CN115403135B - Flexible electrode assembly, anaerobic electrobiological denitrification system and application - Google Patents
Flexible electrode assembly, anaerobic electrobiological denitrification system and application Download PDFInfo
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- CN115403135B CN115403135B CN202211075369.XA CN202211075369A CN115403135B CN 115403135 B CN115403135 B CN 115403135B CN 202211075369 A CN202211075369 A CN 202211075369A CN 115403135 B CN115403135 B CN 115403135B
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Classifications
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/005—Combined electrochemical biological processes
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/30—Aerobic and anaerobic processes
- C02F3/302—Nitrification and denitrification treatment
- C02F3/303—Nitrification and denitrification treatment characterised by the nitrification
-
- C—CHEMISTRY; METALLURGY
- C02—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F—TREATMENT OF WATER, WASTE WATER, SEWAGE, OR SLUDGE
- C02F3/00—Biological treatment of water, waste water, or sewage
- C02F3/30—Aerobic and anaerobic processes
- C02F3/302—Nitrification and denitrification treatment
- C02F3/305—Nitrification and denitrification treatment characterised by the denitrification
Abstract
The invention provides a flexible electrode assembly, which comprises a flexible insulating framework, and a conductive fiber positive electrode and a conductive fiber negative electrode which are positioned on two sides of the framework and are not conducted, wherein the conductive fiber positive electrode and the conductive fiber negative electrode are formed by flexible high-conductive carbon fibers or active carbon fibers sprayed with a conductive metal layer, and a metal diversion net is clamped between the conductive fiber positive electrode and the conductive fiber negative electrode and the flexible insulating framework. The invention also provides an anaerobic electrobiological denitrification system and application, comprising an anaerobic electrobiological denitrification reactor, wherein the flexible electrode assembly can be arranged in a container or a water tank, the bottom of the anaerobic electrobiological denitrification reactor is provided with a stirrer, the positive electrode and the negative electrode of the conductive fiber are respectively connected with a power supply through a metal diversion net, and a biomembrane electrode is formed by domestication of an externally applied electric field, so that the hydrogen of the negative electrode of the conductive fiber is separated, and the carbon dioxide is separated from the positive electrode as denitrification energy. The flexible electrode assembly improves the conductivity of the electrode, and improves the denitrification efficiency when being applied to an anaerobic electrobiological denitrification system.
Description
Technical Field
The invention belongs to the technical field of water treatment, and particularly relates to a flexible electrode assembly, an anaerobic electrobiological denitrification system and application thereof, wherein the flexible electrode assembly and the anaerobic electrobiological denitrification system are used in the urban sewage treatment process.
Background
The ammonia nitrogen-containing wastewater has the characteristics of wide sources, high toxicity and complex components, has become a hot spot for research by industry experts, and the treatment technology for low-concentration or high-concentration ammonia nitrogen wastewater is also endless, wherein the treatment means of the ammonia nitrogen wastewater comprise physical treatment, chemical treatment, biological treatment, some comprehensive treatments and the like. The traditional biological denitrification process is developed by slightly improving the basic principle of the purification effect of microorganisms on ammonia nitrogen in nature, has defects of high treatment cost, high energy consumption and the like when being applied to sewage treatment, and is a novel biological denitrification process through the efforts of the technicians in the field, such as synchronous nitrification and denitrification, short-range nitrification and denitrification, anaerobic ammonia oxidation and the like. Aiming at the defects that the self reaction is slow and the time is long no matter what biological denitrification technology is combined with the treatment of high ammonia nitrogen wastewater, at present, the latest research is to combine an electric auxiliary method with a microbiological method to form a novel electric auxiliary microbiological system and degrade ammonia nitrogen through organic matters, so that the reaction time is shortened, the reaction rate is improved, the organic matters originally contained in the sewage can be reasonably utilized to degrade the ammonia nitrogen, and the defect of the traditional anaerobic biological treatment of the ammonia nitrogen is overcome.
The electric auxiliary microorganism system (Electrically Assisted Microbial System, EAMS) is called an electric biological system for short, and is a special microorganism electrolytic cell system (Microbial Electrolysis Cell, MEC). In an electrobiological system, microorganisms with electrocatalytical activity are attached to an electrode material through the action of an applied voltage to form a biomembrane electrode, and an anode and a cathode in the system respectively perform oxidation and reduction reactions. Electrobioreactors are largely divided into single-chamber, double-chamber and multi-chamber reactors. The distinction between them is mainly whether or not there is an ion exchange membrane. The single-chamber reactor has a cathode and an anode in one reactor and no ion exchange membrane, the double-chamber reactor has a cathode and an anode in two different reactors and an ion exchange membrane, and the multi-chamber reactor is composed of a plurality of cathodes and anodes, and an ion exchange membrane is arranged between every two adjacent cathode chambers and anode chambers. The cost of the single-chamber reactor is greatly reduced compared with that of the other two reactors because the ion exchange membrane is expensive, and the intermediate products generated after the pollutant reacts at the cathode can move to the anode to be oxidized and decomposed because the anode and the cathode are arranged in one reactor, so that a redox reaction cycle is formed.
For the electric auxiliary microorganism system, a metal plate or a graphite plate and the like are used as electrode plates for research, and the metal plate or the graphite plate and the ion exchange membrane have the problems of high price, complicated installation, small specific surface area of materials, slow microorganism film formation and the like, and are the main reasons for difficult large-scale application.
Therefore, it is necessary to solve the above-described drawbacks of the prior art.
Disclosure of Invention
The invention aims to overcome the defects of the prior art, and firstly provides the flexible electrode assembly used in the urban sewage treatment process, so that the efficiency of removing industrial source ammonia nitrogen in sewage is improved, the cost is low, and the flexible electrode assembly can be produced and applied in large scale.
The invention provides a flexible electrode assembly, which comprises a flexible insulating framework, and a conductive fiber positive electrode (anode) and a conductive fiber negative electrode (cathode) which are respectively attached to two sides of the flexible insulating framework and are non-conductive, wherein the conductive fiber positive electrode and the conductive fiber negative electrode are formed by flexible high-conductivity carbon fibers or active carbon fibers sprayed with conductive metal layers, a metal diversion net is respectively clamped between the conductive fiber positive electrode and the conductive fiber negative electrode and the flexible insulating framework, and a compression fixing net for connecting the flexible insulating framework, the conductive fiber positive electrode, the conductive fiber negative electrode and the metal diversion net into a whole is respectively arranged outside the conductive fiber positive electrode and the conductive fiber negative electrode.
In the flexible electrode assembly, the electrode is formed by adopting flexible high-conductivity carbon fibers or active carbon fibers sprayed with a conductive metal layer, and is combined with the metal diversion net, the resistance of the metal diversion net is 0 ohm, so that electrode current can longitudinally accelerate to pass, and meanwhile, the characteristics of excellent comprehensive performance, high conductivity and the like of the flexible high-conductivity carbon fibers are combined with the transverse conductivity of the metal diversion net, or the internal resistance of the active carbon fibers is reduced by spraying the conductive metal layer on the surface of the active carbon fibers, so that the transverse conductivity of the electrode and the metal diversion net is enhanced; electron transfer makes substances with relatively large polarity or charged molecules such as glucose, amino acid, ions and the like not pass through the membrane freely, and the transport of the substances is mediated by membrane proteins to carry out passive transport, and the energy required by the electron transfer is used for driving the separation of a receptor and a ligand, so that the active transport mode for completing the recycling of the receptor has more advantages than the passive transport mode, and the rapid formation of a biomembrane electrode is promoted; microorganisms are attached to an electrode material, a biomembrane electrode can be rapidly formed through external electric field domestication, so that a negative electrode of the conductive fiber performs hydrogen evolution reaction, a positive electrode of the conductive fiber performs carbon dioxide evolution, bacteria use active hydrogen as energy sources and assimilate carbon dioxide, when the microbial hydrogen evolution catalyst is applied to an anaerobic denitrification system, two hydrogen products of the cathodic hydrogen evolution reaction are respectively active hydrogen and hydrogen molecules, the active hydrogen is firstly utilized by denitrifying bacteria, and autotrophic denitrifying bacteria convert nitrate into nitrogen through denitrification by utilizing the active hydrogen of the cathode, so that ammonia nitrogen and nitrate nitrogen are removed.
