Screening method of oil-containing wastewater degrading bacteria and application thereof in oil-containing wastewater treatment

Abstract

This invention discloses a method for screening bacteria that degrade oily wastewater. The method includes culturing and screening bacterial sources using liquid culture medium, acclimatization culture medium, and screening culture medium. The liquid culture medium, acclimatization culture medium, and screening culture medium have the same components, all using oily substances as the main carbon source. Each culture medium contains a co-metabolizing matrix composed of rhamnolipin and tea saponin. This invention optimizes the composition of the culture medium for oily wastewater-degrading bacteria. By using a combination of rhamnolipin and tea saponin as the co-metabolizing matrix, it solves the problems of insufficient emulsification and dispersion effect of single surfactants and insufficient contact between the bacterial community and the oil phase, effectively addressing the practical problem of oily wastewater treatment.

Description

Technical Field

[0001] This invention relates to the field of oily wastewater treatment technology, and in particular to a method for screening oily wastewater degrading bacteria and its application in oily wastewater treatment. Background Technology

[0002] Oily wastewater refers to wastewater containing oily substances discharged during industrial production processes, especially in petroleum extraction and processing, coking plants, and gasification plants. The oily substances in this wastewater mainly include natural petroleum, petroleum products, tar and its fractions, as well as edible animal and vegetable oils and fats. Based on the state of the oily substances in the wastewater, it can be divided into floating oil, emulsified oil, and dissolved oil. Floating oil refers to oily substances existing in the wastewater as large particles, generally larger than 100µm in diameter, which are easily separated from the wastewater. Floating oil is the main component of oily wastewater, especially in refinery wastewater, where it can account for 60%–80% of the oil content. Emulsified oil is characterized by a stable film formed by emulsifiers on the surface of oil droplets, causing mutual repulsion between droplets and making it difficult to coalesce into large particles, thus making it difficult to separate from the wastewater. Emulsified oil droplets have a smaller diameter, generally between 0.1-2µm. Dissolved oil refers to oily substances dissolved in water at the molecular level, with extremely low solubility, typically only a few milligrams per liter. The droplets of dissolved oil are smaller than those of emulsified oil, some as small as a few nanometers.

[0003] The hazards of oily wastewater are mainly manifested in the following ways: the oil surface covers the water, preventing reoxygenation and causing the water to lose its self-purification ability, becoming foul-smelling and affecting human health; the presence of floating oil also increases the risk of surface fires; and the high concentration of organic matter in emulsified oil poses a serious pollution hazard to water bodies. If this oily wastewater is not treated or is discharged into natural water bodies without meeting discharge standards, it will cause serious environmental pollution. Oily wastewater has complex water quality and poor biodegradability, making it difficult to treat using traditional activated sludge processes.

[0004] Currently, the most common industrial wastewater treatment process is the dissolved air flotation (DAF)-MBR process. DAF is a highly efficient solid-liquid or liquid-liquid separation technology that can effectively remove most oil droplets, as well as suspended solids, heavy metal ions, bacteria, and viruses. However, DAF does not completely remove oil from wastewater, and a small amount of oil droplets will still enter the next treatment unit—the MBR process. This can cause significant fouling of the MBR membrane, thus affecting the entire wastewater treatment process. Furthermore, the culture medium for petroleum-degrading bacteria has a single component design, lacking synergistic functional components. A single surfactant has limited emulsifying and dispersing effects on oil, resulting in insufficient contact between the bacteria and the oil phase. In the DAF-MBR process, residual oil droplets easily adhere to the membrane surface due to poor dispersibility, exacerbating membrane fouling, and the single-bacterial nutrient system leads to low degradation efficiency. Existing technologies do not consider the environmental friendliness and synergistic effects of surfactant formulations; some synthetic surfactants can easily cause secondary pollution and have poor compatibility with the bacterial community.

[0005] The core of bioaugmentation technology is the activity and proliferation capacity of efficient degradation bacteria. The optimization of the culture medium composition directly affects the effectiveness of the bacteria. Existing culture media often use a single co-metabolite matrix (such as Tween 80), which can slightly improve the solubility of oils, but has limited dispersion effect on emulsified oils, resulting in insufficient contact between the bacteria and the oil phase and limited degradation efficiency. At the same time, single surfactants are easily deactivated in complex wastewater systems and cannot continuously provide a stable oil-water contact environment for the bacteria. Summary of the Invention

[0006] To address the shortcomings of existing technologies, the present invention aims to provide a method for screening oily wastewater-degrading bacteria and its application in oily wastewater treatment. This method optimizes the composition of the culture medium for oily wastewater-degrading bacteria by using a combination of rhamnolipin and tea saponin as a synergistic co-metabolism matrix. This solves the problems of insufficient emulsification and dispersion effects of single surfactants and inadequate contact between the bacterial community and the oil phase, constructing a highly efficient culture medium system for rapid expansion and formation of bacterial agents, effectively solving the practical problem of oily wastewater treatment.

