Method and equipment for purifying high-concentration COD and ammonia nitrogen in fermentation wastewater from biological sources

Abstract

The present application belongs to the technical field of wastewater purification, and particularly relates to a purification method and equipment for high-concentration COD and ammonia nitrogen in fermentation wastewater of biological origin. The present application is aimed at the problems of high cost, incomplete purification, and difficult resource utilization of flue gas CO2 in the purification of high-concentration COD, ammonia nitrogen, and other pollution components in fermentation wastewater of biological origin. The present application provides the following scheme: step one, introducing CO2 in flue gas into fermentation wastewater, introducing CO2 in flue gas into fermentation wastewater through a flue gas capturing device to form CO2 saturated wastewater A, CO2 exists in the form of HCO3 ‑ , H2CO3 * (CO2·HO2+H2CO3) in A liquid; step two, constructing a calcium bridge environment, first acidifying A liquid, adding dilute acid to A liquid, at this time, HCO3 ‑ in A liquid is all converted into H2CO3 * , water-soluble NH + 4, Na + , K + and other cations in A liquid are paired with anions introduced by dilute acid to form a stable solution, wherein H2CO3 * is the combination of CO2·H2O and H2CO3; then adding calcium, and adding an appropriate amount of calcium-containing material according to the volume of A liquid, so as to achieve the purpose of purifying fermentation wastewater of biological origin and fixing flue gas CO2 in an efficient and low-cost manner.

Description

Technical Field

[0001] This invention relates to the field of wastewater purification technology, and in particular to a method and equipment for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater. Background Technology

[0002] The wastewater produced by biological anaerobic fermentation is collectively referred to here as "biological fermentation wastewater / liquid".

[0003] For the treatment of biogas slurry from pig farms, a combined process of "aeration biological oxidation to remove biodegradable organic matter, flocculation to reduce COD, and stripping to remove ammonia nitrogen" reduces the content of pollutants such as COD and ammonia nitrogen in biogas slurry (similar invention patent such as 201110147233.0). However, this process has high energy consumption and the treatment effect is not ideal. At the same time, it cannot reduce the antibiotic content in biogas slurry, which objectively leads to insufficient willingness of farm owners to implement it.

[0004] Another currently promoted method for reducing biogas slurry pollutants is to utilize wetlands such as paddy fields and oxidation ponds to dilute the ammonia nitrogen concentration in the biogas slurry, and then use organisms such as bacteria and algae to absorb the ammonia nitrogen, thereby achieving the purpose of reducing ammonia levels. Examples include invention patents 201210018944.2, 202010122002.3, 202110173831.9, and 201710041473.X. In this method, the recalcitrant colloidal and particulate organic matter in the biogas slurry precipitates in the paddy field wetland, reducing COD content, and simultaneously harvesting bacteria and algae for animal feed. This model is effective in reducing ammonia nitrogen in biogas slurry, but it also has insurmountable limitations. First, a large amount of antibiotics in the biogas slurry cannot be removed, still posing a pollution threat to the environment. Second, the implementation of this method requires large areas of paddy fields and other wetlands, which most general farms do not possess. Third, the biogas slurry remains in the paddy field for a long time, and its downward seepage leads to groundwater pollution.

[0005] To address the pain points of deep purification of biogas slurry and its cost, CN113200634B proposed a biogas slurry co-precipitation-electrodialysis purification process. This process first removes particulate and colloidal organic matter from the biogas slurry using AlCl3-CaO co-precipitant, and then removes small molecule organic matter and ammonia nitrogen from the remaining supernatant using electrodialysis-electrooxidation. The results are good, but the "co-precipitation" process still suffers from the problem of high AlCl3 material cost.

[0006] Currently, a relatively successful method for treating landfill leachate is "biological oxidation for nitrogen removal followed by ultrafiltration / nanofiltration / reverse osmosis for organic matter removal." This method first uses biological oxidation to convert ammonia nitrogen in the leachate into NOx and N2, which are then released. The remaining liquid is then purified through a series of filtration processes including ultrafiltration, nanofiltration, and reverse osmosis to obtain purified water and concentrated water. The purified water is discharged, while the concentrated water undergoes further treatment before safe discharge. The purified water produced by this process fully meets emission standards and has a good purification effect. However, the process has high energy consumption, high equipment maintenance costs, and an overall extremely high wastewater treatment cost (130 yuan / ton of wastewater).

[0007] Currently, technologies for reducing CO2 emissions and utilizing resources in flue gas mainly include carbon capture and storage (CCS) and carbon capture and utilization (CCU). CCS technology reduces emissions by capturing CO2 from flue gas and injecting it deep underground; while CCU technology utilizes CO2 by capturing it and converting it into useful chemicals or fuels.

[0008] While existing technologies can treat biogas slurry and reduce CO2 emissions from flue gas to some extent, they still have many limitations. First, traditional biogas slurry treatment technologies are difficult to completely remove harmful substances from the slurry and have high treatment costs. Second, technologies for reducing CO2 emissions and utilizing resources from flue gas generated by waste incineration power generation in landfills are still immature, and problems such as high energy consumption and low conversion efficiency exist. Summary of the Invention

[0009] This invention provides a method and equipment for purifying high-concentration COD and ammonia nitrogen in bio-derived fermentation wastewater. It utilizes the bio-derived fermentation wastewater to absorb and fix CO2 from flue gas, while simultaneously using the flue gas CO2 as the main raw material for purifying the bio-derived fermentation wastewater. This method rapidly and efficiently purifies the bio-derived wastewater, solving both the removal of pollutants from the bio-derived fermentation wastewater and the fixation of CO2 from flue gas in a low-consumption and high-efficiency manner, thereby realizing the resource utilization of wastewater and waste gas.

[0010] This invention provides the following technical solution:

[0011] On the one hand, this application provides a method for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater, comprising the following steps:

[0012] Step 1: Introduce CO2 from the flue gas into the fermentation waste liquid.

