Electrochemically enhanced anaerobic-ammonium-oxidation membrane bioreactor based on conductive separation membrane, and biological nitrogen-removal method using same

Abstract

Disclosed in the present invention are an electrochemically enhanced anaerobic-ammonium-oxidation membrane bioreactor based on a conductive separation membrane, and a biological nitrogen-removal method using same. The membrane bioreactor comprises a reactor shell, an anode, a cathode, a direct-current power supply, a water intake line and a water output line, wherein anaerobic-ammonium-oxidation bacteria are loaded into the reactor shell, and a water inlet is provided at the bottom of the reactor shell and is connected to the water intake line; the anode and the cathode are located in the reactor shell; a positive electrode of the direct-current power supply is connected to the anode, and a negative electrode of the direct-current power supply is connected to the cathode; and the cathode is a conductive membrane assembly, and a water outlet is provided at the top of the conductive membrane assembly and is connected to the water output line. In the present invention, a membrane biological treatment is coupled with an electrochemical technique, such that anaerobic-ammonium-oxidation bacteria can be effectively retained and enriched, the nitrogen-removal effect of the anaerobic-ammonium-oxidation bacteria is enhanced, and membrane fouling is alleviated by means of electrostatic repulsion. The device has a good nitrogen-removal performance, effectively alleviates membrane fouling, is easily operated and has broad application prospects.

Description

An electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane and a biological denitrification method thereof Technical Field

[0001] The present invention relates to the technical field of sewage treatment, and in particular to an electrochemically enhanced anaerobic ammonia oxidation membrane bioreactor based on a conductive separation membrane and a biological denitrification method thereof. Background Art

[0002] Traditional biological denitrification processes of nitrification and denitrification require aeration and the addition of additional carbon sources, resulting in high operating costs. Anaerobic ammonium oxidation (Anammox) uses nitrite as an electron acceptor and ammonia nitrogen as an electron donor to generate nitrogen gas under anaerobic conditions. Compared with traditional denitrification processes, the anaerobic ammonium oxidation process has the advantages of saving external carbon sources, saving oxygen supply energy consumption, reducing residual sludge production and reducing greenhouse gas emissions. Therefore, it is considered to be a very promising new denitrification process. However, anaerobic ammonium oxidizing bacteria are difficult to enrich and have low biological activity, resulting in a long process startup time and difficulty in stable operation, which seriously hinders the large-scale application of the process. Therefore, taking effective measures to enhance the enrichment and biological activity of anaerobic ammonium oxidizing bacteria is an urgent task to achieve the promotion and application of this technology.

[0003] The anaerobic ammonium oxidation (ANAMMOX) process based on a membrane bioreactor can effectively intercept ANAMMOX bacteria and maintain a high sludge concentration in the reactor, thereby achieving the enrichment and cultivation of ANAMMOX bacteria, accelerating the startup process, and improving the denitrification effect. However, similar to the conventional MBR process, during the operation of the ANAMMOX process based on a membrane bioreactor, part of the ANAMMOX sludge is adsorbed on the membrane surface, thereby clogging the membrane pores and affecting the efficiency of the membrane pores. Therefore, its effluent flux gradually decreases with the operating time, which is the membrane clogging problem. Taking into account the characteristic that membrane foulants carry a negative charge, a conductive membrane is prepared using a conductive material, and a negative bias is applied to the surface to hinder sludge adhesion through electrical repulsion, which is expected to alleviate membrane fouling.

[0004] Anaerobic ammonium-oxidizing bacteria, on the other hand, have the characteristic of growing in clusters. Their surfaces contain large amounts of EPS, which carry a negative charge. Applying a positive bias to the anode material creates electrostatic adsorption with the negatively charged microorganisms, enhancing the formation of anaerobic ammonium-oxidizing bacteria on the electrode surface, thereby promoting their accumulation and enhancing their denitrification effectiveness.

