A method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology

Abstract

This invention belongs to the field of wastewater treatment technology, specifically relating to a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using an ammonia-mediated iron cycle technology. This invention proposes a novel strategy involving ammonium oxidation-mediated Fenton iron sludge regeneration of Fe(II) and Fenton oxidation removal of organic pollutants from wastewater. Ammonium ions are used as a resource to mediate the Fenton iron cycle reaction. During the Fenton reaction, Fe(II) reacts with the oxidant H₂O₂ to generate trivalent iron sludge, and then NH₄⁺... + -N reacts with Fe(III) in Fenton iron sludge via a Feammox reaction to regenerate Fe(II), which is then reused in the Fenton reaction. This achieves iron recycling within the reactor and reduces secondary pollution from the iron sludge. Therefore, applying the method of this invention to wastewater treatment offers significant advantages, including low treatment costs, reduced secondary pollution from iron sludge, and simultaneous removal of ammonia nitrogen and toxic organic compounds from the wastewater.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a method for in-situ treatment of wastewater containing high levels of ammonia nitrogen and toxic organic matter using ammonia-mediated iron cycle technology. Background Technology

[0002] Due to rapid economic and industrial development, large quantities of wastewater containing high levels of ammonia nitrogen and toxic organic matter are discharged into urban wastewater systems. These pollutants cause environmental pollution globally, leading to problems such as eutrophication, ecotoxicity, and increased cancer risk. Therefore, the treatment of wastewater containing high concentrations of ammonia nitrogen and toxic organic matter has always been a crucial aspect of environmental governance.

[0003] Currently, biological methods are a common wastewater treatment approach. These methods utilize the metabolic functions of microorganisms to degrade dissolved and colloidal organic pollutants in wastewater, transforming them into harmless substances and thus purifying the wastewater. Examples include activated sludge processes, biofilm processes, and anaerobic biological treatment. However, the efficiency of biological wastewater treatment is significantly affected by temperature; microbial activity decreases at low temperatures. Larger reactors are typically required to accommodate microbial growth, and toxic organic compounds can be harmful to organisms, making it difficult to completely degrade highly toxic and carcinogenic organic wastewater.

[0004] The traditional Fenton process, an advanced oxidation process (AOP), is commonly used to treat organic wastewater due to its simple operation, high degradation efficiency, and easy-to-use equipment. It effectively removes pollutants from wastewater through hydroxyl radicals. However, this method still suffers from drawbacks such as high reagent consumption and Fenton sludge pollution. To address this issue, while adding an iron complexing agent to the Fenton reactor can increase the regeneration rate of Fe(II) under near-neutral pH conditions and reduce reagent consumption, and adding additional reducing agents can promote the reduction of precipitated Fe(III) and reduce the accumulation of Fenton sludge, these additions incur additional costs and may introduce new pollutants into the reactor. Among these, homogeneous Fenton technology, due to its strong oxidizing properties, is widely used in the treatment of recalcitrant and toxic organic wastewater, but its effectiveness in treating wastewater with high ammonia nitrogen concentrations is less than ideal. Heterogeneous Fenton oxidation systems utilize iron-containing solids or iron fixed on a support to react with hydrogen peroxide and oxygen instead of homogeneous ferrous salts. This retains the advantages of homogeneous Fenton oxidation, such as non-selective degradation and rapid reaction rates, but it requires higher processing costs, involves high reagent consumption and preparation costs, and suffers from low catalyst stability. Therefore, a low-cost, high-efficiency technology is needed to simultaneously remove ammonia nitrogen and toxic organic pollutants from wastewater.

