In-situ chemical remediation simulation method for benzene pollution in aquifer

Abstract

The application provides a simulation method for in-situ chemical remediation of aquifer benzene pollution, and belongs to the field of groundwater pollution remediation. The simulation method comprises the following steps: constructing a reaction kinetics model for degradation of benzene by ozone and hydrogen peroxide in the aquifer; using Fortran language to write the reaction kinetics model into a dynamic link library and embedding the dynamic link library into an RT3D user-defined module; using the RT3D user-defined module to establish a reactive solute transport model; and running the RT3D user-defined module to run the RT3D custom module for simulation remediation. The simulation method simulates the process of using the advanced oxidation technology of combined use of ozone and hydrogen peroxide to treat the benzene-polluted groundwater, and can provide a basis for the selection of a remediation scheme for a demander.

Description

TECHNICAL FIELD

[0001] The application belongs to the field of groundwater pollution remediation, and particularly relates to a simulation method for in-situ chemical remediation of aquifer benzene pollution. BACKGROUND

[0002] Groundwater is an important fresh water resource and is closely related to human life. However, in recent years, due to unreasonable exploitation and utilization of groundwater, excessive discharge of pollutants and some sudden pollution leakage events, groundwater has been seriously polluted. Benzene organic compounds are a common type of pollutants in groundwater, among which benzene, toluene, ethylbenzene, xylene (BTEX) and nitrobenzene are important raw materials in the petroleum industry. Leakage and seepage phenomena caused by transportation, use and production of petroleum and its derivatives can cause pollution problems of benzene organic compounds in the underground environment. Benzene pollutants in the underground environment exist in the form of non-aqueous phase liquids (NAPLs). BTEX belongs to light non-aqueous phase liquids (LNAPLs), and nitrobenzene belongs to heavy non-aqueous phase liquids (DNAPLs), which are highly toxic pollutants and have the effects of "carcinogenic, teratogenic and mutagenic". Once they enter the groundwater, they will pose a great threat to human health. Therefore, the control and remediation of benzene organic compound pollution in groundwater have attracted more and more widespread attention. There are many methods for controlling and treating benzene organic compound pollution in groundwater, such as extraction-treatment method, air disturbance method, microbial treatment method and permeable reaction wall method. These remediation technologies have their own advantages, but also have disadvantages. Some methods have poor adaptability to contaminated sites, some methods have high remediation cost, and some methods have large environmental disturbance.

[0003] Chemical remediation refers to the conversion of harmful pollutants into harmless or less toxic compounds by chemical methods to achieve the purpose of remediation of contaminated sites. In-situ chemical remediation can be divided into in-situ chemical reduction remediation technology (ISCR) and in-situ chemical oxidation remediation technology (ISCO) according to the reaction type. ISCR remediation technology is a method for converting pollutants into low-toxicity compounds by injecting reducing agents into the underground environment and reacting with the pollutants. This technology can not only remove a variety of pollutants dissolved in groundwater, but also remove NAPLs pollutants which are considered as long-term pollution sources. It is most commonly used in the remediation of sites contaminated with metal chromium, trichloroethylene (TCE) or TCE-DNAPL. ISCO technology is a method for oxidizing pollutants into non-toxic or low-toxicity compounds by injecting oxidizing agents into the underground environment. This technology can quickly and completely remove a variety of pollutants in soil and groundwater, has a wide range of applications and moderate cost, and has been rapidly developed and widely applied at home and abroad in recent years. Currently, permanganate, ozone, persulfate, hydrogen peroxide and percarbonate are commonly used ISCO oxidizing agents.

[0004] Although there are many remediation methods for treating benzene pollution in groundwater, the research on reactive solute transport simulation of benzene is still insufficient, so it is difficult to provide important reference support for engineering practice. In addition, the simulation method of in-situ chemical remediation of benzene pollution in aquifer needs to be further proposed and improved. SUMMARY

[0005] The purpose of the present application is to solve the problems existing in the prior art, and to provide a basis for the selection of remediation schemes for the needs of the users by simulating the process of treating benzene contaminated groundwater by advanced oxidation technology using ozone and hydrogen peroxide in combination.

