Wastewater treatment method by coupling electrostatic field with aerobic nitrification

Abstract

The invention discloses a wastewater treatment method by coupling an electrostatic field with aerobic nitrification, and belongs to the technical field of wastewater treatment. Adding the domesticated sludge, wastewater and an insulated electrode into an aerobic nitration reactor, applying voltage outside the aerobic nitration reactor to form a 0-2 V / cm electrostatic field, and controlling the organic load in the wastewater to be 500-4000 mg / L and the ammonia nitrogen concentration to be 100-400 mg / L, so as to realize wastewater treatment. The invention discloses the internal mechanism of the electric field coupled activated sludge system for treating the ammonia-nitrogen wastewater, enriches the knowledge of the microbial electrochemical field, clarifies the influence rule of each factor on the activity and function of microorganisms, provides a new perspective for understanding the action mechanism of the microorganisms in wastewater treatment, and can obviously improve the treatment efficiency of the ammonia-nitrogen wastewater. The pollutant content is reduced, the environmental pollution is reduced, and the water environment quality and ecological safety are guaranteed; the aeration-related energy demand can be reduced, and the ammonia-nitrogen wastewater treatment cost is reduced.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment, and in particular relates to a wastewater treatment method of electrostatic field coupled aerobic nitrification. Background Art

[0002] The information disclosed in this background technology section is only intended to enhance understanding of the overall background of the invention and should not necessarily be regarded as an admission or any form of suggestion that the information constitutes the prior art already known to those skilled in the art.

[0003] Efficient treatment of ammonia-nitrogen wastewater is a key challenge in environmental engineering. Currently, biological methods (particularly aerobic nitrification) are widely used to treat ammonia-nitrogen wastewater. However, when treating high-concentration ammonia-nitrogen wastewater, they often face challenges such as inhibition of nitrifying bacteria, low treatment efficiency, and sludge loss. To improve treatment efficiency, existing research has attempted to incorporate physical field enhancement techniques. For example, the closest prior art discloses a novel low-carbon denitrification process enhanced by micro-electric fields. The wastewater undergoes anaerobic fermentation followed by autotrophic simultaneous nitrification and denitrification. During this process, the anaerobic fermentation wastewater is electrolyzed by a power source. Under the action of the micro-electric field, the carbon-autotrophic nitrifying bacteria and hydrogen-autotrophic denitrifying bacteria within the reactor migrate in a targeted manner, creating an oxygen-limited environment within the system. Ammonia-nitrogen in the wastewater is converted to nitrate-nitrogen, completing the nitrification process. By precisely controlling the dissolved oxygen (DO) concentration, temperature, and applied current within the reactor, this process successfully optimizes the removal of low-concentration ammonia-nitrogen (typically below 100 mg / L).

[0004] However, this new process is primarily designed for low-concentration ammonia nitrogen wastewater, and its control strategy revolves around dissolved oxygen, temperature, and current. When treating wastewater with higher concentrations of ammonia nitrogen (significantly above 100 mg / L), this approach faces significant limitations: First, high concentrations of ammonia nitrogen themselves exert a stronger inhibitory effect on nitrifying bacteria; second, relying solely on DO, temperature, and current control is unable to effectively overcome the impact of high loads and fails to fully utilize the potential advantages of electrostatic fields in treating high-concentration pollutants. Summary of the Invention

[0005] In order to address the deficiencies of the prior art, the purpose of the present invention is to provide a wastewater treatment method using an electrostatic field coupled aerobic nitrification system. The present invention adopts an electrostatic field coupled aerobic nitrification system to significantly improve the ammonia nitrogen wastewater treatment efficiency, reduce the pollutant content, reduce environmental pollution, and ensure the water environment quality and ecological safety.

[0006] In order to achieve the above object, the technical solution of the present invention is: A first aspect of the present invention provides a wastewater treatment method using electrostatic field coupled aerobic nitrification, comprising: Acclimated sludge, wastewater and insulated electrodes are added to the aerobic nitrification reactor, and a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0-2 V / cm. The organic load in the wastewater is controlled to 500-4000 mg / L and the ammonia nitrogen concentration is controlled to 100-400 mg / L to achieve wastewater treatment.

[0007] In some embodiments of the invention, the acclimation comprises: The activated sludge was centrifugally washed and added to the aerobic nitrification reactor with water at a volume ratio of 3:7. Carbon source and nitrogen source were added. A voltage was applied outside the aerobic nitrification reactor to form an electrostatic field of 0-2 V / cm, and the reactor was acclimated for 6-7 days.

[0008] In some embodiments of the present invention, after the sludge is acclimated, the acclimated sludge is poured out and mixed to clean the aerobic nitrification reactor. After cleaning, the acclimated sludge and wastewater are added in a volume ratio of 1:3.8-4.2 to treat the wastewater.

[0009] 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.

[0010] In some embodiments of the present invention, the carbon source comprises at least one of glucose, sodium acetate, methanol, citric acid, propionic acid, potassium bicarbonate, calcium carbonate and sodium carbonate.

[0011] In some embodiments of the present invention, the nitrogen source comprises ammonium chloride.

[0012] In some embodiments of the present invention, the method for preparing the insulated electrode includes: Carbon nanotubes, nickel chloride, and polytetrafluoroethylene are dissolved in an ethanol aqueous solution, heated, rolled onto a titanium mesh, and dried to obtain a pre-electrode; The pre-electrode is subjected to hydrophilic treatment to obtain a polarized electrode; A waterproof material is coated on the outer surface of the polarized electrode to form a waterproof layer to obtain an insulating electrode.

[0013] In some embodiments of the present invention, a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0.5-1 V / cm, and the organic load in the wastewater is controlled to be 1000-4000 mg / L and the ammonia nitrogen concentration is controlled to be 100-200 mg / L.

[0014] 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, and the organic load in the wastewater is controlled to be 4000 mg / L and the ammonia nitrogen concentration is controlled to be 200 mg / L.

[0015] 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.

