Andmbr dynamic membrane assembly based on electrode polarity conversion, and control method

Abstract

Disclosed in the present invention are an AnDMBR dynamic membrane assembly based on electrode polarity conversion, and a control method. Specifically, in the present invention, flat-sheet membranes and conductive titanium meshes are combined and are then connected to a power source; and by means of an electrode polarity conversion method, the formation of a dynamic membrane layer is accelerated at a starting stage by using the characteristic of charges of opposite polarities attracting each other, and when the dynamic membrane layer is excessively thick, a sludge cake layer is peeled off by using the characteristic of charges of the same polarity repelling each other, so as to alleviate membrane fouling, thereby achieving effective control over membrane fouling, and ensuring the long-term and stable operation of a reactor.

Description

AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to the Chinese patent application filed with the China Patent Office on September 1, 2023, with application number 202311128482.4 and invention name “AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion”, the entire contents of which are incorporated by reference into this application. Technical Field

[0003] The invention belongs to the technical field of sludge anaerobic digestion and relates to an AnDMBR dynamic membrane component based on electrode polarity conversion and a control method. Background Art

[0004] The anaerobic dynamic membrane bioreactor (AnDMBR) is a water treatment technology that combines membrane separation technology with the activated sludge process. When applied to anaerobic sludge digestion, it uses a large-pore, inexpensive substrate as the support layer of the dynamic membrane assembly. When the sludge liquid is filtered through the substrate, a biomass layer, namely the dynamic membrane layer, will gradually form on the surface of the substrate, thereby exerting a retention effect similar to that of a traditional filter membrane, but this process usually requires a long cycle. In addition, the AnDMBR process can achieve an increase in operating concentration by decoupling the hydraulic retention time and the solid retention time. However, long-term operation at high sludge concentrations will inevitably make the dynamic membrane layer too thick, causing the formation of a connected mud cake on the membrane surface, resulting in an excessively high transmembrane pressure difference or an excessively low membrane flux, thereby reducing the operating efficiency of the dynamic membrane. As a result, it is necessary to frequently open the lid and remove the dynamic membrane assembly for flushing outside the reactor.

[0005] In conventional AnDMBR processes, the formation of a dynamic membrane is generally controlled by adjusting the membrane effluent flux and the daily sludge discharge volume, and during the operation of the reactor, biogas circulation is used to form a membrane surface cross-flow rate to alleviate the sludge deposition on the membrane surface, thereby controlling the formation of a mud cake layer. During the startup process of the above-mentioned dynamic membrane, the reactor controls the formation of the dynamic membrane based on the set daily sludge discharge volume and membrane effluent flux. This usually takes a long time to form a relatively ideal dense dynamic membrane layer, which consumes a large amount of time and is not conducive to the rapid performance of the reactor. In addition, when the sludge concentration and viscosity in the membrane area are high, the membrane surface cross-flow rate formed by using biogas circulation alone is limited, and the biogas circulation volume depends on the digestion effect of the sludge. When the digestion condition is poor and the biogas production is insufficient, it will cause the mud cake on the membrane surface to deposit rapidly, thereby reducing the performance of the AnDMBR system.

[0006] In view of the above situation, in order to effectively shorten the startup time of the AnDMBR system and slow down the membrane fouling rate, reduce the frequency of opening the cover for cleaning or replacing the membrane assembly, and achieve long-term stable operation of the dynamic membrane, it is necessary to develop an AnDMBR dynamic membrane control method to provide technical support for the long-term stable operation of the reactor.

[0007] Summary of the Invention

[0008] In response to the above-mentioned defects in the prior art, the purpose of the present invention is to provide an AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion. Specifically, the present invention composites a flat membrane with a conductive titanium mesh and connects it to a power supply. Through the method of electrode polarity conversion, the formation of the dynamic membrane layer is accelerated during the startup phase by utilizing the mutual attraction of opposite charges. When the dynamic membrane layer is too thick, the mutual repulsion of like charges is utilized to peel off the mud cake layer, alleviate membrane contamination, thereby achieving effective control of membrane contamination and ensuring the long-term stable operation of the reactor.

