A wastewater treatment method for electrostatic field coupled aerobic nitrification

Abstract

This invention discloses a wastewater treatment method using electrostatic field-coupled aerobic nitrification, belonging to the field of wastewater treatment technology. Acclimated sludge, wastewater, and insulating electrodes are added to an aerobic nitrification reactor. A voltage of 0-2 V / cm is applied outside the reactor to form an electrostatic field, controlling the organic load in the wastewater to be 500-4000 mg / L and the ammonia nitrogen concentration to be 100-400 mg / L, thus achieving wastewater treatment. This invention reveals the intrinsic mechanism of an electric field-coupled activated sludge system for treating ammonia nitrogen wastewater, enriching knowledge in the field of microbial electrochemistry, clarifying the influence of various factors on microbial activity and function, providing a new perspective for understanding the role of microorganisms in wastewater treatment, significantly improving ammonia nitrogen wastewater treatment efficiency, reducing pollutant content, reducing environmental pollution, and ensuring water quality and ecological safety; it also reduces aeration-related energy requirements and lowers the cost of ammonia nitrogen wastewater treatment.

Description

Technical Field

[0001] This invention belongs to the field of wastewater treatment technology, specifically relating to a wastewater treatment method involving electrostatic field coupling and aerobic nitrification. Background Technology

[0002] The information disclosed in this background section is intended only to enhance understanding of the overall background of the invention and is not necessarily to be construed as an admission or in any way implying that such information constitutes prior art known to those skilled in the art.

[0003] The efficient treatment of ammonia nitrogen wastewater is one of the key challenges in the field of environmental engineering. Currently, biological methods (especially aerobic nitrification) are widely used for treating ammonia nitrogen wastewater. However, when treating high-concentration ammonia nitrogen wastewater, problems such as inhibited nitrifying bacteria activity, low treatment efficiency, and easy sludge loss are often encountered. In existing technologies, to improve treatment efficiency, some studies have attempted to introduce physical field enhancement methods. For example, the closest existing technology discloses a novel low-carbon nitrogen removal process enhanced by a micro-electric field. The wastewater first undergoes anaerobic fermentation, followed by an autotrophic simultaneous nitrification-denitrification reaction. During the reaction, the wastewater after anaerobic fermentation is electrolyzed by a power source. Under the action of a micro-electric field, carbon-autotrophic nitrifying bacteria and hydrogen-autotrophic denitrifying bacteria move directionally within the reactor, creating an oxygen-limited environment within the system. Ammonia nitrogen in the wastewater is converted into nitrate nitrogen, completing the nitrification process. This process successfully optimizes the removal of low-concentration ammonia nitrogen (typically below 100 mg / L) by precisely controlling the dissolved oxygen (DO) concentration, temperature, and applied current within the reactor.

[0004] However, this new process is primarily designed for low-concentration ammonia nitrogen wastewater environments, and its control strategy revolves around dissolved oxygen, temperature, and current. When treating higher concentrations of ammonia nitrogen wastewater (significantly above 100 mg / L), the above method faces significant limitations: on the one hand, high concentrations of ammonia nitrogen themselves exert a stronger inhibitory effect on nitrifying bacteria; on the other hand, relying solely on the control of DO, temperature, and current is insufficient to effectively overcome the impact of high loads and cannot fully utilize the potential advantages of electrostatic fields in treating high-concentration pollutants. Summary of the Invention

[0005] To address the shortcomings of existing technologies, the purpose of this invention is to provide a wastewater treatment method using electrostatic field-coupled aerobic nitrification. This invention employs an electrostatic field-coupled aerobic nitrification system, which significantly improves the treatment efficiency of ammonia nitrogen wastewater, reduces pollutant content, minimizes environmental pollution, and ensures water quality and ecological safety.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows:

[0007] A first aspect of the present invention provides a wastewater treatment method for electrostatically coupled aerobic nitrification, comprising:

[0008] Acclimated sludge, wastewater, and insulating electrodes are added to an aerobic nitrification reactor. A voltage of 0-2 V / cm is applied outside the reactor to form an electrostatic field, controlling the organic load in the wastewater to be 500-4000 mg / L and the ammonia nitrogen concentration to be 100-400 mg / L, thereby achieving wastewater treatment.

[0009] In some embodiments of the present invention, the domestication includes:

[0010] After centrifugation and washing, the activated sludge is added to the aerobic nitrification reactor along with water at a volume ratio of 3:7. Carbon and nitrogen sources are also added. An electrostatic field of 0-2 V / cm is applied outside the aerobic nitrification reactor, and the reactor is acclimated for 6-7 days.

[0011] In some embodiments of the present invention, after the sludge acclimation is completed, the acclimated sludge is poured out and mixed to clean the aerobic nitrification reactor. After cleaning, the acclimated sludge and wastewater are added at a volume ratio of 1:3.8-4.2 for wastewater treatment.

[0012] In some embodiments of the present invention, the concentration of the carbon source is 0.4-0.6 g / L, and the concentration of the nitrogen source is 0.09-0.11 g / L.

[0013] In some embodiments of the present invention, the carbon source includes at least one selected from glucose, sodium acetate, methanol, citric acid, propionic acid, potassium bicarbonate, calcium carbonate, and sodium carbonate.

[0014] In some embodiments of the present invention, the nitrogen source includes ammonium chloride.

[0015] In some embodiments of the present invention, the method for preparing the insulating electrode includes:

[0016] Carbon nanotubes, nickel chloride, and polytetrafluoroethylene were dissolved in an aqueous ethanol solution, heated, rolled onto a titanium mesh, and dried to obtain a pre-electrode.

[0017] The pre-electrode is hydrophilically treated to obtain the polarized electrode;

[0018] A waterproof layer is formed by coating the outer surface of the polarized electrode with a waterproof material, thus obtaining an insulating electrode.

[0019] In some embodiments of the present invention, a voltage of 0.5-1 V / cm is applied outside the aerobic nitrification reactor to form an electrostatic field, thereby controlling the organic load in the wastewater to be 1000-4000 mg / L and the ammonia nitrogen concentration to be 100-200 mg / L.

[0020] In some embodiments of the present invention, a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0.5 V / cm, thereby controlling the organic load in the wastewater to be 4000 mg / L and the ammonia nitrogen concentration to be 200 mg / L.

[0021] In some embodiments of the present invention, during the wastewater treatment process, the aeration rate of the aerobic nitrification reactor is 0.1-0.2 L / min, preferably 0.15 L / min.

[0022] The beneficial effects of this invention are as follows:

[0023] This invention introduces a low-voltage electric field into an activated sludge aerobic nitrification reactor, deeply coupling aerobic nitrification and electric field catalysis. Utilizing the unique stimulating effect of the electrostatic field, it stimulates the growth of heterotrophic nitrifying bacteria and positively influences their physiological characteristics. This overcomes the rate-limiting steps in traditional activated sludge processes, increasing the rate and efficiency of nitrogen removal, making the oxidation of ammonia nitrogen faster and more thorough, converting ammonia nitrogen into nitrate nitrogen and other final products in a shorter time, thus improving the overall treatment capacity of the denitrification system. Furthermore, the presence of the electrostatic field selectively enriches microbial communities with high nitrification capabilities. By adjusting the electric field strength, organic load, and ammonia nitrogen concentration, this invention achieves a synergistic effect, allowing aerobic nitrifying bacteria with stronger tolerance and adaptability to dominate the system, improving nitrification efficiency. Moreover, the method provided by this invention can simultaneously remove pollutants and nitrogen. The electric field promotes the oxidative decomposition of organic matter, enabling better treatment of some recalcitrant organic matter, achieving simultaneous removal of organic matter and pollutants such as ammonia nitrogen, and improving the overall effect of wastewater treatment. Attached Figure Description

[0024] The accompanying drawings, which form part of this invention, are used to provide a further understanding of the invention. The illustrative embodiments of the invention and their descriptions are used to explain the invention and do not constitute an improper limitation of the invention.

