Method for treating high-nitrogen phenol-containing wastewater by coupling microbial electrolysis cell with anaerobic ammonia oxidation

Abstract

The invention relates to a method for treating high-nitrogen phenolic wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation, which comprises the following steps: S1, constructing a microbial electrolysis cell reactor with a single reaction chamber, placing an anode and a cathode of the reactor in the same reaction chamber, and inoculating activated sludge containing anaerobic ammonia oxidation bacteria in the reactor; s2, performing toxicity domestication on the activated sludge; s3, high-nitrogen phenolic wastewater is introduced into the reactor, voltage is applied to the anode and the cathode through an adjustable direct-current stabilized power supply, and denitrification and phenol degradation are synchronously achieved through coupling of the microbial electrolysis cell and the anaerobic ammonia oxidation reaction. Compared with the prior art, the method has the advantages that the single-reaction-chamber microbial electrolytic tank is coupled with the anaerobic ammonium oxidation process, targeted phenol toxicity domestication is carried out on anaerobic ammonium oxidation bacterium activated sludge, and voltage is applied to enhance the microbial activity, so that high-nitrogen phenol-containing wastewater denitrification and phenol degradation are synchronously carried out, and an external carbon source and aeration are not needed; the domestication period is short, and the pollutant removal efficiency is high.

Description

Technical Field

[0001] This invention relates to the field of wastewater treatment technology, specifically to a method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation. Background Technology

[0002] Anammox is one of the most important discoveries in biological nitrogen removal and microbiology over the past 20 years. Nitrification-denitrification processes require significant energy consumption for oxygen during nitrification and additional organic carbon sources such as methanol during denitrification, placing a substantial economic burden on wastewater treatment plants. Compared to traditional nitrification-denitrification biological nitrogen removal processes, anammox is economical, energy-efficient, and environmentally friendly. It provides a more innovative and environmentally friendly nitrogen removal pathway. As chemoautotrophic microorganisms, anammox bacteria can directly oxidize NH4 under anaerobic conditions. + NO2 - As an electron acceptor, it does not require an external carbon source; in addition, it has lower oxygen consumption and produces less sludge.

[0003] Microbial electrolysis cells (MECs) are electrochemical systems in which electrochemically active microorganisms, facilitated by an external power source, bio-oxidize the reactor substrate and release electrons at the anode. These electrons then travel through an external circuit to the cathode, where they combine with electron acceptors involved in a reduction reaction. Therefore, coupling MECs with anaerobic ammonia oxidation holds promise for enhancing the treatment capacity of anaerobic ammonia oxidation systems. Furthermore, applying voltage can accelerate bacterial growth, reconcile the conflicting growth rates of bacteria, and improve the bacterial community structure.

[0004] Applying anammox technology to wastewater denitrification can theoretically reduce operating costs by 90% and decrease land area by 50%. Studies have found that under conditions of 30-40℃, the doubling time of anammox bacteria is approximately 10-14 days. Furthermore, anammox microorganisms are highly sensitive to changes in environmental conditions. Existing research indicates that certain organic matter, including toxic and non-toxic substances, can adversely affect anammox bacteria. However, in the presence of organic matter (propionates and acetates), anammox bacteria can also accumulate to high densities. Currently, research on the application of anammox technology in wastewater treatment largely focuses on simulating inorganic wastewater or actual wastewater with high ammonia nitrogen and low carbon-to-nitrogen ratios. However, almost all actual wastewater contains varying amounts of organic matter. Phenol, an important organic chemical raw material, is found in many industrial wastewaters, such as those from pulp mills, textile industries, petrochemical plants, and coking plants. It is one of the four common types of toxic organic compounds, capable of inhibiting anaerobic ammonia oxidizing bacteria by poisoning microorganisms or inactivating corresponding enzymes; this inhibition is often irreversible. Therefore, when using anaerobic ammonia oxidation processes based on anaerobic ammonia oxidation cultures for denitrification of these wastewaters, there is a risk of inactivation of anaerobic ammonia oxidizing bacteria, which may affect the operational stability of the treatment system. In view of this, cultivating phenol-tolerant anaerobic ammonia oxidation sludge is highly beneficial for treating phenol-containing industrial wastewater.

