A method for constructing a bio-digester aeration system

Abstract

The application discloses a construction method of a bio-heap ventilation system, and comprises the following steps: S1, based on the fact that the oxygen consumption rate of microorganisms in the bio-heap is equal to the oxygen supply rate of a fan under a balance condition, the air extraction rate q of the bio-heap satisfying the oxygen supply balance condition is calculated; S2, based on the air extraction rate q, the equivalent relationship of the soil air permeability calculation process is used to calculate the air guide layer vacuum degree ΔP required by the air guide layer of the bio-heap under specific soil conditions; and S3, based on the air extraction rate q and the air guide layer vacuum degree ΔP, a negative pressure fan with appropriate specifications and models is selected to form a ventilation system by using the negative pressure fan to construct the bio-heap, so that when the bio-heap is used for soil remediation, sufficient ventilation can be ensured to avoid oxygen deficiency of soil microorganisms, and excessive ventilation can be prevented to avoid energy waste.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of biopile remediation of soil organic pollutants, in particular to a construction method of a biopile aeration system. BACKGROUND

[0002] Biopile technology refers to excavating soil containing organic pollutants and stacking it in an impermeable area with a leachate collection system according to certain requirements, providing appropriate moisture and nutrients through forced aeration, and using indigenous microorganisms in the soil or exogenous high-efficiency degrading bacteria to remove organic pollutants.

[0003] Currently, the construction guidelines for biopiles are "Polluted Soil Remediation Engineering Technical Specifications Biopile" HJ 1283-2023, which lacks theoretical derivation and calculation of the overall air extraction rate of the biopile aeration system and the required negative pressure of the air guide layer. In the actual construction process, it still mainly relies on engineering experience parameters, and the air extraction rate and negative pressure level of the air guide layer of different engineering cases differ greatly. The lack of theoretical design and calculation of key process parameters leads to: on the one hand, it is not conducive to the design of different scale biopiles, and on the other hand, it cannot provide reasonable reference value for the selection of equipment in the early stage of the aeration system, causing insufficient aeration in the remediation process, causing anaerobic conditions or excessive aeration wasting energy. SUMMARY

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

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

[0006] A construction method of a biopile aeration system, characterized in that it comprises:

[0007] Step S1, sample preparation from contaminated soil to prepare test soil, and perform oxygen consumption rate determination test to determine the unit soil volume oxygen consumption rate of the test soil Accordingly, the air extraction rate q of the biopile that can meet the oxygen supply balance condition is calculated as follows: m 3 ·min -1 ; wherein the unit soil volume oxygen consumption rate has a unit of mol·min -1 ·m -3 , indicating the rate at which indigenous microorganisms in the test soil or added exogenous microorganisms consume oxygen in the soil during the metabolic process;

[0008] Step S2, sample preparation from contaminated soil to prepare test soil, and carry out air permeability coefficient determination test, and determine the soil air permeability coefficient K of the test soil, so as to calculate: when the oxygen supply of the bio-pile reaches the air extraction rate q, the air guide layer of the bio-pile needs to maintain the air guide layer vacuum degree ΔP, unit: kPa, which represents the pressure difference between the atmospheric pressure of the soil pile surface of the bio-pile and the internal air pressure of the air guide layer; wherein, the unit of soil air permeability coefficient K is m 3 / (㎡·kPa·min), which is a parameter closely related to soil quality. If wood chips or other loose auxiliary materials are added during the bio-pile repair process, the mesh number and addition ratio of the wood chips have a great influence on the soil air permeability coefficient K;

[0009] The preparation components and proportions of the test soil in steps S1 and S2 are the same as the bio-pile soil used to build the bio-pile, and the bio-pile soil is prepared from the contaminated soil, so that the test soil is close to the soil used in the bio-pile repair process; the test soil and the bio-pile soil are formed by adding bacteria, nutrient solution, moisture and auxiliary materials in a certain proportion on the basis of the contaminated soil, and then mixing uniformly, the bacteria are exogenous microorganisms for removing organic pollutants in the soil, and the auxiliary materials are used to change the pore condition of the soil;

