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Title:
COMPOSITION AND PROCESS FOR IN SITU TREATMENT OF ACID TAR AND CONTAMINATED SOIL
Document Type and Number:
WIPO Patent Application WO/2021/221524
Kind Code:
A1
Abstract:
The invention relates to a composition and process for the physical and chemical stabilization, in situ, of acid tar from tar pits and of soil contaminated with acid tar, having TPH values below 200,000 mg / kg and DOC values below 1000 mg / kg dry matter, by neutralization, solidification and stabilization processes. A process for stabilizing and encapsulating acid tar with TPH values below 200,000 mg / kg and DOC values below 1000 mg / kg dry matter, according to the invention, comprises the following steps: removal of surface water from the tar pit, which will be collected through drainage systems and sent to the treatment plant, before the stabilization procedure; delimitation of work areas, excavation of acid tar, mixing and homogenization thereof in an acid tar treatment plant connected to a gas capture station; calculation of DOC, TPH, pH and metal concentrations values to determine the correct stabilization recipe; neutralization of acid tar by in situ by mixing the acid tar and contaminated soil from the first working area with CaO (3-8%), MgO (1-2%) NaOH (1 - 10%), absorbent (1-5%) and, optionally, metasilicate (0.3 - 0.8%); encapsulation of the tar and neutralized soil, by applying emulsifying detergent (1 - 4%) bentonite (1 - 2.8%), cement (3 - 20%), sand (2 - 5%), hardening additives (1%), depending on the chemical composition of the tar; storage of stabilized tar in situ, in the tar pit prepared by waterproofing with geomembranes and installing a water drainage installation; covering / closing the site.

Inventors:
TITA MIHAELA (RO)
Application Number:
PCT/RO2021/000002
Publication Date:
November 04, 2021
Filing Date:
April 27, 2021
Export Citation:
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Assignee:
TITA MIHAELA (RO)
International Classes:
B09C1/00; B09B3/00; B09C1/08; C04B14/04; C04B14/06; C04B14/10; C04B14/30
Foreign References:
RO123548B12013-07-30
Other References:
"Stabilisation/Solidification Treatment and Remediation : Proceedings of the International Conference on Stabilisation/Solidification Treatment and Remediation, 12-13 April 2005, Cambridge, UK", 14 April 2005, TAYLOR & FRANCIS, ISBN: 978-1-4398-3393-3, article PENSAERT S: "The remediation of the acid tar lagoons, Rieme Belgium : Proceedings of the International Conference on Stabilisation/Solidification Treatment and Remediation, 12-13 April 2005, Cambridge, UK", pages: 255 - 259, XP055835655, DOI: 10.1201/9781439833933.ch32
Attorney, Agent or Firm:
INTELLECTUAL PROPERTY OFFICE SRL (RO)
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Claims:
CLAIMS

1. Composition for stabilization and encapsulation of acid tar with TPH values below 200,000 mg / kg and DOC below 1000 mg / kg dry matter characterized in that it comprises in mass percentages:

- emulsifying detergent: 1-4%

- calcium oxide: 3-8%

- magnesium oxide 0.1-2%

- bentonite: 1-2.8%

- sand: 2-5%

- cement 3-20%

- hardening additives 1%

- absorbent 1 % - 5%

- sodium hydroxide 1% - 10%

- the rest up to 100% being the acid tar subject to stabilization.

2. Composition for stabilizing and encapsulating the acid tar according to claim 1, characterized in that it further comprises 0.3-0.8% sodium metasilicate.

3. Composition for stabilizing and encapsulating acid tar according to claim 1, characterized in that the emulsifying detergent is 1%, calcium oxide is 8%, magnesium oxide 0.1%, bentonite is 1%, sand is 2%, cement is 3%, absorbent is 1%, sodium hydroxide is 1%.

4. Composition for stabilizing and encapsulating acid tar according to claims 2 and 3, characterized in that the sodium metasilicate is 0.3%.

5. Composition for stabilizing and encapsulating acid tar according to claim 1, characterized in that the emulsifying detergent is 3.5%, calcium oxide is 3%, magnesium oxide 0.2%, bentonite is 2%, sand is 5%, cement is 5%, absorbent is 1%, sodium hydroxide is 1%.

6. Composition for stabilizing and encapsulating acid tar according to claims 2 and 5, characterized in that the sodium metasilicate is 0.5%.

7. Composition for stabilizing and encapsulating acid tar according to claim 1, characterized in that the emulsifying detergent is 4%, calcium oxide is 7%, magnesium oxide 0.3%, bentonite is 2.8%, sand is 3%, cement is 8%, absorbent is 1%, sodium hydroxide is 1%.

8. Composition for stabilizing and encapsulating acid tar according to claims 2 and 7, characterized in that the sodium metasilicate is 0.8%.

