Device and method for enhancing wastewater anaerobic treatment process and biogas in-situ purification through electrochemical iron

Abstract

The invention relates to an electrochemical iron enhanced wastewater anaerobic treatment process and a device and a method for in-situ purification of biogas. According to the method, an iron electrode is used as an anode, an electrochemical method is adopted for strengthening a wastewater anaerobic treatment process and a biogas in-situ purification process, pollutants such as organic matters in to-be-treated wastewater are degraded by microorganisms in an anaerobic reactor, treated wastewater is obtained, biogas is generated, and main components of the biogas are CH4, CO2, H2S and other impurities; in the electrochemical reaction with the iron electrode as the anode, Fe < 2 + > is generated in situ at the anode, H2 and OH <-> are synchronously generated in situ at the cathode, CO2 and H2S in biogas generated by wastewater anaerobic treatment react with electrochemical reaction products to generate precipitates or generate CH4 to be removed in situ, and meanwhile, the wastewater anaerobic treatment effect is effectively improved. The method is simple, convenient, efficient, short in process, few in equipment, low in investment and operation cost and convenient to operate and maintain.

Description

Technical Field

[0001] The invention belongs to the technical field of wastewater treatment and biogas purification, and specifically relates to an electrochemical iron-enhanced wastewater anaerobic treatment process and a device and a method for in-situ biogas purification. Background Art

[0002] Compared with traditional aerobic wastewater treatment processes, anaerobic treatment processes have become an important direction for sewage treatment plants to achieve carbon neutrality and one of the key core technologies for achieving green and low-carbon transformation of wastewater treatment processes because of their advantages such as high treatment load, low energy consumption, low operating costs, low sludge yield, and the ability to recover energy through biogas (the main component is methane).

[0003] However, in addition to methane (CH4), biogas produced by anaerobic wastewater treatment also contains a large amount of impurities such as carbon dioxide (CO2) and hydrogen sulfide (H2S). Biogas usually contains a high CO2 content (20-50%), which significantly reduces the calorific value of biogas and makes it difficult to compress it, while H2S in biogas causes odor and safety issues as well as equipment corrosion risks.

[0004] At present, most of the biogas in my country has not been utilized or utilized in a green, low-carbon and high-value manner. Large enterprises usually use on-site combustion for heating or power generation, while small and medium-sized enterprises generally use direct air combustion of biogas. Because the unpurified biogas has poor combustion effect and low utilization rate, it leads to incomplete combustion. On the one hand, a large amount of sulfide and carbon-containing compound pollution is generated, which poses a safety risk. On the other hand, the energy in the biogas is not utilized or utilized to the maximum extent, resulting in huge waste and carbon emissions, which cannot meet the requirements of green and low-carbon.

[0005] The high content of CO2 and H2S in biogas has become the main obstacle to the green, low-carbon and high-value utilization of biogas. After the biogas is purified to remove CO2 and H2S, its combustion characteristics are greatly improved and it can be directly used as vehicle fuel or natural gas to achieve high-value utilization.

[0006] At present, the biogas purification processes that have been researched and developed at home and abroad all have desulfurization (removal of H2S) and decarbonization (removal of CO2) as their main goals. They generally have problems such as high operating costs, serious secondary pollution, large carbon emissions, or serious impact on anaerobic treatment processes. There is an urgent need to develop new green, low-carbon and efficient biogas purification technologies.

[0007] The prior art discloses that ferrous ions can be used to desulfurize biogas, such as Chinese patent application CN116392962 A. However, the existing technology of removing hydrogen sulfide using ferrous ions has the defects of significantly reducing the desulfurization effect due to the decrease in system pH caused by the addition of ferrous ions, or significantly increasing the amount of ferrous ions and further reducing the pH caused by it, and significantly reducing the anaerobic treatment effect. On the other hand, the prior art does not have a method for decarbonizing biogas using ferrous ions, and the decarbonization of biogas using ferrous ions is also highly dependent on pH and is significantly negatively affected by lower pH. In addition, the prior art does not have a method for in-situ desulfurization and decarbonization of biogas and enhancing the anaerobic treatment effect of wastewater using an electrochemical iron-coupled wastewater anaerobic treatment system. Summary of the invention

[0008] In order to solve the shortcomings and deficiencies of the existing biogas desulfurization technology, as well as the technical difficulties such as the coupling of electrochemical methods and anaerobic treatment processes and the regulation of their synergistic effects, the primary purpose of the present invention is to provide an electrochemical iron-enhanced wastewater anaerobic treatment process and a device for in-situ purification of biogas, which can efficiently remove carbon dioxide and hydrogen sulfide in situ from the biogas produced by anaerobic treatment of wastewater, realize in-situ purification of biogas, and effectively enhance the effect of anaerobic treatment of wastewater.

[0009] The present invention also provides a wastewater treatment method based on the above device. The present invention constructs a new strategy of electrochemical iron synergistic anaerobic treatment system, and uses electrochemical methods to generate Fe in situ at the iron anode. 2+ , and H2 and OH are simultaneously generated in situ at the cathode - , and obtained a multi-objective solution for practical application, including simultaneous and efficient in-situ removal of CO2 and H2S from biogas in an anaerobic reactor, overcoming pH drop, and improving the anaerobic treatment effect of wastewater. This method is applied to the treatment of domestic sewage, papermaking wastewater and other wastewater.