[0009] To achieve the above object, the present invention adopts the following technical solutions:

[0010] The first aspect of the present invention provides an AnDMBR dynamic membrane module based on electrode polarity conversion, comprising a membrane frame and a plurality of conductive flat membranes arranged in parallel in the membrane frame;

[0011] The conductive flat membrane includes a diaphragm frame, a first conductive titanium mesh arranged on the diaphragm frame, and conductive diaphragms symmetrically arranged on both sides of the diaphragm frame; the diaphragm frame is provided with a membrane water outlet; the conductive diaphragm is composed of a second conductive titanium mesh and a supporting diaphragm; the first conductive titanium mesh and the second conductive titanium mesh are both connected to electrode sheets connected to a power supply.

[0012] Preferably, the power supply is connected to the electrode sheet of the first conductive titanium mesh and the electrode sheet of the second conductive titanium mesh respectively through a positive and negative switching element.

[0013] Preferably, the electrode sheet of the first conductive titanium mesh and the electrode sheet of the second conductive titanium mesh are respectively arranged on both sides of the membrane water outlet.

[0014] Preferably, the supporting membrane is made of polyester mesh or nylon mesh.

[0015] The second aspect of the present invention provides a method for controlling an AnDMBR dynamic membrane using the AnDMBR dynamic membrane assembly based on electrode polarity conversion according to the first aspect of the present invention, comprising the following steps:

[0016] S1, during the startup phase of AnDMBR, the conductive flat membrane of the dynamic membrane assembly is connected to a power source, the first conductive titanium mesh acts as a cathode, and the second conductive titanium mesh acts as an anode, attracting negatively charged sludge particles to gather on the surface of the conductive flat membrane, accelerating the formation of the dynamic membrane layer;

[0017] S2, during the stable operation stage of AnDMBR, the transmembrane pressure difference of the membrane area is detected in real time. When the transmembrane pressure difference is greater than 30kPa, the first conductive titanium mesh is switched to the anode and the second conductive titanium mesh is switched to the cathode to peel off the mud cake of the dynamic membrane layer and alleviate membrane pollution.

[0018] Preferably, in step S1, the voltage of the first conductive titanium mesh is -2 to 0V, and the voltage of the second conductive titanium mesh is +2 to +3V.

[0019] Preferably, in step S2, during the stable operation phase of the AnDMBR, when the transmembrane pressure difference of the membrane zone is ≥2 kPa and ≤30 kPa, the dynamic membrane module is disconnected from the power supply.

[0020] Preferably, in step S2, when the transmembrane pressure difference of the membrane region is greater than 30 kPa, the voltage of the first conductive titanium mesh is 0 to 2 V, and the voltage of the second conductive titanium mesh is -2 to -3 V.

[0021] Preferably, after completing step S2, if the transmembrane pressure difference of the membrane zone is less than 2 kPa, the process returns to step S1.

[0022] Preferably, after completing step S2, if the transmembrane pressure difference of the membrane zone cannot be restored to below 30 kPa, the membrane assembly is removed and the surface of the conductive flat membrane is dynamically cleaned by hydraulic flushing.

[0023] The present invention provides an AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion, which also has the following beneficial effects:

[0024] 1. The present invention relates to an AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion. A flat membrane is composited with a conductive titanium mesh and connected to a power supply. By converting the electrode polarity, the formation of a dynamic membrane layer is accelerated during the startup phase by utilizing the mutual attraction of opposite charges. When the dynamic membrane layer is too thick, the mutual repulsion of like charges is utilized to peel off the mud cake layer, thereby alleviating membrane fouling. This effectively controls membrane fouling and ensures the long-term stable operation of the reactor.