The invention also provides an anaerobic electrobiological denitrification system, which comprises an anaerobic electrobiological denitrification reactor, wherein the anaerobic electrobiological denitrification reactor is characterized in that the flexible electrode assembly is arranged in a container or a water tank, a stirrer is arranged at the bottom of the container or the water tank, the positive electrode of the conductive fiber and the negative electrode of the conductive fiber in the flexible electrode assembly are respectively connected with a power supply through a metal guide net communicated with the positive electrode of the conductive fiber, a biological membrane electrode is formed by domesticating denitrifying bacteria through an external electric field, the positive electrode of the conductive fiber separates out carbon dioxide, and the active hydrogen and the carbon dioxide are used as denitrification energy sources to be applied to denitrification of the anaerobic denitrification system.
When the anaerobic electrobiological denitrification system is used for sewage treatment, the degradation rate of nitrite nitrogen in water is very fast, the nitrite nitrogen in water can be completely degraded within 5 hours, the degradation effect of ammonia nitrogen in water is over 85 percent in 12 hours, and the degradation rate of the nitrite nitrogen after adding acetic acid or sodium acetate as a reaction substrate reaches 95 percent in 12 hours.
The anaerobic electrobiological denitrification system has low external voltage, effectively reduces the cost of industrialized implementation, solves the problems of difficult scale engineering application, high device manufacturing cost and the like of the traditional electrode such as a metal plate, graphite and the like, meets the requirements of the current industry, and has very wide application prospect.
The invention also provides application of the flexible electrode assembly in a wastewater treatment process, the flexible electrode assembly can be applied to a hydrolytic acidification process before anaerobic or aerobic treatment, and organic matters which are difficult to biodegrade in a ring chain or a long chain can be hydrolyzed into organic matters which are easy to degrade in a short chain and low molecules, so that the biodegradability of sewage is effectively improved, and the denitrification efficiency is improved.
Drawings
FIG. 1A is a schematic view of a flexible electrode assembly of the present invention;
FIG. 1B is a schematic diagram of the arrangement of the components of FIG. 1;
FIG. 2 is a diagram showing an embodiment of a flexible highly conductive carbon fiber woven structure of a conductive fiber positive electrode in a flexible electrode assembly according to the present invention;
FIG. 3 is a schematic view of the flexible electrode assembly of the present invention after being wound;
FIG. 4 is a schematic view of a plurality of flexible electrode assemblies of the present invention in combination;
FIG. 5 is a schematic view of an electrobioreactor assembly of the present invention;
FIG. 6 is a schematic diagram of an anaerobic electrobiological denitrification system according to the invention;
FIG. 7 is a graph showing the degradation effects of a pair of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in an embodiment of an anaerobic electrobiological nitrogen removal system according to the present invention;
FIG. 8 is a graph showing the degradation effect of two pairs of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the anaerobic electrobiological nitrogen removal system of the present invention;
FIG. 9 is a graph showing the degradation effects of three pairs of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in an embodiment of an anaerobic electrobiological nitrogen removal system according to the present invention;
FIG. 10 is a graph showing the degradation effect of the fourth pair of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the anaerobic electrobiological nitrogen removal system according to the embodiment of the present invention.
Detailed Description
The present invention will be described in further detail with reference to the following examples in order to make the objects, technical solutions and advantages of the present invention more apparent. It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.
Referring to fig. 1A-1B, the flexible electrode assembly 1 provided by the invention comprises at least one flexible insulating framework 11, wherein the flexible insulating framework 11 is a substrate of the flexible electrode assembly 1, and can be a corrosion-resistant and flexible-deformation net-shaped member, and a non-conductive fiber positive electrode 13 and a conductive fiber negative electrode 14 are respectively arranged on two sides of the flexible insulating framework 11, and the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 can be formed by flexible high-conductive carbon fibers or by active carbon fibers sprayed with a conductive metal layer, wherein the flexible high-conductive carbon fibers are high-conductive materials, have excellent comprehensive properties, and have the characteristics of corrosion resistance, wear resistance, high temperature resistance, high strength, light weight and the like; the conductive metal layer is sprayed on the surface of the activated carbon fiber, so that the internal resistance of the activated carbon fiber can be reduced, and the contact with a wastewater interface and the smoothness of an electronic channel are facilitated. The metal current-guiding net 12 is respectively clamped between the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 and the flexible insulating framework 11, the metal current-guiding net 12 can longitudinally accelerate the electrode current, the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 adopt flexible high-conductivity carbon fibers or adopt active carbon fibers sprayed with conductive metal layers to transversely pass through the current, when the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 are combined with the metal current-guiding net 12, the transverse conductivity of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 can be further increased, and the electron transfer can lead some relatively large polar or charged molecules such as glucose, amino acid, ions and other substances to not pass through the membrane freely. The transport of these substances requires the mediation of membrane proteins for passive transport, and the energy required by electron transfer drives the separation of the receptor and the ligand, so that the active transport mode for completing the recycling of the receptor is more advantageous than the passive transport mode, and the rapid formation of the biomembrane electrode is promoted. The outside at conductive fiber positive electrode 13 and conductive fiber negative electrode 14 is equipped with compresses tightly fixed network 15, compresses tightly fixed network 15 surface and can arrange many stainless steel fixed strips 16, can compress tightly each other laminating of conductive fiber positive electrode 13, metal water conservancy diversion net 12, flexible insulating skeleton 11 and conductive fiber negative electrode 14 of arranging, through mounting 17, can connect each component fixed in an organic wholely, forms holistic flexible electrode assembly 1.
As a preferable mode of the flexible electrode assembly 1, the flexible insulating framework 11 adopts a geotechnical mat made of melt-blown PP material, and the thickness is 1.6-2.5 cm. The geotechnical mat is a member formed by multi-layer lapping of PP (Polypropylene) random filaments, has a large number of irregular transverse and longitudinal mesh channels, has a larger specific surface area compared with the regular round holes or honeycomb hole net members in the prior art, is very favorable for microbial film formation, is corrosion-resistant, high-pressure-resistant and high in open pore density, and has the functions of omnibearing water supply and horizontal drainage.
As a preferable mode of the flexible electrode assembly 1, the metal diversion net 12 is formed by weaving stainless steel 316S wires with the single wire diameter of 0.1-2mm, and is used for improving the longitudinal and transverse conductivity of the electrode, and the mesh size of the metal diversion net 12 is 2-5mm, so that the metal diversion net is beneficial to interface contact with waste water and smoothness of an electronic channel. It will be appreciated that stainless steel is a corrosion resistant conductive material, and that other corrosion resistant conductive materials may be used to ensure the useful life of the flexible electrode assembly.
The flexible high-conductivity carbon fiber is mainly used for transversely receiving the current transmitted by the metal diversion net 12, providing an peace place for microorganisms, and domesticating denitrifying bacteria by an external electric field under an anaerobic working condition to form a biomembrane electrode. The flexible high-conductivity carbon fiber is formed by weaving polypropylene fiber and conductive carbon fiber in a one-time mixed mode by a rapier loom; the flexible high-conductivity carbon fiber is woven, and polypropylene fiber monofilaments of 100-300D of the flexible high-conductivity carbon fiber mixed row of 1K-12K are twisted as warps and wefts, namely a strand of the polypropylene fiber mixed row of one strand of the conductive carbon fiber. The method comprises the steps of weaving 1K-12K electric carbon fibers and 100-300D polypropylene fibers into a plurality of large field-shaped units in longitudinal and transverse arrangement, wherein each large field-shaped unit comprises four small field-shaped units, each large field-shaped unit uses thick warps and thick wefts which are mixed by conductive carbon fibers and polypropylene fibers as frames, the middle large cross-shaped rib A adopts thick warps and thick wefts in the conductive carbon fibers and serves as frames of the four small field-shaped units, the middle small cross-shaped rib B of each small field-shaped unit adopts conductive carbon fiber warps and wefts, and a plurality of polypropylene fiber monofilaments and monofilaments are longitudinally and transversely arranged on two sides of each small cross-shaped rib B to form curtain grid cloth.