[0005] In addition, anaerobic ammonium oxidizing bacteria have the ability to transfer extracellular electrons, transferring electrons to the extracellular space through intracellular cytochrome c, and exchanging electrons with extracellular insoluble substances. This extracellular electron transfer has the ability to enhance bacterial enrichment and improve its metabolic activity. The anode material can serve as a receptor for extracellular electron transfer of anaerobic ammonium oxidizing bacteria. Applying a positive bias voltage on the surface of the anode material can accelerate the extracellular electron transfer process, thereby enhancing the activity of anaerobic ammonium oxidizing bacteria. At the same time, the external electrical stimulation can increase the storage capacity of cytochrome c on the edge of the anaerobic ammonium oxidizing body membrane, accelerate the intracellular electron transfer rate, and thus enhance the activity of anaerobic ammonium oxidizing bacteria.

[0006] Summary of the Invention

[0007] The purpose of the present invention is to provide an electrochemically enhanced anaerobic ammonia oxidation membrane bioreactor based on a conductive separation membrane and a biological denitrification method thereof, which uses a conductive membrane component as the basic separation unit and as the cathode, and uses a carbon material or metal material with good conductivity and biological affinity, economic and environmental protection as the anode. Under the action of an applied voltage, the cathode of the reactor is used to intercept microorganisms to maintain a high sludge concentration and effectively alleviate membrane pollution. The anode is attached to a biofilm to enhance the biofilm formation and metabolic activity of anaerobic ammonia oxidation bacteria, thereby achieving efficient denitrification.

[0008] In order to achieve the above object, the technical solution of the present invention is as follows:

[0009] On the one hand, the present invention provides an electrochemically enhanced anaerobic ammonia oxidation membrane bioreactor based on a conductive separation membrane, wherein the membrane bioreactor comprises a reactor shell, an anode, a cathode, a DC power supply, a water inlet pipe and a water outlet pipe; the reactor shell is filled with anaerobic ammonia oxidizing bacteria, a water inlet is provided at the bottom, and the water inlet is connected to the water inlet pipe; the anode and the cathode are located in the reactor shell; the positive pole of the DC power supply is connected to the anode, and the negative pole is connected to the cathode; the cathode is a conductive membrane assembly, and a water outlet is provided at the top of the conductive membrane assembly, and the water outlet is connected to the water outlet pipe.

[0010] The anaerobic ammonium oxidation reactor includes anode materials and conductive membrane components, the conductive membrane components serve as cathodes, and a DC regulated power supply is provided outside the reactor. The anode materials and the conductive membrane components are connected to the external DC regulated power supply through wires.

[0011] In the above technical solution, further, the anode material includes a carbon material or a metal material, the carbon material is one of a carbon fiber brush, carbon felt, carbon cloth, and a carbon rod, and the metal material is one of a titanium mesh, a ruthenium-iridium-titanium plate, a ruthenium-iridium-titanium sheet, a stainless steel mesh, a stainless steel sheet, a copper mesh, and a copper sheet.

[0012] In the above technical solution, further, the conductive material for preparing the conductive membrane assembly includes one of carbon nanotubes, MXene, graphene, graphene oxide, conductive carbon black, and conductive graphite, and the conductive membrane assembly includes one of a hollow fiber membrane assembly, a tubular membrane assembly, and a flat membrane assembly.

[0013] In the above technical solution, further, the membrane in the conductive membrane assembly includes an ultrafiltration membrane and a microfiltration membrane.

[0014] On the other hand, the present invention provides a biological denitrification method using the above-mentioned membrane bioreactor, wherein sewage and wastewater enter the membrane bioreactor through the water inlet through the water inlet pipe, and after sufficient contact with the anaerobic ammonia-oxidizing bacteria, it is discharged through the water outlet at the top of the conductive membrane assembly through the water outlet pipe.

[0015] In the above technical solution, further, the voltage applied to the reactor is 0-2.0V, the corresponding anode potential is 0-0.5V vs. Ag / AgCl, and the cathode potential is 0--1.5V vs. Ag / AgCl.

[0016] In the above technical solution, further, the internal temperature of the reactor is 10-40°C.

[0017] The beneficial effects of the present invention are:

[0018] (1) Using a membrane bioreactor, anaerobic ammonia-oxidizing bacteria are effectively trapped in the reactor to achieve an enrichment effect. At the same time, the negative bias applied to the cathode relieves the adhesion of EPS on the membrane surface through electrical repulsion, thereby achieving the purpose of alleviating membrane fouling.

