A method for rapid harmless treatment of oil-containing sludge by photo-coupled biodegradation

Abstract

This invention relates to the field of harmless treatment technology for oily sludge generated during crude oil extraction, specifically to a method for rapid harmless treatment of oily sludge through photo-coupled biodegradation. Conventional methods for harmless treatment of oily sludge are inefficient and energy-intensive. To address these problems, this invention provides a method for rapid harmless treatment of oily sludge through photo-coupled biodegradation. This method fully utilizes the sunny summer conditions in Northwest China, creating a "greenhouse effect" by covering and stacking the sludge with plastic film. This significantly raises the temperature of the stack without an external heat source, providing a suitable high-temperature environment for thermophilic petroleum hydrocarbon-degrading bacteria, greatly increasing the biodegradation rate of petroleum hydrocarbons, and shortening the traditional biological treatment cycle from several months to several weeks, thus achieving rapid harmless treatment of oily sludge.

Description

Technical Field

[0001] This invention relates to the field of harmless treatment technology for oily sludge generated during crude oil extraction, specifically to a method for rapid harmless treatment of oily sludge through photo-coupled biodegradation. Background Technology

[0002] Oily sludge is one of the main solid wastes generated during oilfield extraction, gathering, transportation, and refining. It contains large amounts of petroleum hydrocarbons, heavy metals, and various toxic and hazardous substances, and has been listed in the National Hazardous Waste Inventory. If not properly disposed of, pollutants in oily sludge can be released into the soil and groundwater over a long period, posing a serious threat to the ecological environment and human health. How to achieve the harmless and resource-oriented treatment of oily sludge has always been a challenging problem for the petroleum industry.

[0003] Currently, the mainstream technologies for treating oily sludge include pyrolysis / incineration, chemical thermal washing, and traditional biocomposting. While pyrolysis or incineration can completely remove petroleum hydrocarbons, they require dedicated pyrolysis or incineration furnaces, resulting in huge equipment investments, extremely high energy consumption, and the potential generation of secondary pollutants such as dioxins during incineration. Therefore, their economic and environmental benefits are not ideal, making them particularly unsuitable for remote, dispersed oilfields. Chemical thermal washing typically requires the addition of large amounts of surfactants and consumes significant amounts of hot water, leading to high water consumption and the generation of complex wastewater requiring wastewater treatment facilities. This makes it extremely difficult to apply in arid and water-scarce regions like Northwest China, and there is also a risk of chemical residues. Traditional biocomposting or biopile technology, although relatively environmentally friendly, often has a treatment cycle of several months or even longer, requiring regular turning and aeration, which can easily generate foul odors that pollute the surrounding environment. Furthermore, the degradation efficiency of petroleum hydrocarbons is significantly affected by temperature and humidity, almost completely halting during cold seasons. Although some studies have attempted to use solar greenhouses for biological treatment, the construction cost of the greenhouses is high, the temperature and humidity control is not precise enough, and the heating effect is limited, failing to fully utilize the advantages of the strong solar radiation resources in Northwest China.

[0004] It is evident that existing technologies struggle to achieve efficient, rapid, low-cost, and pollution-free treatment of oily sludge without relying on complex and expensive equipment, consuming large amounts of water resources, or requiring additional energy. This problem is particularly acute in the sparsely populated, sunny but relatively underdeveloped Northwest oilfield region. Therefore, developing a rapid and harmless treatment method for oily sludge that is suitable for this region, fully utilizes natural sunlight resources, and requires no external heat sources or large amounts of water is of significant practical importance. Summary of the Invention

[0005] The existing technology has the problem that conventional methods for the harmless treatment of oily sludge are inefficient and consume a lot of energy. To address these problems, this invention provides a rapid and harmless treatment method for oily sludge using photo-coupled biodegradation, comprising the following steps:

[0006] (1) Mix the oily sludge with organic solid waste and compound biomass synergist evenly to obtain a mixture, and control the moisture content of the mixture to ≤65%;

[0007] (2) Stack the mixed materials into a pile;

[0008] (3) The entire stack is completely, tightly and tightly covered with plastic film, and then placed under light for high-temperature continuous fermentation. During the fermentation process, the stack is turned over every 7-15 days. Fermentation continues until the final oil content of the mixture is ≤2%. The film is removed and the mixture is allowed to mature under natural light for 5-15 days to obtain the soil conditioner.