Fig. 2 is a diagram showing an embodiment of a structure of each of the large "field" shaped unit braids of the flexible highly conductive carbon fiber. On a rapier loom, each big 'field' shaped unit is provided with a strand of 12K conductive carbon fiber mixed-arranged 250D polypropylene fiber serving as a thick warp 1313 at intervals of 5-10 cm from the selvedge 133 to the right according to warp, and a strand of 12K conductive carbon fiber mixed-arranged 250D polypropylene fiber serving as a thick weft 1323 is provided at intervals of 5-10 cm from top to bottom according to weft to form a frame. Then arranging a single-strand 6K conductive carbon fiber middle thick warp 1312 in the middle of each thick warp 1313, arranging a single-strand 6K conductive carbon fiber middle thick weft 1322 in the middle of each thick weft 1323, and intersecting to form a large cross rib A to form a large field-shaped unit; a strand of 3K conductive carbon fiber warp 1311 is further arranged at the two sides of the thick warp 1312 in the 6K conductive carbon fiber at equal distance, a strand of 3K conductive carbon fiber weft 1321 is further arranged at the two sides of the thick weft 1322 in the 6K conductive carbon fiber at equal distance, and the small cross ribs B are formed by crossing to form four small cross units; three 100D polypropylene fiber monofilament warp 1314 are further arranged equidistantly on both sides of the 3K conductive carbon fiber warp 1311, and three 100D polypropylene fiber monofilament weft 1324 are further arranged equidistantly on both sides of the 3K conductive carbon fiber weft 1321, so that a plurality of grids are arranged in the middle of each small "field" shaped unit. When the warp and weft are woven, at least 4 weft feeders are used for sequentially feeding the polypropylene fiber warp and weft of the conductive carbon fiber mixed row 250D of 12K, the conductive carbon fiber warp and weft of the single strand 6K and the conductive carbon fiber warp and weft of the single strand 3K and the polypropylene fiber warp and weft of six strands 100D into a woven curtain type grid cloth with 9 warp-wise woven belts and 8 empty warp-weft woven transverse nets, the length of the conductive carbon fiber grid cloth is 50-100 m, the conductive carbon fiber grid cloth is cut into 1-8 m woven grid conductive carbon fiber cloth according to the length required by practical application when in use, the resistance is detected to be less than 50 ohm through a universal meter, and compared with the stainless steel porous plate or stainless steel net resistance in the prior art, the conductive carbon fiber grid cloth has the advantages of low manufacturing cost, large specific surface area and the like, the cost of the woven grid conductive carbon fiber grid cloth is only 20-30 percent of the conductive carbon fiber cloth woven by the conductive carbon fiber wires, and the flexible high conductive effect is achieved, and the conductive carbon fiber grid cloth can be used as the positive electrode material and negative electrode material of the flexible electrode assembly 1.
Further, after the flexible high-conductivity carbon fiber is woven into the grid cloth, the middle position of the small cross rib B in the middle of each small cross-shaped unit can be cut into cross-shaped cuts by using a cutter, namely, the middle of the crossed conductive carbon fiber warp 1311 and the crossed conductive carbon fiber weft 1321 in the middle of each small cross-shaped unit are cut, the frame of each small cross-shaped unit is not damaged by the cut positions, 4 cross-shaped cuts are formed in each large cross-shaped unit, and the cut conductive carbon fiber thread ends can float out from the cuts and extend outwards freely. Or cutting off the polypropylene fiber monofilament warp and weft along the edges of the small cross ribs B of each small cross-shaped unit, forming L-shaped incisions at the small cross ribs B, forming 4L-shaped incisions at each small cross-shaped unit, forming 16L-shaped incisions at each large cross-shaped unit, and reserving the connection of the small cross ribs B of each small cross-shaped unit so that the cut polypropylene fiber monofilament thread ends float out from the incisions and extend outwards freely. After the flexible high-conductivity carbon fiber mesh cloth is cut, the stretched fiber yarn floats in water, so that the film forming amount of microorganisms can be increased, the electron transfer rate of a conductive fiber electrode can be improved, substances with relatively larger polarity or charged molecules such as glucose, amino acid and ions can not freely pass through the film, the transportation of the substances all needs to be mediated by film proteins for passive transportation, the energy required for electron transfer is used for driving the separation of a receptor and a ligand, the active transportation mode for completing the recycling of the receptor is more advantageous than the passive transportation mode, the rapid formation of a biomembrane electrode is promoted, and the smooth reaction of the biomembrane is ensured.
The main function of the activated carbon fiber is also to transversely receive the current transmitted by the metal diversion net 12 and provide peace for microorganismsAnd (3) in a place (film forming), domesticating denitrifying bacteria by an external electric field under an anaerobic working condition to form a biomembrane electrode. The conductive metal layer of the activated carbon fiber is prepared by impregnating activated carbon fiber cloth with 10-15% melamine polyphosphate for 2 hours, and after flame retarding, the activated carbon fiber cloth is coated with the melamine polyphosphate at a concentration of 5Kg/cm 2 Under compressed air, a plasma spraying mode is adopted to melt and spray conductive metal (such as stainless steel 316S wires) on one surface of the activated carbon fiber cloth, and the surface sprayed with the conductive metal layer is opposite to the metal diversion net 12 and is attached to the metal diversion net 12. After spraying, the conductive metal permeates one surface of the activated carbon fiber to form a conductive framework network structure, and the other surface of the activated carbon fiber cloth (the surface without stainless steel 316S) still maintains the characteristic of the conductive framework network structure, so that the internal resistance of the contact surface of the metal diversion net 12 is reduced to the greatest extent, the characteristics of large specific surface area, strong adsorption performance, corrosion resistance, good conductivity and stable electrochemical characteristics of the activated carbon fiber are maintained, the adsorption of organic matters in water on the surface of the activated carbon fiber is ensured, and the stainless steel 316S wire is fused and sprayed on the surface of the activated carbon fiber cloth to be combined with the metal diversion net 12, so that the transverse conductivity of the activated carbon fiber electrode can be further enhanced.
The activated carbon fiber cloth is prepared by the following steps:
s1, impregnating the viscose-based non-woven fabric with 10-15% melamine polyphosphate for 2 hours.
The melamine polyphosphate is a nitrogen-containing flame retardant, and is subjected to decomposition reaction when heated, and the nitrogen-containing flame retardant is mainly melamine, derivatives thereof and related heterocyclic compounds, and is more superior to halogen-containing flame retardants and red phosphorus in properties. Melamine is very effective in flame retarding when used with metal oxides, certain organic phosphoric acids or alkali or alkaline earth metal salts. The viscose-based non-woven fabric is impregnated with melamine polyphosphate before carbonization, so that combustion and oxidization of the viscose-based non-woven fabric in the carbonization process can be avoided.
S2, preoxidizing for 30-60 min at 200-250 ℃ to convert the linear molecular chains of the viscose into heat-resistant ladder-shaped structures, so that the raw materials are ensured not to be oxidized and burnt in the carbonization process, and the fiber state is maintained without melting and not burning in the subsequent high-temperature carbonization.
S3, carbonizing treatment is carried out for 1-2 hours at the temperature of 250-350 ℃ under the protection atmosphere (argon or helium) to enable the viscose-based non-woven fabric to be fibrillated. The heating rate is controlled in the carbonization process, so that the front high and rear low are basically ensured, and the front is slow and rear is rapid.