[0013] The CO2 from the flue gas is introduced into the fermentation waste liquid through a flue gas capture device, forming CO2-saturated waste liquid A. In liquid A, CO2 is converted into HCO3-. - H2CO3 * It exists in the form of (CO2·HO2+H2CO3);

[0014] Step 2: Constructing a calcium bridge environment

[0015] First, acidify solution A by adding dilute acid to solution A. At this point, the HCO3- content in solution A will... - All converted to H2CO3 * Water-soluble NH in solution A + 4. Na + K+ cations pair with anions introduced by dilute acid to form a stable solution, in which H2CO3 * It is a collective term for CO2·H2O and H2CO3;

[0016] Add calcium as needed. Take an appropriate amount of calcium-containing substance based on the volume of solution A, dissolve it in water or dilute acid, and add it to solution A. The calcium added at this time should be in the form of Ca. 2+ Form exists;

[0017] Finally, alkalize the solution by adding dilute alkali to solution A. The resulting mixture is called solution B.

[0018] At this time, the H2CO3 in solution B * It was then completely converted into HCO3. - Ca 2+ and HCO3 - The pairing is completed, forming water-soluble Ca(HCO3)2, Ca 2+ It exists in solution B as a highly active free ion, while the remaining HCO3-... - It then pairs with the cations introduced by the dilute alkali to form the corresponding water-soluble salt. In this environment, because solution B is weakly alkaline, the organic colloids in solution B carry a negative charge, and the highly active Ca... 2+ It rapidly bridges with negatively charged organic colloids via a unit of Ca. 2+ It links with two units of organic colloids respectively, thereby rapidly initiating flocculation and achieving complete separation of pollutants from the water in the organic colloids; simultaneously, the Ca in the remaining B solution... 2+ It combines with phosphate ions, arsenate ions, trivalent chromate ions, or VI chromate ions to form different calcium salt precipitates, thereby removing water-soluble inorganic phosphorus, arsenic, and chromium anion pollutants from the wastewater; ammonia nitrogen combines with CO2 to form NH4. + Some NH4 + Adsorbed by negatively charged organic colloids, it separates from water along with the flocculation of the organic colloids; Pb 2+ Cd 2+ Cationic heavy metals react with OH- in weakly alkaline solution B - The precipitate is formed and separated from the water, thus removing heavy metal cations.

[0019] As a further improvement to the above scheme.

[0020] Preferably, in step one, the pH of the waste liquid is adjusted to 9.0-11.0 before the flue gas is introduced. The optimal pH of the waste liquid should correspond to its organic carbon content; that is, a higher organic carbon content corresponds to a higher pH adjustment. The alkali used to adjust the fermentation wastewater to alkalinity can be a water-soluble alkali such as NaOH or a slightly soluble alkali such as Ca(OH)2. Adjusting the pH of the waste liquid to 9.0-11.0 ensures that OH- under alkaline conditions... - The introduced CO2 is rapidly converted into CO3. 2- or HCO3 - This allows CO2 in the flue gas to be absorbed quickly.

[0021] Preferably, in step two, the dilute acid used for acidification can be hydrochloric acid, sulfuric acid, acetic acid, or other water-soluble acids. In step two, solution A is acidified to a pH value of 2.0-3.0.

[0022] Preferably, in step two, the added calcium source is a water-soluble or acid-soluble calcium-containing substance, such as calcium chloride or calcium hydroxide. The amount of calcium added is calculated and determined based on the stoichiometric ratio of calcium to organic carbon in the flocculated precipitate. For example, the stoichiometric ratio of calcium to organic carbon in pig farm biogas slurry flocculation is 1:0.9, and the stoichiometric ratio of calcium to organic carbon in landfill leachate flocculation is 1:1.4.

[0023] Preferably, in step two, the alkali raw material used for alkalization is a water-soluble alkali, such as NaOH, and the pH is adjusted to 8.2-8.3 after alkalization with solution B.

[0024] On the other hand, this application provides a purification device for high-concentration COD ammonia nitrogen in biological fermentation wastewater, including a flue gas capture device and a mixing and clarification device. The flue gas capture device includes a flue gas inlet pipe, a fermentation waste liquid vortex spiral pipe and a gas CO2 absorption tank. The mixing and clarification device includes a mixing tank and a vertical flow sedimentation tank.

[0025] One end of the flue gas inlet pipe is connected to the flue gas source and the chimney, and the other end is connected to a Venturi jet injector. The Venturi jet injector is connected to a fermentation waste liquid vortex spiral tube. One end of the fermentation waste liquid vortex spiral tube is connected to a pipe spiral blade mixer, and the other end is connected to a water pump. The pipe spiral blade mixer is connected to the upper side wall of the flue gas CO2 absorption tank. The water pump is connected to the near-bottom side wall of the flue gas CO2 absorption tank. The exhaust port of the flue gas CO2 absorption tank is connected to a flocculation mixing tank through a pipe. The flocculation mixing tank is connected to a vertical flow sedimentation tank. A supernatant overflow weir is installed at the top of the vertical flow sedimentation tank. The flocculation mixture outlet valve is connected to a pipe extending into the vertical flow sedimentation tank.

[0026] As a further improvement to the above scheme.

[0027] Preferably, the other end of the flue gas inlet pipe is connected to the inlet port of a Venturi jet, the inlet port of the Venturi jet is connected to the outlet at the end of the upper section of the fermentation waste liquid vortex spiral tube, and the outlet port of the Venturi jet is connected to the inlet of the lower section of the fermentation waste liquid vortex spiral tube.

[0028] Preferably, the outlet of the lower section of the fermentation waste liquid vortex spiral tube is connected to the inlet end of the pipe spiral mixer, the outlet end of the pipe spiral mixer is connected to the inlet valve of the circulation pipe, the inlet valve of the circulation pipe is connected to the upper side wall of the flue gas CO2 absorption tank through a straight pipe, the inlet port of the upper section of the fermentation waste liquid vortex spiral tube is connected to the outlet port of the water pump, the inlet port of the water pump is connected to the circulation pipe valve, and the circulation pipe valve is connected to the near-bottom side wall of the flue gas CO2 absorption tank through a straight pipe.

