Synergistic extraction and recovery method of biodegradable plastic and blue iron stone for sewage treatment

Abstract

The invention relates to a synergistic extraction and recovery method of biodegradable plastic and blue iron stone for sewage treatment, which is characterized in that efficient recovery of biodegradable plastic and blue iron stone is realized by utilizing microbial metabolism by constructing a reaction mode of double electron acceptor supply under anaerobic-aerobic alternate reaction. The method comprises the following steps: firstly, selectively domesticating biodegradable plastic synthetic bacteria and dissimilatory iron reducing bacteria; in the anaerobic stage, Fe < 3 + > in the sewage is reduced into Fe < 2 + > by the dissimilatory iron reducing bacteria, the Fe < 2 + > reacts with phosphate to form blue iron stone, and a carbon source is converted into intracellular biodegradable plastic by the biodegradable plastic synthetic bacteria; in the aerobic stage, the biodegradable plastic synthetic bacteria utilize part of biodegradable plastic as electron donors to supply energy to microorganisms, the activity of the biodegradable plastic synthetic bacteria is maintained, and the biodegradable plastic synthetic bacteria are further enriched. According to the invention, by adjusting the mode of supplying the double electron acceptors in stages, the biodegradable plastic and the blue iron stone can be recovered in the same reactor at the same time, and the resource utilization efficiency is improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of sewage treatment and resource utilization thereof, and specifically relates to a method for the coordinated extraction and recovery of biodegradable plastics and blue iron stone in sewage treatment, wherein the coordinated extraction and recovery of biodegradable plastics and blue iron stone is achieved by constructing a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction. Background Art

[0002] Wastewater from breweries, paper mills and livestock operations often contains high concentrations of chemical oxygen demand (COD) and phosphorus. Direct discharge of untreated wastewater into natural water bodies will not only aggravate eutrophication of the water bodies, but also lead to a large amount of resource waste. Effective treatment of wastewater and recycling it into high-value products is one of the most promising sustainable development models. Phosphate immobilization through the formation of blue iron ore is an efficient method for phosphorus recovery from wastewater. Dissimilatory iron reduction is an important biochemical process in the formation of blue iron ore. Dissimilatory iron-reducing bacteria utilize Fe under anaerobic conditions to 3+ As an electron acceptor, it is reduced to Fe 2+ , thus forming blue iron stone. 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 blue iron stone has significant economic and recyclable value, and can be used as a raw material for slow-release phosphate fertilizer and a synthetic raw material for lithium-ion batteries. In addition, with the widespread use of plastics, the probability of them entering the sewage system has gradually increased. Microplastics have become an emerging pollutant, posing a potential hazard to the environment and human health. The degradation characteristics of biodegradable plastics are different from those of traditional plastics. They can be degraded by microorganisms under specific conditions, so they are regarded as an environmentally friendly bioplastic that can alleviate global plastic waste pollution. Biodegradable plastics are usually biodegradable polymers in microbial cells, which are usually used as carbon sources for energy storage under conditions of nutritional imbalance. Under anaerobic conditions, there are no electron acceptors available to biodegradable plastic-synthesizing bacteria in the environment. Biodegradable plastic-synthesizing bacteria will degrade intracellular polyphosphates to produce ATP, and use organic substrates to synthesize and store intracellular biodegradable plastics. Under aerobic conditions, biodegradable bacteria use oxygen as an electron acceptor to oxidize biodegradable plastics to provide energy for cell metabolism and growth. However, under aerobic conditions, Fe 2+ It is very easy to be oxidized, which may affect the crystallization efficiency of blue iron stone. The dependence of biodegradable plastic synthesis bacteria on oxygen makes the synergistic extraction of blue iron stone and biodegradable plastics challenging.

[0003] Therefore, there is an urgent need to develop a new comprehensive treatment technology that can simultaneously achieve efficient recycling of biodegradable plastics and blue iron ore, promote the recycling of resources, and reduce energy consumption in order to cope with the increasingly serious water pollution problem. Summary of the invention

[0004] In order to solve the technical problems raised in the background technology, the present invention proposes a method for the synergistic extraction and recovery of biodegradable plastics and blue iron stone in sewage treatment, which overcomes the nutritional competition of biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria for the coexistence environment by means of the phased supply of double electron acceptors, enables microorganisms to carry out cascade metabolism of organic substrates, realizes the co-production of microbial metabolites, and further simultaneously extracts biodegradable plastics and blue iron stone from high COD and high phosphorus sewage or sludge.

