WO2009132464A1

WO2009132464A1 - Method for removing inorganic contaminants from soils via a physicochemical extraction technique

Info

Publication number: WO2009132464A1
Application number: PCT/CA2009/000601
Authority: WO
Inventors: Marie Josée LAMOTHE; Claude Gauthier; Marc André BERGERON; Kathleen Dube
Original assignee: Northex Environnement Inc
Priority date: 2008-05-02
Filing date: 2009-05-04
Publication date: 2009-11-05
Also published as: MX2010011908A; CN102099129B; CA2630894A1; MX343510B; CN102099129A; CA2723101C; CA2723101A1

Abstract

A method for decontaminating soils that are contaminated with an inorganic contaminant, comprising: screening the contaminated soils in order to obtain coarse and fine fractions; sieving the screened soils in order to retain therefrom the coarse fractions and, concurrently, washing the screened soils in order to obtain a first effluent comprising the washing liquid and the fine fractions flowing from the sieve and comprising fines and particles with dimensions greater than those of the fines; separating the fines from the first effluent in order to recirculate fresh water and thus obtain a second effluent; ensuring the supply of the washing operation; and conveying the contaminated fines separated from the first effluent to a chemical chamber where a portion of the first effluent and a chemical solution are added in order to produce a third effluent (acid), the latter containing metals dissolved in the fines that it is necessary to separate. The fourth effluent comprises the fines and a precipitation of this effluent is produced in order to extract the precipitated contaminants, so as to obtain a fifth effluent, whereby the inorganic contaminant is extracted and it is possible to reuse the fifth effluent for recirculation in the treatment process.

Description

TITLE OF THE INVENTION

METHOD FOR REMOVING INORGANIC CONTAMINANTS FROM SOILS BY A PHYSICO-CHEMICAL EXTRACTION TECHNIQUE

REFERENCE TO RELATED APPLICATIONS

The present patent application claims priority over the Canadian patent application No. 2,630,894 filed May 2, 2008, the latter being incorporated by reference to the present application.

FIELD OF THE INVENTION

The present invention relates to a method for removing soil from inorganic contaminants by physical-chemical extractions in aqueous phase The present invention consists in concentrating in an aqueous solution inorganic contaminants amalgamated with fine fractions of the soil, in order to extract them.

TECHNOLOGICAL BACKGROUND

The purpose of soil decontamination techniques by physico-chemical treatments is to lower or eliminate the concentration of contaminants to a level comparable to the background of natural soils inorganic industrial contaminants unrelated to the natural elements must necessarily be eliminated for reasons of human health, animal health or for environmental reasons Physico-chemical decontamination techniques are enjoying a boom at the moment, given the economic costs resulting from exceedances of contaminant concentrations beyond acceptable or permissible standards this is particularly true in northern European countries

[0004] A contaminant present in the soil may be of organic, inorganic or mixed, ie organic / inorganic, type. Inorganic contaminants are generally present in soils in a solid form. In the solid form, inorganic contaminants may be present in the soil. These metal contaminants, also known as "heavy metals" or "metallic trace elements", are typically in the form of angular particles whose diameter generally does not exceed 100 μm. Zinc, lead cadmium and copper are some examples of inorganic contaminants

STATEMENT OF THE INVENTION

The present invention therefore aims to develop a method and a treatment system for extracting inorganic contaminants from soils

Thus, according to the present invention, there is provided a method for removing soil from inorganic contaminants, the method comprising cπbier the contaminated soil to obtain coarse fractions and fine fractions, wash the sieved grounds with a washing effluent, in order to obtain a first effluent comprising the washing liquid and the sols flowing in the sieve and sieving the soils in order to retain the coarse fractions and concurrently, the fractions flowing from the sieve comprise fines and the particles of dimensions In addition to the fine fines, the washing effluent is subjected to an extraction of the particles larger than those of the fines and thus to obtain a second effluent which is returned to the washing unit and / or a fraction can be returned to a chemical chamber, producing in the chemical chamber an extraction of the second effluent containing the contaminated fines to dissolve the metals, to obtain a third effluent, and precipitating and / or neutralizing the third effluent and filtering off the precipitate to obtain a fourth effluent, whereby the inorganic contaminant is precipitated for extraction into a fourth effluent