[0010] The purpose of the present invention is achieved through the following technical solutions: The present invention provides an electrochemical iron-enhanced wastewater anaerobic treatment process and a device for in-situ biogas purification, the device comprising an anode, a cathode, a power supply, an electrolytic cell, a stirrer, an anaerobic reactor and a pH value control system; the anode, the cathode and the stirrer are arranged in the electrolytic cell, and the anode, the cathode, the power supply and the electrolytic cell constitute an electrochemical system; the two ends of the power supply are respectively connected to the anode and the cathode through a power line to provide voltage and current to the electrochemical system; the electrolytic cell is connected to the anaerobic reactor; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump, and the acid solution supply system includes an acid solution preparation device and an acid solution pump; the alkali solution preparation device is connected to the electrolytic cell through the alkali solution pump; the acid solution preparation device is connected to the electrolytic cell through the acid solution pump; the pH detector is connected to the anaerobic reactor; The electrolytic cell is provided with a wastewater inlet, and the anaerobic reactor is provided with a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

[0011] As another embodiment of the present invention, the electrochemical iron-enhanced wastewater anaerobic treatment process and biogas in-situ purification device comprises an anode, a cathode, a power supply, an electrolytic cell, a stirrer, an anaerobic reactor and a pH value control system; the anode, cathode and stirrer are arranged in the electrolytic cell, and the anode, cathode, power supply and electrolytic cell constitute an electrochemical system; the two ends of the power supply are respectively connected to the anode and cathode through a power line; the electrolytic cell is connected to the anaerobic reactor; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump, and the acid solution supply system includes an acid solution preparation device and an acid solution pump; the alkali solution preparation device is connected to the electrolytic cell through the alkali solution pump; the acid solution preparation device is connected to the electrolytic cell through the acid solution pump; the pH detector is connected to the anaerobic reactor; The anaerobic reactor is also connected to the electrolytic cell through a circulating water pipeline; the electrolytic cell is provided with a circulating water inlet and outlet, and the anaerobic reactor is provided with a circulating water outlet and inlet, a wastewater inlet, an iron precipitation product outlet, a wastewater outlet, and a biogas outlet. In this embodiment, the circulating water of the anaerobic reactor enters the electrolytic cell and reacts with the Fe generated by the anode reaction. 2+ , H2 and OH generated by cathode reaction - After being evenly mixed, it enters the anaerobic reactor; the wastewater to be treated is directly transported to the anaerobic reactor.

[0012] As another embodiment of the present invention, the electrochemical iron-enhanced wastewater anaerobic treatment process and the device for in-situ biogas purification include an anode, a cathode, a power supply, an anaerobic reactor and a pH value control system; the anode and the cathode are arranged in the anaerobic reactor, and the anode, the cathode, the power supply and the anaerobic reactor constitute an electrochemical system; the two ends of the power supply are respectively connected to the anode and the cathode through a power line to provide voltage and current to the electrochemical system; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump, and the acid solution supply system includes an acid solution preparation device and an acid solution pump; the alkali solution preparation device is connected to the anaerobic reactor through the alkali solution pump; the acid solution preparation device is connected to the anaerobic reactor through the acid solution pump; the pH detector is connected to the anaerobic reactor; the anaerobic reactor is provided with a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

[0013] Preferably, in the above device, the iron electrode includes but is not limited to iron plate, carbon steel, stainless steel, scrap iron or iron-containing composite electrode and other iron-containing electrode materials.

[0014] Preferably, in the above device, the cathode is a metal electrode, a carbon-based material electrode or a composite electrode; the metal electrode includes an iron electrode or a non-ferrous metal electrode.

[0015] Preferably, in the above device, the anaerobic reactor includes an anaerobic baffle reactor, a UASB anaerobic reactor, etc.

[0016] Based on the device described in the present invention, the present invention also provides an electrochemical iron-enhanced wastewater anaerobic treatment process and a method for in-situ biogas purification, comprising the following steps: (1) The wastewater to be treated is transported into the electrolytic cell, and the voltage / current of the electrochemical system is regulated to generate Fe by the anode reaction in the electrolytic cell. 2+ , cathode reaction generates H2 and OH - and evenly mixed with the wastewater to be treated through the action of the agitator; (2) Next, Fe 2+ , H2 and OH - The wastewater to be treated is transported into the anaerobic reactor for anaerobic treatment of the wastewater. The organic matter and other pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of the biogas are CH4 and CO2, as well as impurities such as H2S. (3) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the electrolytic cell, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (4) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, and the purified biogas and treated wastewater are discharged from the anaerobic reactor. The iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

