CN113926838A - Fossil fuel contaminated soil remediation system and remediation method - Google Patents
Fossil fuel contaminated soil remediation system and remediation method Download PDFInfo
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- CN113926838A CN113926838A CN202111359383.8A CN202111359383A CN113926838A CN 113926838 A CN113926838 A CN 113926838A CN 202111359383 A CN202111359383 A CN 202111359383A CN 113926838 A CN113926838 A CN 113926838A
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/10—Reclamation of contaminated soil microbiologically, biologically or by using enzymes
- B09C1/105—Reclamation of contaminated soil microbiologically, biologically or by using enzymes using fungi or plants
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/005—Extraction of vapours or gases using vacuum or venting
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- B—PERFORMING OPERATIONS; TRANSPORTING
- B09—DISPOSAL OF SOLID WASTE; RECLAMATION OF CONTAMINATED SOIL
- B09C—RECLAMATION OF CONTAMINATED SOIL
- B09C1/00—Reclamation of contaminated soil
- B09C1/06—Reclamation of contaminated soil thermally
Abstract
The invention discloses a system and a method for repairing fossil fuel polluted soil, and relates to the technical field of soil repair. The invention provides a heat-enhanced vapor extraction-microbial degradation combined repair device and a repair method, which fully utilize the combined advantages of three technologies of heat enhancement, vapor extraction and microbial degradation, solve the respective technical shortages and increase the repair effect. The restoration method provided by the invention adopts different restoration processes in stages on the basis of fully considering the actual pollution condition of the polluted site, combines the advantages of different restoration techniques, reduces the restoration cost, shortens the restoration period and improves the environmental friendliness of the restoration process while realizing the efficient standard restoration of the polluted site.
Description
Technical Field
The invention belongs to the technical field of polluted soil remediation, and relates to a system and a method for remediating fossil fuel polluted soil.
Background
In the field of polluted soil and groundwater remediation, in-situ remediation technologies mainly comprising in-situ thermal desorption and gas phase/multiphase extraction are increasingly applied. Compared with the ex-situ remediation technology, the in-situ remediation technology has the advantages of relatively low cost and less secondary pollution, can avoid the problems of large soil disturbance, high excavation cost, more secondary pollution links and the like caused by ex-situ remediation, and is suitable for remediation of the production pollution site under most conditions.
The polluted soil remediation technologies are numerous, and are generally divided into physical methods, chemical methods and biological methods according to different mechanisms, and the specific technologies include vapor phase extraction (SVE), electric remediation, thermal desorption, soil leaching, chemical oxidation methods, microbial degradation and the like, and the technologies have various characteristics in practical application. The gas-phase extraction method is a soil and underground water remediation technology with high utilization rate, has the advantages of simple operation, high removal efficiency, short remediation time and the like, but has a trailing effect in the later treatment period; the thermal desorption technology is also called as thermal desorption technology, has the advantages of higher treatment efficiency and no influence of pollutant concentration, but has larger energy consumption and relatively high repair cost; the microbial degradation remediation has the advantages of low cost, environmental protection and the like, but has low efficiency and long remediation period, and is suitable for remediation of soil and underground water with low pollution degree. Various restoration technology combinations are applied to the contaminated site, the rebounding and tailing problems in the later restoration period can be effectively solved, the defect of a single restoration technology is overcome, and the standard-reaching restoration of the contaminated site is realized.
The method has the particularity in the treatment of the pollution site, such as gas stations, oil depots and the like, a plurality of gas stations with pollution still operate, the space of a repair area is limited, and particularly in dense areas, the requirements on repair technology are high, so that the pollution site can be effectively repaired, the national standard repair requirements are met, the normal production and operation of enterprises are not greatly influenced, and the repair cost is controlled within a low range. The existing contaminated soil remediation technology still needs to be improved in the aspects of remediation efficiency, environmental protection, remediation cost reduction and the like, meanwhile, the remediation equipment has a large improvement space for the remediation applicability of different contaminated sites, and the modular arrangement of the remediation device is favorable for improving the remediation applicability and the remediation capability of the remediation device.
In view of this, the invention is particularly proposed.
Disclosure of Invention
The invention aims to overcome the defects of the prior art and provide a system and a method for repairing soil polluted by fossil fuel.
