Remediation method for polycyclic aromatic hydrocarbon contaminated soil by ultrasonic mud bioreactor

Abstract

According to the method for repairing the soil polluted by the polycyclic aromatic hydrocarbon through the ultrasonic mud bioreactor, ultrasonic pretreatment is added on the basis of the mud bioreactor, so that desorption and degradation of the polycyclic aromatic hydrocarbon are promoted, and the soil polluted by the polycyclic aromatic hydrocarbon is repaired. According to the method for repairing the polycyclic aromatic hydrocarbon contaminated soil through the ultrasonic slurry bioreactor, ultrasonic and the biological slurry reactor are combined, optimal ultrasonic setting parameters and selection of efficient degrading bacteria are given, the degrading effect is improved, and meanwhile cost and energy consumption are reduced.

Description

Technical Field

[0001] This invention relates to the field of soil remediation technology, and more specifically, to a method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor. Background Technology

[0002] Polycyclic aromatic hydrocarbons (PAHs) are a special class of cyclic organic compounds composed of at least two benzene rings linked in a conjugated manner. Their chemical structure endows them with excellent stability and bioaccumulation properties. PAHs are ubiquitous in the environment, found in petrochemical products, rubber, plastics, lubricants, rust inhibitors, and in incompletely burned organic matter.

[0003] Because of their genotoxic, mutagenic, and carcinogenic properties, these substances can cause various harms to the human body and are recognized as major organic pollutants affecting human health. Of the more than 500 known carcinogens, over 200 are related to polycyclic aromatic hydrocarbons (PAHs). Animal experiments have shown that some PAHs can affect the reproductive function of animals, leading to birth defects and low birth weight in offspring. Simultaneously, PAHs may also damage the human respiratory, circulatory, and nervous systems, and harm organs such as the liver and kidneys.

[0004] Because PAHs pose significant hazards to the environment and human health, many countries and regions around the world have formulated relevant control standards and requirements to restrict their use in different products and fields, such as the EU's Directive 76 / 769 / EEC, Germany's LMBG regulation, the US EPA standard, and China's national standards such as GB, GB / T, and GHZ. The U.S. Environmental Protection Agency (EPA) regulates PAHs and has identified 16 priority PAHs for control: Naphthalene (Nap), Acy, Ace, Flo, Phe, Anthracite (Ant), Fluorine (Flu), Pyrene (Pyr), Benzo[a]anthracene (BaA), Chr, Benzo[b]fluorine anthracene (BbF), Benzo[k]fluorine anthracene (BkF), Benzo[a]pyrene (BaP), Dibenzo[a,h]anthracene (DahA), Indo[1,2,3-cd]pyrene (IcdP), and Benzo[g,h,i]perylene (BghiP).

[0005] Patent document CN101195122A discloses a method for ultrasonic remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil, specifically disclosing that the method involves treating a PAH-contaminated soil slurry with a water content of 5%–95% and a PAH concentration of 10–10000 μg / kg under ultrasonic irradiation conditions; the ultrasonic output frequency is 20 kHz–100 kHz, the ultrasonic output power is 100 W–2.0 kW, and the ultrasonic irradiation time is 5 min–4 h; the PAHs are among the 16 priority PAH compounds specified in US EPA 610; this method mainly utilizes the cavitation effect of ultrasound to degrade or reduce persistent organic pollutants such as PAHs in the soil.

[0006] The remediation method in patent document CN101195122A has the following drawbacks: While moderately increasing the power and extending the ultrasonic treatment time can improve the removal rate of PAHs in the soil to some extent, using high-power, prolonged, and excessive ultrasonic treatment alone not only requires more energy consumption but may also damage microorganisms and inhibit the degradation process. Experiments show that high-power, prolonged, and excessive ultrasonic treatment not only fails to promote the desorption of PAHs but may also inhibit the degradation reaction of some microorganisms due to the generation of toxic substances from ultrasonic fragmentation, thus reducing degradation efficiency. The ultrasonic power output used in patent document CN101195122A is 100W to 2.0kW. High-power ultrasonic treatment inevitably requires more energy, leading to a significant increase in energy consumption and soil remediation costs. The ultrasonic irradiation time in patent document CN101195122A is 5min to 4h, and Example 1 describes an ultrasonic irradiation time of 30min. The ultrasonic wave is emitted using a trough-type device. The polycyclic aromatic hydrocarbon (PAH) content in the remediated soil was 68.78 ug / kg, with a removal rate of 77.1%. Example 4 recorded that when the ultrasonic irradiation time was 10 min, the removal rate of PAHs in the soil was 39.6%; when the ultrasonic irradiation time was 1 h, the removal rate of PAHs in the soil was 85.2%. It can be seen that the ultrasonic irradiation time in patent document CN101195122A is limited to a range of 30 min to 4 h. Long-term ultrasonic treatment will inevitably require more energy, resulting in a significant increase in energy consumption and soil remediation costs.

[0007] In view of this, the present invention is hereby proposed. Summary of the Invention

[0008] The purpose of this invention is to address the shortcomings of existing technologies by providing an ultrasonic mud bioreactor method for the remediation of polycyclic aromatic hydrocarbon (PAH) contaminated soil. This method combines the advantages of ultrasound and biological mud reactors, improving degradation efficiency while reducing cost and energy consumption.

[0009] In order to achieve the above-mentioned objectives of the present invention, the following technical solution is adopted: An ultrasonic mud bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil is proposed. This method involves adding low-dose ultrasonic pretreatment to a biological mud bioreactor to promote the desorption and degradation of PAHs and thus remediate PAH-contaminated soil.

[0010] Furthermore, ultrasonic pretreatment was added to the biological mud reactor, which can degrade the polycyclic aromatic hydrocarbons to at least one of naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, α, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, indo[1,2,3-cd]pyrene, and benzo[g,h,i]perylene.

[0011] Furthermore, the ultrasonic power in the ultrasonic pretreatment is 60W~90W.

[0012] Furthermore, the ultrasonic pretreatment time is 10 min to 35 min.

[0013] Furthermore, the ultrasonic temperature during ultrasonic pretreatment is 20℃~35℃.

[0014] Furthermore, the size of the ultrasonic amplitude transformer in the ultrasonic pretreatment is ≤8mm.

[0015] Furthermore, the polycyclic aromatic hydrocarbon contaminated soil is pretreated to a particle size of 0.1 mm to 2 mm; the water-to-soil ratio in the ultrasonic mud reactor is 1:1 to 3:1.

[0016] Furthermore, after ultrasonic pretreatment, highly efficient degrading bacteria are added for biodegradation; the highly efficient degrading bacteria are at least one of the following: highly efficient degrading bacteria acclimated from coking plant sludge, highly efficient degrading bacteria acclimated from urban sewage treatment plant sludge, and highly efficient degrading bacteria acclimated from polycyclic aromatic hydrocarbon contaminated soil.

[0017] Furthermore, the amount of highly efficient degrading bacteria added is 10% to 15% of the treatment volume of the ultrasonic mud reactor.

[0018] Furthermore, the highly efficient degrading bacteria are highly efficient degrading bacteria acclimated from coking plant sludge, and the amount of the highly efficient degrading bacteria acclimated from coking plant sludge added is 10% of the treatment volume of the ultrasonic sludge reactor.

[0019] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil using an ultrasonic slurry bioreactor. It combines the advantages of both ultrasound and a biological slurry reactor. Using ultrasound alone may damage microorganisms, and using a slurry reactor alone results in relatively slow and low degradation efficiency. This invention combines low-dose ultrasound with a biological slurry reactor, providing optimal ultrasound settings and selection of highly efficient degrading bacteria, thereby improving degradation efficiency while reducing cost and energy consumption.

[0020] 2. The microbial community added to the ultrasonic mud reactor in this invention can retain strains carrying genes such as NAH (naphthalene degradation) and PHN (polycyclic aromatic hydrocarbon hydroxylase) through natural selection. The microbial community has evolved mechanisms to resist the toxicity of PAHs, such as: secreting biosurfactants (e.g., rhamnolipids) to enhance the solubility of PAHs; and producing antioxidant enzymes (SOD, catalase) to resist reactive oxygen species (ROS) produced by PAH metabolism, which can effectively improve the degradation rate of PAHs.

[0021] 3. The ultrasonic mud bioreactor of this invention remediates contaminated soil. The ultrasonic pretreatment has low power, short ultrasonic time, and low ultrasonic temperature (remediation can be carried out at room temperature), avoiding the inhibitory effect of excessive ultrasonic treatment on the degradation process. While improving the degradation effect, it significantly reduces energy consumption and soil remediation costs. Attached Figure Description

[0022] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific 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 from these drawings without creative effort.

[0023] Figure 1 Photograph of the experimental apparatus for the ultrasonic mud bioreactor of this invention; Figure 2 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 300 mg / kg PHE in soil and aqueous phases under different ultrasonic power conditions in the present invention. Figure 3 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 200 mg / kg PHE in soil and aqueous phases under different ultrasonic power conditions. Figure 4 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PHE in soil and aqueous phases under different ultrasonic power conditions in the present invention. Figure 5 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 150 mg / kg PYR in soil and aqueous phases under different ultrasonic power conditions. Figure 6 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PYR in soil and aqueous phases under different ultrasonic power conditions. Figure 7 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 50 mg / kg PYR in soil and aqueous phases under different ultrasonic power conditions in the present invention. Figure 8 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 300 mg / kg PHE in soil and aqueous phases under different ultrasonic time conditions. Figure 9 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 200 mg / kg PHE in soil and aqueous phases under different ultrasonic time conditions. Figure 10 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PHE in soil and aqueous phases under different ultrasonic time conditions.

[0024] Figure 11 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 150 mg / kg PYR in soil and aqueous phases under different ultrasonic time conditions. Figure 12 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PYR in soil and aqueous phases under different ultrasonic time conditions. Figure 13 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 50 mg / kg PYR in soil and aqueous phases under different ultrasonic time conditions. Figure 14 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 300 mg / kg PHE in soil and aqueous phases under different ultrasonic temperature conditions. Figure 15 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 200 mg / kg PHE in soil and aqueous phases under different ultrasonic temperature conditions. Figure 16 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PHE in soil and aqueous phases under different ultrasonic temperature conditions. Figure 17 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 150 mg / kg PYR in soil and aqueous phases under different ultrasonic temperature conditions. Figure 18 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PYR in soil and aqueous phases under different ultrasonic temperature conditions. Figure 19 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 50 mg / kg PYR in soil and aqueous phases under different ultrasonic temperature conditions. Figure 20 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 300 mg / kg PHE in soil and aqueous phases under different ultrasonic amplitude transformer sizes. Figure 21 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 200 mg / kg PHE in soil and aqueous phases under different ultrasonic amplitude transformer sizes. Figure 22 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PHE in soil and aqueous phases under different ultrasonic amplitude transformer sizes. Figure 23 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 150 mg / kg PYR in soil and aqueous phases under different ultrasonic amplitude transformer sizes. Figure 24 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 100 mg / kg PYR in soil and aqueous phases under different ultrasonic amplitude transformer sizes. Figure 25 This invention demonstrates the degradation effect of contaminated soil samples with an initial concentration of 50 mg / kg PYR in soil and aqueous phases under different ultrasonic amplitude transformer sizes. Figure 26 This invention demonstrates the degradation effect of PHE in soil and water phases under different initial soil pollutant concentrations. Figure 27 This invention demonstrates the degradation effect of PYR in soil and water phases under different initial soil pollutant concentrations. Figure 28 This invention demonstrates the degradation effect of PHE in soil and water phases under different soil particle size conditions. Figure 29 This invention demonstrates the degradation effect of PYR in soil and water phases under different soil particle size conditions. Figure 30 This invention demonstrates the degradation effect of PHE in soil and water phases under different water-to-soil ratios. Figure 31 This invention demonstrates the degradation effect of PYR in soil and water phases under different water-to-soil ratios. Figure 32 The degradation effect of this invention on PHE in soil and water phases under different rotation speed conditions; Figure 33 The degradation effect of this invention on PYR in soil and water phases under different rotation speed conditions; Figure 34 The invention describes the degradation effect of highly efficient degrading bacteria (JGJ) on PHE and PYR under different addition amounts of coking plant sludge after domestication. Figure 35 This invention demonstrates the degradation effect of highly efficient degrading bacteria (WGJ) on PHE and PYR under different addition amounts of acclimated sludge from urban wastewater treatment plants. Figure 36 The degradation effect of the highly efficient degrading bacteria (TGJ) on PHE and PYR in contaminated soil after domestication with 300 mg / kg PHE and 150 mg / kg PYR according to this invention was investigated. Figure 37 The effect of the addition amount on the degradation effect of PHE and PYR when the highest degradation rate of PHE and PYR is achieved by different bacterial sources and highly efficient degrading bacteria under the degradation action of this invention. Detailed Implementation

[0025] The technical solution of the present invention will be clearly and completely described below with reference to specific embodiments. However, those skilled in the art will understand that the embodiments described below are some embodiments of the present invention, but not all embodiments, and are only used to illustrate the present invention, and should not be regarded as limiting the scope of the present invention. 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. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall be followed. Where the manufacturers of reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0026] An ultrasonic mud bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil is proposed. This method involves adding low-dose ultrasonic pretreatment to a biological mud bioreactor to promote the desorption and degradation of PAHs and thus remediate PAH-contaminated soil.

