Liquid purification or separation – Processes – Treatment by living organism
Patent
1985-07-09
1987-07-28
Wyse, Tom
Liquid purification or separation
Processes
Treatment by living organism
210610, 210747, 210903, C02F 172
Patent
active
046830642
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a process for decreasing the content of nitrate in ground water, artificial ground water, that is infiltrated surface water, or surface water.
In certain areas, especially intensively cultivated areas, ground water and surface water may contain nitrate contents so high that it will be necessary to reduce said contents to levels below the existing limit value for nitrate in drinking water.
SE-A-7502197-2 describes a process for removing noxious nitrogen compounds, e.g. nitrates, from water, especially ground water. In said process water containing denitrification microorganisms is introduced continuously or intermittently into an aquifer around a ground water well. The present invention is an improvement of said known process wherein a clearly defined denitrification zone is formed at a desired distance from an extraction well, thereby permitting an optimal nitrate reduction in the water to be purified.
Thus, the present invention relates to a process for decreasing the content of nitrate in ground water, artificial ground water, that is infiltrated surface water, or surface water flowing through an aquifer or through a basin or a filter containing naturally occurring filter material, in which process water containing denitrification organisms and/or substrate therefore is introduced intermittently through a number of injection wells or injection pipes arranged around one or more extraction wells or extraction pipes for purified water. This process is characterized in that, during each introduction of water containing denitrification organisms and/or substrate therefore, said water is fed to only some of the injection wells or injection pipes, and that simultaneously water is drawn from nearby, adjacent or intervening injection wells or injection pipes for the purpose of creating a denitrification zone at a distance sufficiently far from the extraction well or extraction pipe.
The water fed to some of the injection wells may consist of a portion of the water drawn from the extraction well and/or water drawn from other, nearby injection wells.
If water containing denitrification organisms and/or substrate therefore is introduced into injection wells and simultaneously water is pumped from the extraction well but no water is pumped from one or more of the injection wells, the water added will flow in narrow zones from the respective injection wells directly towards the extraction well. This means that the injection water will not cover the whole area between the injection wells, and impure water will flow between said narrow zones directly towards the extraction well. In such a case the purification process will not work satisfactorily, resulting in a deteriorated water quality.
On the other hand, if in accordance with the invention water is introduced into some injection wells and simultaneously water is drawn from adjacent or intervening injection wells the water thus introduced will flow in the aquifer in a manner such that the areas between the injection wells are covered completely, with a concomitant formation of a clearly defined denitrification zone at a distance sufficiently far from the extraction well. All water drawn from the extraction well will thus pass through said zone, whereby the best possible nitrate reduction is attained.
The preferred embodiment of the invention, viz. decreasing the nitrate content in situ in an aquifer, will be described in greater detail below.
Nitrate ions may be eliminated from ground water by activating denitrification organisms normally existing in the aquifer. If necessary, denitrification organisms have to be added at an early stage. The microorganisms utilized require a supply of organic carbon to bring about a denitrification. Examples of useful substrates are sucrose, methanol, ethanol, an acetate or molasses. The substrate is dissolved in or mixed with the water introduced through the injection wells.
If a sufficiently large strain of denitrification organisms is available all the organic carbon injected will be utilized for d
REFERENCES:
patent: 4576717 (1986-03-01), Collin et al.
Hallberg Rolf O.
Martinell Rudolf H.
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