A side-stream micro-aeration coupled with mainstream electro-driven anaerobic digestion method

Abstract

The present invention relates to an anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driven, comprising the following steps: After pretreatment, organic waste enters the side-stream reaction system, and aeration gas is injected through an aeration device, and the ORP is feedback-regulated to anaerobically ferment the organic waste under micro-aerobic or facultative anaerobic conditions to obtain a mixed liquid and a mixed gas; The obtained mixed gas enters the collection device or enters the gas disturbance system, and the obtained mixed liquid is pre-stirred by the gas disturbance system to obtain a pre-stirred mixed liquid, which enters the mainstream reaction system; The mainstream reaction system eliminates residual free radicals in the obtained pre-stirred mixed liquid and promotes its digestion to produce methane through the layout of functional electrodes and the introduction of micro-voltage. Compared with the prior art, the anaerobic digestion method of the present invention improves the reaction efficiency through the coupling design of the side-stream reaction system and the mainstream reaction system, and can realize the treatment and disposal of organic solid waste with higher efficiency, higher stability and higher resource recovery ability.

Description

Technical Field

[0001] The present invention relates to the technical field of anaerobic digestion treatment, and in particular to an anaerobic digestion method coupling side-stream micro-aeration and mainstream electro-driving. Background Art

[0002] Anaerobic digestion is an important means to realize the reduction, stabilization, harmlessness and resource utilization of organic solid waste. A good anaerobic digestion reaction system is the guarantee for the efficient operation of anaerobic digestion. The traditional anaerobic digestion reaction system is completed in one reaction system, and multiple-step reactions and various microbial metabolic processes are carried out in one system. Its reaction efficiency is limited by the slowest step reaction or the most sensitive microorganism. Therefore, most of the current anaerobic digestion regulation methods are to carry out pretreatment before the mainstream reaction system, or to add functional materials or change reaction conditions in the mainstream reaction system. For example, patents CN202011184885.7 "Anaerobic digestion device and method for sludge based on electron transfer coupling microbial electrolytic cell" and CN202111231427.9 "Anaerobic treatment device and method for wet waste coupling micro-aeration and microbial electrolytic cell" etc. all start from this idea to strengthen the anaerobic digestion performance of the mainstream reaction system.

[0003] However, the introduction of microbial electrolytic cells or micro-aeration, although each has a promoting effect on a certain type of microorganism or a certain stage of reaction, inevitably disturbs other microbial communities or other reactions in the complex system. Therefore, its reaction process is a "temporary stable solution" after the balance of multiple-step reactions, rather than an "optimal solution" that maximizes the promotion of each stage of the whole anaerobic digestion process. Summary of the Invention

[0004] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies and provide an anaerobic digestion method coupling side-stream micro-aeration and mainstream electro-driving. This anaerobic digestion method can solve the problem of low anaerobic digestion efficiency caused by the mutual restraint of each stage in the mainstream reaction system by designing a side-stream reaction system and a mainstream reaction system.

[0005] The purpose of the present invention can be realized by the following technical solutions:

[0006] The purpose of the present invention is to provide an anaerobic digestion method coupling side-stream micro-aeration and mainstream electro-driving, including the following steps:

[0007] S1. After the organic waste is pretreated, it enters the side-stream reaction system, and aeration gas is injected through the aeration device, and the ORP is feedback-regulated to make the organic waste anaerobically ferment under micro-oxic or facultative anaerobic conditions to obtain a mixed liquid and a mixed gas;

[0008] S2. The mixed gas obtained in step S1 enters the collection device or the gas perturbation system. The mixed liquid obtained in step S1 is pre-stirred by the gas perturbation system to obtain a pre-stirred mixed liquid, which then enters the main reaction system.

[0009] S3. The main reaction system eliminates the residual free radicals in the pre-stirred mixed liquid obtained in step S2 through the layout of functional electrodes and the introduction of micro-voltage, and promotes its digestion to produce methane.

[0010] Preferably, for organic waste with large pH fluctuations, the pretreatment of the organic waste in step S1 includes adjusting the pH to 6.0 - 8.0.

[0011] Preferably, the aeration gas in step S1 is air or oxygen; the gas flow rate of the aeration gas is 0.01 mL / min - 100 mL / min.

