Zero-energy-consumption method for strengthening anaerobic bacteria treatment of PBAT wastewater

Abstract

The invention discloses a method for treating PBAT wastewater by zero-energy-consumption enhanced anaerobic bacteria, which comprises the following steps: (1) uniformly mixing Fe3O4 and GAC according to a certain mass ratio, so that Fe3O4 powder is uniformly attached to the surface of the GAC to prepare a Fe3O4-coated GAC complexing agent, and adding the Fe3O4-coated GAC complexing agent into an anaerobic reactor filled with PBAT wastewater and anaerobic sludge; and (2) forming a magnetic field environment on the outer side of the anaerobic reactor, and coupling the Fe3O4-coated GAC complexing agent with an exogenous magnetic field to form an endogenous current to strengthen anaerobic bacteria in the anaerobic sludge to treat the PBAT wastewater until COD is not degraded any more. According to the zero-energy-consumption method for strengthening anaerobic bacteria treatment of the PBAT wastewater, no chemical agent needs to be added, the operation cost is low, secondary pollution is avoided, generated fuel gas such as methane can be recycled, secondary economic benefits can be generated, the method has the advantages of being efficient, environmentally friendly and economical, and a new solution is provided for treatment of the PBAT wastewater.

Description

Technical Field

[0001] The present invention relates to a method for treating PBAT wastewater by strengthening anaerobic bacteria with zero energy consumption, belonging to the technical field of PBAT wastewater treatment. Background Art

[0002] Poly(butylene adipate-co-terephthalate) (PBAT), as an important biodegradable plastic, generates a large amount of wastewater with complex components during the production process. Such wastewater usually contains various organic substances such as 1,4-butanediol, cyclopentanone, volatile fatty acids, and tetrahydrofuran, and has characteristics such as low pH value, high concentration of refractory organic substances, and strong microbial toxicity. It belongs to typical toxic and refractory industrial wastewater, and its effective treatment is a technical problem faced in the current wastewater treatment field.

[0003] Anaerobic biological treatment technology is a common method for treating high-concentration organic wastewater. However, when conventional anaerobic technology is directly applied to the treatment of PBAT wastewater, the inherent low pH and high-concentration toxic organic substances in the wastewater will have a significant inhibitory or even toxic effect on anaerobic microorganisms, especially methanogenic archaea that are sensitive to pH and toxicity. In addition, in the complex organic matter degradation chain, the low efficiency of interspecies electron transfer (IET) between bacteria and archaea is also a key factor restricting the treatment efficiency. These factors together result in poor treatment effects of existing anaerobic treatment processes on PBAT wastewater, manifested as low chemical oxygen demand (COD) removal rate and low methane production.

[0004] To improve the anaerobic digestion efficiency, existing technologies have proposed to promote the cooperative metabolism between microorganisms by strengthening direct interspecies electron transfer (DIET). Reported ways to strengthen DIET include using the conductive structures possessed by microorganisms themselves (such as extracellular conductive nanowires / pili, cytochrome c, etc.) or adding conductive materials (such as biochar, carbon nanotubes, graphene, etc.) to the system as electron transfer mediators.

[0005] However, the above methods for strengthening DIET have limitations. The method relying on the structure of microorganisms themselves is limited by the presence and physiological state of specific microorganisms, and the stability is poor. For the method of adding conventional conductive materials, its strengthening effect largely depends on the physical contact efficiency and stability between the conductive materials and microorganisms, and it is difficult to ensure continuous and efficient electron transfer in the complex anaerobic reactor flow pattern and biological environment.

[0006] Therefore, the existing technology still lacks an effective method that can stably and efficiently enhance interspecies electron transfer in the anaerobic system, especially for the treatment efficiency of toxic and refractory wastewater such as PBAT. There is an urgent need to develop new technical means to overcome the deficiencies of existing anaerobic treatment and DIET enhancement technologies in order to effectively treat such wastewater. Summary of the Invention

[0007] In view of the problems existing in the above-mentioned prior art, the present invention provides a method for enhancing the treatment of PBAT wastewater by anaerobic bacteria with zero energy consumption, which enhances the treatment effect of PBAT wastewater by improving the direct interspecies electron efficiency among anaerobic microorganisms.

