Method for improving sewage treatment efficiency of constructed wetland through advanced oxidation of manganese bacteria coupled peroxydisulfate

Abstract

The invention discloses a method for improving sewage treatment efficiency of a constructed wetland through advanced oxidation by coupling manganese bacteria with peroxydisulfate, which comprises the following steps: firstly, filling biochar and gravel particles into the front end (main body reaction zone 1) of the constructed wetland, and filling the gravel particles into the rear end (main body reaction zone 2) of the constructed wetland; an iron-plated layer graphite rod and a graphite rod are respectively inserted into the filler layer at the front end of the wetland, the iron-plated layer graphite rod is connected with an anode of an external direct-current power supply, and the graphite rod is connected with a cathode of the external direct-current power supply. After being electrified, the iron-plated layer graphite rod releases O2 and Fe < 2 + >. Then, a mixed solution of urban domestic sewage and an isometric peroxydisulfate and manganese chloride solution is used as wetland device inlet water, and degradation of pollutants in the sewage is enhanced through the effects of microorganisms, catalysis, electrolysis, advanced oxidation, adsorption and the like. The invention aims to form a method for improving the sewage treatment efficiency of the constructed wetland according to an electrochemical and manganese bacteria and peroxydisulfate advanced oxidation coupling principle.

Description

Technical Field

[0001] The invention belongs to the technical field of artificial wetland sewage treatment, and specifically relates to a method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation. Background Art

[0002] Constructed wetland technology is a promising sewage treatment technology with its environmental protection, low energy consumption, simple management, nitrogen and phosphorus removal, etc. However, problems such as easy clogging, large area, low pollutant load and low treatment efficiency of constructed wetlands have become the main factors restricting its engineering application.

[0003] In order to improve the ability of artificial wetlands to degrade sewage, the applicant uses electrolysis, biocatalysis, persulfate advanced oxidation, manganese bacteria, manganese oxide adsorption and other principles to enhance the sewage treatment efficiency of artificial wetlands. The iron-plated graphite rods in the wetland and the biochar particles that form anodes after conducting electricity are used as anodes to produce O2 and Fe 2+ As well as oxidizing organic matter, electrolyzing the dissolved Fe 2+ Can catalyze peroxydisulfate in water to generate SO4 - · SO4 - · and its hydrolysis product (·OH) are both highly oxidizing, which can enhance the wetland's removal effect on organic pollutants. The dissolved oxygen content near the anode electrode in the wetland is relatively high, and the area far away from the anode electrode is an anaerobic zone. The aerobic-anaerobic alternating area / interface and the addition of manganese ion solution to the influent are conducive to accelerating the enrichment of manganese bacteria. The biochar in the wetland provides a good carrier for manganese bacteria. Manganese elements exist in the wetland influent and soil layer. Under the mediation of manganese bacteria, manganese oxides with strong adsorption and catalytic oxidation capabilities are generated, which can enhance the wetland's removal effect on heavy metals and organic pollutants. Therefore, the present invention proposes a method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation: the wetland influent is first treated with coagulation and precipitation, and then an equal volume of peroxydisulfate (concentration of 100-200 mg / L) + manganese chloride (2-10 mg / L) solution is added, and through the main reaction zone, multi-principle coupling is achieved to improve the sewage treatment efficiency of artificial wetlands. Summary of the invention

[0004] Aiming at the problem of low efficiency in treating urban domestic sewage in artificial wetlands, the present invention proposes a method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation.

[0005] In order to solve the above technical problems, the present invention proposes a method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation. A pair of electrodes is inserted into the main reaction zone 1 of the wetland and connected to an external DC power supply. When the output voltage of the external DC power supply is 2 to 8V, an electrolysis reaction occurs, and one of the anode electrolysis products is O2, which makes the area close to the anode aerobic (main reaction zone 1) and the area far from the anode anaerobic (main reaction zone 2). Through aerobic / anaerobic (O / A n ) The two-stage spatial design and the addition of manganese ion solution to the influent are conducive to the rapid enrichment of manganese bacteria in the wetland. The main reaction area 1 of the wetland device is filled with mixed particles of biochar and gravel. Biochar has a large pore structure, which can provide a good carrier for microorganisms including manganese bacteria, which is conducive to the growth of microorganisms. At the same time, under the stimulation of the external electric field, the composition of the microbial community is richer. Microorganisms such as electrogenic bacteria and manganese bacteria effectively increase the stability and hierarchy of the microbial community structure and the metabolic activity of pollutants. Manganese bacteria convert manganese ions in the influent into manganese oxides, which are loaded on the surface of biochar and gravel, which not only effectively increases the specific surface area, adsorption performance and microbial carrier capacity of the wetland filler, but also can effectively catalyze microbial biochemical reactions and accelerate the biodegradation rate of pollutants in the water. Under the condition of an applied electric field, the mixed particles of biochar and gravel can be used as an extension of the traditional two-dimensional electrode to form a three-dimensional electrode structure, which not only obtains higher current efficiency and smaller internal resistance than the two-dimensional electrode, but also allows the microorganisms to be fully exposed to a large area of ​​electric field environment, which is conducive to enhancing the stimulation of the applied electric field on the wetland microbial community, electrode reaction and the removal effect of pollutants (especially organic matter). Another product of anode electrolysis is Fe 2+ , dissolved Fe 2+ Adsorbed / loaded on the surface of biochar to form iron-based biochar, which can effectively catalyze the decomposition of peroxydisulfate (S2O8 2- ), and improve the stability, dispersion and rapid precipitation of iron, slow-release Fe 2+ Catalytic S2O8 2- Sulfate free radicals (SO4 - ·), sulfate radicals and their hydrolysis products (hydroxyl radicals) have strong oxidizing properties and can oxidize most of the organic matter in the water, thus improving the removal efficiency of wetland organic matter.

