PROCESS FOR SOIL AND GROUNDWATER DECONTAMINATION IN AN AREA TO BE DECONTAMINATED FROM ORGANIC AND INORGANIC CONTAMINANTS AND PLANT FOR CARRYING OUT SUCH A PROCESS

DESCRIPTION

Field of the invention

The present invention relates to a plant for the treatment of subsoil and aqui fer which is able to reduce , up to completely eliminate , organic and/or inorganic substances contaminating the same .

The invention relates , furthermore , to a process for the decontamination of subsoil and aqui fer .

Description of the prior art

As known, in the subsoil and groundwater are normally present contaminants of anthropic or natural origin, which, accumulating over time, can exceed the limits beyond which they are dangerous for the health of human beings and for the health of the environment .

In particular, the soils are highly contaminated at the industrial sites , even though abandoned from a long time, in the waste disposal areas , but also in areas where particular intensive agricultural practices are carried out .

The main contaminants detected at the industrial sites are normally lubricant oils , fuels , chloride solvents , aromatic compounds , dioxins , Polychlorinated biphenyls ( PCBs ) , but also heavy metals , ionic compounds , etc .

The agricultural activities can contribute to increase the subsoil and groundwater pollution due to the use of pesticides , fungicides , parasiticides , phosphates , nitrates etc .

The quality of subsoil can also be compromised due to the storage of chemical products , because some quantity of these substances can move in the soil and trigger chemicalphysical processes which produce toxic, or cancerogenic substances .

Therefore , over time, processes and plants have been studied for removing the aforementioned contaminant substances from the subsoil and from the groundwater .

However, the processes and the plants that have been designed are not very effective due to the great depth at which the operations have to be carried out, in addition to the high volumes to be treated, which make the operations necessary to carry out the decontamination of the target area highly expensive and technically complex .

The known processes are specifically designed for the decontamination of saturated or unsaturated zones of the soil , or of the aqui fer . Technologies are not known that are effective contemporaneously on all the aforementioned environmental compartments .

Another drawback is that the known processes are generally selective on the contamination target and, therefore, specific, alternatively, for removing organic or inorganic contaminants .

Unto this day, for example, technologies are known which provide to inj ect in the subsoil determined chemical or biological products by traditional piezometers . The piezometers , at the saturated zone of the soil , are provided with windows through which the reagent products are introduced in the aquifer .

These technologies are not able to decontaminate the unsaturated zone of the soil .

Othe technologies use system for insufflating air or oxygen for stimulating biological degrative processes in the soil at the saturated and unsaturated zones .

These technologies are not effective on the inorganic contamination and are used for the treatment of soils characterized by low concentrations of organic contaminants .

In the prior art systems are also known for in situ fluxing of the soil , that can be used on the unsaturated zone of the soil , that, however, are exclusively based on the leaching capacity of the fluxing fluid, without activating biodegradative processes of the organic decontamination .

Other prior art solutions are described in KR101119394 , US 6158924 and US3706384 .

In particular, the document KR101119394 describes a movable system for purifying the leachate generated by a buried place of livestock carcass . The decontamination system is mounted on a vehicle and provides a pumping device for pumping the leachate from a well to subj ect the same to a Fenton treatment and to a filtering process . However, the solution described in KR101119394 is not able to satisfactory reduce organic and inorganic contaminants in particular of large areas .

Another drawback of the solution described in KR101119394 is that the process is not versatile, that means that cannot be modi fied depending on the type of soil and/or groundwater to be decontaminated . Therefore , the effectiveness of the described treatment is limited only to determined types of contaminants .

Summary of the invention

It is , therefore , an obj ect of the present invention to provide a plant for in si tu decontamination of soil and groundwater of a predetermined area to be decontaminated which allows to remove from the treated material both organic contaminants and inorganic contaminants by biological and chemical mechanisms .

It is also an obj ect of the present invention to provide a plant for in si tu decontamination of soil and groundwater that is highly versatile and that can be modi fied on the basis of the type of organic and/or inorganic contaminants which are present in the soil and groundwater to be decontaminated .

It is , furthermore , an obj ect of the present invention to provide a process for in si tu decontamination of soil and groundwater having the same advantages .

These and other obj ects are achieved by a plant , according to the invention, for in si tu decontamination of soil and/or groundwater in a predetermined area to be decontaminated from organic and inorganic contaminants , wherein said soil and/or said groundwater to be decontaminated have been preliminary subj ected to a characterization step for designing a conceptual multidimensional model , whose main characteristic is that it comprises :

- an extraction section configured to extract a predetermined flow-rate of said groundwater to be decontaminated; - a pre-treatment section hydraulically connected a said extraction section, said pre-treatment section comprising at least a primary sedimentation device configured to separate determined floating substances and sludge from said groundwater obtaining a pretreated aqueous solution;

- a physical-chemical treatment section hydraulically connected to said pre-treatment section for feeding in said physical-chemical treatment section a predetermined flow-rate of said pre-treated aqueous solution, said physical-chemical treatment section comprising :

