Electrochemical enhanced low-pressure ultrafiltration system and method for recycling livestock and poultry breeding tail water

Abstract

The invention belongs to the technical field of livestock and poultry breeding wastewater treatment and agricultural reuse, and particularly relates to an electrochemical enhanced low-pressure ultrafiltration system and method for livestock and poultry breeding tail water reuse, and the electrochemical low-pressure ultrafiltration system comprises a water inlet tank, a constant water level water tank, a gravity-driven low-pressure ultrafiltration membrane assembly, a water collecting device and a constant-voltage driving power supply; the gravity-driven low-pressure ultrafiltration membrane assembly comprises a reactor, and an anode, an ultrafiltration membrane and a cathode pre-filtering layer which are arranged in the reactor, wherein the cathode pre-filtering layer consists of a biological filter cake layer and a cathode. According to the electrochemical enhanced low-pressure ultrafiltration system and the electrochemical enhanced low-pressure ultrafiltration method for recycling livestock and poultry breeding tail water, the electrochemical enhanced gravity-driven low-pressure ultrafiltration system driven by external source constant voltage is adopted according to the characteristics of livestock and poultry breeding waste water tail water; heavy metal reduction, antibiotic degradation, pathogen interception, resistance gene transmission inhibition and membrane pollution control can be synchronously realized under the condition of low energy consumption, nitrogen and phosphorus resources in wastewater are reserved, and safe recycling of agricultural irrigation is guaranteed.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of livestock and poultry breeding wastewater treatment and agricultural reuse, and particularly relates to an electrochemically enhanced low-pressure ultrafiltration system and method for livestock and poultry breeding tail water reuse. BACKGROUND

[0002] After the front-stage treatment of livestock and poultry breeding wastewater, the tail water still contains a high concentration of organic matter (COD about 80-150 mg / L) and nitrogen and phosphorus nutrients. Recharging the farmland can greatly reduce the application amount of nitrogen and phosphorus fertilizers. However, the tail water contains excessive heavy metals such as Cu 2+ , Zn 2+ , pathogenic microorganisms such as Escherichia coli and roundworm eggs, and a high concentration of tetracycline and sulfonamide antibiotics and ARBs resistant bacteria, which will make the tail water of livestock and poultry breeding wastewater unsafe for reuse. If such wastewater is directly reused in farmland, it is easy to cause heavy metal and antibiotic compound pollution and induce the spread of antibiotic resistance genes (ARGs), which threatens the soil ecology and the safety of agricultural products.

[0003] At present, the biological electrochemical system (BES) and gravity-driven low-pressure ultrafiltration (GDM) coupling technology is tried to be used for the advanced treatment of such wastewater. However, in actual operation, especially for typical livestock and poultry breeding wastewater tail water with a COD concentration of about 120 mg / L, the biological electrochemical system has the following obvious defects: 1. The output voltage is extremely low and unstable: under the condition of a COD concentration in this range and a high concentration of antibiotics and heavy metals, the output voltage of the system under an external resistance of 100-1000 Ω is only 20-50 mV, which is not enough to drive the effective reduction and passivation of most heavy metal ions.

[0004] 2. Microbial activity is inhibited: the residual antibiotics and heavy metals in the wastewater have biological toxicity to anodic electroactive microorganisms, resulting in slow startup of the system, large fluctuation of current output, and unstable long-term operation performance; 3. The removal efficiency of pollutants is limited: the effective reduction and passivation rate of heavy metal ions is low under low voltage, which aggravates the selective pressure and leads to the proliferation and spread of ARBs and ARGs; in addition, the degradation of antibiotics under low voltage depends on microbial metabolism, which is low in efficiency and easy to cause the accumulation of intermediate products such as nitrite; 4. Membrane fouling control is insufficient: the removal of heavy metals and antibiotics is insufficient, and the cumulative toxic effect will inhibit microbial activity and weaken the long-term flux stability of GDM, which restricts the flux performance of the system.

[0005] In summary, the existing biological electrochemical coupling low-pressure ultrafiltration technology cannot meet the actual needs of efficient, stable, and rapid advanced treatment and resource reuse of livestock and poultry breeding wastewater tail water. SUMMARY

[0006] The present application aims to provide an electrochemically enhanced low-voltage ultrafiltration system and method for livestock breeding tail water reuse, which introduces an external constant voltage to replace the biological electrochemical process dependent on microbial metabolism, so as to solve the problems of extremely low and unstable output voltage, inhibited microbial activity, limited pollution removal efficiency and insufficient membrane pollution control in the existing treatment system.

[0007] The present application is realized by the following technical solutions: An electrochemically enhanced low-voltage ultrafiltration system for livestock breeding tail water reuse mainly comprises a water inlet tank 1, a constant water level tank 2, a gravity-driven low-voltage ultrafiltration membrane assembly 3, a water collecting device 8 and a constant voltage driving power supply 9. The gravity-driven low-voltage ultrafiltration membrane assembly 3 comprises a reactor and an anode 4, an ultrafiltration membrane 7 and a cathode pre-filter layer installed in the reactor; the cathode pre-filter layer is composed of a biological filter cake layer 5 and a cathode 6; the cathode 6 is laid on the ultrafiltration membrane 7, and the biological filter cake layer 5 is arranged above the cathode 6; the biological filter cake layer 5 is composed of initial inoculated microorganisms, microorganisms proliferated and retained by the cathode 6 and the ultrafiltration membrane 7 during long-term operation, and retained substances. The water inlet tank 1 is filled with livestock breeding wastewater tail water, the bottom of the water inlet tank 1 is connected to the constant water level tank 2 through a pipeline, a float valve and a water level sensor are arranged in the constant water level tank 2 to control the amount of water flowing from the water inlet tank 1 to the constant water level tank 2, the bottom of the constant water level tank 2 is connected to the top of the reactor of the gravity-driven low-voltage ultrafiltration membrane assembly 3 through a connecting pipeline, and the outlet of the ultrafiltration membrane 7 at the bottom of the reactor is connected to the water collecting device 8 through a connecting pipeline. The anode 4 is connected to the positive electrode of the constant voltage driving power supply 9 through a connecting wire, and the negative electrode of the constant voltage driving power supply 9 is connected to the cathode 6 below the anode 4 through a connecting wire.

[0008] Further, a stop valve is arranged on the connecting pipeline between the constant water level tank 2 and the gravity-driven low-voltage ultrafiltration membrane assembly 3 and on the connecting pipeline between the reactor and the water collecting device 8.