[0027] Preferably, ultrasonic pretreatment is added to the biological mud reactor, which can degrade polycyclic aromatic hydrocarbons such as naphthalene (Nap), acenaphthene (Acy), acenaphthene (Ace), fluorene (Flo), phenanthrene (Phe), anthracene (Ant), fluoranthene (Flu), pyrene (Pyr), benzo[a]anthracene (BaA), chromium (Chr), benzo[b]fluoranthene (BbF), benzo[k]fluoranthene (BkF), benzo[a]pyrene (BaP), dibenzo[a,h]anthracene (DahA), indo[1,2,3-cd]pyrene (IcdP), and benzo[g,h,i]perylene (BghiP); Preferably, the ultrasonic power in the ultrasonic pretreatment is 60W~90W, including but not limited to 60W, 65W, 70W, 75W, 80W, 85W, and 90W, with 90W being the most preferred; Preferably, the ultrasonic pretreatment time is 10 min to 35 min, including but not limited to 10 min, 15 min, 20 min, 25 min, 30 min, and 35 min, with 20 min being the most preferred; Preferably, the ultrasonic temperature in the ultrasonic pretreatment is 20℃~35℃, including but not limited to 20℃, 21℃, 22℃, 23℃, 24℃, 25℃, 26℃, 27℃, 28℃, 29℃, 30℃, 31℃, 32℃, 33℃, 34℃, and 35℃, with 25℃ or 20℃ being the most preferred. Preferably, the size of the ultrasonic amplitude transformer in the ultrasonic pretreatment is ≤8mm; Preferably, the size of the ultrasonic amplitude transformer in the ultrasonic pretreatment is 5 mm to 8 mm, including but not limited to 5 mm, 5.5 mm, 6 mm, 6.5 mm, 7 mm, 7.5 mm, 8 mm, and preferably 6 mm; Preferably, the polycyclic aromatic hydrocarbon contaminated soil is pretreated to a particle size of 0.1 mm to 2 mm, including but not limited to 0.1 mm, 0.2 mm, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, 0.8 mm, 0.9 mm, 1 mm, 1.1 mm, 1.2 mm, 1.3 mm, 1.4 mm, 1.5 mm, 1.6 mm, 1.7 mm, 1.8 mm, 1.9 mm, and 2.0 mm, with 0.2 mm being the most preferred. Preferably, the water-to-soil ratio in the ultrasonic mud reactor is 1:1 to 3:1, including but not limited to 1:1, 1.5:1, 2:1, 2.5:1, 3:1, with 2:1 being the most preferred; Preferably, the ultrasonic mud reactor is equipped with a stirring mechanism with a stirring speed of 200 rpm to 300 rpm, including but not limited to 200 rpm, 210 rpm, 220 rpm, 230 rpm, 240 rpm, 250 rpm, 260 rpm, 270 rpm, 280 rpm, 290 rpm, and 300 rpm, with 200 rpm being the most preferred. Preferably, after ultrasonic pretreatment, highly efficient degrading bacteria are added for biodegradation; the highly efficient degrading bacteria are at least one of the following: highly efficient degrading bacteria acclimated from coking plant sludge (JGJ), highly efficient degrading bacteria acclimated from urban sewage treatment plant sludge (WGJ), and highly efficient degrading bacteria acclimated from polycyclic aromatic hydrocarbon contaminated soil. Preferably, the highly efficient degrading bacteria after acclimation of polycyclic aromatic hydrocarbon contaminated soil are highly efficient degrading bacteria (TGJ) after acclimation of contaminated soil with 300 mg / kg PHE and 150 mg / kg PYR. Preferably, the amount of highly efficient degrading bacteria (JGJ) added after coking plant sludge acclimation is 10% to 15% of the treatment volume of the ultrasonic sludge reactor, including but not limited to 10%, 11%, 12%, 13%, 14%, and 15%, with 10% being preferred; Preferably, the amount of highly efficient degrading bacteria (WGJ) added after sludge acclimation in urban wastewater treatment plants is 10%~15%, including but not limited to 10%, 11%, 12%, 13%, 14%, and 15%, preferably 10% or 15%; Preferably, the amount of highly efficient degrading bacteria (TGJ) after acclimation of contaminated soil with 300 mg / kg PHE and 150 mg / kg PYR is 10% to 15% of the treatment volume of the ultrasonic mud reactor, including but not limited to 10%, 11%, 12%, 13%, 14%, and 15%, preferably 10% or 15%.

[0028] Example 1 An ultrasonic mud bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil involves first performing ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25 °C, and an ultrasonic amplitude transformer of 6 mm. Then, 10% of the volume of highly efficient degrading bacteria (JGJ) acclimated from coking plant sludge is added to the ultrasonic mud bioreactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured to be 85.16% for PHE and 87.01% for PYR.

[0029] Example 2 An ultrasonic mud bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil involves first performing ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25 °C, and an ultrasonic amplitude transformer of 6 mm. Then, 15% of the volume of highly efficient degrading bacteria (JGJ) acclimated from coking plant sludge is added to the ultrasonic mud bioreactor for further ultrasonic pretreatment. The PAH-contaminated soil was then remediated. The degradation rates were measured as follows: PHE degradation rate 83.89%, and PYR degradation rate 82.54%.

[0030] Example 3 An ultrasonic slurry bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil was disclosed. The method involved ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25℃, and an ultrasonic amplitude transformer of 6 mm. Then, 15% of the volume of highly efficient degrading bacteria (WGJ) acclimated from urban wastewater treatment plant sludge was added to the ultrasonic slurry reactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured as follows: PHE degradation rate 74.33%, and PYR degradation rate 81.39%.

[0031] Example 4 An ultrasonic slurry bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil was disclosed. The method involved ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25℃, and an ultrasonic amplitude transformer of 6 mm. Then, 10% of the volume of highly efficient degrading bacteria (WGJ) acclimated from urban wastewater treatment plant sludge was added to the ultrasonic slurry bioreactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured as follows: PHE degradation rate 73.71%, and PYR degradation rate 79.16%.

[0032] Example 5 A method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil using an ultrasonic mud bioreactor involves first performing ultrasonic pretreatment (ultrasonic power 90 W, ultrasonic time 20 min, ultrasonic temperature 25℃, ultrasonic amplitude bar 6 mm). Then, highly efficient degrading bacteria (TGJ) acclimated to the contaminated soil (300 mg / kg PHE and 150 mg / kg PYR, accounting for 15% of the volume) are added to the ultrasonic mud bioreactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured as follows: PHE degradation rate 77.62%, and PYR degradation rate 81.66%.

[0033] Example 6 A method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil using an ultrasonic mud bioreactor involves first performing ultrasonic pretreatment (ultrasonic power 90 W, ultrasonic time 20 min, ultrasonic temperature 25℃, ultrasonic amplitude bar 6 mm). Then, highly efficient degrading bacteria (TGJ) acclimated to the contaminated soil (300 mg / kg PHE and 150 mg / kg PYR, accounting for 10% of the volume) are added to the ultrasonic mud bioreactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured as follows: PHE degradation rate 75.29%, and PYR degradation rate 80.11%.

[0034] Comparative Example 1 A method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil using an ultrasonic mud bioreactor involves first performing ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25℃, and an ultrasonic amplitude transformer of 6 mm. Then, 5% by volume of highly efficient degrading bacteria (JGJ) acclimated from coking plant sludge is added to the ultrasonic mud bioreactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured to be 73.67% for PHE and 74.81% for PYR.

[0035] Comparative Example 2 An ultrasonic slurry bioreactor method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil was disclosed. The method involved first performing ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25℃, and an ultrasonic amplitude transformer of 6 mm. Then, 5% (by volume) of highly efficient degrading bacteria (WGJ) acclimated from urban wastewater treatment plant sludge was added to the ultrasonic slurry reactor to remediate PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured as follows: PHE degradation rate 70.35%, and PYR degradation rate 76.92%.

[0036] Comparative Example 3 A method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil using an ultrasonic mud bioreactor involves first performing ultrasonic pretreatment with an ultrasonic power of 90 W, an ultrasonic time of 20 min, an ultrasonic temperature of 25℃, and an ultrasonic amplitude transformer of 6 mm. Then, highly efficient degrading bacteria (TGJ) acclimated to the contaminated soil (300 mg / kg PHE and 150 mg / kg PYR, accounting for 5% of the volume) are added to the ultrasonic mud bioreactor to remediate the PAH-contaminated soil. The degradation rates of PAH-contaminated soil were measured to be 71.78% for PHE and 77.97% for PYR.

[0037] Experimental example: like Figure 1 As shown, the ultrasonic mud bioreactor of the present invention utilizes an ultrasonic generator combined with a mud reactor, and the ultrasonic generator uses a low-temperature ultrasonic extractor to simulate related operations.

[0038] I. The Influence of Ultrasonic Power on Desorption Efficiency To investigate the effect of different ultrasonic powers on the degradation rate of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil, and considering that different pollutant concentrations may also affect the desorption efficiency, contaminated soil samples with different concentrations (100 g of 300 mg / kg PHE and 150 mg / kg PYR, 200 mg / kg PHE and 100 mg / kg PYR, 100 mg / kg PHE and 50 mg / kg PYR) were taken, and 200 ml of deionized water was added. The samples were ultrasonicated at 25℃ for 20 min, and the ultrasonic power was varied at 0 W, 15 W, 30 W, 45 W, 60 W, 90 W, 150 W, and 450 W to observe the effect of different ultrasonic powers on the desorption efficiency of PAHs during the ultrasonic pretreatment process. Figures 2-4 The degradation effects of contaminated soil samples with initial concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg PHE in the soil and aqueous phases are shown in order. Figures 5-7 The degradation effects of contaminated soil samples with initial concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg PYR in the soil and aqueous phases are shown in order.

[0039] like Figure 2 The degradation effects of contaminated soil samples with an initial concentration of 300 mg / kg PHE in the soil and aqueous phases showed the following: ① When the ultrasonic power increased from 0 W to 60 W, the concentration of PHE in the soil phase of the contaminated soil sample with an initial concentration of 300 mg / kg PHE showed a steady decreasing trend, from an initial 142.28 mg / kg to 88.06 mg / kg. The degradation rate of PHE reached 38.11% at an ultrasonic power of 60 W. When the ultrasonic power increased from 60 W to 90 W, the concentration of PHE in the soil phase decreased significantly to 45.98 mg / kg, and the degradation rate of PHE reached its highest level of 67.68% at an ultrasonic power of 90 W. This may be because the vibration generated during the ultrasonic process promoted the degradation of PAHs when the power was between 0 W and 60 W, and when the power was between 60 W and 90 W, the ultrasonic process also generated cavitation bubbles to a certain extent, which had an oxidation effect and more effectively promoted the degradation of PAHs. The study of ultrasound shows that ultrasound can improve the removal efficiency of pollutants in contaminated soil. When the ultrasonic power was increased again from 90 W, the PHE concentration in the soil phase actually increased, while the PHE degradation rate decreased instead of increasing. This may be because excessive ultrasonic power can break down cell structures and produce toxic substances, thus inhibiting the degradation process. Studies on ultrasound have shown that excessive ultrasound has an inhibitory effect on pollutant removal, which is consistent with the experimental results. ② When the ultrasonic power was increased from 0 W to 15 W, the PHE concentration in the aqueous phase actually increased, possibly because ultrasound caused some PHE in the soil phase to transfer to the aqueous phase. When the power was increased from 15 W to 90 W, the PHE concentration in the aqueous phase decreased from 75.12 mg / L to 17.44 mg / L. The PHE degradation rate in the aqueous phase reached its highest level of 75.11% at an ultrasonic power of 90 W. Higher ultrasonic power not only failed to promote PHE desorption but may also inhibit the degradation reaction of some microorganisms due to the toxic substances produced by ultrasonic disruption. Considering the degradation effects of PHE in both the soil and aqueous phases, the optimal ultrasonic power for contaminated soil samples with an initial concentration of 300 mg / kg PHE was 90 W.

[0040] like Figure 3The degradation effects of contaminated soil samples with an initial concentration of 200 mg / kg PHE in the soil and aqueous phases showed the following: ① Unlike the contaminated soil samples with an initial concentration of 300 mg / kg PHE, the concentration of PHE in the soil phase of the 200 mg / kg PHE contaminated soil samples showed a steady decreasing trend when the ultrasonic power increased from 0 W to 90 W, steadily decreasing from an initial 93.85 mg / kg to 26.83 mg / kg. The degradation rate of PHE reached its highest point of 71.41% at an ultrasonic power of 90 W. This is because ultrasonic pretreatment promotes the removal of pollutants from contaminated soil. When the ultrasonic power was increased again from 90 W, the concentration of PHE in the soil phase increased instead, and the PHE degradation rate decreased instead of increasing. This is similar to the contaminated soil samples with an initial concentration of 300 mg / kg PHE. This may be because excessive ultrasonic power can break down cell structures and produce toxic substances, thus inhibiting the removal of pollutants. Studies on ultrasound have shown that excessive ultrasound has an inhibitory effect on the removal of pollutants, which is similar to the experimental data. ② Similar to the soil sample with an initial PHE concentration of 300 mg / kg, the PHE concentration in the aqueous phase actually increased when the ultrasonic power increased from 0 W to 15 W. This may be because ultrasound caused some PHE to transfer from the soil phase to the aqueous phase. Unlike the soil sample with an initial PHE concentration of 300 mg / kg, when the power increased from 15 W to 60 W, the PHE concentration in the aqueous phase decreased from 56.43 mg / L to 11.82 mg / L. At an ultrasonic power of 60 W, the PHE degradation rate in the aqueous phase reached its highest level of 75.03%. Similarly, beyond 60 W, higher ultrasonic power not only failed to promote PHE desorption but may also inhibit the reaction due to the generation of toxic substances from ultrasonic fragmentation. Since the ultimate goal is to remove PAHs pollutants from the soil, the degradation effect of PHE in the soil phase is the primary focus. Considering the degradation effects of PHE in both the soil and aqueous phases, the optimal ultrasonic power for the soil sample with an initial PHE concentration of 200 mg / kg was 90 W.

