A device and process for enhancing degradation of agricultural waste based on intermittent aeration coupled with carbon quantum dots

Abstract

The application discloses a device and a process for reinforcing degradation of agricultural waste based on intermittent aeration coupling carbon quantum dots, and belongs to the technical field of anaerobic fermentation. The device mainly comprises a feeding pool, a gas collecting device, a heat preservation layer, an anaerobic reactor, an intermittent aeration device and a discharge pool. The treatment process is as follows: livestock and poultry manure is put into the feeding pool, inoculated sludge and carbon quantum dots are added, and after being uniformly stirred, the mixture is pumped into the anaerobic reactor, intermittent aeration is carried out in the anaerobic reactor through the aeration device, the temperature in the anaerobic reactor is controlled to be 30-37 DEG C, the pH is controlled to be 7-8, and the hydraulic retention time is controlled to be 25-35 days; an exhaust valve is opened, and biogas generated is collected; a discharge valve is opened, and a certain volume of fermentation products is discharged into the discharge pool. Micro-aeration is used to provide growth of facultative bacteria and to produce more cellulase and protease hydrolysis enzymes, so that higher hydrolysis efficiency is achieved. The carbon quantum dots are used to enrich methanogenic electroactive bacteria, reinforce degradation of cow manure and improve methanogenic efficiency.

Description

Technical Field

[0001] This invention belongs to the field of anaerobic fermentation technology, specifically relating to a device and process for promoting the treatment of agricultural waste based on intermittent aeration coupled with carbon quantum dots to enhance biological advanced oxidation. Background Technology

[0002] With the rapid development of my country's economy and society and the improvement of people's living standards, the demand for meat, eggs, and dairy products is constantly increasing. my country is a major agricultural country, and animal husbandry, as a crucial component of its largest industry, provides vital support for economic development. China's annual livestock and poultry manure production is approximately 3.8 billion tons, of which cow manure accounts for about 45.3% of the total. Cow manure is mainly composed of cellulose. my country's animal husbandry industry is developing rapidly. However, untreated livestock and poultry waste, washed into water bodies by rainwater, leads to eutrophication. Direct irrigation of farmland with untreated livestock and poultry waste easily causes soil compaction, and the accumulation of harmful pollutants in the soil seriously affects crop growth. However, if this abundant livestock and poultry manure can be further treated and utilized using advanced technologies, it can not only solve environmental pollution problems but also conform to the sustainable development policy of resource recycling.

[0003] Because livestock and poultry manure contains a large number of substances that are difficult for microorganisms to degrade, such as lignin, cellulose, and hemicellulose, which all have hard crystalline structures, enzyme molecules and water molecules have difficulty penetrating them to hydrolyze them, thus limiting the subsequent methanation process and reducing the treatment efficiency of livestock and poultry manure. By creating a microaerobic environment through micro-aeration in the anaerobic digestion system, some bacteria capable of extracellular respiration can produce reactive oxygen species (ROS) using O2 as the electron acceptor for extracellular respiration. ROS have high oxidizing properties and can accelerate the decomposition of recalcitrant substances such as lignin and hemicellulose. Micro-aeration can also promote the growth of some facultative bacteria, thereby secreting more hydrolytic enzymes and accelerating the decomposition of some recalcitrant substances.

[0004] Carbon quantum dots have been proven to be a zero-dimensional carbon nanomaterial with electron accepting and transporting capabilities. Therefore, they can accelerate electron transport efficiency and enhance interspecies electron transport (DIET) in anaerobic systems. Furthermore, carbon quantum dots can effectively enrich electroactive bacteria in anaerobic systems, thereby enhancing DIET and avoiding the hydrogen partial pressure inhibition and thermodynamic limitations that occur when hydrogen and formic acid are used as electron acceptors. This accelerates electron transport efficiency and the methanogenesis process.

[0005] However, to date, no research has been reported on enhancing biological advanced oxidation through intermittent aeration coupled with carbon quantum dots to improve agricultural waste treatment efficiency and methane production. Summary of the Invention

[0006] Therefore, the purpose of this invention is to provide a device and process for enhancing the degradation of agricultural waste based on intermittent aeration coupled with carbon quantum dots. By adding carbon quantum dots and performing micro-aeration during the anaerobic digestion of agricultural waste, the rate and efficiency of interspecific electron transfer in the anaerobic system of agricultural waste are accelerated, thereby improving the efficiency and stability of the anaerobic reactor, enhancing the degradation of high organic waste such as livestock and poultry manure, and promoting the efficient methanogenesis process of the anaerobic system.

