A method for enhancing microbial remediation of soil and groundwater through in-situ injection of slow-release oxygen materials

Abstract

This invention discloses a method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater. The method involves preparing a slow-release oxygen material suspension slurry by mixing calcium peroxide and bentonite with water in a specific ratio. This slurry is then injected under pressure into a specific depth in the target stratum. The slurry fills the soil fissures formed by high-pressure fracturing during the injection process around the injection point, achieving effective dispersion and long-term oxygen release of the slow-release oxygen material in the contaminated stratum. This creates a slow-release oxygen-rich underground environment conducive to aerobic microbial remediation, thereby enhancing the ability of microorganisms to remediate soil and groundwater.

Description

Technical Field

[0001] This invention relates to the field of environmental remediation technology, and in particular to a method for enhancing microbial remediation of soil and groundwater by in-situ injection of slow-release oxygen materials. Background Technology

[0002] With increasing emphasis on the cost-effectiveness and long-term monitoring of contaminated site remediation, the advantages of bioremediation technology will gradually become more apparent.

[0003] Microbial aerobic metabolism mineralizes organic pollutants to a much higher degree than anaerobic metabolism, thus aerobic microbial remediation has certain technical advantages. However, increasing the oxygen content in soil and groundwater environments is a key factor affecting the efficiency of aerobic remediation. Slow-release oxygen compounds can react with water to release oxygen, thereby promoting the aerobic biodegradation of organic pollutants. Currently, there is research in China on developing oxygen-releasing materials using slow-release oxygen compounds for the treatment of black and odorous river sediments and groundwater remediation with permeable reactive barriers. The main forms of these materials are solid particles and tablets with millimeter or centimeter particle sizes. Disintegration and slow release are controlled through methods such as encapsulation and coating. Application methods mainly involve in-situ mixing of solid materials with topsoil or in-situ insertion into permeable reactive barriers as filler. This approach is not suitable for remediation scenarios where functional materials are formulated into slurry form and injected in situ into different locations and depths of contaminated strata.

[0004] Therefore, in response to the need for long-term, low-consumption, and green remediation of soil and groundwater in organically contaminated sites, by combining in-situ injection engineering technology with research on slow-release oxygen functional materials, the problem of effective dispersion and long-term oxygen release of slow-release oxygen functional materials in in-situ contaminated strata can be solved. This can form a low-cost, high-efficiency, environmentally friendly microbial enhanced remediation technology system suitable for promotion and application in in-situ remediation of soil and groundwater in organically contaminated sites, thereby achieving better comprehensive social, economic, and environmental benefits. Summary of the Invention

[0005] In view of this, the present invention provides a method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater. This method involves preparing a slow-release oxygen material suspension slurry by adding water to calcium peroxide and bentonite in a specific ratio. The slurry is then injected under pressure into a specific depth in the target stratum. This allows the slow-release oxygen material suspension slurry to fill the soil fissures formed by high-pressure fracturing during the injection process around the injection point. This achieves effective dispersion and long-term oxygen release of the slow-release oxygen material in the contaminated stratum, thereby creating a slowly releasing oxygen-friendly underground environment conducive to aerobic microbial remediation and enhancing the ability of microorganisms to remediate soil and groundwater.

[0006] A method for enhancing microbial remediation of soil groundwater through in-situ injection of slow-release oxygen materials includes the following steps:

[0007] S1, slightly soluble peroxides are selected as the active component of the slow-release oxygen material, and suspended adsorbents with pulping properties are selected as the inert component of the slow-release oxygen material.

[0008] S2, determine the ratio of active to inert components of the slow-release oxygen material based on the in-situ injection formation conditions;

[0009] S3, the active and inert components of the slow-release oxygen material are mixed evenly with water on-site according to the component ratio to prepare a slow-release oxygen material suspension slurry. The slow-release oxygen material suspension slurry is then injected under pressure into a specific depth of the target stratum using a pressure injection device, so that the slow-release oxygen material suspension slurry fills the soil fissures formed by high-pressure splitting during the pressure injection process around the injection point.

[0010] Preferably, the active component of the slow-release oxygen material in step S1 is calcium peroxide or magnesium peroxide, and the inert component of the slow-release oxygen material is bentonite.

[0011] Preferably, the active component of the slow-release oxygen material is calcium peroxide with a purity of 75% and a particle size of not less than 200 mesh;

[0012] The inert component of the slow-release oxygen material is bentonite with a particle size of not less than 200 mesh.

