Process for soil decontamination by oxidation and vacuum extraction

• US 5,615,974 A
• Filed: 04/04/1994
• Issued: 04/01/1997
• Est. Priority Date: 01/07/1992
• Status: Expired due to Term

• Current Assignee: Terra VAC Incorporated
• Original Assignee: Terra VAC Incorporated
• Inventors: Oberle, Daniel, Malot, James J., Papa, Louis C., Land, Christopher A., Pezzullo, Joseph A.
• Primary Examiner(s): Suchfield, George A.
• Application Number:
  US08/211,559
• Time in Patent Office: 1,093 Days
• Field of Search: 405/128, 405/129, 405/131, 405/258, 405/263, 588/249
• US Class Current: 405/128.35
• CPC Class Codes: B09C 1/005 Extraction of vapours or gases using vacuum or venting
• CPC Class Codes: B09C 1/08 chemically
• CPC Class Codes: B09C 2101/00 In situ
• CPC Class Codes: C02F 1/20 by degassing, i.e. liberation of dissolved gases degasification of liquids in general B01D19/00; arrangement of degassing apparatus in boiler feed supply F22D
• CPC Class Codes: C02F 1/722 Oxidation by peroxides
• CPC Class Codes: C02F 2103/06 Contaminated groundwater or leachate

Abstract

A process for in situ treatment of a contaminated subsurface zone of the earth containing volatile liquid or semisolid organic contaminants, semivolatile liquid or semisolid organic contaminants and/or nonvolatile organic contaminants in liquid, semisolid and/or solidified form which comprises treating said contaminants with an oxidant such as hydrogen peroxide and conducting vacuum extraction to remove volatilized contaminants, volatilized oxidation products of contaminants and/or liquid oxidation products of contaminants. The oxidant application may be made in a contaminated subsurface vadose zone, a contaminated subsurface capillary fringe or beneath the surface of a contaminated water table. Vacuum extraction may be conducted in the contaminated zone itself or, in the vadose zone directly above the contaminated capillary fringe or the contaminated water table and may be utilized, e.g., to withdraw water containing oxidation products of contaminants. The treatment may enhance natural biodegradation of some contaminants and may be conducted in a variety of ways.

Claims

1. An in situ process for removing one or more volatile, semivolatile or nonvolatile organic contaminants present in liquid, semisolid or solid form in a contaminated subsurface zone, which process comprises the steps of:

(a) introducing into said contaminated subsurface zone an oxidant having the capability to react exothermically with said contaminants to form oxidation products thereof;

(b) allowing said oxidant to react exothermically with said contaminants to form oxidation products;

(c) installing at least one vacuum extraction well into the contaminated subsurface zone or into another subsurface zone at a position proximate to the position in the contaminated zone at which oxidant was introduced;

(d) applying to the top of said vacuum extraction well a vacuum that is sufficient to create a negative pressure gradient in the subsurface; and

(e) removing through said vacuum extraction well to the surface oxidation products of said contaminants.

2. The process of claim 1 in which said oxidant is hydrogen peroxide.

3. The process of claim 2 in which Fenton'"'"'s reagent is also present.

4. The process of claim 1 in which steps (b) and (d) are conducted simultaneously.

5. The process of claim 1 wherein the contaminated subsurface zone is a subsurface vadose zone, the vacuum extraction well extends into said vadose zone and the vacuum applied is effective to volatilize volatile contaminants present and to draw substantial quantities of air through said vadose zone.

6. The process of claim 1 wherein the said oxidant is introduced by injecting it below the surface of the water table through at least one conduit which extends into said water table.

7. The process of claim 6 wherein said conduit which extends into said water table is contained in an injection borehole that also acts as a vacuum extraction well through which groundwater containing oxidation products of said contaminants is withdrawn.

8. The process of claim 7 wherein another vacuum extraction well also extends into a proximate position in the vadose zone and removal of oxidation products of said contaminants in vapor form is effected therethrough.

9. The process of claim 1 wherein said oxidant is introduced into the subsurface capillary fringe zone.

10. The process of claim 1 wherein said vacuum extraction well extends into a proximate position in the vadose zone and removal of vaporized oxidation products of said contaminants is effected therethrough.

11. The process of claim 1 wherein said oxidant is introduced in liquid form by spreading said liquid on the surface of the ground above said contaminated subsurface zone and allowing it to seep into said subsurface zone.

12. The process of claim 1 wherein aerobic bacteria in the contaminated subsurface zone concomitantly act to biodegrade a portion of the contaminants present.

13. The process of claim 1 wherein said oxidant is introduced to the contaminated subsurface zone by means of at least one injection well.

14. The process of claim 1 wherein said oxidant is introduced to the contaminated subsurface zone by means of pressurized injection thereof.

15. The process of claim 14 wherein said oxidant is introduced into the contaminated subsurface zone using a jet grouting technique.

16. The process of claim 1 wherein said oxidant is introduced to the contaminated subsurface zone through at least one horizontally sited conduit located beneath the surface and provided with perforations throughout at least a portion of its length, through which said oxidant is caused to percolate into the subsurface beneath it.

17. The process of claim 1 wherein said oxidant is introduced into the contaminated subsurface zone at a plurality of points and at more than one subsurface depth.

18. The process of claim 1 further comprising the step of treating the effluents from step (e) to remove or otherwise render harmless the vaporized contaminants contained therein.

19. The process of claim 1 further comprising the step of discharging to the atmosphere vaporized oxidation products of contaminants.

20. The process of claim 1 wherein the heat generated in the exothermic reaction of step (b) is controlled within a temperature range of from about 10°

C. to about 35°

C.

21. The process of claim 1 wherein said oxidant is introduced to the contaminated subsurface zone through at least one horizontally sited conduit located beneath the surface and provided with perforations throughout at least a portion of its length, through which said oxidant is caused to flow into the subsurface.

22. The process of claim 7 further comprising the step of treating at the surface said groundwater containing oxidation products of said contaminants to remove oxidation products.

23. The process of claim 1 wherein volatilized organic contaminants are also removed through said vacuum extraction well.