NL2024124B1 - A combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for treating wastewater containing farm chemicals - Google Patents

Abstract

The invention provides a combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for treating wastewater containing pesticides. They are, in turn from left to right, the artificial simulated wastewater pool, peristaltic pump and the combined iron-carbon microelectrolysis - microbial fuel cell - constructed wetland system. The wastewater in the artificial simulated wastewater pool is delivered by the peristaltic pump through the water distribution pipe to the combined system. The invented installation is provided with a trapezoidal compartment for iron-carbon microelectrolysis on the bottom and the top. First of all, this considerably improves the biodegradability of wastewater. By decomposing macromolecular phosphate ester organic pesticides into small molecules, it improves pollutant removal efficiency and electron transfer efficiency as well as the treatment effect and electricity-generating effect of follow-up constructed wetland microbial fuel cell.

Description

A COMBINED INSTALLATION OF IRON-CARBON MICROELECTROLYSIS - MICROBIAL FUEL CELL - CONSTRUCTED WETLAND FOR TREATING WASTEWATER CONTAINING FARM CHEMICALS

FIELD OF INVENTION The invention relates to the field of refractory organic sewage/ wastewater treatment, specifically a combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for treating wastewater containing pesticides.

BACKGROUND OF THE PRESENT INVENTION Energy is an important issue that needs to be solved at present. It is also the primary issue related to the destiny of human beings and the development of society. The issue of energy is, above all, the shortage of resources and environmental pollution, so we need to find alternative energy while trying to reduce environmental pollution. Clean, diversified and recyclable energy is the focus of future research.

Pesticide is a kind of chemical agent, which plays an indispensable role in mcreasing yield in agricultural production. However, continuous economic development leads to the abuse of pesticides, resulting in the pollution of residual pesticides, which ruins the soil condition, water and agricultural creatures, as well as harms human body through ecological circulation. The low popularity of scientific knowledge and environmental protection awareness leads to the irrational use of pesticides in agricultural production, which not only affects the yield of agricultural crops, but also ruins the natural chemical composition of soil, contaminates the source of drinking water and threatens human health and life safety. Properties of the pesticides determine that it cannot be decomposed and eliminated through natural ways, and its residual remains in soil, resulting in environmental pollution due to repeated abuse of pesticides.

Microelectrolysis mainly uses metal and inert carbon sources to form galvanic cells to reduce and degrade pollutants. Iron 1s usually used as the metal electrode and activated carbon particles are used as the inert electrode. The iron electrode has a low potential, so the iron loses electrons and the electrons flow to the carbon electrode. On the cathode, electrons and electron receptors combine to form a reduction product and reduce the pollutant at the same time. Meanwhile, the reaction process also includes electrochemical enrichment, coagulation adsorption, and ion precipitation, etc. This method can decompose a variety of refractory organic matters and improve the biodegradability of wastewater, so it is mostly used in pretreatment of wastewater. The researchers pretreated nitrobenzene wastewater with iron-copper microelectrolysis, and the nitrobenzene was decomposed into aniline, which was more biodegradable, thus effectively improving the biodegradability of wastewater. The galvanic cell reaction composed of iron and carbon can effectively remove COD in the refractory organic matter, so as to improve the biodegradability of wastewater and facilitate subsequent biological treatment. Therefore, the iron-carbon microelectrolysis method is often used in combination with the biochemical method.

Constructed wetland microbial fuel cell (CW-MFC) is a new wastewater treatment process that combines the technology of constructed wetland and microbial fuel cell. The anode 1s mostly under anaerobic conditions, and the organic matter 1s decomposed by anaerobic electricity-producing microorganisms to generate electrons, which are transferred to the cathode through the external circuit to generate current and complete the redox reaction. Electrodes are usually made of porous materials with good electrical conductivity, such as activated carbon particles that are used for most of the time. Sufficient dissolved oxygen can be provided for the cathode by growing plants on the top. Currently, CW-MFC has good performance in treating azo dye wastewater, antibiotic wastewater and livestock wastewater. At present, the research of microbial fuel cell constructed wetland system has been carried out step by step. Initial results show that the microbial fuel cell constructed wetland system demonstrates electricity-generating efficiency while not affecting or even enhancing the CW wastewater treatment effect. It is therefore of good application prospect.