The invention is realized by the following steps:
the invention provides a fossil fuel contaminated soil remediation system, which mainly comprises: a plurality of extraction wells disposed in the contaminated site soil; a plurality of injection wells disposed in the contaminated site soil; the hot air supply module is communicated with the injection well through a hot air supply pipeline and is used for injecting hot air into the soil of the polluted site; the microorganism supply module is communicated with the injection well and the extraction well through a microorganism supply pipeline and is used for injecting microorganism liquid into the soil of the polluted site; the inlet end of the gas phase extraction module is communicated with the extraction wells through extraction pipelines, and gas and liquid containing pollutants in the soil where each extraction well is located are extracted through negative pressure; and the inlet end of the gas-liquid treatment module is communicated with the gas-phase extraction module through a conveying pipeline, and gas and liquid containing pollutants in the soil extracted by the gas-liquid separation treatment gas-phase extraction module are extracted.
The invention also provides a method for restoring fossil fuel contaminated soil by adopting the restoration system, which comprises the following steps:
the method comprises the following steps of firstly, starting a vapor extraction module and a gas-liquid treatment module, wherein the vapor extraction module generates negative pressure, extracts volatile organic matters in the polluted soil through an extraction well, and treats the extracted volatile organic matters through the gas-liquid treatment module;
after the negative pressure pumping process is finished, the whole device is started, hot air generated by the hot air supply module is injected into the polluted soil to be subjected to heat-enhanced gas phase extraction treatment, volatile semi-volatile heavy component organic matters in the polluted soil are extracted through the extraction well, the extracted volatile semi-volatile heavy component organic matters are treated through the gas-liquid treatment module, after the tailing stage of the heat-enhanced gas phase extraction, the microorganism supply module is started again to carry out microorganism remediation, and pollutant components which are difficult to extract above C13 in the polluted soil are continuously removed through the degradation reaction of microorganisms until the pollutant concentration in the well to be monitored reaches a remediation target, so that the remediation of the fossil fuel polluted soil is completed.
The invention has the following beneficial effects:
the invention provides a system and a method for repairing fossil fuel polluted soil. The repair system of the present invention mainly comprises: the repair system is utilized, in the primary stage, the gas phase extraction module and the gas-liquid treatment module are started, air is driven to flow through a soil gap by negative pressure generated by the gas phase extraction module, an extract carrying light-component volatile organic matters flows to an extraction opening, and a gas-liquid mixture extracted from the extraction well is treated in the gas-liquid treatment module; after the negative pressure extraction is finished, starting the whole device, injecting high-temperature hot air generated by a hot air supply module into an injection well, wherein the high-temperature hot air can promote the pollutants in the polluted soil to be transferred to a gas phase, and extracting and treating volatile semi-volatile heavy component organic pollutants in the soil; after entering the tailing stage of the hot air vapor extraction module, starting microbial degradation repair, and removing pollutant components which are difficult to extract and are above C13 in the polluted soil through the degradation reaction of microbes. The restoration method provided by the invention adopts different restoration processes in stages on the basis of fully considering the actual pollution condition of the polluted site, combines the advantages of different restoration techniques, reduces the restoration cost and shortens the restoration period while realizing the high-efficiency standard restoration of the polluted site.
Drawings
In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings needed to be used in the embodiments will be briefly described below, it should be understood that the following drawings only illustrate some embodiments of the present invention and therefore should not be considered as limiting the scope, and for those skilled in the art, other related drawings can be obtained according to the drawings without inventive efforts.
Fig. 1 is a schematic structural diagram of a repair device of the present invention, wherein the numbers are as follows: 1-a gas-liquid separation tank, 2-a vacuum pump, 3-a gas adsorption tower, 4-a liquid pump, 5-an oil-water separation tank, 6-a liquid pump, 7-a wastewater collection tank, 8-an oil phase collection tank, 9-a high-temperature air heater and 10-a buffer tank;
FIG. 2 is a graph of the concentration of petroleum hydrocarbons over time for the contaminated soil treated by the three techniques of example 1;
FIG. 3 is a graph of the removal rate of petroleum hydrocarbons from contaminated soil treated by three techniques as a function of time in example 1;
fig. 4 is a schematic view of the field implementation of the repairing device in embodiment 2.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are not indicated by the manufacturer, and are all conventional products available commercially.
In order to effectively solve the problem of repairing a contaminated site, reduce the repairing cost and improve the environmental friendliness of the repairing process, the invention provides a heat-enhanced vapor extraction-microbial degradation combined repairing device and a repairing method, which fully utilize the combined advantages of three technologies of heat enhancement, vapor extraction and microbial degradation to realize efficient, green and low-cost repairing of the contaminated site, particularly the contaminated site.