[0025] Figure 1 The structure of the reactor used in Embodiment 1 of the present invention;

[0026] Figure 2 The structure of the reactor used in Comparative Example 2 of this invention;

[0027] Figure 3 The different ammonia nitrogen concentrations of NH4 in Examples 1 and 2 of this invention + -N(a), NO2 - -N(b), NO3 - Comparison chart of -N(c), TN(d), COD(e), and pH(f);

[0028] Figure 4This is a comparison of nitrogen removal under different electric fields in Example 1 and Comparative Example 2 of the present invention, wherein (a) is NH4 + -N, (b) is TN;

[0029] Figure 5 The comparison of CV and EIS of the bulk solution at the beginning and end of the experiment in Examples 1 and 2 of the present invention is shown, where (a) is CV and (b) is EIS.

[0030] Figure 6 The relative abundance of microorganisms at the phylum (a), class (b), and genus (c) levels in different reactors in Examples 1 and 2 of this invention is shown in the genus correlation coefficient heatmap (d).

[0031] Figure 7 The diagram shows the denitrification mechanism of ammonia nitrogen wastewater treatment enhanced by electric field in Examples 1, 2, 3, and 4 of this invention. Detailed Implementation

[0032] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0033] This invention provides a wastewater treatment method for electrostatically coupled aerobic nitrification, comprising:

[0034] Acclimated sludge, wastewater, and insulating electrodes are added to an aerobic nitrification reactor. A voltage of 0-2 V / cm is applied outside the reactor to form an electrostatic field, controlling the organic load in the wastewater to be 500-4000 mg / L and the ammonia nitrogen concentration to be 100-400 mg / L, thereby achieving wastewater treatment.

[0035] Traditional biological nitrogen removal processes suffer from numerous drawbacks, preventing them from achieving the desired results. Furthermore, nitrifying and denitrifying bacteria in biological nitrogen removal technologies are extremely sensitive to their environment, often leading to instability in the aerobic nitrification reaction. Therefore, addressing the various problems of traditional aerobic nitrification nitrogen removal processes, this invention focuses on potential improvement factors in traditional aerobic nitrification nitrogen and phosphorus removal processes. It attempts to introduce a low-voltage electrostatic field, leveraging the advantages and characteristics of the electric field to enhance the stability of the reaction system and improve the overall treatment performance of the biological nitrogen removal system. This provides a new approach and method for solving the challenges of traditional biological nitrogen removal processes.

[0036] Based on this, this invention introduces a low-voltage electric field into the activated sludge aerobic nitrification reactor, deeply coupling the aerobic nitrification process and electric field catalysis technology. Utilizing the unique stimulating effect of the electrostatic field, it stimulates the growth of heterotrophic nitrifying bacteria and positively influences their physiological characteristics, breaking through the rate-limiting steps in traditional activated sludge processes and improving the rate and efficiency of nitrogen removal. Simultaneously, the newly constructed system can utilize electroactive bacteria to further promote the nitrogen removal process, comprehensively advancing the nitrogen removal process. Since the problem of superimposed inhibition by organic matter and ammonia nitrogen loads often occurs in aerobic nitrification, this invention also explores and analyzes the effect of adding a low-voltage electric field on the chemical oxygen demand (COD) removal efficiency, providing theoretical and experimental basis for improving the stability of aerobic nitrification of ammonia nitrogen wastewater.

[0037] Furthermore, establishing a rational community structure under aerobic conditions to promote the symbiotic metabolism among electroactive bacteria, heterotrophic bacteria, nitrifying bacteria, and denitrifying bacteria is of great significance for achieving rapid degradation of ammonia nitrogen wastewater. Therefore, this invention will utilize advanced molecular biology techniques to elucidate the functional bacterial communities under different conditions, understand the relationship and distribution between community structure and function, explore the denitrification metabolic pathway of the electric field-coupled activated sludge process, and investigate the connection between biological communities and electron transfer and substrate decomposition.

[0038] It is understood that the aerobic nitrification reactor described in this invention is a commonly used aerobic nitrification reactor in the art, and may also be a sequencing batch reactor made of high borosilicate glass, such as... Figure 1 As shown, the reactor 1 has three outlets on its cover: an aeration port, a sampling port, and a normally open gas outlet. The aeration port is externally connected to an air pump and internally connected to an air stone at the bottom of the reactor. Electrodes are placed inside the reactor, with one end of each electrode connected to a DC power supply via a titanium wire passing through the reactor cover.

[0039] This invention does not impose requirements on wastewater treatment time, as long as efficient removal of ammonia nitrogen from the wastewater is achieved. Those skilled in the art can select an appropriate treatment time based on actual needs. For example, the wastewater treatment time should be at least 3 days; to allow for more complete aerobic nitrification, a treatment time of 7 days is set.

[0040] In some embodiments of the present invention, the domestication includes:

[0041] After centrifugation and washing, the activated sludge is added to the aerobic nitrification reactor along with water at a volume ratio of 3:7. Carbon and nitrogen sources are also added. An electrostatic field of 0-2 V / cm is applied outside the aerobic nitrification reactor, and the reactor is acclimated for 6-7 days.

[0042] In some embodiments of the present invention, after the sludge acclimation is completed, in order to ensure the uniform distribution of subsequent microorganisms, the acclimated sludge is poured out and mixed, and the aerobic nitrification reactor is cleaned to remove impurities. After cleaning, the acclimated sludge and wastewater are added at a volume ratio of 1:3.8-4.2 for wastewater treatment.

[0043] The process involves allowing the sludge to stand, then removing the sediment layer and adding it to the cleaned aerobic nitrification reactor.

[0044] In some embodiments of the present invention, the concentration of the carbon source is 0.4-0.6 g / L, and the concentration of the nitrogen source is 0.09-0.11 g / L. The carbon and nitrogen sources provide the necessary nutrients for microbial growth.

[0045] In some embodiments of the present invention, the carbon source includes at least one selected from glucose, sodium acetate, methanol, citric acid, propionic acid, potassium bicarbonate, calcium carbonate, and sodium carbonate.

[0046] In some embodiments of the present invention, the nitrogen source includes ammonium chloride.

[0047] In some embodiments of the present invention, the method for preparing the insulating electrode includes:

[0048] Carbon nanotubes, nickel chloride, and polytetrafluoroethylene were dissolved in an aqueous ethanol solution, heated, rolled onto a titanium mesh, and dried to obtain a pre-electrode.

[0049] The pre-electrode is hydrophilically treated to obtain the polarized electrode;

[0050] A waterproof layer is formed by coating the outer surface of the polarized electrode with a waterproof material, thus obtaining an insulating electrode.

[0051] Specifically, the method for preparing the insulating electrode includes:

[0052] Carbon nanotubes were soaked in concentrated nitric acid for 20-25 hours and then washed until neutral. The washed carbon nanotubes, nickel chloride, and polytetrafluoroethylene were dissolved in an aqueous ethanol solution and heated to obtain a paste-like liquid.