[0012] Preferably, the ORP regulation range in step S1 is -350 mV - 100 mV.

[0013] Preferably, the components of the mixed gas obtained in step S1 include nitrogen, carbon dioxide, and hydrogen.

[0014] Preferably, the oxygen concentration in the mixed gas obtained in step S1 does not exceed 10%, and the methane concentration does not exceed 20%.

[0015] Preferably, the gas flow rate of the pre-stirring of the gas perturbation system in step S2 is 0.01 mL / min - 50 mL / min, and the time is 0.5 h - 5 h.

[0016] Preferably, the functional electrodes in the main reaction system are annular electrodes, and the arrangement method is vertical interval distribution.

[0017] Preferably, the volume ratio of the effective reaction areas of the side-stream reaction system and the main reaction system is 1:1 - 1:5.

[0018] Preferably, the side-stream reaction system and the main reaction system are connected by a conduit and a peristaltic pump.

[0019] The principle of the present invention is as follows: By designing a side-stream reaction system and a main reaction system, micro-aeration is carried out in the side-stream reaction system, and the aeration volume is precisely regulated by ORP to achieve the enrichment of facultative bacteria and efficiently hydrolyze organic waste; the mixed gas in the side-stream can pre-stir the mixed liquid entering the main stream through the gas perturbation system to optimize its reaction mass transfer interface; after the mixed liquid in the side-stream enters the main stream, the residual reactive oxygen species (ROS) in it are quickly utilized by the microorganisms in the functional electrodes in the main reaction system, thereby reducing the toxicity to methanogens; the electroactive microorganisms enriched on the functional electrodes in the main reaction system can efficiently methaneize the volatile fatty acids (VFA) in the side-stream mixed liquid.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] 1) The anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driving provided by this technical solution, by designing a side-stream reaction system and a mainstream reaction system, coupling side-stream micro-aeration with mainstream electro-driving, has a high degradation efficiency and a higher hydrolysis efficiency of organic waste.

[0022] 2) The anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driving provided by this technical solution has a high treatment efficiency and a shorter sludge retention time (SRT).

[0023] 3) The anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driving provided by this technical solution has good stability and better stability under higher organic loading rate (OLR) conditions.

[0024] 4) The anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driving provided by this technical solution, the electroactive microorganisms enriched on the functional electrode plates in the mainstream reaction system can achieve efficient methanation of volatile fatty acids (VFA) in the side-stream mixed liquor, with a high energy recovery rate, and has a higher methane production and methane content. Description of the Drawings

[0025] Figure 1 It is a schematic flow chart of an anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driving of the present invention.

[0026] Figure 2 It is a schematic structural diagram of an anaerobic digestion system coupling side-stream micro-aeration with mainstream electro-driving in the embodiment of the present invention.

[0027] The reference numerals in the figure are shown as follows:

[0028] 1. First stirring motor; 2. Feed inlet; 3. First stirring paddle; 4. First electric heating rod; 5. Discharge outlet; 6. Aeration pipe; 7. Aeration disk; 8. ORP probe; 9. First biogas collection pipe; 10. Peristaltic pump; 11. Biological anode plate; 12. Biological cathode plate. Detailed Embodiments

[0029] The present invention will be described in detail below with reference to the drawings and specific embodiments. Features such as component models, material names, connection structures, control methods, etc. that are not clearly described in this technical solution are regarded as common technical features disclosed in the prior art.

[0030] An anaerobic digestion method coupling side-stream micro-aeration with mainstream electro-driving includes the following steps:

[0031] S1. The organic waste is pretreated and then enters the sidestream reaction system. Aeration gas is introduced through the aeration device, and the ORP is feedback-regulated to anaerobically ferment the organic waste under microaerobic or facultative anaerobic conditions, obtaining a mixed liquid and a mixed gas.

[0032] S2. The mixed gas obtained in step S1 enters the collection device or the gas perturbation system. The mixed liquid obtained in step S1 is pre-stirred by the gas perturbation system to obtain a pre-stirred mixed liquid, which then enters the mainstream reaction system.

[0033] S3. The mainstream reaction system eliminates the residual free radicals in the pre-stirred mixed liquid obtained in step S2 and promotes its digestion and methane production through the layout of functional electrodes and the introduction of a micro-voltage.