Also, according to the present invention, there is provided a method for removing inorganic contaminants from soils, the method comprising a) washing a contaminated soil with a washing effluent, to obtain a first effluent comprising the washing effluent and fines while the particles of dimensions larger than those of the fines are retained, b) subjecting the first effluent to an extraction of particles larger than those of the fines and thus obtain a second effluent which is returned to the washing unit and / or a fraction can be fed to step c), c) produce an extraction of the second effluent containing the fine contaminants to dissolve the metals, to obtain a third effluent, and d) produce a precipitation and / or neutralization of the third effluent and extracting the precipitate by filtration to obtain a fourth effluent, whereby the inorganic contaminant is precipitated for extraction ns a fourth effluent

Also, according to the present invention there is provided a method for removing inorganic soil contaminants, the method comprising a) subjecting a first effluent containing inorganic contaminants to a filter in order to extract particles of dimensions greater than those of and thus obtain a second effluent, c) produce an extraction of the second effluent containing the contaminated fines to dissolve the metals, thereby obtaining a third effluent and d) produce a precipitation and / or neutralization of the third effluent and extract by filtration the precipitate to obtain a fourth effluent, through which the inorganic contaminant is precipitated for extraction in a fourth effluent

The foregoing, as well as other objects, advantages and features of the present invention will become apparent upon reading the non-limiting description of an embodiment, provided to illustrate the present invention, and given as a only, with reference to the accompanying drawings.

SUMMARY DESCRIPTION OF THE DRAWINGS

Having thus generally described the nature of the invention, a preferred embodiment of the present invention will now be described with reference to the accompanying drawings, in which

Figure 1 is a schematic diagram illustrating an embodiment of a method for decontaminating soils of an inorganic contaminant according to the present invention; and

Figure 2 is a schematic representation of a decontamination plant according to the method of the present invention illustrated in Figure 1

DETAILED DESCRIPTION OF THE INVENTION

Thus, according to the present invention, it is presented a method

100 to extract inorganic contaminants from soils. Method 100 comprises dry screening 102, in order to extract coarse fractions from soils, the fractions thus removed being recovered according to the reuse potential Method 100 also comprises a wet screen 104 which subtracts the average fines fractions The soils are mechanically screened, with the use of a washing liquid, generating an effluent comprising the washing liquid and the fine fractions that flow from the sieve, ie the effluent # 1. The average fractions withdrawn are valued according to their quality. Method 100 also comprises a magnetic screen 106 to which the fine fractions and Effiuent 1 are subjected, in order to recover the magnetic fractions which are valued.

Then, in the method 100, the effluent 1 travels to the separation unit by filtration and cycloning 108 distributed in four calibers, and at the outlet of the last unit, the effluent is returned to the cable of washing (effluent # 2) for reuse or to the chemical area for the treatment of fines Subsequently, method 100 proposes a chemical extraction 1 10 which consists in dissolving the fines of the metallic contaminant contained in the soils with a acid and the effluent # 3 At the end of this step, the effluent # 3 is separated from these acid sludge and these will be conditioned in step 114, in order to neutralize them and make them valued according to the potential ones. In Method 100, virtually solids-free effluent # 3 is subjected to basic conditions at 112 and generates effluent # 4. Step 114 allows generation, treatment and conditioning of sludge, and flocs (metal). can be extracted. Then, a fifth effluent and last effluent is neutralized at 116 (effluent # 5), returns to the wet screening unit or to the chemical unit and starts the loop again in the process

Thus the method 100 which is the subject of the present invention can be used in general to extract inorganic contaminants from soils. The term "inorganic contaminant" is given here in a broad sense, that is to say that the inorganic contaminant may be single or multiple, comprising more than one element, compound or inorganic substance. "decontaminate" may contain varying proportions of blocks, pebbles, gravel, coarse sand to Silts or clay The pH of soils is generally in the range of 6.0 to 8.0 Method 100 allows inorganic contaminants to be concentrated in the fine fractions of soils to be decontaminated, which fines have a d about 100 μm or less

As used herein, the term "efflυent" refers to a liquid from a processing step or sub-step.

