A device and process for enhancing magnetite degradation of organic matter based on intermittent aeration

Abstract

The present invention discloses a device and process for enhancing the degradation of organic matter by magnetite based on intermittent aeration, and belongs to the technical field of anaerobic fermentation. The device for enhancing the degradation of organic matter by magnetite based on intermittent aeration of the present invention comprises a feed tank, a water bath insulation layer, an anaerobic digestion reactor, a motor, a gas collection device, a water outlet tank and an intermittent aeration device. The wastewater of macromolecular toxic organic matter is used as a substrate, and anaerobic digestion is enhanced by intermittent aeration and the addition of magnetite. The present invention drives Fe(III) / Fe(II) of the anaerobic digestion system by intermittent aeration, promotes continuous dissimilatory iron reduction, enriches electroactive bacteria, and constructs a new methanogenic pathway of direct electron transfer; aeration produces free radicals, accelerates the degradation of macromolecular organic matter, provides more substrates for methanogenesis, and finally promotes the methanogenesis process. The present invention can effectively treat macromolecular toxic organic pollutants and solve the problem of low methanogenesis efficiency.

Description

Technical Field

[0001] The invention belongs to the technical field of anaerobic fermentation, and in particular relates to a device and a process for degrading organic matter through magnetite based on intermittent aeration. Background Art

[0002] With the rapid development of my country's economy and society, water pollution and related problems in its governance process have become increasingly prominent. According to the "China Ecological Environment Statistical Yearbook" released by the Ministry of Ecology and Environment, although COD emissions from industrial sources have dropped significantly in recent years under the background of vigorously promoting green, low-carbon and circular development, total COD emissions remain high. The water pollution problem facing my country remains severe. Anaerobic digestion is one of the most realistic and effective methods to reduce and recycle medium and high concentration organic wastewater. However, due to the relatively complex anaerobic digestion process, there are many types of microorganisms involved in the process, and the main microorganisms (such as methanogens) are environmentally sensitive microorganisms. Due to the rate limitation of hydrolysis of complex organic matter, the traditional anaerobic digestion of methane production has low efficiency. Therefore, how to maintain the stability and long-term operation of anaerobic digestion and develop efficient anaerobic processes have always been the most concerned issues for researchers. Summary of the invention

[0003] In order to solve the problems of difficulty in anaerobic digestion and hydrolysis of macromolecular organic matter and low methane production efficiency, the purpose of the present invention is to provide a device and process for enhancing the degradation of organic matter by magnetite based on intermittent aeration. The present invention uses intermittent aeration to promote Fe(III) / Fe(II) in the anaerobic system and generate free radicals, accelerate the degradation of macromolecular organic matter, thereby improving the efficiency and stability of the anaerobic reactor, and promoting the methane production process of the anaerobic system.

[0004] The object of the present invention is achieved by the following methods:

[0005] The present invention provides a device for degrading organic matter by strengthening magnetite based on intermittent aeration, comprising a feed tank 1, a water bath insulation layer 4, an anaerobic digestion reactor 7, a motor 10, a gas collection device 13, a water outlet tank 19 and an intermittent aeration device, wherein the water bath insulation layer 4 is arranged on the outer wall of the anaerobic digestion reactor 7, a cover plate 8 is sealed and connected above the anaerobic digestion reactor 7, a motor 10 is arranged on the top of the cover plate 8, a rotating shaft 9 is fixedly connected to the shaft of the motor 10, the rotating shaft 9 penetrates the cover plate 8 and vertically extends into the interior of the anaerobic digestion reactor 7, a rotating sealing component is arranged between the rotating shaft 9 and the through hole on the cover plate 8, and a blade 6 is arranged on the rotating shaft 9 extending into the interior of the anaerobic digestion reactor 7; the pores on the cover plate 8 are connected to the gas collection device 13 through a pipe II 12; magnetite 5 is uniformly distributed inside the anaerobic digestion reactor 7; the outlet connected to the bottom side wall of the anaerobic digestion reactor 7 is connected to the discharge tank 19 through a pipe IV 17, and the feed tank 1 is connected to the discharge tank 19 through a pipe IV 17. 2 is connected to the top of the side wall of the anaerobic digestion reactor 7; the intermittent aeration device includes an air inlet valve 22, an air inlet pump 23, an oxygen bag 24 and a pipe V 21, the oxygen bag 24 is connected to the bottom of the anaerobic digestion reactor 7 through the pipe V 21, and the pipe V 21 is provided with an air inlet valve 22 and an air inlet pump 23.