[0041] like Figure 4The degradation effects of contaminated soil samples with an initial concentration of 100 mg / kg PHE in the soil and aqueous phases showed the following: ① When the ultrasonic power increased from 0 W to 90 W, the concentration of PHE in the soil phase of the contaminated soil sample with an initial concentration of 100 mg / kg PHE showed a decreasing trend, decreasing from an initial 41.68 mg / kg to 16.86 mg / kg. The degradation rate of PHE reached its highest point of 59.55% when the ultrasonic power was 90 W. The ultrasound study indicates that ultrasound can improve the removal efficiency of pollutants in contaminated soil, which is consistent with the data results. Similar to the contaminated soil samples with initial concentrations of 300 mg / kg PHE and 200 mg / kg PHE, when the ultrasonic power was increased again from 90 W, the concentration of PHE in the soil phase actually increased, while the PHE degradation rate decreased instead of increasing. This may be because excessive ultrasonic power can break down cell structures and produce toxic substances, thus inhibiting the degradation process. The ultrasound study indicates that excessive ultrasound has an inhibitory effect on pollutant removal, which is consistent with the experimental results. ② Similarly, when the ultrasonic power increased from 0 W to 15 W, the PHE concentration in the aqueous phase actually increased. This may be because ultrasound caused some PHE in the soil phase to transfer to the aqueous phase. Unlike the contaminated soil samples with initial concentrations of 300 mg / kg PHE and 200 mg / kg PHE, when the power increased from 15 W to 60 W, the PHE concentration in the aqueous phase decreased from 27.96 mg / L to 12.99 mg / L. The degradation rate of PHE in the aqueous phase reached its highest level of 40.33% at an ultrasonic power of 60 W. When the power increased from 60 W to 90 W, the PHE concentration in the aqueous phase was actually higher than the initial concentration at 0 W. Increasing the power again from 90 W resulted in a further increase in the degradation rate. This indicates that there is a threshold for ultrasonic power in the process of ultrasonic pretreatment to degrade PAHs contaminated soil. For example, the ultrasonic power threshold for the contaminated soil sample with an initial concentration of 100 mg / kg PHE is 90 W. The degradation effect is worst under this ultrasonic power, and this threshold should be avoided. Studies on ultrasound have shown that ultrasonic pretreatment can promote the removal of pollutants from contaminated soil. However, higher ultrasonic power not only fails to promote the desorption of PHE, but may also inhibit the reaction due to the generation of toxic substances from ultrasonic fragmentation, similar to the experimental results here. Although the ultimate goal is to remove PAHs from the soil, it is also necessary to avoid the ultrasonic power threshold required for removing PAHs from the aqueous phase. Considering the degradation effects of PHE in both soil and aqueous phases, the optimal ultrasonic power for contaminated soil samples with an initial concentration of 100 mg / kg PHE is 60 W.

[0042] like Figure 5The degradation effects of contaminated soil samples with an initial concentration of 150 mg / kg PYR in the soil and aqueous phases showed the following: ① When the ultrasonic power increased from 0 W to 90 W, the concentration of PYR in the soil phase of the contaminated soil sample with an initial concentration of 150 mg / kg PYR showed a steady decreasing trend, decreasing from an initial 70.76 mg / kg to 17.87 mg / kg. The degradation rate of PYR reached its highest point of 74.75% at an ultrasonic power of 90 W. When the ultrasonic power was increased again from 90 W, the concentration of PYR in the soil phase increased, similar to that of PHE, but the degradation rate decreased instead of increasing. This may be because PYR, like PHE, belongs to PAHs pollutants, and excessive ultrasonic power can break down cell structures and produce toxic substances, thus inhibiting the degradation. Studies on ultrasound have shown that excessive ultrasound has an inhibitory effect on pollutant removal, which is similar to the experimental data. ② Similar to the changes in PHE, when the ultrasonic power increased from 0 W to 15 W, the concentration of PYR in the aqueous phase actually increased. This is likely because ultrasound caused some PYR in the soil phase to transfer to the aqueous phase, which played a major role in the ultrasonic pretreatment process. When the power increased from 30 W to 60 W, the PYR concentration in the aqueous phase decreased from 33.77 mg / L to 23.71 mg / L, with the highest degradation rate of 24.61% achieved at an ultrasonic power of 60 W. When the power increased from 60 W to 90 W, the PYR concentration in the aqueous phase increased, and the degradation rate decreased to 22.42% at 90 W. Although the higher power slightly reduced the degradation effect, it was still close to the highest value. However, when the power was increased from 90 W to 150 W and even 450 W, the concentration of PYR in the aqueous phase was actually higher than the initial concentration at 0 W, and the degradation rate did not increase as before. This indicates that the threshold of ultrasonic power in the degradation process of contaminated soil samples with an initial concentration of 150 mg / kg PYR may be between 150 W and 450 W, or even higher than 450 W. Ultimately, it is sufficient to avoid this power threshold. Studies on ultrasound have shown that ultrasonic pretreatment has a certain promoting effect on the removal of pollutants in contaminated soil. However, higher ultrasonic power not only fails to promote the desorption of PYR, but may also inhibit the reaction due to the generation of toxic substances from ultrasonic fragmentation, which is consistent with the experimental data here. Considering both maximizing the removal rate of PAHs pollutants in the soil and avoiding the ultrasonic power threshold for PAHs pollutant removal in the aqueous phase, and taking into account the degradation effect of PYR in both the soil and aqueous phases, the optimal ultrasonic power for contaminated soil samples with an initial concentration of 150 mg / kg PYR is 90 W.

[0043] like Figure 6The degradation effects of contaminated soil samples with an initial concentration of 100 mg / kg PYR in the soil and aqueous phases showed that: ① When the ultrasonic power increased from 0 W to 45 W, the concentration of PYR in the soil phase of the contaminated soil sample with an initial concentration of 100 mg / kg PYR showed a rapid decreasing trend, from an initial concentration of 41.08 mg / kg to 12.82 mg / kg. The degradation rate of PYR reached 68.79% at an ultrasonic power of 45 W. When the ultrasonic power increased from 45 W to 90 W, the concentration of PYR in the soil phase slowly decreased to 45.98 mg / kg. The degradation rate of PYR reached its highest level of 76.8% at a power of 90 W. This may be because when the power is between 0 W and 45 W, the ultrasonic pretreatment process has already degraded most of the PYR, thus reducing the baseline amount (relative content) of PYR in the soil phase and slowing down the degradation efficiency. ② Similar to the previous data changes, the PYR concentration in the aqueous phase actually increased when the ultrasonic power increased from 0 W to 15 W. This may be because ultrasound caused some PYR in the soil phase to transfer to the aqueous phase, which played a major role in the ultrasonic pretreatment process. When the power increased from 30 W to 60 W, the PYR concentration in the aqueous phase decreased from 28.69 mg / L to 15.02 mg / L, with the highest degradation rate of 32.25% at an ultrasonic power of 60 W. When the power increased from 60 W to 90 W, the PYR concentration in the aqueous phase rose sharply, and the degradation rate decreased to 12.72% at 90 W. Although the PYR degradation rate increased slightly to 18.13% at an ultrasonic power of 150 W, it plummeted to 4.92% when the power continued to increase to 450 W. Studies on ultrasound have shown that ultrasonic pretreatment can promote the removal of pollutants from contaminated soil. However, higher ultrasonic power not only fails to promote the desorption of PYR, but may also inhibit the reaction due to the generation of toxic substances caused by ultrasonic disruption, similar to the experimental results here. To avoid the ultrasonic power threshold during the degradation of PYR in the aqueous phase, the optimal power is 60 W. Considering both maximizing the removal rate of PAHs pollutants in soil and avoiding the ultrasonic power threshold for PAHs pollutant removal in the aqueous phase, based on... Figure 6 The degradation effect of PYR in soil and water phases was investigated. The optimal ultrasonic power for contaminated soil samples with an initial concentration of 100 mg / kg PYR was 60 W.

[0044] like Figure 7The degradation effects of contaminated soil samples with an initial PYR concentration of 50 mg / kg in the soil and aqueous phases showed the following: ① Similar to the contaminated soil samples with an initial PYR concentration of 100 mg / kg, as the ultrasonic power increased from 0 W to 45 W, the PYR concentration in the soil phase showed a rapid decreasing trend, rapidly decreasing from the initial 18.12 mg / kg to 6.7 mg / kg. The PYR degradation rate reached 63.02% at an ultrasonic power of 45 W. When the ultrasonic power increased from 45 W to 90 W, the PYR concentration in the soil phase slowly decreased to 5.58 mg / kg, and the PYR degradation rate reached its highest point of 69.21% at a power of 90 W. This may be because, at power levels between 0 W and 45 W, the ultrasonic pretreatment process had already degraded most of the PYR, thus reducing the baseline amount (relative content) of PYR in the soil phase and slowing down the degradation efficiency. ② Similarly, when the ultrasonic power increased from 0 W to 15 W, the PYR concentration in the aqueous phase actually increased. This is likely because ultrasound caused some PYR in the soil phase to transfer to the aqueous phase, which played a major role in the ultrasonic pretreatment process. When the power increased from 30 W to 60 W, the PYR concentration in the aqueous phase decreased from 10.96 mg / L to 4.64 mg / L, with the highest degradation rate of 52.99% achieved at an ultrasonic power of 60 W. As the ultrasonic power continued to increase, the degradation rate of PYR in the aqueous phase decreased significantly. Studies on ultrasound indicate that ultrasonic pretreatment has a certain promoting effect on the removal of pollutants from contaminated soil. However, higher ultrasonic power not only fails to promote the desorption of PYR but may also inhibit the reaction due to the generation of toxic substances from ultrasonic fragmentation, similar to the experimental data here. Considering the degradation effects of PYR in both soil and aqueous phases, and taking into account that higher ultrasonic power inevitably requires more energy, leading to a significant increase in economic consumption, the optimal ultrasonic power for contaminated soil samples with an initial PYR concentration of 50 mg / kg is 60 W, taking into account practical applications, experimental results, and economic factors.

[0045] Depend on Figures 2-7 It can be seen that ultrasonic power has a significant impact on the desorption efficiency of PAHs contaminated soil. The degradation rates of PHE and PYR vary with different ultrasonic powers, and their responses to ultrasonic power also differ depending on the initial concentration of PHE and PYR. The optimal ultrasonic power for contaminated soil samples with initial concentrations of 300 mg / kg PHE and 200 mg / kg PHE is 90 W; the optimal ultrasonic power for contaminated soil samples with an initial concentration of 100 mg / kg PHE is 60 W; the optimal ultrasonic power for contaminated soil samples with an initial concentration of 150 mg / kg PYR is 90 W; and the optimal ultrasonic power for contaminated soil samples with initial concentrations of 100 mg / kg and 50 mg / kg PYR is 60 W.

[0046] Typically, the appropriate power is selected based on the initial concentration; higher initial concentrations require higher power, while lower initial concentrations can be appropriately reduced. However, considering that higher ultrasonic power requires more energy, leading to a significant increase in economic costs, a power of 60 W is generally chosen based on practical applications, considering both experimental results and economic factors. However, 60 W is insufficient for highly polluted soil and may not achieve the best degradation effect, sometimes even less than half the desired degradation. To more comprehensively consider the potential impact of various factors, an optimal ultrasonic power of 90 W is selected. A power of 90 W yields the best PAH removal effect in the soil. To ensure the accuracy of this 90 W setting... Simultaneously, the results of adding ultrasonic power of 85 W and 95 W to mud containing 300 mg / kg PHE and 150 mg / kg PYR were as follows: At 85 W, the aqueous and soil phases of PHE were 20.23 mg / L and 60.71 mg / kg, respectively, with degradation rates of 71.13% and 57.33%; the aqueous and soil phases of PYR were 24.18 mg / L and 20.61 mg / kg, respectively, with degradation rates of 23.11% and 70.87%. At 95 W, the aqueous and soil phases of PHE were 21.18 mg / L and 48.46 mg / kg, respectively, with degradation rates of 69.77% and 65.94%; the aqueous and soil phases of PYR were 26.62 mg / L and 18.84 mg / kg, respectively, with degradation rates of 15.35% and 73.37%. In summary, the optimal ultrasonic power is 90 W.