S4, pore forming treatment is carried out on the carbonized viscose-based non-woven fabric fiber by using water vapor, and activation treatment is carried out for 6-8 hours at the temperature of 900-1000 ℃ for removing impurities of a micropore channel; the viscose-based non-woven fabric fiber is activated at high temperature to form an active carbon fiber, micropores are distributed on the surface of the fiber, and the active carbon fiber has a larger specific surface area and is used for adsorbing pollutants in wastewater.
In the step, the activation temperature is high, which is favorable for improving the specific surface area, but the excessive temperature is easy to cause the collapse of the micropore structure; the long activation time is favorable for thorough activation, but the yield of the activated carbon fiber cloth is easily reduced, the pore diameter and pore distribution of the final product are required to be controlled, and the dosage of the activation medium is strictly controlled at different positions in the activation stage.
S5, washing with sulfuric acid with the concentration of 20% to remove impurities (including dust and harmful metal elements) in the activated carbon fiber cloth, washing with boiled deionized water to be neutral, and drying in an oven.
The specific surface area of the activated carbon fiber cloth prepared by the method can reach 1590m 2 The mesoporous content can reach 30 percent, the carbon content exceeds 95 percent, the porous structure has ideal pore size distribution and higher specific surface area, the micropore structure is very developed, the resistance is less than 50 ohms through the detection of a universal meter, and compared with the resistance of a stainless steel porous plate or a stainless steel net in the prior art, the porous structure has the advantages of low manufacturing cost, large specific surface area and the like, and can be used as the positive and negative electrode material of the flexible electrode assembly 1.
Referring to fig. 3, the flexible electrode assembly 1 of the present invention may be wound in a spiral shape, the middle is separated by the isolation net 2 or the flexible insulation skeleton 11, a plurality of isolation posts 3 may be disposed on the isolation net 2, the length is 1.6-2.5cm, it is ensured that each layer of flexible electrode assembly 1 maintains an equal distance, and the nonconductive conductive fiber positive electrode and conductive fiber negative electrode are respectively connected with the positive electrode lead-out wire 4 and the negative electrode lead-out wire 5, so as to form a cylindrical-like electric bioreactor assembly composed of a single flexible electrode assembly.
Referring to fig. 4, when the flexible electrode assemblies 1 of the present invention are assembled in multiple pieces, an insulating separation net 2 may be used to separate each flexible electrode assembly 1, and separation columns 3 may be disposed on the separation net 2, so that the flexible electrode assemblies 1 may maintain the same spacing, and the separation net 2 may be replaced by a flexible insulating skeleton 11. In order to ensure that the plurality of flexible electrode assemblies 1 still have the flexible performance after being integrally combined and connected, the fixing parts 17 and the setting positions of the isolation columns 3 are staggered. Referring to fig. 5, after a plurality of flexible electrode assemblies 1 are combined, a non-conductive fibrous positive electrode 13 and a conductive fibrous negative electrode 14 in the flexible electrode assemblies 1 are respectively connected with a positive electrode lead-out wire 4 and a negative electrode lead-out wire 5 to form an electric bioreactor assembly composed of a plurality of flexible electrode assemblies.
Referring to fig. 6, the present invention provides an anaerobic electrobiological denitrification system comprising an anaerobic electrobiological denitrification reactor 6, the anaerobic electrobiological denitrification reactor 6 having a vessel or basin (vessel 66 in the drawing), a flexible electrode assembly 1 disposed within the vessel 66 and supported by a mesh support plate 61 disposed within the vessel 66. The conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 in the flexible electrode assembly 1 are connected to the direct current power supply 7 (power supply voltage 0.3-0.8V) through the positive electrode lead-out wire 4 and the negative electrode lead-out wire 5, respectively. A plug-flow stirrer 62 is arranged at the bottom of the container 66, is connected with the output shaft of a motor 63 and is driven to rotate by the motor 63. The sewage to be treated enters from the water inlet 64, reacts for a certain time in an anaerobic state, is discharged from the water outlet 67, the plug-flow type stirrer 62 is connected with a power supply during the reaction, the motor 63 drives the plug-flow type stirrer 62 to work intermittently under the control of the control system, a biological membrane electrode is formed by domesticating denitrifying bacteria through an external electric field under an anaerobic working condition through the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14, the conductive fiber positive electrode 13 separates out carbon dioxide, bacteria utilize hydrogen as energy sources and assimilate carbon dioxide, so that the flexible electrode assembly 1 is applied to an anaerobic denitrifying system, two types of hydrogen products of the cathodic hydrogen separation reaction are respectively active hydrogen and hydrogen molecules, the active hydrogen is firstly utilized by denitrifying bacteria, and the autotrophic denitrifying bacteria utilizes the active hydrogen of the cathode to convert nitrate into nitrogen through denitrification, thereby achieving the aim of high-efficiency denitrification.
Furthermore, the anaerobic electrobiological denitrification system can also be provided with a dosing port 65 on the water inlet 64, acetic acid or sodium acetate is added as a reaction substrate when sewage enters the reactor, the adding amount of the sewage is calculated by taking the carbon-nitrogen ratio as 2, the precipitation of negative electrode hydrogen is facilitated, hydrogen bacteria utilize hydrogen as an energy source and assimilate carbon dioxide, therefore, the denitrification path of the activated carbon fiber electrode with enhanced conductivity and the EAMS system thereof react to obtain two hydrogen products, namely active hydrogen and hydrogen molecules, wherein the active hydrogen is firstly utilized by denitrifying bacteria, and the autotrophic denitrifying bacteria convert nitrate into nitrogen by utilizing the active hydrogen and carbon dioxide generated by two poles, so that the aim of denitrification is achieved.
The traditional biological denitrification system utilizes the principle of natural nitrogen circulation to create an environment suitable for the growth of different microorganism populations in water treatment, improves the biological nitrification and denitrification rate, and achieves the aim of removing nitrogen in wastewater through ammoniation, nitrification and denitrification.
(1) Ammoniation: organic nitrogen in untreated municipal sewage mainly comprises proteins, amino acids, urea, amines, cyanide, nitro compounds and the like. The organic nitrogen compound is decomposed and converted into ammonia nitrogen under the action of aerobic bacteria and ammoniation bacteria.
(2) Nitration reaction: the biological nitrification reaction is that nitrite nitrogen and nitrate nitrogen are oxidized by nitrite bacteria and nitrifying bacteria, and is completed by a group of autotrophic aerobic microorganisms through two processes: the first step is to convert ammonia nitrogen into nitrite by nitrite bacteria, called nitrosation reaction, and the second step is to oxidize nitrite into nitrate by nitrate bacteria.
(3) Denitrification reaction: biological denitrification is a process of reducing nitrate or nitrite produced in a nitrification process to gaseous nitrogen or nitrogen oxides under an anoxic state, and is accomplished by assimilation and dissimilation of a group of heterotrophic microorganisms. The catabolism is the reduction of nitrite and nitrate to nitrogen and oxides of nitrogen, mainly nitrogen. And the assimilation is that the denitrifying bacteria reduce nitrite and nitrate into ammonia nitrogen for the synthesis of new cells.
Biological denitrification is mainly completed by two processes of nitrification and denitrification. The nitrifying reaction is completed by autotrophic aerobic microorganisms, and comprises two stages, wherein nitrite bacteria is used for converting ammonia nitrogen into nitrite nitrogen in the first stage; in the second stage, nitrite nitrogen is further oxidized into nitrate nitrogen by nitrate bacteria. Nitrite and nitrate are collectively referred to as nitrites. Nitrobacteria are obligate aerobic bacteria, which utilize inorganic substances such as CO 3 2- 、HCO 3- 、CO 2 Etc. as carbon source, from NH 3 -N and NO 2 Energy is obtained in the oxidation reaction of N. Denitrification is a biochemical process carried out by heterotrophic microorganisms. Its main role is in hypoxia (DO<0.3-0.5 mg/L) to reduce nitrite and nitrate produced in the nitrifying process into gaseous nitrogen (N) 2 、N 2 O or NO). During the denitrification reaction, there are two conversion pathways for nitrogen nitrate to pass through the metabolic activity of denitrifying bacteria: one is assimilation denitrification, i.e. cell synthesis, which ultimately forms organic nitrogen compounds as part of the cell; another approach is catabolism, i.e., decomposition, with gaseous nitrogen as the final product.
