Device and method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by an internal iron-carbon dual anode

Abstract

The present invention discloses a device and method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by means of an internal iron-carbon dual anode. The device includes a reactor main body, iron sheets, a water pipe, carbon cloth, a gas collecting pipe, a sealing cover, and carbon brushes. The top of the reactor main body is open. The method includes: (1) inoculation and startup of the electro-fermentation system and domestication of functional microorganisms; (2) operation of the electro-fermentation system: first, the concentrated sludge is pretreated with hot alkali, and then iron sheets are added to the domesticated reactor as a new anode for electro-fermentation. The present invention adds high-purity iron sheets as the second anode material to the reactor and controls the application time of the applied voltage, and investigates the operation efficiency of electro-fermentation under different energization times, including the utilization of organic matter, the hydrogen production under different iron sources, and the formation effect of vivianite, providing a new idea for the resource utilization of excess sludge.

Description

Technical Field

[0001] The present invention relates to a device and method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by means of an internal iron-carbon dual anode. Specifically, an electro-fermentation system reactor is used to treat excess sludge to simultaneously achieve the maximum recovery of hydrogen and vivianite; it belongs to the field of waste treatment and energy recovery and utilization. Background Art

[0002] Due to the shortage of phosphorus resources and the limitations of existing phosphorus recovery methods, phosphorus recovered in the form of vivianite has attracted much attention due to its natural universality, easy availability and foreseeable economic value, and it is currently the mainstream trend of phosphorus recovery.

[0003] The activated sludge process can effectively remove organic matter and inorganic matter in sewage, and it is the most widely used technology in urban sewage treatment plants. Most of the phosphorus in nature eventually accumulates in excess sludge (WAS) through urban sewage treatment processes and chemical flocculation, etc. The phosphorus in the sludge accounts for more than 90% of the phosphorus load in the sewage.

[0004] At the same time, excess sludge contains high-calorie organic matter and nutrient elements, and has the potential for energy and resource utilization. Most of the phosphorus in the sewage is concentrated in the sludge after phosphorus removal treatment, making the sludge an important secondary phosphorus-containing resource. The microbial electro-fermentation system, through an internal bioelectrode and an applied micro-voltage, stimulates the growth of microorganisms through current and drives the microbial metabolic activities, while reducing the volume of excess sludge and producing high-purity H2. Compared with the traditional anaerobic fermentation process, it has the advantages of short treatment time, high hydrogen purity, and significant phosphorus release efficiency. However, using the traditional electro-fermentation system to treat sludge is easily restricted by low electron transfer efficiency, resulting in technical difficulties such as incomplete conversion of organic matter, low energy recovery rate, and difficult phosphorus recovery, which in turn limits its popularization and application. At the same time, there are often problems such as insufficient iron source and non-meeting of the reductive conditions of the water body when recovering phosphorus from sludge in the form of vivianite.

[0005] As an important component of cytochromes and various enzymes, iron participates in the microbial energy metabolism process, enhances cell reproduction, and at the same time plays an electron transfer role, promoting the degradation of organic matter and hydrogen production. At the same time, in the electrochemical system, iron can release a large amount of divalent iron through electrochemical corrosion, which serves as a key iron source supplement for vivianite synthesis. In addition, iron salts can improve the flocculation and precipitation performance of sludge and enhance the purification function of activated sludge. Due to its low cost and environmental friendliness, it is widely used in sewage treatment and groundwater purification. Therefore, the electro-fermentation system technology has great potential. Therefore, developing a dual anode of high-purity iron sheets and carbon brushes as the microbial electro-fermentation system to strengthen extracellular electron transfer while achieving maximum hydrogen production from organic matter and phosphorus recovery from vivianite is undoubtedly a new attempt and breakthrough in the efficient recovery of sludge resources and energy. Summary of the Invention

[0006] The present invention aims to provide a device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by an internal iron-carbon dual anode, to explore the influence of the internal dual anode system on hydrogen generation and vivianite crystal formation under controlled energization time, and to solve the problem that the difference in the crystallinity of iron sources may limit the growth and metabolism of microorganisms in anaerobic process sludge.