The method 100 for extracting soils from inorganic contaminants will now be described, in a non-restrictive embodiment, provided for purposes of illustration and which relates to an inorganic contaminant of metallic type, ie a metallic contaminant. However, it is understood that it is within reach of people paid in! how to apply this method to inorganic contaminants other than those of a metallic nature

Method 100 will now be described generally with reference to FIG. 1

The first step of the method 100 is a step of dry screening of the floors The floors to be décontamtnés are loaded into a bucket that routes the soil to a rotary screen cable, whose function is to perform a screening coarse contaminated soils The sieve subtracts the fraction greater than 75.0 mm which includes blocks, stones and debris The fraction equal to or less than 75.0 mm is homogenized The barrel of the rotary sieve is configured so as to retain the components larger than 75 0 mm, while 0-75.0 mm components pass through the cables This dry procedure makes it possible to screen clays and silts with a soft consistency without the latter clogging the sieving barrel The second step of the method 100 is a wet screening step 104 The fraction of 75.0 mm and less is introduced into the wet screening unit via a receiving bin twinned to a conveyor This wet cabling unit lava and simultaneously separating the fractions 00 mm to 75.0 mm, 2.50 mm to 4.99 mm, 2.00 mm to 2.49 mm and 1.99 mm and less. The components 0-75 0 mm are subjected to a washing liquid, in order to concentrate the contaminants to be extracted in fine fractions, that is to say fractions of size 1 99 mm or less while coarse fractions, that is to say fractions of more than 200 The washing liquid may be simply water or water modified with surfactants and / or chemical reagents. Following wet screening 104 two products are obtained. The aggregates are valued from 200 mm to 75%. are subjected to a ferrous separator The second product is an effluent (effluent # 1) containing Fractions of 1.99 mm and less (that is, less than 200 mm) and the metal fraction to be extracted

The effluent # 1 chemistry of the wet screening unit 104 to

Magnetic unit 106 (third step of method 100), which recovers the magnetic fraction and its alloys The wet screening step 104 is operated continuously, in order to recover in a given batch the fine fractions which will be subsequently treated in a chemical chamber

The fourth step of the method 100 is a separation step by filtration and cycloning 108 The effluent # 1 which comes out of the magnetic unit 106 and which accumulates in the primary reservoir can be subjected, as the case may be, to a phase d light oxidation in aqueous medium Effluent # 1 is introduced into the primary tank or the residence time is approximately fifteen minutes At the outlet of the primary tank I effluent is subjected to a first filtration and cycloning which retains the fraction 0 2 mm (200 μm) at 200 mm Depending on the results, this fraction is available for recovery The effluent # 1 passes to the secondary storage tank, where the residence time is also fifteen minutes At the outlet of the secondary tank, the effluent is subjected to a fiitration and secondary cyclone where the fraction 80 microns to 199 μm is separated

The effluent # 1 travels to the tertiary reservoir, where the residence time is also fifteen minutes The separation and cyclone tertiary reservoir separates the fraction 25 microns to 79 microns.

The effluent # 1 ends its race to the tank four After fifteen minutes of residence, the effluent is subjected to separation and cycloning where the fraction 5 micron to 24 microns is retained.

The filters use the centrifugal force to separate and allow to remove from the effluent # 1 the fines fractions (a size is about 0.005 mm (5 microns) to 2.00 mm while the fine fractions of less than 5 μm, that is to say the fines, remain in suspension in the effluent # 1 obtained following the separation step by filter 108. The effluent # 1 is more or less loaded with fines and depending on the quality of the water, it will be recirculated to the washing screen 104 (effluent # 2) or to the chemical chamber (efficient # 3) for chemical soil treatment

The fifth step of the method 100 is a dissolution step of the fines of the metal contaminant 110. The effluent # 1, resulting from the final separation step 108, contains the fraction 5 microns or less and a part this effluent is sent to a chemical conditioning tank and becomes effluent # 3 when the addition of chemicals and soils to be treated At this step acids are added and the metals associated with fine and receptive to acids solubilize The effluent # 3, acid, resides in the acidification tanks about 30 to 40 minutes and is then filtered. Filter residues (acid sludge) are neutralized (in 1 14) in a precipitation and neutralization tank, dehydrated if necessary and can be recovered according to their own quality. Effluent # 3 travels to other precipitation reservoirs and neutralization, in order to be neutralized by the addition of bases, coagulants and coagulants, and become the effluent # 4 of step 112

Step 112 consists in precipitating the metallic tones of the effluent # 4, in order to promote flocculation and the neutralization of the metallic contaminant being in suspension with the fines in the effluent # 4 Flocculation produces flocs, which are decanted thus forming a neutralized sludge in the effluent. The effluent # 4 resulting from the precipitation step of the metals 112, will undergo a filtration step to collect the neutralized sludge 114 and allow recirculation in the process of the effluent # 5, conditioned in step 1.