[0005] The present invention overcomes the nutritional competition between biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria for the coexistence environment by constructing a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction, utilizes the microbial cascade metabolic process to realize efficient recovery of biodegradable plastic and blue iron stone, realizes the coordinated recovery of organic and inorganic matter in sludge, and greatly improves resource utilization.

[0006] The technical solution of the present invention realizes: a method for synergistically extracting and recovering biodegradable plastics and blue iron stone from sewage treatment, which specifically comprises the following steps:

[0007] (1) The sludge is inoculated into the SBR reactor and the pH is controlled at 7-7.5;

[0008] (2) The inoculated sludge was cultivated in a 12 or 24-hour reaction cycle to construct a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction: under anaerobic conditions, the dissimilatory iron-reducing bacteria used ferric citrate as the electron acceptor, and the DO was less than 0.1; under aerobic conditions, the biodegradable plastic synthesizing bacteria used oxygen as the electron acceptor, and the DO was 3-4; the nutrient competition between the biodegradable plastic synthesizing bacteria and the dissimilatory iron-reducing bacteria for the coexistence environment was overcome by the phased supply of double electron acceptors;

[0009] (3) After 8-10 weeks of reaction, the blue-green transparent crystals at the bottom of the reactor were centrifuged, vacuum dried at 60-70°C for 15 hours, and stored anaerobically to obtain recovered blue iron stone with a yield of 1.81-4.02 g / g PO4 3- ;

[0010] (4) After 8-10 weeks of reaction, the sludge in the reactor is centrifuged, and the lower precipitate is freeze-dried at -50-60°C for 24 hours to obtain the recovered biodegradable plastic with a yield of 0.38-0.92 g / g sodium acetate.

[0011] Furthermore, the reaction cycle of step (1) includes pumping the culture medium for 10 minutes, anaerobic stirring for 10-20 minutes, aerobic aeration stirring for 3-40 minutes, sedimentation for 6 minutes, and removing the supernatant for 10 minutes, and the cycle continues.

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

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

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

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

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

[0017] Furthermore, the concentration of ferric citrate added to the influent water is 1-3 mM each time.

[0018] The principle of the present invention is mainly based on the combination of biochemical reactions and physical and chemical processes. It overcomes the nutritional competition of biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria in the coexistence environment by supplying double electron acceptors in stages, conducts cascade metabolism of organic substrates, realizes the co-production of microbial metabolites, and further extracts and recycles biodegradable plastics and blue iron stone. The specific principles can be divided into the following aspects:

[0019] 1) Microbial domestication and cultivation: Overcoming the nutritional competition of biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria in the coexistence environment by supplying double electron acceptors in stages, and enriching biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria;

[0020] 2) Recycling of biodegradable plastics: Under anaerobic conditions, there are no electron acceptors available to biodegradable plastic-synthesizing bacteria in the environment. Biodegradable plastic-synthesizing bacteria will degrade intracellular polyphosphates to produce ATP. At the same time, through their metabolic activities, they will convert carbon sources in sewage into intracellular biodegradable plastics and store them, thereby realizing the recycling of biodegradable plastics in sewage;

[0021] 3) Energy supply from biodegradable plastics: In the aerobic stage, biodegradable plastic synthesizing bacteria use oxygen as an electron acceptor and biodegradable plastics as electron donors to release energy, maintain their growth and metabolic activities, and further enrich biodegradable plastic synthesizing bacteria to the next cycle.

[0022] 4) Dissimilatory iron reduction process: Under anaerobic conditions, dissimilatory iron-reducing bacteria can utilize Fe in water 3+ As an electron acceptor, it undergoes dissimilatory iron reduction. 3+ Reduced to Fe 2+, while releasing energy. This process not only helps remove heavy metal elements from sewage, but also promotes the precipitation of blue iron stone;

[0023] 5) Precipitation and crystallization of iron and phosphorus: During the process of dissimilatory iron reduction, the dissolved phosphate in the sewage reacts with the reduced iron ions to form insoluble blue iron stone. This process can optimize the formation of precipitation and improve the recovery rate of blue iron stone by controlling the receptor supply mode;

