Apparatus and method for removing volatile contaminants from phreatic water

• US 5,575,589 A
• Filed: 04/11/1995
• Issued: 11/19/1996
• Est. Priority Date: 04/11/1995
• Status: Expired due to Term

• Current Assignee: Piedmont Olsen Hensley, Inc. (Arcadis N.V.)
• Original Assignee: Geraghty & Miller, Inc. (Arcadis N.V.)
• Inventors: Suthersan, Suthan S.
• Primary Examiner(s): Neuder, William P.
• Application Number:
  US08/420,224
• Time in Patent Office: 588 Days
• Field of Search: 405/128, 166/266, 166/267
• US Class Current: 405/128.25
• CPC Class Codes: B09C 1/002 involving in-situ ground water treatment
• CPC Class Codes: B09C 1/005 Extraction of vapours or gases using vacuum or venting
• CPC Class Codes: B09C 2101/00 In situ
• CPC Class Codes: E21B 43/305 comprising at least one inclined or horizontal well
• CPC Class Codes: E21B 43/40 Separation associated with re-injection of separated materials E21B43/385 takes precedence

Abstract

A method and apparatus for removing volatile contaminants from the phreatic zone of a contaminated region in the ground. The apparatus is a system comprised of a trench cut into the phreatic zone of contaminated ground containing fluid-permeable fill material, an air injection line submerged in the lower portion of the trench and an air/contaminant gas extraction line in the trench above the water table. Air is injected into the contaminated ground water to allow sparging of the volatile contaminants. The volatile contaminants are captured by the injected air and carded to the extraction line for removal and/or treatment.

Claims

1. A closed-loop process for removing volatile contaminants from a contaminated area of the earth, wherein the contaminated area of the earth has a phreatic zone, the contaminant being present in the phreatic zone, which comprises the steps of:

establishing a trench extending downwardly from the surface of the ground within the contaminated area, said trench having a lower portion substantially within the phreatic zone and an upper portion substantially within the vadose zone;

placing an injection pipe having a perforated surface in the bottom of said lower portion of said trench;

filling fluid-permeable fill material into said lower portion of said trench above the water table so that said fill material will permit fluid to flow readily through said lower portion;

placing an extraction pipe having a perforated surface into said trench upper portion;

filling fluid-permeable fill material into said upper portion of said trench up to the ground surface so that said fill material will permit fluid to flow readily through said upper portion;

sealing said trench at said ground surface to prevent gas passage between said trench and the atmosphere;

applying air under pressure to said injection pipe effective to induce a flow of air from said injection pipe into said trench lower portion; and

applying a vacuum to said extraction pipe effective to induce a flow of air and a gas containing vapor of said contaminant present in said trench upper portion into said extraction pipe so that said contaminant is removed from said ground.

2. The process of claim 1 wherein both the vacuum and pressurized air are supplied by an air pump in fluid communication with both said injection pipe and said extraction pipe.

3. The process of claim 1 further comprising the step of separating the volatile contaminants removed from said extraction pipe from said air.

4. The process of claim 3 further comprising the step of returning the air to said injection pipe.

5. The process of claim 1 further comprising the step of delineating the extent of the contaminated area and locating said trench downstream of said contaminated area.

6. The process of claim 1 wherein the contaminated area of earth comprises a soil formation which is finer than fine sand.

7. A contaminant removal system for removing volatile contaminants from the phreatic zone of a contaminated ground area, said contaminant removal system comprising:

a trench having a lower portion and an upper portion, said lower portion substantially disposed within the phreatic zone, said upper portion substantially disposed within the vadose zone;

a first conduit disposed within said lower portion of said trench having a perforated surface;

a second conduit disposed within said upper portion of said trench having a perforated surface;

a fluid-permeable fill material filling said upper portion and said lower portion of said trench;

a seal at the ground surface on said trench effective to prevent gas passage between said trench upper portion and the atmosphere;

a vacuum operatively connected to said second conduit wherein said second conduit is in fluid flow communication with said vacuum; and

a blower operatively connected to said first conduit wherein said first conduit is in fluid flow communication with said blower.

8. The system of claim 7 which further comprises a contaminant treatment system operatively connected in fluid communication with said second conduit.

9. The system of claim 7 wherein said vacuum and blower comprise an air pump.

10. The system of claim 7 which further comprises a series of trenches.

11. The system of claim 7 wherein said first and second conduit comprises screened PVC pipe.

12. The system of claim 7 wherein the contaminated ground area comprises soil formations which are finer than fine sand.