Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Biocides; animal or insect repellents or attractants
Reexamination Certificate
2000-01-18
2003-05-20
Levy, Neil S. (Department: 1617)
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Biocides; animal or insect repellents or attractants
C424S405000, C424S409000, C424S420000, C424S078090, C504S150000, C504S152000, C514S386000, C514S389000
Reexamination Certificate
active
06565868
ABSTRACT:
BACKGROUND
1,3-Dihalo-5,5-dialkylhydantoins are effective as biocides for aqueous systems such as industrial cooling water, recreational water, and wastewater.
Widely used for such purposes are N,N′-bromochloro-5,5-dialkylhydantoins. One of the features emphasized for such materials is that in use, the chlorine released from the biocide regenerates active bromine from inactive bromide species formed during the water treatment operation. In other words, the chlorine atom in the initial N,N′-bromochloro-5,5-dialkylhydantoin is in effect regarded as a precursor for additional active bromine for sanitation purposes.
As is well known in the art, a deficiency of chlorine, of hypochlorites, and of certain halogenated organic water-treating agents is the formation, during usage, of undesirable disinfection by-products. These by-products are undesirable both from the standpoint of environmental concerns and also from the standpoint of toxicological considerations.
Another very serious problem in connection with water disinfection is biofilm development. Biofilms are bacterial films which tenaciously adhere to surfaces in contact with water such as heat exchanger surfaces, conduit interiors, filters, and other processing equipment. These films are very undesirable because they can harbor dangerous pathogens, and cause damage to the surfaces to which they have become attached. Moreover, the bacteria form a slime layer of extra-cellular polysaccharide which affords protection to the bacteria and in addition constitute an effective barrier against penetration of biocidal agents used in an attempt to combat such bacteria. In situations where the water is prone to development of calcium carbonate scale, the presence of such gelatinous extra-cellular polysaccharides can result in the formation of layers of scale bonded to the substrate surface by the gelatinous polysaccharides. Polysaccharide films and films of scale bonded by means of polysaccharides can greatly interfere with the operation of heat exchangers by virtue of their insulating characteristics, and can markedly interfere with the functioning of filters and the flow of water through pipes and conduits by virtue of the clogging tendencies of such polysaccharide films.
Thus a need exists for a biocidal agent which is highly effective in providing biocidal control, especially eradication, or at least minimization, of biofilms in water systems, and in addition, a biocidal agent which has the capability of providing such biocidal control even though used at very low concentrations in water.
SUMMARY OF THE INVENTION
This invention involves, inter alia, the surprising discovery that 1,3-dibromo-5,5-dimethylhydantoin when used in treating water achieves the requirements mandated by the U.S. Environmental Protection Agency at a dosage level that is only one-half of that required when using one or a mixture of N,N′-bromochloro-5,5-dialkylhydantoins. This discovery enables the use of extremely small concentrations of the. 1,3-dibromo-5,5-dimethylhydantoin to effectively sanitize water while at the same time achieving excellent microbiological control. Further, the ability to effectively utilize such small concentrations is expected to result in significant reduction in formation of disinfection by-products.
Another important facet of this invention is the fact that so far as is presently known, 1,3-dibromo-5,5-dimethylhydantoin has never before been used as the sole disinfecting agent for sanitizing water. Instead, in the prior art, only when in admixture with much larger quantities of N,N′-bromochloro-5,5-dimethylhydantoin was 1,3-dibromo-5,5-dimethylhydantoin deemed suitable for use in water sanitation.
Another totally unexpected benefit resulting from the use of 1,3-dibromo-5,5-dimethylhydantoin in water systems is its exceptional effectiveness in destruction and removal of biofilm. Indeed, 1,3-dibromo-5,5-dimethylhydantoin has been found to be almost twice as effective in biofilm eradication as N,N′-bromochloro-5,5-dimethylhydantoin and even more effective in this regard than a number of other known biocidal agents. Because of such great effectiveness, 1,3-dibromo-5,5-dimethylhydantoin can be effectively utilized for biofilm control at extremely low concentrations. This in turn results in substantial benefits from an environmental standpoint and from the standpoint of operating costs.