[0047] II. The Influence of Ultrasonic Time on Desorption Efficiency To investigate the effect of different ultrasonic times on the degradation rate of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil, and considering that different pollutant concentrations may also affect the desorption efficiency, the optimal ultrasonic power was determined to be 90 W. Therefore, 100 g of contaminated soil samples with different concentrations (100 mg / kg PHE and 150 mg / kg PYR, 200 mg / kg PHE and 100 mg / kg PYR, 100 mg / kg PHE and 50 mg / kg PYR) were added to 200 ml of deionized water. Ultrasonic times of 0 min, 5 min, 10 min, 20 min, 35 min, 55 min, 80 min, and 120 min were simultaneously varied at an ultrasonic power of 90 W and an ultrasonic temperature of 25 °C to observe the effect of different ultrasonic times during the ultrasonic pretreatment process on the desorption efficiency of PAHs. Figures 8-10The degradation effects of contaminated soil samples with initial concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg PHE in the soil and aqueous phases are shown in order. Figures 11-13 The degradation effects of contaminated soil samples with initial concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg PYR in the soil and aqueous phases are shown in order.

[0048] like Figure 8 The degradation effects of contaminated soil samples with an initial concentration of 300 mg / kg PHE in the soil and aqueous phases showed that: ① When the ultrasonic time increased from 0 min to 20 min, the concentration of PHE in the soil phase decreased significantly, rapidly decreasing from 142.28 mg / kg to 46.66 mg / kg. The degradation rate of PHE reached 67.21% after 20 min. As the ultrasonic time continued to increase, the PHE concentration continued to decrease, but the rate of decrease slowed significantly. When the ultrasonic time increased from 20 min to 35 min, the PHE concentration only decreased from 46.66 mg / kg to 42.25 mg / kg, and the degradation rate of PHE in the soil phase only increased from 67.21% to 70.31%. Even when the ultrasonic time increased from 35 min to 120 min, the degradation rate of PHE only increased by about 3%. Although the degradation rate of PHE in the soil phase is higher under ultrasonic time of 35 min or longer, longer ultrasonic time inevitably requires more energy, which significantly increases economic consumption. Based on practical application, considering both experimental results and economic factors, an ultrasonic time of 20 min is sufficient. ② Similar to the soil phase, the concentration of PHE in the aqueous phase also decreased significantly from 0 min to 20 min, rapidly decreasing from an initial 70.06 mg / L to 17.48 mg / L. At 20 min, the PHE degradation rate reached 75.05%. However, unlike the soil phase, as the ultrasonic time continued to increase, the PHE concentration in the aqueous phase increased instead of decreasing, and the degradation rate decreased. Although the increase in PHE concentration was small, it still shows that ultrasound can promote the degradation of PAHs, while excessive ultrasound not only requires more energy but also inhibits the degradation process. Considering the degradation effects of PHE in both the soil and aqueous phases, the optimal ultrasonic time for contaminated soil samples with an initial concentration of 300 mg / kg PHE is 20 min.

[0049] like Figure 9The degradation effects of contaminated soil samples with an initial concentration of 200 mg / kg PHE in the soil and aqueous phases showed the following: ① Consistent with the contaminated soil samples with an initial concentration of 300 mg / kg PHE, the concentration of PHE in the soil phase of the contaminated soil samples with an initial concentration of 200 mg / kg PHE showed a significant decreasing trend when the ultrasonic time increased from 0 min to 20 min, rapidly decreasing from the initial 93.85 mg / kg to 26.58 mg / kg. The degradation rate of PHE reached 71.59% at the ultrasonic time of 20 min. This is because ultrasonic pretreatment promotes the removal of pollutants from contaminated soil. When the ultrasonic time continued to increase, the PHE concentration still decreased, but the rate of decrease slowed significantly. When the ultrasonic time increased from 20 min to 35 min, the PHE concentration only decreased from 26.58 mg / kg to 26.05 mg / kg, and the degradation rate of PHE in the soil phase only increased from 71.59% to 72.24%. Even when the ultrasonic time increased from 35 min to 120 min, the degradation rate of PHE only increased by about 1%. Although the degradation rate of PHE in the soil phase was higher under ultrasonic time conditions of 35 min and longer, longer ultrasonic time inevitably requires more energy, which would significantly increase economic consumption. Based on practical application, considering both experimental results and economic factors, an ultrasonic time of 20 min is sufficient to meet the requirements. ② The concentration of PHE in the aqueous phase was consistent with that in the soil phase, showing a significant decrease from 0 min to 20 min, rapidly decreasing from an initial 47.33 mg / L to 12.48 mg / L. At 20 min, the degradation rate of PHE had reached 73.63%. However, as the ultrasonic time continued to increase, the concentration of PHE in the aqueous phase no longer changed, and the degradation rate tended to plateau. This shows that ultrasound can promote the degradation of PAHs; moderate ultrasonic conditions are sufficient, while excessive ultrasound not only requires more energy consumption but may not necessarily produce better results. Considering the degradation effect of PHE in both soil and water phases, the optimal ultrasonic time for contaminated soil samples with an initial concentration of 200 mg / kg PHE is also 20 min.

[0050] like Figure 10The degradation effects of contaminated soil samples with an initial concentration of 100 mg / kg PHE in the soil and aqueous phases showed the following: ① Consistent with the previous results, when the ultrasonic time increased from 0 min to 20 min, the concentration of PHE in the soil phase of the contaminated soil sample with an initial concentration of 100 mg / kg PHE showed a significant decreasing trend, rapidly decreasing from the initial 41.68 mg / kg to 16.53 mg / kg. At the 20 min ultrasonic time, the PHE degradation rate had already reached 60.03%. When the ultrasonic time continued to increase, the PHE concentration continued to decrease, but the rate of decrease slowed significantly. When the ultrasonic time increased from 20 min to 35 min, the PHE concentration only decreased from 16.53 mg / kg to 16.25 mg / kg, and the PHE degradation rate in the soil phase only increased from 60.03% to 61.01%. Even when the ultrasonic time increased from 35 min to 120 min, the PHE degradation rate only increased by about 1.4%. Therefore, an ultrasonic time of 20 min is sufficient. ② Unlike previous studies where the aqueous PHE degradation rate reached near its maximum after 20 minutes, in this case, the PHE concentration in the soil sample with an initial concentration of 100 mg / kg PHE had already decreased to its minimum value after 10 minutes of sonication. A significant decrease occurred between 0 and 10 minutes of sonication, rapidly decreasing from an initial 21.77 mg / L to 12.98 mg / L, indicating a PHE degradation rate of 40.38% after 10 minutes. Furthermore, as the sonication time continued to increase, the PHE concentration in the aqueous phase remained stable, and the degradation rate plateaued. Therefore, based on economic considerations, a sonication time of only 10 minutes for the aqueous PHE was sufficient. The ultimate goal is to remove PAHs contaminants from the soil, thus focusing more on the PHE degradation effect in the soil phase. However, the degradation rate of PHE in the soil phase was still significantly improved between 10 and 20 minutes. Considering the degradation effects of PHE in both soil and water phases, the optimal ultrasonic time for contaminated soil samples with an initial concentration of 100 mg / kg PHE was 15 minutes.

[0051] like Figure 11The degradation effects of contaminated soil samples with an initial concentration of 150 mg / kg PYR in the soil and aqueous phases showed that: When the ultrasonic time increased from 0 min to 20 min, the concentration of PYR in the soil phase decreased significantly, rapidly dropping from 70.76 mg / kg to 18.13 mg / kg. At 20 min, the degradation rate of PYR reached 74.38%. As the ultrasonic time continued to increase, the PYR concentration continued to decrease, but the rate of decrease slowed significantly. When the ultrasonic time increased from 20 min to 35 min, the PYR concentration only decreased from 18.13 mg / kg to 17.74 mg / kg, and the degradation rate of PYR in the soil phase only increased from 74.38% to 74.93%. Even when the ultrasonic time increased from 35 min to 120 min, the degradation rate of PYR only increased by about 1.2%. Although the degradation rate of PYR in the soil phase was higher under ultrasonication times of 35 min or longer, longer ultrasonication times inevitably require more energy, which would significantly increase economic costs. Based on practical application, considering both experimental results and economic factors, an ultrasonication time of 20 min was sufficient. ② The concentration of PYR in the aqueous phase was similar to that in the soil phase, showing a significant decrease from 0 min to 20 min, rapidly dropping from an initial 31.45 mg / L to 24.33 mg / L. At 20 min, the degradation rate of PYR had reached 22.64%. When the ultrasonication time continued to increase, the concentration of PYR in the aqueous phase increased instead of decreasing, and the degradation rate declined. Although the increase in PYR concentration was small, it still shows that ultrasound can promote the degradation of PAHs, while excessive ultrasound not only requires more energy but also inhibits the degradation process. Considering the degradation effects of PYR in both soil and water phases, the optimal ultrasonic time for contaminated soil samples with an initial concentration of 150 mg / kg PYR was 20 min.

[0052] like Figure 12The degradation effects of contaminated soil samples with an initial concentration of 100 mg / kg PYR in the soil and aqueous phases showed the following: ① Consistent with the contaminated soil samples with an initial concentration of 150 mg / kg PYR, the concentration of PYR in the soil phase of the contaminated soil samples with an initial concentration of 100 mg / kg PYR decreased significantly from 41.08 mg / kg to 9.68 mg / kg during the ultrasonic treatment time from 0 min to 20 min. The degradation rate of PYR reached 76.44% at 20 min. When the ultrasonic treatment time continued to increase, the PYR concentration continued to decrease, but the rate of decrease slowed down significantly. When the ultrasonic treatment time increased from 20 min to 35 min, the PYR concentration only decreased from 9.68 mg / kg to 9.35 mg / kg, and the degradation rate of PYR in the soil phase only increased from 76.44% to 77.24%. Even when the ultrasonic time increased from 35 min to 120 min, the degradation rate of PYR only increased by about 2%. Although the degradation rate of PYR in the soil phase was higher under ultrasonic time conditions of 35 min and longer, longer ultrasonic time inevitably requires more energy, which would significantly increase economic consumption. Based on practical application, considering both experimental results and economic factors, an ultrasonic time of 20 min is sufficient to meet the requirements. ② Similar to the soil phase, the concentration of PYR in the aqueous phase also decreased significantly from 0 min to 20 min, rapidly decreasing from an initial 22.17 mg / L to 19.32 mg / L. At 20 min, the degradation rate of PYR had already reached 12.86%. When the ultrasonic time continued to increase, the concentration of PYR in the aqueous phase increased instead of decreasing, and the degradation rate decreased. Although the increase in PYR concentration was small, it still shows that ultrasound can promote the degradation of PAHs, while excessive ultrasound not only requires more energy consumption but also inhibits the degradation process. Considering the degradation effects of PYR in both soil and water phases, the optimal ultrasonic time for contaminated soil samples with an initial concentration of 100 mg / kg PYR is 20 min.

[0053] like Figure 13The degradation effects of contaminated soil samples with an initial concentration of 50 mg / kg PYR in the soil and aqueous phases showed the following: ① Consistent with the former, when the ultrasonic time increased from 0 min to 20 min, the concentration of PYR in the soil phase of the contaminated soil sample with an initial concentration of 50 mg / kg PYR decreased significantly, rapidly decreasing from the initial 18.12 mg / kg to 5.78 mg / kg. The degradation rate of PYR reached 68.10% at 20 min. When the ultrasonic time continued to increase, the PYR concentration continued to decrease, but the rate of decrease slowed significantly. When the ultrasonic time increased from 20 min to 35 min, the PYR concentration only decreased from 5.78 mg / kg to 5.76 mg / kg, and the degradation rate of PYR in the soil phase only increased from 68.10% to 68.21%. Even when the ultrasonic time increased from 35 min to 120 min, the degradation rate of PYR only increased by about 0.4%. Although the degradation rate of PYR in the soil phase is higher under ultrasonication times of 35 min or longer, longer ultrasonication times inevitably require more energy, which significantly increases economic costs. Based on practical application, considering both experimental results and economic factors, an ultrasonication time of 20 min is sufficient. ② Similarly, the concentration of PYR in the aqueous phase also decreased significantly from 0 min to 20 min, rapidly decreasing from an initial 9.83 mg / L to 6.65 mg / L. At 20 min, the degradation rate of PYR reached 32.35%. When the ultrasonication time continued to increase, the concentration of PYR in the aqueous phase increased instead of decreasing, and the degradation rate decreased. Although the increase in PYR concentration was small, it still shows that ultrasound can promote the degradation of PAHs, while excessive ultrasound not only requires more energy but also inhibits the degradation process. Considering the degradation effects of PYR in both soil and aqueous phases, the optimal ultrasonication time for contaminated soil samples with an initial PYR concentration of 50 mg / kg is 20 min.