- a predetermined number of reaction tanks inside of which said predetermined flow-rate of said pretreated solution is arranged to be fed to subj ect said pre-treated aqueous solution to at least a reaction by adding first predetermined reagents adapted to cause the precipitation of determined contaminants which are present in said pre-treated aqueous solution;

- at least a secondary sedimentation device hydraulically connected to at least a reaction tank of said predetermined number of reaction tanks and configured to physically separate said precipitated contaminants from an aqueous solution;

- at least a filtering device hydraulically connected to said secondary sedimentation device , said or each filtering device being configured to filter said aqueous solution, obtaining a filtered aqueous solution;

- an enrichment section configured to add second predetermined chemical reagents and at least one predetermined enrichment biological solution to said filtered aqueous solution obtaining an enriched aqueous solution, said second predetermined chemical reagents and said or each enrichment biological solution being selected according to said conceptual multidimensional model ;

- an inj ection section configured to inj ect at a predetermined depth in said soil of said predetermined area to be decontaminated, a predetermined inj ection flow-rate of said enriched aqueous solution to obtain a saturation of the unsaturated zone of said soil of said predetermined area to be decontaminated and to stimulate a hydraulic circulation both at the saturated zone and at the unsaturated zone of the soil , in such a way to promote a biostimulation, a bioaugmentation and a leaching of said inorganic and organic contaminants .

In this way, the typical characteristics of the soil identi fied in the preliminary characteri zation step allows to design a conceptual multidimensional model for calibrating the enrichment step of the filtered aqueous solution .

In particular, in the enriched aqueous solution microorganisms can be added that are selected on the basis of the results of a metagenomic analysis of the soil and/or groundwater carried out in the preliminary characteri zation step .

Other technical characteristics of the invention and related embodiments are defined in the dependent claims .

In particular, at the enrichment section the addition of a predetermined quantity of oxygen or air to the filtered aqueous solution, can be, furthermore, provided . More in particular, the aforementioned predetermined quantity of oxygen can be set according to the conceptual multidimensional model .

In particular, during the aforementioned preliminary characterization step a plurality of physical-chemical and/or nutrient parameters is measured . More in particular, the aforementioned plurality of physical-chemical and/or nutrient parameters can be chosen among : soil texture, soil structure, apparent density, electrical conductivity, pH, Redox potential , humidity content, mineralogical and geochemical composition, cation exchange capacity, plugging capacity, organic material content, nutrients content, for example organic Carbon, Total Carbon, Total Nitrogen, Phosphorus and available Potassium, or a combination thereof .

In particular, during the aforementioned preliminary characteri zation step, the contamination factors are analysed . More in particular, the aforementioned analysis of the aforementioned contamination factors can be chosen among : analysis of the concentration in soil and in groundwater of heavy metals and metalloids , polycyclic aromatic hydrocarbon, petroleum hydrocarbons , polychlorobiphenyls , dioxins and furans , pesticides , sequential extraction procedure ( SEP ) , metals and metalloids , in particular according to the BCR fractionation method 1997 , Srithongkul 2020 , Wenzel 2001 .

In particular, during the aforementioned preliminary characteri zation step an analysis is carried out of the autochthonous microbial community of the contaminated soils . More in particular, the aforementioned analysis of the aforementioned microbial community can be carried out by extracting the total genomic DNA of the environmental matrix by metabarcoding and predictive functional metagenomic .

In particular, during the aforementioned preliminary characteri zation step the analysis of the toxicity of the environmental matrix is carried out . More in particular, the aforementioned analysis of the toxicity of the environmental matrix can be carried out by : micronucleus test ISO 29200 : 2020 , acute toxicity test , eluate test WET , phytotoxicity test .

The data acquired with the aforementioned preliminary characteri zation step are introduced into a data-base and converted into a conceptual model of the site that can be represented in a multidimensional space , the evolution of which i s monitored during the treatment , thanks to the execution of successive characteri zation campaigns of the treated matrices , i . e . groundwater and soil .

In particular, the enrichment section comprises at least a bioreactor containing a predetermined biological solution . More in particular, the aforementioned biological solution comprises at least a species of microorganisms selected on the basis of the results of the aforementioned preliminary characteri zation step of the soil and/or groundwater .

In an embodiment of the invention, the aforementioned biological solution comprises at least a species of microorganisms selected among :

- Ascomycetes fungi , preferably of Fusarium Oxysporum sp genus ; - Bacteria of Proteobacteria species and/or

Actinobacteria species ;

- or a combination thereof .

Advantageously, the enrichment section can comprise at least one mechanical mixer configured to mix a predetermined quantity of air or oxygen with a predetermined flow of the filtered aqueous solution .

In particular, the or each mechanical mixer can be adapted to mix a predetermined quantity of micro-bubbles and/or nano-bubbles of air and/or of oxygen with the filtered aqueous solution . In this way, the quantity of oxygen dissolved in the filtered aqueous solution increases . This allows to promote , as anticipated above , chemical and aerobic biological processes in the subsoil and in the groundwater of the area to be decontaminated .