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

[0025] The core principle of the present invention is to overcome the nutritional competition of biodegradable plastic synthesis bacteria and dissimilatory iron-reducing bacteria for the coexistence environment by supplying two electron acceptors in stages, carry out cascade metabolism of organic substrates, realize the co-production of microbial metabolites, and further extract and recycle biodegradable plastics and blue iron. By constructing a reaction mode of two electron acceptor supply under anaerobic-aerobic alternating reaction, biodegradable plastic synthesis bacteria and dissimilatory iron-reducing bacteria are selectively domesticated. In the anaerobic stage, dissimilatory iron-reducing bacteria convert Fe in sewage into 3+ Reduction to Fe 2+ It reacts with phosphate to form blue iron stone. At the same time, biodegradable plastic synthesizing bacteria can convert carbon sources in sewage into biodegradable plastics and store them. In the aerobic stage, biodegradable plastic synthesizing bacteria use oxygen as an electron acceptor for efficient enrichment, further improving the recycling efficiency of biodegradable plastics. The setting of high anaerobic time avoids the impact of oxygen on the metabolic activity of dissimilatory iron-reducing bacteria, further realizing the co-production of microbial metabolites. This synergistic effect not only improves the recycling efficiency of both, but also simplifies the sewage treatment process and saves energy costs. This comprehensive treatment method provides a new idea for sewage resource utilization, with broad application prospects and market potential.

[0026] Beneficial Effects

[0027] The present invention not only provides an effective technical means for sewage treatment, but also has important application value in environmental protection and resource recovery, as shown in the following:

[0028] 1. Synergistic extraction and recovery method of biodegradable plastics and blue iron ore: This system can achieve the synergistic extraction and recovery of biodegradable plastics and blue iron ore by constructing a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction in the same reactor, which significantly improves the treatment efficiency and reduces the complexity and time cost of sewage treatment.

[0029] 2. Resource utilization: The blue iron stone recovered by this method can be used in a variety of industrial applications, such as fertilizer production, synthetic lithium-ion batteries, synthetic dyes, etc., which promotes the recycling of resources and reduces the demand for industrial raw materials.

[0030] 3. Reduce environmental pollution: The present invention effectively removes COD and phosphorus in sewage, reduces water pollution, helps improve water quality, protects the ecological environment, and meets the requirements of sustainable development.

[0031] 4. Economic benefits: The present invention reduces the cost of sewage treatment and realizes economic benefits through resource utilization, especially in the field of industrial sewage treatment and resource recovery, and has good market prospects.

[0032] 5. Simplify the treatment process: Use a single reactor for treatment to simplify the sewage treatment process. This 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 scope of application: The present invention is applicable to various types of sewage treatment, including industrial sewage and urban sewage, has strong adaptability and flexibility, and can meet the needs of different fields.

[0034] 7. Promote technological progress: The present invention provides a solution for wastewater treatment containing multiple pollutants by using a phased supply of dual-electron acceptors to recover multiple resources, which promotes the development of related technologies and the advancement of environmental protection technologies, and has important academic and practical significance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 An experimental device for the coordinated extraction and recovery of biodegradable plastics and blue iron stone used in sewage treatment in the present invention;

[0036] Figure 2 is the microbial community structure of the present invention;

[0037] Figure 3 Microscope image of blue iron stone recovered by the present invention:

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

[0039] Figure 4 This is the biodegradable plastic content recovered by the present invention.

[0040] Figure 5 This is a performance parameter diagram of the reactor of the present invention. DETAILED DESCRIPTION

[0041] The present invention is further described below in conjunction with examples, but the embodiments of the present invention include but are not limited to these.

[0042] like Figure 1 The figure shows a schematic diagram of the experimental device for the synergistic extraction and recovery of biodegradable plastics and blue iron stone used in sewage treatment. The activated sludge is inoculated into the SBR reactor, and the synergistic extraction and recovery method of biodegradable plastics and blue iron stone used in sewage treatment specifically includes the following steps:

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

[0044] (2) The inoculated sludge was cultivated in a 12- or 24-hour reaction cycle to construct a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction. Under anaerobic conditions, the dissimilatory iron-reducing bacteria used ferric citrate as an electron acceptor to convert Fe in the sewage into 3+ Reduction to Fe 2+ It reacts with phosphate to form blue iron stone, while the biodegradable plastic-synthetic bacteria convert the carbon source in the sewage into biodegradable plastic and store it;

