A method and apparatus for microbial treatment of oil-containing sludge

Abstract

The application discloses a method and device for treating oily sludge by using microorganisms, and comprises the following steps: mixing oily sludge, water, a microbial agent and nutrients to obtain a culture system; and adjusting the temperature and pH of the culture system to degrade oil hydrocarbons in the oily sludge. The application screens out a good strain for degrading residual oil hydrocarbons in oily sludge obtained after thermal chemical cleaning, and improves the culture conditions to realize efficient degradation.

Description

Technical Field

[0001] This invention relates to the field of oily sludge treatment technology, and in particular to a method and apparatus for microbial treatment of oily sludge. Background Technology

[0002] Oily sludge is a complex system containing oil, solid particles, heavy metals, water, and other components generated during petroleum production and processing. It is reported that China's petroleum extraction industry alone generates approximately 1 million tons of oily sludge annually. Due to its high stability and difficulty in treatment, oily sludge has been listed as a hazardous waste.

[0003] In recent years, various technologies such as solvent extraction, supercritical water oxidation, ultrasound, pyrolysis, and thermochemical cleaning have been used to treat oily sludge. Compared with other technologies, thermochemical cleaning is simple to operate, low in cost, and low in energy consumption, attracting much attention from scholars both domestically and internationally. It is one of the most widely used and mature treatment technologies. However, the effect of a single technology is limited, and multiple technologies are often used in combination to achieve the goals of resource recovery, harmlessness, and volume reduction in oily sludge treatment. Bioremediation refers to the process of using bacteria and fungi to assimilate and degrade petroleum hydrocarbons in the soil as carbon sources, ultimately achieving complete mineralization and transforming them into harmless inorganic substances (CO2 and H2O). This method is characterized by thorough treatment and no secondary pollution. Utilizing microorganisms to deeply treat the oily sludge residue after thermal washing can provide a new approach to ensuring that the treated oily sludge meets agricultural land standards.

[0004] Some technologies combine thermochemical cleaning with biodegradation to treat oily sludge. For example, Lei Jianghui's laboratory experimental study on the treatment of oily sludge using a biothermal washing + microbial degradation technology, published in *Crude Oil Gathering and Processing* in 2020, showed that after treating the oily sludge with biosurfactants, nutrients and microbial agents were added for degradation, achieving a petroleum degradation rate of 85.5%. However, this method did not specify the exact types of microbial agents used.

[0005] Therefore, it is necessary to select suitable bacterial strains for use in oily sludge after thermochemical treatment. Summary of the Invention

[0006] This application provides a method and apparatus for microbial treatment of oily sludge to solve the above-mentioned problems.

[0007] This invention provides a method for microbial treatment of oily sludge, comprising:

[0008] A culture system is obtained by mixing oily sludge, water, microbial agents and nutrients;

[0009] Adjusting the temperature and pH of the culture system degrades petroleum hydrocarbons in oily sludge.

[0010] Optionally, the microbial agent is a mixture of 2-4 of the following: Alcaligenes, Acinetobacter veneris, Flavobacterium, Pseudomonas aeruginosa, Pseudomonas aeruginosa, and Alcaligenes faecalis.

[0011] Optionally, the microbial agent is a mixture of Acinetobacter venereum, Pseudomonas aeruginosa, and Pseudomonas aeruginosa in a mass ratio of 1:1:1.

[0012] It may be made by mixing Flavobacterium, Pseudomonas aeruginosa, and Pseudomonas aeruginosa in a mass ratio of 1:1:1.

[0013] Optionally, the volume ratio of the oily sludge to the water is 1:3 to 1:10;

[0014] The inoculum amount of the microbial agent is 10-50% of the volume of the oily sludge;

[0015] The mass ratio of nitrogen (N) to phosphorus (P) in the nutrients is 2:1 to 8:1.

[0016] Optionally, the temperature is 25-40°C; the pH is 6-8.

[0017] Optionally, the process of adjusting the temperature and pH of the culture system to degrade petroleum hydrocarbons in oily sludge further includes,

[0018] Aeration should be performed at intervals of 1-4 hours.

[0019] Optionally, after adjusting the temperature and pH of the culture system to degrade petroleum hydrocarbons in the oily sludge, the process further includes...

[0020] The culture system after degradation was completed was separated, and the supernatant suspension was collected;

[0021] The suspension was used as a microbial agent to treat oily sludge.

[0022] Optionally, the oily sludge includes oily mud obtained from oil fields and hot-washed oily sludge residue after treatment with hot washing agents.

