequent replacement of the cathode liquid for this purpose increases water resource consumption and generates additional wastewater and treatment costs. Therefore, in order for the microbial electrochemical system to achieve catholyte recycling and continuous ammonia capture while treating and converting wastewater into energy, it is necessary to consider innovative designs for the cathode liquid regeneration process.

[0006] A forward osmosis membrane is a material that uses osmotic pressure differences to drive water separation. In existing reports, in microbial electrochemical systems, an external forward osmosis membrane can be used to reduce the amount of anolyte; during this process, high-concentration ammonium bicarbonate is used to extract water from the anode to reduce the amount of anolyte. However, the forward osmosis membrane cannot shield the diffusion of ammonium ions. Therefore, this reported application of forward osmosis membranes, while recovering some water from the effluent of the anode chamber, reduces the ammonia recovery rate, and its usage model urgently needs further optimization. Summary of the Invention

[0007] The present invention aims to realize the recycling ammonia recovery of the cathode liquid in the microbial electrolysis system, and utilizes the form of step-by-step heat extraction to realize the recovery of water resources and ammonia resources, and then utilizes the forward osmosis membrane to realize the restoration of the conductivity of the cathode liquid with the help of the water resources in the sewage in the anode chamber, so that the cathode liquid in the microbial electrolysis system can be regenerated and recycled. It not only realizes the sewage treatment and energy conversion process of the microbial electrolysis system, but also realizes the effects of cyclic and continuous ammonia recovery, water recovery and sewage reduction. The present invention realizes the efficient utilization of external energy and improves the overall resource energy recovery rate of sewage for multiple resource components. Compared with the existing system that uses cathode gas stripping and other technologies for ammonia recovery, it breaks the limitation of the continuous accumulation of non-ammonia cations in the cathode liquid on the efficient operation of the system and ammonia recovery, and also avoids the loss of resource materials caused by the penetration of ammonium ions in the forward osmosis membrane.

[0008] The synchronous circulation ammonia and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis of the present invention is composed of a microbial electrolysis cell system, a heat extraction unit and a forward osmosis unit;

[0009] The microbial electrolysis cell system is composed of an anode chamber (1) and a cathode chamber (4), wherein the anode chamber (1) and the cathode chamber (4) are separated by a cation exchange membrane (3), the anode (2) is arranged in the anode chamber (1), the cathode (5) is arranged in the cathode chamber (4), a power supply (17) is arranged between the anode (2) and the cathode (5), the positive pole of the power supply (17) is connected to the anode (2), and the negative pole of the power supply (17) is connected to the cathode (5); the anode chamber (1) is filled with high-ammonia nitrogen organic wastewater, and the cathode chamber (4) is filled with cathode liquid;

[0010] The heat extraction unit is composed of a carbon-nitrogen primary recovery device (6), a carbon-nitrogen secondary recovery device (8), a carbon-nitrogen terminal recovery device (12), a first condenser (13), a second condenser (14), a first-stage heat extraction device (15), and a second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is connected to the heat generating end of the first-stage heat extraction device (15); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is connected to the heat generating end of the second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is provided with a first carbon dioxide inlet pipe (61), a carbon-nitrogen primary recovery device exhaust pipe (62), a carbon-nitrogen primary recovery device liquid inlet pipe (63), and a carbon-nitrogen primary recovery device liquid discharge pipe (64); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is provided with a carbon-nitrogen secondary recovery device liquid inlet pipe (81) and a carbon-nitrogen secondary recovery device liquid discharge pipe (84). The gas pipe (82); the liquid inlet of the reaction container of the carbon-nitrogen primary recovery device (6) is connected to the cathode liquid outlet of the cathode chamber (4) through the carbon-nitrogen primary recovery device liquid inlet pipe (63), the carbon-nitrogen primary recovery device exhaust pipe (62) is connected to the air inlet of the first condenser (13), and the carbon-nitrogen primary recovery device exhaust pipe (62) is provided with an air pump. The liquid discharge port of the first condenser (13) is connected to the carbon-nitrogen secondary recovery device liquid inlet pipe (81), the carbon-nitrogen secondary recovery device exhaust pipe (82) is connected to the air inlet of the second condenser (14), and the exhaust port of the second condenser (14) is connected to the air inlet of the carbon-nitrogen terminal recovery device (12) through the carbon-nitrogen terminal recovery device inlet pipe (121); the air pump is provided on the carbon-nitrogen primary recovery device exhaust pipe (62) so that the front section pressure is lower than the standard atmospheric pressure and the rear section pressure is higher than the standard atmospheric pressure, thereby facilitating the rapid escape of ammonia from the first stage heat extraction;

[0011] The forward osmosis unit is composed of a raw liquid chamber (9) and an extraction liquid chamber (10), and the raw liquid chamber (9) and the extraction liquid chamber (10) are separated by a forward osmosis membrane (11); the liquid inlet of the raw liquid chamber (9) is connected to the liquid outlet of the anode chamber (1), the liquid outlet of the extraction liquid chamber (10) is connected to the liquid inlet of the cathode chamber (4), the liquid inlet of the extraction liquid chamber (10) is connected to the liquid outlet (64) of the carbon and nitrogen primary recovery device, and the liquid outlet (64) of the carbon and nitrogen primary recovery device is provided with a second carbon dioxide inlet pipe (65); and a third carbon dioxide inlet pipe (66) is provided on the connecting pipe between the liquid outlet of the extraction liquid chamber (10) and the liquid inlet of the cathode chamber (4).

[0012] The method for extracting ammonia and carbon fixation by using a synchronous circulating ammonia and carbon fixation and wastewater reduction device for treating high ammonia nitrogen organic wastewater based on microbial electrolysis is carried out in the following steps:

[0013] Step 1: Add high-ammonia nitrogen organic wastewater to the anode chamber (1), and grow electroactive microorganisms on the anode (2). The electroactive microorganisms use the organic matter in the wastewater to generate electrons and protons. The electrons are transferred to the anode (2) through the extracellular electron transfer process of the microorganisms, and then transferred to the cathode (5) through the external circuit, thereby forming an electric current. The power supply (17) increases the energy of the electrons, and a hydrogen evolution reaction occurs at the cathode (5), generating hydrogen gas and hydroxide ions, thereby increasing the alkalinity of the cathode liquid. Under the action of the internal electric field, the anions and cations inside the reactor begin to move in a directional manner, wherein the anions move toward the anode (2) and the cations move toward the cathode (5). The cation exchange membrane (3) has the function of selectively permeating cations. Driven by the internal electric field, the positively charged cations in the high-ammonia nitrogen organic wastewater in the anode chamber (1) pass through the cation exchange membrane (3) and enter the cathode liquid in the cathode (5); NH4 + Under the action of the internal electric field, the anode chamber (1) migrates to the cathode chamber (4) and is enriched in the cathode chamber (4), thereby obtaining a cathode solution with a high pH and a high ammonia concentration;

[0014] Step 2: The flue gas generated during the combustion process or the exhaust gas generated during the anaerobic fermentation process is introduced into the carbon dioxide inlet pipe, which includes a first carbon dioxide inlet pipe (61), a second carbon dioxide inlet pipe (65), and a third carbon dioxide inlet pipe (66);