[0007] The present invention strengthens the synchronous hydrogen production from excess sludge and vivianite recovery by arranging an iron anode in the electro-fermentation system. The main principles and technical concepts are as follows: (1) The electrochemical corrosion of the iron electrode can produce ferrous iron required for vivianite, making up for the deficiency of the iron source in the sludge itself for phosphorus recovery; (2) By constructing a new electro-fermentation system, effective enrichment of anaerobic fermentative bacteria, electrochemically active bacteria, iron-reducing bacteria and phosphate-accumulating bacteria can be achieved under the action of a micro-voltage, strengthening the extracellular electron transfer process, realizing the efficient conversion of organic matter in the sludge, and increasing the hydrogen production; (3) The reaction habitat of the new electro-fermentation system conforms to the neutral and weakly alkaline conditions (pH < 9) for vivianite formation. At the same time, the presence of carbon brush and carbon cloth bioelectrodes is beneficial to the formation of vivianite crystals. In summary, this new electro-fermentation system is expected to achieve efficient hydrogen production from waste biomass such as excess sludge and vivianite recovery of phosphorus.

[0008] The present invention provides a device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by an internal iron-carbon dual anode, including: a reactor main body, iron sheets, a water pipe, a carbon cloth, a gas collecting pipe, a sealing cover, and a carbon brush; the top of the reactor main body is open.

[0009] The sealing cover is hermetically buckled on the top opening of the reactor main body. The water pipe and the gas collecting pipe extend into the reactor main body from the top of the sealing cover. The carbon cloth, the iron sheets, and the carbon brush are fixed by platinum wires and then suspended inside the reactor main body through the rubber stoppers on the sealing cover; the positions where the water pipe, the gas collecting pipe, and the connecting rod pass through the sealing cover are all sealed; the sludge fermentation liquid enters the reactor through the water pipe and flows out of the reactor through the water pipe; the outlet of the gas collecting pipe is connected to a gas sampling bag.

[0010] In the present invention, the electro-fermentation system (i.e., the device described in the present invention) uses the form of an internal iron-carbon dual anode for sludge electro-fermentation, solving the problems of low hydrogen production rate caused by low electron transfer efficiency in the traditional electro-fermentation system and insufficient iron source in the process of vivianite recovery in the sludge under the condition of no external iron source.

[0011] Furthermore, the electrolytic cell structure: the carbon cloth, the iron sheets, and the carbon brush are distributed in a triangle with a side length of 1.0 cm, ensuring a sufficient anode-cathode distance, and the gas collecting pipe and the inlet and outlet water pipes are in a relative position of 1.5 cm.

[0012] The internally installed iron-carbon dual anode reactor designed in the present invention organically combines microbial electrolysis and anaerobic fermentation, uses the electrochemical corrosion of iron to strengthen extracellular electron transfer, and realizes the synthesis of vivianite while achieving the efficient conversion of sludge organic matter to produce hydrogen. As an important constituent element of cytochromes, iron has a positive effect on the metabolism of intracellular enzymes and microbial growth. Moreover, iron can strengthen the anaerobic environment in the reactor, improve the redox potential, and can also enhance the rate of electron transfer between microorganisms as an electron donor or acceptor, thereby promoting the efficient degradation and conversion of organic matter in sludge.

[0013] The present invention provides a method for realizing electro-fermentation of excess sludge to produce hydrogen and recovering vivianite by means of an internally installed iron-carbon dual anode, comprising the following steps:

[0014] (1) Inoculation and startup of the electro-fermentation system (i.e., the device described in the present invention) and domestication of functional microorganisms;

[0015] (2) Operation of the electro-fermentation system: First, concentrated sludge is pretreated with hot alkali, and then iron sheets are added as new anodes to the reactor that has been domesticated, and electro-fermentation is carried out.

