Method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matters by using ammonia-mediated iron circulation technology

Abstract

The invention belongs to the technical field of sewage treatment, and particularly relates to a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matters by using an ammonia-mediated iron circulation technology. The invention provides a new strategy, and the strategy relates to regeneration of Fe (II) by ammonium oxidation mediated Fenton iron mud and removal of organic pollutants in wastewater by Fenton oxidation. Ammonium radicals are used as resources for mediating Fenton iron circulation reaction. When the Fenton reaction is carried out, Fe (II) reacts with an oxidizing agent H2O2 to generate ferric iron mud, then NH4 < + >-N and Fe (III) in the Fenton iron mud are subjected to Fammox reaction to generate Fe (II), and the Fe (II) is applied to the Fenton reaction again, so that the circulation of iron is realized in the reactor, and the secondary pollution of the iron mud is reduced. Therefore, when being applied to wastewater treatment, the method disclosed by the invention has the remarkable advantages of low treatment cost, reduction of secondary pollution of the iron mud, removal of ammonia nitrogen and toxic and harmful organic matters in the wastewater and the like.

Description

Technical Field

[0001] The invention belongs to the technical field of sewage treatment, and specifically relates to a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter by utilizing an ammonia-mediated iron circulation technology. Background Art

[0002] Due to the rapid development of economy and industry, a large amount of wastewater containing high ammonia nitrogen and toxic organic matter is discharged into urban wastewater. These pollutants have caused environmental pollution worldwide, such as eutrophication, ecotoxicity and increased cancer risk. Therefore, the treatment of wastewater containing high ammonia nitrogen concentration and toxic organic matter has always been an important part of environmental governance.

[0003] At present, biological method is a common sewage treatment method. This method uses the metabolic function of microorganisms to degrade and convert organic pollutants in dissolved and colloidal states in sewage into harmless substances, so that sewage can be purified. For example, activated sludge method, biofilm method, and anaerobic biological treatment method. However, the efficiency of biological wastewater treatment is greatly affected by temperature. The activity of microorganisms decreases at low temperatures, and a larger space is usually required to accommodate the reactor for microbial growth. In addition, toxic and harmful organic matter has a certain toxic effect on organisms, and it is difficult to completely degrade toxic organic wastewater with high toxicity and carcinogenicity.

[0004] As an advanced oxidation process (AOP), the traditional Fenton process is often used to treat organic wastewater because of its simple operation, high degradation efficiency and simple equipment. It can effectively remove pollutants in wastewater through hydroxyl radicals. However, this method still has the disadvantages of high reagent consumption and Fenton iron sludge pollution. To address this problem, although the reagent consumption can be reduced by adding an iron chelating agent to the Fenton reactor to increase the regeneration rate of Fe(Ⅱ) in a near-neutral pH environment; and adding an additional reductant to the Fenton reactor to promote the reduction of precipitated Fe(Ⅲ) and reduce the accumulation of Fenton iron sludge. However, the addition of reagents requires additional costs and may introduce new pollutants into the reactor. Among them, the homogeneous Fenton technology is widely used in the treatment of difficult-to-biodegrade, toxic and harmful organic wastewater due to its strong oxidizing property, but the treatment effect is not ideal for wastewater containing high ammonia nitrogen concentrations. The heterogeneous Fenton oxidation system refers to the use of iron-containing solid substances or the fixation of iron on a carrier to replace the homogeneous ferrous salts to react with hydrogen peroxide and oxygen, which retains the advantages of homogeneous Fenton such as non-selective degradation and fast reaction speed, but requires higher processing costs, high reagent consumption, high preparation costs, and low stability of heterogeneous catalysts. Therefore, it is necessary to design a low-cost, high-efficiency technology for removing ammonia nitrogen and toxic and harmful organic matter from wastewater at the same time.