[0005] Studies have shown that introducing anaerobic ammonia oxidation (ANAO) into the photo-Fenton process can simultaneously remove ammonia nitrogen and toxic organic compounds. However, existing technologies combining photo-Fenton and ANAO still suffer from drawbacks such as high reagent consumption, high preparation costs, and low stability. Therefore, finding a low-cost, low-carbon, and efficient method to simultaneously remove high concentrations of ammonia nitrogen and toxic organic compounds from wastewater remains a significant challenge. Summary of the Invention

[0006] To overcome the shortcomings of the existing technology, this invention proposes a method for in-situ treatment of wastewater containing high levels of ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology. The ammonia nitrogen pollutant in the wastewater is used as a resource, and Fe(III) is reduced to Fe(II) at a near-neutral pH. This ammonia-mediated AOP can effectively remove NH4 from the wastewater simultaneously by consuming only a low concentration of hydrogen peroxide. + -N and toxic and harmful organic matter. When treating wastewater using the method of this invention, the amount of reagents required can be significantly reduced, thus reducing secondary pollution from iron sludge treated using the traditional Fenton process.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0008] This invention provides a method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron cycle technology. Specifically, the method uses a funnel-shaped reactor with an anaerobic reactor equipped with a CEM cation exchange membrane placed in the middle, forming two chambers, an inner and an outer chamber, which are connected by a pump. The wastewater containing high ammonia nitrogen and toxic 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.

[0009] The inner chamber is an autotrophic Feammox unit, NH4 + Fe(III) enters the inner chamber from the cation exchange membrane and undergoes a reduction reaction, NH4+ + -N undergoes a Feammox reaction with Fe(III), driving the reduction of Fe(III) to Fe(II) while simultaneously reducing NH4+ in the wastewater. + Concentration decreased;

[0010] The outer chamber is the Fenton oxidation unit. Fe(II) generated by the reduction of Fe(III) enters the outer chamber through the cation exchange membrane and undergoes a Fenton reaction with the oxidant under weakly acidic conditions to produce hydroxyl radicals ·OH and iron sludge. Then, the toxic and harmful organic matter in the wastewater is removed by Fenton oxidation.

[0011] The precipitated Fe(III) in the iron sludge in the outer chamber is transferred back to the inner chamber to continue reacting with NH4. +-N undergoes the Feammox reaction, reducing Fe(III) to Fe(II), thus realizing the Fe(III) / Fe(II) cycle, ultimately achieving the goal of simultaneously removing ammonia nitrogen and toxic and harmful organic matter from wastewater.

[0012] This invention utilizes ammonia nitrogen, a pollutant in wastewater, as a resource, reducing Fe(III) to Fe(II) under weakly acidic conditions. This ammonia-mediated AOP can effectively remove NH4 from wastewater simultaneously by consuming only a low concentration 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 from 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 this invention converts ammonia nitrogen into a resource-driven iron cycle in Fenton treatment, thus utilizing ammonia nitrogen as a resource. Ammonia nitrogen reacts with precipitated iron via a Feammox reaction, driving the regeneration of Fe(III) into Fe(II). This Fenton oxidation technology treats wastewater containing high concentrations of ammonia nitrogen and toxic organic pollutants, requiring only a low concentration of oxidant (such as H₂O₂) to simultaneously remove both ammonia nitrogen and toxic organic pollutants. Simultaneously, the regeneration of Fe(II) reduces the accumulation of large amounts of iron sludge produced by the traditional Fenton process, saving on subsequent treatment costs. By using ammonia nitrogen as a resource for treating wastewater with high ammonia nitrogen and toxic organic pollutants, sustainable operation is achieved while removing ammonia nitrogen. Compared to existing technologies, this invention can simultaneously and effectively remove ammonia nitrogen and toxic organic pollutants, including perfluorooctanoic acid and its derivatives, saving on reagent input and reducing secondary pollution from Fenton iron sludge, effectively saving on technology costs.

[0014] Preferably, the inner and outer chambers are connected by a pump. This facilitates the pumping of precipitated Fe(III) into the cation exchange membrane, allowing it to continue reacting with NH4 in the inner chamber. + -N undergoes the Feammox reaction, reducing Fe(III) to Fe(II), thus realizing the Fe(III) / Fe(II) cycle.

[0015] Preferably, the oxidant includes H2O2, peracetic acid (PAA), and persulfate (PMS).