The precipitation step of the metal ions 1 12 comprises the addition of bases, coagulants and coagulants, if necessary, to the effluent # 3 resulting from step 110, to promote precipitation the resulting metal contaminant The resulting precipitate is decanted and forms a sludge via a filter

The method 100 also comprises a sludge treatment step 114 produced by steps 110 and 1 12, and a step of conditioning the effluent 116

The method 100 will now be described in more detail, with reference to FIG. 2.

Dry screening step 102

Contaminated soils are first loaded into a receiving bin, where they are subjected to a dry screening which consists of subjecting the contaminated soil to the action of a rotating screen The material travels within the cage, each steel rod is spaced less than 15 cm By rotation, the floors are spread over the entire surface of the cage and the coarse fraction retained inside the screen is expelled on one side and the fraction of 75.0 mm and less passes through the sieve and this material will be routed to a wet screening unit for processing. Contaminated trees undergo dry crushing, which homogenize them and break them into coarse pieces, stones and debris are valorised.

The rotary screen has a circumference of more than one (1) meter and a length of more than three (3) meters. The steel cables are stretched over the full length of the barrel and are spaced less than 15 cm apart. The cables are configured to retain pieces larger than 75.0 mm. Pieces larger than 75 mm are sampled and analyzed in order to check the quality. According to the results of analyzes, they can be either directly valorized or conveyed to a mobile washing area Contaminated soil components having a dimension between 0 mm and 75.0 mm, that is to say the components 0 - 75.0 mm, are conveyed to the receiving bin 1 (Figure 2) of the treatment plant.

Wet screening stage 104

Referring to FIG. 2, the 0-75.0 mm components are loaded into the bucket 1 with a view to the wet coking stage 104. The bucket 1 may comprise a gπzzly, in order to limit the size of the components to the Exit of the bucket At the outlet of the bucket 1, the components 0-75 0 mm are conveyed by means of a dry conveyor 6 to the wet screening unit 104 comprising a washing screen 10, itself comprising three levels of horizontal sieving The washing screen 10 is equipped with pressurized injectors which allow the injection of the washing liquid. Submission of the 0-75.0 mm components to the washing liquid under pressure makes it possible to carry out a separation of the 0-1 components. 99 mm and coarse particles, that is to say those larger than 2.00 mm In fact, while the fine particles pass through the three horizontal bearings 10, the coarse particles are retained, concurrently under the effect of washing under pressure, the particles of the metal contaminant on the surface of the coarse particles are entrained with the fine particles in the washing liquid

In the present embodiment the washing liquid may be of

I water of the aqueduct or water amended with surfactants and / or reagents The rate of conveyance of the soil by the dry conveyor 6, which is typically a conveyor varies between 40 and 100 tons / hour, while the maximum flow rate of the washing liquid is 1890 liters per minute (500 USGPM), or 31 5 liters per second (l / s). Typically, the three horizontal levels of the screen 10 have different mesh sizes, so as to hold back in trots separate steps pebbles, gravel and finally coarse sands with grains greater than 2.00 mm in diameter

The coarse particles typically contain pebbles, gravel, sand and, generally, particles larger than 2.00 mm, they are routed to a ferrous and non-ferrous separator 9 by means of a dry conveyor The coarse particles are thus conveyed to the ferrous and non-ferrous separator. The ferrous materials are stored in a storage container 18 in order to be recovered. The clean non-ferrous materials, that is, ie coarse particles of more than 2.00 mm non-ferrous contaminants-free are transported to a storage area 14 Fractions are separated as follows for possible control for partial recovery 5.00 mm to 75.0 mm, fraction 2.50 mm to 4.99 mm and fraction 2.00 mm to 2.49 mm

Thus separated from the coarse particles following the wet screening step 104, the washed fine particles (0-1, 99 mm) and metal contaminant are suspended in the washing liquid, thus forming the effluent # 1. resulting from step 104. The efflueπt of step 104 is routed to a magnetic unit 5 of step 106.

Magnetic screening step 106

Thus separated coarse particles following the wet screening step 104, the fine particles and the metal contaminant are found in suspension in the effluent # 1 and are routed to the magnetic unit 5, step 106 The magnetic separation makes it possible to retain the magnetic components included in the soil. Next, the effluent # 1 continues its course towards the storage tanks 15 for the purpose of storage and specific filtration 108.

