Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-07-19
2002-09-03
Hoey, Betsey Morrison (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C210S760000, C210S765000
Reexamination Certificate
active
06444131
ABSTRACT:
TECHNICAL FIELD
This invention relates generally to the treatment of contaminated liquids with oxidizing gases and oxidizing liquids, and more particularly to the treatment of liquids of the type having organic and/or biological contaminants contained therein with oxidizing gases such as ozone and chlorine dioxide and with oxidizing liquids such as hydrogen peroxide.
BACKGROUND AND SUMMARY OF THE INVENTION
As is well known, various liquids are contaminated by organic materials. For example, used lubricating oil frequently includes organic materials comprising products of combustion. Waste water is almost always contaminated by organic materials such as human and animal waste, decaying vegetable materials, biological microorganisms, etc.
As is also well known, organic and/or biological contaminants can be removed from liquids by exposing the contaminated liquids to oxidizing agents, particularly oxidizing gases. Ozone and chlorine dioxide are among the most potent of the oxidizing gases, and therefore offer tremendous potential with respect to the removal of organic contaminants from used lubricating oil, waste water, drinking water, and other liquids. Unfortunately, the inherent instability of ozone and chlorine dioxide has heretofore limited the efficient commercial utilization thereof in the removal of organic contaminants from liquids.
Another problem involved in the removal of organic contaminants from liquids is the time duration of the exposure of an oxidizing agent to the contaminants in the liquid. As is known from Stoke's Law, larger bubbles rise faster in a given liquid. Because it has heretofore not been possible to generate sub-micron size bubbles of oxidizing gases, much larger bubbles, bubbles in the 100-500 micron range, have necessarily been used. Due to the relatively rapid movement of larger bubbles, towers having substantial vertical height have been required in order to increase the time duration of the exposure of the oxidizing gas to the contaminated liquid. Unfortunately, increasing height of the tower increases the pressure that is necessary to overcome head pressure in order to disperse the oxidizing gas in the liquid to be treated. Especially with ozone, the compression of the oxidizing gas can lead to decomposition of the gas through the following reaction, which is, at least partially, a second order kinetic mechanism.
2O
3
→3O
2
Thus, requiring higher pressure in the oxidizing gas can be detrimental in several ways.
Organic contaminants can also be removed from liquids by means of oxidizing liquids such as hydrogen peroxide. Oxidizing liquids are typically quite expensive relative to oxidizing gases. For this reason it has heretofore been impractical to utilize oxidizing liquids in wastewater treatment and similar large scale operations.
The present invention comprises a method of and apparatus for utilizing oxidizing gases and oxidizing liquids to remove organic and/or biological contaminants from liquids which overcomes the foregoing and other problems long since associated with the prior art. In accordance with the one aspect of the invention, oxidizing gas is utilized at its source and is formed into sub-micron size bubbles which are immediately dispersed into a flowing liquid to be decontaminated. Due to the sub-micron size of the bubbles, the surface area of the oxidizing gas is greatly increased, thereby greatly increasing the efficiency of the gas in transferring to the liquid and ultimately oxidizing organic and/or biological contaminants from the liquid. This in turn substantially reduces the vertical height necessary to effectively treat the contaminated liquid, thereby substantially reducing the pressure at which the oxidizing gas is used.
In accordance with a first application of the invention, an oxidizing gas is selected from the group including ozone and chlorine dioxide. The oxidizing gas is formed into sub-micron size bubbles by directing it through a sintered glass, sintered ceramic, or porous ceramic tube. Used lubricating oil is caused to flow over the surface of the sintered/porous tube. The flowing liquid cleaves sub-micron size bubbles of the oxidizing gas from the surface of the tube. The sub-micron size bubbles of oxidizing gas are dispersed into the used lubricating oil, whereupon organic contaminants contained within the used lubricating oil are efficiently oxidized.
In accordance with a second application of the invention, an oxidizing gas is selected from the group including ozone and chlorine dioxide. The oxidizing gas is formed into sub-micron sized bubbles by directing it through a sintered glass, sintered ceramic, or porous ceramic tube. Waste water or drinking water is caused to flow over the surface of the tube. The flowing liquid cleaves sub-micron size bubbles of the oxidizing gas from the surface of the tube. The sub-micron size bubbles of oxidizing gas are dispersed into the water, whereupon organic and/or biological contaminants contained within the waste water are efficiently oxidized.
In accordance with a third aspect of the invention, the surface of the sintered glass, sintered ceramic or porous ceramic tube is provided with a coating of a radiation-activated catalyst such as titanium dioxide. During operation, the catalyst is activated by exposure to ultraviolet radiation, sunlight, visible light, or other electromagnetic radiation. Activation of the catalyst causes the formation of hydroxyl radicals in contaminated water which augment the action of an oxidizing gas or an oxidizing liquid in the removal of organic contaminants from the water.
In accordance with a fourth aspect of the invention, ultraviolet radiation is directed through a contaminated liquid during the dispersal of sub-micron size bubbles comprising an oxidizing gas therein. The oxidizing gas is preferably selected from the group including ozone and chlorine dioxide. The ultraviolet energy substantially improves the kinetics of the reaction whereby contaminants in the liquid are rapidly oxidized. Further, in the case of ozone, the UV light activates the ozone and destroys residual ozone minimizing or eliminating after treatment.
In accordance with a fifth aspect of the invention, sodium hydroxide or other base is injected into the flowing contaminated liquid such that the pH is greater than 8 prior to contacting the liquid with the ozone. The higher pH ensures the conversion of ozone to hydroxyl radical, a powerful oxidizing agent. Further, the higher pH ensures complete ozone destruction.
In accordance with a sixth embodiment of the invention, two or more gas contacting chambers may be placed in series. The gas contacting chambers may be constructed in accordance with any of the various aspects of the invention described hereinabove.
REFERENCES:
patent: 4141830 (1979-02-01), Last
patent: 5849201 (1998-12-01), Bradley
patent: 6030526 (2000-02-01), Porter
GRT, Inc.
Hoey Betsey Morrison
O'Neil Michael A.
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