Wastewater biological treatment method and device based on humic acid'energy battery '

Abstract

The invention belongs to the field of organic wastewater resourceful treatment, and particularly relates to a humic acid'energy battery '-based wastewater biological treatment method and a humic acid'energy battery'-based wastewater biological treatment device. According to the invention, humic acid and a magnetic material are coupled to prepare a recyclable magnetic humic acid composite material; a wastewater resourceful treatment method is developed on the basis of the material and comprises the following cycle steps of a charging link, a degradation treatment link and a magnetic adsorption link. A treatment device is further developed on the basis of the characteristic, and intermittent charging and recycling of the magnetic humic acid composite material are achieved on the basis of the device. Charges are obtained from an electrode by utilizing the pseudocapacitance effect of natural organic matter humic acid, and are used as an energy battery to directly charge a microbial electron transfer path, so that the limitation of traditional interspecific electron transfer of microorganisms is broken through, and the problem of low microbial electron transfer efficiency in the biotransformation process of organic matters can be fundamentally solved; and the method has creative significance.

Description

Technical Field

[0001] The present invention belongs to the field of resource treatment of organic wastewater, and particularly relates to a wastewater treatment method and device for enhancing microbial electro-metabolism by using a magnetic humic acid material. Background Art

[0002] The biological resource treatment of organic wastewater is a key technology for realizing sustainable development. However, currently, there are problems such as poor pollutant removal effect, high operation cost, and unqualified effluent caused by low biological conversion efficiency of wastewater organic matter. Enhancing microbial electron transfer can improve the biological conversion efficiency of organic pollutants. The existing solutions mainly focus on expanding the microbial electron transfer pathway, including enhancing the microbial self-electron transfer ability, adding conductive materials, and applying electron shuttles. Although the microbial electron transfer efficiency can be enhanced, it is still limited by the lack of electrons in the microbial metabolism itself. The bioelectrochemical system can provide exogenous electrons for microorganisms, completely solving the problem of insufficient electron supply; however, the conductivity and biocompatibility of the electrode material are poor, resulting in a high electron transfer barrier and low efficiency at the bio-non-biological interface.

[0003] The biological conversion of organic matter highly depends on efficient electron transfer. How to stimulate microbial electron transfer is a hot topic in the field of biological conversion of organic matter at present, and the research mainly focuses on how to "lay" or "broaden" the microbial electron transfer pathway. For example, the electron flow distribution in anaerobic digestion is closely related to the methane production efficiency. Microbial electron transfer includes direct interspecies electron transfer (DIET) and mediated interspecies electron transfer (MIET). Among them, although DIET has high efficiency, its occurrence conditions are harsh, and a direct physical connection needs to be formed between specific electroactive bacteria or archaea; for example, the electroactive microorganism Geobacter and the methanogenic archaea Methanosaeta need to carry out direct electron transfer through conductive pili; the DIET process can be enhanced by adding conductive media such as biochar, graphene, and metal oxides. The potential of MIET is large, but it is also limited by soluble electron mediators (hydrogen and formic acid). Adding abiotic electron transfer agents such as humic acid and anthraquinone-2,6-disulfonic acid (AQDS) can effectively promote MIET.

[0004] The problem to be solved by the present invention is the problem of incomplete degradation or low conversion efficiency caused by insufficient microbial electrons and low transfer efficiency during the biological conversion of wastewater organic matter. Summary of the Invention

[0005] In order to solve the problems existing in the prior art, the present invention provides a wastewater treatment method for enhancing microbial electro-metabolism by using a magnetic humic acid material (humic acid "energy battery") and a device for implementing the method.

[0006] The inventors found that humic acid, as a natural organic macromolecule, has excellent biocompatibility and electrical conductivity, and can promote the biotransformation of organic pollutants by assisting microbial electron transfer. In the electrochemical system for wastewater biological treatment, humic acid can not only act as an electron shuttle to expand the microbial electron transfer pathway, but also serve as a "bridge" to efficiently transport electrode electrons to microorganisms, solving the problem of insufficient electron supply.

[0007] Based on this, the present invention proposes to utilize the energy storage effect of the pseudocapacitance of humic acid to develop an "energy battery" suitable for microbial electro-metabolism, and connect a "power supply" to the well-laid microbial electron transfer pathway, which can completely solve the bottleneck problem of low microbial electron transfer efficiency.

[0008] The first aspect of the present invention is to provide a wastewater treatment method for enhancing anaerobic digestion by in-situ charging and discharging of humic acid, which is based on a magnetic humic acid material prepared by compounding a magnetic material and humic acid.