[0053] The paste-like liquid is rolled onto a titanium mesh and dried to obtain a pre-electrode.

[0054] The pre-electrode is immersed in an aqueous solution of sodium dodecyl sulfate for 20-25 h to further improve the hydrophilicity of the electrode, thereby obtaining a polarized electrode;

[0055] After drying the polarized electrode, a waterproof material such as epoxy resin is coated on its outer surface, and the electrode is left to stand to form a waterproof layer, thus obtaining an insulating electrode.

[0056] The insulating electrode of this invention is not wrapped around the outer wall of the aerobic nitrification reactor, but rather added inside the reactor to provide a uniform electrostatic field. Compared to not installing electrodes inside the reactor, installing polarized electrodes to provide an electrostatic field accelerates the treatment of ammonia nitrogen wastewater. This may be due to the interaction of titanium, nickel, and carbon elements in the electrode or the formation of micro-galvanic cells with the wastewater. In this process, the more reactive metal (such as nickel) acts as the anode and is corroded, producing metal ions. A reduction reaction occurs on the cathode surface (such as carbon), such as reducing dissolved oxygen in the water to hydrogen peroxide. The hydrogen peroxide and the metal ions dissolved from the anode form a Fenton system, generating highly oxidizing hydroxyl radicals that oxidize and decompose organic matter. To prevent electrode corrosion, this invention coats the polarized electrode with epoxy resin to form an insulating layer. Testing showed that the treatment effect of the insulating electrode and the polarized electrode was not significantly different from the control. This is because the epoxy resin coating on the outer layer of the polarization electrode does not affect the formation of the electrostatic field and can separate the wastewater from the electrode, avoiding the influence of the electrode on the wastewater. This also prevents the electrode from directly contacting the water after energization and causing the water electrolysis reaction, thus saving energy and reducing unnecessary power loss.

[0057] In some embodiments of the present invention, the ratio of the washed carbon nanotubes and nickel chloride, polytetrafluoroethylene and ethanol aqueous solution is (3-5 g):(0.2-0.3 g):(0.4-0.6 g):(140-160 mL).

[0058] In some embodiments of the present invention, the concentration of ethanol in the aqueous ethanol solution is 75-85%.

[0059] In some embodiments of the present invention, the concentration of sodium dodecyl sulfate in the aqueous solution of sodium dodecyl sulfate is 0.5-1.5%.

[0060] In some embodiments of the present invention, a voltage of 0.5-1 V / cm is applied outside the aerobic nitrification reactor to form an electrostatic field, thereby controlling the organic load in the wastewater to be 1000-4000 mg / L and the ammonia nitrogen concentration to be 100-200 mg / L.

[0061] In some embodiments of the present invention, a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0.5 V / cm, thereby controlling the organic load in the wastewater to be 4000 mg / L and the ammonia nitrogen concentration to be 200 mg / L.

[0062] Specifically, the intensity of the electrostatic field has a decisive impact on the treatment effect of ammonia nitrogen wastewater. Among them, an electrostatic field of 0.5 V / cm exhibits the best performance. This intensity of electrostatic field can significantly stimulate the electron transfer process of microorganisms, greatly enhancing the denitrification metabolic pathway. Analysis of the microbial community revealed that key electroactive bacteria... Thauera and Limnobacter Effective enrichment was achieved, especially Thauera This process played a central role. Through the synergistic action of these bacteria, NH4... + The removal efficiency of -N can reach up to 99.9%, effectively promoting the decomposition of nitrogen-containing compounds and greatly improving the treatment efficiency of ammonia nitrogen wastewater. Changes in the concentration of organic carbon sources have a significant impact on the degradation effect of ammonia nitrogen wastewater. When the concentration of organic carbon sources is appropriate (500-4000 mg / L), microorganisms can obtain sufficient energy and material supply, thereby promoting synergistic effects among microorganisms and significantly improving the system's treatment efficiency for ammonia nitrogen wastewater.

[0063] Organic carbon sources are essential nutrients for microbial growth, and their proper concentration control is crucial for optimizing the treatment performance of electric field-coupled activated sludge systems. High COD content... Exiguobucterium and Pseudofulvimonas This provides favorable conditions for the growth and reproduction of bacteria, which form a mutually beneficial relationship with nitrifying bacteria, denitrifying bacteria, and electroactive bacteria. This synergistic effect greatly enhances the system's ability to decompose nitrogenous compounds and organic matter, NH4+. + The removal rates of nitrogen (N) reached 99.9%, total nitrogen (TN) 58.7%, and carbon dioxide (COD) 96.3%. This fully demonstrates the importance of a suitable carbon-to-nitrogen ratio and the synergistic effect among microbial communities in improving wastewater treatment efficiency in an electric field-coupled activated sludge system.

[0064] The effect of ammonia nitrogen concentration on the aerobic nitrification efficiency of ammonia nitrogen wastewater exhibits a significant dual effect. The treatment effect reaches its optimal state when the ammonia nitrogen concentration reaches 200 mg / L, at which point NH4+... + The removal rates of nitrogen (N) reached 99.9%, total nitrogen (TN) 65.1%, and COD 94.1%. At low ammonia nitrogen concentrations, the electric field enhanced the uptake of limited substrates by nitrifying bacteria, increasing their substrate affinity and enabling them to utilize ammonia nitrogen more efficiently, maintaining good nitrification activity. At high ammonia nitrogen concentrations, the electric field helped alleviate the toxic inhibitory effect of free ammonia produced by high concentrations on nitrifying bacteria, ensuring normal physiological metabolism and growth, thus maintaining high nitrification efficiency.

[0065] In some embodiments of the present invention, during the wastewater treatment process, the aeration rate of the aerobic nitrification reactor is 0.1-0.2 L / min, preferably 0.15 L / min.

[0066] To enable those skilled in the art to better understand the technical solution of the present invention, the technical solution of the present invention will be described in detail below with reference to specific embodiments.

[0067] The raw materials and equipment used in this invention are all commercially available products that can be purchased.

[0068] The electrode construction method used in the following experiments includes the following steps:

[0069] The anode and cathode of the electrode are constructed by coating carbon nanotubes (CNTs) onto the surface of a titanium mesh.

[0070] First, the CNTs were pretreated in concentrated nitric acid (HNO3) solution for 24 hours to remove impurities. Afterward, the pretreated CNTs were washed in tap water for at least 12 hours until the pH reached neutral. Next, 4 g of CNTs, 0.25 g of nickel chloride (NiCl2), and 0.5 g of polytetrafluoroethylene (PTFE) were weighed and dissolved in a beaker containing 150 mL of 80% ethanol. The beaker was heated in a water bath until the solution became a paste. After cooling, the treated material was evenly rolled onto a titanium mesh and placed in a 50°C oven to remove any remaining ethanol. The electrodes were then immersed in a 1% concentration of sodium dodecyl sulfate (C... 12 H 25 The electrode was immersed in a NaO4S solution for 24 hours to further enhance its hydrophilicity, thus creating a polarized electrode. The polarized electrode was then dried and coated with epoxy resin, which was repeatedly applied to the electrode. It was allowed to stand naturally until the resin adhered to the electrode and hardened, completing the fabrication of the insulating electrode.

[0071] The following methods were used for analysis and calculation in the experiments below:

[0072] (1) The voltage applied through the DC power supply during the reaction, due to being in a uniform electrostatic field, can be transmitted through... Convert to electrostatic field strength, where U is the applied voltage (V) and d is the distance between the insulating electrodes (cm).

