A method for remediating petroleum hydrocarbon pollution in groundwater based on microorganisms

Abstract

The present invention discloses a method for remediating petroleum hydrocarbon pollution in groundwater based on microorganisms, wherein nitrate slow-release rod-hollow ball materials are loaded in layers into a PRB permeable reaction wall, and composite microbial liquid is sprayed on each layer of nitrate slow-release rod-hollow ball materials, and then a flow-blocking wall is constructed on the water inlet side of the PRB permeable reaction wall, and petroleum hydrocarbons in groundwater are degraded by the nitrate slow-release rod-hollow ball materials and composite microbial liquid loaded in the PRB permeable reaction wall. The present invention efficiently degrades and removes petroleum hydrocarbon pollutants in groundwater passing through the PRB permeable reaction wall by loading nitrate slow-release rod-hollow ball materials in the PRB permeable reaction wall and cooperating with composite microbial liquid, and the degradation rate of petroleum hydrocarbon pollution in groundwater is as high as more than 90%, which can significantly improve the efficiency of microbial remediation of petroleum hydrocarbon pollution in groundwater.

Description

Technical Field

[0001] The invention relates to the technical field of groundwater pollution control, and in particular to a method for repairing petroleum hydrocarbon pollution in groundwater based on microorganisms. Background Art

[0002] Groundwater petroleum hydrocarbon pollution is a serious environmental problem, mainly involving the leakage and discharge of petroleum hydrocarbon substances in activities such as oil extraction, petrochemicals, gas stations and corporate oil depots. Petroleum hydrocarbon pollutants are relatively stable in the environment and difficult to degrade naturally. In addition, some petroleum hydrocarbon pollutants are volatile and may spread further through the air. In addition, petroleum hydrocarbon pollutants enter the human body through groundwater and other channels. They are toxic to organisms and will cause harm to human health and the ecological environment.

[0003] Groundwater petroleum hydrocarbon contamination can be repaired by extraction treatment, in-situ chemical oxidation and other technologies, but chemical methods are prone to chemical leakage, causing secondary pollution. Therefore, bioremediation technology would be a more effective treatment method, which utilizes the metabolic activities of microorganisms to degrade petroleum hydrocarbon pollutants in groundwater. However, the current bioremediation technology for the treatment of groundwater petroleum hydrocarbon contamination still needs to be improved. A microbial remediation method that can efficiently treat petroleum hydrocarbon contamination in groundwater is needed to improve the remediation effect. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a method for remediating petroleum hydrocarbon pollution in groundwater based on microorganisms.

[0005] The technical scheme of the present invention is: a method for remediating petroleum hydrocarbon pollution in groundwater based on microorganisms, wherein nitrate slow-release rods-hollow ball materials are loaded into a PRB permeable reaction wall in layers, and composite microbial bacterial liquid is sprayed on each layer of nitrate slow-release rods-hollow ball materials, and then a flow-blocking wall is constructed on the water inlet side of the PRB permeable reaction wall, and petroleum hydrocarbons in groundwater are degraded by the nitrate slow-release rods-hollow ball materials and composite microbial bacterial liquid loaded in the PRB permeable reaction wall;

[0006] Among them, the nitrate slow-release rod-hollow ball material is formed by mixing oxygen-releasing material and modified carbon material to obtain a hollow ball material and is composed of a nitrate slow-release rod filled in the hollow ball material. The nitrate slow-release rod is composed of modified carbon material and magnetic powder as a magnetic center rod frame, and a nitrate slow-release rubber material is attached to the magnetic center rod frame.

[0007] Furthermore, the filling thickness of each layer of nitrate slow-release rods-hollow ball material is 15 to 30 cm, and a magnetic filter is laid on each layer of nitrate slow-release rods-hollow ball material.

[0008] Description: By filling each layer with a magnetic filter, on the one hand, the stability of the nitrate slow-release rods-hollow balls loaded inside the PRB permeable reaction wall can be improved, and on the other hand, magnetic force can be provided for the nitrate slow-release rods in each nitrate slow-release rod-hollow ball. Therefore, when groundwater flows through the PRB permeable reaction wall, the nitrate slow-release rods-hollow balls are slightly vibrated by the disturbance of the groundwater on the nitrate slow-release rods-hollow balls and the flipping of the nitrate slow-release rods under the influence of magnetic force, thereby improving the degradation treatment effect of the nitrate slow-release rods-hollow balls loaded with microorganisms on petroleum hydrocarbons in groundwater.