9. Process for stabilizing and encapsulating acid tar with TPH values below 200,000 mg / kg and DOC below 1000 mg / kg dry matter, characterized in that it comprises the following steps:

- Step 1: removal of surface water from the tar pits, which is collected through drainage systems and sent to the treatment plant, before the stabilization procedure. - Step 2: Batches are delimited within the tar pit. The acid tar in the first batch is excavated and then mixed and homogenized in an acid tar treatment plant connected to a gas capture station.

- Step 3: The value of DOC, TPH, pH and metal concentrations of the homogenized tar of the First batch is calculated, in order to determine the correct stabilization recipe.

- Step 4: A suction hood is installed at the drilling / mixing / dosing plant for absorbing and treating the emissions during the works, avoiding their release into the atmosphere.

- Step 5: Neutralization of the acid tar in situ by mixing of acid tar and soil contaminated from the first working area with CaO (3-8%), MgO (1-2%) NaOH (1 - 10%), absorbent (1 -5%) and, optionally, metasilicate (0.3 - 0.8%), depending on the chemical composition of the tar, calculated by the analyzes performed in the previous step. The neutralizing composition is applied over the entire depth of soil contamination by mixing up and down vertically, for several times, in the mixing tanks, also for homogenizing the resulting composition both vertically and horizontally.

- Step 6: Encapsulation of the tar and contaminated soil from the first work area, neutralized in the previous step; for encapsulation, emulsifying detergent (1-4%), bentonite (1 - 2.8%), cement (3 - 20%), sand (2 - 5%), hardening additives (1%) are applied, depending on the chemical composition of the tar calculated by the analyzes performed in the previous step. The composition having the role of neutralization is applied over the entire depth of soil contamination by mixing up and down vertically, for several times, in the mixing tanks, also for homogenizing the resulting composition both vertically and horizontally.

- Step 7: Storage of tar stabilized in situ, in the initial tar pit, prepared by waterproofing with geomembranes and by installing of a water drainage installation.

- Step 8: Covering / closing the site, can begin and unfold sequentially, with the stabilization of a work area and the creation of another by moving the sheet piles, thus systematically reducing the areas in tar pit exposed to surface water penetration and rainfall.

- After treating the tar in the first work area, the procedure is repeated one at a time for the tar in each of the following work areas.

- The drainage installation is installed for the collection of rainwater in some tanks, for its analysis and treatment, in case pollutant concentration above the maximum allowed values occurs.

10. Process for stabilizing and encapsulating acid tar according to claim 9, characterized in that, the sheet piles are mounted to create a first, second and third working areas isolated from the rest of the tar pit, when the tar has a non- homogeneous composition, the work areas being created successively from the outside to the inside of the tar pit.

11. Process for stabilizing and encapsulating acid tar according to claim 9, characterized in that sheet piles are used for sectioning the tar pit when the tar mass is developed as a compact block, followed by emptying two volumes of the tar pit, one being used for crushing and mixing in the additives, and the other for resetting the stabilized and encapsulated material.

Description:
Composition and process for in situ treatment of acid tar and contaminated soil

TECHNICAL FIELD

The invention relates to a composition and process for the physical and chemical stabilization, in situ, of acid tar in tar pits and of soil contaminated by acid tar, by processes of neutralization, solidification and stabilization.

The composition and process apply in particular to acid tar with TPH (total petroleum hydrocarbons) below 200,000 mg / kg and DOC (dissolved organic carbon) indicator values of less than 1000 mg / kg dry matter, which does not have a uniform composition. The values of pH, TPH, heavy metals, TOC (total organic carbon), DOC, sulphates can vary from meter to meter, both in length and in depth.

STATE OF THE ART

Acid tars are liquid or solid, brown waste resulting from the refining of oils and petroleum residues and sulfuric acid, having a complex composition. The product that remained after the refining process was usually stored in lagoons or open tar pits, constituting sources of pollution for air, soil, subsoil and groundwater.

Tar pit acid tar is a complex of substances comprising more or less modified compounds under the action of sulfuric acid and compounds formed as a result of copolymerization, sulfonation, addition of unsaturated compounds. Benzene hydrocarbons, naphthalene, anthracene, phenols, cresols thionaphthene, thiophene, pyridines, quinolines, carbazole, sulfuric acid, sulfonic and thiosulfonic acids, complex copolymers and other impurities in coke gas or sulfuric acid are found in raw tar. The acid tar in the tar pit also contains small amounts of heavy metals from coal and sulfuric acid. The environment being acidic, most of the heavy metals in the tar are found in soluble forms.

The acid tar deposited in the tar pit is permanently exposed to precipitation and solar radiation. Precipitation gradually washes away soluble substances from the acid tar, primarily sulfuric acid and sulfonic acid, the heavy metals being discharged from the tar pit, the tar pit being, therefore, a source of pollution for soil and groundwater.

The heating of the mass of tar from the tar pit during the summer leads to the evaporation and evacuation in the atmosphere of substances with low or sublimating boiling temperatures (naphthalene), thus producing air pollution. Sulfur dioxide and acid fumes are also part of the emissions from the acid tar pit.

