Treatment method for synchronously removing ammonia nitrogen and organic matters in biogas slurry

Abstract

The invention discloses a treatment method for synchronously removing ammonia nitrogen and organic matters in biogas slurry, which comprises the following steps: the biogas slurry is subjected to electrochemical treatment and ultraviolet radiation treatment at the same time, the anode adopted in the electrochemical treatment comprises a ruthenium iridium titanium electrode, and the cathode comprises an iron-doped modified carbon felt electrode. The preparation method of the iron-doped modified carbon felt electrode comprises the following steps: a, carrying out ultrasonic cleaning on a carbon felt; b, the cleaned carbon felt is soaked in acid liquor to be activated; c, dipping the activated carbon felt in a polytetrafluoroethylene solution; d, coating one side of the carbon felt treated in the step c with a solution containing carbon powder and polytetrafluoroethylene, and drying to obtain a carbon felt containing a catalyst layer; and e, dropwise adding an iron-containing precursor solution onto the carbon felt catalyst layer, and calcining to obtain the iron-doped modified carbon felt electrode. The treatment method provided by the invention realizes in-situ generation and activation of hydrogen peroxide, enhances removal of organic pollutants, reduces consumption of active chlorine by organic matters, and realizes synchronous removal of ammonia nitrogen and organic matters in the biogas slurry.

Description

Technical Field

[0001] The invention belongs to the technical field of kitchen waste biogas slurry treatment, and specifically relates to a treatment method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry. Background Art

[0002] Low-carbon and energy-saving garbage disposal methods are constantly improving, and garbage anaerobic nitrification technology has gradually attracted the attention of environmental personnel. Compared with landfill and incineration treatment methods, this technology has broad prospects and realizes the resource utilization of garbage based on the concept of sustainable development. The anaerobic fermentation technology for treating kitchen waste can be combined with other treatment technologies to reduce the treatment area and effectively reduce carbon emissions. However, kitchen waste will produce a large amount of biogas slurry under the decomposition and metabolism of anaerobic microorganisms. The characteristics of this biogas slurry are high ammonia nitrogen concentration, low carbon-nitrogen ratio, and a large amount of inorganic salt components such as chloride ions, and poor biodegradability. Therefore, it is difficult to achieve effective treatment of biogas slurry with traditional biochemical processes. In order to facilitate subsequent biochemical treatment and improve its biodegradability, it is urgent to develop efficient treatment processes to achieve efficient removal of ammonia nitrogen.

[0003] The removal of ammonia nitrogen is mainly based on physical, chemical and biological methods. The physical method mainly includes air stripping, adsorption and membrane filtration. However, the physical method only enriches and transfers ammonia nitrogen, and still requires subsequent treatment. The chemical method is generally the magnesium ammonium phosphate chemical precipitation method, which uses chemicals such as phosphates and magnesium salts to generate struvite chemical precipitation with ammonium ions and supplies it to industries such as fertilizers. However, in large-scale use, this method requires a large amount of chemical drugs, resulting in relatively high costs, which hinders its large-scale use. At the same time, the pollution of biogas slurry is complicated, and the recovery of high-purity struvite is difficult. Biological methods are widely used in the field of water treatment due to their lower economic cost and smaller environmental impact. However, the biogas slurry has a complex composition, high salt and high ammonia nitrogen, which leads to a certain inhibitory effect on activated sludge. Therefore, it is necessary to conduct in-depth research to develop a simple process and no secondary pollution high-efficiency ammonia nitrogen organic matter simultaneous removal technology. Summary of the invention