[0017] As another embodiment of the present invention, the electrochemical iron enhanced anaerobic wastewater treatment process and the method for in-situ biogas purification comprises the following steps: (1) The circulating water from the anaerobic reactor is transported into the electrolytic cell. By regulating the voltage / current of the electrochemical system, the anode reaction in the electrolytic cell generates Fe 2+ , cathode reaction generates H2 and OH - and is evenly mixed with the circulating water through the action of the agitator; (2) Next, Fe 2+ , H2 and OH - The circulating water is transported into the anaerobic reactor, and the wastewater to be treated is directly transported to the anaerobic reactor for anaerobic treatment. The organic matter and other pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of biogas are CH4 and CO2, as well as impurities such as H2S. (3) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the electrolytic cell, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (4) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, the purified biogas is discharged from the anaerobic reactor, the treated wastewater is discharged from the anaerobic reactor or used as circulating water, the iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

[0018] As another embodiment of the present invention, the electrochemical iron enhanced anaerobic wastewater treatment process and the method for in-situ biogas purification comprises the following steps: (1) The wastewater to be treated is directly transported into the anaerobic reactor, where the anode reaction generates Fe 2 + , cathode reaction generates H2 and OH - The wastewater is mixed evenly with the wastewater to be treated, and the wastewater to be treated is anaerobically treated. The organic matter and other pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of the biogas are CH4 and CO2, as well as impurities such as H2S. (2) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the anaerobic reactor, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (3) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, and the purified biogas and treated wastewater are discharged from the anaerobic reactor. The iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

[0019] Preferably, the wastewater to be treated in the above method includes domestic sewage or papermaking wastewater.

[0020] In the above method, the product of the electrochemical reaction, Fe 2+ OH - It also plays the role of effectively improving microbial activity and overcoming pH drop, and utilizing the product Fe of the electrochemical reaction 2+ The flocculation effect is used to improve the sludge sedimentation and dewatering performance and remove organic matter, thereby effectively improving the effect of anaerobic wastewater treatment.

[0021] Compared with the prior art, the principles, advantages and beneficial effects of the present invention are described as follows: When the wastewater to be treated or the circulating water from the anaerobic reactor enters the electrolytic cell, the Fe 2+ , and H2 and OH generated at the cathode - The dissolved mixture enters into the wastewater to be treated or the circulating water of the anaerobic reactor and is mixed evenly.

[0022] Therefore, when the product Fe generated by the electrochemical reaction is contained 2+ , H2 and OH - When the wastewater to be treated or the circulating water of the anaerobic reactor enters the anaerobic reactor, multiple practical goals are achieved, such as simultaneous and efficient in-situ removal of CO2 and H2S in the biogas in the anaerobic reactor, overcoming the pH drop, and improving the anaerobic treatment effect of wastewater.

[0023] First, the Fe generated by the iron anode 2+ It reacts with CO2 in the biogas produced during the anaerobic treatment of wastewater to generate FeCO3 precipitation, removes most of the CO2 in the biogas, and forms a CO2 sink (Formula ①, ②); at the same time, the H2 generated at the cathode of the electrochemical system reacts with the CO2 in the biogas to generate CH4 (Formula ③). 2+ The synergistic effect of the H2 generated at the cathode enables efficient in-situ removal of CO2 from biogas in the anaerobic reactor.

[0024] ① ② ③ At the same time, the Fe generated by the iron anode of the electrochemical system 2+ It reacts with H2S in the biogas produced during the anaerobic treatment of wastewater to generate FeS precipitate, and simultaneously achieves efficient in-situ removal of H2S in the biogas in the anaerobic reactor (Formula ④).

[0025] ④ In the case of adding ferrous ions to the anaerobic treatment process of wastewater for biogas desulfurization, in fact, the addition of ferrous ions to the wastewater has an important impact on the pH value of the system. This is because ferrous salts are strongly acidic compounds, and the commonly used ferrous salt dosage will reduce the pH value of the wastewater. Especially in the anaerobic treatment process of wastewater containing high concentrations of organic matter, the acidification and deterioration of the anaerobic process caused by the accumulation of volatile fatty acids is a common and serious problem, and the addition of ferrous ions makes this problem more serious.

[0026] At the same time, the precipitation reaction of ferrous ions with H2S is highly dependent on pH and is significantly negatively affected by lower pH values, especially under the pH conditions of wastewater biological treatment (i.e., 6-8). For example, a decrease from pH 7.0 to 6.5 results in an increase of more than 200% in the iron salt dosage requirement to achieve the same sulfide concentration. In addition, the decrease in pH also shifts the reaction equilibrium from HS - Transfer to volatile H2S, resulting in the release of more H2S, causing problems such as reduced H2S removal effect, reduced biogas methane purity, equipment corrosion and safety risks. On the other hand, the reduction in pH will also lead to a significant decrease in biogas decarbonization effect, acidification and deterioration of anaerobic treatment process, and a significant decrease in pollutant removal effect and biogas yield.

[0027] The present invention utilizes OH generated at the cathode of the electrochemical system - , which can effectively maintain the alkaline environment inside the anaerobic reactor. By adjusting the current value of the electrochemical system and setting the pH value control system, the pH value inside the anaerobic reactor can be fine-tuned so that the pH value inside the anaerobic reactor can be stably maintained within the range of 7.1±0.1. Therefore, the purposes of simultaneously and efficiently removing CO2 and H2S from biogas in situ, effectively alleviating the acidification deterioration of the anaerobic process caused by the accumulation of volatile fatty acids during the anaerobic treatment of wastewater, and improving the process effect of anaerobic treatment of wastewater are achieved.