[0054] Depend on Figures 8-13It can be seen that when the ultrasonic time is 20 min, the removal efficiency of soil phase PHE and PYR is close to the maximum value, and after 20 min, their degradation efficiency slows down. However, the removal efficiency of aqueous phase PHE and PYR is different. The soil samples with initial concentrations of 300 mg / kg PHE, 100 mg / kg PHE, and 100 mg / kg PYR approach the maximum value when the ultrasonic time is 10 min, while the soil samples with initial concentrations of 200 mg / kg PHE, 150 mg / kg PYR, and 50 mg / kg PYR only approach the maximum value when the ultrasonic time is 20 min. Furthermore, soil samples with initial PHE concentrations of 200 mg / kg and 100 mg / kg showed a stable degradation efficiency after longer ultrasonic treatment times, while soil samples with other initial concentrations exhibited a decrease in degradation efficiency after longer ultrasonic treatment times. This may be because the ultrasonic effect in the aqueous phase had reached saturation, and PAHs pollutants in the soil phase were desorbed into the aqueous phase by ultrasonic treatment, thus reducing the degradation rate of PAHs in the aqueous phase. Considering that the degradation effect of high-concentration pollutants reduced to low-concentration initial concentrations did not match that of low-concentration soil samples, this may be related to the initial pollutant concentration or the area affected by the ultrasonic treatment. The study shows that different initial pollutant concentrations have different effects on the ultrasonic treatment process.

[0055] Generally, considering that more ultrasound time requires more energy and will significantly increase economic consumption, based on practical application, comprehensive experimental results and economic factors, the optimal solution for ultrasound time is set at 20 min.

[0056] III. The Influence of Ultrasonic Temperature on Desorption Efficiency To investigate the effect of different ultrasonic temperatures on the degradation rate of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil, and considering that different pollutant concentrations may also affect the desorption efficiency, the optimal ultrasonic power was determined to be 90 W and the optimal ultrasonic time to be 20 min. Therefore, 100 g of contaminated soil samples with different concentrations of 300 mg / kg PHE and 150 mg / kg PYR, 200 mg / kg PHE and 100 mg / kg PYR, and 100 mg / kg PHE and 50 mg / kg PYR were taken, and 200 ml of deionized water was added. Under ultrasonic power of 90 W and ultrasonic time of 20 min, the ultrasonic temperature was simultaneously varied at 5℃, 10℃, 20℃, 35℃, 55℃, and 80℃ to observe the effect of different ultrasonic temperatures during ultrasonic pretreatment on the desorption efficiency of PAHs. Figures 14-16 The degradation effects of contaminated soil samples with initial concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg PHE in the soil and aqueous phases are shown in order. Figures 17-19The degradation effects of contaminated soil samples with initial concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg PYR in the soil and aqueous phases are shown in order.

[0057] like Figures 14-16 The degradation effects of contaminated soil samples with initial concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg PHE in the soil and aqueous phases were shown: ① The soil samples with initial PHE concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg showed similar responses to changes in ultrasonic temperature. For the soil sample with an initial PHE concentration of 300 mg / kg, the concentration of PHE in the soil phase decreased significantly from 61.15 mg / kg to 47.17 mg / kg as the ultrasonic temperature increased from 5℃ to 20℃, while the degradation rate increased from 57.02% to 66.85%. As the ultrasonic temperature continued to increase, the rate of decrease in PHE concentration slowed, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate increased by only about 2%. For the soil sample with an initial PHE concentration of 200 mg / kg, the concentration of PHE in the soil phase decreased significantly from 33.85 mg / kg to 27.08 mg / kg as the ultrasonic temperature increased from 5℃ to 20℃, while the degradation rate increased from 63.93% to 71.15%. As the ultrasonic temperature continued to increase, the decreasing trend of PHE concentration slowed down, and the increase in degradation rate became smaller. When the temperature increased from 20℃ to 80℃, the degradation rate only increased by about 2%. For soil samples with an initial PHE concentration of 100 mg / kg, when the ultrasonic temperature increased from 5℃ to 20℃, the soil PHE concentration showed a significant decreasing trend, rapidly decreasing from the initial 20.85 mg / kg to 17.11 mg / kg, and the degradation rate increased from 49.98% to 58.94%. As the ultrasonic temperature continued to increase, the decreasing trend of PHE concentration slowed down, and the increase in degradation rate became smaller. However, when the temperature increased from 55℃ to 80℃, the degradation rate increased by about 3%, which may be because the higher ultrasonic temperature made some degrading microorganisms more active, promoting the effect of ultrasonic pretreatment desorption. ② Similarly, the responses of contaminated soil samples with initial PHE concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg in the aqueous phase to changes in ultrasonic temperature were similar. For the soil sample with an initial PHE concentration of 300 mg / kg, the concentration of PHE in the aqueous phase showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from an initial 26.41 mg / L to 17.92 mg / L, while the degradation rate increased from 62.30% to 74.42%. As the ultrasonic temperature continued to increase, the decreasing trend of PHE concentration slowed, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate increased by only about 4%. For soil samples with an initial PHE concentration of 200 mg / kg, the concentration of PHE in the aqueous phase showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from 17.67 mg / L to 12.96 mg / L, while the degradation rate increased from 62.67% to 72.62%. As the ultrasonic temperature continued to increase, the decreasing trend of PHE concentration slowed, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate increased by only about 4%. For soil samples with an initial PHE concentration of 100 mg / kg, the concentration of PHE in the aqueous phase also showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from 15.82 mg / L to 13.24 mg / L, while the degradation rate increased from 27.33% to 39.18%. As the ultrasonic temperature continued to increase, the downward trend of PHE concentration slowed down, and the increase in degradation rate became smaller. When the temperature increased from 20℃ to 80℃, the degradation rate only increased by about 3%.

[0058] Depend on Figures 14-16 It can be concluded that, considering the degradation effect of PHE in both soil and water phases, the optimal ultrasonic temperature for contaminated soil samples with initial concentrations of 300 mg / kg PHE, 200 mg / kg PHE, and 100 mg / kg PHE is 20℃.

[0059] like Figures 17-19 The degradation effects of contaminated soil samples with initial concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg PYR in the soil and aqueous phases were shown as follows: ① The initial PYR concentrations of contaminated soil samples at 150 mg / kg, 100 mg / kg, and 50 mg / kg showed similar responses to changes in ultrasonic temperature. For the soil sample with an initial PYR concentration of 150 mg / kg, the PYR concentration in the soil phase decreased significantly from 23.41 mg / kg to 18.56 mg / kg as the ultrasonic temperature increased from 5℃ to 20℃, while the degradation rate increased from 66.92% to 73.77%. As the ultrasonic temperature continued to increase, the rate of decrease in PYR concentration slowed, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate increased by only about 3.5%. For soil samples with an initial PYR concentration of 100 mg / kg, the PYR concentration in the soil phase showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from 12.25 mg / kg to 9.83 mg / kg, while the degradation rate increased from 70.18% to 76.07%. As the ultrasonic temperature continued to increase, the decreasing trend of PYR concentration slowed, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate increased by only about 2.5%. Similarly, for soil samples with an initial PYR concentration of 50 mg / kg, the PYR concentration in the soil phase showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from 7.12 mg / kg to 5.91 mg / kg, while the degradation rate increased from 60.71% to 67.38%. As the ultrasonic temperature continued to increase, the downward trend of PYR concentration slowed down, and the increase in degradation rate became smaller. When the temperature increased from 20℃ to 80℃, the degradation rate only increased by about 3%. ② Unlike PHE, the degradation rate of PYR in the aqueous phase was generally low. This may be due to the different responses of different pollutants to ultrasonic pretreatment, or it may be because the initial concentration of pollutants was low, making it difficult for ultrasonic pretreatment to effectively desorb and degrade low concentrations of PAHs. However, the responses of contaminated soil samples with initial PYR concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg in the aqueous phase to changes in ultrasonic temperature were similar. For the contaminated soil sample with an initial PYR concentration of 150 mg / kg, the concentration of PYR in the aqueous phase showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from an initial 30.24 mg / L to 24.57 mg / L, and the degradation rate increased from 3.85% to 21.88%. As the ultrasonic temperature continued to increase, the decreasing trend of PYR concentration slowed down, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate only increased by about 3.5%. For soil samples with an initial PYR concentration of 100 mg / kg, the concentration of PYR in the aqueous phase showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from 21.87 mg / L to 19.65 mg / L, while the degradation rate increased from 1.35% to 11.37%. As the ultrasonic temperature continued to increase, the decreasing trend of PYR concentration slowed, and the increase in degradation rate became smaller; when the temperature increased from 20℃ to 80℃, the degradation rate increased by only about 3%. For soil samples with an initial PYR concentration of 50 mg / kg, the concentration of PYR in the aqueous phase also showed a significant decreasing trend when the ultrasonic temperature increased from 5℃ to 20℃, rapidly decreasing from 8.66 mg / L to 6.93 mg / L, while the degradation rate increased from 11.90% to 29.09%. As the ultrasonic temperature continued to increase, the decreasing trend of PYR concentration slowed down, and the increase in degradation rate became smaller. When the temperature increased from 20℃ to 80℃, the degradation rate only increased by about 4%. Unlike previous experiments, the degradation rate of PYR in aqueous phase with lower initial concentrations was better with temperature changes. This may be because the baseline of ultrasonic pretreatment of low-concentration PYR is smaller, and the relative treatment effect of ultrasonic pretreatment is more significant compared to high-concentration PYR. Therefore, appropriate ultrasonic temperature also plays a role in the desorption and degradation of PAHs.

[0060] Higher ultrasonic temperatures lead to higher degradation rates of PHE and PYR in both soil and aqueous phases, but the degradation efficiency slows down between 20-35℃. While maximizing the removal rate of PAHs in soil, it's also important to avoid excessively low removal rates in aqueous phases. Considering the degradation effects of PYR in both soil and aqueous phases, the optimal ultrasonic temperature for contaminated soil samples with initial concentrations of 150 mg / kg PYR, 100 mg / kg PYR, and 50 mg / kg PYR is also 20℃.

[0061] Considering the possibility that the volatile content of PHE and PYR in the aqueous phase might be affected by temperature, thus impacting the removal rate of the ultrasonic mud reactor and causing significant errors in the experiment, corresponding modifications were made to the reactor. It is known that phenanthrene (PHE) is sparingly soluble in water, slightly soluble in ethanol, and soluble in organic solvents such as glacial acetic acid, benzene, carbon tetrachloride, and sulfur dioxide. Pyrene (PYR) is insoluble in water but readily soluble in ethanol and diethyl ether. Since diethyl ether is unstable and a hazardous compound, ethanol was used as the absorption solvent.

[0062] In the experiment, a gas collecting bottle was connected to the reactor, and 200 ml of ethanol solution was added. The total weight of the bottle plus the solution was measured to be 405.742 g. The total weight was then measured again at the corresponding temperature under the reaction conditions. When the temperature was between 0℃ and 10℃, the total weight decreased slightly, possibly due to the thermal expansion and contraction of the air inside the bottle. Subsequently, as the temperature continued to increase, the total weight of the gas collecting bottle also increased, but the overall increase was very small. Throughout the entire process from 0℃ to 80℃, the volatilization of PHE and PYR increased by only about 0.006 g, which can be considered negligible. Therefore, this experiment can eliminate the influence of temperature-induced volatilization of polycyclic aromatic hydrocarbons on the significant error in the removal rate of the ultrasonic mud reactor.

[0063] Depend on Figures 14-19 It can be seen that when the ultrasonic temperature is 20℃, the removal efficiency of PHE and PYR in soil and aqueous phases with different initial concentrations is close to the maximum value, and there is a slight increase between 20℃ and 35℃. Under normal circumstances, the working room temperature is generally around 25℃. Although a relatively good desorption and degradation effect can be achieved at 20℃, lowering the temperature from room temperature of 25℃ to 20℃ will inevitably require energy consumption, which will significantly increase the economic cost. Therefore, considering practical applications, and taking into account both experimental results and economic factors, a temperature of 25℃ is selected as the optimal reaction condition for ultrasonic pretreatment.

[0064] IV. The Influence of Sound Energy Density on Desorption Efficiency In this experiment, the variable of acoustic energy density under reaction conditions can be achieved by changing the amplitude transformer of the ultrasonic pretreatment. Acoustic energy density refers to the acoustic energy within a small unit volume near a point in a sound field; it is defined as the mechanical energy possessed by a unit volume of medium in the sound field, and its unit is joules per cubic meter (J / m³). 3 ).

[0065] The formula for calculating sound energy density is: D=p 2 / (ρ0c 2 ), where (p) is the sound pressure, (ρ0) is the medium density, and (c) is the sound speed.

[0066] As can be seen from the above formulas, the sound pressure and sound velocity of the sound energy density are determined by the ultrasonic instrument itself. Since the experimental soils were all PAH-contaminated soils, the difference in medium density can be ignored. According to the principle of conservation of vibration energy, the change in the cross-sectional area of ​​the amplitude transformer leads to a change in energy density: the smaller the cross-section, the higher the energy density, and the amplitude is amplified accordingly.

