A method and application of polylactic acid plastic synergistically using rhamnolipid to improve sewage treatment efficiency

Abstract

The present invention discloses a method and application of using polylactic acid plastic to cooperate with rhamnolipid to improve sewage treatment efficiency, and belongs to the field of water treatment and environmental protection technology. The present invention purifies and cultures the extracted microorganisms, and then conducts colonization experiments of microorganisms, density determination of suspended microorganisms, concentration determination of microorganisms on the surface of polylactic acid, and analysis of microbial community structure. According to the experimental results, the optimization effect of using polylactic acid plastic to cooperate with rhamnolipid to improve sewage treatment efficiency is evaluated. The method uses polylactic acid plastic pretreated with rhamnolipid as a filler for microorganisms. Through the synergistic effect of polylactic acid plastic and rhamnolipid, the colonization amount and activity of microorganisms on the surface of polylactic acid plastic are improved, the density of suspended microorganisms is increased, and the characteristic that polylactic acid particles are easily colonized by microorganisms after rhamnolipid is attached is brought into play, so as to adjust the proportion of microorganisms such as degrading complex organic matter and nitrifying bacteria, and optimize the application of sewage biochemical treatment process.

Description

Technical Field

[0001] The present invention belongs to the field of water treatment and environmental protection technology, and specifically relates to a method and application of improving sewage treatment efficiency by cooperating with polylactic acid plastic and rhamnolipid. Background Art

[0002] During the sewage treatment process, fillers are typically used in the aerobic section as carriers for microbial attachment, degrading pollutants such as organic matter and ammonia nitrogen in the sewage. Because the surface of the filler provides a site for microorganisms to attach, it effectively promotes their colonization and growth. Therefore, the properties of the filler directly affect the treatment effect and efficiency. Common plastic fillers include polypropylene (PP) and polyethylene (PE), which have high chemical stability and long service life and are therefore widely used in sewage treatment systems. However, while these traditional plastic fillers can provide carriers for microbial attachment, they have poor biodegradability and may cause environmental pollution due to long-term use.

[0003] Polylactic acid has good environmental compatibility. Compared with traditional non-biodegradable plastics, polylactic acid can decompose faster under the action of microorganisms, thus avoiding the plastic pollution problem caused by traditional plastics in the sewage treatment process. However, the effect of single polylactic acid in sewage treatment is not obvious. At present, the effect of polylactic acid in changing microbial communities and increasing microbial colonization still needs further research, and there are no reports on the synergistic effects of plastics and rhamnolipids in sewage treatment. Therefore, the present invention attempts to provide a process for optimizing the efficiency of sewage biochemical treatment, a new idea for reducing the potential harm of plastics to the environment, and achieving an effective optimization process for sewage biochemical treatment. Summary of the Invention

[0004] This study aimed to explore the synergistic effect of polylactic acid and rhamnolipid on promoting microbial colonization and its application potential in optimizing treatment processes.

[0005] A method for improving sewage treatment efficiency by using polylactic acid particles as a filler in conjunction with rhamnolipids comprises the following steps:

[0006] (1) Pre-treating the polylactic acid plastic, drying it, and storing it in a sterile bag for later use;

[0007] (2) Extracting microorganisms from sewage treatment plants, purifying and culturing the microorganisms;

[0008] (3) Rhamnolipids were mixed with pretreated polylactic acid plastics and purified cultured microorganisms in an inorganic culture medium to conduct a microbial colonization experiment. The density of suspended microorganisms, the concentration of microorganisms on the polylactic acid surface, and the microbial community structure were then measured. The optimization effect was evaluated by the colonization amount of microorganisms, the density of microorganisms, and the microbial community structure. The proportion of microorganisms such as those that degrade complex organic matter and nitrifying bacteria was adjusted through the combined action of polylactic acid and rhamnolipids, thereby optimizing the wastewater biochemical treatment process.

[0009] In this embodiment, the microorganisms are purified and cultured by inoculating them into an expansion medium to culture the microorganisms.

[0010] In this embodiment, the culture medium in step (3) is an inorganic salt culture medium containing sodium acetate, and the entire process of the microbial colonization experiment lasts for 30 days in an aerobic state.

[0011] As this embodiment, the density of the suspended microorganisms is measured using an ultraviolet spectrophotometer to measure their growth.

