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<br />5,605,634
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<br />the diffusion tube being substantially imperforate, and
<br />being thereby closed to the escape of fluid out of the
<br />diffusion tube, other than by molecular diffusion
<br />through the material of the tube, between the entry end
<br />and the exit end thereof,
<br />providing a circulation means comprising a means for
<br />pressurising the fluid substance, and for conducting the
<br />fluid substance to the entry end of the diffusion tube,
<br />conducting the fluid substance through the diffusion
<br />tube from end to and thereof, and for collecting the
<br />fluid substance emerging from the exit end of the
<br />diffusion tube, and for circulating the fluid substance
<br />and returning same to the entry end,
<br />and circulating the fluid substance through the diffusion
<br />tube
<br />2 Procedure of claim 1, wherein the procedure includes
<br />the step of circulating the fluid substance for a short time
<br />periodically, and keeping the fluid to the diffusion tube
<br />substantially still when not being circulated
<br />3 Apparatus for placing small concentrations of a sub-
<br />stance into groundwater moving through a borehole in an
<br />aquifer, wherein
<br />the borehole is of the kind into which groundwater can
<br />enter from the aquifer, can pass through the borehole
<br />laterally and then re-enter the aquifer,
<br />the apparatus includes a diffusion tube, located in the
<br />borehole, and extending down from the ground surface
<br />into the depth of the borehole,
<br />the apparatus includes a source of the substance in fluid
<br />form,
<br />the diffusion tube is made of material of the kind which
<br />enables the slow molecular diffusion of the said fluid
<br />substance therethrough,
<br />the diffusion tube has an entry end and an exit end and
<br />forms a means for passing the fluid substance through
<br />the diffusion tube, from the entry end to the exit end
<br />thereof,
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<br />the diffusion tube is substantially imperforate, and is
<br />thereby closed to the escape of fluid out of the diffusion
<br />tube, other than by molecular diffusion through the
<br />material of the tube, between the entry end and the exit
<br />5 end thereof,
<br />the apparatus includes a circulation means, comprising a
<br />pump means and a conduit means,
<br />the pump means is operable, and is effective, when
<br />operated, to move the fluid substance,
<br />to the conduit means is a means for conducting the fluid
<br />substance to the entry end of the diffusion tube, for
<br />conducting the fluid substance through the diffusion
<br />tube from entry end to exit end thereof, and for col-
<br />lecting the fluid substance emerging from the exit end
<br />15 " of the diffusion tube, and for circulating the fluid
<br />substance and returning same to the entry end
<br />4 Apparatus of claim 3, wherein the diffusion tube is
<br />made of a plastic polymer material, of the kind which is at
<br />zo least partly amorphous
<br />5 Apparatus of claim 4, wherein the diffusion tube is
<br />made from low density polyethylene (LDPE) tubing
<br />6 Apparatus of claim 5, wherein the wall thickness of the
<br />LDPE tubing is at least 0 3 mm.
<br />7 Apparatus of claim 5, wherein the tubing is in the
<br />2' diameter range 5 mm to 5 cm overall
<br />S Apparatus of claim 3, wherein the diffusion tube
<br />comprises a length of dialysis tubing
<br />9 Apparatus of claim 3, wherein the fluid substance
<br />comprises a treatment substance tamed by a tamer liquid
<br />30 10 Apparatus of claim 9, wherein the treatment substance
<br />is dissolved at a dilute, non saturated concentration in the
<br />carver liquid
<br />11 Apparatus of claim 3, wherein the apparatus includes
<br />a means for pressurizing the fluid in the diffusion tube,
<br />35 whereby the fluid is at a higher pressure inside the tube than
<br />the pressure of the groundwater outside the tube
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