Construction method of biological reactor ventilation system

Abstract

The invention discloses a construction method of a biological reactor ventilation system, which comprises the following steps of: S1, calculating to obtain an air exhaust rate q of a biological reactor capable of meeting an oxygen supply balance condition on the basis that the oxygen consumption rate of microorganisms in the biological reactor is equal to the oxygen supply rate of a fan under the balance condition, and S2, on the basis of meeting the air exhaust rate q, calculating the air exhaust rate q of the biological reactor on the basis of the air exhaust rate q; calculating an air guide layer vacuum degree delta P required to be maintained by an air guide layer of the biological pile under a specific soil texture condition by utilizing an equivalent relationship in a soil permeability calculation process; thirdly, according to the air exhaust rate q and the vacuum degree delta P of the air guide layer, a negative pressure fan with the proper specification and model is selected, the negative pressure fan is used for forming a ventilation system to build the biological pile, and therefore when the biological pile is used for soil remediation, it can be guaranteed that enough ventilation capacity is achieved, soil microorganism oxygen deficit is avoided, and soil remediation efficiency is improved. And energy waste caused by excessive ventilation can be prevented.

Description

Technical Field

[0001] The invention relates to the technical field of biopile remediation of soil organic pollutants, in particular to a method for constructing a biopile ventilation system. Background Art

[0002] Biopile technology refers to a remediation process in which soil containing organic pollution is excavated and piled in an anti-seepage area equipped with a leachate collection system according to certain requirements. Organic pollutants are removed by indigenous microorganisms or exogenous high-efficiency degradation bacteria in the soil through forced ventilation and provision of appropriate amounts of water and nutrients.

[0003] The current guideline for the construction of biopile is "Technical Specifications for Biopile for Contaminated Soil Remediation Engineering" HJ 1283-2023, which lacks theoretical derivation and calculation of the overall air extraction volume of the biopile ventilation system and the negative pressure required for the air guide layer. The actual construction process still mainly relies on engineering experience parameters, and the air extraction volume and negative pressure level of the air guide layer vary greatly in different engineering cases. The lack of theoretical design and calculation of key process parameters leads to: on the one hand, it is not conducive to the large-scale design of biopile of different scales, and on the other hand, it cannot provide a reasonable reference value for the early equipment selection of the ventilation system, resulting in insufficient ventilation and hypoxia or excessive ventilation during the remediation process, which wastes energy. Summary of the invention

[0004] The technical problem to be solved by the present invention is to provide a construction method of a biopile ventilation system.

[0005] To solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] A method for constructing a biopile ventilation system, characterized by comprising:

[0007] Step S1: Take samples from the contaminated soil to prepare test soil, and conduct an oxygen consumption rate test to determine the oxygen consumption rate per unit soil volume of the test soil. Based on this calculation, we can get: the extraction rate q of the biopile that can meet the oxygen supply balance condition, the unit is m 3 ·min -1 ; Among them, the oxygen consumption rate per unit soil volume The unit is mol·min -1 ·m -3 , which indicates the rate at which the indigenous microorganisms in the test soil or the added exogenous microorganisms consume oxygen in the soil during metabolism;

[0008] Step S2, sampling the contaminated soil to prepare test soil, and conducting an air permeability test to obtain the soil air permeability K of the test soil, and based on this, calculate: when the oxygen supply of the biopile reaches the said extraction rate q, the air conduction layer vacuum ΔP of the biopile needs to be maintained, the unit is kPa, which represents the pressure difference between the atmospheric pressure on the biopile surface and the air pressure inside the air conduction layer; wherein the unit of the soil permeability K is m 3 / (㎡·kPa·min), which is a parameter strongly related to soil quality. If loose auxiliary materials such as sawdust need to be added during the biopile restoration process, the mesh size and addition ratio of the sawdust will have a great influence on the soil permeability coefficient K;

[0009] The test soil in step S1 and step S2 has the same components and proportions as the biopile soil used to construct the biopile, and the biopile soil is prepared from the contaminated soil so that the test soil is close to the soil used in the biopile remediation process; the test soil and biopile soil are formed by adding microbial agents, nutrient solution, water and auxiliary materials in a certain proportion to the contaminated soil, and then mixing them evenly, the microbial agents are exogenous microorganisms used to remove organic pollutants in the soil, and the auxiliary materials are used to change the pore conditions of the soil;