[0005] Patent CN116534992A discloses a method for treating ammonia nitrogen wastewater based on extracellular electron transport-type anaerobic ammonia oxidation. Utilizing the extracellular respiration capacity of Anammox bacteria, an extracellular electron transport-type anaerobic ammonia oxidation system is constructed by using the anode of a microbial electrolysis cell as the extracellular electron acceptor. This breaks the dependence of the anaerobic ammonia oxidation process on nitrite, achieving highly efficient removal of ammonia nitrogen under anaerobic and nitrite-free conditions. However, the initial ammonia nitrogen removal efficiency during the start-up phase of this process is approximately 17%, and after 20 days, the removal efficiency stabilizes at around 65%, indicating that the system's removal efficiency for NH3-N is too low and not conducive to practical application.

[0006] Patent CN103420481A discloses a method for nitrogen removal by anaerobic ammonia oxidation coupled with heterotrophic denitrification. This method uses anaerobic ammonia oxidation granular sludge as inoculum sludge; artificially prepared water is added with ammonium chloride and sodium nitrite, and phenol is added as organic matter to achieve enrichment and cultivation of anaerobic ammonia oxidizing bacteria and heterotrophic denitrifying bacteria. The competitive and synergistic relationships between these two bacteria are determined. After 30-60 days of cultivation, a mixed bacterial community of anaerobic ammonia oxidizing bacteria and heterotrophic denitrifying bacteria is achieved. The initial concentrations of ammonia nitrogen and nitrite nitrogen in this experiment are 50-70 mg / L and 80-100 mg / L, respectively, with removal rates exceeding 85% and effluent nitrate nitrogen concentrations of 7-10 mg / L. However, this experimental reactor has a long start-up period, increasing the difficulty and time cost of practical application.

[0007] Patent CN115124143 A discloses a method and apparatus for autotrophic denitrification acclimation of coking wastewater to withstand phenol inhibition. The method includes the following steps: Step I: Initiating an anaerobic ammonia oxidation reaction in the apparatus; Step II: Setting a phenol concentration gradient, and after each gradient increase and reaction period, reducing the phenol concentration to the level of the previous stage, then adding a trace element inducer and performing sludge external circulation to allow the anaerobic ammonia oxidation reaction to have a recovery process to reduce phenol inhibition. The tolerance of the anaerobic ammonia oxidation bacteria is improved by alternately increasing the phenol concentration and enhancing the reaction activity. The acclimated autotrophic denitrification process of coking wastewater can tolerate a phenol concentration range of 50–175 mg / L, with an acclimation period of 1–2 months. However, the actual phenol concentration in phenol-containing wastewater often reaches 300–600 mg / L; therefore, the experimental results are still far from meeting the requirements of practical applications. Summary of the Invention

[0008] The purpose of this invention is to overcome the shortcomings of existing anaerobic ammonia oxidation methods for treating high-nitrogen phenol-containing wastewater, such as poor phenol tolerance of bacterial agents, low nitrogen and phenol removal efficiency, long acclimation periods, and high operating costs. This invention provides a method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation. This method enhances microbial activity through an external electric field in a single-chamber microbial electrolysis cell reactor, and combines this with targeted acclimation to phenol toxicity to improve the phenol tolerance of anaerobic ammonia oxidizing bacteria. This achieves simultaneous and efficient nitrogen removal and phenol degradation, without the need for external carbon sources or aeration. It features a short acclimation period, simple process structure, and low operating costs, making it suitable for practical industrial wastewater treatment.

[0009] The objective of this invention can be achieved through the following technical solutions: A method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation includes: S1. Construct a single-reaction-chamber microbial electrolysis reactor, in which the anode and cathode are placed in the same reaction chamber, and activated sludge containing anaerobic ammonia oxidizing bacteria is inoculated in the reactor. S2. Toxicity acclimatization of activated sludge; S3. High-nitrogen phenol-containing wastewater is introduced into the reactor. Voltage is applied to the anode and cathode through an adjustable DC regulated power supply. Denitrification and phenol degradation are achieved simultaneously through a microbial electrolysis cell coupled with an anaerobic ammonia oxidation reaction.

[0010] Furthermore, in S1, the volume of the activated sludge is 10 to 80% of the effective volume of the reactor.