[0025] 2. The AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion of the present invention can effectively shorten the start-up time of the reactor, extend the service life of the dynamic membrane, and maintain continuous and stable operation of the device for more than 50 days;

[0026] 3. The AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion of the present invention combines a flat membrane with a conductive titanium mesh and connects it to a power source. By converting the electrode polarity, the dynamic membrane layer can be quickly formed or membrane contamination can be effectively controlled according to demand.

[0027] 4. The AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion of the present invention constructs a conductive flat membrane. Utilizing the negatively charged characteristic of sludge particles, the electrode polarity conversion of the conductive flat membrane is determined based on the transmembrane pressure difference. This not only applies positive charge to the conductive flat membrane to accelerate sludge deposition on the membrane surface to form a dynamic membrane layer, thus shortening the startup time of the AnDMBR, but also applies negative charge to the conductive flat membrane to strip off the mud cake, achieving effective control of membrane fouling, thereby reducing operating and management costs and ensuring the long-term stable operation of the reactor.

[0028] 5. The AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion of the present invention have a high degree of automation, can effectively shorten the startup time of the AnDMBR system, effectively control the mud cake layer contamination on the membrane surface, slow down the membrane fouling rate, and reduce the frequency of opening the cover to clean or replace the membrane assembly. In addition, the applied voltage is small, the energy consumption is low, the effect is stable and reliable, and it can be promoted. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Other features, objects and advantages of the present invention will become more apparent upon reading the detailed description of non-limiting embodiments with reference to the following drawings:

[0030] FIG1 is a schematic flow diagram of an AnDMBR dynamic membrane control method based on electrode polarity conversion of the present invention;

[0031] In FIG2 , (a) is a schematic diagram of the structure of the conductive diaphragm, (b) is a schematic diagram of the structure of the diaphragm skeleton and the first conductive titanium mesh assembly, and (c) is a schematic diagram of the structure of the conductive flat membrane;

[0032] FIG3 is a schematic diagram of the electrode distribution of the conductive flat membrane during the startup phase of the present invention;

[0033] FIG4 is a schematic diagram of the electrode distribution during the mud cake stripping stage of the conductive flat membrane of the present invention.

[0034] Component reference numerals 10 Diaphragm frame 11 Membrane outlet 12 First conductive titanium mesh 13 Second conductive titanium mesh 14 Supporting diaphragm 15 Conductive diaphragm 16 Conductive flat membrane DETAILED DESCRIPTION

[0035] In order to better understand the above technical solution of the present invention, the technical solution of the present invention is further described below with reference to embodiments.

[0036] The present invention provides an AnDMBR dynamic membrane assembly based on electrode polarity conversion, comprising a membrane frame and a plurality of conductive flat membranes 16 arranged in parallel within the membrane frame; wherein, as shown in FIG2(c), the conductive flat membrane 16 comprises a diaphragm skeleton 10, a first conductive titanium mesh 12 arranged on the diaphragm skeleton 10, and conductive diaphragms 15 symmetrically arranged on both sides of the diaphragm skeleton 10. As shown in FIG2(b), the diaphragm skeleton 10 is a square frame with a membrane outlet 11 provided above it. As shown in FIG2(a), the conductive diaphragm 15 is composited by a second conductive titanium mesh 13 and a supporting diaphragm 14, wherein in a specific embodiment, the supporting diaphragm 14 is made of a polyester mesh or a nylon mesh. When the conductive diaphragm 15 is fixed, the supporting diaphragm 14 is exposed on the outside. Both the first conductive titanium mesh 12 and the second conductive titanium mesh 13 are connected to electrode sheets connected to a power supply. The AnDMBR dynamic membrane assembly of the present invention charges the conductive flat membrane 16 through an external power supply. When the second conductive titanium mesh 13 (the surface of the conductive flat membrane 16) is positively charged (see Figure 3), the negatively charged characteristics of the sludge particles and the principle of mutual attraction between opposite charges can be utilized to accelerate the attraction of the sludge to the surface of the conductive flat membrane 16, thereby promoting the formation of the dynamic membrane layer; when the dynamic membrane layer is too thick and membrane contamination is formed, the second conductive titanium mesh 13 (the surface of the conductive flat membrane 16) is negatively charged through electrode conversion (see Figure 4), and the negatively charged characteristics of the sludge particles and the principle of mutual repulsion between like charges are utilized to peel the mud cake off the surface of the conductive membrane layer, thereby alleviating membrane contamination.

