Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Using direct contact with electrical or electromagnetic...
Reexamination Certificate
2000-11-28
2002-09-10
Thornton, Krisanne (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Using direct contact with electrical or electromagnetic...
C250S458100, C218S078000
Reexamination Certificate
active
06447721
ABSTRACT:
BACKGROUND OF THE INVENTION
(1) Field of the Invention
The present invention relates generally to a system and method for ultraviolet disinfection and, more particularly, to a system and method for ultraviolet disinfection of drinking water.
(2) Description of the Prior Art
UV Mechanism of Action
It is well known in the art to use ultraviolet light (UV) for the disinfection treatment of water. Ultraviolet light, at the germicidal wavelengths, alters the genetic (DNA) material in cells so that bacteria, viruses, molds, algae and other microorganisms can no longer reproduce. The microorganisms are considered dead, and the risk of disease from them is eliminated. As the water flows past the UV lamps in UV disinfection systems, the microorganisms are exposed to a lethal dose of UV energy. UV dose is measured as the product of UV light intensity times the exposure time within the UV lamp array. Microbiologists have determined the effective dose of UV energy to be approximately about 34,000 microwatt- seconds/cm2 needed to destroy pathogens as well as indicator organisms found in water. Typical prior art disinfection systems and devices emit UV light at approximately 254 nm, which penetrates the outer cell membrane of microorganisms, passes through the cell body, reaches the DNA and alters the genetic material of the microorganism, destroying it without chemicals by rendering it unable to reproduce.
Ultraviolet light is classified into three wavelength ranges: UV-C, from about 200 nanometers (nm) to about 280 nm; UV-B, from about 280 nm to about 315 nm; and UV-A, from about 315 nm to about 400 nm. Generally, UV light, and in particular, UV-C light is “germicidal,” i.e., it deactivates the DNA of bacteria, viruses and other pathogens and thus destroys their ability to multiply and cause disease, effectively resulting in sterilization of the microorganisms. Specifically, UV “C” light causes damage to the nucleic acid of microorganisms by forming covalent bonds between certain adjacent bases in the DNA. The formation of these bonds prevents the DNA codon from being read correctly for replication, and the organism is neither able to produce molecules essential for life process, nor is it able to reproduce. In fact, when an organism is unable to produce these essential molecules or is unable to replicate, it dies. UV light with a wavelength of approximately between about 250 to about 260 nm provides the highest germicidal effectiveness. While susceptibility to UV light varies, exposure to UV energy for about 20 to about 34 milliwatt-seconds/cm
2
is adequate to deactivate approximately 99 percent of the pathogens.
Regulation of Drinking Water Standards
Exposure to pathogens does not always cause disease; whether drinking contaminated water could produce disease depends on the type and quantity of pathogen ingested and the health (nutritional and immunological) status of the person drinking the water. After studying certain variables, including the species and number of pathogens, the World Health Organization (WHO) has determined a standard of performance that must be met by acceptable water disinfection systems. The standard requires that an acceptable water disinfection system must be able to process contaminated water with 100,000 CFUs (colony forming units) of
Escherichia coli
(
E. coli
) per 100 ml of water and produce outlet water with less than one CFU per 100 ml.
United States Environmental Protection Agency (EPA) standards, as set forth in the National Primary Drinking Water Regulations (NPDWRs), have specific requirements for the levels of certain bacteria, protozoa, and viruses.
Giardia lamblia
, a protozoon, and all viruses must be 99.9% killed or inactivated. Heterotrophic microorganisms cannot exceed 500 colony-forming units (CFUs) per ml. No more than 5.0% of samples can be total coliform-positive in a month, and there can be no fecal coliforms present. Fecal coliforms and
E. coli
are bacteria whose presence indicates that the water may be contaminated with human or animal wastes. Microbes in these wastes can cause diarrhea, cramps, nausea, headaches, or other symptoms.
Prior Art
Typically, prior art devices and systems for disinfecting water via ultraviolet light exposure commonly employ standard ultraviolet light sources or lamps encased in quartz sleeves and suspended in the water being treated. Benefits of using ultraviolet light for disinfecting water include the following: no chemicals, like chlorine, are needed to ensure effective water disinfection provided that the proper number of lamps are used and properly positioned for a given influent and flow rate; since no chemicals are required in the disinfection process, no storage and/or handling of toxic chemicals is required; no heating or cooling is required to ensure disinfection; no storage tanks or ponds are necessary because the water can be treated as it flows through the system; no water is wasted in the process; no change in pH, chemical or resistivity of the water being treated; approximately at least 99.99% of all waterborne bacteria and viruses are killed via UV light exposure for disinfection; thereby providing increased safety of using the system and effectiveness of same.
As set forth in the foregoing, prior art UV water treatment systems disinfect and remove microorganisms and other substances from untreated, contaminated water sources and produce clean, safe drinking water. The core technology employed in WaterHealth International's system includes a patented, non-submerged UV light. This technology is claimed by WHI to be a recent and tested innovation developed at the Lawrence Berkeley National Laboratory, a premier, internationally respected laboratory of the U.S. Department of Energy managed by the University of California. This prior art system delivers a UV dose of up to 120 mJ/cm
2
, which is more than three times the NSF International requirement of 38 mJ/cm
2
and exceeds World Health Organization and EPA water quality standards and effectively treats bacteria, viruses and Cryptosporidium in drinking water. In addition, recent research conducted at two different laboratories indicates that UV doses of 10 mJ/cm
2
or less produce 4-log reductions in Giardia. Based on this research, UV dosage of up to 120 mJ/cm
2
greatly exceeds the dosage required for inactivation of Giardia. Additional components included in WaterHealth International's systems effectively treat specific problems such as turbidity, silt, tastes, odors and various chemicals.
The UV light source used in prior art are typically low pressure mercury lamps, which can effectively clean water of dangerous and illness-causing viruses and bacteria, including intestinal protozoa such as Cryptosporidium, Giardia, and
E. coli
, provided that the proper number and configuration of lamps are included in the system.
Prior art UV disinfectant systems work best when the water temperature is between about 35 and about 110 degrees Fahrenheit, since extreme cold or heat will interfere with the UV system performance. Home temperatures are typically in this range.
Among applications for UV disinfection systems for water include the beverage industry, wastewater treatment, and surface treatment. By way of example and explanation, hot filled beverages, cold filled beer and other sensitive drinks are susceptible to contaminants introduced by the liners of closures. Mold is of particular concern since packaging headspace frequently contains low levels of oxygen. Medium pressure UV inactivates mold spores to prevent this problem, including contamination of beverages during production and storage, which can cause discoloration, unusual taste or bad flavor, and reduced shelf life. UV disinfection systems solve these issues by eliminating problem microorganisms without adding chemicals or heat. Disinfection of municipal water using UV light avoids problems associated with storage, transport and use of chemicals and associated regulation for them. Ultraviolet light can help improve shelf life of products and allow processors to reduce chem
Garrett Kurt Anthony
Horton, III Isaac B.
Glasgow Law Firm PLLC
Remotelight, Inc.
Thornton Krisanne
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