System for alleviating DNAPL contamination in groundwater

• US 6,274,048 B1
• Filed: 03/22/2000
• Issued: 08/14/2001
• Est. Priority Date: 03/22/2000
• Status: Expired due to Term

• Current Assignee: University of Waikato
• Original Assignee: University of Waikato
• Inventors: Parker, Beth Louise, Nelson, Matthew David, Cherry, John Anthony
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): LAWRENCE JR, FRANK M
• Application Number:
  US09/532,784
• Time in Patent Office: 510 Days
• Field of Search: 210/747, 210/758, 210/759, 210/752, 210/170, 210/198.1, 210/908, 210/925, 405/128, 405/258, 405/52, 405/263, 588/248, 588/206
• US Class Current: 210/747.8
• CPC Class Codes: B09C 1/002 involving in-situ ground water treatment

Abstract

Lenses of DNAPL suspended on clay strata in a sandy aquifer are treated with potassium permanganate. The solution is injected out into the aquifer from a port, and forms a horizontal disc of treatment liquid. The (heavy) liquid then gradually percolates down onto the DNAPL lens.

Claims

1. Procedure for treating contaminated groundwater in its native aquifer, wherein:

the material of the aquifer is porous, and the aquifer is permeable to the through-flow of groundwater, at least laterally, to the extent that liquid readily moves and spreads laterally through the pore spaces in the aquifer;

the aquifer has a hydraulic conductivity greater than 10<sup>−

6</sup> cm/sec;

the aquifer includes a bed-layer, which has a hydraulic conductivity lower than 10<sup>−

7</sup> cm/sec;

the contaminant is a dense non-aqueous-phase liquid, which has settled on the bed-layer, and is in the form of a liquid lens, of comparatively small vertical height and large lateral extent;

the procedure includes introducing treatment liquid into the aquifer, and of injecting the treatment-liquid in the form of a coherent layer of the treatment-liquid, termed a treatment-lens;

the treatment-liquid is concentrated enough to cause chemical breakdown of the DNAPL contaminants in the groundwater;

the treatment-liquid is substantially more dense than the groundwater, whereby, upon injection of the treatment liquid into the aquifer, the treatment liquid starts to sink down;

and the procedure includes the steps of so placing the treatment-lens of the treatment-liquid in the aquifer as to overlie a portion of the lens of DNAPL, just above the lens, whereby the dense treatment-liquid, in sinking, spreads out progressively laterally for a large distance, over the bed-layer and over the lens of DNAPL.

2. Procedure of claim 1, wherein the dense treatment liquid is a solution of permanganate, of more than 1 gram per liter concentration.

3. Procedure of claim 1, wherein the procedure is carried out by:

providing an injecting structure, having an injection-port, and providing a means for injecting treatment liquid through the port, under pressure, into the aquifer;

placing the injecting-structure down into the aquifer, until the port is located just above the DNAPL;

and then injecting the treatment liquid out through the port.

4. Procedure for treating contaminated groundwater in its native aquifer, wherein:

the material of the aquifer is porous, and the aquifer is permeable to the through-flow of groundwater;

the porous material of the aquifer is stratified, to the extent that liquid readily moves and spreads laterally through the pore spaces in the aquifer, following the lie of the strata, to a substantially greater degree than the liquid moves and spreads vertically;

the aquifer has a hydraulic conductivity greater than 10<sup>−

6</sup> centimeters per second;

the procedure includes introducing a quantity of treatment-liquid into the aquifer;

introducing the treatment-liquid in the form of a coherent layer of the treatment-liquid, termed a treatment-lens;

so placing the treatment-lens in the aquifer as to overlie a treatment-zone of the aquifer;

immediately upon the treatment-lens being formed in the aquifer, the treatment-lens comprises a volume VL cubic meters of treatment-liquid, and the treatment-liquid occupies a volume VL cubic meters of aquifer-pore-volume, termed the lens-pore-volume;

the lens-pore-volume of the aquifer, being the volume of the aquifer-pore-volume occupied by the treatment-lens immediately upon the treatment-lens being formed, has an average lateral diameter of D meters, occupies a horizontal area of A square meters of the aquifer, and has an overall vertical thickness in the aquifer of Z meters;

the lens-pore-volume of the aquifer is disc-shaped, in that the aspect ratio of the treatment-lens, being the ratio of the diameter D of the lens-pore-volume to the vertical thickness Z of the lens-pore-volume, is at least two-to-one;

the treatment-liquid is concentrated enough to cause chemical breakdown of the contaminants in the groundwater;

the treatment-liquid is substantially more dense than the groundwater, whereby the treatment liquid sinks down out of the lens-pore-volume and into an under-lens-pore-volume of the aquifer;