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

[0011] Step S4, build a bio-pile, including: burying the 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 the bearing capacity thereof should be greater than that of the soil pile of the bio-pile, and the contact surface between the air guide layer and the ground is covered with an HDPE impermeable film; connect the air extraction port of the negative pressure fan and the inside of the air guide layer with an air extraction pipe, and the air extraction pipe is provided with a plurality of air extraction holes in the inside of the air guide layer; lay a geomembrane on the ground and cover the top surface of the air guide layer with the geomembrane; pile up the bio-pile soil on the geomembrane to form a quadrangular prism-shaped soil pile, wherein the bio-pile soil is prepared from the contaminated soil; wherein the slope of the side surface of the soil pile should be controlled within a range that can keep the soil pile stable under natural conditions, and the surface part of the soil pile in contact with air can be uncovered, covered with grass or covered with other types of covering structures that allow air to pass through, so as to ensure that external air can enter the soil pile through the surface. Therefore, the surface of the soil pile cannot be covered with airtight and impermeable film structure.

[0012] The working principle of the above bio-pile is: when the bio-pile is repairing the soil, the negative pressure generated by the negative pressure fan to the air guide layer through air extraction makes the external air flow from the surface to the inside of the soil pile, so as to supply oxygen to the soil microorganisms, and realize the removal and repair of the organic pollutants in the contaminated soil by the soil microorganisms.

[0013] Therefore, the application calculates the air extraction rate q of the bio-heap that can meet the oxygen supply balance condition based on the oxygen consumption rate of the microorganisms in the bio-heap under the balance condition being equal to the oxygen supply rate of the fan through step S1, and calculates the vacuum degree ΔP of the air guide layer of the bio-heap under the specific soil condition that needs to be maintained by the air guide layer through the equivalent relationship of the soil air permeability calculation process based on meeting the air extraction rate q through step S2; and then selects the negative pressure fan with appropriate specifications and models based on the air extraction rate q and the vacuum degree ΔP of the air guide layer through step S3, so as to use the negative pressure fan to form the ventilation system to build the bio-heap, so that when the bio-heap is used for soil remediation, sufficient ventilation can be ensured to avoid oxygen deficiency of the soil microorganisms, and over-ventilation can be prevented to avoid energy waste.

[0014] Preferably, the oxygen consumption rate determination test of step S1 and the air permeability coefficient determination test of step S2 are both implemented based on the soil column test device.

[0015] Referring to Figure 5 , the soil column test device comprises a vertical pipe body, a negative pressure cavity and a vacuum pump, the side wall of the vertical pipe body is connected with a soil gas sampling hole, the upper pipe opening of the vertical pipe body is detachably installed with a sealing cover plate, the lower pipe opening of the vertical pipe body is fixed on the top surface of the negative pressure cavity, and the lower pipe opening of the vertical pipe body is communicated with the inner cavity of the negative pressure cavity 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 with the inner cavity of the negative pressure cavity through a flow meter, and the inner cavity of the negative pressure cavity is connected with a pressure gauge.

[0016] Preferably, the oxygen consumption rate determination test of step S1 comprises:

[0017] Step S1-1, filling the test soil in the vertical pipe body;

[0018] Step S1-2, opening the sealing cover plate to ventilate the test soil in the vertical pipe body through the upper pipe opening of the vertical pipe 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 air, then sealing the upper pipe opening of the vertical pipe 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 is ended is denoted as in %;

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

[0020] Step S1-4: Record the average room temperature when performing steps S1-2 and S1-3, and look up the gas molar volume v corresponding to the average room temperature, in L / mol.

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

[0022] In the formula, ω represents the noncapillary porosity of the test soil, expressed as a percentage (%).

[0023] Steps S1-1 to S1-5 can be repeated three times to obtain three sets of data, and the average value 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 open and the soil gas sampling hole closed, fill the upright tube with test soil of the same height H as the soil pile.