[0015] The cathode liquid discharged from the cathode chamber (4) enters the reaction vessel of the carbon and nitrogen primary recovery device (6) through the liquid inlet pipe (63) of the carbon and nitrogen primary recovery device. The cathode liquid contains ammonia enriched at the cathode and is alkaline. The cathode liquid absorbs carbon dioxide in the flue gas generated in the combustion process or the exhaust gas generated in the anaerobic fermentation process to form a carbon and nitrogen co-absorption liquid; the first-stage heat extraction device (15) provides heat for the reaction vessel of the carbon and nitrogen primary recovery device (6), and the second-stage heat extraction device (16) provides heat for the reaction vessel of the carbon and nitrogen secondary recovery device (8); the first-stage heat extraction device (15) heats the carbon and nitrogen co-absorption liquid in the reaction vessel of the carbon and nitrogen primary recovery device (6) to the boiling point temperature, at which time water vapor carries carbon dioxide and ammonia and escapes (if necessary, the boiling point temperature can also be lowered by reducing the pressure of the carbon and nitrogen primary recovery device (6) reaction vessel to achieve the utilization of low-grade waste heat); the water vapor carrying carbon dioxide and ammonia is condensed through the first condenser (13) to form a carbon and nitrogen primary extraction liquid, and the carbon and nitrogen primary extraction liquid enters the reaction vessel of the carbon and nitrogen secondary recovery device (8); the second The heat extraction device (16) heats the carbon-nitrogen primary extraction liquid to 1-5°C below the boiling point, accelerates the condensation of water vapor into condensed water and retains it in the carbon-nitrogen secondary recovery device (8), realizes the recovery of water resources, and carbon dioxide and ammonia escape and enter the carbon-nitrogen terminal recovery device (12) to realize the co-recovery of carbon and nitrogen; after the heat extraction, the residual liquid of the carbon-nitrogen co-absorption liquid in the reaction container of the carbon-nitrogen primary recovery device (6) is reduced by evaporation of water, and the residual liquid of the carbon-nitrogen co-absorption liquid is transported to the extraction liquid chamber (10) as the extraction liquid of the forward osmosis unit, The effluent from the anode chamber (1) of the microbial electrolysis cell is transported to the raw liquid chamber (9) as the raw liquid of the forward osmosis unit; at this time, since the ammonia nitrogen and carbon dioxide in the carbon-nitrogen co-absorption liquid have already escaped, the ammonia nitrogen will not return to the effluent from the anode chamber (1), but water can be drawn from the effluent from the anode chamber (1), thereby reducing the discharge of the effluent from the anode chamber (1); during the forward osmosis process, the water in the raw liquid enters the drawn liquid, and the drawn liquid after the forward osmosis continues to be added to the cathode chamber (4) as the cathode liquid of the microbial electrolysis cell, thereby realizing recycling;

[0016] Smoke generated by a combustion process or exhaust gas generated by an anaerobic fermentation process, where both the combustion process and the anaerobic fermentation process are generated by devices other than those in this application;

[0017] The typical reaction equations for the carbon-nitrogen terminal recovery unit (12) to fix carbon dioxide and absorb ammonia nitrogen are as follows:

[0018] Calcium chloride solution: CaCl2+2NH3+H2O+CO2→CaCO3↓+ 2NH4Cl

[0019] Nearly saturated industrial brine: NaCl (concentrated brine) + NH3 + H2O + CO2 → NH4Cl + NaHCO3↓

[0020] Sun-dried brine: 2MgCl2 (concentrated brine) + 4NH4OH + CO2 → 4NH4Cl + Mg2(OH)2CO3↓ + H2O

[0021] Phosphogypsum solution: CaSO4+2NH3+H2O+CO2→CaCO3↓+(NH4)2SO4

[0022] It should be noted that the above reaction is not the only one; it represents a typical reaction. Depending on the pH and crystallization environment, the precipitated phase, anion-cation ratio, and the amount of water of crystallization may vary. Calcium chloride solution is a recyclable industrial waste generated from residual ammonium chloride solution in the ammonia-soda industry process.

[0023] The first carbon dioxide inlet pipe (61), the second carbon dioxide inlet pipe (65) and the third carbon dioxide inlet pipe (66) can all serve as carbon dioxide absorption sites of the device to transport the flue gas generated by the combustion process or the exhaust gas generated by the anaerobic fermentation process into the device, thereby achieving the regulation of carbon dioxide concentration and the regulation of carbon dioxide absorption efficiency. When the first carbon dioxide inlet pipe (61) is used for transportation, CO2-containing gas is introduced into the effluent of the cathode chamber (4) of the microbial electrolysis cell. The effluent of the cathode chamber (4) of the microbial electrolysis cell contains a large amount of CO3 2- OH - and NH4 + , its pH is high, and the effluent is alkaline, which is conducive to improving the CO2 absorption efficiency and capture amount. When CO2 gas is introduced into it, a large amount of HCO3 will be produced. - and NH4 + When the second carbon dioxide inlet pipe (65) is used for transportation, the carbon-nitrogen co-absorption liquid heated by the first-stage heat extraction device (15) undergoes heat extraction, causing water vapor, ammonia and carbon dioxide to escape. After the CO2-containing gas is added to the residual liquid after the carbon-nitrogen co-absorption liquid is heat-extracted through the second carbon dioxide inlet pipe (65), the CO2 gas dissolves in the residual liquid, increasing the ion concentration of the residual liquid, which is beneficial for extracting more water in the subsequent forward osmosis process, reducing the volume of wastewater discharged from the anode (2), and supplementing the volume loss of heat recovery of the cathode chamber (4). When the third carbon dioxide inlet pipe (66) is used for transportation, the CO2-containing gas is introduced into the extracted liquid after the forward osmosis process is completed. Carbon dioxide is an acidic gas that can reduce the pH of the water inlet to the cathode (5) of the microbial electrolysis cell when the cathode liquid circulates and enters the cathode chamber again, thereby improving the hydrogen production performance of the microbial electrolysis cell.

[0024] The principles and beneficial effects of the present invention are:

[0025] 1. The present invention continuously recycles the cathode liquid and performs carbon capture and ammonia recovery, thereby avoiding the accumulation of a large amount of cations in the cathode liquid, preventing the blocking of ammonium radical migration to the cathode due to the continuous non-replacement of the cathode liquid, and reducing the wastewater and electrolyte loss generated by the continuous disposal of the cathode liquid.

[0026] 2. The present invention can recover the water-borne energy, ammonia resources and water resources carried by organic matter in sewage, among which the recovery efficiency of ammonia nitrogen resources is >90%, which greatly reduces the consumption of subsequent denitrification and recovers active nitrogen resources.

[0027] 3. The present invention can avoid ammonia loss in the forward osmosis device, and the ammonia recovery efficiency is significantly improved.

[0028] 4. The present invention can improve system efficiency by optimizing the specific sites of carbon capture (carbon dioxide absorption sites).

[0029] 5. The present invention recovers the sewage added to the anode chamber into the cathode liquid through forward osmosis. The cathode liquid produces a portion of distilled water during subsequent heating, thereby realizing partial water recovery in the sewage and reducing the amount of sewage. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 This is a schematic structural diagram of the synchronous circulating ammonia and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis in Example 1;

[0031] Figure 2 This is the current output curve diagram of the microbial electrolysis cell system startup process;

[0032] Figure 3 Figure 2 is a graph of carbon and nitrogen capture during heat recovery at different CO2 absorption sites;

[0033] Figure 4 The conductivity change diagram of the raw liquid (MEC anode chamber effluent) before and after passing through the forward osmosis treatment unit in operation modes 1-4;

[0034] Figure 5 This is a volume concentration rate diagram of the raw liquid (MEC anode chamber effluent) after forward osmosis in the embodiment;

[0035] Figure 6 This is the conductivity change diagram of the draw solution (circulating MEC cathode solution) in multi-cycle operation of operation mode 1;

[0036] Figure 7 The diagram of MEC current changes at each CO2 absorption site;

[0037] Figure 8 is the two-step ammonia nitrogen recovery efficiency of the microbial electrolysis cell and forward osmosis unit;

[0038] Figure 9 This is a physical picture of the product obtained after CO2 mineralization and carbonation of the recovered brine;

[0039] Figure 10 This is the XRD pattern of the product obtained after the recovered brine was subjected to CO2 mineralization and carbonation;

[0040] Figure 11 This is a physical picture of the product obtained after CO2 mineralization and carbonation of phosphogypsum as the recovered liquid;

[0041] Figure 12 This is the XRD diagram of the product obtained after CO2 mineralization and carbonation of the recovered liquid phosphogypsum;

[0042] Figure 13 This is a physical picture of the product obtained after CO2 mineralization and carbonation using saturated industrial concentrated brine as the recovered liquid;

[0043] Figure 14 This is the XRD diagram of the product obtained after CO2 mineralization and carbonation using saturated industrial brine as the recovered liquid. DETAILED DESCRIPTION

[0044] The technical solution of the present invention is not limited to the specific implementation methods listed below, but also includes any reasonable combination of the specific implementation methods.

[0045] Specific embodiment 1: This embodiment of the invention is based on microbial electrolysis to treat high ammonia nitrogen organic wastewater. The synchronous circulation ammonia and carbon fixation and wastewater reduction device consists of a microbial electrolysis cell system, a heat extraction unit and a forward osmosis unit.