[0028] On the other hand, Fe generated in situ at the iron anode of the electrochemical system 2+ The activity of microorganisms in the anaerobic reactor is improved by strengthening the activity of certain biological enzymes, and the flocculation effect is used to improve the sludge sedimentation and dewatering performance and remove organic matter, thereby effectively improving the effect of the wastewater anaerobic treatment process.

[0029] The method of the present invention is simple and efficient, has a short process, requires less equipment, has low investment and operating costs, is easy to operate and maintain, and can simultaneously and efficiently remove CO2 and H2S in biogas in one step, achieving the purpose of in-situ purification of biogas, while effectively improving the effect of the wastewater anaerobic treatment process, and has good application prospects.

[0030] Furthermore, the iron content in the electrochemical iron precipitation product obtained by the present invention can reach about 57%, and it has the potential to be used as an iron ore raw material; at the same time, the electrochemical iron precipitation product obtained by the present invention can be applied to wastewater and sludge treatment processes, effectively improving the dehydration and precipitation performance of the sludge, and has significant resource recovery and utilization value. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 It is a schematic diagram of one embodiment of the device for the electrochemical iron-enhanced anaerobic wastewater treatment process and in-situ biogas purification of the present invention; Figure 2 A schematic diagram of another embodiment of the device for the electrochemical iron-enhanced anaerobic wastewater treatment process and in-situ biogas purification of the present invention; Figure 3 A schematic diagram of another embodiment of the device for the electrochemical iron-enhanced anaerobic wastewater treatment process and in-situ biogas purification of the present invention; Among them, 1-electrolytic cell, 2-anode, 3-cathode, 4-power supply, 5-anaerobic reactor, 6-agitator, 7-pH detector, 8-acid preparation device, 9-acid pump, 10-alkali preparation device, 11-alkali pump. DETAILED DESCRIPTION

[0032] The present invention is further described in detail below in conjunction with the examples and drawings, but the embodiments of the present invention are not limited thereto. The raw materials involved in the present invention can be purchased directly from the market. For process parameters not particularly noted, conventional techniques can be used.

[0033] Figure 1Provided is a schematic diagram of one embodiment of an electrochemical iron-enhanced wastewater anaerobic treatment process and a biogas in-situ purification device, comprising an electrolytic cell 1, an anode 2, a cathode 3, a power supply 4, an anaerobic reactor 5, a stirrer 6 and a pH value control system, wherein the anode 2, the cathode 3 and the stirrer 6 are arranged in the electrolytic cell 1, and the anode 2, the cathode 3, the power supply 4 and the electrolytic cell 1 constitute an electrochemical system; the two ends of the power supply 4 are respectively connected to the anode 2 and the cathode 3 through a power line to provide voltage and current to the electrochemical system; the electrolytic cell 1 is connected to the anaerobic reactor 5; the anode 2 is an iron electrode; The pH value control system includes a pH detector 7, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device 10 and an alkali solution pump 11, and the acid solution supply system includes an acid solution preparation device 8 and an acid solution pump 9; the alkali solution preparation device 10 is connected to the electrolytic cell 1 through the alkali solution pump 11; the acid solution preparation device 8 is connected to the electrolytic cell 1 through the acid solution pump 9; the pH detector 7 is connected to the anaerobic reactor 5; the electrolytic cell 1 is provided with a wastewater inlet, and the anaerobic reactor is provided with a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

[0034] Figure 2 A schematic diagram of another embodiment of the electrochemical iron-enhanced wastewater anaerobic treatment process and the device for in-situ biogas purification is provided. The device comprises an anode 2, a cathode 3, a power supply 4, an electrolytic cell 1, a stirrer 6, an anaerobic reactor 5 and a pH value control system; the anode 2, the cathode 3 and the stirrer 6 are arranged in the electrolytic cell 1, and the anode 2, the cathode 3, the power supply 4 and the electrolytic cell 1 constitute an electrochemical system; the two ends of the power supply 4 are respectively connected to the anode 2 and the cathode 3 through a power line to provide voltage and current to the electrochemical system; the electrolytic cell 1 is connected to the anaerobic reactor 5; the anode 2 is an iron electrode; the The pH value control system includes a pH detector 7, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device 10 and an alkali solution pump 11, and the acid solution supply system includes an acid solution preparation device 8 and an acid solution pump 9; the alkali solution preparation device 10 is connected to the electrolytic cell 1 through the alkali solution pump 11; the acid solution preparation device 8 is connected to the electrolytic cell 1 through the acid solution pump 9; the pH detector 7 is connected to the anaerobic reactor 5; the anaerobic reactor 5 is also connected to the electrolytic cell 1 through a circulating water pipeline; the electrolytic cell 1 is provided with a circulating water inlet and outlet, and the anaerobic reactor 5 is provided with a circulating water outlet and inlet, a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

[0035] exist Figure 2 In the device of the embodiment shown, when the circulating water of the anaerobic reactor 5 enters the electrolytic cell 1, the iron anode of the electrochemical system generates Fe 2+At the same time, the cathode generates H2 and OH through electrochemical reaction. - Therefore, these electrochemically generated products Fe 2+ , H2 and OH - The dissolved mixed circulating water enters the anaerobic reactor 5. When the product Fe generated by the electrochemical reaction is contained 2+ , H2 and OH - When the circulating water of the anaerobic reactor 5 enters the anaerobic reactor, the electrochemical reaction product Fe 2+ , H2 reacts with CO2 and H2S in the biogas produced in the anaerobic treatment process of wastewater to form precipitates (FeCO3, FeS) or generate CH4, and CO2 and H2S in the biogas are simultaneously and efficiently removed in situ in the anaerobic reactor.

