Magnetic powder coupling micro electric field membrane bioreactor and application thereof

Abstract

The invention discloses a magnetic powder coupling micro electric field membrane bioreactor and application thereof, and belongs to the technical field of sewage treatment. The method comprises the following steps: adding a magnetic material into a micro-electric field membrane bioreactor which takes a conductive metal material embedded in a membrane component as a cathode and a graphite material as an anode, and providing a micro-electric field by utilizing a direct-current stabilized power supply to form a magnetic powder and micro-electric field membrane bioreactor coupling system. The magnetic biological effect and micro electric field stimulation are utilized to obviously influence the microbial composition and metabolic characteristics, so that the coupling system has high degradation capacity on ciprofloxacin antibiotics, and EPS secretion is reduced. The negative electric field is applied near the membrane surface according to the principle that like poles repel to increase the repulsive action on the pollutants, the membrane pollutants are pushed away from the membrane surface, and hydrogen peroxide generated by applying the micro electric field near the membrane surface can remove part of pollutants on the membrane surface and in membrane holes by virtue of the oxidation capacity of the hydrogen peroxide, so that the anti-pollution capacity is improved.

Description

Technical Field

[0001] The invention relates to a magnetic powder coupling micro-electric field membrane bioreactor and application thereof, belonging to the technical field of sewage treatment and membrane bioreactor (MBR). Background Art

[0002] With the vigorous development of medical and animal husbandry industries, the consumption of antibiotics is increasing. The frequent use of antibiotics has led to increasingly severe environmental pollution problems, which has attracted widespread attention and high attention from scholars around the world. Fluoroquinolones are a series of broad-spectrum synthetic antibiotics that are widely used as human and veterinary drugs. Ciprofloxacin is the most widely prescribed fluoroquinolone antibiotic used in disease treatment, and high concentrations of residues are often detected in the environment. Antibiotics entering the environment will not only induce the production of resistant microorganisms and resistance genes in the environment, but also accelerate the spread and diffusion of antibiotic resistance, so it is urgent to solve the problem of antibiotic residues. At present, the methods for controlling antibiotics mainly include physical methods, chemical methods and biological methods. Compared with physical and chemical methods, biological methods have the advantages of low cost and simple degradation process, and are currently more economical and effective methods.

[0003] Membrane bioreactor (MBR) is widely used in the treatment of antibiotic wastewater due to its advantages such as small footprint, high volumetric load and good effluent quality. However, in actual promotion and application, membrane fouling is a technical obstacle that restricts the widespread application of MBR. Membrane fouling in MBR refers to the phenomenon that sludge flocs, colloidal particles, soluble organic matter, inorganic salts and extracellular polymers (EPS) in the mixed liquor are deposited on the membrane surface to form a filter cake layer due to physical and chemical interactions or mechanical effects between membranes, or the membrane pores are blocked due to adsorption in the membrane pores, which increases the resistance of water passing through the membrane, reduces the filtration performance, and thus leads to a decrease in membrane flux. In view of the essence of membrane fouling, the methods for controlling membrane fouling in MBR mainly revolve around the following four aspects: (1) membrane modification (2) regulating the properties of sludge mixed liquor (3) optimizing reactor operating conditions (4) membrane cleaning. However, the above membrane fouling methods all have certain defects. Whether it is membrane modification, regulating the properties of sludge mixed liquor (adding adsorbents, flocculants, suspended particles and other chemical agents) or optimizing reactor operating conditions (adjusting aeration volume and membrane flux, etc.), it will increase the operating and maintenance costs of MBR. The physical cleaning effect of membrane cleaning is limited and cannot guarantee subsequent use. Chemical cleaning will affect the stability of membrane materials and may cause secondary pollution.

[0004] In recent years, a new technology has attracted the attention of many scholars, namely, electrochemical assisted technology, in view of the fact that activated sludge flocs, colloidal particles, and membrane pollutants such as EPS in MBR are all negatively charged. Electrochemical assisted technology mainly uses the principle of mutual repulsion between like charges to reduce the adsorption and deposition of negatively charged pollutants on the membrane surface through electric field repulsion, reduce the membrane pollution rate, and extend the membrane filtration operation cycle, thereby achieving the purpose of controlling membrane pollution. At the same time, under the action of electrochemistry, a certain amount of hydrogen peroxide is produced near the cathode membrane assembly. Hydrogen peroxide has a strong oxidizing ability and can oxidize and remove membrane surface pollutants to a certain extent, thereby improving the membrane's anti-pollution ability.