[0046] The microbial electrolysis cell system is composed of an anode chamber (1) and a cathode chamber (4), wherein the anode chamber (1) and the cathode chamber (4) are separated by a cation exchange membrane (3), the anode (2) is arranged in the anode chamber (1), the cathode (5) is arranged in the cathode chamber (4), a power supply (17) is arranged between the anode (2) and the cathode (5), the positive pole of the power supply (17) is connected to the anode (2), and the negative pole of the power supply (17) is connected to the cathode (5); the anode chamber (1) is filled with high-ammonia nitrogen organic wastewater, and the cathode chamber (4) is filled with cathode liquid;

[0047] The heat extraction unit is composed of a carbon-nitrogen primary recovery device (6), a carbon-nitrogen secondary recovery device (8), a carbon-nitrogen terminal recovery device (12), a first condenser (13), a second condenser (14), a first-stage heat extraction device (15), and a second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is connected to the heat generating end of the first-stage heat extraction device (15); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is connected to the heat generating end of the second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is provided with a first carbon dioxide inlet pipe (61), a carbon-nitrogen primary recovery device exhaust pipe (62), a carbon-nitrogen primary recovery device liquid inlet pipe (63), and a carbon-nitrogen primary recovery device liquid discharge pipe (64); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is provided with a carbon-nitrogen secondary recovery device liquid inlet pipe (81) and a carbon-nitrogen secondary recovery device liquid discharge pipe (84). The gas pipe (82); the liquid inlet of the reaction container of the carbon-nitrogen primary recovery device (6) is connected to the cathode liquid outlet of the cathode chamber (4) through the carbon-nitrogen primary recovery device liquid inlet pipe (63), the carbon-nitrogen primary recovery device exhaust pipe (62) is connected to the air inlet of the first condenser (13), and the carbon-nitrogen primary recovery device exhaust pipe (62) is provided with an air pump. The liquid discharge port of the first condenser (13) is connected to the carbon-nitrogen secondary recovery device liquid inlet pipe (81), the carbon-nitrogen secondary recovery device exhaust pipe (82) is connected to the air inlet of the second condenser (14), and the exhaust port of the second condenser (14) is connected to the air inlet of the carbon-nitrogen terminal recovery device (12) through the carbon-nitrogen terminal recovery device inlet pipe (121); the air pump is provided on the carbon-nitrogen primary recovery device exhaust pipe (62) so that the front section pressure is lower than the standard atmospheric pressure and the rear section pressure is higher than the standard atmospheric pressure, thereby facilitating the rapid escape of ammonia from the first stage heat extraction;

[0048] The forward osmosis unit is composed of a raw liquid chamber (9) and an extraction liquid chamber (10), and the raw liquid chamber (9) and the extraction liquid chamber (10) are separated by a forward osmosis membrane (11); the liquid inlet of the raw liquid chamber (9) is connected to the liquid outlet of the anode chamber (1), the liquid outlet of the extraction liquid chamber (10) is connected to the liquid inlet of the cathode chamber (4), the liquid inlet of the extraction liquid chamber (10) is connected to the liquid outlet (64) of the carbon and nitrogen primary recovery device, and the liquid outlet (64) of the carbon and nitrogen primary recovery device is provided with a second carbon dioxide inlet pipe (65); and a third carbon dioxide inlet pipe (66) is provided on the connecting pipe between the liquid outlet of the extraction liquid chamber (10) and the liquid inlet of the cathode chamber (4).

[0049] This embodiment has the following beneficial effects:

[0050] 1. The present embodiment continuously recycles the cathode liquid and performs carbon capture and ammonia recovery, thereby avoiding the accumulation of a large amount of cations in the cathode liquid, preventing the blocking of ammonium radical migration to the cathode due to the continuous non-replacement of the cathode liquid, and reducing the wastewater and electrolyte loss generated by the continuous disposal of the cathode liquid.

[0051] 2. This embodiment can recover the water-borne energy, ammonia resources and water resources carried by organic matter in sewage, among which the recovery efficiency of ammonia nitrogen resources is >90%, which greatly reduces the consumption of subsequent denitrification and recovers active nitrogen resources.

[0052] 3. This embodiment can avoid ammonia loss in the forward osmosis device, and the ammonia recovery efficiency is significantly improved.

[0053] 4. This embodiment can improve system efficiency by optimizing the specific sites of carbon capture (carbon dioxide absorption sites).

[0054] 5. In this embodiment, the sewage added to the anode chamber is recovered into the cathode liquid through forward osmosis. The cathode liquid produces a portion of distilled water during subsequent heating, thereby realizing partial water recovery in the sewage and reducing the amount of sewage.

[0055] Specific embodiment 2: This embodiment differs from specific embodiment 1 in that: the anode (2) is a carbon-based anode or a metal-based anode; the carbon-based anode is a carbon fiber brush, carbon felt, carbon cloth, carbon paper, graphite plate or activated carbon particles; the metal-based anode is an iron-based anode or a titanium-based anode.

[0056] Specific embodiment three: The difference between this embodiment and specific embodiment two is that: the carbon-based anode or metal-based anode is surface modified or pretreated; the surface modification is high-temperature N doping, surface modification of iron compounds, polyaniline / polydopamine organic compound modification; the pretreatment is high-temperature removal of colloid on the surface of the carbon material, acid treatment, alkali treatment, ultraviolet ozone oxidation treatment, and plasma surface treatment.

[0057] Specific embodiment 4: This embodiment differs from any one of specific embodiments 1 to 3 in that the cathode (5) material is stainless steel mesh, nickel foam, carbon felt, carbon fiber brush, activated carbon particles, etc.

[0058] Specific embodiment 5: This embodiment differs from specific embodiments 1 to 4 in that: the cathode (5) is coated with a hydrogen evolution catalyst; the hydrogen evolution catalyst is Pt, NiO, etc.; carbon-based or metal-based materials with good conductivity, no biotoxicity and good biocompatibility can be used as the anode in the present invention.

[0059] Specific embodiment six: This embodiment differs from any one of specific embodiments one to five in that: the carbon-nitrogen terminal recovery device (12) is a pressure-bearing reactor filled with recovery liquid.

[0060] Specific embodiment seven: This embodiment differs from specific embodiment six in that the recovered liquid is calcium chloride solution, concentrated brine, phosphogypsum solution, and salt brine; calcium chloride solution, concentrated brine, phosphogypsum solution, and salt brine are all industrial waste.

[0061] Specific embodiment eight: This embodiment differs from any one of specific embodiments one to seven in that: the first-stage heat extraction device (15) and the second-stage heat extraction device (16) are heat exchangers; and the heat sources of the first-stage heat extraction device (15) and the second-stage heat extraction device (16) are flue gas waste heat or biogas combustion heat.

[0062] Specific embodiment nine: This embodiment uses a synchronous circulating ammonia and carbon fixation and sewage reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis to perform a method for ammonia and carbon fixation according to the following steps: Step 1: High-ammonia nitrogen organic wastewater is added to the anode chamber (1), and electroactive microorganisms grow on the anode (2). The electroactive microorganisms use organic matter in the wastewater to generate electrons and protons. The electrons are transferred to the anode (2) through the extracellular electron transfer process of the microorganisms, and then transferred to the cathode (5) through the external circuit, thereby forming an electric current. The power supply (17) increases the energy of the electrons, and a hydrogen evolution reaction occurs at the cathode (5), generating hydrogen gas and hydroxide ions, thereby increasing the alkalinity of the cathode liquid; the anions and cations inside the reactor begin to move in a directional manner under the action of the internal electric field, wherein the anions move toward the anode (2) and the cations move toward the cathode (5); the cation exchange membrane (3) has the function of selectively permeating cations. Driven by the internal electric field, the positively charged cations in the high-ammonia nitrogen organic wastewater in the anode chamber (1) pass through the cation exchange membrane (3) and enter the cathode liquid in the cathode (5); NH4 + Under the action of the internal electric field, the anode chamber (1) migrates to the cathode chamber (4) and is enriched in the cathode chamber (4), thereby obtaining a cathode solution with a high pH and a high ammonia concentration;