[0013] Preferably, in step S2, when determining the ratio of active to inert components of the slow-release oxygen material based on the in-situ injection site conditions, the ratio of active to inert components of the slow-release oxygen material is determined to be 100 parts: 150 parts to 100 parts: 400 parts based on the soil properties within the in-situ remediation area.

[0014] Preferably, the soil properties include clay soil, silty soil, and sandy soil;

[0015] When the soil within the in-situ remediation area is clayey soil, the ratio of active to inert components of the slow-release oxygen material is a high value ratio.

[0016] When the soil within the in-situ remediation area is silty soil, the ratio of active to inert components of the slow-release oxygen material is the median ratio.

[0017] When the soil within the in-situ remediation area is sandy soil, the ratio of active to inert components of the slow-release oxygen material should be low.

[0018] Preferably, when the soil within the in-situ remediation area is clay soil, the ratio of the active component to the inert component of the slow-release oxygen material is 100 parts: 150 parts to 100 parts: 233 parts.

[0019] When the soil within the in-situ remediation area is silty soil, the ratio of active component to inert component of the slow-release oxygen material is 100 parts: 186 parts to 100 parts: 300 parts.

[0020] When the soil within the in-situ remediation area is sandy soil, the ratio of active to inert components of the slow-release oxygen material is 100 parts: 233 parts to 100 parts: 400 parts.

[0021] Preferably, in step S3, the amount / flow rate of the agent injected by the pressure injection device at a single injection point and the injection influence range are determined based on the soil properties and injection depth within the in-situ remediation range.

[0022] Preferably, the pressure injection device is a diaphragm pump, plunger pump, or screw pump, with an injection pressure of 0.5 MPa to 5.5 MPa.

[0023] Preferably, multiple injection points are arranged within the in-situ repair area, and the injection depth of different injection points is different.

[0024] The beneficial effects of this invention are:

[0025] 1. This invention prepares a slow-release oxygen material suspension slurry by mixing calcium peroxide and bentonite with water in a specific ratio. The slow-release oxygen material suspension slurry is then injected under pressure into a specific depth in the target stratum. This allows the slow-release oxygen material suspension slurry to fill the soil fissures formed by high-pressure splitting during the injection process around the injection point. This achieves effective dispersion and long-term oxygen release of the slow-release oxygen material in the in-situ contaminated stratum, thereby creating an underground environment that slowly releases oxygen and is conducive to aerobic microbial remediation, thus enhancing the ability of microorganisms to remediate soil and groundwater.

[0026] 2. This invention prepares a slow-release oxygen material suspension slurry by mixing calcium peroxide and bentonite with water in a specific ratio. Due to the inert components of clay minerals such as bentonite, the slow-release oxygen material is mixed, dispersed, encapsulated, and isolated. When the in-situ injected material is injected into the target formation under pressure, the in-situ injected material itself forms a microenvironment that is conducive to prolonging the oxygen release capacity of the slow-release oxygen compounds. As oxygen is released stably at the interface between the in-situ injected material and the soil and groundwater over a long period of time, the inert components of clay minerals such as bentonite in the in-situ injected material are used to adsorb and retain pollutants in the groundwater, further maintaining an aerobic microbial remediation environment with efficient mass transfer at the remediation interface of the contaminated formation, thus achieving long-term, low-consumption microbial enhanced green remediation.

[0027] 3. This invention injects a slow-release oxygen material suspension slurry under pressure into a specific depth of the target stratum, causing the slow-release oxygen material to slowly release oxygen into the soil and groundwater contaminated strata, stimulating the activity of indigenous aerobic microorganisms, forming an underground environment conducive to aerobic remediation, improving the microbial remediation capacity, and accelerating the degradation and transformation of pollutants.

[0028] 4. This invention injects a slow-release oxygen material suspension slurry under pressure into a specific depth of the target stratum. The high-pressure injection of the suspension slurry creates soil fracturing around the injection point, which can enhance or create local fractures in strata with low effective porosity, such as cohesive soils. This greatly expands the contact interface between the injected slow-release oxygen material and the contaminated soil and groundwater, resulting in a green and efficient aerobic biostimulation remediation effect where the injected material is in full contact with the contaminated medium, releases oxygen stably, and is in good contact with the contaminated medium.