Some Chinese patents, such as the application numbers CN201110187473, CN201110195615, present several types of wastewater treatment plants using microbial fuel cell coupled with constructed wetland. These plants can generate electric energy while meeting the requirement for wastewater treatment, but they are not 1deal in the effect of treating refractory organic matter. The patent whose application number is CN201720653737 uses high and low potential energy flow to set aluminum screen on the cathode in order to achieve the effect of removing plumbum, zinc and other heavy metal pollutants. However, the patent applicant did not consider the anaerobic conditions of the anode, and the positive and negative poles were separated with a perforated partition, so the electricity- generating efficiency was limited; the passivation of aluminum and the hardening of filter material were also not considered, which leads to little effect m removing macromolecular organic pollutants.

SUMMARY OF THE INVENTION In view of the defects of traditional microbial fuel cell constructed wetland that is easily blocked up due low inlet water quality and which 1s difficult to degrade macromolecular organic pollutants, the invention provides a combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for treating wastewater containing pesticides.

Specifically, a combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for treating wastewater containing pesticides. They are, in turn from left to right, the artificial simulated wastewater pool, peristaltic pump and the combined iron-carbon microelectrolysis - microbial fuel cell - constructed wetland system.

The volume of the artificial simulated wastewater pool is 20L, in which the wastewater is delivered through a BT-100EA variable speed peristaltic pump, whose regulation speed is 100ml/min, and it is connected to the combined system via the water distribution pipe whose DN 1s 0.5cm. Wherein the combined system, in turn from bottom to top, includes: The trapezoidal compartment for iron-carbon microelectrolysis and the inverse trapezoidal compartment on support layer, wherein the trapezoidal compartment for iron-carbon microelectrolysis is 20cm high, with 15cm in length of bottom side and 6cm in length of top side. The inverse trapezoidal compartment on support layer has same dimensions. Both compartments are arranged head to tail. The trapezoidal compartment for iron-carbon microelectrolysis on the bottom layer 1s provided in four groups and the inverse trapezoidal compartment on support layer is in three groups. The wastewater in the artificial simulated wastewater pool is delivered through the water distribution pipe to the trapezoidal compartment for iron-carbon microelectrolysis and the inverse trapezoidal compartment on support layer. The trapezoidal compartment for iron-carbon microelectrolysis is provided with a layer of stainless steel wire screen in the lower section. Beneath the screen a sludge discharge pipe (DN1.5cm) is provided.

The anode layer uses the integrated GAC-SSM electrodes combining 15- mesh stainless steel screen SSM (with wire diameter of 0.32mm) and active carbon granules GAC (grain size of 1-3mm), with an overall thickness being about 18cm and an effective surface area of 600cm?. With DN0.5mm brass wire, the 5 anode layer is connected through an external circuit to a 100002 constant external resistance.

The trapezoidal compartment for iron-carbon microelectrolysis and the mverse trapezoidal compartment on support layer, wherein the trapezoidal compartment for iron-carbon microelectrolysis is provided with a layer of stainless steel wire screen in the lower section. Beneath the screen a sludge discharge pipe (DN1.5cm) is provided. The trapezoidal compartment for iron- carbon microelectrolysis and the inverse trapezoidal compartment on support layer are provided with DN1.5cm aerator pipes in the bottom, which are 25cm long and are provided with an air vent at 3cm intervals for intermittent aeration, with dissolved oxygen concentration controlled at 4mg/L.

Cathode pool and vegetation growing area; water outlet arranged at the leftmost end; The external circuit includes wires and external resistance, which forms a loop with the anode layer and cathode pool.

Further, the combined system is wholly made of organic glass in the form of PMMA plate about 1cm thick and 65cm high.

Further, the stainless steel wire screen is a 20-mesh screen, with wire diameter of 0.25mm and a thickness about 3cm.