[0036] Figure 3 A schematic diagram of another embodiment of the electrochemical iron-enhanced wastewater anaerobic treatment process and the device for in-situ biogas purification is provided, comprising an anode 2, a cathode 3, a power supply 4, an anaerobic reactor 5 and a pH value control system; the anode 2 and the cathode 3 are arranged in the anaerobic reactor 5, and the anode 2, the cathode 3, the power supply 4 and the anaerobic reactor 5 constitute an electrochemical system; the anode 2 is an iron electrode; the two ends of the power supply 4 are respectively connected to the anode 2 and the cathode 3 through a power line to provide voltage and current to the electrochemical system; the pH value control system comprises a pH detector 7, an alkali supply system, an acid supply system and a control system, the alkali supply system comprises an alkali preparation device 10 and an alkali pump 11, and the acid supply system comprises an acid preparation device 8 and an acid pump 9; the alkali preparation device 10 is connected to the anaerobic reactor 5 through the alkali pump 11; the acid preparation device 8 is connected to the anaerobic reactor 5 through the acid pump 9; the pH detector 7 is connected to the anaerobic reactor 5; the anaerobic reactor is provided with a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

[0037] exist Figure 3 In the device shown, when the wastewater to be treated enters the anaerobic reactor 5, the anode 2 of the electrochemical system generates Fe 2+ At the same time, the cathode 3 generates H2 and OH through electrochemical reaction. - Therefore, the products of these electrochemical reactions, Fe 2+ , H2 and OH - It is dissolved and mixed into the wastewater to be treated, and reacts with CO2 and H2S in the biogas produced during the anaerobic treatment of the wastewater to form precipitates (FeCO3, FeS) or generate CH4, and simultaneously and efficiently removes CO2 and H2S in the biogas in situ in the anaerobic reactor.

[0038] In the electrochemical iron-enhanced wastewater anaerobic treatment process and the device for in-situ purification of biogas of the present invention, the pH value control system detects the pH value inside the anaerobic reactor in real time through the pH detector installed on the anaerobic reactor, and controls the alkali pump or the acid pump through the control system to maintain the pH value inside the anaerobic reactor within the range of 7.1±0.1. Specifically, when the pH value detected by the pH detector is greater than 7.2, the alkali pump is controlled by the control system to reduce the amount of alkali added, or the acid pump is controlled by the control system to increase the amount of acid added, so that the pH value inside the anaerobic reactor decreases and is maintained within the range of 7.1±0.1; conversely, when the pH value detected by the pH detector is less than 7.0, the alkali pump is controlled by the control system to increase the amount of alkali added, or the acid pump is controlled by the control system to reduce the amount of acid added, so that the pH value inside the anaerobic reactor rises and is maintained within the range of 7.1±0.1.

[0039] Example 1 This embodiment refers to Figure 1 The anaerobic reactor is preferably an anaerobic baffled reactor, and the anode 2 and the cathode 3 are both made of low-carbon steel plates as electrode materials. An electrochemical iron-coupled anaerobic baffled reactor wastewater treatment system is constructed and applied to treat domestic sewage. The average water quality of the wastewater is: COD is 898 mg / L, SS is 420 mg / L, and ammonia nitrogen is 45 mg / L; the treatment method steps are as follows: (1) The wastewater to be treated is transported into the electrolytic cell, and the voltage / current of the electrochemical system is regulated to generate Fe by the anode reaction in the electrolytic cell. 2+ , cathode reaction generates H2 and OH - and evenly mixed with the wastewater to be treated through the action of the agitator; (2) Next, Fe 2+ , H2 and OH - The wastewater to be treated is transported into the anaerobic baffled reactor and flows through the five compartments of the anaerobic baffled reactor in sequence for anaerobic treatment of the wastewater. The treated wastewater is output from the outlet of the anaerobic baffled reactor, and the biogas generated during the anaerobic treatment process is collected for measurement and analysis. The sludge concentration (MLSS) of the anaerobic baffled reactor is 10±2.0 g / L, and the sludge is evenly distributed in the five compartments of the anaerobic baffled reactor. The inlet pH is adjusted to 7.1±0.1, and the temperature of the anaerobic baffled reactor is adjusted to 35±2℃ through the temperature control system. The hydraulic retention time is 24h; (3) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the electrolytic cell, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (4) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, and the purified biogas and treated wastewater are discharged from the anaerobic reactor. The iron precipitation products (FeCO3, FeS) generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

[0040] In the above method, first, Fe generated by the iron anode is used 2+ It reacts with CO2 in the biogas produced during the anaerobic treatment of wastewater to generate FeCO3 precipitation, removes most of the CO2 in the biogas, and forms a CO2 sink (Formula ①, ②); at the same time, the H2 generated at the cathode of the electrochemical system reacts with the CO2 in the biogas to generate CH4 (Formula ③). 2+ The synergistic effect of the H2 generated at the cathode enables efficient in-situ removal of CO2 from biogas in the anaerobic reactor.

