The method of cleaning soil from organic contaminants

 

(57) Abstract:

The invention relates to means for cleaning soils from organic contaminants. The method involves the introduction into the soil of the electrodes, passing between the electrodes through the soil constant electric current and an introduction to the area of cleaning the cleaning solution, for example, oxidizing the contamination of microorganisms; the direction is supplied to the electrodes constant electric current periodically change; in the purification zone periodically to deliver air under pressure; in the purification zone is injected substances emitting in the process of decomposition of oxygen. The invention provides a complete decomposition of impurities in the purification zone, eliminates the need for transportation and elimination, improves the efficiency of the cleaning process. 4 C.p. f-crystals, 1 Il.

The invention relates to the field of electroosmotic cleaning capillary-porous media, in particular soil contaminated by oil, oil products, phenols and other organic substances.

A known method of cleaning soil from organic contaminants by injecting into the ground electrodes and feeding them a constant electric current (see, for example, ABT. St. USSR N 1708196, class A 01 G 25/00, 1990). This is provides the binding of the cationic part of the impurities in the clay, and anion - exchange calcium (with the formation of difficultly soluble compounds). However, the evacuation of pollutants is not happening (pollution only translated in the bound form from the soil in the subsurface layer). Thanks to the implementation of the method only prevents migration and an increase in the concentration of heavy metals and radionuclides.

There is also known a method of cleaning soil from organic contaminants such as oil, is injected into the cleared ground electrodes, the supply to the electrodes constant electric current and the introduction in the area of cleaning the cleaning solution (see U.S. patent N 5074986, CL C 25 C 1/22 (U. S. CI-204/130), 1991.

The disadvantage of this method is due to the fact that it does not remove from the sanitized environment of light, medium and heavy oil fractions, firmly bound to soil particles.

A known method of cleaning soil from organic contaminants such as oil, is injected into the cleared ground electrodes, the supply to the electrodes constant electric current and the introduction into the treatment zone of the scrubbing solution containing the microorganisms - destructors of oil (see the application for the grant of a patent of Russian Federation N 96115093/02 (021565), class C 25 C 1/22, 1996, the decision to grant a patent from 05.01.1997 year). PR is the working fluid. This technical solution adopted for the prototype.

The main disadvantage of this method is the fact that pollution is decomposed in the treatment zone under the action of microorganisms only partially. A significant portion of the contaminants are separated from the solution, remote from the hollow cathodes (electrodes connected to the negative pole of the current source), with the help of a centrifuge. This raises problems of transportation, disposal or elimination of these contaminants. In addition, when applying an electric current to the electrodes the decomposition of water with oxygen at the anode (the electrode connected to the positive pole of the same source). Electric power can distract the flow of liquid oxygen to the cathode, however, due to diffusion processes is the localization of the oxygen on the surface of the soil in the zone of the well. Thus, eye-catching due to electrolysis oxygen is not distributed evenly throughout the volume of the cleaning zones. It worsens the conditions of supply of aerobic microorganisms and reduces the efficiency of oxidation of the organic contaminants. In addition, the cleaning solution circulating between the anodes and the cathodes are periodically subjected to dielectr is on microorganisms and reduces the cleaning efficiency.

The present invention laid the task of creating such a method of cleaning soil from organic contaminants, which would provide a full decomposition in cleaning zones and prevented from entering the cleaning solution in areas with high or low pH values.

According to the invention this problem is solved due to the fact that in the method of cleaning soil from organic contaminants such as oil, is injected into the cleared ground electrodes, passing between the electrodes through the soil constant electric current and the introduction into the treatment zone of the scrubbing solution, such as solution of oxidizing contamination of microorganisms, the direction of the noise between the electrodes through the soil constant electric current periodically change; in the treatment zone to provide living conditions of microorganisms by maintaining a temperature in the range of 15-40oC; in the purification zone may be periodically supplied air under pressure, when it is filtered the resulting evaporation of the organic contaminants in the cleaning zone can be introduced substances (for example, an aqueous solution of hydrogen peroxide) produced by the process of decomposition of oxygen.

Thanks to the implementation of the distinguishing features of the invention (in conjunction with evidence contained in the restrictive part of the formula of the invention) gives the following important new properties (effect):

- due to the periodic change of polarity of the cleaning solution and soil moisture commit multiple oscillatory movement between the electrodes; however, the contaminated solution is not out of the zone cleanup; contamination contained in it, over time decays to a minimum value, which eliminates the problem of their disposal or liquidation;

- multiple oscillatory process in the purification zone helps to improve its efficiency due to mechanical mixing of moisture in the soil, and a more uniform distribution of oxygen throughout the treatment zone;

since the cleaning solution containing microorganisms, mostly misses in areas with extreme pH values, increased time activity microorganismal, which would contain information about the impact of the distinctive features of the invention for achieving the above technical result. This leads, according to the applicant, the proposed technical solutions to the criterion of "inventive step".