In an anaerobic electrobiological denitrification system, under the condition of oxygen deficiency (DO <0.3-0.5 mg/L), microorganisms play a leading role in degrading ammonia nitrogen, an external voltage plays an auxiliary role, and the voltage applied to the whole system is used for enabling electrons generated by electrodes to stimulate the metabolic activity and the reduction activity of the system, and the electrode coupling microorganism strains play a synergistic role in degrading ammonia nitrogen, so that the degradation effect of ammonia nitrogen can be greatly improved. When the pure microbial system degrades ammonia nitrogen, electrons required by the oxidative degradation of the ammonia nitrogen are mainly from microorganisms, and the ammonia nitrogen is only degraded in a small amount due to the fact that the microorganisms lack a large amount of electron donors, and the ammonia nitrogen with little degradation needs a long time; when the pure electrochemical system degrades ammonia nitrogen, the ammonia nitrogen can be degraded in a small extent in the system because a large amount of electron donors can be provided for the oxidative degradation of the ammonia nitrogen, but the degradation speed is very slow, and the main reason for the problem is probably that the ammonia nitrogen is difficult to degrade due to the accumulation of redox intermediates; when the electrobiological system degrades ammonia nitrogen, on one hand, microorganisms are attached to the surface of the electrode to form a biological electrode due to the coupling effect of microorganisms and the electrode, after an external voltage is provided, the negative electrode can provide more electrons under a smaller voltage, and the microorganisms can efficiently utilize electrons generated by the electrode to stimulate the metabolic activity and the reduction activity of the electrode, so that the ammonia nitrogen can be degraded better, and on the other hand, the reaction of pollutants in the electrobiological system can degrade intermediate products generated by partial negative electrode, so that the degradation reaction of the ammonia nitrogen can be performed more smoothly. The electrobiological system is a coupling body of a pure electrochemical system and a microbial system, can embody the advantages of the two systems, also avoids the respective defects of the two systems, and can reduce the cost for industrialized implementation because the applied voltage is not high, thus providing a new idea for treating ammonia nitrogen.
The anaerobic electrobiological denitrification system is characterized in that a traditional hydrolytic acidification system or an anaerobic system is modified through a flexible electrode assembly, and the flexible electrode is used for enabling microorganisms to pass through an Anjia place through a huge specific surface by utilizing an electrochemical principle and a biological principle, and a biological membrane electrode is formed by domesticating denitrifying bacteria of an external electric field, so that active hydrogen generated by a conductive fiber electrode is efficiently utilized by the denitrifying bacteria, and the denitrification of the organisms is facilitated.
The principles described above fully combine electrochemical and bio-membrane processes, including electrochemical and bio-principles.
(1) Electrochemical principle: in each electrode assembly, a certain current is applied, hydrogen is separated out from the negative electrode, carbon dioxide is separated out from the positive electrode, bacteria utilize active hydrogen as energy sources and assimilate the carbon dioxide, the electrode assemblies are applied to an anaerobic denitrification system, autotrophic denitrifying bacteria utilize the active hydrogen and the carbon dioxide generated by two poles, and nitrate is converted into nitrogen through the denitrifying bacteria.
Industrial wastewater treatment station and selfThe water from water works and municipal sewage treatment plants generally contains: h + ,OH - ,Cl - ,Ca 2+ ,Mg 2 + ,Na + ,NO 3- And (3) plasma.
Then the possible reaction formulae at the negative electrode:
（Fe）：Fe – 2e→Fe 2+ E0（Fe 2＋ /Fe）= –0.44V
Ca 2+ +2e =Cae =-2.868V
Mg 2+ +2e = Mge =-2.372V
Na + + e= Nae =-2.71V
2H + +2e = H 2 e =0V
NO 3- +2H + +e =NO 2 +H 2 O e=0.799V
NO 3- + 4H + +2e =NO + 2H 2 O e=0.957V
the possible reaction formula on the positive electrode:
（C）：2H + ＋2e→H 2 E0（H + ＋/H 2 ）= 0V
2Cl - = Cl 2 + 2e e =1.35V
C+2H 2 O=CO 2 +4H + +4e e = 0.207V
4OH - = O 2 + 2H 2 O +4e e = 0.401V
what product is precipitated first on the electrode depends on various factors such as the concentration of such ions, overpotential, etc., and the oxidation reaction performed at the positive electrode is first a reduced substance whose precipitation potential (actual precipitation electrode potential after consideration of overpotential, etc.) is small in value; the reduction reaction proceeds on the negative electrode, first, to precipitate an oxidized substance having a large potential value.
Based on this principle, there are:
(1) on the cathode, metal ions such as Ca with very small electrode potential 2+ ，Na + And the like, is not easily reduced at the cathode. Although it is、/>Are all greater than->But NO 3- Ions hardly get close to the cathode, NO in the vicinity of the cathode 3- The concentration is low such that NO 3- Has a precipitation potential less than H + So that H is at the cathode + First, electrons are obtained which are reduced to active hydrogen. To react with: 2H (H) + +2e=H 2 Mainly.
(2) On the anode of the anode tube, a cathode is arranged,=10-7，/>=Pφ, />p phi. Regardless of the overpotential, there are:
＜/>and->Far less than->So on the anode, carbon will be oxidized, carbon dioxide will be evolved to react: C+2H 2 O = CO 2 + 4H + +4e is dominant.
Thus, the hydrogen gas generated at the cathode and the carbon dioxide generated at the anode provide necessary hydrogen and carbon sources for autotrophic denitrification of autotrophic denitrifying bacteria.
(2) Biological principle: the electrode biomembrane method mainly cultures autotrophic bacteria with denitrification capability to convert nitrate into nitrogen so as to achieve the aim of denitrification. Denitrifying bacteria are facultative anaerobes that breathe aerobically with oxygen under aerobic conditions, but when dissolved oxygen concentrations are low they extract oxygen from the nitrate, thereby converting the nitrate to nitrogen. The denitrifying bacteria are of a plurality of types and mainly comprise: achromobacter, aerobacter, alcaligenes, bacillus, flavobacterium, micrococcus, pseudomonas, proteus), and Thiobacillus, etc. Denitrifying bacteria can be classified into heterotrophic denitrifying bacteria and autotrophic denitrifying bacteria according to the carbon source utilized for bacterial growth.
Heterotrophic denitrifying bacteria are denitrifying bacteria which utilize organic matters as nutrient sources, and common organic matters include methanol, ethanol, acetic acid and the like, and the reaction formula is as follows:
NO 3- +1.08CH 3 OH+0.24H2CO 3 0.06C 5 H 7 O 2 N + 0.47 N 2 +1.68H 2 O+HCO 3- ①
7.03CH 3 COOH+8.58NO 3- 0.58C 5 H 7 O 2 N+11.16CO 2 +8.58OH - +7.74H 2 O+4N 2 ②
autotrophic denitrifying bacteria are bacteria that synthesize a carbon source by using inorganic carbon such as bicarbonate ions and carbonic acid dissolved in water as bacteria. Active hydrogen, simple substance S and sulfide are used as inorganic electron donors, and the reaction formula is as follows:
55S+50NO 3- +38H 2 O+20CO 2 +4NH 4 4C 5 H 7 O 2 N+55SO 4 2- +25N 2 +64H + ③
2.16NO 3- +7.24H 2 +0.8CO 2 0.16C 5 H 7 O 2 N+N 2 +5.6H 2 O+2.16OH - ④
the reaction formula (4) is a reaction formula in which hydrogen bacteria use active hydrogen as an energy source and assimilate carbon dioxide to convert nitrate into nitrogen. Hydrogen bacteria are of a large variety and are facultative autotrophic. They are classified into Pseudomonas, paracoccus, flavobacterium, alcaligenes, nocardia and the like, and most of them are gram-negative bacteria, most are aerobic, and the others are anaerobic or facultative anaerobic. Such as oxidation of H by Paracoccus denitrificans under anaerobic conditions 2 In this case, the denitrification is performed using nitric acid as a final electron acceptor. Most of the hydrogen bacteria are medium-temperature bacteria, are suitable for growth under neutral or slightly alkaline conditions, and in chemolithotrophic bacteria, the hydrogen bacteria are the type with the highest growth speed (the growth period is generally several hours), and the cell yield is also high. The cell yield per gram of energy source is about 15 times that of nitrifying bacteria, 71 times that of nitrifying bacteria and 24 times that of sulfur bacteria respectively.