[0009] The volume ratio of oily sludge to organic solid waste is 1:1 to 1:0.3 (preferably 1:0.8 to 1:0.5). The added mass of the compound biomass synergist is 0.5%-3% (preferably 1%-1.2%) of the total mass of the mixture. The compound biomass synergist is composed of plant-derived surfactants that have a surface emulsifying effect on crude oil, biochar loaded with thermophilic petroleum hydrocarbon degrading bacteria, and potassium humate-seaweed extract that maintains microbial activity and metabolic efficiency in a mass ratio of (10-20):(70-75):(10-20). The number of effective viable bacteria in the biochar loaded with thermophilic petroleum hydrocarbon degrading bacteria is ≥5×10⁻⁶. 8 CFU / g.

[0010] Preferably, the organic solid waste is at least one of livestock and poultry manure, crop straw, and plant residues.

[0011] Preferably, the livestock and poultry manure includes at least one of chicken manure, pig manure, and cow manure.

[0012] Preferably, the potassium humate-seaweed extract is formed by combining potassium humate and seaweed extract, and the mass ratio of potassium humate to seaweed extract is (2-3):(1-2), preferably 3:2.

[0013] Preferably, in step (2), the stack height is 0.8-1.5 meters and the width is 1.5-2.5 meters.

[0014] Preferably, the lighting method is outdoor exposure to the sun in the Northwest region during summer.

[0015] Preferably, the plant-derived surfactant includes at least one of soapberry powder, soapberry peel extract, and tea saponin.

[0016] Preferably, the thermophilic petroleum hydrocarbon degrading bacteria are at least one of thermophilic Bacillus stearothermophilus or thermophilic oleophilic Bacillus.

[0017] Preferably, the film is transparent or black, and the film is ordinary PE food preservation film or agricultural plastic film.

[0018] Beneficial effects:

[0019] (1) The method of the present invention can make full use of the sunny summer conditions in Northwest China. By covering and stacking with plastic film, a "greenhouse effect" is formed, which can significantly increase the temperature of the pile without the need for an external heat source. This provides a suitable high-temperature environment for thermophilic petroleum hydrocarbon degrading bacteria (under the sunny summer conditions in Northwest China, the internal temperature of the pile can rapidly rise to above 60°C within 1-2 days, or even reach 70-80°C), greatly improving the biodegradation rate of petroleum hydrocarbons and shortening the cycle of several months required by traditional biological treatment to several weeks, thus realizing the rapid and harmless treatment of oily sludge.

[0020] (2) This invention does not require complex and expensive equipment such as pyrolysis furnaces and incinerators, nor does it require a large amount of hot water and chemical cleaning agents. It only requires plastic film covering and regular turning. The equipment investment is small, the operating cost is low, and the energy consumption is minimal. It is especially suitable for promotion and application in the Northwest Oilfield area, which is sparsely populated, has weak infrastructure, but has abundant sunshine.

[0021] (3) This invention uses a compound biomass synergist, in which plant-derived surfactants (such as soapberry powder, soapberry extract, etc.) can effectively emulsify and disperse crude oil in oily sludge, increasing the contact area between petroleum hydrocarbons and microorganisms; thermophilic petroleum hydrocarbon degrading bacteria (such as thermophilic Bacillus stearothermophilus, etc.) have strong metabolic activity at high temperatures, and their degradation efficiency for petroleum hydrocarbons is significantly higher than that of bacteria at room temperature; potassium humate-seaweed extract can maintain microbial activity and metabolic efficiency, and prolong the effective degradation cycle. The synergistic effect of the three significantly improves the degradation rate of petroleum hydrocarbons. Experimental test results show that the oil content of the material treated by the method of this invention for 20 days can be reduced to below 2%.