[0016] Further, inoculation and startup of the electro-fermentation system (i.e., the device described in the present invention) and domestication of functional microorganisms: Start the reactor of the electro-fermentation system, add fresh sludge and phosphate buffer solution (concentration: 100 mM, composition: NH4Cl: 0.62 g / L, KCl: 0.26 g / L; Na2HPO4: 9.152 g / L; Na2HPO4·2H2O: 5.544 g / L) to the reactor in a volume ratio of 1:9 for startup, and add 1.0 - 1.5 g / L of acetic acid to domesticate functional microorganisms. Connect the reactor to a power supply, detect the change in current in the series 10 Ω resistance circuit, take 5 - 7 d as a cycle, for a total of 3 - 4 cycles. During the 3 - 4 cycles, inoculate sludge, and then run for 15 - 20 cycles. The running time of each cycle is 1 - 2 d, without inoculating sludge during this period, and adjust the concentration of anhydrous sodium acetate to 0.5 - 1.0 g / L. Until the reaction Coulombic efficiency reaches 90%, the current is stable and higher than 2 mA, that is, the inoculation and startup of the device are completed.

[0017] The concentrated sludge was pretreated with hot alkali by heating at 85 °C and pH = 12.0 for 60 min. After cooling to room temperature, fresh sludge and the sludge pretreated with hot alkali were mixed at a volume ratio of 1:9, and the pH was adjusted to 7.0. Fermentation was carried out at 120 rpm and 35 °C for 4 - 6 d. After successful startup, iron sheets were additionally added as a new anode in the reactor that had been domesticated. The sludge fermentation broth and a 10 - 60 mmol / L NaCl mixed solution were added to the reactor at a volume ratio of 1:1, and the pH was adjusted to 7.0 - 8.0 respectively for electro-fermentation for 5 - 7 d.

[0018] The above acetic acid concentration and the corresponding various parameters are beneficial to the inoculation and startup of the reactor.

[0019] In actual operation, due to the requirements of microorganisms for environmental temperature, pH, etc., devices such as a pH monitor and a gas flowmeter can be considered for further connection during the connection of the reactor.

[0020] Advantages of the present invention:

[0021] The present invention adds high-purity iron sheets as the second anode material to the reactor, and controls the application time of the applied voltage, and examines the operation efficiency of electro-fermentation under different power-on times, including the utilization of organic matter, the H2 production under different iron sources, and the formation effect of vivianite, providing new ideas for the resource utilization of excess sludge. Description of the drawings

[0022] Figure 1 Schematic structural diagram of the built-in iron-carbon dual-anode electro-fermentation reactor of the present invention;

[0023] Figure 2 It is a schematic diagram of the structure and dimensions of the built-in iron-carbon dual-anode electro-fermentation reactor;

[0024] Figure 3 It is a distribution diagram of the hole positions and dimensions of the sealing cover of the built-in iron-carbon dual-anode electro-fermentation reactor;

[0025] Figure 4 It is the cumulative hydrogen production of Examples 1 - 3 and the comparative example at different power-on times;

[0026] Figure 5 It is the morphology of the recovered product in Example 1 under a 24 h / d power-on time.

[0027] In the figure: 1 is the reactor main body, 2 is the iron sheet, 3 is the water pipe, 4 is the carbon cloth, 5 is the gas collecting pipe, 6 is the gas bag, 7 is the sealing cover, and 8 is the carbon brush. Detailed implementation manners

[0028] The present invention will be further described below through embodiments, but is not limited to the following embodiments, and also includes the integration between various specific embodiments.

[0029] As Figures 1 to 3 shown, the present invention provides a device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by an internal iron-carbon dual anode, which includes a reactor main body 1, an iron sheet 2, a water pipe 3, a carbon cloth 4, a gas collecting pipe 5, a gas bag 6, a sealing cover 7, and a carbon brush 8. Among them, the sludge fermentation liquid in the reactor main body 1 enters and exits the reactor through the inlet and outlet water pipe 3. The present invention sets the iron sheet 2 as the second anode of the electro-fermentation system reactor, which solves various problems such as insufficient iron content in the reaction process affecting the formation of vivianite, hydrogen production amount, and the performance of microorganisms in the reactor.

[0030] As Figure 2 、 3 shown, the diameter of the sealing cover is 70 mm and the height is 10 mm; the diameter of the reactor main body is 60 mm and the height is 82 mm. The air holes and the inlet and outlet water holes are symmetrically arranged with the iron anode holes, and the iron anode holes, biological anode holes, and cathode holes are distributed in a triangle with a side length of 1.0 cm.

