System for alleviating DNAPL contamination in groundwater

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 10−6 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.

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 10−6 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.