Liquid purification or separation – Processes – Chemical treatment
Reexamination Certificate
2000-05-04
2001-07-31
Simmons, David A. (Department: 1724)
Liquid purification or separation
Processes
Chemical treatment
C252S180000
Reexamination Certificate
active
06267897
ABSTRACT:
FIELD OF THE INVENTION
This invention relates generally to the field of water treatment technologies and, more particularly, to a method of inhibiting biofilm formation in commercial and industrial water systems.
BACKGROUND OF THE INVENTION
Biofouling has always been problematic in commercial and industrial water systems, such as cooling tower waters and air washers, because it can adversely affect heat transfer efficiency and fluid frictional resistance, thereby subsequently reducing production rates. Biofouling is also a problem in pulp and paper mill systems because the growth of microorganisms in papermachine fluids can adversely affect finished paper products, thereby requiring the papermachine to be shut down, resulting in the loss of productivity brought on by the down time of the machine. Furthermore, biofouling plays an important role in microbiologically influenced corrosion.
The presence of microorganisms in commercial and industrial waters cannot be totally eliminated, even with the excessive use of chemical biocides. The most common way to control biofouling is through the application of toxic chemical biocides such as chlorine, bromine, isothiazolones, glutaraldehyde or other antimicrobials. These biocides are added in an attempt to kill both planktonic and attached microorganisms.
Some microorganisms attach to inert surfaces forming aggregates with a complex matrix consisting of extracellular polymeric substances (EPS). This consortium of attached microorganisms and the associated EPS is commonly referred to as a biofilm. Biocides have difficulty penetrating biofilms and removing them from surfaces. Although excessive biocide dosages may be able to control biofouling, such use is costly and the presence of biocides in effluent waters is usually environmentally unacceptable.
Accordingly, it would be desirable to provide a method of inhibiting biofilm formation in commercial and industrial water systems which utilizes a low-cost, non-biocidal substance.
SUMMARY OF THE INVENTION
The method of the invention calls for adding one or more plant oils to a commercial or industrial water system. The addition of plant oil efficiently and effectively inhibits biofilm formation in commercial and industrial water systems. Moreover, the inventive method is economically appealing and environmentally acceptable because plant oils are low in cost and non-biocidal.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is directed to a method of inhibiting biofilm formation in commercial and industrial water systems. In accordance with this invention, one or more plant oils are added to the commercial or industrial water system.
“Plant oils” (which are also known in the art as “natural oils” or “essential oils”) are generally defined as volatile oils obtained from plants which possess the odor and other characteristics of the plant. The plant oils that may be used in the practice of this invention include eucalyptus, cinnamon, retsin, tea tree, clove, camphor, pine, spruce, neem, peppermint, spearmint, wintergreen, lime, orange, grapefruit, mandarin, lemongrass and citronella oils, as well as mixtures thereof. Eucalyptus oil and cinnamon oil are the most preferred plant oils.
The plant oils can be added to the commercial or industrial water system by any conventional method at a concentration which effectively inhibits biofilm formation. It is preferred that the amount of plant oil which is added to the commercial or industrial water system be in the range of about 1 ppm to about 10,000 ppm. More preferably, the amount of plant oil is from about 1 ppm to about 5,000 ppm, with about 1 ppm to about 250 ppm being most preferred.
The commercial and industrial water systems to which the plant oils may be added to inhibit biofilm formation include cooling waters; food, beverage and industrial process waters; pulp and paper mill systems; brewery pasteurizers; sweetwater systems; air washer systems; oil field drilling fluids and muds; petroleum recovery processes; industrial lubricants; cutting fluids; heat transfer systems; gas scrubber systems; latex systems; clay and pigment systems; decorative fountains; water intake pipes; ballast water tanks; and ship reservoirs, among others.
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K.A. Hammer et al., Antimicrobial activity of essential oils and other plant extracts. Journal of Applied Microbiology 1999, 86, 985-990.
S. Cosentino et al., In-vitro antimicrobial activity and chemical composition of Sardinian Thymus essential oils. Letters in Applied Microbiology 1999, 29, 130-135.
Kehoe Victoria M.
Rice Laura E.
Robertson Linda R.
Shetty Chandrashekar
Breininger Thomas M.
Cummings Kelly L.
Hoey Betsey Morrison
Nalco Chemical Company
Simmons David A.
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