[0009] Furthermore, the following steps are included:

[0010] Step 1, constructing a PRB permeable reaction wall on the flow path of groundwater, filling nitrate slow-release rods-hollow ball materials into the PRB permeable reaction wall in layers, and the filling thickness of each layer of nitrate slow-release rods-hollow ball materials is 15-30 cm, and then spraying each layer of nitrate slow-release rods-hollow ball materials with a composite microbial bacterial liquid accounting for 15-30% of the mass of each layer of nitrate slow-release rods-hollow ball materials, and covering it with a magnetic filter;

[0011] Step 2, repeat step 1 until the nitrate slow-release rod-hollow ball material fills the PRB permeable reaction wall, and then build a flow barrier on the water inlet side of the PRB permeable reaction wall to control the water flow rate entering the PRB permeable reaction wall at 4-6 min / L. Regularly test the petroleum hydrocarbons on the water outlet side of the PRB permeable reaction wall. If the petroleum hydrocarbon content exceeds the standard, replace the nitrate slow-release rod-hollow ball material.

[0012] Description: The use of a single layer of nitrate slow-release rods-hollow balls with the above filling thickness can improve the stability of the magnetic filter in the PRB permeable reaction wall loaded with nitrate slow-release rods-hollow balls as much as possible, while ensuring that the number of magnetic filters used is reduced, and provide magnetic force for the nitrate slow-release rods in each nitrate slow-release rod-hollow ball.

[0013] Spraying 15-30wt% of the composite microbial liquid can ensure that these petroleum hydrocarbon degrading microorganisms reach adsorption saturation in the nitrate slow-release rod-hollow ball material. Adding excessive composite microbial liquid is likely to cause a large number of microorganisms to be lost, thereby increasing the treatment cost and having poor economic efficiency. At the same time, if a small amount of composite microbial liquid is added, the adsorption amount of these petroleum hydrocarbon degrading microorganisms in the nitrate slow-release rod-hollow ball material is likely to be small, making it difficult to efficiently degrade the petroleum hydrocarbon pollution in the groundwater.

[0014] Furthermore, the composite microbial liquid is composed of any one or more of Clostridium, Pseudomonas, Alcaligenes, and Xanthomonas.

[0015] Description: The use of these highly efficient oil-degrading bacteria can play an important role in the treatment of oil pollution such as petroleum hydrocarbons. They can rapidly reproduce and degrade oil pollutants such as petroleum hydrocarbons, thereby eliminating petroleum hydrocarbon pollutants in groundwater. In addition, by utilizing the life metabolic activities of these highly efficient oil-degrading bacteria to degrade petroleum hydrocarbon pollutants in groundwater, it is green and environmentally friendly, without secondary pollution.

[0016] At the same time, each of the above-mentioned composite microbial cultures was prepared using OD 600 The volume ratio of the bacterial solution of Bacillus fusiformis, the bacterial solution of Pseudomonas, the bacterial solution of Alcaligenes, and the bacterial solution of Xanthomonas is 1.5 to 1.9, and the bacterial solution can be combined and used in any ratio, for example, the bacterial solution of Bacillus fusiformis and the bacterial solution of Pseudomonas are mixed in a volume ratio of 2:1.

[0017] Furthermore, the oxygen-releasing material is a mixture of calcium peroxide, sodium bentonite, sodium alginate and starch in a mass ratio of 20-30:5-10:1-2:40-50, and when mixed with the modified carbon material, water accounting for 20-30% of the total mass of the modified carbon material and the oxygen-releasing material is added.

[0018] Note: The sample material mixed in the above ratio can release oxygen by reacting calcium peroxide with water on the one hand, and can provide a basis for mixed molding with modified carbon materials on the other hand. At the same time, in order to ensure that the nitrate slow-release rod can be loaded into the hollow ball material, the hollow ball material should adopt a semi-spherical manufacturing method or a perforated manufacturing method. For example, when the semi-spherical manufacturing method is adopted, the nitrate slow-release rod is placed in two hemispheres and the hemispheres are merged and bonded; when the perforated manufacturing method is adopted, an opening is retained for placing the nitrate slow-release rod, and the opening can be sealed later or not.

[0019] Furthermore, the modified carbon material is obtained by heating biochar powder to 70-90° C., adding it to a nitrate aqueous solution for 1-3 minutes, removing it, repeating the process 2-5 times, and then naturally drying the biochar to obtain a powder material; wherein the mass concentration of nitrate in water is 10-15%.