In a first aspect, an embodiment of the present invention provides a system for remediating fossil-fuel-contaminated soil, where the system mainly includes: a plurality of extraction wells disposed in the contaminated site soil; a plurality of injection wells disposed in the contaminated site soil; the hot air supply module is communicated with the injection well through a hot air supply pipeline and is used for injecting hot air into the soil of the polluted site; the microorganism supply module is communicated with the injection well and the extraction well through a microorganism supply pipeline and is used for injecting microorganism liquid into the soil of the polluted site; the inlet end of the gas phase extraction module is communicated with the extraction wells through extraction pipelines, and gas and liquid containing pollutants in the soil where each extraction well is located are extracted through negative pressure; and the inlet end of the gas-liquid treatment module is communicated with the gas-phase extraction module through a conveying pipeline, and gas and liquid containing pollutants in the soil extracted by the gas-liquid separation treatment gas-phase extraction module are extracted.
The embodiment of the invention provides a fossil fuel contaminated soil remediation system, which mainly comprises a hot air supply module, a microorganism supply module, an injection well, an extraction well, a gas phase extraction module and a gas-liquid treatment module, wherein the hot air supply module and the microorganism supply module are respectively used for injecting high-temperature hot air and microorganism liquid into the injection well, the gas phase extraction module can extract pollutant components in the contaminated soil through the extraction well, and the gas-liquid treatment module can perform gas-liquid separation treatment on the extracted pollutants. The repairing device provided by the embodiment of the invention is a heat-enhanced vapor extraction-microbial degradation combined repairing device, and can fully utilize the combined advantages of three technologies of heat enhancement, vapor extraction and microbial degradation to realize efficient, green and low-cost repairing of a polluted site, particularly a production site. The technology is an optimal repairing technology aiming at repairing polluted soil in an aeration zone of a production and gas station.
In an alternative embodiment, the gas-liquid treatment module comprises: the device comprises a gas-liquid separation module, an extraction gas purification module and an oil-water separation module, wherein the gas-liquid separation module comprises a gas outlet and a liquid outlet, the gas outlet is connected with the extraction gas purification module, and the liquid outlet is connected with the oil-water separation module;
preferably, the extraction gas purification module consists of two gas adsorption towers, adsorbents are filled in the gas adsorption towers, and gas outlets of the adsorption towers are all provided with an online VOCs concentration detector;
preferably, the oil-water separation module consists of an oil-water separation tank, a liquid pump, a wastewater collection tank and an oil phase collection tank, and liquid from the gas-liquid separation module enters the oil-water separation tank for oil-water separation.
In an optional embodiment, the vapor extraction module is disposed between the gas outlet of the gas-liquid separation module and the extraction gas purification module, and the vapor extraction module can deliver the gas separated by the gas-liquid separation module to the extraction gas purification module.
Preferably, the vapor extraction module consists of two vacuum pumps, and single extraction or parallel extraction is carried out through valve control.
In an alternative embodiment, the microorganism supply module is communicated with the injection well and the extraction well through a microorganism supply pipeline, and the microorganism injection module mainly comprises a nutrient solution tank, a bacteria solution tank and a related pipe valve.
In an alternative embodiment, the repair system further comprises: and the online monitoring and control module consists of online monitoring equipment and a DCS control system so as to realize automatic control and monitoring of the whole device.
Therefore, an embodiment of the present invention provides a heat-enhanced vapor extraction-microbial degradation combined apparatus for repairing a contaminated site, which is shown in fig. 1 and includes:
a. the hot air supply module mainly comprises a high-temperature air heater 9 and a buffer tank 10, wherein the high-temperature air heater 9 generates hot air, the temperature regulation range of the hot air is between room temperature and 400 ℃, the hot air enters the buffer tank 10, and the other end of the buffer tank 10 is connected with an injection well;
b. the gas phase extraction module consists of two vacuum pumps 2, single extraction or parallel extraction can be carried out through valve control, the front end of the extraction module is connected with a top gas outlet of the gas-liquid separation tank 1, and the rear end of the extraction module is connected with an extraction gas purification module;
c. the gas-liquid separation module consists of a gas-liquid separation tank 1, a liquid pump 4 and a gas pipeline, wherein a mixture extracted from the extraction well enters the gas-liquid separation tank 1 for gas-liquid separation, the separated liquid is conveyed to the oil-water separation module through the liquid pump 4, and the gas separated from the top is connected with the vacuum pump 2;
d. the extraction gas purification module consists of two gas adsorption towers 3, gas from the gas phase extraction module enters the adsorption towers, adsorbents are filled in the towers, the adsorbents are preferably activated carbon or molecular sieves, the two adsorption towers are controlled to be connected in series or in parallel according to set valves, the extraction gas purification module can also operate in a single tower, gas outlets of the adsorption towers are all provided with online VOCs concentration detectors, and the purified gas is exhausted into the atmosphere after meeting the emission requirement;
e. the oil-water separation module consists of an oil-water separation tank 5, a liquid pump 6, a wastewater collection tank 7 and an oil phase collection tank 8. Liquid from the gas-liquid separation module enters an oil-water separation tank for oil-water separation, separated sewage is conveyed to a waste water collection tank through a liquid pump, and separated waste oil enters an oil phase collection tank;
f. the on-line monitoring and controlling system consists of on-line monitoring equipment and a DCS control system, and realizes the automatic control and monitoring of the whole device.