[0009] The magnetic humic acid material is added to the anaerobic digestion wastewater treatment system; the magnetic humic acid material stores and transfers the charges of the electrochemical system to the microbial electron transfer chain, and the magnetic humic acid material can be charged under the action of the electrochemical system.

[0010] The treatment method includes the following cyclic steps:

[0011] S11. Charging step: Turn on the electrochemical system and the magnetic switch to charge the magnetic humic acid material adsorbed near the cathode of the electrochemical system.

[0012] S12. Degradation treatment step: After charging is completed, turn off the electrochemical system and the magnetic switch, and release the charged magnetic humic acid material into the system to degrade pollutants.

[0013] S13. Magnetic adsorption step: After the charge is consumed, turn on the magnetic switch to adsorb the magnetic humic acid material near the cathode of the electrochemical system.

[0014] Further, the magnetic material is selected from nano-zero-valent iron, iron oxide, and magnetite.

[0015] In some embodiments of the present invention, the mass ratio of humic acid to iron in the magnetic humic acid material is 0.5:1 - 1:1.

[0016] In some preferred embodiments, the magnetic material is magnetite, and the magnetic humic acid material is denoted as Fe3O4@HA.

[0017] In one embodiment of the present invention, the method for preparing the magnetic humic acid material (Fe3O4@HA) includes the steps:

[0018] S21: Dissolve a certain amount of Fe 3+ and Fe 2+ in water and heat to 80 - 100 °C;

[0019] S22: Sequentially add a certain amount of ammonium hydroxide and humic acid;

[0020] S23: Stir the mixture at 80 - 100 °C for 20 - 60 minutes, separate the solid and liquid after cooling, collect the solid phase, wash and dry it.

[0021] In some preferred embodiments, Fe 3+ and Fe 2+ are respectively from FeCl3 and FeSO4; in step S21, the dosing concentration of FeCl3·6H2O is 50.0 - 70.0 g / L, and the dosing concentration of FeSO4·7H2O is 40.0 - 50.0 g / L; in step S22, the dosing concentration of ammonium hydroxide is 10 - 30 g / L. Humic acid should be sourced from natural materials such as sludge, and the dosing concentration is 1 - 10 g / L.

[0022] Furthermore, the suspended solid content of the wastewater to be treated should be ≤ 10.0 g / L; the substrate of the wastewater treatment device using the humic acid "energy battery" to enhance microbial electro - metabolism is organic wastewater, which is particularly suitable for treating biologically refractory organic wastewater or the organic matter biotransformation system lacking electron donors, but the wastewater suspended solid concentration should be ≤ 10.0 g / L, otherwise it may affect the adsorption charging and recycling of the humic acid "energy battery".

[0023] Furthermore, in the anaerobic digestion system, the concentration of the magnetic humic acid material is ≤ 2.0 g / L; too high a humic acid concentration will have an inhibitory effect on microorganisms.

[0024] Furthermore, the specific capacitance of the magnetic humic acid material is ≥ 2.0 F / g; the humic acid "energy battery" needs to obtain and store charges from the electrode, and the energy storage size directly affects its enhancement effect on microbial electro - metabolism and the charging frequency, etc.

[0025] Furthermore, the applied voltage of the electrochemical system is 0.2 - 1.5 V; the size of the applied voltage needs to be accurately determined according to parameters such as electrode resistance and the distance between the anode and cathode.

[0026] Furthermore, the reaction is carried out under stirring conditions, and the stirring speed is ≤ 150 rpm and ≥ 10 rpm. Both too large and too small stirring intensities are not conducive to the progress of microbial electro - metabolism.

[0027] Furthermore, the activated sludge concentration in the reactor is ≤ 20 g / L. Too high a sludge concentration will affect the adsorption and recovery of the humic acid "energy battery".

[0028] In some embodiments of the present invention, in step S12, the charging time is 5.0-48.0 hours; in some embodiments of the present invention, in step S13, the adsorption time is 5-30 minutes. When adsorbing and recovering the humic acid "energy battery", it is necessary to turn on the power supply of the magnetic rod 5-30 minutes in advance, and then turn on the power supply of the electrochemical system to ensure that the humic acid "energy battery" can be fully adsorbed. And the charging time of the humic acid "energy battery" is 5.0-48.0 hours, which needs to be regulated according to the enhancement of the conversion of organic matter or methane production by the humic acid "energy battery".

