An anaerobic baffled-microbial electrolysis-artificial wetland coupled process for rural domestic sewage treatment

Abstract

The application discloses application of an anaerobic baffle-microbial electrolysis-artificial wetland coupling process in rural domestic sewage treatment, and is based on a novel volatile fatty acid (VFA) comprehensive utilization technology. The anaerobic baffle-microbial electrolysis-artificial wetland coupling process is mainly composed of a four-chamber anaerobic baffle reactor and a multi-stage microbial electrolysis and horizontal subsurface flow artificial wetland coupling reactor, and the specific working process is as follows: (1) rural domestic sewage is used as influent, and is firstly introduced into the anaerobic baffle reactor to produce VFAs and gas through anaerobic hydrolysis; (2) the microbial electrolysis-artificial wetland coupling reactor is started; and (3) the effluent and the produced gas of the anaerobic baffle reactor are introduced into the microbial electrolysis-artificial wetland coupling reactor to integrate and control the microbial community structure and activity, efficiently degrade VFAs into CO2 and CH4, remove nitrogen and phosphorus pollutants, and realize resource utilization of the sewage treatment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of rural sewage treatment, and particularly relates to an anaerobic baffle-microbial electrolysis-artificial wetland coupled process for rural domestic sewage treatment. BACKGROUND

[0002] Rural domestic sewage has the characteristics of wide distribution and large discharge, and is a key object of rural water environment remediation. Artificial wetlands are a kind of treatment system that utilizes the synergistic effect of plants, soil, microorganisms, substrates, etc. to remove pollutants in a controllable environment, and have the characteristics of low construction and operation cost, and are widely used in the field of rural sewage treatment. However, the problems of low pollutant load (water load, organic load, etc.), easy clogging and low treatment efficiency have become the main factors restricting the application of artificial wetland engineering.

[0003] In order to improve the clogging phenomenon of artificial wetlands and improve the treatment load and water quality, it is necessary to reasonably combine and transform the process. The anaerobic baffle is an anaerobic biological reactor, which has the effects of uniform water quality, water volume adjustment, and improvement of the biodegradability of subsequent treatment. In addition, the microbial electrolysis cell technology has the characteristics of multiple types of inorganic / organic substrates that can be utilized and high activity of electricity-producing microorganisms, and can improve the stability of the microbial community structure and the diversity of functional bacteria of the artificial wetland system based on the principle of ecology. Therefore, the application proposes an anaerobic baffle-microbial electrolysis-artificial wetland coupled process for rural domestic sewage treatment: the influent is first treated by the anaerobic baffle reactor to generate a large amount of VFAs and biogas, and then the anaerobic reactor effluent and gas production are introduced into the multi-stage microbial electrolysis-artificial wetland coupled system to realize the synergistic improvement of the treatment effect of electricity-producing microbial flora, the regulation of biofilm thickness, the improvement of substrate clogging, and the reduction of mass transfer resistance, and finally to strengthen the overall treatment efficiency of the coupled system. SUMMARY

[0004] The technical problem to be solved by the application is to propose an anaerobic baffle-microbial electrolysis-artificial wetland coupled process and its application method to solve the engineering application defects of artificial wetlands in treating rural sewage.

[0005] To solve the above technical problems, the technical scheme adopted by the application is:

[0006] The application discloses a kind of anaerobic baffles-microbial electrolysis-artificial wetland coupling process for rural domestic sewage treatment, its characterized in that, rural domestic sewage is pumped into anaerobic baffles reactor (3) by sewage collection tank (1) through water inlet pipe, anaerobic reactor water inlet pump (2) is arranged on water inlet pipe, sewage collection tank (1) effluent is pumped into anaerobic reactor (3) by anaerobic reactor water inlet (11).Anaerobic reactor (3) effluent is pumped into horizontal subsurface artificial wetland (6) by artificial wetland water inlet pump (4), artificial wetland (6) is divided into water distribution area (5), main reaction zone (7) and effluent zone (8), effluent zone (8) effluent is pumped into effluent tank (10) by effluent pump (9).Anaerobic baffles reactor (3) is composed of four series communication compartments (15), each compartment top is equipped with exhaust pipe (26).Baffle (14) is used to separate compartment, and the lower baffle (14) is equipped with reflector (13).Water flow can pass through baffle (16) in turn, and the end of baffle (16) is equipped with guide vane (12).Under the action of return sludge pump (24), return sludge is returned to inlet (25) by pipeline through sludge discharge port (23).Horizontal subsurface artificial wetland (6) main reaction zone (7) is composed of plant layer (18), soil layer (19), filler layer (20), gravel layer (21), rammed base layer (22).Six pairs of electrodes (34) are inserted into wetland filler layer (20) respectively, each pair of electrode is connected with the positive and negative poles of constant voltage direct current power supply (32) respectively, and each pair of electrode and constant voltage direct current power supply (32) is connected with external resistance (33) in series. Meanwhile, under the action of vacuum pump (27), gas generated by anaerobic reactor (3) is collected through exhaust pipe (26) and then passes through buffer tank (28) and diffusion pipe (29) in turn and is introduced into main reaction zone (7) of horizontal subsurface artificial wetland (6).The diffusion pipe (29) is arranged in the gravel layer (21).Diffusion pipe (30) and pressure monitoring table (31) are used for monitoring and removing high-pressure gas in diffusion pipe.

[0007] Preferably, for the anaerobic baffled reactor structure design, a three-phase separator is arranged in front of each exhaust pipe and water outlet: to ensure the three-phase separation effect of gas, liquid and solid sludge, to ensure that each compartment of the anaerobic reactor maintains a high sludge concentration, and to promptly discharge the gas generated in each compartment of the anaerobic biochemical reaction from the reactor, avoiding the interference of the gas product in the front section on the biochemical reaction in the rear section, and ensuring efficient production of VFAs in the anaerobic reaction. The baffle plate and the reflection plate are perpendicular. The width of the upflow zone compartment is greater than that of the downflow zone compartment, thereby slowing down the upflow velocity in the upflow zone and being conducive to the settlement and interception of sludge in the reaction zone. The distance between the partitions gradually decreases along the direction of the water flow. The flow guiding effect of the baffle plate and the reflection plate can promote the water flow to the center area of the upflow zone, reduce the impact strength of the water flow entering the compartment, and play the role of uniform water distribution, buffer flow and improve the sludge concentration of the reactor. For the structure design of the artificial wetland, reed, canna, alocasia and the like are selected as plants to provide organic matter and oxygen for the growth of microorganisms (including electrochemically active bacteria) through rhizosphere effect. 8-16mm ceramic filter material is selected, which has high biofilm formation efficiency, small water head loss and strong pollution interception capacity. For the structure design of the microbial electrolysis and artificial wetland coupled system, 6 pairs of electrodes are selected, the electrode material is carbon rod, and the cathode surface is coated with Pt catalyst.

[0008] According to the process flow of claim 1, the microbial electrolysis-artificial wetland coupled system adopts a multi-section multi-stage design, the artificial wetland is divided into two sections, 2 pairs of electrodes are inserted into the front section, and 4 pairs of electrodes are inserted into the rear section, the number of electrodes in the rear section is twice that in the front section, so that the current density of the electrodes in the rear section is larger and the internal resistance is smaller, which can strengthen the synergistic degradation and specific degradation activity of the electrogenic bacteria. Moreover, the electrodes are not continuously powered on, but adopt an alternating working mode of power on / power off, which ensures the treatment effect while effectively reducing the operating energy consumption. The gas (mainly CH4 and CO2) generated by the anaerobic reactor is input into the artificial wetland by a vacuum pump, and the gas is used to regulate the microbial community structure and activity of the wetland.