[0007] To achieve the above objectives, the present invention adopts the following technical solution:

[0008] A method for screening bacteria that degrade oily wastewater includes culturing and screening bacterial sources using a liquid culture medium, wherein a co-metabolizing matrix is ​​added to the liquid culture medium, and the co-metabolizing matrix is ​​composed of rhamnolipin and tea saponin.

[0009] The screening method for oil-degrading bacteria includes the following steps:

[0010] S1. Source of bacteria collection: Collect activated sludge from an environment contaminated with oily substances as the original source of bacteria;

[0011] S2, Acclimation and Enrichment: The original bacterial source was inoculated into a liquid culture medium containing a co-metabolizing matrix and subjected to multiple rounds of acclimation culture under aerobic conditions;

[0012] S3. Gradient pressure acclimatization: During the acclimatization process, the concentration of oil-based carbon sources in the acclimatization medium is gradually increased to apply selective pressure to the microbial community and obtain a mixed culture of the microbial community.

[0013] S4. Microbial community isolation and purification: The domesticated microbial community mixture was inoculated into the screening medium, and the degrading microbial community was obtained after multiple transfer cultures.

[0014] Preferably, the concentration of rhamnolipin in the aforementioned culture medium is 50-150 mg / L, the concentration of tea saponin is 50-150 mg / L, and the mass ratio of rhamnolipin to tea saponin is (0.8:1.2)-(1.2:0.8).

[0015] Preferably, in step S3 above, the method for gradient pressure acclimatization is as follows:

[0016] (1) The bacterial community was cultured for 3-5 rounds of degradation under the condition that the concentration of oil carbon source was 0.5 g / L;

[0017] (2) Increase the concentration of oil carbon source to 2.0 g / L and continue the degradation culture for 3-5 rounds to obtain the microbial mixed culture.

[0018] Preferably, in step S2, the liquid culture medium further includes basic nutrient components, which include multiple sources of nitrogen, phosphorus, potassium, magnesium, calcium, iron, sodium salt, and trace elements.

[0019] Preferably, the specific components of the aforementioned liquid culture medium include: mineral oil 0.5 g / L, NH4NO3 1.0 g / L, KH2PO4 1.0 g / L, K2HPO4 1.0 g / L, MgSO4·7H2O 0.2 g / L, CaCl2 0.02 g / L, FeCl3 0.05 g / L, NaCl 10 g / L, rhamnolipid 100 mg / L, tea saponin 100 mg / L, and trace element mixture 1.0 mL / L;

[0020] The culture conditions are: pH 7.2-7.8, temperature 26-30℃, and aerobic culture.

[0021] The method for preparing petroleum-degrading bacteria inoculants includes the following steps:

[0022] (1) Seed tank culture: The selected petroleum-degrading bacteria are inoculated into a seed tank and cultured to obtain seed liquid;

[0023] (2) Fermentation tank expansion: The seed liquid is inoculated into the fermentation tank for expansion culture. After the fermentation is completed, a highly efficient degrading agent is obtained.

[0024] Preferably, in step (1) above, the inoculum amount of the degrading bacteria is 1%-10%, and the specific components of the seed tank are: mineral oil 2g / L, NH4NO3 2g / L, KH2PO4 2g / L, K2HPO4 2g / L, MgSO4·7H2O 0.4g / L, CaCl2 0.04g / L, FeCl3 0.1g / L, NaCl 10g / L, trace element mixture 1mL / L, rhamnolipid 100mg / L, tea saponin 100mg / L; the culture temperature is 25-30℃, the culture time is 6-8 days, the pH is 7.2-7.8, and the dissolved oxygen (DO) is 4-8 mg / L.

[0025] In step (2), the inoculation amount of the seed culture is 1%-10%, and the composition and culture conditions of the fermenter culture medium are the same as those of the seed tank; the effective viable count of the highly efficient degrading agent is 10. 9 per mL.

[0026] The application of microbial agents in the treatment of oily wastewater involves adding microbial agents to the aerobic treatment unit of a membrane bioreactor to degrade COD in the oily wastewater.