Under the influence of solar radiation, copolymerization and oxidation reactions occur with the oxygen in the air, so that the acid tar stored for a long time becomes more viscous or even solid. After decades in these tar pits, the characteristics of the tar vary from those of a solid, coal-like material at the bottom of the tar pit, to a mixture of liquid sulfuric acid, other acidic waste products and rainwater at the surface. In other cases, these tar pits can be very heterogeneous with different layers of acid waste. The most dangerous remains the pollution of groundwater that can affect the population in the surrounding areas which use groundwater for consumption, for sanitation or irrigation.

Treatment of this acidic waste is difficult due to several factors. First, as described above, waste is very complex. As understood in the art, the composition of waste varies from one area of a tar pit to another, and often from one depth to another within the same area of a tar pit. Secondly, the acid content of the tar also varies, most often from less than 1 to 50%, but some tars are extremely acidic, with an acidity of 90%. Thirdly, when these acidic materials are disturbed, hazardous concentrations of acidic gases, mainly sulfur dioxide and, to a much lesser extent, hydrogen sulphide, can be emitted.

The only alternative technology for removing acid tar from the platform is coincineration / incineration, provided that the leach values obtained from neutralizing the acid tar are accepted by the companies providing these services or off-site storage of the stabilized tar according to Order no. 95/2005, for TPH values higher than 200,000 mg / kg.

When the values of the concentrations of the analyzed indicators of the stabilized acid tar waste do not fall within the limits of acceptability to be co-incinerated, the only possibility to eliminate them is incineration by specialized companies.

A composition for the treatment of acid tar with the following ingredients is known in the Environmental Agreement:

- Cement without additives 25% (by weight)

- Bentonite 2.5% (by weight)

- Acid tar 36% (by weight)

- Loamy soil 18% (by weight)

- Clay 18% (by weight)

The disadvantages of applying this composition are that, after mixing the acid tar with bentonite, loamy soil and clay, the pH of the eluate 1/10 L / S had values between 2- 3 (acid medium).

The solidification / stabilization treatment applied to the acid tar had the following disadvantages:

• the dissolved components were not chemically bound;

• the particles of contaminants were not encapsulated in an impermeable coating;

• hazardous components have not been chemically bonded by reducing their solubility;

• the toxicity of contaminants has not been reduced.

Following the sampling of acid tar, the recipe described according to the Environmental Agreement was implemented; several attempts were made to obtain the neutralization process by bringing the acid pH to an alkaline pH, then an attempt was made to carry out the process of stabilization with cement without additives and the rest of the ingredients specified in the recipe to make the setting. Based on the results obtained, no stabilization process could be performed, because the applied recipe has a high content of loamy soil and clay that does not give strength to the acid tar to be stabilized. The recipe in the Environmental Agreement is not applicable for the proposed purpose, because the acid tar does not stabilize.

TECHNICAL PROBLEM

The technical problem solved by the present invention is to treat in situ tar pit acid tar, with TPH below 200,000 mg / kg and DOC indicator values lower than 1000 mg / kg dry matter, which does not have a uniform composition, so as to become harmless to the environment with a small increase in volume of up to 5%.

A product falling within the values of Order 95/2005 is considered harmless for the environment.

The maximum allowed values for the leachate obtained from tar are:

BRIEF DESCRIPTION OF THE INVENTION

The composition for stabilizing and encapsulating acid tar with TPH values below 200,000 mg / kg and DOC below 1000 mg / kg dry matter, according to the invention, comprises in percentages by weight:

- emulsifying detergent: 1-4%

- calcium oxide: 3-8%

- magnesium oxide 0.1-2% - bentonite: 1-2.8%

- sand: 2-5%

- cement 3-20%

- hardening additives 1%

- absorbent 1 % - 5%

- sodium hydroxide 1% - 10%

- the remaining up to 100% is represented by the acid tar subject to stabilization Optionally, 0.3 - 0.8% sodium metasilicate is added.

The process for stabilizing and encapsulating acid tar with TPH values below 200,000 mg / kg and DOC below 1000 mg / kg dry matter, according to the invention, comprises the following steps:

- Step 1 : removal of surface water from the tar pits, which is collected through drainage systems and sent to the treatment plant, before the stabilization procedure.

- Step 2: Batches are delimited within the tar pit. The acid tar in the first batch is excavated and then mixed and homogenized in an acid tar treatment plant connected to a gas capture station.

- Step 3: The values of DOC, TPH, pH and metal concentrations of the homogenized tar in the first batch are calculated, in order to determine the correct stabilization recipe.

- Step 4: A suction hood is installed at the drilling / mixing / dosing for absorbing and treating the emissions during the works, avoiding their release into the atmosphere.

- Step 5: Neutralization of acid tar by the in situ mixing of acid tar and soil contaminated from the first working area with CaO (3-8%), MgO (1-2%) NaOH (1 - 10%), absorbent (1 - 5%) and, optionally, metasilicate (0.3 - 0.8%), depending on the chemical composition of the tar, calculated by the analyzes performed in the previous step. The neutralizing composition is applied over the entire depth of soil contamination by mixing up and down vertically, several times, in the mixing tanks, also for homogenizing the resulting composition both vertically and horizontally.