Separation stage by filtration and cycionage 108

At the exit of step 106, the effluent # 1 continues its course to the storage tanks 15-1 to 15-4 for storage and specific filtration 108. The storage tanks 15 ( here, 15-1 to 15-4). which typically have a capacity of 8,000 to 10,000 US gallons (28,883 to 37,854 liters), are equipped with agitators (mechanical or air) to maintain fine particles in suspension The effluent # 1 of step 106 is then pumped and accumulates in the primary reservoir 15-1, where effluent # 1 can be subjected, as appropriate, to a light oxidation phase in an aqueous medium. The effluent # 1 is then introduced into the primary reservoir 15-1 and the residence time is about fifteen minutes. At the outlet of the primary reservoir 15-1, the effluent # 1 is subjected to a first filtration and cycloning 11-1 (dehydration), which retains the fraction 0.2 mm (200 microns) to 2.00 mm. According to the analysis results, this fraction is available for recovery.

The effluent # 1 passes to the secondary storage tank 15-

2. where the residence time is also fifteen minutes. At the outlet of the tank 15-2, the effluent # 1 is subjected to secondary filtration and cycloning 11-2 where the fraction 80 μm to 199 μm is separated.

The effluent # 1 travels to the tertiary reservoir 15-3, and the residence time is also fifteen minutes. The separation and cycloning 11-3 to the tertiary reservoir 15-3 separate the fraction 25 microns to 79 microns.

The effluent # 1 ends its race to the tank four 15-4 and after fifteen minutes of residence, Peffiuent is subjected to the separation and cycloπage 11-4 where the fraction 5 micron to 24 microns is retained.

[0044] The filters used to decant the effluent # 1 use centrifugal force and make it possible to remove from the effluent # 1 fine fractions of which the size is from about 0.005 mm (5 μm) to 2.00 μm. mm whereas the fine fractions of dimensions less than 5 microns, that is to say the fines, remain in suspension in the effluent # 1 obtained after ('step of separation by filter 108 effluent # 1 is more or less loaded with fines and according to the quality of it, it is recirculated to the washing screen (effluent # 2) or to a chemical chamber for the treatment of fines [00453 The four storage tanks 15 are provided with a filtration and cycloning system 11 and are installed in parallel Ns are designed to operate at the maximum expected flow rate at the inlet is 1890 liters per minute (500 USGPM) Each filter is used in order to remove fine fractions of varying sizes from the effluent The filtration and cycloning system 11 makes it possible to extract from the effluent # 1 of step 106 particles, whose diameter is between about 5 μm and 2 μm, 00 mm, that is to say that form sludge resulting from step 108 According to the analyzes, these soils will be treated in a chemical chamber or valued according to the quality On the other hand, the particles having a smaller diameter that 5 microns, that is to say the lightest, remain in suspension in the washing liquid and constitute the effluent of step 108

The sludge resulting from step 108, which contains fine fractions of size between 5 microns and 200 microns and between 200 microns and 2.00 mm are conveyed by 6 "conveyors to a storage area at a point of fall. The effluent # 1 flowing from the fractions during storage at the storage area can be recovered by means of drains and returned to a packaging line.

Typically, the washing effluent of step 108 has a maximum flow rate of 500 USGPM. This effiuent (effluent # 2) is returned to the wet soil sifting unit 10 and / or a part of this water ( effluent # 3) can be used for the treatment of fines in the chemical chamber II consists of the following elements

• Neutral wash effluent or with the possibility of surfactants, oxidizing or other,

• soil particles with a diameter of less than 5 μm and

• a quantity of the metallic contaminant, either in the form of particles having a diameter of less than 5 μm, or dissolved in the liquid of washing

The concentration of suspended matter (MES) in the effluent of step 108 depends on the nature of the soils that are treated by the method 100. For example, when the soils consist essentially of sands, the effluent of step 108 will tend to be rather liquid due to the low concentration of SS, including the particles of the opposite metal contaminant, a soil consisting of a clay matrix may result in an effluent of step 108 whose concentration of MES can be higher.

Step of solution of the fines of the metallic contaminant 110

The fines from 5 to 200 microns from step 108 are analyzed and according to the results, recovered or will be treated in the chemical chamber to reduce the metal concentrations. The dissolving step of the fines of the metallic contaminant 110 comprises sub-steps.