[0008] In order to achieve the above object, a method for enhancing the treatment of PBAT wastewater by anaerobic bacteria with zero energy consumption adopted by the present invention includes the following steps:

[0009] (1) Mix Fe3O4 and GAC evenly according to a certain mass ratio so that the Fe3O4 powder is evenly attached to the surface of GAC to make the Fe3O4@GAC composite agent, and then add it to the anaerobic reactor filled with PBAT wastewater and anaerobic sludge;

[0010] (2) Form a magnetic field environment outside the anaerobic reactor, and the Fe3O4@GAC composite agent couples with the external magnetic field to form an endogenous current to enhance the treatment of PBAT wastewater by anaerobic bacteria in the anaerobic sludge until the COD no longer degrades.

[0011] Preferably, in step (1), the mass ratio of Fe3O4 to GAC is 1:1 - 1:4.

[0012] Preferably, the particle size of Fe3O4 is 20nm - 10um, and the particle size of GAC is 0.5mm - 5.0mm.

[0013] Preferably, in step (1), the COD concentration of the PBAT wastewater is 5000 - 15000mg / L, and the temperature is 20°C - 55°C.

[0014] Preferably, calculated by COD, the mass ratio of the Fe3O4@GAC composite agent to the PBAT wastewater in step (1) is 1:1 - 1:10.

[0015] Preferably, calculated by COD, the mass ratio of the anaerobic sludge to the PBAT wastewater is 5:1 - 1:5.

[0016] Preferably, the MLVSS of the anaerobic sludge is 5 - 50g / L.

[0017] Preferably, a circulation system is also connected to the anaerobic reactor;

[0018] The circulation system includes a circulation pipeline, a peristaltic circulation pump installed on the circulation pipeline, and a sludge-blocking grid. The two ends of the circulation pipeline are respectively connected to the anaerobic reactor. The sludge-blocking grid is installed at the connection between the circulation pipeline and the anaerobic reactor. The aperture of the sludge-blocking grid is 5-10 mm (the aperture of the grid is larger than the particle size of Fe3O4@GAC and smaller than the particle size of granular sludge), which is used to retain anaerobic sludge in the anaerobic reactor. The peristaltic circulation pump is used to drive the PBAT wastewater and the Fe3O4@GAC composite agent to flow in the circulation pipeline.

[0019] In a preferred embodiment, the magnetic field environment in step (2) is formed by cooperating multiple magnet blocks placed on both sides of the anaerobic reactor.

[0020] In a preferred embodiment, the magnetic field intensity of the magnetic field environment is 5 mT - 50 mT.

[0021] The present invention realizes the efficient degradation of PBAT wastewater and energy recovery through the following mechanisms:

[0022] (1) Generation of endogenous current: Fe3O4 acts as an electron shuttle and cuts the magnetic induction line in the magnetic field to generate a stable and controllable endogenous current.

[0023] (2) Biological enrichment: GAC (granular activated carbon) is an ideal place for the enrichment of anaerobic microorganisms. A large number of organic matter-degrading bacteria, acetic acid-producing methanogenic archaea, hydrogenotrophic methanogenic archaea, etc. can be enriched on the surface of GAC.

[0024] (3) Enhancement of electron transfer: The granular activated carbon GAC serves as a stable carrier. Its porous structure enables the Fe3O4 powder to be evenly attached to its surface, forming the Fe3O4@GAC composite agent, which has a natural electron transfer channel. The Fe3O4@GAC composite agent provides a multi-level conductive path (activated carbon skeleton + Fe3O4 powder), and the electron transfer efficiency is higher than that of a single material. The endogenous current directionally enhances the electron transfer rate between bacteria and archaea, simultaneously improving the degradation of pollutants and the methane production.

[0025] (4) Energy self-sufficiency: No external electric energy is required, and the generated methane can be recycled.

[0026] Compared with the prior art, the method for treating PBAT wastewater by zero-energy enhanced anaerobic bacteria in the present invention has no consumption of chemical agents, low operating costs and no secondary pollution, and can recycle the generated fuel gases such as methane, which can generate secondary economic benefits. It has the advantages of high efficiency, environmental protection and economy, and provides a new solution for the treatment of PBAT wastewater. Description of the Drawings

[0027] Figure 1 is a schematic structural diagram of the present invention;

[0028] Figure 2 Influence of magnetic field-Fe3O4@GAC on methane production from anaerobic digestion of PBAT wastewater in Example 1 of the present invention; (a) is methane production, and (b) is COD concentration;

[0029] Figure 3 Influence of magnetic field-Fe3O4@GAC on methane production from anaerobic digestion of PBAT wastewater in Example 2 of the present invention; (a) is methane production, and (b) is COD concentration;

[0030] In the figure: 1. Anaerobic reactor, 2. Magnet block, 3. Peristaltic circulation pump, 4. Fe3O4@GAC composite agent, 5. Anaerobic sludge, 6. Inlet, 7. Outlet, 8. Biogas outlet, 9. Mud-blocking grid. Specific implementation manners

[0031] The following embodiments are further descriptions of the content of the present invention to illustrate the technical content of the present invention. However, the substantial content of the present invention is not limited to what is described in the following embodiments. Those of ordinary skill in the art can and should know that any simple changes or substitutions based on the substantial spirit of the present invention should fall within the protection scope required by the present invention.