[0063] Step 2: The flue gas generated during the combustion process or the exhaust gas generated during the anaerobic fermentation process is introduced into the carbon dioxide inlet pipe, which includes a first carbon dioxide inlet pipe (61), a second carbon dioxide inlet pipe (65), and a third carbon dioxide inlet pipe (66);

[0064] The cathode liquid discharged from the cathode chamber (4) enters the reaction vessel of the carbon and nitrogen primary recovery device (6) through the liquid inlet pipe (63) of the carbon and nitrogen primary recovery device. The cathode liquid contains ammonia enriched at the cathode and is alkaline. The cathode liquid absorbs carbon dioxide in the flue gas generated in the combustion process or the exhaust gas generated in the anaerobic fermentation process to form a carbon and nitrogen co-absorption liquid; the first-stage heat extraction device (15) provides heat for the reaction vessel of the carbon and nitrogen primary recovery device (6), and the second-stage heat extraction device (16) provides heat for the reaction vessel of the carbon and nitrogen secondary recovery device (8); the first-stage heat extraction device (15) heats the carbon and nitrogen co-absorption liquid in the reaction vessel of the carbon and nitrogen primary recovery device (6) to the boiling point temperature, at which time water vapor carries carbon dioxide and ammonia and escapes (if necessary, the boiling point temperature can also be lowered by reducing the pressure of the carbon and nitrogen primary recovery device (6) reaction vessel to achieve the utilization of low-grade waste heat); the water vapor carrying carbon dioxide and ammonia is condensed through the first condenser (13) to form a carbon and nitrogen primary extraction liquid, and the carbon and nitrogen primary extraction liquid enters the reaction vessel of the carbon and nitrogen secondary recovery device (8); the second The heat extraction device (16) heats the carbon-nitrogen primary extraction liquid to 1-5°C below the boiling point, accelerates the condensation of water vapor into condensed water and retains it in the carbon-nitrogen secondary recovery device (8), realizes the recovery of water resources, and carbon dioxide and ammonia escape and enter the carbon-nitrogen terminal recovery device (12) to realize the co-recovery of carbon and nitrogen; after the heat extraction, the residual liquid of the carbon-nitrogen co-absorption liquid in the reaction container of the carbon-nitrogen primary recovery device (6) is reduced by evaporation of water, and the residual liquid of the carbon-nitrogen co-absorption liquid is transported to the extraction liquid chamber (10) as the extraction liquid of the forward osmosis unit, The effluent from the anode chamber (1) of the microbial electrolysis cell is transported to the raw liquid chamber (9) as the raw liquid of the forward osmosis unit; at this time, since the ammonia nitrogen and carbon dioxide in the carbon-nitrogen co-absorption liquid have escaped, the ammonia nitrogen will not return to the effluent from the anode chamber (1), but water can be drawn from the effluent from the anode chamber (1), thereby reducing the discharge of the effluent from the anode chamber (1); during the forward osmosis process, the water in the raw liquid enters the drawn liquid, and the drawn liquid after the forward osmosis continues to be added to the cathode chamber (4) as the cathode liquid of the microbial electrolysis cell, thereby realizing recycling.

[0065] 1. The present embodiment continuously recycles the cathode liquid and performs carbon capture and ammonia recovery, thereby avoiding the accumulation of a large amount of cations in the cathode liquid, preventing the blocking of ammonium radical migration to the cathode due to the continuous non-replacement of the cathode liquid, and reducing the wastewater and electrolyte loss generated by the continuous disposal of the cathode liquid.

[0066] 2. This embodiment can recover the water-borne energy, ammonia resources and water resources carried by organic matter in sewage, among which the recovery efficiency of ammonia nitrogen resources is >90%, which greatly reduces the consumption of subsequent denitrification and recovers active nitrogen resources.

[0067] 3. This embodiment can avoid ammonia loss in the forward osmosis device, and the ammonia recovery efficiency is significantly improved.

[0068] 4. This embodiment can improve system efficiency by optimizing the specific sites of carbon capture (carbon dioxide absorption sites).

[0069] 5. In this embodiment, the sewage added to the anode chamber is recovered into the cathode liquid through forward osmosis. The cathode liquid produces a portion of distilled water during subsequent heating, thereby realizing partial water recovery in the sewage and reducing the amount of sewage.

[0070] Specific embodiment ten: This embodiment differs from specific embodiment nine in that: during operation, the microbial electrolysis cell system adopts continuous flow or batch operation, with an operation cycle of 4h~7d, the applied voltage of the power supply (17) is 0.2~2V, and the pH value of the anolyte is adjusted to 4~11; based on the membrane area of the ion exchange membrane of the microbial electrolysis cell system, the current density during the operation of the microbial electrolysis cell system is 0.1A / m 2 ~100A / m 2 (Based on the membrane area of the ion exchange membrane of the microbial electrolysis cell system), both the ammonia recovery rate and the ammonia concentration of the absorption liquid can be regulated.

[0071] Example 1:

[0072] The synchronous circulating ammonia and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis in this embodiment is composed of a microbial electrolysis cell system, a heat extraction unit and a forward osmosis unit;

[0073] The microbial electrolysis cell system is composed of an anode chamber (1) and a cathode chamber (4), wherein the anode chamber (1) and the cathode chamber (4) are separated by a cation exchange membrane (3), the anode (2) is arranged in the anode chamber (1), the cathode (5) is arranged in the cathode chamber (4), a power supply (17) is arranged between the anode (2) and the cathode (5), the positive pole of the power supply (17) is connected to the anode (2), and the negative pole of the power supply (17) is connected to the cathode (5); the anode chamber (1) is filled with high-ammonia nitrogen organic wastewater, and the cathode chamber (4) is filled with cathode liquid;

[0074] The heat extraction unit is composed of a carbon-nitrogen primary recovery device (6), a carbon-nitrogen secondary recovery device (8), a carbon-nitrogen terminal recovery device (12), a first condenser (13), a second condenser (14), a first-stage heat extraction device (15), and a second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is connected to the heat generating end of the first-stage heat extraction device (15); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is connected to the heat generating end of the second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is provided with a first carbon dioxide inlet pipe (61), a carbon-nitrogen primary recovery device exhaust pipe (62), a carbon-nitrogen primary recovery device liquid inlet pipe (63), and a carbon-nitrogen primary recovery device liquid discharge pipe (64); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is provided with a carbon-nitrogen secondary recovery device liquid inlet pipe (81) and a carbon-nitrogen secondary recovery device liquid discharge pipe (84). The gas pipe (82); the liquid inlet of the reaction container of the carbon-nitrogen primary recovery device (6) is connected to the cathode liquid outlet of the cathode chamber (4) through the carbon-nitrogen primary recovery device liquid inlet pipe (63), the carbon-nitrogen primary recovery device exhaust pipe (62) is connected to the air inlet of the first condenser (13), and the carbon-nitrogen primary recovery device exhaust pipe (62) is provided with an air pump. The liquid discharge port of the first condenser (13) is connected to the carbon-nitrogen secondary recovery device liquid inlet pipe (81), the carbon-nitrogen secondary recovery device exhaust pipe (82) is connected to the air inlet of the second condenser (14), and the exhaust port of the second condenser (14) is connected to the air inlet of the carbon-nitrogen terminal recovery device (12) through the carbon-nitrogen terminal recovery device inlet pipe (121); the air pump is provided on the carbon-nitrogen primary recovery device exhaust pipe (62) so that the front section pressure is lower than the standard atmospheric pressure and the rear section pressure is higher than the standard atmospheric pressure, thereby facilitating the rapid escape of ammonia from the first stage heat extraction;

[0075] The carbon and nitrogen terminal recovery device (12) is a pressure-bearing reactor filled with a recovery liquid;

[0076] The first-stage heat extraction device (15) and the second-stage heat extraction device (16) are heat exchangers; the heat source of the first-stage heat extraction device (15) and the second-stage heat extraction device (16) is flue gas waste heat;

[0077] The forward osmosis unit is composed of a raw liquid chamber (9) and an extraction liquid chamber (10), and the raw liquid chamber (9) and the extraction liquid chamber (10) are separated by a forward osmosis membrane (11); the liquid inlet of the raw liquid chamber (9) is connected to the liquid outlet of the anode chamber (1), the liquid outlet of the extraction liquid chamber (10) is connected to the liquid inlet of the cathode chamber (4), the liquid inlet of the extraction liquid chamber (10) is connected to the liquid outlet (64) of the carbon and nitrogen primary recovery device, and the liquid outlet (64) of the carbon and nitrogen primary recovery device is provided with a second carbon dioxide inlet pipe (65); and a third carbon dioxide inlet pipe (66) is provided on the connecting pipe between the liquid outlet of the extraction liquid chamber (10) and the liquid inlet of the cathode chamber (4);