Based on the principle, the anaerobic electrobiological denitrification reactor 6 is adopted to form an anaerobic electrobiological denitrification system under the anaerobic working condition, a certain current is externally applied to the flexible electrode assembly 1, the conductive fiber negative electrode 14 separates hydrogen, the conductive fiber positive electrode 13 separates out carbon dioxide, bacteria utilize the active hydrogen as energy sources and assimilate the carbon dioxide, so that the flexible electrode assembly 1 is applied to an anaerobic denitrification system, autotrophic denitrifying bacteria convert nitrate into nitrogen by utilizing the active hydrogen and the carbon dioxide generated by two poles, and the denitrification effect is achieved.
The anaerobic electrobiological denitrification reactor 6 forms an anaerobic electrobiological denitrification system under an anaerobic working condition, and the system takes acetic acid or sodium acetate as a reaction substrate, because the number of sodium acetate hydrogen bond acceptors is 2 and the number of covalent bond units is 2, firstly, a reduced substance with a small potential coefficient value is separated out in the oxidation reaction carried out at the positive electrode; therefore, the hydrogen evolution reaction of the conductive fiber negative electrode 14 can be accelerated, carbon dioxide can be rapidly assimilated, and the removal of medium-low concentration ammonia nitrogen and nitrate nitrogen can be realized through denitrifying bacteria; the flexible electrode assembly 1 with stronger conductivity improves conductivity and stability, has low resistance, high structural strength, can be rolled and folded, is convenient to install, and the anaerobic electrobiological denitrification system formed by the flexible electrode assembly solves the problems that the traditional electrodes such as metal, graphite and the like have high manufacturing cost, are difficult to apply on a large scale and the like.
The invention also provides application of the flexible electrode assembly in a wastewater treatment process, the flexible electrode assembly 1 can be applied to a hydrolysis acidification process before aerobic or anaerobic treatment, electrode biomembrane is utilized for denitrification and denitrification, a metabolic pathway between microorganisms and pollutants is activated, and organic matters which are difficult to biodegrade and have a cyclic chain or a long chain are enabled, particularly organic matters which are difficult to biodegrade and contain strong electronegative groups, such as nitroaromatic hydrocarbons, halogenated compounds, azo compounds and the like are hydrolyzed into organic matters which are easy to degrade and have short chain low molecules, so that the complexity or the oxidability of the difficult-to-degrade pollutants is reduced, the decolorization, detoxification and dehalogenation of wastewater are enhanced, the COD removal efficiency of the whole process is improved, and the biodegradability and the overall treatment efficiency of the wastewater are improved, and the overall operation cost is reduced.
The present invention will be described in further detail with reference to examples.
Embodiment one:
1. the main parameters are as follows:
(1) Anaerobic electrobiological denitrification reactor 6 size: diameter 500 mm x 1500 mm;
(2) Effective volume of anaerobic electrobiological denitrification reactor 6: 270L;
(3) Single flexible electrode assembly 1, dimensions: the length is 4700 mm, the width is 1000 mm, and the thickness is 25 mm;
wherein: two pieces of activated carbon fibers melt-blown with stainless steel 316S as a conductive fiber positive electrode 13 and a conductive fiber negative electrode 14, size: the length is 4700 mm, the width is 1000 mm, and the thickness is 3 mm;
Two pieces of metal guide net 12 woven by stainless steel 316S wire, size: the length is 4700 mm, the width is 1000 mm, and the thickness is 0.8 mm;
two pieces of plastic compress the fixed mesh 15, size: the length is 4700 mm, the width is 1000 mm, and the thickness is 1.7 mm;
stainless steel fixing strips 16 and fixing pieces 17 are arranged.
The components are arranged according to a conductive fiber positive electrode 13, a metal diversion net 12, a flexible insulating framework 11, the metal diversion net 12 and a conductive fiber negative electrode 14, the outer sides of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 are respectively pressed by a plastic pressing fixing net 15, and then are fixed into a whole by a fixing piece 17 after being pressed with a stainless steel fixing strip 16 at intervals, so that the flexible electrode assembly 1 is formed.
(4) Insulating isolation net 2: size: the length is 4700 mm, the width is 1000 mm, and the thickness is 20 mm;
(5) Submersible mixer: QJB 0.37/6; 220V power supply, 100-900 r/min (with frequency converter);
(6) DC power supply: the output voltage is 0-12V, the actual use voltage is 0.8V, and the maximum output current is 5A.
The flexible electrode assembly 1 and the insulating isolation net 2 are laminated and rolled together to form a cylinder, so that a cylindrical electrobiological assembly with an interval of 2cm is obtained, and the electrodes of the cylindrical electrobiological assembly are sequentially provided with a conductive fiber negative electrode 14, a conductive fiber positive electrode 13, a conductive fiber negative electrode 14 and a conductive fiber positive electrode 13 from inside to outside, wherein the interval is 2 cm. The positive electrode outgoing line 4 is connected with the positive electrode of the direct current power supply 7, the positive electrode outgoing line 4 is connected with the negative electrode of the direct current power supply 7, and the flexible electrode assembly of the whole reactor is connected with the direct current stabilized voltage power supply in series through a guide net lead wire woven by stainless steel 316S wires to form an anaerobic electro-biological denitrification system (EAMS). The reactor is a sequencing batch anaerobic electrobiological denitrification system.
And selecting ammonia nitrogen as a target pollutant to be treated, and testing the degradation performance of the target pollutant to the ammonia nitrogen.
2. The starting conditions are as follows:
(1) EAMS System operation
Anaerobic start is carried out under the condition of room temperature, the voltage of a direct current stabilized power supply in the test is changed according to the different tests, the stirring rotating speed of a plug-flow stirrer 62 is controlled to be 500 r/min, and anaerobic ammonia oxidation bacteria which are required to be cultivated when the anaerobic ammonia oxidation reaction test is started are produced under the anoxic condition, so that the experimental device is not sealed, but is selectively cultivated in an open mode without aeration to keep the anoxic condition.
(2) Biological film on surface of positive electrode 13 and negative electrode 14 of conductive fiber is domesticated and cultured
The sludge used in this time is obtained from anaerobic sludge acclimation of Shenzhen cross guard sewage treatment plant (second period), the ratio of VSS (volatile solid) to TSS (suspended solids concentration) is 0.67, the water content of the sludge is about 97%, the sludge sedimentation ratio is 35%, and the suspended solids concentration of the mixed solution is about 2100mg/L. The activated sludge and the prepared wastewater are placed in a device for anaerobic stirring, and are connected with a direct current power supply 7 for culturing and acclimating the sludge. Only basic nutrients and sodium acetate are added when the culture is started for two weeks, and ammonia nitrogen and nitrite ions are added for domestication after the sludge is adapted. The concentration of the ammonia nitrogen wastewater added for the first time is 10mg/L, and the sludge is changed every other day (namely, the hydraulic retention time is 48 and h). When water is changed, the supernatant is poured out from the water outlet 67 of the anaerobic electrobiological denitrification reactor 6, the water changing proportion is 2/3, namely, 1/3 of activated sludge at the bottom is reserved, then the reconfigured wastewater is added, the supernatant is discharged after the secondary precipitation of the changed sludge supernatant, and a small amount of activated sludge at the bottom is poured back into the reactor, so that the sludge is guaranteed to flow back and the large amount of sludge is not lost. The ammonia nitrogen is added by 10mg/L at the end of each acclimation period when water is distributed in the new acclimation period, and the like until the standard ammonia nitrogen concentration (75 mg/L) required by the experiment is increased. In addition, when the water distribution concentration of ammonia nitrogen is increased by 10mg/L, the domestication period is increased by one week so that the strain is adapted, and the strain does not die too quickly. After more than 60 days of domestication, a layer of microorganisms is attached to the surfaces of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 in the anaerobic biological denitrification reactor 6, which means that biological membrane electrodes are formed around the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 in the anaerobic biological denitrification reactor 6, thereby being beneficial to the degradation of ammonia nitrogen by microorganisms.
