Multi-level energy efficiency evaluation method for contaminated soil in-situ heat treatment coupling technology remediation

Abstract

The invention discloses a multi-level energy efficiency evaluation method for contaminated soil in-situ heat treatment coupling technology remediation. The method comprises the following steps: S1, contaminated land parcel remediation; s2, calculating a pollutant removal rate; s3, comprehensively evaluating the reutilization performance of the land parcel: S3-1, determining a comprehensive calculation formula; s3-2, weight determination is carried out; s3-4, checking the judgment matrix; and S4, performing multi-level energy efficiency evaluation. According to the method, on the basis of a land utilization mode, according to use scenes of different land utilization modes, human health risks, building safety risks, ecological risks, underground water utilization and soil fertility during subsequent land development and utilization are comprehensively considered, and related standards in China are combined; the method for evaluating the comprehensive remediation effect of the localized in-situ heat treatment and coupling technology thereof is constructed, and a more comprehensive evaluation method is provided for comparison and selection of organic pollution site remediation technologies in China.

Description

Technical Field

[0001] The present invention relates to the technical field of soil treatment, and in particular to a multi-level energy efficiency evaluation method for the restoration of contaminated soil by in-situ thermal treatment coupling technology. Background Art

[0002] At present, the remediation of contaminated soil in my country still focuses on human health risk control. When choosing remediation technology, people usually only focus on the removal effect of target pollutants, while ignoring the changes in the properties of soil and groundwater caused by different remediation technologies. However, soil and groundwater are both important functional carriers, and changes in their properties will inevitably affect the subsequent development and utilization of land. Therefore, it is necessary to select the best remediation technology based on the way the land is used and the comprehensive consideration of the positive and negative effects of the remediation technology on the subsequent development and utilization of land.

[0003] In different construction land scenarios, in addition to paying attention to human health risks, the availability of land after contaminated soil remediation in terms of planting vegetation, building construction, groundwater extraction, etc. also needs to be paid attention to. However, the current selection of contaminated soil remediation technologies in my country usually only considers the cost, cycle and control effect of the remediation technology on human health risks, without considering other needs for subsequent actual development and utilization of land (such as building construction, park green space development, etc.). Therefore, there is a certain one-sidedness in the current selection of remediation technologies.

[0004] On the other hand, remediation technology has also been proven to change the properties of soil and groundwater after remediation, and this change may be beneficial or harmful. For example, in the joint remediation of petroleum hydrocarbon contaminated soil by plants and microorganisms, the fertility of the soil after remediation has been significantly improved due to the need to apply fertilizers in plant remediation technology (Ma Wencui, 2017); while thermal desorption technology also significantly changes soil properties while removing target pollutants, mainly reflected in the changes in soil organic matter content, soil mineral composition, soil pH, plant-available nutrients, soil microbial communities, soil mechanical properties and other indicators, and the degree of change is significantly affected by heating temperature (Estabragh et al., 2018; O'Brien et al., 2018; Weng, Lin, and Lee, 2020); Taking soil microbial community indicators as an example, heating is usually not good for microorganisms in the soil. Even at a lower heating temperature (50°C to 125°C), it can cause the death of some of the majority of microorganisms; under heating conditions, the main microorganisms in the microbial community gradually become heat-resistant bacteria. Although thermal desorption usually kills microorganisms in the soil, when soil remediation is completed, microorganisms can reproduce in the soil, and their recolonization is determined by factors such as the temperature of the repaired soil, the organic matter content in the soil, the available nutrients in the soil, and the inoculation of foreign microorganisms (O'Brien et al., 2018).

[0005] Therefore, it is necessary to conduct a comprehensive assessment of the site after remediation by in-situ heat treatment coupling technology from multiple aspects. Summary of the invention

[0006] In view of the above-mentioned problems, the present invention provides a multi-level energy efficiency evaluation method for the remediation of contaminated soil by in-situ thermal treatment coupling technology.

[0007] The technical solution of the present invention is:

[0008] The multi-level energy efficiency evaluation method for the remediation of contaminated soil by in-situ thermal treatment coupled technology includes the following steps:

[0009] S1. Remediation of contaminated land: The contaminated land is remediated by in-situ thermal treatment coupling technology;

[0010] S2. Calculation of pollutant removal rate: Calculate the removal rate of each pollutant in the polluted land according to the concentration of pollutants before and after the restoration of the polluted land, and screen out the pollutants with the highest boiling point, and calculate the maximum removal rate of the pollutant with the highest boiling point, which is calculated as η bmax , the unit is mg / kg;

[0011] S3. Comprehensive evaluation of land reuse performance:

[0012] The human health risk index HRI, groundwater quality index GQI, building suitability index CSI, ecological risk index ERI, and soil fertility index SFI are selected as evaluation indicators. The weights of each evaluation indicator are calculated first, and then the comprehensive evaluation index RSI of soil and groundwater reuse of the contaminated land is determined according to the above evaluation indicators and their corresponding weights. The reuse performance of the land is comprehensively evaluated by the comprehensive evaluation index RSI;

[0013] S3-1. Determine the weight of each evaluation indicator:

[0014] Construct a judgment matrix for the five evaluation indicators, and set the judgment matrix to be A=(a ij )n×n, that is:

[0015]