[0004] The present invention is based on the inventor's discovery and understanding of the following facts and problems: the electrochemical method has the advantages of simple process, convenient operation, green environmental protection, and wide application range, so it has good potential in the industrial application of environmental governance. For the electrochemical oxidation removal of ammonia nitrogen, it mainly includes two categories: direct oxidation and indirect oxidation. The direct oxidation process requires adjusting the solution to alkalinity, converting ammonia nitrogen into ammonia gas, and adsorbing it to the anode surface to gradually complete the dehydrogenation process to form nitrogen. However, the direct oxidation of ammonia nitrogen is limited by the electron transfer rate and anode materials, resulting in less application. Indirect oxidation can not only play the role of direct oxidation of the anode to a certain extent, but also use the generated strong oxidizing active species to further enhance degradation, and has good application prospects. Traditional active oxygen species are difficult to effectively oxidize and remove ammonia nitrogen, while the electrochlorination process can use anode oxidation to realize the conversion of chloride ions to active chlorine, and active chlorine has obvious advantages in the conversion of ammonia nitrogen to nitrogen. The biogas slurry contains a large amount of chloride ions, omitting the process of additional addition of chlorine source, and can realize a green treatment mode of waste treatment. However, due to the high COD in biogas slurry, organic pollutants will compete with ammonia nitrogen for active chlorine, thereby reducing the removal efficiency of ammonia nitrogen. Therefore, the electrochemical treatment method of biogas slurry needs further research and improvement.

[0005] The present invention aims to solve at least one of the technical problems in the related art to a certain extent. To this end, an embodiment of the present invention proposes a treatment method for the simultaneous removal of ammonia nitrogen and organic matter in biogas slurry. On the basis of promoting the electrochemical generation of active chlorine at the anode to enhance the oxidation of ammonia nitrogen, a modified carbon felt cathode is used to achieve the in-situ generation and activation of hydrogen peroxide, thereby promoting the removal of organic matter while reducing the production of added hydrogen peroxide and homogeneous Fenton iron mud. Hydrogen peroxide and its activated products have good removal efficiency for organic pollutants, but cannot effectively oxidize ammonia nitrogen. Therefore, the introduction of an active cathode can reduce the consumption of active chlorine by organic matter, thereby achieving the simultaneous removal of ammonia nitrogen and organic matter in biogas slurry.

[0006] The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry in an embodiment of the present invention comprises: subjecting the biogas slurry to electrochemical treatment and simultaneously subjecting it to ultraviolet irradiation treatment, wherein the anode used in the electrochemical treatment comprises a ruthenium-iridium-titanium electrode and the cathode comprises an iron-doped modified carbon felt electrode.

[0007] The advantages and technical effects of the treatment method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry in the embodiment of the present invention are as follows: 1. In the embodiment of the present invention, a modified carbon felt electrode is used as the cathode for electrochemical treatment, which promotes the conversion of molecular oxygen into hydrogen peroxide, enhances the exposure and hydrophobicity of surface active sites, improves the mass transfer efficiency of molecular oxygen, strengthens the efficient generation of hydrogen peroxide, and iron doping realizes the in-situ activation of hydrogen peroxide; 2. In the embodiment of the present invention, with the help of chloride ions contained in the biogas slurry, active chlorine (such as Cl2, HClO, ClO - and chlorine-containing free radicals, etc.), strengthening the directional conversion of ammonia nitrogen to nitrogen. At the same time, the introduction of ultraviolet light source irradiation during the electrochemical treatment process effectively solved the relatively difficult problem of the conversion of chloride ions to highly active chlorine-containing free radicals, and strengthened the conversion of HClO, ClO - and Cl2 are rapidly photolyzed to generate OH· and Cl· with higher oxidation potentials, further promoting the removal of ammonia nitrogen and organic pollutants; 3. In the embodiment of the present invention, the biogas slurry is treated by coupling electrochemical treatment and ultraviolet irradiation, so that the hydrogen peroxide generated at the cathode and the active chlorine species generated at the anode are in situ activated under the irradiation of ultraviolet light, and the modified carbon felt cathode is conducive to the efficient removal of organic matter, thereby reducing the consumption of active chlorine generated at the anode by organic matter, significantly improving the removal efficiency of ammonia nitrogen and organic matter, and realizing the simultaneous removal of ammonia nitrogen and organic matter in wastewater. At the same time, the increase in the carbon-nitrogen ratio is conducive to subsequent biochemical treatment, and the treatment system has good stability and can operate stably for a long time.