[0006] The purpose of the present application is achieved by providing an in-situ chemical remediation simulation method for benzene pollution in aquifer, comprising the following steps:

[0007] Step 1, constructing a reaction kinetics model of benzene degradation by ozone and hydrogen peroxide in aquifer

[0008] The aquifer is contaminated by benzene, and the pollutants of the benzene pollution include benzene, phenol, benzenediol, benzoquinone, maleic acid and oxalic acid, wherein phenol, benzenediol, benzoquinone, maleic acid and oxalic acid are intermediate products of benzene degradation by ozone and hydrogen peroxide;

[0009] A reaction kinetics model of benzene degradation by hydrogen peroxide and ozone is constructed, and its expression is as follows:

[0010]

[0011] In the formula, [OZ] is the concentration of ozone in the degradation reaction, koh is the first-order degradation rate of ozone, [JP] is the concentration of hydrogen peroxide in the degradation reaction, [Be] is the concentration of benzene in the degradation reaction, kbe is the first-order degradation rate of benzene, [OH] is the hydroxyl radical, [Ph] is the concentration of phenol in the degradation reaction, kpph is the first-order degradation rate of phenol, [Hy] is the concentration of benzenediol in the degradation reaction, khy is the first-order degradation rate of benzenediol, [Pbe] is the concentration of benzoquinone in the degradation reaction, kpbe is the first-order degradation rate of benzoquinone, [Ma] is the concentration of maleic acid in the degradation reaction, kma is the first-order degradation rate of maleic acid, [Ox] is the concentration of oxalic acid in the degradation reaction, and kox is the first-order degradation rate of oxalic acid;

[0012] Step 2, using Fortran language to write the reaction kinetics model obtained in step 1 as a dynamic link library

[0013] The reaction kinetics model is written as a dynamic link library using Fortran language, which is embedded into the RT3D user-defined module, and is ready for the construction of the reactive solute transport model;

[0014] Step 3, building a reactive solute transport model

[0015] Step 3.1, first build a flow model by using the MODFLOW module in the software GMS, as follows:

[0016] Suppose that there is a benzene contaminated area in the aquifer, denoted as a benzene remediation area, and the benzene remediation area is a three-dimensional isotropic confined aquifer; simplify the benzene remediation area as a rectangular body parallel to the ground plane, and take any cross section perpendicular to the ground plane as the remediation area A, and suppose that the remediation area A is a rectangle;

[0017] Establish a plane coordinate system with an end point of the remediation area A as the origin, and the long side of the remediation area A is parallel to the X axis and the short side of the remediation area A is parallel to the Y axis; let the two long sides be impervious boundaries and the two short sides be constant head boundaries, wherein the short side coinciding with the Y axis is denoted as boundary 1 and the other short side is denoted as boundary 2, suppose that the flow direction is the same as the positive direction of the X axis, and the water head of the boundary 1 is greater than that of the boundary 2; suppose that the porosity of the aquifer is 0.3, the longitudinal dispersion coefficient is 10 m / s, and the permeability coefficient is 4 m / d; 2

[0018] Step 3.2, build a reactive solute transport model by using the RT3D user-defined module on the basis of the flow model built in step 3.1, as follows:

[0019] Denote the benzene contaminated area in the remediation area A as a benzene contaminated area B, and suppose that the benzene contaminated area B is located in the interval of 0.27α

[0020] Suppose that N monitoring wells are uniformly arranged in the remediation area A, and any one of them is denoted as monitoring well i, i = 1, 2, …, N; suppose that Γ injection wells are uniformly arranged in the benzene contaminated area B, and any one of them is denoted as injection well j, j = 1, 2, …, Γ;

[0021] Suppose that each day is a time period during the remediation process, and a total of N s remediation time periods are experienced, and any one of the remediation time periods is denoted as remediation time period s, s = 1, 2, …, N s ;

[0022] Suppose that hydrogen peroxide and ozone are continuously injected into the benzene contaminated area B through the Γ injection wells for N s days during the remediation process, and suppose that the hydrogen peroxide and ozone instantaneously react to generate hydroxyl radicals after the hydrogen peroxide and ozone are injected, the concentration of the injected ozone is Tumol / 1, and the concentration of the hydrogen peroxide is Pumol / l;​

[0023] Setting the repair target, the repair target is the remaining concentration of each kind of pollutants in the repair area A reaches the groundwater IV class standard;

[0024] Step 4, running RT3D custom module for simulation repair, and through N monitoring wells i observation N s The concentration change of each pollutant in the repair area A in N repair time period is recorded.

