Pulsed light sterilization of drinking water and drinking...

Details Pulsed light sterilization of drinking water and drinking... Pulsed light sterilization of drinking water and drinking...

2000-04-10

2002-08-13

Berman, Jack (Department: 2881)

Radiant energy

Supported for nonsignalling objects of irradiation

With source support

C250S492100, C422S024000

Reexamination Certificate

active

06433344

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to sterilization of drinking water and drinking water containers by inactivation of microorganisms located therein and/or thereon. More particularly, the present invention relates to sterilization of drinking water and drinking water bottles using pulsed light sterilization of sealed drinking water bottles. Also described herein, are methods and apparatus for the sterilization of drinking water and drinking water containers by deactivation of microorganisms in drinking water or on said drinking water containers including sterilization of drinking water after being sealed within a drinking water container, using high-intensity, short-duration pulses of incoherent, polychromatic light in a broad spectrum. Finally, the present invention relates to monitoring and controlling key pulsed light parameters to verify sterilization has been achieved.
Various methods of sterilization are known to those of skill in the art, including for example, heat sterilization, e.g., autoclaving, irradiation sterilization, e.g., using gamma radiation, and chemical sterilization. These conventional methods are unsuited to the sterilization of drinking water for a variety of reasons.
A typical drinking water purification process as currently practiced in the art treats water with a series of filters and perhaps other water treatment devices. After filtration and treatment the drinking water is containerized. For example, a water source is provided which introduces drinking water into a multimedia filter which the directs the filtered water into, for example, an activated carbon filter which directs the twice filtered water into a cartridge filter, for example, a 1 &mgr;m filter. This thrice filtered drinking water can then be treated with UV radiation or ozone treated before being introduce to a drinking water container which is filled and capped. This allows ample opportunity for post filtration/treatment contamination of the drinking water. Numerous other water treatment schemes have been tried but none have the advantage of being able to treat drinking water after it has been sealed within its container.
A more recently developed, and hence less well known, method of deactivating microorganisms on and/or within target objects uses high-intensity, short-duration pulses of incoherent, polychromatic light in a broad spectrum to sterilize target objects.
The polychromatic light sterilization techniques and apparatus embodied in the present invention has several significant advantages over conventional sterilization techniques. The first being that the present invention accomplishes sterilization far more quickly than conventional methods. The embodiments of the present invention can sterilize most drinking water and most sizes of drinking water containers in less than a few minutes, as only a few flashes, having durations of a few seconds to less than a minute, are required to achieve sterilization. Second, high-intensity, short-duration pulses of incoherent, polychromatic light can achieve a degree of sterility not possible with current drinking water purification techniques. Also, the embodiments of the present invention accomplish this goal with a higher degree of reliability than purification techniques commonly used to purify drinking water. Third, the present embodiments accomplish these goals using less floor space and at less cost.
An example of these advantages is demonstrated by comparison with the current best method of sterilization, autoclaving. Autoclaving requires, a great deal of time to complete (2-3 hours) and has a high energy cost associated with water heating. Moreover, to autoclave the large amounts of water needed in commercial drinking water applications requires huge amounts of floor space to house the autoclaving machines. These cost and space constraints are so prohibitive that autoclaving is not used to purify drinking water. The methods and embodiments of the present invention allow high volume sterilization of drinking water and drinking water containers in a much smaller space than autoclaving while taking far less time.
A further limitation of conventional methods of terminal sterilization, such as autoclaving, is that they are unsuitable for use with polyethylene containers or thin polypropylene containers, because such containers are unable to withstand the temperatures (e.g., between 100 and 200° C.) or pressures of autoclaving (polypropylene containers are able to withstand some amount of commercially useful autoclaving, however, they are required to be thicker and more expensive to withstand autoclaving than would need be in the absence of this high heat and pressure treatment). Thus, there exists a need for an approach to deactivating microorganisms in drinking water through a container that does not require the use of heat that may damage the container or its contents.
The embodiments of the present invention can sterilize drinking water contained in many different types of packaging materials, such as olefins (e.g., polyethylene or polypropylene); nylon, or a composite material, either laminated or co-extruded structure (including both monolayer and multilayer structures), and the like. The term container as used herein is intended to be interpreted broadly, including but not limited to, bags, bottles, hoses, tubes, water feed lines, or other means of containing drinking water.
Other sterilization processes, e.g., using gamma radiation to achieve terminal sterilization can damage the polymeric structure of olefin containers (i.e., gamma radiation degrades container integrity), which can result in weakened container integrity, leakage, increased gas permeability and other such problems. Gamma radiation can also attack the container and/or its contents to produce other adverse changes, such as darkening, off-colors or color changes, etc. in the container or its contents. Furthermore, gamma radiation inherently causes the generation of highly reactive species, such as hydroxyl radicals, during the gamma irradiation of water, that may detrimentally alter the chemical structure of the product being treated. Thus, there exists a need for an improved sterilization process usable with polyolefins and the like that does not employ gamma radiation, or other such reactive processes, to achieve sterilization.
Other problems with heat treatment, i.e., autoclaving, and conventional gamma radiation treatment techniques include the “batch” nature of such processes. Specifically, with heat or gamma radiation treatment, product containers are treated in groups or batches, which problematically requires additional handling of the product not required if an on-line continuous process is used. In addition, careful inventorying and product handling are required in order to assure that each batch is segregated, and separately treated and tested.
Using conventional terminal sterilization techniques it is nearly impossible to monitor all of the parameters necessary to assure adequate deactivation of microorganisms in all of the product containers in a given batch (i.e., parametric control is nearly impossible). (For example, it is difficult to monitor the temperature within the autoclave at enough points so than one can assure that every part of every container in the batch received enough heat and saturated steam pressure to achieve adequate deactivation of microorganisms.) Because such parametric control is not generally possible with heretofore employed terminal sterilization techniques, such containers must be observed after treatment, e.g., a fourteen day period following terminal sterilization to determine whether any contaminants are present in selected (or all) containers from each batch. This unfortunately further complicates product and product container treatment and delays usage of the containers and products having been treated. An approach that can be performed in a continuous manner, e.g., as a part of a packaging process, thus eliminating the need for “batch” handling and “batch” testing; and an approach that allow

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