[0008] In some embodiments, the method for preparing the modified carbon felt electrode comprises:

[0009] a. Ultrasonic cleaning of carbon felt to remove impurities;

[0010] b. The carbon felt after cleaning in step a is immersed in an acid solution for acid immersion activation treatment;

[0011] c. The activated carbon felt is immersed in a solution containing polytetrafluoroethylene for hydrophobic modification;

[0012] d. applying a solution containing carbon powder and polytetrafluoroethylene to one side of the carbon felt modified in step c, and drying to obtain a modified carbon felt containing a catalytic layer;

[0013] e. dropping the iron-containing precursor solution onto the catalytic layer of the modified carbon felt obtained in step d, and after calcination, obtaining an iron-doped modified carbon felt electrode.

[0014] In some embodiments, in step a, the cleaning solution used for cleaning includes at least one of water, ethanol or acetone.

[0015] In some embodiments, in step b, the acid solution includes at least one of concentrated nitric acid and concentrated sulfuric acid, and the concentration of the acid solution is 60-95wt%.

[0016] In some embodiments, in step b, the temperature of the acid leaching activation treatment is 60-90° C., and the treatment time is 9-12 hours.

[0017] In some embodiments, in step c, the concentration of polytetrafluoroethylene is 1-5wt%, and the immersion time is 30-60min.

[0018] In some embodiments, in step d, the content of carbon powder in the solution is 1-5 g / L, and the mass ratio of carbon powder to polytetrafluoroethylene is 3:1-1:7.

[0019] In some embodiments, in step e, the iron-containing precursor solution includes at least one of ferric nitrate, ferrous nitrate, ferric chloride, ferrous chloride, ferrous sulfate or ferrous sulfate. Preferably, the iron-containing precursor solution is a mixed solution including divalent iron ions and trivalent iron ions. More preferably, the molar ratio of the divalent iron ions to the trivalent iron ions is 1:3-3:1.

[0020] In some embodiments, in the step e, the calcination temperature is 350-500° C., and the calcination time is 30-300 min.

[0021] In some embodiments, an ultraviolet light source is provided at the cathode and / or anode used in the electrochemical treatment.

[0022] In some embodiments, during the electrochemical treatment, oxygen is introduced into the cathode.

[0023] In some embodiments, the COD of the biogas slurry is 1500-3500 mg / L, the ammonia nitrogen is 1500-2000 mg / L, the total nitrogen is 1600-2500 mg / L, and the chloride ion concentration is 5000-15000 mg / L. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 It is a flow chart of a method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to an embodiment of the present invention.

[0025] Figure numerals: 1. liquid storage tank, 2. peristaltic pump, 3. electrochemical reactor, 4. ultraviolet lamp, 5. anode, 6. cathode, 7. DC power supply, 8. aeration device. DETAILED DESCRIPTION

[0026] Embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0027] The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry in an embodiment of the present invention comprises: subjecting the biogas slurry to electrochemical treatment and simultaneously subjecting it to ultraviolet irradiation treatment, wherein the anode used in the electrochemical treatment comprises a ruthenium-iridium-titanium electrode and the cathode comprises an iron-doped modified carbon felt electrode.

[0028] In the treatment method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry in the embodiment of the present invention, a modified carbon felt electrode is used as the cathode for electrochemical treatment, which enhances the exposure and hydrophobicity of the surface active sites, improves the mass transfer efficiency of molecular oxygen, strengthens the efficient generation of hydrogen peroxide, and the iron doping realizes the in-situ activation of hydrogen peroxide. In the embodiment of the present invention, active chlorine (such as Cl2, HClO, ClO) is generated by anode electrochlorination with the help of chloride ions contained in the biogas slurry. - and chlorine-containing free radicals, etc.), strengthening the directional conversion of ammonia nitrogen to nitrogen. At the same time, the introduction of ultraviolet light source irradiation during the electrochemical treatment process effectively solved the relatively difficult problem of the conversion of chloride ions to highly active chlorine-containing free radicals, and strengthened the conversion of HClO, ClO - and Cl2 are rapidly photolyzed to generate OH· and Cl· with higher oxidation potentials, further promoting the removal of ammonia nitrogen and organic pollutants. In the embodiment of the present invention, the biogas slurry is treated by coupling electrochemical treatment and ultraviolet irradiation, so that the hydrogen peroxide generated at the cathode and the active chlorine species generated at the anode are activated in situ under the irradiation of ultraviolet light. The modified carbon felt cathode is conducive to the efficient removal of organic matter, thereby reducing the consumption of active chlorine generated at the anode by organic matter, significantly improving the removal efficiency of ammonia nitrogen and organic matter, and realizing the simultaneous removal of ammonia nitrogen and organic matter in wastewater. At the same time, the improvement of the carbon-nitrogen ratio is conducive to subsequent biochemical treatment, and the treatment system has good stability and can operate stably for a long time.