[0009] The above-mentioned anaerobic baffled-microbial electrolysis-artificial wetland coupled process for treating rural domestic sewage is characterized in that the process comprises the following steps:

[0010] (1) Influent water passes through the anaerobic baffled reactor, and anaerobic hydrolysis occurs to produce VFAs and gas: the water temperature in the anaerobic baffled reactor is controlled at 35±2℃, the stirring rate is 80±20 rpm / min, and the hydraulic retention time (HRT) of the anaerobic baffled reactor is 12 h. Anaerobic sludge needs to be inoculated before starting the anaerobic reactor. The anaerobic reactor is operated in a continuous flow mode. The vacuum pump is used to draw the exhaust pipe to negative pressure at a constant rate, so that the gas in each compartment of the anaerobic reactor can be smoothly discharged; (2) Start-up of the microbial electrolysis and constructed wetland coupled system: first, insert the anode (electrode type: carbon rod) of the microbial fuel cell or microbial electrolysis cell which has been stably running for more than one month into the constructed wetland, and insert another carbon rod coated with Pt catalyst as the cathode into the constructed wetland. Insert 2 pairs of electrodes in the front section of the wetland and 4 pairs of electrodes in the rear section of the wetland. Each pair of electrodes, constant voltage DC power supply and external resistance (10-20 Ω) in series form a stage of microbial electrolysis cell system, and 6 pairs of electrodes form a 6-stage microbial electrolysis cell system. Then, record the current change of the external resistance series circuit of each stage of the microbial electrolysis cell system. When the current of the electrolysis cell system reaches the peak value and shows a downward trend, replace the influent water of the wetland. When the peak values of the current generated by the influent water after three consecutive times are not significantly different, it is considered that the anode electrode surface has been enriched with biofilm, and the start-up of this stage system is completed; (3) The effluent and gas from the anaerobic reactor are input into the microbial electrolysis and constructed wetland coupled system to integrate and control the microbial community structure and activity: the constant voltage DC power supply is connected to each stage of the microbial electrolysis cell system, with a voltage of 0.4-0.8 V and an external resistance of 10-20 Ω in series. The HRT is 48 h, the power-on mode is 2 h on / 0.5 h off, and a pressure relief valve is installed on the gas diffusion pipe in the wetland. When the pressure threshold is exceeded, the escape pipe (into the atmosphere) is opened.

[0011] Preferably, the biogas (main components are CH4 and CO2) generated by the anaerobic baffled reactor is diffused into the interior of the wetland through the gas diffusion pipe, which has the following effects: (1) provides inorganic carbon source, hydrogen and other electron donors for specific functional microorganisms (such as autotrophic denitrifying bacteria, etc.), improving the denitrification performance of the coupled system; (2) using the effects of vibration, shear and friction on the biofilm attached to the solid surface by the rising gas flow and gas bubbles, enhancing the water and gas scouring intensity, controlling the thickness of the biofilm on the solid surface such as substrate, soil and electrode, and alleviating the substrate blockage phenomenon; (3) reducing the mass transfer resistance of the coupled system, improving the supply of oxygen and other nutrients, the release of CO2 and other biochemical reaction products, and the utilization degree of H2 generated near the cathode.

[0012] Regarding gas collection and pipeline pressure safety measures, the biogas produced by the anaerobic reactor is first pumped into a buffer tank containing clean water using a vacuum pump, and then diffused into the wetland through a diffuser. The gas flow rate in the diffuser is 8 m / s (wetland startup) and 5 m / s (wetland normal operation). An escape pipe and pressure gauge are used to monitor the gas pressure in the pipe to ensure it remains below the threshold of 0.5 MPa, thus guaranteeing pressure safety.

[0013] The main beneficial effects of this invention are as follows:

[0014] 1) A wastewater treatment process based on the coupling of multiple reaction principles is proposed to achieve comprehensive utilization of VFAs: Typically, acetic acid is the carbon source that methanogens can directly utilize in anaerobic digestion systems. However, wastewater or sludge contains not only acetic acid, which can be directly utilized by methanogens, but also a large amount of multi-carbon volatile organic fatty acids (VFAs). These VFAs cannot be directly utilized by methanogens and need to be hydrolyzed and fermented to produce acetic acid during anaerobic digestion before they can be utilized by the methanogens. Therefore, the anaerobic digestion process is relatively complex, and the untimely utilization of acids results in a low biogas production rate. Thus, traditional anaerobic digestion or anaerobic fermentation suffers from metabolic obstacles, meaning that substrates mainly composed of small-molecule organic matter (VFAs) cannot be fully utilized. On the other hand, wastewater containing organic pollutants can produce large amounts of VFAs through anaerobic or aerobic fermentation processes, and these VFAs have high economic value. Traditional VFA utilization technologies mainly involve anaerobic digestion or biosynthesis to produce substances such as methane, alcohol, and biodegradable plastics. Microbial electrolysis, as an emerging bioelectrochemical technology, works by utilizing electrogenic microorganisms to degrade organic matter, generating hydrogen or methane. Microbial electrolysis utilizes a wide variety of substrates, including small-molecule organic acids such as acetic acid, propionic acid, and butyric acid. Since volatile organic compounds (VFAs) can rapidly accumulate in the fermentation broth through anaerobic reactions, and simultaneously serve as an effective carbon source for microbial electrolysis, they overcome the metabolic barriers of organic substrates in traditional anaerobic digestion / fermentation. Therefore, based on the feasibility of microbial electrolysis of VFAs from anaerobic wastewater fermentation, a novel coupled technology of anaerobic reaction-microbial electrolysis-constructed wetland using VFAs as a medium is proposed. This technology enhances the comprehensive utilization of VFAs, not only increasing the targeted yield of VFAs but also improving the organic matter degradation rate of microbial electrolysis and constructed wetlands. This creates a comprehensive technological system that fully utilizes VFAs through a tiered organic matter utilization design.

[0015] For anaerobic reaction, the application proposes a new type of baffle plate reactor form. In the four compartments of the reactor, the microbial community of each compartment presents good population distribution, and each compartment domesticates and cultivates a microbial community suitable for the water quality and environmental conditions of the compartment. In order to promote the along-the-way separation of anaerobic acid-producing phase reaction and methanogenic phase reaction, the distance between the baffles is gradually reduced along the water flow direction, and the anaerobic fermentation process is controlled in the fermentation acid-producing stage by shortening the HRT, that is, the hydrolysis acid-producing bacteria are mainly used in the baffle plate reactor, the growth of methanogenic bacteria is inhibited, and the maximum cumulative concentration of VFAs is obtained by using the influent organic matter. At the same time, in order to avoid the influence of excessive acidification of the first compartment on the stable operation of the system, a sludge return system is added, which not only can increase the pH value of the compartment, inhibit the growth of filamentous bacteria, dilute toxic and harmful substances in the influent, but also can maintain a high sludge concentration in the compartment. The above technical effects can effectively promote the production of VFAs of the system. It should be pointed out that the sludge return system uses a return sludge pump to return directly to the sludge inlet of the anaerobic reactor through a pipeline, without adopting the traditional method of first returning to the sludge storage tank and then returning from the storage tank to the sludge inlet. The traditional method will make the sludge in the intermediate sludge storage tank produce methane and other reactions, which will destroy the microbial community structure of the baffle plate reactor, so the direct sludge return method is also considered from the perspective of improving the VFAs production of the system.

[0016] The new baffle plate reactor used in the application sets a three-phase separator and an independent exhaust pipe at the top of each compartment (before each exhaust pipe and water outlet) in order to avoid the adverse effects of gas partial pressure in the system on the VFAs production of the system, and to timely remove the biogas (CH4, CO2 and other gases) produced by anaerobic reaction, so that the intermediate metabolites in different compartments can carry out independent extracellular organic matter hydrolysis reaction and VFAs production reaction of hydrolysis products under different gas partial pressure conditions, and ensure different stages of acid-producing reaction. In addition, by reasonably setting the distance between the baffles, the width of the upflow zone is greater than that of the downflow zone, the upflow velocity in the upflow zone is slowed down, which is beneficial to the settlement and interception of sludge in the main reaction zone of the reactor. The guide plate at the end of the baffle plate can make the water flow to the center area of the upflow zone, and avoid the impact of the water flow when entering the chamber, which can uniformly distribute water, buffer water flow and improve the sludge concentration of the reactor, thereby facilitating the growth of fermentation acid-producing bacteria and improving the VFAs production of the system.