[0016] Where n = 5, i represents the i-th evaluation index, i∈[1~5], j represents the j-th evaluation index, j∈[1~5], n represents the total number of evaluation indexes, a ij Indicates the relative weights of the two evaluation indicators in the next layer relative to the previous layer. ij The quantitative standard of the judgment value is assigned using a 9-level scaling method;

[0017] Calculate the geometric mean W of each row of the judgment matrix A i , and its calculation formula is as follows:

[0018]

[0019] The geometric mean W i The result of standardization is the weight W of the evaluation index. i 0 , and its calculation formula is as follows:

[0020]

[0021] Calculate the weight W of the human health risk index in turn H , weight of groundwater quality index W G , the weight of the building suitability index W B , the weight of ecological risk index W E , weight of soil fertility index W S ;

[0022] S3-2. Calculate the comprehensive evaluation index RSI of soil and groundwater reuse of the polluted land. The calculation formula is as follows:

[0023] RSI=HRI×W H +GQI×W G +BAI×WB +ERI×W E +SFI×W S

[0024] S3-3, comprehensively evaluating the reuse performance of the plot through the reuse comprehensive evaluation index RSI, the larger the reuse comprehensive evaluation index RSI, the worse the site reuse performance, and the smaller the reuse comprehensive evaluation index RSI, the better the site reuse performance;

[0025] S4, multi-level energy efficiency evaluation: Taking into account the target pollutant removal efficiency based on the restoration of the contaminated land in step S2 and the reuse performance of the restored land in step S3, the energy efficiency index β is introduced as an indicator parameter for multi-level energy efficiency evaluation, and its calculation formula is as follows:

[0026]

[0027] Where X2 represents the volume energy consumption of contaminated soil and water, that is, the energy consumed for site remediation per unit volume of contaminated soil or groundwater, in kJ / m 3 ;

[0028] The larger the β value, the higher the overall energy efficiency of contaminated site remediation.

[0029] Furthermore, the heat treatment coupling technology in step S1 includes one or more of steam-enhanced extraction, in-situ heat-enhanced microbial degradation, and in-situ heat-enhanced chemical oxidation / reduction.

[0030] Description: Coupling in-situ thermal desorption with heat treatment can improve the remediation effect of contaminated sites. It is also a method that will be widely used in the future, which can reflect the forward-looking nature of the evaluation method of the present invention.

[0031] Furthermore, the calculation formula of the removal rate η of each pollutant in step S2 is as follows:

[0032]

[0033] Where, η represents the removal rate of pollutants, in %; C T,i represents the remediation target value of the i-th pollutant, in mg / kg; C i It represents the concentration of the i-th pollutant before remediation, in mg / kg.

[0034] Furthermore, the calculation formula of the human health risk index HRI in step S3 is as follows:

[0035]

[0036] Where, HRI irepresents the human health risk index of the i-th sample in soil or groundwater; N s Represents the total number of soil samples from contaminated plots; N g Indicates the total number of groundwater samples from the contaminated plot;

[0037] in,

[0038] Where, HRI i，j represents the human health risk index of the jth pollutant in the i-th sample of soil or groundwater;

[0039] in,

[0040] In the formula, C i,j represents the content of the jth pollutant in the i-th sample of soil or groundwater, C Tj represents the remediation target value of the jth pollutant in soil or groundwater. The remediation target of pollutants in soil is calculated in accordance with the Technical Guidelines for Risk Assessment of Soil Pollution in Construction Land (HJ 25.3), and the remediation target of pollutants in groundwater is calculated in accordance with the Guidelines for Health Risk Assessment of Groundwater Pollution. Ij It represents the ideal value of the jth pollutant, that is, the concentration of the pollutant in uncontaminated soil and groundwater. For organic pollutants, the ideal value is 0, and for heavy metal pollutants, the ideal value is the background value. HRI i,j The output value is between 0 and 1, where 0 represents no risk to human health and 0 < HRI i,j ≤0.5 means that the risk to human health is acceptable, 0.5<HRI i,j ≤1 means the risk to human health is unacceptable.

[0041] Furthermore, the calculation formula of the groundwater quality index GQI in step S3 is as follows:

[0042]

[0043] In the formula, GQI i represents the water quality index of the i-th groundwater sample in the polluted plot; N represents the total number of groundwater samples in the polluted plot;

[0044] in,

[0045] In the formula, GQI i,j represents the index of the jth water quality index in the i-th groundwater sample;

[0046] in,

[0047] In the formula, C i,jrepresents the content of the jth water quality index in the i-th groundwater sample, CS i,j It indicates the standard limit of a water quality index in a groundwater sample. The Class IV water quality of Groundwater Quality Standard (GB / T 14848-2017) is used as the water quality comparison benchmark. j It indicates the ideal value of a water quality index in groundwater samples. The ideal value refers to the value of each index of pure water. Except for the pH value of 7.0, the ideal values ​​of other indexes are 0.