g. The microorganism injection structure mainly comprises a nutrient solution tank, a bacteria solution tank and related pipe valves. The nutrient solution tank is connected with the extraction well and the injection well, and nutrient solution is injected into the extraction well and the injection well under the control of a valve; the bacteria liquid tank is connected with the extraction well and the injection well, and after the nutrient solution is injected, the microorganism is injected through the valve control.
In a second aspect, the embodiment of the present invention further provides a method for remediating fossil fuel contaminated soil by using the remediation system, including the following steps:
the method comprises the following steps of firstly, starting a vapor extraction module and a gas-liquid treatment module, wherein the vapor extraction module generates negative pressure, extracts volatile organic matters in the polluted soil through an extraction well, and treats the extracted volatile organic matters through the gas-liquid treatment module;
after the negative pressure pumping process is finished, the whole device is started, hot air generated by the hot air supply module is injected into the polluted soil to be subjected to heat enhanced gas phase extraction treatment, volatile semi-volatile heavy component organic matters in the polluted soil are extracted through the extraction well, the extracted volatile semi-volatile heavy component organic matters are treated through the gas-liquid treatment module, after the tailing stage of the heat enhanced gas phase extraction, the microorganism supply module is started again to carry out microorganism remediation, and pollutant components which are difficult to extract above C13 in the polluted soil are removed through the degradation reaction of microorganisms until the concentration of the pollutants in the well to be extracted is basically unchanged, so that the remediation of the fossil fuel polluted soil is finished.
The embodiment of the invention also provides a method for repairing the polluted soil by using the fossil fuel polluted soil repairing system, which comprises the following steps:
in the first stage, a gas phase extraction module is started firstly, negative pressure generated by the gas phase extraction module drives air to flow through porous pores of a polluted soil space for desorption, light-component volatile organic components are entrained to flow to an extraction opening of an extraction well, extraction gas enters a gas-liquid treatment module for gas-liquid separation, namely volatile light-component pollutants in the polluted soil are extracted and treated, namely the negative pressure generated by the gas phase extraction module is utilized in the first stage to drive air to flow through gaps of the polluted soil and entrain volatile light-component organic matters such as straight-chain alkane, isoparaffin, aromatic hydrocarbon and the like of a gasoline section C4-C12 until the concentration and the flow of the pollutants in the extraction well become small, and the volatile light-component organic matters in the polluted soil are removed after the extraction enters a tailing stage;
in the second stage, the hot air supply module is started, high-temperature air is introduced into the polluted soil, heat-enhanced vapor extraction is carried out, the volatile semi-volatile heavy component organic matters in the polluted soil are promoted to be transferred to the vapor phase, the desorption of volatile semi-volatile heavy component organic pollutants in soil particles is enhanced, and most heavy semi-volatile pollution components such as benzene series substances in the field soil and underground water can be removed through the injected hot air; entering a tailing stage of heat-enhanced gas-phase extraction, then starting microbial degradation repair, firstly injecting nutrient solution into the extraction well and the injection well, then injecting microbial solution, and removing heavy pollutant components which are difficult to extract in the polluted soil by more than 13 through degradation reaction of microbes.
In the first stage and the second stage, the extraction gas flow of the extraction well generally increases along with the increase of the extraction vacuum degree, and particularly, the extraction gas flow and the extraction vacuum degree can be adjusted according to the change of the extraction gas flow and the pollutant concentration under the condition of good site soil permeability in a linear relationship, so that the extraction speed of the pollutants is accelerated.