[0010] Step S3, selecting the specification and model of the negative pressure fan, so that: the air extraction speed of the negative pressure fan on the air guide layer meets the air extraction rate q, and the negative pressure vacuum degree formed by the negative pressure fan exhausting the air guide layer meets the air guide layer vacuum degree ΔP;

[0011] Step S4, constructing a biopile, comprising: burying an air guide layer below the ground, and making the top surface of the air guide layer flush with the ground, wherein the air guide layer generally adopts a PP module support structure, and its bearing capacity should be greater than that of the soil pile of the biopile, and the contact surface between the air guide layer and the underground is covered with a HDPE anti-permeability membrane; connecting the air outlet of the negative pressure fan and the inside of the air guide layer with an exhaust pipe, and the exhaust pipe is provided with a plurality of exhaust holes inside the air guide layer; laying a geomembrane on the ground, and making the geomembrane cover the top surface of the air guide layer; piling the biopile soil on the geomembrane to form a quadrangular pyramid-shaped soil pile, wherein the biopile soil is prepared from the contaminated soil; wherein the side slope of the soil pile should be controlled within a range that allows the soil pile to remain stable under natural conditions, and the surface portion of the soil pile in contact with the air may be uncovered, covered with grass, or covered with other types of covering structures through which air can pass, so as to ensure that external air can enter the soil pile through the surface, and therefore the surface of the soil pile cannot be covered with a closed and airtight membrane structure.

[0012] The working principle of the above-mentioned biopile is as follows: when the biopile is carrying out soil remediation, the air guide layer is evacuated by a negative pressure fan to generate negative pressure, so that the external air flows from the surface to the inside of the soil pile, so as to achieve the purpose of supplying oxygen to soil microorganisms, thereby enabling soil microorganisms to remove and remediate organic pollutants that contaminate the soil.

[0013] Therefore, the present invention calculates the suction rate q of the biopile that can meet the oxygen supply balance condition based on the oxygen consumption rate of the microorganisms in the biopile being equal to the oxygen supply rate of the fan under equilibrium conditions through step S1, and calculates the vacuum degree ΔP of the air conducting layer of the biopile under specific soil conditions by using the equivalent relationship of the soil permeability calculation process on the basis of satisfying the suction rate q through step S2; and then selects a negative pressure fan of suitable specifications and models based on the suction rate q and the vacuum degree ΔP of the air conducting layer through step S3, and constructs the biopile by using the negative pressure fan to form a ventilation system, so that: when the biopile is used for soil remediation, it can ensure sufficient ventilation to avoid hypoxia of soil microorganisms, and can also prevent excessive ventilation from causing energy waste.

[0014] Preferably: the oxygen consumption rate determination test in step S1 and the air permeability coefficient determination test in step S2 are both implemented based on a soil column test device;

[0015] See also Figure 5 The soil column test device includes a vertical tube body, a negative pressure chamber and a vacuum pump. The side wall of the vertical tube body is connected with a soil gas sampling hole. The upper tube mouth of the vertical tube body is detachably installed with a sealing cover plate. The lower tube mouth of the vertical tube body is fixed on the top surface of the negative pressure chamber, and the lower tube mouth of the vertical tube body is connected to the inner cavity of the negative pressure chamber through a sieve plate, and the sieve holes of the sieve plate can pass air but not soil; the air inlet of the vacuum pump is connected to the inner cavity of the negative pressure chamber through a flow meter, and the inner cavity of the negative pressure chamber is connected with a pressure gauge.