[0026] Step S2-2: Start the vacuum pump to evacuate the negative pressure chamber until it reaches a stable state where the internal pressure no longer changes. Then start timing to measure the air flow rate Q and the vacuum degree Δp of the negative pressure chamber within a preset air permeation time ΔT. The air permeation time ΔT is in minutes (min), and the air flow rate Q is the air flow rate of the vacuum pump during the evacuation of the negative pressure chamber within the air permeation time ΔT, measured by the flow meter, in cubic meters per second (m³). 3 The vacuum degree Δp of the negative pressure chamber is the pressure difference between the internal pressure of the negative pressure chamber and the atmospheric pressure under the steady state, which is measured by the pressure gauge and the unit is kPa.

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

[0028]

[0029] In the formula, the aerated soil area F is the cross-sectional area of ​​the soil column formed by the test soil filled in the vertical tube, in m². 2 η 25 η is the air viscosity at an air temperature of 25°C, expressed in Pa·s. T The air viscosity is expressed in Pa·s at an ambient temperature of t℃; the soil permeability coefficient K is expressed in m³. 3(m3·kPa·min), its physical meaning is: when the viscosity of the gas is 1P (1P=0.1Pa·s), the air amount per unit area, per unit soil thickness per unit time under unit air pressure; due to the small viscosity of the gas, the viscosity of the air at a certain fixed temperature (such as 25℃) is usually corrected as a standard.

[0030] In the step S1, the air extraction 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 of the biological pile per unit time = the oxygen supply of the biological pile ventilation system per unit time; in the formula, is the oxygen consumption rate per unit soil volume, V is the soil pile volume of the biological pile, and the unit is m 3 , is the molar concentration of oxygen in the air, and the unit is mol·m -3 .

[0033] The soil pile shape of the biological pile is a quadrangular frustum, the bottom width is M, the bottom length is L, the height is H, and the unit is m, the slope is i, then the calculation formula of the soil pile volume V of the biological pile is: V=[(L-2H / i)×(M-2H / i)+L×M+(2L-2H / i)×(2M-2H / i)]×H / 6.

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

[0035] In the step S2, the air guide layer vacuum degree ΔP is calculated according to the following formula:

[0036] q=(K×F×ΔP / H)×(η 25 / η t );

[0037] In the formula, q is the air extraction rate, K is the soil permeability coefficient, and F is the soil surface area of ​​the part of the biomass in contact with air, in m². 2 η represents the cross-sectional area of ​​external air entering the interior of the biomound, equivalent to the sum of the areas of the four sides and the top of the truncated pyramid shape of the biomound. H is the thickness of the soil layer above the air-conducting layer of the biomound, which is also the height of the biomound. 25 η is the air viscosity at an air temperature of 25°C, expressed in Pa·s. t The viscosity of air is given at an ambient temperature of t℃, expressed in Pa·s.

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

[0039] This invention, through step S1, calculates the extraction rate q that the bio-pil can meet the oxygen supply balance condition based on the fact that the oxygen consumption rate of microorganisms in the bio-pil is equal to the oxygen supply rate of the blower under equilibrium conditions. Then, through step S2, based on the extraction rate q, the vacuum degree ΔP of the air-conducting layer 1 of the bio-pil needs to be maintained under specific soil conditions is calculated using the quantitative relationship in the soil permeability calculation process. Finally, through step S3, based on the extraction rate q and the air-conducting layer vacuum degree ΔP, a suitable negative pressure blower 3 is selected, and the negative pressure blower 3 is used to form a ventilation system to construct the bio-pil. This ensures that when the bio-pil is used for soil remediation, it can guarantee sufficient ventilation to avoid oxygen deficiency in soil microorganisms, while also preventing excessive ventilation and energy waste. Attached Figure Description

[0040] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments:

[0041] Figure 1 This is a three-dimensional structural diagram of the bio-pile in this invention;

[0042] Figure 2 This is a schematic diagram of the planar structure of the bio-pile in this invention;

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

[0044] Figure 4 for Figure 2 BB section view;

[0045] Figure 5 This is a schematic diagram of the soil column test device in this invention. Detailed Implementation

[0046] The present application will be described in detail below with reference to the embodiments and the accompanying drawings to help the skilled in the art better understand the inventive concept of the present application, but the protection scope of the claims of the present application is not limited to the following embodiments, and all other embodiments obtained by the skilled in the art without creative labor on the premise of not departing from the inventive concept of the present application belong to the protection scope of the present application.

