Method for synergistic extraction and recovery of biodegradable plastics and blue vitriol from sewage treatment

Abstract

The application relates to a method for synergistically extracting and recycling biodegradable plastics and blue vitriol in sewage treatment, which realizes high-efficiency recycling of biodegradable plastics and blue vitriol by constructing a reaction mode of double-electron acceptor supply under anaerobic-aerobic alternating reaction and utilizing microbial metabolism. First, biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria are selectively domesticated. In the anaerobic stage, the dissimilatory iron-reducing bacteria reduce Fe 3+ in sewage into Fe 2+ , which reacts with phosphate to form blue vitriol, and the biodegradable plastic synthetic bacteria convert carbon sources into intracellular biodegradable plastics; in the aerobic stage, the biodegradable plastic synthetic bacteria utilize part of the biodegradable plastics as electron donors to provide energy for the microorganisms, maintain the activity of the biodegradable plastic synthetic bacteria and further enrich the biodegradable plastics. By adjusting the stage-by-stage supply of double-electron acceptors, the application realizes simultaneous recycling of biodegradable plastics and blue vitriol in the same reactor, and improves the resource utilization efficiency.

Description

TECHNICAL FIELD

[0001] The present application belongs to the technical field of sewage treatment and resource utilization, and particularly relates to a method for synergistic extraction and recovery of biodegradable plastics and vivianite in sewage treatment, which realizes the synergistic extraction and recovery of biodegradable plastics and vivianite by constructing a reaction mode of double-electron acceptor supply under anaerobic-aerobic alternating reaction. BACKGROUND

[0002] Beer breweries, paper mills and livestock wastewater usually contain high concentrations of chemical oxygen demand (COD) and phosphorus. Direct discharge of untreated wastewater into natural water bodies not only exacerbates water eutrophication, but also leads to a large amount of resource waste. Effective treatment and recycling of wastewater into high-value products is one of the most promising sustainable development models. Phosphate immobilization by forming vivianite is an efficient method for wastewater phosphorus recovery. Dissimilatory iron reduction is an important biochemical process for vivianite formation, and dissimilatory iron-reducing bacteria use Fe 3+ as an electron acceptor to be reduced to Fe 2+ , thereby forming vivianite. At the same time, the organic substrate is oxidized by dissimilatory iron-reducing bacteria as an electron donor to obtain energy for microbial metabolism. The recovered vivianite has significant economic and recyclable value, which can be used as a raw material for slow-release phosphorus fertilizer and a synthetic raw material for lithium-ion batteries. In addition, with the widespread application of plastics, the probability of their entering the sewage system gradually increases, and microplastics have become emerging pollutants, posing a potential threat to the environment and human health. Biodegradable plastics have different degradation characteristics from traditional plastics and can be degraded by microorganisms under certain conditions, and thus are considered as an environmentally friendly bioplastic that can alleviate global plastic waste pollution. Biodegradable plastics are usually biodegradable polymers in microbial cells and are often used as carbon sources for energy storage under nutrient imbalance conditions. Under anaerobic conditions, there is no electron acceptor available to biodegradable plastic synthetic bacteria in the environment, and biodegradable plastic synthetic bacteria will degrade intracellular polyphosphate to produce ATP, while synthesizing and storing intracellular biodegradable plastics using organic substrates. Under aerobic conditions, biodegradable bacteria use oxygen as an electron acceptor to oxidize biodegradable plastics to provide energy for cell metabolism and growth. However, Fe 2+ is easily oxidized under aerobic conditions, which may affect the crystallization efficiency of vivianite. The dependence of biodegradable plastic synthetic bacteria on oxygen makes it challenging to synergistically extract vivianite and biodegradable plastics.