[0029] The mechanism involved in the method of the embodiment of the present invention is as follows:

[0030] Anode active chlorine generation process:

[0031] 2Cl - →Cl2+2e -

[0032] Cl2+H2O→HClO+Cl -

[0033] Cl - +2OH - →OCl - +H2O+2e -

[0034] Cl - →Cl·+e -

[0035] Cl·+Cl - →Cl2 -

[0036] HClO+Cl·→ClO·+H + +Cl -

[0037] The process of producing hydrogen peroxide by reduction of molecular oxygen at cathode:

[0038] O2+2H + +2e - →H2O2

[0039] The specific reaction process is as follows:

[0040] O2+*+H + +e - →HOO *

[0041] HOO * +H + +e - →H2O2+*

[0042] UV irradiation enhancement mechanism:

[0043] HClO+hv→HO·+Cl·

[0044] H2O2+hv→2HO·

[0045] In some embodiments, the method for preparing the modified carbon felt electrode comprises:

[0046] a. ultrasonically cleaning the carbon felt to remove impurities, preferably, the cleaning solution used in the cleaning comprises at least one of water, ethanol or acetone;

[0047] b. Soaking the carbon felt cleaned in step a in an acid solution for acid leaching activation treatment; preferably, the acid solution comprises at least one of concentrated nitric acid or sulfuric acid, and the concentration of the acid solution is 60-95wt%; preferably, the temperature of the acid leaching activation treatment is 60-90°C, and the treatment time is 9-12h; In the embodiment of the present invention, the carbon felt is acid-leached with a strong acid, which is beneficial to enhance the exposure of the active sites on the cathode surface and further improve the generation efficiency of hydrogen peroxide;

[0048] c. The activated carbon felt is immersed in a solution containing polytetrafluoroethylene for hydrophobic modification; preferably, the concentration of the polytetrafluoroethylene is 1-5wt%, and the immersion time is 30-60min; In the embodiment of the present invention, the improvement of hydrophobicity is conducive to improving the capture and utilization of molecular oxygen and promoting the conversion of molecular oxygen into hydrogen peroxide;

[0049] d. The carbon powder solution and the polytetrafluoroethylene solution are mixed evenly and then applied to one side of the carbon felt modified in step c, and dried to obtain a modified carbon felt containing a catalytic layer; preferably, the carbon powder content in the solution is 1-5 g / L, and the mass ratio of carbon powder to polytetrafluoroethylene is 3:1-1:7;

[0050] e. dropping the iron-containing precursor solution onto the catalytic layer of the modified carbon felt obtained in step d, and after calcination, obtaining an iron-doped modified carbon felt electrode.

[0051] Preferably, the iron-containing precursor solution includes at least one of ferric nitrate, ferrous nitrate, ferric chloride, ferrous chloride, ferrous sulfate or ferrous sulfate. Further preferably, the iron-containing precursor solution is a mixed solution including divalent iron ions and trivalent iron ions, and more preferably, the molar ratio of the divalent iron ions to the trivalent iron ions is 1:3-3:1. In the embodiment of the present invention, the introduction of iron doping improves the in-situ activation efficiency of hydrogen peroxide, reduces the dependence of the treatment process on iron ions in the solution, and reduces the generation of iron mud in the homogeneous Fenton reaction. Metal doping is carried out while modifying the surface of carbon felt, and the generated hydrogen peroxide is activated in situ, so that the efficient conduction of the heterogeneous Fenton reaction is achieved, and the organic pollutants are effectively decomposed and mineralized. The consumption of active chlorine produced by anode electrochlorination by organic matter is reduced, and the oxidation and removal of ammonia nitrogen by active chlorine is indirectly promoted, and the carbon-nitrogen ratio is improved to a certain extent, thereby improving the biodegradability of the treated sewage.