the under-lens-pore-volume is that zone of the aquifer-pore-volume that lies contiguously underneath the lens-pore-volume, and is the zone of the aquifer into which the dense treatment-liquid from the lens-pore-volume permeates down and through;

the nature of the aquifer is such that the dense treatment-liquid can permeate down through the under-lens-pore-volume of the aquifer, under gravity, by virtue of its density contrast with groundwater in the aquifer;

the nature of the aquifer is such that the dense treatment-liquid starts to permeate down from the lens-pore-volume, into and through the under-lens-pore-volume, immediately upon the treatment-lens being formed;

the procedure includes forming the treatment-lens in the aquifer over a relatively short period of time, and of then refraining from adding further treatment-liquid into a refrain-pore-volume of the aquifer, for a relatively long refrain-period of time, being RP days;

the refrain-period RP is at least three days;

the refrain-pore-volume includes both the lens-pore-volume and the portion of the under-lens-pore-volume that lies contiguously underneath the lens-pore-volume;

the refrain-pore-volume, being VR cubic meters, is greater than twice the lens-pore-volume VL.

5. Procedure of claim 4, wherein the refrain-pore-volume, VR, is greater than five times the lens-pore-volume.

6. Procedure of claim 4, wherein the groundwater is contaminated with a contaminant that includes a phase that is dissolved in the groundwater.

7. Procedure of claim 6, wherein contamination is substantially not present in the groundwater other than in the dissolved phase.

8. Procedure of claim 7, wherein the dense treatment liquid is a solution of permanganate, of more than 0.5 grams per liter concentration.

9. Procedure of claim 4, further including:

providing an injection-structure, which extends down from the ground surface into a contaminated region of the aquifer;

wherein the injection-structure includes a port, through which the treatment-liquid can be injected into the aquifer, a reservoir of the treatment-liquid, and an operable injector for injecting treatment-liquid through the port, into the aquifer, under pressure;

wherein the port is of such limited height, PH meters, as to enable the treatment-liquid, upon being injected, to form a treatment-disc of the said aspect-ratio or higher;

configuring the injection-structure and operating the injector in such a manner as to form a plurality of the treatment-lenses at the same plan-location, at different depths in the aquifer, one lens above the other;

in respect of one of the treatment-lenses, being treatment-lens A, the treatment-lens A, immediately upon being injected, lies separated from the adjacent treatment-lens below, being treatment-lens B, by a vertical-blank-spacing, VBS meters, being the distance in the aquifer between the highest point of lens B and the lowest point of lens A.

10. Procedure of claim 9, wherein the procedure includes:

determining the largest diameter of disc that that aquifer will support;

reading off the volume To be injected for that size of disc, from the table of FIG. 8;

injecting a treatment-volume of a magnitude that lies between the volume indicated in FIG. 8 and twice that volume.

11. Procedure of claim 9, wherein the port height PH is no more than about 60 centimeters, and the procedure includes arranging the discs on a vertical pitch spacing of about 1.5 meters, or greater.

12. Procedure of claim 9, wherein the vertical-blank-spacing VBS between adjacent treatment-lenses, is longer than about 10 centimeters for every 100 liters of the total volume VL of treatment-liquid injected to form the upper treatment-lens.

13. Procedure of claim 9, including setting the injection-structure so as to provide many boreholes, spaced apart laterally, and arranged in a grid pattern of such dimensions that the discs of treatment material, immediately upon injection, in plan-view, approximately just overlap.

14. Procedure of claim 9, including injecting a further treatment volume, after the refrain-period.

15. Procedure of claim 9, including carrying out measurements, and assessing whether the injected treatment-liquid is still able to break down further contaminant, and if not, injecting a further treatment-volume.

16. Procedure of claim 9, wherein the injection-structure is so arranged as to inject two or more discs, at different depths, in the same borehole;

and the procedure includes spacing the upper extremity of the port, when injecting a lower one of the discs, at least twice the height of the port vertically from the lower extremity of the port when injecting the adjacent upper disc.

25. Apparatus of claim 14, wherein the aquifer conditions are such that the groundwater has a lateral translational velocity of no more than 200 cm/day.

17. Apparatus for treating groundwater in an aquifer, being groundwater that contains a contaminant, wherein;

the apparatus includes a porous aquifer, having a water-table, and containing groundwater, and the aquifer is permeable to the through-flow of groundwater, having a hydraulic conductivity of at least 10<sup>−