[0047] As shown in Figures 1 to 4 , the present application discloses a construction method of a bio-pile aeration system, comprising:

[0048] Step S1, sample preparation from contaminated soil to prepare test soil, and carry out oxygen consumption rate determination test, and determine the unit soil volume oxygen consumption rate of test soil According to the calculation, the air extraction rate q of the bio-pile that can meet the oxygen supply balance condition is m 3 ·min -1 ; wherein the unit soil volume oxygen consumption rate is mol·min -1 ·m -3 , indicating the rate of oxygen consumption in the soil by indigenous microorganisms or added exogenous microorganisms in the test soil during the metabolic process;

[0049] In the step S1, the air extraction rate q is calculated according to the following formula:

[0050]

[0051] The above formula represents the oxygen supply balance condition, i.e. the oxygen consumption of the bio-pile per unit time = the oxygen supply of the bio-pile aeration system per unit time; wherein, is the unit soil volume oxygen consumption rate, V is the soil pile volume of the bio-pile, unit is m 3 , is the molar concentration of oxygen in air, unit is mol·m -3 .

[0052] The soil pile shape of the bio-pile of the present application is a quadrangular frustum, and its bottom width is M, bottom length is L, height is H, and unit is m, and the slope is i, then the calculation formula of the soil pile volume V of the bio-pile 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 air can take the value under ideal conditions, i.e. at 25℃, 1.01×10 5Pa, the molar concentration of oxygen in air is calculated according to the physical properties of air, the volume fraction of oxygen in air is taken as 20.9%, 25℃, 1.01×10 5 Pa, the molar volume of gas is 24.5L mol -1 , and the molar concentration of oxygen in air is 8.53mol·m -3 -3. The molar concentration of oxygen in air can also be calculated according to the measured atmospheric temperature and oxygen content in air.

[0054] In step S2, the test soil is prepared from the contaminated soil, and the air permeability coefficient determination test is performed to determine the soil air permeability coefficient K of the test soil, so as to calculate the air guide layer vacuum degree ΔP of the air guide layer 1 required to maintain the air supply amount of the bio-heap to reach the air extraction rate q, which is the pressure difference between the atmospheric pressure on the surface of the soil pile 2 of the bio-heap and the internal air pressure of the air guide layer 1, and is expressed in kPa; wherein the unit of the soil air permeability coefficient K is m 3 / (㎡·kPa·min), which is a parameter strongly related to soil quality, and if wood chips or other loose auxiliary materials are added during the bio-heap repair process, the mesh size and addition ratio of the wood chips have a great influence on the soil air permeability coefficient K;

[0055] In step S2, the air guide layer vacuum degree ΔP is calculated according to the following formula:

[0056] q=(K×F×ΔP / H)×(η 25 / η t );

[0057] In the formula, q is the air extraction rate, K is the soil air permeability coefficient, F is the soil surface area of the soil pile 2 of the bio-heap in contact with air, which is expressed in m 2 , which is the cross-sectional area of the external air entering the internal part of the soil pile 2 of the bio-heap, and is equivalent to the sum of the areas of the four sides and the top surface of the quadrangular frustum-shaped soil pile 2, H is the thickness of the soil layer on the upper part of the air guide layer 1 of the bio-heap, i.e. the height of the soil pile 2 of the bio-heap, η 25 is the air viscosity corresponding to the air temperature of 25℃, which is expressed in Pa·s, and η t is the air viscosity corresponding to the test environment temperature of t℃, which is expressed in Pa·s.