[0027] Preferably, the specific steps for adding the microbial agent are as follows:

[0028] (1) Initial addition: Add 0.5-1.5 g / L of high-efficiency degradation bacteria to the aerobic MBR tank in one go;

[0029] (2) External maintenance: During the operation of the system, nutrients and trace elements are added, including rhamnose lipids and tea saponins.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) This invention uses rhamnolipin and tea saponin as a synergistic co-metabolism matrix to optimize the composition of the culture medium for oily wastewater degrading bacteria. Through structural complementarity, a more stable mixed monolayer is formed, which significantly reduces the interfacial tension between oil and water, improves the dispersibility and stability of the oil phase in the aqueous phase, and thus enhances the contact efficiency between the degrading bacteria and petroleum pollutants.

[0032] (2) This invention determines the optimal compound ratio and concentration of rhamnolipin and tea saponin, combines nutrient optimization, constructs an efficient culture medium system, rapidly expands the culture to form a bacterial agent, adds bacterial strains in the aerobic MBR treatment stage, and works synergistically with the original microbial community in the tank to play a role in bio-enhancement, and solves the problem of membrane oil clogging in the aerobic MBR plate in the sewage treatment process. Attached Figure Description

[0033] Figure 1 This is a flow chart of the oily wastewater treatment process of the present invention;

[0034] Figure 2 The curve showing the COD concentration change during the degradation test of petroleum wastewater by the bacterial agent prepared in Example 1 is shown.

[0035] Figure 3 The curve showing the change in COD concentration during the degradation test of the bacterial agent prepared in Example 1 on actual oily wastewater;

[0036] Figure 4 The diagram shows the relative abundance of the microbial community before and after the bacterial agent prepared in Example 1 was added to the MBR tank.

[0037] Figure 5 The graph shows the changes in the pressure difference monitoring data between the inside and outside of the membrane in the No. 1 bacterial addition group pool and the No. 2 control group pool.

[0038] Figure 6 A comparison chart of petroleum degradation rates under different co-metabolite matrix components;

[0039] Figure 7 This is a graph showing the change in emulsion stratification rate under different co-metabolite matrix components. Detailed Implementation

[0040] To clearly illustrate the technical features of this solution, the following detailed implementation method will be used to explain the solution.

[0041] Example 1

[0042] The preparation of the microbial agent includes the following steps:

[0043] (1) Domestication and enrichment:

[0044] The petroleum-degrading bacteria described in this invention were directly screened from activated sludge in a biochemical tank of an oil refinery. The activated sludge dosage was 5 g / L, and the screening method was as follows:

[0045] Liquid culture medium: carbon source 0.5 g / L, using mineral oil sample as carbon source; NH4NO3 1.0 g; KH2PO4 1.0 g; K2HPO4 1.0 g; MgSO4·7H2O 0.2 g; CaCl2 0.02 g; FeCl3 0.05 g; NaCl 10 g; rhamnolipid 100 mg; tea saponin 100 mg; trace element mixture 1 mL; distilled water 1000 mL; pH 7.2-7.8; temperature 26-30℃; aerobic culture. COD, petroleum hydrocarbons, and other indicators were monitored regularly during the experiment. After 3-5 rounds of degradation, the concentration of petroleum hydrocarbon carbon source was gradually increased to 2 g / L, and another 3-5 rounds of degradation were completed to obtain a mixed culture of bacteria capable of tolerating petroleum hydrocarbon wastewater up to 2 g / L.

[0046] The bacterial culture mixture was transferred to a new acclimatization liquid medium at a transfer rate of 1%. The first acclimatization liquid medium used for transfer had a petroleum carbon source of 0.5 g / L, and other components were the same as those in the liquid medium. After multiple acclimatization transfers using the liquid medium, highly efficient bacteria were enriched. Mineral oil has low solubility in water, and a small amount of biosurfactant was added during the culture process to enhance the contact between the microorganisms and petroleum. COD, petroleum and other indicators were monitored regularly during the experiment. After 2-3 rounds of transfer, petroleum-degrading bacteria were obtained.

[0047] (2) Fermentation

[0048] The petroleum-degrading bacteria obtained in (1) were transferred to a 1L seed tank at an inoculation rate of 5% for cultivation. The temperature of the seed tank was maintained at 30℃ and the dissolved oxygen (DO) was controlled at 5 mg / L. The seed tank formula was as follows: mineral oil 2g / L, NH4NO3 2g, KH2PO4 2g, K2HPO4 2g, MgSO4·7H2O 0.4g, CaCl2 0.04g, FeCl3 0.1g, NaCl 10g, trace element mixture 1mL, rhamnolipin 100mg, tea saponin 100mg, distilled water 1000mL; pH 7.2-7.8; temperature 26-30℃; aerobic culture for 7 days.