In addition, or alternatively, to the or each mechanical mixer, the enrichment section can comprise at least one storage tank containing at least a reagent adapted to be added to the filtered aqueous solution at the enrichment section, in particular to a predetermined flow-rate of this , to be , then, inj ected at the successive inj ection section .

More precisely, the or each storage tank contains at least one reagent chosen among :

- a solution of hydrogen peroxide at a concentration of between 30% and 40%, for example 35% ;

- a solution of 60% sodium dithionite ;

- a solution of ascorbic acid and ammonium oxalate ;

- a solution of ethylenediaminetetraacetic acid, or EDTA, in particular at a concentration of 1 % ; or a combination thereof . In an embodiment of the invention, the aforementioned extraction section comprises at least one extraction well, preferably a slotted extraction well. Preferably, at least one pumping device is provided adapted to pump the aforementioned aqueous solution to be decontaminated and to form a flow to be decontaminated.

In particular, the aforementioned injection section can comprise at least an injection duct hydraulically connected to at least one pump for pumping the enriched aqueous solution into the or each injection duct.

In particular, the aforementioned pre-treatment section can provide a plurality of primary sedimentation devices arranged in series or in parallel to each other.

Advantageously, the aforementioned reaction tanks can comprise at least one reaction tank selected among:

- a tank containing sodium hydroxide, in particular a solution of sodium hydroxide at a concentration of between 25% and 35%, preferably 30%;

- a tank containing aluminium polychloride, or PAG, in particular at a concentration of between 15% and 20%, preferably 17%, or 18%;

- a tank containing sodium hydrosulphide, in particular at a concentration of between 5% and 15%, preferably al 10%;

- a tank containing at least a polyelectrolyte, in particular at a concentration of between 0.05% and 0.2%, preferably 0.1%;

- a tank containing hydrogen peroxide, in particular at a concentration of between 25% and 35%, preferably at a concentration of 30%;

- a tank containing sodium hypochlorite, in particular at a concentration of between 10% and 20% , preferably at a concentration of 14% .

Preferably, the flow-rate extracted at the extraction section is greater than the flow-rate of the inj ected aqueous solution at the inj ection section .

According to another aspect of the invention, a process for in si tu decontamination of soil and/or groundwater in a predetermined area to be decontaminated from organic and inorganic contaminants comprises the steps of :

- chemical , physical and biological characterization of the soil and/or groundwater to be decontaminated;

- designing a conceptual multidimensional model of the area to be decontaminated on the basis of said chemical , physical and biological characterization;

- extracting a predetermined flow-rate of said groundwater from said area to be decontaminated;

- pre-treating said groundwater for removing floating substances and sludge obtaining a pre-treated aqueous solution;

- physical-chemical treatment of said pre-treated aqueous solution, said physical-chemical treatment comprising the steps of :

- adding first predetermined chemical reagents to said pre-treated solution to cause the precipitation of determined contaminants which are present in said pre-treated solution;

- sedimentation of an aqueous solution obtained by said adding step of said first predetermined chemical reagents to said pre-treated solution to cause a physical separation of said precipitated contaminants from an aqueous solution;

- filtering said aqueous solution obtaining a filtered aqueous solution;

- enrichment of said filtered aqueous solution by adding second predetermined chemical reagents and at least a predetermined enrichment biological solution, to said filtered aqueous solution obtaining an enriched aqueous solution, said second predetermined chemical reagents and said, or each, predetermined enrichment biological solution being selected according to said conceptual multidimensional model ;

- inj ecting, at a predetermined depth, in said soil of said predetermined area to be decontaminated, a predetermined flow-rate of said enriched aqueous solution to obtain a saturation of the unsaturated zone of said soil of said predetermined area to be decontaminated and to stimulate a hydraulic circulation at the saturated zone and at the unsaturated zone of soil , in such a way to promote a biostimulation, a bioaugmentation and a leaching of said organic and inorganic contaminants .

In particular, the enrichment step can provide, furthermore, a mixing of a predetermined quantity of oxygen, or air, to the filtered aqueous solution . More in particular, the aforementioned predetermined quantity, in particular the flow-rate , of oxygen, or air, mixed to the filtered aqueous solution can be set, or modulated, according to the conceptual multidimensional model .

In particular, a dehydration step can be , furthermore , provided of the sludge coming from the primary sedimentation and from the secondary sedimentation . Brief description of the drawings

The invention will now be shown with the following description of its exemplary embodiments , exempli fying but not limitative , with reference to the attached drawings in which :

Fig . 1 shows a possible functional scheme of the plant, according to the invention, for the decontamination of soil and groundwater of a predetermined area to be decontaminated from organic and inorganic contaminants ;

Fig . 2 shows the conceptual scheme of the plant of figure 1 to highlight some technical characteristics ;

Fig . 3 shows a complete plant configuration provided by the invention of the plant of figure 1 for soil and groundwater decontamination of a predetermined area to be decontaminated from organic and inorganic contaminants ;

Fig . 4 diagrammatically shows a plan view of the plant of figure 3 to show some technical characteristics ;