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

[0017] Preferably, the toxic organic compound 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 under weakly acidic conditions is 5.5-6.9. The inner chamber is a proton (H+) chamber. + The first chamber is a consumption reaction, during which a small amount of acid is added via a pH controller to adjust the pH from 5.5 to 6.9. The second chamber is an alkalinity-degrading (proton release) reaction, during which the pH will decrease from the initial 7 to around 5.5-6.

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

[0021] The pH did not change significantly, so no significant pH adjustment was made.

[0022] Compared with the prior art, the beneficial effects of the present invention are:

[0023] The efficiency of biological wastewater treatment is significantly affected by temperature; microbial activity decreases at low temperatures, typically requiring a large reactor to accommodate microbial growth. Furthermore, toxic organic compounds can be harmful to organisms. Homogeneous Fenton oxidation technology cannot treat wastewater with high ammonia nitrogen content. It cannot fully mineralize organic matter into carbon dioxide and water, potentially leaving some organic pollutants in the treated wastewater. Low H2O2 utilization leads to the consumption of large amounts of H2O2 and the generation of large quantities of iron-containing sludge, increasing treatment costs. Heterogeneous Fenton oxidation technology suffers from the same drawbacks as homogeneous Fenton oxidation, and the preparation of intermediates also increases costs. In all these treatment methods, ammonium ions are considered pollutants, increasing treatment costs and difficulty. Therefore, a low-cost, low-carbon, and practical strategy for simultaneously removing ammonia and toxic organic compounds from wastewater remains lacking.

[0024] To address this, the present invention proposes a novel strategy for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron cycling technology. This strategy relies on a reactor with an inner and outer chamber formed by placing a CEM cation exchange membrane in the middle. The reactor configuration consists of two main parts: an autotrophic Feammox unit (inner chamber) and an NH4+-... + -N oxidation and Fe(III) reduction are coupled, causing NH4+ to... + -N acts as an electron donor to regenerate dissolved iron (II) from iron sludge. Another unit is the Fenton oxidation unit (outer chamber), where Fenton oxidation removes toxic and harmful organic matter from wastewater at a near-neutral pH. Furthermore, a pump connects the inner and outer chambers, pumping precipitated Fe(III) into the cation exchange membrane, allowing it to continue reacting with NH4+ in the inner chamber. + -N undergoes the Feammox reaction, reducing Fe(III) to Fe(II), thus achieving the Fe(III) / Fe(II) cycle. This strategy uses ammonium ions as a resource to mediate the Fenton reaction. During the Fenton reaction, Fe(II) reacts with the oxidant H₂O₂ to generate trivalent iron sludge, which is then converted into NH₄⁺. + -N reacts with Fe(III) in a Feammox reaction to regenerate Fe(II), which is then reused in the Fenton reaction. This achieves iron recycling within the reactor and reduces secondary pollution from iron sludge. The resource utilization of ammonia nitrogen and the Fe(III) / Fe(II) cycle enable low-cost, high-efficiency wastewater treatment. Furthermore, the iron sludge formed in the outer chamber can adsorb perfluorooctanoic acid (PFOA) and its derivatives. Subsequently, during Fe(II) regeneration in the inner chamber of the reactor, PFOA and its derivatives are degraded via the Feammox reaction. Therefore, when applying the method of this invention to treat wastewater containing high concentrations of ammonia nitrogen and toxic organic pollutants, it offers significant advantages such as low treatment costs, reduced secondary pollution from iron sludge, and simultaneous removal of ammonia nitrogen and various toxic organic pollutants from the wastewater. Attached Figure Description

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

[0026] Figure 2 The variation patterns of ammonium ions in the inner and outer chambers of the reactor (a) and the variation patterns of electrical conductivity in the inner and outer chambers of the reactor (b);

[0027] Figure 3 Fe for the inner and outer chambers of the reactor 2+ The variation pattern (a) and the pH variation pattern in the inner and outer chambers of the reactor (b);