[0012] As this embodiment, the concentration of microorganisms on the plastic surface is determined by using the BCA method to first determine the protein concentration on the surface of the polylactic acid particles, thereby measuring the amount of microorganisms colonized on the surface of the polylactic acid particles.

[0013] As an embodiment of this invention, when analyzing the structure of the microbial community, the 16S rRNA method is used to detect at the phylum level and the gene level, and the changes in the proportion of sewage treatment-related microorganisms are classified and analyzed. The surface morphology of the plastic is observed with a scanning electron microscope, and the community distribution and formation of the biofilm on the surface of the polylactic acid particles are studied.

[0014] In this embodiment, the optimization effect is evaluated using the amount of colonized microorganisms, the density of the microorganisms, and the community structure.

[0015] As this implementation plan, polypropylene particles are selected as the control filler and fatty alcohol polyvinyl ether is used as the control experimental group. The microbial colonization and microbial community structure are compared with those of polylactic acid particles to analyze the optimization effect of polylactic acid particles on the biochemical treatment process.

[0016] As this implementation plan, the conditions related to rhamnolipids, plastic particles and rhamnolipids in each system must remain consistent.

[0017] The method for improving sewage treatment efficiency described in the present invention is to use polylactic acid particles as fillers. The dominant bacteria on the polylactic acid have the ability to degrade complex organic matter, and the treatment with rhamnolipid RHA increases the proportion of nitrifying bacteria in suspended microorganisms, which has a good optimization process in the application of degrading complex organic matter and nitrifying bacteria in the sewage biochemical treatment process.

[0018] In order to achieve the above purpose, the technical solution adopted specifically includes the following steps:

[0019] (1) Treatment of plastic particles: Soak the polypropylene and polylactic acid plastic particles in 75% ethanol for one hour to remove any microorganisms that may exist on their surfaces. Then, after drying, place them in sterile bags for storage.

[0020] (2) Purification and cultivation of microorganisms: The microorganisms used in the experiment were obtained from Kunming No. 7 and No. 8 Water Purification Plant A. 2 In the aerobic section of the / O process, the sludge was mixed in the laboratory and transferred to a 500mL conical flask, the bottle mouth was sealed with a sealing film, and then the conical flask was placed in a constant temperature water bath shaker at 37°C and 180rpm for purification for 72 hours. After the purification was completed, the conical flask was taken out and allowed to stand in a fume hood for 1 hour to allow the activated sludge to stand and stratify. Then, 5mL of the supernatant of the activated sludge was added to a pre-sterilized 500mL expansion culture medium and expanded for 24 hours. Then, in an ultra-clean workbench, the microorganisms and glycerol were mixed in a ratio of 20% glycerol: bacteria = 3:7 for a total of 4mL, and the strain was stored in a -80°C refrigerator for use.

[0021] During the purification and cultivation of microorganisms, the components of the expansion culture medium are 10.00 g / L peptone, 5.00 g / L yeast powder, and 10.00 g / L sodium chloride. The culture medium is heated in a high-pressure steam sterilizer at 121°C for 30 minutes before use, and then taken out and placed at room temperature before use.

[0022] (3) Microbial colonization experiment: 10 g of plastic with a concentration of 1.46×10 7 The concentration of CFU / mL of microorganisms, rhamnolipids and fatty alcohol polyoxyethylene ethers was 0.1%, inorganic salt culture medium was added, 1g / L sodium acetate was added as a carbon source, the total volume was controlled to 200mL, the constant temperature shaker was set to 130rpm and the temperature was 28°C, the experimental period was 30 days, 4mL of reaction solution was taken every 5 days, and 5mL of inorganic salt culture medium containing sodium acetate was added; 1.5g of plastic was taken every 15 days to study the microorganisms colonizing the plastic surface and the properties of the plastic.

[0023] In the microbial colonization embodiment, the rhamnolipid (RHA) is produced by biological metabolism and the fatty alcohol polyoxyethylene ether (AEO) is chemically synthesized.

[0024] In the implementation scheme for colonization of microorganisms, the components of the inorganic salt culture medium are: 1.00 g / L of sodium chloride, 0.80 g / L of ammonium chloride, 0.50 g / L of potassium dihydrogen phosphate, 0.60 g / L of dipotassium hydrogen phosphate, 0.20 g / L of magnesium chloride hexahydrate, 0.05 g / L of calcium chloride dihydrate, and 1 g / L of sodium acetate. The culture medium is heated in a high-pressure steam sterilizer at 121°C for 30 minutes before use, and then taken out and placed at room temperature before use.