[0020] Description: Using nitrate aqueous solution to soak biochar powder in a sudden cooling temperature difference treatment can help improve the structural stability of the modified carbon material and help maintain the porosity of the modified carbon material, thereby maintaining the excellent performance of the modified carbon material. At the same time, through the treatment of nitrate, its pore structure, specific surface area and adsorption performance can be further improved, so that the modified carbon material can better cooperate with microorganisms to treat petroleum hydrocarbon pollutants in groundwater.

[0021] Furthermore, the nitrate sustained-release adhesive is composed of 30 to 50 parts of nitrate and 80 to 100 parts of setting agent by weight; the magnetic center rod frame is composed of 40 to 70 parts of modified carbon material, 40 to 70 parts of magnetic powder and 50 to 80 parts of setting agent by weight, and the magnetic center rod frame is a combined structure composed of two rectangular blocks, and the short sides of the two rectangular blocks are perpendicular to each other.

[0022] Description: The structural design of the nitrate slow-release rod can be used with the assistance of a magnetic filter to disturb and vibrate the groundwater when it flows through, thereby improving the contact effect with the groundwater and enhancing the degradation effect of the nitrate slow-release rod-hollow ball material loaded with microorganisms on petroleum hydrocarbons in the groundwater;

[0023] At the same time, the use of the above-mentioned nitrate slow-release adhesive can make the nitrate have a long release period, which can significantly improve the degradation efficiency of petroleum hydrocarbon pollutants in groundwater by microorganisms, thereby enhancing the repair and treatment rate of petroleum hydrocarbon pollution in groundwater;

[0024] Furthermore, the flat portions are arranged perpendicular to each other, i.e., the angle is 90°, so that the magnetic center rod frame can be in a slightly suspended, unstable state under the magnetic filter. As a result, when the groundwater flows through, the nitrate slow-release rods-hollow ball materials are disturbed, and the nitrate slow-release rods will flip over, thereby causing a slight collision with the hollow ball materials, causing the nitrate slow-release rods-hollow ball materials as a whole to vibrate.

[0025] Furthermore, the setting agent is a mixture obtained by mixing sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 8-12:1-2:15-20:25-35, and then adding water accounting for 20-30% of the total mass of sodium bentonite, sodium alginate, fine sand and cement.

[0026] Description: The setting agent with the above ratio can play a good role in shaping and shaping, and can make the nitrate slow-release adhesive material stably adhere to the magnetic center rod frame, and also provide basic materials for the preparation of the magnetic center rod frame.

[0027] Furthermore, the preparation method of the nitrate sustained-release rod is: heating the magnetic center rod frame to 40-50°C, applying the nitrate sustained-release adhesive to both sides of the magnetic center rod frame for multiple reheating, specifically, the single application thickness of the nitrate sustained-release adhesive is controlled at 1-2 mm, and after the surface temperature of the magnetic center rod frame is heated back to 40-50°C, it is applied again until the nitrate sustained-release adhesive is applied, thereby obtaining the nitrate sustained-release rod; wherein, the coating thickness on both sides of the magnetic center rod frame is the same.

[0028] Description: Multiple re-warming and coating of silicate slow-release adhesive can improve the long-term slow-release effect of silicate, and in the temperature difference attachment treatment between nitrate slow-release adhesive and magnetic center rod frame, on the one hand, it can improve the attachment efficiency and effect of nitrate slow-release adhesive, and at the same time, under the multi-layer distribution treatment, it can avoid the silicate slow-release adhesive from falling off significantly when the nitrate slow-release rod is slightly vibrated, thereby improving the use stability of the nitrate slow-release rod.

[0029] The beneficial effects of the present invention are:

[0030] (1) The method of the present invention efficiently degrades and removes petroleum hydrocarbon pollutants in groundwater passing through the PRB permeable reaction wall by loading nitrate slow-release rods-hollow balls in combination with composite microbial liquid. Compared with the 72.41% degradation rate of biochar and composite microbial liquid in combination, the degradation rate of petroleum hydrocarbon pollution in groundwater by the method of the present invention is as high as over 90%, which significantly improves the efficiency of microbial remediation of petroleum hydrocarbon pollution in groundwater.

[0031] (2) The present invention adopts a layered filling method to load nitrate slow-release rods-hollow balls into the PRB permeable reaction wall, which can ensure that the petroleum hydrocarbon-degrading microorganisms in the sprayed composite microbial liquid reach adsorption saturation in the nitrate slow-release rods-hollow balls, thereby ensuring that the method of the present invention can efficiently degrade and remove petroleum hydrocarbon pollution in groundwater during microbial remediation.