The invention is illustrated by the drawing, which is given diagram illustrating the implementation of the proposed method.

In the cleaning zone of the soil contaminated in the specific example gasoline and diesel fuel with a total concentration of 5 g/kg, administered electrodes. The depth of contamination 0-1,5 m, the area of contamination 14 m2. The electrodes are divided into two groups 1 and 2, six electrodes each, the length of the electrode 1.5 m, diameter 50 mm Electrodes made of ferrosilicon alloy characterized by a very low coefficient of anodic dissolution. The distance between adjacent electrodes within the group 1 and group 2 is 1.2 m, and the distance between the electrode group 1 and the electrode group 2 is 2 m

Source 3 DC consists of a power transformer and thyristor rectifier. Output voltage 150 C. the Electrodes are connected to source 3 constant current through the switching unit 4, which allows to change the paragraph is amennye between the electrodes of both groups. The tube 7 is provided with perforations at the bottom, the pipe diameter is 40 mm

To supply air to the zone cleaning use a compressor 8 which communicates with the pipe 7 through line 6.

The method is implemented as follows. In the cleaning zone of the reservoir 5 serves a cleaning solution containing a specific example of a widely known biologic "Poutical" in the amount of 50 l concentration of microorganisms (1 - 10 g/l titer 1108- 11012cells/ml When the valve 10 is open and the valve 9 is closed. The solution passes through line 6 and enters the pipe 7, and then passes through a perforation in the ground. The electrodes connect the power source 3: in the beginning, for example, to the electrode group 1 is connected to the positive pole and the electrode group 2, respectively the negative pole of the power source.

Near the surface of contact between the pore water present in the soil, with the walls of the pores, there is always the electric double layer, i.e. two systems of oppositely charged particles, anions and cations. These charges represent the plates of electric double layer. One of these plates, formed by anions adsorption is associated with the walls of the pores, and so the dka, formed by the cations located in the fluid filling the pore, and capable of moving under the action of electric forces generated by electrodes. As a result of moving ions occurs electroosmotic flow of a fluid, consisting of soil moisture and cleansing solution. This stream carries organic pollution in the direction of the electrode group 1 to the electrode group 2. Feature electroosmotic process is highly effective in temporaty clay soils.

After some time (in the specific example - after seven days) using the switching unit 4 to change the polarity of the electrode groups 1 and 2. This electroosmotic flow changes its direction. After seven days the polarity change again and so the process continued in the specific example 60 days.

The current was changed within 7-20 A temperature in the treatment zone increased from 16 to 35oC and was maintained constantly with a small (1-2oC) fluctuations around this value.

In the processing of petroleum products was reduced to values not exceeding 80 mg/kg, after which the process was stopped.

To improve the efficiency of processesa, for example, on the cathode electrodes, occasionally (2 times a day for an hour) in the area of clean air was supplied from a compressor 8 with a pressure of 1-2 at. When the valve 9 was opened, and the valve 10 is closed. The resulting evaporation of hydrocarbons was filtered through carbon filters, thereby preventing the escape of these vapors into the atmosphere. If aeration is insufficient, for example, at great depths, to improve the efficiency of oxidation in the purification zone is injected substances emitting in the process of decomposition of oxygen. This may be, for example, used 10-20% solution of hydrogen peroxide.

For the implementation of the proposed method apply the usual industrial equipment, any known biological products containing microorganisms - destructors of oil and other organic substances.

These circumstances allow, according to the applicant, to conclude that according to the invention, the criterion of "industrial applicability".

1. The method of cleaning soil from organic contaminants such as oil, is injected into the cleared ground electrodes, passing between the electrodes through the soil constant electric current and the introduction into the treatment zone PTS is the noise between the electrodes constant electric current periodically change.

2. The method according to p. 1, characterized in that the treatment zone to provide living conditions of microorganisms by maintaining a temperature in the range 15 - 40oC.

3. The method according to p. 1, characterized in that the cleaning zone periodically to deliver air under pressure, when it is filtered the resulting evaporation of the organic contaminants.

4. The method according to p. 1, characterized in that the cleaning zone is injected substances emitting in the process of decomposition of oxygen.

5. The method according to p. 1, characterized in that the electrode wells periodic served in the air for removing hydrocarbon films, to prevent the ingress of hydrocarbon films in the atmosphere above the surface of the wells installed carbon filters.

 

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2 ex

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2 ex

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