[0031] The following examples and comparative experiments are used to verify the beneficial effects of the present invention:

[0032] Example 1:

[0033] The method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery by an internal iron-carbon dual anode is adopted in this example, and the specific steps are as follows:

[0034] I. Pretreatment of the carbon cloth: According to the calculation that 0.5 g of platinum-carbon is required per square centimeter of the cathode surface, first weigh 90 mg of platinum-carbon with a mass fraction of 10%, then add 50 μL of deionized water, vortex and oscillate, then add 400 μL of Nafion membrane solution and 200 μL of isopropanol, vortex and oscillate, and then evenly brush the dissolved platinum-carbon paste on the opposite side of the diffusion layer of the carbon cloth, and let the coating air dry for at least 24 h for standby.

[0035] II. Treatment of the carbon brush: The carbon brush is first soaked in acetone for 24 h, then calcined at 450 °C for 30 min. After the carbon rod is cooled to room temperature, the carbon brush is placed in deionized water and soaked for 24 h for use.

[0036] III. Assembly of the reactor: The reactor is a single-chamber reactor with a volume of 200 mL. The reactor material is organic glass, and the whole device is in a sealed anaerobic environment.

[0037] IV. Assembly and connection of the electrochemical workstation data recorder, which is used to record the reactor current data in real time. The instrument model is Keithley2700 data recorder.

[0038] V. Startup of the electro-fermentation system: The sludge taken from the secondary sedimentation tank of a domestic sewage treatment plant was used as the inoculum. A voltage of 0.8 V was applied externally to the reactor. Fresh excess sludge and a phosphate buffer solution (concentration: 100 mM, composition: NH4Cl: 0.62 g / L, KCl: 0.26 g / L; Na2HPO4: 9.152 g / L; Na2HPO4·2H2O: 5.544 g / L) were introduced into the device in a ratio of 1:9 for startup, and the pH was adjusted to 7.0. To better screen and enrich the bacterial community, the reaction duration of the first 3 cycles of this reactor was designed to be 7 days. During this period, inoculated sludge was used, and the concentration of sodium acetate anhydrous was 1.5 g / L. Then, it was operated for 15 cycles, with the operation duration of each cycle being 1 d. During this period, no sludge was inoculated, and the concentration of sodium acetate anhydrous was adjusted to 1.0 g / L. Until the reaction Coulombic efficiency reached 90%, the current was stable and higher than 2 mA, the startup of the device was completed.

[0039] VI. Operation of the electro-fermentation system:

[0040] 1. The concentrated sludge was pretreated with hot alkali. It was heated at 85 °C and pH = 12.0 for 60 min. After cooling to room temperature, the fresh sludge and the pretreated sludge (heated at 85 °C and pH = 12.0 for 60 min) were mixed in a volume ratio of 1:9, and the pH was adjusted to 7.0. Fermentation was carried out at 35 °C for 4 d at 120 rpm.

[0041] 2. Another iron sheet was added as a new anode to the reactor that had been domesticated. The fermentation wastewater and a 10 mmol / L NaCl mixed solution were added to the reactor in a volume ratio of 1:1, and the pH was adjusted to 7.0 respectively. Electro-fermentation was carried out for 7 d to complete the process of hydrogen production and vivianite formation by electro-fermentation.

[0042] 3. The closed-circuit time of the iron anode of the reactor was set to 24 h / d, and other conditions remained unchanged.

[0043] VII. In actual operation, due to the requirements of microorganisms for environmental temperature, pH, etc., during the connection of the reactor, devices such as a pH monitor and a gas flow meter can be considered for connection in the next step.

[0044] VIII. During the experiment, the cumulative hydrogen production was 193.51 mL, and a rhombic layered structure similar to vivianite crystals could be clearly observed under electron microscopy.