[0049] Expansion culture: The petroleum-degrading bacterial culture from the seed tank was transferred to a 10L fermenter at a 5% inoculum rate for expansion culture. The fermenter culture medium composition was the same as that of the seed tank, and the physicochemical parameters were: temperature 30℃, dissolved oxygen 8 mg / L, and fermentation time 7 days. After fermentation, the effective viable bacteria count in the fermenter reached 10. 9 When the number of bacteria per mL is above a certain level, the petroleum-based high-efficiency degrading bacterial agent can be obtained by packaging the fermentation broth in plastic buckets after it is discharged from the fermentation tank.

[0050] High-throughput sequencing of the bacterial community identified the main dominant strains as *Agrobacterium radiobacter*, *Paracoccus pantotrophus*, and *Paracoccus denitrificans*. 16S rRNA sequencing analysis of the three strains was performed, and their sequences SEQ ID NO.1-SEQ ID NO.3 are shown in the sequence listing.

[0051] Example 2: Degradation test of petroleum-based wastewater by highly efficient petroleum-degrading bacteria agent.

[0052] 1% of the highly efficient petroleum-degrading bacterial agent prepared in Example 1 was added to a shake flask containing 0.5 g / L petroleum-based single carbon source medium (1 L system, COD concentration 1600 mg / L). The medium formulation included: mineral oil 0.5 g / L, NH4NO3 0.5 g, KH2PO4 0.5 g, K2HPO4 0.5 g, MgSO4·7H2O 0.1 g, CaCl2 0.01 g, FeCl3 0.02 g, NaCl 10 g, trace element mixture 1 mL, rhamnolipid 100 mg, tea saponin 100 mg, and distilled water 1000 mL; pH 7.8, temperature 28℃, aerated culture, and DO controlled at 4 mg / L. COD concentration was measured at 0 h, 12 h, 24 h, 48 h, 72 h, and 96 h. Specific results are shown in […]. Figure 2 .

[0053] Depend on Figure 2 It can be seen that after 96 hours of cultivation, the COD in the wastewater decreased to 25 mg / L, achieving complete degradation.

[0054] Example 3: Degradation test of petroleum-based high-efficiency degrading bacteria on actual oily wastewater.

[0055] A wastewater treatment plant in Jiangsu Province primarily serves nearby textile mills. These mills use large amounts of lubricating oil for sizing during their production processes, generating oily wastewater. Samples of this oily wastewater were taken from the plant's equalization tank. Testing revealed a COD concentration of approximately 450 mg / L and a petroleum hydrocarbon concentration (based on extractable petroleum hydrocarbons (C6H2O)). 10 -C 40 The COD concentration was approximately 80 mg / L. The petroleum-degrading bacterial agent obtained in Example 1 was directly added to the wastewater at an inoculum rate of 1%, and the pH of the system was adjusted to 7.8 to meet the needs of normal microbial growth. Under room temperature conditions, COD changes in the system were monitored at regular intervals of 0h, 16h, 24h, 48h, and 72h. Specific results are shown in […]. Figure 3 .

[0056] like Figure 3It can be seen that after 48 hours, the COD dropped to below 50 mg / L, meeting the discharge standards of the wastewater treatment plant. The above experimental data demonstrate that the degradation agent of this invention also has good treatment effects in actual oily wastewater and has broad application prospects.

[0057] Example 4: Changes in the microbial community after adding petroleum-based high-efficiency degrading bacteria to an MBR tank.

[0058] In Example 3, the wastewater treatment plant adopts a combined process of fine screen + equalization tank + primary air flotation + lift pump + secondary air flotation + aerobic MBR + contact disinfection, with a scale of 30,000 m³. 3 / d.

