CN117303559A - An electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on conductive separation membrane and its biological denitrification method - Google Patents

Abstract

The invention discloses an electrochemical reinforced anaerobic ammonia oxidation membrane bioreactor based on a conductive separation membrane and a biological denitrification method thereof. The membrane bioreactor comprises a reactor shell, an anode, a cathode, a direct current power supply, a water inlet pipeline and a water outlet pipeline; the reactor shell is filled with anaerobic ammonia oxidizing bacteria, the bottom of the reactor shell is provided with a water inlet, and the water inlet is connected with a water inlet pipeline; the anode and the cathode are positioned in the reactor shell; the positive electrode of the direct current power supply is connected with the anode, and the negative electrode of the direct current power supply is connected with the cathode; the cathode is a conductive film component, the top of the conductive film component is provided with a water outlet, and the water outlet is connected with a water outlet pipeline. The invention couples membrane biological treatment with electrochemical technology, can effectively intercept and enrich anaerobic ammonia oxidation bacteria and strengthen denitrification effect of the anaerobic ammonia oxidation bacteria, and simultaneously relieves membrane pollution through electrostatic repulsion. The device has good denitrification performance, effectively relieves membrane pollution, is simple to operate, and has wide application prospect.

Description

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

Technical field

The present invention relates to the technical field of sewage treatment, specifically, to an electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane and its biological denitrification method.

Background technique

Traditional nitrification and denitrification biological denitrification processes require aeration and addition of additional carbon sources, resulting in high operating costs. Anaerobic ammonium oxidation (Anammox) uses nitrite as the electron acceptor and ammonia nitrogen as the electron donor to generate nitrogen under anaerobic conditions. Compared with the traditional denitrification process, 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 a promising new denitrification process. . However, anaerobic ammonium oxidizing bacteria are difficult to enrich and have low biological activity, which results in long start-up time and difficulty in stable operation, which seriously hinders the large-scale application of this process. Therefore, taking effective measures to enhance the enrichment and biological activity of anaerobic ammonium oxidizing bacteria is a top priority to promote the application of this technology.

The anaerobic ammonium oxidation (Membrane Bioreactor for Anammox) process based on membrane bioreactors can effectively intercept anaerobic ammonium oxidizing bacteria and maintain a high sludge concentration in the reactor, thereby achieving enrichment and cultivation of anaerobic ammonium oxidizing bacteria and accelerating Start the process and improve the denitrification effect. However, similar to the conventional MBR process, during the operation of the anaerobic ammonium oxidation process based on membrane bioreactors, part of the anammox sludge is adsorbed on the membrane surface and blocks the membrane pores, affecting the membrane pore efficiency. Therefore, its effluent flux gradually decreases with operation time, which is a membrane clogging problem. Taking into account the negative charge of membrane fouling substances, using conductive materials to prepare conductive films and applying a negative bias voltage on the surface can hinder sludge adhesion through electrical repulsion, which is expected to alleviate membrane fouling.

On the other hand, anaerobic ammonium oxidizing bacteria have aggregate growth characteristics, and the surface of the microorganisms contains a large amount of EPS, which is negatively charged. Applying a positive bias voltage to the surface of the anode material can produce electrostatic adsorption with negatively charged microorganisms on the surface, thereby strengthening the deposition of anaerobic ammonium oxidizing bacteria on the electrode surface, thereby promoting the enrichment of anaerobic ammonium oxidizing bacteria and enhancing its denitrification effect.

In addition, anaerobic ammonium oxidizing bacteria have extracellular electron transfer capabilities. They transfer electrons to the outside of the cell through intracellular cytochrome c and exchange electrons with extracellular insoluble substances. This extracellular electron transfer has the ability to enhance bacterial enrichment and increase their metabolic activity. The anode material can serve as a receptor for extracellular electron transfer by 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, external electrical stimulation can increase the storage of cytochrome c on the edge of the anammox body membrane, speed up the intracellular electron transfer rate, and thereby enhance the activity of anaerobic ammonium oxidizing bacteria.

Contents of the invention

The purpose of the present invention is to provide an electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor and its biological denitrification method based on a conductive separation membrane, which uses a conductive membrane component as the basic separation unit and as the cathode, using conductive properties and biological Carbon materials or metal materials with good affinity, economical and environmental protection are used as anodes. Under the action of external voltage, the cathode of the reactor is used to intercept microorganisms to maintain a high sludge concentration and effectively alleviate membrane fouling and microbial adhesion to the anode. Membrane is used to strengthen the membrane and metabolic activity of anaerobic ammonium oxidizing bacteria to achieve efficient denitrification.