[0048] Furthermore, the calculation formula of the building suitability index CSI in step S3 is as follows:

[0049]

[0050] In the formula, COR represents the corrosiveness of the contaminated land; EMP represents the mechanical properties of the contaminated land;

[0051] Among them, COR conducts corresponding corrosion evaluation according to the type of building materials and groundwater occurrence, referring to the Code for Geotechnical Engineering Investigation (GB50021-2001). The code divides the corrosion level into four levels: slight, weak, medium and strong. Normalized calculation is performed according to the corrosion level, with slight set to 0, weak set to 0.33, medium set to 0.67, and strong set to 1. Referring to the corrosion evaluation principles in the Code for Geotechnical Engineering Investigation (GB50021-2001), the maximum value of the corrosion results of multiple soil and groundwater samples is taken as the comprehensive corrosion evaluation result of the local block;

[0052] in,

[0053] Where, EMP i An index representing the mechanical properties of the i-th sample in the contaminated plot;

[0054] in,

[0055] Where, EMP i，j represents the index of the jth mechanical index in the i-th sample of the contaminated plot;

[0056] in,

[0057] Where V i,j represents the jth mechanical index value of the i-th sample in the contaminated plot, V 0,j It represents the jth mechanical index value in the uncontaminated control soil of the contaminated plot.

[0058] Furthermore, the calculation formula of the ecological risk index ERI in step S3 is as follows:

[0059]

[0060] Where, ERI i represents the risk index of all pollutants in the i-th sample of the contaminated plot soil to all reference ecological receptors; N represents the total number of contaminated plot soil samples;

[0061] in,

[0062] Where, ERI i,k represents the risk index of all pollutants in the i-th sample of the contaminated soil for the k-th ecological receptor,

[0063] in,

[0064] Where, ERI i,j,k It represents the risk index of the jth pollutant in the i-th sample of the contaminated soil for the k-th ecological receptor;

[0065] in,

[0066] In the formula, C i,j represents the content of the jth pollutant in the i-th sample of the soil in the polluted plot, CT j,k It represents the screening value of the jth pollutant in the soil of the contaminated plot for the kth ecological receptor, referring to the soil ecological screening value published by the US Environmental Protection Agency, CI j It represents the ideal value of the jth pollutant in the soil of the polluted plot, that is, the concentration of the pollutant in the uncontaminated soil. For organic pollutants, the ideal value is 0, and for heavy metal pollutants, the ideal value is the background value.

[0067] Furthermore, the calculation formula of the soil fertility index SFI in step S3 is as follows:

[0068]

[0069] Where SFI i represents the fertility characteristic index of the i-th soil sample in the contaminated plot; N represents the total number of soil samples in the contaminated plot;

[0070] in,

[0071] Where SFI i,j represents the index of the jth fertility index in the i-th sample of the contaminated plot soil;

[0072] in,

[0073] Where, CF i,j represents the content of the jth fertility index in the i-th sample of the contaminated soil, CFT,j It represents the reference value of the jth fertility index of the soil in the polluted plot, which is taken from Table C.1 in "Diagnosis and Evaluation of Soil Fertility of Cultivated Land in Southern China NY / T1749-2009", which contains the recommended reference standard values ​​of the main physical and chemical indicators for soil fertility evaluation in southern China, including organic matter, total nitrogen, available phosphorus, available potassium, and cation exchange capacity.

[0074] Furthermore, the 9-level scaling method in step S3 is:

[0075] Scale 1 means that the two evaluation indicators have the same importance;

[0076] Scale 3 means that compared with the two evaluation indicators, the former is slightly more important than the latter;

[0077] Scale 5 means that compared with the two evaluation indicators, the former is obviously more important than the latter;

[0078] Scale 7 means that compared with the two evaluation indicators, the former is extremely important than the latter;

[0079] Scale 9 means that compared with the two evaluation indicators, the former is more important than the latter;

[0080] Scales 2, 4, 6, and 8 represent the middle values ​​of the above adjacent judgments;

[0081] The reciprocal of the scale 1 to 9 represents the importance of comparing the corresponding two evaluation indicators in the order of exchange, that is, the judgment a of the comparison of evaluation indicator i with j ij , then the judgment a of factor j compared with i ji =1 / a ij .

[0082] Furthermore, the step S3 also includes step S3-4,

[0083] S3-4. Judgment matrix test: solving the largest characteristic root λ max , and its calculation formula is as follows:

[0084]

[0085] Among them, λ mi It represents the eigenvalue of each row of the judgment matrix A, and its calculation formula is as follows:

[0086]

[0087] In the formula, A Wi 0 Represents the judgment matrix A and weight W i 0 The matrix dot multiplication result is calculated as follows:

[0088]

[0089] Then solve the consistency ratio CR, which is calculated as follows:

[0090]

[0091] In the formula, CI is the consistency index, and its calculation formula is as follows:

[0092]

[0093] The RI value is determined by referring to the average random consistency index table, as follows:

[0094] When n is 1, RI is 0;

[0095] When n is 2, RI is 0;

[0096] When n is 3, RI is 0.52;

[0097] When n is 4, RI is 0.89;

[0098] When n is 5, RI is 1.12;

[0099] When n is 6, RI is 1.26;

[0100] When n is 7, RI is 1.36;

[0101] When n is 8, RI is 1.41;

[0102] When n is 9, RI is 1.46;

[0103] When n is 10, RI is 1.49;

[0104] CR=0 means that the judgment matrix A is completely consistent. The larger the CR is, the more serious the inconsistency of the judgment matrix A is. If CR<0.1, it is considered that the consistency of the judgment matrix A is within the allowable range, and the judgment matrix A can be used for evaluation.

[0105] The beneficial effects of the present invention are:

[0106] (1) The multi-level energy efficiency evaluation method for the in-situ heat treatment coupled technology remediation of contaminated soil of the present invention is based on land use methods and according to the usage scenarios of different land use methods. It comprehensively considers the human health risks, building safety risks, ecological risks, groundwater utilization and soil fertility faced in subsequent land development and utilization, and combines relevant standards in my country to construct a localized in-situ heat treatment and its coupled technology comprehensive remediation effect evaluation method, which provides a more comprehensive evaluation method for the comparison and selection of organic contaminated site remediation technologies in my country.