(3) Design of EAMS System operating parameters
In the degradation effect test of ammonia nitrogen in an EAMS system, when the initial ammonia nitrogen concentration is 75mg/L, the voltage is regulated to be 0.8V, the current density of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 is 0.05mA/cm, T=25+/-2 ℃, PH=7.2, and other conditions are unchanged.
The apparatus used in this example was a TU-1810ASPC ultraviolet-visible spectrophotometer, and the spectral scanning measurement showed that the maximum absorption wavelength of ammonia nitrogen in wastewater was 420 nm, so that the absorption wavelength of the apparatus was controlled at 420 run, water was used as a blank, and Nahner reagent spectrophotometry (HJ 535-2009) for measuring aqueous ammonia nitrogen was used to measure ammonia nitrogen in wastewater.
The degradation effect of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the EAMS system within 12h is shown in figure 7:
(1) In an EAMS system, the degradation rate of nitrite nitrogen is very fast, and the nitrite nitrogen with the concentration of 56mg/L is completely degraded after 5 hours, and the degradation rate reaches 100 percent.
(2) The degradation effect of the EAMS system on ammonia nitrogen is found that the ammonia nitrogen content is gradually degraded along with the increase of treatment time, and the degradation rate of the ammonia nitrogen with the concentration of 75mg/L reaches 86.66% after 12 hours.
(3) The EAMS system degrades the nitrate nitrogen slowly with little continued degradation after 5 hours.
Embodiment two:
this example utilized anaerobic electrobiological denitrification reactor 6 (EAMS) similar to the example except that this example had no metal diversion net 12, and at the same time, the conductive fiber positive electrode 13 and conductive fiber negative electrode 14 were replaced with conventional activated carbon fibers as electrodes, and the starting conditions were as follows:
(1) EAMS System operation
The same as in the first embodiment.
(2) Domestication culture of biomembrane on surface of traditional active carbon fiber
The procedure is the same as in example one.
(3) Design of EAMS System operating parameters
In the degradation effect test of ammonia nitrogen in an EAMS system, the operation parameters are the same as those in the first embodiment, the voltage is regulated to be 0.8V when the initial ammonia nitrogen concentration is 75mg/L, the current density of the activated carbon fiber electrode is 0.05mA/cm, the temperature T=25+/-2 ℃, the pH=7.2, and other conditions are unchanged.
The apparatus used in this example was a TU-1810ASPC ultraviolet-visible spectrophotometer, and the spectral scanning measurement showed that the maximum absorption wavelength of ammonia nitrogen in wastewater was 420 nm, so that the absorption wavelength of the apparatus was controlled at 420 run, water was used as a blank, and Nahner reagent spectrophotometry (HJ 535-2009) for measuring aqueous ammonia nitrogen was used to measure ammonia nitrogen in wastewater.
The degradation effect of the system on ammonia nitrogen, nitrite nitrogen and nitrate nitrogen within 12h is examined in the embodiment, and the result is shown in fig. 8:
(1) In an EAMS system, the degradation rate of nitrite nitrogen with the concentration of 56mg/L reaches 44.66% after 12 hours.
(2) In an EAMS system, ammonia nitrogen content is gradually degraded along with the increase of treatment time, and the degradation rate of ammonia nitrogen with the concentration of 75mg/L reaches 52% after 12 hours.
(3) In an EAMS system, the degradation rate of the nitrate nitrogen with the concentration of 10mg/L reaches 55.35 percent after 12 hours.
As can be seen from the first comparative example, the combination of the metal diversion net 2, the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 in the flexible electrode assembly 1 of the present invention is far higher than the conventional active carbon fiber electrode, and has degradation effect on ammonia nitrogen, nitrite nitrogen and nitrate nitrogen.
Embodiment III:
an anaerobic electrobiological denitrification system (EAMS) similar to the embodiment is adopted, and acetic acid is applied to a chemical adding port 65 on a water inlet 64 at the bottom of the anaerobic electrobiological denitrification reactor 6 as a reaction substrate, so that the denitrification effect is examined. The starting conditions are as follows:
(1) EAMS System operation
Anaerobic start is carried out under the condition of room temperature, the voltage of the direct current power supply 7 in the test is changed according to the test, the rotating speed of the plug-flow stirrer 62 is also controlled to be 500 r/min, and the anaerobic ammonia oxidation bacteria which are to be cultivated when the anaerobic ammonia oxidation reaction test is started are produced under the anoxic condition, so that the experimental device is not sealed, but is cultivated in an open way without aeration, so that the anoxic condition is maintained.
(2) The biological film on the surfaces of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 is domestically cultured in the same way as the first embodiment;
(3) Design of EAMS System operating parameters
In the degradation effect test of ammonia nitrogen in an EAMS system, the operation parameters are the same as those in the first embodiment, when the initial ammonia nitrogen concentration is 75mg/L, the voltage is regulated to be 0.8V, the current density of the positive electrode 13 of the conductive fiber and the negative electrode 14 of the conductive fiber is 0.05mA/cm, acetic acid is applied to a dosing port 65 on a water inlet 64 at the bottom of the anaerobic electro-biological denitrification reactor 6 as a reaction substrate, the dosing amount is calculated by taking the carbon-nitrogen ratio as 2, the temperature of T=25+/-2 ℃ and the pH=7.2, and other conditions are unchanged.
The apparatus used in this example was a TU-1810ASPC ultraviolet-visible spectrophotometer, and the spectral scanning measurement showed that the maximum absorption wavelength of ammonia nitrogen in wastewater was 420 nm, so that the absorption wavelength of the apparatus was controlled at 420 run, water was used as a blank, and Nahner reagent spectrophotometry (HJ 535-2009) for measuring aqueous ammonia nitrogen was used to measure ammonia nitrogen in wastewater.
The degradation effect of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the EAMS system within 12h is shown in figure 9:
(1) In an EAMS system, the degradation rate of nitrite nitrogen is very fast, the nitrite nitrogen with the concentration of 56mg/L is almost completely degraded within 4 hours, and the degradation rate reaches 100 percent, which is not greatly different from the first embodiment.
(2) The degradation effect of the EAMS system on ammonia nitrogen is found that the ammonia nitrogen content is increased along with the treatment time, the ammonia nitrogen is degraded continuously, and the degradation rate of 75mg/L ammonia nitrogen reaches 94.66% at 12 hours.
(3) The EAMS system has the degradation rate of 96 percent after 12 hours for nitrate nitrogen with the concentration of 10 mg/L.
The result shows that acetic acid is applied to a dosing port 65 on a water inlet 64 at the bottom of the anaerobic electro-biological denitrification reactor 6 as a reaction substrate, the dosing amount is calculated by taking the carbon-nitrogen ratio as 2, and the precipitation of hydrogen in a negative electrode is facilitated, hydrogen bacteria utilize hydrogen as energy and assimilate carbon dioxide, so that by adopting the anaerobic electro-biological denitrification system (EAMS) provided by the invention, two types of hydrogen products, namely active hydrogen and hydrogen molecules, are reacted, autotrophic denitrifying bacteria utilize active hydrogen and carbon dioxide generated by two poles, and nitrate is converted into nitrogen through denitrification, so that the denitrification purpose is achieved.
