PROCESS FOR TREATING CONTAMINATED SUBSOIL

Abstract

A process is described for injecting re-agents or amendants for treating a contaminated subsoil, comprising the steps of: arranging at least one hole (3) in the subsoil; inserting into the hole (3) at least one piping (1), the piping (1) being longitudinally equipped with at least one first valve (2); inserting or arranging at least one injecting means into the piping (1); injecting (7) at least one fluid into the subsoil through the injecting means, next to the first valve (2) in open configuration; removing possible residuals present in the piping (1) following the injection (7) of the fluid, the process being adapted to inject substances for decontaminating the subsoil by selectively injecting an amount of the fluid, through one or more valves included between at least one natural level (8) and at least one terminal depth (9).

Claims

1. A process for treating a contaminated subsoil, characterized in that it comprises the steps of: arranging at least one hole (3) in said subsoil; inserting into said hole (3) at least one piping (1), said piping (1) being longitudinally equipped with at least one first valve (2); inserting or arranging at least one injecting means into said piping (1); injecting (7) at least one fluid into said subsoil, through said injecting means, next to said first valve (2) in open configuration; and removing possible residuals present in said piping (1) following said injection (7) of said fluid.

2. The process according to claim 1, characterized in that it further comprises the step of arranging at least one hollow space (4) interposed between at least one external surface of said piping (1) and at least one internal surface of said hole (3).

3. The process according to claim 2, characterized in that it comprises the steps of: moving said injecting means along a longitudinal axis of said piping (1); positioning said injecting means next to at least one second valve (2); injecting said fluid into said subsoil, through said injecting means, next to said second valve (2) in open configuration; possibly repeating said two previous steps next to at least one third valve (2); and removing possible residuals present in said piping (1) following said injections (7) of said fluid.

4. The process according to claim 3, characterized in that said fluid is a mixture of reacting products.

5. The process according to claim 2, characterized in that it comprises at least one step of sealing said hollow space (4), said sealing being adapted to prevent a rise of said fluid along said piping (1), preventing said fluid from flowing in at least one path at higher hydraulic conductivity formed during said step of arranging said hole (3).

6. The process according to claim 1, characterized in that said piping (1) crosses said subsoil from at least a natural level (8) till said terminal depth (9).

7. The process according to claim 1, characterized in that said first valve (2) is placed along said piping (1) for at least one preset length, preferably at established intervals.

8. The process according to claim 7, characterized in that said first valve (2) is upwards and downwards delimited by at least one shutter device (5).

9. The process according to claim 8, characterized in that said shutter device (5) is adapted, depending on at least one pressure and flow-rate value of said injection (7), to enable at least one passage from a closed configuration to said open configuration, and vice versa, for said first valve (2).

10. The process according to claim 1, characterized in that said injecting means injects into said subsoil, through said first valve (2) in said open configuration, said amount of said fluid depending on said terminal depth (9).

11. The process according to claim 2, characterized in that it comprises at least one step of activating said first valve (2), through the injection of at least one fluid product through said shutter device (5), adapted to perform at least one fracturing of said hollow space (4), enabling a penetration of said fluid into said subsoil.

12. The process according to claim 2, characterized in that said first, second, third and/or more valves (2) are arranged along said piping (1) for at least one preset length at pre-established intervals.

Description

[0029] The present invention will be better described by some preferred embodiments thereof, provided as a non-limiting example, with reference to the enclosed drawings, in which FIGS. 1 to 5 show schematic side sectional views of some steps for implementing a preferred embodiment of the process for treating contaminated subsoil according to the present invention.

[0030] With reference to the Figures, it is possible to note that the process of injecting reagents or amendants for treating contaminated subsoil, and also contaminated aquifers and/or capillary flanges according to the present invention comprises the steps of:

[0031] arranging at least one hole 3, such as for example a vertical, horizontal or inclined hole in the subsoil, crossing the subsoil or the aquifer from a natural level 8 till a terminal depth 9 required by the project; the hole 3 can be obtained through any drilling technique suitable for the object of the present invention, such as, for example, a rotation, or a percussion, or a direct push, or a rotary percussion, or a sonic-drilling;

[0032] inserting into the hole 3 at least one piping 1 of a preset length, longitudinally equipped with at least one first valve 2, such as, for example a non-return valve, placed along the piping 1, as shown for example in FIG. 1;

[0033] possibly, arranging at least one hollow space 4 interposed between at least one external surface of the piping 1 and at least one internal surface of said hole 3, as shown for example in FIG. 2;

[0034] inserting or arranging at least one injecting means into said piping 1;

[0035] injecting 7 at least one fluid, into the subsoil, and preferably in the aquifer, through the injecting means, next to the first valve 2 in open configuration, as shown for example in FIG. 4;

[0036] removing the possible residuals present in the piping 1 following the injections 7 of the fluid.