[0025] (4) Determination of suspended microbial density: 1 mL of bacterial solution was cultured in an expansion medium in a constant temperature oscillator at 37°C and 120 rpm for 24 hours. Then, 1 mL of the bacterial solution that had been expanded for one day was added to another bottle of expansion medium. After three expansions, the microbial concentration was confirmed to be 2.91 × 10 9 CFU / mL, the expanded microbial solution was diluted in the ratio of 0.005, 0.01, 0.02, 0.1, 0.2, 0.5 and 1, and its absorbance at 600 nm was detected by UV spectrophotometer, and a standard curve was drawn. The solution at 0, 5, 10, 15, 20, 25 and 30 days in step (4) was added to the cuvette and its absorbance at 600 nm was measured (OD 600 ), comparative analysis of the effects of plastics, rhamnolipids, and fatty alcohol polyethylene ethers on the concentration of suspended microorganisms. During the experiment, ensure the cleanliness of instruments and cuvettes to avoid contamination or errors.

[0026] (5) Determination of the concentration of microorganisms colonizing the plastic surface: The BCA method was used to determine the protein content of microorganisms attached to the plastic. 0.5 g of plastic was taken into 2 mL centrifuge tubes, and 1.0 mL of physiological saline was added to each of the tubes. The tubes were ultrasonically treated for 30 min to separate the plastic from the culture medium. The tubes were oscillated at high speed for 2 minutes using a homogenizer. 20 μL of the solution was taken out of the centrifuge tubes and subjected to a color reaction with the BCA solution.

[0027] (6) Analysis of microbial community structure: 0.5 g of plastic was removed from the experimental group, 1 mL of saline was added, and the microorganisms on its surface were eluted into the saline using a shaker. DNA was extracted using the EZNA Mag-Bind Soil DNA Kit (Omega, M5635-02, USA) according to the manufacturer's instructions. The quality and concentration of DNA were assessed by 1% agarose gel electrophoresis and a Qubit 4.0 fluorometer (Thermo Fisher Scientific, USA). The V3-V4 region of the bacterial 16S rRNA gene was amplified using the forward amplification primer 341F (5'-CCTACGGGNGGCWGCAG-3') and the reverse amplification primer 805R (5'-GACTACHVGGGTATCTAATCC-3'). DNA samples of microorganisms colonizing the plastic surface in different experimental groups were sequenced on the Illumina MiSeq platform of Shanghai Sangon Biotechnology Co., Ltd. The suspended microorganisms were taken from the experimental group solution and detected and analyzed in the same way.

[0028] The method of improving sewage treatment efficiency by using polylactic acid plastic in collaboration with rhamnolipids according to the present invention has shown excellent effects in the application of sewage biochemical treatment processes.

[0029] Compared with the prior art, the present invention has the following advantages:

[0030] (1) The present invention uses polylactic acid attached with rhamnolipid as a carrier of aerobic microorganisms. Under the synergistic effect of rhamnolipid and polylactic acid, the activity of microorganisms on the surface of polylactic acid particles is enhanced, thereby increasing the amount of surface colonized microorganisms, adjusting the proportion of microorganisms such as degrading complex organic matter and nitrifying bacteria, and optimizing the microbial community structure. The optimization effect is evaluated by the amount of colonized microorganisms and the density and community structure of the microorganisms, thereby optimizing the sewage biochemical treatment process.

[0031] (2) The biodegradable properties of polylactic acid used in the method of the present invention reduce environmental risks, comply with the concepts of environmental protection and sustainable development, are low-cost and easy to promote, and provide a new direction for the selection of fillers in the biochemical treatment section of sewage treatment plants, and provide new ideas for optimizing the efficiency of sewage biological treatment and reducing the potential harm of plastics to the environment. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1 The absorbance at 600 nm of suspended microorganisms at different times under different simulation conditions in Example 1 is shown in Figure (a) for the polypropylene experimental group, Figure (b) for the polylactic acid experimental group, and Figure (c) for the microorganism experimental group.