[0034] Example

[0035] This example provides an anaerobic digestion method coupling sidestream micro-aeration and mainstream electro-driving, which is carried out in an anaerobic digestion system coupling sidestream micro-aeration and mainstream electro-driving.

[0036] The above-mentioned anaerobic digestion system coupling sidestream micro-aeration and mainstream electro-driving includes a sidestream reaction system and a mainstream reaction system. The sidestream reaction system and the mainstream reaction system are connected by a conduit and a peristaltic pump 10.

[0037] The sidestream reaction system includes a first reactor tank, a first stirring motor 1, a feed inlet 2, a first stirring paddle 3, a first electric heating rod 4, a discharge outlet 5, an aeration pipe 6, an aeration disk 7, an ORP probe 8, and a first biogas collection pipe 9. The first stirring paddle 3 penetrates through the first reactor tank. The output end of the first stirring motor 1 is connected to the first stirring paddle 3 to drive the first stirring paddle 3 to rotate. The first electric heating rod 4 penetrates through the first reactor tank. The feed inlet 2, the first discharge outlet 5, and the first biogas collection pipe 9 are all arranged on the first reactor tank. The aeration disk 7 and the ORP probe 8 are arranged at the bottom of the sidestream reaction system. The aeration pipe 6 is connected to the aeration disk 7, and a valve is provided on the aeration pipe. The valve is wirelessly or wiredly connected to the controller, and the controller is communicatively connected to the ORP probe 8. The ORP data in the sidestream reaction system is collected by the ORP probe 8 and uploaded to the controller, and the controller controls the opening and closing of the valve to achieve precise control of the aeration volume, thereby achieving the enrichment of facultative microorganisms and further achieving the efficient hydrolysis of organic matter in solid waste.

[0038] The mainstream reaction system includes a second reactor tank, a second stirring motor, a second stirring paddle, a second electric heating rod, a biological anode plate 11 and a biological cathode plate 12; the second stirring paddle penetrates through the second reactor tank; the output end of the second stirring motor is connected to the second stirring paddle to drive the second stirring paddle to rotate; the second electric heating rod penetrates through the second reactor tank; a second discharge port and a second biogas collection pipe are both arranged on the second reactor tank; the biological anode plate 11 and the biological cathode plate 12 are annular electrode plates, and their arrangement is vertically spaced, and they are fixed on the wall of the mainstream reaction system; the biological anode plate 11 and the biological cathode plate 12 are arranged at upper and lower intervals and are connected in series by two vertically arranged wires, and the two vertically arranged wires are respectively connected to the positive and negative poles of an external DC power supply, so as to achieve efficient removal of residual oxidizing substances in the side-stream influent biogas slurry to protect the methanogens in the mainstream, and can also achieve efficient methanation of hydrolysis and acidification products. The plates of the microbial electrolytic cell MEC are arranged in the mainstream reaction system. On the one hand, it can be used to eliminate the residual active oxygen in the biogas slurry from the side-stream reaction system to protect the methanogens, and on the other hand, it can enrich electroactive microorganisms to achieve efficient methanation of hydrolysis and acidification products.

[0039] In the side-stream micro-aeration coupled with mainstream electro-driven anaerobic digestion method in this embodiment, a side-stream micro-aeration coupled with mainstream electro-driven anaerobic digestion system is used to treat food waste. The effective volume of the side-stream reaction system is 1 L, and the effective volume of the mainstream reaction system is 2 L. The food waste is taken from the swill bucket of a university cafeteria. After bringing the food waste back to the laboratory, it is crushed, and its total solid content (TS) is measured to be 8.72 ± 0.17%, and the volatile matter ratio (VS / TS) is 96.76 ± 0.50%.