[0023] The present invention also provides an apparatus for microbial treatment of oily sludge, comprising,

[0024] The degradation unit is used to mix oily sludge, water, microbial agents, and nutrients to obtain a culture system; and to adjust the temperature and pH of the culture system to degrade petroleum hydrocarbons in the oily sludge.

[0025] Optionally, the device further includes a feeding unit, a ventilation unit, and a circulation unit, each connected to the degradation unit.

[0026] The feeding unit is used to transport oily sludge, water, microbial agents and nutrients into the degradation unit;

[0027] A ventilation unit is used to aerate the degradation unit at intervals of 1-4 hours.

[0028] The circulation unit is used to collect the upper suspension of the culture system after degradation and transport the suspension as a microbial agent to the degradation unit.

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

[0030] This invention screens out bacterial strains that effectively degrade residual petroleum hydrocarbons in oil sludge obtained after thermochemical cleaning and improves culture conditions to achieve efficient degradation. A bacterial agent prepared by mixing Acinetobacter venereum, Pseudomonas aeruginosa, and Pseudomonas aeruginosa in a 1:1:1 mass ratio degrades hot-washed oil sludge residue after surfactant heat treatment. Intermittent aeration treatment ensures thorough mixing of the oil sludge residue with water, bacterial solution, and nutrients, promoting the full function of the microbial agent in degrading petroleum hydrocarbon components in the oil sludge. This results in a reduction of oil content in the hot-washed oil sludge residue from 55800 mg / kg to 2280 mg / kg, with an average removal rate of 94.6%.

[0031] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the steps or apparatus pointed out in the description and the drawings. Attached Figure Description

[0032] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0033] Figure 1 The degradation rate of oil recovery by the microbial strains selected in this invention is shown.

[0034] Figure 2a The tolerance of the mixed bacteria 1 of the present invention to Tween 20 was demonstrated;

[0035] Figure 2b The tolerance of mixed bacteria 1 to Tween 80 was demonstrated;

[0036] Figure 2c The tolerance of mixed bacteria 1 to sodium dodecylbenzenesulfonate was demonstrated;

[0037] Figure 3a The tolerance of the mixed bacteria 2 of the present invention to Tween 20 was demonstrated;

[0038] Figure 3b The tolerance of mixed bacteria 2 to Tween 80 was demonstrated;

[0039] Figure 3c The tolerance of mixed bacteria 2 to sodium dodecylbenzenesulfonate was demonstrated;

[0040] Figure 4 A schematic diagram of the structure of the microbial treatment apparatus for oily sludge of the present invention is shown. Detailed Implementation

[0041] The inventive concept of this invention is as follows: based on the characteristic that the combination of thermochemical cleaning and bioremediation has a better effect on degrading petroleum hydrocarbons in soil, the invention screens out bacterial strains that are good at degrading residual petroleum hydrocarbons in the oil sludge residue obtained after thermochemical cleaning, and improves the culture conditions to achieve efficient degradation.

[0042] To this end, the inventors selected Alcaligenes, Acinetobacter veneris, Flavobacterium, Pseudomonas aeruginosa, Pseudomonas aeruginosa, and Alcaligenes faecalis as typical degrading bacteria and conducted the following experiments.

[0043] In this invention, the English name of the *Pseudomonas aeruginosa* is *Pseudomonaspseudoalcaligenes*, which was screened from soil in Dagang; the English name of the *Acinetobacter venetianus* is *Acinetobacter venetianus*, which was screened from soil in Dagang; the English name of the *Microbacterium maritypicum* is *Microbacterium maritypicum*, which was screened from soil in Xinjiang; the English name of the *Pseudomonas guguanensis* is *Pseudomonas guguanensis*, which was screened from soil in Dagang; the English name of the *Pseudomonas aeruginosa* is *Pseudomonas aeruginosa*, which was screened from soil in Xinjiang; and the English name of the *Alcaligenes faecalis* is *Alcaligenes faecalis*, which was screened from soil in Xinjiang.

[0044] Antagonistic experiments were conducted on *Alcaligenes faecalis* (NK1), *Acinetobacter venereum* (NK2), *Flavobacterium* (NK3), *Pseudomonas aeruginosa* (NK4), *Pseudomonas aeruginosa* (C1A), and *Alcaligenes faecalis* (B29). The mass ratio of each microorganism in the mixed inoculum was equal. Strains without antagonistic effects were selected and mixed together to conduct diesel fuel degradation rate experiments.