Therefore, the restoration method provided by the embodiment of the invention adopts different restoration processes in stages on the basis of fully considering the actual pollution condition of the polluted site, combines the advantages of different restoration technologies, reduces the restoration cost and shortens the restoration period while realizing the efficient standard restoration of the polluted site. Compared with a mode of soil remediation by adopting soil steam thermal desorption, the hot air injection mode has wider application range, lower cost and lower extraction amount of gas-liquid mixture needing aftertreatment, especially liquid phase pollutants. The Topsis method calculation result shows that the technology aims at the remediation of the polluted soil of the aeration zone at a production and filling station, and the approach of the technology to the ideal remediation technology is 0.68. The technology is an optimal repairing technology aiming at repairing polluted soil in an aeration zone of a production and gas station.
In an alternative embodiment, the repair method comprises the steps of:
the method comprises the steps that firstly, a gas phase extraction module and a gas-liquid treatment module are started, the gas phase extraction module is driven to generate negative pressure, the generated negative pressure drives air to flow through gaps in the polluted soil, volatile organic matters in the polluted soil are extracted through an extraction well, the extracted volatile organic matters are treated through the gas-liquid treatment module, extraction operation is finished when the concentration of the volatile organic matters in the extraction well is unchanged, and sampling detection is carried out on the concentration of pollutants in the polluted soil;
after the pumping process is finished, starting the whole device, injecting hot air generated by a hot air supply module into an injection well for heat-enhanced vapor extraction, promoting the transfer of pollutants in the polluted soil to a vapor phase, stopping the heat-enhanced vapor extraction when the concentration change of volatile semi-volatile heavy component organic matters in the pumped gas is not obvious, and sampling and detecting the concentration of the pollutants in the polluted soil; and after entering a thermal enhanced gas phase extraction tailing stage, starting a microorganism supply module to inject microorganism bacteria liquid into the extraction well and the injection well, and removing pollutant components which are difficult to extract above C13 in the polluted soil through degradation reaction of microorganisms until the pollutant concentration of the repair site meets the requirement, thereby completing the repair.
In an alternative embodiment, the hot air supply module generates hot air at a temperature between room temperature and 400 deg.C, and the hot air is injected into the injection well at an injection temperature of 180 deg.C and 300 deg.C and an injection pressure of 20-40 kPa.
In an optional implementation mode, after entering a tailing stage, starting microbial degradation remediation, firstly injecting nutrient solution into the extraction well and the injection well to enable the nutrient solution to be uniformly distributed in the polluted site, then injecting microbial solution to enable the microbial solution to be uniformly distributed in the polluted site, and after injection is completed, continuously ventilating the extraction well and the gas injection well, wherein the ventilation pressure is 5-30kPa to provide oxygen for the processes of metabolism and pollutant degradation of microorganisms.
In an alternative embodiment, the restoration method can be used for in-situ restoration of a medium-high concentration polluted site, is more suitable for restoration of an in-service polluted site, and is particularly suitable for on-site restoration of a petroleum hydrocarbon polluted site.
Therefore, the embodiment of the invention also provides a method for repairing fossil fuel polluted site soil by using the repairing system, the heat-enhanced vapor extraction-microbial degradation combined repairing device is applied for repairing, and the steps are as follows:
(1) before remediation begins, checks ensure proper connections between the remediation device, the extraction well, and the injection well.
(2) Starting a gas phase extraction system, adjusting the vacuum degree according to the field operation condition, generating negative pressure by a vacuum pump to drive air to flow through porous pores of a polluted soil space to be desorbed and carry volatile organic components to flow to an extraction opening, enabling the extracted gas to enter a gas-liquid separation module of a repair device for gas-liquid separation, enabling the separated tail gas to enter a purification module for tail gas purification, controlling an adsorption tower through a valve, and performing parallel or serial operation of the adsorption tower according to the actual condition of the repair field or operating in a single tower; the separated liquid enters an oil-water separation module for oil-water separation, and the separated sewage is collected in a wastewater collection tank and then enters a municipal sewage treatment pipe network for treatment; and the dirty oil enters an oil phase collecting tank and then is sent to a professional waste oil treatment mechanism for treatment. In the phase of gas phase extraction, the operation can be carried out at fixed time every day, the gas sampling of the extraction wells is carried out at fixed time intervals, the concentration of light-component Volatile Organic Compounds (VOCs) in each extraction well is recorded according to the daily average value, the extraction operation is finished when the concentration change of the VOCs in the extraction wells is small, and the sampling detection is carried out on the concentration of pollutants in the soil.