[0003] Therefore, there is an urgent need to develop a new comprehensive treatment technology that can simultaneously achieve efficient recovery of biodegradable plastics and vivianite, promote resource recycling, and reduce energy consumption to address the increasingly severe water pollution problem. SUMMARY

[0004] To solve the technical problems proposed in the background art, the present application proposes a method for the synergistic extraction and recovery of biodegradable plastics and blue iron ore in sewage treatment, which overcomes the nutrient competition of biodegradable plastic synthesis bacteria and dissimilatory iron-reducing bacteria for the coexisting environment by means of phased supply of double-electron acceptors, enables microorganisms to perform organic substrate cascade metabolism, realizes the co-metabolism of microbial metabolites, and further extracts biodegradable plastics and blue iron ore from sewage or sludge with high COD and high phosphorus at the same time.

[0005] The present application overcomes the nutrient competition of biodegradable plastic synthesis bacteria and dissimilatory iron-reducing bacteria for the coexisting environment by means of phased supply of double-electron acceptors under anaerobic-aerobic alternating reaction mode, realizes the efficient recovery of biodegradable plastics and blue iron ore by means of microbial cascade metabolism, and realizes the synergistic recovery of organic matter and inorganic matter in sludge, greatly improving the resource utilization rate.

[0006] The technical scheme of the present application realizes the method for the synergistic extraction and recovery of biodegradable plastics and blue iron ore in sewage treatment, which specifically comprises the following steps:

[0007] (1) Inoculate sludge into an SBR reactor, and control the pH at 7-7.5;

[0008] (2) Perform inoculation sludge acclimation culture in a 12 or 24 hour reaction cycle to construct a double-electron acceptor supply reaction mode under anaerobic-aerobic alternating reaction: under anaerobic conditions, dissimilatory iron-reducing bacteria take ferric citrate as the electron acceptor, and the DO is less than 0.1; under aerobic conditions, biodegradable plastic synthesis bacteria take oxygen as the electron acceptor, and the DO is 3-4; the nutrient competition of biodegradable plastic synthesis bacteria and dissimilatory iron-reducing bacteria for the coexisting environment is overcome by means of phased supply of double-electron acceptors;

[0009] (3) After 8-10 weeks of reaction, take the blue-green transparent crystals at the bottom of the reactor, perform centrifugation, vacuum drying at 60-70℃ for 15 hours, and anaerobic preservation to obtain recovered blue iron ore, with a yield of 1.81-4.02g / g PO4 3- ;

[0010] (4) After 8-10 weeks of reaction, perform centrifugation on the sludge in the reactor, freeze-dry the lower sediment at-50--60℃ for 24 hours to obtain recovered biodegradable plastics, with a yield of 0.38-0.92g / g sodium acetate.

[0011] Further, the reaction cycle of step (1) comprises pumping in culture medium for 10 minutes, anaerobic stirring for 1020 minutes, aerobic aeration stirring for 340 minutes, sedimentation for 6 minutes, and removal of supernatant for 10 minutes, and the cycle is repeated.

[0012] Further, the ratio of anaerobic time to aerobic time in step (2) is 1:3-3:1.

[0013] Further, the reaction cycle time of step (2) is 12 hours, and the ratio of anaerobic time to aerobic time is 3:1.

[0014] Further, the reaction cycle time of step (2) is 24 hours, and the ratio of anaerobic time to aerobic time is 3:1.

[0015] Further, the centrifugation condition of step (3) is 8000-12000 rpm for 3-10 minutes.

[0016] Further, the centrifugation condition of step (4) is 8000-12000 rpm for 10-20 minutes.

[0017] Further, the concentration of ferric citrate is 1-3 mM per time in the influent.

[0018] The principle of the present application is mainly based on the combination of biochemical reactions and physical and chemical processes, which overcomes the nutrient competition of biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria for the coexisting environment through the way of two-electron acceptor phased supply, carries out organic substrate cascade metabolism, realizes microbial metabolic product co-operation, and further extracts and recycles biodegradable plastics and blue vitriol. The specific principle can be divided into the following aspects:

[0019] 1) Microbial domestication and culture: through the way of two-electron acceptor phased supply, the nutrient competition of biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria for the coexisting environment is overcome, and biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria are enriched;

[0020] 2) Biodegradable plastic recycling: under anaerobic conditions, there is no electron acceptor available to biodegradable plastic synthetic bacteria in the environment, biodegradable plastic synthetic bacteria will degrade intracellular polyphosphate to produce ATP, and at the same time, through its metabolic activity, the carbon source in the sewage is converted into intracellular biodegradable plastics and stored, thereby realizing the recycling of biodegradable plastics in the sewage;

[0021] 3) Biodegradable plastic energy supply: in the aerobic stage, biodegradable plastic synthetic bacteria use oxygen as an electron acceptor, and biodegradable plastics as an electron donor to release energy, maintain their growth and metabolic activity, and further enrich biodegradable plastic synthetic bacteria for the next cycle.