[0045] Under aerobic conditions, biodegradable plastic-synthesizing bacteria use oxygen as an electron acceptor, and biodegradable plastic-synthesizing bacteria use oxygen as an electron acceptor for efficient enrichment;

[0046] Overcoming the nutritional competition between biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria in the coexistence environment by supplying two electron acceptors in stages;

[0047] (3) After 8-10 weeks of reaction, the blue-green transparent crystals at the bottom of the reactor are centrifuged, vacuum dried at 60-70° C. for 15 hours, and stored anaerobically to obtain recovered blue iron stone;

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

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

[0050] Example 1

[0051] Under normal temperature conditions, the oxygen supply mode of the reactor in good operation is adjusted to maintain each reaction cycle time of 24 hours, including pumping the culture medium for 10 minutes, anaerobic stirring for 340 minutes, aerobic aeration stirring for 1020 minutes, sedimentation for 60 minutes, and removal of the supernatant for 10 minutes, so that the anaerobic time: aerobic time in the reaction cycle is 1:3. After running for 8-10 weeks, the blue-green transparent crystals at the bottom of the reactor are centrifuged, vacuum dried, and anaerobically stored, such as Figure 2 After 8-10 weeks of operation, the sludge in the reactor is centrifuged and the lower sediment is freeze-dried. Figure 3 As shown, the biodegradable plastic recycling is completed. Under this electron acceptor supply mode, the yields of blue iron and biodegradable plastic are shown in Table 1. The blue iron yield reaches 1.81g / g PO4 3- , the yield of biodegradable plastics reached 0.38g / g sodium acetate.

[0052] Example 2

[0053] Under normal temperature conditions, the oxygen supply mode of the reactor in good operation is adjusted to maintain each reaction cycle time of 24 hours, including pumping the culture medium for 10 minutes, anaerobic stirring for 680 minutes, aerobic aeration stirring for 680 minutes, sedimentation for 60 minutes, and removal of the supernatant for 10 minutes, so that the anaerobic time and aerobic time in the reaction cycle are 1:1. After running for 8-10 weeks, the blue-green transparent crystals at the bottom of the reactor are centrifuged, vacuum dried, and anaerobically stored, such as Figure 2 After 8-10 weeks of operation, the sludge in the reactor is centrifuged and the lower sediment is freeze-dried. Figure 3 As shown, the biodegradable plastic recycling is completed. Under this electron acceptor supply mode, the yields of blue iron and biodegradable plastic are shown in Table 1. The blue iron yield reaches 1.99g / g PO4 3- , the yield of biodegradable plastic reached 0.47g / g sodium acetate.

[0054] Example 3

[0055] Under normal temperature conditions, the oxygen supply mode of the reactor in good operation is adjusted to maintain each reaction cycle time of 24 hours, including pumping culture medium for 10 minutes, anaerobic stirring for 10-20 minutes, aerobic aeration stirring for 3-40 minutes, sedimentation for 60 minutes, and removal of supernatant for 10 minutes, so that the anaerobic time: aerobic time in the reaction cycle is 3:1. After running for 8-10 weeks, the blue-green transparent crystals at the bottom of the reactor are centrifuged, vacuum dried, and anaerobically stored, such as Figure 2 After 8-10 weeks of operation, the sludge in the reactor is centrifuged and the lower sediment is freeze-dried. Figure 3As shown, the biodegradable plastic recycling is completed. Under this electron acceptor supply mode, the yields of blue iron and biodegradable plastic are shown in Table 1. The blue iron yield reaches 4.02g / g PO4 3- , the yield of biodegradable plastic reached 0.92g / g sodium acetate.

[0056] Example 4

[0057] Under normal temperature conditions, the oxygen supply mode of the reactor in good operation is adjusted to maintain each reaction cycle time of 12 hours, including pumping culture medium for 10 minutes, anaerobic stirring for 5-10 minutes, aerobic aeration stirring for 170 minutes, sedimentation for 60 minutes, and removal of supernatant for 10 minutes, so that the anaerobic time: aerobic time in the reaction cycle is 3:1. After running for 8-10 weeks, the blue-green transparent crystals at the bottom of the reactor are centrifuged, vacuum dried, and anaerobically stored, such as Figure 2 After 8-10 weeks of operation, the sludge in the reactor is centrifuged and the lower sediment is freeze-dried. Figure 3 As shown, the biodegradable plastic recycling is completed. Under this electron acceptor supply mode, the yields of blue iron and biodegradable plastic are shown in Table 1. The blue iron yield reaches 2.89g / g PO4 3- , the yield of biodegradable plastic reached 0.67g / g sodium acetate.