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

[0029] Figure 5 The effect of ammonia-mediated iron recycling process on the removal of perfluorooctanoic acid and its derivatives;

[0030] Figure 6 Scanning electron microscopy and energy dispersive spectroscopy analysis of precipitates and granular sludge during the biocatalytic process in the reactor chamber. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

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

[0034] (1) Wastewater containing high levels of ammonia nitrogen and toxic organic matter is placed in a funnel-shaped plexiglass reactor. An anaerobic reactor equipped with a CEM cation exchange membrane (purchased from Membrane International, USA, model CMI-7000S) is placed inside the reactor, separating the funnel-shaped reactor into two chambers, forming two main parts: one is an autotrophic Feammox unit (inner chamber), containing NH4+. + Fe(III) enters the middle inner chamber from the cation exchange membrane and undergoes a reduction reaction, NH4+. + -N oxidation and Fe(III) reduction are coupled, causing NH4+ to... + -N acts as an electron donor to regenerate dissolved iron (II) from iron sludge. Another unit is the Fenton oxidation unit (outer chamber), where, under weakly acidic conditions, Fenton oxidation removes toxic and harmful organic matter from the wastewater. Furthermore, a pump connects the inner and outer chambers, transferring precipitated Fe(III) from the outer chamber to the inner chamber, allowing it to continue reacting with NH4+ in the inner chamber. + -N undergoes the 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 removed. + -N is not considered a pollutant, but rather a resource used to drive the reduction of Fe(III) to Fe(II), NH4. + -N and Fe(III) undergo the Feammox reaction, in which NH4 is consumed. + NH4 in wastewater + The concentration decreased.

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

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

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

[0039] (3) The ·OH in the wastewater undergoes an oxidation reaction with toxic and harmful organic matter, converting it into non-toxic and harmless substances such as CO2 and H2O. Fe(III) then passes through the cation exchange membrane and re-enters the middle inner chamber, thereby removing NH4 from the wastewater. +Simultaneously, dissolved Fe(II) was successfully regenerated through the precipitation of Fe(III). Furthermore, the iron sludge formed in the outer chamber could adsorb perfluorooctanoic acid (PFOA) and its derivatives, which were then degraded by the Feammox reaction during the regeneration of Fe(II) in the inner chamber of the reactor.

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

[0041] The following detailed description of the treatment principle and effect of the ammonia-mediated iron circulation process for wastewater containing high ammonia nitrogen and toxic organic matter is further illustrated by specific embodiments.

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

[0043] The plexiglass reactor is a funnel-shaped reactor. A horizontal anaerobic reactor, composed of a CEM cation exchange membrane and plexiglass, is horizontally positioned in the center of the reactor, forming two chambers (the anaerobic reactor is the inner chamber) to separate high-ammonia nitrogen and toxic organic wastewater. A small hole is opened on the side of the plexiglass in the inner chamber, and a pump connects the inner and outer chambers through this hole. The anaerobic reactor has a cubic structure, and the CEM cation exchange membrane is vertically installed on the side walls and top of the anaerobic reactor, creating a sealed environment and thus an anaerobic environment.

[0044] 1000mL containing 3000mg / LNH4 +-N high ammonia nitrogen and toxic organic compounds (11 toxic organic compounds that can be removed by Fenton oxidation: 1-h-benzotriazole, 830 μg / L; 5-Chlorobenzotriazole, 880 μg / L; 5-Methyl-1H-benzotriazole, 870 μg / L; bezafibrate, 1000 μg / L; carbamazepine, 770 μg / L; diclofenac, 580 μg / L; iopromide, 910 μg / L; ketorpofen, 350 μg / L; metoprolol, 490 μg / L; sulfamethoxazole, 620 μg / L; venlafaxine, 700 μg / L and 5 toxic organic compounds that are difficult to remove by Fenton oxidation: perfluorooctanoic acid, 0.54 μg / L; perfluorooctane sulfonic acid... Wastewater containing the following compounds (acid, 0.21 μg / L; perfluorodecanoic acid, 0.18 μg / L; perfluoroheptanoic acid, 0.66 μg / L; perfluorohexane sulfonic acid, 0.04 μg / L) 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 determination of the treatment effect of different oxidants, all other results are based on the addition of H₂O₂). The following tests were then conducted:

[0045] (1) The permeation and transfer patterns of ammonium ions and the changes in conductivity

[0046] like Figure 2 As shown in Figure a, after 10 days of reaction, the NH4+ in the outer chamber of the reactor... + The -N concentration gradually decreased from 3000 mg / L to 2500 mg / L, with a removal rate of 17%. This is because the volume of wastewater in the outer chamber is 2.5 times that of the inner chamber. If NH4... + -N was not removed and was entirely transferred to the inner chamber; theoretically, the NH4+ in the inner chamber... + -N concentration can rise to 1250 mg / L. However, the NH4+ concentration in the inner chamber... + The -N concentration only rose to 616 mg / L, indicating that the NH4+ concentration in the inner chamber was low. + -N is removed by microbial catalysis using Fe(III) as an electron donor.

[0047] Furthermore, not only did the concentration of ammonium ions decrease in the outer chamber, but the conductivity also decreased from 27.6 ms / cm to 16.6 ms / cm. Meanwhile, the conductivity in the inner chamber increased from 0.8 ms / cm to 6.8 ms / cm. This change in conductivity may be related to the permeation and migration of ammonium ions from the outer chamber to the inner chamber.

[0048] (2)Fe 2+ Osmosis, transfer patterns and pH changes

[0049] Dissolved Fe 2+ It is a key ion for activating H2O2 to remove toxic organic matter. Therefore, the dissolved Fe in the inner and outer chambers was further measured. 2+ .like Figure 3 As shown in figure a, dissolved Fe in the reactor chamber 2+ The concentration increased from 0 mg / L to 133.9 mg / L, and then fluctuated. Dissolved Fe in the inner chamber... 2+ The concentration variation may be affected by factors such as pH and the conductivity difference between the inner and outer chambers. The dissolved Fe in the inner chamber... 2+ The rise and NH4 + The decrease in -N concentration compared to the theoretical concentration may indicate that ammonium ions mediated the conversion of precipitated Fe(III) to Fe under biocatalysis. 2+ The transformation. Dissolved Fe in the outer chamber. 2+ The concentration gradually increased from 0 to 115.9 mg / L. The homogeneous Fenton chromatography requires dissolved Fe to remove toxic organic matter. 2+ The concentration range is 1-150 mg / L, indicating that the dissolved Fe produced by the method of this invention... 2+ It has the potential to remove high concentrations of toxic organic matter.

[0050] Theoretically, in the ammonium-mediated regeneration of Fenton iron mud, dissolved Fe... 2+ In the reaction (reaction 1), protonated hydrogen is consumed. However, dissolved Fe... 2+ Precipitation easily forms and is readily oxidized at pH values ​​greater than 7. Therefore, a small amount of pH-adjusting reagent is added to the inner chamber to bring its pH below 7 (approximately 6.7). The pH of the outer chamber remains unadjusted. 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 conditions were conducive to the homogeneous Fenton reaction to remove toxic organic matter.

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

[0052] The removal efficiency of 11 toxic organic compounds from different industries was measured in the wastewater from the external chamber. For example... Figure 4As shown, when H2O2 is used as the oxidant, the removal rate of toxic organic compounds is 74-82%. When PAA and PMS are used as oxidants, the removal rates of sparingly soluble organic compounds are 89.8% and 82.5%, respectively. These results indicate that different oxidants can be used to improve the removal performance of toxic organic compounds in this system.