[0022] 4) Dissimilatory iron reduction process: under anaerobic conditions, dissimilatory iron-reducing bacteria can utilize Fe 3+ in the water body as an electron acceptor to carry out dissimilatory iron reduction reaction. In this process, Fe 3+ is reduced to Fe 2+Simultaneously releasing energy. This process not only helps remove heavy metal elements from wastewater, but also promotes the precipitation of blue vitriol;

[0023] 5) Iron phosphate precipitation and crystallization: During the dissimilatory iron reduction reaction, dissolved phosphate in wastewater reacts with reduced iron ions to form insoluble blue vitriol. This process can be optimized by controlling the supply mode of the acceptor to improve the recovery rate of blue vitriol;

[0024] 6) Resource utilization: The generated blue vitriol is recovered through physical separation techniques such as precipitation, filtration or centrifugation, etc. The recovered blue vitriol can be further processed into industrial raw materials or used in water treatment and other fields, realizing the recycling of resources.

[0025] The core principle of the present application is to overcome the nutritional competition between biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria in the coexistence environment through the phased supply of double-electron acceptors, to carry out organic substrate cascade metabolism, to realize microbial metabolic product co-operation, and to further extract and resource biodegradable plastics and blue vitriol. By constructing a double-electron acceptor supply reaction mode under anaerobic-aerobic alternating reaction, selective domestication of biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria is carried out. In the anaerobic stage, dissimilatory iron-reducing bacteria reduce Fe 3+ to Fe 2+ and reacts with phosphate to form blue vitriol, while biodegradable plastic synthetic bacteria can convert carbon sources in wastewater into biodegradable plastics and store them; In the aerobic stage, biodegradable plastic synthetic bacteria efficiently enrich with oxygen as the electron acceptor, further improving the recovery efficiency of biodegradable plastics; The setting of high anaerobic duration avoids the impact of oxygen on the metabolic activity of dissimilatory iron-reducing bacteria, further realizing microbial metabolic product co-operation. This synergistic effect not only improves the recovery efficiency of both, but also simplifies the wastewater treatment process and saves energy costs. This comprehensive treatment method provides a new idea for wastewater resource utilization, with broad application prospects and market potential.

[0026] Advantages

[0027] The present application not only provides an effective technical means for wastewater treatment, but also has important application value in environmental protection and resource recovery, which is specifically manifested as follows:

[0028] 1. Synergistic extraction and recovery method of biodegradable plastics and blue vitriol: The system can realize the synergistic extraction and recovery of biodegradable plastics and blue vitriol by constructing a double-electron acceptor supply reaction mode under anaerobic-aerobic alternating reaction in the same reactor, significantly improving the treatment efficiency and reducing the complexity and time cost of wastewater treatment.

[0029] 2. Resource utilization: The vivianite recovered through this method can be used in various industrial applications, such as producing fertilizers, synthesizing lithium-ion batteries, and synthesizing dyes, promoting resource recycling and reducing the demand for industrial raw materials.

[0030] 3. Reducing environmental pollution: The invention effectively removes COD and phosphorus in wastewater, reducing pollution of water bodies, helping to improve water quality, protect the ecological environment, and meet the requirements of sustainable development.

[0031] 4. Economic benefits: The invention reduces wastewater treatment costs and achieves economic benefits through resource utilization, especially in the fields of industrial wastewater treatment and resource recovery, with good market prospects.

[0032] 5. Simplifying the treatment process: The single reactor is used for treatment, simplifying the wastewater treatment process. Not only reduces the equipment and operation links, but also reduces the dependence on chemical agents, reduces the risk of secondary pollution, and improves the greenness of the overall treatment process.