[0078] In this embodiment, the anode chamber (1) and cathode chamber (4) of the microbial electrolysis cell system are made of transparent organic glass, including an anode chamber (1) with a working volume of 28 mL and a cathode chamber (4) with a working volume of 14 mL. The two chambers are separated by a 7.1 cm 2 The anode chamber (1) and the cathode chamber (4) are separated by a cation exchange membrane. There are covers (5cm×5cm×0.5cm) at both ends of the anode chamber (1) and the cathode chamber (4). The covers are fastened to the chamber by bolts and nuts. A layer of rubber gasket is sandwiched between the covers and the chamber to improve the sealing and prevent water leakage. There are one or two sampling holes with a diameter of 1cm on the top of the anode chamber (1) and the cathode chamber (4), which are used to replace the electrode liquid and serve as hydrogen collection holes, and are equipped with rubber plugs to form a closed chamber. A carbon fiber brush anode with a size of φ:2.5cm×L:2.5cm is installed in the anode chamber (1). The titanium wire of the carbon fiber brush passes through the cover of the anode chamber (1), and the brush body extends into the cathode chamber (4) and is completely immersed in the anode electrolyte. A double-layer stainless steel mesh is installed on the side of the cathode chamber (4) close to the cover as a cathode.

[0079] The first-stage heat extraction device (15) and the second-stage heat extraction device (16) use simulated flue gas (80% N2 + 20% CO2) carrying residual heat as the heat source; the first-stage heat extraction device (15) provides heat for the reaction vessel of the carbon-nitrogen primary recovery device (6) to heat the carbon-nitrogen co-absorption liquid to the boiling point temperature (99.8°C). Since the carbon-nitrogen co-absorption liquid is a high-salt solution with a boiling point higher than that of water, it will not boil and is in a slightly boiling state. The second-stage heat extraction device (16) provides heat for the reaction vessel of the carbon-nitrogen secondary recovery device (8) to heat it to 1-5°C below the boiling point. A portion of the condensate remains in the reaction vessel of the carbon-nitrogen secondary recovery device (8), while most of the ammonia nitrogen and carbon dioxide continue to escape and are condensed again and flow into the carbon-nitrogen terminal recovery device (12). The working volume of the raw liquid chamber (9) of the forward osmosis unit is 28 mL, and the working volume of the extraction liquid chamber (10) is 14 mL. The two chambers are separated by a 7.1 cm 2 The forward osmosis membrane (11) is separated;

[0080] Figure 2 The current output curve of the microbial electrolysis cell system during startup is shown in Figure 1. A 0.9V external voltage is supplied to the MEC via a power supply (17) adapter (DC output 0~12V). In the initial startup phase, the anode microorganisms use the supernatant of anaerobic sludge from the sewage treatment plant as the bacterial source. The anode liquid contains sodium acetate as the main organic pollutant, with a concentration of about 2g / L; ammonium chloride as ammonia nitrogen, NH4 +The -N concentration was approximately 1 g / L; the anolyte contained the following ions: 4.58 g / L Na₂HPO₄, 2.77 g / L NaH₂PO₄·2H₂O, and 0.13 g / L KCl. These salts were dissolved using domestic sewage to simulate high-ammonia nitrogen organic wastewater. The initial conductivity of the anolyte was approximately 14.5 mS / cm, while the initial catholyte consisted of a Na₂CO₃ solution with a conductivity of 11 mS / cm. The microbial electrolysis cell system was operated in sequencing batch mode with a hydraulic retention time of 24 hours. After 15 to 30 days of acclimation, an electroactive biofilm gradually formed at the anode. The system was considered fully activated when the reactor current curve stabilized and three consecutive, reproducible sequencing batch current curves were obtained.

[0081] After the start-up is completed, within each residence time of 24 hours, the anode microorganisms metabolize the organic matter in the anode liquid (high ammonia nitrogen organic wastewater), release the electrons in the organic matter to the anode, and use the ability of the organic matter to be oxidized to drive the electrons to flow to the cathode. The electrons obtain energy compensation from the external power supply (17) in the external circuit, thereby completing the hydrogen evolution process at the cathode and realizing partial recovery of the energy in the wastewater in the form of hydrogen. The cathode can also have other forms, such as oxygen reduction, oxide reduction, heavy metal reduction, etc., to complete the utilization of electrons, which are not listed here. In the solution inside the microbial electrolysis cell, under the action of the internal electric field driving force, an internal current is also generated. The current in the solution phase is formed by the directional migration of charged ions. However, since an ion exchange membrane that only allows cations to pass is added between the anode and cathode chambers in the microbial electrolysis cell, the cations in the anode chamber, mainly ammonium ions, migrate to the cathode side. The cathode chamber releases hydrogen in the process of electrolysis of water to produce hydrogen, leaving behind hydroxide ions, which combine with cations that migrate from the anode chamber to the cathode chamber to maintain electrical neutrality. Once the organic pollutants in the anode chamber have been consumed, the entire migration process is complete. The cathode liquid is enriched with ammonia nitrogen that has migrated from the anode chamber and is alkaline. At this time, simulated flue gas rich in carbon dioxide (80% N2 and 20% CO2) is passed into the reaction vessel of the carbon and nitrogen primary recovery device (6). When its pH drops to 7.8-8.5, it is considered to be completely absorbed and becomes a carbon and nitrogen co-absorption liquid.

[0082] The carbon-nitrogen co-absorption liquid obtained in the reaction vessel of the carbon-nitrogen primary recovery device (6) is heated by a heat extraction device to extract water vapor, ammonia and carbon dioxide. The heating temperature is the boiling point temperature of the carbon-nitrogen co-absorption liquid at the working pressure at that time. In the embodiment, the heat source of the heat extraction device is heated simulated flue gas (simulating flue gas carrying residual heat). The residual liquid extracted from the reaction vessel of the carbon-nitrogen primary recovery device (6) is used as the draw liquid in the forward osmosis process and enters the draw liquid chamber. At the same time, the effluent from the anode chamber of the microbial electrolysis cell is used as the raw liquid and enters the raw liquid chamber of the forward osmosis system. During the forward osmosis process, water in the raw liquid enters the draw liquid, and the volume and conductivity of the raw liquid and the draw liquid will change. The diluted draw liquid continues to be recycled as the cathode electrolyte of the MEC.

[0083] After the carbon-nitrogen co-absorption liquid is subjected to heat extraction in the reaction vessel of the carbon-nitrogen primary recovery device (6), water vapor, ammonia, and carbon dioxide are released; the above gases are condensed by heat dissipation and enter the reaction vessel of the carbon-nitrogen secondary recovery device (8). The reaction vessel of the carbon-nitrogen secondary recovery device (8) is also heated by the heat extraction device, but the temperature is slightly lower than the boiling point temperature at the working pressure at this time by 1-5°C. At this time, the evaporation of water vapor decreases, but ammonia and carbon dioxide will escape and enter the subsequent carbon-nitrogen terminal recovery device (12). In the carbon-nitrogen terminal recovery device (12), carbon dioxide can be absorbed and fixed by industrial waste (such as industrial concentrated brine, phosphogypsum solution, salt brine, etc.) to produce carbonate products. Ammonia dissolves in water to provide cations, and ammonium ions combine with chloride ions to form ammonium chloride solution. High-concentration ammonium chloride can be used as liquid fertilizer, or it can be crystallized to precipitate ammonium chloride products.