[0059] To simulate this treatment process, the pilot-scale MBR tank was simultaneously fed with activated sludge from the wastewater treatment plant and the biodegrading bacteria agent prepared in Example 1. The dosage of activated sludge from the wastewater treatment plant was consistent with that in the on-site MBR tank, and the dosage of the petroleum-based high-efficiency biodegrading bacteria agent was 1 g / L. The temperature inside the device was 26℃, dissolved oxygen (DO) was 4 mg / L, and pH was 7.5. The retention time was set to 24 h, and nutrients and trace elements were added. The nutrient dosages were: NaCl 6%, NaHCO3 0.2%, MgSO4 0.05%, CaCl2 0.02%, yeast extract 0.01%, tea saponin 0.01%, and rhamnolipid 0.01%, and the pH was maintained between 7.2 and 7.8. The dosage of trace elements was: Fe 10 mg / L, Cu 0.3 mg / L, Mo 0.1 mg / L, Zn 0.1 mg / L, Co 0.1 mg / L, and Mn 0.1 mg / L. Microbial diversity was analyzed in the original MBR tank and the MBR tank after the addition of petroleum-based high-efficiency degradation bacteria. The results are shown below. Figure 4 .

[0060] Depend on Figure 4 Bacterial diversity analysis showed no significant changes at the phylum level, but at the genus level, the relative abundance of petroleum-degrading bacteria Rhodanobacter sp, Bacillus sp, Thermomonas sp, and Parvibaculum sp all increased significantly.

[0061] Example 5: Simulation of MBR membrane fouling after adding highly efficient degrading bacteria.

[0062] An automated pilot-scale device (including membrane pressure difference monitoring) for verifying the performance of highly efficient degrading bacteria was used in the experiment. This device consisted of a No. 1 inoculated group tank and a No. 2 control group tank. Both tanks contained MBR membrane modules and were equipped with automatic aeration devices, connected to automatic influent, automatic effluent, and automatic backwashing. The operation of No. 1 and No. 2 was identical. Both the No. 1 inoculated group tank and the No. 2 control group tank were fed with the sludge-water mixture from the MBR tank in the wastewater treatment plant of Example 3. Simultaneously, 1% of the highly efficient degrading bacteria agent prepared in Example 1 was added to the No. 1 inoculated group tank. Automatic influent and effluent were used, with a hydraulic retention time (HRT) of 8 hours. After three months of operation, the membrane pressure difference (TMP) was recorded continuously for 30 days. Specific results are shown in […]. Figure 5 .

[0063] according to Figure 5 The data shows that the increase in the pressure difference between the inside and outside of the membrane in the #1 bacterial addition group was significantly lower than that in the #2 control group, indicating that the petroleum-based high-efficiency degradation bacteria fermented in this invention can significantly reduce MBR membrane fouling.

[0064] Example 6: Optimizing the ratio of rhamnolipin to tea saponin in the culture medium

[0065] In Example 1, the mass ratios of rhamnolipin to tea saponin in the liquid culture medium were set to 1:0, 0.8:0.2, 0.5:0.5, 0.2:0.8, and 0:1, respectively, with a total concentration of 200 mg / L. All other culture medium components remained unchanged. The following comparative examples were also set up:

[0066] Comparative Example 1: No rhamnolipin and tea saponin were added to the liquid culture medium, while the other components of the culture medium remained unchanged.

[0067] Comparative Example 2: 200 mg / L Tween 80 was added to the liquid culture medium, while the other components of the culture medium remained unchanged.

[0068] The bacterial agents prepared in Example 6 and Comparative Examples 1 and 2 were inoculated into oily wastewater (1% inoculum amount). During the cultivation process, the pH was 7.5 and the temperature was 28°C. The petroleum hydrocarbon (COD) degradation rate and emulsion stability were measured after 72 hours. Specific results are shown in [link to results]. Figure 6 and Figure 7 .

[0069] Depend on Figure 6 It can be seen that when the mass ratio of rhamnolipin to tea saponin is 1:1, the degradation rate of petroleum-derived substances reaches 75% (25% higher than that of rhamnolipin alone). From Figure 7It was found that when the mass ratio of rhamnolipin to tea saponin was 1:1, the emulsion separation rate after standing for 72 hours was only 5%, which is the optimal compounding ratio. Therefore, the compounding system in Example 6 exhibits a synergistic effect. Although rhamnolipin itself has good surface tension reducing ability, the large molecular backbone of tea saponin inserted into the micelles shields the electrostatic repulsion between the rhamnolipin head groups, further reducing the minimum surface tension of the compounding system and improving emulsion stability. This abrupt change in physicochemical properties is unpredictable with a single component.

[0070] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the above embodiments do not limit the present invention in any way, and all technical solutions obtained by equivalent substitution or equivalent transformation fall within the protection scope of the present invention.