- Step 6: Encapsulation of tar and contaminated soil from the first work area, neutralized in the previous step; for encapsulation bentonite (1 - 2.8%), cement (3 - 20%), sand (2 - 5%), hardening additives (1%) are applied, depending on the chemical composition of the tar resulted from the analyzes performed in the previous step. The composition having the role of neutralization is applied over the entire depth of soil contamination by mixing up and down vertically, several times, in the mixing tanks, also for homogenizing the resulting composition both vertically and horizontally.

- Step 7: Storage of tar stabilized in situ, in the tar pit prepared by waterproofing with geomembranes and by installing a water drainage installation.

- Step 8: Covering / closing the site, can begin and unfold sequentially, with the stabilization of a work area and the creation of another by moving the sheet piles, thus systematically reducing the areas in tar pit exposed to surface water penetration and rainfall.

- After treating the tar in the first work area, the procedure is repeated one at a time for the tar in each of the following work areas.

- The drainage installation is installed for the collection of rainwater in some tanks, for analysis and treatment thereof, in case pollutant concentration above the maximum allowed values occurs. ADVANTAGES OF THE INVENTION

The advantage of the composition according to the invention, compared to other known technical solutions, is that the composition applied to the acid tar produces the stabilization of the tar, the upper encapsulation of the pollutants, in the conditions of a maximum volume increase of 5%.

The advantages of the proposed technical solution for the stabilization of acid tars in- situ are represented by the elimination of the costs of handling, transport, storage in other places than in the initial spaces where the acid tar is stored, respectively in tar pits.

Also, the tar can be stored in the places where it is excavated for treatment, provided that a geomembrane is installed to permanently waterproof the stabilized and encapsulated acid tar.

This technical solution eliminates in the long run the possibility of pollution of all environmental factors, the tar pits in which it is stored being safe spaces for the environment.

The advantages of the present invention over incineration are the elimination of transportation and incineration costs.

BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 - Tar pit 17 - pH values before and after the treatment according to the invention FIG. 2 - Tar pit 17 - chloride values before and after the treatment according to the invention

FIG. 3 - Tar pit 17 - sulphate values before and after the treatment according to the invention

FIG. 4 - Tar pit 17 - TDS values before and after the treatment according to the invention

FIG. 5 - Tar pit 17 - DOC values before and after the treatment according to the invention

FIG. 6 - Tar pit 17 - TOC values before and after the treatment according to the invention

FIG. 7 - Tar pit 17 - As values before and after the treatment according to the invention FIG. 8 - Tar pit 17 - Cd values before and after the treatment according to the invention FIG. 9 - Tar pit 17 - total Cr values before and after the treatment according to the invention

FIG. 10 - Tar pit 17 - Cu values before and after the treatment according to the invention

FIG. 11 - Tar pit 17 - Ni values before and after the treatment according to the invention FIG. 12 - Tar pit 17 - Pb values before and after the treatment according to the invention

FIG. 13 - Tar pit 17 - Ba values before and after the treatment according to the invention FIG. 14 - Tar pit 17 - Zn values before and after the treatment according to the invention

FIG. 15 - Tar pit 19 - pH values before and after the treatment according to the invention

FIG. 16 - Tar pit 19 - chloride values before and after the treatment according to the invention

FIG. 17 - Tar pit 19 - sulphates values before and after treatment according to the invention

FIG. 18 - Tar pit 19 - TDS values before and after the treatment according to the invention

FIG. 19 - Tar pit 19 - DOC values before and after the treatment according to the invention

FIG. 20 - Tar pit 19 - TOC values before and after the treatment according to the invention

FIG. 21 - Tar pit 19 - As values before and after the treatment according to the invention

FIG. 22 - Tar pit 19 - Cd values before and after the treatment according to the invention

FIG. 23 - Tar pit 19 - total Cr values before and after the treatment according to the invention

FIG. 24 - Tar pit 19 - Cu values before and after treatment values according to the invention

FIG. 25 - Tar pit 19 - Ni values before and after the treatment according to the invention FIG. 26 - Tar pit 19 - Pb values before and after the treatment according to the invention

FIG. 27 - Tar pit 19 - Ba values before and after the treatment according to the invention

FIG. 28 - Tar pit 19 - Zn values before and after the treatment according to the invention

FIG. 29 - Tar pit 20 - pH values before and after the treatment according to the invention

Fig.30 - Tar pit 20 - chloride values before and after the treatment according to the invention

FIG. 31 - Tar pit 20 - sulphates values before and after treatment according to the invention

FIG. 32 - Tar pit 20 - TDS values before and after treatment according to the invention FIG. 33 - Tar pit 20 - DOC values before and after the treatment according to the invention

FIG. 34 - Tar pit 20 - TOC values before and after treatment according to the invention FIG. 35 - Tar pit 20 - As values before and after the treatment according to the invention