[0005] Studies have shown that the introduction of anaerobic ammonium oxidation reaction based on the photo-Fenton technology can achieve the effect of removing ammonia nitrogen and toxic and harmful organic matter at the same time. However, the existing technology combining photo-Fenton and anaerobic ammonium oxidation reaction still has the disadvantages of high reagent consumption, high preparation cost and low stability. Therefore, how to remove high-concentration ammonia nitrogen and toxic and harmful organic matter in wastewater at low cost, low carbon emissions and high efficiency is still a huge challenge at present. Summary of the invention

[0006] In order to overcome the shortcomings of the above-mentioned prior art, the present invention proposes a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology, which uses the pollutant ammonia nitrogen in the wastewater as a resource and reduces Fe(III) to Fe(II) at a pH value close to neutral. This ammonia-mediated AOP can effectively remove NH4 in the wastewater at the same time by consuming only low concentrations of hydrogen peroxide. + -N and toxic and harmful organic matter. When the method of the present invention is used to treat wastewater, the amount of reagents added can be greatly reduced, and the secondary pollution of iron sludge treated by the traditional Fenton method can be reduced.

[0007] In order to achieve the above object, the technical solution adopted by the present invention is:

[0008] The present invention provides a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter by using ammonia-mediated iron circulation technology, specifically: the reactor used in the method is a funnel-shaped reactor, an anaerobic reactor with a CEM cation exchange membrane is placed in the middle of the reactor to form an inner and outer chamber, and the inner and outer chambers are connected by a pump; the wastewater containing high ammonia nitrogen and toxic and harmful organic matter is placed in the outer chamber of the reactor, and an oxidant is added to the outer chamber, and tap water is added to the inner chamber;

[0009] The inner chamber is the autotrophic Feammox unit, NH4 + and Fe(Ⅲ) enters the inner chamber from the cation exchange membrane to undergo reduction reaction, NH4 + -N and Fe(Ⅲ) undergo Feammox reaction, driving Fe(Ⅲ) to be reduced to Fe(Ⅱ) while generating NH4 + Concentration decreases;

[0010] The outer chamber is a Fenton oxidation unit. Fe(II) generated by the reduction of Fe(III) enters the outer chamber through the cation exchange membrane and reacts with the oxidant under weak acid conditions to produce hydroxyl radicals ·OH and iron sludge, thereby removing toxic and harmful organic matter from the wastewater through Fenton oxidation.

[0011] The precipitated Fe(Ⅲ) in the iron sludge in the outer chamber is re-transferred to the inner chamber and continues to react with NH4 +-N undergoes Feammox reaction, reducing Fe(Ⅲ) to Fe(Ⅱ), realizing Fe(Ⅲ) / Fe(Ⅱ) cycle, and finally achieving the purpose of removing ammonia nitrogen and toxic and harmful organic matter in wastewater at the same time.

[0012] The present invention uses ammonia nitrogen, a pollutant in wastewater, as a resource to reduce Fe(III) to Fe(II) under weak acid conditions. This ammonia-mediated AOP can effectively remove NH4 in wastewater by consuming only low concentrations of hydrogen peroxide. + -N and toxic and harmful organic matter. The reaction process involves Feammox (coupling of ammonia nitrogen oxidation and Fe(Ⅲ) reduction), Fenton oxidation to remove organic pollutants in wastewater, and Fe(Ⅱ) regeneration. The resource utilization of ammonia nitrogen and the Fe(Ⅲ) / Fe(Ⅱ) cycle achieve low-cost and high-efficiency wastewater treatment.

[0013] The bioreactor of the present invention converts ammonia nitrogen into resources to drive the iron cycle in Fenton treatment, and utilizes ammonia nitrogen as a resource. Ammonia nitrogen reacts with precipitated iron to drive Fe(III) to regenerate Fe(II). Fenton oxidation technology is used to treat wastewater containing high-concentration ammonia nitrogen and toxic and harmful organic matter, and only low-concentration oxidants (such as H2O2) are consumed to achieve the effect of simultaneously removing ammonia nitrogen and toxic and harmful organic matter. At the same time, the regeneration of Fe(II) reduces the accumulation of a large amount of iron sludge produced by the traditional Fenton method, saving the cost of subsequent treatment. Ammonia nitrogen is used as a resource for treating wastewater with high ammonia nitrogen and toxic and harmful organic matter, and sustainable operation is achieved while removing ammonia nitrogen. Compared with the prior art, the method of the present invention can effectively remove ammonia nitrogen and toxic and harmful organic matter including perfluorooctanoic acid and its derivatives at the same time, saving the input amount of reagents, and reducing the secondary pollution of Fenton iron sludge, effectively saving technical costs.