[0107] (2) The method of constructing a judgment matrix in the hierarchical analysis method of the multi-level energy efficiency evaluation method for the remediation of contaminated soil by in-situ thermal treatment coupling technology of the present invention is the consistent matrix method, that is: not all factors are compared together, but are compared with each other. At this time, a relative scale is used to minimize the difficulty of comparing factors of different natures to improve accuracy; hierarchical single sorting and consistency test are carried out on the constructed judgment matrix. Hierarchical single sorting is to calculate the weight value of the importance order of all nodes connected to a node in the previous layer according to the judgment matrix, so as to sort the importance according to the weight, and finally obtain a scientific and reasonable weight value. BRIEF DESCRIPTION OF THE DRAWINGS

[0108] Figure 1 It is a flow chart of the multi-level energy efficiency evaluation method for the in-situ heat treatment coupling technology remediation of contaminated soil of the present invention;

[0109] Figure 2 It is a plan view of the contaminated land restoration by the in-situ heat treatment coupling technology in Experimental Example 1 of the present invention;

[0110] Figure 3 It is the energy efficiency evaluation result of the thermal desorption zone and the coupling zone under different scenarios in Experimental Example 2 of the present invention. DETAILED DESCRIPTION

[0111] Example 1

[0112] The multi-level energy efficiency evaluation method for the remediation of contaminated soil by in-situ thermal treatment coupled technology includes the following steps:

[0113] S1. Remediation of contaminated land: The contaminated land is remediated by in-situ thermal desorption coupled with steam enhanced extraction;

[0114] S2. Calculation of pollutant removal rate: The removal rate of each pollutant in the polluted land is calculated based on the concentration of pollutants before and after the restoration of the polluted land. The calculation formula of the removal rate η of each pollutant is as follows:

[0115]

[0116] Where, η represents the removal rate of pollutants, in %; C T,i represents the remediation target value of the i-th pollutant, in mg / kg; C i represents the concentration of the i-th pollutant before remediation, in mg / kg; and screens out the pollutant with the highest boiling point, and calculates the maximum removal rate of the pollutant with the highest boiling point, which is η bmax , the unit is mg / kg; the larger the index is, the more serious the pollution level of the site is;

[0117] S3. Comprehensive evaluation of land reuse performance:

[0118] The human health risk index HRI, groundwater quality index GQI, building suitability index CSI, ecological risk index ERI, and soil fertility index SFI are selected as evaluation indicators. The weights of each evaluation indicator are calculated first, and then the comprehensive evaluation index RSI of soil and groundwater reuse of the contaminated land is determined according to the above evaluation indicators and their corresponding weights. The reuse performance of the land is comprehensively evaluated by the comprehensive evaluation index RSI;

[0119] S3-1. Determine the weight of each evaluation indicator:

[0120] Construct a judgment matrix for the five evaluation indicators, and set the judgment matrix to be A=(a ij )n×n, that is:

[0121]

[0122] Where n = 5, i represents the i-th evaluation index, i∈[1~5], j represents the j-th evaluation index, j∈[1~5], n represents the total number of evaluation indexes, a ij Indicates the relative weights of the two evaluation indicators in the next layer relative to the previous layer. ij The quantitative standard of the judgment value is assigned using a 9-level scaling method;

[0123] The 9-level scale is:

[0124] Scale 1 means that the two evaluation indicators have the same importance;

[0125] Scale 3 means that compared with the two evaluation indicators, the former is slightly more important than the latter;

[0126] Scale 5 means that compared with the two evaluation indicators, the former is obviously more important than the latter;

[0127] Scale 7 means that compared with the two evaluation indicators, the former is extremely important than the latter;

[0128] Scale 9 means that compared with the two evaluation indicators, the former is more important than the latter;

[0129] Scales 2, 4, 6, and 8 represent the middle values ​​of the above adjacent judgments;

[0130] The reciprocal of the scale 1 to 9 represents the importance of comparing the corresponding two evaluation indicators in the order of exchange, that is, the judgment a of the comparison of evaluation indicator i with j ij , then the judgment a of factor j compared with i ji =1 / a ij ;

[0131] Calculate the geometric mean W of each row of the judgment matrix A i , and its calculation formula is as follows:

[0132]

[0133] The geometric mean W i The result of standardization is the weight W of the evaluation index. i 0 , and its calculation formula is as follows:

[0134]

[0135] Calculate the weight W of the human health risk index in turn H , weight of groundwater quality index W G , the weight of the building suitability index W B , the weight of ecological risk index W E , weight of soil fertility index W S ;

[0136] S3-2. Calculate the comprehensive evaluation index RSI of soil and groundwater reuse of the polluted land. The calculation formula is as follows:

[0137] RSI=HRI×W H +GQI×W G +BAI×W B +ERI×W E +SFI×W S

[0138] The calculation formula of human health risk index HRI is as follows:

[0139]

[0140] Where, HRI i represents the human health risk index of the i-th sample in soil or groundwater; N s Represents the total number of soil samples from contaminated plots; N g Indicates the total number of groundwater samples from the contaminated plot;

