Liquid purification or separation – Processes – Utilizing electrical or wave energy directly applied to...
Reexamination Certificate
2001-03-28
2003-01-07
Hoey, Betsey Morrison (Department: 1724)
Liquid purification or separation
Processes
Utilizing electrical or wave energy directly applied to...
C210S750000, C210S760000, C210S194000, C210S198100, C261S074000, C261S075000
Reexamination Certificate
active
06503403
ABSTRACT:
BACKGROUND
1. Field of Invention
The invention relates to methods and apparatus for increasing the contact efficiency between a fluid and a liquid by a) inducing rotational movement in the liquid, and b) injecting very fine fluid bubbles into the liquid.
The method and apparatus can be applied to many fields, including purification of liquids and treatment of contaminated liquids by dissolving ozone into the liquid. The invention can also be used to treat any type of liquid with any type of fluid.
2. Description of Related Art
Establishing and maintaining efficient gas-liquid contact is essential for efficient mass transfer or absorption of a gas into a liquid. The gas can be diffused for many purposes, including purification and treatment of contaminated liquids with ozone.
The present invention generally relates to the field of water purification and treatment of flowable hazardous waste. Recent developments in water purification and treatment require ozone (O
3
) to be diffused into the liquid as part of the treatment process to destroy contaminants. There have long been various methods and devices for the treatment of biological and chemical contaminants in waste fluids. Large-scale water treatment facilities have been traditionally used for the treatment, removal, and processing of both human and low levels of industrial waste. With increased urbanization, these same water treatment facilities have been required to additionally treat complex mixtures of toxic and hazardous material from both private and industrial users. As a result, many of these same water treatment facilities are now unable to adequately treat the increased waste flow resulting in accidental or deliberate discharge of untreated material directly into the environment.
To combat the increased flow and more complex nature of current waste fluids, many wastewater utilities throughout the country require industrial generators of organic wastes high in biochemical oxygen demand (food waste, fats and oils, etc.,), recalcitrant xenobiotics (synthetic organic compounds foreign natural biological systems), heavy metals (Cd, Hg, Pb, etc.) and/or highly acid or alkaline pH to pre-treat their waste stream on-site prior to delivery to a waste water treatment facility. Although pre-treatment is required of many industries, liquid wastes generated by hospitals, medical facilities, medical examiners offices, healthcare offices, research facilities, nursing homes, food processing and animal handling facilities, diagnostic laboratories, veterinary clinics, analytical, chemical, microbiological, biotechnology and university laboratories in many instances are not required to pre-treat their collective wastewater stream even though this waste material is known to contain a variety of toxicogenic/mutagenic/ teragenic/carcinogenic chemicals and viable, infectious, or genetically altered microbial pathogens. Many of the current pre-treatment units presently in use are expensive to operate, require trained personnel to maintain and require the use of caustic and/or toxic chemicals or expendable filters and cartridges which must be disposed of as a hazardous substance.
Ozone has been used for more than sixty years for water treatment on the European continent. The role of ozone in waste fluid treatment may be classified as both an oxidant and a germicidal compound. There are at least four distinct recognized applications of ozone: (1) as a bactericide; (2) as a viricide; (3) as a powerful chemical oxidant; and (4) as a promoter of hydroxyl radicals when combined with ultraviolet radiation. The potent germicidal properties of ozone have been attributed to its high oxidation potential. Research indicates that disinfection by ozone is a direct result of bacterial cell wall disintegration. This is known as the “lysis phenomenon”.
Ozone has several attributes in the treatment of waste fluids such as odor control, color removal, and iron and manganese removal. Ozone oxidizes inorganic substances completely and rapidly, e.g., sulfides to sulfates, and nitrites to nitrates. Of even greater importance is ozone's capability of breaking down complex organic chemicals. Oxidation of organic materials is more selective and incomplete at the concentrations and pH values of aqueous ozonation. Unsaturated and aromatic compounds are oxidized and split at the classical double bonds, producing carboxylic acids and ketones as products. Ozone also exerts a powerful and bleaching action on organic chemicals, which contribute to the color removal in waste fluids.
Many of the treatment systems employing ozone are limited in their commercial application due to their relatively small scale and ability to deliver an adequate concentration of ozone sufficient for bacterial inactivation and chemical destruction. Typically these combined treatment systems have only been utilized for “in-home” domestic potable water treatment to remove taste and odor problems resulting from chlorination. As a result there has been considerable interest in improving ozone treatment systems and techniques to allow for the treatment of more complex waste fluids at higher flow rates, maximum efficiency and at minimal cost.
When treating a liquid, such as drinking water or contaminated water, by diffusing a gas, such as ozone, it has been recognized that the greater the area of interface between the water and the gas, the greater the amount of gas that will be dissolved into the liquid. Therefore, the goal is to put as many very fine gas bubbles into the liquid as is feasible. It has also been recognized that the amount of gas diffused into the liquid is in direct proportion that the time the bubble liquid interface is maintained. Therefore, an additional goal is then to keep the gas bubbles in the liquid being treated as long as possible before the bubbles reach the top of the reactor vessel (gas holdup). It has also been recognized that the dissolution occurs more efficiently if the bubbles move through the liquid rather than remaining relatively stationary in the liquid. This maintains the greatest concentration gradient at the gas-liquid interface. Therefore, an additional goal is then to have the gas bubbles move through the liquid over time.
Existing methods for establishing and maintaining the gas-liquid contact include a simple porous plate, punctured membranes, fans and turbines, to complicated motive jets mounted in reaction vessels to mix the gas and liquid. U.S. Pat. No. 5,720,905—Ho discloses a porous plate with openings between 0.2-2 mm to produce bubbles in liquid in a reaction vessel. Ho does not establish any means to reduce the size of the bubbles or increase the gas-liquid contact time. In Ho, the bubbles simply float directly to the surface of the liquid in the reaction vessel. U.S. Pat. No. 4,581,137—Edwards, uses a flexible membrane with plurality of minute punctures to discharge the gas in fine bubbles. U.S. Pat No.s 5,399,261—Martin, and U.S. Pat. No. 4,072,613—Alig, both disclose a mechanical stirrer blade mounted in the reaction vessel to breakup the gas bubbles to speed the dissolution of ozone into the liquid. U.S. Pat. No. 5,314,076—La Place, discloses turbines mounted in the reaction vessel to mix the gas bubbles in the liquid. The mechanical devices all require the expense of manufacturing the fans or turbines, increase the complexity of the system, and increase maintenance requirements by immersing mechanical devices in the liquid be treated.
U.S. Pat. No.s 6,139,755—Marte, and 4,162,970—Zlokarnik, both use complex nozzles to mix the gas and liquid. Marte discloses at least one jet nozzle to mix the gas and liquid, and produce an unstationary flow and cavitational flow to dissolve the gas. Zlokamik uses a single nozzle to disburse the gas into very fine bubbles, but no rotational flow is induced in the reaction vessel to increase the gas-liquid contact time and to move the gas bubbles through the liquid.
For the foregoing reasons, there is a need for a simple, efficient, non-mechanical apparatus, inexpensive to make and maintain, to enhance and
Green Lawrence M.
Nickelsen Michael G.
Garrison David L.
Garrison & Assoc. PS
Hoey Betsey Morrison
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