[0022] (4) This invention uses organic solid waste (livestock and poultry manure, crop straw, etc.) mixed with oily sludge. On the one hand, the moisture content of the material is adjusted to a suitable range (50-65%) to ensure aerobic fermentation conditions; on the other hand, the rich nutrients in the organic waste are used to promote microbial proliferation, thus realizing the synergistic treatment and resource utilization of oily sludge and agricultural / livestock waste. The final product is a soil conditioner with high organic matter content, which can be used for saline-alkali land improvement or barren soil remediation, achieving the unity of harmlessness and resource utilization.

[0023] (5) The entire treatment process of this invention does not produce secondary pollutants such as dioxins from incineration, does not produce complex wastewater containing surfactants and heavy metals, and does not release large amounts of malodorous gases (the film covering effectively inhibits the diffusion of odors). It is environmentally friendly and conforms to the technological development trend of green and low-carbon treatment. The post-ripening stage is carried out under natural light to further stabilize the properties of the materials and improve the quality of the soil conditioner. Detailed Implementation

[0024] The present invention will be described in detail below with reference to embodiments. However, it should be understood that the following embodiments are merely illustrative examples of implementation of the present invention and are not intended to limit the scope of the present invention.

[0025] The biochar loaded with thermophilic petroleum hydrocarbon-degrading bacteria used in this invention is prepared by the following method:

[0026] A *Bacillus stearothermophilus* strain was cultured at 60°C to form a suspension. This suspension was then loaded onto a biochar carrier via impregnation. After impregnation, the biochar carrier was removed and dried at low temperature to obtain the target product. The effective viable count on the obtained biochar carrier was 5 × 10⁻⁶. 8 CFU / g.

[0027] The biochar carrier was obtained by pyrolysis and carbonization of corn stalks under anaerobic conditions at 500℃. *Bacillus stearothermophilus* was purchased from the China General Microbiological Culture Collection Center (accession number CGMCC 1.16087).

[0028] The seaweed extract used in this invention is prepared by the following method:

[0029] After pulverizing dried kelp, add cellulase and pectinase and enzymatically hydrolyze at 55°C for 4 hours. After enzyme inactivation, filter, concentrate and dry to obtain seaweed extract powder.

[0030] Experiment 1: Oil sludge with an oil content of approximately 12.5% ​​was collected from an oilfield in Xinjiang (based on the industry-university-research cooperation base established by Changzhou University in Xinjiang). 1500 kg of oil sludge was mixed evenly with pretreated chicken manure at a volume ratio of 1:0.5, and then divided into five equal volumes for experimental use: Oil Sludge 1 (used in Example 1), Oil Sludge 2 (used in Comparative Example 1), Oil Sludge 3 (used in Comparative Example 2), Oil Sludge 4 (used in Comparative Example 3), and Oil Sludge 5 (used in Comparative Example 4).

[0031] The method for preparing pretreated chicken manure is as follows:

[0032] (1) Spread the collected fresh chicken manure in a well-ventilated area to a thickness of about 20-30 cm, and let it air dry naturally for 1-2 days until the moisture content drops below 60%.

[0033] (2) Remove visible impurities (feathers, plastic bags, stones, etc.) using a forklift or manually;

[0034] (3) Use a loader to turn the chicken manure 2-3 times to make the texture uniform.

[0035] Example 1

[0036] (1) Mix the oily sludge with the compound biomass synergist evenly to obtain a mixture. Control the moisture content of the mixture to 50%. The amount of compound biomass synergist added is 1% of the total mass of the mixture. The compound biomass synergist is composed of soapberry powder and biochar loaded with thermophilic Bacillus stearothermophilus (the effective viable count of the agent is 5×10⁻⁶). 8 The potassium humate-seaweed extract is composed of potassium humate and seaweed extract in a mass ratio of 12:75:13 (CFU / g). The potassium humate-seaweed extract is composed of potassium humate and seaweed extract in a mass ratio of 3:2.