[0007] The objective of this invention is achieved through the following means:

[0008] This invention provides a device for enhancing the degradation of cow manure based on intermittent aeration coupled with carbon quantum dots. The device mainly includes a feeding tank 1, a gas collection device 4, a heat insulation layer 10, an anaerobic reactor 11, an intermittent aeration device 12, and a discharge tank 14. The anaerobic reactor 11 is filled with a mixture of carbon quantum dots and cow manure 15. The feeding tank 1 is connected to the top of the side wall of the anaerobic reactor 11 through a pipe. The top 6 of the anaerobic reactor is connected to the gas collection device 4 through a pipe to collect the biogas produced by the anaerobic reactor 11. The intermittent aeration device 12 is connected to the bottom of the anaerobic reactor 11 through a pipe, and the pipe extends into the inner bottom of the anaerobic reactor 11 and is connected to a gas distributor. A constant temperature layer 10 is provided on the outer wall of the anaerobic reactor 11, and the bottom of the side wall of the anaerobic reactor 11 is connected to the discharge tank 14 through a pipe.

[0009] Based on the above technical solution, a feed pump 2 and a feed valve 3 are further provided on the pipeline between the feed tank 1 and the anaerobic reactor 11.

[0010] Based on the above technical solution, an exhaust valve 5 is further provided on the pipe connecting the top 6 of the anaerobic reactor to the gas collection device 4.

[0011] Based on the above technical solution, further, the outlet of the constant temperature layer 10 is connected to the inlet of the water bath 9 through a pipe, and the outlet of the water bath 9 is connected to the inlet of the constant temperature layer 10 through a pipe. The outlet of the constant temperature layer 10 is located at the top of the side wall of the anaerobic reactor 11, and the inlet of the constant temperature layer 10 is located at the bottom of the side wall of the anaerobic reactor 11. A water outlet valve 16 is installed on the pipe connecting the outlet of the constant temperature layer 10 to the inlet of the water bath 9, and a peristaltic pump 7 and an inlet valve 8 are installed on the pipe connecting the outlet of the water bath 9 to the inlet of the constant temperature layer 10.

[0012] Based on the above technical solution, a discharge valve 13 is further provided on the pipe connecting the anaerobic reactor 11 and the discharge tank 14.

[0013] Based on the above technical solution, the synthesis process of carbon quantum dots is as follows: citric acid is dissolved in ultrapure water at a concentration of 1-10 g / mL, transferred to a hydrothermal synthesis reactor made of polytetrafluoroethylene, and kept at 170-190℃ for 4-6 h. After cooling to room temperature, the reaction solution is filtered through a 0.22 μm filter membrane, then filtered through a 500D dialysis bag, and then freeze-dried under vacuum to obtain carbon quantum dots.

[0014] The present invention also provides a process for enhancing the degradation of livestock and poultry manure by intermittent aeration coupled with carbon quantum dots using the above-described device, comprising the following steps:

[0015] 1) Mix the livestock and poultry manure thoroughly and put it into the feeding tank 1. Add the seed sludge and carbon quantum dots and mix well.

[0016] 2) Open the feed pump 2 and feed valve 3, and pump the mixture obtained in step 1) into the anaerobic reactor 11 through the pipeline;

[0017] 3) Turn on the aeration device 12 and intermittently aerate the anaerobic reactor 11 through the gas distributor;

[0018] 4) Control the temperature inside the anaerobic reactor 11 to 30-37℃ and the pH to 7-8;

[0019] 5) Control the hydraulic retention time of anaerobic reactor 11 to be between 25 and 35 days;

[0020] 6) Open the exhaust valve 5, and the biogas produced by the anaerobic reactor 11 is collected through the gas collection device 4;

[0021] 7) Open the discharge valve 13 and discharge a certain volume of fermentation products from the anaerobic reactor into the discharge tank 14 through the pipeline.