[0029] Preferably, the top of the flue gas CO2 absorption tank is provided with a feed inlet, a pressure gauge and a sampling hole, the upper part of the side wall of the flue gas CO2 absorption tank is provided with a circulation inlet, a circulation pipe inlet valve is installed on the outer side of the circulation inlet wall, the lower part of the side wall of the flue gas absorption tank is provided with a circulation outlet and a discharge hole, a circulation pipe valve is installed on the outer side of the circulation outlet wall and a discharge hole valve is installed on the outer side of the discharge hole wall.

[0030] Preferably, the flocculation tank is provided with a feeding port at the top, the mixing tank has a CO2 absorbent inlet at the upper part of the side wall and a flocculation mixture outlet at the lower part of the side wall, a CO2 absorbent inlet valve is installed at the CO2 absorbent inlet, a mixture outlet valve is installed at the flocculation mixture outlet, and a flocculation mixing tank impeller is installed inside the flocculation mixing tank.

[0031] It should be understood that the above general description and the following detailed description are merely exemplary and do not limit the invention.

[0032] This invention proposes a method for coupling bio-derived fermentation wastewater such as biogas slurry and landfill leachate with flue gas CO2 fixation. By using bio-derived fermentation wastewater to absorb and fix flue gas CO2, and using flue gas CO2 as raw material to purify bio-derived fermentation wastewater, the method achieves the purpose of purifying bio-derived wastewater and fixing flue gas CO2 in a highly efficient and low-consumption manner. Attached Figure Description

[0033] Figure 1 This is a schematic diagram of the flue gas capture device provided in an embodiment of the present invention;

[0034] Figure 2 This is a schematic diagram of the flocculation and clarification device provided in an embodiment of the present invention;

[0035] Figure 3 This is a schematic diagram illustrating the relationship between flue gas capture time and partial pressure of the flue gas CO2 absorption tank provided in an embodiment of the present invention;

[0036] Figure 4 This is a schematic diagram showing the relationship between the calcium-bridged organic matter flocculation and co-precipitation effects under different treatments with two different calcium sources provided in this embodiment of the invention.

[0037] Figure 5 This is a schematic diagram illustrating the effect of different calcium oxide treatments on the removal of organic carbon provided in the embodiments of the present invention;

[0038] Figure 6 This is a schematic diagram illustrating the effect of calcium chloride under different treatments on the removal of organic carbon according to an embodiment of the present invention;

[0039] Figure 7 The optimal CO2 and Ca provided in the embodiments of the present invention 2+ Schematic diagram of organic C concentration at different pH values ​​in the supernatant under input conditions;

[0040] Figure 8 Different concentrations of Ca in the supernatant under the optimal pH and optimal CO2 input conditions provided in the embodiments of the present invention. 2 + - Dynamics of organic C concentration.

[0041] Figure label:

[0042] 1. Flue gas inlet pipe; 2. Water pump; 3. Venturi jet injector; 4. Fermentation waste liquid vortex spiral tube; 4-1. Upper section of fermentation waste liquid vortex spiral tube; 4-2. Upper section of fermentation waste liquid vortex spiral tube; 5-1. Circulation pipeline outlet valve; 5-2. Circulation pipeline inlet valve; 6. Pipeline spiral blade mixer; 7. Feed inlet; 8. Pressure gauge; 9. Sampling port; 10. Discharge port valve; 11. CO2 absorbent inlet valve; 12. Feed port; 13. Flocculation tank; 14. Flocculated mixture outlet valve; 15. Flocculation tank impeller; 16. Supernatant overflow weir; 17. Vertical flow sedimentation tank; 20. Flue gas source; 21. Chimney; 22. Flue gas CO2 absorption tank. Detailed Implementation

[0043] The embodiments of the present invention will now be described with reference to the accompanying drawings.

[0044] In the description of the embodiments of the present invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "connection" and "installation" should be interpreted broadly. For example, "connection" can be a detachable connection or a non-detachable connection; it can be a direct connection or an indirect connection through an intermediate medium. Furthermore, "connection" can be a direct connection or an indirect connection through an intermediate medium. "Fixed" means that the devices are connected to each other and their relative positional relationship remains unchanged after the connection. The directional terms mentioned in the embodiments of the present invention, such as "inner," "outer," "top," and "bottom," are only for reference to the directions in the accompanying drawings. Therefore, the directional terms used are for better and clearer explanation and understanding of the embodiments of the present invention, and are not intended to indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on the embodiments of the present invention.

[0045] In this embodiment of the invention, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined with "first" and "second" may explicitly or implicitly include one or more of that feature.

[0046] In this embodiment of the invention, "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent three cases: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0047] References to "one embodiment" or "some embodiments" as used in this specification mean that a particular feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the invention. Therefore, the phrases "in one embodiment," "in some embodiments," "in other embodiments," "in still other embodiments," etc., appearing in different parts of this specification do not necessarily refer to the same embodiment, but rather mean "one or more, but not all, embodiments," unless otherwise specifically emphasized. The terms "comprising," "including," "having," and variations thereof mean "including, but not limited to," unless otherwise specifically emphasized.

[0048] Reference Figures 1-8 This application provides a method for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater, comprising the following steps:

[0049] On the one hand, this application provides a method for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater, comprising the following steps:

[0050] Step 1: Introduce CO2 from the flue gas into the fermentation waste liquid.

[0051] The CO2 from the flue gas is introduced into the fermentation waste liquid through a flue gas capture device, forming CO2-saturated waste liquid A. In liquid A, CO2 is converted into HCO3-. - H2CO3 * The wastewater exists in the form of (CO2·HO2+H2CO3); in step one, the pH of the wastewater is adjusted to 9.0-11.0 before the flue gas is introduced; the optimal pH of the wastewater should correspond to the organic carbon content of the wastewater, that is, the higher the organic carbon content of the wastewater, the larger the pH value should be. The raw material alkali used to adjust the fermentation wastewater to alkalinity can be a water-soluble alkali such as NaOH or a slightly soluble alkali such as Ca(OH)2. The pH of the wastewater is adjusted to 9.0-11.0 so that OH under alkaline conditions... - The introduced CO2 is rapidly converted into CO3. 2- or HCO3 - This allows for the rapid absorption of CO2 from the flue gas.