Fig . 5 diagrammatically shows an elevational side view of an extraction well which can be used by the plant, according to the invention, for extracting soil and groundwater;

Fig . 6 diagrammatically shows an elevational side view of an inj ection well which can be used by the plant, according to the invention, for inj ecting in the subsoil the water subj ected to the process carried out by the decontamination plant, according to the invention; Fig . 7 diagrammatically shows an elevational side view of a possible embodiment of a detection probe for detecting the soil gases which can be used by the plant according to the invention;

Fig . 8 diagrammatically shows an elevational side view of a possible embodiment of a groundwater monitoring well , which can be used by the plant according to the invention;

Fig . 9 diagrammatically shows a possible sequence of steps of the process , according to the invention, for the decontamination of soil and groundwater from organic and inorganic contaminants .

Detailed description of some exemplary embodiments of the invention

In figure 1 a plant 1 , according to the invention, is diagrammatically shown for in si tu decontamination of soil and/or groundwater of a predetermined area to be decontaminated simultaneously from contaminants of organic type , in particular Polycyclic Aromatic Hydrocarbon ( PAH) and Total petroleum hydrocarbons ( TPH) , and of inorganic type , in particular iron, Manganese , Cadmium, Copper, Chrome , Magnesium, Nichel , Lead, Zinc and Arsenic .

In particular, according to what is provided by the invention, and described in detail below, the soil and/or the groundwater of the area to be decontaminated are preliminary subj ected to a characterization in order to design a conceptual multidimensional model by collecting and analysing a series of data related to physical-chemical and/or nutrient parameters .

In particular, the plant 1 comprises an extraction section 10 configured to extract a predetermined flow-rate of groundwater of the area to be decontaminated at a predetermined depth, for example at a depth comprised between 6 and 10 m, for example at a depth of about 8 metres . More in particular, the extraction section 10 is configured to produce a predetermined groundwater extraction flow-rate . The extraction section 10 provides at least an extraction well 15 , in particular at least a slotted well that means provided, at a passageway portion 15 ' , with a series of slots , or slits ( see in particular figure 5 ) . The or each extraction well 15 is connected to at least one pumping device, such as a volumetric pump, connected to the or each extraction well 15 by one or more ducts . In this way, it is possible to extract the groundwater and to generate the aforementioned extraction flow-rate of groundwater . The extraction section 10 is hydraulically connected to a pre-treatment section 20 . This can, advantageously, comprise at least a primary sedimentation device 25 configured to separate the floating substances which are present in the groundwater that concentrate , as known, at the superficial zone , from the sludge , which, instead, concentrate at the bottom of the sedimentation device 25 .

In the alternative embodiment that is diagrammatically shown in figure 3 , at the sedimentation section 20 a first and a second primary sedimentation device 25a and 25b are provided connected in parallel to each other .

Once that the primary sedimentation step which has been carried out at the pre-treatment section 20 is completed, from the starting solution of the groundwater a pre-treated aqueous solution is obtained . This is , then, sent , for example by at least a pumping device 26 , from the pre-treatment section 20 to a physical-chemical treatment section 30 , diagrammatically shown in figure 1 with a block with a broken line .

As diagrammatically shown in figure 1 , the physicalchemical treatment section 30 can provide a first filtering device 31 , preferably a basket filter, to remove residual quantity of sludge which has not been removed at the pre-treatment section 20 . In particular, the physicalchemical treatment section 30 can comprise , advantageously, at least one reaction tank 35 inside of which the pre-treated solution is subj ected to at least one reaction, in particular an oxidation reaction, by adding one or more first predetermined chemical reagents in order to cause the precipitation of determined contaminants which are present into the pre-treated aqueous solution .

In the embodiment which is diagrammatically shown in figure 3 , a first , a second, a third and a fourth reaction tank 35a-35d are provided connected in series with each other . In an embodiment according to the invention, in the first reaction tank 35a can be fed a solution of 17 % , or 18 % polyaluminium chloride , or PAG, and a solution of 30% sodium hydroxide (NaOH) to cause a first reaction . In particular, the polyaluminium chloride , or PAG, is used to lower the pH in the first reaction tank 35a, advantageously up to a value comprised between 4 . 6 and 4 . 8 , i . e . 4 . 6<pH<4 . 8 . In the second reaction tank 35b the aforementioned solution of 30% sodium hydroxide (NaOH) can be fed together with a solution of 30% sodium hydrosulphide in order to cause a second reaction . The solution of 30% NaOH in the second reaction tank 35b is , in particular, used to bring the pH back to basic values in such a way to allow the hydroxides to precipitate .

In the third reaction tank 35c a solution containing a polymer, in particular a 0 . 1 % polyelectrolyte , can be fed . Still according to the embodiment of figure 2 , in the fourth reaction tank a solution of 15% sodium hypochlorite and a solution of 30% , or 35% hydrogen peroxide can be fed .