[0084] 1. Testing of different CO2 absorption sites: CO2 absorption site 1 is the effluent from the cathode chamber of the MEC unit (microbial electrolysis cell) (simulated flue gas containing CO2 is passed into the first CO2 inlet pipe 61); CO2 absorption site 2 is after the heat recovery process (simulated flue gas containing CO2 is passed into the second CO2 inlet pipe 65); CO2 absorption site 3 is after forward osmosis treatment (simulated flue gas containing CO2 is passed into the third CO2 inlet pipe 66). A combined CO2 absorption method was also considered. However, during implementation, it was found that the pH of the draw solution could be reduced to approximately 8.5 after the "carbon capture (CO2 absorption site 1) - heat recovery - forward osmosis" process, which is very close to the end point of CO2 aeration. Therefore, when absorption site 1 is present, it is not very meaningful to aerate absorption site 3. Therefore, absorption sites 1 and 2 were selected as a combined carbon absorption method, which is the fourth carbon absorption mode in addition to the three absorption sites. The specific test results are as follows:

[0085] 1. Effects of different carbon dioxide absorption sites on carbon and nitrogen capture rates

[0086] Carbon (or nitrogen) capture rate during heat recovery ( or ,%) is defined as:

[0087]

[0088] Where n0 is the initial carbon (or nitrogen) content in the cathode liquid, mmol; n t is the carbon (or nitrogen) content after heat recovery (the effluent from the carbon and nitrogen primary recovery device), mmol. The value of carbon (or nitrogen) capture is equal to .

[0089] Figure 3 Figure 2. Carbon and nitrogen capture during heat recovery at different CO2 absorption sites. (The horizontal axis is represented as "ab," where a represents the CO2 absorption site and b represents the cycle period. For example, 1+2-2 represents absorption sites 1+2 and a cycle period of 2.) Figure 3 This reflects the amount of carbon and nitrogen captured during the heat recovery process. It can be seen that the nitrogen capture amounts of the systems corresponding to the four different CO2 absorption sites are relatively small, and the nitrogen capture rates are all above 90%. However, considering the three operating cycles, the nitrogen capture amounts of the systems corresponding to absorption sites 1 and 1+2 are generally higher than those of absorption sites 1 and 3. By the third cycle at absorption sites 1 and 1+2, the nitrogen capture rates reached 99.84% and 99.80%, respectively.

[0090] Unlike the results for nitrogen capture, carbon capture varied significantly across the various absorption sites. At CO2 absorption sites 2 and 3, carbon capture rates increased with increasing cycle number, reaching maximum values of 36.36% and 33.15%, respectively, corresponding to carbon capture capacities of 2.91 mmol and 2.88 mmol, respectively. However, these values were only approximately one-third of the carbon capture rates at CO2 absorption sites 1 and CO2 absorption sites 1+2. At CO2 absorption site 1 and the combined CO2 absorption sites 1+2, carbon capture results fluctuated over the three cycles, but remained close to 10 mmol. Carbon capture rates also reached their maximum values in the second cycle (73.32% and 63.11%). Regarding carbon and nitrogen capture, absorption sites 1 and 1+2 outperformed the other two absorption sites.

[0091] 2. Impact of different CO2 absorption sites on wastewater reduction

[0092] During the heat recovery process, the volume of the catholyte decreases and its ion concentration increases, making it suitable for use as a draw solution. After treatment in the anode chamber, the conductivity of wastewater decreases due to the degradation of organic matter and the migration of cations such as ammonium to the cathode chamber, making it suitable for use as a feed solution. During forward osmosis, water molecules in the feed solution diffuse into the draw solution, enabling water extraction.

[0093] Operation mode 1: After the ammonia in the anode electrolyte of the MEC system migrates into the cathode liquid, the cathode chamber effluent is transferred to the reaction vessel of the carbon-nitrogen primary recovery device (6). Simulated flue gas is introduced at this point (CO2 absorption point 1). The ammonia-rich cathode chamber effluent absorbs carbon dioxide and becomes a carbon-nitrogen co-absorption liquid. After the first cycle of thermal extraction, the volume loss of the carbon-nitrogen co-absorption liquid in the reaction vessel of the carbon-nitrogen primary recovery device (6) is 24±4.3%, and the conductivity of the extracted residual liquid is 14.8±0.8mS / cm. The residual liquid after thermal extraction is used as the draw liquid. After forward osmosis, the volume increases by 16±4.5%, and the conductivity decreases to 12.3±0.4mS / cm. Forward osmosis reduces the volume of the raw liquid (MEC anode chamber effluent) by 21±1.6%, and the conductivity increases from 10.0±0.02mS / cm to 11.3±0.22mS / cm. According to the operating procedure, the draw liquid after water absorption is returned to the cathode chamber and used as the cathode liquid again to start the second cycle. During the third cycle, the carbon-nitrogen co-absorption liquid, after heat extraction in the reaction vessel of the carbon-nitrogen primary recovery device (6), had a volume loss rate of 32±3.1%, and the conductivity of the residual liquid was 20±1.3 mS / cm. The residual liquid after heat extraction was used as the draw liquid and subjected to forward osmosis, and its volume increased by 28±2.6%, while its conductivity decreased to 15.4±0.5 mS / cm. Forward osmosis reduced the volume of the feed liquid (MEC anode chamber effluent) by 26±1.5%, and its conductivity increased from 10.4±0.04 mS / cm to 14.3±0.6 mS / cm.

[0094] Operation Mode 2: Operation Mode 2 differs from Operation Mode 1 in that CO2 gas is not introduced into the reaction vessel of the primary carbon and nitrogen recovery unit (6). Instead, CO2 gas is introduced into the residual liquid after thermal extraction (CO2 absorption site 2). After thermal extraction in the third cycle, the volume loss of the carbon and nitrogen co-absorption liquid was 36.4%. Forward osmosis reduced the volume of the feed liquid (MEC anode chamber effluent) by 22.1%, and the conductivity increased from 10.57 mS / cm to 12.93 mS / cm.

[0095] Operation Mode 3: Operation Mode 3 differs from Operation Mode 1 in that CO2 gas is not introduced into the reaction vessel of the primary carbon and nitrogen recovery unit (6). Instead, CO2 gas is introduced into the diluted draw solution after forward osmosis (CO2 absorption site 3). After the third cycle of thermal extraction, the volume loss of the carbon and nitrogen co-absorbent solution was 47.2%. Forward osmosis reduced the volume of the feed solution (MEC anode chamber effluent) by 20.3%, and the conductivity increased from 10.8 mS / cm to 13.4 mS / cm.

[0096] Operation Mode 4: Operation Mode 4 selects CO2 absorption site 1 and CO2 absorption site 2 for combined carbon capture. Carbon dioxide gas is introduced into the reaction vessel of the carbon-nitrogen primary recovery unit (6), and carbon dioxide gas is also introduced into the residual liquid after thermal extraction. After the third cycle of thermal extraction, the volume loss of the carbon-nitrogen co-absorption liquid was 53.2%. Forward osmosis reduced the volume of the feed liquid (MEC anode chamber effluent) by 34.2%, and the conductivity increased from 10.8 mS / cm to 14.9 mS / cm.

[0097] In each operating mode, the conductivity of the anode chamber effluent (raw solution) before forward osmosis is between 10 and 11 mScm. –1 However, the ability to absorb moisture from the raw liquid varies in each operating mode. After three cycles, the conductivity of the raw liquid generated by CO2 absorption site 1 and CO2 absorption site 1+2 is more significantly improved ( Figure 4 ), which can achieve significant sewage reduction ( Figure 5 , which is manifested by a high volume concentration rate). Regarding the results of forward osmosis treatment of the MEC anode effluent, the effects at CO2 absorption site 1 and CO2 absorption site 1+2 were better than those at the other two absorption sites.

[0098] Figure 4 Conductivity changes of the feed solution (MEC anode chamber effluent) before and after passing through the forward osmosis treatment unit in operating modes 1-4 (the horizontal axis is represented in the form of "ab", where a represents the operating mode and b represents the cycle period);

[0099] Figure 5 Volume concentration rate diagram of the feed solution (MEC anode chamber effluent) after forward osmosis in the embodiment; (the abscissa is represented in the form of "ab", where a represents the operating mode and b represents the cycle period);

[0100] Figure 6 The conductivity change diagram of the draw solution (circulating MEC cathode solution) in multi-cycle operation mode 1; after 5 cycles of operation mode 1, the conductivity of the draw solution reached a peak value of 22.6±0.7mScm in the fourth cycle. –1 , and began to decrease slightly in the 5th cycle, reaching 21±1mScm –1 After the forward osmosis stage, the conductivity of the draw solution decreases after absorbing water from the anode chamber effluent. In the first cycle, it can be reduced to 12.3±0.4mScm –1 , the fourth cycle reached a maximum value of 15.5±0.4mScm –1 , and then began to decrease in the fifth cycle. This indicates that the conductivity of the draw solution can eventually reach a stable state. Therefore, the present invention does not require frequent replacement of the MEC catholyte, and can be recycled for a long time or discarded in small quantities to achieve stable operation.