[0073] (2) The content of ammonia nitrogen (ammonium nitrogen) in the bulk solution was determined by the national standard method (Nessler's reagent spectrophotometric method).

[0074] The content of nitrite nitrogen in the bulk solution was determined using the national standard method (spectrophotometry).

[0075] The content of nitrate nitrogen in the bulk solution was determined using the national standard method (ultraviolet spectrophotometer method).

[0076] The total nitrogen content is calculated by adding nitrate nitrogen, nitrite nitrogen, and ammonium nitrogen together.

[0077] The COD of the bulk solution was determined using the national standard potassium dichromate method.

[0078] The TS and VS of the bulk solution were measured by gravimetric method.

[0079] (3) Electrochemical analysis

[0080] At the end of the experiment, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were performed in the bulk solution using an electrochemical workstation (China CHI1000C).

[0081] Cyclic voltammetry (CV) measurements were performed using a three-electrode system: a titanium mesh as the working and counter electrode, and Ag / AgCl as the reference electrode. The CV was scanned for 10 cycles at a rate of 50 mV / s within the range of -1 V to 1 V. CV curves were plotted to obtain the redox current peaks and potential peaks. EIS measurements were performed in the frequency range of 104 Hz to 106 Hz. Equivalent current maps were fitted using Zsimpwin software to obtain the internal resistance and charge transfer resistance of the solution, and EIS dot plots were plotted using Origin 2025 software.

[0082] Electrochemical impedance spectroscopy (EIS) measurements were performed under open-circuit conditions using AC impedance spectra ranging from 100 kHz to 10 MHz. Raw EIS data were obtained and fitted using ZSimDemo software with a Randle equivalent circuit. The equivalent circuit consisted of a solution resistor connected in series with a double-layer capacitor, and was composed of a capacitor and a charge transfer resistor in parallel, a Warburg element, and a Faraday reaction impedance connected in series. Processed data were analyzed using Origin software.

[0083] (4) Microbial community analysis

[0084] After the experiment, the bulk solution samples were stored at -20°C for high-throughput sequencing of the microorganisms to analyze changes in the microbial community. High-throughput sequencing was performed using the Illumina platform (Illumina Miseq PE300) with PCR amplification products of the highly variable 16S rRNA regions (V3-V4) of standard bacteria in the oncogenetic fluid. The diversity of the microbial community under this environment was analyzed, including species classification and abundance information. Based on the 16S rRNA gene sequencing results, the taxonomic composition of the microorganisms was analyzed, and a relative abundance map of species was constructed.

[0085] Example 1

[0086] A wastewater treatment method for electrostatic field-coupled aerobic nitrification includes:

[0087] (1) Prepare artificial ammonia nitrogen wastewater:

[0088] Anhydrous sodium acetate (CH3COONa) and potassium bicarbonate (KHCO3) were used as carbon sources, and ammonium chloride (NH4Cl) was used as a nitrogen source. 1.0 mL of trace element I and 1.0 mL of trace element II were added to 1 L of artificial wastewater. The composition of the artificial wastewater and trace element solutions is shown in Tables 1 and 2. The composition of the artificial ammonia wastewater is shown in Table 3.

[0089] The concentration of ammonia nitrogen in the artificial ammonia nitrogen wastewater was 200 mg / L.

[0090] Table 1. Trace Element I Culture Medium Ratio

[0091]

[0092] Table 2. Trace Element II Culture Medium Ratio

[0093]

[0094] Table 3 Properties of Ammonia Nitrogen Wastewater, Activated Sludge, and Mixed Liquor

[0095]

[0096] (2) Acclimatization of activated sludge and reactor operation:

[0097] Activated sludge was collected from the secondary sedimentation tank of a wastewater treatment plant at a certain industrial university. After being collected and allowed to stand for 24 hours, the supernatant was poured off, the solid suspension was removed, and larger impurities were sieved (0.5 mm mesh). The homogenized sludge was then cultured in a laboratory aeration thermostat, with carbon and nitrogen sources added periodically to maintain sludge activity. Before each round of experiments, a quantitative amount of sludge was taken, centrifuged at 6000 r / min for 5 min, and washed 2-3 times with deionized water.

[0098] Add activated sludge and deionized water at a volume ratio of 3:7. Figure 1 Activated sludge was acclimated in the reactor shown. After 7 days of cultivation, the activated sludge was poured out and the reactor was cleaned. After the poured-out activated sludge was allowed to stand, 50 mL of the lower sediment was taken and added to each reactor. The volume ratio of ammonia nitrogen wastewater added to activated sludge was 4:1.

[0099] The reactor was placed on a heating plate to maintain the internal temperature at 35±1℃. Electrodes were installed at 2 cm intervals at relative positions within the reactor, and a voltage was applied to generate an electrostatic field with a strength of 0.5 V / cm. The inlet gas volume was adjusted to 0.15 L / min using a rotor flow meter. The reactor was run for 7 days. The experiment was performed in three cycles to ensure the validity of the data.

[0100] Example 2

[0101] A wastewater treatment method using electrostatic field-coupled aerobic nitrification differs from Example 1 in that the ammonia nitrogen concentration in the prepared artificial ammonia nitrogen wastewater is 0, 100, 400, 800, or 1600 mg / L. The remaining steps are completely identical to those in Example 1.

[0102] Comparative Example 1

[0103] A method for treating wastewater through static aerobic nitrification differs from Example 1 in that the ammonia nitrogen concentration in the prepared artificial ammonia nitrogen wastewater is 0, 100, 200, 400, 800, or 1600 mg / L, but no electrostatic field is applied. The remaining steps are completely consistent with those of Example 1.

[0104] Comparative Example 2

[0105] A wastewater treatment method for electrostatically coupled aerobic nitrification differs from Example 1 in that it uses a coil electric field to apply an electric field to the aerobic nitrification reactor. The coil electric field structure is as follows: Figure 2 As shown.

[0106] The wastewater treatment methods of Examples 1 and 2 and Comparative Examples 1 and 2 were analyzed.

[0107] (1) Effect of ammonia nitrogen concentration on aerobic nitrification efficiency of ammonia nitrogen wastewater

[0108] Table 4 Comparison of wastewater degradation at different ammonia nitrogen concentrations

[0109]

[0110] From Table 4 and Figure 3 As can be seen in Figure (a), NH4 + The removal rate of ammonia nitrogen (-N) varies significantly with ammonia nitrogen concentration, expressed as the coefficient R. At 1600 mg / L, the removal rate is low (0.99 ± 0.01). However, when the ammonia nitrogen concentration decreases to 200 mg / L, the removal rate continuously increases to 1.07 ± 0.02, the highest observed value. This indicates that excessively high ammonia nitrogen concentrations may shift the chemical equilibrium of the reaction system. Excessive ammonia nitrogen may lead to the accumulation of reaction products, inhibiting the reaction from proceeding in the forward direction, thereby reducing the ammonia nitrogen removal rate. From a microbiological perspective, excessively high ammonia nitrogen concentrations may inhibit microbial activity. On the one hand, high concentrations of ammonia nitrogen alter the osmotic pressure inside and outside microbial cells, leading to cell dehydration and affecting normal cellular physiological functions; on the other hand, certain forms of ammonia nitrogen (such as free ammonia) may be toxic to microbial enzyme systems, hindering the activity of key enzymes in microbial metabolism, thus reducing the microorganisms' ability to degrade ammonia nitrogen.

