Liquid purification or separation – Processes – Making an insoluble substance or accreting suspended...
Patent
1993-03-03
1994-11-08
Hruskoci, Peter A.
Liquid purification or separation
Processes
Making an insoluble substance or accreting suspended...
166268, 210719, 210721, 210722, 210747, 210757, 210758, 210170, 210199, 210220, 261 93, C02F 152
Patent
active
053624009
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to water purification, and more particularly to a process for creating, in an aquifer, an oxidation and precipitation zone for in situ precipitation of substances in the ground water the content of which it is desired to decrease, or a reduction zone for the reduction of substances not desired in the ground water.
BACKGROUND OF THE INVENTION
The Swedish patent specification 8206393-4 (corresponds to European patent specification 0160774) describes a process for decreasing the contents of iron and manganese in ground water flowing through an aquifer, wherein a "curtain-type" zone for the oxidation and precipitation of iron and manganese is created by intermittently introducing water containing oxygen or oxygen-releasing substances through a number of injection wells arranged around one or more extraction wells for purified water. During each introduction of water containing oxygen or oxygen-releasing substances the water is fed to only some of the injection wells and simultaneously water is drawn from nearby, adjacent or intervening injection wells. The oxygen-containing water thus introduced creates a suitable environment for certain bacteria so that these, in combination with purely chemical processes, will bring about precipitation of the iron and manganese in the existing ground layers which will thus serve as a filter. The oxygen-containing water is added intermittently, for example, for a period of about 24 hours.
The Swedish patent specification 8400190-8 (corresponds to European patent specification 0154105) describes a process for decreasing the content of nitrate in ground water by reducing the nitrate to nitrogen in a reduction zone (denitrification zone) created between a number of injection wells arranged around one or more extraction wells for purified water. The reduction zone is formed in the same manner as the above described oxidation zone but water containing denitrification organisms and/or substrate therefore is fed to the injection wells instead of water containing oxygen or oxygen-releasing substances. Normally only substrate (oxygen-consuming substance) is added, such as sucrose, methanol, ethanol, an acetate or molasses.
For the creation of such oxidation and reduction zones an extensive pipe system is required, for example, for oxygenating water in an oxygenator station and pumping water to and from the injection wells. Moreover, the wells need to have a rather large diameter, of about 125 mm for accommodating an submersible pump.
SUMMARY OF THE INVENTION
According to the present invention such oxidation and reduction zones are created in a different and simpler manner. Thus, according to one embodiment the invention relates to a process for creating, in an aquifer, an oxidation and precipitation zone between a number of injection wells arranged around one or more extraction wells for purified water, which zone is intended for in situ precipitation of substances not desired in the ground water. This process is characterized in that the zone desired is created intermittently between each pair of adjacent injection wells by (i) introducing oxygen, oxygen-containing gas or an oxygen-releasing substance into the water in both wells and (ii) pumping the water in one well from below upwards while pumping the water in the other well from above downwards, whereby a circulation circuit is formed in the aquifer between the two wells.
Thus, in the well wherein the water is pumped from below upwards water will flow in through the lower part of an apertured well tube (or through one or more lower portions of apertured well tubes) and flow out through the upper part of the apertured well tube (or through one or more upper portions of an apertured well tube). The opposite is true for the well wherein the water is pumped from above downwards. It may sometimes be appropriate to reverse the pumping direction in the two wells after a certain time. Such oxygenation and circulation flow may be effected simultaneously between two or more pairs
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patent: 4478765 (1984-10-01), Tubbs
patent: 4638064 (1987-07-01), Hallberg et al.
patent: 4755304 (1988-07-01), Hallberg et al.
patent: 4879046 (1989-11-01), Kojima
patent: 5006250 (1991-04-01), Roberts et al.
Hruskoci Peter A.
Paref AB
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