[0033] Figure 2 The change of contact angle of plastic surface after treatment with rhamnolipid and fatty alcohol polyethylene in Example 2, Figure 2 (a) virgin polypropylene, Figure 2 (b) original polylactic acid, Figure 2 (c) Polypropylene after rhamnolipid attachment, Figure 2 (d) is polypropylene after fatty alcohol polyethylene ether is attached, Figure (e) is polylactic acid after rhamnolipid is attached, and Figure (f) is polylactic acid after fatty alcohol polyethylene ether is attached.

[0034] Figure 3 These are the scanning electron microscope images of the plastic surface biofilms in each experimental group of Example 3, Figure (a) is a scanning electron microscope image of the original polypropylene, Figure (b) is a scanning electron microscope image of the original polylactic acid, Figure (c) is a scanning electron microscope image of the polypropylene surface biofilm, Figure (d) is a scanning electron microscope image of the polylactic acid surface biofilm, Figure (e) is a scanning electron microscope image of the polypropylene surface biofilm with the addition of rhamnolipid, Figure (f) is a scanning electron microscope image of the polylactic acid surface biofilm with the addition of rhamnolipid, Figure (g) is a scanning electron microscope image of the polypropylene surface biofilm with the addition of fatty alcohol polyoxyethylene ether, and Figure (h) is a scanning electron microscope image of the polylactic acid surface biofilm with the addition of fatty alcohol polyoxyethylene ether.

[0035] Figure 4 The graphs are comparative diagrams of protein concentration on the plastic surface after 15 days and 30 days, respectively, in Example 4.

[0036] Figure 5 This is the microbial community analysis at the genus level in Example 5. Figure (a) is the analysis of the microbial community colonizing the plastic surface, and Figure (b) is the analysis of the suspended microbial community.

[0037] Figure 6 Figure 2 shows the proportion of microorganisms colonizing the plastic surface and the proportion of different types of suspended microorganisms in each experimental group. Figure (a) shows the proportion of microorganisms colonizing the plastic surface, and Figure (b) shows the proportion of suspended microorganisms. DETAILED DESCRIPTION

[0038] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. However, the protection scope of the present invention is not limited to the described contents. Any changes made based on the teachings of the present invention fall within the protection scope of the present invention.

[0039] Example 1

[0040] A method and application of using polylactic acid plastic in conjunction with rhamnolipid to improve sewage treatment efficiency, studying the effects of rhamnolipid (RHA), fatty alcohol polyoxyacetic acid ether (AEO), and plastic on colonized microorganisms and suspended microorganisms, including the following steps:

[0041] (1) Treatment of plastic particles: Soak the polylactic acid and polypropylene plastic particles in 75% ethanol for one hour to remove any microorganisms that may exist on their surfaces. Then, after drying, place them in sterile bags for storage.

[0042] (2) Purification and cultivation of microorganisms: The microorganisms used in the experiment were obtained from Kunming No. 7 and No. 8 Water Purification Plant A. 2 In the aerobic section of the / O process, the sludge was mixed in the laboratory and transferred to a 500mL conical flask, the bottle mouth was sealed with a sealing film, and then the conical flask was placed in a constant temperature water bath shaker at 37℃ and 180rpm for purification for 72h. After purification, the conical flask was taken out and placed in a fume hood for 1h to allow the activated sludge to stand and stratify. Then 5mL of the supernatant was added to 500mL of pre-sterilized expansion culture medium consisting of 10.00g / L peptone, 5.00g / L yeast powder, and 10.00g / L sodium chloride. All culture media were heated in a high-pressure steam autoclave at 121℃ for 30min before use, taken out and placed at room temperature before use. After culturing for 24h, the microorganisms and glycerol were mixed in proportion (20% glycerol: bacteria = 3:7, a total of 4mL) in an ultra-clean workbench, and the strains were stored in a -80℃ refrigerator for use.