[0037] The process is adapted to decontaminate the subsoil, by injecting, even selectively or at one or more different depths included between the natural level 8 and the terminal depth 9, an amount of the fluid through the first valve 2.

[0038] Possibly, the process according to the present invention can further comprise the steps of:

[0039] moving the injecting means along a longitudinal axis of the piping 1;

[0040] positioning the injecting means next to at least one second valve 2;

[0041] injecting 7 the fluid into the subsoil, and preferably into the aquifer, through the injecting means, next to the second valve 2 in open configuration, as shown for example in FIG. 5;

[0042] possibly, repeating the two previous steps next to at least one third valve 2. Possibly the first, second and third valve 2 are respectively arranged along the piping 1 for a preset length at established intervals.

[0043] The fluid injected into the subsoil or aquifer is preferably a mixture of homogeneous or heterogeneous reacting products, such as, for example, liquids, or gas-oversaturated liquids, or foams, or emulsions, or solid foams, or gels, or suspensions of particles; moreover, the fluid is characterized by a Newtonian or non-Newtonian, viscous or viscous-elastic rheological behaviour and can contain surface-active components, co-solvents, reactive components, possibly inert solid particles, oxidants, reducing agents, dispersing gases and fluids, adsorbents, and solutes adapted to biodegrading or interacting with possible contaminants present in the subsoil or aquifer.

[0044] The process according to the present invention can further comprise a step of sealing the hollow space 4 through, for example, a preset sealing, made first by inserting the piping 1 inside the hole 3, through the use of bentonite products or of packers arranged externally to the piping 1, or for example, a waterproofing in situ, as shown in FIG. 2, through the insertion due to gravity inside the hollow space 4 of a cement or bentonite suspension or granular bentonite; moreover, the sealing is obtained by injecting inside the hollow space 4, at a certain pressure value, a sealing mixture through the first valve 2, and possibly through the second and third valve 2, of the piping 1 after having inserted the piping 1 into the hole 3. Injection of the sealing mixture is performed through the help of known partialization systems of the piping 1 till the mixture goes out of the natural level 8. It is necessary to wait for a certain time interval aimed to the complete hydration of the bentonite material or the drying of the used waterproofing mixture.

[0045] The sealing of the hollow space 4 has the purpose of preventing a rise of the fluid along the piping 1, and of preventing the fluid from flowing along paths with a higher hydraulic conductivity, possibly being formed during the drilling procedure. Moreover, the cement or bentonite or granular bentonite suspension, given its mechanical strength features due to its composition, will be easily fractured by the injecting pressure, thereby allowing the expansion of fluid in the subsoil or in the aquifer to be decontaminated.

[0046] As shown for example in FIG. 3, the fracturing of the hollow space 4 can be urged by a procedure of activating the first valve 2, and possibly the possible further valves 2, adapted to enable a communication between the piping 1 and the subsoil, or the aquifer, by injecting a fluid, preferably water, through a shutter device 5 which can be dilated and reversible, such as for example a double or single packer.

[0047] The injecting means are adapted to inject 7, into the subsoil and into the aquifer, through the first valve 2, and possibly through the possible further valves 2, in open configuration, the fluid in predefined amounts depending on the depths 9 required by the project. As shown for example in FIGS. 3, 4 and 5, the first valve 2, and possibly the possible further valves 2, is upwards and downwards delimited by the shutter device 5, the shutter device 5 being adapted, depending on at least one value of the injecting pressure and flow-rate 7, to enable the passage from the closed configuration to the open configuration, and vice versa, for the first valve 2, and possibly for the further valves. Obviously, if it is necessary to inject from all valves simultaneously, the lower shutter device would not be necessary.

[0048] The process according to the present invention is therefore highly efficient, being it possible to perform multiple injections of the fluid through at least the valves 2. In particular, it is possible to perform multiple injections ensuring a cleaning of the piping 1 and of the valves from possible residuals of the previous injection.

[0049] The components used during the process according to the present invention, in particular the piping 1, the shutter device 5 and the valve 2, and possibly the further valves 2, are composed of materials resisting to known contaminants and N capable of operating at high pressures. The materials, such as for example PVC, or HDPE, or stainless steel, Teflon, rubbers, elastomers, etc., used for making the present invention, have been obtained and studied for this purpose and have been subjected, by the Applicant, to laboratory tests for determining their mechanical characteristics, and their resistance to atmospheric agents, hydrocarbons, solvents, oils, heat and low temperatures.

[0050] Herein below a description will be given of the decontamination activities activated on two aquifers by using the process according to the present invention.

[0051] The first activity provides for the decontamination from chlorinated aliphatic hydrocarbons, with a width of about 35 m and depths included between 14 and 34 m from the natural level, of an aquifer characterized by a gravely-sandy matrix, with hydraulic conductivity of about 510.sup.4 m/s, and hydraulic gradient of about 0.4%.