[0032] (3) The present invention designs the structure of the nitrate slow-release rod-hollow ball material and, with the assistance of a magnetic filter, can vibrate when the groundwater is disturbed by the flow, thereby improving the contact effect between the nitrate slow-release rod-hollow ball material and the groundwater, thereby enhancing the degradation effect of the nitrate slow-release rod-hollow ball material loaded with microorganisms on petroleum hydrocarbons in the groundwater. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] Figure 1 It is a schematic diagram of the simulated structure of the nitrate sustained-release rod-hollow ball material of the present invention. DETAILED DESCRIPTION

[0034] The present invention is further described in detail below in conjunction with specific implementation methods to better reflect the advantages of the present invention.

[0035] Embodiment 1: A method for remediating petroleum hydrocarbon pollution in groundwater based on microorganisms, wherein nitrate slow-release rods-hollow balls are loaded in layers into a PRB permeable reaction wall, and a composite microbial liquid is sprayed on each layer of nitrate slow-release rods-hollow balls, and then a flow-blocking wall is constructed on the water inlet side of the PRB permeable reaction wall, and petroleum hydrocarbons in groundwater are degraded by the nitrate slow-release rods-hollow balls and the composite microbial liquid loaded in the PRB permeable reaction wall; and a composite microbial liquid accounting for 25% of the mass of the nitrate slow-release rods-hollow balls of the layer is sprayed on each layer of nitrate slow-release rods-hollow balls; the composite microbial liquid is a mixture of Clostridium liquid, Pseudomonas liquid, Alcaligenes liquid, and Xanthomonas liquid in a volume ratio of 2:1:1:1;

[0036] like Figure 1 As shown, the nitrate slow-release rod-hollow ball material is formed by mixing oxygen-releasing material and modified carbon material to obtain a hollow ball material and a nitrate slow-release rod filled in the hollow ball material. The particle size of the hollow ball material is 30 mm and the wall thickness is 5 mm; the length of the nitrate slow-release rod is 18 mm.

[0037] like Figure 1 As shown, the magnetic center rod frame is a combined structure composed of two rectangular blocks, and the short sides of the two rectangular blocks are perpendicular to each other, that is, the short side angle of the two rectangular blocks is 90°. Specifically, the length of the magnetic center rod frame is 18 mm, and the rectangular blocks are all 9 mm long, 8 mm wide, and 4 mm thick, that is, the two flat parts are perpendicular to each other.

[0038] The oxygen-releasing material is a mixture of calcium peroxide, sodium bentonite, sodium alginate and starch in a mass ratio of 260:70:15:450, and water accounting for 25% of the total mass of the modified carbon material and the oxygen-releasing material is added when mixed with the modified carbon material, that is, the modified carbon material and the oxygen-releasing material are mixed to obtain a mixture, and then water accounting for 25% of the mass of the mixture is added to the mixture; the modified carbon material is a powder obtained by heating biochar powder to 85°C, adding it to a nitrate aqueous solution for 150s, taking it out, repeating the process 4 times, and then naturally drying the biochar; wherein the nitrate is sodium nitrate, and the mass concentration of sodium nitrate in water is 12%;

[0039] The nitrate slow-release rod is composed of modified carbon material and magnetic powder as the main materials of the magnetic center rod frame, and the nitrate slow-release adhesive is attached to the magnetic center rod frame. The preparation method of the nitrate slow-release rod is as follows: the nitrate slow-release adhesive is evenly applied to the flat parts on both sides of the magnetic center rod frame, and the application thickness is controlled to be 8mm; the nitrate slow-release adhesive is composed of 45 parts of sodium nitrate and 90 parts of setting agent by weight; the magnetic center rod frame is composed of 60 parts of modified carbon material, 65 parts of magnetic powder and 65 parts of setting agent by weight; the setting agent is a mixture of sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 55:8:90:150, and then water accounting for 25% of the total mass of sodium bentonite, sodium alginate, fine sand and cement is added to obtain a mixture, that is, sodium bentonite, sodium alginate, fine sand and cement are mixed to obtain a mixture, and then water accounting for 25% of the mass of the mixture is added to the mixture;

[0040] It can be understood that the PRB permeable reactive wall is a very mature permeable reactive wall repair technology, and the present embodiment can use a permeable reactive wall constructed by the existing method.