[0040] The above-mentioned side-stream micro-aeration coupled with mainstream electro-driven anaerobic digestion method includes the following steps:

[0041] S1. After the organic waste is pretreated, it enters the side-stream reaction system, and aeration gas is injected through the aeration device, and the ORP is feedback-regulated to make the organic waste undergo anaerobic fermentation under micro-aerobic or facultative anaerobic conditions to obtain a mixed liquid and a mixed gas;

[0042] S2. The mixed gas obtained in step S1 enters the collection device or enters the gas disturbance system. The mixed liquid obtained in step S1 is pre-stirred by the gas disturbance system to obtain a pre-stirred mixed liquid, and then enters the mainstream reaction system;

[0043] S3. The mainstream reaction system eliminates the residual free radicals in the pre-stirred mixed liquid obtained in step S2 through the arrangement of functional plates and the introduction of micro-voltage, and promotes its digestion and methanation.

[0044] The specific implementation steps are as follows:

[0045] First, 1 L and 2 L of inoculated sludge were added to the sidestream reaction system and the mainstream reaction system respectively. The inoculated sludge was from the sludge anaerobic fermentation tank of a sewage treatment plant in Shanghai. Nitrogen was introduced into the two reactors for 10 minutes to create an anaerobic environment.

[0046] Subsequently, 100 mL of food waste was added to the sidestream reaction system through the sample inlet 2. Similarly, 100 mL of biogas slurry in the sidestream reaction system was transported to the mainstream reaction system by the peristaltic pump 10, and at the same time, 100 mL of sludge was discharged from the mainstream reaction system.

[0047] Subsequently, the first stirring motor 1 of the sidestream reaction system was turned on. The first stirring motor 1 drove the first stirring paddle 3 to mix the biogas slurry in the side-flow micro-aeration reactor. The second stirring motor of the mainstream reaction system was turned on, and the second stirring motor drove the second stirring paddle to mix the biogas slurry in the mainstream reaction system. At the same time, the biogas slurry in the two reactors was also mixed. At the same time, air entered the sidestream reaction system through the air supply pipe 6 and was evenly dispersed in the sidestream reaction system through the air diffuser 7.

[0048] Subsequently, the ORP probe 8 began to record the ORP value in the sidestream reaction system and uploaded it to the controller. When it was detected that the ORP in the system was higher than -350 mV, the controller controlled the closing of the air supply pipe valve and the aeration stopped.

[0049] Subsequently, with the introduction of air (micro-oxygen), a large number of microorganisms in the sidestream reaction system proliferated. Among them, facultative anaerobes could use oxygen as the final electron acceptor for respiration to obtain higher energy, and their proliferation rate was the fastest.

[0050] Subsequently, the dissolved oxygen in the sidestream reaction system was gradually consumed by the microorganisms in the sidestream reaction system, and the ORP value in the sidestream reaction system gradually decreased. When it decreased to -420 mV, the controller controlled the opening of the switch on the air supply pipe 6 to conduct micro-aeration on the sidestream reaction system.

[0051] When the biogas slurry in the sidestream reaction system was transported to the mainstream reaction system by the peristaltic pump 10, the residual reactive oxygen species (ROS) in the biogas slurry were quickly utilized by the microorganisms on the biological anode plate 11, thus avoiding the poisoning of the methanogens in the system by ROS.

[0052] Subsequently, the methanogens in the mainstream reaction system, including the microorganisms on the biological cathode plate 12, efficiently methanated the organic matter in the biogas slurry, and the generated biogas was discharged to the collection device outside the mainstream reaction system through the biogas collection pipe.

[0053] Among them, only when sampling was it necessary to manually turn on the switch of the peristaltic pump 10, and at other times, the sidestream reaction system and the mainstream reaction system each ran automatically.

[0054] After the mainstream reaction system operates stably, the pH value in the mainstream reaction system does not decrease significantly with the operation of the system, which can increase the sample injection volume, thereby shortening the SRT and achieving more efficient food waste treatment efficiency.

[0055] The anaerobic digestion and digestion system adopting the method of this embodiment is compared with the anaerobic digestion system (comparative example) adopting conventional introduction of a microbial electrolytic cell or / and micro-aeration. Under the same micro-aeration volume and the same voltage intensity, the maximum values of dissolved organic matter protein and dissolved polysaccharide in the embodiment are both increased by more than 20% compared with the comparative example, and the hydrolysis efficiency is greatly improved; the sludge retention time can be shortened by 30% compared with the comparative example; the maximum daily methane production in the example is 350 mL / g VS, while that in the comparative example is only 278 mL / g VS, an increase of more than 25%, and the methane content is also increased from 68% to 75%, which fully illustrates the substantial technical effects of the technical solution of this embodiment.