[0016] The beneficial effects of the present invention are: The present 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 has a positive impact on the physiological characteristics of heterotrophic nitrifying bacteria. This breaks through the rate-limiting step in the traditional activated sludge process, improves the rate and efficiency of denitrification, and makes the oxidation process of ammonia nitrogen more rapid and thorough, converting ammonia nitrogen into end products such as nitrate nitrogen in a shorter time, thereby improving the treatment capacity of the entire denitrification system. Furthermore, the presence of the electrostatic field can selectively enrich microbial flora with efficient nitrification capabilities. By adjusting the electric field intensity, organic load, and ammonia nitrogen concentration, the present invention achieves a synergistic effect, allowing aerobic nitrifying bacteria with stronger tolerance and adaptability to dominate the system and improve nitrification efficiency. Furthermore, the method provided by the present invention can also simultaneously remove pollutants and denitrify. The electric field can promote the oxidative decomposition of organic matter, allowing some difficult-to-degrade organic matter to be better treated, achieving the simultaneous removal of pollutants such as organic matter and ammonia nitrogen, and improving the overall effect of wastewater treatment. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The accompanying drawings, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0018] Figure 1 The structure of the reactor used in Example 1 of the present invention; Figure 2 The structure of the reactor used in Comparative Example 2 of the present invention; Figure 3 NH4 at different ammonia nitrogen concentrations in Examples 1 and 2 of the present invention + -N(a), NO2 - -N(b), NO3 - -N (c), TN (d), COD (e), pH (f) comparison chart; Figure 4 Comparison of denitrification in different electric fields in Example 1 and Comparative Example 2 of the present invention, where (a) is NH4 + -N, (b) is TN; Figure 5 Comparison of CV and EIS of the bulk solution at the initial and final stages of the experiment in Examples 1 and 2 of the present invention, where (a) is CV and (b) is EIS; Figure 6The relative abundance of microorganisms at the phylum (a), class (b), and genus (c) levels in different reactors in Examples 1 and 2 of the present invention, and the genus correlation coefficient heat map (d); Figure 7 This is a diagram of the denitrification mechanism of electric field enhanced ammonia nitrogen wastewater treatment in Examples 1, 2, 3, and 4 of the present invention. DETAILED DESCRIPTION

[0019] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0020] The present invention provides a wastewater treatment method using electrostatic field coupled aerobic nitrification, comprising: Acclimated sludge, wastewater and insulated electrodes are added to the aerobic nitrification reactor, and a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0-2 V / cm. The organic load in the wastewater is controlled to 500-4000 mg / L and the ammonia nitrogen concentration is controlled to 100-400 mg / L to achieve wastewater treatment.

[0021] Since the traditional biological denitrification process has many shortcomings, these defects result in the inability to achieve the expected results using traditional biological denitrification technology. Moreover, the nitrifying bacteria and denitrifying bacteria in the biological denitrification technology are extremely sensitive to the environment in which they are located, which often causes instability in the operation of the aerobic nitrification reaction. Therefore, in response to the various problems existing in the traditional aerobic nitrification denitrification process, the present invention takes the potential improvement factors of the traditional aerobic nitrification denitrification and phosphorus removal process as the starting point, attempts to introduce a low-voltage electrostatic field, and uses the advantages and characteristics of the electric field to enhance the stability of the reaction system, improve the processing performance of the entire biological denitrification system, and provide a new idea and method for solving the difficult problems of the traditional biological denitrification process.

[0022] Based on this, the present invention introduces a low-voltage electric field into the activated sludge aerobic nitrification reactor, deeply couples the aerobic nitrification process and electric field catalysis technology, and uses the unique stimulation of the electrostatic field to stimulate the growth of heterotrophic nitrifying bacteria, and has a positive impact on the physiological characteristics of heterotrophic nitrifying bacteria, breaking through the rate-limiting step in the traditional activated sludge process and improving the rate and efficiency of denitrification. At the same time, in the newly constructed system, electroactive bacteria can also be used to further promote the denitrification process, promoting the smooth progress of the denitrification process in an all-round way. Since the problem of superimposed inhibition of organic matter and ammonia nitrogen loads often occurs in the aerobic nitrification process, the present invention also explores and analyzes the effect of the addition of a low-voltage electric field on the removal efficiency of chemical oxygen demand (COD), providing a theoretical and experimental basis for improving the stability of aerobic nitrification of ammonia nitrogen wastewater. Furthermore, establishing a rational population structure under aerobic conditions and promoting symbiotic metabolism between electroactive bacteria and heterotrophic bacteria, nitrifying bacteria, and denitrifying bacteria are crucial for achieving rapid degradation of ammonia-nitrogen wastewater. Therefore, this study 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 pathways in the electric field-coupled activated sludge process, and explore the connection between the biological community, electron transfer, and substrate decomposition. It can be understood that the aerobic nitrification reactor of the present invention is a commonly used aerobic nitrification reactor in the art, and can 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 lid: an aeration port, a sampling port, and a normally open gas outlet. The aeration port is externally connected to an air pump and internally to an air stone at the bottom of the reactor. Electrodes are placed inside the reactor, one end of which is connected to a DC power supply via a titanium wire passing through the reactor lid.

[0023] The present invention does not impose any specific requirements on the wastewater treatment time, as long as efficient removal of ammonia nitrogen from ammonia nitrogen 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, and for more complete aerobic nitrification, the treatment time is set to 7 days.

[0024] In some embodiments of the invention, the acclimation comprises: The activated sludge was centrifugally washed and added to the aerobic nitrification reactor with water at a volume ratio of 3:7. Carbon source and nitrogen source were added. A voltage was applied outside the aerobic nitrification reactor to form an electrostatic field of 0-2 V / cm, and the reactor was acclimated for 6-7 days.

[0025] In some embodiments of the present invention, after the sludge is acclimated, in order to ensure uniform distribution of subsequent microorganisms, the acclimated sludge is poured out and mixed, and the aerobic nitrification reactor is cleaned and impurities are removed. After cleaning, the acclimated sludge and wastewater are added in a volume ratio of 1:3.8-4.2 for wastewater treatment.

[0026] The poured sludge is allowed to stand, and the lower layer of sediment is taken out and added into the cleaned aerobic nitrification reactor.

[0027] 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 source and nitrogen source can provide the nutrients required for microbial growth.

[0028] In some embodiments of the present invention, the carbon source comprises at least one of glucose, sodium acetate, methanol, citric acid, propionic acid, potassium bicarbonate, calcium carbonate and sodium carbonate.

[0029] In some embodiments of the present invention, the nitrogen source comprises ammonium chloride.

[0030] In some embodiments of the present invention, the method for preparing the insulated electrode includes: Carbon nanotubes, nickel chloride, and polytetrafluoroethylene are dissolved in an ethanol aqueous solution, heated, rolled onto a titanium mesh, and dried to obtain a pre-electrode; The pre-electrode is subjected to hydrophilic treatment to obtain a polarized electrode; A waterproof material is coated on the outer surface of the polarized electrode to form a waterproof layer to obtain an insulating electrode.