Embodiment four:
an anaerobic electrobiological denitrification system (EAMS) similar to the embodiment is adopted, a metal guide net 12 is arranged in the flexible electrode assembly 1, a conductive fiber positive electrode 13 and a conductive fiber negative electrode 14 are woven by adopting high-conductivity carbon fiber wires, and acetic acid is applied to a chemical adding port 65 on a water inlet 64 at the bottom of the anaerobic electrobiological denitrification reactor 6 to serve as a reaction substrate, so that the denitrification effect is examined. The starting conditions are as follows:
(1) The operation condition of the EAMS system is the same as that of the embodiment;
(2) The biological film on the surfaces of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 is domestically cultured as in the embodiment;
(3) Designing the operation parameters of the EAMS system to be the same as those of the embodiment;
the apparatus used in this example was a TU-1810ASPC ultraviolet-visible spectrophotometer, and the spectral scanning measurement showed that the maximum absorption wavelength of ammonia nitrogen in wastewater was 420 nm, so that the absorption wavelength of the apparatus was controlled at 420 run, water was used as a blank, and Nahner reagent spectrophotometry (HJ 535-2009) for measuring aqueous ammonia nitrogen was used to measure ammonia nitrogen in wastewater.
The degradation effect of ammonia nitrogen, nitrite nitrogen and nitrate nitrogen in the EAMS system within 12h is shown in figure 10:
(1) The EAMS system, the degradation rate of nitrite nitrogen of 56mg/L is not different from that of the third embodiment.
(2) The degradation effect of the EAMS system on ammonia nitrogen is found that the ammonia nitrogen content increases along with the treatment time, the ammonia nitrogen is degraded continuously, the degradation rate of the ammonia nitrogen with the concentration of 75mg/L for 12 hours reaches 94.00%, and the difference from the third embodiment is not great.
(3) The EAMS system has a degradation rate of 95.60% after 12 hours for 10mg/L of nitrate nitrogen, which is not much different from the third embodiment.
The results show that the denitrification effect of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 woven by the high conductive carbon fiber filaments is basically the same as that of the conductive fiber positive electrode 13 and the conductive fiber negative electrode 14 made of the active carbon fibers sprayed with the conductive metal layers.
The above-described embodiments of the present invention are only some of the preferred embodiments of the present invention and are not intended to limit the present invention, and any modifications, equivalent substitutions and improvements made by those skilled in the art without departing from the spirit of the present invention shall fall within the scope of the present invention./>
Claims (9)
1. The flexible electrode assembly is characterized by comprising a flexible insulating framework, and a conductive fiber positive electrode and a conductive fiber negative electrode which are respectively attached to two sides of the flexible insulating framework and are not conductive, wherein the conductive fiber positive electrode and the conductive fiber negative electrode are formed by flexible high-conductivity carbon fibers, a metal diversion net is respectively clamped between the conductive fiber positive electrode and the conductive fiber negative electrode and the flexible insulating framework, and a compression fixing net for connecting the flexible insulating framework, the conductive fiber positive electrode, the conductive fiber negative electrode and the metal diversion net into a whole is respectively arranged outside the conductive fiber positive electrode and the conductive fiber negative electrode;
The flexible high-conductivity carbon fiber is formed by mixing and weaving polypropylene fibers and conductive carbon fibers, the flexible high-conductivity carbon fiber is formed by mixing and weaving 1K-12K conductive carbon fibers and 100-300D polypropylene fibers into a plurality of large cross-shaped units which are vertically and horizontally arranged, each large cross-shaped unit comprises four small cross-shaped units, each large cross-shaped unit takes thick warps and thick wefts of the conductive carbon fibers and the polypropylene fiber mixed yarns as frames, large cross-shaped ribs in the middle of the large cross-shaped units are formed by crossing thick warps and thick wefts in the conductive carbon fibers, small cross-shaped ribs in the middle of the small cross-shaped units are formed by crossing the thick warps and the thick wefts in the conductive carbon fibers, and a plurality of polypropylene fiber monofilaments and monofilament wefts are vertically and horizontally arranged on two sides of each small cross-shaped rib to form curtain grid cloth; cutting a small cross-shaped notch by a cutter at the middle of each small cross-shaped unit to enable the conductive carbon fiber thread end formed after the small cross-shaped notch is cut off to float out from the notch and extend outwards freely; or cutting off the polypropylene fiber monofilament warp and the monofilament weft at the edges of the small cross ribs in the middle of each small cross-shaped unit, so that four L-shaped cuts are formed in each small cross-shaped unit, and after cutting off, the polypropylene fiber thread ends are formed to float out from the cuts and extend outwards freely.
2. The flexible electrode assembly of claim 1, wherein the flexible insulating skeleton is a geotextile mat of melt blown PP material.
3. The flexible electrode assembly of claim 1, wherein the metallic current conducting mesh is woven from stainless steel 316S filaments having a monofilament diameter of 0.1-2 mm.
4. The flexible electrode assembly is characterized by comprising a flexible insulating framework, and a conductive fiber positive electrode and a conductive fiber negative electrode which are respectively attached to two sides of the flexible insulating framework and are not conductive, wherein the conductive fiber positive electrode and the conductive fiber negative electrode are formed by active carbon fibers sprayed with a conductive metal layer;
the conductive metal layer of the activated carbon fiber is formed by dipping activated carbon fiber cloth with melamine polyphosphate with the concentration of 10-15% for 2 hours, and then adopting a plasma spraying mode to melt-spray stainless steel 316S wires on one surface of the activated carbon fiber cloth, wherein the conductive metal layer is positioned on the surface opposite to the metal flow guide net, and the mass of the stainless steel 316S wires sprayed on the surface of the activated carbon fiber cloth is 10-15% of the mass of the activated carbon fiber cloth;
The activated carbon fiber cloth is prepared by the following steps:
s1, impregnating a viscose-based non-woven fabric with 10-15% melamine polyphosphate for 2 hours;
s2 is pre-oxidized for 30-60 min at the temperature of 200-250 ℃;
s3, carbonizing at 250-350 ℃ for 30-60 min under protective atmosphere;
s4, carrying out pore-forming treatment on the carbonized viscose-based non-woven fabric by using water vapor, and then carrying out activation treatment for 6-8 hours at 900-1000 ℃;
s5, washing with sulfuric acid with the concentration of 20%, then washing with boiling deionized water to be neutral, and drying to obtain the activated carbon fiber cloth.
5. The flexible electrode assembly of claim 4, wherein the flexible insulating skeleton is a geotextile mat of meltblown PP material.
6. The flexible electrode assembly of claim 4, wherein the metallic current conducting mesh is woven from stainless steel 316S filaments having a monofilament diameter of 0.1-2 mm.
7. An anaerobic electrobiological denitrification system, which is characterized by comprising an anaerobic electrobiological denitrification reactor, wherein one or more flexible electrode assemblies according to any one of claims 1-6 are arranged in a container or a water tank, a stirrer is arranged at the bottom of the container or the water tank, a conductive fiber positive electrode and a conductive fiber negative electrode in the flexible electrode assemblies are respectively connected with a power supply through a communicated metal guide net, and denitrifying bacteria are acclimated to form a biomembrane electrode through an external electric field, so that hydrogen is separated from the conductive fiber negative electrode, and the conductive fiber positive electrode separates out carbon dioxide, and is applied to denitrification of an anaerobic denitrification system by utilizing active hydrogen and carbon dioxide as denitrification energy.
8. The anaerobic electrobiological denitrification system according to claim 7, wherein a dosing port for dosing acetic acid or sodium acetate is provided on the water inlet line of the container or the water tank.
9. The use of a flexible electrode assembly according to any one of claims 1-6 in a wastewater treatment process, wherein the flexible electrode assembly is applied in a hydrolytic acidification process prior to anaerobic or aerobic treatment to hydrolyze ring-chain or long-chain non-biodegradable organics to short-chain low-molecular readily degradable organics.
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