[0041] The specific method includes the following steps:

[0042] Step 1, constructing a PRB permeable reaction wall on the flow path of groundwater, filling nitrate slow-release rods-hollow ball materials into the PRB permeable reaction wall in layers, and the filling thickness of each layer of nitrate slow-release rods-hollow ball materials is 24 cm, and then spraying each layer of nitrate slow-release rods-hollow ball materials with a composite microbial bacterial liquid accounting for 25% of the mass of each layer of nitrate slow-release rods-hollow ball materials, and covering it with a magnetic filter;

[0043] Step 2, repeat step 1 until the nitrate slow-release rod-hollow ball material fills the PRB permeable reaction wall, and then construct a flow-blocking wall on the water inlet side of the PRB permeable reaction wall. Specifically, the flow-blocking wall can be a wall structure with a commercially available water pump. The water flow rate entering the PRB permeable reaction wall is controlled at 5 min / L by the water pump. The petroleum hydrocarbons on the water outlet side of the PRB permeable reaction wall are regularly tested. If the petroleum hydrocarbon content exceeds the standard, the nitrate slow-release rod-hollow ball material is replaced.

[0044] The petroleum hydrocarbon contaminated groundwater from an abandoned factory in this city was used as an experimental sample to verify the degradation efficiency of petroleum hydrocarbons in groundwater by this method. The degradation of petroleum hydrocarbons after the PRB permeable reaction wall was operated for 30 days was studied. The test results are shown in Table 1 below:

[0045] Table 1 Petroleum hydrocarbon degradation after 30 days of operation of PRB permeable reaction wall

[0046] project Inlet area Outlet area TPH degradation rate 0％ 92.57％

[0047] It can be seen from the results in Table 1 above that the degradation rate of petroleum hydrocarbons in groundwater can still reach more than 90% after the PRB permeable reaction wall has been in operation for 30 days. It can be seen that the method of the present invention can significantly improve the efficiency of microbial remediation of petroleum hydrocarbon pollution in groundwater;

[0048] At the same time, in order to further verify the effect of the method of the present invention and the combination of biochar + composite microbial liquid, the biochar was loaded into the PRB permeable reaction wall using the above method to study the degradation of petroleum hydrocarbons in the PRB permeable reaction wall after 30 days of operation. The results are shown in Table 2 below:

[0049] Table 1 Petroleum hydrocarbon degradation after 30 days of operation of PRB permeable reaction wall

[0050] project Inlet area Outlet area TPH degradation rate 0％ 72.41％

[0051] From the comparison results of Table 2 and Table 1 above, it can be seen that when biochar is directly loaded into the PRB permeable reaction wall, the petroleum hydrocarbon degradation rate in the effluent area has decreased significantly. It can be seen that this method is significantly different from the commonly used microbial degradation method. The use of nitrate slow-release rods-hollow balls can significantly enhance the treatment effect of microorganisms on petroleum hydrocarbon pollution.

[0052] It should be noted that in the actual contaminated site remediation process, there are many factors, such as pollutant characteristics, hydrogeological conditions, depth, etc., which will affect the final remediation efficiency of the PRB permeable reactive wall.

[0053] Example 2: This example is different from Example 1 in that a composite microbial solution accounting for 15% of the mass of the nitrate slow-release rods-hollow ball material in each layer is sprayed.

[0054] Example 3: This example is different from Example 1 in that a composite microbial solution accounting for 30% of the mass of the nitrate slow-release rods-hollow ball material in each layer is sprayed.

[0055] Example 4: This example is different from Example 1 in that the oxygen-releasing material is a mixture of calcium peroxide, sodium bentonite, sodium alginate, and starch in a mass ratio of 20:5:1:40, and water accounting for 20% of the total mass is added when mixed with the modified carbon material.

[0056] Example 5: This example is different from Example 1 in that the oxygen-releasing material is a mixture of calcium peroxide, sodium bentonite, sodium alginate, and starch in a mass ratio of 30:10:2:50, and 30% of water is added to the total mass when mixed with the modified carbon material.

[0057] Example 6: This example is different from Example 1 in that the modified carbon material is prepared by heating biochar powder to 70°C, adding the powder to a nitrate aqueous solution for 1 minute, removing the powder, repeating the process twice, and then naturally drying the biochar.

[0058] Example 7: This example is different from Example 1 in that the modified carbon material is prepared by heating biochar powder to 90°C, adding the powder to a nitrate aqueous solution for 3 minutes, removing the powder, and repeating the process for 5 times before naturally drying the biochar.

[0059] Example 8: This example is different from Example 1 in that the nitrate sustained-release adhesive is composed of 30 parts of nitrate and 80 parts of setting agent by weight; the setting agent is a mixture of sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 8:1:15:25, and then 20% of water is added to the total mass to obtain a mixture.

[0060] Example 9: This example is different from Example 1 in that the nitrate sustained-release adhesive is composed of 50 parts of nitrate and 100 parts of setting agent by weight; the setting agent is a mixture of sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 12:2:20:35, and then 30% of water is added to the total mass to obtain a mixture.