FIG. 36 - Tar pit 20 - Cd values before and after the treatment according to the invention

FIG. 37 - Tar pit 20 - total Cr values before and after the treatment according to the invention FIG. 38 - Tar pit 20 - Cu values before and after the treatment according to the invention

FIG. 39 - Tar pit 20 - Ni values before and after the treatment according to the invention FIG. 40 - Tar pit 20 - Pb values before and after the treatment according to the invention

FIG. 41 - Tar pit 20 - Ba values before and after the treatment according to the invention

FIG. 42 - Tar pit 20 - Zn values before and after the treatment according to the invention

FIG. 43 - Tar pit 7-12 - pH values before and after the treatment according to the invention

FIG. 44 - Tar pit 7-12 - chloride values before and after the treatment according to the invention

FIG. 45 - Tar pit 7-12 - sulphates values before and after the treatment according to the invention

FIG. 46 - Tar pit 7-12 - TDS values before and after the treatment according to the invention

FIG. 47 - Tar pit 7-12 - DOC values before and after the treatment according to the invention

FIG. 48 - Tar pit 7-12 - TOC values before and after the treatment according to the invention

FIG. 49 - Tar pit 7-12 - As values before and after the treatment according to the invention

FIG. 50 - Tar pit 7-12 - Cd values before and after the treatment according to the invention

FIG. 51 - Tar pit 7-12 - total Cr values before and after the treatment according to the invention

FIG. 52 - Tar pit 7-12 - Cu values before and after treatment values according to the invention

FIG. 53 - Tar pit 7-12 - Ni values before and after the treatment according to the invention

FIG. 54 - Tar pit 7-12 - Pb values before and after the treatment according to the invention

FIG. 55 - Tar pit 7-12 - Ba values before and after the treatment according to the invention

FIG. 56 - Tar pit 7-12 - Zn values before and after the treatment according to the invention

DETAILED PRESENTATION OF THE INVENTION, WITH AT LEAST ONE EMBODIMENT

In order to stabilize and encapsulate the acid tar, for meeting the requirements of Order 95/2005 and to be able to be stored, the following treatments were carried out:

- being acidic tars, the pH values vary between 0.3 - 1. In order to stabilize the tar, it is necessary to neutralize it with hydrated lime by bringing the pH to alkaline values (pH = 9-10) and passing the metals into water-soluble combinations.

- this neutralizing reaction, which is exothermic, produces, in addition to bringing the pH to alkaline values, also changes in the sublimating compounds (e.g. naphthalene), as well as changes in the structures of the carbon chains (by reducing them).

- the neutralization operation is mandatory, being also the legal requirement in all EU states for the handling, transportation of acid tars for storage or disposal.

The composition for neutralizing and encapsulating acid tar comprises in percentage by mass:

- emulsifying detergent: 1-4%

- calcium oxide: 3-8%

- magnesium oxide 0.1-2%

- bentonite: 1-2.8%

- sand: 2-5%

- cement 3-20%

- hardening additives 1%

- absorbent 1 % - 5%

- sodium hydroxide 1% - 10%

- optional, sodium metasilicate 0.3-0.8%, when the acid tar contains a lot of water. The remaining up to 100% is the acid tar to be stabilized.

The emulsifying detergent has the role of stabilizing the pH and obtaining a homogeneous mixture of stabilized tar. Due to the breaking effect of the hydrocarbon chains and the faster and deeper incorporation of the ingredients, the presence of the emulsifying detergent leads to a higher degree of encapsulation of the tar.

Calcium / magnesium oxide has a neutralizing effect on the acid tar.

In addition to neutralizing the pH, calcium or magnesium oxide and the emulsifier are also used to move the metals from the volatile phase to a stable phase.

Bentonite and cement are used to harden / encapsulate the acid tar.

The absorbent is used if it is necessary to reduce the volume of the treated tar. Sodium hydroxide is used to neutralize the tar, but the reaction is strongly exothermic. Metasilicate is used optionally, with the effect of removing water.

After the completion of the treatment, the stabilized tar is presented in the form of a compacted block, and the values of the pollutants identified in its leachate are within the maximum values allowed according to Order 95/2005. A stabilized and encapsulated material is obtained, with low permeability, low leachability and moderate to high strength, which meets all performance criteria.

The volume of treated tar increases by up to 5% of the initial volume of the acid tar before treatment. This aspect is particularly important, because it allows the treatment of tar in situ, using only the limited space of the already existing tar pits, without the need to dig additional tar pits for storing the surplus.

The composition according to the invention has been applied to four acid tar pits having the following characteristics:

Acid tar samples were taken from tar pits 17, 19, 20 and 7-12 and their composition was determined, observing the following indicators: pH, TPH, heavy metals, chlorides, DOC, sulphates, TDS, TOC and their comparison with the value limits imposed by Order no. 95/2005.

The sampling depth was in the range of approx. 5 -30 cm for all locations.