[0037] In a specific embodiment, the power supply is connected to the electrode sheet of the first conductive titanium mesh 12 and the electrode sheet of the second conductive titanium mesh 13 through the positive and negative switching elements respectively; the conductive flat membrane 16 converts the electrode polarity through the positive and negative switching elements, thereby accelerating the formation of the dynamic membrane or the peeling of the mud cake on the surface of the conductive flat membrane 16.

[0038] As shown in FIG. 2 ( c ), the electrode sheets of the first conductive titanium mesh 12 and the electrode sheets of the second conductive titanium mesh 13 are respectively disposed on both sides of the membrane water outlet 11 .

[0039] As shown in FIG1 , the present invention provides a control method for an AnDMBR dynamic membrane based on electrode polarity conversion, which is applicable to an AnDMBR system with a sludge concentration in the membrane area of ​​30 to 60 g / L. The membrane area adopts the above-mentioned AnDMBR dynamic membrane assembly based on electrode polarity conversion. The control method for the AnDMBR dynamic membrane comprises the following steps:

[0040] S1, during the startup phase of AnDMBR, the conductive flat membrane of the dynamic membrane assembly is connected to a power source, the first conductive titanium mesh acts as a cathode, and the second conductive titanium mesh acts as an anode, attracting negatively charged sludge particles to gather on the surface of the conductive flat membrane, accelerating the formation of the dynamic membrane layer;

[0041] The specific process is as follows: During the startup phase of the AnDMBR, the transmembrane pressure difference (TMP) of the membrane zone is less than 2 kPa, and the AnDMBR adopts a pump-suction constant flux operation mode. To accelerate the formation of the dynamic membrane layer, the conductive flat membrane of the dynamic membrane assembly is connected to a power supply; as shown in Figure 3, the first conductive titanium mesh serves as the cathode (the negative pole of the external power supply), with a voltage of -2 to 0 V; the second conductive titanium mesh serves as the anode (the positive pole of the external power supply), with a voltage of +2 to +3 V. This makes the surface of the conductive flat membrane positively charged, and utilizes the negative charge of sludge particles and the principle of mutual attraction between opposite charges to attract sludge particles to the surface of the conductive flat membrane. As the dynamic membrane layer gradually thickens, the transmembrane pressure difference begins to increase, and the operation of the AnDMBR system enters a stable stage.

[0042] S2, during the stable operation stage of AnDMBR, the transmembrane pressure difference of the membrane area is detected in real time. When the transmembrane pressure difference is greater than 30kPa, the first conductive titanium mesh is switched to the anode and the second conductive titanium mesh is switched to the cathode to peel off the mud cake of the dynamic membrane layer and alleviate membrane pollution.