[0041] At the same time, the Fe generated by the iron anode of the electrochemical system 2+ It reacts with H2S in the biogas produced during the anaerobic treatment of wastewater to generate FeS precipitate, and simultaneously achieves efficient in-situ removal of H2S in the biogas in the anaerobic reactor (Formula ④).

[0042] The Fe generated in situ at the iron anode of the electrochemical system 2+ The activity of microorganisms in the anaerobic reactor is improved by strengthening the activity of certain biological enzymes, and the flocculation effect is used to improve the sludge sedimentation and dewatering performance and remove organic matter; the OH generated in situ at the cathode - It can effectively alleviate the problem of acidification and deterioration of the anaerobic process caused by the accumulation of volatile fatty acids during the anaerobic treatment of wastewater, thereby effectively improving the effect of the anaerobic wastewater treatment process.

[0043] In order to verify the effectiveness of the present invention, a control group was also constructed in this embodiment. Except that the electrochemical system was not set up, the anaerobic reactor and other wastewater treatment process and parameters of the control group were the same as those of the electrochemical iron-coupled anaerobic baffled reactor wastewater treatment system.

[0044] In this embodiment, the current of the electrochemical system and the electrochemical iron Fe 2+ The relationship between the CH4 yield of the anaerobic reactor and the content and concentration of CO2 and H2S in the discharged biogas are shown in Table 1. In Table 2, the data of the experimental group are the experimental results of the electrochemical iron coupled anaerobic baffled reactor for treating wastewater, while the data of the control group are the results of the experiment without setting up the electrochemical system (that is, without adding electrochemical iron Fe 2+) experimental results of the anaerobic baffled reactor for treating wastewater system.

[0045] Table 1 Current and electrochemical iron Fe 2+ The relationship between yield Table 2 Changes in CH4 production rate and CO2, H2S content and concentration in the discharged biogas from the anaerobic reactor As shown in Table 2, the product Fe generated by the electrochemical reaction in the anaerobic reactor 2+ , H2 and OH - The presence of can effectively remove CO2 and H2S in the biogas produced in the anaerobic treatment process of wastewater, achieving the purpose of efficient in-situ purification of biogas. At the same time, it can be seen from Table 2 that the electrochemical reaction product Fe 2+ , H2 and OH - The presence of significantly increased the methane yield of the anaerobic treatment process (increased by 10-20%), and the average removal rates of COD and SS in the wastewater increased by 8.3% and 7.6% respectively, effectively improving the effect of anaerobic wastewater treatment.

[0046] In addition, the iron content in the electrochemical iron precipitation product obtained by the present invention can reach about 57%, which has the potential to be used as an iron ore raw material; at the same time, the electrochemical iron precipitation product obtained by the present invention can be applied to wastewater and sludge treatment processes, effectively improving the dehydration and precipitation performance of sludge, and the sludge volume index (SVI) is reduced from 122 to 74 ml / g, and the specific filtration resistance (SRF) is reduced from 2.45×10 13 Down to 1.42×10 13 This indicates that the electrochemical iron precipitation product obtained by the present invention has significant resource recovery and utilization value.

[0047] Example 2 This embodiment refers to Figure 2 The anaerobic reactor is preferably an anaerobic baffled reactor, the anode 2 uses a low-carbon steel plate as the electrode material, and the cathode 3 uses a carbon-based material electrode to construct an electrochemical iron-coupled anaerobic baffled reactor wastewater treatment system. The device is applied to treat papermaking wastewater. The average water quality of the wastewater is: COD is 3080 mg / L, SS is 210 mg / L, and ammonia nitrogen is 125 mg / L. The specific steps are as follows: (1) The circulating water from the anaerobic baffled reactor is transported into the electrolytic cell. By regulating the voltage / current of the electrochemical system, the anode reaction in the electrolytic cell generates Fe 2+ , cathode reaction generates H2 and OH - and is evenly mixed with the circulating water through the action of the agitator; (2) Next, Fe 2+ , H2 and OH - The circulating water is transported into the anaerobic baffled reactor, and the wastewater to be treated is directly transported to the anaerobic baffled reactor and flows through the five compartments of the anaerobic baffled reactor in sequence to perform anaerobic treatment of the wastewater. The treated wastewater is output from the outlet of the anaerobic baffled reactor, and the biogas generated during the anaerobic treatment process is collected for measurement and analysis; the sludge concentration (MLSS) of the anaerobic baffled reactor is 10±2.0 g / L, and the sludge is evenly distributed in the five compartments of the anaerobic baffled reactor, the inlet pH is adjusted to 7.1±0.1, the temperature of the anaerobic baffled reactor is adjusted to 35±2℃ through the temperature control system, and the hydraulic retention time is 24h; (3) The pH value control system detects the pH value inside the anaerobic baffled reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the electrolytic cell, so that the pH value inside the anaerobic baffled reactor is stably maintained at 7.1±0.1; (4) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, the purified biogas is discharged from the anaerobic reactor, the treated wastewater is discharged from the anaerobic reactor or used as circulating water, the iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