After introducing the acid tar in a treatment plant connected to a gas capture station, it is mixed and homogenized. Depending on the value of TPH, pH and metal concentrations, one of the following recipes will be applied:

For tars with high pH and low TPH values, recipe 1 applies. For tars with low pH and high TPH values, recipe 3 is usually used. For tars with medium values, recipe 2. However, the efficiency of the recipe is influenced not only by TPH and pH values, but also by other indicators, including the concentrations of various metals. Therefore, if the application of the chosen recipe does not give the expected results and does not decrease the parameters below the limits provided in Order 95/2005, one of the other two recipes is chosen. If the second recipe does not give the expected results, the third recipe is used. EXAMPLE 1

Following the investigations carried out on the samples taken from the Tar pit site no. 17, it was found that the acid tar does not have a uniform composition, the values of the main indicators analyzed being included as follows:

- TPH between 24031-298446 mg / kg dry matter

- Metals with values exceeding the allowed limits: o Cadmium from values below the limit of quantification <LQ (0.2) at 4 mg / kg dry matter o Lead between 45-4778 mg / kg dry matter o Copper between 3 - 701 mg / kg dry matter o Total chromium between 6-152 mg / kg dry matter o Arsenic between 11 - 419 mg / kg dry matter o Nickel between 1 - 310 mg / kg dry matter o Mercury from values recorded below the limit of quantification of the method of determination <0.9 to 1 mg / kg dry matter o Zn between 9 - 62 mg / kg dry matter o Molybdenum from values below the limit of quantification of the determination method <LQ (0.5) at 38 mg / kg dry matter o Barium from values below the limit of quantification of the method of determination <LQ (0.5) to 825 mg / kg dry matter o Selenium from values below the limit of quantification of the method of determination <LQ (0.5) at 3 mg / kg dry matter o Antimony from values below the limit of quantification of the method of determination <LQ (0.5) at 41 mg / kg dry matter

The values recorded for leachate in acid tar are:

- pH between 0.35 - 2.03

- Chlorides between 51.47 - 2752.05 mg / kg dry matter

- Sulphates between 172.71 - 85708.08 mg / kg dry matter

- TDS between 4647.5 - 143767.99 mg / kg dry matter

- DOC between 343.16 - 3751 .92 mg / kg dry matter

- TOC between 2.1 - 9.2%

- Arsenic between 0.6 - 82 mg / kg dry matter

- Cadmium from values below the limit of quantification <0.0004 (LQ) to values of 0.015 mg / kg dry matter

- Total chromium between 0.14 - 22.66 mg / kg dry matter

- Copper between 0.23 - 23.41 mg / kg dry matter

- Nickel between 0.23 - 34.37 mg / kg dry matter

- Lead between 2.63 - 312 mg / kg dry matter

- Barium from values below the limit of quantification <0.002 (LQ) to values of 520 mg / kg dry matter

- Molybdenum from values recorded below the limit of quantification of the method of determination <0.002 to 1 mg / kg dry matter - Antimony from values recorded below the limit of quantification of the method of determination <0.002 at 9 mg / kg dry matter

- Selenium with values recorded below the limit of quantification of the method of determination <0.002 mg / kg dry matter

- Zinc between 0.6 - 33 mg / kg dry matter

- Mercury with values recorded below the limit of quantification of the method of determination <0.003 mg / kg dry matter

After applying of the recipes according to the invention, a significant decrease of the parameters was found and their compliance with the norms provided by Order no. 95/2005. The values obtained are summarized in table no. 1

Table 1

EXAMPLE 2

Following the investigations carried out on the samples taken from the site of tar pit no. 19, it was found that the acid tar does not have a uniform composition, the values of the main indicators analyzed being summarized as follows:

- TPH between 46881 - 344213 mg / kg dry matter

- Metals with values exceeding the allowed limits: o Cadmium from values below the limit of quantification <LQ (0.2) at 4 mg / kg dry matter o Lead between 46 - 1213 mg / kg dry matter o Copper between 2 - 191 mg / kg dry matter o Total chromium between 0 - 117 mg / kg dry matter o Arsenic between 8 - 174 mg / kg dry matter o Nickel between 5 - 189 mg / kg dry matter o Mercury with values recorded below the limit of quantification of the method of determination <0.9 mg / kg dry matter o Zn between 5 - 62 mg / kg dry matter o Molybdenum from values below the limit of quantification of the method of determination <LQ (0.5) at 3 mg / kg dry matter o Barium from values below the limit of quantification of the method of determination <LQ (0.5) to values 1081 mg / kg dry matter o Selenium with values below the limit of quantification of the method of determination <LQ (0.5) mg / kg dry matter o Antimony from values below the limit of quantification of the method of determination <LQ (0.5) at 30 mg / kg dry matter

The values recorded for leachate from the acid tar (before treatment) are:

- pH between 0.62 - 3.05

- Chlorides between 89 - 2938 mg / kg dry matter

- Sulphates between 368 - 40368 mg / kg dry matter

- TDS between 3166 - 319526 mg / kg dry matter

- DOC between 121-3216 mg / kg dry matter

- TOC between 0.5 - 8.9%

- Arsenic between 2.17 - 16.36 mg / kg dry matter

- Cadmium between 0.003 - 5.27 mg / kg dry matter

- Chromium with values between 0.055 - 5.96 mg / kg dry matter

- Copper with values between 0.73-5.81 mg / kg dry matter

- Nickel with values between 0.99 of 9.80 mg / kg dry matter

- Lead between 0.41-10.58 mg / kg dry matter

- Zinc between 0.6 - 22 mg / kg dry matter

- Barium from values below the limit of quantification <0.002 (LQ) to values of 301 mg / kg dry matter

- Molybdenum from values recorded below the limit of quantification of the method of determination <0.002 to 1 mg / kg dry matter

- Antimony from values recorded below the limit of quantification of the method of determination <0.002 at 9 mg / kg dry matter

- Selenium with values recorded below the limit of quantification of the method of determination <0.002 mg / kg dry matter

- Zinc between 0.6-7.4 mg / kg dry matter

- Mercury with values recorded below the limit of quantification of the method of determination <0.003 mg / kg dry matter

After the application of the recipes according to the invention, a significant decrease of the parameters was found and their compliance with the norms of Order no.

95/2005. The values obtained are summarized in table no. 2: Table 2

EXAMPLE 3

Following the investigations carried out on the samples taken from the site of tar pit no. 3, it was found that acid tar does not have a uniform composition, the values of the main indicators analyzed being summarized as follows:

- TPH between 32273 - 222967 mg / kg dry matter

- Metals with values exceeding the allowed limits: o Cadmium from values below the limit of quantification <LQ (0.2) to values of 6 mg / kg dry matter; o Lead between 32 - 434 mg / kg dry matter o Copper between 4 - 115 mg / kg dry matter o Total chromium from values below the limit of quantification <LOQ (0.5) at 133 mg / kg dry matter o Arsenic between 1-34 mg / kg dry matter o Nickel between 1-28 mg / kg dry matter o Mercury with values recorded below the limit of quantification of the method of determination <0.9 mg / kg dry matter o Zn between 2 - 93 mg / kg dry matter o Molybdenum from values below the limit of quantification of the method of determination <LQ (0,5) mg / kg dry matter at values 5 mg / kg dry matter o Barium from values below the limit of quantification of the determination method <LQ (0.5) to values 359 mg / kg dry matter o Selenium from values below the limit of quantification of the method of determination <LQ (0.5) mg / kg dry matter at values of 1 mg / kg dry matter o Antimony from values below the limit of quantification of the method of determination <LQ (0.5) mg / kg dry matter at values of 26 mg / kg dry matter

The values recorded for leachate from the acid tar (before treatment) are:

- pH between 0.88 - 3.12

- Chlorides between 56 - 1227 mg / kg dry matter

- Sulphates between 707-20053 mg / kg dry matter

- TDS between 2406 - 60249 mg / kg dry matter

- DOC between 106-1555 mg / kg dry matter

- OCD between 0.22 - 8.86%

- Arsenic between 0.19 - 6.27 mg / kg dry matter

- Cadmium between 0.010 - 0.09 mg / kg dry matter

- Chromium with values between 0.10 - 6.97 mg / kg dry matter

- Copper with values between 0.03 - 5.23 mg / kg dry matter

- Nickel with values between 0.11 - 8.17 mg / kg dry matter

- Lead between 0.15-4.71 mg / kg dry matter

- Barium from values below the limit of quantification <0.002 (LQ) to values of 154 mg / kg dry matter

- Molybdenum from values below the limit of quantification of the method of determination <0.002 mg / kg dry matter at values of 1 mg / kg dry matter

- Antimony from values below the limit of quantification of the determination method <0.002 mg / kg dry matter at 0.9 mg / kg dry matter

- Selenium with values recorded below the limit of quantification of the method of determination <0.002 mg / kg dry matter

- Zinc between 0.03 - 13.62 mg / kg dry matter

- Mercury with values recorded below the limit of quantification of the method of determination <0.003 mg / kg dry matter

After the application of the recipes according to the invention, a significant decrease of the parameters was found and their compliance with the norms of Order no.

95/2005. The values obtained are summarized in table no. 3: Table 3

EXAMPLE 4

Following the investigations carried out on the samples taken from the site of tar pit no. 4, it was found that the acid tar does not have a uniform composition, the values of the main indicators analyzed being summarized as follows:

- TPH between 8000 -287240 mg / kg dry matter

- Metals with values above the allowed limits o Cadmium between 0 - 4 mg / kg dry matter o Lead between 50 - 208 mg / kg dry matter o Copper between 8 - 77 mg / kg dry matter o Total chromium between 0 - 4 mg / kg dry matter o Arsenic between 5 - 53 mg / kg dry matter o Nickel between 5 - 94 mg / kg dry matter o Mercury between 0-1 mg / kg dry matter o Zn between 2 - 64 mg / kg dry matter o Molybdenum between 0 - 6 mg / kg dry matter o Barium between 13 - 146 mg / kg dry matter o Selenium between 0 - 0.6 mg / kg dry matter o Antimony between 10 - 39 mg / kg dry matter