[0009] Further, the distance between the cathode 6 and the anode 4 is 10-20 cm, and the voltage of the constant voltage driving power supply 9 is 0.3-1.0 V.

[0010] Further, a float valve and a water level sensor are arranged in the constant water level tank 2 to control the amount of water flowing from the water inlet tank 1 to the constant water level tank 2, so that the liquid level difference between the constant water level tank 2 and the ultrafiltration membrane 7 is maintained at 0.2-1.0 bar.

[0011] Further, the anode 4 adopts carbon-based materials or metal materials, wherein the carbon-based materials include carbon paper, carbon felt, carbon rod, carbon fiber sheet, carbon brush, carbon foam, graphite plate, graphite rod, graphite sheet, graphite cloth, graphite particles, activated carbon and reticular glass carbon; the metal materials include metal electrodes of transition metals or noble metals doped with N, P and S elements; the transition metals are Ni and Fe; the noble metals are Au and Pd.

[0012] Further, the cathode 6 adopts carbon-based materials, wherein the carbon-based materials include carbon paper, carbon felt, carbon rod, carbon fiber sheet, carbon brush, carbon foam, graphite plate, graphite rod, graphite sheet, graphite cloth, graphite particles, activated carbon and reticular glass carbon.

[0013] Further, the ultrafiltration membrane 7 includes flat plate ultrafiltration membrane and hollow fiber membrane.

[0014] An application of an electrochemically enhanced low-pressure ultrafiltration system for livestock and poultry breeding tail water reuse, which is used for treating livestock and poultry breeding wastewater tail water, and the treated water can be used for agricultural irrigation.

[0015] An electrochemically enhanced low-pressure ultrafiltration method for livestock and poultry breeding tail water reuse, comprising the following steps: A, assembly of an electrochemically enhanced gravity-driven low-pressure ultrafiltration treatment system: A1, connecting the bottom of the water inlet tank 1 to the constant water level water tank 2 equipped with a float valve and a water level sensor through a connecting pipe, and connecting the bottom of the constant water level water tank 2 to the top of the reactor through a connecting pipe; A2, inoculating microorganisms on the cathode 6 to form a cathode pre-filter layer, then tightly laying the cathode pre-filter layer on the ultrafiltration membrane 7, and installing it in the reactor, the biological filter cake layer 5 formed on the cathode 6 can be filtered and retained through the cathode 6 during the treatment process, and continue to proliferate; installing the anode 4 on the cathode 6 at a position of 10-20 cm above the cathode 6 in the reactor; connecting the reactor side to the water collecting device 8 through a connecting pipe; A3, connecting the anode 4 to the positive electrode of the constant voltage driving power supply 9 through a connecting wire, and connecting the negative electrode of the constant voltage driving power supply 9 to the cathode 6 through a connecting wire; B, liquid level difference regulation between the liquid surface of the constant water level water tank 2 and the ultrafiltration membrane 7: The livestock breeding wastewater tail water flows into the water inlet tank 1, and the livestock breeding wastewater tail water flows into the constant water level tank 2 located below the bottom pipeline of the water inlet tank 1, and then flows into the reactor through the bottom pipeline of the constant water level tank 2; during the flowing process, the water amount is controlled by combining the position information of the floating ball valve in the constant water level tank 2 and the water level sensor data, and controlling the stop valve on the pipeline connecting the water inlet tank 1 and the constant water level tank 2 and the interception valve on the pipeline connecting the constant water level tank 2 and the reactor, so that the liquid level difference between the liquid surface of the constant water level tank 2 and the ultrafiltration membrane 7 is kept at 0.2-1.0 bar, and the gravity potential energy generated by 20-100 cm water head is used to realize that the ultrafiltration membrane 7 generates 0.2-1.0 bar transmembrane pressure difference; C, coupling of electrochemistry and gravity-driven low-pressure ultrafiltration: Under the constant voltage of 0.3-1.0 V, the organic matter and antibiotics of the livestock breeding wastewater tail water can be degraded and removed by the biological filter cake layer 5, and can also be removed by the active oxygen generated on the anode 4 and the microbial oxidation, the pathogens and resistant bacteria are removed by being intercepted by the ultrafiltration membrane 7, and the heavy metals can be removed by being electrostatically adsorbed and reduced and passivated by the cathode 6, through the coupling of electrochemistry and gravity-driven low-pressure ultrafiltration, the effective removal of organic matter, antibiotics, heavy metals and pathogens in the livestock breeding wastewater tail water is realized, so as to reduce the heavy metal-antibiotic selective pressure and reduce the generation and spread risk of ARGs; D, collection of the treated livestock breeding wastewater tail water: The treated livestock breeding wastewater tail water flows out through the side connecting pipe of the reactor and is collected in the water collecting device 8.

[0016] Compared with the prior art, the beneficial effects of the present application are: 1, stable voltage and high efficiency: 0.3-1.0 V external constant voltage is adopted, which completely gets rid of the problem of low voltage of 20-50 mV caused by the restriction of COD concentration and pollutant toxicity of the bioelectrochemical system, and guarantees the continuous and stable operation of the system; 2, rapid reduction of heavy metals: the constant voltage can drive Cu 2+ , Cd 2+ , Cr 6+ and other heavy metals to undergo electrochemical reduction on the surface of the cathode, and the efficient removal of heavy metal ions can be realized on the first day of system start-up; 3, high-efficiency degradation of antibiotics: active oxygen species such as ·OH, H2O2 and O2 - are generated in situ in the electrochemical process, and under the more effective stimulation of microorganisms, tetracycline and sulfonamides and other antibiotics can be rapidly degraded, and there is no nitrite accumulation during operation; 4. Significantly reduced membrane fouling: The cathode carbon felt has a negative charge on its surface, which effectively blocks negatively charged dissolved organic matter, humic acid and other pollutants in the water through electrostatic repulsion. The stable flux of the system is 50-120% higher than that of the bioelectrochemical system. 5. Rapid start-up and stable operation: The system starts up quickly without relying on microbial enrichment and activation, and is unaffected by the combined toxicity of antibiotics and heavy metals. 6. Comprehensive protection for safe reuse: The ultrafiltration membrane efficiently retains pathogens and resistant bacteria, effectively inhibits the spread of ARGs, and simultaneously achieves deep removal of pollutants and retention of nitrogen and phosphorus resources, so that the effluent meets the water quality requirements for agricultural irrigation. Attached Figure Description

[0017] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0018] Figure 1 This is a schematic diagram of the electrochemically enhanced low-pressure ultrafiltration system for the reuse of livestock and poultry breeding wastewater according to the present invention. Figure 2 This is a schematic diagram showing the change of chemical oxygen demand (COD) concentration over time. Figure 3 ammonia nitrogen NH4 + Schematic diagram of -N concentration change over time; Figure 4 Nitrite nitrogen NO2 + Schematic diagram of -N concentration change over time; Figure 5 Nitrate nitrogen NO3 + Schematic diagram of -N concentration change over time; Figure 6 This is a schematic diagram showing the change of total phosphorus (TP) concentration over time. Figure 7 This is a schematic diagram showing the change of copper (Cu) concentration over time. Figure 8 This is a schematic diagram showing the change in tetracycline (TC) concentration over time. Figure 9 This is a schematic diagram of flux changes from 0 to 60 days. Figure 10 A schematic diagram of the voltage at which the electrochemical low-pressure ultrafiltration system is stable and the voltage of the electrochemical gravity-driven low-pressure ultrafiltration system.