[0019] (2) A positive bias voltage is applied to the anode, and anaerobic ammonia-oxidizing bacteria are enriched at the anode through electrosorption.

[0020] (3) Under the action of an external electric field, the storage capacity of cytochrome c attached to the small bodies in the anaerobic ammonium oxidizing bacteria increases, which accelerates the intracellular electron transfer rate and improves the activity of anaerobic ammonium oxidizing bacteria.

[0021] (4) The anode acts as an extracellular electron acceptor. The positive bias applied to the anode material surface accelerates the extracellular electron transfer rate, further improving the activity of anaerobic ammonium oxidizing bacteria. The device has good denitrification performance, effectively alleviates membrane fouling, and is easy to operate, which is conducive to the promotion and application of anaerobic ammonium oxidation membrane bioreactor technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention will be further described below with reference to the accompanying drawings.

[0023] FIG1 is a schematic structural diagram of an electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane according to the present invention;

[0024] FIG2 is a partial schematic diagram of the electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane in Example 1, a is a main view, and b is a top view;

[0025] Figure 3 shows the bacterial flora in the R2 reactor in Example 1;

[0026] FIG4 shows the change of transmembrane pressure difference in Example 1;

[0027] In the figure: 1. Water inlet tank, 2. Water inlet pump, 3. Conductive membrane assembly, 4. Anode, 5. Agitator, 6. DC power supply, 7. Circulation pump, 8. Water bath, 9. Water outlet pump, 10. Vacuum gauge, 11. Water outlet bucket, 12. Reactor shell, 13. Water inlet pipe, 14. Water outlet pipe. DETAILED DESCRIPTION

[0028] The following examples may enable those skilled in the art to more fully understand the present invention, but are not intended to limit the present invention in any way.

[0029] Unless otherwise specified, the materials used in the examples of the present invention can be obtained from commercial sources or prepared according to conventional methods well known to those skilled in the art.

[0030] An electrochemically enhanced anaerobic ammonia oxidation membrane bioreactor based on a conductive separation membrane, as shown in Figure 1, comprises a reactor shell, an anode, a cathode, a DC power supply, an inlet pipe and an outlet pipe; the reactor shell is filled with anaerobic ammonia oxidizing bacteria, a water inlet is provided at the bottom, and the water inlet is connected to the water inlet pipe; the anode and the cathode are located in the reactor shell; the positive pole of the DC power supply is connected to the anode, and the negative pole is connected to the cathode; the cathode is a conductive membrane assembly, and a water outlet is provided on the top of the conductive membrane assembly, and the water outlet is connected to the outlet pipe.

[0031] In the following Example 1, a single CNTs-PVDF hollow fiber membrane was prepared according to patent CN108927012A, and its relevant characteristic parameters are shown in Table 1.

[0032] Table 1 Characteristic parameters of single CNTs-PVDF hollow fiber membrane

[0033] Example 1

[0034] Three anaerobic ammonium oxidation membrane bioreactors were established. The anode material used was a carbon fiber brush, and the cathode material was a conductive membrane assembly consisting of eight CNTs-PVDF hollow fiber membranes connected in parallel. The anode was placed around the conductive membrane assembly. The membrane material parameters are shown in Table 1. The effective membrane area of ​​the anode was 50-100 times that of the cathode. Different applied voltages were applied to the three reactors: the control group (R0) had no applied voltage, while the experimental groups (R1 and R2) had applied voltages of 0.5 V and 1.0 V, respectively. The corresponding anode potentials were 0.23 V vs. Ag / AgCl and 0.32 V vs. Ag / AgCl, respectively, and the cathode potentials were -0.26 V vs. Ag / AgC and -0.66 V vs. Ag / AgCl, respectively. The hydraulic retention times were 24, 16, and 10 h, respectively.

[0035] The specific operating parameters of the reactors are as follows: Anaerobic ammonium oxidation sludge comes from laboratory acclimation culture, and the sludge concentration in each reactor is above 3200 mg / L. When the influent total nitrogen concentration is 200-300 mg / L, the average TN removal rate in the effluent of the different reactors is 60% (R0), 68% (R1), and 74% (R2). The TN removal rates of the R1 and R2 reactors are 14% and 23% higher than those of the R0 reactor, respectively.

