Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-05-04
2002-03-26
Barry, Chester T. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S760000, C210S763000, C210S765000
Reexamination Certificate
active
06361697
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to waste water decontamination. For example, one embodiment of the invention relates to a reactor system for and method of maintaining a substantially two-phase (liquid/solid) operating environment within an ozone supersaturated decontamination reactor, thereby maximizing the contact of contaminants with ozone and oxygen particles, while minimizing loss of catalytic material due to turbulence associated with expansion of free ozone and/or oxygen. The invention, however, is not limited to this specific embodiment.
2. Background Art
Ozone-based decontamination of water is known. For instance, U.S. Pat. No. 4,696,739 (hereinafter “the '739 patent”) discloses a water purification apparatus having multiple countercurrent ozone extraction columns. The apparatus, however, involves a three-way (gas/liquid/solid) reaction vessel. See Col. 2, lines 56-64. The apparatus is designed to bubble the ozone through the liquid. Col. 1, line 51.
The device disclosed in U.S. Pat. No. 3,336,099 (hereinafter “the '099 patent”) is an apparatus for sanitizing liquids. The '099 patent apparatus includes baffles, to enhance the gas/liquid contact. However, the '099 patent apparatus, like the '739 patent apparatus, permits the ozone/air to bubble in the reactor.
U.S. Pat. No. 5,114,576 discloses a first ozonation of waste water followed by a catalytic decomposition of the remaining ozone before discharge of the cleansed fluid. U.S. Pat. No. 5,116,574 (hereinafter “the '574 patent”) discloses multiple extraction systems with recycled exhaust gas to increase overall ozone usage efficiency. The '574 patent also discloses the use of discrete modules to effect a fixed percent improvement for each module.
U.S. Pat. No. 4,007,118 (hereinafter “the '118 patent”) discloses an apparatus for ozone oxidation of waste water using catalytic media reactors where the granules are contained in a filter bag. The '118 patent also discloses the use of an upflow, dispersed catalyst bed where the granules are dispersed with ozone-containing gas, while the fines are collected downstream of the dispersed bed and recycled back to the bed. The '118 patent further discloses operating the catalytic reactors at pressures above atmospheric.
U.S. Pat. No. 5,173,257 discloses the simultaneous use of gaseous ozone and dissolved ozone to sanitize solid particles and react with dissolved contaminants. U.S. Pat. No. 5,190,659 discloses the use of a complex filter/valve apparatus to automate the necessary steps of cleaning, backwashing and reusing an ozone-reactive filter. U.S. Pat. No. 4,898,679 (hereinafter “the '679 patent”) discloses the use of near freezing temperatures to increase the concentration of ozone in water. In the '679 patent, the supercharged water is then heated at the point of use and used to disinfect or decontaminate sludge, other contaminated fluids or equipment.
In prior systems, the task of ozonating water and catalytically decomposing the ozone to continue the decontamination has been complicated by the demands of handling a 3-phase system (gas/liquid/solid). Therefore, there exists a need for an apparatus and method capable of performing decontamination substantially in two phases while maximizing ozone concentration.
Investigators Hoigne and Bader originally elucidated a complex, core free-radical mechanism and their work was added to by Peyton and Zappi. Their mechanism dictates that ozone and hydrogen peroxide form hydroxyl free radicals which in turn oxidize the refractory organics or halogenated organics. The hydroxyl radical is formed from a number of sources: (1) from added hydrogen peroxide that is irradiated with UV light and forms radicals directly; (2) from added peroxide that dissociates in water, where the anionic species then becomes a radical; (3) from dissolved ozone that is irradiated with UTV light to become a radical directly; (4) from dissolved ozone that is irradiated with UV light and, with water, becomes hydrogen peroxide and, thereafter, a radical; (5) from dissolved ozone that decays directly into radicals; or (6) from dissolved ozone that is catalytically decomposed into free radicals, through an as yet undefined mechanism.
Each of these mechanisms has a different reaction rates and equilibrium constants. For example, the amount of ionic species available to make radicals is strongly affected by pH. The effective dose of free radicals, those that work to oxidize contaminants is strongly consumed by naturally occurring free radical terminators. Terminators include dissolved bicarbonates, humic and fulvic acids. High doses of hydrogen peroxide also terminate free radical reactions. High doses of radicals also terminate, i.e., self-extinguish, when two radicals collide. The net effective dose is the total dose of radicals less the radicals that terminate.
Hoigne first proposed, and Peyton confirmed, that a radical propagating mechanism exists with available oxygen. If a radical mechanism is initiated, and if the number of initiators exceeds the number of terminators, then the oxygen radical propagation step may occur. Peyton demonstrated this propagation step by bubbling ozone-in-oxygen gas through a batch reactor. Once the radical process was initiated, the ozonator was shut off and the oxygen left on. The rate of substrate removal clean up did not change after the ozone was turned off until the substrate was consumed.
This process approach effectively demonstrated the chemistry of radical chain reactions in a batch reactor. But the continued bubbling of large amounts of gas through a continuous flow reactor stirs and mixes the two fluids, thus destroying any plug flow characteristics in the reactor. Plug flow reactors are the design of choice when oxidizing micro-levels of pollutants down to non-detect levels. It is well understood that it takes three or more stirred reactors in series to simulate the kinetics of a single plug flow reactor. Adding multiple reactors in series to overcome the difference between a stirred reactor and a plug flow reactor adds cost and complexity.
A substantial number of aqueous streams must be treated to meet government laws for release into the environment. Such aqueous streams typically contain one or more impurities, such as suspended solids, dissolved organic matter, microorganisms, dissolved mineral matter and the like. Ozone has been used for decades to remove low concentrations of these contaminants. Historically, ozone has not been used for highly concentrated contaminants because it is difficult to get enough ozone into the water and the capital and energy costs are too high versus competing technologies. For example, ozone is widely used to disinfect drinking water, or to tertiary treat municipal waste, but it is not used to treat water produced from oil and gas recovery because it is cheaper to deep well inject this water. Likewise, the water from making pesticide and herbicide intermediates, which can have a COD (“Chemical Oxygen Demand”) of 10,000 is hauled off and deep well injected as a hazardous waste because the nitro phenols would otherwise poison the municipal treatment plant. In addition, these high concentration fluids are very sudsy. Using a gas to oxidize the contaminants introduces a problem of stable suds formation pump and consequent cavitation.
Ozone, however, has found use in specific high concentration environments where no other technology will work, such as color removal from non-biodegradable color components in the pulp and paper industry, where it is common to encounter a low sudsing stream because the biodegradable components have already been removed by traditional processes. U.S. Pat. No. 5,397,490 to Dickerson describes a process that provides ozone doses that are 2-4 times the normal solubility of ozone in water per multi-zone treatment at gas-to-liquid ratios of 2:1. Improved results are reported as the dose increases. Unfortunately, the Dickerson process leaves behind increasing amount
Bettle, III Griscom
Coury William S.
Barry Chester T.
Needle & Rosenberg P.C.
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