[0031] Specifically, the method for preparing the insulating electrode includes: Soak the carbon nanotubes in concentrated nitric acid for 20-25 hours and then wash them until they are neutral. Dissolve the washed carbon nanotubes, nickel chloride, and polytetrafluoroethylene in an ethanol aqueous solution and heat to obtain a paste-like liquid. The paste liquid is rolled onto a titanium mesh and dried to obtain a pre-electrode; Immersing the pre-electrode in an aqueous solution of sodium dodecyl sulfate for 20-25 h to further improve the hydrophilicity of the electrode to obtain a polarized electrode; The polarized electrode is dried and coated with a waterproof material such as epoxy resin on the outer surface, and allowed to stand to form a waterproof layer to obtain an insulating electrode.

[0032] The insulated electrodes of the present invention are not wound around the outer wall of the aerobic nitrification reactor. Instead, the electrodes are added to the interior of the aerobic nitrification reactor to provide a uniform electrostatic field. Compared to not installing electrodes in the reactor, installing polarized electrodes to provide an electrostatic field accelerates the treatment of ammonia nitrogen wastewater. This may be because the titanium, nickel, and carbon elements in the electrodes contact each other or form a tiny galvanic cell with the wastewater. In this process, the more active metal (such as nickel) acts as the anode and is corroded to produce metal ions. A reduction reaction occurs on the surface of the cathode (such as carbon), such as reducing the 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, the present invention coats the polarized electrodes with epoxy resin to form an insulating layer. Testing has shown that the treatment effects of the insulated and polarized electrodes are not much different from those of the control. This is because the epoxy resin coated on the outer layer of the polarized electrode does not affect the formation of the electrostatic field, and can separate the wastewater and the electrode, avoiding the influence of the electrode on the wastewater. This also prevents the electrode from directly contacting the water after power is turned on, causing electrolysis reaction, saving energy and reducing unnecessary electricity loss.

[0033] In some embodiments of the present invention, the ratio of the washed carbon nanotubes to nickel chloride, polytetrafluoroethylene and ethanol aqueous solution is (3-5 g): (0.2-0.3 g): (0.4-0.6 g): (140-160 mL).

[0034] In some embodiments of the present invention, the concentration of ethanol in the ethanol aqueous solution is 75-85%.

[0035] In some embodiments of the present invention, the concentration of sodium lauryl sulfate in the sodium lauryl sulfate aqueous solution is 0.5-1.5%.

[0036] In some embodiments of the present invention, a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0.5-1 V / cm, and the organic load in the wastewater is controlled to be 1000-4000 mg / L and the ammonia nitrogen concentration is controlled to be 100-200 mg / L.

[0037] 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, and the organic load in the wastewater is controlled to be 4000 mg / L and the ammonia nitrogen concentration is controlled to be 200 mg / L.

[0038] Specifically, the electrostatic field strength has a decisive influence on the treatment effect of ammonia nitrogen wastewater. Among them, the electrostatic field of 0.5 V / cm shows the best performance. This intensity of electrostatic field can significantly stimulate the electron transfer process of microorganisms, greatly enhancing the denitrification metabolic pathway of microorganisms. Through the analysis of microbial communities, it was found that key electroactive bacteria Thauera and Limnobacter Effective enrichment, especially Thauera In this process, NH4 + The system achieves a maximum -N removal efficiency of 99.9%, effectively promoting the decomposition of nitrogen-containing compounds and significantly improving the treatment efficiency of ammonia-nitrogen wastewater. Variations in organic carbon source concentration significantly affect the degradation of ammonia-nitrogen wastewater. When the organic carbon source concentration is optimal (500-4000 mg / L), the microorganisms receive sufficient energy and material supply, promoting synergistic interactions among the microorganisms and significantly improving the system's treatment efficiency for ammonia-nitrogen wastewater.

[0039] Organic carbon source is an important nutrient for microbial growth, and reasonable control of its concentration is crucial to optimizing the treatment performance of the electric field coupled activated sludge system. Exiguobucterium and Pseudofulvimonas It provides favorable conditions for the growth and reproduction of bacteria such as nitrifying bacteria, denitrifying bacteria and electroactive bacteria, forming a mutually promoting relationship. This synergistic effect greatly improves the system's ability to decompose nitrogenous compounds and organic matter. + The -N removal rate reached 99.9%, the TN removal rate reached 58.7%, and the COD removal rate reached 96.3%. This fully demonstrates the importance of a suitable carbon-nitrogen ratio and the synergistic effect between microbial communities in improving wastewater treatment efficiency in the electric field coupled activated sludge system.

[0040] The influence of ammonia nitrogen concentration on the aerobic nitrification efficiency of ammonia nitrogen wastewater shows an obvious dual effect. When the ammonia nitrogen concentration reaches 200 mg / L, the treatment effect reaches the best state. At this time, NH4 + The removal rate of -N reached 99.9%, the removal rate of TN reached 65.1%, and the removal rate of COD reached 94.1%. At low ammonia nitrogen concentrations, the electric field can enhance the nitrifying bacteria's ability to absorb limited substrates and improve their substrate affinity, allowing nitrifying bacteria to utilize ammonia nitrogen more efficiently and maintain good nitrification activity. At high ammonia nitrogen concentrations, the electric field helps alleviate the toxic inhibitory effect of free ammonia produced by high ammonia nitrogen concentrations on nitrifying bacteria, ensuring the normal physiological metabolism and growth and reproduction of nitrifying bacteria, thereby maintaining a high nitrification efficiency.

[0041] 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.

[0042] In order to enable those skilled in the art to more clearly 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.

[0043] The raw materials and equipment used in the present invention are all conventional commercially available products and can be purchased.

[0044] The construction method of the electrodes used in the following experiments includes the following steps: The anode and cathode of the electrode are constructed by coating the surface of a titanium mesh with carbon nanotubes (CNTs).

[0045] First, the CNTs were pretreated in concentrated nitric acid (HNO3) solution for 24 hours to remove impurities. The pretreated CNTs were then washed in tap water for more than 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 of 150 mL of ethanol (ethanol concentration was 80%). The beaker was placed in a water bath and heated 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 the remaining ethanol. By immersing the electrode in 1% sodium dodecyl sulfate (C 12 H 25 The electrode is then placed in a NaO₄S solution for 24 hours to further increase its hydrophilicity, creating a polarized electrode. The resulting polarized electrode is then dried and coated with epoxy resin. The epoxy resin is then repeatedly applied to the electrode. The electrode is then allowed to stand until the resin adheres to the electrode and hardens, completing the insulated electrode.

[0046] The following methods are used for analysis and calculation in the following experiments: (1) The voltage applied by the DC power supply during the reaction can be Converted to electrostatic field strength, U is the applied voltage (V) and d is the distance between the insulating electrodes (cm).