[0006] In order to achieve the above object, the technical solution adopted in the present invention is:

[0007] A method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation, characterized in that it comprises the following steps:

[0008] Step 1: Pretreatment of iron-plated graphite rods. The graphite rods are cleaned with acetone, anhydrous ethanol and pure water in turn, and each cleaning solution is cleaned under ultrasonic conditions for 20 minutes, then dried at room temperature, and finally an iron metal coating is formed on the surface of the anode graphite rod by electroplating.

[0009] Step 2: Filler pretreatment: Biochar and gravel were used as fillers for the wetland device, and pebbles were used as the supporting layer for the wetland device. The fillers were washed 5 times with tap water and then dried naturally.

[0010] Step 3: Construction of artificial wetland device. The size of the wetland device is: 1.2m long × 0.4m wide × 0.6m high. The device is made of plexiglass. According to the flow direction of sewage, the device is divided into a water distribution area, a main reaction area and a water outlet area. Each area is separated by a perforated plexiglass plate. The main reaction area is divided into main reaction area 1 and main reaction area 2. The artificial wetland device adopts horizontal undercurrent. The main reaction area is vertically composed of a plant layer, a soil layer, a filler layer, and a support layer. The filler layer of the main reaction area 1 is a mixture of biochar particles and gravel particles, and the main reaction area 2 is gravel particles. The device is built according to the following process: First, the pebble particles are loaded at the bottom of the device to form a support layer with a thickness of 15 cm. Next, one iron-coated graphite rod and one graphite rod (length 400mm, diameter 5mm) were placed in the mixed packing layer of biochar and gravel in the main reaction zone 1, centered, with a distance of 20cm between the iron-coated graphite rod and the graphite rod. The iron-coated graphite rod was connected to the positive pole of the external DC power supply through a wire, and the graphite rod was connected to the negative pole of the external DC power supply through a wire (and connected in series with an external resistor, 10-20Ω); the biochar particles and gravel particles were mixed evenly, and naturally stacked on the supporting layer to form a packing layer with a thickness of 20cm. The role of non-conductor particles (gravel) is to prevent the biochar particles from connecting to each other and forming a short circuit after conducting electricity, while the biochar particles as conductors can be polarized under the electric field of the anode iron-coated graphite rod and the cathode graphite rod, so that each biochar particle becomes an independent three-dimensional electrode particle, and the positive electrode particles and the positive iron-coated graphite rod undergo oxidation reaction, that is, the oxidation of organic matter in sewage or the dissolution of iron ions in the iron-coated layer (such as Fe 2+ ) or the hydroxide ions (OH - ) is oxidized into oxygen (O2). Finally, soil is loaded on the filler layer to form a soil layer with a thickness of 15 cm; wetland plants are planted on the soil layer, and reeds, calamus, black trifoliate vine, etc. are selected as wetland plants to form a plant layer.

[0011] Step 4: Operation of artificial wetland device. A mixture of urban domestic sewage (after coagulation pretreatment to make SS < 120 mg / L to avoid clogging the wetland) and an equal volume of persulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L) is used as the inlet water of the wetland device, which is introduced into the wetland water distribution area (i.e., the front end of the wetland is filled with gravel with larger particle size) through the wetland inlet pipe, and passes through the main reaction area 1, main reaction area 2, and outlet area of ​​the horizontal subsurface flow artificial wetland in turn. Under an applied voltage of 2-8V, the hydraulic retention time of the wetland is 2d. Since the manganese ion solution is added to the wetland inlet water, the rapid enrichment of manganese bacteria in the wetland device is stimulated.