[0111] When the ammonia nitrogen concentration is less than 200 mg / L, NH4 +-N removal rate decreases. This may be because a decrease in ammonia nitrogen concentration leads to a reduction in the concentration gradient of the reaction system. According to the principles of chemical reaction kinetics, this weakens the driving force of the reaction, reduces the reaction rate, and ultimately leads to a decrease in ammonia nitrogen removal rate.

[0112] Compared with the control group (CR, Comparative Example 1) without an applied electric field, the pollutant removal efficiency of the experimental groups (EFAR, i.e., Examples 1 and 2) was improved after the application of an electric field. Among the six experimental groups using different ammonia nitrogen concentrations, the reactor group with an ammonia nitrogen concentration of 100 mg / L showed the best organic matter degradation effect, with a removal efficiency of 94.3 ± 1.2% (Table 4), followed by the reactor group with an ammonia nitrogen concentration of 400 mg / L (94.3 ± 0.8%) and the reactor group with an ammonia nitrogen concentration of 200 mg / L (94.1 ± 0.9%). NH4 + -N removal rates all reached 99.9%, but the NH4 group at 200 mg / L... + The highest removal efficiency for -N was 1.07 ± 0.02. Among the experimental groups, the lowest pollutant degradation efficiency was observed in the 1600 mg / L group, with a COD removal rate of only 47.7 ± 1.7%. This is likely because excessively high ammonia nitrogen concentrations affect the microbial community and pollutant metabolism.

[0113] Figure 3 Figures (b) and (c) show NO2. - -N and NO3 - -N concentration varies with time and different ammonia nitrogen concentrations. At lower ammonia nitrogen concentrations, NO2... - The reduction rate of -N is faster at higher ammonia nitrogen concentrations, indicating that an appropriate ammonia nitrogen concentration is beneficial for the balance between nitrification and denitrification. At higher field strengths (e.g., 800 and 1600 mg / L), this balance may be disrupted, resulting in suboptimal nitrogen removal efficiency.

[0114] The COD degradation curve of the bulk solution during the reaction process is as follows: Figure 2 As shown in Figure (e), the degradation efficiency and rate were optimal at an ammonia nitrogen concentration of 200 mg / L. However, the degradation efficiency of COD decreased with increasing ammonia nitrogen concentration, possibly because excessively high ammonia nitrogen concentrations inhibited the growth of certain microorganisms, leading to a slower COD degradation rate.

[0115] Figure 3The pH value in Figure (f) generally shows a trend of first increasing and then decreasing. This may be because, under the influence of the electric field, in the initial stage of aerobic nitrification, microorganisms such as ammonia-oxidizing bacteria first utilize ammonia nitrogen in the water for metabolic activities. During the oxidation of ammonia nitrogen to nitrite nitrogen, a certain amount of hydrogen ions are consumed, resulting in a relative excess of hydroxide ions in the solution, thus causing the pH value to rise. In the initial stage, the microorganisms consume hydrogen ions relatively quickly, reducing the number of hydrogen ions in the system and increasing the pH value. The subsequent decrease in pH value may be due to the fact that as the nitrification reaction continues, nitrite nitrogen is further oxidized to nitrate nitrogen. As the reaction proceeds, alkalinity is continuously consumed to produce hydrogen ions, leading to a gradual decrease in pH value. Furthermore, as the reaction progresses, some acidic substances produced by microbial metabolism, such as carbon dioxide, may accumulate in the system. Carbon dioxide dissolves in water to form carbonic acid, which increases the acidity of the solution and decreases the pH value.

[0116] The results of Examples 1 and 2 and Comparative Example 1 show that changing the ammonia nitrogen concentration can significantly enhance the degradation of ammonia nitrogen in wastewater, with the removal of NH4+ at an ammonia nitrogen concentration of 200 mg / L being particularly effective. + -N is most effective. At this intensity, the increased nitrogen removal rate indicates that moderate ammonia nitrogen concentrations stimulate microbial activity and promote nitrification-denitrification processes. However, at higher ammonia nitrogen concentrations, NH4+... + The reduced removal efficiency of -N may be due to the inhibitory effect of excessive ammonia nitrogen on microbial growth and metabolism.

[0117] (2) Comparison of the effects of coil electric field and electrode electric field on the denitrification rate of ammonia nitrogen wastewater

[0118] like Figure 4 As shown in Figure (a), the removal efficiency of ammonia nitrogen is greatly affected by the electric field. After applying the electric field, the denitrification rate of ammonia nitrogen increases significantly. However, the difference between the electrode electric field and the coil electric field has little effect on the removal of ammonia nitrogen.

[0119] Figure 4Figure (b) shows the total nitrogen removal effect. Applying an electric field significantly improved TN removal, but the coil electric field differed considerably from the electrode electric field. This may be because the electric field strength generated by the coil rapidly decreases with increasing distance from the coil. Different locations within the reactor have varying distances from the coil, resulting in significant differences in electric field strength and poor uniformity. This non-uniform electric field leads to insufficient electric field strength in some areas of the reactor, hindering the denitrification reaction, while excessively high electric field strength in others may negatively impact microorganisms or chemical reactions. The electric field generated by the electrode is relatively uniform within a certain region near the electrode. This relatively uniform and moderately strong electric field provides a more stable and favorable environment for the denitrification reaction, improving the denitrification effect. The electric field generated by the coil exerts a relatively weak force on ions, and its direction and magnitude vary complexly with position, hindering ion directional migration and affecting the denitrification reaction. The electric field generated by the electrodes can produce a strong electrostatic field, which has a clear directional force on ions. This can effectively promote the migration of ammonia nitrogen to the anode and nitrate ions to the cathode, making the distribution of ions in the reactor more conducive to the denitrification reaction and improving the efficiency of the denitrification reaction.

[0120] (3) The effect of changes in the ammonia nitrogen gradient on the electrochemical analysis of the bulk solution

[0121] observe Figure 5 In the cyclic voltammetry curves of Figure (a), significant reduction and oxidation peaks are clearly observed in the initial stage of the reaction. This is likely because the initial solution is rich in contaminants such as ammonia nitrogen. Under the influence of the electric field, these contaminants undergo redox reactions on the electrode surface, resulting in a significant current response. In the final stage of the reaction, the reduction and oxidation peaks in the reactor bulk solution with an ammonia nitrogen concentration of 1600 mg / L are particularly prominent. This may be because excessively high ammonia nitrogen concentrations inhibit the removal of other pollutants. Excessive ammonia nitrogen may occupy active sites on the electrode surface, hindering effective contact between other contaminants and the electrode, making it difficult for them to undergo redox reactions on the electrode surface, thus affecting their removal efficiency. In other reactors, no significant reduction and oxidation peaks were detected, possibly because the ammonia nitrogen concentration was within a suitable range, providing favorable conditions for the removal of other contaminants. Appropriate amounts of ammonia nitrogen can participate in the redox reaction network on the electrode surface, promoting electron transfer, allowing other contaminants to undergo redox reactions smoothly on the electrode surface and be largely removed.

[0122] Electrochemical impedance spectroscopy of different reactors Figure 5 Analysis of Figure (b) revealed that the reactors with ammonia nitrogen concentrations of 0 mg / L and 1600 mg / L had higher charge transfer resistance, which further corroborates the experimental results that their reactivity was low and their pollutant removal efficiency was poor.