[0019] In the figure, 1. water inlet tank; 2. constant water level tank; 3. gravity-driven low-pressure ultrafiltration membrane assembly; 4. anode; 5. biological filter cake layer; 6. cathode; 7. ultrafiltration membrane; 8. water collecting device; 9. constant voltage driving power supply. DETAILED DESCRIPTION

[0020] The application will be further described below in conjunction with the embodiments: The application will be further described below in conjunction with the embodiments and drawings. It can be understood that the specific embodiments described herein are only used to explain the application, and not to limit the application. In addition, it should be noted that, for the convenience of description, only the parts related to the application are shown in the drawings, not all the structures.

[0021] It should be noted that: similar labels and letters represent similar items in the following drawings, therefore, once an item is defined in one drawing, it does not need to be further defined and explained in subsequent drawings. At the same time, in the description of the application, the terms "first", "second" and the like are only used to distinguish the description, and cannot be understood as indicating or implying relative importance.

[0022] The existing bio-electrochemical coupling low-pressure ultrafiltration system has the following technical bottlenecks when treating typical livestock and poultry breeding wastewater tail water: (1) The system output voltage is low (20-50 mV) and unstable, which makes it difficult to achieve efficient electrochemical reduction of heavy metals; (2) Antibiotic and heavy metal complex toxicity inhibits microbial activity, resulting in slow system startup and performance fluctuations; (3) The degradation rate of antibiotics is slow, and is accompanied by nitrite accumulation problem; (4) Membrane fouling control relies on biological action, and the cumulative toxic effect on microbial community in long-term operation will significantly reduce the flux. Therefore, the application adopts an electrochemically enhanced gravity-driven low-pressure ultrafiltration system driven by an external constant voltage for treating livestock and poultry breeding wastewater tail water, which is used to simultaneously achieve heavy metal reduction, antibiotic degradation, pathogen interception, resistance gene transmission inhibition and membrane fouling control under low energy consumption conditions, and retains nitrogen and phosphorus resources in wastewater to ensure agricultural irrigation safety reuse.

[0023] As shown in Figures 1-9 The electrochemically enhanced low-pressure ultrafiltration system for livestock and poultry breeding tail water reuse of the application mainly comprises a water inlet tank 1, a constant water level tank 2, a gravity-driven low-pressure ultrafiltration membrane assembly 3, a water collecting device 8 and a constant voltage driving power supply 9.

[0024] The gravity-driven low-pressure ultrafiltration membrane assembly 3 comprises a reactor, and an anode 4, an ultrafiltration membrane 7 and a cathode pre-filter layer installed in the reactor. The gravity-driven low-pressure ultrafiltration membrane assembly 3 is provided with an operating pressure of 0.2-1.0 bar by water depth, i.e. the gravity potential energy generated by a height of 20-100 cm of water depth is used to generate a transmembrane pressure difference of 0.2-1.0 bar for the ultrafiltration membrane 7, for continuous flow filtration.

[0025] The cathode pre-filter layer is composed of a biological filter cake layer 5 and a cathode 6, which is laid on the ultrafiltration membrane 7 and is provided with the biological filter cake layer 5 above.

[0026] The water inlet tank 1 is filled with livestock and poultry breeding wastewater tail water, and the bottom of the water inlet tank 1 is connected to a constant water level tank 2 through a pipeline provided with a stop valve.

[0027] The constant water level tank 2 is provided with a float valve and a water level sensor, which are used to control the amount of water flowing into the constant water level tank 2 from the water inlet tank 1, so as to keep the liquid level difference between the constant water level tank 2 and the ultrafiltration membrane 7 constant.

[0028] The bottom of the constant water level tank 2 is connected to the top of the reactor of the gravity-driven low-pressure ultrafiltration membrane assembly 3 through a connecting pipeline, and a stop valve is installed on the connecting pipeline.

[0029] The outlet end of the ultrafiltration membrane 7 at the bottom of the reactor is connected to a water collecting device 8 through a connecting pipeline, and a stop valve is also installed on the connecting pipeline.

[0030] The anode 4 is connected to the positive electrode of a constant voltage driving power source 9 through a connecting wire, and the negative electrode of the constant voltage driving power source 9 is connected to the cathode 6 through a connecting wire. The cathode 6 is located below the anode 4, and the distance between the cathode and the anode is 10-20 cm. Specifically, the voltage of the constant voltage driving power source 9 is 0.3-1.0 V, the negative electrode is connected to the carbon-based material in the cathode pre-filter layer, and the positive electrode is connected to the carbon-based material or metal material of the anode 4, so as to realize the coupling of electrochemistry and gravity-driven low-pressure ultrafiltration.

[0031] Specifically, the anode 4 is made of carbon-based material or metal material, wherein the carbon-based material includes carbon paper (CP), carbon felt (CF), carbon rod (CR), carbon fiber sheet (CS), carbon brush (CB), carbon foam (CFO), graphite plate (GP), graphite rod (GR), graphite sheet (GS), graphite cloth (GC), graphite particles (GG), activated carbon (AC) and reticular glassy carbon (RGC). The metal material includes metal electrodes doped with transition metals or noble metals and elements such as N, P and S; the transition metals are Ni, Fe, etc.; and the noble metals are Au, Pd, etc.

[0032] The biological filter cake layer 5 is composed of the initial inoculated microorganisms, the microorganisms proliferated and retained by the cathode 6 and the ultrafiltration membrane 7 under long-term operation, and the retained substances.