[0012] Preferably, in step 1, there is one pair of electrodes, i.e., one iron-plated graphite rod and one graphite rod, and the electrode material is a graphite rod, wherein the surface of the anode graphite rod is electroplated to form a layer of iron metal on the surface of the electrode. The specific operation steps are as follows: place the graphite rod in an electrolyte at 80°C to form an oxide film on its surface; pour the FeSO4 plating solution into the electroplating tank, and place the graphite rod as a cathode into the electroplating tank to form an iron metal coating on the surface of the graphite rod through an electroplating reaction at a voltage of 8 to 10V; after the electroplating is completed, take the graphite rod out of the electroplating tank, rinse it with pure water, and dry it at room temperature.

[0013] Preferably, in step 2, the particle size of the biochar particles is 4-8 mm, the particle size of the gravel particles is 4-10 mm, and the particle size of the pebbles is 40-80 mm. In step 3, the filler layer of the main reaction zone 1 is a mixed particle of biochar particles and gravel particles, and the filling volume ratio is 1:4 (biochar: gravel), so as to prevent excessive addition of biochar and thus reduce the permeability of the filler matrix.

[0014] Preferably, the perforated organic glass plate in step 3 has a hole diameter of 2 mm, a hole center spacing of 4 mm, an orthogonal arrangement, and the edges are Figure 2 The tenon joint shown is fixed in a reserved slot to separate various areas of the wetland. For example, the water distribution area and the main reaction area, the main reaction area 1 and the main reaction area 2, and the main reaction area and the water outlet area. At the same time, the perforated organic glass plate can prevent the fillers in the main reaction area 1 and the main reaction area 2 from mixing, and is conducive to the formation of an aerobic-anaerobic interface, which is conducive to the rapid enrichment of manganese bacteria in the artificial wetland system.

[0015] Preferably, the electrolysis-constructed wetland coupling system in step 3 adopts an aerobic / anaerobic (O / An) two-stage spatial design, a pair of electrodes is inserted into the main reaction zone 1, and an external resistor (10-20Ω) and a DC power supply (2-8V) are connected in series between the anode (iron-plated graphite rod) and the cathode (graphite rod). At the anode (iron-plated graphite rod and biochar particles that form the anode after conduction), O2, one of the electrolysis products, is conducive to the formation of an aerobic (O) section; in contrast, since the main reaction zone 2 has no electrodes, the organic matter in the sewage is degraded and the dissolved oxygen in the water is consumed during the aerobic microbial biochemical reaction, forming an anaerobic (An) section. During the operation of the wetland, an external power supply continuously supplies power to the electrodes to ensure the formation of aerobic and anaerobic areas in the wetland system. The applicant has found that the existence of the boundary area between aerobic and anaerobic areas is conducive to the enrichment of manganese bacteria. It should be pointed out that the wetland has a transition area between the aerobic area and the anaerobic area, namely the anoxic area. Due to the existence of anoxic-aerobic environmental conditions, the wetland device can achieve biological denitrification efficiency, namely, the degradation and nitrification of organic matter occur simultaneously in the main reaction zone 1 (aerobic section), and nitrifying bacteria convert nitrogen-containing substances into nitrates. In the transition area from the main reaction zone 1 to the main reaction zone 2 (anaerobic section), due to the existence of anoxic conditions, denitrification occurs, and denitrifying bacteria reduce nitrates to gaseous nitrogen, thereby realizing the biological denitrification function of the wetland.

[0016] Preferably, the influent in step 4 is a mixture of urban domestic sewage and an equal volume of peroxydisulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L), and the typical components and concentrations of the above-mentioned mixture are: C6H 12 O6 (80 mg / L), CH3COONa (50 mg / L), KNO3 (100 mg / L), NH4Cl (80 mg / L), MgSO4·7H2O (30 mg / L), KH2PO4 (15 mg / L), anhydrous CaCl2 (5 mg / L), Na2S2O8 (100~200) mg / L, MnCl2 (2-10 mg / L).

[0017] The main beneficial effects of the present invention are as follows:

[0018] 1) Compared with traditional artificial wetland technology, the present invention couples the principles of microorganisms, biocatalysis, electrolysis, advanced oxidation, adsorption and other principles with artificial wetland technology, and is based on the coupling of multiple reaction principles to enhance the purification efficiency of artificial wetland systems, which is mainly reflected in the following aspects: the anode (iron-plated graphite rod and biochar particles that form the anode after conduction) in the wetland electrolyzes to produce O2, making the area close to the anode in the wetland system aerobic and the area far from the anode anaerobic. The alternating aerobic-anaerobic environment of the wetland is conducive to the rapid enrichment of manganese bacteria. In addition, the addition of manganese ions to the influent can stimulate the growth of manganese bacteria, which convert the manganese ions in the influent into manganese oxides. This substance is loaded on the surface of biochar and gravel, which not only effectively increases the specific surface area of ​​the wetland filler, the pollutant adsorption performance and the microbial carrier capacity, but also effectively catalyzes microbial biochemical reactions and accelerates the biodegradation rate of pollutants in the water. Another product of anode electrolysis in the wetland is Fe 2+ It has many functions, including: promoting the expression of functional iron complex transport genes in microorganisms, thereby improving the biotransformation and catalytic effect of manganese oxides; Fe 2+ Reacts with phosphate in water to form insoluble salts, accompanied by Fe 2+ Strong hydrolysis and various polymerization reactions occur, generating a variety of multinuclear hydroxyl complexes, which cause the colloids in the water to condense and precipitate through the compression of the double electric layer, electrical neutralization, adsorption bridging and flocculent netting. 2+ The complexation and coagulation of the anode can achieve phosphorus removal from sewage; the Fe 2+ Adsorbed / loaded on the surface of biochar to form iron-based biochar, which can effectively catalyze the oxidation of peroxydisulfate (S2O8 2- ), the high specific surface area and porous structure of biochar are conducive to the fixation of Fe 2+ And evenly dispersed on its surface, otherwise if the Fe 2+ Solution (not the electrolytic anode Fe produced by the present invention) 2+ pathway), and full activation of peroxydisulfate requires the addition of excess Fe 2+ solution, and the anions introduced by the addition of divalent iron salts will inhibit the Fe 2+ Catalyze the reaction of peroxydisulfate. Therefore, it can be seen that directly adding Fe 2+ The solution is added once, not only does it need to add excess Fe 2+ solution, and caused the anions brought in by the divalent iron salt, excess Fe 2+ The sulfate radicals produced by the competition with pollutants in water are a problem. The electrolytic anode used in the present invention produces Fe 2+ pathway, combined with biochar adsorption / loading of Fe 2+ Technology not only realizes the Fe 2+ concentration control, and has a slow release of Fe2+ The technical method adopted in this application improves the stability, dispersibility and rapid precipitation of iron, and prevents Fe 2+ Loss too fast, slow release of Fe 2+ Catalytic S2O8 in water 2- Sulfate free radicals (SO4 - ·), SO4 - · and its hydrolysis product (·OH) are both highly oxidizing, and the two together improve the wetland system's degradation effect on organic pollutants. Under the stimulation of an external electric field, the composition of the microbial community in the wetland becomes richer, and microorganisms such as electrogenic bacteria and manganese bacteria effectively increase the stability, hierarchy, mutualism and pollutant metabolic activity of the microbial community structure. Combining the above effects, a method of improving the efficiency of artificial wetland sewage treatment by coupling manganese bacteria with peroxydisulfate advanced oxidation improves the effect of wetland sewage treatment and effectively solves the bottleneck problem of artificial wetland systems in removing difficult-to-degrade organic matter.

[0019] 2) Traditional artificial wetlands can use biochar as filler, which has the function of absorbing pollutants in water and providing microbial carriers. The present invention improves the function of biochar, not only through manganese oxide and Fe 2+ Loaded on biochar, the loading of manganese oxide effectively increases the specific surface area of ​​biochar and the function of microbial carrier, manganese oxide and Fe 2+ The loading of FeO2 / Biochar forms multiple heterogeneous catalytic reaction systems in the wetland system, that is, manganese oxide / biochar acts as a heterogeneous catalyst to catalyze the biochemical reaction of microorganisms degrading pollutants in the wetland system. 2+ / Biochar as a heterogeneous catalyst for S2O8 in wetland systems 2- Sulfate radicals are continuously formed. Moreover, biochar plays an important role as a three-dimensional electrode in the wetland electrolysis system. Under the action of an external electric field, each working electrode particle (biochar particle) in the wetland filler layer becomes an independent three-dimensional electrode, forming a micro-electrolysis cell with an anode at one end and a cathode at the other end. On the one hand, it provides more active reaction sites, has better proton diffusion performance, improves the efficiency and speed of electrochemical reactions, and thus enhances the removal efficiency of organic pollutants; on the other hand, the surface of biochar particles generates hydroxyl radicals ·OH with strong oxidizing properties, which can achieve oxidation of difficult-to-degrade organic matter in water. By mixing biochar particles and gravel particles in an appropriate proportion as fillers, the hydraulic effect of the wetland can be improved when biochar particles are used alone as fillers, ensuring good hydraulic permeability of the wetland filler layer; at the same time, non-conductor particles (gravel particles) can maintain the stable structure and shape of the three-dimensional electrode system, avoiding short circuits between biochar particles after conduction.