[0061] Example 10: The difference between this example and Example 1 is that the magnetic center rod frame is composed of 40 parts of modified carbon material, 40 parts of magnetic powder and 50 parts of setting agent by weight; the setting agent is a mixture of sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 8:1:15:25, and then 20% of water is added to the total mass to obtain a mixture.

[0062] Example 11: The difference between this example and Example 1 is that the magnetic center rod frame is composed of 70 parts of modified carbon material, 70 parts of magnetic powder and 80 parts of setting agent by weight; the setting agent is a mixture of sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 12:2:20:35, and then 30% of water is added to the total mass to obtain a mixture.

[0063] Example 12: This example differs from Example 1 in that the flow rate of water entering the PRB permeable reaction wall is controlled at 4 min / L.

[0064] Example 13: This example differs from Example 1 in that the flow rate of water entering the PRB permeable reaction wall is controlled at 6 min / L.

[0065] In order to further verify the influence of various parameters of the method on the effect of repairing petroleum hydrocarbon contamination in groundwater, the petroleum hydrocarbon contaminated groundwater of an abandoned factory in this city was also used as an experimental sample to study the petroleum hydrocarbon degradation of the PRB permeable reaction wall of each embodiment after 30 days of operation. The measurement results are shown in Table 3 below:

[0066] Table 3 Petroleum hydrocarbon degradation after 30 days of operation of PRB permeable reaction wall

[0067]

[0068]

[0069] From the results in Table 3 above, it can be seen that the degradation rates of the effluent area of ​​the treatment of petroleum hydrocarbon pollution in groundwater under different method parameters are different, but the petroleum hydrocarbon removal rates of each embodiment are all above 90%;

[0070] When spraying different doses of composite microbial liquid, through the comparison between Example 3 and Example 2 and Example 1, increasing the spraying amount of the composite microbial liquid on the basis of Example 1 did not have a significant effect on the degradation rate of petroleum hydrocarbons. At the same time, due to adsorption saturation, a large number of microorganisms were easily lost, which increased the treatment cost and had poor economic efficiency. On the basis of Example 1, reducing the spraying amount of the composite microbial liquid, the degradation rate showed a significant decrease. This may be because the adsorption amount of these petroleum hydrocarbon degrading microorganisms in the nitrate slow-release rod-hollow ball material is small, so it is difficult to perform more efficient degradation of petroleum hydrocarbon pollution in groundwater like the method of Example 1;

[0071] When different oxygen-releasing materials are used, through the comparison between Example 4 and Example 5 and Example 1, different ratios of calcium peroxide, sodium bentonite, sodium alginate and starch have certain effects on the use effect of the finally obtained nitrate slow-release rod-hollow ball material. This may be because the appropriate reaction of calcium peroxide and water will make the hollow ball material have more pores, thereby affecting the use effect of the nitrate slow-release rod-hollow ball material, among which the oxygen-releasing material ratio of Example 1 has the best use effect; at the same time, in order to verify the role of sodium alginate in the oxygen-releasing material, we also set up relevant controls, and the oxygen-releasing material (control) is calcium peroxide, sodium bentonite, and starch mixed in a mass ratio of 260:70:450. The measurement results are shown in Table 4 below:

[0072] Table 4 Petroleum hydrocarbon degradation after 30 days of operation of PRB permeable reaction wall

[0073] Group project Inlet area Outlet area Oxygen-releasing material (control) TPH degradation rate 0％ 90.24％

[0074] It can be seen from Table 4 above that after changing the composition of the oxygen-releasing material, the degradation rate of petroleum hydrocarbons is significantly lower than that of Example 1, Example 4 and Example 5. It can be seen that adding sodium alginate to the oxygen-releasing material can improve the use effect of the nitrate slow-release rod-hollow ball material.

[0075] When using different modified carbon material preparation methods, through the comparison of Example 6 and Example 7 with Example 1, different modified carbon material preparation parameters have a certain influence on the use effect of the final nitrate slow-release rod-hollow ball material. Among them, the use effect of Example 7 and Example 1 is relatively optimal, but through comparison, it is found that the use effect of Example 7 is not significantly improved, and Example 7 uses a longer processing time. Therefore, the method of Example 1 is better overall; at the same time, in order to verify the role of modified carbon material in nitrate slow-release rod-hollow ball material, relevant controls are also set up, and the carbon material (control) is untreated biochar powder. The measurement results are shown in Table 5 below:

[0076] Table 5 Petroleum hydrocarbon degradation after 30 days of operation of PRB permeable reaction wall

[0077] Group project Inlet area Outlet area Carbon material (control) TPH degradation rate 0％ 89.31％

[0078] It can be seen from Table 5 above that after using untreated biochar powder, the degradation rate of petroleum hydrocarbons is significantly lower than that of Example 1, Example 6 and Example 7. It can be seen that the use effect of nitrate slow-release rods-hollow ball materials can be improved after using modified carbon materials.