[0029] In some preferred embodiments, the wastewater treatment method further comprises step S14. Recovering the sludge: when water or sludge is required, the magnetic switch is turned on to allow the magnetic humic acid material to be adsorbed on the surface of the stirring shaft, and the advance time is 10-120 minutes.

[0030] The second aspect of the present invention is to provide a wastewater treatment device for implementing the method by microbial electro-metabolism, comprising: an anaerobic reactor and an electrochemical system;

[0031] The anaerobic reactor is provided with a water inlet and a water outlet, and a water-sealed exhaust port is provided on the top; the anaerobic reactor is provided with a charging stirring device;

[0032] The charging stirring device comprises a motor, a stirring paddle, a stirring shaft, and a sleeve; the sleeve is made of a conductive material, and the stirring shaft is installed inside the sleeve; the sleeve and the stirring shaft are isolated by insulating material; the stirring paddle is arranged at one end of the stirring shaft, and the transmission shaft of the motor is connected to the other end of the stirring shaft;

[0033] The inner wall of the anaerobic reactor is provided with carbon cloth as the anode of the electrochemical system; the shaft sleeve of the stirring device is the cathode of the electrochemical system.

[0034] In some possible implementations, the stirring shaft is made of electromagnetic material and is magnetic when powered.

[0035] The third aspect of the present invention is to provide application of the method or the device in the field of resource utilization of organic wastewater.

[0036] Beneficial effects:

[0037] (1) The present invention has developed a new type of humic acid "energy battery" suitable for microorganisms and a recycling method thereof. The pseudocapacitor effect of humic acid, which can store electrons and transfer them to microorganisms, is used in a bioelectrochemical system; and humic acid is combined with ferroferric oxide to prepare a magnetic humic acid composite material, which further improves the electron storage and transfer capacity of humic acid, and makes humic acid magnetic, which can be recovered by electric magnetic adsorption, reducing the loss of humic acid, greatly reducing operating costs, greatly simplifying the operating steps, and having a high application value.

[0038] (2) The present invention realizes the intermittent charging and recycling of the humic acid "energy battery" through the ingenious design of the bioelectrochemical reactor, especially the stirring paddle; the device can stimulate microbial electron transfer and promote the biological transformation of organic matter.

[0039] (3) The treatment method provided by the present invention completely solves the problem of insufficient electron supply in microbial electrical metabolism. Humic acid is used as an "energy battery" to quickly obtain electrons from the electrode by utilizing its good biocompatibility, conductivity and pseudocapacitance effect. Driven by an external voltage potential, the electron-carrying humic acid battery migrates directionally to the microbial aggregation area to supply power to the microbial electron transport chain. Not only can it achieve electrical energy transmission without relying on physical contact between microorganisms and electrodes, but it can also dynamically release electrons according to the metabolic needs of the microorganisms. It makes up for the strict restrictions of traditional direct interspecies electron transfer of microorganisms on physical spatial location, and also avoids the serious dependence of indirect interspecies electron transfer of microorganisms on biological electron shuttles, thus realizing the integration of energy storage, mobility and energy supply.

[0040] (4) The efficiency of biological transformation of organic matter in wastewater has been improved. Enhancing microbial electron transfer can improve the efficiency of biological transformation of organic matter. Existing solutions focus on expanding the microbial electron transfer pathway, including improving the electron transfer ability of microorganisms themselves, adding conductive materials, and applying electron shuttles. Although the efficiency of microbial electron transfer has been significantly enhanced, it is still limited by the lack of electrons in microbial metabolism itself. The present invention opens up the electron transfer pathway between microorganisms and electrodes, allowing microorganisms to continuously obtain exogenous electrons, greatly promoting the microbial metabolic process and the transformation efficiency of organic matter, and achieving efficient resource treatment of organic waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] The accompanying drawings are used to provide a further understanding of the present application and constitute a part of the specification. Together with the embodiments of the present application, they are used to explain the present application and do not constitute a limitation of the present application. In the accompanying drawings:

[0042] Figure 1 This is a schematic diagram of a wastewater treatment device that uses humic acid "energy batteries" to enhance microbial electrical metabolism;

[0043] Figure 2 Operation flow chart of a wastewater treatment device using a humic acid "energy battery" to enhance microbial electro-metabolism;

[0044] Figure 3 Enhanced pseudocapacitance effect by humic acid loaded with nano-Fe3O4;

[0045] Figure 4 Fourier transform infrared spectrum of magnetic humic acid

[0046] Figure 5 The effect of a humic acid "energy battery" providing electrons to replace sodium acetate as an external carbon source for denitrification and nitrogen removal of wastewater;

