Method and apparatus for in situ groundwater remediation

DETAILED DESCRIPTION OF THE INVENTION Turning now to the drawings, wherein like components are designated by like reference numerals throughout the various figures, FIGS.
1 and 2 show a well 10.
The well or well borehole extends from ground level 14, through vadose zone 16, and into a saturated zone 20 below water table 18 containing the groundwater.
The lower extremity of saturated zone 20 may be defined by an impervious zone or aquitard 22.
Recirculating unit or system 24 (See also FIG.
2) may include an inner casing 26 extending into the well near the bottom thereof.
The casing has two permeable sections 28 and 29.
Sections 28 and 29 may be screened sections that permit groundwater water to enter and leave casing 26.
Well 10 may be sealed by means of a seal 30 in the top 11 thereof to prevent the escape of contaminated gases from the well.
Casing 26 may be surrounded by an outer protective casing 32 which extends the length of the well borehole.
Casing 32 may have slots 33 at least along the portion thereof located in saturated zone 20.
As such, screened sections 28 and 29 may be in fluid communication with the groundwater in saturated zone 20.
Casing 26 may be held in position in outer casing 32 by packers 41.
As shown in FIG.
2, recirculating unit 24 may include a pump 25 located within casing 26 between screened sections 28 and 29.
As will be discussed below, casing 26 may be configured to provide a venturi-shaped aerator, designated generally by reference numeral 27 in FIG.
2.
Pump 25 may be positioned above the aerator.
Pump 25 is preferably a variable flow pump.
Pump 25, for example, may be capable of pumping water at a rate of about twenty-four gallons per minute (GPM) against a pressure head of twenty-five feet of water.
Permeable section 28 is preferably located near bottom 13 of well 10 and permeable section 29 is located a distance above section 28.
Screened section 28 is located above aquitard 22.
For example, for a well having a diameter of about one foot, and in conditions where water table 18 is located at about thirty feet below ground surface 14 and aquitard 22 is located at about 45 feet below the water table, sections 28 and 29 may each have a length of about three feet