In particular, the aforementioned reacting solutions can be contained in the respective storage tanks , in the case of figure 3 , six storage tanks 36a-36f , and can be fed into the respective reaction tanks 35a-35d by respective pumping devices 37a-37 f . Downstream of the or each reaction tank 35 , or 35a-35d, a secondary sedimentation device 39 , for example a lamellar settler, is provided . Also in this case , the fraction of floating substances will be concentrated at the surface , whilst the heavier parts at the bottom . From the secondary sedimentation device 39 , the sludge produced by the sedimentation process are sent , preferably by a Mohno pump 33 , to a dehydration device 60 in such a way to reduce its water content . In this way, the successive treatment and disposal operations provided by the process are greatly simpli fied and cheaper . The water removed at the dehydration device 60 is sent , by a pumping device 65 , to the pre-treatment section 20 in order to subj ect the same to a further sedimentation process .

The aqueous solution which is present in the secondary sedimentation device 39 , in particular a clari fied or substantially clari fied aqueous solution, which can exit from this by overflowing, or alternatively by drawing the same by a pumping device , is fed, for example by drawing it from a collecting tank 34 , inside of which can be collected, into at least a filtering device 32 to be filtered .

As diagrammatically shown in the alternative embodiment of figure 3 , a plurality of filtering devices 32 , for example four filtering devices 32a-32d arranged in series with each other, can be provided . For example , the four filtering devices 32a-32d can be two groups of filtering devices 32a, 32b and 32c, 32d which can work in parallel or in series . For example , the four filtering devices 32a-32d can comprise in combination or singularly, at least one sand filtering device 32a, preferably quartz sand, at least one pyrolusite filtering device 32b, at least one zeolite filtering device 32c, and at least one activated carbon filtering device 32d . The water removed at the or each filtering device 32a-32d is recirculated upstream of the plant 100 and fed to the or each primary sedimentation device 25 to be there subj ected to a further sedimentation process .

From what is described above and from the plan scheme of the plant 1 of figure 4 , the physical-chemical treatment section 30 can be ideally divided into a sub-section of chemical treatment 30a, at which the reaction tanks 35a-35d are provided, and into a sub-section of physical treatment 30b, at which the filters 32a-32d are provided . The filtered aqueous solution exiting the or each filtering device 32a-32d, instead, is , advantageously, sent to a collecting tank 70 . From here, the filtered aqueous solution is sent to an enrichment section 40 . More precisely, at the enrichment section 40 the filtered aqueous solution can be subj ected to treatments in order to increase the quantity of oxygen which is present in the same and/or the content of determined biological substances obtaining an enriched aqueous solution . More in detail , the enrichment of the aqueous solution 40 can be carried out by adding to the filtered aqueous solution second predetermined chemical reagents selected according to the results obtained in a preliminary characteri zation step of the soil and/or groundwater to be decontaminated . The preliminary characterization of the soil and/or groundwater is carried out by extracting a predetermined number of samples of the soil and/or groundwater at predetermined depths and analysing such samples , in particular in such a way to identify the organic and inorganic contaminants which are present and, therefore , to design a conceptual multidimensional model of the area to be decontaminated .

In particular, during the characterization step all or a part of the following physical-chemical and/or nutrient parameters can be measured : soil texture , soil structure, apparent density, electrical conductivity, pH, Redox potential , humidity content, mineralogical and geochemical composition, cation exchange capacity, plugging capacity, organic material content, nutrients content, such as organic Carbon and total Carbon, total Nitrogen, Phosphorus and available Potassium, heavy metal or metalloid content, in particular Arsenic, Cadmium, Copper, Chrome , Mercury, Nichel , Lead, and Zinc, content of Polycyclic Aromatic Hydrocarbon ( PAH) , Total petroleum hydrocarbons ( TPH) , or a combination thereof . More in detail , the determination of the geo-chemical association of the heavy metals to the main phases of the soil ( exchangeable, reducible, oxidizable and residual fraction) allows to estimate the leaching potential and, therefore, to direct the composition of the base composition of the leaching solution .

In addition, or alternatively, during the preliminary characteri zation step a microbiological characteri zation of the soil and/or groundwater can be carried out . In particular, the microbiological characteri zation can be obtained by a metagenomic analysis . This , as known, allows to classi fy the microorganisms of the soil and to determine their potential functions . The presence of particular microorganisms can be detected by extracting and sequencing their DNA, which can be then characterised revealing the nature of the microorganism contained in the same . From the analysis of the DNA sequences , is , in fact , possible to determine the di f ferent species which are present in the sample . In this way, it is possible to select the species of microorganisms which is more suitable to the treatment and able to guarantee an ef fective bioremediation of the soil and/or groundwater . Furthermore , in the enrichment section 40 the feeding of a predetermined flow-rate of oxygen or air can be provided, and its mixing with the filtered aqueous solution in order to increase the content of oxygen of this latter .

For example , as diagrammatically shown in figure 2 , the enrichment section 40 can be equipped with a mechanical mixer 45 adapted to mix a predetermined quantity of air, preferably micro-bubbles , or nanobubbles , of air, or oxygen, in the aqueous solution in order to increase the quantity of oxygen of the same . In particular, the aforementioned predetermined quantity of micro-bubbles and/or nano-bubbles of air or oxygen can be set according to the aforementioned conceptual multidimensional model .