[0067] The ultrasonic cavitation effect originates from the propagation of ultrasonic vibrations in a liquid medium. When the peak sound pressure reaches the level of standard atmospheric pressure, the alternating sound pressure can create a localized, transient negative pressure environment (although no actual negative pressure exists), causing the intermolecular forces of the liquid to be overcome and cavitation bubbles to form. These near-vacuum cavitation bubbles collapse when the ultrasonic negative pressure phase reaches its extreme value. The intense shock wave generated at the moment of their collapse can strip away the adhering substances on the surface of an object. This physical effect caused by the collapse of countless cavitation bubbles is called the "cavitation" phenomenon. The duration of a cavitation bubble is approximately 0.1 μs, and the energy released during its rapid collapse process can form a microjets with a velocity of up to 110 m / s and extremely strong impact force, with a collision density as high as 1.5 kg / cm³. 2 Simultaneously, a localized instantaneous high-temperature and high-pressure environment (5000K, 1800atm) is encountered, with a cooling rate reaching 109 K / s. These extreme physical conditions enhance heterogeneous reactions through the following mechanisms: first, they promote mass transfer at the phase interface, achieving uniform mixing of reactants; second, they accelerate the mass transfer process, shortening the diffusion path of reaction products; and third, they induce the formation of new phases and regulate particle size distribution.

[0068] When the ultrasonic energy exceeds the threshold, the original tiny bubbles (cavitation nuclei) in the liquid vibrate periodically, grow and accumulate energy under the action of the sound field until the shock wave energy released at the moment of collapse significantly enhances the reaction efficiency of the heterogeneous system. This process breaks through the limitations of traditional reaction kinetics through the spatiotemporal concentration characteristics of energy.

[0069] Regardless of whether it's a liquid phase, solid phase, or heterogeneous phase, the energy propagation of ultrasound is always wave-like, resulting in uneven pretreatment effects. Furthermore, in a confined space, the rebound energy from ultrasonic waves colliding with the reaction walls may also collide with the originally transmitted energy, impacting the reaction process. Therefore, to avoid uneven dispersion of the ultrasonic effect, additional reaction conditions, such as stirring, are necessary for regulation. Ultrasonic cavitation bubbles vibrate under ultrasonic waves; once the sound pressure reaches a certain value, the bubbles rapidly expand and then suddenly collapse. The shock wave generated at the moment of bubble collapse has a certain promoting effect on the reaction process.

[0070] The ultrasonic amplitude transformer plays a crucial role in the ultrasonic vibration system. Its main function is to amplify the displacement or velocity of mechanically vibrating particles and concentrate ultrasonic energy over a small area to achieve a focused energy effect. To investigate the effect of different acoustic energy densities on the degradation rate of polycyclic aromatic hydrocarbons (PAHs) in contaminated soil, and considering that different pollutant concentrations may also affect desorption, the optimal ultrasonic power, optimal ultrasonic time, and optimal ultrasonic temperature of 25℃ were determined from the above. Therefore, 100 g of contaminated soil samples with different concentrations (100 mg / kg PHE and 150 mg / kg PYR, 200 mg / kg PHE and 100 mg / kg PYR, and 100 mg / kg PHE and 50 mg / kg PYR) were added to 200 ml of deionized water. Under ultrasonic power of 90 W, ultrasonic time of 20 min, and ultrasonic temperature of 25℃, the size of the amplitude transformer was changed to 6 mm, 8 mm, 10 mm, and 15 mm to change the acoustic energy density. The effect of different ultrasonic temperatures on the desorption effect of PAHs during ultrasonic pretreatment was observed. Figures 20-23 The degradation effects of contaminated soil samples with initial concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg PHE in the soil and aqueous phases are shown in order. Figures 23-26 The degradation effects of contaminated soil samples with initial concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg PYR in the soil and aqueous phases are shown in order.

[0071] like Figures 20-23 The degradation effects of contaminated soil samples with initial concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg PHE in the soil and aqueous phases were shown as follows: ① The initial PHE concentrations of contaminated soil samples at 300 mg / kg, 200 mg / kg, and 100 mg / kg showed consistent responses to different ultrasonic amplitude rods. For the soil sample with an initial PHE concentration of 300 mg / kg, the PHE concentration in the soil phase increased from 46.44 mg / kg to 55.14 mg / kg as the ultrasonic amplitude rod increased from 6 mm to 15 mm, while the degradation rate decreased from 67.36% to 61.25%, a decrease of approximately 6% overall. For the soil sample with an initial PHE concentration of 200 mg / kg, the PHE concentration in the soil phase also increased from 26.59 mg / kg to 31.05 mg / kg as the ultrasonic amplitude rod increased from 6 mm to 15 mm, while the degradation rate decreased from 71.67% to 66.92%, a decrease of approximately 5% overall. In soil samples with an initial PHE concentration of 100 mg / kg, the PHE concentration in the soil phase showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 16.71 mg / kg to 18.54 mg / kg. The degradation rate decreased from 59.91% to 55.52%, a decrease of approximately 4.5% overall. This indicates that as the cross-sectional area of ​​the ultrasonic amplitude rod increases, the overall degradation effect of PHE in the soil phase tends to decrease. ② Compared with the soil phase, the responses of contaminated soil samples with initial PHE concentrations of 300 mg / kg, 200 mg / kg, and 100 mg / kg in the aqueous phase to different ultrasonic amplitude rods were similar. For the contaminated soil sample with an initial PHE concentration of 300 mg / kg, the concentration of PHE in the aqueous phase showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 17.31 mg / L to 24.68 mg / L, while the degradation rate decreased from 75.29% to 64.77%, an overall decrease of approximately 8.5%. For the contaminated soil sample with an initial PHE concentration of 200 mg / kg, the concentration of PHE in the aqueous phase also showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 12.57 mg / L to 16.04 mg / L, while the degradation rate decreased from 73.44% to 66.11%, an overall decrease of approximately 7%. In soil samples with an initial PHE concentration of 100 mg / kg, the concentration of PHE in the aqueous phase showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 12.95 mg / L to 14.32 mg / L. The degradation rate decreased from 40.51% to 34.22%, a decrease of approximately 6% overall. Similarly, it can be observed that the degradation effect of PHE in the aqueous phase generally decreases with a larger ultrasonic amplitude rod cross-sectional area.

[0072] Considering the degradation effect of PHE in both soil and water phases, the optimal ultrasonic amplitude rod for contaminated soil samples with initial concentrations of 300 mg / kg PHE, 200 mg / kg PHE, and 100 mg / kg PHE is 6 mm.

[0073] like Figures 23-26 The degradation effects of contaminated soil samples with initial concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg PYR in the soil and aqueous phases were shown as follows: ① The initial concentrations of PYR in contaminated soil samples of 150 mg / kg, 100 mg / kg, and 50 mg / kg showed consistent responses to different ultrasonic amplitude rods. For the soil sample with an initial PYR concentration of 150 mg / kg, the concentration of PYR in the soil phase increased from 18.52 mg / kg to 25.33 mg / kg as the ultrasonic amplitude rod increased from 6 mm to 15 mm, while the degradation rate decreased from 73.83% to 64.20%, a decrease of approximately 9.5% overall. For the soil sample with an initial PYR concentration of 100 mg / kg, the concentration of PYR in the soil phase increased from 9.88 mg / kg to 13.07 mg / kg as the ultrasonic amplitude rod increased from 6 mm to 15 mm, while the degradation rate decreased from 75.95% to 68.18%, a decrease of approximately 8% overall. In soil samples with an initial PYR concentration of 50 mg / kg, the PYR concentration in the soil phase showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 5.93 mg / kg to 7.29 mg / kg. The degradation rate decreased from 67.27% to 59.77%, a decrease of approximately 7.5% overall. This indicates that as the cross-sectional area of ​​the ultrasonic amplitude rod increases, the degradation effect of PYR in the soil phase generally decreases. ② Similarly, the responses of contaminated soil samples with initial PYR concentrations of 150 mg / kg, 100 mg / kg, and 50 mg / kg in the aqueous phase to different ultrasonic amplitude rods were similar. For the contaminated soil sample with an initial PYR concentration of 150 mg / kg, the concentration of PYR in the aqueous phase showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 24.49 mg / L to 26.57 mg / L, while the degradation rate decreased from 22.13% to 15.52%, an overall decrease of approximately 6.5%. For the contaminated soil sample with an initial PYR concentration of 100 mg / kg, the concentration of PYR in the aqueous phase also showed an increasing trend as the ultrasonic amplitude rod increased from 6 mm to 15 mm, rising from 19.57 mg / L to 20.93 mg / L, while the degradation rate decreased from 11.73% to 5.59%, an overall decrease of approximately 6%. In soil samples with an initial PYR concentration of 50 mg / kg, the concentration of PYR in the aqueous phase increased from 6.95 mg / L to 7.91 mg / L as the ultrasonic amplitude bar increased from 6 mm to 15 mm. The degradation rate decreased from 29.30% to 19.53%, a decrease of approximately 10% overall. The decrease in degradation rate from an initial concentration of 150 mg / kg PYR to 100 mg / kg can be attributed to the primary influence of the initial pollutant concentration; higher initial concentrations result in better degradation effects from ultrasonic pretreatment. However, the degradation rate increased from an initial concentration of 100 mg / kg PYR to 50 mg / kg, even exceeding that of the soil samples with an initial concentration of 150 mg / kg PYR. This may be because the energy shock waves generated by the breaking of cavitation bubbles produced by ultrasound more effectively contacted the PYR pollutant, leading to more efficient removal.

[0074] Considering the degradation effects of PYR in both soil and aqueous phases, the optimal ultrasonic amplitude transformer for contaminated soil samples with initial concentrations of 150 mg / kg PYR, 100 mg / kg PYR, and 50 mg / kg PYR is also 6 mm. A larger amplitude transformer cross-sectional area results in a smaller amplitude, a smaller velocity ratio, and a relatively lower acoustic energy density, thus reducing efficiency. Due to equipment limitations, it cannot be determined whether a smaller amplitude transformer would actually decrease removal efficiency. Therefore, generally considering economic costs and practical applications, and taking into account both experimental results and economic factors, an ultrasonic amplitude transformer of 6 mm is selected as the optimal reaction condition for ultrasonic pretreatment.

[0075] V. The impact of initial soil pollutant concentration on degradation efficiency The experiments described above have investigated the different responses of different initial soil pollutant concentrations (PHE and PYR) to ultrasonic pretreatment, but only three concentrations were used, which is insufficient to explore the influence of initial soil pollutant concentrations on desorption efficiency. Therefore, an additional batch of contaminated soils with concentrations of 400 mg / kg PHE, 500 mg / kg PHE, 200 mg / kg PYR, and 250 mg / kg PYR were prepared here.

[0076] 100 g of contaminated soil samples were taken at concentrations of 500 mg / kg PHE, 400 mg / kg PHE, 300 mg / kg PHE, 200 mg / kg PHE, 100 mg / kg PHE, 250 mg / kg PYR, 200 mg / kg PYR, 150 mg / kg PYR, 100 mg / kg PYR, and 50 mg / kg PYR. 200 ml of deionized water was added to each sample. The ultrasonic power was set to 90 W, the ultrasonic time to 20 min, the ultrasonic temperature to 25℃, and the ultrasonic amplitude bar to 6 mm. All other reaction conditions were kept consistent across groups. The effect of ultrasonic pretreatment on the degradation rates of PHE and PYR in soil and aqueous phases under different initial soil contaminant concentrations was investigated.

[0077] The actual concentrations of PHE in the soil and aqueous phases before treatment were 197.94 mg / kg and 86.25 mg / L, respectively; the actual concentrations of PHE in the soil and aqueous phases before treatment were 251.07 mg / kg and 112.47 mg / L, respectively; the actual concentrations of PYR in the soil and aqueous phases before treatment were 93.37 mg / kg and 45.93 mg / L, respectively; and the actual concentrations of PYR in the soil and aqueous phases before treatment were 129.86 mg / kg and 57.63 mg / L, respectively.

[0078] Depend on Figure 26It can be seen that: ① The higher the initial concentration of PHE in the soil phase, the better the degradation effect of ultrasonic pretreatment. When the initial concentration increased from 300 mg / kg to 500 mg / kg, the degradation rate of PHE in the soil phase increased from 67.68% to 76.70%, an increase of about 9%. However, when the initial concentration was 200 mg / kg PHE, the degradation rate of PHE in the soil phase showed a turning point. The sudden increase in the PHE degradation rate may be because at this pollutant concentration, ultrasonic pretreatment not only efficiently degraded PHE in the soil phase but also desorbed most of the PHE in the soil phase into the aqueous phase through ultrasonic extraction, thereby improving the overall degradation efficiency of the soil phase. ② The degradation rate of PHE in the aqueous phase also increased with the increase of the initial concentration. When the concentration increased from 100 mg / kg to 200 mg / kg, the degradation rate of PHE in the aqueous phase rapidly increased from 40.51% to 73.44%, an increase of about 33%. However, as the initial concentration continued to increase, the overall degradation efficiency of the aqueous phase tended to plateau. This may be because ultrasonic pretreatment desorbed some PHE into the aqueous phase during its action on the soil phase, thereby inhibiting and slowing down the overall degradation efficiency of PHE in the aqueous phase. Considering the overall degradation effect of PHE in both the soil and aqueous phases, it can be concluded that the higher the initial PHE concentration, the better the degradation effect of ultrasonic pretreatment.