[0020] 3) The present invention adds an equal volume of peroxydisulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L) to the wetland influent, so as to activate the peroxydisulfate in the water by biochar loading iron and promote the enrichment of manganese bacteria and the formation of manganese oxides by adding manganese ions to the influent to catalyze the biochemical reaction of microorganisms. Through the synergy of multiple catalytic mechanisms, the sewage treatment efficiency of the artificial wetland is enhanced. In the wetland system, the iron-plated graphite rod is used as the anode. When an external voltage is applied, the electrolysis produces Fe 2+ or O2.Fe 2+ Adsorbed by biochar in the wetland filler layer to form biochar-loaded Fe 2+ , slowly releasing Fe into the wetland water environment 2 + , Fe released into water 2+ It can give an electron to peroxydisulfate in water, causing the OO bond of peroxydisulfate to break, resulting in the following reaction and generating SO4 - ·: Fe 2+ +S2O8 2- →Fe 3+ +SO4 ·- +SO4 2- The above reaction product SO4 - ·Can non-selectively oxidize most organic pollutants; in addition, SO4 - ·React with water molecules or other reducing substances in water to generate ·OH, which also has the function of oxidizing and decomposing organic matter; when Fe 2+ When coexisting with other heteroatoms in biochar (such as N, S, etc.), it can change the electronic structure of carbon materials, induce electron transfer, and promote the non-radical activation of peroxydisulfate. - During the hydrolysis process to generate OH, Fe 2+ As a catalyst, Fe 2+ With S2O8 2- The reaction system can continuously and effectively degrade organic pollutants.

[0021] 4) The artificial wetland device is divided into two sections in terms of space: the front section is the aerobic (O) section and the rear section is the anaerobic (A) section. n )part. O / A n Under the two-stage structure, organic matter degradation, nitrification and phosphorus absorption reactions occur simultaneously in the main reaction zone 1 (O stage). The nitrification reaction uses nitrifying bacteria to convert nitrogen-containing substances into nitrates, and the main reaction zone 2 (A stage) nThe alternating environment and interface of aerobic and anaerobic sections are conducive to the rapid proliferation of manganese bacteria. At the same time, there is an anoxic section in the transition area from aerobic section to anaerobic section. In this section, denitrification reaction occurs, and denitrifying bacteria are used to reduce nitrate to gaseous nitrogen. Therefore, artificial wetlands have the function of denitrification and phosphorus removal. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation as described in the present invention, and its process structure cross-sectional diagram.

[0023] Figure 2 It is a top view of the process structure described in the present invention.

[0024] Figure numerals: 1-water inlet pipe, 2-iron-plated graphite rod (anode), 3-resistance (10-20Ω), 4-external DC power supply (2-8V), 5-graphite rod (cathode), 6-organic glass porous baffle, 7-main reaction zone (horizontal subsurface flow artificial wetland), 8-soil layer, 9-gravel filler layer, 10-pebble support layer, 11-water outlet pipe, 12-water distribution area, 13-water outlet area, 14-organic glass porous baffle, 15-biochar and gravel mixed filler layer, 16-main reaction zone 1, 17-main reaction zone 2 DETAILED DESCRIPTION

[0025] The technical solution of the present invention is clearly and completely described below in conjunction with specific embodiments.

[0026] Step 1: Pretreatment of iron-plated graphite rods. The graphite rods are cleaned with acetone, anhydrous ethanol and pure water in turn, and each cleaning solution is cleaned under ultrasonic conditions for 20 minutes, then dried at room temperature, and finally an iron metal coating is formed on the surface of the anode graphite rod by electroplating.

[0027] Step 2: Filler pretreatment: Biochar and gravel were used as fillers for the wetland device, and pebbles were used as the supporting layer for the wetland device. The fillers were washed 5 times with tap water and then dried naturally.

[0028] Step 3: Construction of artificial wetland device. The size of the wetland device is: 1.2m long × 0.4m wide × 0.6m high. The device is made of plexiglass. According to the flow direction of sewage, the device is divided into a water distribution area, a main reaction area and a water outlet area. Each area is separated by a perforated plexiglass plate. The main reaction area is divided into main reaction area 1 and main reaction area 2. The artificial wetland device adopts horizontal undercurrent. The main reaction area is vertically composed of a plant layer, a soil layer, a filler layer, and a support layer. The filler layer of the main reaction area 1 is a mixture of biochar particles and gravel particles, and the main reaction area 2 is gravel particles. The device is built according to the following process: First, the pebble particles are loaded at the bottom of the device to form a support layer with a thickness of 15 cm. Next, one iron-coated graphite rod and one graphite rod (length 400mm, diameter 5mm) were placed in the mixed packing layer of biochar and gravel in the main reaction zone 1, centered, with a distance of 20cm between the iron-coated graphite rod and the graphite rod. The iron-coated graphite rod was connected to the positive pole of the external DC power supply through a wire, and the graphite rod was connected to the negative pole of the external DC power supply through a wire (and connected in series with an external resistor, 10-20Ω); the biochar particles and gravel particles were mixed evenly, and naturally stacked on the supporting layer to form a packing layer with a thickness of 20cm. The role of non-conductor particles (gravel) is to prevent the biochar particles from connecting to each other and forming a short circuit after conducting electricity, while the biochar particles as conductors can be polarized under the electric field of the anode iron-coated graphite rod and the cathode graphite rod, so that each biochar particle becomes an independent three-dimensional electrode particle, and the positive electrode particles and the positive iron-coated graphite rod undergo oxidation reaction, that is, the oxidation of organic matter in sewage or the dissolution of iron ions in the iron-coated layer (such as Fe 2+ ) or the hydroxide ions (OH - ) is oxidized into oxygen (O2). Finally, soil is loaded on the filler layer to form a soil layer with a thickness of 15 cm; wetland plants are planted on the soil layer, and reeds, calamus, black trifoliate vine, etc. are selected as wetland plants to form a plant layer.