• an acid dosage,

• a mixture of the acid with the effluent,

• a dosage of coagulant and aid-coagulant (if necessary);

• decantation of SS (if necessary); and

• a filtration

Determination of acid

The acid dosage is performed depending on the nature of the metal contaminant, that is to say according to the types and concentrations of metals contained therein, to put in solution and pH conditions to meet to get this solution in solution. PH measurements by means of pH meters allow the reaction to be monitored The acid dosage is carried out while a part of the effluent # 1 of step 108 is routed to the mixing tanks 16 (with mechanical stirrer or air), ie the tanks 16-1 to 16-3, intended for in solution of the metals The fines of 5 to 200 μm dehydrated are incorporated in the effluent # 1 and will be mixed with the acid The amount of water to be added is determined according to the percentage of fines to be treated, the type and the concentration contaminants present

Mixing of acid with effiuent

Mixing the acid with the effluent # 1 and the fines to generate the effluent # 3 acid

Following the assay, a solution of acid, for example hydrochloric acid, sulfuric or nitric, is injected into a pipe, during the delivery of the effluent # 1 of step 108 to the reservoirs Each of the mixing tanks 16 typically has a capacity of 2883 to 37854 liters (8,000 to 10,000 US gallons) and is equipped with a stirrer, with which the effluent # 1 of the step 108 and the injected acid solution are mixed to give the effluent # 3 The retention time in the mixing tanks 16 is typically of the order of 40 minutes for a continuous feed mode The mixing tanks 16 can also be operated in batch mode, that is to say in batch mode, for example in the case where a reaction time greater than 40 minutes is necessary

Assaying coagulant and coagulant aid

Then, if necessary, a coagulant for example alum ferric sulfate or equivalent, a coagulant aid or ffoculants can be added piped to the effluent at the outlet of the acid mixing tanks

16

[0056] Decantation of the MES

If necessary, the addition of the coagulant and the coagulant aid has the function of promoting coagulation of the MES in the effluent at the outlet of the mixing tanks 16 and then allowing settling. This double function is to serve as a contact basin to ensure the coagulation of the MESs and then to allow a static settling so that the acid sludge thus formed is deposited at the bottom of the tanks.

Fiitration

Typically, at the outlet of the contact tank or acid mixture 16, the effluent # 3 loaded with acidified metals and fines (5 μm to 200 μm) is pumped and must be filtered 11-5 through a filter to separate the following products

o Effluent # 3 loaded with dissolved metals containing fines (0-25 microns), must be neutralized at step 112 (precipitation of metals)

o Acid sludge from 25 to 200 microns

The treated fines must be neutralized and managed in the sludge treatment stage 114

Typically, the effluent # 3 loaded with metals at the outlet of the filter 11 -5 has a maximum flow rate of 80 USGPM. The pH of the effluent # 3 is lower. at 5.0 and depends on the nature of the metals to be dissolved. It contains fines of 25 microns and less (0-25 microns), which must be neutralized and filtered.

Step precipitation of metal ions 112

The acid efflueπt # 3 (0 to 25 μm) at the outlet of the filter 11-5 generally contains dissolved ions of the metal contaminant.

Step 112 of precipitation of the metal ions of the effluent

# 3 includes

_• dosing and mixing of the base with effluent # 3,

_• d _e decantation MES and

• a filtration

Dosage and mixing of your base with the effluent

The acid effluent # 3 (0 to 25 μm) at the outlet of the filter 11-5 is collected by a pipe and conveyed to 17-2 and 17-3 metal ion precipitation tanks. A basic solution, for example! sodium hydroxide or other equivalent bases is injected into the line between the filter 11-5 and the precipitation tank metal ions to p _re cipiter ies metals or to neutralize the effluent # 3 and its contents then if necessary a coagulant, Example of alum, ferric sulphate or an equivalent and a coagulating aid may be added in an effluent line.

[0065] The # 4 effluent is neutral or basic depending on the metal to precipitate (S) réservoιr (s) of precipitation of the effluent 17 # 4 are equipped ^with a _stirrer, in order to carry out the mixing mode of operation of the

[$ 21 - 45 | ^> 514 397 8515 | ® receiv ed Precipitation of the metals, that is to say continuously or in batch, is determined by the steps described above, as well as the reaction time to the pH required to form metal precipitates The dosage of the basic solution depends on the nature of the metal ions in solution in the effluent # 3 acid at the outlet of the filter 11-5 and pH conditions to achieve to promote the precipitation of metal ions for this purpose, pH measurements are made using pH meters and allow MONITORING.