[0052] Step 2: Constructing a calcium bridge environment

[0053] First, acidify solution A by adding dilute acid to solution A. At this point, the HCO3- content in solution A will... - All converted to H2CO3 * Water-soluble NH in solution A + 4. Na + K+ cations pair with anions introduced by dilute acid to form a stable solution, in which H2CO3 * It is a collective term for CO2·H2O and H2CO3. The dilute acid used for acidification can be hydrochloric acid, sulfuric acid, acetic acid and other water-soluble acids. In step two, solution A is acidified to make its pH value 2.0-3.0.

[0054] Add calcium as needed. Take an appropriate amount of calcium-containing substance based on the volume of solution A, dissolve it in water or dilute acid, and add it to solution A. The calcium added at this time should be in the form of Ca. 2+ The calcium source is water-soluble or acid-soluble calcium-containing substances, such as calcium chloride and calcium hydroxide. The amount of calcium added is calculated and determined based on the stoichiometric ratio of calcium to organic carbon in the flocculated precipitate.

[0055] Finally, alkalize the solution by adding dilute alkali to solution A. The resulting mixture is called solution B. The alkali used for alkalization is a water-soluble alkali, such as NaOH. The pH value of solution B after alkalization is 8.2-8.3.

[0056] At this time, the H2CO3 in solution B * It was then completely converted into HCO3. - Ca 2+ and HCO3 - The pairing is completed, forming water-soluble Ca(HCO3)2, Ca 2+It exists in solution B as a highly active free ion, while the remaining HCO3-... - It then pairs with the cations introduced by the dilute alkali to form the corresponding water-soluble salt. In this environment, the organic colloids in solution B carry a negative charge, which is why solution B is weakly alkaline. The high activity of Ca... 2+ It rapidly bridges with negatively charged organic colloids via a unit of Ca. 2+ It links with two units of organic colloids respectively, thereby rapidly initiating flocculation and achieving complete separation of pollutants from the water in the organic colloids. Simultaneously, the remaining Ca in solution B... 2+ It combines with phosphate ions, arsenate ions, trivalent chromate ions, or VI chromate ions to form different calcium salt precipitates, thereby removing water-soluble inorganic phosphorus, arsenic, and chromium anion pollutants from the wastewater; ammonia nitrogen combines with CO2 to form NH4. + Some NH4 + Adsorbed by negatively charged organic colloids, it separates from water along with the flocculation of the organic colloids; Pb 2+ Cd 2+ Cationic heavy metals react with OH- in weakly alkaline solution B - By combining and forming a precipitate, the heavy metal cations can be removed from the water.

[0057] The principle behind the above method is as follows:

[0058] Using flue gas CO2 as HCO3 - The source is introduced through a flue gas capture device to collect fermentation waste liquid;

[0059] The pH of the waste liquid is increased to achieve OH- under alkaline conditions. - The introduced CO2 is rapidly converted into CO3. 2- or HCO3 - This allows CO2 in the flue gas to be absorbed quickly.

[0060] The optimal pH value of the waste liquid should correspond to the organic carbon content of the waste liquid; that is, the higher the organic carbon content of the waste liquid, the larger the pH value should be.

[0061] Based on the organic carbon content of the fermentation waste liquid, the pH of the fermentation waste liquid is adjusted to between 9.0 and 11.0 before capturing and introducing CO2 from the flue gas.

[0062] After the CO2 from the flue gas is absorbed and fixed into the fermentation waste liquid, the mixed waste liquid is acidified with dilute acid to adjust the pH value to 2.0-3.0. Then, water-soluble or acid-soluble calcium-containing substances are added. Finally, the pH is adjusted to 8.0-8.3 with dilute alkali to form a Ca(HCO3)2 environment. At this time, calcium ions remain highly active, and the organic colloids in the waste liquid carry a negative charge, Ca... 2+In this environment, organic colloids of different molecules can be bridged, and the organic colloids can be instantly flocculated and separated from water, achieving the complete removal of organic colloidal COD, organic colloidal nitrogen, organic colloidal phosphorus, and organic colloidal heavy metals from fermentation waste liquid.

[0063] Calcium in the waste liquid exists in the form of Ca(HCO3)2, but its actual form in the solution is Ca. 2+ and HCO3 - Ca 2+ With HCO3 - The stoichiometric ratio is 1:2, and the pH of the waste liquid is maintained within the range of 8.2-8.3. At this time, Ca... 2+ It exhibits high activity, and the organic colloids in the waste liquid carry a negative charge. Under this microenvironment, one unit of Ca... 2+ It bridges with two units of organic colloids, thereby rapidly initiating flocculation. The process is as follows:

[0064] [OM]O - +Ca 2+- O[OM]→[OM]-O-Ca-O-[OM]↓ (1)

[0065] In the above formula, "OM" represents organic colloid.

[0066] At the same time, because Ca 2+ In a free state in wastewater, it combines with phosphate, arsenate, trivalent chromate, or VI-valent chromate ions to form different calcium salt precipitates, thereby removing phosphorus, arsenic, and chromium from the wastewater. Furthermore, in a weakly alkaline environment with a pH of 8.2-8.3, Pb... 2+ Cd 2+ Cationic heavy metals react with OH- to form precipitates and are separated from water, thus achieving the removal of heavy metal cations.