[0141] The calculation formula of groundwater quality index GQI is as follows:

[0142]

[0143] In the formula, GQI i represents the water quality index of the i-th groundwater sample in the polluted plot; N represents the total number of groundwater samples in the polluted plot;

[0144] in,

[0145] In the formula, GQI i,jrepresents the index of the jth water quality index in the i-th groundwater sample;

[0146] in,

[0147] In the formula, C i,j represents the content of the jth water quality index in the i-th groundwater sample, CS i,j It indicates the standard limit of a water quality index in a groundwater sample. The Class IV water quality of Groundwater Quality Standard (GB / T 14848-2017) is used as the water quality comparison benchmark. j It indicates the ideal value of a water quality index in groundwater samples. The ideal value refers to the value of each index of pure water. Except for the pH value of 7.0, the ideal values ​​of other indexes are 0.

[0148] The calculation formula of the building suitability index CSI is as follows:

[0149]

[0150] In the formula, COR represents the corrosiveness of the contaminated land; EMP represents the mechanical properties of the contaminated land;

[0151] Among them, COR conducts corresponding corrosion evaluation according to the type of building materials and groundwater occurrence, referring to the Code for Geotechnical Engineering Investigation (GB50021-2001). The code divides the corrosion level into four levels: slight, weak, medium and strong. Normalized calculation is performed according to the corrosion level, with slight set to 0, weak set to 0.33, medium set to 0.67, and strong set to 1. Referring to the corrosion evaluation principles in the Code for Geotechnical Engineering Investigation (GB50021-2001), the maximum value of the corrosion results of multiple soil and groundwater samples is taken as the comprehensive corrosion evaluation result of the local block;

[0152] in,

[0153] Where, EMP i An index representing the mechanical properties of the i-th sample in the contaminated plot;

[0154] in,

[0155] Where, EMP i，j represents the index of the jth mechanical index in the i-th sample of the contaminated plot;

[0156] in,

[0157] Where V i,j represents the jth mechanical index value of the i-th sample in the contaminated plot, V 0,j represents the value of the jth mechanical index in the unpolluted control soil of the polluted plot;

[0158] The calculation formula of ecological risk index ERI is as follows:

[0159]

[0160] Where, ERI i represents the risk index of all pollutants in the i-th sample of the contaminated plot soil to all reference ecological receptors; N represents the total number of contaminated plot soil samples;

[0161] in,

[0162] Where, ERI i,k represents the risk index of all pollutants in the i-th sample of the contaminated soil for the k-th ecological receptor,

[0163] in,

[0164] Where, ERI i,j,k It represents the risk index of the jth pollutant in the i-th sample of the contaminated soil for the k-th ecological receptor;

[0165] in,

[0166] In the formula, C i,j represents the content of the jth pollutant in the i-th sample of the soil in the polluted plot, CT j,k It represents the screening value of the jth pollutant in the soil of the contaminated plot for the kth ecological receptor, referring to the soil ecological screening value published by the US Environmental Protection Agency, CI j It represents the ideal value of the jth pollutant in the soil of the polluted plot, that is, the concentration of the pollutant in the uncontaminated soil. For organic pollutants, the ideal value is 0, and for heavy metal pollutants, the ideal value is the background value;

[0167] The calculation formula of soil fertility index SFI is as follows:

[0168]

[0169] Where SFI i represents the fertility characteristic index of the i-th soil sample in the contaminated plot; N represents the total number of soil samples in the contaminated plot;

[0170] in,

[0171] Where SFI i,j represents the index of the jth fertility index in the i-th sample of the contaminated plot soil;

[0172] in,

[0173] Where, CF i,j represents the content of the jth fertility index in the i-th sample of the contaminated soil, CF T,j It represents the reference value of the jth fertility index of the soil in the polluted plot, which is taken from Table C.1 of the "Diagnosis and Evaluation of Soil Fertility of Cultivated Land in Southern China NY / T1749-2009" Recommended Reference Standard Values ​​of the Main Physical and Chemical Indicators for Soil Fertility Evaluation in Southern China, including organic matter, total nitrogen, available phosphorus, available potassium, and cation exchange capacity;

[0174] S3-3, comprehensively evaluating the reuse performance of the plot through the reuse comprehensive evaluation index RSI, the larger the reuse comprehensive evaluation index RSI, the worse the site reuse performance, and the smaller the reuse comprehensive evaluation index RSI, the better the site reuse performance;

[0175] S3-4. Judgment matrix test: solving the largest characteristic root λ max , and its calculation formula is as follows:

[0176]

[0177] Among them, λ mi It represents the eigenvalue of each row of the judgment matrix A, and its calculation formula is as follows:

[0178]

[0179] In the formula, A Wi 0 Represents the judgment matrix A and weight W i 0 The matrix dot multiplication result is calculated as follows:

[0180]

[0181] Then solve the consistency ratio CR, which is calculated as follows:

[0182]

[0183] In the formula, CI is the consistency index, and its calculation formula is as follows:

[0184]

[0185] The RI value is determined by referring to the average random consistency index table, as follows:

[0186] When n is 1, RI is 0;

[0187] When n is 2, RI is 0;

[0188] When n is 3, RI is 0.52;

[0189] When n is 4, RI is 0.89;

[0190] When n is 5, RI is 1.12;

[0191] When n is 6, RI is 1.26;

[0192] When n is 7, RI is 1.36;

[0193] When n is 8, RI is 1.41;

[0194] When n is 9, RI is 1.46;

[0195] When n is 10, RI is 1.49;

[0196] CR = 0 means that the judgment matrix A is completely consistent. The larger the CR is, the more serious the inconsistency of the judgment matrix A is. If CR < 0.1, it is considered that the consistency of the judgment matrix A is within the allowable range, and the judgment matrix A can be used for evaluation. If CR ≥ 0.1, this method may have errors and needs to be used with caution. However, in the following experimental examples, we have collected a large amount of data from different regions and found that the values ​​of multiple groups of experimental data are basically within 0.1, so this method can be used in most cases.