[0079] When different nitrate slow-release sizing materials are used, through the comparison between Example 8 and Example 9 and Example 1, different nitrate slow-release sizing materials have a certain influence on the use effect of the finally obtained nitrate slow-release rod-hollow ball material, among which the nitrate slow-release sizing material of Example 1 has the best preparation effect;

[0080] When different magnetic center rod racks are used, through the comparison between Example 10 and Example 11 and Example 1, different magnetic center rod racks have a certain influence on the use effect of the finally obtained nitrate sustained-release rod-hollow ball material, among which the preparation effect of the magnetic center rod rack of Example 1 is the best;

[0081] When controlling different groundwater flow rates, through comparison between Example 12 and Example 13 and Example 1, the petroleum hydrocarbon removal rate decreased to a certain extent after increasing the flow rate on the basis of Example 1, while the petroleum hydrocarbon removal rate did not increase significantly after reducing the flow rate. Considering the efficiency of groundwater treatment, the flow rate control of Example 1 is the most economical.

[0082] Example 14: The difference between this example and Example 1 is that the preparation method of the nitrate sustained-release rod is: heating the magnetic center rod frame to 48°C, and applying the nitrate sustained-release adhesive to both sides of the magnetic center rod frame after reheating for multiple times. Specifically, the single application thickness of the nitrate sustained-release adhesive is controlled at 2 mm, and after the surface temperature of the magnetic center rod frame is heated back to 48°C, it is applied again until the nitrate sustained-release adhesive is applied, thereby obtaining a nitrate sustained-release rod; wherein, the coating thickness on both sides of the magnetic center rod frame is the same.

[0083] Example 15: This example is different from Example 1 in that the magnetic center rod frame is heated to 40°C, and the coating is applied again after the surface temperature of the magnetic center rod frame is heated back to 40°C.

[0084] Example 16: The difference between this example and Example 1 is that the magnetic center rod frame is heated to 50°C, and the coating is applied again after the surface temperature of the magnetic center rod frame is heated back to 50°C.

[0085] Example 17: This example is different from Example 1 in that the single coating thickness of the nitrate sustained-release adhesive is controlled at 1 mm.

[0086] In order to further verify the influence of various parameters of the above method on the effect of repairing petroleum hydrocarbon contamination in groundwater, the petroleum hydrocarbon contaminated groundwater of an abandoned factory in this city was also used as an experimental sample to study the petroleum hydrocarbon degradation of the PRB permeable reaction wall of each embodiment after 30 days of operation. The measurement results are shown in Table 6 below:

[0087] Table 6 Petroleum hydrocarbon degradation after 30 days of operation of PRB permeable reaction wall

[0088]

[0089] It can be seen from the results in Table 6 above that the nitrate slow-release rod obtained by using the preparation method of Example 14 has a certain improvement in the use effect of the finally obtained nitrate slow-release rod-hollow ball material. It can be seen that the adjustment of the preparation method of the nitrate slow-release rod can further improve the removal rate of petroleum hydrocarbon pollution by this method. This may be because the preparation method of Example 14 can improve the adhesion efficiency and effect of the nitrate slow-release rubber material. At the same time, under the multi-layer distribution treatment, it can avoid the nitrate slow-release rod from falling off significantly when the silicate slow-release rubber material is slightly vibrated, thereby improving the use stability of the nitrate slow-release rod;

[0090] At the same time, through the comparison of Example 15, Example 16 and Example 14, it can be seen that the above method at different temperatures has a certain influence on the removal rate of petroleum hydrocarbon pollution, among which Example 14 has a better use effect;

[0091] By comparing Example 17 with Example 14, it can be seen that Example 17 has better use effect, but its preparation time is significantly extended compared with Example 14, but its use effect is not significantly improved compared with Example 14. Therefore, from the perspective of economy and other aspects, Example 14 is relatively better.