[0047] (2) The ammonia nitrogen (ammonium nitrogen) content in the bulk solution was determined using the national standard method (Nessler's reagent spectrophotometry).

[0048] The national standard method (spectrophotometry) was used to determine the nitrite nitrogen content in the bulk solution.

[0049] The national standard method (ultraviolet spectrophotometer method) was used to determine the nitrate nitrogen content in the bulk solution.

[0050] The total nitrogen content was calculated by adding nitrate nitrogen, nitrite nitrogen and ammonium nitrogen to total nitrogen.

[0051] The COD of the bulk solution was determined using the national standard potassium dichromate method.

[0052] The TS and VS of the bulk solution were measured gravimetrically.

[0053] (3) Electrochemical analysis At the end of the experiment, cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) measurements were performed in bulk solution using an electrochemical workstation (CHI1000C, China).

[0054] Cyclic voltammetry (CV) measurements were performed using a three-electrode system consisting of titanium mesh as the working and counter electrodes and Ag / AgCl as the reference electrode. CV scans were performed for 10 cycles at a rate of 50 mV / s in the range of -1 V to 1 V. CV curves were plotted to obtain the redox current peak and potential peak values. Electrochemical impedance spectroscopy (EIS) measurements were performed in the frequency range of 104 Hz to 106 Hz. Equivalent current diagrams were fitted using Zsimpwin software to obtain the internal resistance and charge transfer resistance of the solution. EIS point-line plots were then generated using Origin 2025 software.

[0055] Electrochemical impedance spectroscopy (EIS) measurements were performed under open-circuit conditions using an AC impedance spectrum ranging from 100 kHz to 10 MHz. Raw EIS data were analyzed using ZSimDemo software and fitted using a Randles equivalent circuit. This equivalent circuit uses a double-layer capacitor in series with a solution resistor, and consists of a capacitor in parallel with a charge transfer resistor, and a Warburg element and a Farage reaction impedance in series. The processed data were analyzed using Origin software.

[0056] (4) Microbial community analysis After the experiment, the bulk solution samples were stored in a -20°C freezer and high-throughput sequencing was performed to analyze changes in the microbial community. High-throughput sequencing was performed using the Illumina platform (Illumina Miseq PE300) using PCR amplification products of the 16S rRNA hypervariable region (V3-V4) of standard bacteria in the individual fluids. The diversity of the microbial community in this environment, including taxonomic and abundance information, was analyzed. 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.

[0057] Example 1 A wastewater treatment method using electrostatic field coupled aerobic nitrification, comprising: (1) Preparation of artificial ammonia nitrogen wastewater: Anhydrous sodium acetate (CH3COONa) and potassium bicarbonate (KHCO3) were used as carbon sources, and ammonium chloride (NH4Cl) was used as the 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 compositions of the artificial wastewater and trace element solutions are shown in Tables 1 and 2. The composition of the artificial ammonia wastewater is shown in Table 3.

[0058] The ammonia nitrogen concentration in the configured artificial ammonia nitrogen wastewater is 200 mg / L.

[0059] Table 1 Trace element I culture medium ratio

[0060] Table 2 Proportions of trace element II culture medium

[0061] Table 3 Properties of ammonia nitrogen wastewater, activated sludge and mixed liquor

[0062] (2) Acclimation of activated sludge and reactor operation: Activated sludge was collected from the secondary sedimentation tank of a reclaimed water treatment plant at an industrial university. After 24 hours of sludge sludge sludge was collected and allowed to settle. The supernatant was then decanted, the suspended solids removed, and large impurities were removed by sieving (0.5 mm sieve opening). The sieved homogenized sludge was incubated in a laboratory aeration thermostat with regular carbon and nitrogen source supplementation to maintain sludge activity. Before each experimental run, a fixed amount of sludge was collected, centrifuged at 6000 rpm for 5 minutes, and washed two to three times with deionized water.

[0063] Add activated sludge deionized water at a volume ratio of 3:7 Figure 1 Activated sludge was acclimated in the reactors shown. After 7 days of incubation, the activated sludge was poured out and the reactors were cleaned. The poured activated sludge was allowed to settle, and 50 mL of the lower sediment was added to each reactor. The volume ratio of ammonia nitrogen wastewater to activated sludge was 4:1.

[0064] The reactor was placed on a hot plate to maintain the internal temperature at 35 ± 1°C. Electrodes were installed at opposing positions within the reactor at intervals of 2 cm. A voltage was applied to generate an electrostatic field with an electrostatic strength of 0.5 V / cm. The reactor inlet volume was adjusted to 0.15 L / min by adjusting the rotameter. The reactor was operated for 7 days. Three cycles were performed to ensure data validity.

[0065] Example 2 A wastewater treatment method using electrostatic field coupled aerobic nitrification differs from Example 1 in that the artificial ammonia nitrogen wastewater used has ammonia nitrogen concentrations of 0, 100, 400, 800, and 1600 mg / L. The remaining steps are identical to those of Example 1.

[0066] Comparative Example 1 A method for treating wastewater by static aerobic nitrification differs from Example 1 in that the artificial ammonia nitrogen wastewater is prepared with ammonia nitrogen concentrations of 0, 100, 200, 400, 800, and 1600 mg / L, but no electrostatic field is applied. The remaining steps are identical to those of Example 1.

[0067] Comparative Example 2 A wastewater treatment method for electrostatic field coupled aerobic nitrification is different from Example 1 in that a coil electric field is used to apply an electric field to the aerobic nitrification reactor. The coil electric field structure is as follows Figure 2 shown.

[0068] Analysis of the wastewater treatment methods of Examples 1 and 2 and Comparative Examples 1 and 2 (1) Effect of ammonia nitrogen concentration on aerobic nitrification efficiency of ammonia nitrogen wastewater Table 4 Comparison of degradation of wastewater with different ammonia nitrogen concentrations

[0069] From Table 4 and Figure 3 As can be seen from Figure (a), NH4 + The -N removal rate varied significantly with ammonia nitrogen concentration, as expressed by the coefficient R. At 1600 mg / L, the removal rate was low (0.99 ± 0.01). However, when the ammonia nitrogen concentration decreased to 200 mg / L, the removal rate continued to increase, reaching the highest observed value of 1.07 ± 0.02. This suggests that excessive 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 forward reaction and thus reducing the ammonia nitrogen removal rate. Regarding microorganisms, excessive ammonia nitrogen concentrations may inhibit microbial activity. On the one hand, high ammonia nitrogen concentrations alter the osmotic pressure inside and outside microbial cells, leading to cell dehydration and affecting normal physiological functions. On the other hand, certain forms of ammonia nitrogen (such as free ammonia) may be toxic to microbial enzyme systems, inhibiting the activity of key enzymes in microbial metabolism and thus reducing the microbial ability to degrade ammonia nitrogen.