[0053] In terms of removal rate, PAA as the oxidant showed the highest removal rate for recalcitrant organic compounds. This is presumably because Fe(II) activation of PAA generates a wider variety of free radicals (such as CH3C(O)O· and ·CH3) than activation of H2O2. At near-neutral pH levels, these free radicals may contribute to the removal of stubborn organic compounds. Meanwhile, PMS as the oxidant showed slightly better removal efficiency for recalcitrant organic compounds than H2O2. Unlike the ·OH generated in the Fenton reaction, using PMS as an oxidant can generate SO4. - · Due to SO4 - It possesses a high standard redox potential (2.5-3.1 V), comparable to that of hydroxyl radicals (·OH, 1.9-2.7 V), and is thus considered a strong oxidizing agent. In terms of cost, the unit prices of H₂O₂ (35%), PAA (12%), and PMS are $0.35, $0.8, and $2 per kilogram, respectively. The cost per unit mass of H₂O₂ is 15% and 50% of that of PAA and PMS, respectively. These results indicate that among the three reagents, H₂O₂ is the most cost-effective for ammonia-mediated AOP.

[0054] Furthermore, the wastewater contains perfluorooctanoic acid (PFOA) and its derivatives, and traditional Fenton treatment has proven ineffective in removing PFOA 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, research has shown that the ammonia-mediated iron recycling process of this invention can effectively degrade PFOA and its derivatives. Figure 5 As shown, after the removal of the 11 toxic organic compounds mentioned above, the iron sludge formed in the outer chamber adsorbed five organic compounds: perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFBS), perfluorodecanoic acid (PFDA), perfluoroheptanoic acid (pFHPA), and perfluorohexane sulfonic acid (PFHxS). Subsequently, during the regeneration of Fe(II) in the reactor's inner chamber, the iron sludge degraded these five organic compounds, including PFOA, through the Feammox reaction. After dissolving the iron sludge in the inner chamber, except for PFOA, whose concentration decreased to 0.015 μg / L, the concentrations of the other four organic compounds, including PFOA, were all below the detection limit (see [link to specific concentrations]). Figure 5 , finalconcentration), was completely removed.

[0055] In summary, this system achieves efficient removal of various organic compounds through multiple mechanisms, including 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 contamination, limits its large-scale application.

[0058] As shown in Table 1, the ammonia-mediated iron recycling process of this invention not only has a significant operating cost advantage compared to the classic Fenton process, but also can simultaneously remove ammonia nitrogen and toxic organic matter from wastewater. Compared to the bioelectric Fenton technology that has received much attention in recent years, this technology also has significant advantages in cost and removal efficiency.

[0059] It is evident that the ammonia-mediated iron recycling 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, and has high commercial potential. It may also make a significant contribution to industrial development and environmental protection.

[0060] Table 1. Different technologies for processing 1m 3 Wastewater operation cost comparison

[0061]

[0062] Specifically, the classic Fenton process is referenced in 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 is referenced in 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)”; and the classic bio-electro-Fenton process is referenced in 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 microbial community structure of the new system's internal chamber granular sludge compared to the initial granular sludge

[0064] The community structure of the original granular sludge and the granular sludge in the inner chamber was determined using 16S rRNA sequencing analysis (specific operation method referred to the literature "Improved Fe(II) regeneration from actual ferric sludge using a biocathode with granular sludge," Journal of Cleaner Production 389(2023)136118). The microbial coverage of both the inner chamber granular sludge and the initial granular sludge was 100%, indicating that the results are representative of the actual situation. The Chao and Shannon indices were used to analyze richness and diversity, respectively. Higher values ​​indicated greater richness and diversity. The Chao and Shannon values ​​of the granular sludge in the inner chamber were slightly lower than those of the granular sludge in the inner chamber, indicating that the microbial community in the inner chamber had higher selectivity.