[0017] The acid production by anaerobic fermentation is generally divided into three stages: the first stage is that complex organic matters such as sugars, fats and proteins are hydrolyzed into simple soluble monomers or dimers; the second stage is that the simple organic matters produced in the hydrolysis stage are converted into VFAs and alcohols such as formic acid, acetic acid, propionic acid, butyric acid, valeric acid and ethanol by acid-producing fermentation bacteria; and the third stage is that the organic acids and alcohols containing more than two carbon atoms except acetic acid produced in the fermentation acid production stage are converted into acetic acid, hydrogen and CO2 and the like by hydrogen-producing and acetic acid-producing bacteria. + By using the baffle plate reactor, the extracellular polymer hydrolysis and intracellular NADH / NAD

[0018] The formation of the above-mentioned "electric environment mutual trophism" relationship is related to the concentration ratio of various substances in the influent VFAs, the introduction of the microbial electrolysis system and the introduction of anaerobic gas into the wetland. Since the microbial electrolysis system is introduced into the artificial wetland, it is beneficial to promote the improvement of the microbial population activity in the wetland by providing additional electrons. Since CH4 and CO2 are introduced into the wetland, the thickness of the substrate and the biological membrane on the electrode surface in the coupling system is regulated by providing inorganic carbon source, electron donor, water scouring effect and reducing the mass transfer resistance of gas-liquid-solid interface, so as to alleviate the substrate blockage phenomenon. By establishing the microbial community of "electric environment mutual trophism", the coupling system shows good treatment effect, effectively solving the technical problems of artificial wetland system in aspects of siltation and blockage, high load and removal of refractory organic matter.

[0019] 2) The economic efficiency of the process in engineering application scenarios: the anaerobic baffled reactor is simple in structure, has no moving parts, and has low cost and operating costs. The microbial electrolysis cell uses low-cost electrode materials. The multi-stage design feature not only ensures stable purification efficiency, but also uses the intermittent operation mode of multiple electrodes alternating power-on / power-off to save energy. The intermittent power-on operation mode can effectively slow down the deposition of anode salt crystals and ensure the effective biological activity of the anode biofilm. Overall, the coupled system has good cost control characteristics and has potential for promotion in the field of rural sewage treatment.

[0020] 3) Multi-stage design ideas and details: For the microbial electrolysis-artificial wetland coupled system, a multi-stage electrode layout form is adopted, which is designed according to the characteristics of organic matter degradation in the wetland, i.e. organic matter degradation in wastewater mainly occurs in the first half of the wetland. Therefore, in the second half of the wetland, the main form of pollutants in wastewater is refractory organic matter. In view of the above characteristics of organic matter, the number of electrodes in the second half of the wetland is doubled (the number of electrodes in the second half is twice that in the first half), and the electrode layout form is improved from asymmetric to approximately symmetric. Due to the symmetric arrangement, electrons in the system can be transmitted to the cathode from multiple directions, improving the current density of bioelectrocatalytic reactions and reducing the internal resistance of the system. The dense electrode quantity can stimulate plant growth and development, expand the anoxic environment space represented by the cathode vicinity, and fully exert the biochemical synergistic effect of the microbial population of the "electronic environment mutualism" relationship of the coupled system, thereby improving the treatment effect of refractory organic matter.

[0021] 4) Anaerobic gas production regulation microbial electrolysis-artificial wetland coupled system biofilm thickness: the biogas produced by the anaerobic baffle reactor (main components are CH4 and CO2) is diffused into the interior of the wetland through the gas diffusion pipe arranged in the wetland, which has the following effects: (1) providing inorganic carbon source, hydrogen gas (hydrogen gas produced by the cathode of the microbial electrolysis system, methane and other gases) as electron donor for specific functional microorganisms (such as autotrophic denitrifying bacteria), which does not need to add additional organic carbon source, and improves the denitrification performance of the wetland system under low carbon source influent conditions; (2) using the vibration, shear, friction and other effects of the rising gas flow and bubbles on the biofilm attached to the solid surface of the substrate, soil and electrode, the disturbance effect on the substrate layer gradually increases during the rising process of the bubbles, which enhances the water and gas scouring intensity, regulates the biofilm thickness of the solid surface of the substrate, soil and electrode, avoids the thickness being too large, and alleviates the substrate clogging phenomenon; (3) reducing the mass transfer resistance in the coupled system: there are different mass transfer resistances of gas-liquid, gas-solid and solid-liquid in the microbial electrolysis-artificial wetland coupled reaction system, which are quite different between different interfaces, forming a differentiated gas concentration gradient, which affects the growth and metabolism of functional microorganisms. There is a discontinuous gas-liquid-solid three-phase coexistence system on the surface of the filler, electrode and soil in the coupled system, and the improvement of the mass transfer resistance of the three-phase interface by only relying on the hydraulic state of the horizontal flow of the wastewater in the system is limited. The present application introduces the gas produced by the anaerobic reactor into the coupled system, which improves the concentration gradient, the only diffusion driving force, due to the diffusion, disturbance and other effects of the introduced gas, effectively reduces the mass transfer resistance of the three-phase interface, and improves the supply of oxygen and other nutrients, the release of CO2 and other biochemical reaction products, and the utilization degree of H2 produced near the cathode. BRIEF DESCRIPTION OF DRAWINGS