[0067] Under the aforementioned aquatic environment, NH3·H2O in the waste liquid combines with the captured and introduced CO2 to transform into NH4. + NH4 + It is then adsorbed by negatively charged organic colloids, and separated from the water along with the flocculation of the organic colloids. The process is as follows:

[0068] NH3·H2O + CO2 → NH4 + +HCO3 - (2)

[0069] NH4 + +[OM]-O-Ca-O-[OM]-O - →[OM]-O-Ca-O-[OM]-O-NH4↓ ⑶

[0070] This application provides a purification device for high-concentration COD and ammonia nitrogen in biological fermentation wastewater, including a flue gas source 20 and a chimney 21. The chimney is connected to a flue gas inlet pipe 1, which is connected to the inlet port of a Venturi jet injector 3. The inlet port of the Venturi jet injector 3 is connected to the outlet port at the end of the upper section 4-1 of the fermentation wastewater vortex spiral tube, and the outlet port of the Venturi jet injector 3 is connected to the inlet port of the lower section 4-2 of the fermentation wastewater vortex spiral tube. The inlet is connected to the inlet of the spiral blade mixer 6 in the pipeline, and the outlet of the spiral blade mixer 6 in the pipeline is connected to the inlet valve 5-2 of the circulating pipeline. The inlet valve 5-2 of the circulating pipeline is connected to the upper side wall of the flue gas CO2 absorption tank 22 through a straight pipe. The inlet end of the upper section 4-1 of the fermentation waste liquid vortex spiral tube is connected to the outlet port of the water pump 2. The inlet port of the water pump 2 is connected to the circulating pipeline valve 5-1. The circulating pipeline valve 5-1 is connected to the near bottom side wall of the flue gas CO2 absorption tank 22 through a straight pipe.

[0071] The top of the flue gas CO2 absorption tank 22 is provided with a feed inlet 7, a pressure gauge 8, and a sampling hole 9. The upper part of the side wall of the flue gas CO2 absorption tank 22 is provided with a circulation inlet, and a circulation pipe inlet valve 5-2 is installed on the outer side of the circulation inlet wall. The lower part of the side wall of the flue gas CO2 absorption tank 22 is provided with a circulation outlet and a discharge hole. A circulation pipe valve 5-1 is installed on the outer side of the circulation outlet wall, and a discharge hole valve 10 is installed on the outer side of the discharge hole wall.

[0072] The exhaust port of the flue gas CO2 absorption tank 22 is connected to the flocculation tank 13 through a pipe. The top of the flocculation tank 13 is provided with a feeding port 12. The upper part of the side wall of the mixing tank 13 is provided with a flocculation mixture inlet, and the lower part of the side wall is provided with a flocculation mixture outlet. A mixture inlet valve 10 is installed at the flocculation mixture inlet, and a mixture outlet valve 14 is installed at the flocculation mixture outlet. A flocculation mixing tank impeller 15 is installed inside the flocculation mixing tank 13.

[0073] The mixing tank 13 is connected to the vertical flow sedimentation tank 17. The upper part of the vertical flow sedimentation tank 17 is equipped with a supernatant overflow weir 16. The mixed liquid outlet valve 14 is connected to a pipe extending into the vertical flow sedimentation tank 17. The flue gas inlet pipe 1, the fermentation waste liquid vortex spiral pipe 4, and the flue gas CO2 absorption tank are flue gas capture devices. The mixing tank 13 and the vertical flow sedimentation tank 17 are mixing and clarification devices.

[0074] The working principle of this application is as follows:

[0075] Flue gas is drawn from the furnace chimney 20 via flue gas inlet pipe 1. A Venturi jet injector 3 is installed near the end of flue gas inlet pipe 1. The inlet and outlet ports of the Venturi jet injector 3 are connected to the outlet of the upper section 4-1 and the inlet of the lower section 4-2 of the fermentation waste liquid vortex spiral tube 4, respectively. The fermentation waste liquid inside the fermentation waste liquid vortex spiral tube 4 flows at high speed. This rapid flow of waste liquid creates negative pressure within the flue gas inlet pipe 1 connected to the Venturi jet injector 3, accelerating the input of flue gas into the fermentation waste liquid. The upper section 4-1 of the fermentation waste liquid vortex spiral tube 4 is connected to the lower side wall near the bottom of the sealed flue gas absorption tank 22 via a straight pipe that connects to the water pump 2 and the circulation pipe outlet valve 5-1 in series. The lower section 4-2 of the fermentation waste liquid vortex spiral tube is connected to the upper side wall circulation liquid inlet of the sealed flue gas absorption tank 22 via a straight pipe that connects to the pipe spiral blade mixer 6 and the circulation pipe inlet valve 5-2 in series. The water pump 2 draws the fermentation waste liquid from the bottom of the flue gas CO2 absorption tank and pumps it into the spiral section of the fermentation waste liquid vortex spiral tube 4, causing the fermentation waste liquid to move in a high-speed vortex motion in the spiral section of the pipe. A pressure gauge 8 is installed on the top of the flue gas CO2 absorption tank to measure the partial pressure of CO2 inside the flue gas CO2 absorption tank. A liquid inlet 7 and a sampling hole 9 are also opened on the top of the flue gas CO2 absorption tank. During operation, the inlet 7 and the sampling hole 9 are sealed.

[0076] The negative pressure in the flue gas inlet pipe 1 is greatly increased by the Venturi jet 3. With the acceleration effect of the Coriolis force, the biogas liquid in the fermentation waste liquid vortex spiral tube 4 moves in a vortex and the flow rate is accelerated. A large negative pressure is generated in the flue gas inlet pipe 1 connected to it through the Venturi jet, making it easier for the flue gas in the flue gas inlet pipe 1 to be introduced into the biogas liquid.

[0077] The flue gas and fermentation waste stream are thoroughly mixed through the pipe spiral blade mixer 6;

[0078] Before the device is put into operation, fermentation waste liquid is introduced into the device through feed inlet 7, and the pH value of the fermentation waste liquid is adjusted to 9.0-11.0.

[0079] Start the device and continuously input flue gas. After the gas pressure in the co-precipitation tank of fermentation waste liquid reaches the predetermined pressure, stop the operation of water pump 2, close the inlet valve 5-2 and outlet valve 5-1 of the flue gas CO2 absorption tank circulation pipeline, and proceed to the next process.

[0080] Following the previous step, collect a mixed water sample from sampling port 9. Adjust the pH of the mixed water sample to 2.0–3.0 and record the amount of dilute acid used. Then, adjust the pH to 8.0–8.3 using dilute alkali and record the amount of dilute alkali used. Based on the stoichiometric ratio of calcium to organic carbon in the flocculated mixture and the organic carbon content of the fermentation waste liquid, calculate the amount of calcium to be added per unit volume of fermentation waste liquid. Combine this with the volume of fermentation waste liquid treated to calculate the amount of calcium-containing substances to be added.