[0045] Example 2: The method for realizing hydrogen production from excess sludge and recovering vivianite by electro-fermentation using an internal iron-carbon dual anode in this experiment was specifically carried out according to the following steps:

[0046] I. Pretreatment of carbon cloth: Calculate according to the requirement of 0.5 g platinum-carbon per square centimeter of the cathode surface. First, weigh 90 mg of platinum-carbon with a mass fraction of 10% (the mass percentage of platinum in platinum-carbon), then add 75 μL of deionized water. After vortex oscillation, add 400 μL of Nafion membrane solution with a mass fraction of 5% and 200 μL of isopropanol, and vortex oscillate again. Then, evenly brush the pasty platinum-carbon on the carbon cloth and dry it for 24 h for standby.

[0047] II. Treatment of carbon brush: The carbon brush is first soaked in acetone for 24 h and then put into a muffle furnace. It is burned at 450 °C for 30 min. The timing starts after the temperature of the muffle furnace rises to 450 °C. When the temperature of the carbon rod drops to room temperature, the carbon brush is placed in deionized water and soaked for 24 h for use.

[0048] III. Reactor configuration: The reactor adopts a single-chamber microbial electrolytic cell with a volume of 200 mL. The reactor material is plexiglass. After domestication is completed in the reactor main body, iron sheets are added as the new anode, and the whole device is in a sealed anaerobic environment.

[0049] Electrolytic cell structure: To ensure sufficient anode-cathode spacing, the carbon cloth, carbon brush, and iron sheet are distributed in a triangle with a side length of 1.0 cm, and the gas collecting pipe and the inlet and outlet water pipes are in a relative position of 1.5 cm.

[0050] IV. Assemble and connect the electrochemical workstation data recorder, which is used to record the reactor current data in real time. The model of the data recorder is Keithley2700.

[0051] V. Start-up of the electro-fermentation system: The sludge taken from the secondary sedimentation tank of the domestic sewage treatment plant is used as the inoculum. While setting the voltage to 0.8 V, fresh excess sludge and phosphate buffer solution (concentration: 100 mM, composition: NH4Cl: 0.62 g / L, KCl: 0.26 g / L; Na2HPO4: 9.152 g / L; Na2HPO4·2H2O: 5.544 g / L) are introduced into the device in a ratio of 1:9 for start-up, and the pH is adjusted to 7.0. To better screen and enrich the microbial community, the reaction duration of the first 3 cycles of this reactor is designed to be 7 d, during which inoculated sludge is added and the concentration of sodium acetate anhydrous is 1.5 g / L. Then, it runs for 15 cycles, with each cycle lasting for 1 d. During this period, no sludge is inoculated, and the concentration of sodium acetate anhydrous is adjusted to 1.0 g / L. When the reaction Coulombic efficiency reaches 90%, the current is stable and higher than 2 mA, the start-up of the device is completed.

[0052] VI. Operation of the electro-fermentation system:

[0053] 1. The concentrated sludge is pretreated with hot alkali at 85 °C and pH = 12.0 for 60 min, and then cooled to room temperature

[0054] Afterwards, fresh sludge and pretreated sludge (heated at 85 °C, pH = 12.0 for 60 min) were mixed at a volume ratio of 1:9, and the pH was adjusted to 7.0, followed by fermentation at 120 rpm and 35 °C for 4 days.

[0055] 2. Another iron sheet was added as a new anode to the already domesticated reactor. A mixture of fermented wastewater and 10 mmol / L NaCl solution was added to the reactor at a ratio of 1:1, and the pH was adjusted to 7.0 respectively, followed by electro-fermentation for 7 days.

[0056] 3. The closed-circuit time of the reactor was set to 12 h / d, and other conditions remained unchanged.

[0057] VII. In actual operation, due to the requirements of microorganisms for environmental temperature, pH, etc., devices such as a pH monitor and a gas flow meter can be considered for connection during the connection of the reactor.

[0058] VIII. During the experiment, the cumulative hydrogen production was 121.211 mL, and a rhombic layered structure similar to vivianite crystals could be clearly observed under electron microscopy.