[0029] Step 4: Operation of artificial wetland device. A mixture of urban domestic sewage (after coagulation pretreatment to make SS < 120 mg / L to avoid clogging the wetland) and an equal volume of persulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L) is used as the inlet water of the wetland device, which is introduced into the wetland water distribution area (i.e., the front end of the wetland is filled with gravel with larger particle size) through the wetland inlet pipe, and passes through the main reaction area 1, main reaction area 2, and outlet area of ​​the horizontal subsurface flow artificial wetland in turn. Under an applied voltage of 2-8V, the hydraulic retention time of the wetland is 2d. Since the manganese ion solution is added to the wetland inlet water, the rapid enrichment of manganese bacteria in the wetland device is stimulated.

[0030] Preferably, in step 1, there is one pair of electrodes, i.e., one iron-plated graphite rod and one graphite rod, and the electrode material is a graphite rod, wherein the surface of the anode graphite rod is electroplated to form a layer of iron metal on the surface of the electrode. The specific operation steps are as follows: place the graphite rod in an electrolyte at 80°C to form an oxide film on its surface; pour the FeSO4 plating solution into the electroplating tank, and place the graphite rod as a cathode into the electroplating tank to form an iron metal coating on the surface of the graphite rod through an electroplating reaction at a voltage of 8 to 10V; after the electroplating is completed, take the graphite rod out of the electroplating tank, rinse it with pure water, and dry it at room temperature.

[0031] Preferably, in step 2, the particle size of the biochar particles is 4-8 mm, the particle size of the gravel particles is 4-10 mm, and the particle size of the pebbles is 40-80 mm. In step 3, the filler layer of the main reaction zone 1 is a mixed particle of biochar particles and gravel particles, and the filling volume ratio is 1:4 (biochar: gravel), so as to prevent excessive addition of biochar and thus reduce the permeability of the filler matrix.

[0032] Preferably, the perforated organic glass plate in step 3 has a hole diameter of 2 mm, a hole center spacing of 4 mm, an orthogonal arrangement, and the edges are Figure 2 The tenon joint shown is fixed in a reserved slot to separate various areas of the wetland. For example, the water distribution area and the main reaction area, the main reaction area 1 and the main reaction area 2, and the main reaction area and the water outlet area. At the same time, the perforated organic glass plate can prevent the fillers in the main reaction area 1 and the main reaction area 2 from mixing, and is conducive to the formation of an aerobic-anaerobic interface, which is conducive to the rapid enrichment of manganese bacteria in the artificial wetland system.

[0033] Preferably, the electrolysis-constructed wetland coupling system in step 3 adopts aerobic / anaerobic (O / A n ) Two-stage spatial design, a pair of electrodes are inserted into the main reaction zone 1, and an external resistor (10-20Ω) and a DC power supply (2-8V) are connected in series between the anode (iron-plated graphite rod) and the cathode (graphite rod). At the anode (iron-plated graphite rod and biochar particles that form the anode after conduction), O2, one of the electrolysis products, is conducive to the formation of an aerobic (O) stage; in contrast, since there is no electrode in the main reaction zone 2, the organic matter in the sewage is degraded and the dissolved oxygen in the water is consumed during the biochemical reaction of aerobic microorganisms, forming an anaerobic (A) stage. n) section. During the operation of the wetland, the external power supply continuously supplies power to the electrodes to ensure that two areas, aerobic and anaerobic, are formed in the wetland system. The applicant has found that the existence of the boundary area between aerobic and anaerobic areas is conducive to the enrichment of manganese bacteria. It should be pointed out that there is a transition area between the aerobic area and the anaerobic area in the wetland, namely the anoxic area. Due to the anoxic-aerobic environmental conditions, the wetland device can achieve biological denitrification efficiency, namely, the degradation and nitrification of organic matter occur simultaneously in the main reaction zone 1 (aerobic section), and nitrifying bacteria convert nitrogen-containing substances into nitrates. In the transition area from the main reaction zone 1 to the main reaction zone 2 (anaerobic section), due to the existence of anoxic conditions, denitrification occurs, and denitrifying bacteria reduce nitrates to gaseous nitrogen, thereby realizing the biological denitrification function of the wetland.