[0011] Further, in S2, the process conditions for the toxicity acclimation of the activated sludge are as follows: the reactor is kept in the dark, the temperature is set at 30 ± 1℃, the pH value is 7.0 ~ 7.5, the dissolved oxygen is controlled below 0.5 mg / L, the hydraulic retention time is 12 hours to 120 hours, the influent ammonia nitrogen concentration is controlled at 10 ~ 100 mg / L, the influent nitrite nitrogen concentration is controlled at 20 ~ 120 mg / L, and the phenol concentration is controlled at 10 ~ 100 mg / L. Acclimation is completed when the removal rates of ammonia nitrogen, nitrite nitrogen, and phenol in the system reach more than 80%. Preferably, the influent ammonia nitrogen concentration is 50 mg / L and 80 mg / L; the influent nitrite nitrogen concentration is 66 mg / L and 105 mg / L.

[0012] Furthermore, the anode material of the reactor is carbon felt.

[0013] Furthermore, the cathode material of the reactor is carbon felt.

[0014] Furthermore, the pretreatment method for the carbon felt includes: sequentially soaking it in hydrochloric acid, sodium hydroxide solution and anhydrous ethanol, rinsing it with deionized water until neutral, and then drying it in an oven at 105°C.

[0015] Furthermore, the carbon felt is provided with titanium wires for connecting an adjustable DC regulated power supply.

[0016] Furthermore, the voltage is controlled to operate within the range of 0.1 to 0.9V by an adjustable DC regulated power supply. Preferably, the voltage is 0.3V, 0.4V, 0.5V, or 0.6V.

[0017] Compared with the prior art, the present invention has the following advantages: (1) This invention utilizes the advantages of a single-chamber microbial electrolysis cell, namely its simple structure, improved efficiency, and low cost. Anodic electroactive microorganisms, driven by an applied voltage, oxidize and degrade phenol, releasing electrons. These electrons are then transferred through the electrodes to power the cathode reaction, eliminating the toxic inhibitory effect of phenol on anaerobic ammonia oxidizing bacteria. The cathode provides a favorable reducing environment for these bacteria, which use ammonia nitrogen as an electron donor and nitrite nitrogen as an electron acceptor, directly converting both into nitrogen gas for efficient denitrification. The electric field generated by the applied voltage enhances the electron supply and reaction rate of anaerobic ammonia oxidation, thereby improving efficiency and simultaneously completing phenol degradation and nitrogen removal. This invention is more suitable for practical wastewater treatment and energy recovery scenarios, and has greater potential in treating complex wastewater or large-scale applications.

[0018] (2) By gradually increasing the phenol concentration, the anaerobic ammonia oxidation bacteria can gradually adapt to the toxic environment, improve their tolerance to phenol, and reduce the inhibition of microbial activity by phenol. Through phenol toxicity acclimatization, anaerobic ammonia oxidation sludge can be applied more flexibly to the denitrification treatment of phenol-containing industrial wastewater, which has both technical feasibility and economic advantages.

[0019] (3) This invention requires no external carbon source or aeration, saving operating costs and greatly reducing energy consumption. It also requires less floor space, and the removal of phenol, ammonia nitrogen and nitrite nitrogen is completed in one reaction system. Attached Figure Description

[0020] Figure 1 This is a structural diagram of the microbial electrolysis cell of the present invention.

[0021] The numbers in the diagram indicate: 1-Inlet pipe; 2-Outlet pipe; 3-Titanium wire; 4-Anode; 5-Cathode; 6-Adjustable DC regulated power supply. Detailed Implementation

[0022] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments. These embodiments are implemented based on the technical solution of the present invention, providing detailed implementation methods and specific operating procedures. However, the scope of protection of the present invention is not limited to the following embodiments.

[0023] The embodiments provided by this invention all utilize the microbial electrolysis cell coupled with anaerobic ammonia oxidation device described in this invention to treat high-nitrogen phenol-containing wastewater.

[0024] In the following examples, the concentration of ammonia nitrogen was determined by Nessler's reagent spectrophotometry, the concentration of nitrite nitrogen was determined by N-(1-naphthyl)-ethylenediamine spectrophotometry, and the concentration of phenol was measured by 4-aminoantipyrine spectrophotometry.

[0025] The anaerobic ammonia oxidation sludge was taken from an anaerobic activated sludge plant.

[0026] Unless otherwise specified, all reagents used are commercially available, and all detection methods and techniques used are conventional in this field.