[0059] Example 3:

[0060] The method for realizing electro-fermentation of excess sludge to produce hydrogen and recovering vivianite by using an internal iron-carbon dual anode in this experiment was specifically carried out according to the following steps:

[0061] I. Pretreatment of carbon cloth: According to the calculation that 0.5 g of platinum-carbon is required per square centimeter of the cathode surface, first weigh 90 mg of 10% platinum-carbon by mass, then add 50 μL of deionized water, vortex and oscillate, then add 400 μL of Nafion membrane solution and 200 μL of isopropanol, vortex and oscillate, and then evenly brush the pasty platinum-carbon on the opposite side of the diffusion layer of the carbon cloth, and let the coating air dry for at least 24 h for standby.

[0062] II. Treatment of carbon brush: The carbon brush was first soaked in acetone for 24 h, then calcined at 450 °C for 30 min. After the carbon rod cooled to room temperature, the carbon brush was placed in deionized water and soaked for 24 h for use.

[0063] III. Assembly of the reactor: The reactor was a single-chamber reactor with a volume of 200 mL. The reactor material was plexiglass, and the whole device was a sealed anaerobic environment.

[0064] IV. Assembly and connection of an electrochemical workstation data recorder, which was used to record the reactor current data in real time. The data recorder with the model Keithley2700 was adopted.

[0065] V. Startup of the electro-fermentation system: The sludge taken from the secondary sedimentation tank of a domestic sewage treatment plant was used as the inoculum. While setting the voltage at 0.8 V, fresh excess sludge and phosphate buffer solution (concentration: 100 mM, composition: NH4Cl: 0.62 g / L, KCl: 0.26 g / L; Na2HPO4: 9.152 g / L; Na2HPO4·2H2O: 5.544 g / L) were introduced into the device in a ratio of 1:9 for startup, and the pH was adjusted to 7.0. To better screen and enrich the microbial community, the reaction duration of the first 3 cycles of this reactor was designed to be 7 days, during which inoculated sludge was used and the concentration of sodium acetate anhydrous was 1.5 g / L. After that, it ran for 15 cycles, with the operation duration of each cycle being 1 day. During this period, no sludge was inoculated, and the concentration of sodium acetate anhydrous was adjusted to 1.0 g / L until the reaction Coulombic efficiency reached 90%, the current was stable and higher than 2 mA, indicating the completion of the startup of the device.

[0066] VI. Operation of the electro-fermentation system:

[0067] 1. The concentrated sludge was pretreated with hot alkali, heated at 85 °C and pH = 12.0 for 60 min. After cooling to room temperature, fresh sludge and the pretreated sludge (heated at 85 °C and pH = 12.0 for 60 min) were mixed at a volume ratio of 1:9, and the pH was adjusted to 7.0, followed by fermentation at 35 °C and 120 rpm for 4 days.

[0068] 2. Another iron sheet was added as the new anode to the domesticated reactor. The fermentation wastewater and 10 mmol / L NaCl mixture were added to the reactor in a ratio of 1:1, and the pH was adjusted to 7.0 respectively, followed by electro-fermentation for 5 days.

[0069] 3. The closed-circuit time of the reactor was set to 6 h / d, and other conditions remained unchanged.

[0070] VII. In actual operation, due to the requirements of microorganisms for environmental temperature, pH, etc., devices such as a pH monitor and a gas flowmeter can be considered during the connection of the reactor.

[0071] VIII. During the experiment, the cumulative hydrogen production was 102.19 mL, and a rhombic layered structure similar to vivianite crystals could be clearly observed under electron microscopy.

[0072] Comparative example: (The comparative example was carried out according to the equipment of the present invention, except that no iron sheet was used as the second anode)

[0073] The method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery in this comparative example using a traditional electro-fermentation system was specifically carried out according to the following steps:

[0074] I. Pretreatment of carbon cloth: According to the requirement of 0.5 g platinum-carbon per square centimeter of the cathode surface, first weigh 90 mg of 10% platinum-carbon by mass, then add 50 μL of deionized water. After vortex oscillation, add 400 μL of Nafion membrane solution and 200 μL of isopropanol, and vortex oscillate again. Then evenly brush the pasty platinum-carbon on the opposite side of the diffusion layer of the carbon cloth, and let the coating air dry for at least 24 h for standby.