[0014] Preferably, a pump is used to connect the inner and outer chambers. This facilitates pumping the precipitated Fe(III) into the cation exchange membrane so that it continues to react with NH4 + -N undergoes Feammox reaction, reducing Fe(Ⅲ) to Fe(Ⅱ), thus realizing the Fe(Ⅲ) / Fe(Ⅱ) cycle.

[0015] Preferably, the oxidant comprises H2O2, peracetic acid (PAA), peroxymonosulfate (PMS).

[0016] Preferably, the toxic organic substances include venlafaxine, sulfamethoxazole, metoprolol, ketorpofen, iopromide, diclofenac, carbamazepine, bezafibrate, 5-methyl-1H-benzotriazole, 5-chlorobenzotriazole, and 1H-benzotriazole.

[0017] Preferably, the toxic organic matter also includes perfluorooctanoic acid and its derivatives.

[0018] More preferably, the perfluorooctanoic acid and its derivatives include perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFBS), perfluorodecanoic acid (PFDA), perfluoroheptanoic acid (pFHPA), and perfluorohexane sulfonic acid (PFHxS).

[0019] Preferably, the pH value of the weak acid condition is 5.5-6.9. + ) consumption reaction, during which a small amount of acid is added by the pH controller to adjust the pH from 5.5 to 6.9. The outer chamber is an alkalinity reduction (proton release) reaction, and during the reaction, the pH will drop from the initial 7 to about 5.5-6.

[0020] Preferably, the oxidant is used at a concentration of 9-17 mg / L.

[0021] No significant pH changes, no significant pH adjustment

[0022] Compared with the prior art, the present invention has the following beneficial effects:

[0023] The efficiency of biological wastewater treatment is greatly affected by temperature. The activity of microorganisms decreases at low temperatures. Usually, a larger space is required to accommodate the reactor for microbial growth. In addition, toxic and harmful organic matter has a certain toxic effect on organisms. Homogeneous Fenton oxidation technology cannot treat wastewater containing high ammonia nitrogen. When treating organic matter, it cannot fully mineralize organic matter into carbon dioxide and water, which may cause some organic pollutants to still be contained in the treated wastewater. The utilization rate of H2O2 is not high, which leads to the need to consume a large amount of H2O2. At the same time, a large amount of iron-containing sludge will be produced, which increases the treatment cost. In addition to the above-mentioned disadvantages of homogeneous Fenton, the preparation of intermediates in heterogeneous Fenton oxidation technology will also increase the corresponding cost. In the above-mentioned treatment methods, ammonium ions are all used as pollutants, which increases the treatment cost and difficulty. Therefore, there is still a lack of a low-cost, low-carbon emission and practical strategy to simultaneously remove ammonia and toxic and harmful organic matter from wastewater.

[0024] To this end, the present invention proposes a new strategy, namely, using ammonia-mediated iron circulation technology to in situ treat wastewater containing high ammonia nitrogen and toxic organic matter. The strategy relies on a device that places a CEM cation exchange membrane in the middle to form an inner and outer chamber reactor, so that the reactor configuration consists of two main parts: one is the autotrophic Feammox unit (inner chamber), the NH4 + -N oxidation and Fe(Ⅲ) reduction are coupled to make NH4 + -N acts as an electron donor to regenerate dissolved iron (II) from iron sludge, and the other is the Fenton oxidation unit (outer chamber). At a pH close to neutral, Fenton oxidation removes toxic and harmful organic matter from wastewater. In addition, a pump is used to connect the inner and outer chambers to pump the precipitated Fe (III) into the cation exchange membrane so that it continues to react with NH4 in the inner chamber. + -N undergoes Feammox reaction, reducing Fe(Ⅲ) to Fe(Ⅱ), thus realizing Fe(Ⅲ) / Fe(Ⅱ) cycle. This strategy uses ammonium as a resource to mediate Fenton reaction. When Fenton reaction occurs, Fe(Ⅱ) reacts with oxidant H2O2 to generate trivalent iron sludge, and then NH4 + -N and Fe(Ⅲ) undergo Feammox reaction to regenerate Fe(Ⅱ), which is reused in the Fenton reaction, realizing the iron cycle in the reactor and reducing the secondary pollution of iron sludge. The resource utilization of ammonia nitrogen and the Fe(Ⅲ) / Fe(Ⅱ) cycle realize low-cost and high-efficiency wastewater treatment. In addition, the iron sludge formed in the outer chamber can also adsorb perfluorooctanoic acid and its derivatives, and then the iron sludge degrades perfluorooctanoic acid and its derivatives through the Feammox reaction when regenerating Fe(II) in the inner chamber of the reactor. Therefore, when the method of the present invention is applied to the treatment of wastewater containing high concentrations of ammonia nitrogen and toxic and harmful organic matter, it has significant advantages such as low treatment cost, reduction of secondary pollution of iron sludge, and simultaneous removal of ammonia nitrogen and various toxic and harmful organic matter in wastewater. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The schematic diagram of the process for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter by using ammonia oxidation-mediated iron recycling technology;