[0101] 3. Effects of different CO2 absorption sites on MEC current

[0102] Figure 7 Figure 2 shows the MEC current changes at various CO2 absorption sites. The baseline values in the figure refer to the MEC current data without catholyte circulation. The first cycle in each group used fresh artificial water, and the MEC operation results were similar. Therefore, the MEC power generation data without catholyte circulation were used as the basis for comparison. Compared with the control group, peak currents were increased after catholyte circulation at each absorption site. Higher current values are beneficial for ammonia enrichment in the cathode compartment and hydrogen evolution in the microbial electrolysis unit. Similar to other results, the peak currents at CO2 absorption site 1 and CO2 absorption sites 1+2 were 3.4 and 3.5 mA, respectively, significantly higher than those at CO2 absorption sites 2 and 3. CO2 absorption sites 1+2 had the highest peak current. Therefore, CO2 absorption sites 1 and 1+2 continue to be superior in terms of power generation.

[0103] 4. The impact of different CO2 absorption sites on the recovery of ammonia nitrogen from wastewater in this system

[0104] The first recovery pathway is the accumulation of ammonium ions from the anode to the cathode in a microbial electrolysis cell. The second recovery pathway is the diffusion of the remaining ammonium ions in the anode effluent through the forward osmosis membrane into the draw solution (the effluent from the cathode chamber after thermal extraction). Figure 8 is the two-step ammonia nitrogen recovery efficiency of the microbial electrolysis cell and forward osmosis unit; Figure 8 This reflects the cumulative results of the two denitrifications in each cycle. Overall, the two ammonia nitrogen recovery pathways exhibit a relationship of increasing and decreasing. At each absorption site, the ammonia nitrogen recovery rate of the first recovery pathway was the highest in the first cycle, exceeding 70%, and then decreased. For the second recovery pathway, that is, the ammonia nitrogen recovery rate through the forward osmosis unit, it basically reached its highest level in the third cycle at each CO2 absorption site, with ammonia nitrogen recovery rates of 21.8%, 23.04%, and 28.54% at CO2 absorption sites 1, 3, and 1+2, respectively. The total ammonia nitrogen recovery rate was highest in the third cycle at CO2 absorption site 1, at 97.28%, followed by the third cycle at CO2 absorption sites 1+2 (93.19%). Figure 8 The ammonia nitrogen recovery efficiency of the two microbial electrolysis cells and the forward osmosis unit, operating mode 1, that is, the ammonia nitrogen removal rate of the CO2 absorption site 1 is higher than that of other absorption sites.

[0105] Based on the above analysis, the carbon and nitrogen capture, wastewater concentration and denitrification, and MEC power generation results at CO2 absorption sites 1 and 1+2 were superior to those at CO2 absorption sites 2 and 3. Furthermore, the ammonia nitrogen removal rate at CO2 absorption site 1 was higher than that at CO2 absorption sites 1+2.

[0106] 2. Analysis of carbon and nitrogen resource recovery products:

[0107] The carbon and nitrogen terminal recovery device (12) is filled with recovery liquids such as calcium chloride solution, concentrated brine, phosphogypsum solution, and sun-dried brine;

[0108] Calcium chloride solution: Use relatively pure calcium chloride to make a concentrated solution (the concentration of CaCl2·2H2O is 11.17 g·L −1 ) absorbs ammonia and carbon dioxide, at which point ammonia plays a role in balancing the pH. The products are high-purity calcium carbonate and a high-concentration ammonium chloride solution (which can be used as liquid fertilizer), which have high economic value. During this process, the proportion of ammonia captured in the carbon-nitrogen terminal recovery device (12) is greater than 95%, and the proportion of carbon dioxide captured in the carbon-nitrogen terminal recovery device (12) is greater than 95%. The proportion of carbon dioxide converted into calcium carbonate is approximately 75-80%, and the rest exists in the carbon-nitrogen terminal recovery device (12) in the form of dissolved carbon dioxide and other forms.

[0109] Solar brine: Because brine (primarily composed of sodium chloride, potassium chloride, magnesium chloride, and magnesium sulfate, with a near-saturated concentration of magnesium chloride) contains a large amount of magnesium ions, the resulting precipitate is theoretically magnesium carbonate, basic magnesium carbonate, and a small amount of calcium carbonate. Due to the high concentration of NaCl in the brine, the product may contain a variety of salt components, making it relatively moist. The bittern-soda process is commonly used industrially to produce basic magnesium carbonate. This involves using bittern or salt brine and soda ash as raw materials, then adding soda ash under constant stirring. After the reaction is complete, further processing yields the product. Since basic magnesium carbonate is virtually insoluble in water, the product obtained in this experiment can be washed with deionized water to remove impurities and then calcined to produce activated magnesium oxide. At this point, ammonium ions are in the solution phase, forming an anion-cation equilibrium with chloride ions. The composition of the products produced by the mineralization of CO2 absorbed by solar brine was determined using XRD analysis. The product spectrum is consistent with the standard spectrum JCPDS # 70-1177, and is a typical hydrated basic magnesium carbonate (molecular formula: 4MgCO3·Mg(OH)2·4H2O) crystal phase.

[0110] Table 1 Main chemical components of seawater brine

[0111] Components <![CDATA[MgCl2·6H2O]]> <![CDATA[CaCl2·2H2O]]> NaCl KCl <![CDATA[Concentration (g·L −1 )]]> 210.6 0.037 157.9 16.2

[0112] Calcium carbonate products are obtained after phosphogypsum (main component CaSO4) absorbs carbon dioxide. Due to the presence of impurity iron oxide in phosphogypsum, the final product exhibits a certain brick red color. After XRD testing, its spectrum is consistent with the standard spectrum of CaCO3. Obvious CaCO3 peak signals appear near 23°, 29.4°, 48° and 56.5°, corresponding to the (012), (104), (116) and (211) crystal planes, respectively, indicating that this reaction produces CaCO3 products. At this time, ammonium ions are in the solution phase, forming an anion-cation balance with sulfate ions.

[0113] Concentrated brine: The product obtained after the carbon dioxide absorption reaction in concentrated brine (mainly NaCl, 25 wt.% or more) is flaky crystals. The XRD pattern shows Na2CO3 peak signals near 28.6° and 36.1°, corresponding to the (002) and (112) crystal planes, respectively. This indicates that NaHCO3 is generated during the carbon dioxide recovery process. However, during the drying process of the product, NaHCO3 decomposes into Na2CO3, so the measured crystals are Na2CO3 peak signals.