[0022] Based on the above technical solution, further, in step 1), the solid content of livestock and poultry manure is controlled at 14% to 17%, the VSS of the introduced sludge is 20 to 30 g / L, preferably 25 g / L; the volume ratio of livestock and poultry manure to introduced sludge is 1 / 20 to 1 / 60.

[0023] Based on the above technical solution, further, the livestock and poultry manure mentioned in step 1) includes cow manure.

[0024] Based on the above technical solution, further, the amount of carbon quantum dots added in step 1) is 0.05 to 0.5 g / L.

[0025] Based on the above technical solution, further, the aeration rate of intermittent aeration in step 3) is 2-20 ml / (L·h), and aeration is carried out for 12 hours per day.

[0026] Based on the above technical solution, further, in step 4), the temperature inside the anaerobic reactor 11 is controlled at 37℃; the pH value is controlled at 7.8; and in step 5), the hydraulic retention time of the anaerobic reactor 11 is controlled at 30 days.

[0027] The advantages of this invention over the prior art are as follows:

[0028] The device for enhancing cow manure degradation based on intermittent aeration coupled with carbon quantum dots of the present invention utilizes intermittent aeration to effectively increase the function of some bacterial communities, secrete more hydrolytic enzymes, and enhance the hydrolysis of cow manure; carbon quantum dots can effectively accept and transfer electrons and are biocompatible with bacteria, thus fully accelerating electron transfer; in addition, it can effectively enrich electroactive bacterial communities, improve the rate and efficiency of direct electron transfer between microorganisms in the anaerobic reactor system, thereby improving the efficiency and stability of the anaerobic reactor, enhancing the degradation of high-organic-content wastes such as cow manure, and promoting the efficient methanogenesis process of the anaerobic system. Attached Figure Description

[0029] To more clearly illustrate the embodiments of the present invention, the accompanying drawings involved in the embodiments will be briefly described below.

[0030] Figure 1 This is a schematic diagram of the device for intermittent aeration coupled with carbon quantum dots to enhance the anaerobic degradation of cow manure according to the present invention, wherein: 1-feeding tank, 2-feeding pump, 3-feeding valve, 4-gas collection device, 5-exhaust valve, 6-top of anaerobic reactor, 7-peristaltic pump, 8-water inlet valve, 9-water bath, 10-constant temperature layer, 11-anaerobic reactor, 12-intermittent aeration device, 13-discharge valve, 14-discharge tank, 15-mixture of carbon quantum dots and cow manure, 16-water outlet valve. Detailed Implementation

[0031] The present invention will be described in detail below with reference to the embodiments. However, the implementation of the present invention is not limited thereto. Obviously, the embodiments described below are only some embodiments of the present invention. For those skilled in the art, other similar embodiments can be obtained without creative effort and all fall within the protection scope of the present invention.

[0032] Example 1

[0033] This embodiment provides a device for enhancing the degradation of cow manure based on intermittent aeration coupled with carbon quantum dots, as shown in the attached diagram. Figure 1The device mainly includes a feed tank 1, a gas collection device 4, an insulation layer 10, an anaerobic reactor 11, an intermittent aeration device 12, and a discharge tank 14. The anaerobic reactor 11 is filled with carbon quantum dots (the synthesis process of carbon quantum dots is as follows: 0.25g of citric acid is dissolved in 10ml of ultrapure water, and then the dissolved solution is transferred to the lining of a hydrothermal synthesis reactor made of polytetrafluoroethylene. The reactor is then placed in a vacuum drying oven and heated at a constant temperature of 180℃ for 5 hours until the reaction proceeds). After the reaction is completed, the reactor is cooled to room temperature. The reaction solution is filtered through a 0.22 μm filter membrane, then filtered through a 500D dialysis bag for 12 hours, and then dried in a vacuum freeze dryer for 12 hours to obtain a mixture of carbon quantum dots and cow dung 15. The feed tank 1 is connected to the top of the side wall of the anaerobic reactor 11 through a pipe. A feed pump 2 and a feed valve 3 are installed on the pipe between the feed tank 1 and the anaerobic reactor 11. The top 6 of the anaerobic reactor is connected to a gas collection device 4 through a pipe to collect the gas from the anaerobic reactor 1. The biogas produced is connected to the top of the anaerobic reactor 11 by a pipe connected to the gas collection device 4, which is equipped with an exhaust valve 5. An intermittent aeration device 12 is connected to the bottom of the anaerobic reactor 11 via a pipe, and the pipe extends into the inner bottom of the anaerobic reactor 11 and connects to a gas distributor. A constant temperature layer 10 is installed on the outer wall of the anaerobic reactor 11. The outlet of the constant temperature layer 10 is connected to the inlet of the water bath 9 via a pipe, and the outlet of the water bath 9 is connected to the inlet of the constant temperature layer 10 via a pipe. The outlet of the anaerobic reactor 10 is located at the top of the side wall of the anaerobic reactor 11, and the inlet of the constant temperature layer 10 is located at the bottom of the side wall of the anaerobic reactor 11. A water outlet valve 16 is installed on the pipe connecting the outlet of the constant temperature layer 10 to the inlet of the water bath 9. A peristaltic pump 7 and an inlet valve 8 are installed on the pipe connecting the outlet of the water bath 9 to the inlet of the constant temperature layer 10. The bottom of the side wall of the anaerobic reactor 11 is connected to the discharge tank 14 through a pipe. A discharge valve 13 is installed on the pipe connecting the anaerobic reactor 11 and the discharge tank 14.