[0025] Compared with the prior art, the beneficial effects of the present application are:

[0026] 1. The in-situ chemical oxidation repair module of benzene in the RT3D custom module is first proposed, and a reactive solute transport simulation model is established;

[0027] 2. The accumulation of simulation repair data provides a decision basis for the selection of the final repair scheme for the demander. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a schematic diagram of the water flow model in the simulation method of the present application;

[0029] Figure 2 It is a benzene concentration change curve graph in the repair process of the embodiment of the present application;

[0030] Figure 3 It is a phenol concentration change curve graph in the repair process of the embodiment of the present application;

[0031] Figure 4 It is a hydroquinone concentration change curve graph in the repair process of the embodiment of the present application;

[0032] Figure 5 It is a benzoquinone concentration change curve graph in the repair process of the embodiment of the present application;

[0033] Figure 6 It is a maleic acid concentration change curve graph in the repair process of the embodiment of the present application;

[0034] Figure 7 It is an oxalic acid concentration change curve graph in the repair process of the embodiment of the present application. DETAILED DESCRIPTION

[0035] The present application will be further described below in combination with specific embodiments and drawings.

[0036] The present application provides a simulation method for in-situ chemical repair of benzene pollution in aquifer, comprising the following steps:

[0037] Step 1, constructing the reaction kinetics model of ozone and hydrogen peroxide degrading benzene in aquifer

[0038] The aqueous layer has benzene pollution, and the pollutants of the benzene pollution include benzene, phenol, benzenediol, benzoquinone, maleic acid and oxalic acid, wherein the phenol, benzenediol, benzoquinone, maleic acid and oxalic acid are intermediate products of benzene degradation by ozone and hydrogen peroxide;

[0039] A reaction kinetics model of hydrogen peroxide and ozone degrading benzene is constructed, and the expression is as follows:

[0040]

[0041]

[0042] In the formula, [OZ] is the concentration of ozone in the degradation reaction, koh is the first-order degradation rate of ozone, [HP] is the concentration of hydrogen peroxide in the degradation reaction, [Be] is the concentration of benzene in the degradation reaction, kbe is the first-order degradation rate of benzene, [OH] is the hydroxyl radical, [Ph] is the concentration of phenol in the degradation reaction, kpph is the first-order degradation rate of phenol, [Hy] is the concentration of benzenediol in the degradation reaction, khy is the first-order degradation rate of benzenediol, [Pbe] is the concentration of benzoquinone in the degradation reaction, kpbe is the first-order degradation rate of benzoquinone, [Ma] is the concentration of maleic acid in the degradation reaction, kma is the first-order degradation rate of maleic acid, [Ox] is the concentration of oxalic acid in the degradation reaction, and kox is the first-order degradation rate of oxalic acid.

[0043] Step 2, using Fortran language to write the reaction kinetics model obtained in step 1 as a dynamic link library

[0044] Using Fortran language to write the reaction kinetics model as a dynamic link library, embedded into the RT3D user-defined module, ready for the next step of building the reactive solute transport model.

[0045] Step 3, building a reactive solute transport model

[0046] Step 3.1, first use the MODFLOW module in the software GMS to build a water flow model, as follows:

[0047] There is a benzene pollution area in the aquifer, which is denoted as a benzene repair area, and the benzene repair area is a three-dimensional isotropic confined aquifer; the benzene repair area is simplified as a rectangular body with height parallel to the ground plane, and an arbitrary cross section perpendicular to the ground plane is denoted as repair area A, which is a rectangle;

[0048] A plane coordinate system is established with one end of the repair area A as the origin, and the long side of the repair area A is parallel to the X axis, and the short side of the repair area A is parallel to the Y axis; two long sides are taken as water-resisting boundaries, and two short sides are taken as constant water head boundaries, wherein the short side coinciding with the Y axis is denoted as boundary 1, and the other short side is denoted as boundary 2; the water flow direction is the same as the positive direction of the X axis, and the water head of the boundary 1 is greater than that of the boundary 2; the porosity of the aquifer is 0.3, the longitudinal dispersion coefficient is 10 m / s, and the permeability coefficient is 4 m / d. 2

[0049] In the embodiment, the repair area A is a rectangular field with a size of 510 m x 310 m, that is, a = 510 m and β = 310 m. The water head of the boundary 1 is kept at 100 m, the hydraulic gradient is 0.0392, the porosity is 0.3, the longitudinal dispersion coefficient of the aquifer is 10 m / s, and the permeability coefficient is 4 m / d.