Claims

1. A method for remediating petroleum hydrocarbon contamination in groundwater based on microorganisms, characterized in that: The nitrate slow-release rods-hollow ball materials are loaded in layers into a PRB permeable reaction wall, and a composite microbial liquid is sprayed on each layer of the nitrate slow-release rods-hollow ball materials, and then a flow-blocking wall is constructed on the water inlet side of the PRB permeable reaction wall, and the petroleum hydrocarbons in the groundwater are degraded by the nitrate slow-release rods-hollow ball materials and the composite microbial liquid loaded in the PRB permeable reaction wall; The nitrate slow-release rod-hollow ball material is composed of a hollow ball material obtained by mixing an oxygen-releasing material and a modified carbon material, and a nitrate slow-release rod filled in the hollow ball material. The nitrate slow-release rod is composed of a modified carbon material and magnetic powder as a magnetic center rod frame, and a nitrate slow-release rubber material is attached to the magnetic center rod frame; The preparation method of the nitrate slow-release stick is as follows: heating the magnetic center stick frame to 40-50°C, applying the nitrate slow-release adhesive to both sides of the magnetic center stick frame after reheating for multiple times, specifically, the single application thickness of the nitrate slow-release adhesive is controlled at 1-2 mm, and applying again after the surface temperature of the magnetic center stick frame is heated back to 40-50°C, until the nitrate slow-release adhesive is applied, thereby obtaining the nitrate slow-release stick; wherein the application thickness on both sides of the magnetic center stick frame is the same; The magnetic center rod frame is a combined structure consisting of two rectangular blocks, and the short sides of the two rectangular blocks are perpendicular to each other; The nitrate slow-release rod-hollow ball material is loaded in layers into the PRB permeable reaction wall, the filling thickness of each layer of the nitrate slow-release rod-hollow ball material is 15-30 cm, and a magnetic filter is laid on each layer of the nitrate slow-release rod-hollow ball material; the following steps are included: Step 1, constructing a PRB permeable reaction wall on the flow path of groundwater, filling nitrate slow-release rods-hollow ball materials into the PRB permeable reaction wall in layers, and the filling thickness of each layer of nitrate slow-release rods-hollow ball materials is 15-30 cm, and then spraying each layer of nitrate slow-release rods-hollow ball materials with a composite microbial liquid accounting for 15-30% of the mass of each layer of nitrate slow-release rods-hollow ball materials, and covering it with a magnetic filter; Step 2, repeat step 1 until the nitrate slow-release rod-hollow ball material fills the PRB permeable reaction wall, and then build a flow barrier on the water inlet side of the PRB permeable reaction wall to control the water flow rate entering the PRB permeable reaction wall at 4-6 min / L. Regularly test the petroleum hydrocarbons on the water outlet side of the PRB permeable reaction wall. If the petroleum hydrocarbon content exceeds the standard, replace the nitrate slow-release rod-hollow ball material.

2. A method for remediating petroleum hydrocarbon contamination in groundwater based on microorganisms as claimed in claim 1, characterized in that: The composite microbial bacterial liquid is composed of any one or more of fusobacterium, pseudomonas, alcaligenes and xanthophyll.

3. A method for remediating petroleum hydrocarbon contamination in groundwater based on microorganisms as claimed in claim 1, characterized in that: The oxygen-releasing material is a mixture of calcium peroxide, sodium bentonite, sodium alginate and starch in a mass ratio of 20-30:5-10:1-2:40-50, and water accounting for 20-30% of the total mass of the modified carbon material and the oxygen-releasing material is added when mixed with the modified carbon material.

4. A method for remediating petroleum hydrocarbon contamination in groundwater based on microorganisms as claimed in claim 1, characterized in that: The modified carbon material is prepared by heating biochar powder to 70-90° C., adding the powder to a nitrate aqueous solution for 1-3 minutes, removing the powder, repeating the process 2-5 times, and then naturally drying the biochar to obtain a powder material; wherein the mass concentration of nitrate in water is 10-15%.

5. A method for remediating petroleum hydrocarbon pollution in groundwater based on microorganisms as claimed in claim 1, characterized in that: The nitrate sustained-release adhesive material is composed of 30-50 parts of nitrate and 80-100 parts of setting agent by weight; the magnetic center rod frame is composed of 40-70 parts of modified carbon material, 40-70 parts of magnetic powder and 50-80 parts of setting agent by weight.

6. A method for remediating petroleum hydrocarbon contamination in groundwater based on microorganisms as claimed in claim 5, characterized in that: The setting agent is prepared by mixing sodium bentonite, sodium alginate, fine sand and cement in a mass ratio of 8-12:1-2:15-20:25-35, and then adding water accounting for 20-30% of the total mass of sodium bentonite, sodium alginate, fine sand and cement to obtain a mixture.

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