[0075] II. Treatment of carbon brush: The carbon brush is first soaked in acetone for 24 h, then burned at 450 °C for 30 min. After the carbon rod cools to room temperature, the carbon brush is placed in deionized water and soaked for 24 h for use.

[0076] III. Assembly of the reactor: The reactor is a single-chamber reactor with a volume of 200 mL. The reactor material is plexiglass, and the whole device is in a sealed anaerobic environment.

[0077] IV. Assembly and connection of the electrochemical workstation data recorder, which is used to record the reactor current data in real time. The instrument model is Keithley2700 data recorder.

[0078] V. Start-up of the electro-fermentation system: The sludge taken from the secondary sedimentation tank of the domestic sewage treatment plant is used as the inoculum. An external voltage of 0.8 V is applied to the reactor. Fresh excess sludge and phosphate buffer solution (concentration: 100 mM, composition: NH4Cl: 0.62 g / L, KCl: 0.26 g / L; Na2HPO4: 9.152 g / L; Na2HPO4·2H2O: 5.544 g / L) are introduced into the device in a ratio of 1:9 for start-up, and the pH is adjusted to 7.0. In order to better screen and enrich the microbial community, the reaction duration of the first 3 cycles of the reactor is designed to be 7 days, during which inoculated sludge is used and the concentration of sodium acetate anhydrous is 1.5 g / L. Then it runs for 15 cycles, with the running duration of each cycle being 1 d, during which no inoculated sludge is used, and the concentration of sodium acetate anhydrous is adjusted to 1.0 g / L. Until the reaction Coulombic efficiency reaches 90%, the current is stable and higher than 2 mA, which means the start-up of the device is completed.

[0079] VI. Operation of the electro-fermentation system:

[0080] 1. The concentrated sludge is pretreated with hot alkali at 85 °C and pH = 12.0 for 60 min. After cooling to room temperature, the fresh sludge and the pretreated sludge (heated at 85 °C and pH = 12.0 for 60 min) are mixed at a volume ratio of 1:9, and the pH is adjusted to 7.0. Fermentation is carried out at 35 °C for 4 d at 120 rpm.

[0081] 2. The fermentation wastewater and 10 mmol / L NaCl mixture were added to the reactor at a volume ratio of 1:1, and the pH was adjusted to 7.0 respectively. Electro-fermentation was carried out for 7 days to complete the processes of hydrogen production by electro-fermentation and vivianite formation.

[0082] 3. The closed-circuit time of the traditional electro-fermentation reactor was set to 24 h / d, and other conditions remained unchanged.

[0083] VII. In actual operation, due to the requirements of microorganisms for environmental temperature, pH, etc., during the connection of the reactor, the connection of devices such as a pH monitor and a gas flowmeter can be considered in the next step.

[0084] VIII. During the experiment, the cumulative hydrogen production was 25.23 mL, and a small amount of rhombic layered structures similar to vivianite crystals could be clearly observed under scanning electron microscopy.

[0085] Combined with the attached drawings for explanation:

[0086] Figure 4 shows the cumulative hydrogen production of Examples 1-3 and the comparative example at different power-on times. The results show that the cumulative production of the 24 h / d power-on group is the highest at 193.51 mL. Comparing Examples 1-3, the cumulative hydrogen production at 24 h / d power-on time is increased by 59.65% and 89.36% respectively compared with 12 h / d and 6 h / d power-on. The main reason is that: a longer power-on time is beneficial to the electrochemical oxidation of organic matter and the release of iron by electrochemical corrosion. While effectively strengthening extracellular electron transfer, it promotes the utilization of organic matter and the conversion of hydrogen. Compared with the examples and the comparative example, it can be seen that the present invention adds the step of "adding iron sheets as a new anode to the reactor that has been domesticated", and the cumulative hydrogen production has been significantly improved, indicating that the method of the present invention promotes the utilization of organic matter and the conversion of hydrogen.

[0087] Figure 5 is the scanning electron micrograph of Example 1 at 24 h / d power-on time. As Figure 5 shown, through the scanning electron microscope image, it was observed that the cathode precipitate in the electro-fermentation system was in a layered structure and aggregated, which was consistent with the morphology of vivianite crystals.