(3) Then starting a high-pressure hot air system, introducing high-temperature air into the injection well, carrying out heat-enhanced gas phase extraction to promote the transfer of pollutants in the polluted soil to the gas phase, gradually increasing the temperature of the high-temperature air according to the field pollution condition, and adjusting the injection pressure, wherein the temperature is generally 180-300 ℃ and the injection pressure is 20-40 kPa; the thermal enhanced extraction operation can be carried out intermittently at fixed time, extraction well gas sampling is carried out at fixed time intervals, the concentration of volatile semi-volatile heavy component organic compounds (VOCs) is detected, when the concentration change of the volatile semi-volatile heavy component organic compounds (VOCs) in the extracted gas is not obvious, the thermal enhanced extraction work is stopped, and the concentration of pollutants in the soil is sampled and detected.
(4) After entering a tailing stage, starting microbial degradation remediation, firstly injecting nutrient solution into an extraction well and an injection well, uniformly distributing the nutrient solution in a polluted field through repeated operation for many times, and then injecting microbial solution into a zone according to a pollution condition, wherein the injection amount of the microbial solution is relatively large in a heavy pollution area, and the injection amount is relatively small in a light pollution area; repeated operation for many times ensures that the injected microbial liquid is uniformly distributed in the polluted site as much as possible. After the injection of the microbial liquid is finished, the extraction well and the gas injection well are continuously ventilated, the ventilation pressure is 5-30kPa, and oxygen is provided for the metabolism of microorganisms and the pollutant degradation process. Through the degradation reaction of microorganisms, pollutant components which are difficult to extract and are above C13 in the polluted soil are removed.
(5) And in the later stage of restoration, regularly detecting the pollutant concentration of the restoration site at the frequency of 1 month, 3 months and half a year until the restoration target is reached.
The heat-enhanced vapor extraction-microbial degradation combined repair device and the repair method provided by the invention can be used for in-situ repair of a medium-high concentration polluted site, are suitable for in-service repair of a polluted site, and are particularly suitable for in-situ repair of a petroleum hydrocarbon polluted site.
The features and properties of the present invention are described in further detail below with reference to examples.
Example 1
In a laboratory, the effect of the gas phase extraction-biodegradation coupling technology (SVE-BV), the heat-enhanced gas phase extraction-biodegradation coupling technology (TSVE-BV) and the single biodegradation technology (BV) on the petroleum hydrocarbon polluted soil is compared and researched by adopting experimental soil columns, the result is shown in the figure and the figure, the test time is 76 days, and the simulated pollutant is C5-C22 gasoline and diesel oil.
The test conditions are as follows: SVE-BV extraction air volume 2m3H, the vacuum degree is 0.05MPa, and the temperature is 25 ℃; TSVE-BV extraction air volume 2m3H, the vacuum degree is 0.05MPa, and the temperature is 50 ℃; BV temperature 25 ℃ as can be seen from fig. 2 and 3, the Total Petroleum Hydrocarbon (TPH) removal rate was 88% using the TSVE-BV technique during the tail-out period at 28 d; entering a tailing period at 35d by adopting SVE-BV, wherein the TPH removal rate is 82%; the tail period was entered at 62d using BV techniques. Compared with the gas phase extraction-biodegradation coupling technology and the simple biodegradation, the technology has the advantages of excellent effect of treating the petroleum hydrocarbon polluted soil, shorter repair time and higher removal rate.
Example 2
The method comprises the steps of taking a polluted site of a certain gas station as a test area, firstly carrying out site investigation on the polluted site, and displaying that the detection rate of total petroleum hydrocarbons and benzene series in a soil sample is high and exceeds the screening value of the second-class site of GB36600, the initial total petroleum hydrocarbon TPH (C10-40) concentration of point-location soil with the highest pollution concentration is 5312mg/kg, the maximum benzene concentration is 24mg/kg, and the detection result of underground water shows that pollutants are not migrated into the underground water from the soil. And determining to adopt a heat-enhanced vapor extraction-biodegradation technology for on-site remediation according to the pollution investigation result. And (3) setting 10 extraction wells and 5 gas injection wells on site (arranging the extraction wells and the injection wells in the method shown in figure 4), and entering a repairing stage after the repairing device and the pipeline are connected.
