Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment
Reexamination Certificate
2000-06-19
2001-04-10
Phasge, Arun S. (Department: 1341)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
C205S688000, C205S742000, C205S754000, C205S766000, C204S515000, C204S648000, C204S666000, C588S253000
Reexamination Certificate
active
06214202
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to treatment of contaminated groundwater, particularly to in situ treatment of contaminated groundwater, and more particularly to a method and apparatus for in situ treatment of contaminated groundwater by catalytic reductive dehalogenation facilitated by water electrolysis with an electrode pair or array.
Contamination of groundwater resources by halogenated organic compounds poses a significant environmental problem, of requiring some form of groundwater treatment to protect public health. These common groundwater contaminants include trichloroethylene (TCE) and tetrachloroethylene (PCE). However, many conventional treatment technologies merely transfer the contaminant from one medium (water) to another medium (e.g., activated carbon), thus producing a secondary waste stream. Moreover, surface treatment systems can be cumbersome in that they often require a large surface footprint to house equipment. Recently, see U.S. Pat. No. 5,332,496 issued Jul. 26, 1994 to F. Rasouli, et al., a treatment technology has been developed involving catalytic reductive dehalogenation by hydrogen with a palladium catalyst in a system located above the ground surface.
The present invention addresses these issues, by providing a compact in situ groundwater treatment system based on chemical reduction by electrolytically-derived hydrogen for deployment within a pair or an array of well bores housing electrodes that conduct a DC current. In addition, contaminated water in fine-grained sediments between the electrodes will be drawn to the cathode well by electro-osmosis. All of the essential physical components of the treatment system are located within the well-bore (e.g., the hydrogen source and the catalyst bed), requiring only pipelines or hoses and a DC power supply to be present at the surface, thus having a minimal surface footprint and also not generating secondary waste streams.
SUMMARY OF THE INVENTION
It is an object of the present invention to provide in situ treatment for contaminated groundwater.
A further object of the invention is to provide in situ treatment for contaminated groundwater while producing only a minimal surface footprint and no secondary waste streams.
A further object of the invention is to provide a method and apparatus for in situ treatment of contaminated groundwater by catalytic reductive dehalogenation facilitated by water electrolysis with an electrode pair or array.
Another object of the invention is to provide a system for in situ treatment of contaminated groundwater wherein all of the essential physical components of the treatment system are located with the well-bores, except for electrode well to electrode well transfer pipes and a DC power supply, located above ground surface.
Another object of the invention is to provide a method and apparatus for in situ treatment of contaminated groundwater using a pair or an array of electrodes located in well-bores and a DC current is placed across each pair of electrodes, or form an electrode to one or more cathode electrodes, so that hydrogen is generated at the cathodes and oxygen at the anodes, and the well-bores each contain a treatment unit including a packet catalyst bed.
Other objects and advantages of the present invention will become apparent from the following description and accompanying drawings. The invention involves in situ treatment of contaminated groundwater by catalytic reductive dehalogenation facilitated by water electrolysis with an electrode pair or array. The apparatus for carrying out the method of this invention is primarily located within well-bores, leaving only a minimal surface footprint, and the in situ treatment method results in the production or generation of environmentally benign species such as ethane, methane, or ethene and free chloride, thereby generating no secondary waste streams. The apparatus, in addition to the well-bores, the electrodes and the packed catalyst beds located in the well-bores, includes a pump in the cathode well-bore or well bores, a water transfer pipe between cathode-to-anode well-bores, a DC power supply, an acid injection line for each cathode well-bore, and an oxygen (O
2
) vent line for each anode well-bore. The acid injection line provides a small stream of acid which is used to titrate the solution in the cathode well-bore to thus suppress the formation of mineral deposits. The catalyst material in the packed beds may, for example, consist of 1% palladium (by weight) coated onto alumina or carbon support material in granular form. The system polarity may be periodically switched to assist in regeneration of the catalyst and for controlling the formation of mineral deposits at the cathode well-bore. Also, electro-osomotic transport of contaminants toward the cathode also contributes to contaminant mass removal. Thus, the present invention provides a compact treatment system with a minimal surface footprint and the in situ destruction of halogenated organic contaminants without generating secondary waste streams.
REFERENCES:
patent: 5332496 (1994-07-01), Rasouli et al.
patent: 5398756 (1995-03-01), Brodsky et al.
patent: 5403450 (1995-04-01), Mellor et al.
patent: 5458747 (1995-10-01), Marks et al.
patent: 5476992 (1995-12-01), Ho et al.
patent: 6004451 (1999-12-01), Rock et al.
McNab, Jr. Walt W.
Pico Tristan M.
Ruiz Roberto
Carnahan L. E.
Phasge Arun S,.
The Regents of the University of California
Thompson Alan H.
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