[0005] Liu Lifen and others invented a method for making polyaniline modified neutral conductive membrane (patent publication number CN103100314A). Wang Zhiwei and others invented a conductive filter membrane and its application (patent publication number CN104289114A). However, in the above invention studies, organic membranes are used as the basis in the preparation process of the conductive membrane, and organic membranes have disadvantages such as short service life and poor chemical stability, which restricts their promotion in practical applications; typical materials such as polyvinylidene fluoride (PVDF), polyether sulfone (PES) or polytetrafluoroethylene (PTFE) are used for casting liquid and scraping membrane materials, and the processing process is complicated and the preparation cost is high. More importantly, the electric field applied during the implementation of the above inventions is too high, which further aggravates the energy consumption in MBR.

[0006] As an inert material, magnetic powder can remain stable in the environment and undergo no or weak chemical changes. It has good adsorption and can absorb pollutants in water. In addition, the magnetic biological effect produced by microorganisms under the action of the magnetic field can enhance the activity of microorganisms, improve the treatment efficiency of ciprofloxacin antibiotic wastewater, and reduce the generation of membrane pollutants EPS. Liu et al. added magnetic powder to the MBR system to treat domestic sewage. The study found that magnetic powder has an inhibitory effect on the production of EPS, thereby slowing down membrane pollution. In addition, since magnetic powder has good conductivity, it can enhance the conductivity of the mixed liquid in the MBR, thereby reducing the electric field applied by the reaction; at the same time, magnetic powder is a low-priced material that can be recycled and reused, effectively controlling operating costs and maintenance costs, and therefore has considerable social, economic and environmental benefits. At present, there is no report on the combination of magnetic powder and micro-electric field membrane bioreactor to treat ciprofloxacin antibiotic wastewater in the field of wastewater treatment.

[0007] The present invention starts from the dual perspectives of improving the degradation efficiency of ciprofloxacin antibiotic wastewater and slowing down membrane pollution, couples magnetic powder with a micro-electric field membrane bioreactor, fully utilizes their respective advantages, and cooperates with each other to invent a magnetic powder coupled micro-electric field membrane bioreactor. The invention of this coupling system realizes the efficient treatment of ciprofloxacin antibiotic wastewater, reduces the frequency of membrane cleaning, increases the service life of membrane components, reduces the process operation cost, and has obvious advantages in practical applications. Summary of the invention

[0008] The purpose of the present invention is to provide a magnetic powder coupled micro-electric field membrane bioreactor, which can effectively control the MBR membrane pollution in situ under the dual effects of magnetic biological effect and micro-electric field force, and improve the degradation efficiency of ciprofloxacin antibiotics while slowing down the membrane pollution.

[0009] The technical scheme of the present invention is: the device used: a micro-electric field membrane bioreactor of a traditional flat membrane assembly is used as a reactor, wherein an embedded conductive metal material is used as both a cathode and a filter medium, a graphite material is used as an anode, and a magnetic powder material is added to the space between the cathode and the anode to form a magnetic powder coupling micro-electric field membrane bioreactor; sewage treatment plant sludge is used as a microbial source, and a cathode and anode of a magnetic powder coupling micro-electric field membrane bioreactor (wherein magnetic powder is mixed in the antibiotic wastewater) with antibiotic wastewater are treated by direct current; the electric field force formed by an external electric field is used to push negatively charged membrane pollutants and extracellular polymers (EPS) away from the membrane surface, thereby effectively controlling membrane pollution; a certain amount of hydrogen peroxide is generated near the cathode membrane by the electrochemical effect formed by the external electric field, and hydrogen peroxide, as an active oxygen species, has a strong oxidizing ability and can oxidize and remove membrane surface pollutants, and finally realize the in-situ membrane pollution control of the MBR system. At the same time, the magnetic biological effect generated by microorganisms under the action of the magnetic field can reduce the generation of membrane pollutants EPS; improve the activity of microorganisms, and then improve the treatment efficiency of ciprofloxacin antibiotic wastewater.