Further, the cathode pool is an electrode integrated with 15-mesh (with wire diameter of 0.32mm) stainless steel wire screen and 1-3mm grain-sized active carbon granules. The hollow inner spaces can be used for growing vegetation. The hollow area is about 700cm? and effective cathode area is about 2100cm?.

Further, the cathode pool is an extendable air cathode whose surface area is two times the upper surface area of the cylindrical shell, and it is divided into four sections, with each section uniformly filled with 1-3mm grain-sized active carbon granules; the effective area of each section is about 500cm?. The four sections are connected with DN0.5mm brass wires.

Further, the trapezoidal compartment for iron-carbon microelectrolysis is filled with iron scraps and carbon granules, which are to be pretreated, before filling, by soaking the iron scraps in 10% sodium hydroxide for one hour in order to remove its surface dirt, soaking it in 10% sulfuric acid for one hour in order to remove its surface oxides, and flushing it with 7 pH distilled water until it 1s neutralized.

Further, the inverse trapezoidal compartment on support layer 1s filled with 1-3cm grain-sized dolomite matrix, which is to be pretreated, before filling, by soaking the dolomite in 10% sodium hydroxide for one hour in order to remove its surface dirt, soaking it in 10% sulfuric acid for one hour in order to remove its surface oxides, and flushing it with 7 pH distilled water until it is neutralized.

Further, the upper part of the cathode pool is planted with reeds, which are to 40 cm long and slightly droopy, wherein a spikelet, 1.4 cm long, white 20 green, contains 4 to 7 flowers, with inflorescence being about 15 to 25 cm long.

Further, the cathode 1s on the same level with the overflow port. Overflow water of the cylindrical shell goes directly into the cathode.

Compared with existing methods, this invention provides a technical solution with the following advantages and benefits: (1) Compared with the traditional constructed wetland microbial fuel cells, the combined installation of iron-carbon microelectrolysis - microbial fuel cells

- constructed wetland uses the iron-carbon microelectrolysis principle to treat wastewater containing phosphorous pesticides by decomposing residual organophosphorus pesticides into small molecule organic compound, which increases the biodegradability of subsequent treatment and is favorable for the follow-up treatment by CW-MFC. The iron-carbon microelectrolysis section is packed with iron scraps and active carbon particles. In view of the CW-MFC mechanism, the good aerobic condition of cathode is more beneficial to electricity generation of the installation, and the improvement of biodegradability of inlet water is also beneficial to subsequent treatment.

(2) Compared with other available microbial fuel cell constructed wetland, the invented installation is provided with a trapezoidal compartment for iron- carbon microelectrolysis on the bottom and the top. First of all, this considerably improves the biodegradability of wastewater. By decomposing macromolecular phosphate ester organic pesticides into small molecules, it improves pollutant removal efficiency and electron transfer efficiency and enhances the treatment effect and power-generating effect of follow-up constructed wetland microbial fuel cell.

(3) Compared with other available microbial fuel cell constructed wetland, CW-MFC uses an electrode integrated with 0.32mm diameter stainless steel wire screen and active carbon particles, which facilitates the collection of electrons and generation of electricity. In addition, dolomite is used as the anode and cathode matrix, which is calcium and magnesium compound that provides more efficient adsorption of phosphorus pesticides pollutants in water. The iron- carbon microelectrolysis section is packed with iron scraps and active carbon particles.

(4) Compared with other available microbial fuel cell constructed wetland, the invention uses externally extended cathode. With increase of the area of the cathode, it is beneficial for the cathode to contact with oxygen, thus improving electricity generation of the installation.

BRIEF DESCRIPTION OF THE DRAWINGS Figure 1 is a diagram of the invented installation; Figure 2 is a diagram of the bird view of the cathode pool of the invention.

Wherein: 1- artificial simulated wastewater pool, 2- peristaltic pump, 3- water distribution pipe, 4- inverse trapezoidal compartment on support layer, 5- trapezoidal compartment for iron-carbon microelectrolysis, 6- sludge discharge pipe, 7- anode layer, 8- aerator pipe, 9- water outlet, 10- vegetation, 11- cathode pool, 12- external resistance, 13- screen, 14- active carbon electrode, 15- vegetation growing area

DETAILED DESCRIPTION The following is a further detailed description of the specific embodiment of this application in combination with the attached drawings.

