Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
1998-03-16
2001-06-05
Hruskoci, Peter A. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C162S161000, C210S698000, C424S078090
Reexamination Certificate
active
06241898
ABSTRACT:
BACKGROUND OF THE INVENTION
Bacterial attachment to surfaces in virtually any non-sterile aquatic environment is a well-established phenomenon. Industrial efforts to prevent colonization or to clean fouled surfaces amount to costly expenditures in a number of industrial sectors. Often, such expenditures are made for cleaning programs that include the use of surfactants. Surfactants are regularly employed in water treatment programs as agents believed to play a role in the removal of organic masses from surfaces, in the enhancement of biocide efficacy or in the assistance in the water miscibility of various biocidal agents. Surfactants are also regularly used in the agrichemical business, particularly to enhance the action of herbicides. This is accomplished by using the surfactants to alter the surface behavior of the applied droplets, maximizing their interaction with the leaf surface.
One of the desirable benefits of many surfactants is their relative handling safety due to the low mammalian toxicity of many of these compounds. Additionally, many surfactants are also biodegradable. These properties have resulted in increased attention being paid to these materials as process treatment chemicals that may allow for the reduction or elimination of some proportion of the less environmentally sensitive compounds currently in regular use.
There are numerous examples of surfactants which are able to inhibit the colonization of surfaces by inhibiting the overall growth of the organisms in the target environment. Most surfactants, regardless of class, show some inhibition of surface colonization when used at concentrations high enough to impede bacterial growth. In the water treatment industry, the most well known surfactants which impart a measure of colonization resistance to submerged surfaces are the cationic quaternary amine surfactants, which also function as biocides. However, even the relatively mild nonionic surfactants can exhibit toxic effects upon microbes, e.g., bacteria or fungi; the concentration of nonionic surfactants necessary to mediate toxicity is typically substantially higher than for cationic surfactants, however.
In addition, the use of surfactants at high concentrations typically results in the discharge of large amounts of the surfactant into water treatment facilities or into the environment. Depending on the specific surfactant, the release of large quantities of these materials into the ground water may have significant environmental consequences, particularly in the absence of rapid biodegradation.
Other examples of using surfactants to prevent adhesion of bacteria to surfaces exist in the prior art. One class of surfactant that has been seen to exhibit some degree of efficacy is the polyoxyethylene-polyoxypropylene block copolymers. These materials have been demonstrated to have limited usefulness under specific conditions. Some have demonstrated efficacy for inhibiting bacterial colonization of surfaces when applied at reasonably low levels. These materials, however, only displayed efficacy for hydrophobic surfaces.
Examples of nontoxic control of surface colonization typically require the use of high concentrations of surfactants not feasible in water treatment industries where thousands or millions of gallons of water would be treated.
The present invention relates to the use of surfactants which act by inhibiting microbial adhesion to surfaces in contact with an aqueous system. The materials of the present invention have been previously used in areas such as fiber wetting in the textile industry. These materials function to inhibit adhesion at concentrations below which toxicity has been observed for the tested organisms.
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Johnson M. Christine
Wright J. Barry
BetzDearborn Inc.
Greenblum & Bernstein P.L.C.
Hruskoci Peter A.
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