[0123] As shown in Table 5, the carbon-to-nitrogen ratio significantly affects key electrochemical parameters such as ohmic resistance (Rs), charge transfer resistance (Rct), capacitance, and Warburg impedance. The ohmic resistance (Rs, 22.53 Ω) is highest at an ammonia nitrogen concentration of 100 mg / L, followed by 19.87 Ω at 200 mg / L, while the charge transfer resistance (Rs, 0.014 kΩ) is lowest at the same concentration. This indicates that increasing the ammonia nitrogen concentration increases the total resistance of the solution and also enhances electron transfer processes in microorganisms at appropriate ammonia nitrogen concentrations.

[0124] Table 5. EIS analysis parameters of bulk solutions in different reactors at the beginning and end of the experiment.

[0125]

[0126] At higher ammonia nitrogen concentrations, such as 1600 mg / L, the Rs value (14.33 Ω) was significantly lower than other groups, while the charge transfer resistance (0.071 kΩ) was higher. The increase in Rs may be due to the high concentration of ammonia nitrogen promoting microbial growth; however, excessively high ammonia nitrogen concentrations also inhibit electron transfer in the microorganisms. Warburg impedance analysis results show that the electron transfer efficiency of the system increases with increasing ammonia nitrogen concentration at low concentrations; however, when the ammonia nitrogen concentration exceeds 400 mg / L, the electron transfer efficiency decreases with increasing ammonia nitrogen concentration. This indicates that excessively high or low ammonia nitrogen concentrations inhibit microbial growth and electron transfer, leading to reduced reactor performance.

[0127] (4) The effect of changes in ammonia nitrogen gradient on the analysis of microbial community in bulk solution

[0128] In the experiment, three different reactors (ammonia nitrogen concentrations of 100 mg / L, 400 mg / L, and 1600 mg / L) were selected for microbial analysis.

[0129] exist Figure 6 In this context, when an electrostatic field is applied, the dominant bacterial genus belonging to the phylum Proteobacteria ( ) Thauera The relative abundance of ) increased significantly. Thauera The genera become the most abundant after an electrostatic field is applied. Thauera It is a well-known electroactive microorganism capable of external electron transfer (EET), which enhances its degradation of NH4 under electrochemical conditions. + The ability to generate nitrogen (-N). This genus is often associated with denitrification processes, in which it reduces nitrates and nitrites to nitrogen gas, thus completing the nitrogen cycle in wastewater treatment systems. ThaueraThe high relative abundance indicates that the electrostatic field stimulated its growth and metabolic activity, thereby promoting NH4+. + -N degradation. Under an electric field, with Thauera The predominantly enriched microbial community may have accelerated nitrification and denitrification processes, leading to increased NH4+ levels. + The efficient conversion of -N further supports the idea that electrostatic fields promote nitrogen removal by enhancing electron transfer between key microbial communities.

[0130] Electroactive bacteria such as Thauera The enrichment under an electrostatic field can be attributed to several factors. First, the application may enhance the microbial EET process, enabling these bacteria to transfer electrons more efficiently in nitrification and denitrification reactions. EET is a key metabolic pathway for many electroactive microorganisms, and the presence of an electrostatic field promotes its occurrence, creating a favorable environment for electron movement. This, in turn, increases NH4+. + -N removal rate. Secondly, the electrostatic field can selectively promote the growth of electroactive bacteria by stimulating their metabolic pathways. For example, Thauera It has been shown to possess genes responsible for nitrogen metabolism, including nitrate reductase and nitrite reductase, which are essential for denitrification. The presence of these genes enables... Thauera It plays a central role in the nitrogen cycle, especially under electrochemical conditions that enhance electron transfer. Furthermore, Thauera Its ability to switch between aerobic and anaerobic metabolic pathways enables it to thrive under electrostatically induced dynamic redox conditions, explaining its dominant position in microbial communities under these conditions. In reactors exposed to electrostatic fields, Thauera Enrichment of isoelectrically active bacteria and NH4 + The enhanced degradation of -N is directly related to this. The increased electron transfer rate promoted by the electrostatic field may accelerate these processes, leading to higher overall denitrification efficiency.

[0131] Interestingly, at higher ammonia nitrogen concentrations (1600 mg / L), the relative abundance of electroactive bacteria decreased. This suggests that excessively high ammonia nitrogen concentrations may inhibit microbial growth and reproduction. This may be due to the osmotic pressure balance between microbial cells and their surrounding environment. When the external ammonia nitrogen concentration is too high, the extracellular osmotic pressure increases significantly, thereby inhibiting microbial growth and reproduction. Furthermore, in a high ammonia nitrogen environment, microorganisms need to consume more energy to cope with the toxicity of ammonia nitrogen, thus reducing the energy available for uptake of other nutrients and metabolic activities. Simultaneously, excessively high ammonia nitrogen concentrations may, to some extent, affect the absorption and utilization of other essential nutrients such as carbon and phosphorus sources by microorganisms, leading to insufficient nutrient supply and limiting microbial growth and reproduction.

[0132] The application of electrostatic fields significantly enriched key electroactive bacterial genera, especially NH4 in wastewater. + -N plays a key role in degradation Thauera and Limnobacter These bacteria thrive in a moderate electrostatic field, where enhanced electron transfer leads to increased nitrogen removal efficiency. The results show that when the electrostatic field strength is 0.5 V / cm, NH4+ removal efficiency is improved by stimulating microbial growth and electron transfer. + -N exhibits the highest degradation rate. However, higher electric field strengths may inhibit microbial activity, highlighting the importance of optimizing electrostatic field conditions for efficient wastewater treatment.

[0133] (5) The effect of changes in ammonia nitrogen gradient on the analysis of metabolic pathways in bulk solution

[0134] The data in Table 6 reveal how different ammonia nitrogen concentrations affect different metabolic pathways, thus providing a clearer understanding of the relationship between microbial activity and NH4. + The relationship between -N degradation and metabolism was investigated. Comparison of metabolic pathways at different ammonia nitrogen concentrations revealed an increase in the abundance of key microbial metabolic pathways (such as GLUCOSE1PMETAB-PWY and LEU-DEG2-PWY) under the influence of an electrostatic field. The PWY-5420 pathway, associated with aromatic compound degradation, showed the highest abundance (1301.22) at an ammonia nitrogen concentration of 400 mg / L. This enhancement suggests that the electrostatic field stimulates electron transfer in microorganisms, which is crucial for the breakdown of complex organic molecules and subsequent nitrogen compounds (such as NH4+). + The removal of -N) is crucial.

[0135] A comparison of metabolic pathways at different ammonia nitrogen concentrations across three gradients revealed that both key microbial metabolic pathways and aromatic compound degradation pathways reached their peak at an ammonia nitrogen concentration of 400 mg / L. This may be because microbial growth and metabolism require a suitable ratio of various nutrients. At an ammonia nitrogen concentration of 400 mg / L, the ratio of ammonia nitrogen to other nutrients (such as carbon and phosphorus sources) is relatively appropriate, meeting the needs of microbial growth and metabolism, allowing microorganisms to efficiently carry out metabolic activities to synthesize cellular materials and obtain energy. If the ammonia nitrogen concentration is too low, it becomes a limiting factor for microbial growth, leading to a decrease in the activity of metabolic pathways. Conversely, if the ammonia nitrogen concentration is too high, it disrupts the nutrient balance, and microorganisms may use excessive energy to cope with the toxicity of ammonia nitrogen or to regulate metabolism to adapt to the high ammonia nitrogen environment, thereby affecting other normal metabolic pathways.

