Method for improving sewage treatment efficiency through cooperation of polylactic acid plastic and rhamnolipid and application

Abstract

The invention discloses a method for improving sewage treatment efficiency through cooperation of polylactic acid plastic and rhamnolipid and application, and belongs to the technical field of water treatment and environmental protection. The method comprises the following steps: purifying and culturing extracted microorganisms, carrying out a colonization experiment on the microorganisms, measuring the density of suspended microorganisms, measuring the concentration of microorganisms on the surface of polylactic acid, and analyzing a microbial community structure, and evaluating the optimization effect of improving the sewage treatment efficiency by the polylactic acid plastic and rhamnolipid according to the experiment result. According to the method, the polylactic acid plastic subjected to rhamnolipid attachment pretreatment is used as a filler of microorganisms, and through the synergistic effect of the polylactic acid plastic and the rhamnolipid, the colonization amount and activity of the microorganisms on the surface of the polylactic acid plastic are improved, and the density of suspended microorganisms is improved; the characteristic that polylactic acid particles are easy to colonize by microorganisms after rhamnolipid is attached is exerted, the proportion of microorganisms such as complex organic matters and nitrifying bacteria is adjusted and degraded, and the application of a sewage biochemical treatment process is optimized.

Description

Technical Field

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

[0002] In the sewage treatment process, the aerobic stage usually uses fillers as carriers for microbial attachment to degrade organic matter, ammonia nitrogen and other pollutants in sewage. Since the surface of the filler provides a place for microorganisms to attach, it can effectively promote the colonization and growth of microorganisms. Therefore, the properties of the filler directly affect the treatment effect and efficiency. Common plastic fillers include polypropylene (PP), polyethylene (PE) and other materials. They have high chemical stability and long service life, so they are widely used in sewage treatment systems. However, although these traditional plastic fillers can provide carriers for microbial attachment, they have poor biodegradability and long-term use may cause environmental pollution.

[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, polylactic acid still needs further research in changing microbial communities and increasing microbial colonization, 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 effectively optimizing the process of sewage biochemical treatment. Summary of the invention

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

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

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

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

[0008] (3) Rhamnolipids were mixed with pretreated polylactic acid plastics and purified cultured microorganisms in an inorganic culture medium for a microbial colonization experiment. The density of suspended microorganisms, the concentration of microorganisms on the polylactic acid surface, and the structure of the microbial community were then measured. The optimization effect was evaluated by the colonization amount of microorganisms, the density of microorganisms, and the structure of the microbial community. 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 method of wastewater biochemical treatment process.

[0009] As this embodiment, the microorganism purification and culture is inoculated into an expansion medium to culture the microorganism.

[0010] As 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 by 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 the present implementation scheme, when analyzing the structure of the microbial community, the 16S rRNA method is used to perform detection at the phylum level and the gene level, and the changes in the proportion of microorganisms related to sewage treatment 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 by the amount of colonized microorganisms, the density of microorganisms, and the community structure.

[0015] As this implementation scheme, polypropylene particles are selected as control fillers and fatty alcohol polyvinyl ether is used as a control experimental group. The microbial colonization situation 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 proportion of nitrifying bacteria in suspended microorganisms is increased after treatment with rhamnolipid RHA. It 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 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 Seventh and Eighth Water Purification Plant A 2 In the aerobic stage 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 for expansion culture 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 strains were 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 121°C high-pressure steam sterilizer 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 be 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 supplemented; 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 sodium chloride, 0.80 g / L ammonium chloride, 0.50 g / L potassium dihydrogen phosphate, 0.60 g / L dipotassium hydrogen phosphate, 0.20 g / L magnesium chloride hexahydrate, 0.05 g / L calcium chloride dihydrate, and 1 g / L 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 extended medium in a constant temperature oscillator at 37°C and 120 r / min for 24 h. Then, 1 mL of bacterial solution that had been expanded for one day was added to another bottle of extended medium. After three expansions, the microbial concentration was confirmed to be 2.91 × 10 by the plate spreading method. 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 600nm 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 600nm was measured (OD 600 ), compare and analyze the effects of plastics, rhamnolipids, and fatty alcohol polyethylene ethers on the concentration of suspended microorganisms. During the experiment, ensure the cleanliness of the instruments and cuvettes to avoid contamination or errors.