[0050] Step 3.2. On the basis of the water flow model constructed in step 3.1, a reactive solute transport model is constructed by using the RT3D user-defined module, and the details are as follows:

[0051] The benzene contaminated area in the repair area A is denoted as benzene contaminated area B, and it is assumed that the benzene contaminated area B is located in the interval of 0.27a < X < 0.51a and 0.32β < Y < 0.68β, and the benzene concentration in the interval is Wumol / l, wherein a is the length of the long side of the repair area A, and β is the length of the short side of the repair area A.

[0052] It is assumed that N monitoring wells are uniformly arranged in the repair area A, and any one of them is denoted as monitoring well i, i = 1, 2,..., N; it is assumed that Γ injection wells are uniformly arranged in the benzene contaminated area B, and any one of them is denoted as injection well j, j = 1, 2,..., Γ.

[0053] It is assumed that each day is a time period during the repair process, and a total of N s repair time periods are experienced, and any one of the repair time periods is denoted as repair time period s, s = 1, 2,..., N s .

[0054] It is assumed that hydrogen peroxide and ozone are continuously injected into the benzene contaminated area B through the Γ injection wells for N s days during the repair process, and it is assumed that hydrogen peroxide and ozone react instantaneously to generate hydroxyl radicals after being injected; the concentration of the injected ozone is Tumol / 1, and the concentration of the injected hydrogen peroxide is Pumol / 1.

[0055] A repair target is set, and the repair target is that the residual concentration of each pollutant in the repair area A reaches the groundwater IV standard.

[0056] ​In the embodiment, the benzene pollution area B is located in the interval of 140mX<270m, 100mY<220m, and the benzene pollution concentration is 36umol / l. Γ=9, that is, 9 injection wells are uniformly arranged in the benzene pollution area B, and the specific coordinates are (16, 11), (21, 11), (26, 11), (16, 16), (21, 16), (26, 16), (16, 22), (21, 22), (26, 22). N=8, that is, 8 monitoring wells are uniformly arranged in the repair area A, and the specific coordinates are (13, 19), (19, 19), (24, 19), (33, 19), (13, 13), (19, 13), (24, 13), (33, 13).

[0057] In the embodiment, N s =100, that is, the repair period is 100 days. Specifically, the 9 injection wells continuously inject ozone and hydrogen peroxide into the benzene pollution area B for 100 days, the ozone concentration is 6000umol / l, the hydrogen peroxide concentration is 3000umol / l, and the concentration changes of various pollutants in the repair area A are observed through the 8 monitoring wells within 100 days, so as to detect the effectiveness of the repair method.

[0058] Step 4, running the RT3D self-defined module for simulation repair, and observing the concentration changes of various pollutants in the repair area A in the N s repair time periods through the N monitoring wells i, and recording.

[0059] Figures 2-7 The benzene pollutant concentration-time curve drawn according to the simulation repair record is given. As shown in the figure, Figure 2 in the repair area A, the benzene concentration monitored by each monitoring well reaches the fourth class water standard (120ug / l) on the 100th day. As shown in the figure, Figure 3 in the repair area A, the phenol concentration monitored by each monitoring well first increases and then decreases, and the remaining concentration reaches the fourth class water standard (10ug / l) on the 100th day. As shown in the figure, Figure 4 in the repair area A, the benzene diol concentration monitored by each monitoring well first increases and then decreases, and the remaining concentration reaches the fourth class water standard (10ug / l) on the 100th day. As shown in the figure, Figure 5 in the repair area A, the benzene diol concentration monitored by each monitoring well first increases and then decreases, and the remaining concentration reaches the fourth class water standard (10ug / l) on the 100th day. As shown in the figure, Figure 6 in the repair area A, the maleic acid concentration monitored by each monitoring point first increases and then decreases, and the remaining concentration is very small at the end of the repair period. As shown in the figure, Figure 7 in the repair area A, the oxalic acid concentration monitored by each monitoring point first increases and then decreases, and the remaining concentration is very small at the end of the repair period.