[0034] The working mechanism of this device based on intermittent aeration coupled with carbon quantum dots to enhance the anaerobic degradation of cow manure is as follows:

[0035] 1. Microbial interspecies electron transfer is a novel mechanism for interspecies electron exchange in microorganisms. It does not require reducing molecules such as hydrogen and formic acid; free electrons are directly transferred from one cell to another, reducing CO2 to CH4. In this microbial metabolic pathway, fatty acids or ethanol can directly produce methane and carbon dioxide through inter-aerobic metabolism.

[0036] 2. Intermittent aeration can provide a small amount of oxygen to the anaerobic tank, which can enhance the anaerobic hydrolysis stage. On the one hand, intermittent aeration can promote the growth of some facultative bacteria, secrete more cellulase and proteolytic enzymes, and accelerate the decomposition of difficult-to-decompose substances. On the other hand, intermittent aeration can reduce the total VFA concentration in the system, thereby reducing the inhibitory effect on methanogens.

[0037] 3. Carbon quantum dots are a zero-dimensional carbon nanomaterial that has been proven to be effective as a medium for electron acceptance and transfer. They can effectively contact microorganisms to accelerate the efficiency and rate of electron transfer. On the other hand, carbon quantum dots can effectively enrich electroactive bacteria and improve the efficiency and rate of electron transfer between interspecies microorganisms in anaerobic reactors, thereby effectively improving the stability and high load capacity of anaerobic reactors.

[0038] Example 2

[0039] This embodiment provides a process for enhancing the degradation of cow manure using the device in Embodiment 1. The specific process is as follows: Cow manure is mixed using a mixer, and the solid content of the treated cow manure is 15.34%. An anaerobic digestion reactor with an effective volume of 2L is used. Cow manure and sludge (anaerobic sludge taken from the anaerobic fermentation tank of a large-scale cow manure anaerobic treatment plant, with a VSS of 25g / L) are mixed at a volume ratio of 1:30. At the same time, carbon quantum dots are added at a concentration of 0.1g / L. After being mixed evenly in the feed tank 1, the mixture is pumped into the anaerobic reactor 11. The internal temperature of the reactor is maintained at 37℃, the pH is 7.8, the hydraulic retention time is 30 days, the aeration rate of the intermittent aeration device is 10ml / h, and the aeration time is 12h per day.

[0040] After the experiment, the cumulative methane production in the experimental group was 2066.08±8.96 ml. The removal rates of TS and VS in the experimental group reached 41.56% and 52.79% respectively, which were 6.49% and 7.65% higher than those in the blank group.

[0041] Comparative Example 1

[0042] The blank experimental group also used an anaerobic digester with an effective volume of 2L. Cow manure and introduced sludge were mixed at a volume ratio of 1:30. The difference from the experimental group was that carbon quantum dots were not added. After being thoroughly mixed in feed tank 1, the mixture was pumped into anaerobic reactor 11. The reactor internal temperature was maintained at 37℃, pH at 7.8, hydraulic retention time at 30 days, and the intermittent aeration device aeration rate of 10ml / h for 12 hours per day.