[0016] Preferably, the oxygen consumption rate determination test in step S1 includes:

[0017] Step S1-1, filling the vertical tube with test soil;

[0018] Step S1-2, opening the sealing cover plate to allow external air to ventilate the test soil in the vertical tube body through the upper tube opening of the vertical tube body; and continuously detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole until the detected oxygen content reaches the oxygen content of the air, and then sealing the upper tube opening of the vertical tube body with the sealing cover plate to end the ventilation of the test soil; wherein the oxygen content measured through the soil gas sampling hole when the ventilation of the test soil ends is recorded as The unit is %;

[0019] Step S1-3, in a state where the sealing cover plate seals the upper tube opening of the vertical tube body, detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole; wherein the oxygen content measured through the soil gas sampling hole at the end of step S1-3 is recorded as The unit is %, and the measured and The time difference is recorded as the reaction time Δt, in min;

[0020] Step S1-4, recording the average room temperature when executing step S1-2 and step S1-3, and querying to obtain the gas molar volume v corresponding to the average room temperature, in units of L / mol;

[0021] Step S1-5: Calculate the oxygen consumption rate per unit soil volume of the test soil according to the following formula:

[0022] Wherein, ω is the non-capillary porosity of the test soil, in %.

[0023] Here, steps S1-1 to S1-5 can be repeated three times to obtain three sets of data, and the average is taken as the oxygen consumption rate per unit soil volume.

[0024] Preferably, the air permeability coefficient determination test in step S2 includes:

[0025] Step S2-1, with the sealing cover plate open and the soil gas sampling hole closed, filling the vertical tube with test soil having a height equal to the height H of the soil pile;

[0026] Step S2-2, start the vacuum pump to evacuate the negative pressure chamber until the negative pressure chamber reaches a stable state where the internal pressure of the negative pressure chamber no longer changes, and start timing to measure the ventilation volume Q and the vacuum degree Δp of the negative pressure chamber within a preset ventilation time ΔT; wherein the ventilation time ΔT is in units of min, and the ventilation volume Q is the ventilation volume of the negative pressure chamber evacuated by the vacuum pump within the ventilation time ΔT, measured by the flow meter, and the unit is m 3 ; The vacuum degree Δp of the negative pressure chamber is the pressure difference between the inner cavity pressure of the negative pressure chamber and the atmospheric pressure in the stable state, measured by the pressure gauge, in kPa;

[0027] Step S2-3, calculate the soil permeability coefficient K of the test soil corresponding to the height H by the following formula:

[0028]

[0029] Where, the aerated soil area F is the cross-sectional area of ​​the soil column formed by the test soil filled in the vertical tube, and the unit is m 2 ; η 25 is the air viscosity corresponding to the air temperature of 25°C, in Pa·s, η T is the air viscosity corresponding to the test environment temperature of t℃, in Pa·s; the soil permeability coefficient K is in m 3 / (㎡·kPa·min), its physical meaning is: when the viscosity of the gas is 1P (1P=0.1Pa·s), the amount of air passing through per unit area and unit soil thickness per unit time under unit air pressure; because the viscosity of the gas is too small, it is usually calibrated with the air viscosity at a fixed temperature (such as 25℃) as the standard.

[0030] Wherein, in step S1, the pumping rate q is calculated according to the following formula:

[0031]

[0032] The above formula represents the oxygen supply balance condition, that is, the oxygen consumption per unit time of the biopile = the oxygen supply per unit time of the biopile ventilation system; where, is the oxygen consumption rate per unit soil volume, V is the soil volume of the biopile, in m 3 , is the molar concentration of oxygen in the air, in mol·m -3 .

[0033] The biopile of the present invention has a quadrangular pyramidal shape. Assuming that its bottom width is M, bottom length is L, height is H, all in m, and slope is i, the calculation formula for the biopile volume V is: V=[(L-2H / i)×(M-2H / i)+L×M+(2L-2H / i)×(2M-2H / i)]×H / 6.

[0034] The molar concentration of oxygen in the above air The value under ideal conditions can be taken, that is: at 25°C, 1.01×10 5 Pa, the molar concentration of oxygen in the air is calculated according to the physical properties of air. The volume fraction of oxygen in the air is 20.9%, 25°C, 1.01×10 5 The molar volume of the gas at Pa is 24.5 L mol -1 , then the corresponding molar concentration of oxygen in the air is 8.53 mol·m -3 ; The molar concentration of oxygen in the above air The molar concentration of oxygen in the current air can also be calculated based on the measured atmospheric temperature and air oxygen content.