[0065] The dominant phyla in the original granular sludge were Proteobacteria, Thermotogota, and Verrucomicrobiota, which showed a significant shift in the granular sludge community of the inner chamber. Specifically, the dominant phyla in the inner chamber granular sludge community were Euryarchaeota, Bacteroidota, and Desulfobacterota. The proportions of Euryarchaeota and Desulfobacterota decreased in the inner chamber granular sludge community, while the proportions of Proteobacteria and Bacteroidota increased. Nitrospirota contains nitrifying groups that oxidize nitrite to nitrate, while Commamox bacteria can convert ammonia to both nitrite and nitrate. Furthermore, the abundance of Nitrospirota in the inner chamber granular sludge community increased significantly, reaching 2 × 10⁻⁶ compared to the original granular sludge community. 9 times.

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

[0067] The morphology and elemental distribution of the precipitates and granular sludge in the reactor chamber were also analyzed, and the reaction phenomena and processes of regenerating Fe(II) from precipitated Fe(III) were studied. Figure 6As shown, the surface of the granular sludge in the reaction system is loose and porous, and its structure has not changed significantly compared with the initial granular sludge, indicating that the structure of the granular sludge has not been destroyed after long-term operation. Furthermore, 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 suggest that the granular sludge in the inner chamber may adsorb precipitated iron onto its 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 elemental distribution were determined. Compared to the initial iron sludge, the morphology of the precipitates in the inner chamber changed from dense lumps to dispersed flakes. Interestingly, the iron content of 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 be present in the precipitates and participate in the regeneration reaction of Fe(II) on the surface of the granular sludge.

[0069] In summary, this invention's method for in-situ treatment of wastewater containing high levels of ammonia nitrogen and toxic organic matter using ammonia-mediated iron cycling technology offers significant advantages in operating costs compared to the classic Fenton method, while simultaneously removing both ammonia nitrogen and toxic organic matter. Compared to the bioelectric Fenton technology that has garnered considerable attention in recent years, this invention also demonstrates clear advantages in both cost and removal efficiency.

[0070] The embodiments of the present invention have been 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 can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope 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 recycling technology, characterized in that, The reactor used in this method is a funnel-shaped reactor, with an anaerobic reactor equipped with a CEM cation exchange membrane placed in the middle, forming two chambers, an inner and an outer chamber, 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 oxidant is selected from H2O2, peracetic acid, and persulfate. The inner chamber is an autotrophic Feammox unit, NH4 + Fe(III) enters the inner chamber from the cation exchange membrane and undergoes a reduction reaction, NH4+ + -N undergoes a Feammox reaction with Fe(III), driving the reduction of Fe(III) to Fe(II) while simultaneously reducing NH4+ in the wastewater. + Concentration decreased; The outer chamber is the Fenton oxidation unit. Fe(II) generated by the reduction of Fe(III) enters the outer chamber through the cation exchange membrane and undergoes a Fenton reaction with the oxidant under weakly acidic conditions to produce hydroxyl radicals ·OH and iron sludge. Then, the toxic and harmful organic matter in the wastewater is removed by Fenton oxidation. The precipitated Fe(III) in the iron sludge in the outer chamber is transferred back to the inner chamber to continue reacting with NH4. + -N undergoes the Feammox reaction, reducing Fe(III) to Fe(II), thus realizing the Fe(III) / Fe(II) cycle, ultimately achieving the goal of simultaneously removing ammonia nitrogen and toxic and harmful organic matter from wastewater.

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 toxic organic compounds include venlafaxine, sulfamethoxazole, metoprolol, ketoperidone, iopromide, diclofenac, carbamazepine, bezafibrate, 5-methyl-1H-benzotriazole, 5-chlorobenzotriazole, and 1H-benzotriazole.

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 compounds also include perfluorooctanoic acid and its derivatives.

4. A method for in-situ treatment of wastewater containing high ammonia nitrogen and toxic organic matter using ammonia-mediated iron circulation technology according to claim 3, characterized in that, The perfluorooctanoic acid and its derivatives include perfluorooctanoic acid, perfluorooctane sulfonic acid, perfluorodecanoic acid, perfluoroheptanoic acid, and perfluorohexane sulfonic acid.

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 1, characterized in that, The pH value for weakly acidic conditions is 5.5-6.

9.

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

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