The enrichment section 40 can, furthermore , provide at least one enrichment tank 42 containing a respective enrichment solution . This can be , in particular, a chemical solution or a biological solution . Advantageously, at the enrichment section 40 at least a first tank 42 can be provided containing a chemical solution and at least a second tank 43 containing a determined nutrient solution, or a determined biological solution .

In the embodiment of figure 3 , the plant 100 , at the enrichment section 40 , provides 3 tanks 42a-42c containing respective reagents , in particular determined enrichment solutions . For example , the enrichment solutions can be a solution of hydrogen peroxide , in particular at a concentration of between 25% and 35% , advantageously 30% , a solution of sodium dithionite , in particular at a concentration of between 55% and 65% , advantageously 60% , and a solution of ascorbic acid and ammonium oxalate . In addition, or alternatively, to the aforementioned reagents , a solution of ethylenediaminetetraacetic acid, or EDTA, in particular at a concentration of 1 % can be provided .

In the case that from the preliminary characteri zation of the soil and/or groundwater the presence of heavy metals , in particular Lead, Cadmium, Copper, Chrome , Manganese , Magnesium, Nichel , Zinc, is detected, as reagent can be , advantageously, used a solution of 60% sodium dithionite and of 1 % EDTA.

In the case that from the aforementioned preliminary characteri zation of soil , a signi ficant presence of metalloids is detected, in particular Arsenic, a solution of ascorbic acid and ammonium oxalate can be preferably used .

In particular, it has been veri fied that i f the soil contains a high concentration of organic contaminants using as reagent a solution of 35% hydrogen peroxide and of 1 % EDTA, in addition to solubili ze the inorganic contaminants , it is possible to act on the organic contaminants thus increasing their biodegradability, in particular by the fragmentation of the molecules , the incorporation of oxygen atoms which leads to the formation of alcohols and carboxylic acids .

The aforementioned second predetermined reagents can be , advantageously, withdrawn from respective tanks 42a- 42c and can be sent , for example by respective pumping devices , for example respective volumetric pumps , along a feeding line , in order to generate a flow-rate established based on the textural parameters of soil and the recharge capacity of the aqui fer .

For example , the flow-rate of the inj ected solution can be comprised between 20 1/h and 50 1/h, advantageously comprised between 30 1/h and 40 1/h .

In particular, the addition to the filtered aqueous solution of one or more of the aforementioned second predetermined reagents , allows to obtain, when the enriched aqueous solution so obtained is inj ected in the subsoil at the extraction section, a leaching of the soil at the unsaturated zone 202 .

As known, in fact , see in particular figure 2 , starting from the so called "ground level" 201 and going in the depth, it is possible to identi fy several zones in the soil 200 . These are di fferent from each other basically on the water saturation level and on the granulometric and textural characteristics .

In particular, immediately below the ground level 201 a zone called "unsaturated zone" 202 is present . Here empty spaces are present comprised between the soil granules that are not completely full of water, which is able to move towards below by gravity, and towards above by capillarity .

Below the unsaturated zone 202 there is the so-called "capillary fringe" 203 which is a zone of passage between the unsaturated zone and the falda 204 . At the capillary fringe 203 the pores are almost completely occupied by the liquid phase , which is kept here by capillarity at a pressure which increases with the depth, but however less than the atmospheric . Its thickness changes considerably with the granulometry of the soil passing from few centimetres in the gravel up to a pair of metres in the clay . Below the capillary fringe 203 the " saturated zone" , or "aqui fer" 204 is located . This contains the groundwater, whose boundary with the capillary fringe 203 is the piezometric surface , defined as the surface along which the groundwater pressure is equal to the atmospheric pressure . At the aqui fer all the pores or slits are saturated with water and this moves mainly along a hori zontal direction .

The aforementioned leaching allows to carry out the removal of inorganic contaminants such as Arsenic, Lead, Cadmium, but also Copper, Zinc, Magnesium, Manganese , etc . from the soil .

These inorganic contaminants are , then, removed from the extracted aqueous solution at the extraction section 10 through the di f ferent sections which form the plant 100 , according to the invention .

Downstream of the aforementioned storage tanks 42a-42c a fourth storage tank 43 can be , furthermore , provided containing a soil amendment solution, preferably a solution containing the macronutrients of soil , in particular Nitrogen, Phosphorus and Potassium .

In particular, the amendments can be UREA, monobasic potassium phosphate , KH2PO4 , and Potassium bicarbonate , KHCO3.

Downstream of the storage tanks 42a-42c, or the fourth tank 43 i f present , can be , furthermore , provided a bioreactor 44 containing the aforementioned biological solution . This , for example , can contain at least a species of microorganisms , in particular selected on the basis of the aforementioned preliminary characteri zation step of the soil and/or groundwater .

In particular, the second chemical reagents and/or the enrichment biological solutions to add to the filtered aqueous solution at the enrichment section 40 , are selected according to the conceptual multidimensional model . Analogously, the flow-rate of oxygen which is added to the filtered aqueous solution at the enrichment section 40 is modulated according to the conceptual multidimensional model .