[0026] (5) Determination of concentration of microorganisms colonizing on plastic surface: The BCA method was used to determine the protein content of microorganisms attached to plastic. 0.5 g of plastic was taken into 2 mL centrifuge tubes, and 1.0 mL of physiological saline was added to each tube. 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 min using a homogenizer, and 20 μL of the solution was taken out from the centrifuge tubes for color development 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 the surface were eluted into the saline using an oscillating mixer. 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 the DNA were evaluated 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 Shenggong 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 of the present invention shows 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 improved, thereby increasing the amount of microorganisms colonizing the surface, adjusting the proportion of microorganisms such as degrading complex organic matter and nitrifying bacteria, and optimizing the structure of the microbial community. The amount of colonized microorganisms, the density of microorganisms, and the community structure are used to evaluate the optimization effect, thereby optimizing the sewage biochemical treatment process.

[0031] (2) The biodegradable properties of polylactic acid used in the method described in 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 a new idea 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 simulation conditions at different times in Example 1, Figure (a) is the polypropylene experimental group, Figure (b) is the polylactic acid experimental group, and Figure (c) is the microbial 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 polyvinyl ether is attached, (e) is polylactic acid after rhamnolipid is attached, and (f) is polylactic acid after fatty alcohol polyvinyl ether is attached.

[0034] Figure 3 Figure 3 is the scanning electron microscope image of the plastic surface biofilm in each experimental group of Example 3, Figure (a) is the scanning electron microscope image of the original polypropylene, Figure (b) is the scanning electron microscope image of the original polylactic acid, Figure (c) is the scanning electron microscope image of the polypropylene surface biofilm, Figure (d) is the scanning electron microscope image of the polylactic acid surface biofilm, Figure (e) is the scanning electron microscope image of the polypropylene surface biofilm with the addition of rhamnolipid, Figure (f) is the scanning electron microscope image of the polylactic acid surface biofilm with the addition of rhamnolipid, Figure (g) is the scanning electron microscope image of the polypropylene surface biofilm with the addition of fatty alcohol polyoxyethylene ether, and Figure (h) is the 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 in Example 4.

[0036] Figure 5 This is the microbial community analysis at the genus level of Example 5, Figure (a) is the analysis of the microbial community colonized on 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 on the plastic surface and the proportion of different types of suspended microorganisms in each experimental group. Figure (a) shows the proportion of microorganisms colonizing on the plastic surface, and Figure (b) shows the proportion of suspended microorganisms. DETAILED DESCRIPTION

[0038] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited to the described contents, and 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 to cooperate 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, comprising 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 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 Seventh and Eighth 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 placed in a fume hood for 1 hour to allow the activated sludge to stand and stratify. Then 5mL of the supernatant was added to 500mL of pre-sterilized expansion culture medium with components of 10.00g / L peptone, 5.00g / L yeast powder, and 10.00g / L sodium chloride. All the culture media were heated in a 121°C high-pressure steam autoclave for 30min before use, and were placed at room temperature before use. After culturing for 24 hours, the microorganisms and glycerol were mixed in proportion in an ultra-clean workbench (20% glycerol: bacteria = 3:7, a total of 4mL), and the strains were stored in a -80°C refrigerator for standby use.

[0043] (3) Microbial colonization experiment: 10 g of plastic with a concentration of 1.46×10 7 CFU / mL of microorganisms and 0.1% rhamnolipid and fatty alcohol polyoxyacetic acid ether concentrations 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. The culture media were heated in a 121°C high-pressure steam autoclave for 30 min before use, and then placed at room temperature before use. The total volume was controlled to be 200 mL, and the constant temperature shaker was set to a speed of 130 rpm and a temperature of 28°C. The experimental period was 30 days, 4 mL of the reaction solution was taken every 5 days, and 5 mL of the inorganic salt culture medium containing sodium acetate was added thereto; 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 r / min. 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 the ratio of 0.005, 0.01, 0.02, 0.1, 0.2, 0.5 and 1, and its absorbance at 600nm wavelength was detected by ultraviolet spectrophotometer, and a standard curve was drawn. The reaction solution at 0, 5, 10, 15, 20, 25 and 30 days obtained in step (4) was added to the cuvette. During the experiment, the instrument and cuvette were kept clean to avoid contamination or error, and the absorbance at 600nm wavelength (OD 600 ), the measured absorbance value was combined with the drawn standard curve to obtain a comparative analysis of the effects of plastics, rhamnolipids RHA and fatty alcohol polyoxyacetic acid ether 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 polyoxyacetate 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 polylactic acid plastics in cooperation with rhamnolipids to improve sewage treatment efficiency, and an analysis of the change in the hydrophilicity of plastics after the attachment of rhamnolipids (RHA) and fatty alcohol polyoxyacetic acid ethers (AEO), the method is as follows:

[0048] Two original plastics, polypropylene and polylactic acid, were mixed with rhamnolipid (RHA) and fatty alcohol polyoxyacetate ether (AEO) at a concentration of 0.1% for 24 hours, freeze-dried and pressed into tablets. The moment when ultrapure water was dropped on the surface was recorded using a contact angle meter. The surface contact angle of the plastics with rhamnolipid and fatty alcohol polyoxyacetate ether attached 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 Figure 2. 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. The hydrophilicity of polylactic acid is stronger than that of 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 nutrient-rich film that quickly attracts microbial colonization.