[0070] When the ammonia nitrogen concentration is less than 200 mg / L, NH4 + -N removal rate decreased. This may be because the decrease in ammonia nitrogen concentration will lead to a decrease in the concentration gradient of the reaction system. According to the principles of chemical reaction kinetics, this will weaken the driving force of the reaction, reduce the reaction rate, and ultimately lead to a decrease in ammonia nitrogen removal rate.

[0071] The experimental groups (EFAR, i.e., Examples 1 and 2) were compared with the control group (CR, i.e., Comparative Example 1) without the application of an electric field. The pollutant removal efficiency of the experimental groups (EFAR, i.e., Examples 1 and 2) was improved after the application of the electric field. Among the six experimental groups using different ammonia nitrogen concentrations, the group with an ammonia nitrogen concentration of 100 mg / L had the best organic matter degradation effect, with a removal efficiency of 94.3±1.2% (Table 4), followed by the group with an ammonia nitrogen concentration of 400 mg / L (94.3±0.8%) and the group with an ammonia nitrogen concentration of 200 mg / L (94.1±0.9%). +-N removal rate reached 99.9%, but the 200 mg / L group NH4 + The highest ammonia nitrogen removal efficiency was 1.07 ± 0.02. Among the experimental groups, the lowest pollutant degradation efficiency was in the 1600 mg / L group, with a COD removal rate of only 47.7 ± 1.7%. This may be because the high ammonia nitrogen concentration affects the microbial community and pollutant metabolism.

[0072] Figure 3 Figures (b) and (c) show NO2 - -N and NO3 - -N concentration changes with time and different ammonia nitrogen concentrations. NO2 at lower ammonia nitrogen concentrations - The reduction rate of -N was faster than that at higher ammonia nitrogen concentrations, indicating that the appropriate ammonia nitrogen concentration is conducive to 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.

[0073] The COD degradation curve of the bulk solution during the reaction is as follows: Figure 2 As shown in Figure (e), the degradation effect and rate are optimal at an ammonia nitrogen concentration of 200 mg / L. However, as the ammonia nitrogen concentration increases, the COD degradation effect decreases. This may be because excessive ammonia nitrogen concentration inhibits the growth of certain microorganisms, resulting in a slower COD degradation rate.

[0074] Figure 3 The pH value in Figure (f) generally shows a trend of first increasing and then decreasing. This is likely due to the fact that, under the action of an electric field, at the beginning of the aerobic nitrification process, microorganisms such as ammonia-oxidizing bacteria first utilize ammonia nitrogen in the water for metabolic activities. The oxidation of ammonia nitrogen to nitrite nitrogen consumes a certain amount of hydrogen ions, resulting in a relative excess of hydroxide ions in the solution, which in turn causes the pH to rise. Initially, the microorganisms consume hydrogen ions at a relatively rapid rate, resulting in a decrease in hydrogen ions in the system and an increase in pH. The subsequent decrease in pH is likely due to the continued oxidation of nitrite nitrogen to nitrate nitrogen. As the reaction proceeds, alkalinity is continuously consumed and hydrogen ions are produced, leading to a gradual decrease in pH. As the reaction proceeds, acidic substances produced by microbial metabolism, such as carbon dioxide, may also accumulate in the system. Carbon dioxide dissolves in water to form carbonic acid, which increases the acidity of the solution and decreases the pH.

[0075] The results of Examples 1, 2 and Comparative Example 1 show that the degradation of ammonia nitrogen in wastewater can be significantly enhanced by changing the ammonia nitrogen concentration, wherein the removal of NH4 +-N was most effective. At this intensity, the improvement in nitrogen removal efficiency indicated that moderate ammonia nitrogen concentrations stimulated microbial activity and promoted the nitrification-denitrification process. However, at higher ammonia nitrogen concentrations, NH4 + The removal efficiency of -N was reduced, which may be due to the inhibitory effect of excessive ammonia nitrogen on microbial growth and metabolism.

[0076] (2) Comparison of denitrification rates of ammonia nitrogen wastewater by coil electric field and electrode electric field like Figure 4 As shown in Figure (a), the removal effect of ammonia nitrogen is greatly affected by the electric field. After the electric field is applied, the denitrification rate of ammonia nitrogen is greatly improved, but the difference between the electrode electric field and the coil electric field has little effect on the removal of ammonia nitrogen.

[0077] Figure 4 Figure (b) shows the total nitrogen removal effect. The application of the electric field significantly improved the TN removal effect, but the coil electric field remained significantly lower than the electrode electric field. This may be because the electric field strength generated by the coil decays rapidly with increasing distance from the coil. The varying distances from the coil at different locations within the reactor lead to significant variations in electric field strength and poor field uniformity. This uneven electric field can cause the electric field strength to be too low in some areas within the reactor, effectively failing to promote denitrification. Alternatively, the electric field strength may be too high in other areas, potentially adversely affecting microbial or chemical reactions. The electric field generated by the electrode is relatively uniform within a specific area near the electrode. This relatively uniform and moderately strong electric field provides a more stable and favorable environment for denitrification, thereby improving denitrification efficiency. The electric field generated by the coil exerts a relatively weak force on ions, and its direction and magnitude vary complexly with position. This hinders the directional migration of ions and thus affects the denitrification reaction. The electric field generated by the electrode can produce a strong electrostatic field, which has a clear directional force on the ions, effectively promoting the migration of ammonia nitrogen to the anode and the migration of 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.

[0078] (3) Effect of changes in ammonia nitrogen gradient on electrochemical analysis of bulk solution observe Figure 5In the cyclic voltammetry curves in Figure (a), significant reduction and oxidation peaks are clearly observed in the initial reaction phase. This is likely due to the presence of pollutants such as ammonia nitrogen in the initial solution. Under the influence of the electric field, these pollutants undergo redox reactions on the electrode surface, resulting in a significant current response. At the end of the reaction, the reduction and oxidation peaks are particularly prominent in the bulk solution of the reactor with an ammonia nitrogen concentration of 1600 mg / L. This may be due to the excessively high ammonia nitrogen concentration inhibiting the removal of other pollutants. Excessive ammonia nitrogen may occupy active sites on the electrode surface, hindering effective contact between other pollutants and the electrode, making it difficult for other pollutants to undergo redox reactions on the electrode surface, thereby affecting their removal. In contrast, no significant reduction and oxidation peaks were detected in the other reactors, likely because the ammonia nitrogen concentration was within an appropriate range, creating favorable conditions for the removal of other pollutants. A moderate amount of ammonia nitrogen can participate in the redox reaction network on the electrode surface, promoting electron transfer and enabling other pollutants to undergo redox reactions smoothly on the electrode surface, leading to their substantial removal.