[0026] Figure 2 The ammonium radical variation law in the inner chamber and the outer chamber of the reactor (a) and the conductivity variation law in the inner chamber and the outer chamber of the reactor (b);

[0027] Figure 3 is the Fe in the inner and outer chambers of the reactor 2+ Change rules (a) and pH change rules of the inner and outer chambers of the reactor (b);

[0028] Figure 4 The removal effect of toxic organic matter by the ammonia-mediated iron cycle process using different oxidants (H2O2, PAA and PMS);

[0029] Figure 5 The removal effect of PFOA and its derivatives by ammonia-mediated iron recycling process;

[0030] Figure 6 Scanning electron microscopy and energy spectrum analysis of sediment and granular sludge during biocatalytic process in the reactor chamber. DETAILED DESCRIPTION

[0031] The specific embodiments of the present invention are further described below. It should be noted that the description of these embodiments is used to help understand the present invention, but does not constitute a limitation of the present invention. In addition, the technical features involved in each embodiment of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] The experimental methods in the following examples are conventional methods unless otherwise specified, and the experimental materials used in the following examples are commercially available unless otherwise specified.

[0033] The present invention provides a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter by using ammonia-mediated iron circulation technology (hereinafter referred to as ammonia-mediated iron circulation process), which comprises the following process flow ( Figure 1 ):

[0034] (1) Wastewater containing high ammonia nitrogen and toxic and hazardous organic matter was placed in a funnel-shaped organic glass reactor, in which an anaerobic reactor with a CEM cation exchange membrane (purchased from the United States membrane international, model CMI-7000S) was placed. The funnel-shaped reactor was separated to form two inner and outer chambers, which consisted of two main parts: one was the autotrophic Feammox unit (inner chamber), and the NH4 + and Fe(Ⅲ) enters the middle chamber from the cation exchange membrane to undergo reduction reaction, NH4 + -N oxidation and Fe(Ⅲ) reduction are coupled to make NH4 + -N acts as an electron donor to regenerate dissolved iron (II) from iron sludge, and the other is a Fenton oxidation unit (external chamber). In weak acid conditions, Fenton oxidation removes toxic and harmful organic matter from wastewater. In addition, a pump is used to connect the inner and outer chambers to transfer the precipitated Fe (III) in the outer chamber to the inner chamber, so that it continues to react with NH4 + -N undergoes Feammox reaction, reducing Fe(Ⅲ) to Fe(Ⅱ), thus realizing the Fe(Ⅲ) / Fe(Ⅱ) cycle.

[0035] In this reaction, the high concentration of NH4 in the wastewater is no longer + -N is not considered as a pollutant, but as a resource to drive the reduction of Fe(Ⅲ) to Fe(Ⅱ), NH4 + -N and Fe(Ⅲ) undergo Feammox reaction, consuming NH4 in this process + , so that NH4 + The concentration decreases.

[0036] 3Fe(OH)3+5H + +NH4 + →3Fe 2+ +9H2O+0.5N2 (reaction 1);

[0037] (2) Fe(II) generated by the reduction of Fe(III) enters the outer chamber through the cation exchange membrane and reacts with the oxidant (H2O2, peracetic acid PAA, etc.) added to the outer chamber of the reactor under weak acid conditions to produce hydroxyl radicals ·OH and iron sludge.