In order to achieve the above objects, the technical solutions of the present invention are as follows:

In one aspect, the present invention provides an electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane. The membrane bioreactor includes 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 ammonium oxidizing bacteria, and a water inlet is provided at the bottom, and the water inlet is connected to a water inlet pipe; the anode and cathode are located in the reactor shell; the positive electrode of the DC power supply is connected to the anode, The negative electrode is connected to the cathode; the cathode is a conductive membrane assembly, a water outlet is provided on the top of the conductive membrane assembly, and the water outlet is connected to a water outlet pipe.

The anaerobic ammonium oxidation reactor includes an anode material and a conductive membrane component inside. The conductive membrane component serves as the cathode. A DC regulated power supply is set outside the reactor. The anode material and conductive membrane component are connected to an external DC regulated power supply through wires.

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

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

In the above technical solution, further, the membranes in the conductive membrane module include ultrafiltration membranes and microfiltration membranes.

On the other hand, the present invention provides a biological denitrification method using the above-mentioned membrane bioreactor. The sewage enters the membrane bioreactor through the water inlet through the water inlet pipe, and after full contact with the anaerobic ammonium oxidizing bacteria, passes through the top of the conductive membrane component. The water outlet is discharged through the water outlet pipe.

In the above technical solution, further, the applied voltage of 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.

In the above technical solution, further, the internal temperature of the reactor is 10 to 40°C.

The beneficial effects of the present invention are:

(1) Use a membrane bioreactor to effectively trap anaerobic ammonium oxidizing bacteria in the reactor to achieve an enrichment effect. At the same time, the negative bias voltage applied on the cathode relieves the adhesion of EPS on the membrane surface through electrical repulsion, thereby achieving the purpose of alleviating membrane fouling.

(2) A positive bias voltage is applied to the anode, and anaerobic ammonium oxidizing bacteria are enriched on the anode through electroadsorption.

(3) Under the action of an external electric field, the storage amount of cytochrome c attached to the bodies in the anaerobic ammonium oxidizing bacteria increases, speeding up the intracellular electron transfer rate and improving the activity of the anaerobic ammonium oxidizing bacteria.

(4) The anode serves as an extracellular electron acceptor, and the positive bias applied on the surface of the anode material accelerates the extracellular electron transfer rate and further improves the activity of anaerobic ammonium oxidizing bacteria. The device has good denitrification performance, effectively alleviates membrane pollution, is simple to operate, and is conducive to the promotion and application of anaerobic ammonium oxidation membrane bioreactor technology.

Description of the drawings

The present invention will be further described below in conjunction with the accompanying drawings.

Figure 1 is a schematic structural diagram of the electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on the conductive separation membrane of the present invention;

Figure 2 is a partial schematic diagram of the electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on the conductive separation membrane in Example 1, a is the main view, and b is the top view;

Figure 3 shows the bacterial population in the R2 reactor in Example 1;

Figure 4 shows the changes in transmembrane pressure difference in Example 1;

In the picture: 1. Water inlet, 2. Water inlet pump, 3. Conductive membrane component, 4. Anode, 5. Stirrer, 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 ways

The following examples can enable those of ordinary skill in the art to understand the present invention more comprehensively, but do not limit the present invention in any way.

Unless otherwise specified, the materials used in the examples of the present invention can be obtained commercially or prepared according to conventional methods well known to those skilled in the art.

An electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane, as shown in Figure 1. The membrane bioreactor includes a reactor shell, anode, cathode, DC power supply, water inlet pipe and water outlet pipe; reaction The reactor shell is filled with anaerobic ammonium oxidizing bacteria, and a water inlet is provided at the bottom, which is connected to the water inlet pipe; the anode and cathode are located in the reactor shell; the positive electrode of the DC power supply is connected to the anode, and the negative electrode is connected to the cathode; the cathode is A conductive membrane module is provided with a water outlet on the top of the conductive membrane module, and the water outlet is connected to the water outlet pipe.