[0047] Figure 6 Promoting effect of a humic acid "energy battery" after energy storage at different voltages on methane production from anaerobic digestion of wastewater;

[0048] Figure 7 Promoting effect of continuous charge and discharge of a humic acid "energy battery" on anaerobic digestion gas production performance;

[0049] Figure 8 Change of specific capacitance during continuous charge and discharge of a humic acid "energy battery". Detailed implementation manners

[0050] To make the above objects, features and advantages of the present invention more obvious and understandable, the following describes the detailed implementation manners of the present invention in combination with the embodiments of the specification. Many specific details are set forth in the following description in order to fully understand the present invention, but the present invention can also be implemented in other ways different from those described herein. Those skilled in the art can make similar promotions without departing from the connotation of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed below.

[0051] The experimental methods described in the following embodiments are all conventional methods unless otherwise specified; the reagents and materials are all commercially available unless otherwise specified.

[0052] Preparation of sludge humic acid used in the examples:

[0053] The sludge humic acid was extracted by the extraction method specified by IHSS. The dehydrated sludge and the hydrolyzed sludge solution after hydrolysis at 180°C were freeze-dried and ground into powder, and the following steps were carried out in sequence:

[0054] First, add an appropriate amount of 6 mol / L HCl solution to the obtained humic acid powder to make the pH of the dissolved humic acid equal to 1.0. Then, add 0.1 mol / L HCl solution so that the volume ratio of the humic acid solution to the mass of the humic acid powder is 10:1. Then, place the humic acid solution in a 35°C air bath shaker and shake it for 1 h, and then take it out and let it stand to collect the precipitate. Next, under the condition of N2 bubbling, dissolve the precipitate with 6 mol / L NaOH, and then shake the mixed solution in a shaker for 15 h, take it out, let it stand and precipitate to obtain the supernatant. Then, adjust the pH of the supernatant to 1.0 with 6 mol / L HCl, let it stand for 15 h, and then centrifuge it. The precipitate is the humic acid extract, and the supernatant is the fulvic acid extract.

[0055] Purification of humic acid: Completely dissolve the humic acid extract with 0.1 mol / L KOH, then add potassium chloride so that the concentration of potassium ions is about 0.3 mol / L, and then let it stand and precipitate. If there are impurities, centrifuge the humic acid solution to remove suspended impurities and then continue the purification. If not, directly adjust the humic acid solution with 6 mol / L HCl to make the pH = 1.0, let it stand for 15 h, and then centrifuge to obtain the solid extract. Then, dissolve the humic acid extract with a mixed solution of 0.1 mol / L HCl and 0.3 mol / L HF (volume ratio 1:1), shake the dissolved humic acid solution in a shaker, take it out after 12 h, and centrifuge to obtain the humic acid precipitate. Finally, wash the precipitate with ultrapure water multiple times to remove chloride ions, and use silver nitrate to detect whether silver chloride precipitate will be formed until no precipitate is produced; finally, select the vacuum freeze-drying technology to freeze-dry the humic acid extract into powder.

[0056] Performance detection and evaluation methods used in the examples:

[0057] (1) Cyclic voltammetry of humic acid capacitance

[0058] The test instrument is Chenhua CHI660E electrochemical workstation, three-electrode system, including a glassy carbon working electrode loaded with humic acid, a platinum wire counter electrode, and an Ag / AgCl reference electrode (Lerton R0303, Shanghai). All potentials in the present invention are based on the saturated Ag / AgCl reference electrode. The measurement is carried out in the potential range of -1.0 to +1.0 V (relative to Ag / AgCl) under anaerobic conditions, the scanning rate is 10 mV / s, the test temperature is 30°C, the electrolyte solution is selected as 50 mM phosphate buffer solution (pH = 7.0), and it is purged with N2 and saturated with the solution for 1 h to eliminate oxygen.

[0059] Fixing method for humic acid working electrode: Immobilize platinum sheet electrode with humic acid using Nafion as the binder. First, prepare a mixed solution with ethanol and water in a volume ratio of 1:4. Then, disperse 10 mg of humic acid and 40 μL of Nafion into 1 mL of the mixed solution by ultrasonic dispersion. Then, drop 40 μL of the obtained dispersion on the surface of the working electrode and dry it at room temperature for 20 h.