[0010] Under the dual effects of micro-electric field and magnetic-induced biological effect, the invention improves the anti-pollution performance of the membrane and realizes the efficient degradation of ciprofloxacin.

[0011] In the present invention, the magnetic powder material is ferroferric oxide, and its dosage in the coupling system is 0.5-2 g / L.

[0012] In the present invention, the conductive metal material is a good conductor with certain corrosion resistance, and its material is titanium metal or stainless steel, and its structure includes mesh or wire.

[0013] In the present invention, the graphite anode material is any one of graphite plate, graphite felt or graphite cloth.

[0014] In the present invention, the micro-electric field is provided by a DC regulated power supply, and the applied voltage is 0.1-0.5 V / cm.

[0015] In the present invention, the membrane bioreactor is a general membrane bioreactor, including a water inlet and water level control system, a water outlet system, an aeration system, and an electric field supply system.

[0016] Beneficial effects of the present invention:

[0017] 1. The membrane material of the present invention is a conductive metal material embedded in a conventional flat membrane assembly, which does not require a conductive membrane material with a complicated preparation process, thus saving time and production costs;

[0018] 2. The magnetic powder material used in the present invention has a wide range of sources, stable chemical properties, low cost, can be recycled for secondary use, and will not cause secondary pollution;

[0019] 3. The electric field applied by the present invention is an external constant micro electric field, and the operating energy consumption is low;

[0020] 4. The present invention directly acts on the conductive membrane through an external electric field to generate a certain amount of hydrogen peroxide, thereby controlling the membrane pollution in situ;

[0021] 5. The magnetic powder coupled micro-electric field membrane bioreactor of the present invention realizes the efficient treatment of ciprofloxacin antibiotic wastewater, reduces the membrane cleaning frequency, and increases the service life of the membrane assembly. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a schematic diagram of a magnetic powder coupled micro-electric field membrane bioreactor device;

[0023] Figure 2 This is a diagram showing the generation of EPS according to an embodiment of the present invention;

[0024] Figure 3 This is a diagram of the degradation of ciprofloxacin in an embodiment of the present invention. DETAILED DESCRIPTION

[0025] The present invention is further described below by way of examples in conjunction with the accompanying drawings. However, the present invention is not limited to the following examples.

[0026] The microorganisms in the following examples were sourced from the secondary sedimentation tank of a sewage treatment plant in Beijing, with a sludge inoculation rate of 5 g / L. Aeration rate: 0.2 L / min.

[0027] Magnetic powder source: micron-grade Fe3O4

[0028] Example 1: The magnetic powder coupled micro-electric field membrane bioreactor is a general membrane bioreactor, which includes a common water inlet and water level control system, a water outlet system, an aeration system, and an electric field supply system.

[0029] The water inlet and water level control system is a high-level water tank and a balance water tank. The high-level water tank stores water, and the balance water tank controls the liquid level in the reactor through a ball valve. The inlet water is artificially simulated ciprofloxacin antibiotic wastewater. The outlet water system uses a peristaltic pump to pump out water, and a vacuum gauge is placed at the front end of the peristaltic pump to monitor the transmembrane pressure of the membrane assembly. The aeration system uses an air aerator for aeration. A conventional flat membrane assembly with an embedded stainless steel mesh is used as the cathode and filter medium, and a graphite plate material is used as the anode; the magnetic powder material is Fe3O4; the constant electric field is provided by a DC regulated power supply. The activity of dehydrogenase is used to represent the activity of microorganisms. Two sets of reactors are adopted, one with an external electric field and Fe3O4 added as the experimental group; one without an electric field and Fe3O4 as the control group, and the rest are the same.

[0030] The artificial simulated ciprofloxacin antibiotic wastewater was: 1g / L NH4(SO4)2, 1g / L K2HPO4, 1.3g / L Na2HPO4, 3mg / L ciprofloxacin. The experimental group (G1) reactor was added with 0.5V / cm voltage and 0.5g / L Fe3O4; the control group (G0) was not added with electric field and magnetic powder. The reactor was heated at 65L / (m 2 ·h) flux operation, when the transmembrane pressure reaches 30kPa, it is considered as the operation end point. The EPS production of the experimental group (G1) is 81.2mg / g·VSS, the degradation rate of ciprofloxacin is 78.2%, and the membrane cleaning cycle is 34 days; the EPS production of the control group (G0) is 137.4mg / g·VSS, the degradation rate of ciprofloxacin is 69.6%, and the membrane cleaning cycle is 26 days.