[0045] The microorganisms were cultured in LB medium for 16 hours and then inoculated at a 10% inoculum into an inorganic salt medium containing 1 g / L diesel fuel. After 7 days of incubation at 30°C and a shaking rate of 150 rpm, the diesel fuel degradation rates of single and mixed cultures were determined by infrared spectroscopy. Figure 1 As shown, the diesel degradation rates of mixed bacteria 1 and mixed bacteria 2 reached 81.8% and 70.8%, respectively, which was 26.8% higher than that of single bacteria.

[0046] LB medium: tryptone 10 g / L, yeast extract 5 g / L, sodium chloride 10 g / L

[0047] Inorganic salt culture medium: ammonium chloride 1g / L, potassium dihydrogen phosphate 1g / L, dipotassium hydrogen phosphate 1g / L, magnesium sulfate 0.2g / L.

[0048] The results are as follows Figure 1 As shown, mixed bacteria 1 is composed of Acinetobacter venereum, Pseudomonas aeruginosa and Pseudomonas aeruginosa in a mass ratio of 1:1:1; mixed bacteria 2 is composed of Flavobacterium, Pseudomonas aeruginosa and Pseudomonas aeruginosa in a mass ratio of 1:1:1, and their degradation rates are 81.8% and 70.8%, respectively.

[0049] Because the oil sludge residue contains hot washing agents, it may affect microbial growth. The tolerance of mixed bacteria 1 and mixed bacteria 2 to typical hot washing agents was studied, such as... Figures 2a-3c As shown.

[0050] Hot wash agents include Tween 20 (0%, 5%, 10%, 15% and 20%), Tween 80 (0%, 5%, 10%, 15% and 20%) and sodium dodecylbenzenesulfonate (0%, 1%, 2%, 3% and 4%).

[0051] The mixed bacteria were cultured on LB medium and then inoculated at a 10% inoculum onto an inorganic salt medium containing hot washing agents of different concentrations of oil.

[0052] The results showed that 1% sodium dodecylbenzenesulfonate significantly inhibited the growth of the strain. Tween 80 and Tween 20 at 5% concentrations did not significantly inhibit the growth of the strain, but concentrations above 10% showed significant inhibitory effects. These results indicate that, after dilution, mixed bacteria 1 and mixed bacteria 2 can be used for subsequent degradation of the hot-washed sludge residue after surfactant heat treatment.

[0053] Based on the above experimental results, the present invention provides a method for microbial treatment of oily sludge, comprising,

[0054] S1. A culture system is obtained by mixing oily sludge, water, microbial agents and nutrients;

[0055] S2. Adjust the temperature and pH of the culture system to degrade petroleum hydrocarbons in oily sludge.

[0056] Preferably, the microbial agent is a mixture of 2-4 of the following: Alcaligenes faecalis, Acinetobacter veneris, Flavobacterium, Pseudomonas aeruginosa, Pseudomonas aeruginosa, and Alcaligenes faecalis.

[0057] More preferably, the microbial agent is a mixture of Acinetobacter venereum, Pseudomonas aeruginosa, and Pseudomonas aeruginosa in a mass ratio of 1:1:1;

[0058] It may be made by mixing Flavobacterium, Pseudomonas aeruginosa, and Pseudomonas aeruginosa in a mass ratio of 1:1:1.

[0059] Preferably, the volume ratio of the oily sludge to the water is 1:3 to 1:10;

[0060] The inoculum amount of the microbial agent is 10-50% of the volume of the oily sludge;

[0061] The mass ratio of nitrogen (N) to phosphorus (P) in the nutrients is 2:1 to 8:1, and the nutrients include one or more of yeast extract, ammonium chloride, potassium dihydrogen phosphate, and dipotassium hydrogen phosphate.

[0062] Preferably, the temperature is 25-40°C; and the pH is 6-8.

[0063] Increasing dissolved oxygen content improves the rate of microbial degradation, which helps microorganisms attach to and proliferate on sludge particles. Step S2 also includes aeration treatment at intervals of 1-4 hours, with an aeration time of up to 30 minutes.

[0064] To further utilize the microorganisms, after step S2 is completed, the culture system after degradation is completed is separated and the upper suspension is collected; the suspension is used as a microbial agent to treat oily sludge.

[0065] It should be noted that the oily sludge treated by the present invention includes oily mud obtained from oil fields and oily sludge residue after being treated with hot washing agents.

[0066] To better implement the method of the present invention, the present invention also provides an apparatus for microbial treatment of oily sludge, comprising a degradation unit for mixing oily sludge, water, microbial agents and nutrients to obtain a culture system; and adjusting the temperature and pH of the culture system to degrade petroleum hydrocarbons in the oily sludge.