[0038] Fe(Ⅱ)+H2O2→Fe(OH)3+O2↑+·OH (Reaction 2);

[0039] (3) ·OH in the wastewater undergoes an oxidation reaction with toxic and harmful organic matter, converting the toxic and harmful organic matter into non-toxic and harmless substances such as CO2 and H2O. Fe(III) then enters the middle inner chamber through the cation exchange membrane, thereby removing NH4 +-N, while successfully regenerating dissolved Fe(II) through precipitated Fe(III). In addition, the iron sludge formed in the outer chamber can also adsorb PFOA and its derivatives, and then degrade PFOA and its derivatives through the Feammox reaction when the iron sludge regenerates Fe(II) in the inner chamber of the reactor.

[0040] OH+organic pollutant→CO2↑+H2O (Reaction 3).

[0041] The treatment principle and treatment effect of the above-mentioned ammonia-mediated iron circulation process on wastewater containing high ammonia nitrogen and toxic organic matter are further explained in detail below by way of specific embodiments.

[0042] Example: Ammonia-mediated iron circulation process for treating wastewater containing high ammonia nitrogen and toxic organic matter

[0043] The organic glass reactor is a funnel-shaped reactor, in the middle of which an anaerobic reactor composed of a CEM cation exchange membrane and organic glass is horizontally arranged to form two inner and outer chambers (the anaerobic reactor is the inner chamber) to separate high ammonia nitrogen and toxic organic wastewater, wherein a small hole is opened on the side of the organic glass of the inner chamber, and a pump is used to connect the inner and outer chambers at the small hole. The anaerobic reactor is a cubic structure, and the CEM cation exchange membrane is vertically arranged on the side wall and the upper part of the anaerobic reactor, so that the reactor forms a sealed environment to create an anaerobic environment.

[0044] 1000mL containing 3000mg / LNH4 +-N high ammonia nitrogen and toxic organic matter (11 toxic organic matter that can be removed by Fenton oxidation: 1-h-benzotriazole, 830μg / L; 5-Chlorobenzotriazole, 880μg / L; 5-Methyl-1H-benzotriazole, 870μg / L; bezafibrate, 1000μg / L; carbamazepine, 770μg / L; diclofenac, 580μg / L; iopromide, 910μg / L; ketorpofen, 350μg / L; metoprolol, 490μg / L; sulfamethoxazole, 620μg / L; venlafaxine, 700μg / L and 5 toxic organic matter that are difficult to be removed by Fenton oxidation: Perfluorooctanoic acid, 0.54μg / L; perfluorooctane sulfonic Wastewater containing 100 μg / L of 2-hydroxy-2-nitropropene (2-hydroxy-2-nitropropene) was added to the outer chamber of the reactor, and 400 mL of tap water was added to the inner chamber. Then 10 mg / L of oxidant was added to the outer chamber (except for the treatment effect of different oxidants, all other results are the test results when H2O2 was added). Then the following tests were carried out:

[0045] (1) Ammonium penetration, transfer rules and changes in electrical conductivity

[0046] like Figure 2 As shown in a, after 10 days of reaction, the NH4 + -N concentration gradually decreased from 3000mg / L to 2500mg / L, and the removal rate was 17%. Since the volume of the wastewater in the outer chamber is 2.5 times that of the inner chamber. If NH4 + -N is not removed and all transferred to the inner chamber. Theoretically, the NH4 + -N concentration will rise to 1250mg / L. However, NH4 + -N concentration only rose to 616 mg / L, indicating that NH4 + -N is removed under the catalysis of microorganisms using Fe(III) as an electron donor.

[0047] In addition, not only the concentration of ammonium radicals in the outer chamber decreased, but also the conductivity decreased from 27.6 ms / cm to 16.6 ms / cm. The conductivity of the inner chamber increased from 0.8 ms / cm to 6.8 ms / cm. The change in conductivity may be related to the penetration and migration of ammonium radicals from the outer chamber to the inner chamber.