More particularly, it has been discovered that in the AOAC Official Method: Disinfectants For Swimming Pools (also referred to as Presumptive Efficacy Test) only 1 milligram of bromine (as Br
2
) from 1,3-dibromo-5,5-dimethylhydantoin per liter of water satisfies these official requirements for labeling purposes. In sharp: contrast, parallel tests conducted using N,N′-bromochloro-5,5-dimethylhydantoin required 2 milligrams of bromine (as Br
2
) per liter of water in order to satisfy these official requirements.
Similarly, it has been discovered that in standard tests developed at the University of Calgary for measuring effectiveness in control of biofilms, 1,3-dibromo-5,5-dimethylhydantoin was effective against
Pseudomonas aeruginosa
biofilms at levels as small as 1.4 mg/L (total halogen measured as Br
2
) whereas levels of at least 2.5 mg/L (total halogen measured as Br
2
) were required when using N,N′-bromochloro-5,5-dimethylhydantoin.
Accordingly, this invention provides, in one of its embodiments, a method of treating water for microbiological control and/or biofilm eradication, said method comprising introducing into the water to be treated an amount of 1,3-dibromo-5,5-dimethylhydantoin that is far less than the amount of N,N′-bromochloro-5,5-dimethylhydantoin required to achieve the same microbiological control and/or biofilm eradication.
Another embodiment of this invention is the method of combating
Escherichia coli
in an aqueous medium, which method comprises introducing into said medium a biocidally effective amount of 1,3-dibromo-5,5-dimethylhydantoin. This amount is far less than the amount of N,N′-bromochloro-5,5-dimethylhydantoin required to achieve the same level of effectiveness against
Escherichia coli.
Still another embodiment of this invention is the method of combating
Enterococcus faecium
in an aqueous medium, which method comprises introducing into said medium a biocidally effective amount of 1,3-dibromo-5,5-dimethylhydantoin. This amount is far less than the amount of N,N′-bromochloro-5,5-dimethylhydantoin required to achieve the same level of effectiveness against
Enterococcus faecium.
A preferred embodiment of this invention is the method of concurrently controlling
Escherichia coli
and
Enterococcus faecium
in an aqueous medium, which method comprises introducing into the aqueous medium a biocidally effective amount of 1,3-dibromo-5,5-dimethylhydantoin. Here again, the amount of 1,3-dibromo-5,5-dimethylhydantoin required to achieve this concurrent control of
Escherichia coli
and
Enterococcus faecium
is much lower than the amount required when, utilizing N,N′-bromochloro-5,5-dimethylhydantoin.
A further embodiment of this invention is the method of eradicating or at least reducing
Pseudomonas aeruginosa
biofilm on a surface contacted by an aqueous medium, which method comprises introducing into the aqueous medium, a biocidally effective amount of 1,3-dibromo-5,5-dimethylhydantoin to eradicate or substantially eradicate such biofilm. As noted above, this amount of 1,3-dibromo-5,5-dimethylhydantoin is significantly less than the amount of N,N′-bromochloro-5,5-dimethylhydantoin required to achieve the same effectiveness in removal of such biofilm.
Yet another embodiment of this invention is the method of purveying a microbiological control agent for water in accordance with U.S. Environmental Protection Agency regulations, which method comprises purveying a container of a water control agent comprising 1,3-dibromo-5,5-dimethylhydantoin, said container bearing a label having thereon dosage levels pursuant to requirements promulgated by the U.S. E
Howarth Jonathan N.
Nalepa Christopher J.
Sanders Michael J.
Shelton David L.
Albemarle Corporation
Levy Neil S.
Spielman, Jr. Edgar E.
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