[0034] Preferably, the influent in step 4 is a mixture of urban domestic sewage and an equal volume of peroxydisulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L), and the typical components and concentrations of the above-mentioned mixture are: C6H 12 O6 (80 mg / L), CH3COONa (50 mg / L), KNO3 (100 mg / L), NH4Cl (80 mg / L), MgSO4·7H2O (30 mg / L), KH2PO4 (15 mg / L), anhydrous CaCl2 (5 mg / L), Na2S2O8 (100~200) mg / L, MnCl2 (2-10 mg / L).

[0035] Embodiment 1:

[0036] The method of improving the sewage treatment efficiency of artificial wetlands by coupling the above-mentioned manganese bacteria with persulfate advanced oxidation was used to treat urban domestic sewage: wherein, in step 3, a 20Ω resistor and a 6V DC regulated power supply were connected in series between the anode iron-plated graphite rod and the cathode graphite rod of the wetland device, the HRT was 48h, and the power-on mode was continuous power-on; in step 4, the COD concentration of a certain urban domestic sewage was 176.24mg / L, the total nitrogen concentration was 31.70mg / L, the total phosphorus concentration was 3.26mg / L, and the added Na2S2O8 concentration was 100mg / L. After the process system was stably operated for 20 days, the effluent water quality was tested. Considering that the artificial wetland system is composed of a complex microbial community and has strong ecological characteristics, the sampling time is set to 7:00, 15:00, and 21:00 on the same day, and each sampling is carried out at an interval of 5 days. A water quality analysis of 12 samples obtained on four sampling days showed that the average COD concentration of the wetland effluent was 16.85 mg / L, with a removal rate of 90.44%, the total nitrogen concentration was 6.52 mg / L, with a removal rate of 79.43%, and the total phosphorus concentration was 0.97 mg / L, with a removal rate of 70.25%.

[0037] Embodiment 2:

[0038] The method of improving the sewage treatment efficiency of artificial wetlands by coupling the above-mentioned manganese bacteria with persulfate advanced oxidation was used to treat urban domestic sewage: wherein, in step 3, a 10Ω resistor and an 8V DC regulated power supply were connected in series between the anode iron-plated graphite rod and the cathode graphite rod of the wetland device, the HRT was 48h, and the power-on mode was continuous power-on; in step 4, the COD concentration of a certain town’s domestic sewage was 340.38mg / L, the total nitrogen concentration was 60.24mg / L, the total phosphorus concentration was 5.86mg / L, and the added Na2S2O8 concentration was 200mg / L. After the process system had been running stably for 30 days, the effluent water quality was tested. The sampling time was set at 9:00, 14:00, and 20:00 on the same day, and each sampling was conducted at an interval of 7 days. A water quality analysis of 15 samples obtained on 5 sampling days showed that the average COD concentration of the wetland effluent was 32.57 mg / L, with a removal rate of 90.43%, the total nitrogen concentration was 11.54 mg / L, with a removal rate of 80.84%, and the total phosphorus concentration was 1.72 mg / L, with a removal rate of 70.65%.

[0039] The above results indicate that the method of improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation effectively improves the removal efficiency of organic matter and nitrogen and phosphorus pollutants in artificial wetlands, and can be widely used in the field of domestic sewage treatment in small and medium-sized towns or rural areas.