[0035] Wherein, in step S2, the vacuum degree ΔP of the air conducting layer is calculated according to the following formula:

[0036] q=(K×F×ΔP / H)×(η 25 / η t );

[0037] Where q is the air extraction rate, K is the soil permeability coefficient, and F is the soil surface area of ​​the biopile in contact with the air, in m 2 , represents the cross-sectional area of ​​the soil pile where the external air enters the biopile, which is equivalent to the sum of the areas of the four sides and the top of the quadrangular pyramid-shaped soil pile. H is the thickness of the soil layer above the air-conducting layer of the biopile, that is, the height of the soil pile of the biopile. η 25 is the air viscosity corresponding to the air temperature of 25°C, in Pa·s, η t It is the air viscosity corresponding to the test environment temperature of t℃, in Pa·s.

[0038] Compared with the prior art, the present invention has the following beneficial effects:

[0039] The present invention calculates the suction rate q of the biopile that can meet the oxygen supply balance condition based on the fact that the oxygen consumption rate of microorganisms in the biopile is equal to the oxygen supply rate of the fan under equilibrium conditions through step S1, and calculates the air conduction layer vacuum ΔP required to be maintained by the air conduction layer 1 of the biopile under specific soil conditions through step S2 on the basis of satisfying the suction rate q and using the equivalent relationship of the soil permeability calculation process; and then through step S3, based on the suction rate q and the air conduction layer vacuum ΔP, selects a negative pressure fan 3 of suitable specifications and models, and uses the negative pressure fan 3 to form a ventilation system to build the biopile, so that: when the biopile is used for soil remediation, it can ensure sufficient ventilation to avoid soil microbial hypoxia, and can also prevent excessive ventilation from causing energy waste. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] The present invention is further described in detail below in conjunction with the accompanying drawings and specific embodiments:

[0041] Figure 1 It is a schematic diagram of the three-dimensional structure of the biopile in the present invention;

[0042] Figure 2 It is a schematic diagram of the planar structure of the biopile in the present invention;

[0043] Figure 3 for Figure 2 AA section view;

[0044] Figure 4 for Figure 2 BB cross-sectional view;

[0045] Figure 5 It is a structural schematic diagram of the soil column test device in the present invention. DETAILED DESCRIPTION

[0046] The present invention is described in detail below in conjunction with the embodiments and the accompanying drawings to help those skilled in the art better understand the inventive concept of the present invention. However, the protection scope of the claims of the present invention is not limited to the following embodiments. For those skilled in the art, all other embodiments obtained without creative work without departing from the inventive concept of the present invention belong to the protection scope of the present invention.

[0047] like Figures 1 to 4 As shown, the present invention discloses a method for constructing a biopile ventilation system, comprising:

[0048] Step S1: Take samples from the contaminated soil to prepare test soil, and conduct an oxygen consumption rate test to determine the oxygen consumption rate per unit soil volume of the test soil. Based on this calculation, we can get: the extraction rate q of the biopile that can meet the oxygen supply balance condition, the unit is m 3 ·min -1 ; Among them, the oxygen consumption rate per unit soil volume The unit is mol·min -1 ·m -3 , which indicates the rate at which the indigenous microorganisms in the test soil or the added exogenous microorganisms consume oxygen in the soil during metabolism;

[0049] Wherein, in step S1, the pumping rate q is calculated according to the following formula:

[0050]

[0051] The above formula represents the oxygen supply balance condition, that is, the oxygen consumption per unit time of the biopile = the oxygen supply per unit time of the biopile ventilation system; where, is the oxygen consumption rate per unit soil volume, V is the soil volume of the biopile, in m 3 , is the molar concentration of oxygen in the air, in mol·m -3 .

[0052] The biopile of the present invention has a quadrangular pyramidal shape. Assuming that its bottom width is M, bottom length is L, height is H, all in m, and slope is i, the calculation formula for the biopile volume V is: V=[(L-2H / i)×(M-2H / i)+L×M+(2L-2H / i)×(2M-2H / i)]×H / 6.