[0079] Depend on Figure 27 It can be seen that: ① The higher the initial concentration of PYR in the soil phase, the better the degradation effect of ultrasonic pretreatment. When the initial concentration increased from 150 mg / kg to 250 mg / kg, the degradation rate of PYR in the soil phase increased from 74.75% to 77.74%, an increase of about 3%. However, when the initial concentration was 100 mg / kg PYR, the degradation rate of PYR in the soil phase showed a turning point. The sudden increase in the PYR degradation rate may be because at this pollutant concentration, ultrasonic pretreatment not only efficiently degraded PYR in the soil phase but also desorbed most of the PYR in the soil phase into the aqueous phase through ultrasonic extraction, thereby improving the overall degradation efficiency of the soil phase. ② The degradation rate of PYR in the aqueous phase also increased with the increase of the initial concentration. When the concentration increased from 100 mg / kg to 250 mg / kg, the degradation rate of PYR in the aqueous phase rapidly increased from 12.72% to 30.78%, an increase of about 18%. However, when the initial concentration was even lower, at 50 mg / kg, the degradation rate of PYR in the aqueous phase increased sharply. This may be because the energy shock wave generated by the breaking of cavitation bubbles during ultrasonic pretreatment more effectively contacted the scattered pollutants PYR, allowing them to react fully and thus achieve more effective removal.

[0080] Considering the overall degradation effect of PYR in both soil and aqueous phases, it can be concluded that the higher the initial concentration of PYR, the better the degradation effect of ultrasonic pretreatment. The higher the initial concentration of pollutants in the soil, the better the overall removal effect of PAHs in the soil. This is because a higher concentration results in a larger overall base, leading to a greater relative effect of ultrasonic pretreatment and a higher desorption rate. Furthermore, the experimental results are similar to those in the previous study on the effect of ultrasonic power on desorption, thus meeting the requirements.

[0081] VI. The Influence of Soil Particle Size on Degradation Efficiency The contaminated soil used in the above experiment was only divided into 0.2 mm and 2 mm particle sizes. To investigate the effect of soil particle size (soil density) on the desorption effect of ultrasonic pretreatment, three groups of contaminated soil with particle sizes of 0.2 mm, 2 mm, and 5 mm were prepared. As mentioned above, the higher the initial concentration of pollutants in the soil, the better the overall removal effect of PAHs in the soil. Moreover, the concentration of pollutants in actual application treatment is generally large. Therefore, considering practical application, and taking into account both experimental results and economic factors, 100 g of contaminated soil samples with 300 mg / kg PHE and 150 mg / kg PYR were taken, 200 ml of deionized water was added, and the ultrasonic power was set to 90 W, the ultrasonic time to 20 min, the ultrasonic temperature to 25℃, and the ultrasonic amplitude bar to 6 mm. Other reaction conditions were kept consistent for all groups.

[0082] from Figure 28 and Figure 29 The data results show that for both PHE and PYR contaminated soil samples, the smaller the soil particle size (i.e., the greater the density), the better the desorption effect of ultrasonic pretreatment. Figure 28 As shown, for PHE-contaminated soil samples, when the soil particle size decreased from 5 mm to 0.2 mm, the concentration of PHE in the soil phase decreased from 61.51 mg / kg to 46.72 mg / kg, and the degradation rate increased from 56.77% to 67.16%, an overall increase of approximately 10.5%. In the aqueous phase, the concentration of PHE decreased from 20.67 mg / L to 17.13 mg / L, and the degradation rate increased from 70.50% to 75.55%, an overall increase of approximately 5%. The increase in the degradation rate of PHE in the soil phase was almost twice that in the aqueous phase. This may be because the ultrasonic pretreatment of high-concentration PHE-contaminated soil samples, while degrading pollutants in both the soil and aqueous phases, also desorbed PHE adhering to the soil surface into the aqueous phase, thus slowing down the increase in the degradation rate of PHE in the aqueous phase.

[0083] like Figure 29As shown, unlike PHE, for PYR-contaminated soil samples, when the soil particle size decreased from 5 mm to 0.2 mm, the concentration of PYR in the soil phase decreased from 22.17 mg / kg to 19.09 mg / kg, and the degradation rate increased from 68.67% to 73.02%, an overall increase of approximately 4.5%. In the aqueous phase, the concentration of PYR decreased from 29.11 mg / L to 24.08 mg / L, and the degradation rate increased from 7.44% to 23.43%, an overall increase of approximately 16%. The degradation rate of PYR in the aqueous phase increased much more than that in the soil phase. This may be because the ultrasonic pretreatment effect on the desorption of soil pollutants in low-concentration PYR-contaminated soil samples was close to the critical value. At the same time, the ultrasonic pretreatment desorbed some PYR from the soil phase into the aqueous phase. In addition, the energy shock wave generated by the breaking of cavitation bubbles during the ultrasonic pretreatment more effectively contacted the scattered PYR pollutants, allowing them to react fully and thus achieving more effective removal.

[0084] Based on the combined results of PHE and PYR contaminated soil samples, the smaller the soil particle size, the greater its density, and the better the desorption effect of ultrasonic pretreatment. This is partly because the smaller the particle size, the larger the specific surface area of ​​the soil particles, resulting in a better ultrasonic effect. Another reason is that the smaller the particle size, the greater the possibility of polycyclic aromatic hydrocarbons adsorbed on the particle surface coming into contact with the water medium, thus leading to a better desorption effect.

[0085] VII. The Influence of Soil-Water Ratio on Degradation Efficiency The soil-water ratio used in the above experiments was consistently 2:1. Considering that different soil-water ratios might have varying effects on ultrasonic pretreatment, contaminated soil samples of 300 mg / kg PHE and 150 mg / kg PYR were used. The ultrasonic power was set to 90 W, the ultrasonic time to 20 min, the ultrasonic temperature to 25℃, and the ultrasonic amplitude transformer to 6 mm. All other reaction conditions were kept consistent across groups, with soil-water ratio gradients of 1:2, 1:1, 2:1, 3:1, and 5:1, to investigate the effect of ultrasonic pretreatment on the degradation rates of PHE and PYR in the soil and aqueous phases under different soil-water ratios.

[0086] Depend on Figures 30-32It can be seen that the degradation rates of both PHE and PYR contaminated soil samples generally showed a trend of first increasing and then decreasing with the increase of the soil-to-water ratio. The highest degradation rates were observed for both PHE and PYR at a soil-to-water ratio of 2:1, with degradation rates of 67.44% and 74.10% in the soil phase and 75.49% and 23.15% in the aqueous phase, respectively. It can also be seen that the response of ultrasonic pretreatment to different pollutants varies. PHE is significantly more affected by the soil-to-water ratio than PYR. The maximum difference in degradation rate for PHE in the soil phase was about 30%, while the maximum difference for PYR was only about 15%, a difference of almost double. This may be because the ring number of PYR is more easily affected by ultrasonic degradation. The overall degradation rate of PHE in the aqueous phase was higher than that of PYR, possibly due to the influence of pollutant concentration; lower concentrations are more difficult to degrade.

[0087] The degradation rate is lower when the water-to-soil ratio is low. This is because the polluted soil is more viscous when mixed, resulting in low ultrasonic energy transfer efficiency, weakened cavitation effect, and soil particle aggregation, which reduces the contact area between pollutants and ultrasonic waves.

[0088] The degradation rate reaches its peak at a water-to-soil ratio of 2:1. At this ratio, the fluidity of the contaminated soil mixture is moderate, ultrasonic wave propagation efficiency is high, cavitation effect is significant, and pollutants are fully exposed at the liquid-solid interface, enhancing reactivity. Higher water-to-soil ratios result in a further decrease in degradation rate because excessive water dilutes the pollutant concentration, reducing reaction efficiency per unit volume, and the energy of cavitation bubbles is dispersed, weakening the local high-temperature and high-pressure effect.

[0089] In experiments and practical applications, an excessively high water-to-soil ratio can cause mud splashing and increase economic costs. Therefore, considering the results of PHE and PYR contaminated soil samples, experimental safety, and economic factors, a water-to-soil ratio of 2:1 was selected as the optimal solution for ultrasonic pretreatment.

[0090] VIII. Effect of Reactor Stirring Rate on Degradation Efficiency The effect of ultrasonic pretreatment is not uniform in energy transfer during the reaction, which can affect the degradation of pollutants. Therefore, external stirring was attempted to ensure a more complete reaction and to accommodate the subsequent addition of a mud reactor. Contaminated soil samples containing 300 mg / kg PHE and 150 mg / kg PYR were used. The ultrasonic power was set to 90 W, the ultrasonic time to 20 min, the ultrasonic temperature to 25℃, and the ultrasonic amplitude transformer to 6 mm. All other reaction conditions were kept consistent across groups, with rotation speed gradients of 100 rpm, 150 rpm, 200 rpm, 250 rpm, and 300 rpm. The effect of ultrasonic pretreatment under different rotation speeds on the degradation rates of PHE and PYR in the soil and aqueous phases was investigated.

[0091] from Figures 32-34 The data results show that the degradation rates of both PHE and PYR contaminated soil samples generally increased with increasing rotation speed. For PHE contaminated soil samples, the degradation rates of PHE in both the soil and aqueous phases gradually increased with increasing rotation speed. When the rotation speed increased from 100 rpm to 200 rpm, the increase in degradation rate was more significant. The concentration of PHE in the soil phase decreased from 66.05 mg / kg to 46.99 mg / kg, and the degradation rate increased from 53.58% to 66.97%, an increase of about 13.5%. The concentration of PHE in the aqueous phase decreased from 23.18 mg / L to 17.79 mg / L, and the degradation rate increased from 66.91% to 74.61%, an increase of about 8%. When the rotation speed continued to increase, the increase in PHE degradation rate slowed down. When the rotation speed increased from 200 rpm to 300 rpm, the degradation rate of PHE in the soil phase increased by only about 4%, and the degradation rate of PHE in the aqueous phase increased by only about 2%.

[0092] Similar to the degradation rate trend of PHE-contaminated soil samples, the increase in degradation rate was significant when the rotation speed increased from 100 rpm to 200 rpm. The concentration of PYR in the soil phase decreased from 27.62 mg / kg to 18.51 mg / L, while the degradation rate increased from 60.97% to 73.84%, an increase of approximately 13%. In the aqueous phase, the concentration of PYR decreased from 26.58 mg / L to 24.99 mg / L, while the degradation rate increased from 15.48% to 20.54%, an increase of approximately 6%. However, as the rotation speed continued to increase, the rate of increase in PHE degradation slowed down. When the rotation speed increased from 200 rpm to 300 rpm, the degradation rate of PHE in the soil phase increased by only about 4.5%, and the degradation rate of PHE in the aqueous phase increased by only about 3%.

[0093] Increasing the rotation speed allows pollutants to be fully dispersed, increasing the probability of contact with ultrasound. The resulting turbulence accelerates the migration of pollutants from the surface of soil particles to the liquid phase, promoting the reaction of free radicals (such as ·OH) with pollutants. At the same time, stirring helps to ensure the uniform distribution of cavitation bubbles and avoids local energy overload or attenuation.

[0094] In summary, the degradation rates of PHE and PYR are positively correlated with the rotation speed. However, 200 rpm is the critical value for the increase in degradation rate; once the rotation speed reaches 200 rpm, it becomes the threshold for further improvement in degradation rate. Although further increasing the rotation speed does not significantly improve the reaction efficiency, and in practical applications, increasing the rotation speed means increased energy consumption, greatly increasing economic costs. Based on this, considering both experimental results and economic factors, a rotation speed of 200 rpm is chosen as the optimal solution for ultrasonic pretreatment.

[0095] IX. Optimization of the addition amount of highly efficient degrading bacteria from different bacterial sources In this part of the experiment, the highly efficient degrading bacteria were cultured and acclimatized in an inorganic salt medium using phenanthrene and pyrene as the sole carbon sources from contaminated soil (300 mg / kg PHE), coking plant sludge, and municipal wastewater treatment plant sludge (150 mg / kg PYR), respectively. The coking plant sludge was collected from a coking plant in Xuzhou, and the municipal wastewater treatment plant sludge was collected from the wastewater treatment plant of China University of Mining and Technology. To ensure the diversity of soil samples, a five-point method was used to collect mixed soil samples, which were then sieved through a 20-mesh sieve for later use. The specific culture and acclimatization steps are as follows: 1. Weigh 10g of sieved soil and sludge, add them to 90mL of inorganic salt culture medium with PHE and PYR as the sole carbon sources, and place them in a 250mL Erlenmeyer flask.

[0096] 2. Fix the conical flask in a constant temperature shaking incubator and set the culture conditions to 25℃ and 200 rpm. Gradually increase the concentrations of PHE and PYR in the culture medium using a gradient acclimatization method. The concentrations of PHE in the culture medium are 50 mg / L, 100 mg / L and 200 mg / L, and the concentrations of PYR are 25 mg / L, 50 mg / L and 100 mg / L, respectively.

[0097] 3. For each concentration gradient, three groups of culture media were set up for cultivation. The group with the best effect on the degradation of PHE and PYR was selected as the specific and efficient degradation group, and the group was enriched.

[0098] 4. To ensure that the properties of the highly efficient degrading bacteria do not change over time, the enriched highly efficient degrading bacteria should be stored frozen at -80°C.

[0099] Among them, the enrichment of highly efficient degrading bacteria: In a 2L bioreactor, under constant temperature of 25℃, with an aeration rate of 0.5L / min and a stirring speed of 20rpm, the highly efficient degrading bacteria were enriched through a continuous and stable operating environment.

