Liquid purification or separation – Filter – Material
Reexamination Certificate
2002-07-24
2004-09-28
Smith, Duane (Department: 1724)
Liquid purification or separation
Filter
Material
C210S764000, C210S766000, C422S026000, C422S027000, C422S028000
Reexamination Certificate
active
06796436
ABSTRACT:
BACKGROUND
The present invention pertains to methods of preparing water treatment equipment for shipping and/or storage. The invention also pertains to the treatment of water, and to methods of setting up and commissioning water treatment plants. Such water treatment equipment may include, but is not limited to pressure vessels, carbon columns, ion exchange columns, ultrafiltration modules or assemblies, microfiltration modules or assemblies, nanofiltration modules or assemblies, reverse osmosis modules or assemblies, and associated pumps, conduits, valves, and instrumentation.
Modern water treatment plants are usually built in transportable size modules, e.g., in assemblies of several basic treatment units and their supporting equipment, that may be packaged on “skids” or in “trailers” for shipment to a final site for installation. These modules are usually tested before shipping. One common test is a hydrostatic pressure test. For this test the interior liquid holding volume of the module, including all piping, is filled with water and is pressurized to test for leakage and the equipment's ability to withstand pressures above normal rated design operating pressure. Quality assurance testing of the system or assembly, including operational performance testing of some components may also be performed. For example, the operational performance of an electrodialysis stack, or the pressure and response performance of pumps and other units, may be checked. After testing, the equipment is drained and/or flushed with gas, usually air, to force out as much liquid as possible. The equipment may also be partially disassembled, e.g., broken down into smaller, more transportable sub-units.
It is, however, extremely difficult, if not impossible, to remove all water from the system or assembly. Traces of water therefore remain; this may include ponded water in dead end legs of the plumbing or in crannies of the active treatment modules. This residual water may provide an environment that supports the growth of microorganisms, particularly bacteria, fungi, and molds, including biofilms, e.g., slime-enclosed colonies of microorganisms.
Normally equipment is shipped in this wetted condition and, if any sterilization and/or disinfection of the system or assembly is later needed, it is usually performed after final installation of the equipment at its destination. The interval between the completion of testing and completion of equipment installation at an intended treatment plant provides substantial time in which biological growth and/or spread of biological contamination may occur in the system or assembly. The resulting growth can make it difficult to sterilize the equipment in preparation for use in the production of treated water, particularly if biofilms have grown. As a result, it may be necessary to perform aggressive cleaning of the equipment, and perhaps to also implement a number of rather time-consuming safeguards, such as isolating certain components during cleaning, before the treatment apparatus is allowed to operate in its intended use.
That is, water treatment equipment, broadly defined, is frequently fabricated off-site, at a location other than the intended end use site, is tested at the fabrication site to some extent, and then is shipped, or is partly disassembled into shippable modules or sub-assemblies, each of which can be transported on a highway trailer or in an ocean-going container. Typically, important modules or sub-assemblies are tested with water or an aqueous solution, and several modules may be connected together during the testing procedure. The advantage of testing off site is that a dedicated test site can typically perform testing and troubleshooting more cheaply and more effectively than is possible at a remote construction site.
However, as a trade-off, before final testing and acceptance of the completed treatment plant by the end user, a system must pass through many stages, which generally comprise the following:
i. assembly or “pre-fabrication” of a treatment unit at the off-site facility
ii. testing of the treatment unit at the off-site facility;
iii. preparing the unit for shipping or storage;
iv. optionally, storing the unit prior to shipment;
v. shipping the unit;
vi. storing the unit at the end user site before assembly into a complete treatment system;
vii. assembly of several units into a complete plant; and
viii. sanitization and testing before acceptance by the end user.
The required degree of sanitization may vary greatly depending on the intended end use. However, for economic reasons, one would like to make the on-site sanitization, including whatever degree of disinfection or sterilization may be required, as quick and as straightforward as possible.
SUMMARY OF THE INVENTION
The present invention provides a method that eliminates or minimizes growth of microorganisms in a treatment system or assembly intended for purification of water or other liquids, during storage and/or shipping of the assembly prior to use. The method assures that the treatment equipment may be shipped, stored, and then set up or commissioned without lengthy cleaning operations in the completed treatment plant at the end-user site. The invention also includes a method of providing a treatment plant, and purifying water using equipment that has been sterilized, shipped, and stored in an aseptic state prior to end user site assembly.
Practice of the invention includes a step of providing a sterilizing condition prior to shipping or storage. This is done by introducing a biocidal agent to interior regions or fluid-containing volumes of the system for a biocidally effective level or residence time, e.g., effective, for example, to sanitize the equipment, for example, to bring about substantially 100 percent kill of microorganisms in the system or components. The method also includes the step of effectively sealing shippable units of the system or assembly against subsequent ingress of additional microorganisms.
In one embodiment of the invention, a biocidal agent is added directly to fluid that is used to test the water treatment system or assembly to provide a substantially 100 percent kill of microorganisms in the system or assembly. A substantially 100 percent kill, as used herein, means a bacteriologically significant level of kill. The level may be high, e.g., at least 99%, and is preferably a level of kill that is effective to completely eliminate viable microbial growth such that colonies of microbes do not form, or are not detected by relevant assays, during the period before final installation of the tested equipment. Preferably, water used for testing the system or assembly is treated so that it is sterile, thereby preventing introduction of live microorganisms. The water may, for example, be pretreated by means of sterile filters, passage through an effective ultraviolet light sterilization device, passage through a silver impregnated carbon column, or similar treatment prior to passage through the equipment. For ultrapure water treatment systems, preferred biocidal agents are selected from the group consisting of heat (e.g., in the form of a heated fluid), ozonated water, ozone, and hydrogen peroxide, all of which leave no residue and thus do not contaminate an ultrapure water system or assembly. Alternatively, for some embodiments of this invention, radiation treatment, such as gamma radiation, may be used as an effective biocidal agent. For drinking water treatment systems, a biocidal agent that leaves no toxic residue, or one that may be flushed out with clean water, may be used. For commercial and industrial water treatment systems or assemblies, a biocidal agent that is compatible with the end use of the water, or a biocidal agent that is easily flushed out with clean water may be used. After the system or assembly is disinfected in accordance with this invention, the disinfecting liquid is drained from the system, and ingress by microorganisms is effectively blocked by closing system openings, e.g., with microporous diaphragms or filters to seal t
Carson William W.
Mack Bernard
Ritz Robert J.
Sims Keith J.
Whitehill William C.
David Silverstein Andover-IP-Law
Ionics Incorporated
Pham Minh-Chau T.
Smith Duane
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