[0066] Decantation of the MES

If necessary, the addition of the coagulant, coagulant aid and flocculants has the function of promoting a settling of the MES in the effluent at the outlet of the mixing tanks 17 The tanks have a dual function, ie to serve as a contact basin to ensure the coagulation and flocculation of the MESs and then to allow a static settling of the flocs formed by the flocculation, so that the neutralized or basic sludge thus formed are deposited at the bottom of the tanks

Filtration

After mixing the effluent # 4 neutralizes at the outlet of the tank for the precipitation of metal ions 17 is routed to a filtration unit and separation 11-7 to separate precipitates formed following the injection of the base This step will make it possible to separate the effluent containing 0-25 microns of the precipitated metals. The unit of filtration will make it possible to filter at 5 microns.

o The effluent neutralizes,

The neutralized effluent that flows at the outlet of the filter has a maximum flow equivalent to that of the inlet The pH of the effluent will be between 6.0 and 8.0

o Neutralized fines from 5 to 25 microns

The neutralized fines are conveyed to the sludge treatment unit 114 by dehydration and thereafter, take an exit conveyor for analysis prior to management.

Sludge treatment stage 114

The activities that constitute this treatment step include dehydration of the sludge generated at the different stages of the chemical treatment process (steps 110 and 112) and the management thereof Sludge is of two (2) natures

acidic sludge from 25 to 200 microns (step 110)

neutralized sludge of 5 to 25 microns (step 112)

At the outlet of the filter 11-5, the acid sludge of 25 to 200 microns must be neutralized to carry out the management thereof They are pumped into a reservoir (or equivalent) 17-1 and therein, Neutralizing products are injected. The packaged sludge will be transported to a dewatering unit of centrifugal filtration type 11 -6 so as to increase the dryness of the latter. At the outlet of the dehydration unit, the material to be discharged on the conveyor ( or equivalent) is clean and neutralize II will be sampled for determination of the final management mode

The neutralized sludge of 5 to 25 microns is conveyed to the dewatering unit of filtration type by centrifuge 11-7, so to increase the dryness of these and use an exit conveyor (or equivalent) to be analyzed before final management The neutralized effluent extracted from the sludge will be recovered and returned to the storage tanks and neutralization to recirculate the water in the process 1 16.

Stage of conditioning of the effluent after the precipitation of the metal ions 116

The effluent collected at the outlet of the chemical chamber is reused as process water. The activities that constitute this treatment step are as follows:

o pH adjustment (if necessary and water storage) o Recirculation

Surface drainage water can also be integrated into this packaging industry

PH adjustment

The neutralized effluent from the precipitation unit

112 Routing to the neutralization and storage area 4. An acid or base may be injected at the entrance of the first tank if the water is not neutral for recirculation. The minimum retention time in the tank is of the order of 40 minutes to a method ^of feeding the continuous system will be operated batchwise (batch), if the reaction time is greater than the pH of lens must meet be between 6.0 and 8.0 before returning to the process Continuous pH measurements using pH meters will track set points [0076] Reαrcuiation

When the quality of this water is acceptable to allow its reuse as water to proceed within the treatment stream, it is pumped into the distribution line.

Method 100 may also include aspects of the management and treatment of gaseous effluents

Control and analysis of treated soils

[0080] Different soil fractions resulting from the application of the method 100 are stored in dedicated areas. In summary these fractions are as follows.

• pebbles, »gravel,

• coarse and fine sands,

Fine particles (200 μm to 2.00 mm in diameter), and

• sludges containing fines less than 200 μm in size

These different fractions are characterized and analyzed to determine their level of contamination If for a given fraction the contamination rate remains high, it can be returned to undergo the method 100 again, possibly with a corresponding adjustment of the parameters of operations Soils will be subsequently disposed according to the quality criteria and the management methods that apply to contaminated soils According to the results of analyzes obtained these different fractions of Soils can be reused for different uses, that is to say valued, depending on their characteristics in relation to the applicable criteria.