[0197] S4, multi-level energy efficiency evaluation: Taking into account the target pollutant removal efficiency based on the restoration of the contaminated land in step S2 and the reuse performance of the restored land in step S3, the energy efficiency index β is introduced as an indicator parameter for multi-level energy efficiency evaluation, and its calculation formula is as follows:

[0198]

[0199] Where X2 represents the volume energy consumption of contaminated soil and water, that is, the energy consumed for site remediation per unit volume of contaminated soil or groundwater, in kJ / m 3 ; The smaller the index is, the lower the energy consumption is;

[0200] The larger the β value, the higher the overall energy efficiency of contaminated site remediation.

[0201] Example 2

[0202] The difference between this embodiment and embodiment 1 is that:

[0203] S1. Remediation of contaminated land: The contaminated land is remediated by in-situ thermal desorption treatment coupled with in-situ thermally enhanced chemical oxidation / reduction.

[0204] Example 3

[0205] The difference between this embodiment and embodiment 1 is that:

[0206] S1. Remediation of contaminated land: The contaminated land is remediated by in-situ thermal desorption treatment coupled with in-situ thermally enhanced microbial degradation.

[0207] Example 4

[0208] The difference between this embodiment and embodiment 1 is that:

[0209] S1. Remediation of contaminated land: The contaminated land is remediated by in-situ thermal desorption treatment coupled with steam-enhanced extraction, in-situ thermally enhanced microbial degradation, and in-situ thermally enhanced chemical oxidation / reduction.

[0210] Experimental Example 1

[0211] Next, we apply the method in Example 1 to actual plots, with the aim of exploring the computability of the comprehensive evaluation index RSI for soil and groundwater reuse of contaminated plots.

[0212] The site was originally the site of Tianjin Chemical Reagent Factory No. 1. The main pollutants in the soil are vinyl chloride, 1,2-dichloroethane, trichloroethylene and chloroform; the main pollutants in the groundwater are 1,1,1,2-tetrachloroethane, 1,1-dichloroethane, bromobenzene and methyl bromide. The contaminated site is equipped with in-situ thermal desorption remediation areas and in-situ thermal desorption coupled chemical oxidation remediation areas, such as Figure 2 shown.

[0213] According to the evaluation method provided in Example 1, we evaluate 6 land use methods, as shown in Table 1:

[0214] Table 1 Typical land development and utilization methods under different scenarios

[0215]

[0216] The results obtained after the comprehensive evaluation of the land reuse performance in step S3 are shown in Tables 2 to 8:

[0217] Table 2 Scenario 1 judgment matrix and consistency test results

[0218]

[0219] Table 3 Judgment matrix and consistency test results for scenario 2

[0220]

[0221]

[0222] Table 4. Judgment matrix of scenario three and consistency test results

[0223]

[0224] Table 5. Judgment matrix of the four scenarios and consistency test results

[0225]

[0226] Table 6 Judgment matrix and consistency test results of scenario five

[0227]

[0228] Table 7 Six-time judgment matrix and consistency test results of the scenario

[0229]

[0230] Table 8 Comprehensive evaluation index of soil and groundwater reuse in different scenarios

[0231]

[0232] Experimental Example 2

[0233] Next, we continue to explore the feasibility of the multi-level energy efficiency evaluation method of the present invention. The experimental area is the Hefei Magang demonstration site, and the contaminated soil area in the experimental area is 1835.7m 2 The maximum contamination depth is 7.5m, and the repair earthwork volume is 12952.65m 3 The pollution factors and maximum concentrations in this area are benzo[a]pyrene (369mg / kg), dibenzo[a,h]anthracene (78.5mg / kg), petroleum hydrocarbons C10-C40 (8060mg / kg), naphthalene (583mg / kg), phenanthrene (247mg / kg), and anthracene (136mg / kg). The pollutants exceeding the standard are benzo[a]pyrene and dibenzo[a,h]anthracene, and the remediation target values ​​are 1.52mg / kg.

[0234] According to the comprehensive evaluation of the land reuse performance in step S3, five reuse evaluation indicators of the thermal desorption zone and the coupling zone are calculated as shown in Table 9:

[0235] Table 9 Evaluation results of thermal desorption zone and coupling zone reuse

[0236]

[0237] Finally, according to the multi-level energy efficiency evaluation in step S4, the energy efficiency index β of thermal desorption and coupling zone under different scenarios of the site is obtained as shown in Table 10:

[0238] Table 10 Evaluation results of thermal desorption zone and coupling zone reuse

[0239]

[0240] It is estimated that the removal rates of benzo[a]pyrene in the coupling zone are 15.6%-99.2%, and the removal rates of dibenzo[a,h]anthracene are 5.0%-96.2%; the removal rates of benzo[a]pyrene in the in-situ thermal desorption control zone are 32.9%-79.6%, and the removal rates of dibenzo[a,h]anthracene are 15.6%-80.8%.