[0043] (3) Microbial colonization experiment: 10 g of plastic with a concentration of 1.46×10 7 Microorganisms with a CFU / mL and a concentration of 0.1% rhamnolipid and fatty alcohol polyoxyacetic acid ether were added to an inorganic salt culture medium composed of 1.00 g / L sodium chloride, 0.80 g / L ammonium chloride, 0.50 g / L potassium dihydrogen phosphate, 0.60 g / L potassium hydrogen phosphate, 0.20 g / L magnesium chloride hexahydrate, 0.05 g / L calcium chloride dihydrate, and 1 g / L sodium acetate. All culture media were heated in a 121°C high-pressure steam sterilizer for 30 minutes before use, and then placed at room temperature before use. The total volume was controlled to 200 mL, and the constant temperature shaker was set at a speed of 130 rpm and a temperature of 28°C. The experimental period was 30 days, and 4 mL of the reaction solution was taken every 5 days, and 5 mL of inorganic salt culture medium containing sodium acetate was added to it; 1.5 g of plastic was taken every 15 days to study the microorganisms colonizing the plastic surface and the properties of the plastic.

[0044] (4) Determination of suspended microbial density: 1 mL of bacterial solution was cultured in an expansion medium in a constant temperature oscillator at 37°C and 120 rpm. After 24 hours, 1 mL of bacterial solution from one day of expansion culture was added to another bottle of expansion medium. After three expansion cultures, the microbial concentration was confirmed to be 2.91 × 10 9CFU / mL, the expanded microbial solution was diluted in proportions of 0.005, 0.01, 0.02, 0.1, 0.2, 0.5 and 1, and its absorbance at a wavelength of 600 nm was detected using a UV spectrophotometer to draw a standard curve. The reaction solution obtained in step (4) at 0, 5, 10, 15, 20, 25 and 30 days was added to a cuvette. During the experiment, the instrument and cuvette were kept clean to avoid contamination or error. The absorbance at a wavelength of 600 nm (OD 600 ), the absorbance value was combined with the standard curve to obtain a comparative analysis of the effects of plastics, rhamnolipids RHA and fatty alcohol polyoxyacetic acid ethers AEO on the concentration of suspended microorganisms. The results are as follows Figure 1 shown.

[0045] according to Figure 1 It can be seen that rhamnolipid RHA and fatty alcohol polyoxyacetic acid ether AEO both inhibited the growth of suspended microorganisms, but polylactic acid significantly increased the density of suspended microorganisms. Compared with polylactic acid and polypropylene, polylactic acid had a stronger effect on suspended microorganisms.

[0046] Example 2

[0047] A method and application of using polylactic acid plastic in conjunction with rhamnolipid to improve wastewater treatment efficiency. The hydrophilicity change of the plastic after the attachment of rhamnolipid (RHA) and fatty alcohol polyoxyacetic acid ether (AEO) is analyzed as follows:

[0048] Two original plastics, polypropylene and polylactic acid, were mixed with rhamnolipid (RHA) and fatty alcohol polyoxyacetic acid ether (AEO) at a concentration of 0.1% for 24 hours, freeze-dried, and then pressed into tablets. A contact angle meter was used to record the moment when ultrapure water was dropped on the surface. The surface contact angle of the plastics after the attachment of rhamnolipid and fatty alcohol polyoxyacetic acid ether was measured and compared with the two original plastics to analyze the effects of RHA and AEO on the plastic surface contact angle. The results are shown in the figure. Figure 2 shown.

[0049] according to Figure 2 (a) and (b) show that the surface contact angles of original polypropylene and original polylactic acid are 101.04°±0.86 and 66.4°±3.5, respectively. The contact angle of polylactic acid is much lower than that of polypropylene. Polylactic acid is more hydrophilic than polypropylene, which makes it easier for microorganisms to form biofilms on the surface of polylactic acid. Figure 2 From the comparison of (c) to (f), it can be seen that the polylactic acid plastic attached with rhamnolipid and fatty alcohol polyvinyl ether exhibits super hydrophilicity, and the more hydrophilic surface of microplastics can easily adsorb organic and inorganic nutrients in the surrounding environment, forming a layer of nutrient-rich film that will quickly attract microbial colonization.

[0050] Example 3

[0051] A method and application of using polylactic acid plastic in conjunction with rhamnolipid to improve sewage treatment efficiency, and observing the biofilm morphology on the plastic surface, the steps are as follows:

[0052] The microorganisms colonized on the plastic surface were fixed with 2.5% glutaraldehyde for 5 hours. Subsequently, they were gradually dehydrated in 10%, 30%, 50%, 70% and 90% ethanol solutions for 10 minutes each time. Finally, they were dehydrated twice in 100% ethanol solution for 15 minutes each time to completely dehydrate and wash away surface impurities and excess fixative. The samples were then freeze-dried for 24 hours. After the samples were fixed on a substrate and subjected to gold spraying, the colonization status and morphological characteristics of the microorganisms on the surface were observed by scanning electron microscopy at an acceleration voltage of 5kV and a magnification of 5000 times. The results are shown in Figure 2. Figure 3 shown.