The values recorded for leachate from the acid tar (before treatment) are:

- pH between 2.87 - 6.41

- Chlorides between 62 - 396 mg / kg dry matter

- Sulphates between 231 - 3536 mg / kg dry matter

- TDS between 1373 - 16540 mg / kg dry matter

- DOC between 125 - 1778 mg/kg dry matter

- TOC between 0.4 - 7.2 %

- Arsenic between 0.3 - 4.88 mg/kg dry matter

- Cadmium between 0.010 - 0.096 mg/kg dry matter - Total chromium between 0.66 - 5.28 mg/kg dry matter

- Copper between 0.84 - 5.80 mg/kg dry matter

- Nickel between 0,63 - 5,81 mg/kg dry matter

- Lead between 1 ,49 - 35 mg/kg dry matter

- Barium between 3,1 - 44 mg/kg dry matter

- Molibdenum with values below the limit of quantification <LOQ(0,002) mg/kg dry matter

- Antimony with values below the limit of quantification <LOQ(0,002) mg/kg dry matter

- Selenium with values recorded below the limit of quantification of the method of determination <0,002 mg/kg dry matter

- Zinc between 1 ,6 - 29 mg/kg dry matter

- Mercury with values recorded below the limit of quantification of the method of determination <0,003 mg/kg dry matter

After applying the recipes according to the invention a significant decrease of the parameters was observed and their compliance with the norms of Order no. 95/2005. The obtained values are summarized in Table no. 4:

Table 4

THE PROCESS

The process according to the invention is applied for the stabilization and encapsulation of acid tar with TPH below 200,000 mg / kg and with DOC indicator values lower than 1000 mg / kg dry matter, using additive mixing and dosing devices and comprises the following steps:

- Step : removal of surface water in batches, which will be collected through drainage systems and sent to the treatment plant, before the stabilization operation.

- Step 2: Boundaries are delimited within the tar pit. The acid tar in the first batch is excavated and then mixed and homogenized in an acid tar treatment plant connected to a gas capture station.

- Step 3: From the homogenized tar, the values of DOC, TPH, pH and metals are determined for the first batch, in order to establish the correct stabilization recipe.

- Step 4: A suction hood is installed at the drilling / mixing / dosing plant to absorb and treat the emissions during the works, avoiding their release into the atmosphere.

- Step 5: Neutralization of the acid tar in situ by mixing of acid tar and soil contaminated from the first working area with CaO (3-8%), MgO (1-2%) NaOH (1 - 10%), absorbent (1 -5%) and, optionally, metasilicate (0.3 - 0.8%), depending on the chemical composition of the tar, calculated by the analyzes performed in the previous step. The neutralizing composition is applied over the entire depth of soil contamination by mixing up and down vertically, for several times, in the mixing tanks, also for homogenizing the resulting composition both vertically and horizontally.

- Encapsulation of the tar and contaminated soil from the first work area, neutralized in the previous step; for encapsulation, emulsifying detergent (1-4%), bentonite (1 - 2.8%), cement (3 - 20%), sand (2 - 5%), hardening additives (1%) are applied, depending on the chemical composition of the tar calculated by the analyzes performed in the previous step. The composition having the role of neutralization is applied over the entire depth of soil contamination by mixing up and down vertically, for several times, in the mixing tanks, also for homogenizing the resulting composition both vertically and horizontally.

- Step 7: Storage of tar stabilized in situ, in the initial tar pit, prepared by waterproofing with geomembranes and by installing of a water drainage installation.

- Step 8: Covering / closing the site, can begin and unfold sequentially, with the stabilization of a work area and the creation of another by moving the sheet piles, thus systematically reducing the areas in tar pit exposed to surface water penetration and rainfall.

- After treating the tar in the first work area, the procedure is repeated one at a time for the tar in each of the following work areas.

- The drainage installation is installed for the collection of rainwater in some tanks, for its analysis and treatment, in case pollutant concentration above the maximum allowed values occurs.

Optionally, if the tar has a non-homogeneous composition, some sheet piles are mounted to create a first, a second and a third work area isolated from the rest of the tar pit, if necessary. The work areas will be created successively with the help of sheet piles (if necessary), from the outside to the inside of the tar pit, the already solidified areas allowing the creation of access to the untreated areas.

Optionally, when the tar mass is developed as a compact block, the sheet piles will be used for sectioning the tar pit, followed by emptying two volumes of the tar pit, one being used for crushing and mixing in additives, and the other for resetting the stabilized / solidified material.

Taking into account the successively covered areas and the slopes of surface water or rainfall draining, the contour gutter relative to the area / tar pit worked will be arranged. Two post-closure surface / rainwater collection tanks are provided, in different areas, each with a volume of 100 m 3 .