[0081] The mixture in the CO2 absorption tank is transferred from the discharge port into the mixing tank 13. According to the volume of the mixture and the above-mentioned dilute acid dosage parameters, an appropriate amount of dilute acid is added and mixed well. An appropriate amount of calcium-containing substance that has been dissolved in water or acid is added and mixed well again. Finally, an appropriate amount of dilute alkali is added according to the above-mentioned dilute alkali parameters and mixed well. Flocculation is generated instantly and the mixture becomes clear.

[0082] The supernatant and the flocculated sediment mixture are transferred to the vertical flow sedimentation tank 17. The supernatant overflows at the upper edge of the vertical flow sedimentation tank, and the flocculated sediment settles and accumulates at the bottom of the funnel-shaped tank, thus completing the removal of pollutants such as organic colloidal COD, organic colloidal nitrogen, organic colloidal phosphorus, organic colloidal heavy metals, inorganic phosphorus, cationic heavy metals, some anionic heavy metals, and most ammonia nitrogen from the fermentation waste liquid.

[0083] In this application, the principle of negative pressure being formed in the circulation path during the high-speed circulation of fluid is utilized to introduce flue gas CO2 into the fermentation waste liquid circulation channel, so that the flue gas CO2 is mixed evenly with the high-speed flowing weak alkaline waste liquid and is absorbed and fixed.

[0084] After absorbing and fixing the CO2 from the flue gas into the fermentation waste liquid, the mixed waste liquid is acidified to pH 2.0-3.0 with dilute acid, a calcium solution is added, and finally the pH is adjusted to 8.0-8.3 with dilute alkali to maintain the activity of calcium ions and also to make the organic colloids in the waste liquid negatively charged. Thus, the calcium... 2+ In this environment, organic colloids of different molecules can be bridged, causing them to flocculate and separating organic matter from water instantaneously, thus achieving the complete removal of organic colloidal COD, organic colloidal nitrogen, organic colloidal phosphorus, and organic colloidal heavy metals from fermentation waste liquid. Simultaneously, because Ca... 2+ In a free state in wastewater, it combines with phosphate, arsenate, and chromate ions (III or VI valence) to form different calcium salt precipitates, thereby removing phosphorus, arsenic, and chromium from the wastewater. Furthermore, in a weakly alkaline environment with a pH of 8.0-8.3, Pb... 2+ Cd 2+ Cationic heavy metals and OH - The process involves precipitation and water separation to remove heavy metal cations; ammonia in the waste liquid combines with the input CO2 to form NH4HCO3, in which NH4+ is released. + The ammonia nitrogen is adsorbed by the negatively charged organic colloids in the waste liquid and separated from the water along with the flocculation of the organic colloids, thus achieving the purpose of partial removal of ammonia nitrogen.

[0085] Example 1: Empirical Results of the Flue Gas CO2 Capture Device

[0086] refer to Figure 3As shown, using biogas slurry samples from early spring as the experimental subject, 4L of raw biogas slurry was accurately added to the flue gas CO2 absorption tank. Water pump 2 was started, and the pressure readings on pressure gauge 8 were recorded at time points of 0, 0.5, 1, 1.5, 2.5, 4, 4.5, 5, 5.5, 7, 10, 14, 18, 20, and 30 minutes. The relationship between aeration time and CO2 partial pressure was plotted. The results are shown in the figure. Figure 3 .Depend on Figure 3 It can be seen that as the aeration time increases, the partial pressure of CO2 in the flue gas CO2 absorption tank also gradually increases. Within 0-20 minutes, the CO2 partial pressure increases rapidly with increasing aeration time, reaching approximately 1.28 kPa at 20 minutes. However, after the aeration time exceeds 20 minutes, the CO2 partial pressure gradually stabilizes, indicating that the biogas slurry is approaching saturation in capturing CO2 from the flue gas. Therefore, a CO2 partial pressure of approximately 1.28 kPa, corresponding to an aeration time of approximately 20 minutes, can be used as an indicator parameter for when 4L of biogas slurry reaches saturation in capturing CO2 from the flue gas.

[0087] Example 2: Verification of the "Calcium Bridge" Flocculation Mechanism

[0088] Using biogas slurry from early spring as the experimental subject, 50 ml of saturated aerated biogas slurry at 1.28 kPa with an initial pH of 8.10 was taken. CaCl2 and CaO were added in groups (0.555 g of CaCl2 and 0.28 g of CaO, meaning the calcium concentration in both calcium source mixtures was 100 mmol / L). The study investigated different treatments using the two calcium sources, setting up control, acidification, alkalization, and acidification-then-alkalization groups. The calcium-bridging co-precipitation effect on organic matter was compared among different groups. The sediment from the four treatment groups with different calcium sources was filtered, and the organic carbon content of the supernatant was measured. The results are shown in [Figure number missing]. Figure 4 ,Depend on Figure 4 As can be seen, the organic carbon content in the four treatment groups with different calcium sources, in descending order, was: control group > acidification group > alkalization group > acidification followed by alkalization group. Compared with the other treatment groups, the organic carbon content in the CaCl2 and CaO groups treated with acidification followed by alkalization was significantly lower, at approximately 19.85 mg / L and 17.23 mg / L, respectively, followed by the alkalization group. This indicates that the "calcium bridge" environment formed by the acidification followed by alkalization treatment is conducive to the formation of organic colloid flocculation.

[0089] See Figures 5-6 In the group treated with acidification followed by alkali treatment, the removal rates of organic C using CaO and CaCl2 as calcium sources reached 88.43% and 86.67%, respectively, which were significantly higher than those without acid or alkali treatment, only acidification treatment, and only alkali treatment.

[0090] Example 3: Verification of the effect of the "calcium bridge" flocculation method through a process of acidification followed by alkalization.