In an embodiment of the invention, the microorganisms can be Fusarium Oxysporum species belonging to Ascomycetes fungi .

More in particular, the selected microorganisms can be extracted and enriched starting from samples of soil of the area to be subj ected to the decontamination process according to the invention .

Once that the aqueous solution has been enriched by adding the aforementioned enrichment solutions , an enriched aqueous solution is obtained that is re-inj ected in the subsoil at a predetermined depth, in particular, as anticipated above , at the unsaturated zone 202 , advantageously at a depth between 2 m and 8 m, at an inj ection section 50 . This can comprise , for example , one or more ducts , preferably made of HDPE (High Density Polyethylene ) hydraulically connected to at least a pumping device 51 .

In particular, the inj ection in the subsoil of the enriched aqueous solution, as described above , allows to obtain a saturation of the unsaturated zone of the soil and to stimulate a hydraulic circulation both at the saturated zone and at the unsaturated zone of the soil . In this way, it is possible to promote a biostimulation, a bioaugmentation, and a leaching of the inorganic and organic contaminants which are present . In particular, the aforementioned leaching, in particular owing to the presence of the aforementioned second chemical reagents , allows to remove from the soil and/or groundwater, contaminants such as Arsenic, Lead, Cadmium, but also Copper, Chrome , manganese , Zinc, Magnesium, etc . and organic contaminants .

In particular, according to the invention, the inj ection section 50 can be adapted to inj ect in the subsoil the aforementioned enriched aqueous solution by adding the or each reagent withdrawn from a respective storage tank 42a-42c in a first inj ection step, and after this first inj ection step, to inj ect water, or an enriched aqueous solution by adding micro-bubbles , or nano-bubbles of air, as described above , in a second inj ection step following the first one .

The plant 100 as described above and diagrammatically shown in particular in the figures 1 and 3 , therefore , carry out a closed cycle which, starting from an aqueous solution to be decontaminated comprising groundwater extracted at the extraction section 10 , which acts as the transport fluid of soil to be decontaminated and which in turn is treated to be decontaminated, to be , then, reinj ected in the subsoil at the inj ection section 50 once they have been "enriched" as described above , to promote and help biological processes in the subsoil .

Preferably, the flow-rate of the extracted aqueous solution at the extraction section 10 is greater than the flow-rate of the inj ected aqueous solution at the inj ection section 50 . In this way the "water table" , i . e . the surface where the water pressure head is equal to the atmospheric pressure, is constantly at a pressure lower than the atmospheric one . The volume of clarified water in excess can be in part stored to be used again, or discharged from the plant to the sewerage, or in a body of water .

In particular, the flow-rate of the extracted solution is determined on the basis of the hydraulic conductivity of soil (determined from its texture ) and the recharge capacity of the aquifer . For example, the flow-rate of the extracted solution can be less than 10 m ³ /h, for example comprised between 2 m ³ /h and 10 m ³ /h, advantageously comprised between 8 m ³ /h and 10 m ³ /h .

As diagrammatically shown in figure 4 , the plant 100 according to the invention, can, furthermore , provide at least a monitoring device 80 , for example 4 monitoring devices 80a-80d, configured to monitor the level and the chemical quality of the aquifer outside the area to be decontaminated 110 . In particular, as diagrammatically shown in figure 8 , the or each monitoring device can be a piezometer 80a-80d, i . e . a monitoring well .

In an embodiment provided by the invention, the plant 100 can, furthermore, provide at least a detection device 85 ( see figure 7 ) adapted to measure some gases that can be produced during the soil treatment .

Advantageously, the plant 100 can, furthermore, comprise at least one storage tank 90 at which the rainwater is collected to be fed, for example by a pumping device, to the pre-treatment section 20 .

As diagrammatically shown in figure 9, the plant 100 as described above with reference to the figures from 1 to 8 , therefore, carries out a process of decontamination of soil and groundwater by a sequence of successive operations . In particular, the process provides an extraction starting step of the groundwater and/or the soil at the area to be decontaminated, block 301 . The groundwater is , therefore, subj ected to a starting treatment which provides a starting sedimentation, block 302 . This is carried out by one or more sedimentation devices 25, where, advantageously, can be used reagents , in particular flocculant and coagulant substances . In this way, the water is separated from the floating substances , block 309 and from the sludge which is present in the treated solution, block 310 . This , as anticipated above, is dehydrated, block 312 , before being sent to the dump, or used, for example , to produce energy .

After the primary sedimentation step, a step is provided for the physical-chemical treatment of the water so obtained, and a secondary sedimentation for separating the water from the heavy substances which are present, block 303 . The physical-chemical treatment provides , in general , to use a series of first chemical reagents to carry out a series of reactions , in particular reactions of oxidation, coagulation, flocculation and filtration, block 306.

The sludge exiting the physical-chemical treatment section is , then, sent, also in this case, to a dehydration section, block 312 .

