Liquid purification or separation – Processes – Including geographic feature
Reexamination Certificate
1999-09-22
2001-07-03
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Including geographic feature
C210S758000, C405S128350
Reexamination Certificate
active
06254786
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to the removal of iron and manganese from groundwater. More particularly, this invention relates to the removal of iron and manganese released from the treatment media of a primary in-situ groundwater treatment system.
2. Description of Related Art
Groundwater in many localities has become contaminated by both natural and manmade impurities. Due to the considerable reliance on groundwater as a primary source of potable water, treatment of polluted groundwater to remove such contaminants has gained significant interest within the last decade. Many treatment systems for the removal of groundwater contaminants have been proposed, including pump-and-treat systems, well injection of treatment agents, and in-situ treatment. Due to the significant cost savings, in-situ treatment of groundwater has drawn considerable interest in recent years. In-situ treatment of groundwater is discussed in
NEW APPROACH TO IN
-
SITU TREATMENT OF CONTAMINATED GROUNDWATERS;
McMurty et at.,
Environmental Progress
1985.
McMurtry discusses the use of permeable barrier walls placed in trenches excavated into native aquifers to treat contaminated groundwater. The permeable barrier contains appropriate treatment media, such that the quality of the contaminated groundwater flowing through the media is significantly improved. McMurtry states that most in-situ groundwater treatments will be in isothermal, anaerobic, reducing environments. Many in-situ groundwater treatment systems take advantage of this anaerobic, reducing environment, in conjunction with the selected treatment material to remove or transform the chemical contaminants in the groundwater into nonhazardous material. Typically treatment materials are limestone, activated carbon, active metals, or biological agents. These in-situ treatment systems, while removing or neutralizing many dangerous contaminants, may add other manmade contaminants to the groundwater. For example, a common treatment material for in-situ treatment is elemental or zero valent iron. While removing many contaminants, elemental iron adds iron and other metallic impurities (e.g., manganese) to the groundwater. Removal or neutralization of these manmade impurities from groundwater is essential in returning groundwater in a native aquifer to a useable state.
BRIEF SUMMARY OF THE INVENTION
An object of this invention is to provide a method to remove iron and manganese impurities present in groundwater due to a primary in-situ groundwater treatment material.
This and other objectives of the invention, which will become apparent from the following description, have been achieved by a novel improvement to in-situ groundwater treatment systems to remove secondary sources of groundwater contamination released by the treatment media from primary in-situ treatment systems into native aquifers. The primary in-situ treatment system, for use with the treatment system of this invention, relies on the flow of groundwater, through an aquifer, into the primary treatment system to decontaminate the groundwater through the use of a metallic treatment material. The primary treatment system may add metallic-based contaminants while decontaminating the groundwater. The improvement of this invention is to oxygenate the oxygen-deficient groundwater after in-situ treatment by the metallic treatment material in order to remove the metallic-based contaminants added to groundwater by the primary in-situ treatment system. The treatment system of this invention is particularly useful when the groundwater is maintained in an anaerobic condition, and the primary treatment system and media is maintained under anaerobic conditions.
The primary in-situ groundwater treatment process includes determining the conditions of the groundwater in the aquifer and the contaminate; selecting and placing the primary metallic-based treatment material into the aquifer; directing the flow of the anaerobic groundwater through the primary treatment material to neutralize the contaminant while maintaining the groundwater under an anaerobic environment and permitting the treated groundwater to reenter the aquifer. During the course of treatment, a portion of the metallic-based primary treatment agent becomes soluble in the groundwater. The process of the invention relates to the oxygenation of the anaerobic groundwater by permitting it to pass through a second treatment material that provides a source of oxygen, thereby converting the solublized metal-based treatment media into insoluble metallic oxides. Preferably, the process of this invention oxygenates the oxygen deficient groundwater contaminated by metallic-based impurities from the primary treatment source by passing the contaminated groundwater through porous treatment media through which a flow of oxygenated gas is directed.
More specifically, the primary in-situ groundwater treatment process comprises, determining the direction, volume and velocity of a region of contaminated material dissolved within a stream of groundwater flowing through an aquifer. A metallic-based primary treatment material is provided. A primary repository is formed within the aquifer for containing a primary treatment material. The primary treatment material is placed in the primary repository such that the primary treatment material lies in the path of the region of contaminated material. The primary repository is oriented such that the region of contaminated material enters the primary repository through the upstream side thereof. The placement of the repository being such that the flow of the groundwater in the aquifer in which the primary repository is located causes the region of contaminated material to pass from the aquifer into the primary repository, pass through the treatment media within the primary repository, and exit from the downstream side of the primary repository. The permeability of the primary treatment material being such that the resistance to the passage of groundwater through the primary repository is substantially no greater that the resistance of the native aquifer to the passage of groundwater through the aquifer. The primary treatment material causes the dissolved contaminated material to be rendered inactive in the groundwater. During the course of the primary treatment, a portion of the primary treatment media dissolves in the stream of groundwater flowing through the primary repository, exits in the groundwater flowing therethrough, and enters into the native aquifer.
The improvement, as outlined hereinabove comprises: forming a secondary repository within the aquifer downstream of the first repository for containing a porous media. A source of oxygenating gas is placed adjacent to the base of the repository. Porous media is installed above the source of oxygenating gas such that the porous media lies in the path of the flow of dissolved primary treatment material. The orientation of the secondary repository is such that the flow of dissolved metallic-based contaminants from the primary treatment material enters the second repository through the upstream side thereof. The placement of the secondary repository being such that the flow of the groundwater in the aquifer in which the second repository is located causes the flow of dissolved primary treatment material to pass from the aquifer into the second repository, pass through the second repository from side to side thereof, and exit from the downstream side of the second repository. The permeability of porous media is such that the resistance to the passage of groundwater through the second repository is substantially no greater that the resistance of the native aquifer to the passage of groundwater through the aquifer. The oxygenating gas is directed up though porous medium such that the flow of groundwater containing the dissolved contaminants, based on the primary treatment material, in the groundwater is oxygenated thereby making the dissolved primary treatment material insoluble.
The process is of particular utility when the prima
Carpenter Clay E.
Morrison Stanley J.
Anderson Thomas G.
Gottlieb Paul A.
Hoey Betsey Morrison
LaMarre Mark F.
Simmons David A.
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