[0060] (2) Testing method for NO3 - -N concentration

[0061] Determine the NO3 - -N concentration by ultraviolet spectrophotometry (220 nm). Pipette 1 mL of the sample solution into a 10 mL colorimetric tube, add 1.0 mL of 1 mol / L hydrochloric acid solution, and select 220 nm and 275 nm as the measurement wavelength and reference wavelength to measure nitrate nitrogen.

[0062] Use ΔA = A 220 -kA 275 to calculate the corrected absorbance. (k = 1)

[0063]

[0064] In the formula: θ is the NO3 - -N concentration (mg / kg); C0 is the mass concentration of the sample solution obtained from the standard curve (μg / mL); V 总 is the total volume of the colorimetric determination solution (mL); d is the extraction solution aliquot multiple; m is the mass of the sample (g).

[0065] (3) Testing method for methane volume

[0066] Measure the volume of the gas generated in the gas bag by syringe extraction method. Use a manual injector to extract 1 mL of the collected gas and inject it from the injection port of the gas chromatograph. Use a gas chromatograph (GC9790II, Fuli, China) to determine the gas components. The basic configuration of the gas chromatograph is as follows: thermal conductivity detector (TCD), silica gel column (length: 0.5 m, inner diameter: 3.2 mm, heat resistance upper limit: 250 °C), and molecular sieve packed column (length: 3 m, inner diameter: 3.2 mm, heat resistance upper limit: 280 °C). The detection conditions are as follows: use hydrogen as the carrier gas, with a flow rate set at 23 mL / min; the valve drive gas is air, with a pressure of 0.3 - 0.5 MPa; the detector current is adjusted to 80 mA; the column temperature of the chromatographic column is set at 70 °C, and the temperatures of the injector and detector are 100 °C.

[0067] The treatment device of the present invention:

[0068] The wastewater treatment device for enhancing microbial electro-metabolism using humic acid "energy battery" provided by the present invention is as follows Figure 1 as shown. The main body of the device is a cylindrical closed reactor; the anaerobic digestion reaction is carried out in the reactor. A motor is installed at the top of the reactor, and the transmission shaft of the motor is coaxially connected to the stirring shaft. The lower end of the stirring shaft is connected with a stirring paddle. The outside of the stirring shaft is a shaft sleeve made of conductive material, and the shaft sleeve and the stirring shaft are insulated by insulating materials; the material of the stirring shaft is an electromagnetic material and has magnetism when electrified. A feed port and a sampling port are arranged at the lower part of the reactor; a water seal exhaust port is arranged at the top, and a discharge port and a drain port are arranged at the bottom. The stirring shaft and the shaft sleeve are controlled by different electric control systems. The inner wall of the anaerobic reactor is provided with carbon cloth as the anode of the electrochemical system; the shaft sleeve of the stirring device is the cathode of the electrochemical system.

[0069] When the device is running, the wastewater enters from the feed port of the reactor. Under the mixing action of the stirring device, microorganisms degrade or transform the organic matter in the wastewater into biogas. Humic acid "energy battery" is added to the reactor to enhance the electro-metabolism of microorganisms and promote the biological transformation and metabolism effect of pollutants, and can quickly store the charge of the electrochemical system and efficiently transfer it to the microbial electron transfer chain. The wastewater treatment process of the treatment device of the present invention is as follows

[0070] The operation steps of the wastewater treatment device for enhancing microbial electro-metabolism using humic acid "energy battery" are as follows Figure 2 as shown

[0071] As Figure 2-1 shown: Under normal operation conditions, turn on the stirring equipment of the reaction vessel, and use microorganisms (activated sludge) to adsorb and degrade the organic pollutants in the wastewater. At the same time, the humic acid "energy battery" transfers the charge to the microorganisms through collision and contact, strengthens its electro-metabolism, and promotes the degradation and transformation of pollutants. As Figure 2-2 shown: When the charge of the humic acid "energy battery" is exhausted, the removal effect of organic pollutants will become worse, or the biogas production will decrease significantly. Turn on the power supply of the magnetic bar (stirring shaft) and maintain the stirring state, so that the magnetic humic acid "energy battery" is adsorbed on the surface or near the stirring shaft, and turn on the power supply of the electrochemical system to charge the humic acid "energy battery". As Figure 2-3 shown: After charging, turn off the power supply of the magnetic bar and the electrochemical system, so that the charged humic acid "energy battery" returns to the reaction system again to continue to provide electrons for microbial metabolism. As Figure 2-4 shown: When the reaction vessel needs to drain water or sludge, turn on the power supply of the magnetic bar in advance, recover the humic acid "energy battery" on the surface or near the stirring shaft, then stop the stirring device, drain the supernatant (i.e., the effluent), and appropriately drain the remaining sludge according to the sludge concentration.