[0136] The increased activity of the GLUCOSE1PMETAB-PWY pathway involved in carbohydrate degradation further supports the view that electrostatic fields and appropriate ammonia nitrogen concentrations promote microbial metabolism. At an ammonia nitrogen concentration of 400 mg / L, the abundance of GLUCOSE1PMETAB-PWY reached 700.719, indicating that moderate ammonia nitrogen concentrations enhance microbial utilization of carbon sources, which are essential for microbial growth and activity. Increased or decreased ammonia nitrogen concentrations directly affect NH4+ levels in the reactor. + Degradation of -N.

[0137] LEU-DEG2-PWY represents the primary redox pathway in the reaction. This pathway is significantly enhanced under the influence of an electric field. In the electric field-coupled aerobic nitrification process, redox reactions are primarily achieved through several key pathways: Ammonia oxidation to nitrite: Under aerobic conditions, nitrifying bacteria first oxidize ammonia nitrogen to hydroxylamine, a process requiring oxygen and consuming ATP. The generated hydroxylamine is further oxidized to nitrite by hydroxylamine oxidoreductase, and then nitrite is oxidized to nitrate by nitrite oxidoreductase. This process is a crucial oxidation step in denitrification, helping to convert nitrogen into a more easily removed form. Finally, under the influence of an electric field, denitrifying bacteria utilize organic carbon sources as electron donors to gradually reduce nitrate to nitrogen gas.

[0138] However, at higher ammonia nitrogen concentrations, such as 1600 mg / L, the abundance of these pathways decreases. For example, the abundance of the PWY-5420 pathway drops to 1176.76, and the abundance of the GLUCOSE1PMETAB-PWY pathway also drops to 630.595. This decrease in pathway activity may be due to the inhibitory effect of excessively high ammonia nitrogen concentrations. High concentrations of ammonia nitrogen may damage cell structure, inhibit enzyme activity, interfere with metabolic processes, and affect the microbial community, inhibiting the growth of other microorganisms symbiotic with nitrifying bacteria, thereby affecting the growth and metabolism of nitrifying bacteria. These metabolic pathways constitute a complex network, with enzymes and proteins working together to regulate and drive various metabolic activities between and within microorganisms, maintaining microbial growth and reproduction.

[0139] Ammonia nitrogen concentration is also important for improving the microbial denitrification pathway and NH4+ in wastewater treatment systems. + Ammonia nitrogen concentration is one of the key factors in nitrogen (NH4) degradation. Moderate ammonia nitrogen concentrations significantly increase the abundance of metabolic pathways such as carbon utilization, aromatic compound degradation, and redox reactions, thereby improving nitrogen removal efficiency. However, excessively high or low electric field strengths may inhibit microbial activity, highlighting the importance of optimizing ammonia nitrogen concentration conditions to obtain maximum NH4+. + The importance of -N removal efficiency.

[0140] Table 6. Comparison of microbial abundance in metabolic pathways of different reactors

[0141]

[0142] Example 3

[0143] A wastewater treatment method using electrostatic field-coupled aerobic nitrification differs from Example 1 in that the properties of the prepared artificial ammonia nitrogen wastewater are shown in Table 7. To investigate the effect of different organic loads on the aerobic nitrification efficiency of the ammonia nitrogen wastewater, the COD concentrations in the prepared artificial ammonia nitrogen wastewater were 0, 500, 1000, 2000, 4000, and 8000 mg / L. The remaining steps are completely consistent with those in Example 1.

[0144] Table 7 Properties of Artificial Ammonia Nitrogen Wastewater and Activated Sludge

[0145]

[0146] Comparative Example 2

[0147] An aerobic nitrification wastewater treatment method differs from Example 3 in that no electrostatic field is applied. The remaining steps are completely identical to those in Example 3.

[0148] The wastewater treatment methods of Example 3 and Comparative Example 2 were analyzed.

[0149] (1) Effect of changes in organic load on the aerobic nitrification efficiency of electric field-enhanced ammonia nitrogen wastewater

[0150] As shown in Table 8, the experimental group exhibited significantly better degradation efficiency and rates for ammonium nitrogen, nitrate nitrogen, total nitrogen, and COD than the control group. Specifically, the experimental group showed the highest degradation efficiency for ammonia nitrogen and total nitrogen at a COD concentration of 4000 mg / L. Under carbon source-free conditions (COD = 0 mg / L), the degradation efficiency for ammonia nitrogen was significantly enhanced. These findings highlight the potential for optimizing the denitrification process through electric field stimulation.

[0151] Changes in organic loading significantly impact the treatment efficiency of ammonia nitrogen wastewater. The optimal treatment effect is achieved when the organic loading reaches 4000 mg / L. Compared to the control group without applied voltage, at the optimal organic loading (4000 mg / L), the TN removal rate increased by 16.1%, and the COD removal rate increased by 7.1%. Applying an electric field effectively stimulates the electron transfer process of microorganisms and enriches key electroactive bacteria. Thauera The performance was particularly outstanding. The high content of chemical oxygen demand (COD) was... Exiguobucterium and Pseudofulvimonas The growth and reproduction of isoheterotrophic bacteria provide favorable conditions. These bacteria form a mutually reinforcing relationship with nitrifying bacteria, denitrifying bacteria, and electroactive bacteria, leading to an increase in ammonia nitrogen (NH4+).+ The removal rates of nitrogenous nitrogen (N-N) reached 99.9%, total nitrogen (TN) 58.7%, and carbon dioxide (COD) 96.3%. These bacteria efficiently promoted the decomposition of nitrogenous compounds and organic matter by enhancing nitrification and denitrification. Furthermore, the experimental results showed that the electric field played a positive role in wastewater treatment. Whether the wastewater contained organic or inorganic ammonia nitrogen, the treatment effect was significantly improved under the influence of the electrostatic field compared to the control group. Therefore, integrating electrostatic field technology into existing wastewater treatment processes has significant advantages.

[0152] Table 8 Degradation of ammonia nitrogen in wastewater under different organic loads

[0153]

[0154] (2) Effect of changes in organic loading on the electrochemical analysis of bulk solution

[0155] As shown in Table 9, under higher organic loadings, such as 2000 mg / L and 4000 mg / L, the Rs values ​​(20.3 Ω and 20.05 Ω, respectively) were significantly lower than those of other groups, and the corresponding microbial activity was also improved. The increase in Rs may be due to the appropriate carbon-to-nitrogen ratio promoting microbial growth. The Warburg impedance results show that the electron transfer efficiency of the system increases with increasing organic loading (9.407 1 / Ω at 4000 mg / L COD). Interestingly, it decreases at 8000 mg / L COD (8.315 1 / Ω). This indicates that excessively high organic matter content inhibits microbial growth and electron transfer, leading to a decrease in reactor performance.

[0156] Table 9. EIS analysis parameters of bulk solutions in different reactors at the beginning and end of the experiment.

[0157]

[0158] Example 4

[0159] A wastewater treatment method using electrostatic field-coupled aerobic nitrification differs from Example 1 in that the properties of the prepared artificial ammonia nitrogen wastewater are shown in Table 10. To ensure the integrity of the experiment, applied voltages above 12 V were explored. When the voltage exceeded 12 V, severe corrosion occurred on the electrodes and titanium wires. To ensure the stability of the reactor, voltages below 12 V were selected for the experiment, with applied voltages of 0 V, 1 V, 2 V, 4 V, 8 V, and 12 V. The electrostatic field strengths corresponding to applied voltages of 0 V, 1 V, 2 V, 4 V, 8 V, and 12 V were calculated to be 0 V / cm, 0.5 V / cm, 1 V / cm, 2 V / cm, 4 V / cm, and 6 V / cm, respectively. The remaining steps were completely consistent with those in Example 1.