[0053] In the experimental group where only microorganisms were added, only a small number of microorganisms attached to the plastic surface, e.g. Figure 3 (a)-(d) show that no visible biofilm was formed after 30 days. Figure 3 As shown in (e)-(h), in the experimental groups with the addition of RHA and AEO, relatively complete biofilms were formed on the plastic surfaces, and the biofilms formed on the polylactic acid surface were significantly more than those on the polypropylene surface, indicating that the microbial enrichment ability of polylactic acid is better than that of polypropylene, and both RHA and AEO can promote the formation of biofilms on the plastic surface.

[0054] Example 4

[0055] A method and application of using polylactic acid plastic in conjunction with rhamnolipid to improve sewage treatment efficiency, and determining the colonization content of microbial protein attached to the plastic, as follows:

[0056] The BCA method was used to determine the content of microbial protein attached to the plastic: 0.5 g of polylactic acid plastic and polypropylene plastic were respectively placed in 2 mL centrifuge tubes, 1.0 mL of normal saline was added to each, and ultrasonic treatment was performed for 30 minutes to separate the plastic from the culture medium. The mixture was shaken at high speed using a homogenizer for 2 minutes, and 20 μL of the solution was taken out from the centrifuge tube for color reaction with the BCA solution.

[0057] according to Figure 4It can be seen that at 30 days, the protein concentration on the plastic surface in PLA-microbes reached 0.12 mg / mL, while the protein concentration on the plastic surface in PP-microbes was only 0.03 mg / mL. The number of microorganisms colonized on the polylactic acid surface was about 4 times that of the polypropylene surface. Compared with polypropylene, polylactic acid was more conducive to microbial colonization. The protein concentration on the plastic surface in the polylactic acid experimental group with added RHA and AEO increased by 57.43% and 10.53% respectively, indicating that the effect of rhamnolipids in increasing microbial colonization was significantly higher than that of fatty alcohol polyvinyl ether.

[0058] Example 5

[0059] A method and application of polylactic acid plastic in combination with rhamnolipid to improve sewage treatment efficiency, and analysis of the community structure of colonized and suspended microorganisms, the steps are as follows:

[0060] 0.5 g of polylactic acid (PLA) and polypropylene (PP) plastic were removed from the PLA-microbes, PLA-microbes-RHA, PLA-microbes-AEO, and PP-microbes, PP-microbes-RHA, and PP-microbes-AEO experimental groups. 1 mL of saline was added to the plastic and the microorganisms on the plastic were eluted into the saline using a shaker. DNA was extracted using the EZNAMag-Bind Soil DNA Kit (Omega, M5635-02, USA) according to the manufacturer's instructions. DNA quality and concentration were assessed by 1% agarose gel electrophoresis using a Qubit 4.0 fluorometer (Thermo Fisher Scientific, USA). Bacterial 16S was amplified using forward primer 341F (5'-CCTACGGGNGGCWGCAG-3') and reverse primer 805R (5'-GACTACHVGGGTATCTAATCC-3'). The V3-V4 region of the rRNA gene was amplified, and the DNA samples of the microorganisms colonizing the plastic surface in different experimental groups were sequenced on the Illumina MiSeq platform of Shanghai Sangon Biotechnology Co., Ltd. The suspended microorganisms were taken from the experimental group solution and detected and analyzed in the same way. The results are shown in the figure below. Figure 5 shown.

[0061] according to Figure 5It can be seen that the proportion of microorganisms that degrade complex organic matter colonized on the surfaces of polypropylene and polylactic acid are 36.31% and 70.65%, respectively. The dominant bacteria on polylactic acid have the ability to degrade complex organic matter. The addition of rhamnolipid RHA increases the proportion of nitrifying bacteria in suspended microorganisms, while the addition of fatty alcohol polyoxyacetic acid ether AEO reduces the proportion of nitrifying bacteria. These changes prove that the presence of polylactic acid and rhamnolipid RHA is beneficial to the degradation of pollutants such as organic matter and ammonia nitrogen in biochemical treatment, which is of great significance for optimizing the treatment process.