[0032] Example 1

[0033] A 250 mL anaerobic vial was used as the anaerobic reactor 1. One end of the anaerobic vial was provided with an inlet 6, and the other end was provided with an outlet 7 and a biogas outlet 8. The biogas outlet 8 was used to collect fuel gases such as methane generated. A plurality of magnet blocks 2 (permanent magnets) were fixed outside the anaerobic vial. By adjusting the size and position of the permanent magnets, the magnetic field strength in the anaerobic vial could be controlled to be 10 mT. 120 mL of PBAT wastewater and 30 mL of anaerobic sludge were added into the anaerobic vial. The MLVSS (mixed liquor volatile suspended solids) of the anaerobic sludge was 14.6 ± 0.5 g / L. PBAT wastewater with an initial COD concentration of 14600 mg / L was selected, and the MLVSS:COD in the anaerobic vial was 1:4.

[0034] Among them, the Fe3O4@GAC composite agent 4 was added into the anaerobic reactor 1 containing PBAT wastewater and anaerobic sludge, so that the Fe3O4@GAC composite agent 4 was fully mixed with the anaerobic sludge 5. The Fe3O4@GAC was uniformly blended by mixing Fe3O4 and GAC in a mass ratio of 1:1. The particle size of Fe3O4 was 20 - 50 nm, and the particle size of GAC was 0.5 - 2 mm. The mass ratio of the Fe3O4@GAC composite agent to the PBAT wastewater (calculated based on COD) was 1:4.87.

[0035] At the same time, a circulation system was connected to the anaerobic reactor 1, such as Figure 1As shown, the circulation system includes a circulation pipeline, a peristaltic circulation pump 3 installed on the circulation pipeline, and a mud-blocking grid 9. The two ends of the circulation pipeline are respectively connected to the anaerobic reactor 1. The mud-blocking grid 9 is installed at the connection between the circulation pipeline and the anaerobic reactor 1. The aperture of the mud-blocking grid 9 is 6 mm. The aperture of the grid is larger than the particle size of Fe3O4@GAC and smaller than the particle size of granular sludge. The mud-blocking grid 9 is used to retain the anaerobic granular sludge in the anaerobic reactor 1. The peristaltic circulation pump 3 is used to drive the PBAT wastewater and the Fe3O4@GAC composite agent to flow in the circulation pipeline.

[0036] The experiment was divided into eight groups, namely the blank group (no magnetic field, no Fe3O4, no GAC), the single magnetic field group (10 mT), the Fe3O4 group (2.5 g / L), the GAC group (2.5 g / L), the magnetic field-Fe3O4 group (10 mT, 2.5 g / L), the magnetic field-GAC group (10 mT, 2.5 g / L), the Fe3O4@GAC group (2.5 g / L), and the magnetic field-Fe3O4@GAC (10 mT, 2.5 g / L); three parallel samples were set for each experimental group.

[0037] After adding anaerobic sludge, Fe3O4, GAC, Fe3O4@GAC, and PBAT wastewater into the anaerobic reactor 1, it was purged and sealed with high-purity nitrogen, and the temperature was 35°. Analyze the strengthening effect of Fe3O4@GAC on the anaerobic digestion of PBAT wastewater, as Figure 2 shown.