[0033] The cathode 6 adopts a carbon-based material, wherein the carbon-based material includes carbon paper (CP), carbon felt (CF), carbon rod (CR), carbon fiber sheet (CS), carbon brush (CB), carbon foam (CFO), graphite plate (GP), graphite rod (GR), graphite sheet (GS), graphite cloth (GC), graphite particle (GG), activated carbon (AC) and reticulated vitreous carbon (RGC).

[0034] The ultrafiltration membrane 7 includes a flat plate ultrafiltration membrane and a hollow fiber membrane.

[0035] The application of the electrochemically enhanced low-pressure ultrafiltration system for livestock and poultry breeding tail water reuse is used for treating livestock and poultry breeding wastewater tail water, and the treated water can be used for agricultural irrigation.

[0036] The electrochemically enhanced low-pressure ultrafiltration method for livestock and poultry breeding tail water reuse comprises the following steps: A, assembly of the electrochemically enhanced gravity-driven low-pressure ultrafiltration treatment system: A1, the bottom of the water inlet tank 1 is connected with the constant water level water tank 2 provided with a float ball valve and a water level sensor through a connecting pipe, and the bottom of the constant water level water tank 2 is connected with the top of the reactor through a connecting pipe; A2, inoculate microorganisms on the cathode 6 to form a cathode pre-filter layer, then tightly lay the cathode pre-filter layer on the ultrafiltration membrane 7 and install it in the reactor, and the biological filter cake layer 5 formed on the cathode 6 can be filtered and retained through the cathode 6 during the treatment process and continue to proliferate; the anode 4 is installed 10-20 cm above the cathode 6 in the reactor; the water outlet end of the ultrafiltration membrane 7 at the bottom of the reactor is connected with the water collecting device 8 through a connecting pipeline; A3, connect the anode 4 with the positive electrode of the constant voltage driving power supply 9 through a connecting wire, and connect the negative electrode of the constant voltage driving power supply 9 with the cathode 6 through a connecting wire; B, liquid level difference regulation between the liquid surface of the constant water level water tank 2 and the ultrafiltration membrane 7: The livestock and poultry breeding wastewater tail water flows into the water inlet tank 1, then flows into the constant water level water tank 2 located below the water inlet tank 1 through the bottom pipeline of the water inlet tank 1, and then flows into the reactor through the bottom pipeline of the constant water level water tank 2; during the flowing process, the position information of the float ball valve and the water level sensor data in the constant water level water tank 2 are combined, the water amount is controlled by controlling the stop valve on the connecting pipeline between the water inlet tank 1 and the constant water level water tank 2 and the retention valve on the connecting pipeline between the constant water level water tank 2 and the reactor, so that the liquid level difference between the liquid surface of the constant water level water tank 2 and the ultrafiltration membrane 7 is kept at 0.2-1.0 bar; C, coupling of electrochemistry and gravity-driven low-pressure ultrafiltration: The gravity potential generated by 20-100 cm water head is used to generate 0.2-1.0 bar transmembrane pressure difference of the ultrafiltration membrane 7, at the same time, under the constant voltage of 0.3-1.0 V, the organic matter and antibiotics in the livestock and poultry breeding wastewater tail water can be degraded and removed by the biological filter cake layer 5, and can also be removed by the active oxygen generated on the anode 4 and the microbial oxidation, the pathogens and resistant bacteria are removed by the ultrafiltration membrane 7, and the heavy metals can be removed by the electrostatic adsorption and reduction passivation of the cathode 6. Through the coupling of electrochemistry and gravity-driven low-pressure ultrafiltration, the effective removal of organic matter, antibiotics, heavy metals and pathogens in the livestock and poultry breeding wastewater tail water is realized, so as to reduce the selective pressure of heavy metal-antibiotics, reduce the generation of ARGs, and reduce the risk of ARGs transmission; D, collection of livestock and poultry breeding wastewater tail water after treatment: The treated livestock and poultry breeding wastewater tail water flows out through the side connection pipe of the reactor and is collected in the water collecting device 8.

[0037] Example 1: An electrochemically enhanced low-pressure ultrafiltration system for livestock and poultry breeding tail water reuse, which is composed of a water inlet tank 1, a constant water level tank 2, a gravity-driven low-pressure ultrafiltration membrane assembly 3, an anode 4, a biological filter cake layer 5, a cathode 6, an ultrafiltration membrane 7, a water collecting device 8 and a constant voltage driving power supply 9.

[0038] The gravity-driven low-pressure ultrafiltration membrane assembly 3 includes a reactor, and an anode 4, an ultrafiltration membrane 7 and a cathode pre-filter layer installed in the reactor. The gravity-driven low-pressure ultrafiltration membrane assembly 3 provides an operating pressure of 0.7 bar by water depth, for continuous flow filtration. The gravity potential generated by 70 cm water head is used to generate 0.7 bar transmembrane pressure difference of the ultrafiltration membrane 7. The cathode pre-filter layer is composed of the biological filter cake layer 5 and the cathode 6, the cathode 6 is laid on the ultrafiltration membrane 7, and the biological filter cake layer 5 is arranged above the cathode 6. The biological filter cake layer 5 is composed of microorganisms inoculated initially, microorganisms proliferated and filtered and retained by the cathode 6 and the ultrafiltration membrane 7 during long-term operation, and retained substances. The ultrafiltration membrane is a flat plate ultrafiltration membrane UP150.

[0039] The water inlet tank 1 is filled with livestock and poultry breeding wastewater tail water, and the bottom of the water inlet tank 1 is connected to the constant water level tank 2 through a pipeline. The constant water level tank 2 is provided with a float valve and a water level sensor for controlling the amount of water flowing from the water inlet tank 1 into the constant water level tank 2, so that the liquid level difference between the constant water level tank 2 and the ultrafiltration membrane 7 is kept constant. The bottom of the constant water level tank 2 is connected to the top of the reactor of the gravity-driven low-pressure ultrafiltration membrane assembly 3 through a connecting pipeline. The outlet end of the ultrafiltration membrane 7 at the bottom of the reactor is connected to the water collecting device 8 through a connecting pipeline. The connecting pipelines between the constant water level tank 2 and the gravity-driven low-pressure ultrafiltration membrane assembly 3 and between the reactor and the water collecting device 8 are provided with stop valves.

[0040] The anode 4 is connected to the positive pole of the constant voltage driving power supply 9 through a connecting wire, and the negative pole of the constant voltage driving power supply 9 is connected to the cathode 6 below the anode 4. The voltage of the constant voltage driving power supply 9 is 0.8 V. The distance between the cathode 6 and the anode 4 is 20 cm, the anode 4 is a carbon brush, and the cathode 6 is a carbon felt.