[0079] Electrochemical impedance spectroscopy of different reactors Figure 5 Analysis of Figure (b) shows that the reactors with ammonia nitrogen concentrations of 0 mg / L and 1600 mg / L have higher charge transfer resistance, which further supports the experimental results of low reaction activity and poor pollutant removal efficiency.

[0080] As shown in Table 5, the carbon-nitrogen ratio significantly affected key electrochemical parameters such as ohmic resistance (Rs), charge transfer resistance (Rct), capacitance, and Warburg impedance. The ohmic resistance (Rs, 22.53 Ω) was highest at an ammonia nitrogen concentration of 100 mg / L, followed by that at 200 mg / L (Rs, 19.87 Ω). The charge transfer resistance (0.014 kΩ) was lowest at 200 mg / L. This suggests that increasing ammonia nitrogen concentration increases the total resistance of the solution and, at appropriate ammonia nitrogen concentrations, enhances the electron transfer process of the microorganisms.

[0081] Table 5 EIS analysis indicators of bulk solutions in different reactors at the beginning and end of the experiment

[0082] At higher ammonia nitrogen concentrations, such as 1600 mg / L, the Rs value (14.33 Ω) was significantly lower than that of the other groups, while the charge transfer resistance (0.071 kΩ) was higher. This increase in Rs may be due to the fact that high ammonia nitrogen concentrations promote microbial growth, but excessive ammonia nitrogen concentrations, on the other hand, inhibit microbial electron transfer. Warburg impedance measurements show that the system's electron transfer efficiency increases with increasing ammonia nitrogen concentrations at low concentrations, but decreases when the concentration exceeds 400 mg / L. This indicates that excessively high or low ammonia nitrogen concentrations inhibit microbial growth and electron transfer, leading to reduced reactor performance.

[0083] (4) Effects of changes in ammonia nitrogen gradient on bulk solution microbial community analysis In the experiment, three pairs of different reactors (ammonia nitrogen concentrations of 100 mg / L, 400 mg / L, and 1600 mg / L) were selected for microbial analysis.

[0084] exist Figure 6 When an electrostatic field was applied, the dominant bacterial genus ( Thauera ) increased significantly in relative abundance. Thauera genus, which became the most enriched genus after application of the electrostatic field. Thauera is a well-known electroactive microorganism capable of external electron transfer (EET), which enhances its ability to degrade NH4 under electrochemical conditions. + -N capability. This genus is often associated with the process of denitrification, in which it reduces nitrates and nitrites to nitrogen gas, thus completing the nitrogen cycle in wastewater treatment systems. Thauera The high relative abundance of NH4 + -N degradation. Under the electric field, Thauera The enriched microbial community dominated by + The efficient conversion of -N further supports the idea that electrostatic fields promote nitrogen removal by enhancing electron transfer between key microbial groups.

[0085] Electroactive bacteria such as Thauera The enrichment under the electrostatic field can be attributed to several factors. First, the application field may enhance the microbial EET process, allowing 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 the electrostatic field promotes its occurrence, creating a favorable environment for electron movement. This increases NH4 + Secondly, electrostatic fields 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 required for denitrification. Thauera Plays a central role in the nitrogen cycle, especially under electrochemical conditions where electron transfer is enhanced. Thauera The ability to switch between aerobic and anaerobic metabolic pathways enables it to thrive under the dynamic redox conditions induced by the electrostatic field, explaining its dominance in the microbial community under these conditions. Thauera Enrichment of Isoelectrically Active Bacteria and NH4 + The enhanced electron transfer rate promoted by the electrostatic field may have accelerated these processes, leading to a higher overall denitrification efficiency.

[0086] Interestingly, at higher ammonia nitrogen concentrations (1600 mg / L), the relative abundance of electroactive bacteria decreased. This suggests that excessive ammonia nitrogen concentrations may inhibit microbial growth and reproduction. This may be due to the existence of an osmotic pressure balance between microbial cells and the surrounding environment. When the external ammonia nitrogen concentration is too high, the extracellular osmotic pressure increases significantly, thereby inhibiting the growth and reproduction of microorganisms. In addition, in a high ammonia nitrogen environment, microorganisms need to consume more energy to cope with the toxicity of ammonia nitrogen, thereby reducing the energy available for the uptake of other nutrients and metabolic activities. At the same time, excessively high ammonia nitrogen concentrations may, to a certain extent, affect the microbial absorption and utilization of other essential nutrients such as carbon and phosphorus sources, leading to insufficient nutrient supply and limiting microbial growth and reproduction.

[0087] The application of electrostatic fields significantly enriched key electroactive bacterial genera, especially in NH4 + -N degradation plays a key role Thauera and Limnobacter These bacteria thrive under moderate electrostatic fields, and the electron transfer process is enhanced, leading to improved nitrogen removal efficiency. The results show that when the electrostatic field strength is 0.5 V / cm, NH4 + The degradation rate of -N was the highest. However, higher electric field strength may inhibit microbial activity, which highlights the importance of optimizing electrostatic field conditions for efficient wastewater treatment.

[0088] (5) Effect of ammonia nitrogen gradient changes on bulk solution metabolic pathway analysis 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 +-N degradation. By comparing the metabolic pathways under different ammonia nitrogen concentrations, it was found that the abundance of key microbial metabolic pathways (such as GLUCOSE1PMETAB-PWY and LEU-DEG2-PWY) increased under the influence of the electrostatic field. The PWY-5420 pathway related to the degradation of aromatic compounds had 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 important for the decomposition of complex organic molecules and the subsequent degradation of nitrogen compounds (such as NH4 + -N) is crucial.

[0089] Comparison of metabolic pathways under different ammonia nitrogen concentrations across three gradients revealed that key microbial metabolic pathways and aromatic compound degradation pathways reached their peak activity at an ammonia nitrogen concentration of 400 mg / L. This is likely due to the fact that 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 optimal, meeting the needs of microbial growth and metabolism, enabling efficient metabolic activities for synthesizing cellular substances and obtaining energy. If ammonia nitrogen concentration is too low, it becomes a limiting factor for microbial growth, leading to decreased metabolic pathway activity. However, if ammonia nitrogen concentration is too high, the nutrient balance may be disrupted, and microorganisms may divert excessive energy to cope with ammonia nitrogen toxicity or adjust their metabolism to adapt to the high ammonia nitrogen environment, thereby impacting other normal metabolic pathways. The increase in the 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 enhanced the utilization of carbon sources by microorganisms, which are necessary for microbial growth and activity. Increases or decreases in ammonia nitrogen concentrations directly affect the NH4 + -N degradation.