[0040] The above shows and describes the basic principles, main features and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation, characterized in that: The following steps are involved: Step 1: Pretreatment of iron-plated graphite rods. The graphite rods were cleaned with acetone, anhydrous ethanol and pure water in turn. Each cleaning solution was cleaned under ultrasonic conditions for 20 minutes, and then dried at room temperature. Finally, an iron metal coating is formed on the surface of the anode graphite rod by electroplating. Step 2: Filler pretreatment: Biochar and gravel were used as fillers for the wetland device, and pebbles were used as the supporting layer for the wetland device. The fillers were washed 5 times with tap water and then dried naturally. Step 3: Construction of artificial wetland device. Wetland device size: 1.2m long × 0.4m wide × 0.6m high, The device is made of plexiglass. According to the flow direction of sewage, the device is divided into water distribution area, main reaction area and water outlet area. Each area is separated by perforated plexiglass plates. The main reaction area is divided into main reaction area 1 and main reaction area 2. The artificial wetland device adopts horizontal underflow. The main reaction area is vertically composed of plant layer, soil layer, filler layer and support layer. The filler layer of main reaction area 1 is a mixture of biochar particles and gravel particles, and the main reaction area 2 is gravel particles. The device was built according to the following process: First, pebble particles were loaded at the bottom of the device to form a support layer with a thickness of 15 cm. Then, 1 iron-coated graphite rod and 1 graphite rod (length 400 mm, diameter 5 mm) were placed in the mixed filling layer of biochar and gravel in the main reaction zone 1, centered, with a distance of 20 cm between the iron-coated graphite rod and the graphite rod. The iron-coated graphite rod was connected to the positive pole of the external DC power supply through a wire, and the graphite rod was connected to the negative pole of the external DC power supply through a wire (and connected in series with an external resistor, 10-20Ω); the biochar particles and gravel particles were mixed evenly, The biochar particles are loaded on the support layer in a natural stacking manner to form a packing layer with a thickness of 20 cm. The role of non-conductor particles (gravel) is to prevent the biochar particles from connecting to each other and forming a short circuit after conducting electricity. The biochar particles, as conductors, can be polarized under the electric field of the anode iron-plated graphite rod and the cathode graphite rod, making each biochar particle an independent three-dimensional electrode particle. The positive electrode particles and the positive iron-plated graphite rod undergo oxidation reaction, that is, the oxidation of sewage organic matter or the dissolution of iron ions in the iron-plated layer (such as Fe 2+ ) or the hydroxide ions (OH - ) is oxidized into oxygen (O2). Finally, soil is loaded on the filler layer to form a soil layer with a thickness of 15 cm; wetland plants are planted on the soil layer, and reeds, calamus, black trifoliate vine, etc. are selected as wetland plants to form a plant layer. Step 4: Operation of artificial wetland device. A mixture of urban domestic sewage (after coagulation pretreatment to make SS < 120 mg / L to avoid clogging the wetland) and an equal volume of persulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L) is used as the inlet water of the wetland device, which is introduced into the wetland water distribution area (i.e., the front end of the wetland is filled with gravel with larger particle size) through the wetland inlet pipe, and passes through the main reaction area 1, main reaction area 2, and outlet area of ​​the horizontal subsurface flow artificial wetland in turn. Under an applied voltage of 2-8V, the hydraulic retention time of the wetland is 2d. Since the manganese ion solution is added to the wetland inlet water, the rapid enrichment of manganese bacteria in the wetland device is stimulated.

2. The method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation according to claim 1, characterized in that: In the step 1, there is one pair of electrodes, namely one iron-plated graphite rod and one graphite rod, and the electrode material is a graphite rod, wherein the surface of the anode graphite rod is electroplated with an iron metal layer on the surface of the electrode.

3. The method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation according to claim 1, characterized in that: In the step 2, the particle size of the biochar particles is 4-8 mm, the particle size of the gravel particles is 4-10 mm, and the particle size of the pebbles is 40-80 mm.

4. The method of improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation according to claim 1, characterized in that: The perforated plexiglass plate in step three has a hole diameter of 2 mm and a hole center spacing of 4 mm. It is arranged orthogonally, and the edge is fixed in the reserved slot using the tenon joint shown in Figure 2 to separate the various areas of the wetland.

5. The method for improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation according to claim 1, characterized in that: In the step 3, the filler layer of the main reaction zone 1 is a mixture of biochar and gravel particles, with a filling volume ratio of 1:4 (biochar: gravel).

6. The method of improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation according to claim 1, characterized in that: In step 3, the electrolysis-constructed wetland coupling system adopts aerobic / anaerobic (O / A n ) Two-stage design, a pair of electrodes is inserted into the main reaction zone 1: at the anode (iron-plated graphite rod and biochar particles that form the anode after conduction), O2, one of the electrolysis products, is conducive to the formation of an aerobic (O) stage; in contrast, since there is no electrode in the main reaction zone 2, the organic matter in the sewage is degraded during the aerobic microbial biochemical reaction and consumes the dissolved oxygen in the water, forming an anaerobic (A) stage. n ) section. During the operation of the wetland, the external power supply continuously supplies power to the electrodes to ensure the formation of an aerobic and anaerobic interface area in the wetland system. The applicant has found that the existence of an aerobic and anaerobic interface area is conducive to the enrichment of manganese bacteria.

7. The method of improving the sewage treatment efficiency of artificial wetlands by coupling manganese bacteria with peroxydisulfate advanced oxidation according to claim 1, characterized in that: The influent in step 4 is a mixture of urban domestic sewage and an equal volume of peroxydisulfate (concentration of 100-200 mg / L) + manganese chloride solution (2-10 mg / L). The typical components and concentrations of the above mixture are: C6H 12 O6 (80 mg / L), CH3COONa (50 mg / L), KNO3 (100 mg / L), NH4Cl (80 mg / L), MgSO4·7H2O (30 mg / L), KH2PO4 (15 mg / L), anhydrous CaCl2 (5 mg / L), Na2S2O8 (100~200) mg / L, MnCl2 (2-10 mg / L).

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