[0036] The bacterial community in the R2 reactor is shown in Figure 3. A large number of "red bacteria" are attached to the surface of the carbon fiber brush, indicating that the reactor effectively intercepts and enriches anaerobic ammonium oxidizing bacteria, and the addition of electricity enhances the activity of anaerobic ammonium oxidizing bacteria, thereby improving the denitrification performance of anaerobic ammonium oxidizing bacteria.

[0037] Membrane fouling of the conductive separation membrane in Test Example 1 under electrochemical strengthening:

[0038] As shown in Figure 4, during the operation cycle, the transmembrane pressure (TMP) gradually increased during operation and immediately decreased after cleaning. The trends were similar, but the ΔTMP values ​​for each conductive membrane module group varied during operation and after cleaning, with the experimental group generally outperforming the control group. Over a 28-day operation cycle (HRT = 16 hours), the ΔTMP values ​​for the membrane modules in the different reactors were 0.015 MPa (R0), 0.012 MPa (R1), and 0.011 MPa (R2), respectively. This indicates that the ΔTMP values ​​for the modules in the powered group were lower than those in the unpowered condition, indicating that the application of power alleviated membrane fouling. After hydraulic cleaning, the TMP values ​​for the modules in the powered group were 0.03 MPa (R0), 0.027 MPa (R1), and 0.023 MPa (R2), respectively. This indicates that the application of power also alleviated membrane fouling.

[0039] The above embodiments are merely preferred embodiments of the present invention and are not intended to limit the scope of the present invention. The scope of protection of the present invention shall be determined by the scope defined in the claims. Other variations or modifications may be made based on the above description. Obvious variations or modifications derived therefrom shall remain within the scope of protection of the present invention.

Claims

1. An electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane, characterized in that: The membrane bioreactor comprises a reactor shell, an anode, a cathode, a DC power supply, an inlet pipe and an outlet pipe; the reactor shell is filled with anaerobic ammonia-oxidizing bacteria, a water inlet is arranged at the bottom, and the water inlet is connected to the inlet pipe; the anode and the cathode are located in the reactor shell; the positive pole of the DC power supply is connected to the anode, and the negative pole is connected to the cathode; the cathode is a conductive membrane assembly, a water outlet is arranged on the top of the conductive membrane assembly, and the water outlet is connected to the outlet pipe.

2. The electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane according to claim 1, characterized in that: The anode material includes a carbon material or a metal material, the carbon material is one of a carbon fiber brush, carbon felt, carbon cloth, and a carbon rod, and the metal material is one of a titanium mesh, a ruthenium-iridium-titanium plate, a ruthenium-iridium-titanium sheet, a stainless steel mesh, a stainless steel sheet, a copper mesh, and a copper sheet.

3. The electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane according to claim 1, characterized in that: The conductive material for preparing the conductive membrane assembly includes one of carbon nanotubes, MXene, graphene, graphene oxide, conductive carbon black, and conductive graphite. The conductive membrane assembly includes one of a hollow fiber membrane assembly, a tubular membrane assembly, and a flat membrane assembly.

4. The electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane according to claim 3, characterized in that: The membranes in the conductive membrane assembly include ultrafiltration membranes and microfiltration membranes.

5. A biological denitrification method using the membrane bioreactor according to any one of claims 1 to 4, characterized in that: Sewage and wastewater enter the membrane bioreactor through the water inlet through the water inlet pipe, and after fully contacting with the anaerobic ammonia-oxidizing bacteria, they are discharged through the water outlet at the top of the conductive membrane assembly through the water outlet pipe.

6. The biological denitrification method according to claim 5, characterized in that: The voltage applied to the reactor is 0-2.0 V, the corresponding anode potential is 0-0.5 V vs. Ag / AgCl, and the cathode potential is 0--1.5 V vs. Ag / AgCl.

7. The biological denitrification method according to claim 5, characterized in that: The internal temperature of the reactor is 10-40°C.

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