[0006] Based on the above technical solution, further, the top of the water bath insulation layer 4 is connected to the inlet of the water bath pot 25 through the tube III 15, and the outlet of the water bath pot 25 is connected to the bottom of the water bath insulation layer 4 through the tube VI 28. The tube III 15 is provided with a water outlet valve 14, and the tube VI 28 is provided with a water inlet valve 26 and a peristaltic pump 27.

[0007] Based on the above technical solution, further, a reactor base 20 is provided at the bottom of the anaerobic digestion reactor 7 .

[0008] Based on the above technical solution, further, a feed valve 3 is provided on the tube I 2, and an exhaust valve 11 is provided on the tube II 12.

[0009] Based on the above technical solution, further, a discharge valve 16 and a discharge pump 18 are provided on the pipe IV 17 .

[0010] The present invention also provides a process for degrading organic matter using the above-mentioned device, comprising the following steps:

[0011] 1) The wastewater to be treated is transported into the feed tank 1 after nitrogen blowing for 10-30 minutes, the feed valve 3 is opened, and the wastewater enters the anaerobic digestion reactor 7 through the pipe 1;

[0012] 2) taking anaerobic sludge, the TSS of the anaerobic sludge is 55-65 g / L, using 20-40% of the volume of the sludge to start the anaerobic digestion reactor 7, and placing magnetite into the anaerobic digestion reactor 7 along with the anaerobic sludge, with the dosage of 20-40 mM;

[0013] 3) The motor 10 controls the rotating shaft 9 to drive the blades 6 to rotate for stirring, stirring for 5 to 10 minutes per hour, and the rotating shaft speed is set to 40 to 60 rpm, so that the magnetite is evenly distributed in the anaerobic reactor sludge;

[0014] 4) The temperature inside the anaerobic digestion reactor 7 is controlled at 35-40° C., the pH value is controlled at 7.5-8.2, and the hydraulic retention time is controlled at 28-32 hours;

[0015] 5) Control the oxygen aeration volume to 0.02-0.10mL / (L·min), and aerate for 20-40min every 2-4h to achieve intermittent aeration;

[0016] 6) Open the exhaust valve 11, and collect the biogas generated by the anaerobic digestion reactor 7 through the gas collection device 13;

[0017] 7) Open the discharge valve 16 and discharge the fermentation product from the anaerobic digestion reactor 7 into the discharge tank 19 through the pipe IV 17.

[0018] Based on the above technical solution, further, the COD of the wastewater in step 1) is 2500-7500 mg / L, and the phenol concentration is 500-3000 mg / L.

[0019] Based on the above technical solution, further, in step 2), the TSS of the anaerobic sludge is 60 g / L, and the dosage of magnetite is 30 mM.

[0020] Based on the above technical solution, further, in step 3), stirring is performed for 10 minutes per hour, and the rotation speed of the rotating shaft is set to 50 rpm.

[0021] Based on the above technical solution, further, in step 4), the temperature inside the anaerobic digestion reactor 7 is 37°C; the value is 7.8, and the hydraulic retention time is 30h.

[0022] Based on the above technical solution, further, in step 5), the oxygen aeration volume is controlled to be 0.06 mL / (L·min), and aeration is performed for 30 min every 3 h.

[0023] The beneficial effects of the present invention compared with the prior art are as follows:

[0024] 1. Traditionally, oxygen or air exposure should be avoided as much as possible in AD systems to reduce their negative effects on anaerobic microorganisms. The device of the present invention uses intermittent aeration, and part of the Fe(II) in the anaerobic digestion reactor will be oxidized to Fe(III); when Fe(II) and O2 coexist at a neutral pH, Fe(II) is easily chemically oxidized by O2. During the oxidation of Fe(II) by O2, secondary oxidants ( . O2- , H2O2 and . OH), which is a reactive oxygen free radical. The precipitated Fe(III) (hydroxide) can serve as a surface catalyst for further Fe(II) oxidation. Therefore, the introduction of trace amounts of O2 in the anaerobic digestion system can promote Fe(III) / Fe(II). In this process, the continuous heterotrophic iron reduction brought about by the generation of Fe(III) will also accelerate the decomposition of organic matter. In addition, the oxidation and reduction of iron will be accompanied by the generation of free radicals, which will attack large molecular organic matter and promote its cracking, which will provide more substrates for methanogens to promote methanogenesis.