[0067] It also includes a feeding unit, a ventilation unit, and a circulation unit, which are respectively connected to the degradation unit.

[0068] The feeding unit is used to transport oily sludge, water, microbial agents and nutrients into the degradation unit;

[0069] A ventilation unit is used to aerate the degradation unit at intervals of 1-4 hours.

[0070] The circulation unit is used to collect the upper suspension of the culture system after degradation is completed, and to transport the suspension as a microbial agent to the degradation unit.

[0071] In one embodiment of the present invention, such as Figure 4 As shown, the degradation unit includes a degradation tank and five pipelines: an oily sludge pipeline, an inlet water pipeline, a microbial agent and nutrient pipeline, an aeration pipeline, and a discharge pipeline. The feeding unit includes a settling tank, a clear water tank, a water pump, a microbial agent and nutrient pipeline tank for conveying microbial agents and nutrients, and an oily sludge tank connected to the oily sludge pipeline. The water pump can pump liquid from the settling tank and clear water tank to the degradation tank.

[0072] One degradation vessel is provided. The effective processing capacity is 5L, with a cylindrical vessel diameter of 300mm and a height of 700mm. The degradation vessel is a benchtop type, constructed of high-silica borosilicate glass with a polishing precision Ra≤0.4, conforming to GMP standards. The top cover is openable, and the vessel has good sealing performance. The material of the degradation vessel meets the requirements for high-temperature and high-pressure sterilization (121℃, 15min). The top cover has a sample inlet, and the top has four pre-drilled ports, each 20mm in diameter. An outlet valve is located at the bottom of the vessel, connected to a settling tank via a pipe. A drain outlet is also provided at the bottom of the vessel.

[0073] Two sampling ports, each 30mm in diameter, are located on the left side of the tank. This meets both sampling and testing requirements. The sampling ports are on the same plane, distributed at different elevations, and spaced 500mm apart. All pre-installed ports and sampling ports on the tank are sealed with rubber stoppers. A stainless steel perforated plate with 5mm holes is installed at the bottom of the degradation tank to separate the tank body from the bottom. All connecting pipes of the degradation tank use quick-connect fittings for easy disassembly.

[0074] The circulation unit includes a sedimentation tank, a clear water tank, and a water pump. Its basic function is to pump water from the sedimentation tank and clear water tank back to the degradation tank.

[0075] The settling tank is made of corrosion-resistant titanium steel, measuring 20cm×20cm×10cm with a volume of 4L. It is equipped with an outlet and an outlet valve. The clear water tank is a horizontal square tank made of PE material, also measuring 20cm×20cm×10cm with a volume of 4L. It is equipped with an outlet and an outlet valve. The water pump flow rate is 0.0015-380mL / min, powered by 220V with a power consumption of <22W, and the speed is adjusted using a digital knob.

[0076] The ventilation unit includes an aeration pump, aeration pipes, and valves. The unit's basic function is to aerate the degradation tank using the aeration pump. The aeration pump has an airflow rate of 40 L / min and an air pressure of 0.7 MPa. The aeration pump must be securely fixed to the frame base. The aeration pipes are connected using rigid PVC pipes. An electrically controlled valve is installed at the aeration pipe inlet, interlocked with a PLC for automatic start / stop control. A gas flow meter is also installed at the aeration pipe inlet. The flow meter's range is 0.25-2.5 m³ / h, with local display showing both instantaneous and cumulative readings.

[0077] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention. In the embodiments, all original reagent materials are commercially available, and experimental methods without specific conditions are conventional methods and conditions well known in the art, or according to the conditions recommended by the instrument manufacturer.

[0078] In one embodiment of the present invention, a water pump and an oily sludge tank are used to add 1 kg of hot-washed oily sludge residue with an oil content of 55800 mg / kg and clean water to a degradation tank. The volume ratio of clean water to oily sludge residue in the degradation tank is 3:1. Subsequently, ammonium chloride 4-10 g / L, potassium dihydrogen phosphate 1-3 g / L, dipotassium hydrogen phosphate 1-3 g / L, magnesium sulfate 0.2-2 g / L are added through a microbial agent and nutrient pipeline tank, along with 0.3 L of mixed bacteria 1 (composed of Acinetobacter veneris). A mixture of *Pseudomonas aeruginosa* and *Pseudomonas guanyense* at a mass ratio of 1:1:1 was cultured in a degradation tank. The pH of the culture system was adjusted to 6-8, and the temperature was controlled between 20-40℃. An aeration pump was activated every 1-4 hours to degrade petroleum hydrocarbons in the oily sludge. During degradation, air was introduced into the container at a rate of 10-40 L / min to ensure thorough mixing of the oily sludge residue, water, bacterial solution, and nutrients, promoting the full function of the microbial agent in degrading petroleum hydrocarbon components in the oily sludge. The degradation process was run continuously for one week. After degradation, the treated sludge was collected, and the petroleum content was measured using an infrared oil analyzer. The final oil content in the sludge decreased to 2280 mg / kg, with an average removal rate of 94.6%. The culture system after degradation was separated, and the supernatant bacterial solution was collected. This bacterial solution can be used as a microbial agent to treat the next batch of hot-wash oily sludge residue.