[0053] The molar concentration of oxygen in the above air The value under ideal conditions can be taken, that is: at 25°C, 1.01×10 5Pa, the molar concentration of oxygen in the air is calculated according to the physical properties of air. The volume fraction of oxygen in the air is 20.9%, 25°C, 1.01×10 5 The molar volume of the gas at Pa is 24.5 L mol -1 , then the corresponding molar concentration of oxygen in the air is 8.53 mol·m -3 ; The molar concentration of oxygen in the above air The molar concentration of oxygen in the current air can also be calculated based on the measured atmospheric temperature and air oxygen content.

[0054] Step S2, sampling the contaminated soil to prepare the test soil, and conducting the air permeability test to obtain the soil air permeability K of the test soil, and then calculating the following: when the oxygen supply of the biopile reaches the said extraction rate q, the air conduction layer vacuum ΔP of the biopile air conduction layer 1 needs to maintain, the unit is kPa, which represents the pressure difference between the atmospheric pressure on the surface of the soil pile 2 of the biopile and the air pressure inside the air conduction layer 1; wherein the unit of the soil air permeability K is m 3 / (㎡·kPa·min), which is a parameter strongly related to soil quality. If loose auxiliary materials such as sawdust need to be added during the biopile restoration process, the mesh size and addition ratio of the sawdust will have a great influence on the soil permeability coefficient K;

[0055] Wherein, in step S2, the vacuum degree ΔP of the air conducting layer is calculated according to the following formula:

[0056] q=(K×F×ΔP / H)×(η 25 / η t );

[0057] Where q is the air extraction rate, K is the soil permeability coefficient, and F is the soil surface area of ​​the biopile that is in contact with the air, in m 2 , represents the cross-sectional area of ​​the soil pile 2 of the biopile through which the external air enters, which is equivalent to the sum of the areas of the four sides and the top of the quadrangular pyramid-shaped soil pile 2, H is the thickness of the soil layer above the air guide layer 1 of the biopile, that is, the height of the soil pile 2 of the biopile, η 25 is the air viscosity corresponding to the air temperature of 25°C, in Pa·s, η t It is the air viscosity corresponding to the test environment temperature of t℃, in Pa·s.

[0058] Among them, the preparation components and proportions of the test soil in step S1 and step S2 are the same as those of the biopile soil used to build the biopile, and the biopile soil is prepared from the contaminated soil so that the test soil is close to the soil used in the biopile remediation process; the test soil and biopile soil are formed by adding microbial agents, nutrient solution, water and auxiliary materials in a certain proportion on the basis of the contaminated soil, and then mixing them evenly, the microbial agents are exogenous microorganisms used to remove organic pollutants in the soil, and the auxiliary materials are used to change the pore conditions of the soil.

[0059] Preferably: the oxygen consumption rate determination test in step S1 and the air permeability coefficient determination test in step S2 are both implemented based on a soil column test device;

[0060] See also Figure 5 The soil column test device includes a vertical tube body 6, a negative pressure chamber 7 and a vacuum pump 8. The side wall of the vertical tube body 6 is connected with a soil gas sampling hole 6a. The upper tube mouth of the vertical tube body 6 is detachably installed with a sealing cover plate 9. The lower tube mouth of the vertical tube body 6 is fixed on the top surface of the negative pressure chamber 7, and the lower tube mouth of the vertical tube body 6 is connected to the inner cavity of the negative pressure chamber 7 through a sieve plate 10, and the sieve holes of the sieve plate 10 can pass air but not soil; the air inlet of the vacuum pump 8 is connected to the inner cavity of the negative pressure chamber 7 through a flow meter 11, and the inner cavity of the negative pressure chamber 7 is connected with a pressure gauge 12.