[0072] Example 1: Preparation of iron salt coupled with humic acid

[0073] The Fe3O4@HA composite material was synthesized by the co-precipitation method. The specific operation was as follows: 6.1 g of FeCl3·6H2O and 4.2 g of FeSO4·7H2O were dissolved in 100 mL of anaerobic water and heated to 90 °C, while maintaining an anaerobic environment with nitrogen. Subsequently, 10 mL of 25% ammonium hydroxide solution and 0.5 g of sodium humate (HA) solution dissolved in 50 mL of deionized water were rapidly added in sequence. The reaction system should theoretically be adjusted to alkaline pH to promote the precipitation of Fe3O4 and the loading and combination of HA. After the mixture was continuously stirred at 90 °C for 30 min, it was naturally cooled to room temperature. The obtained black precipitate was washed with water several times until neutral, and finally, Fe3O4@HA nanoparticles were obtained after vacuum drying, with a yield of about 2 g.

[0074] The electrochemical properties of three materials, HA, Fe3O4, and Fe3O4@HA, were evaluated by cyclic voltammetry (CV) tests. The results are as Figure 3 shown. The CV curve of Fe3O4@HA shows the largest closed-loop area in the voltage window (-1.0 to +1.0 V), much larger than those of HA and Fe3O4 alone, indicating that it has a stronger charge storage capacity. The inset bar chart in the figure further verifies this result: the specific capacitance per unit mass of Fe3O4@HA reaches about 18 F / g, significantly higher than that of Fe3O4 (about 8 F / g) and HA (about 6 F / g), indicating that this composite material has better electrochemical properties under the same mass.

[0075] The increase in the specific capacitance of the Fe3O4@HA composite material is mainly attributed to the synergistic effect between the two materials. The results are as Figure 4 shown. Humic acid (HA) contains abundant oxygen functional groups (such as carboxyl and quinone groups) that can provide pseudocapacitance contributions and participate in the charge transfer process. The Fe3O4 nanoparticles, as a conductive framework, not only enhance the electron conduction ability but also provide more reactive sites for the stable loading of HA on its surface and efficient electron exchange. The combination of the two not only improves the overall conductivity but also enhances the charge transfer and storage efficiency, making Fe3O4@HA have a stronger electron release ability.

[0076] Example 2: Electroactive humic acid promotes denitrification of wastewater

[0077] By constructing different electron-donating systems, four groups were set up, namely the control group (CK), the group with only sodium acetate added (CK+C), the group with only humic acid pretreated electrochemically for 24 h added (CK+eHA), and the group with both sodium acetate and electrochemically treated humic acid added synergistically (CK+C+eHA), to investigate their effects on the removal of nitrate nitrogen (NO3 - -N).

[0078] AsFigure 5 As shown, the initial NO3 - -N concentration in the experiment was approximately 56 mg / L. Sodium acetate (200 mg / L) was used as the carbon source. eHA was obtained by pre-charging humic acid at a constant voltage of 0.6 V for 24 h. The entire experiment was statically reacted for 30 h under airtight anaerobic conditions, and the NO3 - -N content and its removal rate were monitored at different time points.

[0079] The experimental results showed that in the blank group CK, NO3 - -N was hardly significantly removed throughout the reaction cycle, only dropping to approximately 45 mg / L, and the removal rate was less than 15%. In contrast, both the CK+C and CK+eHA groups showed an obvious downward trend in NO3 - -N. Among them, the final removal rate of CK+C reached approximately 60%, and the removal rate of CK+eHA was approximately 45%. The co-added group CK+C+eHA showed the most significant denitrification effect, with the NO3 - -N concentration dropping below 10 mg / L within 30 h, and the removal rate approaching 80%. In addition, at the initial stage of the reaction (the first 5–10 h), the removal rate of the CK+C+eHA group was significantly faster than that of other groups, showing a more rapid denitrification start-up process.

[0080] The above results indicate that under the condition of no input of traditional organic carbon source, electrochemically activated humic acid (eHA) can be used as an electron donor to support part of the denitrification process. Its structure is rich in electroactive groups such as quinones and has good electron release and shuttle functions. Although the removal rate of using eHA alone is limited, it is significantly better than the blank, confirming its characteristics as a bioavailable electron donor. Under the condition of co-dosing with sodium acetate, eHA may provide instantaneous electrons through the pseudocapacitance mechanism and enhance the electron transfer efficiency of the system, thereby quickly starting denitrification in the early stage and increasing the total removal rate. This result verifies that eHA can be used as an auxiliary electron donor or regulator, effectively reducing the dependence on external carbon sources and having application potential in constructing an efficient and sustainable denitrification system.