[0160] Table 10 Properties of Ammonia Nitrogen Wastewater, Activated Sludge, and Mixed Liquor

[0161]

[0162] Comparative Example 3

[0163] An aerobic nitrification wastewater treatment method differs from Example 4 in that no electrostatic field is applied. The remaining steps are completely identical to those of Example 4.

[0164] The wastewater treatment methods of Example 4 and Comparative Example 3 were analyzed.

[0165] (1) Effect of electrostatic field strength on the treatment efficiency of ammonia nitrogen wastewater

[0166] NH4 + The removal of -N can be divided into three stages: initial NH4+ + -N removal phase (0-2 days), followed by NO2 removal. - -N removal phase (1-4 days), finally NO3. - -N formation phase (3-6 days). This sequential transformation of nitrogen-containing compounds demonstrates a classic nitration process, in which NH4+ is generated. + -N is first oxidized to NO2. - -N, which is then further oxidized to NO3. - -N. Experimental data show that the electrostatic field significantly enhances the effect of the electrostatic field on NH4+ in the first stage of the reaction. + The removal rate of -N reaches its peak at 0.5 V / cm.

[0167] Table 11 Degradation of ammonia nitrogen wastewater under different electrostatic field strengths

[0168]

[0169] (2) Effect of changes in electrostatic field strength on the electrochemical analysis of bulk solution

[0170] The combined CV and EIS analyses showed that the electrostatic field can effectively enhance electron transfer in microorganisms, thereby improving NH4+. +-N degradation, particularly under moderate field strengths (e.g., 0.5 V / cm). This finding is consistent with other studies demonstrating that electroactive microorganisms can thrive under optimized electrochemical conditions where electrostatic fields facilitate electron transfer between microbial species. Increased microbial activity under these conditions accelerates the nitrification process, allowing for faster ammonia nitrogen removal.

[0171] Table 12 EIS Analytical Indicators of Bulk Solutions in Different Reactors at the Beginning and End of the Experiment

[0172]

[0173] (3) Effect of changes in electrostatic field strength on the analysis of microbial community in bulk solution

[0174] Electrostatic fields significantly enhanced the microbial denitrification metabolic pathway in ammonia nitrogen wastewater treatment. Applying an electrostatic field of 0.5 V / cm stimulated electron transfer in microorganisms and enriched key electroactive bacteria, particularly... Thauera and Limnobacter NH4 + -N removal efficiency was highest (99.9%). These bacteria effectively promoted the decomposition of nitrogenous compounds by enhancing nitrification and denitrification. This study highlights the dual benefits of electrostatic fields: improved microbial performance and reduced energy demands typically associated with aeration in conventional wastewater treatment systems. Furthermore, integrating electrostatic fields into existing wastewater treatment plants offers significant advantages. The relatively simple and inexpensive retrofit process allows for seamless adoption without major infrastructure modifications. Future work should focus on scaling up the technology, optimizing on-site advantages, and ensuring long-term operational stability under diverse wastewater conditions to maximize the benefits of electrostatic field-assisted nitrogen removal.

[0175] (4) Analysis of the mechanism of ammonia nitrogen removal from wastewater enhanced by electric field

[0176] After an electric field is applied to the system, the electrostatic field can enhance the electron transfer process, thereby improving the microbial nitrification and denitrification pathways in the wastewater treatment system. Figure 7Under a moderate electrostatic field, especially 0.5 V / cm, the metabolic rate and removal rate of ammonia nitrogen and organic matter are significantly enhanced. This is because appropriate electric field stimulation can affect the activity of microorganisms. Microbial activity may be enhanced under the action of an electric field, thereby accelerating the metabolism of ammonia nitrogen and helping to convert ammonia nitrogen into nitrite, nitrate, etc. Furthermore, some ammonia nitrogen may be directly converted into H2 for removal under the action of an electric field. The electric field may also change the permeability of the microbial cell membrane, which is also conducive to the exchange of substances inside and outside the cell. Cells can more easily absorb nutrients such as ammonia nitrogen from wastewater, providing sufficient substrates for microbial growth and metabolism, thus strengthening the denitrification function of microorganisms. The electrostatic field also has different effects on different microorganisms. Some electroactive bacteria, heterotrophic, and denitrifying microorganisms can grow and function better in an electric field, thereby optimizing the microbial community structure. For others, such as some microorganisms that are not conducive to ammonia nitrogen denitrification, their growth and metabolism may be inhibited by the electric field, thus effectively improving the efficiency of the entire denitrification system.

[0177] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A wastewater treatment method for electrostatically coupled aerobic nitrification, characterized in that, include: Acclimated sludge, wastewater, and insulating electrodes are added to an aerobic nitrification reactor. A voltage of 0.5-1 V / cm is applied outside the reactor to form an electrostatic field. The organic load in the wastewater is controlled at 1000-4000 mg / L and the ammonia nitrogen concentration is controlled at 100-200 mg / L, thereby achieving wastewater treatment.

2. The wastewater treatment method as described in claim 1, characterized in that, The domestication includes: After centrifugation and washing, the activated sludge is added to the aerobic nitrification reactor along with water at a volume ratio of 3:

7. Carbon and nitrogen sources are also added. An electrostatic field of 0-2 V / cm is applied outside the aerobic nitrification reactor, and the reactor is acclimated for 6-7 days.

3. The wastewater treatment method as described in claim 2, characterized in that, After the sludge acclimation is completed, the acclimated sludge is poured out and mixed to clean the aerobic nitrification reactor. After cleaning, the acclimated sludge and wastewater are added at a volume ratio of 1:3.8-4.2 for wastewater treatment.

4. The wastewater treatment method as described in claim 2, characterized in that, The concentration of the carbon source is 0.4-0.6 g / L, and the concentration of the nitrogen source is 0.09-0.11 g / L.

5. The wastewater treatment method as described in claim 2, characterized in that, The carbon source includes at least one of glucose, sodium acetate, methanol, citric acid, propionic acid, potassium bicarbonate, calcium carbonate, and sodium carbonate.

6. The wastewater treatment method as described in claim 2, characterized in that, The nitrogen source includes ammonium chloride.

7. The wastewater treatment method as described in claim 1, characterized in that, The method for preparing the insulating electrode includes: Carbon nanotubes, nickel chloride, and polytetrafluoroethylene were dissolved in an aqueous ethanol solution, heated, rolled onto a titanium mesh, and dried to obtain a pre-electrode. The pre-electrode is hydrophilically treated to obtain the polarized electrode; A waterproof layer is formed by coating the outer surface of the polarized electrode with a waterproof material, thus obtaining an insulating electrode.

8. The wastewater treatment method as described in claim 1, characterized in that, A voltage of 0.5 V / cm was applied outside the aerobic nitrification reactor to form an electrostatic field, controlling the organic load in the wastewater to be 4000 mg / L and the ammonia nitrogen concentration to be 200 mg / L.

9. The wastewater treatment method as described in claim 1, characterized in that, During the wastewater treatment process, the aeration rate of the aerobic nitrification reactor is 0.1-0.2 L / min.

10. The wastewater treatment method as described in claim 9, characterized in that, The aeration rate of the aerobic nitrification reactor is 0.15 L / min.

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