[0029] 5. The combination ratio of the slow-release oxygen compound and bentonite in this invention can be flexibly adjusted according to the in-situ injection site conditions of soils with different properties such as cohesive, silty, and sandy soils, thereby selecting the optimal inert component mixing ratio, ensuring a sufficiently long slow-release oxygen effect while reducing the dosage of injected drugs and reducing injection construction costs.

[0030] 6. This invention adopts in-situ injection technology with direct injection rod propulsion. By setting up different injection points within the remediation range, setting different injection depths at the injection points, and controlling the injection volume at each point and depth, it can achieve precise injection remediation in both horizontal and depth directions within the in-situ contaminated soil and groundwater range. It is suitable for sites using slurry or highly viscous liquid remediation agents, or sites with uneven soil strata or contamination distribution. Attached Figure Description

[0031] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0032] Figure 1 This is a schematic diagram of in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater.

[0033] Figure 2 This is a diagram illustrating the effect of calcium peroxide's ability to release oxygen slowly.

[0034] Figure 3 This is a diagram illustrating the effect of bentonite as an inert component on the sustained-release effect.

[0035] Figure 4 This is a verification diagram showing the effect of diatomaceous earth as an inert component on the sustained-release effect.

[0036] Figure 5 This is a verification effect diagram of the effect of powdered activated carbon as an inert component on the sustained-release effect.

[0037] Figure 6 This is a diagram verifying the effectiveness of the slow-release oxygen material. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the invention is described below with reference to specific embodiments shown in the accompanying drawings. However, it should be understood that these descriptions are merely exemplary and not intended to limit the scope of the invention. Furthermore, descriptions of well-known structures and technologies are omitted in the following description to avoid unnecessarily obscuring the concept of the invention.

[0039] The terminology used in this disclosure is for the purpose of describing particular embodiments only and is not intended to be limiting of the disclosure. The singular forms “a,” “the,” and “the” as used in this disclosure and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise. It should also be understood that the term “and / or” as used herein refers to and includes any and all possible combinations of one or more of the associated listed items.

[0040] This invention provides a method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil groundwater, comprising the following steps:

[0041] S1, slightly soluble peroxides are selected as the active component of the slow-release oxygen material, and suspended adsorbents with pulping properties are selected as the inert component of the slow-release oxygen material.

[0042] S2, determine the ratio of active to inert components of the slow-release oxygen material based on the in-situ injection formation conditions;

[0043] S3, the active and inert components of the slow-release oxygen material are mixed evenly with water on-site according to the component ratio to prepare a slow-release oxygen material suspension slurry. The slow-release oxygen material suspension slurry is then injected under pressure into a specific depth of the target stratum using a pressure injection device, so that the slow-release oxygen material suspension slurry fills the soil fissures formed by high-pressure splitting during the pressure injection process around the injection point.

[0044] This invention prepares a slow-release oxygen material suspension slurry by mixing calcium peroxide and bentonite with water in a specific ratio. The slow-release oxygen material suspension slurry is then injected under pressure into a specific depth in the target stratum. This allows the slow-release oxygen material suspension slurry to fill the soil fissures formed by high-pressure fracturing during the injection process around the injection point. This achieves effective dispersion and long-term oxygen release of the slow-release oxygen material in the in-situ contaminated stratum, thereby creating an underground environment that slowly releases oxygen and is conducive to aerobic microbial remediation, thus enhancing the ability of microorganisms to remediate soil and groundwater.

[0045] To better understand the technical solution of the present invention, the present invention will be described in detail below with reference to the accompanying drawings.

[0046] This invention provides a method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil groundwater, specifically including the following steps:

[0047] Step S1: Select slightly soluble peroxides as the active components of the slow-release oxygen material. The slightly soluble peroxides are mainly calcium peroxide, magnesium peroxide, etc. In actual selection, the specific selection should be determined by comprehensively considering factors such as the price, purity, and impact on soil pH of the peroxide. However, priority should be given to peroxides that are economical, easy to obtain, and have a controllable impact on soil pH.

[0048] Suspended adsorbents with pulping properties are selected as inert components of slow-release oxygen materials. The suspended adsorbents are mainly bentonite, etc. In actual selection, the inert components of slow-release oxygen materials should be selected by comprehensively considering factors such as price, particle size, and performance. However, inert components that are economical, easy to pulp, and have a significant delaying effect on the oxygen release reaction of slow-release oxygen compounds in soil and groundwater environments should be given priority.

[0049] In this embodiment, the bentonite has good dispersion, suspension, adsorption, purification and slurry-making properties, so bentonite is selected as the inert component of the slow-release oxygen material.

