Chemistry: analytical and immunological testing – Process or composition for sterility or package integrity test
Reexamination Certificate
2001-01-08
2003-07-22
Alexander, Lyle A. (Department: 1743)
Chemistry: analytical and immunological testing
Process or composition for sterility or package integrity test
C436S164000, C422S082050, C422S024000, C250S372000, C250S474100
Reexamination Certificate
active
06596542
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to apparatus for accurately determining the level of exposure to ultraviolet light of a liquid that flows through a passageway within which ultraviolet light sources are disposed. More particularly, the present invention relates to a chemical actinometer for determining the absolute ultraviolet light dose that is directed to water flowing through a disinfection reactor, for monitoring the effectiveness of the disinfection process.
2. Description of the Related Art
Water disinfection reactors having ultraviolet light sources disposed within the passageways through which the water to be disinfected flows have been known for some time. The ultraviolet light deactivates pathogenic microorganisms without producing residuals or hazardous byproducts, and it avoids the need to use hazardous disinfection chemicals.
Generally, the output of ultraviolet lamps utilized in disinfection reactors diminishes gradually over time. Such diminution results from aging of the lamps and also from blockage of the light by deposits on the surfaces of the lamp housings. The deposits are typically dissolved minerals in the water that adhere to the surfaces of the quartz tubes or sleeves within which the ultraviolet lamps are usually housed, and the deposits either physically block the light path or they absorb ultraviolet light. As a consequence, the effectiveness of the disinfection process must be monitored by periodically determining the amount of ultraviolet light that actually passes through the water being treated.
Typically, ultraviolet-light-based disinfection reactors are equipped with photocells that are sensitive to ultraviolet light. The photocells measure relative changes in the ultraviolet fluence rate (or irradiance) within the flowing water. Changes in ultraviolet irradiance patterns in the reactor because of lamp aging, buildup of light-blocking deposits on the surfaces of the quartz sleeves, or changes in the ultraviolet transmittance of the fluid being irradiated, can be sensed by the photocells. But the photocells only indicate relative values of ultraviolet light irradiance, and they cannot be used to determine the absolute value of ultraviolet light irradiance to which the fluid is subjected. Consequently, the photocells can only provide an indication of a decrease in the ultraviolet irradiance output, but they cannot be used to directly determine the ultraviolet dose, which is expressed as the product of irradiance in mW/cm
2
and time in seconds, to demonstrate compliance with disinfection requirements.
In addition to their inability to directly determine the ultraviolet dose to which the water to be treated is exposed, the sensitivity of photocells decreases with use. Such decreases are caused by surface damage from ultraviolet light radiation and also by aging of the photocells. Accordingly, recalibration of the photocells is required at regular intervals, to assure that they can be relied upon to accurately monitor the changes in the irradiance output from the ultraviolet light sources. Those same limitations apply to other forms of physical detectors, such as thermopiles, joulemeters, photodiodes, and the like.
Another limitation of most light detectors that are based upon physically measuring the ultraviolet light is that they are typically mounted on the wall of the reactor vessel and can only measure incident ultraviolet light from a single direction. Thus, in reactors within which some of the ultraviolet light is reflected from the reactor walls, in addition to the light that passes directly from the light source to the detector, the effects of such reflected light are not accurately detected and indicated by the physical detectors.
It is therefore an object of the present invention to provide an actinometer-based ultraviolet monitor that can measure the actual exposure of a flowing liquid to ultraviolet light in an ultraviolet light reactor vessel, and to overcome the deficiencies and limitations of the previously-used devices.
SUMMARY OF THE INVENTION
Briefly stated, in accordance with one aspect of the present invention, a flow-through chemical actinometer system is provided for monitoring ultraviolet light radiation. The actinometer system includes a source vessel containing an actinometric solution that is responsive to ultraviolet light in a germicidal treatment range. A collection vessel is provided for receiving the actinometric solution after it has been exposed to ultraviolet light. Extending from the source vessel to the collection vessel is a flow conduit that passes through an ultraviolet reactor vessel and includes at least one sample cell having a transparent section through which the actinometric solution flows for exposure to ultraviolet light. A pump conveys the actinometric solution from the source vessel, through the conduit, to the collection vessel.
In accordance with another aspect of the present invention, a method is provided for assessing the ultraviolet light dose to which a liquid containing microorganisms is exposed while flowing through a reactor containing an ultraviolet light source for inactivating the microorganisms. The method includes providing an actinometric chemical solution that is reactive to ultraviolet light in a germicidal treatment wavelength range. The actinometric solution is passed through an opaque conduit that extends into the ultraviolet reactor and that includes a sample cell having a predetermined area of transparency to expose the actinometric solution to ultraviolet light within the reactor. The exposed actinometric solution is analyzed for chemical changes and the ultraviolet light dose to which the liquid to be treated has been exposed within the reactor is determined based upon the analyzed chemical changes.
REFERENCES:
patent: 4763011 (1988-08-01), Smith
patent: 5036311 (1991-07-01), Moran et al.
patent: 5500532 (1996-03-01), Koziki
patent: 6183695 (2001-02-01), Godec et al.
Technical Note, entitled, “Potassium Iodide as a chemical Actinometer for 254nm Radiation: Use of Iodate as an Electron Scavenger,” by Ronald O. Rahn, Photochemistry and Photobiology, 1997, 66(4), pp. 450-455.
Alexander Lyle A.
Mangels Alfred J.
LandOfFree
Flow-through chemical actinometer for ultraviolet... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Flow-through chemical actinometer for ultraviolet..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Flow-through chemical actinometer for ultraviolet... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3009310