[0061] Preferably, the oxygen consumption rate determination test in step S1 includes:

[0062] Step S1-1, filling the vertical tube 6 with test soil;

[0063] Step S1-2, opening the sealing cover plate 9 so that the external air can ventilate the test soil in the vertical tube body 6 through the upper tube opening of the vertical tube body 6; and continuously detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole 6a until the detected oxygen content reaches the oxygen content of the air, and then sealing the upper tube opening of the vertical tube body 6 with the sealing cover plate 9 to end the ventilation of the test soil; wherein, the oxygen content measured through the soil gas sampling hole 6a when the ventilation of the test soil ends is recorded as The unit is %;

[0064] Step S1-3, in a state where the sealing cover plate 9 seals the upper tube opening of the vertical tube body 6, the oxygen content in the gas generated by the test soil is detected through the soil gas sampling hole 6a; wherein the oxygen content measured through the soil gas sampling hole 6a at the end of step S1-3 is recorded as The unit is %, and the measured and The time difference is recorded as the reaction time Δt, in min;

[0065] Step S1-4, recording the average room temperature when executing step S1-2 and step S1-3, and querying to obtain the gas molar volume v corresponding to the average room temperature, in units of L / mol;

[0066] Step S1-5: Calculate the oxygen consumption rate per unit soil volume of the test soil according to the following formula:

[0067] Wherein, ω is the non-capillary porosity of the test soil, in %.

[0068] Here, steps S1-1 to S1-5 can be repeated three times to obtain three sets of data, and the average is taken as the oxygen consumption rate per unit soil volume.

[0069] Preferably, the air permeability coefficient determination test in step S2 includes:

[0070] Step S2-1, with the sealing cover plate 9 opened and the soil gas sampling hole 6a closed, filling the vertical tube 6 with test soil having a height equal to the height H of the soil pile 2;

[0071] Step S2-2, start the vacuum pump 8 to evacuate the negative pressure chamber 7 until the negative pressure chamber 7 reaches a stable state where the internal pressure of the negative pressure chamber 7 no longer changes, and start timing to measure the ventilation volume Q and the vacuum degree Δp of the negative pressure chamber within a preset ventilation time ΔT; wherein the ventilation time ΔT is in units of min, and the ventilation volume Q is the ventilation volume of the vacuum pump 8 evacuating the negative pressure chamber 7 within the ventilation time ΔT, measured by the flow meter 11, and the unit is m 3 The vacuum degree of the negative pressure chamber Δp is the pressure difference between the inner cavity pressure of the negative pressure chamber 7 and the atmospheric pressure in the stable state, measured by the pressure gauge 12, in kPa;

[0072] Step S2-3, calculate the soil permeability coefficient K of the test soil corresponding to the height H by the following formula:

[0073]

[0074] Wherein, the aerated soil area F is the cross-sectional area of ​​the soil column formed by the test soil filled in the vertical pipe body 6, and the unit is m 2 ; η 25 is the air viscosity corresponding to the air temperature of 25°C, in Pa·s, η t is the air viscosity corresponding to the test environment temperature of t℃, in Pa·s; the soil permeability coefficient K is in m 3 / (m 2·kPa·min), its physical meaning is: when the viscosity of the gas is 1P (1P=0.1Pa·s), the amount of air that passes through per unit area and unit soil thickness per unit time under unit air pressure; due to the low viscosity of the gas, it is usually calibrated with the air viscosity at a fixed temperature (such as 25℃) as the standard.

[0075] Step S3, selecting the specification and model of the negative pressure fan 3 so that: the air extraction speed of the negative pressure fan 3 on the air guide layer 1 satisfies the air extraction rate q, and the negative pressure vacuum degree formed by the negative pressure fan 3 exhausting the air guide layer 1 satisfies the air guide layer vacuum degree ΔP.

[0076] Step S4, constructing a biopile, comprising: burying an air guide layer 1 below the ground, and making the top surface of the air guide layer 1 flush with the ground, wherein the air guide layer 1 generally adopts a PP module support structure, and its bearing capacity should be greater than the soil pile 2 of the biopile, and the contact surface between the air guide layer 1 and the ground is covered with a HDPE anti-permeability membrane; connecting the air outlet of the negative pressure fan 3 and the inside of the air guide layer 1 with an air extraction pipe 4, and the air extraction pipe 4 is provided with a plurality of air extraction holes 4a in the air guide layer 1; laying a geomembrane 5 on the ground, and making the geomembrane 5 cover the ground; The top surface of the air-conducting layer 1; the biopile soil is piled on the geomembrane 5 to form a quadrangular pyramid-shaped soil pile 2, and the biopile soil is prepared from the contaminated soil; wherein the side slope of the soil pile 2 should be controlled within a range that allows the soil pile 2 to remain stable under natural conditions, and the surface portion of the soil pile 2 in contact with the air may be uncovered, covered with grass, or covered with other types of covering structures through which air can pass, so as to ensure that external air can enter the soil pile 2 through the surface, and therefore the surface of the soil pile 2 cannot be covered with a closed and airtight membrane structure.