[0022] Figure 1 The figure is a structural schematic diagram of the anaerobic baffle-microbial electrolysis-artificial wetland coupled process.

[0023] The figure is a structural schematic diagram of the anaerobic baffle-microbial electrolysis-artificial wetland coupled process. DETAILED DESCRIPTION

[0024] The technical solutions in the present application will be described clearly and completely in combination with specific embodiments.

[0025] Example 1

[0026] The anaerobic baffled-microbial electrolysis-conjunctive process structure is shown in Figure 1 The anaerobic baffled-microbial electrolysis-conjunctive process structure is shown in

[0027] Example 2

[0028] The anaerobic baffled-microbial electrolysis-conjunctive process structure is shown in

[0029] Step one, the influent water passes through the anaerobic baffled reactor, and anaerobic hydrolysis occurs to produce VFAs and gas: the water temperature in the anaerobic baffled reactor is controlled at 35±2℃, the stirring rate is 80±20 rpm / min, and the hydraulic retention time (HRT) of the anaerobic baffled reactor is 12 h. Anaerobic sludge is inoculated before starting the anaerobic reactor. The anaerobic reactor is operated in a continuous flow mode. The vacuum pump is used to draw the exhaust pipe to negative pressure at a constant rate, so that the gas in each compartment of the anaerobic reactor can be smoothly discharged.

[0030] Step two, start-up of the microbial electrolysis and constructed wetland coupled system: first, the anode (electrode type: carbon rod) of the microbial fuel cell or microbial electrolysis cell which has been stably running for more than one month is inserted into the constructed wetland, and a carbon rod coated with Pt catalyst is used as the cathode, which is also inserted into the constructed wetland. Two pairs of electrodes are inserted into the front section of the wetland, and four pairs of electrodes are inserted into the rear section of the wetland. Each pair of electrodes, together with a constant voltage direct current power supply and an external resistance (10-20Ω) connected in series, constitutes a stage of the microbial electrolysis cell system, and six pairs of electrodes constitute six stages of the microbial electrolysis cell system. Then, the current change of the external resistance series circuit of each stage of the microbial electrolysis cell system is recorded. When the current of the electrolysis cell system reaches the peak value and shows a downward trend, the influent water of the wetland is replaced. When the peak values of the current generated after three consecutive influents are not significantly different, it is considered that the anode electrode surface has been enriched with biofilm, and the start-up of this stage of the system is completed.

[0031] Step three, the effluent and gas from the anaerobic reactor are input into the microbial electrolysis and constructed wetland coupled system to integrate and control the microbial community structure and activity: a constant voltage direct current power supply is connected to each stage of the microbial electrolysis cell system, with a voltage of 0.4-0.8 V and an external resistance of 10-20Ω connected in series. The HRT is 48 h, the power-on mode is 2 h on / 0.5 h off, and a pressure relief valve is installed on the gas diffusion pipe in the wetland, which will open the escape pipe (into the atmosphere) when the pressure threshold is exceeded.