[0090] LEU-DEG2-PWY is the main redox pathway in the reaction. This pathway is greatly enhanced under the action of the electric field. In the denitrification process of electric field-coupled aerobic nitrification, redox is mainly achieved through several key pathways: Ammonia oxidation to nitrite Under aerobic conditions, nitrifying bacteria first oxidize ammonia nitrogen to hydroxylamine. This process requires the participation of oxygen and consumes ATP. The generated hydroxylamine is further oxidized to nitrite by hydroxylamine oxidoreductase, and nitrite is oxidized to nitrate by nitrite oxidoreductase. This process is an important oxidation step in denitrification, which helps to convert nitrogen into a form that is easier to remove. Finally, under the action of the electric field, denitrifying bacteria use organic carbon sources as electron donors to gradually reduce nitrate to nitrogen gas.

[0091] However, at higher ammonia nitrogen concentrations, such as 1600 mg / L, the abundance of these pathways decreased. For example, the abundance of the PWY-5420 pathway dropped to 1176.76, and the abundance of the GLUCOSE1PMETAB-PWY pathway also dropped to 630.595. This decrease in pathway activity may be due to the inhibitory effect of excessive ammonia nitrogen concentrations. High concentrations of ammonia nitrogen may damage cell structure, inhibit enzyme activity, interfere with metabolic processes, and affect microbial communities, inhibiting the growth of other microorganisms that coexist with nitrifying bacteria, thereby affecting the growth and metabolism of nitrifying bacteria. These metabolic pathways form a complex network, in which enzymes and proteins work together to regulate and promote various metabolic activities between and within microorganisms, maintaining microbial growth and reproduction.

[0092] Ammonia nitrogen concentration is also a key factor in improving the microbial denitrification pathway and NH4 + -N degradation. Moderate ammonia nitrogen concentration significantly increases the abundance of metabolic pathways such as carbon utilization, aromatic compound degradation and redox reactions, thereby improving nitrogen removal efficiency. However, too high or too low electric field strength may inhibit the activity of microorganisms, which highlights the importance of optimizing ammonia nitrogen concentration conditions to obtain maximum NH4 + Importance of -N removal efficiency.

[0093] Table 6 Comparison of microbial abundance in metabolic pathways of different reactors

[0094] Example 3 A wastewater treatment method using electrostatic field-coupled aerobic nitrification differs from Example 1 in that the properties of the artificial ammonia nitrogen wastewater used are shown in Table 7. To investigate the effect of varying organic loadings on the aerobic nitrification efficiency of ammonia nitrogen wastewater, the COD concentrations in the artificial ammonia nitrogen wastewater used were 0, 500, 1000, 2000, 4000, and 8000 mg / L, respectively. The remaining steps were identical to those in Example 1.

[0095] Table 7 Properties of artificial ammonia nitrogen wastewater and activated sludge

[0096] Comparative Example 2 A wastewater treatment method using aerobic nitrification differs from Example 3 in that no electrostatic field is applied. The remaining steps are identical to those of Example 3.

[0097] Analysis of the wastewater treatment methods of Example 3 and Comparative Example 2 (1) Effect of organic load changes on the efficiency of aerobic nitrification of ammonia nitrogen wastewater enhanced by electric field As shown in Table 8, the degradation efficiency and rate of the experimental group for ammonium nitrogen, nitrate nitrogen, total nitrogen, and COD were significantly superior to those of the control group. The degradation efficiency of ammonia nitrogen and total nitrogen in the experimental group was highest at a COD concentration of 4000 mg / L. Under carbon-free conditions (COD = 0 mg / L), the degradation efficiency of ammonia nitrogen was significantly enhanced. These findings highlight the potential of electric field stimulation to optimize denitrification processes.

[0098] The change of organic load has a significant impact on the treatment efficiency of ammonia nitrogen wastewater. When the organic load reaches 4000 mg / L, the treatment effect reaches the best state. Under the optimal organic load (4000 mg / L), the TN removal rate increased by 16.1% and the COD removal rate increased by 7.1% compared with the control group without voltage application. By applying an electric field, the electron transfer process of microorganisms can be effectively stimulated, and key electroactive bacteria can be enriched at the same time. Thauera The performance is particularly outstanding. High levels of chemical oxygen demand (COD) are Exiguobucterium and Pseudofulvimonas It provides favorable conditions for the growth and reproduction of heterotrophic bacteria, which form a mutually promoting relationship with nitrifying bacteria, denitrifying bacteria and electroactive bacteria, making ammonia nitrogen (NH4 + The removal rates for N-nitrogen (NH4+), TN (N-nitrogen) and COD (COD) reached 99.9%, 58.7%, and 96.3%, respectively. These bacteria effectively promoted the decomposition of nitrogenous compounds and organic matter by enhancing nitrification and denitrification. Furthermore, the experimental results demonstrated that electric fields play a positive role in wastewater treatment. Compared to the control group, treatment efficacy was significantly improved under the electrostatic field for both organic and inorganic ammonia nitrogen-containing wastewater. Therefore, integrating electrostatic field technology into existing wastewater treatment processes offers significant advantages.

[0099] Table 8 Degradation of ammonia nitrogen in wastewater under different organic loading conditions

[0100] (2) Effect of organic load changes on electrochemical analysis of bulk solution As shown in Table 9, at higher organic loadings, such as 2000 mg / L and 4000 mg / L, the Rs values ​​(20.3Ω and 20.05 Ω, respectively) were significantly lower than those in the other groups, correspondingly indicating improved microbial activity. This increase in Rs is likely due to the appropriate carbon-nitrogen ratio enabling microbial growth. Warburg impedance data show that the system's electron transfer efficiency increases with increasing organic loading (9.407 1 / Ω at a COD of 4000 mg / L). Interestingly, it decreases at a COD of 8000 mg / L (8.315 1 / Ω). This suggests that excessively high organic matter content inhibits microbial growth and electron transfer, leading to reduced reactor performance.