6</sup> cm/sec;

the apparatus includes a contaminant, which is present in the aquifer in the form of one or more substantially static lenses;

the apparatus includes a treatment material, and the contaminant is of the kind that is capable of being chemically transformed upon exposure thereof to the treatment material;

the treatment material comprises a liquid, which is substantially more dense than the groundwater, whereby the treatment liquid sinks down through the groundwater and down through the aquifer;

the apparatus includes an injection-structure, which extends down from the ground surface into a region of the aquifer containing one or more of the lenses of the contaminant;

the injection-structure includes a port, and the apparatus includes a means for injecting the treatment material, as a liquid, out into the aquifer material, from the port;

the porous material of the aquifer is stratified, to the extent that liquid injected out, under pressure, from the port in the injection-structure readily moves and spreads radially outwards, following the lie of the strata, to a substantially greater degree than the injected liquid moves and spreads vertically;

the porosity and permeability of the porous material of the aquifer is such that a dense liquid present within the porous material tends to percolate downwards gradually through the porous material;

the apparatus includes a means for injecting a treatment volume of the treatment liquid, out through the port;

whereby the treatment volume of the treatment liquid, upon being injected, spreads out laterally into the aquifer, and the treatment liquid then gradually percolates downwards through the aquifer, and into contact with the lens of contaminant.

18. Apparatus of claim 17, wherein:

the contaminant is, or is a component of, a dense, non-aqueous-phase liquid (DNAPL);

the DNAPL is a liquid that is substantially immiscible with the groundwater;

the DNAPL is a liquid that is substantially more dense than the groundwater, and the DNAPL is present in the aquifer in the sense that the DNAPL has sunk down through the groundwater and down through the aquifer, and has collected in the aquifer in discrete blobs or lenses each lens comprising a substantial volume of DNAPL.

19. Apparatus of claim 18, wherein the treatment material is a strong oxidant, and the DNAPL is of the kind that is broken down by a strong oxidant.

20. Apparatus of claim 19, wherein the treatment material is permanganate.

21. Apparatus of claim 20, wherein the permanganate is wholly dissolved in water prior to being injected, and the concentration of the solution is at least 1 gram per liter.

22. Apparatus of claim 17, wherein the injection-structure, containing the port, is so structured and arranged as to be capable of being lowered into and raised out of the ground.

23. Apparatus of claim 22, wherein the injection-structure comprises a drill, and the apparatus includes a means for driving the drill into the ground.

24. Apparatus of claim 17, wherein:

the port is adapted to eject treatment liquid uniformly all around the circumference of the injection-structure;

the port is adapted to eject treatment liquid only over a zone of narrow vertical extent;

the aquifer material is of such stratification that the treatment volume, immediately after being injected from the port, forms a disc;

in that the treatment volume spreads out radially for a meter or more, but occupies a substantially smaller vertical height.

26. Apparatus of claim 17, wherein:

the injection-structure includes a plurality of the said ports, each at a different depth;

the apparatus includes an operable means for injecting treatment liquid from each of the ports;

the means for injecting treatment liquid is effective, when operated, to inject respective predetermined treatment volumes of treatment liquid individually from the ports.

27. Apparatus of claim 17, wherein the injection-structure is so arranged as to inject discs in several boreholes, arranged in a horizontal grid, the boreholes being spaced apart horizontally between 1 and 10 meters.

28. Apparatus of claim 17, wherein the apparatus includes a means for injecting the liquid from the port at a pressure below 150 psi.

29. Apparatus of claim 17, wherein the aquifer material comprises a general matrix of sand, streaked with layers of silt.

30. Apparatus of claim 17, wherein the port has a height over which the treatment liquid is ejected therefrom, of no more than 2 meters.

31. Apparatus of claim 17, wherein the port has a height over which the treatment liquid is ejected therefrom, of no more than 30 cm.

32. Apparatus of claim 17, wherein the port has a height over which the treatment liquid is ejected therefrom, of no more than 10 cm.

33. Apparatus of claim 17, wherein the apparatus includes operable means for injecting the treatment liquid episodically, comprising means for operating the means for injecting the said treatment volume of the liquid at an injection-point in the aquifer, being the point in the aquifer at which the port is located, from the port in a substantially continuous stream, and then for ceasing further injection at that same injection-point for a period of time.

34. Apparatus of claim 33, wherein the period of time is at least three days.

35. Apparatus of claim 33, wherein, in respect of the table set out in FIG. 7b hereof, the number of liters of treatment liquid ejected in one injection episode, in respect of the type of aquifer into which the treatment liquid is being injected, is at least the figure indicated in FIG. 7b for that type of aquifer, but is no more than twice that figure.

36. Apparatus of claim 33, wherein, in respect of the table set out in FIG. 7b hereof, the number of liters of treatment liquid ejected in one injection episode, in respect of the type of aquifer into which the treatment liquid is being injected, is no more than the figure indicated in FIG. 7b for that type of aquifer, but is at least half that figure.

37. Procedure for treating contaminated groundwater in an aquifer, comprising:

providing apparatus as claimed in claim 18,

mapping the location, at least generally, of at least one of the lenses of DNAPL;

positioning the injection-structure generally above the as-mapped location of the lens.