[0025] 2. The magnetite added in the present invention can promote the degradation of macromolecular organic matter through dissimilatory iron reduction and enhance the anaerobic methanogenesis performance. In addition, intermittent aeration can oxidize Fe 2+ , promote continuous dissimilatory iron reduction, continuously enrich electroactive microorganisms dominated by dissimilatory iron-reducing bacteria, and construct a new methanogenic pathway. The present invention utilizes intermittent aeration to promote Fe(III) / Fe(II) in the anaerobic system and generate free radicals, accelerate the degradation of macromolecular organic matter, thereby improving the efficiency and stability of the anaerobic reactor, and promoting the methane production process of the anaerobic system. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the embodiments of the present invention, the drawings related to the embodiments are briefly introduced below.

[0027] Figure 1 The present invention is a schematic diagram of the device process for enhancing the degradation of macromolecular organic matter by magnetite based on intermittent aeration, wherein: 1: feed tank, 2: pipe I, 3: feed valve, 4: water bath insulation layer, 5: magnetite, 6: blades, 7: anaerobic digestion reactor, 8: cover plate, 9: rotating shaft, 10: motor, 11: exhaust valve, 12: pipe II, 13: gas collection device, 14: water outlet valve, 15: pipe III, 16: discharge valve, 17: pipe IV, 18: discharge pump, 19: discharge tank, 20: reactor base, 21: pipe V, 22: air inlet valve, 23: air inlet pump, 24: oxygen bag, 25: water bath, 26: water inlet valve, 27: peristaltic pump, 28: pipe VI. DETAILED DESCRIPTION

[0028] The present invention is described in detail below with reference to the embodiments, but the embodiments of the present invention are not limited thereto. Obviously, the embodiments described below are only partial embodiments of the present invention. For those skilled in the art, other similar embodiments obtained without creative labor all fall within the protection scope of the present invention.

[0029] Example 1

[0030] This embodiment provides a device for enhancing the degradation of organic matter by magnetite based on intermittent aeration, such as Figure 1 As shown, it includes a feed tank 1, a water bath insulation layer 4, an anaerobic digestion reactor 7, a motor 10, a gas collection device 13, a water outlet tank 19 and an intermittent aeration device. The water bath insulation layer 4 is arranged on the outer wall of the anaerobic digestion reactor 7, and a reactor base 20 is arranged at the bottom of the anaerobic digestion reactor 7. A cover plate 8 is sealed and connected to the top of the anaerobic digestion reactor 7. The motor 10 is arranged on the top of the cover plate 8. A rotating shaft 9 is fixedly connected to the shaft of the motor 10. The rotating shaft 9 passes through the cover plate 8 and vertically extends into the interior of the anaerobic digestion reactor 7. A rotating sealing component is arranged between the rotating shaft 9 and the through hole on the cover plate 8. A blade 6 is arranged on the rotating shaft 9 extending into the interior of the anaerobic digestion reactor 7; the air hole on the cover plate 8 is connected to the gas collection device 13 through a pipe II 12, and an exhaust valve 11 is arranged on the pipe II 12; magnetite 5 is evenly distributed inside the anaerobic digestion reactor 7; the outlet connected to the bottom side wall of the anaerobic digestion reactor 7 is connected to the discharge tank 19 through a pipe IV 17, and the pipe IV 17 is provided with a discharge valve 16 and a discharge pump 18, the feed tank 1 is connected to the top of the side wall of the anaerobic digestion reactor 7 through the pipe I 2, and the pipe I 2 is provided with a feed valve 3; the top of the water bath insulation layer 4 is connected to the inlet of the water bath pot 25 through the pipe III 15, and the outlet of the water bath pot 25 is connected to the bottom of the water bath insulation layer 4 through the pipe VI 28, the pipe III 15 is provided with a water outlet valve 14, and the pipe VI 28 is provided with a water inlet valve 26 and a peristaltic pump 27; the intermittent aeration device includes an air inlet valve 22, an air inlet pump 23, an oxygen bag 24 and a pipe V 21, the oxygen bag 24 is connected to the bottom of the anaerobic digestion reactor 7 through the pipe V 21, and the pipe V 21 is provided with an air inlet valve 22 and an air inlet pump 23.