[0041] Example 2 An electrochemical enhanced low-pressure ultrafiltration system for livestock breeding tail water reuse comprises a water inlet tank 1, a constant water level tank 2, a gravity-driven low-pressure ultrafiltration membrane assembly 3, an anode 4, a biological filter cake layer 5, a cathode 6, an ultrafiltration membrane 7, a water collecting device 8, and a constant voltage driving power supply 9.

[0042] The gravity-driven low-pressure ultrafiltration membrane assembly 3 comprises a reactor, and the anode 4, the ultrafiltration membrane 7, and the cathode pre-filter layer installed in the reactor. The gravity-driven low-pressure ultrafiltration membrane assembly 3 provides an operating pressure of 0.7 bar by water depth, for continuous flow filtration. The gravity potential energy generated by a water head of 70 cm is used to generate a transmembrane pressure difference of 0.7 bar for the ultrafiltration membrane 7. The cathode pre-filter layer is composed of the biological filter cake layer 5 and the cathode 6, the cathode 6 is laid on the ultrafiltration membrane 7, and the biological filter cake layer 5 is arranged above the cathode 6. The biological filter cake layer 5 is composed of microorganisms inoculated initially, microorganisms proliferated and filtered and retained by the cathode 6 and the ultrafiltration membrane 7 during long-term operation, and retained substances. The ultrafiltration membrane is a flat plate ultrafiltration membrane UP150.

[0043] The water inlet tank 1 contains livestock breeding wastewater tail water, and the bottom of the water inlet tank 1 is connected to the constant water level tank 2 through a pipeline. A float valve and a water level sensor are arranged in the constant water level tank 2 to control the amount of water flowing from the water inlet tank 1 to the constant water level tank 2, so that the liquid level difference between the constant water level tank 2 and the ultrafiltration membrane 7 is kept constant. The bottom of the constant water level tank 2 is connected to the top of the reactor of the gravity-driven low-pressure ultrafiltration membrane assembly 3 through a connecting pipeline. The water outlet end of the ultrafiltration membrane 7 at the bottom of the reactor is connected to the water collecting device 8 through a connecting pipeline. Stop valves are arranged on the connecting pipelines between the constant water level tank 2 and the gravity-driven low-pressure ultrafiltration membrane assembly 3, and on the connecting pipelines between the reactor and the water collecting device 8.

[0044] The anode 4 is connected to the positive pole of the constant voltage driving power supply 9 through a connecting wire, and the negative pole of the constant voltage driving power supply 9 is connected to the cathode 6 below the anode 4. The voltage of the constant voltage driving power supply 9 is 0.6 V. The distance between the cathode 6 and the anode 4 is 15 cm, the anode 4 is a carbon brush, and the cathode 6 is a carbon felt.

[0045] Example 3 An electrochemical enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse, comprising a water inlet tank 1, a constant water level tank 2, a gravity driven low pressure ultrafiltration membrane assembly 3, an anode 4, a biological filter cake layer 5, a cathode 6, an ultrafiltration membrane 7, a water collecting device 8 and a constant voltage driving power supply 9.

[0046] The gravity driven low pressure ultrafiltration membrane assembly 3 comprises a reactor, and an anode 4, an ultrafiltration membrane 7 and a cathode pre-filter layer installed in the reactor. The gravity driven low pressure ultrafiltration membrane assembly 3 is provided with an operating pressure of 0.2 bar by water depth, for continuous flow filtration. The gravity potential energy generated by a water head of 20 cm is used to generate a transmembrane pressure difference of 0.2 bar for the ultrafiltration membrane 7. The cathode pre-filter layer is composed of the biological filter cake layer 5 and the cathode 6, and the cathode 6 is laid on the ultrafiltration membrane 7 closely, and the biological filter cake layer 5 is arranged above the cathode 6. The biological filter cake layer 5 is composed of microorganisms inoculated initially, microorganisms and intercepted substances formed by filtration and proliferation of the cathode 6 and the ultrafiltration membrane 7 under long-term operation. The ultrafiltration membrane is a flat plate ultrafiltration membrane UP150.

[0047] The water inlet tank 1 is filled with livestock and poultry breeding wastewater tail water, and the bottom of the water inlet tank 1 is connected to the constant water level tank 2 through a pipeline. A float valve and a water level sensor are arranged in the constant water level tank 2, for controlling the amount of water flowing from the water inlet tank 1 to the constant water level tank 2, so that the liquid level difference between the constant water level tank 2 and the ultrafiltration membrane 7 is kept constant. The bottom of the constant water level tank 2 is connected to the top of the reactor of the gravity driven low pressure ultrafiltration membrane assembly 3 through a connecting pipeline. The water outlet end of the ultrafiltration membrane 7 at the bottom of the reactor is connected to the water collecting device 8 through a connecting pipeline. Stop valves are arranged on the connecting pipelines between the constant water level tank 2 and the gravity driven low pressure ultrafiltration membrane assembly 3, and between the reactor and the water collecting device 8.

[0048] The anode 4 is connected to the positive electrode of the constant voltage driving power supply 9 through a connecting wire, and the negative electrode of the constant voltage driving power supply 9 is connected to the cathode 6 below the anode 4 through a connecting wire. The voltage of the constant voltage driving power supply 9 is 0.3 V. The distance between the cathode 6 and the anode 4 is 10 cm, the anode 4 is a carbon brush, and the cathode 6 is a carbon felt.

[0049] Example 4: An electrochemical enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse, comprising a water inlet tank 1, a constant water level tank 2, a gravity driven low pressure ultrafiltration membrane assembly 3, an anode 4, a biological filter cake layer 5, a cathode 6, an ultrafiltration membrane 7, a water collecting device 8 and a constant voltage driving power supply 9.

[0050] The gravity-driven low-pressure ultrafiltration membrane assembly 3 comprises a reactor, an anode 4, an ultrafiltration membrane 7 and a cathode pre-filter layer installed in the reactor. The gravity-driven low-pressure ultrafiltration membrane assembly 3 is provided with an operating pressure of 1.0 bar by water depth, for continuous flow filtration. The gravity potential energy generated by a water head of 100 cm is used to generate a transmembrane pressure difference of 1.0 bar for the ultrafiltration membrane 7. The cathode pre-filter layer is composed of a biological filter cake layer 5 and a cathode 6, the cathode 6 is laid on the ultrafiltration membrane 7, and the biological filter cake layer 5 is arranged above the cathode 6. The biological filter cake layer 5 is composed of microorganisms inoculated initially, microorganisms filtered and retained by the cathode 6 and the ultrafiltration membrane 7 and proliferated during long-term operation, and retained substances. The ultrafiltration membrane is a flat plate ultrafiltration membrane UP150.