[0077] The working principle of the above-mentioned biopile is as follows: when the biopile is used for soil remediation, the negative pressure fan 3 is used to evacuate the air guide layer 1 to generate negative pressure, so that the external air flows from the surface to the inside of the soil pile 2, so as to achieve the purpose of supplying oxygen to the soil microorganisms, thereby realizing the removal and remediation of organic pollutants in the contaminated soil by the soil microorganisms.

[0078] Therefore, the present invention calculates the suction rate q of the biopile that can meet the oxygen supply balance condition based on the oxygen consumption rate of the microorganisms in the biopile being equal to the oxygen supply rate of the fan under equilibrium conditions through step S1, and calculates the air conduction layer vacuum ΔP required to be maintained by the air conduction layer 1 of the biopile under specific soil conditions through step S2 on the basis of satisfying the suction rate q by using the equivalent relationship of the soil permeability calculation process; and then selects the negative pressure fan 3 of suitable specifications and models based on the suction rate q and the air conduction layer vacuum ΔP through step S3, so as to construct the biopile by forming a ventilation system with the negative pressure fan 3, so that: when the biopile is used for soil remediation, it can ensure sufficient ventilation to avoid hypoxia of soil microorganisms, and can also prevent excessive ventilation from causing energy waste.

[0079] The present invention is not limited to the above-mentioned specific implementation modes. According to the above-mentioned contents, in accordance with the common technical knowledge and customary means in the field, without departing from the above-mentioned basic technical ideas of the present invention, the present invention can also make other various forms of equivalent modifications, replacements or changes, all of which fall within the protection scope of the present invention.

Claims

1. A method for constructing a biopile ventilation system, characterized in that: include: Step S1: Take samples from the contaminated soil to prepare test soil, and conduct an oxygen consumption rate test to determine the oxygen consumption rate per unit soil volume of the test soil. Based on this, we can calculate: the air extraction rate q at which the biopile can meet the oxygen supply balance condition; Step S2, sampling the contaminated soil to prepare test soil, and conducting an air permeability test to obtain the soil air permeability K of the test soil, so as to calculate the vacuum degree ΔP of the air conduction layer (1) of the biopile that needs to be maintained when the oxygen supply of the biopile reaches the said extraction rate q; Wherein, the preparation components and proportions of the test soil in step S1 and step S2 are the same as those of the biopile soil used for building the biopile, and the biopile soil is prepared from the contaminated soil; Step S3, selecting the specifications and models of the negative pressure fan (3) so that: the air extraction speed of the negative pressure fan (3) on the air guide layer (1) satisfies the air extraction rate q, and the negative pressure vacuum degree formed by the negative pressure fan (3) extracting air from the air guide layer (1) satisfies the air guide layer vacuum degree ΔP; Step S4, constructing a biopile, comprising: burying an air guide layer (1) below the ground, and making the top surface of the air guide layer (1) flush with the ground; connecting the air outlet of a negative pressure fan (3) and the inside of the air guide layer (1) with an air extraction pipe (4), and the air extraction pipe (4) is provided with a plurality of air extraction holes (4a) inside the air guide layer (1); laying a geomembrane (5) on the ground, and making the geomembrane (5) cover the top surface of the air guide layer (1); and piling the biopile soil on the geomembrane (5) to form a quadrangular pyramid-shaped soil pile (2), wherein the biopile soil is prepared from the contaminated soil.