[0241] According to step S4, the comprehensive energy efficiency evaluation results of the thermal coupling area and the in-situ thermal desorption control area in the experimental area under 6 different scenarios are calculated as follows: Figure 3 As shown in the figure, in scenarios 1 to 3, when groundwater is used for drinking, the comprehensive energy efficiency value of thermal coupling technology is 2.87×10 -6 ~3.14×10 -6 The comprehensive energy efficiency of thermal desorption technology is 3.59×10 -6 ~3.79×10 -6 In comparison, the comprehensive energy efficiency of thermal coupling technology is only 80-89% of that of thermal desorption technology. In scenarios 4 to 6, when groundwater is used for drinking, the comprehensive energy efficiency of thermal coupling technology is 3.49×10 -6 ~4.81×10 -6 The comprehensive energy efficiency of thermal desorption technology is 2.21×10 -6 ~2.36×10 -6 ; In comparison, the comprehensive energy efficiency of thermal coupling technology is 0.5 to 1.16 times that of thermal desorption technology. Therefore, based on the comprehensive evaluation of energy consumption, restoration goals, efficiency and reusability, under the current state, the energy efficiency of in-situ thermal desorption technology in scenarios 1 to 3 is better than that of thermal coupling technology; the energy efficiency of thermal coupling technology in scenarios 4 to 6 is better than that of in-situ thermal desorption technology. Since soil and groundwater have natural recovery capabilities and some coupling technologies have delayed effects, dynamic evaluation can be carried out to accurately reflect their energy efficiency.

Claims

1. A multi-level energy efficiency assessment method for the remediation of contaminated soil by in-situ thermal treatment coupled technology, characterized in that: The following steps are involved: S1. Remediation of contaminated land: The contaminated land is remediated using in-situ thermal treatment coupled technology; S2. Calculation of pollutant removal rate: Calculate the removal rate of each pollutant in the contaminated land according to the concentration of pollutants before and after remediation, and screen out the pollutants with the highest boiling point. Calculate the maximum removal rate of the pollutant with the highest boiling point, which is η bmax , unit is mg / kg; S3. Comprehensive evaluation of land reuse performance: The human health risk index (HRI), groundwater quality index (GQI), building suitability index (CSI), ecological risk index (ERI), and soil fertility index (SFI) were selected as evaluation indicators. The weights of each evaluation indicator were first calculated. Then, the comprehensive evaluation index (RSI) of soil and groundwater reuse of the contaminated land was determined based on the above evaluation indicators and their corresponding weights. The RSI was used to comprehensively evaluate the reuse performance of the land. S3-1. Determine the weight of each evaluation indicator: Construct a judgment matrix for the five evaluation indicators, and set the judgment matrix as A=(a ij )n×n, that is: Among them, n=5, i represents the i-th evaluation index, i∈[1~5], j represents the j-th evaluation index, j∈[1~5], n represents the total number of evaluation indicators, a ij Indicates the relative weight of the two evaluation indicators in the next layer relative to the previous layer. ij The quantitative standard of the judgment value is assigned using a 9-level scaling method; Calculate the geometric mean W of each row of the judgment matrix A i , which is calculated as follows: The geometric mean W i The result of standardization is the weight of the evaluation index W i 0 , which is calculated as follows: Calculate the weight W of the human health risk index in sequence H , weight of groundwater quality index W G , the weight of the building suitability index W B , the weight of ecological risk index W E , weight of soil fertility index W S ; S3-2. Calculate the comprehensive evaluation index (RSI) of soil and groundwater reuse for the contaminated land. The calculation formula is as follows: RSI=HRI×W H +GQI×W G +BAI×W B +ERI×W E +SFI×W S S3-3. Comprehensively evaluate the reuse performance of the land parcel using the reuse comprehensive evaluation index (RSI). The larger the RSI, the worse the site's reuse performance; the smaller the RSI, the better the site's reuse performance. S4. Multi-level energy efficiency evaluation: Taking into account the target pollutant removal efficiency based on the remediation of the contaminated land in step S2 and the reuse performance of the remediated land in step S3, the energy efficiency index β is introduced as an indicator parameter for the multi-level energy efficiency evaluation. The calculation formula is as follows: Where X2 represents the volume energy consumption of contaminated soil and water, that is, the energy consumed per unit volume of contaminated soil or groundwater for site remediation, in kJ / m 3 ; The larger the β value, the higher the comprehensive energy efficiency of contaminated site remediation.

2. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The heat treatment coupling technology in step S1 includes one or more of steam-enhanced extraction, in-situ heat-enhanced microbial degradation, and in-situ heat-enhanced chemical oxidation / reduction.

3. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The calculation formula for the removal rate η of each pollutant in step S2 is as follows: Where, η represents the removal rate of pollutants, the unit is %; C T,i represents the remediation target value of the i-th pollutant, in mg / kg; C i It represents the concentration of the i-th pollutant before remediation, in mg / kg.

4. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The calculation formula of the human health risk index HRI in step S3 is as follows: Where, HRI i represents the human health risk index of the i-th sample in soil or groundwater; N s Indicates the total number of soil samples from contaminated plots; N g Indicates the total number of groundwater samples from the contaminated plot; in, Where, HRI i，j represents the human health risk index of the jth pollutant in the i-th soil or groundwater sample; in, Where C i,j Indicates the content of the jth pollutant in the i-th sample of soil or groundwater, CT j represents the remediation target value of the jth pollutant in soil or groundwater, CI j It represents the ideal value of the jth pollutant, that is, the concentration of the pollutant in uncontaminated soil and groundwater. For organic pollutants, the ideal value is 0, and for heavy metal pollutants, the ideal value is the background value. i,j The output value is between 0 and 1, where 0 represents no risk to human health and 0 < HRI i,j ≤0.5 means the risk to human health is acceptable, 0.5<HRI i,j ≤1 means the risk to human health is unacceptable.

5. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The calculation formula of the groundwater quality index GQI in step S3 is as follows: Where, GQI i represents the water quality index of the i-th groundwater sample in the contaminated plot; N represents the total number of groundwater samples in the contaminated plot; in, Where, GQI i,j represents the index of the jth water quality index in the i-th groundwater sample; in, Where C i,j represents the content of the jth water quality index in the i-th groundwater sample, CS i,j Indicates the standard limit of a water quality index in a groundwater sample, CI j It indicates the ideal value of a water quality indicator in the groundwater sample. The ideal value refers to the value of each indicator of pure water. Except for the pH value of 7.0, the ideal values ​​of other indicators are 0.

6. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The calculation formula of the building suitability index CSI in step S3 is as follows: Where COR represents the corrosiveness of the contaminated land; EMP represents the mechanical properties of the contaminated land; in, Where, EMP i The index representing the mechanical properties of the i-th sample in the contaminated plot; in, Where, EMP i，j represents the index of the jth mechanical index in the i-th sample of the contaminated plot; in, Where V i,j represents the jth mechanical index value of the i-th sample in the contaminated plot, V 0,j It represents the jth mechanical index value in the uncontaminated control soil of the contaminated plot.

7. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The calculation formula of the ecological risk index ERI in step S3 is as follows: Where, ERI i represents the risk index of all pollutants in the i-th sample of the contaminated plot soil to all reference ecological receptors; N represents the total number of soil samples from the contaminated plot; in, Where, ERI i,k represents the risk index of all pollutants in the i-th sample of the contaminated soil for the k-th ecological receptor, in, Where, ERI i,j,k represents the risk index of the jth pollutant in the i-th sample of the contaminated soil for the k-th ecological receptor; in, Where C i,j Indicates the content of the jth pollutant in the i-th sample of the contaminated soil, CT j,k represents the screening value of the jth pollutant in the soil of the polluted plot for the kth ecological receptor, CI j It represents the ideal value of the jth pollutant in the contaminated soil, that is, the concentration of the pollutant in the uncontaminated soil. For organic pollutants, the ideal value is 0, and for heavy metal pollutants, the ideal value is the background value.

8. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The calculation formula of the soil fertility index SFI in step S3 is as follows: Where SFI i represents the fertility characteristic index of the i-th soil sample in the contaminated plot; N represents the total number of soil samples in the contaminated plot; in, Where SFI i,j represents the index of the jth fertility index in the i-th sample of the contaminated plot soil; in, Where, CF i,j represents the content of the jth fertility index in the i-th sample of the contaminated soil, CF T,j It represents the reference value of the jth fertility index of the soil in the polluted plot.

9. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1 is characterized in that: The 9-level scaling method in step S3 is: Scale 1 means that the two evaluation indicators have the same importance; Scale 3 means that compared with the two evaluation indicators, the former is slightly more important than the latter; Scale 5 means that compared with the two evaluation indicators, the former is obviously more important than the latter; Scale 7 means that compared with the two evaluation indicators, the former is extremely important than the latter; Scale 9 means that compared with the two evaluation indicators, the former is more important than the latter; Scales 2, 4, 6, and 8 represent the middle values ​​of the above adjacent judgments; The reciprocal of the scale 1 to 9 represents the importance of comparing the corresponding two evaluation indicators in the exchange order, that is, the judgment a of the comparison of evaluation indicators i and j ij , then the judgment a of factor j compared with i ji =1 / a ij .

10. The multi-level energy efficiency assessment method for contaminated soil remediation using in-situ thermal treatment coupled technology according to claim 1, characterized in that: The step S3 also includes step S3-4, S3-4. Judgment Matrix Test: Solving for the Maximum Eigenvalue λ max , which is calculated as follows: Among them, λ mi It represents the eigenvalue of each row of the judgment matrix A, and its calculation formula is as follows: Where A Wi 0 Represents the judgment matrix A and weight W i 0 The matrix dot multiplication result is calculated as follows: Then solve the consistency ratio CR, which is calculated as follows: Where CI is the consistency index, and its calculation formula is as follows: The RI value is determined by referring to the average random consistency index table, as follows: When n is 1, RI is 0; When n is 2, RI is 0; When n is 3, RI is 0.52; When n is 4, RI is 0.89; When n is 5, RI is 1.12; When n is 6, RI is 1.26; When n is 7, RI is 1.36; When n is 8, RI is 1.41; When n is 9, RI is 1.46; When n is 10, RI is 1.49; CR=0 means that the judgment matrix A is completely consistent. The larger the CR is, the more serious the inconsistency of the judgment matrix A is. If CR<0.1, it is considered that the consistency of the judgment matrix A is within the allowable range, and the judgment matrix A can be used for evaluation.

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