[0032] After the process system has been stably running for 30 days, the effluent water quality is detected. Considering that the constructed wetland system is composed of complex microbial communities and has strong ecological characteristics, the sampling time is set at 8:00, 15:00, and 19:00 every day, with a 7-day interval between each sampling. The results of the composition analysis of the 15 samples obtained on 5 sampling days show that the average COD concentration of the samples is 14.4 mg / L, the removal rate is 0.909, the total nitrogen concentration is 6.7 mg / L, the removal rate is 0.802, and the total phosphorus concentration is 0.14 mg / L, the removal rate is 0.705. The test results show that the anaerobic baffled-microbial electrolysis-constructed wetland coupled process has the ability to remove organic matter and denitrify and dephosphorize throughout the period, and the anti-fouling capacity is significantly improved, which has the potential to be applied to rural sewage treatment.

[0033] The pressure threshold of the wetland gas diffusion pipe is set to 0.5 Mpa, and according to the pressure monitoring index, the coupling process does not appear over-limit situation in the actual operation cycle, which meets the safety standard of the actual sewage treatment application scene.

[0034] The above shows and describes the basic principles, main features and advantages of the present application. Those skilled in the art should understand that the present application is not limited to the above examples, and the above examples and descriptions in the specification are only to illustrate the principles of the present application. Without departing from the spirit and scope of the present application, various changes and improvements can be made to the present application, and these changes and improvements all fall within the scope of the claimed present application. The scope of protection of the present application is defined by the appended claims and their equivalents.

Claims

1. A coupled method of anaerobic baffle plate-microbial electrolysis-constructed wetland for rural domestic sewage treatment, characterized in that, Rural domestic sewage flows from the sewage collection tank (1) into the anaerobic baffle reactor (3) through the inlet pipe. An anaerobic reactor inlet pump (2) is installed on the inlet pipe to pump the effluent from the sewage collection tank (1) into the anaerobic baffle reactor (3) through the anaerobic reactor inlet (11). The effluent from the anaerobic baffle reactor (3) is pumped into the horizontal subsurface flow constructed wetland (6) by the constructed wetland inlet pump (4). The horizontal subsurface flow constructed wetland (6) is divided into a water distribution zone (5), a main reaction zone (7), and an effluent zone (8). The effluent from the effluent zone (8) is pumped into the effluent tank (10) by the effluent pump (9). The anaerobic baffle reactor (3) The horizontal subsurface flow constructed wetland (6) consists of four interconnected cells (15), each with an exhaust pipe (26) at the top; partitions (14) are used to separate the cells, and reflectors (13) are installed under the partitions (14); water flows through folding plates (16) in sequence, and guide plates (12) are installed at the ends of the folding plates (16); the returned sludge flows back to the inlet (25) through the pipeline from the sludge discharge port (23) under the action of the returned sludge pump (24); the main reaction zone (7) of the horizontal subsurface flow constructed wetland (6) consists of a plant layer (18), a soil layer (19), a filler layer (20), a gravel layer (21), and a compacted base layer (22). 2) Composition; Six pairs of electrodes (34) are inserted into the wetland packing layer (20) respectively, and each pair of electrodes is connected to the positive and negative terminals of the constant voltage DC power supply (32) respectively. An external resistor (33) is connected in series between each pair of electrodes and the constant voltage DC power supply (32); At the same time, the gas generated by the anaerobic baffle reactor (3) is collected by the exhaust pipe (26) under the action of the vacuum pump (27) and then passes through the buffer tank (28) and the diffuser (29) in sequence, and is introduced into the main reaction zone (7) of the horizontal subsurface flow constructed wetland (6) to regulate the structure and activity of the wetland microbial community using gas; The diffuser (29) is arranged in The gravel layer (21) contains an escaping pipe (30) and a pressure monitoring gauge (31) for monitoring and removing high-pressure gas from the diffuser. The microbial electrolysis-constructed wetland coupling system adopts a multi-segment, multi-stage design. The horizontal subsurface flow constructed wetland (6) is divided into two segments. Two pairs of electrodes are inserted in the front segment, and four pairs of electrodes are inserted in the back segment. The number of electrodes in the back segment is twice that in the front segment, resulting in a larger current density and lower internal resistance in the back segment electrodes, which enhances the synergistic degradation and specific degradation activity of the electrochemical microbial population. Moreover, the electrodes are not energized continuously, and an alternating energization / de-energization working mode is adopted to ensure the treatment effect while effectively reducing operating energy consumption.