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

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

Example 1

Establish three anaerobic ammonium oxidation membrane bioreactors. The anode material uses carbon fiber brushes, and the cathode material uses a conductive membrane module composed of 8 CNTs-PVDF hollow fiber membranes connected in parallel. The anodes are placed around the conductive membrane module, and the various parameters of the membrane material The parameters are shown in Table 1. The effective membrane area of the anode is 50-100 times that of the cathode. The three groups of reactors are set with different applied voltages: the control group R0 has no applied voltage, the applied voltages of the experimental groups R1 and R2 are 0.5V and 1.0V respectively, and the corresponding anode potentials are 0.23V vs.Ag/AgCl and 0.32V vs .Ag/AgCl, the cathode potentials are -0.26V vs.Ag/AgC, -0.66V vs.Ag/AgCl respectively; the hydraulic retention times are 24, 16, and 10h respectively.

The specific operating parameters of the reactor are as follows: the anaerobic ammonium oxidation sludge comes from laboratory domestication and cultivation. The sludge concentration in each reactor is above 3200mg/L. When the total nitrogen concentration of the inlet water is 200-300mg/L, the effluent of different reactors The average TN removal rates were 60% (R0), 68% (R1), and 74% (R2). The TN removal rates of R1 and R2 reactors were increased by 14% and 23% respectively compared with R0.

The bacterial flora 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 the anaerobic ammonium oxidizing bacteria, and the addition of electricity strengthens the anaerobic ammonium oxidizing bacteria. activity, improving the denitrification performance of anaerobic ammonium oxidizing bacteria.

Test the membrane fouling of the conductive separation membrane in Example 1 under the action of electrochemical strengthening:

As shown in Figure 4, during the operation cycle, the transmembrane pressure difference (Transmembrane Pressure, TMP) gradually increases during operation and decreases immediately after cleaning. The changing trends are similar, but the △TMP of each group of conductive membrane modules is different during operation, and the TMP after cleaning is also different. Overall, the experimental group is better than the control group. During the 28-day operating cycle (HRT=16h), the △TMP of the membrane components in different reactors are 0.015Mpa (R0), 0.012Mpa (R1), and 0.011Mpa (R2) respectively. It can be seen that the membrane component △ of the power-on group The TMPs are all smaller than those without power, indicating that adding power alleviates the membrane fouling problem. After hydraulic cleaning, the TMPs of the inner membrane components of different reactors are 0.03Mpa (R0), 0.027Mpa (R1), and 0.023Mpa (R2) respectively. It can be seen that the transmembrane pressure difference of the powered group after hydraulic cleaning is also smaller than that of the unpowered condition. , which also shows that adding power alleviates the membrane fouling problem.

The above embodiments are only preferred embodiments of the present invention and are not intended to limit the implementation. The protection scope of the present invention shall be subject to the scope defined by the claims. Other changes or changes in different forms can also be made on the basis of the above description. Obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims (7)

1. An electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on a conductive separation membrane, characterized in that: the membrane bioreactor includes 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 ammonium oxidizing bacteria, and a water inlet is provided at the bottom, and the water inlet is connected to the water inlet pipe; the anode and cathode are located in the reactor shell; the positive electrode of the DC power supply is connected to the anode , the negative electrode is connected to the cathode; the cathode is a conductive membrane assembly, a water outlet is provided on the top of the conductive membrane assembly, and the water outlet is connected to a water outlet pipe. 2. The electrochemically enhanced anaerobic ammonium oxidation membrane bioreactor based on conductive separation membrane according to claim 1, characterized in that: the anode material includes carbon material or metal material, and the carbon material is carbon fiber brush, carbon One of felt, carbon cloth, and carbon rod, and the metal material is one of titanium mesh, ruthenium-iridium titanium plate, ruthenium-iridium titanium sheet, stainless steel mesh, stainless steel sheet, copper mesh, and 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 materials for preparing the conductive membrane assembly include carbon nanotubes, MXene, graphene, and graphene oxide. , conductive carbon black, conductive graphite, and the conductive membrane module includes one of a hollow fiber membrane module, a tubular membrane module, and a flat membrane module. 4. The immersed conductive membrane module according to claim 3, characterized in that: the membranes in the conductive membrane module 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 interact with anaerobic ammonium oxidizing bacteria. After full contact, it is discharged through the water outlet pipe through the water outlet on the top of the conductive membrane module. 6. The biological denitrification method according to claim 5, characterized in that: the applied voltage of the reactor is 0~2.0V, the corresponding anode potential is 0~0.5V vs.Ag/AgCl, and the cathode potential is 0~2.0V. -1.5V 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.