[0050] Example 3

[0051] A method and application of using polylactic acid plastic to cooperate with rhamnolipid to improve sewage treatment efficiency, and observing the morphology of biofilm 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, and then gradually dehydrated in 10%, 30%, 50%, 70% and 90% ethanol solutions for 10 minutes each time, and finally dehydrated twice in 100% ethanol solution for 15 minutes each time to completely dehydrate and wash away the impurities and excess fixative on the surface, and then freeze-dried for 24 hours. After the sample was fixed on a substrate and gold-sprayed, the colonization and morphological characteristics of the microorganisms on its surface were observed by scanning electron microscopy at an acceleration voltage of 5kV, and the magnification of the scanning electron microscope was 5000 times. The results are as follows 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) and 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, which indicates 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 combination with rhamnolipid to improve sewage treatment efficiency, and determining the colonization content of microbial protein attached to the plastic, the method is as follows:

[0056] The BCA method was used to determine the content of microbial protein attached to plastics: 0.5 g of polylactic acid plastic and polypropylene plastic were taken into 2 mL centrifuge tubes respectively, 1.0 mL of normal saline was added thereto, and ultrasonic treatment was performed for 30 min to separate the plastic from the culture medium. A homogenizer was used to oscillate at high speed 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 on the polypropylene surface. Polylactic acid was more conducive to microbial colonization than polypropylene. The protein concentration on the plastic surface in the polylactic acid experimental group with the addition of 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 plastic (PLA) and polypropylene plastic (PP) were taken out from the experimental groups of PLA-microbes, PLA-microbes-RHA, PLA-microbes-AEO and PP-microbes, PP-microbes-RHA, PP-microbes-AEO, and 1 mL of normal saline was added and the microorganisms on the surface were eluted into normal saline using a shaking mixer. DNA was extracted using EZNA Mag-Bind Soil DNA Kit (Omega, M5635-02, USA) according to the manufacturer's instructions. The quality and concentration of DNA were evaluated by 1% agarose gel electrophoresis and Qubit 4.0 fluorometer (Thermo Fisher Scientific, USA). The forward amplification primer 341F (5'-CCTACGGGNGGCWGCAG-3') and the reverse amplification primer 805R (5'-GACTACHVGGGTATCTAATCC-3') were used for the amplification of bacterial 16S 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 Shenggong 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. 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 were 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 is replaced with trehalose lipid and lecithin, respectively, and a comparative experiment is carried out under the same experimental conditions to determine its analysis of the microbial community structure. The steps are as follows:

[0064] The structure of the microbial community was analyzed using 16S rRNA sequencing technology, and 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 suggests 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 bacterial communities or change the ecological functions of the community.

[0065] By comparing Examples 1-5 with the comparative example, it is shown 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 nitrates and reduce 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 to facilitate the understanding and use of the invention by those skilled in the art. It is obvious that those skilled in the art can easily make various modifications to these embodiments and apply the general principles described herein to other embodiments without creative work. Therefore, the present invention is not limited to the above embodiments, and 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 collaboration with rhamnolipid, characterized in that: The following steps are involved: (1) Pretreating polylactic acid plastic with 75% ethanol, drying and setting aside; (2) Extracting microorganisms from sewage treatment plants, purifying and culturing 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 by 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 microorganism purification and cultivation are inoculated into an expansion medium to cultivate the microorganism.

3. The method for improving sewage treatment efficiency by using polylactic acid plastic in cooperation 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 in an aerobic state.

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 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.

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 the biofilm on the surface of polylactic acid particles were studied.

8. The method for improving sewage treatment efficiency by using polylactic acid plastic in cooperation with rhamnolipid according to claim 1, characterized in that: Polypropylene particles were selected as the control filler, and fatty alcohol polyvinyl ether was used as the control experimental group to compare the microbial colonization and microbial community structure with polylactic acid particles as the filler.

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

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