2. The method according to claim 1, characterized in that, Three-phase separation can be achieved before each exhaust pipe (26) and outlet (17) of the anaerobic baffle reactor (3); the guide plate (12) and the reflector plate (13) are perpendicular to each other; as the water flows through the compartments (15) in sequence, the water flow in each compartment (15) either rises or falls. The width of the compartment (15) in the rising flow zone is greater than that in the falling flow zone, thereby slowing down the rising flow velocity in the rising flow zone, which is conducive to the sedimentation and retention of sludge in the reaction zone; the spacing of the baffles (14) gradually decreases along the direction of water flow; the guiding effect of the guide plate (12) and the reflector plate (13) promotes the water flow to the center area of ​​the rising flow zone, reduces the impact intensity when the water flows into the compartment (15), and plays the role of uniform water distribution, buffering water flow, and increasing the sludge concentration in the reactor.

3. The method according to claim 1, characterized in that, The horizontal subsurface flow constructed wetland (6) uses reeds, canna lilies and calamus as plants, and provides organic matter and oxygen for microbial growth through the rhizosphere effect; the horizontal subsurface flow constructed wetland (6) uses 8-16mm ceramic granules as filter media, which has high biofilm formation efficiency, low head loss and strong interception capacity.

4. The method according to claim 1, characterized in that, The electrode (34) is made of carbon rods, with a platinum Pt catalyst coated on the cathode surface.

5. The method according to claim 1, characterized in that... The specific operating steps are as follows: (1) The influent passes through the anaerobic baffle reactor, where anaerobic hydrolysis occurs to produce VFAs and gas: the water temperature in the anaerobic baffle reactor is controlled at 35±2℃, the stirring rate is 80±20rpm / min, and the hydraulic retention time (HRT) of the anaerobic baffle reactor is 12h; anaerobic sludge needs to be inoculated before the anaerobic reactor is started; the anaerobic reactor adopts a continuous flow operation mode; the vacuum pump draws the exhaust pipe to negative pressure at a constant rate to facilitate the smooth discharge of gas from each compartment of the anaerobic reactor; (2) Start-up of the microbial electrolysis and constructed wetland coupling system: First, insert the positive electrode of the microbial fuel cell or microbial electrolysis cell that has been running stably for more than one month into the constructed wetland. Also insert a carbon rod coated with Pt catalyst as the cathode into the constructed wetland. Insert two pairs of electrodes into the front section of the wetland and four pairs of electrodes into the rear section of the wetland. Each pair of electrodes, a constant voltage DC power supply, and an external resistor connected in series form a first-stage microbial electrolysis cell system. The six pairs of electrodes constitute a six-stage microbial electrolysis cell system. Next, record the current change of the external resistor series circuit of each stage of the microbial electrolysis cell system. When the current of the stage of the electrolysis cell system reaches its peak and shows a downward trend, replace the wetland inlet water. When the peak current generated after three consecutive water inlets is not significantly different, it is considered that the surface of the anode electrode has been enriched with biofilm, and the system has been successfully started up. (3) The effluent and gas produced by the anaerobic reactor are respectively input into the microbial electrolysis and artificial wetland coupling system to integrate and regulate the structure and activity of the microbial community: Each microbial electrolysis cell system is connected to an external DC power supply with a voltage of 0.4-0.8V, a series external resistance of 10-20Ω, an HRT of 48h, and a power-on mode of 2h / 0.5h. A pressure relief valve is installed on the gas diffusion pipe in the wetland, and the diffusion pipe is opened when the pressure threshold is exceeded.

6. The method according to claim 5, characterized in that, In step (1), the biogas produced by the anaerobic reactor is first pumped into a buffer tank containing clean water by a vacuum pump, and then diffused to the wetland through a diffuser. When the wetland is started, the gas flow rate in the diffuser is 8 m / s, and when the wetland is running normally, the gas flow rate in the diffuser is 5 m / s. The gas pressure in the diffuser is monitored using an escaping pipe and a pressure gauge to ensure that it is below the threshold of 0.5 MPa to ensure gas pressure safety.

Images