[0033] 6. Wide application range: The invention is suitable for various types of wastewater treatment, including industrial wastewater and municipal wastewater, with strong adaptability and flexibility, capable of meeting the needs of different fields.

[0034] 7. Promoting technological progress: The invention provides a solution for multi-resource recovery through a two-electron acceptor stage-by-stage supply method for wastewater treatment containing multiple pollutants, promoting the development of related technologies, driving the progress of environmental protection technologies, and having important academic and practical significance. BRIEF DESCRIPTION OF DRAWINGS

[0035] Figure 1 The biodegradable plastic and vivianite used in the wastewater treatment of the invention are shown in the figure.

[0036] Figure 2 The microbial community structure of the invention is shown in the figure.

[0037] Figure 3 The microscope image of the vivianite recovered by the invention is shown in the figure.

[0038] a Example 1; b Example 2; c Example 3; d Example 4;

[0039] Figure 4 The biodegradable plastic content recovered by the invention is shown in the figure.

[0040] Figure 5 The reactor performance parameter diagram of the invention is shown in the figure. DETAILED DESCRIPTION

[0041] The invention will be further described below in conjunction with examples, but the embodiments of the invention include but are not limited to this.

[0042] like Figure 1 The diagram shows a schematic of the experimental apparatus for the synergistic extraction and recovery of biodegradable plastics and sappanite in wastewater treatment, as used in this invention. Activated sludge is inoculated into an SBR reactor. The synergistic extraction and recovery method for biodegradable plastics and sappanite in wastewater treatment specifically includes the following steps:

[0043] (1) Sludge is inoculated into the SBR reactor;

[0044] (2) The inoculated sludge was acclimated and cultured in cycles of 12 or 24 hours to construct a reaction mode with dual electron acceptor supply under alternating anaerobic and aerobic conditions. Under anaerobic conditions, dissimilatory iron-reducing bacteria used ferric citrate as the electron acceptor, and dissimilatory iron-reducing bacteria converted Fe from wastewater. 3+ Reduced to Fe 2+ It reacts with phosphate to form sapphire, while biodegradable plastic-synthesizing bacteria convert carbon sources in wastewater into biodegradable plastics and store them.

[0045] Under aerobic conditions, biodegradable plastic-synthesizing bacteria use oxygen as an electron acceptor to efficiently enrich the material.

[0046] The nutritional competition between biodegradable plastic synthesizing bacteria and dissimilar iron-reducing bacteria in the coexisting environment is overcome by using a phased supply method with dual electron acceptors.

[0047] (3) After 8-10 weeks of reaction, take the blue-green transparent crystals from the bottom of the reactor, centrifuge them, vacuum dry them at 60-70℃ for 15 hours, and anaerobic store them to obtain the recovered blue iron stone;

[0048] (4) After 8-10 weeks of reaction, the sludge in the reactor is centrifuged, and the lower sediment is freeze-dried at -50-60℃ for 24 hours to obtain the recovered biodegradable plastic.

[0049] The concentration of suspended solids, volatile suspended solids, sludge settling ratio, and sludge volume index in the mixed liquor were measured to reflect the sludge growth status. After the sludge growth status stabilized, a reaction mode with dual electron acceptor supply under anaerobic-aerobic alternating reaction was constructed to achieve the synergistic extraction and recovery of sapphire and biodegradable plastics.

[0050] Example 1

[0051] The oxygen supply method of the reactor, which was operating well, was adjusted under ambient temperature conditions to maintain each reaction cycle at 24 hours. This included 10 minutes of culture medium pumping, 340 minutes of anaerobic stirring, 1020 minutes of aerobic aeration and stirring, 60 minutes of sedimentation, and 10 minutes of supernatant removal, ensuring a 1:3 ratio of anaerobic to aerobic time in the reaction cycle. After 8-10 weeks of operation, the blue-green transparent crystals at the bottom of the reactor were centrifuged, vacuum-dried, and anaerobically stored. Figure 2 As shown, the recovery of lapis lazuli is complete. After 8-10 weeks of operation, the sludge in the reactor is centrifuged, and the lower sediment is freeze-dried, as shown. Figure 3 As shown in Table 1, the recycling of biodegradable plastics was completed. Under this electron acceptor supply method, the yields of salicylic acid and biodegradable plastics are as shown in Table 1, with a salicylic acid yield reaching 1.81 g / g PO4. 3- The yield of biodegradable plastics reached 0.38 g / g sodium acetate.