[0052] Preferably, the calcination temperature is 350-500°C, and the calcination time is 30-300 minutes. In the embodiment of the present invention, the carbon felt after the iron-containing solution is drip-coated is calcined to effectively dope the carbon felt with iron, which is beneficial to further promote the in-situ activation of the generated hydrogen peroxide, thereby achieving efficient heterogeneous Fenton reaction. If the calcination temperature is too high, it will affect the content of functional groups on the surface of the carbon felt. If the calcination temperature is too low, it will affect the doping load of the iron-containing substance.

[0053] In some embodiments, an ultraviolet light source is provided at the cathode and / or anode used in the electrochemical treatment. In the embodiments of the present invention, there is no particular limitation on the ultraviolet light source used, and any ultraviolet light source commonly used in the art can be applied to the present invention.

[0054] In some embodiments, oxygen is introduced into the cathode during the electrochemical treatment process. In the embodiments of the present invention, oxygen is introduced to provide a raw material for molecular oxygen activation, and in-situ generation and activation of hydrogen peroxide is achieved by modifying the cathode.

[0055] In some embodiments, the COD in the biogas slurry is 1500-3500 mg / L, the ammonia nitrogen is 1500-2000 mg / L, the total nitrogen is 1600-2500 mg / L, and the chloride ion concentration is 5000-15000 mg / L. The method of the embodiment of the present invention can efficiently treat biogas slurry with high COD, high ammonia nitrogen, and high chloride, and can simultaneously remove organic matter and ammonia nitrogen in the biogas slurry.

[0056] The present invention is described in detail below with reference to the embodiments and the accompanying drawings.

[0057] Example 1 Preparation of modified carbon felt electrode

[0058] The carbon felt was ultrasonically cleaned with water, ethanol, acetone, ethanol and water in turn to remove impurities. The cleaned carbon felt was soaked in 68wt% concentrated nitric acid and acid-activated at 80°C for 10h. The carbon felt treated with nitric acid was soaked in a 2wt% polytetrafluoroethylene solution for 30min. Then, a solution containing carbon powder and polytetrafluoroethylene was evenly applied on one side of the carbon felt, wherein the content of carbon powder in the solution was 3g / L, and the mass ratio of carbon powder to polytetrafluoroethylene was 1:3. The carbon felt was dried to form a catalytic layer on the surface of the carbon felt, and a mixed solution of ferric nitrate and ferrous nitrate was evenly added to the catalytic layer of the carbon felt. The molar ratio of ferric nitrate to ferrous nitrate in the mixed solution was 1:1. The mixture was calcined at 400°C for 2h to obtain an iron-doped modified carbon felt electrode.

[0059] Example 2

[0060] The biogas slurry used in this embodiment is taken from the water body of the regulating tank (before entering the biochemical treatment) after anaerobic fermentation of kitchen waste at a garbage treatment station in Beijing, after plate and frame filter pressing. The water quality is as follows: COD is 2060 mg / L, ammonia nitrogen is 1506.1 mg / L, total nitrogen is 1612.4 mg / L, and chloride ion concentration is 6752.6 mg / L.

[0061] like Figure 1 As shown, the biogas slurry in the liquid storage tank 1 is sent to the electrochemical reactor 3 through the peristaltic pump 2, and the flow rate of the biogas slurry is 200ml / min, and a continuous flow experiment is carried out. The anode 5 adopts a ruthenium iridium titanium mesh electrode, and the cathode 6 adopts a modified carbon felt electrode prepared in Example 1. An ultraviolet light source 4 is set at the anode 5 and the cathode 6, and the anode 5 and the cathode 6 are connected to a DC power supply 7. The cathode area in the electrochemical reactor 3 is aerated through the aeration device 8, wherein the oxygen volume concentration is 90% and the flow rate is 1L / min. The plate area of ​​the anode 5 and the cathode 6 is 10cm×10cm.