[0056] The above description of the embodiments is for the convenience of those of ordinary skill in the art to understand and use the invention. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative labor. Therefore, the present invention is not limited to the above embodiments, and the improvements and modifications made by those skilled in the art without departing from the scope of the present invention according to the disclosure of the present invention should be within the protection scope of the present invention.

Claims

1. A side-stream micro-aeration coupled with main-stream electro-driven anaerobic digestion method, characterized in that, It includes the following steps: S1. After the organic waste is pretreated, it enters the side-stream reaction system. Aeration gas is introduced through the aeration device, and the ORP is feedback-regulated to anaerobically ferment the organic waste under micro-aerobic or facultative anaerobic conditions to obtain a mixed liquid and a mixed gas; S2. The mixed gas obtained in step S1 enters the collection device or the gas disturbance system. The mixed liquid obtained in step S1 is pre-stirred by the gas disturbance system to obtain a pre-stirred mixed liquid and then enters the main-stream reaction system; S3. The main-stream reaction system eliminates the residual free radicals in the pre-stirred mixed liquid obtained in step S2 and promotes its digestion to produce methane through the layout of functional electrode plates and the introduction of micro-voltage; The volume ratio of the effective reaction areas of the side-stream reaction system and the main-stream reaction system is 1:1 - 1:5; The side walls of the side-stream reaction system and the main-stream reaction system are connected by a conduit and a peristaltic pump (10). The biogas slurry in the side-stream reaction system is transported to the main-stream reaction system through the peristaltic pump (10). The biogas slurry enters the main-stream reaction system in a side-stream manner, and at the same time, 100 mL of sludge is discharged in the main-stream reaction system; The main-stream reaction system includes a second reactor tank body, a second stirring motor, a second stirring paddle, a second electric heating rod, a biological anode plate (11) and a biological cathode plate (12); the second stirring paddle penetrates the second reactor tank body; the output end of the second stirring motor is connected to the second stirring paddle to drive the second stirring paddle to rotate; the second electric heating rod penetrates the second reactor tank body; the second discharge port and the second biogas collection pipe are both arranged on the second reactor tank body; the biological anode plate (11) and the biological cathode plate (12) are annular electrode plates, and their arrangement method is vertical interval distribution and they are fixed on the wall of the main-stream reaction system; the biological anode plate (11) and the biological cathode plate (12) are arranged at upper and lower intervals and are connected in series by two vertically arranged wires. The two vertically arranged wires are respectively connected to the positive and negative poles of an external DC power supply, thereby realizing the removal of the residual oxidizing substances in the side-stream biogas slurry to protect the methanogens in the main stream and also realizing the methanation of the hydrolysis and acidification products.

2. The anaerobic digestion method coupling side-stream micro-aeration and mainstream electro-driving according to claim 1, wherein In step S1, the pretreatment of the organic waste includes adjusting the pH to 6.0 - 8.

0.

3. The anaerobic digestion method of side-stream micro-aeration coupled with mainstream electric drive according to claim 1, characterized in that, In step S1, the aeration gas is air or oxygen; The gas flow rate of the aeration gas is 0.01 mL / min - 100 mL / min.

4. The anaerobic digestion method of coupling side-stream micro-aeration with mainstream electric drive according to claim 1, characterized in that In step S1, the ORP regulation range is -350 mV - 100 mV.

5. The anaerobic digestion method coupling side-stream micro-aeration with mainstream electric drive according to claim 1, wherein, The components of the mixed gas obtained in step S1 include nitrogen, carbon dioxide and hydrogen.

6. The anaerobic digestion method coupling side-stream micro-aeration with mainstream electric drive according to claim 5, characterized in that, The oxygen concentration in the mixed gas obtained in step S1 does not exceed 10%, and the methane concentration does not exceed 20%.

7. The anaerobic digestion method of side-stream micro-aeration coupled with mainstream electric drive according to claim 1, characterized in that, In step S2, the gas flow rate of the pre-stirring by the gas disturbance system is 0.01 mL / min - 50 mL / min, and the time is 0.5 h - 5 h.

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