[0051] The water inlet tank 1 is filled with livestock and poultry breeding wastewater tail water, and the bottom of the water inlet tank 1 is connected to the constant water level tank 2 through a pipeline. The constant water level tank 2 is provided with a float valve and a water level sensor for controlling the amount of water flowing into the constant water level tank 2 from the water inlet tank 1, so that the liquid level difference between the constant water level tank 2 and the ultrafiltration membrane 7 is kept constant. The bottom of the constant water level tank 2 is connected to the top of the reactor of the gravity-driven low-pressure ultrafiltration membrane assembly 3 through a connecting pipeline. The water outlet end of the ultrafiltration membrane 7 at the bottom of the reactor is connected to the water collecting device 8 through a connecting pipeline. The connecting pipelines between the constant water level tank 2 and the gravity-driven low-pressure ultrafiltration membrane assembly 3 and between the reactor and the water collecting device 8 are provided with stop valves.

[0052] The anode 4 is connected to the positive electrode of the constant voltage driving power supply 9 through a connecting wire, and the negative electrode of the constant voltage driving power supply 9 is connected to the cathode 6 below the anode 4 through a connecting wire. The voltage of the constant voltage driving power supply 9 is 1.0 V. The distance between the cathode 6 and the anode 4 is 20 cm, the anode 4 is a carbon brush, and the cathode 6 is a carbon felt.

[0053] Example 5: An electrochemically enhanced low-pressure ultrafiltration method for livestock and poultry breeding tail water reuse, comprising the following steps: A, assembly of an electrochemically enhanced gravity-driven low-pressure ultrafiltration treatment system: A1, connect the bottom of the water inlet tank 1 to the constant water level tank 2 provided with a float valve and a water level sensor through a connecting pipe, and connect the bottom of the constant water level tank 2 to the top of the reactor through a connecting pipe; A2, inoculate microorganisms on the cathode 6 to form a cathode pre-filter layer, then lay the cathode pre-filter layer closely on the ultrafiltration membrane 7 and install it in the reactor, the biological filter cake layer 5 formed on the cathode 6 can be filtered and retained by the cathode 6 during the treatment process and continue to proliferate; install the anode 4 20 cm above the cathode 6 in the reactor; connect the reactor side to the water collecting device 8 through a connecting pipeline; A3, the anode 4 is connected to the positive pole of the constant voltage driving power supply 9 through a connecting wire, and the negative pole of the constant voltage driving power supply 9 is connected to the cathode 6 through a connecting wire; B, the liquid level difference between the liquid surface of the constant water level tank 2 and the ultrafiltration membrane 7 is regulated: The livestock and poultry breeding wastewater tail water flows into the water inlet tank 1, and then flows into the constant water level tank 2 below the water inlet tank 1 through the bottom pipeline of the constant water level tank 2, and then flows into the reactor through the bottom pipeline of the constant water level tank 2; during the flowing process, the water amount is controlled by combining the position information of the floating ball valve in the constant water level tank 2 and the water level sensor data, and by controlling the stop valve on the pipeline connecting the water inlet tank 1 and the constant water level tank 2 and the interception valve on the pipeline connecting the constant water level tank 2 and the reactor, so that the liquid level difference between the liquid surface of the constant water level tank 2 and the ultrafiltration membrane 7 is kept at 0.7 bar, and the gravity potential energy generated by a water head of 70 cm is used to generate a transmembrane pressure difference of 0.7 bar for the ultrafiltration membrane 7; C, coupling of electrochemistry and gravity-driven low-pressure ultrafiltration: Under the constant voltage of 0.8 V, the organic matter and antibiotics in the livestock and poultry breeding wastewater tail water can be degraded and removed by the biological filter cake layer 5, and can also be removed by the active oxygen generated on the anode 4 and the microbial oxidation, the pathogens and resistant bacteria are removed by being intercepted by the ultrafiltration membrane 7, and the heavy metals can be removed by being electrostatically adsorbed and reduced and passivated by the cathode 6, through the coupling of electrochemistry and gravity-driven low-pressure ultrafiltration, the effective removal of organic matter, antibiotics, heavy metals and pathogens in the livestock and poultry breeding wastewater tail water is realized, so as to reduce the heavy metal-antibiotic selective pressure, reduce the generation of ARGs, and reduce the risk of ARGs transmission; D, collection of treated livestock and poultry breeding wastewater tail water: The treated livestock and poultry breeding wastewater tail water flows out through the side connecting pipe of the reactor and is collected in the water collecting device 8.

[0054] Example 6: The existing biologically electrochemical low-pressure ultrafiltration system and the electrochemically enhanced low-pressure ultrafiltration system for livestock and poultry breeding tail water reuse in the present embodiment 1 were respectively used to treat the treated tail water of a pig farm in Jilin, and the water quality was as follows: the COD value was 98-136 mg / L, the ammonia nitrogen concentration was 25.1-27.2 mg / L, the nitrite nitrogen concentration was 0 mg / L, the nitrate nitrogen concentration was 2.3-3.3 mg / L, the TP concentration was 4.5-4.9 mg / L, the Cu 2+The concentration of tetracycline is 475-510 ug / L. The ultrafiltration membrane used in both systems is a flat sheet ultrafiltration membrane (UP150). The gravity potential energy generated by a water head of 70 cm is used to achieve a transmembrane pressure difference of 0.7 bar. Both are continuous flow filtration. The difference is that the cathode of the bioelectrochemical low-pressure ultrafiltration system is a carbon brush, the anode is a carbon felt, and the distance between the cathode and the anode is 69 cm. The external circuit is connected through a 1000 ohm resistor. In this embodiment, the anode of the electrochemical gravity-driven low-pressure ultrafiltration system is a carbon brush, the cathode is a carbon felt, the constant output voltage is 0.8 V, and the distance between the cathode and the anode is 20 cm. The existing bioelectrochemical low-pressure ultrafiltration system generates electricity through microorganisms, which requires an oxygen concentration gradient, i.e. the cathode needs to be in an aerobic state and the anode needs to be in an anaerobic state. Since it is a single chamber, a higher anode-cathode distance and anaerobic conditions produced by the biological filter cake layer are required to achieve electricity generation. The constant voltage power supply used in this application does not require an oxygen concentration gradient, nor does it require a distance of 69 cm between the cathode and the anode. In this embodiment, a distance of 20 cm is set.