[0031] The application mechanism of the above-mentioned device for enhancing the degradation of organic matter by magnetite based on intermittent aeration is:

[0032] 1. Adding magnetite to induce the production of dissimilatory iron reduction in the anaerobic system is beneficial to the degradation of macromolecular organic matter. Through intermittent aeration, the product of dissimilatory iron reduction, Fe 2+ Reoxidized to Fe 3+ , which can promote sustained dissimilatory iron reduction, enrich dissimilatory iron-reducing microorganisms, accelerate extracellular electron transfer, and is beneficial to the construction of direct interspecies electron transfer among microorganisms, which is beneficial to efficient methane production.

[0033] 2. Intermittent aeration in oxidation of Fe 2+ During the process, secondary oxidants ( . O2 - , H2O2 and .OH), that is, active oxygen free radicals, are conducive to the destruction and degradation of macromolecular organic matter. In addition, during intermittent aeration, microorganisms can directly transfer the electrons generated by oxidizing organic matter to molecular oxygen, and can also produce active oxygen free radicals to accelerate the degradation of macromolecular organic matter. It provides more substrates for the methanogenic process and reduces the toxic effects of toxic organic matter.

[0034] Example 2

[0035] This embodiment provides a process for degrading macromolecular organic matter using the above-mentioned device in embodiment 1, comprising the following steps:

[0036] 1) Synthetic wastewater was prepared with glucose and phenol as main substrates, COD was 7500 mg / L, phenol concentration was 2000 mg / L, and the synthetic wastewater entered the feed tank 1 after nitrogen blowing for 20 minutes;

[0037] 2) Open the feed valve 3, and the synthetic wastewater enters the anaerobic digestion reactor 7 through the pipe 1;

[0038] 3) Obtain anaerobic sludge discharged from the anaerobic fermentation tank of the sewage treatment plant, the anaerobic sludge TSS is 60g / L, use 30% of the sludge by volume to start the anaerobic digestion reactor 7, and place magnetite into the anaerobic digestion reactor 7 along with the anaerobic sludge, with a dosage of 30mM;

[0039] 4) The motor 10 controls the rotating shaft 9 to drive the blades 6 to rotate for stirring, stirring for 10 minutes per hour, and the rotating shaft speed is set to 50 rpm, so that the magnetite is evenly distributed in the anaerobic reactor sludge;

[0040] 5) The internal temperature of the anaerobic digestion reactor 7 is controlled at 37°C;

[0041] 6) The pH value in the anaerobic digestion reactor 7 is controlled at 7.8;

[0042] 7) Control the hydraulic retention time of the anaerobic digestion reactor 7 to 30 hours;

[0043] 8) Control the oxygen aeration volume to 0.06 mL / (L·min), and aerate for 30 min every 3 h to achieve intermittent aeration;

[0044] 9) Open the exhaust valve 11, and collect the biogas generated by the anaerobic digestion reactor 7 through the gas collection device 13;

[0045] 10) Open the discharge valve 16 and discharge the fermentation product from the anaerobic digestion reactor 7 into the discharge tank 19 through the pipe IV 17.

[0046] The experimental device operated stably. In the last 20 days, the average daily methane production was 1593.90 mL, the average COD removal rate was 81.92%, and the average phenol removal rate was 71.23%. The methane production increased by 59.47% compared with the comparative example 1, the COD removal rate increased by 27.87%, and the phenol removal rate increased by 41.54%.

[0047] Comparative Example 1

[0048] The operation process of this comparative example is the same as that of Example 2, except that only magnetite is added and no intermittent aeration step is performed.

[0049] The experimental device operated stably. In the last 20 days, the average daily methane production was 999.52 mL, the average COD removal rate was 54.04%, and the phenol removal rate was 29.68%.