[0079] It should be noted that the experimental soil in this apparatus was collected from oil sludge residue after hot washing at the Daqing Oilfield Refinery. Its physicochemical properties are as follows: pH 9.36, organic carbon 13.6 g / kg. -1 Total nitrogen 3380 mg / kg -1Available phosphorus 19.4 mg / kg -1 Organic matter 211 mg / kg -1 Petroleum products 55800 mg / kg -1 .

[0080] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for microbial treatment of oily sludge, characterized in that, include, A culture system is prepared by mixing oily sludge, water, microbial agents, and nutrients; the volume ratio of oily sludge to water is 1:3-1:10; the inoculum amount of the microbial agent is 10-50% of the volume of the oily sludge; the mass ratio of nitrogen (N) to phosphorus (P) in the nutrients is 2:1-8:1; the microbial agent is composed of Acinetobacter ventricosa, Pseudomonas aeruginosa, and Pseudomonas aeruginosa mixed in a mass ratio of 1:1:1; the oily sludge includes hot-washed oily sludge residue after treatment with hot washing agents. Adjusting the temperature and pH of the culture system degrades petroleum hydrocarbons in oily sludge.

2. The method according to claim 1, characterized in that, The temperature is 25-40℃; the pH is 6-8.

3. The method according to claim 1, characterized in that, The process of adjusting the temperature and pH of the culture system to degrade petroleum hydrocarbons in oily sludge also includes... Aeration should be performed at intervals of 1-4 hours.

4. The method according to claim 1, characterized in that, After adjusting the temperature and pH of the culture system to degrade petroleum hydrocarbons in the oily sludge, the process also includes... The culture system after degradation was completed was separated, and the supernatant suspension was collected; The suspension was used as a microbial agent to treat oily sludge.

5. A device for microbial treatment of oily sludge, characterized in that, include, The degradation unit, and the feeding unit and ventilation unit connected to the degradation unit; The degradation unit is used to mix oily sludge, water, microbial agents and nutrients to obtain a culture system; and to adjust the temperature and pH of the culture system to degrade petroleum hydrocarbons in the oily sludge; the degradation unit includes a degradation tank and five pipes, namely an oily sludge pipe, an inlet water pipe, a microbial agent and nutrient pipe, an aeration pipe, and a discharge pipe. The feeding unit is used to transport oily sludge, water, microbial agents and nutrients into the degradation unit; the feeding unit includes a settling tank, a clear water tank, a water pump, a microbial agent and nutrient pipeline tank for transporting microbial agents and nutrients, and an oily sludge tank connected to the oily sludge pipeline; the water pump pumps the liquid from the settling tank and the clear water tank to the degradation tank. A ventilation unit is used to aerate the degradation unit at intervals of 1-4 hours. The ventilation unit includes an aeration pump, an aeration pipe, and valves. The aeration pump ventilates and aerates the degradation tank. An electric control valve is installed at the inlet of the aeration pipe, which is interlocked with a PLC and can automatically control the start and stop. A gas flow meter is also installed at the inlet of the aeration pipe. The volume ratio of the oily sludge to the water is 1:3-1:10; the inoculum amount of the microbial agent is 10-50% of the volume of the oily sludge; the mass ratio of N to P in the nutrients is 2:1-8:1; the microbial agent is a mixture of Acinetobacter ventricosa, Pseudomonas aeruginosa, and Pseudomonas aeruginosa in a mass ratio of 1:1:1; the oily sludge includes hot-washed oily sludge residue after treatment with hot washing agents.

6. The apparatus according to claim 5, characterized in that, It also includes a circulation unit connected to the degradation unit. The circulation unit is used to collect the upper suspension of the culture system after degradation is completed, and to transport the suspension as a microbial agent to the degradation unit.

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