[0052] Example 2

[0053] The oxygen supply method of the reactor, which was operating well, was adjusted under ambient temperature conditions to maintain each reaction cycle at 24 hours. This included 10 minutes of culture medium injection, 680 minutes of anaerobic stirring, 680 minutes of aerobic aeration and stirring, 60 minutes of sedimentation, and 10 minutes of supernatant removal, ensuring a 1:1 ratio of anaerobic to aerobic time in each cycle. After 8-10 weeks of operation, the blue-green transparent crystals at the bottom of the reactor were centrifuged, vacuum-dried, and anaerobically stored. Figure 2 As shown, the recovery of lapis lazuli is complete. After 8-10 weeks of operation, the sludge in the reactor is centrifuged, and the lower sediment is freeze-dried, as shown. Figure 3 As shown in Table 1, the recycling of biodegradable plastics was completed. Under this electron acceptor supply method, the yields of salicylic acid and biodegradable plastics are as shown in Table 1, with a salicylic acid yield reaching 1.99 g / g PO4. 3- The yield of biodegradable plastics reached 0.47 g / g sodium acetate.

[0054] Example 3

[0055] The oxygen supply method of the reactor, which was operating well, was adjusted under ambient temperature conditions to maintain each reaction cycle at 24 hours. This included 10 minutes of culture medium pumping, 10-20 minutes of anaerobic stirring, 3-40 minutes of aerobic aeration and stirring, 60 minutes of sedimentation, and 10 minutes of supernatant removal, ensuring a 3:1 ratio of anaerobic to aerobic time in the reaction cycle. After 8-10 weeks of operation, the blue-green transparent crystals at the bottom of the reactor were centrifuged, vacuum-dried, and anaerobically stored. Figure 2 As shown, the recovery of lapis lazuli is complete. After 8-10 weeks of operation, the sludge in the reactor is centrifuged, and the lower sediment is freeze-dried, as shown. Figure 3The biodegradable plastic recovery was completed. Under this electron acceptor supply mode, the production of blue vitriol and biodegradable plastic was as shown in Table 1, and the production of blue vitriol reached 4.02 g / g PO4 3- The biodegradable plastic yield reached 0.92 g / g sodium acetate.

[0056] Example 4

[0057] The oxygen supply mode of the reactor in good operating condition was adjusted at room temperature, and the reaction cycle time was maintained at 12 hours, including 10 minutes of pumping medium, 510 minutes of anaerobic stirring, 170 minutes of aerobic aeration stirring, 60 minutes of sedimentation, and 10 minutes of removing supernatant, so that the anaerobic time: aerobic time in the reaction cycle was 3:1. After 8-10 weeks of operation, the blue-green transparent crystals at the bottom of the reactor were centrifuged, vacuum dried, and anaerobically stored, as shown in Figure 2 The blue vitriol recovery was completed. After 8-10 weeks of operation, the sludge in the reactor was centrifuged, and the lower sediment was freeze-dried, as shown in Figure 3 The biodegradable plastic recovery was completed. Under this electron acceptor supply mode, the production of blue vitriol and biodegradable plastic was as shown in Table 1, and the production of blue vitriol reached 2.89 g / g PO4 3- The biodegradable plastic yield reached 0.67 g / g sodium acetate.

[0058] Table 1 shows the results of blue vitriol and biodegradable plastic recovery in different examples under the mode of two-electron acceptor supply in stages

[0059]

[0060] Figure 2 The biodegradable plastic and blue vitriol were recovered by adjusting the two-electron acceptor supply in stages according to the present application. After the reaction, the microbial community structure in the system was enriched with biodegradable plastic synthesis bacteria and dissimilatory iron-reducing bacteria.