[0027] Example 1 This embodiment provides a method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation, comprising the following steps: S1. Construct a single-chamber microbial electrolysis reactor. The anode 4 and cathode 5 of this reactor are placed in the same reaction chamber. Activated sludge containing anaerobic ammonia-oxidizing bacteria is inoculated into the reactor. See the detailed structure below. Figure 1 ; Specifically, the microbial electrolysis cell reactor is selected from high borosilicate glass bottles with an effective volume of 500 ml; Carbon felt (3×5×0.2 cm) was selected as both the anode and cathode material. The carbon felt was connected to an adjustable DC regulated power supply (6) via titanium wire (0.6 mm in diameter) to apply a 0.6V voltage to the reaction system. The carbon felt required pretreatment before use, including: sequentially soaking it in 1 mol / L hydrochloric acid, 1 mol / L sodium hydroxide solution, and anhydrous ethanol for 24 h; rinsing with deionized water until neutral; and drying in an oven at 105℃. The reactor is inoculated with activated sludge containing anaerobic ammonia-oxidizing bacteria, and the volume of the inoculated sludge is 20% of the effective volume of the reactor.

[0028] S2. Toxicity acclimatization of activated sludge; the specific process is as follows: The reactor was placed in a constant temperature chamber away from light, with the temperature set at 30±1℃, pH value at 7.0~7.5, dissolved oxygen controlled below 0.5mg / L, and hydraulic retention time at 48 hours. 80% of the reactor's effective volume was replaced each time the water was changed.

[0029] The initial influent concentrations of ammonia nitrogen and nitrite nitrogen were controlled at 50 mg / L and 66 mg / L, respectively. A phenol concentration gradient of 10 mg / L was set, and 10 mg / L of phenol was added to the influent. After the reaction lasted for 2 days, the phenol concentration was increased to 20 mg / L, and then gradually increased to 50 mg / L. The acclimatization process lasted for 10 days. The acclimatization was completed when the removal rates of ammonia nitrogen, nitrite nitrogen, and phenol in the system reached more than 80%.

[0030] S3. High-nitrogen phenol-containing wastewater is introduced into the reactor through inlet pipe 1. Voltage is applied to the anode and cathode through an adjustable DC regulated power supply. Denitrification and phenol degradation are simultaneously achieved through a microbial electrolysis cell coupled with an anaerobic ammonia oxidation reaction. The inlet parameters for the high-nitrogen phenol-containing wastewater are: ammonia nitrogen concentration 80 mg / L, nitrite nitrogen concentration 105 mg / L, and phenol concentration 50 mg / L. Samples are taken from outlet pipe 2 every 48 hours to measure the effluent concentration. The results are shown in Table 1.

[0031] Example 2: This embodiment provides a method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation. The method is the same as that in Embodiment 1, except that the applied voltage is 0.3V.

[0032] Example 3 This embodiment provides a method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation. The method is the same as that in Embodiment 1, except that the influent parameters for the high-nitrogen phenol-containing wastewater are ammonia nitrogen concentration of 80 mg / L, nitrite nitrogen concentration of 105 mg / L, and phenol concentration of 100 mg / L. Samples are taken every 48 hours to measure the effluent concentration.

[0033] Comparative Example 1 This comparative example is basically the same as Example 1, except that there is no sludge toxicity acclimation in this comparative example. The method for treating high-nitrogen phenol-containing wastewater in this comparative example includes the following steps: S1. Construct a single-chamber microbial electrolysis reactor, in which the anode and cathode are placed in the same reaction chamber. The reactor is inoculated with activated sludge containing anaerobic ammonia-oxidizing bacteria. See the detailed structure below. Figure 1 ; Specifically, the microbial electrolysis cell reactor is selected from high borosilicate glass bottles with an effective volume of 500 ml; Carbon felt (3×5×0.2 cm) was selected as both the anode and cathode material. The carbon felt was connected to an adjustable DC regulated power supply via titanium wire (0.6 mm in diameter) to apply a 0.6V voltage to the reaction system. The carbon felt required pretreatment before use, including: sequentially soaking in 1 mol / L hydrochloric acid, 1 mol / L sodium hydroxide solution, and anhydrous ethanol for 24 h; rinsing with deionized water until neutral; and drying in an oven at 105℃. The reactor is inoculated with activated sludge containing anaerobic ammonia-oxidizing bacteria, and the volume of the inoculated sludge is 20% of the effective volume of the reactor.

[0034] The apparatus was placed in a constant temperature chamber away from light, with the temperature set at 30±1℃, pH value at 7.0~7.5, dissolved oxygen controlled below 0.5mg / L, and hydraulic retention time at 48 hours. 80% of the reactor's effective volume was replaced each time the water was changed.