[0050] After adding a certain amount of 75% pure calcium peroxide to pure water, sodium sulfite was added as a reducing agent to consume oxygen, depending on the saturated or supersaturated dissolved oxygen content in the water. The oxygen-releasing capacity of the added sodium peroxide was verified by comparing the result with a pure water blank sample. After 35 days of continuous testing, the sample with added 75% pure calcium peroxide maintained a stable oxygen-releasing capacity even after consuming a certain amount of sodium sulfite daily. Figure 2 As shown. Therefore, in this embodiment, calcium peroxide is selected as the active component of the slow-release oxygen material.

[0051] A certain amount of 75% pure calcium peroxide was thoroughly mixed with bentonite, diatomaceous earth, and powdered activated carbon in different proportions to form a slow-release oxygen test material. After adding the test material in different proportions to pure water, sodium sulfite was added as a reducing agent to consume oxygen according to the saturated or supersaturated dissolved oxygen content in the water. The results were compared with those of a sample without added inert components to compare the performance of suspended adsorbents such as bentonite, diatomaceous earth, and powdered activated carbon as inert components of slow-release oxygen materials, and to screen out inert components suitable for compounding with calcium peroxide.

[0052] After 31 days of continuous testing, it was found that samples with a higher proportion (80%) of bentonite showed a significant enhanced sustained-release effect. Samples with different proportions of diatomaceous earth had little effect on the sustained-release effect; in fact, samples with a higher proportion (80%) of diatomaceous earth significantly enhanced the release of oxygen from calcium peroxide, leading to an increase in dissolved oxygen levels. Samples with different proportions of powdered activated carbon all showed an increase in dissolved oxygen levels compared to samples without inert components. The sample with a medium proportion (50%) of powdered activated carbon showed the most significant enhancement in oxygen release from calcium peroxide. Figure 3 , 4As shown in Figures 5 and 6. Therefore, after experimental screening, in this embodiment, a higher proportion of bentonite is more suitable as an inert component for formulating slow-release oxygen materials.

[0053] Preferably, the active component of the slow-release oxygen material is calcium peroxide with a purity of 75% and a particle size of not less than 200 mesh (micrometer level); the inert component of the slow-release oxygen material is bentonite with a particle size of not less than 200 mesh (micrometer level).

[0054] Step S2: Based on the soil properties within the in-situ remediation area, determine the ratio of active to inert components of the slow-release oxygen material to be 100 parts: 150 parts to 100 parts: 400 parts.

[0055] Specifically, the soil properties include clay soil, silty soil and sandy soil;

[0056] When the soil within the in-situ remediation area is clayey soil, the ratio of active to inert components of the slow-release oxygen material is a high value ratio.

[0057] When the soil within the in-situ remediation area is silty soil, the ratio of active to inert components of the slow-release oxygen material is the median ratio.

[0058] When the soil within the in-situ remediation area is sandy soil, the ratio of active to inert components of the slow-release oxygen material should be low.

[0059] In this embodiment, when the soil within the in-situ remediation area is clay soil, the preferred ratio of the active component to the inert component of the slow-release oxygen material is 100 parts: 150 parts to 100 parts: 233 parts.

[0060] When the soil within the in-situ remediation area is silty soil, the preferred ratio of active component to inert component of slow-release oxygen material is 100 parts: 186 parts to 100 parts: 300 parts.

[0061] When the soil within the in-situ remediation area is sandy soil, the preferred ratio of active to inert components of the slow-release oxygen material is 100 parts: 233 parts to 100 parts: 400 parts.

[0062] Step S3: Based on the soil properties within the in-situ remediation area, the active and inert components of the slow-release oxygen material are mixed evenly with water on-site according to the component ratio described in Step S2. A pressure injection device is then used to directly inject the slow-release oxygen material suspension slurry to a predetermined depth at the injection point, injecting it into the saturated soil or groundwater. Because the slow-release oxygen material suspension slurry is injected into the soil under high pressure, high-pressure fracturing occurs around the injection point during the injection process. This allows the slow-release oxygen material suspension slurry to fill the soil fissures formed by the high-pressure fracturing around the injection point, thereby creating an environment conducive to aerobic microbial remediation in the soil and groundwater contaminated strata, achieving long-term, low-consumption microbial-enhanced green remediation.

[0063] Multiple injection points can be set up within the in-situ remediation area. The injection depth of different injection points can be set according to the soil conditions at each location, and the injection depth of different injection points can be different.