[0050] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements 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 degrading organic matter by magnetite based on intermittent aeration, characterized in that: The following steps are involved: 1) The wastewater to be treated is transported into the feed tank after nitrogen blowing for 10-30 min, the feed valve is opened, and the wastewater enters the anaerobic digestion reactor through pipe I; 2) Take anaerobic sludge, the TSS of anaerobic sludge is 55-65 g / L, use 20-40% sludge by volume to start the anaerobic digestion reactor, and put magnetite into the anaerobic digestion reactor with the anaerobic sludge, and the dosage is 20-40 mM; 3) The motor controls the shaft to drive the blades to rotate for stirring, stirring for 5-10 minutes per hour, and the shaft speed is set to 40-60 rpm to evenly distribute the magnetite into the anaerobic reactor sludge; 4) The temperature inside the anaerobic digestion reactor is controlled at 35-40°C, the pH value is controlled between 7.5-8.2, and the hydraulic retention time is controlled between 28-32 h; 5) Control the oxygen aeration volume to 0.02-0.10 mL / (L·min), and aerate for 20-40 min every 2-4 h to achieve intermittent aeration; 6) Open the exhaust valve, and collect the biogas generated by the anaerobic digestion reactor through the gas collection device; 7) Open the discharge valve and discharge the fermentation product from the anaerobic digestion reactor into the discharge tank through pipe IV.

2. The process for degrading organic matter by magnetite based on intermittent aeration enhancement according to claim 1, characterized in that: The COD of the wastewater in step 1) is 2500-7500 mg / L, and the phenol concentration is 500-3000 mg / L.

3. The process according to claim 1, characterized in that In step 2), the TSS of anaerobic sludge is 60 g / L and the dosage of magnetite is 30 mM.

4. The process for degrading organic matter with magnetite by intermittent aeration according to claim 1, characterized in that: In step 3), stirring was performed for 10 min every hour, and the rotation speed of the rotating shaft was set to 50 rpm.

5. The process for degrading organic matter by magnetite based on intermittent aeration enhancement according to claim 1, characterized in that: In step 4), the temperature inside the anaerobic digestion reactor is 37° C., the pH value is 7.8, and the hydraulic retention time is 30 h.

6. The process for degrading organic matter by magnetite based on intermittent aeration enhancement according to claim 1, characterized in that: In step 5), the oxygen aeration rate was controlled at 0.06 mL / (L·min), and aeration was performed for 30 min every 3 h.

7. A device for degrading organic matter by using the process for degrading organic matter with magnetite based on intermittent aeration as claimed in any one of claims 1 to 6, characterized in that: The invention comprises a feed tank, a water bath insulation layer, an anaerobic digestion reactor, a motor, a gas collecting device, a water outlet tank and an intermittent aeration device. The outer wall of the anaerobic digestion reactor is provided with a water bath insulation layer. A cover plate is sealed and connected to the top of the anaerobic digestion reactor. A motor is provided on the top of the cover plate. A rotating shaft is fixedly connected to the shaft of the motor. The rotating shaft passes through the cover plate and vertically extends into the interior of the anaerobic digestion reactor. A rotating sealing component is provided between the rotating shaft and the through hole on the cover plate. A blade is provided on the rotating shaft extending into the interior of the anaerobic digestion reactor. The air holes on the cover plate are connected to the gas collecting device through a pipe II. Magnetite is uniformly distributed inside the anaerobic digestion reactor. The outlet connected to the bottom side wall of the anaerobic digestion reactor is connected to the discharge tank through a pipe IV, and the feed tank is connected to the top of the side wall of the anaerobic digestion reactor through a pipe I. The intermittent aeration device comprises an air inlet valve, an air inlet pump, an oxygen bag and a pipe V. The oxygen bag is connected to the bottom of the anaerobic digestion reactor through the pipe V, and the pipe V is provided with an air inlet valve and an air inlet pump.

8. The device for degrading organic matter according to claim 7, wherein the top of the water bath insulation layer is connected to the inlet of the water bath pot through a pipe III, the outlet of the water bath pot is connected to the bottom of the water bath insulation layer through a pipe VI, a water outlet valve is provided on the pipe III, and a water inlet valve and a peristaltic pump are provided on the pipe VI.

9. The device for degrading organic matter according to claim 7, wherein a reactor base is provided at the bottom of the anaerobic digestion reactor; a feed valve is provided on pipe I, and an exhaust valve is provided on pipe II.

10. The device for degrading organic matter according to claim 7, wherein a discharge valve and a discharge pump are provided on the pipe IV.

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