[0058] The preparation components and proportions of the test soil in steps S1 and S2 are the same as those of the bio-pile soil used for building the bio-pile, and the bio-pile soil is prepared from the contaminated soil so that the test soil is close to the soil used in the bio-pile remediation process; the test soil and the bio-pile soil are formed by adding a microbial agent, a nutrient solution, water, and auxiliary materials, etc. in a certain proportion on the basis of the contaminated soil, and then uniformly mixing, the microbial agent is an exogenous microorganism for removing organic pollutants in the soil, and the auxiliary material is 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 based on a soil column test device;

[0060] Referring to Figure 5 , the soil column test device comprises a vertical pipe body 6, a negative pressure cavity 7, and a vacuum pump 8, the side wall of the vertical pipe body 6 is connected with a soil gas sampling hole 6a, the upper pipe opening of the vertical pipe body 6 is detachably installed with a sealing cover plate 9, the lower pipe opening of the vertical pipe body 6 is fixed on the top surface of the negative pressure cavity 7, and the lower pipe opening of the vertical pipe body 6 is communicated with the inner cavity of the negative pressure cavity 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 with the inner cavity of the negative pressure cavity 7 through a flow meter 11, and the inner cavity of the negative pressure cavity 7 is connected with a pressure gauge 12.

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

[0062] Step S1-1, filling the test soil in the vertical pipe body 6;

[0063] Step S1-2, opening the sealing cover plate 9 to ventilate the test soil in the vertical pipe body 6 through the upper pipe opening of the vertical pipe 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, then sealing the upper pipe opening of the vertical pipe 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 is ended is denoted as in %;

[0064] Step S1-3, detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole 6a under the condition that the sealing cover plate 9 seals the upper pipe opening of the vertical pipe body 6; wherein the oxygen content measured through the soil gas sampling hole 6a at the end of step S1-3 is denoted as in %, and the measured and time difference is denoted as the reaction time Δt, in min;

[0065] Step S1-4, record the average room temperature during the execution of step S1-2 and step S1-3, and query the corresponding gas molar volume v of the average room temperature, unit: L / mol;

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

[0067] In the formula, ω is the non-capillary porosity of the test soil, unit: %.

[0068] Wherein, steps S1-1 to S1-5 can be repeatedly executed three times to obtain three groups of data, and the average is taken as the unit soil volume oxygen consumption rate

[0069] Preferably, the air permeability coefficient determination test of step S2 comprises:

[0070] Step S2-1, fill the test soil with the same height as the height H of the soil pile 2 in the vertical pipe body 6 under the condition that the sealing cover plate 9 is opened and the soil gas sampling hole 6a is closed;

[0071] Step S2-2, start the vacuum pump 8 to vacuumize the negative pressure cavity 7, and start timing when the negative pressure cavity 7 reaches a stable state where the internal cavity pressure of the negative pressure cavity 7 no longer changes, to measure the ventilation amount Q and the negative pressure cavity vacuum degree Δp in the preset air permeation time ΔT; wherein, the air permeation time ΔT is in min, the ventilation amount Q is the ventilation amount of the vacuum pump 8 to vacuumize the negative pressure cavity 7 in the air permeation time ΔT, which is measured by the flow meter 11, unit: m 3 ; the negative pressure cavity vacuum degree Δp is the pressure difference between the internal cavity pressure of the negative pressure cavity 7 and the atmospheric pressure in the stable state, which is measured by the pressure gauge 12, unit: kPa;

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

[0073]

[0074] In the formula, F is the cross-sectional area of the soil column formed by the test soil filled in the vertical pipe body 6, unit: m 2 ; η 25 is the air viscosity corresponding to the air temperature of 25℃, unit: Pa·s, η t is the air viscosity corresponding to the test environment temperature of t℃, unit: Pa·s; the unit of soil air permeability coefficient K is m 3 / (m 2·kPa·min), which has a physical meaning that when the viscosity of the gas is 1P (1P=0.1 Pa·s), the air quantity per unit area per unit soil thickness per unit time under unit air pressure; due to the too small viscosity of the gas, the viscosity of the air at a certain fixed temperature (such as 25℃) is usually taken as a standard for correction.

[0075] Step S3, the specification of the negative pressure fan 3 is selected so that the air extraction speed of the negative pressure fan 3 to the air guide layer 1 meets the air extraction rate q, and the negative pressure vacuum degree formed by the air extraction of the negative pressure fan 3 to the air guide layer 1 meets the air guide layer vacuum degree ΔP.