[0038] In the anaerobic reactor, the PBAT wastewater undergoes anaerobic digestion for methane production for 400 h, and the cumulative methane production tends to be stable. The highest methane production in the blank group (without magnetic field, without Fe3O4, without GAC) is 353.5 mL, the lowest COD concentration reaches 2770 mg / L, and the COD removal rate is 81%; the highest methane production in the single magnetic field group is 449.3 mL, the lowest COD concentration reaches 1310 mg / L, and the COD removal rate is 91%; the highest methane production in the single Fe3O4 group is 428.53 mL, the lowest COD concentration reaches 365 mg / L, and the COD removal rate is 97.5%; the highest methane production in the single GAC group is GAC, the lowest COD concentration reaches 467 mg / L, and the COD removal rate is 96.8%; the highest methane production in the magnetic field-Fe3O4 group is 493.89 mL, exceeding 428.53 mL of the Fe3O4 group. In terms of COD degradation: the degradation efficiency of the Fe3O4 group is 97.5%, and the COD degradation efficiency of the magnetic field-Fe3O4 group is 99.15%. The highest methane production in the magnetic field-GAC group is 414 mL, exceeding 358 mL of the GAC group; in terms of COD degradation: the degradation efficiency of the GAC group is 96.8%, and the COD degradation efficiency of the magnetic field-GAC group is 98.0%. The highest methane production in the magnetic field-Fe3O4@GAC group is 504.56 mL, exceeding 493 mL of the magnetic field-Fe3O4 group; in terms of COD degradation: the degradation efficiency of the Fe3O4@GAC group is 97.5%, and the COD degradation efficiency of the magnetic field-Fe3O4@GAC group is 99.75%.

[0039] Example 2

[0040] A 500 mL anaerobic vial is used as the anaerobic reactor 1. One end of the anaerobic vial is provided with a water inlet 6, and the other end is provided with a water outlet 7 and a biogas outlet 8. The biogas outlet 8 is used to collect fuel gases such as methane produced; a plurality of magnet blocks 2 (permanent magnets) are fixed on the outer side of the anaerobic vial. By adjusting the size and position of the permanent magnet, the magnetic field strength in the anaerobic vial can be controlled to be 5 mT; 250 mL of PBAT wastewater and 60 mL of anaerobic sludge are added into the anaerobic vial. The MLVSS of the anaerobic sludge is 15 g / L. The PBAT wastewater with an initial COD concentration of 15000 mg / L is selected, and the MLVSS:COD in the anaerobic vial is 1:4.17.

[0041] Among them, the Fe3O4@GAC composite agent 4 is added into the anaerobic reactor 1 filled with PBAT wastewater and anaerobic sludge, so that the Fe3O4@GAC composite agent 4 is fully mixed with the anaerobic sludge 5. The Fe3O4@GAC is uniformly blended by mixing Fe3O4 and GAC according to a mass ratio of 1:1. The particle size of Fe3O4 is 50-100 nm, and the particle size of GAC is 2-5 mm. The mass ratio (calculated by COD) of the Fe3O4@GAC composite agent to the PBAT wastewater is 1:4.87.

[0042] Meanwhile, a circulation system is connected to the anaerobic reactor, as Figure 1 shown. The circulation system includes a circulation pipeline, a peristaltic circulation pump 3 installed on the circulation pipeline, and a sludge retention grid 9. Both ends of the circulation pipeline are respectively communicated with the anaerobic reactor 1. The sludge retention grid 9 is installed at the connection of the circulation pipeline and the anaerobic reactor 1. The aperture of the sludge retention grid 9 is 8 mm, which is used to retain the anaerobic granular sludge in the anaerobic reactor 1. The peristaltic circulation pump 3 is used to drive the PBAT wastewater to flow in the circulation pipeline.

[0043] The experiment is divided into eight groups, namely a blank group (no magnetic field, no Fe3O4, no GAC), a single magnetic field group (10 mT), an Fe3O4 group (2.5 g / L), a GAC group (2.5 g / L), a magnetic field-Fe3O4 group (10 mT, 2.5 g / L), a magnetic field-GAC group (10 mT, 2.5 g / L), an Fe3O4@GAC group (2.5 g / L), and a magnetic field-Fe3O4@GAC (10 mT, 2.5 g / L); three parallel samples are set for each experimental group.

[0044] After adding anaerobic sludge, Fe3O4, GAC, Fe3O4@GAC, and PBAT wastewater into the anaerobic reactor 1, it is purged and sealed with high-purity nitrogen, and the temperature is 35°. Analyze the strengthening effect of Fe3O4@GAC on the anaerobic digestion of PBAT wastewater, as Figure 3 shown.