[0055] The bioelectrochemical low-pressure ultrafiltration system uses anode microorganisms to oxidize organic matter and antibiotics to generate electrons and electricity, and the electrode close to the ultrafiltration membrane is the anode. The electrochemical gravity-driven low-pressure ultrafiltration system of the present application is directly connected to the external constant voltage power supply 9, and the electrode close to the ultrafiltration membrane 7 is the cathode 6. The present application uses a coupling method of electrochemistry and gravity-driven low-pressure ultrafiltration. Organic matter and antibiotics can be removed by active oxygen generated on the anode 4 and microbial oxidation, and can also be removed by the biological filter cake layer 5 of the cathode 6. Heavy metals are removed by electrostatic adsorption and reduction passivation at the cathode. Pathogens and resistant bacteria are removed by being intercepted by the ultrafiltration membrane 7, preventing the spread of resistant genes. In addition, due to the deep removal of antibiotics and heavy metals, the resulting resistant genes and resistant bacteria will also be reduced. At the same time, since the cathode 6 is negatively charged, and the main organic pollutants in livestock and poultry breeding wastewater, such as humic acid, are also negatively charged, membrane fouling is alleviated by electrostatic repulsion, effectively achieving membrane fouling control.

[0056] The results show that: 1. Both the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system achieved >99.99% removal of pathogens; 2. The Cu 2+ The effluent concentration was reduced by 47.21% compared to the bioelectrochemical low-pressure ultrafiltration system; 3. The tetracycline effluent concentration of the electrochemical gravity-driven low-pressure ultrafiltration system was reduced by 56.99% compared to the bioelectrochemical low-pressure ultrafiltration system; 4. The electrochemical gravity-driven low-pressure ultrafiltration system has almost no nitrite nitrogen in the effluent, while the bioelectrochemical low-pressure ultrafiltration system has 1.34 mg / L of nitrite nitrogen in the effluent; 5、The TP effluent concentration of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 9.87% compared with the bioelectrochemical low-pressure ultrafiltration system; 6、The stable flux of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 93% compared with the bioelectrochemical low-pressure ultrafiltration system. It can be seen that the constant voltage can significantly improve the heavy metals and antibiotics in livestock and poultry breeding wastewater, increase the stable flux, and maintain a high concentration of nitrogen and phosphorus resources, realizing the safe reuse of agricultural irrigation of livestock and poultry breeding wastewater.

[0057] As shown in Figure 2 , the COD effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 46.53 mg / L and 30.54 mg / L respectively, and the COD removal rate of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 34.36%. As shown in Figure 3 , the NH4 + -N effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 8.16 mg / L and 15.3 mg / L respectively, and the NH4 + -N retention of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 8.75%. As shown in Figure 4 , the NO2 - -N effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 1.34 mg / L and 0.004 mg / L respectively, and the electrochemical gravity-driven low-pressure ultrafiltration system has almost no NO2 - -N. As shown in Figure 5 , the NO3 - -N effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 0.00 mg / L and 0.01 mg / L respectively, and the electrochemical gravity-driven low-pressure ultrafiltration system has almost no NO3 - -N. As shown in Figure 6 , the TP effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 3.85 mg / L and 4.23 mg / L respectively, and the TP retention of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 9.87%. As shown in Figure 7 , the Cu effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 0.725 mg / L and 0.383 mg / L respectively, and the Cu removal rate of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 95.3%. As shown in Figure 8 , the tetracycline effluent concentrations of the bioelectrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 90.53 ug / L and 38.94 ug / L respectively, and the Cu removal rate of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 56.99%.Figure 9 As shown, the stable fluxes of the bio-electrochemical low-pressure ultrafiltration system and the electrochemical gravity-driven low-pressure ultrafiltration system are 1.434 LMH and 2.768 LMH, respectively, and the stable flux of the electrochemical gravity-driven low-pressure ultrafiltration system is increased by 93%. Figure 10 As shown, the voltage of the bio-electrochemical low-pressure ultrafiltration system is 0.037 mV when stable, while the voltage of the electrochemical gravity-driven low-pressure ultrafiltration system is always 0.8 V.

[0058] Example 7: The electrochemical enhanced low-pressure ultrafiltration system for livestock breeding tail water reuse in Example 2 is used to treat the treated tail water of a pig farm in Jilin, and the water quality is as follows: the COD value is 88-124 mg / L, the ammonia nitrogen concentration is 18.1-24.5 mg / L, the TN concentration is 55.4-64.23 mg / L, the TP concentration is 3.57-5.62 mg / L, the Cu 2+ concentration is 1.35-1.87 mg / L, and the tetracycline concentration is 279-337 ug / L. The results show that: 1. >99.99% of pathogens are removed; 2. The Cu 2+ concentration of the effluent is less than 0.22 mg / L; 3. The tetracycline concentration of the effluent is 25.4-47.3 ug / L; 4. The stable effluent flux is 2.1-2.6 L / m 2 .h; 5. The TN concentration of the effluent is 37.23-45.64 mg / L; 6. The TP concentration of the effluent is 2.9-4.5 mg / L.

[0059] It can be seen that the use of constant voltage can significantly improve the heavy metals and antibiotics in livestock breeding wastewater, improve the stable flux, and maintain a high concentration of nitrogen and phosphorus resources, realizing the safe reuse of livestock breeding wastewater for agricultural irrigation.

[0060] Note that the above is only the preferred embodiment of the present application and the technical principle applied. Those skilled in the art will understand that the present application is not limited to the specific embodiments described herein, and those skilled in the art can make various obvious changes, re-adjustments and substitutions without departing from the scope of the present application. Therefore, although the present application has been described in more detail through the above examples, the present application is not limited to the above examples, and can include more other equivalent embodiments without departing from the concept of the present application, and the scope of the present application is determined by the scope of the appended claims.