[0076] Step S4, the construction of the bio-pile, including: burying the 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, the bearing capacity of which should be greater than that of the soil pile 2 of the bio-pile, and the contact surface of the air guide layer 1 with the ground is covered with an HDPE impermeable film; connecting the air extraction port of the negative pressure fan 3 and the inside of the air guide layer 1 with the air extraction pipe 4, and the air extraction pipe 4 is provided with a plurality of air extraction holes 4a in the inside of the air guide layer 1; laying the geomembrane 5 on the ground and covering the top surface of the air guide layer 1 with the geomembrane 5; forming a quadrangular prism-shaped soil pile 2 on the geomembrane 5 by piling the bio-pile soil, which is prepared from the contaminated soil; wherein the side slope of the soil pile 2 should be controlled within a range that can keep the soil pile 2 stable under natural conditions, and the surface part of the soil pile 2 in contact with the air can be uncovered, covered with grass or covered with other types of covering structures that can allow air to pass through, so as to ensure that the external air can pass through the surface and enter the soil pile 2, and therefore the surface of the soil pile 2 cannot be covered with a sealed and air-tight film structure.

[0077] The working principle of the above bio-pile is that when the soil is repaired in the bio-pile, the negative pressure is generated by the air extraction of the negative pressure fan 3 to the air guide layer 1, 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 and realize the removal and repair of the organic pollutants in the contaminated soil by the soil microorganisms.

[0078] Therefore, by step S1, based on the balance condition that the oxygen consumption rate of the microorganisms in the bio-pile is equal to the oxygen supply rate of the fan, the air extraction rate q of the bio-pile that can meet the oxygen supply balance condition is calculated, and by step S2, on the basis of meeting the air extraction rate q, the air guide layer vacuum degree ΔP required by the air guide layer 1 of the bio-pile under specific soil conditions is calculated by using the equivalent relationship of the soil permeability calculation process; and by step S3, the specification of the negative pressure fan 3 is selected according to the air extraction rate q and the air guide layer vacuum degree ΔP, so as to use the negative pressure fan 3 to form a ventilation system to construct the bio-pile, so that when the soil is repaired in the bio-pile, both sufficient ventilation and prevention of excessive ventilation to cause energy waste can be ensured.

[0079] The present application is not limited to the above-described specific embodiments, and according to the above-described content, other various forms of equivalent modifications, substitutions or changes can be made in accordance with ordinary technical knowledge and means in the art without departing from the above-described basic technical idea of the present application, and all fall within the scope of protection of the present application.

Claims

1. A method of constructing a bio-tower aeration system, characterized by, Comprising: Step S1, test soil is prepared from the contaminated soil and an oxygen consumption rate measurement test is performed, and the unit soil volume oxygen consumption rate of the test soil is measured Accordingly, the air extraction rate q at which the biological pile can satisfy the oxygen supply balance condition is calculated. Step S2, sample preparation from contaminated soil to prepare test soil, and carry out air permeability coefficient determination test, and determine the soil air permeability coefficient K of the test soil, so as to calculate: when the oxygen supply amount of the biological pile reaches the air extraction rate q, the air guide layer (1) of the biological pile needs to maintain the air guide layer vacuum degree ΔP; Wherein, the preparation components and proportions of the test soil in steps S1 and S2 are the same as the biological pile soil used for building the biological pile, and the biological pile soil is prepared from the contaminated soil; Step S3, select the specification and model of the negative pressure fan (3), so that: the air extraction speed of the negative pressure fan (3) to the air guide layer (1) meets the air extraction rate q, and the negative pressure vacuum degree formed by the negative pressure fan (3) to the air guide layer (1) meets the air guide layer vacuum degree ΔP; Step S4, build a biological pile, including: burying the 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 extraction pipe (4) between the air extraction port of the negative pressure fan (3) and the inside of the air guide layer (1), and the air extraction pipe (4) is provided with a plurality of air extraction holes (4a) in the inside of the air guide layer (1); lay the geomembrane (5) on the ground, and make the geomembrane (5) cover the top surface of the air guide layer (1); pile up the biological pile soil on the geomembrane (5) to form a quadrangular pyramid shaped soil pile (2), and the biological pile soil is prepared from the contaminated soil.