[0043] After the experiment, the cumulative methane production in the blank test group was 1768±9.28 ml, and the TS and VS removal rates in the blank test group were 35.07% and 45.14%, respectively.

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, and not to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some or all of the technical features therein. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for enhancing the degradation of livestock and poultry manure using an apparatus that couples carbon quantum dots with intermittent aeration, characterized in that, The device mainly includes a feeding tank (1), a gas collection device (4), a constant temperature layer (10), an anaerobic reactor (11), an intermittent aeration device (12), and a discharge tank (14). The anaerobic reactor (11) is filled with a mixture of carbon quantum dots and cow manure (15). The feeding tank (1) is connected to the top of the side wall of the anaerobic reactor (11) through a pipe. The top (6) of the anaerobic reactor is connected to the gas collection device (4) through a pipe to collect the biogas produced by the anaerobic reactor (11). The intermittent aeration device (12) is connected to the bottom of the anaerobic reactor (11) through a pipe, and the pipe extends into the bottom of the anaerobic reactor (11) and is connected to the gas distributor. A constant temperature layer (10) is provided on the outer wall of the anaerobic reactor (11). The bottom of the side wall of the anaerobic reactor (11) is connected to the discharge tank (14) through a pipe. Includes the following steps: 1) Mix the livestock and poultry manure evenly and put it into the feeding tank (1). Add the introduced sludge and carbon quantum dots and mix evenly. 2) Open the feed pump (2) and feed valve (3) to pump the mixture obtained in step 1) into the anaerobic reactor (11) through the pipeline; 3) Turn on the intermittent aeration device (12) and intermittently aerate the anaerobic reactor (11) through the gas distributor; 4) Control the temperature inside the anaerobic reactor (11) to 30~37℃ and control the pH to 7~8; 5) Control the hydraulic retention time of the anaerobic reactor (11) to be between 25 and 35 days; 6) Open the exhaust valve (5), and the biogas produced by the anaerobic reactor (11) is collected through the gas collection device (4); 7) Open the discharge valve (13) and discharge a certain volume of fermentation products from the anaerobic reactor into the discharge tank (14) through the pipeline. In step 1), the solid content of livestock and poultry manure is controlled at 14%~17%, and the VSS of the introduced sludge is 20~30 g / L; the volume ratio of livestock and poultry manure to introduced sludge is 1 / 20~1 / 60. The aeration rate for intermittent aeration described in step 3) is 2~20 ml / (L·h), and aeration is carried out for 12 hours per day.

2. The process according to claim 1, characterized in that, A feed pump (2) and a feed valve (3) are installed on the pipeline between the feed tank (1) and the anaerobic reactor (11).

3. The process according to claim 1, characterized in that, An exhaust valve (5) is installed on the pipe connecting the top (6) of the anaerobic reactor to the gas collection device (4).

4. The process according to claim 1, characterized in that, The outlet of the constant temperature layer (10) is connected to the inlet of the water bath (9) through a pipe, and the outlet of the water bath (9) is connected to the inlet of the constant temperature layer (10) through a pipe. The outlet of the constant temperature layer (10) is located at the top of the side wall of the anaerobic reactor (11), and the inlet of the constant temperature layer (10) is located at the bottom of the side wall of the anaerobic reactor (11). A water outlet valve (16) is installed on the pipe connecting the outlet of the constant temperature layer (10) to the inlet of the water bath (9), and a peristaltic pump (7) and an inlet valve (8) are installed on the pipe connecting the outlet of the water bath (9) to the inlet of the constant temperature layer (10).

5. The process according to claim 1, characterized in that, A discharge valve (13) is installed on the pipe connecting the anaerobic reactor (11) and the discharge tank (14).

6. The process according to claim 1, characterized in that, The VSS of the introduced sludge mentioned in step 1) is 25 g / L.

7. The process according to claim 1, characterized in that, The livestock and poultry manure mentioned in step 1) includes cow manure; the amount of carbon quantum dots added is 0.05~0.5g / L.

8. The process according to claim 1, characterized in that, In step 4), the temperature inside the anaerobic reactor (11) is controlled at 37℃; the pH value is controlled at 7.8; and in step 5), the hydraulic retention time of the anaerobic reactor (11) is controlled at 30 days.

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