Claims

1. A device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode, characterized in that Including: A reactor body (1), an iron sheet (2), a water pipe (3), a carbon cloth (4), a gas collecting pipe (5), a sealing cover (7), a carbon brush (8); the top of the reactor body is open; The sealing cover is hermetically buckled on the top opening of the reactor body. The water pipe and the gas collecting pipe extend into the interior of the reactor body from the top of the sealing cover. The carbon cloth, the iron sheet, and the carbon brush are fixed by platinum wires and then suspended in the reactor body through rubber stoppers on the sealing cover; The positions where the water pipe, the gas collecting pipe, and the platinum wire pass through the sealing cover are all sealed. The sludge fermentation broth enters the reactor through the water pipe and flows out of the reactor through the water pipe; the outlet of the gas collecting pipe is connected to a gas sampling bag; The carbon cloth, the iron sheet, and the carbon brush are distributed in an equilateral triangle, ensuring a sufficient anode and cathode spacing, and the gas collecting pipe and the water pipe are arranged oppositely.

2. The device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode according to claim 1, characterized in that: The reactor body is also connected to a pH monitor and a gas flow meter.

3. The device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode according to claim 1, characterized in that: The diameter of the sealing cover is 70 mm and the height is 10 mm; the diameter of the reactor body is 60 mm and the height is 82 mm; the iron anode holes, the biological anode holes, and the cathode holes are distributed in a triangle with a spacing of 1.0 cm; the iron anode holes refer to the holes through which the iron sheet passes, the biological anode holes refer to the holes through which the carbon brush passes, and the cathode holes refer to the holes through which the carbon cloth passes.

4. A method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode, using the device for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode according to any one of claims 1 to 3, characterized in that Including the following steps: (1) Inoculation and startup of the electro-fermentation system and domestication of functional microorganisms; (2) Operation of the electro-fermentation system: First, the concentrated sludge is pretreated with hot alkali, and then another iron sheet is added to the domesticated reactor as a new anode for electro-fermentation.

5. The method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode according to claim 4, characterized in that: For the inoculation and startup of the electro-fermentation system and the domestication of functional microorganisms, the specific operation is as follows: Start the electro-fermentation system reactor, add fresh sludge and a phosphate buffer solution to the reactor at a volume ratio of 1:9 for startup, and add 1.0 - 1.5 g / L of acetic acid to domesticate the functional microorganisms. Connect the reactor to a power supply and detect the change in current in a series circuit with a 10 Ω resistor. Take 5 - 7 d as a cycle, for a total of 3 - 4 cycles. During the 3 - 4 cycles, inoculate the sludge, and then run for 15 - 20 cycles. The running time of each cycle is 1 - 2 d, without inoculating sludge during this period, and adjust the concentration of sodium acetate anhydrous to 0.5 - 1.0 g / L; until the reaction Coulomb efficiency reaches 90%, the current is stable and higher than 2 mA, which means the inoculation and startup of the device are completed; The composition of the phosphate buffer solution is as follows: Concentration: 100 mM, components are NH4Cl: 0.62 g / L, KCl: 0.26 g / L; Na2HPO4: 9.152 g / L; Na2HPO4·2H2O: 5.544 g / L.

6. The method for realizing electro-fermentation hydrogen production from excess sludge and vivianite recovery with an internal iron-carbon dual anode according to claim 4, characterized in that: The concentrated sludge was subjected to thermal alkali pretreatment by heating at 85 °C and pH = 12.0 for 60 min, and then cooled to room temperature. The fresh sludge and the sludge after thermal alkali pretreatment were mixed at a volume ratio of 1:9, and the pH was adjusted to 7.

0. Fermentation was carried out at 35 °C and 120 rpm for 4 - 6 d. After successful startup, iron sheets were added as new anodes to the reactor that had been domesticated. The sludge fermentation broth and a mixed solution of 10 - 60 mmol / L NaCl were added to the reactor at a volume ratio of 1:1, and the pH was adjusted to 7.0 - 8.0 respectively for electro-fermentation for 5 - 7 d.

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