2. The method of constructing a bio-tower aeration system according to claim 1, wherein: The oxygen consumption rate determination test in step S1 and the air permeability coefficient determination test in step S2 are both based on a soil column test device; The soil column test device comprises a vertical pipe body (6), a negative pressure cavity (7) and a vacuum pump (8), the side wall of the vertical pipe body (6) is connected with a soil gas sampling hole (6a), the upper pipe opening of the vertical pipe body (6) is detachably installed with a sealing cover plate (9), the lower pipe opening of the vertical pipe body (6) is fixed on the top surface of the negative pressure cavity (7), and the lower pipe opening of the vertical pipe body (6) is communicated with the inner cavity of the negative pressure cavity (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 with the inner cavity of the negative pressure cavity (7) through a flow meter (11), and the inner cavity of the negative pressure cavity (7) is connected with a pressure gauge (12).

3. The method of constructing a bio-tower aeration system according to claim 2, wherein: The oxygen consumption rate determination test in step S1, comprising: Step S1-1, fill the test soil in the vertical pipe body (6); Step S1-2, open the sealing cover plate (9) to ventilate the test soil in the standing tube body (6) through the upper tube opening of the standing tube body (6) with external air; and continuously detect 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, seal the upper tube opening of the standing 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 is ended is denoted as O2end. Step S1-3, detecting the oxygen content in the gas generated by the test soil through the soil gas sampling hole (6a) in the state that the sealing cover plate (9) seals the upper pipe opening of the pipe body (6); wherein the oxygen content detected by the soil gas sampling hole (6a) at the end time of step S1-3 is denoted as O2 (t1) The measured And The time difference is denoted as the reaction time Δt; Step S1-4, record the average room temperature during the execution of steps S1-2 and S1-3, and query the corresponding gas molar volume v of the average room temperature; Step S1-5, the unit soil volume oxygen consumption rate of the test soil is calculated according to the following formula In the formula, ω is the non-capillary porosity of the test soil.

4. The method of claim 2, wherein the method further comprises: The air permeability coefficient determination test in step S2, comprising: ​ Step S2-1, fill the test soil in the vertical pipe body (6) to the same height as the height H of the soil pile (2) under the condition that the sealing cover plate (9) is opened and the soil gas sampling hole (6a) is closed; Step S2-2, start the vacuum pump (8) to negative pressure cavity (7) vacuum, until the negative pressure cavity (7) reaches its inner cavity pressure no longer changes when the steady state, start timing, to determine the preset ventilation time ΔT ventilation Q and negative pressure cavity vacuum Δp; wherein, the ventilation Q is the vacuum pump (8) in the ventilation time ΔT ventilation Q for negative pressure cavity (7) vacuum, measured by the flow meter (11); the negative pressure cavity vacuum Δp is the negative pressure cavity (7) of the inner cavity pressure in the steady state and the pressure difference of atmospheric pressure, measured by the pressure gauge (12); Step S2-3, calculate the height H corresponding to the test soil soil soil air permeability coefficient K by the following formula: wherein F is the cross-sectional area of the soil column formed by the test soil filled in the vertical pipe body (6); η 25 η is the air viscosity corresponding to the air temperature of 25°C t η is the air viscosity corresponding to the test ambient temperature of t°C.

5. The method according to any one of claims 1 to 4, wherein the method is for constructing a bio-tower aeration system. In the step S1, the air extraction rate q is calculated according to the following formula: wherein is the oxygen consumption rate per unit soil volume, V is the volume of the soil pile of the biopile, is the molar concentration of oxygen in the air.

6. The method according to any one of claims 1 to 4, wherein the method is for constructing a bio-tower aeration system. In the step S2, the air guide layer vacuum degree ΔP is calculated according to the following formula: q = (K x F x ΔP / H) x (η 25 / η t ); where q is the air extraction rate, K is the soil air permeability coefficient, F is the soil surface area of the soil pile (2) in contact with air in the bio- pile, H is the thickness of the soil layer at the upper part of the air guide layer (1) of the bio- pile, η 25 is the air viscosity corresponding to the air temperature of 25°C, and η t is the air viscosity corresponding to the test environment temperature of t°C.

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