[0037] (2) Stack the mixture into a pile (1m high);

[0038] (3) The entire stack was completely, tightly and tightly covered with a transparent PE plastic film with a thickness of 0.08mm. Then it was placed under the sunlight in Xinjiang in August for high-temperature continuous fermentation for several days (the number of fermentation days only counted the number of sunny days). During the fermentation process, the stack was turned over once every 7 days. After the fermentation was completed, the film was removed and the stack was allowed to mature under natural light for 7 days to obtain the soil conditioner.

[0039] Comparative Example 1 is the same as Example 1, except that the mixture in Comparative Example 1 is only oily sludge II.

[0040] Comparative Example 2 is the same as Example 1, except that the compound biomass synergist in Comparative Example 2 is only soapberry powder, while Comparative Example 2 uses oily sludge.

[0041] Comparative Example 3 is the same as Example 1, except that the compound biomass synergist in Comparative Example 3 is only biochar loaded with Bacillus stearothermophilus, while Comparative Example 3 uses oily sludge.

[0042] Comparative Example 4 is the same as Example 1, except that the compound biomass synergist in Comparative Example 4 is only potassium humate-seaweed extract, while Comparative Example 4 uses oily sludge.

[0043] The oil content of the stacks corresponding to Embodiment 1 and Comparative Examples 1-4 of the present invention was sampled and monitored during the same period of sunlight exposure. The specific monitoring results are shown in Table 1.

[0044] Table 1

[0045] Test Items Initial oil content (%) Oil content (%) on day 7 Oil content (%) on day 15 Oil content (%) on day 22 Oil content (%) on day 30 Final degradation rate (%) Example 1 12.5 9.1 5.8 2.9 1.1 91.2 Comparative Example 1 12.5 11.8 10.2 8.7 6.9 44.8 Comparative Example 2 12.5 10.9 8.5 6.1 4.3 65.6 Comparative Example 3 12.5 10.2 7.8 5.5 3.6 71.2 Comparative Example 4 12.5 11.2 9.4 7.6 5.8 53.6

[0046] Table 1 shows that the degradation effect of Example 1 is far superior to that of Comparative Examples 1-4. Within the same time frame, its final oil content (1.1%) and degradation rate (91.2%) both reached their optimal levels. Although Comparative Examples 2-3 showed some improvement over Comparative Example 1, their individual effects were limited. This demonstrates that plant-derived surfactants do indeed greatly help accelerate the degradation of petroleum hydrocarbons. The degrading bacteria are the core of the transformation, and potassium humate-seaweed extract effectively maintained the activity and metabolic intensity of the bacterial community at high temperatures. All three are indispensable, and their synergistic effect is significant.

[0047] Product characteristics: The soil conditioner obtained in Example 1 is loose and has no oily odor, while the other groups, especially Comparative Examples 1 and 4, have a slightly stronger oily feel.

[0048] The above experimental results demonstrate that the three-component compound of plant-derived surfactant, thermophilic petroleum hydrocarbon-degrading bacteria, and potassium humate-seaweed extract added simultaneously during the stacking process of this invention has a synergistic mechanism of "solubilization-degradation-promoting growth," achieving an exponential improvement in the degradation efficiency of oily sludge, which is the core of the inventive concept of this invention.

[0049] This invention not only monitored the oil content in the stack corresponding to Example 1, but also monitored the temperature change of the stack. The monitoring results showed that the core temperature of the stack corresponding to Example 1 rose to 72°C on the second day after the film was covered, and the high temperature period (>60°C) lasted for 16 days, which was significantly longer than the single group (10-13 days) of Comparative Examples 2-3 and Comparative Example 1 (7 days).

[0050] To investigate the optimal combination of plant-derived surfactants, biochar loaded with thermophilic petroleum hydrocarbon-degrading bacteria, and potassium humate-seaweed extract for maintaining microbial activity and metabolic efficiency in stacking, the present invention designed the following comparative experiment:

[0051] Experiment 2: Tank bottom sludge with an oil content of approximately 16% was collected from an oilfield in Qinghai (based on the petrochemical industry-education integration cooperation base established by Changzhou University in Qinghai). 1,600 kg of tank bottom sludge was mixed evenly with cow dung at a volume ratio of 1:0.8, and then divided into four equal volumes for experimental use: oily sludge six (used in Example 2), oily sludge seven (used in Comparative Example 5), oily sludge eight (used in Comparative Example 6), and oily sludge nine (used in Comparative Example 7).

