Electrolysis: processes – compositions used therein – and methods – Electrolytic material treatment – Organic
Reexamination Certificate
1998-12-07
2001-11-13
Phasge, Arun S. (Department: 1741)
Electrolysis: processes, compositions used therein, and methods
Electrolytic material treatment
Organic
C205S742000, C205S746000, C205S758000, C204S228300, C204S228600, C204S229200, C204S229400, C204S230200, C204S255000, C204S256000, C204S263000, C204S266000, C204S270000, C204S272000, C204S275100
Reexamination Certificate
active
06315886
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to the purification of aqueous solutions, and more specifically, to electrochemical methods and more efficient and safer electrolytic apparatus for the destruction of pollutants in drinking water, industrial waste waters and contaminated ground water.
BACKGROUND OF THE INVENTION
Wastewater can be a valuable resource in cities and towns where population is growing and water supplies are limited. In addition to easing the strain on limited fresh water supplies, the reuse of wastewater can improve the quality of streams and lakes by reducing the effluent discharges they receive. Wastewater may be reclaimed and reused for crop and landscape irrigation, groundwater recharge, or recreational purposes.
The provision of water suitable for drinking is another essential of life. The quality of naturally available water varies from location-to-location, and frequently it is necessary to remove microorganisms, such as bacteria, fungi, spores and other organisms like crypto sporidium; salts, heavy metal ions, organics and combinations of such contaminants.
Over the past several years, numerous primary, secondary and tertiary processes have been employed for the decontamination of industrial wastewater, the purification of ground water and treatment of municipal water supplies rendering them safer for drinking. They include principally combinations of mechanical and biological processes, like comminution, sedimentation, sludge digestion, activated sludge filtration, biological oxidation, nitrification, and so on. Physical and chemical processes have also been widely used, such as flocculation and coagulation with chemical additives, precipitation, filtration, treatment with chlorine, ozone, Fenton's reagent, reverse osmosis, UV sterilization, to name but a few.
Numerous electrochemical technologies have also been proposed for the decontamination of industrial wastewater and ground water, including treatment of municipal water supplies for consumption. While growing in popularity, the role of electrochemistry in water and effluent treatment heretofore has been relatively small compared to some of the mechanical, biological and chemical processes previously mentioned. In some instances, alternative technologies were found to be more economic in terms of initial capital costs, and in the consumption of energy. Too often, earlier electrochemical methods were not cost competitive, both in initial capital costs and operating costs with more traditional methods like chlorination, ozonation, coagulation, and the like.
Earlier electrochemical processes required the introduction of supporting electrolytes as conductivity modifiers which adds to operating costs, and can create further problems with the disposal of by-products. Electrochemical processes in some instances have been ineffective in treating solutions by reducing concentrations of contaminants to levels permitted under government regulations. Heretofore, such electrochemical processes have often lacked sufficient reliability for consistently achieving substantially complete mineralization of organic contaminants, as well as the ability to remove sufficient color from industrial waste waters in compliance with government regulations.
Notwithstanding the foregoing shortcomings associated with earlier electrochemical technologies, electrochemistry is still viewed quite favorably as a primary technology in the decontamination of aqueous solutions. Accordingly, there is a need for more efficient and safer electrochemical cell configurations and processes for more economic treatment of large volumes of industrial waste waters, effluent streams and contaminated ground water, including the decontamination of municipal water supplies making them suitable for drinking.
SUMMARY OF THE INVENTION
The present invention relates to improved means for electropurification of aqueous solutions, particularly effluent streams comprising waste waters polluted with a broad spectrum of chemical and biological contaminants, including members from such representative groups as organic and certain inorganic chemical compounds. Representative susceptible inorganic pollutants include ammonia, hydrazine, sulfides, sulfites, nitrites, nitrates, phosphites, and so on. Included as organic contaminants are organometallic compounds; dyes from textile mills; carbohydrates, fats and proteinaceous substances from food processing plants; effluent streams, such as black liquor from pulp and paper mills containing lignins and other color bodies; general types of water pollutants, including pathogenic microorganisms, i.e., bacteria, fungi, molds, spores, cysts, protozoa and other infectious agents like viruses; oxygendemanding wastes, and so on.
While it is impractical to specifically identify by name all possible contaminants which may be treated successfully according to the claimed methods, it will be understood that language appearing in the claims, namely “contaminated aqueous electrolyte solution”, or variations thereof is intended to encompass all susceptible pollutants whether organic, inorganic or biological.
The electropurification methods and apparatus for practicing this invention are particularly noteworthy in their ability to effectively purify virtually any aqueous solution comprising one or more organic, certain inorganic and biological contaminants present in concentrations ranging from as low as <1 ppm to as high as >300,000 ppm.
Only electricity is required to achieve the desired chemical change in the composition of the contaminant(s), in most cases. The conductivity of tap water is sufficient for operation of the improved cell design. Hence, it is neither required, nor necessarily desirable to incorporate additives into the contaminated aqueous solutions to modify the conductivity of the solution being treated to achieve the desired decomposition of the pollutant/contaminant. Advantageously, in most instances solid by-products are not produced in the electropurification reactions as to create costly disposal problems. The improved electrochemical processes of the invention are able to achieve complete or virtually complete color removal; complete mineralization of organic contaminants and total destruction of biological pollutants even in the presence of mixed contaminants, and at a cost which is competitive with traditional non-electrochemical methods, such as chlorination, ozonation and coagulation, and thereby meet or exceed government regulations.
Accordingly, it is a principal object of the invention to provide an electrolysis cell which comprises at least one anode and at least one cathode as electrodes positioned in an electrolyzer zone. The electrodes are preferably spaced sufficiently close as to provide an interelectrode gap capable of minimizing cell voltage and IR loss. Means are provided for directly feeding the contaminated aqueous electrolyte solution to the electrodes for distribution through the interelectrode gap(s). Means are provided for regulating the residency time of the aqueous electrolyte solution in the electrolyzer zone for modification of contaminants ether electrochemically by direct means and/or by chemical modification of contaminants to less hazardous substances during residency in the cell. Additional means are provided for collecting decontaminated aqueous electrolyte solution descending from the electrolyzer zone. It is also significant, the electrolysis cell according to the invention has an “configuration”.
In addition to the electrochemical cell of this invention, further means are provided for practical and efficient operation, directly feeding contaminated aqueous electrolyte solution to the cell by pump means or by gravity; pretreatment means for the contaminated aqueous electrolyte solutions, for example, means for aeration, pH adjustment, heating, filtering of larger particulates; as well as means for post-treatment, for example, pH adjustment and cooling, or chlorination to provide residual kill for drinking water applications. In addition, th
Weinberg Norman L.
Zappi Guillermo Daniel
Ellis Howard M.
Phasge Arun S,.
The Electrosynthesis Company, Inc.
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