[0091] refer to Figure 7Using biogas slurry from early spring as the experimental subject, 100 ml of saturated aerated biogas slurry at 1.28 kPa was taken, and 1.11 g of CaCl2 was added. The CO2-biogas slurry mixture was acidified with hydrochloric acid to lower the pH to 2.2. Then, NaOH was used to adjust the pH to different values ​​to determine the optimal pH parameters for the polymerization of organic matter by calcium bridges. Figure 7 It can be seen that the removal rate of organic C increases from pH 5.5 to 8.3, and decreases when pH exceeds 8.3.

[0092] Example 4: Verification of the effect of calcium dosage using the "calcium bridge" flocculation method

[0093] refer to Figure 8 Using biogas slurry from early spring as the research object, 50 ml of saturated aerated biogas slurry at 1.28 kPa was taken. CaCl2 was used as the calcium source, and different amounts of calcium ions were added sequentially. The CO2-biogas slurry mixture was acidified with hydrochloric acid to pH 2.2, and then the pH of the mixture was adjusted to 8.3 with NaOH to explore the optimal pH and optimal CO2 input conditions for different concentrations of CaCl2. 2+ - Dynamics of organic C concentration, see Figure 8 As calcium concentration increases, the content of organic carbon in the primary treatment solution gradually decreases. When the calcium ion concentration is 100 mmol / L, organic carbon in the primary treatment solution can be completely purified, that is, the organic carbon removal rate reaches 100%; when it exceeds 100 mmol / L, the organic carbon content in the primary treatment solution gradually increases.

[0094] In summary, among the formation mechanisms of "calcium bridges" in biogas slurry, acidification followed by alkalization is the most effective and conducive to the function of "calcium bridges." Under optimal CO2 conditions, a pH of 8.3 and a calcium ion concentration of 100 mmol / L represent the optimal concentration for the treated liquid. The optimal calcium content is related to the amount of CO2 introduced and the organic carbon content of the waste liquid.

[0095] Example 5: The effect of the "calcium bridge" flocculation method on the removal of main pollutants in fermentation waste liquid

[0096] The main component contents of the supernatant (primary treatment solution A) obtained after treating spring and autumn biogas slurry using the "calcium bridge" flocculation co-precipitation method under the above-mentioned optimal parameters are shown in Table 1. After treatment by the "calcium bridge" flocculation co-precipitation method, the removal rate of organic carbon reached 93%-95%, the removal rate of total phosphorus reached 79%-80%, the removal rate of ammonia nitrogen reached 91%-93%, and the removal rate of inorganic phosphorus, copper, and zinc reached 100%. The removal rate of the three antibiotics was relatively low, only 9%-18%.

[0097] Table 1. Content and removal rate of major pollutants in primary treated biogas slurry samples from different seasons.

[0098]

[0099] The asterisk (*) indicates that the calcium dosage is calculated based on the stoichiometric ratio of calcium to organic carbon in the flocculated precipitate of biogas slurry samples taken in early spring.

[0100] It is worth emphasizing that the amount of calcium added to the biogas slurry in autumn was calculated based on the stoichiometric ratio of calcium to organic carbon in the flocculated sediment of the biogas slurry in spring. The treatment effect showed that the removal rates of the main pollutants were all high. Clearly, calculating the calcium dosage based on the stoichiometric ratio of calcium to organic carbon in the flocculated sediment is reliable, and this also simplifies the use of the method of this invention to treat fermentation wastewater.

[0101] The supernatant produced after the calcium bridge process was then combined with the "electro-oxidation-electrodialysis" process, and the purification effect is shown in Table 2. As can be seen from Table 2, the dilute solution produced after the "electro-oxidation-electrodialysis" process of the supernatant after the calcium bridge process completely removed pollutants such as organophosphorus compounds, ammonia nitrogen, organic carbon, copper, zinc, and antibiotics, with a removal rate of 100%.

[0102] Table 2. Effect of the "Calcium Bridge" Coprecipitation-Electro-oxidation / Electrodialysis Process on Biogas Slurry Purification

[0103]

[0104]

[0105] Example 6: Effect of using the "calcium bridge" flocculation method to remove the main pollutants in landfill leachate

[0106] Table 3 shows that the "calcium bridge" precipitation method for treating landfill leachate achieved removal rates of 98.7% for organic carbon, 91.3% for ammonia nitrogen, and 78.6% for total phosphorus, while removing 100% for inorganic phosphorus, total cadmium, total lead, total arsenic, total chromium, and hexavalent chromium, respectively. The results are significant. When combined with the "electro-oxidation / electrodialysis" process, the removal rates of all the aforementioned pollutants can reach 100%.

[0107] Table 3. Purification effect of the "calcium bridge" coprecipitation-electro-oxidation / electrodialysis process on landfill leachate.

[0108]

[0109] The above are merely specific embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the technical scope disclosed in the present invention should be included within the scope of protection of the present invention. In the absence of conflict, the embodiments and features of the embodiments of the present invention can be combined with each other. Therefore, the scope of protection of the present invention should be determined by the scope of the claims.

Claims

1. A method for purifying high-concentration COD and ammonia nitrogen in biological fermentation wastewater, characterized in that, Includes the following steps: Step 1: Introduce CO2 from the flue gas into the fermentation waste liquid. The CO2 from the flue gas is introduced into the fermentation waste liquid through a flue gas capture device, forming CO2-saturated waste liquid A. In liquid A, CO2 is converted into HCO3-. - H2CO3 * Form exists; Step 2: Constructing a calcium bridge environment First, acidify solution A by adding an appropriate amount of dilute acid to solution A. At this point, the HCO3- content in solution A will decrease. - All converted to H2CO3 * The water-soluble cation NH in solution A + 4. Na + K⁺ pairs with the anions introduced by dilute acid to form a stable solution, in which H₂CO₃ * It is a collective term for CO2·H2O and H2CO3; Add calcium as needed. Take an appropriate amount of calcium-containing substance based on the volume of solution A, dissolve it in water or dilute acid, and add it to solution A. The calcium added at this time should be in the form of Ca. 2+ Form exists; Finally, alkalize the solution by adding dilute alkali to solution A. The resulting mixture is called solution B. At this time, the H2CO3 in solution B * It was then completely converted into HCO3. - Ca 2+ and HCO3 - The pairing is completed, forming water-soluble Ca(HCO3)2, Ca 2+ It exists in solution B as a highly active free ion, while the remaining HCO3-... - It then pairs with the cations introduced by the dilute alkali to form the corresponding water-soluble salt. In this environment, the organic colloids in solution B carry a negative charge, and the highly active Ca... 2+ It rapidly bridges with negatively charged organic colloids, while simultaneously, the Ca in the remaining solution B... 2+ It combines with phosphate ions, arsenate ions, trivalent chromate ions, or VI chromate ions to form different calcium salt precipitates; ammonia nitrogen combines with CO2 to form NH4. + Some NH4 + Adsorbed by negatively charged organic colloids, it separates from water along with the flocculation of the organic colloids; Pb 2+ Cd 2+ Cationic heavy metals react with OH- in weakly alkaline solution B - The precipitate is formed and separated from the water. In step two, the dilute acid used for acidification is hydrochloric acid, sulfuric acid, acetic acid and other water-soluble acids. The pH of solution A is acidified to 2.0-3.