[0052] Example 2

[0053] (1) Mix the oily sludge with the compound biomass synergist evenly to obtain a mixture. Control the moisture content of the mixture to 65%. The amount of compound biomass synergist added is 1.2% of the total mass of the mixture. The compound biomass synergist is composed of soapberry powder and biochar loaded with thermophilic Bacillus stearothermophilus (the effective viable count of the agent is 5×10⁻⁶).8 The potassium humate-seaweed extract is composed of potassium humate and seaweed extract in a mass ratio of 12:75:13 (CFU / g). The potassium humate-seaweed extract is composed of potassium humate and seaweed extract in a mass ratio of 3:2.

[0054] (2) Stack the mixture into a pile (1m high);

[0055] (3) The entire stack was completely, tightly and tightly covered with a transparent PE plastic film with a thickness of 0.08mm. Then it was placed under the sunlight in Qinghai in August for high-temperature continuous fermentation for several days (the number of fermentation days only counted the number of sunny days). During the fermentation process, the stack was turned over once every 7 days. After the fermentation was completed, the film was removed and the stack was allowed to mature for 5 days under natural sunlight to obtain the soil conditioner.

[0056] Comparative Example 5 is the same as Example 2, except that the compound biomass synergist in Comparative Example 5 is composed of saponin powder and biochar loaded with Bacillus stearothermophilus (the effective viable count of the microbial agent is 5 × 10⁻⁶). 8 The composition of CFU / g and potassium humate-seaweed extract was in a mass ratio of 20:70:10. Comparative Example 5 used oily sludge.

[0057] Comparative Example 6 is the same as Example 2, except that the compound biomass synergist in Comparative Example 6 is composed of saponin powder and biochar loaded with Bacillus stearothermophilus (the effective viable count of the microbial agent is 5 × 10⁻⁶). 8 The composition of CFU / g and potassium humate-seaweed extract was in a mass ratio of 10:85:5. Comparative Example 6 used oily sludge.

[0058] Comparative Example 7 is the same as Example 2, except that the compound biomass synergist in Comparative Example 7 is composed of saponin powder and biochar loaded with Bacillus stearothermophilus (the effective viable count of the microbial agent is 5 × 10⁻⁶). 8 The composition of CFU / g and potassium humate-seaweed extract was in a mass ratio of 15:65:20. Comparative Example 7 used oily sludge.

[0059] In Example 2 of this invention and Comparative Examples 5-7, the stacks were exposed to sunlight for the same period of time. The oil content of the stacks was sampled and monitored during the sunlight exposure. The specific monitoring results are shown in Table 2.

[0060] Table 2

[0061] Test Items Initial oil content (%) Oil content (%) on day 5 Oil content (%) on day 10 Oil content (%) on day 15 Oil content (%) on day 20 Final degradation rate (%) Duration of high-temperature period (>60℃) Example 2 16 13.5 9.8 5.1 1.3 91.9% 16 days Comparative Example 5 16 13.9 10.5 6.4 2.7 83.10% 13 days Comparative Example 6 16 14.1 11.2 7.9 3.5 78.10% 14 days Comparative Example 7 16 14 10.9 7.2 2.9 81.90% 12 days

[0062] As can be seen from the test data in Table 2, Example 2, which uses the preferred dosage ratio (12:75:13) of the present invention, has the fastest degradation rate throughout the entire process. After 20 days, the oil content drops to 1.3%, and the degradation rate is as high as 91.9%, which is the best effect.

[0063] The effects of imbalanced proportions:

[0064] Comparative Example 5 (Excessive Surfactant): In the early stage (5-10 days), the solubilizing effect was strong and the start-up was slightly faster. However, in the middle and late stages, due to the relative insufficiency of the bacterial community and activating components, the degradation was weak. Furthermore, excessive surfactant may inhibit some microorganisms, and the final effect was inferior to Example 2.

