Chemical apparatus and process disinfecting – deodorizing – preser – Process disinfecting – preserving – deodorizing – or sterilizing – Maintaining environment nondestructive to metal
Reexamination Certificate
1998-12-10
2001-01-30
Warden, Sr., Robert J. (Department: 1744)
Chemical apparatus and process disinfecting, deodorizing, preser
Process disinfecting, preserving, deodorizing, or sterilizing
Maintaining environment nondestructive to metal
C422S028000, C210S636000, C210S639000, C210S652000, C252S175000
Reexamination Certificate
active
06180056
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to certain compositions and processes useful for minimizing biological and colloidal fouling. The present invention further relates to compositions and methods for minimizing biological and colloidal fouling in aqueous systems that use separation membranes. General embodiments of such aqueous systems, include but are not limited to, nanofiltration, ultrafiltration, microfiltration and particularly reverse osmosis processes. The compositions of the present invention preferably show unexpected efficacy in minimizing biological and colloidal fouling.
Reverse osmosis (RO) is a process commonly used in commercial, industrial, and home liquid purification systems. RO processes purify liquids that contain undissolved and dissolved impurities. The liquid to be purified is passed over a RO membrane. The “permeate” passes through the reverse osmosis membrane and is collected as purified liquid, while the remaining liquid, or “concentrate” is discarded or further processed. The successful practice of a RO process is inhibited by accumulating colloidal dispersions and biofouling.
Biofouling can be considered as one of the last major unresolved problems affecting RO processes. This is because the most common RO membrane type in use today cannot tolerate chlorine or other oxidizing biocides. For this reason, chlorine must generally be removed from the feedstreams to these systems. However, without the presence of a chlorine residual, microorganisms quickly colonize and biofoul membrane surfaces. The approach of the industry thus far has been either to ignore the problem and accept high operating costs due to biofouling, or to add non-oxidizing biocides to these plants. It has been estimated that the cost of biofouling may total as high as $0.25 per 1000 gallons of RO permeate produced. This high cost makes biofouling control by non-oxidizing biocides economically attractive.
However, there are a significant number of drawbacks to many of the non-oxidizing biocides currently available. Specifically, non-oxidizing biocides are known to be highly toxic, incompatible with RO membranes, produce unwanted side reactions with other treatment chemicals or feedwater constituents, and/or adversely affect downstream processes where excess biocides passes through RO membranes.
Accordingly, there is a need in the art for a biocidal composition that overcomes these and other problems.
SUMMARY OF THE INVENTION
It is therefore an object of the present invention to provide a novel method and composition for minimizing biological and colloidal fouling, preferably without one or more of the drawbacks discussed above.
Additional features and advantages of the invention will be set forth in the description, which follows, and in part will be apparent from the description, or may be learned by practice of the present invention. The advantages of the present invention will be realized and obtained by the method and composition of matter, particularly, pointed out in the written description and claims thereof.
To achieve these and other advantages and in accordance with the purpose of the invention, as embodied and broadly described, the present invention relates to a composition which includes at least one anionic antiscalant and at least one cationically-charged biocide. The anionic antiscalant and cationically-charged biocide are present in any amount effective to control or minimize colloidal and/or biological fouling.
The present invention also relates to a method to control colloidal and/or biological fouling in an aqueous system involving the use of a separation membrane system. The method involves the introduction of a formulation containing at least one anionic antiscalant and at least one cationic biocide to an aqueous system upstream of the separation membrane, in an effective amount to control or reduce the colloidal and/or biological fouling in the aqueous solution.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.
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Anstead Maryam Z.
Clark Richard A.
Comstock Daniel L.
McNeel Thomas E.
Buckman Laboratories International Inc.
Kilyk & Bowersox P.L.L.C.
Warden, Sr. Robert J.
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