[0062] After 120 minutes of reaction treatment, the ammonia nitrogen removal rate of the biogas slurry in this embodiment was 84.2%, the total nitrogen removal rate was 79.5%, and the COD removal rate was 60.8%. The carbon-nitrogen ratio (COD / total nitrogen) of the biogas slurry after treatment increased from 1.28 to 2.44, and the carbon-nitrogen ratio increased by 90.6%. The biodegradability was significantly improved, reducing the load of subsequent biochemical treatment.

[0063] The experiment in this embodiment was repeated 20 times. After the 20th treatment, the ammonia nitrogen removal rate was 72.7%, the total nitrogen removal rate was 67.5%, and the COD removal rate was 51.9%.

[0064] Example 3

[0065] The method is the same as that in Example 2, except that the treated biogas slurry is taken from the biogas slurry after anaerobic fermentation of kitchen waste in a garbage disposal station. The water quality of the biogas slurry is: COD is 1500 mg / L, ammonia nitrogen is 1518.6 mg / L, total nitrogen is 2095.1 mg / L, and chloride ion content is 13070.2 mg / L.

[0066] After 120 minutes of reaction treatment, the ammonia nitrogen removal rate of the biogas slurry in this embodiment was 90.1%, the total nitrogen removal rate was 76.2%, and the COD removal rate was 60.3%. The carbon-nitrogen ratio of the biogas slurry after treatment increased from 0.716 to 1.19, and the carbon-nitrogen ratio increased by 66.2%.

[0067] This embodiment repeated the experiment 20 times. After the 20th treatment, the ammonia nitrogen removal rate was 80.9%, the total nitrogen removal rate was 65.8%, and the COD removal rate was 50.8%.

[0068] Comparative Example 1

[0069] The method is the same as that of Example 2, except that the cathode is the raw carbon felt that has not been modified in Example 1.

[0070] After 120 minutes of reaction treatment, the ammonia nitrogen removal rate of the biogas slurry in comparative example 1 was 73.6%, the total nitrogen removal rate was 64.6%, and the COD removal rate was 47.2%. The carbon-nitrogen ratio of the biogas slurry after treatment increased from 1.28 to 1.91, and the carbon-nitrogen ratio increased by 49.2%.

[0071] This comparative example was repeated 20 times. After the 20th treatment, the ammonia nitrogen removal rate was 60.3%, the total nitrogen removal rate was 54.5%, and the COD removal rate was 40.1%.

[0072] Comparative Example 2

[0073] The method is the same as that of Example 2, except that no ultraviolet light source 4 is provided at the anode 5 and the cathode 6.

[0074] After 120 minutes of reaction treatment, the ammonia nitrogen removal rate of the biogas slurry in comparative example 2 was 72.6%, the total nitrogen removal rate was 64.5%, and the COD removal rate was 56.5%. The carbon-nitrogen ratio of the biogas slurry after treatment increased from 1.28 to 1.57, and the carbon-nitrogen ratio increased by 22.7%.

[0075] This comparative example experiment was repeated 20 times. After the 20th treatment, the ammonia nitrogen removal rate was 62.8%, the total nitrogen removal rate was 53.9%, and the COD removal rate was 50.2%.

[0076] In the embodiment of the present invention, modified carbon felt is used as the cathode material and ultraviolet irradiation treatment is used at the same time as electrochemical treatment, which effectively improves the removal rate of ammonia nitrogen and organic matter. The ammonia nitrogen removal rate can be as high as 84% ​​or more, the COD removal rate can reach more than 60%, and the total nitrogen removal rate can reach more than 75%. At the same time, after being treated by the method of the embodiment of the present invention, the carbon-nitrogen ratio of the biogas slurry is significantly improved. Compared with before treatment, the carbon-nitrogen ratio of the biogas slurry can be increased by more than 66%. In particular, in embodiment 2, the carbon-nitrogen ratio can be increased by more than 90%, which effectively improves the biodegradability of the biogas slurry after treatment and reduces the load of subsequent biochemical treatment.