[0065] Comparative Example 6 (excessive degradation agent): Although the bacterial count was sufficient, the initial availability of petroleum hydrocarbons and the activity of the bacterial community under high temperature stress were limited due to the low proportion of surfactants and activating ingredients, and the overall degradation efficiency failed to reach the optimal level.

[0066] Comparative Example 7 (Potassium Humate-Seaweed Extract): Excessive activating ingredients failed to match sufficient "food" (petroleum hydrocarbons solubilized by surfactants) and "workers" (degrading bacteria), resulting in resource waste. Furthermore, the high-temperature period was the shortest, and the degradation efficiency was generally low.

[0067] Synergistic effect verification: The formulation in Example 2 ensured that the surfactant was sufficient to fully emulsify petroleum hydrocarbons, providing ample and readily available substrate for the predominantly degrading bacteria. Simultaneously, the appropriate proportion of seaweed extract effectively mitigated the inhibition of the bacterial community by high temperatures and metabolites, ensuring sustained and efficient metabolism during the high-temperature period. Imbalances in the proportions of these three components would disrupt this optimal synergistic state, leading to a decrease in treatment effectiveness.

[0068] This embodiment of the experiment found that, by using a compound biomass synergist with the following dosage ratios as follows: 10-20% plant-derived surfactant, 70-75% thermophilic petroleum hydrocarbon-degrading bacteria, and 10-20% potassium humate-seaweed extract, oily sludge can be degraded faster and more thoroughly.

[0069] Based on the above-described preferred embodiments of the present invention, and through the foregoing description, those skilled in the art can make various changes and modifications without departing from the inventive concept. The technical scope of this invention is not limited to the contents of the specification, but must be determined according to the scope of the claims.

Claims

1. A method for rapid and harmless treatment of oily sludge through photo-coupled biodegradation, characterized in that, Includes the following steps: (1) Mix the oily sludge with organic solid waste and compound biomass synergist evenly to obtain a mixture, and control the moisture content of the mixture to ≤65%; (2) Stack the mixed materials into a pile; (3) The entire stack is completely, tightly and tightly covered with plastic film, and then placed under light for high-temperature continuous fermentation. During the fermentation process, the stack is turned over every 7-15 days. Fermentation continues until the oil content of the mixture is ≤2%. The film is removed and the mixture is allowed to mature under natural light to obtain the soil conditioner. The volume ratio of oily sludge to organic solid waste is 1:1 to 1:0.

3. The mass of the compound biomass synergist added is 0.5%-3% of the total mass of the mixture. The compound biomass synergist is composed of plant-derived surfactants that have a surface emulsifying effect on crude oil, biochar loaded with thermophilic petroleum hydrocarbon degrading bacteria, and potassium humate-seaweed extract that maintains microbial activity and metabolic efficiency in a mass ratio of (10-20):(70-75):(10-20).

2. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, Organic solid waste includes at least one of livestock and poultry manure, crop straw, and plant residues.

3. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 2, characterized in that, Livestock and poultry manure includes at least one of chicken manure, pig manure, and cow manure.

4. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, Potassium humate-seaweed extract is a compound of potassium humate and seaweed extract, with a mass ratio of potassium humate to seaweed extract of (2-3):(1-2).

5. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, In step (2), the height of the stack is 0.8-1.5 meters and the width is 1.5-2.5 meters.

6. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, The lighting method is the same as that of outdoor sun exposure in Northwest China during the summer.

7. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, Plant-derived surfactants include at least one of soapberry powder, soapberry peel extract, and tea saponin.

8. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, The thermophilic petroleum hydrocarbon degrading bacteria are at least one of thermophilic lipophilic Bacillus or thermophilic oleophilic Bacillus.

9. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, The film is either transparent or black.

10. The method for rapid and harmless treatment of oily sludge by photo-coupled biodegradation according to claim 1, characterized in that, The film is ordinary PE food preservation film or agricultural plastic film.