Firstly, starting a vacuum extraction system, setting the vacuum degree to be 15-25kPa and the extraction air quantity to be 17-23Nm3Processing the extracted gas-liquid mixture in a gas-liquid processing module, after intermittent extraction for 20 days, detecting that the concentration of total petroleum hydrocarbon in soil is reduced to 4087mg/kg when the concentration of volatile organic matters in the gas extracted from each extraction well is changed very little;
starting a high-pressure hot air system, wherein the temperature of injected hot air is 180-250 ℃, the injection pressure is 20-40kPa, the average concentration of VOCs in 10 extraction wells is obviously improved, and the concentration of VOCs in the extraction wells is 0-6mg/m after the heat-enhanced extraction is carried out for 15 days3The variation range is very small, the tailing stage of heat-enhanced vapor extraction repair is entered, and the concentration of total petroleum hydrocarbon in soil is 1205 mg/kg; after entering a tailing stage, starting a microorganism supply module, entering a microorganism degradation and restoration stage, firstly injecting nutrient solution into an extraction well and an injection well to ensure that the nutrient solution is uniformly distributed in a polluted site, then injecting microorganism solution according to a pollution condition in a subarea manner, continuously introducing air, and carrying out sampling detection after 180 days, wherein the concentration of total petroleum hydrocarbon in soil is 203mg/kg, the concentration is far lower than the standard value of construction land of GB36600, the removal rate of pollutants reaches 96.2%, and benzene series is not detected. By utilizing the heat-enhanced extraction-microbial degradation coupling restoration technology, the restoration period of the polluted site is greatly shortened, and the efficient green restoration of the petroleum hydrocarbon polluted site is realized.
In summary, the embodiment of the invention provides a system and a method for repairing fossil fuel contaminated soil. The provided heat-enhanced extraction-microbial degradation combined repair device and the repair method integrate the advantages of three technologies of heat treatment, vapor extraction and microbial degradation, solve respective technical shortages, and have the following characteristics: the repairing device realizes modular and skid-mounted design, has compact structure and small occupied area, can be used for in-situ repairing of medium and high concentration polluted sites, and is preferentially suitable for in-situ repairing of petroleum hydrocarbon polluted sites; secondly, coupling a vapor extraction technology, and reducing the energy consumption and high temperature of an in-situ heat treatment technology; the efficiency of microbial remediation is improved, and the remediation period is shortened; thirdly, the efficiency of microorganism restoration and vapor extraction technology is improved and the restoration period is shortened by coupling the heat treatment technology; fourthly, coupling the microbial treatment technology, reducing the energy consumption and high temperature of the in-situ heat treatment technology; solves the tailing effect of the vapor extraction technology.
The combined repairing device and the repairing method provided by the embodiment of the invention are efficient and environment-friendly, and can effectively reduce the repairing cost of the polluted site. The combined remediation device provided by the embodiment of the invention is used for treating and remedying the petroleum hydrocarbon polluted site of a certain gas station, the removal rate of the petroleum hydrocarbon reaches more than 85%, and the final residual quantity is far lower than the standard of GB36600 construction land. The restoration method provided by the embodiment of the invention adopts different restoration processes in stages on the basis of fully considering the actual pollution condition of the polluted site, combines the advantages of different restoration techniques, reduces the restoration cost and shortens the restoration period while realizing the high-efficiency standard restoration of the polluted site. The calculation result of the Topsis method shows that the technology is the optimal repairing technology for repairing the polluted soil of the aeration zone at a production and filling station, and the approach of the technology to the ideal repairing technology calculated by the Topsis method is 0.68. Compared with single in-situ thermal desorption technology, in-situ biological ventilation technology and in-situ gas phase extraction technology, the cost can be respectively reduced by 78.3 percent, 27.6 percent and 5.0 percent, and the repair period can be respectively shortened by-33.3 percent, 86.7 percent and 84 percent.
The above is only a preferred embodiment of the present invention, and is not intended to limit the present invention, and various modifications and changes will occur to those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.
Claims (10)
1. A system for remediation of soil contaminated with fossil fuels, the system consisting essentially of: a plurality of extraction wells disposed in the contaminated site soil; a plurality of injection wells disposed in the contaminated site soil; the hot air supply module is communicated with the injection well through a hot air supply pipeline and is used for injecting hot air into the soil of the polluted site; the microorganism supply module is communicated with the injection well and the extraction well through a microorganism supply pipeline and is used for injecting microorganism liquid into the soil of the polluted site; the inlet end of the gas phase extraction module is communicated with the extraction wells through extraction pipelines, and gas and liquid containing pollutants in the soil where each extraction well is located are extracted through negative pressure; and the inlet end of the gas-liquid treatment module is communicated with the gas-phase extraction module through a conveying pipeline, and gas and liquid containing pollutants in the soil extracted by the gas-liquid extraction module are treated through gas-liquid separation.