2. The method for constructing a biopile ventilation system according to claim 1, characterized in that: The oxygen consumption rate determination test described in step S1 and the air permeability coefficient determination test described in step S2 are both implemented based on a soil column test device; The soil column test device comprises a vertical tube body (6), a negative pressure chamber (7) and a vacuum pump (8); the side wall of the vertical tube body (6) is connected to a soil gas sampling hole (6a); the upper tube mouth of the vertical tube body (6) is detachably mounted with a sealing cover plate (9); the lower tube mouth of the vertical tube body (6) is fixed to the top surface of the negative pressure chamber (7); the lower tube mouth of the vertical tube body (6) is connected to the inner cavity of the negative pressure chamber (7) through a sieve plate (10); the sieve holes of the sieve plate (10) can pass air but cannot pass soil; the air inlet of the vacuum pump (8) is connected to the inner cavity of the negative pressure chamber (7) through a flow meter (11); the inner cavity of the negative pressure chamber (7) is connected to a pressure gauge (12).

3. The method for constructing a biopile ventilation system according to claim 2, characterized in that: The oxygen consumption rate determination test described in step S1 includes: Step S1-1, filling the vertical tube (6) with test soil; Step S1-2, opening the sealing cover plate (9) so that the external air can ventilate the test soil in the vertical tube body (6) through the upper tube opening of the vertical tube body (6); and continuously detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole (6a) until the detected oxygen content reaches the oxygen content of air, and then sealing the upper tube opening of the vertical tube body (6) with the sealing cover plate (9) to terminate the ventilation of the test soil; wherein the oxygen content measured through the soil gas sampling hole (6a) when the ventilation of the test soil is terminated is recorded as Step S1-3, in a state where the sealing cover plate (9) seals the upper tube opening of the vertical tube body (6), detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole (6a); wherein the oxygen content measured through the soil gas sampling hole (6a) at the end of step S1-3 is recorded as Will measure and The time difference is recorded as the reaction time Δt; Step S1-4, recording the average room temperature when executing step S1-2 and step S1-3, and querying to obtain the gas molar volume v corresponding to the average room temperature; Step S1-5: Calculate the oxygen consumption rate per unit soil volume of the test soil according to the following formula: Wherein, ω is the non-capillary porosity of the test soil.

4. The method for constructing a biopile ventilation system according to claim 2, characterized in that: The air permeability coefficient measurement test described in step S2 includes: Step S2-1, with the sealing cover plate (9) open and the soil gas sampling hole (6a) closed, filling the vertical tube (6) with test soil having a height equal to the height H of the soil pile (2); Step S2-2, start the vacuum pump (8) to evacuate the negative pressure chamber (7), until the negative pressure chamber (7) reaches a stable state where the inner cavity pressure no longer changes, and then start timing to measure the ventilation volume Q and the negative pressure chamber vacuum degree Δp within a preset ventilation time ΔT; wherein the ventilation volume Q is the ventilation volume of the negative pressure chamber (7) evacuated by the vacuum pump (8) within the ventilation time ΔT, measured by the flow meter (11); the negative pressure chamber vacuum degree Δp is the pressure difference between the inner cavity pressure of the negative pressure chamber (7) and the atmospheric pressure in the stable state, measured by the pressure gauge (12); Step S2-3, calculate the soil permeability coefficient K of the test soil corresponding to the height H by the following formula: Wherein, the aerated soil area F is the cross-sectional area of ​​the soil column formed by the test soil filled in the vertical pipe (6); η 25 is the air viscosity corresponding to the air temperature of 25°C, η t is the air viscosity corresponding to the test environment temperature of t℃.

5. The method for constructing a biopile ventilation system according to any one of claims 1 to 4, characterized in that: In step S1, the pumping rate q is calculated according to the following formula: In the formula, is the oxygen consumption rate per unit soil volume, V is the soil volume of the biopile, is the molar concentration of oxygen in air.

6. The method for constructing a biopile ventilation system according to any one of claims 1 to 4, characterized in that: In step S2, the vacuum degree ΔP of the gas conducting layer is calculated according to the following formula: q=(K×F×ΔP / H)×(η 25 / or t ); Where q is the air extraction rate, K is the soil permeability coefficient, F is the soil surface area of ​​the biopile (2) in contact with the air, H is the thickness of the soil layer above the biopile's air-conducting layer (1), and η 25 is the air viscosity corresponding to the air temperature of 25°C, η t is the air viscosity corresponding to the test environment temperature of t℃.

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