Claims

1. A synchronous circulating ammonia and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis, characterized by: The synchronous circulation ammonia and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis consists of a microbial electrolysis cell system, a heat extraction unit and a forward osmosis unit. The microbial electrolysis cell system is composed of an anode chamber (1) and a cathode chamber (4), wherein the anode chamber (1) and the cathode chamber (4) are separated by a cation exchange membrane (3), the anode (2) is arranged in the anode chamber (1), the cathode (5) is arranged in the cathode chamber (4), a power supply (17) is arranged between the anode (2) and the cathode (5), the positive pole of the power supply (17) is connected to the anode (2), and the negative pole of the power supply (17) is connected to the cathode (5); the anode chamber (1) is filled with high-ammonia nitrogen organic wastewater, and the cathode chamber (4) is filled with cathode liquid; The heat extraction unit is composed of a carbon-nitrogen primary recovery device (6), a carbon-nitrogen secondary recovery device (8), a carbon-nitrogen terminal recovery device (12), a first condenser (13), a second condenser (14), a first-stage heat extraction device (15), and a second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is connected to the heat generating end of the first-stage heat extraction device (15); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is connected to the heat generating end of the second-stage heat extraction device (16); the reaction vessel of the carbon-nitrogen primary recovery device (6) is provided with a first carbon dioxide inlet pipe (61), a carbon-nitrogen primary recovery device exhaust pipe (62), a carbon-nitrogen primary recovery device liquid inlet pipe (63), and a carbon-nitrogen primary recovery device liquid discharge pipe (64); the reaction vessel of the carbon-nitrogen secondary recovery device (8) is provided with a carbon-nitrogen secondary recovery device liquid inlet pipe (81) and a carbon-nitrogen secondary recovery device liquid discharge pipe (84). The gas pipe (82); the liquid inlet of the reaction container of the carbon-nitrogen primary recovery device (6) is connected to the cathode liquid outlet of the cathode chamber (4) through the carbon-nitrogen primary recovery device liquid inlet pipe (63), the carbon-nitrogen primary recovery device exhaust pipe (62) is connected to the air inlet of the first condenser (13), and the carbon-nitrogen primary recovery device exhaust pipe (62) is provided with an air pump. The liquid discharge port of the first condenser (13) is connected to the carbon-nitrogen secondary recovery device liquid inlet pipe (81), the carbon-nitrogen secondary recovery device exhaust pipe (82) is connected to the air inlet of the second condenser (14), and the exhaust port of the second condenser (14) is connected to the air inlet of the carbon-nitrogen terminal recovery device (12) through the carbon-nitrogen terminal recovery device inlet pipe (121); the air pump is provided on the carbon-nitrogen primary recovery device exhaust pipe (62) so that the front section pressure is lower than the standard atmospheric pressure and the rear section pressure is higher than the standard atmospheric pressure, thereby facilitating the rapid escape of ammonia from the first stage heat extraction; The forward osmosis unit is composed of a raw liquid chamber (9) and an extraction liquid chamber (10), and the raw liquid chamber (9) and the extraction liquid chamber (10) are separated by a forward osmosis membrane (11); the liquid inlet of the raw liquid chamber (9) is connected to the liquid outlet of the anode chamber (1), the liquid outlet of the extraction liquid chamber (10) is connected to the liquid inlet of the cathode chamber (4), the liquid inlet of the extraction liquid chamber (10) is connected to the liquid outlet (64) of the carbon and nitrogen primary recovery device, and the liquid outlet (64) of the carbon and nitrogen primary recovery device is provided with a second carbon dioxide inlet pipe (65); and a third carbon dioxide inlet pipe (66) is provided on the connecting pipe between the liquid outlet of the extraction liquid chamber (10) and the liquid inlet of the cathode chamber (4).

2. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 1 is characterized by: The anode (2) is a carbon-based anode or a metal-based anode; The carbon-based anode is a carbon fiber brush, carbon felt, carbon cloth, carbon paper, graphite plate or activated carbon particles; The metal-based anode is an iron-based anode or a titanium-based anode.

3. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 2 is characterized by: The carbon-based anode or metal-based anode is surface-modified or pre-treated; The surface modification is high temperature N doping, surface modification with iron compounds, and polyaniline / polydopamine organic compound modification; The pretreatment is high temperature removal of colloid on the surface of the carbon material, acid treatment, alkali treatment, ultraviolet ozone oxidation treatment or plasma surface treatment.

4. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 1 is characterized by: The cathode (5) material is stainless steel mesh, nickel foam, carbon felt, carbon fiber brush or activated carbon particles.

5. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 1 is characterized by: The cathode (5) is coated with a hydrogen evolution catalyst; the hydrogen evolution catalyst is Pt or NiO.

6. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 1 is characterized by: The carbon-nitrogen terminal recovery device (12) is a pressure-bearing reactor filled with recovery liquid.

7. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 6 is characterized by: The recovered liquid is calcium chloride solution, concentrated brine, phosphogypsum solution, and salt brine.

8. The synchronous circulation ammonia extraction and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 1 is characterized by: The first-stage heat extraction device (15) and the second-stage heat extraction device (16) are heat exchangers; The heat sources of the first-stage heat extraction device (15) and the second-stage heat extraction device (16) are flue gas waste heat or biogas combustion heat.

9. A method for extracting and fixing ammonia and carbon using the synchronous circulating ammonia and carbon fixation and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 1, characterized in that: Follow these steps: Step 1: High-ammonia nitrogen organic wastewater is added to the anode chamber (1), and electroactive microorganisms grow on the anode (2). The electroactive microorganisms use organic matter in the wastewater to generate electrons and protons. The electrons are transferred to the anode (2) through the microorganism's extracellular electron transfer process, and then transferred to the cathode (5) through an external circuit, thereby forming an electric current. The power supply (17) increases the energy of the electrons, and a hydrogen evolution reaction occurs at the cathode (5), generating hydrogen gas and hydroxide ions, thereby increasing the alkalinity of the cathode liquid; The anions and cations inside the reactor begin to move in a directional manner under the action of the internal electric field, wherein the anions move toward the anode (2) and the cations move toward the cathode (5); the cation exchange membrane (3) has the function of selectively permeating cations. Driven by the internal electric field, the positively charged cations in the high-ammonia nitrogen organic wastewater in the anode chamber (1) pass through the cation exchange membrane (3) and enter the cathode liquid in the cathode (5); NH4 + Under the action of the internal electric field, the anode chamber (1) migrates to the cathode chamber (4) and is enriched in the cathode chamber (4), thereby obtaining a cathode solution with a high pH and a high ammonia concentration; Step 2: The flue gas generated during the combustion process or the exhaust gas generated during the anaerobic fermentation process is introduced into the carbon dioxide inlet pipe, which includes a first carbon dioxide inlet pipe (61), a second carbon dioxide inlet pipe (65), and a third carbon dioxide inlet pipe (66); The cathode liquid discharged from the cathode chamber (4) enters the reaction vessel of the carbon and nitrogen primary recovery device (6) through the liquid inlet pipe (63) of the carbon and nitrogen primary recovery device. The cathode liquid contains ammonia enriched at the cathode and is alkaline. The cathode liquid absorbs carbon dioxide in the flue gas generated in the combustion process or the exhaust gas generated in the anaerobic fermentation process to form a carbon and nitrogen co-absorption liquid. The first-stage heat extraction device (15) provides heat for the reaction vessel of the carbon-nitrogen primary recovery device (6), and the second-stage heat extraction device (16) provides heat for the reaction vessel of the carbon-nitrogen secondary recovery device (8); the first-stage heat extraction device (15) heats the carbon-nitrogen co-absorption liquid in the reaction vessel of the carbon-nitrogen primary recovery device (6) to a boiling point, at which point water vapor carries carbon dioxide and ammonia and escapes; The water vapor carrying carbon dioxide and ammonia is condensed through the first condenser (13) to form a carbon-nitrogen primary extract, which enters the reaction vessel of the carbon-nitrogen secondary recovery device (8); the second-stage heat extraction device (16) heats the carbon-nitrogen primary extract to 1-5°C below the boiling point, accelerating the condensation of the water vapor into condensed water and retaining it in the carbon-nitrogen secondary recovery device (8), thereby realizing the recovery of water resources, and the carbon dioxide and ammonia escape and enter the carbon-nitrogen terminal recovery device (12) to realize the co-recovery of carbon and nitrogen; After heat extraction, the residual liquid of the carbon-nitrogen co-absorption liquid in the reaction vessel of the carbon-nitrogen primary recovery device (6) is reduced in volume due to evaporation, and the residual liquid of the carbon-nitrogen co-absorption liquid is transported to the draw liquid chamber (10) as the draw liquid of the forward osmosis unit, and the effluent from the anode chamber (1) of the microbial electrolysis cell is transported to the raw liquid chamber (9) as the raw liquid of the forward osmosis unit; during the forward osmosis process, the water in the raw liquid enters the draw liquid, and the draw liquid after the forward osmosis continues to be added to the cathode chamber (4) as the cathode liquid of the microbial electrolysis cell, thereby realizing recycling.

10. The method for extracting and fixing ammonia and carbon using a synchronous circulating ammonia and carbon removal and wastewater reduction device for treating high-ammonia nitrogen organic wastewater based on microbial electrolysis according to claim 9, characterized in that: During operation, the microbial electrolysis cell system adopts continuous flow or batch operation with an operation cycle of 4 hours to 7 days; the applied voltage of the power supply (17) is 0.2 to 2V, and the pH value of the anolyte is adjusted to 4 to 11; the current density during the operation of the microbial electrolysis cell system is 0.1A / m 2 ~100A / m 2 .

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