[0048] (2)Fe 2+ Permeation, transfer rules and pH changes

[0049] Dissolved Fe 2+ It is the key ion to activate H2O2 to remove toxic organic matter. To this end, the dissolved Fe in the inner and outer chambers was further determined. 2+ .like Figure 3 As shown in a, the dissolved Fe in the reactor chamber 2+ The concentration of Fe in the inner chamber increased from 0 mg / L to 133.9 mg / L, and then the concentration fluctuated. 2+ The concentration change of may be affected by factors such as pH and the difference in electrical conductivity between the inner and outer chambers. 2+ The rise of NH4 + The decrease in -N concentration compared to the theoretical concentration may indicate that ammonium ions mediate the conversion of precipitated Fe(III) to Fe under biocatalysis. 2+ The dissolved Fe in the outer chamber 2+ The concentration of Fe gradually increased from 0 to 115.9 mg / L. 2+ The concentration range of the dissolved Fe 2+ Has the potential to remove high concentrations of toxic organic matter.

[0050] Theoretically, the dissolved Fe 2+ In the reaction (reaction 1), proton hydrogen will be consumed. However, dissolved Fe 2+ When the pH is greater than 7, precipitation is easily formed and oxidation is easily caused. Therefore, a small amount of pH adjusting agent is added to the inner chamber to make the pH of the inner chamber less than 7 (about 6.7). The pH of the outer chamber is not adjusted, such as Figure 3 As shown in b, the pH of the outer chamber showed a fluctuating downward trend. After 5 days of operation, the pH of the outer chamber was between 5.5 and 6, and the weakly acidic condition was conducive to the homogeneous Fenton reaction to remove toxic organic matter.

[0051] (3) Removal effect of toxic organic matter

[0052] In the wastewater of the outer chamber, the removal effect of 11 toxic organic substances from different industries was measured. Figure 4As shown in the figure, when H2O2 is used as the oxidant, the removal rate of toxic organic matter is 74-82%. When PAA and PMS are used as the oxidants, the removal rates of poorly soluble organic matter are 89.8% and 82.5% respectively. The above results show that the system can use different oxidants to improve the removal performance of toxic organic matter.

[0053] In terms of removal rate, PAA has the highest removal rate for difficult-to-degrade organic matter when used as an oxidant. The reason is speculated to be that Fe(Ⅱ) activated PAA can produce more types of free radicals (such as CH3C(O)O· and ·CH3) than activated H2O2. At a pH value close to neutral, these free radicals may help remove stubborn organic matter. At the same time, the use of PMS as an oxidant is slightly better than that of H2O2 in removing difficult-to-degrade organic matter. Unlike the ·OH generated in the Fenton reaction, the use of PMS as an oxidant can generate SO4 - ·. Due to SO4 - ·It has a high standard redox potential (2.5-3.1V), which is comparable to the hydroxyl radical (·OH, 1.9-2.7V), and is known as a strong oxidant. In terms of cost, the unit prices of H2O2 (35%), PAA (12%), and PMS are 0.35, 0.8, and 2 USD per kg, respectively. The cost per unit mass of H2O2 is 15% and 50% of that of PAA and PMS, respectively. The results show that among the three reagents, H2O2 is the most cost-effective reagent for ammonia-mediated AOP.

[0054] In addition, wastewater also contains perfluorooctanoic acid and its derivatives, and traditional Fenton treatment has been proven to be difficult to effectively remove perfluorooctanoic acid and its derivatives (Resistance of perfluorooctanoic acid to degradation by the microbially driven Fenton reaction, FEMS MICROBIOLOGY LETTER, Volume 368 Issue 21-24, DOI 10.1093 / femsle / fnab158.). However, according to research, the ammonia-mediated iron cycle process of the present invention can effectively degrade perfluorooctanoic acid and its derivatives. Figure 5 As shown in the figure, after the 11 toxic organic compounds were removed, the iron mud formed in the outer chamber adsorbed five organic compounds, namely, perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFBS), perfluorodecanoic acid (PFDA), perfluoroheptanoic acid (pFHPA), and perfluorohexane sulfonic acid (PFHxS). Then, when the iron mud regenerated Fe(II) in the inner chamber of the reactor, it degraded the five organic compounds, including perfluorooctanoic acid, through the Feammox reaction. After the iron mud in the inner chamber was dissolved, except for the concentration of perfluorodecanoic acid, which was reduced to 0.015 μg / L, the concentrations of the four organic compounds, including perfluorooctanoic acid, were all below the detection limit (see the specific concentrations). Figure 5 , final concentration), is completely removed.