Embodiment 1As shown in Figure 1, the invention is a combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for treating wastewater containing pesticides. They are, in turn from left to right, the artificial simulated wastewater pool (1), peristaltic pump (2) and the combined iron-carbon microelectrolysis - microbial fuel cell - constructed wetland system.

The wastewater in the artificial simulated wastewater pool (1) is delivered through a BT-100EA variable speed peristaltic pump (2), whose regulation speed is 100ml/min, and it is connected to the combined system via the water distribution pipe (3) whose DN is 0.5cm.The combined system is wholly made of organic glass in a height of about 65cm. The combined system, in turn from bottom to top, includes: The trapezoidal compartment for iron-carbon microelectrolysis (5) and the inverse trapezoidal compartment on support layer (4). Wastewater is delivered through the water distribution pipe (3) from the artificial simulated wastewater pool (1) into the trapezoidal compartment for iron- carbon microelectrolysis (5) and the inverse trapezoidal compartment on support layer (4). The trapezoidal compartment for iron-carbon microelectrolysis (5) is provided on its lower part a stainless steel wire screen (13), beneath which there provided with a sludge discharge pipe (6).

The trapezoidal compartment for iron-carbon microelectrolysis (5) and the inverse trapezoidal compartment on support layer (4), wherein the trapezoidal compartment for iron-carbon microelectrolysis (5) is 20cm high, with 15cm in length of bottom side and 6cm in length of top side. The inverse trapezoidal compartment on support layer (4) has same dimensions. Both compartments are arranged head to tail. The trapezoidal compartment for iron-carbon microelectrolysis (5) on the bottom layer is provided in four groups and the inverse trapezoidal compartment on support layer (4) is provided in three groups. The wastewater in the artificial simulated wastewater pool (1) is delivered through the water distribution pipe (3) to the trapezoidal compartment for iron-carbon microelectrolysis (5) and the inverse trapezoidal compartment on support layer (4). The trapezoidal compartment for iron-carbon microelectrolysis (5) is provided with a layer of stainless steel wire screen in the lower section. Beneath the screen a sludge discharge pipe (6) (DN1.5cm) is provided. The anode layer uses the integrated GAC-SSM electrodes combining 15- mesh stainless steel wire screen SSM (with wire diameter of 0.32mm) and active carbon granules GAC (grain size of 1-3mm), with an overall thickness being about 18cm and an effective surface area of 600cm?. With DN0.5mm brass wire, the anode layer is connected through an external circuit to a 10002 constant external resistance (12).

The trapezoidal compartment for iron-carbon microelectrolysis (5) and the mverse trapezoidal compartment on support layer (4), wherein the trapezoidal compartment for iron-carbon microelectrolysis (5) is provided with a layer of stainless steel wire screen (13) in the lower section. The stainless steel wire screen (13) 1s a 20-mesh stainless wire screen made of 0.25mm diameter wires. Beneath the screen a sludge discharge pipe (6) (DNI1.5cm) is provided to prevent the mstallation from plugging the screen. The trapezoidal compartment for iron- carbon microelectrolysis (5) and the inverse trapezoidal compartment on support layer (4) are provided with a DN1.5cm aerator pipes (8) in the bottom, which are 25cm long and are provided with an air vent at 3cm intervals for intermittent aeration, with dissolved oxygen concentration controlled at 4mg/L.

The cathode pool (11) and vegetation growing area (15) use an electrode integrated with 15-mesh (with wire diameter of 0.32mm) stainless steel wire screen and active carbon particles to provide a hollow space for growing vegetation (10). The cathode pool (11) 1s an externally extended air cathode, whose surface area is two times that of the cylindrical shell and is divided into four sections that are connected with wires. The water outlet is set up to the leftmost end.

The external circuit includes wires and external resistance (12), which forms a loop with the anode layer and cathode pool.