[0062] Comparative Example

[0063] In this example, the rhamnolipid in the system was replaced with trehalose lipid and lecithin, respectively, and a comparative experiment was conducted under the same experimental conditions to determine its analysis of the microbial community structure. The steps are as follows:

[0064] The microbial community structure was analyzed using 16S rRNA sequencing technology. The results showed that in the presence of trehalose lipids and lecithin, the composition and diversity of the microbial community did not change significantly. This result indicates that the effects of trehalose lipids and lecithin on the microbial community are relatively limited, and they fail to significantly promote the growth of specific functional bacteria or change the ecological functions of the community.

[0065] Comparison between Examples 1-5 and the comparative example demonstrates that rhamnolipid (RHA) exhibits significant advantages in the experimental system. Specifically, RHA can effectively promote the growth of nitrifying bacteria, thereby optimizing the biochemical treatment process. Nitrifying bacteria play a key role in wastewater treatment, environmental remediation, and other processes. They can convert ammonia nitrogen into nitrate, reducing nitrogen pollution in water bodies. At the same time, RHA further improves the denitrification capacity of the system by enhancing the activity of nitrifying bacteria, providing important support for the optimization of the biochemical treatment process.

[0066] The above description of the embodiments is intended to facilitate understanding and use of the invention by those skilled in the art. It will be apparent that those skilled in the art can readily make various modifications to these embodiments and apply the general principles described herein to other embodiments without requiring inventive effort. Therefore, the present invention is not limited to the above-described embodiments. Improvements and modifications made by those skilled in the art based on the disclosure of the present invention, without departing from the scope of the present invention, should be within the scope of protection of the present invention.

Claims

1. A method for improving sewage treatment efficiency by using polylactic acid plastic in conjunction with rhamnolipid, characterized in that: The following steps are involved: (1) Pretreat polylactic acid plastic with 75% ethanol, dry it, and set aside; (2) Extracting microorganisms from sewage treatment plants, purifying and cultivating microorganisms; (3) Rhamnolipid, pretreated polylactic acid plastic, and purified cultured microorganisms were mixed in a culture medium to conduct a microbial colonization experiment. The density of suspended microorganisms, the concentration of microorganisms on the polylactic acid surface, and the microbial community structure were then measured. The optimization effect was evaluated based on the microbial colonization amount, microbial density, and microbial community structure.

2. The method for improving sewage treatment efficiency by using polylactic acid plastic in combination with rhamnolipid according to claim 1, characterized in that: The purification and cultivation of the microorganisms include inoculating the microorganisms into an expansion medium for cultivation.

3. The method for improving sewage treatment efficiency by using polylactic acid plastic in combination with rhamnolipid according to claim 1, characterized in that: The culture medium in step (3) is an inorganic salt culture medium containing sodium acetate. The entire process of the microbial colonization experiment lasts for 30 days and is in an aerobic state throughout.

4. The method for improving sewage treatment efficiency by using polylactic acid plastic in combination with rhamnolipid according to claim 1, characterized in that: The density of the suspended microorganisms is measured using an ultraviolet spectrophotometer.

5. The method for improving sewage treatment efficiency by using polylactic acid plastic in combination with rhamnolipid according to claim 1, characterized in that: The concentration of microorganisms on the surface of the polylactic acid plastic is determined by using the BCA method to first determine the protein concentration on the surface of the polylactic acid particles, thereby measuring the amount of microorganisms colonized on the surface of the polylactic acid particles.

6. The method for improving sewage treatment efficiency by using polylactic acid plastic in combination with rhamnolipid according to claim 1, characterized in that: The 16S rRNA method was used to detect at the phylum level and gene level, and the changes in the proportion of sewage treatment-related microorganisms were classified and analyzed.

7. The method for improving sewage treatment efficiency by using polylactic acid plastic in combination with rhamnolipid according to claim 1, characterized in that: The surface morphology of the plastic was observed using a scanning electron microscope, and the community distribution and formation of biofilm on the surface of polylactic acid particles were studied.

8. Application of the method according to any one of claims 1 to 7 in a wastewater biochemical treatment process.

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