[0043] The specific process is as follows: During the stable operation phase of the AnDMBR, the transmembrane pressure difference of the membrane area is detected in real time. When the transmembrane pressure difference of the membrane area is ≥2kPa, the dynamic membrane assembly is disconnected from the power supply, and the transmembrane pressure difference continues to increase, and the circulating biogas forms a cross flow on the surface of the conductive flat membrane to alleviate membrane fouling. When the transmembrane pressure difference exceeds 30kPa, the dynamic membrane layer is too thick and the membrane separation efficiency is reduced. The conductive flat membrane of the dynamic membrane assembly is connected to the power supply, and the positive and negative electrode switching elements are used to switch the electrodes, making the conductive flat membrane surface negatively charged. At this time, as shown in Figure 4, the first conductive titanium mesh is switched to the anode (the positive electrode of the external power supply), and the voltage on the first conductive titanium mesh is 0-2V. The second conductive titanium mesh is switched to the cathode (the negative electrode of the external power supply), and the voltage on the second conductive titanium mesh is -2-3V. By utilizing the negative charge of sludge particles and the principle of mutual repulsion of like charges, the mud cake layer on the surface of the conductive flat membrane is peeled off, alleviating membrane fouling. After the sludge cake layer is peeled off and the transmembrane pressure difference in the membrane zone is less than 2kPa, the process returns to step S1, switching the electrodes via the positive and negative switching elements to promote the aggregation of sludge particles on the conductive flat membrane, allowing the dynamic membrane layer to reform. When the transmembrane pressure difference in the membrane zone is ≥2kPa and ≤30kPa, the AnDMBR can operate stably. At this time, the dynamic membrane assembly is disconnected from the power supply to slow the increase in the thickness of the dynamic membrane layer and extend the stable operation period of the AnDMBR. Furthermore, if the transmembrane pressure difference cannot be restored to below 30kPa after step S2, the dynamic membrane assembly must be removed and hydraulically flushed.

[0044] The following further introduces an AnDMBR dynamic membrane assembly and control method based on electrode polarity conversion of the present invention with reference to specific examples.

[0045] Example 1

[0046] The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion of this embodiment adopts the above-mentioned AnDMBR dynamic membrane assembly based on electrode polarity conversion, and the specific process is as follows:

[0047] The sludge concentration in the main reaction zone of AnDMBR is 36.5g / L, and the sludge concentration in the membrane zone is 43.3g / L. Taking a single conductive flat membrane as an example, the conductive membrane 15 on both sides is 20cm long and 10cm wide. The conductive membrane 15 is composed of a supporting membrane 14 and a second conductive titanium mesh 13 of the same size. A first conductive titanium mesh 12 of the same size is set in the membrane skeleton 10. The hydraulic retention time of the AnDMBR system is set to 10d (where d represents days) and the solid retention time is 30d. Under the conditions of a membrane flux of 4.7LMH and a transmembrane pressure difference of less than 2kPa, the first conductive titanium mesh 12 is connected to an external cathode (voltage of -1.5V), and the second titanium mesh 13 in the conductive membrane 15 is connected to an external anode (2.5V). The negatively charged characteristics of the sludge particles are used to attract them to accelerate deposition on the membrane surface, so that the TMP of the dynamic membrane can quickly reach 2-4kPa, and then the power is disconnected. On the 85th day, the TMP reached 30 kPa, the polarity was reversed and the suction was stopped, the first conductive titanium mesh 12 was connected to the anode (voltage was 1.5 V), and the second conductive titanium mesh 13 was connected to the cathode (-2.0 V). The negatively charged sludge particles were used to make the mud cake on the membrane surface begin to peel off, and the TMP gradually recovered to 2.8 kPa. The power supply connected to the membrane was disconnected and the system continued to operate. Under the condition that the transmembrane pressure difference was less than 30 kPa, the AnDMBR system could operate stably for more than 80 days without membrane cleaning.

[0048] Example 2

[0049] The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion of this embodiment adopts the above-mentioned AnDMBR dynamic membrane assembly based on electrode polarity conversion, and the specific process is as follows:

[0050] This example is largely identical to Example 1, with the following differences: the solid residence time was adjusted to 40 days, the sludge concentration in the main reaction zone of the AnDMBR was 41.6 g / L, and the sludge concentration in the membrane zone was 51.0 g / L. When the membrane flux was 5.3 LMH and the TMP reached 30 kPa on the 23rd day, the polarity was reversed and suction was stopped. The first conductive titanium mesh 12 was externally connected to the anode (voltage of 1.5 V) and the second conductive titanium mesh was externally connected to the cathode (-2.5 V). The negatively charged sludge particles were utilized to cause the membrane surface mud cake to begin to peel off, and the TMP gradually recovered to 3.3 kPa. The power was disconnected and operation was continued. Under the condition that the transmembrane pressure difference was less than 30 kPa, the reactor operated stably for more than 50 days without cleaning.