[0031] Example 2: The reaction system in Example 1 was used to treat artificial ciprofloxacin antibiotic wastewater. The experimental group (G2) reactor was subjected to an external voltage of 0.3 V / cm and 1 g / L Fe3O4 was added. The control group (G0) was subjected to no electric field and no magnetic powder. The reactor was heated at 65 L / (m 2 ·h) flux operation, when the transmembrane pressure reaches 30kPa, it is considered as the operation end point. The EPS production of the experimental group (G2) is 50.3mg / g·VSS, the degradation rate of ciprofloxacin is 83.0%, and the membrane cleaning cycle is 38 days; the EPS production of the control group (G0) is 137.4mg / g·VSS, the degradation rate of ciprofloxacin is 69.6%, and the membrane cleaning cycle is 26 days.

[0032] Example 3: The reaction system in Example 1 was used to treat artificial ciprofloxacin antibiotic wastewater. The experimental group (G3) reactor was subjected to an external voltage of 0.1 V / cm and 2 g / L Fe3O4 was added. The control group (G0) was subjected to no electric field and no magnetic powder. The reactor was heated at 65 L / (m 2h) flux operation, when the transmembrane pressure reaches 30 kPa, it is considered as the operation end point. The EPS production of the experimental group (G3) is 61.6 mg / g·VSS, the degradation rate of ciprofloxacin is 74.2%, and the membrane cleaning cycle is 30 days; the EPS production of the control group (G0) is 137.4 mg / g·VSS, the degradation rate of ciprofloxacin is 69.6%, and the membrane cleaning cycle is 26 days.

Claims

1. A magnetic powder coupled micro-electric field membrane bioreactor, characterized in that: A traditional flat membrane component micro-electric field membrane bioreactor is used as the reactor, in which an embedded conductive metal material is used as both the cathode and the filter medium, a graphite material is used as the anode, magnetic powder material is added into the space between the cathode and the anode, and a DC regulated power supply is used to provide a micro-electric field to form a magnetic powder coupled micro-electric field membrane bioreactor.

2. A magnetic powder coupled micro-electric field membrane bioreactor according to claim 2, characterized in that: The conductive metal material is titanium or stainless steel, and its structure includes mesh or filament; the graphite anode material is any one of graphite plate, graphite felt or graphite cloth.

3. A magnetic powder coupled micro-electric field membrane bioreactor according to claim 2, characterized in that: The magnetic powder coupled micro-electric field membrane bioreactor includes a water inlet and water level control system, a water outlet system, an aeration system, and an electric field supply system.

4. A method for treating sewage using the magnetic powder coupled micro-electric field membrane bioreactor according to any one of claims 1 to 3, characterized in that: Using sewage treatment plant sludge as the source of microorganisms, direct current was passed through the cathode and anode of the magnetic powder coupled micro-electric field membrane bioreactor to treat the antibiotic wastewater. The magnetic particles are mixed in the antibiotic wastewater.

5. The method according to claim 4, characterized in that: The magnetic powder is ferroferric oxide, and its dosage in the coupling system is 0.5-2 g / L.

6. The method according to claim 4, characterized in that: The micro-electric field is provided by a DC voltage-stabilized power supply, and the applied voltage is 0.1-0.5 V / cm.

7. The method according to claim 4, characterized in that: The antibiotic wastewater is wastewater containing ciprofloxacin antibiotic.

8. The method according to claim 7, characterized in that: The electric field force formed by the external electric field is used to push the negatively charged membrane pollutants and extracellular polymers (EPS) away from the membrane surface, thereby effectively controlling membrane pollution. The electrochemical effect formed by the external electric field is used to produce a certain amount of hydrogen peroxide near the cathode membrane. As an active oxygen species, hydrogen peroxide has a strong oxidizing ability and can oxidize and remove membrane surface pollutants, ultimately achieving in-situ membrane pollution control of the MBR system. At the same time, the magnetic biological effect produced by microorganisms under the action of the magnetic field can reduce the production of membrane pollutants EPS, improve the activity of microorganisms, and thereby improve the treatment efficiency of ciprofloxacin antibiotic wastewater.

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