0.

2. The method for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater according to claim 1, characterized in that, In step one, before introducing flue gas, the pH of the waste liquid is adjusted to 9.0-11.

0. The optimal pH value of the waste liquid corresponds to its organic carbon content; that is, a higher organic carbon content requires a larger pH adjustment. The alkali used to adjust the fermentation wastewater to alkalinity is either water-soluble NaOH or slightly soluble Ca(OH)2. Adjusting the pH of the waste liquid to 9.0-11.0 ensures that OH- under alkaline conditions... - The introduced CO2 is rapidly converted into CO3. 2- or HCO3 - .

3. The method for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater according to claim 1, characterized in that, In step two, the added calcium source is a water-soluble or acid-soluble calcium-containing substance, such as calcium chloride or calcium hydroxide. The amount of calcium added is calculated and determined based on the stoichiometric ratio of calcium to organic carbon in the flocculated precipitate. The stoichiometric ratio of calcium to organic carbon in pig farm biogas slurry is 1:0.9, and the stoichiometric ratio of calcium to organic carbon in landfill leachate is 1:1.

4.

4. The method for purifying high-concentration COD ammonia nitrogen in biological fermentation wastewater according to claim 3, characterized in that, In step two, the alkali raw material used for alkalization is water-soluble NaOH, and the pH value of solution B after alkalization is 8.2-8.

3.

5. A purification device for high-concentration COD and ammonia nitrogen in biological fermentation wastewater, used to implement the purification method as described in any one of claims 1-4, characterized in that, It includes a flue gas capture device and a mixing and clarification device. The flue gas capture device includes a flue gas inlet pipe, a fermentation waste liquid vortex spiral tube, and a flue gas CO2 absorption tank. The mixing and clarification device includes a flocculation mixing tank and a vertical flow sedimentation tank. One end of the flue gas inlet pipe is connected to the flue gas source and the chimney, and the other end is connected to a Venturi jet injector. The Venturi jet injector is connected to a fermentation waste liquid vortex spiral tube. One end of the fermentation waste liquid vortex spiral tube is connected to a pipe spiral blade mixer, and the other end is connected to a water pump. The pipe spiral blade mixer is connected to the upper side wall of the flue gas CO2 absorption tank. The water pump is connected to the near-bottom side wall of the flue gas CO2 absorption tank. The exhaust port of the flue gas CO2 absorption tank is connected to a flocculation mixing tank through a pipe. The flocculation mixing tank is connected to a vertical flow sedimentation tank. A supernatant overflow weir is installed at the top of the vertical flow sedimentation tank. The flocculation mixture outlet valve is connected to a pipe extending into the vertical flow sedimentation tank.

6. The purification equipment for high-concentration COD and ammonia nitrogen in biological fermentation wastewater according to claim 5, characterized in that, The other end of the flue gas inlet pipe is connected to the inlet port of the Venturi jet, the inlet port of the Venturi jet is connected to the outlet at the end of the upper section of the fermentation waste liquid vortex spiral tube, and the outlet port of the Venturi jet is connected to the inlet port of the lower section of the fermentation waste liquid vortex spiral tube.

7. The purification equipment for high-concentration COD and ammonia nitrogen in biological fermentation wastewater according to claim 6, characterized in that, The outlet of the lower section of the fermentation waste liquid vortex spiral tube is connected to the inlet end of the pipe spiral mixer. The outlet end of the pipe spiral mixer is connected to the inlet valve of the circulation pipe. The inlet valve of the circulation pipe is connected to the upper side wall of the flue gas CO2 absorption tank through a straight pipe. The inlet end of the upper section of the fermentation waste liquid vortex spiral tube is connected to the outlet port of the water pump. The inlet port of the water pump is connected to the circulation pipe valve. The circulation pipe valve is connected to the near-bottom side wall of the flue gas CO2 absorption tank through a straight pipe.

8. The purification equipment for high-concentration COD and ammonia nitrogen in biological fermentation wastewater according to claim 5, characterized in that, The top of the flue gas CO2 absorption tank is provided with a feed inlet, a pressure gauge and a sampling hole. The upper part of the side wall of the flue gas CO2 absorption tank is provided with a circulation inlet, and a circulation pipe inlet valve is installed on the outer side of the circulation inlet wall. The lower part of the side wall of the flue gas absorption tank is provided with a circulation outlet and a discharge hole. A circulation pipe valve is installed on the outer side of the circulation outlet wall and a discharge hole valve is installed on the outer side of the discharge hole wall.

9. The purification equipment for high-concentration COD and ammonia nitrogen in biological fermentation wastewater according to claim 5, characterized in that, The flocculation mixing tank is provided with a feeding port at the top, a CO2 absorbent inlet is provided on the upper part of the side wall of the flocculation mixing tank, and a flocculation mixture outlet is provided on the lower part of the side wall. A CO2 absorbent inlet valve is installed at the CO2 absorbent inlet, and a mixture outlet valve is installed at the flocculation mixture outlet. A flocculation mixing tank impeller is installed inside the flocculation mixing tank.

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