[0081] Example 3: Promotion of sludge anaerobic digestion by charge and discharge of humic acid

[0082] First, dissolve humic acid with PBS (phosphate buffer solution) and alkali, adjust the pH of the humic acid solution to 7±0.2. The purpose of adding PBS is to maintain the acidity and alkalinity of humic acid. Place the humic acid solution in an electrochemical reactor and expose it to nitrogen for 10 min. Then, apply voltages of 0.4 V, 0.6 V, 0.8 V, and 1.2 V to the humic acid solution respectively for five days to explore the effects of different voltage treatments on humic acid.

[0083] The present invention uses glucose - simulated wastewater to study the effect of humic acid on methane production in anaerobic digestion. Glucose - simulated wastewater with a concentration of 10 g / L is prepared, and then the simulated wastewater is adjusted to neutral pH. Next, humic acid solutions treated with different voltages are added, and the concentration is controlled at 0.6 g / L. Secondly, according to the volume ratio of substrate to inoculum sludge of 9:1 and a total volume of 300 ml, the inoculum sludge and the humic acid solutions treated with different voltages are transferred together into a serum bottle and sealed. Two control groups are set up. One is a blank control group without humic acid named Control One, and the other is a group adding humic acid without electrical treatment named Control Two. Then nitrogen is purged for 20 minutes to evacuate the oxygen in the serum bottle to ensure an anaerobic environment. Each serum bottle is connected to a 1 - L gas bag and placed in a shaker at 37°C for 12 days. The methane production in each gas bag is measured by gas chromatography every other day.

[0084] After measurement, it is found that, as Figure 6 shown, humic acid treated at 0.6 V voltage can increase the methane production and biogas production in anaerobic digestion. The methane production and biogas production are increased by 36.3% and 29.6% respectively compared with Control One, and by 24.5% and 20.1% respectively compared with Control Two.

[0085] Example 4: Promotion of anaerobic digestion of kitchen waste by continuous charge - discharge of humic acid

[0086] An electro - fermentation system is constructed. The working volume of the reactor is 300 mL, the inoculation ratio is 10%, the pH of the reaction system is 7.0 ± 0.1, and the organic load is set at 2.0 kg / L·d during the blank control stage -1 , the hydraulic retention time is 6 days, and the feeding frequency is 1 day / time. In the initial stage, simulated wastewater without humic acid is fed in and out every day. After the system stably produces gas, simulated wastewater containing 0.6 g / L humic acid is fed in and out. After 6 days, it enters the charge - discharge stage of the humic acid capacitor and no more feeding and discharging are carried out. 2 g of glucose is added to the system every day to supplement the organic substrate consumed by gas production, and the reactor is charged at a certain frequency. The cyclic voltammetry curves of the original humic acid, the humic acid after the first 24 - hour charging, and the humic acid after 5 charge - discharge cycles are measured to obtain its specific capacitance. The calculation method of the specific capacitance is according to formula (1).

[0087] The experimental results are as Figure 7 shown. After the first charging of humic acid, the daily methane production in the anaerobic digestion system jumps from 113.3 mL to 179.2 mL. After 5 charge - discharges, humic acid can still promote the gas - producing performance of anaerobic digestion. The experimental results are as Figure 8 (a) - (c) shown. After the first charging of humic acid, the specific capacitance increases significantly to 2.53 F / g, which is 30% higher than that of the original sludge humic acid. After 5 charge - discharge cycles, the specific capacitance of humic acid drops to 1.09 F / g, which is 2.3 times lower than that of the original humic acid.

[0088] This indicates that the electrons stored in the humic acid are fully released, directly verifying the formation of the electron storage capacity.

[0089]

[0090] In formula (2): I represents the current (A), m is the mass of humic acid (g), k is the scanning rate (mV / s), and V2 - V1 is the voltage difference (V).

[0091] In summary, the present invention couples humic acid with magnetic materials to prepare a magnetic humic acid composite material that can be conveniently recycled; and develops a wastewater resource treatment method based on this material, including the following cyclic steps: charging link, degradation treatment link, and magnetic adsorption link. Further, a treatment device is developed. This device utilizes the good biocompatibility and unique pseudocapacitance effect of humic acid, obtains charges from the electrode as an "energy battery" and stores them in its electroactive functional groups, and finally transfers them to the microbial electron metabolic chain to accelerate the biological transformation of organic pollutants. The present invention not only couples humic acid with magnetite to prepare a magnetic humic acid composite material, but also realizes the intermittent charging and recycling of the humic acid "energy battery" through the ingenious design of the agitator of the bioelectrochemical reactor.