[0061] Figure 3 The blue vitriol recovered by the reaction mode of two-electron acceptor supply under anaerobic-aerobic alternating reaction according to the present application is shown in the microscope image. The image shows that blue-green transparent crystals appear in the reactor, indicating that blue vitriol is successfully recovered by adjusting the two-electron acceptor supply in stages. At the same time, the biodegradable plastic yield was detected, Figure 4 It is shown that the change of the two-electron acceptor supply in stages will affect the yield of biodegradable plastic.

[0062] Figure 5 The temperature, pH, and dissolved oxygen change process during the synthesis according to the present application.

[0063] The results show that the best effect of simultaneous recovery of blue vitriol and biodegradable plastics is achieved by running for 24 hours in the form of 3:1 of anaerobic time to aerobic time with the way of two-electron acceptor supplied in stages. Under this condition, the way of two-electron acceptor supplied in stages overcomes the nutritional competition of biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria for the coexistence environment, efficiently enriches biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria, and high anaerobic time avoids the impact of oxygen on dissimilatory iron-reducing bacteria, further realizing the co-metabolism of microbial metabolites.

Claims

1. A method for synergistic extraction and recovery of biodegradable plastics and blue iron from sewage treatment, characterized by, The method comprises the following steps: (1) inoculating sludge into an SBR reactor, and controlling pH at 7-7.5; (2) carrying out inoculated sludge domestication culture in a reaction cycle of 12 or 24 hours, and constructing a reaction mode of double-electron-receptor supply under anaerobic-aerobic alternation reaction: Under anaerobic conditions, dissimilatory iron-reducing bacteria use ferric citrate as an electron acceptor, and the DO is less than 0.1, and the dissimilatory iron-reducing bacteria reduce Fe 3+ in the wastewater to Fe 2+ and form vivianite with phosphate, and at the same time, the plastic-synthesizing bacteria can convert the carbon source in the wastewater into biodegradable plastics and store them; Under aerobic conditions, biodegradable plastic synthetic bacteria take oxygen as an electron receptor, and DO is 3-4; biodegradable plastic synthetic bacteria take oxygen as an electron receptor and are efficiently enriched; Through the mode of double-electron-receptor stage supply, the nutrient competition of biodegradable plastic synthetic bacteria and dissimilatory iron-reducing bacteria for the coexisting environment is overcome; (3) After 8-10 weeks of reaction, the blue-green transparent crystals at the bottom of the reactor were taken out for centrifugation, vacuum drying and anaerobic preservation to obtain recovered vivianite with a yield of 1.81-4.02 g / g PO4 3- ; (4) after 8-10 weeks of reaction, centrifuging sludge in the reactor, freezing and drying the lower precipitate to obtain recovered biodegradable plastics, and the yield is 0.38-0.92 g / g of sodium acetate; The ratio of anaerobic time to aerobic time in the step (2) is 1:3-3:

1.

2. The method of claim 1, wherein, The reaction cycle of the step (2) comprises the following steps: pumping culture medium for 10 minutes, anaerobic stirring for 1020 minutes, aerobic aeration stirring for 340 minutes, precipitation for 60 minutes, and removing supernatant for 10 minutes, and the steps are cycled.

3. The method of claim 1, wherein, The reaction cycle time of the step (2) is 24 hours, and the ratio of anaerobic time to aerobic time is 3:

1.

4. The method of claim 1, wherein, The reaction cycle time of the step (2) is 12 hours, and the ratio of anaerobic time to aerobic time is 3:

1.

5. The method of claim 1, wherein, The centrifugation condition of the step (3) is 8000-12000 rpm for 3-10 minutes.

6. The method of claim 1, wherein, The centrifugation condition of the step (4) is 8000-12000 rpm for 10-20 minutes.

7. The method of claim 1, wherein, The vacuum drying temperature of the step (3) is 60-70 DEG C.

8. The method of claim 1, wherein, The freeze-drying temperature of the step (4) is -50-60 DEG C.

9. The method of claim 1, wherein, The concentration of the iron citrate is 1-3 mM each time.

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