[0058] Table 1 shows the results of blue iron stone and biodegradable plastic recycling in different embodiments under the dual electron acceptor phased supply mode

[0059]

[0060] Figure 2 The present invention performs coordinated extraction and recovery of biodegradable plastic and blue iron stone by adjusting the phased supply of two-electron acceptors. After the reaction is completed, the microbial community structure in the system is efficiently enriched with biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria.

[0061] Figure 3 This is a microscope image of blue iron stone recovered by constructing a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction in the present invention. The image shows that blue iron stone appears in the reactor, indicating that blue iron stone is successfully recovered by regulating the double electron acceptor supply mode in stages. At the same time, the yield of biodegradable plastics is tested. Figure 4 It is shown that changes in the phased supply of two-electron acceptors can affect the yield of biodegradable plastics.

[0062] Figure 5 This is the temperature, pH and dissolved oxygen change process of the synthesis process of the present invention.

[0063] The above results show that the best effect of synergistic extraction and recovery of blue iron stone and biodegradable plastics is achieved by running the system for 24 hours with a phased supply of double electron acceptors in the form of anaerobic time: aerobic time of 3:1. Under this condition, the nutritional competition of biodegradable plastic synthesizing bacteria and alien iron-reducing bacteria for the coexistence environment is overcome by the phased supply of double electron acceptors, and biodegradable plastic synthesizing bacteria and alien iron-reducing bacteria are efficiently enriched. The high anaerobic time avoids the impact of oxygen on alien iron-reducing bacteria, further realizing the co-production of microbial metabolites.

Claims

1. A method for the synergistic extraction and recovery of biodegradable plastics and blue iron stone for sewage treatment, characterized in that: The steps include: (1) The sludge is inoculated into the SBR reactor and the pH is controlled at 7-7.5; (2) The inoculated sludge was cultivated in a 12- or 24-hour reaction cycle to construct a reaction mode of double electron acceptor supply under anaerobic-aerobic alternating reaction: Under anaerobic conditions, dissimilatory iron-reducing bacteria use ferric citrate as an electron acceptor and DO is less than 0.

1. 3+ Reduction to Fe 2+ It reacts with phosphate to form blue iron stone, while the biodegradable plastic-synthetic bacteria convert the carbon source in the sewage into biodegradable plastic and store it; Under aerobic conditions, biodegradable plastic synthesis bacteria use oxygen as an electron acceptor. When DO is 3-4, biodegradable plastic synthesis bacteria use oxygen as an electron acceptor for efficient enrichment. Overcoming the nutritional competition between biodegradable plastic synthesizing bacteria and dissimilatory iron-reducing bacteria in the coexistence environment by supplying two electron acceptors in stages; (3) After 8-10 weeks of reaction, the blue-green transparent crystals at the bottom of the reactor were centrifuged, vacuum dried, and stored anaerobically to obtain recovered blue iron stone with a yield of 1.81-4.02 g / g PO4 3- ; (4) After 8-10 weeks of reaction, the sludge in the reactor is centrifuged, and the lower precipitate is freeze-dried to obtain the recovered biodegradable plastic with a yield of 0.38-0.92 g / g sodium acetate; In the step (2), the ratio of the anaerobic time to the aerobic time is 1:3-3:

1.

2. The method according to claim 1, characterized in that The reaction cycle of step (2) includes pumping the culture medium for 10 minutes, anaerobic stirring for 10-20 minutes, aerobic aeration stirring for 3-40 minutes, sedimentation for 60 minutes, and removing the supernatant for 10 minutes, and the cycle continues.

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

1.

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

1.

5. The method according to claim 1, characterized in that The centrifugation condition of step (3) is 8000-12000 rpm for 3-10 minutes.

6. The method according to claim 1, characterized in that The centrifugation condition of step (4) is 8000-12000 rpm for 10-20 minutes.

7. The method according to claim 1, characterized in that The vacuum drying temperature in step (3) is 60-70°C.

8. The method according to claim 1, characterized in that The freeze drying in step (4) is carried out at -50-60°C.

9. The method according to claim 1, characterized in that: The concentration of ferric citrate added to the influent water is 1-3 mM each time.

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