[0048] In the method described in this embodiment, the current of the electrochemical system is adjusted to 80 mA, the electrochemical Fe 2+ Under the condition of 300 mg / L of addition, the CH4 yield of the wastewater anaerobic treatment process increased by more than 15% compared with the control group, the CO2 content in the biogas decreased from about 26% (volume ratio) in the control group to below 5.0% (volume ratio), and the H2S concentration decreased from 12500 mg / m 3 Decreased to about 85 mg / m 3 At the same time, the COD and SS removal rates of wastewater were increased by about 7.3% and 8.7% respectively compared with the control group.

[0049] Example 3 This embodiment refers to Figure 3The anaerobic reactor is preferably an anaerobic baffled reactor, the anode 2 uses scrap steel plate as the electrode material, and the cathode 3 uses a carbon-based material electrode. An electrochemical iron-coupled anaerobic baffled reactor wastewater treatment system is constructed and applied to treat papermaking wastewater. The average water quality of the wastewater is: COD is 1880 mg / L, SS is 130 mg / L, and ammonia nitrogen is 95 mg / L; the sludge concentration (MLSS) of the anaerobic baffled reactor is 10±2.0 g / L, and the sludge is evenly distributed in the 5 compartments of the anaerobic baffled reactor. The inlet pH is adjusted to 7.1±0.1, and the temperature of the anaerobic baffled reactor is adjusted to 35±2℃ through the temperature adjustment system. The hydraulic retention time is 24h. The treatment method includes the following steps: (1) The wastewater to be treated is directly transported into the anaerobic reactor, where the anode reaction generates Fe 2 + , cathode reaction generates H2 and OH - The wastewater is mixed evenly with the wastewater to be treated, and the wastewater to be treated is anaerobically treated. The organic matter and other pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of the biogas are CH4 and CO2, as well as impurities such as H2S. (2) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the anaerobic reactor, so that the pH value inside the anaerobic reactor is stably maintained within the range of 7.1±0.1; (3) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, and the purified biogas and treated wastewater are discharged from the anaerobic reactor. The iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

[0050] In the method described in this embodiment, in the electrochemical Fe 2+ Under the condition of 300 mg / L of addition, the CH4 yield of the wastewater anaerobic treatment process increased by more than 13% compared with the control group, the CO2 content in the biogas decreased from about 25% (volume ratio) in the control group to below 5.0% (volume ratio), and the H2S concentration increased from 10000 mg / m 3 Decreased to around 75 mg / m 3 At the same time, the COD and SS removal rates of wastewater were increased by about 6.3% and 8.1% respectively compared with the control group.

[0051] The above embodiments are preferred implementation modes of the present invention, but the implementation modes of the present invention are not limited to the above embodiments. Any other changes, modifications, substitutions, combinations, and simplifications that do not deviate from the spirit and principles of the present invention should be equivalent replacement methods and are included in the protection scope of the present invention.

Claims

1. An electrochemical iron-enhanced anaerobic wastewater treatment process and an apparatus for in-situ biogas purification, characterized in that: The device comprises an anode, a cathode, a power supply, an electrolytic cell, a stirrer, an anaerobic reactor and a pH value control system; the anode, cathode and stirrer are arranged in the electrolytic cell, and the anode, cathode, power supply and electrolytic cell constitute an electrochemical system; the two ends of the power supply are respectively connected to the anode and cathode through a power line; the electrolytic cell is connected to the anaerobic reactor; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump, and the acid solution supply system includes an acid solution preparation device and an acid solution pump; the alkali solution preparation device is connected to the electrolytic cell through the alkali solution pump; the acid solution preparation device is connected to the electrolytic cell through the acid solution pump; the pH detector is connected to the anaerobic reactor; The electrolytic cell is provided with a wastewater inlet, and the anaerobic reactor is provided with a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

2. An electrochemical iron-enhanced anaerobic wastewater treatment process and an apparatus for in-situ biogas purification, characterized in that: The device comprises an anode, a cathode, a power supply, an electrolytic cell, a stirrer, an anaerobic reactor and a pH value control system; the anode, cathode and stirrer are arranged in the electrolytic cell, and the anode, cathode, power supply and electrolytic cell constitute an electrochemical system; the two ends of the power supply are respectively connected to the anode and cathode through a power line; the electrolytic cell is connected to the anaerobic reactor; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump, and the acid solution supply system includes an acid solution preparation device and an acid solution pump; the alkali solution preparation device is connected to the electrolytic cell through the alkali solution pump; the acid solution preparation device is connected to the electrolytic cell through the acid solution pump; the pH detector is connected to the anaerobic reactor; The anaerobic reactor is also connected to the electrolytic cell through a circulating water pipeline; the electrolytic cell is provided with a circulating water inlet and outlet, and the anaerobic reactor is provided with a circulating water outlet and inlet, a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