Claims

1. A method of in-situ chemical remediation of benzene contamination in an aquifer, characterized in that, The method comprises the following steps: Step 1, constructing a reaction kinetics model of benzene degradation by ozone and hydrogen peroxide in the aquifer The aquifer is polluted by benzene, and the pollutants of the benzene pollution include benzene, phenol, benzenediol, benzoquinone, maleic acid and oxalic acid, wherein the phenol, benzenediol, benzoquinone, maleic acid and oxalic acid are intermediate products of benzene degradation by ozone and hydrogen peroxide; A reaction kinetics model of benzene degradation by hydrogen peroxide and ozone is constructed, and the expression is as follows: In the formula, [OZ] is the concentration of ozone in the degradation reaction, koh is the first-order degradation rate of ozone, [HP] is the concentration of hydrogen peroxide in the degradation reaction, [Be] is the concentration of benzene in the degradation reaction, kbe is the first-order degradation rate of benzene, [OH] is a hydroxyl radical, [Ph] is the concentration of phenol in the degradation reaction, kpph is the first-order degradation rate of phenol, [Hy] is the concentration of benzenediol in the degradation reaction, khy is the first-order degradation rate of benzenediol, [Pbe] is the concentration of benzoquinone in the degradation reaction, kpbe is the first-order degradation rate of benzoquinone, [Ma] is the concentration of maleic acid in the degradation reaction, kma is the first-order degradation rate of maleic acid, [Ox] is the concentration of oxalic acid in the degradation reaction, and kox is the first-order degradation rate of oxalic acid; Step 2, using Fortran language to write the reaction kinetics model obtained in step 1 into a dynamic link library The reaction kinetics model is written into a dynamic link library by using Fortran language, and is embedded into the RT3D user-defined module, so as to prepare for the construction of the reactive solute transport model; Step 3, constructing a reactive solute transport model Step 3.1, first, a water flow model is constructed by using the MODFLOW module in the software GMS, and the specific process is as follows: There is a benzene pollution area in the aquifer, which is recorded as a benzene remediation area, and the benzene remediation area is a three-dimensional isotropic confined aquifer; the benzene remediation area is simplified as a rectangular body with a height parallel to the ground plane, and an arbitrary cross section perpendicular to the ground plane is recorded as a remediation area A, and the remediation area A is a rectangle; A plane coordinate system is established with one end of the repair area A as the origin, and the long side of the repair area A is parallel to the X axis, and the short side of the repair area A is parallel to the Y axis; two long sides are taken as water-resisting boundaries, and two short sides are taken as constant water head boundaries, wherein the short side coinciding with the Y axis is recorded as boundary 1, and the other short side is recorded as boundary 2; the water flow direction is the same as the positive direction of the x axis, and the water head of the boundary 1 is greater than that of the boundary 2; the porosity of the aquifer is 0.3, the longitudinal dispersion coefficient is 10 m 2 / s, and the permeability coefficient is 4 m / d; Step 3.2, on the basis of the water flow model constructed in step 3.1, a reactive solute transport model is constructed by using the RT3D user-defined module, and the specific process is as follows: The benzene pollution area in the remediation area A is recorded as a benzene pollution area B, and the benzene pollution area B is located in the interval of 0.27α<X<0.51α, 0.32β<Y<0.68β, and the pollution concentration of benzene in the interval is Wumol / l, wherein α is the long side length of the remediation area A, and β is the short side length of the remediation area A; A total of Γ injection wells are uniformly arranged in the benzene pollution area B, and an arbitrary one of the injection wells is recorded as injection well j, j = 1, 2,..., Γ; a total of N monitoring wells are uniformly arranged in the remediation area A, and an arbitrary one of the monitoring wells is recorded as monitoring well i, i = 1, 2,..., N, and the positions of the N monitoring wells are uniformly distributed in the benzene pollution area B and the upstream and downstream; Assume each day during the repair process is a time period, and a total of N days are recorded. s There are several repair time periods, and any one of these repair time periods is denoted as repair time period s, where s = 1, 2, ..., N. s ; Injecting continuously hydrogen peroxide and ozone N into the benzene pollution area B through Γ injection wells during the remediation process s The instant reaction of hydrogen peroxide and ozone to generate hydroxyl radicals after the injection of hydrogen peroxide and ozone, the concentration of the injected ozone is T umol / l, and the concentration of the injected hydrogen peroxide is P umol / l. A remediation target is set, and the remediation target is that the residual concentration of each pollutant in the remediation area A reaches the groundwater IV standard; Step 4, run the RT3D custom module for simulation remediation, and observe the concentration changes of each pollutant in the remediation zone A in N monitoring wells i and record them in N monitoring wells i during N remediation time periods. s Step 4, run the RT3D custom module for simulation remediation, and observe the concentration changes of each pollutant in the remediation zone A in N monitoring wells i and record them in N monitoring wells i during N remediation time periods.

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