[0052] Seven verticals for multiple injection are arranged, each point characterized by a piping equipped with 18 valves for injecting 43 tons of a muddy mixture with water base with biopolymers and iron particles adapted to confer it a non-Newtonian rheological behaviour, for a total of 130,000 l of mixture.

[0053] Under application conditions, the high contamination depth does not allow using known injecting techniques.

[0054] The use, under application conditions, of the process according to the present invention allows performing injections at high depths, performing repeated injections of the fluid in wide time intervals, and guaranteeing the functionalities of the components under highly polluting conditions, like the one described above.

[0055] Herein below, the steps will be described which characterize the process for decontaminating the aquifer from chlorinated aliphatic hydrocarbons, according to the present invention:

[0056] arranging a hole whose diameter is 101/127 mm through rotary drilling at a depth of 34 m from the ground surface;

[0057] inserting and installing a piping equipped with non-return valves placed along the length of the piping at pre-established intervals between 14 and 34 m from the natural level;

[0058] arranging a sealed hollow space interposed between the external surface of the piping and the internal surface of the hole;

[0059] preparing the fluid through the use of a mixing and injecting plant equipped with 2 tanks whose capacity is 200 l each;

[0060] inserting, on the bottom of the piping, an injecting means, adapted to selectively inject at the depths required by the project;

[0061] activating two valves, included between the two shutter devices;

[0062] injecting the fluid next to the two open valve with a pressure value, included in a range between 0.5 and 40 bar, allowing to inject the amount of desired product for each depth;

[0063] moving the injecting means on 2 valves overlapping the previous ones and repeating the two previous steps;

[0064] repeating the two previous steps for the following valves;

[0065] removing the residuals of the injected product ensuring the functionality of the station for the following injection.

[0066] The above described process is applied to all seven points arranged for decontaminating the aquifer.

[0067] After about one month from the injection step, bacteria are inoculated in each of the stations, increasing the amount of bacteria present in the environmental matrix and enabling the removal of the contaminant.

[0068] The second activity provides for the decontamination, from chlorinated solvents and aromatic hydrocarbons, of an aquifer characterized by a sandy matrix, with hydraulic conductivity of about 410.sup.4 m/s, and upper confined by a layer of clay, as an average 7-8 m thick.

[0069] Three injection points are arranged inside an industrial plant and, for each station, 3 injections are performer with a mixture of water and slow oxygen release substances.

[0070] Initially, injection through traditional piezometers has been used as decontamination technique for the aquifer, but the injected mixture reflowed and rose along the piezometer walls and along the gravel pack in the hollow space between the hole and the well piping, moving along the preferential ways; moreover, the mixture, being dispersed, did not release enough amounts of oxygen inside the aquifer to be decontaminated; finally, an amount of the injected mixture is deposited on the bottom of the piezometric piping, being the piezometric piping not equipped with non-return valves, usually adapted to avoid the reflow of the injected produce inside the piezometer or of the piping.

[0071] Under application conditions and in view of the difficulties encountered by using the injecting technique in traditional piezometers, the process according to the present invention is performed, which provides for the following steps:

[0072] perforating a hole whose drilling diameter is 101/127 mm through a rotation probe at 20 m of depth from the natural level;

[0073] inserting and installing a piping whose diameter is 1 equipped with 12 non-return valves placed along the piping every 50 cm, from 14.25 m to 19.75 m from the natural level;

[0074] arranging a sealed hollow space interposed between the external surface of the piping and the internal surface of the hole;

[0075] preparing the mixture of reacting products, 126 kg of reacting product mixed with 600 l of water, through the use of a mixing and injecting plant equipped with 2 tanks, each with a capacity of 200 l;

[0076] inserting, on the bottom of the piping, an injecting means, adapted to selectively inject at the desired depths;

[0077] activating 3 valves included between two shutter devices;

[0078] injecting, with a certain pressure value, fluid next to the 3 valves, allowing to inject the amount of desired product for each depth;

[0079] moving the injecting means on 3 valves overlapping the previous ones and repeating the two previous steps

[0080] repeating the two previous steps for the following valves;

[0081] removing the residuals of the injected product ensuring the functionalities of the station for the following injection.

[0082] The invention has the following advantages:

[0083] enabling the injection into the subsoil or the aquifer of a selected amount of reacting products at designed depths;

[0084] avoiding daylighting of products injected into the subsoil or the aquifer, inside a piping inserted into a suitable hole;

[0085] allowing the single or multiple injections of reagents into the subsoil;

[0086] allowing the injection into the subsoil of products by low pressure permeation and/or by preferential flow at high injection pressure;

[0087] allowing the injection of products also inside porous, fractured or karst aquifers;

[0088] enabling to perform vertical, horizontal, or inclined probing in the subsoil or the aquifer;

[0089] allowing the installation of a valve-type piping also when there are environmental aquifer or matrixes which are highly polluted by aggressive contaminants, guaranteeing the functionalities of materials in time.