2. The repair system of claim 1, wherein the gas-liquid treatment module comprises: the gas-liquid separation module comprises a gas outlet and a liquid outlet, wherein the gas outlet is connected with the extraction gas purification module, and the liquid outlet is connected with the oil-water separation module;
preferably, the extraction gas purification module consists of two gas adsorption towers, adsorbents are filled in the gas adsorption towers, and gas outlets of the adsorption towers are provided with online organic matter (VOCs) concentration detectors;
preferably, the oil-water separation module is composed of an oil-water separation tank, a liquid pump, a wastewater collection tank and an oil phase collection tank, and liquid from the gas-liquid separation module enters the oil-water separation tank for oil-water separation.
3. The repair system of claim 2, wherein the vapor extraction module is disposed between a gas outlet of the gas-liquid separation module and the extraction gas purification module, and the vapor extraction module is capable of delivering the gas separated by the gas-liquid separation module to the extraction gas purification module;
preferably, the vapor extraction module consists of two vacuum pumps, and single extraction or parallel extraction is performed through valve control.
4. The remediation system of claim 1 wherein said microorganism supply module is in communication with said injection and extraction wells via a microorganism supply conduit, said microorganism injection module consisting essentially of a nutrient solution tank, a bacteria solution tank and associated tubing valve components.
5. The repair system of any of claims 1-4, further comprising: and the online monitoring and control module consists of online monitoring equipment and a DCS (distributed control system) control system so as to realize automatic control and monitoring of the whole device.
6. A method of remediating fossil fuel contaminated soil using the remediation system of any one of claims 1-5, comprising the steps of:
the method comprises the following steps that firstly, a vapor extraction module and a gas-liquid treatment module are started, the vapor extraction module generates negative pressure, volatile organic matters in polluted soil are extracted through an extraction well, and the extracted volatile organic matters are treated through the gas-liquid treatment module;
after the negative pressure pumping process is finished, starting the whole device, injecting hot air generated by the hot air supply module into the polluted soil for heat-enhanced gas phase extraction treatment, pumping volatile semi-volatile heavy component organic matters out of the polluted soil through the extraction well, treating the pumped volatile semi-volatile heavy component organic matters through the gas-liquid treatment module, entering a heat-enhanced gas phase extraction tailing stage, then starting the microorganism supply module for microorganism remediation, and removing pollutant components which are difficult to extract out of the polluted soil above C13 through degradation reaction of microorganisms until the concentration of the pollutants in the extraction well is basically unchanged, thereby completing the remediation of the fossil fuel polluted soil.
7. The method of claim 6, comprising the steps of:
the method comprises the steps that firstly, a vapor extraction module and a gas-liquid treatment module are started, the vapor extraction module generates negative pressure, the generated negative pressure drives air to flow through gaps in polluted soil, volatile organic matters in the polluted soil are extracted through an extraction well, the extracted volatile organic matters are treated through the gas-liquid treatment module, extraction operation is finished when the concentration of the volatile organic matters in the extraction well is unchanged, and sampling detection is carried out on the concentration of pollutants in the polluted soil;
after the negative pressure pumping process is finished, starting the whole device, injecting hot air generated by the hot air supply module into the injection well for heat-enhanced gas-phase extraction, promoting the pollutant in the polluted soil to transfer to the gas phase, stopping the heat-enhanced gas-phase extraction when the concentration of the volatile semi-volatile heavy component organic matter in the pumped gas does not change significantly, sampling and detecting the concentration of the pollutant in the polluted soil, entering a heat-enhanced gas-phase extraction tailing stage, starting the microorganism supply module to inject microorganism bacterial liquid into the extraction well and the injection well, and removing the pollutant components which are difficult to extract above C13 in the polluted soil through the degradation reaction of microorganisms until the concentration of the pollutant in the repair site meets the requirement, thereby completing the repair.
8. The method as claimed in claim 7, wherein the hot air temperature generated by the hot air supply module is between room temperature and 400 ℃, the injection temperature for injecting the hot air into the injection well is 180-300 ℃, and the injection pressure is 20-40 kPa.
9. The method of claim 7, wherein after entering the tailing stage of the heat-enhanced vapor extraction, the microbial degradation remediation is initiated by: firstly, injecting nutrient solution into the extraction well and the injection well to ensure that the nutrient solution is uniformly distributed in a polluted field, then injecting microbial solution to ensure that the microbial solution is uniformly distributed in the polluted field, and after the injection is finished, continuously ventilating the extraction well and the injection well, wherein the ventilating pressure is kept between 5 and 30 kPa.
10. The method according to any one of claims 6 to 9, wherein the method is used for in-situ remediation of sites contaminated with high concentrations of petroleum hydrocarbons in service.
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