[0100] The specific method for preparing the gradient acclimatization medium is as follows: Accurately weigh 1.00 g of PHE and 0.50 g of PYR powder using an analytical balance, dissolve them in 50 mL of n-hexane, and then treat the solution in a low-temperature ultrasonic bath until completely dissolved. Transfer the solution to a 100 mL volumetric flask and dilute to the mark with n-hexane to prepare a PHE and PYR stock solution of 10 g / L PHE and 5 g / L PYR. Based on the required amounts of PHE and PYR for the culture medium, accurately measure a certain amount of the stock solution using a pipette and add it to 90 mL of inorganic salt culture medium.

[0101] Using contaminated soil containing 300 mg / kg PHE and 150 mg / kg PYR as examples of highly efficient degrading bacteria, 16S rRNA sequencing was performed on the highly efficient degrading bacterial community after domestication using the above methods to analyze biodiversity. The community structure characteristics were analyzed at the phylum and genus levels to assess the impact of the domestication process on microbial composition. The relevant community structure analysis results are as follows: (1) Species composition at the phylum level of the domesticated highly efficient degrading bacteria community: The dominant phyla and proportions of the domesticated highly efficient degrading bacteria community were: Proteobacteria (72.14%) and Firmicutes (21.52%). Among the domesticated highly efficient degrading bacteria community, Proteobacteria accounted for the largest proportion (72.14%). Proteobacteria is a key participant in PAH degradation, indicating that the domesticated highly efficient degrading bacteria community has the ability to specifically and efficiently degrade PAHs. This is similar to the results of other studies: after using the biostimulation method to remediate PAHs in the soil, the abundance of Firmicutes and Proteobacteria in the soil increased; (2) Species composition at the genus level of the domesticated highly efficient degrading bacteria: The dominant genera and percentages of the domesticated highly efficient degrading bacteria were Pseudochrobactrum (63.78%), Lysinibacillus (23.65%), Brevundimonas diminuta (3.59%), and Paenibacillus favisporu (1.91%). Pseudochrobactrum was the dominant genus after domestication. Studies in other literature have shown that Pseudochrobactrum is a genus capable of degrading PAHs, which is consistent with the results of this study, indicating that the domesticated highly efficient degrading bacteria can specifically and effectively remove PAHs.

[0102] The main objective of this experiment was to determine the optimal addition amount of highly efficient degrading bacteria from different bacterial sources in an ultrasonic slurry reactor. Under optimal ultrasonic conditions: ultrasonic power 90 W, ultrasonic time 20 min, ultrasonic temperature 25℃, ultrasonic amplitude bar 6 mm, and other reaction conditions consistent across groups, the addition amounts of highly efficient degrading bacteria (JGJ) acclimated from coking plant sludge, highly efficient degrading bacteria (WGJ) acclimated from municipal wastewater treatment plant sludge, and highly efficient degrading bacteria (TGJ) acclimated from contaminated soil at 300 mg / kg PHE and 150 mg / kg PYR were controlled at 0%, 5%, 10%, and 15% of the slurry reactor treatment volume, respectively. The degradation rates of PAHs contaminated soil were measured as follows: Figures 34-37 As shown.

[0103] Coking plant sludge may contain indigenous microorganisms adapted to coking wastewater, which, in synergy with ultrasound, can release intracellular enzymes to promote the degradation of pollutants. However, the degradation efficiency is moderate, the microorganisms are diverse and lack specificity, the decomposition rate of recalcitrant organic matter (such as PAHs) is slow, and the toxicity risk is high. The sludge may contain heavy metals and toxic organic matter, and ultrasound may release these substances, causing secondary pollution. However, through the acclimatization of coking plant sludge, highly efficient degrading bacteria cultivated using it as a source of bacteria can greatly promote the degradation of PAHs-contaminated soil, avoiding pollution while fully realizing the improvement and resource utilization.

[0104] Depend on Figure 34 The results showed that the optimal addition amount of highly efficient degrading bacteria (JGJ) for coking plant sludge acclimation was 10%, at which point the degradation rates of PHE and PYR climbed to the highest levels of 85.16% and 87.01%, respectively.

[0105] The amount of PAHs-degrading bacteria added is generally proportional to the PAHs degradation rate. However, as can be seen from the table above, the amount added is not necessarily better the higher it is. When the amount added is higher than 10%, the degradation rate will actually decrease. This may be because when the amount added is too high, the competition among microorganisms for living space and soil nutrients intensifies. However, the external microorganisms have weak competitive ability, which leads to the death of a large number of them, thus reducing the degradation rate.

[0106] Sludge from urban wastewater treatment plants possesses high microbial diversity, containing various functional bacterial communities, and can treat mixed pollutants (such as COD and ammonia nitrogen). It also boasts advantages such as large production volume, low treatment costs, strong stability, and adaptability of complex microbial communities to environmental fluctuations. However, its degradation efficiency for recalcitrant organic matter (such as phenols and PAHs) in coking wastewater is relatively low, and the previously complex microbial diversity may have inhibited the activity of specific high-efficiency bacteria. However, through the acclimatization of urban wastewater treatment plant sludge, highly efficient degrading bacteria cultured using it as a source can promote the degradation of PAHs-contaminated soil, thus fully realizing the resource utilization of the improved soil.

[0107] Depend on Figure 35 The results showed that when the amount of highly efficient degrading bacteria (WGJ) for sludge acclimation in urban wastewater treatment plants was 15%, the degradation rates of PHE and PYR reached the highest levels of 74.33% and 81.39%, respectively.

[0108] As the amount of WGJ added increases, the degradation rates of PHE and PYR also increase, consistent with the general rule that the amount of PAH-degrading bacteria added is directly proportional to the PAH degradation rate. However, due to... Figure 35 It can be seen that the rate of increase in degradation rate slows down significantly when the addition amount increases from 10% to 15%. Considering both degradation effect and cost, it is sufficient to choose an addition amount of 10% highly efficient degrading bacteria (WGJ).

[0109] Since contaminated soils with 300 mg / kg PHE and 150 mg / kg PYR exhibit targeted degradation capabilities for specific pollutants, ultrasound-assisted degradation can significantly enhance mass transfer efficiency and enzyme activity. Under optimized conditions, the domesticated high-efficiency bacterial strains show good tolerance to ultrasound, exhibit more stable degradation processes, and do not introduce additional pollutants (such as heavy metals). However, the costs of strain selection, cultivation, preservation, and application are high, and their adaptability to complex pollutants or environmental fluctuations (such as pH and temperature changes) may be poor. Through the domestication of contaminated soils with 300 mg / kg PHE and 150 mg / kg PYR, the high-efficiency degrading bacteria cultured using these as the inoculum have a certain promoting effect on the degradation of PAHs contaminated soils.

[0110] Depend on Figure 36 The results showed that when the amount of highly efficient degrading bacteria (TGJ) for acclimatizing contaminated soil (300 mg / kg PHE and 150 mg / kg PYR) added was 15%, the degradation rates of PHE and PYR reached the highest levels of 77.62% and 81.66%, respectively.

[0111] Similar to the trend of highly efficient degrading bacteria (WGJ) in the acclimatization of sludge from urban wastewater treatment plants, the degradation rate of PHE and PYR by highly efficient degrading bacteria (TGJ) increases with the increase of the amount added. However, when the amount added is from 10% to 15%, the rate of increase in degradation rate slows down significantly. Therefore, based on a comprehensive consideration of experimental degradation effect and cost, it is generally sufficient to choose an addition amount of 10% highly efficient degrading bacteria (TGJ).

[0112] 10. Comparison of degradation effects of highly efficient degrading bacteria from different bacterial sources To investigate the degradation efficiency of three different biodegrading bacteria in the remediation of PAHs-contaminated soil using an ultrasonic mud reactor, the effects of adding PHE and PYR at the highest degradation rates under different biodegrading bacteria sources on the degradation improvement of the ultrasonic mud reactor were compared. Figure 37 As shown.

[0113] As can be seen from the above, when the degradation rates of PHE and PYR reach their highest levels, the addition amount of highly efficient degrading bacteria (JGJ) after coking plant sludge acclimation is 10%, and the addition amount of highly efficient degrading bacteria (WGJ) after urban sewage treatment plant sludge acclimation and highly efficient degrading bacteria (TGJ) after acclimation of contaminated soil with 300 mg / kg PHE and 150 mg / kg PYR is 15%.

[0114] Depend on Figure 37Comparison of experimental data shows that the overall degradation rates of PHE and PYR by the highly efficient degrading bacteria (JGJ) acclimated to coking plant sludge at a 10% addition rate were higher than those of the other two highly efficient degrading bacteria. The degradation rate of PYR by the highly efficient degrading bacteria (WGJ) acclimated to urban wastewater treatment plant sludge was almost the same as that of the highly efficient degrading bacteria (TGJ) acclimated to contaminated soil at 300 mg / kg PHE and 150 mg / kg PYR, but its degradation rate of PHE was much lower than that of TGJ. Therefore, JGJ showed the best degradation effect, followed by TGJ, and lastly WGJ. This may be because coking plant sludge has long been exposed to complex pollutants such as tar and PAHs, and the bacterial community, through natural selection, retains strains carrying genes such as NAH (naphthalene degradation) and PHN (polycyclic aromatic hydrocarbon hydroxylase). The bacterial community has evolved mechanisms to combat PAH toxicity, such as secreting biosurfactants (e.g., rhamnolipids) to enhance PAH solubility and producing antioxidant enzymes (SOD, catalase) to resist reactive oxygen species (ROS) produced by PAH metabolism. While the microbial communities in PHE and PYR contaminated soils have partially adapted to the PAHs environment, their degradation efficiency is limited by long-term exposure to low concentrations, potentially failing to reach the gene expression threshold. Furthermore, the complex carbon sources in the soil may lead to the degradation bacteria being inhibited by heterotrophic bacteria. Wastewater treatment plant sludge primarily treats easily degradable organic matter (carbohydrates, proteins) and lacks the key enzyme system for PAH degradation. It has almost no ability to degrade high molecular weight PAHs (4 rings or more), such as fluoranthene and benzo[a]pyrene, whose degradation rates are often below 10%. Moreover, the microbial communities are sensitive to the toxicity of PAHs, easily experiencing cell membrane damage and metabolic inhibition.

[0115] In summary, the optimal choice is coking plant sludge acclimation microbial community (JGJ), which exhibits the highest degradation rate of PAHs, making it particularly suitable for treating complex and highly toxic pollutants. Secondly, polycyclic aromatic hydrocarbon (PAH) contaminated soil acclimation microbial community (TGJ) can be selected, as its efficiency can be improved through bioaugmentation, making it suitable for in-situ remediation. Finally, wastewater treatment plant sludge microbial community (WGJ) has limited PAH degradation capacity and can be used in conjunction with other technologies. Ultimately, a 10% addition of highly efficient degrading bacteria (JGJ) from coking plant sludge acclimation is chosen.

Claims

1. A method for remediating polycyclic aromatic hydrocarbon (PAH) contaminated soil using an ultrasonic mud bioreactor, characterized in that, By adding low-dose ultrasonic pretreatment to the biological mud reactor, polycyclic aromatic hydrocarbons (PAHs) can be desorbed and degraded, thereby remediating PAH-contaminated soil.

2. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 1, characterized in that, Based on the biological mud reactor, ultrasonic pretreatment was added, which can degrade the polycyclic aromatic hydrocarbons, including at least one of naphthalene, acenaphthene, acenaphthene, fluorene, phenanthrene, anthracene, fluoranthene, pyrene, benzo[a]anthracene, α, benzo[b]fluoranthene, benzo[k]fluoranthene, benzo[a]pyrene, dibenzo[a,h]anthracene, indo[1,2,3-cd]pyrene, and benzo[g,h,i]perylene.

3. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 1, characterized in that, The ultrasonic power in the ultrasonic pretreatment is 60W~90W.

4. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 3, characterized in that, The ultrasonic pretreatment time is 10 min to 35 min.

5. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 4, characterized in that, The ultrasonic temperature during ultrasonic pretreatment is 20℃~35℃.

6. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 5, characterized in that, The size of the ultrasonic amplitude transformer in ultrasonic pretreatment is ≤8mm.

7. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 1, characterized in that, The polycyclic aromatic hydrocarbon contaminated soil is pretreated to a particle size of 0.1 mm to 2 mm before being added; the water-to-soil ratio in the ultrasonic mud reactor is 1:1 to 3:

1.

8. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to any one of claims 1 to 7, characterized in that, After ultrasonic pretreatment, highly efficient degrading bacteria are added for biodegradation. The highly efficient degrading bacteria are at least one of the following: highly efficient degrading bacteria after acclimation to sludge from coking plants, highly efficient degrading bacteria after acclimation to sludge from urban sewage treatment plants, and highly efficient degrading bacteria after acclimation to polycyclic aromatic hydrocarbon contaminated soil.

9. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 8, characterized in that, The amount of highly efficient degrading bacteria added is 10% to 15% of the treatment volume of the ultrasonic mud reactor.

10. The method for remediating polycyclic aromatic hydrocarbon contaminated soil using an ultrasonic mud bioreactor according to claim 9, characterized in that, The highly efficient degrading bacteria are those acclimated from coking plant sludge, and the amount of these bacteria added is 10% of the treatment volume of the ultrasonic sludge reactor.

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