[0045] In the anaerobic reactor, the PBAT wastewater undergoes anaerobic digestion to produce methane for 400 h, and the cumulative methane production tends to be stable. As Figure 3As shown, the highest methane production of the blank group (no magnetic field, no Fe3O4, no GAC) was 291.14 mL, the lowest COD concentration reached 2133 mg / L, and the COD removal rate was 83.10%; the highest methane production of the single magnetic field was 320.80 mL, the lowest COD concentration reached 1750 mg / L, and the COD removal rate was 86.11%; the highest methane production of the single Fe3O4 was 308.91 mL, the lowest COD concentration reached 1103 mg / L, and the COD removal rate was 91.20%; the highest methane production of the single GAC was 289.84 mL, the lowest COD concentration reached 766 mg / L, and the COD removal rate was 93.92%; the highest methane production of the magnetic field-Fe3O4 group was 350 mL, exceeding 308.91 mL of the Fe3O4 group. In terms of COD degradation: the degradation efficiency of the Fe3O4 group was 91.20%, and the COD degradation efficiency of the magnetic field-Fe3O4 group was 93.87%. The highest methane production of the magnetic field-GAC group was 311 mL, exceeding 289.84 mL of the GAC group. In terms of COD degradation: the degradation efficiency of the GAC group was 93.92%, and the COD degradation efficiency of the magnetic field-GAC group was 95.79%; the highest methane production of the magnetic field-Fe3O4@GAC group was 369.31 mL, exceeding 350 mL of the magnetic field-Fe3O4 group and exceeding 311 mL of the magnetic field-GAC group. In terms of COD degradation: the degradation efficiency of the Fe3O4@GAC group was 93.87%, and the COD degradation efficiency of the magnetic field-Fe3O4@GAC group was 98.65%.

[0046] The method for zero-energy consumption enhanced anaerobic treatment of PBAT wastewater of the present invention has no consumption of chemical agents, low operating cost and no secondary pollution, and can recover fuel gases such as methane generated, and can generate secondary economic benefits, having the advantages of high efficiency, environmental protection and economy, and providing a new solution for the treatment of PBAT wastewater.

[0047] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements or improvements made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A method for treating PBAT wastewater by enhancing anaerobic bacteria with zero energy consumption, characterized in that, It includes the following steps: (1) Mix Fe3O4 and GAC evenly according to a certain mass ratio, so that the Fe3O4 powder is evenly attached to the surface of GAC to make the Fe3O4@GAC composite agent, and then add it to the anaerobic reactor filled with PBAT wastewater and anaerobic sludge; (2) A magnetic field environment is formed outside the anaerobic reactor, and the Fe3O4@GAC composite agent couples with the external magnetic field to form an endogenous current to strengthen the anaerobic bacteria in the anaerobic sludge to treat PBAT wastewater until the COD no longer degrades.

2. The method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria according to claim 1, characterized in that, In the step (1), the mass ratio of Fe3O4 to GAC is 1:1 - 1:

4.

3. A method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria, according to claim 2, characterized in that, The particle size of the Fe3O4 is 20nm - 10um, and the particle size of the GAC is 0.5mm - 5.0mm.

4. A method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria, according to claim 1, characterized in that In the step (1), the COD concentration of the PBAT wastewater is 5000 - 15000mg / L, and the temperature is 20℃ - 55℃.

5. A method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria, according to claim 1, characterized in that, Calculated by COD, the mass ratio of the Fe3O4@GAC composite agent to the PBAT wastewater in the step (1) is 1:1 - 1:

10.

6. The method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria according to claim 1 or 5, characterized in that, Calculated by COD, the mass ratio of the anaerobic sludge to the PBAT wastewater is 5:1 - 1:

5.

7. A method for treating PBAT wastewater by enhancing anaerobic bacteria with zero energy consumption according to claim 1, characterized in that, The MLVSS of the anaerobic sludge is 5 - 50g / L.

8. A method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria, according to claim 1, characterized in that, A circulation system is also connected to the anaerobic reactor; The circulation system includes a circulation pipeline, a peristaltic circulation pump installed on the circulation pipeline, and a mud-blocking grid. The two ends of the circulation pipeline are respectively connected to the anaerobic reactor. The mud-blocking grid is installed at the connection of the circulation pipeline and the anaerobic reactor. The aperture of the mud-blocking grid is 5 - 10mm, which is used to retain the anaerobic sludge in the anaerobic reactor. The peristaltic circulation pump is used to drive the PBAT wastewater and the Fe3O4@GAC composite agent to flow in the circulation pipeline.

9. A method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria, according to claim 1, characterized in that, The magnetic field environment in the step (2) is formed by the cooperation of multiple magnet blocks placed on both sides of the anaerobic reactor.

10. A method for treating PBAT wastewater by zero - energy enhanced anaerobic bacteria, according to claim 1 or 9, characterized in that, The magnetic field intensity of the magnetic field environment is 5mT - 50mT.

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