The water obtained at the end of the physical-chemical treatment is , then, subj ected to an enrichment step, block 304 , before being inj ected by one or more ducts in the subsoil , block 305. In particular, during the enrichment step second chemical reagents and at least one enrichment biological solution are added, block 307 . These are selected according to a conceptual multidimensional model , block 321 , which is designed on the basis of a preliminary characterization of the soil and groundwater of the area to be decontaminated, block 320 .

EXPERIMENTAL DATA

In the following, the results obtained on a series of samples coming from a plant , according to the invention, installed in Bilbao for the in si tu decontamination of soil and/or groundwater, simultaneously, from contaminants of organic and inorganic type are reported.

In particular, 3 different samples were extracted from 9 different surveys. Each sample is representative of a stratigraphic horizon of interest. The 3 stratigraphic horizons are: one superficial, immediately under the concrete pavement, and precisely at an altitude of -0.60 m, the second at an altitude of -2.0 m and the third at an altitude of 3.5 m.

More precisely, the samples have been characterized by measuring for each of them at a distance of 7 months and precisely on August 2022 and on March 2023, the content of Arsenic (As) , Cadmium (Cd) , Chrome (Cr) , Nickel (Ni) , Lead (Pb) , Copper (Cu) , Mercury (Hg) , Zinc(Zn) , Total petroleum hydrocarbons cl0-c40, Dibenzo (a, h) anthracene, Benzo (a) pyrene, Indeno (1, 2, 3-cd) pyrene, pyrene, Benzo (a) anthracene, Chrysene, Benzo (b) fluoranthene, Benzo (k) fluoranthene and Polycyclic Aromatic Hydrocarbon, or IPA.

The treatment has been carried out, in particular, using as a reagent a solution of 35% hydrogen peroxide and of 1% EDTA. This chosen has been made because the results of the preliminary characterization have verified that the soil had a high concentration of organic contaminants. The aforementioned reagent, in fact, in addition to be able to solubilize the inorganic contaminants, is also able to act on the organic contaminants increasing the biodegradability of the same, in particular by molecules fragmentation, the incorporation of oxygen atoms which leads to the formation of alcohols and carboxylic acids. A flow-rate of the solution of 35% hydrogen peroxide and EDTA injected at about 30 1/h has been used . The treatment with this reagent has been interrupted after 6 days during which cycles of inj ection and extraction have been repeated, at the end of which 1500 1 of solution have been used .

A second reagent has been, furthermore, used and precisely a solution of ammonium oxalate and ascorbic acid . This solution resulted very effective in the removal of Arsenic, in particular Arsenic legato to Iron and Manganese oxides . In this case, a flow-rate of solution of ammonium oxalate and ascorbic acid inj ected at about 40 1/h has been used . The treatment with this reagent has lasted for 6 days during which 1500 1 of solution have been used .

The data which refer to the average decrease of some inorganic contaminants , and precisely : Arsenic, Cadmium, Chrome , Nickel , Lead, Copper and Zinc in a time period of 90 working days are reproduced in the following table ( Tab . 1 ) .

Tab . 1

As can be noted from the data reproduced in table 1 , Chrome is the inorganic contaminant with the lowest , even though signi ficant , percentage of decrease and precisely a decrease of 31 % , whilst the best results have been obtained for Arsenic, for which an average decrease of 97 % has been recorded . An analogous decrease has been also obtained for Lead, Copper and Zinc . The treatment of the organic contamination has been carried out by inoculation of a bacteria consortium selected using instruments of metabarcoding and the predictive metagenomic analysis .

The data which refer to the average decrease of the target organic contaminants and precisely: Total petroleum hydrocarbons cl 0-c40 , Dibenzo ( a, h) anthracene, Benzo (a) pyrene, Indeno ( 1 , 2 , 3-cd) pyrene, pyrene, Benzo (a) anthracene, Chrysene, Benzo (b) fluoranthene, Benzo ( k) fluoranthene and Polycyclic Aromatic Hydrocarbon, or PAH have been reproduced in the following table 2 ( Tab . 2 ) .

Tab . 2

As can be noted from the data reported in table 2 , practically for all the analysed organic contaminants , a very high decrease has been obtained up to reach a decrease even of 99% for the Benzo ( a) anthracene . A decrease of about 97% has been obtained for about all the organic contaminants , except for the petroleum hydrocarbons cl O- c40 , for which a decrease of about 85% , and, therefore, very high, has been, however, obtained .

In light of the above, the process according to the invention results to be highly effective in reducing the main inorganic and organic contaminants .

The foregoing description exemplary embodiments of the invention will so fully reveal the invention according to the conceptual point of view, so that others , by applying current knowledge , will be able to modi fy and/or adapt for various applications such embodiment without further research and without parting from the invention, and, accordingly, it is therefore to be understood that such adaptations and modi fications will have to be considered as equivalent to the speci fic embodiments . The means and the materials to reali ze the di f ferent functions described herein could have a di f ferent nature without , for this reason, departing from the field of the invention . It is to be understood that the phraseology or terminology that is employed herein is for the purpose of description and not of limitation .