The trapezoidal compartment for iron-carbon microelectrolysis (5) 1s filled with iron scraps and carbon granules, which are to be pretreated, before filling, by soaking the iron scraps in 10% sodium hydroxide for one hour in order to remove its surface dirt, soaking it in 10% sulfuric acid for one hour in order to remove its surface oxides, and flushing 1t with 7 pH distilled water until it is neutralized.

The inverse trapezoidal compartment on support layer (4) is filled with dolomite matrix, which is to be pretreated, before filling, by soaking the dolomite in 10% sodium hydroxide for one hour in order to remove its surface dirt, soaking it in 10% sulfuric acid for one hour in order to remove its surface oxides, and flushing it with 7 pH distilled water until it is neutralized. The vegetation (10) to be grown on top of the cathode pool (11) is reed.

Embodiment 2A method of using the combined installation of iron-carbon microelectrolysis - microbial fuel cell - constructed wetland for purifying wastewater includes the following steps: (1) Inject the manually prepared wastewater containing phosphorus pesticides into the water distribution tank of the artificial simulated wastewater pool; adjust the pH value to 7-8, and leave it for 50 to 70 minutes before turning on the peristaltic pump (2). Water in the distribution tank is delivered, through the distribution pipe (3), from the lower part of the combined system of 1ron- carbon microelectrolysis - microbial fuel cell - constructed wetland partially into the inverse trapezoidal compartment on support layer (4) and partially into the trapezoidal compartment for iron-carbon microelectrolysis (5).

(2) The wastewater enters the anode layer after pretreatment in the bottom trapezoidal compartment for iron-carbon microelecrolysis (5). The electricity- generating microorganism in the anode uses the organic matter in water to produce electricity. After passing through the anode, the wastewater enters the bottom trapezoidal compartment for iron-carbon microelecrolysis (5) and the inverse trapezoidal compartment on support layer (4) for secondary treatment. Now, open the pre-installed aerator pipe (8) for intermittent aeration.

(3) Then, the wastewater overflows from the installation to the pre-designed externally-extended cathode zone, where it is in contact with the active carbon of the cathode zone. Electrons are reduced on the cathode to produce electric current and a loop is formed via connection with an external circuit.

Application test: The installation should be pre-inoculated by culturing the activated sludge taken from a sewage treatment plant.

The culture of sludge lasts for 20 days.

Start experiment after stable operation and electricity production of the installation.

Simulate that the wastewater containing pesticides passes through the peristaltic pump and enters the installation via the distribution pipe beneath the installation.

The invention selects stainless steel wire screen as metal anode and activated carbon particles as inert electrode.

At the lower potential iron anode, the iron loses electrons, which flow to the carbon cathode, where the pollutants in the water are reduced.

As the reaction process in the installation also includes physical absorption, coagulation adsorption and electrochemical enrichment, to ensure the effectiveness of iron-carbon microelectrolysis, the invention does not use continuous feeding of water but sets up HRT to 5 days, with COD concentration controlled at 800mg/L and pesticides concentration at 10mg/L, in addition to full aeration.

Take samples respectively from the anode and cathode layers of the iron- carbon microelectrolysis - constructed wetland - microbial fuel cell and measure the pH value, COD and pesticides concentration of the effluent each day while monitoring voltage change during operation.

Table 1 Effluent from the anode Retention ee Id 2d 3d 4d sd On) (HRT) COD (mg/L) 425 258 136 98 49 91.2 es 8.8 7.9 7.1 6.8 5.7 43 pH 68 6.6 63 62 6.1 -

Table 2 Effluent from the cathode (final effluent)

Hydraulic Max Rate Retention Time 1d 2d 3d 4d 5d of Removal

(HRT) (%)

COD (mg/L) 336 146 89 49 <20 >97.5 es 3.5 2.1 0.9 0.4 <0.2 >98 pH 7.5 7.8 7.8 8.1 8.2 - As shown in Table 1 and Table 2, the pH value of anode tends to decrease during operation of the installation while the pH of cathode tends to rise.

With the increase of HRT time, the effect of hydrolysis and acidification in anode anaerobic zone is enhanced, and the pH value decreases, which 1s further helpful for decomposition of organic matter.