Claims

1. A method for screening bacteria that degrade oily wastewater, characterized in that, The method includes culturing and screening bacterial sources using a liquid culture medium, wherein a co-metabolizing matrix is ​​added to the liquid culture medium, and the co-metabolizing matrix is ​​composed of rhamnolipin and tea saponin.

2. The method for screening oily wastewater degrading bacteria according to claim 1, characterized in that, Includes the following steps: S1. Source of bacteria collection: Collect activated sludge from an environment contaminated with oily substances as the original source of bacteria; S2, Acclimation and Enrichment: The original bacterial source was inoculated into a liquid culture medium containing a co-metabolizing matrix and subjected to multiple rounds of acclimation culture under aerobic conditions; S3. Gradient pressure acclimatization: During the acclimatization process, the concentration of oil-based carbon sources in the acclimatization medium is gradually increased to apply selective pressure to the microbial community and obtain a mixed culture of the microbial community. S4. Microbial community isolation and purification: The domesticated microbial community mixture was inoculated into the screening medium, and the degrading microbial community was obtained after multiple transfer cultures.

3. The method for screening oily wastewater degrading bacteria according to claim 2, characterized in that, The concentration of rhamnolipin in the culture medium is 50-150 mg / L, the concentration of tea saponin is 50-150 mg / L, and the mass ratio of rhamnolipin to tea saponin is (0.8:1.2)-(1.2:0.8).

4. The method for screening oily wastewater degrading bacteria according to claim 2, characterized in that, In step S3, the gradient pressure training method is as follows: (1) The bacterial community was cultured for 3-5 rounds of degradation under the condition that the concentration of oil carbon source was 0.5 g / L; (2) Increase the concentration of oil carbon source to 2.0 g / L and continue the degradation culture for 3-5 rounds to obtain the microbial mixed culture.

5. The method for screening oily wastewater degrading bacteria according to claim 2, characterized in that, In step S2, the liquid culture medium also includes basic nutrient components, which include multiple sources of nitrogen, phosphorus, potassium, magnesium, calcium, iron, sodium salt, and trace elements.

6. The method for screening oily wastewater degrading bacteria according to claim 5, characterized in that, The specific components of the liquid culture medium include: mineral oil 0.5 g / L, NH4NO3 1.0 g / L, KH2PO4 1.0 g / L, K2HPO4 1.0 g / L, MgSO4·7H2O 0.2 g / L, CaCl2 0.02 g / L, FeCl3 0.05 g / L, NaCl 10 g / L, rhamnolipid 100 mg / L, tea saponin 100 mg / L, and trace element mixture 1.0 mL / L; The culture conditions are: pH 7.2-7.8, temperature 26-30℃, and aerobic culture.

7. A method for preparing a bacterial agent from the degrading bacteria screened by any one of claims 1-6, characterized in that, Includes the following steps: (1) Seed tank culture: The selected petroleum-degrading bacteria are inoculated into a seed tank and cultured to obtain seed liquid; (2) Fermentation tank expansion: The seed liquid is inoculated into the fermentation tank for expansion culture. After fermentation, a highly efficient degrading agent is obtained.

8. The method for preparing the microbial agent according to claim 7, characterized in that, In step (1), the inoculum size of the degrading bacteria is 1%-10%, and the specific components of the seed tank are: mineral oil 2g / L, NH4NO3 2g / L, KH2PO4 2g / L, K2HPO4 2g / L, MgSO4·7H2O 0.4g / L, CaCl2 0.04g / L, FeCl3 0.1g / L, NaCl 10g / L, trace element mixture 1mL / L, rhamnolipid 100mg / L, tea saponin 100mg / L; the culture temperature is 25-30℃, the culture time is 6-8 days, the pH is 7.2-7.8, and the dissolved oxygen (DO) is 4-8 mg / L. In step (2), the inoculation amount of the seed liquid is 1%-10%, and the composition and culture conditions of the fermenter culture medium are the same as those of the seed tank; the effective viable count of the highly efficient degrading agent is 10. 9 per mL.

9. The application of the bacterial agent prepared by the method according to any one of claims 7-8 in the treatment of oily wastewater, characterized in that, The microbial agent is added to the aerobic treatment unit of the membrane bioreactor to degrade COD in oily wastewater and reduce MBR membrane fouling.

10. The application according to claim 9, characterized in that, The specific steps for adding the microbial agent are as follows: (1) Initial addition: Add 0.5-1.5 g / L of high-efficiency degradation bacteria to the aerobic MBR tank in one go; (2) External maintenance: During the operation of the system, nutrients and trace elements are added, including rhamnose lipids and tea saponins.

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