In Figure 2, it is noted that the reference 3 denotes reservoirs and dosing pumps, that reference 7 denotes a receiving body, that reference 8 denotes a return to water treatment, that the reference A denotes water storage tanks, that reference B denotes a separator water / hut, that reference C denotes pressurized filters that reference D denotes clean water storage tanks, and that the reference DP denotes a floor drain

Although the present invention has been described above by means of a non-restrictive embodiment for purposes of illustration, this embodiment can be modified at will, within the scope of the invention, without departing from of the spirit and nature of the subject matter of the invention

Claims

CLAIMS:

1 A method for removing soil from inorganic contaminants, the method comprising: screening the contaminated soils to obtain coarse fractions and fine fractions, washing the sieved soils with a washing effluent, to obtain a first effluent comprising the washing liquid and soils flowing through the sieve and sieving the soils to retain the coarse fractions and concurrently the fractions flowing from the sieve comprise fines and the particles larger than those of the fines are retained, subjecting the washing effluent to extraction of particles larger than those of fines and thus obtain a second effluent that is returned to the washing unit and / or a fraction can be returned to a chemical chamber, produce in the chemical chamber an extraction of the second effluent containing the contaminated fines to dissolve the metals, in order to obtain a third effluent, and pro precipitating and / or neutralizing the third effluent and filtering off the precipitate to obtain a fourth effluent, whereby the inorganic contaminant is precipitated for extraction in a fourth effluent

The method of claim 1, wherein the inorganic contaminant contains a metallic contaminant

The method of claim 2, wherein the metal contaminant contains more than one metal element

The method of claim 2, wherein the metal contaminant is selected from the group consisting of aluminum, arsenic, silver, barium, cadmium, chromium, cobalt, copper, tin, iron, manganese, magnesium, mercury, molybdenum, nickel, lead, sulfur, selenium, sodium, zinc and all combination of these

The method of claim 1, wherein producing an extraction of the third effluent comprises adding an acid to the first effluent

The method of claim 1, wherein the production of a flocculation of the third effluent comprises the addition of a coagulant, a coagulant or a flocculant.

The method of claim 1, wherein producing a precipitation of the fourth effluent comprises adding a base, a coagulant or a flocculant to the third effluent.

The method of claim 1 wherein the extraction of particles larger than those of fines comprises a filtration of particles larger than fines.

The method of claim 1, wherein the washing of the soil comprises the addition of surfactants, oxidants to the first effluent

The method of claim 1, wherein a substantially contaminant-free effluent becomes a fifth effluent

The method of claim 10, wherein the fifth effluent is recirculated in the treatment process.

The method of claim 1, wherein after washing the sieved soils, the first effluent is magnetically stripped to remove magnetic fractions. The method of claim 1, wherein in the step where the wash effluent is subjected to extraction, this extraction of fines is done by filtration and cyclone separation, with the finest particles remaining in suspension in the first effluent following this step, the first effluent then becoming the second effluent.

14 A method for removing inorganic soil contaminants, the method comprising. a) washing a contaminated soil with a washing effluent, in order to obtain a first effluent comprising the washing effluent and fines while the particles of dimensions greater than those of the fines are retained, b) subjecting the first effluent to a extraction of the particles larger than those of the fines and thus obtain a second effluent which is returned to the washing unit and / or a fraction can be conveyed to step c), c) produce an extraction of the second effluent containing the fines contaminated to dissolve the metals, to obtain a third effluent, and d) to produce a precipitation and / or neutralization of the third effluent and extract by filtration! the precipitate to obtain a fourth effluent; by which the inorganic contaminant is precipitated for extraction into a fourth effluent

The method of claim 14 wherein prior to step a) there is a step of separating contaminated soil into coarse fractions and fine fractions

The method of claim 15, wherein the separation is by screening The method of claim 14, wherein step a) is by wet screening

The method of claim 14 wherein prior to step b) there is a step in which the first effluent is magnetically stripped to remove magnetic fractions.

The method of claim 14, wherein after step d), the substantially contaminant-free effluent becomes a fifth effluent.

The method of claim 19, wherein the fifth effluent is recirculated in the treatment process

A method for removing inorganic contaminants from soils, the method comprising a) subjecting a first effluent containing inorganic contaminants to filtering in order to extract particles larger than fines and thus obtain a second effluent, c) producing an extraction of the second effluent containing the fine contaminants to dissolve the metals, thus obtaining a third effluent and d) producing a precipitation and / or neutralization of the third effluent and extracting by filtration the precipitate to obtain a fourth effluent by lequei the inorganic contaminant is precipitated for extraction into a fourth effluent