[0055] In summary, the system achieved efficient removal of various organic matter through multiple mechanisms such as Fenton-like oxidation, adsorption, and Feammox reaction.

[0056] (4) Comparison of operating costs of different technologies

[0057] Homogeneous Fenton is considered a promising technology for industrial wastewater treatment. However, the high cost of this technology due to the consumption of Fe(II) reagents, hydrogen peroxide and pH adjusters, as well as iron sludge pollution, limits its large-scale application.

[0058] As shown in Table 1, the ammonia-mediated iron cycle process of the present invention not only has obvious operating cost advantages compared to the classic Fenton process, but can also remove ammonia nitrogen and toxic organic matter in wastewater at the same time. Compared with the bioelectric Fenton technology that has received much attention in recent years, this technology also has obvious cost and removal effect advantages.

[0059] It can be seen that the ammonia-mediated iron circulation process of the present invention has multiple advantages such as low operating cost, high processing efficiency, small footprint, less secondary pollution, and easy management. It may be applied to multiple chemical fields such as landfill leachate, pharmaceuticals, and coking. It has high commercial potential and is likely to make a significant contribution to industrial development and environmental protection.

[0060] Table 1 Different technologies for processing 1m 3 Comparison of operating costs for wastewater

[0061]

[0062] Among them, the classic Fenton process refers to the literature "Neyens, E. & Baeyens, J. A review of classic Fenton's peroxidation as an advanced oxidation technique. J. Hazard. Mater. 98, 33–50 (2003)."; the near-neutral Fenton process refers to the literature "Sun, G., Zhang, Y., Gao, Y., Han, X. & Yang, M. Removal of hard COD from biological effluent of coking wastewater using synchronized oxidation-adsorption technology: Performance, mechanism, and full-scale application. Water Res. 173, 115517 (2020)."; the classic bio-electro-Fenton process refers to the literature "Zou, R., Angelidaki, I., Jin, B. & Zhang, Y. Feasibility and applicability of the scaling-up of bio-electro-Fenton system for textile wastewatertreatment.Environ.Int.(2020)doi:10.1016 / j.envint.2019.105352."

[0063] (5) Changes in the bacterial community structure of the new system's chamber granular sludge compared to the initial granular sludge

[0064] The 16S rRNA sequencing analysis method (for specific operation methods, please refer to the literature "Improved Fe(II)regeneration from actual ferric sludge using a biocathode with granularsludge, Journal of Cleaner Production 389(2023)136118.") was used to determine the community structure of the original granular sludge and the granular sludge in the inner chamber. The bacterial community coverage of the inner chamber granular sludge and the initial granular sludge was 100%, indicating that the results can represent the actual situation. The Chao and Shannon indexes are used to analyze richness and diversity, respectively. The larger their values, the higher the richness and diversity of the sample. The Chao and Shannon values ​​of the granular sludge in the inner chamber are slightly lower than those of the granular sludge in the inner chamber, indicating that the bacterial community in the inner chamber has higher selectivity.

[0065] The dominant phyla in the original granular sludge were Proteobacteria, Thermotogota, and Verrucomicrobiota, which underwent a significant shift in the granular sludge flora of the inner chamber. Among them, the dominant phyla in the granular sludge flora of the inner chamber were Euryarchaeota, Bacteroidota, and Desulfobacterota. The proportions of Euryarchaeota and Desulfobacterota in the granular sludge flora of the inner chamber decreased, while the proportions of Proteobacteria and Bacteroidota increased. Nitrospirota contains nitrifying groups that oxidize nitrite to nitrate, while Commamox bacteria can convert ammonia into nitrite and nitrate. In addition, the abundance of Nitrospirota in the granular sludge flora of the inner chamber increased significantly, which was 2×10 9 times.