3. An electrochemical iron-enhanced anaerobic wastewater treatment process and an apparatus for in-situ biogas purification, characterized in that: The device comprises an anode, a cathode, a power supply, an anaerobic reactor and a pH value control system; the anode and the cathode are arranged in the anaerobic reactor, and the anode, the cathode, the power supply and the anaerobic reactor constitute an electrochemical system; the two ends of the power supply are respectively connected to the anode and the cathode through a power line; the anode is an iron electrode; The pH value control system includes a pH detector, an alkali solution supply system, an acid solution supply system and a control system. The alkali solution supply system includes an alkali solution preparation device and an alkali solution pump, and the acid solution supply system includes an acid solution preparation device and an acid solution pump; the alkali solution preparation device is connected to the anaerobic reactor through the alkali solution pump; the acid solution preparation device is connected to the anaerobic reactor through the acid solution pump; the pH detector is connected to the anaerobic reactor; The anaerobic reactor is provided with a wastewater inlet, an iron precipitation product outlet, a wastewater outlet and a biogas outlet.

4. The electrochemical iron-enhanced anaerobic wastewater treatment process and the device for in-situ biogas purification according to any one of claims 1 to 3, characterized in that: The iron electrode includes, but is not limited to, iron plate, carbon steel, stainless steel, scrap iron or iron-containing composite electrodes and other iron-containing electrode materials.

5. The electrochemical iron-enhanced anaerobic wastewater treatment process and the device for in-situ biogas purification according to any one of claims 1 to 3, characterized in that: The cathode is a metal electrode, a carbon-based material electrode or a composite electrode; the metal electrode includes an iron electrode or a non-ferrous metal electrode.

6. The electrochemical iron-enhanced anaerobic wastewater treatment process and the device for in-situ biogas purification according to any one of claims 1 to 3, characterized in that: The anaerobic reactor comprises an anaerobic baffled reactor.

7. An electrochemical iron-enhanced anaerobic wastewater treatment process and a method for in-situ biogas purification based on the device according to any one of claims 1, 4, 5 or 6, characterized in that: The method comprises the following steps: (1) The wastewater to be treated is transported into the electrolytic cell, and the voltage / current of the electrochemical system is regulated to generate Fe by the anode reaction in the electrolytic cell. 2+ , cathode reaction generates H2 and OH - and evenly mixed with the wastewater to be treated through the action of the agitator; (2) Next, Fe 2+ , H2 and OH - The wastewater to be treated is transported into the anaerobic reactor for anaerobic treatment of the wastewater. The organic pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of the biogas are CH4, CO2, and H2S. (3) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the electrolytic cell, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (4) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, and the purified biogas and treated wastewater are discharged from the anaerobic reactor. The iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

8. An electrochemical iron-enhanced anaerobic wastewater treatment process and a method for in-situ biogas purification based on the device according to any one of claims 2, 4, 5 or 6, characterized in that: The method comprises the following steps: (1) The circulating water from the anaerobic reactor is transported into the electrolytic cell. By regulating the voltage / current of the electrochemical system, the anode reaction of the electrochemical system in the electrolytic cell generates Fe 2+ , cathode reaction generates H2 and OH - and is evenly mixed with the circulating water through the action of the agitator; (2) Next, Fe 2+ , H2 and OH - The circulating water is transported into the anaerobic reactor, and the wastewater to be treated is directly transported to the anaerobic reactor for anaerobic treatment. The organic pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of biogas are CH4, CO2, and H2S. (3) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the electrolytic cell, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (4) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, the purified biogas is discharged from the anaerobic reactor, the treated wastewater is discharged from the anaerobic reactor or used as circulating water, the iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

9. An electrochemical iron-enhanced anaerobic wastewater treatment process and a method for in-situ biogas purification based on the device according to any one of claims 3, 4, 5 or 6, characterized in that: The method comprises the following steps: (1) The wastewater to be treated is directly transported to an anaerobic reactor for anaerobic treatment. The anode reaction in the anaerobic reactor generates Fe 2+ , cathode reaction generates H2 and OH - The wastewater is mixed evenly with the wastewater to be treated. The organic pollutants in the wastewater are degraded by microorganisms in the anaerobic reactor to obtain treated wastewater and produce biogas. The main components of the biogas are CH4, CO2, and H2S. (2) The pH control system detects the pH value inside the anaerobic reactor through a pH detector and controls the acid pump or alkali pump to supply a certain amount of acid or alkali to the anaerobic reactor, so that the pH value inside the anaerobic reactor is stably maintained at 7.1±0.1; (3) In the anaerobic reactor, CO2, H2S and Fe in biogas 2+ , H2 reacts to form precipitation products, or generates CH4 and is removed in situ, and the purified biogas and treated wastewater are discharged from the anaerobic reactor. The iron precipitation products generated during the biogas purification process are regularly discharged from the anaerobic reactor, and the H2 generated by the electrochemical cathode reaction is also discharged with the purified biogas, completing the process of anaerobic wastewater treatment and in-situ biogas purification.

10. The method according to any one of claims 7 to 9, characterized in that: The wastewater to be treated includes domestic sewage or papermaking wastewater.

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