[0064] In this embodiment, the injection volume / flow rate and injection impact range of the pressure injection device at a single injection point are determined based on the soil properties and injection depth within the in-situ remediation area.

[0065] Preferably, the pressure injection device is a high-pressure injection pump of the type such as a diaphragm pump, plunger pump or screw pump. The high-pressure injection pump is equipped with a drug tubing of the same pressure rating, and the injection pressure of the high-pressure injection pump is 0.5MPa to 5.5MPa.

[0066] To verify the slow-release effect of the oxygen-releasing material suspension slurry described in this application, a certain amount of 75% pure calcium peroxide was thoroughly mixed with bentonite in different proportions to form a slow-release oxygen test material. After adding the test material in different proportions to pure water, sodium sulfite was added as a reducing agent to consume oxygen according to the saturated or supersaturated dissolved oxygen content in the water. The performance of different proportions of bentonite as the inert component of the slow-release oxygen material was compared with that of the sample without added inert components, and the most suitable bentonite ratio as the inert component to be combined with calcium peroxide was screened.

[0067] After 22 days of continuous testing, samples containing different proportions of bentonite were used to prepare slow-release oxygen materials with 60%–80% (by mass) bentonite. These materials achieved a significantly enhanced slow-release effect, maintaining a low dissolved oxygen concentration of 10–15 mg / L. Furthermore, even after consuming a certain amount of sodium sulfite daily, the materials maintained a stable oxygen release capacity. Figure 6 As shown.

[0068] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

Claims

1. A method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil groundwater, characterized in that, Specifically, the following steps are included: S1, slightly soluble peroxides are selected as the active component of the slow-release oxygen material, and suspended adsorbents with pulping properties are selected as the inert component of the slow-release oxygen material. The active component of the slow-release oxygen material is calcium peroxide or magnesium peroxide, and the inert component of the slow-release oxygen material is bentonite. S2, determine the ratio of active to inert components of the slow-release oxygen material based on the in-situ injection formation conditions; S3, mix the active and inert components of the slow-release oxygen material with water on site according to the component ratio to make a slow-release oxygen material suspension slurry. Use a pressure injection device to inject the slow-release oxygen material suspension slurry under pressure into a specific depth of the target stratum, so that the slow-release oxygen material suspension slurry fills the soil fissures formed by high-pressure splitting during the pressure injection process around the injection point. When determining the ratio of active to inert components of the slow-release oxygen material based on the in-situ injection site conditions, the ratio of active to inert components of the slow-release oxygen material is determined to be 100 parts: 150 parts to 100 parts: 400 parts based on the soil properties within the in-situ remediation area. The soil properties include clay soil, silty soil and sandy soil; When the soil within the in-situ remediation area is clayey soil, the ratio of active to inert components of the slow-release oxygen material is a high value ratio. When the soil within the in-situ remediation area is silty soil, the ratio of active to inert components of the slow-release oxygen material is the median ratio. When the soil within the in-situ remediation area is sandy soil, the ratio of active to inert components of the slow-release oxygen material should be low. When the soil within the in-situ remediation area is clay soil, the ratio of active component to inert component of the slow-release oxygen material is 100 parts: 150 parts to 100 parts: 233 parts. When the soil within the in-situ remediation area is silty soil, the ratio of active to inert components of the slow-release oxygen material is 100 parts: 186 parts to 100 parts: 300 parts. When the soil within the in-situ remediation area is sandy soil, the ratio of active to inert components of the slow-release oxygen material is 100 parts: 233 parts to 100 parts: 400 parts.

2. The method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater according to claim 1, characterized in that, The active component of the slow-release oxygen material is calcium peroxide with a purity of 75% and a particle size of not less than 200 mesh. The inert component of the slow-release oxygen material is bentonite with a particle size of not less than 200 mesh.

3. The method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater according to claim 1, characterized in that, In step S3, the amount / flow rate of the agent injected by the pressure injection device at a single injection point and the injection impact range are determined based on the soil properties and injection depth within the in-situ remediation range.

4. The method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater according to claim 1 or 3, characterized in that, The pressure injection device is a diaphragm pump, plunger pump, or screw pump, with an injection pressure of 0.5 MPa to 5.5 MPa.

5. The method for in-situ injection of slow-release oxygen materials to enhance microbial remediation of soil and groundwater according to claim 3, characterized in that, Multiple injection points are arranged within the in-situ repair area, and the injection depth varies at different injection points.

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