With the increase of HRT, COD and pesticides concentrations decrease gradually.

What more, the treatment effect of cathode is better than the anode as the rate of COD removal reaches 97.5% and the rate of removing pesticides reaches 98%. The anode is under anaerobic condition, and the simulated wastewater contact with the microelectrolysis compartment is not sufficient, so the removal effect is lower than that of the cathode.

Fan Chuang 4 et al used the constructed wetland to treat wastewater containing triazophos and utilized the property of aluminum sludge that absorbs phosphor to treat the wastewater.

The rate of COD removal reaches 90% and the rate of removing triazophos reaches 96%. However, the rate of removal drops obviously when the concentration of triazophos is above 10mg/L.

The reason lies in that triazophos without pretreatment is directly delivered into the installation, which causes death of microorganism due to toxic effect.

For the invention in which the concentration of pesticides in feeding water is 10mg/L, the final rate of removal 1s up to 98%. Microelectrolysis can decompose refractory pesticides into small molecules that can be easily treated, greatly reduce the toxicity of farm chemical wastewater, and provide a more stable environment for the growth and reproduction of microorganisms, which is more favorable for continuous removal of pollutants.

The invention combines iron-carbon microelectrolysis with constructed wetland microbial fuel cell.

It improves the rate of COD removal by 50% as compared with a single iron-carbon microelectrolysis system.

Zeng Chao {2 et al. used the principle of iron-carbon microelectrolysis to treat printing and dyeing wastewater.

Under the condition without pH adjustment, COD removal rate of printing and dyeing wastewater was about 50.1% to 68%. The invention adopts iron-carbon microelectrolysis pretreatment, and then wastewater flows through the constructed wetland microbial fuel cell for further treatment.

Finally, the rate of COD removal can reach above 95%, and the dolomite matrix provides better treatment effect for refractory organic pesticides pollutants.

Table 3 Electricity generation efficiency of the system Retention Time 1d 2d 3d 4d sd (HRT) Avg. voltage (V) 0.91 1.1 1.2 1.3 1.2 ma 0.88 0.98 LI! 1.19 111 As shown in Table 3, with increase of HRT, the electricity generation voltage and power density of the system rise steadily at the beginning and become stable around the third day.

With a shorter HRT, organic matter cannot be decomposed completely, and a longer HRT leads to reduction of nutrient substances and the drop of biological activity.

So the installation reaches its optimum operating condition when HRT is equal to three days.

Chinese patent application No.

CN108178320A, an installation of microbial fuel cell constructed wetland and a method of wastewater purification, wherein hydrolytic acidification is used for pretreatment of sewage/wastewater, with the maximum voltage and maximum power density being 0.72V and 0.55W/m3 respectively and the maximum rate of COD removal being around 80%. However, the maximum voltage of the invention is up to 1V and the maximum rate of COD removal can be more than

95%. Since the invention adopts an externally extended air cathode and the cathode area 1s large and the contact area with air is large enough to form a large redox potential difference, the electricity production efficiency and COD removal effect of the vention are significantly higher than other installations. References:

[1] Fan Chuang. Removing wastewater containing pesticides with aluminum sludge constructed wetland combined with microbial fuel cells [D]. Xi'an: Chang'an University, 2017.

[2] Zeng Chao. Study of the acting mechanism of iron-carbon microelectrolysis - coagulation depth treatment of printing and dyeing wastewater [D]. Shanghai: Donghua University, 2015.

What described above are only better embodiments of the invention. The scope of protection under the invention is not limited to these embodiments. A simple change or equivalent replacement of a technical solution apparently obtainable by any technician familiar with the technical field within the technical scope disclosed by the invention falls into the protection scope of the invention.