[0066] (6) Morphology and element distribution of precipitates and particles

[0067] The morphology and element distribution of the sediment and granular sludge in the reactor chamber were also analyzed, and the reaction phenomenon and process of Fe(II) regeneration from precipitated Fe(III) were studied. Figure 6As shown, the surface of the granular sludge in the reaction system was loose and porous, and its structure did not change significantly compared with the initial granular sludge, indicating that the structure of the granular sludge was not destroyed after long-term operation. In addition, the iron content increased from below the detection limit (initial granular sludge) to 73% (granular sludge in the inner chamber), and the iron content in the initial iron sludge was also high (67.5%). These results indicate that the granular sludge in the inner chamber may adsorb precipitated iron to the surface. This provides an opportunity for direct contact between bacteria and precipitated Fe(III), which may increase the rate of extracellular electron transfer.

[0068] In addition to granular sludge with a particle size greater than 0.2 mm, dispersed precipitates were also found in the inner chamber. Their morphology and element distribution were also determined. Compared with the initial iron sludge, the morphology of the precipitates in the inner chamber changed from dense blocks to dispersed flakes. Interestingly, the proportion of iron in the precipitates in the inner chamber was only 8.7%. However, the proportions of C and O in the inner chamber increased significantly, and these elements also accounted for a large proportion of bacteria, indicating that bacteria may also exist in the precipitates, and they are also involved in the regeneration reaction of Fe(Ⅱ) on the surface of granular sludge.

[0069] In summary, the method of in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter by using ammonia-mediated iron circulation technology not only has obvious operating cost advantages compared to the classic Fenton, but can also remove ammonia nitrogen and toxic organic matter in wastewater at the same time. Compared with the bioelectric Fenton technology that has received much attention in recent years, the present invention also has obvious cost and removal effect advantages.

[0070] The embodiments of the present invention are described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions and variations of these embodiments are made without departing from the principles and spirit of the present invention, and still fall within the scope of protection of the present invention.

Claims

1. A method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology, characterized in that: The reactor used in this method is a funnel-shaped reactor, in which an anaerobic reactor with a CEM cation exchange membrane is placed in the middle of the reactor to form two inner and outer chambers, which are connected by a pump; wastewater containing high ammonia nitrogen and toxic and harmful organic matter is placed in the outer chamber of the reactor, and an oxidant is added to the outer chamber, while tap water is added to the inner chamber; The inner chamber is the autotrophic Feammox unit, NH4 + and Fe(Ⅲ) enters the inner chamber from the cation exchange membrane to undergo reduction reaction, NH4 + -N and Fe(Ⅲ) undergo Feammox reaction, driving Fe(Ⅲ) to be reduced to Fe(Ⅱ) while generating NH4 + Concentration decreases; The outer chamber is a Fenton oxidation unit. Fe(II) generated by the reduction of Fe(III) enters the outer chamber through the cation exchange membrane and reacts with the oxidant under weak acid conditions to produce hydroxyl radicals ·OH and iron sludge, thereby removing toxic and harmful organic matter from the wastewater through Fenton oxidation. The precipitated Fe(Ⅲ) in the iron sludge in the outer chamber is re-transferred to the inner chamber and continues to react with NH4 + -N undergoes Feammox reaction, reducing Fe(Ⅲ) to Fe(Ⅱ), realizing Fe(Ⅲ) / Fe(Ⅱ) cycle, and finally achieving the purpose of removing ammonia nitrogen and toxic and harmful organic matter in wastewater at the same time.

2. The method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 1, characterized in that: The oxidizing agent includes H2O2, peracetic acid, and peroxymonosulfate.

3. The method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 1, characterized in that: The toxic organic substances include venlafaxine, sulfamethoxazole, metoprolol, ketomorphin, iopromide, diclofenac, carbamazepine, bezafibrate, 5-methyl-1H-benzotriazole, 5-chlorobenzazotriazole, and 1H-benzotriazole.

4. The method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 1, characterized in that: The toxic organic substances also include perfluorooctanoic acid and its derivatives.

5. The method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 4, characterized in that: The perfluorooctanoic acid and its derivatives include perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorodecanoic acid, perfluoroheptanoic acid, and perfluorohexane sulfonic acid.

6. The method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 1, characterized in that: The pH value of weak acid conditions is 5.5-6.

9.

7. The method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 1, characterized in that: The oxidant is used at a concentration of 9-17 mg / L.

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