[0051] Those skilled in the art should recognize that the above embodiments are merely intended to illustrate the present invention and are not intended to limit the present invention. As long as they are within the spirit of the present invention, any changes or modifications to the above embodiments will fall within the scope of the claims of the present invention.

Claims

1. An AnDMBR dynamic membrane module based on electrode polarity conversion, characterized in that: It comprises a membrane frame and a plurality of conductive flat membranes arranged in parallel in the membrane frame; The conductive flat membrane includes a diaphragm frame, a first conductive titanium mesh arranged on the diaphragm frame, and conductive diaphragms symmetrically arranged on both sides of the diaphragm frame; a membrane water outlet is provided on the diaphragm frame; the conductive diaphragm is composed of a second conductive titanium mesh and a supporting diaphragm; the first conductive titanium mesh and the second conductive titanium mesh are both connected to electrode sheets connected to a power source.

2. The AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 1, characterized in that, The power source is connected to the electrode sheet of the first conductive titanium mesh and the electrode sheet of the second conductive titanium mesh respectively through a positive and negative switching element.

3. The AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 2, characterized in that, The electrode sheet of the first conductive titanium mesh and the electrode sheet of the second conductive titanium mesh are respectively arranged on both sides of the membrane water outlet.

4. The AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 1, characterized in that, The supporting membrane is made of polyester mesh or nylon mesh.

5. A method for controlling an AnDMBR dynamic membrane using an AnDMBR dynamic membrane assembly based on electrode polarity conversion as described in any one of claims 1 to 4, characterized in that: The following steps are involved: S1, in the startup stage of AnDMBR, the conductive flat membrane of the dynamic membrane assembly is connected to a power source, the first conductive titanium mesh is used as a cathode, and the second conductive titanium mesh is used as an anode to attract negatively charged sludge particles to gather on the surface of the conductive flat membrane, thereby accelerating the formation of a dynamic membrane layer; S2, during the stable operation stage of AnDMBR, the transmembrane pressure difference of the membrane area is detected in real time. When the transmembrane pressure difference is greater than 30 kPa, the first conductive titanium mesh is switched to the anode and the second conductive titanium mesh is switched to the cathode to peel off the mud cake of the dynamic membrane layer and alleviate membrane pollution.

6. The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 5, characterized in that, In the step S1, the voltage of the first conductive titanium mesh is -2 to 0V, and the voltage of the second conductive titanium mesh is +2 to +3V.

7. The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 5, characterized in that, In the step S2, during the stable operation stage of the AnDMBR, when the transmembrane pressure difference of the membrane zone is ≥2 kPa and ≤30 kPa, the dynamic membrane module is disconnected from the power supply.

8. The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 5, characterized in that, In the step S2, when the transmembrane pressure difference of the membrane region is greater than 30 kPa, the voltage of the first conductive titanium mesh is 0 to 2V, and the voltage of the second conductive titanium mesh is -2 to -3V.

9. The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 5, characterized in that, After completing step S2, if the transmembrane pressure difference of the membrane zone is less than 2 kPa, the process returns to step S1.

10. The control method of the AnDMBR dynamic membrane of the AnDMBR dynamic membrane assembly based on electrode polarity conversion according to claim 5, characterized in that: After completing step S2, if the transmembrane pressure difference of the membrane zone cannot be restored to below 30 kPa, the dynamic membrane assembly is taken out for hydraulic flushing.

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