Claims (8)

Conclusions 1. A ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device for treating pesticide wastewater, which from left to right are an artificial simulated wastewater tank, a peristaltic pump and a ferrocarbon microelectrolysis-microbial fuel cell composite wetland composite system . The artificial simulated wastewater tank has an effective volume of 20L, the wastewater passes through a BT-100EA variable speed peristaltic pump and the rotation speed is adjusted to 100ml/min and is connected to the composite system through a DN 0.5cm water distribution pipe, characterized in that the composite system comprises in order from bottom to top: The trapezoidal compartment of iron-carbon microelectrolysis and the inverted trapezoidal compartment of the support layer, wherein the trapezoidal compartment of iron-carbon microelectrolysis has a height of 20 cm, a length of the bottom of 15 cm and a length of the top of 6 cm, and the inverted trapezoidal compartment of the support layer is the same size. The two are staggered by inverting each other. There are 4 sets of trapezoidal compartments of iron-carbon microelectrolysis, and there are 3 sets of inverted trapezoidal compartments of the support layer. The wastewater in the artificial simulated wastewater bath enters the iron-carbon microelectrolysis trapezoidal compartment and the inverted trapezoidal compartment of the support layer through a water distribution pipe, and the iron-carbon microelectrolysis trapezoidal compartment is provided with a layer of stainless steel mesh wall. The drain pipe of DN 1.5 cm is fitted under the partition; The anode layer is a GAC-SSM integrated electrode consisting of a 15-mesh stainless steel mesh SSM with a wire diameter of 0.32 mm and a GAC with activated carbon particles with a particle diameter of 1-3 mm. The total thickness is about 18 cm, the effective area is 600 cm? and the anode layer is connected to a 100092 stable external resistance through an external circuit through a DN 0.5mm copper wire; The trapezoidal compartment of iron-carbon microelectrolysis and the inverted trapezoidal compartment of the support layer, wherein the trapezoidal compartment of iron-carbon microelectrolysis is provided with a layer of stainless steel mesh wall. The drain pipe of DN 1.5 cm is fitted under the partition; The bottom of the trapezoidal compartment with iron-carbon microelectrolysis and the inverted trapezoidal compartment of the support layer is provided with a DN 1.5 cm aeration tube, the length of which is 25 cm, and an air hole is provided every 3 cm for intermittent aeration , and the dissolved oxygen concentration is controlled to 4 mg/L; A cathode tank and a plant growing area; the water outlet is located at the far left end; Wherein the outer circuit comprises a wire and an outer resistor, and the anode layer and the cathode tank form a loop. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that the composite material of the composite system is made of plexiglass and is made of an acrylic sheet with a thickness of about 1 cm and a height of about 65 cm. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that the stainless steel mesh was cut into a 20-mesh stainless steel having a wire diameter of 0.25 mm and having a thickness of about 3cm. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that the cathode tank is an integrated electrode of a 15-mesh stainless steel mesh having a wire diameter of 0.32 mm and activated carbon particles having a particle diameter of 1-3mm, and is hollowed out in the center to facilitate planting, the hollow area is about 700cm? and the effective cathode area is about 2100 cm. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that the cathode pole is an externally expanding air cathode, the surface of which is twice the surface of the cylinder, and is divided into four parts, each part is evenly filled with active particles of a particle size of 1-3 mm, and the effective area of each part is about 500 cm -1 , and the 4 parts are connected by DN0.5 mm copper wires. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that the trapezoidal compartment of iron-carbon microelectrolysis is filled with iron shavings and carbon particles, and the iron shavings and carbon particles must be be pre-treated before filling. The treatment method is as follows: the iron shavings is soaked for 1 hour with sodium hydroxide to remove surface dirt, and then immersed in sulfuric acid for 1 hour to remove surface oxide, and then rinsed to neutral with pH 7 distilled water, then fill. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that the inverted trapezoidal compartment of the support layer adopts a dolomite matrix having a particle size of 1-3 cm and is pretreated before filling. The treatment method is as follows: dolomite is soaked for 1 hour with 10% sodium hydroxide to remove surface dirt, and then immersed in 10% sulfuric acid for 1 hour to remove surface oxide, and then rinsed to neutral with pH 7 distilled water, then fill. The ferrocarbon microelectrolysis-microbial fuel cell synthetic wetland composite device according to claim 1, characterized in that The plantlet on the upper part of the cathode tank is a reed.