[0092] The test results show that this device can stimulate microbial electron transfer, promote the biological transformation of organic matter, increase the methane production by 60%, reduce the residual organic matter in the biogas slurry by 52%, increase the microbial electron transfer efficiency by 65%, and significantly enrich electroactive microorganisms. This project proposes to obtain charges from the electrode using the pseudocapacitance effect of natural organic matter humic acid and directly "charge" the microbial electron transfer pathway as an "energy battery", breaking through the limitations of traditional interspecies microbial electron transfer, and fundamentally solving the problem of low microbial electron transfer efficiency in the process of organic matter biological transformation, which has pioneering significance.

[0093] It should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not restrictive. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the present invention.

Claims

1. A wastewater treatment method based on a "humic acid energy battery", characterized in that, The method is based on a magnetic humic acid material prepared by combining magnetic material and humic acid. Adding the magnetic humic acid material into the anaerobic digestion wastewater treatment system; The processing method includes the following cyclic steps: S11. Charging step: Turn on the electrochemical system and the magnetic switch to charge the magnetic humic acid material adsorbed near the cathode of the electrochemical system; S12. Degradation treatment: After charging is completed, the electrochemical system and the magnetic switch are turned off, and the charged magnetic humic acid material is released into the system to degrade pollutants; S13. Magnetic adsorption step: after the charge is consumed, the magnetic switch is turned on to adsorb the magnetic humic acid material near the cathode of the electrochemical system.

2. The processing method according to claim 1, wherein The magnetic material is selected from nano zero-valent iron, ferric oxide, and ferrosoferric oxide; And / or, the mass ratio of humic acid to iron in the magnetic humic acid material is 0.5:1-1:

1.

3. The processing method according to claim 2, characterized in that, The magnetic material is ferroferric oxide; The preparation method comprises the steps of: S21: A certain amount of Fe 3+ and Fe 2+ Dissolve in water and heat to 80-100°C; S22: adding a certain amount of ammonium hydroxide and humic acid in sequence; S23: stirring the mixture at 80-100°C for 20-60 minutes, cooling it to separate the solid and liquid, collecting the solid phase, washing and drying it.

4. The processing method according to claim 1, characterized in that: The concentration of the magnetic humic acid material is ≤2.0g / L, and the suspended solid content of the wastewater is required to be ≤10.0g / L; And / or, the reaction is carried out under stirring conditions, with a stirring speed of ≤150rpm and ≥10rpm, and an activated sludge concentration of ≤20g / L.

5. The processing method according to claim 1, characterized in that The specific capacitance of the magnetic humic acid material is ≥2.0F / g; And / or, the applied voltage of the electrochemical system is 0.2-1.5V.

6. The processing method according to claim 1, wherein In step S12, the charging time is 5.0-48.0 hours; And / or, in step S13, the adsorption time is 5-30 minutes.

7. The processing method according to claim 1, characterized in that Also includes step S14; S14. Recycling and discharging mud: When water or mud is needed, turn on the magnetic switch to allow the magnetic humic acid material to adsorb on the surface of the stirring shaft. The advance time is 10-120 minutes.

8. A wastewater treatment device for microbial electro-metabolism based on the method according to any one of claims 1-7, characterized in that, include: Anaerobic reactors and electrochemical systems; The anaerobic reactor is provided with a water inlet and a water outlet, and a water seal exhaust port is provided on the top; The anaerobic reactor is provided with a charging stirring device; The charging stirring device comprises a motor, a stirring paddle, a stirring shaft, and a sleeve; the sleeve is made of a conductive material, and the stirring shaft is installed inside the sleeve; the sleeve and the stirring shaft are isolated by insulating material; the stirring paddle is arranged at one end of the stirring shaft, and the transmission shaft of the motor is connected to the other end of the stirring shaft; The inner wall of the anaerobic reactor is provided with carbon cloth as the anode of the electrochemical system; the shaft sleeve of the stirring device is the cathode of the electrochemical system.

9. The wastewater treatment device for microbial electro-metabolism according to claim 8, wherein, The stirring shaft is made of electromagnetic material and has magnetism when electricity is supplied.

10. Use of the method or device according to any one of claims 1 to 10 in the field of resource utilization of organic wastewater.

Images