Claims

1. An electrochemically enhanced low pressure ultrafiltration system for livestock and poultry farming tail water reuse, characterized in that: It is mainly composed of an inlet water tank (1), a constant water level water tank (2), a gravity-driven low-pressure ultrafiltration membrane assembly (3), a water collecting device (8) and a constant voltage driving power supply (9); The gravity-driven low-pressure ultrafiltration membrane assembly (3) comprises a reactor and an anode (4), an ultrafiltration membrane (7) and a cathode pre-filter layer installed in the reactor; the cathode pre-filter layer is composed of a biological filter cake layer (5) and a cathode (6); the cathode (6) is laid on the ultrafiltration membrane (7) above it, and the biological filter cake layer (5) is arranged above the cathode (6); the biological filter cake layer (5) is composed of microorganisms inoculated initially, microorganisms proliferated by being filtered and retained by the cathode (6) and the ultrafiltration membrane (7) during long-term operation, and retained substances; The inlet water tank (1) is filled with livestock and poultry breeding wastewater tail water, and the bottom of the inlet water tank (1) is connected to the constant water level water tank (2) through a pipeline; the constant water level water tank (2) is provided with a float valve and a water level sensor for controlling the amount of water flowing from the inlet water tank (1) into the constant water level water tank (2); the bottom of the constant water level water tank (2) is connected to the top of the reactor of the gravity-driven low-pressure ultrafiltration membrane assembly (3) through a connecting pipeline; the outlet of the ultrafiltration membrane (7) at the bottom of the reactor is connected to the water collecting device (8) through a connecting pipeline; The anode (4) is connected to the positive electrode of the constant voltage driving power supply (9) through a connecting wire, and the negative electrode of the constant voltage driving power supply (9) is connected to the cathode (6) below the anode (4) through a connecting wire.

2. The electrochemically enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse according to claim 1, characterized in that: The connecting pipeline between the constant water level water tank (2) and the gravity-driven low-pressure ultrafiltration membrane assembly (3) and the connecting pipeline between the reactor and the water collecting device (8) are provided with stop valves.

3. The electrochemically enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse according to claim 1, characterized in that: The distance between the cathode (6) and the anode (4) is 10-20 cm, and the voltage of the constant voltage driving power supply (9) is 0.3-1.0 V.

4. The electrochemically enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse according to claim 1, characterized in that: The constant water level water tank (2) is provided with a float valve and a water level sensor for controlling the amount of water flowing from the inlet water tank (1) into the constant water level water tank (2), so that the liquid level difference between the constant water level water tank (2) and the ultrafiltration membrane (7) is maintained at 0.2-1.0 bar.

5. The electrochemically enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse according to claim 1, characterized in that: The anode (4) is made of carbon-based materials or metal materials, wherein the carbon-based materials include carbon paper, carbon felt, carbon rod, carbon fiber sheet, carbon brush, carbon foam, graphite plate, graphite rod, graphite sheet, graphite cloth, graphite particles, activated carbon and reticular glassy carbon; the metal materials include metal electrodes doped with transition metals or noble metals and N, P and S elements; the transition metals are Ni and Fe; the noble metals are Au and Pd.

6. The electrochemically enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse according to claim 1, characterized in that: The cathode (6) is made of carbon-based materials, wherein the carbon-based materials include carbon paper, carbon felt, carbon rod, carbon fiber sheet, carbon brush, carbon foam, graphite plate, graphite rod, graphite sheet, graphite cloth, graphite particles, activated carbon and reticular glassy carbon.

7. The electrochemically enhanced low pressure ultrafiltration system for livestock and poultry breeding tail water reuse according to claim 1, characterized in that: The ultrafiltration membrane (7) includes flat plate ultrafiltration membrane and hollow fiber membrane.

8. Application of an electrochemically enhanced low-pressure ultrafiltration system for livestock and poultry breeding tail water recycling, which is used for treating livestock and poultry breeding wastewater tail water, and the treated water can be used for agricultural irrigation.

9. An electrochemically enhanced low pressure ultrafiltration method for livestock and poultry breeding tail water reuse, characterized in that, The application comprises the following steps: A. Assembly of the electrochemically enhanced gravity-driven low-pressure ultrafiltration treatment system: A1, the bottom of the water inlet tank (1) is connected with the constant water level water tank (2) through a connecting pipe, the constant water level water tank (2) is connected with the top of the reactor through a connecting pipe; A2, inoculate microorganisms on the cathode (6) to form a cathode pre-filter layer, then lay the cathode pre-filter layer closely on the ultrafiltration membrane (7) and install it in the reactor, the biological filter cake layer (5) formed on the cathode (6) can be filtered and retained by the cathode (6) during the treatment process and continue to proliferate; an anode (4) is installed 10-20 cm above the cathode (6) in the reactor; the water outlet end of the ultrafiltration membrane (7) at the bottom of the reactor is connected with the water collecting device (8) through a connecting pipe; A3, the anode (4) is connected with the positive electrode of the constant voltage driving power supply (9) through a connecting wire, and the negative electrode of the constant voltage driving power supply (9) is connected with the cathode (6) through a connecting wire; B, the liquid level difference between the liquid surface of the constant water level water tank (2) and the ultrafiltration membrane (7) is controlled: The livestock and poultry breeding wastewater tail water flows into the water inlet tank (1), then flows into the constant water level water tank (2) below through the bottom pipe of the water inlet tank (1), and then flows into the reactor through the bottom pipe of the constant water level water tank (2); during the flow process, the water volume is controlled by controlling the stop valve on the connecting pipe between the water inlet tank (1) and the constant water level water tank (2) and the retention valve on the connecting pipe between the constant water level water tank (2) and the reactor, combined with the position information of the float valve in the constant water level water tank (2) and the water level sensor data, so that the liquid level difference between the liquid surface of the constant water level water tank (2) and the ultrafiltration membrane (7) is kept at 0.2-1.0 bar, and the gravity potential energy generated by 20-100 cm water head is used to realize the transmembrane pressure difference of 0.2-1.0 bar generated by the ultrafiltration membrane (7); C, coupling of electrochemistry and gravity-driven low-pressure ultrafiltration: Under the constant voltage of 0.3-1.0 V, the organic matter and antibiotics in the livestock and poultry breeding wastewater tail water can be degraded and removed by the biological filter cake layer (5), and can also be removed by the active oxygen generated on the anode (4) and the microbial oxidation, the pathogens and resistant bacteria are retained and removed by the ultrafiltration membrane (7), and the heavy metals can be removed by the electrostatic adsorption and reduction passivation of the cathode (6), through the coupling of electrochemistry and gravity-driven low-pressure ultrafiltration, the effective removal of organic matter, antibiotics, heavy metals and pathogens in the livestock and poultry breeding wastewater tail water is realized, so as to reduce the heavy metal-antibiotic selective pressure, and reduce the generation and transmission risk of ARGs; D, collection of treated livestock and poultry breeding wastewater tail water: The treated livestock and poultry breeding wastewater tail water flows out through the side connecting pipe of the reactor and is collected in the water collecting device (8).

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