[0077] In Comparative Example 1, compared with Example 2, the use of unmodified carbon felt is not conducive to the removal of organic matter. The organic matter consumes the active chlorine produced by the anode, thereby significantly reducing the ammonia nitrogen removal rate. The carbon-nitrogen ratio of the treated biogas slurry can only be increased from 1.28 to 1.91, an increase of 49%, which is significantly lower than 90.6% of Example 2.

[0078] In Comparative Example 2, compared with Example 2, no ultraviolet light source is provided, the content of chlorine-containing free radicals is reduced, and the ammonia nitrogen removal effect is significantly reduced. The ammonia nitrogen removal rate is greatly reduced to 72.6%, the total nitrogen removal rate is reduced to 64.5%, and the COD removal rate is slightly reduced to 56.5%. The carbon-nitrogen ratio of the treated biogas slurry is increased from the original 1.28 to 1.57, and the carbon-nitrogen ratio can only be increased by 22.7%, which has little improvement on the biodegradability of the biogas slurry.

[0079] In the present invention, the terms "one embodiment", "some embodiments", "examples", "specific examples", or "some examples" etc. mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the described specific features, structures, materials or characteristics may be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art may combine and combine the different embodiments or examples described in this specification and the features of the different embodiments or examples, without contradiction.

[0080] Although the embodiments of the present invention have been shown and described above, it is to be understood that the above embodiments are exemplary and are not to be construed as limitations of the present invention. A person skilled in the art may change, modify, replace and vary the above embodiments within the scope of the present invention.

Claims

1. A method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry, characterized in that: include: The biogas slurry is subjected to electrochemical treatment and ultraviolet irradiation treatment at the same time. The anode used in the electrochemical treatment includes a ruthenium-iridium-titanium electrode, and the cathode includes an iron-doped modified carbon felt electrode.

2. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 1, characterized in that: The preparation method of the modified carbon felt electrode comprises: a. Ultrasonic cleaning of carbon felt to remove impurities; b. The carbon felt after cleaning in step a is immersed in an acid solution for acid immersion activation treatment; c. The activated carbon felt is immersed in a solution containing polytetrafluoroethylene for hydrophobic modification; d. The solution containing carbon powder and polytetrafluoroethylene is applied to one side of the carbon felt after modification in step c, and dried to obtain a modified carbon felt containing a catalytic layer; e. dropping the iron-containing precursor solution onto the catalytic layer of the modified carbon felt obtained in step d, and after calcination, obtaining an iron-doped modified carbon felt electrode.

3. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 2, characterized in that: In the step a, the cleaning solution used for cleaning includes at least one of water, ethanol or acetone.

4. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 2, characterized in that: In the step b, the acid solution includes at least one of concentrated nitric acid and concentrated sulfuric acid, the concentration of the acid solution is 60-95wt%, the temperature of the acid leaching activation treatment is 60-90°C, and the treatment time is 9-12h.

5. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 2, characterized in that: In the step c, the concentration of the polytetrafluoroethylene is 1-5wt%, and the immersion time is 30-60min.

6. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 2, characterized in that: In the step d, the content of carbon powder in the solution is 1-5 g / L, and the mass ratio of carbon powder to polytetrafluoroethylene is between 3:1 and 1:

7.

7. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 2, characterized in that: In the step e, the iron-containing precursor solution includes at least one of ferric nitrate, ferrous nitrate, ferric chloride, ferrous chloride, ferrous sulfate or ferrous sulfate. Preferably, the iron-containing precursor solution is a mixed solution including divalent iron ions and trivalent iron ions. More preferably, the molar ratio of the divalent iron ions to the trivalent iron ions is 1:3-3:1; And / or, the calcination temperature is 350-500° C., and the calcination time is 30-300 min.

8. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 1, characterized in that: An ultraviolet light source is arranged at the cathode and / or anode used in the electrochemical treatment.

9. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 1, characterized in that: During the electrochemical treatment, oxygen is introduced into the cathode.

10. The method for simultaneously removing ammonia nitrogen and organic matter from biogas slurry according to claim 1, characterized in that: The biogas slurry has a COD of 1500-3500 mg / L, an ammonia nitrogen of 1500-2000 mg / L, a total nitrogen of 1600-2500 mg / L, and a chloride ion concentration of 5000-15000 mg / L.

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