[0035] High-nitrogen phenol-containing wastewater was directly introduced into the system. The influent parameters were: ammonia nitrogen concentration of 80 mg / L, nitrite nitrogen concentration of 105 mg / L, and phenol concentration of 50 mg / L. Samples were taken every 48 hours to measure the effluent concentration.

[0036] Table 1 Comparison of the effects of the embodiments and comparative examples. As shown in Table 1, if high-nitrogen phenol-containing wastewater is treated directly without sludge toxicity acclimation, the anaerobic ammonia oxidizing bacteria will be inhibited by the toxicity of phenols, resulting in the inability to effectively remove nitrogen from the wastewater.

[0037] The method of gradually increasing phenol concentration and applying voltage to enhance reaction activity adopted in this invention can improve the tolerance of anaerobic ammonia-oxidizing bacteria, greatly reduce the inhibitory effect of phenol, and this acclimatization method can tolerate a wide range of phenol concentrations and has a short acclimatization period, which is beneficial for realizing the autotrophic denitrification treatment process of wastewater containing high nitrogen and phenol.

[0038] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention in any other way. Any person skilled in the art may make changes or modifications to the above-disclosed technical content to create equivalent embodiments. However, any simple modifications, equivalent changes, and modifications made to the above embodiments based on the technical essence of the present invention without departing from the scope of the present invention shall still fall within the protection scope of the present invention.

Claims

1. A method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation, characterized in that, include: S1. Construct a single-reaction-chamber microbial electrolysis reactor, in which the anode and cathode are placed in the same reaction chamber, and activated sludge containing anaerobic ammonia oxidizing bacteria is inoculated in the reactor. S2. Toxicity acclimatization of activated sludge; S3. High-nitrogen phenol-containing wastewater is introduced into the reactor. Voltage is applied to the anode and cathode through an adjustable DC regulated power supply. Denitrification and phenol degradation are achieved simultaneously through a microbial electrolysis cell coupled with an anaerobic ammonia oxidation reaction.

2. The method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation according to claim 1, characterized in that, In S1, the volume of the activated sludge is 10 to 80% of the effective volume of the reactor.

3. The method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation according to claim 1, characterized in that, In S2, the process conditions for the toxicity acclimatization of the activated sludge are as follows: the reactor is in a light-protected state, the temperature is set at 30 ± 1℃, the pH value is 7.0 ~ 7.5, the dissolved oxygen is controlled below 0.5 mg / L, the hydraulic retention time is 12 ~ 120 hours, the influent ammonia nitrogen concentration is controlled at 10 ~ 100 mg / L, the influent nitrite nitrogen concentration is controlled at 20 ~ 120 mg / L, and the phenol concentration is controlled at 10 ~ 100 mg / L. Acclimatization is completed when the removal rates of ammonia nitrogen, nitrite nitrogen, and phenol in the system reach more than 80%.

4. The method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation according to claim 3, characterized in that, The influent concentrations of ammonia nitrogen are 50 mg / L and 80 mg / L; the influent concentrations of nitrite nitrogen are 66 mg / L and 105 mg / L.

5. The method for treating high-nitrogen phenol-containing wastewater by coupled microbial electrolysis and anaerobic ammonia oxidation according to claim 1, characterized in that, The anode material of the reactor is carbon felt.

6. The method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation according to claim 1, characterized in that, The cathode material of the reactor is carbon felt.

7. A method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation according to claim 5 or 6, characterized in that, The pretreatment method for the carbon felt includes: sequentially soaking it in hydrochloric acid, sodium hydroxide solution and anhydrous ethanol, rinsing it with deionized water until neutral, and then drying it in an oven at 105°C.

8. A method for treating high-nitrogen phenol-containing wastewater using a microbial electrolysis cell coupled with anaerobic ammonia oxidation according to claim 5 or 6, characterized in that, The carbon felt is provided with titanium wires for connecting an adjustable DC regulated power supply.

9. The method for treating high-nitrogen phenol-containing wastewater by coupled microbial electrolysis and anaerobic ammonia oxidation according to claim 1, characterized in that, The voltage is controlled within the range of 0.1~0.9V by an adjustable DC regulated power supply.

10. The method for treating high-nitrogen phenol-containing wastewater by coupling a microbial electrolysis cell with anaerobic ammonia oxidation according to claim 9, characterized in that, The voltage is 0.3V, 0.4V, 0.5V or 0.6V.

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