[0101] Table 9 EIS analysis indicators of bulk solutions in different reactors at the beginning and end of the experiment

[0102] Example 4 A wastewater treatment method of electrostatic field coupled aerobic nitrification is different from Example 1 in that the properties of the artificial ammonia nitrogen wastewater are shown in Table 10. In order to ensure the integrity of the experiment, an applied voltage of 12 V or more was explored. When the voltage exceeded 12 V, the plate and titanium wire were severely corroded. In order to ensure the stability of the reactor, a voltage below 12 V was selected for the test, and the applied voltages were 0 V, 1 V, 2 V, 4 V, 8 V and 12 V respectively. Calculations show that the electrostatic field intensities corresponding to applied voltages of 0 V, 1 V, 2 V, 4 V, 8 V, and 12 V are 0 V / cm, 0.5 V / cm, 1 V / cm, 2 V / cm, 4 V / cm, and 6 V / cm, respectively. The remaining steps are identical to those of Example 1.

[0103] Table 10 Properties of ammonia nitrogen wastewater, activated sludge and mixed liquor

[0104] Comparative Example 3 A wastewater treatment method using aerobic nitrification differs from Example 4 in that no electrostatic field is applied. The remaining steps are identical to those of Example 4.

[0105] Analysis of the wastewater treatment methods of Example 4 and Comparative Example 3 (1) Effect of electrostatic field intensity on ammonia nitrogen wastewater treatment efficiency NH4 + -N removal can be divided into three stages: initial NH4 + -N removal phase (0-2 days), followed by NO2- -N removal phase (1-4 days), and finally NO3 - -N generation phase (3-6 days). This sequential conversion of nitrogenous compounds demonstrates the classic nitrification process, in which NH4 + -N is first oxidized to NO2 - -N, which is then further oxidized to NO3 - -N. Experimental data show that the effect of electrostatic field significantly improves the first stage of the reaction to NH4 + The removal rate of -N reaches its peak at 0.5 V / cm.

[0106] Table 11 Degradation of ammonia nitrogen wastewater under different electrostatic field intensities

[0107] (2) Effect of changes in electrostatic field strength on electrochemical analysis of bulk solutions The combination of CV and EIS analysis showed that electrostatic field can effectively enhance the electron transfer of microorganisms, thereby improving NH4 + The researchers also found that electroactive microorganisms can thrive under optimized electrochemical conditions, where the electrostatic field promotes electron transfer between microbial species. The increased microbial activity under these conditions accelerates the nitrification process, allowing for faster ammonia removal.

[0108] Table 12 EIS analysis indicators of bulk solutions in different reactors at the beginning and end of the experiment

[0109] (3) Effect of changes in electrostatic field intensity on analysis of microbial communities in bulk solutions Electrostatic field significantly enhances the microbial denitrification metabolic pathway in ammonia nitrogen wastewater treatment. Applying an electrostatic field of 0.5 V / cm stimulates the electron transfer of microorganisms and enriches key electroactive bacteria, especially Thauera and Limnobacter , NH4 + The highest removal efficiency for -N was 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 requirements typically associated with aeration in traditional 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 varying wastewater conditions to maximize the benefits of electrostatic field-assisted nitrogen removal.

[0110] (4) Analysis of the mechanism of denitrification of ammonia nitrogen wastewater by electric field enhancement After the electric field is applied to the system, the electrostatic field can enhance the electron transfer process and thus improve the microbial nitrification and denitrification pathways in the wastewater treatment system ( Figure 7 Under moderate electrostatic fields, particularly those at 0.5 V / cm, the metabolic rate and removal rate of ammonia nitrogen and organic matter were significantly enhanced. This is because appropriate electric field stimulation can influence microbial activity. Microbial activity may be enhanced under the influence of the electric field, thereby accelerating the metabolism of ammonia nitrogen and facilitating its conversion to nitrites, nitrates, and other substances. Furthermore, some ammonia nitrogen is directly converted into hydrogen and removed under the influence of the electric field. The electric field may also alter the permeability of microbial cell membranes, facilitating the exchange of substances inside and outside the cells. This makes it easier for cells to absorb nutrients such as ammonia nitrogen in the wastewater, providing ample substrate for microbial growth and metabolism, thereby enhancing their denitrification capabilities. Electrostatic fields have varying effects on different microorganisms. Some electroactive, heterotrophic, and denitrifying microorganisms thrive in electric fields, thereby optimizing the microbial community structure. However, the growth and metabolism of other microorganisms, such as those not conducive to ammonia nitrogen removal, may be inhibited by the electric field, effectively improving the efficiency of the entire denitrification system.

[0111] The foregoing description is merely a preferred embodiment of the present invention and is not intended to limit the present invention. Those skilled in the art will readily appreciate that various modifications and variations of the present invention are possible. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present invention are intended to be within the scope of protection of the present invention.

Claims

1. A wastewater treatment method using electrostatic field coupled aerobic nitrification, characterized in that: include: Acclimated sludge, wastewater and insulated electrodes are added to the aerobic nitrification reactor, and a voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0-2 V / cm. The organic load in the wastewater is controlled to 500-4000 mg / L and the ammonia nitrogen concentration is controlled to 100-400 mg / L to achieve wastewater treatment.

2. The wastewater treatment method according to claim 1, wherein The domestication includes: The activated sludge was centrifugally washed and added to the aerobic nitrification reactor with water at a volume ratio of 3:

7. Carbon source and nitrogen source were added. A voltage was applied outside the aerobic nitrification reactor to form an electrostatic field of 0-2 V / cm, and the reactor was acclimated for 6-7 days.

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

4. The wastewater treatment method according to claim 2, wherein 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 according to claim 2, wherein: 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 according to claim 2, wherein: The nitrogen source includes ammonium chloride.

7. The wastewater treatment method according to claim 1, wherein The method for preparing the insulated electrode comprises: Carbon nanotubes, nickel chloride, and polytetrafluoroethylene are dissolved in an ethanol aqueous solution, heated, rolled onto a titanium mesh, and dried to obtain a pre-electrode; The pre-electrode is subjected to hydrophilic treatment to obtain a polarized electrode; A waterproof material is coated on the outer surface of the polarized electrode to form a waterproof layer to obtain an insulating electrode.

8. The wastewater treatment method according to claim 1, wherein A voltage is applied outside the aerobic nitrification reactor to form an electrostatic field of 0.5-1 V / cm, and the organic load in the wastewater is controlled to 1000-4000 mg / L and the ammonia nitrogen concentration to 100-200 mg / L.

9. The wastewater treatment method according to claim 8, wherein: A voltage was applied outside the aerobic nitrification reactor to form an electrostatic field of 0.5 V / cm, and the organic load in the wastewater was controlled at 4000 mg / L and the ammonia nitrogen concentration was controlled at 200 mg / L.

10. The wastewater treatment method according to claim 1, wherein 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.

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